id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2309.03833 | Anson Chen | Anson Chen, Rachel Gray and Tessa Baker | Testing the nature of gravitational wave propagation using dark sirens
and galaxy catalogues | null | null | 10.1088/1475-7516/2024/02/035 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | The dark sirens method enables us to use gravitational wave events without
electromagnetic counterparts as tools for cosmology and tests of gravity.
Furthermore, the dark sirens analysis code gwcosmo can now robustly account for
information coming from both galaxy catalogues and the compact object mass
distribution. We present here an extension of the gwcosmo code and methodology
to constrain parameterized deviations from General Relativity that affect the
propagation of gravitational waves. We show results of our analysis using data
from the GWTC-3 gravitational wave catalogues, in preparation for application
to the O4 observing run. After testing our pipelines using the First Two Years
mock data set, we reanalyse 46 events from GWTC-3, and combine the posterior
for BBH and NSBH sampling results for the first time. We obtain joint
constraints on H0 and parameterized deviations from General Relativity in the
Power Law + Peak BBH population model. With increased galaxy catalogue support
in the future, our work sets the stage for dark sirens to become a powerful
tool for testing gravity.
| [
{
"created": "Thu, 7 Sep 2023 16:48:14 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Sep 2023 12:22:43 GMT",
"version": "v2"
}
] | 2024-02-23 | [
[
"Chen",
"Anson",
""
],
[
"Gray",
"Rachel",
""
],
[
"Baker",
"Tessa",
""
]
] | The dark sirens method enables us to use gravitational wave events without electromagnetic counterparts as tools for cosmology and tests of gravity. Furthermore, the dark sirens analysis code gwcosmo can now robustly account for information coming from both galaxy catalogues and the compact object mass distribution. We present here an extension of the gwcosmo code and methodology to constrain parameterized deviations from General Relativity that affect the propagation of gravitational waves. We show results of our analysis using data from the GWTC-3 gravitational wave catalogues, in preparation for application to the O4 observing run. After testing our pipelines using the First Two Years mock data set, we reanalyse 46 events from GWTC-3, and combine the posterior for BBH and NSBH sampling results for the first time. We obtain joint constraints on H0 and parameterized deviations from General Relativity in the Power Law + Peak BBH population model. With increased galaxy catalogue support in the future, our work sets the stage for dark sirens to become a powerful tool for testing gravity. |
1001.2946 | Chikun Ding | Chikun Ding, Jiliang Jing | Deformation of contour and Hawking temperature | 14 pages, 1 figure, Accepted by CQG | Class. Quantum Grav. 27 (2010) 035004 | 10.1088/0264-9381/27/3/035004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was found that, in an isotropic coordinate system, the tunneling approach
brings a factor of 1/2 for the Hawking temperature of a Schwarzschild black
hole. In this paper, we address this kind of problem by studying the relation
between the Hawking temperature and the deformation of integral contour for the
scalar and Dirac particles tunneling. We find that correct Hawking temperature
can be obtained exactly as long as the integral contour deformed corresponding
to the radial coordinate transform if the transformation is a non-regular or
zero function at the event horizon.
| [
{
"created": "Mon, 18 Jan 2010 06:07:32 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Jan 2010 02:40:21 GMT",
"version": "v2"
}
] | 2010-01-19 | [
[
"Ding",
"Chikun",
""
],
[
"Jing",
"Jiliang",
""
]
] | It was found that, in an isotropic coordinate system, the tunneling approach brings a factor of 1/2 for the Hawking temperature of a Schwarzschild black hole. In this paper, we address this kind of problem by studying the relation between the Hawking temperature and the deformation of integral contour for the scalar and Dirac particles tunneling. We find that correct Hawking temperature can be obtained exactly as long as the integral contour deformed corresponding to the radial coordinate transform if the transformation is a non-regular or zero function at the event horizon. |
2004.07925 | Muhammad Sharif | M. Sharif and Qanitah Ama-Tul-Mughani | Anisotropic Spherical Solutions through Extended Gravitational
Decoupling Approach | 32 pages, 11 figures | Ann. Phys. 415(2020)168122 | 10.1016/j.aop.2020.168122 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is devoted to evaluating exact anisotropic spherical solutions for
static self-gravitating systems through extended geometric deformation
decoupling technique. For this purpose, we consider an isotropic Tolman IV
solution and extend it to anisotropic domain by transforming both temporal as
well as radial metric potentials. To examine the physical viability and
stability of interior anisotropic solutions, we plot energy bounds, TOV
equation, causality condition and adiabatic index for the stars Her X-I and PSR
J 1416-2230. It is found that both obtained models show realistic behavior as
they fulfill all physical constraints as well as stability criterion. We
conclude that the extended gravitational decoupling approach provides more
proficient results to discuss the interior configuration of stellar structures.
| [
{
"created": "Mon, 13 Apr 2020 07:58:03 GMT",
"version": "v1"
}
] | 2020-04-22 | [
[
"Sharif",
"M.",
""
],
[
"Ama-Tul-Mughani",
"Qanitah",
""
]
] | This paper is devoted to evaluating exact anisotropic spherical solutions for static self-gravitating systems through extended geometric deformation decoupling technique. For this purpose, we consider an isotropic Tolman IV solution and extend it to anisotropic domain by transforming both temporal as well as radial metric potentials. To examine the physical viability and stability of interior anisotropic solutions, we plot energy bounds, TOV equation, causality condition and adiabatic index for the stars Her X-I and PSR J 1416-2230. It is found that both obtained models show realistic behavior as they fulfill all physical constraints as well as stability criterion. We conclude that the extended gravitational decoupling approach provides more proficient results to discuss the interior configuration of stellar structures. |
0903.0505 | Carlos F. Sopuerta | Priscilla Canizares, Carlos F. Sopuerta (ICE, CSIC-IEEC) | An Efficient Pseudospectral Method for the Computation of the Self-force
on a Charged Particle: Circular Geodesics around a Schwarzschild Black Hole | 15 pages, 9 figures, Revtex 4. Minor changes to match published
version | Phys.Rev.D79:084020,2009 | 10.1103/PhysRevD.79.084020 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The description of the inspiral of a stellar-mass compact object into a
massive black hole sitting at a galactic centre is a problem of major relevance
for the future space-based gravitational-wave observatory LISA (Laser
Interferometer Space Antenna), as the signals from these systems will be buried
in the data stream and accurate gravitational-wave templates will be needed to
extract them. The main difficulty in describing these systems lies in the
estimation of the gravitational effects of the stellar-mass compact object on
his own trajectory around the massive black hole, which can be modeled as the
action of a local force, the self-force. In this paper, we present a new
time-domain numerical method for the computation of the self-force in a
simplified model consisting of a charged scalar particle orbiting a nonrotating
black hole. We use a multi-domain framework in such a way that the particle is
located at the interface between two domains so that the presence of the
particle and its physical effects appear only through appropriate boundary
conditions. In this way we eliminate completely the presence of a small length
scale associated with the need of resolving the particle. This technique also
avoids the problems associated with the impact of a low differentiability of
the solution in the accuracy of the numerical computations. The spatial
discretization of the field equations is done by using the pseudospectral
collocation method and the time evolution, based on the method of lines, uses a
Runge-Kutta solver. We show how this special framework can provide very
efficient and accurate computations in the time domain, which makes the
technique amenable for the intensive computations required in the
astrophysically-relevant scenarios for LISA.
| [
{
"created": "Tue, 3 Mar 2009 11:52:13 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Apr 2009 15:12:27 GMT",
"version": "v2"
}
] | 2010-03-12 | [
[
"Canizares",
"Priscilla",
"",
"ICE, CSIC-IEEC"
],
[
"Sopuerta",
"Carlos F.",
"",
"ICE, CSIC-IEEC"
]
] | The description of the inspiral of a stellar-mass compact object into a massive black hole sitting at a galactic centre is a problem of major relevance for the future space-based gravitational-wave observatory LISA (Laser Interferometer Space Antenna), as the signals from these systems will be buried in the data stream and accurate gravitational-wave templates will be needed to extract them. The main difficulty in describing these systems lies in the estimation of the gravitational effects of the stellar-mass compact object on his own trajectory around the massive black hole, which can be modeled as the action of a local force, the self-force. In this paper, we present a new time-domain numerical method for the computation of the self-force in a simplified model consisting of a charged scalar particle orbiting a nonrotating black hole. We use a multi-domain framework in such a way that the particle is located at the interface between two domains so that the presence of the particle and its physical effects appear only through appropriate boundary conditions. In this way we eliminate completely the presence of a small length scale associated with the need of resolving the particle. This technique also avoids the problems associated with the impact of a low differentiability of the solution in the accuracy of the numerical computations. The spatial discretization of the field equations is done by using the pseudospectral collocation method and the time evolution, based on the method of lines, uses a Runge-Kutta solver. We show how this special framework can provide very efficient and accurate computations in the time domain, which makes the technique amenable for the intensive computations required in the astrophysically-relevant scenarios for LISA. |
2206.02161 | Reggie Pantig | Reggie C. Pantig, Ali \"Ovg\"un | Testing dynamical torsion effects on the charged black hole's shadow,
deflection angle and greybody with M87* and Sgr. A* from EHT | 18 pages, 15 figures. Finalized version of the paper | Annals of Physics 448 (2023) 169197 | 10.1016/j.aop.2022.169197 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Poincar\'e Gauge's theory of gravity is the most noteworthy alternative
extension of general relativity that has a correspondence between spin and
spacetime geometry. In this paper, we use Reissner-Nordstrom-de Sitter and
anti-de Sitter solutions, where torsion $\tau$ is added as an independent
field, to analyze the weak deflection angles $\hat{\alpha}$ of massive and null
particles in finite distance regime. We then apply $\hat{\alpha}$ to determine
the Einstein ring formation in M87* and Sgr. A* and determine that relative to
Earth's location from these black holes, massive torsion effects can provide
considerable deviation, while the cosmological constant's effect remains
negligible. Furthermore, we also explore how the torsion parameter affects the
shadow radius perceived by both static and co-moving (with cosmic expansion)
observers in a Universe dominated by dark energy, matter, and radiation. Our
findings indicate that torsion and cosmological constant parameters affect the
shadow radius differently between observers in static and co-moving states. We
also show how the torsion parameter affects the luminosity of the photonsphere
by studying the shadow with infalling accretion. The calculation of the
quasinormal modes, greybody bounds, and high-energy absorption cross-section
are also affected by the torsion parameter considerably.
| [
{
"created": "Sun, 5 Jun 2022 12:22:18 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Dec 2022 07:34:38 GMT",
"version": "v2"
}
] | 2022-12-23 | [
[
"Pantig",
"Reggie C.",
""
],
[
"Övgün",
"Ali",
""
]
] | Poincar\'e Gauge's theory of gravity is the most noteworthy alternative extension of general relativity that has a correspondence between spin and spacetime geometry. In this paper, we use Reissner-Nordstrom-de Sitter and anti-de Sitter solutions, where torsion $\tau$ is added as an independent field, to analyze the weak deflection angles $\hat{\alpha}$ of massive and null particles in finite distance regime. We then apply $\hat{\alpha}$ to determine the Einstein ring formation in M87* and Sgr. A* and determine that relative to Earth's location from these black holes, massive torsion effects can provide considerable deviation, while the cosmological constant's effect remains negligible. Furthermore, we also explore how the torsion parameter affects the shadow radius perceived by both static and co-moving (with cosmic expansion) observers in a Universe dominated by dark energy, matter, and radiation. Our findings indicate that torsion and cosmological constant parameters affect the shadow radius differently between observers in static and co-moving states. We also show how the torsion parameter affects the luminosity of the photonsphere by studying the shadow with infalling accretion. The calculation of the quasinormal modes, greybody bounds, and high-energy absorption cross-section are also affected by the torsion parameter considerably. |
0803.1853 | Emanuele Berti | Nicolas Yunes and Emanuele Berti | Accuracy of the Post-Newtonian Approximation: Optimal Asymptotic
Expansion for Quasi-Circular, Extreme-Mass Ratio Inspirals | 17 pages, 14 figures, 5 Tables, 1 Appendix. We added an Erratum to
correct some mistakes in tables and figures. The main conclusions of the
original paper are still valid | Phys.Rev.D77:124006,2008; Erratum-ibid.D83:109901,2011 | 10.1103/PhysRevD.77.124006 10.1103/PhysRevD.83.109901 | IGC-08/3-1 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the accuracy of the post-Newtonian (PN) approximation and its formal
region of validity, by investigating its optimal asymptotic expansion for the
quasi-circular, adiabatic inspiral of a point particle into a Schwarzschild
black hole. By comparing the PN expansion of the energy flux to numerical
calculations in the perturbative Teukolsky formalism, we show that (i) the
inclusion of higher multipoles is necessary to establish the accuracy of
high-order PN terms, and (ii) the region of validity of PN theory is largest at
relative O(1/c^6) (3PN order). The latter result suggests that the series
diverges beyond 3PN order, at least in the extreme mass-ratio limit, probably
due to the appearance of logarithmic terms in the energy flux. The study
presented here is a first formal attempt to determine the region of validity of
the PN approximation using asymptotic analysis. Therefore, it should serve as a
template to perform similar studies on other systems, such as comparable-mass
quasi-circular inspirals computed by high-accuracy numerical relativistic
simulations.
| [
{
"created": "Thu, 13 Mar 2008 18:15:43 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Mar 2011 20:11:03 GMT",
"version": "v2"
}
] | 2011-05-12 | [
[
"Yunes",
"Nicolas",
""
],
[
"Berti",
"Emanuele",
""
]
] | We study the accuracy of the post-Newtonian (PN) approximation and its formal region of validity, by investigating its optimal asymptotic expansion for the quasi-circular, adiabatic inspiral of a point particle into a Schwarzschild black hole. By comparing the PN expansion of the energy flux to numerical calculations in the perturbative Teukolsky formalism, we show that (i) the inclusion of higher multipoles is necessary to establish the accuracy of high-order PN terms, and (ii) the region of validity of PN theory is largest at relative O(1/c^6) (3PN order). The latter result suggests that the series diverges beyond 3PN order, at least in the extreme mass-ratio limit, probably due to the appearance of logarithmic terms in the energy flux. The study presented here is a first formal attempt to determine the region of validity of the PN approximation using asymptotic analysis. Therefore, it should serve as a template to perform similar studies on other systems, such as comparable-mass quasi-circular inspirals computed by high-accuracy numerical relativistic simulations. |
gr-qc/9907034 | Philippe Ruelle | J.-M. Gerard and S. Pireaux | The observable light deflection angle | 11 pages, 1 figure | null | null | UCL-IPT-99-08 | gr-qc | null | The physical deflection angle of a light ray propagating in a space-time
supplied with an asymptotically flat metric has to be expressed in terms of the
impact parameter.
| [
{
"created": "Thu, 8 Jul 1999 08:38:58 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gerard",
"J. -M.",
""
],
[
"Pireaux",
"S.",
""
]
] | The physical deflection angle of a light ray propagating in a space-time supplied with an asymptotically flat metric has to be expressed in terms of the impact parameter. |
2101.02461 | Li-Ming Cao | Li-Ming Cao and Liang-Bi Wu | Hyperbolicity and Causality of Einstein-Gauss-Bonnet Gravity in Warped
Product Spacetimes | Revtex, 32 pages, 5 figures; two references added, typos corrected | Phys. Rev. D 103, 064054 (2021) | 10.1103/PhysRevD.103.064054 | ICTS-USTC/PCFT-21-02 | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In Einstein-Gauss-Bonnet gravity, for a group of warped product spacetimes,
we get a generalized master equation for the perturbation of tensor type. We
show that the "effective metric" or "acoustic metric" for the tensor
perturbation equation can be defined even without a static condition. Since
this master equation does not depend on the mode expansion, the hyperbolicity
and causality of the tensor perturbation equation can be investigated for every
mode of the perturbation. Based on the master equation, we study the
hyperbolicity and causality for all relavent vacuum solutions of this theory.
For each solution, we give the exact hyperbolic condition of the tensor
perturbation equations. Our approach can also applied to dynamical spacetimes,
and Vaidya spacetime have been investigated as an example.
| [
{
"created": "Thu, 7 Jan 2021 10:05:45 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jan 2021 10:42:45 GMT",
"version": "v2"
}
] | 2021-03-31 | [
[
"Cao",
"Li-Ming",
""
],
[
"Wu",
"Liang-Bi",
""
]
] | In Einstein-Gauss-Bonnet gravity, for a group of warped product spacetimes, we get a generalized master equation for the perturbation of tensor type. We show that the "effective metric" or "acoustic metric" for the tensor perturbation equation can be defined even without a static condition. Since this master equation does not depend on the mode expansion, the hyperbolicity and causality of the tensor perturbation equation can be investigated for every mode of the perturbation. Based on the master equation, we study the hyperbolicity and causality for all relavent vacuum solutions of this theory. For each solution, we give the exact hyperbolic condition of the tensor perturbation equations. Our approach can also applied to dynamical spacetimes, and Vaidya spacetime have been investigated as an example. |
2206.10887 | Mamma Emma | Mattia Emma, Federico Schianchi, Francesco Pannarale, Violetta Sagun
and Tim Dietrich | Numerical Simulations of Dark Matter Admixed Neutron Star Binaries | null | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Multi-messenger observations of compact binary mergers provide a new way to
constrain the nature of dark matter that may accumulate in and around neutron
stars. In this article, we extend the infrastructure of our
numerical-relativity code BAM to enable the simulation of neutron stars that
contain an additional mirror dark matter component. We perform single star
tests to verify our code and the first binary neutron star simulations of this
kind. We find that the presence of dark matter reduces the lifetime of the
merger remnant and favors a prompt collapse to a black hole. Furthermore, we
find differences in the merger time for systems with the same total mass and
mass ratio, but different amounts of dark matter. Finally, we find that
electromagnetic signals produced by the merger of binary neutron stars admixed
with dark matter are very unlikely to be as bright as their dark matter free
counterparts. Given the increasing sensitivity of multi-messenger facilities,
our analysis gives a new perspective on how to probe the presence of dark
matter.
| [
{
"created": "Wed, 22 Jun 2022 07:38:23 GMT",
"version": "v1"
}
] | 2022-06-23 | [
[
"Emma",
"Mattia",
""
],
[
"Schianchi",
"Federico",
""
],
[
"Pannarale",
"Francesco",
""
],
[
"Sagun",
"Violetta",
""
],
[
"Dietrich",
"Tim",
""
]
] | Multi-messenger observations of compact binary mergers provide a new way to constrain the nature of dark matter that may accumulate in and around neutron stars. In this article, we extend the infrastructure of our numerical-relativity code BAM to enable the simulation of neutron stars that contain an additional mirror dark matter component. We perform single star tests to verify our code and the first binary neutron star simulations of this kind. We find that the presence of dark matter reduces the lifetime of the merger remnant and favors a prompt collapse to a black hole. Furthermore, we find differences in the merger time for systems with the same total mass and mass ratio, but different amounts of dark matter. Finally, we find that electromagnetic signals produced by the merger of binary neutron stars admixed with dark matter are very unlikely to be as bright as their dark matter free counterparts. Given the increasing sensitivity of multi-messenger facilities, our analysis gives a new perspective on how to probe the presence of dark matter. |
1605.05356 | Eugenio Bianchi | Eugenio Bianchi, Jonathan Guglielmon, Lucas Hackl, Nelson Yokomizo | Squeezed vacua in loop quantum gravity | 14 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce squeezed vacua in loop quantum gravity, a new overcomplete basis
of states that contain prescribable correlations between geometric operators.
We study the behavior of long-range correlations and discuss the relevance of
these states for the reconstruction of a semiclassical spacetime from loop
quantum gravity.
| [
{
"created": "Tue, 17 May 2016 20:35:46 GMT",
"version": "v1"
}
] | 2016-05-19 | [
[
"Bianchi",
"Eugenio",
""
],
[
"Guglielmon",
"Jonathan",
""
],
[
"Hackl",
"Lucas",
""
],
[
"Yokomizo",
"Nelson",
""
]
] | We introduce squeezed vacua in loop quantum gravity, a new overcomplete basis of states that contain prescribable correlations between geometric operators. We study the behavior of long-range correlations and discuss the relevance of these states for the reconstruction of a semiclassical spacetime from loop quantum gravity. |
1805.04679 | Ramil Izmailov N | K. K. Nandi, R. N. Izmailov, E. R. Zhdanov and Amrita Bhattacharya | Strong field lensing by Damour-Solodukhin wormhole | 6 pages | JCAP 07 (2018) 027 | 10.1088/1475-7516/2018/07/027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the strong field lensing observables for the Damour-Solodukhin
wormhole and examine how small the values of the deviation parameter $\lambda $
need be for reproducing the observables for the Schwarzschild black hole. While
the extremely tiny values of $\lambda$ indicated by the matter accretion or
Hawking evaporation are not disputed, it turns out that $\lambda $ could
actually assume values considerably higher than those tiny values and still
reproduce black hole lensing signatures. The lensing observations thus provide
a surprising counterexample to the intuitive expectation that all experiments
ought to lead to the mimicking of black holes for the same range of values of
$\lambda$.
| [
{
"created": "Sat, 12 May 2018 07:27:21 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Nov 2023 08:48:52 GMT",
"version": "v2"
}
] | 2023-11-17 | [
[
"Nandi",
"K. K.",
""
],
[
"Izmailov",
"R. N.",
""
],
[
"Zhdanov",
"E. R.",
""
],
[
"Bhattacharya",
"Amrita",
""
]
] | We investigate the strong field lensing observables for the Damour-Solodukhin wormhole and examine how small the values of the deviation parameter $\lambda $ need be for reproducing the observables for the Schwarzschild black hole. While the extremely tiny values of $\lambda$ indicated by the matter accretion or Hawking evaporation are not disputed, it turns out that $\lambda $ could actually assume values considerably higher than those tiny values and still reproduce black hole lensing signatures. The lensing observations thus provide a surprising counterexample to the intuitive expectation that all experiments ought to lead to the mimicking of black holes for the same range of values of $\lambda$. |
2206.02453 | Sohrab Rahvar | Sohrab Rahvar | Hamiltonian Formalism for dynamics of particles in MOG | 5 pages, accepted in Monthly Notices of the Royal Astronomical
Society | null | 10.1093/mnras/stac1560 | null | gr-qc astro-ph.GA | http://creativecommons.org/licenses/by/4.0/ | MOG as a modified gravity theory is designed to be replaced with dark matter.
In this theory, in addition to the metric tensor, a massive vector is a gravity
field where each particle has a charge proportional to the inertial mass and
couples to the vector field through the four-velocity of a particle. In this
work, we present the Hamiltonian formalism for the dynamics of particles in
this theory. The advantage of Hamiltonian formalism is a better understanding
and analyzing the dynamics of massive and massless particles. The massive
particles deviate from the geodesics of space-time and photons follow the
geodesics. We also study the dynamics of particles in the Newtonian and
post-Newtonian regimes for observational purposes. An important result of
Hamiltonian formalism is that while lensing on large scales is compatible with
the observations, however the deflection angle from stellar size lensing is
larger than General Relativity. This result can rule out this theory unless we
introduce a screening mechanism to change the effective gravitational constant
near compact objects like stars.
| [
{
"created": "Mon, 6 Jun 2022 09:32:46 GMT",
"version": "v1"
}
] | 2022-06-22 | [
[
"Rahvar",
"Sohrab",
""
]
] | MOG as a modified gravity theory is designed to be replaced with dark matter. In this theory, in addition to the metric tensor, a massive vector is a gravity field where each particle has a charge proportional to the inertial mass and couples to the vector field through the four-velocity of a particle. In this work, we present the Hamiltonian formalism for the dynamics of particles in this theory. The advantage of Hamiltonian formalism is a better understanding and analyzing the dynamics of massive and massless particles. The massive particles deviate from the geodesics of space-time and photons follow the geodesics. We also study the dynamics of particles in the Newtonian and post-Newtonian regimes for observational purposes. An important result of Hamiltonian formalism is that while lensing on large scales is compatible with the observations, however the deflection angle from stellar size lensing is larger than General Relativity. This result can rule out this theory unless we introduce a screening mechanism to change the effective gravitational constant near compact objects like stars. |
gr-qc/9707061 | Alfredo Vasquez | Alfredo V\'azquez-Cruz | Gravitational Properties of Quantum Bosonic Strings | Ph.D Thesis. 143 pages, 25 figures inluded. Primary Latex file:
Thesisroot.tex (56 subsidiary files). | null | null | null | gr-qc hep-th | null | In this thesis we are interested in the study of the gravitational properties
of quantum bosonic strings. We start by computing the quantum energy-momentum
tensor ${\hat T}^{\mu\nu}(x)$ for strings in Minkowski space-time. We perform
the calculation of its expectation value for different physical string states
both for open and closed bosonic strings. The states we consider are described
by normalizable wave-packets in the centre of mass coordinates. Amongst our
results, we find in particular that ${\hat T}^{\mu\nu}(x)$ becomes a non-local
operator at the quantum level, its position appears to be smeared out by
quantum fluctuations. We find that the expectation value acquires a non-zero
value for both massive and massless string states. After computing $<{\hat
T}^{\mu\nu}(x)>$ we proceed to calculate the gravitational field due to a
quantum massless bosonic string in the framework of a weak-field approximation
to Einstein's equations. We obtain a multipole expansion for the weak-field
metric $h^{\mu\nu}(x)$ and present its gravitational properties, including the
gravitational radiation produced by such a string. Our results are then
compared to those found for classical (cosmic) strings.
| [
{
"created": "Wed, 30 Jul 1997 14:29:00 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Jul 1997 08:16:00 GMT",
"version": "v2"
}
] | 2016-08-15 | [
[
"Vázquez-Cruz",
"Alfredo",
""
]
] | In this thesis we are interested in the study of the gravitational properties of quantum bosonic strings. We start by computing the quantum energy-momentum tensor ${\hat T}^{\mu\nu}(x)$ for strings in Minkowski space-time. We perform the calculation of its expectation value for different physical string states both for open and closed bosonic strings. The states we consider are described by normalizable wave-packets in the centre of mass coordinates. Amongst our results, we find in particular that ${\hat T}^{\mu\nu}(x)$ becomes a non-local operator at the quantum level, its position appears to be smeared out by quantum fluctuations. We find that the expectation value acquires a non-zero value for both massive and massless string states. After computing $<{\hat T}^{\mu\nu}(x)>$ we proceed to calculate the gravitational field due to a quantum massless bosonic string in the framework of a weak-field approximation to Einstein's equations. We obtain a multipole expansion for the weak-field metric $h^{\mu\nu}(x)$ and present its gravitational properties, including the gravitational radiation produced by such a string. Our results are then compared to those found for classical (cosmic) strings. |
0909.3014 | Galin Gyulchev | Galin N. Gyulchev, Stoytcho S. Yazadjiev | Analytical Kerr-Sen Dilaton-Axion Black Hole Lensing in the Weak
Deflection Limit | 36 pages, 8 figures | Phys.Rev.D81:023005,2010 | 10.1103/PhysRevD.81.023005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate analytically gravitational lensing by charged, stationary,
axially symmetric Kerr-Sen dilaton-axion black hole in the weak deflection
limit. Approximate solutions to the lightlike equations of motion are present
up to and including third-order terms in $M/b$, $a/b$ and $r_{\alpha}/b$, where
$M$ is the black hole mass, $a$ is the angular momentum, $r_{\alpha}=Q^2/M$,
$Q$ being the charge and $b$ is the impact parameter of the light ray. We
compute the positions of the two weak field images, the corresponding signed
and absolute magnifications up to post-Newtonian order. It is shown that there
are static post-Newtonian corrections to the signed magnification and their sum
as well as to the critical curves, which are functions of the charge. The shift
of the critical curves as a function of the lens angular momentum is found, and
it is shown that they decrease slightly with the increase of the charge. The
point-like caustics drift away from the optical axis and do not depend on the
charge. All of the lensing quantities are compared to particular cases as
Schwarzschild and Kerr black holes as well as the
Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole.
| [
{
"created": "Wed, 16 Sep 2009 15:06:03 GMT",
"version": "v1"
}
] | 2010-03-25 | [
[
"Gyulchev",
"Galin N.",
""
],
[
"Yazadjiev",
"Stoytcho S.",
""
]
] | We investigate analytically gravitational lensing by charged, stationary, axially symmetric Kerr-Sen dilaton-axion black hole in the weak deflection limit. Approximate solutions to the lightlike equations of motion are present up to and including third-order terms in $M/b$, $a/b$ and $r_{\alpha}/b$, where $M$ is the black hole mass, $a$ is the angular momentum, $r_{\alpha}=Q^2/M$, $Q$ being the charge and $b$ is the impact parameter of the light ray. We compute the positions of the two weak field images, the corresponding signed and absolute magnifications up to post-Newtonian order. It is shown that there are static post-Newtonian corrections to the signed magnification and their sum as well as to the critical curves, which are functions of the charge. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightly with the increase of the charge. The point-like caustics drift away from the optical axis and do not depend on the charge. All of the lensing quantities are compared to particular cases as Schwarzschild and Kerr black holes as well as the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole. |
1504.04746 | Javad Taghizadeh Firouzjaee | Rahim Moradi, Javad T. Firouzjaee and Reza Mansouri | Cosmological black holes: the spherical perfect fluid collapse with
pressure in a FRW background | 14 pages, 11 figures, a few discussion added accepted version for
Class. Quantum Grav. arXiv admin note: substantial text overlap with
arXiv:1301.1480 | Class. Quantum Grav. 32 (2015) 215001 | 10.1088/0264-9381/32/21/215001 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | We have constructed a spherically symmetric structure model in a cosmological
background filled with perfect fluid with non-vanishing pressure as an exact
solution of Einstein equations using the Lema\^{i}tre solution. To study its
local and quasi-local characteristics including the novel features of its
central black hole, we have suggested an algorithm to integrate the equations
numerically. The result shows intriguing effects of the pressure inside the
structure. The evolution of the central black hole within the FRW universe, its
decoupling from the expanding parts of the model, the structure of its
space-like apparent horizon, the limiting case of the dynamical horizon tending
to a slowly evolving horizon, and the decreasing mass in-fall to the black hole
is also studied. The cosmological redshift of a light emitted from the
cosmological structure to an observer in the FRW background is also calculated.
This cosmological redshift includes local and cosmic part which are explicitly
separated. We have also formulated a modified NFW density profile for a
structure to match the exact solution conditions.
| [
{
"created": "Sat, 18 Apr 2015 17:54:59 GMT",
"version": "v1"
},
{
"created": "Sun, 4 Oct 2015 05:08:51 GMT",
"version": "v2"
}
] | 2015-10-07 | [
[
"Moradi",
"Rahim",
""
],
[
"Firouzjaee",
"Javad T.",
""
],
[
"Mansouri",
"Reza",
""
]
] | We have constructed a spherically symmetric structure model in a cosmological background filled with perfect fluid with non-vanishing pressure as an exact solution of Einstein equations using the Lema\^{i}tre solution. To study its local and quasi-local characteristics including the novel features of its central black hole, we have suggested an algorithm to integrate the equations numerically. The result shows intriguing effects of the pressure inside the structure. The evolution of the central black hole within the FRW universe, its decoupling from the expanding parts of the model, the structure of its space-like apparent horizon, the limiting case of the dynamical horizon tending to a slowly evolving horizon, and the decreasing mass in-fall to the black hole is also studied. The cosmological redshift of a light emitted from the cosmological structure to an observer in the FRW background is also calculated. This cosmological redshift includes local and cosmic part which are explicitly separated. We have also formulated a modified NFW density profile for a structure to match the exact solution conditions. |
1401.1485 | Gil de Oliveira-Neto | G. Oliveira-Neto, M. Silva de Oliveira, G. A. Monerat and E. V.
Corr\^ea Silva | Noncommutativity in the early Universe | 25 pages and 13 figures. Modifications in the text and in the
references, 9 figures added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work, we study the noncommutative version of a quantum
cosmology model. The model has a Friedmann-Robertson-Walker geometry, the
matter content is a radiative perfect fluid and the spatial sections have zero
constant curvature. In this model the scale factor takes values in a bounded
domain. Therefore, its quantum mechanical version has a discrete energy
spectrum. We compute the discrete energy spectrum and the corresponding
eigenfunctions. The energies depend on a noncommutative parameter $\beta$. We
compute the scale factor expected value ($\left<a\right>$) for several values
of $\beta$. For all of them, $\left<a\right>$ oscillates between maxima and
minima values and never vanishes. It gives an initial indication that those
models are free from singularities, at the quantum level. We improve this
result by showing that if we subtract a quantity proportional to the standard
deviation of $a$ from $\left<a\right>$, this quantity is still positive. The
$\left<a\right>$ behavior, for the present model, is a drastic modification of
the $\left<a\right>$ behavior in the corresponding commutative version of the
present model. There, $\left<a\right>$ grows without limits with the time
variable. Therefore, if the present model may represent the early stages of the
Universe, the results of the present paper give an indication that
$\left<a\right>$ may have been, initially, bounded due to noncommutativity. We
also compute the Bohmian trajectories for $a$, which are in accordance with
$\left<a\right>$, and the quantum potential $Q$. From $Q$, we may understand
why that model is free from singularities, at the quantum level.
| [
{
"created": "Tue, 7 Jan 2014 19:58:22 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Jul 2014 22:05:02 GMT",
"version": "v2"
},
{
"created": "Thu, 18 Dec 2014 17:13:45 GMT",
"version": "v3"
},
{
"created": "Wed, 4 May 2016 15:22:49 GMT",
"version": "v4"
}
] | 2016-05-05 | [
[
"Oliveira-Neto",
"G.",
""
],
[
"de Oliveira",
"M. Silva",
""
],
[
"Monerat",
"G. A.",
""
],
[
"Silva",
"E. V. Corrêa",
""
]
] | In the present work, we study the noncommutative version of a quantum cosmology model. The model has a Friedmann-Robertson-Walker geometry, the matter content is a radiative perfect fluid and the spatial sections have zero constant curvature. In this model the scale factor takes values in a bounded domain. Therefore, its quantum mechanical version has a discrete energy spectrum. We compute the discrete energy spectrum and the corresponding eigenfunctions. The energies depend on a noncommutative parameter $\beta$. We compute the scale factor expected value ($\left<a\right>$) for several values of $\beta$. For all of them, $\left<a\right>$ oscillates between maxima and minima values and never vanishes. It gives an initial indication that those models are free from singularities, at the quantum level. We improve this result by showing that if we subtract a quantity proportional to the standard deviation of $a$ from $\left<a\right>$, this quantity is still positive. The $\left<a\right>$ behavior, for the present model, is a drastic modification of the $\left<a\right>$ behavior in the corresponding commutative version of the present model. There, $\left<a\right>$ grows without limits with the time variable. Therefore, if the present model may represent the early stages of the Universe, the results of the present paper give an indication that $\left<a\right>$ may have been, initially, bounded due to noncommutativity. We also compute the Bohmian trajectories for $a$, which are in accordance with $\left<a\right>$, and the quantum potential $Q$. From $Q$, we may understand why that model is free from singularities, at the quantum level. |
2202.09343 | Maximiliano Ujevic | Maximiliano Ujevic, Alireza Rashti, Henrique Gieg, Wolfgang Tichy, Tim
Dietrich | High-accuracy high-mass ratio simulations for binary neutron stars and
their comparison to existing waveform models | 10 pages, 7 figures | null | 10.1103/PhysRevD.106.023029 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The subsequent observing runs of the advanced gravitational-wave detector
network will likely provide us with various gravitational-wave observations of
binary neutron star systems. For an accurate interpretation of these
detections, we need reliable gravitational-wave models. To test and to point
out how existing models could be improved, we perform a set of high-resolution
numerical-relativity simulations for four different physical setups with mass
ratios $q$ = $1.25$, $1.50$, $1.75$, $2.00$, and total gravitational mass $M =
2.7M_\odot$ . Each configuration is simulated with five different resolutions
to allow a proper error assessment. Overall, we find approximately 2nd order
converging results for the dominant $(2,2)$, but also subdominant $(2,1)$,
$(3,3)$, $(4,4)$ modes, while, generally, the convergence order reduces
slightly for an increasing mass ratio. Our simulations allow us to validate
waveform models, where we find generally good agreement between
state-of-the-art models and our data, and to prove that scaling relations for
higher modes currently employed for binary black hole waveform modeling also
apply for the tidal contribution. Finally, we also test if the current NRTidal
model to describe tidal effects is a valid description for high-mass ratio
systems. We hope that our simulation results can be used to further improve and
test waveform models in preparation for the next observing runs.
| [
{
"created": "Fri, 18 Feb 2022 18:18:43 GMT",
"version": "v1"
}
] | 2022-08-17 | [
[
"Ujevic",
"Maximiliano",
""
],
[
"Rashti",
"Alireza",
""
],
[
"Gieg",
"Henrique",
""
],
[
"Tichy",
"Wolfgang",
""
],
[
"Dietrich",
"Tim",
""
]
] | The subsequent observing runs of the advanced gravitational-wave detector network will likely provide us with various gravitational-wave observations of binary neutron star systems. For an accurate interpretation of these detections, we need reliable gravitational-wave models. To test and to point out how existing models could be improved, we perform a set of high-resolution numerical-relativity simulations for four different physical setups with mass ratios $q$ = $1.25$, $1.50$, $1.75$, $2.00$, and total gravitational mass $M = 2.7M_\odot$ . Each configuration is simulated with five different resolutions to allow a proper error assessment. Overall, we find approximately 2nd order converging results for the dominant $(2,2)$, but also subdominant $(2,1)$, $(3,3)$, $(4,4)$ modes, while, generally, the convergence order reduces slightly for an increasing mass ratio. Our simulations allow us to validate waveform models, where we find generally good agreement between state-of-the-art models and our data, and to prove that scaling relations for higher modes currently employed for binary black hole waveform modeling also apply for the tidal contribution. Finally, we also test if the current NRTidal model to describe tidal effects is a valid description for high-mass ratio systems. We hope that our simulation results can be used to further improve and test waveform models in preparation for the next observing runs. |
0706.0205 | David Coule | D. H. Coule | On initial conditions for inflationary and bouncing cosmologies | 28pages, updated | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the question of deriving initial conditions for scalar fields in
driving both an early and late quintessence phase. The dark energy field
presents an unresolved uniformity problem. Further difficulties with initial
conditions for assisted, kinetic and phantom inflation are presented. We review
the use of the canonical measure and find the negative conclusions of Gibbons
and Hawking can be allayed by means of a reasonable quantum cosmological input.
We remark upon some attempts at incorporating inflationary schemes into cyclic
and bouncing models.
| [
{
"created": "Fri, 1 Jun 2007 19:34:26 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Jun 2007 18:50:50 GMT",
"version": "v2"
},
{
"created": "Wed, 27 Jun 2007 17:38:27 GMT",
"version": "v3"
},
{
"created": "Thu, 20 Sep 2007 15:31:52 GMT",
"version": "v4"
},
{
"cr... | 2012-12-20 | [
[
"Coule",
"D. H.",
""
]
] | We consider the question of deriving initial conditions for scalar fields in driving both an early and late quintessence phase. The dark energy field presents an unresolved uniformity problem. Further difficulties with initial conditions for assisted, kinetic and phantom inflation are presented. We review the use of the canonical measure and find the negative conclusions of Gibbons and Hawking can be allayed by means of a reasonable quantum cosmological input. We remark upon some attempts at incorporating inflationary schemes into cyclic and bouncing models. |
0708.1926 | Dirk Puetzfeld | Dirk Puetzfeld, Yuri N. Obukhov | Probing non-Riemannian spacetime geometry | 8 pages, 1 figure, matches published version including the erratum in
Phys. Lett. A 373 (2009) 1600 | Phys.Lett.A372:6711-6716,2008 | 10.1016/j.physleta.2008.09.041 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The equations of motion for matter in non-Riemannian spacetimes are derived
via a multipole method. It is found that only test bodies with microstructure
couple to the non-Riemannian spacetime geometry. Consequently it is impossible
to detect spacetime torsion with the satellite experiment Gravity Probe B,
contrary to some recent claims in the literature.
| [
{
"created": "Tue, 14 Aug 2007 16:53:04 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Oct 2008 11:06:34 GMT",
"version": "v2"
},
{
"created": "Mon, 30 Mar 2009 11:48:11 GMT",
"version": "v3"
}
] | 2009-03-30 | [
[
"Puetzfeld",
"Dirk",
""
],
[
"Obukhov",
"Yuri N.",
""
]
] | The equations of motion for matter in non-Riemannian spacetimes are derived via a multipole method. It is found that only test bodies with microstructure couple to the non-Riemannian spacetime geometry. Consequently it is impossible to detect spacetime torsion with the satellite experiment Gravity Probe B, contrary to some recent claims in the literature. |
2307.04379 | Koray D\"uzta\c{s} | Koray D\"uzta\c{s} | Challenging event horizons with spin (3/2) fields | Published in EPJC | Eur. Phys. J. C (2023) 83:567 | 10.1140/epjc/s10052-023-11764-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We attempt to destroy the event horizons of Kerr black holes by perturbing
them with massless spin (3/2) fields. We carry out a detailed analysis by
incorporating the explicit form of the absorption probabilities and
backreaction effects due to the self energy of the test fields. For extremal
and nearly extremal black holes, backreaction effects dominate for
perturbations with large magnitudes. However, small perturbations can destroy
the event horizons of extremal black holes and drive nearly extremal black
holes closer to extremality. Eventually, nearly extremal black holes reach a
certain stage where they can be continuously driven to extremality and beyond.
Both the cosmic censorship conjecture and the third law of black hole dynamics
can be violated by spin (3/2) fields. This directly follows from the fact that
fermionic fields do not satisfy the null energy condition. Therefore this
result does not contradict with the fact that cosmic censorship and the laws of
black hole mechanics remain valid for perturbations satisfying the null energy
condition.
| [
{
"created": "Mon, 10 Jul 2023 07:25:44 GMT",
"version": "v1"
}
] | 2023-07-11 | [
[
"Düztaş",
"Koray",
""
]
] | We attempt to destroy the event horizons of Kerr black holes by perturbing them with massless spin (3/2) fields. We carry out a detailed analysis by incorporating the explicit form of the absorption probabilities and backreaction effects due to the self energy of the test fields. For extremal and nearly extremal black holes, backreaction effects dominate for perturbations with large magnitudes. However, small perturbations can destroy the event horizons of extremal black holes and drive nearly extremal black holes closer to extremality. Eventually, nearly extremal black holes reach a certain stage where they can be continuously driven to extremality and beyond. Both the cosmic censorship conjecture and the third law of black hole dynamics can be violated by spin (3/2) fields. This directly follows from the fact that fermionic fields do not satisfy the null energy condition. Therefore this result does not contradict with the fact that cosmic censorship and the laws of black hole mechanics remain valid for perturbations satisfying the null energy condition. |
1606.07959 | Amir Hadi Ziaie | Hamid Shabani and Amir Hadi Ziaie | Stability of the Einstein static Universe in $f(R,T)$ gravity | 27 pages, 6 figures, major revision | Eur. Phys. J. C (2017) 77: 31 | 10.1140/epjc/s10052-017-4597-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Einstein static (ES) universe has played a major role in various emergent
scenarios recently proposed in order to cure the problem of initial singularity
of the standard model of cosmology. In the herein model, we study the existence
and stability of ES universe in the context of $f(R,T)$ modified theories of
gravity. Considering specific forms of $f(R,T)$ function, we seek for the
existence of solutions representing ES state. Using dynamical system techniques
along with numerical analysis, we find two classes of solutions: the first one
is always unstable of the saddle type while the second is always stable so that
its dynamical behavior corresponds to a center equilibrium point. The
importance of the second class of solutions is due to the significant duty they
have in constructing non-singular emergent models in which the universe could
have experienced past-eternally, a series of infinite oscillations about such
an initial static state after which, it enters through a suitable physical
mechanism, to an inflationary era. Considering specific forms for the
functionality of $f(R,T)$, we show that this theory is capable of providing
cosmological solutions which admit emergent universe (EU) scenarios. We also
investigate homogeneous scalar perturbations for the mentioned models. The
stability regions of the solutions are parametrized by a linear equation of
state (EoS) parameter and other free parameters that will be introduced for the
models. Our results suggest that modifications in $f(R,T)$ gravity would lead
to stable solutions which are unstable in $f(R)$ gravity model.
| [
{
"created": "Sat, 25 Jun 2016 20:13:54 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Sep 2016 08:26:19 GMT",
"version": "v2"
}
] | 2017-01-23 | [
[
"Shabani",
"Hamid",
""
],
[
"Ziaie",
"Amir Hadi",
""
]
] | The Einstein static (ES) universe has played a major role in various emergent scenarios recently proposed in order to cure the problem of initial singularity of the standard model of cosmology. In the herein model, we study the existence and stability of ES universe in the context of $f(R,T)$ modified theories of gravity. Considering specific forms of $f(R,T)$ function, we seek for the existence of solutions representing ES state. Using dynamical system techniques along with numerical analysis, we find two classes of solutions: the first one is always unstable of the saddle type while the second is always stable so that its dynamical behavior corresponds to a center equilibrium point. The importance of the second class of solutions is due to the significant duty they have in constructing non-singular emergent models in which the universe could have experienced past-eternally, a series of infinite oscillations about such an initial static state after which, it enters through a suitable physical mechanism, to an inflationary era. Considering specific forms for the functionality of $f(R,T)$, we show that this theory is capable of providing cosmological solutions which admit emergent universe (EU) scenarios. We also investigate homogeneous scalar perturbations for the mentioned models. The stability regions of the solutions are parametrized by a linear equation of state (EoS) parameter and other free parameters that will be introduced for the models. Our results suggest that modifications in $f(R,T)$ gravity would lead to stable solutions which are unstable in $f(R)$ gravity model. |
1809.00935 | Domenico Giulini J.W. | Daniel Pook-Kolb and Domenico Giulini | Numerical Approach for Corvino-Type Gluing of Brill-Lindquist Initial
Data | 16 pages, 11 figures | Classical and Quantum Gravity, Year 2019, Volume 36, Number 4,
Article 045011 (16 pages) | 10.1088/1361-6382/aaff0f | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Building on the work of Giulini and Holzegel (2005), a new numerical approach
is developed for computing Cauchy data for Einstein's equations by gluing a
Schwarzschild end to a Brill-Lindquist metric via a Corvino-type construction.
In contrast to, and in extension of, the numerical strategy of Doulis and Rinne
(2016), the overdetermined Poisson problem resulting from the Brill wave ansatz
is decomposed to obtain two uniquely solvable problems. A pseudospectral method
and Newton-Krylov root finder are utilized to perform the gluing. The
convergence analysis strongly indicates that the numerical strategy developed
here is able to produce highly accurate results. It is observed that
Schwarzschild ends of various ADM masses can be glued to the same interior
configuration using the same gluing radius.
| [
{
"created": "Tue, 4 Sep 2018 13:15:30 GMT",
"version": "v1"
}
] | 2019-02-12 | [
[
"Pook-Kolb",
"Daniel",
""
],
[
"Giulini",
"Domenico",
""
]
] | Building on the work of Giulini and Holzegel (2005), a new numerical approach is developed for computing Cauchy data for Einstein's equations by gluing a Schwarzschild end to a Brill-Lindquist metric via a Corvino-type construction. In contrast to, and in extension of, the numerical strategy of Doulis and Rinne (2016), the overdetermined Poisson problem resulting from the Brill wave ansatz is decomposed to obtain two uniquely solvable problems. A pseudospectral method and Newton-Krylov root finder are utilized to perform the gluing. The convergence analysis strongly indicates that the numerical strategy developed here is able to produce highly accurate results. It is observed that Schwarzschild ends of various ADM masses can be glued to the same interior configuration using the same gluing radius. |
1105.0636 | Alok Laddha | Alok Laddha, Madhavan Varadarajan | The Diffeomorphism Constraint Operator in Loop Quantum Gravity | 37 pages, 6 figures | Class.Quant.Grav. 28 (2011) 195010 | 10.1088/0264-9381/28/19/195010 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct the smeared diffeomorphism constraint operator at finite
triangulation from the basic holonomy- flux operators of Loop Quantum Gravity,
evaluate its continuum limit on the Lewandowski- Marolf habitat and show that
the action of the continuum operator provides an anomaly free representation of
the Lie algebra of diffeomorphisms of the 3- manifold. Key features of our
analysis include: (i) finite triangulation approximants to the curvature,
$F_{ab}^i$ of the Ashtekar- Barbero connection which involve not only small
loop holonomies but also small surface fluxes as well as an explicit dependence
on the edge labels of the spin network being acted on (ii) the dependence of
the small loop underlying the holonomy on both the direction and magnitude of
the shift vector field (iii) continuum constraint operators which do {\em not}
have finite action on the kinematic Hilbert space, thus implementing a key
lesson from recent studies of parameterised field theory by the authors.
Features (i) and (ii) provide the first hints in LQG of a conceptual
similarity with the so called "mu- bar" scheme of Loop Quantum Cosmology. We
expect our work to be of use in the construction of an anomaly free quantum
dynamics for LQG.
| [
{
"created": "Tue, 3 May 2011 17:19:04 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Laddha",
"Alok",
""
],
[
"Varadarajan",
"Madhavan",
""
]
] | We construct the smeared diffeomorphism constraint operator at finite triangulation from the basic holonomy- flux operators of Loop Quantum Gravity, evaluate its continuum limit on the Lewandowski- Marolf habitat and show that the action of the continuum operator provides an anomaly free representation of the Lie algebra of diffeomorphisms of the 3- manifold. Key features of our analysis include: (i) finite triangulation approximants to the curvature, $F_{ab}^i$ of the Ashtekar- Barbero connection which involve not only small loop holonomies but also small surface fluxes as well as an explicit dependence on the edge labels of the spin network being acted on (ii) the dependence of the small loop underlying the holonomy on both the direction and magnitude of the shift vector field (iii) continuum constraint operators which do {\em not} have finite action on the kinematic Hilbert space, thus implementing a key lesson from recent studies of parameterised field theory by the authors. Features (i) and (ii) provide the first hints in LQG of a conceptual similarity with the so called "mu- bar" scheme of Loop Quantum Cosmology. We expect our work to be of use in the construction of an anomaly free quantum dynamics for LQG. |
2109.13961 | Gregorio Carullo | Gregorio Carullo, Danny Laghi, Nathan K. Johnson-McDaniel, Walter Del
Pozzo and Oscar J.C. Dias, Mahdi Godazgar, Jorge E. Santos | Constraints on Kerr-Newman black holes from merger-ringdown
gravitational-wave observations | 21 pages, 11 figures, 4 tables. Matches published version | Phys. Rev. D 105, 062009 (2022) | 10.1103/PhysRevD.105.062009 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a template to model the post-merger phase of a binary black hole
coalescence in the presence of a remnant $U(1)$ charge. We include the
quasi-normal modes typically dominant during a binary black hole coalescence,
$(\ell,m,n) = \{(2,2,0), (2,2,1)\}$ and also present analytical fits for the
quasinormal mode frequencies of a Kerr-Newman black hole in terms of its spin
and charge, here also including the $(3,3,0)$ mode. Aside from astrophysical
electric charge, our template can accommodate extensions of the Standard Model,
such as a dark photon. Applying the model to LIGO-Virgo detections, we find
that we are unable to distinguish between the charged and uncharged hypotheses
from a purely post-merger analysis of the current events. However, restricting
the mass and spin to values compatible with the analysis of the full signal, we
obtain a 90th percentile bound $\bar{q} < 0.33$ on the black hole
charge-to-mass ratio, for the most favorable case of GW150914. Under similar
assumptions, by simulating a typical loud signal observed by the LIGO-Virgo
network at its design sensitivity, we assess that this model can provide a
robust measurement of the charge-to-mass ratio only for values $\bar{q} \gtrsim
0.5$; here we also assume that the mode amplitudes are similar to the uncharged
case in creating our simulated signal. Lower values, down to $\bar{q} \sim
0.3$, could instead be detected when evaluating the consistency of the
pre-merger and post-merger emission.
| [
{
"created": "Tue, 28 Sep 2021 18:03:43 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Apr 2022 14:05:16 GMT",
"version": "v2"
}
] | 2022-04-12 | [
[
"Carullo",
"Gregorio",
""
],
[
"Laghi",
"Danny",
""
],
[
"Johnson-McDaniel",
"Nathan K.",
""
],
[
"Del Pozzo",
"Walter",
""
],
[
"Dias",
"Oscar J. C.",
""
],
[
"Godazgar",
"Mahdi",
""
],
[
"Santos",
"Jorge E.",... | We construct a template to model the post-merger phase of a binary black hole coalescence in the presence of a remnant $U(1)$ charge. We include the quasi-normal modes typically dominant during a binary black hole coalescence, $(\ell,m,n) = \{(2,2,0), (2,2,1)\}$ and also present analytical fits for the quasinormal mode frequencies of a Kerr-Newman black hole in terms of its spin and charge, here also including the $(3,3,0)$ mode. Aside from astrophysical electric charge, our template can accommodate extensions of the Standard Model, such as a dark photon. Applying the model to LIGO-Virgo detections, we find that we are unable to distinguish between the charged and uncharged hypotheses from a purely post-merger analysis of the current events. However, restricting the mass and spin to values compatible with the analysis of the full signal, we obtain a 90th percentile bound $\bar{q} < 0.33$ on the black hole charge-to-mass ratio, for the most favorable case of GW150914. Under similar assumptions, by simulating a typical loud signal observed by the LIGO-Virgo network at its design sensitivity, we assess that this model can provide a robust measurement of the charge-to-mass ratio only for values $\bar{q} \gtrsim 0.5$; here we also assume that the mode amplitudes are similar to the uncharged case in creating our simulated signal. Lower values, down to $\bar{q} \sim 0.3$, could instead be detected when evaluating the consistency of the pre-merger and post-merger emission. |
1809.06511 | Xi-Long Fan | Zhang Hongsheng, Fan Xilong | Poisson-Arago spot for gravitational waves | null | Sci. China-Phys. Mech. Astron. 64, 120462 (2021) | 10.1007/s11433-021-1764-y | LIGO-P1800127 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For the observer at infinity, a Schwarzschild black hole serves as an
attractive opaque disk with a radius of 3$\sqrt{3} M$ that will produce the
diffraction pattern of gravitational waves (GWs). In this study, we demonstrate
that a bright spot, which is a diffraction effect analogous to the
Poisson-Arago spot in optics, will appear when an ingoing (quasi-) plane GW is
diffracted by a Schwarzschild black hole. Here, we propose the diffraction
effect of the GWs described by the exact diffraction solution of the GWs using
the Heun function. For the first time, the Fresnel half-wave zone method is
proposed to calculate the angular part of the GW scattering stripes for the
observer at infinity. The prospect of observing the diffraction bright spot is
discussed with an eikonal approximation. For normal incidence (quasi)-plane
waves with 100 Hz (0.1 Hz) frequency diffracted by the central black hole of
the Milky Way, the time delay between the Earth bathed in a bright spot and the
minimum of the first dark stripe is 3.86 (3860) days. We will witness the
second bright fringe (40% amplitude of the central bright spot) after 6.2
(6200) days. This new diffraction pattern involving the early phase of
inspirals and pulsars as continuous gravitational wave sources is a potential
scientific target for future space-and ground-based gravitational wave
detectors, respectively.
| [
{
"created": "Tue, 18 Sep 2018 02:39:32 GMT",
"version": "v1"
},
{
"created": "Tue, 11 May 2021 14:07:31 GMT",
"version": "v2"
},
{
"created": "Tue, 9 Nov 2021 06:17:51 GMT",
"version": "v3"
}
] | 2021-11-10 | [
[
"Hongsheng",
"Zhang",
""
],
[
"Xilong",
"Fan",
""
]
] | For the observer at infinity, a Schwarzschild black hole serves as an attractive opaque disk with a radius of 3$\sqrt{3} M$ that will produce the diffraction pattern of gravitational waves (GWs). In this study, we demonstrate that a bright spot, which is a diffraction effect analogous to the Poisson-Arago spot in optics, will appear when an ingoing (quasi-) plane GW is diffracted by a Schwarzschild black hole. Here, we propose the diffraction effect of the GWs described by the exact diffraction solution of the GWs using the Heun function. For the first time, the Fresnel half-wave zone method is proposed to calculate the angular part of the GW scattering stripes for the observer at infinity. The prospect of observing the diffraction bright spot is discussed with an eikonal approximation. For normal incidence (quasi)-plane waves with 100 Hz (0.1 Hz) frequency diffracted by the central black hole of the Milky Way, the time delay between the Earth bathed in a bright spot and the minimum of the first dark stripe is 3.86 (3860) days. We will witness the second bright fringe (40% amplitude of the central bright spot) after 6.2 (6200) days. This new diffraction pattern involving the early phase of inspirals and pulsars as continuous gravitational wave sources is a potential scientific target for future space-and ground-based gravitational wave detectors, respectively. |
1804.08950 | Oliver J. Tattersall | Oliver J. Tattersall, Pedro G. Ferreira | Quasi-normal modes of black holes in Horndeski gravity | 10 pages, 4 figures. Submitted to PRD | Phys. Rev. D 97, 104047 (2018) | 10.1103/PhysRevD.97.104047 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the perturbations to General Relativistic black holes (i.e. those
without scalar hair) in Horndeski scalar-tensor gravity. First, we derive the
equations of odd and even parity perturbations of both the metric and scalar
field in the case of a Schwarzschild black hole, and show that the
gravitational waves emitted from such a system contain a mixture of
quasi-normal mode frequencies from the usual General Relativistic spectrum and
those from the new scalar field spectrum, with the new scalar spectrum
characterised by just two free parameters. We then specialise to the sub-family
of Horndeski theories in which gravitational waves propagate at the speed of
light $c$ on cosmological backgrounds; the scalar quasi-normal mode spectrum of
such theories is characterised by just a single parameter $\mu$ acting as an
effective mass of the scalar field. Analytical expressions for the quasi-normal
mode frequencies of the scalar spectrum in this sub-family of theories are
provided for both static and slowly rotating black holes. In both regimes
comparisons to quasi-normal modes calculated numerically show good agreement
with those calculated analytically in this work.
| [
{
"created": "Tue, 24 Apr 2018 10:56:01 GMT",
"version": "v1"
}
] | 2018-05-30 | [
[
"Tattersall",
"Oliver J.",
""
],
[
"Ferreira",
"Pedro G.",
""
]
] | We study the perturbations to General Relativistic black holes (i.e. those without scalar hair) in Horndeski scalar-tensor gravity. First, we derive the equations of odd and even parity perturbations of both the metric and scalar field in the case of a Schwarzschild black hole, and show that the gravitational waves emitted from such a system contain a mixture of quasi-normal mode frequencies from the usual General Relativistic spectrum and those from the new scalar field spectrum, with the new scalar spectrum characterised by just two free parameters. We then specialise to the sub-family of Horndeski theories in which gravitational waves propagate at the speed of light $c$ on cosmological backgrounds; the scalar quasi-normal mode spectrum of such theories is characterised by just a single parameter $\mu$ acting as an effective mass of the scalar field. Analytical expressions for the quasi-normal mode frequencies of the scalar spectrum in this sub-family of theories are provided for both static and slowly rotating black holes. In both regimes comparisons to quasi-normal modes calculated numerically show good agreement with those calculated analytically in this work. |
2405.10321 | Jorge Russo | Jorge G. Russo | Probing Hidden Dimensions via Muon Lifetime Measurements | Honorable Mention in the Gravity Research Foundation 2024 Awards for
Essays on Gravitation. 11 pages | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of Kaluza-Klein theories, the time dilation of charged
particles in an external field depends on the charge in a specific way.
Experimental tests are proposed to search for extra dimensions using this
distinctive feature.
| [
{
"created": "Thu, 16 May 2024 17:59:52 GMT",
"version": "v1"
}
] | 2024-05-17 | [
[
"Russo",
"Jorge G.",
""
]
] | In the context of Kaluza-Klein theories, the time dilation of charged particles in an external field depends on the charge in a specific way. Experimental tests are proposed to search for extra dimensions using this distinctive feature. |
0704.0399 | Gerard Clement | G. Clement, J.C. Fabris and G.T. Marques | Hawking radiation of linear dilaton black holes | 9 pages | Phys.Lett.B651:54-57,2007 | 10.1016/j.physletb.2007.05.052 | LAPTH-1178/07 | gr-qc hep-th | null | We compute exactly the semi-classical radiation spectrum for a class of
non-asymptotically flat charged dilaton black holes, the so-called linear
dilaton black holes. In the high frequency regime, the temperature for these
black holes generically agrees with the surface gravity result. In the special
case where the black hole is massless, we show that, although the surface
gravity remains finite, there is no radiation, in agreement with the fact that
massless objects cannot radiate.
| [
{
"created": "Tue, 3 Apr 2007 14:00:51 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Clement",
"G.",
""
],
[
"Fabris",
"J. C.",
""
],
[
"Marques",
"G. T.",
""
]
] | We compute exactly the semi-classical radiation spectrum for a class of non-asymptotically flat charged dilaton black holes, the so-called linear dilaton black holes. In the high frequency regime, the temperature for these black holes generically agrees with the surface gravity result. In the special case where the black hole is massless, we show that, although the surface gravity remains finite, there is no radiation, in agreement with the fact that massless objects cannot radiate. |
2302.09038 | Raghvendra Singh | Raghvendra Singh, Kabir Khanna, Dawood Kothawala | Decoherence due to Spacetime Curvature | 8 pages, 2 figures, typos fixed | null | null | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | There has been considerable interest over the past years in investigating the
role of gravity in quantum phenomenon such as entanglement and decoherence. In
particular, gravitational time dilation is believed to decohere superpositions
of center of mass of composite quantum systems. Since true effects of gravity
are encoded in the curvature of spacetime, the universality of such decoherence
must be characterized through components of Riemann tensor $R_{abcd}$, with a
clear separation from non-inertial kinematic effects. We obtain the reduced
density matrix of a composite system in a generic curved spacetime and express
the decoherence time scale explicitly in terms of curvature. The decoherence in
an inertial frame is caused by tidal acceleration. We also analyze the effects
of self-gravity and show that the coupling of gravitational interaction with
external curvature can not be captured by the replacement $m \to m + H_{\rm
int}/c^2$.
| [
{
"created": "Fri, 17 Feb 2023 18:12:15 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Mar 2023 15:27:33 GMT",
"version": "v2"
}
] | 2023-04-03 | [
[
"Singh",
"Raghvendra",
""
],
[
"Khanna",
"Kabir",
""
],
[
"Kothawala",
"Dawood",
""
]
] | There has been considerable interest over the past years in investigating the role of gravity in quantum phenomenon such as entanglement and decoherence. In particular, gravitational time dilation is believed to decohere superpositions of center of mass of composite quantum systems. Since true effects of gravity are encoded in the curvature of spacetime, the universality of such decoherence must be characterized through components of Riemann tensor $R_{abcd}$, with a clear separation from non-inertial kinematic effects. We obtain the reduced density matrix of a composite system in a generic curved spacetime and express the decoherence time scale explicitly in terms of curvature. The decoherence in an inertial frame is caused by tidal acceleration. We also analyze the effects of self-gravity and show that the coupling of gravitational interaction with external curvature can not be captured by the replacement $m \to m + H_{\rm int}/c^2$. |
1710.07962 | Andrea Addazi AndAdd | Andrea Addazi, Antonino Marciano | Evaporation and Antievaporation instabilities | Accepted in Symmetry, invited by Prof.S.Odintsov for special issue | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review (anti)evaporation phenomena within the context of quantum gravity
and extended theories of gravity. The (anti)evaporation effect is an
instability of the black hole horizon discovered in many different scenarios:
quantum dilaton-gravity, $f(R)$-gravity, $f(T)$-gravity, string inspired black
holes and brane-world cosmology. Evaporating and antievaporating black holes
seem to have completely different thermodynamical features compared to standard
semiclassical black holes. The purpose of this review is to provide an
introduction to conceptual and technical aspects of (anti)evaporation effects,
while discussing problems that are still open.
| [
{
"created": "Sun, 22 Oct 2017 15:27:19 GMT",
"version": "v1"
}
] | 2017-10-24 | [
[
"Addazi",
"Andrea",
""
],
[
"Marciano",
"Antonino",
""
]
] | We review (anti)evaporation phenomena within the context of quantum gravity and extended theories of gravity. The (anti)evaporation effect is an instability of the black hole horizon discovered in many different scenarios: quantum dilaton-gravity, $f(R)$-gravity, $f(T)$-gravity, string inspired black holes and brane-world cosmology. Evaporating and antievaporating black holes seem to have completely different thermodynamical features compared to standard semiclassical black holes. The purpose of this review is to provide an introduction to conceptual and technical aspects of (anti)evaporation effects, while discussing problems that are still open. |
1108.1496 | Theodore A. Jacobson | Ted Jacobson | Initial value constraints with tensor matter | 9 pages | null | 10.1088/0264-9381/28/24/245011 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In generally covariant metric gravity theories with tensor matter fields, the
initial value constraint equations, unlike in general relativity, are in
general not just the 0\mu-components of the metric field equation. This happens
because higher derivatives can occur in the matter stress tensor. A universal
form for these constraints is derived here from a generalized Bianchi identity
that includes matter fields. As an application, the constraints for
Einstein-aether theory are found.
| [
{
"created": "Sat, 6 Aug 2011 16:52:12 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Jacobson",
"Ted",
""
]
] | In generally covariant metric gravity theories with tensor matter fields, the initial value constraint equations, unlike in general relativity, are in general not just the 0\mu-components of the metric field equation. This happens because higher derivatives can occur in the matter stress tensor. A universal form for these constraints is derived here from a generalized Bianchi identity that includes matter fields. As an application, the constraints for Einstein-aether theory are found. |
gr-qc/0605074 | Naresh Dadhich | Naresh Dadhich (IUCAA, Pune) | A Unified View of the Basic Forces | 4 pages, latex, To appear in Proceedings of the Einstein Centennial
Maeting, University of Kwazulu-Natal, Durban, Sept. 25-26, 2005 | null | null | null | gr-qc astro-ph hep-lat hep-ph hep-th | null | In this essay we wish to seek a unifying thread between the basic forces. We
propose that there exists a universal force which is shared by all that
physically exists. Universality is characterized by the two properties: (i)
universal linkage and (ii) long range. They uniquely identify Einstein gravity
as the unversal force. All other forces then arise as these properties are
peeled off. For instance, relaxing (i) but retaining (ii) will lead to Maxwell
electromagnetic force. This unified outlook makes interesting suggestions and
predictions: if there exists a new force, it can only be a short range
non-abelian vector or a scalar field, and there should exist in an appropriate
space duality relations between weak and electric, and between strong and
gravity.
| [
{
"created": "Fri, 12 May 2006 04:18:51 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Dadhich",
"Naresh",
"",
"IUCAA, Pune"
]
] | In this essay we wish to seek a unifying thread between the basic forces. We propose that there exists a universal force which is shared by all that physically exists. Universality is characterized by the two properties: (i) universal linkage and (ii) long range. They uniquely identify Einstein gravity as the unversal force. All other forces then arise as these properties are peeled off. For instance, relaxing (i) but retaining (ii) will lead to Maxwell electromagnetic force. This unified outlook makes interesting suggestions and predictions: if there exists a new force, it can only be a short range non-abelian vector or a scalar field, and there should exist in an appropriate space duality relations between weak and electric, and between strong and gravity. |
2012.14428 | Behnam Pourhassan | Behnam Pourhassan, Mohsen Dehghani, Mir Faizal, Sanjib Dey | Non-Pertubative Quantum Corrections to a Born-Infeld Black Hole and its
Information Geometry | 17 pages, 15 figures. Accepted in Class. Quantum Grav | Class. Quantum Grav. 38 (2021) 105001 | 10.1088/1361-6382/abdf6f | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the non-perturbative quantum corrections to a Born-Infeld black hole
in a spherical cavity. These quantum corrections produce a non-trivial short
distances modification to the relation between the entropy and area of this
black hole. The non-perturbative quantum correction appears as an exponential
term in the black hole entropy. This in turn modifies the thermodynamics of a
given system, for example reduced value of the Helmholtz free energy. Moreover,
the first law of black hole thermodynamics modified due to quantum corrections.
We also investigate the effect of such non-perturbative corrections on the
information geometry of this system. This is done using some famous information
metrics.
| [
{
"created": "Sat, 26 Dec 2020 20:34:53 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Jan 2021 05:34:44 GMT",
"version": "v2"
}
] | 2021-04-20 | [
[
"Pourhassan",
"Behnam",
""
],
[
"Dehghani",
"Mohsen",
""
],
[
"Faizal",
"Mir",
""
],
[
"Dey",
"Sanjib",
""
]
] | We study the non-perturbative quantum corrections to a Born-Infeld black hole in a spherical cavity. These quantum corrections produce a non-trivial short distances modification to the relation between the entropy and area of this black hole. The non-perturbative quantum correction appears as an exponential term in the black hole entropy. This in turn modifies the thermodynamics of a given system, for example reduced value of the Helmholtz free energy. Moreover, the first law of black hole thermodynamics modified due to quantum corrections. We also investigate the effect of such non-perturbative corrections on the information geometry of this system. This is done using some famous information metrics. |
gr-qc/9806112 | Andrei V. Frolov | Andrei V. Frolov | Self-Similar Collapse of Scalar Field in Higher Dimensions | RevTex 3.1, 15 pages, 3 figures; references added | Class.Quant.Grav.16:407-417,1999 | 10.1088/0264-9381/16/2/007 | null | gr-qc | null | This paper constructs continuously self-similar solution of a spherically
symmetric gravitational collapse of a scalar field in n dimensions. The
qualitative behavior of these solutions is explained, and closed-form answers
are provided where possible. Equivalence of scalar field couplings is used to
show a way to generalize minimally coupled scalar field solutions to the model
with general coupling.
| [
{
"created": "Mon, 29 Jun 1998 00:44:30 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Nov 1998 19:29:52 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Frolov",
"Andrei V.",
""
]
] | This paper constructs continuously self-similar solution of a spherically symmetric gravitational collapse of a scalar field in n dimensions. The qualitative behavior of these solutions is explained, and closed-form answers are provided where possible. Equivalence of scalar field couplings is used to show a way to generalize minimally coupled scalar field solutions to the model with general coupling. |
2011.06466 | Grigory Volovik | G.E. Volovik | Combined Lorentz symmetry: lessons from superfluid 3He | 8 pages, no figures, accepted in J. Low Temp. Phys | null | 10.1007/s10909-021-02630-7 | null | gr-qc cond-mat.other hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the possibility of the scenario in which the $P$, $T$ and Lorentz
symmetry of the relativistic quantum vacuum are all the combined symmetries.
These symmetries emerge as a result of the symmetry breaking of the more
fundamental $P$, $T$ and Lorentz symmetries of the original vacuum, which is
invariant under separate groups of the coordinate transformations and spin
rotations. The condensed matter vacua (ground states) suggest two possible
scenarios of the origin of the combined Lorentz symmetry, both are realized in
the superfluid phases of liquid $^3$He: the $^3$He-A scenario and the $^3$He-B
scenario. In these scenarios the gravitational tetrads are considered as the
order parameter of the symmetry breaking in the quantum vacuum. The $^3$He-B
scenarios applied to the Minkowski vacuum leads to the continuous degeneracy of
the Minkowski vacuum with respect to the $O(3,1)$ spin rotations. The symmetry
breaking leads to the corresponding topological objects, which appear due to
the nontrivial topology of the manifold of the degenerate Minkowski vacua, such
as torsion strings. The 4-fold degeneracy of the Minkowski vacuum with respect
to discrete $P$ and $T$ symmetries suggests that the Weyl fermions are
described by four different tetrad fields: the tetrad for the left-handed
fermions, the tetrad for the right-handed fermions, and the tetrads for their
antiparticles. This may lead to the gravity with several metric fields, so that
the parity violation may lead to the breaking of equivalence principle. Finally
we considered the application of the gravitational tetrads for the solution of
the cosmological constant problem.
| [
{
"created": "Thu, 12 Nov 2020 16:17:40 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Aug 2021 17:25:21 GMT",
"version": "v10"
},
{
"created": "Mon, 27 Sep 2021 15:52:07 GMT",
"version": "v11"
},
{
"created": "Mon, 7 Dec 2020 10:55:46 GMT",
"version": "v2"
},
{
"c... | 2021-11-17 | [
[
"Volovik",
"G. E.",
""
]
] | We consider the possibility of the scenario in which the $P$, $T$ and Lorentz symmetry of the relativistic quantum vacuum are all the combined symmetries. These symmetries emerge as a result of the symmetry breaking of the more fundamental $P$, $T$ and Lorentz symmetries of the original vacuum, which is invariant under separate groups of the coordinate transformations and spin rotations. The condensed matter vacua (ground states) suggest two possible scenarios of the origin of the combined Lorentz symmetry, both are realized in the superfluid phases of liquid $^3$He: the $^3$He-A scenario and the $^3$He-B scenario. In these scenarios the gravitational tetrads are considered as the order parameter of the symmetry breaking in the quantum vacuum. The $^3$He-B scenarios applied to the Minkowski vacuum leads to the continuous degeneracy of the Minkowski vacuum with respect to the $O(3,1)$ spin rotations. The symmetry breaking leads to the corresponding topological objects, which appear due to the nontrivial topology of the manifold of the degenerate Minkowski vacua, such as torsion strings. The 4-fold degeneracy of the Minkowski vacuum with respect to discrete $P$ and $T$ symmetries suggests that the Weyl fermions are described by four different tetrad fields: the tetrad for the left-handed fermions, the tetrad for the right-handed fermions, and the tetrads for their antiparticles. This may lead to the gravity with several metric fields, so that the parity violation may lead to the breaking of equivalence principle. Finally we considered the application of the gravitational tetrads for the solution of the cosmological constant problem. |
2207.00057 | Vyacheslav Dokuchaev | V. A. Berezin and V. I. Dokuchaev | Cosmological particle creation in Weyl geometry | 18 pages | 2023 Class. Quantum Grav. 40 015006 | 10.1088/1361-6382/aca57e | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigated the possibility of the homogeneous and isotropic cosmological
solution in Weyl geometry, which differs from the Riemannian geometry by adding
the so called Weyl vector. The Weyl gravity is obtained by constructing the
gravitational Lagrangian both to be quadratic in curvatures and conformal
invariant. It is found that such solution may exist provided there exists the
direct interaction between the Weyl vector and the matter fields. Assuming the
matter Lagrangian is that of the perfect fluid, we found how such an
interaction can be implemented. Due to the existence of quadratic curvature
terms and the direct interaction the perfect fluid particles may be created
straight from the vacuum, and we found the expression for the rate of their
production which appeared to be conformal invariant. In the case of creating
the universe ``from nothing'' in the vacuum state, we investigated the problem,
whether this vacuum may persist or not. It is shown that the vacuum may persist
with respect to producing the non-dust matter (with positive pressure), but
cannot resist to producing the dust particles. These particles, being
non-interactive, may be considered as the candidates for dark matter.
| [
{
"created": "Thu, 30 Jun 2022 18:43:06 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Dec 2022 08:22:13 GMT",
"version": "v2"
}
] | 2022-12-06 | [
[
"Berezin",
"V. A.",
""
],
[
"Dokuchaev",
"V. I.",
""
]
] | We investigated the possibility of the homogeneous and isotropic cosmological solution in Weyl geometry, which differs from the Riemannian geometry by adding the so called Weyl vector. The Weyl gravity is obtained by constructing the gravitational Lagrangian both to be quadratic in curvatures and conformal invariant. It is found that such solution may exist provided there exists the direct interaction between the Weyl vector and the matter fields. Assuming the matter Lagrangian is that of the perfect fluid, we found how such an interaction can be implemented. Due to the existence of quadratic curvature terms and the direct interaction the perfect fluid particles may be created straight from the vacuum, and we found the expression for the rate of their production which appeared to be conformal invariant. In the case of creating the universe ``from nothing'' in the vacuum state, we investigated the problem, whether this vacuum may persist or not. It is shown that the vacuum may persist with respect to producing the non-dust matter (with positive pressure), but cannot resist to producing the dust particles. These particles, being non-interactive, may be considered as the candidates for dark matter. |
2005.08426 | Luca Buoninfante | Luca Buoninfante | Echoes from corpuscular black holes | V2: 16 pages, 1 figure. Version accepted for publication in JCAP | null | 10.1088/1475-7516/2020/12/041 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the corpuscular picture of black hole there exists no geometric notion of
horizon which, instead, only emerges in the semi-classical limit. Therefore, it
is very natural to ask - what happens if we send a signal towards a corpuscular
black hole? We show that quantum effects at the horizon scale imply the
existence of a surface located at an effective radius $R=R_s(1+\epsilon)$
slightly larger than the Schwarzschild radius $R_s,$ where $\epsilon=1/N$ and
$N$ is the number of gravitons composing the system. Consequently, the
reflectivity of the object can be non-zero and, indeed, we find that incoming
waves with energies comparable to the Hawking temperature can have a
probability of backscattering of order one. Thus, modes can be trapped between
the two potential barriers located at the photon sphere and at the surface of a
corpuscular black hole, and periodic echoes can be produced. The time delay of
echoes turns out to be of the same order of the scrambling time, i.e., in units
of Planck length it reads $\sqrt{N}\,{\rm log}\,N.$ We also show that the
$\epsilon$-parameter, or in other words the compactness, of a corpuscular black
hole coincides with the quantum coupling that measures the interaction strength
among gravitons, and discuss the physical implications of this remarkable
feature.
| [
{
"created": "Mon, 18 May 2020 02:15:47 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Dec 2020 07:26:50 GMT",
"version": "v2"
}
] | 2021-01-06 | [
[
"Buoninfante",
"Luca",
""
]
] | In the corpuscular picture of black hole there exists no geometric notion of horizon which, instead, only emerges in the semi-classical limit. Therefore, it is very natural to ask - what happens if we send a signal towards a corpuscular black hole? We show that quantum effects at the horizon scale imply the existence of a surface located at an effective radius $R=R_s(1+\epsilon)$ slightly larger than the Schwarzschild radius $R_s,$ where $\epsilon=1/N$ and $N$ is the number of gravitons composing the system. Consequently, the reflectivity of the object can be non-zero and, indeed, we find that incoming waves with energies comparable to the Hawking temperature can have a probability of backscattering of order one. Thus, modes can be trapped between the two potential barriers located at the photon sphere and at the surface of a corpuscular black hole, and periodic echoes can be produced. The time delay of echoes turns out to be of the same order of the scrambling time, i.e., in units of Planck length it reads $\sqrt{N}\,{\rm log}\,N.$ We also show that the $\epsilon$-parameter, or in other words the compactness, of a corpuscular black hole coincides with the quantum coupling that measures the interaction strength among gravitons, and discuss the physical implications of this remarkable feature. |
0904.2577 | Enrico Barausse | Enrico Barausse (UMD), Luciano Rezzolla (AEI) | Predicting the direction of the final spin from the coalescence of two
black holes | 5 pages, 3 figures. Significant changes to text and figures to match
version accepted for publication in ApJ Letters | Astrophys.J.Lett.704:L40-L44,2009; Astrophys.J.704:L40-L44,2009 | 10.1088/0004-637X/704/1/L40 | null | gr-qc astro-ph.CO astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Knowledge of the spin of the black hole resulting from the merger of a
generic black-hole binary is of great importance for studying the cosmological
evolution of supermassive black holes. Several attempts have been made to model
the spin via simple expressions exploiting the results of numerical-relativity
simulations. While these expressions are in reasonable agreement with the
simulations, they neglect the precession of the binary's orbital plane, and
cannot therefore be applied directly -- i.e., without evolving the system to
small separations using post-Newtonian theory -- to binaries with separations
larger than a few hundred gravitational radii. While not a problem in
principle, this may be impractical if the formulas are employed in cosmological
merger-trees or N-body simulations, which provide the spins and angular
momentum of the two black holes when their separation is of hundreds or
thousands of gravitational radii. The formula that we propose is instead built
on improved assumptions and gives, for any separation, a very accurate
prediction both for the norm of the final spin and for its direction. By
comparing with the numerical data, we also show that the final-spin direction
is very accurately aligned with the binary's total angular momentum at large
separation. Hence, observations of the final-spin direction (e.g. via a jet)
can provide information on the binary's orbital plane at large separations and
could be relevant, for instance, for studying X-shaped radio sources.
| [
{
"created": "Thu, 16 Apr 2009 22:16:20 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Sep 2009 16:57:19 GMT",
"version": "v2"
}
] | 2011-05-24 | [
[
"Barausse",
"Enrico",
"",
"UMD"
],
[
"Rezzolla",
"Luciano",
"",
"AEI"
]
] | Knowledge of the spin of the black hole resulting from the merger of a generic black-hole binary is of great importance for studying the cosmological evolution of supermassive black holes. Several attempts have been made to model the spin via simple expressions exploiting the results of numerical-relativity simulations. While these expressions are in reasonable agreement with the simulations, they neglect the precession of the binary's orbital plane, and cannot therefore be applied directly -- i.e., without evolving the system to small separations using post-Newtonian theory -- to binaries with separations larger than a few hundred gravitational radii. While not a problem in principle, this may be impractical if the formulas are employed in cosmological merger-trees or N-body simulations, which provide the spins and angular momentum of the two black holes when their separation is of hundreds or thousands of gravitational radii. The formula that we propose is instead built on improved assumptions and gives, for any separation, a very accurate prediction both for the norm of the final spin and for its direction. By comparing with the numerical data, we also show that the final-spin direction is very accurately aligned with the binary's total angular momentum at large separation. Hence, observations of the final-spin direction (e.g. via a jet) can provide information on the binary's orbital plane at large separations and could be relevant, for instance, for studying X-shaped radio sources. |
gr-qc/0209030 | Valdir B. Bezerra | Geusa de A. Marques (UFPb) and V. B. Bezerra (UFPb) | Hydrogen atom in the gravitational fields of topological defects | 17 pages, LATEX file | Phys.Rev. D66 (2002) 105011 | 10.1103/PhysRevD.66.105011 | null | gr-qc | null | We consider a hydrogen atom in the background spacetimes generated by an
infinitely thin cosmic string and by a point-like global monopole. In both
cases, we find the solutions of the corresponding Dirac equations and we
determine the energy levels of the atom. We investigate how the geometric and
topological features of these spacetimes leads to shifts in the energy levels
as compared with the flat Minkowski spacetime.
| [
{
"created": "Mon, 9 Sep 2002 17:54:06 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Marques",
"Geusa de A.",
"",
"UFPb"
],
[
"Bezerra",
"V. B.",
"",
"UFPb"
]
] | We consider a hydrogen atom in the background spacetimes generated by an infinitely thin cosmic string and by a point-like global monopole. In both cases, we find the solutions of the corresponding Dirac equations and we determine the energy levels of the atom. We investigate how the geometric and topological features of these spacetimes leads to shifts in the energy levels as compared with the flat Minkowski spacetime. |
1105.3385 | Johannes Tambornino | Etera R. Livine, Johannes Tambornino | Spinor Representation for Loop Quantum Gravity | 36 pages, minor corrections and improvements, matches published
version | J. Math. Phys. 53, 012503 (2012) | 10.1063/1.3675465 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a quantization of the loop gravity phase space purely in terms of
spinorial variables, which have recently been shown to provide a direct link
between spin network states and simplicial geometries. The natural Hilbert
space to represent these spinors is the Bargmann space of holomorphic
square-integrable functions over complex numbers. We show the unitary
equivalence between the resulting generalized Bargmann space and the standard
loop quantum gravity Hilbert space by explicitly constructing the unitary map.
The latter maps SU(2)-holonomies, when written as a function of spinors, to
their holomorphic part. We analyze the properties of this map in detail. We
show that the subspace of gauge invariant states can be characterized
particularly easy in this representation of loop gravity. Furthermore, this map
provides a tool to efficiently calculate physical quantities since integrals
over the group are exchanged for straightforward integrals over the complex
plane.
| [
{
"created": "Tue, 17 May 2011 14:11:43 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Feb 2012 16:51:47 GMT",
"version": "v2"
}
] | 2012-02-03 | [
[
"Livine",
"Etera R.",
""
],
[
"Tambornino",
"Johannes",
""
]
] | We perform a quantization of the loop gravity phase space purely in terms of spinorial variables, which have recently been shown to provide a direct link between spin network states and simplicial geometries. The natural Hilbert space to represent these spinors is the Bargmann space of holomorphic square-integrable functions over complex numbers. We show the unitary equivalence between the resulting generalized Bargmann space and the standard loop quantum gravity Hilbert space by explicitly constructing the unitary map. The latter maps SU(2)-holonomies, when written as a function of spinors, to their holomorphic part. We analyze the properties of this map in detail. We show that the subspace of gauge invariant states can be characterized particularly easy in this representation of loop gravity. Furthermore, this map provides a tool to efficiently calculate physical quantities since integrals over the group are exchanged for straightforward integrals over the complex plane. |
2402.15336 | N V Krishnendu | N. V. Krishnendu and Sumanta Chakraborty | Probing black hole `charge' from the binary black hole inspiral | 13 pages, 9 figures, PRD Published version | Phys. Rev. D 109, 124047, Published 20 June 2024 | 10.1103/PhysRevD.109.124047 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent gravitational wave (GW) observations have enabled us to look beyond
the standard paradigm of gravitational physics, namely general relativity (GR).
Along with the mass and the angular momentum, which typical astrophysical black
holes (BHs) are endowed with, theories beyond GR generically induce `charge' to
these BHs. Notably, for BHs carrying the extra `charge' hair, we expect the BH
absorption effects to modify accordingly and alter the tidal heating terms.
Hence, the inclusion of the corrections in the GW waveform model, arising from
the BH `charge', allows us to test the consistency of the observed binaries
with Kerr BHs in GR. We compute the explicit dependence of the binary inspiral
phase on the `charge' parameter arising from the tidal heating effect and study
the measurability of the same from GW observations of binary mergers.
Specifically, we employ the {\tt TaylorF2} waveform model, which accurately
models the inspiral evolution of an aligned-spin binary merger, and Bayesian
analysis-based GW data inference to measure the `charge' parameter for a
selected set of detected binaries. We also present a detailed simulation study
to investigate the possibility of measuring the charge parameter from binaries
with different masses, spins and source locations. The analysis of selected GW
events from the third GW transient catalogue shows that the `charge' parameter
constraints are poor from the observed signals with the current sensitivity. In
contrast, the simulation studies indicate that the spinning binaries with
significant mass asymmetry provide the best constraints on the BH `charge'
parameter. Finally, we study the prospects of measuring the BH `charge'
parameter from a future GW detector with improved sensitivity.
| [
{
"created": "Fri, 23 Feb 2024 14:15:59 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Jun 2024 09:21:23 GMT",
"version": "v2"
}
] | 2024-06-25 | [
[
"Krishnendu",
"N. V.",
""
],
[
"Chakraborty",
"Sumanta",
""
]
] | Recent gravitational wave (GW) observations have enabled us to look beyond the standard paradigm of gravitational physics, namely general relativity (GR). Along with the mass and the angular momentum, which typical astrophysical black holes (BHs) are endowed with, theories beyond GR generically induce `charge' to these BHs. Notably, for BHs carrying the extra `charge' hair, we expect the BH absorption effects to modify accordingly and alter the tidal heating terms. Hence, the inclusion of the corrections in the GW waveform model, arising from the BH `charge', allows us to test the consistency of the observed binaries with Kerr BHs in GR. We compute the explicit dependence of the binary inspiral phase on the `charge' parameter arising from the tidal heating effect and study the measurability of the same from GW observations of binary mergers. Specifically, we employ the {\tt TaylorF2} waveform model, which accurately models the inspiral evolution of an aligned-spin binary merger, and Bayesian analysis-based GW data inference to measure the `charge' parameter for a selected set of detected binaries. We also present a detailed simulation study to investigate the possibility of measuring the charge parameter from binaries with different masses, spins and source locations. The analysis of selected GW events from the third GW transient catalogue shows that the `charge' parameter constraints are poor from the observed signals with the current sensitivity. In contrast, the simulation studies indicate that the spinning binaries with significant mass asymmetry provide the best constraints on the BH `charge' parameter. Finally, we study the prospects of measuring the BH `charge' parameter from a future GW detector with improved sensitivity. |
gr-qc/0106050 | Ernst Schmutzer | E.Schmutzer | Dark Matter and Rotation Curves of Stars in Galaxies | 14 pages, 4 figures, LaTex | Astron. Nachr. 322 (2001) 103 | 10.1002/1521-3994(200106)322:2<103::AID-ASNA103>3.0.CO;2-V | null | gr-qc | null | The dark matter accretion theory (around a central body) of the author on the
basis of his 5-dimensional Projective Unified Field Theory (PUFT) is applied to
the orbital motion of stars around the center of the Galaxy. The departure of
the motion from Newtonian mechanics leads to approximately flat rotation curves
being in rough accordance with the empirical facts. The spirality of the motion
is investigated.
| [
{
"created": "Thu, 14 Jun 2001 14:56:02 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Schmutzer",
"E.",
""
]
] | The dark matter accretion theory (around a central body) of the author on the basis of his 5-dimensional Projective Unified Field Theory (PUFT) is applied to the orbital motion of stars around the center of the Galaxy. The departure of the motion from Newtonian mechanics leads to approximately flat rotation curves being in rough accordance with the empirical facts. The spirality of the motion is investigated. |
2403.18709 | Zhengcheng Liang | Zheng-Cheng Liang, Zhi-Yuan Li, En-Kun Li, Jian-dong Zhang, and
Yi-Ming Hu | Revisiting Stochastic Gravitational-wave Background in the Strong Signal
Case | 11 pages, 7 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Weak-signal limit is often used in estimating stochastic gravitational-wave
background (SGWB) intensities. This approximation fails and the signal-to-noise
ratio (SNR) can be much weaker when background signals are loud compared to the
detector noise. In this work, we highlight this limitation for the SGWB
detection using space-borne detector networks. For the TianQin + LISA network,
the SNR estimated under the weak-signal limit might be off by as large as an
order of magnitude. Contour plots of SNR over the parameter spaces are also
presented to indicate regions susceptible to this discrepancy. Our results
suggest that DA and DB type extragalactic double white dwarfs may yield an SGWB
with SNR surpassing 100 after 1 year of operation in the weak-signal-limit
scenario, with a redshift-independent merger rate of about $500\,\,{\rm
Mpc^{-3}\,Myr^{-1}}$. In fact, this value falls significantly below the
necessary threshold. Similar influences arise for first-order phase
transitions, yet pinning down parameter regions remains formidable due to model
uncertainties.
| [
{
"created": "Wed, 27 Mar 2024 15:57:30 GMT",
"version": "v1"
}
] | 2024-03-28 | [
[
"Liang",
"Zheng-Cheng",
""
],
[
"Li",
"Zhi-Yuan",
""
],
[
"Li",
"En-Kun",
""
],
[
"Zhang",
"Jian-dong",
""
],
[
"Hu",
"Yi-Ming",
""
]
] | Weak-signal limit is often used in estimating stochastic gravitational-wave background (SGWB) intensities. This approximation fails and the signal-to-noise ratio (SNR) can be much weaker when background signals are loud compared to the detector noise. In this work, we highlight this limitation for the SGWB detection using space-borne detector networks. For the TianQin + LISA network, the SNR estimated under the weak-signal limit might be off by as large as an order of magnitude. Contour plots of SNR over the parameter spaces are also presented to indicate regions susceptible to this discrepancy. Our results suggest that DA and DB type extragalactic double white dwarfs may yield an SGWB with SNR surpassing 100 after 1 year of operation in the weak-signal-limit scenario, with a redshift-independent merger rate of about $500\,\,{\rm Mpc^{-3}\,Myr^{-1}}$. In fact, this value falls significantly below the necessary threshold. Similar influences arise for first-order phase transitions, yet pinning down parameter regions remains formidable due to model uncertainties. |
1704.07211 | Aindri\'u Conroy Mr. | Aindri\'u Conroy | Infinite Derivative Gravity: A Ghost and Singularity-free Theory | PhD Thesis, April 2017, Lancaster University Physics Department, 146
pages, 5 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The objective of this thesis is to present a viable extension of general
relativity free from cosmological singularities. A viable cosmology, in this
sense, is one that is free from ghosts, tachyons or exotic matter, while
staying true to the theoretical foundations of General Relativity such as
general covariance, as well as observed phenomenon such as the accelerated
expansion of the universe and inflationary behaviour at later times. To this
end, an infinite derivative extension of relativity is introduced, with the
gravitational action derived and the non-linear field equations calculated,
before being linearised around both Minkowski space and de Sitter space. The
theory is then constrained so as to avoid ghosts and tachyons by appealing to
the modified propagator, which is also derived. Finally, the Raychaudhuri
Equation is employed in order to describe the ghost-free, defocusing behaviour
around both Minkowski and de Sitter spacetimes, in the linearised regime.
| [
{
"created": "Mon, 24 Apr 2017 13:30:19 GMT",
"version": "v1"
}
] | 2017-04-25 | [
[
"Conroy",
"Aindriú",
""
]
] | The objective of this thesis is to present a viable extension of general relativity free from cosmological singularities. A viable cosmology, in this sense, is one that is free from ghosts, tachyons or exotic matter, while staying true to the theoretical foundations of General Relativity such as general covariance, as well as observed phenomenon such as the accelerated expansion of the universe and inflationary behaviour at later times. To this end, an infinite derivative extension of relativity is introduced, with the gravitational action derived and the non-linear field equations calculated, before being linearised around both Minkowski space and de Sitter space. The theory is then constrained so as to avoid ghosts and tachyons by appealing to the modified propagator, which is also derived. Finally, the Raychaudhuri Equation is employed in order to describe the ghost-free, defocusing behaviour around both Minkowski and de Sitter spacetimes, in the linearised regime. |
2106.11555 | Weifeng Ding | Weifeng Ding, Zhaoying Wang | Laser propagation in Rindler accelerated reference frame based on matrix
optics | 7 pages,4 figures | null | 10.1364/OE.434951 | null | gr-qc physics.optics | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Rindler spacetime describing a series of accelerating observers is Ricci
flat, but it still has novel optical effects. In the case of WKB approximation,
we derive the light geodesics in the Rindler frame based on the covariant wave
equation and geodesic equations. Then, we use ABCD matrix optics method to
explore the propagation characteristics of Rindler frame, thus link three
different optical transformation scenes (geometry, gravity and vacuum
refractive index) together. Moreover, the propagation characteristics of hollow
beam in Rindler spacetime are described analytically. Those characteristics are
quite different from the ones in the flat spacetime. Based on these
calculations, we simply demonstrate the position uncertain relationship between
the transverse beam size and the momentum, which surprisingly coincides with
the derivation of quantization. We hope that we can provide one simple method
to analyze the beam propagation in the accelerated frame.
| [
{
"created": "Tue, 22 Jun 2021 06:20:46 GMT",
"version": "v1"
}
] | 2021-09-01 | [
[
"Ding",
"Weifeng",
""
],
[
"Wang",
"Zhaoying",
""
]
] | The Rindler spacetime describing a series of accelerating observers is Ricci flat, but it still has novel optical effects. In the case of WKB approximation, we derive the light geodesics in the Rindler frame based on the covariant wave equation and geodesic equations. Then, we use ABCD matrix optics method to explore the propagation characteristics of Rindler frame, thus link three different optical transformation scenes (geometry, gravity and vacuum refractive index) together. Moreover, the propagation characteristics of hollow beam in Rindler spacetime are described analytically. Those characteristics are quite different from the ones in the flat spacetime. Based on these calculations, we simply demonstrate the position uncertain relationship between the transverse beam size and the momentum, which surprisingly coincides with the derivation of quantization. We hope that we can provide one simple method to analyze the beam propagation in the accelerated frame. |
1203.6448 | Kouji Nakamura | Kouji Nakamura | Gauge-invariant variables in general-relativistic perturbations:
globalization and zero-mode problem | (v1) 16 pages, no figure; (v2) 9 pages, no figure. Compactified for
"2012 Awards for Essays on Gravitation" promoted by Gravity Research
Foundation. References are deleted. no ingredients is changed. This version
received Honorable Mention for 2012 | International Journal of Modern Physics D Vol. 21, No. 11 (2012)
1242004 | 10.1142/S0218271812420047 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An outline of a proof of the local decomposition of linear metric
perturbations into gauge-invariant and gauge-variant parts on an arbitrary
background spacetime is briefly explained. We explicitly construct the
gauge-invariant and gauge-variant parts of the linear metric perturbations
based on some assumptions. We also point out the zero-mode problem is an
essential problem to globalize of this decomposition of linear metric
perturbations. The resolution of this zero-mode problem implies the possibility
of the development of the higher-order gauge-invariant perturbation theory on
an arbitrary background spacetime in a global sense.
| [
{
"created": "Thu, 29 Mar 2012 07:15:57 GMT",
"version": "v1"
},
{
"created": "Thu, 17 May 2012 07:24:34 GMT",
"version": "v2"
}
] | 2012-10-16 | [
[
"Nakamura",
"Kouji",
""
]
] | An outline of a proof of the local decomposition of linear metric perturbations into gauge-invariant and gauge-variant parts on an arbitrary background spacetime is briefly explained. We explicitly construct the gauge-invariant and gauge-variant parts of the linear metric perturbations based on some assumptions. We also point out the zero-mode problem is an essential problem to globalize of this decomposition of linear metric perturbations. The resolution of this zero-mode problem implies the possibility of the development of the higher-order gauge-invariant perturbation theory on an arbitrary background spacetime in a global sense. |
gr-qc/0211012 | Hanno Sahlmann | Abhay Ashtekar, Jerzy Lewandowski, and Hanno Sahlmann | Polymer and Fock representations for a Scalar field | 13 pages, no figures | Class.Quant.Grav. 20 (2003) L11-1 | 10.1088/0264-9381/20/1/103 | ESI-1233, CGPG-02/11-1 | gr-qc | null | In loop quantum gravity, matter fields can have support only on the
`polymer-like' excitations of quantum geometry, and their algebras of
observables and Hilbert spaces of states can not refer to a classical,
background geometry. Therefore, to adequately handle the matter sector, one has
to address two issues already at the kinematic level. First, one has to
construct the appropriate background independent operator algebras and Hilbert
spaces. Second, to make contact with low energy physics, one has to relate this
`polymer description' of matter fields to the standard Fock description in
Minkowski space. While this task has been completed for gauge fields, important
gaps remained in the treatment of scalar fields. The purpose of this letter is
to fill these gaps.
| [
{
"created": "Mon, 4 Nov 2002 17:59:27 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Lewandowski",
"Jerzy",
""
],
[
"Sahlmann",
"Hanno",
""
]
] | In loop quantum gravity, matter fields can have support only on the `polymer-like' excitations of quantum geometry, and their algebras of observables and Hilbert spaces of states can not refer to a classical, background geometry. Therefore, to adequately handle the matter sector, one has to address two issues already at the kinematic level. First, one has to construct the appropriate background independent operator algebras and Hilbert spaces. Second, to make contact with low energy physics, one has to relate this `polymer description' of matter fields to the standard Fock description in Minkowski space. While this task has been completed for gauge fields, important gaps remained in the treatment of scalar fields. The purpose of this letter is to fill these gaps. |
gr-qc/9608068 | null | Bj{\o}rn Jensen and Svend E. Hjelmeland | A stringy black string and a stringy black hole in four dimensions | 4 pages, twocolumn, Revtex, no figures. New results and references
added. Presentation and discussion improved | null | null | OSLO-TP-8-96 | gr-qc | null | We uplift the static three dimensional black hole solution found by Banados,
Teitelboim and Zanelli (BTZ) into four dimensional space time. In this way we
obtain a black string solution with a relativistic string source, as well as a
new black hole solution which is also generated by a relativistic ``stringy''
source. It is shown that when passing continuously from the region of the one
dimensional parameter spaces which characterize these solutions, containing
naked singular strings or naked singular ``points'', and into the region
containing black strings or black holes, the metrics ``blow up'' at a critical
point in both parameter spaces. We show that a similar ``separation'' mechanism
can be introduced in three dimensions. In this way we also obtain a
generalization of the BTZ solution. The ``separation'' mechanism, and its
immediate consequences, offers an hitherto missing technical argument needed in
order to exclude the naked singularities (the ``mass gap'') from the space of
``physically permissible'' solutions in three dimensional Einstein theory
coupled to a negative cosmological constant.
PACS nos.: 04.40.Nr, 04.20.Cv
| [
{
"created": "Thu, 29 Aug 1996 13:29:47 GMT",
"version": "v1"
},
{
"created": "Sun, 1 Sep 1996 12:41:28 GMT",
"version": "v2"
},
{
"created": "Mon, 23 Sep 1996 10:35:05 GMT",
"version": "v3"
}
] | 2008-02-03 | [
[
"Jensen",
"Bjørn",
""
],
[
"Hjelmeland",
"Svend E.",
""
]
] | We uplift the static three dimensional black hole solution found by Banados, Teitelboim and Zanelli (BTZ) into four dimensional space time. In this way we obtain a black string solution with a relativistic string source, as well as a new black hole solution which is also generated by a relativistic ``stringy'' source. It is shown that when passing continuously from the region of the one dimensional parameter spaces which characterize these solutions, containing naked singular strings or naked singular ``points'', and into the region containing black strings or black holes, the metrics ``blow up'' at a critical point in both parameter spaces. We show that a similar ``separation'' mechanism can be introduced in three dimensions. In this way we also obtain a generalization of the BTZ solution. The ``separation'' mechanism, and its immediate consequences, offers an hitherto missing technical argument needed in order to exclude the naked singularities (the ``mass gap'') from the space of ``physically permissible'' solutions in three dimensional Einstein theory coupled to a negative cosmological constant. PACS nos.: 04.40.Nr, 04.20.Cv |
1004.2477 | Jolyon Bloomfield | Jolyon K. Bloomfield and \'Eanna \'E. Flanagan | A four-dimensional description of five-dimensional N-brane models | 26 pages, 1 figure. Version 2 adds a new section 2, and clarifies
sections 4 and 5C | Phys.Rev.D82:124013,2010 | 10.1103/PhysRevD.82.124013 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new method for obtaining the four-dimensional effective
gravitational theory for five-dimensional braneworld models with arbitrary
numbers of branes in a low energy regime, based on a two-lengthscale expansion.
The method is straightforward and computationally efficient, and is applicable
to both compactified and uncompactified models. Particular emphasis is placed
on the behavior of the radion modes of the model, while the massive effective
fields are automatically truncated. Generally, the radion modes are found to
form a (N-1)-dimensional nonlinear sigma model. We illustrate the method for a
N-brane model in an uncompactified extra dimension.
| [
{
"created": "Wed, 14 Apr 2010 19:16:41 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Sep 2010 21:28:53 GMT",
"version": "v2"
}
] | 2011-12-02 | [
[
"Bloomfield",
"Jolyon K.",
""
],
[
"Flanagan",
"Éanna É.",
""
]
] | We propose a new method for obtaining the four-dimensional effective gravitational theory for five-dimensional braneworld models with arbitrary numbers of branes in a low energy regime, based on a two-lengthscale expansion. The method is straightforward and computationally efficient, and is applicable to both compactified and uncompactified models. Particular emphasis is placed on the behavior of the radion modes of the model, while the massive effective fields are automatically truncated. Generally, the radion modes are found to form a (N-1)-dimensional nonlinear sigma model. We illustrate the method for a N-brane model in an uncompactified extra dimension. |
2110.15046 | Aleksandr Kulitskii | Aleksadr Kulitskii and Elena Melkumova | Newman-Penrose-Debye formalism for fields of various spins in pp-wave
backgrounds | null | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using Newman-Penrose formalism in tetrad and spinor notation, we perform
separation of variables in the wave equations for massless fields of various
spins s=1/2, 1, 3/2, 2 on the background of exact plane-fronted gravitational
wave metrics. Then, applying Wald's method of adjoint operators, we derive
equations for Debye potentials generating these fields and find inverse
projection operators expressing multicomponet fields in terms of scalar
potentials. For a number of shock wave backgrounds, as a special case of
non-vacuum pp-waves, the exact solutions for Debye potentials are constructed
explicitly. The possibility of generalization to the case of massive fields, in
particular, construction of exact solutions to the Dirac and Proca equations
are discussed. These results can be used in supergravity models on pp-wave
backgrounds.
| [
{
"created": "Thu, 28 Oct 2021 12:19:50 GMT",
"version": "v1"
}
] | 2021-10-29 | [
[
"Kulitskii",
"Aleksadr",
""
],
[
"Melkumova",
"Elena",
""
]
] | Using Newman-Penrose formalism in tetrad and spinor notation, we perform separation of variables in the wave equations for massless fields of various spins s=1/2, 1, 3/2, 2 on the background of exact plane-fronted gravitational wave metrics. Then, applying Wald's method of adjoint operators, we derive equations for Debye potentials generating these fields and find inverse projection operators expressing multicomponet fields in terms of scalar potentials. For a number of shock wave backgrounds, as a special case of non-vacuum pp-waves, the exact solutions for Debye potentials are constructed explicitly. The possibility of generalization to the case of massive fields, in particular, construction of exact solutions to the Dirac and Proca equations are discussed. These results can be used in supergravity models on pp-wave backgrounds. |
1111.5043 | Gregory L. Comer | G. L. Comer, Patrick Peter, N. Andersson | Multi-fluid cosmology: An illustration of fundamental principles | 12 pages, 6 figures, version taking account of referee remarks | Physical Review D 85 (2012) 103006 | 10.1103/PhysRevD.85.103006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Our current understanding of the Universe depends on the interplay of several
distinct "matter" components, which interact mainly through gravity, and
electromagnetic radiation. The nature of the different components, and possible
interactions, tends to be based on the notion of coupled perfect fluids (or
scalar fields). This approach is somewhat naive, especially if one wants to be
able to consider issues involving heat flow, dissipative mechanisms, or
Bose-Einstein condensation of dark matter. We argue that a more natural
starting point would be the multi-purpose variational relativistic multi-fluid
system that has so far mainly been applied to neutron star astrophysics. As an
illustration of the fundamental principles involved, we develop the formalism
for determining the non-linear cosmological solutions to the Einstein equations
for a general relativistic two-fluid model for a coupled system of matter
(non-zero rest mass) and "radiation" (zero rest mass). The two fluids are
allowed to interpenetrate and exhibit a relative flow with respect to each
other, implying, in general, an anisotropic Universe. We use initial conditions
such that the massless fluid flux dominates early on so that the situation is
effectively that of a single fluid and one has the usual
Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime. We find that there is a
Bianchi I transition epoch out of which the matter flux dominates. The
situation is then effectively that of a single fluid and the spacetime evolves
towards the FLRW form. Such a transition opens up the possibility of imprinting
observable consequences at the specific scale corresponding to the transition
time.
| [
{
"created": "Mon, 21 Nov 2011 21:54:48 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Mar 2012 21:27:34 GMT",
"version": "v2"
}
] | 2012-08-28 | [
[
"Comer",
"G. L.",
""
],
[
"Peter",
"Patrick",
""
],
[
"Andersson",
"N.",
""
]
] | Our current understanding of the Universe depends on the interplay of several distinct "matter" components, which interact mainly through gravity, and electromagnetic radiation. The nature of the different components, and possible interactions, tends to be based on the notion of coupled perfect fluids (or scalar fields). This approach is somewhat naive, especially if one wants to be able to consider issues involving heat flow, dissipative mechanisms, or Bose-Einstein condensation of dark matter. We argue that a more natural starting point would be the multi-purpose variational relativistic multi-fluid system that has so far mainly been applied to neutron star astrophysics. As an illustration of the fundamental principles involved, we develop the formalism for determining the non-linear cosmological solutions to the Einstein equations for a general relativistic two-fluid model for a coupled system of matter (non-zero rest mass) and "radiation" (zero rest mass). The two fluids are allowed to interpenetrate and exhibit a relative flow with respect to each other, implying, in general, an anisotropic Universe. We use initial conditions such that the massless fluid flux dominates early on so that the situation is effectively that of a single fluid and one has the usual Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime. We find that there is a Bianchi I transition epoch out of which the matter flux dominates. The situation is then effectively that of a single fluid and the spacetime evolves towards the FLRW form. Such a transition opens up the possibility of imprinting observable consequences at the specific scale corresponding to the transition time. |
1901.03755 | E. Harikumar | Bhanu Kiran. S, E. Harikumar and Vishnu Rajagopal | Superdense star in a space-time with minimal length | 25 pages, 3 figures | Mod. Phys. Lett A 34(2019) 1050116 | 10.1142/S0217732319501165 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we generalise core-envelope model of superdense star to a
non-commutative space-time and study the modifications due to the existence of
a minimal length, predicted by various approaches to quantum gravity. We first
derive Einstein's field equation in $\kappa$-deformed space-time and use this
to set up non-commutative version of core-envelope model describing superdense
stars. We derive $\kappa$-deformed law of density variation, valid up to first
order approximation in deformation parameter and obtain radial and tangential
pressures in $\kappa$-deformed space-time. We also derive $\kappa$-deformed
strong energy conditions and obtain a bound on the deformation parameter.
| [
{
"created": "Mon, 7 Jan 2019 04:51:55 GMT",
"version": "v1"
}
] | 2019-05-13 | [
[
"S",
"Bhanu Kiran.",
""
],
[
"Harikumar",
"E.",
""
],
[
"Rajagopal",
"Vishnu",
""
]
] | In this paper we generalise core-envelope model of superdense star to a non-commutative space-time and study the modifications due to the existence of a minimal length, predicted by various approaches to quantum gravity. We first derive Einstein's field equation in $\kappa$-deformed space-time and use this to set up non-commutative version of core-envelope model describing superdense stars. We derive $\kappa$-deformed law of density variation, valid up to first order approximation in deformation parameter and obtain radial and tangential pressures in $\kappa$-deformed space-time. We also derive $\kappa$-deformed strong energy conditions and obtain a bound on the deformation parameter. |
1312.6790 | Rituparno Goswami | Anne Marie Nzioki, Rituparno Goswami and Peter K. S. Dunsby | Jebsen-Birkhoff theorem and its stability in f(R) gravity | 11 pages, Revtex4-1. arXiv admin note: text overlap with
arXiv:1101.4520 | Phys. Rev. D 89, 064050 (2014) | 10.1103/PhysRevD.89.064050 | null | gr-qc astro-ph.SR hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove a Jebsen-Birkhoff like theorem for f(R) theories of gravity in order
to to find the necessary conditions required for the existence of the
Schwarzschild solution in these theories and demonstrate that the rigidity of
such solutions of f(R) gravity is valid even in the perturbed scenario.
| [
{
"created": "Tue, 24 Dec 2013 10:42:40 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"Nzioki",
"Anne Marie",
""
],
[
"Goswami",
"Rituparno",
""
],
[
"Dunsby",
"Peter K. S.",
""
]
] | We prove a Jebsen-Birkhoff like theorem for f(R) theories of gravity in order to to find the necessary conditions required for the existence of the Schwarzschild solution in these theories and demonstrate that the rigidity of such solutions of f(R) gravity is valid even in the perturbed scenario. |
1506.04008 | Guihua Tian | Guihua Tian and Huihui Wang | Research on the recurrence relations for the spin-weighted spheroidal
harmonics | some modification, including some formula, error corrected | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the recurrence relations in the spin-weighted
spheroidal harmonics (SWSHs) through super-symmetric quantum mechanics. We use
the shape invariance property to solve the spin-weighted spheroidal wave
equations. The result shows the relation among SWSHs with a special condition
of the same parameter magnetic quantum number m but different spin-weight s.
The conclusions can be reduced to the famous recurrence relations of
spin-weighted spherical harmonics. These contents are the first investigation
of this kind recurrence relation concerning SWSHs and make it possible to
derive SWSHs from the spheroidal harmonics, so they are very important both in
theoretical background and in the astrophysical applications. Keywords:
spin-weighted spheroidal harmonics, recurrence relation, super-symmetric
quantum mechanics, shape-invariance
| [
{
"created": "Wed, 10 Jun 2015 04:13:47 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Oct 2015 07:28:17 GMT",
"version": "v2"
}
] | 2015-10-26 | [
[
"Tian",
"Guihua",
""
],
[
"Wang",
"Huihui",
""
]
] | In this paper we study the recurrence relations in the spin-weighted spheroidal harmonics (SWSHs) through super-symmetric quantum mechanics. We use the shape invariance property to solve the spin-weighted spheroidal wave equations. The result shows the relation among SWSHs with a special condition of the same parameter magnetic quantum number m but different spin-weight s. The conclusions can be reduced to the famous recurrence relations of spin-weighted spherical harmonics. These contents are the first investigation of this kind recurrence relation concerning SWSHs and make it possible to derive SWSHs from the spheroidal harmonics, so they are very important both in theoretical background and in the astrophysical applications. Keywords: spin-weighted spheroidal harmonics, recurrence relation, super-symmetric quantum mechanics, shape-invariance |
1709.08732 | Joao Paulo Morais Graca | J. P. Morais Gra\c{c}a, A. de P\'adua Santos, Eug\^enio R. Bezerra de
Mello, and V. B. Bezerra | Non-Abelian cosmic string in the Starobinsky model of gravity | 16 pages, 9 figures, accepted for publication in IJMPD | null | 10.1142/S0218271818500128 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we analyze numerically the behaviour of the solutions
corresponding to a non-Abelian cosmic string in the framework of the
Starobinsky model, i.e. where $f(R)=R + \zeta R^2$. We perform the calculations
for both an asymptotically flat and asymptotically (anti)de Sitter spacetimes.
We found that the angular deficit generated by the string decreases as the
parameter $\zeta$ increases, in the case of a null cosmological constant. For a
positive cosmological constant, we found that the cosmic horizon is affected in
a non-trivial way by the parameter $\zeta$.
| [
{
"created": "Mon, 25 Sep 2017 21:59:31 GMT",
"version": "v1"
}
] | 2018-02-14 | [
[
"Graça",
"J. P. Morais",
""
],
[
"Santos",
"A. de Pádua",
""
],
[
"de Mello",
"Eugênio R. Bezerra",
""
],
[
"Bezerra",
"V. B.",
""
]
] | In this paper, we analyze numerically the behaviour of the solutions corresponding to a non-Abelian cosmic string in the framework of the Starobinsky model, i.e. where $f(R)=R + \zeta R^2$. We perform the calculations for both an asymptotically flat and asymptotically (anti)de Sitter spacetimes. We found that the angular deficit generated by the string decreases as the parameter $\zeta$ increases, in the case of a null cosmological constant. For a positive cosmological constant, we found that the cosmic horizon is affected in a non-trivial way by the parameter $\zeta$. |
gr-qc/9811054 | Laszlo A. Gergely | L\'aszl\'o \'A. Gergely | Colliding spherically symmetric null dust in equilibrium | 4 pages, 1 figure, sprocl.sty included, to appear in the Proceedings
of the ERES98 Conference | null | null | null | gr-qc | null | We present two recently obtained solutions of the Einstein equations with
spherical symmetry and one additional Killing vector, describing colliding null
dust streams.
| [
{
"created": "Tue, 17 Nov 1998 13:29:01 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gergely",
"László Á.",
""
]
] | We present two recently obtained solutions of the Einstein equations with spherical symmetry and one additional Killing vector, describing colliding null dust streams. |
0810.4031 | Tatyana P. Shestakova | T. P. Shestakova | The "extended phase space" approach to quantum geometrodynamics: what
can it give for the development of quantum gravity? | 12 pages, talk presented at the III Stueckelberg Workshop on
Relativistic Field Theories, Pescara, Italy, July 2008 | Proceedings of the 3rd Stueckelberg Workshop on Relativistic Field
Theories, eds. N. Carlevaro, R. Ruffini and G. V. Vereshchagin, Cambridge
Scientific Publishers, 2010, P. 293 - 301 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The talk is devoted to the "extended phase space" approach to Quantum
Geometrodynamics. The premises that have led to the formulation of this
approach are briefly reviewed, namely, non-trivial topology of the Universe
which implies the absence of asymptotic states, in contrast to situations one
usually deals in ordinary quantum field theory; parametrization noninvariance
in the Wheeler - DeWitt theory; the problem of time and the absence of
dynamical evolution. Then we discuss the main features of the approach:
Hamiltonian dynamics in extended phase space, gauge-dependent Schrodinger
equation for the wave function of the Universe, the description of quantum
Universe from the viewpoint of observers in a wide enough class of reference
frames. After all, we analyse problems arising in this approach: the structure
of Hilbert space in Quantum Geometrodynamics, the relations between solutions
for the wave function of the Universe corresponding to various reference
frames, properties of a medium to be necessary to fix a reference frame, the
transition to classical limit.
| [
{
"created": "Wed, 22 Oct 2008 11:07:14 GMT",
"version": "v1"
}
] | 2011-01-18 | [
[
"Shestakova",
"T. P.",
""
]
] | The talk is devoted to the "extended phase space" approach to Quantum Geometrodynamics. The premises that have led to the formulation of this approach are briefly reviewed, namely, non-trivial topology of the Universe which implies the absence of asymptotic states, in contrast to situations one usually deals in ordinary quantum field theory; parametrization noninvariance in the Wheeler - DeWitt theory; the problem of time and the absence of dynamical evolution. Then we discuss the main features of the approach: Hamiltonian dynamics in extended phase space, gauge-dependent Schrodinger equation for the wave function of the Universe, the description of quantum Universe from the viewpoint of observers in a wide enough class of reference frames. After all, we analyse problems arising in this approach: the structure of Hilbert space in Quantum Geometrodynamics, the relations between solutions for the wave function of the Universe corresponding to various reference frames, properties of a medium to be necessary to fix a reference frame, the transition to classical limit. |
1001.2302 | Carlos A. R. Herdeiro | Miguel Zilhao, Helvi Witek, Ulrich Sperhake, Vitor Cardoso, Leonardo
Gualtieri, Carlos Herdeiro, Andrea Nerozzi | Numerical relativity for D dimensional axially symmetric space-times:
formalism and code tests | 31 pages, 6 figures; v2 Minor changes and added two references.
Matches the published version in PRD. | Phys.Rev.D81:084052,2010 | 10.1103/PhysRevD.81.084052 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The numerical evolution of Einstein's field equations in a generic background
has the potential to answer a variety of important questions in physics: from
applications to the gauge-gravity duality, to modelling black hole production
in TeV gravity scenarios, analysis of the stability of exact solutions and
tests of Cosmic Censorship. In order to investigate these questions, we extend
numerical relativity to more general space-times than those investigated
hitherto, by developing a framework to study the numerical evolution of D
dimensional vacuum space-times with an SO(D-2) isometry group for D\ge 5, or
SO(D-3) for D\ge 6.
Performing a dimensional reduction on a (D-4)-sphere, the D dimensional
vacuum Einstein equations are rewritten as a 3+1 dimensional system with source
terms, and presented in the Baumgarte, Shapiro, Shibata and Nakamura (BSSN)
formulation. This allows the use of existing 3+1 dimensional numerical codes
with small adaptations. Brill-Lindquist initial data are constructed in D
dimensions and a procedure to match them to our 3+1 dimensional evolution
equations is given. We have implemented our framework by adapting the LEAN code
and perform a variety of simulations of non-spinning black hole space-times.
Specifically, we present a modified moving puncture gauge which facilitates
long term stable simulations in D=5. We further demonstrate the internal
consistency of the code by studying convergence and comparing numerical versus
analytic results in the case of geodesic slicing for D=5,6.
| [
{
"created": "Wed, 13 Jan 2010 21:00:07 GMT",
"version": "v1"
},
{
"created": "Mon, 3 May 2010 15:51:41 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"Zilhao",
"Miguel",
""
],
[
"Witek",
"Helvi",
""
],
[
"Sperhake",
"Ulrich",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Gualtieri",
"Leonardo",
""
],
[
"Herdeiro",
"Carlos",
""
],
[
"Nerozzi",
"Andrea",
""
]
] | The numerical evolution of Einstein's field equations in a generic background has the potential to answer a variety of important questions in physics: from applications to the gauge-gravity duality, to modelling black hole production in TeV gravity scenarios, analysis of the stability of exact solutions and tests of Cosmic Censorship. In order to investigate these questions, we extend numerical relativity to more general space-times than those investigated hitherto, by developing a framework to study the numerical evolution of D dimensional vacuum space-times with an SO(D-2) isometry group for D\ge 5, or SO(D-3) for D\ge 6. Performing a dimensional reduction on a (D-4)-sphere, the D dimensional vacuum Einstein equations are rewritten as a 3+1 dimensional system with source terms, and presented in the Baumgarte, Shapiro, Shibata and Nakamura (BSSN) formulation. This allows the use of existing 3+1 dimensional numerical codes with small adaptations. Brill-Lindquist initial data are constructed in D dimensions and a procedure to match them to our 3+1 dimensional evolution equations is given. We have implemented our framework by adapting the LEAN code and perform a variety of simulations of non-spinning black hole space-times. Specifically, we present a modified moving puncture gauge which facilitates long term stable simulations in D=5. We further demonstrate the internal consistency of the code by studying convergence and comparing numerical versus analytic results in the case of geodesic slicing for D=5,6. |
1110.2429 | Sean Gryb B | Sean Gryb and Karim Thebault | The role of time in relational quantum theories | 22 pages, 2 figures, section on gravity added, published version
(accepted by Found of Phys) | null | 10.1007/s10701-012-9665-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a solution to the problem of time for systems with a single global
Hamiltonian constraint. Our solution stems from the observation that, for these
theories, conventional gauge theory methods fail to capture the full classical
dynamics of the system and must therefore be deemed inappropriate. We propose a
new strategy for consistently quantizing systems with a relational notion of
time that does capture the full classical dynamics of the system and allows for
evolution parametrized by an equitable internal clock. This proposal contains
the minimal temporal structure necessary to retain the ordering of events
required to describe classical evolution. In the context of Shape Dynamics (an
equivalent formulation of general relativity that is locally scale invariant
and free of the local problem of time) our proposal can be shown to constitute
a natural methodology for describing dynamical evolution in quantum gravity and
to lead to a quantum theory analogous to the Dirac quantization of unimodular
gravity.
| [
{
"created": "Tue, 11 Oct 2011 16:54:52 GMT",
"version": "v1"
},
{
"created": "Thu, 24 May 2012 11:34:52 GMT",
"version": "v2"
}
] | 2015-05-30 | [
[
"Gryb",
"Sean",
""
],
[
"Thebault",
"Karim",
""
]
] | We propose a solution to the problem of time for systems with a single global Hamiltonian constraint. Our solution stems from the observation that, for these theories, conventional gauge theory methods fail to capture the full classical dynamics of the system and must therefore be deemed inappropriate. We propose a new strategy for consistently quantizing systems with a relational notion of time that does capture the full classical dynamics of the system and allows for evolution parametrized by an equitable internal clock. This proposal contains the minimal temporal structure necessary to retain the ordering of events required to describe classical evolution. In the context of Shape Dynamics (an equivalent formulation of general relativity that is locally scale invariant and free of the local problem of time) our proposal can be shown to constitute a natural methodology for describing dynamical evolution in quantum gravity and to lead to a quantum theory analogous to the Dirac quantization of unimodular gravity. |
gr-qc/0309121 | Alexander E. Shalyt-Margolin | A.E.Shalyt-Margolin | Non-Unitary and Unitary Transitions in Generalized Quantum Mechanics and
Information Problem Solving | Latex,12 pages,no figures,some corrections | null | null | null | gr-qc | null | The present work is a study of the unitarity problem for Quantum Mechanics at
Planck Scale considered as Quantum Mechanics with Fundamental Length (QMFL).In
the process QMFL is described as deformation of a well-known Quantum Mechanics
(QM). Similar to previous works of the author, the basic approach is based on
deformation of the density matrix (density pro-matrix) with concurrent
development of the wave function deformation in the respective Schrodinger
picture. It is demonstrated that the existence of black holes in the suggested
approach in the end twice results in nonunitary transitions (first after the
Big Bang of QMFL to QM, and then when on trapping of the matter into the black
hole the situation is just the opposite - from QM to QMFL)and hence in recovery
of the unitarity. In parallel this problem is considered in the deformation
terms of Heisenberg algebra, showing the identity of the basic results. From
this an explicit solution for Hawking's informaion paradox has been derived
| [
{
"created": "Thu, 25 Sep 2003 12:04:43 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Nov 2003 09:24:02 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Shalyt-Margolin",
"A. E.",
""
]
] | The present work is a study of the unitarity problem for Quantum Mechanics at Planck Scale considered as Quantum Mechanics with Fundamental Length (QMFL).In the process QMFL is described as deformation of a well-known Quantum Mechanics (QM). Similar to previous works of the author, the basic approach is based on deformation of the density matrix (density pro-matrix) with concurrent development of the wave function deformation in the respective Schrodinger picture. It is demonstrated that the existence of black holes in the suggested approach in the end twice results in nonunitary transitions (first after the Big Bang of QMFL to QM, and then when on trapping of the matter into the black hole the situation is just the opposite - from QM to QMFL)and hence in recovery of the unitarity. In parallel this problem is considered in the deformation terms of Heisenberg algebra, showing the identity of the basic results. From this an explicit solution for Hawking's informaion paradox has been derived |
1302.0573 | J\"org Hennig | Gernot Neugebauer and J\"org Hennig | Stationary black-hole binaries: A non-existence proof | 20 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1105.5830 | General Relativity, Cosmology and Astrophysics - Perspectives 100
years after Einstein's stay in Prague, Fundamental Theories of Physics 177,
209 (Springer, 2014) | 10.1007/978-3-319-06349-2_9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We resume former discussions of the question, whether the spin-spin repulsion
and the gravitational attraction of two aligned black holes can balance each
other. Based on the solution of a boundary problem for disconnected (Killing)
horizons and the resulting violation of characteristic black hole properties,
we present a non-existence proof for the equilibrium configuration in question.
From a mathematical point of view, this result is a further example for the
efficiency of the inverse ("scattering") method in non-linear theories.
| [
{
"created": "Mon, 4 Feb 2013 02:54:24 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Jun 2014 01:26:18 GMT",
"version": "v2"
}
] | 2014-06-24 | [
[
"Neugebauer",
"Gernot",
""
],
[
"Hennig",
"Jörg",
""
]
] | We resume former discussions of the question, whether the spin-spin repulsion and the gravitational attraction of two aligned black holes can balance each other. Based on the solution of a boundary problem for disconnected (Killing) horizons and the resulting violation of characteristic black hole properties, we present a non-existence proof for the equilibrium configuration in question. From a mathematical point of view, this result is a further example for the efficiency of the inverse ("scattering") method in non-linear theories. |
1608.01174 | Ivano Dami\~ao Soares | Ivano Dami\~ao Soares | A boosted Kerr black hole solution and the structure of a general
astrophysical black hole | 11 pages, 1figure | General Relativity and Gravitation (2017) 49:77 | 10.1007/s10714-017-2239-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A solution of Einstein's vacuum field equations that describes a boosted Kerr
black hole relative to an asymptotic Lorentz frame at the future null infinity
is derived. The solution has three parameters (mass, rotation and boost) and
corresponds to the most general configuration that an astrophysical black hole
must have; it reduces to the Kerr solution when the boost parameter is zero. In
this solution the ergosphere is north-south asymmetric, with dominant lobes in
the direction opposite to the boost. However the event horizon, the Cauchy
horizon and the ring singularity, which are the core of the black hole
structure, do not alter, being independent of the boost parameter. Possible
consequences for astrophysical processes connected with Penrose processes in
the asymmetric ergosphere are discussed.
| [
{
"created": "Wed, 3 Aug 2016 13:05:02 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Nov 2016 17:11:38 GMT",
"version": "v2"
},
{
"created": "Wed, 24 May 2017 18:39:10 GMT",
"version": "v3"
}
] | 2017-05-26 | [
[
"Soares",
"Ivano Damião",
""
]
] | A solution of Einstein's vacuum field equations that describes a boosted Kerr black hole relative to an asymptotic Lorentz frame at the future null infinity is derived. The solution has three parameters (mass, rotation and boost) and corresponds to the most general configuration that an astrophysical black hole must have; it reduces to the Kerr solution when the boost parameter is zero. In this solution the ergosphere is north-south asymmetric, with dominant lobes in the direction opposite to the boost. However the event horizon, the Cauchy horizon and the ring singularity, which are the core of the black hole structure, do not alter, being independent of the boost parameter. Possible consequences for astrophysical processes connected with Penrose processes in the asymmetric ergosphere are discussed. |
2007.04022 | Edward Teo | Edward Teo | Spherical orbits around a Kerr black hole | 40 pages, published version | Gen. Rel. Grav. 53 (2021) 10 | 10.1007/s10714-020-02782-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A special class of orbits known to exist around a Kerr black hole are
spherical orbits -- orbits with constant coordinate radii that are not
necessarily confined to the equatorial plane. Spherical time-like orbits were
first studied by Wilkins almost 50 years ago. In the present paper, we perform
a systematic and thorough study of these orbits, encompassing and extending
previous works on them. We first present simplified forms for the parameters of
these orbits. The parameter space of these orbits is then analysed in detail;
in particular, we delineate the boundaries between stable and unstable orbits,
bound and unbound orbits, and prograde and retrograde orbits. Finally, we
provide analytic solutions of the geodesic equations, and illustrate a few
representative examples of these orbits.
| [
{
"created": "Wed, 8 Jul 2020 10:52:56 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Jan 2021 08:24:05 GMT",
"version": "v2"
}
] | 2021-01-21 | [
[
"Teo",
"Edward",
""
]
] | A special class of orbits known to exist around a Kerr black hole are spherical orbits -- orbits with constant coordinate radii that are not necessarily confined to the equatorial plane. Spherical time-like orbits were first studied by Wilkins almost 50 years ago. In the present paper, we perform a systematic and thorough study of these orbits, encompassing and extending previous works on them. We first present simplified forms for the parameters of these orbits. The parameter space of these orbits is then analysed in detail; in particular, we delineate the boundaries between stable and unstable orbits, bound and unbound orbits, and prograde and retrograde orbits. Finally, we provide analytic solutions of the geodesic equations, and illustrate a few representative examples of these orbits. |
0807.2309 | Piotr T. Chru\'sciel | Piotr T. Chru\'sciel, Julien Cortier | Maximal analytic extensions of the Emparan-Reall black ring | minor changes, typos corrected, version identical to the journal one | Journal of Differential Geometry 84 (2010) 19-44 | null | null | gr-qc hep-th math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a Kruskal-Szekeres-type analytic extension of the Emparan-Reall
black ring, and investigate its geometry. We prove that the extension is
maximal, globally hyperbolic, and unique within a natural class of extensions.
The key to those results is the proof that causal geodesics are either
complete, or approach a singular boundary in finite affine time. Alternative
maximal analytic extensions are also constructed.
| [
{
"created": "Tue, 15 Jul 2008 06:40:59 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Dec 2008 12:40:48 GMT",
"version": "v2"
},
{
"created": "Fri, 8 Oct 2010 18:49:31 GMT",
"version": "v3"
}
] | 2013-12-11 | [
[
"Chruściel",
"Piotr T.",
""
],
[
"Cortier",
"Julien",
""
]
] | We construct a Kruskal-Szekeres-type analytic extension of the Emparan-Reall black ring, and investigate its geometry. We prove that the extension is maximal, globally hyperbolic, and unique within a natural class of extensions. The key to those results is the proof that causal geodesics are either complete, or approach a singular boundary in finite affine time. Alternative maximal analytic extensions are also constructed. |
1706.02121 | Hamed Pejhan | Kazuharu Bamba, Surena Rahbardehghan and Hamed Pejhan | Vacuum states for gravitons field in de Sitter space | 10 pages, version accepted for publication in Physical Review D | Phys. Rev. D 96, 106009 (2017) | 10.1103/PhysRevD.96.106009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, considering the linearized Einstein equation with a
two-parameter family of linear covariant gauges in de Sitter spacetime, we
examine possible vacuum states for the gravitons field with respect to
invariance under the de Sitter group $SO_0(1,4)$. Our calculations explicitly
reveal that there exists no natural de Sitter-invariant vacuum state (the
Euclidean state) for the gravitons field. Indeed, on the foundation of a
rigorous group theoretical reasoning, we prove that if one insists on full
covariance as well as causality for the theory, has to give up the positivity
requirement of the inner product. However, one may still look for states with
as much symmetry as possible, more precisely, a restrictive version of
covariance by considering the gravitons field and the associated vacuum state
which are, respectively, covariant and invariant with respect to some maximal
subgroup of the full de Sitter group. In this regard, we treat $SO(4)$ case,
and find a family of $SO(4)$-invariant states. The associated $SO(4)$-covariant
quantum field is given, as well.
| [
{
"created": "Wed, 7 Jun 2017 10:46:20 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Oct 2017 17:48:45 GMT",
"version": "v2"
}
] | 2017-11-22 | [
[
"Bamba",
"Kazuharu",
""
],
[
"Rahbardehghan",
"Surena",
""
],
[
"Pejhan",
"Hamed",
""
]
] | In this paper, considering the linearized Einstein equation with a two-parameter family of linear covariant gauges in de Sitter spacetime, we examine possible vacuum states for the gravitons field with respect to invariance under the de Sitter group $SO_0(1,4)$. Our calculations explicitly reveal that there exists no natural de Sitter-invariant vacuum state (the Euclidean state) for the gravitons field. Indeed, on the foundation of a rigorous group theoretical reasoning, we prove that if one insists on full covariance as well as causality for the theory, has to give up the positivity requirement of the inner product. However, one may still look for states with as much symmetry as possible, more precisely, a restrictive version of covariance by considering the gravitons field and the associated vacuum state which are, respectively, covariant and invariant with respect to some maximal subgroup of the full de Sitter group. In this regard, we treat $SO(4)$ case, and find a family of $SO(4)$-invariant states. The associated $SO(4)$-covariant quantum field is given, as well. |
gr-qc/9611065 | Ruth A. W. Gregory | Caroline Santos and Ruth Gregory | Cosmology in Brans-Dicke theory with a scalar potential | 28 pages harvmac, 7 figures | Annals Phys. 258 (1997) 111-134 | 10.1006/aphy.1997.5691 | DTP-96-55 | gr-qc astro-ph | null | We consider the general behaviour of cosmologies in Brans-Dicke theory where
the dilaton is self-interacting via a potential $V(\Phi)$. We show that the
general radiation universe is a two-dimensional dynamical system whereas the
dust or false vacuum universe is three-dimensional. This is in contrast to the
non-interacting dilaton which has uniformly a two-dimensional phase space. We
find the phase spaces in each case and the general behaviour of the
cosmologies.
| [
{
"created": "Wed, 27 Nov 1996 16:29:59 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Santos",
"Caroline",
""
],
[
"Gregory",
"Ruth",
""
]
] | We consider the general behaviour of cosmologies in Brans-Dicke theory where the dilaton is self-interacting via a potential $V(\Phi)$. We show that the general radiation universe is a two-dimensional dynamical system whereas the dust or false vacuum universe is three-dimensional. This is in contrast to the non-interacting dilaton which has uniformly a two-dimensional phase space. We find the phase spaces in each case and the general behaviour of the cosmologies. |
gr-qc/0702083 | Edward Anderson | Edward Anderson | Classical dynamics on triangleland | Rewritten, publication reference added | Class.Quant.Grav.24:5317-5341,2007 | 10.1088/0264-9381/24/22/001 | null | gr-qc | null | In Euclidean relational particle mechanics (ERPM) only relative times,
relative angles and relative separations are meaningful, while in similarity
relational particle mechanics (SRPM) only relative times, relative angles and
ratios of relative separations are. These theories are clearly of interest in
the absolute or relative motion debate. In this paper, ERPM and SRPM are
provided in fully reduced form for 3 particles in 2D, i.e. the classical
dynamics on triangleland in 2D with and without scale. Exact solutions to each
of these are then found, and simple Newton--Coulomb-like and harmonic
oscillator-like SRPM models are studied numerically. The mathematics one
arrives at thus overlaps in many ways with that which arises in the absolutist
approach. The ERPM gives standard mathematics, while the SRPM has standard
small-relative-scale behaviour and an unexpected but in itself standard
universal large-relative-scale behaviour. One way in which SRPM is unusual is
that it is a model in which a symmetry principle underlies an unexpected
departure from standard physical behaviour at sufficiently large relative
scales (interpolation between the abovementioned two behaviours). ERPM and SRPM
are also theoretically interesting at the quantum level, both on their own
merit and as toy models for the development of various approaches to the
problems of time and of observables in quantum general relativity.
| [
{
"created": "Thu, 15 Feb 2007 01:14:01 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Apr 2007 16:11:54 GMT",
"version": "v2"
},
{
"created": "Fri, 2 Nov 2007 15:00:45 GMT",
"version": "v3"
}
] | 2009-08-26 | [
[
"Anderson",
"Edward",
""
]
] | In Euclidean relational particle mechanics (ERPM) only relative times, relative angles and relative separations are meaningful, while in similarity relational particle mechanics (SRPM) only relative times, relative angles and ratios of relative separations are. These theories are clearly of interest in the absolute or relative motion debate. In this paper, ERPM and SRPM are provided in fully reduced form for 3 particles in 2D, i.e. the classical dynamics on triangleland in 2D with and without scale. Exact solutions to each of these are then found, and simple Newton--Coulomb-like and harmonic oscillator-like SRPM models are studied numerically. The mathematics one arrives at thus overlaps in many ways with that which arises in the absolutist approach. The ERPM gives standard mathematics, while the SRPM has standard small-relative-scale behaviour and an unexpected but in itself standard universal large-relative-scale behaviour. One way in which SRPM is unusual is that it is a model in which a symmetry principle underlies an unexpected departure from standard physical behaviour at sufficiently large relative scales (interpolation between the abovementioned two behaviours). ERPM and SRPM are also theoretically interesting at the quantum level, both on their own merit and as toy models for the development of various approaches to the problems of time and of observables in quantum general relativity. |
gr-qc/0311028 | Naresh Dadhich | Naresh Dadhich | Universalization as a physical guiding principle | RevTeX, 22 pages. This is an essay propounding a new perspective and
it is open for discussion. Comments and criticism will be most welcome. It
will be kept live and would be updated from time to time with proper
acknowledgement to comments and criticism | null | null | null | gr-qc astro-ph hep-th | null | In this essay, I wish to share a novel perspective based on the principle of
universalization in arriving at the relativistic and quantum world from the
classical world. I also delve on some insightful discussion on going
``beyond''.
| [
{
"created": "Sat, 8 Nov 2003 09:16:52 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Dadhich",
"Naresh",
""
]
] | In this essay, I wish to share a novel perspective based on the principle of universalization in arriving at the relativistic and quantum world from the classical world. I also delve on some insightful discussion on going ``beyond''. |
gr-qc/9803061 | Klemm Dietmar | Dietmar Klemm and Luciano Vanzo (University of Trento, Italy) | Quantum Properties of Topological Black Holes | 31 pages, one additional figure, enlarged discussion of the higher
genus case, comment on the mass and new references added | Phys.Rev. D58 (1998) 104025 | 10.1103/PhysRevD.58.104025 | UTF 412 | gr-qc | null | We examine quantum properties of topological black holes which are
asymptotically anti--de Sitter. First, massless scalar fields and Weyl spinors
which propagate in the background of an anti--de Sitter black hole are
considered in an exactly soluble two--dimensional toy model. The Boulware--,
Unruh--, and Hartle--Hawking vacua are defined. The latter results to coincide
with the Unruh vacuum due to the boundary conditions necessary in
asymptotically adS spacetimes. We show that the Hartle--Hawking vacuum
represents a thermal equilibrium state with the temperature found in the
Euclidean formulation. The renormalized stress tensor for this quantum state is
well--defined everywhere, for any genus and for all solutions which do not have
an inner Cauchy horizon, whereas in this last case it diverges on the inner
horizon. The four--dimensional case is finally considered, the equilibrium
states are discussed and a luminosity formula for the black hole of any genus
is obtained. Since spacelike infinity in anti--de Sitter space acts like a
mirror, it is pointed out how this would imply information loss in
gravitational collapse. The black hole's mass spectrum according to
Bekenstein's view is discussed and compared to that provided by string theory.
| [
{
"created": "Tue, 17 Mar 1998 15:54:58 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Mar 1998 15:11:18 GMT",
"version": "v2"
},
{
"created": "Fri, 12 Jun 1998 14:53:19 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Klemm",
"Dietmar",
"",
"University of Trento, Italy"
],
[
"Vanzo",
"Luciano",
"",
"University of Trento, Italy"
]
] | We examine quantum properties of topological black holes which are asymptotically anti--de Sitter. First, massless scalar fields and Weyl spinors which propagate in the background of an anti--de Sitter black hole are considered in an exactly soluble two--dimensional toy model. The Boulware--, Unruh--, and Hartle--Hawking vacua are defined. The latter results to coincide with the Unruh vacuum due to the boundary conditions necessary in asymptotically adS spacetimes. We show that the Hartle--Hawking vacuum represents a thermal equilibrium state with the temperature found in the Euclidean formulation. The renormalized stress tensor for this quantum state is well--defined everywhere, for any genus and for all solutions which do not have an inner Cauchy horizon, whereas in this last case it diverges on the inner horizon. The four--dimensional case is finally considered, the equilibrium states are discussed and a luminosity formula for the black hole of any genus is obtained. Since spacelike infinity in anti--de Sitter space acts like a mirror, it is pointed out how this would imply information loss in gravitational collapse. The black hole's mass spectrum according to Bekenstein's view is discussed and compared to that provided by string theory. |
gr-qc/9603005 | Don N. Page | Don N. Page (University of Alberta, Edmonton, Canada) | Stress Tensors for Instantaneous Vacua in 1+1 Dimensions | LaTeX, 28 pages, last term of Eq. (79) corrected | Class.Quant.Grav. 14 (1997) 3041-3061 | 10.1088/0264-9381/14/11/007 | Alberta-Thy-02-96 | gr-qc hep-th | null | The regularized expectation value of the stress-energy tensor for a massless
bosonic or fermionic field in 1+1 dimensions is calculated explicitly for the
instantaneous vacuum relative to any Cauchy surface (here a spacelike curve) in
terms of the length L of the curve (if closed), the local extrinsic curvature K
of the curve, its derivative K' with respect to proper distance x along the
curve, and the scalar curvature R of the spacetime: T_{00} = - epsilon
pi/(6L^2) - K^2/(24 pi), T_{01} = - K'/(12 pi), T_{11} = - epsilon pi/(6L^2) -
K^2/(24 pi) + R/(24 pi), in an orthonormal frame with the spatial vector
parallel to the curve. Here epsilon = 1 for an untwisted (i.e., periodic in x)
one-component massless bosonic field or for a twisted (i.e., antiperiodic in x)
two-component massless fermionic field, epsilon = -1/2 for a twisted
one-component massless bosonic field, and epsilon = - 2 for an untwisted
two-component massless fermionic field. The calculation uses merely the
energy-momentum conservation law and the trace anomaly (for which a very simple
derivation is also given herein, as well as the expression for the Casimir
energy of bosonic and fermionic fields twisted by an arbitrary amount in
R^{D-1} x S^1). The two coordinate and conformal invariants of a quantum state
that are (nonlocally) determined by the stress-energy tensor are given.
Applications to topologically modified deSitter spacetimes, to a flat cylinder,
and to Minkowski spacetime are discussed.
| [
{
"created": "Tue, 5 Mar 1996 23:10:15 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Jun 1997 22:26:36 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Page",
"Don N.",
"",
"University of Alberta, Edmonton, Canada"
]
] | The regularized expectation value of the stress-energy tensor for a massless bosonic or fermionic field in 1+1 dimensions is calculated explicitly for the instantaneous vacuum relative to any Cauchy surface (here a spacelike curve) in terms of the length L of the curve (if closed), the local extrinsic curvature K of the curve, its derivative K' with respect to proper distance x along the curve, and the scalar curvature R of the spacetime: T_{00} = - epsilon pi/(6L^2) - K^2/(24 pi), T_{01} = - K'/(12 pi), T_{11} = - epsilon pi/(6L^2) - K^2/(24 pi) + R/(24 pi), in an orthonormal frame with the spatial vector parallel to the curve. Here epsilon = 1 for an untwisted (i.e., periodic in x) one-component massless bosonic field or for a twisted (i.e., antiperiodic in x) two-component massless fermionic field, epsilon = -1/2 for a twisted one-component massless bosonic field, and epsilon = - 2 for an untwisted two-component massless fermionic field. The calculation uses merely the energy-momentum conservation law and the trace anomaly (for which a very simple derivation is also given herein, as well as the expression for the Casimir energy of bosonic and fermionic fields twisted by an arbitrary amount in R^{D-1} x S^1). The two coordinate and conformal invariants of a quantum state that are (nonlocally) determined by the stress-energy tensor are given. Applications to topologically modified deSitter spacetimes, to a flat cylinder, and to Minkowski spacetime are discussed. |
gr-qc/0005048 | Robert Beig | Robert Beig | Multipole Moments of Static Spacetimes | 9 pages, LaTeX 2.09 | null | null | UWThPh-1999-53 | gr-qc | null | This paper reviews work, largely due to W. Simon and the author, on multipole
theory of static spacetimes. The main purpose is to make this work, which lies
at the interface of potential theory, conformal geometry and general
relativity, known to mathematicians and to perhaps motivate them to look at the
open problems which still remain.
| [
{
"created": "Sat, 13 May 2000 08:26:07 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Beig",
"Robert",
""
]
] | This paper reviews work, largely due to W. Simon and the author, on multipole theory of static spacetimes. The main purpose is to make this work, which lies at the interface of potential theory, conformal geometry and general relativity, known to mathematicians and to perhaps motivate them to look at the open problems which still remain. |
1604.07764 | Alejandro Corichi | Alejandro Corichi, Irais Rubalcava-Garcia and Tatjana Vukasinac | Actions, topological terms and boundaries in first order gravity: A
review | Review paper. 56 pages, 2 figures | Int. J. Mod. Phys. D25 (2016) no.04, 1630011 | 10.1142/S0218271816300111 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this review we consider first order gravity in four dimensions. In
particular, we focus our attention in formulations where the fundamental
variables are a tetrad $e_a^I$ and a SO(3,1) connection ${\omega_{aI}}^J$. We
study the most general action principle compatible with diffeomorphism
invariance. This implies, in particular, considering besides the standard
Einstein-Hilbert-Palatini term, other terms that either do not change the
equations of motion, or are topological in nature. Having a well defined action
principle sometimes involves the need for additional boundary terms, whose
detailed form may depend on the particular boundary conditions at hand. In this
work, we consider spacetimes that include a boundary at infinity, satisfying
asymptotically flat boundary conditions and/or an internal boundary satisfying
isolated horizons boundary conditions. We focus on the covariant Hamiltonian
formalism where the phase space $\Gamma$ is given by solutions to the equations
of motion. For each of the possible terms contributing to the action we
consider the well posedness of the action, its finiteness, the contribution to
the symplectic structure, and the Hamiltonian and Noether charges. For the
chosen boundary conditions, standard boundary terms warrant a well posed
theory. Furthermore, the boundary and topological terms do not contribute to
the symplectic structure, nor the Hamiltonian conserved charges. The Noether
conserved charges, on the other hand, do depend on such additional terms. The
aim of this manuscript is to present a comprehensive and self-contained
treatment of the subject, so the style is somewhat pedagogical. Furthermore,
along the way we point out and clarify some issues that have not been clearly
understood in the literature.
| [
{
"created": "Tue, 26 Apr 2016 17:36:28 GMT",
"version": "v1"
}
] | 2016-04-27 | [
[
"Corichi",
"Alejandro",
""
],
[
"Rubalcava-Garcia",
"Irais",
""
],
[
"Vukasinac",
"Tatjana",
""
]
] | In this review we consider first order gravity in four dimensions. In particular, we focus our attention in formulations where the fundamental variables are a tetrad $e_a^I$ and a SO(3,1) connection ${\omega_{aI}}^J$. We study the most general action principle compatible with diffeomorphism invariance. This implies, in particular, considering besides the standard Einstein-Hilbert-Palatini term, other terms that either do not change the equations of motion, or are topological in nature. Having a well defined action principle sometimes involves the need for additional boundary terms, whose detailed form may depend on the particular boundary conditions at hand. In this work, we consider spacetimes that include a boundary at infinity, satisfying asymptotically flat boundary conditions and/or an internal boundary satisfying isolated horizons boundary conditions. We focus on the covariant Hamiltonian formalism where the phase space $\Gamma$ is given by solutions to the equations of motion. For each of the possible terms contributing to the action we consider the well posedness of the action, its finiteness, the contribution to the symplectic structure, and the Hamiltonian and Noether charges. For the chosen boundary conditions, standard boundary terms warrant a well posed theory. Furthermore, the boundary and topological terms do not contribute to the symplectic structure, nor the Hamiltonian conserved charges. The Noether conserved charges, on the other hand, do depend on such additional terms. The aim of this manuscript is to present a comprehensive and self-contained treatment of the subject, so the style is somewhat pedagogical. Furthermore, along the way we point out and clarify some issues that have not been clearly understood in the literature. |
1302.4035 | Soichiro Isoyama Mr | Soichiro Isoyama, Ryuichi Fujita, Hiroyuki Nakano, Norichika Sago,
Takahiro Tanaka | Evolution of the Carter constant for a resonant inspiral into a Kerr
black hole: I. The scalar case | 18pages, no figures, matches version published in PTEP | Prog. Theor. Exp. Phys. (2013) 063E01 | 10.1093/ptep/ptt034 | YITP-12-102 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the inspiral of a small body around a Kerr black hole. When the
time scale of the radiation reaction is sufficiently longer than its orbital
period, the leading order orbital evolution is described only by the knowledge
of the averaged evolution of the constants of motion, i.e., the energy,
azimuthal angular momentum and the Carter constant. Although there is no
conserved current composed of the perturbation field corresponding to the
Carter constant, it has been shown that the averaged rate of change of the
Carter constant can be given by a simple formula, when there exists a
simultaneous turning point of the radial and polar oscillations. However, an
inspiralling orbit may cross a "resonance" point, where the frequencies of the
radial and polar orbital oscillations are in a rational ratio. At the resonance
point, one cannot find a simultaneous turning point in general. Hence, even for
the averaged rate of change of the Carter constant, a direct computation of the
'self-force", which is still challenging especially in the case of the Kerr
background, seems to be necessary. In this paper, we present a method of
computing the averaged rate of change of the Carter constant in a relatively
simple manner at the "resonance" point.
| [
{
"created": "Sun, 17 Feb 2013 06:53:11 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Jun 2013 11:32:57 GMT",
"version": "v2"
}
] | 2013-06-04 | [
[
"Isoyama",
"Soichiro",
""
],
[
"Fujita",
"Ryuichi",
""
],
[
"Nakano",
"Hiroyuki",
""
],
[
"Sago",
"Norichika",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | We discuss the inspiral of a small body around a Kerr black hole. When the time scale of the radiation reaction is sufficiently longer than its orbital period, the leading order orbital evolution is described only by the knowledge of the averaged evolution of the constants of motion, i.e., the energy, azimuthal angular momentum and the Carter constant. Although there is no conserved current composed of the perturbation field corresponding to the Carter constant, it has been shown that the averaged rate of change of the Carter constant can be given by a simple formula, when there exists a simultaneous turning point of the radial and polar oscillations. However, an inspiralling orbit may cross a "resonance" point, where the frequencies of the radial and polar orbital oscillations are in a rational ratio. At the resonance point, one cannot find a simultaneous turning point in general. Hence, even for the averaged rate of change of the Carter constant, a direct computation of the 'self-force", which is still challenging especially in the case of the Kerr background, seems to be necessary. In this paper, we present a method of computing the averaged rate of change of the Carter constant in a relatively simple manner at the "resonance" point. |
2309.17044 | Pankaj Chaturvedi | Pankaj Chaturvedi, Utkarsh Kumar, Udaykrishna Thattarampilly, and
Vishnu Kakkat | Rotating black hole solutions for $f(R)$ gravity and Newman Janis
Algorithm | 12 pages and one table | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We show that the $f(R)$-gravity theories with constant Ricci scalar in the
Jordan/Einstein frame can be described by Einstein or Einstein-Maxwell gravity
with a cosmological term and a modified gravitational constant. We also propose
a modified Newmann-Janis algorithm to obtain the rotating axisymmetric
solutions for the Einstein/Einstein-Maxwell gravity with a cosmological
constant. Using the duality between the two gravity theories we show that the
stationary or static solutions for the Einstein/Einstein-Maxwell gravity with a
cosmological constant will also be the solutions for the dual $f(R)$-gravity
with constant Ricci scalar.
| [
{
"created": "Fri, 29 Sep 2023 08:11:04 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Oct 2023 04:30:59 GMT",
"version": "v2"
}
] | 2023-10-10 | [
[
"Chaturvedi",
"Pankaj",
""
],
[
"Kumar",
"Utkarsh",
""
],
[
"Thattarampilly",
"Udaykrishna",
""
],
[
"Kakkat",
"Vishnu",
""
]
] | We show that the $f(R)$-gravity theories with constant Ricci scalar in the Jordan/Einstein frame can be described by Einstein or Einstein-Maxwell gravity with a cosmological term and a modified gravitational constant. We also propose a modified Newmann-Janis algorithm to obtain the rotating axisymmetric solutions for the Einstein/Einstein-Maxwell gravity with a cosmological constant. Using the duality between the two gravity theories we show that the stationary or static solutions for the Einstein/Einstein-Maxwell gravity with a cosmological constant will also be the solutions for the dual $f(R)$-gravity with constant Ricci scalar. |
2404.11002 | Yongqiang Wang | Chen-Hao Hao, Xin Su, Yong-Qiang Wang | AdS Ellis wormholes with scalar field | 23 pages, 8 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the spherically symmetric traversable wormholes with
a scalar field supported by a phantom field in the anti-de Sitter (AdS)
asymptotic spacetime. Despite coupling the scalar matter field, these wormholes
remain massless and symmetric for reflection of the radial coordinate $r
\rightarrow -r$. The solution possesses a finite Noether charge $Q$, which
varies as a function of frequency $\omega$ with changes in the cosmological
constant $\Lambda$ and the throat size $r_0$. Under specific conditions, an
approximate ``event horizon'' will appear at the throat.
| [
{
"created": "Wed, 17 Apr 2024 02:24:53 GMT",
"version": "v1"
}
] | 2024-04-18 | [
[
"Hao",
"Chen-Hao",
""
],
[
"Su",
"Xin",
""
],
[
"Wang",
"Yong-Qiang",
""
]
] | In this paper, we study the spherically symmetric traversable wormholes with a scalar field supported by a phantom field in the anti-de Sitter (AdS) asymptotic spacetime. Despite coupling the scalar matter field, these wormholes remain massless and symmetric for reflection of the radial coordinate $r \rightarrow -r$. The solution possesses a finite Noether charge $Q$, which varies as a function of frequency $\omega$ with changes in the cosmological constant $\Lambda$ and the throat size $r_0$. Under specific conditions, an approximate ``event horizon'' will appear at the throat. |
1710.00836 | Shahar Hod | Shahar Hod | On the number of light rings in curved spacetimes of ultra-compact
objects | 5 pages | Physics Letters B 776, 1 (2018) | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a very interesting paper, Cunha, Berti, and Herdeiro have recently claimed
that ultra-compact objects, self-gravitating horizonless solutions of the
Einstein field equations which have a light ring, must possess at least {\it
two} (and, in general, an even number of) light rings, of which the inner one
is {\it stable}. In the present compact paper we explicitly prove that, while
this intriguing theorem is generally true, there is an important exception in
the presence of degenerate light rings which, in the spherically symmetric
static case, are characterized by the simple dimensionless relation $8\pi
r^2_{\gamma}(\rho+p_{\text{T}})=1$ [here $r_{\gamma}$ is the radius of the
light ring and $\{\rho,p_{\text{T}}\}$ are respectively the energy density and
tangential pressure of the matter fields]. Ultra-compact objects which belong
to this unique family can have an {\it odd} number of light rings. As a
concrete example, we show that spherically symmetric constant density stars
with dimensionless compactness $M/R=1/3$ possess only {\it one} light ring
which, interestingly, is shown to be {\it unstable}.
| [
{
"created": "Mon, 2 Oct 2017 18:00:08 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Dec 2017 13:18:46 GMT",
"version": "v2"
}
] | 2017-12-07 | [
[
"Hod",
"Shahar",
""
]
] | In a very interesting paper, Cunha, Berti, and Herdeiro have recently claimed that ultra-compact objects, self-gravitating horizonless solutions of the Einstein field equations which have a light ring, must possess at least {\it two} (and, in general, an even number of) light rings, of which the inner one is {\it stable}. In the present compact paper we explicitly prove that, while this intriguing theorem is generally true, there is an important exception in the presence of degenerate light rings which, in the spherically symmetric static case, are characterized by the simple dimensionless relation $8\pi r^2_{\gamma}(\rho+p_{\text{T}})=1$ [here $r_{\gamma}$ is the radius of the light ring and $\{\rho,p_{\text{T}}\}$ are respectively the energy density and tangential pressure of the matter fields]. Ultra-compact objects which belong to this unique family can have an {\it odd} number of light rings. As a concrete example, we show that spherically symmetric constant density stars with dimensionless compactness $M/R=1/3$ possess only {\it one} light ring which, interestingly, is shown to be {\it unstable}. |
gr-qc/9410008 | Sergei V. Sushkov | Sergey Sushkov | Quantum Complex Scalar Field in the Two-Dimensional Spacetime with
Closed Timelike Curves and a Time-Machine Problem | 21(Latex)Postscript file of the figure may be received from author,
CQG-94-1006 | Class.Quant.Grav.12:1685-1698,1995 | 10.1088/0264-9381/12/7/010 | null | gr-qc | null | It is considered the quantum complex scalar field which obeys the
authomorphic condition in the two-dimensional spacetime with closed timelike
curves and the chronology horizon. The renormalized stress-energy tensor is
obtained. It is shown that the value of the stress-energy tensor is regular at
the chronology horizon for specific authomorphic parameters. Thus the
particular example of field configuration is given for which the Hawking's
chronology protection conjecture is violated.
| [
{
"created": "Fri, 7 Oct 1994 12:35:24 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Sushkov",
"Sergey",
""
]
] | It is considered the quantum complex scalar field which obeys the authomorphic condition in the two-dimensional spacetime with closed timelike curves and the chronology horizon. The renormalized stress-energy tensor is obtained. It is shown that the value of the stress-energy tensor is regular at the chronology horizon for specific authomorphic parameters. Thus the particular example of field configuration is given for which the Hawking's chronology protection conjecture is violated. |
gr-qc/0405107 | Enrique Alvarez | Enrique Alvarez | Quantum Gravity | Lectures given at Karpacz. 40 pages, submitted to Lecture Notes in
Physics. Bigger figures | null | 10.1007/11377306_2 | IFT-UAM/CSIC-04-26 | gr-qc | null | General lectures on quantum gravity.
| [
{
"created": "Wed, 19 May 2004 14:00:37 GMT",
"version": "v1"
},
{
"created": "Fri, 21 May 2004 09:08:24 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Alvarez",
"Enrique",
""
]
] | General lectures on quantum gravity. |
2407.13235 | Pasquale Bosso | Pasquale Bosso | Minimal-length quantum field theory: a first-principle approach | 24 pages, 2 figures, 3 appendices | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Phenomenological models of quantum gravity often consider the existence of
some form of minimal length. This feature is commonly described in the context
of quantum mechanics and using the corresponding formalism and techniques.
Although few attempts at a quantum field-theoretical description of a minimal
length has been proposed, they are rather the exception and there is no general
agreement on the correct one. Here, using the quantum-mechanical model as a
guidance, we propose a first-principle definition of a quantum field theory
including a minimal length. Specifically, we propose a two-step procedure, by
first describing the quantum-mechanical models as a classical field theory and
subsequently quantizing it. We are thus able to provide a foundation for
further exploration of the implications of a minimal length in quantum field
theory.
| [
{
"created": "Thu, 18 Jul 2024 07:45:10 GMT",
"version": "v1"
}
] | 2024-07-19 | [
[
"Bosso",
"Pasquale",
""
]
] | Phenomenological models of quantum gravity often consider the existence of some form of minimal length. This feature is commonly described in the context of quantum mechanics and using the corresponding formalism and techniques. Although few attempts at a quantum field-theoretical description of a minimal length has been proposed, they are rather the exception and there is no general agreement on the correct one. Here, using the quantum-mechanical model as a guidance, we propose a first-principle definition of a quantum field theory including a minimal length. Specifically, we propose a two-step procedure, by first describing the quantum-mechanical models as a classical field theory and subsequently quantizing it. We are thus able to provide a foundation for further exploration of the implications of a minimal length in quantum field theory. |
2403.09756 | Hasan El Moumni | L. Chakhchi, H. El Moumni, K. Masmar | Signatures of the accelerating black holes with a cosmological constant
from the $\textrm{Sgr~A}^\star$ and $\textrm{M87}^\star$ shadow prospects | 37 pages, 10 figures, references updated | Physics of the Dark Universe 44 (2024) 101501 | 10.1016/j.dark.2024.101501 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, the Event Horizon Telescope (EHT) achieved the realization of an
image of the supermassive black hole $\textrm{Sgr~A}^\star$ showing an angular
shadow diameter $\mathcal{D}= 48.7 \pm 7\mu as$ and the fractional deviation
$\mathbf{\delta} =
-0.08^{+0.09}_{-0.09}~\text{(VLTI)},-0.04^{+0.09}_{-0.10}~\text{(Keck)}$,
alongside the earlier image of $\textrm{M87}^\star$ with angular diameter $
\mathcal{D}=42 \pm 3 \mu as$, deviation $\mathbf{\delta}=-0.01^{+0.17}_{-0.17}$
and deviations from circularity estimated to be $\Delta \mathcal{C}\lesssim
10\%$. In addition, the shadow radii are assessed within the ranges $3.38 \le
\frac{r_{\text{s}}}{M} \le 6.91$ for $\textrm{M87}^\star$ and $3.85 \le
\frac{r_{\text{s}}}{M} \le 5.72$ as well as $3.95 \le \frac{r_{\text{s}}}{M}
\le 5.92$ for $\textrm{Sgr~A}^\star$ using the Very Large Telescope
Interferometer (VLTI) and Keck observatories, respectively. These values are
provided with $1$-$\sigma$ and $2$-$\sigma$ measurements. Such realizations can
unveil a better comprehension of gravitational physics at the horizon scale. In
this paper, we use the EHT observational results for $\textrm{M87}^\star$ and
$\textrm{Sgr~A}^\star$ to elaborate the constraints on parameters of
accelerating black holes with a cosmological constant. Concretely, we utilize
the mass and distance of both black holes to derive the observables associated
with the accelerating black hole shadow. First, we compare our findings with
observed quantities such as angular diameter, circularity, shadow radius, and
the fractional deviation from the $\textrm{M87}^\star$ data. This comparison
reveals constraints within the acceleration parameter and the cosmological
constant...
Lastly, one cannot rule out the possibility of the negative values for the
cosmological constant on the emergence of accelerated black hole solutions
within the context of minimal gauged supergravity...
| [
{
"created": "Thu, 14 Mar 2024 14:38:30 GMT",
"version": "v1"
},
{
"created": "Sun, 21 Apr 2024 10:18:31 GMT",
"version": "v2"
}
] | 2024-04-23 | [
[
"Chakhchi",
"L.",
""
],
[
"Moumni",
"H. El",
""
],
[
"Masmar",
"K.",
""
]
] | Recently, the Event Horizon Telescope (EHT) achieved the realization of an image of the supermassive black hole $\textrm{Sgr~A}^\star$ showing an angular shadow diameter $\mathcal{D}= 48.7 \pm 7\mu as$ and the fractional deviation $\mathbf{\delta} = -0.08^{+0.09}_{-0.09}~\text{(VLTI)},-0.04^{+0.09}_{-0.10}~\text{(Keck)}$, alongside the earlier image of $\textrm{M87}^\star$ with angular diameter $ \mathcal{D}=42 \pm 3 \mu as$, deviation $\mathbf{\delta}=-0.01^{+0.17}_{-0.17}$ and deviations from circularity estimated to be $\Delta \mathcal{C}\lesssim 10\%$. In addition, the shadow radii are assessed within the ranges $3.38 \le \frac{r_{\text{s}}}{M} \le 6.91$ for $\textrm{M87}^\star$ and $3.85 \le \frac{r_{\text{s}}}{M} \le 5.72$ as well as $3.95 \le \frac{r_{\text{s}}}{M} \le 5.92$ for $\textrm{Sgr~A}^\star$ using the Very Large Telescope Interferometer (VLTI) and Keck observatories, respectively. These values are provided with $1$-$\sigma$ and $2$-$\sigma$ measurements. Such realizations can unveil a better comprehension of gravitational physics at the horizon scale. In this paper, we use the EHT observational results for $\textrm{M87}^\star$ and $\textrm{Sgr~A}^\star$ to elaborate the constraints on parameters of accelerating black holes with a cosmological constant. Concretely, we utilize the mass and distance of both black holes to derive the observables associated with the accelerating black hole shadow. First, we compare our findings with observed quantities such as angular diameter, circularity, shadow radius, and the fractional deviation from the $\textrm{M87}^\star$ data. This comparison reveals constraints within the acceleration parameter and the cosmological constant... Lastly, one cannot rule out the possibility of the negative values for the cosmological constant on the emergence of accelerated black hole solutions within the context of minimal gauged supergravity... |
1004.3149 | Cosimo Bambi | Cosimo Bambi, Naoki Yoshida | Shape and position of the shadow in the $\delta = 2$ Tomimatsu-Sato
space-time | 9 pages, 3 figures. v3: refereed version | Class.Quant.Grav.27:205006,2010 | 10.1088/0264-9381/27/20/205006 | IPMU10-0061 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within 5-10 years, very long baseline interferometry facilities will be able
to observe the "shadow" of super-massive black hole candidates. This will
allow, for the first time, to test gravity in the strong field regime. In this
paper, we study numerically the photon orbits in the $\delta = 2$
Tomimatsu-Sato space-time. The $\delta = 2$ Tomimatsu-Sato space-time is a
stationary, axisymmetric, and asymptotically flat exact solution of the vacuum
Einstein equations. We compare the associated shadow with the one of Kerr black
holes. The shape of the shadow in the $\delta = 2$ Tomimatsu-Sato space-time is
oblate and the difference between the two axes can be as high as 6% when viewed
on the equatorial plane. We argue that future space sub-mm interferometers
(e.g. VSOP-3) may distinguish the two cases, and thus are able to test the
Cosmic Censorship Conjecture.
| [
{
"created": "Mon, 19 Apr 2010 10:32:33 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Apr 2010 00:45:36 GMT",
"version": "v2"
},
{
"created": "Fri, 30 Jul 2010 12:40:52 GMT",
"version": "v3"
}
] | 2010-09-09 | [
[
"Bambi",
"Cosimo",
""
],
[
"Yoshida",
"Naoki",
""
]
] | Within 5-10 years, very long baseline interferometry facilities will be able to observe the "shadow" of super-massive black hole candidates. This will allow, for the first time, to test gravity in the strong field regime. In this paper, we study numerically the photon orbits in the $\delta = 2$ Tomimatsu-Sato space-time. The $\delta = 2$ Tomimatsu-Sato space-time is a stationary, axisymmetric, and asymptotically flat exact solution of the vacuum Einstein equations. We compare the associated shadow with the one of Kerr black holes. The shape of the shadow in the $\delta = 2$ Tomimatsu-Sato space-time is oblate and the difference between the two axes can be as high as 6% when viewed on the equatorial plane. We argue that future space sub-mm interferometers (e.g. VSOP-3) may distinguish the two cases, and thus are able to test the Cosmic Censorship Conjecture. |
1806.00361 | Ping Li | Ping Li, Miao He, Jia-Cheng Ding, Xian-Ru Hu and Jian-Bo Deng | Thermodynamics of charged AdS black holes in rainbow gravity | 16 pages, 6 figures | Advances in High Energy Physics Volume 2018, 6 pages | 10.1155/2018/1043639 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, the thermodynamic property of charged AdS black holes is
studied in rainbow gravity. By the Heisenberg Uncertainty Principle and the
modified dispersion relation, we obtain deformed temperature. Moreover, in
rainbow gravity we calculate the heat capacity in a fixed charge and discuss
the thermal stability. We also obtain a similar behaviour with the liquid-gas
system in extending phase space (including \(P\) and \(r\)) and study its
critical behavior with the pressure given by the cosmological constant and with
a fixed black hole charge \(Q\). Furthermore, we study the Gibbs function and
find its characteristic swallow tail behavior, which indicates the phase
transition. We also find there is a special value about the mass of test
particle which would lead the black hole to zero temperature and a diverging
heat capacity with a fixed charge.
| [
{
"created": "Thu, 31 May 2018 13:11:31 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Jan 2019 08:54:20 GMT",
"version": "v2"
}
] | 2019-01-04 | [
[
"Li",
"Ping",
""
],
[
"He",
"Miao",
""
],
[
"Ding",
"Jia-Cheng",
""
],
[
"Hu",
"Xian-Ru",
""
],
[
"Deng",
"Jian-Bo",
""
]
] | In this paper, the thermodynamic property of charged AdS black holes is studied in rainbow gravity. By the Heisenberg Uncertainty Principle and the modified dispersion relation, we obtain deformed temperature. Moreover, in rainbow gravity we calculate the heat capacity in a fixed charge and discuss the thermal stability. We also obtain a similar behaviour with the liquid-gas system in extending phase space (including \(P\) and \(r\)) and study its critical behavior with the pressure given by the cosmological constant and with a fixed black hole charge \(Q\). Furthermore, we study the Gibbs function and find its characteristic swallow tail behavior, which indicates the phase transition. We also find there is a special value about the mass of test particle which would lead the black hole to zero temperature and a diverging heat capacity with a fixed charge. |
1312.7119 | Deepak Vaid | Deepak Vaid | Superconducting and Anti-Ferromagnetic Phases of Spacetime | 6 pages, no figures, shortened for journal submission, comments
welcome :) | null | 10.1155/2017/7935185 | null | gr-qc cond-mat.supr-con | http://creativecommons.org/licenses/by-nc-sa/4.0/ | A correspondence between the $SO(5)$ theory of High-T${}_C$ superconductivity
and antiferromagnetism, put forward by Zhang and collaborators, and a theory of
gravity arising from symmetry breaking of a $SO(5)$ gauge field is presented. A
physical correspondence between the order parameters of the unified SC/AF
theory and the generators of the gravitational gauge connection is conjectured.
A preliminary identification of regions of geometry, in solutions of Einstein's
equations describing charged-rotating black holes embedded in deSitter
spacetime, with SC and AF phases is carried out.
| [
{
"created": "Thu, 26 Dec 2013 15:16:14 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Aug 2016 18:40:43 GMT",
"version": "v2"
}
] | 2018-01-03 | [
[
"Vaid",
"Deepak",
""
]
] | A correspondence between the $SO(5)$ theory of High-T${}_C$ superconductivity and antiferromagnetism, put forward by Zhang and collaborators, and a theory of gravity arising from symmetry breaking of a $SO(5)$ gauge field is presented. A physical correspondence between the order parameters of the unified SC/AF theory and the generators of the gravitational gauge connection is conjectured. A preliminary identification of regions of geometry, in solutions of Einstein's equations describing charged-rotating black holes embedded in deSitter spacetime, with SC and AF phases is carried out. |
gr-qc/9802004 | Maurice van Putten | Maurice H.P.M. van Putten (MIT) | Approximate black holes from a variable cosmological constant | 3 pages,latex,2 figures; corrected typos and existence proof | null | null | null | gr-qc astro-ph | null | The small or zero cosmological constant, $\Lambda$, probably results from a
macroscopic cancellation mechanism of the zero-point energies. However, nearby
horizon surfaces any macroscopic mechanism is expected to result in imperfect
cancellations. A phenomenological description is given for the residual
variable cosmological constant. In the static, spherically symmetric case it
produces approximate black holes. The model describes the case of exponential
decay by $\Box\ln\Lambda=-3a$, were $a$ is a positive constant.
| [
{
"created": "Mon, 2 Feb 1998 21:36:58 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Apr 1998 00:10:31 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"van Putten",
"Maurice H. P. M.",
"",
"MIT"
]
] | The small or zero cosmological constant, $\Lambda$, probably results from a macroscopic cancellation mechanism of the zero-point energies. However, nearby horizon surfaces any macroscopic mechanism is expected to result in imperfect cancellations. A phenomenological description is given for the residual variable cosmological constant. In the static, spherically symmetric case it produces approximate black holes. The model describes the case of exponential decay by $\Box\ln\Lambda=-3a$, were $a$ is a positive constant. |
2404.07186 | Martin Pijnenburg | Martin Pijnenburg, Giulia Cusin, Cyril Pitrou, Jean-Philippe Uzan | Wave optics lensing of gravitational waves: theory and phenomenology of
triple systems in the LISA band | 26 pages, 8 figures | null | null | null | gr-qc astro-ph.CO astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We study lensing of gravitational waves by a black hole in the deep wave
optics regime, i.e. when the wavelength is much larger than the black hole
Schwarzschild radius. We apply it to triple systems, with a binary of stellar
mass objects in the inspiraling phase orbiting around a central massive black
hole. We describe the full polarisation structure of the wave and derive
predictions for the polarisation modes of the scattered wave measured by the
observer. We show that lensing in the wave optics regime is not helicity
preserving, as opposed to lensing in the geometric optics regime. The amplitude
of the total wave is modulated due to interference between the directly
transmitted and lensed components. The relative amplitude of the modulation is
fixed by the lensing geometry and can reach unity in the most favourable
settings. This indicates that wave optics lensing is potentially detectable by
LISA for sufficiently high SNR systems. Our findings show that in the wave
optics regime it is necessary to go beyond the usual lensing description where
the amplification factor is assumed to be the same for both helicity modes.
While motivated by GW190521 and the AGN formation scenario, our results apply
more broadly to stellar-mass binaries orbiting a third body described as a
Schwarzschild black hole, with a period comparable to the GW observation time.
| [
{
"created": "Wed, 10 Apr 2024 17:40:34 GMT",
"version": "v1"
}
] | 2024-04-11 | [
[
"Pijnenburg",
"Martin",
""
],
[
"Cusin",
"Giulia",
""
],
[
"Pitrou",
"Cyril",
""
],
[
"Uzan",
"Jean-Philippe",
""
]
] | We study lensing of gravitational waves by a black hole in the deep wave optics regime, i.e. when the wavelength is much larger than the black hole Schwarzschild radius. We apply it to triple systems, with a binary of stellar mass objects in the inspiraling phase orbiting around a central massive black hole. We describe the full polarisation structure of the wave and derive predictions for the polarisation modes of the scattered wave measured by the observer. We show that lensing in the wave optics regime is not helicity preserving, as opposed to lensing in the geometric optics regime. The amplitude of the total wave is modulated due to interference between the directly transmitted and lensed components. The relative amplitude of the modulation is fixed by the lensing geometry and can reach unity in the most favourable settings. This indicates that wave optics lensing is potentially detectable by LISA for sufficiently high SNR systems. Our findings show that in the wave optics regime it is necessary to go beyond the usual lensing description where the amplification factor is assumed to be the same for both helicity modes. While motivated by GW190521 and the AGN formation scenario, our results apply more broadly to stellar-mass binaries orbiting a third body described as a Schwarzschild black hole, with a period comparable to the GW observation time. |
gr-qc/0411035 | Amit Ghosh | A. Ghosh and P. Mitra | An improved estimate of black hole entropy in the quantum geometry
approach | 5 pages, LaTeX; references and remarks added | Phys.Lett. B616 (2005) 114-117 | 10.1016/j.physletb.2005.05.003 | null | gr-qc hep-th | null | A proper counting of states for black holes in the quantum geometry approach
shows that the dominant configuration for spins are distributions that include
spins exceeding one-half at the punctures. This raises the value of the Immirzi
parameter and the black hole entropy. However, the coefficient of the
logarithmic correction remains -1/2 as before.
| [
{
"created": "Mon, 8 Nov 2004 11:00:54 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Nov 2004 10:44:00 GMT",
"version": "v2"
},
{
"created": "Mon, 30 May 2005 09:04:11 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Ghosh",
"A.",
""
],
[
"Mitra",
"P.",
""
]
] | A proper counting of states for black holes in the quantum geometry approach shows that the dominant configuration for spins are distributions that include spins exceeding one-half at the punctures. This raises the value of the Immirzi parameter and the black hole entropy. However, the coefficient of the logarithmic correction remains -1/2 as before. |
2103.03476 | Abhik Kumar Sanyal Dr. | Abhik Kumar Sanyal and D. Ray | Scalar meson field in a conformally flat space | 5 pages, 0 figures | Journal of Mathematical Physics 25, 1977 (1984) | 10.1063/1.526389 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Among several authors, who studied massive and massless scalar meson fields
in general relativity, attempts to obtain a complete set of solutions for a
conformally flat metric $e^{\psi}\left({dx^1}^2 + {dx^2}^2 + {dx^3}^2 -
{dx^4}^2\right)$ were made by Ray for massive and massless mesons and Gursay
for massless mesons. Both of them concluded that $\psi$ must be a function of
$K_0\left({dx^1}^2 + {dx^2}^2 + {dx^3}^2 -{dx^4}^2\right) + K_1 x^1 + K_2 x^2 +
K_3 x^3 + K_4 x^4$, where, where $K_0,~K_1,~ K_2,~K_3,~K_4$ are all constants.
Both Ray and Gursay, however, overlooked an important particular case, which is
studied here. As a by-product certain equations obtained by Auria and Regge in
connection with "Gravitational theories with asymptotic flat Instantons," are
solved under less restrictive assumptions.
| [
{
"created": "Fri, 5 Mar 2021 05:18:17 GMT",
"version": "v1"
}
] | 2021-03-08 | [
[
"Sanyal",
"Abhik Kumar",
""
],
[
"Ray",
"D.",
""
]
] | Among several authors, who studied massive and massless scalar meson fields in general relativity, attempts to obtain a complete set of solutions for a conformally flat metric $e^{\psi}\left({dx^1}^2 + {dx^2}^2 + {dx^3}^2 - {dx^4}^2\right)$ were made by Ray for massive and massless mesons and Gursay for massless mesons. Both of them concluded that $\psi$ must be a function of $K_0\left({dx^1}^2 + {dx^2}^2 + {dx^3}^2 -{dx^4}^2\right) + K_1 x^1 + K_2 x^2 + K_3 x^3 + K_4 x^4$, where, where $K_0,~K_1,~ K_2,~K_3,~K_4$ are all constants. Both Ray and Gursay, however, overlooked an important particular case, which is studied here. As a by-product certain equations obtained by Auria and Regge in connection with "Gravitational theories with asymptotic flat Instantons," are solved under less restrictive assumptions. |
gr-qc/0512063 | Nadja Magalh\~aes Sim\~ao | Nadja S. Magalhaes | Challenges in Signal Analysis of Resonant-Mass Gravitational Wave
Detectors | 6 pages, 3 figures, presented at the international conference "100
Years of Relativity" (Sao Paulo, Brazil, 22-24 August 2005), to appear in
Brazilian Journal of Physics (Dec. 2005) | Braz.J.Phys. 35 (2005) 1195-1200 | 10.1590/S0103-97332005000700049 | null | gr-qc | null | An overview of the main points related to data analysis in resonant-mass
gravitational wave detectors will be presented. Recent developments on the data
analysis system for the Brazilian detector SCHENBERG will be emphasized.
| [
{
"created": "Sun, 11 Dec 2005 15:03:02 GMT",
"version": "v1"
}
] | 2017-02-01 | [
[
"Magalhaes",
"Nadja S.",
""
]
] | An overview of the main points related to data analysis in resonant-mass gravitational wave detectors will be presented. Recent developments on the data analysis system for the Brazilian detector SCHENBERG will be emphasized. |
2203.01598 | Genly Le\'on | Andronikos Paliathanasis (DUT, Durban and Chile Austral U., Valdivia),
Genly Leon (Catolica del Norte U. and DUT, Durban) | Hyperbolic inflationary model with nonzero curvature | 13 pages. Major revision. One calculation error was amended | null | 10.1016/j.physletb.2022.137407 | null | gr-qc astro-ph.CO hep-ph | http://creativecommons.org/licenses/by/4.0/ | We consider a cosmological model consisting of two scalar fields defined in
the hyperbolic plane known as hyperbolic inflation. For the background space,
we consider a homogeneous and isotropic spacetime with nonzero curvature. We
study the asymptotic behaviour of solutions and we search for attractors in the
expanding regime. We prove that two hyperbolic inflationary stages are stable
solutions that can solve the flatness problem and describe acceleration for
both open and closed models, and additionally we obtain a Milne-like attractor
solution for the open model. We also investigate the contracting branch
obtaining mirror solutions with the opposite dynamical behaviours.
| [
{
"created": "Thu, 3 Mar 2022 09:55:50 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Mar 2022 10:12:54 GMT",
"version": "v2"
},
{
"created": "Fri, 20 May 2022 17:44:21 GMT",
"version": "v3"
}
] | 2022-08-31 | [
[
"Paliathanasis",
"Andronikos",
"",
"DUT, Durban and Chile Austral U., Valdivia"
],
[
"Leon",
"Genly",
"",
"Catolica del Norte U. and DUT, Durban"
]
] | We consider a cosmological model consisting of two scalar fields defined in the hyperbolic plane known as hyperbolic inflation. For the background space, we consider a homogeneous and isotropic spacetime with nonzero curvature. We study the asymptotic behaviour of solutions and we search for attractors in the expanding regime. We prove that two hyperbolic inflationary stages are stable solutions that can solve the flatness problem and describe acceleration for both open and closed models, and additionally we obtain a Milne-like attractor solution for the open model. We also investigate the contracting branch obtaining mirror solutions with the opposite dynamical behaviours. |
1106.1693 | David Wiltshire | David L. Wiltshire | What is dust? - Physical foundations of the averaging problem in
cosmology | 39 pages, 3 figures, Invited review accepted by Classical and Quantum
Gravity for the special issue "Inhomogeneous Cosmological Models and
Averaging in Cosmology" | Class.Quant.Grav.28:164006, 2011 | 10.1088/0264-9381/28/16/164006 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The problems of coarse-graining and averaging of inhomogeneous cosmologies,
and their backreaction on average cosmic evolution, are reviewed from a
physical viewpoint. A particular focus is placed on comparing different notions
of average spatial homogeneity, and on the interpretation of observational
results. Among the physical questions we consider are: the nature of an average
Copernican principle, the role of Mach's principle, the issue of quasilocal
gravitational energy and the different roles of spacetime, spatial and null
cone averages. The observational interpretation of the timescape scenario is
compared to other approaches to cosmological averaging, and outstanding
questions are discussed.
| [
{
"created": "Thu, 9 Jun 2011 00:54:55 GMT",
"version": "v1"
}
] | 2011-08-08 | [
[
"Wiltshire",
"David L.",
""
]
] | The problems of coarse-graining and averaging of inhomogeneous cosmologies, and their backreaction on average cosmic evolution, are reviewed from a physical viewpoint. A particular focus is placed on comparing different notions of average spatial homogeneity, and on the interpretation of observational results. Among the physical questions we consider are: the nature of an average Copernican principle, the role of Mach's principle, the issue of quasilocal gravitational energy and the different roles of spacetime, spatial and null cone averages. The observational interpretation of the timescape scenario is compared to other approaches to cosmological averaging, and outstanding questions are discussed. |
1702.05347 | Ira Georg | Ira Georg, Charles Hellaby | Symmetry and Equivalence in Szekeres Models | 16 pages, 3 figures | Phys. Rev. D 95, 124016 (2017) | 10.1103/PhysRevD.95.124016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We solve for all Szekeres metrics that have a single Killing vector. For
quasi hyperboloidal ($\epsilon = -1$) metrics, we find that translational
symmetries are possible, but only in metrics that have shell crossings
somewhere, while metrics that can be made free of shell crossings only permit
rotations. The quasi planar metrics ($\epsilon = 0$) either have no Killing
vectors or they admit full planar symmetry. Single symmetries in quasi
spherical metrics ($\epsilon = +1$) are all rotations. The rotations correspond
to a known family of axially symmetric metrics, which for each $\epsilon$
value, are equivalent to each other. We consider Szekeres metrics in which the
line of dipole extrema is required to be geodesic in the 3-space, and show the
same set of families emerges. We investigate when two Szekeres metrics are
physically equivalent, and complete a previous list of transformations of the
arbitrary functions.
| [
{
"created": "Fri, 17 Feb 2017 14:07:12 GMT",
"version": "v1"
}
] | 2017-06-14 | [
[
"Georg",
"Ira",
""
],
[
"Hellaby",
"Charles",
""
]
] | We solve for all Szekeres metrics that have a single Killing vector. For quasi hyperboloidal ($\epsilon = -1$) metrics, we find that translational symmetries are possible, but only in metrics that have shell crossings somewhere, while metrics that can be made free of shell crossings only permit rotations. The quasi planar metrics ($\epsilon = 0$) either have no Killing vectors or they admit full planar symmetry. Single symmetries in quasi spherical metrics ($\epsilon = +1$) are all rotations. The rotations correspond to a known family of axially symmetric metrics, which for each $\epsilon$ value, are equivalent to each other. We consider Szekeres metrics in which the line of dipole extrema is required to be geodesic in the 3-space, and show the same set of families emerges. We investigate when two Szekeres metrics are physically equivalent, and complete a previous list of transformations of the arbitrary functions. |
gr-qc/0206071 | Zvi Bern | Zvi Bern | Perturbative Quantum Gravity and its Relation to Gauge Theory | Minor corrections included; 50 pages; to appear in Living Reviews in
Relativity http://www.livingreviews.org | LivingRev.Rel.5:5,2002 | 10.12942/lrr-2002-5 | UCLA/02/TEP/9 | gr-qc hep-ph hep-th | null | In this review we describe a non-trivial relationship between perturbative
gauge theory and gravity scattering amplitudes. At the semi-classical or tree
level, the scattering amplitudes of gravity theories in flat space can be
expressed as a sum of products of well defined pieces of gauge theory
amplitudes. These relationships were first discovered by Kawai, Lewellen and
Tye in the context of string theory, but hold more generally. In particular,
they hold for standard Einstein gravity. A method based on D-dimensional
unitarity can then be used to systematically construct all quantum loop
corrections order-by-order in perturbation theory using as input the gravity
tree amplitudes expressed in terms of gauge theory ones. More generally, the
unitarity method provides a means for perturbatively quantizing massless
gravity theories without the usual formal apparatus associated with the
quantization of constrained systems. As one application, this method was used
to demonstrate that maximally supersymmetric gravity is less divergent in the
ultraviolet than previously thought.
| [
{
"created": "Tue, 25 Jun 2002 18:05:16 GMT",
"version": "v1"
},
{
"created": "Sat, 20 Jul 2002 21:14:37 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Bern",
"Zvi",
""
]
] | In this review we describe a non-trivial relationship between perturbative gauge theory and gravity scattering amplitudes. At the semi-classical or tree level, the scattering amplitudes of gravity theories in flat space can be expressed as a sum of products of well defined pieces of gauge theory amplitudes. These relationships were first discovered by Kawai, Lewellen and Tye in the context of string theory, but hold more generally. In particular, they hold for standard Einstein gravity. A method based on D-dimensional unitarity can then be used to systematically construct all quantum loop corrections order-by-order in perturbation theory using as input the gravity tree amplitudes expressed in terms of gauge theory ones. More generally, the unitarity method provides a means for perturbatively quantizing massless gravity theories without the usual formal apparatus associated with the quantization of constrained systems. As one application, this method was used to demonstrate that maximally supersymmetric gravity is less divergent in the ultraviolet than previously thought. |
gr-qc/9503027 | Karen Brewster | Lee Smolin | Experimental Signatures of Quantum Gravity | TEX File, Minor Changes Made, 23 pages | null | null | CGPG-95/3-2 | gr-qc astro-ph hep-th | null | I review several different calculations, coming from string theory,
nonperturbative quantum gravity and analyses of black holes that lead to
predictions of phenomena that would uniquely be signatures of quantum
gravitational effects.
These include: 1) deviations from a thermal spectra for evaporating black
holes, 2) upper limits on the entropy and energy content of bounded regions, 3)
suppression of ultra-high energy scattering amplitudes, consistent with a
modified uncertainty principle, 4) physical volumes and areas have discrete
spectra, 5), violations of $CPT$ and universal violations of $CP$, 6) otherwise
inexplicable conditions on the initial state of the universe or otherwise
inexplicable correlations between cosmological and microscopic parameters.
Consideration of all of these together suggests the possibility of connections
between perturbative and nonperturbative approaches to quantum gravity.
| [
{
"created": "Thu, 16 Mar 1995 16:13:28 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Jan 1996 21:38:01 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Smolin",
"Lee",
""
]
] | I review several different calculations, coming from string theory, nonperturbative quantum gravity and analyses of black holes that lead to predictions of phenomena that would uniquely be signatures of quantum gravitational effects. These include: 1) deviations from a thermal spectra for evaporating black holes, 2) upper limits on the entropy and energy content of bounded regions, 3) suppression of ultra-high energy scattering amplitudes, consistent with a modified uncertainty principle, 4) physical volumes and areas have discrete spectra, 5), violations of $CPT$ and universal violations of $CP$, 6) otherwise inexplicable conditions on the initial state of the universe or otherwise inexplicable correlations between cosmological and microscopic parameters. Consideration of all of these together suggests the possibility of connections between perturbative and nonperturbative approaches to quantum gravity. |
1607.00182 | Etera R. Livine | Alexandre Feller, Etera R. Livine | Surface state decoherence in loop quantum gravity, a first toy model | 21 pages | Class.Quant.Grav. 34 (2017) no.4, 045004 | 10.1088/1361-6382/aa525c | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The quantum-to-classical transition through decoherence is a major facet of
the semi-classical analysis of quantum models that are supposed to admit a
classical regime, as quantum gravity should be. A particular problem of
interest is the decoherence of black hole horizons and holographic screens
induced by the bulk-boundary coupling with interior degrees of freedom. Here in
this paper we present a first toy-model, in the context of loop quantum
gravity, for the dynamics of a surface geometry as an open quantum system at
fixed total area. We discuss the resulting decoherence and recoherence and
compare the exact density matrix evolution to the commonly used master equation
approximation {\it \`a la} Lindblad underlining its merits and limitations. The
prospect of this study is to have a clearer understanding of the boundary
decoherence of black hole horizons seen by outside observers.
| [
{
"created": "Fri, 1 Jul 2016 09:49:14 GMT",
"version": "v1"
}
] | 2017-04-04 | [
[
"Feller",
"Alexandre",
""
],
[
"Livine",
"Etera R.",
""
]
] | The quantum-to-classical transition through decoherence is a major facet of the semi-classical analysis of quantum models that are supposed to admit a classical regime, as quantum gravity should be. A particular problem of interest is the decoherence of black hole horizons and holographic screens induced by the bulk-boundary coupling with interior degrees of freedom. Here in this paper we present a first toy-model, in the context of loop quantum gravity, for the dynamics of a surface geometry as an open quantum system at fixed total area. We discuss the resulting decoherence and recoherence and compare the exact density matrix evolution to the commonly used master equation approximation {\it \`a la} Lindblad underlining its merits and limitations. The prospect of this study is to have a clearer understanding of the boundary decoherence of black hole horizons seen by outside observers. |
1010.1444 | Surajit Chattopadhyay | Surajit Chattopadhyay (Pailan College of Management and Technology,
Kolkata), Ujjal Debnath (Bengal Engineering and Science University, Howrah) | Interaction between Tachyon and Hessence (or Hantom) dark energies | null | null | 10.1007/s10773-011-0819-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have considered that the universe is filled with tachyon,
hessence (or hantom) dark energies. Subsequently we have investigated the
interactions between tachyon and hessence (hantom) dark energies and calculated
the potentials considering the power law form of the scale factor. It has been
revealed that the tachyonic potential always decreases and hessence (or hantom)
potential increases with corresponding fields. Furthermore, we have considered
a correspondence between the hessence (or hantom) dark energy density and new
variable modified Chaplygin gas energy density. From this, we have found the
expressions of the arbitrary positive constants B0 and C of new variable
modified Chaplygin gas.
| [
{
"created": "Thu, 7 Oct 2010 14:39:23 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Chattopadhyay",
"Surajit",
"",
"Pailan College of Management and Technology,\n Kolkata"
],
[
"Debnath",
"Ujjal",
"",
"Bengal Engineering and Science University, Howrah"
]
] | In this paper, we have considered that the universe is filled with tachyon, hessence (or hantom) dark energies. Subsequently we have investigated the interactions between tachyon and hessence (hantom) dark energies and calculated the potentials considering the power law form of the scale factor. It has been revealed that the tachyonic potential always decreases and hessence (or hantom) potential increases with corresponding fields. Furthermore, we have considered a correspondence between the hessence (or hantom) dark energy density and new variable modified Chaplygin gas energy density. From this, we have found the expressions of the arbitrary positive constants B0 and C of new variable modified Chaplygin gas. |
2202.10598 | Vladimir Dergachev Ph.D. | Vladimir Dergachev and Maria Alessandra Papa | A frequency resolved atlas of the sky in continuous gravitational waves | null | null | 10.1103/PhysRevX.13.021020 | null | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first atlas of the continuous gravitational wave sky, produced
using LIGO O3a public data. For each 0.045 Hz frequency band and every point on
the sky the atlas provides gravitational wave amplitude upper limits,
signal-to-noise ratios (SNR) and frequencies where the search measures the
maximum SNR. The approximately top 1.5% of the atlas results are reanalyzed
with a series of more sensitive searches with the purpose of finding high SNR
long coherence signals from isolated neutron stars. However, these searches do
not reveal the presence of such signals. The results presented in the atlas are
produced with the Falcon pipeline and cover nearly monochromatic
gravitational-wave signals in the 500-1000 Hz band, with up to +/- 5e-11 Hz/s
frequency derivative. The Falcon pipeline computes loosely coherent power
estimates to search data using a succession of coherence lengths. For this
search we used 6 months of data, started with a 12 hour coherence length and
progressed to 6 days. Compared to the most sensitive results previously
published (also produced with the Falcon pipeline) our upper limits are 50%
more constraining. Neutron stars with ellipticity of 1e-8 can be detected up to
150 pc away, while allowing for a large fraction of the stars' energy to be
lost through non-gravitational channels. These results are within an order of
magnitude of the _minimum_ neutron star ellipticity of 1e-9 suggested in [33].
| [
{
"created": "Tue, 22 Feb 2022 00:40:42 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Apr 2023 04:45:53 GMT",
"version": "v2"
}
] | 2024-01-25 | [
[
"Dergachev",
"Vladimir",
""
],
[
"Papa",
"Maria Alessandra",
""
]
] | We present the first atlas of the continuous gravitational wave sky, produced using LIGO O3a public data. For each 0.045 Hz frequency band and every point on the sky the atlas provides gravitational wave amplitude upper limits, signal-to-noise ratios (SNR) and frequencies where the search measures the maximum SNR. The approximately top 1.5% of the atlas results are reanalyzed with a series of more sensitive searches with the purpose of finding high SNR long coherence signals from isolated neutron stars. However, these searches do not reveal the presence of such signals. The results presented in the atlas are produced with the Falcon pipeline and cover nearly monochromatic gravitational-wave signals in the 500-1000 Hz band, with up to +/- 5e-11 Hz/s frequency derivative. The Falcon pipeline computes loosely coherent power estimates to search data using a succession of coherence lengths. For this search we used 6 months of data, started with a 12 hour coherence length and progressed to 6 days. Compared to the most sensitive results previously published (also produced with the Falcon pipeline) our upper limits are 50% more constraining. Neutron stars with ellipticity of 1e-8 can be detected up to 150 pc away, while allowing for a large fraction of the stars' energy to be lost through non-gravitational channels. These results are within an order of magnitude of the _minimum_ neutron star ellipticity of 1e-9 suggested in [33]. |
1805.00813 | Justin Feng | Justin Feng, Mark Baumann, Bryton Hall, Joel Doss, Lucas Spencer,
Richard Matzner | PoMiN: A Post-Minkowskian $N$-Body Solver | 11 pages w/ 3 figures. Revised to match published version | 2018 ApJ 859 130 | 10.3847/1538-4357/aac209 | UTTG-02-18 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we introduce PoMiN, a lightweight $N$-body code based on the
post-Minkowskian $N$-body Hamiltonian of Ledvinka et. al., which includes
general relativistic effects up to first order in Newton's constant $G$, and
all orders in the speed of light $c$. PoMiN is written in C and uses a
fourth-order Runge-Kutta integration scheme. PoMiN has also been written to
handle an arbitrary number of particles (both massive and massless), with a
computational complexity that scales as $O(N^2)$. We describe the methods we
used to simplify and organize the Hamiltonian, and the tests we performed
(convergence, conservation, and analytical comparison tests) to validate the
code.
| [
{
"created": "Mon, 30 Apr 2018 18:27:53 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jul 2018 14:55:19 GMT",
"version": "v2"
}
] | 2018-07-25 | [
[
"Feng",
"Justin",
""
],
[
"Baumann",
"Mark",
""
],
[
"Hall",
"Bryton",
""
],
[
"Doss",
"Joel",
""
],
[
"Spencer",
"Lucas",
""
],
[
"Matzner",
"Richard",
""
]
] | In this paper, we introduce PoMiN, a lightweight $N$-body code based on the post-Minkowskian $N$-body Hamiltonian of Ledvinka et. al., which includes general relativistic effects up to first order in Newton's constant $G$, and all orders in the speed of light $c$. PoMiN is written in C and uses a fourth-order Runge-Kutta integration scheme. PoMiN has also been written to handle an arbitrary number of particles (both massive and massless), with a computational complexity that scales as $O(N^2)$. We describe the methods we used to simplify and organize the Hamiltonian, and the tests we performed (convergence, conservation, and analytical comparison tests) to validate the code. |
gr-qc/0501080 | Burkhard Zink | Burkhard Zink, Nikolaos Stergioulas, Ian Hawke, Christian D. Ott, Erik
Schnetter and Ewald Mueller | Black hole formation through fragmentation of toroidal polytropes | 4 pages, 3 figures | Phys.Rev.Lett.96:161101,2006 | 10.1103/PhysRevLett.96.161101 | null | gr-qc astro-ph.HE | null | We investigate new paths to black hole formation by considering the general
relativistic evolution of a differentially rotating polytrope with toroidal
shape. We find that this polytrope is unstable to nonaxisymmetric modes, which
leads to a fragmentation into self-gravitating, collapsing components. In the
case of one such fragment, we apply a simplified adaptive mesh refinement
technique to follow the evolution to the formation of an apparent horizon
centered on the fragment. This is the first study of the one-armed instability
in full general relativity.
| [
{
"created": "Wed, 26 Jan 2005 16:38:31 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Feb 2005 00:37:26 GMT",
"version": "v2"
}
] | 2010-11-16 | [
[
"Zink",
"Burkhard",
""
],
[
"Stergioulas",
"Nikolaos",
""
],
[
"Hawke",
"Ian",
""
],
[
"Ott",
"Christian D.",
""
],
[
"Schnetter",
"Erik",
""
],
[
"Mueller",
"Ewald",
""
]
] | We investigate new paths to black hole formation by considering the general relativistic evolution of a differentially rotating polytrope with toroidal shape. We find that this polytrope is unstable to nonaxisymmetric modes, which leads to a fragmentation into self-gravitating, collapsing components. In the case of one such fragment, we apply a simplified adaptive mesh refinement technique to follow the evolution to the formation of an apparent horizon centered on the fragment. This is the first study of the one-armed instability in full general relativity. |
1605.04204 | Andronikos Paliathanasis | Andronikos Paliathanasis and P.G.L. Leach | Analytical solutions in $R+qR^{n}$ cosmology from singularity analysis | 6 pages, discussion improved, to be published in Phys. Lett. A | Phys. Lett. A 380 (2016) 2815-2818 | 10.1016/j.physleta.2016.06.053 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The integrability of higher-order theories of gravity is of importance in the
determining the properties of these models and so their viability as models of
reality. An important tool in the establishment of integrability is the
singularity analysis. We apply this analysis to the case of fourth-order theory
of gravity $f(R) = R + qR^{n}$ to establish those values of the free parameters
$q$ and $n$ for which integrability in this sense exists. As a prelininary we
examine the well-known case of $n = 4/3$.
| [
{
"created": "Fri, 13 May 2016 15:04:35 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Jun 2016 13:44:30 GMT",
"version": "v2"
}
] | 2016-08-04 | [
[
"Paliathanasis",
"Andronikos",
""
],
[
"Leach",
"P. G. L.",
""
]
] | The integrability of higher-order theories of gravity is of importance in the determining the properties of these models and so their viability as models of reality. An important tool in the establishment of integrability is the singularity analysis. We apply this analysis to the case of fourth-order theory of gravity $f(R) = R + qR^{n}$ to establish those values of the free parameters $q$ and $n$ for which integrability in this sense exists. As a prelininary we examine the well-known case of $n = 4/3$. |
1308.2159 | Ralf Schutzhold | R. Sch\"utzhold and W. G. Unruh | Hawking radiation with dispersion versus breakdown of WKB | 6 pages | null | 10.1103/PhysRevD.88.124009 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inspired by the condensed matter analogues of black holes (a.k.a. dumb
holes), we study Hawking radiation in the presence of a modified dispersion
relation which becomes super-luminal at large wave-numbers. In the usual
stationary coordinates $(t,x)$, one can describe the asymptotic evolution of
the wave-packets in WKB, but this WKB approximation breaks down in the vicinity
of the horizon, thereby allowing for a mixing between initial and final
creation and annihilation operators. Thus, one might be tempted to identify
this point where WKB breaks down with the moment of particle creation. However,
using different coordinates $(\tau,U)$, we find that one can evolve the waves
so that WKB in these coordinates is valid throughout this transition region --
which contradicts the above identification of the breakdown of WKB as the cause
of the radiation. Instead, our analysis suggests that the tearing apart of the
waves into two different asymptotic regions (inside and outside the horizon) is
the major ingredient of Hawking radiation.
| [
{
"created": "Fri, 9 Aug 2013 15:30:07 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Schützhold",
"R.",
""
],
[
"Unruh",
"W. G.",
""
]
] | Inspired by the condensed matter analogues of black holes (a.k.a. dumb holes), we study Hawking radiation in the presence of a modified dispersion relation which becomes super-luminal at large wave-numbers. In the usual stationary coordinates $(t,x)$, one can describe the asymptotic evolution of the wave-packets in WKB, but this WKB approximation breaks down in the vicinity of the horizon, thereby allowing for a mixing between initial and final creation and annihilation operators. Thus, one might be tempted to identify this point where WKB breaks down with the moment of particle creation. However, using different coordinates $(\tau,U)$, we find that one can evolve the waves so that WKB in these coordinates is valid throughout this transition region -- which contradicts the above identification of the breakdown of WKB as the cause of the radiation. Instead, our analysis suggests that the tearing apart of the waves into two different asymptotic regions (inside and outside the horizon) is the major ingredient of Hawking radiation. |
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