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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2310.06321 | Alvin Chua | Ruiting Mao, Jeong Eun Lee, Ollie Burke, Alvin J. K. Chua, Matthew C.
Edwards, Renate Meyer | Calibrating approximate Bayesian credible intervals of
gravitational-wave parameters | 24 pages, 12 figures | Phys. Rev. D 109, 083002 (2024) | 10.1103/PhysRevD.109.083002 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Approximations are commonly employed in realistic applications of scientific
Bayesian inference, often due to convenience if not necessity. In the field of
gravitational-wave (GW) data analysis, fast-to-evaluate but approximate
waveform models of astrophysical GW signals are sometimes used in lieu of more
accurate models to infer properties of a true GW signal buried within detector
noise. In addition, a Fisher-information-based normal approximation to the
posterior distribution can also be used to conduct inference in bulk, without
the need for extensive numerical calculations such as Markov chain Monte Carlo
(MCMC) simulations. Such approximations can generally lead to an inaccurate
posterior distribution with poor statistical coverage of the true posterior. In
this article, we present a novel calibration procedure that calibrates the
credible sets for a family of approximate posterior distributions, to ensure
coverage of the true posterior at a level specified by the analyst. Tools such
as autoencoders and artificial neural networks are used within our calibration
model to compress the data (for efficiency) and to perform tasks such as
logistic regression. As a proof of principle, we demonstrate our formalism on
the GW signal from a high-mass binary black hole merger, a promising source for
the near-future space-based GW observatory LISA.
| [
{
"created": "Tue, 10 Oct 2023 05:33:08 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Jan 2024 04:14:16 GMT",
"version": "v2"
}
] | 2024-04-03 | [
[
"Mao",
"Ruiting",
""
],
[
"Lee",
"Jeong Eun",
""
],
[
"Burke",
"Ollie",
""
],
[
"Chua",
"Alvin J. K.",
""
],
[
"Edwards",
"Matthew C.",
""
],
[
"Meyer",
"Renate",
""
]
] | Approximations are commonly employed in realistic applications of scientific Bayesian inference, often due to convenience if not necessity. In the field of gravitational-wave (GW) data analysis, fast-to-evaluate but approximate waveform models of astrophysical GW signals are sometimes used in lieu of more accurate models to infer properties of a true GW signal buried within detector noise. In addition, a Fisher-information-based normal approximation to the posterior distribution can also be used to conduct inference in bulk, without the need for extensive numerical calculations such as Markov chain Monte Carlo (MCMC) simulations. Such approximations can generally lead to an inaccurate posterior distribution with poor statistical coverage of the true posterior. In this article, we present a novel calibration procedure that calibrates the credible sets for a family of approximate posterior distributions, to ensure coverage of the true posterior at a level specified by the analyst. Tools such as autoencoders and artificial neural networks are used within our calibration model to compress the data (for efficiency) and to perform tasks such as logistic regression. As a proof of principle, we demonstrate our formalism on the GW signal from a high-mass binary black hole merger, a promising source for the near-future space-based GW observatory LISA. |
0910.5818 | Giacomo Tommei | G. Tommei, A. Milani, D. Vokrouhlicky | Light-time computations for the BepiColombo radioscience experiment | 14 pages, 7 figures, corrected references | null | 10.1007/s10569-010-9273-7 | null | gr-qc astro-ph.EP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The radioscience experiment is one of the on board experiment of the Mercury
ESA mission BepiColombo that will be launched in 2014. The goals of the
experiment are to determine the gravity field of Mercury and its rotation
state, to determine the orbit of Mercury, to constrain the possible theories of
gravitation (for example by determining the post-Newtonian (PN) parameters), to
provide the spacecraft position for geodesy experiments and to contribute to
planetary ephemerides improvement. This is possible thanks to a new technology
which allows to reach great accuracies in the observables range and range rate;
it is well known that a similar level of accuracy requires studying a suitable
model taking into account numerous relativistic effects. In this paper we deal
with the modelling of the space-time coordinate transformations needed for the
light-time computations and the numerical methods adopted to avoid rounding-off
errors in such computations.
| [
{
"created": "Fri, 30 Oct 2009 09:21:07 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Nov 2009 08:55:14 GMT",
"version": "v2"
}
] | 2015-05-14 | [
[
"Tommei",
"G.",
""
],
[
"Milani",
"A.",
""
],
[
"Vokrouhlicky",
"D.",
""
]
] | The radioscience experiment is one of the on board experiment of the Mercury ESA mission BepiColombo that will be launched in 2014. The goals of the experiment are to determine the gravity field of Mercury and its rotation state, to determine the orbit of Mercury, to constrain the possible theories of gravitation (for example by determining the post-Newtonian (PN) parameters), to provide the spacecraft position for geodesy experiments and to contribute to planetary ephemerides improvement. This is possible thanks to a new technology which allows to reach great accuracies in the observables range and range rate; it is well known that a similar level of accuracy requires studying a suitable model taking into account numerous relativistic effects. In this paper we deal with the modelling of the space-time coordinate transformations needed for the light-time computations and the numerical methods adopted to avoid rounding-off errors in such computations. |
1704.05945 | Vasilis Oikonomou | S. Nojiri, S.D. Odintsov, V.K. Oikonomou | Constant-roll Inflation in $F(R)$ Gravity | CQG accepted | null | 10.1088/1361-6382/aa92a4 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose the study of constant-roll inflation in $F(R)$ gravity. We use two
different approaches, one that relates an $F(R)$ gravity to well known scalar
models of constant-roll and a second that examines directly the constant-roll
condition in $F(R)$ gravity. With regards to the first approach, by using well
known techniques, we find the $F(R)$ gravity which realizes a given
constant-roll evolution in the scalar-tensor theory. We also perform a
conformal transformation in the resulting $F(R)$ gravity and we find the
Einstein frame counterpart theory. As we demonstrate, the resulting scalar
potential is different in comparison to the original scalar constant-roll case,
and the same applies for the corresponding observational indices. Moreover, we
discuss how cosmological evolutions that can realize constant-roll to
constant-roll eras transitions in the scalar-tensor description, can be
realized by vacuum $F(R)$ gravity. With regards to the second approach, we
examine directly the effects of the constant-roll condition on the inflationary
dynamics of vacuum $F(R)$ gravity. We present in detail the formalism of
constant-roll $F(R)$ gravity inflationary dynamics and we discuss how the
inflationary indices become in this case. We use two well known $F(R)$
gravities in order to illustrate our findings, the $R^2$ model and a power-law
$F(R)$ gravity in vacuum. As we demonstrate, in both cases the parameter space
is enlarged in comparison to the slow-roll counterparts of the models, and in
effect, the models can also be compatible with the observational data. Finally,
we briefly address the graceful exit issue.
| [
{
"created": "Wed, 19 Apr 2017 22:13:21 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Jun 2017 18:35:12 GMT",
"version": "v2"
},
{
"created": "Wed, 11 Oct 2017 20:34:09 GMT",
"version": "v3"
}
] | 2017-12-06 | [
[
"Nojiri",
"S.",
""
],
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | We propose the study of constant-roll inflation in $F(R)$ gravity. We use two different approaches, one that relates an $F(R)$ gravity to well known scalar models of constant-roll and a second that examines directly the constant-roll condition in $F(R)$ gravity. With regards to the first approach, by using well known techniques, we find the $F(R)$ gravity which realizes a given constant-roll evolution in the scalar-tensor theory. We also perform a conformal transformation in the resulting $F(R)$ gravity and we find the Einstein frame counterpart theory. As we demonstrate, the resulting scalar potential is different in comparison to the original scalar constant-roll case, and the same applies for the corresponding observational indices. Moreover, we discuss how cosmological evolutions that can realize constant-roll to constant-roll eras transitions in the scalar-tensor description, can be realized by vacuum $F(R)$ gravity. With regards to the second approach, we examine directly the effects of the constant-roll condition on the inflationary dynamics of vacuum $F(R)$ gravity. We present in detail the formalism of constant-roll $F(R)$ gravity inflationary dynamics and we discuss how the inflationary indices become in this case. We use two well known $F(R)$ gravities in order to illustrate our findings, the $R^2$ model and a power-law $F(R)$ gravity in vacuum. As we demonstrate, in both cases the parameter space is enlarged in comparison to the slow-roll counterparts of the models, and in effect, the models can also be compatible with the observational data. Finally, we briefly address the graceful exit issue. |
0909.2490 | Jiliang Jing | Chikun Ding, Songbai Chen, Jiliang Jing | Dynamical evolution of scalar perturbation in Ho\v{r}ava-Lifshitz
black-hole spacetimes | 14 pages, 5 figures | Phys.Rev.D81:024028,2010 | 10.1103/PhysRevD.81.024028 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the dynamical evolution of a massless scalar perturbation in the
Ho\v{r}ava-Lifshitz black-hole spacetimes with the coupling constants
$\lambda={1/3}$, $\lambda={1/2}$ and $\lambda=3$, respectively. Our calculation
shows that, for the three cases, the scalar perturbations decay without any
oscillation in which the decay rate imprints the parameter of the
Ho\v{r}ava-Lifshitz black hole. The results are quite different from those in
the Schwarzschild AdS black hole and can help us understand more about the
Ho\v{r}ava-Lifshitz gravity.
| [
{
"created": "Mon, 14 Sep 2009 09:03:38 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Ding",
"Chikun",
""
],
[
"Chen",
"Songbai",
""
],
[
"Jing",
"Jiliang",
""
]
] | We study the dynamical evolution of a massless scalar perturbation in the Ho\v{r}ava-Lifshitz black-hole spacetimes with the coupling constants $\lambda={1/3}$, $\lambda={1/2}$ and $\lambda=3$, respectively. Our calculation shows that, for the three cases, the scalar perturbations decay without any oscillation in which the decay rate imprints the parameter of the Ho\v{r}ava-Lifshitz black hole. The results are quite different from those in the Schwarzschild AdS black hole and can help us understand more about the Ho\v{r}ava-Lifshitz gravity. |
gr-qc/0110116 | Lorenzo Iorio | Lorenzo Iorio | Is it possible to test directly General Relativity in the gravitational
field of the Moon? | Latex2e, 7 pages, no figures, ets2000.cls and art12.sty used. Major
rewriting in introduction. References added | Class.Quant.Grav. 19 (2002) 2393-2398 | 10.1088/0264-9381/19/9/305 | null | gr-qc astro-ph | null | In this paper the possibility of measuring some general relativistic effects
in the gravitational field of the Moon via selenodetic missions, with
particular emphasis to the future Japanese SELENE mission, is investigated. For
a typical selenodetic orbital configuration the post-Newtonian Lense-Thirring
gravitomagnetic and the Einstein's gravitoelectric effects on the satellites
orbits are calculated and compared to the present-day orbit accuracy of lunar
missions. It turns out that for SELENE's Main Orbiter, at present, the
gravitoelectric periselenium shift, which is the largest general relativistic
effect, is 1 or 2 orders of magnitude smaller than the experimental
sensitivity. The systematic error induced by the mismodelled classical
periselenium precession due to the first even zonal harmonic J2 of the Moon's
non-spherical gravitational potential is 3 orders of magnitude larger than the
general relativistic gravitoelectric precession. The estimates of this work
could be used for future lunar missions having as their goals relativistic
measurements as well.
| [
{
"created": "Fri, 26 Oct 2001 14:08:10 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Oct 2001 22:28:20 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Feb 2002 18:43:21 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Iorio",
"Lorenzo",
""
]
] | In this paper the possibility of measuring some general relativistic effects in the gravitational field of the Moon via selenodetic missions, with particular emphasis to the future Japanese SELENE mission, is investigated. For a typical selenodetic orbital configuration the post-Newtonian Lense-Thirring gravitomagnetic and the Einstein's gravitoelectric effects on the satellites orbits are calculated and compared to the present-day orbit accuracy of lunar missions. It turns out that for SELENE's Main Orbiter, at present, the gravitoelectric periselenium shift, which is the largest general relativistic effect, is 1 or 2 orders of magnitude smaller than the experimental sensitivity. The systematic error induced by the mismodelled classical periselenium precession due to the first even zonal harmonic J2 of the Moon's non-spherical gravitational potential is 3 orders of magnitude larger than the general relativistic gravitoelectric precession. The estimates of this work could be used for future lunar missions having as their goals relativistic measurements as well. |
1502.03988 | Yashar Akrami | Henrik Nersisyan, Yashar Akrami, Luca Amendola | Consistent metric combinations in cosmology of massive bigravity | 17 pages, no figures. Version published in PRD | Phys. Rev. D 92, 104034 (2015) | 10.1103/PhysRevD.92.104034 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Massive bigravity models are interesting alternatives to standard cosmology.
In most cases, however, these models have been studied for a simplified
scenario in which both metrics take homogeneous and isotropic forms
[Friedmann-Lema\^itre-Robertson-Walker (FLRW)] with the same spatial
curvatures. The interest to consider more general geometries arises, in
particular, in view of the difficulty so far encountered in building stable
cosmological solutions with homogeneous and isotropic metrics. Here we consider
a number of cases in which the two metrics take more general forms, namely FLRW
with different spatial curvatures---Lema\^itre, Lema\^itre-Tolman-Bondi (LTB),
and Bianchi I---as well as cases where only one metric is linearly perturbed.
We discuss possible consistent combinations and find that only some special
cases of FLRW--Lema\^itre, LTB--LTB, and FLRW--Bianchi I combinations give
consistent, nontrivial solutions.
| [
{
"created": "Fri, 13 Feb 2015 13:50:28 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Apr 2015 15:50:17 GMT",
"version": "v2"
},
{
"created": "Sat, 7 Nov 2015 22:14:02 GMT",
"version": "v3"
}
] | 2015-11-18 | [
[
"Nersisyan",
"Henrik",
""
],
[
"Akrami",
"Yashar",
""
],
[
"Amendola",
"Luca",
""
]
] | Massive bigravity models are interesting alternatives to standard cosmology. In most cases, however, these models have been studied for a simplified scenario in which both metrics take homogeneous and isotropic forms [Friedmann-Lema\^itre-Robertson-Walker (FLRW)] with the same spatial curvatures. The interest to consider more general geometries arises, in particular, in view of the difficulty so far encountered in building stable cosmological solutions with homogeneous and isotropic metrics. Here we consider a number of cases in which the two metrics take more general forms, namely FLRW with different spatial curvatures---Lema\^itre, Lema\^itre-Tolman-Bondi (LTB), and Bianchi I---as well as cases where only one metric is linearly perturbed. We discuss possible consistent combinations and find that only some special cases of FLRW--Lema\^itre, LTB--LTB, and FLRW--Bianchi I combinations give consistent, nontrivial solutions. |
2204.03091 | Derek Davis | Derek Davis, Max Trevor, Simone Mozzon, Laura K. Nuttall | Incorporating information from LIGO data quality streams into the PyCBC
search for gravitational waves | 14 pages, 5 figures | null | 10.1103/PhysRevD.106.102006 | LIGO-P2200078 | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new method which accounts for changes in the properties of
gravitational-wave detector noise over time in the PyCBC search for
gravitational waves from compact binary coalescences. We use information from
LIGO data quality streams that monitor the status of each detector and its
environment to model changes in the rate of noise in each detector. These data
quality streams allow candidates identified in the data during periods of
detector malfunctions to be more efficiently rejected as noise. This method
allows data from machine learning predictions of the detector state to be
included as part of the PyCBC search, increasing the the total number of
detectable gravitational-wave signals by up to 5%. When both machine learning
classifications and manually-generated flags are used to search data from
LIGO-Virgo's third observing run, the total number of detectable
gravitational-wave signals is increased by up to 20% compared to not using any
data quality streams. We also show how this method is flexible enough to
include information from large numbers of additional arbitrary data streams
that may be able to further increase the sensitivity of the search.
| [
{
"created": "Wed, 6 Apr 2022 21:10:10 GMT",
"version": "v1"
}
] | 2022-12-07 | [
[
"Davis",
"Derek",
""
],
[
"Trevor",
"Max",
""
],
[
"Mozzon",
"Simone",
""
],
[
"Nuttall",
"Laura K.",
""
]
] | We present a new method which accounts for changes in the properties of gravitational-wave detector noise over time in the PyCBC search for gravitational waves from compact binary coalescences. We use information from LIGO data quality streams that monitor the status of each detector and its environment to model changes in the rate of noise in each detector. These data quality streams allow candidates identified in the data during periods of detector malfunctions to be more efficiently rejected as noise. This method allows data from machine learning predictions of the detector state to be included as part of the PyCBC search, increasing the the total number of detectable gravitational-wave signals by up to 5%. When both machine learning classifications and manually-generated flags are used to search data from LIGO-Virgo's third observing run, the total number of detectable gravitational-wave signals is increased by up to 20% compared to not using any data quality streams. We also show how this method is flexible enough to include information from large numbers of additional arbitrary data streams that may be able to further increase the sensitivity of the search. |
0707.1066 | Max Chaves | Max Chaves | The quantization of gravity and the vacuum energy of quantum fields | 18 pages & no figures | null | null | null | gr-qc hep-th | null | We construct a unified covariant derivative that contains the sum of an
affine connection and a Yang-Mills field. With it we construct a lagrangian
that is invariant both under diffeomorphisms and Yang-Mills gauge
transformations. We assume that metric and symmetric affine connection are
independent quantities, and make the observation that the metric must be able
to generate curvature, just as the connection, so there should be an extra
tensor similar to Riemann's in the equations but constructed from metrics and
not connections. We find the equations generated by the lagrangian and
introduce the huge natural scale due to the vacuum energy of quantum fields.
This scale allows for a perturbative solution of the equations of motion. We
prove the system has a vacuum state that forces the metricity of the metric and
results in General Relativity for low energies. The vacuum energy of the
quantum fields cancels, becoming unobservable. At very high energies, the
metric does not appear differentiated in the lagrangian and so it is not a
quantum field, just a background classical field. The true quantum fields are
the connections. The theory becomes very similar to a Yang-Mills, with affine
connections taking the place of Yang-Mills vector fields. It should be
renormalizable since it has a coupling constant with no units and correct
propagators after fixing the gauge (diffeomorphisms). The weakness of gravity
turns out to be due to the large vacuum energy of the quantum fields.
| [
{
"created": "Mon, 9 Jul 2007 14:35:27 GMT",
"version": "v1"
}
] | 2007-07-10 | [
[
"Chaves",
"Max",
""
]
] | We construct a unified covariant derivative that contains the sum of an affine connection and a Yang-Mills field. With it we construct a lagrangian that is invariant both under diffeomorphisms and Yang-Mills gauge transformations. We assume that metric and symmetric affine connection are independent quantities, and make the observation that the metric must be able to generate curvature, just as the connection, so there should be an extra tensor similar to Riemann's in the equations but constructed from metrics and not connections. We find the equations generated by the lagrangian and introduce the huge natural scale due to the vacuum energy of quantum fields. This scale allows for a perturbative solution of the equations of motion. We prove the system has a vacuum state that forces the metricity of the metric and results in General Relativity for low energies. The vacuum energy of the quantum fields cancels, becoming unobservable. At very high energies, the metric does not appear differentiated in the lagrangian and so it is not a quantum field, just a background classical field. The true quantum fields are the connections. The theory becomes very similar to a Yang-Mills, with affine connections taking the place of Yang-Mills vector fields. It should be renormalizable since it has a coupling constant with no units and correct propagators after fixing the gauge (diffeomorphisms). The weakness of gravity turns out to be due to the large vacuum energy of the quantum fields. |
1902.06356 | Chandrima Ganguly | Chandrima Ganguly, Marco Bruni | Quasi-isotropic cycles and non-singular bounces in a Mixmaster cosmology | 5 pages, 4 figures | Phys. Rev. Lett. 123, 201301 (2019) | 10.1103/PhysRevLett.123.201301 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A Bianchi IX Mixmaster spacetime is the most general spatially homogeneous
solution of Einstein's equations and it can represent the space-averaged
Universe. We introduce two novel mechanisms resulting in a Mixmaster Universe
with non-singular bounces which are quasi-isotropic. A fluid with a non-linear
equation of state allows non-singular bounces. Using negative anisotropic
stresses successfully isotropises this Universe and mitigates the well known
Mixmaster chaotic behaviour. Thus the Universe can be an eternal Mixmaster,
going through an infinite series of different cycles separated by bounces, with
a sizable fraction of cycles isotropic enough to be well approximated by a
standard Friedmann-Lema\^itre-Robertson-Walker model from the radiation era
onward.
| [
{
"created": "Mon, 18 Feb 2019 00:08:31 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Mar 2019 00:39:01 GMT",
"version": "v2"
}
] | 2019-11-20 | [
[
"Ganguly",
"Chandrima",
""
],
[
"Bruni",
"Marco",
""
]
] | A Bianchi IX Mixmaster spacetime is the most general spatially homogeneous solution of Einstein's equations and it can represent the space-averaged Universe. We introduce two novel mechanisms resulting in a Mixmaster Universe with non-singular bounces which are quasi-isotropic. A fluid with a non-linear equation of state allows non-singular bounces. Using negative anisotropic stresses successfully isotropises this Universe and mitigates the well known Mixmaster chaotic behaviour. Thus the Universe can be an eternal Mixmaster, going through an infinite series of different cycles separated by bounces, with a sizable fraction of cycles isotropic enough to be well approximated by a standard Friedmann-Lema\^itre-Robertson-Walker model from the radiation era onward. |
2407.21649 | Francisco Lobo | Ednaldo L. B. Junior, Jos\'e Tarciso S. S. Junior, Francisco S. N.
Lobo, Manuel E. Rodrigues, Diego Rubiera-Garcia, Lu\'is F. Dias da Silva,
Henrique A. Vieira | Black bounces in Cotton gravity | 14 pages, 6 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, J. Harada proposed a theory relating gravity to the Cotton tensor,
dubbed as ''Cotton gravity'' (CG). This is an extension of General Relativity
such that every solution of the latter turns out to be a solution of the former
(but the converse is not true) and, furthermore, it is possible to derive the
cosmological constant as an integration constant within it. In this work we
investigate CG by coupling it to both non-linear electrodynamics (NLED) and
scalar fields. We study static and spherically symmetric solutions implementing
a bouncing behaviour in the radial function so as to avoid the development of
singularities, inspired by the Simpson-Visser black bounce and the Bardeen
model, both interpreted as magnetic monopoles. We identify the NLED Lagrangian
density and the scalar field potential generating such solutions, and
investigate the corresponding gravitational configurations in terms of
horizons, behaviour of the metric functions, and regularity of the Kretchsman
curvature scalar. Our analysis extends the class of non-singular geometries
found in the literature and paves the ground for further analysis of black
holes in CG.
| [
{
"created": "Wed, 31 Jul 2024 14:50:49 GMT",
"version": "v1"
}
] | 2024-08-01 | [
[
"Junior",
"Ednaldo L. B.",
""
],
[
"Junior",
"José Tarciso S. S.",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Rodrigues",
"Manuel E.",
""
],
[
"Rubiera-Garcia",
"Diego",
""
],
[
"da Silva",
"Luís F. Dias",
""
],
[
"Vieira",
"Henrique A.",
""
]
] | Recently, J. Harada proposed a theory relating gravity to the Cotton tensor, dubbed as ''Cotton gravity'' (CG). This is an extension of General Relativity such that every solution of the latter turns out to be a solution of the former (but the converse is not true) and, furthermore, it is possible to derive the cosmological constant as an integration constant within it. In this work we investigate CG by coupling it to both non-linear electrodynamics (NLED) and scalar fields. We study static and spherically symmetric solutions implementing a bouncing behaviour in the radial function so as to avoid the development of singularities, inspired by the Simpson-Visser black bounce and the Bardeen model, both interpreted as magnetic monopoles. We identify the NLED Lagrangian density and the scalar field potential generating such solutions, and investigate the corresponding gravitational configurations in terms of horizons, behaviour of the metric functions, and regularity of the Kretchsman curvature scalar. Our analysis extends the class of non-singular geometries found in the literature and paves the ground for further analysis of black holes in CG. |
1304.6492 | Andrzej Okolow | Andrzej Okolow | Kinematic quantum states for the Teleparallel Equivalent of General
Relativity | 41 pages, no figures, Latex2e | Gen. Rel. Grav. 46:1653 (2014) | 10.1007/s10714-013-1653-3 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A space of kinematic quantum states for the Teleparallel Equivalent of
General Relativity is constructed by means of projective techniques. The states
are kinematic in this sense that their construction bases merely on the
structure of the phase space of the theory and does not take into account
constraints on it. The space of quantum states is meant to serve as an element
of a canonical quantization of the theory.
| [
{
"created": "Wed, 24 Apr 2013 07:24:34 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Jul 2014 15:03:05 GMT",
"version": "v2"
}
] | 2014-07-15 | [
[
"Okolow",
"Andrzej",
""
]
] | A space of kinematic quantum states for the Teleparallel Equivalent of General Relativity is constructed by means of projective techniques. The states are kinematic in this sense that their construction bases merely on the structure of the phase space of the theory and does not take into account constraints on it. The space of quantum states is meant to serve as an element of a canonical quantization of the theory. |
gr-qc/0604088 | Christopher Eling | Christopher Eling and Ted Jacobson | Black Holes in Einstein-Aether Theory | 22 pages, 6 figures; v2: minor editing; v3: corrected overall sign in
twist formula and an error in the equation for the aether stress tensor.
Results unchanged since correct form was used in calculations; v4: corrected
minor typo | Class.Quant.Grav.23:5643-5660,2006; Erratum-ibid.27:049802,2010 | 10.1088/0264-9381/23/18/009 10.1088/0264-9381/27/4/049802 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study black hole solutions in general relativity coupled to a unit
timelike vector field dubbed the "aether". To be causally isolated a black hole
interior must trap matter fields as well as all aether and metric modes. The
theory possesses spin-0, spin-1, and spin-2 modes whose speeds depend on four
coupling coefficients. We find that the full three-parameter family of local
spherically symmetric static solutions is always regular at a metric horizon,
but only a two-parameter subset is regular at a spin-0 horizon. Asymptotic
flatness imposes another condition, leaving a one-parameter family of regular
black holes. These solutions are compared to the Schwarzschild solution using
numerical integration for a special class of coupling coefficients. They are
very close to Schwarzschild outside the horizon for a wide range of couplings,
and have a spacelike singularity inside, but differ inside quantitatively. Some
quantities constructed from the metric and aether oscillate in the interior as
the singularity is approached. The aether is at rest at spatial infinity and
flows into the black hole, but differs significantly from the the 4-velocity of
freely-falling geodesics.
| [
{
"created": "Thu, 20 Apr 2006 19:49:09 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Aug 2006 20:17:20 GMT",
"version": "v2"
},
{
"created": "Sun, 6 Dec 2009 14:52:16 GMT",
"version": "v3"
},
{
"created": "Sun, 28 Mar 2010 12:58:03 GMT",
"version": "v4"
}
] | 2010-03-30 | [
[
"Eling",
"Christopher",
""
],
[
"Jacobson",
"Ted",
""
]
] | We study black hole solutions in general relativity coupled to a unit timelike vector field dubbed the "aether". To be causally isolated a black hole interior must trap matter fields as well as all aether and metric modes. The theory possesses spin-0, spin-1, and spin-2 modes whose speeds depend on four coupling coefficients. We find that the full three-parameter family of local spherically symmetric static solutions is always regular at a metric horizon, but only a two-parameter subset is regular at a spin-0 horizon. Asymptotic flatness imposes another condition, leaving a one-parameter family of regular black holes. These solutions are compared to the Schwarzschild solution using numerical integration for a special class of coupling coefficients. They are very close to Schwarzschild outside the horizon for a wide range of couplings, and have a spacelike singularity inside, but differ inside quantitatively. Some quantities constructed from the metric and aether oscillate in the interior as the singularity is approached. The aether is at rest at spatial infinity and flows into the black hole, but differs significantly from the the 4-velocity of freely-falling geodesics. |
2403.04827 | Pablo Antonio Cano Molina-Ni\~nirola | Pablo Bueno, Pablo A. Cano, Robie A. Hennigar | Regular Black Holes From Pure Gravity | 5 pages+appendix, 1 figure; v2: references added. Version sent to the
journal | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show via an explicit construction how an infinite tower of
higher-curvature corrections generically leads to a resolution of the
Schwarzschild singularity in any spacetime dimension $D \ge 5$. The theories we
consider have two key properties that ensure the results are general and
robust: (1) they provide a basis for (vacuum) gravitational effective field
theory in five and higher-dimensions, (2) for each value of the mass, they have
a unique static spherically symmetric solution. We present several exact
solutions of the theories that include the Hayward black hole and metrics
similar to the Bardeen and Dymnikova ones. Unlike previous constructions, these
regular black holes arise as vacuum solutions, as we include no matter fields
whatsoever in our analysis. We show how the black hole thermodynamics can be
studied in a completely universal and unambiguous way for all solutions.
| [
{
"created": "Thu, 7 Mar 2024 19:00:01 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Mar 2024 14:31:07 GMT",
"version": "v2"
}
] | 2024-03-20 | [
[
"Bueno",
"Pablo",
""
],
[
"Cano",
"Pablo A.",
""
],
[
"Hennigar",
"Robie A.",
""
]
] | We show via an explicit construction how an infinite tower of higher-curvature corrections generically leads to a resolution of the Schwarzschild singularity in any spacetime dimension $D \ge 5$. The theories we consider have two key properties that ensure the results are general and robust: (1) they provide a basis for (vacuum) gravitational effective field theory in five and higher-dimensions, (2) for each value of the mass, they have a unique static spherically symmetric solution. We present several exact solutions of the theories that include the Hayward black hole and metrics similar to the Bardeen and Dymnikova ones. Unlike previous constructions, these regular black holes arise as vacuum solutions, as we include no matter fields whatsoever in our analysis. We show how the black hole thermodynamics can be studied in a completely universal and unambiguous way for all solutions. |
2209.09241 | Khalil El Bourakadi | K. El Bourakadi, Z. Sakhi and M. Bennai | Preheating constraints in $\alpha$-attractor inflation and Gravitational
Waves production | arXiv admin note: text overlap with arXiv:2209.08581 | null | 10.1142/S0217751X22501172 | International Journal of Modern Physics AVol. 37, No. 17, 2250117
(2022) | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a scenario where preheating occurs for a specific duration that is
parametrized by an e-folds number $N_{pre}$, our results suggest a direct
correlation between the preheating duration and the density of gravitational
waves (GWs) produced during this phase. Moreover, we investigate the
consequences of the inflationary parameters on the $\alpha$-attractor E model
in the small $\alpha$ limits. In this framework, we perform investigations on
the preheating parameters involving the number of e-folds $N_{pre}$, and the
temperature of reheating $T_{re}$, then we show that the parameter $n$
associated with the E model of $\alpha$-attractor inflation has a negligible
effect on the preheating duration, and we demonstrate that gravitational wave
generation during preheating satisfies the restrictions from Planck's recent
data.
| [
{
"created": "Sun, 18 Sep 2022 15:22:56 GMT",
"version": "v1"
}
] | 2022-09-21 | [
[
"Bourakadi",
"K. El",
""
],
[
"Sakhi",
"Z.",
""
],
[
"Bennai",
"M.",
""
]
] | We propose a scenario where preheating occurs for a specific duration that is parametrized by an e-folds number $N_{pre}$, our results suggest a direct correlation between the preheating duration and the density of gravitational waves (GWs) produced during this phase. Moreover, we investigate the consequences of the inflationary parameters on the $\alpha$-attractor E model in the small $\alpha$ limits. In this framework, we perform investigations on the preheating parameters involving the number of e-folds $N_{pre}$, and the temperature of reheating $T_{re}$, then we show that the parameter $n$ associated with the E model of $\alpha$-attractor inflation has a negligible effect on the preheating duration, and we demonstrate that gravitational wave generation during preheating satisfies the restrictions from Planck's recent data. |
1110.3973 | W. M. Stuckey | W.M. Stuckey, T.J. McDevitt and M. Silberstein | Modified Regge calculus as an explanation of dark energy | 15 pages text, 6 figures. Revised as accepted for publication in
Class. Quant. Grav | Classical & Quantum Gravity 29, 055015 (2012) | 10.1088/0264-9381/29/5/055015 | null | gr-qc astro-ph.CO quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using Regge calculus, we construct a Regge differential equation for the time
evolution of the scale factor $a(t)$ in the Einstein-de Sitter cosmology model
(EdS). We propose two modifications to the Regge calculus approach: 1) we allow
the graphical links on spatial hypersurfaces to be large, as in direct particle
interaction when the interacting particles reside in different galaxies, and 2)
we assume luminosity distance $D_L$ is related to graphical proper distance
$D_p$ by the equation $D_L = (1+z)\sqrt{\overrightarrow{D_p}\cdot
\overrightarrow{D_p}}$, where the inner product can differ from its usual
trivial form. The modified Regge calculus model (MORC), EdS and $\Lambda$CDM
are compared using the data from the Union2 Compilation, i.e., distance moduli
and redshifts for type Ia supernovae. We find that a best fit line through
$\displaystyle \log{(\frac{D_L}{Gpc})}$ versus $\log{z}$ gives a correlation of
0.9955 and a sum of squares error (SSE) of 1.95. By comparison, the best fit
$\Lambda$CDM gives SSE = 1.79 using $H_o$ = 69.2 km/s/Mpc, $\Omega_{M}$ = 0.29
and $\Omega_{\Lambda}$ = 0.71. The best fit EdS gives SSE = 2.68 using $H_o$ =
60.9 km/s/Mpc. The best fit MORC gives SSE = 1.77 and $H_o$ = 73.9 km/s/Mpc
using $R = A^{-1}$ = 8.38 Gcy and $m = 1.71\times 10^{52}$ kg, where $R$ is the
current graphical proper distance between nodes, $A^{-1}$ is the scaling factor
from our non-trival inner product, and $m$ is the nodal mass. Thus, MORC
improves EdS as well as $\Lambda$CDM in accounting for distance moduli and
redshifts for type Ia supernovae without having to invoke accelerated
expansion, i.e., there is no dark energy and the universe is always
decelerating.
| [
{
"created": "Mon, 17 Oct 2011 18:55:38 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Jan 2012 14:59:14 GMT",
"version": "v2"
}
] | 2015-05-30 | [
[
"Stuckey",
"W. M.",
""
],
[
"McDevitt",
"T. J.",
""
],
[
"Silberstein",
"M.",
""
]
] | Using Regge calculus, we construct a Regge differential equation for the time evolution of the scale factor $a(t)$ in the Einstein-de Sitter cosmology model (EdS). We propose two modifications to the Regge calculus approach: 1) we allow the graphical links on spatial hypersurfaces to be large, as in direct particle interaction when the interacting particles reside in different galaxies, and 2) we assume luminosity distance $D_L$ is related to graphical proper distance $D_p$ by the equation $D_L = (1+z)\sqrt{\overrightarrow{D_p}\cdot \overrightarrow{D_p}}$, where the inner product can differ from its usual trivial form. The modified Regge calculus model (MORC), EdS and $\Lambda$CDM are compared using the data from the Union2 Compilation, i.e., distance moduli and redshifts for type Ia supernovae. We find that a best fit line through $\displaystyle \log{(\frac{D_L}{Gpc})}$ versus $\log{z}$ gives a correlation of 0.9955 and a sum of squares error (SSE) of 1.95. By comparison, the best fit $\Lambda$CDM gives SSE = 1.79 using $H_o$ = 69.2 km/s/Mpc, $\Omega_{M}$ = 0.29 and $\Omega_{\Lambda}$ = 0.71. The best fit EdS gives SSE = 2.68 using $H_o$ = 60.9 km/s/Mpc. The best fit MORC gives SSE = 1.77 and $H_o$ = 73.9 km/s/Mpc using $R = A^{-1}$ = 8.38 Gcy and $m = 1.71\times 10^{52}$ kg, where $R$ is the current graphical proper distance between nodes, $A^{-1}$ is the scaling factor from our non-trival inner product, and $m$ is the nodal mass. Thus, MORC improves EdS as well as $\Lambda$CDM in accounting for distance moduli and redshifts for type Ia supernovae without having to invoke accelerated expansion, i.e., there is no dark energy and the universe is always decelerating. |
2309.07931 | Suresh Tiwari dr | S. C. Tiwari | Comments on "A clarification on prevailing misconceptions in unimodular
gravity" | 2 pages additional reference with short discussion in the updated
version | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | In this comment on arXiv:2308.07360 it is pointed out that though the authors
raise an important question on the prevailing presentations of the unimodular
gravity their own presentation is incomplete as well as confusing equating
assumptions to misconceptions. We focus on the notion of diffeomorphism
invariance, general covariance and the conservation/nonconservation of the
energy-momentum tensor in this short note to delineate the fundamental issues
in unimodular gravity. The present discussion is intended to offer a wider and
deeper perspective on the objective set by the authors in their paper.
| [
{
"created": "Wed, 13 Sep 2023 18:50:34 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Jun 2024 05:35:29 GMT",
"version": "v2"
}
] | 2024-06-04 | [
[
"Tiwari",
"S. C.",
""
]
] | In this comment on arXiv:2308.07360 it is pointed out that though the authors raise an important question on the prevailing presentations of the unimodular gravity their own presentation is incomplete as well as confusing equating assumptions to misconceptions. We focus on the notion of diffeomorphism invariance, general covariance and the conservation/nonconservation of the energy-momentum tensor in this short note to delineate the fundamental issues in unimodular gravity. The present discussion is intended to offer a wider and deeper perspective on the objective set by the authors in their paper. |
1211.2581 | George Moutsopoulos | George Moutsopoulos | Homogeneous anisotropic solutions of topologically massive gravity with
cosmological constant and their homogeneous deformations | latex, 56 pages, pdf figures, tikz figures. v3: corrected deformation
graph, added discussion on de Sitter / hyperbolic deformation, typo
corrections, more notation crossrefs, changed so(theta) to iso(theta)
notation, a few more refs, publication version, no major changes | Class. Quantum Grav. 30 125014 (2013) | 10.1088/0264-9381/30/12/125014 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We solve the equations of topologically massive gravity with potentially
non-vanishing cosmological constant for homogeneous metrics without isotropy.
We only reproduce known solutions. We also discuss their homogeneous
deformations, possibly with isotropy. We show that de Sitter space and
hyperbolic space cannot be infinitesimally homogeneously deformed in TMG. We
clarify some of their Segre-Petrov types and discuss the warped de Sitter
spacetime.
| [
{
"created": "Mon, 12 Nov 2012 11:50:57 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Nov 2012 19:17:35 GMT",
"version": "v2"
},
{
"created": "Thu, 2 May 2013 10:36:30 GMT",
"version": "v3"
}
] | 2013-05-30 | [
[
"Moutsopoulos",
"George",
""
]
] | We solve the equations of topologically massive gravity with potentially non-vanishing cosmological constant for homogeneous metrics without isotropy. We only reproduce known solutions. We also discuss their homogeneous deformations, possibly with isotropy. We show that de Sitter space and hyperbolic space cannot be infinitesimally homogeneously deformed in TMG. We clarify some of their Segre-Petrov types and discuss the warped de Sitter spacetime. |
1310.4481 | Enrico Barausse | Carlos Palenzuela, Enrico Barausse, Marcelo Ponce and Luis Lehner | Dynamical scalarization of neutron stars in scalar-tensor gravity
theories | 17 pages, 20 figures; matches version published in PRD | Phys. Rev. D 89, 044024 (2014) | 10.1103/PhysRevD.89.044024 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a framework to study generic neutron-star binaries in
scalar-tensor theories of gravity. Our formalism achieves this goal by suitably
interfacing a post-Newtonian orbital evolution (described by a set of ordinary
differential equations) with a set of non-linear algebraic equations, which
provide a description of the scalar charge of each binary's component along the
evolution in terms of isolated-star data. We validate this semi-analytical
procedure by comparing its results to those of fully general-relativistic
simulations, and use it to investigate the behavior of binary systems in large
portions of the parameter space of scalar-tensor theories. This allows us to
shed further light on the phenomenon of "dynamical scalarization", which we
uncovered in [Barausse, Palenzuela, Ponce and Lehner, Phys. Rev. D 87,
081506(R) (2013)] and which takes place in tight binaries, even for stars that
have exactly zero scalar charge in isolation. We also employ our formalism to
study representative binary systems, obtain their gravitational-wave signals
and discuss the extent to which deviations from General Relativity can be
detected. The insights gained by this framework allow us to additionally show
that eccentric binaries can undergo scalarization/de-scalarization phenomena.
| [
{
"created": "Wed, 16 Oct 2013 19:02:05 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Mar 2014 12:28:44 GMT",
"version": "v2"
}
] | 2014-03-07 | [
[
"Palenzuela",
"Carlos",
""
],
[
"Barausse",
"Enrico",
""
],
[
"Ponce",
"Marcelo",
""
],
[
"Lehner",
"Luis",
""
]
] | We present a framework to study generic neutron-star binaries in scalar-tensor theories of gravity. Our formalism achieves this goal by suitably interfacing a post-Newtonian orbital evolution (described by a set of ordinary differential equations) with a set of non-linear algebraic equations, which provide a description of the scalar charge of each binary's component along the evolution in terms of isolated-star data. We validate this semi-analytical procedure by comparing its results to those of fully general-relativistic simulations, and use it to investigate the behavior of binary systems in large portions of the parameter space of scalar-tensor theories. This allows us to shed further light on the phenomenon of "dynamical scalarization", which we uncovered in [Barausse, Palenzuela, Ponce and Lehner, Phys. Rev. D 87, 081506(R) (2013)] and which takes place in tight binaries, even for stars that have exactly zero scalar charge in isolation. We also employ our formalism to study representative binary systems, obtain their gravitational-wave signals and discuss the extent to which deviations from General Relativity can be detected. The insights gained by this framework allow us to additionally show that eccentric binaries can undergo scalarization/de-scalarization phenomena. |
1501.00103 | Farhad Darabi | F. Darabi, M. Mousavi, K. Atazadeh | Geodesic Deviation Equation in $f(T)$ gravity | 13 pages, 7 figures | Phys. Rev. D 91, 084023 (2015) | 10.1103/PhysRevD.91.084023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we show that it is possible to study the notion of geodesic
deviation equation in $f(T)$ gravity, in spite of the fact that in teleparallel
gravity there is no notion of geodesics, and the torsion is responsible for the
appearance of gravitational interaction. In this regard, we obtain the GR
equivalent equations for $f(T)$ gravity which are in the modified gravity form
such as $f(R)$ gravity. Then, we obtain the GDE within the context of this
modified gravity. In this way, the obtained geodesic deviation equation will
correspond to the $f(T)$ gravity. Eventually, we extend the calculations to
obtain the modification of Matting relation.
| [
{
"created": "Wed, 31 Dec 2014 09:58:47 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Apr 2015 03:57:55 GMT",
"version": "v2"
}
] | 2015-06-23 | [
[
"Darabi",
"F.",
""
],
[
"Mousavi",
"M.",
""
],
[
"Atazadeh",
"K.",
""
]
] | In this work, we show that it is possible to study the notion of geodesic deviation equation in $f(T)$ gravity, in spite of the fact that in teleparallel gravity there is no notion of geodesics, and the torsion is responsible for the appearance of gravitational interaction. In this regard, we obtain the GR equivalent equations for $f(T)$ gravity which are in the modified gravity form such as $f(R)$ gravity. Then, we obtain the GDE within the context of this modified gravity. In this way, the obtained geodesic deviation equation will correspond to the $f(T)$ gravity. Eventually, we extend the calculations to obtain the modification of Matting relation. |
gr-qc/0612161 | Anil Zengino\u{g}lu C | Anil Zenginoglu, Sascha Husa | Hyperboloidal foliations with scri-fixing in spherical symmetry | 3 pages, 1 figure; uses World Scientific style; submitted to the
Proceedings of the Eleventh Marcel Grossmann Meeting, July 23-29, 2006,
Berlin | null | null | AEI-2006-101 | gr-qc | null | We study in spherical symmetry the conformal compactification for
hyperboloidal foliations with nonvanishing constant mean curvature. The
conformal factor and the coordinates are chosen such that null infinity is at a
fixed radial coordinate location.
| [
{
"created": "Mon, 25 Dec 2006 16:27:08 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Zenginoglu",
"Anil",
""
],
[
"Husa",
"Sascha",
""
]
] | We study in spherical symmetry the conformal compactification for hyperboloidal foliations with nonvanishing constant mean curvature. The conformal factor and the coordinates are chosen such that null infinity is at a fixed radial coordinate location. |
2209.14398 | Tessa Baker | Tessa Baker, Enrico Barausse, Anson Chen, Claudia de Rham, Mauro
Pieroni, and Gianmassimo Tasinato | Testing gravitational wave propagation with multiband detections | 11 pages, 4 figures. Updated to match the version published in JCAP | JCAP03(2023)044 | 10.1088/1475-7516/2023/03/044 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | Effective field theories (EFT) of dark energy (DE) -- built to parameterise
the properties of DE in an agnostic manner -- are severely constrained by
measurements of the propagation speed of gravitational waves (GW). However, GW
frequencies probed by ground-based interferometers lie around the typical
strong coupling scale of the EFT, and it is likely that the effective
description breaks down before even reaching that scale. We discuss how this
leaves the possibility that an appropriate ultraviolet completion of DE
scenarios, valid at scales beyond an EFT description, can avoid present
constraints on the GW speed. Instead, additional constraints in the lower
frequency LISA band would be harder to escape, since the energies involved are
orders of magnitude lower. By implementing a method based on GW multiband
detections, we show indeed that a single joint observation of a GW150914-like
event by LISA and a terrestrial interferometer would allow one to constrain the
speed of light and gravitons to match to within $10^{-15}$. Multiband GW
observations can therefore firmly constrain scenarios based on the EFT of DE,
in a robust and unambiguous way.
| [
{
"created": "Wed, 28 Sep 2022 19:48:20 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Mar 2023 21:58:47 GMT",
"version": "v2"
}
] | 2023-03-29 | [
[
"Baker",
"Tessa",
""
],
[
"Barausse",
"Enrico",
""
],
[
"Chen",
"Anson",
""
],
[
"de Rham",
"Claudia",
""
],
[
"Pieroni",
"Mauro",
""
],
[
"Tasinato",
"Gianmassimo",
""
]
] | Effective field theories (EFT) of dark energy (DE) -- built to parameterise the properties of DE in an agnostic manner -- are severely constrained by measurements of the propagation speed of gravitational waves (GW). However, GW frequencies probed by ground-based interferometers lie around the typical strong coupling scale of the EFT, and it is likely that the effective description breaks down before even reaching that scale. We discuss how this leaves the possibility that an appropriate ultraviolet completion of DE scenarios, valid at scales beyond an EFT description, can avoid present constraints on the GW speed. Instead, additional constraints in the lower frequency LISA band would be harder to escape, since the energies involved are orders of magnitude lower. By implementing a method based on GW multiband detections, we show indeed that a single joint observation of a GW150914-like event by LISA and a terrestrial interferometer would allow one to constrain the speed of light and gravitons to match to within $10^{-15}$. Multiband GW observations can therefore firmly constrain scenarios based on the EFT of DE, in a robust and unambiguous way. |
2108.04060 | Gamal G.L. Nashed | G.G.L. Nashed | Anisotropic compact stars in the mimetic gravitational theory | 18 pages, 7 figures 2 tables | The Astrophysical Journal, 919:113, (2021) | 10.3847/1538-4357/ac19bb | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper, we consider the mimetic gravitational theory to derive a novel
category of anisotropic star models. To end and to put the resulting
differential equations into a closed system, the form of the metric potential
$g_{rr}$ as used by Tolman (Tolman 1939) is assumed as well as a linear form of
the equation-of-state. The resulting energy-momentum components,
energy-density, and radial and tangential pressures contain five constants;
three of these are determined through the junction condition, matching the
interior with the exterior Schwarzschild solution the fourth is constrained by
the vanishing of the radial pressure on the boundary and the fifth is
constrained by a real compact star. The physical acceptability of our model is
tested using the data of the pulsar 4U 1820-30. The stability of this model is
evaluated using the Tolman-Oppenheimer-Volkoff equation and the adiabatic index
and it is shown to be stable. Finally, our model is challenged with other
compact stars demonstrating that it is consistent with those stars.
| [
{
"created": "Thu, 5 Aug 2021 18:40:18 GMT",
"version": "v1"
},
{
"created": "Sat, 14 Aug 2021 06:54:43 GMT",
"version": "v2"
},
{
"created": "Fri, 8 Oct 2021 09:26:48 GMT",
"version": "v3"
}
] | 2021-10-11 | [
[
"Nashed",
"G. G. L.",
""
]
] | In this paper, we consider the mimetic gravitational theory to derive a novel category of anisotropic star models. To end and to put the resulting differential equations into a closed system, the form of the metric potential $g_{rr}$ as used by Tolman (Tolman 1939) is assumed as well as a linear form of the equation-of-state. The resulting energy-momentum components, energy-density, and radial and tangential pressures contain five constants; three of these are determined through the junction condition, matching the interior with the exterior Schwarzschild solution the fourth is constrained by the vanishing of the radial pressure on the boundary and the fifth is constrained by a real compact star. The physical acceptability of our model is tested using the data of the pulsar 4U 1820-30. The stability of this model is evaluated using the Tolman-Oppenheimer-Volkoff equation and the adiabatic index and it is shown to be stable. Finally, our model is challenged with other compact stars demonstrating that it is consistent with those stars. |
1712.09399 | Anzhong Wang | Fei-hung Ho, Shao-Jun Zhang, Hai-Shan Liu, and Anzhong Wang | Smarr Integral Formula of D-dimensional Stationary Spacetimes in
Einstein-\AE ther-Maxwell Theroy | No figures and tables. Phys. Let. B782 (2018) 723-727 | Phys. Let. B782 (2018) 723-727 | 10.1016/j.physletb.2018.06.027 | null | gr-qc astro-ph.GA hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the Wald formalism, we investigate the thermodynamics of charged black
holes in D-dimensional stationary spacetimes with or without rotations in
Einstein-\ae ther-Maxwell theory. In particular, assuming the existence of a
scaling symmetry of the action, we obtain the Smarr integral formula, which can
be applied to both Killing and universal horizons. When restricted to
4-dimensional spherically symmetric spacetimes, previous results obtained by a
different method are re-derived.
| [
{
"created": "Tue, 26 Dec 2017 20:39:31 GMT",
"version": "v1"
},
{
"created": "Sat, 6 Jan 2018 16:46:44 GMT",
"version": "v2"
},
{
"created": "Thu, 10 May 2018 00:10:50 GMT",
"version": "v3"
},
{
"created": "Fri, 15 Jun 2018 07:39:40 GMT",
"version": "v4"
},
{
"created": "Thu, 28 Jun 2018 10:20:25 GMT",
"version": "v5"
}
] | 2018-06-29 | [
[
"Ho",
"Fei-hung",
""
],
[
"Zhang",
"Shao-Jun",
""
],
[
"Liu",
"Hai-Shan",
""
],
[
"Wang",
"Anzhong",
""
]
] | Using the Wald formalism, we investigate the thermodynamics of charged black holes in D-dimensional stationary spacetimes with or without rotations in Einstein-\ae ther-Maxwell theory. In particular, assuming the existence of a scaling symmetry of the action, we obtain the Smarr integral formula, which can be applied to both Killing and universal horizons. When restricted to 4-dimensional spherically symmetric spacetimes, previous results obtained by a different method are re-derived. |
gr-qc/0509097 | Jin Yoshida | John D. Barrow, Yoshida Jin, Kei-ichi Maeda | Cosmological Co-evolution of Yang-Mills Fields and Perfect Fluids | 13 pages, 5 figures, submitted to PRD | Phys.Rev. D72 (2005) 103512 | 10.1103/PhysRevD.72.103512 | null | gr-qc astro-ph | null | We study the co-evolution of Yang-Mills fields and perfect fluids in Bianchi
type I universes. We investigate numerically the evolution of the universe and
the Yang-Mills fields during the radiation and dust eras of a universe that is
almost isotropic. The Yang-Mills field undergoes small amplitude chaotic
oscillations, which are also displayed by the expansion scale factors of the
universe. The results of the numerical simulations are interpreted analytically
and compared with past studies of the cosmological evolution of magnetic fields
in radiation and dust universes. We find that, whereas magnetic universes are
strongly constrained by the microwave background anisotropy, Yang-Mills
universes are principally constrained by primordial nucleosynthesis and the
bound is comparatively weak, and Omega_YM < 0.105 Omega_rad.
| [
{
"created": "Mon, 26 Sep 2005 01:57:56 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Sep 2005 09:04:13 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Barrow",
"John D.",
""
],
[
"Jin",
"Yoshida",
""
],
[
"Maeda",
"Kei-ichi",
""
]
] | We study the co-evolution of Yang-Mills fields and perfect fluids in Bianchi type I universes. We investigate numerically the evolution of the universe and the Yang-Mills fields during the radiation and dust eras of a universe that is almost isotropic. The Yang-Mills field undergoes small amplitude chaotic oscillations, which are also displayed by the expansion scale factors of the universe. The results of the numerical simulations are interpreted analytically and compared with past studies of the cosmological evolution of magnetic fields in radiation and dust universes. We find that, whereas magnetic universes are strongly constrained by the microwave background anisotropy, Yang-Mills universes are principally constrained by primordial nucleosynthesis and the bound is comparatively weak, and Omega_YM < 0.105 Omega_rad. |
1309.4915 | Valerio Faraoni | Valerio Faraoni (Bishop's University) | Evolving black hole horizons in General Relativity and alternative
gravity | 75 pages, 6 figures, invited paper to appear in "Aspects of Black
Hole Physics", special issue of "Galaxies" edited by L. Vanzo | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | From the microscopic point of view, realistic black holes are time-dependent
and the teleological concept of event horizon fails. At present, the apparent
or the trapping horizon seem its best replacements in various areas of black
hole physics. We discuss the known phenomenology of apparent and trapping
horizons for analytical solutions of General Relativity and alternative
theories of gravity. These specific examples (we focus on spherically symmetric
inhomogeneities in a background cosmological spacetime) may be useful as toy
models for research on various aspects of black hole physics.
| [
{
"created": "Thu, 19 Sep 2013 09:52:03 GMT",
"version": "v1"
}
] | 2013-09-20 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
]
] | From the microscopic point of view, realistic black holes are time-dependent and the teleological concept of event horizon fails. At present, the apparent or the trapping horizon seem its best replacements in various areas of black hole physics. We discuss the known phenomenology of apparent and trapping horizons for analytical solutions of General Relativity and alternative theories of gravity. These specific examples (we focus on spherically symmetric inhomogeneities in a background cosmological spacetime) may be useful as toy models for research on various aspects of black hole physics. |
2202.08513 | I-Ching Yang | I-Ching Yang | On the energy of Schwarzschild spacetime with the post-Newtonian
approximation | 7 pages | null | 10.1142/S0217732322501383 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | With the post-Newtonian approxination, the energy of Schwarzschild spacetime
in the Weinberg prescription is obtained. The energy for the first
post-Newtonian approximation $E^{(1)} = m$ gives the Newtonian treatment of
Schwarzschild spacetime. However, for the second post-Newtonian approximation,
the erergy is shown that $E^{(1)}$ adds extra terms $E^{(2)}$ which consist of
the energy stored in the configuration $E_{\rm config}$, in the gravitational
field $E_{\rm field}$. and a term of surface integral. These extra terms gives
post-Newtonian corrections to the Newtonian treatment.
| [
{
"created": "Thu, 17 Feb 2022 08:36:40 GMT",
"version": "v1"
}
] | 2022-10-05 | [
[
"Yang",
"I-Ching",
""
]
] | With the post-Newtonian approxination, the energy of Schwarzschild spacetime in the Weinberg prescription is obtained. The energy for the first post-Newtonian approximation $E^{(1)} = m$ gives the Newtonian treatment of Schwarzschild spacetime. However, for the second post-Newtonian approximation, the erergy is shown that $E^{(1)}$ adds extra terms $E^{(2)}$ which consist of the energy stored in the configuration $E_{\rm config}$, in the gravitational field $E_{\rm field}$. and a term of surface integral. These extra terms gives post-Newtonian corrections to the Newtonian treatment. |
2204.06437 | Oem Trivedi | Oem Trivedi and Maxim Khlopov | Singularity formation in asymptotically safe cosmology with
inhomogeneous equation of state | v2, 22 pages with no figures with minor changes, matches the
published version in JCAP | JCAP11(2022)007 | 10.1088/1475-7516/2022/11/007 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Interest in cosmological singularities has remarkably grown in recent times,
particularly on future singularities with the discovery of late-time
acceleration of the universe and dark energy. While such explorations have
previously been done in various modified gravity and quantum gravitationally
inspired cosmologies (besides standard general relativistic cosmology), no such
an endeavour has been taken up till now in the realms of renormalization group
approaches to cosmology and we have hence took up on this journey. In this
work, we consider the formation of cosmological singularities in an
asymptotically safe cosmology where the cut off scale is proportional to the
Hubble parameter. We consider a well motivated inhomogeneous form of the
equation of state(EOS) as well. We firstly delve into some basics of this
cosmology and show that such a scenario permits a transition between phantom
and quintessence forms of universal evolution. We then show that one can have
Type I - Type IV singularities in such a cosmology for various version of the
EOS and that the singularities can occur both in finite and infinite time. The
conditions in which these singularities occur is significantly different than
how they occur in the standard cosmology, with the formulations being even more
involved. Interestingly this difference comes about without the need of any
free parameters in the cosmological models, which is usually what one observes
when one goes for the same pursuit via various modified gravity/ QG inspired
cosmological approaches. Furthermore, we showed that usual singularity removal
methods like conformal anomaly effects and f(R) gravity effects do not offer
much hope for singularity removal in this cosmology.
| [
{
"created": "Wed, 13 Apr 2022 14:54:54 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Nov 2022 17:55:30 GMT",
"version": "v2"
}
] | 2022-11-10 | [
[
"Trivedi",
"Oem",
""
],
[
"Khlopov",
"Maxim",
""
]
] | Interest in cosmological singularities has remarkably grown in recent times, particularly on future singularities with the discovery of late-time acceleration of the universe and dark energy. While such explorations have previously been done in various modified gravity and quantum gravitationally inspired cosmologies (besides standard general relativistic cosmology), no such an endeavour has been taken up till now in the realms of renormalization group approaches to cosmology and we have hence took up on this journey. In this work, we consider the formation of cosmological singularities in an asymptotically safe cosmology where the cut off scale is proportional to the Hubble parameter. We consider a well motivated inhomogeneous form of the equation of state(EOS) as well. We firstly delve into some basics of this cosmology and show that such a scenario permits a transition between phantom and quintessence forms of universal evolution. We then show that one can have Type I - Type IV singularities in such a cosmology for various version of the EOS and that the singularities can occur both in finite and infinite time. The conditions in which these singularities occur is significantly different than how they occur in the standard cosmology, with the formulations being even more involved. Interestingly this difference comes about without the need of any free parameters in the cosmological models, which is usually what one observes when one goes for the same pursuit via various modified gravity/ QG inspired cosmological approaches. Furthermore, we showed that usual singularity removal methods like conformal anomaly effects and f(R) gravity effects do not offer much hope for singularity removal in this cosmology. |
1704.01590 | Junwu Huang | Solomon Endlich, Victor Gorbenko, Junwu Huang, Leonardo Senatore | An effective formalism for testing extensions to General Relativity with
gravitational waves | v1: 43+16 pages, 11 figures, 2 tables; v2: minor corrections; v3:
minor corrections, JHEP published version | null | 10.1007/JHEP09(2017)122 | null | gr-qc astro-ph.CO astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent direct observation of gravitational waves (GW) from merging black
holes opens up the possibility of exploring the theory of gravity in the strong
regime at an unprecedented level. It is therefore interesting to explore which
extensions to General Relativity (GR) could be detected. We construct an
Effective Field Theory (EFT) satisfying the following requirements. It is
testable with GW observations; it is consistent with other experiments,
including short distance tests of GR; it agrees with widely accepted principles
of physics, such as locality, causality and unitarity; and it does not involve
new light degrees of freedom. The most general theory satisfying these
requirements corresponds to adding to the GR Lagrangian operators constructed
out of powers of the Riemann tensor, suppressed by a scale comparable to the
curvature of the observed merging binaries. The presence of these operators
modifies the gravitational potential between the compact objects, as well as
their effective mass and current quadrupoles, ultimately correcting the
waveform of the emitted GW.
| [
{
"created": "Wed, 5 Apr 2017 18:00:06 GMT",
"version": "v1"
},
{
"created": "Wed, 17 May 2017 18:05:40 GMT",
"version": "v2"
},
{
"created": "Mon, 25 Sep 2017 13:38:33 GMT",
"version": "v3"
}
] | 2017-10-25 | [
[
"Endlich",
"Solomon",
""
],
[
"Gorbenko",
"Victor",
""
],
[
"Huang",
"Junwu",
""
],
[
"Senatore",
"Leonardo",
""
]
] | The recent direct observation of gravitational waves (GW) from merging black holes opens up the possibility of exploring the theory of gravity in the strong regime at an unprecedented level. It is therefore interesting to explore which extensions to General Relativity (GR) could be detected. We construct an Effective Field Theory (EFT) satisfying the following requirements. It is testable with GW observations; it is consistent with other experiments, including short distance tests of GR; it agrees with widely accepted principles of physics, such as locality, causality and unitarity; and it does not involve new light degrees of freedom. The most general theory satisfying these requirements corresponds to adding to the GR Lagrangian operators constructed out of powers of the Riemann tensor, suppressed by a scale comparable to the curvature of the observed merging binaries. The presence of these operators modifies the gravitational potential between the compact objects, as well as their effective mass and current quadrupoles, ultimately correcting the waveform of the emitted GW. |
gr-qc/0702123 | Malcolm MacCallum | J. Gariel, M. A. H. MacCallum, G. Marcilhacy and N. O. Santos | Kerr Geodesics, the Penrose Process and Jet Collimation by a Black Hole | Accepted by Astronomy and Astrophysics. AA style with 3 EPS figures.
Content amended after AA's refereeing. Discussion of geodesics also corrected
and expanded earlier. Conclusions amended accordingly | null | 10.1051/0004-6361/200913678 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We re-examine the possibility that astrophysical jet collimation may arise
from the geometry of rotating black holes and the presence of high-energy
particles resulting from a Penrose process, without the help of magnetic
fields. Our analysis uses the Weyl coordinates, which are revealed better
adapted to the desired shape of the jets. We numerically integrate the
2D-geodesics equations. We give a detailed study of these geodesics and give
several numerical examples. Among them are a set of perfectly collimated
geodesics with asymptotes $\rho =\rho_{1}$ parallel to the $z-$ axis, with
$\rho_{1}$ only depending on the ratios $\frac{\mathcal{Q}}{E^{2}-1}$ and
$\frac{a}{M}$, where $a$ and $M$ are the parameters of the Kerr black hole, $E$
the particle energy and $\mathcal{Q}$ the Carter's constant.
| [
{
"created": "Fri, 23 Feb 2007 15:50:36 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Jun 2009 16:43:23 GMT",
"version": "v2"
},
{
"created": "Tue, 2 Mar 2010 21:58:34 GMT",
"version": "v3"
}
] | 2023-01-18 | [
[
"Gariel",
"J.",
""
],
[
"MacCallum",
"M. A. H.",
""
],
[
"Marcilhacy",
"G.",
""
],
[
"Santos",
"N. O.",
""
]
] | We re-examine the possibility that astrophysical jet collimation may arise from the geometry of rotating black holes and the presence of high-energy particles resulting from a Penrose process, without the help of magnetic fields. Our analysis uses the Weyl coordinates, which are revealed better adapted to the desired shape of the jets. We numerically integrate the 2D-geodesics equations. We give a detailed study of these geodesics and give several numerical examples. Among them are a set of perfectly collimated geodesics with asymptotes $\rho =\rho_{1}$ parallel to the $z-$ axis, with $\rho_{1}$ only depending on the ratios $\frac{\mathcal{Q}}{E^{2}-1}$ and $\frac{a}{M}$, where $a$ and $M$ are the parameters of the Kerr black hole, $E$ the particle energy and $\mathcal{Q}$ the Carter's constant. |
gr-qc/0301104 | Banibrata Mukhopadhyay | Banibrata Mukhopadhyay and Naresh Dadhich | Scalar and Spinor Perturbation to the Kerr-NUT Spacetime | 31 pages including 20 figures, RevTeX style: Final version to appear
in Classical and Quantum Gravity | Class.Quant.Grav. 21 (2004) 3621-3644 | 10.1088/0264-9381/21/15/001 | null | gr-qc astro-ph | null | We study the scalar and spinor perturbation, namely the Klein-Gordan and
Dirac equations, in the Kerr-NUT space-time. The metric is invariant under the
duality transformation involving the exchange of mass and NUT parameters on one
hand and radial and angle coordinates on the other. We show that this
invariance is also shared by the scalar and spinor perturbation equations.
Further, by the duality transformation, one can go from the Kerr to the dual
Kerr solution, and vice versa, and the same applies to the perturbation
equations. In particular, it turns out that the potential barriers felt by the
incoming scalar and spinor fields are higher for the dual Kerr than that for
the Kerr. We also comment on existence of horizon and singularity.
| [
{
"created": "Fri, 24 Jan 2003 18:14:40 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Jun 2004 15:19:14 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Mukhopadhyay",
"Banibrata",
""
],
[
"Dadhich",
"Naresh",
""
]
] | We study the scalar and spinor perturbation, namely the Klein-Gordan and Dirac equations, in the Kerr-NUT space-time. The metric is invariant under the duality transformation involving the exchange of mass and NUT parameters on one hand and radial and angle coordinates on the other. We show that this invariance is also shared by the scalar and spinor perturbation equations. Further, by the duality transformation, one can go from the Kerr to the dual Kerr solution, and vice versa, and the same applies to the perturbation equations. In particular, it turns out that the potential barriers felt by the incoming scalar and spinor fields are higher for the dual Kerr than that for the Kerr. We also comment on existence of horizon and singularity. |
1311.0062 | Francisco Navarro-Lerida | Jose Luis Blazquez-Salcedo, Jutta Kunz and Francisco Navarro-Lerida | Properties of rotating Einstein-Maxwell-Dilaton black holes in odd
dimensions | 40 pages, 10 figures | Phys. Rev. D 89, 024038 (2014) | 10.1103/PhysRevD.89.024038 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate rotating Einstein-Maxwell-Dilaton (EMd) black holes in odd
dimensions. Focusing on black holes with equal-magnitude angular momenta, we
determine the domain of existence of these black holes. Non-extremal black
holes reside with the boundaries determined by the static and the extremal
rotating black holes. The extremal EMd black holes show proportionality of
their horizon area and their angular momenta. Thus the charge does not enter.
We also address the Einstein-Maxwell case, where the extremal rotating black
holes exhibit two branches. On the branch emerging from the Myers-Perry
solutions their angular momenta are proportional to their horizon area, whereas
on the branch emerging from the static solutions their angular momenta are
proportional to their horizon angular momenta. Only subsets of the near-horizon
solutions are realized globally. Investigating the physical properties of these
EMd black holes, we note that one can learn much about the extremal rotating
solutions from the much simpler static solutions. The angular momenta of the
extremal black holes are proportional to the area of the static ones for the
Kaluza-Klein value of the dilaton coupling constant, and remain analogous for
other values. The same is found for the horizon angular velocities of the
extremal black holes, which possess an analogous behavior to the surface
gravity of the static black holes. The gyromagnetic ratio is rather well
approximated by the `static' value, obtained perturbatively for small angular
momenta.
| [
{
"created": "Thu, 31 Oct 2013 23:36:32 GMT",
"version": "v1"
}
] | 2014-09-02 | [
[
"Blazquez-Salcedo",
"Jose Luis",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Navarro-Lerida",
"Francisco",
""
]
] | We investigate rotating Einstein-Maxwell-Dilaton (EMd) black holes in odd dimensions. Focusing on black holes with equal-magnitude angular momenta, we determine the domain of existence of these black holes. Non-extremal black holes reside with the boundaries determined by the static and the extremal rotating black holes. The extremal EMd black holes show proportionality of their horizon area and their angular momenta. Thus the charge does not enter. We also address the Einstein-Maxwell case, where the extremal rotating black holes exhibit two branches. On the branch emerging from the Myers-Perry solutions their angular momenta are proportional to their horizon area, whereas on the branch emerging from the static solutions their angular momenta are proportional to their horizon angular momenta. Only subsets of the near-horizon solutions are realized globally. Investigating the physical properties of these EMd black holes, we note that one can learn much about the extremal rotating solutions from the much simpler static solutions. The angular momenta of the extremal black holes are proportional to the area of the static ones for the Kaluza-Klein value of the dilaton coupling constant, and remain analogous for other values. The same is found for the horizon angular velocities of the extremal black holes, which possess an analogous behavior to the surface gravity of the static black holes. The gyromagnetic ratio is rather well approximated by the `static' value, obtained perturbatively for small angular momenta. |
gr-qc/0303089 | Chiao | Raymond Y. Chiao and Walter J. Fitelson | Time and Matter in the Interaction between Gravity and Quantum Fluids:
Are there Macroscopic Quantum Transducers between Gravitational and
Electromagnetic waves? | 16 pages, 4 figures, in proceedings of the "Time and Matter"
conference in Venice of 2002, to be published by World Scientific | null | null | null | gr-qc | null | Measurements of the tunneling time are briefly reviewed. Next, time and
matter in general relativity and quantum mechanics is examined. In particular,
the question arises: How does gravitational radiation interact with a coherent
quantum many-body system (a ``quantum fluid'')? A minimal coupling rule for the
coupling of the electron spin to curved spacetime in general relativity implies
the possibility of a coupling between electromagnetic (EM) and gravitational
(GR) radiation mediated by a quantum Hall fluid. This suggests that quantum
transducers between these two kinds of radiation fields might exist. We report
here on a first attempt at a Hertz-type experiment, in which a high-$\rm{T_c}$
superconductor (YBCO) was the material used as a quantum transducer to convert
EM into GR microwaves, and a second piece of YBCO in a separate apparatus was
used to back-convert GR into EM microwaves. An upper limit on the conversion
efficiency of YBCO was measured to be $1.6\times10^{-5}$.
| [
{
"created": "Sun, 23 Mar 2003 22:27:59 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Mar 2003 02:04:02 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Apr 2003 19:02:56 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Chiao",
"Raymond Y.",
""
],
[
"Fitelson",
"Walter J.",
""
]
] | Measurements of the tunneling time are briefly reviewed. Next, time and matter in general relativity and quantum mechanics is examined. In particular, the question arises: How does gravitational radiation interact with a coherent quantum many-body system (a ``quantum fluid'')? A minimal coupling rule for the coupling of the electron spin to curved spacetime in general relativity implies the possibility of a coupling between electromagnetic (EM) and gravitational (GR) radiation mediated by a quantum Hall fluid. This suggests that quantum transducers between these two kinds of radiation fields might exist. We report here on a first attempt at a Hertz-type experiment, in which a high-$\rm{T_c}$ superconductor (YBCO) was the material used as a quantum transducer to convert EM into GR microwaves, and a second piece of YBCO in a separate apparatus was used to back-convert GR into EM microwaves. An upper limit on the conversion efficiency of YBCO was measured to be $1.6\times10^{-5}$. |
2405.18496 | Maxence Corman | Maxence Corman and William E. East | Black hole-neutron star mergers in Einstein-scalar-Gauss-Bonnet gravity | 19 pages,12 figures | null | null | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave observations of black hole-neutron star binaries,
particularly those where the black hole has a lower mass compared to other
observed systems, have the potential to place strong constraints on
modifications to general relativity that arise at small curvature length
scales. Here we study the dynamics of black hole-neutron star mergers in
shift-symmetric Einstein-scalar-Gauss-Bonnet gravity, a representative example
of such a theory, by numerically evolving the full equations of motion. We
consider quasi-circular binaries with different mass-ratios that are consistent
with recent gravitational wave observations, including cases with and without
tidal disruption of the star, and quantify the impact of varying the coupling
controlling deviations from general relativity on the gravitational wave signal
and scalar radiation. We find that the main effect on the late inspiral is the
accelerated frequency evolution compared to general relativity, and that--even
considering Gauss-Bonnet coupling values approaching those where the theory
breaks down--the impact on the merger gravitational wave signal is mild,
predominately manifesting as a small change in the amplitude of the ringdown.
We compare our results to current post-Newtonian calculations and find
consistency throughout the inspiral.
| [
{
"created": "Tue, 28 May 2024 18:07:44 GMT",
"version": "v1"
}
] | 2024-05-30 | [
[
"Corman",
"Maxence",
""
],
[
"East",
"William E.",
""
]
] | Gravitational wave observations of black hole-neutron star binaries, particularly those where the black hole has a lower mass compared to other observed systems, have the potential to place strong constraints on modifications to general relativity that arise at small curvature length scales. Here we study the dynamics of black hole-neutron star mergers in shift-symmetric Einstein-scalar-Gauss-Bonnet gravity, a representative example of such a theory, by numerically evolving the full equations of motion. We consider quasi-circular binaries with different mass-ratios that are consistent with recent gravitational wave observations, including cases with and without tidal disruption of the star, and quantify the impact of varying the coupling controlling deviations from general relativity on the gravitational wave signal and scalar radiation. We find that the main effect on the late inspiral is the accelerated frequency evolution compared to general relativity, and that--even considering Gauss-Bonnet coupling values approaching those where the theory breaks down--the impact on the merger gravitational wave signal is mild, predominately manifesting as a small change in the amplitude of the ringdown. We compare our results to current post-Newtonian calculations and find consistency throughout the inspiral. |
1502.07644 | Daniel Kapec | Daniel Kapec, Vyacheslav Lysov, Sabrina Pasterski and Andrew
Strominger | Higher-Dimensional Supertranslations and Weinberg's Soft Graviton
Theorem | 24 pages | Annals of Mathematical Sciences and Applications, Volume 2 (2017),
pp 69-94 | 10.4310/AMSA.2017.v2.n1.a2 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Asymptotic symmetries of theories with gravity in d=2m+2 spacetime dimensions
are reconsidered for m>1 in light of recent results concerning d=4 BMS
symmetries. Weinberg's soft graviton theorem in 2m+2 dimensions is re-expressed
as a Ward identity for the gravitational S-matrix. The corresponding asymptotic
symmetries are identified with 2m+2-dimensional supertranslations. An alternate
derivation of these asymptotic symmetries as diffeomorphisms which preserve
finite-energy boundary conditions at null infinity and act non-trivially on
physical data is given. Our results differ from those of previous analyses
whose stronger boundary conditions precluded supertranslations for d>4. We find
for all even d that supertranslation symmetry is spontaneously broken in the
conventional vacuum and identify soft gravitons as the corresponding Goldstone
bosons.
| [
{
"created": "Thu, 26 Feb 2015 17:36:09 GMT",
"version": "v1"
}
] | 2017-03-30 | [
[
"Kapec",
"Daniel",
""
],
[
"Lysov",
"Vyacheslav",
""
],
[
"Pasterski",
"Sabrina",
""
],
[
"Strominger",
"Andrew",
""
]
] | Asymptotic symmetries of theories with gravity in d=2m+2 spacetime dimensions are reconsidered for m>1 in light of recent results concerning d=4 BMS symmetries. Weinberg's soft graviton theorem in 2m+2 dimensions is re-expressed as a Ward identity for the gravitational S-matrix. The corresponding asymptotic symmetries are identified with 2m+2-dimensional supertranslations. An alternate derivation of these asymptotic symmetries as diffeomorphisms which preserve finite-energy boundary conditions at null infinity and act non-trivially on physical data is given. Our results differ from those of previous analyses whose stronger boundary conditions precluded supertranslations for d>4. We find for all even d that supertranslation symmetry is spontaneously broken in the conventional vacuum and identify soft gravitons as the corresponding Goldstone bosons. |
1407.3846 | Sergei Kopeikin | Sergei M. Kopeikin (University of Missouri, USA) and Alexander N.
Petrov (Moscow State University, Russia) | Dynamic Field Theory and Equations of Motion in Cosmology | 62 pages, no figures. Accepted to the Annals of Physics | Annals of Physics, Volume 350, 379-440, 2015 | 10.1016/j.aop.2014.07.029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a field-theoretical approach based on variational principle to
derive the field and hydrodynamic equations of motion of baryonic matter
governed by cosmological perturbations of dark matter and dark energy. The
action depends on the gravitational and matter Lagrangian. The gravitational
Lagrangian depends on the metric tensor and its first and second derivatives.
The matter Lagrangian includes dark matter, dark energy and the ordinary
baryonic matter. The total Lagrangian is expanded in an asymptotic Taylor
series around the background manifold defined as a solution of Einstein's
equations in the form of the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric
tensor. The small parameter of the decomposition is the magnitude of the metric
tensor perturbation. Each term of the series expansion is gauge-invariant and
all of them together form a basis for the successive post-Friedmannian
approximations. The approximation scheme is covariant and the asymptotic nature
of the Lagrangian decomposition does not require the post-Friedmannian
perturbations to be small though computationally it works the most effectively
when the perturbed metric is close enough to the background FLRW metric. The
temporal evolution of the background metric is governed by dark matter and dark
energy and we associate the large scale inhomogeneities in these two components
as those generated by the primordial cosmological perturbations. The small
scale inhomogeneities are generated by the condensations of baryonic matter
considered as the bare perturbations. We explicitly work out the covariant
field equations of the successive post-Friedmannian approximations of
Einstein's equations and derive equations of motion of large and small scale
inhomogeneities of dark matter and dark energy. We apply these equations to
derive the post-Friedmannian equations of motion of the baryonic matter.
| [
{
"created": "Mon, 14 Jul 2014 23:14:11 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Jul 2014 23:11:39 GMT",
"version": "v2"
}
] | 2015-01-27 | [
[
"Kopeikin",
"Sergei M.",
"",
"University of Missouri, USA"
],
[
"Petrov",
"Alexander N.",
"",
"Moscow State University, Russia"
]
] | We discuss a field-theoretical approach based on variational principle to derive the field and hydrodynamic equations of motion of baryonic matter governed by cosmological perturbations of dark matter and dark energy. The action depends on the gravitational and matter Lagrangian. The gravitational Lagrangian depends on the metric tensor and its first and second derivatives. The matter Lagrangian includes dark matter, dark energy and the ordinary baryonic matter. The total Lagrangian is expanded in an asymptotic Taylor series around the background manifold defined as a solution of Einstein's equations in the form of the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric tensor. The small parameter of the decomposition is the magnitude of the metric tensor perturbation. Each term of the series expansion is gauge-invariant and all of them together form a basis for the successive post-Friedmannian approximations. The approximation scheme is covariant and the asymptotic nature of the Lagrangian decomposition does not require the post-Friedmannian perturbations to be small though computationally it works the most effectively when the perturbed metric is close enough to the background FLRW metric. The temporal evolution of the background metric is governed by dark matter and dark energy and we associate the large scale inhomogeneities in these two components as those generated by the primordial cosmological perturbations. The small scale inhomogeneities are generated by the condensations of baryonic matter considered as the bare perturbations. We explicitly work out the covariant field equations of the successive post-Friedmannian approximations of Einstein's equations and derive equations of motion of large and small scale inhomogeneities of dark matter and dark energy. We apply these equations to derive the post-Friedmannian equations of motion of the baryonic matter. |
0810.0283 | Keith Riles | LIGO Scientific Collaboration | All-sky LIGO Search for Periodic Gravitational Waves in the Early S5
Data | 6 pages, 1 figure | Phys.Rev.Lett.102:111102,2009 | 10.1103/PhysRevLett.102.111102 | LIGO-P080024 | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report on an all-sky search with the LIGO detectors for periodic
gravitational waves in the frequency range 50--1100 Hz and with the frequency's
time derivative in the range -5.0E-9 Hz/s to zero. Data from the first eight
months of the fifth LIGO science run (S5) have been used in this search, which
is based on a semi-coherent method (PowerFlux) of summing strain power.
Observing no evidence of periodic gravitational radiation, we report 95%
confidence-level upper limits on radiation emitted by any unknown isolated
rotating neutron stars within the search range. Strain limits below 1.E-24 are
obtained over a 200-Hz band, and the sensitivity improvement over previous
searches increases the spatial volume sampled by an average factor of about 100
over the entire search band. For a neutron star with nominal equatorial
ellipticity of 1.0E-6, the search is sensitive to distances as great as 500
pc--a range that could encompass many undiscovered neutron stars, albeit only a
tiny fraction of which would likely be rotating fast enough to be accessible to
LIGO. This ellipticity is at the upper range thought to be sustainable by
conventional neutron stars and well below the maximum sustainable by a strange
quark star.
| [
{
"created": "Wed, 1 Oct 2008 20:36:45 GMT",
"version": "v1"
}
] | 2012-08-27 | [
[
"LIGO Scientific Collaboration",
"",
""
]
] | We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50--1100 Hz and with the frequency's time derivative in the range -5.0E-9 Hz/s to zero. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semi-coherent method (PowerFlux) of summing strain power. Observing no evidence of periodic gravitational radiation, we report 95% confidence-level upper limits on radiation emitted by any unknown isolated rotating neutron stars within the search range. Strain limits below 1.E-24 are obtained over a 200-Hz band, and the sensitivity improvement over previous searches increases the spatial volume sampled by an average factor of about 100 over the entire search band. For a neutron star with nominal equatorial ellipticity of 1.0E-6, the search is sensitive to distances as great as 500 pc--a range that could encompass many undiscovered neutron stars, albeit only a tiny fraction of which would likely be rotating fast enough to be accessible to LIGO. This ellipticity is at the upper range thought to be sustainable by conventional neutron stars and well below the maximum sustainable by a strange quark star. |
0811.3772 | Sean Carroll | Sean M. Carroll | What if Time Really Exists? | Submission to the Foundational Questions Institute Essay Competition
on "The Nature of Time." | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Despite the obvious utility of the concept, it has often been argued that
time does not exist. I take the opposite perspective: let's imagine that time
does exist, and the universe is described by a quantum state obeying ordinary
time-dependent quantum mechanics. Reconciling this simple picture with the
known facts about our universe turns out to be a non-trivial task, but by
taking it seriously we can infer deep facts about the fundamental nature of
reality. The arrow of time finds a plausible explanation in a "Heraclitean
universe," described by a quantum state eternally evolving in an
infinite-dimensional Hilbert space.
| [
{
"created": "Sun, 23 Nov 2008 21:07:47 GMT",
"version": "v1"
}
] | 2008-11-25 | [
[
"Carroll",
"Sean M.",
""
]
] | Despite the obvious utility of the concept, it has often been argued that time does not exist. I take the opposite perspective: let's imagine that time does exist, and the universe is described by a quantum state obeying ordinary time-dependent quantum mechanics. Reconciling this simple picture with the known facts about our universe turns out to be a non-trivial task, but by taking it seriously we can infer deep facts about the fundamental nature of reality. The arrow of time finds a plausible explanation in a "Heraclitean universe," described by a quantum state eternally evolving in an infinite-dimensional Hilbert space. |
0809.2208 | Steven Hergt | Steven Hergt, Gerhard Sch\"afer | Higher-order-in-spin interaction Hamiltonians for binary black holes
from Poincar\'e invariance | REVTeX4, 14 pages; center-of-mass-vector corrected Eq. (2.25) and
modified coefficients of the Hamiltonian Eq. (7.3) and corresponding source
terms Eqs. (7.5) and (7.6) following hereof; version to appear in Phys Rev D | Phys.Rev.D78:124004,2008 | 10.1103/PhysRevD.78.124004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The fulfillment of the space-asymptotic Poincar\'e algebra is used to derive
new higher-order-in-spin interaction Hamiltonians for binary black holes in the
Arnowitt-Deser-Misner canonical formalism almost completing the set of the
formally $1/c^4$ spin-interaction Hamiltonians involving nonlinear spin terms.
To linear order in $G$, the expressions for the $S^3p$- and the
$S^2p^2$-Hamiltonians are completed. It is also shown that there are no quartic
nonlinear $S^4$-Hamiltonians to linear order in $G$.
| [
{
"created": "Fri, 12 Sep 2008 13:05:08 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Nov 2008 15:24:10 GMT",
"version": "v2"
}
] | 2008-12-30 | [
[
"Hergt",
"Steven",
""
],
[
"Schäfer",
"Gerhard",
""
]
] | The fulfillment of the space-asymptotic Poincar\'e algebra is used to derive new higher-order-in-spin interaction Hamiltonians for binary black holes in the Arnowitt-Deser-Misner canonical formalism almost completing the set of the formally $1/c^4$ spin-interaction Hamiltonians involving nonlinear spin terms. To linear order in $G$, the expressions for the $S^3p$- and the $S^2p^2$-Hamiltonians are completed. It is also shown that there are no quartic nonlinear $S^4$-Hamiltonians to linear order in $G$. |
1009.0455 | Rolando Gaitan Deveras RGD | Rolando Gaitan Deveras | On unitarity of a linearized Yang-Mills formulation for massless and
massive gravity with propagating torsion | To appear in International Journal of Modern Physics A | Int.J.Mod.Phys.A25:4911-4932,2010 | 10.1142/S0217751X10050561 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A perturbative regime based on contortion as a dynamical variable and metric
as a (classical) fixed background, is performed in the context of a pure
Yang-Mills formulation for gravity in a $2+1$ dimensional space-time. In the
massless case we show that the theory contains three degrees of freedom and
only one is a non-unitary mode. Next, we introduce quadratical terms dependent
on torsion, which preserve parity and general covariance. The linearized
version reproduces an analogue Hilbert-Einstein-Fierz-Pauli unitary massive
theory plus three massless modes, two of them represents non-unitary ones.
Finally we confirm the existence of a family of unitary Yang-Mills-extended
theories which are classically consistent with Einstein's solutions coming from
non massive and topologically massive gravity. The unitarity of these
YM-extended theories is shown in a perturbative regime. A possible way to
perform a non-perturbative study is remarked.
| [
{
"created": "Thu, 2 Sep 2010 15:55:20 GMT",
"version": "v1"
}
] | 2010-11-05 | [
[
"Deveras",
"Rolando Gaitan",
""
]
] | A perturbative regime based on contortion as a dynamical variable and metric as a (classical) fixed background, is performed in the context of a pure Yang-Mills formulation for gravity in a $2+1$ dimensional space-time. In the massless case we show that the theory contains three degrees of freedom and only one is a non-unitary mode. Next, we introduce quadratical terms dependent on torsion, which preserve parity and general covariance. The linearized version reproduces an analogue Hilbert-Einstein-Fierz-Pauli unitary massive theory plus three massless modes, two of them represents non-unitary ones. Finally we confirm the existence of a family of unitary Yang-Mills-extended theories which are classically consistent with Einstein's solutions coming from non massive and topologically massive gravity. The unitarity of these YM-extended theories is shown in a perturbative regime. A possible way to perform a non-perturbative study is remarked. |
1505.01104 | Ahmad Sheykhi | M. Honarvaryan, A. Sheykhi, H. Moradpour | Thermodynamical description of the ghost dark energy model | 11 pages | Int. J. Mod. Phys. D 2 Vol. 24, No. 6 (2015) 1550048 | 10.1142/S0218271815500480 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we point out thermodynamical description of ghost dark energy
and its generalization to the early universe. Thereinafter, we find expressions
for the entropy changes of these dark energy candidates. In addition,
considering thermal fluctuations, thermodynamics of the dark energy component
interacting with a dark matter sector is addressed. {We will also find the
effects of considering the coincidence problem on the mutual interaction
between the dark sectors, and thus the equation of state parameter of dark
energy.} Finally, we derive a relation between the mutual interaction of the
dark components of the universe, accelerated with the either ghost dark energy
or its generalization, and the thermodynamic fluctuations.
| [
{
"created": "Sat, 2 May 2015 13:28:30 GMT",
"version": "v1"
}
] | 2015-05-06 | [
[
"Honarvaryan",
"M.",
""
],
[
"Sheykhi",
"A.",
""
],
[
"Moradpour",
"H.",
""
]
] | In this paper, we point out thermodynamical description of ghost dark energy and its generalization to the early universe. Thereinafter, we find expressions for the entropy changes of these dark energy candidates. In addition, considering thermal fluctuations, thermodynamics of the dark energy component interacting with a dark matter sector is addressed. {We will also find the effects of considering the coincidence problem on the mutual interaction between the dark sectors, and thus the equation of state parameter of dark energy.} Finally, we derive a relation between the mutual interaction of the dark components of the universe, accelerated with the either ghost dark energy or its generalization, and the thermodynamic fluctuations. |
2304.12935 | S Habib Mazharimousavi | S. Habib Mazharimousavi | Dirty black hole supported by a uniform electric field in
Einstein-Nonlinear Electrodynamics-Dilaton theory | 16 pages 6 figures, final copy with minor corrections in figures 5
and 6, published in EPJC | Eur. Phys. J. C (2023) 83:406 | 10.1140/epjc/s10052-023-11544-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this study, we present an exact dirty/hairy black hole solution in the
context of gravity coupled minimally to a nonlinear electrodynamic (NED) and a
Dilaton field. The NED model is known in the literature as the square-root (SR)
model i.e., $\mathcal{L}\sim \sqrt{-\mathcal{F}}.$ The black hole solution
which is supported by a uniform radial electric field and a singular Dilaton
scalar field is non-asymptotically flat and singular with the singularity
located at its center. An appropriate transformation results in an interesting
line element $ds^{2}=-\left( 1-\frac{2M}{\rho ^{\eta ^{2}}} \right) \rho
^{2\left( \eta ^{2}-1\right) }d\tau ^{2}+\left( 1-\frac{2M}{ \rho ^{\eta
^{2}}}\right) ^{-1}d\rho ^{2}+\varkappa ^{2}\rho ^{2}d\Omega ^{2} $ with two
parameters - namely the mass $M$ and the Dilaton parameter $ \eta ^{2}>1$
($\varkappa ^{2}=\frac{1}{\eta ^{2}}$) - which may be simply considered as the
dirty Schwarzschild black hole. This is because with $\eta ^{2}\rightarrow 1$
the spacetime reduces to the Schwarzschild black hole. We show that although
the causal structure of the above spacetime is similar to the Schwarzschild
black hole, it is thermally stable for $\eta ^{2}>2$. Furthermore, the tidal
force of this black hole behaves the same as a Schwarzschild black hole,
however, its magnitude depends on $\eta ^{2}$\ such that its minimum is not
corresponding to $\eta ^{2}=1$\ (Schwarzschild limit).
| [
{
"created": "Mon, 24 Apr 2023 13:53:51 GMT",
"version": "v1"
},
{
"created": "Wed, 24 May 2023 20:51:02 GMT",
"version": "v2"
}
] | 2023-05-26 | [
[
"Mazharimousavi",
"S. Habib",
""
]
] | In this study, we present an exact dirty/hairy black hole solution in the context of gravity coupled minimally to a nonlinear electrodynamic (NED) and a Dilaton field. The NED model is known in the literature as the square-root (SR) model i.e., $\mathcal{L}\sim \sqrt{-\mathcal{F}}.$ The black hole solution which is supported by a uniform radial electric field and a singular Dilaton scalar field is non-asymptotically flat and singular with the singularity located at its center. An appropriate transformation results in an interesting line element $ds^{2}=-\left( 1-\frac{2M}{\rho ^{\eta ^{2}}} \right) \rho ^{2\left( \eta ^{2}-1\right) }d\tau ^{2}+\left( 1-\frac{2M}{ \rho ^{\eta ^{2}}}\right) ^{-1}d\rho ^{2}+\varkappa ^{2}\rho ^{2}d\Omega ^{2} $ with two parameters - namely the mass $M$ and the Dilaton parameter $ \eta ^{2}>1$ ($\varkappa ^{2}=\frac{1}{\eta ^{2}}$) - which may be simply considered as the dirty Schwarzschild black hole. This is because with $\eta ^{2}\rightarrow 1$ the spacetime reduces to the Schwarzschild black hole. We show that although the causal structure of the above spacetime is similar to the Schwarzschild black hole, it is thermally stable for $\eta ^{2}>2$. Furthermore, the tidal force of this black hole behaves the same as a Schwarzschild black hole, however, its magnitude depends on $\eta ^{2}$\ such that its minimum is not corresponding to $\eta ^{2}=1$\ (Schwarzschild limit). |
2104.14400 | Oleksandr Sobol Dr. | O.O. Sobol, E.V. Gorbar, O.M. Teslyk, and S.I. Vilchinskii | Generation of an electromagnetic field nonminimally coupled to gravity
during Higgs inflation | 23 pages, 10 figures | Phys. Rev. D 104, 043509 (2021) | 10.1103/PhysRevD.104.043509 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of Higgs inflation, we consider the electromagnetic field
nonminimally coupled to gravity via the parity-preserving $\propto RF^{2}$ and
parity-violating $\propto RF\tilde{F}$ terms. Using the perturbation theory to
the leading order in these couplings, we study the generation of the
electromagnetic field during the inflation stage. We derive the effective
kinetic and axial coupling functions arising in the Einstein frame in the usual
metric as well as Palatini formulations of gravity. For both formulations, we
determine the power spectrum, energy density, and helicality of the generated
electromagnetic fields for different values of the nonminimal coupling
constants. Finally, we estimate the maximal present-day magnitude of the
magnetic field as $10^{-14}-10^{-15}\,$G with the correlation length of order
10 pc.
| [
{
"created": "Tue, 27 Apr 2021 13:25:04 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Aug 2021 14:41:29 GMT",
"version": "v2"
}
] | 2021-08-11 | [
[
"Sobol",
"O. O.",
""
],
[
"Gorbar",
"E. V.",
""
],
[
"Teslyk",
"O. M.",
""
],
[
"Vilchinskii",
"S. I.",
""
]
] | In the framework of Higgs inflation, we consider the electromagnetic field nonminimally coupled to gravity via the parity-preserving $\propto RF^{2}$ and parity-violating $\propto RF\tilde{F}$ terms. Using the perturbation theory to the leading order in these couplings, we study the generation of the electromagnetic field during the inflation stage. We derive the effective kinetic and axial coupling functions arising in the Einstein frame in the usual metric as well as Palatini formulations of gravity. For both formulations, we determine the power spectrum, energy density, and helicality of the generated electromagnetic fields for different values of the nonminimal coupling constants. Finally, we estimate the maximal present-day magnitude of the magnetic field as $10^{-14}-10^{-15}\,$G with the correlation length of order 10 pc. |
1705.05521 | Hiromi Saida | Hiromi Saida | An Axiomatic Review of Israel-Stewart Hydrodynamics and Extended
Irreversible Thermodynamics | 19 pages, 1 figure | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The causality of dissipative phenomena can not be treated in traditional
theories of dissipations, Fourier laws and Navier-Stokes equations. This is the
reason why the dissipative phenomena have not been studies well in relativistic
situations. Furthermore, the interactions among dissipations, e.g. the heating
of fluid due to viscous flow and the occurrence of viscous flow due to heat
flux, are not explicitly described in those traditional laws. One of the
phenomenologies which describe the causality and interaction of dissipations is
the Extended Irreversible Thermodynamics (EIT). (Israel-Stewart theory of
dissipative hydrodynamics is one approximate form of EIT.) This manuscript
reviews an axiomatic construction of EIT and Israel-Stewart hydrodynamic
theory. Also, we point out that the EIT is also applicable to radiative
transfer in optically \emph{thick} matters. However, radiative transfer in
optically \emph{thin} matters can not be described by EIT, because the
non-self-interacting nature of photons is incompatible with a basic requirement
of EIT, "the bilinear form of entropy production rate". The break down of EIT
in optically thin situation is not explicitly recognized in standard references
of EIT and Israel-Stewart theory. Some detail of how EIT fails to describe a
radiative transfer in optically thin situations is also explained. (This
manuscript is a revision of the contribution to a book Ref.[26] published in
2011. So, recent developments made after 2011 may not be cited.)
| [
{
"created": "Tue, 16 May 2017 04:19:55 GMT",
"version": "v1"
}
] | 2017-05-17 | [
[
"Saida",
"Hiromi",
""
]
] | The causality of dissipative phenomena can not be treated in traditional theories of dissipations, Fourier laws and Navier-Stokes equations. This is the reason why the dissipative phenomena have not been studies well in relativistic situations. Furthermore, the interactions among dissipations, e.g. the heating of fluid due to viscous flow and the occurrence of viscous flow due to heat flux, are not explicitly described in those traditional laws. One of the phenomenologies which describe the causality and interaction of dissipations is the Extended Irreversible Thermodynamics (EIT). (Israel-Stewart theory of dissipative hydrodynamics is one approximate form of EIT.) This manuscript reviews an axiomatic construction of EIT and Israel-Stewart hydrodynamic theory. Also, we point out that the EIT is also applicable to radiative transfer in optically \emph{thick} matters. However, radiative transfer in optically \emph{thin} matters can not be described by EIT, because the non-self-interacting nature of photons is incompatible with a basic requirement of EIT, "the bilinear form of entropy production rate". The break down of EIT in optically thin situation is not explicitly recognized in standard references of EIT and Israel-Stewart theory. Some detail of how EIT fails to describe a radiative transfer in optically thin situations is also explained. (This manuscript is a revision of the contribution to a book Ref.[26] published in 2011. So, recent developments made after 2011 may not be cited.) |
2012.14984 | Manuel Hohmann | Manuel Hohmann | xPPN: An implementation of the parametrized post-Newtonian formalism
using xAct for Mathematica | 35 pages, no figures, journal version | Eur. Phys. J. C 81 (2021) 504 | 10.1140/epjc/s10052-021-09183-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a package for the computer algebra system Mathematica, which
implements the parametrized post-Newtonian (PPN) formalism. This package, named
xPPN, is built upon the widely used tensor algebra package suite xAct, and in
particular the package xTensor therein. The main feature of xPPN is to provide
functions to perform a proper $3+1$ decomposition of tensors, as well as a
perturbative expansion in so-called velocity orders, which are central tasks in
the PPN formalism. Further, xPPN implements various rules for quantities
appearing in the PPN formalism, which aid in perturbatively solving the field
equations of any metric theory of gravity. Besides Riemannian geometry, also
teleparallel and symmetric teleparallel geometry are implemented.
| [
{
"created": "Wed, 30 Dec 2020 00:12:37 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Jun 2021 14:13:23 GMT",
"version": "v2"
}
] | 2021-06-18 | [
[
"Hohmann",
"Manuel",
""
]
] | We present a package for the computer algebra system Mathematica, which implements the parametrized post-Newtonian (PPN) formalism. This package, named xPPN, is built upon the widely used tensor algebra package suite xAct, and in particular the package xTensor therein. The main feature of xPPN is to provide functions to perform a proper $3+1$ decomposition of tensors, as well as a perturbative expansion in so-called velocity orders, which are central tasks in the PPN formalism. Further, xPPN implements various rules for quantities appearing in the PPN formalism, which aid in perturbatively solving the field equations of any metric theory of gravity. Besides Riemannian geometry, also teleparallel and symmetric teleparallel geometry are implemented. |
gr-qc/9308018 | Donald Marolf | Jorma Louko and Donald M. Marolf | Solution space of 2+1 gravity on ${\bf R} \times T^2$ in Witten's
connection formulation | 23 pages, REVTeX v3.0, SU-GP-93/7-6, CGPG-93/8-3. (Discussion on the
gauge equivalence of degenerate and nondegenerate metrics extended.) | Class.Quant.Grav.11:311-330,1994 | 10.1088/0264-9381/11/2/005 | null | gr-qc hep-th | null | We investigate the space ${\cal M}$ of classical solutions to Witten's
formulation of 2+1 gravity on the manifold ${\bf R} \times T^2$. ${\cal M}$ is
connected, unlike the spaces of classical solutions in the cases where $T^2$ is
replaced by a higher genus surface. Although ${\cal M}$ is neither Hausdorff
nor a manifold, removing from ${\cal M}$ a set of measure zero yields a
manifold which is naturally viewed as the cotangent bundle over a non-Hausdorff
base space~${\cal B}$. We discuss the relation of the various parts of ${\cal
M}$ to spacetime metrics, and various possibilities of quantizing~${\cal M}$.
There exist quantizations in which the exponentials of certain momentum
operators, when operating on states whose support is entirely on the part of
${\cal B}$ corresponding to conventional spacetime metrics, give states whose
support is entirely outside this part of~${\cal B}$. Similar results hold when
the gauge group ${\rm SO}_0(2,1)$ is replaced by ${\rm SU}(1,1)$.
| [
{
"created": "Thu, 19 Aug 1993 22:51:00 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Nov 1993 23:25:00 GMT",
"version": "v2"
}
] | 2010-04-06 | [
[
"Louko",
"Jorma",
""
],
[
"Marolf",
"Donald M.",
""
]
] | We investigate the space ${\cal M}$ of classical solutions to Witten's formulation of 2+1 gravity on the manifold ${\bf R} \times T^2$. ${\cal M}$ is connected, unlike the spaces of classical solutions in the cases where $T^2$ is replaced by a higher genus surface. Although ${\cal M}$ is neither Hausdorff nor a manifold, removing from ${\cal M}$ a set of measure zero yields a manifold which is naturally viewed as the cotangent bundle over a non-Hausdorff base space~${\cal B}$. We discuss the relation of the various parts of ${\cal M}$ to spacetime metrics, and various possibilities of quantizing~${\cal M}$. There exist quantizations in which the exponentials of certain momentum operators, when operating on states whose support is entirely on the part of ${\cal B}$ corresponding to conventional spacetime metrics, give states whose support is entirely outside this part of~${\cal B}$. Similar results hold when the gauge group ${\rm SO}_0(2,1)$ is replaced by ${\rm SU}(1,1)$. |
2004.08065 | Igor Fomin | Igor Fomin | Gauss-Bonnet term corrections in scalar field cosmology | 18 pages | null | 10.1140/epjc/s10052-020-08718-w | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The influence of non-minimal coupling of a scalar field and the Gauss-Bonnet
term on the inflationary stage of evolution of the universe is investigated in
this paper. The main cosmological effects of such a coupling were considered.
The deviations between Einstein-Gauss-Bonnet inflation and standard one based
on Einstein gravity were determined. The corrections of a weak GB coupling
preserving the type of the scalar field potential to standard inflationary
models is considered as well.
| [
{
"created": "Fri, 17 Apr 2020 05:17:15 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Jul 2020 13:48:09 GMT",
"version": "v2"
}
] | 2020-12-30 | [
[
"Fomin",
"Igor",
""
]
] | The influence of non-minimal coupling of a scalar field and the Gauss-Bonnet term on the inflationary stage of evolution of the universe is investigated in this paper. The main cosmological effects of such a coupling were considered. The deviations between Einstein-Gauss-Bonnet inflation and standard one based on Einstein gravity were determined. The corrections of a weak GB coupling preserving the type of the scalar field potential to standard inflationary models is considered as well. |
0905.2000 | Luca Perotti | Daniel Bessis and Luca Perotti | J-transform applied to the detection of Gravitational Waves: preliminary
results | 12 pages, 7 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose to apply to the detection of Gravitational Waves a new method
developed for the spectral analysis of noisy time-series of damped oscillators.
From the Pad\'e Approximations of the time-series Z-transform, a Jacobi
Matrix (J-Matrix) is constructed. We show that the J-Matrix has bound states
with eigenvalues strictly inside the unit circle. Each bound state can be
identified with one precise damped oscillator. Beside these bound states, there
is an essential spectrum sitting on the unit circle which represents the noise.
In this picture, signal and noise are clearly separated and identified in the
complex plane. Furthermore, we show that the J-transform enjoys the exceptional
feature of lossless undersampling. We take advantage of the above properties of
the J-transform to develop a procedure for the search of Gravitational Wave
bursts in interferometric data series such as those of LIGO and VIRGO projects.
Successful application of our procedure to simulated data having a poor signal
to noise ratio, highlights the power of our method.
| [
{
"created": "Wed, 13 May 2009 02:09:41 GMT",
"version": "v1"
}
] | 2009-05-14 | [
[
"Bessis",
"Daniel",
""
],
[
"Perotti",
"Luca",
""
]
] | We propose to apply to the detection of Gravitational Waves a new method developed for the spectral analysis of noisy time-series of damped oscillators. From the Pad\'e Approximations of the time-series Z-transform, a Jacobi Matrix (J-Matrix) is constructed. We show that the J-Matrix has bound states with eigenvalues strictly inside the unit circle. Each bound state can be identified with one precise damped oscillator. Beside these bound states, there is an essential spectrum sitting on the unit circle which represents the noise. In this picture, signal and noise are clearly separated and identified in the complex plane. Furthermore, we show that the J-transform enjoys the exceptional feature of lossless undersampling. We take advantage of the above properties of the J-transform to develop a procedure for the search of Gravitational Wave bursts in interferometric data series such as those of LIGO and VIRGO projects. Successful application of our procedure to simulated data having a poor signal to noise ratio, highlights the power of our method. |
1001.1564 | Viktor Toth | John W. Moffat and Viktor T. Toth | Modified Jordan-Brans-Dicke theory with scalar current and the
Eddington-Robertson gamma-parameter | 7 pages, accepted for publication in International Journal of Modern
Physics D | Int. J. Mod. Phys. D21, No. 12 (2012) 1250084 | 10.1142/S0218271812500848 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Jordan-Brans-Dicke theory of gravitation, which promotes the
gravitational constant to a dynamical scalar field, predicts a value for the
Eddington-Robertson post-Newtonian parameter gamma that is significantly
different from the general relativistic value of unity. This contradicts
precision solar system measurements that tightly constrain gamma around 1. We
consider a modification of the theory, in which the scalar field is sourced
explicitly by matter. We find that this leads to a modified expression for the
gamma-parameter. In particular, a specific choice of the scalar current yields
gamma=1, just as in general relativity, while the weak equivalence principle is
also satisfied. This result has important implications for theories that mimic
Jordan-Brans-Dicke theory in the post-Newtonian limit in the solar system,
including our scalar-tensor-vector modified gravity theory (MOG).
| [
{
"created": "Mon, 11 Jan 2010 20:42:30 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Feb 2010 02:12:27 GMT",
"version": "v2"
},
{
"created": "Fri, 5 Oct 2012 17:38:06 GMT",
"version": "v3"
}
] | 2012-12-12 | [
[
"Moffat",
"John W.",
""
],
[
"Toth",
"Viktor T.",
""
]
] | The Jordan-Brans-Dicke theory of gravitation, which promotes the gravitational constant to a dynamical scalar field, predicts a value for the Eddington-Robertson post-Newtonian parameter gamma that is significantly different from the general relativistic value of unity. This contradicts precision solar system measurements that tightly constrain gamma around 1. We consider a modification of the theory, in which the scalar field is sourced explicitly by matter. We find that this leads to a modified expression for the gamma-parameter. In particular, a specific choice of the scalar current yields gamma=1, just as in general relativity, while the weak equivalence principle is also satisfied. This result has important implications for theories that mimic Jordan-Brans-Dicke theory in the post-Newtonian limit in the solar system, including our scalar-tensor-vector modified gravity theory (MOG). |
gr-qc/0202022 | L. C. Garcia de Andrade | L.C.Garcia de Andrade | Metric perturbations in Einstein-Cartan Cosmology | Latex file | null | null | null | gr-qc | null | Metric perturbations the stability of solution of Einstein-Cartan cosmology
(ECC) are given. The first addresses the stability of solutions of
Einstein-Cartan (EC) cosmological model against Einstein static universe
background. In this solution we show that the metric is stable against
first-order perturbations and correspond to acoustic oscillations. The second
example deals with the stability of de Sitter metric also against first-order
perturbations. Torsion and shear are also computed in these cases. The
resultant perturbed anisotropic spacetime with torsion is only de Sitter along
one direction or is unperturbed along one direction and perturbed against the
other two. Cartan torsion contributes to the frequency of oscillations in the
model. Therefore gravitational waves could be triggered by the spin-torsion
scalar density .
| [
{
"created": "Thu, 7 Feb 2002 08:47:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Andrade",
"L. C. Garcia",
""
]
] | Metric perturbations the stability of solution of Einstein-Cartan cosmology (ECC) are given. The first addresses the stability of solutions of Einstein-Cartan (EC) cosmological model against Einstein static universe background. In this solution we show that the metric is stable against first-order perturbations and correspond to acoustic oscillations. The second example deals with the stability of de Sitter metric also against first-order perturbations. Torsion and shear are also computed in these cases. The resultant perturbed anisotropic spacetime with torsion is only de Sitter along one direction or is unperturbed along one direction and perturbed against the other two. Cartan torsion contributes to the frequency of oscillations in the model. Therefore gravitational waves could be triggered by the spin-torsion scalar density . |
2108.01461 | Francisco Fern\'andez-\'Alvarez | Francisco Fern\'andez-\'Alvarez and Jos\'e M. M. Senovilla | The peeling theorem with arbitrary cosmological constant | 10 pages, 1 figure | Class. Quant. Grav. 39 10LT01 2022 | 10.1088/1361-6382/ac528b | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A method for deriving the asymptotic behaviour of any physical field is
presented. This leads to a geometrically meaningful derivation of the peeling
properties for arbitrary values of the cosmological constant. Application to
the outstanding case of the physical Weyl tensor provides the explicit form of
all terms that determine its asymptotic behaviour along arbitrary lightlike
geodesics. The results follow under the assumption of a conformal completion
\`a la Penrose. The only freedom available is the choice of a null vector at
the conformal boundary of the space-time (which determines the lightlike
geodesic arriving there).
| [
{
"created": "Tue, 3 Aug 2021 12:55:21 GMT",
"version": "v1"
}
] | 2022-08-23 | [
[
"Fernández-Álvarez",
"Francisco",
""
],
[
"Senovilla",
"José M. M.",
""
]
] | A method for deriving the asymptotic behaviour of any physical field is presented. This leads to a geometrically meaningful derivation of the peeling properties for arbitrary values of the cosmological constant. Application to the outstanding case of the physical Weyl tensor provides the explicit form of all terms that determine its asymptotic behaviour along arbitrary lightlike geodesics. The results follow under the assumption of a conformal completion \`a la Penrose. The only freedom available is the choice of a null vector at the conformal boundary of the space-time (which determines the lightlike geodesic arriving there). |
0811.0655 | Molin Liu | Molin Liu and Hongya Liu | The Dynamic Behavior of Quantum Statistical Entropy in 5D Ricci-flat
Black String with Thin-layer Approach | 9 pages, 1 figure, this work is dedicated to the memory of Professor
Hongya Liu | Phys.Lett.B661:365-369,2008 | 10.1016/j.physletb.2008.02.037 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, the statistical-mechanical entropies of 5D Ricci-flat black
string is calculated through the wave modes of the quantum field with improved
thin-layer brick-wall method. The modes along the fifth dimension are
semi-classically quantized by Randall-Sundrum mass relationship. We use the
two-dimensional area to describe this black string's entropy which, in the
small-mass approximation, is a linear sum of the area of the black hole horizon
and the cosmological horizon. The proportionality coefficients of entropy are
discretized with quantized extra dimensional modes. It should be noted that the
small-mass approximation used in our calculation is naturally justified by the
assumption that the two branes are located far apart.
| [
{
"created": "Wed, 5 Nov 2008 06:57:30 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Liu",
"Molin",
""
],
[
"Liu",
"Hongya",
""
]
] | In this paper, the statistical-mechanical entropies of 5D Ricci-flat black string is calculated through the wave modes of the quantum field with improved thin-layer brick-wall method. The modes along the fifth dimension are semi-classically quantized by Randall-Sundrum mass relationship. We use the two-dimensional area to describe this black string's entropy which, in the small-mass approximation, is a linear sum of the area of the black hole horizon and the cosmological horizon. The proportionality coefficients of entropy are discretized with quantized extra dimensional modes. It should be noted that the small-mass approximation used in our calculation is naturally justified by the assumption that the two branes are located far apart. |
1107.1566 | Alexander Garkun S. | A.S. Garkun, V.I. Kudin, A.V. Minkevich and Yu.G. Vasilevsky | Numerical analysis of cosmological models for accelerating Universe in
Poincare gauge theory of gravity | 19 pages, 6 figures, jcappub style file | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Homogeneous isotropic models with two torsion functions built in the
framework of the Poincare gauge theory of gravity based on general expression
of gravitational Lagrangian by certain restrictions on indefinite parameters
are analyzed numerically. Special points of cosmological solutions at
asymptotics and conditions of their stability in dependence of indefinite
parameters are found. Procedure of numerical integration of the system of
gravitational equations at asymptotics is considered. Numerical solution for
accelerating Universe without dark energy and dark matter is obtained. It is
shown that by certain restrictions on indefinite parameters obtained
cosmological solutions are in agreement with SNe Ia observational data and Big
Bang Nucleosynthesis predictions. Statefinder diagnostics is discussed in order
to compare considered cosmological model with other models.
| [
{
"created": "Fri, 8 Jul 2011 06:46:49 GMT",
"version": "v1"
}
] | 2015-03-19 | [
[
"Garkun",
"A. S.",
""
],
[
"Kudin",
"V. I.",
""
],
[
"Minkevich",
"A. V.",
""
],
[
"Vasilevsky",
"Yu. G.",
""
]
] | Homogeneous isotropic models with two torsion functions built in the framework of the Poincare gauge theory of gravity based on general expression of gravitational Lagrangian by certain restrictions on indefinite parameters are analyzed numerically. Special points of cosmological solutions at asymptotics and conditions of their stability in dependence of indefinite parameters are found. Procedure of numerical integration of the system of gravitational equations at asymptotics is considered. Numerical solution for accelerating Universe without dark energy and dark matter is obtained. It is shown that by certain restrictions on indefinite parameters obtained cosmological solutions are in agreement with SNe Ia observational data and Big Bang Nucleosynthesis predictions. Statefinder diagnostics is discussed in order to compare considered cosmological model with other models. |
gr-qc/0501020 | J. Mark Heinzle | Robert Beig, J. Mark Heinzle | CMC-Slicings of Kottler-Schwarzschild-de Sitter Cosmologies | 39 pages, 14 figures; some remarks added, to appear in Commun. Math.
Phys | Commun.Math.Phys. 260 (2005) 673-709 | 10.1007/s00220-005-1431-5 | null | gr-qc | null | There is constructed, for each member of a one-parameter family of
cosmological models, which is obtained from the Kottler-Schwarzschild-de Sitter
spacetime by identification under discrete isometries, a slicing by spherically
symmetric Cauchy hypersurfaces of constant mean curvature. These slicings are
unique up to the action of the static Killing vector. Analytical and numerical
results are found as to when different leaves of these slicings do not
intersect, i.e. when the slicings form foliations.
| [
{
"created": "Fri, 7 Jan 2005 17:36:06 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Feb 2005 14:55:46 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Beig",
"Robert",
""
],
[
"Heinzle",
"J. Mark",
""
]
] | There is constructed, for each member of a one-parameter family of cosmological models, which is obtained from the Kottler-Schwarzschild-de Sitter spacetime by identification under discrete isometries, a slicing by spherically symmetric Cauchy hypersurfaces of constant mean curvature. These slicings are unique up to the action of the static Killing vector. Analytical and numerical results are found as to when different leaves of these slicings do not intersect, i.e. when the slicings form foliations. |
1212.3271 | Aaron Zimmerman | Huan Yang, Fan Zhang, Aaron Zimmerman, David A. Nichols, Emanuele
Berti, Yanbei Chen | Branching of quasinormal modes for nearly extremal Kerr black holes | 5 pages, 3 figures | Phys. Rev. D 87, 041502(R) (2013) | 10.1103/PhysRevD.87.041502 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that nearly extremal Kerr black holes have two distinct sets of
quasinormal modes, which we call zero-damping modes (ZDMs) and damped modes
(DMs). The ZDMs exist for all harmonic indices $l$ and $m \ge 0$, and their
frequencies cluster onto the real axis in the extremal limit. The DMs have
nonzero damping for all black hole spins; they exist for all counterrotating
modes ($m<0$) and for corotating modes with $0\leq \mu\lesssim \mu_c=0.74$ (in
the eikonal limit), where $\mu\equiv m/(l+1/2)$. When the two families coexist,
ZDMs and DMs merge to form a single set of quasinormal modes as the black hole
spin decreases. Using the effective potential for perturbations of the Kerr
spacetime, we give intuitive explanations for the absence of DMs in certain
areas of the spectrum and for the branching of the spectrum into ZDMs and DMs
at large spins.
| [
{
"created": "Thu, 13 Dec 2012 19:08:12 GMT",
"version": "v1"
}
] | 2013-03-05 | [
[
"Yang",
"Huan",
""
],
[
"Zhang",
"Fan",
""
],
[
"Zimmerman",
"Aaron",
""
],
[
"Nichols",
"David A.",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Chen",
"Yanbei",
""
]
] | We show that nearly extremal Kerr black holes have two distinct sets of quasinormal modes, which we call zero-damping modes (ZDMs) and damped modes (DMs). The ZDMs exist for all harmonic indices $l$ and $m \ge 0$, and their frequencies cluster onto the real axis in the extremal limit. The DMs have nonzero damping for all black hole spins; they exist for all counterrotating modes ($m<0$) and for corotating modes with $0\leq \mu\lesssim \mu_c=0.74$ (in the eikonal limit), where $\mu\equiv m/(l+1/2)$. When the two families coexist, ZDMs and DMs merge to form a single set of quasinormal modes as the black hole spin decreases. Using the effective potential for perturbations of the Kerr spacetime, we give intuitive explanations for the absence of DMs in certain areas of the spectrum and for the branching of the spectrum into ZDMs and DMs at large spins. |
2202.08608 | Tao Yang | Tao Yang, Rong-Gen Cai, Zhoujian Cao, Hyung Mok Lee | Eccentricity of Long Inspiraling Compact Binaries Sheds Light on Dark
Sirens | 6 pages, 2 figures, to match the published PRL version | Phys. Rev. Lett. 129, 191102 (2022) | 10.1103/PhysRevLett.129.191102 | null | gr-qc astro-ph.CO astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The localization and distance inference of gravitational waves are two
crucial factors for dark sirens as precise probes of cosmology, astrophysics,
and fundamental physics. In this Letter, for the first time we investigate the
parameter estimation of gravitational waves emitted by the eccentric compact
binaries in the mid-frequency (0.1--10 Hz) band. Based on the configuration of
one cluster of DECIGO (B-DECIGO), we simulate five types of typical compact
binaries in GWTC-3 with component mass ranging from
$\mathcal{O}(1\sim100)~M_{\odot}$. For each type of binaries, we assign
discrete eccentricities from 0 to 0.4 at 0.1 Hz in $10^3$ random orientations.
The multiple harmonics induced by eccentricity can break the degeneracy between
parameters. We find that with eccentricity $e_0=0.4$, these typical binaries
can achieve $\mathcal{O}(10^2-10^4)$ improvement for the distance inference in
the near face-on orientations, compared to the circular case. More importantly,
a nonvanishing eccentricity ($0.01\sim0.4$) can significantly improve the
source localization of the typical binary black holes, most by $1.5\sim{3.5}$
orders of magnitude. Our result shows the remarkable significance of
eccentricity for dark sirens in the mid-band as precise probes of the Universe.
| [
{
"created": "Thu, 17 Feb 2022 11:43:14 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Oct 2022 15:53:00 GMT",
"version": "v2"
}
] | 2022-11-01 | [
[
"Yang",
"Tao",
""
],
[
"Cai",
"Rong-Gen",
""
],
[
"Cao",
"Zhoujian",
""
],
[
"Lee",
"Hyung Mok",
""
]
] | The localization and distance inference of gravitational waves are two crucial factors for dark sirens as precise probes of cosmology, astrophysics, and fundamental physics. In this Letter, for the first time we investigate the parameter estimation of gravitational waves emitted by the eccentric compact binaries in the mid-frequency (0.1--10 Hz) band. Based on the configuration of one cluster of DECIGO (B-DECIGO), we simulate five types of typical compact binaries in GWTC-3 with component mass ranging from $\mathcal{O}(1\sim100)~M_{\odot}$. For each type of binaries, we assign discrete eccentricities from 0 to 0.4 at 0.1 Hz in $10^3$ random orientations. The multiple harmonics induced by eccentricity can break the degeneracy between parameters. We find that with eccentricity $e_0=0.4$, these typical binaries can achieve $\mathcal{O}(10^2-10^4)$ improvement for the distance inference in the near face-on orientations, compared to the circular case. More importantly, a nonvanishing eccentricity ($0.01\sim0.4$) can significantly improve the source localization of the typical binary black holes, most by $1.5\sim{3.5}$ orders of magnitude. Our result shows the remarkable significance of eccentricity for dark sirens in the mid-band as precise probes of the Universe. |
2007.12636 | Jhonny Andres Agudelo Ruiz J. A. Agudelo Ruiz | Jhonny A. Agudelo Ruiz, J\'ulio C. Fabris, Alan M. Velasquez-Toribio
and Ilya L. Shapiro | Constraints from observational data for a running cosmological constant
and warm dark matter with curvature | 19 pages, 3 figures, 1 table. Two misprints corrected, accepted in
"Gravitation and Cosmology" | Gravitation and Cosmology, 26, Issue 4 (2020) 316-325 | 10.1134/S0202289320040106 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is known than the inclusion of spatial curvature can modify the evolution
of matter perturbations and affect the Large Scale Structure (LSS) formation.
We quantify the effects of the non-zero space curvature in terms of LSS
formation for a cosmological model with a running vacuum energy density and a
warm dark matter component. The evolution of density perturbations and the
modified shape of its power spectrum are constructed and analyzed.
| [
{
"created": "Fri, 24 Jul 2020 16:43:53 GMT",
"version": "v1"
},
{
"created": "Sun, 23 Aug 2020 19:10:57 GMT",
"version": "v2"
}
] | 2020-12-08 | [
[
"Ruiz",
"Jhonny A. Agudelo",
""
],
[
"Fabris",
"Júlio C.",
""
],
[
"Velasquez-Toribio",
"Alan M.",
""
],
[
"Shapiro",
"Ilya L.",
""
]
] | It is known than the inclusion of spatial curvature can modify the evolution of matter perturbations and affect the Large Scale Structure (LSS) formation. We quantify the effects of the non-zero space curvature in terms of LSS formation for a cosmological model with a running vacuum energy density and a warm dark matter component. The evolution of density perturbations and the modified shape of its power spectrum are constructed and analyzed. |
gr-qc/9908057 | Bernhard Haisch | Bernhard Haisch and Alfonso Rueda | The Zero-Point Field and Inertia | 8 pages, no figs | in "Causality and Locality in Modern Physics" (G. Hunter, S.
Jeffers, J.-P. Vigier (eds.), Kluwer Acad. Publ., pp. 171-178, (1998) | null | null | gr-qc | null | A brief overview is presented of the basis of the electromagnetic zero-point
field in quantum physics and its representation in stochastic electrodynamics.
Two approaches have led to the proposal that the inertia of matter may be
explained as an electromagnetic reaction force. The first is based on the
modeling of quarks and electrons as Planck oscillators and the method of
Einstein and Hopf to treat the interaction of the zero-point field with such
oscillators. The second approach is based on analysis of the Poynting vector of
the zero-point field in accelerated reference frames. It is possible to derive
both Newton's equation of motion, F=ma, and its relativistic co-variant form
from Maxwell's equations as applied to the zero-point field of the quantum
vacuum. This appears to account, at least in part, for the inertia of matter.
| [
{
"created": "Thu, 19 Aug 1999 22:10:33 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Haisch",
"Bernhard",
""
],
[
"Rueda",
"Alfonso",
""
]
] | A brief overview is presented of the basis of the electromagnetic zero-point field in quantum physics and its representation in stochastic electrodynamics. Two approaches have led to the proposal that the inertia of matter may be explained as an electromagnetic reaction force. The first is based on the modeling of quarks and electrons as Planck oscillators and the method of Einstein and Hopf to treat the interaction of the zero-point field with such oscillators. The second approach is based on analysis of the Poynting vector of the zero-point field in accelerated reference frames. It is possible to derive both Newton's equation of motion, F=ma, and its relativistic co-variant form from Maxwell's equations as applied to the zero-point field of the quantum vacuum. This appears to account, at least in part, for the inertia of matter. |
gr-qc/0503080 | Ronghua Pan | Ronghua Pan and Joel A. Smoller | Blowup of smooth solutions for relativistic Euler equations | 30 pages | Commun.Math.Phys. 262 (2006) 729-755 | 10.1007/s00220-005-1464-9 | null | gr-qc math-ph math.AP math.MP | null | We study the singularity formation of smooth solutions of the relativistic
Euler equations in $(3+1)$-dimensional spacetime for both finite initial energy
and infinite initial energy. For the finite initial energy case, we prove that
any smooth solution, with compactly supported non-trivial initial data, blows
up in finite time. For the case of infinite initial energy, we first prove the
existence, uniqueness and stability of a smooth solution if the initial data is
in the subluminal region away from the vacuum. By further assuming the initial
data is a smooth compactly supported perturbation around a non-vacuum constant
background, we prove the property of finite propagation speed of such a
perturbation. The smooth solution is shown to blow up in finite time provided
that the radial component of the initial "generalized" momentum is sufficiently
large.
| [
{
"created": "Fri, 18 Mar 2005 19:19:42 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Pan",
"Ronghua",
""
],
[
"Smoller",
"Joel A.",
""
]
] | We study the singularity formation of smooth solutions of the relativistic Euler equations in $(3+1)$-dimensional spacetime for both finite initial energy and infinite initial energy. For the finite initial energy case, we prove that any smooth solution, with compactly supported non-trivial initial data, blows up in finite time. For the case of infinite initial energy, we first prove the existence, uniqueness and stability of a smooth solution if the initial data is in the subluminal region away from the vacuum. By further assuming the initial data is a smooth compactly supported perturbation around a non-vacuum constant background, we prove the property of finite propagation speed of such a perturbation. The smooth solution is shown to blow up in finite time provided that the radial component of the initial "generalized" momentum is sufficiently large. |
gr-qc/0703005 | Christos Tsagas | Christos G. Tsagas | On constraint-consistency, covariant operators, gauge-invariance, etc | 4 pages | null | null | null | gr-qc | null | We look at the covariant techniques and the ideas on constraints and
gauge-invariance, which were recently employed in [gr-qc/0702104] to support
earlier work by the same authors. That work was criticised in [gr-qc/0503042].
Using very simple and well known examples we show that, when adopted, the
methods and views of [gr-qc/0702104] lead to basic-level mathematical problems,
with analogous consequences for the physics. We provide a few simple rules that
should help to avoid similar problems in the future.
| [
{
"created": "Thu, 1 Mar 2007 18:14:32 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Tsagas",
"Christos G.",
""
]
] | We look at the covariant techniques and the ideas on constraints and gauge-invariance, which were recently employed in [gr-qc/0702104] to support earlier work by the same authors. That work was criticised in [gr-qc/0503042]. Using very simple and well known examples we show that, when adopted, the methods and views of [gr-qc/0702104] lead to basic-level mathematical problems, with analogous consequences for the physics. We provide a few simple rules that should help to avoid similar problems in the future. |
1204.3696 | Alexis Larranaga PhD | Alexis Larranaga, Sindi Mojica | Geometric Thermodynamics of Kerr-AdS black hole with a Cosmological
Constant as State Variable | 10 pages, no figures. arXiv admin note: substantial text overlap with
arXiv:1108.2205 | The Abraham Zelmanov Journal. 5. 68-77 (2012) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The thermodynamics of the Kerr-AdS black hole is reformulated within the
context of the formalism of geometrothermodynamics (GTD) and the cosmological
constant is considered as a new thermodynamical parameter. We conclude that the
mass of the black hole corresponds to the total enthalpy of this system.
Choosing appropriately the metric in the equilibrium states manifold, we study
the phase transitions as a divergence of the thermodynamical curvature scalar.
This approach reproduces the Hawking-Page transition and shows that considering
the cosmological constant as a thermodynamical parameter does not contribute
with new phase transitions.
| [
{
"created": "Tue, 17 Apr 2012 03:57:51 GMT",
"version": "v1"
}
] | 2012-04-18 | [
[
"Larranaga",
"Alexis",
""
],
[
"Mojica",
"Sindi",
""
]
] | The thermodynamics of the Kerr-AdS black hole is reformulated within the context of the formalism of geometrothermodynamics (GTD) and the cosmological constant is considered as a new thermodynamical parameter. We conclude that the mass of the black hole corresponds to the total enthalpy of this system. Choosing appropriately the metric in the equilibrium states manifold, we study the phase transitions as a divergence of the thermodynamical curvature scalar. This approach reproduces the Hawking-Page transition and shows that considering the cosmological constant as a thermodynamical parameter does not contribute with new phase transitions. |
1311.6319 | Giulia Ricciardi | Salvatore Capozziello, Mariafelicia De Laurentis, Mariacristina
Paolella, Giulia Ricciardi | Effective field theory from modified gravity with massive modes | 11 pages, no figures; title and text match published version | Int.J.Geom.Meth.Mod.Phys. 12 (2015) 1550004 | 10.1142/S0219887815500048 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Massive gravitational modes in effective field theories can be recovered by
extending General Relativity and taking into account generic functions of the
curvature invariants, not necessarily linear in the Ricci scalar R. In
particular, adopting the minimal extension of f(R) gravity, an effective field
theory with massive modes is straightforwardly recovered. This approach allows
to evade shortcomings like ghosts and discontinuities if a suitable choice of
expansion parameters is performed.
| [
{
"created": "Mon, 25 Nov 2013 14:44:42 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Nov 2013 16:41:30 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Jan 2015 15:39:50 GMT",
"version": "v3"
}
] | 2015-01-22 | [
[
"Capozziello",
"Salvatore",
""
],
[
"De Laurentis",
"Mariafelicia",
""
],
[
"Paolella",
"Mariacristina",
""
],
[
"Ricciardi",
"Giulia",
""
]
] | Massive gravitational modes in effective field theories can be recovered by extending General Relativity and taking into account generic functions of the curvature invariants, not necessarily linear in the Ricci scalar R. In particular, adopting the minimal extension of f(R) gravity, an effective field theory with massive modes is straightforwardly recovered. This approach allows to evade shortcomings like ghosts and discontinuities if a suitable choice of expansion parameters is performed. |
1607.03099 | Michael Kalisch | Michael Kalisch and Marcus Ansorg | Pseudo-spectral construction of non-uniform black string solutions in
five and six spacetime dimensions | null | Michael Kalisch and Marcus Ansorg 2016 Class. Quantum Grav. 33
215005 | 10.1088/0264-9381/33/21/215005 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we describe in detail a scheme for the construction of highly
accurate numerical solutions to Einstein's field equations in five and six
spacetime dimensions corresponding to non-uniform black strings. The scheme
consists of a sophistically adapted multi-domain pseudo-spectral method which
incorporates a detailed understanding of the solution's behavior at the domain
boundaries and at critical points. In particular, the five-dimensional case is
exceedingly demanding as logarithmic terms appear which need to be treated with
special care. The scheme resolves these issues and permits the investigation of
unprecedentedly strong deformations of the black string horizon. As a
consequence, we are able to study in detail the critical regime in phase
diagrams displaying characteristic thermodynamic quantities such as mass and
entropy. Our results show typical spiral curves in such diagrams which provides
a strong support of previous numerical works.
| [
{
"created": "Mon, 11 Jul 2016 19:59:21 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jul 2016 05:58:09 GMT",
"version": "v2"
}
] | 2016-10-20 | [
[
"Kalisch",
"Michael",
""
],
[
"Ansorg",
"Marcus",
""
]
] | In this paper, we describe in detail a scheme for the construction of highly accurate numerical solutions to Einstein's field equations in five and six spacetime dimensions corresponding to non-uniform black strings. The scheme consists of a sophistically adapted multi-domain pseudo-spectral method which incorporates a detailed understanding of the solution's behavior at the domain boundaries and at critical points. In particular, the five-dimensional case is exceedingly demanding as logarithmic terms appear which need to be treated with special care. The scheme resolves these issues and permits the investigation of unprecedentedly strong deformations of the black string horizon. As a consequence, we are able to study in detail the critical regime in phase diagrams displaying characteristic thermodynamic quantities such as mass and entropy. Our results show typical spiral curves in such diagrams which provides a strong support of previous numerical works. |
2108.06582 | Gerardo Garc\'ia-Moreno | Carlos Barcel\'o, Ra\'ul Carballo-Rubio, Luis J. Garay, Gerardo
Garc\'ia-Moreno | Toward a mechanism for the emergence of gravity | 35 pages, 1 figure; Contribution to the Special Issue Analogue
Gravitational Dynamics; v2: Minor changes introduced in the text to match the
published version | Appl. Sci. 2021, 11(18), 8763 | 10.3390/app11188763 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the main problems that emergent-gravity approaches face is explaining
how a system that does not contain gauge symmetries ab initio might develop
them effectively in some regime. We review a mechanism introduced by some of
the authors for the emergence of gauge symmetries in [JHEP 10 (2016) 084] and
discuss how it works for interacting Lorentz-invariant vector field theories as
a warm-up exercise for the more convoluted problem of gravity. Then, we apply
this mechanism to the emergence of linear diffeomorphisms for the most general
Lorentz-invariant linear theory of a two-index symmetric tensor field, which
constitutes a generalization of the Fierz-Pauli theory describing linearized
gravity. Finally we discuss two results, the well-known Weinberg-Witten theorem
and a more recent theorem by Marolf, that are often invoked as no-go theorems
for emergent gravity. Our analysis illustrates that, although these results
pinpoint some of the particularities of gravity with respect to other gauge
theories, they do not constitute an impediment for the emergent gravity program
if gauge symmetries (diffeomorphisms) are emergent in the sense discussed in
this paper.
| [
{
"created": "Sat, 14 Aug 2021 16:49:52 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Sep 2021 14:02:05 GMT",
"version": "v2"
}
] | 2021-09-22 | [
[
"Barceló",
"Carlos",
""
],
[
"Carballo-Rubio",
"Raúl",
""
],
[
"Garay",
"Luis J.",
""
],
[
"García-Moreno",
"Gerardo",
""
]
] | One of the main problems that emergent-gravity approaches face is explaining how a system that does not contain gauge symmetries ab initio might develop them effectively in some regime. We review a mechanism introduced by some of the authors for the emergence of gauge symmetries in [JHEP 10 (2016) 084] and discuss how it works for interacting Lorentz-invariant vector field theories as a warm-up exercise for the more convoluted problem of gravity. Then, we apply this mechanism to the emergence of linear diffeomorphisms for the most general Lorentz-invariant linear theory of a two-index symmetric tensor field, which constitutes a generalization of the Fierz-Pauli theory describing linearized gravity. Finally we discuss two results, the well-known Weinberg-Witten theorem and a more recent theorem by Marolf, that are often invoked as no-go theorems for emergent gravity. Our analysis illustrates that, although these results pinpoint some of the particularities of gravity with respect to other gauge theories, they do not constitute an impediment for the emergent gravity program if gauge symmetries (diffeomorphisms) are emergent in the sense discussed in this paper. |
gr-qc/0408082 | Jeanette E. Nelson | J. E. Nelson (University of Turin, Italy) and R. F. Picken (Instituto
Superior Tecnico, Lisbon, Portugal) | Quantum Holonomies in (2+1)-Dimensional Gravity | 5 pages, to appear in the proceedings of 10th Marcel Grossmann
Meeting on Recent Developments in Theoretical and Experimental General
Relativity, Gravitation and Relativistic Field Theories (MG X MMIII), Rio de
Janeiro, Brazil, 20-26 Jul 2003 | null | 10.1142/9789812704030_0318 | null | gr-qc | null | We describe an approach to the quantization of (2+1)--dimensional gravity
with topology R x T^2 and negative cosmological constant, which uses two
quantum holonomy matrices satisfying a q--commutation relation. Solutions of
diagonal and upper--triangular form are constructed, which in the latter case
exhibit additional, non--trivial internal relations for each holonomy matrix.
This leads to the notion of quantum matrix pairs. These are pairs of matrices
with non-commuting entries, which have the same pattern of internal relations,
q-commute with each other under matrix multiplication, and are such that
products of powers of the matrices obey the same pattern of internal relations
as the original pair. This has implications for the classical moduli space,
described by ordered pairs of commuting SL(2,R) matrices modulo simultaneous
conjugation by SL(2,R) matrices.
| [
{
"created": "Wed, 25 Aug 2004 12:11:14 GMT",
"version": "v1"
}
] | 2016-11-09 | [
[
"Nelson",
"J. E.",
"",
"University of Turin, Italy"
],
[
"Picken",
"R. F.",
"",
"Instituto\n Superior Tecnico, Lisbon, Portugal"
]
] | We describe an approach to the quantization of (2+1)--dimensional gravity with topology R x T^2 and negative cosmological constant, which uses two quantum holonomy matrices satisfying a q--commutation relation. Solutions of diagonal and upper--triangular form are constructed, which in the latter case exhibit additional, non--trivial internal relations for each holonomy matrix. This leads to the notion of quantum matrix pairs. These are pairs of matrices with non-commuting entries, which have the same pattern of internal relations, q-commute with each other under matrix multiplication, and are such that products of powers of the matrices obey the same pattern of internal relations as the original pair. This has implications for the classical moduli space, described by ordered pairs of commuting SL(2,R) matrices modulo simultaneous conjugation by SL(2,R) matrices. |
1504.06866 | Vasilis Oikonomou | S.D. Odintsov, V.K. Oikonomou | Bouncing cosmology with future singularity from modified gravity | PRD version | null | 10.1103/PhysRevD.92.024016 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate which Jordan frame $F(R)$ gravity can describe a Type IV
singular bouncing cosmological evolution, with special emphasis given near the
point at which the Type IV singularity occurs. The cosmological bounce is
chosen in such a way so that the bouncing point coincides exactly with Type IV
singularity point. The stability of the resulting $F(R)$ gravity is examined
and in addition, we study the Einstein frame scalar-tensor theory counterpart
of the resulting Jordan frame $F(R)$ gravity. Also, by assuming that the Jordan
frame metric is chosen in such a way so that, when conformally transformed in
the Einstein frame, it yields a quasi de Sitter or de Sitter
Friedmann-Robertson-Walker metric, we study the observational indexes which
turn out to be consistent with Planck 2015 data in the case of the Einstein
frame scalar theory. Finally, we study the behavior of the effective equation
of state corresponding to the Type IV singular bounce and after we compare the
resulting picture with other bouncing cosmologies, we critically discuss the
implications of our analysis.
| [
{
"created": "Sun, 26 Apr 2015 18:52:27 GMT",
"version": "v1"
},
{
"created": "Sat, 27 Jun 2015 09:47:40 GMT",
"version": "v2"
}
] | 2015-08-06 | [
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | We investigate which Jordan frame $F(R)$ gravity can describe a Type IV singular bouncing cosmological evolution, with special emphasis given near the point at which the Type IV singularity occurs. The cosmological bounce is chosen in such a way so that the bouncing point coincides exactly with Type IV singularity point. The stability of the resulting $F(R)$ gravity is examined and in addition, we study the Einstein frame scalar-tensor theory counterpart of the resulting Jordan frame $F(R)$ gravity. Also, by assuming that the Jordan frame metric is chosen in such a way so that, when conformally transformed in the Einstein frame, it yields a quasi de Sitter or de Sitter Friedmann-Robertson-Walker metric, we study the observational indexes which turn out to be consistent with Planck 2015 data in the case of the Einstein frame scalar theory. Finally, we study the behavior of the effective equation of state corresponding to the Type IV singular bounce and after we compare the resulting picture with other bouncing cosmologies, we critically discuss the implications of our analysis. |
2404.03682 | Muhammad Zubair | M. Zubair, Saira Waheed, Quratulien Muneer, M. Ahmad | Thermodynamics and Perturbative Analysis of Some Newly Developed
$\mathcal{F}(R,L_m, T)$ Theories Under the Scenario of Conserved
Energy-momentum Tensor | 24 pages, 13 figures | Fortschr. Phys. 2023, 71, 2300018 | 10.1002/prop.202300018 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The present work is devoted to explore some interesting cosmological features
of a newly proposed theory of gravity namely $\mathcal{F}(R,L_m,T)$ theory,
where $R$ and $T$ represent the Ricci scalar and trace of energy
momentum-tensor, respectively. Firstly, a non-equilibrium thermodynamical
description is considered on the apparent horizon of the Friedmann's cosmos.
The Friedmann equations are demonstrated to be equivalent to the first law of
thermodynamics, i.e.,
${T_{Ah}d\varepsilon_{h}^\prime+T_{Ah}d_{i}\varepsilon_{h}^\prime=-d\hat{E}+\hat{W}dV}$,
where ${d_{i}\varepsilon_{h}^\prime}$ refers to entropy production term. We
also formulate the constraint for validity of generalized second law of
thermodynamics and check it for some simple well-known forms of generic
function $\mathcal{F}(R,L_m,T)$. Next, we develop the energy bounds for this
framework and constraint the free variables by finding the validity regions for
NEC and WEC. Further, we reconstruct some interesting cosmological solutions
namely power law, $\Lambda$CDM and de Sitter models in this theory. The
reconstructed solutions are then examined by checking the validity of GSLT and
energy bounds. Lastly, we analyze the stability of all reconstructed solutions
by introducing suitable perturbations in the field equations. It is concluded
that obtained solutions are stable and cosmologically viable.
| [
{
"created": "Mon, 1 Apr 2024 06:43:21 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Apr 2024 05:04:01 GMT",
"version": "v2"
}
] | 2024-04-09 | [
[
"Zubair",
"M.",
""
],
[
"Waheed",
"Saira",
""
],
[
"Muneer",
"Quratulien",
""
],
[
"Ahmad",
"M.",
""
]
] | The present work is devoted to explore some interesting cosmological features of a newly proposed theory of gravity namely $\mathcal{F}(R,L_m,T)$ theory, where $R$ and $T$ represent the Ricci scalar and trace of energy momentum-tensor, respectively. Firstly, a non-equilibrium thermodynamical description is considered on the apparent horizon of the Friedmann's cosmos. The Friedmann equations are demonstrated to be equivalent to the first law of thermodynamics, i.e., ${T_{Ah}d\varepsilon_{h}^\prime+T_{Ah}d_{i}\varepsilon_{h}^\prime=-d\hat{E}+\hat{W}dV}$, where ${d_{i}\varepsilon_{h}^\prime}$ refers to entropy production term. We also formulate the constraint for validity of generalized second law of thermodynamics and check it for some simple well-known forms of generic function $\mathcal{F}(R,L_m,T)$. Next, we develop the energy bounds for this framework and constraint the free variables by finding the validity regions for NEC and WEC. Further, we reconstruct some interesting cosmological solutions namely power law, $\Lambda$CDM and de Sitter models in this theory. The reconstructed solutions are then examined by checking the validity of GSLT and energy bounds. Lastly, we analyze the stability of all reconstructed solutions by introducing suitable perturbations in the field equations. It is concluded that obtained solutions are stable and cosmologically viable. |
1709.02197 | Genly Le\'on | L. Karpathopoulos, S. Basilakos, G. Leon (Catolica del Norte U.), A.
Paliathanasis, and M. Tsamparlis | Cartan symmetries and global dynamical systems analysis in a
higher-order modified teleparallel theory | Minor changes; accepted for publication by General Relativity and
Gravitation | null | 10.1007/s10714-018-2400-6 | null | gr-qc astro-ph.CO math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a higher-order modified teleparallel theory cosmological we present
analytical cosmological solutions. In particular we determine forms of the
unknown potential which drives the scalar field such that the field equations
form a Liouville integrable system. For the determination of the conservation
laws we apply the Cartan symmetries. Furthermore, inspired from our solutions,
a toy model is studied and it is shown that it can describe the Supernova data,
while at the same time introduces dark matter components in the Hubble
function. When the extra matter source is a stiff fluid then we show how
analytical solutions for Bianchi I universes can be constructed from our
analysis. Finally, we perform a global dynamical analysis of the field
equations by using variables different from that of the Hubble-normalization.
| [
{
"created": "Thu, 7 Sep 2017 12:15:40 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Jun 2018 17:31:34 GMT",
"version": "v2"
}
] | 2018-06-11 | [
[
"Karpathopoulos",
"L.",
"",
"Catolica del Norte U."
],
[
"Basilakos",
"S.",
"",
"Catolica del Norte U."
],
[
"Leon",
"G.",
"",
"Catolica del Norte U."
],
[
"Paliathanasis",
"A.",
""
],
[
"Tsamparlis",
"M.",
""
]
] | In a higher-order modified teleparallel theory cosmological we present analytical cosmological solutions. In particular we determine forms of the unknown potential which drives the scalar field such that the field equations form a Liouville integrable system. For the determination of the conservation laws we apply the Cartan symmetries. Furthermore, inspired from our solutions, a toy model is studied and it is shown that it can describe the Supernova data, while at the same time introduces dark matter components in the Hubble function. When the extra matter source is a stiff fluid then we show how analytical solutions for Bianchi I universes can be constructed from our analysis. Finally, we perform a global dynamical analysis of the field equations by using variables different from that of the Hubble-normalization. |
2407.18975 | Arun Kenath Dr | Louise Rebecca, C Sivaram, Dominic Sebastian, Kenath Arun | Can Hubble tension be eased by invoking a finite range for gravity? | 12 pages, 2 figures, 28 equations | Modern Physics Letters A, 2450073, 2024 | 10.1142/S0217732324500731 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The estimation of the Hubble constant in the past few decades has
increasingly become more accurate with the advance of new techniques. But its
value seems to depend on the epoch at which the measurements are made. The
Planck estimate of the Hubble constant from the observations of the cosmic
microwave background radiation in the early universe is about 67 km/s/Mpc,
whereas that obtained from the distance indicators at the current epoch is
about 73-74 km/s/Mpc. This discrepancy between the two groups of measurement is
termed as the Hubble tension which has gained much attention in the past few
decades with growing significance as measurements from both, the early and the
late universe, studies continue to produce results with increasing precision.
In this work, we propose a modification to gravity by considering a finite
range gravitational field as an alternate explanation for this discrepancy in
the value of the Hubble constant.
| [
{
"created": "Mon, 22 Jul 2024 13:11:03 GMT",
"version": "v1"
}
] | 2024-07-30 | [
[
"Rebecca",
"Louise",
""
],
[
"Sivaram",
"C",
""
],
[
"Sebastian",
"Dominic",
""
],
[
"Arun",
"Kenath",
""
]
] | The estimation of the Hubble constant in the past few decades has increasingly become more accurate with the advance of new techniques. But its value seems to depend on the epoch at which the measurements are made. The Planck estimate of the Hubble constant from the observations of the cosmic microwave background radiation in the early universe is about 67 km/s/Mpc, whereas that obtained from the distance indicators at the current epoch is about 73-74 km/s/Mpc. This discrepancy between the two groups of measurement is termed as the Hubble tension which has gained much attention in the past few decades with growing significance as measurements from both, the early and the late universe, studies continue to produce results with increasing precision. In this work, we propose a modification to gravity by considering a finite range gravitational field as an alternate explanation for this discrepancy in the value of the Hubble constant. |
2101.09615 | Jeremy Peters | Jeremy M. Peters, Alan Coley, Erik Schnetter | Curvature Invariants and the Geometric Horizon Conjecture in a Binary
Black Hole Merger | 16 pages, 4 figures; v2. included three right-hand panels to Figure 2
and updated corresponding explanations. Updated introduction and discussion
for clarity. Included mention of future work in discussion/conclusion. Made
various minor corrections. To appear in General Relativity and Gravitation | null | null | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | We study curvature invariants in a binary black hole merger. It has been
conjectured that one could define a quasi-local and foliation independent black
hole horizon by finding the level--$0$ set of a suitable curvature invariant of
the Riemann tensor. The conjecture is the geometric horizon conjecture and the
associated horizon is the geometric horizon. We study this conjecture by
tracing the level--$0$ set of the complex scalar polynomial invariant,
$\mathcal{D}$, through a quasi-circular binary black hole merger. We
approximate these level--$0$ sets of $\mathcal{D}$ with level--$\varepsilon$
sets of $|\mathcal{D}|$ for small $\varepsilon$. We locate the local minima of
$|\mathcal{D}|$ and find that the positions of these local minima correspond
closely to the level--$\varepsilon$ sets of $|\mathcal{D}|$ and we also compare
with the level--$0$ sets of $\text{Re}(\mathcal{D})$. The analysis provides
evidence that the level--$\varepsilon$ sets track a unique geometric horizon.
By studying the behaviour of the zero sets of $\text{Re}(\mathcal{D})$ and
$\text{Im}(\mathcal{D})$ and also by studying the MOTSs and apparent horizons
of the initial black holes, we observe that the level--$\varepsilon$ set that
best approximates the geometric horizon is given by $\varepsilon = 10^{-3}$.
| [
{
"created": "Sun, 24 Jan 2021 00:47:01 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Jun 2022 18:28:53 GMT",
"version": "v2"
}
] | 2022-06-16 | [
[
"Peters",
"Jeremy M.",
""
],
[
"Coley",
"Alan",
""
],
[
"Schnetter",
"Erik",
""
]
] | We study curvature invariants in a binary black hole merger. It has been conjectured that one could define a quasi-local and foliation independent black hole horizon by finding the level--$0$ set of a suitable curvature invariant of the Riemann tensor. The conjecture is the geometric horizon conjecture and the associated horizon is the geometric horizon. We study this conjecture by tracing the level--$0$ set of the complex scalar polynomial invariant, $\mathcal{D}$, through a quasi-circular binary black hole merger. We approximate these level--$0$ sets of $\mathcal{D}$ with level--$\varepsilon$ sets of $|\mathcal{D}|$ for small $\varepsilon$. We locate the local minima of $|\mathcal{D}|$ and find that the positions of these local minima correspond closely to the level--$\varepsilon$ sets of $|\mathcal{D}|$ and we also compare with the level--$0$ sets of $\text{Re}(\mathcal{D})$. The analysis provides evidence that the level--$\varepsilon$ sets track a unique geometric horizon. By studying the behaviour of the zero sets of $\text{Re}(\mathcal{D})$ and $\text{Im}(\mathcal{D})$ and also by studying the MOTSs and apparent horizons of the initial black holes, we observe that the level--$\varepsilon$ set that best approximates the geometric horizon is given by $\varepsilon = 10^{-3}$. |
gr-qc/0601076 | Soumya Mohanty | Soumya D. Mohanty, Malik Rakhmanov, Sergei Klimenko, Guenakh
Mitselmakher | Variability of signal to noise ratio and the network analysis of
gravitational wave burst signals | 13 pages, 6 figures | Class.Quant.Grav.23:4799-4810,2006 | 10.1088/0264-9381/23/15/001 | null | gr-qc | null | The detection and estimation of gravitational wave burst signals, with {\em a
priori} unknown polarization waveforms, requires the use of data from a network
of detectors. For determining how the data from such a network should be
combined, approaches based on the maximum likelihood principle have proven to
be useful. The most straightforward among these uses the global maximum of the
likelihood over the space of all waveforms as both the detection statistic and
signal estimator. However, in the case of burst signals, a physically
counterintuitive situation results: for two aligned detectors the statistic
includes the cross-correlation of the detector outputs, as expected, but this
term disappears even for an infinitesimal misalignment. This {\em two detector
paradox} arises from the inclusion of improbable waveforms in the solution
space of maximization. Such waveforms produce widely different responses in
detectors that are closely aligned. We show that by penalizing waveforms that
exhibit large signal-to-noise ratio (snr) variability, as the corresponding
source is moved on the sky, a physically motivated restriction is obtained that
(i) resolves the two detector paradox and (ii) leads to a better performing
statistic than the global maximum of the likelihood. Waveforms with high snr
variability turn out to be precisely the ones that are improbable in the sense
mentioned above. The coherent network analysis method thus obtained can be
applied to any network, irrespective of the number or the mutual alignment of
detectors.
| [
{
"created": "Wed, 18 Jan 2006 20:17:31 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Mohanty",
"Soumya D.",
""
],
[
"Rakhmanov",
"Malik",
""
],
[
"Klimenko",
"Sergei",
""
],
[
"Mitselmakher",
"Guenakh",
""
]
] | The detection and estimation of gravitational wave burst signals, with {\em a priori} unknown polarization waveforms, requires the use of data from a network of detectors. For determining how the data from such a network should be combined, approaches based on the maximum likelihood principle have proven to be useful. The most straightforward among these uses the global maximum of the likelihood over the space of all waveforms as both the detection statistic and signal estimator. However, in the case of burst signals, a physically counterintuitive situation results: for two aligned detectors the statistic includes the cross-correlation of the detector outputs, as expected, but this term disappears even for an infinitesimal misalignment. This {\em two detector paradox} arises from the inclusion of improbable waveforms in the solution space of maximization. Such waveforms produce widely different responses in detectors that are closely aligned. We show that by penalizing waveforms that exhibit large signal-to-noise ratio (snr) variability, as the corresponding source is moved on the sky, a physically motivated restriction is obtained that (i) resolves the two detector paradox and (ii) leads to a better performing statistic than the global maximum of the likelihood. Waveforms with high snr variability turn out to be precisely the ones that are improbable in the sense mentioned above. The coherent network analysis method thus obtained can be applied to any network, irrespective of the number or the mutual alignment of detectors. |
0705.1058 | Farook Rahaman | F.Rahaman, M.Kalam, B.C.Bhui and S.Chakraborty | Construction of 3D wormhole supported by phantom energy | 9 papge, 4 figures. Accepted for publication in Physica Scripta | Phys.Scripta76:56-59,2007 | 10.1088/0031-8949/76/1/010 | null | gr-qc | null | In this article, we have found a series solution of 3D Einstein equations
describing a wormhole for an inhomogeneous distribution of phantom energy.
Here, we assume equation of state is linear but highly anistropic.
| [
{
"created": "Tue, 8 May 2007 10:15:56 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Rahaman",
"F.",
""
],
[
"Kalam",
"M.",
""
],
[
"Bhui",
"B. C.",
""
],
[
"Chakraborty",
"S.",
""
]
] | In this article, we have found a series solution of 3D Einstein equations describing a wormhole for an inhomogeneous distribution of phantom energy. Here, we assume equation of state is linear but highly anistropic. |
1505.03719 | Pierre-Andr\'e Mandrin Ph.D. | Pierre A. Mandrin | A non-dynamical approach for quantum gravity | 7 pages, 6 figures. v2: Case of non-orientable boundary space
included, slightly better explanation of the construction of the (d+1)-space,
typos. v3: More details on the assumptions (abstract, introduction) | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By quantising the gravitational dynamics, space and time are usually forced
to play fundamentally different roles. This raises the question whether
physically relevent configurations could also exist which would not admit
space-time-splitting. This has led to the investigation of an approach not
based on quantum dynamical assumptions. The assumptions are mainly restricted
to a constrained statistical concept of ordered partitions (NDA). For the time
being, the continuum description is restricted in order to allow the
application of the rules of differential geometry. It is verified that NDA
yields equations of the same form as general relativity and quantum field
theory for 3+1 dimensions and within the limits of experimental evidence. The
derivations are shown in detail. First results are compared to the path
integral approach to quantum gravity.
| [
{
"created": "Thu, 14 May 2015 17:28:38 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Jul 2015 17:01:06 GMT",
"version": "v2"
},
{
"created": "Wed, 15 Jul 2015 14:26:30 GMT",
"version": "v3"
}
] | 2015-07-16 | [
[
"Mandrin",
"Pierre A.",
""
]
] | By quantising the gravitational dynamics, space and time are usually forced to play fundamentally different roles. This raises the question whether physically relevent configurations could also exist which would not admit space-time-splitting. This has led to the investigation of an approach not based on quantum dynamical assumptions. The assumptions are mainly restricted to a constrained statistical concept of ordered partitions (NDA). For the time being, the continuum description is restricted in order to allow the application of the rules of differential geometry. It is verified that NDA yields equations of the same form as general relativity and quantum field theory for 3+1 dimensions and within the limits of experimental evidence. The derivations are shown in detail. First results are compared to the path integral approach to quantum gravity. |
gr-qc/9908054 | Manasse R. Mbonye | Manasse Mbonye | Horizon Dynamics of Evaporating Black Holes in a Higher Dimensional
Inflationary Universe | RevTex,19 pages, no figures; accepted for publication in Phys. Rev. D | Phys.Rev.D60:124007,1999 | 10.1103/PhysRevD.60.124007 | null | gr-qc | null | Spherically symmetric Black Holes of the Vaidya type are examined in an
asymptotically de Sitter, higher dimensional spacetime. The various horizons
are located. The structure and dynamics of such horizons are studied.
| [
{
"created": "Thu, 19 Aug 1999 20:28:49 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Mbonye",
"Manasse",
""
]
] | Spherically symmetric Black Holes of the Vaidya type are examined in an asymptotically de Sitter, higher dimensional spacetime. The various horizons are located. The structure and dynamics of such horizons are studied. |
gr-qc/0602030 | Sunil Maharaj | M. Chaisi and S. D. Maharaj | Anisotropic static solutions in modelling highly compact bodies | 9 pages, to appear in Pramana - J. Phys | Pramana66:609-614,2006 | 10.1007/BF02704504 | null | gr-qc | null | Einstein field equations for anisotropic spheres are solved and exact
interior solutions obtained. This paper extends earlier treatments to include
anisotropic models which accommodate a wider variety of physically viable
energy densities. Two classes of solutions are possible. The first class
contains the limiting case $\mu\propto r^{-2}$ for the energy density which
arises in many astrophysical applications. In the second class the singularity
at the center of the star is not present in the energy density. The models
presented in this paper allow for increasing and decreasing profiles in the
behavior of the energy density.
| [
{
"created": "Wed, 8 Feb 2006 13:31:27 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Chaisi",
"M.",
""
],
[
"Maharaj",
"S. D.",
""
]
] | Einstein field equations for anisotropic spheres are solved and exact interior solutions obtained. This paper extends earlier treatments to include anisotropic models which accommodate a wider variety of physically viable energy densities. Two classes of solutions are possible. The first class contains the limiting case $\mu\propto r^{-2}$ for the energy density which arises in many astrophysical applications. In the second class the singularity at the center of the star is not present in the energy density. The models presented in this paper allow for increasing and decreasing profiles in the behavior of the energy density. |
2110.13756 | Francesco Sartini | Francesco Sartini | Group quantization of the black hole minisuperspace | 22 pages + 4 pages of appendix, 2 figures | Phys.Rev.D 105 (2022) 12, 126003 | 10.1103/PhysRevD.105.126003 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The emergence of nontrivial symmetries for black holes minisuperspaces has
been recently pointed out. These Noether symmetries possess non-null charges
and hence map physical solutions to different ones. The symmetry group is
isomorphic to the finite-dimensional Poincar\'e group ISO(2,1), whose
irreducible representations are well known. This structure is used to build a
consistent quantum theory of black hole minisuperspace. This has, among other
consequences, the striking consequence of implying a continuous spectrum for
the mass operator. Following loop quantum cosmology, we obtain a regularization
scheme compatible with the symmetry structure. It is possible to study the
evolution of coherent states following the classical trajectories in the low
curvature regime. We show that this produces an effective metric where the
singularity is replaced by a Killing horizon merging two asymptotically flat
regions. The quantum correction comes from a fundamental discreteness of
spacetime, and the uncertainty on the energy of the system. Remarkably, the
effective evolution of semiclassical states is described by an effective
Hamiltonian, related to the original one through a canonical transformation.
| [
{
"created": "Tue, 26 Oct 2021 15:06:40 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Feb 2022 08:08:35 GMT",
"version": "v2"
},
{
"created": "Fri, 9 Sep 2022 15:22:55 GMT",
"version": "v3"
}
] | 2022-09-12 | [
[
"Sartini",
"Francesco",
""
]
] | The emergence of nontrivial symmetries for black holes minisuperspaces has been recently pointed out. These Noether symmetries possess non-null charges and hence map physical solutions to different ones. The symmetry group is isomorphic to the finite-dimensional Poincar\'e group ISO(2,1), whose irreducible representations are well known. This structure is used to build a consistent quantum theory of black hole minisuperspace. This has, among other consequences, the striking consequence of implying a continuous spectrum for the mass operator. Following loop quantum cosmology, we obtain a regularization scheme compatible with the symmetry structure. It is possible to study the evolution of coherent states following the classical trajectories in the low curvature regime. We show that this produces an effective metric where the singularity is replaced by a Killing horizon merging two asymptotically flat regions. The quantum correction comes from a fundamental discreteness of spacetime, and the uncertainty on the energy of the system. Remarkably, the effective evolution of semiclassical states is described by an effective Hamiltonian, related to the original one through a canonical transformation. |
0911.2393 | Remo Garattini | Remo Garattini | Running Cosmological Constant and Running Newton Constant in Modified
Gravity Theories | Proceedings of the Conference "The Invisible Universe" Paris, June
29-July 3, 2009 10 pages | AIP Conf.Proc.1241:866-875,2010 | 10.1063/1.3462727 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss how to extract information about the cosmological constant from
the Wheeler-DeWitt equation, considered as an eigenvalue of a Sturm-Liouville
problem in a de Sitter and Anti-de Sitter background. The equation is
approximated to one loop with the help of a variational approach with Gaussian
trial wave functionals. A canonical decomposition of modes is used to separate
transverse-traceless tensors (graviton) from ghosts and scalar. We show that no
ghosts appear in the final evaluation of the cosmological constant. A zeta
function regularization is used to handle with divergences. A renormalization
procedure is introduced to remove the infinities together with a
renormalization group equation. We apply this procedure on the induced
cosmological constant $\Lambda$ and, as an alternative, on the Newton constant
$G$. A brief discussion on the extension to a $f(R)$ theory is considered.
| [
{
"created": "Thu, 12 Nov 2009 13:56:08 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Garattini",
"Remo",
""
]
] | We discuss how to extract information about the cosmological constant from the Wheeler-DeWitt equation, considered as an eigenvalue of a Sturm-Liouville problem in a de Sitter and Anti-de Sitter background. The equation is approximated to one loop with the help of a variational approach with Gaussian trial wave functionals. A canonical decomposition of modes is used to separate transverse-traceless tensors (graviton) from ghosts and scalar. We show that no ghosts appear in the final evaluation of the cosmological constant. A zeta function regularization is used to handle with divergences. A renormalization procedure is introduced to remove the infinities together with a renormalization group equation. We apply this procedure on the induced cosmological constant $\Lambda$ and, as an alternative, on the Newton constant $G$. A brief discussion on the extension to a $f(R)$ theory is considered. |
2106.04084 | Cosimo Bambi | Cosimo Bambi | Testing General Relativity with black hole X-ray data: a progress report | 8 pages, 3 figures. Talk given at the "International Workshop on
Relativistic Astrophysics and Gravitation" (IWRAG-2021); Ulugh Beg
Astronomical Institute, Uzbekistan, 12-14 May 2021 | Arab. J. Math. 11, 81-90 (2022) | 10.1007/s40065-021-00336-y | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Einstein's theory of General Relativity is one of the pillars of modern
physics. For decades, the theory has been mainly tested in the weak field
regime with experiments in the Solar System and observations of binary pulsars.
Thanks to a new generation of observational facilities, the past 5 years have
seen remarkable changes in this field and there are now numerous efforts for
testing General Relativity in the strong field regime with black holes and
neutron stars using different techniques. Here I will review the work of my
group at Fudan University devoted to test General Relativity with black hole
X-ray data.
| [
{
"created": "Tue, 8 Jun 2021 03:46:48 GMT",
"version": "v1"
}
] | 2022-06-06 | [
[
"Bambi",
"Cosimo",
""
]
] | Einstein's theory of General Relativity is one of the pillars of modern physics. For decades, the theory has been mainly tested in the weak field regime with experiments in the Solar System and observations of binary pulsars. Thanks to a new generation of observational facilities, the past 5 years have seen remarkable changes in this field and there are now numerous efforts for testing General Relativity in the strong field regime with black holes and neutron stars using different techniques. Here I will review the work of my group at Fudan University devoted to test General Relativity with black hole X-ray data. |
2006.05948 | G. Andr\'e Oliva | G. Andr\'e Oliva and Francisco Frutos-Alfaro | Effects of the treatment of the mass quadrupole moment on ray-tracing
applications for rapidly-rotating neutron stars | Accepted for publication in Monthly Notices of the Royal Astronomical
Society | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Neutron Star Interior Composition Explorer (NICER) mission has provided a
unique opportunity to constrain the equation of state of neutron stars by using
the technique of pulse-profile modelling. This technique requires accurate and
efficient ray tracing, that in turn requires a robust representation of the
spacetime around a neutron star. Several exact and approximate metrics have
been proposed, and used, to perform ray tracing around neutron stars, with both
moderate and fast rotation. In this paper, we perform a comparison between
several of these metrics, when used for ray tracing. We calculate the shape of
the neutron star as seen by a distant observer using two different surface
formulae, the thermal spectrum and pulse profiles from circular and
crescent-shaped hotspots, for four configurations of pulsars with rotation
rates ranging from 622 to 1000 Hz, and using both a moderate and a stiff
equation of state to include realistic and extreme cases. We find small
differences between the metrics for rotation frequencies starting at ~700 Hz
that could theoretically be used for constraining the quadrupole moment or the
spacetime models. We also determine the practicality of use of each metric in
larger-scale applications such as pulse-profile
| [
{
"created": "Wed, 10 Jun 2020 16:54:13 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Jun 2020 09:00:35 GMT",
"version": "v2"
},
{
"created": "Fri, 14 Aug 2020 18:32:06 GMT",
"version": "v3"
},
{
"created": "Tue, 11 May 2021 07:51:31 GMT",
"version": "v4"
}
] | 2021-05-12 | [
[
"Oliva",
"G. André",
""
],
[
"Frutos-Alfaro",
"Francisco",
""
]
] | The Neutron Star Interior Composition Explorer (NICER) mission has provided a unique opportunity to constrain the equation of state of neutron stars by using the technique of pulse-profile modelling. This technique requires accurate and efficient ray tracing, that in turn requires a robust representation of the spacetime around a neutron star. Several exact and approximate metrics have been proposed, and used, to perform ray tracing around neutron stars, with both moderate and fast rotation. In this paper, we perform a comparison between several of these metrics, when used for ray tracing. We calculate the shape of the neutron star as seen by a distant observer using two different surface formulae, the thermal spectrum and pulse profiles from circular and crescent-shaped hotspots, for four configurations of pulsars with rotation rates ranging from 622 to 1000 Hz, and using both a moderate and a stiff equation of state to include realistic and extreme cases. We find small differences between the metrics for rotation frequencies starting at ~700 Hz that could theoretically be used for constraining the quadrupole moment or the spacetime models. We also determine the practicality of use of each metric in larger-scale applications such as pulse-profile |
1503.02566 | Thomas Buchert | Alexandre Alles, Thomas Buchert, Fosca Al Roumi, and Alexander Wiegand | Lagrangian theory of structure formation in relativistic cosmology III:
gravitoelectric perturbation and solution schemes at any order | 17 pages, a few minor extensions to match the published version in
PRD | Phys. Rev. D 92, 023512 (2015) | 10.1103/PhysRevD.92.023512 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The relativistic generalization of the Newtonian Lagrangian perturbation
theory is investigated. In previous works, the first-order trace solutions that
are generated by the spatially projected gravitoelectric part of the Weyl
tensor were given together with extensions and applications for accessing the
nonperturbative regime. We furnish here construction rules to obtain from
Newtonian solutions the gravitoelectric class of relativistic solutions, for
which we give the complete perturbation and solution schemes at any order of
the perturbations. By construction, these schemes generalize the complete
hierarchy of solutions of the Newtonian Lagrangian perturbation theory.
| [
{
"created": "Mon, 9 Mar 2015 17:25:58 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Jul 2015 12:59:43 GMT",
"version": "v2"
}
] | 2015-07-15 | [
[
"Alles",
"Alexandre",
""
],
[
"Buchert",
"Thomas",
""
],
[
"Roumi",
"Fosca Al",
""
],
[
"Wiegand",
"Alexander",
""
]
] | The relativistic generalization of the Newtonian Lagrangian perturbation theory is investigated. In previous works, the first-order trace solutions that are generated by the spatially projected gravitoelectric part of the Weyl tensor were given together with extensions and applications for accessing the nonperturbative regime. We furnish here construction rules to obtain from Newtonian solutions the gravitoelectric class of relativistic solutions, for which we give the complete perturbation and solution schemes at any order of the perturbations. By construction, these schemes generalize the complete hierarchy of solutions of the Newtonian Lagrangian perturbation theory. |
1105.1678 | Valeria Ferrari | Valeria Ferrari | Gravitational waves from perturbed stars | 22 pages, 5 figures, to appear in the Chandra Centennial issue of the
Bulletin of the Astronomical Society of India, Vol. 39, (2011) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Non radial oscillations of neutron stars are associated with the emission of
gravitational waves. The characteristic frequencies of these oscillations can
be computed using the theory of stellar perturbations, and they are shown to
carry detailed information on the internal structure of the emitting source.
Moreover, they appear to be encoded in various radiative processes, as for
instance in the tail of the giant flares of Soft Gamma Repeaters. Thus, their
determination is central to the theory of stellar perturbation. A viable
approach to the problem consists in formulating this theory as a problem of
resonant scattering of gravitational waves incident on the potential barrier
generated by the spacetime curvature. This approach discloses some unexpected
correspondences between the theory of stellar perturbations and the theory of
quantum mechanics, and allows us to predict new relativistic effects.
| [
{
"created": "Mon, 9 May 2011 14:19:38 GMT",
"version": "v1"
}
] | 2011-05-10 | [
[
"Ferrari",
"Valeria",
""
]
] | Non radial oscillations of neutron stars are associated with the emission of gravitational waves. The characteristic frequencies of these oscillations can be computed using the theory of stellar perturbations, and they are shown to carry detailed information on the internal structure of the emitting source. Moreover, they appear to be encoded in various radiative processes, as for instance in the tail of the giant flares of Soft Gamma Repeaters. Thus, their determination is central to the theory of stellar perturbation. A viable approach to the problem consists in formulating this theory as a problem of resonant scattering of gravitational waves incident on the potential barrier generated by the spacetime curvature. This approach discloses some unexpected correspondences between the theory of stellar perturbations and the theory of quantum mechanics, and allows us to predict new relativistic effects. |
2107.00947 | Alejandro Garc\'ia-Quismondo | Alejandro Garc\'ia-Quismondo and Guillermo A. Mena Marug\'an | Exploring alternatives to the Hamiltonian calculation of the
Ashtekar-Olmedo-Singh black hole solution | 12 pages, accepted for publication in Frontiers of Astronomy and
Space Sciences | Front. Astron. Space Sci. 8, 701723 (2021) | 10.3389/fspas.2021.701723 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, we reexamine the derivation of the dynamical equations of
the Ashtekar-Olmedo-Singh black hole model in order to determine whether it is
possible to construct a Hamiltonian formalism where the parameters that
regulate the introduction of quantum geometry effects are treated as true
constants of motion. After arguing that these parameters should capture
contributions from two distinct sectors of the phase space that had been
considered independent in previous analyses in the literature, we proceed to
obtain the corresponding equations of motion and analyze the consequences of
this more general choice. We restrict our discussion exclusively to these
dynamical issues. We also investigate whether the proposed procedure can be
reconciled with the results of Ashtekar, Olmedo, and Singh, at least in some
appropriate limit.
| [
{
"created": "Fri, 2 Jul 2021 10:15:04 GMT",
"version": "v1"
}
] | 2021-07-23 | [
[
"García-Quismondo",
"Alejandro",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
]
] | In this article, we reexamine the derivation of the dynamical equations of the Ashtekar-Olmedo-Singh black hole model in order to determine whether it is possible to construct a Hamiltonian formalism where the parameters that regulate the introduction of quantum geometry effects are treated as true constants of motion. After arguing that these parameters should capture contributions from two distinct sectors of the phase space that had been considered independent in previous analyses in the literature, we proceed to obtain the corresponding equations of motion and analyze the consequences of this more general choice. We restrict our discussion exclusively to these dynamical issues. We also investigate whether the proposed procedure can be reconciled with the results of Ashtekar, Olmedo, and Singh, at least in some appropriate limit. |
2308.00804 | Sujay Kr. Biswas | Trishit Banerjee, Goutam Mandal, Atreyee Biswas, and Sujay Kr. Biswas | Effects of particle creation rate in two-fluid interacting cosmologies | 27 pages, 14 captioned figures. The title is changed and thoroughly
modified. The version is accepted for publication in the journal Monthly
Notices of the Royal Astronomical Society | null | 10.1093/mnras/stae1047 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, a two-fluid interacting model in a flat FLRW universe has been
studied considering particle creation mechanism with a particular form of
particle creation rate $\Gamma=\Gamma_0 H+\frac{\Gamma_1}{H}$ from different
aspects. Statistical analysis with a combined data set of SNe Ia (Supernovae
Type Ia) and Hubble data is performed to achieve the best-fit values of the
model parameters, and the model is compatible with current observational data.
We also perform a dynamical analysis of this model to get an overall
qualitative description of the cosmological evolution by converting the
governing equations into a system of ordinary differential equations
considering a proper transformation of variables. We find some non-isolated
sets of critical points, among which some usually are normally hyperbolic sets
of points that describe the present acceleration of the universe dominated by
dark energy mimicking cosmological constant or phantom fluid. Scaling solutions
are also obtained from this analysis, and they can alleviate the coincidence
problem successfully. Statefinder diagnosis is also carried out for this model
to compare it with the $\Lambda$CDM, and any other dark energy models by
finding various statefinder parameters. Finally, the thermodynamic analysis
shows that the generalized second law of thermodynamics is valid in an
irreversible thermodynamic context.
| [
{
"created": "Wed, 2 Aug 2023 12:09:51 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Apr 2024 13:51:32 GMT",
"version": "v2"
}
] | 2024-05-01 | [
[
"Banerjee",
"Trishit",
""
],
[
"Mandal",
"Goutam",
""
],
[
"Biswas",
"Atreyee",
""
],
[
"Biswas",
"Sujay Kr.",
""
]
] | In this work, a two-fluid interacting model in a flat FLRW universe has been studied considering particle creation mechanism with a particular form of particle creation rate $\Gamma=\Gamma_0 H+\frac{\Gamma_1}{H}$ from different aspects. Statistical analysis with a combined data set of SNe Ia (Supernovae Type Ia) and Hubble data is performed to achieve the best-fit values of the model parameters, and the model is compatible with current observational data. We also perform a dynamical analysis of this model to get an overall qualitative description of the cosmological evolution by converting the governing equations into a system of ordinary differential equations considering a proper transformation of variables. We find some non-isolated sets of critical points, among which some usually are normally hyperbolic sets of points that describe the present acceleration of the universe dominated by dark energy mimicking cosmological constant or phantom fluid. Scaling solutions are also obtained from this analysis, and they can alleviate the coincidence problem successfully. Statefinder diagnosis is also carried out for this model to compare it with the $\Lambda$CDM, and any other dark energy models by finding various statefinder parameters. Finally, the thermodynamic analysis shows that the generalized second law of thermodynamics is valid in an irreversible thermodynamic context. |
0811.1009 | Savely G. Karshenboim | Savely G. Karshenboim (Max-Planck-Institut fuer Quantenoptik,
Garching, and D. I. Mendeleev Institute for Metrology, St.Petersburg) | K0 meson physics in the gravitation field: a constraint on the
equivalence principle | null | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | K0-K0bar oscillations are extremely sensitive to the K0 and K0bar energy at
rest. Even assuming m_K0=m_K0bar, the energy is not granted to be the same if
gravitational effects on K0 and K0bar slightly differ. We consider various
gravitation fields present and, in particular, galactic fields, which provide a
negligible acceleration, but relatively large gravitational potential energy. A
constraint from a possible effect of this potential energy on the kaon
oscillations isfound to be
|(m_g/m_i)_K0-(m_g/m_i)_K0bar| < 8 x 10^-13 atCL=90%.
The derived constraint is competitive with other tests of universality of the
free fall. Other applications are also discussed.
| [
{
"created": "Thu, 6 Nov 2008 18:19:20 GMT",
"version": "v1"
}
] | 2008-11-07 | [
[
"Karshenboim",
"Savely G.",
"",
"Max-Planck-Institut fuer Quantenoptik,\n Garching, and D. I. Mendeleev Institute for Metrology, St.Petersburg"
]
] | K0-K0bar oscillations are extremely sensitive to the K0 and K0bar energy at rest. Even assuming m_K0=m_K0bar, the energy is not granted to be the same if gravitational effects on K0 and K0bar slightly differ. We consider various gravitation fields present and, in particular, galactic fields, which provide a negligible acceleration, but relatively large gravitational potential energy. A constraint from a possible effect of this potential energy on the kaon oscillations isfound to be |(m_g/m_i)_K0-(m_g/m_i)_K0bar| < 8 x 10^-13 atCL=90%. The derived constraint is competitive with other tests of universality of the free fall. Other applications are also discussed. |
2208.06246 | Rabia Saleem | Xiao-Xiong Zeng, M. Israr Aslam and Rabia Saleem | The Optical Appearance of Charged Four-Dimensional Gauss-Bonnet Black
Hole with Strings Cloud and Non-Commutative Geometry Surrounded by Various
Accretions Profiles | 16 pages, 9 figures | null | 10.1140/epjc/s10052-023-11274-8 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | Thanks for the releasing image of supermassive black holes (BHs) by the event
horizon telescope (EHT) at the heart of the $M87$ galaxy. After the discovery
of this mysterious object, scientists paid attention to exploring the BH shadow
features under different gravitational backgrounds. In this scenario, we study
the light rings and observational properties of BH shadow surrounded by
different accretion flow models and then investigate the effect of model
parameters on the observational display and space-time structure of BHs in the
framework of our considering system. Under the incompatible configuration of
the emission profiles, the images of BHs comprise that the observed luminosity
is mainly determined by direct emission, while the lensing ring will provide a
small contribution of the total observed flux and the photon ring makes a
negligible contribution due to its exponential narrowness. More importantly,
the observed regions and specific intensities of all emission profiles are
changed correspondingly under variations of parameters. For optically thin
accreting matters, we analyze the profile and specific intensity of the shadows
with static and infalling accretions models, respectively. We find that with an
infalling motion the interior region of the shadows will be darker than in a
static case, due to the Doppler effect of the infalling movement. Finally, it
is concluded that these findings support that the change of BH state parameters
will change the way of space-time geometry, thus affecting the BH shadows
dynamics.
| [
{
"created": "Thu, 11 Aug 2022 11:01:26 GMT",
"version": "v1"
}
] | 2023-03-01 | [
[
"Zeng",
"Xiao-Xiong",
""
],
[
"Aslam",
"M. Israr",
""
],
[
"Saleem",
"Rabia",
""
]
] | Thanks for the releasing image of supermassive black holes (BHs) by the event horizon telescope (EHT) at the heart of the $M87$ galaxy. After the discovery of this mysterious object, scientists paid attention to exploring the BH shadow features under different gravitational backgrounds. In this scenario, we study the light rings and observational properties of BH shadow surrounded by different accretion flow models and then investigate the effect of model parameters on the observational display and space-time structure of BHs in the framework of our considering system. Under the incompatible configuration of the emission profiles, the images of BHs comprise that the observed luminosity is mainly determined by direct emission, while the lensing ring will provide a small contribution of the total observed flux and the photon ring makes a negligible contribution due to its exponential narrowness. More importantly, the observed regions and specific intensities of all emission profiles are changed correspondingly under variations of parameters. For optically thin accreting matters, we analyze the profile and specific intensity of the shadows with static and infalling accretions models, respectively. We find that with an infalling motion the interior region of the shadows will be darker than in a static case, due to the Doppler effect of the infalling movement. Finally, it is concluded that these findings support that the change of BH state parameters will change the way of space-time geometry, thus affecting the BH shadows dynamics. |
1610.06797 | Mercedes Martin-Benito | Jer\'onimo Cortez, Beatriz Elizaga Navascu\'es, Mercedes
Mart\'in-Benito, Guillermo A. Mena Marug\'an, Javier Olmedo, Jos\'e M.
Velhinho | Uniqueness of the Fock quantization of scalar fields in a Bianchi I
cosmology with unitary dynamics | 23 pages. Updated to match published version | Phys. Rev. D 94, 105019 (2016) | 10.1103/PhysRevD.94.105019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Fock quantization of free scalar fields is subject to an infinite
ambiguity when it comes to choosing a set of annihilation and creation
operators, choice that is equivalent to the determination of a vacuum state. In
highly symmetric situations, this ambiguity can be removed by asking vacuum
invariance under the symmetries of the system. Similarly, in stationary
backgrounds, one can demand time-translation invariance plus positivity of the
energy. However, in more general situations, additional criteria are needed.
For the case of free (test) fields minimally coupled to a homogeneous and
isotropic cosmology, it has been proven that the ambiguity is resolved by
introducing the criterion of unitary implementability of the quantum dynamics,
as an endomorphism in Fock space. This condition determines a specific
separation of the time dependence of the field, so that this splits into a very
precise background dependence and a genuine quantum evolution. Furthermore,
together with the condition of vacuum invariance under the spatial Killing
symmetries, unitarity of the dynamics selects a unique Fock representation for
the canonical commutation relations, up to unitary equivalence. In this work,
we generalize these results to anisotropic spacetimes with shear, which are
therefore not conformally symmetric, by considering the case of a free scalar
field in a Bianchi I cosmology.
| [
{
"created": "Fri, 21 Oct 2016 14:15:34 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Nov 2016 11:36:10 GMT",
"version": "v2"
}
] | 2016-12-21 | [
[
"Cortez",
"Jerónimo",
""
],
[
"Navascués",
"Beatriz Elizaga",
""
],
[
"Martín-Benito",
"Mercedes",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
],
[
"Olmedo",
"Javier",
""
],
[
"Velhinho",
"José M.",
""
]
] | The Fock quantization of free scalar fields is subject to an infinite ambiguity when it comes to choosing a set of annihilation and creation operators, choice that is equivalent to the determination of a vacuum state. In highly symmetric situations, this ambiguity can be removed by asking vacuum invariance under the symmetries of the system. Similarly, in stationary backgrounds, one can demand time-translation invariance plus positivity of the energy. However, in more general situations, additional criteria are needed. For the case of free (test) fields minimally coupled to a homogeneous and isotropic cosmology, it has been proven that the ambiguity is resolved by introducing the criterion of unitary implementability of the quantum dynamics, as an endomorphism in Fock space. This condition determines a specific separation of the time dependence of the field, so that this splits into a very precise background dependence and a genuine quantum evolution. Furthermore, together with the condition of vacuum invariance under the spatial Killing symmetries, unitarity of the dynamics selects a unique Fock representation for the canonical commutation relations, up to unitary equivalence. In this work, we generalize these results to anisotropic spacetimes with shear, which are therefore not conformally symmetric, by considering the case of a free scalar field in a Bianchi I cosmology. |
1108.3057 | Julian Barbour | Julian Barbour | Mach's Principle: A Response to Mashhoon and Wesson's Paper arXiv:
1106.6036 | 8 pages, 2 figures, to be submitted to Annalen der Physik and
followed by a response by Mashhoon and Wesson | null | 10.1002/andp.201100235 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In their recent "Mach's principle and higher-dimensional dynamics", Mashhoon
and Wesson argue that Mach's principle is not properly incorporated into
general relativity and that in Einstein's theory "the origin of inertia remains
essentially the same as in Newtonian physics." While it is true that the motion
of a single test particle in a Newtonian inertial frame of reference appears
essentially the same as in an Einsteinian local inertial frame, this misses the
point. The issue is not what motion looks like in an inertial frame of
reference but what is the origin of the inertial frame. Unlike Newtonian
dynamics, general relativity does implement Mach's principle when considered
from this correctly formulated point of view.
| [
{
"created": "Mon, 15 Aug 2011 18:56:30 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Barbour",
"Julian",
""
]
] | In their recent "Mach's principle and higher-dimensional dynamics", Mashhoon and Wesson argue that Mach's principle is not properly incorporated into general relativity and that in Einstein's theory "the origin of inertia remains essentially the same as in Newtonian physics." While it is true that the motion of a single test particle in a Newtonian inertial frame of reference appears essentially the same as in an Einsteinian local inertial frame, this misses the point. The issue is not what motion looks like in an inertial frame of reference but what is the origin of the inertial frame. Unlike Newtonian dynamics, general relativity does implement Mach's principle when considered from this correctly formulated point of view. |
gr-qc/0608044 | Guihua Tian | Gui-hua Tian, Shi-kun Wang, Shuquan Zhong | The tortoise coordinates and the cauchy problem in the stable study of
the Schwarzschild black hole | null | null | null | null | gr-qc | null | Generally, the Schwarzschild black hole was proved stable through two
different methods: the mode-decomposition method and the integral method. In
the paper, we show the integral method can only apply to the initial data
vanishing at both the horizon and the spatial infinity. It can not treat the
initial data only vanishing at the spatial infinity. We give an example to show
the misleading information caused by the use of the tortoise coordinates in the
perturbation equations. Subsequently, the perturbation equation in the
Schwarzschild coordinates is shown not sufficient for the stable study.
| [
{
"created": "Wed, 9 Aug 2006 09:22:51 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Tian",
"Gui-hua",
""
],
[
"Wang",
"Shi-kun",
""
],
[
"Zhong",
"Shuquan",
""
]
] | Generally, the Schwarzschild black hole was proved stable through two different methods: the mode-decomposition method and the integral method. In the paper, we show the integral method can only apply to the initial data vanishing at both the horizon and the spatial infinity. It can not treat the initial data only vanishing at the spatial infinity. We give an example to show the misleading information caused by the use of the tortoise coordinates in the perturbation equations. Subsequently, the perturbation equation in the Schwarzschild coordinates is shown not sufficient for the stable study. |
gr-qc/9210020 | Fay Dowker | Fay Dowker | SO(4) Invariant States in Quantum Cosmology | 15 pages | Class.Quant.Grav.10:1435-1446,1993 | 10.1088/0264-9381/10/8/006 | FERMILAB-Pub-92/294-A | gr-qc | null | The phenomenon of linearisation instability is identified in models of
quantum cosmology that are perturbations of mini-superspace models. In
particular, constraints that are second order in the perturbations must be
imposed on wave functions calculated in such models. It is shown explicitly
that in the case of a model which is a perturbation of the mini-superspace
which has $S^3$ spatial sections these constraints imply that any wave
functions calculated in this model must be SO(4) invariant. (This replaces the
previous corrupted version.)
| [
{
"created": "Fri, 30 Oct 1992 21:12:14 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Nov 1992 23:12:00 GMT",
"version": "v2"
},
{
"created": "Tue, 3 Nov 1992 22:51:17 GMT",
"version": "v3"
}
] | 2010-04-06 | [
[
"Dowker",
"Fay",
""
]
] | The phenomenon of linearisation instability is identified in models of quantum cosmology that are perturbations of mini-superspace models. In particular, constraints that are second order in the perturbations must be imposed on wave functions calculated in such models. It is shown explicitly that in the case of a model which is a perturbation of the mini-superspace which has $S^3$ spatial sections these constraints imply that any wave functions calculated in this model must be SO(4) invariant. (This replaces the previous corrupted version.) |
1504.04009 | Ahmad Sheykhi | A. Sheykhi, S. Hajkhalili | Dilaton black holes coupled to nonlinear electrodynamic field | 22 pages | Phys Rev D 89 (2014) 104019 | 10.1103/PhysRevD.89.104019 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The theory of nonlinear electrodynamics has got a lot of attentions in recent
years. It was shown that Born-Infeld nonlinear electrodynamics is not the only
modification of the linear Maxwell's field which keeps the electric field of a
charged point particle finite at the origin, and other type of nonlinear
Lagrangian such as exponential and logarithmic nonlinear electrodynamics can
play the same role. In this paper, we generalize the study on the exponential
nonlinear electrodynamics by adding a scalar dilaton field to the action. By
suitably choosing the coupling of the matter field to the dilaton field, we
vary the action and obtain the corresponding field equations. Then, by making a
proper ansatz, we construct a new class of charged dilaton black hole solutions
coupled to the exponential nonlinear electrodynamics field in the presence of
two Liouville-type potentials for the dilaton field. Due to the presence of the
dilaton field, the asymptotic behavior of these solutions are neither flat nor
(A)dS. In the limiting case where the nonlinear parameter $\beta^2$ goes to
infinity, our solution reduces to the Einstein-Maxwell dilaton black holes. We
obtain the mass, temperature, entropy and electric potential of these
solutions. We also study the behaviour of the electric field as well as the
electric potential of these black holes near the origin. We find that the
electric field has a finite value \textit{near} the origin, which is the same
as the electric field of Born-Infeld nonlinear electrodynamics, but it can
diverge exactly at $r=0$ depending on the model parameters. We also investigate
the effects of the dilaton field on the behaviour of the electric field and
electric potential. Finally, we check the validity of the first law of black
hole thermodynamics on the black hole horizon.
| [
{
"created": "Wed, 15 Apr 2015 17:52:48 GMT",
"version": "v1"
}
] | 2015-04-17 | [
[
"Sheykhi",
"A.",
""
],
[
"Hajkhalili",
"S.",
""
]
] | The theory of nonlinear electrodynamics has got a lot of attentions in recent years. It was shown that Born-Infeld nonlinear electrodynamics is not the only modification of the linear Maxwell's field which keeps the electric field of a charged point particle finite at the origin, and other type of nonlinear Lagrangian such as exponential and logarithmic nonlinear electrodynamics can play the same role. In this paper, we generalize the study on the exponential nonlinear electrodynamics by adding a scalar dilaton field to the action. By suitably choosing the coupling of the matter field to the dilaton field, we vary the action and obtain the corresponding field equations. Then, by making a proper ansatz, we construct a new class of charged dilaton black hole solutions coupled to the exponential nonlinear electrodynamics field in the presence of two Liouville-type potentials for the dilaton field. Due to the presence of the dilaton field, the asymptotic behavior of these solutions are neither flat nor (A)dS. In the limiting case where the nonlinear parameter $\beta^2$ goes to infinity, our solution reduces to the Einstein-Maxwell dilaton black holes. We obtain the mass, temperature, entropy and electric potential of these solutions. We also study the behaviour of the electric field as well as the electric potential of these black holes near the origin. We find that the electric field has a finite value \textit{near} the origin, which is the same as the electric field of Born-Infeld nonlinear electrodynamics, but it can diverge exactly at $r=0$ depending on the model parameters. We also investigate the effects of the dilaton field on the behaviour of the electric field and electric potential. Finally, we check the validity of the first law of black hole thermodynamics on the black hole horizon. |
1610.02369 | Ronaldo S. S. Vieira | Ronaldo S. S. Vieira, Javier Ramos-Caro, Alberto Saa | Vertical stability of circular orbits in relativistic razor-thin disks | 13 pages, 4 figures; Accepted for publication in Physical Review D | Phys. Rev. D 94, 104016 (2016) | 10.1103/PhysRevD.94.104016 | null | gr-qc astro-ph.GA nlin.CD | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | During the last few decades, there has been a growing interest in exact
solutions of Einstein equations describing razor-thin disks. Despite the
progress in the area, the analytical study of geodesic motion crossing the disk
plane in these systems is not yet so developed. In the present work, we propose
a definite vertical stability criterion for circular equatorial timelike
geodesics in static, axially symmetric thin disks, possibly surrounded by other
structures preserving axial symmetry. It turns out that the strong energy
condition for the disk stress-energy content is sufficient for vertical
stability of these orbits. Moreover, adiabatic invariance of the vertical
action variable gives us an approximate third integral of motion for oblique
orbits which deviate slightly from the equatorial plane. Such new approximate
third integral certainly points to a better understanding of the analytical
properties of these orbits. The results presented here, derived for static
spacetimes, may be a starting point to study the motion around rotating,
stationary razor-thin disks. Our results also allow us to conjecture that the
strong energy condition should be sufficient to assure transversal stability of
periodic orbits for any singular timelike hypersurface, provided it is
invariant under the geodesic flow.
| [
{
"created": "Fri, 7 Oct 2016 18:43:12 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Nov 2016 16:57:53 GMT",
"version": "v2"
}
] | 2016-11-09 | [
[
"Vieira",
"Ronaldo S. S.",
""
],
[
"Ramos-Caro",
"Javier",
""
],
[
"Saa",
"Alberto",
""
]
] | During the last few decades, there has been a growing interest in exact solutions of Einstein equations describing razor-thin disks. Despite the progress in the area, the analytical study of geodesic motion crossing the disk plane in these systems is not yet so developed. In the present work, we propose a definite vertical stability criterion for circular equatorial timelike geodesics in static, axially symmetric thin disks, possibly surrounded by other structures preserving axial symmetry. It turns out that the strong energy condition for the disk stress-energy content is sufficient for vertical stability of these orbits. Moreover, adiabatic invariance of the vertical action variable gives us an approximate third integral of motion for oblique orbits which deviate slightly from the equatorial plane. Such new approximate third integral certainly points to a better understanding of the analytical properties of these orbits. The results presented here, derived for static spacetimes, may be a starting point to study the motion around rotating, stationary razor-thin disks. Our results also allow us to conjecture that the strong energy condition should be sufficient to assure transversal stability of periodic orbits for any singular timelike hypersurface, provided it is invariant under the geodesic flow. |
2105.06488 | Cristian Martinez | Mat\'ias Brice\~no, Cristi\'an Mart\'inez and Jorge Zanelli | Overspinning naked singularities in AdS$_3$ spacetime | 28 pages, 8 figures, 4 tables | Phys. Rev. D 104, 044023 (2021) | 10.1103/PhysRevD.104.044023 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The BTZ black hole belongs to a family of locally three-dimensional anti-de
Sitter (AdS$_3$) spacetimes labeled by their mass $M$ and angular momentum $J$.
The case $M \ell \geq |J|$, where $\ell$ is the anti-de Sitter radius, provides
the black hole. Extending the metric to other values of of $M$ and $J$ leads to
geometries with the same asymptotic behavior and global symmetries, but
containing a naked singularity at the origin. The case $M \ell \leq -|J|$
corresponds to spinning conical singularities that are reasonably well
understood. Here we examine the remaining case, that is $-|J|<M\ell<|J|$. These
naked singularities are mathematically acceptable solutions describing
classical spacetimes. They are obtained by identifications of the covering
pseudosphere in $\mathbb{R}^{2,2}$ and are free of closed timelike curves. Here
we study the causal structure and geodesics around these \textit{overspinning}
geometries. We present a review of the geodesics for the entire BTZ family. The
geodesic equations are completely integrated, and the solutions are expressed
in terms of elementary functions. Special attention is given to the
determination of circular geodesics, where new results are found. According to
the radial bounds, eight types of noncircular geodesics appear in the BTZ
spacetimes. For the case of overspinning naked singularity, null and spacelike
geodesics can reach infinity passing by a point nearest to the singularity,
others extend from the central singularity to infinity, and others still have a
radial upper bound and terminate at the singularity. Timelike geodesics cannot
reach infinity; they either loop around the singularity or fall into it. The
spatial projections of the geodesics (orbits) exhibit self-intersections, whose
number is determined for null and spacelike geodesics, and it is found a
special class of timelike geodesics whose spatial projections are closed.
| [
{
"created": "Thu, 13 May 2021 18:00:38 GMT",
"version": "v1"
}
] | 2021-08-18 | [
[
"Briceño",
"Matías",
""
],
[
"Martínez",
"Cristián",
""
],
[
"Zanelli",
"Jorge",
""
]
] | The BTZ black hole belongs to a family of locally three-dimensional anti-de Sitter (AdS$_3$) spacetimes labeled by their mass $M$ and angular momentum $J$. The case $M \ell \geq |J|$, where $\ell$ is the anti-de Sitter radius, provides the black hole. Extending the metric to other values of of $M$ and $J$ leads to geometries with the same asymptotic behavior and global symmetries, but containing a naked singularity at the origin. The case $M \ell \leq -|J|$ corresponds to spinning conical singularities that are reasonably well understood. Here we examine the remaining case, that is $-|J|<M\ell<|J|$. These naked singularities are mathematically acceptable solutions describing classical spacetimes. They are obtained by identifications of the covering pseudosphere in $\mathbb{R}^{2,2}$ and are free of closed timelike curves. Here we study the causal structure and geodesics around these \textit{overspinning} geometries. We present a review of the geodesics for the entire BTZ family. The geodesic equations are completely integrated, and the solutions are expressed in terms of elementary functions. Special attention is given to the determination of circular geodesics, where new results are found. According to the radial bounds, eight types of noncircular geodesics appear in the BTZ spacetimes. For the case of overspinning naked singularity, null and spacelike geodesics can reach infinity passing by a point nearest to the singularity, others extend from the central singularity to infinity, and others still have a radial upper bound and terminate at the singularity. Timelike geodesics cannot reach infinity; they either loop around the singularity or fall into it. The spatial projections of the geodesics (orbits) exhibit self-intersections, whose number is determined for null and spacelike geodesics, and it is found a special class of timelike geodesics whose spatial projections are closed. |
2103.17165 | Vittorio De Falco Dr | Vittorio De Falco, Maciek Wielgus | Three-dimensional general relativistic Poynting-Robertson effect. IV.
Slowly rotating and non-spherical quadrupolar massive source | 11 pages, 4 figures; accepted on Phys. Rev. D (31/03/2021) | null | 10.1103/PhysRevD.103.084056 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | We consider a further extension of our previous works in the treatment of the
three-dimensional general relativistic Poynting-Robertson effect, which
describes the motion of a test particle around a compact object as affected by
the radiation field originating from a rigidly rotating and spherical emitting
source, which produces a radiation pressure, opposite to the gravitational
pull, and a radiation drag force, which removes energy and angular momentum
from the test particle. The gravitational source is modeled as a non-spherical
and slowly rotating compact object endowed with a mass quadrupole moment and an
angular momentum and it is formally described by the Hartle-Thorne metric. We
derive the test particle's equations of motion in the three-dimensional and
two-dimensional cases. We then investigate the properties of the critical
hypersurfces (regions, where a balance between gravitational and radiation
forces is established). Finally, we show how this model can be applied to treat
radiation phenomena occurring in the vicinity of a neutron star.
| [
{
"created": "Wed, 31 Mar 2021 15:38:27 GMT",
"version": "v1"
}
] | 2021-05-12 | [
[
"De Falco",
"Vittorio",
""
],
[
"Wielgus",
"Maciek",
""
]
] | We consider a further extension of our previous works in the treatment of the three-dimensional general relativistic Poynting-Robertson effect, which describes the motion of a test particle around a compact object as affected by the radiation field originating from a rigidly rotating and spherical emitting source, which produces a radiation pressure, opposite to the gravitational pull, and a radiation drag force, which removes energy and angular momentum from the test particle. The gravitational source is modeled as a non-spherical and slowly rotating compact object endowed with a mass quadrupole moment and an angular momentum and it is formally described by the Hartle-Thorne metric. We derive the test particle's equations of motion in the three-dimensional and two-dimensional cases. We then investigate the properties of the critical hypersurfces (regions, where a balance between gravitational and radiation forces is established). Finally, we show how this model can be applied to treat radiation phenomena occurring in the vicinity of a neutron star. |
0805.4192 | Geoffrey Lovelace | Geoffrey Lovelace, Robert Owen, Harald P. Pfeiffer, Tony Chu | Binary-black-hole initial data with nearly-extremal spins | null | Phys.Rev.D78:084017,2008 | 10.1103/PhysRevD.78.084017 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There is a significant possibility that astrophysical black holes with
nearly-extremal spins exist. Numerical simulations of such systems require
suitable initial data. In this paper, we examine three methods of constructing
binary-black-hole initial data, focusing on their ability to generate black
holes with nearly-extremal spins: (i) Bowen-York initial data, including
standard puncture data (based on conformal flatness and Bowen-York extrinsic
curvature), (ii) standard quasi-equilibrium initial data (based on the
extended-conformal-thin-sandwich equations, conformal flatness, and maximal
slicing), and (iii) quasi-equilibrium data based on the superposition of
Kerr-Schild metrics. We find that the two conformally-flat methods (i) and (ii)
perform similarly, with spins up to about 0.99 obtainable at the initial time.
However, in an evolution, we expect the spin to quickly relax to a
significantly smaller value around 0.93 as the initial geometry relaxes. For
quasi-equilibrium superposed Kerr-Schild (SKS) data [method (iii)], we
construct initial data with \emph{initial} spins as large as 0.9997. We evolve
SKS data sets with spins of 0.93 and 0.97 and find that the spin drops by only
a few parts in 10^4 during the initial relaxation; therefore, we expect that
SKS initial data will allow evolutions of binary black holes with relaxed spins
above 0.99. [Abstract abbreviated; full abstract also mentions several
secondary results.]
| [
{
"created": "Tue, 27 May 2008 19:31:20 GMT",
"version": "v1"
},
{
"created": "Wed, 28 May 2008 00:45:39 GMT",
"version": "v2"
},
{
"created": "Thu, 16 Oct 2008 16:05:56 GMT",
"version": "v3"
}
] | 2009-02-23 | [
[
"Lovelace",
"Geoffrey",
""
],
[
"Owen",
"Robert",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Chu",
"Tony",
""
]
] | There is a significant possibility that astrophysical black holes with nearly-extremal spins exist. Numerical simulations of such systems require suitable initial data. In this paper, we examine three methods of constructing binary-black-hole initial data, focusing on their ability to generate black holes with nearly-extremal spins: (i) Bowen-York initial data, including standard puncture data (based on conformal flatness and Bowen-York extrinsic curvature), (ii) standard quasi-equilibrium initial data (based on the extended-conformal-thin-sandwich equations, conformal flatness, and maximal slicing), and (iii) quasi-equilibrium data based on the superposition of Kerr-Schild metrics. We find that the two conformally-flat methods (i) and (ii) perform similarly, with spins up to about 0.99 obtainable at the initial time. However, in an evolution, we expect the spin to quickly relax to a significantly smaller value around 0.93 as the initial geometry relaxes. For quasi-equilibrium superposed Kerr-Schild (SKS) data [method (iii)], we construct initial data with \emph{initial} spins as large as 0.9997. We evolve SKS data sets with spins of 0.93 and 0.97 and find that the spin drops by only a few parts in 10^4 during the initial relaxation; therefore, we expect that SKS initial data will allow evolutions of binary black holes with relaxed spins above 0.99. [Abstract abbreviated; full abstract also mentions several secondary results.] |
1704.07175 | Hiroyuki Nakano | Hiroyuki Nakano, Norichika Sago, Hideyuki Tagoshi, Takahiro Tanaka | Black hole ringdown echoes and howls | 10 pages, 5 figures, matches the published version | null | 10.1093/ptep/ptx093 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently the possibility of detecting echoes of ringdown gravitational waves
from binary black hole mergers was shown. The presence of echoes is expected if
the black hole is surrounded by a mirror that reflects gravitational waves near
the horizon. Here, we present slightly more sophisticated templates motivated
by a waveform which is obtained by solving the linear perturbation equation
around a Kerr black hole with a complete reflecting boundary condition in the
stationary traveling wave approximation. We estimate that the proposed template
can bring about $10\%$ improvement in the signal-to-noise ratio.
| [
{
"created": "Mon, 24 Apr 2017 12:30:58 GMT",
"version": "v1"
},
{
"created": "Mon, 1 May 2017 09:04:41 GMT",
"version": "v2"
},
{
"created": "Mon, 24 Jul 2017 06:19:11 GMT",
"version": "v3"
}
] | 2017-07-25 | [
[
"Nakano",
"Hiroyuki",
""
],
[
"Sago",
"Norichika",
""
],
[
"Tagoshi",
"Hideyuki",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | Recently the possibility of detecting echoes of ringdown gravitational waves from binary black hole mergers was shown. The presence of echoes is expected if the black hole is surrounded by a mirror that reflects gravitational waves near the horizon. Here, we present slightly more sophisticated templates motivated by a waveform which is obtained by solving the linear perturbation equation around a Kerr black hole with a complete reflecting boundary condition in the stationary traveling wave approximation. We estimate that the proposed template can bring about $10\%$ improvement in the signal-to-noise ratio. |
2311.15850 | Zakaria Belkhadria | Zakaria Belkhadria and Alexandre M. Pombo | Mixed scalarization of charged black holes: from spontaneous to
non-linear scalarization | 15 pages, 5 figures | Phys. Rev. D 110, 044014 (2024) | 10.1103/PhysRevD.110.044014 | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | Scalarized black holes (BH) have been shown to form dynamically in
extended-scalar-tensor theories, either through spontaneous scalarization --
when the BH is unstable against linear perturbations -- or through a non-linear
scalarization. In the latter, linearly stable BHs can ignite scalarization when
sufficiently perturbed. These phenomena are, however, not incompatible and
mixed scalarization is also possible. We explore two aspects of the
Einstein-Maxwell-Scalar model: solutions containing, simultaneously, linear
(\textit{aka} standard) and non-linear scalarization; and the effects of having
one of the coupling constants with an 'opposite sign' to the one leading to
scalarization. Both points are addressed by constructing and examining the
mixed scalarization's domain of existence. An overall dominance of the
spontaneous scalarization over the non-linear scalarization is observed.
Thermodynamically, an entropical preference for mixed over the standard
scalarization (spontaneous or non-linear) exists. In the presence of counter
scalarization, a quench of the scalarization occurs, mimicking the effect of a
scalar particle's mass/positive self-interaction term.
| [
{
"created": "Mon, 27 Nov 2023 14:17:39 GMT",
"version": "v1"
},
{
"created": "Sun, 19 May 2024 23:48:40 GMT",
"version": "v2"
}
] | 2024-08-06 | [
[
"Belkhadria",
"Zakaria",
""
],
[
"Pombo",
"Alexandre M.",
""
]
] | Scalarized black holes (BH) have been shown to form dynamically in extended-scalar-tensor theories, either through spontaneous scalarization -- when the BH is unstable against linear perturbations -- or through a non-linear scalarization. In the latter, linearly stable BHs can ignite scalarization when sufficiently perturbed. These phenomena are, however, not incompatible and mixed scalarization is also possible. We explore two aspects of the Einstein-Maxwell-Scalar model: solutions containing, simultaneously, linear (\textit{aka} standard) and non-linear scalarization; and the effects of having one of the coupling constants with an 'opposite sign' to the one leading to scalarization. Both points are addressed by constructing and examining the mixed scalarization's domain of existence. An overall dominance of the spontaneous scalarization over the non-linear scalarization is observed. Thermodynamically, an entropical preference for mixed over the standard scalarization (spontaneous or non-linear) exists. In the presence of counter scalarization, a quench of the scalarization occurs, mimicking the effect of a scalar particle's mass/positive self-interaction term. |
2003.13104 | Rahul Kumar | Arun Kumar, Rahul Kumar Walia and Sushant G. Ghosh | Bardeen Black Holes in the Regularized $4D$ Einstein--Gauss--Bonnet
Gravity | 15 pages and 4 figures. This was an invited manuscript published in
the special issue "Dark Matter and Dark Energy: Particle Physics, Cosmology,
and Experimental Searches" | Universe 8 (2022) 4, 232 | 10.3390/universe8040232 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We obtain exact Bardeen black holes to the regularized $4D$
Einstein--Gauss--Bonnet (EGB) gravity minimally coupled with the nonlinear
electrodynamics (NED). In turn, we analyze the horizon structure to determine
the effect of GB parameter $\alpha$ on the minimum cutoff values of mass,
$M_0$, and magnetic monopole charge, $g_0$, for the existence of a black hole
horizon. We obtain an exact expression for thermodynamic quantities, namely,
Hawking temperature $T_+$, entropy $S_+$, Helmholtz free energy $F_+$, and
specific heat $C_+$ associated with the black hole horizon, and they show
significant deviations from the $4D$ EGB case owing to NED. Interestingly,
there exists a critical value of horizon radius, $r_+^{c}$, corresponding to
the local maximum of Hawking temperature, at which heat capacity diverges,
confirming the second-order phase transition. A discussion on the black holes
of alternate regularized $4D$ EGB gravity belonging to the scalar-tensor theory
is appended.
| [
{
"created": "Sun, 29 Mar 2020 18:44:25 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Mar 2020 13:50:08 GMT",
"version": "v2"
},
{
"created": "Mon, 18 Apr 2022 11:56:55 GMT",
"version": "v3"
}
] | 2022-04-19 | [
[
"Kumar",
"Arun",
""
],
[
"Walia",
"Rahul Kumar",
""
],
[
"Ghosh",
"Sushant G.",
""
]
] | We obtain exact Bardeen black holes to the regularized $4D$ Einstein--Gauss--Bonnet (EGB) gravity minimally coupled with the nonlinear electrodynamics (NED). In turn, we analyze the horizon structure to determine the effect of GB parameter $\alpha$ on the minimum cutoff values of mass, $M_0$, and magnetic monopole charge, $g_0$, for the existence of a black hole horizon. We obtain an exact expression for thermodynamic quantities, namely, Hawking temperature $T_+$, entropy $S_+$, Helmholtz free energy $F_+$, and specific heat $C_+$ associated with the black hole horizon, and they show significant deviations from the $4D$ EGB case owing to NED. Interestingly, there exists a critical value of horizon radius, $r_+^{c}$, corresponding to the local maximum of Hawking temperature, at which heat capacity diverges, confirming the second-order phase transition. A discussion on the black holes of alternate regularized $4D$ EGB gravity belonging to the scalar-tensor theory is appended. |
1502.06755 | Saskia Grunau | Saskia Grunau, Hendrik Neumann | Thermodynamics of a rotating black hole in minimal five-dimensional
gauged supergravity | 12 pages, 7 figures | null | 10.1088/0264-9381/32/17/175004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we study the thermodynamics of a general non-extremal
rotating black hole in minimal five-dimensional gauged supergravity. We analyse
the entropy-temperature diagram and the free energy. Additionally we consider
the thermodynamic stability by calculating the specific heat, the isothermal
moment of inertia tensor and the adiabatic compressibility.
| [
{
"created": "Tue, 24 Feb 2015 10:41:44 GMT",
"version": "v1"
}
] | 2015-08-26 | [
[
"Grunau",
"Saskia",
""
],
[
"Neumann",
"Hendrik",
""
]
] | In this article we study the thermodynamics of a general non-extremal rotating black hole in minimal five-dimensional gauged supergravity. We analyse the entropy-temperature diagram and the free energy. Additionally we consider the thermodynamic stability by calculating the specific heat, the isothermal moment of inertia tensor and the adiabatic compressibility. |
2111.00253 | Fabiano Feleppa | Fabiano Feleppa, Hooman Moradpour, Christian Corda, Sarah Aghababaei | Constraining the generalized uncertainty principle with neutron
interferometry | 6 pages + references | EPL (Europhysics Letters) 135(4), 40003 (2021) | 10.1209/0295-5075/ac1240 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The non-zero minimal length arises in various theories of gravity, leading to
the so-called generalized uncertainty principle (GUP). In this short paper we
analyze the GUP effects on neutron interferometry, showing that the obtained
phase shifts depend on the mass and velocity of the particle. New upper bounds
on the dimensionless GUP parameter have been found that are in agreement with
the literature.
| [
{
"created": "Sat, 30 Oct 2021 14:05:39 GMT",
"version": "v1"
}
] | 2021-11-02 | [
[
"Feleppa",
"Fabiano",
""
],
[
"Moradpour",
"Hooman",
""
],
[
"Corda",
"Christian",
""
],
[
"Aghababaei",
"Sarah",
""
]
] | The non-zero minimal length arises in various theories of gravity, leading to the so-called generalized uncertainty principle (GUP). In this short paper we analyze the GUP effects on neutron interferometry, showing that the obtained phase shifts depend on the mass and velocity of the particle. New upper bounds on the dimensionless GUP parameter have been found that are in agreement with the literature. |
2010.15715 | Edward Malec | Wojciech Kulczycki and Edward Malec | On extensions of the Penrose inequality with angular momentum | Revised and expanded: a new Section 3 on numerical integration;
misprints corrected; minor stylistic changes. Conclusions are unchanged | Phys. Rev. D 103, 064025 (2021) | 10.1103/PhysRevD.103.064025 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We numerically investigate the validity of recent modifications of the
Penrose inequality that include angular momentum. Formulations expressed in
terms of asymptotic mass and asymptotic angular momentum are contradicted. We
analyzed numerical solutions describing polytropic stationary toroids around
spinning black holes.
| [
{
"created": "Thu, 29 Oct 2020 15:57:36 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Feb 2021 12:38:22 GMT",
"version": "v2"
}
] | 2021-03-24 | [
[
"Kulczycki",
"Wojciech",
""
],
[
"Malec",
"Edward",
""
]
] | We numerically investigate the validity of recent modifications of the Penrose inequality that include angular momentum. Formulations expressed in terms of asymptotic mass and asymptotic angular momentum are contradicted. We analyzed numerical solutions describing polytropic stationary toroids around spinning black holes. |
1503.02441 | Jonas Pedro Pereira | Jonas P. Pereira and Jorge A. Rueda | Energy decomposition within Einstein-Born-Infeld black holes | 9 pages, 5 figures, accepted for publication in Phys. Rev. D | null | 10.1103/PhysRevD.91.064048 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the consequences of the recently found generalization of the
Christodoulou-Ruffini black hole mass decomposition for Einstein-Born-Infeld
black holes [characterized by the parameters $(Q,M,b)$, where $M =
M(M_{irr},Q,b)$, $b$ scale field, $Q$ charge, $M_{irr}$ "irreducible mass",
physically meaning the energy of a black hole when its charge is null] and
their interactions. We show in this context that their description is largely
simplified and can basically be split into two families depending upon the
parameter $b|Q|$. If $b|Q|\leq 1/2$, then black holes could have even zero
irreducible masses and they always exhibit single, non degenerated, horizons.
If $b|Q|>1/2$, then an associated black hole must have a minimum irreducible
mass (related to its minimum energy) and has two horizons up to a transitional
irreducible mass. For larger irreducible masses, single horizon structures
raise again. By assuming that black holes emit thermal uncharged scalar
particles, we further show in light of the black hole mass decomposition that
one satisfying $b|Q|>1/2$ takes an infinite amount of time to reach the zero
temperature, settling down exactly at its minimum energy. Finally, we argue
that depending on the fundamental parameter $b$, the radiation (electromagnetic
and gravitational) coming from Einstein-Born-Infeld black holes could differ
significantly from Einstein-Maxwell ones. Hence, it could be used to assess
such a parameter.
| [
{
"created": "Mon, 9 Mar 2015 12:01:45 GMT",
"version": "v1"
}
] | 2015-06-24 | [
[
"Pereira",
"Jonas P.",
""
],
[
"Rueda",
"Jorge A.",
""
]
] | We analyze the consequences of the recently found generalization of the Christodoulou-Ruffini black hole mass decomposition for Einstein-Born-Infeld black holes [characterized by the parameters $(Q,M,b)$, where $M = M(M_{irr},Q,b)$, $b$ scale field, $Q$ charge, $M_{irr}$ "irreducible mass", physically meaning the energy of a black hole when its charge is null] and their interactions. We show in this context that their description is largely simplified and can basically be split into two families depending upon the parameter $b|Q|$. If $b|Q|\leq 1/2$, then black holes could have even zero irreducible masses and they always exhibit single, non degenerated, horizons. If $b|Q|>1/2$, then an associated black hole must have a minimum irreducible mass (related to its minimum energy) and has two horizons up to a transitional irreducible mass. For larger irreducible masses, single horizon structures raise again. By assuming that black holes emit thermal uncharged scalar particles, we further show in light of the black hole mass decomposition that one satisfying $b|Q|>1/2$ takes an infinite amount of time to reach the zero temperature, settling down exactly at its minimum energy. Finally, we argue that depending on the fundamental parameter $b$, the radiation (electromagnetic and gravitational) coming from Einstein-Born-Infeld black holes could differ significantly from Einstein-Maxwell ones. Hence, it could be used to assess such a parameter. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.