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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1308.0548 | Francisco Navarro-Lerida | Jose Luis Blazquez-Salcedo, Jutta Kunz, Francisco Navarro-Lerida, and
Eugen Radu | Sequences of extremal radially excited rotating black holes | 5 pages, 6 figures | Phys. Rev. Lett. 112, 011101 (2014) | 10.1103/PhysRevLett.112.011101 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In Einstein-Maxwell-Chern-Simons theory the extremal Reissner-Nordstr\"om
solution is no longer the single extremal solution with vanishing angular
momentum, when the Chern-Simons coupling constant reaches a critical value.
Instead a whole sequence of rotating extremal J=0 solutions arises, labeled by
the node number of the magnetic U(1) potential. Associated with the same near
horizon solution, the mass of these radially excited extremal solutions
converges to the mass of the extremal Reissner-Nordstr\"om solution. On the
other hand, not all near horizon solutions are also realized as global
solutions
| [
{
"created": "Fri, 2 Aug 2013 15:59:57 GMT",
"version": "v1"
}
] | 2014-09-02 | [
[
"Blazquez-Salcedo",
"Jose Luis",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Navarro-Lerida",
"Francisco",
""
],
[
"Radu",
"Eugen",
""
]
] | In Einstein-Maxwell-Chern-Simons theory the extremal Reissner-Nordstr\"om solution is no longer the single extremal solution with vanishing angular momentum, when the Chern-Simons coupling constant reaches a critical value. Instead a whole sequence of rotating extremal J=0 solutions arises, labeled by the node number of the magnetic U(1) potential. Associated with the same near horizon solution, the mass of these radially excited extremal solutions converges to the mass of the extremal Reissner-Nordstr\"om solution. On the other hand, not all near horizon solutions are also realized as global solutions |
1406.0704 | Hamid Reza Sepangi | F. Kheyri, M. Khodadi and H. R. Sepangi | Horava-Lifshitz cosmology, entropic interpretation and quark-hadron
phase transition | 17 pages, 7 figures. arXiv admin note: text overlap with
arXiv:0710.0354 by other authors | Annals of Physics 332 (2012) 75 | 10.1016/j.aop.2013.01.014 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on the assumptions of the standard model of cosmology, a phase
transition associated with chiral symmetry breaking after the electroweak
transition has occurred at approximately $10\mu$ seconds after the Big Bang to
convert a plasma of free quarks and gluons into hadrons. We consider such a
phase transition in the context of a deformed Horava-Lifshitz cosmology. The
Friedmann equation for the deformed Horava-Lifshitz universe is obtained using
the entropic interpretation of gravity, proposed by Verlinde. We investigate
the effects of the parameter $\omega$ appearing in the theory on the evolution
of the physical quantities relevant to a description of the early universe,
namely, the energy density and temperature before, during and after the phase
transition. Finally, we study the cross-over phase transition in both high and
low temperature regions in view of the recent lattice QCD simulations data.
| [
{
"created": "Tue, 3 Jun 2014 13:27:07 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Jul 2014 06:46:00 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Kheyri",
"F.",
""
],
[
"Khodadi",
"M.",
""
],
[
"Sepangi",
"H. R.",
""
]
] | Based on the assumptions of the standard model of cosmology, a phase transition associated with chiral symmetry breaking after the electroweak transition has occurred at approximately $10\mu$ seconds after the Big Bang to convert a plasma of free quarks and gluons into hadrons. We consider such a phase transition in the context of a deformed Horava-Lifshitz cosmology. The Friedmann equation for the deformed Horava-Lifshitz universe is obtained using the entropic interpretation of gravity, proposed by Verlinde. We investigate the effects of the parameter $\omega$ appearing in the theory on the evolution of the physical quantities relevant to a description of the early universe, namely, the energy density and temperature before, during and after the phase transition. Finally, we study the cross-over phase transition in both high and low temperature regions in view of the recent lattice QCD simulations data. |
1108.4539 | Joanna Ja{\l}mu\.zna | Joanna Ja{\l}mu\.zna, Andrzej Rostworowski, Piotr Bizo\'n | A comment on AdS collapse of a scalar field in higher dimensions | 3 pages, 2 figures | Phys. Rev. D 84, 085021 (2011) | 10.1103/PhysRevD.84.085021 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We point out that the weakly turbulent instability of anti-de Sitter space,
recently found in arXiv:1104.3702 for four dimensional spherically symmetric
Einstein-massless-scalar field equations with negative cosmological constant,
is present in all dimensions $d+1$ for $d\geq 3$, contrary to a claim made in
arXiv:1106.2339.
| [
{
"created": "Tue, 23 Aug 2011 09:53:58 GMT",
"version": "v1"
}
] | 2016-08-14 | [
[
"Jałmużna",
"Joanna",
""
],
[
"Rostworowski",
"Andrzej",
""
],
[
"Bizoń",
"Piotr",
""
]
] | We point out that the weakly turbulent instability of anti-de Sitter space, recently found in arXiv:1104.3702 for four dimensional spherically symmetric Einstein-massless-scalar field equations with negative cosmological constant, is present in all dimensions $d+1$ for $d\geq 3$, contrary to a claim made in arXiv:1106.2339. |
2404.04872 | Kayoomars Karami | Iraj Safaei and Kayoomars Karami | Observational constraints on degeneracy of non-canonical inflation
driven by quartic potential | 25 pages, 6 figures, 3 tables | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | Here, the quartic inflationary potential $V(\phi)=\frac{\lambda}{4}\phi^4$ in
non-canonical framework with a power-law Lagrangian is investigated. We
demonstrate that the predictions of this potential in non-canonical framework
align with the observational data of Planck 2018. We determine how the
predictions of the model vary with changes in the non-canonical parameter
$\alpha$ and the number of $e$-folds $N$. The sound speed, non-Gaussianity
parameter, scalar spectral index, and tensor-to-scalar ratio are all influenced
by $\alpha$. However, the scalar spectral index exhibits degeneracy with
respect to changes in $\alpha$. It is found that, this degeneracy does not
break through reheating consideration. But the length of the reheating epoch
constrains the length of the inflation period and the value of $\alpha$.
Therefore, we investigate relic gravitational waves (GWs) and show that, the
degeneracy of the model with respect to the $\alpha$ parameter can be broken
using the relic GWs. Additionally, the density of relic GWs falls within the
sensitivity range of GWs detectors for the specific $e$-folds number between 55
and 55.7.
| [
{
"created": "Sun, 7 Apr 2024 08:36:18 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Jul 2024 08:04:11 GMT",
"version": "v2"
}
] | 2024-07-02 | [
[
"Safaei",
"Iraj",
""
],
[
"Karami",
"Kayoomars",
""
]
] | Here, the quartic inflationary potential $V(\phi)=\frac{\lambda}{4}\phi^4$ in non-canonical framework with a power-law Lagrangian is investigated. We demonstrate that the predictions of this potential in non-canonical framework align with the observational data of Planck 2018. We determine how the predictions of the model vary with changes in the non-canonical parameter $\alpha$ and the number of $e$-folds $N$. The sound speed, non-Gaussianity parameter, scalar spectral index, and tensor-to-scalar ratio are all influenced by $\alpha$. However, the scalar spectral index exhibits degeneracy with respect to changes in $\alpha$. It is found that, this degeneracy does not break through reheating consideration. But the length of the reheating epoch constrains the length of the inflation period and the value of $\alpha$. Therefore, we investigate relic gravitational waves (GWs) and show that, the degeneracy of the model with respect to the $\alpha$ parameter can be broken using the relic GWs. Additionally, the density of relic GWs falls within the sensitivity range of GWs detectors for the specific $e$-folds number between 55 and 55.7. |
2209.14321 | Guillaume Dideron | Guillaume Dideron, Suvodip Mukherjee and Luis Lehner | SCoRe: A New Framework to Study Unmodeled Physics from Gravitational
Wave Data | 18 pages, 9 figures | null | 10.1103/PhysRevD.107.104023 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A confident discovery of physics beyond what has been consistently modeled
from gravitational wave (GW) data requires a technique that can distinguish
between noise artifacts and unmodeled signatures while also shedding light on
the underlying physics. We propose a new data analysis method, \texttt{SCoRe}
(Structured Correlated Residual), to search for unmodeled physics in the GW
data which can cover both of these aspects. The method searches for structure
in the cross-correlation power spectrum of the residual strain between pairs of
GW detectors. It does so by projecting this power spectrum onto a
frequency-dependent template. The template may be model-independent or
model-dependent and is constructed based on the properties of the GW source
parameters. The projection of the residual strain enables the distinction
between noise artifacts and any true signal while capturing possible dependence
on the GW source parameters. Our method is constructed in a Bayesian framework
and we have shown its application on a model-independent toy example and for a
model motivated by an effective field theory of gravity. The method developed
here will be useful to search for a large variety of new physics and
yet-to-be-modeled known physics in the GW data accessible from the current
network of LIGO-Virgo-KAGRA detectors and from future earth- and space-based GW
detectors such as A+, LISA, Cosmic Explorer, and Einstein Telescope.
| [
{
"created": "Wed, 28 Sep 2022 18:00:11 GMT",
"version": "v1"
},
{
"created": "Tue, 2 May 2023 17:03:58 GMT",
"version": "v2"
}
] | 2023-05-24 | [
[
"Dideron",
"Guillaume",
""
],
[
"Mukherjee",
"Suvodip",
""
],
[
"Lehner",
"Luis",
""
]
] | A confident discovery of physics beyond what has been consistently modeled from gravitational wave (GW) data requires a technique that can distinguish between noise artifacts and unmodeled signatures while also shedding light on the underlying physics. We propose a new data analysis method, \texttt{SCoRe} (Structured Correlated Residual), to search for unmodeled physics in the GW data which can cover both of these aspects. The method searches for structure in the cross-correlation power spectrum of the residual strain between pairs of GW detectors. It does so by projecting this power spectrum onto a frequency-dependent template. The template may be model-independent or model-dependent and is constructed based on the properties of the GW source parameters. The projection of the residual strain enables the distinction between noise artifacts and any true signal while capturing possible dependence on the GW source parameters. Our method is constructed in a Bayesian framework and we have shown its application on a model-independent toy example and for a model motivated by an effective field theory of gravity. The method developed here will be useful to search for a large variety of new physics and yet-to-be-modeled known physics in the GW data accessible from the current network of LIGO-Virgo-KAGRA detectors and from future earth- and space-based GW detectors such as A+, LISA, Cosmic Explorer, and Einstein Telescope. |
1503.06636 | Wlodek Klu\'zniak | Mateusz Wi\'sniewicz, Dorota Gondek-Rosi\'nska, W{\l}odzimierz
Klu\'zniak and Nikolaos Stergioulas | Unusual behavior of epicyclic frequencies around rapidly rotating
compact stars | 6 pages, 2 figures (4 panels). To appear in Proceedings of RAGtime
14/15/16, S. Hledik and Z. Stuchlik, eds | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report on numerical calculations of orbital and epicyclic frequencies in
nearly circular orbits around rotating neutron stars and strange quark stars.
The FPS equation of state was used to describe the neutron star structure while
the MIT bag model was used to model the equation of state of strange quark
stars. The uniformly rotating stellar configurations were computed in full
general relativity. We find that the vertical epicyclic frequency is very
sensitive to the oblateness of the rotating star. For models of rotating
neutron stars of moderate mass, as well as for strange quark star models, the
sense of the nodal precession of test particle orbits close to the star changes
at a certain stellar rotation rate. These findings may have implications for
models of kHz QPOs.
| [
{
"created": "Mon, 23 Mar 2015 13:38:12 GMT",
"version": "v1"
}
] | 2015-03-24 | [
[
"Wiśniewicz",
"Mateusz",
""
],
[
"Gondek-Rosińska",
"Dorota",
""
],
[
"Kluźniak",
"Włodzimierz",
""
],
[
"Stergioulas",
"Nikolaos",
""
]
] | We report on numerical calculations of orbital and epicyclic frequencies in nearly circular orbits around rotating neutron stars and strange quark stars. The FPS equation of state was used to describe the neutron star structure while the MIT bag model was used to model the equation of state of strange quark stars. The uniformly rotating stellar configurations were computed in full general relativity. We find that the vertical epicyclic frequency is very sensitive to the oblateness of the rotating star. For models of rotating neutron stars of moderate mass, as well as for strange quark star models, the sense of the nodal precession of test particle orbits close to the star changes at a certain stellar rotation rate. These findings may have implications for models of kHz QPOs. |
0712.2396 | Fernando de Felice | D. Bini, F. de Felice and A. Geralico | Strains and Jets in Black Hole Fields | To appear in the Proceedings of the Spanish Relativity Meeting 2007
held in Tenerife (Spain) 3 Figures | null | 10.1051/eas:0830011 | null | gr-qc | null | We study the behaviour of an initially spherical bunch of particles emitted
along trajectories parallel to the symmetry axis of a Kerr black hole. We show
that, under suitable conditions, curvature and inertial strains compete to
generate jet-like structures.
| [
{
"created": "Fri, 14 Dec 2007 17:16:05 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Bini",
"D.",
""
],
[
"de Felice",
"F.",
""
],
[
"Geralico",
"A.",
""
]
] | We study the behaviour of an initially spherical bunch of particles emitted along trajectories parallel to the symmetry axis of a Kerr black hole. We show that, under suitable conditions, curvature and inertial strains compete to generate jet-like structures. |
1712.02038 | Igor Loutsenko | Igor Loutsenko | On the Role of Caustic in Solar Gravitational Lens Imaging | 33pages, 12 figures | Progress of Theoretical and Experimental Physics, Volume 2018,
Issue 12, 1 December 2018, 123A02 | 10.1093/ptep/pty119 | null | gr-qc astro-ph.EP astro-ph.IM physics.optics | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider scattering of electromagnetic waves from a distant point source
by the gravitational field of the sun, taking the field oblateness due to the
quadrupole moment of the sun into account. Effects of the field oblateness can
play an important role in the high resolution solar gravitational lens imaging
in the sub-micrometer wavelength range of the electromagnetic spectrum.
| [
{
"created": "Wed, 6 Dec 2017 04:39:51 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Dec 2017 00:39:50 GMT",
"version": "v2"
},
{
"created": "Mon, 12 Feb 2018 14:00:33 GMT",
"version": "v3"
},
{
"created": "Sun, 20 May 2018 13:35:52 GMT",
"version": "v4"
},
{
"created": "Wed, 18 Jul 2018 19:38:00 GMT",
"version": "v5"
},
{
"created": "Wed, 10 Oct 2018 18:55:19 GMT",
"version": "v6"
}
] | 2019-02-26 | [
[
"Loutsenko",
"Igor",
""
]
] | We consider scattering of electromagnetic waves from a distant point source by the gravitational field of the sun, taking the field oblateness due to the quadrupole moment of the sun into account. Effects of the field oblateness can play an important role in the high resolution solar gravitational lens imaging in the sub-micrometer wavelength range of the electromagnetic spectrum. |
1412.2045 | Ruxandra Bondarescu | Ruxandra Bondarescu, Andreas Sch\"arer, Philippe Jetzer, Raymond
Ang\'elil, Prasenjit Saha, and Andrew Lundgren | Testing General Relativity and Alternative Theories of Gravity with
Space-based Atomic Clocks and Atom Interferometers | 12 pages, 4 figures, 2 tables. Proceeding for ICNFP 2014 | EPJ Web of Conferences 95, 02002 (2015) | null | null | gr-qc astro-ph.EP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The successful miniaturisation of extremely accurate atomic clocks and atom
interferometers invites prospects for satellite missions to perform precision
experiments. We discuss the effects predicted by general relativity and
alternative theories of gravity that can be detected by a clock, which orbits
the Earth. Our experiment relies on the precise tracking of the spacecraft
using its observed tick-rate. The spacecraft's reconstructed four-dimensional
trajectory will reveal the nature of gravitational perturbations in Earth's
gravitational field, potentially differentiating between different theories of
gravity. This mission can measure multiple relativistic effects all during the
course of a single experiment, and constrain the Parametrized Post-Newtonian
Parameters around the Earth. A satellite carrying a clock of fractional timing
inaccuracy of $\Delta f/f \sim 10^{-16}$ in an elliptic orbit around the Earth
would constrain the PPN parameters $|\beta -1|, |\gamma-1| \lesssim 10^{-6}$.
We also briefly review potential constraints by atom interferometers on scalar
tensor theories and in particular on Chameleon and dilaton models.
| [
{
"created": "Fri, 5 Dec 2014 16:09:03 GMT",
"version": "v1"
}
] | 2015-06-10 | [
[
"Bondarescu",
"Ruxandra",
""
],
[
"Schärer",
"Andreas",
""
],
[
"Jetzer",
"Philippe",
""
],
[
"Angélil",
"Raymond",
""
],
[
"Saha",
"Prasenjit",
""
],
[
"Lundgren",
"Andrew",
""
]
] | The successful miniaturisation of extremely accurate atomic clocks and atom interferometers invites prospects for satellite missions to perform precision experiments. We discuss the effects predicted by general relativity and alternative theories of gravity that can be detected by a clock, which orbits the Earth. Our experiment relies on the precise tracking of the spacecraft using its observed tick-rate. The spacecraft's reconstructed four-dimensional trajectory will reveal the nature of gravitational perturbations in Earth's gravitational field, potentially differentiating between different theories of gravity. This mission can measure multiple relativistic effects all during the course of a single experiment, and constrain the Parametrized Post-Newtonian Parameters around the Earth. A satellite carrying a clock of fractional timing inaccuracy of $\Delta f/f \sim 10^{-16}$ in an elliptic orbit around the Earth would constrain the PPN parameters $|\beta -1|, |\gamma-1| \lesssim 10^{-6}$. We also briefly review potential constraints by atom interferometers on scalar tensor theories and in particular on Chameleon and dilaton models. |
0704.1638 | Yury F. Pirogov | Yu. F. Pirogov | Accelerated expansion of the Universe filled up with the scalar
gravitons | 5 pages | Phys.Atom.Nucl.71:728-731,2008 | 10.1134/S1063778808040145 | null | gr-qc astro-ph hep-ph | null | The concept of the scalar graviton as the source of the dark matter and dark
energy of the gravitaional origin is applied to study the evolution of the
isotropic homogeneous Universe. A realistic self-consistent solution to the
modified pure gravity equations, which correctly describes the accelerated
expansion of the spatially flat Universe, is found and investigated. It is
argued that the scenario with the scalar gravitons filling up the Universe may
emulate the LCDM model, reducing thus the true dark matter to an artefact.
| [
{
"created": "Thu, 12 Apr 2007 18:30:02 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Pirogov",
"Yu. F.",
""
]
] | The concept of the scalar graviton as the source of the dark matter and dark energy of the gravitaional origin is applied to study the evolution of the isotropic homogeneous Universe. A realistic self-consistent solution to the modified pure gravity equations, which correctly describes the accelerated expansion of the spatially flat Universe, is found and investigated. It is argued that the scenario with the scalar gravitons filling up the Universe may emulate the LCDM model, reducing thus the true dark matter to an artefact. |
1203.4842 | Felipe Guzman Cervantes | Frank Steier, Felipe Guzm\'an Cervantes, Antonio F. Garc\'ia Mar\'in,
Domenico Gerardi, Gerhard Heinzel and Karsten Danzmann | The end-to-end testbed of the Optical Metrology System on-board LISA
Pathfinder | null | Classical and Quantum Gravity 26 094010 (2009) | 10.1088/0264-9381/26/9/094010 | null | gr-qc astro-ph.IM physics.ins-det physics.optics physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | LISA Pathfinder is a technology demonstration mission for the Laser
Interferometer Space Antenna (LISA). The main experiment on-board LISA
Pathfinder is the so-called LISA Technology Package (LTP) which has the aim to
measure the differential acceleration between two free-falling test masses with
an accuracy of 3x10^(-14) ms^(-2)/sqrt[Hz] between 1 mHz and 30 mHz. This
measurement is performed interferometrically by the Optical Metrology System
(OMS) on-board LISA Pathfinder. In this paper we present the development of an
experimental end-to-end testbed of the entire OMS. It includes the
interferometer and its sub-units, the interferometer back-end which is a
phasemeter and the processing of the phasemeter output data. Furthermore,
3-axes piezo actuated mirrors are used instead of the free-falling test masses
for the characterisation of the dynamic behaviour of the system and some parts
of the Drag-free and Attitude Control System (DFACS) which controls the test
masses and the satellite. The end-to-end testbed includes all parts of the LTP
that can reasonably be tested on earth without free-falling test masses. At its
present status it consists mainly of breadboard components. Some of those have
already been replaced by Engineering Models of the LTP experiment. In the next
steps, further Engineering Models and Flight Models will also be inserted in
this testbed and tested against well characterised breadboard components. The
presented testbed is an important reference for the unit tests and can also be
used for validation of the on-board experiment during the mission.
| [
{
"created": "Wed, 21 Mar 2012 21:34:58 GMT",
"version": "v1"
}
] | 2012-03-23 | [
[
"Steier",
"Frank",
""
],
[
"Cervantes",
"Felipe Guzmán",
""
],
[
"Marín",
"Antonio F. García",
""
],
[
"Gerardi",
"Domenico",
""
],
[
"Heinzel",
"Gerhard",
""
],
[
"Danzmann",
"Karsten",
""
]
] | LISA Pathfinder is a technology demonstration mission for the Laser Interferometer Space Antenna (LISA). The main experiment on-board LISA Pathfinder is the so-called LISA Technology Package (LTP) which has the aim to measure the differential acceleration between two free-falling test masses with an accuracy of 3x10^(-14) ms^(-2)/sqrt[Hz] between 1 mHz and 30 mHz. This measurement is performed interferometrically by the Optical Metrology System (OMS) on-board LISA Pathfinder. In this paper we present the development of an experimental end-to-end testbed of the entire OMS. It includes the interferometer and its sub-units, the interferometer back-end which is a phasemeter and the processing of the phasemeter output data. Furthermore, 3-axes piezo actuated mirrors are used instead of the free-falling test masses for the characterisation of the dynamic behaviour of the system and some parts of the Drag-free and Attitude Control System (DFACS) which controls the test masses and the satellite. The end-to-end testbed includes all parts of the LTP that can reasonably be tested on earth without free-falling test masses. At its present status it consists mainly of breadboard components. Some of those have already been replaced by Engineering Models of the LTP experiment. In the next steps, further Engineering Models and Flight Models will also be inserted in this testbed and tested against well characterised breadboard components. The presented testbed is an important reference for the unit tests and can also be used for validation of the on-board experiment during the mission. |
gr-qc/0005049 | Vitorio A. De Lorenci | V. A. De Lorenci, R. Klippert, M. Novello and J. M. Salim | Light propagation in non linear electrodynamics | 3 pages, latex, no figures (to appear in Phys. Lett. B) | Phys.Lett. B482 (2000) 134-140 | 10.1016/S0370-2693(00)00522-0 | null | gr-qc | null | Working on the approximation of low frequency, we present the light cone
conditions for a class of theories constructed with the two gauge invariants of
the Maxwell field without making use of average over polarization states.
Different polarization states are thus identified describing birefringence
phenomena. We make an application of the formalism to the case of
Euler-Heisenberg effective Lagrangian and well know results are obtained.
| [
{
"created": "Sat, 13 May 2000 19:43:17 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"De Lorenci",
"V. A.",
""
],
[
"Klippert",
"R.",
""
],
[
"Novello",
"M.",
""
],
[
"Salim",
"J. M.",
""
]
] | Working on the approximation of low frequency, we present the light cone conditions for a class of theories constructed with the two gauge invariants of the Maxwell field without making use of average over polarization states. Different polarization states are thus identified describing birefringence phenomena. We make an application of the formalism to the case of Euler-Heisenberg effective Lagrangian and well know results are obtained. |
1512.02331 | Stephen McCormick | Stephen McCormick | The Hilbert manifold of asymptotically flat metric extensions | 24 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In [Comm. Anal. Geom., 13(5):845-885, 2005.], Bartnik described the phase
space for the Einstein equations, modelled on weighted Sobolev spaces with
local regularity $(g,\pi)\in H^2\times H^1$. In particular, it was established
that the space of solutions to the contraints form a Hilbert submanifold of
this phase space. The motivation for this work was to study the quasilocal mass
functional now bearing his name. However, the phase space considered there was
over a manifold without boundary. Here we demonstrate that analogous results
hold in the case where the manifold has an interior compact boundary, where
Dirichlet boundary conditions are imposed on the metric. Then, still following
Bartnik's work, we demonstrate the critical points of the mass functional over
this space of extensions correspond to stationary solutions. Furthermore, if
this solution is sufficiently regular then it is in fact a static black hole
solution. In particular, in the vacuum case, critical points only occur at
exterior Schwarzschild solutions; that is, critical points of the mass over
this space do not exist generically. Finally, we briefly discuss the case when
the boundary data is Bartnik's geometric data.
| [
{
"created": "Tue, 8 Dec 2015 05:23:59 GMT",
"version": "v1"
}
] | 2015-12-09 | [
[
"McCormick",
"Stephen",
""
]
] | In [Comm. Anal. Geom., 13(5):845-885, 2005.], Bartnik described the phase space for the Einstein equations, modelled on weighted Sobolev spaces with local regularity $(g,\pi)\in H^2\times H^1$. In particular, it was established that the space of solutions to the contraints form a Hilbert submanifold of this phase space. The motivation for this work was to study the quasilocal mass functional now bearing his name. However, the phase space considered there was over a manifold without boundary. Here we demonstrate that analogous results hold in the case where the manifold has an interior compact boundary, where Dirichlet boundary conditions are imposed on the metric. Then, still following Bartnik's work, we demonstrate the critical points of the mass functional over this space of extensions correspond to stationary solutions. Furthermore, if this solution is sufficiently regular then it is in fact a static black hole solution. In particular, in the vacuum case, critical points only occur at exterior Schwarzschild solutions; that is, critical points of the mass over this space do not exist generically. Finally, we briefly discuss the case when the boundary data is Bartnik's geometric data. |
1710.07906 | Kaushik Bhattacharya | Kaushik Bhattacharya, Saikat Chakraborty | Nonlinear anisotropy growth in Bianchi-I spacetime in metric $f(R)$
cosmology | The article is made a bit shorter. Contains 24 pages and 5 figures.
To be published in PRD | Phys. Rev. D 99, 023520 (2019) | 10.1103/PhysRevD.99.023520 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/publicdomain/zero/1.0/ | The present work is related to anisotropic cosmological evolution in metric
$f(R)$ theory of gravity. The initial part of the paper develops the general
cosmological dynamics of homogeneous anisotropic Bianchi-I spacetime in $f(R)$
cosmology. The anisotropic spacetime is pervaded by a barotropic fluid which
has isotropic pressure. The paper predicts nonlinear growth of anisotropy in
such spacetimes. In the later part of the paper we display the predictive power
of the nonlinear differential equation responsible for the cosmological
anisotropy growth in various relevant cases. We present the exact solutions of
anisotropy growth in Starobinsky inflation driven by quadratic gravity and
exponential gravity theory. Semi-analytical results are presented for the
contraction phase in quadratic gravity bounce. The various examples of
anisotropy growth in Bianchi-I model universe shows the complex nature of the
problem at hand.
| [
{
"created": "Sun, 22 Oct 2017 07:59:50 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Oct 2017 16:57:58 GMT",
"version": "v2"
},
{
"created": "Mon, 28 May 2018 14:23:57 GMT",
"version": "v3"
},
{
"created": "Tue, 8 Jan 2019 04:51:33 GMT",
"version": "v4"
}
] | 2019-01-23 | [
[
"Bhattacharya",
"Kaushik",
""
],
[
"Chakraborty",
"Saikat",
""
]
] | The present work is related to anisotropic cosmological evolution in metric $f(R)$ theory of gravity. The initial part of the paper develops the general cosmological dynamics of homogeneous anisotropic Bianchi-I spacetime in $f(R)$ cosmology. The anisotropic spacetime is pervaded by a barotropic fluid which has isotropic pressure. The paper predicts nonlinear growth of anisotropy in such spacetimes. In the later part of the paper we display the predictive power of the nonlinear differential equation responsible for the cosmological anisotropy growth in various relevant cases. We present the exact solutions of anisotropy growth in Starobinsky inflation driven by quadratic gravity and exponential gravity theory. Semi-analytical results are presented for the contraction phase in quadratic gravity bounce. The various examples of anisotropy growth in Bianchi-I model universe shows the complex nature of the problem at hand. |
2201.06138 | Ran Li | Ran Li, Jin Wang | Kinetics of Hawking-Page phase transition with the non-Markovian effects | null | null | 10.1007/JHEP05(2022)128 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on the free energy landscape description of Hawking-Page phase
transition, the transition process from the Schwarzschild-anti-de Sitter black
hole to the thermal anti-de Sitter space are considered to be stochastic under
the thermal fluctuations. If the correlation time of the effective thermal bath
is comparable or even longer than the oscillating time of the spacetime state
in the potential well on the free energy landscape, the non-Markovian model of
the black hole phase transition is required to study the kinetics of the
transition processes. The non-Markovian or memory effect is represented by the
time dependent friction kernel and the kinetics is then governed by the
generalized Langevin equation complemented by the free energy potential. As the
concrete examples, we study the effects of the exponentially decay friction
kernel and the oscillatory friction kernel on the kinetics of Hawking-Page
phase transition. For the exponentially decayed friction, the non-Markovian
effects promote the transition process, and for the oscillatory friction,
increasing the oscillating frequency also speeds up the transition process.
| [
{
"created": "Sun, 16 Jan 2022 21:27:16 GMT",
"version": "v1"
}
] | 2022-06-08 | [
[
"Li",
"Ran",
""
],
[
"Wang",
"Jin",
""
]
] | Based on the free energy landscape description of Hawking-Page phase transition, the transition process from the Schwarzschild-anti-de Sitter black hole to the thermal anti-de Sitter space are considered to be stochastic under the thermal fluctuations. If the correlation time of the effective thermal bath is comparable or even longer than the oscillating time of the spacetime state in the potential well on the free energy landscape, the non-Markovian model of the black hole phase transition is required to study the kinetics of the transition processes. The non-Markovian or memory effect is represented by the time dependent friction kernel and the kinetics is then governed by the generalized Langevin equation complemented by the free energy potential. As the concrete examples, we study the effects of the exponentially decay friction kernel and the oscillatory friction kernel on the kinetics of Hawking-Page phase transition. For the exponentially decayed friction, the non-Markovian effects promote the transition process, and for the oscillatory friction, increasing the oscillating frequency also speeds up the transition process. |
0802.1031 | Gabriel Bela Nagy | M. Holst, G. Nagy, G. Tsogtgerel | Far-from-constant mean curvature solutions of Einstein's constraint
equations with positive Yamabe metrics | 4 pages, no figures, accepted for publication in Physical Review
Letters. (Abstract shortenned and other minor changes reflecting v4 version
of arXiv:0712.0798) | Phys.Rev.Lett.100:161101,2008 | 10.1103/PhysRevLett.100.161101 | null | gr-qc math.AP | null | In this article we develop some new existence results for the Einstein
constraint equations using the Lichnerowicz-York conformal rescaling method.
The mean extrinsic curvature is taken to be an arbitrary smooth function
without restrictions on the size of its spatial derivatives, so that it can be
arbitrarily far from constant. The rescaled background metric belongs to the
positive Yamabe class, and the freely specifiable part of the data given by the
traceless-transverse part of the rescaled extrinsic curvature and the matter
fields are taken to be sufficiently small, with the matter energy density not
identically zero. Using topological fixed-point arguments and global barrier
constructions, we then establish existence of solutions to the constraints. Two
recent advances in the analysis of the Einstein constraint equations make this
result possible: A new type of topological fixed-point argument without
smallness conditions on spatial derivatives of the mean extrinsic curvature,
and a new construction of global super-solutions for the Hamiltonian constraint
that is similarly free of such conditions on the mean extrinsic curvature. For
clarity, we present our results only for strong solutions on closed manifolds.
However, our results also hold for weak solutions and for other cases such as
compact manifolds with boundary; these generalizations will appear elsewhere.
The existence results presented here for the Einstein constraints are
apparently the first such results that do not require smallness conditions on
spatial derivatives of the mean extrinsic curvature.
| [
{
"created": "Thu, 7 Feb 2008 18:10:00 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Feb 2008 19:29:49 GMT",
"version": "v2"
},
{
"created": "Sat, 12 Apr 2008 09:10:13 GMT",
"version": "v3"
}
] | 2010-01-13 | [
[
"Holst",
"M.",
""
],
[
"Nagy",
"G.",
""
],
[
"Tsogtgerel",
"G.",
""
]
] | In this article we develop some new existence results for the Einstein constraint equations using the Lichnerowicz-York conformal rescaling method. The mean extrinsic curvature is taken to be an arbitrary smooth function without restrictions on the size of its spatial derivatives, so that it can be arbitrarily far from constant. The rescaled background metric belongs to the positive Yamabe class, and the freely specifiable part of the data given by the traceless-transverse part of the rescaled extrinsic curvature and the matter fields are taken to be sufficiently small, with the matter energy density not identically zero. Using topological fixed-point arguments and global barrier constructions, we then establish existence of solutions to the constraints. Two recent advances in the analysis of the Einstein constraint equations make this result possible: A new type of topological fixed-point argument without smallness conditions on spatial derivatives of the mean extrinsic curvature, and a new construction of global super-solutions for the Hamiltonian constraint that is similarly free of such conditions on the mean extrinsic curvature. For clarity, we present our results only for strong solutions on closed manifolds. However, our results also hold for weak solutions and for other cases such as compact manifolds with boundary; these generalizations will appear elsewhere. The existence results presented here for the Einstein constraints are apparently the first such results that do not require smallness conditions on spatial derivatives of the mean extrinsic curvature. |
1812.04589 | Marek Nowakowski | Sergio Bravo Medina, Marek Nowakowski, Davide Batic | Einstein-Cartan Cosmologies | 41 pages, 21 figures | Annals of Physics 400 (2019) 64-108 | 10.1016/j.aop.2018.11.002 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmologies based on General Relativity encompassing an anti-symmetric
connection (torsion) can display nice desirable features as the absence of the
initial singularity and the possibility of inflation in the early stage of the
universe. After briefly reviewing the standard approach to the cosmology with
torsion, we generalize it to demonstrate that several theories of torsion
gravity are possible using different choices of the diffeomorphic invariants in
the Lagrangians. As a result, distinct cosmologies emerge. In all of them it is
possible that the universe avoids the initial singularity and passes through an
initial accelerated expansion. Differences between these theories are
highlighted.
| [
{
"created": "Tue, 11 Dec 2018 18:17:14 GMT",
"version": "v1"
}
] | 2018-12-12 | [
[
"Medina",
"Sergio Bravo",
""
],
[
"Nowakowski",
"Marek",
""
],
[
"Batic",
"Davide",
""
]
] | Cosmologies based on General Relativity encompassing an anti-symmetric connection (torsion) can display nice desirable features as the absence of the initial singularity and the possibility of inflation in the early stage of the universe. After briefly reviewing the standard approach to the cosmology with torsion, we generalize it to demonstrate that several theories of torsion gravity are possible using different choices of the diffeomorphic invariants in the Lagrangians. As a result, distinct cosmologies emerge. In all of them it is possible that the universe avoids the initial singularity and passes through an initial accelerated expansion. Differences between these theories are highlighted. |
1910.02801 | Fethi M. Ramazanoglu | Fethi M. Ramazano\u{g}lu, K{\i}van\c{c} \.I. \"Unl\"ut\"urk | Generalized disformal coupling leads to spontaneous tensorization | 9 pages, to appear in Phys. Rev. D | Phys. Rev. D 100, 084026 (2019) | 10.1103/PhysRevD.100.084026 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that gravity theories involving disformally transformed metrics in
their matter coupling lead to spontaneous growth of various fields in a similar
fashion to the spontaneous scalarization scenario in scalar-tensor theories.
Scalar-dependent disformal transformations have been investigated in this
context, and our focus is understanding the transformations that depend on more
general fields. We show that vector-dependent disformal couplings can be
obtained in various different ways, each leading to spontaneous vectorization
as indicated by the instabilities in linearized equations of motion. However,
we also show that spontaneous growth is not evident beyond vectors. For
example, we could not identify a spontaneous growth mechanism for a spinor
field through disformal transformations, even though there is a known example
for conformal transformations. This invites further work on the fundamental
differences between the two types of metric transformations. We argue that our
results are relevant for observations in strong gravity such as gravitational
wave detections due to their promise of large deviations from general
relativity in this regime.
| [
{
"created": "Mon, 7 Oct 2019 14:00:59 GMT",
"version": "v1"
}
] | 2019-10-15 | [
[
"Ramazanoğlu",
"Fethi M.",
""
],
[
"Ünlütürk",
"Kıvanç İ.",
""
]
] | We show that gravity theories involving disformally transformed metrics in their matter coupling lead to spontaneous growth of various fields in a similar fashion to the spontaneous scalarization scenario in scalar-tensor theories. Scalar-dependent disformal transformations have been investigated in this context, and our focus is understanding the transformations that depend on more general fields. We show that vector-dependent disformal couplings can be obtained in various different ways, each leading to spontaneous vectorization as indicated by the instabilities in linearized equations of motion. However, we also show that spontaneous growth is not evident beyond vectors. For example, we could not identify a spontaneous growth mechanism for a spinor field through disformal transformations, even though there is a known example for conformal transformations. This invites further work on the fundamental differences between the two types of metric transformations. We argue that our results are relevant for observations in strong gravity such as gravitational wave detections due to their promise of large deviations from general relativity in this regime. |
1811.02960 | Diego S\'aez-Chill\'on G\'omez | Emilio Elizalde, Sergei D. Odintsov, Tanmoy Paul and Diego
Saez-Chillon Gomez | The inflationary universe in F(R) gravity with antisymmetric tensor
fields and their suppression during the universe evolution | 36 pages, 13 figures, version to be published in PRD | Phys. Rev. D 99, 063506 (2019) | 10.1103/PhysRevD.99.063506 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The intriguing question, why the present scale of the universe is free from
any perceptible footprints of rank-2 antisymmetric tensor fields? (generally
known as Kalb-Ramond fields) is addressed. A quite natural explanation of this
issue is given from the angle of higher-curvature gravity, both in four- and in
five-dimensional spacetime. The results here obtained reveal that the amplitude
of the Kalb-Ramond field may be actually large and play a significant role
during the early universe, while the presence of higher-order gravity
suppresses this field during the cosmological evolution, so that it eventually
becomes negligible in the current universe. Besides the suppression of the
Kalb-Ramond field, the extra degree of freedom in $F(R)$ gravity, usually known
as scalaron, also turns out to be responsible for inflation. Such F(R) gravity
with Kalb-Ramond fields may govern the early universe to undergo an
inflationary stage at early times (with the subsequent graceful exit) for wider
range of F(R) gravity than without antisymmetric fields.. Furthermore, the
models---in four- and five-dimensional spacetimes---are linked to observational
constraints, with the conclusion that the corresponding values of the spectral
index and tensor-to-scalar ratio closely match the values provided by the
Planck survey 2018 data.
| [
{
"created": "Wed, 7 Nov 2018 16:20:36 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Nov 2018 19:16:16 GMT",
"version": "v2"
},
{
"created": "Wed, 6 Feb 2019 13:42:24 GMT",
"version": "v3"
}
] | 2019-03-27 | [
[
"Elizalde",
"Emilio",
""
],
[
"Odintsov",
"Sergei D.",
""
],
[
"Paul",
"Tanmoy",
""
],
[
"Gomez",
"Diego Saez-Chillon",
""
]
] | The intriguing question, why the present scale of the universe is free from any perceptible footprints of rank-2 antisymmetric tensor fields? (generally known as Kalb-Ramond fields) is addressed. A quite natural explanation of this issue is given from the angle of higher-curvature gravity, both in four- and in five-dimensional spacetime. The results here obtained reveal that the amplitude of the Kalb-Ramond field may be actually large and play a significant role during the early universe, while the presence of higher-order gravity suppresses this field during the cosmological evolution, so that it eventually becomes negligible in the current universe. Besides the suppression of the Kalb-Ramond field, the extra degree of freedom in $F(R)$ gravity, usually known as scalaron, also turns out to be responsible for inflation. Such F(R) gravity with Kalb-Ramond fields may govern the early universe to undergo an inflationary stage at early times (with the subsequent graceful exit) for wider range of F(R) gravity than without antisymmetric fields.. Furthermore, the models---in four- and five-dimensional spacetimes---are linked to observational constraints, with the conclusion that the corresponding values of the spectral index and tensor-to-scalar ratio closely match the values provided by the Planck survey 2018 data. |
1012.3144 | Leo Stein | Leo C. Stein and Nicolas Yunes | Effective Gravitational Wave Stress-energy Tensor in Alternative
Theories of Gravity | 19 pages. v3: Clarified averaging properties and gauge choice.
Version accepted to PRD | Phys.Rev.D83:064038,2011 | 10.1103/PhysRevD.83.064038 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The inspiral of binary systems in vacuum is controlled by the stress-energy
of gravitational radiation and any other propagating degrees of freedom. For
gravitational waves, the dominant contribution is characterized by an effective
stress-energy tensor at future null infinity. We employ perturbation theory and
the short-wavelength approximation to compute this stress-energy tensor in a
wide class of alternative theories. We find that this tensor is generally a
modification of that first computed by Isaacson, where the corrections can
dominate over the general relativistic term. In a wide class of theories,
however, these corrections identically vanish at asymptotically flat, future,
null infinity, reducing the stress-energy tensor to Isaacson's. We exemplify
this phenomenon by first considering dynamical Chern-Simons modified gravity,
which corrects the action via a scalar field and the contraction of the Riemann
tensor and its dual. We then consider a wide class of theories with dynamical
scalar fields coupled to higher-order curvature invariants, and show that the
gravitational wave stress-energy tensor still reduces to Isaacson's. The
calculations presented in this paper are crucial to perform systematic tests of
such modified gravity theories through the orbital decay of binary pulsars or
through gravitational wave observations.
| [
{
"created": "Tue, 14 Dec 2010 19:40:58 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Dec 2010 18:30:11 GMT",
"version": "v2"
},
{
"created": "Fri, 21 Jan 2011 16:52:17 GMT",
"version": "v3"
}
] | 2011-05-10 | [
[
"Stein",
"Leo C.",
""
],
[
"Yunes",
"Nicolas",
""
]
] | The inspiral of binary systems in vacuum is controlled by the stress-energy of gravitational radiation and any other propagating degrees of freedom. For gravitational waves, the dominant contribution is characterized by an effective stress-energy tensor at future null infinity. We employ perturbation theory and the short-wavelength approximation to compute this stress-energy tensor in a wide class of alternative theories. We find that this tensor is generally a modification of that first computed by Isaacson, where the corrections can dominate over the general relativistic term. In a wide class of theories, however, these corrections identically vanish at asymptotically flat, future, null infinity, reducing the stress-energy tensor to Isaacson's. We exemplify this phenomenon by first considering dynamical Chern-Simons modified gravity, which corrects the action via a scalar field and the contraction of the Riemann tensor and its dual. We then consider a wide class of theories with dynamical scalar fields coupled to higher-order curvature invariants, and show that the gravitational wave stress-energy tensor still reduces to Isaacson's. The calculations presented in this paper are crucial to perform systematic tests of such modified gravity theories through the orbital decay of binary pulsars or through gravitational wave observations. |
1907.00715 | Jiawei Hu | Shijing Cheng, Jiawei Hu, Hongwei Yu | Spontaneous excitation of an accelerated atom coupled with quantum
fluctuations of spacetime | 15 pages, 1 figure, published version | Phys. Rev. D 100, 025010 (2019) | 10.1103/PhysRevD.100.025010 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A direct consequence of quantization of gravity would be quantum
gravitational vacuum fluctuations which induce quadrupole moments in
gravitationally polarizable atoms. In this paper, we study the spontaneous
excitation of a gravitationally polarizable atom with a uniform acceleration
$a$ in interaction with a bath of fluctuating quantum gravitational fields in
vacuum, and compare the result with that of a static one in a thermal bath of
gravitons at the Unruh temperature. We find that, under the fluctuations of
spacetime itself, transitions to higher-lying excited states from the ground
state are possible for both the uniformly accelerated atom in vacuum and the
static one in a thermal bath. The appearance of terms in the transition rates
proportional to $a^4$ and $a^2$ indicates that the equivalence between uniform
acceleration and thermal field is lost.
| [
{
"created": "Mon, 1 Jul 2019 12:34:47 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Jul 2019 13:05:09 GMT",
"version": "v2"
}
] | 2019-07-25 | [
[
"Cheng",
"Shijing",
""
],
[
"Hu",
"Jiawei",
""
],
[
"Yu",
"Hongwei",
""
]
] | A direct consequence of quantization of gravity would be quantum gravitational vacuum fluctuations which induce quadrupole moments in gravitationally polarizable atoms. In this paper, we study the spontaneous excitation of a gravitationally polarizable atom with a uniform acceleration $a$ in interaction with a bath of fluctuating quantum gravitational fields in vacuum, and compare the result with that of a static one in a thermal bath of gravitons at the Unruh temperature. We find that, under the fluctuations of spacetime itself, transitions to higher-lying excited states from the ground state are possible for both the uniformly accelerated atom in vacuum and the static one in a thermal bath. The appearance of terms in the transition rates proportional to $a^4$ and $a^2$ indicates that the equivalence between uniform acceleration and thermal field is lost. |
gr-qc/0605018 | Carlos F. Sopuerta | Carlos F. Sopuerta (1), Ulrich Sperhake (1 and 2), and Pablo Laguna
(1) ((1) CGWP, Penn State, (2) TPI, Jena) | Hydro-without-Hydro Framework for Simulations of Black Hole-Neutron Star
Binaries | 16 pages, 7 figures. To appear in the Classical and Quantum Gravity
special issue on Numerical Relativity | Class.Quant.Grav. 23 (2006) S579-S598 | 10.1088/0264-9381/23/16/S15 | null | gr-qc astro-ph | null | We introduce a computational framework which avoids solving explicitly
hydrodynamic equations and is suitable to study the pre-merger evolution of
black hole-neutron star binary systems. The essence of the method consists of
constructing a neutron star model with a black hole companion and freezing the
internal degrees of freedom of the neutron star during the course of the
evolution of the space-time geometry. We present the main ingredients of the
framework, from the formulation of the problem to the appropriate computational
techniques to study these binary systems. In addition, we present numerical
results of the construction of initial data sets and evolutions that
demonstrate the feasibility of this approach.
| [
{
"created": "Tue, 2 May 2006 16:13:51 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Sopuerta",
"Carlos F.",
"",
"CGWP, Penn State"
],
[
"Sperhake",
"Ulrich",
"",
"1 and 2"
],
[
"Laguna",
"Pablo",
"",
"CGWP, Penn State"
]
] | We introduce a computational framework which avoids solving explicitly hydrodynamic equations and is suitable to study the pre-merger evolution of black hole-neutron star binary systems. The essence of the method consists of constructing a neutron star model with a black hole companion and freezing the internal degrees of freedom of the neutron star during the course of the evolution of the space-time geometry. We present the main ingredients of the framework, from the formulation of the problem to the appropriate computational techniques to study these binary systems. In addition, we present numerical results of the construction of initial data sets and evolutions that demonstrate the feasibility of this approach. |
0710.1291 | Valerio Faraoni | Valerio Faraoni (Bishop's University) | A viability criterion for modified gravity with an extra force | 4 latex pages, to appear in Phys. Rev. D | Phys.Rev.D76:127501,2007 | 10.1103/PhysRevD.76.127501 | null | gr-qc | null | A recently proposed theory of modified gravity with an explicit ``anomalous''
coupling of the Ricci curvature to matter is discussed, and an inequality is
derived which expresses a necessary and sufficient condition to avoid the
notorius Dolgov-Kawasaki instability.
| [
{
"created": "Fri, 5 Oct 2007 18:48:39 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
]
] | A recently proposed theory of modified gravity with an explicit ``anomalous'' coupling of the Ricci curvature to matter is discussed, and an inequality is derived which expresses a necessary and sufficient condition to avoid the notorius Dolgov-Kawasaki instability. |
1605.07193 | Sam Dolan Dr | Sam R Dolan and Jake O Shipley | Stable photon orbits in stationary axisymmetric electrovacuum spacetimes | 14 pages, 5 figures. Expanded version with two new figures and one
appendix | Phys. Rev. D 94, 044038 (2016) | 10.1103/PhysRevD.94.044038 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the existence and phenomenology of stable photon orbits (SPOs)
in stationary axisymmetric electrovacuum spacetimes in four dimensions. First,
we review the classification of equatorial circular photon orbits on
Kerr-Newman spacetimes in the charge-spin plane. Second, using a Hamiltonian
formulation, we show that Reissner-Nordstr\"om di-holes (a family encompassing
the Majumdar-Papapetrou and Weyl-Bach special cases) admit SPOs, in a certain
parameter regime that we investigate. Third, we explore the transition from
order to chaos for typical SPOs bounded within a toroidal region around a
di-hole, via a selection of Poincar\'e sections. Finally, for general
axisymmetric stationary spacetimes, we show that the Einstein-Maxwell field
equations allow for the existence of SPOs in electrovacuum; but not in pure
vacuum.
| [
{
"created": "Mon, 23 May 2016 20:00:18 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Jun 2016 14:23:08 GMT",
"version": "v2"
}
] | 2016-08-23 | [
[
"Dolan",
"Sam R",
""
],
[
"Shipley",
"Jake O",
""
]
] | We investigate the existence and phenomenology of stable photon orbits (SPOs) in stationary axisymmetric electrovacuum spacetimes in four dimensions. First, we review the classification of equatorial circular photon orbits on Kerr-Newman spacetimes in the charge-spin plane. Second, using a Hamiltonian formulation, we show that Reissner-Nordstr\"om di-holes (a family encompassing the Majumdar-Papapetrou and Weyl-Bach special cases) admit SPOs, in a certain parameter regime that we investigate. Third, we explore the transition from order to chaos for typical SPOs bounded within a toroidal region around a di-hole, via a selection of Poincar\'e sections. Finally, for general axisymmetric stationary spacetimes, we show that the Einstein-Maxwell field equations allow for the existence of SPOs in electrovacuum; but not in pure vacuum. |
gr-qc/0610088 | Andrew Lundgren | Andrew P. Lundgren, Bjoern S. Schmekel, James W. York Jr | Self-Renormalization of the Classical Quasilocal Energy | 7 pages, 4 figures | Phys.Rev.D75:084026,2007 | 10.1103/PhysRevD.75.084026 | null | gr-qc hep-th | null | Pointlike objects cause many of the divergences that afflict physical
theories. For instance, the gravitational binding energy of a point particle in
Newtonian mechanics is infinite. In general relativity, the analog of a point
particle is a black hole and the notion of binding energy must be replaced by
quasilocal energy. The quasilocal energy (QLE) derived by York, and elaborated
by Brown and York, is finite outside the horizon but it was not considered how
to evaluate it inside the horizon. We present a prescription for finding the
QLE inside a horizon, and show that it is finite at the singularity for a
variety of types of black hole. The energy is typically concentrated just
inside the horizon, not at the central singularity.
| [
{
"created": "Wed, 18 Oct 2006 03:26:24 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Lundgren",
"Andrew P.",
""
],
[
"Schmekel",
"Bjoern S.",
""
],
[
"York",
"James W.",
"Jr"
]
] | Pointlike objects cause many of the divergences that afflict physical theories. For instance, the gravitational binding energy of a point particle in Newtonian mechanics is infinite. In general relativity, the analog of a point particle is a black hole and the notion of binding energy must be replaced by quasilocal energy. The quasilocal energy (QLE) derived by York, and elaborated by Brown and York, is finite outside the horizon but it was not considered how to evaluate it inside the horizon. We present a prescription for finding the QLE inside a horizon, and show that it is finite at the singularity for a variety of types of black hole. The energy is typically concentrated just inside the horizon, not at the central singularity. |
1001.4617 | Luciano Vanzo | Roberto Di Criscienzo, Luciano Vanzo and Sergio Zerbini | Applications of the Tunneling Method to Particle Decay and Radiation
from Naked Singularities | LaTex document, 14 pages, two figures | JHEP 1005:092,2010 | 10.1007/JHEP05(2010)092 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following recent literature on dS instability in presence of interactions, we
study the decay of massive particles in general FRW models and the emission
from naked singularities either associated with 4D charged black holes or with
2D shock waves, by means of the Hamilton--Jacobi tunneling method. It is shown
that the two-dimensional semi-classical tunneling amplitude from a naked
singularity computed in that way is the same as the one-loop result of quantum
field theory.
| [
{
"created": "Tue, 26 Jan 2010 09:38:11 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Di Criscienzo",
"Roberto",
""
],
[
"Vanzo",
"Luciano",
""
],
[
"Zerbini",
"Sergio",
""
]
] | Following recent literature on dS instability in presence of interactions, we study the decay of massive particles in general FRW models and the emission from naked singularities either associated with 4D charged black holes or with 2D shock waves, by means of the Hamilton--Jacobi tunneling method. It is shown that the two-dimensional semi-classical tunneling amplitude from a naked singularity computed in that way is the same as the one-loop result of quantum field theory. |
gr-qc/0306010 | Novak | Jerome Novak and Emmanuel Marcq | Gyromagnetic ratio of rapidly rotating compact stars in general
relativity | 11 pages, 6 figures, accepted for publication in Classical and
Quantum Gravity | Class.Quant.Grav. 20 (2003) 3051-3060 | 10.1088/0264-9381/20/14/307 | null | gr-qc | null | We numerically calculate equilibrium configurations of uniformly rotating and
charged neutron stars, in the case of insulating material and neglecting the
electromagnetic forces acting on the equilibrium of the fluid. This allows us
to study the behaviour of the gyromagnetic ratio for those objects, when
varying rotation rate and equation of state for the matter. Under the
assumption of low charge and incompressible fluid, we find that the
gyromagnetic ratio is directly proportional to the compaction parameter M/R of
the star, and very little dependent on its angular velocity. Nevertheless, it
seems impossible to have g=2 for these models with low charge-to-mass ratio,
where matter consists of a perfect fluid and where the collapse limit is never
reached.
| [
{
"created": "Tue, 3 Jun 2003 08:24:31 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Novak",
"Jerome",
""
],
[
"Marcq",
"Emmanuel",
""
]
] | We numerically calculate equilibrium configurations of uniformly rotating and charged neutron stars, in the case of insulating material and neglecting the electromagnetic forces acting on the equilibrium of the fluid. This allows us to study the behaviour of the gyromagnetic ratio for those objects, when varying rotation rate and equation of state for the matter. Under the assumption of low charge and incompressible fluid, we find that the gyromagnetic ratio is directly proportional to the compaction parameter M/R of the star, and very little dependent on its angular velocity. Nevertheless, it seems impossible to have g=2 for these models with low charge-to-mass ratio, where matter consists of a perfect fluid and where the collapse limit is never reached. |
2306.09943 | Dipankar Barman | Dipankar Barman, Bibhas Ranjan Majhi | Are multiple reflecting boundaries capable of enhancing entanglement
harvesting? | Minor corrections done, published in Phys. Rev. D | Phys.Rev.D 108 (2023) 8, 085007 | 10.1103/PhysRevD.108.085007 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum entanglement harvesting in the relativistic setup attracted a lot of
attention in recent times. Acquiring more entanglement within two qubits may be
very desirable to establish fruitful communication between them. On the other
hand use of reflecting boundaries in a spacetime has close resemblance to the
cavity quantum optomechanical systems. Here, in presence of two reflecting
boundaries, we study the generation of entanglement between two uniformly
accelerated Unruh-DeWitt detectors which are interacting with the background
scalar fields. Like no boundary and single boundary situations, entanglement
harvesting is possible for their motions in opposite Rindler wedges. We observe
that the reflecting boundaries can play double roles. In some parameter space
it causes suppression, while in other parameter space we can have enhancement
of entanglement compared to no boundary and single boundary cases. Thus
increase of boundaries has significant impact in this phenomena and a suitable
choices of parameters provides desirable increment of it.
| [
{
"created": "Fri, 16 Jun 2023 16:25:12 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Oct 2023 10:56:12 GMT",
"version": "v2"
}
] | 2023-10-17 | [
[
"Barman",
"Dipankar",
""
],
[
"Majhi",
"Bibhas Ranjan",
""
]
] | Quantum entanglement harvesting in the relativistic setup attracted a lot of attention in recent times. Acquiring more entanglement within two qubits may be very desirable to establish fruitful communication between them. On the other hand use of reflecting boundaries in a spacetime has close resemblance to the cavity quantum optomechanical systems. Here, in presence of two reflecting boundaries, we study the generation of entanglement between two uniformly accelerated Unruh-DeWitt detectors which are interacting with the background scalar fields. Like no boundary and single boundary situations, entanglement harvesting is possible for their motions in opposite Rindler wedges. We observe that the reflecting boundaries can play double roles. In some parameter space it causes suppression, while in other parameter space we can have enhancement of entanglement compared to no boundary and single boundary cases. Thus increase of boundaries has significant impact in this phenomena and a suitable choices of parameters provides desirable increment of it. |
gr-qc/0106041 | Dr. Bikash Chandra Paul | B. C. Paul (North Bengal University) | Probability for Primordial Black Holes in Higher Dimensional Universe | 13 pages, no figure, LaTex | Phys.Rev.D61:024032,2000 | 10.1103/PhysRevD.61.024032 | null | gr-qc | null | We investigate higher dimensional cosmological models in the semiclassical
approximation with Hartle-Hawking Boundary conditions, assuming a gravitational
action which is described by the scalar curvature with a cosmological constant.
In the framework the probability for quantum creation of an inflationary
universe with a pair of black holes in a multidimensional universe is
evaluated. The probability for creation of a universe with a spatial section
with $S^{1}XS^{D -2}$ topology is then compared with that of a higher
dimensional de Sitter universe with $S^{D -1}$ spatial topology. It is found
that a higher dimensional universe with a product space with primordial black
holes pair is less probable to nucleate when the extra dimensions scale factors
do not vary in an inflating universe.
| [
{
"created": "Wed, 13 Jun 2001 04:54:13 GMT",
"version": "v1"
}
] | 2010-05-28 | [
[
"Paul",
"B. C.",
"",
"North Bengal University"
]
] | We investigate higher dimensional cosmological models in the semiclassical approximation with Hartle-Hawking Boundary conditions, assuming a gravitational action which is described by the scalar curvature with a cosmological constant. In the framework the probability for quantum creation of an inflationary universe with a pair of black holes in a multidimensional universe is evaluated. The probability for creation of a universe with a spatial section with $S^{1}XS^{D -2}$ topology is then compared with that of a higher dimensional de Sitter universe with $S^{D -1}$ spatial topology. It is found that a higher dimensional universe with a product space with primordial black holes pair is less probable to nucleate when the extra dimensions scale factors do not vary in an inflating universe. |
0905.2170 | Leonardo Modesto | Francesco Caravelli, Leonardo Modesto | Fractal Dimension in 3d Spin-Foams | 5 pages, 9 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we perform the calculation of the spectral dimension of the
space-time in 3d quantum gravity using the dynamics of the Ponzano-Regge vertex
(PR) and its quantum group generalization (Turaev-Viro model (TV)). We realize
this considering a very simple decomposition of the 3d space-time and
introducing a boundary state which selects a classical geometry on the
boundary. We obtain that the spectral dimension of the space-time runs from 2
to 3, across a 1.5 phase, when the energy of a probe scalar field decreases
from high to low energy. For the TV model the spectral dimension at hight
energy increase with the value of the cosmological constant. At low energy the
presence of the cosmological constant does not change the spectral dimension.
| [
{
"created": "Wed, 13 May 2009 19:10:50 GMT",
"version": "v1"
}
] | 2009-05-19 | [
[
"Caravelli",
"Francesco",
""
],
[
"Modesto",
"Leonardo",
""
]
] | In this paper we perform the calculation of the spectral dimension of the space-time in 3d quantum gravity using the dynamics of the Ponzano-Regge vertex (PR) and its quantum group generalization (Turaev-Viro model (TV)). We realize this considering a very simple decomposition of the 3d space-time and introducing a boundary state which selects a classical geometry on the boundary. We obtain that the spectral dimension of the space-time runs from 2 to 3, across a 1.5 phase, when the energy of a probe scalar field decreases from high to low energy. For the TV model the spectral dimension at hight energy increase with the value of the cosmological constant. At low energy the presence of the cosmological constant does not change the spectral dimension. |
2305.09725 | Abhishek Hegade K R | Abhishek Hegade K R, Justin L. Ripley and Nicol\'as Yunes | The non-relativistic limit of first-order relativistic viscous fluids | v2-matches published version in PRD | null | 10.1103/PhysRevD.107.124029 | null | gr-qc hep-th math-ph math.MP nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Out-of-equilibrium effects may play an important role in the dynamics of
neutron star mergers and in heavy-ion collisions. Bemfica, Disconzi, Noronha
and Kovtun (BDNK) recently derived a causal, locally well-posed, and modally
stable relativistic fluid model that incorporates the effects of viscosity and
heat diffusion. We study the non-relativistic limit of this fluid model and
show that causality for relativistic motion restricts the transport
coefficients in the non-relativistic limit. This restriction provides an upper
bound on the ratio of the shear viscosity to the entropy density for fluids
that can be described as relativistic within the BDNK model and can be exactly
modeled using the Navier-Stokes equation in the non-relativistic limit.
Furthermore, we show that the Fourier law of heat conduction must be modified
by higher gradient corrections for such fluids. We also show that the
non-relativistic limit of the BDNK equations of motion are never hyperbolic, in
contrast to the non-relativistic limit of extended variable models, whose
non-relativistic equations of motion can be hyperbolic or not depending on the
scaling of the transport coefficients present in the auxiliary equations for
viscous degrees of freedom.
| [
{
"created": "Tue, 16 May 2023 18:01:03 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Jun 2023 23:10:46 GMT",
"version": "v2"
}
] | 2023-07-05 | [
[
"R",
"Abhishek Hegade K",
""
],
[
"Ripley",
"Justin L.",
""
],
[
"Yunes",
"Nicolás",
""
]
] | Out-of-equilibrium effects may play an important role in the dynamics of neutron star mergers and in heavy-ion collisions. Bemfica, Disconzi, Noronha and Kovtun (BDNK) recently derived a causal, locally well-posed, and modally stable relativistic fluid model that incorporates the effects of viscosity and heat diffusion. We study the non-relativistic limit of this fluid model and show that causality for relativistic motion restricts the transport coefficients in the non-relativistic limit. This restriction provides an upper bound on the ratio of the shear viscosity to the entropy density for fluids that can be described as relativistic within the BDNK model and can be exactly modeled using the Navier-Stokes equation in the non-relativistic limit. Furthermore, we show that the Fourier law of heat conduction must be modified by higher gradient corrections for such fluids. We also show that the non-relativistic limit of the BDNK equations of motion are never hyperbolic, in contrast to the non-relativistic limit of extended variable models, whose non-relativistic equations of motion can be hyperbolic or not depending on the scaling of the transport coefficients present in the auxiliary equations for viscous degrees of freedom. |
1505.07272 | Sumanta Chakraborty | Sumanta Chakraborty | Lanczos-Lovelock gravity from a thermodynamic perspective | Revised Version, Published, 39 pages, no figures | JHEP 1508, 029 (2015) | 10.1007/JHEP08(2015)029 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The deep connection between gravitational dynamics and horizon thermodynamics
leads to several intriguing features both in general relativity and in
Lanczos-Lovelock theories of gravity. Recently in arXiv:1312.3253 several
additional results strengthening the above connection have been established
within the framework of general relativity. In this work we provide a
generalization of the above setup to Lanczos-Lovelock gravity as well. To our
expectation it turns out that most of the results obtained in the context of
general relativity generalize to Lanczos-Lovelock gravity in a straightforward
but non-trivial manner.
Another very interesting feature for gravity is that gravitational field
equations for arbitrary static and spherically symmetric spacetimes with
horizon can be written as a thermodynamic identity in the near horizon limit.
This result holds in both general relativity and in Lanczos-Lovelock gravity as
well. In a previous work [arXiv:1505.05297] we have shown that, for an
arbitrary spacetime, the gravitational field equations near any null surface
generically leads to a thermodynamic identity. In this work, we have also
generalized this result to Lanczos-Lovelock gravity by showing that
gravitational field equations for Lanczos-Lovelock gravity near an arbitrary
null surface can be written as a thermodynamic identity. By taking appropriate
limit to general relativity we can reproduce the results presented in
arXiv:1312.3253 and arXiv:1505.05297.
| [
{
"created": "Tue, 26 May 2015 04:30:06 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Aug 2015 09:48:14 GMT",
"version": "v2"
}
] | 2015-08-18 | [
[
"Chakraborty",
"Sumanta",
""
]
] | The deep connection between gravitational dynamics and horizon thermodynamics leads to several intriguing features both in general relativity and in Lanczos-Lovelock theories of gravity. Recently in arXiv:1312.3253 several additional results strengthening the above connection have been established within the framework of general relativity. In this work we provide a generalization of the above setup to Lanczos-Lovelock gravity as well. To our expectation it turns out that most of the results obtained in the context of general relativity generalize to Lanczos-Lovelock gravity in a straightforward but non-trivial manner. Another very interesting feature for gravity is that gravitational field equations for arbitrary static and spherically symmetric spacetimes with horizon can be written as a thermodynamic identity in the near horizon limit. This result holds in both general relativity and in Lanczos-Lovelock gravity as well. In a previous work [arXiv:1505.05297] we have shown that, for an arbitrary spacetime, the gravitational field equations near any null surface generically leads to a thermodynamic identity. In this work, we have also generalized this result to Lanczos-Lovelock gravity by showing that gravitational field equations for Lanczos-Lovelock gravity near an arbitrary null surface can be written as a thermodynamic identity. By taking appropriate limit to general relativity we can reproduce the results presented in arXiv:1312.3253 and arXiv:1505.05297. |
2107.01050 | Sujay Kr. Biswas | Goutam Mandal, Sujay Kr. Biswas, Subhajit Saha and Abdulla Al Mamon | Dynamical system analysis of logotropic dark fluid with a power law in
the rest-mass energy density | 13 pages, 4 captioned figures. Version accepted for publication in
Physics of the Dark Universe | null | 10.1016/j.dark.2022.100970 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a spatially flat FLRW universe. We assume that it is filled with
dark energy in the form of logotropic dark fluid coupled with dark matter in
the form of a perfect fluid having a barotropic equation of state. We employ
dynamical system tools to obtain a complete qualitative idea of the evolution
of such a universe. It is interesting to note that we ought to consider an
approximation for the pressure of the logotropic dark fluid in the form of an
infinite series so as to be able to construct the autonomous system required
for a dynamical system study. This series form provides us with a power law in
the rest-mass energy density of the logotropic dark fluid. We compute the
critical points of the autonomous system and analyze these critical points by
applying linear stability theory. Our analysis reveal a scenario of late-time
accelerated universe dominated by the logotropic fluid which behaves as
cosmological constant, preceded by an intermediate phase of the Universe
dominated by logotropic fluid which behaves as dark matter in the form of
perfect fluid. Moreover, it also crosses the phantom divide line.
| [
{
"created": "Thu, 1 Jul 2021 14:44:54 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Feb 2022 13:43:51 GMT",
"version": "v2"
}
] | 2022-02-03 | [
[
"Mandal",
"Goutam",
""
],
[
"Biswas",
"Sujay Kr.",
""
],
[
"Saha",
"Subhajit",
""
],
[
"Mamon",
"Abdulla Al",
""
]
] | We consider a spatially flat FLRW universe. We assume that it is filled with dark energy in the form of logotropic dark fluid coupled with dark matter in the form of a perfect fluid having a barotropic equation of state. We employ dynamical system tools to obtain a complete qualitative idea of the evolution of such a universe. It is interesting to note that we ought to consider an approximation for the pressure of the logotropic dark fluid in the form of an infinite series so as to be able to construct the autonomous system required for a dynamical system study. This series form provides us with a power law in the rest-mass energy density of the logotropic dark fluid. We compute the critical points of the autonomous system and analyze these critical points by applying linear stability theory. Our analysis reveal a scenario of late-time accelerated universe dominated by the logotropic fluid which behaves as cosmological constant, preceded by an intermediate phase of the Universe dominated by logotropic fluid which behaves as dark matter in the form of perfect fluid. Moreover, it also crosses the phantom divide line. |
1502.05493 | Salvatore Capozziello | Alireza Sepehri, Salvatore Capozziello, Mohammad Reza Setare | A bridge between unified cosmic history by $f(R)$-gravity and BIonic
system | 12 pages | null | 10.1007/s10714-016-2051-4 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, the cosmological deceleration-acceleration transition redshift in
$f(R)$ gravity has been considered in order to address consistently the problem
of cosmic evolution. It is possible to show that the deceleration parameter
changes sign at a given redshift according to observational data. Furthermore,
a $f(R)$ gravity cosmological model can be constructed in brane-antibrane
system starting from the very early universe and accounting for the
cosmological redshift at all phases of cosmic history, from inflation to late
time acceleration. Here we propose a $f(R)$ model where transition redshifts
correspond to inflation-deceleration and deceleration-late time acceleration
transitions starting froma BIon system. At the point where the universe was
born, due to the transition of $k$ black fundamental strings to the BIon
configuration, the redshift is approximately infinity and decreases with
reducing temperature ($z\sim T^{2}$). The BIon is a configuration in flat space
of a universe-brane and a parallel anti-universe-brane connected by a wormhole.
This wormhole is a channel for flowing energy from extra dimensions into our
universe, occurring at inflation and decreasing with redshift as $z\sim
T^{4+1/7}$. Dynamics consists with the fact that the wormhole misses its energy
and vanishes as soon as inflation ends and deceleration begins. Approaching two
universe branes together, a tachyon is originated, it grows up and causes the
formation of a wormhole. We show that, in the framework of $f(R)$ gravity, the
cosmological redshift depends on the tachyonic potential and has a significant
decrease at deceleration-late time acceleration transition point ($z\sim
T^{2/3}$). As soon as today acceleration approaches, the redshift tends to zero
and the cosmological model reduces to the standard $\Lambda$CDM cosmology.
| [
{
"created": "Thu, 19 Feb 2015 08:38:23 GMT",
"version": "v1"
}
] | 2016-04-27 | [
[
"Sepehri",
"Alireza",
""
],
[
"Capozziello",
"Salvatore",
""
],
[
"Setare",
"Mohammad Reza",
""
]
] | Recently, the cosmological deceleration-acceleration transition redshift in $f(R)$ gravity has been considered in order to address consistently the problem of cosmic evolution. It is possible to show that the deceleration parameter changes sign at a given redshift according to observational data. Furthermore, a $f(R)$ gravity cosmological model can be constructed in brane-antibrane system starting from the very early universe and accounting for the cosmological redshift at all phases of cosmic history, from inflation to late time acceleration. Here we propose a $f(R)$ model where transition redshifts correspond to inflation-deceleration and deceleration-late time acceleration transitions starting froma BIon system. At the point where the universe was born, due to the transition of $k$ black fundamental strings to the BIon configuration, the redshift is approximately infinity and decreases with reducing temperature ($z\sim T^{2}$). The BIon is a configuration in flat space of a universe-brane and a parallel anti-universe-brane connected by a wormhole. This wormhole is a channel for flowing energy from extra dimensions into our universe, occurring at inflation and decreasing with redshift as $z\sim T^{4+1/7}$. Dynamics consists with the fact that the wormhole misses its energy and vanishes as soon as inflation ends and deceleration begins. Approaching two universe branes together, a tachyon is originated, it grows up and causes the formation of a wormhole. We show that, in the framework of $f(R)$ gravity, the cosmological redshift depends on the tachyonic potential and has a significant decrease at deceleration-late time acceleration transition point ($z\sim T^{2/3}$). As soon as today acceleration approaches, the redshift tends to zero and the cosmological model reduces to the standard $\Lambda$CDM cosmology. |
0709.2784 | Jan Ambjorn | J. Ambjorn, R. Loll, W. Westra and S. Zohren | Putting a cap on causality violations in CDT | 17 pages, 4 figures | JHEP0712:017,2007 | 10.1088/1126-6708/2007/12/017 | null | gr-qc hep-th | null | The formalism of causal dynamical triangulations (CDT) provides us with a
non-perturbatively defined model of quantum gravity, where the sum over
histories includes only causal space-time histories. Path integrals of CDT and
their continuum limits have been studied in two, three and four dimensions.
Here we investigate a generalization of the two-dimensional CDT model, where
the causality constraint is partially lifted by introducing weighted branching
points, and demonstrate that the system can be solved analytically in the
genus-zero sector.
| [
{
"created": "Tue, 18 Sep 2007 10:22:18 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ambjorn",
"J.",
""
],
[
"Loll",
"R.",
""
],
[
"Westra",
"W.",
""
],
[
"Zohren",
"S.",
""
]
] | The formalism of causal dynamical triangulations (CDT) provides us with a non-perturbatively defined model of quantum gravity, where the sum over histories includes only causal space-time histories. Path integrals of CDT and their continuum limits have been studied in two, three and four dimensions. Here we investigate a generalization of the two-dimensional CDT model, where the causality constraint is partially lifted by introducing weighted branching points, and demonstrate that the system can be solved analytically in the genus-zero sector. |
gr-qc/9509016 | null | J. P\'erez-Mercader, T. Goldman, D. Hochberg and R. Laflamme | Renormalization Group Calculation of the Galaxy-Galaxy Correlation
Function | Based on a talk presented at the International Workshop on Elementary
Particle Physics, Valencia, Spain, June 1995. Six pages using the macro which
is appended at the end of the paper. Runs using standard LaTex 2.09. Strip
off this macro and place in separate file to be named sprocl.sty | null | null | LAEFF-95-13 and FTUAM-95-29 | gr-qc | null | The observable Universe is described by a collection of equal mass galaxies
linked into a common unit by their mutual gravitational interaction. The
partition function of this system is cast in terms of Ising model spin
variables and maps exactly onto a three-dimensional stochastic scalar classical
field theory. The full machinery of the renormalization group and critical
phenomena is brought to bear on this field theory allowing one to calculate the
galaxy-galaxy correlation function, whose critical exponent is predicted to be
between 1.530 to 1.862, compared to the phenomenological value of 1.6 to 1.8
| [
{
"created": "Fri, 8 Sep 1995 10:51:08 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Pérez-Mercader",
"J.",
""
],
[
"Goldman",
"T.",
""
],
[
"Hochberg",
"D.",
""
],
[
"Laflamme",
"R.",
""
]
] | The observable Universe is described by a collection of equal mass galaxies linked into a common unit by their mutual gravitational interaction. The partition function of this system is cast in terms of Ising model spin variables and maps exactly onto a three-dimensional stochastic scalar classical field theory. The full machinery of the renormalization group and critical phenomena is brought to bear on this field theory allowing one to calculate the galaxy-galaxy correlation function, whose critical exponent is predicted to be between 1.530 to 1.862, compared to the phenomenological value of 1.6 to 1.8 |
2201.00664 | Jie Jiang | Aofei Sang and Jie Jiang | Strong Cosmic Censorship in Einstein-Maxwell-Scalar-Gauss-Bonnet Theory | 9 pages, 9 figures and 1 table | null | 10.1103/PhysRevD.105.084047 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | Recently, it is found that the strong cosmic censorship (SCC) is violated in
RNdS black hole by a minimal coupled neutral massless scalar field at the
linear perturbation level. For the Einstein-Maxwell-Scalar-Gauss-Bonnet theory
which is famous for the spontaneous scalarization phenomenon, there exists the
scalar field coupled with the Gauss-Bonnet term. Whether the SCC of the RNdS
black hole can be repaired by the non-minimal coupled scalar field perturbation
at the linear level becomes an interesting question. In this paper, we firstly
investigate the extendibility of the metric beyond the Cauchy horizon in the
Einstein-Maxwell-Scalar-Gauss-Bonnet theory. Then, we examine the SCC of the
RNdS black hole by calculating the quasinormal mode of the non-minimal coupled
scalar field and find that the SCC can be recovered under some parameters.
| [
{
"created": "Mon, 3 Jan 2022 13:57:51 GMT",
"version": "v1"
}
] | 2022-05-11 | [
[
"Sang",
"Aofei",
""
],
[
"Jiang",
"Jie",
""
]
] | Recently, it is found that the strong cosmic censorship (SCC) is violated in RNdS black hole by a minimal coupled neutral massless scalar field at the linear perturbation level. For the Einstein-Maxwell-Scalar-Gauss-Bonnet theory which is famous for the spontaneous scalarization phenomenon, there exists the scalar field coupled with the Gauss-Bonnet term. Whether the SCC of the RNdS black hole can be repaired by the non-minimal coupled scalar field perturbation at the linear level becomes an interesting question. In this paper, we firstly investigate the extendibility of the metric beyond the Cauchy horizon in the Einstein-Maxwell-Scalar-Gauss-Bonnet theory. Then, we examine the SCC of the RNdS black hole by calculating the quasinormal mode of the non-minimal coupled scalar field and find that the SCC can be recovered under some parameters. |
1512.03560 | Xiaobo Guo | Xiaobo Guo and Peng Wang and Haitang Yang | The Classical Limit of Minimal Length Uncertainty Relation:Revisit with
the Hamilton-Jacobi Method | 24 pages | null | 10.1088/1475-7516/2016/05/062 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The existence of a minimum measurable length could deform not only the
standard quantum mechanics but also classical physics. The effects of the
minimal length on classical orbits of particles in a gravitation field have
been investigated before, using the deformed Poisson bracket or Schwarzschild
metric. In this paper, we use the Hamilton-Jacobi method to study motions of
particles in the context of deformed Newtonian mechanics and general
relativity. Specifically, the precession of planetary orbits, deflection of
light, and time delay in radar propagation are considered in this paper. We
also set limits on the deformation parameter by comparing our results with the
observational measurements. Finally, comparison with results from previous
papers is given at the end of this paper.
| [
{
"created": "Fri, 11 Dec 2015 09:15:31 GMT",
"version": "v1"
}
] | 2016-06-01 | [
[
"Guo",
"Xiaobo",
""
],
[
"Wang",
"Peng",
""
],
[
"Yang",
"Haitang",
""
]
] | The existence of a minimum measurable length could deform not only the standard quantum mechanics but also classical physics. The effects of the minimal length on classical orbits of particles in a gravitation field have been investigated before, using the deformed Poisson bracket or Schwarzschild metric. In this paper, we use the Hamilton-Jacobi method to study motions of particles in the context of deformed Newtonian mechanics and general relativity. Specifically, the precession of planetary orbits, deflection of light, and time delay in radar propagation are considered in this paper. We also set limits on the deformation parameter by comparing our results with the observational measurements. Finally, comparison with results from previous papers is given at the end of this paper. |
1401.7038 | Jonathan Blackman | Jonathan Blackman, Bela Szilagyi, Chad R. Galley, Manuel Tiglio | A sparse representation of gravitational waves from precessing compact
binaries | 5 pages, 3 figures. The parameters selected for the basis of
precessing waveforms can be found in the source files | Phys. Rev. Lett. 113, 021101 (2014) | 10.1103/PhysRevLett.113.021101 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Many relevant applications in gravitational wave physics share a significant
common problem: the seven-dimensional parameter space of gravitational
waveforms from precessing compact binary inspirals and coalescences is large
enough to prohibit covering the space of waveforms with sufficient density. We
find that by using the reduced basis method together with a parametrization of
waveforms based on their phase and precession, we can construct ultra-compact
yet high-accuracy representations of this large space. As a demonstration, we
show that less than $100$ judiciously chosen precessing inspiral waveforms are
needed for $200$ cycles, mass ratios from $1$ to $10$ and spin magnitudes $\le
0.9$. In fact, using only the first $10$ reduced basis waveforms yields a
maximum mismatch of $0.016$ over the whole range of considered parameters. We
test whether the parameters selected from the inspiral regime result in an
accurate reduced basis when including merger and ringdown; we find that this is
indeed the case in the context of a non-precessing effective-one-body model.
This evidence suggests that as few as $\sim 100$ numerical simulations of
binary black hole coalescences may accurately represent the seven-dimensional
parameter space of precession waveforms for the considered ranges.
| [
{
"created": "Mon, 27 Jan 2014 22:16:30 GMT",
"version": "v1"
}
] | 2014-07-16 | [
[
"Blackman",
"Jonathan",
""
],
[
"Szilagyi",
"Bela",
""
],
[
"Galley",
"Chad R.",
""
],
[
"Tiglio",
"Manuel",
""
]
] | Many relevant applications in gravitational wave physics share a significant common problem: the seven-dimensional parameter space of gravitational waveforms from precessing compact binary inspirals and coalescences is large enough to prohibit covering the space of waveforms with sufficient density. We find that by using the reduced basis method together with a parametrization of waveforms based on their phase and precession, we can construct ultra-compact yet high-accuracy representations of this large space. As a demonstration, we show that less than $100$ judiciously chosen precessing inspiral waveforms are needed for $200$ cycles, mass ratios from $1$ to $10$ and spin magnitudes $\le 0.9$. In fact, using only the first $10$ reduced basis waveforms yields a maximum mismatch of $0.016$ over the whole range of considered parameters. We test whether the parameters selected from the inspiral regime result in an accurate reduced basis when including merger and ringdown; we find that this is indeed the case in the context of a non-precessing effective-one-body model. This evidence suggests that as few as $\sim 100$ numerical simulations of binary black hole coalescences may accurately represent the seven-dimensional parameter space of precession waveforms for the considered ranges. |
1401.8208 | Surajit Chattopadhyay | Surajit Chattopadhyay, Antonio Pasqua and Martiros Khurshudyan | New holographic reconstruction of scalar field dark energy models in the
framework of chameleon Brans-Dicke cosmology | 25 pages, 13 figures. arXiv admin note: text overlap with
arXiv:0810.4296 by other authors | Eur. Phys. J. C (2014) 74:3080 | 10.1140/epjc/s10052-014-3080-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the work of Yang et al., \emph{Mod. Phys. Lett. A}, \textbf{26},
191 (2011), we report a study on the New Holographic Dark Energy (NHDE) model
with energy density given by $\rho_D=\frac{3\phi^2}{4\omega}(\mu H^2+\nu
\dot{H})$ in the framework of chameleon Brans-Dicke cosmology. We have studied
a correspondence between the quintessence, the DBI-essence and the tachyon
scalar field models with the NHDE model in the framework of chameleon
Brans-Dicke cosmology. Deriving an expression of the Hubble parameter $H$ and,
accordingly, $\rho_D$ in the context of chameleon Brans-Dicke chameleon
cosmology, we have reconstructed the potentials and dynamics for these scalar
field models. Furthermore, we have examined the stability for the obtained
solutions of the crossing of the phantom divide under a quantum correction of
massless conformally-invariant fields and we have seen that quantum correction
could be small when the phantom crossing occurs and the obtained solutions of
the phantom crossing could be stable under the quantum correction. It has also
been noted that the potential increases as the matter-chameleon coupling gets
stronger with the evolution of the universe.
| [
{
"created": "Thu, 30 Jan 2014 11:10:31 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Jun 2014 06:55:45 GMT",
"version": "v2"
},
{
"created": "Fri, 13 Jun 2014 10:29:18 GMT",
"version": "v3"
},
{
"created": "Sun, 31 Aug 2014 11:40:11 GMT",
"version": "v4"
}
] | 2014-10-31 | [
[
"Chattopadhyay",
"Surajit",
""
],
[
"Pasqua",
"Antonio",
""
],
[
"Khurshudyan",
"Martiros",
""
]
] | Motivated by the work of Yang et al., \emph{Mod. Phys. Lett. A}, \textbf{26}, 191 (2011), we report a study on the New Holographic Dark Energy (NHDE) model with energy density given by $\rho_D=\frac{3\phi^2}{4\omega}(\mu H^2+\nu \dot{H})$ in the framework of chameleon Brans-Dicke cosmology. We have studied a correspondence between the quintessence, the DBI-essence and the tachyon scalar field models with the NHDE model in the framework of chameleon Brans-Dicke cosmology. Deriving an expression of the Hubble parameter $H$ and, accordingly, $\rho_D$ in the context of chameleon Brans-Dicke chameleon cosmology, we have reconstructed the potentials and dynamics for these scalar field models. Furthermore, we have examined the stability for the obtained solutions of the crossing of the phantom divide under a quantum correction of massless conformally-invariant fields and we have seen that quantum correction could be small when the phantom crossing occurs and the obtained solutions of the phantom crossing could be stable under the quantum correction. It has also been noted that the potential increases as the matter-chameleon coupling gets stronger with the evolution of the universe. |
2307.15867 | Seraphim Jarov | Seraphim Jarov, Sarah Thiele, Siddharth Soni, Julian Ding, Jess
McIver, Raymond Ng, Rikako Hatoya, Derek Davis | A new method to distinguish gravitational-wave signals from detector
noise transients with Gravity Spy | 11 pages, 7 figures, submitted to PHYSICAL REVIEW D | null | null | null | gr-qc astro-ph.HE astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | The Advanced LIGO and Advanced Virgo detectors have enabled the confident
detection of dozens of mergers of black holes and neutron stars. However, the
presence of detector noise transients (glitches) hinders the search for these
gravitational wave (GW) signals. We prototyped a restructuring of Gravity Spy's
classification model to distinguish between glitches and astrophysical signals.
Our method is able to correctly classify three-quarters of retracted candidate
events in O3b as non-astrophysical and 100\% of the confirmed astrophysical
events as true signals. This approach will inform candidate event validation
efforts in the latest observing run.
| [
{
"created": "Sat, 29 Jul 2023 02:18:27 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Feb 2024 05:09:30 GMT",
"version": "v2"
}
] | 2024-02-06 | [
[
"Jarov",
"Seraphim",
""
],
[
"Thiele",
"Sarah",
""
],
[
"Soni",
"Siddharth",
""
],
[
"Ding",
"Julian",
""
],
[
"McIver",
"Jess",
""
],
[
"Ng",
"Raymond",
""
],
[
"Hatoya",
"Rikako",
""
],
[
"Davis",
"Derek",
""
]
] | The Advanced LIGO and Advanced Virgo detectors have enabled the confident detection of dozens of mergers of black holes and neutron stars. However, the presence of detector noise transients (glitches) hinders the search for these gravitational wave (GW) signals. We prototyped a restructuring of Gravity Spy's classification model to distinguish between glitches and astrophysical signals. Our method is able to correctly classify three-quarters of retracted candidate events in O3b as non-astrophysical and 100\% of the confirmed astrophysical events as true signals. This approach will inform candidate event validation efforts in the latest observing run. |
1507.03620 | Fabricio Matos Ferreira | Fabricio M. Ferreira, Ilya L. Shapiro and Poliane M. Teixeira | On the conformal properties of topological terms in even dimensions | New results and important references added, some formulations
improved. Fits published version | Eur. Phys. J. Plus (2016) 131: 164 | 10.1140/epjp/i2016-16164-9 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Conformal properties of the topological gravitational terms in $D=2$, $D=4$
and $D=6$ are discussed. It is shown that in the last two cases the integrands
of these terms, when being settled into the dimension $D-1$ and multiplied by a
scalar, become conformal invariant. Furthermore we present a simple covariant
derivation of the Paneitz operator in $D=4$ and formulate two general
conjectures concerning the conformal properties of topological structures in
even dimensions.
| [
{
"created": "Mon, 13 Jul 2015 21:09:47 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Jul 2015 22:00:01 GMT",
"version": "v2"
},
{
"created": "Tue, 24 May 2016 16:40:25 GMT",
"version": "v3"
}
] | 2016-05-25 | [
[
"Ferreira",
"Fabricio M.",
""
],
[
"Shapiro",
"Ilya L.",
""
],
[
"Teixeira",
"Poliane M.",
""
]
] | Conformal properties of the topological gravitational terms in $D=2$, $D=4$ and $D=6$ are discussed. It is shown that in the last two cases the integrands of these terms, when being settled into the dimension $D-1$ and multiplied by a scalar, become conformal invariant. Furthermore we present a simple covariant derivation of the Paneitz operator in $D=4$ and formulate two general conjectures concerning the conformal properties of topological structures in even dimensions. |
2209.00450 | Rikpratik Sengupta | Prasenjit Paul, Rikpratik Sengupta and Saibal Ray | Weyl transformation: a dynamical degree of freedom in the light of
Dirac's Large Number Hypothesis | 11 Pages, Previously this version appeared as arXiv:2005.09458v2
which was submitted as a replacement work by accident | International Journal of Modern Physics D Vol. 29, No. 03, 2050027
(2020) | 10.1142/S0218271820500273 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In Einstein's Field Equation(EFE) the geometry of the space-time is connected
with the matter distribution. The geometry or the gravitational sector deals
with classical macroscopic objects involving gravitational units while the
matter sector can be better described by quantum theory involving atomic units.
It has been argued by Bisabr that there exists an epoch-dependent conversion
factor between these two unit systems present in two different conformal
frames,i.e. the conformal factor is epoch dependent. We argue that the
conformal transformation is a dynamical degree of freedom describing it's
possible relevance in inflation in context to the graceful exit problem,
dynamics of the cosmological constant {\Lambda} and justify the argument in the
light of consequences of Dirac's Large Number hypothesis(LNH).
| [
{
"created": "Wed, 31 Aug 2022 11:12:27 GMT",
"version": "v1"
}
] | 2022-09-07 | [
[
"Paul",
"Prasenjit",
""
],
[
"Sengupta",
"Rikpratik",
""
],
[
"Ray",
"Saibal",
""
]
] | In Einstein's Field Equation(EFE) the geometry of the space-time is connected with the matter distribution. The geometry or the gravitational sector deals with classical macroscopic objects involving gravitational units while the matter sector can be better described by quantum theory involving atomic units. It has been argued by Bisabr that there exists an epoch-dependent conversion factor between these two unit systems present in two different conformal frames,i.e. the conformal factor is epoch dependent. We argue that the conformal transformation is a dynamical degree of freedom describing it's possible relevance in inflation in context to the graceful exit problem, dynamics of the cosmological constant {\Lambda} and justify the argument in the light of consequences of Dirac's Large Number hypothesis(LNH). |
0801.2110 | S Habib Mazharimousavi | S. Habib Mazharimousavi and M. Halilsoy | Black Hole solutions in Einstein-Maxwell-Yang-Mills-Gauss-Bonnet Theory | 20 pages, 5 figures, to be published in JCAP | J. Cosmol. Astropart. Phys. 12 (2008) 005 | 10.1088/1475-7516/2008/12/005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider Maxwell and Yang-Mills (YM) fields together, interacting through
gravity both in Einstein and Gauss-Bonnet (GB) theories. For this purpose we
choose two different sets of Maxwell and metric ansaetze. In our first ansatz,
asymptotically for $r\to 0$ (and $N>4$) the Maxwell field dominants over the YM
field. In the other asymptotic region, $r\to \infty $, however, the YM field
becomes dominant. For N=3 and N=4, where the GB term is absent, we recover the
well-known Ba\U{f1}ados-Teitelboim-Zanelli (BTZ) and Reissner-Nordstr\U{f6}m
(RN) metrics, respectively. The second ansatz corresponds to the case of
constant radius function for $S^{N-2}$ part in the metric. This leads to the
Bertotti-Robinson (BR) type solutions in the underlying theory.
| [
{
"created": "Mon, 14 Jan 2008 16:31:13 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Mar 2008 11:56:53 GMT",
"version": "v2"
},
{
"created": "Thu, 30 Oct 2008 16:42:23 GMT",
"version": "v3"
},
{
"created": "Thu, 13 Nov 2008 15:44:15 GMT",
"version": "v4"
}
] | 2009-11-13 | [
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Halilsoy",
"M.",
""
]
] | We consider Maxwell and Yang-Mills (YM) fields together, interacting through gravity both in Einstein and Gauss-Bonnet (GB) theories. For this purpose we choose two different sets of Maxwell and metric ansaetze. In our first ansatz, asymptotically for $r\to 0$ (and $N>4$) the Maxwell field dominants over the YM field. In the other asymptotic region, $r\to \infty $, however, the YM field becomes dominant. For N=3 and N=4, where the GB term is absent, we recover the well-known Ba\U{f1}ados-Teitelboim-Zanelli (BTZ) and Reissner-Nordstr\U{f6}m (RN) metrics, respectively. The second ansatz corresponds to the case of constant radius function for $S^{N-2}$ part in the metric. This leads to the Bertotti-Robinson (BR) type solutions in the underlying theory. |
gr-qc/9410004 | null | P.T. Chrusciel, R.M. Wald | On the topology of stationary black holes | 7 pages, Latex | Class.Quant.Grav.11:L147-L152,1994 | 10.1088/0264-9381/11/12/001 | null | gr-qc | null | We prove that the domain of outer communication of a stationary, globally
hyperbolic spacetime satisfying the null energy condition must be simply
connected. Under suitable additional hypotheses, this implies, in particular,
that each connected component of a cross-section of the event horizon of a
stationary black hole must have spherical topology.
| [
{
"created": "Wed, 5 Oct 1994 09:28:12 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Chrusciel",
"P. T.",
""
],
[
"Wald",
"R. M.",
""
]
] | We prove that the domain of outer communication of a stationary, globally hyperbolic spacetime satisfying the null energy condition must be simply connected. Under suitable additional hypotheses, this implies, in particular, that each connected component of a cross-section of the event horizon of a stationary black hole must have spherical topology. |
gr-qc/0104015 | Luis Bento | Luis Bento and Jose P. S. Lemos | Interaction between gravitational waves and domain walls | 15 pages | Phys.Rev. D64 (2001) 024011 | 10.1103/PhysRevD.64.024011 | null | gr-qc astro-ph hep-th | null | We study the gravitational perturbations of thick domain walls. The
refraction index and spin properties of the solutions interior to the wall are
analyzed in detail. It is shown that the gravitational waves suffer a
refraction process by domain walls. The reflection and transmission
coefficients are derived in the thin wall limit. In relation to the spin
content, it is shown that the ``$\times$'' helicity 2 gravitational wave mode
maintains in the domain wall the same polarization state as in vacuum. On the
contrary, the ``+'' mode, of pure helicity 2 in vacuum, is contaminated inside
the wall with a spin 0 state, as well as with spin 2, helicity 0 and 1 states.
| [
{
"created": "Wed, 4 Apr 2001 15:47:57 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Jun 2001 16:34:56 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Bento",
"Luis",
""
],
[
"Lemos",
"Jose P. S.",
""
]
] | We study the gravitational perturbations of thick domain walls. The refraction index and spin properties of the solutions interior to the wall are analyzed in detail. It is shown that the gravitational waves suffer a refraction process by domain walls. The reflection and transmission coefficients are derived in the thin wall limit. In relation to the spin content, it is shown that the ``$\times$'' helicity 2 gravitational wave mode maintains in the domain wall the same polarization state as in vacuum. On the contrary, the ``+'' mode, of pure helicity 2 in vacuum, is contaminated inside the wall with a spin 0 state, as well as with spin 2, helicity 0 and 1 states. |
gr-qc/0012069 | Jljing | Jiliang Jing, Mu-Lin Yan | Effect of spins on the quantum entropy of black holes | 10 pages, no figure, to appear in Phys. Rev. D | Phys.Rev. D63 (2001) 084028 | 10.1103/PhysRevD.63.084028 | null | gr-qc hep-th | null | By using the Newman-Penrose formalism and 't Hooft brick-wall model, the
quantum entropies of the Kerr-Newman black hole due to the Dirac and
electromagnetic fields are calculated and the effects of the spins of the
photons and Dirac particles on the entropies are investigated. It is shown that
the entropies depend only on the square of the spins of the particles and the
contribution of the spins is dependent on the rotation of the black hole,
except that different fields obey different statistics.
| [
{
"created": "Tue, 19 Dec 2000 13:13:53 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Mar 2001 08:55:31 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Jing",
"Jiliang",
""
],
[
"Yan",
"Mu-Lin",
""
]
] | By using the Newman-Penrose formalism and 't Hooft brick-wall model, the quantum entropies of the Kerr-Newman black hole due to the Dirac and electromagnetic fields are calculated and the effects of the spins of the photons and Dirac particles on the entropies are investigated. It is shown that the entropies depend only on the square of the spins of the particles and the contribution of the spins is dependent on the rotation of the black hole, except that different fields obey different statistics. |
1811.12292 | Paulo Luz | Paulo Luz, Filipe C. Mena, Amir Hadi Ziaie | Influence of intrinsic spin in the formation of singularities for
inhomogeneous effective dust space-times | 18 pages, 4 figures, to appear in Classical and Quantum Gravity | Class.Quant.Grav. 36 (2019) no.1, 015003 | 10.1088/1361-6382/aae9ff | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The evolution of inhomogeneous space-times composed of uncharged fermions is
studied for Szekeres metrics which have no Killing vectors, in general. Using
the Einstein-Cartan theory to include the effects of (intrinsic) matter spin in
General Relativity, the dynamics of a perfect fluid with non-null spin degrees
of freedom is considered. It is shown that, if the matter is composed by
effective dust and certain constraints on the initial data are verified, a
singularity will not form. Various special cases are discussed, such as
Lema\^itre-Tolman-Bondi and Bianchi I space-times, where the results are
further extended or shown explicitly to be verified.
| [
{
"created": "Thu, 29 Nov 2018 16:33:11 GMT",
"version": "v1"
}
] | 2019-01-04 | [
[
"Luz",
"Paulo",
""
],
[
"Mena",
"Filipe C.",
""
],
[
"Ziaie",
"Amir Hadi",
""
]
] | The evolution of inhomogeneous space-times composed of uncharged fermions is studied for Szekeres metrics which have no Killing vectors, in general. Using the Einstein-Cartan theory to include the effects of (intrinsic) matter spin in General Relativity, the dynamics of a perfect fluid with non-null spin degrees of freedom is considered. It is shown that, if the matter is composed by effective dust and certain constraints on the initial data are verified, a singularity will not form. Various special cases are discussed, such as Lema\^itre-Tolman-Bondi and Bianchi I space-times, where the results are further extended or shown explicitly to be verified. |
0812.3948 | Dmitri Vassiliev | James Burnett, Olga Chervova and Dmitri Vassiliev | Dirac equation as a special case of Cosserat elasticity | Submitted to Analysis, Partial Differential Equations and
Applications - The Vladimir Maz'ya Anniversary Volume (Operator Theory:
Advances and Applications) Birkauser Verlag | Analysis, Partial Differential Equations and Applications - The
Vladimir Maz'ya Anniversary Volume (ed. A.Cialdea, F.Lanzara and P.E.Ricci),
series Operator Theory: Advances and Applications, vol. 193, Birkhauser
Verlag, 2009, p. 15-29. | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We suggest an alternative mathematical model for the electron in which the
dynamical variables are a coframe (field of orthonormal bases) and a density.
The electron mass and external electromagnetic field are incorporated into our
model by means of a Kaluza-Klein extension. Our Lagrangian density is
proportional to axial torsion squared. The advantage of our approach is that it
does not require the use of spinors, Pauli matrices or covariant
differentiation. The only geometric concepts we use are those of a metric,
differential form, wedge product and exterior derivative. We prove that in the
special case with no dependence on the third spatial coordinate our model is
equivalent to the Dirac equation. The crucial element of the proof is the
observation that our Lagrangian admits a factorisation.
| [
{
"created": "Mon, 22 Dec 2008 15:47:47 GMT",
"version": "v1"
}
] | 2009-10-03 | [
[
"Burnett",
"James",
""
],
[
"Chervova",
"Olga",
""
],
[
"Vassiliev",
"Dmitri",
""
]
] | We suggest an alternative mathematical model for the electron in which the dynamical variables are a coframe (field of orthonormal bases) and a density. The electron mass and external electromagnetic field are incorporated into our model by means of a Kaluza-Klein extension. Our Lagrangian density is proportional to axial torsion squared. The advantage of our approach is that it does not require the use of spinors, Pauli matrices or covariant differentiation. The only geometric concepts we use are those of a metric, differential form, wedge product and exterior derivative. We prove that in the special case with no dependence on the third spatial coordinate our model is equivalent to the Dirac equation. The crucial element of the proof is the observation that our Lagrangian admits a factorisation. |
0707.3525 | Lorenzo Iorio | Lorenzo Iorio | On the orbital and physical parameters of the HDE 226868/Cygnus X-1
binary system | Latex2e, 7 pages, 1 table, 4 figures. To appear in ApSS (Astrophysics
and Space Science) | Astrophys.SpaceSci.315:335-340,2008 | 10.1007/s10509-008-9839-y | null | gr-qc astro-ph | null | In this paper we explore the consequences of the recent determination of the
mass m=(8.7 +/- 0.8)M_Sun of Cygnus X-1, obtained from the Quasi-Periodic
Oscillation (QPO)-photon index correlation scaling, on the orbital and physical
properties of the binary system HDE 226868/Cygnus X-1. By using such a result
and the latest spectroscopic optical data of the HDE 226868 supergiant star we
get M=(24 +/- 5)M_Sun for its mass. It turns out that deviations from the third
Kepler law significant at more than 1-sigma level would occur if the
inclination i of the system's orbital plane to the plane of the sky falls
outside the range 41-56 deg: such deviations cannot be due to the first
post-Newtonian (1PN) correction to the orbital period because of its smallness;
interpreted in the framework of the Newtonian theory of gravitation as due to
the stellar quadrupole mass moment Q, they are unphysical because Q would take
unreasonably large values. By conservatively assuming that the third Kepler law
is an adequate model for the orbital period we obtain i=(48 +/- 7) deg which
yields for the relative semimajor axis a=(42 +/- 9)R_Sun. Our estimate for the
Roche's lobe of HDE 226868 is r_M = (21 +/- 6)R_Sun.
| [
{
"created": "Tue, 24 Jul 2007 11:00:19 GMT",
"version": "v1"
},
{
"created": "Mon, 26 May 2008 16:01:24 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Iorio",
"Lorenzo",
""
]
] | In this paper we explore the consequences of the recent determination of the mass m=(8.7 +/- 0.8)M_Sun of Cygnus X-1, obtained from the Quasi-Periodic Oscillation (QPO)-photon index correlation scaling, on the orbital and physical properties of the binary system HDE 226868/Cygnus X-1. By using such a result and the latest spectroscopic optical data of the HDE 226868 supergiant star we get M=(24 +/- 5)M_Sun for its mass. It turns out that deviations from the third Kepler law significant at more than 1-sigma level would occur if the inclination i of the system's orbital plane to the plane of the sky falls outside the range 41-56 deg: such deviations cannot be due to the first post-Newtonian (1PN) correction to the orbital period because of its smallness; interpreted in the framework of the Newtonian theory of gravitation as due to the stellar quadrupole mass moment Q, they are unphysical because Q would take unreasonably large values. By conservatively assuming that the third Kepler law is an adequate model for the orbital period we obtain i=(48 +/- 7) deg which yields for the relative semimajor axis a=(42 +/- 9)R_Sun. Our estimate for the Roche's lobe of HDE 226868 is r_M = (21 +/- 6)R_Sun. |
gr-qc/9911098 | Lee Samuel Finn | Soma Mukherjee and Lee Samuel Finn | Removing Instrumental Artifacts: Suspension Violin Modes | 7 pages, 2 embedded figures. To appear in proceedings of the Third
Edoardo Amaldi Conference | null | 10.1063/1.1291880 | null | gr-qc | null | We describe the design of a Kalman filter that identifies suspension violin
modes in an interferometric gravitational wave detectors data channel. We
demonstrate the filter's effectiveness by applying it to data taken on the
LIGO~40M prototype.
| [
{
"created": "Thu, 25 Nov 1999 01:30:43 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Mukherjee",
"Soma",
""
],
[
"Finn",
"Lee Samuel",
""
]
] | We describe the design of a Kalman filter that identifies suspension violin modes in an interferometric gravitational wave detectors data channel. We demonstrate the filter's effectiveness by applying it to data taken on the LIGO~40M prototype. |
1501.00977 | Vitor Cardoso | Vitor Cardoso, Gaurav Khanna | Black holes in anti-de Sitter: quasinormal modes, tails and tales of
flat spacetime | 6 pages, RevTex4. Accepted for publication in Physical Review D. v2:
References added | null | 10.1103/PhysRevD.91.024031 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes in asymptotically anti-de Sitter (AdS) spacetimes have been the
subject of intense scrutiny, including detailed frequency-domain analysis and
full nonlinear evolutions. Remarkably, studies of linearized perturbations in
the time-domain are scarce or non-existing. We close this gap by evolving
linearized scalar wavepackets in the background of rotating BHs in AdS
spacetimes. Our results show a number of interesting features. Small BHs in AdS
behave as asymptotically flat BHs for early/intermediate times, displaying the
same ringdown modes and power-law tails. As the field bounces back and forth
between the horizon and the timelike boundary it "thermalizes" and the modes of
AdS settle in. Finally, we have indications that wavepackets in the vicinity of
fastly spinning BHs grow exponentially in time, signalling a superradiant
instability of the geometry previously reported through a frequency-domain
analysis.
| [
{
"created": "Mon, 5 Jan 2015 21:00:09 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Jan 2015 15:20:11 GMT",
"version": "v2"
}
] | 2015-06-23 | [
[
"Cardoso",
"Vitor",
""
],
[
"Khanna",
"Gaurav",
""
]
] | Black holes in asymptotically anti-de Sitter (AdS) spacetimes have been the subject of intense scrutiny, including detailed frequency-domain analysis and full nonlinear evolutions. Remarkably, studies of linearized perturbations in the time-domain are scarce or non-existing. We close this gap by evolving linearized scalar wavepackets in the background of rotating BHs in AdS spacetimes. Our results show a number of interesting features. Small BHs in AdS behave as asymptotically flat BHs for early/intermediate times, displaying the same ringdown modes and power-law tails. As the field bounces back and forth between the horizon and the timelike boundary it "thermalizes" and the modes of AdS settle in. Finally, we have indications that wavepackets in the vicinity of fastly spinning BHs grow exponentially in time, signalling a superradiant instability of the geometry previously reported through a frequency-domain analysis. |
0807.2523 | Sylvain Brechet | S. D. Brechet, M. P. Hobson, A. N. Lasenby | Classical big-bounce cosmology: dynamical analysis of a homogeneous and
irrotational Weyssenhoff fluid | 34 pages, 18 figures | Class. Quantum Grav. 25 (2008) 245016 (35pp) | 10.1088/0264-9381/25/24/245016 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A dynamical analysis of an effective homogeneous and irrotational Weyssenhoff
fluid in general relativity is performed using the 1+3 covariant approach that
enables the dynamics of the fluid to be determined without assuming any
particular form for the space-time metric. The spin contributions to the field
equations produce a bounce that averts an initial singularity, provided that
the spin density exceeds the rate of shear. At later times, when the spin
contribution can be neglected, a Weyssenhoff fluid reduces to a standard
cosmological fluid in general relativity. Numerical solutions for the time
evolution of the generalised scale factor in spatially-curved models are
presented, some of which exhibit eternal oscillatory behaviour without any
singularities. In spatially-flat models, analytical solutions for particular
values of the equation-of-state parameter are derived. Although the scale
factor of a Weyssenhoff fluid generically has a positive temporal curvature
near a bounce, it requires unreasonable fine tuning of the equation-of-state
parameter to produce a sufficiently extended period of inflation to fit the
current observational data.
| [
{
"created": "Wed, 16 Jul 2008 09:36:04 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Dec 2008 10:43:20 GMT",
"version": "v2"
}
] | 2009-11-13 | [
[
"Brechet",
"S. D.",
""
],
[
"Hobson",
"M. P.",
""
],
[
"Lasenby",
"A. N.",
""
]
] | A dynamical analysis of an effective homogeneous and irrotational Weyssenhoff fluid in general relativity is performed using the 1+3 covariant approach that enables the dynamics of the fluid to be determined without assuming any particular form for the space-time metric. The spin contributions to the field equations produce a bounce that averts an initial singularity, provided that the spin density exceeds the rate of shear. At later times, when the spin contribution can be neglected, a Weyssenhoff fluid reduces to a standard cosmological fluid in general relativity. Numerical solutions for the time evolution of the generalised scale factor in spatially-curved models are presented, some of which exhibit eternal oscillatory behaviour without any singularities. In spatially-flat models, analytical solutions for particular values of the equation-of-state parameter are derived. Although the scale factor of a Weyssenhoff fluid generically has a positive temporal curvature near a bounce, it requires unreasonable fine tuning of the equation-of-state parameter to produce a sufficiently extended period of inflation to fit the current observational data. |
2404.15792 | Marcos Vinicius De Sousa Silva | Marcos V. de S. Silva, Manuel E. Rodrigues | Orbits around a black bounce spacetime | 17 pages, 10 figures. Published in International Journal of
Theoretical Physics. V2: corrected typos, added references | International Journal of Theoretical Physics (2024) 63:101 | 10.1007/s10773-024-05644-5 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this work, the trajectories of particles around a black bounce spacetime
are considered, with the Simpson-Visser model serving as an example.
Trajectories for massless and massive particles are obtained through the study
of null and time-like geodesics. As the Simpson-Visser solution is derived via
the Einstein equations for a source involving nonlinear electrodynamics and a
scalar field, photon trajectories are investigated by considering an effective
metric in which photons follow null geodesics. The stability of circular orbits
is analyzed by examining the behavior of maxima and minima of the effective
potential associated with geodesics. It is also studied what type of geodesic
photons follow when the usual metric is considered instead of the effective
one. The main focus of this work is to obtain corrections to the trajectories
of photons when considering that the solution arises from nonlinear
electrodynamics.
| [
{
"created": "Wed, 24 Apr 2024 10:32:59 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Apr 2024 14:50:04 GMT",
"version": "v2"
}
] | 2024-04-29 | [
[
"Silva",
"Marcos V. de S.",
""
],
[
"Rodrigues",
"Manuel E.",
""
]
] | In this work, the trajectories of particles around a black bounce spacetime are considered, with the Simpson-Visser model serving as an example. Trajectories for massless and massive particles are obtained through the study of null and time-like geodesics. As the Simpson-Visser solution is derived via the Einstein equations for a source involving nonlinear electrodynamics and a scalar field, photon trajectories are investigated by considering an effective metric in which photons follow null geodesics. The stability of circular orbits is analyzed by examining the behavior of maxima and minima of the effective potential associated with geodesics. It is also studied what type of geodesic photons follow when the usual metric is considered instead of the effective one. The main focus of this work is to obtain corrections to the trajectories of photons when considering that the solution arises from nonlinear electrodynamics. |
1004.2040 | Ariel Zhitnitsky | Ariel R. Zhitnitsky | The Gauge Fields and Ghosts in Rindler Space | Final version to appear in Phys. Rev. D. Comments on relation with
energy momentum computations and few new refs are added | Phys.Rev.D82:103520,2010 | 10.1103/PhysRevD.82.103520 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider 2d Maxwell system defined on the Rindler space with metric
ds^2=\exp(2a\xi)\cdot(d\eta^2-d\xi^2) with the goal to study the dynamics of
the ghosts. We find an extra contribution to the vacuum energy in comparison
with Minkowski space time with metric ds^2= dt^2-dx^2. This extra contribution
can be traced to the unphysical degrees of freedom (in Minkowski space). The
technical reason for this effect to occur is the property of Bogolubov's
coefficients which mix the positive and negative frequencies modes. The
corresponding mixture can not be avoided because the projections to positive
-frequency modes with respect to Minkowski time t and positive -frequency modes
with respect to the Rindler observer's proper time \eta are not equivalent. The
exact cancellation of unphysical degrees of freedom which is maintained in
Minkowski space can not hold in the Rindler space. In BRST approach this effect
manifests itself as the presence of BRST charge density in L and R parts. An
inertial observer in Minkowski vacuum |0> observes a universe with no net BRST
charge only as a result of cancellation between the two. However, the Rindler
observers who do not ever have access to the entire space time would see a net
BRST charge. In this respect the effect resembles the Unruh effect. The effect
is infrared (IR) in nature, and sensitive to the horizon and/or boundaries. We
interpret the extra energy as the formation of the "ghost condensate" when the
ghost degrees of freedom can not propagate, but nevertheless do contribute to
the vacuum energy. Exact computations in this simple 2d model support the claim
made in [1] that the ghost contribution might be responsible for the observed
dark energy in 4d FLRW universe.
| [
{
"created": "Mon, 12 Apr 2010 20:00:03 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Aug 2010 19:08:30 GMT",
"version": "v2"
},
{
"created": "Wed, 20 Oct 2010 17:30:14 GMT",
"version": "v3"
}
] | 2010-12-09 | [
[
"Zhitnitsky",
"Ariel R.",
""
]
] | We consider 2d Maxwell system defined on the Rindler space with metric ds^2=\exp(2a\xi)\cdot(d\eta^2-d\xi^2) with the goal to study the dynamics of the ghosts. We find an extra contribution to the vacuum energy in comparison with Minkowski space time with metric ds^2= dt^2-dx^2. This extra contribution can be traced to the unphysical degrees of freedom (in Minkowski space). The technical reason for this effect to occur is the property of Bogolubov's coefficients which mix the positive and negative frequencies modes. The corresponding mixture can not be avoided because the projections to positive -frequency modes with respect to Minkowski time t and positive -frequency modes with respect to the Rindler observer's proper time \eta are not equivalent. The exact cancellation of unphysical degrees of freedom which is maintained in Minkowski space can not hold in the Rindler space. In BRST approach this effect manifests itself as the presence of BRST charge density in L and R parts. An inertial observer in Minkowski vacuum |0> observes a universe with no net BRST charge only as a result of cancellation between the two. However, the Rindler observers who do not ever have access to the entire space time would see a net BRST charge. In this respect the effect resembles the Unruh effect. The effect is infrared (IR) in nature, and sensitive to the horizon and/or boundaries. We interpret the extra energy as the formation of the "ghost condensate" when the ghost degrees of freedom can not propagate, but nevertheless do contribute to the vacuum energy. Exact computations in this simple 2d model support the claim made in [1] that the ghost contribution might be responsible for the observed dark energy in 4d FLRW universe. |
1609.03573 | Ian Jubb | Michel Buck, Fay Dowker, Ian Jubb, Rafael Sorkin | The Sorkin-Johnston State in a Patch of the Trousers Spacetime | null | Class.Quant.Grav. 34 (2017) 5, 055002 | 10.1088/1361-6382/aa589c | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A quantum scalar field in a patch of a fixed, topology-changing, $1+1$
dimensional "trousers" spacetime is studied using the Sorkin-Johnston
formalism. The isometry group of the patch is the dihedral group, the symmetry
group of the square. The theory is shown to be pathological in a way that can
be interpreted as the topology change giving rise to a divergent energy, in
agreement with previous results. In contrast to previous results, it is shown
that the infinite energy is localised not only on the future light cone of the
topology changing singularity, but also on the past cone, due to the time
reversal symmetry of the Sorkin-Johnston state.
| [
{
"created": "Mon, 12 Sep 2016 20:00:07 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Feb 2017 15:05:05 GMT",
"version": "v2"
}
] | 2017-02-17 | [
[
"Buck",
"Michel",
""
],
[
"Dowker",
"Fay",
""
],
[
"Jubb",
"Ian",
""
],
[
"Sorkin",
"Rafael",
""
]
] | A quantum scalar field in a patch of a fixed, topology-changing, $1+1$ dimensional "trousers" spacetime is studied using the Sorkin-Johnston formalism. The isometry group of the patch is the dihedral group, the symmetry group of the square. The theory is shown to be pathological in a way that can be interpreted as the topology change giving rise to a divergent energy, in agreement with previous results. In contrast to previous results, it is shown that the infinite energy is localised not only on the future light cone of the topology changing singularity, but also on the past cone, due to the time reversal symmetry of the Sorkin-Johnston state. |
1911.01128 | Yu Han | Yu Han | Loop quantum cosmological dynamics of scalar-tensor theory in the Jordan
frame | 22 pages | Phys. Rev. D 100, 123541 (2019) | 10.1103/PhysRevD.100.123541 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The effective dynamics of scalar-tensor theory (STT) in the Jordan frame is
studied in the context of loop quantum cosmology with holonomy corrections.
After deriving the effective Hamiltonian from the connection dynamics
formulation, we obtain the holonomy-corrected evolution equations of STT on
spatially flat Friedmann-Robterson-Walker background, which exhibit some
interesting features unique to the Jordan frame of STT. In particular, the
linear term of the cosine function appearing in the equations could lead to
dynamics much different from the classical theory in the low-energy limit. In
the latter part of this paper, we choose a particular model in STT -- the
Brans-Dicke theory to specifically illustrate these features. It is found that
in Brans-Dicke theory the effective evolution equations can be classified into
four different cases. Exact solutions of the Friedmann equation in terms of the
internal time are obtained in these cases. Moreover, the solutions in terms of
the proper time describing the late time evolution of the Universe are also
obtained under certain approximation; in two cases the solutions coincide with
the existing solutions in classical Brans-Dicke theory while in the other two
cases the solutions do not.
| [
{
"created": "Mon, 4 Nov 2019 11:01:46 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Dec 2019 02:50:26 GMT",
"version": "v2"
}
] | 2020-01-01 | [
[
"Han",
"Yu",
""
]
] | The effective dynamics of scalar-tensor theory (STT) in the Jordan frame is studied in the context of loop quantum cosmology with holonomy corrections. After deriving the effective Hamiltonian from the connection dynamics formulation, we obtain the holonomy-corrected evolution equations of STT on spatially flat Friedmann-Robterson-Walker background, which exhibit some interesting features unique to the Jordan frame of STT. In particular, the linear term of the cosine function appearing in the equations could lead to dynamics much different from the classical theory in the low-energy limit. In the latter part of this paper, we choose a particular model in STT -- the Brans-Dicke theory to specifically illustrate these features. It is found that in Brans-Dicke theory the effective evolution equations can be classified into four different cases. Exact solutions of the Friedmann equation in terms of the internal time are obtained in these cases. Moreover, the solutions in terms of the proper time describing the late time evolution of the Universe are also obtained under certain approximation; in two cases the solutions coincide with the existing solutions in classical Brans-Dicke theory while in the other two cases the solutions do not. |
1010.5822 | Andrew Randono | Andrew Randono | Gauge Gravity: a forward-looking introduction | 62 pages, 8 figures | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article is a review of modern approaches to gravity that treat the
gravitational interaction as a type of gauge theory. The purpose of the article
is twofold. First, it is written in a colloquial style and is intended to be a
pedagogical introduction to the gauge approach to gravity. I begin with a
review of the Einstein-Cartan formulation of gravity, move on to the
Macdowell-Mansouri approach, then show how gravity can be viewed as the
symmetry broken phase of an (A)dS-gauge theory. This covers roughly the first
half of the article. Armed with these tools, the remainder of the article is
geared toward new insights and new lines of research that can be gained by
viewing gravity from this perspective. Drawing from familiar concepts from the
symmetry broken gauge theories of the standard model, we show how the
topological structure of the gauge group allows for an infinite class of new
solutions to the Einstein-Cartan field equations that can be thought of as
degenerate ground states of the theory. We argue that quantum mechanical
tunneling allows for transitions between the degenerate vacua. Generalizing the
tunneling process from a topological phase of the gauge theory to an arbitrary
geometry leads to a modern reformulation of the Hartle-Hawking "no boundary"
proposal.
| [
{
"created": "Wed, 27 Oct 2010 22:59:17 GMT",
"version": "v1"
}
] | 2010-10-29 | [
[
"Randono",
"Andrew",
""
]
] | This article is a review of modern approaches to gravity that treat the gravitational interaction as a type of gauge theory. The purpose of the article is twofold. First, it is written in a colloquial style and is intended to be a pedagogical introduction to the gauge approach to gravity. I begin with a review of the Einstein-Cartan formulation of gravity, move on to the Macdowell-Mansouri approach, then show how gravity can be viewed as the symmetry broken phase of an (A)dS-gauge theory. This covers roughly the first half of the article. Armed with these tools, the remainder of the article is geared toward new insights and new lines of research that can be gained by viewing gravity from this perspective. Drawing from familiar concepts from the symmetry broken gauge theories of the standard model, we show how the topological structure of the gauge group allows for an infinite class of new solutions to the Einstein-Cartan field equations that can be thought of as degenerate ground states of the theory. We argue that quantum mechanical tunneling allows for transitions between the degenerate vacua. Generalizing the tunneling process from a topological phase of the gauge theory to an arbitrary geometry leads to a modern reformulation of the Hartle-Hawking "no boundary" proposal. |
1104.3401 | Tayebeh Tahamtan | Tayebeh Tahamtan and Mustafa Halilsoy | Stable Magnetic Universes Revisited | 11 pages, 3figures | Astrophysics and Space Science, 343, 435 (2013) | 10.1007/s10509-012-1217-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A regular class of static, cylindrically symmetric pure magnetic field
metrics is rederived in a different metric ansatz in all dimensions. Radial,
time dependent perturbations show that for dimensions d>3 such spacetimes are
stable at both near r\approx0 and large radius r\rightarrow\infty. In a
different gauge these stability analysis and similar results were known
beforehand. For d=3, however, simultaneous stability requirement at both, near
and far radial distances can not be reconciled for time - dependent
perturbations. Restricted, numerical geodesics for neutral particles reveal a
confinement around the center in the polar plane. Charged, time-like geodesics
for d=4 on the other hand are shown numerically to run toward infinity.
| [
{
"created": "Mon, 18 Apr 2011 07:44:35 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Jun 2011 07:00:19 GMT",
"version": "v2"
}
] | 2016-09-30 | [
[
"Tahamtan",
"Tayebeh",
""
],
[
"Halilsoy",
"Mustafa",
""
]
] | A regular class of static, cylindrically symmetric pure magnetic field metrics is rederived in a different metric ansatz in all dimensions. Radial, time dependent perturbations show that for dimensions d>3 such spacetimes are stable at both near r\approx0 and large radius r\rightarrow\infty. In a different gauge these stability analysis and similar results were known beforehand. For d=3, however, simultaneous stability requirement at both, near and far radial distances can not be reconciled for time - dependent perturbations. Restricted, numerical geodesics for neutral particles reveal a confinement around the center in the polar plane. Charged, time-like geodesics for d=4 on the other hand are shown numerically to run toward infinity. |
gr-qc/0702071 | Yun-Song Piao | Yun-Song Piao | Primordial Perturbations Spectra in a Holographic Phase | 5 pages, 3 eps figures, to be published in PRD | Phys.Rev.D76:043509,2007 | 10.1103/PhysRevD.76.043509 | null | gr-qc hep-th | null | In this paper, we suppose that the universe begins in a holographic thermal
equilibrium phase with the diverged correlation length, and the phase
transition to the radiation phase of standard cosmology goes with the abrupt
reducing of correlation length. In this case, the primordial perturbations may
be induced by thermal fluctuations in this holographic phase. We calculate the
spectra of this holographic primordial perturbations, and find that the scalar
spectrum has a slightly red tilt and the tensor perturbation amplitude has a
moderate ratio, which may be tested in coming observations. The results plotted
in r-n_s plane is similar to that of large field inflation models. However, for
fixed efolding number, they are generally in different positions.
| [
{
"created": "Tue, 13 Feb 2007 10:25:38 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Jul 2007 03:18:10 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Piao",
"Yun-Song",
""
]
] | In this paper, we suppose that the universe begins in a holographic thermal equilibrium phase with the diverged correlation length, and the phase transition to the radiation phase of standard cosmology goes with the abrupt reducing of correlation length. In this case, the primordial perturbations may be induced by thermal fluctuations in this holographic phase. We calculate the spectra of this holographic primordial perturbations, and find that the scalar spectrum has a slightly red tilt and the tensor perturbation amplitude has a moderate ratio, which may be tested in coming observations. The results plotted in r-n_s plane is similar to that of large field inflation models. However, for fixed efolding number, they are generally in different positions. |
1401.0075 | Christopher Beetle | Christopher Beetle and Shawn Wilder | A note on axial symmetries | 6 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This note describes a local scheme to characterize and normalize an axial
Killing field on a general Riemannian geometry. No global assumptions are
necessary, such as that the orbits of the Killing field all have period $2
\pi$. Rather, any Killing field that vanishes at at least one point necessarily
has the expected global properties.
| [
{
"created": "Tue, 31 Dec 2013 03:06:15 GMT",
"version": "v1"
}
] | 2014-01-03 | [
[
"Beetle",
"Christopher",
""
],
[
"Wilder",
"Shawn",
""
]
] | This note describes a local scheme to characterize and normalize an axial Killing field on a general Riemannian geometry. No global assumptions are necessary, such as that the orbits of the Killing field all have period $2 \pi$. Rather, any Killing field that vanishes at at least one point necessarily has the expected global properties. |
gr-qc/0503024 | Yongge Ma | Muxin Han, Yongge Ma, You Ding, Li Qin | Hamiltonian analysis of $n$-dimensional Palatini gravity with matter | 7 pages, accepted for pubilcation in Mod. Phys. Lett. A | Mod.Phys.Lett. A20 (2005) 725-732 | 10.1142/S0217732305017068 | null | gr-qc | null | We consider the Palatini formalism of gravity with cosmological constant
$\Lambda$ coupled to a scalar field $\phi$ in $n$-dimensions. The
$n$-dimensional Einstein equations with $\Lambda$ can be derived by the
variation of the coupled Palatini action provided $n>2$. The Hamiltonian
analysis of the coupled action is carried out by a $1+(n-1)$ decomposition of
the spacetime. It turns out that both Palatini action and Hilbert action lead
to the same geometric dynamics in the presence of $\Lambda$ and $\phi$. While,
the $n$-dimensional Palatini action could not give a connection dynamics
formalism directly.
| [
{
"created": "Sat, 5 Mar 2005 04:13:11 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Han",
"Muxin",
""
],
[
"Ma",
"Yongge",
""
],
[
"Ding",
"You",
""
],
[
"Qin",
"Li",
""
]
] | We consider the Palatini formalism of gravity with cosmological constant $\Lambda$ coupled to a scalar field $\phi$ in $n$-dimensions. The $n$-dimensional Einstein equations with $\Lambda$ can be derived by the variation of the coupled Palatini action provided $n>2$. The Hamiltonian analysis of the coupled action is carried out by a $1+(n-1)$ decomposition of the spacetime. It turns out that both Palatini action and Hilbert action lead to the same geometric dynamics in the presence of $\Lambda$ and $\phi$. While, the $n$-dimensional Palatini action could not give a connection dynamics formalism directly. |
2210.06598 | Giovanni Otalora | Giovanni Otalora, Emmanuel N. Saridakis | Effective dark energy through spin-gravity coupling | 8 pages, 4 figures, version published in Phys.Lett.B | null | 10.1016/j.physletb.2023.137970 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate cosmological scenarios with spin-gravity coupling. In
particular, due to the spin of the baryonic and dark matter particles and its
coupling to gravity, they probe an effective spin-dependent metric, which can
be calculated semi-classically in the Mathisson-Papapetrou-Tulczyjew-Dixon
formalism. Hence, the usual field equations give rise to modified Friedmann
equations, in which the extra terms can be identified as an effective
dark-energy sector. Additionally, we obtain an effective interaction between
the matter and dark-energy sectors. In the case where the spin-gravity coupling
switches off, we recover standard $\Lambda$CDM cosmology. We perform a
dynamical system analysis and we find a matter-dominated point that can
describe the matter era, and a stable late-time solution corresponding to
acceleration and dark-energy domination. For small values of the spin coupling
parameter, deviations from $\Lambda$CDM concordance scenario are small, however
for larger values they can be brought to the desired amount, leading to
different dark-energy equation-of-state parameter behavior, as well as to
different transition redshift from acceleration to deceleration. Finally, we
confront the model predictions with Hubble function data.
| [
{
"created": "Wed, 12 Oct 2022 21:30:48 GMT",
"version": "v1"
},
{
"created": "Mon, 22 May 2023 03:46:36 GMT",
"version": "v2"
}
] | 2023-05-23 | [
[
"Otalora",
"Giovanni",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] | We investigate cosmological scenarios with spin-gravity coupling. In particular, due to the spin of the baryonic and dark matter particles and its coupling to gravity, they probe an effective spin-dependent metric, which can be calculated semi-classically in the Mathisson-Papapetrou-Tulczyjew-Dixon formalism. Hence, the usual field equations give rise to modified Friedmann equations, in which the extra terms can be identified as an effective dark-energy sector. Additionally, we obtain an effective interaction between the matter and dark-energy sectors. In the case where the spin-gravity coupling switches off, we recover standard $\Lambda$CDM cosmology. We perform a dynamical system analysis and we find a matter-dominated point that can describe the matter era, and a stable late-time solution corresponding to acceleration and dark-energy domination. For small values of the spin coupling parameter, deviations from $\Lambda$CDM concordance scenario are small, however for larger values they can be brought to the desired amount, leading to different dark-energy equation-of-state parameter behavior, as well as to different transition redshift from acceleration to deceleration. Finally, we confront the model predictions with Hubble function data. |
2106.04141 | S. Shankaranarayanan | Vijay Nenmeli, S. Shankaranarayanan (IIT Bombay), Vasil Todorinov and
Saurya Das (University of Lethbridge) | Maximal momentum GUP leads to quadratic gravity | 22 Pages, 2 Figures, Title modified, References Added, Version to
appear in Physics Letters B | null | 10.1016/j.physletb.2021.136621 | null | gr-qc astro-ph.CO hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | Quantum theories of gravity predict interesting phenomenological features
such as a minimum measurable length and maximum momentum. We use the
Generalized Uncertainty Principle (GUP), which is an extension of the standard
Heisenberg Uncertainty Principle motivated by Quantum Gravity, to model the
above features. In particular, we use a GUP with modelling maximum momentum to
establish a correspondence between the GUP-modified dynamics of a massless
spin-2 field and quadratic (referred to as Stelle) gravity. In other words,
Stelle gravity can be regarded as the classical manifestation of a maximum
momentum and the related GUP. We explore the applications of Stelle gravity to
cosmology and specifically show that Stelle gravity applied to a homogeneous
and isotropic background leads to inflation with an exit. Using the above, we
obtain strong bounds on the GUP parameter from CMB observations. Unlike
previous works, which fixed only upper bounds for GUP parameters, we obtain
both \emph{lower and upper bounds} on the GUP parameter.
| [
{
"created": "Tue, 8 Jun 2021 06:57:17 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Sep 2021 02:53:54 GMT",
"version": "v2"
}
] | 2021-09-10 | [
[
"Nenmeli",
"Vijay",
"",
"IIT Bombay"
],
[
"Shankaranarayanan",
"S.",
"",
"IIT Bombay"
],
[
"Todorinov",
"Vasil",
"",
"University of Lethbridge"
],
[
"Das",
"Saurya",
"",
"University of Lethbridge"
]
] | Quantum theories of gravity predict interesting phenomenological features such as a minimum measurable length and maximum momentum. We use the Generalized Uncertainty Principle (GUP), which is an extension of the standard Heisenberg Uncertainty Principle motivated by Quantum Gravity, to model the above features. In particular, we use a GUP with modelling maximum momentum to establish a correspondence between the GUP-modified dynamics of a massless spin-2 field and quadratic (referred to as Stelle) gravity. In other words, Stelle gravity can be regarded as the classical manifestation of a maximum momentum and the related GUP. We explore the applications of Stelle gravity to cosmology and specifically show that Stelle gravity applied to a homogeneous and isotropic background leads to inflation with an exit. Using the above, we obtain strong bounds on the GUP parameter from CMB observations. Unlike previous works, which fixed only upper bounds for GUP parameters, we obtain both \emph{lower and upper bounds} on the GUP parameter. |
1406.0369 | Jaume Haro | Jaume Haro and Jaume Amor\'os | Viability of the matter bounce scenario in Loop Quantum Cosmology for
general potentials | A section about reheating in the matter bounce scenario has been
added. Version accepted for publication in JCAP | JCAP(12) 031 (2014) | 10.1088/1475-7516/2014/12/031 | 1406.0369 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the matter bounce scenario in Loop Quantum Cosmology (LQC) for
physical potentials that at early times provide a nearly matter dominated
Universe in the contracting phase, having a reheating mechanism in the
expanding phase, i.e., being able to release the energy of the scalar field
creating particles that thermalize in order to match with the hot Friedmann
Universe, and finally at late times leading to the current cosmic acceleration.
For these models, numerically solving the dynamical equations we have seen that
the teleparallel version of LQC leads to theoretical results that fit well with
current observational data. More precisely, in teleparallel LQC there is a set
of solutions which leads to theoretical results that match correctly with last
BICEP2 data, and there is another set whose theoretical results fit well with
{\it Planck's} experimental data. On the other hand, in holonomy corrected LQC
the theoretical value of the tensor/scalar ratio is smaller than in
teleparallel LQC, which means that there is always a set of solutions that
matches with {\it Planck's} data, but for some potentials BICEP2 experimental
results disfavours holonomy corrected LQC.
| [
{
"created": "Mon, 2 Jun 2014 13:49:56 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Jun 2014 11:14:46 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Aug 2014 18:23:22 GMT",
"version": "v3"
},
{
"created": "Mon, 1 Dec 2014 14:49:27 GMT",
"version": "v4"
}
] | 2015-06-19 | [
[
"Haro",
"Jaume",
""
],
[
"Amorós",
"Jaume",
""
]
] | We consider the matter bounce scenario in Loop Quantum Cosmology (LQC) for physical potentials that at early times provide a nearly matter dominated Universe in the contracting phase, having a reheating mechanism in the expanding phase, i.e., being able to release the energy of the scalar field creating particles that thermalize in order to match with the hot Friedmann Universe, and finally at late times leading to the current cosmic acceleration. For these models, numerically solving the dynamical equations we have seen that the teleparallel version of LQC leads to theoretical results that fit well with current observational data. More precisely, in teleparallel LQC there is a set of solutions which leads to theoretical results that match correctly with last BICEP2 data, and there is another set whose theoretical results fit well with {\it Planck's} experimental data. On the other hand, in holonomy corrected LQC the theoretical value of the tensor/scalar ratio is smaller than in teleparallel LQC, which means that there is always a set of solutions that matches with {\it Planck's} data, but for some potentials BICEP2 experimental results disfavours holonomy corrected LQC. |
gr-qc/0604112 | Wojciech Kami\'nski | W. Kaminski, J. Lewandowski, A. Okolow | Background independent quantizations: the scalar field II | 51 pages, LaTeX, no figures, revised version | Class.Quant.Grav. 23 (2006) 5547-5586 | 10.1088/0264-9381/23/18/005 | null | gr-qc | null | We are concerned with the issue of quantization of a scalar field in a
diffeomorphism invariant manner. We apply the method used in Loop Quantum
Gravity. It relies on the specific choice of scalar field variables referred to
as the polymer variables. The quantization, in our formulation, amounts to
introducing the `quantum' polymer *-star algebra and looking for positive
linear functionals, called states. Assumed in our paper homeomorphism
invariance allows to derive the complete class of the states. They are
determined by the homeomorphism invariant states defined on the CW-complex
*-algebra. The corresponding GNS representations of the polymer *-algebra and
their self-adjoint extensions are derived, the equivalence classes are found
and invariant subspaces characterized. In the preceding letter (the part I) we
outlined those results. Here, we present the technical details.
| [
{
"created": "Wed, 26 Apr 2006 13:55:29 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Sep 2006 11:56:25 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Kaminski",
"W.",
""
],
[
"Lewandowski",
"J.",
""
],
[
"Okolow",
"A.",
""
]
] | We are concerned with the issue of quantization of a scalar field in a diffeomorphism invariant manner. We apply the method used in Loop Quantum Gravity. It relies on the specific choice of scalar field variables referred to as the polymer variables. The quantization, in our formulation, amounts to introducing the `quantum' polymer *-star algebra and looking for positive linear functionals, called states. Assumed in our paper homeomorphism invariance allows to derive the complete class of the states. They are determined by the homeomorphism invariant states defined on the CW-complex *-algebra. The corresponding GNS representations of the polymer *-algebra and their self-adjoint extensions are derived, the equivalence classes are found and invariant subspaces characterized. In the preceding letter (the part I) we outlined those results. Here, we present the technical details. |
2405.20246 | David McNutt | David McNutt, Eivind Schneider | Detecting horizons of symmetric black holes using relative differential
invariants | 29+3 pages | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Let $\mathfrak{k}$ be a nontrivial finite-dimensional Lie algebra of vector
fields on a manifold M, and consider the family of Lorentzian metrics on M
whose Killing algebra contains $\mathfrak{k}$. We show that scalar relative
differential invariants, with respect to a Lie algebra of vector fields on M
preserving $\mathfrak{k}$, can be used to detect the horizons of several
well-known black holes. In particular, using the Lie algebra structure of
$\mathfrak{k}$, we construct a general relative differential invariant of order
0 that always vanishes on $\mathfrak{k}$-invariant Killing horizons.
| [
{
"created": "Thu, 30 May 2024 16:55:05 GMT",
"version": "v1"
}
] | 2024-05-31 | [
[
"McNutt",
"David",
""
],
[
"Schneider",
"Eivind",
""
]
] | Let $\mathfrak{k}$ be a nontrivial finite-dimensional Lie algebra of vector fields on a manifold M, and consider the family of Lorentzian metrics on M whose Killing algebra contains $\mathfrak{k}$. We show that scalar relative differential invariants, with respect to a Lie algebra of vector fields on M preserving $\mathfrak{k}$, can be used to detect the horizons of several well-known black holes. In particular, using the Lie algebra structure of $\mathfrak{k}$, we construct a general relative differential invariant of order 0 that always vanishes on $\mathfrak{k}$-invariant Killing horizons. |
gr-qc/9608043 | Luis Lehner | Simonetta Frittelli, Luis Lehner, Carlo Rovelli (Univ. of Pittsburgh) | The complete spectrum of the area from recoupling theory in loop quantum
gravity | typos corrected in eqn.(21). Latex with IOP and epsf styles, 1 figure
(eps postscript file), 12 pages. To appear in Class. Quantum Grav | Class.Quant.Grav. 13 (1996) 2921-2932 | 10.1088/0264-9381/13/11/008 | null | gr-qc | null | We compute the complete spectrum of the area operator in the loop
representation of quantum gravity, using recoupling theory. This result extends
previous derivations, which did not include the ``degenerate'' sector, and
agrees with the recently computed spectrum of the connection-representation
area operator.
| [
{
"created": "Fri, 16 Aug 1996 18:16:35 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Aug 1996 14:34:27 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Frittelli",
"Simonetta",
"",
"Univ. of Pittsburgh"
],
[
"Lehner",
"Luis",
"",
"Univ. of Pittsburgh"
],
[
"Rovelli",
"Carlo",
"",
"Univ. of Pittsburgh"
]
] | We compute the complete spectrum of the area operator in the loop representation of quantum gravity, using recoupling theory. This result extends previous derivations, which did not include the ``degenerate'' sector, and agrees with the recently computed spectrum of the connection-representation area operator. |
1911.03965 | Sebasti\'an Bahamonde Dr | Sebastian Bahamonde, Ugur Camci | Exact Spherically Symmetric Solutions in Modified Teleparallel gravity | 22 pages; Matches published version in Symmetry | Symmetry 2019, 11(12), 1462 | 10.3390/sym11121462 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Finding spherically symmetric exact solutions in modified gravity is usually
a difficult task. In this paper we use the Noether's symmetry approach for a
modified Teleparallel theory of gravity labelled as $f(T,B)$ gravity where $T$
is the scalar torsion and $B$ the boundary term. Using the Noether's theorem,
we were able to find exact spherically symmetric solutions for different forms
of the function $f(T,B)$ coming from the Noether's symmetries.
| [
{
"created": "Sun, 10 Nov 2019 17:24:18 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Nov 2019 14:43:54 GMT",
"version": "v2"
}
] | 2019-12-02 | [
[
"Bahamonde",
"Sebastian",
""
],
[
"Camci",
"Ugur",
""
]
] | Finding spherically symmetric exact solutions in modified gravity is usually a difficult task. In this paper we use the Noether's symmetry approach for a modified Teleparallel theory of gravity labelled as $f(T,B)$ gravity where $T$ is the scalar torsion and $B$ the boundary term. Using the Noether's theorem, we were able to find exact spherically symmetric solutions for different forms of the function $f(T,B)$ coming from the Noether's symmetries. |
gr-qc/0310003 | Vladimir Majernik | V. Majernik | Is the Energy Density of the Cosmic Quaternionic Field a Possible
Candidate for the Black Energy? | 9 pages | null | null | null | gr-qc | null | We try to show that the energy density of the cosmic quaternionic field might
be a possible candidate for the black energy.
| [
{
"created": "Wed, 1 Oct 2003 09:24:48 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Majernik",
"V.",
""
]
] | We try to show that the energy density of the cosmic quaternionic field might be a possible candidate for the black energy. |
2007.01326 | Laszlo Arpad Gergely | Cec\'ilia Gergely, Zolt\'an Keresztes, L\'aszl\'o \'Arp\'ad Gergely | Minimally coupled scalar fields as imperfect fluids | 6 pages, to appear in Physical Review D | Phys. Rev. D 102, 024044 (2020) | 10.1103/PhysRevD.102.024044 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the issue of the fluid description of minimally coupled scalar
fields. While in a cosmological setup the interpretation of a time-evolving
scalar field as a perfect fluid is well-understood, the situation is more
intricate when the scalar field is static, but has a spatial gradient, a
situation motivated by black hole perturbations in scalar-tensor theories. Then
the scalar field is interpreted as either a particular imperfect fluid of type
I or a superposition of a pair of leftgoing (incoming) and rightgoing
(outgoing) null dusts with a perfect fluid. Finally, when the scalar gradient
is null, it is equivalent to an imperfect fluid of type II, degenerating into
null dust when the energy conditions are imposed. We also propose the suitable
action in terms of the fluid pressure components for each case and discuss the
variational principle for a generic class of minimally coupled scalar fields.
| [
{
"created": "Thu, 2 Jul 2020 18:08:00 GMT",
"version": "v1"
}
] | 2020-07-21 | [
[
"Gergely",
"Cecília",
""
],
[
"Keresztes",
"Zoltán",
""
],
[
"Gergely",
"László Árpád",
""
]
] | We revisit the issue of the fluid description of minimally coupled scalar fields. While in a cosmological setup the interpretation of a time-evolving scalar field as a perfect fluid is well-understood, the situation is more intricate when the scalar field is static, but has a spatial gradient, a situation motivated by black hole perturbations in scalar-tensor theories. Then the scalar field is interpreted as either a particular imperfect fluid of type I or a superposition of a pair of leftgoing (incoming) and rightgoing (outgoing) null dusts with a perfect fluid. Finally, when the scalar gradient is null, it is equivalent to an imperfect fluid of type II, degenerating into null dust when the energy conditions are imposed. We also propose the suitable action in terms of the fluid pressure components for each case and discuss the variational principle for a generic class of minimally coupled scalar fields. |
2004.11303 | Joao G. Rosa | Paulo B. Ferraz, Thomas W. Kephart and Jo\~ao G. Rosa | Superradiant pion clouds around primordial black holes | 17 pages, 8 figures | null | 10.1088/1475-7516/2022/07/026 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that highly spinning primordial black holes of mass $M\sim 10^{12}$
kg, potentially born in a matter-dominated era after inflation, can produce
clouds of pions in their vicinity via the superradiant instability, with
densities up to that of nuclear matter. We discuss the electromagnetic
signatures of this process, via neutral pion decay and charged pion
annihilation into photons, computing in particular their contribution to the
isotropic gamma-ray background. This allows us to place upper bounds on the
abundance of such primordial black holes that are comparable to the ones
obtained from Hawking evaporation. We also discuss the possibility of directly
observing such clouds in high-redshift superclusters.
| [
{
"created": "Thu, 23 Apr 2020 16:35:53 GMT",
"version": "v1"
}
] | 2022-07-27 | [
[
"Ferraz",
"Paulo B.",
""
],
[
"Kephart",
"Thomas W.",
""
],
[
"Rosa",
"João G.",
""
]
] | We show that highly spinning primordial black holes of mass $M\sim 10^{12}$ kg, potentially born in a matter-dominated era after inflation, can produce clouds of pions in their vicinity via the superradiant instability, with densities up to that of nuclear matter. We discuss the electromagnetic signatures of this process, via neutral pion decay and charged pion annihilation into photons, computing in particular their contribution to the isotropic gamma-ray background. This allows us to place upper bounds on the abundance of such primordial black holes that are comparable to the ones obtained from Hawking evaporation. We also discuss the possibility of directly observing such clouds in high-redshift superclusters. |
1911.12431 | Giannis Papagiannopoulos | G. Papagiannopoulos, Pavlina Tsiapi, Spyros Basilakos and Andronikos
Paliathanasis | Dynamics and cosmological evolution in {\Lambda}-varying cosmology | This manuscript has been accepted for publication in the European
Physical Journal C | null | 10.1140/epjc/s10052-019-7600-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the dynamical properties of a large body of varying vacuum
cosmologies for which dark matter interacts with vacuum. In particular,
performing the critical point analysis we investigate the existence and the
stability of cosmological solutions which describe de-Sitter, radiation and
matter dominated eras. We find several cases of varying vacuum models that
admit stable critical points, hence they can be used in describing the cosmic
history.
| [
{
"created": "Wed, 27 Nov 2019 21:36:46 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Jan 2020 00:15:08 GMT",
"version": "v2"
}
] | 2020-02-19 | [
[
"Papagiannopoulos",
"G.",
""
],
[
"Tsiapi",
"Pavlina",
""
],
[
"Basilakos",
"Spyros",
""
],
[
"Paliathanasis",
"Andronikos",
""
]
] | We study the dynamical properties of a large body of varying vacuum cosmologies for which dark matter interacts with vacuum. In particular, performing the critical point analysis we investigate the existence and the stability of cosmological solutions which describe de-Sitter, radiation and matter dominated eras. We find several cases of varying vacuum models that admit stable critical points, hence they can be used in describing the cosmic history. |
2312.16522 | Francisco F. Lopez-Ruiz | Victor Aldaya, Julio Guerrero and Francisco F. L\'opez-Ruiz | Tachyons in "momentum-space'' representation | 13 pages | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The momentum space associated with "tachyonic particles" proves to be rather
intricate, departing very much from the ordinary dual to Minkowski space
directly parametrized by space-time translations of the Poincar\'e group. In
fact, although described by the constants of motion (Noether invariants)
associated with space-time translations, they depend non-trivially on the
parameters of the rotation subgroup. However, once the momentum space is
parametrized by the Noether invariants, it behaves exactly as that of ordinary
particles. On the other hand, the evolution parameter is no longer the one
associated with time translation, whose Noether invariant, $P_o$, is now a
basic one. Evolution takes place in a spatial direction. These facts not only
make difficult the computation of the corresponding representation, but also
force us to a sound revision of several traditional ingredients related to
Cauchy hypersurface, scalar product and, of course, causality. After that, the
theory becomes consistent and could shed new light on some special physical
situations like inflation or traveling inside a black hole.
| [
{
"created": "Wed, 27 Dec 2023 11:01:34 GMT",
"version": "v1"
}
] | 2023-12-29 | [
[
"Aldaya",
"Victor",
""
],
[
"Guerrero",
"Julio",
""
],
[
"López-Ruiz",
"Francisco F.",
""
]
] | The momentum space associated with "tachyonic particles" proves to be rather intricate, departing very much from the ordinary dual to Minkowski space directly parametrized by space-time translations of the Poincar\'e group. In fact, although described by the constants of motion (Noether invariants) associated with space-time translations, they depend non-trivially on the parameters of the rotation subgroup. However, once the momentum space is parametrized by the Noether invariants, it behaves exactly as that of ordinary particles. On the other hand, the evolution parameter is no longer the one associated with time translation, whose Noether invariant, $P_o$, is now a basic one. Evolution takes place in a spatial direction. These facts not only make difficult the computation of the corresponding representation, but also force us to a sound revision of several traditional ingredients related to Cauchy hypersurface, scalar product and, of course, causality. After that, the theory becomes consistent and could shed new light on some special physical situations like inflation or traveling inside a black hole. |
2109.13260 | Jorma Louko | Keith K. Ng, Chen Zhang, Jorma Louko, Robert B. Mann | A Little Excitement Across the Horizon | 11 pages, 7 figures. v4: Presentational expansion and reorganisation | New J. Phys. 24, 103018 (2022) | 10.1088/1367-2630/ac9547 | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | We analyse numerically the transitions in an Unruh-DeWitt detector, coupled
linearly to a massless scalar field, in radial infall in (3+1)-dimensional
Schwarzschild spacetime. In the Hartle-Hawking and Unruh states, the transition
probability attains a small local extremum near the horizon-crossing and is
then moderately enhanced on approaching the singularity. In the Boulware state,
the transition probability drops on approaching the horizon. The unexpected
near-horizon extremum arises numerically from angular momentum superpositions,
with a deeper physical explanation to be found.
| [
{
"created": "Mon, 27 Sep 2021 18:00:04 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Oct 2021 07:13:22 GMT",
"version": "v2"
},
{
"created": "Mon, 2 May 2022 22:13:52 GMT",
"version": "v3"
},
{
"created": "Mon, 24 Oct 2022 13:42:32 GMT",
"version": "v4"
}
] | 2022-10-25 | [
[
"Ng",
"Keith K.",
""
],
[
"Zhang",
"Chen",
""
],
[
"Louko",
"Jorma",
""
],
[
"Mann",
"Robert B.",
""
]
] | We analyse numerically the transitions in an Unruh-DeWitt detector, coupled linearly to a massless scalar field, in radial infall in (3+1)-dimensional Schwarzschild spacetime. In the Hartle-Hawking and Unruh states, the transition probability attains a small local extremum near the horizon-crossing and is then moderately enhanced on approaching the singularity. In the Boulware state, the transition probability drops on approaching the horizon. The unexpected near-horizon extremum arises numerically from angular momentum superpositions, with a deeper physical explanation to be found. |
1309.6375 | Shao-Wen Wei | Shao-Wen Wei, Yu-Xiao Liu | Establishing a universal relation between gravitational waves and black
hole lensing | 6 pages, 3 figures | Phys. Rev. D 89, 047502 (2014) | 10.1103/PhysRevD.89.047502 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black hole lensing and gravitational waves are, respectively, closely
dependent of the property of the lens and radiation source. In this letter, a
universal relation between them is established for a rotating black hole acting
simultaneously as a lens and a gravitational wave source, in an asymptotically
flat spacetime. The relation only relies on the lens geometry and observable,
while is independent of the specific nature of the black hole. Therefore, the
possible gravitational wave sources could be located with modern astronomical
instrument from the side of the lensing without knowing the specific nature of
the black hole lens. Moreover, the low bound of the frequency of the
gravitational waves can also be well determined.
| [
{
"created": "Wed, 25 Sep 2013 00:47:02 GMT",
"version": "v1"
}
] | 2014-02-26 | [
[
"Wei",
"Shao-Wen",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | Black hole lensing and gravitational waves are, respectively, closely dependent of the property of the lens and radiation source. In this letter, a universal relation between them is established for a rotating black hole acting simultaneously as a lens and a gravitational wave source, in an asymptotically flat spacetime. The relation only relies on the lens geometry and observable, while is independent of the specific nature of the black hole. Therefore, the possible gravitational wave sources could be located with modern astronomical instrument from the side of the lensing without knowing the specific nature of the black hole lens. Moreover, the low bound of the frequency of the gravitational waves can also be well determined. |
2005.01122 | Suratna Das | Suratna Das and Rudnei O. Ramos | On the graceful exit problem in warm inflation | 8 pages, 4 figures, double column, v2: 12 pages, 5 figures, version
matched with the published version in PRD | Phys. Rev. D 103, 123520 (2021) | 10.1103/PhysRevD.103.123520 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A seemingly simple question, how does warm inflation exit gracefully?, has a
more complex answer than in a cold paradigm. It has been highlighted here that
whether warm inflation exits gracefully depends on three independent choices:
The form of the potential, the choice of the warm inflation model (i.e., on the
form of its dissipative coefficient) and the regime, of weak or strong
dissipation, characterizing the warm inflation dynamics. Generic conditions on
slow-roll parameters and several constraints on the different model parameters
required for warm inflation to exit gracefully are derived.
| [
{
"created": "Sun, 3 May 2020 16:05:15 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Jun 2021 16:55:40 GMT",
"version": "v2"
}
] | 2021-06-16 | [
[
"Das",
"Suratna",
""
],
[
"Ramos",
"Rudnei O.",
""
]
] | A seemingly simple question, how does warm inflation exit gracefully?, has a more complex answer than in a cold paradigm. It has been highlighted here that whether warm inflation exits gracefully depends on three independent choices: The form of the potential, the choice of the warm inflation model (i.e., on the form of its dissipative coefficient) and the regime, of weak or strong dissipation, characterizing the warm inflation dynamics. Generic conditions on slow-roll parameters and several constraints on the different model parameters required for warm inflation to exit gracefully are derived. |
gr-qc/9512004 | Beverly Berger | Beverly K. Berger | Numerical Investigation of Cosmological Singularities | Based on lectures given at WE-Heraeus-Seminar on Relativity and
Scientific Computing. 24 pages, Latex, 9 figures in separate file BHfigs.uu,
uses psfig.tex | null | null | null | gr-qc | null | We describe a numerical approach to address the BKL conjecture that the
generic cosmological singularity is locally Mixmaster-like. We consider
application of a symplectic PDE solver to three models of increasing
complexity--spatially homogeneous (vacuum) Mixmaster cosmologies where we
compare the symplectic ODE solver to a Runge-Kutta one, the (plane symmetric,
vacuum) Gowdy universe on $T^3 \times R$ whose dynamical degrees of freedom
satisfy nonlinearly coupled PDE's in one spatial dimension and time, and U(1)
symmetric, vacuum cosmologies on $T^3 \times R$ which are the simplest
spatially inhomogeneous universes in which local Mixmaster dynamics is allowed.
| [
{
"created": "Fri, 1 Dec 1995 21:25:19 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Berger",
"Beverly K.",
""
]
] | We describe a numerical approach to address the BKL conjecture that the generic cosmological singularity is locally Mixmaster-like. We consider application of a symplectic PDE solver to three models of increasing complexity--spatially homogeneous (vacuum) Mixmaster cosmologies where we compare the symplectic ODE solver to a Runge-Kutta one, the (plane symmetric, vacuum) Gowdy universe on $T^3 \times R$ whose dynamical degrees of freedom satisfy nonlinearly coupled PDE's in one spatial dimension and time, and U(1) symmetric, vacuum cosmologies on $T^3 \times R$ which are the simplest spatially inhomogeneous universes in which local Mixmaster dynamics is allowed. |
1302.5695 | Martin Bojowald | Martin Bojowald, Golam Mortuza Hossain, Mikhail Kagan, Casey Tomlin | Quantum matter in quantum space-time | 17 pages, v2: further references and more detailed conclusions | Quantum Matter 2 (2013) 436-443 | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum matter in quantum space-time is discussed using general properties of
energy-conservation laws. As a rather radical conclusion, it is found that
standard methods of differential geometry and quantum field theory on curved
space-time are inapplicable in canonical quantum gravity, even at the level of
effective equations.
| [
{
"created": "Fri, 22 Feb 2013 20:30:10 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Mar 2013 12:24:43 GMT",
"version": "v2"
}
] | 2013-11-13 | [
[
"Bojowald",
"Martin",
""
],
[
"Hossain",
"Golam Mortuza",
""
],
[
"Kagan",
"Mikhail",
""
],
[
"Tomlin",
"Casey",
""
]
] | Quantum matter in quantum space-time is discussed using general properties of energy-conservation laws. As a rather radical conclusion, it is found that standard methods of differential geometry and quantum field theory on curved space-time are inapplicable in canonical quantum gravity, even at the level of effective equations. |
gr-qc/0208055 | null | K. Ghosh | Entropy of A Scalar Field In (3 + 1)-dimensional Taub-NUT Space-Time | Revtex, 26 pages, A few sections are added | null | 10.1103/PhysRevD.67.124027 | null | gr-qc | null | In this article we discuss a few aspects of the space-time description of
fields and particles. In sectionn II and III we demonstrate that fields are as
fundamental as particles. In section IV we discuss non-equivalence of the
Schwarzschild coordinates and the Kruskal-Szekeres coordinates. In section V we
discuss that it is not possible to define causal structure in discrete
space-time manifolds. In App.B we show that a line is not just a collection of
points and we will have to introduce one-dimensional line-intervals as
fundamental geometric elements. Similar discussions are valid for area and
volume-elements. In App.C and App.D we make a comparative study of Quantum
Field Theory and Quantum Mechanics and contradictions associated with
probabilistics interpretation of these theories with space-time dimensional
analysis. In App.E and App.F we discuss the geometry of Robertson-Walker model
and electrostatic behavior of dielectrics respectively. In Sup.I we discuss the
regularity of Spin-Spherical harmonics and also derive an energy-spectrum which
is free of back-reaction problem. In Sup.II we discuss that in general the
integral version of Gauss's divergence law in Electrodynamics is not valid and
rederive Gauss's law and Ampere's law. We also show that under duality
transformation magnetic charge conservation law do not remain time reversal
symmetric. In Sup.III we derive the complete equation for viscous compressible
fluids and make a few comments regarding some cotradictions associated with
boundary conditions for fluid dynamics. In Sup.IV we discuss a few aspects on
double slit interference experiments. We conclude this article with a few
questions in Sup.V.
| [
{
"created": "Mon, 19 Aug 2002 10:58:52 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Nov 2002 08:06:15 GMT",
"version": "v2"
},
{
"created": "Sun, 19 Nov 2006 18:31:34 GMT",
"version": "v3"
}
] | 2015-06-25 | [
[
"Ghosh",
"K.",
""
]
] | In this article we discuss a few aspects of the space-time description of fields and particles. In sectionn II and III we demonstrate that fields are as fundamental as particles. In section IV we discuss non-equivalence of the Schwarzschild coordinates and the Kruskal-Szekeres coordinates. In section V we discuss that it is not possible to define causal structure in discrete space-time manifolds. In App.B we show that a line is not just a collection of points and we will have to introduce one-dimensional line-intervals as fundamental geometric elements. Similar discussions are valid for area and volume-elements. In App.C and App.D we make a comparative study of Quantum Field Theory and Quantum Mechanics and contradictions associated with probabilistics interpretation of these theories with space-time dimensional analysis. In App.E and App.F we discuss the geometry of Robertson-Walker model and electrostatic behavior of dielectrics respectively. In Sup.I we discuss the regularity of Spin-Spherical harmonics and also derive an energy-spectrum which is free of back-reaction problem. In Sup.II we discuss that in general the integral version of Gauss's divergence law in Electrodynamics is not valid and rederive Gauss's law and Ampere's law. We also show that under duality transformation magnetic charge conservation law do not remain time reversal symmetric. In Sup.III we derive the complete equation for viscous compressible fluids and make a few comments regarding some cotradictions associated with boundary conditions for fluid dynamics. In Sup.IV we discuss a few aspects on double slit interference experiments. We conclude this article with a few questions in Sup.V. |
2205.06240 | Hector O. Silva | Matthew Elley, Hector O. Silva, Helvi Witek, Nicol\'as Yunes | Spin-induced dynamical scalarization, de-scalarization and stealthness
in scalar-Gauss-Bonnet gravity during black hole coalescence | 16 pages, 12 figures | null | 10.1103/PhysRevD.106.044018 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | Particular couplings between a scalar field and the Gauss-Bonnet invariant
lead to spontaneous scalarization of black holes. Here we continue our work on
simulating this phenomenon in the context of binary black hole systems. We
consider a negative coupling for which the black-hole spin plays a major role
in the scalarization process. We find two main phenomena: (i) dynamical
descalarization, in which initially scalarized black holes form an unscalarized
remnant, and (ii) dynamical scalarization, whereby the late merger of initially
unscalarized black holes can cause scalar hair to grow. An important
consequence of the latter case is that modifications to the gravitational
waveform due to the scalar field may only occur post-merger, as its presence is
hidden during the entirety of the inspiral. However, with a sufficiently strong
coupling, we find that scalarization can occur before the remnant has even
formed. We close with a discussion of observational implications for
gravitational-wave tests of general relativity.
| [
{
"created": "Thu, 12 May 2022 17:37:17 GMT",
"version": "v1"
}
] | 2022-08-31 | [
[
"Elley",
"Matthew",
""
],
[
"Silva",
"Hector O.",
""
],
[
"Witek",
"Helvi",
""
],
[
"Yunes",
"Nicolás",
""
]
] | Particular couplings between a scalar field and the Gauss-Bonnet invariant lead to spontaneous scalarization of black holes. Here we continue our work on simulating this phenomenon in the context of binary black hole systems. We consider a negative coupling for which the black-hole spin plays a major role in the scalarization process. We find two main phenomena: (i) dynamical descalarization, in which initially scalarized black holes form an unscalarized remnant, and (ii) dynamical scalarization, whereby the late merger of initially unscalarized black holes can cause scalar hair to grow. An important consequence of the latter case is that modifications to the gravitational waveform due to the scalar field may only occur post-merger, as its presence is hidden during the entirety of the inspiral. However, with a sufficiently strong coupling, we find that scalarization can occur before the remnant has even formed. We close with a discussion of observational implications for gravitational-wave tests of general relativity. |
1306.1177 | Jorge P\'aramos | Orfeu Bertolami, Jorge P\'aramos | Homogeneous spherically symmetric bodies with a nonminimal coupling
between curvature and matter: the choice of the Lagrangian density for matter | 18 pages, 3 figures. Published in General Relativity and Gravitation | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study how a nonminimal coupling between matter and gravity
can modify the structure of a homogeneous spherical body. The physical
relevance of the adopted Lagrangian density is ascertained, with results
obtained for two different choices of the latter.
| [
{
"created": "Wed, 5 Jun 2013 17:15:43 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Nov 2014 19:42:39 GMT",
"version": "v2"
}
] | 2014-11-19 | [
[
"Bertolami",
"Orfeu",
""
],
[
"Páramos",
"Jorge",
""
]
] | In this work we study how a nonminimal coupling between matter and gravity can modify the structure of a homogeneous spherical body. The physical relevance of the adopted Lagrangian density is ascertained, with results obtained for two different choices of the latter. |
1511.05420 | Sijie Gao | Sijie Gao and Xiaobao Wang | A static spherically symmetric thin shell wormhole colliding with a
spherical thin shell | 14 pages, 4 figures | Phys. Rev. D 93, 064027 (2016) | 10.1103/PhysRevD.93.064027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a static spherically symmetric thin shell wormhole collides with
another thin shell consisting of ordinary matter. By employing the geometrical
constraint, which leads to the conservation of energy and momentum, we show
that the state after the collision can be solved from the initial data. In the
low speed approximation, the solutions are rather simple. The shell may either
bounce back or pass through the wormhole. In either case, the wormhole shrinks
right after the collision. In the "bouncing" case, a surprising result is that
the radial speeds before and after the collision satisfy an addition law, which
is independent of the masses of the wormhole and the shell. Once the shell
passes through the wormhole, we find that the shell always expands. However,
the expansion rate is the same as its collapsing rate right before the
collision. Finally, we find out the solution for the shell moving together with
the wormhole.
| [
{
"created": "Tue, 17 Nov 2015 14:40:09 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Mar 2016 13:18:32 GMT",
"version": "v2"
}
] | 2016-03-23 | [
[
"Gao",
"Sijie",
""
],
[
"Wang",
"Xiaobao",
""
]
] | We consider a static spherically symmetric thin shell wormhole collides with another thin shell consisting of ordinary matter. By employing the geometrical constraint, which leads to the conservation of energy and momentum, we show that the state after the collision can be solved from the initial data. In the low speed approximation, the solutions are rather simple. The shell may either bounce back or pass through the wormhole. In either case, the wormhole shrinks right after the collision. In the "bouncing" case, a surprising result is that the radial speeds before and after the collision satisfy an addition law, which is independent of the masses of the wormhole and the shell. Once the shell passes through the wormhole, we find that the shell always expands. However, the expansion rate is the same as its collapsing rate right before the collision. Finally, we find out the solution for the shell moving together with the wormhole. |
0712.3539 | Stephen Merkowitz | Stephen M. Merkowitz, Philip W. Dabney, Jeffrey C. Livas, Jan F.
McGarry, Gregory A. Neumann, and Thomas W. Zagwodzki | Laser Ranging for Gravitational, Lunar, and Planetary Science | 14 pages, 3 figures, To appear in the International Journal of Modern
Physics D | Int.J.Mod.Phys.D16:2151-2164,2008 | 10.1142/S0218271807011565 | null | gr-qc | null | More precise lunar and Martian ranging will enable unprecedented tests of
Einstein's theory of General Relativity and well as lunar and planetary
science. NASA is currently planning several missions to return to the Moon, and
it is natural to consider if precision laser ranging instruments should be
included. New advanced retroreflector arrays at carefully chosen landing sites
would have an immediate positive impact on lunar and gravitational studies.
Laser transponders are currently being developed that may offer an advantage
over passive ranging, and could be adapted for use on Mars and other distant
objects. Precision ranging capability can also be combined with optical
communications for an extremely versatile instrument. In this paper we discuss
the science that can be gained by improved lunar and Martian ranging along with
several technologies that can be used for this purpose.
| [
{
"created": "Thu, 20 Dec 2007 19:22:40 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Merkowitz",
"Stephen M.",
""
],
[
"Dabney",
"Philip W.",
""
],
[
"Livas",
"Jeffrey C.",
""
],
[
"McGarry",
"Jan F.",
""
],
[
"Neumann",
"Gregory A.",
""
],
[
"Zagwodzki",
"Thomas W.",
""
]
] | More precise lunar and Martian ranging will enable unprecedented tests of Einstein's theory of General Relativity and well as lunar and planetary science. NASA is currently planning several missions to return to the Moon, and it is natural to consider if precision laser ranging instruments should be included. New advanced retroreflector arrays at carefully chosen landing sites would have an immediate positive impact on lunar and gravitational studies. Laser transponders are currently being developed that may offer an advantage over passive ranging, and could be adapted for use on Mars and other distant objects. Precision ranging capability can also be combined with optical communications for an extremely versatile instrument. In this paper we discuss the science that can be gained by improved lunar and Martian ranging along with several technologies that can be used for this purpose. |
1906.05861 | G. S. Bisnovatyi-Kogan | G.S. Bisnovatyi-Kogan and M. Merafina | Two body problem in presence of cosmological constant | 15 pages, 3 figures | null | 10.1142/S0218271819501554 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the Kepler two-body problem in presence of the cosmological
constant $\Lambda$. Contrary to the classical case, where finite solutions
exist for any angular momentum of the system $L$, in presence of $\Lambda$
finite solutions exist only in the interval $0<L< L_{lim}(\Lambda)$. The
qualitative picture of the two-body motion is described, and critical
parameters of the problem are found. Application are made to the relative
motion of the Local Group and Virgo cluster.
| [
{
"created": "Thu, 13 Jun 2019 16:09:12 GMT",
"version": "v1"
}
] | 2019-10-23 | [
[
"Bisnovatyi-Kogan",
"G. S.",
""
],
[
"Merafina",
"M.",
""
]
] | We consider the Kepler two-body problem in presence of the cosmological constant $\Lambda$. Contrary to the classical case, where finite solutions exist for any angular momentum of the system $L$, in presence of $\Lambda$ finite solutions exist only in the interval $0<L< L_{lim}(\Lambda)$. The qualitative picture of the two-body motion is described, and critical parameters of the problem are found. Application are made to the relative motion of the Local Group and Virgo cluster. |
gr-qc/9811069 | Esteban Calzetta | Esteban Calzetta | Noise induced inflation | Latex, 15 pages, 3 figures in eps format. To appear in the
Proceedings of the 1998 Peiresq Workshop, M. Castagnino, E. Gunzig and E.
Verdaguer (editors) | Int.J.Theor.Phys.38:2755-2778,1999 | 10.1023/A:1026687527635 | EX112-1 | gr-qc | null | We consider a closed Friedmann-Robertson-Walker Universe driven by the back
reaction from a massless, non-conformally coupled quantum scalar field. We show
that the back-reaction of the quantum field is able to drive the cosmological
scale factor over the barrier of the classical potential so that if the
universe starts near zero scale factor (initial singularity) it can make the
transition to an exponentially expanding de Sitter phase, with a probability
comparable to that from quantum tunneling processes. The emphasis throughout is
on the stochastic nature of back reaction, which comes from the quantum
fluctuations of the fundamental fields.
| [
{
"created": "Thu, 19 Nov 1998 20:27:21 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Calzetta",
"Esteban",
""
]
] | We consider a closed Friedmann-Robertson-Walker Universe driven by the back reaction from a massless, non-conformally coupled quantum scalar field. We show that the back-reaction of the quantum field is able to drive the cosmological scale factor over the barrier of the classical potential so that if the universe starts near zero scale factor (initial singularity) it can make the transition to an exponentially expanding de Sitter phase, with a probability comparable to that from quantum tunneling processes. The emphasis throughout is on the stochastic nature of back reaction, which comes from the quantum fluctuations of the fundamental fields. |
gr-qc/0203037 | Masaru Shibata | Masaru Shibata and Koji Uryu | Gravitational Waves from the Merger of Binary Neutron Stars in a Fully
General Relativistic Simulation | 40 pages; pubslihed in Prog. Theor. Phys. 107 (2002), 265 | Prog.Theor.Phys. 107 (2002) 265 | 10.1143/PTP.107.265 | null | gr-qc | null | We performed 3D numerical simulations of the merger of equal-mass binary
neutron stars in full general relativity using a new large scale supercomputer.
We take the typical grid size as (505,505,253) for (x,y,z) and the maximum grid
size as (633,633,317). These grid numbers enable us to put the outer boundaries
of the computational domain near the local wave zone and hence to calculate
gravitational waveforms of good accuracy (within $\sim 10%$ error) for the
first time. To model neutron stars, we adopt a $\Gamma$-law equation of state
in the form $P=(\Gamma-1)\rho\epsilon$, where P, $\rho$, $\varep$ and $\Gamma$
are the pressure, rest mass density, specific internal energy, and adiabatic
constant. It is found that gravitational waves in the merger stage have
characteristic features that reflect the formed objects. In the case that a
massive, transient neutron star is formed, its quasi-periodic oscillations are
excited for a long duration, and this property is reflected clearly by the
quasi-periodic nature of waveforms and the energy luminosity. In the case of
black hole formation, the waveform and energy luminosity are likely damped
after a short merger stage. However, a quasi-periodic oscillation can still be
seen for a certain duration, because an oscillating transient massive object is
formed during the merger. This duration depends strongly on the initial
compactness of neutron stars and is reflected in the Fourier spectrum of
gravitational waves. To confirm our results and to calibrate the accuracy of
gravitational waveforms, we carried out a wide variety of test simulations,
changing the resolution and size of the computational domain.
| [
{
"created": "Tue, 12 Mar 2002 03:27:50 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Shibata",
"Masaru",
""
],
[
"Uryu",
"Koji",
""
]
] | We performed 3D numerical simulations of the merger of equal-mass binary neutron stars in full general relativity using a new large scale supercomputer. We take the typical grid size as (505,505,253) for (x,y,z) and the maximum grid size as (633,633,317). These grid numbers enable us to put the outer boundaries of the computational domain near the local wave zone and hence to calculate gravitational waveforms of good accuracy (within $\sim 10%$ error) for the first time. To model neutron stars, we adopt a $\Gamma$-law equation of state in the form $P=(\Gamma-1)\rho\epsilon$, where P, $\rho$, $\varep$ and $\Gamma$ are the pressure, rest mass density, specific internal energy, and adiabatic constant. It is found that gravitational waves in the merger stage have characteristic features that reflect the formed objects. In the case that a massive, transient neutron star is formed, its quasi-periodic oscillations are excited for a long duration, and this property is reflected clearly by the quasi-periodic nature of waveforms and the energy luminosity. In the case of black hole formation, the waveform and energy luminosity are likely damped after a short merger stage. However, a quasi-periodic oscillation can still be seen for a certain duration, because an oscillating transient massive object is formed during the merger. This duration depends strongly on the initial compactness of neutron stars and is reflected in the Fourier spectrum of gravitational waves. To confirm our results and to calibrate the accuracy of gravitational waveforms, we carried out a wide variety of test simulations, changing the resolution and size of the computational domain. |
1410.7698 | Gregory B. Cook | Gregory B. Cook and Maxim Zalutskiy | Gravitational perturbations of the Kerr geometry: High-accuracy study | 30 pages, 24 figures; Corrected typos, including misspelling in
author's name | null | 10.1103/PhysRevD.90.124021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present results from a new code for computing gravitational perturbations
of the Kerr geometry. This new code carefully maintains high precision to allow
us to obtain high-accuracy solutions for the gravitational quasinormal modes of
the Kerr space-time. Part of this new code is an implementation of a spectral
method for solving the angular Teukolsky equation that, to our knowledge, has
not been used before for determining quasinormal modes. We focus our attention
on two main areas. First, we explore the behavior of these quasinormal modes in
the extreme limit of Kerr, where the frequency of certain modes approaches
accumulation points on the real axis. We compare our results with recent
analytic predictions of the behavior of these modes near the accumulation
points and find good agreement. Second, we explore the behavior of solutions of
modes that approach the special frequency $M\omega=-2i$ in the Schwarzschild
limit. Our high-accuracy methods allow us to more closely approach the
Schwarzschild limit than was possible with previous numerical studies. Unlike
previous work, we find excellent agreement with analytic predictions of the
behavior near this special frequency. We include a detailed description of our
methods, and make use of the theory of confluent Heun differential equations
throughout. In particular, we make use of confluent Heun polynomials to help
shed some light on the controversy of the existence, or not, of quasinormal and
total-transmission modes at certain special frequencies in the Schwarzschild
limit.
| [
{
"created": "Tue, 28 Oct 2014 17:01:09 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Nov 2014 15:15:02 GMT",
"version": "v2"
}
] | 2015-06-23 | [
[
"Cook",
"Gregory B.",
""
],
[
"Zalutskiy",
"Maxim",
""
]
] | We present results from a new code for computing gravitational perturbations of the Kerr geometry. This new code carefully maintains high precision to allow us to obtain high-accuracy solutions for the gravitational quasinormal modes of the Kerr space-time. Part of this new code is an implementation of a spectral method for solving the angular Teukolsky equation that, to our knowledge, has not been used before for determining quasinormal modes. We focus our attention on two main areas. First, we explore the behavior of these quasinormal modes in the extreme limit of Kerr, where the frequency of certain modes approaches accumulation points on the real axis. We compare our results with recent analytic predictions of the behavior of these modes near the accumulation points and find good agreement. Second, we explore the behavior of solutions of modes that approach the special frequency $M\omega=-2i$ in the Schwarzschild limit. Our high-accuracy methods allow us to more closely approach the Schwarzschild limit than was possible with previous numerical studies. Unlike previous work, we find excellent agreement with analytic predictions of the behavior near this special frequency. We include a detailed description of our methods, and make use of the theory of confluent Heun differential equations throughout. In particular, we make use of confluent Heun polynomials to help shed some light on the controversy of the existence, or not, of quasinormal and total-transmission modes at certain special frequencies in the Schwarzschild limit. |
2304.06481 | Shouvik Sadhukhan Mr | Shouvik Sadhukhan, Alokananda Kar and Surajit Chattopadhyay | A Non-Linear Type Equation of State and Cosmic Fluid Dynamics | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this chapter we have introduced a special type of non-linear equation of
state to discuss the cosmological evolution mechanism. The new equation of
state is a four parameters model which can be represented as
$p=A\rho+B\rho^2-\frac{C}{\rho^{\alpha}}$ where $B=A\beta-\gamma$. The
evolution of universe have been interpreted by fluid dynamics. The
reconstruction of Chaplygin gas and Van-Der-Waals (VDW) fluid equation of
states have been done from the parametric analysis of this new non-linear
model. Different cosmological phases like Quintom, Quintessence and warm
universe have been discussed here. Finally, we have provided a comparative
studies of this model with other non-linear fluid solutions.
| [
{
"created": "Tue, 4 Apr 2023 08:05:49 GMT",
"version": "v1"
}
] | 2023-04-14 | [
[
"Sadhukhan",
"Shouvik",
""
],
[
"Kar",
"Alokananda",
""
],
[
"Chattopadhyay",
"Surajit",
""
]
] | In this chapter we have introduced a special type of non-linear equation of state to discuss the cosmological evolution mechanism. The new equation of state is a four parameters model which can be represented as $p=A\rho+B\rho^2-\frac{C}{\rho^{\alpha}}$ where $B=A\beta-\gamma$. The evolution of universe have been interpreted by fluid dynamics. The reconstruction of Chaplygin gas and Van-Der-Waals (VDW) fluid equation of states have been done from the parametric analysis of this new non-linear model. Different cosmological phases like Quintom, Quintessence and warm universe have been discussed here. Finally, we have provided a comparative studies of this model with other non-linear fluid solutions. |
gr-qc/0506056 | Richard Woodard | N. C. Tsamis (University of Crete) and R. P. Woodard (University of
Florida) | Dimensionally Regulated Graviton 1-Point Function in de Sitter | 25 pages, LaTeX 2epsilon, uses Axodraw for one figure, revised to add
some references | Annals Phys. 321 (2006) 875-893 | 10.1016/j.aop.2005.08.004 | UFIFT-QG-05-03 | gr-qc astro-ph hep-ph | null | We use dimensional regularization to compute the 1PI 1-point function of
quantum gravity at one loop order in a locally de Sitter background. As with
other computations, the result is a finite constant at this order. It
corresponds to a small positive renormalization of the cosmological constant.
| [
{
"created": "Thu, 9 Jun 2005 14:30:59 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Aug 2005 21:30:04 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Tsamis",
"N. C.",
"",
"University of Crete"
],
[
"Woodard",
"R. P.",
"",
"University of\n Florida"
]
] | We use dimensional regularization to compute the 1PI 1-point function of quantum gravity at one loop order in a locally de Sitter background. As with other computations, the result is a finite constant at this order. It corresponds to a small positive renormalization of the cosmological constant. |
gr-qc/0306053 | Andreas Freise | A. Freise (GEO600 team) | Dual recycling for GEO600 | 6 pages | null | null | null | gr-qc | null | Dual recycling is the combination of signal recycling and power recycling;
both optical techniques improve the shot-noise-limited sensitivity of
interferometric gravitational-wave detectors. In addition, signal recycling can
reduce the loss of light power due to imperfect interference and allows, in
principle, to beat the standard quantum limit. The interferometric
gravitational-wave detector GEO600 is the first detector to use signal
recycling. We have recently equipped the detector with a signal-recycling
mirror with a transmittance of 1%. In this paper, we present details of the
detector commissioning and the first locks of the dual- recycled
interferometer.
| [
{
"created": "Thu, 12 Jun 2003 15:55:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Freise",
"A.",
"",
"GEO600 team"
]
] | Dual recycling is the combination of signal recycling and power recycling; both optical techniques improve the shot-noise-limited sensitivity of interferometric gravitational-wave detectors. In addition, signal recycling can reduce the loss of light power due to imperfect interference and allows, in principle, to beat the standard quantum limit. The interferometric gravitational-wave detector GEO600 is the first detector to use signal recycling. We have recently equipped the detector with a signal-recycling mirror with a transmittance of 1%. In this paper, we present details of the detector commissioning and the first locks of the dual- recycled interferometer. |
2207.14778 | Marco Antonelli | Lorenzo Gavassino, Marco Antonelli, Brynmor Haskell | Symmetric-hyperbolic quasi-hydrodynamics | 25 pages, 4 figures | Phys. Rev. D 106, 056010 - Published 13 September 2022 | 10.1103/PhysRevD.106.056010 | null | gr-qc hep-th physics.flu-dyn | http://creativecommons.org/licenses/by/4.0/ | We set up a general framework for systematically building and classifying, in
the linear regime, causal and stable dissipative hydrodynamic theories that,
alongside with the usual hydrodynamic modes, also allow for an arbitrary number
of non-hydrodynamic modes with complex dispersion relation (such theories are
often referred to as "quasi-hydrodynamic"). To increase the number of
non-hydrodynamic modes one needs to add more effective fields to the model. The
system of equations governing this class of quasi-hydrodynamic theories is
symmetric hyperbolic, thermodynamically consistent (i.e. the entropy is a
Lyapunov function) and can be derived from an action principle. As a first
application of the formalism, we prove that, in the linear regime, the
Israel-Stewart theory in the Eckart frame and the Israel-Stewart theory in the
Landau frame are exactly the same theory. In addition, with an Onsager-Casimir
analysis, we show that in strongly coupled plasmas the non-equilibrium degrees
of freedom typically appear in pairs, whose members acquire opposite phase
under time reversal. We use this insight to modify Cattaneo's model for
diffusion, in a way to make its initial transient consistent with the transient
dynamics of holographic plasmas.
| [
{
"created": "Fri, 29 Jul 2022 16:41:42 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Sep 2022 10:28:51 GMT",
"version": "v2"
}
] | 2022-09-22 | [
[
"Gavassino",
"Lorenzo",
""
],
[
"Antonelli",
"Marco",
""
],
[
"Haskell",
"Brynmor",
""
]
] | We set up a general framework for systematically building and classifying, in the linear regime, causal and stable dissipative hydrodynamic theories that, alongside with the usual hydrodynamic modes, also allow for an arbitrary number of non-hydrodynamic modes with complex dispersion relation (such theories are often referred to as "quasi-hydrodynamic"). To increase the number of non-hydrodynamic modes one needs to add more effective fields to the model. The system of equations governing this class of quasi-hydrodynamic theories is symmetric hyperbolic, thermodynamically consistent (i.e. the entropy is a Lyapunov function) and can be derived from an action principle. As a first application of the formalism, we prove that, in the linear regime, the Israel-Stewart theory in the Eckart frame and the Israel-Stewart theory in the Landau frame are exactly the same theory. In addition, with an Onsager-Casimir analysis, we show that in strongly coupled plasmas the non-equilibrium degrees of freedom typically appear in pairs, whose members acquire opposite phase under time reversal. We use this insight to modify Cattaneo's model for diffusion, in a way to make its initial transient consistent with the transient dynamics of holographic plasmas. |
1102.3490 | Y. M. Cho | Y. M. Cho, S. H. Oh, and Sang-Woo Kim | Abelian Decomposition of General Relativity | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on the view that Einstein's theory can be interpreted as a gauge theory
of Lorentz group, we decompose the gravitational connection (the gauge
potential of Lorentz group) $\vGm_\mu$ into the restricted connection made of
the potential of the maximal Abelian subgroup $H$ of Lorentz group $G$ and the
valence connection made of $G/H$ part of the potential which transforms
covariantly under Lorentz gauge transformation. With this decomposition we show
that the Einstein's theory can be decomposed into the restricted part made of
the restricted connection which has the full Lorentz gauge invariance and the
valence part made of the valence connection which plays the role of
gravitational source of the restricted gravity. We show that there are two
different Abelian decomposition of Einstein's theory, the light-like (or null)
decomposition and the non light-like (or non-null) decomposition, because
Lorentz group has two maximal Abelian subgroups. In this decomposition the role
of the metric $g_\mn$ is replaced by a four-index metric tensor $\vg_\mn$ which
transforms covariantly under the Lorentz group, and the metric-compatibility
condition $\nabla_\alpha g_\mn=0$ of the connection is replaced by the gauge
and generally covariant condition ${\mathscr D}_\mu \vg^\mn=0$. The
decomposition shows the existence of a restricted theory of gravitation which
has the full general invariance but is much simpler and has less physical
degrees of freedom than Einstein's theory. Moreover, it tells that the
restricted gravity can be written as an Abelian gauge theory, which implies
that the graviton can be described by a massless spin-one field.
| [
{
"created": "Thu, 17 Feb 2011 04:05:43 GMT",
"version": "v1"
}
] | 2011-02-18 | [
[
"Cho",
"Y. M.",
""
],
[
"Oh",
"S. H.",
""
],
[
"Kim",
"Sang-Woo",
""
]
] | Based on the view that Einstein's theory can be interpreted as a gauge theory of Lorentz group, we decompose the gravitational connection (the gauge potential of Lorentz group) $\vGm_\mu$ into the restricted connection made of the potential of the maximal Abelian subgroup $H$ of Lorentz group $G$ and the valence connection made of $G/H$ part of the potential which transforms covariantly under Lorentz gauge transformation. With this decomposition we show that the Einstein's theory can be decomposed into the restricted part made of the restricted connection which has the full Lorentz gauge invariance and the valence part made of the valence connection which plays the role of gravitational source of the restricted gravity. We show that there are two different Abelian decomposition of Einstein's theory, the light-like (or null) decomposition and the non light-like (or non-null) decomposition, because Lorentz group has two maximal Abelian subgroups. In this decomposition the role of the metric $g_\mn$ is replaced by a four-index metric tensor $\vg_\mn$ which transforms covariantly under the Lorentz group, and the metric-compatibility condition $\nabla_\alpha g_\mn=0$ of the connection is replaced by the gauge and generally covariant condition ${\mathscr D}_\mu \vg^\mn=0$. The decomposition shows the existence of a restricted theory of gravitation which has the full general invariance but is much simpler and has less physical degrees of freedom than Einstein's theory. Moreover, it tells that the restricted gravity can be written as an Abelian gauge theory, which implies that the graviton can be described by a massless spin-one field. |
gr-qc/0404022 | Silke Weinfurtner | Silke E. Ch. Weinfurtner | Simulation of gravitational objects in Bose-Einstein condensates | Diplom-arbeit [Master's thesis, written in German], Technical
University of Munich and Max-Planck-Institut for Quantenoptik in Garching,
129 pages, LaTeX | null | null | null | gr-qc cond-mat.stat-mech | null | In this diplom-arbeit I consider a specific class of "analogue models" of
curved spacetime that are specifically based on the use of Bose-Einstein
condensates.
As is usual in "analogue models", we are primarily interested in the
kinematics of fields and quanta immersed in a curved-space background. We are
not directly concerned with the Einstein equations of general relativity. Over
the last few years numerous papers concerning "analogue models" have been
published, the key result being that in many dynamical systems the
perturbations have equations of motion that are governed by an "effective
metric" that can often be interpreted in terms of an equivalent gravitational
field.
After a brief introduction concerning Bose-Einstein condensates and general
relativity, I explain the connection between these two fields. Several specific
examples are then explored in a little more detail:
1) Sinks and acoustic black holes [dumb holes].
2) Ring-shaped Laval nozzles and acoustic horizons.
3) the de Sitter universe.
In particular, the de Sitter universe is modelled by a freely expanding
condensate obtained by suddenly switching off the trap that normally holds the
condensate in place.
| [
{
"created": "Tue, 6 Apr 2004 12:43:15 GMT",
"version": "v1"
}
] | 2009-09-29 | [
[
"Weinfurtner",
"Silke E. Ch.",
""
]
] | In this diplom-arbeit I consider a specific class of "analogue models" of curved spacetime that are specifically based on the use of Bose-Einstein condensates. As is usual in "analogue models", we are primarily interested in the kinematics of fields and quanta immersed in a curved-space background. We are not directly concerned with the Einstein equations of general relativity. Over the last few years numerous papers concerning "analogue models" have been published, the key result being that in many dynamical systems the perturbations have equations of motion that are governed by an "effective metric" that can often be interpreted in terms of an equivalent gravitational field. After a brief introduction concerning Bose-Einstein condensates and general relativity, I explain the connection between these two fields. Several specific examples are then explored in a little more detail: 1) Sinks and acoustic black holes [dumb holes]. 2) Ring-shaped Laval nozzles and acoustic horizons. 3) the de Sitter universe. In particular, the de Sitter universe is modelled by a freely expanding condensate obtained by suddenly switching off the trap that normally holds the condensate in place. |
2303.14031 | Tanima Duary | Tanima Duary, Narayan Banerjee and Ananda Dasgupta | Signature flip in deceleration parameter: A thermodynamic phase
transition? | Title has been changed | Eur. Phys. J. C 83, 815 (2023) | 10.1140/epjc/s10052-023-11995-w | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the Hayward-Kodama temperature for the apparent horizon, it is found
that matter content in the Universe is not thermodynamically stable, and the
entry to the late accelerated expansion is actually a second order phase
transition. The cosmological model used for the purpose is one that imitates
the $\Lambda$CDM model, the favoured model for the present Universe.
| [
{
"created": "Fri, 24 Mar 2023 14:44:36 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Sep 2023 06:31:08 GMT",
"version": "v2"
}
] | 2023-09-14 | [
[
"Duary",
"Tanima",
""
],
[
"Banerjee",
"Narayan",
""
],
[
"Dasgupta",
"Ananda",
""
]
] | Using the Hayward-Kodama temperature for the apparent horizon, it is found that matter content in the Universe is not thermodynamically stable, and the entry to the late accelerated expansion is actually a second order phase transition. The cosmological model used for the purpose is one that imitates the $\Lambda$CDM model, the favoured model for the present Universe. |
1910.10091 | Martin Bojowald | Martin Bojowald, Suddhasattwa Brahma, Ding Ding, Michele Ronco | Deformed covariance in spherically symmetric vacuum models of loop
quantum gravity: Consistency in Euclidean and self-dual gravity | 37 pages | Phys. Rev. D 101 (2020) 026001 | 10.1103/PhysRevD.101.026001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Different versions of consistent canonical realizations of hypersurface
deformations of spherically symmetric space-times have been derived in models
of loop quantum gravity, modifying the classical dynamics and sometimes also
the structure of space-time. Based on a canonical version of effective field
theory, this paper provides a unified treatment, showing that modified
space-time structures are generic in this setting. The special case of
Euclidean gravity demonstrates agreement also with existing operator
calculations.
| [
{
"created": "Tue, 22 Oct 2019 16:32:02 GMT",
"version": "v1"
}
] | 2020-02-13 | [
[
"Bojowald",
"Martin",
""
],
[
"Brahma",
"Suddhasattwa",
""
],
[
"Ding",
"Ding",
""
],
[
"Ronco",
"Michele",
""
]
] | Different versions of consistent canonical realizations of hypersurface deformations of spherically symmetric space-times have been derived in models of loop quantum gravity, modifying the classical dynamics and sometimes also the structure of space-time. Based on a canonical version of effective field theory, this paper provides a unified treatment, showing that modified space-time structures are generic in this setting. The special case of Euclidean gravity demonstrates agreement also with existing operator calculations. |
0912.0162 | Tomasz Pawlowski | Wojciech Kaminski, Tomasz Pawlowski | The LQC evolution operator of FRW universe with positive cosmological
constant | RevTex4, 8 pages | Phys.Rev.D81:024014,2010 | 10.1103/PhysRevD.81.024014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The self-adjointness of an evolution operator $\Theta_{\Lambda}$
corresponding to the model of flat FRW universe with massless scalar field and
cosmological constant quantized in the framework of Loop Quantum Cosmology is
studied in the case $\Lambda>0$. It is shown, that for
$\Lambda<\Lambda_c\approx 10.3 \lPl^{-2}$ the operator admits many self-adjoint
extensions, each of the purely discrete spectrum. On the other hand for
$\Lambda\geq\Lambda_c$ the operator is essentially self-adjoint, however the
physical Hilbert space of the model does not contain any physically interesting
states.
| [
{
"created": "Tue, 1 Dec 2009 14:32:58 GMT",
"version": "v1"
}
] | 2010-05-12 | [
[
"Kaminski",
"Wojciech",
""
],
[
"Pawlowski",
"Tomasz",
""
]
] | The self-adjointness of an evolution operator $\Theta_{\Lambda}$ corresponding to the model of flat FRW universe with massless scalar field and cosmological constant quantized in the framework of Loop Quantum Cosmology is studied in the case $\Lambda>0$. It is shown, that for $\Lambda<\Lambda_c\approx 10.3 \lPl^{-2}$ the operator admits many self-adjoint extensions, each of the purely discrete spectrum. On the other hand for $\Lambda\geq\Lambda_c$ the operator is essentially self-adjoint, however the physical Hilbert space of the model does not contain any physically interesting states. |
1105.5629 | Andrey Shoom A | Valeri P. Frolov and Andrey A. Shoom | Spinoptics in a stationary spacetime | Added references, 13 pages | Phys.Rev.D84:044026,2011 | 10.1103/PhysRevD.84.044026 | Alberta-Thy-10-11 | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main goal of the present paper is to study how polarization of photons
affects their motion in a gravitational field created by a rotating massive
compact object. We study propagation of the circularly polarized beams of light
in a stationary gravitational field. We use (3+1)-form of the Maxwell equations
to derive a master equation for the propagation of monochromatic
electromagnetic waves of the frequency $\omega$ with a given helicity. We first
analize its solutions in the high frequency approximation using the `standard'
geometrical optics approach. After that we demonstrate how this `standard'
approach can be modified in order to include the effect of the helicity of
photons on their motion. Such an improved method reproduces the standard
results of the geometrical optics at short distances. However, it modifies the
asymptotic behavior of the circularly polarized beams in the late-time regime.
We demonstrate that the corresponding equations for the circularly polarized
beam can be effectively obtained by modification of the background geometry by
including a small factor proportional to $\omega^{-1}$ whose sign corresponds
to photon helicity. We obtain the modified equations for circularly polarized
rays by using such a `renormalization' procedure, and calculate the
corresponding renormalization term for the Kerr geometry.
| [
{
"created": "Fri, 27 May 2011 18:55:07 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Jul 2011 18:11:57 GMT",
"version": "v2"
}
] | 2011-09-08 | [
[
"Frolov",
"Valeri P.",
""
],
[
"Shoom",
"Andrey A.",
""
]
] | The main goal of the present paper is to study how polarization of photons affects their motion in a gravitational field created by a rotating massive compact object. We study propagation of the circularly polarized beams of light in a stationary gravitational field. We use (3+1)-form of the Maxwell equations to derive a master equation for the propagation of monochromatic electromagnetic waves of the frequency $\omega$ with a given helicity. We first analize its solutions in the high frequency approximation using the `standard' geometrical optics approach. After that we demonstrate how this `standard' approach can be modified in order to include the effect of the helicity of photons on their motion. Such an improved method reproduces the standard results of the geometrical optics at short distances. However, it modifies the asymptotic behavior of the circularly polarized beams in the late-time regime. We demonstrate that the corresponding equations for the circularly polarized beam can be effectively obtained by modification of the background geometry by including a small factor proportional to $\omega^{-1}$ whose sign corresponds to photon helicity. We obtain the modified equations for circularly polarized rays by using such a `renormalization' procedure, and calculate the corresponding renormalization term for the Kerr geometry. |
0903.3264 | Iain Brown | Iain A. Brown, Juliane Behrend and Karim A. Malik | Gauges and Cosmological Backreaction | 13 pages. Updated: reference added, typos corrected, exposition
clarified. Version 3: Replaced with version published by JCAP | JCAP 0911:027,2009 | 10.1088/1475-7516/2009/11/027 | HD-THEP-09-03 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a formalism for spatial averaging in cosmology applicable to
general spacetimes and coordinates, and allowing the easy incorporation of a
wide variety of matter sources. We apply this formalism to a
Friedmann-LeMaitre-Robertson-Walker universe perturbed to second-order and
present the corrections to the background in an unfixed gauge. We then present
the corrections that arise in uniform curvature and conformal Newtonian gauges.
| [
{
"created": "Thu, 19 Mar 2009 15:09:31 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Aug 2009 20:25:46 GMT",
"version": "v2"
},
{
"created": "Thu, 26 Nov 2009 14:03:21 GMT",
"version": "v3"
}
] | 2009-12-04 | [
[
"Brown",
"Iain A.",
""
],
[
"Behrend",
"Juliane",
""
],
[
"Malik",
"Karim A.",
""
]
] | We present a formalism for spatial averaging in cosmology applicable to general spacetimes and coordinates, and allowing the easy incorporation of a wide variety of matter sources. We apply this formalism to a Friedmann-LeMaitre-Robertson-Walker universe perturbed to second-order and present the corrections to the background in an unfixed gauge. We then present the corrections that arise in uniform curvature and conformal Newtonian gauges. |
gr-qc/9408043 | Wai Suen | E.S.C. Ching, P.T. Leung, W.M. Suen and K. Young | Quasi-Normal Mode Expansion for Linearized Waves in Gravitational
Systems | 12 pages, WUGRAV-94-9 | Phys.Rev.Lett. 74 (1995) 4588-4591 | 10.1103/PhysRevLett.74.4588 | null | gr-qc | null | The quasinormal modes (QNM's) of gravitational systems modeled by the
Klein-Gordon equation with effective potentials are studied in analogy to the
QNM's of optical cavities. Conditions are given for the QNM's to form a
complete set, i.e., for the Green's function to be expressible as a sum over
QNM's, answering a conjecture by Price and Husain [Phys. Rev. Lett. {\bf 68},
1973 (1992)]. In the cases where the QNM sum is divergent, procedures for
regularization are given. The crucial condition for completeness is the
existence of spatial discontinuities in the system, e.g., the discontinuity at
the stellar surface in the model of Price and Husain.
| [
{
"created": "Wed, 31 Aug 1994 23:38:38 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Ching",
"E. S. C.",
""
],
[
"Leung",
"P. T.",
""
],
[
"Suen",
"W. M.",
""
],
[
"Young",
"K.",
""
]
] | The quasinormal modes (QNM's) of gravitational systems modeled by the Klein-Gordon equation with effective potentials are studied in analogy to the QNM's of optical cavities. Conditions are given for the QNM's to form a complete set, i.e., for the Green's function to be expressible as a sum over QNM's, answering a conjecture by Price and Husain [Phys. Rev. Lett. {\bf 68}, 1973 (1992)]. In the cases where the QNM sum is divergent, procedures for regularization are given. The crucial condition for completeness is the existence of spatial discontinuities in the system, e.g., the discontinuity at the stellar surface in the model of Price and Husain. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.