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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1207.6791 | Alfredo Lopez Ortega | A. Lopez-Ortega | On the quasinormal modes of the de Sitter spacetime | 11 pages, 4 figures | null | 10.1007/s10714-012-1398-4 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | Modifying a method by Horowitz and Hubeny for asymptotically anti-de Sitter
black holes, we establish the classical stability of the quasinormal modes of
the de Sitter spacetime. Furthermore using a straightforward method we
calculate the de Sitter quasinormal frequencies of the gravitational
perturbations and discuss some properties of the radial functions of these
quasinormal modes.
| [
{
"created": "Sun, 29 Jul 2012 18:44:18 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Lopez-Ortega",
"A.",
""
]
] | Modifying a method by Horowitz and Hubeny for asymptotically anti-de Sitter black holes, we establish the classical stability of the quasinormal modes of the de Sitter spacetime. Furthermore using a straightforward method we calculate the de Sitter quasinormal frequencies of the gravitational perturbations and discuss some properties of the radial functions of these quasinormal modes. |
1306.5971 | Mikhail M. Ivanov | Evgeny E. Bukzhalev, Mikhail M. Ivanov and Alexey V. Toporensky | Asymptotic solutions in f(R)-gravity | 23+10 pages, 7 figures, published version | Class. Quantum Grav. 31 (2014) 045017 | 10.1088/0264-9381/31/4/045017 | null | gr-qc astro-ph.CO math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study cosmological solutions in $R + \beta R^{N}$-gravity for an isotropic
Universe filled with ordinary matter with the equation of state parameter
$\gamma$. Using the Bogolyubov-Krylov-Mitropol'skii averaging method we find
asymptotic oscillatory solutions in terms of new functions, which have been
specially introduced by us for this problem and appeared as a natural
generalization of the usual sine and cosine. It is shown that the late-time
behaviour of the Universe in the model under investigation is determined by the
sign of the difference $\gamma-\gamma_{crit}$ where $\gamma_{crit}=2N/(3N-2)$.
If $\gamma < \gamma_{crit}$, the Universe reaches the regime of small
oscillations near values of Hubble parameter and matter density, corresponding
to General Relativity solution. Otherwise higher-curvature corrections become
important at late times. We also study numerically basins of attraction for the
oscillatory and phantom solutions, which are present in the theory for $N>2$.
Some important differences between $N=2$ and $N>2$ cases are discussed.
| [
{
"created": "Tue, 25 Jun 2013 14:00:22 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Jul 2013 14:34:02 GMT",
"version": "v2"
},
{
"created": "Fri, 6 Dec 2013 09:55:13 GMT",
"version": "v3"
},
{
"created": "Mon, 28 Apr 2014 11:07:07 GMT",
"version": "v4"
}
] | 2014-04-29 | [
[
"Bukzhalev",
"Evgeny E.",
""
],
[
"Ivanov",
"Mikhail M.",
""
],
[
"Toporensky",
"Alexey V.",
""
]
] | We study cosmological solutions in $R + \beta R^{N}$-gravity for an isotropic Universe filled with ordinary matter with the equation of state parameter $\gamma$. Using the Bogolyubov-Krylov-Mitropol'skii averaging method we find asymptotic oscillatory solutions in terms of new functions, which have been specially introduced by us for this problem and appeared as a natural generalization of the usual sine and cosine. It is shown that the late-time behaviour of the Universe in the model under investigation is determined by the sign of the difference $\gamma-\gamma_{crit}$ where $\gamma_{crit}=2N/(3N-2)$. If $\gamma < \gamma_{crit}$, the Universe reaches the regime of small oscillations near values of Hubble parameter and matter density, corresponding to General Relativity solution. Otherwise higher-curvature corrections become important at late times. We also study numerically basins of attraction for the oscillatory and phantom solutions, which are present in the theory for $N>2$. Some important differences between $N=2$ and $N>2$ cases are discussed. |
1603.02444 | Ian Harry | Ian Harry, Stephen Privitera, Alejandro Boh\'e and Alessandra Buonanno | Searching for Gravitational Waves from Compact Binaries with Precessing
Spins | 21 pages, 9 figures. Updated to reflect published version in PRD | Phys. Rev. D 94, 024012 (2016) | 10.1103/PhysRevD.94.024012 | null | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Current searches for gravitational waves from compact-object binaries with
the LIGO and Virgo observatories employ waveform models with spins aligned (or
anti-aligned) with the orbital angular momentum. Here, we derive a new
statistic to search for compact objects carrying generic (precessing) spins.
Applying this statistic, we construct banks of both aligned- and generic-spin
templates for binary black holes and neutron-star--black-hole binaries, and
compare the effectualness of these banks towards simulated populations of
generic-spin systems. We then use these banks in a pipeline analysis of
Gaussian noise to measure the increase in background incurred by using generic-
instead of aligned-spin banks. Although the generic-spin banks have a factor of
ten to twenty more templates than the aligned-spin banks, we find an overall
improvement in signal recovery at fixed false-alarm rate for systems with
high-mass ratio and highly precessing spins ---up to 60\% for
neutron-star--black-hole mergers. This gain in sensitivity comes at a small
loss of sensitivity ($\lesssim$4\%) for systems that are already well-covered
by aligned-spin templates. Since the observation of even a single binary merger
with misalinged spins could provide unique astrophysical insights into the
formation of these sources, we recommend that the method described here be
developed further to mount a viable search for generic-spin binary mergers in
LIGO/Virgo data.
| [
{
"created": "Tue, 8 Mar 2016 09:48:45 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jul 2016 09:48:08 GMT",
"version": "v2"
}
] | 2016-07-14 | [
[
"Harry",
"Ian",
""
],
[
"Privitera",
"Stephen",
""
],
[
"Bohé",
"Alejandro",
""
],
[
"Buonanno",
"Alessandra",
""
]
] | Current searches for gravitational waves from compact-object binaries with the LIGO and Virgo observatories employ waveform models with spins aligned (or anti-aligned) with the orbital angular momentum. Here, we derive a new statistic to search for compact objects carrying generic (precessing) spins. Applying this statistic, we construct banks of both aligned- and generic-spin templates for binary black holes and neutron-star--black-hole binaries, and compare the effectualness of these banks towards simulated populations of generic-spin systems. We then use these banks in a pipeline analysis of Gaussian noise to measure the increase in background incurred by using generic- instead of aligned-spin banks. Although the generic-spin banks have a factor of ten to twenty more templates than the aligned-spin banks, we find an overall improvement in signal recovery at fixed false-alarm rate for systems with high-mass ratio and highly precessing spins ---up to 60\% for neutron-star--black-hole mergers. This gain in sensitivity comes at a small loss of sensitivity ($\lesssim$4\%) for systems that are already well-covered by aligned-spin templates. Since the observation of even a single binary merger with misalinged spins could provide unique astrophysical insights into the formation of these sources, we recommend that the method described here be developed further to mount a viable search for generic-spin binary mergers in LIGO/Virgo data. |
1812.00343 | Chongoh Lee | Chong Oh Lee | Configurational entropy of tachyon kinks on unstable Dp-branes | 9 pages, 20 figures, typos corrected, added comments and references,
version to appear in PLB | null | 10.1016/j.physletb.2019.01.026 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We consider tachyon effective theory with Born-Infeld electromagnetic fields
and investigate the configurational entropy of the various tachyon kink
solutions. We find that the configurational entropy stats at a minimum value
and saturates to a maximum value as the negative pressure of pure tachyonic
field increases. In particular, when an electric field is turned on and its
magnitude is larger than or equal to the critical value, we find the
configurational entropy has a global minimum, which is related to the
predominant tachyonic states.
| [
{
"created": "Sun, 2 Dec 2018 06:56:23 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Jan 2019 09:59:53 GMT",
"version": "v2"
}
] | 2019-01-30 | [
[
"Lee",
"Chong Oh",
""
]
] | We consider tachyon effective theory with Born-Infeld electromagnetic fields and investigate the configurational entropy of the various tachyon kink solutions. We find that the configurational entropy stats at a minimum value and saturates to a maximum value as the negative pressure of pure tachyonic field increases. In particular, when an electric field is turned on and its magnitude is larger than or equal to the critical value, we find the configurational entropy has a global minimum, which is related to the predominant tachyonic states. |
1907.10517 | Maximilian Thaller | Maximilian Thaller | Rotating Clouds of Charged Vlasov Matter in General Relativity | 32 pages | null | 10.1088/1361-6382/ab60ba | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The existence of stationary solutions of the Einstein-Vlasov-Maxwell system
which are axially symmetric but not spherically symmetric is proven by means of
the implicit function theorem on Banach spaces. The proof generalises the
methods of an article by H{\aa}kan Andr\'easson, Markus Kunze and Gerhard Rein
where a similar result is obtained for uncharged particles. Among the solutions
constructed in this article there are rotating and non-rotating ones. Static
solutions exhibit an electric but no magnetic field. In the case of rotating
solutions, in addition to the electric field, a purely poloidal magnetic field
is induced by the particle current. The existence of toroidal components of the
magnetic field turns out to be not possible in this setting.
| [
{
"created": "Wed, 24 Jul 2019 15:29:31 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Aug 2019 15:06:23 GMT",
"version": "v2"
},
{
"created": "Mon, 4 Nov 2019 16:10:00 GMT",
"version": "v3"
}
] | 2020-01-29 | [
[
"Thaller",
"Maximilian",
""
]
] | The existence of stationary solutions of the Einstein-Vlasov-Maxwell system which are axially symmetric but not spherically symmetric is proven by means of the implicit function theorem on Banach spaces. The proof generalises the methods of an article by H{\aa}kan Andr\'easson, Markus Kunze and Gerhard Rein where a similar result is obtained for uncharged particles. Among the solutions constructed in this article there are rotating and non-rotating ones. Static solutions exhibit an electric but no magnetic field. In the case of rotating solutions, in addition to the electric field, a purely poloidal magnetic field is induced by the particle current. The existence of toroidal components of the magnetic field turns out to be not possible in this setting. |
0905.2055 | Chen Songbai | Songbai Chen, Jiliang Jing | Strong field gravitational lensing in the deformed H\v{o}rava-Lifshitz
black hole | 12 pages, 2 figures,some references added, Accepted by PRD | Phys.Rev.D80:024036,2009 | 10.1103/PhysRevD.80.024036 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Adopting the strong field limit approach, we studied the properties of strong
field gravitational lensing in the deformed H\v{o}rava-Lifshitz black hole and
obtained the angular position and magnification of the relativistic images.
Supposing that the gravitational field of the supermassive central object of
the galaxy described by this metric, we estimated the numerical values of the
coefficients and observables for gravitational lensing in the strong field
limit. Comparing with the Reissner-Norstr\"{om} black hole, we find that with
the increase of parameter $\alpha$, the angular position $\theta_{\infty}$
decreases more slowly and $r_m$ more quickly, but angular separation $s$
increases more rapidly. This may offer a way to detect the effects of to
distinguish a deformed H\v{o}rava-Lifshitz black hole from a
Reissner-Norstr\"{om} black hole by the astronomical instruments in the future.
| [
{
"created": "Wed, 13 May 2009 10:24:46 GMT",
"version": "v1"
},
{
"created": "Sun, 17 May 2009 03:49:34 GMT",
"version": "v2"
},
{
"created": "Thu, 16 Jul 2009 03:56:35 GMT",
"version": "v3"
}
] | 2009-08-13 | [
[
"Chen",
"Songbai",
""
],
[
"Jing",
"Jiliang",
""
]
] | Adopting the strong field limit approach, we studied the properties of strong field gravitational lensing in the deformed H\v{o}rava-Lifshitz black hole and obtained the angular position and magnification of the relativistic images. Supposing that the gravitational field of the supermassive central object of the galaxy described by this metric, we estimated the numerical values of the coefficients and observables for gravitational lensing in the strong field limit. Comparing with the Reissner-Norstr\"{om} black hole, we find that with the increase of parameter $\alpha$, the angular position $\theta_{\infty}$ decreases more slowly and $r_m$ more quickly, but angular separation $s$ increases more rapidly. This may offer a way to detect the effects of to distinguish a deformed H\v{o}rava-Lifshitz black hole from a Reissner-Norstr\"{om} black hole by the astronomical instruments in the future. |
gr-qc/9412050 | Bernard Linet | B. Linet | Euclidean spinor Green's functions in the spacetime of a straight cosmic
string | 20 pages, latex, no figures | J.Math.Phys. 36 (1995) 3694-3703 | 10.1063/1.530991 | GCR-941201 | gr-qc | null | We determine generally the spinor Green's function and the twisted spinor
Green's function in an Euclidean space with a conical-type line singularity. In
particular, in the neighbourhood of the point source, we expree them as a sum
of the usual Euclidean spinor Green's functin and a regular term. In four
dimensions, we use these determinations to calculate the vacuum energy density
and the twisted one for a massless spinor field in the spacetime of a straight
cosmic string. In the Minkowski spacetime, we determine explicitly the vacuum
energy density for a massive twisted spinor field.
| [
{
"created": "Mon, 19 Dec 1994 16:30:44 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Linet",
"B.",
""
]
] | We determine generally the spinor Green's function and the twisted spinor Green's function in an Euclidean space with a conical-type line singularity. In particular, in the neighbourhood of the point source, we expree them as a sum of the usual Euclidean spinor Green's functin and a regular term. In four dimensions, we use these determinations to calculate the vacuum energy density and the twisted one for a massless spinor field in the spacetime of a straight cosmic string. In the Minkowski spacetime, we determine explicitly the vacuum energy density for a massive twisted spinor field. |
2312.05457 | Chen Lan | Chen Lan, Meng-Hu Li, Yan-Gang Miao | Phase diagrams of quasinormal frequencies for Schwarzschild, Kerr, and
Taub-NUT black holes | Final version appearing in the PRD. 36 pages, 11 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The Newman-Janis algorithm, which involves complex-coordinate
transformations, establishes connections between static and spherically
symmetric black holes and rotating and/or axially symmetric ones, such as
between Schwarzschild black holes and Kerr black holes, and between
Schwarzschild black holes and Taub-NUT black holes. However, the
transformations in the two samples are based on different physical mechanisms.
The former connection arises from the exponentiation of spin operators, while
the latter from a duality operation. In this paper, we mainly investigate how
the connections manifest in the dynamics of black holes. Specifically, we focus
on studying the correlations of quasinormal frequencies among Schwarzschild,
Kerr, and Taub-NUT black holes. This analysis allows us to explore the physics
of complex-coordinate transformations in the spectrum of quasinormal
frequencies.
| [
{
"created": "Sat, 9 Dec 2023 04:02:12 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Aug 2024 09:48:08 GMT",
"version": "v2"
}
] | 2024-08-15 | [
[
"Lan",
"Chen",
""
],
[
"Li",
"Meng-Hu",
""
],
[
"Miao",
"Yan-Gang",
""
]
] | The Newman-Janis algorithm, which involves complex-coordinate transformations, establishes connections between static and spherically symmetric black holes and rotating and/or axially symmetric ones, such as between Schwarzschild black holes and Kerr black holes, and between Schwarzschild black holes and Taub-NUT black holes. However, the transformations in the two samples are based on different physical mechanisms. The former connection arises from the exponentiation of spin operators, while the latter from a duality operation. In this paper, we mainly investigate how the connections manifest in the dynamics of black holes. Specifically, we focus on studying the correlations of quasinormal frequencies among Schwarzschild, Kerr, and Taub-NUT black holes. This analysis allows us to explore the physics of complex-coordinate transformations in the spectrum of quasinormal frequencies. |
0910.4837 | Orest Hrycyna | Orest Hrycyna, Jakub Mielczarek, Marek Szydlowski | Asymmetric cyclic evolution in polymerised cosmology | 10 pages, 4 figs, JHEP3.cls | JCAP 0912:023,2009 | 10.1088/1475-7516/2009/12/023 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamical systems methods are used to study evolution of the polymerised
scalar field cosmologies with the cosmological constant. We have found all
evolutional paths admissible for all initial conditions on the two-dimensional
phase space. We have shown that the cyclic solutions are generic. The exact
solution for polymerised cosmology is also obtained. Two basic cases are
investigated, the polymerised scalar field and the polymerised gravitational
and scalar field part. In the former the division on the cyclic and non-cyclic
behaviour is established following the sign of the cosmological constant. The
value of the cosmological constant is upper bounded purely from the dynamical
setting.
| [
{
"created": "Mon, 26 Oct 2009 19:35:16 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Hrycyna",
"Orest",
""
],
[
"Mielczarek",
"Jakub",
""
],
[
"Szydlowski",
"Marek",
""
]
] | The dynamical systems methods are used to study evolution of the polymerised scalar field cosmologies with the cosmological constant. We have found all evolutional paths admissible for all initial conditions on the two-dimensional phase space. We have shown that the cyclic solutions are generic. The exact solution for polymerised cosmology is also obtained. Two basic cases are investigated, the polymerised scalar field and the polymerised gravitational and scalar field part. In the former the division on the cyclic and non-cyclic behaviour is established following the sign of the cosmological constant. The value of the cosmological constant is upper bounded purely from the dynamical setting. |
2111.11683 | Neeraj Kumar | Neeraj Kumar, Sunandan Gangopadhyay | Effects of Gauss-Bonnet gravity on thermodynamics of (3+1)$-D$ AdS black
holes | 13 pages, 6 figures, Comments are welcome | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We studied the thermodynamics of the black holes with Gauss-Bonnet correction
term in $3+1-$ dimensional AdS spacetime. It is known that the term has no
effect on the equation of motion, however, it modifies the entropy formula of
Wald as it has an effect of the Gauss-Bonnet parameter term. We studied charged
black holes, namely, Reissner-Nordstr\"{o}m and Born-Infeld under this regime.
We encountered divergences in heat capacity. After eliminating the possibility
of first order phase transition, we applied two well trusted methods from
standard thermodynamics, namely, Ehrenfest scheme and Ruppeiner's state space
geometry analysis to ensure the second order nature of phase transition points.
Effects of Gauss-Bonnet and Born-Infeld parameter are also discussed.
| [
{
"created": "Tue, 23 Nov 2021 07:08:05 GMT",
"version": "v1"
}
] | 2021-11-24 | [
[
"Kumar",
"Neeraj",
""
],
[
"Gangopadhyay",
"Sunandan",
""
]
] | We studied the thermodynamics of the black holes with Gauss-Bonnet correction term in $3+1-$ dimensional AdS spacetime. It is known that the term has no effect on the equation of motion, however, it modifies the entropy formula of Wald as it has an effect of the Gauss-Bonnet parameter term. We studied charged black holes, namely, Reissner-Nordstr\"{o}m and Born-Infeld under this regime. We encountered divergences in heat capacity. After eliminating the possibility of first order phase transition, we applied two well trusted methods from standard thermodynamics, namely, Ehrenfest scheme and Ruppeiner's state space geometry analysis to ensure the second order nature of phase transition points. Effects of Gauss-Bonnet and Born-Infeld parameter are also discussed. |
1109.0740 | Johannes Tambornino | Johannes Tambornino | Relational Observables in Gravity: a Review | null | SIGMA 8 (2012), 017, 30 pages | 10.3842/SIGMA.2012.017 | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by-nc-sa/3.0/ | We present an overview on relational observables in gravity mainly from a
loop quantum gravity perspective. The gauge group of general relativity is the
diffeomorphism group of the underlying manifold. Consequently, general
relativity is a totally constrained theory with vanishing canonical
Hamiltonian. This fact, often referred to as the problem of time, provides the
main conceptual difficulty towards the construction of gauge-invariant local
observables. Nevertheless, within the framework of complete observables, that
encode relations between dynamical fields, progress has been made during the
last 20 years. Although analytic control over observables for full gravity is
still lacking, perturbative calculations have been performed and within
de-parameterizable toy models it was possible for the first time to construct a
full set of gauge invariant observables for a background independent field
theory. We review these developments and comment on their implications for
quantum gravity.
| [
{
"created": "Sun, 4 Sep 2011 18:54:27 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Mar 2012 05:16:34 GMT",
"version": "v2"
}
] | 2012-03-29 | [
[
"Tambornino",
"Johannes",
""
]
] | We present an overview on relational observables in gravity mainly from a loop quantum gravity perspective. The gauge group of general relativity is the diffeomorphism group of the underlying manifold. Consequently, general relativity is a totally constrained theory with vanishing canonical Hamiltonian. This fact, often referred to as the problem of time, provides the main conceptual difficulty towards the construction of gauge-invariant local observables. Nevertheless, within the framework of complete observables, that encode relations between dynamical fields, progress has been made during the last 20 years. Although analytic control over observables for full gravity is still lacking, perturbative calculations have been performed and within de-parameterizable toy models it was possible for the first time to construct a full set of gauge invariant observables for a background independent field theory. We review these developments and comment on their implications for quantum gravity. |
1503.06994 | Artur Alho | Artur Alho, Juliette Hell and Claes Uggla | Global dynamics and asymptotics for monomial scalar field potentials and
perfect fluids | 33 pages, 12 figures. Matches final published version | null | null | null | gr-qc astro-ph.CO math.DS | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a minimally coupled scalar field with a monomial potential and a
perfect fluid in flat FLRW cosmology. We apply local and global dynamical
systems techniques to a new three-dimensional dynamical systems reformulation
of the field equations on a compact state space. This leads to a visual global
description of the solution space and asymptotic behavior. At late times we
employ averaging techniques to prove statements about how the relationship
between the equation of state of the fluid and the monomial exponent of the
scalar field affects asymptotic source dominance and asymptotic manifest
self-similarity breaking. We also situate the `attractor' solution in the
three-dimensional state space and show that it corresponds to the
one-dimensional unstable center manifold of a de Sitter fixed point, located on
an unphysical boundary associated with the dynamics at early times. By deriving
a center manifold expansion we obtain approximate expressions for the attractor
solution. We subsequently improve the accuracy and range of the approximation
by means of Pad\'e approximants and compare with the slow-roll approximation.
| [
{
"created": "Tue, 24 Mar 2015 11:42:06 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Aug 2015 15:47:41 GMT",
"version": "v2"
}
] | 2015-08-05 | [
[
"Alho",
"Artur",
""
],
[
"Hell",
"Juliette",
""
],
[
"Uggla",
"Claes",
""
]
] | We consider a minimally coupled scalar field with a monomial potential and a perfect fluid in flat FLRW cosmology. We apply local and global dynamical systems techniques to a new three-dimensional dynamical systems reformulation of the field equations on a compact state space. This leads to a visual global description of the solution space and asymptotic behavior. At late times we employ averaging techniques to prove statements about how the relationship between the equation of state of the fluid and the monomial exponent of the scalar field affects asymptotic source dominance and asymptotic manifest self-similarity breaking. We also situate the `attractor' solution in the three-dimensional state space and show that it corresponds to the one-dimensional unstable center manifold of a de Sitter fixed point, located on an unphysical boundary associated with the dynamics at early times. By deriving a center manifold expansion we obtain approximate expressions for the attractor solution. We subsequently improve the accuracy and range of the approximation by means of Pad\'e approximants and compare with the slow-roll approximation. |
gr-qc/0405127 | Sukratu Barve | Sukratu Barve and A.R.Prasanna | Reissner Nordstr\"{o}m Background Metric in Dynamical Co-ordinates:
Exceptional Behaviour of Hadamard States | null | Class.Quant.Grav. 21 (2004) 1505 | 10.1088/0264-9381/21/6/016 | null | gr-qc | null | We cast the Reissner Nordstrom solution in a particular co-ordinate system
which shows dynamical evolution from initial data. The initial data for the
$E<M$ case is regular. This procedure enables us to treat the metric as a
collapse to a singularity. It also implies that one may assume Wald axioms to
be valid globally in the Cauchy development, especially when Hadamard states
are chosen. We can thus compare the semiclassical behaviour with spherical dust
case, looking upon the metric as well as state specific information as
evolution from initial data. We first recover the divergence on the Cauchy
horizon obtained earlier. We point out that the semiclassical domain extends
right upto the Cauchy horizon. This is different from the spherical dust case
where the quantum gravity domain sets in before. We also find that the
backreaction is not negligible near the central singularity, unlike the dust
case. Apart from these differences, the Reissner Nordstrom solution has a
similarity with dust in that it is stable over a considerable period of time.
The features appearing dust collapse mentioned above were suggested to be
generally applicable within spherical symmetry. Reissner Nordstrom background
(along with the quantum state) generated from initial data, is shown not to
reproduce them.
| [
{
"created": "Wed, 26 May 2004 04:31:09 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Barve",
"Sukratu",
""
],
[
"Prasanna",
"A. R.",
""
]
] | We cast the Reissner Nordstrom solution in a particular co-ordinate system which shows dynamical evolution from initial data. The initial data for the $E<M$ case is regular. This procedure enables us to treat the metric as a collapse to a singularity. It also implies that one may assume Wald axioms to be valid globally in the Cauchy development, especially when Hadamard states are chosen. We can thus compare the semiclassical behaviour with spherical dust case, looking upon the metric as well as state specific information as evolution from initial data. We first recover the divergence on the Cauchy horizon obtained earlier. We point out that the semiclassical domain extends right upto the Cauchy horizon. This is different from the spherical dust case where the quantum gravity domain sets in before. We also find that the backreaction is not negligible near the central singularity, unlike the dust case. Apart from these differences, the Reissner Nordstrom solution has a similarity with dust in that it is stable over a considerable period of time. The features appearing dust collapse mentioned above were suggested to be generally applicable within spherical symmetry. Reissner Nordstrom background (along with the quantum state) generated from initial data, is shown not to reproduce them. |
2311.00659 | Konstantin Osetrin | Konstantin E. Osetrin and Vladimir Y. Epp and Sergey V. Chervon | Propagation of light and retarded time of radiation in a strong
gravitational wave | 27 pages | Annals of Physics 462 (2024), 169619 | null | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by-nc-nd/4.0/ | For the strong gravitational wave model, an explicit transformation is
obtained from a privileged coordinate system with a wave variable to a
synchronous reference frame with separation of time and space variables. In a
synchronous reference frame, a general form of the gravitational wave metric,
solutions to the equations of trajectories for test particles in the
Hamilton-Jacobi formalism, a solution to the eikonal equation for radiation,
and a form of equations for the light cone of an observer in a gravitational
wave were found. Using the obtained relations, the form the retarded time of
radiation in the gravitational wave was found. The general relations obtained
can be applied both in Einstein general theory of relativity and in modified
theories of gravity. The obtained relations were applied in the work for an
exact model of a gravitational wave in the Bianchi type VI universe based on an
exact solution of Einstein vacuum equations.
| [
{
"created": "Wed, 1 Nov 2023 17:07:03 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Feb 2024 07:38:32 GMT",
"version": "v2"
}
] | 2024-02-14 | [
[
"Osetrin",
"Konstantin E.",
""
],
[
"Epp",
"Vladimir Y.",
""
],
[
"Chervon",
"Sergey V.",
""
]
] | For the strong gravitational wave model, an explicit transformation is obtained from a privileged coordinate system with a wave variable to a synchronous reference frame with separation of time and space variables. In a synchronous reference frame, a general form of the gravitational wave metric, solutions to the equations of trajectories for test particles in the Hamilton-Jacobi formalism, a solution to the eikonal equation for radiation, and a form of equations for the light cone of an observer in a gravitational wave were found. Using the obtained relations, the form the retarded time of radiation in the gravitational wave was found. The general relations obtained can be applied both in Einstein general theory of relativity and in modified theories of gravity. The obtained relations were applied in the work for an exact model of a gravitational wave in the Bianchi type VI universe based on an exact solution of Einstein vacuum equations. |
1901.09711 | S Habib Mazharimousavi | M. Halilsoy and S. Habib Mazharimousavi | Interpolating the Schwarzschild and de-Sitter metrics | 6 pages, 3 figures published in IJMPD | International Journal of Modern Physics D 28, 1950038 (2019) | 10.1142/S021827181950038X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The binary potential technique of interpolation (by M. Riesz, Acta Math. 81,
1 (1949)) is applied to some well-known metrics of general relativity. These
include Schwarzschild, de Sitter and 2+1-dimensional BTZ spacetimes. In
particular, the Schwarzschild-de Sitter solution is analyzed in some detail
with a finite range parameter. Reasoning by the high level of non-linearity and
absence of a superposition law necessitates search for alternative approaches.
We propose the method of interpolation between different spacetimes as one such
possibility paving the way toward controlling the two-metric system by a common
parameter.
| [
{
"created": "Fri, 25 Jan 2019 13:29:08 GMT",
"version": "v1"
}
] | 2019-01-29 | [
[
"Halilsoy",
"M.",
""
],
[
"Mazharimousavi",
"S. Habib",
""
]
] | The binary potential technique of interpolation (by M. Riesz, Acta Math. 81, 1 (1949)) is applied to some well-known metrics of general relativity. These include Schwarzschild, de Sitter and 2+1-dimensional BTZ spacetimes. In particular, the Schwarzschild-de Sitter solution is analyzed in some detail with a finite range parameter. Reasoning by the high level of non-linearity and absence of a superposition law necessitates search for alternative approaches. We propose the method of interpolation between different spacetimes as one such possibility paving the way toward controlling the two-metric system by a common parameter. |
1107.0996 | Frank Ohme | Frank Ohme, Mark Hannam, Sascha Husa | Reliability of complete gravitational waveform models for compact binary
coalescences | 16 pages, 8 figures, PDFLaTeX, updated presentation, consistent with
published PRD version | Phys. Rev. D 84, 064029 (2011) | 10.1103/PhysRevD.84.064029 | LIGO-P1100078; AEI-2011-039 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | With recent advances in post-Newtonian (PN) theory and numerical relativity
(NR) it has become possible to construct inspiral-merger-ringdown waveforms by
combining both descriptions into one hybrid signal. While addressing the
reliability of such waveforms, previous studies have identified the PN
contribution as the dominant source of error, which can be reduced by
incorporating longer NR simulations. Here we overcome the two outstanding
issues that make it difficult to determine the minimum NR simulation length
necessary to produce suitably accurate hybrids: (1) the criteria for a GW
search is the mismatch between the true waveform and a set of model waveforms,
optimized over all waveforms in the model, but for discrete hybrids this
optimization was not yet possible. (2) these calculations typically require
that numerical waveforms already exist, while we develop an algorithm to
estimate hybrid mismatches errors without numerical data. Our procedure relies
on combining supposedly equivalent PN models at highest available order with
common data in the NR regime, and their difference serves as a measure of the
uncertainty assumed in each waveform. Contrary to some earlier studies, we
estimate that ~10 NR orbits before merger should allow for the construction of
waveform families that are accurate enough for detection in a broad range of
parameters, only excluding highly spinning, unequal-mass systems. Nonspinning
systems, even with high mass-ratio (q>=20) are well modeled for astrophysically
reasonable component masses. The parameter bias is only of the order of 1% for
total mass and symmetric mass-ratio and less than 0.1 for the dimensionless
spin magnitude. We take the view that similar NR waveform lengths will remain
the state of the art in the advanced detector era, and begin to assess the
limits of the science that can be done with them.
| [
{
"created": "Tue, 5 Jul 2011 21:29:23 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Sep 2011 11:07:16 GMT",
"version": "v2"
}
] | 2011-09-30 | [
[
"Ohme",
"Frank",
""
],
[
"Hannam",
"Mark",
""
],
[
"Husa",
"Sascha",
""
]
] | With recent advances in post-Newtonian (PN) theory and numerical relativity (NR) it has become possible to construct inspiral-merger-ringdown waveforms by combining both descriptions into one hybrid signal. While addressing the reliability of such waveforms, previous studies have identified the PN contribution as the dominant source of error, which can be reduced by incorporating longer NR simulations. Here we overcome the two outstanding issues that make it difficult to determine the minimum NR simulation length necessary to produce suitably accurate hybrids: (1) the criteria for a GW search is the mismatch between the true waveform and a set of model waveforms, optimized over all waveforms in the model, but for discrete hybrids this optimization was not yet possible. (2) these calculations typically require that numerical waveforms already exist, while we develop an algorithm to estimate hybrid mismatches errors without numerical data. Our procedure relies on combining supposedly equivalent PN models at highest available order with common data in the NR regime, and their difference serves as a measure of the uncertainty assumed in each waveform. Contrary to some earlier studies, we estimate that ~10 NR orbits before merger should allow for the construction of waveform families that are accurate enough for detection in a broad range of parameters, only excluding highly spinning, unequal-mass systems. Nonspinning systems, even with high mass-ratio (q>=20) are well modeled for astrophysically reasonable component masses. The parameter bias is only of the order of 1% for total mass and symmetric mass-ratio and less than 0.1 for the dimensionless spin magnitude. We take the view that similar NR waveform lengths will remain the state of the art in the advanced detector era, and begin to assess the limits of the science that can be done with them. |
1408.4958 | Andrea Geralico | Donato Bini and Andrea Geralico | Scattering by an electromagnetic radiation field | 13 pages, 2 figures; published version | Phys. Rev. D 85, 044001 (2012) | 10.1103/PhysRevD.85.044001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motion of test particles in the gravitational field associated with an
electromagnetic plane wave is investigated. The interaction with the radiation
field is modeled by a force term {\it \`a la} Poynting-Robertson entering the
equations of motion given by the 4-momentum density of radiation observed in
the particle's rest frame with a multiplicative constant factor expressing the
strength of the interaction itself. Explicit analytical solutions are obtained.
Scattering of fields by the electromagnetic wave, i.e., scalar (spin 0),
massless spin $\frac12$ and electromagnetic (spin 1) fields, is studied too.
| [
{
"created": "Thu, 21 Aug 2014 11:05:59 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
]
] | Motion of test particles in the gravitational field associated with an electromagnetic plane wave is investigated. The interaction with the radiation field is modeled by a force term {\it \`a la} Poynting-Robertson entering the equations of motion given by the 4-momentum density of radiation observed in the particle's rest frame with a multiplicative constant factor expressing the strength of the interaction itself. Explicit analytical solutions are obtained. Scattering of fields by the electromagnetic wave, i.e., scalar (spin 0), massless spin $\frac12$ and electromagnetic (spin 1) fields, is studied too. |
1604.01798 | Joshua Cooperman | Joshua H. Cooperman | Comments on "Searching for a continuum limit in CDT quantum gravity" | 3 pages plus references | null | null | null | gr-qc hep-lat hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To facilitate the search for a continuum limit of causal dynamical
triangulations, Ambjorn, Coumbe, Gizbert-Studnicki, and Jurkiewicz recently
reported measurements of the lattice spacing as a function of the bare
couplings. Although these authors' methods are technically sound, the
conclusions that they draw from their analyses rest crucially on certain
unstated assumptions. I elucidate these assumptions, and I argue that our
current understanding of causal dynamical triangulations does not entail their
justification.
| [
{
"created": "Wed, 6 Apr 2016 20:20:51 GMT",
"version": "v1"
}
] | 2016-04-08 | [
[
"Cooperman",
"Joshua H.",
""
]
] | To facilitate the search for a continuum limit of causal dynamical triangulations, Ambjorn, Coumbe, Gizbert-Studnicki, and Jurkiewicz recently reported measurements of the lattice spacing as a function of the bare couplings. Although these authors' methods are technically sound, the conclusions that they draw from their analyses rest crucially on certain unstated assumptions. I elucidate these assumptions, and I argue that our current understanding of causal dynamical triangulations does not entail their justification. |
1809.03496 | Purnendu Karmakar | Alexander Ganz, Nicola Bartolo, Purnendu Karmakar, and Sabino
Matarrese | Gravity in mimetic scalar-tensor theories after GW170817 | 20 pages, 0 figures | null | 10.1088/1475-7516/2019/01/056 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the most general mimetic scalar-tensor theory assuming a healthy
"seed" action and accounting for the constraints on the speed of
gravitational-wave propagation arising from the GW170817 event. By analysing
linear perturbations around a flat FLRW background in this model, we obtain a
suitable form of the Poisson equation, which allows us to calculate the
effective gravitational constant felt by "ordinary" matter. By restricting to a
minimally coupled model, such an effective gravitational constant is equivalent
to that obtained within General Relativity, with cold dark matter plus a
perfect fluid dark energy component, with vanishing sound speed. Assuming,
further, a $\Lambda$CDM background, the effective gravitational constant cannot
be distinguished from that of the standard $\Lambda$CDM model, at linear order.
For the full non-minimally coupled mimetic gravity model we obtain a
non-vanishing gravitational slip and an effective gravitational constant which
always differs from that of standard $\Lambda$CDM.
| [
{
"created": "Mon, 10 Sep 2018 21:49:03 GMT",
"version": "v1"
}
] | 2019-02-13 | [
[
"Ganz",
"Alexander",
""
],
[
"Bartolo",
"Nicola",
""
],
[
"Karmakar",
"Purnendu",
""
],
[
"Matarrese",
"Sabino",
""
]
] | We derive the most general mimetic scalar-tensor theory assuming a healthy "seed" action and accounting for the constraints on the speed of gravitational-wave propagation arising from the GW170817 event. By analysing linear perturbations around a flat FLRW background in this model, we obtain a suitable form of the Poisson equation, which allows us to calculate the effective gravitational constant felt by "ordinary" matter. By restricting to a minimally coupled model, such an effective gravitational constant is equivalent to that obtained within General Relativity, with cold dark matter plus a perfect fluid dark energy component, with vanishing sound speed. Assuming, further, a $\Lambda$CDM background, the effective gravitational constant cannot be distinguished from that of the standard $\Lambda$CDM model, at linear order. For the full non-minimally coupled mimetic gravity model we obtain a non-vanishing gravitational slip and an effective gravitational constant which always differs from that of standard $\Lambda$CDM. |
gr-qc/9411062 | Vassilevich Dmitri | Dmitri V.Vassilevich | Heat kernel for antisymmetric tensor field on a disk | Latex, 9 pages, no figures | Phys.Lett. B348 (1995) 39-43 | 10.1016/0370-2693(95)00120-A | IC/94/373 , ICTP, Trieste | gr-qc hep-th | null | We suggest a method of reduction of mixed absolute and relative boundary
conditions to pure ones. The case of rank two tensor is studied in detail. For
four-dimensional disk the corresponding heat kernel is expressed in terms of
scalar heat kernels. The result for scaling behavior $\zeta (0)$ agrees with
previous calculations.
| [
{
"created": "Thu, 24 Nov 1994 16:07:07 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Vassilevich",
"Dmitri V.",
""
]
] | We suggest a method of reduction of mixed absolute and relative boundary conditions to pure ones. The case of rank two tensor is studied in detail. For four-dimensional disk the corresponding heat kernel is expressed in terms of scalar heat kernels. The result for scaling behavior $\zeta (0)$ agrees with previous calculations. |
1602.08914 | Andronikos Paliathanasis | Andronikos Paliathanasis and Salvatore Capozziello | Noether symmetries and duality transformations in cosmology | 12 pages; discussion improved; to appear in MPLA | null | 10.1142/S0217732316501832 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the relation between Noether (point) symmetries and discrete
symmetries for a class of minisuperspace cosmological models. We show that when
a Noether symmetry exists for the gravitational Lagrangian then there exists a
coordinate system in which a reversal symmetry exists. Moreover as far as
concerns the scale-factor duality symmetry of the dilaton field, we show that
it is related to the existence of a Noether symmetry for the field equations,
and the reversal symmetry in the normal coordinates of the symmetry vector
becomes scale-factor duality symmetry in the original coordinates. In
particular the same point symmetry as also the same reversal symmetry exists
for the Brans-Dicke- scalar field with linear potential while now the discrete
symmetry in the original coordinates of the system depends on the Brans-Dicke
parameter and it is a scale-factor duality when $\omega_{BD}=1$. Furthermore,
in the context of the O'Hanlon theory for $f\left( R\right) $-gravity, it is
possible to show how a duality transformation in the minisuperspace can be used
to relate different gravitational models.
| [
{
"created": "Mon, 29 Feb 2016 11:41:56 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Apr 2016 12:33:33 GMT",
"version": "v2"
},
{
"created": "Thu, 21 Apr 2016 12:42:23 GMT",
"version": "v3"
},
{
"created": "Thu, 18 Aug 2016 07:45:31 GMT",
"version": "v4"
}
] | 2016-10-12 | [
[
"Paliathanasis",
"Andronikos",
""
],
[
"Capozziello",
"Salvatore",
""
]
] | We discuss the relation between Noether (point) symmetries and discrete symmetries for a class of minisuperspace cosmological models. We show that when a Noether symmetry exists for the gravitational Lagrangian then there exists a coordinate system in which a reversal symmetry exists. Moreover as far as concerns the scale-factor duality symmetry of the dilaton field, we show that it is related to the existence of a Noether symmetry for the field equations, and the reversal symmetry in the normal coordinates of the symmetry vector becomes scale-factor duality symmetry in the original coordinates. In particular the same point symmetry as also the same reversal symmetry exists for the Brans-Dicke- scalar field with linear potential while now the discrete symmetry in the original coordinates of the system depends on the Brans-Dicke parameter and it is a scale-factor duality when $\omega_{BD}=1$. Furthermore, in the context of the O'Hanlon theory for $f\left( R\right) $-gravity, it is possible to show how a duality transformation in the minisuperspace can be used to relate different gravitational models. |
1403.7277 | Fangyu Li | H. Wen, F.Y. Li, Z.Y. Fang, A. Beckwith | Impulsive cylindrical gravitational wave: one possible radiative form
emitted from cosmic strings and corresponding electromagnetic response | 34 pages, 12 figures | null | 10.1140/epjc/s10052-014-2998-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cosmic strings(CSs) may be one important source of gravitational
waves(GWs), and it has been intensively studied due to its special properties
such as the cylindrical symmetry. The CSs would generate not only usual
continuous GW, but also impulsive GW that brings more concentrated energy and
consists of different GW components broadly covering low-, intermediate- and
high-frequency bands simultaneously. These features might underlie interesting
electromagnetic(EM) response to these GWs generated by the CSs. In this paper,
with novel results and effects, we firstly calculate the analytical solutions
of perturbed EM fields caused by interaction between impulsive cylindrical GWs
(would be one of possible forms emitted from CSs) and background celestial high
magnetic fields or widespread cosmological background magnetic fields, by using
rigorous Einstein - Rosen metric. Results show: perturbed EM fields are also in
the impulsive form accordant to the GW pulse, and asymptotic behaviors of the
perturbed EM fields are fully consistent with the asymptotic behaviors of the
energy density, energy flux density and Riemann curvature tensor of
corresponding impulsive cylindrical GWs. The analytical solutions naturally
give rise to the accumulation effect which is proportional to the term of
distance^1/2, and based on it, we for the first time predict potentially
observable effects in region of the Earth caused by the EM response to GWs from
the CSs.
| [
{
"created": "Fri, 28 Mar 2014 03:54:10 GMT",
"version": "v1"
},
{
"created": "Sun, 4 May 2014 08:22:36 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Wen",
"H.",
""
],
[
"Li",
"F. Y.",
""
],
[
"Fang",
"Z. Y.",
""
],
[
"Beckwith",
"A.",
""
]
] | The cosmic strings(CSs) may be one important source of gravitational waves(GWs), and it has been intensively studied due to its special properties such as the cylindrical symmetry. The CSs would generate not only usual continuous GW, but also impulsive GW that brings more concentrated energy and consists of different GW components broadly covering low-, intermediate- and high-frequency bands simultaneously. These features might underlie interesting electromagnetic(EM) response to these GWs generated by the CSs. In this paper, with novel results and effects, we firstly calculate the analytical solutions of perturbed EM fields caused by interaction between impulsive cylindrical GWs (would be one of possible forms emitted from CSs) and background celestial high magnetic fields or widespread cosmological background magnetic fields, by using rigorous Einstein - Rosen metric. Results show: perturbed EM fields are also in the impulsive form accordant to the GW pulse, and asymptotic behaviors of the perturbed EM fields are fully consistent with the asymptotic behaviors of the energy density, energy flux density and Riemann curvature tensor of corresponding impulsive cylindrical GWs. The analytical solutions naturally give rise to the accumulation effect which is proportional to the term of distance^1/2, and based on it, we for the first time predict potentially observable effects in region of the Earth caused by the EM response to GWs from the CSs. |
gr-qc/9712010 | Matt Visser | Matt Visser (Washington University) | Acoustic black holes: horizons, ergospheres, and Hawking radiation | 34 pages, plain LaTeX. Revisions: Two references added. Minor changes
to the discussion of draining-bathtub geometries, and their relationship to
superfluid vortices and spinning cosmic strings | Class.Quant.Grav. 15 (1998) 1767-1791 | 10.1088/0264-9381/15/6/024 | null | gr-qc hep-th | null | It is a deceptively simple question to ask how acoustic disturbances
propagate in a non-homogeneous flowing fluid. This question can be answered by
invoking the language of Lorentzian differential geometry: If the fluid is
barotropic and inviscid, and the flow is irrotational (though possibly time
dependent), then the equation of motion for the velocity potential describing a
sound wave is identical to that for a minimally coupled massless scalar field
propagating in a (3+1)-dimensional Lorentzian geometry. The acoustic metric
governing the propagation of sound depends algebraically on the density, flow
velocity, and local speed of sound. This rather simple physical system is the
basis underlying a deep and fruitful analogy between the black holes of
Einstein gravity and supersonic fluid flows. Many results and definitions can
be carried over directly from one system to another. For example, I will show
how to define the ergosphere, trapped regions, acoustic apparent horizon, and
acoustic event horizon for a supersonic fluid flow, and will exhibit the close
relationship between the acoustic metric for the fluid flow surrounding a point
sink and the Painleve-Gullstrand form of the Schwarzschild metric for a black
hole. This analysis can be used either to provide a concrete non-relativistic
model for black hole physics, up to and including Hawking radiation, or to
provide a framework for attacking acoustics problems with the full power of
Lorentzian differential geometry.
| [
{
"created": "Mon, 1 Dec 1997 23:19:43 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Dec 1997 02:44:03 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Visser",
"Matt",
"",
"Washington University"
]
] | It is a deceptively simple question to ask how acoustic disturbances propagate in a non-homogeneous flowing fluid. This question can be answered by invoking the language of Lorentzian differential geometry: If the fluid is barotropic and inviscid, and the flow is irrotational (though possibly time dependent), then the equation of motion for the velocity potential describing a sound wave is identical to that for a minimally coupled massless scalar field propagating in a (3+1)-dimensional Lorentzian geometry. The acoustic metric governing the propagation of sound depends algebraically on the density, flow velocity, and local speed of sound. This rather simple physical system is the basis underlying a deep and fruitful analogy between the black holes of Einstein gravity and supersonic fluid flows. Many results and definitions can be carried over directly from one system to another. For example, I will show how to define the ergosphere, trapped regions, acoustic apparent horizon, and acoustic event horizon for a supersonic fluid flow, and will exhibit the close relationship between the acoustic metric for the fluid flow surrounding a point sink and the Painleve-Gullstrand form of the Schwarzschild metric for a black hole. This analysis can be used either to provide a concrete non-relativistic model for black hole physics, up to and including Hawking radiation, or to provide a framework for attacking acoustics problems with the full power of Lorentzian differential geometry. |
2201.04512 | Salvatore Capozziello | Salvatore Capozziello and Francesco Bajardi | Non-Local Gravity Cosmology: an Overview | 43 pages, 5 figures, to appear in Int. J. Mod. Phys. D | null | 10.1142/S0218271822300099 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss some main aspects of theories of gravity containing non-local
terms in view of cosmological applications. In particular, we consider various
extensions of General Relativity based on geometrical invariants as $f(R,
\Box^{-1} R)$, $f({\cal G}, \Box^{-1} {\cal G})$ and $f(T, \Box^{-1} T)$
gravity where $R$ is the Ricci curvature scalar, $\cal G$ is the Gauss-Bonnet
topological invariant, $T$ the torsion scalar and the operator $\Box^{-1}$
gives rise to non-locality. After selecting their functional form by using
Noether Symmetries, we find out exact solutions in a cosmological background.
It is possible to reduce the dynamics of selected models and to find analytic
solutions for the equations of motion. As a general feature of the approach, it
is possible to address the accelerated expansion of the Hubble flow at various
epochs, in particular the dark energy issues, by taking into account
non-locality corrections to the gravitational Lagrangian. On the other hand, it
is possible to search for gravitational non-local effects also at astrophysical
scales. In this perspective, we search for symmetries of $f(R, \Box^{-1} R)$
gravity also in a spherically symmetric background and constrain the free
parameters, Specifically, by taking into account the S2 star orbiting around
the Galactic Centre SgrA$^*$, it is possible to study how non-locality affects
stellar orbits around such a massive self-gravitating object.
| [
{
"created": "Wed, 12 Jan 2022 15:17:04 GMT",
"version": "v1"
}
] | 2022-01-13 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Bajardi",
"Francesco",
""
]
] | We discuss some main aspects of theories of gravity containing non-local terms in view of cosmological applications. In particular, we consider various extensions of General Relativity based on geometrical invariants as $f(R, \Box^{-1} R)$, $f({\cal G}, \Box^{-1} {\cal G})$ and $f(T, \Box^{-1} T)$ gravity where $R$ is the Ricci curvature scalar, $\cal G$ is the Gauss-Bonnet topological invariant, $T$ the torsion scalar and the operator $\Box^{-1}$ gives rise to non-locality. After selecting their functional form by using Noether Symmetries, we find out exact solutions in a cosmological background. It is possible to reduce the dynamics of selected models and to find analytic solutions for the equations of motion. As a general feature of the approach, it is possible to address the accelerated expansion of the Hubble flow at various epochs, in particular the dark energy issues, by taking into account non-locality corrections to the gravitational Lagrangian. On the other hand, it is possible to search for gravitational non-local effects also at astrophysical scales. In this perspective, we search for symmetries of $f(R, \Box^{-1} R)$ gravity also in a spherically symmetric background and constrain the free parameters, Specifically, by taking into account the S2 star orbiting around the Galactic Centre SgrA$^*$, it is possible to study how non-locality affects stellar orbits around such a massive self-gravitating object. |
1510.03138 | Jian-Yang Zhu | Xiao-Min Zhang, Hong-Yang Ma, Peng-Cheng Chu, Jun-Ting Liu, Jian-Yang
Zhu | Primordial non-Gaussianity in warm inflation using $\delta N$ formalism | 9 pages, 5 figures | J. Cosmol. Astropart. Phys. 03(2016)059 | 10.1088/1475-7516/2016/03/059 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A $\delta N$ formalism is used to study the non-Gaussianity of the primordial
curvature perturbation on an uniform density hypersurfaces generated by the
warm inflation for the first time. After introducing the framework of the warm
inflation and the $\delta N$ formalism, we obtain an analytic expression for
the nonlinear parameter $f_{NL}$ that describes the non-Gaussianity in slow
roll approximation, and find that the $\delta N$ formalism gives a very good
result. We analyse the magnitude of $f_{NL}$ and compare our result with those
of the standard inflation. Then we discuss two concrete examples: the quartic
chaotic model and the hilltop model. The quartic potential model can again be
in very good agreement with the Planck results in the warm inflationary
scenario, and we give out the concrete results of how the nonlinear parameter
depends on the dissipation strength of the warm inflation and the amounts of
expansion. We find that the range of the nonlinear parameters in these two
cases are both well inside of the allowed region of Planck.
| [
{
"created": "Mon, 12 Oct 2015 04:43:18 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Nov 2015 14:43:45 GMT",
"version": "v2"
}
] | 2016-04-01 | [
[
"Zhang",
"Xiao-Min",
""
],
[
"Ma",
"Hong-Yang",
""
],
[
"Chu",
"Peng-Cheng",
""
],
[
"Liu",
"Jun-Ting",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] | A $\delta N$ formalism is used to study the non-Gaussianity of the primordial curvature perturbation on an uniform density hypersurfaces generated by the warm inflation for the first time. After introducing the framework of the warm inflation and the $\delta N$ formalism, we obtain an analytic expression for the nonlinear parameter $f_{NL}$ that describes the non-Gaussianity in slow roll approximation, and find that the $\delta N$ formalism gives a very good result. We analyse the magnitude of $f_{NL}$ and compare our result with those of the standard inflation. Then we discuss two concrete examples: the quartic chaotic model and the hilltop model. The quartic potential model can again be in very good agreement with the Planck results in the warm inflationary scenario, and we give out the concrete results of how the nonlinear parameter depends on the dissipation strength of the warm inflation and the amounts of expansion. We find that the range of the nonlinear parameters in these two cases are both well inside of the allowed region of Planck. |
gr-qc/0701094 | Riccardo Benini | Riccardo Benini, Giovanni Montani | Classical and Quantum Aspects of the Inhomogeneous Mixmaster Chaoticity | 3 pages, 2 figures, proceedings of the XI Marcel Grossmann meeting on
Relativistic Astrophysics, July 23-29, 2006, Berlin | null | 10.1142/9789812834300_0284 | null | gr-qc | null | We refine Misner's analysis of the classical and quantum Mixmaster in the
fully inhomogeneous picture; we both connect the quantum behavior to the
ensemble representation, both describe the precise effect of the boundary
conditions on the structure of the quantum states.
| [
{
"created": "Tue, 16 Jan 2007 14:42:49 GMT",
"version": "v1"
}
] | 2016-11-15 | [
[
"Benini",
"Riccardo",
""
],
[
"Montani",
"Giovanni",
""
]
] | We refine Misner's analysis of the classical and quantum Mixmaster in the fully inhomogeneous picture; we both connect the quantum behavior to the ensemble representation, both describe the precise effect of the boundary conditions on the structure of the quantum states. |
1305.6341 | Qing-Yu Cai | Baocheng Zhang, Qing-yu Cai, Ming-sheng Zhan, and Li You | Information conservation is fundamental: recovering the lost information
in Hawking radiation | First Award in the 2013 Awards for Essays on Gravitation | International Journal of Modern Physics D 22 (2013) 1341014 | 10.1142/S0218271813410149 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In both classical and quantum world, information cannot appear or disappear.
This fundamental principle, however, is questioned for a black hole, by the
acclaimed "information loss paradox". Based on the conservation laws of energy,
charge, and angular momentum, we recently show the total information encoded in
the correlations among Hawking radiations equals exactly to the same amount
previously considered lost, assuming the non-thermal spectrum of Parikh and
Wilczek. Thus the information loss paradox can be falsified through experiments
by detecting correlations, for instance, through measuring the covariances of
Hawking radiations from black holes, such as the manmade ones speculated to
appear in LHC experiments. The affirmation of information conservation in
Hawking radiation will shine new light on the unification of gravity with
quantum mechanics.
| [
{
"created": "Mon, 27 May 2013 23:18:28 GMT",
"version": "v1"
}
] | 2013-08-13 | [
[
"Zhang",
"Baocheng",
""
],
[
"Cai",
"Qing-yu",
""
],
[
"Zhan",
"Ming-sheng",
""
],
[
"You",
"Li",
""
]
] | In both classical and quantum world, information cannot appear or disappear. This fundamental principle, however, is questioned for a black hole, by the acclaimed "information loss paradox". Based on the conservation laws of energy, charge, and angular momentum, we recently show the total information encoded in the correlations among Hawking radiations equals exactly to the same amount previously considered lost, assuming the non-thermal spectrum of Parikh and Wilczek. Thus the information loss paradox can be falsified through experiments by detecting correlations, for instance, through measuring the covariances of Hawking radiations from black holes, such as the manmade ones speculated to appear in LHC experiments. The affirmation of information conservation in Hawking radiation will shine new light on the unification of gravity with quantum mechanics. |
1509.06209 | Francesco Pannarale | Francesco Pannarale, Emanuele Berti, Koutarou Kyutoku, Benjamin D.
Lackey, Masaru Shibata | Gravitational-wave cutoff frequencies of tidally disruptive neutron
star-black hole binary mergers | 5 pages, 2 figures, 1 table. arXiv admin note: text overlap with
arXiv:1509.00512 | null | 10.1103/PhysRevD.92.081504 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Tidal disruption has a dramatic impact on the outcome of neutron star-black
hole mergers. The phenomenology of these systems can be divided in three
classes: nondisruptive, mildly disruptive or disruptive. The cutoff frequency
of the gravitational radiation produced during the merger (which is potentially
measurable by interferometric detectors) is very different in each regime, and
when the merger is disuptive it carries information on the neutron star
equation of state. Here we use semianalytical tools to derive a formula for the
critical binary mass ratio $Q=M_{\rm BH}/M_{\rm NS}$ below which mergers are
disruptive as a function of the stellar compactness $\mathcal{C}=M_{\rm
NS}/R_{\rm NS}$ and the dimensionless black hole spin $\chi$. We then employ a
new gravitational waveform amplitude model, calibrated to $134$ general
relativistic numerical simulations of binaries with black hole spin
(anti-)aligned with the orbital angular momentum, to obtain a fit to the
gravitational-wave cutoff frequency in the disruptive regime as a function of
$\mathcal{C}$, $Q$ and $\chi$. Our findings are important to build
gravitational wave template banks, to determine whether neutron star-black hole
mergers can emit electromagnetic radiation (thus helping multimessenger
searches), and to improve event rate calculations for these systems.
| [
{
"created": "Mon, 21 Sep 2015 12:55:08 GMT",
"version": "v1"
}
] | 2015-11-04 | [
[
"Pannarale",
"Francesco",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Kyutoku",
"Koutarou",
""
],
[
"Lackey",
"Benjamin D.",
""
],
[
"Shibata",
"Masaru",
""
]
] | Tidal disruption has a dramatic impact on the outcome of neutron star-black hole mergers. The phenomenology of these systems can be divided in three classes: nondisruptive, mildly disruptive or disruptive. The cutoff frequency of the gravitational radiation produced during the merger (which is potentially measurable by interferometric detectors) is very different in each regime, and when the merger is disuptive it carries information on the neutron star equation of state. Here we use semianalytical tools to derive a formula for the critical binary mass ratio $Q=M_{\rm BH}/M_{\rm NS}$ below which mergers are disruptive as a function of the stellar compactness $\mathcal{C}=M_{\rm NS}/R_{\rm NS}$ and the dimensionless black hole spin $\chi$. We then employ a new gravitational waveform amplitude model, calibrated to $134$ general relativistic numerical simulations of binaries with black hole spin (anti-)aligned with the orbital angular momentum, to obtain a fit to the gravitational-wave cutoff frequency in the disruptive regime as a function of $\mathcal{C}$, $Q$ and $\chi$. Our findings are important to build gravitational wave template banks, to determine whether neutron star-black hole mergers can emit electromagnetic radiation (thus helping multimessenger searches), and to improve event rate calculations for these systems. |
gr-qc/9707027 | Viqar Husain | David Brown and Viqar Husain | Black holes with short hair | 11 pages, latex, reference added, to appear in Int. J. Mod. Phys. D | Int.J.Mod.Phys. D6 (1997) 563-573 | 10.1142/S0218271897000340 | CGPG-97/7-1 | gr-qc hep-th | null | We present spherically symmetric black hole solutions for Einstein gravity
coupled to anisotropic matter. We show that these black holes have arbitrarily
short hair, and argue for stability by showing that they can arise from
dynamical collapse. We also show that a recent `no short hair' theorem does not
apply to these solutions.
| [
{
"created": "Sun, 13 Jul 1997 16:39:35 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Jul 1997 18:17:28 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Brown",
"David",
""
],
[
"Husain",
"Viqar",
""
]
] | We present spherically symmetric black hole solutions for Einstein gravity coupled to anisotropic matter. We show that these black holes have arbitrarily short hair, and argue for stability by showing that they can arise from dynamical collapse. We also show that a recent `no short hair' theorem does not apply to these solutions. |
1207.5626 | XiaoXiong Zeng | YiWen Han, Gang Chen | Thermodynamics, geometrothermodynamics and critical behavior of
(2+1)-dimensional black holes | Accepted by PLB. arXiv admin note: text overlap with arXiv:0811.2524,
arXiv:0902.4488, arXiv:0805.3003 by other authors | PLB 714 (2012) 127-130 | 10.1016/j.physletb.2012.06.068 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | In this paper, we study the properties of the (2+1)-dimensional black holes
from the viewpoint of geometrothermodynamics. We show that the Legendre
invariant metric of the (2+1)-dimensional black holes can produce correctly the
behavior of the thermodynamic interaction and phase transition structure of the
corresponding black hole configurations. We find that they are both curved and
the curvature scalar gives the information about the phase transition point.
| [
{
"created": "Tue, 24 Jul 2012 09:04:54 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Han",
"YiWen",
""
],
[
"Chen",
"Gang",
""
]
] | In this paper, we study the properties of the (2+1)-dimensional black holes from the viewpoint of geometrothermodynamics. We show that the Legendre invariant metric of the (2+1)-dimensional black holes can produce correctly the behavior of the thermodynamic interaction and phase transition structure of the corresponding black hole configurations. We find that they are both curved and the curvature scalar gives the information about the phase transition point. |
gr-qc/0209080 | John Barrow | John D. Barrow | Constants and Variations: From Alpha to Omega | 18 pages, no figures. Plenary Talk presented at the JENAM 2002
Workshop on Varying Fundamental Constants, Porto, 5th September 2002. To be
published in the Conference Proceedings | Astrophys.Space Sci.283:645-660,2003 | 10.1023/A:1022571927342 | null | gr-qc astro-ph hep-th | null | We review some of the history and properties of theories for the variation of
the gravitation and fine structure 'constants'. We highlight some general
features of the cosmological models that exist in these theories with reference
to recent quasar data that is consistent with time-variation in alpha since a
redshift of 3.5. The behaviour of a simple class of varying-alpha cosmologies
is outlined in the light of all the observational constraints. We discuss the
key role played by non-zero vacuum energy and curvature in turning off the
variation of constants in these theories and the issue of comparing
extra-galactic and local observational data. We also show why black hole
thermodynamics does not enable us to distinguish between time variations of
different constants.
| [
{
"created": "Mon, 23 Sep 2002 12:24:52 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Barrow",
"John D.",
""
]
] | We review some of the history and properties of theories for the variation of the gravitation and fine structure 'constants'. We highlight some general features of the cosmological models that exist in these theories with reference to recent quasar data that is consistent with time-variation in alpha since a redshift of 3.5. The behaviour of a simple class of varying-alpha cosmologies is outlined in the light of all the observational constraints. We discuss the key role played by non-zero vacuum energy and curvature in turning off the variation of constants in these theories and the issue of comparing extra-galactic and local observational data. We also show why black hole thermodynamics does not enable us to distinguish between time variations of different constants. |
gr-qc/9607064 | Nils Andersson | Nils Andersson | Evolving test-fields in a black-hole geometry | 13 pages, 6 postscript figures | Phys. Rev. D 55, 468 (1997) | 10.1103/PhysRevD.55.468 | Preprint no WUGRAV 96-6 | gr-qc | null | We consider the initial value problem for a massless scalar field in the
Schwarzschild geometry. When constructed using a complex-frequency approach the
necessary Green's function splits into three components. We discuss all of
these in some detail: 1) The contribution from the singularities (the
quasinormal modes of the black hole) is approximated and the mode-sum is
demonstrated to converge after a certain well defined time in the evolution. A
dynamic description of the mode-excitation is introduced and tested. 2) It is
shown how a straightforward low-frequency approximation to the integral along
the branch cut in the black-hole Green's function leads to the anticipated
power-law fall off at very late times. We also calculate higher order
corrections to this tail and show that they provide an important complement to
the leading order. 3) The high-frequency problem is also considered. We
demonstrate that the combination of the obtained approximations for the
quasinormal modes and the power-law tail provide a complete description of the
evolution at late times. Problems that arise (in the complex-frequency picture)
for early times are also discussed, as is the fact that many of the presented
results generalize to, for example, Kerr black holes.
| [
{
"created": "Thu, 25 Jul 1996 16:28:30 GMT",
"version": "v1"
}
] | 2016-08-24 | [
[
"Andersson",
"Nils",
""
]
] | We consider the initial value problem for a massless scalar field in the Schwarzschild geometry. When constructed using a complex-frequency approach the necessary Green's function splits into three components. We discuss all of these in some detail: 1) The contribution from the singularities (the quasinormal modes of the black hole) is approximated and the mode-sum is demonstrated to converge after a certain well defined time in the evolution. A dynamic description of the mode-excitation is introduced and tested. 2) It is shown how a straightforward low-frequency approximation to the integral along the branch cut in the black-hole Green's function leads to the anticipated power-law fall off at very late times. We also calculate higher order corrections to this tail and show that they provide an important complement to the leading order. 3) The high-frequency problem is also considered. We demonstrate that the combination of the obtained approximations for the quasinormal modes and the power-law tail provide a complete description of the evolution at late times. Problems that arise (in the complex-frequency picture) for early times are also discussed, as is the fact that many of the presented results generalize to, for example, Kerr black holes. |
gr-qc/0005001 | Luis Bel | Ll. Bel | Post-Newtonian Frames of Reference | This preprint will not be submitted for publication, but the Author
is willing to consider any proposal emanating from any interested scientific
journal | null | null | null | gr-qc | null | A general theory of frames of reference proposed in a preceding publication
is considered here in the framework of the post-Newtonian approximation,
assuming that the frame of reference is centered on a time-like geodesic. The
problem of taking into account the rotation of the frame of reference, which is
usually ignored or incorrectly oversimplified, is here discussed in detail and
solved.
| [
{
"created": "Sun, 30 Apr 2000 13:24:28 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bel",
"Ll.",
""
]
] | A general theory of frames of reference proposed in a preceding publication is considered here in the framework of the post-Newtonian approximation, assuming that the frame of reference is centered on a time-like geodesic. The problem of taking into account the rotation of the frame of reference, which is usually ignored or incorrectly oversimplified, is here discussed in detail and solved. |
gr-qc/9710060 | Georges Bressange | C. Barrab\`es, G.F. Bressange and P.A. Hogan | Abrupt Changes in the Multipole Moments of a Gravitating Body | 4 pages, latex, no figures, to appear in the Proceedings of the Eigth
Marcel Grossmann Meeting of Jerusalem (22-27 june, 1997) | null | null | null | gr-qc | null | An example is described in which an asymptotically flat static vacuum Weyl
space-time experiences a sudden change across a null hypersurface in the
multipole moments of its isolated axially symmetric source. A light-like shell
and an impulsive gravitational wave are identified, both having the null
hypersurface as history. The stress-energy in the shell is dominated (at large
distance from the source) by the jump in the monopole moment (the mass) of the
source with the jump in the dipole moment mainly responsible for the stress
being anisotropic. The gravitational wave owes its existence prrincipally to
the jump in th quadrupole moment of the source confirming what would be
expected. This serves as a model of a cataclysmic astrophysical event such as a
supernova.
| [
{
"created": "Fri, 10 Oct 1997 13:49:55 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Barrabès",
"C.",
""
],
[
"Bressange",
"G. F.",
""
],
[
"Hogan",
"P. A.",
""
]
] | An example is described in which an asymptotically flat static vacuum Weyl space-time experiences a sudden change across a null hypersurface in the multipole moments of its isolated axially symmetric source. A light-like shell and an impulsive gravitational wave are identified, both having the null hypersurface as history. The stress-energy in the shell is dominated (at large distance from the source) by the jump in the monopole moment (the mass) of the source with the jump in the dipole moment mainly responsible for the stress being anisotropic. The gravitational wave owes its existence prrincipally to the jump in th quadrupole moment of the source confirming what would be expected. This serves as a model of a cataclysmic astrophysical event such as a supernova. |
1903.01877 | Luciano Combi | Luciano Combi and Gustavo E. Romero | Electromagnetic fields and charges in expanding universes | 19 pages, 2 figures, accepted for publication in PRD | null | 10.1103/PhysRevD.99.064017 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the properties of the electric and magnetic fields in different
reference frames within a cosmological background space-time. First, we
investigate the conformal properties of the electromagnetic fields and charge
currents, discussing how the spatial curvature of the universe affects the
field on different scales. Then, we analyze the effects of the expansion of the
universe on local electromagnetic sources using Fermi coordinates. In
particular, we investigate the energy balance and Poynting flux in this locally
defined reference frame. We show that a charge following the Hubble flow in an
accelerated FLRW universe is accelerated as seen by the local inertial frame,
leading to non-null radiation.
| [
{
"created": "Tue, 5 Mar 2019 14:59:44 GMT",
"version": "v1"
}
] | 2019-03-27 | [
[
"Combi",
"Luciano",
""
],
[
"Romero",
"Gustavo E.",
""
]
] | We analyze the properties of the electric and magnetic fields in different reference frames within a cosmological background space-time. First, we investigate the conformal properties of the electromagnetic fields and charge currents, discussing how the spatial curvature of the universe affects the field on different scales. Then, we analyze the effects of the expansion of the universe on local electromagnetic sources using Fermi coordinates. In particular, we investigate the energy balance and Poynting flux in this locally defined reference frame. We show that a charge following the Hubble flow in an accelerated FLRW universe is accelerated as seen by the local inertial frame, leading to non-null radiation. |
2403.02128 | Giampiero Esposito Dr. | Donato Bini, Giampiero Esposito | Projective path to points at infinity in spherically symmetric
spacetimes | 16 pages in double-column format; 18 plots in 14 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper points out that, in a four-dimensional spacetime manifold, the
four coordinates of any point may be viewed as arising from five homogeneous
coordinates according to the well-established recipes of projective geometry.
Moreover, if the homogeneous coordinates change by a linear transformation,
ruled by the coefficients of a matrix of the group GL(5,R), this induces a
fractional linear transformation of spherically symmetric spacetime coordinates
which can be exploited to bring infinity down to a finite distance. The
boundary of spherically symmetric spacetimes here studied is the disjoint union
of three points: future timelike infinity, past timelike infinity, spacelike
infinity, and the three-dimensional products of half-lines with a 2-sphere. For
the single points, the underlying structure is a projective map which destroys
the 2-sphere, whereas the two products of a half-line with the 2-sphere arise
from a projective map which preserves the 2-sphere. Geodesics are then studied
in the projectively transformed (t',r',theta',phi') coordinates for
Schwarzschild spacetime, with special interest in their way of approaching our
points at infinity. Next, Nariai and de Sitter spacetimes are studied with our
projective method. Since the kinds of infinity here defined depend only on the
symmetry of interest in a spacetime manifold, they have a broad range of
applications, which motivate the innovative analysis of Schwarzschild, Nariai
and de Sitter spacetime.
| [
{
"created": "Mon, 4 Mar 2024 15:35:44 GMT",
"version": "v1"
}
] | 2024-03-05 | [
[
"Bini",
"Donato",
""
],
[
"Esposito",
"Giampiero",
""
]
] | This paper points out that, in a four-dimensional spacetime manifold, the four coordinates of any point may be viewed as arising from five homogeneous coordinates according to the well-established recipes of projective geometry. Moreover, if the homogeneous coordinates change by a linear transformation, ruled by the coefficients of a matrix of the group GL(5,R), this induces a fractional linear transformation of spherically symmetric spacetime coordinates which can be exploited to bring infinity down to a finite distance. The boundary of spherically symmetric spacetimes here studied is the disjoint union of three points: future timelike infinity, past timelike infinity, spacelike infinity, and the three-dimensional products of half-lines with a 2-sphere. For the single points, the underlying structure is a projective map which destroys the 2-sphere, whereas the two products of a half-line with the 2-sphere arise from a projective map which preserves the 2-sphere. Geodesics are then studied in the projectively transformed (t',r',theta',phi') coordinates for Schwarzschild spacetime, with special interest in their way of approaching our points at infinity. Next, Nariai and de Sitter spacetimes are studied with our projective method. Since the kinds of infinity here defined depend only on the symmetry of interest in a spacetime manifold, they have a broad range of applications, which motivate the innovative analysis of Schwarzschild, Nariai and de Sitter spacetime. |
1404.2801 | Viktor Toth | Viktor T. Toth | Accelerating classical charges and the equivalence principle | 3 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compare the behavior of a charged particle in a gravitational field and
empty space. We resolve the apparent conflict between the Lorentz-Dirac
equation and Larmor's formula of radiation by noting that the former describes
an electron that is itself accelerated by an electromagnetic field. If instead,
a hypothetical particle is considered that is accelerated by a
non-electromagnetic force, Larmor's formula is found to be consistent with the
accelerating particle's equation of motion. We consider the consequences
concerning the equivalence principle and find that it is indeed violated if one
demands that the same electromagnetic field be present in both the
gravitational and accelerating cases; however, if one allows for the external
electromagnetic fields to be different, the validity of the equivalence
principle is restored. In either case, the basic idea behind the equivalence
principle, which leads to a geometrized theory of gravity, remains unaffected.
| [
{
"created": "Thu, 10 Apr 2014 13:37:48 GMT",
"version": "v1"
}
] | 2014-04-11 | [
[
"Toth",
"Viktor T.",
""
]
] | We compare the behavior of a charged particle in a gravitational field and empty space. We resolve the apparent conflict between the Lorentz-Dirac equation and Larmor's formula of radiation by noting that the former describes an electron that is itself accelerated by an electromagnetic field. If instead, a hypothetical particle is considered that is accelerated by a non-electromagnetic force, Larmor's formula is found to be consistent with the accelerating particle's equation of motion. We consider the consequences concerning the equivalence principle and find that it is indeed violated if one demands that the same electromagnetic field be present in both the gravitational and accelerating cases; however, if one allows for the external electromagnetic fields to be different, the validity of the equivalence principle is restored. In either case, the basic idea behind the equivalence principle, which leads to a geometrized theory of gravity, remains unaffected. |
gr-qc/0207003 | Giovanni Amelino-Camelia | Alessandra Agostini, Giovanni Amelino-Camelia and Michele Arzano | Dirac spinors for Doubly Special Relativity and $\kappa$-Minkowski
noncommutative spacetime | 26 pages, LaTex. v2: Alessandra Agostini (contributing some results
from her PhD thesis) is added to the list of authors. The results presented
in v1 remain unchanged and are contained in Section 2. Sections 3,4,5 add
results not present in v1, concerning the realization of the DSR-deformed
Dirac equation in kappa-Minkowski noncommutative spacetime. Title changed
accordingly | Class.Quant.Grav. 21 (2004) 2179-2202 | 10.1088/0264-9381/21/8/018 | null | gr-qc | null | We construct a Dirac equation that is consistent with one of the
recently-proposed schemes for a "doubly-special relativity", a relativity with
both an observer-independent velocity scale (still naturally identified with
the speed-of-light constant) and an observer-independent length/momentum scale
(possibly given by the Planck length/momentum). We find that the introduction
of the second observer-independent scale only induces a mild deformation of the
structure of Dirac spinors. We also show that our modified Dirac equation
naturally arises in constructing a Dirac equation in the kappa-Minkowski
noncommutative spacetime. Previous, more heuristic, studies had already argued
for a possible role of doubly-special relativity in kappa-Minkowski, but
remained vague on the nature of the consistency requirements that should be
implemented in order to assure the observer-independence of the two scales. We
find that a key role is played by the choice of a differential calculus in
kappa-Minkowski. A much-studied choice of the differential calculus does lead
to our doubly-special relativity Dirac equation, but a different scenario is
encountered for another popular choice of differential calculus.
| [
{
"created": "Sat, 29 Jun 2002 17:51:38 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Dec 2003 08:09:02 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Agostini",
"Alessandra",
""
],
[
"Amelino-Camelia",
"Giovanni",
""
],
[
"Arzano",
"Michele",
""
]
] | We construct a Dirac equation that is consistent with one of the recently-proposed schemes for a "doubly-special relativity", a relativity with both an observer-independent velocity scale (still naturally identified with the speed-of-light constant) and an observer-independent length/momentum scale (possibly given by the Planck length/momentum). We find that the introduction of the second observer-independent scale only induces a mild deformation of the structure of Dirac spinors. We also show that our modified Dirac equation naturally arises in constructing a Dirac equation in the kappa-Minkowski noncommutative spacetime. Previous, more heuristic, studies had already argued for a possible role of doubly-special relativity in kappa-Minkowski, but remained vague on the nature of the consistency requirements that should be implemented in order to assure the observer-independence of the two scales. We find that a key role is played by the choice of a differential calculus in kappa-Minkowski. A much-studied choice of the differential calculus does lead to our doubly-special relativity Dirac equation, but a different scenario is encountered for another popular choice of differential calculus. |
2302.05125 | Roberto Dale | Roberto Dale, Ramon Lapiedra and Juan Antonio Morales-Lladosa | Cosmic primordial density fluctuations and Bell inequalities | 15 pages, 4 figures | Phys. Rev. D 107, 023506 (2023) | 10.1103/PhysRevD.107.023506 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The temperature measurements, $T$, of the perturbed cosmic microwave
background, performed by the cosmic background explorer satellite (COBE), are
considered. A dichotomist function, $f = \pm 1$, is defined such that $f =+1$
if $\delta T > 0$ and $f =-1$ if $\delta T < 0$, where $\delta T$ stands for
the fluctuation of $T$. Then, it is assumed that behind the appearance of these
fluctuations there is local realism. Under this assumption, some specific
Clauser-Horne-Shimony-Holt (CHSH) inequalities are proved for these fluctuation
temperatures measured by COBE in the different sky directions. The calculation
of these inequalities from the actual temperature measurements shows that these
inequalities are not violated. This result cannot be anticipated by calculating
the commutators of the cosmic density quantum operators. This must be remarked
here since, in the case of a system of two entangled spin ${\textstyle{1 \over
2}}$ particles, its CHSH inequalities violation can be inferred from the
nonvanishing value of the corresponding spin measurement commutators. The above
nonviolation of the observed cosmic CHSH inequalities is compatible with the
existence of local realism behind the cosmic measurement results. Nevertheless,
assuming again local realism, some new cosmic CHSH inequalities can be derived
for the case of the WMAP measurements whose accuracy is better than the one of
the above considered COBE measurements. More specifically, in the WMAP case,
some significant cross correlations between the temperature and polarization
maps are detected, and the new cosmic CHSH inequalities are the ones built with
these cross correlations. Now, the occasional violation of these CHSH
inequalities would mean the failure of the assumed local realism in accordance
with the quantum origin of the primordial temperature and polarization
fluctuations in the framework of standard inflation.
| [
{
"created": "Fri, 10 Feb 2023 09:14:21 GMT",
"version": "v1"
}
] | 2023-02-13 | [
[
"Dale",
"Roberto",
""
],
[
"Lapiedra",
"Ramon",
""
],
[
"Morales-Lladosa",
"Juan Antonio",
""
]
] | The temperature measurements, $T$, of the perturbed cosmic microwave background, performed by the cosmic background explorer satellite (COBE), are considered. A dichotomist function, $f = \pm 1$, is defined such that $f =+1$ if $\delta T > 0$ and $f =-1$ if $\delta T < 0$, where $\delta T$ stands for the fluctuation of $T$. Then, it is assumed that behind the appearance of these fluctuations there is local realism. Under this assumption, some specific Clauser-Horne-Shimony-Holt (CHSH) inequalities are proved for these fluctuation temperatures measured by COBE in the different sky directions. The calculation of these inequalities from the actual temperature measurements shows that these inequalities are not violated. This result cannot be anticipated by calculating the commutators of the cosmic density quantum operators. This must be remarked here since, in the case of a system of two entangled spin ${\textstyle{1 \over 2}}$ particles, its CHSH inequalities violation can be inferred from the nonvanishing value of the corresponding spin measurement commutators. The above nonviolation of the observed cosmic CHSH inequalities is compatible with the existence of local realism behind the cosmic measurement results. Nevertheless, assuming again local realism, some new cosmic CHSH inequalities can be derived for the case of the WMAP measurements whose accuracy is better than the one of the above considered COBE measurements. More specifically, in the WMAP case, some significant cross correlations between the temperature and polarization maps are detected, and the new cosmic CHSH inequalities are the ones built with these cross correlations. Now, the occasional violation of these CHSH inequalities would mean the failure of the assumed local realism in accordance with the quantum origin of the primordial temperature and polarization fluctuations in the framework of standard inflation. |
1603.06997 | Laszlo B. Szabados | L\'aszl\'o B Szabados | Gravity, as a classical regulator for the Higgs field, and the origin of
rest masses and electric charge | 46 pages; significantly rewritten, conclusions sharpened,
arXiv:1605.04811 (on example with the Kantowski--Sachs spacetimes) included,
typos corrected, three figures added; text slightly improved, references
updated. The short version (viz arXiv:1802.04401) appears in Gen.Rel.Grav | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The classical Einstein--Standard Model system with conformally invariant
coupling of the Higgs field to gravity is investigated. We show that the
energy-momentum tensor is not polynomial in the Higgs field, and hence it may
have two singularities: In cosmological spacetimes the usual Big Bang type
singularity with diverging matter field variables, and a second, less violent
one (Small Bang), in which it is only the geometry that is singular but the
matter field variables remain finite. In generic spacetimes, the latter
provides a finite, universal upper bound for the pointwise norm of the Higgs
field in terms of Newton's gravitational constant.
We also show that, in the presence of Friedman--Robertson--Walker or
Kantowski--Sachs symmetries, the energy density can have finite local minimum
only if the transitivity hypersurfaces of the spacetime symmetries are locally
hyperboloidal and their mean curvature is less than a finite critical value. In
particular, in the very early era of an expanding universe or in a nearly
spherically symmetric black hole near the central singularity, the Higgs sector
does not have any instantaneous vacuum state, and hence its rest mass is not
defined, and, via the Brout--Englert--Higgs (BEH) mechanism, the gauge and
spinor fields do not get non-zero rest mass. For smaller mean curvature
instantaneous symmetry breaking vacuum states of the Higgs sector emerge,
yielding non-zero rest mass and electric charge for some of the gauge and
spinor fields via the BEH mechanism. These rest masses are decreasing with
decreasing mean curvature, but the charge remains constant. It is also shown
that globally defined instantaneous vacuum states that are invariant with
respect to the spacetime symmetries do not exist at all in the $k=1,0$
cosmological models and in Kantowski--Sachs spacetimes (e.g. inside spherically
symmetric black holes).
| [
{
"created": "Tue, 22 Mar 2016 21:40:02 GMT",
"version": "v1"
},
{
"created": "Mon, 16 May 2016 15:36:42 GMT",
"version": "v2"
},
{
"created": "Mon, 29 May 2017 23:53:08 GMT",
"version": "v3"
},
{
"created": "Sat, 17 Feb 2018 23:14:33 GMT",
"version": "v4"
}
] | 2018-02-20 | [
[
"Szabados",
"László B",
""
]
] | The classical Einstein--Standard Model system with conformally invariant coupling of the Higgs field to gravity is investigated. We show that the energy-momentum tensor is not polynomial in the Higgs field, and hence it may have two singularities: In cosmological spacetimes the usual Big Bang type singularity with diverging matter field variables, and a second, less violent one (Small Bang), in which it is only the geometry that is singular but the matter field variables remain finite. In generic spacetimes, the latter provides a finite, universal upper bound for the pointwise norm of the Higgs field in terms of Newton's gravitational constant. We also show that, in the presence of Friedman--Robertson--Walker or Kantowski--Sachs symmetries, the energy density can have finite local minimum only if the transitivity hypersurfaces of the spacetime symmetries are locally hyperboloidal and their mean curvature is less than a finite critical value. In particular, in the very early era of an expanding universe or in a nearly spherically symmetric black hole near the central singularity, the Higgs sector does not have any instantaneous vacuum state, and hence its rest mass is not defined, and, via the Brout--Englert--Higgs (BEH) mechanism, the gauge and spinor fields do not get non-zero rest mass. For smaller mean curvature instantaneous symmetry breaking vacuum states of the Higgs sector emerge, yielding non-zero rest mass and electric charge for some of the gauge and spinor fields via the BEH mechanism. These rest masses are decreasing with decreasing mean curvature, but the charge remains constant. It is also shown that globally defined instantaneous vacuum states that are invariant with respect to the spacetime symmetries do not exist at all in the $k=1,0$ cosmological models and in Kantowski--Sachs spacetimes (e.g. inside spherically symmetric black holes). |
2305.12323 | Cheng Liu | Cheng Liu, Haiguang Xu, Hoongwah Siew, Tao Zhu, Qiang Wu, Yuanyuan
Zhao | Constraints on the rotating self-dual black hole with quasi-periodic
oscillations | null | null | 10.1088/1475-7516/2023/11/096 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An impressive feature of loop quantum gravity (LQG) is that it can elegantly
resolve both the big bang and black hole singularities. By using the
Newman-Janis algorithm, a regular and effective rotating self-dual black
hole(SDBH) metric could be constructed, which alters the Kerr geometry with a
polymeric function $P$ from the quantum effects of LQG geometry. In this paper,
we investigate its impact on the frequency characteristics of the X-ray
quasi-periodic oscillations(QPOs) from 5 X-ray binaries and contrast it with
the existing results of the orbital, periastron precession and nodal precession
frequencies within the relativistic precession model. We apply a Monte Carlo
Markov Chain (MCMC) simulation to examine the possible LQG effects on the X-ray
QPOs. We found that the best constraint result for the rotating self-dual
geometry from LQG came from the QPOs of X-ray binary GRO J1655-40, which
establish an upper bound on the polymeric function $P$ less than $6.17\times
10^{-3}$ at 95\% confidence level. This bound leads to a restriction on the
polymeric parameter $\delta$ of LQG to be 0.67.
| [
{
"created": "Sun, 21 May 2023 03:03:32 GMT",
"version": "v1"
},
{
"created": "Tue, 23 May 2023 14:46:47 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Jul 2023 08:49:20 GMT",
"version": "v3"
}
] | 2024-06-03 | [
[
"Liu",
"Cheng",
""
],
[
"Xu",
"Haiguang",
""
],
[
"Siew",
"Hoongwah",
""
],
[
"Zhu",
"Tao",
""
],
[
"Wu",
"Qiang",
""
],
[
"Zhao",
"Yuanyuan",
""
]
] | An impressive feature of loop quantum gravity (LQG) is that it can elegantly resolve both the big bang and black hole singularities. By using the Newman-Janis algorithm, a regular and effective rotating self-dual black hole(SDBH) metric could be constructed, which alters the Kerr geometry with a polymeric function $P$ from the quantum effects of LQG geometry. In this paper, we investigate its impact on the frequency characteristics of the X-ray quasi-periodic oscillations(QPOs) from 5 X-ray binaries and contrast it with the existing results of the orbital, periastron precession and nodal precession frequencies within the relativistic precession model. We apply a Monte Carlo Markov Chain (MCMC) simulation to examine the possible LQG effects on the X-ray QPOs. We found that the best constraint result for the rotating self-dual geometry from LQG came from the QPOs of X-ray binary GRO J1655-40, which establish an upper bound on the polymeric function $P$ less than $6.17\times 10^{-3}$ at 95\% confidence level. This bound leads to a restriction on the polymeric parameter $\delta$ of LQG to be 0.67. |
1401.4846 | Donato Bini | Donato Bini, Andrea Geralico, Daniele Gregoris, Sauro Succi | Scalar field inflation and Shan-Chen fluid models | 9 pages, 5 figures; published version. The title has been changed. A
new section (Section III A) has been added describing the main features of
the Shan-Chen equation of state in the original context wherein it has been
introduced. The stability issue of the model is also discussed in the
Appendix | Phys. Rev. D 90, 044021 (2014) | 10.1103/PhysRevD.90.044021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A scalar field equivalent to a non-ideal "dark energy fluid" obeying a
Shan-Chen-like equation of state is used as the background source of a flat
Friedmann-Robertson-Walker cosmological spacetime to describe the inflationary
epoch of our universe. Within the slow-roll approximation, a number of
interesting features are presented, including the possibility to fulfill
current observational constraints as well as a graceful exit mechanism from the
inflationary epoch.
| [
{
"created": "Mon, 20 Jan 2014 09:59:26 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Aug 2014 10:08:31 GMT",
"version": "v2"
}
] | 2015-06-18 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
],
[
"Gregoris",
"Daniele",
""
],
[
"Succi",
"Sauro",
""
]
] | A scalar field equivalent to a non-ideal "dark energy fluid" obeying a Shan-Chen-like equation of state is used as the background source of a flat Friedmann-Robertson-Walker cosmological spacetime to describe the inflationary epoch of our universe. Within the slow-roll approximation, a number of interesting features are presented, including the possibility to fulfill current observational constraints as well as a graceful exit mechanism from the inflationary epoch. |
1910.01929 | Xiaoning Wu | Xiaoning Wu and Lin Zhang | The Null-Timelike Boundary Problems of Linear Wave Equations in
Asymptotically Anti-de Sitter Space | 18 pages, 2 figures. arXiv admin note: text overlap with
arXiv:1801.02795 | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the linear wave equations in an asymptotically
anti-de Sitter spacetime. We will consider the mixed boundary problem, where
the initial data are given on an outgoing null hypersurface and a timelike
hypersurface, and the asymptotic information is given on conformal infinity.
| [
{
"created": "Thu, 3 Oct 2019 14:49:32 GMT",
"version": "v1"
}
] | 2019-10-07 | [
[
"Wu",
"Xiaoning",
""
],
[
"Zhang",
"Lin",
""
]
] | In this paper, we study the linear wave equations in an asymptotically anti-de Sitter spacetime. We will consider the mixed boundary problem, where the initial data are given on an outgoing null hypersurface and a timelike hypersurface, and the asymptotic information is given on conformal infinity. |
2110.10243 | Richard Udall | Richard Udall, Joshua Brandt, Grihith Manchanda, Adhav Arulanandan,
James Clark, Jacob Lange, Richard O'Shaughnessy, Laura Cadonati | RUNMON-RIFT: Adaptive Configuration and Healing for Large-Scale
Parameter Inference | 9 pages, 2 figures | null | null | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave parameter inference pipelines operate on data containing
unknown sources on distributed hardware with unreliable performance. For one
specific analysis pipeline (RIFT), we have developed a flexible tool
(RUNMON-RIFT) to mitigate the most common challenges introduced by these two
uncertainties. On the one hand, RUNMON provides several mechanisms to identify
and redress unreliable computing environments. On the other hand, RUNMON
provides mechanisms to adjust pipeline-specific run settings, including prior
ranges, to ensure the analysis completes and encompasses the physical source
parameters. We demonstrate both general features with two controlled examples.
| [
{
"created": "Tue, 19 Oct 2021 20:29:10 GMT",
"version": "v1"
}
] | 2021-10-22 | [
[
"Udall",
"Richard",
""
],
[
"Brandt",
"Joshua",
""
],
[
"Manchanda",
"Grihith",
""
],
[
"Arulanandan",
"Adhav",
""
],
[
"Clark",
"James",
""
],
[
"Lange",
"Jacob",
""
],
[
"O'Shaughnessy",
"Richard",
""
]... | Gravitational wave parameter inference pipelines operate on data containing unknown sources on distributed hardware with unreliable performance. For one specific analysis pipeline (RIFT), we have developed a flexible tool (RUNMON-RIFT) to mitigate the most common challenges introduced by these two uncertainties. On the one hand, RUNMON provides several mechanisms to identify and redress unreliable computing environments. On the other hand, RUNMON provides mechanisms to adjust pipeline-specific run settings, including prior ranges, to ensure the analysis completes and encompasses the physical source parameters. We demonstrate both general features with two controlled examples. |
gr-qc/0602095 | Lorenzo Iorio | Lorenzo Iorio | Solar System planetary orbital motions and dark matter | Latex, 8 pages, 2 tables, no figures, 8 references. Revised version
with improved analysis | JCAP 0605 (2006) 002 | 10.1088/1475-7516/2006/05/002 | null | gr-qc astro-ph hep-ph | null | In this paper we explicitly work out the effects that a spherically symmetric
distribution of dark matter with constant density would induce on the Keplerian
orbital elements of the Solar System planets and compare them with the latest
results in planetary orbit determination from the EPM2004 ephemerides. It turns
out that the longitudes of perihelia and the mean longitudes are affected by
secular precessions. The resulting upper bounds on dark matter density,
obtained from the EPM2004 formal errors in the determined mean longitude shifts
over 90 years, lie in the range 10^-19-10^-20 g cm^-3 with a peak of 10^-22 g
cm^-3 for Mars. Suitable combinations of the planetary mean longitudes and
perihelia, which cancel out the aliasing impact of some of the unmodelled or
mismodelled forces of the dynamical models of EPM2004, yield a global upper
bound of 7 10^-20 g cm^-3 and 4 10^-19 g cm^-3, respectively.
| [
{
"created": "Thu, 23 Feb 2006 15:28:02 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Mar 2006 12:50:01 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Iorio",
"Lorenzo",
""
]
] | In this paper we explicitly work out the effects that a spherically symmetric distribution of dark matter with constant density would induce on the Keplerian orbital elements of the Solar System planets and compare them with the latest results in planetary orbit determination from the EPM2004 ephemerides. It turns out that the longitudes of perihelia and the mean longitudes are affected by secular precessions. The resulting upper bounds on dark matter density, obtained from the EPM2004 formal errors in the determined mean longitude shifts over 90 years, lie in the range 10^-19-10^-20 g cm^-3 with a peak of 10^-22 g cm^-3 for Mars. Suitable combinations of the planetary mean longitudes and perihelia, which cancel out the aliasing impact of some of the unmodelled or mismodelled forces of the dynamical models of EPM2004, yield a global upper bound of 7 10^-20 g cm^-3 and 4 10^-19 g cm^-3, respectively. |
2201.00671 | Gustavo Dotti | B\'eatrice Bonga and Gustavo Dotti | Parallel waves in Einstein-non linear sigma models | Final version, to appear in PRD | null | 10.1103/PhysRevD.105.044049 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a family of solutions of Einstein-non linear sigma models with $S^2$
and $SU(2) \sim S^3$ target manifolds. In the $S^2$ case, the solutions are
smooth everywhere, free of conical singularities, and approach asymptotically
the metric of a cosmic string, with a mass per length that is proportional to
the absolute value of the winding number from topological spheres onto the
target $S^2$. This gives an interesting example of a relation between a mass
and a topological charge. The case with target $SU(2)$ generalizes the
stationary solution found in Eur. Phys. J. C (2021) 81:55 to parallel waves
with a non-planar wavefront $\mathcal{W}$. We prove that these
$\mathcal{W}$-fronted parallel waves are sub-quadratic in the classification in
Class. Quant. Grav. \textbf{20} (2003) 2275, and thus causally well behaved.
These spacetimes have a non-vanishing baryon current and their geometry has
many striking features.
| [
{
"created": "Mon, 3 Jan 2022 14:23:46 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Feb 2022 09:20:57 GMT",
"version": "v2"
}
] | 2022-03-09 | [
[
"Bonga",
"Béatrice",
""
],
[
"Dotti",
"Gustavo",
""
]
] | We study a family of solutions of Einstein-non linear sigma models with $S^2$ and $SU(2) \sim S^3$ target manifolds. In the $S^2$ case, the solutions are smooth everywhere, free of conical singularities, and approach asymptotically the metric of a cosmic string, with a mass per length that is proportional to the absolute value of the winding number from topological spheres onto the target $S^2$. This gives an interesting example of a relation between a mass and a topological charge. The case with target $SU(2)$ generalizes the stationary solution found in Eur. Phys. J. C (2021) 81:55 to parallel waves with a non-planar wavefront $\mathcal{W}$. We prove that these $\mathcal{W}$-fronted parallel waves are sub-quadratic in the classification in Class. Quant. Grav. \textbf{20} (2003) 2275, and thus causally well behaved. These spacetimes have a non-vanishing baryon current and their geometry has many striking features. |
0909.0316 | Piotr Bizon | Piotr Bizo\'n, Tadeusz Chmaj, and Andrzej Rostworowski | Reply to the comment by Szpak on leading order asymptotics of late-time
tails for a self-gravitating massless scalar field | 1 page | Class.Quant.Grav.26:248002,2009 | 10.1088/0264-9381/26/24/248002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We respond to N. Szpak's comment [arXiv:0907.5146v2] on our paper "Late-time
tails of a self-gravitating massless scalar field, revisited", Class. Quantum
Grav. 26, 175006 (2009). [arXiv:0812.4333]
| [
{
"created": "Wed, 2 Sep 2009 04:50:55 GMT",
"version": "v1"
}
] | 2010-03-25 | [
[
"Bizoń",
"Piotr",
""
],
[
"Chmaj",
"Tadeusz",
""
],
[
"Rostworowski",
"Andrzej",
""
]
] | We respond to N. Szpak's comment [arXiv:0907.5146v2] on our paper "Late-time tails of a self-gravitating massless scalar field, revisited", Class. Quantum Grav. 26, 175006 (2009). [arXiv:0812.4333] |
2305.04551 | Gang Wang | Rong-Gen Cai, Zong-Kuan Guo, Bin Hu, Chang Liu, Youjun Lu, Wei-Tou Ni,
Wen-Hong Ruan, Naoki Seto, Gang Wang, Yue-Liang Wu | On networks of space-based gravitational-wave detectors | 32 pages, 14 figures, reviews on recent studies about space-borne GW
networks, comments and feedbacks are welcome | null | null | null | gr-qc astro-ph.CO astro-ph.GA astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The space-based laser interferometers, LISA, Taiji and TianQin, are targeting
to observe milliHz gravitational waves (GWs) in the 2030s. The joint
observations from multiple space-based detectors yield significant advantages.
In this work, we recap the studies and investigations for the joint space-based
GW detector networks to highlight: 1) the high precision of sky localization
for the massive binary black hole (BBH) coalescences and the GW sirens in the
cosmological implication, 2) the effectiveness to test the parity violation in
the stochastic GW background observations, 3) the efficiency of subtracting
galactic foreground, 4) the improvement in stellar-mass BBH observations. We
inspect alternative networks by trading off massive BBH observations and
stochastic GW background observation.
| [
{
"created": "Mon, 8 May 2023 08:46:53 GMT",
"version": "v1"
},
{
"created": "Mon, 22 May 2023 09:22:29 GMT",
"version": "v2"
}
] | 2023-05-23 | [
[
"Cai",
"Rong-Gen",
""
],
[
"Guo",
"Zong-Kuan",
""
],
[
"Hu",
"Bin",
""
],
[
"Liu",
"Chang",
""
],
[
"Lu",
"Youjun",
""
],
[
"Ni",
"Wei-Tou",
""
],
[
"Ruan",
"Wen-Hong",
""
],
[
"Seto",
"Naoki",
... | The space-based laser interferometers, LISA, Taiji and TianQin, are targeting to observe milliHz gravitational waves (GWs) in the 2030s. The joint observations from multiple space-based detectors yield significant advantages. In this work, we recap the studies and investigations for the joint space-based GW detector networks to highlight: 1) the high precision of sky localization for the massive binary black hole (BBH) coalescences and the GW sirens in the cosmological implication, 2) the effectiveness to test the parity violation in the stochastic GW background observations, 3) the efficiency of subtracting galactic foreground, 4) the improvement in stellar-mass BBH observations. We inspect alternative networks by trading off massive BBH observations and stochastic GW background observation. |
1608.08684 | Markus P. Mueller | Markus P. Mueller, Sylvain Carrozza, Philipp A Hoehn | Is the local linearity of space-time inherited from the linearity of
probabilities? | 16 pages, 2 figures. Invited contribution to JPA's special issue
"emerging talents". v2: close to published version | J. Phys. A: Math. Theor. 50, 054003 (2017) | 10.1088/1751-8121/aa523b | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The appearance of linear spaces, describing physical quantities by vectors
and tensors, is ubiquitous in all of physics, from classical mechanics to the
modern notion of local Lorentz invariance. However, as natural as this seems to
the physicist, most computer scientists would argue that something like a
"local linear tangent space" is not very typical and in fact a quite surprising
property of any conceivable world or algorithm. In this paper, we take the
perspective of the computer scientist seriously, and ask whether there could be
any inherently information-theoretic reason to expect this notion of linearity
to appear in physics. We give a series of simple arguments, spanning quantum
information theory, group representation theory, and renormalization in quantum
gravity, that supports a surprising thesis: namely, that the local linearity of
space-time might ultimately be a consequence of the linearity of probabilities.
While our arguments involve a fair amount of speculation, they have the virtue
of being independent of any detailed assumptions on quantum gravity, and they
are in harmony with several independent recent ideas on emergent space-time in
high-energy physics.
| [
{
"created": "Tue, 30 Aug 2016 23:02:00 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Jan 2017 13:28:38 GMT",
"version": "v2"
}
] | 2017-02-01 | [
[
"Mueller",
"Markus P.",
""
],
[
"Carrozza",
"Sylvain",
""
],
[
"Hoehn",
"Philipp A",
""
]
] | The appearance of linear spaces, describing physical quantities by vectors and tensors, is ubiquitous in all of physics, from classical mechanics to the modern notion of local Lorentz invariance. However, as natural as this seems to the physicist, most computer scientists would argue that something like a "local linear tangent space" is not very typical and in fact a quite surprising property of any conceivable world or algorithm. In this paper, we take the perspective of the computer scientist seriously, and ask whether there could be any inherently information-theoretic reason to expect this notion of linearity to appear in physics. We give a series of simple arguments, spanning quantum information theory, group representation theory, and renormalization in quantum gravity, that supports a surprising thesis: namely, that the local linearity of space-time might ultimately be a consequence of the linearity of probabilities. While our arguments involve a fair amount of speculation, they have the virtue of being independent of any detailed assumptions on quantum gravity, and they are in harmony with several independent recent ideas on emergent space-time in high-energy physics. |
2305.10939 | Helmut Friedrich | Helmut Friedrich | Cosmological Einstein-Lambda-perfect-fluid solutions with asymptotic
dust or radiation equation of state | 19 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This article introduces the notions of asymptotic dust and asymptotic
radiation equations of state. With these non-linear generalizations of the well
known dust or (incoherent) radiation equations of state the perfect-fluid
equations loose any conformal covariance or privilege. We analyse the conformal
field equations induced with these equations of state. It is shown that the
Einstein-Lambda-perfect-fluid equations with an asymptotic radiation equation
of state allow for large sets of data that develop into solutions which admit
smooth conformal boundaries in the future and smooth extensions beyond.
| [
{
"created": "Thu, 18 May 2023 12:57:52 GMT",
"version": "v1"
}
] | 2023-05-19 | [
[
"Friedrich",
"Helmut",
""
]
] | This article introduces the notions of asymptotic dust and asymptotic radiation equations of state. With these non-linear generalizations of the well known dust or (incoherent) radiation equations of state the perfect-fluid equations loose any conformal covariance or privilege. We analyse the conformal field equations induced with these equations of state. It is shown that the Einstein-Lambda-perfect-fluid equations with an asymptotic radiation equation of state allow for large sets of data that develop into solutions which admit smooth conformal boundaries in the future and smooth extensions beyond. |
1111.5378 | Alexandre Le Tiec | Alexandre Le Tiec, Luc Blanchet, Bernard F. Whiting | The First Law of Binary Black Hole Mechanics in General Relativity and
Post-Newtonian Theory | 43 pages, 3 figures; matches the published version | Phys.Rev.D85:064039,2012 | 10.1103/PhysRevD.85.064039 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | First laws of black hole mechanics, or thermodynamics, come in a variety of
different forms. In this paper, from a purely post-Newtonian (PN) analysis, we
obtain a first law for binary systems of point masses moving along an exactly
circular orbit. Our calculation is valid through 3PN order and includes, in
addition, the contributions of logarithmic terms at 4PN and 5PN orders. This
first law of binary point-particle mechanics is then derived from first
principles in general relativity, and analogies are drawn with the single and
binary black hole cases. Some consequences of the first law are explored for PN
spacetimes. As one such consequence, a simple relation between the PN binding
energy of the binary system and Detweiler's redshift observable is established.
Through it, we are able to determine with high precision the numerical values
of some previously unknown high order PN coefficients in the circular-orbit
binding energy. Finally, we propose new gauge invariant notions for the energy
and angular momentum of a particle in a binary system.
| [
{
"created": "Wed, 23 Nov 2011 00:40:24 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Apr 2012 18:26:08 GMT",
"version": "v2"
}
] | 2013-08-26 | [
[
"Tiec",
"Alexandre Le",
""
],
[
"Blanchet",
"Luc",
""
],
[
"Whiting",
"Bernard F.",
""
]
] | First laws of black hole mechanics, or thermodynamics, come in a variety of different forms. In this paper, from a purely post-Newtonian (PN) analysis, we obtain a first law for binary systems of point masses moving along an exactly circular orbit. Our calculation is valid through 3PN order and includes, in addition, the contributions of logarithmic terms at 4PN and 5PN orders. This first law of binary point-particle mechanics is then derived from first principles in general relativity, and analogies are drawn with the single and binary black hole cases. Some consequences of the first law are explored for PN spacetimes. As one such consequence, a simple relation between the PN binding energy of the binary system and Detweiler's redshift observable is established. Through it, we are able to determine with high precision the numerical values of some previously unknown high order PN coefficients in the circular-orbit binding energy. Finally, we propose new gauge invariant notions for the energy and angular momentum of a particle in a binary system. |
1509.07767 | Igor Pikovski | Igor Pikovski, Magdalena Zych, Fabio Costa, \v{C}aslav Brukner | Brief reply to "Can gravity account for the emergence of classicality?" | 1 page | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a series of comments, Bonder et al. criticized our work on decoherence due
to time dilation [Nature Physics 11, 668-672 (2015)]. First the authors
erroneously claimed that our results contradict the equivalence principle, only
to "resolve" the alleged conflict in a second note. The resolution - relativity
of simultaneity - was already explained in our reply [arXiv:1508.03296], which
Bonder et al. now essentially reiterate. The newly raised points were also
already extensively clarified in our note. The physical prediction of our work
remains valid: systems with internal dynamics decohere if the superposed paths
have different proper times.
| [
{
"created": "Thu, 24 Sep 2015 15:29:59 GMT",
"version": "v1"
}
] | 2015-09-28 | [
[
"Pikovski",
"Igor",
""
],
[
"Zych",
"Magdalena",
""
],
[
"Costa",
"Fabio",
""
],
[
"Brukner",
"Časlav",
""
]
] | In a series of comments, Bonder et al. criticized our work on decoherence due to time dilation [Nature Physics 11, 668-672 (2015)]. First the authors erroneously claimed that our results contradict the equivalence principle, only to "resolve" the alleged conflict in a second note. The resolution - relativity of simultaneity - was already explained in our reply [arXiv:1508.03296], which Bonder et al. now essentially reiterate. The newly raised points were also already extensively clarified in our note. The physical prediction of our work remains valid: systems with internal dynamics decohere if the superposed paths have different proper times. |
2302.14722 | Haroldo Cilas Duarte Lima Junior | Zeus S. Moreira, Haroldo C. D. Lima Junior, Lu\'is C. B. Crispino and
Carlos A. R. Herdeiro | Quasinormal modes of a holonomy corrected Schwarzschild black hole | 12 pages, 7 figures | null | 10.1103/PhysRevD.107.104016 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We analyze the quasinormal modes (QNMs) of a recently obtained solution of a
Schwarzschild black hole (BH) with corrections motivated by Loop Quantum
Gravity (LQG). This spacetime is regular everywhere and presents the global
structure of a wormhole, with a minimal surface whose radius depends on a LQG
parameter. We focus on the investigation of massless scalar field perturbations
over the spacetime. We compute the QNMs with the WKB approximation, as well as
the continued fraction method. The QNM frequency orbits, for $l=0$ and $n>0$,
where $l$ and $n$ are the multipole and overtone numbers, respectively, are
self-intersecting, spiraling curves in the complex plane. These orbits
accumulate to a fixed complex value corresponding to the QNMs of the extremal
case. We obtain that, for small values of the LQG parameter, the overall
damping decreases as we increase the LQG parameter. Moreover the spectrum of
the quantum corrected black hole exhibits an oscillatory pattern, which might
imply in the existence of QNMs with vanishing real part. This pattern suggests
that the limit $n\rightarrow \infty$ for the real part of the QNMs is not
well-defined, what differs from Schwarzschild's case. We also analyze the
time-domain profiles for the scalar perturbations, showing that the LQG
correction does not alter the Schwarzschild power-law tail. We compute the
fundamental mode from the time profile by means of the Prony method, obtaining
excellent agreement with the two previously mentioned methods.
| [
{
"created": "Tue, 28 Feb 2023 16:32:32 GMT",
"version": "v1"
}
] | 2023-05-17 | [
[
"Moreira",
"Zeus S.",
""
],
[
"Junior",
"Haroldo C. D. Lima",
""
],
[
"Crispino",
"Luís C. B.",
""
],
[
"Herdeiro",
"Carlos A. R.",
""
]
] | We analyze the quasinormal modes (QNMs) of a recently obtained solution of a Schwarzschild black hole (BH) with corrections motivated by Loop Quantum Gravity (LQG). This spacetime is regular everywhere and presents the global structure of a wormhole, with a minimal surface whose radius depends on a LQG parameter. We focus on the investigation of massless scalar field perturbations over the spacetime. We compute the QNMs with the WKB approximation, as well as the continued fraction method. The QNM frequency orbits, for $l=0$ and $n>0$, where $l$ and $n$ are the multipole and overtone numbers, respectively, are self-intersecting, spiraling curves in the complex plane. These orbits accumulate to a fixed complex value corresponding to the QNMs of the extremal case. We obtain that, for small values of the LQG parameter, the overall damping decreases as we increase the LQG parameter. Moreover the spectrum of the quantum corrected black hole exhibits an oscillatory pattern, which might imply in the existence of QNMs with vanishing real part. This pattern suggests that the limit $n\rightarrow \infty$ for the real part of the QNMs is not well-defined, what differs from Schwarzschild's case. We also analyze the time-domain profiles for the scalar perturbations, showing that the LQG correction does not alter the Schwarzschild power-law tail. We compute the fundamental mode from the time profile by means of the Prony method, obtaining excellent agreement with the two previously mentioned methods. |
gr-qc/9508023 | James B. Hartle | James B. Hartle (University of California, Santa Barbara) | Quantum Mechanics at the Planck Scale | 17pages, macros included in tex file | null | null | UCSBTH-95-4 | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Usual quantum mechanics requires a fixed, background, spacetime geometry and
its associated causal structure. A generalization of the usual theory may
therefore be needed at the Planck scale for quantum theories of gravity in
which spacetime geometry is a quantum variable. The elements of generalized
quantum theory are briefly reviewed and illustrated by generalizations of usual
quantum theory that incorporate spacetime alternatives, gauge degrees of
freedom, and histories that move forward and backward in time. A generalized
quantum framework for cosmological spacetime geometry is sketched. This theory
is in fully four-dimensional form and free from the need for a fixed causal
structure. Usual quantum mechanics is recovered as an approximation to this
more general framework that is appropriate in those situations where spacetime
geometry behaves classically.
(Talk given at the Workshop on Physics at the Planck Scale, Puri, India,
December12-21, 1994. This talk is a precis of the author's 1992 Les Houches
Lectures: Spacetime Quantum Mechanics and the Quantum Mechanics of Spacetime,
gr-qc/9304006).
| [
{
"created": "Tue, 8 Aug 1995 21:04:11 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Dec 2013 04:24:44 GMT",
"version": "v2"
}
] | 2013-12-05 | [
[
"Hartle",
"James B.",
"",
"University of California, Santa Barbara"
]
] | Usual quantum mechanics requires a fixed, background, spacetime geometry and its associated causal structure. A generalization of the usual theory may therefore be needed at the Planck scale for quantum theories of gravity in which spacetime geometry is a quantum variable. The elements of generalized quantum theory are briefly reviewed and illustrated by generalizations of usual quantum theory that incorporate spacetime alternatives, gauge degrees of freedom, and histories that move forward and backward in time. A generalized quantum framework for cosmological spacetime geometry is sketched. This theory is in fully four-dimensional form and free from the need for a fixed causal structure. Usual quantum mechanics is recovered as an approximation to this more general framework that is appropriate in those situations where spacetime geometry behaves classically. (Talk given at the Workshop on Physics at the Planck Scale, Puri, India, December12-21, 1994. This talk is a precis of the author's 1992 Les Houches Lectures: Spacetime Quantum Mechanics and the Quantum Mechanics of Spacetime, gr-qc/9304006). |
1003.2373 | Alan Coley | Alan Coley, Sigbjorn Hervik, and Nicos Pelavas | Lorentzian manifolds and scalar curvature invariants | submitted to CQG | Class.Quant.Grav.27:102001,2010 | 10.1088/0264-9381/27/10/102001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss (arbitrary-dimensional) Lorentzian manifolds and the scalar
polynomial curvature invariants constructed from the Riemann tensor and its
covariant derivatives. Recently, we have shown that in four dimensions a
Lorentzian spacetime metric is either $\mathcal{I}$-non-degenerate, and hence
locally characterized by its scalar polynomial curvature invariants, or is a
degenerate Kundt spacetime. We present a number of results that generalize
these results to higher dimensions and discuss their consequences and potential
physical applications.
| [
{
"created": "Thu, 11 Mar 2010 17:50:54 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Coley",
"Alan",
""
],
[
"Hervik",
"Sigbjorn",
""
],
[
"Pelavas",
"Nicos",
""
]
] | We discuss (arbitrary-dimensional) Lorentzian manifolds and the scalar polynomial curvature invariants constructed from the Riemann tensor and its covariant derivatives. Recently, we have shown that in four dimensions a Lorentzian spacetime metric is either $\mathcal{I}$-non-degenerate, and hence locally characterized by its scalar polynomial curvature invariants, or is a degenerate Kundt spacetime. We present a number of results that generalize these results to higher dimensions and discuss their consequences and potential physical applications. |
1407.3577 | Rituparno Goswami | George F R Ellis, Rituparno Goswami, Aymen I. M. Hamid and Sunil D.
Maharaj | Astrophysical Black Hole horizons in a cosmological context: Nature and
possible consequences on Hawking Radiation | 14 pages, 4 figures, Minor corrections in the text, Matches the
accepted version in Physical Review D | Phys. Rev. D 90, 084013, 2014 | 10.1103/PhysRevD.90.084013 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper considers the nature of apparent horizons for astrophysical black
hole situated in a realistic cosmological context. Using semi-tetrad covariant
methods we study the local evolutions of the boundaries of the trapped region
in the spacetime. For a collapsing massive star immersed in a cosmology with
Cosmic Background Radiation (CBR), we show that the initial 2 dimensional
marginally trapped surface bifurcates into inner and outer horizons. The inner
horizon is timelike while the continuous CBR influx into the black hole makes
the outer horizon spacelike. We discuss the possible consequences of these
features for Hawking radiation in realistic astrophysical contexts.
| [
{
"created": "Mon, 14 Jul 2014 09:35:29 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Jul 2014 13:05:30 GMT",
"version": "v2"
},
{
"created": "Mon, 29 Sep 2014 14:16:34 GMT",
"version": "v3"
}
] | 2014-11-14 | [
[
"Ellis",
"George F R",
""
],
[
"Goswami",
"Rituparno",
""
],
[
"Hamid",
"Aymen I. M.",
""
],
[
"Maharaj",
"Sunil D.",
""
]
] | This paper considers the nature of apparent horizons for astrophysical black hole situated in a realistic cosmological context. Using semi-tetrad covariant methods we study the local evolutions of the boundaries of the trapped region in the spacetime. For a collapsing massive star immersed in a cosmology with Cosmic Background Radiation (CBR), we show that the initial 2 dimensional marginally trapped surface bifurcates into inner and outer horizons. The inner horizon is timelike while the continuous CBR influx into the black hole makes the outer horizon spacelike. We discuss the possible consequences of these features for Hawking radiation in realistic astrophysical contexts. |
gr-qc/0403103 | Chiang-Mei Chen | James M. Nester, Feng-Feng Meng and Chiang-Mei Chen | Quasilocal Center-of-Mass | 4 pages, contribution to the 6th International Conference of
Gravitation and Astrophysics, Seoul, 2003 (revised version) | J.Korean Phys.Soc. 45 (2004) S22-S25 | null | null | gr-qc | null | Gravitating systems have no well-defined local energy-momentum density.
Various quasilocal proposals have been made, however the center-of-mass moment
(COM) has generally been overlooked. Asymptotically flat graviating systems
have 10 total conserved quantities associated with the Poincar{\'e} symmetry at
infinity. In addition to energy-momentum and angular momentum (associated with
translations and rotations) there is the boost quantity: the COM. A complete
quasilocal formulation should include this quantity. Getting good values for
the COM is a fairly strict requirement, imposing the most restrictive fall off
conditions on the variables. We take a covariant Hamiltonian approach,
associating Hamiltonian boundary terms with quasilocal quantities and boundary
conditions. Unlike several others, our {\it covariant symplectic} quasilocal
expressions do have the proper asymptotic form for all 10 quantities.
| [
{
"created": "Thu, 25 Mar 2004 10:33:44 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Apr 2004 10:17:03 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Nester",
"James M.",
""
],
[
"Meng",
"Feng-Feng",
""
],
[
"Chen",
"Chiang-Mei",
""
]
] | Gravitating systems have no well-defined local energy-momentum density. Various quasilocal proposals have been made, however the center-of-mass moment (COM) has generally been overlooked. Asymptotically flat graviating systems have 10 total conserved quantities associated with the Poincar{\'e} symmetry at infinity. In addition to energy-momentum and angular momentum (associated with translations and rotations) there is the boost quantity: the COM. A complete quasilocal formulation should include this quantity. Getting good values for the COM is a fairly strict requirement, imposing the most restrictive fall off conditions on the variables. We take a covariant Hamiltonian approach, associating Hamiltonian boundary terms with quasilocal quantities and boundary conditions. Unlike several others, our {\it covariant symplectic} quasilocal expressions do have the proper asymptotic form for all 10 quantities. |
2304.14771 | Vahideh Memari Rishakani | M.Halilsoy and V.Memari | Generating spacetimes from colliding sources | 9 pages no figures | J. Math. Phys. 65, 022501 (2024) | 10.1063/5.0156292 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Certain well-known spacetimes of general relativity (GR) are generated from
the collision of suitable null-sources coupled with gravitational waves. This
is a classical process underlying the full nonlinearity of GR that may be
considered alternative to the quantum creativity at a large scale.
Schwarzschild, de Sitter, anti de Sitter and the $\gamma $-metrics are given as
examples.
| [
{
"created": "Fri, 28 Apr 2023 11:32:46 GMT",
"version": "v1"
}
] | 2024-02-08 | [
[
"Halilsoy",
"M.",
""
],
[
"Memari",
"V.",
""
]
] | Certain well-known spacetimes of general relativity (GR) are generated from the collision of suitable null-sources coupled with gravitational waves. This is a classical process underlying the full nonlinearity of GR that may be considered alternative to the quantum creativity at a large scale. Schwarzschild, de Sitter, anti de Sitter and the $\gamma $-metrics are given as examples. |
1807.06261 | Claus Kiefer | Claus Kiefer, Nick Kwidzinski, W{\l}odzimierz Piechocki | On the dynamics of the general Bianchi IX spacetime near the singularity | 20 pages, 5 figures, minor changes | Eur. Phys. J. C (2018) 78:691 | 10.1140/epjc/s10052-018-6155-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the complex dynamics of the general Bianchi IX universe in the
vicinity of the spacelike singularity can be approximated by a simplified
system of equations. Our analysis is mainly based on numerical simulations. The
properties of the solution space can be studied by using this simplified
dynamics. Our results will be useful for the quantization of the general
Bianchi IX model.
| [
{
"created": "Tue, 17 Jul 2018 07:28:15 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Sep 2018 10:09:49 GMT",
"version": "v2"
}
] | 2018-09-06 | [
[
"Kiefer",
"Claus",
""
],
[
"Kwidzinski",
"Nick",
""
],
[
"Piechocki",
"Włodzimierz",
""
]
] | We show that the complex dynamics of the general Bianchi IX universe in the vicinity of the spacelike singularity can be approximated by a simplified system of equations. Our analysis is mainly based on numerical simulations. The properties of the solution space can be studied by using this simplified dynamics. Our results will be useful for the quantization of the general Bianchi IX model. |
1309.4368 | Andrzej Krasi\'nski | Andrzej Krasi\'nski | Accelerating expansion or inhomogeneity? A comparison of the
$\Lambda$CDM and Lema\^{\i}tre - Tolman models | LaTex, 21 pages, 17 figures. Includes small corrections suggested by
the referee. This version matches the published text, except for the caption
to Fig. 7, which is corrected here | Phys. Rev. D 89, 023520 (2014) | 10.1103/PhysRevD.89.023520 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown how certain observations interpreted in the background of the
Friedmann model with $\Lambda < 0 = k$ (the $\Lambda$CDM model) can be
re-interpreted using the $\Lambda = 0$ Lema\^{\i}tre - Tolman (L-T) model so as
to do away with the "dark energy". The purpose of the paper is to clarify the
underlying geometrical relations by doing the calculations as much as possible
analytically or by very simple numerical programs. In the first part of the
paper (fictitious) observations of the distribution of expansion velocity along
the past light cone of the observer are considered. It is shown that the whole
past light cone of the $\Lambda$CDM observer can be reproduced in the L-T model
with $\Lambda = 0 = E$. This is a geometric exercise that has the advantage of
being free of numerical complications. In the second part, the luminosity
distance - redshift relation of the $\Lambda$CDM model is duplicated using the
L-T model with $-k = 2E/r^2 =$ constant $> 0$. The value of $k$ and the
function $t_B(r)$ are determined by the $\Lambda$CDM parameters. General
properties of this L-T model are described. Difficulties of carrying the
numerical calculations through the apparent horizon are presented in detail and
mostly solved. The second model is a counterexample to the claim that an L-T
model mimicking $\Lambda$CDM must contain a void around the center - it has a
peak of density at $R = 0$.
| [
{
"created": "Tue, 17 Sep 2013 16:15:33 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Mar 2014 15:27:41 GMT",
"version": "v2"
}
] | 2014-03-20 | [
[
"Krasiński",
"Andrzej",
""
]
] | It is shown how certain observations interpreted in the background of the Friedmann model with $\Lambda < 0 = k$ (the $\Lambda$CDM model) can be re-interpreted using the $\Lambda = 0$ Lema\^{\i}tre - Tolman (L-T) model so as to do away with the "dark energy". The purpose of the paper is to clarify the underlying geometrical relations by doing the calculations as much as possible analytically or by very simple numerical programs. In the first part of the paper (fictitious) observations of the distribution of expansion velocity along the past light cone of the observer are considered. It is shown that the whole past light cone of the $\Lambda$CDM observer can be reproduced in the L-T model with $\Lambda = 0 = E$. This is a geometric exercise that has the advantage of being free of numerical complications. In the second part, the luminosity distance - redshift relation of the $\Lambda$CDM model is duplicated using the L-T model with $-k = 2E/r^2 =$ constant $> 0$. The value of $k$ and the function $t_B(r)$ are determined by the $\Lambda$CDM parameters. General properties of this L-T model are described. Difficulties of carrying the numerical calculations through the apparent horizon are presented in detail and mostly solved. The second model is a counterexample to the claim that an L-T model mimicking $\Lambda$CDM must contain a void around the center - it has a peak of density at $R = 0$. |
1202.5373 | Jose Edgar Madriz Aguilar | Reyes Luz Marina, Moreno Claudia, Madriz Aguilar Jose Edgar | On gravitational waves generated during inflation under the influence of
a dynamical cosmological "constant" | 5 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study cosmological gravitational waves generated during inflation under
the influence of a decaying cosmological "constant", in the
Transverse-Traceless (TT) gauge. In our approach we consider a non-perturbative
contribution of the dynamical cosmological "constant" to the tensor modes. As
an application of the model we study the well-known cases $\Lambda(t)=\sigma
H^2$ and $\Lambda(t) =\vartheta H$. The spectrum of gravitational waves for the
first case results scale invariant at the end of inflation, whereas for the
second case scale invariance is not achieved, leaving this to new proposals of
the form: $\Lambda(t)=f(H,H^2)$, in order to include inflation in some
$\Lambda(t)$CDM models. We also found that the non-perturbative contributions
of $\Lambda(t)$, accelerate the decreasing of the amplitude of gravitational
waves during a power-law inflationary stage, by an exponential factor.
| [
{
"created": "Fri, 24 Feb 2012 05:16:11 GMT",
"version": "v1"
}
] | 2012-02-27 | [
[
"Marina",
"Reyes Luz",
""
],
[
"Claudia",
"Moreno",
""
],
[
"Edgar",
"Madriz Aguilar Jose",
""
]
] | We study cosmological gravitational waves generated during inflation under the influence of a decaying cosmological "constant", in the Transverse-Traceless (TT) gauge. In our approach we consider a non-perturbative contribution of the dynamical cosmological "constant" to the tensor modes. As an application of the model we study the well-known cases $\Lambda(t)=\sigma H^2$ and $\Lambda(t) =\vartheta H$. The spectrum of gravitational waves for the first case results scale invariant at the end of inflation, whereas for the second case scale invariance is not achieved, leaving this to new proposals of the form: $\Lambda(t)=f(H,H^2)$, in order to include inflation in some $\Lambda(t)$CDM models. We also found that the non-perturbative contributions of $\Lambda(t)$, accelerate the decreasing of the amplitude of gravitational waves during a power-law inflationary stage, by an exponential factor. |
1310.8654 | Edward Wilson-Ewing | Carlo Rovelli, Edward Wilson-Ewing | Why are the effective equations of loop quantum cosmology so accurate? | 6 pages, v2: Clarifications and references added | Phys.Rev.D90:023538,2014 | 10.1103/PhysRevD.90.023538 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We point out that the relative Heisenberg uncertainty relations vanish for
non-compact spaces in homogeneous loop quantum cosmology. As a consequence, for
sharply peaked states quantum fluctuations in the scale factor never become
important, even near the bounce point. This shows why quantum back-reaction
effects remain negligible and explains the surprising accuracy of the effective
equations in describing the dynamics of sharply peaked wave packets. This also
underlines the fact that minisuperspace models ---where it is global variables
that are quantized--- do not capture the local quantum fluctuations of the
geometry.
| [
{
"created": "Thu, 31 Oct 2013 19:41:38 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Jul 2014 15:53:11 GMT",
"version": "v2"
}
] | 2015-06-17 | [
[
"Rovelli",
"Carlo",
""
],
[
"Wilson-Ewing",
"Edward",
""
]
] | We point out that the relative Heisenberg uncertainty relations vanish for non-compact spaces in homogeneous loop quantum cosmology. As a consequence, for sharply peaked states quantum fluctuations in the scale factor never become important, even near the bounce point. This shows why quantum back-reaction effects remain negligible and explains the surprising accuracy of the effective equations in describing the dynamics of sharply peaked wave packets. This also underlines the fact that minisuperspace models ---where it is global variables that are quantized--- do not capture the local quantum fluctuations of the geometry. |
1511.02774 | Sudipto Roy | Sudipto Roy | A Study of Transition of the Expansion of the Universe from a Phase of
Deceleration to Acceleration through a Conversion of Matter into Dark Energy
in the Framework of Brans-Dicke Theory | null | International Journal of Science and Research (IJSR), Volume 4,
Issue 11, pages 885-890, 2015 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present study is based on a generalized form of Brans-Dicke (BD) theory
where, the dimensionless BD parameter is regarded as a function of the scalar
field, which is reciprocal of the gravitational constant. The field equations
have been solved by incorporating an empirical function f(t) in the expression
representing the conservation of matter. This function f(t) has been chosen to
account for a conversion of matter (both dark and baryonic) into some other
form, possibly dark energy, which is known to be responsible for the
accelerated expansion of universe. The requirement of a signature flip of the
deceleration parameter (q), which is evident from other studies, sets the
boundary conditions to be satisfied by the function f(t), leading to the
formulation of its time dependence. A simple empirical relation was initially
assumed to represent the time dependence of f(t), and the constants in this
expression have been determined from these boundary conditions. The BD
parameter has been found to have a negative value throughout the range of
study. The dependence of BD parameter upon the scalar field has been depicted
graphically. A smooth transition of the universe, from a decelerated to an
accelerated phase of expansion, is found to occur due to a conversion of matter
into dark energy. The gravitational constant is found to be increasing with
time.
| [
{
"created": "Fri, 6 Nov 2015 09:54:57 GMT",
"version": "v1"
}
] | 2017-11-07 | [
[
"Roy",
"Sudipto",
""
]
] | The present study is based on a generalized form of Brans-Dicke (BD) theory where, the dimensionless BD parameter is regarded as a function of the scalar field, which is reciprocal of the gravitational constant. The field equations have been solved by incorporating an empirical function f(t) in the expression representing the conservation of matter. This function f(t) has been chosen to account for a conversion of matter (both dark and baryonic) into some other form, possibly dark energy, which is known to be responsible for the accelerated expansion of universe. The requirement of a signature flip of the deceleration parameter (q), which is evident from other studies, sets the boundary conditions to be satisfied by the function f(t), leading to the formulation of its time dependence. A simple empirical relation was initially assumed to represent the time dependence of f(t), and the constants in this expression have been determined from these boundary conditions. The BD parameter has been found to have a negative value throughout the range of study. The dependence of BD parameter upon the scalar field has been depicted graphically. A smooth transition of the universe, from a decelerated to an accelerated phase of expansion, is found to occur due to a conversion of matter into dark energy. The gravitational constant is found to be increasing with time. |
2306.03729 | Jose Perdiguero | Oscar Castillo-Felisola, Jose Perdiguero | Does the metric play a fundamental role in the building of gravitational
models? | null | null | 10.1142/S0219887824300010 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The idea that General Relativity could be an effective model, of a yet
unknown theory of gravity, has gained momentum among theoretical physicists.
The polynomial affine model of gravity is an alternative model of affine
gravity that possesses many desirable features to pursue a quantum theory of
gravitation. In this paper we argue that such features are a consequence of the
lack of a metric structure in the building of the model, even though a emergent
metric could be defined. The model introduces additional degrees of freedom
associated to the geometric properties of the space, which might shed light to
understand the nature of the dark sector of the Universe. When the model is
coupled to a scalar field, it is possible to define inflationary scenarios.
| [
{
"created": "Tue, 6 Jun 2023 14:47:09 GMT",
"version": "v1"
}
] | 2023-10-26 | [
[
"Castillo-Felisola",
"Oscar",
""
],
[
"Perdiguero",
"Jose",
""
]
] | The idea that General Relativity could be an effective model, of a yet unknown theory of gravity, has gained momentum among theoretical physicists. The polynomial affine model of gravity is an alternative model of affine gravity that possesses many desirable features to pursue a quantum theory of gravitation. In this paper we argue that such features are a consequence of the lack of a metric structure in the building of the model, even though a emergent metric could be defined. The model introduces additional degrees of freedom associated to the geometric properties of the space, which might shed light to understand the nature of the dark sector of the Universe. When the model is coupled to a scalar field, it is possible to define inflationary scenarios. |
gr-qc/0108085 | Ulf Leonhardt | U. Leonhardt | A Primer to Slow Light | Contribution to the book Artificial Black Holes edited by Mario
Novello, Matt Visser and Grigori Volovik | null | null | null | gr-qc | null | Laboratory-based optical analogs of astronomical objects such as black holes
rely on the creation of light with an extremely low or even vanishing group
velocity (slow light). These brief notes represent a pedagogical attempt
towards elucidating this extraordinary form of light. This paper is a
contribution to the book Artificial Black Holes edited by Mario Novello, Matt
Visser and Grigori Volovik. The paper is intended as a primer, an introduction
to the subject for non-experts, not as a detailed literature review.
| [
{
"created": "Fri, 31 Aug 2001 10:15:09 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Jan 2002 15:52:41 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Leonhardt",
"U.",
""
]
] | Laboratory-based optical analogs of astronomical objects such as black holes rely on the creation of light with an extremely low or even vanishing group velocity (slow light). These brief notes represent a pedagogical attempt towards elucidating this extraordinary form of light. This paper is a contribution to the book Artificial Black Holes edited by Mario Novello, Matt Visser and Grigori Volovik. The paper is intended as a primer, an introduction to the subject for non-experts, not as a detailed literature review. |
2404.13538 | Pramit Rej | Pramit Rej | Charged analog of anisotropic dark energy star in Rastall gravity | 17 pages, 11 figures, 1 table. Prepared and submitted to EPJC on
08.04.2024 | null | null | null | gr-qc astro-ph.CO astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dark energy is one of the potential strategies for preventing compact objects
from gravitationally collapsing into singularities. Because it is the cause of
the accelerated expansion of our universe, it has the greatest impact on the
cosmos. Thus, it is plausible that dark energy will interact with any stellar
object that is compact in the universe [\textit{Phys. Rev. D} \textbf{103},
084042 (2021)]. Our main goal in this work is to create a simplified model, in
the Rastall gravitational framework, of a charged strange star coupled to
anisotropic dark energy in Krori-Barua spacetime [\textit{J. Phys. A, Math.
Gen.} \textbf{8}:508, 1975]. Here, we consider a specific strange star object,
Her X-1, with observed values of mass $=(0.85 \pm 0.15)M_{\odot}$ and radius $=
8.1_{-0.41}^{+0.41}$ km., so that we can develop our model. In this context, we
began by modeling dark energy using the equation of state (EoS), in which the
dark energy density is proportional to the isotropic perfect fluid
matter-energy density. The Darmois-Israel condition has been used to calculate
the unknown constants that are present in the metric. We perform a detailed
analysis of the model's physical properties, including the mass-radius
relation, pressure, density, metric function, and dark energy parameters, by
varying the Rastall coupling parameter. We also examine the stability and force
equilibrium of our proposed stellar configuration. Following a comprehensive
theoretical analysis, we discovered that our suggested model is both
singularity-free and meets all stability requirements needed to be a stable,
physically reasonable stellar model.
| [
{
"created": "Sun, 21 Apr 2024 05:24:54 GMT",
"version": "v1"
}
] | 2024-04-23 | [
[
"Rej",
"Pramit",
""
]
] | Dark energy is one of the potential strategies for preventing compact objects from gravitationally collapsing into singularities. Because it is the cause of the accelerated expansion of our universe, it has the greatest impact on the cosmos. Thus, it is plausible that dark energy will interact with any stellar object that is compact in the universe [\textit{Phys. Rev. D} \textbf{103}, 084042 (2021)]. Our main goal in this work is to create a simplified model, in the Rastall gravitational framework, of a charged strange star coupled to anisotropic dark energy in Krori-Barua spacetime [\textit{J. Phys. A, Math. Gen.} \textbf{8}:508, 1975]. Here, we consider a specific strange star object, Her X-1, with observed values of mass $=(0.85 \pm 0.15)M_{\odot}$ and radius $= 8.1_{-0.41}^{+0.41}$ km., so that we can develop our model. In this context, we began by modeling dark energy using the equation of state (EoS), in which the dark energy density is proportional to the isotropic perfect fluid matter-energy density. The Darmois-Israel condition has been used to calculate the unknown constants that are present in the metric. We perform a detailed analysis of the model's physical properties, including the mass-radius relation, pressure, density, metric function, and dark energy parameters, by varying the Rastall coupling parameter. We also examine the stability and force equilibrium of our proposed stellar configuration. Following a comprehensive theoretical analysis, we discovered that our suggested model is both singularity-free and meets all stability requirements needed to be a stable, physically reasonable stellar model. |
0810.5241 | Luca Lusanna | Luca Lusanna | Relativistic Atomic Physics: from Atomic Clock Synchronization towards
Relativistic Entanglement | Talk given at the 7th Friedmann International Seminar, Joao Pessoa
(Brasil), June 29 - July 5, 2008 | Int.J.Mod.Phys.A24:1518-1527,2009 | 10.1142/S0217751X09044929 | null | gr-qc astro-ph hep-th physics.atom-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A review is given of the implications of the absence of an intrinsic notion
of instantaneous 3-space, so that a clock synchronization convention has to be
introduced, for relativistic theories.
| [
{
"created": "Wed, 29 Oct 2008 10:58:37 GMT",
"version": "v1"
}
] | 2009-04-24 | [
[
"Lusanna",
"Luca",
""
]
] | A review is given of the implications of the absence of an intrinsic notion of instantaneous 3-space, so that a clock synchronization convention has to be introduced, for relativistic theories. |
gr-qc/9402029 | Socorro | J.A. Nieto, O. Obreg\'on and J. Socorro | The Gauge Theory of the de-Sitter Group and Ashtekar Formulation | 9 pages | Phys.Rev.D50:3583-3586,1994 | 10.1103/PhysRevD.50.R3583 | IFUG-94-001 | gr-qc | null | By adding the Pontrjagin topological invariant to the gauge theory of the de
Sitter group proposed by MacDowell and Mansouri we obtain an action quadratic
in the field-strengths, of the Chern-Simons type, from which the Ashtekar
formulation is derived.
| [
{
"created": "Tue, 22 Feb 1994 18:13:41 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Feb 1994 22:38:56 GMT",
"version": "v2"
}
] | 2010-01-06 | [
[
"Nieto",
"J. A.",
""
],
[
"Obregón",
"O.",
""
],
[
"Socorro",
"J.",
""
]
] | By adding the Pontrjagin topological invariant to the gauge theory of the de Sitter group proposed by MacDowell and Mansouri we obtain an action quadratic in the field-strengths, of the Chern-Simons type, from which the Ashtekar formulation is derived. |
1006.1763 | Thomas Sotiriou | Ted Jacobson and Thomas P. Sotiriou | Might black holes reveal their inner secrets? | Essay written for FQXi essay competition "What is Ultimately Possible
in Physics", Third Prize Winner (based on Phys. Rev. Lett. 103, 141101
(2009), arXiv:0907.4146 [gr-qc]) | null | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes harbor a spacetime singularity of infinite curvature, where
classical spacetime physics breaks down, and current theory cannot predict what
will happen. However, the singularity is invisible from the outside because
strong gravity traps all signals, even light, behind an event horizon. In this
essay we discuss whether it might be possible to destroy the horizon, if a body
is tossed into the black hole so as to make it spin faster and/or have more
charge than a certain limit. It turns out that one could expose a "naked"
singularity if effects of the body's own gravity can be neglected. We suspect
however that such neglect is unjustified.
| [
{
"created": "Wed, 9 Jun 2010 10:52:37 GMT",
"version": "v1"
}
] | 2010-06-10 | [
[
"Jacobson",
"Ted",
""
],
[
"Sotiriou",
"Thomas P.",
""
]
] | Black holes harbor a spacetime singularity of infinite curvature, where classical spacetime physics breaks down, and current theory cannot predict what will happen. However, the singularity is invisible from the outside because strong gravity traps all signals, even light, behind an event horizon. In this essay we discuss whether it might be possible to destroy the horizon, if a body is tossed into the black hole so as to make it spin faster and/or have more charge than a certain limit. It turns out that one could expose a "naked" singularity if effects of the body's own gravity can be neglected. We suspect however that such neglect is unjustified. |
1302.1191 | Muhammad Sharif | M. Sharif and Sadia Arif | Static Cylindrically Symmetric Interior Solutions in f(R) Gravity | 10 pages, no figure | Mod. Phys. Lett. A. 27(2012)1250138 | 10.1142/S0217732312501386 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate some exact static cylindrically symmetric solutions for a
perfect fluid in the metric $f(R)$ theory of gravity. For this purpose, three
different families of solutions are explored. We evaluate energy density,
pressure, Ricci scalar and functional form of $f(R)$. It is interesting to
mention here that two new exact solutions are found from the last approach, one
is in particular form and the other is in the general form. The general form
gives a complete description of a cylindrical star in $f(R)$ gravity.
| [
{
"created": "Sat, 26 Jan 2013 04:55:01 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Sharif",
"M.",
""
],
[
"Arif",
"Sadia",
""
]
] | We investigate some exact static cylindrically symmetric solutions for a perfect fluid in the metric $f(R)$ theory of gravity. For this purpose, three different families of solutions are explored. We evaluate energy density, pressure, Ricci scalar and functional form of $f(R)$. It is interesting to mention here that two new exact solutions are found from the last approach, one is in particular form and the other is in the general form. The general form gives a complete description of a cylindrical star in $f(R)$ gravity. |
gr-qc/9608058 | Mauricio O. Calvao | M. L. Bedran, M. O. Calvao, I. Damiao Soares and F. M. Paiva | Taub's plane-symmetric vacuum spacetime revisited | plain LaTex, four Postscript figures | Phys.Rev. D55 (1997) 3431-3439 | 10.1103/PhysRevD.55.3431 | null | gr-qc | null | The gravitational properties of the {\em only} static plane-symmetric vacuum
solution of Einstein's field equations without cosmological term (Taub's
solution, for brevity) are presented: some already known properties (geodesics,
weak field limit and pertainment to the Schwarzschild family of spacetimes) are
reviewed in a physically much more transparent way, as well as new results
about its asymptotic structure, possible matchings and nature of the source are
furnished. The main results point to the fact that the solution must be
interpreted as representing the exterior gravitational field due to a {\em
negative} mass distribution, confirming previous statements to that effect in
the literature. Some analogies to Kasner's spatially homogeneous cosmological
model are also referred to.
| [
{
"created": "Fri, 23 Aug 1996 22:01:24 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Bedran",
"M. L.",
""
],
[
"Calvao",
"M. O.",
""
],
[
"Soares",
"I. Damiao",
""
],
[
"Paiva",
"F. M.",
""
]
] | The gravitational properties of the {\em only} static plane-symmetric vacuum solution of Einstein's field equations without cosmological term (Taub's solution, for brevity) are presented: some already known properties (geodesics, weak field limit and pertainment to the Schwarzschild family of spacetimes) are reviewed in a physically much more transparent way, as well as new results about its asymptotic structure, possible matchings and nature of the source are furnished. The main results point to the fact that the solution must be interpreted as representing the exterior gravitational field due to a {\em negative} mass distribution, confirming previous statements to that effect in the literature. Some analogies to Kasner's spatially homogeneous cosmological model are also referred to. |
gr-qc/0109020 | Dr A. R. Prasanna | A. R. Prasanna | Inertial Forces as Viewed from the ADM Slicing and their behaviour for
Particles in Non-Circular Geodesics | 16 Latex pages, 1 Table and 3 Figures | null | 10.1142/S0217732302008277 | null | gr-qc astro-ph | null | Considering the definition of inertial forces acting on a test particle,
following non-circular geodesics, in static and stationary space times we show
that the centrifugal force reversal occurs only in the case of particles
following prograde orbits around black holes. We first rewrite the covariant
expressions for the acceleration components in terms of the lapse function,
shift vector and the 3-metric $\gm_{ij}$, using the ADM 3+1 splitting and use
these, for different cases as given by pure radial motion, pure azimuthal
motion and the general non-circular motion. It is found that the reversal
occurs only when the azimuthal angular velocity of the particle supersedes the
radial velocity, which indeed depends upon the physical parameters $E$, $l$ and
the Kerr parameter $a$.
| [
{
"created": "Thu, 6 Sep 2001 13:56:16 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Mar 2002 04:05:28 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Prasanna",
"A. R.",
""
]
] | Considering the definition of inertial forces acting on a test particle, following non-circular geodesics, in static and stationary space times we show that the centrifugal force reversal occurs only in the case of particles following prograde orbits around black holes. We first rewrite the covariant expressions for the acceleration components in terms of the lapse function, shift vector and the 3-metric $\gm_{ij}$, using the ADM 3+1 splitting and use these, for different cases as given by pure radial motion, pure azimuthal motion and the general non-circular motion. It is found that the reversal occurs only when the azimuthal angular velocity of the particle supersedes the radial velocity, which indeed depends upon the physical parameters $E$, $l$ and the Kerr parameter $a$. |
1412.4256 | Spyridon Talaganis | Tirthabir Biswas, Spyridon Talaganis | String-Inspired Infinite-Derivative Theories of Gravity: A Brief
Overview | 22 pages. Accepted review article in "New trends in theory of
gravity," Mod. Phys. Lett. A, v2: very minor changes | Mod. Phys. Lett. A, Vol. 30, Nos. 3 & 4 (2015) 1540009 | 10.1142/S021773231540009X | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In String Theory there often appears a rather interesting class of higher
derivative theories containing an infinite set of derivatives in the form of an
exponential. These theories may provide a way to tame ultraviolet divergences
without introducing ghost-like states. In this invited article we provide a
brief overview on the progress that has been made over the last decade to
construct such infinite derivative theories of gravity which may be able to
address the singularity problems in gravity. In the process we will also be
able to present some general results that applies to covariant torsion-free
metric theories of gravity.
| [
{
"created": "Sat, 13 Dec 2014 17:03:19 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Jan 2015 11:48:23 GMT",
"version": "v2"
}
] | 2015-02-23 | [
[
"Biswas",
"Tirthabir",
""
],
[
"Talaganis",
"Spyridon",
""
]
] | In String Theory there often appears a rather interesting class of higher derivative theories containing an infinite set of derivatives in the form of an exponential. These theories may provide a way to tame ultraviolet divergences without introducing ghost-like states. In this invited article we provide a brief overview on the progress that has been made over the last decade to construct such infinite derivative theories of gravity which may be able to address the singularity problems in gravity. In the process we will also be able to present some general results that applies to covariant torsion-free metric theories of gravity. |
1906.10090 | Claudio Coriano | Claudio Corian\`o, Paul H. Frampton | Holographic Principle, Cosmological Constant and Cyclic Cosmology | 10 pages, version published in Mod. Phys. Lett. A34, 1950355 (2019) | null | 10.1142/S0217732319503553 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The holographic principle provides a deep insight into quantum gravity and
resolves the fine-tuning crisis concerning the cosmological constant.
Holographic dark energy introduces new ultra-violet (UV) and infra-red (IR)
cutoffs into quantum gravity which are necessarily strongly related. The
equation of state for dark energy $\omega = p/\rho$ is discussed from the
holographic point of view. The phantom option of $\omega < -1$ is resurrected,
as in an earlier cyclic cosmology. Such a cyclic model can, however, equally
use the cosmological constant with $\omega = -1$.
| [
{
"created": "Mon, 24 Jun 2019 17:15:08 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Nov 2019 09:16:14 GMT",
"version": "v2"
}
] | 2020-02-19 | [
[
"Corianò",
"Claudio",
""
],
[
"Frampton",
"Paul H.",
""
]
] | The holographic principle provides a deep insight into quantum gravity and resolves the fine-tuning crisis concerning the cosmological constant. Holographic dark energy introduces new ultra-violet (UV) and infra-red (IR) cutoffs into quantum gravity which are necessarily strongly related. The equation of state for dark energy $\omega = p/\rho$ is discussed from the holographic point of view. The phantom option of $\omega < -1$ is resurrected, as in an earlier cyclic cosmology. Such a cyclic model can, however, equally use the cosmological constant with $\omega = -1$. |
2201.03783 | Bivudutta Mishra Dr. | A.S. Agrawal, S.K. Tripathy, Sarmistha Pal, B.Mishra | Role of Extended Gravity Theory in Matter Bounce Dynamics | 17 pages, 22 figures, Accepted version Physica Scripta | Physica Scripta, 97, 025002, 2022 | 10.1088/1402-4896/ac49b2 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we have studied some bouncing cosmologies in the frame work of
$f(R,T)$ gravity. The bouncing scenario has been formulated to avoid the big
bang singularity. The physical and geometrical parameters are investigated. The
effect of the extended gravity theory on the dynamical parameters of the model
is investigated. It is found that, the $f(R,T)$ gravity parameter affects the
cosmic dynamics substantially. We have also, tested the model through the
calculation of the cosmographic coefficients and the $Om(z)$ parameter. A
scalar field reconstruction of the bouncing scenario is also carried out. The
stability of the model are tested under linear, homogeneous and isotropic
perturbations.
| [
{
"created": "Tue, 11 Jan 2022 05:05:35 GMT",
"version": "v1"
}
] | 2022-04-22 | [
[
"Agrawal",
"A. S.",
""
],
[
"Tripathy",
"S. K.",
""
],
[
"Pal",
"Sarmistha",
""
],
[
"Mishra",
"B.",
""
]
] | In this work, we have studied some bouncing cosmologies in the frame work of $f(R,T)$ gravity. The bouncing scenario has been formulated to avoid the big bang singularity. The physical and geometrical parameters are investigated. The effect of the extended gravity theory on the dynamical parameters of the model is investigated. It is found that, the $f(R,T)$ gravity parameter affects the cosmic dynamics substantially. We have also, tested the model through the calculation of the cosmographic coefficients and the $Om(z)$ parameter. A scalar field reconstruction of the bouncing scenario is also carried out. The stability of the model are tested under linear, homogeneous and isotropic perturbations. |
2310.15185 | Ali Mahmoodzadeh | A. Mahmoodzadeh, B. Malakolkalami, K. Ghaderi | Real particle geodesics and thermodynamics of a black hole in Regular
Schwarzschild-Anti de Sitter space-time | 22 pages, 26 figures | null | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | In this work, we illustrate the geodesics of real particles obtained
numerically in a Regular Schwarzschild Anti-de Sitter (RSch-AdS) space-time.
The behavior of these geodesics are considered depending on variation of
effective parameters such as mass distribution, angular momentum and
cosmological constant. Also, using the laws of thermodynamics of black holes,
we will study and discuss some aspect of black hole (BH) described by this
spacetime such as temperature, entropy, heat capacity and Gibbs free energy.
| [
{
"created": "Fri, 20 Oct 2023 18:03:41 GMT",
"version": "v1"
}
] | 2023-10-25 | [
[
"Mahmoodzadeh",
"A.",
""
],
[
"Malakolkalami",
"B.",
""
],
[
"Ghaderi",
"K.",
""
]
] | In this work, we illustrate the geodesics of real particles obtained numerically in a Regular Schwarzschild Anti-de Sitter (RSch-AdS) space-time. The behavior of these geodesics are considered depending on variation of effective parameters such as mass distribution, angular momentum and cosmological constant. Also, using the laws of thermodynamics of black holes, we will study and discuss some aspect of black hole (BH) described by this spacetime such as temperature, entropy, heat capacity and Gibbs free energy. |
gr-qc/0406019 | Sergei A. Klioner | Sergei A. Klioner | Independent Components of an Indexed Object with Linear Symmetries | 9 pages, Proceedings of the CASC'2004 (Computer Algebra in Scienfic
Computing) | null | null | null | gr-qc | null | The problem of finding independent components of an indexed object (e.g., a
tensor) with arbitrary number of indices and arbitrary linear symmetries is
discussed. It is proved that the number of independent components $f(k)$ is a
polynomial of degree not greater than the number of indices $n$, $k$ being the
dimension of the space. Several algorithms to compute $f(k)$ for arbitrary $k$
are described and discussed. It is shown that in the worst case finding $f(k)$
for arbitrary $k$ requires solving at most P(n) systems of linear equations
with at most $(n!)^2$ equations for at most of $n!$ unknowns, P(n) being the
number of partitions of $n$. As a by-product, an efficient algorithm to
parametrize all components of the object through its independent components is
found and implemented in \Mathematica.
| [
{
"created": "Fri, 4 Jun 2004 18:27:33 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Jun 2004 17:31:55 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Klioner",
"Sergei A.",
""
]
] | The problem of finding independent components of an indexed object (e.g., a tensor) with arbitrary number of indices and arbitrary linear symmetries is discussed. It is proved that the number of independent components $f(k)$ is a polynomial of degree not greater than the number of indices $n$, $k$ being the dimension of the space. Several algorithms to compute $f(k)$ for arbitrary $k$ are described and discussed. It is shown that in the worst case finding $f(k)$ for arbitrary $k$ requires solving at most P(n) systems of linear equations with at most $(n!)^2$ equations for at most of $n!$ unknowns, P(n) being the number of partitions of $n$. As a by-product, an efficient algorithm to parametrize all components of the object through its independent components is found and implemented in \Mathematica. |
gr-qc/9211008 | null | David Hochberg and Thomas W. Kephart | Gauge Field Back-reaction on a Black Hole | 17 pages, three figures available on request, in RevTex | Phys.Rev. D47 (1993) 1465-1470 | 10.1103/PhysRevD.47.1465 | VAND-TH-92-3 | gr-qc astro-ph | null | The order $\hbar$ fluctuations of gauge fields in the vicinity of a blackhole
can create a repulsive antigravity region extending out beyond the renormalized
Schwarzschild horizon. If the strength of this repulsive force increases as
higher orders in the back-reaction are included, the formation of a
wormhole-like object could occur.
| [
{
"created": "Thu, 5 Nov 1992 16:59:25 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Hochberg",
"David",
""
],
[
"Kephart",
"Thomas W.",
""
]
] | The order $\hbar$ fluctuations of gauge fields in the vicinity of a blackhole can create a repulsive antigravity region extending out beyond the renormalized Schwarzschild horizon. If the strength of this repulsive force increases as higher orders in the back-reaction are included, the formation of a wormhole-like object could occur. |
2306.01868 | Qi-Xin Xie | He-Yu Gao, Paul M. Saffin, Yi-Jie Wang, Qi-Xin Xie, Shuang-Yong Zhou | Boson Star Superradiance | 10 pages, 6 figures; v2: refs added and clarified | null | null | USTC-ICTS/PCFT-23-16 | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, it has been realized that in some systems internal space rotation
can induce energy amplification for scattering waves, similar to rotation in
real space. Particularly, it has been shown that energy extraction is possible
for a Q-ball, a stationary non-topological soliton that is coherently rotating
in its field space. In this paper, we generalize the analysis to the case of
boson stars, and show that the same energy extraction mechanism still works for
boson stars.
| [
{
"created": "Fri, 2 Jun 2023 18:53:23 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Jun 2023 05:06:43 GMT",
"version": "v2"
}
] | 2023-06-30 | [
[
"Gao",
"He-Yu",
""
],
[
"Saffin",
"Paul M.",
""
],
[
"Wang",
"Yi-Jie",
""
],
[
"Xie",
"Qi-Xin",
""
],
[
"Zhou",
"Shuang-Yong",
""
]
] | Recently, it has been realized that in some systems internal space rotation can induce energy amplification for scattering waves, similar to rotation in real space. Particularly, it has been shown that energy extraction is possible for a Q-ball, a stationary non-topological soliton that is coherently rotating in its field space. In this paper, we generalize the analysis to the case of boson stars, and show that the same energy extraction mechanism still works for boson stars. |
1405.7883 | Lau Loi So | Lau Loi So | The modification of the Bel-Robinson type energy-momentum | 7 pages, a major revision of arXiv:1302.2412 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For describing the non-negative gravitational energy-momentum in terms of a
pure Bel-Robinson type energy-momentum in a quasi-local 2-surface, both the
Bel-Robinson tensor $B$ and tensor $V$ are suitable. We have found that this
Bel-Robinson type energy-momentum can be modified such that it satisfies the
Lorentz covariant, future pointing and non-spacelike properties. We find that
these particular quasi-local energy-momentum properties can be obtained from
(i): $B$ or $V$ plus a tensor $S$ in a small sphere limit, or (ii): directly
evaluating the energy-momentum of $B$ or $V$ in a small ellipsoid region.
(iii): calculate the total energy using the Landau-Lifshitz pseudotensor in a
small ellipsoid, from Jupiter's tidal force to Io in Schwarzchild spacetime, in
an elliptic orbit.
| [
{
"created": "Fri, 30 May 2014 14:58:36 GMT",
"version": "v1"
}
] | 2014-06-02 | [
[
"So",
"Lau Loi",
""
]
] | For describing the non-negative gravitational energy-momentum in terms of a pure Bel-Robinson type energy-momentum in a quasi-local 2-surface, both the Bel-Robinson tensor $B$ and tensor $V$ are suitable. We have found that this Bel-Robinson type energy-momentum can be modified such that it satisfies the Lorentz covariant, future pointing and non-spacelike properties. We find that these particular quasi-local energy-momentum properties can be obtained from (i): $B$ or $V$ plus a tensor $S$ in a small sphere limit, or (ii): directly evaluating the energy-momentum of $B$ or $V$ in a small ellipsoid region. (iii): calculate the total energy using the Landau-Lifshitz pseudotensor in a small ellipsoid, from Jupiter's tidal force to Io in Schwarzchild spacetime, in an elliptic orbit. |
2105.09173 | Benrong Mu | Rui Yin, Jing Liang, Benrong Mu | Joule-Thomson expansion of Reissner-Nordstr\"om-Anti-de Sitter black
holes with cloud of strings and quintessence | 36 pages, 8 figures, 5 tables | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Joule-Thomson expansion is studied for Reissner-Nordstr\"om-Anti-de
Sitter black holes with cloud of strings and quintessence, as well as its
thermodynamics. The cosmological constant is treated as thermodynamic pressure,
whose conjugate variable is considered as the volume. The characteristics of
the Joule-Thomson expansion are studied in four main aspects with the case of
$\omega=-1$ and $\omega=-\frac{2}{3}$, including the Joule-Thomson coefficient,
the inversion curves, the isenthalpic curves and the ratio between
$T_{i}^{min}$ and $T_{c}$. The sign of the Joule-Thomson coefficient is
possible for determining the occurrence of heating or cooling. The scattering
point of the Joule-Thomson coefficient corresponds to the zero point of the
Hawking temperature. Unlike the van der Waals fluids, the inversion curve is
the dividing line between heating and cooling regions, above which the slope of
the isenthalpic curve is positive and cooling occurs, and the cooling-heating
critical point is more sensitive to $Q$. Concerning the ratio
$\frac{T_{i}^{min}}{T_{c}}$, we calculate it separately in the cases where only
the cloud of strings, only quintessence and both are present.
| [
{
"created": "Wed, 19 May 2021 14:44:44 GMT",
"version": "v1"
}
] | 2021-05-20 | [
[
"Yin",
"Rui",
""
],
[
"Liang",
"Jing",
""
],
[
"Mu",
"Benrong",
""
]
] | The Joule-Thomson expansion is studied for Reissner-Nordstr\"om-Anti-de Sitter black holes with cloud of strings and quintessence, as well as its thermodynamics. The cosmological constant is treated as thermodynamic pressure, whose conjugate variable is considered as the volume. The characteristics of the Joule-Thomson expansion are studied in four main aspects with the case of $\omega=-1$ and $\omega=-\frac{2}{3}$, including the Joule-Thomson coefficient, the inversion curves, the isenthalpic curves and the ratio between $T_{i}^{min}$ and $T_{c}$. The sign of the Joule-Thomson coefficient is possible for determining the occurrence of heating or cooling. The scattering point of the Joule-Thomson coefficient corresponds to the zero point of the Hawking temperature. Unlike the van der Waals fluids, the inversion curve is the dividing line between heating and cooling regions, above which the slope of the isenthalpic curve is positive and cooling occurs, and the cooling-heating critical point is more sensitive to $Q$. Concerning the ratio $\frac{T_{i}^{min}}{T_{c}}$, we calculate it separately in the cases where only the cloud of strings, only quintessence and both are present. |
1706.10244 | Bijunath Patla | Neil Ashby, Thomas E. Parker, Bijunath R. Patla | A null test of General Relativity: New limits on Local Position
Invariance and the variation of fundamental constants | null | null | null | null | gr-qc physics.atom-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compare the long-term fractional frequency variation of four hydrogen
masers that are part of an ensemble of clocks comprising the National Institute
of Standards and Technology,(NIST), Boulder, timescale with the fractional
frequencies of primary frequency standards operated by leading metrology
laboratories in the United States, France, Germany, Italy and the United
Kingdom for a period extending more than 14 years. The measure of the assumed
variation of non-gravitational interaction,(LPI parameter, $\beta$)---within
the atoms of H and Cs---over time as the earth orbits the sun, has been
constrained to $\beta=(2.2 \pm 2.5)\times 10^{-7}$, a factor of two improvement
over previous estimates. Using our results together with the previous best
estimates of $\beta$ based on Rb vs. Cs, and Rb vs. H comparisons, we impose
the most stringent limits to date on the dimensionless coupling constants that
relate the variation of fundamental constants such as the fine-structure
constant and the scaled quark mass with strong(QCD) interaction to the
variation in the local gravitational potential. For any metric theory of
gravity $\beta=0$.
| [
{
"created": "Fri, 30 Jun 2017 15:41:58 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Dec 2017 21:34:43 GMT",
"version": "v2"
},
{
"created": "Tue, 20 Feb 2018 17:10:01 GMT",
"version": "v3"
}
] | 2018-02-21 | [
[
"Ashby",
"Neil",
""
],
[
"Parker",
"Thomas E.",
""
],
[
"Patla",
"Bijunath R.",
""
]
] | We compare the long-term fractional frequency variation of four hydrogen masers that are part of an ensemble of clocks comprising the National Institute of Standards and Technology,(NIST), Boulder, timescale with the fractional frequencies of primary frequency standards operated by leading metrology laboratories in the United States, France, Germany, Italy and the United Kingdom for a period extending more than 14 years. The measure of the assumed variation of non-gravitational interaction,(LPI parameter, $\beta$)---within the atoms of H and Cs---over time as the earth orbits the sun, has been constrained to $\beta=(2.2 \pm 2.5)\times 10^{-7}$, a factor of two improvement over previous estimates. Using our results together with the previous best estimates of $\beta$ based on Rb vs. Cs, and Rb vs. H comparisons, we impose the most stringent limits to date on the dimensionless coupling constants that relate the variation of fundamental constants such as the fine-structure constant and the scaled quark mass with strong(QCD) interaction to the variation in the local gravitational potential. For any metric theory of gravity $\beta=0$. |
gr-qc/0301043 | Grigori Volovik | G.E. Volovik | What can the quantum liquid say on the brane black hole, the entropy of
extremal black hole and the vacuum energy? | LaTeX file, 23 pages, 2 Figures, prepared for issue of Foundations of
Physics devoted to the honor of Jacob Bekenstein; misprints are corrected | Found.Phys. 33 (2003) 349-368 | 10.1023/A:1023762013553 | null | gr-qc cond-mat hep-ph | null | Using quantum liquids one can simulate the behavior of the quantum vacuum in
the presence of the event horizon. The condensed matter analogs demonstrate
that in most cases the quantum vacuum resists to formation of the horizon, and
even if the horizon is formed different types of the vacuum instability
develop, which are faster than the process of Hawking radiation. Nevertheless,
it is possible to create the horizon on the quantum-liquid analog of the brane,
where the vacuum life-time is long enough to consider the horizon as the
quasistationary object. Using this analogy we calculate the Bekenstein entropy
of the nearly extremal and extremal black holes, which comes from the fermionic
microstates in the region of the horizon -- the fermion zero modes. We also
discuss how the cancellation of the large cosmological constant follows from
the thermodynamics of the vacuum.
| [
{
"created": "Mon, 13 Jan 2003 09:10:53 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Jan 2003 14:08:56 GMT",
"version": "v2"
}
] | 2022-10-12 | [
[
"Volovik",
"G. E.",
""
]
] | Using quantum liquids one can simulate the behavior of the quantum vacuum in the presence of the event horizon. The condensed matter analogs demonstrate that in most cases the quantum vacuum resists to formation of the horizon, and even if the horizon is formed different types of the vacuum instability develop, which are faster than the process of Hawking radiation. Nevertheless, it is possible to create the horizon on the quantum-liquid analog of the brane, where the vacuum life-time is long enough to consider the horizon as the quasistationary object. Using this analogy we calculate the Bekenstein entropy of the nearly extremal and extremal black holes, which comes from the fermionic microstates in the region of the horizon -- the fermion zero modes. We also discuss how the cancellation of the large cosmological constant follows from the thermodynamics of the vacuum. |
gr-qc/9806047 | Luis J. Garay | Luis J. Garay | Thermal properties of spacetime foam | RevTeX 3.01, 11 pages, no figures | Phys. Rev. D 58, 124015 (1998) | 10.1103/PhysRevD.58.124015 | null | gr-qc quant-ph | null | Spacetime foam can be modeled in terms of nonlocal effective interactions in
a classical nonfluctuating background. Then, the density matrix for the
low-energy fields evolves, in the weak-coupling approximation, according to a
master equation that contains a diffusion term. Furthermore, it is argued that
spacetime foam behaves as a quantum thermal field that, apart from inducing
loss of coherence, gives rise to effects such as gravitational Lamb and Stark
shifts as well as quantum damping in the evolution of the low-energy
observables. These effects can be, at least in principle, experimentally
tested.
| [
{
"created": "Tue, 9 Jun 1998 15:20:13 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Mar 1999 10:45:24 GMT",
"version": "v2"
}
] | 2016-08-25 | [
[
"Garay",
"Luis J.",
""
]
] | Spacetime foam can be modeled in terms of nonlocal effective interactions in a classical nonfluctuating background. Then, the density matrix for the low-energy fields evolves, in the weak-coupling approximation, according to a master equation that contains a diffusion term. Furthermore, it is argued that spacetime foam behaves as a quantum thermal field that, apart from inducing loss of coherence, gives rise to effects such as gravitational Lamb and Stark shifts as well as quantum damping in the evolution of the low-energy observables. These effects can be, at least in principle, experimentally tested. |
1201.0475 | Nikolaos Pappas | Nikolaos D. Pappas | On the preservation of unitarity during black hole evolution and
information extraction from its interior | 8 pages, no figures | Mod. Phys. Lett. A, v27, iss19, pp12501,2012 | 10.1142/S021773231250109X | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For more than 30 years the discovery that black holes radiate like black
bodies of specific temperature has triggered a multitude of puzzling questions
concerning their nature and the fate of information that goes down the black
hole during its lifetime. The most tricky issue in what is known as information
loss paradox is the apparent violation of unitarity during the
formation/evaporation process of black holes. A new idea is proposed based on
the combination of our knowledge on Hawking radiation as well as the
Einstein-Podolsky-Rosen phenomenon, that could resolve the paradox and spare
physicists from the unpalatable idea that unitarity can ultimately be violated
even under special conditions.
| [
{
"created": "Mon, 2 Jan 2012 14:41:19 GMT",
"version": "v1"
},
{
"created": "Tue, 22 May 2012 14:41:15 GMT",
"version": "v2"
}
] | 2012-06-28 | [
[
"Pappas",
"Nikolaos D.",
""
]
] | For more than 30 years the discovery that black holes radiate like black bodies of specific temperature has triggered a multitude of puzzling questions concerning their nature and the fate of information that goes down the black hole during its lifetime. The most tricky issue in what is known as information loss paradox is the apparent violation of unitarity during the formation/evaporation process of black holes. A new idea is proposed based on the combination of our knowledge on Hawking radiation as well as the Einstein-Podolsky-Rosen phenomenon, that could resolve the paradox and spare physicists from the unpalatable idea that unitarity can ultimately be violated even under special conditions. |
gr-qc/0304109 | Bin Wang | Li-Hui Xue, Zai-Xiong Shen, Bin Wang and Ru-Keng Su | Numerical simulation of Quasi-Normal Modes in time-dependent background | 10 pages, 8 figures; reference added | Mod.Phys.Lett. A19 (2004) 239 | 10.1142/S021773230401240X | null | gr-qc astro-ph hep-th | null | We study the massless scalar wave propagation in the time-dependent
Schwarzschild black hole background. We find that the Kruskal coordinate is an
appropriate framework to investigate the time-dependent spacetime. A
time-dependent scattering potential is derived by considering dynamical black
hole with parameters changing with time. It is shown that in the quasinormal
ringing both the decay time-scale and oscillation are modified in the
time-dependent background.
| [
{
"created": "Wed, 30 Apr 2003 13:48:51 GMT",
"version": "v1"
},
{
"created": "Fri, 2 May 2003 13:21:39 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Xue",
"Li-Hui",
""
],
[
"Shen",
"Zai-Xiong",
""
],
[
"Wang",
"Bin",
""
],
[
"Su",
"Ru-Keng",
""
]
] | We study the massless scalar wave propagation in the time-dependent Schwarzschild black hole background. We find that the Kruskal coordinate is an appropriate framework to investigate the time-dependent spacetime. A time-dependent scattering potential is derived by considering dynamical black hole with parameters changing with time. It is shown that in the quasinormal ringing both the decay time-scale and oscillation are modified in the time-dependent background. |
gr-qc/0204085 | Jerry B. Griffiths | J. B. Griffiths and P. Docherty | A disintegrating cosmic string | 3 pages, 1 figure, to appear in Class. Quantum Grav | Class.Quant.Grav. 19 (2002) L109-L112 | 10.1088/0264-9381/19/11/103 | null | gr-qc | null | We present a simple sandwich gravitational wave of the Robinson-Trautman
family. This is interpreted as representing a shock wave with a spherical
wavefront which propagates into a Minkowski background minus a wedge. (i.e. the
background contains a cosmic string.) The deficit angle (the tension) of the
string decreases through the gravitational wave, which then ceases. This leaves
an expanding spherical region of Minkowski space behind it. The decay of the
cosmic string over a finite interval of retarded time may be considered to
generate the gravitational wave.
| [
{
"created": "Mon, 29 Apr 2002 10:56:13 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Griffiths",
"J. B.",
""
],
[
"Docherty",
"P.",
""
]
] | We present a simple sandwich gravitational wave of the Robinson-Trautman family. This is interpreted as representing a shock wave with a spherical wavefront which propagates into a Minkowski background minus a wedge. (i.e. the background contains a cosmic string.) The deficit angle (the tension) of the string decreases through the gravitational wave, which then ceases. This leaves an expanding spherical region of Minkowski space behind it. The decay of the cosmic string over a finite interval of retarded time may be considered to generate the gravitational wave. |
gr-qc/9904073 | Tomohiro Harada | Tomohiro Harada, Ken-ichi Nakao, and Hideo Iguchi | Nakedness and curvature strength of shell-focusing singularity in the
spherically symmetric space-time with vanishing radial pressure | 11 pages, Accepted for Publication in Classical and Quantum Gravity,
References Updated, Grammatical Errors Corrected | Class.Quant.Grav. 16 (1999) 2785-2796 | 10.1088/0264-9381/16/8/315 | KUNS-1551 | gr-qc astro-ph | null | It was recently shown that the metric functions which describe a spherically
symmetric space-time with vanishing radial pressure can be explicitly
integrated. We investigate the nakedness and curvature strength of the
shell-focusing singularity in that space-time. If the singularity is naked, the
relation between the circumferential radius and the Misner-Sharp mass is given
by $R\approx 2y_{0} m^{\beta}$ with $ 1/3<\beta\le 1$ along the first radial
null geodesic from the singularity. The $\beta$ is closely related to the
curvature strength of the naked singularity. For example, for the outgoing or
ingoing null geodesic, if the strong curvature condition (SCC) by Tipler holds,
then $\beta$ must be equal to 1. We define the ``gravity dominance condition''
(GDC) for a geodesic. If GDC is satisfied for the null geodesic, both SCC and
the limiting focusing condition (LFC) by Kr\'olak hold for $\beta=1$ and
$y_{0}\ne 1$, not SCC but only LFC holds for $1/2\le \beta <1$, and neither
holds for $1/3<\beta <1/2$, for the null geodesic. On the other hand, if GDC is
satisfied for the timelike geodesic $r=0$, both SCC and LFC are satisfied for
the timelike geodesic, irrespective of the value of $\beta$. Several examples
are also discussed.
| [
{
"created": "Wed, 28 Apr 1999 05:59:58 GMT",
"version": "v1"
},
{
"created": "Thu, 20 May 1999 08:54:36 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Harada",
"Tomohiro",
""
],
[
"Nakao",
"Ken-ichi",
""
],
[
"Iguchi",
"Hideo",
""
]
] | It was recently shown that the metric functions which describe a spherically symmetric space-time with vanishing radial pressure can be explicitly integrated. We investigate the nakedness and curvature strength of the shell-focusing singularity in that space-time. If the singularity is naked, the relation between the circumferential radius and the Misner-Sharp mass is given by $R\approx 2y_{0} m^{\beta}$ with $ 1/3<\beta\le 1$ along the first radial null geodesic from the singularity. The $\beta$ is closely related to the curvature strength of the naked singularity. For example, for the outgoing or ingoing null geodesic, if the strong curvature condition (SCC) by Tipler holds, then $\beta$ must be equal to 1. We define the ``gravity dominance condition'' (GDC) for a geodesic. If GDC is satisfied for the null geodesic, both SCC and the limiting focusing condition (LFC) by Kr\'olak hold for $\beta=1$ and $y_{0}\ne 1$, not SCC but only LFC holds for $1/2\le \beta <1$, and neither holds for $1/3<\beta <1/2$, for the null geodesic. On the other hand, if GDC is satisfied for the timelike geodesic $r=0$, both SCC and LFC are satisfied for the timelike geodesic, irrespective of the value of $\beta$. Several examples are also discussed. |
1311.3917 | Ignazio Ciufolini | Beatriz Moreno Monge, Rolf Koenig, Grzegorz Michalak, Ignazio
Ciufolini, Antonio Paolozzi, Giampiero Sindoni | Preliminary study for the measurement of the Lense-Thirring effect with
the Galileo satellites | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The precession of the orbital node of a particle orbiting a rotating mass is
known as Lense-Thirring effect (LTE) and is a manifestation of the general
relativistic phenomenon of dragging of inertial frames or frame-dragging. The
LTE has already been measured by using the node drifts of the LAGEOS satellites
and GRACE-based Earth gravity field models with an accuracy of about 10% and
will be improved down to a few percent with the recent LARES experiment. The
Galileo system will provide 27 new node observables for the LTE estimation and
their combination with the LAGEOS and LARES satellites can potentially reduce
even more the error due to the mismodeling in Earth's gravity field. However,
the accurate determination of the Galileo orbits requires the estimation of
many different parameters, which can absorb the LTE on the orbital nodes.
Moreover, the accuracy of the Galileo orbits and hence, of their node drifts,
is mainly limited by the mismodeling in the Solar Radiation Pressure (SRP).
Using simulated data we analyze the effects of the mismodeling in the SRP on
the Galileo nodes and propose optimal orbit parameterizations for the
measurement of the LTE from the future Galileo observations.
| [
{
"created": "Fri, 15 Nov 2013 16:38:57 GMT",
"version": "v1"
}
] | 2013-11-18 | [
[
"Monge",
"Beatriz Moreno",
""
],
[
"Koenig",
"Rolf",
""
],
[
"Michalak",
"Grzegorz",
""
],
[
"Ciufolini",
"Ignazio",
""
],
[
"Paolozzi",
"Antonio",
""
],
[
"Sindoni",
"Giampiero",
""
]
] | The precession of the orbital node of a particle orbiting a rotating mass is known as Lense-Thirring effect (LTE) and is a manifestation of the general relativistic phenomenon of dragging of inertial frames or frame-dragging. The LTE has already been measured by using the node drifts of the LAGEOS satellites and GRACE-based Earth gravity field models with an accuracy of about 10% and will be improved down to a few percent with the recent LARES experiment. The Galileo system will provide 27 new node observables for the LTE estimation and their combination with the LAGEOS and LARES satellites can potentially reduce even more the error due to the mismodeling in Earth's gravity field. However, the accurate determination of the Galileo orbits requires the estimation of many different parameters, which can absorb the LTE on the orbital nodes. Moreover, the accuracy of the Galileo orbits and hence, of their node drifts, is mainly limited by the mismodeling in the Solar Radiation Pressure (SRP). Using simulated data we analyze the effects of the mismodeling in the SRP on the Galileo nodes and propose optimal orbit parameterizations for the measurement of the LTE from the future Galileo observations. |
1504.07476 | Nelson Videla Dr. | Ram\'on Herrera, Nelson Videla, and Marco Olivares | Warm intermediate inflation in the Randall-Sundrum II model in the light
of Planck 2015 and BICEP2 results: A general dissipative coefficient | 26 pages, 3 figures, accepted for publication in the European
Physical Journal C | null | 10.1140/epjc/s10052-015-3433-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A warm inflationary Universe in the Randall-Sundrum II model during
intermediate inflation is studied. For this purpose, we consider a general form
for the dissipative coefficient
$\Gamma(T,\phi)=C_{\phi}\,\frac{T^{m}}{\phi^{m-1}}$, and also analyze this
inflationary model in the weak and strong dissipative regimes. We study the
evolution of the Universe under the slow-roll approximation and find solutions
to the full effective Friedmann equation in the brane-world framework. In order
to constrain the parameters in our model, we consider the recent data from the
BICEP2-Planck 2015 data together with the necessary condition for warm
inflation $T>H$, and also the condition from the weak (or strong) dissipative
regime.
| [
{
"created": "Tue, 28 Apr 2015 13:58:08 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Herrera",
"Ramón",
""
],
[
"Videla",
"Nelson",
""
],
[
"Olivares",
"Marco",
""
]
] | A warm inflationary Universe in the Randall-Sundrum II model during intermediate inflation is studied. For this purpose, we consider a general form for the dissipative coefficient $\Gamma(T,\phi)=C_{\phi}\,\frac{T^{m}}{\phi^{m-1}}$, and also analyze this inflationary model in the weak and strong dissipative regimes. We study the evolution of the Universe under the slow-roll approximation and find solutions to the full effective Friedmann equation in the brane-world framework. In order to constrain the parameters in our model, we consider the recent data from the BICEP2-Planck 2015 data together with the necessary condition for warm inflation $T>H$, and also the condition from the weak (or strong) dissipative regime. |
1012.0644 | Jiliang Jing | Jiliang Jing, Liancheng Wang, Qiyuan Pan, Songbai Chen | Holographic Superconductors in Gauss-Bonnet gravity with Born-Infeld
electrodynamics | 11 pages, 2 figures, 2 tables | Phys.Rev.D83:066010,2011 | 10.1103/PhysRevD.83.066010 | null | gr-qc cond-mat.supr-con hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the holographic superconductors in Gauss-Bonnet gravity with
Born-Infeld electrodynamics. We find that the Gauss-Bonnet constant, the model
parameters and the Born-Infeld coupling parameter will affect the formation of
the scalar hair, the transition point of the phase transition from the second
order to the first order, and the relation connecting the gap frequency in
conductivity with the critical temperature. The combination of the Gauss-Bonnet
gravity and the Born-Infeld electrodynamics provides richer physics in the
phase transition and the condensation of the scalar hair.
| [
{
"created": "Fri, 3 Dec 2010 06:27:32 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Mar 2011 15:17:44 GMT",
"version": "v2"
}
] | 2011-03-22 | [
[
"Jing",
"Jiliang",
""
],
[
"Wang",
"Liancheng",
""
],
[
"Pan",
"Qiyuan",
""
],
[
"Chen",
"Songbai",
""
]
] | We investigate the holographic superconductors in Gauss-Bonnet gravity with Born-Infeld electrodynamics. We find that the Gauss-Bonnet constant, the model parameters and the Born-Infeld coupling parameter will affect the formation of the scalar hair, the transition point of the phase transition from the second order to the first order, and the relation connecting the gap frequency in conductivity with the critical temperature. The combination of the Gauss-Bonnet gravity and the Born-Infeld electrodynamics provides richer physics in the phase transition and the condensation of the scalar hair. |
2306.10487 | Saddam Hussain | Saddam Hussain, Saikat Chakraborty, Nandan Roy, and Kaushik
Bhattacharya | Dynamical Analysis of the Dirac-Born-Infeld type of Tachyon field
minimally coupled with barotropic fluid using EOS parametrization of a field | 5 Pages, 2 figures, Conference proceeding for XXV DAE-BRNS HEP
Symposium 2022 | null | null | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | In this paper, we present a dynamical system analysis of the tachyon dark
energy model by parametrization of the equation of state (EoS) of the dark
energy. The choice of parametrization can constrain the form of the field
potential, and as a result, the theory can be directly constrained from the
observation without assuming a particular form of the potential.
| [
{
"created": "Sun, 18 Jun 2023 06:40:21 GMT",
"version": "v1"
}
] | 2023-06-21 | [
[
"Hussain",
"Saddam",
""
],
[
"Chakraborty",
"Saikat",
""
],
[
"Roy",
"Nandan",
""
],
[
"Bhattacharya",
"Kaushik",
""
]
] | In this paper, we present a dynamical system analysis of the tachyon dark energy model by parametrization of the equation of state (EoS) of the dark energy. The choice of parametrization can constrain the form of the field potential, and as a result, the theory can be directly constrained from the observation without assuming a particular form of the potential. |
2110.00975 | Winfried Zimdahl | Winfried Zimdahl | On the mode structure of imperfect fluids | 11 pages | Cadernos De Astronomia 3 (1) (2022) | 10.47456/Cad.Astro.v3n1.3685. | null | gr-qc astro-ph.CO physics.flu-dyn | http://creativecommons.org/licenses/by/4.0/ | This paper tries to obtain a simple picture of several aspects of the mode
structure in relativistic non-equilibrium thermodynamics. Its pedagogical focus
is on the relation between long-wavelength perturbation modes of the causal
M\"{u}ller-Israel-Stewart (MIS) theory and those of the traditional Eckart
theory. Principally, this issue was clarified in a series of papers by Hiscock
and Lindblom (see [8-10]). Here, I put together some essential features which
do not require the entire formalism of the complete theory.
| [
{
"created": "Sun, 3 Oct 2021 10:41:31 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Feb 2022 09:49:56 GMT",
"version": "v2"
}
] | 2022-02-25 | [
[
"Zimdahl",
"Winfried",
""
]
] | This paper tries to obtain a simple picture of several aspects of the mode structure in relativistic non-equilibrium thermodynamics. Its pedagogical focus is on the relation between long-wavelength perturbation modes of the causal M\"{u}ller-Israel-Stewart (MIS) theory and those of the traditional Eckart theory. Principally, this issue was clarified in a series of papers by Hiscock and Lindblom (see [8-10]). Here, I put together some essential features which do not require the entire formalism of the complete theory. |
2402.14038 | Gholam Hossein Bordbar | Gholam Hossein Bordbar, Mohammad Mazhari and Ahmad Poostforush | Isotropic and anisotropic neutron star structure in 4D Einstein Gauss
Bonnet Gravity | 7 figures and 5 tables | European Physical Journal Plus 139 (2024) 167 | 10.1140/epjp/s13360-024-04959-w | null | gr-qc astro-ph.HE hep-th nucl-th | http://creativecommons.org/licenses/by-nc-nd/4.0/ | With regard to the coupling constant and the strong magnetic field of neutron
stars, we have studied these stars in the 4D Einstein Gauss Bonnet (4D EGB)
gravity model in order to grasp a better understanding of these objects. In
this paper, we have shown that the neutron star properties are considerably
affected by the coupling constant and magnetic field. We have found that as a
consequence of the strong magnetic field and the coupling constant, the maximum
mass and radius of a neutron star are increasing functions of the coupling
constant, while Schwarzschild radius, compactness, surface gravitational
redshift, and Kretschmann scalar are decreasing functions. Additionally, our
study has shown that the physical properties of a magnetized neutron star are
greatly influenced not only by the strong magnetic field, but also by the
anisotropy. Moreover, we have shown that to obtain the hydrostatic equilibrium
configuration of the magnetized material, both the local anisotropy effect and
the anisotropy due to the magnetic field should be considered. Finally, we have
found that in the anisotropic magnetized neutron stars, the maximum mass and
radius do not always increase with increasing the internal magnetic field.
| [
{
"created": "Wed, 21 Feb 2024 06:27:07 GMT",
"version": "v1"
}
] | 2024-02-23 | [
[
"Bordbar",
"Gholam Hossein",
""
],
[
"Mazhari",
"Mohammad",
""
],
[
"Poostforush",
"Ahmad",
""
]
] | With regard to the coupling constant and the strong magnetic field of neutron stars, we have studied these stars in the 4D Einstein Gauss Bonnet (4D EGB) gravity model in order to grasp a better understanding of these objects. In this paper, we have shown that the neutron star properties are considerably affected by the coupling constant and magnetic field. We have found that as a consequence of the strong magnetic field and the coupling constant, the maximum mass and radius of a neutron star are increasing functions of the coupling constant, while Schwarzschild radius, compactness, surface gravitational redshift, and Kretschmann scalar are decreasing functions. Additionally, our study has shown that the physical properties of a magnetized neutron star are greatly influenced not only by the strong magnetic field, but also by the anisotropy. Moreover, we have shown that to obtain the hydrostatic equilibrium configuration of the magnetized material, both the local anisotropy effect and the anisotropy due to the magnetic field should be considered. Finally, we have found that in the anisotropic magnetized neutron stars, the maximum mass and radius do not always increase with increasing the internal magnetic field. |
1109.3012 | Muhammad Sharif | Muhammad Sharif and Ghulam Abbas | Charged Perfect Fluid Cylindrical Gravitational Collapse | 17 pages, 4 figures, accepted for publication in J. Phys. Soc. Jpn | J. Phys. Soc. Jpn. 80(2011)104002 | 10.1143/JPSJ.80.104002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is devoted to study the charged perfect fluid cylindrical
gravitational collapse. For this purpose, we find a new analytical solution of
the field equations for non-static cylindrically symmetric spacetime. We
discuss physical properties of the solution which predict gravitational
collapse. It is concluded that in the presence of electromagnetic field the
outgoing gravitational waves are absent. Further, it turns out that when
longitudinal length reduces to zero due to resultant action of gravity and
electromagnetic field, then the end state of the gravitational collapse is a
conical singularity. We also explore the smooth matching of the collapsing
cylindrical solution to a static cylindrically symmetric solution. In this
matching, we take a special choice of constant radius of the boundary surface.
We conclude that the gravitational and Coulomb forces of the system balance
each other.
| [
{
"created": "Wed, 14 Sep 2011 07:51:03 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Sharif",
"Muhammad",
""
],
[
"Abbas",
"Ghulam",
""
]
] | This paper is devoted to study the charged perfect fluid cylindrical gravitational collapse. For this purpose, we find a new analytical solution of the field equations for non-static cylindrically symmetric spacetime. We discuss physical properties of the solution which predict gravitational collapse. It is concluded that in the presence of electromagnetic field the outgoing gravitational waves are absent. Further, it turns out that when longitudinal length reduces to zero due to resultant action of gravity and electromagnetic field, then the end state of the gravitational collapse is a conical singularity. We also explore the smooth matching of the collapsing cylindrical solution to a static cylindrically symmetric solution. In this matching, we take a special choice of constant radius of the boundary surface. We conclude that the gravitational and Coulomb forces of the system balance each other. |
0801.3874 | Vladimir Dzhunushaliev | V. Dzhunushaliev, V. Folomeev, S. Myrzakul and R. Myrzakulov | Usual and phantom scalar fields in five dimensions: compactification and
flat thick brane solutions | title is changed, new results are added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the model of a gravitating system with two scalar fields (one of which is
phantom), two new types of regular solutions are found: mechanism for
compactification of an extra dimension and a flat thick brane solution. It is
shown that the first model has solutions oscillating over the extra coordinate
and giving a finite radius of compactification of the fifth dimension and the
second model is a flat thick brane embedded in the 5D Minkowski spacetime.
Geometry of both models corresponds to a five-dimensional Minkowski space-time.
Consideration of linear perturbations shows stability of the obtained
solutions.
| [
{
"created": "Fri, 25 Jan 2008 03:30:13 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Oct 2008 16:39:59 GMT",
"version": "v2"
}
] | 2008-10-08 | [
[
"Dzhunushaliev",
"V.",
""
],
[
"Folomeev",
"V.",
""
],
[
"Myrzakul",
"S.",
""
],
[
"Myrzakulov",
"R.",
""
]
] | In the model of a gravitating system with two scalar fields (one of which is phantom), two new types of regular solutions are found: mechanism for compactification of an extra dimension and a flat thick brane solution. It is shown that the first model has solutions oscillating over the extra coordinate and giving a finite radius of compactification of the fifth dimension and the second model is a flat thick brane embedded in the 5D Minkowski spacetime. Geometry of both models corresponds to a five-dimensional Minkowski space-time. Consideration of linear perturbations shows stability of the obtained solutions. |
1903.04339 | Andr\'es Ace\~na | Andr\'es Ace\~na, Ericson L\'opez, and Franklin Ald\'as | Circular geodesics stability in a static black hole in new massive
gravity | 9 pages, no figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the existence and stability of circular geodesics in a family of
asymptotically AdS static black holes in New Massive Gravity. We show that the
existence of such geodesics is determined by the sign of the hair parameter.
For a positive hair parameter the stability regions follow the usual pattern,
with an innermost unstable null geodesic separated from the horizon, followed
by a region of unstable timelike geodesics and then stable timelike geodesics
extending in the asymptotic region.
| [
{
"created": "Mon, 11 Mar 2019 14:51:49 GMT",
"version": "v1"
}
] | 2019-03-12 | [
[
"Aceña",
"Andrés",
""
],
[
"López",
"Ericson",
""
],
[
"Aldás",
"Franklin",
""
]
] | We study the existence and stability of circular geodesics in a family of asymptotically AdS static black holes in New Massive Gravity. We show that the existence of such geodesics is determined by the sign of the hair parameter. For a positive hair parameter the stability regions follow the usual pattern, with an innermost unstable null geodesic separated from the horizon, followed by a region of unstable timelike geodesics and then stable timelike geodesics extending in the asymptotic region. |
2312.10304 | Yiqian Chen | Yiqian Chen, Peng Wang, and Haitang Yang | Interferometric Signatures of Black Holes with Multiple Photon Spheres | 19 pages, 3 figures, references added in revision | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been reported that the photon ring structure in black hole images
produces strong and universal interferometric signatures on long
interferometric baselines, holding promise for measuring black hole parameters
and testing general relativity. This paper investigates the interferometric
signatures of black holes with one or two photon spheres, specifically within
the framework of Einstein-Maxwell-Scalar models. Notably, for black holes
possessing two photon spheres, interference between light rays orbiting the
inner and outer photon spheres manifests as beat signals in the visibility
amplitude, deviating from the universal signatures observed in the
single-photon sphere case.
| [
{
"created": "Sat, 16 Dec 2023 03:43:27 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Jan 2024 08:59:25 GMT",
"version": "v2"
}
] | 2024-01-05 | [
[
"Chen",
"Yiqian",
""
],
[
"Wang",
"Peng",
""
],
[
"Yang",
"Haitang",
""
]
] | It has been reported that the photon ring structure in black hole images produces strong and universal interferometric signatures on long interferometric baselines, holding promise for measuring black hole parameters and testing general relativity. This paper investigates the interferometric signatures of black holes with one or two photon spheres, specifically within the framework of Einstein-Maxwell-Scalar models. Notably, for black holes possessing two photon spheres, interference between light rays orbiting the inner and outer photon spheres manifests as beat signals in the visibility amplitude, deviating from the universal signatures observed in the single-photon sphere case. |
1001.1162 | Amitabha Lahiri | Sourav Bhattacharya and Amitabha Lahiri | On the existence of cosmological event horizon | v2: 7p. title changed, discussions and references added | Class.Quant.Grav.27:165015,2010 | 10.1088/0264-9381/27/16/165015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that, for general static or axisymmetric stationary spacetimes, a
cosmological Killing horizon exists only if $R_{ab}n^{a}n^{b}< 0$ for a
hypersurface orthogonal timelike $n^{a}$, at least over some portion of the
region of interest of the manifold. This implies violation of the strong energy
condition by the matter fields, the simplest example of which is a positive
cosmological constant.
| [
{
"created": "Thu, 7 Jan 2010 21:28:37 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Jun 2010 09:47:39 GMT",
"version": "v2"
}
] | 2010-11-17 | [
[
"Bhattacharya",
"Sourav",
""
],
[
"Lahiri",
"Amitabha",
""
]
] | We show that, for general static or axisymmetric stationary spacetimes, a cosmological Killing horizon exists only if $R_{ab}n^{a}n^{b}< 0$ for a hypersurface orthogonal timelike $n^{a}$, at least over some portion of the region of interest of the manifold. This implies violation of the strong energy condition by the matter fields, the simplest example of which is a positive cosmological constant. |
1807.01731 | Arun Mathew | Arun Mathew and Malay Kumar Nandy | Noncommutative dispersion relation and mass-radius relation of white
dwarfs | 4 figures | null | 10.1088/1674-4527/18/12/151 | null | gr-qc astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The equation of state of the electron degenerate gas in a white dwarf is
usually treated by employing the ideal dispersion relation. However, the effect
of quantum gravity is expected to be inevitably present and when this effect is
considered through a non-commutative formulation, the dispersion relation
undergoes a substantial modification. In this paper, we take such a modified
dispersion relation and find the corresponding equation of state for the
degenerate electron gas in white dwarfs. Hence we solve the equation of
hydrostatic equilibrium and find that this leads to the possibility of the
existence of excessively high values of masses exceeding the Chandrasekhar
limit although the quantum gravity effect is taken to be very small. It is only
when we impose the additional effect of neutronization that we obtain white
dwarfs with masses close to the Chandrasekhar limit with nonzero radii at the
neutronization threshold. We demonstrate these results by giving the numerical
estimates for the masses and radii of $^4He$ and $^{12}C$, and $^{16}O$ white
dwarfs.
| [
{
"created": "Wed, 4 Jul 2018 18:22:48 GMT",
"version": "v1"
}
] | 2019-01-08 | [
[
"Mathew",
"Arun",
""
],
[
"Nandy",
"Malay Kumar",
""
]
] | The equation of state of the electron degenerate gas in a white dwarf is usually treated by employing the ideal dispersion relation. However, the effect of quantum gravity is expected to be inevitably present and when this effect is considered through a non-commutative formulation, the dispersion relation undergoes a substantial modification. In this paper, we take such a modified dispersion relation and find the corresponding equation of state for the degenerate electron gas in white dwarfs. Hence we solve the equation of hydrostatic equilibrium and find that this leads to the possibility of the existence of excessively high values of masses exceeding the Chandrasekhar limit although the quantum gravity effect is taken to be very small. It is only when we impose the additional effect of neutronization that we obtain white dwarfs with masses close to the Chandrasekhar limit with nonzero radii at the neutronization threshold. We demonstrate these results by giving the numerical estimates for the masses and radii of $^4He$ and $^{12}C$, and $^{16}O$ white dwarfs. |
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