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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1808.02764 | Yuan K. Ha | Yuan K. Ha | Weighing the Black Hole via Quasi-local Energy | Editor invited paper. (12 pages). arXiv admin note: text overlap with
arXiv:1706.01768 | Mod. Phys. Lett. A, Vol. 32, No. 24 (2017) 1730021 | 10.1142/S021773231730021X | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We set to weigh the black holes at their event horizons in various spacetimes
and obtain masses which are substantially higher than their asymptotic values.
In each case, the horizon mass of a Schwarzschild, Reissner-Nordstr{\"o}m, or
Kerr black hole is found to be twice the irreducible mass observed at infinity.
The irreducible mass does not contain electrostatic or rotational energy,
leading to the inescapable conclusion that particles with electric charges and
spins cannot exist inside a black hole. The is proposed as the External Energy
Paradigm. A higher mass at the event horizon and its neighborhood is obligatory
for the release of gravitational waves in binary black hole merging. We
describe how these mass values are obtained in the quasi-local energy approach
and applied to the black holes of the first gravitational waves GW150914.
| [
{
"created": "Mon, 6 Aug 2018 20:25:31 GMT",
"version": "v1"
}
] | 2018-08-09 | [
[
"Ha",
"Yuan K.",
""
]
] | We set to weigh the black holes at their event horizons in various spacetimes and obtain masses which are substantially higher than their asymptotic values. In each case, the horizon mass of a Schwarzschild, Reissner-Nordstr{\"o}m, or Kerr black hole is found to be twice the irreducible mass observed at infinity. The irreducible mass does not contain electrostatic or rotational energy, leading to the inescapable conclusion that particles with electric charges and spins cannot exist inside a black hole. The is proposed as the External Energy Paradigm. A higher mass at the event horizon and its neighborhood is obligatory for the release of gravitational waves in binary black hole merging. We describe how these mass values are obtained in the quasi-local energy approach and applied to the black holes of the first gravitational waves GW150914. |
1403.1507 | Brian Dolan | Brian P. Dolan | Thermodynamic stability of asymptotically anti-de Sitter rotating black
holes in higher dimensions | 30 pages, 3 figures. References added, minor typos corrected in v3 | null | 10.1088/0264-9381/31/16/165011 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Conditions for thermodynamic stability of asymptotically anti-de Sitter
rotating black holes in D-dimensions are determined. Local thermodynamic
stability requires not only positivity conditions on the specific heat and the
moment of inertia tensor but it is also necessary that the adiabatic
compressibility be positive. It is shown that, in the absence of a cosmological
constant, neither rotation nor charge is sufficient to ensure full local
thermodynamic stability of a black hole.
Thermodynamic stability properties of anti-de Sitter Myers-Perry black holes
are investigated for both singly spinning and multi-spinning black holes.
Simple expressions are obtained for the specific heat and moment of inertia
tensor in any dimension. An analytic expression is obtained for the boundary of
the region of parameter space in which such space-times are thermodynamically
stable.
| [
{
"created": "Thu, 6 Mar 2014 17:43:34 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Apr 2014 14:46:07 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Jul 2014 17:52:39 GMT",
"version": "v3"
}
] | 2015-06-19 | [
[
"Dolan",
"Brian P.",
""
]
] | Conditions for thermodynamic stability of asymptotically anti-de Sitter rotating black holes in D-dimensions are determined. Local thermodynamic stability requires not only positivity conditions on the specific heat and the moment of inertia tensor but it is also necessary that the adiabatic compressibility be positive. It is shown that, in the absence of a cosmological constant, neither rotation nor charge is sufficient to ensure full local thermodynamic stability of a black hole. Thermodynamic stability properties of anti-de Sitter Myers-Perry black holes are investigated for both singly spinning and multi-spinning black holes. Simple expressions are obtained for the specific heat and moment of inertia tensor in any dimension. An analytic expression is obtained for the boundary of the region of parameter space in which such space-times are thermodynamically stable. |
1605.02627 | Jeremy Neveu | J. Neveu, V. Ruhlmann-Kleider, P. Astier, M. Besan\c{c}on, J. Guy, A.
M\"oller, E. Babichev | Constraining the $\Lambda$CDM and Galileon models with recent
cosmological data | 22 pages, 17 figures, published version in A&A | A&A 600, A40 (2017) | 10.1051/0004-6361/201628878 | LPT-Orsay-16-45 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Galileon theory belongs to the class of modified gravity models that can
explain the late-time accelerated expansion of the Universe. In previous works,
cosmological constraints on the Galileon model were derived, both in the
uncoupled case and with a disformal coupling of the Galileon field to matter.
There, we showed that these models agree with the most recent cosmological
data. In this work, we used updated cosmological data sets to derive new
constraints on Galileon models, including the case of a constant conformal
Galileon coupling to matter. We also explored the tracker solution of the
uncoupled Galileon model. After updating our data sets, especially with the
latest \textit{Planck} data and BAO measurements, we fitted the cosmological
parameters of the $\Lambda$CDM and Galileon models. The same analysis framework
as in our previous papers was used to derive cosmological constraints, using
precise measurements of cosmological distances and of the cosmic structure
growth rate. We showed that all tested Galileon models are as compatible with
cosmological data as the $\Lambda$CDM model. This means that present
cosmological data are not accurate enough to distinguish clearly between both
theories. Among the different Galileon models, we found that a conformal
coupling is not favoured, contrary to the disformal coupling which is preferred
at the $2.3\sigma$ level over the uncoupled case. The tracker solution of the
uncoupled Galileon model is also highly disfavoured due to large tensions with
supernovae and \textit{Planck}+BAO data. However, outside of the tracker
solution, the general uncoupled Galileon model, as well as the general
disformally coupled Galileon model, remain the most promising Galileon
scenarios to confront with future cosmological data. Finally, we also discuss
constraints coming from Lunar Laser Ranging experiment and gravitational wave
speed of propagation.
| [
{
"created": "Mon, 9 May 2016 15:43:08 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Feb 2017 16:36:12 GMT",
"version": "v2"
}
] | 2017-03-29 | [
[
"Neveu",
"J.",
""
],
[
"Ruhlmann-Kleider",
"V.",
""
],
[
"Astier",
"P.",
""
],
[
"Besançon",
"M.",
""
],
[
"Guy",
"J.",
""
],
[
"Möller",
"A.",
""
],
[
"Babichev",
"E.",
""
]
] | The Galileon theory belongs to the class of modified gravity models that can explain the late-time accelerated expansion of the Universe. In previous works, cosmological constraints on the Galileon model were derived, both in the uncoupled case and with a disformal coupling of the Galileon field to matter. There, we showed that these models agree with the most recent cosmological data. In this work, we used updated cosmological data sets to derive new constraints on Galileon models, including the case of a constant conformal Galileon coupling to matter. We also explored the tracker solution of the uncoupled Galileon model. After updating our data sets, especially with the latest \textit{Planck} data and BAO measurements, we fitted the cosmological parameters of the $\Lambda$CDM and Galileon models. The same analysis framework as in our previous papers was used to derive cosmological constraints, using precise measurements of cosmological distances and of the cosmic structure growth rate. We showed that all tested Galileon models are as compatible with cosmological data as the $\Lambda$CDM model. This means that present cosmological data are not accurate enough to distinguish clearly between both theories. Among the different Galileon models, we found that a conformal coupling is not favoured, contrary to the disformal coupling which is preferred at the $2.3\sigma$ level over the uncoupled case. The tracker solution of the uncoupled Galileon model is also highly disfavoured due to large tensions with supernovae and \textit{Planck}+BAO data. However, outside of the tracker solution, the general uncoupled Galileon model, as well as the general disformally coupled Galileon model, remain the most promising Galileon scenarios to confront with future cosmological data. Finally, we also discuss constraints coming from Lunar Laser Ranging experiment and gravitational wave speed of propagation. |
gr-qc/0703101 | Jose Socorro Garcia | C. Ortiz, E. Mena-Barboza, M. Sabido and J. Socorro | (Non)commutative isotropization in Bianchi I with Barotropic perfect
fluid and $\Lambda$ Cosmological | 15 pages, 1 figure | null | 10.1007/s10773-007-9557-1 | null | gr-qc | null | We present the classical solutions to the Einstein field equations derived
using the WKB-like and Hamilton procedures. The investigation is carried out in
the commutative and noncommutative scenario for the Bianchi type I cosmological
model coupled to barotropic perfect fluid and $\lambda $ Cosmological for two
different gauges. Noncommutativity is achieved by modifying the symplectic
structure considering that all minisuperspace variables $\rm q^i$ does not
commute and by a deformation between all the minisuperspace variables. In the
gauge N=1, it is possible to obtain that the anisotropic parameter $\rm
\beta_{\pm nc}$ tend to a constant curvature for large period of time
considering different values in the noncommutative parameters $\theta$ and
cosmological term. However, this behavior give the idea that is necessary
introduce other class of matter in the models, for to have a real
isotropization in the model, such as dark energy or dark matter.
| [
{
"created": "Tue, 20 Mar 2007 17:49:04 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Ortiz",
"C.",
""
],
[
"Mena-Barboza",
"E.",
""
],
[
"Sabido",
"M.",
""
],
[
"Socorro",
"J.",
""
]
] | We present the classical solutions to the Einstein field equations derived using the WKB-like and Hamilton procedures. The investigation is carried out in the commutative and noncommutative scenario for the Bianchi type I cosmological model coupled to barotropic perfect fluid and $\lambda $ Cosmological for two different gauges. Noncommutativity is achieved by modifying the symplectic structure considering that all minisuperspace variables $\rm q^i$ does not commute and by a deformation between all the minisuperspace variables. In the gauge N=1, it is possible to obtain that the anisotropic parameter $\rm \beta_{\pm nc}$ tend to a constant curvature for large period of time considering different values in the noncommutative parameters $\theta$ and cosmological term. However, this behavior give the idea that is necessary introduce other class of matter in the models, for to have a real isotropization in the model, such as dark energy or dark matter. |
2310.09558 | Yuri Pavlov | A. A. Grib, Yu. V. Pavlov | Can the energy of a particle be negative in the absence of external
fields? | 15 pages, 1 figure | Theor. Math. Phys. 216 (2023) 1337-1348 | 10.1134/S0040577923090088 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the question of conditions for the existence of negative-energy
states of particles in the absence of external fields in inertial and
noninertial frames of reference. We show that in the nonrelativistic case in
noninertial reference frames, there always exist domains where the energy of
particles is negative. We also show that in the relativistic case, the
existence of negative-energy states of point particles does not lead to
violations of the energy dominance condition. We consider conditions for the
appearance of negative and zero energies of particles in the Milne universe and
Rindler space-time.
| [
{
"created": "Sat, 14 Oct 2023 10:58:51 GMT",
"version": "v1"
}
] | 2023-10-17 | [
[
"Grib",
"A. A.",
""
],
[
"Pavlov",
"Yu. V.",
""
]
] | We study the question of conditions for the existence of negative-energy states of particles in the absence of external fields in inertial and noninertial frames of reference. We show that in the nonrelativistic case in noninertial reference frames, there always exist domains where the energy of particles is negative. We also show that in the relativistic case, the existence of negative-energy states of point particles does not lead to violations of the energy dominance condition. We consider conditions for the appearance of negative and zero energies of particles in the Milne universe and Rindler space-time. |
2205.13072 | Mahdi Godazgar | Oscar J. C. Dias, Mahdi Godazgar, Jorge E. Santos | Eigenvalue repulsions and quasinormal mode spectra of Kerr-Newman: an
extended study | 64 pages, 31 figures | null | 10.1007/JHEP07(2022)076 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | The frequency spectra of the gravito-electromagnetic perturbations of the
Kerr-Newman (KN) black hole with the slowest decay rate have been computed
recently. It has been found that KN has two families $-$ the photon sphere and
the near-horizon families $-$ of quasinormal modes (QNMs), which display the
interesting phenomenon of eigenvalue repulsion. The perturbation equations, in
spite of being a coupled system of two PDEs, are amenable to an analytic
solution using the method of separation of variables in a near-horizon
expansion around the extremal KN black hole. This leads to an analytical
formula for the QNM frequencies that provides an excellent approximation to the
numerical data near-extremality. In the present manuscript we provide an
extended study of these properties that were not detailed in the original
studies. This includes: 1) a full derivation of a gauge invariant system of two
coupled PDEs that describes the perturbation equations \cite{Dias:2015wqa}, 2)
a derivation of the eikonal frequency approximation
\cite{Zimmerman:2015trm,Dias:2021yju} and its comparison with the numerical QNM
data, 3) a derivation of the near-horizon frequency approximation
\cite{Dias:2021yju} and its comparison with the numerical QNMs, and 4) more
details on the phenomenon of eigenvalue repulsion (also known as \emph{level
repulsion}, \emph{avoided crossing} or \emph{Wigner-Teller effect}) and a first
principles understanding of it that was missing in the previous studies.
Moreover, we provide the frequency spectra of other KN QNM families of interest
to demonstrate that they are more damped than the ones we discuss in full
detail.
| [
{
"created": "Wed, 25 May 2022 22:38:33 GMT",
"version": "v1"
}
] | 2022-07-27 | [
[
"Dias",
"Oscar J. C.",
""
],
[
"Godazgar",
"Mahdi",
""
],
[
"Santos",
"Jorge E.",
""
]
] | The frequency spectra of the gravito-electromagnetic perturbations of the Kerr-Newman (KN) black hole with the slowest decay rate have been computed recently. It has been found that KN has two families $-$ the photon sphere and the near-horizon families $-$ of quasinormal modes (QNMs), which display the interesting phenomenon of eigenvalue repulsion. The perturbation equations, in spite of being a coupled system of two PDEs, are amenable to an analytic solution using the method of separation of variables in a near-horizon expansion around the extremal KN black hole. This leads to an analytical formula for the QNM frequencies that provides an excellent approximation to the numerical data near-extremality. In the present manuscript we provide an extended study of these properties that were not detailed in the original studies. This includes: 1) a full derivation of a gauge invariant system of two coupled PDEs that describes the perturbation equations \cite{Dias:2015wqa}, 2) a derivation of the eikonal frequency approximation \cite{Zimmerman:2015trm,Dias:2021yju} and its comparison with the numerical QNM data, 3) a derivation of the near-horizon frequency approximation \cite{Dias:2021yju} and its comparison with the numerical QNMs, and 4) more details on the phenomenon of eigenvalue repulsion (also known as \emph{level repulsion}, \emph{avoided crossing} or \emph{Wigner-Teller effect}) and a first principles understanding of it that was missing in the previous studies. Moreover, we provide the frequency spectra of other KN QNM families of interest to demonstrate that they are more damped than the ones we discuss in full detail. |
1611.06182 | Elena Kopteva | E. Kopteva, P. Jaluvkova, Z. Stuchlik | The generalized Lemaitre-Tolman-Bondi solutions with nonzero pressure in
modeling the cosmological black holes | 8 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we have obtained the set of new exact solutions of the Einstein
equations that generalize the known Lemaitre-Tolman-Bondi solution for the
certain case of nonzero pressure under zero spatial curvature. These solutions
are pretending to describe the black hole immersed in the nonstatic
cosmological background and give a possibility to investigate the problems
concerning the effects of the cosmological expansion in gravitationally bounded
systems. They may also be used as a seed models in the problem of structure
formation in the universe at the epoch of matter and radiation decoupling. It
was shown that each of the solutions obtained contains either the
Reissner-Nordstrom or the Schwarzschild black hole in the central region of the
space. It is demonstrated that the approach of the mass function use in solving
the Einstein equations allows clear physical interpretation of the resulting
solutions that is of much benefit to any their further application.
| [
{
"created": "Fri, 18 Nov 2016 18:02:22 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Nov 2016 14:20:15 GMT",
"version": "v2"
}
] | 2016-11-29 | [
[
"Kopteva",
"E.",
""
],
[
"Jaluvkova",
"P.",
""
],
[
"Stuchlik",
"Z.",
""
]
] | In this work we have obtained the set of new exact solutions of the Einstein equations that generalize the known Lemaitre-Tolman-Bondi solution for the certain case of nonzero pressure under zero spatial curvature. These solutions are pretending to describe the black hole immersed in the nonstatic cosmological background and give a possibility to investigate the problems concerning the effects of the cosmological expansion in gravitationally bounded systems. They may also be used as a seed models in the problem of structure formation in the universe at the epoch of matter and radiation decoupling. It was shown that each of the solutions obtained contains either the Reissner-Nordstrom or the Schwarzschild black hole in the central region of the space. It is demonstrated that the approach of the mass function use in solving the Einstein equations allows clear physical interpretation of the resulting solutions that is of much benefit to any their further application. |
2111.15660 | Jay Solanki | Jay Solanki | Gravitational collapse of compact stars in $ f(R) = \xi R^4 $ gravity | null | Int. J. Geom. Methods Mod. Phys. 19(02):2250021, 2022 | 10.1142/S0219887822500219 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Model of gravitational collapse of anisotropic compact stars in a new theory
of $ f(R) $ gravity has been developed. The author considers the modified
gravity model of $ f(R) = \xi R^4 $ to investigate a physically acceptable
model of gravitational collapse of anisotropic compact stars. First, the author
presents a brief review of the development of field equations of gravitational
collapse in $ f(R) $ gravity for a particular interior metric for compact
stars. Then analytical solutions for various physical quantities of collapsing
anisotropic compact stars in $ \xi R^4 $ gravity have been developed. By
analyzing plots of various physical parameters and conditions, it is shown that
the model is physically acceptable for describing the gravitational collapse of
anisotropic compact stars in $ f(R) = \xi R^4 $ gravity.
| [
{
"created": "Thu, 25 Nov 2021 17:15:21 GMT",
"version": "v1"
}
] | 2022-04-01 | [
[
"Solanki",
"Jay",
""
]
] | Model of gravitational collapse of anisotropic compact stars in a new theory of $ f(R) $ gravity has been developed. The author considers the modified gravity model of $ f(R) = \xi R^4 $ to investigate a physically acceptable model of gravitational collapse of anisotropic compact stars. First, the author presents a brief review of the development of field equations of gravitational collapse in $ f(R) $ gravity for a particular interior metric for compact stars. Then analytical solutions for various physical quantities of collapsing anisotropic compact stars in $ \xi R^4 $ gravity have been developed. By analyzing plots of various physical parameters and conditions, it is shown that the model is physically acceptable for describing the gravitational collapse of anisotropic compact stars in $ f(R) = \xi R^4 $ gravity. |
0903.3532 | Luis Herrera | L. Herrera, J. Ospino, A. Di Prisco, E. Fuenmayor and O. Troconis | Structure and evolution of self-gravitating objects and the orthogonal
splitting of the Riemann tensor | 32 pages, Latex | Phys.Rev.D79:064025,2009 | 10.1103/PhysRevD.79.064025 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The full set of equations governing the structure and the evolution of
self--gravitating spherically symmetric dissipative fluids with anisotropic
stresses, is written down in terms of five scalar quantities obtained from the
orthogonal splitting of the Riemann tensor, in the context of general
relativity. It is shown that these scalars are directly related to fundamental
properties of the fluid distribution, such as: energy density, energy density
inhomogeneity, local anisotropy of pressure, dissipative flux and the active
gravitational mass. It is also shown that in the static case, all possible
solutions to Einstein equations may be expressed explicitly through these
scalars. Some solutions are exhibited to illustrate this point.
| [
{
"created": "Fri, 20 Mar 2009 15:04:12 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Herrera",
"L.",
""
],
[
"Ospino",
"J.",
""
],
[
"Di Prisco",
"A.",
""
],
[
"Fuenmayor",
"E.",
""
],
[
"Troconis",
"O.",
""
]
] | The full set of equations governing the structure and the evolution of self--gravitating spherically symmetric dissipative fluids with anisotropic stresses, is written down in terms of five scalar quantities obtained from the orthogonal splitting of the Riemann tensor, in the context of general relativity. It is shown that these scalars are directly related to fundamental properties of the fluid distribution, such as: energy density, energy density inhomogeneity, local anisotropy of pressure, dissipative flux and the active gravitational mass. It is also shown that in the static case, all possible solutions to Einstein equations may be expressed explicitly through these scalars. Some solutions are exhibited to illustrate this point. |
0807.1324 | Holger Pletsch | Holger J. Pletsch | Parameter-space correlations of the optimal statistic for continuous
gravitational-wave detection | 17 pages, 10 figures | Phys.Rev.D78:102005,2008 | 10.1103/PhysRevD.78.102005 | LIGO-P080051-02-Z, AEI-2008-043 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The phase parameters of matched-filtering searches for continuous
gravitational-wave signals are sky position, frequency and frequency
time-derivatives. The space of these parameters features strong global
correlations in the optimal detection statistic. For observation times smaller
than one year, the orbital motion of the Earth leads to a family of
global-correlation equations which describes the "global maximum structure" of
the detection statistic. The solution to each of these equations is a different
hypersurface in parameter space. The expected detection statistic is maximal at
the intersection of these hypersurfaces. The global maximum structure of the
detection statistic from stationary instrumental-noise artifacts is also
described by the global-correlation equations. This permits the construction of
a veto method which excludes false candidate events.
| [
{
"created": "Wed, 9 Jul 2008 09:32:32 GMT",
"version": "v1"
},
{
"created": "Tue, 19 May 2009 21:00:17 GMT",
"version": "v2"
}
] | 2009-05-19 | [
[
"Pletsch",
"Holger J.",
""
]
] | The phase parameters of matched-filtering searches for continuous gravitational-wave signals are sky position, frequency and frequency time-derivatives. The space of these parameters features strong global correlations in the optimal detection statistic. For observation times smaller than one year, the orbital motion of the Earth leads to a family of global-correlation equations which describes the "global maximum structure" of the detection statistic. The solution to each of these equations is a different hypersurface in parameter space. The expected detection statistic is maximal at the intersection of these hypersurfaces. The global maximum structure of the detection statistic from stationary instrumental-noise artifacts is also described by the global-correlation equations. This permits the construction of a veto method which excludes false candidate events. |
1702.07766 | Farhad Darabi | Y. Heydarzade, F. Darabi | Black Hole Solutions Surrounded by Perfect Fluid in Rastall Theory | 15 Paes, 6 Tables | Physics Letters B, 771, (2017) 365-373 | 10.1016/j.physletb.2017.05.064 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we obtain uncharged\charged Kiselev-like black holes as a new
class of black hole solutions surrounded by perfect fluid in the context of
Rastall theory. Then, we study the specific cases of the uncharged\charged
black holes surrounded by regular matter like dust and radiation, or exotic
matter like quintessence, cosmological constant and phantom fields. By
comparing the Kiselev-like black hole solutions in Rastall theory with the
Kiselev black hole solutions in GR, we find an effective perfect fluid
behaviour for the black hole's surrounding field. It is shown that the
corresponding effective perfect fluid has interesting characteristic features
depending on the different ranges of the parameters in Rastall theory. For
instance, Kiselev-like black holes surrounded by regular matter in Rastall
theory may be considered as Kiselev black holes surrounded by exotic matter in
GR, or Kiselev-like black holes surrounded by exotic matter in Rastall theory
may be considered as Kiselev black holes surrounded by regular matter in GR.
| [
{
"created": "Fri, 24 Feb 2017 21:13:23 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Jun 2017 20:47:53 GMT",
"version": "v2"
}
] | 2017-06-09 | [
[
"Heydarzade",
"Y.",
""
],
[
"Darabi",
"F.",
""
]
] | In this work, we obtain uncharged\charged Kiselev-like black holes as a new class of black hole solutions surrounded by perfect fluid in the context of Rastall theory. Then, we study the specific cases of the uncharged\charged black holes surrounded by regular matter like dust and radiation, or exotic matter like quintessence, cosmological constant and phantom fields. By comparing the Kiselev-like black hole solutions in Rastall theory with the Kiselev black hole solutions in GR, we find an effective perfect fluid behaviour for the black hole's surrounding field. It is shown that the corresponding effective perfect fluid has interesting characteristic features depending on the different ranges of the parameters in Rastall theory. For instance, Kiselev-like black holes surrounded by regular matter in Rastall theory may be considered as Kiselev black holes surrounded by exotic matter in GR, or Kiselev-like black holes surrounded by exotic matter in Rastall theory may be considered as Kiselev black holes surrounded by regular matter in GR. |
2008.12932 | Sebastian Khan | Sebastian Khan, Rhys Green | Gravitational-wave surrogate models powered by artificial neural
networks: The ANN-Sur for waveform generation | null | Phys. Rev. D 103, 064015 (2021) | 10.1103/PhysRevD.103.064015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inferring the properties of black holes and neutron stars is a key science
goal of gravitational-wave (GW) astronomy. To extract as much information as
possible from GW observations we must develop methods to reduce the cost of
Bayesian inference. In this paper, we use artificial neural networks (ANNs) and
the parallelisation power of graphics processing units (GPUs) to improve the
surrogate modelling method, which can produce accelerated versions of existing
models. As a first application of our method, ANN-Sur, we build a time-domain
surrogate model of the spin-aligned binary black hole (BBH) waveform model
SEOBNRv4. We achieve median mismatches of 2e-5 and mismatches no worse than
2e-3. For a typical BBH waveform generated from 12 Hz with a total mass of $60
M_\odot$ the original SEOBNRv4 model takes 1812 ms. Existing bespoke code
optimisations (SEOBNRv4opt) reduced this to 91.6 ms and the interpolation
based, frequency-domain surrogate SEOBNRv4ROM can generate this waveform in 6.9
ms. Our ANN-Sur model, when run on a CPU takes 2.7 ms and just 0.4 ms when run
on a GPU. ANN-Sur can also generate large batches of waveforms simultaneously.
We find that batches of up to 10^4 waveforms can be evaluated on a GPU in just
163 ms, corresponding to a time per waveform of 0.016 ms. This method is a
promising way to utilise the parallelisation power of GPUs to drastically
increase the computational efficiency of Bayesian parameter estimation.
| [
{
"created": "Sat, 29 Aug 2020 07:54:58 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Nov 2020 10:23:43 GMT",
"version": "v2"
}
] | 2021-03-17 | [
[
"Khan",
"Sebastian",
""
],
[
"Green",
"Rhys",
""
]
] | Inferring the properties of black holes and neutron stars is a key science goal of gravitational-wave (GW) astronomy. To extract as much information as possible from GW observations we must develop methods to reduce the cost of Bayesian inference. In this paper, we use artificial neural networks (ANNs) and the parallelisation power of graphics processing units (GPUs) to improve the surrogate modelling method, which can produce accelerated versions of existing models. As a first application of our method, ANN-Sur, we build a time-domain surrogate model of the spin-aligned binary black hole (BBH) waveform model SEOBNRv4. We achieve median mismatches of 2e-5 and mismatches no worse than 2e-3. For a typical BBH waveform generated from 12 Hz with a total mass of $60 M_\odot$ the original SEOBNRv4 model takes 1812 ms. Existing bespoke code optimisations (SEOBNRv4opt) reduced this to 91.6 ms and the interpolation based, frequency-domain surrogate SEOBNRv4ROM can generate this waveform in 6.9 ms. Our ANN-Sur model, when run on a CPU takes 2.7 ms and just 0.4 ms when run on a GPU. ANN-Sur can also generate large batches of waveforms simultaneously. We find that batches of up to 10^4 waveforms can be evaluated on a GPU in just 163 ms, corresponding to a time per waveform of 0.016 ms. This method is a promising way to utilise the parallelisation power of GPUs to drastically increase the computational efficiency of Bayesian parameter estimation. |
1602.03309 | Vasilis Oikonomou | S.D. Odintsov, V.K. Oikonomou | Singular $F(R)$ Cosmology Unifying Early and Late-time Acceleration with
Matter and Radiation Domination Era | CQG accepted | null | 10.1088/0264-9381/33/12/125029 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present some cosmological models which unify the late and early-time
acceleration eras with the radiation and the matter domination era, and we
realize the cosmological models by using the theoretical framework of $F(R)$
gravity. Particularly, the first model unifies the late and early-time
acceleration with the matter domination era, and the second model unifies all
the evolution eras of our Universe. The two models are described in the same
way at early and late times, and only the intermediate stages of the evolution
have some differences. Each cosmological model contains two Type IV
singularities which are chosen to occur one at the end of the inflationary era
and one at the end of the matter domination era. The cosmological models at
early times are approximately identical to the $R^2$ inflation model, so these
describe a slow-roll inflationary era which ends when the slow-roll parameters
become of order one. The inflationary era is followed by the radiation era and
after that the matter domination era follows, which lasts until the second Type
IV singularity, and then the late-time acceleration era follows. The models
produce a nearly scale invariant power spectrum of primordial curvature
perturbations and a scalar-to-tensor ratio which are compatible with the most
recent observational data and it seems that the deceleration acceleration
transition is crucially affected by the presence of the second Type IV
singularity which occurs at the end of the matter domination era. We perform an
analysis of the Hubble horizon evolution, and in addition, we investigate which
$F(R)$ gravity can successfully realize each of the four cosmological epochs.
| [
{
"created": "Wed, 10 Feb 2016 09:45:57 GMT",
"version": "v1"
},
{
"created": "Sat, 14 May 2016 10:04:12 GMT",
"version": "v2"
}
] | 2016-06-01 | [
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] | We present some cosmological models which unify the late and early-time acceleration eras with the radiation and the matter domination era, and we realize the cosmological models by using the theoretical framework of $F(R)$ gravity. Particularly, the first model unifies the late and early-time acceleration with the matter domination era, and the second model unifies all the evolution eras of our Universe. The two models are described in the same way at early and late times, and only the intermediate stages of the evolution have some differences. Each cosmological model contains two Type IV singularities which are chosen to occur one at the end of the inflationary era and one at the end of the matter domination era. The cosmological models at early times are approximately identical to the $R^2$ inflation model, so these describe a slow-roll inflationary era which ends when the slow-roll parameters become of order one. The inflationary era is followed by the radiation era and after that the matter domination era follows, which lasts until the second Type IV singularity, and then the late-time acceleration era follows. The models produce a nearly scale invariant power spectrum of primordial curvature perturbations and a scalar-to-tensor ratio which are compatible with the most recent observational data and it seems that the deceleration acceleration transition is crucially affected by the presence of the second Type IV singularity which occurs at the end of the matter domination era. We perform an analysis of the Hubble horizon evolution, and in addition, we investigate which $F(R)$ gravity can successfully realize each of the four cosmological epochs. |
1011.2463 | Madhavan Varadarajan | Alok Laddha and Madhavan Varadarajan | The Hamiltonian constraint in Polymer Parametrized Field Theory | 53 pages | Phys.Rev.D83:025019,2011 | 10.1103/PhysRevD.83.025019 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, a generally covariant reformulation of 2 dimensional flat spacetime
free scalar field theory known as Parameterised Field Theory was quantized
using Loop Quantum Gravity (LQG) type `polymer' representations. Physical
states were constructed, without intermediate regularization structures, by
averaging over the group of gauge transformations generated by the constraints,
the constraint algebra being a Lie algebra. We consider classically equivalent
combinations of these constraints corresponding to a diffeomorphism and a
Hamiltonian constraint, which, as in gravity, define a Dirac algebra. Our
treatment of the quantum constraints parallels that of LQG and obtains the
following results, expected to be of use in the construction of the quantum
dynamics of LQG:(i) the (triangulated) Hamiltonian constraint acts only on
vertices, its construction involves some of the same ambiguities as in LQG and
its action on diffeomorphism invariant states admits a continuum limit (ii)if
the regulating holonomies are in representations tailored to the edge labels of
the state, all previously obtained physical states lie in the kernel of the
Hamiltonian constraint, (iii) the commutator of two (density weight 1)
Hamiltonian constraints as well as the operator correspondent of their
classical Poisson bracket converge to zero in the continuum limit defined by
diffeomorphism invariant states, and vanish on the Lewandowski- Marolf (LM)
habitat (iv) the rescaled density 2 Hamiltonian constraints and their
commutator are ill defined on the LM habitat despite the well defined- ness of
the operator correspondent of their classical Poisson bracket there (v) there
is a new habitat which supports a non-trivial representation of the Poisson-
Lie algebra of density 2 constraints
| [
{
"created": "Wed, 10 Nov 2010 19:30:06 GMT",
"version": "v1"
}
] | 2015-01-30 | [
[
"Laddha",
"Alok",
""
],
[
"Varadarajan",
"Madhavan",
""
]
] | Recently, a generally covariant reformulation of 2 dimensional flat spacetime free scalar field theory known as Parameterised Field Theory was quantized using Loop Quantum Gravity (LQG) type `polymer' representations. Physical states were constructed, without intermediate regularization structures, by averaging over the group of gauge transformations generated by the constraints, the constraint algebra being a Lie algebra. We consider classically equivalent combinations of these constraints corresponding to a diffeomorphism and a Hamiltonian constraint, which, as in gravity, define a Dirac algebra. Our treatment of the quantum constraints parallels that of LQG and obtains the following results, expected to be of use in the construction of the quantum dynamics of LQG:(i) the (triangulated) Hamiltonian constraint acts only on vertices, its construction involves some of the same ambiguities as in LQG and its action on diffeomorphism invariant states admits a continuum limit (ii)if the regulating holonomies are in representations tailored to the edge labels of the state, all previously obtained physical states lie in the kernel of the Hamiltonian constraint, (iii) the commutator of two (density weight 1) Hamiltonian constraints as well as the operator correspondent of their classical Poisson bracket converge to zero in the continuum limit defined by diffeomorphism invariant states, and vanish on the Lewandowski- Marolf (LM) habitat (iv) the rescaled density 2 Hamiltonian constraints and their commutator are ill defined on the LM habitat despite the well defined- ness of the operator correspondent of their classical Poisson bracket there (v) there is a new habitat which supports a non-trivial representation of the Poisson- Lie algebra of density 2 constraints |
2405.02879 | Hossein Khodabakhshi | H. Khodabakhshi, M. Farhang, F. Shojai, H. L\"u | Cosmology with Higher-Derivative Gravities | 9 pages, 1 table | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by-sa/4.0/ | We introduce an ingenious approach to explore cosmological implications of
higher-derivative gravity theories. The key novelty lies in the
characterization of the additional massive spin-0 modes constructed from Hubble
derivatives as an effective density, with the corresponding pressure uniquely
determined by energy conservation, while terms with no Hubble derivatives
directly alter Friedmann equations. This classification of the various
high-derivative contributions to Friedmann equations develops insight about
their cosmological impacts and is essential for understanding the universe's
evolution across energy scales. Various examples of higher-derivative gravity
theories illustrate the power of this method in efficiently solving Friedmann
equations and exploring new phenomena. Using CMB and BAO data, we apply this
method to assess the observational feasibility of wall-bouncing universes, as
predicted by scenarios with, e.g., certain third order modifications to general
relativity. These models also provide an inflationary phase without the need to
introduce extra scalar fields.
| [
{
"created": "Sun, 5 May 2024 10:25:18 GMT",
"version": "v1"
},
{
"created": "Tue, 14 May 2024 05:18:18 GMT",
"version": "v2"
}
] | 2024-05-15 | [
[
"Khodabakhshi",
"H.",
""
],
[
"Farhang",
"M.",
""
],
[
"Shojai",
"F.",
""
],
[
"Lü",
"H.",
""
]
] | We introduce an ingenious approach to explore cosmological implications of higher-derivative gravity theories. The key novelty lies in the characterization of the additional massive spin-0 modes constructed from Hubble derivatives as an effective density, with the corresponding pressure uniquely determined by energy conservation, while terms with no Hubble derivatives directly alter Friedmann equations. This classification of the various high-derivative contributions to Friedmann equations develops insight about their cosmological impacts and is essential for understanding the universe's evolution across energy scales. Various examples of higher-derivative gravity theories illustrate the power of this method in efficiently solving Friedmann equations and exploring new phenomena. Using CMB and BAO data, we apply this method to assess the observational feasibility of wall-bouncing universes, as predicted by scenarios with, e.g., certain third order modifications to general relativity. These models also provide an inflationary phase without the need to introduce extra scalar fields. |
1105.1996 | Stefan Hollands | Stefan Hollands | Massless interacting quantum fields in deSitter spacetime | 40 pages, several figures, v2: added references, more discussion in
app.C and in proof of thm.1, other minor changes | null | 10.1007/s00023-011-0140-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We generalize key aspects of arXiv:1010.5367 (and also arXiv:1010.5327) to
the case of {\em massless} $\lambda \phi^{2n}$ quantum field theory on deSitter
spacetime. As in that paper, our key objective is to derive a suitable
"Mellin-Barnes-type" representation of deSitter correlation functions in a
deSitter-invariant state, which holds to arbitrary orders in perturbation
theory, and which incorporates renormalization. The representation is suitable
for the study of large distance/time properties of correlation functions. It is
arrived at via an analytic continuation from the corresponding objects on the
sphere, and, as in the massive case, relies on the use of graph-polynomials and
their properties, as well as other tools. However, the perturbation expansion
is organized somewhat differently in the massless case, due to the well-known
subtleties associated with the "zero-mode" of the quantum field. In particular,
the correlation functions do not possess a well-defined limit as the
self-coupling constant of the field goes to zero, reflecting the well-known
non-existence of a deSitter invariant state in the free massless scalar theory.
We establish that generic correlation functions cannot grow more than
polynomially in proper time for large time-like separations of the points. Our
results thus leave open the possibility of quantum induced IR-instabilities of
deSitter spacetime on very large time-scales.
| [
{
"created": "Tue, 10 May 2011 16:54:11 GMT",
"version": "v1"
},
{
"created": "Fri, 20 May 2011 12:08:10 GMT",
"version": "v2"
}
] | 2015-05-28 | [
[
"Hollands",
"Stefan",
""
]
] | We generalize key aspects of arXiv:1010.5367 (and also arXiv:1010.5327) to the case of {\em massless} $\lambda \phi^{2n}$ quantum field theory on deSitter spacetime. As in that paper, our key objective is to derive a suitable "Mellin-Barnes-type" representation of deSitter correlation functions in a deSitter-invariant state, which holds to arbitrary orders in perturbation theory, and which incorporates renormalization. The representation is suitable for the study of large distance/time properties of correlation functions. It is arrived at via an analytic continuation from the corresponding objects on the sphere, and, as in the massive case, relies on the use of graph-polynomials and their properties, as well as other tools. However, the perturbation expansion is organized somewhat differently in the massless case, due to the well-known subtleties associated with the "zero-mode" of the quantum field. In particular, the correlation functions do not possess a well-defined limit as the self-coupling constant of the field goes to zero, reflecting the well-known non-existence of a deSitter invariant state in the free massless scalar theory. We establish that generic correlation functions cannot grow more than polynomially in proper time for large time-like separations of the points. Our results thus leave open the possibility of quantum induced IR-instabilities of deSitter spacetime on very large time-scales. |
1910.14044 | Christian Pfeifer | Manuel Hohmann, Christian Pfeifer, Nicoleta Voicu | Relativistic kinetic gases as direct sources of gravity | 13 pages, updated to journal version | Phys. Rev. D 101, 024062 (2020) | 10.1103/PhysRevD.101.024062 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new model for the description of a gravitating multi particle
system, viewed as a kinetic gas. The properties of the, colliding or
non-colliding, particles are encoded into a so called one-particle distribution
function, which is a density on the space of allowed particle positions and
velocities, i.e. on the tangent bundle of the spacetime manifold. We argue that
an appropriate theory of gravity, describing the gravitational field generated
by a kinetic gas, must also be modeled on the tangent bundle. The most natural
mathematical framework for this task is Finsler spacetime geometry. Following
this line of argumentation, we construct a coupling between the kinetic gas and
a recently proposed Finsler geometric extension of general relativity.
Additionally, we explicitly show how the coordinate invariance of the action of
the kinetic gas leads to a novel formulation of conservation of the
energy-momentum distribution of the gas on the tangent bundle.
| [
{
"created": "Wed, 30 Oct 2019 18:00:01 GMT",
"version": "v1"
},
{
"created": "Sun, 9 Feb 2020 11:36:45 GMT",
"version": "v2"
}
] | 2020-02-11 | [
[
"Hohmann",
"Manuel",
""
],
[
"Pfeifer",
"Christian",
""
],
[
"Voicu",
"Nicoleta",
""
]
] | We propose a new model for the description of a gravitating multi particle system, viewed as a kinetic gas. The properties of the, colliding or non-colliding, particles are encoded into a so called one-particle distribution function, which is a density on the space of allowed particle positions and velocities, i.e. on the tangent bundle of the spacetime manifold. We argue that an appropriate theory of gravity, describing the gravitational field generated by a kinetic gas, must also be modeled on the tangent bundle. The most natural mathematical framework for this task is Finsler spacetime geometry. Following this line of argumentation, we construct a coupling between the kinetic gas and a recently proposed Finsler geometric extension of general relativity. Additionally, we explicitly show how the coordinate invariance of the action of the kinetic gas leads to a novel formulation of conservation of the energy-momentum distribution of the gas on the tangent bundle. |
0905.4564 | Josep M. Pons | J. M. Pons, D. C. Salisbury, K. A. Sundermeyer | Revisiting observables in generally covariant theories in the light of
gauge fixing methods | 24 pages. New paragraph in conclusions and references added. To
appear in Physical Review D | Phys.Rev.D80:084015,2009 | 10.1103/PhysRevD.80.084015 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive for generally covariant theories the generic dependency of
observables on the original fields, corresponding to coordinate-dependent gauge
fixings. This gauge choice is equivalent to a choice of intrinsically defined
coordinates accomplished with the aid of spacetime scalar fields. With our
approach we make full contact with, and give a new perspective to, the
"evolving constants of motion" program. We are able to directly derive generic
properties of observables, especially their dynamics and their Poisson algebra
in terms of Dirac brackets, extending earlier results in the literature. We
also give a new interpretation of the observables as limits of canonical maps.
| [
{
"created": "Thu, 28 May 2009 06:59:47 GMT",
"version": "v1"
},
{
"created": "Sun, 11 Oct 2009 14:41:36 GMT",
"version": "v2"
}
] | 2009-10-29 | [
[
"Pons",
"J. M.",
""
],
[
"Salisbury",
"D. C.",
""
],
[
"Sundermeyer",
"K. A.",
""
]
] | We derive for generally covariant theories the generic dependency of observables on the original fields, corresponding to coordinate-dependent gauge fixings. This gauge choice is equivalent to a choice of intrinsically defined coordinates accomplished with the aid of spacetime scalar fields. With our approach we make full contact with, and give a new perspective to, the "evolving constants of motion" program. We are able to directly derive generic properties of observables, especially their dynamics and their Poisson algebra in terms of Dirac brackets, extending earlier results in the literature. We also give a new interpretation of the observables as limits of canonical maps. |
gr-qc/9311019 | Jesus Barbero | J. Fernando Barbero | A Real Polynomial Formulation of General Relativity in terms of
Connections | 13 pages, LATEX, Preprint CGPG-93/11-3 | Phys.Rev.D49:6935-6938,1994 | 10.1103/PhysRevD.49.6935 | null | gr-qc | null | I show in this letter that it is possible to construct a Hamiltonian
description for Lorentzian General Relativity in terms of two real $SO(3)$
connections. The constraints are simple polynomials in the basic variables. The
present framework gives us a new formulation of General Relativity that keeps
some of the interesting features of the Ashtekar formulation without the
complications associated with the complex character of the latter.
| [
{
"created": "Thu, 11 Nov 1993 19:34:27 GMT",
"version": "v1"
}
] | 2017-03-24 | [
[
"Barbero",
"J. Fernando",
""
]
] | I show in this letter that it is possible to construct a Hamiltonian description for Lorentzian General Relativity in terms of two real $SO(3)$ connections. The constraints are simple polynomials in the basic variables. The present framework gives us a new formulation of General Relativity that keeps some of the interesting features of the Ashtekar formulation without the complications associated with the complex character of the latter. |
1503.04556 | Alberto Balfagon | Alberto C. Balfagon | Accelerated Expansion of the universe based on Particle
Creation-Destruction Processes and Dark Energy in FLRW universes | 11 pages, 2 figures | Gen. Relativ. Gravit. (2015) 47:111 issue 10 - October 2015 | 10.1007/s10714-015-1954-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Particle creation has been considered as a possible justification for the
accelerated expansion of the universe, obeying the second law of
thermodynamics, together with the possible existence of Dark Energy. This paper
introduces the possibility that the destruction of baryonic and/or dark matter
particles also verifies the second law of thermodynamics thanks to a particle
exchange with dark energy. General equations for the variation of the number of
particles in accelerated universes have been obtained. Finally, a new model of
the universe has been developed which predicts dark energy properties as well
as particle exchange processes between dark energy and baryonic and/or dark
matter.
| [
{
"created": "Mon, 16 Mar 2015 08:07:57 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Oct 2015 06:29:59 GMT",
"version": "v2"
}
] | 2015-10-05 | [
[
"Balfagon",
"Alberto C.",
""
]
] | Particle creation has been considered as a possible justification for the accelerated expansion of the universe, obeying the second law of thermodynamics, together with the possible existence of Dark Energy. This paper introduces the possibility that the destruction of baryonic and/or dark matter particles also verifies the second law of thermodynamics thanks to a particle exchange with dark energy. General equations for the variation of the number of particles in accelerated universes have been obtained. Finally, a new model of the universe has been developed which predicts dark energy properties as well as particle exchange processes between dark energy and baryonic and/or dark matter. |
1911.02828 | Carles Bona | Carles Bona | The horizon problem as a clue: a smooth big bang? | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The necessary and sufficient condition for the absence of particle horizons
in a big bang Friedmann-Robertson-Walker universe is provided. It happens to be
a "smooth big bang" initial condition: the proper time derivative of the
expansion factor $a(t)$ must be finite at the big bang. Equivalently, the
energy density must not diverge faster than $a^{-2}$ at the big bang. This is
just an initial condition: only the scale factor asymptotic behavior at the
very moment of the big bang matters. The causal connection between remote space
regions could then take place immediately after the big bang. Even $10^{-36}$
seconds of proper time, would allow for an infinite number of light crossing
times between any two space regions, no matter how far apart. This justifies
inflationary scenarios starting from a quasi-homogeneous scalar field close to
equilibrium. The high degree of homogeneity of the Cosmological Background
Radiation can be seen then not as a problem, but rather as a clue to the
equation of state in the big bang limit.
| [
{
"created": "Thu, 7 Nov 2019 10:19:05 GMT",
"version": "v1"
}
] | 2019-11-11 | [
[
"Bona",
"Carles",
""
]
] | The necessary and sufficient condition for the absence of particle horizons in a big bang Friedmann-Robertson-Walker universe is provided. It happens to be a "smooth big bang" initial condition: the proper time derivative of the expansion factor $a(t)$ must be finite at the big bang. Equivalently, the energy density must not diverge faster than $a^{-2}$ at the big bang. This is just an initial condition: only the scale factor asymptotic behavior at the very moment of the big bang matters. The causal connection between remote space regions could then take place immediately after the big bang. Even $10^{-36}$ seconds of proper time, would allow for an infinite number of light crossing times between any two space regions, no matter how far apart. This justifies inflationary scenarios starting from a quasi-homogeneous scalar field close to equilibrium. The high degree of homogeneity of the Cosmological Background Radiation can be seen then not as a problem, but rather as a clue to the equation of state in the big bang limit. |
gr-qc/9402045 | Peter Boschung | P. Boschung, O. Brodbeck, F. Moser, N. Straumann and M. Volkov | Instability of Gravitating Sphalerons | replaced mainly due to LaTex problems', 11p, Latex, ZU-TH 7-94 | Phys.Rev. D50 (1994) 3842-3846 | 10.1103/PhysRevD.50.3842 | null | gr-qc hep-th | null | We prove the instability of the gravitating regular sphaleron solutions of
the $SU(2)$ Einstein-Yang-Mills-Higgs system with a Higgs doublet, by studying
the frequency spectrum of a class of radial perturbations. With the help of a
variational principle we show that there exist always unstable modes. Our
method has the advantage that no detailed knowledge of the equilibrium solution
is required. It does, however, not directly apply to black holes.
| [
{
"created": "Mon, 28 Feb 1994 15:34:03 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Mar 1994 10:52:21 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Boschung",
"P.",
""
],
[
"Brodbeck",
"O.",
""
],
[
"Moser",
"F.",
""
],
[
"Straumann",
"N.",
""
],
[
"Volkov",
"M.",
""
]
] | We prove the instability of the gravitating regular sphaleron solutions of the $SU(2)$ Einstein-Yang-Mills-Higgs system with a Higgs doublet, by studying the frequency spectrum of a class of radial perturbations. With the help of a variational principle we show that there exist always unstable modes. Our method has the advantage that no detailed knowledge of the equilibrium solution is required. It does, however, not directly apply to black holes. |
1901.03055 | Amir Hadi Ziaie | A. H. Ziaie, H. Moradpour and S. Ghaffari | Gravitational Collapse in Rastall Gravity | 6 pages and 1 figure | Physics Letters B 793 (2019) 276 | 10.1016/j.physletb.2019.04.055 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study spherically symmetric gravitational collapse of a homogeneous
perfect fluid in Rastall gravity. Considering a linear equation of state (EoS)
for the fluid profiles, we examine the conditions under which the collapse
scenario could end in a spacetime singularity. Depending on the model
parameters, the singularity could be either naked or covered by a horizon. We
find that a non-vanishing Rastall parameter could affect the formation of
apparent horizon so that, naked singularities may form for those values of EoS
parameter for which a homogeneous perfect fluid collapse in general relativity
(GR) terminates at the black hole formation. Hence the visibility of the
resulting singularity depends on the Rastall parameter. The solutions we obtain
respect the weak energy condition (WEC) which is crucial for physical validity
of the model.
| [
{
"created": "Thu, 10 Jan 2019 08:42:07 GMT",
"version": "v1"
},
{
"created": "Mon, 6 May 2019 18:57:14 GMT",
"version": "v2"
}
] | 2019-05-08 | [
[
"Ziaie",
"A. H.",
""
],
[
"Moradpour",
"H.",
""
],
[
"Ghaffari",
"S.",
""
]
] | We study spherically symmetric gravitational collapse of a homogeneous perfect fluid in Rastall gravity. Considering a linear equation of state (EoS) for the fluid profiles, we examine the conditions under which the collapse scenario could end in a spacetime singularity. Depending on the model parameters, the singularity could be either naked or covered by a horizon. We find that a non-vanishing Rastall parameter could affect the formation of apparent horizon so that, naked singularities may form for those values of EoS parameter for which a homogeneous perfect fluid collapse in general relativity (GR) terminates at the black hole formation. Hence the visibility of the resulting singularity depends on the Rastall parameter. The solutions we obtain respect the weak energy condition (WEC) which is crucial for physical validity of the model. |
1905.01231 | Igor Khavkine | Alfonso Garc\'ia-Parrado, Igor Khavkine | Conformal Killing Initial Data | v1: 12 pages; v2: 22 pages, major reorganization, main results in
previous version were incomplete | J Math Phys 60, 122502 (2019) | 10.1063/1.5126683 | null | gr-qc math-ph math.DG math.MP | http://creativecommons.org/licenses/by/4.0/ | We find necessary and sufficient conditions ensuring that the vacuum
development of an initial data set of the Einstein's field equations admits a
conformal Killing vector. We refer to these conditions as conformal Killing
initial data (CKID) and they extend the well-known Killing initial data (KID)
that have been known for a long time. The procedure used to find the CKID is a
classical argument, which is reviewed and presented in a form that may have an
independent interest, based on identifying a suitable propagation identity and
checking the well-posedness of the corresponding initial value problem. As
example applications, we review the derivation of the KID conditions, as well
as give a more thorough treatment of the homothetic Killing initial data (HKID)
conditions than was previously available in the literature.
| [
{
"created": "Fri, 3 May 2019 15:39:37 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Sep 2019 04:29:28 GMT",
"version": "v2"
}
] | 2019-12-24 | [
[
"García-Parrado",
"Alfonso",
""
],
[
"Khavkine",
"Igor",
""
]
] | We find necessary and sufficient conditions ensuring that the vacuum development of an initial data set of the Einstein's field equations admits a conformal Killing vector. We refer to these conditions as conformal Killing initial data (CKID) and they extend the well-known Killing initial data (KID) that have been known for a long time. The procedure used to find the CKID is a classical argument, which is reviewed and presented in a form that may have an independent interest, based on identifying a suitable propagation identity and checking the well-posedness of the corresponding initial value problem. As example applications, we review the derivation of the KID conditions, as well as give a more thorough treatment of the homothetic Killing initial data (HKID) conditions than was previously available in the literature. |
0902.2531 | Florian Beyer | Florian Beyer | Non-genericity of the Nariai solutions: I. Asymptotics and spatially
homogeneous perturbations | 22 pages, 2 figures, uses psfrag and hyperref, largely rewritten
version essentially equal to the published version but more details, no
change of conclusions | Class.Quant.Grav.26:235015 | 10.1088/0264-9381/26/23/235015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is the first of two papers where we study the asymptotics of the
generalized Nariai solutions and its relation to the cosmic no-hair conjecture.
According to the cosmic no-hair conjecture, generic expanding solutions of
Einstein's field equations in vacuum with a positive cosmological constant
isotropize and approach the de-Sitter solution asymptotically. The family of
solutions which we introduce as "generalized Nariai solutions", however, shows
quite unusual asymptotics and hence should be non-generic in some sense. In
this paper, we list basic facts for the Nariai solutions and characterize their
asymptotic behavior geometrically. One particular result is a rigorous proof of
the fact that the Nariai solutions do not possess smooth conformal boundaries.
We proceed by explaining the non-genericity within the class of spatially
homogeneous solutions. It turns out that perturbations of the three isometry
classes of generalized Nariai solutions are related to different mass regimes
of Schwarzschild de-Sitter solutions. A motivation for our work here is to
prepare the second paper devoted to the study of the instability of the Nariai
solutions for Gowdy symmetry. We will be particularly interested in the
construction of new and in principle arbitrarily complicated cosmological black
hole solutions.
| [
{
"created": "Sun, 15 Feb 2009 09:48:08 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Nov 2009 04:36:14 GMT",
"version": "v2"
}
] | 2011-03-28 | [
[
"Beyer",
"Florian",
""
]
] | This is the first of two papers where we study the asymptotics of the generalized Nariai solutions and its relation to the cosmic no-hair conjecture. According to the cosmic no-hair conjecture, generic expanding solutions of Einstein's field equations in vacuum with a positive cosmological constant isotropize and approach the de-Sitter solution asymptotically. The family of solutions which we introduce as "generalized Nariai solutions", however, shows quite unusual asymptotics and hence should be non-generic in some sense. In this paper, we list basic facts for the Nariai solutions and characterize their asymptotic behavior geometrically. One particular result is a rigorous proof of the fact that the Nariai solutions do not possess smooth conformal boundaries. We proceed by explaining the non-genericity within the class of spatially homogeneous solutions. It turns out that perturbations of the three isometry classes of generalized Nariai solutions are related to different mass regimes of Schwarzschild de-Sitter solutions. A motivation for our work here is to prepare the second paper devoted to the study of the instability of the Nariai solutions for Gowdy symmetry. We will be particularly interested in the construction of new and in principle arbitrarily complicated cosmological black hole solutions. |
0905.2719 | Farook Rahaman | Farook Rahaman, Mubasher Jamil, Ashis Ghosh and Kausik Chakraborty | On generating some known black hole solutions | 11 pages, Some sections are extended and several references are
added, Accepted for publication in Mod.Phys.Lett.A | Mod.Phys.Lett.A25:835-842,2010 | 10.1142/S0217732310031440 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have presented an algorithm to generate various black hole
solutions in general relativity and alternative theories of gravity. The
algorithm involves few dimensional parameters that are assigned suitable values
to specify the required black hole.
| [
{
"created": "Sun, 17 May 2009 07:13:21 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Jun 2009 18:28:58 GMT",
"version": "v2"
},
{
"created": "Mon, 22 Jun 2009 15:46:06 GMT",
"version": "v3"
},
{
"created": "Mon, 3 Aug 2009 18:01:48 GMT",
"version": "v4"
}
] | 2010-04-28 | [
[
"Rahaman",
"Farook",
""
],
[
"Jamil",
"Mubasher",
""
],
[
"Ghosh",
"Ashis",
""
],
[
"Chakraborty",
"Kausik",
""
]
] | In this paper, we have presented an algorithm to generate various black hole solutions in general relativity and alternative theories of gravity. The algorithm involves few dimensional parameters that are assigned suitable values to specify the required black hole. |
1006.3274 | Albert Roura | E. T. Akhmedov, Albert Roura, A. Sadofyev | Classical radiation by free-falling charges in de Sitter spacetime | 31 pages, REVTeX4, minor changes, one reference added, version to
appear in Phys. Rev. D | Phys.Rev.D82:044035,2010 | 10.1103/PhysRevD.82.044035 | AEI-2010-114 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the classical radiation emitted by free-falling charges in de Sitter
spacetime coupled to different kinds of fields. Specifically we consider the
cases of the electromagnetic field, linearized gravity and scalar fields with
arbitrary mass and curvature coupling. Given an arbitrary set of such charges,
there is a generic result for sufficiently late times which corresponds to each
charge being surrounded by a field zone with negligible influence from the
other charges. Furthermore, we explicitly find a static solution in the static
patch adapted to a charge (implying no energy loss by the charge) which can be
regularly extended beyond the horizon to the full de Sitter spacetime, and show
that any other solution decays at late times to this one. On the other hand,
for non-conformal scalar fields the inertial observers naturally associated
with spatially flat coordinates will see a non-vanishing flux far from the
horizon, which will fall off more slowly than the inverse square of the
distance for sufficiently light fields (m^2 + \xi R < 5H^2/4) and give rise to
a total integrated flux that grows unboundedly with the radius. This can be
qualitatively interpreted as a consequence of a classical parametric
amplification of the field generated by the charge due to the time-dependent
background spacetime. Most of these results do not hold for massless minimally
coupled scalar fields, whose special behavior is analyzed separately.
| [
{
"created": "Wed, 16 Jun 2010 17:11:39 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Aug 2010 15:49:59 GMT",
"version": "v2"
}
] | 2010-10-11 | [
[
"Akhmedov",
"E. T.",
""
],
[
"Roura",
"Albert",
""
],
[
"Sadofyev",
"A.",
""
]
] | We study the classical radiation emitted by free-falling charges in de Sitter spacetime coupled to different kinds of fields. Specifically we consider the cases of the electromagnetic field, linearized gravity and scalar fields with arbitrary mass and curvature coupling. Given an arbitrary set of such charges, there is a generic result for sufficiently late times which corresponds to each charge being surrounded by a field zone with negligible influence from the other charges. Furthermore, we explicitly find a static solution in the static patch adapted to a charge (implying no energy loss by the charge) which can be regularly extended beyond the horizon to the full de Sitter spacetime, and show that any other solution decays at late times to this one. On the other hand, for non-conformal scalar fields the inertial observers naturally associated with spatially flat coordinates will see a non-vanishing flux far from the horizon, which will fall off more slowly than the inverse square of the distance for sufficiently light fields (m^2 + \xi R < 5H^2/4) and give rise to a total integrated flux that grows unboundedly with the radius. This can be qualitatively interpreted as a consequence of a classical parametric amplification of the field generated by the charge due to the time-dependent background spacetime. Most of these results do not hold for massless minimally coupled scalar fields, whose special behavior is analyzed separately. |
2007.06089 | J. Robel Arenas | Fernando Castro and J. Robel Arenas | Hawking Radiation of Black Shells | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A black shell consists of a massive thin spherical shell contracting toward
its gravitational radius, coinciding with 't Hooft's brick wall, from the point
of view of an external observer far from the shell. This object was conceived
by J.R.Arenas and W.Israel in order to effectively model the gravitational
collapse dynamics and the thermodynamics of a black hole [5,6,21,1]. We show in
this article that a black shell presents the same emission rate of a black hole
when we consider Klein-Gordon equation in the near horizon limit. We will use
Parikh-Wilczek tunneling approach to obtain the black shell emission rate [2].
| [
{
"created": "Sun, 12 Jul 2020 20:27:51 GMT",
"version": "v1"
}
] | 2020-07-14 | [
[
"Castro",
"Fernando",
""
],
[
"Arenas",
"J. Robel",
""
]
] | A black shell consists of a massive thin spherical shell contracting toward its gravitational radius, coinciding with 't Hooft's brick wall, from the point of view of an external observer far from the shell. This object was conceived by J.R.Arenas and W.Israel in order to effectively model the gravitational collapse dynamics and the thermodynamics of a black hole [5,6,21,1]. We show in this article that a black shell presents the same emission rate of a black hole when we consider Klein-Gordon equation in the near horizon limit. We will use Parikh-Wilczek tunneling approach to obtain the black shell emission rate [2]. |
2101.00714 | Benjamin J. Owen | Binod Rajbhandari, Benjamin J. Owen, Santiago Caride, and Ra Inta | First searches for gravitational waves from r-modes of the Crab pulsar | 6 pages, 2 figures | null | 10.1103/PhysRevD.104.122008 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We present the first searches for gravitational waves from r-modes of the
Crab pulsar, coherently and separately integrating data from three stretches of
the first two observing runs of Advanced LIGO using the F-statistic. The second
run was divided in two by a glitch of the pulsar roughly halfway through. The
frequencies and derivatives searched were based on radio measurements of the
pulsar's spin-down parameters as described in Caride et al., Phys. Rev. D 100,
064013 (2019). We did not find any evidence of gravitational waves. Our best
90% confidence upper limits on gravitational wave intrinsic strain were 1.5e-25
for the first run, 1.3e-25 for the first stretch of the second run, and 1.1e-25
for the second stretch of the second run. These are the first upper limits on
gravitational waves from r-modes of a known pulsar to beat its spin-down limit,
and they do so by more than an order of magnitude in amplitude or two orders of
magnitude in luminosity.
| [
{
"created": "Sun, 3 Jan 2021 22:19:02 GMT",
"version": "v1"
}
] | 2022-01-12 | [
[
"Rajbhandari",
"Binod",
""
],
[
"Owen",
"Benjamin J.",
""
],
[
"Caride",
"Santiago",
""
],
[
"Inta",
"Ra",
""
]
] | We present the first searches for gravitational waves from r-modes of the Crab pulsar, coherently and separately integrating data from three stretches of the first two observing runs of Advanced LIGO using the F-statistic. The second run was divided in two by a glitch of the pulsar roughly halfway through. The frequencies and derivatives searched were based on radio measurements of the pulsar's spin-down parameters as described in Caride et al., Phys. Rev. D 100, 064013 (2019). We did not find any evidence of gravitational waves. Our best 90% confidence upper limits on gravitational wave intrinsic strain were 1.5e-25 for the first run, 1.3e-25 for the first stretch of the second run, and 1.1e-25 for the second stretch of the second run. These are the first upper limits on gravitational waves from r-modes of a known pulsar to beat its spin-down limit, and they do so by more than an order of magnitude in amplitude or two orders of magnitude in luminosity. |
1511.08382 | Petros Terzis A. | Adamantia Zampeli, Theodoros Pailas, Petros A. Terzis, T.
Christodoulakis | Conditional symmetries in axisymmetric quantum cosmologies with scalar
fields and the fate of the classical singularities | 29 pages, LaTeX2e source file, no figures; v2 References and a new
appendix added. Typo in title corected. Matches accepted version in JCAP | JCAP 05 (2016) 066 | 10.1088/1475-7516/2016/05/066 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, the classical and quantum solutions of some axisymmetric
cosmologies coupled to a massless scalar field are studied in the context of
minisuperspace approximation. In these models, the singular nature of the
Lagrangians entails a search for possible conditional symmetries. These have
been proven to be the simultaneous conformal symmetries of the supermetric and
the superpotential. The quantization is performed by adopting the Dirac
proposal for constrained systems, i.e. promoting the first-class constraints to
operators annihilating the wave function. To further enrich the approach, we
follow \cite{Christodoulakis:2012eg} and impose the operators related to the
classical conditional symmetries on the wave function. These additional
equations select particular solutions of the Wheeler-DeWitt equation. In order
to gain some physical insight from the quantization of these cosmological
systems, we perform a semiclassical analysis following the Bohmian approach to
quantum theory. The generic result is that, in all but one model, one can find
appropriate ranges of the parameters, so that the emerging semiclassical
geometries are non-singular. An attempt for physical interpretation involves
the study of the effective energy-momentum tensor which corresponds to an
imperfect fluid.
| [
{
"created": "Thu, 26 Nov 2015 13:21:22 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Jun 2016 14:40:37 GMT",
"version": "v2"
}
] | 2016-06-03 | [
[
"Zampeli",
"Adamantia",
""
],
[
"Pailas",
"Theodoros",
""
],
[
"Terzis",
"Petros A.",
""
],
[
"Christodoulakis",
"T.",
""
]
] | In this paper, the classical and quantum solutions of some axisymmetric cosmologies coupled to a massless scalar field are studied in the context of minisuperspace approximation. In these models, the singular nature of the Lagrangians entails a search for possible conditional symmetries. These have been proven to be the simultaneous conformal symmetries of the supermetric and the superpotential. The quantization is performed by adopting the Dirac proposal for constrained systems, i.e. promoting the first-class constraints to operators annihilating the wave function. To further enrich the approach, we follow \cite{Christodoulakis:2012eg} and impose the operators related to the classical conditional symmetries on the wave function. These additional equations select particular solutions of the Wheeler-DeWitt equation. In order to gain some physical insight from the quantization of these cosmological systems, we perform a semiclassical analysis following the Bohmian approach to quantum theory. The generic result is that, in all but one model, one can find appropriate ranges of the parameters, so that the emerging semiclassical geometries are non-singular. An attempt for physical interpretation involves the study of the effective energy-momentum tensor which corresponds to an imperfect fluid. |
1511.08665 | Alessandro Pesci | Alessandro Pesci | Spacetime atoms and extrinsic curvature of equi-geodesic surfaces | 7 pages; some editing, it matches the published version | Eur. Phys. J. Plus 134 (2019) 374 | 10.1140/epjp/i2019-12749-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A recently-introduced function $\rho$ of spacetime event $P$ expressing
spacetime as made of 'spacetime atoms' of quantum origin is considered. Using
its defining relation, we provide an exact expression for $\rho$ involving the
van Vleck biscalar, and show it can be recast in terms of the extrinsic
curvature of suitable equi-geodesic surfaces centered at $P$. Moreover, looking
at the role $\rho$ plays in the statistical description of spacetime, we point
out that this quantity should actually be understood as counting the quantum
states of the collection of spacetime atoms rather than counting directly the
spacetime atoms themselves (or the degrees of freedom associated to them), and
would correspond to the ratio of the number of quantum states 'at $P$' for an
assigned spacetime configuration to the number of quantum states for flat
spacetime.
| [
{
"created": "Fri, 27 Nov 2015 13:32:38 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Mar 2016 15:16:16 GMT",
"version": "v2"
},
{
"created": "Fri, 20 May 2016 12:10:00 GMT",
"version": "v3"
},
{
"created": "Tue, 30 Jan 2018 07:37:12 GMT",
"version": "v4"
},
{
"c... | 2019-08-01 | [
[
"Pesci",
"Alessandro",
""
]
] | A recently-introduced function $\rho$ of spacetime event $P$ expressing spacetime as made of 'spacetime atoms' of quantum origin is considered. Using its defining relation, we provide an exact expression for $\rho$ involving the van Vleck biscalar, and show it can be recast in terms of the extrinsic curvature of suitable equi-geodesic surfaces centered at $P$. Moreover, looking at the role $\rho$ plays in the statistical description of spacetime, we point out that this quantity should actually be understood as counting the quantum states of the collection of spacetime atoms rather than counting directly the spacetime atoms themselves (or the degrees of freedom associated to them), and would correspond to the ratio of the number of quantum states 'at $P$' for an assigned spacetime configuration to the number of quantum states for flat spacetime. |
1701.00431 | Jonas Pedro Pereira | Herman J. Mosquera Cuesta, Gaetano Lambiase, Jonas P. Pereira | Probing nonlinear electrodynamics in slowly rotating spacetimes through
neutrino astrophysics | 17 pages, 9 figures, accepted for publication in Phys. Rev. D | Phys. Rev. D 95, 025011 (2017) | 10.1103/PhysRevD.95.025011 | null | gr-qc astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Huge electromagnetic fields are known to be present during the late stages of
the dynamics of supernovae. Thus, when dealing with electrodynamics in this
context, the possibility may arise to probe nonlinear theories (generalizations
of the Maxwellian electromagnetism). We firstly solve Einstein field equations
minimally coupled to an arbitrary (current-free) nonlinear Lagrangian of
electrodynamics (NLED) in the slow rotation regime $a\ll M$ (black hole's
mass), up to first order in $a/M$. We then make use of the robust and
self-contained Born-Infeld Lagrangian in order to compare and contrast the
physical properties of such NLED spacetime with its Maxwellian counterpart (a
slowly rotating Kerr-Newman spacetime), especially focusing on the astrophysics
of both neutrino flavor oscillations ($\nu_e \rightarrow \nu_\mu, \nu_\tau$)
and spin-flip ($\nu_l \rightarrow \nu_r$, "$l$" stands for "left" and "$r$"
stands for "right", change of neutrino handedness) mass level-crossings, the
equivalent to gyroscopic precessions. Such analysis proves that in the
spacetime of a slowly rotating nonlinear charged black hole (RNCBH),
intrinsically associated with the assumption the electromagnetism is nonlinear,
the neutrino dynamics in core-collapse supernovae could be significantly
changed. In such astrophysical environment a positive enhancement (reduction of
the electron fraction $Y_e<0.5$) of the r-process may take place. Consequently,
it might result in hyperluminous supernova explosions due to enlargement, in
atomic number and amount, of the decaying nuclides. Finally, we envisage some
physical scenarios that may lead to short-lived charged black holes with high
charge-to-mass ratios (associated with unstable highly magnetized neutron
stars) and ways to possibly disentangle theories of the electromagnetism from
other black holes observables (by means of light polarization measurements).
| [
{
"created": "Mon, 2 Jan 2017 15:58:38 GMT",
"version": "v1"
}
] | 2017-01-25 | [
[
"Cuesta",
"Herman J. Mosquera",
""
],
[
"Lambiase",
"Gaetano",
""
],
[
"Pereira",
"Jonas P.",
""
]
] | Huge electromagnetic fields are known to be present during the late stages of the dynamics of supernovae. Thus, when dealing with electrodynamics in this context, the possibility may arise to probe nonlinear theories (generalizations of the Maxwellian electromagnetism). We firstly solve Einstein field equations minimally coupled to an arbitrary (current-free) nonlinear Lagrangian of electrodynamics (NLED) in the slow rotation regime $a\ll M$ (black hole's mass), up to first order in $a/M$. We then make use of the robust and self-contained Born-Infeld Lagrangian in order to compare and contrast the physical properties of such NLED spacetime with its Maxwellian counterpart (a slowly rotating Kerr-Newman spacetime), especially focusing on the astrophysics of both neutrino flavor oscillations ($\nu_e \rightarrow \nu_\mu, \nu_\tau$) and spin-flip ($\nu_l \rightarrow \nu_r$, "$l$" stands for "left" and "$r$" stands for "right", change of neutrino handedness) mass level-crossings, the equivalent to gyroscopic precessions. Such analysis proves that in the spacetime of a slowly rotating nonlinear charged black hole (RNCBH), intrinsically associated with the assumption the electromagnetism is nonlinear, the neutrino dynamics in core-collapse supernovae could be significantly changed. In such astrophysical environment a positive enhancement (reduction of the electron fraction $Y_e<0.5$) of the r-process may take place. Consequently, it might result in hyperluminous supernova explosions due to enlargement, in atomic number and amount, of the decaying nuclides. Finally, we envisage some physical scenarios that may lead to short-lived charged black holes with high charge-to-mass ratios (associated with unstable highly magnetized neutron stars) and ways to possibly disentangle theories of the electromagnetism from other black holes observables (by means of light polarization measurements). |
1506.08297 | Morgan Le Delliou | J. Lorca Espiro, Morgan Le Delliou (IFT-UNESP) | A topological origin for Dark Energy | The problem presented is ill-defined and therefore the solutions are
not consistent as claimed. First, the variational problem is not redefined
after the characteristic classes are added into the action, which is
necessary. Secondly, the paper assumes certain restrictions over the
contortion that forces the topology in a very cumbersome way which is, as we
see it, still very poorly justified | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmology struggles with the theoretical problems generated by the observed
value and recent emergence of a cosmological constant, in the standard model of
cosmology, i.e. the concordance model. We propose to provide a more natural
explanation for its value than the conventional quantum vacuum energy in the
guise of topological invariants. Introducing topological classes densities as
Lagrange multipliers, an effective cosmological constant is generated. General
Relativity is reestablished by cancelling the torsion thus generated, which
provides constraints on the invariants and yield the form of the effective
cosmological constant. As it is divided by the total volume of spacetime, its
small value compared to the Planck scale is therefore natural. It also provides
a direct measurement of the global Euler number.
| [
{
"created": "Sat, 27 Jun 2015 14:37:23 GMT",
"version": "v1"
},
{
"created": "Tue, 7 May 2019 03:38:50 GMT",
"version": "v2"
}
] | 2019-05-08 | [
[
"Espiro",
"J. Lorca",
"",
"IFT-UNESP"
],
[
"Delliou",
"Morgan Le",
"",
"IFT-UNESP"
]
] | Cosmology struggles with the theoretical problems generated by the observed value and recent emergence of a cosmological constant, in the standard model of cosmology, i.e. the concordance model. We propose to provide a more natural explanation for its value than the conventional quantum vacuum energy in the guise of topological invariants. Introducing topological classes densities as Lagrange multipliers, an effective cosmological constant is generated. General Relativity is reestablished by cancelling the torsion thus generated, which provides constraints on the invariants and yield the form of the effective cosmological constant. As it is divided by the total volume of spacetime, its small value compared to the Planck scale is therefore natural. It also provides a direct measurement of the global Euler number. |
1207.4812 | Gonzalo Olmo | Gonzalo J. Olmo | Birkhoff's theorem and perturbations in $f(R)$ theories | 2 pages, 1 figure | Annalen Phys. 524 (2012) 87-88 | 10.1002/andp.201200721 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Invited contribution to Annalen der Physik (Expert Opinion).
| [
{
"created": "Thu, 19 Jul 2012 21:18:39 GMT",
"version": "v1"
}
] | 2012-07-23 | [
[
"Olmo",
"Gonzalo J.",
""
]
] | Invited contribution to Annalen der Physik (Expert Opinion). |
2212.02026 | Sunil Choudhary | Sunil Choudhary, Sukanta Bose, Prasanna Joshi, Sanjeev Dhurandhar | Improved binary black hole searches through better discrimination
against noise transients | 12pages, 6 figures | null | null | LIGO-DCC-P2200288 | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The short-duration noise transients in LIGO and Virgo detectors significantly
affect the search sensitivity of compact binary coalescence (CBC) signals,
especially in the high mass region. In the previous work by the authors
\cite{Joshi_2021}, a $\chi^2$ statistic was proposed to distinguish them from
CBCs. This work is an extension where we demonstrate the improved
noise-discrimination of the optimal $\chi^2$ statistic in real LIGO data. The
tuning of the optimal $\chi^2$ includes accounting for the phase of the CBC
signal and a well informed choice of sine-Gaussian basis vectors to discern how
CBC signals and some of the most worrisome noise-transients project differently
on them~\cite{sunil_2022}. We take real blip glitches (a type of short-duration
noise disturbance) from the second observational (O2) run of LIGO-Hanford and
LIGO-Livingston detectors. The binary black hole signals were simulated using
\textsc{IMRPhenomPv2} waveform and injected into real LIGO data from the same
run. We show that in comparison to the traditional $\chi^2$, the optimal
$\chi^2$ improves the signal detection rate by around 4\% in a lower-mass bin
($m_1,m_2 \in [20,40]M_{\odot}$) and by more than 5\% in a higher-mass bin
($m_1,m_2 \in [60,80]M_{\odot}$), at a false alarm probability of $10^{-3}$. We
find that the optimal $\chi^2$ also achieves significant improvement over the
sine-Gaussian $\chi^2$.
| [
{
"created": "Mon, 5 Dec 2022 04:46:19 GMT",
"version": "v1"
}
] | 2022-12-06 | [
[
"Choudhary",
"Sunil",
""
],
[
"Bose",
"Sukanta",
""
],
[
"Joshi",
"Prasanna",
""
],
[
"Dhurandhar",
"Sanjeev",
""
]
] | The short-duration noise transients in LIGO and Virgo detectors significantly affect the search sensitivity of compact binary coalescence (CBC) signals, especially in the high mass region. In the previous work by the authors \cite{Joshi_2021}, a $\chi^2$ statistic was proposed to distinguish them from CBCs. This work is an extension where we demonstrate the improved noise-discrimination of the optimal $\chi^2$ statistic in real LIGO data. The tuning of the optimal $\chi^2$ includes accounting for the phase of the CBC signal and a well informed choice of sine-Gaussian basis vectors to discern how CBC signals and some of the most worrisome noise-transients project differently on them~\cite{sunil_2022}. We take real blip glitches (a type of short-duration noise disturbance) from the second observational (O2) run of LIGO-Hanford and LIGO-Livingston detectors. The binary black hole signals were simulated using \textsc{IMRPhenomPv2} waveform and injected into real LIGO data from the same run. We show that in comparison to the traditional $\chi^2$, the optimal $\chi^2$ improves the signal detection rate by around 4\% in a lower-mass bin ($m_1,m_2 \in [20,40]M_{\odot}$) and by more than 5\% in a higher-mass bin ($m_1,m_2 \in [60,80]M_{\odot}$), at a false alarm probability of $10^{-3}$. We find that the optimal $\chi^2$ also achieves significant improvement over the sine-Gaussian $\chi^2$. |
gr-qc/0102038 | Thomas Thiemann | H. Sahlmann, T. Thiemann, O. Winkler | Coherent States for Canonical Quantum General Relativity and the
Infinite Tensor Product Extension | 37 p., latex2e, no figures | Nucl.Phys. B606 (2001) 401-440 | 10.1016/S0550-3213(01)00226-7 | AEI-2001-011 | gr-qc hep-lat hep-th quant-ph | null | We summarize a recently proposed concrete programme for investigating the
(semi)classical limit of canonical, Lorentzian, continuum quantum general
relativity in four spacetime dimensions. The analysis is based on a novel set
of coherent states labelled by graphs. These fit neatly together with an
Infinite Tensor Product (ITP) extension of the currently used Hilbert space.
The ITP construction enables us to give rigorous meaning to the infinite volume
(thermodynamic) limit of the theory which has been out of reach so far.
| [
{
"created": "Fri, 9 Feb 2001 14:03:15 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Sahlmann",
"H.",
""
],
[
"Thiemann",
"T.",
""
],
[
"Winkler",
"O.",
""
]
] | We summarize a recently proposed concrete programme for investigating the (semi)classical limit of canonical, Lorentzian, continuum quantum general relativity in four spacetime dimensions. The analysis is based on a novel set of coherent states labelled by graphs. These fit neatly together with an Infinite Tensor Product (ITP) extension of the currently used Hilbert space. The ITP construction enables us to give rigorous meaning to the infinite volume (thermodynamic) limit of the theory which has been out of reach so far. |
1709.09792 | J\"org Hennig | J\"org Frauendiener and J\"org Hennig | Fully pseudospectral solution of the conformally invariant wave equation
near the cylinder at spacelike infinity. III: Nonspherical Schwarzschild
waves and singularities at null infinity | 20 pages, 5 figures | Class. Quantum Grav. 35, 065015 (2018) | 10.1088/1361-6382/aaac8d | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend earlier numerical and analytical considerations of the conformally
invariant wave equation on a Schwarzschild background from the case of
spherically symmetric solutions, discussed in Class. Quantum Grav. 34, 045005
(2017), to the case of general, nonsymmetric solutions. A key element of our
approach is the modern standard representation of spacelike infinity as a
cylinder. With a decomposition into spherical harmonics, we reduce the
four-dimensional wave equation to a family of two-dimensional equations. These
equations can be used to study the behaviour at the cylinder, where the
solutions turn out to have logarithmic singularities at infinitely many orders.
We derive regularity conditions that may be imposed on the initial data, in
order to avoid the first singular terms. We then demonstrate that the fully
pseudospectral time evolution scheme can be applied to this problem leading to
a highly accurate numerical reconstruction of the nonsymmetric solutions. We
are particularly interested in the behaviour of the solutions at future null
infinity, and we numerically show that the singularities spread from the
cylinder to null infinity. The observed numerical behaviour is consistent with
similar logarithmic singularities found analytically on the cylinder. Finally,
we demonstrate that even solutions with singularities at low orders can be
obtained with high accuracy by virtue of a coordinate transformation that
converts functions with logarithmic singularities into smooth solutions.
| [
{
"created": "Thu, 28 Sep 2017 03:33:43 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Feb 2018 20:34:01 GMT",
"version": "v2"
}
] | 2018-02-23 | [
[
"Frauendiener",
"Jörg",
""
],
[
"Hennig",
"Jörg",
""
]
] | We extend earlier numerical and analytical considerations of the conformally invariant wave equation on a Schwarzschild background from the case of spherically symmetric solutions, discussed in Class. Quantum Grav. 34, 045005 (2017), to the case of general, nonsymmetric solutions. A key element of our approach is the modern standard representation of spacelike infinity as a cylinder. With a decomposition into spherical harmonics, we reduce the four-dimensional wave equation to a family of two-dimensional equations. These equations can be used to study the behaviour at the cylinder, where the solutions turn out to have logarithmic singularities at infinitely many orders. We derive regularity conditions that may be imposed on the initial data, in order to avoid the first singular terms. We then demonstrate that the fully pseudospectral time evolution scheme can be applied to this problem leading to a highly accurate numerical reconstruction of the nonsymmetric solutions. We are particularly interested in the behaviour of the solutions at future null infinity, and we numerically show that the singularities spread from the cylinder to null infinity. The observed numerical behaviour is consistent with similar logarithmic singularities found analytically on the cylinder. Finally, we demonstrate that even solutions with singularities at low orders can be obtained with high accuracy by virtue of a coordinate transformation that converts functions with logarithmic singularities into smooth solutions. |
1804.00070 | Craig J. Hogan | Craig Hogan | Value of the Cosmological Constant in Emergent Quantum Gravity | Essay written for the Gravity Research Foundation 2018 Awards for
Essays on Gravitation | null | null | FERMILAB-PUB-18-088-A | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is suggested that the exact value of the cosmological constant could be
derived from first principles, based on entanglement of the Standard Model
field vacuum with emergent holographic quantum geometry. For the observed value
of the cosmological constant, geometrical information is shown to agree closely
with the spatial information density of the QCD vacuum, estimated in a
free-field approximation. The comparison is motivated by a model of exotic
rotational fluctuations in the inertial frame that can be precisely tested in
laboratory experiments. Cosmic acceleration in this model is always positive,
but fluctuates with characteristic coherence length $\approx 100$km and
bandwidth $\approx 3000$ Hz.
| [
{
"created": "Fri, 30 Mar 2018 22:17:04 GMT",
"version": "v1"
}
] | 2018-04-03 | [
[
"Hogan",
"Craig",
""
]
] | It is suggested that the exact value of the cosmological constant could be derived from first principles, based on entanglement of the Standard Model field vacuum with emergent holographic quantum geometry. For the observed value of the cosmological constant, geometrical information is shown to agree closely with the spatial information density of the QCD vacuum, estimated in a free-field approximation. The comparison is motivated by a model of exotic rotational fluctuations in the inertial frame that can be precisely tested in laboratory experiments. Cosmic acceleration in this model is always positive, but fluctuates with characteristic coherence length $\approx 100$km and bandwidth $\approx 3000$ Hz. |
gr-qc/0601072 | Alicia M. Sintes | Manuel Luna and Alicia M. Sintes | Parameter estimation of compact binaries using the inspiral and ringdown
waveforms | matching cqg version | Class.Quant.Grav. 23 (2006) 3763-3782 | 10.1088/0264-9381/23/11/006 | null | gr-qc | null | We analyze the problem of parameter estimation for compact binary systems
that could be detected by ground-based gravitational wave detectors.
So far this problem has only been dealt with for the inspiral and the
ringdown phases separately. In this paper, we combine the information from both
signals, and we study the improvement in parameter estimation, at a fixed
signal-to-noise ratio, by including the ringdown signal without making any
assumption on the merger phase. The study is performed for both initial and
advanced LIGO and VIRGO detectors.
| [
{
"created": "Wed, 18 Jan 2006 11:26:39 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Jun 2006 16:38:23 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Luna",
"Manuel",
""
],
[
"Sintes",
"Alicia M.",
""
]
] | We analyze the problem of parameter estimation for compact binary systems that could be detected by ground-based gravitational wave detectors. So far this problem has only been dealt with for the inspiral and the ringdown phases separately. In this paper, we combine the information from both signals, and we study the improvement in parameter estimation, at a fixed signal-to-noise ratio, by including the ringdown signal without making any assumption on the merger phase. The study is performed for both initial and advanced LIGO and VIRGO detectors. |
1412.2285 | Shahn Majid | Shahn Majid and Wen-Qing Tao | Cosmological constant from quantum spacetime | 13 pages latex no figures. Compared to version 1, we put in the
correct name `Bertotti-Robinson' and its context | null | null | null | gr-qc hep-th math.QA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that a hypothesis that spacetime is quantum with coordinate algebra
$[x^i,t]=\lambda_P x^i$, and spherical symmetry under rotations of the $x^i$,
essentially requires in the classical limit that the spacetime metric is the
Bertotti-Robinson metric, i.e. a solution of Einstein's equations with
cosmological constant and a non-null electromagnetic field. Our arguments do
not give the value of the cosmological constant or the Maxwell field strength
but they cannot both be zero. We also describe the quantum geometry and the
full moduli space of metrics that can emerge as classical limits from this
algebra.
| [
{
"created": "Sat, 6 Dec 2014 21:34:31 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Dec 2014 13:32:43 GMT",
"version": "v2"
}
] | 2014-12-16 | [
[
"Majid",
"Shahn",
""
],
[
"Tao",
"Wen-Qing",
""
]
] | We show that a hypothesis that spacetime is quantum with coordinate algebra $[x^i,t]=\lambda_P x^i$, and spherical symmetry under rotations of the $x^i$, essentially requires in the classical limit that the spacetime metric is the Bertotti-Robinson metric, i.e. a solution of Einstein's equations with cosmological constant and a non-null electromagnetic field. Our arguments do not give the value of the cosmological constant or the Maxwell field strength but they cannot both be zero. We also describe the quantum geometry and the full moduli space of metrics that can emerge as classical limits from this algebra. |
gr-qc/0505091 | Fabrizio Canfora | F. Canfora, G. Vilasi | The Holographic Principle and the Early Universe | Revised version to be pubblished on Physics Letters B: a reference,
which provides the results of the paper with further supports, has been
added; typos have been corrected; 11 pages no figures | Phys.Lett. B625 (2005) 171-176 | 10.1016/j.physletb.2005.08.079 | null | gr-qc astro-ph hep-ph hep-th | null | A scenario is proposed in which the matter-antimatter asymmetry behaves like
a seed for the inflationary phase of the universe. The mechanism which makes
this scenario plausible is the holographic principle: this scheme is supported
by a good prediction of the number of e-folds. It seems that such a mechanism
can only work in the presence of a Hagedorn-like phase transition. The issue of
the "graceful exit" can also be naturally accounted for.
| [
{
"created": "Wed, 18 May 2005 07:49:46 GMT",
"version": "v1"
},
{
"created": "Sat, 27 Aug 2005 14:49:33 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Canfora",
"F.",
""
],
[
"Vilasi",
"G.",
""
]
] | A scenario is proposed in which the matter-antimatter asymmetry behaves like a seed for the inflationary phase of the universe. The mechanism which makes this scenario plausible is the holographic principle: this scheme is supported by a good prediction of the number of e-folds. It seems that such a mechanism can only work in the presence of a Hagedorn-like phase transition. The issue of the "graceful exit" can also be naturally accounted for. |
1512.02422 | Amitabh Virmani | Soumyabrata Chatterjee, Suman Ganguli, and Amitabh Virmani | Charged Vaidya Solution Satisfies Weak Energy Condition | 21 pages; 1 LaTeX figure; v2 refs added, journal version | General Relativity and Gravitation, 48(7), 1-22, 2016 | 10.1007/s10714-016-2089-3 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The external matter stress-tensor supporting charged Vaidya solution appears
to violate weak energy condition in certain region of the spacetime. Motivated
by this, a new interpretation of charged Vaidya solution was proposed by Ori
[1] in which the energy condition continues to be satisfied. In this
construction, one glues an outgoing Vaidya solution to the original ingoing
Vaidya solution provided the surface where the external stress-tensor vanishes
is spacelike. We revisit this study and extend it to higher-dimensions, to AdS
settings, and to higher-derivative f(R) theories. In asymptotically flat space
context, we explore in detail the case when the mass function m(v) is
proportional to the charge function q(v). When the proportionality constant \nu
= q(v)/m(v) lies in between zero and one, we show that the surface where the
external stress-tensor vanishes is spacelike and lies in between the inner and
outer apparent horizons.
| [
{
"created": "Tue, 8 Dec 2015 12:21:15 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Jun 2016 10:58:10 GMT",
"version": "v2"
}
] | 2016-06-21 | [
[
"Chatterjee",
"Soumyabrata",
""
],
[
"Ganguli",
"Suman",
""
],
[
"Virmani",
"Amitabh",
""
]
] | The external matter stress-tensor supporting charged Vaidya solution appears to violate weak energy condition in certain region of the spacetime. Motivated by this, a new interpretation of charged Vaidya solution was proposed by Ori [1] in which the energy condition continues to be satisfied. In this construction, one glues an outgoing Vaidya solution to the original ingoing Vaidya solution provided the surface where the external stress-tensor vanishes is spacelike. We revisit this study and extend it to higher-dimensions, to AdS settings, and to higher-derivative f(R) theories. In asymptotically flat space context, we explore in detail the case when the mass function m(v) is proportional to the charge function q(v). When the proportionality constant \nu = q(v)/m(v) lies in between zero and one, we show that the surface where the external stress-tensor vanishes is spacelike and lies in between the inner and outer apparent horizons. |
1707.04222 | James Weatherall | Robert Geroch and James Owen Weatherall | The Motion of Small Bodies in Space-time | 30 pages, forthcoming in Communications in Mathematical Physics | null | 10.1007/s00220-018-3268-8 | null | gr-qc math-ph math.AP math.DG math.MP physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the motion of small bodies in general relativity. The key result
captures a sense in which such bodies follow timelike geodesics (or, in the
case of charged bodies, Lorentz-force curves). This result clarifies the
relationship between approaches that model such bodies as distributions
supported on a curve, and those that employ smooth fields supported in small
neighborhoods of a curve. This result also applies to "bodies" constructed from
wave packets of Maxwell or Klein-Gordon fields. There follows a simple and
precise formulation of the optical limit for Maxwell fields.
| [
{
"created": "Thu, 13 Jul 2017 16:53:42 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Sep 2018 13:19:27 GMT",
"version": "v2"
}
] | 2018-11-14 | [
[
"Geroch",
"Robert",
""
],
[
"Weatherall",
"James Owen",
""
]
] | We consider the motion of small bodies in general relativity. The key result captures a sense in which such bodies follow timelike geodesics (or, in the case of charged bodies, Lorentz-force curves). This result clarifies the relationship between approaches that model such bodies as distributions supported on a curve, and those that employ smooth fields supported in small neighborhoods of a curve. This result also applies to "bodies" constructed from wave packets of Maxwell or Klein-Gordon fields. There follows a simple and precise formulation of the optical limit for Maxwell fields. |
1601.03143 | Saheb Soroushfar | Saheb Soroushfar, Reza Saffari, Ehsan Sahami | Geodesic equations in the static and rotating dilaton black holes:
Analytical solutions and applications | 29 figures, 4 tables, 35 pages | Phys. Rev. D 94, 024010 (2016) | 10.1103/PhysRevD.94.024010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we consider the timelike and null geodesics around the static
[GMGHS (Gibbons, Maeda, Garfinkle, Horowitz and Strominger), magnetically
charged GMGHS, electrically charged GMGHS] and the rotating (Kerr-Sen
dilaton-axion) dilaton black holes. The geodesic equations are solved in terms
of Weierstrass elliptic functions. To classify the trajectories around the
black holes, we use the analytical solution and effective potential techniques
and then characterize the different types of the resulting orbits in terms of
the conserved energy and angular momentum. Also, using the obtained results we
study astrophysical applications.
| [
{
"created": "Wed, 13 Jan 2016 06:54:56 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Jul 2016 08:19:05 GMT",
"version": "v2"
}
] | 2016-07-21 | [
[
"Soroushfar",
"Saheb",
""
],
[
"Saffari",
"Reza",
""
],
[
"Sahami",
"Ehsan",
""
]
] | In this paper, we consider the timelike and null geodesics around the static [GMGHS (Gibbons, Maeda, Garfinkle, Horowitz and Strominger), magnetically charged GMGHS, electrically charged GMGHS] and the rotating (Kerr-Sen dilaton-axion) dilaton black holes. The geodesic equations are solved in terms of Weierstrass elliptic functions. To classify the trajectories around the black holes, we use the analytical solution and effective potential techniques and then characterize the different types of the resulting orbits in terms of the conserved energy and angular momentum. Also, using the obtained results we study astrophysical applications. |
1903.12479 | Seyed Hossein Hendi Dr. | S. H. Hendi, R. Ramezani-Arani and E. Rahimi | Thermal stability of a special class of black hole solutions in F(R)
gravity | 14 pages with 7 captioned figures. Some additional notes are added.
Accepted in EPJC | EPJC 79 (2019) 472 | 10.1140/epjc/s10052-019-6972-4 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we work on the topological Lifshitz-like black hole solutions
of a special class of vacuum $F(R)-$gravity that are static and spherically
symmetric. We investigate geometric and thermodynamic properties of the
solutions with due respect to the validity of the first law of thermodynamics.
We examine the van der Waals like behavior for asymptotically AdS solutions
with spherical horizon by studying the $P-v$, $G-T$ and $C_{Q,P}-r_{+}$
diagrams and find a consistent result. We also investigate the same behavior
for hyperbolic horizon and interestingly find that the system under study can
experience a phase transition with negative temperature.
| [
{
"created": "Wed, 27 Mar 2019 11:34:54 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Oct 2019 05:40:13 GMT",
"version": "v2"
}
] | 2019-10-30 | [
[
"Hendi",
"S. H.",
""
],
[
"Ramezani-Arani",
"R.",
""
],
[
"Rahimi",
"E.",
""
]
] | In this paper, we work on the topological Lifshitz-like black hole solutions of a special class of vacuum $F(R)-$gravity that are static and spherically symmetric. We investigate geometric and thermodynamic properties of the solutions with due respect to the validity of the first law of thermodynamics. We examine the van der Waals like behavior for asymptotically AdS solutions with spherical horizon by studying the $P-v$, $G-T$ and $C_{Q,P}-r_{+}$ diagrams and find a consistent result. We also investigate the same behavior for hyperbolic horizon and interestingly find that the system under study can experience a phase transition with negative temperature. |
1512.04304 | Przemyslaw Malkiewicz | Przemyslaw Malkiewicz | Affine Coherent States in Quantum Cosmology | 6 pages, Proceedings of the 14th Marcel Grossmann Meeting (Rome, July
12-18, 2015) | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A brief summary of the application of coherent states in the examination of
quantum dynamics of cosmological models is given. We discuss quantization maps,
phase space probability distributions and semiclassical phase spaces. The
implementation of coherent states based on the affine group resolves the
hardest singularities, renders self-adjoint Hamiltonians without boundary
conditions and provides a completely consistent semi-classical description of
the involved quantum dynamics. We consider three examples: the closed Friedmann
model, the anisotropic Bianchi Type I model and the deep quantum domain of the
Bianchi Type IX model.
| [
{
"created": "Mon, 14 Dec 2015 13:35:59 GMT",
"version": "v1"
}
] | 2015-12-15 | [
[
"Malkiewicz",
"Przemyslaw",
""
]
] | A brief summary of the application of coherent states in the examination of quantum dynamics of cosmological models is given. We discuss quantization maps, phase space probability distributions and semiclassical phase spaces. The implementation of coherent states based on the affine group resolves the hardest singularities, renders self-adjoint Hamiltonians without boundary conditions and provides a completely consistent semi-classical description of the involved quantum dynamics. We consider three examples: the closed Friedmann model, the anisotropic Bianchi Type I model and the deep quantum domain of the Bianchi Type IX model. |
2304.13577 | Gustaf Rydbeck | Gustaf Rydbeck | Bounce inflation with a conserved frame of rest | 5 pages, 4 figures | null | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | Some form of approximately exponential inflation is generally assumed to be
the origin of our present universe. The inflation is thought to be driven by a
scalar field potential where the field first slowly slides along the potential
and then comes to a steep slope where the field rapidly falls and then
oscillates around zero transforming into particles. The slowly sliding scalar
field inflation leads to an exponentially expanding de Sitter space. A scalar
field as well as the deSitter space are both Lorentz invariant. Thus no global
frame of rest can be established in this scenario, while particle creation
requires a preferred frame of rest. Observations of the cosmic microwave
background show, when the redshift is corrected for our local velocity, a very
even temperature and redshift distribution requiring a global preferred frame
of rest. We suggest here that a density dependent equilibrium relation between
matter/radiation and a scalar energy density could maintain a preferred frame
of rest throughout the bounce and inflation and thereby solve the problem.
| [
{
"created": "Wed, 26 Apr 2023 14:12:49 GMT",
"version": "v1"
}
] | 2023-04-27 | [
[
"Rydbeck",
"Gustaf",
""
]
] | Some form of approximately exponential inflation is generally assumed to be the origin of our present universe. The inflation is thought to be driven by a scalar field potential where the field first slowly slides along the potential and then comes to a steep slope where the field rapidly falls and then oscillates around zero transforming into particles. The slowly sliding scalar field inflation leads to an exponentially expanding de Sitter space. A scalar field as well as the deSitter space are both Lorentz invariant. Thus no global frame of rest can be established in this scenario, while particle creation requires a preferred frame of rest. Observations of the cosmic microwave background show, when the redshift is corrected for our local velocity, a very even temperature and redshift distribution requiring a global preferred frame of rest. We suggest here that a density dependent equilibrium relation between matter/radiation and a scalar energy density could maintain a preferred frame of rest throughout the bounce and inflation and thereby solve the problem. |
1509.04066 | Christopher Moore | Christopher J. Moore, Christopher P. L. Berry, Alvin J. K. Chua and
Jonathan R. Gair | Improving gravitational-wave parameter estimation using Gaussian process
regression | 25 pages, 11 figures, Published March 2016 | Phys. Rev. D 93, 064001 (2016) | 10.1103/PhysRevD.93.064001 | LIGO-P1500162 | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Folding uncertainty in theoretical models into Bayesian parameter estimation
is necessary in order to make reliable inferences. A general means of achieving
this is by marginalizing over model uncertainty using a prior distribution
constructed using Gaussian process regression (GPR). As an example, we apply
this technique to the measurement of chirp mass using (simulated)
gravitational-wave signals from binary black holes that could be observed using
advanced-era gravitational-wave detectors. Unless properly accounted for,
uncertainty in the gravitational-wave templates could be the dominant source of
error in studies of these systems. We explain our approach in detail and
provide proofs of various features of the method, including the limiting
behavior for high signal-to-noise, where systematic model uncertainties
dominate over noise errors. We find that the marginalized likelihood
constructed via GPR offers a significant improvement in parameter estimation
over the standard, uncorrected likelihood both in our simple one-dimensional
study, and theoretically in general. We also examine the dependence of the
method on the size of training set used in the GPR; on the form of covariance
function adopted for the GPR, and on changes to the detector noise power
spectral density.
| [
{
"created": "Mon, 14 Sep 2015 12:49:45 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Mar 2016 13:17:48 GMT",
"version": "v2"
}
] | 2016-03-04 | [
[
"Moore",
"Christopher J.",
""
],
[
"Berry",
"Christopher P. L.",
""
],
[
"Chua",
"Alvin J. K.",
""
],
[
"Gair",
"Jonathan R.",
""
]
] | Folding uncertainty in theoretical models into Bayesian parameter estimation is necessary in order to make reliable inferences. A general means of achieving this is by marginalizing over model uncertainty using a prior distribution constructed using Gaussian process regression (GPR). As an example, we apply this technique to the measurement of chirp mass using (simulated) gravitational-wave signals from binary black holes that could be observed using advanced-era gravitational-wave detectors. Unless properly accounted for, uncertainty in the gravitational-wave templates could be the dominant source of error in studies of these systems. We explain our approach in detail and provide proofs of various features of the method, including the limiting behavior for high signal-to-noise, where systematic model uncertainties dominate over noise errors. We find that the marginalized likelihood constructed via GPR offers a significant improvement in parameter estimation over the standard, uncorrected likelihood both in our simple one-dimensional study, and theoretically in general. We also examine the dependence of the method on the size of training set used in the GPR; on the form of covariance function adopted for the GPR, and on changes to the detector noise power spectral density. |
gr-qc/0307020 | Nils Andersson | N Andersson and C.J. Howls | The asymptotic quasinormal mode spectrum of non-rotating black holes | 18 pages, RevTeX, 3 eps figures | Class.Quant.Grav.21:1623-1642,2004 | 10.1088/0264-9381/21/6/021 | null | gr-qc hep-th | null | A conjectured connection to quantum gravity has led to a renewed interest in
highly damped black hole quasinormal modes (QNMs). In this paper we present
simple derivations (based on the WKB approximation) of conditions that
determine the asymptotic QNMs for both Schwarzschild and Reissner-Nordstrom
black holes. This confirms recent results obtained by
Motl and Neitzke, but our analysis fills several gaps left by their
discussion. We study the Reissner-Nordstrom results in some detail, and show
that, in contrast to the asymptotic QNMs of a Schwarzschild black hole, the
Reissner-Nordstrom QNMs are typically not periodic in the imaginary part of the
frequency. This leads to the charged black hole having peculiar properties
which complicate an interpretation of the results.
| [
{
"created": "Fri, 4 Jul 2003 15:34:59 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Andersson",
"N",
""
],
[
"Howls",
"C. J.",
""
]
] | A conjectured connection to quantum gravity has led to a renewed interest in highly damped black hole quasinormal modes (QNMs). In this paper we present simple derivations (based on the WKB approximation) of conditions that determine the asymptotic QNMs for both Schwarzschild and Reissner-Nordstrom black holes. This confirms recent results obtained by Motl and Neitzke, but our analysis fills several gaps left by their discussion. We study the Reissner-Nordstrom results in some detail, and show that, in contrast to the asymptotic QNMs of a Schwarzschild black hole, the Reissner-Nordstrom QNMs are typically not periodic in the imaginary part of the frequency. This leads to the charged black hole having peculiar properties which complicate an interpretation of the results. |
2401.09577 | Scott A. Hughes | Scott A. Hughes | Parameterizing black hole orbits for adiabatic inspiral | 10 pages, 5 figures, version to appear in Physical Review D.
Incorporates helpful feedback from the referee and a few other comments
received since this paper was originally posted. Posting includes Mathematica
notebook and C++ code which implements the methods developed in this paper | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Adiabatic binary inspiral in the small mass ratio limit treats the small body
as moving along a geodesic of a large Kerr black hole, with the geodesic slowly
evolving due to radiative backreaction. Up to initial conditions, geodesics are
typically parameterized in two ways: using the integrals of motion energy $E$,
axial angular momentum $L_z$, and Carter constant $Q$; or, using orbit geometry
parameters semi-latus rectum $p$, eccentricity $e$, and (cosine of )
inclination $x_I \equiv \cos I$. The community has long known how to compute
orbit integrals as functions of the orbit geometry parameters, i.e., as
functions expressing $E(p, e, x_I)$, and likewise for $L_z$ and $Q$. Mappings
in the other direction -- functions $p(E, L_z, Q)$, and likewise for $e$ and
$x_I$ -- have not yet been developed in general. In this note, we develop
generic mappings from ($E$, $L_z$, $Q$) to ($p$, $e$, $x_I$). The mappings are
particularly simple for equatorial orbits ($Q = 0$, $x_I = \pm1$), and can be
evaluated efficiently for generic cases. These results make it possible to more
accurately compute adiabatic inspirals by eliminating the need to use a
Jacobian which becomes singular as inspiral approaches the last stable orbit.
| [
{
"created": "Wed, 17 Jan 2024 19:57:45 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Mar 2024 22:16:57 GMT",
"version": "v2"
}
] | 2024-03-28 | [
[
"Hughes",
"Scott A.",
""
]
] | Adiabatic binary inspiral in the small mass ratio limit treats the small body as moving along a geodesic of a large Kerr black hole, with the geodesic slowly evolving due to radiative backreaction. Up to initial conditions, geodesics are typically parameterized in two ways: using the integrals of motion energy $E$, axial angular momentum $L_z$, and Carter constant $Q$; or, using orbit geometry parameters semi-latus rectum $p$, eccentricity $e$, and (cosine of ) inclination $x_I \equiv \cos I$. The community has long known how to compute orbit integrals as functions of the orbit geometry parameters, i.e., as functions expressing $E(p, e, x_I)$, and likewise for $L_z$ and $Q$. Mappings in the other direction -- functions $p(E, L_z, Q)$, and likewise for $e$ and $x_I$ -- have not yet been developed in general. In this note, we develop generic mappings from ($E$, $L_z$, $Q$) to ($p$, $e$, $x_I$). The mappings are particularly simple for equatorial orbits ($Q = 0$, $x_I = \pm1$), and can be evaluated efficiently for generic cases. These results make it possible to more accurately compute adiabatic inspirals by eliminating the need to use a Jacobian which becomes singular as inspiral approaches the last stable orbit. |
1805.01233 | Konstantinos Dialektopoulos F. | Salvatore Capozziello, Konstantinos F. Dialektopoulos and Orlando
Luongo | Maximum turnaround radius in $f(R)$ gravity | 8 pages, 1 figure | null | 10.1142/S0218271819500585 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The accelerating behavior of cosmic fluid opposes to the gravitational
attraction, at present epoch, whereas standard gravity is dominant at small
scales. As a consequence, there exists a \emph{point} where the effects are
counterbalanced, dubbed \emph{turnaround radius}, $r_{\text{ta}}$. By
construction, it provides a bound on maximum structure sizes of the observed
universe. Once an upper bound on $r_{\text{ta}}$ is provided, i.e.
$R_{\text{TA,max}}$, one can check whether cosmological models guarantee
structure formation. Here, we focus on $f(R)$ gravity, without imposing \emph{a
priori} the form of $f(R)$. We thus provide an analytic expression for the
turnaround radius in the framework of $f(R)$ models. To figure this out, we
compute the turnaround radius in two distinct cases: 1) under the hypothesis of
static and spherically symmetric space-time, and 2) by using the cosmological
perturbation theory. We thus find a criterion to enable large scale structures
to be stable in $f(R)$ models, circumscribing the class of $f(R)$ theories as
suitable alternative to dark energy. In particular, we get that for constant
curvature, the viability condition becomes $R_{\text{dS}}f'(R_{\text{dS}}) \leq
5.48 \Lambda \Rightarrow f'(R_{\text{dS}}) \leq 1.37$, with $\Lambda$ and
$R_{\text{dS}}$ respectively the observed cosmological constant and the Ricci
curvature. This prescription rules out models which do not pass the
aforementioned $R_{\text{TA,max}}$ limit.
| [
{
"created": "Thu, 3 May 2018 11:33:09 GMT",
"version": "v1"
}
] | 2019-02-20 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Dialektopoulos",
"Konstantinos F.",
""
],
[
"Luongo",
"Orlando",
""
]
] | The accelerating behavior of cosmic fluid opposes to the gravitational attraction, at present epoch, whereas standard gravity is dominant at small scales. As a consequence, there exists a \emph{point} where the effects are counterbalanced, dubbed \emph{turnaround radius}, $r_{\text{ta}}$. By construction, it provides a bound on maximum structure sizes of the observed universe. Once an upper bound on $r_{\text{ta}}$ is provided, i.e. $R_{\text{TA,max}}$, one can check whether cosmological models guarantee structure formation. Here, we focus on $f(R)$ gravity, without imposing \emph{a priori} the form of $f(R)$. We thus provide an analytic expression for the turnaround radius in the framework of $f(R)$ models. To figure this out, we compute the turnaround radius in two distinct cases: 1) under the hypothesis of static and spherically symmetric space-time, and 2) by using the cosmological perturbation theory. We thus find a criterion to enable large scale structures to be stable in $f(R)$ models, circumscribing the class of $f(R)$ theories as suitable alternative to dark energy. In particular, we get that for constant curvature, the viability condition becomes $R_{\text{dS}}f'(R_{\text{dS}}) \leq 5.48 \Lambda \Rightarrow f'(R_{\text{dS}}) \leq 1.37$, with $\Lambda$ and $R_{\text{dS}}$ respectively the observed cosmological constant and the Ricci curvature. This prescription rules out models which do not pass the aforementioned $R_{\text{TA,max}}$ limit. |
gr-qc/0212107 | Valery Gavrilov | H. Dehnen, V. R. Gavrilov and V. N. Melnikov | General solutions for flat Friedmann universe filled by perfect fluid
and scalar field with exponential potential | 13 pages, Latex, 1 figure, submit. to Class. Quantum Grav | Grav.Cosmol. 9 (2003) 189-195 | null | IGC-PFUR-05/2002 | gr-qc | null | We study integrability by quadrature of a spatially flat Friedmann model
containing both a minimally coupled scalar field $\phi$ with an exponential
potential $V(\phi)\sim\exp[-\sqrt{6}\sigma\kappa\phi]$, $\kappa=\sqrt{8\pi
G_N}$, of arbitrary sign and a perfect fluid with barotropic equation of state
$p=(1-h)\rho$. From the mathematical view point the model is pseudo-Euclidean
Toda-like system with 2 degrees of freedom. We apply the methods developed in
our previous papers, based on the Minkowsky-like geometry for 2 characteristic
vectors depending on the parameters $\sigma$ and $h$. In general case the
problem is reduced to integrability of a second order ordinary differential
equation known as the generalized Emden-Fowler equation, which was investigated
by discrete-group methods. We present 4 classes of general solutions for the
parameters obeying the following relations: {\bf A}. $\sigma$ is arbitrary,
$h=0$; {\bf B}. $\sigma=1-h/2$, $0<h<2$; {\bf C1}. $\sigma=1-h/4$, $0<h\leq 2$;
{\bf C2}. $\sigma=|1-h|$, $0<h\leq 2$, $h\neq 1,4/3$. We discuss the properties
of the exact solutions near the initial singularity and at the final stage of
evolution.
| [
{
"created": "Thu, 26 Dec 2002 12:04:42 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Dehnen",
"H.",
""
],
[
"Gavrilov",
"V. R.",
""
],
[
"Melnikov",
"V. N.",
""
]
] | We study integrability by quadrature of a spatially flat Friedmann model containing both a minimally coupled scalar field $\phi$ with an exponential potential $V(\phi)\sim\exp[-\sqrt{6}\sigma\kappa\phi]$, $\kappa=\sqrt{8\pi G_N}$, of arbitrary sign and a perfect fluid with barotropic equation of state $p=(1-h)\rho$. From the mathematical view point the model is pseudo-Euclidean Toda-like system with 2 degrees of freedom. We apply the methods developed in our previous papers, based on the Minkowsky-like geometry for 2 characteristic vectors depending on the parameters $\sigma$ and $h$. In general case the problem is reduced to integrability of a second order ordinary differential equation known as the generalized Emden-Fowler equation, which was investigated by discrete-group methods. We present 4 classes of general solutions for the parameters obeying the following relations: {\bf A}. $\sigma$ is arbitrary, $h=0$; {\bf B}. $\sigma=1-h/2$, $0<h<2$; {\bf C1}. $\sigma=1-h/4$, $0<h\leq 2$; {\bf C2}. $\sigma=|1-h|$, $0<h\leq 2$, $h\neq 1,4/3$. We discuss the properties of the exact solutions near the initial singularity and at the final stage of evolution. |
1112.5776 | Christian Corda cordac | Christian Corda | Tuning the stochastic background of gravitational waves using the WMAP
data | 9 pages, 2 figures, published in Modern Physics Letters A. arXiv
admin note: substantial text overlap with arXiv:0901.1193 | Mod. Phys. Lett. A, 22, 16, 1167-1173 (2007) | 10.1142/S0217732307023523 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cosmological bound of the stochastic background of gravitational waves is
analyzed with the aid of the WMAP data, differently from lots of works in
literature, where the old COBE data were used. From our analysis, it will
result that the WMAP bounds on the energy spectrum and on the characteristic
amplitude of the stochastic background of gravitational waves are greater than
the COBE ones, but they are also far below frequencies of the earth-based
antennas band. At the end of this letter a lower bound for the integration time
of a potential detection with advanced LIGO is released and compared with the
previous one arising from the old COBE data. Even if the new lower bound is
minor than the previous one, it results very long, thus for a possible
detection we hope in the LISA interferometer and in a further growth in the
sensitivity of advanced projects.
| [
{
"created": "Sun, 25 Dec 2011 11:29:46 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Corda",
"Christian",
""
]
] | The cosmological bound of the stochastic background of gravitational waves is analyzed with the aid of the WMAP data, differently from lots of works in literature, where the old COBE data were used. From our analysis, it will result that the WMAP bounds on the energy spectrum and on the characteristic amplitude of the stochastic background of gravitational waves are greater than the COBE ones, but they are also far below frequencies of the earth-based antennas band. At the end of this letter a lower bound for the integration time of a potential detection with advanced LIGO is released and compared with the previous one arising from the old COBE data. Even if the new lower bound is minor than the previous one, it results very long, thus for a possible detection we hope in the LISA interferometer and in a further growth in the sensitivity of advanced projects. |
2305.02184 | Christian Corda Prof. | Christian Corda | Black hole spectra from Vaz's quantum gravitational collapse | Final version matching the one published in Fortschritte der Physik -
Progress of Physics. Comments are welcome | Fortschr. Phys. 2023, 2300028 | 10.1002/prop.202300028 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In 2014, in a famous paper Hawking strongly criticized the firewall paradox
by claiming that it violates the equivalence principle and breaks the CPT
invariance of quantum gravity. He proposed that the final result of the
gravitational collapse should not be an event horizon, but an apparent horizon
instead. On the other hand, Hawking did not give a mechanism for how this could
work. In the same year, Vaz endorsed Hawking's proposal in a quantum
gravitational model of dust collapse by winning the Second Prize in the 2014
Gravity Research Foundation Essay Competition. He indeed showed that continued
collapse to a singularity can only be obtained if one combines two independent
and entire solutions of the Wheeler-DeWitt equation. Vaz's interpretation of
the paradox was in terms of simply forbidding such a combination. This leads
naturally to matter condensing on the apparent horizon during quantum collapse.
In that way, an entirely new framework for black holes (BHs) has emerged. The
approach of Vaz was also consistent with Einstein's idea in 1939 of the
localization of the collapsing particles within a thin spherical shell. In this
work we derive the BH mass and energy spectra via a Schrodinger-like approach,
by further supporting Vaz's conclusions that instead of a spacetime singularity
covered by an event horizon, the final result of the gravitational collapse is
an essentially quantum object, an extremely compact "dark star". This
"gravitational atom" is held up not by any degeneracy pressure but by quantum
gravity in the same way that ordinary atoms are sustained by quantum mechanics.
Finally, by evoking the generalized uncertainty principle, the maximum value of
the density of Vaz's shell will be estimated.
| [
{
"created": "Sat, 29 Apr 2023 09:37:58 GMT",
"version": "v1"
},
{
"created": "Sun, 14 May 2023 10:14:55 GMT",
"version": "v2"
}
] | 2023-05-16 | [
[
"Corda",
"Christian",
""
]
] | In 2014, in a famous paper Hawking strongly criticized the firewall paradox by claiming that it violates the equivalence principle and breaks the CPT invariance of quantum gravity. He proposed that the final result of the gravitational collapse should not be an event horizon, but an apparent horizon instead. On the other hand, Hawking did not give a mechanism for how this could work. In the same year, Vaz endorsed Hawking's proposal in a quantum gravitational model of dust collapse by winning the Second Prize in the 2014 Gravity Research Foundation Essay Competition. He indeed showed that continued collapse to a singularity can only be obtained if one combines two independent and entire solutions of the Wheeler-DeWitt equation. Vaz's interpretation of the paradox was in terms of simply forbidding such a combination. This leads naturally to matter condensing on the apparent horizon during quantum collapse. In that way, an entirely new framework for black holes (BHs) has emerged. The approach of Vaz was also consistent with Einstein's idea in 1939 of the localization of the collapsing particles within a thin spherical shell. In this work we derive the BH mass and energy spectra via a Schrodinger-like approach, by further supporting Vaz's conclusions that instead of a spacetime singularity covered by an event horizon, the final result of the gravitational collapse is an essentially quantum object, an extremely compact "dark star". This "gravitational atom" is held up not by any degeneracy pressure but by quantum gravity in the same way that ordinary atoms are sustained by quantum mechanics. Finally, by evoking the generalized uncertainty principle, the maximum value of the density of Vaz's shell will be estimated. |
0909.4194 | Goffredo Chirco | G. Chirco, S. Liberati | Non-equilibrium Thermodynamics of Spacetime: the Role of Gravitational
Dissipation | 13 pages, 1 figure | Phys.Rev.D81:024016,2010 | 10.1103/PhysRevD.81.024016 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In arXiv:gr-qc/9504004 it was shown that the Einstein equation can be derived
as a local constitutive equation for an equilibrium spacetime thermodynamics.
More recently, in the attempt to extend the same approach to the case of $f(R)$
theories of gravity, it was found that a non-equilibrium setting is indeed
required in order to fully describe both this theory as well as classical GR
(arXiv:gr-qc/0602001). Here, elaborating on this point, we show that the
dissipative character leading to a non-equilibrium spacetime thermodynamics is
actually related -- both in GR as well as in $f(R)$ gravity -- to non-local
heat fluxes associated with the purely gravitational/internal degrees of
freedom of the theory. In particular, in the case of GR we show that the
internal entropy production term is identical to the so called tidal heating
term of Hartle-Hawking. Similarly, for the case of $f(R)$ gravity, we show that
dissipative effects can be associated with the generalization of this term plus
a scalar contribution whose presence is clearly justified within the
scalar-tensor representation of the theory. Finally, we show that the allowed
gravitational degrees of freedom can be fixed by the kinematics of the local
spacetime causal structure, through the specific Equivalence Principle
formulation. In this sense, the thermodynamical description seems to go beyond
Einstein's theory as an intrinsic property of gravitation.
| [
{
"created": "Wed, 23 Sep 2009 12:46:44 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Chirco",
"G.",
""
],
[
"Liberati",
"S.",
""
]
] | In arXiv:gr-qc/9504004 it was shown that the Einstein equation can be derived as a local constitutive equation for an equilibrium spacetime thermodynamics. More recently, in the attempt to extend the same approach to the case of $f(R)$ theories of gravity, it was found that a non-equilibrium setting is indeed required in order to fully describe both this theory as well as classical GR (arXiv:gr-qc/0602001). Here, elaborating on this point, we show that the dissipative character leading to a non-equilibrium spacetime thermodynamics is actually related -- both in GR as well as in $f(R)$ gravity -- to non-local heat fluxes associated with the purely gravitational/internal degrees of freedom of the theory. In particular, in the case of GR we show that the internal entropy production term is identical to the so called tidal heating term of Hartle-Hawking. Similarly, for the case of $f(R)$ gravity, we show that dissipative effects can be associated with the generalization of this term plus a scalar contribution whose presence is clearly justified within the scalar-tensor representation of the theory. Finally, we show that the allowed gravitational degrees of freedom can be fixed by the kinematics of the local spacetime causal structure, through the specific Equivalence Principle formulation. In this sense, the thermodynamical description seems to go beyond Einstein's theory as an intrinsic property of gravitation. |
1906.06022 | Dong-han Yeom | Suddhasattwa Brahma, Dong-han Yeom | Can a false vacuum bubble remove the singularity inside a black hole? | 16 pages, 7 figures | Eur.Phys.J. C80 (2020) 713 | 10.1140/epjc/s10052-020-8248-4 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate a regular black hole model with a de Sitter-like core at its
center. This type of a black hole model with a false vacuum core was introduced
with the hope of singularity-resolution and is a common feature shared by many
regular black holes. In this paper, we examine this claim of a singularity-free
black hole by employing the thin-shell formalism, and exploring its dynamics,
within the Vaidya approximation. We find that during gravitational collapse,
the shell necessarily moves along a space-like direction. More interestingly,
during the evaporation phase, the shell and the outer apparent horizon approach
each other but, unless the evaporation takes place very rapidly, the
approaching tendency is too slow to avoid singularity-formation. This shows
that albeit a false vacuum core may remove the singularity along the ingoing
null direction, there still exists a singularity along the outgoing null
direction, unless the evaporation is very strong.
| [
{
"created": "Fri, 14 Jun 2019 05:00:22 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Aug 2020 02:17:48 GMT",
"version": "v2"
}
] | 2020-08-12 | [
[
"Brahma",
"Suddhasattwa",
""
],
[
"Yeom",
"Dong-han",
""
]
] | We investigate a regular black hole model with a de Sitter-like core at its center. This type of a black hole model with a false vacuum core was introduced with the hope of singularity-resolution and is a common feature shared by many regular black holes. In this paper, we examine this claim of a singularity-free black hole by employing the thin-shell formalism, and exploring its dynamics, within the Vaidya approximation. We find that during gravitational collapse, the shell necessarily moves along a space-like direction. More interestingly, during the evaporation phase, the shell and the outer apparent horizon approach each other but, unless the evaporation takes place very rapidly, the approaching tendency is too slow to avoid singularity-formation. This shows that albeit a false vacuum core may remove the singularity along the ingoing null direction, there still exists a singularity along the outgoing null direction, unless the evaporation is very strong. |
1803.09148 | Yan Peng | Yan Peng, Bin Wang, Yunqi Liu | Scalar field condensation behaviors around reflecting shells in Anti-de
Sitter spacetimes | 10 pages,3 figures | Eur.Phys.J. C78 (2018) no.8, 680 | 10.1140/epjc/s10052-018-6169-2 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study scalar condensations around asymptotically Anti-de Sitter(AdS)
regular reflecting shells. We show that the charged scalar field can condense
around charged reflecting shells with both Dirichlet and Neumann boundary
conditions. In particular, the radii of the asymptotically AdS hairy shells are
discrete, which is similar to cases in asymptotically flat spacetimes. We also
provide upper bounds for the radii of the hairy Dirichlet reflecting shells and
above the bound, the scalar field cannot condense around the shell.
| [
{
"created": "Sat, 24 Mar 2018 18:45:14 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Aug 2018 17:38:11 GMT",
"version": "v2"
}
] | 2018-08-29 | [
[
"Peng",
"Yan",
""
],
[
"Wang",
"Bin",
""
],
[
"Liu",
"Yunqi",
""
]
] | We study scalar condensations around asymptotically Anti-de Sitter(AdS) regular reflecting shells. We show that the charged scalar field can condense around charged reflecting shells with both Dirichlet and Neumann boundary conditions. In particular, the radii of the asymptotically AdS hairy shells are discrete, which is similar to cases in asymptotically flat spacetimes. We also provide upper bounds for the radii of the hairy Dirichlet reflecting shells and above the bound, the scalar field cannot condense around the shell. |
1608.02115 | Deyou Chen | Deyou Chen, Xiaoxiong Zeng | Modifying horizon thermodynamics by surface tensions | 12 pages, references added | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The modified first laws of thermodynamics at the black hole horizon and the
cosmological horizon of the Schwarzschild de Sitter black hole and the apparent
horizon of the Friedmann-Robertson-Walker cosmology are derived by the surface
tensions, respectively. The corresponding Smarr relations are obeyed. For the
black hole, the cosmological constant is first treated as a fixed constant, and
then as a variable associated to the pressure. The law at the apparent horizon
takes the same form as that at the cosmological horizon, but is different from
that at the black hole horizon. The positive temperatures guarantee the
appearance of the worked terms in the modified laws at the cosmological and
apparent horizons. While they can disappear at the black hole horizon.
| [
{
"created": "Sat, 6 Aug 2016 14:54:13 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Aug 2016 12:26:48 GMT",
"version": "v2"
},
{
"created": "Fri, 12 Aug 2016 08:18:13 GMT",
"version": "v3"
}
] | 2016-08-15 | [
[
"Chen",
"Deyou",
""
],
[
"Zeng",
"Xiaoxiong",
""
]
] | The modified first laws of thermodynamics at the black hole horizon and the cosmological horizon of the Schwarzschild de Sitter black hole and the apparent horizon of the Friedmann-Robertson-Walker cosmology are derived by the surface tensions, respectively. The corresponding Smarr relations are obeyed. For the black hole, the cosmological constant is first treated as a fixed constant, and then as a variable associated to the pressure. The law at the apparent horizon takes the same form as that at the cosmological horizon, but is different from that at the black hole horizon. The positive temperatures guarantee the appearance of the worked terms in the modified laws at the cosmological and apparent horizons. While they can disappear at the black hole horizon. |
2312.11665 | Michael Kachelrie{\ss} | M. Kachelriess, M. P. N{\o}dtvedt | Lunar response to gravitational waves | 17 pages, 15 pdf figures | null | null | null | gr-qc astro-ph.EP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been suggested to use seismic detectors on the Moon as a tool to
search for gravitational waves in an intermediate frequency range between mHz
and Hz. Employing three different spherically symmetric models for the lunar
interior, we investigate the response of the Moon to gravitational waves in
Einstein and Jordan-Brans-Dicke gravity. We find that the first
eigenfrequencies of the different models depend only weakly on the model
details, with the fundamental frequency $\nu_1$ close to 1\,ms both for
spheroidal and toroidal oscillations. In contrast, the resulting displacement
varies up to a factor two, being in the range $(2.7-5.6)\times 10^{11}/h_0$ cm
for spheroidal oscillations with amplitude $h_0$. Toroidal oscillations are
suppressed by a factor $2\pi\nu R/c$, both in Einstein gravity and in general
scalar-tensor theories.
| [
{
"created": "Mon, 18 Dec 2023 19:17:24 GMT",
"version": "v1"
}
] | 2023-12-20 | [
[
"Kachelriess",
"M.",
""
],
[
"Nødtvedt",
"M. P.",
""
]
] | It has been suggested to use seismic detectors on the Moon as a tool to search for gravitational waves in an intermediate frequency range between mHz and Hz. Employing three different spherically symmetric models for the lunar interior, we investigate the response of the Moon to gravitational waves in Einstein and Jordan-Brans-Dicke gravity. We find that the first eigenfrequencies of the different models depend only weakly on the model details, with the fundamental frequency $\nu_1$ close to 1\,ms both for spheroidal and toroidal oscillations. In contrast, the resulting displacement varies up to a factor two, being in the range $(2.7-5.6)\times 10^{11}/h_0$ cm for spheroidal oscillations with amplitude $h_0$. Toroidal oscillations are suppressed by a factor $2\pi\nu R/c$, both in Einstein gravity and in general scalar-tensor theories. |
2310.14547 | Li-Ying Chou | Li-Ying Chou, Yi-Zen Chu, and Yen-Wei Liu | Scalar Gravitational Waves Can Be Generated Even Without Direct Coupling
Between Dark Energy and Ordinary Matter | 28 pages, 2 figures | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We point out, the scalar sector of gravitational perturbations may be excited
by an isolated astrophysical system immersed in a universe whose accelerated
expansion is not due to the cosmological constant, but due to extra field
degrees of freedom. This is true even if the source of gravitational radiation
did not couple directly to these additional fields. We illustrate this by
considering a universe driven by a single canonical scalar field. By working
within the gauge-invariant formalism, we solve for the electric components of
the linearised Weyl tensor to demonstrate that both the gravitational massless
spin-2 (transverse-traceless) tensor and the (Bardeen) scalar modes are
generated by a generic astrophysical source. For concreteness, the Dark Energy
scalar field is either released from rest, or allowed to asymptote to the
minimum in a certain class of potentials; and we compute the traceless tidal
forces induced by gravitational radiation from a hypothetical compact binary
system residing in such a universe. Though their magnitudes are very small
compared to the tensors', spin zero gravitational waves in such a canonical
scalar driven universe are directly sensitive to both the Dark Energy equation
of state and the eccentricity of the binary's orbit.
| [
{
"created": "Mon, 23 Oct 2023 04:01:58 GMT",
"version": "v1"
}
] | 2023-10-24 | [
[
"Chou",
"Li-Ying",
""
],
[
"Chu",
"Yi-Zen",
""
],
[
"Liu",
"Yen-Wei",
""
]
] | We point out, the scalar sector of gravitational perturbations may be excited by an isolated astrophysical system immersed in a universe whose accelerated expansion is not due to the cosmological constant, but due to extra field degrees of freedom. This is true even if the source of gravitational radiation did not couple directly to these additional fields. We illustrate this by considering a universe driven by a single canonical scalar field. By working within the gauge-invariant formalism, we solve for the electric components of the linearised Weyl tensor to demonstrate that both the gravitational massless spin-2 (transverse-traceless) tensor and the (Bardeen) scalar modes are generated by a generic astrophysical source. For concreteness, the Dark Energy scalar field is either released from rest, or allowed to asymptote to the minimum in a certain class of potentials; and we compute the traceless tidal forces induced by gravitational radiation from a hypothetical compact binary system residing in such a universe. Though their magnitudes are very small compared to the tensors', spin zero gravitational waves in such a canonical scalar driven universe are directly sensitive to both the Dark Energy equation of state and the eccentricity of the binary's orbit. |
1006.4908 | Garrett Lisi | A. Garrett Lisi | An Explicit Embedding of Gravity and the Standard Model in E8 | To be submitted for peer review and publication in the "Proceedings
of the Conference on Representation Theory and Mathematical Physics." 14
pages. No figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The algebraic elements of gravitational and Standard Model gauge fields
acting on a generation of fermions may be represented using real matrices.
These elements match a subalgebra of spin(11,3) acting on a Majorana-Weyl
spinor, consistent with GraviGUT unification. This entire structure embeds in
the quaternionic real form of the largest exceptional Lie algebra, E8. These
embeddings are presented explicitly and their implications discussed.
| [
{
"created": "Fri, 25 Jun 2010 04:39:45 GMT",
"version": "v1"
}
] | 2010-06-28 | [
[
"Lisi",
"A. Garrett",
""
]
] | The algebraic elements of gravitational and Standard Model gauge fields acting on a generation of fermions may be represented using real matrices. These elements match a subalgebra of spin(11,3) acting on a Majorana-Weyl spinor, consistent with GraviGUT unification. This entire structure embeds in the quaternionic real form of the largest exceptional Lie algebra, E8. These embeddings are presented explicitly and their implications discussed. |
gr-qc/9312028 | Herbert Nachbagauer | Herbert Balasin and Herbert Nachbagauer | Distributional Energy-Momentum Tensor of the Kerr-Newman Space-Time
Family | 13 pages, ENSLAPP-A-453/93, TUW 93-28 | Class.Quant.Grav.11:1453-1462,1994 | 10.1088/0264-9381/11/6/010 | null | gr-qc | null | Using the Kerr-Schild decomposition of the metric tensor that employs the
algebraically special nature of the Kerr-Newman space-time family, we calculate
the energy-momentum tensor. The latter turns out to be a well-defined
tensor-distribution with disk-like support.
| [
{
"created": "Fri, 17 Dec 1993 14:13:21 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Balasin",
"Herbert",
""
],
[
"Nachbagauer",
"Herbert",
""
]
] | Using the Kerr-Schild decomposition of the metric tensor that employs the algebraically special nature of the Kerr-Newman space-time family, we calculate the energy-momentum tensor. The latter turns out to be a well-defined tensor-distribution with disk-like support. |
gr-qc/9508001 | Gregory A. Burnett | Gregory A. Burnett (UF) and Alan D. Rendall (IHES) | Existence of maximal hypersurfaces in some spherically symmetric
spacetimes | 8 pages, REVTeX 3.0 | Class.Quant.Grav.13:111-124,1996 | 10.1088/0264-9381/13/1/010 | UF-RAP-95-32 | gr-qc dg-ga math.DG | null | We prove that the maximal development of any spherically symmetric spacetime
with collisionless matter (obeying the Vlasov equation) or a massless scalar
field (obeying the massless wave equation) and possessing a constant mean
curvature $S^1 \times S^2$ Cauchy surface also contains a maximal Cauchy
surface. Combining this with previous results establishes that the spacetime
can be foliated by constant mean curvature Cauchy surfaces with the mean
curvature taking on all real values, thereby showing that these spacetimes
satisfy the closed-universe recollapse conjecture. A key element of the proof,
of interest in itself, is a bound for the volume of any Cauchy surface $\Sigma$
in any spacetime satisfying the timelike convergence condition in terms of the
volume and mean curvature of a fixed Cauchy surface $\Sigma_0$ and the maximal
distance between $\Sigma$ and $\Sigma_0$. In particular, this shows that any
globally hyperbolic spacetime having a finite lifetime and obeying the
timelike-convergence condition cannot attain an arbitrarily large spatial
volume.
| [
{
"created": "Tue, 1 Aug 1995 19:24:23 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Burnett",
"Gregory A.",
"",
"UF"
],
[
"Rendall",
"Alan D.",
"",
"IHES"
]
] | We prove that the maximal development of any spherically symmetric spacetime with collisionless matter (obeying the Vlasov equation) or a massless scalar field (obeying the massless wave equation) and possessing a constant mean curvature $S^1 \times S^2$ Cauchy surface also contains a maximal Cauchy surface. Combining this with previous results establishes that the spacetime can be foliated by constant mean curvature Cauchy surfaces with the mean curvature taking on all real values, thereby showing that these spacetimes satisfy the closed-universe recollapse conjecture. A key element of the proof, of interest in itself, is a bound for the volume of any Cauchy surface $\Sigma$ in any spacetime satisfying the timelike convergence condition in terms of the volume and mean curvature of a fixed Cauchy surface $\Sigma_0$ and the maximal distance between $\Sigma$ and $\Sigma_0$. In particular, this shows that any globally hyperbolic spacetime having a finite lifetime and obeying the timelike-convergence condition cannot attain an arbitrarily large spatial volume. |
gr-qc/9607032 | Douglas Vivian Long | D. V. Long and G. M. Shore | The Schrodinger Wave Functional and Vacuum State in Curved Spacetime II.
Boundaries and Foliations | 26 pages, 4 figures, LATEX | Nucl.Phys. B530 (1998) 279-303 | 10.1016/S0550-3213(98)00409-X | SWAT 96/124 | gr-qc hep-th | null | In a recent paper, general solutions for the vacuum wave functionals in the
Schrodinger picture were given for a variety of classes of curved spacetimes.
Here, we describe a number of simple examples which illustrate how the presence
of spacetime boundaries influences the vacuum wave functional and how physical
quantities are independent of the choice of spacetime foliation used in the
Schrodinger approach despite the foliation dependence of the wave functionals
themselves.
| [
{
"created": "Sun, 14 Jul 1996 19:05:31 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Long",
"D. V.",
""
],
[
"Shore",
"G. M.",
""
]
] | In a recent paper, general solutions for the vacuum wave functionals in the Schrodinger picture were given for a variety of classes of curved spacetimes. Here, we describe a number of simple examples which illustrate how the presence of spacetime boundaries influences the vacuum wave functional and how physical quantities are independent of the choice of spacetime foliation used in the Schrodinger approach despite the foliation dependence of the wave functionals themselves. |
0803.1820 | \'Etienne Racine | Etienne Racine | Analysis of spin precession in binary black hole systems including
quadrupole-monopole interaction | version published in Phys. Rev. D, with improved figures and more
detailed discussion of cubic anharmonic oscillator | Phys.Rev.D78:044021,2008 | 10.1103/PhysRevD.78.044021 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze in detail the spin precession equations in binary black hole
systems, when the tidal torque on a Kerr black hole due to quadrupole-monopole
coupling is taken into account. We show that completing the precession
equations with this term reveals the existence of a conserved quantity at 2PN
order when averaging over orbital motion. This quantity allows one to solve the
(orbit-averaged) precession equations exactly in the case of equal masses and
arbitrary spins, neglecting radiation reaction. For unequal masses, an exact
solution does not exist in closed form, but we are still able to derive
accurate approximate analytic solutions. We also show how to incorporate
radiation reaction effects into our analytic solutions adiabatically, and
compare the results to solutions obtained numerically. For various
configurations of the binary, the relative difference in the accumulated
orbital phase computed using our analytic solutions versus a full numerical
solution vary from about 0.3% to 1.8% over the 80 - 140 orbital cycles
accumulated while sweeping over the orbital frequency range 20 - 300 Hz. This
typically corresponds to a discrepancy of order 5-6 radians. While this may not
be accurate enough for implementation in LIGO template banks, we still believe
that our new solutions are potentially quite useful for comparing numerical
relativity simulations of spinning binary black hole systems with
post-Newtonian theory. They can also be used to gain more understanding of
precession effects, with potential application to the gravitational recoil
problem, and to provide semi-analytical templates for spinning, precessing
binaries.
| [
{
"created": "Wed, 12 Mar 2008 18:35:15 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Mar 2008 00:04:31 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Aug 2008 18:02:22 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Racine",
"Etienne",
""
]
] | We analyze in detail the spin precession equations in binary black hole systems, when the tidal torque on a Kerr black hole due to quadrupole-monopole coupling is taken into account. We show that completing the precession equations with this term reveals the existence of a conserved quantity at 2PN order when averaging over orbital motion. This quantity allows one to solve the (orbit-averaged) precession equations exactly in the case of equal masses and arbitrary spins, neglecting radiation reaction. For unequal masses, an exact solution does not exist in closed form, but we are still able to derive accurate approximate analytic solutions. We also show how to incorporate radiation reaction effects into our analytic solutions adiabatically, and compare the results to solutions obtained numerically. For various configurations of the binary, the relative difference in the accumulated orbital phase computed using our analytic solutions versus a full numerical solution vary from about 0.3% to 1.8% over the 80 - 140 orbital cycles accumulated while sweeping over the orbital frequency range 20 - 300 Hz. This typically corresponds to a discrepancy of order 5-6 radians. While this may not be accurate enough for implementation in LIGO template banks, we still believe that our new solutions are potentially quite useful for comparing numerical relativity simulations of spinning binary black hole systems with post-Newtonian theory. They can also be used to gain more understanding of precession effects, with potential application to the gravitational recoil problem, and to provide semi-analytical templates for spinning, precessing binaries. |
1901.03720 | Khalid Saifullah | Askar Ali and Khalid Saifullah | Magnetized topological black holes of dimensionally continued gravity | Matches the published version | Phys. Rev. D 99, 124052 (2019) | 10.1103/PhysRevD.99.124052 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, a large family of topological black hole solutions of
dimensionally continued gravity are derived. The action of Lovelock gravity is
coupled to the exponential electrodynamics and the equations of motion are
solved in the presence of a pure magnetic source. We work out the metric
functions in terms of the parameter $\beta$ of exponential electrodynamics, and
magnetic charge. Further, we couple Lovelock gravity to power-Yang-Mills theory
and construct black holes, in diverse dimensions, having Yang-Mills magnetic
charge. We also discuss the asymptotic bahaviour of metric functions and
curvature invariants at the origin for both the models. The thermodynamics of
resulting magnetized black hole solutions in the framework of two different
models is also studied. The thermodynamical quantities like Hawking
temperature, entropy and specific heat capacity at constant charge are found
and we show that the resulting quantities satisfy the first law of black hole
thermodynamics. We also study the magnetized hairy black holes of dimensionally
continued gravity.
| [
{
"created": "Fri, 11 Jan 2019 19:23:45 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Jul 2019 08:38:14 GMT",
"version": "v2"
}
] | 2019-07-11 | [
[
"Ali",
"Askar",
""
],
[
"Saifullah",
"Khalid",
""
]
] | In this paper, a large family of topological black hole solutions of dimensionally continued gravity are derived. The action of Lovelock gravity is coupled to the exponential electrodynamics and the equations of motion are solved in the presence of a pure magnetic source. We work out the metric functions in terms of the parameter $\beta$ of exponential electrodynamics, and magnetic charge. Further, we couple Lovelock gravity to power-Yang-Mills theory and construct black holes, in diverse dimensions, having Yang-Mills magnetic charge. We also discuss the asymptotic bahaviour of metric functions and curvature invariants at the origin for both the models. The thermodynamics of resulting magnetized black hole solutions in the framework of two different models is also studied. The thermodynamical quantities like Hawking temperature, entropy and specific heat capacity at constant charge are found and we show that the resulting quantities satisfy the first law of black hole thermodynamics. We also study the magnetized hairy black holes of dimensionally continued gravity. |
1804.03813 | Neda Farhangkhah | N. Farhangkhah | Topologically nontrivial black holes in Lovelock-Born-Infeld gravity | 15 pages, 5 figures, accepted version by Phys. Rev. D | Phys. Rev. D 97, 084031 (2018) | 10.1103/PhysRevD.97.084031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the black hole solutions possessing horizon with
nonconstant-curvature and additional scalar restrictions on the base manifold
in Lovelock gravity coupled to Born-Infeld (BI) nonlinear electrodynamics. The
asymptotic and near origin behavior of the metric is presented and we analyze
different behaviors of the singularity. We find that, in contrast to the case
of the black hole solutions of BI-Lovelock gravity with constant curvature
horizon and Maxwell-Lovelock gravity with nonconstant horizon which has only
timelike singularities, spacelike, and timelike singularities may exist for
BI-Lovelock black holes with nonconstant curvature horizon. By calculating the
thermodynamic quantities, we study the effects of nonlinear electrodynamics via
the Born-Infeld action. Stability analysis shows that black holes with positive
sectional curvature, k, possess an intermediate unstable phase and large and
small black holes are stable. We see that while Ricci flat Lovelock-Born-Infeld
black holes having exotic horizons are stable in the presence of Maxwell field
or either Born Infeld field with large born Infeld parameter beta, unstable
phase appears for smaller values of beta, and therefore nonlinearity brings in
the instability.
| [
{
"created": "Wed, 11 Apr 2018 05:11:30 GMT",
"version": "v1"
}
] | 2018-05-09 | [
[
"Farhangkhah",
"N.",
""
]
] | We present the black hole solutions possessing horizon with nonconstant-curvature and additional scalar restrictions on the base manifold in Lovelock gravity coupled to Born-Infeld (BI) nonlinear electrodynamics. The asymptotic and near origin behavior of the metric is presented and we analyze different behaviors of the singularity. We find that, in contrast to the case of the black hole solutions of BI-Lovelock gravity with constant curvature horizon and Maxwell-Lovelock gravity with nonconstant horizon which has only timelike singularities, spacelike, and timelike singularities may exist for BI-Lovelock black holes with nonconstant curvature horizon. By calculating the thermodynamic quantities, we study the effects of nonlinear electrodynamics via the Born-Infeld action. Stability analysis shows that black holes with positive sectional curvature, k, possess an intermediate unstable phase and large and small black holes are stable. We see that while Ricci flat Lovelock-Born-Infeld black holes having exotic horizons are stable in the presence of Maxwell field or either Born Infeld field with large born Infeld parameter beta, unstable phase appears for smaller values of beta, and therefore nonlinearity brings in the instability. |
0902.2440 | Sunil Maharaj | S. D. Maharaj, S. Thirukkanesh | Generalised isothermal models with strange equation of state | 14 pages, To appear in Pramana - J. Phys | Pramana - J. Phys. 72: 481-494, 2009 | 10.1007/s12043-009-0043-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the linear equation of state for matter distributions that may be
applied to strange stars with quark matter. In our general approach the compact
relativistic body allows for anisotropic pressures in the presence of the
electromagnetic field. New exact solutions are found to the Einstein-Maxwell
system. A particular case is shown to be regular at the stellar centre. In the
isotropic limit we regain the general relativistic isothermal universe. We show
that the mass corresponds to values obtained previously for quark stars when
anisotropy and charge are present.
| [
{
"created": "Sat, 14 Feb 2009 08:15:58 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Maharaj",
"S. D.",
""
],
[
"Thirukkanesh",
"S.",
""
]
] | We consider the linear equation of state for matter distributions that may be applied to strange stars with quark matter. In our general approach the compact relativistic body allows for anisotropic pressures in the presence of the electromagnetic field. New exact solutions are found to the Einstein-Maxwell system. A particular case is shown to be regular at the stellar centre. In the isotropic limit we regain the general relativistic isothermal universe. We show that the mass corresponds to values obtained previously for quark stars when anisotropy and charge are present. |
1401.7378 | Kazuharu Bamba | Kazuharu Bamba, Shin'ichi Nojiri and Sergei D. Odintsov | Trace-anomaly driven inflation in $f(T)$ gravity and in minimal massive
bigravity | 13 pages, no figure, version accepted for publication in Physics
Letters B | Physics Letters B 731 (2014) 257-264 | 10.1016/j.physletb.2014.02.041 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore trace-anomaly driven inflation in modified gravity. It is
explicitly shown that in $T^2$ teleparallel gravity, the de Sitter inflation
can occur, although quasi de Sitter inflation happens in $R^2$ gravity.
Furthermore, we investigate the influence of the trace anomaly on inflation. It
is found that in $f(T)$ gravity, the de Sitter inflation can end because it
becomes unstable due to the trace anomaly, whereas also in higher derivative
gravity, the de Sitter inflation can be realized and it will be over thanks to
the trace anomaly for smaller parameter regions in comparison with those in
teleparallelism. The instability of the de Sitter inflation in $T^2$ gravity
and $R^2$ gravity (both with taking account of the trace anomaly) is examined.
In addition, we study trace-anomaly driven inflation in minimal massive
bigravity, where the contribution from the massive graviton acts as negative
cosmological constant. It is demonstrated that the de Sitter inflation can
occur and continue for long enough duration.
| [
{
"created": "Wed, 29 Jan 2014 00:49:37 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Feb 2014 01:36:21 GMT",
"version": "v2"
}
] | 2014-03-14 | [
[
"Bamba",
"Kazuharu",
""
],
[
"Nojiri",
"Shin'ichi",
""
],
[
"Odintsov",
"Sergei D.",
""
]
] | We explore trace-anomaly driven inflation in modified gravity. It is explicitly shown that in $T^2$ teleparallel gravity, the de Sitter inflation can occur, although quasi de Sitter inflation happens in $R^2$ gravity. Furthermore, we investigate the influence of the trace anomaly on inflation. It is found that in $f(T)$ gravity, the de Sitter inflation can end because it becomes unstable due to the trace anomaly, whereas also in higher derivative gravity, the de Sitter inflation can be realized and it will be over thanks to the trace anomaly for smaller parameter regions in comparison with those in teleparallelism. The instability of the de Sitter inflation in $T^2$ gravity and $R^2$ gravity (both with taking account of the trace anomaly) is examined. In addition, we study trace-anomaly driven inflation in minimal massive bigravity, where the contribution from the massive graviton acts as negative cosmological constant. It is demonstrated that the de Sitter inflation can occur and continue for long enough duration. |
gr-qc/0009077 | Juan Eloy Ayon Beato | Eloy Ay\'on-Beato, Alberto Garc\'ia | The Bardeen Model as a Nonlinear Magnetic Monopole | 4 pages, RevTex; accepted for publication in Phys. Lett. B | Phys.Lett. B493 (2000) 149-152 | 10.1016/S0370-2693(00)01125-4 | null | gr-qc hep-th | null | The Bardeen model -- the first regular black hole model in General Relativity
-- is reinterpreted as the gravitational field of a nonlinear magnetic
monopole, i.e., as a magnetic solution to Einstein equations coupled to a
nonlinear electrodynamics.
| [
{
"created": "Fri, 22 Sep 2000 00:44:55 GMT",
"version": "v1"
}
] | 2016-08-15 | [
[
"Ayón-Beato",
"Eloy",
""
],
[
"García",
"Alberto",
""
]
] | The Bardeen model -- the first regular black hole model in General Relativity -- is reinterpreted as the gravitational field of a nonlinear magnetic monopole, i.e., as a magnetic solution to Einstein equations coupled to a nonlinear electrodynamics. |
2405.18934 | Lorenzo Mirasola | Lorenzo Mirasola, Rodrigo Tenorio | Towards a computationally-efficient follow-up pipeline for blind
continuous gravitational-wave searches | 18 pages, 14 figures, comments welcome | null | null | LIGO-P2400221 | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The sensitivity of continuous gravitational-wave (CW) searches for unknown
neutron stars (NSs) is limited by their parameter space breadth. To fit within
reasonable computing budgets, hierarchical schemes are used to identify
interesting candidates using affordable methods. The resulting sensitivity
critically depends on the number of candidates selected to follow-up. In this
work, we present a novel framework to evaluate the effectiveness of stochastic
CW follow-ups. Our results in realistic datasets allow for a ten-fold reduction
of the computing cost of pyfstat, a well-established follow-up method. We also
simplify the setup of multi-stage follow-ups by removing the need for
parameter-space metrics. The study was conducted on Gaussian and real O3
Advanced LIGO data using realistic durations, and covered both isolated and
binary sources. These results will have a positive impact on the sensitivity of
all-sky searches in the forthcoming observing runs of the LIGO-Virgo-KAGRA
collaboration.
| [
{
"created": "Wed, 29 May 2024 09:38:04 GMT",
"version": "v1"
}
] | 2024-05-30 | [
[
"Mirasola",
"Lorenzo",
""
],
[
"Tenorio",
"Rodrigo",
""
]
] | The sensitivity of continuous gravitational-wave (CW) searches for unknown neutron stars (NSs) is limited by their parameter space breadth. To fit within reasonable computing budgets, hierarchical schemes are used to identify interesting candidates using affordable methods. The resulting sensitivity critically depends on the number of candidates selected to follow-up. In this work, we present a novel framework to evaluate the effectiveness of stochastic CW follow-ups. Our results in realistic datasets allow for a ten-fold reduction of the computing cost of pyfstat, a well-established follow-up method. We also simplify the setup of multi-stage follow-ups by removing the need for parameter-space metrics. The study was conducted on Gaussian and real O3 Advanced LIGO data using realistic durations, and covered both isolated and binary sources. These results will have a positive impact on the sensitivity of all-sky searches in the forthcoming observing runs of the LIGO-Virgo-KAGRA collaboration. |
1806.01903 | John W. Moffat | J. W. Moffat | Regular Rotating MOG Dark Compact Object | 9 pages, 2 figures. Article now matches published version | European Physical Journal C, 81:119 (2021) | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A regular rotating MOG (modified gravity) compact object is derived that
reduces to the Kerr black hole when the parameter $\alpha=0$. Physical
consequences of the dark compact object, which is regular everywhere in
spacetime for $\alpha > \alpha_{\rm crit}=0.674$ and is a rotating Kerr-MOG
black hole for $\alpha < \alpha_{\rm crit}$ are investigated.
| [
{
"created": "Tue, 5 Jun 2018 19:25:03 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Feb 2021 17:23:42 GMT",
"version": "v2"
}
] | 2021-02-15 | [
[
"Moffat",
"J. W.",
""
]
] | A regular rotating MOG (modified gravity) compact object is derived that reduces to the Kerr black hole when the parameter $\alpha=0$. Physical consequences of the dark compact object, which is regular everywhere in spacetime for $\alpha > \alpha_{\rm crit}=0.674$ and is a rotating Kerr-MOG black hole for $\alpha < \alpha_{\rm crit}$ are investigated. |
1209.0862 | Debaprasad Maity | Debaprasad Maity | Semi-realistic Bouncing Domain Wall Cosmology | 19 pages, 2 figures, Typos corrected and little change in title | null | 10.1103/PhysRevD.86.084056 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we constructed a semi-realistic cosmological model in a dynamic
domain wall framework. Our universe is considered to be a (3+1) dimensional
dynamic domain wall in a higher dimensional Einstein-Maxwell-Born-Infeld
background. One of our interesting outcomes from the effective Hubble equation
for the domain wall dynamics is that it contains an additional component of
"dark matter" which is induced from the charge of the bulk Born-Infeld gauge
field. In this background spacetime we have studied the cosmological dynamics
of the domain wall. In addition to the Born-Infield gauge field if we consider
additional pure gauge field, a non-singular bounce happens at the early stage
with a smooth transition between contracting and expanding phase.
| [
{
"created": "Wed, 5 Sep 2012 05:49:16 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Sep 2012 17:25:59 GMT",
"version": "v2"
}
] | 2013-05-30 | [
[
"Maity",
"Debaprasad",
""
]
] | In this paper we constructed a semi-realistic cosmological model in a dynamic domain wall framework. Our universe is considered to be a (3+1) dimensional dynamic domain wall in a higher dimensional Einstein-Maxwell-Born-Infeld background. One of our interesting outcomes from the effective Hubble equation for the domain wall dynamics is that it contains an additional component of "dark matter" which is induced from the charge of the bulk Born-Infeld gauge field. In this background spacetime we have studied the cosmological dynamics of the domain wall. In addition to the Born-Infield gauge field if we consider additional pure gauge field, a non-singular bounce happens at the early stage with a smooth transition between contracting and expanding phase. |
1708.07532 | Shannon Ray | Warner A. Miller, Shannon Ray, Mu-Tao Wang and Shing-Tung Yau | Wang and Yau's Quasi-Local Energy for an Extreme Kerr Spacetime | 25 pages, 10 figures | CQG-104058.R2, 2018 | 10.1088/1361-6382/aaa625 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There exist constant radial surfaces, $\mathcal{S}$, that may not be globally
embeddable in $\mathbb{R}^3$ for Kerr spacetimes with $a>\sqrt{3}M/2$. To
compute the Brown and York (B-Y) quasi-local energy (QLE), one must
isometrically embed $\mathcal{S}$ into $\mathbb{R}^3$. On the other hand, the
Wang and Yau (W-Y) QLE embeds $\mathcal{S}$ into Minkowski space. In this
paper, we examine the W-Y QLE for surfaces that may or may not be globally
embeddable in $\mathbb{R}^3$. We show that their energy functional, $E[\tau]$,
has a critical point at $\tau=0$ for all constant radial surfaces in
$t=constant$ hypersurfaces using Boyer-Lindquist coordinates. For $\tau=0$, the
W-Y QLE reduces to the B-Y QLE. To examine the W-Y QLE in these cases, we write
the functional explicitly in terms of $\tau$ under the assumption that $\tau$
is only a function of $\theta$. We then use a Fourier expansion of
$\tau\left(\theta\right)$ to explore the values of $E[\tau\left(\theta\right)]$
in the space of coefficients. From our analysis, we discovered an open region
of complex values for $E[\tau\left(\theta\right)]$. We also study the physical
properties of the smallest real value of $E[\tau\left(\theta\right)]$, which
lies on the boundary separating real and complex energies.
| [
{
"created": "Thu, 24 Aug 2017 19:26:08 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Jan 2018 19:23:34 GMT",
"version": "v2"
}
] | 2018-03-14 | [
[
"Miller",
"Warner A.",
""
],
[
"Ray",
"Shannon",
""
],
[
"Wang",
"Mu-Tao",
""
],
[
"Yau",
"Shing-Tung",
""
]
] | There exist constant radial surfaces, $\mathcal{S}$, that may not be globally embeddable in $\mathbb{R}^3$ for Kerr spacetimes with $a>\sqrt{3}M/2$. To compute the Brown and York (B-Y) quasi-local energy (QLE), one must isometrically embed $\mathcal{S}$ into $\mathbb{R}^3$. On the other hand, the Wang and Yau (W-Y) QLE embeds $\mathcal{S}$ into Minkowski space. In this paper, we examine the W-Y QLE for surfaces that may or may not be globally embeddable in $\mathbb{R}^3$. We show that their energy functional, $E[\tau]$, has a critical point at $\tau=0$ for all constant radial surfaces in $t=constant$ hypersurfaces using Boyer-Lindquist coordinates. For $\tau=0$, the W-Y QLE reduces to the B-Y QLE. To examine the W-Y QLE in these cases, we write the functional explicitly in terms of $\tau$ under the assumption that $\tau$ is only a function of $\theta$. We then use a Fourier expansion of $\tau\left(\theta\right)$ to explore the values of $E[\tau\left(\theta\right)]$ in the space of coefficients. From our analysis, we discovered an open region of complex values for $E[\tau\left(\theta\right)]$. We also study the physical properties of the smallest real value of $E[\tau\left(\theta\right)]$, which lies on the boundary separating real and complex energies. |
1707.02841 | Mahmood Roshan | Sara Jamali, Mahmood Roshan and Luca Amendola | On the cosmology of scalar-tensor-vector gravity theory | Accepted version for publication in JCAP | null | 10.1088/1475-7516/2018/01/048 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the cosmological consequences of a special scalar-tensor-vector
theory of gravity, known as MOG (for MOdified Gravity), proposed to address the
dark matter problem. This theory introduces two scalar fields $G(x)$ and
$\mu(x)$, and one vector field $\phi_{\alpha}(x)$, in addition to the metric
tensor. We set the corresponding self-interaction potentials to zero, as in the
standard form of MOG. Then using the phase space analysis in the flat
Friedmann-Robertson-Walker background, we show that the theory possesses a
viable sequence of cosmological epochs with acceptable time dependency for the
cosmic scale factor. We also investigate MOG's potential as a dark energy model
and show that extra fields in MOG cannot provide a late time accelerated
expansion. Furthermore, using a dynamical system approach to solve the
non-linear field equations numerically, we calculate the angular size of the
sound horizon, i.e. $\theta_{\text{s}}$, in MOG. We find that $8\times
10^{-3}\text{rad}<\theta_{\text{s}}<8.2\times 10^{-3} \text{rad} $ which is way
outside the current observational bounds. Finally, we generalize MOG to a
modified form called mMOG, and we find that mMOG passes the sound-horizon
constraint. However, mMOG also cannot be considered as a dark energy model
un;ess one adds a cosmological constant, and more importantly, the matter
dominated era is still slightly different from the standard case.
| [
{
"created": "Mon, 10 Jul 2017 13:24:23 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Jan 2018 05:11:16 GMT",
"version": "v2"
}
] | 2018-02-14 | [
[
"Jamali",
"Sara",
""
],
[
"Roshan",
"Mahmood",
""
],
[
"Amendola",
"Luca",
""
]
] | We consider the cosmological consequences of a special scalar-tensor-vector theory of gravity, known as MOG (for MOdified Gravity), proposed to address the dark matter problem. This theory introduces two scalar fields $G(x)$ and $\mu(x)$, and one vector field $\phi_{\alpha}(x)$, in addition to the metric tensor. We set the corresponding self-interaction potentials to zero, as in the standard form of MOG. Then using the phase space analysis in the flat Friedmann-Robertson-Walker background, we show that the theory possesses a viable sequence of cosmological epochs with acceptable time dependency for the cosmic scale factor. We also investigate MOG's potential as a dark energy model and show that extra fields in MOG cannot provide a late time accelerated expansion. Furthermore, using a dynamical system approach to solve the non-linear field equations numerically, we calculate the angular size of the sound horizon, i.e. $\theta_{\text{s}}$, in MOG. We find that $8\times 10^{-3}\text{rad}<\theta_{\text{s}}<8.2\times 10^{-3} \text{rad} $ which is way outside the current observational bounds. Finally, we generalize MOG to a modified form called mMOG, and we find that mMOG passes the sound-horizon constraint. However, mMOG also cannot be considered as a dark energy model un;ess one adds a cosmological constant, and more importantly, the matter dominated era is still slightly different from the standard case. |
gr-qc/0205065 | Stephen Parrott | Stephen Parrott | Asymptotics of a proposed delay-differential equation of motion for
charged particles | The previous version contained all the referees' reports, verbatim.
This version deletes them at the arXiv's request. The previous version is
available from the author--see Section 11, p. 27 for details | null | null | null | gr-qc | null | We study the behavior in the remote past and future of solutions of an
equation of motion for charged particles proposed by F. Rohrlich, for the
special case in which the motion is in one spatial dimension.
We show that if an external force is applied for a finite time, some
solutions exhibit the property of ``preacceleration'', meaning that the
particle accelerates before the force is applied, but that there do exist
solutions without preacceleration. However, most solutions without
preacceleration exhibit ``postacceleration'' into the infinite future (i.e.,
the particle accelerates after the force is removed). Some may consider such
behavior as sufficiently "unphysical" to rule out the equation.
More encouragingly, we show that analogs of the unphysical ``runaway''
solutions of the Lorentz-Dirac equation do not occur for solutions of
Rohrlich's equation. We show that when the external force eventually vanishes,
the proper acceleration vanishes asymptotically in the future, and the
coordinate velocity becomes asymptotically constant.
| [
{
"created": "Thu, 16 May 2002 02:55:43 GMT",
"version": "v1"
},
{
"created": "Thu, 30 May 2002 01:53:38 GMT",
"version": "v2"
},
{
"created": "Thu, 22 Apr 2004 05:56:43 GMT",
"version": "v3"
},
{
"created": "Wed, 28 Jul 2004 03:12:50 GMT",
"version": "v4"
},
{
"c... | 2007-05-23 | [
[
"Parrott",
"Stephen",
""
]
] | We study the behavior in the remote past and future of solutions of an equation of motion for charged particles proposed by F. Rohrlich, for the special case in which the motion is in one spatial dimension. We show that if an external force is applied for a finite time, some solutions exhibit the property of ``preacceleration'', meaning that the particle accelerates before the force is applied, but that there do exist solutions without preacceleration. However, most solutions without preacceleration exhibit ``postacceleration'' into the infinite future (i.e., the particle accelerates after the force is removed). Some may consider such behavior as sufficiently "unphysical" to rule out the equation. More encouragingly, we show that analogs of the unphysical ``runaway'' solutions of the Lorentz-Dirac equation do not occur for solutions of Rohrlich's equation. We show that when the external force eventually vanishes, the proper acceleration vanishes asymptotically in the future, and the coordinate velocity becomes asymptotically constant. |
2111.01595 | Mart\'in G. Richarte MR | Mart\'in G. Richarte, \'Ebano L. Martins, and J\'ulio C. Fabris | Scattering and absorption of a scalar field impinging on a charged black
hole in the Einstein-Maxwell-dilaton theory | Accepted for its publication in Physical Review D | null | 10.1103/PhysRevD.105.064043 | null | gr-qc astro-ph.GA hep-th math-ph math.MP physics.space-ph | http://creativecommons.org/licenses/by/4.0/ | This study revisits the absorption and scattering process by which a massless
scalar field impinges on a charged dilatonic black hole. First, we review the
classical analysis to obtain the deflection angle and the differential
scattering cross-section. Then, using the partial wave method, we determine the
total absorption cross-section numerically in terms of the decoupling parameter
called $M\omega$, finding that the amplitude of the dilatonic black hole is
lower than the Reissner-Nordstr\"om one for mild frequencies. In the
high-frequency limit, the absorption cross-section exhibits two different
complex behaviors; the fine structure and the hyperfine structure. For the
differential scattering cross-section, smaller values of $M\omega$ lead to more
significant amplitudes; the opposite scenario is obtained by increasing the
charge-to-mass ratio. To fully grasp the main properties of the charged
dilatonic black hole, we consider a different framework where the compact
object is impinged by a charged massive scalar field. The superradiant effect
is lessened for intermediate frequency concerning the Reissner-Nordstr\"om
case. However, this effect does not necessarily imply the existence of any
dynamical instability. In order to trigger the superradiant instability,
unstable modes must remain trapped outside the event horizon with a mechanism
based on the reflecting-mirror boundary conditions. In this way, a charged
scalar field plus a charged black hole configure a charged black hole bomb. We
provide an analytic formula (lower bound) for the values of the charge field,
which can trigger this superradiant instability. We extend this minimal setup
by considering the dilaton perturbations while freezing the other degree of
freedom. The new perturbation scheme enhances the superradiance scattering and
reduces the lower bound of the charge-to-mass ratio to develop a superradiant
instability.
| [
{
"created": "Tue, 2 Nov 2021 13:52:28 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Feb 2022 14:41:06 GMT",
"version": "v2"
},
{
"created": "Sat, 26 Feb 2022 13:35:01 GMT",
"version": "v3"
}
] | 2022-03-28 | [
[
"Richarte",
"Martín G.",
""
],
[
"Martins",
"Ébano L.",
""
],
[
"Fabris",
"Júlio C.",
""
]
] | This study revisits the absorption and scattering process by which a massless scalar field impinges on a charged dilatonic black hole. First, we review the classical analysis to obtain the deflection angle and the differential scattering cross-section. Then, using the partial wave method, we determine the total absorption cross-section numerically in terms of the decoupling parameter called $M\omega$, finding that the amplitude of the dilatonic black hole is lower than the Reissner-Nordstr\"om one for mild frequencies. In the high-frequency limit, the absorption cross-section exhibits two different complex behaviors; the fine structure and the hyperfine structure. For the differential scattering cross-section, smaller values of $M\omega$ lead to more significant amplitudes; the opposite scenario is obtained by increasing the charge-to-mass ratio. To fully grasp the main properties of the charged dilatonic black hole, we consider a different framework where the compact object is impinged by a charged massive scalar field. The superradiant effect is lessened for intermediate frequency concerning the Reissner-Nordstr\"om case. However, this effect does not necessarily imply the existence of any dynamical instability. In order to trigger the superradiant instability, unstable modes must remain trapped outside the event horizon with a mechanism based on the reflecting-mirror boundary conditions. In this way, a charged scalar field plus a charged black hole configure a charged black hole bomb. We provide an analytic formula (lower bound) for the values of the charge field, which can trigger this superradiant instability. We extend this minimal setup by considering the dilaton perturbations while freezing the other degree of freedom. The new perturbation scheme enhances the superradiance scattering and reduces the lower bound of the charge-to-mass ratio to develop a superradiant instability. |
1601.01382 | Lorenzo Iorio | Lorenzo Iorio | The Solar Lense-Thirring effect: perspectives for a future measurement | 3 pages, no figures, no tables, 10 references. Contribution to the
proceedings of "The Fourteenth Marcel Grossmann Meeting on General
Relativity" based on a talk delivered at the PT5 parallel session | The Fourteenth Marcel Grossmann Meeting: pp. 3679-3681, World
Scientific, 2017 | 10.1142/9789813226609_0479 | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The predicted Lense-Thirring perihelion precession of Mercury induced by the
Sun's angular momentum through its general relativistic gravitomagnetic field
amounts to 2 milliarcseconds per century. It turned out to be compatible with
the latest experimental determinations of the supplementary perihelion
precession of Mercury with the INPOP15a ephemerides, whose accuracy level has
nowadays reached the magnitude of the predicted relativistic effect itself
thanks to the analysis of some years of tracking data of the MESSENGER
spacecraft, which orbited Mercury from 2011 to 2015. A dedicated analysis of
three years of MESSENGER data with the DE ephemerides allowed for a $25\%$
determination of the Sun's angular momentum by means of the Lense-Thirring
effect, which turned out to be highly correlated with the signature due to the
Solar quadrupole mass moment $J_2^{\odot}$.
| [
{
"created": "Thu, 7 Jan 2016 03:13:57 GMT",
"version": "v1"
}
] | 2017-11-28 | [
[
"Iorio",
"Lorenzo",
""
]
] | The predicted Lense-Thirring perihelion precession of Mercury induced by the Sun's angular momentum through its general relativistic gravitomagnetic field amounts to 2 milliarcseconds per century. It turned out to be compatible with the latest experimental determinations of the supplementary perihelion precession of Mercury with the INPOP15a ephemerides, whose accuracy level has nowadays reached the magnitude of the predicted relativistic effect itself thanks to the analysis of some years of tracking data of the MESSENGER spacecraft, which orbited Mercury from 2011 to 2015. A dedicated analysis of three years of MESSENGER data with the DE ephemerides allowed for a $25\%$ determination of the Sun's angular momentum by means of the Lense-Thirring effect, which turned out to be highly correlated with the signature due to the Solar quadrupole mass moment $J_2^{\odot}$. |
1107.1688 | Darius Bunandar | Darius Bunandar, Scott A. Caveny, and Richard A. Matzner | Measuring emission coordinates in a pulsar-based relativistic
positioning system | 9 pages, 2 figures, v3: replaced with version accepted by Phys. Rev.
D | Physical Review D 84, 104005 (2011) | 10.1103/PhysRevD.84.104005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A relativistic deep space positioning system has been proposed using four or
more pulsars with stable repetition rates. (Each pulsar emits pulses at a fixed
repetition period in its rest frame.) The positioning system uses the fact that
an event in spacetime can be fully described by emission coordinates: the
proper emission time of each pulse measured at the event. The proper emission
time of each pulse from four different pulsars---interpolated as
necessary---provides the four spacetime coordinates of the reception event in
the emission coordinate system. If more than four pulsars are available, the
redundancy can improve the accuracy of the determination and/or resolve
degeneracies resulting from special geometrical arrangements of the sources and
the event.
We introduce a robust numerical approach to measure the emission coordinates
of an event in any arbitrary spacetime geometry. Our approach uses a continuous
solution of the eikonal equation describing the backward null cone from the
event. The pulsar proper time at the instant the null cone intersects the
pulsar world line is one of the four required coordinates. The process is
complete (modulo degeneracies) when four pulsar world lines have been crossed
by the light cone.
The numerical method is applied in two different examples: measuring emission
coordinates of an event in Minkowski spacetime using pulses from four pulsars
stationary in the spacetime; and measuring emission coordinates of an event in
Schwarzschild spacetime using pulses from four pulsars freely falling toward a
static black hole.
These numerical simulations are merely exploratory, but with improved
resolution and computational resources the method can be applied to more
pertinent problems. For instance one could measure the emission coordinates,
and therefore the trajectory, of the Earth.
| [
{
"created": "Fri, 8 Jul 2011 18:03:43 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Aug 2011 04:27:08 GMT",
"version": "v2"
},
{
"created": "Sun, 6 Nov 2011 12:34:29 GMT",
"version": "v3"
},
{
"created": "Thu, 8 Dec 2011 14:21:36 GMT",
"version": "v4"
}
] | 2011-12-09 | [
[
"Bunandar",
"Darius",
""
],
[
"Caveny",
"Scott A.",
""
],
[
"Matzner",
"Richard A.",
""
]
] | A relativistic deep space positioning system has been proposed using four or more pulsars with stable repetition rates. (Each pulsar emits pulses at a fixed repetition period in its rest frame.) The positioning system uses the fact that an event in spacetime can be fully described by emission coordinates: the proper emission time of each pulse measured at the event. The proper emission time of each pulse from four different pulsars---interpolated as necessary---provides the four spacetime coordinates of the reception event in the emission coordinate system. If more than four pulsars are available, the redundancy can improve the accuracy of the determination and/or resolve degeneracies resulting from special geometrical arrangements of the sources and the event. We introduce a robust numerical approach to measure the emission coordinates of an event in any arbitrary spacetime geometry. Our approach uses a continuous solution of the eikonal equation describing the backward null cone from the event. The pulsar proper time at the instant the null cone intersects the pulsar world line is one of the four required coordinates. The process is complete (modulo degeneracies) when four pulsar world lines have been crossed by the light cone. The numerical method is applied in two different examples: measuring emission coordinates of an event in Minkowski spacetime using pulses from four pulsars stationary in the spacetime; and measuring emission coordinates of an event in Schwarzschild spacetime using pulses from four pulsars freely falling toward a static black hole. These numerical simulations are merely exploratory, but with improved resolution and computational resources the method can be applied to more pertinent problems. For instance one could measure the emission coordinates, and therefore the trajectory, of the Earth. |
2403.20164 | Kfir Blum | Kfir Blum and Mehrdad Mirbabayi | A single-bubble source for gravitational waves in a cosmological phase
transition | 15 pages, 1 figure | null | null | null | gr-qc astro-ph.CO hep-ph | http://creativecommons.org/publicdomain/zero/1.0/ | We show that quantum fluctuations of an expanding phase transition bubble
give rise to gravitational wave (GW) emission, even when considering a single
bubble, without bubble collisions or plasma effects. The ratio of GW energy to
the total bubble energy reservoir increases with time as $\propto t$. If the
bubble expands for long enough before percolation destroys it, back-reaction
due to the GW emission becomes important after $t_{\rm br}\sim (16\pi^5) m_{\rm
pl}^2R_0^3$, where $R_0$ is the bubble nucleation radius and $m_{\rm pl}$ is
the reduced Planck mass. As seen by experiments today, the GW energy spectrum
would appear blue. However, simple estimates suggest that the signal falls
short of detection by even ambitious future experiments.
| [
{
"created": "Fri, 29 Mar 2024 13:28:16 GMT",
"version": "v1"
}
] | 2024-04-03 | [
[
"Blum",
"Kfir",
""
],
[
"Mirbabayi",
"Mehrdad",
""
]
] | We show that quantum fluctuations of an expanding phase transition bubble give rise to gravitational wave (GW) emission, even when considering a single bubble, without bubble collisions or plasma effects. The ratio of GW energy to the total bubble energy reservoir increases with time as $\propto t$. If the bubble expands for long enough before percolation destroys it, back-reaction due to the GW emission becomes important after $t_{\rm br}\sim (16\pi^5) m_{\rm pl}^2R_0^3$, where $R_0$ is the bubble nucleation radius and $m_{\rm pl}$ is the reduced Planck mass. As seen by experiments today, the GW energy spectrum would appear blue. However, simple estimates suggest that the signal falls short of detection by even ambitious future experiments. |
1903.03437 | Behnam Pourhassan | M. Rostami, J. Sadeghi, S. Miraboutalebi, and B. Pourhassan | The temperature and entropy corrections on the charged hairy black holes | 23 pages, 13 figures | Annals of Physics 429 (2021) 168488 | 10.1016/j.aop.2021.168488 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we consider the first order correction of the entropy and
temperature in a charged black hole with a scalar field. Here, we apply such
correction for the different cases of black holes. These corrections are due to
the thermal fluctuations of statistical physics. Also, we take advantage of
such corrections and study the $ P - V $ critically and phase transition. Also,
we investigate the effect of correction on the critical point and stability of
the system. We obtain modified thermodynamics quantities and find effects of
thermal fluctuations in the stability of the black hole. We find that stability
of black hole is depend on the thermal fluctuations. Finally, we compare the
results of the corrected and uncorrected by thermodynamical quantities.
| [
{
"created": "Mon, 4 Mar 2019 06:48:55 GMT",
"version": "v1"
},
{
"created": "Wed, 15 May 2019 19:48:43 GMT",
"version": "v2"
}
] | 2021-05-11 | [
[
"Rostami",
"M.",
""
],
[
"Sadeghi",
"J.",
""
],
[
"Miraboutalebi",
"S.",
""
],
[
"Pourhassan",
"B.",
""
]
] | In this paper, we consider the first order correction of the entropy and temperature in a charged black hole with a scalar field. Here, we apply such correction for the different cases of black holes. These corrections are due to the thermal fluctuations of statistical physics. Also, we take advantage of such corrections and study the $ P - V $ critically and phase transition. Also, we investigate the effect of correction on the critical point and stability of the system. We obtain modified thermodynamics quantities and find effects of thermal fluctuations in the stability of the black hole. We find that stability of black hole is depend on the thermal fluctuations. Finally, we compare the results of the corrected and uncorrected by thermodynamical quantities. |
gr-qc/0205128 | Ari Tapani Peltola | J. Makela and A. Peltola | Thermodynamical Properties of Horizons | 13 pages, 3 figures | null | null | null | gr-qc | null | We show, by using Regge calculus, that the entropy of any finite part of a
Rindler horizon is, in the semi-classical limit, one quarter of the area of
that part. We argue that this result implies that the entropy associated with
any horizon of spacetime is, in semi-classical limit, one quarter of its area.
As an example, we derive the Bekenstein-Hawking entropy law for the
Schwarzschild black hole.
| [
{
"created": "Thu, 30 May 2002 12:30:47 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Makela",
"J.",
""
],
[
"Peltola",
"A.",
""
]
] | We show, by using Regge calculus, that the entropy of any finite part of a Rindler horizon is, in the semi-classical limit, one quarter of the area of that part. We argue that this result implies that the entropy associated with any horizon of spacetime is, in semi-classical limit, one quarter of its area. As an example, we derive the Bekenstein-Hawking entropy law for the Schwarzschild black hole. |
2311.18066 | Beatriz Elizaga Navascu\'es | Beatriz Elizaga Navascu\'es | On the evolution of the volume in Loop Quantum Cosmology | 11 pages, revised version | Class. Quantum Grav. 41, 145004, 2024 | 10.1088/1361-6382/ad56ee | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dynamics of the expectation value of the volume is one of the key
ingredients behind the replacement of the Big Bang singularity by a bounce in
Loop Quantum Cosmology. As such, it is of great importance that this quantity
is mathematically well-defined in the space of physical states of the theory. A
number of caveats have been raised about such a definition entering in conflict
with the quantum evolution of states, motivated by the situation found in
quantum geometrodynamics. We show that there are ways around these caveats, all
of which are related to the existence of quantization prescriptions leading to
a nondegenerate curvature operator in Loop Quantum Cosmology. Interestingly,
the properties of the curvature operator that may allow for a good behavior of
the volume are only possible thanks to the discreteness of the geometry
characteristic of the loop quantization procedure.
| [
{
"created": "Wed, 29 Nov 2023 20:30:00 GMT",
"version": "v1"
},
{
"created": "Mon, 13 May 2024 21:08:45 GMT",
"version": "v2"
}
] | 2024-07-04 | [
[
"Navascués",
"Beatriz Elizaga",
""
]
] | The dynamics of the expectation value of the volume is one of the key ingredients behind the replacement of the Big Bang singularity by a bounce in Loop Quantum Cosmology. As such, it is of great importance that this quantity is mathematically well-defined in the space of physical states of the theory. A number of caveats have been raised about such a definition entering in conflict with the quantum evolution of states, motivated by the situation found in quantum geometrodynamics. We show that there are ways around these caveats, all of which are related to the existence of quantization prescriptions leading to a nondegenerate curvature operator in Loop Quantum Cosmology. Interestingly, the properties of the curvature operator that may allow for a good behavior of the volume are only possible thanks to the discreteness of the geometry characteristic of the loop quantization procedure. |
2011.11166 | Julio C\'esar Vera Hern\'andez | Julio C\'esar Vera-Hern\'andez | Quantum Phase Space Description of a Cosmological Minimal Massive
Bigravity Model | This is a post-peer-review, pre-copyedit version of an article
published in General Relativity and Gravitation. The final authenticated
version is available online at: https://doi.org/10.1007/s10714-021-02822-2 25
pages, 10 figures | null | 10.1007/s10714-021-02822-2 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | Bimetric gravity theories describes gravitational interactions in the
presence of an extra spin-2 field. The Hassan-Rosen (HR) nonlinear massive
minimal bigravity theory is a ghost-free bimetric theory formulated with
respect a flat, dynamical reference metric. In this work the deformation
quantization formalism is applied to a HR cosmological model in the
minisuperspace. The quantization procedure is performed explicitly for quantum
cosmology in the minisuperspace. The Friedmann-Lema\^itre-Robertson-Walker
(FLRW) model with flat metrics is worked out and the computation of the Wigner
functions for theHartle-Hawking, Vilenkin and Linde wavefunctions are done
numerically and, in the Hartle-Hawking case, also analytically. From the
stability analysis in the quantum minisuper phase space it is found an
interpretation of the mass of graviton as an emergent cosmological constant and
as a measure of the deviation of classical behavior of the Wigner functions.
Also, from the Hartle-Hawking case, an interesting relation between the
curvature and the mass of graviton in a cusp catastrophe surface is discussed
| [
{
"created": "Mon, 23 Nov 2020 01:47:32 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Apr 2021 16:45:49 GMT",
"version": "v2"
},
{
"created": "Mon, 26 Apr 2021 17:11:59 GMT",
"version": "v3"
},
{
"created": "Wed, 26 May 2021 20:38:35 GMT",
"version": "v4"
}
] | 2021-05-28 | [
[
"Vera-Hernández",
"Julio César",
""
]
] | Bimetric gravity theories describes gravitational interactions in the presence of an extra spin-2 field. The Hassan-Rosen (HR) nonlinear massive minimal bigravity theory is a ghost-free bimetric theory formulated with respect a flat, dynamical reference metric. In this work the deformation quantization formalism is applied to a HR cosmological model in the minisuperspace. The quantization procedure is performed explicitly for quantum cosmology in the minisuperspace. The Friedmann-Lema\^itre-Robertson-Walker (FLRW) model with flat metrics is worked out and the computation of the Wigner functions for theHartle-Hawking, Vilenkin and Linde wavefunctions are done numerically and, in the Hartle-Hawking case, also analytically. From the stability analysis in the quantum minisuper phase space it is found an interpretation of the mass of graviton as an emergent cosmological constant and as a measure of the deviation of classical behavior of the Wigner functions. Also, from the Hartle-Hawking case, an interesting relation between the curvature and the mass of graviton in a cusp catastrophe surface is discussed |
0907.1169 | Deepak Baskaran Dr. | W. Zhao, D. Baskaran, L. P. Grishchuk | Stable indications of relic gravitational waves in Wilkinson Microwave
Anisotropy Probe data and forecasts for the Planck mission | 21 pages, including 12 figures, 2 tables, 2 appendices. Published in
Phys. Rev. D. V.3: minor corrections made to reflect the published version | Phys.Rev.D80:083005,2009 | 10.1103/PhysRevD.80.083005 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The relic gravitational waves (gw) are the cleanest probe of the violent
times in the very early history of the Universe. They are expected to leave
signatures in the observed cosmic microwave background anisotropies. We
significantly improved our previous analysis [1] of the 5-year WMAP $TT$ and
$TE$ data at lower multipoles $\ell$. This more general analysis returned
essentially the same maximum likelihood (ML) result (unfortunately, surrounded
by large remaining uncertainties): the relic gw are present and they are
responsible for approximately 20% of the temperature quadrupole. We identify
and discuss the reasons by which the contribution of gw can be overlooked in a
data analysis. One of the reasons is a misleading reliance on data from very
high multipoles $\ell$, another - a too narrow understanding of the problem as
the search for $B$-modes of polarization, rather than the detection of relic gw
with the help of all correlation functions. Our analysis of WMAP5 data has led
to the identification of a whole family of models characterized by relatively
high values of the likelihood function. Using the Fisher matrix formalism we
formulated forecasts for {\it Planck} mission in the context of this family of
models. We explore in details various `optimistic', `pessimistic' and `dream
case' scenarios. We show that in some circumstances the $B$-mode detection may
be very inconclusive, at the level of signal-to-noise ratio $S/N =1.75$,
whereas a smarter data analysis can reveal the same gw signal at $S/N= 6.48$.
The final result is encouraging. Even under unfavourable conditions in terms of
instrumental noises and foregrounds, the relic gw, if they are characterized by
the ML parameters that we found from WMAP5 data, will be detected by {\it
Planck} at the level $S/N = 3.65$.
| [
{
"created": "Tue, 7 Jul 2009 09:31:37 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Sep 2009 10:55:56 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Oct 2009 13:24:22 GMT",
"version": "v3"
}
] | 2009-11-06 | [
[
"Zhao",
"W.",
""
],
[
"Baskaran",
"D.",
""
],
[
"Grishchuk",
"L. P.",
""
]
] | The relic gravitational waves (gw) are the cleanest probe of the violent times in the very early history of the Universe. They are expected to leave signatures in the observed cosmic microwave background anisotropies. We significantly improved our previous analysis [1] of the 5-year WMAP $TT$ and $TE$ data at lower multipoles $\ell$. This more general analysis returned essentially the same maximum likelihood (ML) result (unfortunately, surrounded by large remaining uncertainties): the relic gw are present and they are responsible for approximately 20% of the temperature quadrupole. We identify and discuss the reasons by which the contribution of gw can be overlooked in a data analysis. One of the reasons is a misleading reliance on data from very high multipoles $\ell$, another - a too narrow understanding of the problem as the search for $B$-modes of polarization, rather than the detection of relic gw with the help of all correlation functions. Our analysis of WMAP5 data has led to the identification of a whole family of models characterized by relatively high values of the likelihood function. Using the Fisher matrix formalism we formulated forecasts for {\it Planck} mission in the context of this family of models. We explore in details various `optimistic', `pessimistic' and `dream case' scenarios. We show that in some circumstances the $B$-mode detection may be very inconclusive, at the level of signal-to-noise ratio $S/N =1.75$, whereas a smarter data analysis can reveal the same gw signal at $S/N= 6.48$. The final result is encouraging. Even under unfavourable conditions in terms of instrumental noises and foregrounds, the relic gw, if they are characterized by the ML parameters that we found from WMAP5 data, will be detected by {\it Planck} at the level $S/N = 3.65$. |
2209.00327 | Sumati Surya | P. Carlip, S. Carlip, S. Surya | Path integral suppression of badly behaved causal sets | 10 pages, 2 figures | null | 10.1088/1361-6382/acc50c | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Causal set theory is a discrete model of spacetime that retains a notion of
causal structure. We understand how to construct causal sets that approximate a
given spacetime, but most causal sets are not at all manifold-like, and must be
dynamically excluded if something like our universe is to emerge from the
theory. Here we show that the most common of these "bad" causal sets, the
Kleitman-Rothschild orders, are strongly suppressed in the gravitational path
integral, and we provide evidence that a large class of other "bad" causal sets
are similarly suppressed. It thus becomes plausible that continuum behavior
could emerge naturally from causal set quantum theory.
| [
{
"created": "Thu, 1 Sep 2022 09:55:30 GMT",
"version": "v1"
}
] | 2023-04-12 | [
[
"Carlip",
"P.",
""
],
[
"Carlip",
"S.",
""
],
[
"Surya",
"S.",
""
]
] | Causal set theory is a discrete model of spacetime that retains a notion of causal structure. We understand how to construct causal sets that approximate a given spacetime, but most causal sets are not at all manifold-like, and must be dynamically excluded if something like our universe is to emerge from the theory. Here we show that the most common of these "bad" causal sets, the Kleitman-Rothschild orders, are strongly suppressed in the gravitational path integral, and we provide evidence that a large class of other "bad" causal sets are similarly suppressed. It thus becomes plausible that continuum behavior could emerge naturally from causal set quantum theory. |
gr-qc/0109092 | I. B. Khriplovich | I.B. Khriplovich | Entropy and Area of Black Holes in Loop Quantum Gravity | 8 pages, no figures; more detailed presentation of the arguments, the
results unchanged | Phys.Lett. B537 (2002) 125-129 | 10.1016/S0370-2693(02)01914-7 | null | gr-qc | null | Simple arguments related to the entropy of black holes strongly constrain the
spectrum of the area operator for a Schwarzschild black hole in loop quantum
gravity. In particular, this spectrum is fixed completely by the assumption
that the black hole entropy is maximum. Within the approach discussed, one
arrives in loop quantum gravity at a quantization rule with integer quantum
numbers $n$ for the entropy and area of a black hole.
| [
{
"created": "Fri, 28 Sep 2001 07:16:26 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Oct 2001 08:14:19 GMT",
"version": "v2"
},
{
"created": "Sun, 31 Mar 2002 06:06:06 GMT",
"version": "v3"
}
] | 2009-11-07 | [
[
"Khriplovich",
"I. B.",
""
]
] | Simple arguments related to the entropy of black holes strongly constrain the spectrum of the area operator for a Schwarzschild black hole in loop quantum gravity. In particular, this spectrum is fixed completely by the assumption that the black hole entropy is maximum. Within the approach discussed, one arrives in loop quantum gravity at a quantization rule with integer quantum numbers $n$ for the entropy and area of a black hole. |
gr-qc/0104019 | Juan M. Aguirregabiria | J. M. Aguirregabiria, Ll. Bel, J. Martin, A. Molina and E. Ruiz | Comparing metrics at large: harmonic vs quo-harmonic coordinates | 27 pages, no figures | Gen.Rel.Grav. 33 (2001) 1809-1838 | 10.1023/A:1013083419220 | null | gr-qc | null | To compare two space-times on large domains, and in particular the global
structure of their manifolds, requires using identical frames of reference and
associated coordinate conditions. In this paper we use and compare two classes
of time-like congruences and corresponding adapted coordinates: the harmonic
and quo-harmonic classes. Besides the intrinsic definition and some of their
intrinsic properties and differences we consider with some detail their
differences at the level of the linearized approximation of the field
equations. The hard part of this paper is an explicit and general determination
of the harmonic and quo-harmonic coordinates adapted to the stationary
character of three well-know metrics, Schwarzschild's, Curzon's and Kerr's, to
order five of their asymptotic expansions. It also contains some relevant
remarks on such problems as defining the multipoles of vacuum solutions or
matching interior and exterior solutions.
| [
{
"created": "Thu, 5 Apr 2001 07:29:28 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Aguirregabiria",
"J. M.",
""
],
[
"Bel",
"Ll.",
""
],
[
"Martin",
"J.",
""
],
[
"Molina",
"A.",
""
],
[
"Ruiz",
"E.",
""
]
] | To compare two space-times on large domains, and in particular the global structure of their manifolds, requires using identical frames of reference and associated coordinate conditions. In this paper we use and compare two classes of time-like congruences and corresponding adapted coordinates: the harmonic and quo-harmonic classes. Besides the intrinsic definition and some of their intrinsic properties and differences we consider with some detail their differences at the level of the linearized approximation of the field equations. The hard part of this paper is an explicit and general determination of the harmonic and quo-harmonic coordinates adapted to the stationary character of three well-know metrics, Schwarzschild's, Curzon's and Kerr's, to order five of their asymptotic expansions. It also contains some relevant remarks on such problems as defining the multipoles of vacuum solutions or matching interior and exterior solutions. |
gr-qc/0607037 | Joan Josep Ferrando | Bartolom\'e Coll, Joan Josep Ferrando, Juan Antonio Morales | Positioning with stationary emitters in a two-dimensional space-time | 14 pages; 5 figures | Phys.Rev. D74 (2006) 104003 | 10.1103/PhysRevD.74.104003 | null | gr-qc | null | The basic elements of the relativistic positioning systems in a
two-dimensional space-time have been introduced in a previous work [Phys. Rev.
D {\bf 73}, 084017 (2006)] where geodesic positioning systems, constituted by
two geodesic emitters, have been considered in a flat space-time. Here, we want
to show in what precise senses positioning systems allow to make {\em
relativistic gravimetry}. For this purpose, we consider stationary positioning
systems, constituted by two uniformly accelerated emitters separated by a
constant distance, in two different situations: absence of gravitational field
(Minkowski plane) and presence of a gravitational mass (Schwarzschild plane).
The physical coordinate system constituted by the electromagnetic signals
broadcasting the proper time of the emitters are the so called {\em emission
coordinates}, and we show that, in such emission coordinates, the trajectories
of the emitters in both situations, absence and presence of a gravitational
field, are identical. The interesting point is that, in spite of this fact,
particular additional information on the system or on the user allows not only
to distinguish both space-times, but also to complete the dynamical description
of emitters and user and even to measure the mass of the gravitational field.
The precise information under which these dynamical and gravimetric results may
be obtained is carefully pointed out.
| [
{
"created": "Mon, 10 Jul 2006 14:27:25 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Nov 2006 13:41:02 GMT",
"version": "v2"
}
] | 2016-08-16 | [
[
"Coll",
"Bartolomé",
""
],
[
"Ferrando",
"Joan Josep",
""
],
[
"Morales",
"Juan Antonio",
""
]
] | The basic elements of the relativistic positioning systems in a two-dimensional space-time have been introduced in a previous work [Phys. Rev. D {\bf 73}, 084017 (2006)] where geodesic positioning systems, constituted by two geodesic emitters, have been considered in a flat space-time. Here, we want to show in what precise senses positioning systems allow to make {\em relativistic gravimetry}. For this purpose, we consider stationary positioning systems, constituted by two uniformly accelerated emitters separated by a constant distance, in two different situations: absence of gravitational field (Minkowski plane) and presence of a gravitational mass (Schwarzschild plane). The physical coordinate system constituted by the electromagnetic signals broadcasting the proper time of the emitters are the so called {\em emission coordinates}, and we show that, in such emission coordinates, the trajectories of the emitters in both situations, absence and presence of a gravitational field, are identical. The interesting point is that, in spite of this fact, particular additional information on the system or on the user allows not only to distinguish both space-times, but also to complete the dynamical description of emitters and user and even to measure the mass of the gravitational field. The precise information under which these dynamical and gravimetric results may be obtained is carefully pointed out. |
0706.2319 | Irene Brito | E.G.L.R. Vaz and Irene Brito | Analysing the elasticity difference tensor of general relativity | 17 pages | Gen.Rel.Grav.40:1947-1966,2008 | 10.1007/s10714-008-0615-7 | null | gr-qc | null | The elasticity difference tensor, used in [1] to describe elasticity
properties of a continuous medium filling a space-time, is here analysed from
the point of view of the space-time connection. Principal directions associated
with this tensor are compared with eigendirections of the material metric.
Examples concerning spherically symmetric and axially symmetric space-times are
then presented.
| [
{
"created": "Fri, 15 Jun 2007 15:35:51 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Vaz",
"E. G. L. R.",
""
],
[
"Brito",
"Irene",
""
]
] | The elasticity difference tensor, used in [1] to describe elasticity properties of a continuous medium filling a space-time, is here analysed from the point of view of the space-time connection. Principal directions associated with this tensor are compared with eigendirections of the material metric. Examples concerning spherically symmetric and axially symmetric space-times are then presented. |
gr-qc/0312046 | Floyd Williams | Floyd L. Williams | Remarks on harmonic maps, solitons, and dilaton gravity | 3 pages, to appear | null | null | null | gr-qc | null | Another connection of harmonic maps to gravity is presented. Using 1-soliton
and anti-soliton solutions of the sine-Gordon equation, we construct a pair of
harmonic maps that we express in terms of a particular dilaton field in
Jackiw-Teitelboim gravity. This field satisfies a linearized sine-Gordon
equation. We use it also to construct an explicit transformation that relates
the corresponding solitonic metric to a two dimensional black hole metric.
| [
{
"created": "Mon, 8 Dec 2003 21:15:44 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Williams",
"Floyd L.",
""
]
] | Another connection of harmonic maps to gravity is presented. Using 1-soliton and anti-soliton solutions of the sine-Gordon equation, we construct a pair of harmonic maps that we express in terms of a particular dilaton field in Jackiw-Teitelboim gravity. This field satisfies a linearized sine-Gordon equation. We use it also to construct an explicit transformation that relates the corresponding solitonic metric to a two dimensional black hole metric. |
1109.4086 | Bernd Schroers | Prince K. Osei and Bernd J. Schroers | On the semiduals of local isometry groups in 3d gravity | 33 pages, new version with expanded introduction and discussion,
similar to version which will appear in Journal of Mathematical Physics | null | 10.1063/1.4731229 | EMPG-11-23 | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use factorisations of the local isometry groups arising in 3d gravity for
Lorentzian and Euclidean signatures and any value of the cosmological constant
to construct associated bicrossproduct quantum groups via semidualisation. In
this way we obtain quantum doubles of the Lorentz and rotation groups in 3d, as
well as kappa-Poincare algebras whose associated r-matrices have spacelike,
timelike and lightlike deformation parameters. We confirm and elaborate the
interpretation of semiduality proposed in [13] as the exchange of the
cosmological length scale and the Planck mass in the context of 3d quantum
gravity. In particular, semiduality gives a simple understanding of why the
quantum double of the Lorentz group and the kappa-Poincare algebra with
spacelike deformation parameter are both associated to 3d gravity with
vanishing cosmological constant, while the kappa-Poincare algebra with a
timelike deformation parameter can only be associated to 3d gravity if one
takes the Planck mass to be imaginary.
| [
{
"created": "Mon, 19 Sep 2011 16:41:59 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Nov 2011 14:17:07 GMT",
"version": "v2"
},
{
"created": "Thu, 28 Jun 2012 20:53:54 GMT",
"version": "v3"
}
] | 2015-05-30 | [
[
"Osei",
"Prince K.",
""
],
[
"Schroers",
"Bernd J.",
""
]
] | We use factorisations of the local isometry groups arising in 3d gravity for Lorentzian and Euclidean signatures and any value of the cosmological constant to construct associated bicrossproduct quantum groups via semidualisation. In this way we obtain quantum doubles of the Lorentz and rotation groups in 3d, as well as kappa-Poincare algebras whose associated r-matrices have spacelike, timelike and lightlike deformation parameters. We confirm and elaborate the interpretation of semiduality proposed in [13] as the exchange of the cosmological length scale and the Planck mass in the context of 3d quantum gravity. In particular, semiduality gives a simple understanding of why the quantum double of the Lorentz group and the kappa-Poincare algebra with spacelike deformation parameter are both associated to 3d gravity with vanishing cosmological constant, while the kappa-Poincare algebra with a timelike deformation parameter can only be associated to 3d gravity if one takes the Planck mass to be imaginary. |
2204.04451 | Vinod Bhardwaj Dr. | Vinod Kumar Bhardwaj, Archana Dixit, Rita Rani, G. K. Goswami, Anirudh
Pradhan | An Axially Symmetric Transitioning models with Observational Constraints | 19 pages, 10 figures | null | 10.1016/j.cjph.2022.09.007 | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | In this study, we have demonstrated the expansion history of an axially
symmetric Bianchi type-I model of the universe. Our model as of now presents an
accelerating universe, which had been in the decelerating phase in the past.
Roles of the two crucial Hubble~$H(z)$ and deceleration~$q(z)$ parameters are
examined. The energy parameters of the universe are estimated with the help of
the latest observational Hubble data (46-data points) and Pantheon data (the
latest compilation of SNIa with 40 binned in the redshift range $0.014 \leq z
\leq 1.62)$. We also discuss the stability analysis of the model by state
finder diagnosis. The analysis reveals that in late time, the model is a
quintessence type and points towards the $\Lambda$CDM model. Our developed
model agrees with observational findings in a proper way. We have discussed
some of the physical aspects of the model.
| [
{
"created": "Sat, 9 Apr 2022 11:27:10 GMT",
"version": "v1"
}
] | 2022-11-30 | [
[
"Bhardwaj",
"Vinod Kumar",
""
],
[
"Dixit",
"Archana",
""
],
[
"Rani",
"Rita",
""
],
[
"Goswami",
"G. K.",
""
],
[
"Pradhan",
"Anirudh",
""
]
] | In this study, we have demonstrated the expansion history of an axially symmetric Bianchi type-I model of the universe. Our model as of now presents an accelerating universe, which had been in the decelerating phase in the past. Roles of the two crucial Hubble~$H(z)$ and deceleration~$q(z)$ parameters are examined. The energy parameters of the universe are estimated with the help of the latest observational Hubble data (46-data points) and Pantheon data (the latest compilation of SNIa with 40 binned in the redshift range $0.014 \leq z \leq 1.62)$. We also discuss the stability analysis of the model by state finder diagnosis. The analysis reveals that in late time, the model is a quintessence type and points towards the $\Lambda$CDM model. Our developed model agrees with observational findings in a proper way. We have discussed some of the physical aspects of the model. |
gr-qc/0106089 | Hans-Juergen Schmidt | H.-J. Schmidt, U. Semmelmann | Cosmic strings and strings in gravitational waves | 13 pages, LaTeX, reprinted from Astron. Nachr. 310 (1989) 103 | null | null | Report UNIPO-MATH-01-JUN-25 | gr-qc | null | We consider strings with the Nambu action as extremal surfaces in a given
space-time, thus, we ignore their back reaction. Especially, we look for
strings sharing one symmetry with the underlying space-time. If this is a
non-null symmetry, the problem of determining the motion of the string can be
dimensionally reduced. We get exact solutions for the following cases: straight
and circle-like strings in a Friedmann background, straight strings in an
anisotropic Kasner background, different types of strings in the metric of a
gravitational wave. The solutions will be discussed.
| [
{
"created": "Thu, 28 Jun 2001 10:36:39 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Schmidt",
"H. -J.",
""
],
[
"Semmelmann",
"U.",
""
]
] | We consider strings with the Nambu action as extremal surfaces in a given space-time, thus, we ignore their back reaction. Especially, we look for strings sharing one symmetry with the underlying space-time. If this is a non-null symmetry, the problem of determining the motion of the string can be dimensionally reduced. We get exact solutions for the following cases: straight and circle-like strings in a Friedmann background, straight strings in an anisotropic Kasner background, different types of strings in the metric of a gravitational wave. The solutions will be discussed. |
2006.03946 | Shin'ichi Nojiri | Shin'ichi Nojiri and Sergei D. Odintsov | The dark universe future and singularities: the account of thermal and
quantum effects | LaTeX, 11 pages, to appear in Physics of the Dark Universe | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The knowledge of the universe future is of fundamental importance for any
advanced civilization. We study the future of singular dark universe where
thermal effects due to the Hawking radiation on the apparent horizon of the FRW
universe are taken in consideration. It is shown that dark universe which ends
up at finite-time Type I and Type III singularity or infinite-time Little Rip
singularity transits to finite-time Type II singularity due to account of
thermal effects. On the same time, the Type II and IV singular universe does
not change its qualitative behavior. The combined account of quantum and
thermal effects shows that depending on specific features of the universe only
one of effects is dominant. When (conformal matter) quantum effects are
dominant, the future singularity is usually removed while for dominant thermal
effects the universe final state is the Type II singularity.
| [
{
"created": "Sat, 6 Jun 2020 19:18:16 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Jul 2020 23:01:40 GMT",
"version": "v2"
}
] | 2020-07-27 | [
[
"Nojiri",
"Shin'ichi",
""
],
[
"Odintsov",
"Sergei D.",
""
]
] | The knowledge of the universe future is of fundamental importance for any advanced civilization. We study the future of singular dark universe where thermal effects due to the Hawking radiation on the apparent horizon of the FRW universe are taken in consideration. It is shown that dark universe which ends up at finite-time Type I and Type III singularity or infinite-time Little Rip singularity transits to finite-time Type II singularity due to account of thermal effects. On the same time, the Type II and IV singular universe does not change its qualitative behavior. The combined account of quantum and thermal effects shows that depending on specific features of the universe only one of effects is dominant. When (conformal matter) quantum effects are dominant, the future singularity is usually removed while for dominant thermal effects the universe final state is the Type II singularity. |
1412.4228 | Ettore Minguzzi | E. Minguzzi | An equivalence of Finslerian relativistic theories | 11 pages. v2: shortened introduction, added references. Changed
title. The previous title was: The definition of Finsler spacetime | Rep. Math. Phys. 77 (2016) 45-55 | 10.1016/S0034-4877(16)30004-0 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Lorentz-Finsler geometry it is natural to define the Finsler Lagrangian
over a cone (Asanov's approach) or over the whole slit tangent bundle (Beem's
approach). In the former case one might want to add differentiability
conditions at the boundary of the (timelike) cone in order to retain the usual
definition of lightlike geodesics. It is shown here that if this is done then
the two theories coincide, namely the `conic' Finsler Lagrangian is the
restriction of a slit tangent bundle Lagrangian. Since causality theory depends
on curves defined through the future cone, this work establishes the essential
uniqueness of (sufficiently regular) Finsler spacetime theories and Finsler
causality.
| [
{
"created": "Sat, 13 Dec 2014 12:08:06 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Sep 2015 14:18:35 GMT",
"version": "v2"
}
] | 2016-06-28 | [
[
"Minguzzi",
"E.",
""
]
] | In Lorentz-Finsler geometry it is natural to define the Finsler Lagrangian over a cone (Asanov's approach) or over the whole slit tangent bundle (Beem's approach). In the former case one might want to add differentiability conditions at the boundary of the (timelike) cone in order to retain the usual definition of lightlike geodesics. It is shown here that if this is done then the two theories coincide, namely the `conic' Finsler Lagrangian is the restriction of a slit tangent bundle Lagrangian. Since causality theory depends on curves defined through the future cone, this work establishes the essential uniqueness of (sufficiently regular) Finsler spacetime theories and Finsler causality. |
1412.1199 | Ahmad Borzou | Ahmad Borzou | A Lorentz Gauge Theory of Gravity | 13 pages, 5 figures, accepted for publication in CQG | Class. Quantum Grav. 33 (2016) 025008 | 10.1088/0264-9381/33/2/025008 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a Lorentz gauge theory of gravity in which the metric is not
dynamical. Spherically symmetric weak field solutions are studied. We show that
this solution contains the Schwarzschild spacetime at least to the first order
of perturbation. Next, we present a special case of the theory. It is shown
that the Schwarzschild metric is now an exact solution. Moreover, we show that
the de Sitter space is an exact vacuum solution and as a result the theory is
able to explain the expansion of the universe with no need for a dark energy.
Within this special case, quantization of the theory is also studied. The basic
Feynman diagrams are derived and renormalizability of the theory is studied
using the power-counting method. We show that under a certain condition the
theory is power-counting renormalizable.
| [
{
"created": "Wed, 3 Dec 2014 05:47:38 GMT",
"version": "v1"
},
{
"created": "Sun, 5 Apr 2015 16:48:06 GMT",
"version": "v2"
},
{
"created": "Sun, 13 Dec 2015 00:08:55 GMT",
"version": "v3"
}
] | 2016-10-27 | [
[
"Borzou",
"Ahmad",
""
]
] | We present a Lorentz gauge theory of gravity in which the metric is not dynamical. Spherically symmetric weak field solutions are studied. We show that this solution contains the Schwarzschild spacetime at least to the first order of perturbation. Next, we present a special case of the theory. It is shown that the Schwarzschild metric is now an exact solution. Moreover, we show that the de Sitter space is an exact vacuum solution and as a result the theory is able to explain the expansion of the universe with no need for a dark energy. Within this special case, quantization of the theory is also studied. The basic Feynman diagrams are derived and renormalizability of the theory is studied using the power-counting method. We show that under a certain condition the theory is power-counting renormalizable. |
1208.4596 | Kazuhiro Hayama | Kazuhiro Hayama and Atsushi Nishizawa | Model-independent test of gravity with a network of ground-based
gravitational-wave detectors | null | null | 10.1103/PhysRevD.87.062003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The observation of gravitational waves with a global network of
interferometric detectors such as advanced LIGO, advanced Virgo, and KAGRA will
make it possible to probe into the nature of space-time structure. Besides
Einstein's general theory of relativity, there are several theories of
gravitation that passed experimental tests so far. The gravitational-wave
observation provides a new experimental test of alternative theories of gravity
because a gravitational wave may have at most six independent modes of
polarization, of which properties and number of modes are dependent on theories
of gravity. This paper proposes a method to reconstruct the independent modes
of polarization in time-series data of an advanced detector network. Since the
method does not rely on any specific model, it gives model-independent test of
alternative theories of gravity.
| [
{
"created": "Wed, 22 Aug 2012 19:55:10 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Mar 2013 13:59:16 GMT",
"version": "v2"
}
] | 2015-03-20 | [
[
"Hayama",
"Kazuhiro",
""
],
[
"Nishizawa",
"Atsushi",
""
]
] | The observation of gravitational waves with a global network of interferometric detectors such as advanced LIGO, advanced Virgo, and KAGRA will make it possible to probe into the nature of space-time structure. Besides Einstein's general theory of relativity, there are several theories of gravitation that passed experimental tests so far. The gravitational-wave observation provides a new experimental test of alternative theories of gravity because a gravitational wave may have at most six independent modes of polarization, of which properties and number of modes are dependent on theories of gravity. This paper proposes a method to reconstruct the independent modes of polarization in time-series data of an advanced detector network. Since the method does not rely on any specific model, it gives model-independent test of alternative theories of gravity. |
1203.2103 | Mubasher Jamil | Mubasher Jamil, D. Momeni, Kazuharu Bamba, Ratbay Myrzakulov | Thermodynamics of a Schwarzschild Black Hole in Phantom Cosmology with
Entropy Corrections | 17 pages, no figure, version accepted for publication in "Int. J.
Mod. Phys. D" | International Journal of Modern Physics D, Vol. 21, (2012) 1250065 | 10.1142/S0218271812500654 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by some earlier works \cite{pavon,sadjadi} dealing with the study
of generalized second law (GSL) of thermodynamics for a system comprising of a
Schwarzschild black accreting a test non-self-gravitating fluid namely phantom
energy in FRW universe, we extend them when the entropy of horizons of black
hole and the cosmological undergo quantum corrections. Two types of such
corrections are relevant here including logarithmic and power-law, while both
are motivated from different theoretical backgrounds. We obtain general
mathematical conditions for the validity of GSL in each case. Further we find
that GSL restricts the mass of black hole for accretion of phantom energy. As
such we obtain upper bounds on the mass of black hole above which the black
hole cannot accrete the phantom fluid, otherwise the GSL is violated.
| [
{
"created": "Thu, 8 Mar 2012 13:35:02 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Jul 2012 05:47:11 GMT",
"version": "v2"
}
] | 2012-07-17 | [
[
"Jamil",
"Mubasher",
""
],
[
"Momeni",
"D.",
""
],
[
"Bamba",
"Kazuharu",
""
],
[
"Myrzakulov",
"Ratbay",
""
]
] | Motivated by some earlier works \cite{pavon,sadjadi} dealing with the study of generalized second law (GSL) of thermodynamics for a system comprising of a Schwarzschild black accreting a test non-self-gravitating fluid namely phantom energy in FRW universe, we extend them when the entropy of horizons of black hole and the cosmological undergo quantum corrections. Two types of such corrections are relevant here including logarithmic and power-law, while both are motivated from different theoretical backgrounds. We obtain general mathematical conditions for the validity of GSL in each case. Further we find that GSL restricts the mass of black hole for accretion of phantom energy. As such we obtain upper bounds on the mass of black hole above which the black hole cannot accrete the phantom fluid, otherwise the GSL is violated. |
1805.06228 | Christian Corda Prof. | Christian Corda | New proof of general relativity through the correct physical
interpretation of the Mossbauer rotor experiment | 7 pages, 1 figure. This Essay received an Honorable Mention in the
2018 Essay Competition of the Gravity Research Foundation. Dedicated to the
memory of Enrico Lista. Founded on the research paper arXiv:1502.04911. arXiv
admin note: substantial text overlap with arXiv:1602.04212 | Int. Journ. Mod. Phys. D 27, 1847016 (2018) | 10.1142/S0218271818470168 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this Essay, we give a correct interpretation of a historical experiment by
Kundig on the transverse Doppler shift in a rotating system (Mossbauer rotor
experiment). This experiment has been recently first reanalyzed, and then
replied by an experimental research group. The results of reanalyzing the
experiment have shown that a correct re-processing of Kundig's experimental
data gives an interesting deviation of a relative redshift between emission and
absorption resonant lines from the standard prediction based on the
relativistic dilatation of time. Subsequent new experimental results by the
reply of Kundig experiment have shown a deviation from the standard prediction
even higher. By using the Equivalence Principle (EP), which states the
equivalence between the gravitational "force" and the pseudo-force experienced
by an observer in a non-inertial frame of reference (included a rotating frame
of reference), here the theoretical framework of the Mossbauer rotor experiment
is reanalyzed directly in the rotating frame of reference through a general
relativistic treatment. It will be shown that previous analyses missed an
important effect of clock synchronization. By adding this new effect, the
correct general relativistic prevision is in perfect agreement with the new
experimental results. Such an effect of clock synchronization has been missed
in various papers in the literature, with some subsequent claim of invalidity
of the relativity theory and/or some attempts to explain the experimental
results through "exotic" effects. The general relativistic interpretation in
this Essay shows, instead, that the new experimental results of the Mossbauer
rotor experiment are a new, strong and independent, proof of general
relativity.
| [
{
"created": "Wed, 16 May 2018 10:16:14 GMT",
"version": "v1"
},
{
"created": "Thu, 17 May 2018 07:45:05 GMT",
"version": "v2"
}
] | 2018-10-22 | [
[
"Corda",
"Christian",
""
]
] | In this Essay, we give a correct interpretation of a historical experiment by Kundig on the transverse Doppler shift in a rotating system (Mossbauer rotor experiment). This experiment has been recently first reanalyzed, and then replied by an experimental research group. The results of reanalyzing the experiment have shown that a correct re-processing of Kundig's experimental data gives an interesting deviation of a relative redshift between emission and absorption resonant lines from the standard prediction based on the relativistic dilatation of time. Subsequent new experimental results by the reply of Kundig experiment have shown a deviation from the standard prediction even higher. By using the Equivalence Principle (EP), which states the equivalence between the gravitational "force" and the pseudo-force experienced by an observer in a non-inertial frame of reference (included a rotating frame of reference), here the theoretical framework of the Mossbauer rotor experiment is reanalyzed directly in the rotating frame of reference through a general relativistic treatment. It will be shown that previous analyses missed an important effect of clock synchronization. By adding this new effect, the correct general relativistic prevision is in perfect agreement with the new experimental results. Such an effect of clock synchronization has been missed in various papers in the literature, with some subsequent claim of invalidity of the relativity theory and/or some attempts to explain the experimental results through "exotic" effects. The general relativistic interpretation in this Essay shows, instead, that the new experimental results of the Mossbauer rotor experiment are a new, strong and independent, proof of general relativity. |
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