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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1503.07418 | Behnam Pourhassan | B. Pourhassan, Mir Faizal | Thermal Fluctuations in a Charged AdS Black Hole | 11 pages, Accepted for publication in EPL | Europhys. Lett. 111: 40006, 2015 | 10.1209/0295-5075/111/40006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we will analyze the effects of thermal fluctuations on a
charged AdS black hole. This will be done by analyzing the corrections to black
hole thermodynamics due to these thermal fluctuations. We will demonstrate that
the entropy of this black hole get corrected by logarithmic term. We will also
calculate other corrections to other important thermodynamic quantities for
this black hole. Finally, we will use the corrected value of the specific heat
to analyze the phase transition in this system.
| [
{
"created": "Sun, 22 Mar 2015 06:38:53 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Mar 2015 06:46:10 GMT",
"version": "v2"
},
{
"created": "Wed, 12 Aug 2015 19:51:40 GMT",
"version": "v3"
}
] | 2015-09-30 | [
[
"Pourhassan",
"B.",
""
],
[
"Faizal",
"Mir",
""
]
] | In this paper, we will analyze the effects of thermal fluctuations on a charged AdS black hole. This will be done by analyzing the corrections to black hole thermodynamics due to these thermal fluctuations. We will demonstrate that the entropy of this black hole get corrected by logarithmic term. We will also calculate other corrections to other important thermodynamic quantities for this black hole. Finally, we will use the corrected value of the specific heat to analyze the phase transition in this system. |
2302.06387 | Gustav Holzegel | Gustav Holzegel and Christopher Kauffman | The wave equation on subextremal Kerr spacetimes with small non-decaying
first order terms | 75 pages, 2 figures | null | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the perturbed covariant wave equation $\Box_{g_{M,a}} \Psi =
\varepsilon \mathbf{B} \Psi$ on the exterior of a fixed subextremal Kerr
spacetime $\left(\mathcal{M},g_{M,a}\right)$. Here $\mathbf{B}$ is a suitably
regular first order differential operator respecting the symmetries of Kerr
whose coefficients are assumed to decay in space but not in time. We establish
integrated decay estimates for solutions of the associated Cauchy problem. The
proof adapts the framework introduced by
Dafermos--Rodnianski--Shlapentokh-Rothman \cite{DRSR} in the $\varepsilon=0$
case. We combine their estimates with a new global pseudodifferential
commutator estimate, which generalises our previous work in the Schwarzschild
case. The construction of the commutator exploits the central observation of
\cite{DRSR} that superradiant frequencies are not trapped. A further major
technical ingredient of the proof consists in establishing appropriate
convolution estimates for expressions arising from the interplay of the
$\mathbf{B}$-term and the time cutoffs in the microlocal framework.
| [
{
"created": "Mon, 13 Feb 2023 14:31:03 GMT",
"version": "v1"
}
] | 2023-02-14 | [
[
"Holzegel",
"Gustav",
""
],
[
"Kauffman",
"Christopher",
""
]
] | We consider the perturbed covariant wave equation $\Box_{g_{M,a}} \Psi = \varepsilon \mathbf{B} \Psi$ on the exterior of a fixed subextremal Kerr spacetime $\left(\mathcal{M},g_{M,a}\right)$. Here $\mathbf{B}$ is a suitably regular first order differential operator respecting the symmetries of Kerr whose coefficients are assumed to decay in space but not in time. We establish integrated decay estimates for solutions of the associated Cauchy problem. The proof adapts the framework introduced by Dafermos--Rodnianski--Shlapentokh-Rothman \cite{DRSR} in the $\varepsilon=0$ case. We combine their estimates with a new global pseudodifferential commutator estimate, which generalises our previous work in the Schwarzschild case. The construction of the commutator exploits the central observation of \cite{DRSR} that superradiant frequencies are not trapped. A further major technical ingredient of the proof consists in establishing appropriate convolution estimates for expressions arising from the interplay of the $\mathbf{B}$-term and the time cutoffs in the microlocal framework. |
1705.00087 | Sergio Guti\'errez | Sergio Guti\'errez, Belen Carvente, Abel Camacho | Mass bounds for Newtonian bosonic starts in theory of ultra-cold gases | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work we address the issue concerning the relation mass versus
radius for bosonic stars, all this in the context of the theory of ultra-cold
gases in the dilute regime and within the realm of Newtonian gravity. It will
be shown that this model predicts a minimum and a maximum for the mass of this
kind of stars, contrary to the current belief present in some results in this
direction.
| [
{
"created": "Fri, 28 Apr 2017 22:30:30 GMT",
"version": "v1"
}
] | 2017-05-02 | [
[
"Gutiérrez",
"Sergio",
""
],
[
"Carvente",
"Belen",
""
],
[
"Camacho",
"Abel",
""
]
] | In the present work we address the issue concerning the relation mass versus radius for bosonic stars, all this in the context of the theory of ultra-cold gases in the dilute regime and within the realm of Newtonian gravity. It will be shown that this model predicts a minimum and a maximum for the mass of this kind of stars, contrary to the current belief present in some results in this direction. |
gr-qc/0607014 | Laurent Freidel | L. Freidel, J. Kowalski--Glikman and A. Starodubtsev | Particles as Wilson lines of gravitational field | 19 pages, some number of comments and clarifications added, to be
published in Phys. Rev. D | Phys.Rev. D74 (2006) 084002 | 10.1103/PhysRevD.74.084002 | null | gr-qc | null | Since the work of Mac-Dowell-Mansouri it is well known that gravity can be
written as a gauge theory for the de Sitter group. In this paper we consider
the coupling of this theory to the simplest gauge invariant observables that
is, Wilson lines. The dynamics of these Wilson lines is shown to reproduce
exactly the dynamics of relativistic particles coupled to gravity, the gauge
charges carried by Wilson lines being the mass and spin of the particles.
Insertion of Wilson lines breaks in a controlled manner the diffeomorphism
symmetry of the theory and the gauge degree of freedom are transmuted to
particles degree of freedom.
| [
{
"created": "Tue, 4 Jul 2006 23:13:44 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Sep 2006 06:30:06 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Freidel",
"L.",
""
],
[
"Kowalski--Glikman",
"J.",
""
],
[
"Starodubtsev",
"A.",
""
]
] | Since the work of Mac-Dowell-Mansouri it is well known that gravity can be written as a gauge theory for the de Sitter group. In this paper we consider the coupling of this theory to the simplest gauge invariant observables that is, Wilson lines. The dynamics of these Wilson lines is shown to reproduce exactly the dynamics of relativistic particles coupled to gravity, the gauge charges carried by Wilson lines being the mass and spin of the particles. Insertion of Wilson lines breaks in a controlled manner the diffeomorphism symmetry of the theory and the gauge degree of freedom are transmuted to particles degree of freedom. |
1910.13452 | Rodrigo Panosso Macedo | Rodrigo Panosso Macedo | Hyperboloidal framework for the Kerr spacetime | 30 pages. Match published version | Classical and Quantum Gravity, Volume 37, Number 6 (2020) | 10.1088/1361-6382/ab6e3e | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the need of a robust geometrical framework for the calculation
of long, and highly accurate waveforms for extreme-mass-ratio inspirals, this
work presents an extensive study of the hyperboloidal formalism for the Kerr
spacetime and the Teukolsky equation. In a first step, we introduce a generic
coordinate system foliating the Kerr spacetime into hypersurfaces of constant
time extending between the black-hole horizon and future null infinity, while
keeping track of the underlying degrees of freedom. Then, we express the
Teukolsky equation in terms of these generic coordinates with focus on
applications in both the time and frequency domains. Specifically, we derive a
wave-like equation in $2+1$ dimensions, whose unique solution follows directly
from the prescription of initial data (no external boundary conditions).
Moreover, we extend the hyperboloidal formulation into the frequency domain. A
comparison with the standard form of the Teukolsky equations allows us to
express the regularisation factors in terms of the hyperboloidal degrees of
freedom. In the second part, we discuss several hyperboloidal gauges for the
Kerr solution. Of particular importance, this paper introduces the minimal
gauge. The resulting expressions for the Kerr metric and underlying equations
are simple enough for eventual (semi)-analytical studies. Despite the
simplicity, the gauge has a very rich structure as it naturally leads to two
possible limits to extremality, namely the standard extremal Kerr spacetime and
its near-horizon geometry. When applied to the Teukolsky equation in the
frequency domain, we show that the minimal gauge actually provides the
spacetime counterpart of the well-known Leaver's formalism. Finally, we recast
the hyperboloidal gauges for the Kerr spacetime available in the literature
within the framework introduced here.
| [
{
"created": "Tue, 29 Oct 2019 18:00:02 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Mar 2020 13:35:55 GMT",
"version": "v2"
}
] | 2020-03-09 | [
[
"Macedo",
"Rodrigo Panosso",
""
]
] | Motivated by the need of a robust geometrical framework for the calculation of long, and highly accurate waveforms for extreme-mass-ratio inspirals, this work presents an extensive study of the hyperboloidal formalism for the Kerr spacetime and the Teukolsky equation. In a first step, we introduce a generic coordinate system foliating the Kerr spacetime into hypersurfaces of constant time extending between the black-hole horizon and future null infinity, while keeping track of the underlying degrees of freedom. Then, we express the Teukolsky equation in terms of these generic coordinates with focus on applications in both the time and frequency domains. Specifically, we derive a wave-like equation in $2+1$ dimensions, whose unique solution follows directly from the prescription of initial data (no external boundary conditions). Moreover, we extend the hyperboloidal formulation into the frequency domain. A comparison with the standard form of the Teukolsky equations allows us to express the regularisation factors in terms of the hyperboloidal degrees of freedom. In the second part, we discuss several hyperboloidal gauges for the Kerr solution. Of particular importance, this paper introduces the minimal gauge. The resulting expressions for the Kerr metric and underlying equations are simple enough for eventual (semi)-analytical studies. Despite the simplicity, the gauge has a very rich structure as it naturally leads to two possible limits to extremality, namely the standard extremal Kerr spacetime and its near-horizon geometry. When applied to the Teukolsky equation in the frequency domain, we show that the minimal gauge actually provides the spacetime counterpart of the well-known Leaver's formalism. Finally, we recast the hyperboloidal gauges for the Kerr spacetime available in the literature within the framework introduced here. |
0704.2099 | Muhammad Sharif | M. Sharif and M. Jamil Amir | Teleparallel Energy-Momentum Distribution of Static Axially Symmetric
Spacetimes | 14 pages, accepted for publication in Mod. Phys. Lett. A | Mod.Phys.Lett.A23:3167-3177,2008 | 10.1142/S0217732308027035 | null | gr-qc | null | This paper is devoted to discuss the energy-momentum for static axially
symmetric spacetimes in the framework of teleparallel theory of gravity. For
this purpose, we use the teleparallel versions of Einstein, Landau-Lifshitz,
Bergmann and M$\ddot{o}$ller prescriptions. A comparison of the results shows
that the energy density is different but the momentum turns out to be constant
in each prescription. This is exactly similar to the results available in
literature using the framework of General Relativity. It is mentioned here that
M$\ddot{o}$ller energy-momentum distribution is independent of the coupling
constant $\lambda$. Finally, we calculate energy-momentum distribution for the
Curzon metric, a special case of the above mentioned spacetime.
| [
{
"created": "Tue, 17 Apr 2007 05:43:49 GMT",
"version": "v1"
}
] | 2009-02-10 | [
[
"Sharif",
"M.",
""
],
[
"Amir",
"M. Jamil",
""
]
] | This paper is devoted to discuss the energy-momentum for static axially symmetric spacetimes in the framework of teleparallel theory of gravity. For this purpose, we use the teleparallel versions of Einstein, Landau-Lifshitz, Bergmann and M$\ddot{o}$ller prescriptions. A comparison of the results shows that the energy density is different but the momentum turns out to be constant in each prescription. This is exactly similar to the results available in literature using the framework of General Relativity. It is mentioned here that M$\ddot{o}$ller energy-momentum distribution is independent of the coupling constant $\lambda$. Finally, we calculate energy-momentum distribution for the Curzon metric, a special case of the above mentioned spacetime. |
1906.08761 | Thomas M\"adler | Emanuel Gallo, Thomas M\"adler | Comment on "Boosted Kerr black holes in general relativity" | null | Phys. Rev. D 101, 028501 (2020) | 10.1103/PhysRevD.101.028501 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a recently presented boosted Kerr black hole solution which had
already been used by other authors. This boosted metric is based on wrong
assumptions regarding asymptotic inertial observers and moreover the performed
boost is not a proper Lorentz transformation. This note aims to clarify some of
the issues when boosting black holes and the necessary care in order to
interpret them. As it is wrongly claimed that the presented boosted Kerr metric
is of Bondi-Sachs type, we recall out some of the necessary requirements and
difficulties, when the casting the Kerr metric into a metric with a surface
forming null coordinate.
| [
{
"created": "Thu, 20 Jun 2019 17:29:14 GMT",
"version": "v1"
}
] | 2020-01-08 | [
[
"Gallo",
"Emanuel",
""
],
[
"Mädler",
"Thomas",
""
]
] | We discuss a recently presented boosted Kerr black hole solution which had already been used by other authors. This boosted metric is based on wrong assumptions regarding asymptotic inertial observers and moreover the performed boost is not a proper Lorentz transformation. This note aims to clarify some of the issues when boosting black holes and the necessary care in order to interpret them. As it is wrongly claimed that the presented boosted Kerr metric is of Bondi-Sachs type, we recall out some of the necessary requirements and difficulties, when the casting the Kerr metric into a metric with a surface forming null coordinate. |
1210.2577 | Aur\'elien Hees | A. Hees, S. Bertone and C. Le Poncin-Lafitte | Frequency shift up to the 2-PM approximation | 4 pages, submitted to proceedings of SF2A | null | null | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A lot of fundamental tests of gravitational theories rely on highly precise
measurements of the travel time and/or the frequency shift of electromagnetic
signals propagating through the gravitational field of the Solar System. In
practically all of the previous studies, the explicit expressions of such
travel times and frequency shifts as predicted by various metric theories of
gravity are derived from an integration of the null geodesic differential
equations. However, the solution of the geodesic equations requires heavy
calculations when one has to take into account the presence of mass multipoles
in the gravitational field or the tidal effects due to the planetary motions,
and the calculations become quite complicated in the post-post-Minkowskian
approximation. This difficult task can be avoided using the time transfer
function's formalism. We present here our last advances in the formulation of
the one-way frequency shift using this formalism up to the
post-post-Minkowskian approximation.
| [
{
"created": "Tue, 9 Oct 2012 12:04:44 GMT",
"version": "v1"
}
] | 2012-10-10 | [
[
"Hees",
"A.",
""
],
[
"Bertone",
"S.",
""
],
[
"Poncin-Lafitte",
"C. Le",
""
]
] | A lot of fundamental tests of gravitational theories rely on highly precise measurements of the travel time and/or the frequency shift of electromagnetic signals propagating through the gravitational field of the Solar System. In practically all of the previous studies, the explicit expressions of such travel times and frequency shifts as predicted by various metric theories of gravity are derived from an integration of the null geodesic differential equations. However, the solution of the geodesic equations requires heavy calculations when one has to take into account the presence of mass multipoles in the gravitational field or the tidal effects due to the planetary motions, and the calculations become quite complicated in the post-post-Minkowskian approximation. This difficult task can be avoided using the time transfer function's formalism. We present here our last advances in the formulation of the one-way frequency shift using this formalism up to the post-post-Minkowskian approximation. |
2205.08931 | Riasat Ali | Riasat Ali, Rimsha Babar and Muhammad Asgher | Gravitational Analysis of Rotating Charged Black Hole-Like Solution in
Einstein-Gauss-Bonnet Gravity | 14 pages,10 figures, version accepted for publication in Annalen der
Physik | Ann. Phys. (Berlin) 2022, 2200074 | 10.1002/andp.202200074 | andp.202200074 | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | This work analyzes the Einstein-Gauss-Bonnet gravity of charged black hole
solutions through Newman-Janis approach. The Hawking temperature for
corresponding black hole is also computed. The solution depends upon rotation
parameter $a$, black hole mass, charge and horizon. Moreover, the graphical
behavior of temperature via event horizon to analyze the stability of black
hole under the effects of rotation parameter is discussed. The graphs are
plotted in the presence/absence of rotation parameter and charge. Furthermore,
the Hawking temperature under gravity effects is studied by using the
semi-classical method. It is also observed that the maximum temperature at
non-zero horizon depicts the BH remnant. Finally, the logarithmic corrected
entropy for given black hole is computed and the logarithmic corrected entropy
under effects of rotation and correction parameter are studied.
| [
{
"created": "Wed, 18 May 2022 13:55:39 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Aug 2022 10:12:13 GMT",
"version": "v2"
}
] | 2022-08-19 | [
[
"Ali",
"Riasat",
""
],
[
"Babar",
"Rimsha",
""
],
[
"Asgher",
"Muhammad",
""
]
] | This work analyzes the Einstein-Gauss-Bonnet gravity of charged black hole solutions through Newman-Janis approach. The Hawking temperature for corresponding black hole is also computed. The solution depends upon rotation parameter $a$, black hole mass, charge and horizon. Moreover, the graphical behavior of temperature via event horizon to analyze the stability of black hole under the effects of rotation parameter is discussed. The graphs are plotted in the presence/absence of rotation parameter and charge. Furthermore, the Hawking temperature under gravity effects is studied by using the semi-classical method. It is also observed that the maximum temperature at non-zero horizon depicts the BH remnant. Finally, the logarithmic corrected entropy for given black hole is computed and the logarithmic corrected entropy under effects of rotation and correction parameter are studied. |
gr-qc/9505005 | Mike Clayton | M. A. Clayton (Department of Physics, University of Toronto ON,
Canada) | Massive NGT and Spherically Symmetric Systems | `Final' version (minor changes have been made to the original), to be
published in J. Math. Phys. Typset using ReVTeX and amssymbols. 29 pages | J.Math.Phys.37:395-420,1996 | 10.1063/1.531397 | UTPT-95-09 | gr-qc | null | The arguments leading to the introduction of the massive Nonsymmetric
Gravitational action are reviewed \cite{Moffat:1994,Moffat:1995b}, leading to
an action that gives asymptotically well-behaved perturbations on GR
backgrounds. Through the analysis of spherically symmetric perturbations about
GR (Schwarzschild) and NGT (Wyman-type) static backgrounds, it is shown that
spherically symmetric systems are not guaranteed to be static, and hence
Birkhoff's theorem is not valid in NGT. This implies that in general one must
consider time dependent exteriors when looking at spherically symmetric systems
in NGT. For the surviving monopole mode considered here there is no energy flux
as it is short ranged by construction. Further work on the spherically
symmetric case will be motivated through a discussion of the possibility that
there remain additional modes that do not show up in weak field situations, but
nonetheless exist in the full theory and may again result in bad global
asymptotics. A presentation of the action and field equations in a general
frame is given in the course of the paper, providing an alternative approach to
dealing with the algebraic complications inherent in NGT, as well as offering a
more general framework for discussing the physics of the antisymmetric sector.
| [
{
"created": "Thu, 4 May 1995 17:32:25 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Sep 1995 19:28:26 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Clayton",
"M. A.",
"",
"Department of Physics, University of Toronto ON,\n Canada"
]
] | The arguments leading to the introduction of the massive Nonsymmetric Gravitational action are reviewed \cite{Moffat:1994,Moffat:1995b}, leading to an action that gives asymptotically well-behaved perturbations on GR backgrounds. Through the analysis of spherically symmetric perturbations about GR (Schwarzschild) and NGT (Wyman-type) static backgrounds, it is shown that spherically symmetric systems are not guaranteed to be static, and hence Birkhoff's theorem is not valid in NGT. This implies that in general one must consider time dependent exteriors when looking at spherically symmetric systems in NGT. For the surviving monopole mode considered here there is no energy flux as it is short ranged by construction. Further work on the spherically symmetric case will be motivated through a discussion of the possibility that there remain additional modes that do not show up in weak field situations, but nonetheless exist in the full theory and may again result in bad global asymptotics. A presentation of the action and field equations in a general frame is given in the course of the paper, providing an alternative approach to dealing with the algebraic complications inherent in NGT, as well as offering a more general framework for discussing the physics of the antisymmetric sector. |
2208.01413 | Abdolhosein Khodam-Mohammadi | A. Khodam-Mohammadi | Unifying turnaround-bounce cosmology in a cyclic universe considering a
running vacuum model | 16 pages, 6 figures | Modern Physics Letters A, Vol. 37, No. 20, 2250127 (2022) | 10.1142/S0217732322501279 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Among many models which can describe the bouncing cosmology, A matter bounce
scenario that is deformed by a running vacuum model of dark energy (RVM-DE) has
been interested. In this research, I show that a class of RVM-CDM (cold dark
matter) model can also describe a cyclical cosmology in which the universe
undergoes cycles of expansion to the contraction phase and vice versa. To this
end, following our previous work, I consider one of the most successful class
of RVM-CDM model in bouncing cosmology, $\rho_x=n_0+n_2 H^2 +n_4 H^4$, in which
the power spectral index gets a red tilt and the running of the spectral index
may give a negative value by choosing the appropriate value of parameters
($n_0,~n_2,~n_4$), which is consistent with the cosmological observations. It
is worthwhile to mention that most matter bounce models do not produce this
negative value. However, the main purpose of this article is to investigate the
RVM-CDM model in the turnaround phase. Far from the bounce in a phantom
expanding universe, the turnaround conditions are investigated before the
occurrence of a sudden big rip. By analyzing the Hubble parameter, equation of
state parameter, and deceleration parameter around the turnaround, we show that
a successful turnaround may occur after an expansion in an \textbf{interacting}
case of RVM-CDM by choosing the appropriate value of parameters. A minimum
value for the interaction parameter is obtained and also finds any relation
between other model parameters. Finally, the effect of each parameter on a
turnaround is studied, and we see that the transition time from accelerating to
decelerating expansion can occur earlier for larger values of interaction
parameters. Also, in several graphs, the effect of the second term in DE
density, including $H^2$, is studied, and we see that by increasing its
coefficient, $n_2$, the transition point leads to lower values.
| [
{
"created": "Sun, 31 Jul 2022 08:36:18 GMT",
"version": "v1"
}
] | 2022-09-13 | [
[
"Khodam-Mohammadi",
"A.",
""
]
] | Among many models which can describe the bouncing cosmology, A matter bounce scenario that is deformed by a running vacuum model of dark energy (RVM-DE) has been interested. In this research, I show that a class of RVM-CDM (cold dark matter) model can also describe a cyclical cosmology in which the universe undergoes cycles of expansion to the contraction phase and vice versa. To this end, following our previous work, I consider one of the most successful class of RVM-CDM model in bouncing cosmology, $\rho_x=n_0+n_2 H^2 +n_4 H^4$, in which the power spectral index gets a red tilt and the running of the spectral index may give a negative value by choosing the appropriate value of parameters ($n_0,~n_2,~n_4$), which is consistent with the cosmological observations. It is worthwhile to mention that most matter bounce models do not produce this negative value. However, the main purpose of this article is to investigate the RVM-CDM model in the turnaround phase. Far from the bounce in a phantom expanding universe, the turnaround conditions are investigated before the occurrence of a sudden big rip. By analyzing the Hubble parameter, equation of state parameter, and deceleration parameter around the turnaround, we show that a successful turnaround may occur after an expansion in an \textbf{interacting} case of RVM-CDM by choosing the appropriate value of parameters. A minimum value for the interaction parameter is obtained and also finds any relation between other model parameters. Finally, the effect of each parameter on a turnaround is studied, and we see that the transition time from accelerating to decelerating expansion can occur earlier for larger values of interaction parameters. Also, in several graphs, the effect of the second term in DE density, including $H^2$, is studied, and we see that by increasing its coefficient, $n_2$, the transition point leads to lower values. |
gr-qc/9404009 | R. Balasubramanian | R. Balasubramanian and S. V. Dhurandhar | Performance of Newtonian filters in detecting gravitational waves from
coalescing binaries | Revtex 9 pages + 6 figures ( Can be obtained by "anonymous" ftp from
144.16.31.1 in dir /pub/rbs. Submitted to Physical Review D. IUCAA 10 | Phys.Rev.D50:6080-6088,1994 | 10.1103/PhysRevD.50.6080 | null | gr-qc | null | Coalescing binary systems are one of the most promising sources of
gravitational waves. The technique of matched filtering used in the detection
of gravitational waves from coalescing binaries relies on the construction of
accurate templates. Until recently filters modelled on the quadrupole or the
Newtonian approximation were deemed sufficient. Recently it was shown that
post-Newtonian effects contribute to a secular growth in the phase difference
between the actual signal and its corresponding Newtonian template. In this
paper we investigate the possibility of compensating for the phase difference
caused by the post-Newtonian terms by allowing for a shift in the Newtonian
filter parameters. We find that Newtonian filters perform adequately for the
purpose of detecting the presence of the signal for both the initial and the
advanced LIGO detectors.
| [
{
"created": "Fri, 1 Apr 1994 21:58:25 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Balasubramanian",
"R.",
""
],
[
"Dhurandhar",
"S. V.",
""
]
] | Coalescing binary systems are one of the most promising sources of gravitational waves. The technique of matched filtering used in the detection of gravitational waves from coalescing binaries relies on the construction of accurate templates. Until recently filters modelled on the quadrupole or the Newtonian approximation were deemed sufficient. Recently it was shown that post-Newtonian effects contribute to a secular growth in the phase difference between the actual signal and its corresponding Newtonian template. In this paper we investigate the possibility of compensating for the phase difference caused by the post-Newtonian terms by allowing for a shift in the Newtonian filter parameters. We find that Newtonian filters perform adequately for the purpose of detecting the presence of the signal for both the initial and the advanced LIGO detectors. |
gr-qc/0202007 | Mauricio Bellini | Mauricio Bellini (IFM, Michoacana University) | Baryogensis in fresh inflation | 11 pages, no figures | Gen.Rel.Grav. 34 (2002) 2127-2134 | 10.1023/A:1021139602851 | null | gr-qc | null | I study the possibility of baryogenesis can take place in fresh inflation. I
find that it is possible that violation of baryon number conservation can occur
during the period out-of-equilibrium in this scenario. Indeed, baryogenesis
could be possible before the thermal equilibrium is restored at the end of
fresh inflation.
| [
{
"created": "Sat, 2 Feb 2002 20:40:36 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Bellini",
"Mauricio",
"",
"IFM, Michoacana University"
]
] | I study the possibility of baryogenesis can take place in fresh inflation. I find that it is possible that violation of baryon number conservation can occur during the period out-of-equilibrium in this scenario. Indeed, baryogenesis could be possible before the thermal equilibrium is restored at the end of fresh inflation. |
gr-qc/9605030 | Daniel Sudarsky | G.E. Matsas, D. Sudarsky, and A. Higuchi | Bremsstrahlung by static charges outside a static black hole ? | Latex file | null | null | null | gr-qc | null | We show that in complete analogy with the usual bremsstrahlung process, when
studied from the coaccelerated observer's point of view, a charge moving along
the integral curves of the static Killing field in the exterior of a static
black hole gives rise to the emission of zero-energy photons, induced by the
thermal bath of Hawking Radiation.
| [
{
"created": "Thu, 16 May 1996 20:31:50 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Matsas",
"G. E.",
""
],
[
"Sudarsky",
"D.",
""
],
[
"Higuchi",
"A.",
""
]
] | We show that in complete analogy with the usual bremsstrahlung process, when studied from the coaccelerated observer's point of view, a charge moving along the integral curves of the static Killing field in the exterior of a static black hole gives rise to the emission of zero-energy photons, induced by the thermal bath of Hawking Radiation. |
0903.1185 | Davood Momeni | Mohammad Mehrpooya, D. Momeni | Spherically symmetric massive scalar fields in GR | 7 pages,No figures,accepted for publication in "International journal
of modern physics A"(IJMPA) | Int.J.Mod.Phys. A25:1429-1438,2010 | 10.1142/S0217751X10048019 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | First we review some of the attempts made to find exact spherically symmetric
solutions of Einstein field equations in the presence of scalar fields .Wyman
solution in both static and non static scalar field is discussed briefly and it
is show that why in the case of non static homogenous matter field, static
metric can not be represented in terms of elementary functions. We mention here
that if our spacetime be static, according to EFE there is two option for
choose scalar field matter: static (time independent) and non static (time
dependent). All these solutions are limited to the minimally coupled massless
scalar fields and also in the absence of the cosmological constant . Then we
show that if we are interesting to have a homogenous isotropic scalar field
matter one can construct a series solution in terms of scalar field's mass and
cosmological constant. This metric is static and posses a locally flat case as
a special chooses of mass of scalar field and can be interpreted as an
effective vacuum. Therefore mass of scalar field eliminates any locally
gravitational effect as tidal forces. Finally we describe why this system is
unstable in the language of dynamical systems.
| [
{
"created": "Fri, 6 Mar 2009 10:39:11 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Mar 2009 13:58:21 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Oct 2009 07:59:10 GMT",
"version": "v3"
},
{
"created": "Mon, 26 Oct 2009 05:16:50 GMT",
"version": "v4"
},
{
"created": "Mon, 9 Nov 2009 12:24:08 GMT",
"version": "v5"
},
{
"created": "Sun, 7 Feb 2010 17:38:14 GMT",
"version": "v6"
}
] | 2014-11-18 | [
[
"Mehrpooya",
"Mohammad",
""
],
[
"Momeni",
"D.",
""
]
] | First we review some of the attempts made to find exact spherically symmetric solutions of Einstein field equations in the presence of scalar fields .Wyman solution in both static and non static scalar field is discussed briefly and it is show that why in the case of non static homogenous matter field, static metric can not be represented in terms of elementary functions. We mention here that if our spacetime be static, according to EFE there is two option for choose scalar field matter: static (time independent) and non static (time dependent). All these solutions are limited to the minimally coupled massless scalar fields and also in the absence of the cosmological constant . Then we show that if we are interesting to have a homogenous isotropic scalar field matter one can construct a series solution in terms of scalar field's mass and cosmological constant. This metric is static and posses a locally flat case as a special chooses of mass of scalar field and can be interpreted as an effective vacuum. Therefore mass of scalar field eliminates any locally gravitational effect as tidal forces. Finally we describe why this system is unstable in the language of dynamical systems. |
1910.05747 | Rong-Jia Yang | Haiyuan Feng, Rong-Jia Yang | Horizon thermodynamics in $f(R,R^{\mu\nu}R_{\mu\nu})$ theory | 6 pages, no figures | Chin.Phys.C 44 (2020) 11, 115101 | 10.1088/1674-1137/abadef | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate whether the new horizon first law still holds in
$f(R,R^{\mu\nu}R_{\mu\nu})$ theory. For this complicated theory, we first
determine the entropy of black hole via Wald method, then we derive the energy
by using the new horizon first law, the degenerate Legendre transformation, and
the gravitational field equations. For application, we consider the
quadratic-curvature gravity and firstly calculate the entropy and the energy
for a static spherically symmetric black hole, which reduces to the results
obtained in literatures for a Schwarzschild-(A)dS black hole.
| [
{
"created": "Sun, 13 Oct 2019 13:20:36 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Apr 2020 08:31:39 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Dec 2020 14:15:09 GMT",
"version": "v3"
}
] | 2020-12-04 | [
[
"Feng",
"Haiyuan",
""
],
[
"Yang",
"Rong-Jia",
""
]
] | We investigate whether the new horizon first law still holds in $f(R,R^{\mu\nu}R_{\mu\nu})$ theory. For this complicated theory, we first determine the entropy of black hole via Wald method, then we derive the energy by using the new horizon first law, the degenerate Legendre transformation, and the gravitational field equations. For application, we consider the quadratic-curvature gravity and firstly calculate the entropy and the energy for a static spherically symmetric black hole, which reduces to the results obtained in literatures for a Schwarzschild-(A)dS black hole. |
1302.5265 | Jorge Pullin | Rodolfo Gambini and Jorge Pullin | Loop quantization of the Schwarzschild black hole | 4 pages, Revtex, version to appear in Physical Review Letters | Phys. Rev. Lett. 110, 211301 (2013) | 10.1103/PhysRevLett.110.211301 | LSU-REL-022113 | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We quantize spherically symmetric vacuum gravity without gauge fixing the
diffeomorphism constraint. Through a rescaling, we make the algebra of
Hamiltonian constraints Abelian and therefore the constraint algebra is a true
Lie algebra. This allows the completion of the Dirac quantization procedure
using loop quantum gravity techniques. We can construct explicitly the exact
solutions of the physical Hilbert space annihilated by all constraints. New
observables living in the bulk appear at the quantum level (analogous to spin
in quantum mechanics) that are not present at the classical level and are
associated with the discrete nature of the spin network states of loop quantum
gravity. The resulting quantum space-times resolve the singularity present in
the classical theory inside black holes.
| [
{
"created": "Thu, 21 Feb 2013 12:37:47 GMT",
"version": "v1"
},
{
"created": "Fri, 10 May 2013 17:35:38 GMT",
"version": "v2"
}
] | 2013-12-18 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | We quantize spherically symmetric vacuum gravity without gauge fixing the diffeomorphism constraint. Through a rescaling, we make the algebra of Hamiltonian constraints Abelian and therefore the constraint algebra is a true Lie algebra. This allows the completion of the Dirac quantization procedure using loop quantum gravity techniques. We can construct explicitly the exact solutions of the physical Hilbert space annihilated by all constraints. New observables living in the bulk appear at the quantum level (analogous to spin in quantum mechanics) that are not present at the classical level and are associated with the discrete nature of the spin network states of loop quantum gravity. The resulting quantum space-times resolve the singularity present in the classical theory inside black holes. |
2305.03064 | M. Ilyas | M. Ilyas, A. R. Athar, F. Khan and Asma Anfal | Effects of $f (R, G)$ gravity on anisotropic charged compact objects | texts modified, typos corrected, version accepted for
publication/published in Physica Scripta | Phys. Scr. 98 095011 (2023) | 10.1088/1402-4896/aceba2 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The present study provides an in-depth analysis of the anisotropic matter
distribution and various physical aspects of compact stars in the context of a
$f(R,G)$-gravity framework. In order to gain an exhaustive understanding of
these aspects, our study focuses on three particular compact stars: VELA X-1
(CS1), SAXJ1808.4-3658 (CS2), and 4U1820-30 (CS3). We conducted calculations on
the relevant characteristics of these compact stars by employing three
different models of $f(R,G)$-gravity. As a convenient approach, the
$f(R,G)$-gravity is organized into two distinct components, which include
$f_1(R)$ and $f_2(G)$. The $R$ dependent component is modeled similarly to the
Hu-Sawicki approach, while for modeling the $G$ dependent component, we chose
logarithmic and power law-like approaches and suggested three viable gravity
models. Graphical methods are used to analyze the physical properties of the
compact stars in the domain of suggested models of gravity.
| [
{
"created": "Thu, 4 May 2023 14:56:35 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Aug 2023 15:25:01 GMT",
"version": "v2"
}
] | 2023-08-22 | [
[
"Ilyas",
"M.",
""
],
[
"Athar",
"A. R.",
""
],
[
"Khan",
"F.",
""
],
[
"Anfal",
"Asma",
""
]
] | The present study provides an in-depth analysis of the anisotropic matter distribution and various physical aspects of compact stars in the context of a $f(R,G)$-gravity framework. In order to gain an exhaustive understanding of these aspects, our study focuses on three particular compact stars: VELA X-1 (CS1), SAXJ1808.4-3658 (CS2), and 4U1820-30 (CS3). We conducted calculations on the relevant characteristics of these compact stars by employing three different models of $f(R,G)$-gravity. As a convenient approach, the $f(R,G)$-gravity is organized into two distinct components, which include $f_1(R)$ and $f_2(G)$. The $R$ dependent component is modeled similarly to the Hu-Sawicki approach, while for modeling the $G$ dependent component, we chose logarithmic and power law-like approaches and suggested three viable gravity models. Graphical methods are used to analyze the physical properties of the compact stars in the domain of suggested models of gravity. |
1503.06294 | Rakesh Tibrewala | Rakesh Tibrewala | Midisuperspace quantization: possibilities for fractional and emergent
spacetime dimensions | 10 pages | Phys. Rev. D 93, 124045 (2016) | 10.1103/PhysRevD.93.124045 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, motivated by certain loop quantum gravity inspired corrections, it
was shown that for spherically symmetric midisuperspace models infinitely many
second derivative theories of gravity exist (as revealed by the presence of
three arbitrary functions in the corresponding Lagrangian/Hamiltonian) and not
just those allowed by spherically symmetric general relativity. This freedom
can be interpreted as the freedom to accommodate certain quantum gravity
corrections in these models even in the absence of higher curvature terms (at a
semi-classical level, at least). For a particular choice of the arbitrary
functions it is shown that the new theories map to spherically symmetric
general relativity in arbitrary number of (integer) dimensions thus explicitly
demonstrating that when working with midisuperspace models, one loses the
information about the dimensionality of the full spacetime. In addition, it is
shown that these new theories can accommodate scenarios of fractional spacetime
dimensions as well as those of emergent spacetime dimensions -- a possibility
suggested by various approaches to quantum gravity.
| [
{
"created": "Sat, 21 Mar 2015 12:37:59 GMT",
"version": "v1"
},
{
"created": "Sat, 16 Jul 2016 04:50:09 GMT",
"version": "v2"
}
] | 2016-07-19 | [
[
"Tibrewala",
"Rakesh",
""
]
] | Recently, motivated by certain loop quantum gravity inspired corrections, it was shown that for spherically symmetric midisuperspace models infinitely many second derivative theories of gravity exist (as revealed by the presence of three arbitrary functions in the corresponding Lagrangian/Hamiltonian) and not just those allowed by spherically symmetric general relativity. This freedom can be interpreted as the freedom to accommodate certain quantum gravity corrections in these models even in the absence of higher curvature terms (at a semi-classical level, at least). For a particular choice of the arbitrary functions it is shown that the new theories map to spherically symmetric general relativity in arbitrary number of (integer) dimensions thus explicitly demonstrating that when working with midisuperspace models, one loses the information about the dimensionality of the full spacetime. In addition, it is shown that these new theories can accommodate scenarios of fractional spacetime dimensions as well as those of emergent spacetime dimensions -- a possibility suggested by various approaches to quantum gravity. |
2210.09237 | Pardyumn Kumar Sahoo | Gaurav N. Gadbail, Sanjay Mandal, P.K. Sahoo | Reconstruction of $\Lambda$CDM Universe in $f(Q)$ Gravity | PLB accepted version | Physics Letters B 835 (2022) 137509 | 10.1016/j.physletb.2022.137509 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this manuscript, we present a number of fascinating explicit
reconstructions for the $f(Q)$ gravity from the background of
Friedmann-La\^imatre-Robertson-Walker (FLRW) evolution history. We find the
more general functions of non-metricity scalar $Q$ that admit exact
$\Lambda$CDM expansion history. Adding extra degrees of freedom to the matter
sector is the only method to get the scale factor to behave in this manner for
more generic functions of $Q$. In addition, a cosmological reconstruction for
modified $f(Q)$ gravity is constructed in terms of e-folding. It is shown how
any FLRW cosmology can arise from a specific $f(Q)$ theory. We also reconstruct
the well-known cosmological evolution for the specific examples of $\Lambda$CDM
cosmology.
| [
{
"created": "Mon, 17 Oct 2022 16:31:58 GMT",
"version": "v1"
}
] | 2022-10-25 | [
[
"Gadbail",
"Gaurav N.",
""
],
[
"Mandal",
"Sanjay",
""
],
[
"Sahoo",
"P. K.",
""
]
] | In this manuscript, we present a number of fascinating explicit reconstructions for the $f(Q)$ gravity from the background of Friedmann-La\^imatre-Robertson-Walker (FLRW) evolution history. We find the more general functions of non-metricity scalar $Q$ that admit exact $\Lambda$CDM expansion history. Adding extra degrees of freedom to the matter sector is the only method to get the scale factor to behave in this manner for more generic functions of $Q$. In addition, a cosmological reconstruction for modified $f(Q)$ gravity is constructed in terms of e-folding. It is shown how any FLRW cosmology can arise from a specific $f(Q)$ theory. We also reconstruct the well-known cosmological evolution for the specific examples of $\Lambda$CDM cosmology. |
gr-qc/0003104 | W. M. Stuckey | W.M. Stuckey and Michael Silberstein | Uniform Spaces in the Pregeometric Modeling of Quantum Non-Separability | 17 pages, no figures; revised version submitted to Int. J. Theor.
Phys | null | null | null | gr-qc quant-ph | null | We introduce a pregeometry employing uniform spaces over the denumerable set
X of spacetime events. The discrete uniformity D_X over X is used to obtain a
pregeometric model of macroscopic spacetime neighborhoods. We then use a
uniformity base generated by a topological group structure over X to provide a
pregeometric model of microscopic spacetime neighborhoods. Accordingly, quantum
non-separability as it pertains to non-locality is understood pregeometrically
as a contrast between microscopic spacetime neighborhoods and macroscopic
spacetime neighborhoods. A nexus between this pregeometry and conventional
spacetime physics is implied per the metric induced by D_X. A metric over the
topological group Z2 x ... x Z2 is so generated. Implications for quantum
gravity are enumerated.
| [
{
"created": "Tue, 28 Mar 2000 20:49:49 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Apr 2001 14:03:29 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Stuckey",
"W. M.",
""
],
[
"Silberstein",
"Michael",
""
]
] | We introduce a pregeometry employing uniform spaces over the denumerable set X of spacetime events. The discrete uniformity D_X over X is used to obtain a pregeometric model of macroscopic spacetime neighborhoods. We then use a uniformity base generated by a topological group structure over X to provide a pregeometric model of microscopic spacetime neighborhoods. Accordingly, quantum non-separability as it pertains to non-locality is understood pregeometrically as a contrast between microscopic spacetime neighborhoods and macroscopic spacetime neighborhoods. A nexus between this pregeometry and conventional spacetime physics is implied per the metric induced by D_X. A metric over the topological group Z2 x ... x Z2 is so generated. Implications for quantum gravity are enumerated. |
1301.0959 | Roberto A. Sussman | Roberto A. Sussman | Weighed scalar averaging in LTB dust models, part II: a formalism of
exact perturbations | 31 pages IOP format, 12 figures. Matches version accepted for
publication in Classical and Quantum Gravity | Classical and Quantum Gravity, 30 (2013) 065016 | 10.1088/0264-9381/30/6/065016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the exact perturbations that arise from the q-average formalism
that was applied in the preceding article (part I) to Lemaitre-Tolman-Bondi
(LTB) models. By introducing an initial value parametrization, we show that all
LTB scalars that take a FLRW "look alike" form (frequently used in the
literature dealing with LTB models) follow as q-averages of covariant scalars
that are common to FLRW models. These q--scalars determine for every averaging
domain a unique FLRW background state through Darmois matching conditions at
the domain boundary, though the definition of this background does not require
an actual matching with a FLRW region (Swiss cheese type models). Local
perturbations describe the deviation from the FLRW background state through the
local gradients of covariant scalars at the boundary of every comoving domain,
while non-local perturbations do so in terms of the intuitive notion of a
"contrast" of local scalars with respect to FLRW reference values that emerge
from q-averages assigned to the whole domain or the whole time slice in the
asymptotic limit. We derive fluid flow evolution equations that completely
determine the dynamics of the models in terms of the q-scalars and both types
of perturbations. A rigorous formalism of exact spherical non-linear
perturbations is defined over the FLRW background state associated to the
q-scalars, recovering the standard results of linear perturbation theory in the
appropriate limit. We examine the notion of the amplitude and illustrate the
differences between local vs non-local perturbations by qualitative diagrams
and through an example of a cosmic density void that follows from the numeric
solution of the evolution equations.
| [
{
"created": "Sun, 6 Jan 2013 02:23:07 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Feb 2013 23:48:35 GMT",
"version": "v2"
}
] | 2015-06-12 | [
[
"Sussman",
"Roberto A.",
""
]
] | We examine the exact perturbations that arise from the q-average formalism that was applied in the preceding article (part I) to Lemaitre-Tolman-Bondi (LTB) models. By introducing an initial value parametrization, we show that all LTB scalars that take a FLRW "look alike" form (frequently used in the literature dealing with LTB models) follow as q-averages of covariant scalars that are common to FLRW models. These q--scalars determine for every averaging domain a unique FLRW background state through Darmois matching conditions at the domain boundary, though the definition of this background does not require an actual matching with a FLRW region (Swiss cheese type models). Local perturbations describe the deviation from the FLRW background state through the local gradients of covariant scalars at the boundary of every comoving domain, while non-local perturbations do so in terms of the intuitive notion of a "contrast" of local scalars with respect to FLRW reference values that emerge from q-averages assigned to the whole domain or the whole time slice in the asymptotic limit. We derive fluid flow evolution equations that completely determine the dynamics of the models in terms of the q-scalars and both types of perturbations. A rigorous formalism of exact spherical non-linear perturbations is defined over the FLRW background state associated to the q-scalars, recovering the standard results of linear perturbation theory in the appropriate limit. We examine the notion of the amplitude and illustrate the differences between local vs non-local perturbations by qualitative diagrams and through an example of a cosmic density void that follows from the numeric solution of the evolution equations. |
1504.02295 | Saulo Pereira H | S. H. Pereira, E. L. Mendon\c{c}a, A. Pinho S. S. and J. F. Jesus | Cosmological bounds on open FLRW solutions of massive gravity | 12 pages, 3 figures. Some references added and also new comments | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we have analysed some cosmological bounds concerning an open
FLRW solution of massive gravity. The constraints with recent observational
$H(z)$ data were found and the best fit values for the cosmological parameters
are in agreement with the $\Lambda$CDM model, and also point to a nearly open
spatial curvature, as expected from the model. The graviton mass dependence
with the constant parameters $\alpha_3$ and $\alpha_4$, related to the
additional lagrangians terms of the model, are also analysed, and we have
obtained a strong dependence with such parameters, although the condition
$m_g\simeq H_0^{-1}$ seems dominant for a long range of the parameters
$\alpha_3$ and $\alpha_4$.
| [
{
"created": "Thu, 9 Apr 2015 13:18:10 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Jun 2015 19:45:39 GMT",
"version": "v2"
}
] | 2015-07-01 | [
[
"Pereira",
"S. H.",
""
],
[
"Mendonça",
"E. L.",
""
],
[
"S.",
"A. Pinho S.",
""
],
[
"Jesus",
"J. F.",
""
]
] | In this work we have analysed some cosmological bounds concerning an open FLRW solution of massive gravity. The constraints with recent observational $H(z)$ data were found and the best fit values for the cosmological parameters are in agreement with the $\Lambda$CDM model, and also point to a nearly open spatial curvature, as expected from the model. The graviton mass dependence with the constant parameters $\alpha_3$ and $\alpha_4$, related to the additional lagrangians terms of the model, are also analysed, and we have obtained a strong dependence with such parameters, although the condition $m_g\simeq H_0^{-1}$ seems dominant for a long range of the parameters $\alpha_3$ and $\alpha_4$. |
1104.2413 | Tae Hoon Lee | Tae Hoon Lee | Degeneracy pressure of relic neutrinos and cosmic coincidence problem | 6 pages, added references | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the universe as a huge $\nu_R$-sphere formed with degenerate
relic neutrinos and suggest that its constant energy density play a role of an
effective cosmological constant. We construct the sphere as a bubble of true
vacuum in a field theory model with a spontaneously broken U(1) global
symmetry, and we interpret the sphere-forming time as the transition time for
recent acceleration of the universe. The coincidence problem may be regarded as
naturally resolved in this model, because the relic neutrinos can make the
$\nu_R$-sphere at the recent past time during the matter-dominated era.
| [
{
"created": "Wed, 13 Apr 2011 08:33:46 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Apr 2011 08:50:52 GMT",
"version": "v2"
}
] | 2011-04-19 | [
[
"Lee",
"Tae Hoon",
""
]
] | We consider the universe as a huge $\nu_R$-sphere formed with degenerate relic neutrinos and suggest that its constant energy density play a role of an effective cosmological constant. We construct the sphere as a bubble of true vacuum in a field theory model with a spontaneously broken U(1) global symmetry, and we interpret the sphere-forming time as the transition time for recent acceleration of the universe. The coincidence problem may be regarded as naturally resolved in this model, because the relic neutrinos can make the $\nu_R$-sphere at the recent past time during the matter-dominated era. |
1704.06630 | Fabio Duvan Lora Clavijo Mr. | Anamaria Navarro, F. D. Lora-Clavijo and Guillermo A. Gonz\'alez | Relativistic Static Thin Disks of Polarized Matter | 7 pages, 4 figures, 70 and 70 Gravitation Fest, 28 September 2016,
Cartagena, Colombia | J.Phys.Conf.Ser. 831 (2017) no.1, 012010 | 10.1088/1742-6596/831/1/012010 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An infinite family of exact solutions of the electrovacuum Einstein-Maxwell
equations is presented. The family is static, axially symmetric and describe
thin disks composed by electrically polarized material in a conformastatic
spacetime. The form of the conformastatic metric allows us to write down the
metric functions and the electromagnetic potentials in terms of a solution of
the Laplace equation. We find a general expression for the surface energy
density of the disk, the pressure, the polarization vector, the electromagnetic
fields and the velocity rotation for circular orbits. As an example, we present
the first model of the family and show the behavior of the different physical
variables.
| [
{
"created": "Fri, 21 Apr 2017 16:46:49 GMT",
"version": "v1"
}
] | 2017-04-24 | [
[
"Navarro",
"Anamaria",
""
],
[
"Lora-Clavijo",
"F. D.",
""
],
[
"González",
"Guillermo A.",
""
]
] | An infinite family of exact solutions of the electrovacuum Einstein-Maxwell equations is presented. The family is static, axially symmetric and describe thin disks composed by electrically polarized material in a conformastatic spacetime. The form of the conformastatic metric allows us to write down the metric functions and the electromagnetic potentials in terms of a solution of the Laplace equation. We find a general expression for the surface energy density of the disk, the pressure, the polarization vector, the electromagnetic fields and the velocity rotation for circular orbits. As an example, we present the first model of the family and show the behavior of the different physical variables. |
2209.09091 | Ksh Newton Singh | Ksh. Newton Singh, S. K. Maurya, Piyali Bhar, Riju Nag | Anisotropic solution for polytropic stars in 4D Einstein-Gauss-Bonnet
gravity | 11 Pages, 10 Figures, 1 Table (to be appeared in EPJC) | null | 10.1140/epjc/s10052-022-10766-3 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the present work we have investigated a new anisotropic solution for
polytropic star in the framework of $4D$ Einstein-Gauss-Bonnet (EGB) gravity.
The possibility of determining the masses and radii of compact stars which puts
some limitations on equation of state (EoS) above the nuclear saturation
density. For this purpose, the $4D$ EGB field equations are solved by taking a
generalized polytropic equation of state (EoS) with Finch-Skea ansatz. The
generalized solution for anisotropic model has been tested for different values
of Gauss-Bonnet constant $\alpha$ which satisfies all the physical criteria
including causality with static stability via mass vs central mass density
($M-\rho_c$), Bondi and Abreu criterion. The adiabatic index shows a minor
influence of the GB coupling constant whereas the central and surface redshifts
in the EGB gravity always remain lower than the GR. We present the possibility
of fitting the mass and radius for some known compact star via $M-R$ curve
which satisfies the recent gravitational wave observations from GW 170817
event.
| [
{
"created": "Wed, 14 Sep 2022 19:13:37 GMT",
"version": "v1"
}
] | 2022-09-20 | [
[
"Singh",
"Ksh. Newton",
""
],
[
"Maurya",
"S. K.",
""
],
[
"Bhar",
"Piyali",
""
],
[
"Nag",
"Riju",
""
]
] | In the present work we have investigated a new anisotropic solution for polytropic star in the framework of $4D$ Einstein-Gauss-Bonnet (EGB) gravity. The possibility of determining the masses and radii of compact stars which puts some limitations on equation of state (EoS) above the nuclear saturation density. For this purpose, the $4D$ EGB field equations are solved by taking a generalized polytropic equation of state (EoS) with Finch-Skea ansatz. The generalized solution for anisotropic model has been tested for different values of Gauss-Bonnet constant $\alpha$ which satisfies all the physical criteria including causality with static stability via mass vs central mass density ($M-\rho_c$), Bondi and Abreu criterion. The adiabatic index shows a minor influence of the GB coupling constant whereas the central and surface redshifts in the EGB gravity always remain lower than the GR. We present the possibility of fitting the mass and radius for some known compact star via $M-R$ curve which satisfies the recent gravitational wave observations from GW 170817 event. |
1609.00102 | Francisco Frutos-Alfaro Dr. rer. nat. | Francisco Frutos-Alfaro and Paulo Montero-Camacho | Approximate Kerr-Newman-like Metric with Quadrupole | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Kerr metric is known to present issues when trying to find an interior
solution. In this work we continue in our efforts to construct a more realistic
exterior metric for astrophysical objects. A new approximate metric
representing the spacetime of a charged, rotating and slightly-deformed body is
obtained by perturbing the Kerr-Newman metric to include the mass-quadrupole
and quadrupole-quadrupole orders. It has a simple form, because is
Kerr-Newman-like. Its post-linear form without charge coincides with
post-linear quadrupole-quadrupole metrics already found.
| [
{
"created": "Thu, 1 Sep 2016 04:10:50 GMT",
"version": "v1"
}
] | 2016-09-02 | [
[
"Frutos-Alfaro",
"Francisco",
""
],
[
"Montero-Camacho",
"Paulo",
""
]
] | The Kerr metric is known to present issues when trying to find an interior solution. In this work we continue in our efforts to construct a more realistic exterior metric for astrophysical objects. A new approximate metric representing the spacetime of a charged, rotating and slightly-deformed body is obtained by perturbing the Kerr-Newman metric to include the mass-quadrupole and quadrupole-quadrupole orders. It has a simple form, because is Kerr-Newman-like. Its post-linear form without charge coincides with post-linear quadrupole-quadrupole metrics already found. |
1705.05807 | Ikjyot Singh Kohli | Ikjyot Singh Kohli | Oscillating Towards the de Sitter Universe | Corrected minor typos | null | null | null | gr-qc math.DS | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we consider spatially flat FLRW cosmological models in two
contexts in an attempt to derive a set of conditions that characterize when
such models exhibit oscillatory behaviour. In the first case, we consider a
spatially flat FLRW model with only a minimally-coupled scalar field, described
by a nonnegative scalar field potential. In the second case, we extended this
model to include barotropic matter. We show that for the case of a positive
cosmological constant, spatial flatness, and barotropic matter, oscillatory
solutions are certainly possible. However, these solutions do not oscillate
indefinitely, they decay over time. Interestingly, it is shown that all such
solutions oscillate and decay towards the de Sitter equilibrium point, which
represents an inflationary epoch in such models. This implies that for certain
families of scalar field potentials, the universe may have undergone several
oscillations \emph{before} entering an inflationary epoch.
| [
{
"created": "Tue, 16 May 2017 17:20:35 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Jun 2017 22:26:09 GMT",
"version": "v2"
}
] | 2017-06-12 | [
[
"Kohli",
"Ikjyot Singh",
""
]
] | In this paper, we consider spatially flat FLRW cosmological models in two contexts in an attempt to derive a set of conditions that characterize when such models exhibit oscillatory behaviour. In the first case, we consider a spatially flat FLRW model with only a minimally-coupled scalar field, described by a nonnegative scalar field potential. In the second case, we extended this model to include barotropic matter. We show that for the case of a positive cosmological constant, spatial flatness, and barotropic matter, oscillatory solutions are certainly possible. However, these solutions do not oscillate indefinitely, they decay over time. Interestingly, it is shown that all such solutions oscillate and decay towards the de Sitter equilibrium point, which represents an inflationary epoch in such models. This implies that for certain families of scalar field potentials, the universe may have undergone several oscillations \emph{before} entering an inflationary epoch. |
2106.11293 | Alan Kostelecky | Alan Kostelecky, Zonghao Li | Searches for beyond-Riemann gravity | 24 pages two-column REVTeX, version accepted in Physical Review D | Phys. Rev. D 104, 044054 (2021) | 10.1103/PhysRevD.104.044054 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Many effective field theories describing gravity cannot arise from an
underlying theory based on Riemann geometry or its extensions to include
torsion and nonmetricity but may instead emerge from another geometry or may
have a nongeometric basis. The Lagrange density for a broad class of such
theories is investigated. The action for fermions coupled to gravity is
linearized about a Minkowski background and is found to include terms
describing small deviations from Lorentz invariance and gravitational gauge
invariance. The corresponding nonrelativistic hamiltonian is derived at second
order in the fermion momentum. The implications for laboratory experiments and
astrophysical observations with fermions are studied, with primary focus on
anomalous spin-gravity couplings. First constraints on some coefficients are
extracted from existing data obtained via measurements at different potentials,
comparisons of gravitational accelerations, interferometric methods, and
investigations of gravitational bound states. Some prospects for future
experimental studies are discussed.
| [
{
"created": "Mon, 21 Jun 2021 17:51:02 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Jul 2021 12:38:08 GMT",
"version": "v2"
}
] | 2021-08-25 | [
[
"Kostelecky",
"Alan",
""
],
[
"Li",
"Zonghao",
""
]
] | Many effective field theories describing gravity cannot arise from an underlying theory based on Riemann geometry or its extensions to include torsion and nonmetricity but may instead emerge from another geometry or may have a nongeometric basis. The Lagrange density for a broad class of such theories is investigated. The action for fermions coupled to gravity is linearized about a Minkowski background and is found to include terms describing small deviations from Lorentz invariance and gravitational gauge invariance. The corresponding nonrelativistic hamiltonian is derived at second order in the fermion momentum. The implications for laboratory experiments and astrophysical observations with fermions are studied, with primary focus on anomalous spin-gravity couplings. First constraints on some coefficients are extracted from existing data obtained via measurements at different potentials, comparisons of gravitational accelerations, interferometric methods, and investigations of gravitational bound states. Some prospects for future experimental studies are discussed. |
1406.7653 | Emilio Elizalde | E. Elizalde, V.V. Obukhov, A.V. Timoshkin | Inhomogeneous viscous dark fluid coupled with dark matter in the FRW
universe | 11 pages, 2 figures, to appear in MPLA | null | 10.1142/S0217732314501326 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A cosmological model with an inhomogeneous viscous dark fluid coupled with
dark matter in a flat Friedman-Robertson-Walker universe is investigated. The
influence of dark matter on the behavior of an inhomogeneous viscous fluid of
this kind, responsible for cosmic acceleration and for the appearance of
different types of singularities, is analyzed in detail. In particular, the
critical points corresponding to the solutions of the background equations in a
useful approximation are obtained explicitly.
| [
{
"created": "Mon, 30 Jun 2014 10:14:13 GMT",
"version": "v1"
}
] | 2015-06-22 | [
[
"Elizalde",
"E.",
""
],
[
"Obukhov",
"V. V.",
""
],
[
"Timoshkin",
"A. V.",
""
]
] | A cosmological model with an inhomogeneous viscous dark fluid coupled with dark matter in a flat Friedman-Robertson-Walker universe is investigated. The influence of dark matter on the behavior of an inhomogeneous viscous fluid of this kind, responsible for cosmic acceleration and for the appearance of different types of singularities, is analyzed in detail. In particular, the critical points corresponding to the solutions of the background equations in a useful approximation are obtained explicitly. |
2403.07044 | Ali \"Ovg\"un Dr. | Erdem Sucu and Ali \"Ovg\"un | The Effect of Quark-antiquark Confinement on the Deflection Angle by the
NED Black Hole | 13 pages. Two-column. Accepted for publication in Physics of the Dark
Universe | Phys.Dark Univ. 44 (2024) 101446 | 10.1016/j.dark.2024.101446 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this study, we explore the influence of quark-antiquark confinement on the
deflection angle within the framework of nonlinear electrodynamic (NED) black
holes. To achieve this, we establish the appropriate optical spacetime metric
and subsequently determine the Gaussian optical curvature. Utilizing the
Gauss-Bonnet theorem, we investigate the impact of quark-antiquark confinement
on the deflection angle exhibited by NED black holes. Additionally, we delve
into the effects of a cold non-magnetized plasma medium and also axion-plasmon
on gravitational lensing. Our findings highlight the significance of the
axion-plasmon effect on the optical properties of NED black holes, particularly
its influence on gravitational lensing. This exploration is particularly
relevant in the context of the axion's potential role as a dark matter
candidate. The multifaceted interplay between quark-antiquark confinement,
nonlinear electrodynamics, and plasma dynamics provides a nuanced understanding
of gravitational lensing phenomena. These insights contribute to ongoing
research in dark matter studies and offer avenues for further theoretical and
observational investigations in astrophysics.
| [
{
"created": "Mon, 11 Mar 2024 17:48:48 GMT",
"version": "v1"
}
] | 2024-03-13 | [
[
"Sucu",
"Erdem",
""
],
[
"Övgün",
"Ali",
""
]
] | In this study, we explore the influence of quark-antiquark confinement on the deflection angle within the framework of nonlinear electrodynamic (NED) black holes. To achieve this, we establish the appropriate optical spacetime metric and subsequently determine the Gaussian optical curvature. Utilizing the Gauss-Bonnet theorem, we investigate the impact of quark-antiquark confinement on the deflection angle exhibited by NED black holes. Additionally, we delve into the effects of a cold non-magnetized plasma medium and also axion-plasmon on gravitational lensing. Our findings highlight the significance of the axion-plasmon effect on the optical properties of NED black holes, particularly its influence on gravitational lensing. This exploration is particularly relevant in the context of the axion's potential role as a dark matter candidate. The multifaceted interplay between quark-antiquark confinement, nonlinear electrodynamics, and plasma dynamics provides a nuanced understanding of gravitational lensing phenomena. These insights contribute to ongoing research in dark matter studies and offer avenues for further theoretical and observational investigations in astrophysics. |
2307.00565 | Hao Xu | Hao Xu, Yun Du | Gauss-Bonnet modification to Hawking evaporation of AdS black holes in
massive gravity | 16 pages;v2: numerical example added in Figure 5, accepted by EPJP | Eur.Phys.J.Plus 139 (2024) 1, 77 | 10.1140/epjp/s13360-023-04853-x | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The Stefan-Boltzmann law can estimate particle emission power and lifetime of
a black hole. However, in modified gravity theories, new parameters in the
action can cause qualitative changes in thermodynamic quantities, thus
obtaining specific thermodynamic properties often requires complicated
calculation with higher degree equations. In this work, we aim to provide a
general model-independent description of the evolution of AdS black holes,
using Gauss-Bonnet massive gravity as an example. We prove that the impact
factor of an infinitely large AdS black hole is equal to the effective AdS
radius, and the black hole is able to evaporate an infinite amount of mass in
finite time, so that the lifetime of the black hole depends on the final state
temperature in the evaporation process. The black hole will evaporate out when
the final state temperature diverges and will transform into a remnant when the
temperature is zero. Since we have analyzed massive gravity in detail, we can
introduce the Gauss-Bonnet term to study how it affects the thermodynamic
quantities. We obtain the final states for different parameter intervals, study
the qualitative properties of black hole evaporation, and classify the
associated cases. This method can also be applied to other models.
| [
{
"created": "Sun, 2 Jul 2023 13:20:24 GMT",
"version": "v1"
},
{
"created": "Sat, 30 Dec 2023 05:58:04 GMT",
"version": "v2"
}
] | 2024-01-31 | [
[
"Xu",
"Hao",
""
],
[
"Du",
"Yun",
""
]
] | The Stefan-Boltzmann law can estimate particle emission power and lifetime of a black hole. However, in modified gravity theories, new parameters in the action can cause qualitative changes in thermodynamic quantities, thus obtaining specific thermodynamic properties often requires complicated calculation with higher degree equations. In this work, we aim to provide a general model-independent description of the evolution of AdS black holes, using Gauss-Bonnet massive gravity as an example. We prove that the impact factor of an infinitely large AdS black hole is equal to the effective AdS radius, and the black hole is able to evaporate an infinite amount of mass in finite time, so that the lifetime of the black hole depends on the final state temperature in the evaporation process. The black hole will evaporate out when the final state temperature diverges and will transform into a remnant when the temperature is zero. Since we have analyzed massive gravity in detail, we can introduce the Gauss-Bonnet term to study how it affects the thermodynamic quantities. We obtain the final states for different parameter intervals, study the qualitative properties of black hole evaporation, and classify the associated cases. This method can also be applied to other models. |
gr-qc/9610009 | Torsten Asselmeyer | T. Asselmeyer | Generation of Source Terms in General Relativity by differential
structures | 14 pages, LaTeX, submitted to Class. Quant. Grav | Class.Quant.Grav. 14 (1997) 749-758 | 10.1088/0264-9381/14/3/016 | null | gr-qc dg-ga hep-th math.DG | null | In this paper the relation between the choice of a differential structure and
a smooth connection in the tangential bundle is discussed. For the case of an
exotic $S^7$ one obtains corrections to the curvature after the change of the
differential structure, which can not be neglected by a gauge transformation.
In the more interesting case of four dimensions we obtain a correction of the
connection constructed by intersections of embedded surfaces. This correction
produce a source term in the equation of the general relativity theory which
can be interpreted as the energy-momentum tensor of a embedded surface.
| [
{
"created": "Wed, 9 Oct 1996 10:45:02 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Asselmeyer",
"T.",
""
]
] | In this paper the relation between the choice of a differential structure and a smooth connection in the tangential bundle is discussed. For the case of an exotic $S^7$ one obtains corrections to the curvature after the change of the differential structure, which can not be neglected by a gauge transformation. In the more interesting case of four dimensions we obtain a correction of the connection constructed by intersections of embedded surfaces. This correction produce a source term in the equation of the general relativity theory which can be interpreted as the energy-momentum tensor of a embedded surface. |
gr-qc/9609022 | Jorge Pullin | Reinaldo Gleiser, Oscar Nicasio, Richard Price, Jorge Pullin | Colliding black holes: how far can the close approximation go? | 6 pages, RevTeX, 2 figures included with epsf | Phys.Rev.Lett. 77 (1996) 4483-4486 | 10.1103/PhysRevLett.77.4483 | CGQG-96/9-1 | gr-qc astro-ph | null | We study the head-on collision of two equal-mass momentarily stationary black
holes, using black hole perturbation theory up to second order. Compared to
first-order results, this significantly improves agreement with numerically
computed waveforms and energy. Much more important, second-order results
correctly indicate the range of validity of perturbation theory. This use of
second-order, to provide ``error bars,'' makes perturbation theory a viable
tool for providing benchmarks for numerical relativity in more generic
collisions and, in some range of collision parameters, for supplying waveform
templates for gravitational wave detection.
| [
{
"created": "Mon, 9 Sep 1996 13:09:14 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Gleiser",
"Reinaldo",
""
],
[
"Nicasio",
"Oscar",
""
],
[
"Price",
"Richard",
""
],
[
"Pullin",
"Jorge",
""
]
] | We study the head-on collision of two equal-mass momentarily stationary black holes, using black hole perturbation theory up to second order. Compared to first-order results, this significantly improves agreement with numerically computed waveforms and energy. Much more important, second-order results correctly indicate the range of validity of perturbation theory. This use of second-order, to provide ``error bars,'' makes perturbation theory a viable tool for providing benchmarks for numerical relativity in more generic collisions and, in some range of collision parameters, for supplying waveform templates for gravitational wave detection. |
gr-qc/0005102 | Emil Mottola | Paul R. Anderson, Wayne Eaker, Salman Habib, Carmen Molina-Paris, Emil
Mottola | Attractor states and infrared scaling in de Sitter space | 30 pages, 6 figures, 46 kB tar.gz file | Phys.Rev. D62 (2000) 124019 | 10.1103/PhysRevD.62.124019 | LA-UR-00-52 | gr-qc | null | The renormalized expectation value of the energy-momentum tensor for a scalar
field with any mass m and curvature coupling xi is studied for an arbitrary
homogeneous and isotropic physical initial state in de Sitter spacetime. We
prove quite generally that <T_{ab}> has a fixed point attractor behavior at
late times, which depends only on m and xi, for any fourth order adiabatic
state that is infrared finite. Specifically, when m^2 + xi R > 0, <T_{ab}>
approaches the Bunch-Davies de Sitter invariant value at late times,
independently of the initial state. When m = xi = 0, it approaches instead the
de Sitter invariant Allen-Folacci value. When m = 0 and xi \ge 0 we show that
this state independent asymptotic value of the energy-momentum tensor is
proportional to the conserved geometrical tensor (3)H_{ab}, which is related to
the behavior of the quantum effective action of the scalar field under global
Weyl rescaling. This relationship serves to generalize the definition of the
trace anomaly in the infrared for massless, non-conformal fields. In the case
m^2 + xi R = 0, but m and xi separately different from zero, <T_{ab}> grows
linearly with cosmic time at late times. For most values of m and xi in the
tachyonic cases, m^2 + xi R < 0, <T_{ab}> grows exponentially at late cosmic
times for all physically admissable initial states.
| [
{
"created": "Tue, 23 May 2000 19:34:13 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Anderson",
"Paul R.",
""
],
[
"Eaker",
"Wayne",
""
],
[
"Habib",
"Salman",
""
],
[
"Molina-Paris",
"Carmen",
""
],
[
"Mottola",
"Emil",
""
]
] | The renormalized expectation value of the energy-momentum tensor for a scalar field with any mass m and curvature coupling xi is studied for an arbitrary homogeneous and isotropic physical initial state in de Sitter spacetime. We prove quite generally that <T_{ab}> has a fixed point attractor behavior at late times, which depends only on m and xi, for any fourth order adiabatic state that is infrared finite. Specifically, when m^2 + xi R > 0, <T_{ab}> approaches the Bunch-Davies de Sitter invariant value at late times, independently of the initial state. When m = xi = 0, it approaches instead the de Sitter invariant Allen-Folacci value. When m = 0 and xi \ge 0 we show that this state independent asymptotic value of the energy-momentum tensor is proportional to the conserved geometrical tensor (3)H_{ab}, which is related to the behavior of the quantum effective action of the scalar field under global Weyl rescaling. This relationship serves to generalize the definition of the trace anomaly in the infrared for massless, non-conformal fields. In the case m^2 + xi R = 0, but m and xi separately different from zero, <T_{ab}> grows linearly with cosmic time at late times. For most values of m and xi in the tachyonic cases, m^2 + xi R < 0, <T_{ab}> grows exponentially at late cosmic times for all physically admissable initial states. |
2308.02114 | Jun-Xian Li | Jun-Xian Li, Jing-Yi Zhang | Corrections to the thermodynamic quantities of Bose system by the
generalized uncertainty principle | null | EPL 139 69003 (2022) | 10.1209/0295-5075/ac8f6a | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper investigated the Bose system in a spherical shell close to the
black hole horizon. Several thermodynamic quantities of the Bose system are
derived, which are different from those in the flat spacetime, by introducing
the generalized uncertainty principle (GUP) into the grand partition function
of statistical mechanics. The internal energy and the pressure of the Bose
system appear to have a correction term of $T^6$, while the entropy has a $T^5$
correction term where both the coefficients are functions of the spacetime
component $g_{00}$ and the brick-wall model parameter $\epsilon$. Taking the
Schwarzschild black hole as an example, the physical quantities of the shell
such as temperature, pressure and entropy are calculated for the final stage of
black hole radiation.
| [
{
"created": "Fri, 4 Aug 2023 02:35:05 GMT",
"version": "v1"
}
] | 2023-08-07 | [
[
"Li",
"Jun-Xian",
""
],
[
"Zhang",
"Jing-Yi",
""
]
] | This paper investigated the Bose system in a spherical shell close to the black hole horizon. Several thermodynamic quantities of the Bose system are derived, which are different from those in the flat spacetime, by introducing the generalized uncertainty principle (GUP) into the grand partition function of statistical mechanics. The internal energy and the pressure of the Bose system appear to have a correction term of $T^6$, while the entropy has a $T^5$ correction term where both the coefficients are functions of the spacetime component $g_{00}$ and the brick-wall model parameter $\epsilon$. Taking the Schwarzschild black hole as an example, the physical quantities of the shell such as temperature, pressure and entropy are calculated for the final stage of black hole radiation. |
2211.11538 | Icaro Daniel Dias De Carvalho | I. D.D. Carvalho, G. Alencar and C. R. Muniz | Thermodynamics of static and stationary black holes in
Einstein-Gauss-Bonnet gravity with dark matter | We add the rotation black hole case. The new version has 22 pages and
11 figures | null | 10.1016/j.dark.2023.101290 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper studies Einstein-Gauss-Bonnet (EGB) black holes surrounded by
three phenomenological distributions of dark matter halos. The main result is
obtaining the analytical solutions for the metric and all thermodynamic
quantities, such as Hawking temperature, entropy, constant-volume heat
capacity, and Gibbs free energy for static and stationary black hole solutions.
Consequently, we determine a non-null horizon radius at which the black hole
halts its evaporation by vanishing the temperature, indicating the emergence of
remnants. In the stationary case, we also obtain the ergosphere regions for the
found solutions and compare them. Finally, we find local and global phase
transitions by studying the behavior of the heat capacity and Gibbs free
energy.
| [
{
"created": "Mon, 21 Nov 2022 15:04:38 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Dec 2022 16:06:04 GMT",
"version": "v2"
}
] | 2023-09-15 | [
[
"Carvalho",
"I. D. D.",
""
],
[
"Alencar",
"G.",
""
],
[
"Muniz",
"C. R.",
""
]
] | This paper studies Einstein-Gauss-Bonnet (EGB) black holes surrounded by three phenomenological distributions of dark matter halos. The main result is obtaining the analytical solutions for the metric and all thermodynamic quantities, such as Hawking temperature, entropy, constant-volume heat capacity, and Gibbs free energy for static and stationary black hole solutions. Consequently, we determine a non-null horizon radius at which the black hole halts its evaporation by vanishing the temperature, indicating the emergence of remnants. In the stationary case, we also obtain the ergosphere regions for the found solutions and compare them. Finally, we find local and global phase transitions by studying the behavior of the heat capacity and Gibbs free energy. |
gr-qc/9312034 | null | B. L. Hu and Yuhong Zhang | Uncertainty Relation for a Quantum Open System | 36 pages,Tex,umdpp93-162,(submitted to Phys. Rev. A) | Int.J.Mod.Phys. A10 (1995) 4537-4562 | 10.1142/S0217751X95002102 | null | gr-qc hep-th | null | We derive the uncertainty relation for a quantum open system comprised of a
Brownian particle interacting with a bath of quantum oscillators at finite
temperature. We examine how the quantum and thermal fluctuations of the
environment contribute to the uncertainty in the canonical variables of the
system. We show that upon contact with the bath (assumed ohmic in this paper)
the system evolves from a quantum-dominated state to a thermal-dominated state
in a time which is the same as the decoherence time in similar models in the
discussion of quantum to classical transition. This offers some insight into
the physical mechanisms involved in the environment-induced decoherence
process. We obtain closed analytic expressions for this generalized uncertainty
relation under the conditions of high temperature and weak damping separately.
We also consider under these conditions an arbitrarily-squeezed initial state
and show how the squeeze parameter enters in the generalized uncertainty
relation. Using these results we examine the transition of the system from a
quantum pure state to a nonequilibrium quantum statistical state and to an
equilibrium quantum statistical state. The three stages are marked by the
decoherence time and the relaxation time respectively. With these observations
we explicate the physical conditions when the two basic postulates of quantum
statistical mechanics become valid. We also comment on the inappropriateness in
the usage of the word classicality in many decoherence studies of quantum to
classical transition.
| [
{
"created": "Thu, 23 Dec 1993 16:33:40 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Hu",
"B. L.",
""
],
[
"Zhang",
"Yuhong",
""
]
] | We derive the uncertainty relation for a quantum open system comprised of a Brownian particle interacting with a bath of quantum oscillators at finite temperature. We examine how the quantum and thermal fluctuations of the environment contribute to the uncertainty in the canonical variables of the system. We show that upon contact with the bath (assumed ohmic in this paper) the system evolves from a quantum-dominated state to a thermal-dominated state in a time which is the same as the decoherence time in similar models in the discussion of quantum to classical transition. This offers some insight into the physical mechanisms involved in the environment-induced decoherence process. We obtain closed analytic expressions for this generalized uncertainty relation under the conditions of high temperature and weak damping separately. We also consider under these conditions an arbitrarily-squeezed initial state and show how the squeeze parameter enters in the generalized uncertainty relation. Using these results we examine the transition of the system from a quantum pure state to a nonequilibrium quantum statistical state and to an equilibrium quantum statistical state. The three stages are marked by the decoherence time and the relaxation time respectively. With these observations we explicate the physical conditions when the two basic postulates of quantum statistical mechanics become valid. We also comment on the inappropriateness in the usage of the word classicality in many decoherence studies of quantum to classical transition. |
gr-qc/0407001 | Badri Krishnan | Badri Krishnan, Alicia M. Sintes, M.A. Papa, Bernard F. Schutz, Sergio
Frasca, Cristiano Palomba | The Hough transform search for continuous gravitational waves | 22 pages, RevTeX4, typos and references corrected. Final PRD version | Phys.Rev. D70 (2004) 082001 | 10.1103/PhysRevD.70.082001 | null | gr-qc | null | This paper describes an incoherent method to search for continuous
gravitational waves based on the Hough transform, a well known technique used
for detecting patterns in digital images. We apply the Hough transform to
detect patterns in the time-frequency plane of the data produced by an
earth-based gravitational wave detector. Two different flavors of searches will
be considered, depending on the type of input to the Hough transform: either
Fourier transforms of the detector data or the output of a coherent
matched-filtering type search. We present the technical details for
implementing the Hough transform algorithm for both kinds of searches, their
statistical properties, and their sensitivities.
| [
{
"created": "Thu, 1 Jul 2004 08:25:28 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Oct 2004 13:04:26 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Krishnan",
"Badri",
""
],
[
"Sintes",
"Alicia M.",
""
],
[
"Papa",
"M. A.",
""
],
[
"Schutz",
"Bernard F.",
""
],
[
"Frasca",
"Sergio",
""
],
[
"Palomba",
"Cristiano",
""
]
] | This paper describes an incoherent method to search for continuous gravitational waves based on the Hough transform, a well known technique used for detecting patterns in digital images. We apply the Hough transform to detect patterns in the time-frequency plane of the data produced by an earth-based gravitational wave detector. Two different flavors of searches will be considered, depending on the type of input to the Hough transform: either Fourier transforms of the detector data or the output of a coherent matched-filtering type search. We present the technical details for implementing the Hough transform algorithm for both kinds of searches, their statistical properties, and their sensitivities. |
2207.14576 | Fabrizio Esposito | Fabrizio Esposito, Sante Carloni and Stefano Vignolo | Bianchi type-I cosmological dynamics in $f(\mathcal{Q})$ gravity: a
covariant approach | 27 pages, 11 figures | Class. Quantum Grav. 39, 235014 (2022) | 10.1088/1361-6382/ac9efd | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Making use of the $1 + 3$ covariant formalism, we show explicitly the effect
that nonmetricity has on the dynamics of the universe. Then, using the
Dynamical System Approach, we analyze the evolution of Bianchi type-I
cosmologies within the framework of $f(\mathcal{Q})$ gravity. We consider
several models of function $f(\mathcal{Q})$, each of them manifesting isotropic
eras of the universe, whether transitional or not. In one case, in addition to
the qualitative analysis provided by the dynamical system method, we also
obtain analytical solutions in terms of the average length scale $l$.
| [
{
"created": "Fri, 29 Jul 2022 09:45:27 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Nov 2022 15:45:00 GMT",
"version": "v2"
}
] | 2022-11-16 | [
[
"Esposito",
"Fabrizio",
""
],
[
"Carloni",
"Sante",
""
],
[
"Vignolo",
"Stefano",
""
]
] | Making use of the $1 + 3$ covariant formalism, we show explicitly the effect that nonmetricity has on the dynamics of the universe. Then, using the Dynamical System Approach, we analyze the evolution of Bianchi type-I cosmologies within the framework of $f(\mathcal{Q})$ gravity. We consider several models of function $f(\mathcal{Q})$, each of them manifesting isotropic eras of the universe, whether transitional or not. In one case, in addition to the qualitative analysis provided by the dynamical system method, we also obtain analytical solutions in terms of the average length scale $l$. |
gr-qc/0611115 | Gerhard Rein | Hakan Andreasson, Markus Kunze, Gerhard Rein | Global existence for the spherically symmetric Einstein-Vlasov system
with outgoing matter | 16 pages | Commun.Part.Diff.Eq.33:656-668,2008 | 10.1080/03605300701454883 | null | gr-qc | null | We prove a new global existence result for the asymptotically flat,
spherically symmetric Einstein-Vlasov system which describes in the framework
of general relativity an ensemble of particles which interact by gravity. The
data are such that initially all the particles are moving radially outward and
that this property can be bootstrapped. The resulting non-vacuum spacetime is
future geodesically complete.
| [
{
"created": "Wed, 22 Nov 2006 15:11:43 GMT",
"version": "v1"
}
] | 2011-02-01 | [
[
"Andreasson",
"Hakan",
""
],
[
"Kunze",
"Markus",
""
],
[
"Rein",
"Gerhard",
""
]
] | We prove a new global existence result for the asymptotically flat, spherically symmetric Einstein-Vlasov system which describes in the framework of general relativity an ensemble of particles which interact by gravity. The data are such that initially all the particles are moving radially outward and that this property can be bootstrapped. The resulting non-vacuum spacetime is future geodesically complete. |
1911.03893 | David McNutt | A. A. Coley, R. J. van den Hoogen and D. D. McNutt | Symmetry and Equivalence in Teleparallel Gravity | 52 pages. Equations have been corrected and a new subsection has been
included on the covariant form of the f(T) field equations | J. Math. Phys. 61, 072503 (2020) | 10.1063/5.0003252 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In theories such as teleparallel gravity and its extensions, the frame basis
replaces the metric tensor as the primary object of study. A choice of
coordinate system, frame basis and spin-connection must be made to obtain a
solution from the field equations of a given teleparallel gravity theory. It is
worthwhile to express solutions in an invariant manner in terms of torsion
invariants to distinguish between different solutions. In this paper we discuss
the symmetries of teleparallel gravity theories, describe the classification of
the torsion tensor and its covariant derivative and define scalar invariants in
terms of the torsion. In particular, we propose a modification of the
Cartan-Karlhede algorithm for geometries with torsion (and no curvature or
nonmetricity). The algorithm determines the dimension of the symmetry group for
a solution and suggests an alternative frame-based approach to calculating
symmetries. We prove that the only maximally symmetric solution to any theory
of gravitation admitting a non-zero torsion tensor is Minkowski space. As an
illustration we apply the algorithm to six particular exact teleparallel
geometries. From these examples we notice that the symmetry group of the
solutions of a teleparallel gravity theory is potentially smaller than their
metric-based analogues in General Relativity.
| [
{
"created": "Sun, 10 Nov 2019 10:43:15 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Jan 2020 16:36:31 GMT",
"version": "v2"
}
] | 2024-02-28 | [
[
"Coley",
"A. A.",
""
],
[
"Hoogen",
"R. J. van den",
""
],
[
"McNutt",
"D. D.",
""
]
] | In theories such as teleparallel gravity and its extensions, the frame basis replaces the metric tensor as the primary object of study. A choice of coordinate system, frame basis and spin-connection must be made to obtain a solution from the field equations of a given teleparallel gravity theory. It is worthwhile to express solutions in an invariant manner in terms of torsion invariants to distinguish between different solutions. In this paper we discuss the symmetries of teleparallel gravity theories, describe the classification of the torsion tensor and its covariant derivative and define scalar invariants in terms of the torsion. In particular, we propose a modification of the Cartan-Karlhede algorithm for geometries with torsion (and no curvature or nonmetricity). The algorithm determines the dimension of the symmetry group for a solution and suggests an alternative frame-based approach to calculating symmetries. We prove that the only maximally symmetric solution to any theory of gravitation admitting a non-zero torsion tensor is Minkowski space. As an illustration we apply the algorithm to six particular exact teleparallel geometries. From these examples we notice that the symmetry group of the solutions of a teleparallel gravity theory is potentially smaller than their metric-based analogues in General Relativity. |
gr-qc/9905066 | Arbab I. Arbab | Arbab I. Arbab | Cosmic Acceleration With A Positive Cosmological Constant | a more revised version | Class.Quant.Grav. 20 (2003) 93-100 | 10.1088/0264-9381/20/1/307 | null | gr-qc astro-ph | null | We have considered a cosmological model with a phenomenological model for the
cosmological constant of the form $\Lambda=\bt\fr{\ddot R}{R}$, $ \bt$ is a
constant. For age parameter consistent with observational data the Universe
must be accelerating in the presence of a positive cosmological constant. The
minimum age of the Universe is $H_0^{-1}$, where $H_0$ is the present Hubble
constant. The cosmological constant is found to decrease as $t^{-2}$. Allowing
the gravitational constant to change with time leads to an ever increasing
gravitational constant at the present epoch. In the presence of a viscous fluid
this decay law for $\Lambda$ is equivalent to the one with $\Lambda=3\alpha
H^2$ ($\alpha=\rm const.$) provided $\alpha=\fr{\bt}{3(\bt-2)}$. The
inflationary solution obtained from this model is that of the de-Sitter type.
| [
{
"created": "Wed, 19 May 1999 17:14:20 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Oct 1999 12:30:55 GMT",
"version": "v2"
},
{
"created": "Fri, 22 Oct 1999 09:48:21 GMT",
"version": "v3"
},
{
"created": "Mon, 14 May 2001 19:49:48 GMT",
"version": "v4"
},
{
"created": "Tue, 17 Dec 2002 00:10:05 GMT",
"version": "v5"
}
] | 2017-08-23 | [
[
"Arbab",
"Arbab I.",
""
]
] | We have considered a cosmological model with a phenomenological model for the cosmological constant of the form $\Lambda=\bt\fr{\ddot R}{R}$, $ \bt$ is a constant. For age parameter consistent with observational data the Universe must be accelerating in the presence of a positive cosmological constant. The minimum age of the Universe is $H_0^{-1}$, where $H_0$ is the present Hubble constant. The cosmological constant is found to decrease as $t^{-2}$. Allowing the gravitational constant to change with time leads to an ever increasing gravitational constant at the present epoch. In the presence of a viscous fluid this decay law for $\Lambda$ is equivalent to the one with $\Lambda=3\alpha H^2$ ($\alpha=\rm const.$) provided $\alpha=\fr{\bt}{3(\bt-2)}$. The inflationary solution obtained from this model is that of the de-Sitter type. |
1601.04315 | Simon Garruto | Lorenzo Fatibene and Simon Garruto | Extended Theories of Gravitation | Workshop Variational principles and conservation laws in General
Relativity, Torino, June 24-25, 2015in memory of Mauro Francaviglia | null | 10.1142/S0219887816500705 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we shall review the equivalence between Palatini$-f(\mathcal
R)$ theories and Brans- Dicke (BD) theories at the level of action principles.
We shall define the Helmholtz Lagrangian associated to Palatini$-f(\mathcal R)$
theory and we will define some transformations which will be useful to recover
Einstein frame and Brans-Dicke frame. We shall see an explicit example of
matter field and we will discuss how the conformal factor affects the physical
quantities.
| [
{
"created": "Sun, 17 Jan 2016 17:31:19 GMT",
"version": "v1"
}
] | 2016-03-28 | [
[
"Fatibene",
"Lorenzo",
""
],
[
"Garruto",
"Simon",
""
]
] | In this paper we shall review the equivalence between Palatini$-f(\mathcal R)$ theories and Brans- Dicke (BD) theories at the level of action principles. We shall define the Helmholtz Lagrangian associated to Palatini$-f(\mathcal R)$ theory and we will define some transformations which will be useful to recover Einstein frame and Brans-Dicke frame. We shall see an explicit example of matter field and we will discuss how the conformal factor affects the physical quantities. |
gr-qc/9302020 | Ted Jacobson | R. Capovilla, J. Dell and T. Jacobson | The Initial Value Problem in Light of Ashtekar's Variables | 15 pages, UMDGR93-140, NSF-ITP-93-20 | null | null | null | gr-qc | null | The form of the initial value constraints in Ashtekar's hamiltonian
formulation of general relativity is recalled, and the problem of solving them
is compared with that in the traditional metric variables. It is shown how the
general solution of the four diffeomorphism constraints can be obtained
algebraically provided the curvature is non-degenerate, and the form of the
remaining (Gauss law) constraints is discussed. The method is extended to cover
the case when matter is included, using an approach due to Thiemann. The
application of the method to vacuum Bianchi models is given. The paper
concludes with a brief discussion of alternative approaches to the initial
value problem in the Ashtekar formulation.
| [
{
"created": "Thu, 18 Feb 1993 22:02:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Capovilla",
"R.",
""
],
[
"Dell",
"J.",
""
],
[
"Jacobson",
"T.",
""
]
] | The form of the initial value constraints in Ashtekar's hamiltonian formulation of general relativity is recalled, and the problem of solving them is compared with that in the traditional metric variables. It is shown how the general solution of the four diffeomorphism constraints can be obtained algebraically provided the curvature is non-degenerate, and the form of the remaining (Gauss law) constraints is discussed. The method is extended to cover the case when matter is included, using an approach due to Thiemann. The application of the method to vacuum Bianchi models is given. The paper concludes with a brief discussion of alternative approaches to the initial value problem in the Ashtekar formulation. |
2103.12473 | Roberta Chiovoloni | Giovanni Montani and Roberta Chiovoloni | A Scenario for a Singularity-free Generic Cosmological Solution | 7 pages, 1 figure | Phys. Rev. D 103, 123516 (2021) | 10.1103/PhysRevD.103.123516 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We develop a scenario for the emergence of a non-singular generic
cosmological solution based on the a WKB characterization of one of the two
anisotropy degrees of freedom. We investigate the dynamics of the so-called
inhomogeneous mixmaster in the "corner" configuration and inferring that one of
the two anisotropic variables becomes small enough to explore the uncertainty
principle. Then, we apply a standard WKB approximation to the dynamics of the
Universe which has macroscopic volume, one macroscopic anisotropy and one
microscopic quantum degree of freedom. Our study demonstrates the possibility
that the Universe acquires a non-singular classical behavior, retaining the
quantum degree of freedom as a small oscillating ripple on a stationary
Universe. The role of the so-called "fragmentation process" is also taken into
account in outlining the generality of such a behavior in independent local
space regions.
| [
{
"created": "Tue, 23 Mar 2021 11:55:18 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Apr 2021 11:51:40 GMT",
"version": "v2"
}
] | 2021-06-16 | [
[
"Montani",
"Giovanni",
""
],
[
"Chiovoloni",
"Roberta",
""
]
] | We develop a scenario for the emergence of a non-singular generic cosmological solution based on the a WKB characterization of one of the two anisotropy degrees of freedom. We investigate the dynamics of the so-called inhomogeneous mixmaster in the "corner" configuration and inferring that one of the two anisotropic variables becomes small enough to explore the uncertainty principle. Then, we apply a standard WKB approximation to the dynamics of the Universe which has macroscopic volume, one macroscopic anisotropy and one microscopic quantum degree of freedom. Our study demonstrates the possibility that the Universe acquires a non-singular classical behavior, retaining the quantum degree of freedom as a small oscillating ripple on a stationary Universe. The role of the so-called "fragmentation process" is also taken into account in outlining the generality of such a behavior in independent local space regions. |
gr-qc/9504022 | Andrei Linde | Juan Garcia-Bellido and Andrei Linde | STATIONARY SOLUTIONS IN BRANS-DICKE STOCHASTIC INFLATIONARY COSMOLOGY | 19 pages, LaTeX | Phys.Rev.D52:6730-6738,1995 | 10.1103/PhysRevD.52.6730 | SU-ITP-95-8, IEM-FT-86/95, SUSSEX-AST-95/4-2 | gr-qc astro-ph hep-ph hep-th | null | In Brans-Dicke theory the Universe becomes divided after inflation into many
exponentially large domains with different values of the effective
gravitational constant. Such a process can be described by diffusion equations
for the probability of finding a certain value of the inflaton and dilaton
fields in a physical volume of the Universe. For a typical chaotic inflation
potential, the solutions for the probability distribution never become
stationary but grow forever towards larger values of the fields. We show here
that a non-minimal conformal coupling of the inflaton to the curvature scalar,
as well as radiative corrections to the effective potential, may provide a
dynamical cutoff and generate stationary solutions. We also analyze the
possibility of large nonperturbative jumps of the fluctuating inflaton scalar
field, which was recently revealed in the context of the Einstein theory. We
find that in the Brans--Dicke theory the amplitude of such jumps is strongly
suppressed.
| [
{
"created": "Sat, 15 Apr 1995 19:24:06 GMT",
"version": "v1"
}
] | 2009-09-29 | [
[
"Garcia-Bellido",
"Juan",
""
],
[
"Linde",
"Andrei",
""
]
] | In Brans-Dicke theory the Universe becomes divided after inflation into many exponentially large domains with different values of the effective gravitational constant. Such a process can be described by diffusion equations for the probability of finding a certain value of the inflaton and dilaton fields in a physical volume of the Universe. For a typical chaotic inflation potential, the solutions for the probability distribution never become stationary but grow forever towards larger values of the fields. We show here that a non-minimal conformal coupling of the inflaton to the curvature scalar, as well as radiative corrections to the effective potential, may provide a dynamical cutoff and generate stationary solutions. We also analyze the possibility of large nonperturbative jumps of the fluctuating inflaton scalar field, which was recently revealed in the context of the Einstein theory. We find that in the Brans--Dicke theory the amplitude of such jumps is strongly suppressed. |
1503.01152 | Alaric Doria | Alaric Doria, Gerardo Munoz | Acceleration without Temperature | 4 pages | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that while some non-uniformly accelerating observers (NUAOs) do
indeed see a Bose-Einstein distribution of particles for the expectation value
of the number operator in the Minkowski vacuum state, the density matrix is
non-thermal and therefore a definition of temperature is not warranted. This is
due to the fact that our NUAOs do not see event horizons in the spacetime. More
specifically, the Minkowski vacuum state is perceived by our NUAOs as a
single-mode squeezed state as opposed to the two-mode squeezed state
characteristic of uniformly accelerating observers. Both single and two-mode
squeezed states are pure quantum states; however, tracing over degrees of
freedom in one of the modes of the two-mode squeezed state reduces the pure
density matrix to a thermal density matrix. It is this property in the two-mode
squeezed state that allows one to consistently define a temperature. In the
single-mode case, an equivalent tracing is neither required nor available.
| [
{
"created": "Tue, 3 Mar 2015 22:41:55 GMT",
"version": "v1"
}
] | 2015-03-05 | [
[
"Doria",
"Alaric",
""
],
[
"Munoz",
"Gerardo",
""
]
] | We show that while some non-uniformly accelerating observers (NUAOs) do indeed see a Bose-Einstein distribution of particles for the expectation value of the number operator in the Minkowski vacuum state, the density matrix is non-thermal and therefore a definition of temperature is not warranted. This is due to the fact that our NUAOs do not see event horizons in the spacetime. More specifically, the Minkowski vacuum state is perceived by our NUAOs as a single-mode squeezed state as opposed to the two-mode squeezed state characteristic of uniformly accelerating observers. Both single and two-mode squeezed states are pure quantum states; however, tracing over degrees of freedom in one of the modes of the two-mode squeezed state reduces the pure density matrix to a thermal density matrix. It is this property in the two-mode squeezed state that allows one to consistently define a temperature. In the single-mode case, an equivalent tracing is neither required nor available. |
2011.13848 | Refik Mansuroglu | Refik Mansuroglu and Hanno Sahlmann | Kinematics of arbitrary spin matter fields in loop quantum gravity | 21 pages v2: Minor changes and rearrangements of the text, removed
various typos. Version essentially identical to the one published in PRD | Phys. Rev. D 103, 106010 (2021) | 10.1103/PhysRevD.103.106010 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Loop quantum gravity envisions a small scale structure of spacetime that is
markedly different from that of the classical spacetime continuum. This has
ramifications for the excitation of matter fields and for their coupling to
gravity. There is a general understanding of how to formulate scalar fields,
spin $\frac{1}{2}$ fields and gauge fields in the framework of loop quantum
gravity. The goal of the present work is to investigate kinematical aspects of
this coupling. We will study implications of the Gau{\ss} and diffeomorphism
constraint for the quantum theory: We define and study a less ambiguous variant
of the Baez-Krasnov path observables, and investigate symmetry properties of
spin network states imposed by diffeomorphism group averaging. We will do this
in a setting which allows for matter excitations of spin $\frac{1}{2}$ and
higher. In the case of spin $\frac{1}{2}$, we will also discuss extensions of
it by introducing an electromagnetic field and antiparticles. We finally
discuss in how far the picture with matter excitations of higher spin can be
obtained from classical actions for higher spin fields.
| [
{
"created": "Fri, 27 Nov 2020 17:27:50 GMT",
"version": "v1"
},
{
"created": "Mon, 10 May 2021 21:29:14 GMT",
"version": "v2"
}
] | 2021-05-19 | [
[
"Mansuroglu",
"Refik",
""
],
[
"Sahlmann",
"Hanno",
""
]
] | Loop quantum gravity envisions a small scale structure of spacetime that is markedly different from that of the classical spacetime continuum. This has ramifications for the excitation of matter fields and for their coupling to gravity. There is a general understanding of how to formulate scalar fields, spin $\frac{1}{2}$ fields and gauge fields in the framework of loop quantum gravity. The goal of the present work is to investigate kinematical aspects of this coupling. We will study implications of the Gau{\ss} and diffeomorphism constraint for the quantum theory: We define and study a less ambiguous variant of the Baez-Krasnov path observables, and investigate symmetry properties of spin network states imposed by diffeomorphism group averaging. We will do this in a setting which allows for matter excitations of spin $\frac{1}{2}$ and higher. In the case of spin $\frac{1}{2}$, we will also discuss extensions of it by introducing an electromagnetic field and antiparticles. We finally discuss in how far the picture with matter excitations of higher spin can be obtained from classical actions for higher spin fields. |
gr-qc/9502021 | Animals have rights | Mauro Carfora and Kamilla Piotrkowska | A Renormalization Group Approach to Relativistic Cosmology | 57 pages, LaTeX, 15 pictures available on request from the Authors | Phys.Rev. D52 (1995) 4393-4424 | 10.1103/PhysRevD.52.4393 | SISSA Ref. 8/95/FM | gr-qc | null | We discuss the averaging hypothesis tacitly assumed in standard cosmology.
Our approach is implemented in a "3+1" formalism and invokes the coarse
graining arguments, provided and supported by the real-space Renormalization
Group (RG) methods. Block variables are introduced and the recursion relations
written down explicitly enabling us to characterize the corresponding RG flow.
To leading order, the RG flow is provided by the Ricci-Hamilton equations
studied in connection with the geometry of three-manifolds. The properties of
the Ricci-Hamilton flow make it possible to study a critical behaviour of
cosmological models. This criticality is discussed and it is argued that it may
be related to the formation of sheet-like structures in the universe. We
provide an explicit expression for the renormalized Hubble constant and for the
scale dependence of the matter distribution. It is shown that the Hubble
constant is affected by non-trivial scale dependent shear terms, while the
spatial anisotropy of the metric influences significantly the scale-dependence
of the matter distribution.
| [
{
"created": "Wed, 8 Feb 1995 21:40:59 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Carfora",
"Mauro",
""
],
[
"Piotrkowska",
"Kamilla",
""
]
] | We discuss the averaging hypothesis tacitly assumed in standard cosmology. Our approach is implemented in a "3+1" formalism and invokes the coarse graining arguments, provided and supported by the real-space Renormalization Group (RG) methods. Block variables are introduced and the recursion relations written down explicitly enabling us to characterize the corresponding RG flow. To leading order, the RG flow is provided by the Ricci-Hamilton equations studied in connection with the geometry of three-manifolds. The properties of the Ricci-Hamilton flow make it possible to study a critical behaviour of cosmological models. This criticality is discussed and it is argued that it may be related to the formation of sheet-like structures in the universe. We provide an explicit expression for the renormalized Hubble constant and for the scale dependence of the matter distribution. It is shown that the Hubble constant is affected by non-trivial scale dependent shear terms, while the spatial anisotropy of the metric influences significantly the scale-dependence of the matter distribution. |
1711.04102 | Zhu Yi | Yungui Gong, Eleftherios Papantonopoulos, Zhu Yi | Constraints on scalar-tensor theory of gravity by the recent
observational results on gravitational waves | 7 pages, 1 figure, typo corrected, references added and updated, Eur.
Phys. J. C in press | Eur. Phys. J. C (2018) 78: 738 | 10.1140/epjc/s10052-018-6227-9 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The speed of gravitational waves provides us a new tool to test alternative
theories of gravity. The constraint on the speed of gravitational waves from
GW170817 and GRB170817A is used to test some classes of Horndeski theory. In
particular, we consider the coupling of a scalar field to Einstein tensor and
the coupling of the Gauss-Bonnet term to a scalar field. The coupling strength
of the Gauss-Bonnet coupling is constrained to be in the order of $10^{-15}$.
In the Horndeski theory we show that in order for this theory to satisfy the
stringent constraint on the speed of GWs the mass scale $M$ introduced in the
non-minimally derivative coupling is constrained to be in the range
$10^{15}\text{GeV}\gg M \gtrsim 2\times 10^{-35}$GeV taking also under
consideration the early times upper bound for the mass scale $M$. The large
mass ranges require no fine-tuning because the effect of non-minimally
derivative coupling is negligible at late times.
| [
{
"created": "Sat, 11 Nov 2017 08:44:21 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Sep 2018 04:40:12 GMT",
"version": "v2"
}
] | 2018-09-19 | [
[
"Gong",
"Yungui",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
],
[
"Yi",
"Zhu",
""
]
] | The speed of gravitational waves provides us a new tool to test alternative theories of gravity. The constraint on the speed of gravitational waves from GW170817 and GRB170817A is used to test some classes of Horndeski theory. In particular, we consider the coupling of a scalar field to Einstein tensor and the coupling of the Gauss-Bonnet term to a scalar field. The coupling strength of the Gauss-Bonnet coupling is constrained to be in the order of $10^{-15}$. In the Horndeski theory we show that in order for this theory to satisfy the stringent constraint on the speed of GWs the mass scale $M$ introduced in the non-minimally derivative coupling is constrained to be in the range $10^{15}\text{GeV}\gg M \gtrsim 2\times 10^{-35}$GeV taking also under consideration the early times upper bound for the mass scale $M$. The large mass ranges require no fine-tuning because the effect of non-minimally derivative coupling is negligible at late times. |
2005.11324 | Bruno Le Floch | Bruno Le Floch, Philippe G. LeFloch, Gabriele Veneziano | Cyclic spacetimes through singularity scattering maps. The laws of
quiescent bounces | 54 pages. v2: Construction of plane-symmetric cyclic spacetimes moved
to arXiv:2106.09666. v3: Version published in JHEP | JHEP 2022, 95 (2022) | 10.1007/JHEP04(2022)095 | CERN-TH-2020-100 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For spacetimes containing quiescent singularity hypersurfaces we propose a
general notion of junction conditions based on a prescribed singularity
scattering map, as we call it, and we introduce the notion of a cyclic
spacetime (also called a multiverse) consisting of spacetime domains bounded by
spacelike or timelike singularity hypersurfaces, across which our scattering
map is applied. A local existence theory is established here while, in a
companion paper, we construct plane-symmetric cyclic spacetimes. We study the
singularity data space consisting of the suitably rescaled metric, extrinsic
curvature, and matter fields which can be prescribed on each side of the
singularity, and for the class of so-called quiescent singularities we
establish restrictions that a singularity scattering map must satisfy. We
obtain a full characterization of all scattering maps that are covariant and
ultralocal, in a sense we define and, in particular, we distinguish between, on
the one hand, three laws of bouncing cosmology of universal nature and, on the
other hand, model-dependent junction conditions. The theory proposed in this
paper applies to spacelike and timelike hypersurfaces and without symmetry
restriction. It encompasses bouncing-cosmology scenarios, both in string theory
and in loop quantum cosmology, and puts strong restrictions on their possible
explicit realizations.
| [
{
"created": "Fri, 22 May 2020 18:00:00 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Jun 2021 17:09:51 GMT",
"version": "v2"
},
{
"created": "Thu, 21 Apr 2022 09:03:45 GMT",
"version": "v3"
}
] | 2024-04-09 | [
[
"Floch",
"Bruno Le",
""
],
[
"LeFloch",
"Philippe G.",
""
],
[
"Veneziano",
"Gabriele",
""
]
] | For spacetimes containing quiescent singularity hypersurfaces we propose a general notion of junction conditions based on a prescribed singularity scattering map, as we call it, and we introduce the notion of a cyclic spacetime (also called a multiverse) consisting of spacetime domains bounded by spacelike or timelike singularity hypersurfaces, across which our scattering map is applied. A local existence theory is established here while, in a companion paper, we construct plane-symmetric cyclic spacetimes. We study the singularity data space consisting of the suitably rescaled metric, extrinsic curvature, and matter fields which can be prescribed on each side of the singularity, and for the class of so-called quiescent singularities we establish restrictions that a singularity scattering map must satisfy. We obtain a full characterization of all scattering maps that are covariant and ultralocal, in a sense we define and, in particular, we distinguish between, on the one hand, three laws of bouncing cosmology of universal nature and, on the other hand, model-dependent junction conditions. The theory proposed in this paper applies to spacelike and timelike hypersurfaces and without symmetry restriction. It encompasses bouncing-cosmology scenarios, both in string theory and in loop quantum cosmology, and puts strong restrictions on their possible explicit realizations. |
0802.0936 | M. Alessandra Papa | M. Alessandra Papa | Progress towards Gravitational Wave Astronomy | Based on a talk presented at the joint "18th International Conference
on General Relativity and Gravitation" and "7th Amaldi Conference on
Gravitational Waves", 8-13 July 2007, Sydney, Australia | Class.Quant.Grav.25:114009,2008 | 10.1088/0264-9381/25/11/114009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I will review the most recent and interesting results from gravitational wave
detection experiments, concentrating on recent results from the LIGO Scientific
Collaboration (LSC). I will outline the methodologies utilized in the searches,
explain what can be said in the case of a null result, what quantities may be
constrained. I will compare these results with prior expectations and discuss
their significance. As I go along I will outline the prospects for future
improvements.
| [
{
"created": "Thu, 7 Feb 2008 09:57:59 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Mar 2008 13:22:51 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Papa",
"M. Alessandra",
""
]
] | I will review the most recent and interesting results from gravitational wave detection experiments, concentrating on recent results from the LIGO Scientific Collaboration (LSC). I will outline the methodologies utilized in the searches, explain what can be said in the case of a null result, what quantities may be constrained. I will compare these results with prior expectations and discuss their significance. As I go along I will outline the prospects for future improvements. |
2212.04605 | Hongguang Liu | Muxin Han and Hongguang Liu | Covariant ${\bar{\mu}}$-scheme effective dynamics, mimetic gravity, and
non-singular black holes: Applications to spherical symmetric quantum gravity
and CGHS model | 49 pages, 23 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new $\bar{\mu}$-scheme Hamiltonian effective dynamics in the
spherical symmetric sector of Loop Quantum Gravity (LQG). The effective
dynamics is generally covariant as derived from a covariant Lagrangian. The
Lagrangian belongs to the class of extended mimetic gravity Lagrangians in 4
dimensions. We apply the effective dynamics to both cosmology and black hole.
The effective dynamics reproduces the non-singular Loop-Quantum-Cosmology (LQC)
effective dynamics. From the effective dynamics, we obtain the non-singular
black hole solution, which has a killing symmetry in addition to the spherical
symmetry and reduces to the Schwarzschild geometry asymptotically near the
infinity. The black hole spacetime resolves the classical singularity and
approaches asymptotically the Nariai geometry $\mathrm{dS}_2\times S^2$ at the
future infinity in the interior of the black hole. The resulting black hole
spacetime has the complete future null infinity $\mathscr{I}^+$. Thanks to the
general covariance, the effective dynamics can be reformulated in the
light-cone gauge. We generalize the covariant $\bar{\mu}$-scheme effective
dynamics to the Callan-Giddings-Harvey-Strominger (CGHS) model and apply the
light-cone formulation to the CGHS black hole solution with the null-shell
collapse. We focus on the effective dynamics projected along the null shell.
The result shows that both the 2d scalar curvature and the derivative of
dilaton field are finite, in contrast to the divergence in the CGHS model.
| [
{
"created": "Thu, 8 Dec 2022 23:41:01 GMT",
"version": "v1"
}
] | 2022-12-12 | [
[
"Han",
"Muxin",
""
],
[
"Liu",
"Hongguang",
""
]
] | We propose a new $\bar{\mu}$-scheme Hamiltonian effective dynamics in the spherical symmetric sector of Loop Quantum Gravity (LQG). The effective dynamics is generally covariant as derived from a covariant Lagrangian. The Lagrangian belongs to the class of extended mimetic gravity Lagrangians in 4 dimensions. We apply the effective dynamics to both cosmology and black hole. The effective dynamics reproduces the non-singular Loop-Quantum-Cosmology (LQC) effective dynamics. From the effective dynamics, we obtain the non-singular black hole solution, which has a killing symmetry in addition to the spherical symmetry and reduces to the Schwarzschild geometry asymptotically near the infinity. The black hole spacetime resolves the classical singularity and approaches asymptotically the Nariai geometry $\mathrm{dS}_2\times S^2$ at the future infinity in the interior of the black hole. The resulting black hole spacetime has the complete future null infinity $\mathscr{I}^+$. Thanks to the general covariance, the effective dynamics can be reformulated in the light-cone gauge. We generalize the covariant $\bar{\mu}$-scheme effective dynamics to the Callan-Giddings-Harvey-Strominger (CGHS) model and apply the light-cone formulation to the CGHS black hole solution with the null-shell collapse. We focus on the effective dynamics projected along the null shell. The result shows that both the 2d scalar curvature and the derivative of dilaton field are finite, in contrast to the divergence in the CGHS model. |
1103.3538 | Francesco Nicol\`o FN | Giulio Caciotta, Francesco Nicol\`o | Local and Global Analytic Solutions for a Class of Characteristic
Problems of the Einstein Vacuum Equations in the "Double Null Foliation
Gauge" | 68 pages | null | 10.1007/s00023-011-0151-y | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main goal of this work consists in showing that the analytic solutions
for a class of characteristic problems for the Einstein vacuum equations have
an existence region larger than the one provided by the Cauchy-Kowalevski
theorem due to the intrinsic hyperbolicity of the Einstein equations. To prove
this result we first describe a geometric way of writing the vacuum Einstein
equations for the characteristic problems we are considering, in a gauge
characterized by the introduction of a double null cone foliation of the
spacetime. Then we prove that the existence region for the analytic solutions
can be extended to a larger region which depends only on the validity of the
apriori estimates for the Weyl equations, associated to the "Bel-Robinson
norms". In particular if the initial data are sufficiently small we show that
the analytic solution is global. Before showing how to extend the existence
region we describe the same result in the case of the Burger equation, which,
even if much simpler, nevertheless requires analogous logical steps required
for the general proof. Due to length of this work, in this paper we mainly
concentrate on the definition of the gauge we use and on writing in a
"geometric" way the Einstein equations, then we show how the Cauchy-Kowalevski
theorem is adapted to the characteristic problem for the Einstein equations and
we describe how the existence region can be extended in the case of the Burger
equation. Finally we describe the structure of the extension proof in the case
of the Einstein equations. The technical parts of this last result is the
content of a second paper.
| [
{
"created": "Thu, 17 Mar 2011 23:47:20 GMT",
"version": "v1"
}
] | 2015-05-27 | [
[
"Caciotta",
"Giulio",
""
],
[
"Nicolò",
"Francesco",
""
]
] | The main goal of this work consists in showing that the analytic solutions for a class of characteristic problems for the Einstein vacuum equations have an existence region larger than the one provided by the Cauchy-Kowalevski theorem due to the intrinsic hyperbolicity of the Einstein equations. To prove this result we first describe a geometric way of writing the vacuum Einstein equations for the characteristic problems we are considering, in a gauge characterized by the introduction of a double null cone foliation of the spacetime. Then we prove that the existence region for the analytic solutions can be extended to a larger region which depends only on the validity of the apriori estimates for the Weyl equations, associated to the "Bel-Robinson norms". In particular if the initial data are sufficiently small we show that the analytic solution is global. Before showing how to extend the existence region we describe the same result in the case of the Burger equation, which, even if much simpler, nevertheless requires analogous logical steps required for the general proof. Due to length of this work, in this paper we mainly concentrate on the definition of the gauge we use and on writing in a "geometric" way the Einstein equations, then we show how the Cauchy-Kowalevski theorem is adapted to the characteristic problem for the Einstein equations and we describe how the existence region can be extended in the case of the Burger equation. Finally we describe the structure of the extension proof in the case of the Einstein equations. The technical parts of this last result is the content of a second paper. |
2208.01766 | Hector Iglesias | H. L. Iglesias, J. Lange, I. Bartos, S. Bhaumik, R. Gamba, V.
Gayathri, A. Jan, R. Nowicki, R. O'Shaughnessy, D. Shoemaker, R.
Venkataramanan, and K. Wagner | Eccentricity estimation for five binary black hole mergers with
higher-order gravitational wave modes | We have updated our results after performing reruns of our eccentric
and quasi-circular analyses, and we have also included spin-precessing
analyses of all the events selected in this paper | null | null | LIGO-P2200208 | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | The detection of orbital eccentricity for a binary black hole system via
gravitational waves is a key signature to distinguish between the possible
binary origins. The identification of eccentricity has been difficult so far
due to the limited availability of eccentric gravitational waveforms over the
full range of black hole masses and eccentricities. Here we evaluate the
eccentricity of five black hole mergers detected by the LIGO and Virgo
observatories for the first time using the TEOBResumSGeneral model. This model
accounts for the full eccentricity range possible and incorporates higher-order
gravitational wave modes critical to model emission from highly eccentric
orbits. The binaries have been selected due to previous hints of eccentricity
or due to their unusual mass and spin. While other studies found marginal
evidence for eccentricity for some of these events, our analyses do not favor
the incorporation of eccentricity compared to the quasi-circular case. While
lacking the eccentric evidence of other analyses, we find our analyses
marginally shifts the posterior in multiple parameters for several events when
allowing eccentricity to be non-zero.
| [
{
"created": "Tue, 2 Aug 2022 21:45:28 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Sep 2023 22:40:02 GMT",
"version": "v2"
}
] | 2023-09-19 | [
[
"Iglesias",
"H. L.",
""
],
[
"Lange",
"J.",
""
],
[
"Bartos",
"I.",
""
],
[
"Bhaumik",
"S.",
""
],
[
"Gamba",
"R.",
""
],
[
"Gayathri",
"V.",
""
],
[
"Jan",
"A.",
""
],
[
"Nowicki",
"R.",
""
],
[
"O'Shaughnessy",
"R.",
""
],
[
"Shoemaker",
"D.",
""
],
[
"Venkataramanan",
"R.",
""
],
[
"Wagner",
"K.",
""
]
] | The detection of orbital eccentricity for a binary black hole system via gravitational waves is a key signature to distinguish between the possible binary origins. The identification of eccentricity has been difficult so far due to the limited availability of eccentric gravitational waveforms over the full range of black hole masses and eccentricities. Here we evaluate the eccentricity of five black hole mergers detected by the LIGO and Virgo observatories for the first time using the TEOBResumSGeneral model. This model accounts for the full eccentricity range possible and incorporates higher-order gravitational wave modes critical to model emission from highly eccentric orbits. The binaries have been selected due to previous hints of eccentricity or due to their unusual mass and spin. While other studies found marginal evidence for eccentricity for some of these events, our analyses do not favor the incorporation of eccentricity compared to the quasi-circular case. While lacking the eccentric evidence of other analyses, we find our analyses marginally shifts the posterior in multiple parameters for several events when allowing eccentricity to be non-zero. |
2307.02338 | Jia-Hui Huang | Kai-Peng Lu, Wenbin Li and Jia-Hui Huang | Quasinormal modes and stability of higher dimensional rotating black
holes under massive scalar perturbations | 11 pages,9 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We consider the stability of six-dimensional singly rotating Myers-Perry
black holes under massive scalar perturbations. Using Leaver's continued
fraction method, we compute the quasinormal modes of the massive scalar fields.
All modes found are damped under the quasinormal boundary conditions. It is
also found that long-living modes called quasiresonances exist for large scalar
masses as in the four-dimensional Kerr black hole case. Our numerical results
provide a direct and complement evidence for the stability of six-dimensional
MP black holes under massive scalar perturbation.
| [
{
"created": "Wed, 5 Jul 2023 14:48:24 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Jul 2023 00:19:00 GMT",
"version": "v2"
}
] | 2023-07-11 | [
[
"Lu",
"Kai-Peng",
""
],
[
"Li",
"Wenbin",
""
],
[
"Huang",
"Jia-Hui",
""
]
] | We consider the stability of six-dimensional singly rotating Myers-Perry black holes under massive scalar perturbations. Using Leaver's continued fraction method, we compute the quasinormal modes of the massive scalar fields. All modes found are damped under the quasinormal boundary conditions. It is also found that long-living modes called quasiresonances exist for large scalar masses as in the four-dimensional Kerr black hole case. Our numerical results provide a direct and complement evidence for the stability of six-dimensional MP black holes under massive scalar perturbation. |
0801.1554 | S Habib Mazharimousavi | S. Habib Mazharimousavi and M. Halilsoy | Einstein-Yang-Mills black hole solution in higher dimensions by the
Wu-Yang Ansatz | 10 pages, 5 figures | Phys.Lett.B659:471,2008 | 10.1016/j.physletb.2007.11.006 | null | gr-qc | null | By employing the higher dimensional version of the Wu-Yang Ansatz we obtain
black hole solutions in the spherically symmetric Einstein-Yang-Mills (EYM)
theory. Although these solutions were found recently by other means, our method
provides an alternative way in which one identifies the contribution from the
Yang-Mills (YM) charge. Our method has the advantage to be carried out
analytically as well. We discuss some interesting features of the black hole
solutions obtained.
| [
{
"created": "Thu, 10 Jan 2008 08:05:44 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Jan 2008 14:12:08 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Halilsoy",
"M.",
""
]
] | By employing the higher dimensional version of the Wu-Yang Ansatz we obtain black hole solutions in the spherically symmetric Einstein-Yang-Mills (EYM) theory. Although these solutions were found recently by other means, our method provides an alternative way in which one identifies the contribution from the Yang-Mills (YM) charge. Our method has the advantage to be carried out analytically as well. We discuss some interesting features of the black hole solutions obtained. |
1708.00987 | Aharon Davidson | Aharon Davidson | Hydrogen-like Spectrum of Spontaneously Created Brane Universes with
deSitter Ground State | 5 PRL style pages, 4 figures | Phys. Lett. B780, 29 (2018) | 10.1016/j.physletb.2018.01.044 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Unification of Randall-Sundrum and Regge-Teitelboim brane cosmologies gives
birth to a serendipitous Higgs-deSitter interplay. A localized
Dvali-Gabadadze-Porrati scalar field, governed by a particular (analytically
derived) double-well quartic potential, becomes a mandatory ingredient for
supporting a deSitter brane universe. When upgraded to a general Higgs
potential, the brane surface tension gets quantized, resembling a Hydrogen atom
spectrum, with deSitter universe serving as the ground state. This reflects the
local/global structure of the Euclidean manifold: From finite energy density
no-boundary initial conditions, via a novel acceleration divide filter, to
exact matching conditions at the exclusive nucleation point. Imaginary time
periodicity comes as a bonus, with the associated Hawking temperature vanishing
at the continuum limit. Upon spontaneous creation, while a finite number of
levels describe universes dominated by a residual dark energy combined with
damped matter oscillations, an infinite tower of excited levels undergo a Big
Crunch.
| [
{
"created": "Thu, 3 Aug 2017 03:40:48 GMT",
"version": "v1"
}
] | 2018-03-05 | [
[
"Davidson",
"Aharon",
""
]
] | Unification of Randall-Sundrum and Regge-Teitelboim brane cosmologies gives birth to a serendipitous Higgs-deSitter interplay. A localized Dvali-Gabadadze-Porrati scalar field, governed by a particular (analytically derived) double-well quartic potential, becomes a mandatory ingredient for supporting a deSitter brane universe. When upgraded to a general Higgs potential, the brane surface tension gets quantized, resembling a Hydrogen atom spectrum, with deSitter universe serving as the ground state. This reflects the local/global structure of the Euclidean manifold: From finite energy density no-boundary initial conditions, via a novel acceleration divide filter, to exact matching conditions at the exclusive nucleation point. Imaginary time periodicity comes as a bonus, with the associated Hawking temperature vanishing at the continuum limit. Upon spontaneous creation, while a finite number of levels describe universes dominated by a residual dark energy combined with damped matter oscillations, an infinite tower of excited levels undergo a Big Crunch. |
2012.10248 | Alessio Marrani | Piero Truini, Alessio Marrani, Michael Rios, Klee Irwin | Space, Matter and Interactions in a Quantum Early Universe. Part II :
Superalgebras and Vertex Algebras | 1+14 pages, 5 figures | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In our investigation on quantum gravity, we introduce an infinite dimensional
complex Lie algebra $\textbf{${\mathfrak g}_{\mathsf u}$}$ that extends
$\mathbf{e_9}$. It is defined through a symmetric Cartan matrix of a rank 12
Borcherds algebra. We turn $\textbf{${\mathfrak g}_{\mathsf u}$}$ into a Lie
superalgebra $\textbf{$\mathfrak {sg}_{\mathsf u}$}$ with no superpartners, in
order to comply with the Pauli exclusion principle. There is a natural action
of the Poincar\'e group on $\textbf{$\mathfrak {sg}_{\mathsf u}$}$, which is an
automorphism in the massive sector. We introduce a mechanism for scattering
that includes decays as particular {\it resonant scattering}. Finally, we
complete the model by merging the local $\textbf{$\mathfrak {sg}_{\mathsf u}$}$
into a vertex-type algebra.
| [
{
"created": "Fri, 18 Dec 2020 14:01:11 GMT",
"version": "v1"
}
] | 2020-12-21 | [
[
"Truini",
"Piero",
""
],
[
"Marrani",
"Alessio",
""
],
[
"Rios",
"Michael",
""
],
[
"Irwin",
"Klee",
""
]
] | In our investigation on quantum gravity, we introduce an infinite dimensional complex Lie algebra $\textbf{${\mathfrak g}_{\mathsf u}$}$ that extends $\mathbf{e_9}$. It is defined through a symmetric Cartan matrix of a rank 12 Borcherds algebra. We turn $\textbf{${\mathfrak g}_{\mathsf u}$}$ into a Lie superalgebra $\textbf{$\mathfrak {sg}_{\mathsf u}$}$ with no superpartners, in order to comply with the Pauli exclusion principle. There is a natural action of the Poincar\'e group on $\textbf{$\mathfrak {sg}_{\mathsf u}$}$, which is an automorphism in the massive sector. We introduce a mechanism for scattering that includes decays as particular {\it resonant scattering}. Finally, we complete the model by merging the local $\textbf{$\mathfrak {sg}_{\mathsf u}$}$ into a vertex-type algebra. |
1912.10826 | Jie Jiang | Jie Jiang | Static charged Gauss-Bonnet black holes cannot be overcharged by the new
version of gedanken experiments | 6 pages. This paper has been published in PLB | null | 10.1016/j.physletb.2020.135365 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on the new version of the gedanken experiments proposed by Sorce and
Wald, we examine the weak cosmic censorship conjecture (WCCC) under the
spherically charged infalling matter collision process in the static charged
Gauss-Bonnet black holes. After considering the null energy condition and
assuming the stability condition, we derive the perturbation inequality of the
matter source. As a result, we find that the static charged Gauss-Bonnet black
holes cannot be overcharged under the second-order approximation of the
perturbation when the null energy condition is taken into account, although
they can be destroyed in the old version of gedanken experiments. Our result
shows that the WCCC holds for the above collision process in the
Einstein-Maxwell-Gauss-Bonnet gravity and indicates that WCCC may also be valid
in the higher curvature gravitational theories.
| [
{
"created": "Tue, 17 Dec 2019 23:48:37 GMT",
"version": "v1"
},
{
"created": "Sat, 14 Mar 2020 01:44:53 GMT",
"version": "v2"
}
] | 2020-03-17 | [
[
"Jiang",
"Jie",
""
]
] | Based on the new version of the gedanken experiments proposed by Sorce and Wald, we examine the weak cosmic censorship conjecture (WCCC) under the spherically charged infalling matter collision process in the static charged Gauss-Bonnet black holes. After considering the null energy condition and assuming the stability condition, we derive the perturbation inequality of the matter source. As a result, we find that the static charged Gauss-Bonnet black holes cannot be overcharged under the second-order approximation of the perturbation when the null energy condition is taken into account, although they can be destroyed in the old version of gedanken experiments. Our result shows that the WCCC holds for the above collision process in the Einstein-Maxwell-Gauss-Bonnet gravity and indicates that WCCC may also be valid in the higher curvature gravitational theories. |
2401.17589 | Zheng-Wen Long | Meng-Yao Zhang, Hao Chen, Hassan Hassanabadi, Zheng-Wen Long, and Hui
Yang | Critical behavior and Joule-Thomson expansion of charged AdS black holes
surrounded by exotic fluid with modified Chaplygin equation of state | 11 pages,8 figures | Chinese Physics C (2024) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By considering the concept of a unified single fluid model, referred to as
the modified Chaplygin gas (MCG), which amalgamates dark energy and dark
matter. In this study, we explore the thermodynamic characteristics of charged
anti-de Sitter (AdS) black holes existing in an unconventional fluid
accompanied by MCG. To accomplish this objective, we derive the equations of
state by regarding the charge $Q^{2}$ as a thermodynamic variable. The impact
of MCG parameters on the critical thermodynamic quantities ($\psi_{c}$,
$T_{c}$, $Q_{c}^{2}$) are examined, followed by a detailed analysis of the
$Q^{2}-\psi$ diagram. To provide a clearer explanation of the phase transition,
we present an analysis of the Gibbs free energy. It is important to note that
if the Hawking temperature exceeds the critical temperature, there is a
distinct pattern observed known as swallowtail behavior. This indicates that
the system undergoes a first-order phase transition from a smaller black hole
to a larger one. The critical exponent of the system is found to be in complete
agreement with that of the van der Waals fluid system. Furthermore, we
investigate the impact of MCG parameters and black hole charge on the
Joule-Thomson (J-T) expansion in the extended phase space. The J-T coefficient
is examined to pinpoint the exact region experiencing cooling or heating, the
observation reveals that the presence of negative heat capacity results in the
occurrence of a cooling process. In addition, it is worth noting that the
certain parameters exert a significant influence on the ratio
$\frac{T_{min}}{T_{c}}$. The parameters $\gamma$ and $\beta$ have a
non-negligible effect on the isenthalpy curve.
| [
{
"created": "Wed, 31 Jan 2024 04:27:20 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Mar 2024 03:03:51 GMT",
"version": "v2"
}
] | 2024-03-13 | [
[
"Zhang",
"Meng-Yao",
""
],
[
"Chen",
"Hao",
""
],
[
"Hassanabadi",
"Hassan",
""
],
[
"Long",
"Zheng-Wen",
""
],
[
"Yang",
"Hui",
""
]
] | By considering the concept of a unified single fluid model, referred to as the modified Chaplygin gas (MCG), which amalgamates dark energy and dark matter. In this study, we explore the thermodynamic characteristics of charged anti-de Sitter (AdS) black holes existing in an unconventional fluid accompanied by MCG. To accomplish this objective, we derive the equations of state by regarding the charge $Q^{2}$ as a thermodynamic variable. The impact of MCG parameters on the critical thermodynamic quantities ($\psi_{c}$, $T_{c}$, $Q_{c}^{2}$) are examined, followed by a detailed analysis of the $Q^{2}-\psi$ diagram. To provide a clearer explanation of the phase transition, we present an analysis of the Gibbs free energy. It is important to note that if the Hawking temperature exceeds the critical temperature, there is a distinct pattern observed known as swallowtail behavior. This indicates that the system undergoes a first-order phase transition from a smaller black hole to a larger one. The critical exponent of the system is found to be in complete agreement with that of the van der Waals fluid system. Furthermore, we investigate the impact of MCG parameters and black hole charge on the Joule-Thomson (J-T) expansion in the extended phase space. The J-T coefficient is examined to pinpoint the exact region experiencing cooling or heating, the observation reveals that the presence of negative heat capacity results in the occurrence of a cooling process. In addition, it is worth noting that the certain parameters exert a significant influence on the ratio $\frac{T_{min}}{T_{c}}$. The parameters $\gamma$ and $\beta$ have a non-negligible effect on the isenthalpy curve. |
0809.2328 | Yurij Baryshev | Yu. V. Baryshev (Astron.Inst.St.-Petersburg Univ.) | New Possibilities for Observational Distinction Between Geometrical and
Field Gravity Theories | 13 pages, Proceedings of the International conference "Problems of
Practical Cosmology", 23-27 June 2008, St.-Petersburg, Russia, see
http://ppc08.astro.spbu.ru/text_proc.html | PracticalCosmology.1:276-286,2008 | null | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Crucial observational tests of gravity physics are reviewed. Such tests are
able to clarify the key question on the nature of gravitational interaction: is
gravity the curvature of space? or is gravity a matter field in Minkowski flat
space as other physical forces? Up to now all actually performed experiments do
not allow to distinguish between these two alternatives in gravity physics. The
existence of well-defined positive energy-momentum of the gravity field in
Poincare-Feynman approach leads to radical changes in gravity physics and
cosmology which may be tested by laboratory experiments and astrophysical
observations. New possibilities for observational distinction between
geometrical general relativity and field gravity theories are discussed. Among
them: the contribution of the scalar repulsive force into Newtonian
gravitational interaction, post-Newtonian translational motion of rotating
bodies, gravitational deflection of light by small mass bodies, scalar
gravitational radiation from spherically pulsating stars, existence of limiting
radius, surface, magnetic field for massive bodies and absence of singularities
and horizons for relativistic compact objects.
| [
{
"created": "Sat, 13 Sep 2008 09:47:47 GMT",
"version": "v1"
}
] | 2008-11-07 | [
[
"Baryshev",
"Yu. V.",
"",
"Astron.Inst.St.-Petersburg Univ."
]
] | Crucial observational tests of gravity physics are reviewed. Such tests are able to clarify the key question on the nature of gravitational interaction: is gravity the curvature of space? or is gravity a matter field in Minkowski flat space as other physical forces? Up to now all actually performed experiments do not allow to distinguish between these two alternatives in gravity physics. The existence of well-defined positive energy-momentum of the gravity field in Poincare-Feynman approach leads to radical changes in gravity physics and cosmology which may be tested by laboratory experiments and astrophysical observations. New possibilities for observational distinction between geometrical general relativity and field gravity theories are discussed. Among them: the contribution of the scalar repulsive force into Newtonian gravitational interaction, post-Newtonian translational motion of rotating bodies, gravitational deflection of light by small mass bodies, scalar gravitational radiation from spherically pulsating stars, existence of limiting radius, surface, magnetic field for massive bodies and absence of singularities and horizons for relativistic compact objects. |
1510.05604 | Shahar Hod | Shahar Hod | On the branching of the quasinormal resonances of near-extremal Kerr
black holes | 3 pages | The European Physical Journal C 75, 520 (2015) | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has recently been shown by Yang. et. al. [Phys. Rev. D {\bf 87}, 041502(R)
(2013)] that rotating Kerr black holes are characterized by two distinct sets
of quasinormal resonances. These two families of quasinormal resonances display
qualitatively different asymptotic behaviors in the extremal ($a/M\to 1$)
black-hole limit: The zero-damping modes (ZDMs) are characterized by relaxation
times which tend to infinity in the extremal black-hole limit ($\Im\omega\to 0$
as $a/M\to 1$), whereas the damped modes (DMs) are characterized by non-zero
damping rates ($\Im\omega\to$ finite-values as $a/M\to 1$). In this paper we
refute the claim made by Yang et. al. that co-rotating DMs of near-extremal
black holes are restricted to the limited range $0\leq
\mu\lesssim\mu_{\text{c}}\approx 0.74$, where $\mu\equiv m/l$ is the
dimensionless ratio between the azimuthal harmonic index $m$ and the spheroidal
harmonic index $l$ of the perturbation mode. In particular, we use an
analytical formula originally derived by Detweiler in order to prove the
existence of DMs (damped quasinormal resonances which are characterized by
finite $\Im\omega$ values in the $a/M\to 1$ limit) of near-extremal black holes
in the $\mu>\mu_{\text{c}}$ regime, the regime which was claimed by Yang et.
al. not to contain damped modes. We show that these co-rotating DMs (in the
regime $\mu>\mu_{\text{c}}$) are expected to characterize the resonance spectra
of rapidly-rotating (near-extremal) black holes with $a/M\gtrsim 1-10^{-9}$.
| [
{
"created": "Mon, 19 Oct 2015 18:04:47 GMT",
"version": "v1"
}
] | 2016-01-26 | [
[
"Hod",
"Shahar",
""
]
] | It has recently been shown by Yang. et. al. [Phys. Rev. D {\bf 87}, 041502(R) (2013)] that rotating Kerr black holes are characterized by two distinct sets of quasinormal resonances. These two families of quasinormal resonances display qualitatively different asymptotic behaviors in the extremal ($a/M\to 1$) black-hole limit: The zero-damping modes (ZDMs) are characterized by relaxation times which tend to infinity in the extremal black-hole limit ($\Im\omega\to 0$ as $a/M\to 1$), whereas the damped modes (DMs) are characterized by non-zero damping rates ($\Im\omega\to$ finite-values as $a/M\to 1$). In this paper we refute the claim made by Yang et. al. that co-rotating DMs of near-extremal black holes are restricted to the limited range $0\leq \mu\lesssim\mu_{\text{c}}\approx 0.74$, where $\mu\equiv m/l$ is the dimensionless ratio between the azimuthal harmonic index $m$ and the spheroidal harmonic index $l$ of the perturbation mode. In particular, we use an analytical formula originally derived by Detweiler in order to prove the existence of DMs (damped quasinormal resonances which are characterized by finite $\Im\omega$ values in the $a/M\to 1$ limit) of near-extremal black holes in the $\mu>\mu_{\text{c}}$ regime, the regime which was claimed by Yang et. al. not to contain damped modes. We show that these co-rotating DMs (in the regime $\mu>\mu_{\text{c}}$) are expected to characterize the resonance spectra of rapidly-rotating (near-extremal) black holes with $a/M\gtrsim 1-10^{-9}$. |
2206.08200 | Antonio Ferreiro | Antonio Ferreiro and Silvia Pla | Adiabatic regularization and preferred vacuum state for the $\lambda
\phi^4$ field theory in cosmological spacetimes | null | null | 10.1103/PhysRevD.106.065015 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We extend the method of adiabatic regularization by introducing an arbitrary
parameter $\mu$ for a scalar field with quartic self-coupling in a
Friedmann-Lema\^itre-Robertson-Walker (FLRW) spacetime at one-loop order. The
subtraction terms constructed from this extended version allow us to define a
preferred vacuum state at a fixed time $\eta = \eta_0$ for this theory. We
compute this vacuum state for two commonly used background fields in cosmology.
We also give a possible prescription for an adequate value for $\mu$.
| [
{
"created": "Thu, 16 Jun 2022 14:14:41 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Apr 2023 08:52:24 GMT",
"version": "v2"
}
] | 2023-04-21 | [
[
"Ferreiro",
"Antonio",
""
],
[
"Pla",
"Silvia",
""
]
] | We extend the method of adiabatic regularization by introducing an arbitrary parameter $\mu$ for a scalar field with quartic self-coupling in a Friedmann-Lema\^itre-Robertson-Walker (FLRW) spacetime at one-loop order. The subtraction terms constructed from this extended version allow us to define a preferred vacuum state at a fixed time $\eta = \eta_0$ for this theory. We compute this vacuum state for two commonly used background fields in cosmology. We also give a possible prescription for an adequate value for $\mu$. |
gr-qc/9804045 | Benjamin C. Harms | R. Casadio and B. Harms | Perturbations in the Kerr-Newman Dilatonic Black Hole Background:
Maxwell Waves, the Dilaton Background and Gravitational Lensing | 9 pages, 1 figure | Phys.Rev. D58 (1998) 044015 | 10.1103/PhysRevD.58.044015 | UAHEP 979 | gr-qc hep-th | null | In this paper we continue the analysis of our previous papers and study the
affect of the existence of a non-trivial dilaton background on the propagation
of electromagnetic waves in the Kerr-Newman dilatonic black hole space-time.
For this purpose we again employ the double expansion in both the background
electric charge and the wave parameters of the relevant quantities in the
Newman-Penrose formalism and then identify the first order at which the dilaton
background enters the Maxwell equations. We then assume that gravitational and
dilatonic waves are negligible (at that order in the charge parameter) with
respect to electromagnetic waves and argue that this condition is consistent
with the solutions already found in the previous paper. Explicit expressions
are given for the asymptotic behavior of scattered waves, and a simple physical
model is proposed in order to test the effects. An expression for the relative
intensity is obtained for Reissner-Nordstrom dilaton black holes using
geometrical optics. A comparison with the approximation of geometrical optics
for Kerr-Newman dilaton black holes shows that at the order to which the
calculations are carried out gravitational lensing of optical images cannot
probe the dilaton background.
| [
{
"created": "Mon, 20 Apr 1998 21:48:20 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Casadio",
"R.",
""
],
[
"Harms",
"B.",
""
]
] | In this paper we continue the analysis of our previous papers and study the affect of the existence of a non-trivial dilaton background on the propagation of electromagnetic waves in the Kerr-Newman dilatonic black hole space-time. For this purpose we again employ the double expansion in both the background electric charge and the wave parameters of the relevant quantities in the Newman-Penrose formalism and then identify the first order at which the dilaton background enters the Maxwell equations. We then assume that gravitational and dilatonic waves are negligible (at that order in the charge parameter) with respect to electromagnetic waves and argue that this condition is consistent with the solutions already found in the previous paper. Explicit expressions are given for the asymptotic behavior of scattered waves, and a simple physical model is proposed in order to test the effects. An expression for the relative intensity is obtained for Reissner-Nordstrom dilaton black holes using geometrical optics. A comparison with the approximation of geometrical optics for Kerr-Newman dilaton black holes shows that at the order to which the calculations are carried out gravitational lensing of optical images cannot probe the dilaton background. |
0801.0905 | Haiqing Zhang | Chao-Guang Huang, Hai-Qing Zhang, Han-Ying Guo | Cosmological Solutions with Torsion in a Model of de Sitter Gauge Theory
of Gravity | 16 pages, 2 figures | JCAP 0810:010,2008 | 10.1088/1475-7516/2008/10/010 | null | gr-qc | null | The torsion is shown to be vitally important in the explanation of the
evolution of the universe in a large class of gravitational theories containing
quadratic terms of curvature and torsion. The cosmological solutions with
homogeneous and isotropic torsion in a model of de Sitter gauge theory of
gravity are presented, which may explain the observation data for SN Ia when
parameters are suitably chosen and supply a natural transit from decelerating
expansion to accelerating expansion without the help of the introduction of
other strange fields in the theory.
| [
{
"created": "Mon, 7 Jan 2008 05:34:48 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Huang",
"Chao-Guang",
""
],
[
"Zhang",
"Hai-Qing",
""
],
[
"Guo",
"Han-Ying",
""
]
] | The torsion is shown to be vitally important in the explanation of the evolution of the universe in a large class of gravitational theories containing quadratic terms of curvature and torsion. The cosmological solutions with homogeneous and isotropic torsion in a model of de Sitter gauge theory of gravity are presented, which may explain the observation data for SN Ia when parameters are suitably chosen and supply a natural transit from decelerating expansion to accelerating expansion without the help of the introduction of other strange fields in the theory. |
2103.04435 | Patrick Bourg | Carsten Gundlach, Patrick Bourg and Alex Davey | Fully constrained, high-resolution shock-capturing, formulation of the
Einstein-fluid equations in $2+1$ dimensions | 23 pages, 17 figures, Typos corrected. This version has been accepted
by PRD | Phys. Rev. D 104, 024061 (2021) | 10.1103/PhysRevD.104.024061 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Four components of the axisymmetric Einstein equations in 2+1 dimensions with
negative cosmological constant can be written as $\nabla_aM=\dots$ and
$\nabla_aJ=\dots$, where the dots stand for stress-energy terms, and $M$ and
$J$ are scalars. In vacuum, they reduce to the constant mass and angular
momentum parameters of the BTZ solution of the same name. The integrability
conditions for the Einstein equations give rise to two conserved stress-energy
currents $\nabla_aj^a_{(M)}=0$ and $\nabla_aj^a_{(J)}=0$. The angular momentum
current is just the Noether current due to axisymmetry, but the mass current is
unexpected in the presence of rotation. The conserved quantity $M$ exists in
all dimensions in spherical symmetry, known as the Misner-Sharp, Hawking or
Kodama mass, but in 2+1 dimensions $M$ exists also in axisymmetry, even with
rotation. We use $M$ and $J$ to give a fully constrained formulation of the
axisymmetric Einstein equations in 2+1 dimensions, where the Einstein equations
are solved by explicit integration from the center along time slices. We use
the two conserved matter currents in the construction of a high-resolution
shock-capturing formulation of the Einstein-perfect fluid system, in which $M$
and $J$ momentum are then exactly conserved by construction. We demonstrate
convergence of the code in the test cases of generic dispersion and collapse
and stable and unstable rotating stars.
| [
{
"created": "Sun, 7 Mar 2021 19:44:35 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Aug 2021 15:31:56 GMT",
"version": "v2"
}
] | 2021-08-10 | [
[
"Gundlach",
"Carsten",
""
],
[
"Bourg",
"Patrick",
""
],
[
"Davey",
"Alex",
""
]
] | Four components of the axisymmetric Einstein equations in 2+1 dimensions with negative cosmological constant can be written as $\nabla_aM=\dots$ and $\nabla_aJ=\dots$, where the dots stand for stress-energy terms, and $M$ and $J$ are scalars. In vacuum, they reduce to the constant mass and angular momentum parameters of the BTZ solution of the same name. The integrability conditions for the Einstein equations give rise to two conserved stress-energy currents $\nabla_aj^a_{(M)}=0$ and $\nabla_aj^a_{(J)}=0$. The angular momentum current is just the Noether current due to axisymmetry, but the mass current is unexpected in the presence of rotation. The conserved quantity $M$ exists in all dimensions in spherical symmetry, known as the Misner-Sharp, Hawking or Kodama mass, but in 2+1 dimensions $M$ exists also in axisymmetry, even with rotation. We use $M$ and $J$ to give a fully constrained formulation of the axisymmetric Einstein equations in 2+1 dimensions, where the Einstein equations are solved by explicit integration from the center along time slices. We use the two conserved matter currents in the construction of a high-resolution shock-capturing formulation of the Einstein-perfect fluid system, in which $M$ and $J$ momentum are then exactly conserved by construction. We demonstrate convergence of the code in the test cases of generic dispersion and collapse and stable and unstable rotating stars. |
1508.02569 | Scott Robertson | Scott Robertson | The theory of Hawking radiation in laboratory analogues | 87 pages, 20 figures | J. Phys. B: At. Mol. Opt. Phys. 45 163001 (2012) | 10.1088/0953-4075/45/16/163001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hawking radiation, despite being known to theoretical physics for nearly
forty years, remains elusive and undetected. It also suffers, in its original
context of gravitational black holes, from practical and conceptual
difficulties. Of particular note is the trans-Planckian problem, which is
concerned with the apparent origin of the radiation in absurdly high
frequencies. In order to gain better theoretical understanding and, it is
hoped, experimental verification of Hawking radiation, much study is being
devoted to laboratory systems which use moving media to model the spacetime
geometry of black holes, and which, by analogy, are also thought to emit
Hawking radiation. These analogue systems typically exhibit dispersion, which
regularizes the wave behaviour at the horizon at the cost of a more complicated
theoretical framework. This tutorial serves as an introduction to Hawking
radiation and its analogues, developing the moving medium analogy for black
holes and demonstrating how dispersion can be incorporated into this
generalized framework.
| [
{
"created": "Tue, 11 Aug 2015 11:52:31 GMT",
"version": "v1"
}
] | 2015-08-12 | [
[
"Robertson",
"Scott",
""
]
] | Hawking radiation, despite being known to theoretical physics for nearly forty years, remains elusive and undetected. It also suffers, in its original context of gravitational black holes, from practical and conceptual difficulties. Of particular note is the trans-Planckian problem, which is concerned with the apparent origin of the radiation in absurdly high frequencies. In order to gain better theoretical understanding and, it is hoped, experimental verification of Hawking radiation, much study is being devoted to laboratory systems which use moving media to model the spacetime geometry of black holes, and which, by analogy, are also thought to emit Hawking radiation. These analogue systems typically exhibit dispersion, which regularizes the wave behaviour at the horizon at the cost of a more complicated theoretical framework. This tutorial serves as an introduction to Hawking radiation and its analogues, developing the moving medium analogy for black holes and demonstrating how dispersion can be incorporated into this generalized framework. |
2011.02276 | Mubasher Jamil | M. Ghasemi-Nodehi, Mustapha Azreg-A\"inou, Kimet Jusufi, Mubasher
Jamil | Shadow, quasinormal modes and quasiperiodic oscillations of rotating
Kaluza-Klein black holes | 15 pages, 14 captioned figures, to appear in Phys. Rev. D. arXiv
admin note: text overlap with arXiv:2008.08450 | Phys. Rev. D 102, 104032 (2020) | 10.1103/PhysRevD.102.104032 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the shadow of rotating Kaluza-Klein (KK) black holes
and the connection between the shadow radius and the real part of quasi-normal
modes (QNMs) in the eiokonal limit. In addition we have explored the
quasi-periodic oscillations (QPOs) in the rotating KK black hole.
| [
{
"created": "Mon, 2 Nov 2020 07:41:57 GMT",
"version": "v1"
}
] | 2020-11-13 | [
[
"Ghasemi-Nodehi",
"M.",
""
],
[
"Azreg-Aïnou",
"Mustapha",
""
],
[
"Jusufi",
"Kimet",
""
],
[
"Jamil",
"Mubasher",
""
]
] | In this paper we study the shadow of rotating Kaluza-Klein (KK) black holes and the connection between the shadow radius and the real part of quasi-normal modes (QNMs) in the eiokonal limit. In addition we have explored the quasi-periodic oscillations (QPOs) in the rotating KK black hole. |
2404.02435 | Javier Roulet | Javier Roulet, Jonathan Mushkin, Digvijay Wadekar, Tejaswi Venumadhav,
Barak Zackay and Matias Zaldarriaga | Fast marginalization algorithm for optimizing gravitational wave
detection, parameter estimation and sky localization | 19 pages, 7 figures | Phys. Rev. D 110, 044010 (2024) | 10.1103/PhysRevD.110.044010 | null | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce an algorithm to marginalize the likelihood for a gravitational
wave signal from a quasi-circular binary merger over its extrinsic parameters,
accounting for the effects of higher harmonics and spin-induced precession. The
algorithm takes as input the matched-filtering time series of individual
waveform harmonics against the data in all operational detectors, and the
covariances of the harmonics. The outputs are the Gaussian likelihood
marginalized over extrinsic parameters describing the merger time, location and
orientation, along with samples from the conditional posterior of these
parameters. Our algorithm exploits the waveform's known analytical dependence
on extrinsic parameters to efficiently marginalize over them using a single
waveform evaluation. Our current implementation achieves a 10% precision on the
marginalized likelihood within $\approx 50$ ms on a single CPU core and is
publicly available through the package `cogwheel`. We discuss applications of
this tool for gravitational wave searches involving higher modes or precession,
efficient and robust parameter estimation, and generation of sky localization
maps in low latency for electromagnetic followup of gravitational-wave alerts.
The inclusion of higher modes can improve the distance measurement, providing
an advantage over existing low-latency localization methods.
| [
{
"created": "Wed, 3 Apr 2024 03:44:27 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Aug 2024 19:52:10 GMT",
"version": "v2"
}
] | 2024-08-06 | [
[
"Roulet",
"Javier",
""
],
[
"Mushkin",
"Jonathan",
""
],
[
"Wadekar",
"Digvijay",
""
],
[
"Venumadhav",
"Tejaswi",
""
],
[
"Zackay",
"Barak",
""
],
[
"Zaldarriaga",
"Matias",
""
]
] | We introduce an algorithm to marginalize the likelihood for a gravitational wave signal from a quasi-circular binary merger over its extrinsic parameters, accounting for the effects of higher harmonics and spin-induced precession. The algorithm takes as input the matched-filtering time series of individual waveform harmonics against the data in all operational detectors, and the covariances of the harmonics. The outputs are the Gaussian likelihood marginalized over extrinsic parameters describing the merger time, location and orientation, along with samples from the conditional posterior of these parameters. Our algorithm exploits the waveform's known analytical dependence on extrinsic parameters to efficiently marginalize over them using a single waveform evaluation. Our current implementation achieves a 10% precision on the marginalized likelihood within $\approx 50$ ms on a single CPU core and is publicly available through the package `cogwheel`. We discuss applications of this tool for gravitational wave searches involving higher modes or precession, efficient and robust parameter estimation, and generation of sky localization maps in low latency for electromagnetic followup of gravitational-wave alerts. The inclusion of higher modes can improve the distance measurement, providing an advantage over existing low-latency localization methods. |
gr-qc/0406031 | Sujit Chatterjee | A.banerjee and S.Chatterjee | Spherical collapse of a heat conducting fluid in higher dimensions
without horizon | 6 pages | Astrophys.Space Sci. 299 (2005) 219-225 | 10.1007/s10509-005-6849-x | null | gr-qc | null | We consider a scenario where the interior spacetime,described by a heat
conducting fluid sphere is matched to a Vaidya metric in higher
dimensions.Interestingly we get a class of solutions, where following heat
radiation the boundary surface collapses without the appearance of an event
horizon at any stage and this happens with reasonable properties of matter
field.The non-occurrence of a horizon is due to the fact that the rate of mass
loss exactly counterbalanced by the fall of boundary radius.Evidently this
poses a counter example to the so-called cosmic censorship hypothesis.Two
explicit examples of this class of solutions are also given and it is observed
that the rate of collapse is delayed with the introduction of extra
dimensions.The work extends to higher dimensions our previous investigation in
4D.
| [
{
"created": "Tue, 8 Jun 2004 12:35:36 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"banerjee",
"A.",
""
],
[
"Chatterjee",
"S.",
""
]
] | We consider a scenario where the interior spacetime,described by a heat conducting fluid sphere is matched to a Vaidya metric in higher dimensions.Interestingly we get a class of solutions, where following heat radiation the boundary surface collapses without the appearance of an event horizon at any stage and this happens with reasonable properties of matter field.The non-occurrence of a horizon is due to the fact that the rate of mass loss exactly counterbalanced by the fall of boundary radius.Evidently this poses a counter example to the so-called cosmic censorship hypothesis.Two explicit examples of this class of solutions are also given and it is observed that the rate of collapse is delayed with the introduction of extra dimensions.The work extends to higher dimensions our previous investigation in 4D. |
gr-qc/0210083 | Elena Cuoco | G. Cella, E. Cuoco, G.M. Guidi | Adaptive spectral identification techniques in presence of undetected
non linearities | 4 pages, 2 figures, uses ws-procs9x6.cls Proceedings of "Non linear
physics: theory and experiment. II", Gallipoli (Lecce), 2002 | null | 10.1142/9789812704467_0048 | null | gr-qc | null | The standard procedure for detection of gravitational wave coalescing
binaries signals is based on Wiener filtering with an appropriate bank of
template filters. This is the optimal procedure in the hypothesis of addictive
Gaussian and stationary noise. We study the possibility of improving the
detection efficiency with a class of adaptive spectral identification
techniques, analyzing their effect in presence of non stationarities and
undetected non linearities in the noise
| [
{
"created": "Thu, 24 Oct 2002 08:00:37 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Cella",
"G.",
""
],
[
"Cuoco",
"E.",
""
],
[
"Guidi",
"G. M.",
""
]
] | The standard procedure for detection of gravitational wave coalescing binaries signals is based on Wiener filtering with an appropriate bank of template filters. This is the optimal procedure in the hypothesis of addictive Gaussian and stationary noise. We study the possibility of improving the detection efficiency with a class of adaptive spectral identification techniques, analyzing their effect in presence of non stationarities and undetected non linearities in the noise |
1902.03704 | Jos\'e Villanueva | \'Angel Rinc\'on and J.R. Villanueva | The Sagnac effect on a scale-dependent rotating BTZ black hole
background | 6 pages, 5 figures | null | 10.1088/1361-6382/aba17f | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we investigate the Sagnac effect by calculating the difference
in travel time and phase shift observed for photon beams counter--propagating
in a rotating interferometer on a BTZ black hole solution in the context of
scale-dependent gravity, which describes the field around a massive static and
rotating object in $2+1$ gravity.
| [
{
"created": "Mon, 11 Feb 2019 02:30:45 GMT",
"version": "v1"
}
] | 2020-08-26 | [
[
"Rincón",
"Ángel",
""
],
[
"Villanueva",
"J. R.",
""
]
] | In this paper we investigate the Sagnac effect by calculating the difference in travel time and phase shift observed for photon beams counter--propagating in a rotating interferometer on a BTZ black hole solution in the context of scale-dependent gravity, which describes the field around a massive static and rotating object in $2+1$ gravity. |
gr-qc/0302099 | Theodore A. Jacobson | Ted Jacobson and Renaud Parentani | Horizon Entropy | 21 pages, one figure, to appear in a special issue of Foundations of
Physics in honor of Jacob Bekenstein | Found.Phys. 33 (2003) 323-348 | 10.1023/A:1023785123428 | null | gr-qc hep-th | null | Although the laws of thermodynamics are well established for black hole
horizons, much less has been said in the literature to support the extension of
these laws to more general settings such as an asymptotic de Sitter horizon or
a Rindler horizon (the event horizon of an asymptotic uniformly accelerated
observer). In the present paper we review the results that have been previously
established and argue that the laws of black hole thermodynamics, as well as
their underlying statistical mechanical content, extend quite generally to what
we call here "causal horizons". The root of this generalization is the local
notion of horizon entropy density.
| [
{
"created": "Tue, 25 Feb 2003 05:42:47 GMT",
"version": "v1"
}
] | 2022-10-12 | [
[
"Jacobson",
"Ted",
""
],
[
"Parentani",
"Renaud",
""
]
] | Although the laws of thermodynamics are well established for black hole horizons, much less has been said in the literature to support the extension of these laws to more general settings such as an asymptotic de Sitter horizon or a Rindler horizon (the event horizon of an asymptotic uniformly accelerated observer). In the present paper we review the results that have been previously established and argue that the laws of black hole thermodynamics, as well as their underlying statistical mechanical content, extend quite generally to what we call here "causal horizons". The root of this generalization is the local notion of horizon entropy density. |
gr-qc/0011083 | Shijun Yoshida | Toshifumi Futamase, Shijun Yoshida | Possible measurement of Quintessence and density parameter using strong
gravitational lensing events | 5 pages, 1 figure, accepted for publication in Progress of
Theoretical Physics | null | 10.1143/PTP.105.887 | null | gr-qc astro-ph | null | We propose a possible measurement of the time variability of the vacuum
energy using strong gravitational lensing events. As an example we take an
Einstein cross lens HST 14176+5226 and demonstrate that the measurement of the
velocity dispersion with the accuracy of $\pm$ 5 km/sec will have a chance to
determine the time dependence of the vacuum energy as well as the density
parameter with the accuracy of order 0.1 if one fixes the lens model.
| [
{
"created": "Thu, 23 Nov 2000 12:37:59 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Mar 2001 05:12:34 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Futamase",
"Toshifumi",
""
],
[
"Yoshida",
"Shijun",
""
]
] | We propose a possible measurement of the time variability of the vacuum energy using strong gravitational lensing events. As an example we take an Einstein cross lens HST 14176+5226 and demonstrate that the measurement of the velocity dispersion with the accuracy of $\pm$ 5 km/sec will have a chance to determine the time dependence of the vacuum energy as well as the density parameter with the accuracy of order 0.1 if one fixes the lens model. |
0809.3547 | Jorge Ovalle | J Ovalle | Non-uniform Braneworld Stars: an Exact Solution | 22 pages, 3 figures, version to be published in International Journal
of Modern Physics D (IJMPD) | Int.J.Mod.Phys.D18:837-852,2009 | 10.1142/S0218271809014790 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The first exact interior solution to Einstein's field equations for a static
and non-uniform braneworld star with local and non-local bulk terms is
presented. It is shown that the bulk Weyl scalar ${\cal U}(r)$ is always
negative inside the stellar distribution, in consequence it reduces both the
effective density and the effective pressure. It is found that the anisotropy
generated by bulk gravity effect has an acceptable physical behaviour inside
the distribution. Using a Reissner-N\"{o}rdstrom-like exterior solution, the
effects of bulk gravity on pressure and density are found through matching
conditions.
| [
{
"created": "Sun, 21 Sep 2008 02:40:49 GMT",
"version": "v1"
}
] | 2009-07-22 | [
[
"Ovalle",
"J",
""
]
] | The first exact interior solution to Einstein's field equations for a static and non-uniform braneworld star with local and non-local bulk terms is presented. It is shown that the bulk Weyl scalar ${\cal U}(r)$ is always negative inside the stellar distribution, in consequence it reduces both the effective density and the effective pressure. It is found that the anisotropy generated by bulk gravity effect has an acceptable physical behaviour inside the distribution. Using a Reissner-N\"{o}rdstrom-like exterior solution, the effects of bulk gravity on pressure and density are found through matching conditions. |
2301.11052 | Parth Bambhaniya | Vishva Patel, Kauntey Acharya, Parth Bambhaniya and Pankaj S. Joshi | Energy extraction from Janis-Newman-Winicour naked singularity | 11 pages, 18 figures | null | 10.1103/PhysRevD.107.064036 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In general, energy extraction methods such as the Penrose process and the
magnetic Penrose process are thought to be reliant on the existence of an
ergoregion. Inside an ergoregion, there are negative energy states that allow a
particle to extract energy and escape to an observer at infinity. In this
paper, we considered the electromagnetic field in the rotating
Janis-Newman-Winicour (JNW) spacetime. This concept is feasible because an
accretion disc forms an electromagnetic field around compact objects. After
that, we briefly examine negative energy orbits and their significance in
energy extraction. The ergoregion is absent in a rotating JNW geometry, but we
show that the effective ergoregion is there. The change in a negative energy
orbit concerning the magnetic field (B), spin parameter (a), and electric
charge (Q) is analyzed. We find that the total energy extraction efficiency
within this process can be around $60\%$ for the rotating JNW naked
singularity.
| [
{
"created": "Thu, 26 Jan 2023 11:56:59 GMT",
"version": "v1"
}
] | 2023-03-29 | [
[
"Patel",
"Vishva",
""
],
[
"Acharya",
"Kauntey",
""
],
[
"Bambhaniya",
"Parth",
""
],
[
"Joshi",
"Pankaj S.",
""
]
] | In general, energy extraction methods such as the Penrose process and the magnetic Penrose process are thought to be reliant on the existence of an ergoregion. Inside an ergoregion, there are negative energy states that allow a particle to extract energy and escape to an observer at infinity. In this paper, we considered the electromagnetic field in the rotating Janis-Newman-Winicour (JNW) spacetime. This concept is feasible because an accretion disc forms an electromagnetic field around compact objects. After that, we briefly examine negative energy orbits and their significance in energy extraction. The ergoregion is absent in a rotating JNW geometry, but we show that the effective ergoregion is there. The change in a negative energy orbit concerning the magnetic field (B), spin parameter (a), and electric charge (Q) is analyzed. We find that the total energy extraction efficiency within this process can be around $60\%$ for the rotating JNW naked singularity. |
gr-qc/0503095 | Elizabeth Winstanley | Eugen Radu and Elizabeth Winstanley | Conformally coupled scalar solitons and black holes with negative
cosmological constant | 18 pages, 10 figures, minor changes, accepted for publication in
Phys. Rev. D | Phys.Rev. D72 (2005) 024017 | 10.1103/PhysRevD.72.024017 | null | gr-qc hep-th | null | We present arguments for the existence of both globally regular and black
hole solutions of the Einstein equations with a conformally coupled scalar
field, in the presence of a negative cosmological constant, for space-time
dimensions greater than or equal to four. These configurations approach
asymptotically anti-de Sitter spacetime and are indexed by the central value of
the scalar field. We also study the stability of these solutions, and show
that, at least for all the solutions studied numerically, they are linearly
stable.
| [
{
"created": "Tue, 22 Mar 2005 19:35:36 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Jul 2005 11:27:11 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Radu",
"Eugen",
""
],
[
"Winstanley",
"Elizabeth",
""
]
] | We present arguments for the existence of both globally regular and black hole solutions of the Einstein equations with a conformally coupled scalar field, in the presence of a negative cosmological constant, for space-time dimensions greater than or equal to four. These configurations approach asymptotically anti-de Sitter spacetime and are indexed by the central value of the scalar field. We also study the stability of these solutions, and show that, at least for all the solutions studied numerically, they are linearly stable. |
gr-qc/9612024 | Stefano Liberati | F. Belgiorno and S. Liberati | Black Hole Thermodynamics, Casimir Effect and Induced Gravity | 7 pages, RevTex | Gen.Rel.Grav. 29 (1997) 1181-1194 | 10.1023/A:1018895226085 | SISSA-178/96/A | gr-qc hep-th | null | An analogy between the subtraction procedure in the Gibbons-Hawking Euclidean
path integral approach to Horizon's Thermodynamics and the Casimir effect is
shown. Then a conjecture about a possible Casimir nature of the Gibbons-Hawking
subtraction is made in the framework of Sakharov's induced gravity. In this
framework it appears that the degrees of freedom involved in the
Bekenstein-Hawking entropy are naturally identified with zero--point modes of
the matter fields. Some consequences of this view are sketched.
| [
{
"created": "Wed, 11 Dec 1996 09:47:27 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Belgiorno",
"F.",
""
],
[
"Liberati",
"S.",
""
]
] | An analogy between the subtraction procedure in the Gibbons-Hawking Euclidean path integral approach to Horizon's Thermodynamics and the Casimir effect is shown. Then a conjecture about a possible Casimir nature of the Gibbons-Hawking subtraction is made in the framework of Sakharov's induced gravity. In this framework it appears that the degrees of freedom involved in the Bekenstein-Hawking entropy are naturally identified with zero--point modes of the matter fields. Some consequences of this view are sketched. |
gr-qc/0309054 | Giovanni Amelino-Camelia | Giovanni Amelino-Camelia | The three perspectives on the quantum-gravity problem and their
implications for the fate of Lorentz symmetry | 48 pages, LaTex. Based on invited seminars given at "Perspectives on
Quantum Gravity: a tribute to John Stachel" (Boston, March 6-7, 2003) and
"Tenth Marcel Grossmann Meeting on General Relativity" (Rio de Janeiro, July
20-26, 2003) | null | null | null | gr-qc hep-ph hep-th | null | Each approach to the quantum-gravity problem originates from expertise in one
or another area of theoretical physics. The particle-physics perspective
encourages one to attempt to reproduce in quantum gravity as much as possible
of the successes of the Standard Model of particle physics, and therefore, as
done in String Theory, the core features of quantum gravity are described in
terms of graviton-like exchange in a background classical spacetime. From the
general-relativity perspective it is natural to renounce to any reference to a
background spacetime, and to describe spacetime in a way that takes into
account the in-principle limitations of measurements. The Loop Quantum Gravity
approach and the approaches based on noncommutative geometry originate from
this general-relativity perspective. The condensed-matter perspective, which
has been adopted in a few recent quantum-gravity proposals, naturally leads to
scenarios in which some familiar properties of spacetime are only emergent,
just like, for example, some emergent collective degrees of freedom are
relevant to the description of certain physical systems only near a critical
point. Both from the general-relativity perspective and from the
condensed-matter perspective it is natural to explore the possibility that
quantum gravity might have significant implications for the fate of Lorentz
symmetry in the Planckian regime. From the particle-physics perspective there
is instead no obvious reason to renounce to exact Lorentz symmetry, although
(``spontaneous'') Lorentz symmetry breaking is of course possible. A
fast-growing phenomenological programme looking for Planck-scale departures
from Lorentz symmetry can contribute to this ongoing debate.
| [
{
"created": "Tue, 9 Sep 2003 17:58:17 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Amelino-Camelia",
"Giovanni",
""
]
] | Each approach to the quantum-gravity problem originates from expertise in one or another area of theoretical physics. The particle-physics perspective encourages one to attempt to reproduce in quantum gravity as much as possible of the successes of the Standard Model of particle physics, and therefore, as done in String Theory, the core features of quantum gravity are described in terms of graviton-like exchange in a background classical spacetime. From the general-relativity perspective it is natural to renounce to any reference to a background spacetime, and to describe spacetime in a way that takes into account the in-principle limitations of measurements. The Loop Quantum Gravity approach and the approaches based on noncommutative geometry originate from this general-relativity perspective. The condensed-matter perspective, which has been adopted in a few recent quantum-gravity proposals, naturally leads to scenarios in which some familiar properties of spacetime are only emergent, just like, for example, some emergent collective degrees of freedom are relevant to the description of certain physical systems only near a critical point. Both from the general-relativity perspective and from the condensed-matter perspective it is natural to explore the possibility that quantum gravity might have significant implications for the fate of Lorentz symmetry in the Planckian regime. From the particle-physics perspective there is instead no obvious reason to renounce to exact Lorentz symmetry, although (``spontaneous'') Lorentz symmetry breaking is of course possible. A fast-growing phenomenological programme looking for Planck-scale departures from Lorentz symmetry can contribute to this ongoing debate. |
1305.2875 | Frans Klinkhamer | F.R. Klinkhamer | Black-hole solution without curvature singularity and closed timelike
curves | 10 pages; v6: published version | Acta Phys. Pol. B 45, 5 (2014) | 10.5506/APhysPolB.45.5 | KA-TP-11-2013 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | With a prescribed Coulomb-type energy-momentum tensor, an exact solution of
the Einstein field equations over a nonsimply-connected manifold is presented.
This spherically symmetric solution has neither curvature singularities nor
closed timelike curves. It can be considered to be a regularization of the
singular Reissner-Nordstrom solution over a simply-connected manifold.
| [
{
"created": "Mon, 13 May 2013 17:58:24 GMT",
"version": "v1"
},
{
"created": "Thu, 30 May 2013 18:53:06 GMT",
"version": "v2"
},
{
"created": "Fri, 19 Jul 2013 12:55:56 GMT",
"version": "v3"
},
{
"created": "Thu, 10 Oct 2013 08:43:00 GMT",
"version": "v4"
},
{
"created": "Thu, 31 Oct 2013 18:39:29 GMT",
"version": "v5"
},
{
"created": "Sat, 1 Feb 2014 11:29:34 GMT",
"version": "v6"
}
] | 2015-06-15 | [
[
"Klinkhamer",
"F. R.",
""
]
] | With a prescribed Coulomb-type energy-momentum tensor, an exact solution of the Einstein field equations over a nonsimply-connected manifold is presented. This spherically symmetric solution has neither curvature singularities nor closed timelike curves. It can be considered to be a regularization of the singular Reissner-Nordstrom solution over a simply-connected manifold. |
gr-qc/9806115 | Viqar Husain | Viqar Husain | Apparent horizons, black hole entropy and loop quantum gravity | 9 pages, RevTeX, published version (minor changes) | Phys.Rev. D59 (1999) 084019 | 10.1103/PhysRevD.59.084019 | UBC-TH | gr-qc hep-th | null | In recent work on black hole entropy in non-perturbative quantum gravity, an
action for the black hole sector of the phase space is introduced and
(partially) quantized. We give a number of observations on this and related
works. In particular we show that (I) the entropy calculation applies without
change to generally covariant theories having no black hole solutions, (II) the
phase space constraint used to select the black hole sector is not the apparent
horizon equation, which is the natural phase space constraint separating
trapped and untrapped regions on an initial data surface, and (III) there
appears to be at least one other phase space constraint which leads to the
conclusion that the entropy associated with a bounding two-dimensional surface
is proportional to its area.
| [
{
"created": "Mon, 29 Jun 1998 20:01:46 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Apr 1999 20:19:29 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Husain",
"Viqar",
""
]
] | In recent work on black hole entropy in non-perturbative quantum gravity, an action for the black hole sector of the phase space is introduced and (partially) quantized. We give a number of observations on this and related works. In particular we show that (I) the entropy calculation applies without change to generally covariant theories having no black hole solutions, (II) the phase space constraint used to select the black hole sector is not the apparent horizon equation, which is the natural phase space constraint separating trapped and untrapped regions on an initial data surface, and (III) there appears to be at least one other phase space constraint which leads to the conclusion that the entropy associated with a bounding two-dimensional surface is proportional to its area. |
1508.02565 | Koray D\"uzta\c{s} | Koray D\"uzta\c{s}, \.Ibrahim Semiz | The decoupling problem of the Proca equation; and treatment of Dirac,
Maxwell and Proca fields on the resulting pp-wave spacetimes | published version | Gen Relativ Gravit (2016) 48:99 | 10.1007/s10714-016-2097-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we take a formal approach to the problem of decoupling Proca
equations in curved space-times. We use Newman-Penrose (NP) two-spinor
formalism to represent the Proca vector by one complex and two real scalars. We
show that a decoupled second order differential equation for one of the real
scalars can be derived if and only if the background space-time admits a
covariantly constant null vector. Thus, the background space-time must be a
pp-wave vacuum. We evaluate the separability of Proca, Maxwell and Dirac
equations on the resulting pp-wave background.
| [
{
"created": "Tue, 11 Aug 2015 11:35:55 GMT",
"version": "v1"
},
{
"created": "Sun, 23 Aug 2015 22:07:46 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Dec 2015 23:35:15 GMT",
"version": "v3"
},
{
"created": "Tue, 2 Feb 2016 22:56:36 GMT",
"version": "v4"
},
{
"created": "Thu, 23 Jun 2016 01:39:35 GMT",
"version": "v5"
}
] | 2016-06-24 | [
[
"Düztaş",
"Koray",
""
],
[
"Semiz",
"İbrahim",
""
]
] | In this work we take a formal approach to the problem of decoupling Proca equations in curved space-times. We use Newman-Penrose (NP) two-spinor formalism to represent the Proca vector by one complex and two real scalars. We show that a decoupled second order differential equation for one of the real scalars can be derived if and only if the background space-time admits a covariantly constant null vector. Thus, the background space-time must be a pp-wave vacuum. We evaluate the separability of Proca, Maxwell and Dirac equations on the resulting pp-wave background. |
2308.10924 | Jan Ambjorn | Jan Ambjorn and Yoshiyuki Watabiki | Is the present acceleration of the Universe caused by merging with other
universes? | null | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that by allowing our Universe to merge with other universes one is
lead to modified Friedmann equations that explain the present accelerated
expansion of our Universe without the need of a cosmological constant.
| [
{
"created": "Mon, 21 Aug 2023 17:37:24 GMT",
"version": "v1"
}
] | 2023-08-23 | [
[
"Ambjorn",
"Jan",
""
],
[
"Watabiki",
"Yoshiyuki",
""
]
] | We show that by allowing our Universe to merge with other universes one is lead to modified Friedmann equations that explain the present accelerated expansion of our Universe without the need of a cosmological constant. |
2006.06129 | El\'ias Castellanos Dr. | El\'ias Castellanos and Celia Escamilla-Rivera | Dark energy as generalised superfluid excitations | 5 pages, 1 figure | null | null | null | gr-qc cond-mat.stat-mech | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we present a generic form of the cosmological Equation of State
derived from the formalism of Statistical Mechanics, assuming that a cosmic
acceleration scenario can be interpreted as a system of quasi-particles. By
considering a generalised superfluidity approach, in which the energy spectrum
can be modulated via a parameter $s$, a negative equation of state arises as
excitations associated with an \textit{exotic} superfluid system. We show that
for $s\sim 0.293$, $w\simeq-1$, which can be related to the standard equation
of state for the $\Lambda$CDM model.
| [
{
"created": "Thu, 11 Jun 2020 00:41:43 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Dec 2020 04:28:00 GMT",
"version": "v2"
}
] | 2020-12-14 | [
[
"Castellanos",
"Elías",
""
],
[
"Escamilla-Rivera",
"Celia",
""
]
] | In this paper we present a generic form of the cosmological Equation of State derived from the formalism of Statistical Mechanics, assuming that a cosmic acceleration scenario can be interpreted as a system of quasi-particles. By considering a generalised superfluidity approach, in which the energy spectrum can be modulated via a parameter $s$, a negative equation of state arises as excitations associated with an \textit{exotic} superfluid system. We show that for $s\sim 0.293$, $w\simeq-1$, which can be related to the standard equation of state for the $\Lambda$CDM model. |
2004.08292 | Betti Hartmann | Y. Brihaye, L. Ducobu, and B. Hartmann | Boson and neutron stars with increased density | Matches version published in Phys. Lett. B | null | 10.1016/j.physletb.2020.135906 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss boson stars and neutron stars, respectively, in a scalar-tensor
gravity model with an explicitly time-dependent real scalar field. While the
boson stars in our model -- in contrast to the neutron stars -- do not possess
a hard core, we find that the qualitative effects of the formation of scalar
hair are similar in both cases : the presence of the gravity scalar allows both
type of stars to exist for larger central density as well as larger mass at
given radius than their General Relativity counterparts. In particular, we find
new types of neutron stars with scalar hair which have radii very close to the
corresponding Schwarzschild radius and hence are comparable in density to black
holes. This new branch of solutions is stable with respect to the decay into
individual baryons.
| [
{
"created": "Fri, 17 Apr 2020 15:07:34 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Jan 2021 18:26:00 GMT",
"version": "v2"
},
{
"created": "Tue, 3 May 2022 09:01:13 GMT",
"version": "v3"
}
] | 2022-05-04 | [
[
"Brihaye",
"Y.",
""
],
[
"Ducobu",
"L.",
""
],
[
"Hartmann",
"B.",
""
]
] | We discuss boson stars and neutron stars, respectively, in a scalar-tensor gravity model with an explicitly time-dependent real scalar field. While the boson stars in our model -- in contrast to the neutron stars -- do not possess a hard core, we find that the qualitative effects of the formation of scalar hair are similar in both cases : the presence of the gravity scalar allows both type of stars to exist for larger central density as well as larger mass at given radius than their General Relativity counterparts. In particular, we find new types of neutron stars with scalar hair which have radii very close to the corresponding Schwarzschild radius and hence are comparable in density to black holes. This new branch of solutions is stable with respect to the decay into individual baryons. |
gr-qc/9302030 | null | B. L. Hu | Critical Dynamics in the Early Universe | umdpp 93-57, 12 pages, Latex Invited talk given at the Journees
Relativistes, Amsterdam, May 1992. Conference Proceedings edited by W. A. van
Leeuwen to appear in Classical and Quantum Gravity | Class.Quant.Grav.10:S93-S100,1993 | 10.1088/0264-9381/10/S/009 | null | gr-qc | null | Methods and concepts for the study of phase transitions mediated by a
time-dependent order-parameter field in curved spacetimes are discussed. A
practical example is the derivation of an effective (quasi-)potential for the
description of `slow-roll' inflation in the early universe. We first summarize
our early results on viewing the symmetry behavior of constant background
fields in curved but static spacetimes as finite size effect, and the use of
derivative expansions for constructing effective actions for slowly-varying
background fields. We then introduce the notion of dynamical finite size effect
to explain how an exponential expansion of the scale factor imparts a finite
size to the system and how the symmetry behavior in de Sitter space can be
understood qualitatively in this light. We reason why the exponential inflation
can be described equivalently by a scale transformation, thus rendering this
special class of dynamics as effectively static. Finally we show how, in this
view, one can treat the class of `slow-roll' inflation as a dynamic
perturbation off the effectively static class of exponential inflation and
understand it as a dynamical critical phenomenon in cosmology.
| [
{
"created": "Mon, 22 Feb 1993 20:01:00 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Hu",
"B. L.",
""
]
] | Methods and concepts for the study of phase transitions mediated by a time-dependent order-parameter field in curved spacetimes are discussed. A practical example is the derivation of an effective (quasi-)potential for the description of `slow-roll' inflation in the early universe. We first summarize our early results on viewing the symmetry behavior of constant background fields in curved but static spacetimes as finite size effect, and the use of derivative expansions for constructing effective actions for slowly-varying background fields. We then introduce the notion of dynamical finite size effect to explain how an exponential expansion of the scale factor imparts a finite size to the system and how the symmetry behavior in de Sitter space can be understood qualitatively in this light. We reason why the exponential inflation can be described equivalently by a scale transformation, thus rendering this special class of dynamics as effectively static. Finally we show how, in this view, one can treat the class of `slow-roll' inflation as a dynamic perturbation off the effectively static class of exponential inflation and understand it as a dynamical critical phenomenon in cosmology. |
2004.13554 | Sushovan Mondal | Sushovan Mondal, Saif Ali, Shanima S, Narayan Banerjee and Golam
Mortuza Hossain | Propagation of gravitational waves in various cosmological backgrounds | 17 pages, 6 figures | null | 10.1007/s10714-021-02835-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present work investigates some exact solutions of the gravitational wave
equation in some widely used cosmological spacetimes. The examples are taken
from spatially flat and closed isotropic models as well as Kasner metric which
is anisotropic. Various matter distributions are considered, from the standard
dust or radiation distribution to exotic matters like that with an equation of
state $P = - \frac{1}{3} \rho$. In almost all cases the frequency and amplitude
of the wave are found to be decaying with evolution, except for a closed
radiation universe where there is a resurgence of the waveform, consistent with
the recollapse of the universe into the big crunch singularity.
| [
{
"created": "Tue, 28 Apr 2020 14:24:07 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Jul 2021 06:34:27 GMT",
"version": "v2"
}
] | 2021-07-06 | [
[
"Mondal",
"Sushovan",
""
],
[
"Ali",
"Saif",
""
],
[
"S",
"Shanima",
""
],
[
"Banerjee",
"Narayan",
""
],
[
"Hossain",
"Golam Mortuza",
""
]
] | The present work investigates some exact solutions of the gravitational wave equation in some widely used cosmological spacetimes. The examples are taken from spatially flat and closed isotropic models as well as Kasner metric which is anisotropic. Various matter distributions are considered, from the standard dust or radiation distribution to exotic matters like that with an equation of state $P = - \frac{1}{3} \rho$. In almost all cases the frequency and amplitude of the wave are found to be decaying with evolution, except for a closed radiation universe where there is a resurgence of the waveform, consistent with the recollapse of the universe into the big crunch singularity. |
1403.3852 | Adrian Ciprian Sporea | Ciprian A. Sporea | Notes on f(R) Theories of Gravity | 46 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this review paper we present some basic notions about f(R) theories of
gravity and some simple cosmological models derived from it. We first make an
introduction to General Relativity (GR), followed by the discussion of
Gibbons-York-Hawking boundary term in GR. We also discuss boundary terms in
f(R) theories and the application of conformal transformations in order to show
that f(R) theories can be made equivalent to GR minimally coupled with a scalar
filed. In the final sections of the paper a brief review of classical Friedman
and Lemaitre cosmological models is made, followed by the discussion of
cosmological models derived from f(R)gravity.
| [
{
"created": "Sat, 15 Mar 2014 21:33:34 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Mar 2014 16:03:44 GMT",
"version": "v2"
}
] | 2014-03-20 | [
[
"Sporea",
"Ciprian A.",
""
]
] | In this review paper we present some basic notions about f(R) theories of gravity and some simple cosmological models derived from it. We first make an introduction to General Relativity (GR), followed by the discussion of Gibbons-York-Hawking boundary term in GR. We also discuss boundary terms in f(R) theories and the application of conformal transformations in order to show that f(R) theories can be made equivalent to GR minimally coupled with a scalar filed. In the final sections of the paper a brief review of classical Friedman and Lemaitre cosmological models is made, followed by the discussion of cosmological models derived from f(R)gravity. |
gr-qc/9407042 | Christodoulakis Theodosios | T.Christodoulakis, E.Korfiatis, E.C. Vagenas | Simultaneous Hamiltonian Treatment of Class A Spacetimes and Reduction
of Degrees of Freedom at the Quantum Level | Revised in 2002, LaTeX, 12 pages, G&C style, published version | Grav.Cosmol.8:213-221,2002 | null | University of Athens, preprint UA/NPPS-17, June 1994 | gr-qc hep-th | null | We consider the quantization of a general spatially homogeneous space-time
belonging to an arbitrary but fixed Class A Bianchi type. Exploiting the
information furnished by the quantum version of the momentum constraints, we
use as variables the two simplest contractions of $C^{\alpha}_{\beta \gamma}$
and $\gamma_{\alpha \beta}$ as well as the determinant of $\gamma_{\alpha
\beta}$ ; We thus arrive at an equation for the wave function in terms of these
quantities. This fact enables us to treat in a uniform manner all Class A
cosmologies. For these spacetimes the Langrangian used correctly reproduces
Einstein's equations. We also discuss the imposition of simplifying
ans\"{a}tzen at the quantum level in a way that respects the scalings of the
quadratic Hamiltonian constraint.
| [
{
"created": "Thu, 28 Jul 1994 08:38:56 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Jun 2001 09:47:53 GMT",
"version": "v2"
},
{
"created": "Thu, 21 Jun 2001 06:04:21 GMT",
"version": "v3"
},
{
"created": "Wed, 20 Mar 2002 11:12:35 GMT",
"version": "v4"
},
{
"created": "Thu, 10 Oct 2002 08:45:34 GMT",
"version": "v5"
}
] | 2011-07-19 | [
[
"Christodoulakis",
"T.",
""
],
[
"Korfiatis",
"E.",
""
],
[
"Vagenas",
"E. C.",
""
]
] | We consider the quantization of a general spatially homogeneous space-time belonging to an arbitrary but fixed Class A Bianchi type. Exploiting the information furnished by the quantum version of the momentum constraints, we use as variables the two simplest contractions of $C^{\alpha}_{\beta \gamma}$ and $\gamma_{\alpha \beta}$ as well as the determinant of $\gamma_{\alpha \beta}$ ; We thus arrive at an equation for the wave function in terms of these quantities. This fact enables us to treat in a uniform manner all Class A cosmologies. For these spacetimes the Langrangian used correctly reproduces Einstein's equations. We also discuss the imposition of simplifying ans\"{a}tzen at the quantum level in a way that respects the scalings of the quadratic Hamiltonian constraint. |
0902.2764 | Simone Mercuri | Simone Mercuri | Peccei--Quinn mechanism in gravity and the nature of the
Barbero--Immirzi parameter | Accepted for publication on Phys. Rev. Lett | Phys.Rev.Lett.103:081302,2009 | 10.1103/PhysRevLett.103.081302 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A general argument provides the motivation to consider the Barbero--Immirzi
parameter as a field. The specific form of the geometrical effective action
allows to relate the value of the Barbero--Immirzi parameter to other quantum
ambiguities through the analog of the Peccei--Quinn mechanism.
| [
{
"created": "Mon, 16 Feb 2009 19:22:56 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Jul 2009 09:39:11 GMT",
"version": "v2"
}
] | 2009-09-02 | [
[
"Mercuri",
"Simone",
""
]
] | A general argument provides the motivation to consider the Barbero--Immirzi parameter as a field. The specific form of the geometrical effective action allows to relate the value of the Barbero--Immirzi parameter to other quantum ambiguities through the analog of the Peccei--Quinn mechanism. |
1906.06287 | Jose Geraldo Pereira | J. G. Pereira, Y. N. Obukhov | Gauge Structure of Teleparallel Gravity | 8 pages. Contribution to the proceedings of the workshop
"Teleparallel Universes in Salamanca", Salamanca, Spain, 26-28 November 2018 | Universe 5 (2019) 139 | 10.3390/universe5060139 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | During the conference "Teleparallel Universes in Salamanca", we became aware
of a recent paper [M. Fontanini, E. Huguet, and M. Le Delliou, Phys. Rev. D 99
(2019) 064006] in which some criticisms on the interpretation of teleparallel
gravity as a gauge theory for the translation group were put forward. This
triggered a discussion about the arguments on which those criticisms were
based, whose output is described in the present paper. The main conclusion is
that, to a great extent, those arguments are incorrect, and lack mathematical
and physical support.
| [
{
"created": "Fri, 14 Jun 2019 16:50:58 GMT",
"version": "v1"
}
] | 2019-06-17 | [
[
"Pereira",
"J. G.",
""
],
[
"Obukhov",
"Y. N.",
""
]
] | During the conference "Teleparallel Universes in Salamanca", we became aware of a recent paper [M. Fontanini, E. Huguet, and M. Le Delliou, Phys. Rev. D 99 (2019) 064006] in which some criticisms on the interpretation of teleparallel gravity as a gauge theory for the translation group were put forward. This triggered a discussion about the arguments on which those criticisms were based, whose output is described in the present paper. The main conclusion is that, to a great extent, those arguments are incorrect, and lack mathematical and physical support. |
0709.3002 | Fernando de Felice | Fernando de Felice and Giovanni Preti | A generalized Principle of Relativity | 18 pages, no figures | null | null | null | gr-qc | null | In this paper we bring to light an hitherto undisclosed richness of this
Theory, namely its admitting a consistent reformulation which is able to
provide a unified scenario for all kinds of particles, be they lightlike or
not. This result hinges on a "generalized" Principle of Relativity which is
{intrinsic} to Einstein's Theory. The road leading to this generalization
starts, in the very spirit of Relativity, from enhancing full equivalence
between the four spacetime directions by requiring full equivalence between the
"motions" along these four spacetime directions as well. So far, no measurable
spatial velocity in the direction of the time axis has ever been defined, on
the same footing of the usual velocities in the local three-space of a given
observer. In this paper, we show how Relativity allows such a "time-velocity"
to be defined in a very natural way, for any particle and in any reference
frame. As a consequence of this natural definition, it also follows that the
time- and space-velocity vectors sum up to define a spacelike "world-velocity"
vector, the modulus of which turns out to be equal to the Maxwell's constant c,
irrespective of the observer who measures it. This {measurable} world-velocity
therefore represents the speed at which "all" kinds of particles move in
spacetime, according to any observer. As remarked above, the unifying scenario
thus emerging is intrinsic to Einstein's Theory; it extends the role
traditionally assigned to Maxwell's constant c, and can therefore justly be
referred to as "a generalized Principle of Relativity".
| [
{
"created": "Wed, 19 Sep 2007 12:18:35 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Apr 2008 10:26:19 GMT",
"version": "v2"
}
] | 2008-04-14 | [
[
"de Felice",
"Fernando",
""
],
[
"Preti",
"Giovanni",
""
]
] | In this paper we bring to light an hitherto undisclosed richness of this Theory, namely its admitting a consistent reformulation which is able to provide a unified scenario for all kinds of particles, be they lightlike or not. This result hinges on a "generalized" Principle of Relativity which is {intrinsic} to Einstein's Theory. The road leading to this generalization starts, in the very spirit of Relativity, from enhancing full equivalence between the four spacetime directions by requiring full equivalence between the "motions" along these four spacetime directions as well. So far, no measurable spatial velocity in the direction of the time axis has ever been defined, on the same footing of the usual velocities in the local three-space of a given observer. In this paper, we show how Relativity allows such a "time-velocity" to be defined in a very natural way, for any particle and in any reference frame. As a consequence of this natural definition, it also follows that the time- and space-velocity vectors sum up to define a spacelike "world-velocity" vector, the modulus of which turns out to be equal to the Maxwell's constant c, irrespective of the observer who measures it. This {measurable} world-velocity therefore represents the speed at which "all" kinds of particles move in spacetime, according to any observer. As remarked above, the unifying scenario thus emerging is intrinsic to Einstein's Theory; it extends the role traditionally assigned to Maxwell's constant c, and can therefore justly be referred to as "a generalized Principle of Relativity". |
1202.6214 | Martin Cermak | Martin Cermak, Martin Zouhar | Thin static charged dust Majumdar-Papapetrou shells with high symmetry
in D >= 4 | Accepted in Int. J. Theor. Phys | null | 10.1007/s10773-012-1126-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a systematical study of static D >= 4 space-times of high symmetry
with the matter source being a thin charged dust hypersurface shell. The shell
manifold is assumed to have the following structure S_(beta) X R^(D-2-beta),
beta (in the interval <0,...,D-2>) is dimension of a sphere S_(beta). In case
of (beta) = 0, we assume that there are two parallel hyper-plane shells instead
of only one. The space-time has Majumdar-Papapetrou form and it inherits the
symmetries of the shell manifold - it is invariant under both rotations of the
S_(beta) and translations along R^(D-2-beta). We find a general solution to the
Einstein-Maxwell equations with a given shell. Then, we examine some flat
interior solutions with special attention paid to D = 4. A connection to D = 4
non-relativistic theory is pointed out. We also comment on a straightforward
generalisation to the case of Kastor-Traschen space-time, i.e. adding a
non-negative cosmological constant to the charged dust matter source.
| [
{
"created": "Tue, 28 Feb 2012 13:39:09 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Apr 2012 08:41:37 GMT",
"version": "v2"
}
] | 2012-04-30 | [
[
"Cermak",
"Martin",
""
],
[
"Zouhar",
"Martin",
""
]
] | We present a systematical study of static D >= 4 space-times of high symmetry with the matter source being a thin charged dust hypersurface shell. The shell manifold is assumed to have the following structure S_(beta) X R^(D-2-beta), beta (in the interval <0,...,D-2>) is dimension of a sphere S_(beta). In case of (beta) = 0, we assume that there are two parallel hyper-plane shells instead of only one. The space-time has Majumdar-Papapetrou form and it inherits the symmetries of the shell manifold - it is invariant under both rotations of the S_(beta) and translations along R^(D-2-beta). We find a general solution to the Einstein-Maxwell equations with a given shell. Then, we examine some flat interior solutions with special attention paid to D = 4. A connection to D = 4 non-relativistic theory is pointed out. We also comment on a straightforward generalisation to the case of Kastor-Traschen space-time, i.e. adding a non-negative cosmological constant to the charged dust matter source. |
gr-qc/9708014 | null | Vladimir S. Mashkevich (Institute of Physics, Kiev) | Indeterministic Quantum Gravity and Cosmology VIII. Gravilon:
Gravitational Autolocalization | 7 pages, LATEX 2e, uses amssymb | null | null | IP 11/97 | gr-qc | 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].
Gravitational autolocalization of a body is considered. A self-consistent
problem is solved: A quantum state of the center of mass of the body gives rise
to a classical gravitational field, and the state, on the other hand, is an
eigenstate in the field. We call a resulting solution gravilon. Gravilons are
classified, and their properties are studied. Gravitational autolocalization is
predominantly a macroscopic effect. The motion of a gravilon as a whole is
classical.
| [
{
"created": "Thu, 7 Aug 1997 10:33:25 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]. Gravitational autolocalization of a body is considered. A self-consistent problem is solved: A quantum state of the center of mass of the body gives rise to a classical gravitational field, and the state, on the other hand, is an eigenstate in the field. We call a resulting solution gravilon. Gravilons are classified, and their properties are studied. Gravitational autolocalization is predominantly a macroscopic effect. The motion of a gravilon as a whole is classical. |
2310.09905 | Harkirat Singh Sahota | Harkirat Singh Sahota | Imprints of the operator ordering ambiguity on the dynamics of perfect
fluid dominated quantum universe | 21 pages and 7 figures, Matches the published version | null | 10.1088/1361-6382/ad638a | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Sharply peaked quantum states are conjectured to be conducive to the notion
of a quantum-corrected spacetime. We investigate this conjecture for a
flat-FLRW model with perfect fluid, where a generalized ordering scheme is
considered for the gravitational Hamiltonian. We study the implications of
different ordering choices on the dynamics of the quantum universe. We
demonstrate that the imprints of the operator ordering ambiguity are minimal,
and quantum fluctuations are small in the case of sharply peaked states,
leading to a consistent notion of a quantum-corrected spacetime defined via the
expectation value of the scale factor. Surprisingly, the ordering imprints
survive far away from the singularity through the quantum fluctuations in the
quantum-corrected spacetime for broadly peaked states.
| [
{
"created": "Sun, 15 Oct 2023 18:16:24 GMT",
"version": "v1"
},
{
"created": "Sun, 11 Feb 2024 16:29:25 GMT",
"version": "v2"
},
{
"created": "Mon, 29 Jul 2024 14:08:50 GMT",
"version": "v3"
}
] | 2024-07-30 | [
[
"Sahota",
"Harkirat Singh",
""
]
] | Sharply peaked quantum states are conjectured to be conducive to the notion of a quantum-corrected spacetime. We investigate this conjecture for a flat-FLRW model with perfect fluid, where a generalized ordering scheme is considered for the gravitational Hamiltonian. We study the implications of different ordering choices on the dynamics of the quantum universe. We demonstrate that the imprints of the operator ordering ambiguity are minimal, and quantum fluctuations are small in the case of sharply peaked states, leading to a consistent notion of a quantum-corrected spacetime defined via the expectation value of the scale factor. Surprisingly, the ordering imprints survive far away from the singularity through the quantum fluctuations in the quantum-corrected spacetime for broadly peaked states. |
gr-qc/9710078 | Kouji Nakamura | K. Nakamura, H. Ishihara | Cylindrical Domain Walls and Gravitational Waves -- Einstein Rosen wave
emission from momentarily static initial configuration -- | 3 pages, latex requires mprocl.sty, no figures. To appear in the
proceedings of the Eighth Marcel Grossmann Conference on General Relativity
(Jerusalem, Israel, June 1997) | null | null | null | gr-qc | null | A self-gravitating cylindrical domain wall is considered as an example of
non-spherical wall to clarify the interaction between a domain wall and
gravitational waves. We consider the time evolution from a momentarily static
initial configuration within an infinitesimal time interval using the metric
junction formalism. We found that the wall with a large initial radius radiates
large amplitude of the gravitational waves and undergoes its large back
reaction.
| [
{
"created": "Wed, 15 Oct 1997 09:15:53 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Nakamura",
"K.",
""
],
[
"Ishihara",
"H.",
""
]
] | A self-gravitating cylindrical domain wall is considered as an example of non-spherical wall to clarify the interaction between a domain wall and gravitational waves. We consider the time evolution from a momentarily static initial configuration within an infinitesimal time interval using the metric junction formalism. We found that the wall with a large initial radius radiates large amplitude of the gravitational waves and undergoes its large back reaction. |
gr-qc/0608095 | Shuichi Sato | Shuichi Sato, Seiji Kawamura, Keiko Kokeyama, Robert L. Ward, Yanbei
Chen, Archana Pai, and Kentaro Somiya | Demonstration of displacement- and frequency-noise free laser
interferometry using bi-directional Mach-Zehnder interferometers | 5 pages, 5 figures, now on PRL 98, 141101 (2007) | Phys.Rev.Lett.98:141101,2007 | 10.1103/PhysRevLett.98.141101 | null | gr-qc astro-ph | null | We have demonstrated displacement- and frequency-noise free laser
interferometry (DFI) by partially implementing a recently proposed optical
configuration using bi-directional Mach-Zehnder interferometers (MZI). This
partial implementation, the minimum necessary to be called DFI, has confirmed
the essential feature of DFI: the combination of two MZI signals can be carried
out in a way which cancels displacement noise of the mirrors while maintaining
gravitational wave signals. The attained maximum displacement noise suppression
allowed a simulated-SNR of 45dB.
| [
{
"created": "Sun, 20 Aug 2006 04:19:45 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Apr 2007 00:48:35 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Sato",
"Shuichi",
""
],
[
"Kawamura",
"Seiji",
""
],
[
"Kokeyama",
"Keiko",
""
],
[
"Ward",
"Robert L.",
""
],
[
"Chen",
"Yanbei",
""
],
[
"Pai",
"Archana",
""
],
[
"Somiya",
"Kentaro",
""
]
] | We have demonstrated displacement- and frequency-noise free laser interferometry (DFI) by partially implementing a recently proposed optical configuration using bi-directional Mach-Zehnder interferometers (MZI). This partial implementation, the minimum necessary to be called DFI, has confirmed the essential feature of DFI: the combination of two MZI signals can be carried out in a way which cancels displacement noise of the mirrors while maintaining gravitational wave signals. The attained maximum displacement noise suppression allowed a simulated-SNR of 45dB. |
gr-qc/9607044 | Hugo Morales Tecotl | Hugo A. Morales-Tecotl, Luis F. Urrutia and J. David Vergara | Reality conditions for Ashtekar variables as Dirac constraints | 16 pages, plain LaTeX, submitted to Class. Quant. Grav. E-mail:
hugo@xanum.uam.mx | Class.Quant.Grav. 13 (1996) 2933-2940 | 10.1088/0264-9381/13/11/009 | null | gr-qc hep-th | null | We show that the reality conditions to be imposed on Ashtekar variables to
recover real gravity can be implemented as second class constraints a la Dirac.
Thus, counting gravitational degrees of freedom follows accordingly. Some
constraints of the real theory turn out to be non-polynomial, regardless of the
form, polynomial or non-polynomial, taken for the reality conditions. We
comment upon the compatibility of our approach with the recently proposed Wick
transform point of view, as well as on some alternatives for dealing with such
second class constraints.
| [
{
"created": "Sun, 21 Jul 1996 19:22:18 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Morales-Tecotl",
"Hugo A.",
""
],
[
"Urrutia",
"Luis F.",
""
],
[
"Vergara",
"J. David",
""
]
] | We show that the reality conditions to be imposed on Ashtekar variables to recover real gravity can be implemented as second class constraints a la Dirac. Thus, counting gravitational degrees of freedom follows accordingly. Some constraints of the real theory turn out to be non-polynomial, regardless of the form, polynomial or non-polynomial, taken for the reality conditions. We comment upon the compatibility of our approach with the recently proposed Wick transform point of view, as well as on some alternatives for dealing with such second class constraints. |
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