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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0510026 | Dr Mayeul Arminjon | Mayeul Arminjon | Equations of motion according to the asymptotic post-Newtonian scheme
for general relativity | 8 pages, no figure. Text of talks given at the 3rd Workshop "Gravity,
Astrophysics and Strings at the Black Sea" (Kiten, Bulgaria, June 13-20,
2005). Submitted to the Proceedings (P. Fiziev and M. Todorov, eds.) | Gravity, Astrophysics and Strings at the Black Sea (P. Fiziev & M.
Todorov, eds.), St. Kliment Ohridski University Press, Sofia (2006), pp. 1-9 | null | null | gr-qc astro-ph | null | We summarize a recent work done on the title's subject. First, we present the
asymptotic scheme of post-Newtonian (PN) approximation for general relativity
in the harmonic gauge. Then, we discuss the definition of the mass centers and
the derivation of equations for their motion, following that scheme. Finally,
we briefly analyze the reason why a new term has thus been found in the
equations of motion.
| [
{
"created": "Fri, 7 Oct 2005 15:27:40 GMT",
"version": "v1"
}
] | 2007-11-19 | [
[
"Arminjon",
"Mayeul",
""
]
] | We summarize a recent work done on the title's subject. First, we present the asymptotic scheme of post-Newtonian (PN) approximation for general relativity in the harmonic gauge. Then, we discuss the definition of the mass centers and the derivation of equations for their motion, following that scheme. Finally, we briefly analyze the reason why a new term has thus been found in the equations of motion. |
1009.3030 | Nathalie Deruelle | A. Anabalon, N. Deruelle, D. Tempo and R. Troncoso | Remarks on the Myers-Perry and Einstein Gauss-Bonnet Rotating Solutions | null | Int.J.Mod.Phys.D20:639-647,2011 | 10.1142/S0218271811018974 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Kerr-type solutions of the five-dimensional Einstein and
Einstein-Gauss-Bonnet equations look pretty similar when written in Kerr-Schild
form. However the Myers-Perry spacetime is circular whereas the rotating
solution of the Einstein-Gauss-Bonnet theory is not. We explore some
consequences of this difference in particular regarding the (non) existence of
Boyer-Lindquist-type coordinates and the extension of the manifold.
| [
{
"created": "Wed, 15 Sep 2010 20:11:57 GMT",
"version": "v1"
}
] | 2011-05-25 | [
[
"Anabalon",
"A.",
""
],
[
"Deruelle",
"N.",
""
],
[
"Tempo",
"D.",
""
],
[
"Troncoso",
"R.",
""
]
] | The Kerr-type solutions of the five-dimensional Einstein and Einstein-Gauss-Bonnet equations look pretty similar when written in Kerr-Schild form. However the Myers-Perry spacetime is circular whereas the rotating solution of the Einstein-Gauss-Bonnet theory is not. We explore some consequences of this difference in particular regarding the (non) existence of Boyer-Lindquist-type coordinates and the extension of the manifold. |
1501.06270 | Jaume Haro | Jaume Haro and Jaume Amor\'os | Matter Bounce Scenario in F(T) gravity | Communication to the FFP2014 (Frontiers in Fundamental Physics,
Marseille 2014). To appear in Proceedings of Science | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that teleparallel $F(T)$ theories of gravity combined with
holonomy corrected Loop Quantum Cosmology (LQC) support a Matter Bounce
Scenario (MBS) which is a potential alternative to the inflationary paradigm.
The Matter Bounce Scenario is reviewed and, according to the current
observational data provided by PLANCK's team, we have summarized all the
conditions that it has to satisfy in order to be a viable alternative to
inflation, such as to provide a theoretical value of the spectral index and its
running compatible with the latest PLANCK data, to have a reheating process via
gravitational particle production, or to predict some signatures in the
non-gaussianities of the power spectrum. The calculation of the power spectrum
for scalar perturbations and the ratio of tensor to scalar perturbations has
been done, in the simplest case of an exact matter dominated background, for
both holonomy corrected LQC and teleparallel $F(T)$ gravity. Finally, we have
discussed the challenges (essentially, dealing with non-gaussianities, the
calculation of the 3-point function in flat spatial geometries for theories
beyond General Relativity) and problems (Jeans instabilities in the case of
holonomy corrected LQC or local Lorentz dependence in teleparallelism) that
arise in either bouncing scenario.
| [
{
"created": "Mon, 26 Jan 2015 07:31:42 GMT",
"version": "v1"
}
] | 2015-01-27 | [
[
"Haro",
"Jaume",
""
],
[
"Amorós",
"Jaume",
""
]
] | It is shown that teleparallel $F(T)$ theories of gravity combined with holonomy corrected Loop Quantum Cosmology (LQC) support a Matter Bounce Scenario (MBS) which is a potential alternative to the inflationary paradigm. The Matter Bounce Scenario is reviewed and, according to the current observational data provided by PLANCK's team, we have summarized all the conditions that it has to satisfy in order to be a viable alternative to inflation, such as to provide a theoretical value of the spectral index and its running compatible with the latest PLANCK data, to have a reheating process via gravitational particle production, or to predict some signatures in the non-gaussianities of the power spectrum. The calculation of the power spectrum for scalar perturbations and the ratio of tensor to scalar perturbations has been done, in the simplest case of an exact matter dominated background, for both holonomy corrected LQC and teleparallel $F(T)$ gravity. Finally, we have discussed the challenges (essentially, dealing with non-gaussianities, the calculation of the 3-point function in flat spatial geometries for theories beyond General Relativity) and problems (Jeans instabilities in the case of holonomy corrected LQC or local Lorentz dependence in teleparallelism) that arise in either bouncing scenario. |
2303.05530 | Thomas W. Baumgarte | Thomas W. Baumgarte, Carsten Gundlach, and David Hilditch | Critical phenomena in the collapse of quadrupolar and hexadecapolar
gravitational waves | 17 pages, 14 figures | Phys. Rev. D 107, 084012 (2023) | 10.1103/PhysRevD.107.084012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report on numerical simulations of critical phenomena near the threshold
of black hole formation in the collapse of axisymmetric gravitational waves in
vacuum. We discuss several new features of our numerical treatment, and then
compare results obtained from families of quadrupolar and hexadecapolar initial
data. Specifically, we construct (nonlinear) initial data from quadrupolar and
hexadecapolar, time-symmetric wavelike solutions to the linearized Einstein
equations (often referred to as Teukolsky waves), and evolve these using a
shock-avoiding slicing condition. While our degree of fine-tuning to the onset
of black-hole formation is rather modest, we identify several features of the
threshold solutions formed for the two families. Both threshold solutions
appear to display an at least approximate discrete self-similarity with an
accumulation event at the center, and the characteristics of the threshold
solution for the quadrupolar data are consistent with those found previously by
other authors. The hexadecapolar threshold solution appears to be distinct from
the quadrupolar one, providing further support to the notion that there is no
universal critical solution for the collapse of vacuum gravitational waves.
| [
{
"created": "Thu, 9 Mar 2023 19:00:08 GMT",
"version": "v1"
}
] | 2024-06-26 | [
[
"Baumgarte",
"Thomas W.",
""
],
[
"Gundlach",
"Carsten",
""
],
[
"Hilditch",
"David",
""
]
] | We report on numerical simulations of critical phenomena near the threshold of black hole formation in the collapse of axisymmetric gravitational waves in vacuum. We discuss several new features of our numerical treatment, and then compare results obtained from families of quadrupolar and hexadecapolar initial data. Specifically, we construct (nonlinear) initial data from quadrupolar and hexadecapolar, time-symmetric wavelike solutions to the linearized Einstein equations (often referred to as Teukolsky waves), and evolve these using a shock-avoiding slicing condition. While our degree of fine-tuning to the onset of black-hole formation is rather modest, we identify several features of the threshold solutions formed for the two families. Both threshold solutions appear to display an at least approximate discrete self-similarity with an accumulation event at the center, and the characteristics of the threshold solution for the quadrupolar data are consistent with those found previously by other authors. The hexadecapolar threshold solution appears to be distinct from the quadrupolar one, providing further support to the notion that there is no universal critical solution for the collapse of vacuum gravitational waves. |
1810.10505 | K{\i}van\c{c} \.Ibrahim \"Unl\"ut\"urk | Tekin Dereli and K{\i}van\c{c} \.I. \"Unl\"ut\"urk | Hamilton-Jacobi Formulation of the Thermodynamics of
Einstein-Born-Infeld-AdS Black Holes | 5 pages, 2 figures | EPL, 125 (2019) 10005 | 10.1209/0295-5075/125/10005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A Hamilton-Jacobi formalism for thermodynamics was formulated by Rajeev [Ann.
Phys. 323, 2265 (2008)] based on the contact structure of the odd dimensional
thermodynamic phase space. This allows one to derive the equations of state of
a family of substances by solving a Hamilton-Jacobi equation (HJE). In the same
work it was applied to chargeless non-rotating black holes, and the use of
Born-Infeld electromagnetism was proposed to apply it to charged black holes as
well. This paper fulfills this suggestion by deriving the HJE for charged
non-rotating black holes using Born-Infeld theory and a negative cosmological
constant. The most general solution of this HJE is found. It is shown that
there exists solutions which are distinct from the equations of state of the
Einstein-Born-Infeld-AdS black hole. The meaning of these solutions is
discussed.
| [
{
"created": "Wed, 24 Oct 2018 17:27:51 GMT",
"version": "v1"
}
] | 2019-01-31 | [
[
"Dereli",
"Tekin",
""
],
[
"Ünlütürk",
"Kıvanç İ.",
""
]
] | A Hamilton-Jacobi formalism for thermodynamics was formulated by Rajeev [Ann. Phys. 323, 2265 (2008)] based on the contact structure of the odd dimensional thermodynamic phase space. This allows one to derive the equations of state of a family of substances by solving a Hamilton-Jacobi equation (HJE). In the same work it was applied to chargeless non-rotating black holes, and the use of Born-Infeld electromagnetism was proposed to apply it to charged black holes as well. This paper fulfills this suggestion by deriving the HJE for charged non-rotating black holes using Born-Infeld theory and a negative cosmological constant. The most general solution of this HJE is found. It is shown that there exists solutions which are distinct from the equations of state of the Einstein-Born-Infeld-AdS black hole. The meaning of these solutions is discussed. |
1208.3491 | Stephen Fairhurst | S. Babak, R. Biswas, P. R. Brady, D. A. Brown, K. Cannon, C. D.
Capano, J. H. Clayton, T. Cokelaer, J. D. E. Creighton, T. Dent, A. Dietz, S.
Fairhurst, N. Fotopoulos, G. Gonzalez, C. Hanna, I. W. Harry, G. Jones, D.
Keppel, D. J. A. McKechan, L. Pekowsky, S. Privitera, C. Robinson, A. C.
Rodriguez, B. S. Sathyaprakash, A. S. Sengupta, M. Vallisneri, R. Vaulin, A.
J. Weinstein | Searching for gravitational waves from binary coalescence | 18 pages, 15 figures | null | 10.1103/PhysRevD.87.024033 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe the implementation of a search for gravitational waves from
compact binary coalescences in LIGO and Virgo data. This all-sky, all-time,
multi-detector search for binary coalescence has been used to search data taken
in recent LIGO and Virgo runs. The search is built around a matched filter
analysis of the data, augmented by numerous signal consistency tests designed
to distinguish artifacts of non-Gaussian detector noise from potential
detections. We demonstrate the search performance using Gaussian noise and data
from the fifth LIGO science run and demonstrate that the signal consistency
tests are capable of mitigating the effect of non-Gaussian noise and providing
a sensitivity comparable to that achieved in Gaussian noise.
| [
{
"created": "Thu, 16 Aug 2012 20:57:25 GMT",
"version": "v1"
}
] | 2013-05-30 | [
[
"Babak",
"S.",
""
],
[
"Biswas",
"R.",
""
],
[
"Brady",
"P. R.",
""
],
[
"Brown",
"D. A.",
""
],
[
"Cannon",
"K.",
""
],
[
"Capano",
"C. D.",
""
],
[
"Clayton",
"J. H.",
""
],
[
"Cokelaer",
"T.",
""
],
[
"Creighton",
"J. D. E.",
""
],
[
"Dent",
"T.",
""
],
[
"Dietz",
"A.",
""
],
[
"Fairhurst",
"S.",
""
],
[
"Fotopoulos",
"N.",
""
],
[
"Gonzalez",
"G.",
""
],
[
"Hanna",
"C.",
""
],
[
"Harry",
"I. W.",
""
],
[
"Jones",
"G.",
""
],
[
"Keppel",
"D.",
""
],
[
"McKechan",
"D. J. A.",
""
],
[
"Pekowsky",
"L.",
""
],
[
"Privitera",
"S.",
""
],
[
"Robinson",
"C.",
""
],
[
"Rodriguez",
"A. C.",
""
],
[
"Sathyaprakash",
"B. S.",
""
],
[
"Sengupta",
"A. S.",
""
],
[
"Vallisneri",
"M.",
""
],
[
"Vaulin",
"R.",
""
],
[
"Weinstein",
"A. J.",
""
]
] | We describe the implementation of a search for gravitational waves from compact binary coalescences in LIGO and Virgo data. This all-sky, all-time, multi-detector search for binary coalescence has been used to search data taken in recent LIGO and Virgo runs. The search is built around a matched filter analysis of the data, augmented by numerous signal consistency tests designed to distinguish artifacts of non-Gaussian detector noise from potential detections. We demonstrate the search performance using Gaussian noise and data from the fifth LIGO science run and demonstrate that the signal consistency tests are capable of mitigating the effect of non-Gaussian noise and providing a sensitivity comparable to that achieved in Gaussian noise. |
gr-qc/9803041 | null | Vladimir S. Mashkevich (Institute of Physics, Kiev) | Indeterministic Quantum Gravity and Cosmology XI. Quantum Measurement | 7 pages, LATEX 2.09 | null | null | IP 5/98 | gr-qc quant-ph | null | This paper is a sequel to the series of papers [gr-qc/9409010, gr-qc/9505034,
gr-qc/9603022, gr-qc/9609035, gr-qc/9609046, gr-qc/9704033, gr-qc/9704038,
gr-qc/9708014, gr-qc/9802016, gr-qc/9802022]. We define a quantum measurement
as a sequence of binary quantum jumps caused by a macroscopic apparatus. A
dynamical theory of measurement is developed, the role of gravity and cosmology
being emphasized.
| [
{
"created": "Thu, 12 Mar 1998 09:35:20 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Mashkevich",
"Vladimir S.",
"",
"Institute of Physics, Kiev"
]
] | This paper is a sequel to the series of papers [gr-qc/9409010, gr-qc/9505034, gr-qc/9603022, gr-qc/9609035, gr-qc/9609046, gr-qc/9704033, gr-qc/9704038, gr-qc/9708014, gr-qc/9802016, gr-qc/9802022]. We define a quantum measurement as a sequence of binary quantum jumps caused by a macroscopic apparatus. A dynamical theory of measurement is developed, the role of gravity and cosmology being emphasized. |
2302.03951 | Kota Numajiri | Kota Numajiri, Yong-Xiang Cui, Taishi Katsuragawa, Shin'ichi Nojiri | Revisiting compact star in $F(R)$ gravity: Roles of chameleon potential
and energy conditions | 37 pages, 22 figures, 1 table. Version to appear in PRD | Phys. Rev. D 107, 104019 (2023) | 10.1103/PhysRevD.107.104019 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We reexamine the static and spherical symmetric compact star configuration in
the $R^2$ model of the $F(R)$ gravity theory. With asymptotic solutions for the
additional scalar degrees of freedom, we refine analysis on the external
geometry and settle the scalar-hair problem argued in previous works.
Performing the numerical integration of the modified Tolman-Oppenheimer-Volkoff
equations as a two-boundaries-value problem, we further discuss the
scalar-field distribution inside the compact stars and its influence on the
mass-radius relation. We show that the chameleon potential plays an essential
role in determining the scalar-field profile inside the star. The scalar field
often behaves as a quintessential field that effectively decreases the mass of
compact stars with lower central energy density.
| [
{
"created": "Wed, 8 Feb 2023 09:13:48 GMT",
"version": "v1"
},
{
"created": "Sun, 12 Feb 2023 09:34:31 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Apr 2023 15:29:54 GMT",
"version": "v3"
}
] | 2023-05-11 | [
[
"Numajiri",
"Kota",
""
],
[
"Cui",
"Yong-Xiang",
""
],
[
"Katsuragawa",
"Taishi",
""
],
[
"Nojiri",
"Shin'ichi",
""
]
] | We reexamine the static and spherical symmetric compact star configuration in the $R^2$ model of the $F(R)$ gravity theory. With asymptotic solutions for the additional scalar degrees of freedom, we refine analysis on the external geometry and settle the scalar-hair problem argued in previous works. Performing the numerical integration of the modified Tolman-Oppenheimer-Volkoff equations as a two-boundaries-value problem, we further discuss the scalar-field distribution inside the compact stars and its influence on the mass-radius relation. We show that the chameleon potential plays an essential role in determining the scalar-field profile inside the star. The scalar field often behaves as a quintessential field that effectively decreases the mass of compact stars with lower central energy density. |
1006.2206 | Jibitesh Dutta | Jibitesh Dutta, Subenoy Chakraborty and M. Ansari | Non linear equation of state and effective phantom divide in brane
models | null | Int.J.Theor.Phys.49:2680-2690,2010 | 10.1007/s10773-010-0460-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Here, DGP model of brane-gravity is analyzed and compared with the standard
general relativity and Randall-Sundrum cases using non-linear equation of
state. Phantom fluid is known to violate the weak energy condition. In this
paper, it is found that this characteristic of phantom energy is affected
drastically by the negative brane-tension $\lambda$ of the RS-II model. It is
found that in DGP model strong energy condition(SEC) is always violated and the
universe accelerates only where as in RS-II model even SEC is not violated for
$1 < \rho/\lambda < 2$ and the universe decelerates.
| [
{
"created": "Fri, 11 Jun 2010 06:34:31 GMT",
"version": "v1"
}
] | 2015-05-08 | [
[
"Dutta",
"Jibitesh",
""
],
[
"Chakraborty",
"Subenoy",
""
],
[
"Ansari",
"M.",
""
]
] | Here, DGP model of brane-gravity is analyzed and compared with the standard general relativity and Randall-Sundrum cases using non-linear equation of state. Phantom fluid is known to violate the weak energy condition. In this paper, it is found that this characteristic of phantom energy is affected drastically by the negative brane-tension $\lambda$ of the RS-II model. It is found that in DGP model strong energy condition(SEC) is always violated and the universe accelerates only where as in RS-II model even SEC is not violated for $1 < \rho/\lambda < 2$ and the universe decelerates. |
1808.07897 | Luis Lehner | Gwyneth Allwright and Luis Lehner | Towards the nonlinear regime in extensions to GR: assessing possible
options | 11 pages, 6 figures | null | 10.1088/1361-6382/ab0ee1 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Testing General Relativity and exploring possible departures has received
further input with the possibility to do so through gravitational waves emitted
in strongly gravitating/highly dynamical scenarios and also through the
availability of exquisitely sensitive cosmological observations. However, most
extensions suffer from severe pathologies at the mathematical level which have
stymied a thorough exploration of putative theories. With the aid of a model
problem which captures typical pathologies, we explore suggested methods to
control them. We find that the approach that modifies the equations to control
higher-order gradients is both robust and efficient.
| [
{
"created": "Thu, 23 Aug 2018 18:25:15 GMT",
"version": "v1"
}
] | 2019-05-22 | [
[
"Allwright",
"Gwyneth",
""
],
[
"Lehner",
"Luis",
""
]
] | Testing General Relativity and exploring possible departures has received further input with the possibility to do so through gravitational waves emitted in strongly gravitating/highly dynamical scenarios and also through the availability of exquisitely sensitive cosmological observations. However, most extensions suffer from severe pathologies at the mathematical level which have stymied a thorough exploration of putative theories. With the aid of a model problem which captures typical pathologies, we explore suggested methods to control them. We find that the approach that modifies the equations to control higher-order gradients is both robust and efficient. |
0806.0768 | Orchidea Maria Lecian | Marco Valerio Battisti, Orchidea Maria Lecian, Giovanni Montani | Polymer Quantum Dynamics of the Taub Universe | 12 pages, 6 figures; published version | Phys.Rev.D78:103514,2008 | 10.1103/PhysRevD.78.103514 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the framework of non-standard (Weyl) representations of the canonical
commutation relations, we investigate the polymer quantization of the Taub
cosmological model. The Taub model is analyzed within the Arnowitt-Deser-Misner
reduction of its dynamics, by which a time variable arises. While the energy
variable and its conjugate momentum are treated as ordinary Heisenberg
operators, the anisotropy variable and its conjugate momentum are represented
by the polymer technique. The model is analyzed at both classical and quantum
level. As a result, classical trajectories flatten with respect to the
potential wall, and the cosmological singularity is not probabilistically
removed. In fact, the dynamics of the wave packets is characterized by an
interference phenomenon, which, however, is not able to stop the evolution
towards the classical singularity.
| [
{
"created": "Wed, 4 Jun 2008 13:19:50 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Nov 2008 13:47:37 GMT",
"version": "v2"
}
] | 2009-02-23 | [
[
"Battisti",
"Marco Valerio",
""
],
[
"Lecian",
"Orchidea Maria",
""
],
[
"Montani",
"Giovanni",
""
]
] | Within the framework of non-standard (Weyl) representations of the canonical commutation relations, we investigate the polymer quantization of the Taub cosmological model. The Taub model is analyzed within the Arnowitt-Deser-Misner reduction of its dynamics, by which a time variable arises. While the energy variable and its conjugate momentum are treated as ordinary Heisenberg operators, the anisotropy variable and its conjugate momentum are represented by the polymer technique. The model is analyzed at both classical and quantum level. As a result, classical trajectories flatten with respect to the potential wall, and the cosmological singularity is not probabilistically removed. In fact, the dynamics of the wave packets is characterized by an interference phenomenon, which, however, is not able to stop the evolution towards the classical singularity. |
gr-qc/0703092 | Mamdouh Wanas | M.I.Wanas, M.A.Bakry | A Note on General Covariant Stability Theory | Three pages, LaTeX file | null | 10.1142/9789812834300_0341 | null | gr-qc | null | In the present work we suggest a general covariant theory which can be used
to study the stability of any physical system treated geometrically. Stability
conditions are connected to the magnitude of the deviation vector. This theory
is a modification of an earlier joint work, by the same authors, concerning
stability. A comparison between the present work and the earlier one is given.
The suggested theory can be used to study the stability of planetary orbits,
astrophysical configurations and cosmological models.
| [
{
"created": "Sat, 17 Mar 2007 23:55:45 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Mar 2007 13:26:41 GMT",
"version": "v2"
}
] | 2016-11-15 | [
[
"Wanas",
"M. I.",
""
],
[
"Bakry",
"M. A.",
""
]
] | In the present work we suggest a general covariant theory which can be used to study the stability of any physical system treated geometrically. Stability conditions are connected to the magnitude of the deviation vector. This theory is a modification of an earlier joint work, by the same authors, concerning stability. A comparison between the present work and the earlier one is given. The suggested theory can be used to study the stability of planetary orbits, astrophysical configurations and cosmological models. |
gr-qc/0001057 | Sergiu Vacaru | Sergiu I. Vacaru | Stochastic Processes and Thermodynamics on Curved Spaces | latex209, 3 pages | null | null | null | gr-qc astro-ph hep-ph | null | Our approach views the thermodynamics and kinetics in general relativity and
extended gravitational theories (with generic local anisotropy) from the
perspective of the theory of stochastic differential equations on curved
spaces.
Nonequilibrium and irreversible processes in black hole thermodynamics are
considered. The paper summarizes the author's contribution to Journees
Relativistes 99 (12--17 September 1999), Weimar, Germany.
| [
{
"created": "Thu, 20 Jan 2000 11:27:23 GMT",
"version": "v1"
}
] | 2008-11-24 | [
[
"Vacaru",
"Sergiu I.",
""
]
] | Our approach views the thermodynamics and kinetics in general relativity and extended gravitational theories (with generic local anisotropy) from the perspective of the theory of stochastic differential equations on curved spaces. Nonequilibrium and irreversible processes in black hole thermodynamics are considered. The paper summarizes the author's contribution to Journees Relativistes 99 (12--17 September 1999), Weimar, Germany. |
1712.01274 | Faizuddin Ahmed | Faizuddin Ahmed | A Type D Non-Vacuum Spacetime with Causality Violating Curves, and its
Physical Interpretation | 18 pages, 2 figures | Commun. Theor. Phys. vol. 68, No. 06, 735 (2017),
http://ctp.itp.ac.cn | 10.1088/0253-6102/68/6/735 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a topologically trivial, non-vacuum solution of the Einstein's
field equations in four-dimensions, which is regular everywhere. The metric
admits circular closed timelike curves, which appear beyond the null curve, and
these timelike curves are linearly stable under linear perturbations.
Additionally, the spacetime admits null geodesics curve which are not closed,
and the metric is of type D in the Petrov classification scheme. The
stress-energy tensor anisotropic fluid satisfy the different energy conditions
and a generalization of Equation-of-State parameter of perfect fluid
$p=\omega\,\rho$. The metric admits a twisting, shearfree, non-exapnding
timelike geodesic congruence. Finally, the physical interpretation of this
solution, based on the study of the equation of the geodesics deviation, will
be presented.
| [
{
"created": "Mon, 4 Dec 2017 04:29:20 GMT",
"version": "v1"
}
] | 2017-12-06 | [
[
"Ahmed",
"Faizuddin",
""
]
] | We present a topologically trivial, non-vacuum solution of the Einstein's field equations in four-dimensions, which is regular everywhere. The metric admits circular closed timelike curves, which appear beyond the null curve, and these timelike curves are linearly stable under linear perturbations. Additionally, the spacetime admits null geodesics curve which are not closed, and the metric is of type D in the Petrov classification scheme. The stress-energy tensor anisotropic fluid satisfy the different energy conditions and a generalization of Equation-of-State parameter of perfect fluid $p=\omega\,\rho$. The metric admits a twisting, shearfree, non-exapnding timelike geodesic congruence. Finally, the physical interpretation of this solution, based on the study of the equation of the geodesics deviation, will be presented. |
gr-qc/0609126 | H. Casini | H. Casini | Mutual information challenges entropy bounds | 10 pages, 2 figures, minor changes | Class.Quant.Grav.24:1293-1302,2007 | 10.1088/0264-9381/24/5/013 | null | gr-qc hep-th | null | We consider some formulations of the entropy bounds at the semiclassical
level. The entropy S(V) localized in a region V is divergent in quantum field
theory (QFT). Instead of it we focus on the mutual information
I(V,W)=S(V)+S(W)-S(V\cup W) between two different non-intersecting sets V and
W. This is a low energy quantity, independent of the regularization scheme. In
addition, the mutual information is bounded above by twice the entropy
corresponding to the sets involved. Calculations of I(V,W) in QFT show that the
entropy in empty space cannot be renormalized to zero, and must be actually
very large. We find that this entropy due to the vacuum fluctuations violates
the FMW bound in Minkowski space. The mutual information also gives a precise,
cutoff independent meaning to the statement that the number of degrees of
freedom increases with the volume in QFT. If the holographic bound holds, this
points to the essential non locality of the physical cutoff. Violations of the
Bousso bound would require conformal theories and large distances. We speculate
that the presence of a small cosmological constant might prevent such a
violation.
| [
{
"created": "Wed, 27 Sep 2006 16:05:51 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Mar 2007 14:14:09 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Casini",
"H.",
""
]
] | We consider some formulations of the entropy bounds at the semiclassical level. The entropy S(V) localized in a region V is divergent in quantum field theory (QFT). Instead of it we focus on the mutual information I(V,W)=S(V)+S(W)-S(V\cup W) between two different non-intersecting sets V and W. This is a low energy quantity, independent of the regularization scheme. In addition, the mutual information is bounded above by twice the entropy corresponding to the sets involved. Calculations of I(V,W) in QFT show that the entropy in empty space cannot be renormalized to zero, and must be actually very large. We find that this entropy due to the vacuum fluctuations violates the FMW bound in Minkowski space. The mutual information also gives a precise, cutoff independent meaning to the statement that the number of degrees of freedom increases with the volume in QFT. If the holographic bound holds, this points to the essential non locality of the physical cutoff. Violations of the Bousso bound would require conformal theories and large distances. We speculate that the presence of a small cosmological constant might prevent such a violation. |
1009.5179 | Claudio Dappiaggi | Claudio Dappiaggi, Thomas-Paul Hack, Nicola Pinamonti | Approximate KMS states for scalar and spinor fields in
Friedmann-Robertson-Walker spacetimes | 42 pages | null | 10.1007/s00023-011-0111-6 | Desy 10-160, ESI-2266, ZMP-HH/10-19 | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct and discuss Hadamard states for both scalar and Dirac spinor
fields in a large class of spatially flat Friedmann-Robertson-Walker spacetimes
characterised by an initial phase either of exponential or of power-law
expansion. The states we obtain can be interpreted as being in thermal
equilibrium at the time when the scale factor a has a specific value a=a_0. In
the case a_0=0, these states fulfil a strict KMS condition on the boundary of
the spacetime, which is either a cosmological horizon, or a Big Bang
hypersurface. Furthermore, in the conformally invariant case, they are
conformal KMS states on the full spacetime. However, they provide a natural
notion of an approximate KMS state also in the remaining cases, especially for
massive fields. On the technical side, our results are based on a
bulk-to-boundary reconstruction technique already successfully applied in the
scalar case and here proven to be suitable also for spinor fields. The
potential applications of the states we find range over a broad spectrum, but
they appear to be suited to discuss in particular thermal phenomena such as the
cosmic neutrino background or the quantum state of dark matter.
| [
{
"created": "Mon, 27 Sep 2010 07:56:41 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Dappiaggi",
"Claudio",
""
],
[
"Hack",
"Thomas-Paul",
""
],
[
"Pinamonti",
"Nicola",
""
]
] | We construct and discuss Hadamard states for both scalar and Dirac spinor fields in a large class of spatially flat Friedmann-Robertson-Walker spacetimes characterised by an initial phase either of exponential or of power-law expansion. The states we obtain can be interpreted as being in thermal equilibrium at the time when the scale factor a has a specific value a=a_0. In the case a_0=0, these states fulfil a strict KMS condition on the boundary of the spacetime, which is either a cosmological horizon, or a Big Bang hypersurface. Furthermore, in the conformally invariant case, they are conformal KMS states on the full spacetime. However, they provide a natural notion of an approximate KMS state also in the remaining cases, especially for massive fields. On the technical side, our results are based on a bulk-to-boundary reconstruction technique already successfully applied in the scalar case and here proven to be suitable also for spinor fields. The potential applications of the states we find range over a broad spectrum, but they appear to be suited to discuss in particular thermal phenomena such as the cosmic neutrino background or the quantum state of dark matter. |
1801.08173 | Christian Pfeifer | Leonardo Barcaroli and Lukas K. Brunkhorst and Giulia Gubitosi and
Niccol\'o Loret and Christian Pfeifer | Hamilton Geometry - Phase Space Geometry from Modified Dispersion
Relations | 6 pages | Proceedings, 14th Marcel Grossmann Meeting on Recent Developments
in Theoretical and Experimental General Relativity, Astrophysics, and
Relativistic Field Theories (MG14) (In 4 Volumes): Rome, Italy, July 12-18,
2015, Pages: 3929-3934 | 10.1142/9789813226609_0522 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum gravity phenomenology suggests an effective modification of the
general relativistic dispersion relation of freely falling point particles
caused by an underlying theory of quantum gravity. Here we analyse the
consequences of modifications of the general relativistic dispersion on the
geometry of spacetime in the language of Hamilton geometry. The dispersion
relation is interpreted as the Hamiltonian which determines the motion of point
particles. It is a function on the cotangent bundle of spacetime, i.e. on phase
space, and determines the geometry of phase space completely, in a similar way
as the metric determines the geometry of spacetime in general relativity. After
a review of the general Hamilton geometry of phase space we discuss two
examples. The phase space geometry of the metric Hamiltonian
$H_g(x,p)=g^{ab}(x)p_ap_b$ and the phase space geometry of the first order q-de
Sitter dispersion relation of the form $H_{qDS}(x,p)=g^{ab}(x)p_ap_b + \ell
G^{abc}(x)p_ap_bp_c$ which is suggested from quantum gravity phenomenology. We
will see that for the metric Hamiltonian $H_g$ the geometry of phase space is
equivalent to the standard metric spacetime geometry from general relativity.
For the q-de Sitter Hamiltonian $H_{qDS}$ the Hamilton equations of motion for
point particles do not become autoparallels but contain a force term, the
momentum space part of phase space is curved and the curvature of spacetime
becomes momentum dependent.
| [
{
"created": "Wed, 24 Jan 2018 20:10:38 GMT",
"version": "v1"
}
] | 2018-01-26 | [
[
"Barcaroli",
"Leonardo",
""
],
[
"Brunkhorst",
"Lukas K.",
""
],
[
"Gubitosi",
"Giulia",
""
],
[
"Loret",
"Niccoló",
""
],
[
"Pfeifer",
"Christian",
""
]
] | Quantum gravity phenomenology suggests an effective modification of the general relativistic dispersion relation of freely falling point particles caused by an underlying theory of quantum gravity. Here we analyse the consequences of modifications of the general relativistic dispersion on the geometry of spacetime in the language of Hamilton geometry. The dispersion relation is interpreted as the Hamiltonian which determines the motion of point particles. It is a function on the cotangent bundle of spacetime, i.e. on phase space, and determines the geometry of phase space completely, in a similar way as the metric determines the geometry of spacetime in general relativity. After a review of the general Hamilton geometry of phase space we discuss two examples. The phase space geometry of the metric Hamiltonian $H_g(x,p)=g^{ab}(x)p_ap_b$ and the phase space geometry of the first order q-de Sitter dispersion relation of the form $H_{qDS}(x,p)=g^{ab}(x)p_ap_b + \ell G^{abc}(x)p_ap_bp_c$ which is suggested from quantum gravity phenomenology. We will see that for the metric Hamiltonian $H_g$ the geometry of phase space is equivalent to the standard metric spacetime geometry from general relativity. For the q-de Sitter Hamiltonian $H_{qDS}$ the Hamilton equations of motion for point particles do not become autoparallels but contain a force term, the momentum space part of phase space is curved and the curvature of spacetime becomes momentum dependent. |
1102.2001 | Matt Visser | Kane O'Donnell (Victoria University of Wellington) and Matt Visser
(Victoria University of Wellington) | Elementary analysis of the special relativistic combination of
velocities, Wigner rotation, and Thomas precession | V1: 25 pages, 6 figures; V2: 22 pages, 5 figures. The revised version
is shortened and the arguments streamlined. Minor changes in notation and
figures. This version matches the published version | European Journal of Physics 31 (2011) 1033--1047 | 10.1088/0143-0807/32/4/016 | null | gr-qc math-ph math.MP physics.pop-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The purpose of this paper is to provide an elementary introduction to the
qualitative and quantitative results of velocity combination in special
relativity, including the Wigner rotation and Thomas precession. We utilize
only the most familiar tools of special relativity, in arguments presented at
three differing levels: (1) utterly elementary, which will suit a first course
in relativity; (2) intermediate, to suit a second course; and (3) advanced, to
suit higher level students. We then give a summary of useful results, and
suggest further reading in this often obscure field.
| [
{
"created": "Wed, 9 Feb 2011 22:36:17 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Jun 2011 01:39:36 GMT",
"version": "v2"
}
] | 2015-03-18 | [
[
"O'Donnell",
"Kane",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | The purpose of this paper is to provide an elementary introduction to the qualitative and quantitative results of velocity combination in special relativity, including the Wigner rotation and Thomas precession. We utilize only the most familiar tools of special relativity, in arguments presented at three differing levels: (1) utterly elementary, which will suit a first course in relativity; (2) intermediate, to suit a second course; and (3) advanced, to suit higher level students. We then give a summary of useful results, and suggest further reading in this often obscure field. |
2404.16079 | Oleg Zenin | Stanislav Alexeyev, Artem Baiderin, Alexandra Nemtinova, Oleg Zenin | Non-local gravitational corrections in black hole shadow images | 12 pages, 6 figures | Zh. Exp. Teor. Fiz. (JETP, Russian version), 2024, Vol. 165, No 4,
p. 508-515 | 10.31857/S0044451024040059 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | With the help of Newman-Janis method new spinning black hole (BH) solution
for a non-local gravity model was obtained. We show how to account the quantum
gravitational correction part in BH shadows modelling using spinning BH metrics
with a model independent approach. It is confirmed that in the future to follow
the increasing of the experimental accuracy and therefore to reproduce new
results theoretically one could take into account different field correction
terms instead of introducing of new fields and/or curvature expansions.
| [
{
"created": "Wed, 24 Apr 2024 13:12:32 GMT",
"version": "v1"
}
] | 2024-04-26 | [
[
"Alexeyev",
"Stanislav",
""
],
[
"Baiderin",
"Artem",
""
],
[
"Nemtinova",
"Alexandra",
""
],
[
"Zenin",
"Oleg",
""
]
] | With the help of Newman-Janis method new spinning black hole (BH) solution for a non-local gravity model was obtained. We show how to account the quantum gravitational correction part in BH shadows modelling using spinning BH metrics with a model independent approach. It is confirmed that in the future to follow the increasing of the experimental accuracy and therefore to reproduce new results theoretically one could take into account different field correction terms instead of introducing of new fields and/or curvature expansions. |
1908.07381 | Gamal G.L. Nashed | Salvatore Capozziello and Gamal G.L. Nashed | Rotating and non-rotating AdS black holes in $f({\cal T})$ gravity
non-linear electrodynamics | 14 Pages, 3 Ligures, Latex, Will appear in EPJC | null | 10.1140/epjc/s10052-019-7424-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive new exact charged $d$-dimensional black hole solutions for
quadratic teleparallel equivalent gravity, $f({\cal T})=a_0+a_1{\cal
T}+a_2{\cal T}^2$, where $\cal T$ is the torsion scalar, in the case of
non-linear electrodynamics. We give a specific form of electromagnetic function
and find out the form of the unknown functions that characterize the vielbeins
in presence of the electromagnetic field. It is possible to show that the black
holes behave asymptotically as AdS solutions and contain, in addition to the
monopole and quadrupole terms, other higher order terms whose source is the
non-linear electrodynamics field. We calculate the electromagnetic Maxwell
field and show that our d-dimensional black hole solutions coincide with the
previous obtained one \cite{2017JHEP...07..136A}. The structure of the
solutions show that there is a central singularity that is much mild in
comparison with the respective one in General Relativity. Finally, the
thermodynamical properties of the solutions are investigated by calculating the
entropy, the Hawking temperature, the heat capacity, and other physical
quantities. The most important result of thermodynamics is that the entropy is
not proportional to the area of the black hole. This inanition points out that
we must have a constrain on the quadrupole term to get a positive entropy
otherwise we get a negative value.
| [
{
"created": "Sat, 17 Aug 2019 09:54:02 GMT",
"version": "v1"
},
{
"created": "Sat, 19 Oct 2019 14:06:20 GMT",
"version": "v2"
}
] | 2020-01-08 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Nashed",
"Gamal G. L.",
""
]
] | We derive new exact charged $d$-dimensional black hole solutions for quadratic teleparallel equivalent gravity, $f({\cal T})=a_0+a_1{\cal T}+a_2{\cal T}^2$, where $\cal T$ is the torsion scalar, in the case of non-linear electrodynamics. We give a specific form of electromagnetic function and find out the form of the unknown functions that characterize the vielbeins in presence of the electromagnetic field. It is possible to show that the black holes behave asymptotically as AdS solutions and contain, in addition to the monopole and quadrupole terms, other higher order terms whose source is the non-linear electrodynamics field. We calculate the electromagnetic Maxwell field and show that our d-dimensional black hole solutions coincide with the previous obtained one \cite{2017JHEP...07..136A}. The structure of the solutions show that there is a central singularity that is much mild in comparison with the respective one in General Relativity. Finally, the thermodynamical properties of the solutions are investigated by calculating the entropy, the Hawking temperature, the heat capacity, and other physical quantities. The most important result of thermodynamics is that the entropy is not proportional to the area of the black hole. This inanition points out that we must have a constrain on the quadrupole term to get a positive entropy otherwise we get a negative value. |
0911.5376 | Baocheng Zhang | Baocheng Zhang, Qing-yu Cai, and Ming-sheng Zhan | Entropy Conservation in the Transition of Schwarzschild-de Sitter space
to de Sitter space through tunneling | null | Chin. Phys. Lett. 29 (2012) 020401 | 10.1088/0256-307X/29/2/020401 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the Parikh-Wilczek tunneling through the de Sitter horizon and
obtain the tunneling rate in Schwarzschild-de Sitter space, which is
non-thermal and closely related to the change of entropy. We discuss the
thermodynamics of Schwarzschild-de Sitter space and show existence of
correlation which ensured the conservation of the total entropy in the
transition process of Schwarzschild-de Sitter space to de Sitter space. The
correlation and the conserved entropy enlighten a way to explain the entropy in
empty de Sitter space.
| [
{
"created": "Sat, 28 Nov 2009 05:26:22 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Nov 2012 05:52:02 GMT",
"version": "v2"
}
] | 2012-11-15 | [
[
"Zhang",
"Baocheng",
""
],
[
"Cai",
"Qing-yu",
""
],
[
"Zhan",
"Ming-sheng",
""
]
] | We revisit the Parikh-Wilczek tunneling through the de Sitter horizon and obtain the tunneling rate in Schwarzschild-de Sitter space, which is non-thermal and closely related to the change of entropy. We discuss the thermodynamics of Schwarzschild-de Sitter space and show existence of correlation which ensured the conservation of the total entropy in the transition process of Schwarzschild-de Sitter space to de Sitter space. The correlation and the conserved entropy enlighten a way to explain the entropy in empty de Sitter space. |
1507.03728 | Handhika Ramadhan | Handhika S. Ramadhan, Brian A. Cahyo, and Muhammad Iqbal | Flux compactifications in Einstein-Born-Infeld theories | 17 pages, 8 figures | Phys. Rev. D 92 024021 (2015) | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the flux compactification mechanism in simple toy models of
Einstein-Born-Infeld theories. These are the direct generalizations of the
Einstein-Maxwell flux compactifications that recently gained fame as a toy
model for tunneling in the landscape. Our investigation reveals that the
Born-Infeld form does not significantly modify the qualitative result of the
Einstein-Maxwell theory. for the case of Einstein-Higgs theory, however, we
found that the effect of Born-Infeld nonlinearity is to render all q>1
extradimensional compactification unstable against semiclassical tunneling to
nothing.
| [
{
"created": "Tue, 14 Jul 2015 06:09:52 GMT",
"version": "v1"
}
] | 2015-07-15 | [
[
"Ramadhan",
"Handhika S.",
""
],
[
"Cahyo",
"Brian A.",
""
],
[
"Iqbal",
"Muhammad",
""
]
] | We investigate the flux compactification mechanism in simple toy models of Einstein-Born-Infeld theories. These are the direct generalizations of the Einstein-Maxwell flux compactifications that recently gained fame as a toy model for tunneling in the landscape. Our investigation reveals that the Born-Infeld form does not significantly modify the qualitative result of the Einstein-Maxwell theory. for the case of Einstein-Higgs theory, however, we found that the effect of Born-Infeld nonlinearity is to render all q>1 extradimensional compactification unstable against semiclassical tunneling to nothing. |
2112.15112 | Zinnat Hassan | G. Mustafa, Zinnat Hassan, P.K. Sahoo | Traversable wormhole inspired by non-commutative geometries in $f(Q)$
gravity with conformal symmetry | Annals of Physics published version | Annals of Physics 437 (2022) 168751 | 10.1016/j.aop.2021.168751 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | This article is based on the study of wormhole geometries in the context of
symmetric teleparallel gravity or $f(Q)$ gravity, where $Q$ is the
non-metricity scalar, and it is responsible for the gravitational interaction.
To discuss the wormhole solutions, we consider spherically symmetric static
spacetime metric with anisotropic matter contents under well-known
non-commutative distributions known as Gaussian and Lorentzian distributions
with an extra condition of permitting conformal killing vectors (CKV). This
work aims to obtain wormhole solutions under these distributions, and through
we found that wormhole solutions exist under these Gaussian and Lorentzian
sources with viable physical properties. Further, we examine the stability of
our obtained solutions through Tolman-Oppenheimer-Volkoff (TOV) equation and
found that our calculated results are stable.
| [
{
"created": "Thu, 30 Dec 2021 16:11:39 GMT",
"version": "v1"
}
] | 2022-01-11 | [
[
"Mustafa",
"G.",
""
],
[
"Hassan",
"Zinnat",
""
],
[
"Sahoo",
"P. K.",
""
]
] | This article is based on the study of wormhole geometries in the context of symmetric teleparallel gravity or $f(Q)$ gravity, where $Q$ is the non-metricity scalar, and it is responsible for the gravitational interaction. To discuss the wormhole solutions, we consider spherically symmetric static spacetime metric with anisotropic matter contents under well-known non-commutative distributions known as Gaussian and Lorentzian distributions with an extra condition of permitting conformal killing vectors (CKV). This work aims to obtain wormhole solutions under these distributions, and through we found that wormhole solutions exist under these Gaussian and Lorentzian sources with viable physical properties. Further, we examine the stability of our obtained solutions through Tolman-Oppenheimer-Volkoff (TOV) equation and found that our calculated results are stable. |
gr-qc/0209032 | B. V. Ivanov | B.V.Ivanov | The general double-dust solution | 14 pages, RevTex; paper version replacing letter version | null | null | null | gr-qc | null | The gravitational field of two identical rotating and counter-moving dust
beams is found in full generality. The solution depends on an arbitrary
function and a parameter. Some of its properties are studied. Previous
particular solutions are derived as subcases.
| [
{
"created": "Tue, 10 Sep 2002 09:41:37 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Sep 2002 10:04:41 GMT",
"version": "v2"
},
{
"created": "Tue, 4 Feb 2003 09:49:29 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Ivanov",
"B. V.",
""
]
] | The gravitational field of two identical rotating and counter-moving dust beams is found in full generality. The solution depends on an arbitrary function and a parameter. Some of its properties are studied. Previous particular solutions are derived as subcases. |
gr-qc/9401007 | Hideo Kodama | Hideo Kodama, Hideki Ishihara and Yoshihisa Fujiwara | Does a domain wall emit gravitational waves? -- General-relativistic
perturbative treatment | 26pages, LaTeX file with epsfs | Phys.Rev.D50:7292-7303,1994 | 10.1103/PhysRevD.50.7292 | YITP/U-94-01 | gr-qc | null | The behavior of gravitational wave perturbations on a locally Minkowskian
spacetime background containing a planar domain wall is investigated in the
gauge-invariant general relativistic framework. It is shown that for this
particular background the domain wall does not emit gravitational waves
spontaneously by its free oscillation in the first order, although it scatters
incidental gravitational waves.
| [
{
"created": "Mon, 10 Jan 1994 09:09:03 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Kodama",
"Hideo",
""
],
[
"Ishihara",
"Hideki",
""
],
[
"Fujiwara",
"Yoshihisa",
""
]
] | The behavior of gravitational wave perturbations on a locally Minkowskian spacetime background containing a planar domain wall is investigated in the gauge-invariant general relativistic framework. It is shown that for this particular background the domain wall does not emit gravitational waves spontaneously by its free oscillation in the first order, although it scatters incidental gravitational waves. |
1212.2163 | Tsuyoshi Houri | Tsuyoshi Houri and Kei Yamamoto | Killing-Yano symmetry of Kaluza-Klein black holes in five dimensions | 22 pages, no figures, v2: references added, minor changes to section
2 | Class.Quant.Grav.30:075013,2013 | 10.1088/0264-9381/30/7/075013 | DAMTP-2012-83, OCU-PHYS-377 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using a generalised Killing-Yano equation in the presence of torsion,
spacetime metrics admitting a rank-2 generalised Killing-Yano tensor are
investigated in five dimensions under the assumption that its eigenvector
associated with the zero eigenvalue is a Killing vector field. It is shown that
such metrics are classified into three types and the corresponding local
expressions are given explicitly. It is also shown that they cover some classes
of charged, rotating Kaluza-Klein black hole solutions of minimal supergravity
and abelian heterotic supergravity.
| [
{
"created": "Mon, 10 Dec 2012 18:40:47 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Apr 2013 06:21:32 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Houri",
"Tsuyoshi",
""
],
[
"Yamamoto",
"Kei",
""
]
] | Using a generalised Killing-Yano equation in the presence of torsion, spacetime metrics admitting a rank-2 generalised Killing-Yano tensor are investigated in five dimensions under the assumption that its eigenvector associated with the zero eigenvalue is a Killing vector field. It is shown that such metrics are classified into three types and the corresponding local expressions are given explicitly. It is also shown that they cover some classes of charged, rotating Kaluza-Klein black hole solutions of minimal supergravity and abelian heterotic supergravity. |
gr-qc/9807021 | Hagen Kleinert | H. Kleinert | Universality Principle for Orbital Angular Momentum and Spin in Gravity
with Torsion | Author Information under
http://www.physik.fu-berlin.de/~kleinert/institution.html . Latest update of
paper also at http://www.physik.fu-berlin.de/~kleinert/kleiner_re271 | Gen.Rel.Grav. 32 (2000) 1271-1280 | 10.1023/A:1001990604209 | null | gr-qc | null | We argue that compatibility with elementary particle physics requires
gravitational theories with torsion to be unable to distinguish between orbital
angular momentum and spin. An important consequence of this principle is that
spinless particles must move along autoparallel trajectories, not along
geodesics.
| [
{
"created": "Thu, 9 Jul 1998 12:06:00 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Jul 1998 06:54:19 GMT",
"version": "v2"
},
{
"created": "Sat, 11 Jul 1998 10:40:09 GMT",
"version": "v3"
}
] | 2015-06-25 | [
[
"Kleinert",
"H.",
""
]
] | We argue that compatibility with elementary particle physics requires gravitational theories with torsion to be unable to distinguish between orbital angular momentum and spin. An important consequence of this principle is that spinless particles must move along autoparallel trajectories, not along geodesics. |
1410.4779 | Eric Thrane | John T. Giblin Jr. and Eric Thrane | The detectability of cosmological gravitational-wave backgrounds: a rule
of thumb | 6 pages, 1 figure | Phys. Rev. D 90, 107502 (2014) | 10.1103/PhysRevD.90.107502 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recent claim by BICEP2 of evidence for primordial gravitational waves
from inflation has focused interest on the potential for early-Universe
cosmology using observations of gravitational waves. In addition to cosmic
microwave background detectors, efforts are underway to carry out
gravitational-wave astronomy over a wide range of frequencies including pulsar
timing arrays (nHz), space-based detectors (mHz), and terrestrial detectors
($\sim$10-2000 Hz). This multiband effort will probe a wide range of times in
the early Universe (each corresponding to a different energy scale), during
which gravitational-wave backgrounds may have been produced through processes
such as phase transitions or preheating. In this letter, we derive a rule of
thumb (not quite so strong as an upper limit) governing the maximum energy
density of cosmological backgrounds. For most cosmological scenarios, we expect
the energy density spectrum to peak at values of
$\Omega_\text{gw}(f)\lesssim10^{-12\pm2}$. We discuss the applicability of this
rule of thumb and the implications for gravitational-wave astronomy.
| [
{
"created": "Fri, 17 Oct 2014 16:00:29 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Oct 2014 18:57:43 GMT",
"version": "v2"
}
] | 2016-07-11 | [
[
"Giblin",
"John T.",
"Jr."
],
[
"Thrane",
"Eric",
""
]
] | The recent claim by BICEP2 of evidence for primordial gravitational waves from inflation has focused interest on the potential for early-Universe cosmology using observations of gravitational waves. In addition to cosmic microwave background detectors, efforts are underway to carry out gravitational-wave astronomy over a wide range of frequencies including pulsar timing arrays (nHz), space-based detectors (mHz), and terrestrial detectors ($\sim$10-2000 Hz). This multiband effort will probe a wide range of times in the early Universe (each corresponding to a different energy scale), during which gravitational-wave backgrounds may have been produced through processes such as phase transitions or preheating. In this letter, we derive a rule of thumb (not quite so strong as an upper limit) governing the maximum energy density of cosmological backgrounds. For most cosmological scenarios, we expect the energy density spectrum to peak at values of $\Omega_\text{gw}(f)\lesssim10^{-12\pm2}$. We discuss the applicability of this rule of thumb and the implications for gravitational-wave astronomy. |
0711.4909 | Ming Lei Tong | M. L. Tong, Y. Zhang | Detecting very-high-frequency relic gravitational waves by
electromagnetic wave polarizations in a waveguide | 18pages, 10 figures, accepted by ChJAA | Chin. J. Astron. Astrophys. 8, 314, (2008) | 10.1088/1009-9271/8/3/08 | null | gr-qc | null | The polarization vector (PV) of an electromagnetic wave (EW) will experience
a rotation in a region of spacetime perturbed by gravitational waves (GWs).
Based on this idea, Cruise's group has built an annular waveguide to detect
GWs. We give detailed calculations of the rotations of the polarization vector
of an EW caused by incident GWs from various directions and in various
polarization states, and then analyze the accumulative effects on the
polarization vector when the EW passes n cycles along the annular waveguide. We
reexamine the feasibility and limitation of this method to detect GWs of high
frequency around 100 MHz, in particular, the relic gravitational waves (RGWs).
By comparing the spectrum of RGWs in the accelerating universe with the
detector sensitivity of the current waveguide, it is found that the amplitude
of the RGWs is too low to be detected by the waveguide detectors currently
running. Possible ways of improvements on detection are discussed also.
| [
{
"created": "Fri, 30 Nov 2007 11:39:43 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Tong",
"M. L.",
""
],
[
"Zhang",
"Y.",
""
]
] | The polarization vector (PV) of an electromagnetic wave (EW) will experience a rotation in a region of spacetime perturbed by gravitational waves (GWs). Based on this idea, Cruise's group has built an annular waveguide to detect GWs. We give detailed calculations of the rotations of the polarization vector of an EW caused by incident GWs from various directions and in various polarization states, and then analyze the accumulative effects on the polarization vector when the EW passes n cycles along the annular waveguide. We reexamine the feasibility and limitation of this method to detect GWs of high frequency around 100 MHz, in particular, the relic gravitational waves (RGWs). By comparing the spectrum of RGWs in the accelerating universe with the detector sensitivity of the current waveguide, it is found that the amplitude of the RGWs is too low to be detected by the waveguide detectors currently running. Possible ways of improvements on detection are discussed also. |
1203.1151 | Partha Mukhopadhyay | Partha Mukhopadhyay | All order covariant tubular expansion | 27 pages. Corrected an error in a class of coefficients resulting
from a typo. Integral theorem and all other results remain unchanged | Reviews in Mathematical Physics, Vol. 26, No. 1 (2013) 1350019 | 10.1142/S0129055X13500190 | IMSc/2012/3/5 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider tubular neighborhood of an arbitrary submanifold embedded in a
(pseudo-)Riemannian manifold. This can be described by Fermi normal coordinates
(FNC) satisfying certain conditions as described by Florides and Synge in
\cite{FS}. By generalizing the work of Muller {\it et al} in \cite{muller} on
Riemann normal coordinate expansion, we derive all order FNC expansion of
vielbein in this neighborhood with closed form expressions for the curvature
expansion coefficients. Our result is shown to be consistent with certain
integral theorem for the metric proved in \cite{FS}.
| [
{
"created": "Tue, 6 Mar 2012 09:58:03 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Oct 2012 13:34:49 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Nov 2013 09:35:17 GMT",
"version": "v3"
},
{
"created": "Wed, 17 Aug 2016 20:58:56 GMT",
"version": "v4"
},
{
"created": "Wed, 17 Aug 2016 16:10:45 GMT",
"version": "v5"
}
] | 2016-08-22 | [
[
"Mukhopadhyay",
"Partha",
""
]
] | We consider tubular neighborhood of an arbitrary submanifold embedded in a (pseudo-)Riemannian manifold. This can be described by Fermi normal coordinates (FNC) satisfying certain conditions as described by Florides and Synge in \cite{FS}. By generalizing the work of Muller {\it et al} in \cite{muller} on Riemann normal coordinate expansion, we derive all order FNC expansion of vielbein in this neighborhood with closed form expressions for the curvature expansion coefficients. Our result is shown to be consistent with certain integral theorem for the metric proved in \cite{FS}. |
1612.04554 | Panayiotis Stavrinos | Panayiotis C.Stavrinos and Maria Alexiou | Raychaudhuri equation in the Finsler-Randers spacetime and Generalized
scalar-tensor theories | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we obtain the Raychaudhuri equations for various types of
Finsler spaces as the Finsler-Randers (FR) space-time and in a more general
geometrical structure of the space-time manifold which contains two fibres that
are two scalars which represent inflaton fields $\phi^{(1)}, \phi^{(2)}.$In
addition, the energy-conditions are studied in a FR cosmology and are
correlated with FRW model. Finally an application of Raychaudhuri equation for
the model $M \times \{ \phi^{(1)} \} \times \{ \phi^{(2)} \}$ with M a FRW
space is given.
| [
{
"created": "Wed, 14 Dec 2016 09:54:17 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Nov 2017 10:58:35 GMT",
"version": "v2"
}
] | 2017-11-15 | [
[
"Stavrinos",
"Panayiotis C.",
""
],
[
"Alexiou",
"Maria",
""
]
] | In this work, we obtain the Raychaudhuri equations for various types of Finsler spaces as the Finsler-Randers (FR) space-time and in a more general geometrical structure of the space-time manifold which contains two fibres that are two scalars which represent inflaton fields $\phi^{(1)}, \phi^{(2)}.$In addition, the energy-conditions are studied in a FR cosmology and are correlated with FRW model. Finally an application of Raychaudhuri equation for the model $M \times \{ \phi^{(1)} \} \times \{ \phi^{(2)} \}$ with M a FRW space is given. |
1305.6936 | Vitor Cardoso | Vitor Cardoso, Isabella P. Carucci, Paolo Pani, Thomas P. Sotiriou | Matter around Kerr black holes in scalar-tensor theories: scalarization
and superradiant instability | 11 pages, 3 figures. v2: published version | Phys.Rev. D88, 044056 (2013) | 10.1103/PhysRevD.88.044056 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In electrovacuum stationary, asymptotically flat black holes in scalar-tensor
theories of gravity are described by the Kerr-Newman family of solutions, just
as in general relativity. We show that there exist two mechanisms which can
render Kerr black holes unstable when matter is present in the vicinity of the
black hole, as this induces an effective mass for the scalar. The first
mechanism is a tachyonic instability that appears when the effective mass
squared is negative, triggering the development of scalar hair --- a black hole
version of "spontaneous scalarization". The second instability is associated
with superradiance and is present when the effective mass squared is positive
and when the black hole spin exceeds a certain threshold. The second mechanism
is also responsible for a resonant effect in the superradiant scattering of
scalar waves, with amplification factors as large as 10^5 or more.
| [
{
"created": "Wed, 29 May 2013 20:00:40 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Jan 2014 19:53:52 GMT",
"version": "v2"
}
] | 2014-01-23 | [
[
"Cardoso",
"Vitor",
""
],
[
"Carucci",
"Isabella P.",
""
],
[
"Pani",
"Paolo",
""
],
[
"Sotiriou",
"Thomas P.",
""
]
] | In electrovacuum stationary, asymptotically flat black holes in scalar-tensor theories of gravity are described by the Kerr-Newman family of solutions, just as in general relativity. We show that there exist two mechanisms which can render Kerr black holes unstable when matter is present in the vicinity of the black hole, as this induces an effective mass for the scalar. The first mechanism is a tachyonic instability that appears when the effective mass squared is negative, triggering the development of scalar hair --- a black hole version of "spontaneous scalarization". The second instability is associated with superradiance and is present when the effective mass squared is positive and when the black hole spin exceeds a certain threshold. The second mechanism is also responsible for a resonant effect in the superradiant scattering of scalar waves, with amplification factors as large as 10^5 or more. |
1505.05102 | Sergio Ulhoa | J. G. Silva, A. F. Santos and S. C. Ulhoa | On FRW Model in Conformal Teleparallel Gravity | Accepted in EPJC | The European Physical Journal C, 76:167, 2016 | 10.1140/epjc/s10052-016-4023-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we use the conformal teleparallel gravity to study an isotropic
and homogeneous Universe which is settled by the FRW metric. We solve the field
equations and we obtain the behavior of some cosmological parameters such as
scale factor, deceleration parameter and the energy density of the perfect
fluid which is the matter field of our model. The field equations, that we
called modified Friedmann equations, allow us to define a dark fluid, with dark
energy density and dark pressure, responsible for the acceleration in the
Universe.
| [
{
"created": "Sat, 16 May 2015 18:58:47 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Mar 2016 19:22:40 GMT",
"version": "v2"
}
] | 2016-03-30 | [
[
"Silva",
"J. G.",
""
],
[
"Santos",
"A. F.",
""
],
[
"Ulhoa",
"S. C.",
""
]
] | In this paper we use the conformal teleparallel gravity to study an isotropic and homogeneous Universe which is settled by the FRW metric. We solve the field equations and we obtain the behavior of some cosmological parameters such as scale factor, deceleration parameter and the energy density of the perfect fluid which is the matter field of our model. The field equations, that we called modified Friedmann equations, allow us to define a dark fluid, with dark energy density and dark pressure, responsible for the acceleration in the Universe. |
gr-qc/0405098 | Alessandro Fabbri | R. Balbinot, S. Fagnocchi, A. Fabbri | Quantum effects in Acoustic Black Holes: the Backreaction | 23 pages, latex, 1 figure; revised version, to appear in Phys. Rev. D | Phys.Rev. D71 (2005) 064019 | 10.1103/PhysRevD.71.064019 | null | gr-qc cond-mat.other hep-th | null | We investigate the backreaction equations for an acoustic black hole formed
in a Laval nozzle under the assumption that the motion of the fluid is
one-dimensional. The solution in the near-horizon region shows that as phonons
are (thermally) radiated the sonic horizon shrinks and the temperature
decreases. This contrasts with the behaviour of Schwarzschild black holes, and
is similar to what happens in the evaporation of (near-extremal)
Reissner-Nordstrom black holes (i.e. infinite evaporation time). Finally, by
appropriate boundary conditions the solution is extended in both the asymptotic
regions of the nozzle.
| [
{
"created": "Tue, 18 May 2004 14:49:11 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Mar 2005 11:24:33 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Balbinot",
"R.",
""
],
[
"Fagnocchi",
"S.",
""
],
[
"Fabbri",
"A.",
""
]
] | We investigate the backreaction equations for an acoustic black hole formed in a Laval nozzle under the assumption that the motion of the fluid is one-dimensional. The solution in the near-horizon region shows that as phonons are (thermally) radiated the sonic horizon shrinks and the temperature decreases. This contrasts with the behaviour of Schwarzschild black holes, and is similar to what happens in the evaporation of (near-extremal) Reissner-Nordstrom black holes (i.e. infinite evaporation time). Finally, by appropriate boundary conditions the solution is extended in both the asymptotic regions of the nozzle. |
1607.06278 | Masato Minamitsuji | Masato Minamitsuji | Solutions in the generalized Proca theory with the nonminimal coupling
to the Einstein tensor | 11 pages, no figure, the journal version | Phys. Rev. D 94, 084039 (2016) | 10.1103/PhysRevD.94.084039 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the static and spherically symmetric solutions in a class of
the generalized Proca theory with the nonminimal coupling to the Einstein
tensor. First, we show that the solutions in the scalar-tensor theory with the
nonminimal derivative coupling to the Einstein tensor can be those in the
generalized Proca theory with the vanishing field strength. We then show that
when the field strength takes the nonzero value the static and spherically
symmetric solutions can be found only for the specific value of the nonminimal
coupling constant. Second, we investigate the first-order slow-rotation
corrections to the static and spherically symmetric background. We find that
for the background with the vanishing electric field strength the slowly
rotating solution is identical to the Kerr- (anti-) de Sitter solutions in
general relativity. On the other hand, for the background with the nonvanishing
electric field strength the stealth property can realized at the first order in
the slow-rotation approximation.
| [
{
"created": "Thu, 21 Jul 2016 11:46:53 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Oct 2016 22:42:58 GMT",
"version": "v2"
},
{
"created": "Sun, 30 Oct 2016 12:55:36 GMT",
"version": "v3"
}
] | 2016-11-01 | [
[
"Minamitsuji",
"Masato",
""
]
] | We investigate the static and spherically symmetric solutions in a class of the generalized Proca theory with the nonminimal coupling to the Einstein tensor. First, we show that the solutions in the scalar-tensor theory with the nonminimal derivative coupling to the Einstein tensor can be those in the generalized Proca theory with the vanishing field strength. We then show that when the field strength takes the nonzero value the static and spherically symmetric solutions can be found only for the specific value of the nonminimal coupling constant. Second, we investigate the first-order slow-rotation corrections to the static and spherically symmetric background. We find that for the background with the vanishing electric field strength the slowly rotating solution is identical to the Kerr- (anti-) de Sitter solutions in general relativity. On the other hand, for the background with the nonvanishing electric field strength the stealth property can realized at the first order in the slow-rotation approximation. |
2104.06998 | Fabrizio Tamburini | Fabrizio Tamburini, Fabiano Feleppa, Ignazio Licata, and Bo Thid\'e | Kerr spacetime geometric optics for vortex beams | 9 pages, 1 figure | Phys. Rev. A 104, 013718 (2021) | 10.1103/PhysRevA.104.013718 | null | gr-qc astro-ph.HE physics.optics | http://creativecommons.org/licenses/by/4.0/ | We apply the analogy between gravitational fields and optical media in the
general relativistic geometric optics framework to describe how light can
acquire orbital angular momentum (OAM) when it traverses the gravitational
field of a massive rotating compact object and the interplay between OAM and
polarization. Kerr spacetimes are known not only to impose a gravitational
Faraday rotation on the polarization of a light beam, but also to set a
characteristic fingerprint in the orbital angular momentum distribution of the
radiation passing nearby a rotating black hole (BH). Kerr spacetime behaves
like an inhomogeneous and anisotropic medium, in which light can acquire
orbital angular momentum and spin-to-orbital angular momentum conversion can
occur, acting as a polarization and phase changing medium for the
gravitationally lensed light, as confirmed by the data analysis of M87* black
hole.
| [
{
"created": "Wed, 14 Apr 2021 17:29:31 GMT",
"version": "v1"
}
] | 2021-07-28 | [
[
"Tamburini",
"Fabrizio",
""
],
[
"Feleppa",
"Fabiano",
""
],
[
"Licata",
"Ignazio",
""
],
[
"Thidé",
"Bo",
""
]
] | We apply the analogy between gravitational fields and optical media in the general relativistic geometric optics framework to describe how light can acquire orbital angular momentum (OAM) when it traverses the gravitational field of a massive rotating compact object and the interplay between OAM and polarization. Kerr spacetimes are known not only to impose a gravitational Faraday rotation on the polarization of a light beam, but also to set a characteristic fingerprint in the orbital angular momentum distribution of the radiation passing nearby a rotating black hole (BH). Kerr spacetime behaves like an inhomogeneous and anisotropic medium, in which light can acquire orbital angular momentum and spin-to-orbital angular momentum conversion can occur, acting as a polarization and phase changing medium for the gravitationally lensed light, as confirmed by the data analysis of M87* black hole. |
1309.7092 | Edward Glass | E.N. Glass | Generating Anisotropic Collapse and Expansion Solutions of Einstein's
Equations | to appear in Gen. Rel. Gravit | null | 10.1007/s10714-013-1609-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Analytic gravitational collapse and expansion solutions with anisotropic
pressure are generated. Metric functions are found by requiring zero heat flow
scalar. It emerges that a single function generates the anisotropic solutions.
Each generating function contains an arbitrary function of time which can be
chosen to fit various astrophysical time profiles. Two examples are provided: a
bounded collapse metric and an expanding cosmological solution
| [
{
"created": "Fri, 27 Sep 2013 00:52:28 GMT",
"version": "v1"
}
] | 2013-09-30 | [
[
"Glass",
"E. N.",
""
]
] | Analytic gravitational collapse and expansion solutions with anisotropic pressure are generated. Metric functions are found by requiring zero heat flow scalar. It emerges that a single function generates the anisotropic solutions. Each generating function contains an arbitrary function of time which can be chosen to fit various astrophysical time profiles. Two examples are provided: a bounded collapse metric and an expanding cosmological solution |
gr-qc/0601016 | Dan Vollick | Dan N. Vollick | Einstein-Maxwell and Einstein-Proca theory from a modified gravitational
action | 9 pages | null | null | null | gr-qc hep-th | null | A modified gravitational action is considered which involves the quantity
$F_{\mu\nu}=\partial_{\mu}\Gamma_{\nu}-\partial_{\nu}\Gamma_{\mu}$, where
$\Gamma_{\mu}=\Gamma^{\alpha}_{\mu\alpha}$. Since $\Gamma_{\mu}$ transforms
like a U(1) gauge field under coordinate transformations terms such as
$F^{\mu\nu}F_{\mu\nu}$ are invariant under coordinate transformations. If such
a term is added to the usual gravitational action the resulting field
equations, obtained from a Palatini variation, are the Einstein-Proca
equations. The vector field can be coupled to point charges or to a complex
scalar density of weight $ie$, where $e$ is the charge of the field. If this
scalar density is taken to be $g^{-ie/2}$ and the overall factor of the scalar
density Lagrangian takes on a particular value the resulting field equations
are the Einstein-Maxwell equations.
| [
{
"created": "Wed, 4 Jan 2006 19:07:32 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Vollick",
"Dan N.",
""
]
] | A modified gravitational action is considered which involves the quantity $F_{\mu\nu}=\partial_{\mu}\Gamma_{\nu}-\partial_{\nu}\Gamma_{\mu}$, where $\Gamma_{\mu}=\Gamma^{\alpha}_{\mu\alpha}$. Since $\Gamma_{\mu}$ transforms like a U(1) gauge field under coordinate transformations terms such as $F^{\mu\nu}F_{\mu\nu}$ are invariant under coordinate transformations. If such a term is added to the usual gravitational action the resulting field equations, obtained from a Palatini variation, are the Einstein-Proca equations. The vector field can be coupled to point charges or to a complex scalar density of weight $ie$, where $e$ is the charge of the field. If this scalar density is taken to be $g^{-ie/2}$ and the overall factor of the scalar density Lagrangian takes on a particular value the resulting field equations are the Einstein-Maxwell equations. |
1210.7902 | Je-An Gu | Je-An Gu, Sang Pyo Kim, Che-Min Shen | de Sitter Radiation and Backreaction in Quantum Cosmology | 9 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the quantum cosmology description of the de Sitter (dS) radiation
and its backreaction to dS space, inherent in the wave function of the
Wheeler-DeWitt equation for pure gravity with a cosmological constant. We first
investigate the quantum Friedmann-Lemaitre-Robertson-Walker cosmological model
and then consider possible effects of inhomogeneities of the universe on the dS
radiation. In both the cases we obtain the modified Friedmann equation,
including the backreaction from spacetime fluctuations, and the
quantum-corrected dS temperature. It is shown that the quantum correction
increases the dS temperature with the increment characterized by the ratio of
the dS scale to the Planck scale.
| [
{
"created": "Tue, 30 Oct 2012 04:16:22 GMT",
"version": "v1"
}
] | 2012-10-31 | [
[
"Gu",
"Je-An",
""
],
[
"Kim",
"Sang Pyo",
""
],
[
"Shen",
"Che-Min",
""
]
] | We explore the quantum cosmology description of the de Sitter (dS) radiation and its backreaction to dS space, inherent in the wave function of the Wheeler-DeWitt equation for pure gravity with a cosmological constant. We first investigate the quantum Friedmann-Lemaitre-Robertson-Walker cosmological model and then consider possible effects of inhomogeneities of the universe on the dS radiation. In both the cases we obtain the modified Friedmann equation, including the backreaction from spacetime fluctuations, and the quantum-corrected dS temperature. It is shown that the quantum correction increases the dS temperature with the increment characterized by the ratio of the dS scale to the Planck scale. |
1604.08586 | Anna Ijjas | Anna Ijjas, Justin Ripley, Paul J. Steinhardt | NEC violation in mimetic cosmology revisited | 7 pages | Physics Letters B 760 (2016), pp. 132-138 | 10.1016/j.physletb.2016.06.052 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of Einstein gravity, if the null energy condition (NEC) is
satisfied, the energy density in expanding space-times always decreases while
in contracting space-times the energy density grows and the universe eventually
collapses into a singularity. In particular, no non-singular bounce is
possible. It is, though, an open question if this energy condition can be
violated in a controlled way, i.e., without introducing pathologies, such as
unstable negative-energy states or an imaginary speed of sound. In this paper,
we will re-examine the claim that the recently proposed mimetic scenario can
violate the NEC without pathologies. We show that mimetic cosmology is prone to
gradient instabilities even in cases when the NEC is satisfied (except for
trivial examples). Most interestingly, the source of the instability is always
the Einstein-Hilbert term in the action. The matter stress-energy component
does not contribute spatial gradient terms but instead makes the problematic
curvature modes dynamical. We also show that mimetic cosmology can be
understood as a singular limit of known, well-behaved theories involving
higher-derivative kinetic terms and discuss ways of removing the instability.
| [
{
"created": "Thu, 28 Apr 2016 17:43:01 GMT",
"version": "v1"
}
] | 2016-07-04 | [
[
"Ijjas",
"Anna",
""
],
[
"Ripley",
"Justin",
""
],
[
"Steinhardt",
"Paul J.",
""
]
] | In the context of Einstein gravity, if the null energy condition (NEC) is satisfied, the energy density in expanding space-times always decreases while in contracting space-times the energy density grows and the universe eventually collapses into a singularity. In particular, no non-singular bounce is possible. It is, though, an open question if this energy condition can be violated in a controlled way, i.e., without introducing pathologies, such as unstable negative-energy states or an imaginary speed of sound. In this paper, we will re-examine the claim that the recently proposed mimetic scenario can violate the NEC without pathologies. We show that mimetic cosmology is prone to gradient instabilities even in cases when the NEC is satisfied (except for trivial examples). Most interestingly, the source of the instability is always the Einstein-Hilbert term in the action. The matter stress-energy component does not contribute spatial gradient terms but instead makes the problematic curvature modes dynamical. We also show that mimetic cosmology can be understood as a singular limit of known, well-behaved theories involving higher-derivative kinetic terms and discuss ways of removing the instability. |
0906.4269 | Kent Yagi | Kent Yagi, Takahiro Tanaka | Constraining alternative theories of gravity by gravitational waves from
precessing eccentric compact binaries with LISA | 35 pages, 17 figures; some corrections have been made on the Monte
Carlo simulations for the massive graviton case; corresponding tables and
figures have been replaced, but the major result almost unchanged. | Phys.Rev.D81:064008,2010; Erratum-ibid.D81:109902,2010 | 10.1103/PhysRevD.81.064008 10.1103/PhysRevD.81.109902 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate how strongly one can put constraints on alternative theories of
gravity such as Brans-Dicke and massive graviton theories with LISA. We
consider inspiral gravitational waves from a compact binary composed of a
neutron star (NS) and an intermediate mass black hole (IMBH) in Brans-Dicke
(BD) theory and that composed of 2 super massive black holes (SMBHs) in massive
graviton theories. We use the restricted 2PN waveforms including the effects of
spins. We also take both precession and eccentricity of the orbit into account.
For simplicity, we set the fiducial value for the spin of one of the binary
constituents to zero so that we can apply the approximation called
\textit{simple precession}. We perform the Monte Carlo simulations of $10^4$
binaries, estimating the determination accuracy of binary parameters including
the BD parameter $\omega_{\mathrm{BD}}$ and the Compton wavelength of graviton
$\lambda_g$ for each binary using the Fisher matrix method. We find that
including both the spin-spin coupling $\sigma$ and the eccentricity $e$ into
the binary parameters reduces the determination accuracy by an order of
magnitude for the Brans-Dicke case, whilst it has less influence on massive
graviton theories. On the other hand, including precession enhances the
constraint on $\omega_{\mathrm{BD}}$ only 20$%$ but it increases the constraint
on $\lambda_g$ by an order of magnitude. Using a $(1.4+1000)M_{\odot}$ NS/BH
binary of SNR=$\sqrt{200}$, one can put a constraint
$\omega_{\mathrm{BD}}>6944$, whilst using a $(10^7+10^6)M_{\odot}$ BH/BH binary
at 3Gpc, one can put $\lambda_g>3.06\times10^{21}$cm, on average. The latter is
4 orders of magnitude stronger than the one obtained from the solar system
experiment. These results indicate that the effects of precession and
eccentricity must be taken carefully in the parameter estimation analysis.
| [
{
"created": "Tue, 23 Jun 2009 19:57:46 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jun 2009 20:00:59 GMT",
"version": "v2"
},
{
"created": "Tue, 6 Apr 2010 08:55:20 GMT",
"version": "v3"
},
{
"created": "Thu, 13 May 2010 14:13:37 GMT",
"version": "v4"
}
] | 2014-11-20 | [
[
"Yagi",
"Kent",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | We calculate how strongly one can put constraints on alternative theories of gravity such as Brans-Dicke and massive graviton theories with LISA. We consider inspiral gravitational waves from a compact binary composed of a neutron star (NS) and an intermediate mass black hole (IMBH) in Brans-Dicke (BD) theory and that composed of 2 super massive black holes (SMBHs) in massive graviton theories. We use the restricted 2PN waveforms including the effects of spins. We also take both precession and eccentricity of the orbit into account. For simplicity, we set the fiducial value for the spin of one of the binary constituents to zero so that we can apply the approximation called \textit{simple precession}. We perform the Monte Carlo simulations of $10^4$ binaries, estimating the determination accuracy of binary parameters including the BD parameter $\omega_{\mathrm{BD}}$ and the Compton wavelength of graviton $\lambda_g$ for each binary using the Fisher matrix method. We find that including both the spin-spin coupling $\sigma$ and the eccentricity $e$ into the binary parameters reduces the determination accuracy by an order of magnitude for the Brans-Dicke case, whilst it has less influence on massive graviton theories. On the other hand, including precession enhances the constraint on $\omega_{\mathrm{BD}}$ only 20$%$ but it increases the constraint on $\lambda_g$ by an order of magnitude. Using a $(1.4+1000)M_{\odot}$ NS/BH binary of SNR=$\sqrt{200}$, one can put a constraint $\omega_{\mathrm{BD}}>6944$, whilst using a $(10^7+10^6)M_{\odot}$ BH/BH binary at 3Gpc, one can put $\lambda_g>3.06\times10^{21}$cm, on average. The latter is 4 orders of magnitude stronger than the one obtained from the solar system experiment. These results indicate that the effects of precession and eccentricity must be taken carefully in the parameter estimation analysis. |
2205.10168 | Serge Repin Mr. | Serge V. Repin, Mikhail A. Bugaev, Igor D. Novikov and Igor D. Novikov
jr | Silhouettes of wormholes traversed for radiation | 11 pages, 12 figures | Astronomy Reports, vol. 66, issue 10, pp. 835-844 (2022) | 10.1134/S1063772922100122 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | The problem of the passage of light through the mouth of a zero-mass wormhole
and the possibility of observing the objects from another asymptotically flat
space-time through the mouth of a wormhole are considered. It is shown that an
individual star can have several images and the fact that the image of a flat
Lambertian screen has a complex brightness distribution for an observer located
on the opposite side of the throat. Images of two such screens visible inside
the silhouette of a massless wormhole and the distribution of radiation
intensity in their images are constructed.
| [
{
"created": "Fri, 20 May 2022 13:19:27 GMT",
"version": "v1"
}
] | 2023-05-30 | [
[
"Repin",
"Serge V.",
""
],
[
"Bugaev",
"Mikhail A.",
""
],
[
"Novikov",
"Igor D.",
""
],
[
"Novikov",
"Igor D.",
"jr"
]
] | The problem of the passage of light through the mouth of a zero-mass wormhole and the possibility of observing the objects from another asymptotically flat space-time through the mouth of a wormhole are considered. It is shown that an individual star can have several images and the fact that the image of a flat Lambertian screen has a complex brightness distribution for an observer located on the opposite side of the throat. Images of two such screens visible inside the silhouette of a massless wormhole and the distribution of radiation intensity in their images are constructed. |
0807.3072 | Joseph Katz | Jiri Bicak, Joseph Katz and Donald Lynden-Bell | Gravitational waves and dragging effects | Scheduled to appear in Class. Quantum Grav. July 2008 | Class. Quantum Grav. 25 (2008) 165017 | 10.1088/0264-9381/25/16/165017 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Linear and rotational dragging effects of gravitational waves on local
inertial frames are studied in purely vacuum spacetimes. First the linear
dragging caused by a simple cylindrical pulse is investigated. Surprisingly
strong transversal effects of the pulse are exhibited. The angular momentum in
cylindrically symmetric spacetimes is then defined and confronted with some
results in literature. In the main part, the general procedure is developed for
studying weak gravitational waves with translational but not axial symmetry
which can carry angular momentum. After a suitable averaging the rotation of
local inertial frames due to such rotating waves can be calculated explicitly
and illustrated graphically. This is done in detail in the accompanying paper.
Finally, the rotational dragging is given for strong cylindrical waves
interacting with a rotating cosmic string with a small angular momentum.
| [
{
"created": "Sat, 19 Jul 2008 09:35:32 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Bicak",
"Jiri",
""
],
[
"Katz",
"Joseph",
""
],
[
"Lynden-Bell",
"Donald",
""
]
] | Linear and rotational dragging effects of gravitational waves on local inertial frames are studied in purely vacuum spacetimes. First the linear dragging caused by a simple cylindrical pulse is investigated. Surprisingly strong transversal effects of the pulse are exhibited. The angular momentum in cylindrically symmetric spacetimes is then defined and confronted with some results in literature. In the main part, the general procedure is developed for studying weak gravitational waves with translational but not axial symmetry which can carry angular momentum. After a suitable averaging the rotation of local inertial frames due to such rotating waves can be calculated explicitly and illustrated graphically. This is done in detail in the accompanying paper. Finally, the rotational dragging is given for strong cylindrical waves interacting with a rotating cosmic string with a small angular momentum. |
0811.1376 | Roland Steinbauer | Roland Steinbauer, James A. Vickers | On the Geroch-Traschen class of metrics | LaTeX, 22 pages | Class.Quant.Grav.26:065001,2009 | 10.1088/0264-9381/26/6/065001 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compare two approaches to Semi-Riemannian metrics of low regularity. The
maximally "reasonable" distributional setting of Geroch and Traschen is shown
to be consistently contained in the more general setting of nonlinear
distributional geometry in the sense of Colombeau.
| [
{
"created": "Sun, 9 Nov 2008 21:46:47 GMT",
"version": "v1"
}
] | 2011-06-07 | [
[
"Steinbauer",
"Roland",
""
],
[
"Vickers",
"James A.",
""
]
] | We compare two approaches to Semi-Riemannian metrics of low regularity. The maximally "reasonable" distributional setting of Geroch and Traschen is shown to be consistently contained in the more general setting of nonlinear distributional geometry in the sense of Colombeau. |
gr-qc/0006039 | Cenalo Vaz | Cenalo Vaz and Louis Witten | The Quantum States and the Statistical Entropy of the Charged Black Hole | 31 pages, 3 figures, PHYZZX macros. Comments on the wave-functional
in the interior and one reference added. To appear in Phys. Rev. D | Phys.Rev. D63 (2001) 024008 | 10.1103/PhysRevD.63.024008 | UATP-03/00 | gr-qc hep-th | null | We quantize the Reissner-Nordstr\"om black hole using an adaptation of
Kucha\v{r}'s canonical decomposition of the Kruskal extension of the
Schwarzschild black hole. The Wheeler-DeWitt equation turns into a functional
Schroedinger equation in Gaussian time by coupling the gravitational field to a
reference fluid or dust. The physical phase space of the theory is spanned by
the mass, $M$, the charge, $Q$, the physical radius, $R$, the dust proper time,
$\tau$, and their canonical momenta. The exact solutions of the functional
Schroedinger equation imply that the difference in the areas of the outer and
inner horizons is quantized in integer units. This agrees in spirit, but not
precisely, with Bekenstein's proposal on the discrete horizon area spectrum of
black holes. We also compute the entropy in the microcanonical ensemble and
show that the entropy of the Reissner-Nordstr\"om black hole is proportional to
this quantized difference in horizon areas.
| [
{
"created": "Mon, 12 Jun 2000 11:31:29 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Oct 2000 12:35:53 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Vaz",
"Cenalo",
""
],
[
"Witten",
"Louis",
""
]
] | We quantize the Reissner-Nordstr\"om black hole using an adaptation of Kucha\v{r}'s canonical decomposition of the Kruskal extension of the Schwarzschild black hole. The Wheeler-DeWitt equation turns into a functional Schroedinger equation in Gaussian time by coupling the gravitational field to a reference fluid or dust. The physical phase space of the theory is spanned by the mass, $M$, the charge, $Q$, the physical radius, $R$, the dust proper time, $\tau$, and their canonical momenta. The exact solutions of the functional Schroedinger equation imply that the difference in the areas of the outer and inner horizons is quantized in integer units. This agrees in spirit, but not precisely, with Bekenstein's proposal on the discrete horizon area spectrum of black holes. We also compute the entropy in the microcanonical ensemble and show that the entropy of the Reissner-Nordstr\"om black hole is proportional to this quantized difference in horizon areas. |
1508.05083 | Iv\'an E. S\'anchez G. | Emiliano Marachlian, Iv\'an E. S\'anchez G. and Osvaldo P. Santill\'an | Emergent Universe as an interaction in the dark sector | 15 pages, 8 figures | Modern Physics Letters A (MPLA), vol. 32, 28 (2017) | 10.1142/S0217732317501528 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A cosmological scenario where dark matter interacts with a variable vacuum
energy for a spatially flat Friedmann-Robertson-Walker space-time is proposed
and analysed to show that with a linear equation of state and a particular
interaction in the dark sector it is possible to get a model of an Emergent
Universe. In addition, the viability of two particular models is studied by
taking into account recent observations. The updated observational Hubble data
and the JLA supernovae data are used in order to constraint the cosmological
parameters of the models and estimate the amount of dark energy in the
radiation era. It is shown that the two models fulfil the severe bounds of
$\Omega_{x}(z\simeq 1100)<0.009$ at the $2\sigma$ level of Planck.
| [
{
"created": "Thu, 20 Aug 2015 19:41:59 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Sep 2017 17:10:18 GMT",
"version": "v2"
}
] | 2017-09-11 | [
[
"Marachlian",
"Emiliano",
""
],
[
"G.",
"Iván E. Sánchez",
""
],
[
"Santillán",
"Osvaldo P.",
""
]
] | A cosmological scenario where dark matter interacts with a variable vacuum energy for a spatially flat Friedmann-Robertson-Walker space-time is proposed and analysed to show that with a linear equation of state and a particular interaction in the dark sector it is possible to get a model of an Emergent Universe. In addition, the viability of two particular models is studied by taking into account recent observations. The updated observational Hubble data and the JLA supernovae data are used in order to constraint the cosmological parameters of the models and estimate the amount of dark energy in the radiation era. It is shown that the two models fulfil the severe bounds of $\Omega_{x}(z\simeq 1100)<0.009$ at the $2\sigma$ level of Planck. |
1602.04476 | Emanuele Berti | Emanuele Berti | Viewpoint: The First Sounds of Merging Black Holes | APS Physics Viewpoint article on the LIGO gravitational wave
detection paper. I would like to dedicate this Viewpoint to the memory of
Steve Detweiler. I wish he could celebrate with us. v2: Correction of a
statement on tests of general relativity. v3: Minor rephrasing of a sentence.
Animations and a better looking pdf file are available at
http://physics.aps.org/articles/v9/17 | APS Physics 9 (2016) 17 | 10.1103/Physics.9.17 | null | gr-qc astro-ph.HE hep-th physics.pop-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves emitted by the merger of two black holes have been
detected, setting the course for a new era of observational astrophysics.
| [
{
"created": "Sun, 14 Feb 2016 17:07:05 GMT",
"version": "v1"
},
{
"created": "Sat, 27 Feb 2016 01:16:47 GMT",
"version": "v2"
},
{
"created": "Mon, 14 Mar 2016 22:10:10 GMT",
"version": "v3"
}
] | 2016-03-16 | [
[
"Berti",
"Emanuele",
""
]
] | Gravitational waves emitted by the merger of two black holes have been detected, setting the course for a new era of observational astrophysics. |
1503.02858 | Roberto Casadio | Roberto Casadio, Octavian Micu, Dejan Stojkovic | Horizon Wave-Function and the Quantum Cosmic Censorship | RevTeX4, 6 pages, 2 figures. Typos corrected and comments added.
Version to appear in PLB | null | null | null | gr-qc astro-ph.HE hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the Cosmic Censorship Conjecture by means of the horizon
wave-function (HWF) formalism. We consider a charged massive particle whose
quantum mechanical state is represented by a spherically symmetric Gaussian
wave-function, and restrict our attention to the superxtremal case (with
charge-to-mass ratio $\alpha>1$), which is the prototype of a naked singularity
in the classical theory. We find that one can still obtain a normalisable HWF
for $\alpha^2<{2}$, and this configuration has a non-vanishing probability of
being a black hole, thus extending the classically allowed region for a charged
black hole. However, the HWF is not normalisable for $\alpha^2 > 2$, and the
uncertainty in the location of the horizon blows up at $\alpha^2=2$, signalling
that such an object is no more well-defined. This perhaps implies that a
quantum Cosmic Censorhip might be conjectured by stating that no black holes
with charge-to-mass ratio greater than a critical value (of the order of
$\sqrt{2}$) can exist.
| [
{
"created": "Tue, 10 Mar 2015 10:57:18 GMT",
"version": "v1"
},
{
"created": "Mon, 25 May 2015 08:58:11 GMT",
"version": "v2"
}
] | 2015-05-26 | [
[
"Casadio",
"Roberto",
""
],
[
"Micu",
"Octavian",
""
],
[
"Stojkovic",
"Dejan",
""
]
] | We investigate the Cosmic Censorship Conjecture by means of the horizon wave-function (HWF) formalism. We consider a charged massive particle whose quantum mechanical state is represented by a spherically symmetric Gaussian wave-function, and restrict our attention to the superxtremal case (with charge-to-mass ratio $\alpha>1$), which is the prototype of a naked singularity in the classical theory. We find that one can still obtain a normalisable HWF for $\alpha^2<{2}$, and this configuration has a non-vanishing probability of being a black hole, thus extending the classically allowed region for a charged black hole. However, the HWF is not normalisable for $\alpha^2 > 2$, and the uncertainty in the location of the horizon blows up at $\alpha^2=2$, signalling that such an object is no more well-defined. This perhaps implies that a quantum Cosmic Censorhip might be conjectured by stating that no black holes with charge-to-mass ratio greater than a critical value (of the order of $\sqrt{2}$) can exist. |
1204.6358 | Graeme Gossel | V. V. Flambaum, G. H. Gossel, G. F. Gribakin | Narrow resonances and black-hole-like absorption in a non-black-hole
metric | 6 pages, 4 figures | Phys. Rev. D 86, 044042 (2012) | 10.1103/PhysRevD.86.044042 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A massive body with the Schwarzschild interior metric (perfect fluid of
constant density) develops a pressure singularity at the origin when the radius
of the body $R$ approaches $9r_s/8$, where $r_s$ is the Schwarzschild radius.
We show that a quantum scalar particle scattered in this gravitational field
possesses a dense spectrum of narrow resonances. Their density and lifetimes
tend to infinity in the limit $R\rightarrow 9r_s/8$, and we determine the cross
section of the particle capture into these quasibound states. Therefore, a body
that is not a black hole demonstrates black-hole-like absorption.
| [
{
"created": "Sat, 28 Apr 2012 02:13:29 GMT",
"version": "v1"
},
{
"created": "Sun, 5 Aug 2012 06:43:41 GMT",
"version": "v2"
}
] | 2012-10-29 | [
[
"Flambaum",
"V. V.",
""
],
[
"Gossel",
"G. H.",
""
],
[
"Gribakin",
"G. F.",
""
]
] | A massive body with the Schwarzschild interior metric (perfect fluid of constant density) develops a pressure singularity at the origin when the radius of the body $R$ approaches $9r_s/8$, where $r_s$ is the Schwarzschild radius. We show that a quantum scalar particle scattered in this gravitational field possesses a dense spectrum of narrow resonances. Their density and lifetimes tend to infinity in the limit $R\rightarrow 9r_s/8$, and we determine the cross section of the particle capture into these quasibound states. Therefore, a body that is not a black hole demonstrates black-hole-like absorption. |
1907.11732 | Daniele Vernieri | Bruno J. Barros, Elsa M. Teixeira, Daniele Vernieri | Bouncing cosmology in $f(R,\mathcal{G})$ gravity by order reduction | v1: 7 pages; v2: 8 pages. Matches published version in Annals of
Physics | Annals of Physics 419, 168231 (2020) | 10.1016/j.aop.2020.168231 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A bouncing universe is a viable candidate to solve the initial singularity
problem. Here we consider bouncing solutions in the context of
$f(R,\mathcal{G})$ gravity by using an order reduction technique which allows
one to find solutions that are perturbatively close to General Relativity. This
procedure also acts as a model selection approach. Indeed, several covariant
gravitational actions leading to a bounce are directly selected by demanding
that the Friedmann equation derived within such gravity theories coincides with
the one emerging from Loop Quantum Cosmology.
| [
{
"created": "Fri, 26 Jul 2019 18:00:07 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jun 2020 16:12:59 GMT",
"version": "v2"
}
] | 2020-06-24 | [
[
"Barros",
"Bruno J.",
""
],
[
"Teixeira",
"Elsa M.",
""
],
[
"Vernieri",
"Daniele",
""
]
] | A bouncing universe is a viable candidate to solve the initial singularity problem. Here we consider bouncing solutions in the context of $f(R,\mathcal{G})$ gravity by using an order reduction technique which allows one to find solutions that are perturbatively close to General Relativity. This procedure also acts as a model selection approach. Indeed, several covariant gravitational actions leading to a bounce are directly selected by demanding that the Friedmann equation derived within such gravity theories coincides with the one emerging from Loop Quantum Cosmology. |
1209.5000 | Prasanta Mahato Prin. | Prasanta Mahato | Axial Current and Noether Charge | 9 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A decade ago, a Lagrangian density has been proposed by the author where only
the local symmetries of the Lorentz subgroup of (A)ds group is retained. This
formalism has been found to produce some results encompassing that of standard
Einstein-Hilbert formalism. In the present article, the conserved axial vector
matter currents, constructed in some earlier paper, have been found to be a
result of Noether's theorem.
PACS: 04.20.Fy, 04.20.Cv, 11.40.-q Keywords: Torsion, Axial Current,
Noether's Theorem
| [
{
"created": "Sat, 22 Sep 2012 16:35:03 GMT",
"version": "v1"
}
] | 2012-09-25 | [
[
"Mahato",
"Prasanta",
""
]
] | A decade ago, a Lagrangian density has been proposed by the author where only the local symmetries of the Lorentz subgroup of (A)ds group is retained. This formalism has been found to produce some results encompassing that of standard Einstein-Hilbert formalism. In the present article, the conserved axial vector matter currents, constructed in some earlier paper, have been found to be a result of Noether's theorem. PACS: 04.20.Fy, 04.20.Cv, 11.40.-q Keywords: Torsion, Axial Current, Noether's Theorem |
1105.5081 | Alejandro Corichi | Alejandro Corichi, Edison Montoya | Coherent semiclassical states for loop quantum cosmology | 37 pages, 7 figures | Phys.Rev.D84:044021,2011 | 10.1103/PhysRevD.84.044021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The spatially flat Friedman-Robertson-Walker (FRW) cosmological model with a
massless scalar field in loop quantum cosmology admits a description in terms
of a completely solvable model. This has been used to prove that: i) the
quantum bounce that replaces the big bang singularity is generic; ii) there is
an upper bound on the energy density for all states and iii) semiclassical
states at late times had to be semiclassical before the bounce. Here we
consider a family of exact solutions to the theory, corresponding to
generalized coherent Gaussian and squeezed states. We analyze the behavior of
basic physical observables and impose restrictions on the states based on
physical considerations. These turn out to be enough to select, from all the
generalized coherent states, those that behave semiclassical at late times. We
study then the properties of such states near the bounce where the most
`quantum behavior' is expected. As it turns out, the states remain sharply
peaked and semiclassical at the bounce and the dynamics is very well
approximated by the `effective theory' throughout the time evolution. We
compare the semiclassicality properties of squeezed states to those of the
Gaussian semiclassical states and conclude that the Gaussians are better
behaved. In particular, the asymmetry in the relative fluctuations before and
after the bounce are negligible, thus ruling out claims of so called `cosmic
forgetfulness'.
| [
{
"created": "Wed, 25 May 2011 16:36:21 GMT",
"version": "v1"
}
] | 2015-03-19 | [
[
"Corichi",
"Alejandro",
""
],
[
"Montoya",
"Edison",
""
]
] | The spatially flat Friedman-Robertson-Walker (FRW) cosmological model with a massless scalar field in loop quantum cosmology admits a description in terms of a completely solvable model. This has been used to prove that: i) the quantum bounce that replaces the big bang singularity is generic; ii) there is an upper bound on the energy density for all states and iii) semiclassical states at late times had to be semiclassical before the bounce. Here we consider a family of exact solutions to the theory, corresponding to generalized coherent Gaussian and squeezed states. We analyze the behavior of basic physical observables and impose restrictions on the states based on physical considerations. These turn out to be enough to select, from all the generalized coherent states, those that behave semiclassical at late times. We study then the properties of such states near the bounce where the most `quantum behavior' is expected. As it turns out, the states remain sharply peaked and semiclassical at the bounce and the dynamics is very well approximated by the `effective theory' throughout the time evolution. We compare the semiclassicality properties of squeezed states to those of the Gaussian semiclassical states and conclude that the Gaussians are better behaved. In particular, the asymmetry in the relative fluctuations before and after the bounce are negligible, thus ruling out claims of so called `cosmic forgetfulness'. |
1108.1363 | Giovanni Marozzi Dr. | G. Marozzi, G. P. Vacca | Isotropic Observers and the Inflationary Backreaction Problem | 16 pages, latex. Comments added, errors and typos corrected, main
results unchanged. Version accepted for publication in Class. Quantum Grav | Class. Quantum Grav. 29, 115007 (2012) | 10.1088/0264-9381/29/11/115007 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In an inflationary regime driven by a free massive inflaton we derive within
a genuinely gauge invariant approach the backreaction effects due to long
wavelength scalar fluctuations on the effective Hubble factor and equation of
state with respect to a class of observers which sees an inhomogeneous and
isotropic Universe. We find that, for such so-called isotropic observers,
contrary to what happens for the observables defined by free-falling observers,
there is an effect to leading order in the slow-roll parameter in the direction
of slowing down the measured rate of expansion and of having an effective
equation of state less de Sitter like. From a general point of view the
isotropic observers result has to be considered complementary to other cases
(observers) in helping to characterize the physical properties of the models
under investigation.
| [
{
"created": "Fri, 5 Aug 2011 16:18:48 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Oct 2011 17:30:46 GMT",
"version": "v2"
},
{
"created": "Fri, 27 Apr 2012 18:10:13 GMT",
"version": "v3"
}
] | 2012-05-15 | [
[
"Marozzi",
"G.",
""
],
[
"Vacca",
"G. P.",
""
]
] | In an inflationary regime driven by a free massive inflaton we derive within a genuinely gauge invariant approach the backreaction effects due to long wavelength scalar fluctuations on the effective Hubble factor and equation of state with respect to a class of observers which sees an inhomogeneous and isotropic Universe. We find that, for such so-called isotropic observers, contrary to what happens for the observables defined by free-falling observers, there is an effect to leading order in the slow-roll parameter in the direction of slowing down the measured rate of expansion and of having an effective equation of state less de Sitter like. From a general point of view the isotropic observers result has to be considered complementary to other cases (observers) in helping to characterize the physical properties of the models under investigation. |
2004.10773 | Tom Stratton | Tom Stratton, Luiz C. S. Leite, Sam R. Dolan and Lu\'is C. B. Crispino | Series reduction method for scattering of planar waves by Kerr-Newman
black holes | 16 pages, 3 figures | Phys. Rev. D 102, 044025 (2020) | 10.1103/PhysRevD.102.044025 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a practical method for evaluating the scattering amplitude
$f_s(\theta,\phi)$ that arises in the context of the scattering of scalar,
electromagnetic and gravitational planar waves by a rotating black hole. The
partial-wave representation of $f_s$ is a divergent series, but $f_s$ itself
diverges only at a single point on the sphere. Here we show that $f_s$ can be
expressed as the product of a reduced series and a pre-factor that diverges
only at this point. The coefficients of the reduced series are found
iteratively as linear combinations of those in the original series, and the
reduced series is shown to have amenable convergence properties. This
series-reduction method has its origins in an approach originally used in
electron scattering calculations in the 1950s, which we have extended to the
axisymmetric context for all bosonic fields.
| [
{
"created": "Wed, 22 Apr 2020 18:01:11 GMT",
"version": "v1"
}
] | 2020-08-19 | [
[
"Stratton",
"Tom",
""
],
[
"Leite",
"Luiz C. S.",
""
],
[
"Dolan",
"Sam R.",
""
],
[
"Crispino",
"Luís C. B.",
""
]
] | We present a practical method for evaluating the scattering amplitude $f_s(\theta,\phi)$ that arises in the context of the scattering of scalar, electromagnetic and gravitational planar waves by a rotating black hole. The partial-wave representation of $f_s$ is a divergent series, but $f_s$ itself diverges only at a single point on the sphere. Here we show that $f_s$ can be expressed as the product of a reduced series and a pre-factor that diverges only at this point. The coefficients of the reduced series are found iteratively as linear combinations of those in the original series, and the reduced series is shown to have amenable convergence properties. This series-reduction method has its origins in an approach originally used in electron scattering calculations in the 1950s, which we have extended to the axisymmetric context for all bosonic fields. |
1512.08426 | Wei-Tou Ni | Wei-Tou Ni | Equivalence Principles, Spacetime Structure and the Cosmic Connection | 47 pages, 3 tables | International Journal of Modern Physics D Vol. 25, No. 4 (2016)
1630002 (51 pages) | 10.1142/S0218271816300020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | After reviewing the meaning of various equivalence principles and the
structure of electrodynamics, we give a fairly detailed account of the
construction of the light cone and a core metric from the equivalence principle
for the photon (no birefringence, no polarization rotation and no
amplification/attenuation in propagation) in the framework of linear
electrodynamics using cosmic connections/observations as empirical support. The
cosmic nonbirefringent propagation of photons independent of energy and
polarization verifies the Galileo Equivalence Principle [Universality of
Propagation] for photons/electromagnetic wave packets in spacetime. This
nonbirefringence constrains the spacetime constitutive tensor to high precision
to a core metric form with an axion degree and a dilaton degree of freedom.
Thus comes the metric with axion and dilation. Constraints on axion and dilaton
from astrophysical/cosmic propagation are reviewed. E\"otv\"os-type
experiments, Hughes-Drever-type experiments, redshift experiments then
constrain and tie this core metric to agree with the matter metric, and hence a
unique physical metric and universality of metrology. We summarize these
experiments and review how the Galileo equivalence principle constrains the
Einstein Equivalence Principle (EEP) theoretically. In local physics this
physical metric gives the Lorentz/Poincar\'e covariance. Understanding that the
metric and EEP come from the vacuum as a medium of electrodynamics in the
linear regime, efforts to actively look for potential effects beyond this
linear scheme are warranted.
| [
{
"created": "Mon, 28 Dec 2015 14:49:49 GMT",
"version": "v1"
}
] | 2016-03-08 | [
[
"Ni",
"Wei-Tou",
""
]
] | After reviewing the meaning of various equivalence principles and the structure of electrodynamics, we give a fairly detailed account of the construction of the light cone and a core metric from the equivalence principle for the photon (no birefringence, no polarization rotation and no amplification/attenuation in propagation) in the framework of linear electrodynamics using cosmic connections/observations as empirical support. The cosmic nonbirefringent propagation of photons independent of energy and polarization verifies the Galileo Equivalence Principle [Universality of Propagation] for photons/electromagnetic wave packets in spacetime. This nonbirefringence constrains the spacetime constitutive tensor to high precision to a core metric form with an axion degree and a dilaton degree of freedom. Thus comes the metric with axion and dilation. Constraints on axion and dilaton from astrophysical/cosmic propagation are reviewed. E\"otv\"os-type experiments, Hughes-Drever-type experiments, redshift experiments then constrain and tie this core metric to agree with the matter metric, and hence a unique physical metric and universality of metrology. We summarize these experiments and review how the Galileo equivalence principle constrains the Einstein Equivalence Principle (EEP) theoretically. In local physics this physical metric gives the Lorentz/Poincar\'e covariance. Understanding that the metric and EEP come from the vacuum as a medium of electrodynamics in the linear regime, efforts to actively look for potential effects beyond this linear scheme are warranted. |
0803.4449 | Sujitkumar Chatterjee | D. Panigrahi and S. Chatterjee | General relativistic plasma in higher dimensional space time | 17 pages, 3 figures | JCAP0808:032,2008 | 10.1088/1475-7516/2008/08/032 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | The well known (3+1) decomposition of Thorne and Macdonald is invoked to
write down the Einstein-Maxwell equations generalised to (d+1) dimensions and
also to formulate the plasma equations in a flat FRW like spacetime in higher
dimensions (HD). Assuming an equation of state for the background metric we
find solutions as also dispersion relations in different regimes of the
universe in a unified manner both for magnetised(un) cold plasma. We find that
for a free photon in expanding background we get maximum redshift in 4D
spacetime, while for a particular dimension it is so in pre recombination era.
Further wave propagation in magnetised plasma is possible for a restricted
frequency range only, depending on the number of dimensions. Relevant to point
out that unlike the special relativistic result this allowed range evolves with
time. Interestingly the dielectric constant of the plasma media remains
constant, not sharing the expansion of the background, which generalises a
similar 4D result of Holcomb-Tajima in radiation background to the case of
higher dimensions with cosmic matter obeying an equation of state . Further,
analogous to the flat space static case we observe the phenomenon of Faraday
rotation in higher dimensional case also.
| [
{
"created": "Mon, 31 Mar 2008 12:39:18 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Aug 2008 13:14:40 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Panigrahi",
"D.",
""
],
[
"Chatterjee",
"S.",
""
]
] | The well known (3+1) decomposition of Thorne and Macdonald is invoked to write down the Einstein-Maxwell equations generalised to (d+1) dimensions and also to formulate the plasma equations in a flat FRW like spacetime in higher dimensions (HD). Assuming an equation of state for the background metric we find solutions as also dispersion relations in different regimes of the universe in a unified manner both for magnetised(un) cold plasma. We find that for a free photon in expanding background we get maximum redshift in 4D spacetime, while for a particular dimension it is so in pre recombination era. Further wave propagation in magnetised plasma is possible for a restricted frequency range only, depending on the number of dimensions. Relevant to point out that unlike the special relativistic result this allowed range evolves with time. Interestingly the dielectric constant of the plasma media remains constant, not sharing the expansion of the background, which generalises a similar 4D result of Holcomb-Tajima in radiation background to the case of higher dimensions with cosmic matter obeying an equation of state . Further, analogous to the flat space static case we observe the phenomenon of Faraday rotation in higher dimensional case also. |
1109.0842 | Hiromi Saida | Hiromi Saida | Universal Property of Quantum Gravity implied by Uniqueness Theorem of
Bekenstein-Hawking Entropy | 31 pages, 7 figures. Invited as a feature paper, and accepted as a
refereed paper, for the special issue "Black Hole Thermodynamics" in the
journal "Entropy", edited by J.Bekenstein | Entropy 2011, 13(9), 1611-1647 | 10.3390/e13091611 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper consists of three steps. In the first, we prove that the
Bekenstein-Hawking entropy is the unique expression of black hole entropy. Our
proof is constructed in the framework of thermodynamics without any statistical
discussion. In the second, intrinsic properties of quantum mechanics are shown,
which justify the Boltzmann formula to yield a unique entropy in statistical
mechanics. These properties clarify three conditions, one of which is necessary
and others are sufficient for the validity of Boltzmann formula. In the third,
by combining the above results, we find a reasonable suggestion from the
sufficient conditions that the potential of gravitational interaction among
microstates of underlying quantum gravity may not diverge to negative infinity
(such as Newtonian gravity) but is bounded below at a finite length scale. In
addition to that, from the necessary condition, the interaction has to be
repulsive within the finite length scale. The length scale should be Planck
size. Thus, quantum gravity may become repulsive at Planck length. Also, a
relation of these suggestions with action integral of gravity at semi-classical
level is given. These suggestions about quantum gravity are universal in the
sense that they are independent of any existing model of quantum gravity.
| [
{
"created": "Mon, 5 Sep 2011 09:56:59 GMT",
"version": "v1"
}
] | 2011-09-06 | [
[
"Saida",
"Hiromi",
""
]
] | This paper consists of three steps. In the first, we prove that the Bekenstein-Hawking entropy is the unique expression of black hole entropy. Our proof is constructed in the framework of thermodynamics without any statistical discussion. In the second, intrinsic properties of quantum mechanics are shown, which justify the Boltzmann formula to yield a unique entropy in statistical mechanics. These properties clarify three conditions, one of which is necessary and others are sufficient for the validity of Boltzmann formula. In the third, by combining the above results, we find a reasonable suggestion from the sufficient conditions that the potential of gravitational interaction among microstates of underlying quantum gravity may not diverge to negative infinity (such as Newtonian gravity) but is bounded below at a finite length scale. In addition to that, from the necessary condition, the interaction has to be repulsive within the finite length scale. The length scale should be Planck size. Thus, quantum gravity may become repulsive at Planck length. Also, a relation of these suggestions with action integral of gravity at semi-classical level is given. These suggestions about quantum gravity are universal in the sense that they are independent of any existing model of quantum gravity. |
1006.2890 | Kristin Schleich | Kristin Schleich and Donald M. Witt | Singularities from the Topology and Differentiable Structure of
Asymptotically Flat Spacetimes | 22 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that certain asymptotically flat initial data sets with nontrivial
topology and/or differentiable structure collapse to form singularities. The
class of such initial data sets is characterized by a new smooth invariant, the
maximal Yamabe invariant, defined through smooth compactification of the
asymptotically flat manifold. Our singularity theorem applies to spacetimes
admitting a Cauchy surface of nonpositive maximal Yamabe invariant with initial
data that satisfies the dominant energy condition. This class of spacetimes
includes simply connected spacetimes with a single asymptotic region, a class
not covered by prior singularity theorems for topological structures. The
maximal Yamabe invariant can be related to other invariants including, in 4
dimensions, the A-genus and the Seiberg-Witten invariants. In particular,
5-dimensional spacetimes with asymptotically flat Cauchy surfaces with
non-trivial Seiberg-Witten invariants are singular. This singularity is due to
the differentiable structure of the manifold.
| [
{
"created": "Tue, 15 Jun 2010 05:14:28 GMT",
"version": "v1"
}
] | 2010-06-16 | [
[
"Schleich",
"Kristin",
""
],
[
"Witt",
"Donald M.",
""
]
] | We prove that certain asymptotically flat initial data sets with nontrivial topology and/or differentiable structure collapse to form singularities. The class of such initial data sets is characterized by a new smooth invariant, the maximal Yamabe invariant, defined through smooth compactification of the asymptotically flat manifold. Our singularity theorem applies to spacetimes admitting a Cauchy surface of nonpositive maximal Yamabe invariant with initial data that satisfies the dominant energy condition. This class of spacetimes includes simply connected spacetimes with a single asymptotic region, a class not covered by prior singularity theorems for topological structures. The maximal Yamabe invariant can be related to other invariants including, in 4 dimensions, the A-genus and the Seiberg-Witten invariants. In particular, 5-dimensional spacetimes with asymptotically flat Cauchy surfaces with non-trivial Seiberg-Witten invariants are singular. This singularity is due to the differentiable structure of the manifold. |
2210.10204 | Hai-Chao Zhang | Hai-Chao Zhang | Obtaining a scalar fifth force for matter via a conformal coupling to
the scalar field | 12 pages,1 figure | null | null | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | In the framework of special relativity (SR), I propose that matter
conformally couples to a scalar field through the Lagrangian density of matter,
whether matter is characterized by classical or by quantum (statistical)
mechanics. The largest interaction strength of the scalar-mediated force can
achieve the order of $1/\Lambda_E^2$ with the cosmological constant
$\Lambda_E\approx 2.4\,\rm{meV}$. This is about 60 orders of magnitude larger
than Newtonian gravity, i.e., ${(M_{\mathrm{Pl}}/\Lambda_E)}^2\sim 10^{60}$,
where $M_{\mathrm{Pl}}\approx2.4\times 10^{18}\, \rm{GeV} $ is the reduced
Planck energy. However, the discrete $\mathbb{Z}_2$ symmetry of the conformal
coupling does not allow a massless scalar field, satisfying the constraint that
no evidence of the long range force is observed. The interaction range of the
force is inversely proportional to the square root of the ambient density.
Therefore, in the general situation in which the ambient density is larger than
the current cosmic density, the interaction range is always smaller than
$1/\Lambda_E \approx 80\, \mu\rm{m}$. The form of general relativity (GR) still
holds even when the energy-momentum tensors of the quintessence and the
conformal interaction are included. The main purpose here is to overcome the
puzzle in \cite{hcz2}, i.e., which frame is physical.
| [
{
"created": "Tue, 18 Oct 2022 23:08:24 GMT",
"version": "v1"
}
] | 2022-10-20 | [
[
"Zhang",
"Hai-Chao",
""
]
] | In the framework of special relativity (SR), I propose that matter conformally couples to a scalar field through the Lagrangian density of matter, whether matter is characterized by classical or by quantum (statistical) mechanics. The largest interaction strength of the scalar-mediated force can achieve the order of $1/\Lambda_E^2$ with the cosmological constant $\Lambda_E\approx 2.4\,\rm{meV}$. This is about 60 orders of magnitude larger than Newtonian gravity, i.e., ${(M_{\mathrm{Pl}}/\Lambda_E)}^2\sim 10^{60}$, where $M_{\mathrm{Pl}}\approx2.4\times 10^{18}\, \rm{GeV} $ is the reduced Planck energy. However, the discrete $\mathbb{Z}_2$ symmetry of the conformal coupling does not allow a massless scalar field, satisfying the constraint that no evidence of the long range force is observed. The interaction range of the force is inversely proportional to the square root of the ambient density. Therefore, in the general situation in which the ambient density is larger than the current cosmic density, the interaction range is always smaller than $1/\Lambda_E \approx 80\, \mu\rm{m}$. The form of general relativity (GR) still holds even when the energy-momentum tensors of the quintessence and the conformal interaction are included. The main purpose here is to overcome the puzzle in \cite{hcz2}, i.e., which frame is physical. |
0904.1273 | Rainer Verch | Andreas Degner, Rainer Verch | Cosmological particle creation in states of low energy | 24 pages, 7 figures | J.Math.Phys.51:022302,2010 | 10.1063/1.3271106 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The recently proposed states of low energy provide a well-motivated class of
reference states for the quantized linear scalar field on cosmological
Friedmann-Robertson-Walker spacetimes. The low energy property of a state is
localized close to some value of the cosmological time coordinate. We present
calculations of the relative cosmological particle production between a state
of low energy at early time and another such state at later time. In an
exponentially expanding Universe, we find that the particle production shows
oscillations in the spatial frequency modes. The basis of the method for
calculating the relative particle production is completely rigorous.
Approximations are only used at the level of numerical calculation.
| [
{
"created": "Wed, 8 Apr 2009 07:39:41 GMT",
"version": "v1"
}
] | 2011-06-07 | [
[
"Degner",
"Andreas",
""
],
[
"Verch",
"Rainer",
""
]
] | The recently proposed states of low energy provide a well-motivated class of reference states for the quantized linear scalar field on cosmological Friedmann-Robertson-Walker spacetimes. The low energy property of a state is localized close to some value of the cosmological time coordinate. We present calculations of the relative cosmological particle production between a state of low energy at early time and another such state at later time. In an exponentially expanding Universe, we find that the particle production shows oscillations in the spatial frequency modes. The basis of the method for calculating the relative particle production is completely rigorous. Approximations are only used at the level of numerical calculation. |
2002.04421 | P. A. Gonzalez | Ram\'on B\'ecar, P. A. Gonz\'alez and Yerko V\'asquez | Collision of particles near a three-dimensional rotating Ho\v{r}ava AdS
black hole | 14 pages, and 10 figures. arXiv admin note: substantial text overlap
with arXiv:1712.00868 | null | 10.1140/epjc/s10052-021-09041-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a three-dimensional rotating Ho\v{r}ava AdS black hole, that
corresponds to a Lorentz-violating version of the BTZ black hole and we analyze
the effect of the breaking of Lorentz invariance on the possibility that the
black hole can acts as a particle accelerator by analyzing the energy in the
center of mass (CM) frame of two colliding particles in the vicinity of its
horizons. We find that the critical angular momentum of particles increases
when the Ho\v{r}ava parameter $\xi$ increases and when the aether parameter $b$
increases. Also, the particles can collide on the inner horizon with
arbitrarily high CM energy if one of the particles has a critical angular
momentum being possible the BSW process, for the non-extremal rotating
Ho\v{r}ava AdS black hole. Mainly, while that for the extremal BTZ black hole
the particles with critical angular momentum only can exist on the degenerate
horizon, for the Lorentz-violating version of the BTZ black hole the particle
with critical angular momentum can exist in a region from the degenerate
horizon.
| [
{
"created": "Sat, 8 Feb 2020 18:50:48 GMT",
"version": "v1"
}
] | 2021-04-07 | [
[
"Bécar",
"Ramón",
""
],
[
"González",
"P. A.",
""
],
[
"Vásquez",
"Yerko",
""
]
] | We consider a three-dimensional rotating Ho\v{r}ava AdS black hole, that corresponds to a Lorentz-violating version of the BTZ black hole and we analyze the effect of the breaking of Lorentz invariance on the possibility that the black hole can acts as a particle accelerator by analyzing the energy in the center of mass (CM) frame of two colliding particles in the vicinity of its horizons. We find that the critical angular momentum of particles increases when the Ho\v{r}ava parameter $\xi$ increases and when the aether parameter $b$ increases. Also, the particles can collide on the inner horizon with arbitrarily high CM energy if one of the particles has a critical angular momentum being possible the BSW process, for the non-extremal rotating Ho\v{r}ava AdS black hole. Mainly, while that for the extremal BTZ black hole the particles with critical angular momentum only can exist on the degenerate horizon, for the Lorentz-violating version of the BTZ black hole the particle with critical angular momentum can exist in a region from the degenerate horizon. |
1708.03253 | Richard Woodard | D. J. Brooker (Florida), N. C. Tsamis (Crete) and R. P. Woodard
(Florida) | Final Thoughts on the Power Spectra of Scalar Potential Models | 28 pages, 12 figures, uses LaTeX2e | Phys. Rev. D 96, 103531 (2017) | 10.1103/PhysRevD.96.103531 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give final shape to a recent formalism for deriving the functional forms
of the primordial power spectra of single-scalar potential models and theories
which are related to them by conformal transformation. An excellent analytic
approximation is derived for the nonlocal correction factors which are crucial
to capture the "ringing" that can result from features in the potential. We
also present the full algorithm for using our representation, including the
nonlocal factors, to reconstruct the inflationary geometry from the power
spectra.
| [
{
"created": "Wed, 9 Aug 2017 05:51:37 GMT",
"version": "v1"
}
] | 2017-11-29 | [
[
"Brooker",
"D. J.",
"",
"Florida"
],
[
"Tsamis",
"N. C.",
"",
"Crete"
],
[
"Woodard",
"R. P.",
"",
"Florida"
]
] | We give final shape to a recent formalism for deriving the functional forms of the primordial power spectra of single-scalar potential models and theories which are related to them by conformal transformation. An excellent analytic approximation is derived for the nonlocal correction factors which are crucial to capture the "ringing" that can result from features in the potential. We also present the full algorithm for using our representation, including the nonlocal factors, to reconstruct the inflationary geometry from the power spectra. |
2206.09000 | Giovanni Otalora | Yoelsy Leyva and Giovanni Otalora | Revisiting $f(R)$ gravity's rainbow: Inflation and primordial
fluctuations | 18 pages, 4 figures. Updated to match the published version in JCAP | JCAP 04 (2023) 030 | 10.1088/1475-7516/2023/04/030 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study inflation and the generation of primordial fluctuations in $f(R)$
gravity's rainbow. We calculate the cosmological perturbations and then the
scalar and tensor primordial power spectrum. We contrast the predictions of the
model with the current observational data from PLANCK and BICEP/Keck.
Particularly, we found new results for the scalar spectral index $n_s$ and the
tensor-to-scalar ratio $r$ along with new observational constraints on the
rainbow functions.
| [
{
"created": "Fri, 17 Jun 2022 20:43:06 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Apr 2023 14:41:57 GMT",
"version": "v2"
}
] | 2023-04-13 | [
[
"Leyva",
"Yoelsy",
""
],
[
"Otalora",
"Giovanni",
""
]
] | We study inflation and the generation of primordial fluctuations in $f(R)$ gravity's rainbow. We calculate the cosmological perturbations and then the scalar and tensor primordial power spectrum. We contrast the predictions of the model with the current observational data from PLANCK and BICEP/Keck. Particularly, we found new results for the scalar spectral index $n_s$ and the tensor-to-scalar ratio $r$ along with new observational constraints on the rainbow functions. |
2402.13850 | Genly Le\'on | Kevin Marroqu\'in (Catolica del Norte U.), Genly Leon (Catolica del
Norte U. and DUT, Durban), Alfredo D. Millano (Catolica del Norte U.),
Claudio Michea (Catolica del Norte U.) and Andronikos Paliathanasis (DUT,
Durban and Catolica del Norte U.) | Conformal and Non-Minimal Couplings in Fractional Cosmology | 99 pages, 3 tables, 20 compound figures (This article belongs to the
Special Issue Advances in Fractional Modeling and Computation)
https://www.mdpi.com/journal/fractalfract/special_issues/4X6L41Z9X2 | Fractal Fract. 2024, 8(5), 253 | 10.3390/fractalfract8050253 | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | Fractional differential calculus is a mathematical tool that has found
applications in the study of social and physical behaviors considered
``anomalous''. It is often used when traditional integer derivatives models
fail to represent cases where the power law is observed accurately. Fractional
calculus must reflect non-local, frequency- and history-dependent properties of
power-law phenomena. This tool has various important applications, such as
fractional mass conservation, electrochemical analysis, groundwater flow
problems, and fractional spatiotemporal diffusion equations. It can also be
used in cosmology to explain late-time cosmic acceleration without the need for
dark energy. We review some models using fractional differential equations. We
look at the Einstein--Hilbert action, which is based on a fractional derivative
action, and add a scalar field, $\phi$, to create a non-minimal interaction
theory with the coupling, $\xi R \phi^2 $, between gravity and the scalar
field, where $\xi$ is the interaction constant. By employing various
mathematical approaches, we can offer precise schemes to find analytical and
numerical approximations of the solutions. Moreover, we comprehensively study
the modified cosmological equations and analyze the solution space using the
theory of dynamical systems and asymptotic expansion methods. This enables us
to provide a qualitative description of cosmologies with a scalar field based
on fractional calculus formalism.
| [
{
"created": "Wed, 21 Feb 2024 14:52:01 GMT",
"version": "v1"
},
{
"created": "Sat, 4 May 2024 20:09:30 GMT",
"version": "v2"
}
] | 2024-05-07 | [
[
"Marroquín",
"Kevin",
"",
"Catolica del Norte U."
],
[
"Leon",
"Genly",
"",
"Catolica del\n Norte U. and DUT, Durban"
],
[
"Millano",
"Alfredo D.",
"",
"Catolica del Norte U."
],
[
"Michea",
"Claudio",
"",
"Catolica del Norte U."
],
[
"Paliathanasis",
"Andronikos",
"",
"DUT,\n Durban and Catolica del Norte U."
]
] | Fractional differential calculus is a mathematical tool that has found applications in the study of social and physical behaviors considered ``anomalous''. It is often used when traditional integer derivatives models fail to represent cases where the power law is observed accurately. Fractional calculus must reflect non-local, frequency- and history-dependent properties of power-law phenomena. This tool has various important applications, such as fractional mass conservation, electrochemical analysis, groundwater flow problems, and fractional spatiotemporal diffusion equations. It can also be used in cosmology to explain late-time cosmic acceleration without the need for dark energy. We review some models using fractional differential equations. We look at the Einstein--Hilbert action, which is based on a fractional derivative action, and add a scalar field, $\phi$, to create a non-minimal interaction theory with the coupling, $\xi R \phi^2 $, between gravity and the scalar field, where $\xi$ is the interaction constant. By employing various mathematical approaches, we can offer precise schemes to find analytical and numerical approximations of the solutions. Moreover, we comprehensively study the modified cosmological equations and analyze the solution space using the theory of dynamical systems and asymptotic expansion methods. This enables us to provide a qualitative description of cosmologies with a scalar field based on fractional calculus formalism. |
1303.5167 | Arturo Avelino | Arturo Avelino, Ricardo Garcia-Salcedo, Tame Gonzalez, Ulises
Nucamendi, Israel Quiros | Bulk Viscous Matter-dominated Universes: Asymptotic Properties | 26 pages, 13 figures. Replacement with the final (published) version | JCAP 1308 (2013) 012 | 10.1088/1475-7516/2013/08/012 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By means of a combined use of the type Ia supernovae and H(z) data tests,
together with the study of the asymptotic properties in the equivalent phase
space - through the use of the dynamical systems tools - we demonstrate that
the bulk viscous matter-dominated scenario is not a good model to explain the
accepted cosmological paradigm, at least, under the parametrization of bulk
viscosity considered in this paper. The main objection against such scenarios
is the absence of conventional radiation and matter-dominated critical points
in the phase space of the model. This entails that radiation and matter
dominance are not generic solutions of the cosmological equations, so that
these stages can be implemented only by means of unique and very specific
initial conditions, i. e., of very unstable particular solutions. Such a
behavior is in marked contradiction with the accepted cosmological paradigm
which requires of an earlier stage dominated by relativistic species, followed
by a period of conventional non-relativistic matter domination, during which
the cosmic structure we see was formed. Also, we found that the bulk viscosity
is positive just until very late times in the cosmic evolution, around z < 1.
For earlier epochs it is negative, been in tension with the local second law of
thermodynamics.
| [
{
"created": "Thu, 21 Mar 2013 05:03:04 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Aug 2013 03:52:16 GMT",
"version": "v2"
}
] | 2013-08-30 | [
[
"Avelino",
"Arturo",
""
],
[
"Garcia-Salcedo",
"Ricardo",
""
],
[
"Gonzalez",
"Tame",
""
],
[
"Nucamendi",
"Ulises",
""
],
[
"Quiros",
"Israel",
""
]
] | By means of a combined use of the type Ia supernovae and H(z) data tests, together with the study of the asymptotic properties in the equivalent phase space - through the use of the dynamical systems tools - we demonstrate that the bulk viscous matter-dominated scenario is not a good model to explain the accepted cosmological paradigm, at least, under the parametrization of bulk viscosity considered in this paper. The main objection against such scenarios is the absence of conventional radiation and matter-dominated critical points in the phase space of the model. This entails that radiation and matter dominance are not generic solutions of the cosmological equations, so that these stages can be implemented only by means of unique and very specific initial conditions, i. e., of very unstable particular solutions. Such a behavior is in marked contradiction with the accepted cosmological paradigm which requires of an earlier stage dominated by relativistic species, followed by a period of conventional non-relativistic matter domination, during which the cosmic structure we see was formed. Also, we found that the bulk viscosity is positive just until very late times in the cosmic evolution, around z < 1. For earlier epochs it is negative, been in tension with the local second law of thermodynamics. |
1512.00096 | Seyed Ali Hosseini Mansoori | Seyed Ali Hosseini Mansoori, Behrouz Mirza, Mahdi Davoudi Darareh,
Sharooz Janbaz | Entanglement Thermodynamics of the Generalized Charged BTZ Black Hole | 6 pages | Int. J. Mod. Phys. A 31, 1650067 (2016) | 10.1142/S0217751X16500676 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the entanglement entropy for the generalized
charged BTZ black hole through the $AdS_{3}/CFT_{2}$ correspondence. Using the
holographic description of the entanglement entropy for the strip-subsystem in
boundary $CFT_{2}$, we will find the first law-like relation between the
variation of holographic entanglement entropy and the variation of energy of
the subsystem in terms of the mass and the electric charge up to the second
order. We also obtain appropriate counterterms to renormalize the energy tensor
associated with the bulk on-shell actions.
| [
{
"created": "Mon, 30 Nov 2015 23:49:06 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Apr 2016 22:42:01 GMT",
"version": "v2"
},
{
"created": "Mon, 2 May 2016 09:13:12 GMT",
"version": "v3"
}
] | 2016-05-03 | [
[
"Mansoori",
"Seyed Ali Hosseini",
""
],
[
"Mirza",
"Behrouz",
""
],
[
"Darareh",
"Mahdi Davoudi",
""
],
[
"Janbaz",
"Sharooz",
""
]
] | In this paper, we investigate the entanglement entropy for the generalized charged BTZ black hole through the $AdS_{3}/CFT_{2}$ correspondence. Using the holographic description of the entanglement entropy for the strip-subsystem in boundary $CFT_{2}$, we will find the first law-like relation between the variation of holographic entanglement entropy and the variation of energy of the subsystem in terms of the mass and the electric charge up to the second order. We also obtain appropriate counterterms to renormalize the energy tensor associated with the bulk on-shell actions. |
gr-qc/9802003 | Claus Kiefer | C. Kiefer, D. Polarski, A.A. Starobinsky | Quantum-to-classical transition for fluctuations in the early Universe | 9 pages, LATEX | Int.J.Mod.Phys. D7 (1998) 455-462 | 10.1142/S0218271898000292 | Freiburg THEP-97/33 | gr-qc astro-ph hep-th quant-ph | null | According to the inflationary scenario for the very early Universe, all
inhomogeneities in the Universe are of genuine quantum origin. On the other
hand, looking at these inhomogeneities and measuring them, clearly no specific
quantum mechanical properties are observed. We show how the transition from
their inherent quantum gravitational nature to classical behaviour comes about
-- a transition whereby none of the successful quantitative predictions of the
inflationary scenario for the present-day universe is changed. This is made
possible by two properties. First, the quantum state for the spacetime metric
perturbations produced by quantum gravitational effects in the early Universe
becomes very special (highly squeezed) as a result of the expansion of the
Universe (as long as the wavelength of the perturbations exceeds the Hubble
radius). Second, decoherence through the environment distinguishes the field
amplitude basis as being the pointer basis. This renders the perturbations
presently indistinguishable from stochastic classical inhomogeneities.
| [
{
"created": "Mon, 2 Feb 1998 09:00:03 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Kiefer",
"C.",
""
],
[
"Polarski",
"D.",
""
],
[
"Starobinsky",
"A. A.",
""
]
] | According to the inflationary scenario for the very early Universe, all inhomogeneities in the Universe are of genuine quantum origin. On the other hand, looking at these inhomogeneities and measuring them, clearly no specific quantum mechanical properties are observed. We show how the transition from their inherent quantum gravitational nature to classical behaviour comes about -- a transition whereby none of the successful quantitative predictions of the inflationary scenario for the present-day universe is changed. This is made possible by two properties. First, the quantum state for the spacetime metric perturbations produced by quantum gravitational effects in the early Universe becomes very special (highly squeezed) as a result of the expansion of the Universe (as long as the wavelength of the perturbations exceeds the Hubble radius). Second, decoherence through the environment distinguishes the field amplitude basis as being the pointer basis. This renders the perturbations presently indistinguishable from stochastic classical inhomogeneities. |
2103.14141 | Thanasis Karakasis | Thanasis Karakasis, Eleftherios Papantonopoulos, Zi-Yu Tang and Bin
Wang | Exact Black Hole Solutions with a Conformally Coupled Scalar Field and
Dynamic Ricci Curvature in $f(R)$ Gravity Theories | Accepted for publication in EPJC | Eur. Phys. J. C 81, 897 (2021) | 10.1140/epjc/s10052-021-09717-1 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We report exact black hole solutions in asymptotically flat or (A)dS
four-dimensional spacetime with a conformally coupled self-interacting scalar
field in $f(R)$ gravity. We first consider the asymptotically flat model $f(R)
= R -2\alpha \sqrt{R}$ and derive an exact black hole solution. Then, we
consider the asymptotically (A)dS model $f(R) =R -2 \Lambda -2 \alpha \sqrt{R-4
\Lambda }$ and derive an exact black hole solution. In both cases the modified
gravity parameter $\alpha$, which has the dimension of the inverse mass, cannot
be set to zero and the self-interacting potential is determined from the
Klein-Gordon equation, preserving the conformal invariance. The thermodynamics
of the solutions is also studied.
| [
{
"created": "Thu, 25 Mar 2021 21:19:40 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Apr 2021 16:17:41 GMT",
"version": "v2"
},
{
"created": "Thu, 8 Jul 2021 14:21:47 GMT",
"version": "v3"
},
{
"created": "Mon, 11 Oct 2021 06:18:48 GMT",
"version": "v4"
}
] | 2021-10-25 | [
[
"Karakasis",
"Thanasis",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
],
[
"Tang",
"Zi-Yu",
""
],
[
"Wang",
"Bin",
""
]
] | We report exact black hole solutions in asymptotically flat or (A)dS four-dimensional spacetime with a conformally coupled self-interacting scalar field in $f(R)$ gravity. We first consider the asymptotically flat model $f(R) = R -2\alpha \sqrt{R}$ and derive an exact black hole solution. Then, we consider the asymptotically (A)dS model $f(R) =R -2 \Lambda -2 \alpha \sqrt{R-4 \Lambda }$ and derive an exact black hole solution. In both cases the modified gravity parameter $\alpha$, which has the dimension of the inverse mass, cannot be set to zero and the self-interacting potential is determined from the Klein-Gordon equation, preserving the conformal invariance. The thermodynamics of the solutions is also studied. |
gr-qc/0408049 | Lukas Richterek | L. Richterek and J. Horsky | Weyl metrics and the generating conjecture | 10 pages, to appear in Czech.J. Phys | Czech.J.Phys. 54 (2004) 1451-1459 | 10.1007/s10582-004-1202-0 | null | gr-qc | null | By means of Ernst complex potential formalism it is shown, that previously
studied static axisymmetric Einstein-Maxwell fields obtained though the
application of the Horsky-Mitskievitch generating conjecture represent a
combination of Kinnersley's transformations [W. Kinnersley: J. Math. Phys. 14
(1973) 651]. New theoretical background for the conjecture is suggested and
commented.
| [
{
"created": "Mon, 16 Aug 2004 19:45:04 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Richterek",
"L.",
""
],
[
"Horsky",
"J.",
""
]
] | By means of Ernst complex potential formalism it is shown, that previously studied static axisymmetric Einstein-Maxwell fields obtained though the application of the Horsky-Mitskievitch generating conjecture represent a combination of Kinnersley's transformations [W. Kinnersley: J. Math. Phys. 14 (1973) 651]. New theoretical background for the conjecture is suggested and commented. |
1807.02598 | Zahra Altaha Motahar | Zahra Altaha Motahar, Jose Luis Bl\'azquez-Salcedo, Burkhard Kleihaus
and Jutta Kunz | Axial Quasi-Normal Modes of Scalarized Neutron Stars with Realistic
Equations of State | null | Phys. Rev. D 98, 044032 (2018) | 10.1103/PhysRevD.98.044032 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the axial quasi-normal modes of static neutron stars in scalar
tensor theory. In particular, we employ various realistic equations of state
including nuclear, hyperonic and hybrid matter. We investigate the fundamental
curvature mode and compare the results with those of General Relativity. We
find that the frequency of the modes and the damping time are reduced for the
scalarized neutron stars. In addition, we confirm and extend the universal
relations for quasi-normal modes known in General Relativity to this wide range
of realistic equations of state for scalarized neutron stars and confirm the
universality of the scaled frequency and damping time in terms of the scaled
moment of inertia as well as compactness for neutron stars with and without
scalarization.
| [
{
"created": "Sat, 7 Jul 2018 01:01:36 GMT",
"version": "v1"
}
] | 2018-08-29 | [
[
"Motahar",
"Zahra Altaha",
""
],
[
"Blázquez-Salcedo",
"Jose Luis",
""
],
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
]
] | We compute the axial quasi-normal modes of static neutron stars in scalar tensor theory. In particular, we employ various realistic equations of state including nuclear, hyperonic and hybrid matter. We investigate the fundamental curvature mode and compare the results with those of General Relativity. We find that the frequency of the modes and the damping time are reduced for the scalarized neutron stars. In addition, we confirm and extend the universal relations for quasi-normal modes known in General Relativity to this wide range of realistic equations of state for scalarized neutron stars and confirm the universality of the scaled frequency and damping time in terms of the scaled moment of inertia as well as compactness for neutron stars with and without scalarization. |
2011.02326 | Bogeun Gwak | Bogeun Gwak | Thermodynamics of Warped Anti-de Sitter Black Holes under Scattering of
Scalar Field | 15 pages, 6 figures | Chin. Phys. C 45 (2021) 4, 043106 | 10.1088/1674-1137/abdfbf | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the thermodynamics and stability of the horizons in warped
anti-de Sitter black holes of the new massive gravity under the scattering of a
massive scalar field. Under scattering, conserved quantities can be transferred
from the scalar field to the black hole, which change the state of the black
hole. We determine that the changes in the black hole are well coincident with
the laws of thermodynamics. In particular, the Hawking temperature of the black
hole cannot be zero in the process as per the third law of thermodynamics.
Furthermore, the black hole cannot be overspun beyond the extremal condition
under the scattering of any mode of the scalar field.
| [
{
"created": "Wed, 4 Nov 2020 14:56:27 GMT",
"version": "v1"
}
] | 2021-05-13 | [
[
"Gwak",
"Bogeun",
""
]
] | We investigate the thermodynamics and stability of the horizons in warped anti-de Sitter black holes of the new massive gravity under the scattering of a massive scalar field. Under scattering, conserved quantities can be transferred from the scalar field to the black hole, which change the state of the black hole. We determine that the changes in the black hole are well coincident with the laws of thermodynamics. In particular, the Hawking temperature of the black hole cannot be zero in the process as per the third law of thermodynamics. Furthermore, the black hole cannot be overspun beyond the extremal condition under the scattering of any mode of the scalar field. |
2202.01794 | Benjamin Leather | Rodrigo Panosso Macedo, Benjamin Leather, Niels Warburton, Barry
Wardell, An{\i}l Zengino\u{g}lu | Hyperboloidal method for frequency-domain self-force calculations | 25 pages, 19 figures; updated to reflect published version | Phys. Rev. D 105, 104033 (2022) | 10.1103/PhysRevD.105.104033 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational self-force theory is the leading approach for modeling
gravitational wave emission from small mass-ratio compact binaries. This method
perturbatively expands the metric of the binary in powers of the mass ratio.
The source for the perturbations depends on the orbital configuration,
calculational approach, and the order of the perturbative expansion. These
sources fall into three broad classes: (i) distributional, (ii) worldtube, and
(iii) unbounded support. The latter, in particular, is important for emerging
second-order (in the mass ratio) calculations. Traditional frequency domain
approaches employ the variation of parameters method and compute the
perturbation on standard time slices with numerical boundary conditions
supplied at finite radius from series expansions of the asymptotic behavior.
This approach has been very successful, but the boundary conditions
calculations are tedious, and the approach is not well suited to unbounded
sources where homogeneous solutions must be computed at all radii. This work
develops an alternative approach where hyperboloidal slices foliate the
spacetime, and compactifying coordinates simplify the boundary treatment. We
implement this approach with a multi-domain spectral solver with analytic mesh
refinement and use the scalar-field self-force on circular orbits around a
Schwarzschild black hole as an example problem. The method works efficiently
for all three source classes encountered in self-force calculations and has
distinct advantages over the traditional approach. For example, our code
efficiently computes the perturbation for orbits with extremely large orbital
radii ($r_{p}>10^5M$) or modes with very high spherical harmonic mode index
($\ell \ge 100$). Our results indicate that hyperboloidal methods can play an
essential role in self-force calculations.
| [
{
"created": "Thu, 3 Feb 2022 19:00:07 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Jun 2022 14:10:45 GMT",
"version": "v2"
}
] | 2022-06-02 | [
[
"Macedo",
"Rodrigo Panosso",
""
],
[
"Leather",
"Benjamin",
""
],
[
"Warburton",
"Niels",
""
],
[
"Wardell",
"Barry",
""
],
[
"Zenginoğlu",
"Anıl",
""
]
] | Gravitational self-force theory is the leading approach for modeling gravitational wave emission from small mass-ratio compact binaries. This method perturbatively expands the metric of the binary in powers of the mass ratio. The source for the perturbations depends on the orbital configuration, calculational approach, and the order of the perturbative expansion. These sources fall into three broad classes: (i) distributional, (ii) worldtube, and (iii) unbounded support. The latter, in particular, is important for emerging second-order (in the mass ratio) calculations. Traditional frequency domain approaches employ the variation of parameters method and compute the perturbation on standard time slices with numerical boundary conditions supplied at finite radius from series expansions of the asymptotic behavior. This approach has been very successful, but the boundary conditions calculations are tedious, and the approach is not well suited to unbounded sources where homogeneous solutions must be computed at all radii. This work develops an alternative approach where hyperboloidal slices foliate the spacetime, and compactifying coordinates simplify the boundary treatment. We implement this approach with a multi-domain spectral solver with analytic mesh refinement and use the scalar-field self-force on circular orbits around a Schwarzschild black hole as an example problem. The method works efficiently for all three source classes encountered in self-force calculations and has distinct advantages over the traditional approach. For example, our code efficiently computes the perturbation for orbits with extremely large orbital radii ($r_{p}>10^5M$) or modes with very high spherical harmonic mode index ($\ell \ge 100$). Our results indicate that hyperboloidal methods can play an essential role in self-force calculations. |
1308.5156 | El\'ias Castellanos Dr. | E. Castellanos, J. I. Rivas, and V. Dom\'inguez-Rocha | Planck Scale Induced Speed of Sound in a Trapped Bose-Einstein
Condensate | null | EPL, 106 (2014) 60005 | 10.1209/0295-5075/106/60005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work, we analyze the corrections caused by an anomalous
dispersion relation, suggested in several quantum gravity models, upon the
speed of sound in a weakly interacting Bose--Einstein Condensate, trapped in a
potential of the form $V(r)\sim r^{2}$. We show that the corresponding ground
state energy and consequently, the associated speed of sound, present
corrections respect to the usual case, which may be used to explore the
sensitivity to Planck--scale effects on these relevant properties associated
with the condensate. Indeed, we stress that this type of macroscopic bodies may
be more sensitive, under certain conditions, to Planck--scale manifestations
than its constituents. In addition, we prove that the inclusion of a trapping
potential, together with many--body contributions, improves the sensitivity to
Planck--scale signals, compared to the homogeneous system.
| [
{
"created": "Fri, 23 Aug 2013 15:26:00 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Jul 2014 16:28:41 GMT",
"version": "v2"
}
] | 2014-07-14 | [
[
"Castellanos",
"E.",
""
],
[
"Rivas",
"J. I.",
""
],
[
"Domínguez-Rocha",
"V.",
""
]
] | In the present work, we analyze the corrections caused by an anomalous dispersion relation, suggested in several quantum gravity models, upon the speed of sound in a weakly interacting Bose--Einstein Condensate, trapped in a potential of the form $V(r)\sim r^{2}$. We show that the corresponding ground state energy and consequently, the associated speed of sound, present corrections respect to the usual case, which may be used to explore the sensitivity to Planck--scale effects on these relevant properties associated with the condensate. Indeed, we stress that this type of macroscopic bodies may be more sensitive, under certain conditions, to Planck--scale manifestations than its constituents. In addition, we prove that the inclusion of a trapping potential, together with many--body contributions, improves the sensitivity to Planck--scale signals, compared to the homogeneous system. |
0707.3778 | Branko Guberina | Branko Guberina | Renormalization group running cosmologies - from a scale setting to
holographic dark energy | Invited plenary talk given at the 2nd International Conference on
Quantum Theories and Renormalization Group in Gravity and Cosmology (IRGAC
2006), Barcelona, Catalonia, Spain, July 11-15, 2006 | null | null | null | gr-qc astro-ph hep-ph hep-th | null | A scale-dependent cosmological constant $\Lambda$ and the Newton constant G
emerge naturally in quantum field theory in a curved space-time background
leading to renormalization group running cosmologies. A scale-setting procedure
is discussed in these cosmological models and the interpretation of the scale
is emphasized. This setup introduces dark energy without invoking
quintessence-like fields and can be applied to a variety of problems. The
scale-dependent $\Lambda$ and G are also naturally incorporated into the
generalized holographic dark energy model, and applied to different aspects of
cosmology.
| [
{
"created": "Wed, 25 Jul 2007 16:32:12 GMT",
"version": "v1"
}
] | 2007-07-27 | [
[
"Guberina",
"Branko",
""
]
] | A scale-dependent cosmological constant $\Lambda$ and the Newton constant G emerge naturally in quantum field theory in a curved space-time background leading to renormalization group running cosmologies. A scale-setting procedure is discussed in these cosmological models and the interpretation of the scale is emphasized. This setup introduces dark energy without invoking quintessence-like fields and can be applied to a variety of problems. The scale-dependent $\Lambda$ and G are also naturally incorporated into the generalized holographic dark energy model, and applied to different aspects of cosmology. |
gr-qc/0207020 | Janna Levin | Neil J. Cornish and Janna Levin | Comment on "Ruling out chaos in compact binary systems" | 1 page. Published Version | Phys.Rev.Lett. 89 (2002) 179001 | 10.1103/PhysRevLett.89.179001 | null | gr-qc astro-ph | null | In a recent Letter, Schnittman and Rasio argue that they have ruled out chaos
in compact binary systems since they find no positive Lyapunov exponents. In
stark constrast, we find that the chaos discovered in the original paper under
discussion, J.Levin, PRL, 84 3515 (2000), is confirmed by the presence of
positive Lyapunov exponents.
| [
{
"created": "Wed, 3 Jul 2002 17:08:27 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Oct 2002 23:57:43 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Cornish",
"Neil J.",
""
],
[
"Levin",
"Janna",
""
]
] | In a recent Letter, Schnittman and Rasio argue that they have ruled out chaos in compact binary systems since they find no positive Lyapunov exponents. In stark constrast, we find that the chaos discovered in the original paper under discussion, J.Levin, PRL, 84 3515 (2000), is confirmed by the presence of positive Lyapunov exponents. |
2202.08839 | Georgios Doulis | Georgios Doulis, Florian Atteneder, Sebastiano Bernuzzi, Bernd
Br\"ugmann | Entropy-limited higher-order central scheme for neutron star merger
simulations | 22 pages, 21 figures | Phys. Rev. D 106, 024001 (2022) | 10.1103/PhysRevD.106.024001 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Numerical relativity simulations are the only way to calculate exact
gravitational waveforms from binary neutron star mergers and to design
templates for gravitational-wave astronomy. The accuracy of these numerical
calculations is critical in quantifying tidal effects near merger that are
currently one of the main sources of uncertainty in merger waveforms. In this
work, we explore the use of an entropy-based flux-limiting scheme for
high-order, convergent simulations of neutron star spacetimes. The scheme
effectively tracks the stellar surface and physical shocks using the residual
of the entropy equation thus allowing the use of unlimited central flux schemes
in regions of smooth flow. We perform the first neutron star merger simulations
with such a method and demonstrate up to fourth-order convergence in the
gravitational waveform phase. The scheme reduces the phase error up to a factor
five when compared to state-of-the-art high-order characteristic schemes and
can be employed for producing faithful tidal waveforms for gravitational-wave
modelling.
| [
{
"created": "Thu, 17 Feb 2022 18:59:59 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Jul 2022 18:35:29 GMT",
"version": "v2"
}
] | 2022-07-05 | [
[
"Doulis",
"Georgios",
""
],
[
"Atteneder",
"Florian",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Brügmann",
"Bernd",
""
]
] | Numerical relativity simulations are the only way to calculate exact gravitational waveforms from binary neutron star mergers and to design templates for gravitational-wave astronomy. The accuracy of these numerical calculations is critical in quantifying tidal effects near merger that are currently one of the main sources of uncertainty in merger waveforms. In this work, we explore the use of an entropy-based flux-limiting scheme for high-order, convergent simulations of neutron star spacetimes. The scheme effectively tracks the stellar surface and physical shocks using the residual of the entropy equation thus allowing the use of unlimited central flux schemes in regions of smooth flow. We perform the first neutron star merger simulations with such a method and demonstrate up to fourth-order convergence in the gravitational waveform phase. The scheme reduces the phase error up to a factor five when compared to state-of-the-art high-order characteristic schemes and can be employed for producing faithful tidal waveforms for gravitational-wave modelling. |
1406.1576 | Lorenzo Sebastiani | Shynaray Myrzakul, Ratbay Myrzakulov, Lorenzo Sebastiani | Coupled fluids model in FRW space-time | 13 pages, 2 figures, revised version, accepted in Astrophys.Space Sci | Astrophys.Space Sci. 353 (2014) 667-675 | 10.1007/s10509-014-2036-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we analyze a two coupled fluids model by investigating several
solutions for accelerated universe in flat FRW space-time. One of the fluids
can be identified with the matter and the model possesses the standard matter
solution also. Beyond the removal of the coincidence problem, we will see how
the coupling may change the description of the energy contents of the universe
and which features can be aquired with respect to the standard decoupled cases.
| [
{
"created": "Fri, 6 Jun 2014 04:07:39 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Jun 2014 05:48:01 GMT",
"version": "v2"
}
] | 2015-09-21 | [
[
"Myrzakul",
"Shynaray",
""
],
[
"Myrzakulov",
"Ratbay",
""
],
[
"Sebastiani",
"Lorenzo",
""
]
] | In this paper, we analyze a two coupled fluids model by investigating several solutions for accelerated universe in flat FRW space-time. One of the fluids can be identified with the matter and the model possesses the standard matter solution also. Beyond the removal of the coincidence problem, we will see how the coupling may change the description of the energy contents of the universe and which features can be aquired with respect to the standard decoupled cases. |
0901.1938 | Efrain Rojas Marcial | Ruben Cordero, Alberto Molgado and Efrain Rojas | Ostrogradski approach for the Regge-Teitelboim type cosmology | 11 pages, 2 figures, accepted for publication in Phys. Rev. D | Phys.Rev.D79:024024,2009 | 10.1103/PhysRevD.79.024024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an alternative geometric inspired derivation of the quantum
cosmology arising from a brane universe in the context of {\it geodetic
gravity}. We set up the Regge-Teitelboim model to describe our universe, and we
recover its original dynamics by thinking of such field theory as a
second-order derivative theory. We refer to an Ostrogradski Hamiltonian
formalism to prepare the system to its quantization. Our analysis highlights
the second-order derivative nature of the RT model and the inherited
geometrical aspect of the theory. A canonical transformation brings us to the
internal physical geometry of the theory and induces its quantization
straightforwardly. By using the Dirac canonical quantization method our
approach comprises the management of both first- and second-class constraints
where the counting of degrees of freedom follows accordingly. At the quantum
level our Wheeler-De Witt Wheeler equation agrees with previous results
recently found. On these lines, we also comment upon the compatibility of our
approach with the Hamiltonian approach proposed by Davidson and coworkers.
| [
{
"created": "Wed, 14 Jan 2009 07:13:31 GMT",
"version": "v1"
}
] | 2009-02-26 | [
[
"Cordero",
"Ruben",
""
],
[
"Molgado",
"Alberto",
""
],
[
"Rojas",
"Efrain",
""
]
] | We present an alternative geometric inspired derivation of the quantum cosmology arising from a brane universe in the context of {\it geodetic gravity}. We set up the Regge-Teitelboim model to describe our universe, and we recover its original dynamics by thinking of such field theory as a second-order derivative theory. We refer to an Ostrogradski Hamiltonian formalism to prepare the system to its quantization. Our analysis highlights the second-order derivative nature of the RT model and the inherited geometrical aspect of the theory. A canonical transformation brings us to the internal physical geometry of the theory and induces its quantization straightforwardly. By using the Dirac canonical quantization method our approach comprises the management of both first- and second-class constraints where the counting of degrees of freedom follows accordingly. At the quantum level our Wheeler-De Witt Wheeler equation agrees with previous results recently found. On these lines, we also comment upon the compatibility of our approach with the Hamiltonian approach proposed by Davidson and coworkers. |
1301.4778 | Spiros Cotsakis | Spiros Cotsakis | Asymptotic Poincar\'e compactification and finite-time singularities | v2: 14 pages, more references and more discussion, matches version to
appear in Grav. Cosm. arXiv admin note: text overlap with arXiv:1212.6737 | Grav. Cosm. 19 (2013) 240 | 10.1134/S0202289313040099 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide an extension of the method of asymptotic decompositions of vector
fields with finite-time singularities by applying the central extension
technique of Poincar\'e to the dominant part of the vector field on approach to
the singularity. This leads to a bundle of fan-out asymptotic systems whose
equilibria at infinity govern the dynamics of the asymptotic solutions of the
original system. We show how this method can be useful to describe a
single-fluid isotropic universe at the time of maximum expansion, and discuss
possible relations of our results to structural stability and non-compact phase
spaces.
| [
{
"created": "Mon, 21 Jan 2013 08:10:43 GMT",
"version": "v1"
},
{
"created": "Mon, 27 May 2013 07:59:49 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Cotsakis",
"Spiros",
""
]
] | We provide an extension of the method of asymptotic decompositions of vector fields with finite-time singularities by applying the central extension technique of Poincar\'e to the dominant part of the vector field on approach to the singularity. This leads to a bundle of fan-out asymptotic systems whose equilibria at infinity govern the dynamics of the asymptotic solutions of the original system. We show how this method can be useful to describe a single-fluid isotropic universe at the time of maximum expansion, and discuss possible relations of our results to structural stability and non-compact phase spaces. |
gr-qc/0302115 | Paulo M. S\' a | Paulo M. S\'a | Differential rotation of nonlinear r-modes | 9 pages, revtex4; section III revised, comments added in Introduction
and Conclusions, references updated; to appear in Phys. Rev. D | Phys.Rev. D69 (2004) 084001 | 10.1103/PhysRevD.69.084001 | null | gr-qc astro-ph | null | Differential rotation of r-modes is investigated within the nonlinear theory
up to second order in the mode amplitude in the case of a slowly-rotating,
Newtonian, barotropic, perfect-fluid star. We find a nonlinear extension of the
linear r-mode, which represents differential rotation that produces large scale
drifts of fluid elements along stellar latitudes. This solution includes a
piece induced by first-order quantities and another one which is a pure
second-order effect. Since the latter is stratified on cylinders, it cannot
cancel differential rotation induced by first-order quantities, which is not
stratified on cylinders. It is shown that, unlikely the situation in the
linearized theory, r-modes do not preserve vorticity of fluid elements at
second-order. It is also shown that the physical angular momentum and energy of
the perturbation are, in general, different from the corresponding canonical
quantities.
| [
{
"created": "Thu, 27 Feb 2003 12:57:48 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Jan 2004 15:58:18 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Sá",
"Paulo M.",
""
]
] | Differential rotation of r-modes is investigated within the nonlinear theory up to second order in the mode amplitude in the case of a slowly-rotating, Newtonian, barotropic, perfect-fluid star. We find a nonlinear extension of the linear r-mode, which represents differential rotation that produces large scale drifts of fluid elements along stellar latitudes. This solution includes a piece induced by first-order quantities and another one which is a pure second-order effect. Since the latter is stratified on cylinders, it cannot cancel differential rotation induced by first-order quantities, which is not stratified on cylinders. It is shown that, unlikely the situation in the linearized theory, r-modes do not preserve vorticity of fluid elements at second-order. It is also shown that the physical angular momentum and energy of the perturbation are, in general, different from the corresponding canonical quantities. |
1909.03815 | Wen Zhao | Jin Qiao, Tao Zhu, Wen Zhao, Anzhong Wang | Waveform of gravitational waves in the ghost-free parity-violating
gravities | 8 pages, PRD accepted | Phys. Rev. D 100, 124058 (2019) | 10.1103/PhysRevD.100.124058 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves (GWs) provide an excellent opportunity to test the
gravity in the strong gravitational fields. In this article, we calculate the
waveform of GWs, produced by the coalescence of compact binaries, in an
extension of the Chern-Simons gravity by including higher derivatives of the
coupling scalar field. By comparing the two circular polarization modes, we
find the effects of amplitude birefringence and velocity birefringence of GWs
in their propagation caused by the parity violation in gravity, which are
explicitly presented in the GW waveforms by the amplitude and phase
modifications respectively. Combining the two modes, we obtain the GW waveforms
in the Fourier domain, and find that the deviations from those in General
Relativity are dominated by effects of velocity birefringence of GWs. In
addition, we also map the effects of the parity violation on the waveform onto
the parameterized post-Einsteinian (PPE) framework and identify explicitly the
PPE parameters.
| [
{
"created": "Thu, 5 Sep 2019 23:25:49 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Sep 2019 03:22:32 GMT",
"version": "v2"
},
{
"created": "Sat, 21 Sep 2019 17:03:47 GMT",
"version": "v3"
},
{
"created": "Thu, 12 Dec 2019 18:25:42 GMT",
"version": "v4"
}
] | 2020-01-01 | [
[
"Qiao",
"Jin",
""
],
[
"Zhu",
"Tao",
""
],
[
"Zhao",
"Wen",
""
],
[
"Wang",
"Anzhong",
""
]
] | Gravitational waves (GWs) provide an excellent opportunity to test the gravity in the strong gravitational fields. In this article, we calculate the waveform of GWs, produced by the coalescence of compact binaries, in an extension of the Chern-Simons gravity by including higher derivatives of the coupling scalar field. By comparing the two circular polarization modes, we find the effects of amplitude birefringence and velocity birefringence of GWs in their propagation caused by the parity violation in gravity, which are explicitly presented in the GW waveforms by the amplitude and phase modifications respectively. Combining the two modes, we obtain the GW waveforms in the Fourier domain, and find that the deviations from those in General Relativity are dominated by effects of velocity birefringence of GWs. In addition, we also map the effects of the parity violation on the waveform onto the parameterized post-Einsteinian (PPE) framework and identify explicitly the PPE parameters. |
1702.06155 | Martin Scholtz | Norman G\"urlebeck, Martin Scholtz | The Meissner effect for weakly isolated horizons | 7 pages, 4 figures | Phys.Rev.D 95 (2017) 064010 | 10.1103/PhysRevD.95.064010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes are important astrophysical objects describing an end state of
stellar evolution, which are observed frequently. There are theoretical
predictions that Kerr black holes with high spins expel magnetic fields.
However, Kerr black holes are pure vacuum solutions, which do not include
accretion disks, and additionally previous investigations are mainly limited to
weak magnetic fields. We prove for the first time in full general relativity
that generic rapidly spinning black holes including those deformed by accretion
disks still expel even strong magnetic fields. Analogously to a similar
property of superconductors, this is called Meissner effect.
| [
{
"created": "Mon, 20 Feb 2017 19:48:33 GMT",
"version": "v1"
}
] | 2017-03-13 | [
[
"Gürlebeck",
"Norman",
""
],
[
"Scholtz",
"Martin",
""
]
] | Black holes are important astrophysical objects describing an end state of stellar evolution, which are observed frequently. There are theoretical predictions that Kerr black holes with high spins expel magnetic fields. However, Kerr black holes are pure vacuum solutions, which do not include accretion disks, and additionally previous investigations are mainly limited to weak magnetic fields. We prove for the first time in full general relativity that generic rapidly spinning black holes including those deformed by accretion disks still expel even strong magnetic fields. Analogously to a similar property of superconductors, this is called Meissner effect. |
gr-qc/0502113 | Slava G. Turyshev | Slava G. Turyshev, Michael Shao, Kenneth L. Nordtvedt | Optical Design for the Laser Astrometric Test of Relativity | 11 pages, 7 figures, and 2 tables. Invited talk given at ``The XXII
Texas Symposium on Relativistic Astrophysics,'' Stanford University, December
13-17, 2004 | ``The XXII Texas Symposium on Relativistic Astrophysics,''
Stanford University, December 13-17, 2004, edited by P. Chen, E. Bloom, G.
Madejski, and V. Petrosian. SLAC-R-752, Stanford e-Conf #C041213, paper #0306 | null | null | gr-qc | null | This paper discusses the Laser Astrometric Test Of Relativity (LATOR)
mission. By using a combination of independent time-series of highly accurate
gravitational deflection of light in the immediate proximity to the Sun along
with measurements of the Shapiro time delay on the interplanetary scales (to a
precision respectively better than $10^{-13}$ radians and 1 cm), LATOR will
significantly improve our knowledge of relativistic gravity. The primary
mission objective is to i) measure the key post-Newtonian Eddington parameter
$\gamma$ with accuracy of a part in 10$^9$. $(1-\gamma)$ is a direct measure
for presence of a new interaction in gravitational theory, and, in its search,
LATOR goes a factor 30,000 beyond the present best result, Cassini's 2003 test.
Other mission objectives include: ii) first measurement of gravity's non-linear
effects on light to $\sim$0.01% accuracy; including both the traditional
Eddington $\beta$ parameter and also the spatial metric's 2nd order potential
contribution (never been measured before); iii) direct measurement of the solar
quadrupole moment $J_2$ (currently unavailable) to accuracy of a part in 200 of
its expected size; iv) direct measurement of the ``frame-dragging'' effect on
light by the Sun's rotational gravitomagnetic field to one percent accuracy.
LATOR's primary measurement pushes to unprecedented accuracy the search for
cosmologically relevant scalar-tensor theories of gravity by looking for a
remnant scalar field in today's solar system. The key element of LATOR is a
geometric redundancy provided by the laser ranging and long-baseline optical
interferometry. We discuss the mission and optical designs of this proposed
experiment.
| [
{
"created": "Fri, 25 Feb 2005 20:24:39 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Turyshev",
"Slava G.",
""
],
[
"Shao",
"Michael",
""
],
[
"Nordtvedt",
"Kenneth L.",
""
]
] | This paper discusses the Laser Astrometric Test Of Relativity (LATOR) mission. By using a combination of independent time-series of highly accurate gravitational deflection of light in the immediate proximity to the Sun along with measurements of the Shapiro time delay on the interplanetary scales (to a precision respectively better than $10^{-13}$ radians and 1 cm), LATOR will significantly improve our knowledge of relativistic gravity. The primary mission objective is to i) measure the key post-Newtonian Eddington parameter $\gamma$ with accuracy of a part in 10$^9$. $(1-\gamma)$ is a direct measure for presence of a new interaction in gravitational theory, and, in its search, LATOR goes a factor 30,000 beyond the present best result, Cassini's 2003 test. Other mission objectives include: ii) first measurement of gravity's non-linear effects on light to $\sim$0.01% accuracy; including both the traditional Eddington $\beta$ parameter and also the spatial metric's 2nd order potential contribution (never been measured before); iii) direct measurement of the solar quadrupole moment $J_2$ (currently unavailable) to accuracy of a part in 200 of its expected size; iv) direct measurement of the ``frame-dragging'' effect on light by the Sun's rotational gravitomagnetic field to one percent accuracy. LATOR's primary measurement pushes to unprecedented accuracy the search for cosmologically relevant scalar-tensor theories of gravity by looking for a remnant scalar field in today's solar system. The key element of LATOR is a geometric redundancy provided by the laser ranging and long-baseline optical interferometry. We discuss the mission and optical designs of this proposed experiment. |
1511.07142 | N.D. Hari Dass | N. D. Hari Dass and Harini Desiraju | Killing vectors of FLRW metric (in comoving coordinates) and zero modes
of the scalar Laplacian | 30 pages in JHEP style. In this third revision we have revised the
title, abstract, and the body, to stress the coordinate system used, as well
as remove the confusion between components and vectors in the earlier
version. The zero modes in greater detail using the notions of
well-definedness, square integrability and normalizability | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on an examination of the solutions to the Killing Vector equations for
the FLRW-metric in co moving coordinates , it is conjectured and proved that
the components(in these coordinates) of Killing Vectors, when suitably scaled
by functions, are \emph{zero modes} of the corresponding \emph{scalar}
Laplacian. The complete such set of zero modes(infinitely many) are explicitly
constructed for the two-sphere. They are parametrised by an integer n. For
$n\,\ge\,2$, all the solutions are \emph{irregular} (in the sense that they are
neither well defined everywhere nor are \emph{square-integrable}). The
associated 2-d vectors are also \emph{not normalisable}. The $n=0$ solutions
being constants (these correspond to the zero angular momentum solutions) are
regular and normalizable. Not all of the $n=1$ solutions are regular but the
associated vectors are normalizable. Of course, the action of scalar Laplacian
coordinate independent significance only when acting on scalars. However, our
conclusions have an unambiguous meaning as long as one works in this coordinate
system. As an intermediate step, the covariant Laplacians(vector Laplacians) of
Killing vectors are worked out for four-manifolds in two different ways, both
of which have the novelty of not explicitly needing the connections. It is
further shown that for certain maximally symmetric sub-manifolds(hypersurfaces
of one or more constant comoving coordinates) of the FLRW-spaces also, the
scaled Killing vector components are zero modes of their corresponding scalar
Laplacians. The Killing vectors for the maximally symmetric four-manifolds are
worked out using the elegant embedding formalism originally due to
Schr\"odinger . Some consequences of our results are worked out. Relevance to
some very recent works on zero modes in AdS/CFT correspondences , as well as on
braneworld scenarios is briefly commented upon.
| [
{
"created": "Mon, 23 Nov 2015 09:06:00 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Dec 2015 09:10:43 GMT",
"version": "v2"
},
{
"created": "Fri, 26 Feb 2016 03:26:31 GMT",
"version": "v3"
}
] | 2016-02-29 | [
[
"Dass",
"N. D. Hari",
""
],
[
"Desiraju",
"Harini",
""
]
] | Based on an examination of the solutions to the Killing Vector equations for the FLRW-metric in co moving coordinates , it is conjectured and proved that the components(in these coordinates) of Killing Vectors, when suitably scaled by functions, are \emph{zero modes} of the corresponding \emph{scalar} Laplacian. The complete such set of zero modes(infinitely many) are explicitly constructed for the two-sphere. They are parametrised by an integer n. For $n\,\ge\,2$, all the solutions are \emph{irregular} (in the sense that they are neither well defined everywhere nor are \emph{square-integrable}). The associated 2-d vectors are also \emph{not normalisable}. The $n=0$ solutions being constants (these correspond to the zero angular momentum solutions) are regular and normalizable. Not all of the $n=1$ solutions are regular but the associated vectors are normalizable. Of course, the action of scalar Laplacian coordinate independent significance only when acting on scalars. However, our conclusions have an unambiguous meaning as long as one works in this coordinate system. As an intermediate step, the covariant Laplacians(vector Laplacians) of Killing vectors are worked out for four-manifolds in two different ways, both of which have the novelty of not explicitly needing the connections. It is further shown that for certain maximally symmetric sub-manifolds(hypersurfaces of one or more constant comoving coordinates) of the FLRW-spaces also, the scaled Killing vector components are zero modes of their corresponding scalar Laplacians. The Killing vectors for the maximally symmetric four-manifolds are worked out using the elegant embedding formalism originally due to Schr\"odinger . Some consequences of our results are worked out. Relevance to some very recent works on zero modes in AdS/CFT correspondences , as well as on braneworld scenarios is briefly commented upon. |
gr-qc/9510065 | Laurent Querella | Jacques Demaret, Laurent Querella (Institut d'Astrophysique de Liege) | Hamiltonian Formulation of Bianchi Cosmological Models in Quadratic
Theories of Gravity | Latex, 29 pages, accepted for publication in Classical and Quantum
Gravity | Class.Quant.Grav. 12 (1995) 3085-3102 | 10.1088/0264-9381/12/12/023 | COSMO-LQ-95-07 | gr-qc | null | We use Boulware's Hamiltonian formalism of quadratic gravity theories in
order to analyze the classical behaviour of Bianchi cosmological models for a
Lagrangian density containing quadratic terms in the curvature. For this
purpose we define a canonical transformation which leads to a clear distinction
between two main variants of the quadratic theory, namely the R-squared or
conformal Lagrangian densities. In this paper we restrict the study to the
first variant. For Bianchi type I and IX models we give the explicit forms of
the super-Hamiltonian constraint, of the ADM Hamiltonian density and of the
corresponding canonical equations. In the case of a pure R-squared theory we
solve these equations analytically for Bianchi I model. For Bianchi type IX
model, we reduce the first-order equations of the Hamiltonian system to three
coupled second-order equations for the true physical degrees of freedom. This
discussion is extended to isotropic FLRW models.
| [
{
"created": "Tue, 31 Oct 1995 13:11:04 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Demaret",
"Jacques",
"",
"Institut d'Astrophysique de Liege"
],
[
"Querella",
"Laurent",
"",
"Institut d'Astrophysique de Liege"
]
] | We use Boulware's Hamiltonian formalism of quadratic gravity theories in order to analyze the classical behaviour of Bianchi cosmological models for a Lagrangian density containing quadratic terms in the curvature. For this purpose we define a canonical transformation which leads to a clear distinction between two main variants of the quadratic theory, namely the R-squared or conformal Lagrangian densities. In this paper we restrict the study to the first variant. For Bianchi type I and IX models we give the explicit forms of the super-Hamiltonian constraint, of the ADM Hamiltonian density and of the corresponding canonical equations. In the case of a pure R-squared theory we solve these equations analytically for Bianchi I model. For Bianchi type IX model, we reduce the first-order equations of the Hamiltonian system to three coupled second-order equations for the true physical degrees of freedom. This discussion is extended to isotropic FLRW models. |
gr-qc/0505162 | Margarita Safonova Dr. | Z. Turakulov, M. Safonova | Motion of a Vector Particle in a Curved Spacetime. II First Order
Correction to a Geodesic in a Schwarzschild Background | 14 pages, LaTeX2e, second paper in the series (the first one:
gr-qc/0110067), replaced with typos and style corrected version, accepted in
MPLA | Mod.Phys.Lett. A20 (2005) 2785-2798 | 10.1142/S0217732305018852 | IPM preprint no. is IPM/P-2005/049 | gr-qc | null | The influence of spin on a photon's motion in a Schwarzschild and FRW
spacetimes is studied. The first order correction to the geodesic motion is
found. It is shown that unlike the world-lines of spinless particles, the
photons world-lines do not lie in a plane.
| [
{
"created": "Tue, 31 May 2005 15:43:04 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Oct 2005 10:30:45 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Turakulov",
"Z.",
""
],
[
"Safonova",
"M.",
""
]
] | The influence of spin on a photon's motion in a Schwarzschild and FRW spacetimes is studied. The first order correction to the geodesic motion is found. It is shown that unlike the world-lines of spinless particles, the photons world-lines do not lie in a plane. |
gr-qc/9801005 | Student | I-Ching Yang | On the energy of the de Sitter-Schwarzschild black hole | Latex file,9 pages,include 1 figure file | Chin.J.Phys. 38 (2000) 1040-1043 | null | NCKU-HEP/97-05 | gr-qc | null | Using Einstein's and Weinberg's energy complex, we evaluate the energy
distribution of the vaccum nonsingularity black hole solution. The energy
distribution is positive everywhere and be equal to zero at origin.
| [
{
"created": "Mon, 5 Jan 1998 09:17:17 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Yang",
"I-Ching",
""
]
] | Using Einstein's and Weinberg's energy complex, we evaluate the energy distribution of the vaccum nonsingularity black hole solution. The energy distribution is positive everywhere and be equal to zero at origin. |
1703.09267 | Shahram Jalalzadeh | M. Fathi and S. Jalalzadeh | Quantum Hamilton-Jacobi cosmology and classical-quantum correlation | 10 pages, to appear in IJTP | null | 10.1007/s10773-017-3363-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | How the time evolution which is typical for classical cosmology emerges from
quantum cosmology? The answer is not trivial because the Wheeler-DeWitt
equation is time independent. A framework associating the quantum
Hamilton-Jacobi to the minisuperspace cosmological models has been introduced
in [1]. In this paper, we show that time dependence and quantum-classical
correspondence both arise naturally in the quantum Hamilton-Jacobi formalism of
quantum mechanics applied to quantum cosmology. We study the quantum
Hamilton-Jacobi cosmology of spatially flat homogeneous and isotropic early
universe whose matter content is a perfect fluid. The classical cosmology
emerge around one Planck time where its linear size is around a few millimeter,
without needing any classical inflationary phase afterwards to make it grow to
its present size.
| [
{
"created": "Mon, 27 Mar 2017 18:59:49 GMT",
"version": "v1"
}
] | 2017-04-26 | [
[
"Fathi",
"M.",
""
],
[
"Jalalzadeh",
"S.",
""
]
] | How the time evolution which is typical for classical cosmology emerges from quantum cosmology? The answer is not trivial because the Wheeler-DeWitt equation is time independent. A framework associating the quantum Hamilton-Jacobi to the minisuperspace cosmological models has been introduced in [1]. In this paper, we show that time dependence and quantum-classical correspondence both arise naturally in the quantum Hamilton-Jacobi formalism of quantum mechanics applied to quantum cosmology. We study the quantum Hamilton-Jacobi cosmology of spatially flat homogeneous and isotropic early universe whose matter content is a perfect fluid. The classical cosmology emerge around one Planck time where its linear size is around a few millimeter, without needing any classical inflationary phase afterwards to make it grow to its present size. |
1901.08588 | Lucas Lombriser | Lucas Lombriser | On the cosmological constant problem | 5 pages; v2 matches published version | Phys. Lett. B 797, 134804 (2019) | 10.1016/j.physletb.2019.134804 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An additional variation of the Einstein-Hilbert action with respect to the
Planck mass provides a constraint on the average Ricci scalar that prevents
vacuum energy from gravitating. Consideration of the evolution of the
inhomogeneous matter distribution in the Universe with evaluation of the
averaging constraint on disconnected matter cells that ultimately form isolated
gravitationally bound structures yields a backreaction effect that
self-consistently produces the cosmological constant of the background. A
uniform prior on our location in the formation of these isolated structures
implies a mean expectation for the present cosmological constant energy density
parameter of $\Omega_{\Lambda}=0.704$, giving rise to a late-time acceleration
of the cosmic expansion and a coincident current energy density of matter.
| [
{
"created": "Wed, 23 Jan 2019 19:00:02 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Sep 2019 15:33:11 GMT",
"version": "v2"
}
] | 2019-09-18 | [
[
"Lombriser",
"Lucas",
""
]
] | An additional variation of the Einstein-Hilbert action with respect to the Planck mass provides a constraint on the average Ricci scalar that prevents vacuum energy from gravitating. Consideration of the evolution of the inhomogeneous matter distribution in the Universe with evaluation of the averaging constraint on disconnected matter cells that ultimately form isolated gravitationally bound structures yields a backreaction effect that self-consistently produces the cosmological constant of the background. A uniform prior on our location in the formation of these isolated structures implies a mean expectation for the present cosmological constant energy density parameter of $\Omega_{\Lambda}=0.704$, giving rise to a late-time acceleration of the cosmic expansion and a coincident current energy density of matter. |
0905.3285 | Sergey S. Kokarev | Sergey S. Kokarev | Three lectures on Newton's laws | 22 pages, 9 figures, has been reported by parts on several Russian
conferences and seminars | Published in Russian, Collected scientific papers of RSEC Logos,
v1, 2006, pp.45-72 | null | null | gr-qc physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Three small lectures are devoted to three Newton's laws, lying in the
foundation of classical mechanics. These laws are analyzed from the viewpoint
of our contemporary knowledge about space, time and physical interactions. The
lectures were delivered for students of YarGU in RSEC "Logos".
| [
{
"created": "Wed, 20 May 2009 11:52:50 GMT",
"version": "v1"
}
] | 2009-05-21 | [
[
"Kokarev",
"Sergey S.",
""
]
] | Three small lectures are devoted to three Newton's laws, lying in the foundation of classical mechanics. These laws are analyzed from the viewpoint of our contemporary knowledge about space, time and physical interactions. The lectures were delivered for students of YarGU in RSEC "Logos". |
2311.05766 | Jorge Pullin | Rodolfo Gambini and Jorge Pullin | Quantization of spherically symmetric loop quantum gravity coupled to a
scalar field and a clock: the asymptotic limit | 8 pages, RevTex, no figures. To appear in Classical and Quantum
Gravity | Classical and Quantum Graivty 40, 245009 (2023) | 10.1088/1361-6382/ad0b9d | LSU-REL-110923 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We continue our work on the study of spherically symmetric loop quantum
gravity coupled to two spherically symmetric scalar fields, one which acts as a
clock. As a consequence of the presence of the latter, we can define a true
Hamiltonian for the theory. The spherically symmetric context allows to carry
out precise detailed calculations. Here we study the theory for regions of
large values of the radial coordinate. This allows us to define in detail the
vacuum of the theory and study its quantum states, yielding a quantum field
theory on a quantum space time that makes contact with the usual treatment on
classical space times.
| [
{
"created": "Thu, 9 Nov 2023 22:22:00 GMT",
"version": "v1"
}
] | 2023-11-21 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | We continue our work on the study of spherically symmetric loop quantum gravity coupled to two spherically symmetric scalar fields, one which acts as a clock. As a consequence of the presence of the latter, we can define a true Hamiltonian for the theory. The spherically symmetric context allows to carry out precise detailed calculations. Here we study the theory for regions of large values of the radial coordinate. This allows us to define in detail the vacuum of the theory and study its quantum states, yielding a quantum field theory on a quantum space time that makes contact with the usual treatment on classical space times. |
gr-qc/0506100 | Sashideep Gutti | Sashideep Gutti | Gravitational Collapse of Inhomogeneous Dust in (2+1) Dimensions | Accepted for publication in CQG | Class.Quant.Grav. 22 (2005) 3223-3234 | 10.1088/0264-9381/22/16/007 | null | gr-qc | null | We examine the gravitational collapse of spherically symmetric inhomogeneous
dust in (2+1) dimensions, with cosmological constant. We obtain the analytical
expressions for the interior metric. We match the solution to a vacuum
exterior. We discuss the nature of the singularity formed by analyzing the
outgoing radial null geodesics. We examine the formation of trapped surfaces
during the collapse.
| [
{
"created": "Mon, 20 Jun 2005 04:33:54 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Gutti",
"Sashideep",
""
]
] | We examine the gravitational collapse of spherically symmetric inhomogeneous dust in (2+1) dimensions, with cosmological constant. We obtain the analytical expressions for the interior metric. We match the solution to a vacuum exterior. We discuss the nature of the singularity formed by analyzing the outgoing radial null geodesics. We examine the formation of trapped surfaces during the collapse. |
1604.03973 | Adam J. Christopherson | Adam J. Christopherson | Relating metric and covariant perturbation theories in $f(R)$ gravity | 17 pages | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Modified theories of gravity have been invoked recently as an alternative to
dark energy, in an attempt to explain the apparent accelerated expansion of the
universe at the present time. In order to describe inhomogeneities in
cosmological models, cosmological perturbation theory is used, of which two
formalisms exist: the metric approach and the covariant approach. In this paper
I present the relationship between the metric and covariant approaches for
modeling $f(R)$ theories of gravity. This provides a useful resource that
researchers primarily working with one formalism can use to compare or
translate their results to the other formalism.
| [
{
"created": "Wed, 13 Apr 2016 21:00:34 GMT",
"version": "v1"
}
] | 2016-04-15 | [
[
"Christopherson",
"Adam J.",
""
]
] | Modified theories of gravity have been invoked recently as an alternative to dark energy, in an attempt to explain the apparent accelerated expansion of the universe at the present time. In order to describe inhomogeneities in cosmological models, cosmological perturbation theory is used, of which two formalisms exist: the metric approach and the covariant approach. In this paper I present the relationship between the metric and covariant approaches for modeling $f(R)$ theories of gravity. This provides a useful resource that researchers primarily working with one formalism can use to compare or translate their results to the other formalism. |
gr-qc/9910019 | Maurizio Gasperini | M. Gasperini | On the response of gravitational antennas to dilatonic waves | 10 pages, Latex, no figures | Phys.Lett. B470 (1999) 67-72 | 10.1016/S0370-2693(99)01309-X | BA-TH/99-363 | gr-qc hep-th | null | It is pointed out that the coupling of macroscopic test masses to the
gravi-dilaton background of string theory is non geodesic, in general, and
cannot be parametrized by a Brans-Dicke model of scalar-tensor gravity. The
response of gravitational antennas to dilatonic waves should be analyzed
through a generalized equation of geodesic deviation, taking into account the
possible direct coupling of the background to the (composition-dependent)
dilatonic charge of the antenna.
| [
{
"created": "Wed, 6 Oct 1999 08:30:19 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Gasperini",
"M.",
""
]
] | It is pointed out that the coupling of macroscopic test masses to the gravi-dilaton background of string theory is non geodesic, in general, and cannot be parametrized by a Brans-Dicke model of scalar-tensor gravity. The response of gravitational antennas to dilatonic waves should be analyzed through a generalized equation of geodesic deviation, taking into account the possible direct coupling of the background to the (composition-dependent) dilatonic charge of the antenna. |
2204.11384 | Motohiko Yoshimura | M.Yoshimura | Stronger gravity in the early universe | 5 pages | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | Scalar-tensor theories of gravity that embrace conformal coupling to the
scalar curvature are the focal point of cosmology on discussions of inflation
and late-time accelerating universe. Although there exists a stringent
nucleo-synthesis constraint on conformal gravity, one can formulate how to
evade this difficulty by modifying the standard particle theory action
consistently with the principles of gauge invariant quantum field theory. It is
shown that stronger gravity at early epochs of cosmological evolution than
previously thought of is inevitable in a class of conformal gravity models.
This enhances discovery potentials of primordial gravitational wave emission
and primordial black hole formation. The strong gravity effect may be enormous
if massive clumps are energetically dominated by cold dark matter made of
inflaton field, and created black holes may become a major candidate of cold
dark matter.
| [
{
"created": "Mon, 25 Apr 2022 00:44:19 GMT",
"version": "v1"
}
] | 2022-04-26 | [
[
"Yoshimura",
"M.",
""
]
] | Scalar-tensor theories of gravity that embrace conformal coupling to the scalar curvature are the focal point of cosmology on discussions of inflation and late-time accelerating universe. Although there exists a stringent nucleo-synthesis constraint on conformal gravity, one can formulate how to evade this difficulty by modifying the standard particle theory action consistently with the principles of gauge invariant quantum field theory. It is shown that stronger gravity at early epochs of cosmological evolution than previously thought of is inevitable in a class of conformal gravity models. This enhances discovery potentials of primordial gravitational wave emission and primordial black hole formation. The strong gravity effect may be enormous if massive clumps are energetically dominated by cold dark matter made of inflaton field, and created black holes may become a major candidate of cold dark matter. |
2112.08905 | Gabriele Barca | Gabriele Barca, Eleonora Giovannetti, Giovanni Montani | Comparison of the Semiclassical and Quantum Dynamics of the Bianchi I
Cosmology in the Polymer and GUP Extended Paradigms | 23 pages, 6 figures. Invited contribution to IJGMMP special issue for
the conference "Geometric Foundations of Gravity 2021" (Tartu, Estonia, June
28-July 2, 2021). New upload to match published version | IJGMMP 19, 07, 2250097 (2022) | 10.1142/S0219887822500979 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compare in some detail Polymer Quantum Mechanics and the Generalized
Uncertainty Principle approach to clarify to what extent we can treat them on
the same footing. We show that, while on a semiclassical level they may be
formulated as similar modifications of the Poisson algebra, on a quantum level
they intrinsically differ because PQM implies no absolute minimal uncertainty
on position. Then we implement these schemes to Bianchi I cosmology on a
semiclassical level deforming only the algebra of the Universe volume,
searching for alternative formulations able to account for the modified
Friedmann equations emerging in Brane Cosmology and Loop Quantum Cosmology. On
a pure quantum level, we implement the two approaches through their original
setups and reduce the two resulting Wheeler-DeWitt equations to the same
morphological structure, showing how the polymer formalism is associated with a
bouncing dynamics while in the Generalized Uncertainty Principle case the
singularity is still present. The implications of the wavepacket spreading are
also discussed in both approaches, outlining that, when the singularity
survives, the Planckian era must necessarily be approached by a fully quantum
(non-peaked) state of the Universe.
| [
{
"created": "Thu, 16 Dec 2021 14:23:45 GMT",
"version": "v1"
},
{
"created": "Thu, 19 May 2022 14:12:20 GMT",
"version": "v2"
}
] | 2022-05-20 | [
[
"Barca",
"Gabriele",
""
],
[
"Giovannetti",
"Eleonora",
""
],
[
"Montani",
"Giovanni",
""
]
] | We compare in some detail Polymer Quantum Mechanics and the Generalized Uncertainty Principle approach to clarify to what extent we can treat them on the same footing. We show that, while on a semiclassical level they may be formulated as similar modifications of the Poisson algebra, on a quantum level they intrinsically differ because PQM implies no absolute minimal uncertainty on position. Then we implement these schemes to Bianchi I cosmology on a semiclassical level deforming only the algebra of the Universe volume, searching for alternative formulations able to account for the modified Friedmann equations emerging in Brane Cosmology and Loop Quantum Cosmology. On a pure quantum level, we implement the two approaches through their original setups and reduce the two resulting Wheeler-DeWitt equations to the same morphological structure, showing how the polymer formalism is associated with a bouncing dynamics while in the Generalized Uncertainty Principle case the singularity is still present. The implications of the wavepacket spreading are also discussed in both approaches, outlining that, when the singularity survives, the Planckian era must necessarily be approached by a fully quantum (non-peaked) state of the Universe. |
1305.4851 | Zacharias Roupas | Zacharias Roupas | Gravitational-thermodynamic instabilities of isothermal spheres in dS
and AdS | Proceedings contribution; much of the work presented in this talk was
elaborated jointly with Minos Axenides and George Georgiou, and appears
analytically elsewhere | Proceedings of the Barcelona Postgrad Encounters on Fundamental
Physics, editors Daniel Fernandez, Markus B. Frob, Ivan Latella and Aldo
Dector, Facultat de Fisica, Universitat de Barcelona, p.31-42, 2013 | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Thermodynamical stability of fluid spheres is studied in the presence of a
cosmological constant, both in the Newtonian limit, as well as in General
Relativity. In all cases, an increase of the cosmological constant tends to
stabilize the system, making asymptotically de Sitter space more
thermodynamically stable than anti-de Sitter at the purely classical level. In
addition, in the Newtonian case reentrant phase transitions are observed for a
positive cosmological constant, due to its repelling property in this case. In
General Relativity is studied the case of radiation, for which is found that
the critical radius, at which an instability sets in, is always bigger than the
black hole radius of the system and furthermore, at some value of the
cosmological constant this critical radius hits at the cosmological horizon.
| [
{
"created": "Tue, 21 May 2013 15:14:08 GMT",
"version": "v1"
}
] | 2013-05-22 | [
[
"Roupas",
"Zacharias",
""
]
] | Thermodynamical stability of fluid spheres is studied in the presence of a cosmological constant, both in the Newtonian limit, as well as in General Relativity. In all cases, an increase of the cosmological constant tends to stabilize the system, making asymptotically de Sitter space more thermodynamically stable than anti-de Sitter at the purely classical level. In addition, in the Newtonian case reentrant phase transitions are observed for a positive cosmological constant, due to its repelling property in this case. In General Relativity is studied the case of radiation, for which is found that the critical radius, at which an instability sets in, is always bigger than the black hole radius of the system and furthermore, at some value of the cosmological constant this critical radius hits at the cosmological horizon. |
gr-qc/0206015 | Sergiu Vacaru | Sergiu Vacaru and D. E. Goksel | Horizons and Geodesics of Black Ellipsoids with Anholonomic Conformal
Symmetries | 14 pages, latex2e, file modified for publication in "Progress in
Mathematical Physics", Ed. Frank Columbus (Nova Science Publishers, NY, 2003) | "Focus on Mathematical Physics, Research 2004", Ed. Charles V.
Benton (Nova Science Publishers, NY, 2004), pp. 1-14 | null | null | gr-qc astro-ph hep-th math-ph math.DG math.MP | null | The horizon and geodesic structure of static configurations generated by
anisotropic conformal transforms of the Schwarzschild metric is analyzed. We
construct the maximal analytic extension of such off--diagonal vacuum metrics
and conclude that for small deformations there are different classes of vacuum
solutions of the Einstein equations describing "black ellipsoid" objects. This
is possible because, in general, for off--diagonal metrics with deformed
non--spherical symmetries and associated anholonomic frames the conditions of
the uniqueness black hole theorems do not hold.
| [
{
"created": "Wed, 5 Jun 2002 20:02:18 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Jul 2003 16:35:58 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Vacaru",
"Sergiu",
""
],
[
"Goksel",
"D. E.",
""
]
] | The horizon and geodesic structure of static configurations generated by anisotropic conformal transforms of the Schwarzschild metric is analyzed. We construct the maximal analytic extension of such off--diagonal vacuum metrics and conclude that for small deformations there are different classes of vacuum solutions of the Einstein equations describing "black ellipsoid" objects. This is possible because, in general, for off--diagonal metrics with deformed non--spherical symmetries and associated anholonomic frames the conditions of the uniqueness black hole theorems do not hold. |
1203.3761 | Claudio Simeone | Claudio Simeone | Cylindrical thin-shell wormholes and energy conditions | 9 pages; slightly improved version of the article accepted in Int. J.
Mod. Phys. D | null | 10.1142/S0218271812500150 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove the impossibility of cylindrical thin-shell wormholes supported by
matter satisfying the energy conditions everywhere, under reasonable
assumptions about the asymptotic behaviour of the - in general different -
metrics at each side of the throat. In particular, we reproduce for singular
sources previous results corresponding to flat and conical asymptotics, and
extend them to a more general asymptotic behaviour. Besides, we establish
necessary conditions for the possibility of non exotic cylindrical thin-shell
wormholes.
| [
{
"created": "Fri, 16 Mar 2012 16:39:58 GMT",
"version": "v1"
}
] | 2012-03-19 | [
[
"Simeone",
"Claudio",
""
]
] | We prove the impossibility of cylindrical thin-shell wormholes supported by matter satisfying the energy conditions everywhere, under reasonable assumptions about the asymptotic behaviour of the - in general different - metrics at each side of the throat. In particular, we reproduce for singular sources previous results corresponding to flat and conical asymptotics, and extend them to a more general asymptotic behaviour. Besides, we establish necessary conditions for the possibility of non exotic cylindrical thin-shell wormholes. |
0910.0594 | Davood Momeni Dr | D.Momeni | Cosmic strings in a model of non-relativistic gravity | 30pages,It has been accepted for publication in International Journal
of Theoretical Physics-Extended version with 2 new sections about
(Thermodynamics and Dark energy in Horava-Lifshitz gravity),(About the
existence of non-static cylindrical solutions) | Int.J.Theor.Phys.50:1493-1514,2011 | 10.1007/s10773-010-0659-9 | null | gr-qc hep-th math-ph math.CA math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Ho$\check{\textbf{r}}$ava proposed a non-relativistic renormalizable theory
of gravitation, which is reduced to general relativity (GR) in large distances
(infra-red regime (IR)). It is believed that this theory is an ultra-violet
(UV) completion for the classical theory of gravitation. In this paper, after a
brief review of some fundamental features of this theory, we investigate it for
a static cylindrical symmetric solution which describes \emph{Cosmic string} as
a special case. We have also investigated some possible solutions, and have
seen that how the classical GR field equations are modified for generic
potential $V (g)$. In one case there is an algebraic constraint on the values
of three coupling constants. Finally as a pioneering work we deduce the most
general \emph{cosmic string} in this theory. We explicitly show that how the
\emph{coupling constants} distort the mass parameter of \emph{cosmic string}.
We deduce an explicit function for mass per unit length of the space-time as a
function of the \emph{coupling constants}. We compare this function with
another which Aryal et al [58] have found in GR.Also we calculate the
self-force on a massive particle near Ho$\check{\textbf{r}}$ava-Lifshitz
straight string and we give a typical order for the \emph{coupling constants}
$g_{9}$. This order of magnitude proposes a cosmological test for validity of
this theory.
| [
{
"created": "Sun, 4 Oct 2009 10:39:52 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Dec 2010 14:13:56 GMT",
"version": "v10"
},
{
"created": "Sat, 10 Oct 2009 06:20:01 GMT",
"version": "v2"
},
{
"created": "Thu, 12 Nov 2009 10:01:09 GMT",
"version": "v3"
},
{
"created": "Mon, 7 Dec 2009 09:55:55 GMT",
"version": "v4"
},
{
"created": "Mon, 1 Feb 2010 05:44:41 GMT",
"version": "v5"
},
{
"created": "Mon, 15 Mar 2010 08:24:29 GMT",
"version": "v6"
},
{
"created": "Sun, 1 Aug 2010 14:07:16 GMT",
"version": "v7"
},
{
"created": "Sun, 5 Sep 2010 04:29:25 GMT",
"version": "v8"
},
{
"created": "Fri, 26 Nov 2010 08:44:33 GMT",
"version": "v9"
}
] | 2011-04-11 | [
[
"Momeni",
"D.",
""
]
] | Ho$\check{\textbf{r}}$ava proposed a non-relativistic renormalizable theory of gravitation, which is reduced to general relativity (GR) in large distances (infra-red regime (IR)). It is believed that this theory is an ultra-violet (UV) completion for the classical theory of gravitation. In this paper, after a brief review of some fundamental features of this theory, we investigate it for a static cylindrical symmetric solution which describes \emph{Cosmic string} as a special case. We have also investigated some possible solutions, and have seen that how the classical GR field equations are modified for generic potential $V (g)$. In one case there is an algebraic constraint on the values of three coupling constants. Finally as a pioneering work we deduce the most general \emph{cosmic string} in this theory. We explicitly show that how the \emph{coupling constants} distort the mass parameter of \emph{cosmic string}. We deduce an explicit function for mass per unit length of the space-time as a function of the \emph{coupling constants}. We compare this function with another which Aryal et al [58] have found in GR.Also we calculate the self-force on a massive particle near Ho$\check{\textbf{r}}$ava-Lifshitz straight string and we give a typical order for the \emph{coupling constants} $g_{9}$. This order of magnitude proposes a cosmological test for validity of this theory. |
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