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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9912031
|
Scott A. Hughes
|
Scott A. Hughes
|
Gravitational waves from inspiral into massive black holes
|
7 pages, 2 figures. To appear in the proceedings of the 3rd Edoardo
Amaldi meeting
| null | null | null |
gr-qc astro-ph
| null |
Space-based gravitational-wave interferometers such as LISA will be sensitive
to the inspiral of stellar mass compact objects into black holes with masses in
the range of roughly 10^5 solar masses to (a few) 10^7 solar masses. During the
last year of inspiral, the compact body spends several hundred thousand orbits
spiraling from several Schwarzschild radii to the last stable orbit. The
gravitational waves emitted from these orbits probe the strong-field region of
the black hole spacetime and can make possible high precision tests and
measurements of the black hole's properties. Measuring such waves will require
a good theoretical understanding of the waves' properties, which in turn
requires a good understanding of strong-field radiation reaction and of
properties of the black hole's astrophysical environment which could complicate
waveform generation. In these proceedings, I review estimates of the rate at
which such inspirals occur in the universe, and discuss what is being done and
what must be done further in order to calculate the inspiral waveform.
|
[
{
"created": "Wed, 8 Dec 1999 21:47:33 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Hughes",
"Scott A.",
""
]
] |
Space-based gravitational-wave interferometers such as LISA will be sensitive to the inspiral of stellar mass compact objects into black holes with masses in the range of roughly 10^5 solar masses to (a few) 10^7 solar masses. During the last year of inspiral, the compact body spends several hundred thousand orbits spiraling from several Schwarzschild radii to the last stable orbit. The gravitational waves emitted from these orbits probe the strong-field region of the black hole spacetime and can make possible high precision tests and measurements of the black hole's properties. Measuring such waves will require a good theoretical understanding of the waves' properties, which in turn requires a good understanding of strong-field radiation reaction and of properties of the black hole's astrophysical environment which could complicate waveform generation. In these proceedings, I review estimates of the rate at which such inspirals occur in the universe, and discuss what is being done and what must be done further in order to calculate the inspiral waveform.
|
gr-qc/9703080
|
Maartens R. Staf
|
Roy Maartens, William Lesame, George Ellis
|
Consistency of dust solutions with div H=0
|
3 pages Revtex
|
Phys.Rev. D55 (1997) 5219-5221
|
10.1103/PhysRevD.55.5219
|
Portsmouth RCG 96/17
|
gr-qc
| null |
One of the necessary covariant conditions for gravitational radiation is the
vanishing of the divergence of the magnetic Weyl tensor H_{ab}, while H_{ab}
itself is nonzero. We complete a recent analysis by showing that in
irrotational dust spacetimes, the condition div H=0 evolves consistently in the
exact nonlinear theory.
|
[
{
"created": "Thu, 27 Mar 1997 10:43:30 GMT",
"version": "v1"
}
] |
2009-10-30
|
[
[
"Maartens",
"Roy",
""
],
[
"Lesame",
"William",
""
],
[
"Ellis",
"George",
""
]
] |
One of the necessary covariant conditions for gravitational radiation is the vanishing of the divergence of the magnetic Weyl tensor H_{ab}, while H_{ab} itself is nonzero. We complete a recent analysis by showing that in irrotational dust spacetimes, the condition div H=0 evolves consistently in the exact nonlinear theory.
|
gr-qc/0101096
|
Masayuki Tanimoto
|
Masayuki Tanimoto
|
Symmetries of the Gowdy Equations and Spatial Topologies
|
6 pages, 2 figures, LaTeX. To appear in the proceedings of JGRG10,
Osaka, Sept. 11-14, 2000
| null | null | null |
gr-qc
| null |
We examine some kinds of discrete symmetries which are dynamically preserved,
using the (generalized) Gowdy models of the first kind.
|
[
{
"created": "Thu, 25 Jan 2001 14:49:21 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Tanimoto",
"Masayuki",
""
]
] |
We examine some kinds of discrete symmetries which are dynamically preserved, using the (generalized) Gowdy models of the first kind.
|
0705.4120
|
Carlos A. S. Almeida
|
M. O. Tahim, R. R. Landim, and C. A. S. Almeida
|
Spacetime as a deformable solid
|
5 pages, RevTex4
| null | null | null |
gr-qc hep-th
| null |
In this letter we discuss the possibility of treating the spacetime by itself
as a kind of deformable body for which we can define an fundamental lattice,
just like atoms in crystal lattices. We show three signs pointing in that
direction. We simulate the spacetime manifold by a very specific congruence of
curves and use the Landau-Raychadhuri equation to study the behavior of such a
congruence. The lattice appears because we are forced to associate to each
curve of the congruence a sort of fundamental "particle". The world-lines of
these particles should be identified with the congruence fulfilling the
spacetime manifold. The conclusion is that when describing the deformations of
the spacetime the Einstein equations emerge and the spacetime metric should be
treated as a secondary (not fundamental) object of the theory.
|
[
{
"created": "Mon, 28 May 2007 22:33:16 GMT",
"version": "v1"
}
] |
2007-05-30
|
[
[
"Tahim",
"M. O.",
""
],
[
"Landim",
"R. R.",
""
],
[
"Almeida",
"C. A. S.",
""
]
] |
In this letter we discuss the possibility of treating the spacetime by itself as a kind of deformable body for which we can define an fundamental lattice, just like atoms in crystal lattices. We show three signs pointing in that direction. We simulate the spacetime manifold by a very specific congruence of curves and use the Landau-Raychadhuri equation to study the behavior of such a congruence. The lattice appears because we are forced to associate to each curve of the congruence a sort of fundamental "particle". The world-lines of these particles should be identified with the congruence fulfilling the spacetime manifold. The conclusion is that when describing the deformations of the spacetime the Einstein equations emerge and the spacetime metric should be treated as a secondary (not fundamental) object of the theory.
|
1603.05337
|
Rod Aros Mr.
|
Rodrigo Aros and Milko Estrada
|
Study of branes with variable tension
| null |
Commun.Theor.Phys. 68 (2017) no.5, 595
|
10.1088/0253-6102/68/5/595
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this work we study a brane world model with variable tension which gives
rise to four dimensional cosmologies. The brane worlds obtained correspond to
E\"{o}tv\"{o}s branes whose (internal) geometry can be casted as either a four
dimensional (A)dS$_{4}$ or a standard radiation period cosmology. The matter
dominated period is discussed as well.
|
[
{
"created": "Thu, 17 Mar 2016 02:30:55 GMT",
"version": "v1"
}
] |
2017-11-21
|
[
[
"Aros",
"Rodrigo",
""
],
[
"Estrada",
"Milko",
""
]
] |
In this work we study a brane world model with variable tension which gives rise to four dimensional cosmologies. The brane worlds obtained correspond to E\"{o}tv\"{o}s branes whose (internal) geometry can be casted as either a four dimensional (A)dS$_{4}$ or a standard radiation period cosmology. The matter dominated period is discussed as well.
|
2212.10413
|
Vinod Bhardwaj Dr.
|
Archana Dixit, Anirudh Pradhan, Vinod Kumar Bhardwaj, A. Beesham
|
Observational constraints for an axially symmetric transitioning model
with bulk viscosity parameterization
|
25 pages, 14 figures
| null | null | null |
gr-qc
|
http://creativecommons.org/licenses/by-nc-sa/4.0/
|
In this paper, we have analyzed the significance of bulk viscosity in an
axially symmetric Bianchi type-I model to study the accelerated expansion of
the universe. We have considered four bulk viscosity parameterizations for the
matter-dominated cosmological model. The function of the two significant Hubble
$H(z)$ and deceleration parameters are discussed in detail. The energy
parameters of the universe are computed using the most recent observational
Hubble data (57 data points) in the redshift range $0.07 \leq z \leq 2.36)$. In
this model, we obtained all feasible solutions with the viscous component and
analyzed the universe's expansion history. Finally, we analyzed the statefinder
diagnostic and found some interesting results. The outcomes of our developed
model now properly align with observational results.
|
[
{
"created": "Tue, 20 Dec 2022 16:42:47 GMT",
"version": "v1"
}
] |
2022-12-21
|
[
[
"Dixit",
"Archana",
""
],
[
"Pradhan",
"Anirudh",
""
],
[
"Bhardwaj",
"Vinod Kumar",
""
],
[
"Beesham",
"A.",
""
]
] |
In this paper, we have analyzed the significance of bulk viscosity in an axially symmetric Bianchi type-I model to study the accelerated expansion of the universe. We have considered four bulk viscosity parameterizations for the matter-dominated cosmological model. The function of the two significant Hubble $H(z)$ and deceleration parameters are discussed in detail. The energy parameters of the universe are computed using the most recent observational Hubble data (57 data points) in the redshift range $0.07 \leq z \leq 2.36)$. In this model, we obtained all feasible solutions with the viscous component and analyzed the universe's expansion history. Finally, we analyzed the statefinder diagnostic and found some interesting results. The outcomes of our developed model now properly align with observational results.
|
gr-qc/0101098
|
R. M. Kiehn
|
R. M. Kiehn
|
Falaco Solitons, Cosmic Strings in a Swimming Pool
|
6 pages pdf 3 figures included
| null | null | null |
gr-qc
| null |
Topological defects experimentally induced by rotational dynamics in a
continuous media replicate the coherent structure features of cosmic strings as
well as hadrons.
|
[
{
"created": "Thu, 25 Jan 2001 20:34:12 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Kiehn",
"R. M.",
""
]
] |
Topological defects experimentally induced by rotational dynamics in a continuous media replicate the coherent structure features of cosmic strings as well as hadrons.
|
1305.5409
|
Cosimo Bambi
|
Cosimo Bambi
|
Measuring the Kerr spin parameter of a non-Kerr compact object with the
continuum-fitting and the iron line methods
|
1+14 pages, 5 figures. v2: refereed version
|
JCAP 1308:055,2013
|
10.1088/1475-7516/2013/08/055
| null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Under the assumption that astrophysical black hole candidates are the Kerr
black holes of general relativity, the continuum-fitting method and the
analysis of the K$\alpha$ iron line are today the only available techniques
capable of providing a relatively reliable estimate of the spin parameter of
these objects. If we relax the Kerr black hole hypothesis and we try to test
the nature of black hole candidates, we find that there is a strong correlation
between the measurement of the spin and possible deviations from the Kerr
solution. The properties of the radiation emitted in a Kerr spacetime with spin
parameter $a_*$ are indeed very similar, and practically indistinguishable,
from the ones of the radiation emitted around a non-Kerr object with different
spin. In this paper, I address the question whether measuring the Kerr spin
with both the continuum-fitting method and the K$\alpha$ iron line analysis of
the same object can be used to claim the Kerr nature of the black hole
candidate in the case of consistent results. In this work, I consider two
non-Kerr metrics and it seems that the answer does depend on the specific
background. The two techniques may either provide a very similar result (the
case of the Bardeen metric) or show a discrepancy (Johannsen-Psaltis
background).
|
[
{
"created": "Thu, 23 May 2013 13:19:35 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Aug 2013 11:36:47 GMT",
"version": "v2"
}
] |
2013-09-02
|
[
[
"Bambi",
"Cosimo",
""
]
] |
Under the assumption that astrophysical black hole candidates are the Kerr black holes of general relativity, the continuum-fitting method and the analysis of the K$\alpha$ iron line are today the only available techniques capable of providing a relatively reliable estimate of the spin parameter of these objects. If we relax the Kerr black hole hypothesis and we try to test the nature of black hole candidates, we find that there is a strong correlation between the measurement of the spin and possible deviations from the Kerr solution. The properties of the radiation emitted in a Kerr spacetime with spin parameter $a_*$ are indeed very similar, and practically indistinguishable, from the ones of the radiation emitted around a non-Kerr object with different spin. In this paper, I address the question whether measuring the Kerr spin with both the continuum-fitting method and the K$\alpha$ iron line analysis of the same object can be used to claim the Kerr nature of the black hole candidate in the case of consistent results. In this work, I consider two non-Kerr metrics and it seems that the answer does depend on the specific background. The two techniques may either provide a very similar result (the case of the Bardeen metric) or show a discrepancy (Johannsen-Psaltis background).
|
1207.3873
|
Sergei Kopeikin
|
Sergei Kopeikin (University of Missouri, Columbia, USA)
|
Celestial Ephemerides in an Expanding Universe
|
27 pages, accepted to Phys. Rev. D
|
Phys. Rev. D 86, 064004 (2012)
|
10.1103/PhysRevD.86.064004
| null |
gr-qc astro-ph.CO physics.space-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Post-Newtonian theory was instrumental in conducting the critical
experimental tests of general relativity and in building the astronomical
ephemerides of celestial bodies in the solar system with an unparalleled
precision. The cornerstone of the theory is the postulate that the solar system
is gravitationally isolated from the rest of the universe and the background
spacetime is asymptotically flat. The present article extends this theoretical
concept and formulates the principles of celestial dynamics of particles and
light moving in gravitational field of a localized astronomical system embedded
to the expanding Friedmann-Lemaitre-Robertson-Walker (FLRW) universe. We
formulate the precise mathematical concept of the Newtonian limit of Einstein's
field equations in the conformally-flat FLRW spacetime and analyze the geodesic
motion of massive particles and light in this limit. We prove that by doing
conformal spacetime transformations, one can reduce the equations of motion of
particles and light to the classical form of the Newtonian theory. However, the
time arguments in the equations of motion of particles and light differ from
each other in terms being proportional to the Hubble constant, H. This leads to
the important conclusion that the equations of light propagation used currently
by Space Navigation Centers for fitting range and Doppler-tracking observations
of celestial bodies are missing some terms of the cosmological origin that are
proportional to the Hubble constant, H. We also prove that the Hubble expansion
does not affect the atomic time scale used in creation of astronomical
ephemerides. We derive the cosmological correction to the light travel time
equation and argue that their measurement opens an exciting opportunity to
determine the local value of the Hubble constant, H, in the solar system
independently of cosmological observations.
|
[
{
"created": "Tue, 17 Jul 2012 04:07:33 GMT",
"version": "v1"
}
] |
2012-09-06
|
[
[
"Kopeikin",
"Sergei",
"",
"University of Missouri, Columbia, USA"
]
] |
Post-Newtonian theory was instrumental in conducting the critical experimental tests of general relativity and in building the astronomical ephemerides of celestial bodies in the solar system with an unparalleled precision. The cornerstone of the theory is the postulate that the solar system is gravitationally isolated from the rest of the universe and the background spacetime is asymptotically flat. The present article extends this theoretical concept and formulates the principles of celestial dynamics of particles and light moving in gravitational field of a localized astronomical system embedded to the expanding Friedmann-Lemaitre-Robertson-Walker (FLRW) universe. We formulate the precise mathematical concept of the Newtonian limit of Einstein's field equations in the conformally-flat FLRW spacetime and analyze the geodesic motion of massive particles and light in this limit. We prove that by doing conformal spacetime transformations, one can reduce the equations of motion of particles and light to the classical form of the Newtonian theory. However, the time arguments in the equations of motion of particles and light differ from each other in terms being proportional to the Hubble constant, H. This leads to the important conclusion that the equations of light propagation used currently by Space Navigation Centers for fitting range and Doppler-tracking observations of celestial bodies are missing some terms of the cosmological origin that are proportional to the Hubble constant, H. We also prove that the Hubble expansion does not affect the atomic time scale used in creation of astronomical ephemerides. We derive the cosmological correction to the light travel time equation and argue that their measurement opens an exciting opportunity to determine the local value of the Hubble constant, H, in the solar system independently of cosmological observations.
|
1906.07014
|
Yurij Baryshev
|
Yurij Baryshev and Sergey Oschepkov
|
A solution of the van Dam-Veltman-Zakharov discontinuity problem in the
frame of the Poincare-covariant field gravitation theory
|
12 pages, 31 ref
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The van Dam-Veltman-Zakharov (vDVZ) mass discontinuity problem can be solved
in the frame of the linear approximation of the Poincare-covariant second rank
symmetric tensor field gravitation theory. Conservation of the source
energy-momentum tensor, together with gauge invariance of the field equations,
lead to generation of two intrinsic irreducible non-ghost dynamical fields:
4-traceless symmetric tensor (spin-2 universal attraction) and 4-trace (spin-0
universal repulsion). Due to difference in the signs of these forces the total
free field Lagrangian contains different signs for the tensor and scalar
dynamical fields. Generalized Fierz-Pauli mass term in total spin-2 plus spin-0
Lagrangian gives natural massless limit for mg --> 0, so the mass discontinuity
paradox is absent. The Newtonian gravity and relativistic gravity effects,
including positive localizable energy density of both parts of the
gravitational field, are derived. Experimental test of the reality of the
dynamical spin-0 repulsive field can be performed by LIGO-Virgo gravitational
wave observations.
|
[
{
"created": "Fri, 14 Jun 2019 17:46:43 GMT",
"version": "v1"
}
] |
2019-06-18
|
[
[
"Baryshev",
"Yurij",
""
],
[
"Oschepkov",
"Sergey",
""
]
] |
The van Dam-Veltman-Zakharov (vDVZ) mass discontinuity problem can be solved in the frame of the linear approximation of the Poincare-covariant second rank symmetric tensor field gravitation theory. Conservation of the source energy-momentum tensor, together with gauge invariance of the field equations, lead to generation of two intrinsic irreducible non-ghost dynamical fields: 4-traceless symmetric tensor (spin-2 universal attraction) and 4-trace (spin-0 universal repulsion). Due to difference in the signs of these forces the total free field Lagrangian contains different signs for the tensor and scalar dynamical fields. Generalized Fierz-Pauli mass term in total spin-2 plus spin-0 Lagrangian gives natural massless limit for mg --> 0, so the mass discontinuity paradox is absent. The Newtonian gravity and relativistic gravity effects, including positive localizable energy density of both parts of the gravitational field, are derived. Experimental test of the reality of the dynamical spin-0 repulsive field can be performed by LIGO-Virgo gravitational wave observations.
|
gr-qc/9808053
|
S. Mignemi
|
S. Mignemi (Universita di Cagliari)
|
Charged gravitational instantons in five-dimensional
Einstein-Gauss-Bonnet-Maxwell theory
|
8 pages, plain TeX
|
Gen.Rel.Grav. 30 (1998) 1795-1801
|
10.1023/A:1026671212653
|
INFNCA-TH9806
|
gr-qc
| null |
We study a solution of the Einstein-Gauus-Bonnet theory in 5 dimensions
coupled to a Maxwell field, whose euclidean continuation gives rise to an
instanton describing black hole pair production. We also discuss the dual
theory with a 3-form field coupled to gravity.
|
[
{
"created": "Wed, 19 Aug 1998 17:13:06 GMT",
"version": "v1"
}
] |
2015-06-25
|
[
[
"Mignemi",
"S.",
"",
"Universita di Cagliari"
]
] |
We study a solution of the Einstein-Gauus-Bonnet theory in 5 dimensions coupled to a Maxwell field, whose euclidean continuation gives rise to an instanton describing black hole pair production. We also discuss the dual theory with a 3-form field coupled to gravity.
|
2010.05061
|
Orlando Luongo
|
Roberto Giamb\`o, Orlando Luongo and Hernando Quevedo
|
Repulsive regions in Lema\^itre-Tolman-Bondi gravitational collapse
|
12 pages, 3 figures
|
Phys. dark univ., 30, 100721, (2020)
|
10.1016/j.dark.2020.100721
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We show that in the inhomogeneous Lema{\^i}tre-Tolman-Bondi space-time there
are specific regions in which repulsive gravity exists. To find these regions,
we use an invariant definition of repulsive gravity based upon the behavior of
the curvature eigenvalues. In addition, we analyze the effects of repulsive
gravity on the dynamics of the gravitational collapse. In particular, we
investigate the collapse in the case of the parabolic solution for the
effective scale factor of the Lema{\^i}tre-Tolman-Bondi metric, corresponding
to the marginally bound case. Exploring the corresponding cut-offs at which
gravity becomes repulsive, we notice that black holes with dominant repulsive
effects are not excluded \emph{a priori}. Indeed, we demonstrate that the
collapse leads, in general, to the formation of a central naked singularity;
however, for particular values of the free parameters entering the model, black
holes with dominant repulsive gravity can exist. We show that the expected
physical process is not modified as the marginally bound condition is dropped
out. Moreover, we show that this is true independently of the hypothesis that
the energy-momentum tensor is built up in terms of pressureless matter.
Further, we demonstrate that geodesic deviations can depend on the sign of the
curvature eigenvalues. Finally, we give an astrophysical interpretation of
black holes with dominant repulsive gravity. Indeed, we argue that compact
objects with dominant repulsive gravity could be interpreted as progenitors of
Gamma Ray Bursts.
|
[
{
"created": "Sat, 10 Oct 2020 18:18:26 GMT",
"version": "v1"
}
] |
2020-10-13
|
[
[
"Giambò",
"Roberto",
""
],
[
"Luongo",
"Orlando",
""
],
[
"Quevedo",
"Hernando",
""
]
] |
We show that in the inhomogeneous Lema{\^i}tre-Tolman-Bondi space-time there are specific regions in which repulsive gravity exists. To find these regions, we use an invariant definition of repulsive gravity based upon the behavior of the curvature eigenvalues. In addition, we analyze the effects of repulsive gravity on the dynamics of the gravitational collapse. In particular, we investigate the collapse in the case of the parabolic solution for the effective scale factor of the Lema{\^i}tre-Tolman-Bondi metric, corresponding to the marginally bound case. Exploring the corresponding cut-offs at which gravity becomes repulsive, we notice that black holes with dominant repulsive effects are not excluded \emph{a priori}. Indeed, we demonstrate that the collapse leads, in general, to the formation of a central naked singularity; however, for particular values of the free parameters entering the model, black holes with dominant repulsive gravity can exist. We show that the expected physical process is not modified as the marginally bound condition is dropped out. Moreover, we show that this is true independently of the hypothesis that the energy-momentum tensor is built up in terms of pressureless matter. Further, we demonstrate that geodesic deviations can depend on the sign of the curvature eigenvalues. Finally, we give an astrophysical interpretation of black holes with dominant repulsive gravity. Indeed, we argue that compact objects with dominant repulsive gravity could be interpreted as progenitors of Gamma Ray Bursts.
|
2309.09474
|
Mohamed Fawzy Abbas Aly Mr.
|
Fawzi Aly, Dejan Stojkovic
|
In Horizon Penetrating Coordinates: Kerr Black Hole Metric Perturbation
Construction and Completion
| null | null | null | null |
gr-qc math-ph math.MP
|
http://creativecommons.org/licenses/by/4.0/
|
We investigate the Teukolsky equation in horizon-penetrating coordinates to
study the behavior of perturbation waves crossing the outer horizon. For this
purpose, we use the null ingoing/outgoing Eddington-Finkelstein coordinates.
The first derivative of the radial equation is a Fuchsian differential equation
with an additional regular singularity to the ones the radial one has. The
radial functions satisfy the physical boundary conditions without imposing any
regularity conditions. We also observe that the Hertz-Weyl scalar equations
preserve their angular and radial signatures in these coordinates. Using the
angular equation, we construct the metric perturbation for a circularly
orbiting perturber around a black hole in Kerr spacetime in a
horizon-penetrating setting. Furthermore, we completed the missing metric
pieces due to the mass M and angular momentum J perturbations. We also provide
an explicit formula for the metric perturbation as a function of the radial
part, its derivative, and the angular part of the solution to the Teukolsky
equation. Finally, we discuss the importance of the extra singularity in the
radial derivative for the convergence of the metric expansion.
|
[
{
"created": "Mon, 18 Sep 2023 04:13:37 GMT",
"version": "v1"
}
] |
2023-09-19
|
[
[
"Aly",
"Fawzi",
""
],
[
"Stojkovic",
"Dejan",
""
]
] |
We investigate the Teukolsky equation in horizon-penetrating coordinates to study the behavior of perturbation waves crossing the outer horizon. For this purpose, we use the null ingoing/outgoing Eddington-Finkelstein coordinates. The first derivative of the radial equation is a Fuchsian differential equation with an additional regular singularity to the ones the radial one has. The radial functions satisfy the physical boundary conditions without imposing any regularity conditions. We also observe that the Hertz-Weyl scalar equations preserve their angular and radial signatures in these coordinates. Using the angular equation, we construct the metric perturbation for a circularly orbiting perturber around a black hole in Kerr spacetime in a horizon-penetrating setting. Furthermore, we completed the missing metric pieces due to the mass M and angular momentum J perturbations. We also provide an explicit formula for the metric perturbation as a function of the radial part, its derivative, and the angular part of the solution to the Teukolsky equation. Finally, we discuss the importance of the extra singularity in the radial derivative for the convergence of the metric expansion.
|
1501.04879
|
Giuseppe d'Ambrosi
|
G. d'Ambrosi, S. Satish Kumar, J.W. van Holten
|
Covariant hamiltonian spin dynamics in curved space-time
|
14 pages, accepted version for Phys Lett B, added a footnote and two
references
|
Phys. Lett. B 743 (2015), 478
|
10.1016/j.physletb.2015.03.007
|
NIKHEF/2015-001
|
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The dynamics of spinning particles in curved space-time is discussed,
emphasizing the hamiltonian formulation. Different choices of hamiltonians
allow for the description of different gravitating systems. We give full
results for the simplest case with minimal hamiltonian, constructing constants
of motion including spin. The analysis is illustrated by the example of motion
in Schwarzschild space-time. We also discuss a non-minimal extension of the
hamiltonian giving rise to a gravitational equivalent of the Stern-Gerlach
force. We show that this extension respects a large class of known constants of
motion for the minimal case.
|
[
{
"created": "Tue, 20 Jan 2015 16:59:30 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Mar 2015 10:38:41 GMT",
"version": "v2"
}
] |
2015-11-24
|
[
[
"d'Ambrosi",
"G.",
""
],
[
"Kumar",
"S. Satish",
""
],
[
"van Holten",
"J. W.",
""
]
] |
The dynamics of spinning particles in curved space-time is discussed, emphasizing the hamiltonian formulation. Different choices of hamiltonians allow for the description of different gravitating systems. We give full results for the simplest case with minimal hamiltonian, constructing constants of motion including spin. The analysis is illustrated by the example of motion in Schwarzschild space-time. We also discuss a non-minimal extension of the hamiltonian giving rise to a gravitational equivalent of the Stern-Gerlach force. We show that this extension respects a large class of known constants of motion for the minimal case.
|
2007.13165
|
Gabriel German
|
Gabriel German
|
Evolution of the universe during the inflationary epoch
|
14 pages, 13 figures
| null | null | null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We often find in the literature solutions to the Friedmann and fluid
equations for simple cosmological models during the matter, radiation or
cosmological constant dominated epochs. However no solutions appear for the
inflationary era dominated by the potential energy of a scalar field due,
perhaps, to the fact that we do not have as yet a strongly favored model of
inflation; there are, of course, very well motivated models which fit the data.
The purpose of this article is to study with some detail the evolution of the
Universe during inflation in the slow-roll approximation. Taking the
Starobinsky model as an example, we display exact solutions for the time
evolution of the scalar field $\phi(t)$, scale factor $a(t)$, Hubble function
$H(t)$, equation of state parameter $\omega(t)$ and acceleration of the scale
factor $\ddot{a}(t)$ among other quantities of interest.
|
[
{
"created": "Sun, 26 Jul 2020 16:18:29 GMT",
"version": "v1"
}
] |
2020-07-30
|
[
[
"German",
"Gabriel",
""
]
] |
We often find in the literature solutions to the Friedmann and fluid equations for simple cosmological models during the matter, radiation or cosmological constant dominated epochs. However no solutions appear for the inflationary era dominated by the potential energy of a scalar field due, perhaps, to the fact that we do not have as yet a strongly favored model of inflation; there are, of course, very well motivated models which fit the data. The purpose of this article is to study with some detail the evolution of the Universe during inflation in the slow-roll approximation. Taking the Starobinsky model as an example, we display exact solutions for the time evolution of the scalar field $\phi(t)$, scale factor $a(t)$, Hubble function $H(t)$, equation of state parameter $\omega(t)$ and acceleration of the scale factor $\ddot{a}(t)$ among other quantities of interest.
|
1309.3503
|
Jose Javier Arenas Ferrer
|
Jose J. Arenas
|
The effect of the cosmological expansion on local systems:
Post-Newtonian approximation
| null | null | null | null |
gr-qc astro-ph.EP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Frequently, the quantitative effect of the large-scale cosmological expansion
on local systems is studied in the light of Newtonian approach, and the General
Relativity Theory is neglected. We, however, analyze the influence of
cosmological expansion on small systems in the light of Post-Newtonian
approximation. The equations show the product Hc=6.99*10^-10 ms^-2, and it so
happens that the magnitude of this acceleration is very close the apparently
anomalous acceleration of the Pioneer 10 and 11 spacecraft. Furthermore, we
obtain the new radius at which the acceleration due to the cosmological
expansion has the same magnitude as the two-body attraction, and the classical
critical radius is obtained when the Schwarzschild radius approaches zero (for
example, the Solar System).
|
[
{
"created": "Fri, 13 Sep 2013 16:40:07 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Sep 2013 18:44:37 GMT",
"version": "v2"
},
{
"created": "Wed, 2 Oct 2013 18:13:27 GMT",
"version": "v3"
},
{
"created": "Sat, 30 Nov 2013 10:51:20 GMT",
"version": "v4"
}
] |
2013-12-03
|
[
[
"Arenas",
"Jose J.",
""
]
] |
Frequently, the quantitative effect of the large-scale cosmological expansion on local systems is studied in the light of Newtonian approach, and the General Relativity Theory is neglected. We, however, analyze the influence of cosmological expansion on small systems in the light of Post-Newtonian approximation. The equations show the product Hc=6.99*10^-10 ms^-2, and it so happens that the magnitude of this acceleration is very close the apparently anomalous acceleration of the Pioneer 10 and 11 spacecraft. Furthermore, we obtain the new radius at which the acceleration due to the cosmological expansion has the same magnitude as the two-body attraction, and the classical critical radius is obtained when the Schwarzschild radius approaches zero (for example, the Solar System).
|
1910.05908
|
Ratchaphat Nakarachinda
|
Pitayuth Wongjun, Chun-Hung Chen, and Ratchaphat Nakarachinda
|
Quasinormal modes of a massless Dirac field in de Rham-Gabadadze-Tolley
massive gravity
|
35 pages, 7 figures
|
Phys. Rev. D 101, 124033 (2020)
|
10.1103/PhysRevD.101.124033
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The quasinormal modes of a massless Dirac field in the de
Rham-Gabadadze-Tolley (dRGT) massive gravity theory with asymptotically de
Sitter spacetime are investigated using the Wentzel- Kramers-Brillouin (WKB)
approximation. The effective potential for the massless Dirac field due to the
dRGT black hole is derived. It is found that the shape of the potential depends
crucially on the structure of the graviton mass and the behavior of the
quasinormal modes is controlled by the graviton mass parameters. Higher
potentials give stronger damping of the quasinormal modes. We compare our
results to the Schwarzschild-de Sitter case. Our numerical calculations are
checked using Pad$\acute{e}$ approximation and found that the quasinormal mode
frequencies converge to ones with reasonable accuracy.
|
[
{
"created": "Mon, 14 Oct 2019 03:59:55 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Jun 2020 06:51:29 GMT",
"version": "v2"
}
] |
2020-06-19
|
[
[
"Wongjun",
"Pitayuth",
""
],
[
"Chen",
"Chun-Hung",
""
],
[
"Nakarachinda",
"Ratchaphat",
""
]
] |
The quasinormal modes of a massless Dirac field in the de Rham-Gabadadze-Tolley (dRGT) massive gravity theory with asymptotically de Sitter spacetime are investigated using the Wentzel- Kramers-Brillouin (WKB) approximation. The effective potential for the massless Dirac field due to the dRGT black hole is derived. It is found that the shape of the potential depends crucially on the structure of the graviton mass and the behavior of the quasinormal modes is controlled by the graviton mass parameters. Higher potentials give stronger damping of the quasinormal modes. We compare our results to the Schwarzschild-de Sitter case. Our numerical calculations are checked using Pad$\acute{e}$ approximation and found that the quasinormal mode frequencies converge to ones with reasonable accuracy.
|
1107.0242
|
S Habib Mazharimousavi
|
S. Habib Mazharimousavi, M. Halilsoy and T. Tahamtan
|
Regular charged black hole construction in 2+1 -dimensions
|
9 pages, 2 figures, final version for publication in Physics Letters
A
|
Physics Letters A 376 (2012) 893
|
10.1016/j.physleta.2012.01.001
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
It is well-known that unlike its chargeless version the charged
Banados-Teitelboim-Zanelli (BTZ) black hole solution in 2+1- dimensional
spacetime is singular. We construct a charged, regular extension of the BTZ
black hole solution by employing nonlinear Born-Infeld electrodynamics,
supplemented with the Hoffmann term and gluing different spacetimes. The role
of the latter term is to divide spacetime in a natural way into two regions by
a circle and eliminate the inner singularity. Thermodynamics of such a black
hole is investigated by Kaluza-Klein reduction to the 1+1-dimensional dilaton
gravity.
|
[
{
"created": "Fri, 1 Jul 2011 14:51:10 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Jan 2012 10:03:18 GMT",
"version": "v2"
}
] |
2012-02-13
|
[
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Halilsoy",
"M.",
""
],
[
"Tahamtan",
"T.",
""
]
] |
It is well-known that unlike its chargeless version the charged Banados-Teitelboim-Zanelli (BTZ) black hole solution in 2+1- dimensional spacetime is singular. We construct a charged, regular extension of the BTZ black hole solution by employing nonlinear Born-Infeld electrodynamics, supplemented with the Hoffmann term and gluing different spacetimes. The role of the latter term is to divide spacetime in a natural way into two regions by a circle and eliminate the inner singularity. Thermodynamics of such a black hole is investigated by Kaluza-Klein reduction to the 1+1-dimensional dilaton gravity.
|
gr-qc/9802029
|
Nivaldo A. Lemos
|
Flavio G. Alvarenga and Nivaldo A. Lemos
|
Dynamical Vacuum in Quantum Cosmology
|
Latex, 19 pages, to appear in Gen. Rel. Grav
|
Gen.Rel.Grav. 30 (1998) 681-694
|
10.1023/A:1018896900336
| null |
gr-qc
| null |
By regarding the vacuum as a perfect fluid with equation of state p=-rho, de
Sitter's cosmological model is quantized. Our treatment differs from previous
ones in that it endows the vacuum with dynamical degrees of freedom. Instead of
being postulated from the start, the cosmological constant arises from the
degrees of freedom of the vacuum regarded as a dynamical entity, and a time
variable can be naturally introduced. Taking the scale factor as the sole
degree of freedom of the gravitational field, stationary and wave-packet
solutions to the Wheeler-DeWitt equation are found. It turns out that states of
the Universe with a definite value of the cosmological constant do not exist.
For the wave packets investigated, quantum effects are noticeable only for
small values of the scale factor, a classical regime being attained at
asymptotically large times.
|
[
{
"created": "Fri, 13 Feb 1998 17:55:40 GMT",
"version": "v1"
}
] |
2015-06-25
|
[
[
"Alvarenga",
"Flavio G.",
""
],
[
"Lemos",
"Nivaldo A.",
""
]
] |
By regarding the vacuum as a perfect fluid with equation of state p=-rho, de Sitter's cosmological model is quantized. Our treatment differs from previous ones in that it endows the vacuum with dynamical degrees of freedom. Instead of being postulated from the start, the cosmological constant arises from the degrees of freedom of the vacuum regarded as a dynamical entity, and a time variable can be naturally introduced. Taking the scale factor as the sole degree of freedom of the gravitational field, stationary and wave-packet solutions to the Wheeler-DeWitt equation are found. It turns out that states of the Universe with a definite value of the cosmological constant do not exist. For the wave packets investigated, quantum effects are noticeable only for small values of the scale factor, a classical regime being attained at asymptotically large times.
|
gr-qc/9602054
|
Neil Cornish
|
Neil J. Cornish
|
Time and Chaos in General Relativity
|
4 pages, RevTeX, 1 figure
| null | null |
CWRU-P14-95
|
gr-qc
| null |
The study of dynamics in general relativity has been hampered by a lack of
coordinate independent measures of chaos. Here we present a variety of
invariant measures for quantifying chaotic dynamics in relativity by exploiting
the coordinate independence of fractal dimensions. We discuss how preferred
choices of time naturally arise in chaotic systems and how the existence of
invariant signals of chaos allow us to reinstate standard coordinate dependent
measures. As an application, we study the Mixmaster universes and find it to
exhibit transient soft chaos.
|
[
{
"created": "Tue, 27 Feb 1996 19:11:33 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Cornish",
"Neil J.",
""
]
] |
The study of dynamics in general relativity has been hampered by a lack of coordinate independent measures of chaos. Here we present a variety of invariant measures for quantifying chaotic dynamics in relativity by exploiting the coordinate independence of fractal dimensions. We discuss how preferred choices of time naturally arise in chaotic systems and how the existence of invariant signals of chaos allow us to reinstate standard coordinate dependent measures. As an application, we study the Mixmaster universes and find it to exhibit transient soft chaos.
|
2006.01763
|
Kavoos Abbasi
|
Kavoos Abbasi, Shirvan Gharaati
|
A Tsallisian Universe
| null | null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we adopt the Verlinde hypothesis on the origin of gravity as
the consequence of the tendency of systems to increase their entropy, and
employ the Tsallis statistics. Thereinafter, modifications to the Newtonian
second law of motion, its gravity and radial velocity profile are studied. In
addition and in a classical framework, the corresponding cosmology and also its
ability in describing the inflationary phases are investigated.
|
[
{
"created": "Tue, 2 Jun 2020 16:42:57 GMT",
"version": "v1"
}
] |
2020-06-03
|
[
[
"Abbasi",
"Kavoos",
""
],
[
"Gharaati",
"Shirvan",
""
]
] |
In this paper, we adopt the Verlinde hypothesis on the origin of gravity as the consequence of the tendency of systems to increase their entropy, and employ the Tsallis statistics. Thereinafter, modifications to the Newtonian second law of motion, its gravity and radial velocity profile are studied. In addition and in a classical framework, the corresponding cosmology and also its ability in describing the inflationary phases are investigated.
|
2203.05461
|
Atul Kedia
|
Atul Kedia, Hee Il Kim, In-Saeng Suh, Grant J. Mathews
|
Binary neutron star mergers as a probe of quark-hadron crossover
equations of state
|
8 pages, 3 figures
|
Phys. Rev. D 106, 103027 (2022)
|
10.1103/PhysRevD.106.103027
| null |
gr-qc astro-ph.HE nucl-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
It is anticipated that the gravitational radiation detected in future
gravitational wave (GW) detectors from binary neutron star (NS) mergers can
probe the high-density equation of state (EOS). We perform the first
simulations of binary NS mergers which adopt various parametrizations of the
quark-hadron crossover (QHC) EOS. These are constructed from combinations of a
hadronic EOS ($n_{b} < 2~n_0$) and a quark-matter EOS ($n_{b} >~5~n_0$), where
$n_{b}$ and $n_0$ are the baryon number density and the nuclear saturation
density, respectively. At the crossover densities ($2~ n_0 < n_{b} < 5~ n_0$)
the QHC EOSs continuously soften, while remaining stiffer than hadronic and
first-order phase transition EOSs, achieving the stiffness of strongly
correlated quark matter. This enhanced stiffness leads to significantly longer
lifetimes of the postmerger NS than that for a pure hadronic EOS. We find a
dual nature of these EOSs such that their maximum chirp GW frequencies
$f_{max}$ fall into the category of a soft EOS while the dominant peak
frequencies ($f_{peak}$) of the postmerger stage fall in between that of a soft
and stiff hadronic EOS. An observation of this kind of dual nature in the
characteristic GW frequencies will provide crucial evidence for the existence
of strongly interacting quark matter at the crossover densities for QCD.
|
[
{
"created": "Thu, 10 Mar 2022 16:34:30 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Nov 2022 21:53:10 GMT",
"version": "v2"
},
{
"created": "Tue, 22 Nov 2022 16:18:57 GMT",
"version": "v3"
}
] |
2023-11-15
|
[
[
"Kedia",
"Atul",
""
],
[
"Kim",
"Hee Il",
""
],
[
"Suh",
"In-Saeng",
""
],
[
"Mathews",
"Grant J.",
""
]
] |
It is anticipated that the gravitational radiation detected in future gravitational wave (GW) detectors from binary neutron star (NS) mergers can probe the high-density equation of state (EOS). We perform the first simulations of binary NS mergers which adopt various parametrizations of the quark-hadron crossover (QHC) EOS. These are constructed from combinations of a hadronic EOS ($n_{b} < 2~n_0$) and a quark-matter EOS ($n_{b} >~5~n_0$), where $n_{b}$ and $n_0$ are the baryon number density and the nuclear saturation density, respectively. At the crossover densities ($2~ n_0 < n_{b} < 5~ n_0$) the QHC EOSs continuously soften, while remaining stiffer than hadronic and first-order phase transition EOSs, achieving the stiffness of strongly correlated quark matter. This enhanced stiffness leads to significantly longer lifetimes of the postmerger NS than that for a pure hadronic EOS. We find a dual nature of these EOSs such that their maximum chirp GW frequencies $f_{max}$ fall into the category of a soft EOS while the dominant peak frequencies ($f_{peak}$) of the postmerger stage fall in between that of a soft and stiff hadronic EOS. An observation of this kind of dual nature in the characteristic GW frequencies will provide crucial evidence for the existence of strongly interacting quark matter at the crossover densities for QCD.
|
1301.3927
|
Christopher Pope
|
G. W. Gibbons, A. H. Mujtaba and C. N. Pope
|
Ergoregions in Magnetised Black Hole Spacetimes
|
31 pages. Typos corrected, references added, discussion of asymptotic
structure extended
| null | null |
DAMTP-2013-5, MIFPA-13-02
|
gr-qc astro-ph.HE hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The spacetimes obtained by Ernst's procedure for appending an external
magnetic field $B$ to a seed Kerr-Newman black hole are commonly believed to be
asymptotic to the static Melvin solution. We show that this is not in general
true. Unless the electric charge of the black hole satisfies $Q= jB(1+ 1/4 j^2
B^4)$, where $j$ is the angular momentum of the original seed solution, an
ergoregion extends all the way from the black hole horizon to infinity. We give
a self-contained account of the solution-generating procedure, including
including explicit formulae for the metric and the vector potential. In the
case when $Q= jB(1+ 1/4 j^2 B^4)$, we show that there is an arbitrariness in
the choice of asymptotically timelike Killing field $K_\Omega=
\partial/\partial t+ \Omega \partial/\partial \phi$, because there is no
canonical choice of $\Omega$. For one choice, $\Omega=\Omega_s$, the metric is
asymptotically static, and there is an ergoregion confined to the neighbourhood
of the horizon. On the other hand, by choosing $\Omega=\Omega_H$, so that
$K_{\Omega_H}$ is co-rotating with the horizon, then for sufficiently large $B$
numerical studies indicate there is no ergoregion at all. For smaller values,
in a range $B_-<B<B_+$, there is a toroidal ergoregion outside and disjoint
from the horizon. If $B\le B_-$ this ergoregion expands all the way to infinity
in a cylindrical region near to the rotation axis. For black holes whose size
is small compared to the Melvin radius 2/B, we recover Wald's result that it is
energetically favourable for the hole to acquire a charge $2jB$.
|
[
{
"created": "Wed, 16 Jan 2013 21:34:12 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Apr 2013 14:18:58 GMT",
"version": "v2"
}
] |
2013-04-25
|
[
[
"Gibbons",
"G. W.",
""
],
[
"Mujtaba",
"A. H.",
""
],
[
"Pope",
"C. N.",
""
]
] |
The spacetimes obtained by Ernst's procedure for appending an external magnetic field $B$ to a seed Kerr-Newman black hole are commonly believed to be asymptotic to the static Melvin solution. We show that this is not in general true. Unless the electric charge of the black hole satisfies $Q= jB(1+ 1/4 j^2 B^4)$, where $j$ is the angular momentum of the original seed solution, an ergoregion extends all the way from the black hole horizon to infinity. We give a self-contained account of the solution-generating procedure, including including explicit formulae for the metric and the vector potential. In the case when $Q= jB(1+ 1/4 j^2 B^4)$, we show that there is an arbitrariness in the choice of asymptotically timelike Killing field $K_\Omega= \partial/\partial t+ \Omega \partial/\partial \phi$, because there is no canonical choice of $\Omega$. For one choice, $\Omega=\Omega_s$, the metric is asymptotically static, and there is an ergoregion confined to the neighbourhood of the horizon. On the other hand, by choosing $\Omega=\Omega_H$, so that $K_{\Omega_H}$ is co-rotating with the horizon, then for sufficiently large $B$ numerical studies indicate there is no ergoregion at all. For smaller values, in a range $B_-<B<B_+$, there is a toroidal ergoregion outside and disjoint from the horizon. If $B\le B_-$ this ergoregion expands all the way to infinity in a cylindrical region near to the rotation axis. For black holes whose size is small compared to the Melvin radius 2/B, we recover Wald's result that it is energetically favourable for the hole to acquire a charge $2jB$.
|
gr-qc/9405004
|
Mark Trodden
|
R. Moessner and M. Trodden (Brown University)
|
Singularity-Free Two Dimensional Cosmologies
|
15 pages, uses LaTeX, 7 figures (available from the authors),
significant changes to conformal matter section, more figures added
|
Phys.Rev.D51:2801-2807,1995
|
10.1103/PhysRevD.51.2801
|
BROWN-HET-942
|
gr-qc hep-th
| null |
We present a class of theories of two dimensional gravity which admits
homogeneous and isotropic solutions that are nonsingular and asymptotically
approach a FRW matter dominated universe at late times. These models are
generalizations of two dimensional dilaton gravity and both vacuum solutions
and those including conformally coupled matter are investigated. In each case
our construction leads to an inflationary stage driven by the gravitational
sector. Our work comprises a simple example of the `Nonsingular Universe'
constructions of ref. [1].
|
[
{
"created": "Mon, 2 May 1994 17:41:49 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Nov 1994 18:36:25 GMT",
"version": "v2"
}
] |
2011-07-19
|
[
[
"Moessner",
"R.",
"",
"Brown University"
],
[
"Trodden",
"M.",
"",
"Brown University"
]
] |
We present a class of theories of two dimensional gravity which admits homogeneous and isotropic solutions that are nonsingular and asymptotically approach a FRW matter dominated universe at late times. These models are generalizations of two dimensional dilaton gravity and both vacuum solutions and those including conformally coupled matter are investigated. In each case our construction leads to an inflationary stage driven by the gravitational sector. Our work comprises a simple example of the `Nonsingular Universe' constructions of ref. [1].
|
1512.03684
|
Edward Wilson-Ewing
|
Edward Wilson-Ewing
|
Anisotropic loop quantum cosmology with self-dual variables
|
16 pages, v2: Clarifications added, typos corrected
|
Phys. Rev. D 93, 083502 (2016)
|
10.1103/PhysRevD.93.083502
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A loop quantization of the diagonal class A Bianchi models starting from the
complex-valued self-dual connection variables is presented in this paper. The
basic operators in the quantum theory correspond to areas and generalized
holonomies of the Ashtekar connection and the reality conditions are
implemented via the choice of the inner product on the kinematical Hilbert
space. The action of the Hamiltonian constraint operator is given explicitly
for the case when the matter content is a massless scalar field (in which case
the scalar field can be used as a relational clock), and it is shown that the
big-bang and big-crunch singularities are resolved in the sense that singular
and non-singular states decouple under the action of the Hamiltonian constraint
operator.
|
[
{
"created": "Fri, 11 Dec 2015 15:54:26 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Mar 2016 12:24:29 GMT",
"version": "v2"
}
] |
2016-04-13
|
[
[
"Wilson-Ewing",
"Edward",
""
]
] |
A loop quantization of the diagonal class A Bianchi models starting from the complex-valued self-dual connection variables is presented in this paper. The basic operators in the quantum theory correspond to areas and generalized holonomies of the Ashtekar connection and the reality conditions are implemented via the choice of the inner product on the kinematical Hilbert space. The action of the Hamiltonian constraint operator is given explicitly for the case when the matter content is a massless scalar field (in which case the scalar field can be used as a relational clock), and it is shown that the big-bang and big-crunch singularities are resolved in the sense that singular and non-singular states decouple under the action of the Hamiltonian constraint operator.
|
1412.3991
|
Tommi Markkanen Ph.D.
|
Tommi Markkanen
|
Curvature induced running of the cosmological constant
|
4 pages. Version 2; minor changes, added references. Published
version (PRD)
|
Phys. Rev. D 91, 124011; 2 June 2015
| null |
HIP-2014-36/TH
|
gr-qc hep-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this work we investigate the renormalization group flow of the
cosmological constant $\Lambda$ induced by the change in space-time curvature
in the electroweak vacuum. We calculate the generic magnitude resulting from
running in the standard model in a subtraction scheme that respects the
Appelquist-Carazzone decoupling theorem. Interestingly, we find in this
prescription that for a non-minimal coupling $\xi\lesssim 10^4$ the magnitude
of the generated contribution remains below the value consistent with
observations.
|
[
{
"created": "Fri, 12 Dec 2014 13:49:43 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Jun 2015 17:36:31 GMT",
"version": "v2"
}
] |
2015-06-05
|
[
[
"Markkanen",
"Tommi",
""
]
] |
In this work we investigate the renormalization group flow of the cosmological constant $\Lambda$ induced by the change in space-time curvature in the electroweak vacuum. We calculate the generic magnitude resulting from running in the standard model in a subtraction scheme that respects the Appelquist-Carazzone decoupling theorem. Interestingly, we find in this prescription that for a non-minimal coupling $\xi\lesssim 10^4$ the magnitude of the generated contribution remains below the value consistent with observations.
|
1308.3308
|
Tetsuya Shiromizu
|
Tetsuya Shiromizu, Sumio Yamada, Kentaro Tanabe
|
Quasi-local characteristics of dynamical extreme black holes
|
4pages
| null | null | null |
gr-qc hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Introducing the concept of the extreme trapping horizon, we discuss geometric
features of dynamical extreme black holes in four dimensions and then derive
the integral identities which hold for the dynamical extreme black holes. We
address the causal/geometrical features too.
|
[
{
"created": "Thu, 15 Aug 2013 05:26:59 GMT",
"version": "v1"
}
] |
2013-08-16
|
[
[
"Shiromizu",
"Tetsuya",
""
],
[
"Yamada",
"Sumio",
""
],
[
"Tanabe",
"Kentaro",
""
]
] |
Introducing the concept of the extreme trapping horizon, we discuss geometric features of dynamical extreme black holes in four dimensions and then derive the integral identities which hold for the dynamical extreme black holes. We address the causal/geometrical features too.
|
gr-qc/0107010
|
Marc Lachi\`eze-Rey
|
M. Lachi\`eze-Rey (Centre d'Etudes de Saclay, France)
|
Space and Observers in Cosmology
|
21 pages, 6 figures. Astronomy & Astrophysics, in press
| null |
10.1051/0004-6361:20010952
|
CEA-00999
|
gr-qc
| null |
I provide a prescription to define space, at a given moment, for an arbitrary
observer in an arbitrary (sufficiently regular) curved space-time. This
prescription, based on synchronicity (simultaneity) arguments, defines a
foliation of space-time, which corresponds to a family of canonically
associated observers. It provides also a natural global reference frame (with
space and time coordinates) for the observer, in space-time (or rather in the
part of it which is causally connected to him), which remains Minkowskian along
his world-line. This definition intends to provide a basis for the problem of
quantization in curved space-time, and/or for non inertial observers.
Application to Mikowski space-time illustrates clearly the fact that
different observers see different spaces. It allows, for instance, to define
space everywhere without ambiguity, for the Langevin observer (involved in the
Langevin pseudoparadox of twins). Applied to the Rindler observer (with uniform
acceleration) it leads to the Rindler coordinates, whose choice is so justified
with a physical basis. This leads to an interpretation of the Unruh effect, as
due to the observer's dependence of the definition of space (and time). This
prescription is also applied in cosmology, for inertial observers in the
Friedmann - Lemaitre models: space for the observer appears to differ from the
hypersurfaces of homogeneity, which do not obey the simultaneity requirement. I
work out two examples: the Einstein - de Sitter model, in which space, for an
inertial observer, is not flat nor homogeneous, and the de Sitter case.
|
[
{
"created": "Tue, 3 Jul 2001 14:33:59 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Aug 2001 15:20:09 GMT",
"version": "v2"
}
] |
2009-11-07
|
[
[
"Lachièze-Rey",
"M.",
"",
"Centre d'Etudes de Saclay, France"
]
] |
I provide a prescription to define space, at a given moment, for an arbitrary observer in an arbitrary (sufficiently regular) curved space-time. This prescription, based on synchronicity (simultaneity) arguments, defines a foliation of space-time, which corresponds to a family of canonically associated observers. It provides also a natural global reference frame (with space and time coordinates) for the observer, in space-time (or rather in the part of it which is causally connected to him), which remains Minkowskian along his world-line. This definition intends to provide a basis for the problem of quantization in curved space-time, and/or for non inertial observers. Application to Mikowski space-time illustrates clearly the fact that different observers see different spaces. It allows, for instance, to define space everywhere without ambiguity, for the Langevin observer (involved in the Langevin pseudoparadox of twins). Applied to the Rindler observer (with uniform acceleration) it leads to the Rindler coordinates, whose choice is so justified with a physical basis. This leads to an interpretation of the Unruh effect, as due to the observer's dependence of the definition of space (and time). This prescription is also applied in cosmology, for inertial observers in the Friedmann - Lemaitre models: space for the observer appears to differ from the hypersurfaces of homogeneity, which do not obey the simultaneity requirement. I work out two examples: the Einstein - de Sitter model, in which space, for an inertial observer, is not flat nor homogeneous, and the de Sitter case.
|
1406.0497
|
Chris Vuille Ph.D.
|
Chris Vuille, James Ipser, and Jeff Gallagher
|
Einstein-Proca Model, Micro Black Holes, and Naked Singularities
| null |
General Relativity and Gravitation, Volume 34, Number 5, May 2002,
pp.689-696
| null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The Einstein-Proca equations, describing a spin-1 massive vector field in
general relativity, are studied in the static, spherically-symmetric case. The
Proca field equation is a highly nonlinear wave equation, but can be solved to
good accuracy in perturbation theory, which should be very accurate for a wide
range of mass scales. The resulting first order metric reduces to the
Reissner-Nordstrom solution in the limit as the range parameter $\mu$ goes to
zero. The additional terms in the $g_{00}$ metric are positive, as in
Reissner-Nordstrom, in agreement with previous numerical solutions, and hence
involve naked singularities.
|
[
{
"created": "Sat, 31 May 2014 01:59:14 GMT",
"version": "v1"
}
] |
2014-06-04
|
[
[
"Vuille",
"Chris",
""
],
[
"Ipser",
"James",
""
],
[
"Gallagher",
"Jeff",
""
]
] |
The Einstein-Proca equations, describing a spin-1 massive vector field in general relativity, are studied in the static, spherically-symmetric case. The Proca field equation is a highly nonlinear wave equation, but can be solved to good accuracy in perturbation theory, which should be very accurate for a wide range of mass scales. The resulting first order metric reduces to the Reissner-Nordstrom solution in the limit as the range parameter $\mu$ goes to zero. The additional terms in the $g_{00}$ metric are positive, as in Reissner-Nordstrom, in agreement with previous numerical solutions, and hence involve naked singularities.
|
1104.5002
|
Luca Fabbri
|
Luca Fabbri
|
Metric Solutions in Torsionless Gauge for Vacuum Conformal Gravity
|
11 pages
|
J.Math.Phys.54,062501,2013
|
10.1063/1.4808257
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In a recent paper we have established the form of the metric-torsional
conformal gravitational field equations, and in the present paper we study
their vacuum configurations; we will consider a specific situation that will
enable us to look for the torsionless limit: two types of special exact
solutions are found eventually. A discussion on general remarks will follow.
|
[
{
"created": "Tue, 26 Apr 2011 19:45:05 GMT",
"version": "v1"
},
{
"created": "Fri, 31 May 2013 15:48:20 GMT",
"version": "v2"
},
{
"created": "Thu, 10 Apr 2014 12:33:14 GMT",
"version": "v3"
}
] |
2014-04-11
|
[
[
"Fabbri",
"Luca",
""
]
] |
In a recent paper we have established the form of the metric-torsional conformal gravitational field equations, and in the present paper we study their vacuum configurations; we will consider a specific situation that will enable us to look for the torsionless limit: two types of special exact solutions are found eventually. A discussion on general remarks will follow.
|
2112.07730
|
Todd Oliynyk
|
Florian Beyer and Todd A. Oliynyk
|
Localized big bang stability for the Einstein-scalar field equations
|
Final version; agrees with published article
|
Arch. Rational Mech. Anal. 248, 3 (2024)
|
10.1007/s00205-023-01939-9
| null |
gr-qc math.AP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We prove the nonlinear stability in the contracting direction of
Friedmann-Lema\^itre-Robertson-Walker (FLRW) solutions to the Einstein-scalar
field equations in $n\geq 3$ spacetime dimensions that are defined on spacetime
manifolds of the form $(0,t_0]\times \mathbb{T}^{n-1}$, $t_0>0$. Stability is
established under the assumption that the initial data is
\textit{synchronized}, which means that on the initial hypersurface $\Sigma=
\{t_0\}\times \mathbb{T}^{n-1}$ the scalar field $\tau=
\exp\bigl(\sqrt{\frac{2(n-2)}{n-1}}\phi\bigr) $ is constant, that is,
$\Sigma=\tau^{-1}(\{t_0\})$. As we show that all initial data sets that are
sufficiently close to FRLW ones can be evolved via the Einstein-scalar field
equation into new initial data sets that are \textit{synchronized}, no
generality is lost by this assumption. By using $\tau$ as a time coordinate, we
establish that the perturbed FLRW spacetime manifolds are of the form $M =
\bigcup_{t\in (0,t_0]}\tau^{-1}(\{t\})\cong (0,t_0]\times \mathbb{T}^{n-1}$,
the perturbed FLRW solutions are asymptotically pointwise Kasner as $\tau
\searrow 0$, and a big bang singularity, characterised by the blow up of the
scalar curvature, occurs at $\tau=0$. An important aspect of our past stability
proof is that we use a hyperbolic gauge reduction of the Einstein-scalar field
equations. As a consequence, all of the estimates used in the stability proof
can be localized and we employ this property to establish a corresponding
localized past stability result for the FLRW solutions.
|
[
{
"created": "Tue, 14 Dec 2021 20:18:57 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Oct 2022 02:00:36 GMT",
"version": "v2"
},
{
"created": "Mon, 15 Jan 2024 21:13:42 GMT",
"version": "v3"
}
] |
2024-01-17
|
[
[
"Beyer",
"Florian",
""
],
[
"Oliynyk",
"Todd A.",
""
]
] |
We prove the nonlinear stability in the contracting direction of Friedmann-Lema\^itre-Robertson-Walker (FLRW) solutions to the Einstein-scalar field equations in $n\geq 3$ spacetime dimensions that are defined on spacetime manifolds of the form $(0,t_0]\times \mathbb{T}^{n-1}$, $t_0>0$. Stability is established under the assumption that the initial data is \textit{synchronized}, which means that on the initial hypersurface $\Sigma= \{t_0\}\times \mathbb{T}^{n-1}$ the scalar field $\tau= \exp\bigl(\sqrt{\frac{2(n-2)}{n-1}}\phi\bigr) $ is constant, that is, $\Sigma=\tau^{-1}(\{t_0\})$. As we show that all initial data sets that are sufficiently close to FRLW ones can be evolved via the Einstein-scalar field equation into new initial data sets that are \textit{synchronized}, no generality is lost by this assumption. By using $\tau$ as a time coordinate, we establish that the perturbed FLRW spacetime manifolds are of the form $M = \bigcup_{t\in (0,t_0]}\tau^{-1}(\{t\})\cong (0,t_0]\times \mathbb{T}^{n-1}$, the perturbed FLRW solutions are asymptotically pointwise Kasner as $\tau \searrow 0$, and a big bang singularity, characterised by the blow up of the scalar curvature, occurs at $\tau=0$. An important aspect of our past stability proof is that we use a hyperbolic gauge reduction of the Einstein-scalar field equations. As a consequence, all of the estimates used in the stability proof can be localized and we employ this property to establish a corresponding localized past stability result for the FLRW solutions.
|
1006.1614
|
Theo Verwimp
|
Theo Verwimp
|
Anti-de Sitter gauge theory for gravity
|
36 pages;typos corrected on page 18 eqs (5.20)&(5.23)
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
First a review is given of Riemann-Cartan space-time and Einstein-Cartan
gravity. This gives us the necessary tools to handle the SO(2,3) Yang-Mills
gauge theory for gravity. New here is the derivation of the conservation laws.
Finally possible solutions of the field equations are discussed. They depend on
the scale of the de Sitter length. Solutions to the anti-de Sitter field
equations are given in the case of a Schwarzschild and FRW-geometry.
|
[
{
"created": "Tue, 8 Jun 2010 17:08:53 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Dec 2017 14:05:17 GMT",
"version": "v2"
},
{
"created": "Mon, 14 Jun 2021 15:03:05 GMT",
"version": "v3"
},
{
"created": "Fri, 8 Oct 2021 11:06:59 GMT",
"version": "v4"
}
] |
2021-10-11
|
[
[
"Verwimp",
"Theo",
""
]
] |
First a review is given of Riemann-Cartan space-time and Einstein-Cartan gravity. This gives us the necessary tools to handle the SO(2,3) Yang-Mills gauge theory for gravity. New here is the derivation of the conservation laws. Finally possible solutions of the field equations are discussed. They depend on the scale of the de Sitter length. Solutions to the anti-de Sitter field equations are given in the case of a Schwarzschild and FRW-geometry.
|
1605.00764
|
Hang Liu
|
Hang Liu, Xin-he Meng, Wei Xu and Bin Zhu
|
Universal entropy relations: entropy formulae and entropy bound
| null |
Europhys.Lett. 119 (2017) no.2, 20003
|
10.1209/0295-5075/119/20003
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We survey the applications of universal entropy relations in black holes with
multi-horizons. In sharp distinction to conventional entropy product, the
entropy relationship here not only improve our understanding of black hole
entropy but was introduced as an elegant technique trick for handling various
entropy bounds and sum. Despite the primarily technique role, entropy relations
have provided considerable insight into several different types of gravity,
including massive gravity, Einstein-Dilaton gravity and Horava-Lifshitz
gravity. We present and discuss the results for each one.
|
[
{
"created": "Tue, 3 May 2016 07:26:56 GMT",
"version": "v1"
}
] |
2017-10-09
|
[
[
"Liu",
"Hang",
""
],
[
"Meng",
"Xin-he",
""
],
[
"Xu",
"Wei",
""
],
[
"Zhu",
"Bin",
""
]
] |
We survey the applications of universal entropy relations in black holes with multi-horizons. In sharp distinction to conventional entropy product, the entropy relationship here not only improve our understanding of black hole entropy but was introduced as an elegant technique trick for handling various entropy bounds and sum. Despite the primarily technique role, entropy relations have provided considerable insight into several different types of gravity, including massive gravity, Einstein-Dilaton gravity and Horava-Lifshitz gravity. We present and discuss the results for each one.
|
1203.2471
|
Alan D. Rendall
|
Ho Lee and Alan D. Rendall
|
The Einstein-Boltzmann system and positivity
|
24 pages
| null | null |
AEI-2012-022
|
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The Einstein-Boltzmann system is studied, with particular attention to the
non-negativity of the solution of the Boltzmann equation. A new parametrization
of post-collisional momenta in general relativity is introduced and then used
to simplify the conditions on the collision cross-section given by Bancel and
Choquet-Bruhat. The non-negativity of solutions of the Boltzmann equation on a
given curved spacetime has been studied by Bichteler and by Tadmon. By
examining to what extent the results of these authors apply in the framework of
Bancel and Choquet-Bruhat, the non-negativity problem for the
Einstein-Boltzmann system is resolved for a certain class of scattering
kernels. It is emphasized that it is a challenge to extend the existing theory
of the Cauchy problem for the Einstein-Boltzmann system so as to include
scattering kernels which are physically well-motivated.
|
[
{
"created": "Mon, 12 Mar 2012 12:30:59 GMT",
"version": "v1"
}
] |
2012-03-13
|
[
[
"Lee",
"Ho",
""
],
[
"Rendall",
"Alan D.",
""
]
] |
The Einstein-Boltzmann system is studied, with particular attention to the non-negativity of the solution of the Boltzmann equation. A new parametrization of post-collisional momenta in general relativity is introduced and then used to simplify the conditions on the collision cross-section given by Bancel and Choquet-Bruhat. The non-negativity of solutions of the Boltzmann equation on a given curved spacetime has been studied by Bichteler and by Tadmon. By examining to what extent the results of these authors apply in the framework of Bancel and Choquet-Bruhat, the non-negativity problem for the Einstein-Boltzmann system is resolved for a certain class of scattering kernels. It is emphasized that it is a challenge to extend the existing theory of the Cauchy problem for the Einstein-Boltzmann system so as to include scattering kernels which are physically well-motivated.
|
1704.07713
|
Bobir Toshmatov
|
Zden\v{e}k Stuchl\'ik, Jan Schee, Bobir Toshmatov, Jan Hlad\'ik, Jan
Novotn\'y
|
Gravitational instability of polytropic spheres containing region of
trapped null geodesics: a possible explanation of central supermassive black
holes in galactic halos
|
28 pages, 8 figures, 2 tables
|
JCAP 06 (2017) 056
|
10.1088/1475-7516/2017/06/056
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study behaviour of gravitational waves in the recently introduced general
relativistic polytropic spheres containing a region of trapped null geodesics
extended around radius of the stable null circular geodesic that can exist for
the polytropic index $N>2.138$ and the relativistic parameter, giving ratio of
the central pressure $p_\mathrm{c}$ to the central energy density
$\rho_\mathrm{c}$, higher than $\sigma = 0.677$. In the trapping zones of such
polytropes, the effective potential of the axial gravitational wave
perturbations resembles those related to the ultracompact uniform density
objects, giving thus similar long-lived axial gravitational modes. These
long-lived linear perturbations are related to the stable circular null
geodesic and due to additional non-linear phenomena could lead to conversion of
the trapping zone to a black hole. We give in the eikonal limit examples of the
long-lived gravitational modes, their oscillatory frequencies and slow damping
rates, for the trapping zones of the polytropes with $N \in (2.138,4)$.
However, in the trapping polytropes the long-lived damped modes exist only for
very large values of the multipole number $\ell>50$, while for smaller values
of $\ell$ the numerical calculations indicate existence of fast growing
unstable axial gravitational modes. We demonstrate that for polytropes with $N
\geq 3.78$, the trapping region is by many orders smaller than extension of the
polytrope, and the mass contained in the trapping zone is about $10^{-3}$ of
the total mass of the polytrope. Therefore, the gravitational instability of
such trapping zones could serve as a model explaining creation of central
supermassive black holes in galactic halos or galaxy clusters.
|
[
{
"created": "Tue, 25 Apr 2017 14:31:24 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Jul 2017 05:02:43 GMT",
"version": "v2"
}
] |
2017-07-04
|
[
[
"Stuchlík",
"Zdeněk",
""
],
[
"Schee",
"Jan",
""
],
[
"Toshmatov",
"Bobir",
""
],
[
"Hladík",
"Jan",
""
],
[
"Novotný",
"Jan",
""
]
] |
We study behaviour of gravitational waves in the recently introduced general relativistic polytropic spheres containing a region of trapped null geodesics extended around radius of the stable null circular geodesic that can exist for the polytropic index $N>2.138$ and the relativistic parameter, giving ratio of the central pressure $p_\mathrm{c}$ to the central energy density $\rho_\mathrm{c}$, higher than $\sigma = 0.677$. In the trapping zones of such polytropes, the effective potential of the axial gravitational wave perturbations resembles those related to the ultracompact uniform density objects, giving thus similar long-lived axial gravitational modes. These long-lived linear perturbations are related to the stable circular null geodesic and due to additional non-linear phenomena could lead to conversion of the trapping zone to a black hole. We give in the eikonal limit examples of the long-lived gravitational modes, their oscillatory frequencies and slow damping rates, for the trapping zones of the polytropes with $N \in (2.138,4)$. However, in the trapping polytropes the long-lived damped modes exist only for very large values of the multipole number $\ell>50$, while for smaller values of $\ell$ the numerical calculations indicate existence of fast growing unstable axial gravitational modes. We demonstrate that for polytropes with $N \geq 3.78$, the trapping region is by many orders smaller than extension of the polytrope, and the mass contained in the trapping zone is about $10^{-3}$ of the total mass of the polytrope. Therefore, the gravitational instability of such trapping zones could serve as a model explaining creation of central supermassive black holes in galactic halos or galaxy clusters.
|
2211.08159
|
Sahazada Aziz
|
Sahazada Aziz, Sohan Kumar Jha and Anisur Rahaman
|
The inflationary scenario in the $f(R)$ gravity model with a $R^4$ term
|
Published version; 14 pages, 7 figures
|
2021 Class. Quantum Grav. 38 225008
|
10.1088/1361-6382/ac2dd0
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We investigate the cosmic inflation scenario of a specific $f(R)$ model that
contains more than one higher-order term in $R$. The $f(R)$ considered here has
the terms $R^2$, $R^3$, and $R^4$ along with the linear term. A rigorous
investigation has been carried out in the presence of these higher-order terms
to figure out whether it leads to a physically sensible cosmic inflationary
model. We examine in detail, subject to which conditions this $f(R)$ model
renders a viable inflationary scenario, and it has been found that the outcomes
of our study agree well with the recent PLANCK results.
|
[
{
"created": "Tue, 15 Nov 2022 14:12:01 GMT",
"version": "v1"
}
] |
2022-11-16
|
[
[
"Aziz",
"Sahazada",
""
],
[
"Jha",
"Sohan Kumar",
""
],
[
"Rahaman",
"Anisur",
""
]
] |
We investigate the cosmic inflation scenario of a specific $f(R)$ model that contains more than one higher-order term in $R$. The $f(R)$ considered here has the terms $R^2$, $R^3$, and $R^4$ along with the linear term. A rigorous investigation has been carried out in the presence of these higher-order terms to figure out whether it leads to a physically sensible cosmic inflationary model. We examine in detail, subject to which conditions this $f(R)$ model renders a viable inflationary scenario, and it has been found that the outcomes of our study agree well with the recent PLANCK results.
|
gr-qc/9908046
|
Andrei V. Frolov
|
Andrei V. Frolov
|
Continuous Self-Similarity Breaking in Critical Collapse
|
RevTeX 3.1, 28 pages, 5 figures; discussion rewritten to clarify
several issues
|
Phys.Rev. D61 (2000) 084006
|
10.1103/PhysRevD.61.084006
| null |
gr-qc
| null |
This paper studies near-critical evolution of the spherically symmetric
scalar field configurations close to the continuously self-similar solution.
Using analytic perturbative methods, it is shown that a generic growing
perturbation departs from the critical Roberts solution in a universal way. We
argue that in the course of its evolution, initial continuous self-similarity
of the background is broken into discrete self-similarity with echoing period
$\Delta = \sqrt{2}\pi = 4.44$, reproducing the symmetries of the critical
Choptuik solution.
|
[
{
"created": "Mon, 16 Aug 1999 23:20:14 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Dec 1999 03:17:00 GMT",
"version": "v2"
}
] |
2009-10-31
|
[
[
"Frolov",
"Andrei V.",
""
]
] |
This paper studies near-critical evolution of the spherically symmetric scalar field configurations close to the continuously self-similar solution. Using analytic perturbative methods, it is shown that a generic growing perturbation departs from the critical Roberts solution in a universal way. We argue that in the course of its evolution, initial continuous self-similarity of the background is broken into discrete self-similarity with echoing period $\Delta = \sqrt{2}\pi = 4.44$, reproducing the symmetries of the critical Choptuik solution.
|
1004.4007
|
Vitor Cardoso
|
C. Molina, Paolo Pani, Vitor Cardoso, Leonardo Gualtieri
|
Gravitational signature of Schwarzschild black holes in dynamical
Chern-Simons gravity
|
RevTex4, 12 pages, 8 figures, 3 Tables. v2: minor typos corrected and
references added. Published version
|
Phys.Rev.D81:124021,2010
|
10.1103/PhysRevD.81.124021
| null |
gr-qc astro-ph.HE hep-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Dynamical Chern-Simons gravity is an extension of General Relativity in which
the gravitational field is coupled to a scalar field through a parity-violating
Chern-Simons term. In this framework, we study perturbations of spherically
symmetric black hole spacetimes, assuming that the background scalar field
vanishes. Our results suggest that these spacetimes are stable, and small
perturbations die away as a ringdown. However, in contrast to standard General
Relativity, the gravitational waveforms are also driven by the scalar field.
Thus, the gravitational oscillation modes of black holes carry imprints of the
coupling to the scalar field. This is a smoking gun for Chern-Simons theory and
could be tested with gravitational-wave detectors, such as LIGO or LISA. For
negative values of the coupling constant, ghosts are known to arise, and we
explicitly verify their appearance numerically. Our results are validated using
both time evolution and frequency domain methods.
|
[
{
"created": "Thu, 22 Apr 2010 20:07:28 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Jun 2010 01:11:33 GMT",
"version": "v2"
}
] |
2013-12-04
|
[
[
"Molina",
"C.",
""
],
[
"Pani",
"Paolo",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Gualtieri",
"Leonardo",
""
]
] |
Dynamical Chern-Simons gravity is an extension of General Relativity in which the gravitational field is coupled to a scalar field through a parity-violating Chern-Simons term. In this framework, we study perturbations of spherically symmetric black hole spacetimes, assuming that the background scalar field vanishes. Our results suggest that these spacetimes are stable, and small perturbations die away as a ringdown. However, in contrast to standard General Relativity, the gravitational waveforms are also driven by the scalar field. Thus, the gravitational oscillation modes of black holes carry imprints of the coupling to the scalar field. This is a smoking gun for Chern-Simons theory and could be tested with gravitational-wave detectors, such as LIGO or LISA. For negative values of the coupling constant, ghosts are known to arise, and we explicitly verify their appearance numerically. Our results are validated using both time evolution and frequency domain methods.
|
1804.01941
|
Grigorios Fournodavlos
|
Grigorios Fournodavlos, Jan Sbierski
|
Generic blow-up results for the wave equation in the interior of a
Schwarzschild black hole
|
Minor improvements, version accepted for publication
| null |
10.1007/s00205-019-01434-0
| null |
gr-qc math.AP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the behaviour of smooth solutions to the wave equation,
$\square_g\psi=0$, in the interior of a fixed Schwarzschild black hole. In
particular, we obtain a full asymptotic expansion for all solutions towards
$r=0$ and show that it is characterised by its first two leading terms, the
principal logarithmic term and a bounded second order term. Moreover, we
characterise an open set of initial data for which the corresponding solutions
blow up logarithmically on the entirety of the singular hypersurface $\{r=0\}$.
Our method is based on deriving weighted energy estimates in physical space and
requires no symmetries of solutions. However, a key ingredient in our argument
uses a precise analysis of the spherically symmetric part of the solution and a
monotonicity property of spherically symmetric solutions in the interior.
|
[
{
"created": "Thu, 5 Apr 2018 16:31:03 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Jul 2019 14:33:41 GMT",
"version": "v2"
}
] |
2019-09-04
|
[
[
"Fournodavlos",
"Grigorios",
""
],
[
"Sbierski",
"Jan",
""
]
] |
We study the behaviour of smooth solutions to the wave equation, $\square_g\psi=0$, in the interior of a fixed Schwarzschild black hole. In particular, we obtain a full asymptotic expansion for all solutions towards $r=0$ and show that it is characterised by its first two leading terms, the principal logarithmic term and a bounded second order term. Moreover, we characterise an open set of initial data for which the corresponding solutions blow up logarithmically on the entirety of the singular hypersurface $\{r=0\}$. Our method is based on deriving weighted energy estimates in physical space and requires no symmetries of solutions. However, a key ingredient in our argument uses a precise analysis of the spherically symmetric part of the solution and a monotonicity property of spherically symmetric solutions in the interior.
|
gr-qc/0312048
|
Merced Montesinos
|
Mauricio Mondragon and Merced Montesinos
|
Covariant description of parametrized nonrelativistic Hamiltonian
systems
|
15 pages, latex file. corrected typos, minor changes done to match
published version
|
Int.J.Mod.Phys. A19 (2004) 2473-2493
|
10.1142/S0217751X04018063
| null |
gr-qc hep-th physics.class-ph
| null |
The various phase spaces involved in the dynamics of parametrized
nonrelativistic Hamiltonian systems are displayed by using Crnkovic and
Witten's covariant canonical formalism. It is also pointed out that in Dirac's
canonical formalism there exists a freedom in the choice of the symplectic
structure on the extended phase space and in the choice of the equations that
define the constraint surface with the only restriction that these two choices
combine in such a way that any pair (of these two choices) generates the same
gauge transformation. The consequence of this freedom on the algebra of
observables is also discussed.
|
[
{
"created": "Mon, 8 Dec 2003 23:09:26 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Dec 2003 22:50:50 GMT",
"version": "v2"
},
{
"created": "Mon, 30 Jan 2006 22:46:11 GMT",
"version": "v3"
}
] |
2007-05-23
|
[
[
"Mondragon",
"Mauricio",
""
],
[
"Montesinos",
"Merced",
""
]
] |
The various phase spaces involved in the dynamics of parametrized nonrelativistic Hamiltonian systems are displayed by using Crnkovic and Witten's covariant canonical formalism. It is also pointed out that in Dirac's canonical formalism there exists a freedom in the choice of the symplectic structure on the extended phase space and in the choice of the equations that define the constraint surface with the only restriction that these two choices combine in such a way that any pair (of these two choices) generates the same gauge transformation. The consequence of this freedom on the algebra of observables is also discussed.
|
0909.4500
|
Willians Barreto
|
W. Barreto (ULA), L. Castillo (UDO) and E. Barrios (ULA)
|
Central equation of state in spherical characteristic evolutions
|
4 pages; to appear in Physical Review D
|
Phys.Rev.D80:084007,2009
|
10.1103/PhysRevD.80.084007
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the evolution of a perfect--fluid sphere coupled to a scalar
radiation field. By ensuring a Ricci invariant regularity as a conformally flat
spacetime at the central world line we find that the fluid coupled to the
scalar field satisfies the equation of state $\rho_c+3p_c=$ constant at the
center of the sphere, where the energy $\rho_c$ density and the pressure $p_c$
do not necessarily contain the scalar field contribution. The fluid can be
interpreted as anisotropic and radiant because of the scalar field, but it
becomes perfect and non radiative at the center of the sphere. These results
are being currently considered to build up a numerical relativistic
hydrodynamic solver.
|
[
{
"created": "Thu, 24 Sep 2009 17:04:59 GMT",
"version": "v1"
}
] |
2010-05-12
|
[
[
"Barreto",
"W.",
"",
"ULA"
],
[
"Castillo",
"L.",
"",
"UDO"
],
[
"Barrios",
"E.",
"",
"ULA"
]
] |
We study the evolution of a perfect--fluid sphere coupled to a scalar radiation field. By ensuring a Ricci invariant regularity as a conformally flat spacetime at the central world line we find that the fluid coupled to the scalar field satisfies the equation of state $\rho_c+3p_c=$ constant at the center of the sphere, where the energy $\rho_c$ density and the pressure $p_c$ do not necessarily contain the scalar field contribution. The fluid can be interpreted as anisotropic and radiant because of the scalar field, but it becomes perfect and non radiative at the center of the sphere. These results are being currently considered to build up a numerical relativistic hydrodynamic solver.
|
0905.1984
|
Mauricio Bellini
|
Mariano Anabitarte, Mauricio Bellini, Jose Edgar Madriz Aguilar
|
Scale invariant scalar metric fluctuations during inflation:
non-perturbative formalism from a 5D vacuum
|
final version to be published in Eur. Phys. J. C
|
Eur.Phys.J.C65:295-301,2010
|
10.1140/epjc/s10052-009-1180-2
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We extend to 5D an approach of a 4D non-perturbative formalism to study
scalar metric fluctuations of a 5D Riemann-flat de Sitter background metric. In
contrast with the results obtained in 4D, the spectrum of cosmological scalar
metric fluctuations during inflation can be scale invariant and the background
inflaton field can take sub-Planckian values.
|
[
{
"created": "Tue, 12 May 2009 23:19:12 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Sep 2009 11:57:55 GMT",
"version": "v2"
},
{
"created": "Tue, 27 Oct 2009 17:39:11 GMT",
"version": "v3"
}
] |
2014-11-18
|
[
[
"Anabitarte",
"Mariano",
""
],
[
"Bellini",
"Mauricio",
""
],
[
"Aguilar",
"Jose Edgar Madriz",
""
]
] |
We extend to 5D an approach of a 4D non-perturbative formalism to study scalar metric fluctuations of a 5D Riemann-flat de Sitter background metric. In contrast with the results obtained in 4D, the spectrum of cosmological scalar metric fluctuations during inflation can be scale invariant and the background inflaton field can take sub-Planckian values.
|
2104.09007
|
Vladimir Dergachev Ph.D.
|
Vladimir Dergachev and Maria Alessandra Papa
|
The search for continuous gravitational waves from small-ellipticity
sources at low frequencies
|
6 pages, comments welcome
|
Phys. Rev. D 104, 043003 (2021)
|
10.1103/PhysRevD.104.043003
| null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We present the results of an all-sky search for continuous gravitational wave
signals with frequencies in the 20-500 Hz range from neutron stars with
ellipticity of 1e-8. This frequency region is particularly hard to probe
because of the quadratic dependence of signal strength on frequency. The search
employs the Falcon analysis pipeline on LIGO O2 public data. Compared to
previous Falcon analyses the coherence length has been quadrupled, with a
corresponding increase in sensitivity. This enables us to search for small
ellipticity neutron stars in this low frequency region up to 44 pc away. The
frequency derivative range is up to 3e-13 Hz/s easily accommodating sources
with ellipticities of 1e-7 and a corresponding factor of 10 increase in reach.
New outliers are found, many of which we are unable to associate with any
instrumental cause.
|
[
{
"created": "Mon, 19 Apr 2021 01:50:59 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Jul 2021 00:09:04 GMT",
"version": "v2"
}
] |
2021-08-11
|
[
[
"Dergachev",
"Vladimir",
""
],
[
"Papa",
"Maria Alessandra",
""
]
] |
We present the results of an all-sky search for continuous gravitational wave signals with frequencies in the 20-500 Hz range from neutron stars with ellipticity of 1e-8. This frequency region is particularly hard to probe because of the quadratic dependence of signal strength on frequency. The search employs the Falcon analysis pipeline on LIGO O2 public data. Compared to previous Falcon analyses the coherence length has been quadrupled, with a corresponding increase in sensitivity. This enables us to search for small ellipticity neutron stars in this low frequency region up to 44 pc away. The frequency derivative range is up to 3e-13 Hz/s easily accommodating sources with ellipticities of 1e-7 and a corresponding factor of 10 increase in reach. New outliers are found, many of which we are unable to associate with any instrumental cause.
|
2304.08584
|
Marcelo E. Rubio
|
Pablo Montes, Marcelo E. Rubio and Oscar A. Reula
|
Numerical simulations of divergence-type theories for conformal
dissipative fluids
|
22 pages, 14 figures
|
Phys. Rev. D 107, 103041 (2023)
|
10.1103/PhysRevD.107.103041
| null |
gr-qc hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
We present the first numerical simulations of the symmetric--hyperbolic
theory for conformal dissipative relativistic fluids developed in [1]. In this
theory, the information of the fluid dynamics is encoded in a scalar generating
function which depends on three free parameters. By adapting the WENO-Z
high-resolution shock-capturing central scheme, we show numerical solutions
restricted to planar symmetry in Minkowski spacetime, from two qualitatively
different initial data: a smooth bump and a discontinuous step. We perform a
detailed exploration of the effect of the different parameters of the theory,
and numerically assess the constitutive relations associated with the shear
viscosity by analyzing the entropy production rate when shocks are produced.
|
[
{
"created": "Mon, 17 Apr 2023 19:57:00 GMT",
"version": "v1"
}
] |
2023-05-26
|
[
[
"Montes",
"Pablo",
""
],
[
"Rubio",
"Marcelo E.",
""
],
[
"Reula",
"Oscar A.",
""
]
] |
We present the first numerical simulations of the symmetric--hyperbolic theory for conformal dissipative relativistic fluids developed in [1]. In this theory, the information of the fluid dynamics is encoded in a scalar generating function which depends on three free parameters. By adapting the WENO-Z high-resolution shock-capturing central scheme, we show numerical solutions restricted to planar symmetry in Minkowski spacetime, from two qualitatively different initial data: a smooth bump and a discontinuous step. We perform a detailed exploration of the effect of the different parameters of the theory, and numerically assess the constitutive relations associated with the shear viscosity by analyzing the entropy production rate when shocks are produced.
|
1503.07413
|
Saira Waheed
|
Saira Waheed, M. Zubair
|
Energy Constraints and $F(T,T_{G})$ Cosmology
|
24 pages, 11 figures
| null |
10.1007/s10509-015-2438-9
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The present paper is elaborated to discuss the energy condition bounds in a
modified teleparallel gravity namely $F(T,T_{G})$, involving torsion invariant
$T$ and contribution from a term $T_G$, the teleparallel equivalent of the
Gauss-Bonnet term. For this purpose, we consider flat FRW universe with matter
contents as perfect fluid. We formulate the SEC, NEC, WEC and DEC in terms of
some cosmic parameters including Hubble, deceleration, jerk and snap
parameters. By taking two interesting models for $F(T,T_{G})$ and some recent
limits of these cosmic parameters, we explore the constraints on the free
parameters present in both assumed models. We also discuss these constraints
graphically in terms of cosmic time by taking power law cosmology into account.
|
[
{
"created": "Thu, 19 Mar 2015 07:33:09 GMT",
"version": "v1"
}
] |
2015-09-23
|
[
[
"Waheed",
"Saira",
""
],
[
"Zubair",
"M.",
""
]
] |
The present paper is elaborated to discuss the energy condition bounds in a modified teleparallel gravity namely $F(T,T_{G})$, involving torsion invariant $T$ and contribution from a term $T_G$, the teleparallel equivalent of the Gauss-Bonnet term. For this purpose, we consider flat FRW universe with matter contents as perfect fluid. We formulate the SEC, NEC, WEC and DEC in terms of some cosmic parameters including Hubble, deceleration, jerk and snap parameters. By taking two interesting models for $F(T,T_{G})$ and some recent limits of these cosmic parameters, we explore the constraints on the free parameters present in both assumed models. We also discuss these constraints graphically in terms of cosmic time by taking power law cosmology into account.
|
gr-qc/0405134
|
Shinya Tomizawa
|
Shinya Tomizawa, Yuki Uchida and Tetsuya Shiromizu
|
Twist of stationary black hole/ring in five dimensions
|
5 pages, 1 figure, reference added
|
Phys.Rev. D70 (2004) 064020
|
10.1103/PhysRevD.70.064020
| null |
gr-qc
| null |
It is unlikely that uniqueness theorem holds for stationary black holes in
higher dimensional spacetimes. However, we will examine the possibility that
the higher multipole moments classify vacuum solutions uniquely. Especially, we
compute the potentials associated with rotational Killing vectors and look at
the dependence on the total mass M and angular momentum J. Consequently, there
is a potential $\sigma$ which we cannot write down in terms of integer power of
M and J explicitly. This may be regarded as an evidence for the uniqueness
using multipole moments generated by $\sigma$.
|
[
{
"created": "Thu, 27 May 2004 02:56:53 GMT",
"version": "v1"
},
{
"created": "Mon, 31 May 2004 05:21:59 GMT",
"version": "v2"
}
] |
2009-11-10
|
[
[
"Tomizawa",
"Shinya",
""
],
[
"Uchida",
"Yuki",
""
],
[
"Shiromizu",
"Tetsuya",
""
]
] |
It is unlikely that uniqueness theorem holds for stationary black holes in higher dimensional spacetimes. However, we will examine the possibility that the higher multipole moments classify vacuum solutions uniquely. Especially, we compute the potentials associated with rotational Killing vectors and look at the dependence on the total mass M and angular momentum J. Consequently, there is a potential $\sigma$ which we cannot write down in terms of integer power of M and J explicitly. This may be regarded as an evidence for the uniqueness using multipole moments generated by $\sigma$.
|
2104.13761
|
Muhammad Zaeem-Ul-Haq Bhatti
|
M. Z. Bhatti, Z. Yousaf, Z. Tariq
|
Role of Structure Scalars on the evolution of Compact Objects in
Palatini $f(R)$ Gravity
|
33 pages, version accepted for publications in Chinese Journal of
Physics
|
Chin. J. Phys. 72, 18 (2021)
|
10.1016/j.cjph.2021.04.019
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
The utmost concern of this article is the construction of modified scalar
functions (structure scalars) by taking Palatini $f(R)$ gravitational theory
into account. At first, a general formalism is established in which we assess
gravitational stellar equations by putting into use the Palatini's technique.
Later, from the perspective of tilted observer, we Lorentz boosted the
components of energy-momentum tensor using relative velocity $\omega$. To
examine the physical as well as mathematical aspects of the fluid source, we
carry out a detailed analysis of kinematical variables by evaluating shear
tensor and scalar, four-acceleration and expansion scalar. For the fluid
content inside our spherical star, we inferred the mass function (geometric
mass) and the active gravitational mass. Raychaudhuri equation, Bianchi
identities in addition to few other equations are worked out to discern the
structure formation and analyze the object's evolutionary stages. The Riemann
tensor is then broken up orthogonally to set up few scalar functions connected
with fundamental physical characteristics of the fluid source like energy
density, effects of tidal forces and anisotropic stresses etc.
|
[
{
"created": "Tue, 27 Apr 2021 09:59:08 GMT",
"version": "v1"
}
] |
2021-09-02
|
[
[
"Bhatti",
"M. Z.",
""
],
[
"Yousaf",
"Z.",
""
],
[
"Tariq",
"Z.",
""
]
] |
The utmost concern of this article is the construction of modified scalar functions (structure scalars) by taking Palatini $f(R)$ gravitational theory into account. At first, a general formalism is established in which we assess gravitational stellar equations by putting into use the Palatini's technique. Later, from the perspective of tilted observer, we Lorentz boosted the components of energy-momentum tensor using relative velocity $\omega$. To examine the physical as well as mathematical aspects of the fluid source, we carry out a detailed analysis of kinematical variables by evaluating shear tensor and scalar, four-acceleration and expansion scalar. For the fluid content inside our spherical star, we inferred the mass function (geometric mass) and the active gravitational mass. Raychaudhuri equation, Bianchi identities in addition to few other equations are worked out to discern the structure formation and analyze the object's evolutionary stages. The Riemann tensor is then broken up orthogonally to set up few scalar functions connected with fundamental physical characteristics of the fluid source like energy density, effects of tidal forces and anisotropic stresses etc.
|
gr-qc/0508081
|
Frank B. Estabrook
|
Frank B. Estabrook
|
Conservation laws for vacuum tetrad gravity
|
Final version with additional references
|
Class.Quant.Grav.23:2841-2848,2006
|
10.1088/0264-9381/23/9/005
| null |
gr-qc
| null |
Ten conservation laws in useful polynomial form are derived from a Cartan
form and Exterior Differential System (EDS) for the tetrad equations of vacuum
relativity. The Noether construction of conservation laws for well posed EDS is
introduced first, and an illustration given, deriving 15 conservation laws of
the free field Maxwell Equations from symmetries of its EDS. The Maxwell EDS
and tetrad gravity EDS have parallel structures, with their numbers of
dependent variables, numbers of generating 2-forms and generating 3-forms, and
Cartan character tables all in the ratio of 1 to 4. They have 10 corresponding
symmetries with the same Lorentz algebra, and 10 corresponding conservation
laws.
|
[
{
"created": "Sat, 20 Aug 2005 00:01:48 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Sep 2005 20:38:49 GMT",
"version": "v2"
},
{
"created": "Mon, 3 Apr 2006 18:27:51 GMT",
"version": "v3"
}
] |
2014-11-17
|
[
[
"Estabrook",
"Frank B.",
""
]
] |
Ten conservation laws in useful polynomial form are derived from a Cartan form and Exterior Differential System (EDS) for the tetrad equations of vacuum relativity. The Noether construction of conservation laws for well posed EDS is introduced first, and an illustration given, deriving 15 conservation laws of the free field Maxwell Equations from symmetries of its EDS. The Maxwell EDS and tetrad gravity EDS have parallel structures, with their numbers of dependent variables, numbers of generating 2-forms and generating 3-forms, and Cartan character tables all in the ratio of 1 to 4. They have 10 corresponding symmetries with the same Lorentz algebra, and 10 corresponding conservation laws.
|
gr-qc/0504008
|
Vladimir Dzhunushaliev
|
Vladimir Dzhunushaliev and Ratbay Myrzakulov
|
Physical singularity in the regular spacetime and fundamental length
|
changes in the text
|
Int. J. Mod. Phys. D, Vol. 16, 755-761 (2007)
|
10.1142/S0218271807008638
|
IC/IR/2005/009
|
gr-qc hep-th
| null |
It is shown that formally regular solutions in 5D Kaluza-Klein gravity have
singularities. This phenomenon is connected with the existence of a minimal
length in nature. The calculation of the derivative of the $G_{55}$ metric
component leads to the appearance of the Dirac's $\delta-$function. In this
case the Ricci scalar becomes singular since there is a square of this
derivative.
|
[
{
"created": "Sat, 2 Apr 2005 04:12:01 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Jun 2005 11:46:13 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Jun 2007 03:54:17 GMT",
"version": "v3"
}
] |
2009-11-11
|
[
[
"Dzhunushaliev",
"Vladimir",
""
],
[
"Myrzakulov",
"Ratbay",
""
]
] |
It is shown that formally regular solutions in 5D Kaluza-Klein gravity have singularities. This phenomenon is connected with the existence of a minimal length in nature. The calculation of the derivative of the $G_{55}$ metric component leads to the appearance of the Dirac's $\delta-$function. In this case the Ricci scalar becomes singular since there is a square of this derivative.
|
1002.4488
|
Sergey Pavluchenko
|
I.V. Kirnos, S.A. Pavluchenko, A.V. Toporensky
|
New features of flat (4+1)-dimensional cosmological model with a perfect
fluid in Gauss-Bonnet gravity
|
14 pages, 5 figures, 1 table; v2 minor corrections, conclusions
unchanged
|
Grav.Cosmol.16:274-282,2010
|
10.1134/S0202289310040043
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We investigated a flat multidimensional cosmological model in Gauss-Bonnet
gravity in presence of a matter in form of perfect fluid. We found analytically
new stationary regimes (these results are valid for arbitrary number of spatial
dimensions) and studied their stability by means of numerical recipes in
4+1-dimensional case. In the vicinity of the stationary regime we discovered
numerically another non-singular regime which appears to be periodical.
Finally, we demonstrated that the presence of matter in form of a perfect fluid
lifts some constraints on the dynamics of the 4+1-dimensional model which have
been found earlier.
|
[
{
"created": "Wed, 24 Feb 2010 08:32:10 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Mar 2010 15:51:12 GMT",
"version": "v2"
}
] |
2015-03-13
|
[
[
"Kirnos",
"I. V.",
""
],
[
"Pavluchenko",
"S. A.",
""
],
[
"Toporensky",
"A. V.",
""
]
] |
We investigated a flat multidimensional cosmological model in Gauss-Bonnet gravity in presence of a matter in form of perfect fluid. We found analytically new stationary regimes (these results are valid for arbitrary number of spatial dimensions) and studied their stability by means of numerical recipes in 4+1-dimensional case. In the vicinity of the stationary regime we discovered numerically another non-singular regime which appears to be periodical. Finally, we demonstrated that the presence of matter in form of a perfect fluid lifts some constraints on the dynamics of the 4+1-dimensional model which have been found earlier.
|
2103.06862
|
Ismael Delgado Gaspar PhD
|
Ismael Delgado Gaspar, Roberto A. Sussman, David D. McNutt, Alan A.
Coley
|
Comment on "Szekeres universes with homogeneous scalar fields"
|
2 pages. Comment on "Szekeres universes with homogeneous scalar
fields" and "Cyclic Szekeres universes" by Barrow and Paliathanasis, Eur.
Phys. J. C. (2018, 2019); arXiv:1808.00173 and arXiv:1901.09173
| null |
10.1140/epjc/s10052-021-09113-9
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Two recently published papers (J.D. Barrow and A. Paliathanasis, Eur. Phys.
J. C. (2018, 2019)) claim to have found exact solutions of Einstein's field
equations belonging to the class of non-trivial Szekeres models, whose source
is a mixture of dust and a homogeneous time-dependent scalar field, where the
energy-momentum tensors of both mixture components are independently conserved.
We prove that the independent conservation of these two mixture components
necessarily leads to solutions belonging to the set of spatially homogeneous
subcases of the Szekeres family: Friedmann-Lema\^itre-Robertson-Walker for
class I, and Kantowski-Sachs, Bianchi-Behr I or Bianchi-Behr
$\mbox{VI}_{\tiny{\mbox{-1}}}$ for class II.
|
[
{
"created": "Thu, 11 Mar 2021 18:47:24 GMT",
"version": "v1"
}
] |
2021-04-28
|
[
[
"Gaspar",
"Ismael Delgado",
""
],
[
"Sussman",
"Roberto A.",
""
],
[
"McNutt",
"David D.",
""
],
[
"Coley",
"Alan A.",
""
]
] |
Two recently published papers (J.D. Barrow and A. Paliathanasis, Eur. Phys. J. C. (2018, 2019)) claim to have found exact solutions of Einstein's field equations belonging to the class of non-trivial Szekeres models, whose source is a mixture of dust and a homogeneous time-dependent scalar field, where the energy-momentum tensors of both mixture components are independently conserved. We prove that the independent conservation of these two mixture components necessarily leads to solutions belonging to the set of spatially homogeneous subcases of the Szekeres family: Friedmann-Lema\^itre-Robertson-Walker for class I, and Kantowski-Sachs, Bianchi-Behr I or Bianchi-Behr $\mbox{VI}_{\tiny{\mbox{-1}}}$ for class II.
|
1905.07724
|
Behzad Tajahmad
|
Behzad Tajahmad
|
Late-time-accelerated expansion arisen from gauge fields in an
anisotropic background and a fruitful trick for Noether's approach
|
27 pages, 13 figures (26 plots), 1 Table
| null |
10.1007/JHEP02(2020)084
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, a modified teleparallel gravity action containing a coupling
between a scalar field potential and magnetism, in anisotropic and homogeneous
backgrounds, is investigated through Noether symmetry approach. The focus of
this work is to describe late-time-accelerated expansion. Since finding
analytical solutions carrying all conserved currents emerged by Noether
symmetry approach, is very difficult, hence regularly in the literature, the
authors split the total symmetry into sub-symmetries and then select, usually,
some of them to be carried by the solutions. This manner limits the forms of
unknown functions obtained. However, in ref. [68], B.N.S. approach was proposed
in order to solve such problems but its main motivation was carrying more
conserved currents by solutions. In this paper, by eliminating the
aforementioned limitation as much as possible, a trick leading to some graceful
forms of unknown functions is suggested. Through this fruitful approach, the
solutions may carry more conserved currents than usual ways and maybe new forms
of symmetries. I named this new approach to be CSSS-trick (Combination of
Sub-symmetries through Special Selections). With this approach, it is
demonstrated that the unified dark matter potential is deduced by the gauge
fields. Utilizing the $\mathfrak{B}\text{-function}$ method, a detailed data
analysis of results obtained yielding perfect agreements with recent
observational data are performed. And finally, the Wheeler-De Witt (WDW)
equation is discussed to demonstrate recovering the Hartle criterion due to the
oscillating feature of the wave function of the universe.
|
[
{
"created": "Sun, 19 May 2019 11:13:39 GMT",
"version": "v1"
}
] |
2020-03-18
|
[
[
"Tajahmad",
"Behzad",
""
]
] |
In this paper, a modified teleparallel gravity action containing a coupling between a scalar field potential and magnetism, in anisotropic and homogeneous backgrounds, is investigated through Noether symmetry approach. The focus of this work is to describe late-time-accelerated expansion. Since finding analytical solutions carrying all conserved currents emerged by Noether symmetry approach, is very difficult, hence regularly in the literature, the authors split the total symmetry into sub-symmetries and then select, usually, some of them to be carried by the solutions. This manner limits the forms of unknown functions obtained. However, in ref. [68], B.N.S. approach was proposed in order to solve such problems but its main motivation was carrying more conserved currents by solutions. In this paper, by eliminating the aforementioned limitation as much as possible, a trick leading to some graceful forms of unknown functions is suggested. Through this fruitful approach, the solutions may carry more conserved currents than usual ways and maybe new forms of symmetries. I named this new approach to be CSSS-trick (Combination of Sub-symmetries through Special Selections). With this approach, it is demonstrated that the unified dark matter potential is deduced by the gauge fields. Utilizing the $\mathfrak{B}\text{-function}$ method, a detailed data analysis of results obtained yielding perfect agreements with recent observational data are performed. And finally, the Wheeler-De Witt (WDW) equation is discussed to demonstrate recovering the Hartle criterion due to the oscillating feature of the wave function of the universe.
|
gr-qc/0611060
|
E. Kyriakopoulos
|
E. Kyriakopoulos
|
Black Hole in a Model with Dilaton and Monopole Fields II
|
8 pages
|
Int.J.Mod.Phys.D15:2223-2228,2006
|
10.1142/S0218271806009650
| null |
gr-qc
| null |
We present an exact black hole solution in a model having besides gravity a
dilaton and a monopole field, which is a generalization of a black hole
solution we have found. The new solution, as the previous one, has three free
parameters, one of which can be identified with the monopole charge, and
another with the ADM mass. Its metric is asymptotically flat, has two horizon,
irremovable singularity only at $r=0$, and the dilaton field is singular only
at $r=0$. The dominant and the strong energy condition are satisfied outside
and on the external horizon. According to a formulation of the no hair
conjecture the solution is "hairy". Also a reformulation of the model with two
monopole fields is given, which results in the appearance of an additional
symmetry and therefore in the appearance of a conserved dilaton charge.
|
[
{
"created": "Fri, 10 Nov 2006 19:32:37 GMT",
"version": "v1"
}
] |
2008-11-26
|
[
[
"Kyriakopoulos",
"E.",
""
]
] |
We present an exact black hole solution in a model having besides gravity a dilaton and a monopole field, which is a generalization of a black hole solution we have found. The new solution, as the previous one, has three free parameters, one of which can be identified with the monopole charge, and another with the ADM mass. Its metric is asymptotically flat, has two horizon, irremovable singularity only at $r=0$, and the dilaton field is singular only at $r=0$. The dominant and the strong energy condition are satisfied outside and on the external horizon. According to a formulation of the no hair conjecture the solution is "hairy". Also a reformulation of the model with two monopole fields is given, which results in the appearance of an additional symmetry and therefore in the appearance of a conserved dilaton charge.
|
gr-qc/0606060
|
Leonardo Augusto Pach\'on Contreras
|
Leonardo. A. Pachon, Jorge A. Rueda, Jose D. Sanabria-Gomez
|
Realistic Exact Solution for the Exterior Field of a Rotating Neutron
Star
|
13 pages, 13 figures, LaTeX document
|
Phys.Rev.D73:104038,2006
|
10.1103/PhysRevD.73.104038
| null |
gr-qc
| null |
A new six-parametric, axisymmetric and asymptotically flat exact solution of
Einstein-Maxwell field equations having reflection symmetry is presented. It
has arbitrary physical parameters of mass, angular momentum, mass--quadrupole
moment, current octupole moment, electric charge and magnetic dipole, so it can
represent the exterior field of a rotating, deformed, magnetized and charged
object; some properties of the closed-form analytic solution such as its
multipolar structure, electromagnetic fields and singularities are also
presented. In the vacuum case, this analytic solution is matched to some
numerical interior solutions representing neutron stars, calculated by Berti &
Stergioulas (Mon. Not. Roy. Astron. Soc. 350, 1416 (2004)), imposing that the
multipole moments be the same. As an independent test of accuracy of the
solution to describe exterior fields of neutron stars, we present an extensive
comparison of the radii of innermost stable circular orbits (ISCOs) obtained
from Berti & Stergioulas numerical solutions, Kerr solution (Phys. Rev. Lett.
11, 237 (1963)), Hartle & Thorne solution (Ap. J. 153, 807, (1968)), an
analytic series expansion derived by Shibata & Sasaki (Phys. Rev. D. 58 104011
(1998)) and, our exact solution. We found that radii of ISCOs from our solution
fits better than others with realistic numerical interior solutions.
|
[
{
"created": "Tue, 13 Jun 2006 18:54:47 GMT",
"version": "v1"
}
] |
2008-11-26
|
[
[
"Pachon",
"Leonardo. A.",
""
],
[
"Rueda",
"Jorge A.",
""
],
[
"Sanabria-Gomez",
"Jose D.",
""
]
] |
A new six-parametric, axisymmetric and asymptotically flat exact solution of Einstein-Maxwell field equations having reflection symmetry is presented. It has arbitrary physical parameters of mass, angular momentum, mass--quadrupole moment, current octupole moment, electric charge and magnetic dipole, so it can represent the exterior field of a rotating, deformed, magnetized and charged object; some properties of the closed-form analytic solution such as its multipolar structure, electromagnetic fields and singularities are also presented. In the vacuum case, this analytic solution is matched to some numerical interior solutions representing neutron stars, calculated by Berti & Stergioulas (Mon. Not. Roy. Astron. Soc. 350, 1416 (2004)), imposing that the multipole moments be the same. As an independent test of accuracy of the solution to describe exterior fields of neutron stars, we present an extensive comparison of the radii of innermost stable circular orbits (ISCOs) obtained from Berti & Stergioulas numerical solutions, Kerr solution (Phys. Rev. Lett. 11, 237 (1963)), Hartle & Thorne solution (Ap. J. 153, 807, (1968)), an analytic series expansion derived by Shibata & Sasaki (Phys. Rev. D. 58 104011 (1998)) and, our exact solution. We found that radii of ISCOs from our solution fits better than others with realistic numerical interior solutions.
|
0711.2084
|
Lee Lindblom
|
Lee Lindblom, Keith D. Matthews, Oliver Rinne, and Mark A. Scheel
|
Gauge Drivers for the Generalized Harmonic Einstein Equations
|
17 pages, 9 figures
|
Phys.Rev.D77:084001,2008
|
10.1103/PhysRevD.77.084001
| null |
gr-qc
| null |
The generalized harmonic representation of Einstein's equation is manifestly
hyperbolic for a large class of gauge conditions. Unfortunately most of the
useful gauges developed over the past several decades by the numerical
relativity community are incompatible with the hyperbolicity of the equations
in this form. This paper presents a new method of imposing gauge conditions
that preserves hyperbolicity for a much wider class of conditions, including as
special cases many of the standard ones used in numerical relativity: e.g.,
K-freezing, Gamma-freezing, Bona-Masso slicing, conformal Gamma-drivers, etc.
Analytical and numerical results are presented which test the stability and the
effectiveness of this new gauge driver evolution system.
|
[
{
"created": "Tue, 13 Nov 2007 23:33:36 GMT",
"version": "v1"
}
] |
2008-11-26
|
[
[
"Lindblom",
"Lee",
""
],
[
"Matthews",
"Keith D.",
""
],
[
"Rinne",
"Oliver",
""
],
[
"Scheel",
"Mark A.",
""
]
] |
The generalized harmonic representation of Einstein's equation is manifestly hyperbolic for a large class of gauge conditions. Unfortunately most of the useful gauges developed over the past several decades by the numerical relativity community are incompatible with the hyperbolicity of the equations in this form. This paper presents a new method of imposing gauge conditions that preserves hyperbolicity for a much wider class of conditions, including as special cases many of the standard ones used in numerical relativity: e.g., K-freezing, Gamma-freezing, Bona-Masso slicing, conformal Gamma-drivers, etc. Analytical and numerical results are presented which test the stability and the effectiveness of this new gauge driver evolution system.
|
2004.00870
|
Daniele Vigan\`o
|
Daniele Vigan\`o, Ricard Aguilera-Miret, Federico Carrasco, Borja
Mi\~nano, Carlos Palenzuela
|
GRMHD large eddy simulations with gradient subgrid-scale model
|
15 pages, 7 figures Submitted to PRD
|
Phys. Rev. D 101, 123019 (2020)
|
10.1103/PhysRevD.101.123019
| null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The detection of binary neutron star mergers represents one of the most
important astrophysical discoveries of the recent years. Due to the extreme
matter and gravity conditions and the rich dynamics developed, it becomes a
tremendous challenge to accurately simulate numerically all the scales present
during the collision. Here we present how to study such systems by using large
eddy simulations with a self-consistent subgrid-scale gradient model, that we
generalized to the special relativistic case in a previous work and now extend
to the general relativistic case. Adapted from nonrelativistic scenarios, the
so-called gradient model allows to capture part of the effects of the hidden
dynamics on the resolved scales, by means of a physically-agnostic,
mathematically-based Taylor expansion of the nonlinear terms in the
conservative evolution equations' fluxes. We assess the validity of this
approach in bounding-box simulations of the magnetic Kelvin-Helmholtz
instability. Several resolutions and a broad range of scenarios are considered
in order to carefully test the performance of the model under three crucial
aspects: (i) highly curved backgrounds, (ii) jumps on the fluid density
profiles and (iii) strong shocks. The results suggest our extension of the
gradient subgrid-scale model to general relativistic magnetohydrodynamics is a
promising approach for studying binary neutron stars mergers, and potentially
to other relevant astrophysical scenarios.
|
[
{
"created": "Thu, 2 Apr 2020 08:34:58 GMT",
"version": "v1"
}
] |
2020-07-01
|
[
[
"Viganò",
"Daniele",
""
],
[
"Aguilera-Miret",
"Ricard",
""
],
[
"Carrasco",
"Federico",
""
],
[
"Miñano",
"Borja",
""
],
[
"Palenzuela",
"Carlos",
""
]
] |
The detection of binary neutron star mergers represents one of the most important astrophysical discoveries of the recent years. Due to the extreme matter and gravity conditions and the rich dynamics developed, it becomes a tremendous challenge to accurately simulate numerically all the scales present during the collision. Here we present how to study such systems by using large eddy simulations with a self-consistent subgrid-scale gradient model, that we generalized to the special relativistic case in a previous work and now extend to the general relativistic case. Adapted from nonrelativistic scenarios, the so-called gradient model allows to capture part of the effects of the hidden dynamics on the resolved scales, by means of a physically-agnostic, mathematically-based Taylor expansion of the nonlinear terms in the conservative evolution equations' fluxes. We assess the validity of this approach in bounding-box simulations of the magnetic Kelvin-Helmholtz instability. Several resolutions and a broad range of scenarios are considered in order to carefully test the performance of the model under three crucial aspects: (i) highly curved backgrounds, (ii) jumps on the fluid density profiles and (iii) strong shocks. The results suggest our extension of the gradient subgrid-scale model to general relativistic magnetohydrodynamics is a promising approach for studying binary neutron stars mergers, and potentially to other relevant astrophysical scenarios.
|
1211.4631
|
Marco Cariglia Dr
|
Marco Cariglia, Valeri P. Frolov, Pavel Krtous, David Kubiznak
|
Electron in higher-dimensional weakly charged rotating black hole
spacetimes
|
12 pages, no figures
|
Phys. Rev. D 87, 064003 (2013)
|
10.1103/PhysRevD.87.064003
|
pi-stronggrv-303
|
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We demonstrate separability of the Dirac equation in weakly charged rotating
black hole spacetimes in all dimensions. The electromagnetic field of the black
hole is described by a test field approximation, with vector potential
proportional to the primary Killing vector field. It is shown that the
demonstrated separability can be intrinsically characterized by the existence
of a complete set of mutually commuting first order symmetry operators
generated from the principal Killing-Yano tensor. The presented results
generalize the results on integrability of charged particle motion and
separability of charged scalar field studied in [1].
|
[
{
"created": "Tue, 20 Nov 2012 00:00:18 GMT",
"version": "v1"
}
] |
2013-04-10
|
[
[
"Cariglia",
"Marco",
""
],
[
"Frolov",
"Valeri P.",
""
],
[
"Krtous",
"Pavel",
""
],
[
"Kubiznak",
"David",
""
]
] |
We demonstrate separability of the Dirac equation in weakly charged rotating black hole spacetimes in all dimensions. The electromagnetic field of the black hole is described by a test field approximation, with vector potential proportional to the primary Killing vector field. It is shown that the demonstrated separability can be intrinsically characterized by the existence of a complete set of mutually commuting first order symmetry operators generated from the principal Killing-Yano tensor. The presented results generalize the results on integrability of charged particle motion and separability of charged scalar field studied in [1].
|
2111.13501
|
Naoki Tsukamoto
|
Naoki Tsukamoto
|
Gravitational lensing by a Bronnikov-Kim wormhole under a weak-field
approximation and in a strong deflection limit
|
11 pages, 5 figures, minor correction, accepted for publication in
Physical Review D
|
Phys. Rev. D 105, 064013 (2022)
|
10.1103/PhysRevD.105.064013
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
We consider gravitational lensing under a weak-field approximation and in a
strong deflection limit by a Bronnikov-Kim wormhole with the same metric as the
one of a wormhole which has been suggested in Einstein-Dirac-Maxwell theory.
The metric approaches into the metric of an extreme charged
Reissner-Nordstr\"{o}m black hole in a black hole limit and it becomes the
metric of an spatial Schwarzschild wormhole in an ultrastatic limit. In both of
the black hole limit and the ultrastatic limit, the coefficient of a divergent
term and the constant term of the deflection angle of a light in the strong
deflection limit can be obtained exactly without expanding of parameters of the
spacetime. Interestingly, in the both limits to the black hole and the
ultrastatic wormhole, we obtain exactly the same coefficient and constant term
in the strong deflection limit.
|
[
{
"created": "Fri, 26 Nov 2021 13:59:01 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Feb 2022 13:44:21 GMT",
"version": "v2"
},
{
"created": "Tue, 22 Feb 2022 15:50:53 GMT",
"version": "v3"
}
] |
2022-03-08
|
[
[
"Tsukamoto",
"Naoki",
""
]
] |
We consider gravitational lensing under a weak-field approximation and in a strong deflection limit by a Bronnikov-Kim wormhole with the same metric as the one of a wormhole which has been suggested in Einstein-Dirac-Maxwell theory. The metric approaches into the metric of an extreme charged Reissner-Nordstr\"{o}m black hole in a black hole limit and it becomes the metric of an spatial Schwarzschild wormhole in an ultrastatic limit. In both of the black hole limit and the ultrastatic limit, the coefficient of a divergent term and the constant term of the deflection angle of a light in the strong deflection limit can be obtained exactly without expanding of parameters of the spacetime. Interestingly, in the both limits to the black hole and the ultrastatic wormhole, we obtain exactly the same coefficient and constant term in the strong deflection limit.
|
gr-qc/9405056
|
Yongsung Yoon
|
Jewan Kim, C.J. Park and Yongsung Yoon
|
Phase Transition in Conformally Induced Gravity with Torsion
|
7pages, no figure
|
Phys.Rev.D51:562-567,1995
|
10.1103/PhysRevD.51.562
| null |
gr-qc hep-th
| null |
We have considered the quantum behavior of a conformally induced gravity in
the minimal Riemann-Cartan space. The regularized one-loop effective potential
considering the quantum fluctuations of the dilaton and the torsion fields in
the Coleman-Weinberg sector gives a sensible phase transition for an
inflationary phase in De Sitter space. For this effective potential, we have
analyzed the semi-classical equation of motion of the dilaton field in the
slow-rolling regime.
|
[
{
"created": "Thu, 26 May 1994 00:17:05 GMT",
"version": "v1"
}
] |
2010-11-01
|
[
[
"Kim",
"Jewan",
""
],
[
"Park",
"C. J.",
""
],
[
"Yoon",
"Yongsung",
""
]
] |
We have considered the quantum behavior of a conformally induced gravity in the minimal Riemann-Cartan space. The regularized one-loop effective potential considering the quantum fluctuations of the dilaton and the torsion fields in the Coleman-Weinberg sector gives a sensible phase transition for an inflationary phase in De Sitter space. For this effective potential, we have analyzed the semi-classical equation of motion of the dilaton field in the slow-rolling regime.
|
2210.07458
|
Viqar Husain
|
Viqar Husain, Muhammad Muzammil
|
Semiclassical geometrodynamics of homogeneous cosmology
|
13 pages, 5 figures; substantially extended, title changed, version
to appear in Phys Rev D
| null | null | null |
gr-qc hep-th quant-ph
|
http://creativecommons.org/licenses/by/4.0/
|
We study the classical-quantum (CQ) hybrid dynamics of homogeneous cosmology
from a Hamiltonian perspective where the classical gravitational phase space
variables and matter state evolve self-consistently with full backreaction. We
compare numerically the classical and CQ dynamics for isotropic and anisotropic
models, including quantum scalar-field induced corrections to the Kasner
exponents. Our results indicate that full backreaction effects leave traces at
late times in cosmological evolution; in particular, the scalar energy density
at late times provides a potential contribution to dark energy. We also show
that the CQ equations admit exact static solutions for the isotropic, and the
anisotropic Bianchi IX universes with the scalar field in a stationary state.
|
[
{
"created": "Fri, 14 Oct 2022 02:05:03 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Feb 2024 16:30:58 GMT",
"version": "v2"
}
] |
2024-02-23
|
[
[
"Husain",
"Viqar",
""
],
[
"Muzammil",
"Muhammad",
""
]
] |
We study the classical-quantum (CQ) hybrid dynamics of homogeneous cosmology from a Hamiltonian perspective where the classical gravitational phase space variables and matter state evolve self-consistently with full backreaction. We compare numerically the classical and CQ dynamics for isotropic and anisotropic models, including quantum scalar-field induced corrections to the Kasner exponents. Our results indicate that full backreaction effects leave traces at late times in cosmological evolution; in particular, the scalar energy density at late times provides a potential contribution to dark energy. We also show that the CQ equations admit exact static solutions for the isotropic, and the anisotropic Bianchi IX universes with the scalar field in a stationary state.
|
1711.10660
|
Sumanta Chakraborty
|
Sumanta Chakraborty and Kinjalk Lochan
|
Decoding infrared imprints of quantum origins of black holes
|
v3: Published Version; 18 pages, 2 figures
|
Phys. Lett. B 789, 276 (2019)
|
10.1016/j.physletb.2018.12.028
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We analyze the emission spectrum of a (fundamentally quantum) black hole in
the Kerr-Newman family by assuming a discretization of black hole geometry and
the holographic entropy-area relation. We demonstrate that, given the above
structure of black hole entropy, a macroscopic black hole always has
non-continuously separated mass states and therefore they descend down in
discrete manner. We evaluate the step size of the discrete spectrum, which
vanishes in the extremal limit, leading to a continuum spectrum as expected
from thermal nature of black holes. This further reveals an interesting
relation, in each class, between the dynamic and kinematic length scales for
all black holes belonging to the Kerr-Newman family, pointing towards a
possible universal character across the class, dependent only on black hole
mass. Further, we have presented the computation of maximum number of emitted
quanta from the black hole as well as an estimation of its lifetime. We also
argue the independence of these features from the presence of additional
spacetime dimensions.
|
[
{
"created": "Wed, 29 Nov 2017 03:29:06 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jun 2018 11:44:30 GMT",
"version": "v2"
},
{
"created": "Wed, 9 Jan 2019 01:33:54 GMT",
"version": "v3"
}
] |
2019-01-10
|
[
[
"Chakraborty",
"Sumanta",
""
],
[
"Lochan",
"Kinjalk",
""
]
] |
We analyze the emission spectrum of a (fundamentally quantum) black hole in the Kerr-Newman family by assuming a discretization of black hole geometry and the holographic entropy-area relation. We demonstrate that, given the above structure of black hole entropy, a macroscopic black hole always has non-continuously separated mass states and therefore they descend down in discrete manner. We evaluate the step size of the discrete spectrum, which vanishes in the extremal limit, leading to a continuum spectrum as expected from thermal nature of black holes. This further reveals an interesting relation, in each class, between the dynamic and kinematic length scales for all black holes belonging to the Kerr-Newman family, pointing towards a possible universal character across the class, dependent only on black hole mass. Further, we have presented the computation of maximum number of emitted quanta from the black hole as well as an estimation of its lifetime. We also argue the independence of these features from the presence of additional spacetime dimensions.
|
gr-qc/0606071
|
Stefano Viaggiu
|
Stefano Viaggiu
|
Generating anisotropic fluids from vacuum Ernst equations
|
Version published on IJMPD, title changed by the review
|
Int.J.Mod.Phys.D19:1783-1795,2010
|
10.1142/S0218271810018025
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Starting with any stationary axisymmetric vacuum metric, we build anisotropic
fluids. With the help of the Ernst method, the basic equations are derived
together with the expression for the energy-momentum tensor and with the
equation of state compatible with the field equations. The method is presented
by using different coordinate systems: the cylindrical coordinates $\rho, z$
and the oblate spheroidal ones. A class of interior solutions matching with
stationary axisymmetric asymptotically flat vacuum solutions is found in oblate
spheroidal coordinates. The solutions presented satisfy the three energy
conditions.
|
[
{
"created": "Fri, 16 Jun 2006 07:08:39 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Aug 2010 12:00:36 GMT",
"version": "v2"
}
] |
2014-11-17
|
[
[
"Viaggiu",
"Stefano",
""
]
] |
Starting with any stationary axisymmetric vacuum metric, we build anisotropic fluids. With the help of the Ernst method, the basic equations are derived together with the expression for the energy-momentum tensor and with the equation of state compatible with the field equations. The method is presented by using different coordinate systems: the cylindrical coordinates $\rho, z$ and the oblate spheroidal ones. A class of interior solutions matching with stationary axisymmetric asymptotically flat vacuum solutions is found in oblate spheroidal coordinates. The solutions presented satisfy the three energy conditions.
|
1708.05911
|
Rodrigo Avalos
|
Rodrigo Avalos, F\'abio Dahia and Carlos Romero
|
On the $C^k$-embedding of Lorentzian manifolds in Ricci-flat spaces
| null |
Journal of Mathematical Physics 59, 052503 (2018)
|
10.1063/1.5017492
| null |
gr-qc math.DG
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper we investigate the problem of non-analytic embeddings of
Lorentzian manifolds in Ricci-flat semi-Riemannian spaces. In order to do this,
we first review some relevant results in the area, and then motivate both the
mathematical and physical interest in this problem. We show that any
$n$-dimensional compact Lorentzian manifold $(M^{n},g)$, with $g$ in the
Sobolev space $H_{s+3}$, $s>\frac{n}{2}$, admits an isometric embedding in an
$(2n+2)$-dimensional Ricci-flat semi-Riemannian manifold. The sharpest result
available for this type of embeddings, in the general setting, comes as a
corollary of Greene's remarkable embedding theorems [R. Greene, Mem. Am. Math.
Soc. 97, 1 (1970)], which guarantee the embedding of a compact $n$-dimensional
semi-Riemannian manifold into an $n(n+5)$-dimensional semi-Euclidean space,
thereby guaranteeing the embedding into a Ricci-flat space with the same
dimension. The theorem presented here improves this corollary in $n^{2}+3n-2$
codimensions by replacing the Riemann-flat condition with the Ricci-flat one
from the beginning. Finally, we will present a corollary of this theorem, which
shows that a compact strip in an $n$-dimensional globally hyperbolic space-time
can be embedded in a $(2n+2)$-dimensional Ricci-flat semi-Riemannian manifold.
|
[
{
"created": "Sat, 19 Aug 2017 23:22:56 GMT",
"version": "v1"
},
{
"created": "Sat, 19 May 2018 01:29:55 GMT",
"version": "v2"
}
] |
2018-05-22
|
[
[
"Avalos",
"Rodrigo",
""
],
[
"Dahia",
"Fábio",
""
],
[
"Romero",
"Carlos",
""
]
] |
In this paper we investigate the problem of non-analytic embeddings of Lorentzian manifolds in Ricci-flat semi-Riemannian spaces. In order to do this, we first review some relevant results in the area, and then motivate both the mathematical and physical interest in this problem. We show that any $n$-dimensional compact Lorentzian manifold $(M^{n},g)$, with $g$ in the Sobolev space $H_{s+3}$, $s>\frac{n}{2}$, admits an isometric embedding in an $(2n+2)$-dimensional Ricci-flat semi-Riemannian manifold. The sharpest result available for this type of embeddings, in the general setting, comes as a corollary of Greene's remarkable embedding theorems [R. Greene, Mem. Am. Math. Soc. 97, 1 (1970)], which guarantee the embedding of a compact $n$-dimensional semi-Riemannian manifold into an $n(n+5)$-dimensional semi-Euclidean space, thereby guaranteeing the embedding into a Ricci-flat space with the same dimension. The theorem presented here improves this corollary in $n^{2}+3n-2$ codimensions by replacing the Riemann-flat condition with the Ricci-flat one from the beginning. Finally, we will present a corollary of this theorem, which shows that a compact strip in an $n$-dimensional globally hyperbolic space-time can be embedded in a $(2n+2)$-dimensional Ricci-flat semi-Riemannian manifold.
|
gr-qc/9303016
|
Carsten Gundlach
|
Carsten Gundlach
|
The Isaacson expansion in quantum cosmology
|
Revtex, 11 journal or 24 preprint pages. REPLACEMENT: A comment on
previous work by Dowker and Laflamme is corrected. Utah preprint
UU-REL-93/3/10
|
Phys.Rev.D48:1700-1709,1993
|
10.1103/PhysRevD.48.1700
| null |
gr-qc
| null |
This paper is an application of the ideas of the Born-Oppenheimer (or
slow/fast) approximation in molecular physics and of the Isaacson (or
short-wave) approximation in classical gravity to the canonical quantization of
a perturbed minisuperspace model of the kind examined by Halliwell and Hawking.
Its aim is the clarification of the role of the semiclassical approximation and
the backreaction in such a model. Approximate solutions of the quantum model
are constructed which are not semiclassical, and semiclassical solutions in
which the quantum perturbations are highly excited.
|
[
{
"created": "Wed, 10 Mar 1993 23:35:39 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Apr 1993 00:03:10 GMT",
"version": "v2"
}
] |
2010-11-01
|
[
[
"Gundlach",
"Carsten",
""
]
] |
This paper is an application of the ideas of the Born-Oppenheimer (or slow/fast) approximation in molecular physics and of the Isaacson (or short-wave) approximation in classical gravity to the canonical quantization of a perturbed minisuperspace model of the kind examined by Halliwell and Hawking. Its aim is the clarification of the role of the semiclassical approximation and the backreaction in such a model. Approximate solutions of the quantum model are constructed which are not semiclassical, and semiclassical solutions in which the quantum perturbations are highly excited.
|
2405.03510
|
Karol Urba\'nski
|
Karol Urba\'nski (Szko{\l}a Doktorska Nauk \'Scis{\l}ych i
Przyrodniczych, Jagiellonian University)
|
Prolonging The Inevitable: Maximising survival time of an
engine-equipped spacecraft between spatial hypersurfaces, as applied to the
Schwarzschild spacetime
|
28 pages, 11 figures, preprint
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The fate of an astronaut unfortunate -- or foolish -- enough to find
themselves hurtling towards spaghettification after passing the event horizon
of a black hole is a common anecdote told by scientists to the regular
population. However, despite the fact the Schwarzschild spacetime has been
discovered over a century ago, the simple question of how long can such a space
traveller live has not been fully elaborated on since. In fact, a few textbooks
even give a mistaken or easily misread description of what happens. We address
those inconsistencies. We calculate the proper time a space traveller equipped
with means of propulsion can expect to live in these circumstances, giving
analytical expressions (as elliptic integrals) wherever possible. We prove a
principle that explains the best strategy to extend their life, and show its'
generalisation for other spacetimes. Finally, we give quantitative answers to
what gains due to optimal control can be expected in typical and somewhat
`realistic' circumstances.
|
[
{
"created": "Mon, 6 May 2024 14:23:29 GMT",
"version": "v1"
},
{
"created": "Tue, 7 May 2024 14:06:56 GMT",
"version": "v2"
}
] |
2024-05-08
|
[
[
"Urbański",
"Karol",
"",
"Szkoła Doktorska Nauk Ścisłych i\n Przyrodniczych, Jagiellonian University"
]
] |
The fate of an astronaut unfortunate -- or foolish -- enough to find themselves hurtling towards spaghettification after passing the event horizon of a black hole is a common anecdote told by scientists to the regular population. However, despite the fact the Schwarzschild spacetime has been discovered over a century ago, the simple question of how long can such a space traveller live has not been fully elaborated on since. In fact, a few textbooks even give a mistaken or easily misread description of what happens. We address those inconsistencies. We calculate the proper time a space traveller equipped with means of propulsion can expect to live in these circumstances, giving analytical expressions (as elliptic integrals) wherever possible. We prove a principle that explains the best strategy to extend their life, and show its' generalisation for other spacetimes. Finally, we give quantitative answers to what gains due to optimal control can be expected in typical and somewhat `realistic' circumstances.
|
gr-qc/0012081
|
Burkhard Kleihaus
|
B. Kleihaus (University College, Dublin) and J. Kunz (University
Oldenburg)
|
Rotating Hairy Black Holes
|
13 pages, including 4 eps figures, LaTex format
|
Phys.Rev.Lett. 86 (2001) 3704-3707
|
10.1103/PhysRevLett.86.3704
| null |
gr-qc
| null |
We construct stationary black holes in SU(2) Einstein-Yang-Mills theory,
which carry angular momentum and electric charge. Possessing non-trivial
non-abelian magnetic fields outside their regular event horizon, they represent
non-perturbative rotating hairy black holes.
|
[
{
"created": "Wed, 20 Dec 2000 16:03:42 GMT",
"version": "v1"
}
] |
2009-10-31
|
[
[
"Kleihaus",
"B.",
"",
"University College, Dublin"
],
[
"Kunz",
"J.",
"",
"University\n Oldenburg"
]
] |
We construct stationary black holes in SU(2) Einstein-Yang-Mills theory, which carry angular momentum and electric charge. Possessing non-trivial non-abelian magnetic fields outside their regular event horizon, they represent non-perturbative rotating hairy black holes.
|
0906.2162
|
Federico Urban
|
Federico R. Urban and Ariel R. Zhitnitsky
|
The cosmological constant from the QCD Veneziano ghost
|
4 pages, uses revtex4, v2 as published
|
Phys.Lett.B688:9-12,2010
|
10.1016/j.physletb.2010.03.080
| null |
gr-qc astro-ph.CO hep-lat hep-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We suggest that the solution to the cosmological vacuum energy puzzle is
linked to the infrared sector of the effective theory of gravity interacting
with standard model fields, with QCD fields specifically. We work in the
framework of low energy quantum gravity as an effective field theory. In
particular, we compute the vacuum energy in terms of QCD parameters and the
Hubble constant $H$ such that the vacuum energy is $\epsilon_{vac} \sim H \cdot
m_q\la\bar{q}q\ra /m_{\eta'} \sim (3.6\cdot 10^{-3} \text{eV})^4$, which is
amazingly close to the observed value today. The QCD ghost (responsible for the
solution of the $U(1)_A$ problem) plays a crucial r\^ole in the computation of
the vacuum energy, because the ghost's properties at very large but finite
distances slightly deviate (as $\sim H / \Lqcd $) from their infinite volume
Minkowski values. Another important prediction of this framework states that
the vacuum energy owes its existence to the asymmetry of the cosmos. Indeed,
this effect is a direct consequence of the embedding of our Universe on a
non-trivial manifold such as a torus with (slightly) different linear sizes.
Such a violation of cosmological isotropy is apparently indeed supported by
WMAP, and will be confirmed (or ruled out) by future PLANCK data.
|
[
{
"created": "Thu, 11 Jun 2009 17:26:33 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Apr 2010 15:49:01 GMT",
"version": "v2"
}
] |
2010-05-12
|
[
[
"Urban",
"Federico R.",
""
],
[
"Zhitnitsky",
"Ariel R.",
""
]
] |
We suggest that the solution to the cosmological vacuum energy puzzle is linked to the infrared sector of the effective theory of gravity interacting with standard model fields, with QCD fields specifically. We work in the framework of low energy quantum gravity as an effective field theory. In particular, we compute the vacuum energy in terms of QCD parameters and the Hubble constant $H$ such that the vacuum energy is $\epsilon_{vac} \sim H \cdot m_q\la\bar{q}q\ra /m_{\eta'} \sim (3.6\cdot 10^{-3} \text{eV})^4$, which is amazingly close to the observed value today. The QCD ghost (responsible for the solution of the $U(1)_A$ problem) plays a crucial r\^ole in the computation of the vacuum energy, because the ghost's properties at very large but finite distances slightly deviate (as $\sim H / \Lqcd $) from their infinite volume Minkowski values. Another important prediction of this framework states that the vacuum energy owes its existence to the asymmetry of the cosmos. Indeed, this effect is a direct consequence of the embedding of our Universe on a non-trivial manifold such as a torus with (slightly) different linear sizes. Such a violation of cosmological isotropy is apparently indeed supported by WMAP, and will be confirmed (or ruled out) by future PLANCK data.
|
1704.06151
|
Tien-Tien Yu
|
Vitor Cardoso, Paolo Pani, Tien-Tien Yu
|
Superradiance in rotating stars and pulsar-timing constraints on dark
photons
|
13 pages, 4 figures
|
Phys. Rev. D 95, 124056 (2017)
|
10.1103/PhysRevD.95.124056
| null |
gr-qc astro-ph.CO hep-ph physics.class-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In the presence of massive bosonic degrees of freedom, rotational
superradiance can trigger an instability that spins down black holes. This
leads to peculiar gravitational-wave signatures and distribution in the
spin-mass plane, which in turn can impose stringent constraints on ultralight
fields. Here, we demonstrate that there is an analogous spindown effect for
conducting stars. We show that rotating stars amplify low frequency
electromagnetic waves, and that this effect is largest when the time scale for
conduction within the star is of the order of a light crossing time. This has
interesting consequences for dark photons, as massive dark photons would cause
stars to spin down due to superradiant instabilities. The time scale of the
spindown depends on the mass of the dark photon, and on the rotation rate,
compactness, and conductivity of the star. Existing measurements of the
spindown rate of pulsars place direct constraints on models of dark sectors.
Our analysis suggests that dark photons of mass $m_V \sim 10^{-12}$ eV are
excluded by pulsar-timing observations. These constraints also exclude
superradiant instabilities triggered by dark photons as an explanation for the
spin limit of observed pulsars.
|
[
{
"created": "Tue, 18 Apr 2017 18:00:03 GMT",
"version": "v1"
}
] |
2017-07-05
|
[
[
"Cardoso",
"Vitor",
""
],
[
"Pani",
"Paolo",
""
],
[
"Yu",
"Tien-Tien",
""
]
] |
In the presence of massive bosonic degrees of freedom, rotational superradiance can trigger an instability that spins down black holes. This leads to peculiar gravitational-wave signatures and distribution in the spin-mass plane, which in turn can impose stringent constraints on ultralight fields. Here, we demonstrate that there is an analogous spindown effect for conducting stars. We show that rotating stars amplify low frequency electromagnetic waves, and that this effect is largest when the time scale for conduction within the star is of the order of a light crossing time. This has interesting consequences for dark photons, as massive dark photons would cause stars to spin down due to superradiant instabilities. The time scale of the spindown depends on the mass of the dark photon, and on the rotation rate, compactness, and conductivity of the star. Existing measurements of the spindown rate of pulsars place direct constraints on models of dark sectors. Our analysis suggests that dark photons of mass $m_V \sim 10^{-12}$ eV are excluded by pulsar-timing observations. These constraints also exclude superradiant instabilities triggered by dark photons as an explanation for the spin limit of observed pulsars.
|
1707.05011
|
Julio Fernando Abalos
|
Fernando Abalos
|
A necessary condition for strong hyperbolicity of general first order
systems
| null | null |
10.1142/S0219891619500073
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study strong hyperbolicity of first order partial differential equations
for systems with differential constraints. In these cases, the number of
equations is larger than the unknown fields, therefore, the standard Kreiss
necessary and sufficient conditions of strong hyperbolicity do not directly
apply. To deal with this problem one introduces a new tensor, called a
reduction, which selects a subset of equations with the aim of using them as
evolution equations for the unknown. If that tensor leads to a strongly
hyperbolic system we call it a hyperbolizer. There might exist many of them or
none.
A question arises on whether a given system admits any hyperbolization at
all. To sort-out this issue, we look for a condition on the system, such that,
if it is satisfied, there is no hyperbolic reduction. To that purpose we look
at the singular value decomposition of the whole system and study certain one
parameter families ($\varepsilon $) of perturbations of the principal symbol.
We look for the perturbed singular values around the vanishing ones and show
that if they behave as $O\left( \varepsilon ^{l}\right) $, with $l\geq 2$, then
there does not exist any hyperbolizer. In addition, we further notice that the
validity or failure of this condition can be established in a simple and
invariant way.
Finally we apply the theory to examples in physics, such as Force-Free
Electrodynamics in Euler potentials form and charged fluids with finite
conductivity. We find that they do not admit any hyperbolization.
|
[
{
"created": "Mon, 17 Jul 2017 06:36:19 GMT",
"version": "v1"
}
] |
2021-11-17
|
[
[
"Abalos",
"Fernando",
""
]
] |
We study strong hyperbolicity of first order partial differential equations for systems with differential constraints. In these cases, the number of equations is larger than the unknown fields, therefore, the standard Kreiss necessary and sufficient conditions of strong hyperbolicity do not directly apply. To deal with this problem one introduces a new tensor, called a reduction, which selects a subset of equations with the aim of using them as evolution equations for the unknown. If that tensor leads to a strongly hyperbolic system we call it a hyperbolizer. There might exist many of them or none. A question arises on whether a given system admits any hyperbolization at all. To sort-out this issue, we look for a condition on the system, such that, if it is satisfied, there is no hyperbolic reduction. To that purpose we look at the singular value decomposition of the whole system and study certain one parameter families ($\varepsilon $) of perturbations of the principal symbol. We look for the perturbed singular values around the vanishing ones and show that if they behave as $O\left( \varepsilon ^{l}\right) $, with $l\geq 2$, then there does not exist any hyperbolizer. In addition, we further notice that the validity or failure of this condition can be established in a simple and invariant way. Finally we apply the theory to examples in physics, such as Force-Free Electrodynamics in Euler potentials form and charged fluids with finite conductivity. We find that they do not admit any hyperbolization.
|
0901.0261
|
Farook Rahaman
|
F.Rahaman, S.Mal and M. Kalam
|
Vacuumless topological defects in Lyra geometry
|
14 pages, 9 figures. To appear in Astrophys.Space.Sci
|
Astrophys.Space Sci.319:169-175,2009
|
10.1007/s10509-009-9979-8
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Few years ago, Cho and Vilenkin have proposed that topological defects can
arise in symmetry breaking models without having degenerate vacua. These types
of defects are known as vacuumless defects. In the present work, the
gravitational field of a vacuumless global string and global monopole have been
investigated in the context of Lyra geometry. We find the metric of the
vacuumless global string and global monopole in the weak field approximations.
It has been shown that the vacuumless global string can have repulsive whereas
global monopole exerts attractive gravitational effects on a test particle. It
is dissimilar to the case studied in general relativity.
|
[
{
"created": "Fri, 2 Jan 2009 17:47:41 GMT",
"version": "v1"
}
] |
2009-11-18
|
[
[
"Rahaman",
"F.",
""
],
[
"Mal",
"S.",
""
],
[
"Kalam",
"M.",
""
]
] |
Few years ago, Cho and Vilenkin have proposed that topological defects can arise in symmetry breaking models without having degenerate vacua. These types of defects are known as vacuumless defects. In the present work, the gravitational field of a vacuumless global string and global monopole have been investigated in the context of Lyra geometry. We find the metric of the vacuumless global string and global monopole in the weak field approximations. It has been shown that the vacuumless global string can have repulsive whereas global monopole exerts attractive gravitational effects on a test particle. It is dissimilar to the case studied in general relativity.
|
1902.04504
|
Geoffrey Comp\`ere
|
Geoffrey Comp\`ere
|
Are quantum corrections on horizon scale physically motivated?
|
16 pages, 8 figures. v3: published version
| null |
10.1142/S0218271819300192
| null |
gr-qc astro-ph.HE hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The aim of this short review is to give an overview to non-specialists of
recent arguments from fundamental physics in favor and disfavor of quantum
corrections to black hole horizons. I will mainly discuss the black hole
information paradox, its possible resolutions and shortly address its relevance
or irrelevance to astronomy.
|
[
{
"created": "Tue, 12 Feb 2019 17:12:19 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Feb 2019 08:49:45 GMT",
"version": "v2"
},
{
"created": "Mon, 22 Jul 2019 22:16:16 GMT",
"version": "v3"
}
] |
2020-01-08
|
[
[
"Compère",
"Geoffrey",
""
]
] |
The aim of this short review is to give an overview to non-specialists of recent arguments from fundamental physics in favor and disfavor of quantum corrections to black hole horizons. I will mainly discuss the black hole information paradox, its possible resolutions and shortly address its relevance or irrelevance to astronomy.
|
1608.05223
|
Gabriele Gionti S.J.
|
Gabriele Gionti, S.J
|
O(d,d) duality transformations in F(R) theories of gravity
|
6 pages ,contribution to the proceedings of the 14th Marcel Grossmann
Meeting , Rome 12-18 July 2015
| null | null | null |
gr-qc hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The argument of Hodge duality symmetry is introduced starting from the
electromagnetic field. Introducing bosonic string theory, O(d,d) duality
symmetry can be implemented when there exist d-symmetries, which allows one to
write Hodge-dual fields. A tree-level effective gravitational action of bosonic
string theory coupled with the dilaton field is considered. This theory
inherits the Busher's duality of its parent string theory. The dilaton field
can be recast into the Weyl's mode of the metric tensor in the Jordan frame.
This maps the effective one-loop bosonic string theory of gravity into a
Lagrangian of a f(R) function. Constraining this f(R)-Lagrangian on a FLRW
metric and using Noether symmetries approach for extended theory of gravity, it
is possible to show that the Lagrangian exibits a Gasperini-Veneziano duality
symmetry.
|
[
{
"created": "Thu, 18 Aug 2016 10:10:12 GMT",
"version": "v1"
}
] |
2016-08-19
|
[
[
"Gionti",
"Gabriele",
""
],
[
"J",
"S.",
""
]
] |
The argument of Hodge duality symmetry is introduced starting from the electromagnetic field. Introducing bosonic string theory, O(d,d) duality symmetry can be implemented when there exist d-symmetries, which allows one to write Hodge-dual fields. A tree-level effective gravitational action of bosonic string theory coupled with the dilaton field is considered. This theory inherits the Busher's duality of its parent string theory. The dilaton field can be recast into the Weyl's mode of the metric tensor in the Jordan frame. This maps the effective one-loop bosonic string theory of gravity into a Lagrangian of a f(R) function. Constraining this f(R)-Lagrangian on a FLRW metric and using Noether symmetries approach for extended theory of gravity, it is possible to show that the Lagrangian exibits a Gasperini-Veneziano duality symmetry.
|
1712.01326
|
Itzhak Bars
|
Ignacio J. Araya and Itzhak Bars
|
Extended Rindler Spacetime and a New Multiverse Structure
|
61 pages, 11 figures. Version 2 adds a new section VI and includes
minor corrections
|
Phys. Rev. D 97, 085009 (2018)
|
10.1103/PhysRevD.97.085009
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
This is the first of a series of papers in which we use analyticity
properties of quantum fields propagating on a spacetime to uncover a new
multiverse geometry when the classical geometry has horizons and/or
singularities. The nature and origin of the multiverse idea presented in this
paper, that is shared by the fields in the standard model coupled to gravity,
is different from other notions of a multiverse. Via analyticity we are able to
establish definite relations among the universes. In this paper we illustrate
these properties for the extended Rindler space, while black hole spacetime and
the cosmological geometry of mini-superspace (see Appendix B) will appear in
later papers. In classical general relativity, extended Rindler space is
equivalent to flat Minkowski space; it consists of the union of the four wedges
in (u,v) light-cone coordinates as in Fig.(1). In quantum mechanics, the
wavefunction is an analytic function of (u,v) that is sensitive to branch
points at the horizons u=0 or v=0, with branch cuts attached to them. The
wavefunction is uniquely defined by analyticity on an infinite number of sheets
in the cut analytic (u,v) spacetime. This structure is naturally interpreted as
an infinite stack of identical Minkowski geometries, or universes, connected to
each other by analyticity across branch cuts, such that each sheet represents a
different Minkowski universe when (u,v) are analytically continued to the real
axis on any sheet. We show in this paper that, in the absence of interactions,
information doesn't flow from one Rindler sheet to another. By contrast, for an
eternal black hole spacetime, which may be viewed as a modification of Rindler
that includes gravitational interactions, analyticity shows how information is
lost due to a flow to other universes, enabled by an additional branch point
and cut due to the black hole singularity.
|
[
{
"created": "Mon, 4 Dec 2017 20:10:22 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Mar 2018 23:30:55 GMT",
"version": "v2"
}
] |
2018-04-18
|
[
[
"Araya",
"Ignacio J.",
""
],
[
"Bars",
"Itzhak",
""
]
] |
This is the first of a series of papers in which we use analyticity properties of quantum fields propagating on a spacetime to uncover a new multiverse geometry when the classical geometry has horizons and/or singularities. The nature and origin of the multiverse idea presented in this paper, that is shared by the fields in the standard model coupled to gravity, is different from other notions of a multiverse. Via analyticity we are able to establish definite relations among the universes. In this paper we illustrate these properties for the extended Rindler space, while black hole spacetime and the cosmological geometry of mini-superspace (see Appendix B) will appear in later papers. In classical general relativity, extended Rindler space is equivalent to flat Minkowski space; it consists of the union of the four wedges in (u,v) light-cone coordinates as in Fig.(1). In quantum mechanics, the wavefunction is an analytic function of (u,v) that is sensitive to branch points at the horizons u=0 or v=0, with branch cuts attached to them. The wavefunction is uniquely defined by analyticity on an infinite number of sheets in the cut analytic (u,v) spacetime. This structure is naturally interpreted as an infinite stack of identical Minkowski geometries, or universes, connected to each other by analyticity across branch cuts, such that each sheet represents a different Minkowski universe when (u,v) are analytically continued to the real axis on any sheet. We show in this paper that, in the absence of interactions, information doesn't flow from one Rindler sheet to another. By contrast, for an eternal black hole spacetime, which may be viewed as a modification of Rindler that includes gravitational interactions, analyticity shows how information is lost due to a flow to other universes, enabled by an additional branch point and cut due to the black hole singularity.
|
1701.04910
|
Takeshi Chiba
|
Takeshi Chiba, Masashi Kimura
|
A Note on Geodesics in Hayward Metric
|
14 pages, 10 figures, typos corrected, to appear in PTEP
|
PTEP 2017 (2017) 4, 043E01
|
10.1093/ptep/ptx037
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study timelike and null geodesics in a non-singular black hole metric
proposed by Hayward. The metric contains an additional length-scale parameter
$\ell$ and approaches the Schwarzschild metric at large radii while approaches
a constant at small radii so that the singularity is resolved. We tabulate the
various critical values of $\ell$ for timelike and null geodesics: the critical
values for the existence of horizon, marginally stable circular orbit and
photon sphere. We find the photon sphere exists even if the horizon is absent
and two marginally stable circular orbits appear if the photon sphere is absent
and a stable circular orbit for photons exists for a certain range of $\ell$.
We visualize the image of a black hole and find that blight rings appear even
if the photon sphere is absent.
|
[
{
"created": "Wed, 18 Jan 2017 00:59:41 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Mar 2017 04:22:20 GMT",
"version": "v2"
},
{
"created": "Mon, 3 Apr 2017 01:28:03 GMT",
"version": "v3"
}
] |
2017-05-10
|
[
[
"Chiba",
"Takeshi",
""
],
[
"Kimura",
"Masashi",
""
]
] |
We study timelike and null geodesics in a non-singular black hole metric proposed by Hayward. The metric contains an additional length-scale parameter $\ell$ and approaches the Schwarzschild metric at large radii while approaches a constant at small radii so that the singularity is resolved. We tabulate the various critical values of $\ell$ for timelike and null geodesics: the critical values for the existence of horizon, marginally stable circular orbit and photon sphere. We find the photon sphere exists even if the horizon is absent and two marginally stable circular orbits appear if the photon sphere is absent and a stable circular orbit for photons exists for a certain range of $\ell$. We visualize the image of a black hole and find that blight rings appear even if the photon sphere is absent.
|
2307.04141
|
Yu Zhang
|
Qian Li, Chen Ma, Yu Zhang, Zhi-Wen Lin, Peng-Fei Duan
|
Gray-body factor and absorption of the Dirac field in ESTGB gravity
|
11 pages, 7 figures
|
Chinese Journal of Physics 77 (2022) 1269-1277
|
10.1016/j.cjph.2022.03.027
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The gray-body factor and the absorption cross section of the 4D ESTGB gravity
with a mode of nonlinear electrodynamics for the massless Dirac field are
studied in this paper. The magnetic charge value varies between
$-2^{(\frac{5}{3})}/3$ and $0$ as well as the ADM mass is set to $1$, which
corresponds to a non-extreme black hole. The gray-body factor is obtained using
the semi-analytic WKB method after solving the massless Dirac equation. When
the absolute value of magnetic charge is increasing, the gray-body factor
$\gamma(\omega)$ is decreasing. In addition, the partial absorption cross
section and the total absorption cross section are calculated by using the
partial wave method. We find that the maximum value of partial absorption cross
section decreases as $\kappa$ increases. And the existence of magnetic charge
causes the diminishing of the total absorption cross section. Finally, we find
that the absorption cross section of the Dirac field is more sensitive to
electric charge than magnetic charge by comparing the absorption cross section
of the Reissner-Nordstr$\rm\ddot{o}$m and ESTGB-NLED black holes.
|
[
{
"created": "Sun, 9 Jul 2023 10:05:39 GMT",
"version": "v1"
}
] |
2023-07-11
|
[
[
"Li",
"Qian",
""
],
[
"Ma",
"Chen",
""
],
[
"Zhang",
"Yu",
""
],
[
"Lin",
"Zhi-Wen",
""
],
[
"Duan",
"Peng-Fei",
""
]
] |
The gray-body factor and the absorption cross section of the 4D ESTGB gravity with a mode of nonlinear electrodynamics for the massless Dirac field are studied in this paper. The magnetic charge value varies between $-2^{(\frac{5}{3})}/3$ and $0$ as well as the ADM mass is set to $1$, which corresponds to a non-extreme black hole. The gray-body factor is obtained using the semi-analytic WKB method after solving the massless Dirac equation. When the absolute value of magnetic charge is increasing, the gray-body factor $\gamma(\omega)$ is decreasing. In addition, the partial absorption cross section and the total absorption cross section are calculated by using the partial wave method. We find that the maximum value of partial absorption cross section decreases as $\kappa$ increases. And the existence of magnetic charge causes the diminishing of the total absorption cross section. Finally, we find that the absorption cross section of the Dirac field is more sensitive to electric charge than magnetic charge by comparing the absorption cross section of the Reissner-Nordstr$\rm\ddot{o}$m and ESTGB-NLED black holes.
|
2311.18493
|
Salvatore Mignemi
|
S. Mignemi
|
Dyonic black holes in Kaluza-Klein theory with a Gauss-Bonnet action
|
8 pages
| null | null | null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
We consider a five-dimensional Einstein-Gauss-Bonnet model, which gives rise
after dimensional reduction to Einstein gravity nonminimally coupled to
nonlinear electrodynamics. The black hole solutions of the four-dimensional
model modify the Reissner-Nordstrom solutions of general relativity. The
gravitational field presents the standard singularity at $r=0$, while the
electric field can be regular everywhere if the magnetic charge vanishes
|
[
{
"created": "Thu, 30 Nov 2023 12:07:47 GMT",
"version": "v1"
}
] |
2023-12-01
|
[
[
"Mignemi",
"S.",
""
]
] |
We consider a five-dimensional Einstein-Gauss-Bonnet model, which gives rise after dimensional reduction to Einstein gravity nonminimally coupled to nonlinear electrodynamics. The black hole solutions of the four-dimensional model modify the Reissner-Nordstrom solutions of general relativity. The gravitational field presents the standard singularity at $r=0$, while the electric field can be regular everywhere if the magnetic charge vanishes
|
gr-qc/0409038
|
Dejan Stojkovic
|
Dejan Stojkovic
|
Energy flux through the horizon in the black hole-domain wall systems
|
references added, accepted for publication in JHEP
|
JHEP 0409:061,2004
|
10.1088/1126-6708/2004/09/061
| null |
gr-qc astro-ph hep-th
| null |
We study various configurations in which a domain wall (or cosmic string),
described by the Nambu-Goto action, is embedded in a background space-time of a
black hole in $(3+1)$ and higher dimensional models. We calculate energy fluxes
through the black hole horizon. In the simplest case, when a static domain wall
enters the horizon of a static black hole perperdicularly, the energy flux is
zero. In more complicated situations, where parameters which describe the
domain wall surface are time and position dependent, the flux is non-vanishing
is principle. These results are of importance in various conventional
cosmological models which accommodate the existence of domain walls and strings
and also in brane world scenarios.
|
[
{
"created": "Wed, 8 Sep 2004 17:34:10 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Oct 2004 13:35:57 GMT",
"version": "v2"
}
] |
2010-11-19
|
[
[
"Stojkovic",
"Dejan",
""
]
] |
We study various configurations in which a domain wall (or cosmic string), described by the Nambu-Goto action, is embedded in a background space-time of a black hole in $(3+1)$ and higher dimensional models. We calculate energy fluxes through the black hole horizon. In the simplest case, when a static domain wall enters the horizon of a static black hole perperdicularly, the energy flux is zero. In more complicated situations, where parameters which describe the domain wall surface are time and position dependent, the flux is non-vanishing is principle. These results are of importance in various conventional cosmological models which accommodate the existence of domain walls and strings and also in brane world scenarios.
|
1403.5243
|
Ricardo Lopez-Fernandez Dr.
|
Tonatiuh Matos and Ricardo Lopez-Fernandez
|
A SM Singlet Scalar as Dark Matter
|
5 pages, 1 figure
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this work we investigate the possibility that a simple extension of the
Standard Model (SM) can be the dark matter of the universe. We postulate the
existence of a scalar field singlet like the Higgs as an extra term in the SM
Lagrangian. We find that from the astrophysical point of view a very small mass
and self-interaction is more convenient to agree with observations and from
particle detectors observations we do not see any essential constrain to this
settings. Thus, we conclude that a scalar field singlet with a small mass and
self-interaction is a good candidate to be the nature of the dark matter.
|
[
{
"created": "Thu, 20 Mar 2014 19:35:05 GMT",
"version": "v1"
}
] |
2014-03-21
|
[
[
"Matos",
"Tonatiuh",
""
],
[
"Lopez-Fernandez",
"Ricardo",
""
]
] |
In this work we investigate the possibility that a simple extension of the Standard Model (SM) can be the dark matter of the universe. We postulate the existence of a scalar field singlet like the Higgs as an extra term in the SM Lagrangian. We find that from the astrophysical point of view a very small mass and self-interaction is more convenient to agree with observations and from particle detectors observations we do not see any essential constrain to this settings. Thus, we conclude that a scalar field singlet with a small mass and self-interaction is a good candidate to be the nature of the dark matter.
|
2107.11915
|
Martin Lesourd Mr
|
Martin Lesourd and Eric Ling
|
Topological censorship in spacetimes compatible with $\Lambda > 0$
|
Comments are welcome
| null |
10.1007/s00023-022-01200-1
| null |
gr-qc math.DG
|
http://creativecommons.org/publicdomain/zero/1.0/
|
Currently available topological censorship theorems are meant for
gravitationally isolated black hole spacetimes with cosmological constant
$\Lambda=0$ or $\Lambda<0$. Here, we prove a topological censorship theorem
that is compatible with $\Lambda>0$ and which can be applied to whole universes
containing possibly multiple collections of black holes. The main assumption in
the theorem is that distinct black hole collections eventually become isolated
from one another at late times, and the conclusion is that the regions near the
various black hole collections have trivial fundamental group, in spite of
there possibly being nontrivial topology in the universe.
|
[
{
"created": "Mon, 26 Jul 2021 00:39:45 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Nov 2021 23:12:13 GMT",
"version": "v2"
}
] |
2022-11-30
|
[
[
"Lesourd",
"Martin",
""
],
[
"Ling",
"Eric",
""
]
] |
Currently available topological censorship theorems are meant for gravitationally isolated black hole spacetimes with cosmological constant $\Lambda=0$ or $\Lambda<0$. Here, we prove a topological censorship theorem that is compatible with $\Lambda>0$ and which can be applied to whole universes containing possibly multiple collections of black holes. The main assumption in the theorem is that distinct black hole collections eventually become isolated from one another at late times, and the conclusion is that the regions near the various black hole collections have trivial fundamental group, in spite of there possibly being nontrivial topology in the universe.
|
0807.4542
|
Johan Brannlund
|
J Brannlund, A Coley, S Hervik
|
Supersymmetry, holonomy and Kundt spacetimes
|
14 pages. Accepted by Class. Quant. Grav. Some misprints fixed
|
Class.Quant.Grav.25:195007,2008
|
10.1088/0264-9381/25/19/195007
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Supersymmetric solutions of supergravity theories, and consequently metrics
with special holonomy, have played an important role in the development of
string theory. We describe how a Lorentzian manifold is either completely
reducible, and thus essentially known, or not completely reducible so that
there exists a degenerate holonomy invariant lightlike subspace and
consequently admits a covariantly constant or a recurrent null vector and
belongs to the higher-dimensional Kundt class of spacetimes. These Kundt
spacetimes (which contain the vanishing and constant curvature invariant
spacetimes as special cases) are genuinely Lorentzian and have a number of
interesting and unusual properties, which may lead to novel and fundamental
physics.
|
[
{
"created": "Mon, 28 Jul 2008 20:44:53 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Jul 2008 01:00:14 GMT",
"version": "v2"
}
] |
2008-11-26
|
[
[
"Brannlund",
"J",
""
],
[
"Coley",
"A",
""
],
[
"Hervik",
"S",
""
]
] |
Supersymmetric solutions of supergravity theories, and consequently metrics with special holonomy, have played an important role in the development of string theory. We describe how a Lorentzian manifold is either completely reducible, and thus essentially known, or not completely reducible so that there exists a degenerate holonomy invariant lightlike subspace and consequently admits a covariantly constant or a recurrent null vector and belongs to the higher-dimensional Kundt class of spacetimes. These Kundt spacetimes (which contain the vanishing and constant curvature invariant spacetimes as special cases) are genuinely Lorentzian and have a number of interesting and unusual properties, which may lead to novel and fundamental physics.
|
gr-qc/0211021
|
Edward Anderson
|
Julian Barbour
|
Scale-Invariant Gravity: Particle Dynamics
|
28 pages. Published version (minor changes from previous version)
|
Class.Quant.Grav. 20 (2003) 1543-1570
|
10.1088/0264-9381/20/8/310
| null |
gr-qc
| null |
A new and universal method for implementing scale invariance, called best
matching, is presented. It extends to scaling the method introduced by Bertotti
and the author to create a fully relational dynamics that satisfies Mach's
principle. The method is illustrated here in the context of non-relativistic
gravitational particle dynamics.. It leads to far stronger predictions than
general Newtonian dynamics. The energy and angular momentum of an `island
universe' must be exactly zero and its size, measured by its moment of inertia,
cannot change. This constancy is enforced because the scale invariance requires
all potentials to be homogeneous of degree -2. It is remarkable that one can
nevertheless exactly recover the standard observed Newtonian laws and forces,
which are merely accompanied by an extremally weak universal force like the one
due to Einstein's cosmological constant. In contrast to Newtonian and
Einsteinian dynamics, both the gravitational constant G and the strength of the
cosmological force are uniquely determined by the matter distribution of the
universe. Estimates of their values in agreement with observations are
obtained. Best matching implements a dynamics of pure shape for which the
action is a dimensionless number. If the universe obeys such scale invariant
law, steadily increasing inhomogeneity, not expansion of the universe, causes
the Hubble red shift. The application of best matching to geometrodynamics is
treated in a companion paper.
|
[
{
"created": "Wed, 6 Nov 2002 20:43:56 GMT",
"version": "v1"
},
{
"created": "Fri, 2 May 2003 20:35:49 GMT",
"version": "v2"
}
] |
2017-08-23
|
[
[
"Barbour",
"Julian",
""
]
] |
A new and universal method for implementing scale invariance, called best matching, is presented. It extends to scaling the method introduced by Bertotti and the author to create a fully relational dynamics that satisfies Mach's principle. The method is illustrated here in the context of non-relativistic gravitational particle dynamics.. It leads to far stronger predictions than general Newtonian dynamics. The energy and angular momentum of an `island universe' must be exactly zero and its size, measured by its moment of inertia, cannot change. This constancy is enforced because the scale invariance requires all potentials to be homogeneous of degree -2. It is remarkable that one can nevertheless exactly recover the standard observed Newtonian laws and forces, which are merely accompanied by an extremally weak universal force like the one due to Einstein's cosmological constant. In contrast to Newtonian and Einsteinian dynamics, both the gravitational constant G and the strength of the cosmological force are uniquely determined by the matter distribution of the universe. Estimates of their values in agreement with observations are obtained. Best matching implements a dynamics of pure shape for which the action is a dimensionless number. If the universe obeys such scale invariant law, steadily increasing inhomogeneity, not expansion of the universe, causes the Hubble red shift. The application of best matching to geometrodynamics is treated in a companion paper.
|
0804.1360
|
Larry Ford
|
Carlos H. G. Bessa, Valdir B. Bezerra and L. H. Ford
|
Brownian Motion in Robertson-Walker Space-Times from electromagnetic
Vacuum Fluctuations
|
29 pages, 7 figures
|
J.Math.Phys.50:062501,2009
|
10.1063/1.3133946
| null |
gr-qc hep-th quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider classical particles coupled to the quantized electromagnetic
field in the background of a spatially flat Robertson-Walker universe. We find
that these particles typically undergo Brownian motion and acquire a non-zero
mean squared velocity which depends upon the scale factor of the universe. This
Brownian motion can be interpreted as due to non-cancellation of
anti-correlated vacuum fluctuations in the time dependent background
space-time. We consider several types of coupling to the electromagnetic field,
including particles with net electric charge, a magnetic dipole moment, and
electric polarizability. We also investigate several different model scale
factors.
|
[
{
"created": "Tue, 8 Apr 2008 20:32:15 GMT",
"version": "v1"
}
] |
2011-07-19
|
[
[
"Bessa",
"Carlos H. G.",
""
],
[
"Bezerra",
"Valdir B.",
""
],
[
"Ford",
"L. H.",
""
]
] |
We consider classical particles coupled to the quantized electromagnetic field in the background of a spatially flat Robertson-Walker universe. We find that these particles typically undergo Brownian motion and acquire a non-zero mean squared velocity which depends upon the scale factor of the universe. This Brownian motion can be interpreted as due to non-cancellation of anti-correlated vacuum fluctuations in the time dependent background space-time. We consider several types of coupling to the electromagnetic field, including particles with net electric charge, a magnetic dipole moment, and electric polarizability. We also investigate several different model scale factors.
|
gr-qc/9511074
|
Leonid Grishchuk
|
L. P. Grishchuk
|
Statistics of the Microwave Background Anisotropies Caused by
Cosmological Perturbations of Quantum-Mechanical Origin
|
34 pages, REVTEX 3.0
| null | null |
WUGRAV-95-16
|
gr-qc astro-ph hep-ph
| null |
The genuine quantum gravity effects can already be around us. It is likely
that the observed large-angular-scale anisotropies in the microwave background
radiation are induced by cosmological perturbations of quantum-mechanical
origin. Such perturbations are placed in squeezed vacuum quantum states and,
hence, are characterized by large variances of their amplitude. The statistical
properties of the anisotropies should reflect the underlying statistics of the
squeezed vacuum quantum states. In this paper, the theoretical variances for
the temperature angular correlation function are described in detail. It is
shown that they are indeed large and must be present in the observational data,
if the anisotropies are truly caused by the perturbations of quantum-mechanical
origin. Unfortunately, these large theoretical statistical uncertainties will
make the extraction of cosmological information from the measured anisotropies
a much more difficult problem than we wanted it to be. This contribution to the
Proceedings is largely based on references~[42,8]. The Appendix contains an
analysis of the ``standard'' inflationary formula for density perturbations.
|
[
{
"created": "Mon, 27 Nov 1995 18:04:10 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Grishchuk",
"L. P.",
""
]
] |
The genuine quantum gravity effects can already be around us. It is likely that the observed large-angular-scale anisotropies in the microwave background radiation are induced by cosmological perturbations of quantum-mechanical origin. Such perturbations are placed in squeezed vacuum quantum states and, hence, are characterized by large variances of their amplitude. The statistical properties of the anisotropies should reflect the underlying statistics of the squeezed vacuum quantum states. In this paper, the theoretical variances for the temperature angular correlation function are described in detail. It is shown that they are indeed large and must be present in the observational data, if the anisotropies are truly caused by the perturbations of quantum-mechanical origin. Unfortunately, these large theoretical statistical uncertainties will make the extraction of cosmological information from the measured anisotropies a much more difficult problem than we wanted it to be. This contribution to the Proceedings is largely based on references~[42,8]. The Appendix contains an analysis of the ``standard'' inflationary formula for density perturbations.
|
1401.6871
|
Eugeny Babichev
|
Eugeny Babichev and Alessandro Fabbri
|
Stability analysis of black holes in massive gravity: a unified
treatment
|
4 pages; v2: matches the published version
|
Phys. Rev. D 89, 081502 (2014)
|
10.1103/PhysRevD.89.081502
|
LPT-Orsay-14-20
|
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider the analytic solutions of massive (bi)gravity which can be
written in a simple form using advanced Eddington-Finkelstein coordinates. We
analyse the stability of these solutions against radial perturbations. First we
recover the previously obtained result on the instability of the bidiagonal
bi-Schwarzschild solutions. In the non-bidiagonal case (which contains, in
particular, the Schwarzschild solution with Minkowski fiducial metric) we show
that generically there are physical spherically symmetric perturbations, but no
unstable modes.
|
[
{
"created": "Mon, 27 Jan 2014 14:48:55 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Apr 2014 09:00:52 GMT",
"version": "v2"
}
] |
2014-04-23
|
[
[
"Babichev",
"Eugeny",
""
],
[
"Fabbri",
"Alessandro",
""
]
] |
We consider the analytic solutions of massive (bi)gravity which can be written in a simple form using advanced Eddington-Finkelstein coordinates. We analyse the stability of these solutions against radial perturbations. First we recover the previously obtained result on the instability of the bidiagonal bi-Schwarzschild solutions. In the non-bidiagonal case (which contains, in particular, the Schwarzschild solution with Minkowski fiducial metric) we show that generically there are physical spherically symmetric perturbations, but no unstable modes.
|
gr-qc/0101034
|
Roh Suan Tung
|
Roh S. Tung
|
Gravitation as a Super SL(2,C) Gauge Theory
|
4 pages, Proceedings of the 9th Marcel Grossmann Meeting, Rome, 2-8
July, 2000
| null |
10.1142/9789812777386_0168
| null |
gr-qc hep-th
| null |
We present a gauge theory of the super SL(2,C) group. The gauge potential is
a connection of the Super SL(2,C) group. A MacDowell-Mansouri type of action is
proposed where the action is quadratic in the Super SL(2,C) curvature and
depends purely on gauge connection. By breaking the symmetry of the Super
SL(2,C) topological gauge theory to SL(2,C), a metric is naturally defined.
|
[
{
"created": "Tue, 9 Jan 2001 23:04:25 GMT",
"version": "v1"
}
] |
2017-08-23
|
[
[
"Tung",
"Roh S.",
""
]
] |
We present a gauge theory of the super SL(2,C) group. The gauge potential is a connection of the Super SL(2,C) group. A MacDowell-Mansouri type of action is proposed where the action is quadratic in the Super SL(2,C) curvature and depends purely on gauge connection. By breaking the symmetry of the Super SL(2,C) topological gauge theory to SL(2,C), a metric is naturally defined.
|
2212.12901
|
Guangzhou Guo
|
Guangzhou Guo, Yuhang Lu, Peng Wang, Houwen Wu and Haitang Yang
|
Black Holes with Multiple Photon Spheres
|
25 pages, 8 figures, references added
| null |
10.1103/PhysRevD.107.124037
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Recently, asymptotically-flat black holes with multiple photon spheres have
been discovered and found to produce distinctive observational signatures. In
this paper, we focus on whether these black hole solutions are physically
viable, e.g., satisfying energy conditions of interest. Intriguingly, black
hole and naked singularity solutions with two photon spheres and one
anti-photon sphere are shown to exist in physically reasonable models, which
satisfy the null, weak, dominant and strong energy conditions. Our findings
reveal that black holes with multiple photon spheres may not be frequent, but
they are not exotic.
|
[
{
"created": "Sun, 25 Dec 2022 13:35:03 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Dec 2022 02:22:57 GMT",
"version": "v2"
},
{
"created": "Thu, 5 Jan 2023 13:41:05 GMT",
"version": "v3"
}
] |
2023-06-28
|
[
[
"Guo",
"Guangzhou",
""
],
[
"Lu",
"Yuhang",
""
],
[
"Wang",
"Peng",
""
],
[
"Wu",
"Houwen",
""
],
[
"Yang",
"Haitang",
""
]
] |
Recently, asymptotically-flat black holes with multiple photon spheres have been discovered and found to produce distinctive observational signatures. In this paper, we focus on whether these black hole solutions are physically viable, e.g., satisfying energy conditions of interest. Intriguingly, black hole and naked singularity solutions with two photon spheres and one anti-photon sphere are shown to exist in physically reasonable models, which satisfy the null, weak, dominant and strong energy conditions. Our findings reveal that black holes with multiple photon spheres may not be frequent, but they are not exotic.
|
1605.01989
|
Alexey Toporensky
|
Maria Skugoreva and Alexey Toporensky
|
Asymptotic cosmological regimes in scalar-torsion gravity with a perfect
fluid
|
14 pages with 2 tables and 1 eps figure. Minor changes, published
version
|
Eur.Phys.J. C76 (2016) no.6, 340
|
10.1140/epjc/s10052-016-4190-x
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider cosmological dynamics of nonminimally coupled scalar field in the
scalar-torsion gravity in the presence of a hydrodynamical matter. Potential of
the scalar field have been chosen as power-law with negative index, this type
of potentials is usually used in quintessence scenarios. We identify several
asymptotic regimes, including de Sitter, kinetic dominance, kinetic tracker and
tracker solution and study conditions for their existence and stability. We
show that for each combination of coupling constant and potential power index
one of regimes studied in the present paper is stable to the future.
|
[
{
"created": "Fri, 6 May 2016 16:12:50 GMT",
"version": "v1"
},
{
"created": "Sun, 1 Jan 2017 14:03:16 GMT",
"version": "v2"
}
] |
2017-01-03
|
[
[
"Skugoreva",
"Maria",
""
],
[
"Toporensky",
"Alexey",
""
]
] |
We consider cosmological dynamics of nonminimally coupled scalar field in the scalar-torsion gravity in the presence of a hydrodynamical matter. Potential of the scalar field have been chosen as power-law with negative index, this type of potentials is usually used in quintessence scenarios. We identify several asymptotic regimes, including de Sitter, kinetic dominance, kinetic tracker and tracker solution and study conditions for their existence and stability. We show that for each combination of coupling constant and potential power index one of regimes studied in the present paper is stable to the future.
|
2011.14682
|
Roberto Dale
|
R. Dale and D. S\'aez
|
Spherical symmetric dust collapse in a Vector-Tensor gravity
|
22 pages, 1 table
|
Phys. Rev. D 98, 064007 (2018)
|
10.1103/PhysRevD.98.064007
| null |
gr-qc
|
http://creativecommons.org/publicdomain/zero/1.0/
|
There is a viable vector-tensor gravity (VTG) theory, whose vector field
produces repulsive forces leading to important effects. In the background
universe, the effect of these forces is an accelerated expansion identical to
that produced by vacuum energy (cosmological constant). Here, we prove that
another of these effects arises for great enough collapsing masses which lead
to Schwarzschild black holes and singularities in general relativity (GR). For
these masses, pressure becomes negligible against gravitational attraction and
the complete collapse cannot be stopped in the context of GR; however, in VTG,
a strong gravitational repulsion could stop the falling of the shells towards
the symmetry center. A certain study of a collapsing dust cloud is then
developed and, in order to undertake this task, the VTG equations in comoving
coordinates are written. In this sense and, as it happens in general relativity
for a pressureless dust ball, three different solutions are found. These three
situations are analyzed and the problem of the shell crossings is approached.
The apparent horizons and trapped surfaces, whose analysis will lead to diverse
situations, depending on certain theory characteristic parameter value, are
also examined.
|
[
{
"created": "Mon, 30 Nov 2020 10:48:23 GMT",
"version": "v1"
}
] |
2020-12-01
|
[
[
"Dale",
"R.",
""
],
[
"Sáez",
"D.",
""
]
] |
There is a viable vector-tensor gravity (VTG) theory, whose vector field produces repulsive forces leading to important effects. In the background universe, the effect of these forces is an accelerated expansion identical to that produced by vacuum energy (cosmological constant). Here, we prove that another of these effects arises for great enough collapsing masses which lead to Schwarzschild black holes and singularities in general relativity (GR). For these masses, pressure becomes negligible against gravitational attraction and the complete collapse cannot be stopped in the context of GR; however, in VTG, a strong gravitational repulsion could stop the falling of the shells towards the symmetry center. A certain study of a collapsing dust cloud is then developed and, in order to undertake this task, the VTG equations in comoving coordinates are written. In this sense and, as it happens in general relativity for a pressureless dust ball, three different solutions are found. These three situations are analyzed and the problem of the shell crossings is approached. The apparent horizons and trapped surfaces, whose analysis will lead to diverse situations, depending on certain theory characteristic parameter value, are also examined.
|
1802.07371
|
Robert R. Caldwell
|
R. R. Caldwell and C. Devulder
|
Gravitational Wave Opacity from Gauge Field Dark Energy
|
17 pages, 19 figures, revised and clarified text, results unchanged.
V3 minor changes, including additional analysis of opacity effect for 3G
detectors. New version matches published version
|
Phys. Rev. D 100, 103510 (2019)
|
10.1103/PhysRevD.100.103510
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We show that astrophysical gravitational waves can undergo an anomalous
modulation when propagating through cosmic gauge field dark energy. A
sufficiently strong effect, dependent on the gauge field energy density, would
appear as a redshift-dependent opacity, thereby impacting the use of
gravitational wave standard sirens to constrain the expansion history of the
Universe. We investigate a particular model of cosmic gauge field dark energy
and show that at early times it behaves like dark radiation, whereas a novel
interaction causes it to drive cosmic acceleration at late times. Joint
constraints on the cosmological scenario due to type 1a supernovae, baryon
acoustic oscillations, and cosmic microwave background data are presented. In
view of these constraints, we show that standard siren luminosity distances in
the redshift range 0.5 < z < 1.5 would systematically dim by up to 1%, which
may be distinguishable by third-generation gravitational wave detectors.
|
[
{
"created": "Tue, 20 Feb 2018 23:11:58 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Mar 2018 18:10:09 GMT",
"version": "v2"
},
{
"created": "Mon, 16 Dec 2019 02:26:53 GMT",
"version": "v3"
}
] |
2019-12-17
|
[
[
"Caldwell",
"R. R.",
""
],
[
"Devulder",
"C.",
""
]
] |
We show that astrophysical gravitational waves can undergo an anomalous modulation when propagating through cosmic gauge field dark energy. A sufficiently strong effect, dependent on the gauge field energy density, would appear as a redshift-dependent opacity, thereby impacting the use of gravitational wave standard sirens to constrain the expansion history of the Universe. We investigate a particular model of cosmic gauge field dark energy and show that at early times it behaves like dark radiation, whereas a novel interaction causes it to drive cosmic acceleration at late times. Joint constraints on the cosmological scenario due to type 1a supernovae, baryon acoustic oscillations, and cosmic microwave background data are presented. In view of these constraints, we show that standard siren luminosity distances in the redshift range 0.5 < z < 1.5 would systematically dim by up to 1%, which may be distinguishable by third-generation gravitational wave detectors.
|
1602.02687
|
Kofinas Georgios
|
Georgios Kofinas, Eleftherios Papantonopoulos, Emmanuel N. Saridakis
|
Modified Brans-Dicke cosmology with matter-scalar field interaction
|
Minor changes
| null |
10.1088/0264-9381/33/15/155004
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We discuss the cosmological implications of an extended Brans-Dicke theory
presented recently, in which there is an energy exchange between the scalar
field and ordinary matter, determined by the theory. A new mass scale is
generated in the theory which modifies the Friedmann equations with
field-dependent corrected kinetic terms. In a radiation universe the general
solutions are found and there are branches with complete removal of the initial
singularity, while at the same time a transient accelerating period can occur
within deceleration. Entropy production is also possible in the early universe.
In the dust era, late-times acceleration has been found numerically in
agreement with the correct behaviour of the density parameters and the dark
energy equation of state, while the gravitational constant has only a slight
variation over a large redshift interval in agreement with observational
bounds.
|
[
{
"created": "Mon, 8 Feb 2016 18:36:43 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Mar 2016 10:27:53 GMT",
"version": "v2"
},
{
"created": "Fri, 17 Jun 2016 09:58:19 GMT",
"version": "v3"
},
{
"created": "Wed, 6 Jul 2016 20:43:03 GMT",
"version": "v4"
},
{
"created": "Tue, 29 Nov 2016 10:42:21 GMT",
"version": "v5"
}
] |
2016-11-30
|
[
[
"Kofinas",
"Georgios",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] |
We discuss the cosmological implications of an extended Brans-Dicke theory presented recently, in which there is an energy exchange between the scalar field and ordinary matter, determined by the theory. A new mass scale is generated in the theory which modifies the Friedmann equations with field-dependent corrected kinetic terms. In a radiation universe the general solutions are found and there are branches with complete removal of the initial singularity, while at the same time a transient accelerating period can occur within deceleration. Entropy production is also possible in the early universe. In the dust era, late-times acceleration has been found numerically in agreement with the correct behaviour of the density parameters and the dark energy equation of state, while the gravitational constant has only a slight variation over a large redshift interval in agreement with observational bounds.
|
2211.15151
|
Di Wu
|
Di Wu
|
Topological classes of rotating black holes
|
6 pages, 6 figures, 1 table, revtex4-1.cls, to appear in PRD
|
Phys. Rev. D 107, 024024 (2023)
|
10.1103/PhysRevD.107.024024
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we investigate the topological numbers for singly rotating
Kerr black holes in arbitrary dimensions and four-dimensional Kerr-Newman black
hole. We show that for uncharged black holes, the rotation parameter has a
significant effect on the topological number, and for rotating black holes, the
dimension of spacetime has a remarkable effect on the topological number too.
In addition, we find that the topological numbers of the four-dimensional Kerr
and Kerr-Newman black holes are the same, which seems to indicate that the
electric charge parameter has no effect on the topological number of rotating
black holes. Our current research provides more evidence that the conjecture
put forward in Wei et al. [Phys. Rev. Lett. 129, 191101 (2022)], according to
which all black hole solutions should be separated into three different
topological classes, is accurate, at least in the pure Einstein-Maxwell gravity
theory.
|
[
{
"created": "Mon, 28 Nov 2022 09:03:10 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Nov 2022 07:58:12 GMT",
"version": "v2"
},
{
"created": "Sat, 14 Jan 2023 03:15:48 GMT",
"version": "v3"
}
] |
2023-01-20
|
[
[
"Wu",
"Di",
""
]
] |
In this paper, we investigate the topological numbers for singly rotating Kerr black holes in arbitrary dimensions and four-dimensional Kerr-Newman black hole. We show that for uncharged black holes, the rotation parameter has a significant effect on the topological number, and for rotating black holes, the dimension of spacetime has a remarkable effect on the topological number too. In addition, we find that the topological numbers of the four-dimensional Kerr and Kerr-Newman black holes are the same, which seems to indicate that the electric charge parameter has no effect on the topological number of rotating black holes. Our current research provides more evidence that the conjecture put forward in Wei et al. [Phys. Rev. Lett. 129, 191101 (2022)], according to which all black hole solutions should be separated into three different topological classes, is accurate, at least in the pure Einstein-Maxwell gravity theory.
|
gr-qc/0003080
|
Martin Goliath
|
Alan Coley and Martin Goliath
|
Self-similar spherically symmetric cosmological models with a perfect
fluid and a scalar field
|
31 pages, 4 figures
|
Class.Quant.Grav.17:2557-2588,2000
|
10.1088/0264-9381/17/13/309
| null |
gr-qc
| null |
Self-similar, spherically symmetric cosmological models with a perfect fluid
and a scalar field with an exponential potential are investigated. New
variables are defined which lead to a compact state space, and dynamical
systems methods are utilised to analyse the models. Due to the existence of
monotone functions global dynamical results can be deduced. In particular, all
of the future and past attractors for these models are obtained and the global
results are discussed. The essential physical results are that initially
expanding models always evolve away from a massless scalar field model with an
initial singularity and, depending on the parameters of the models, either
recollapse to a second singularity or expand forever towards a flat power-law
inflationary model. The special cases in which there is no barotropic fluid and
in which the scalar field is massless are considered in more detail in order to
illustrate the asymptotic results. Some phase portraits are presented and the
intermediate dynamics and hence the physical properties of the models are
discussed.
|
[
{
"created": "Mon, 20 Mar 2000 09:22:55 GMT",
"version": "v1"
}
] |
2010-11-19
|
[
[
"Coley",
"Alan",
""
],
[
"Goliath",
"Martin",
""
]
] |
Self-similar, spherically symmetric cosmological models with a perfect fluid and a scalar field with an exponential potential are investigated. New variables are defined which lead to a compact state space, and dynamical systems methods are utilised to analyse the models. Due to the existence of monotone functions global dynamical results can be deduced. In particular, all of the future and past attractors for these models are obtained and the global results are discussed. The essential physical results are that initially expanding models always evolve away from a massless scalar field model with an initial singularity and, depending on the parameters of the models, either recollapse to a second singularity or expand forever towards a flat power-law inflationary model. The special cases in which there is no barotropic fluid and in which the scalar field is massless are considered in more detail in order to illustrate the asymptotic results. Some phase portraits are presented and the intermediate dynamics and hence the physical properties of the models are discussed.
|
2004.09384
|
Shintaro Nakamura
|
Antonio De Felice, Shintaro Nakamura, Shinji Tsujikawa
|
Suppressed cosmic growth in coupled vector-tensor theories
|
25 pages, 3 figures
|
Phys. Rev. D 102, 063531 (2020)
|
10.1103/PhysRevD.102.063531
|
YITP-20-56, WUCG-20-02
|
gr-qc astro-ph.CO hep-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study a coupled dark energy scenario in which a massive vector field
$A_{\mu}$ with broken $U(1)$ gauge symmetry interacts with the four-velocity
$u_c^{\mu}$ of cold dark matter (CDM) through the scalar product $Z=-u_c^{\mu}
A_{\mu}$. This new coupling corresponds to the momentum transfer, so that the
background vector and CDM continuity equations do not have explicit interacting
terms analogous to the energy exchange. Hence the observational preference of
uncoupled generalized Proca theories over the $\Lambda$CDM model can be still
maintained at the background level. Meanwhile, the same coupling strongly
affects the evolution of cosmological perturbations. While the effective sound
speed of CDM vanishes, the propagation speed and no-ghost condition of a
longitudinal scalar of $A_{\mu}$ and the CDM no-ghost condition are subject to
nontrivial modifications by the $Z$ dependence in the Lagrangian. We propose a
concrete dark energy model and show that the gravitational interaction on
scales relevant to the linear growth of large-scale structures can be smaller
than the Newton constant at low redshifts. This leads to the suppression of
growth rates of both CDM and total matter density perturbations, so our model
allows an interesting possibility for reducing the tension of matter density
contrast $\sigma_8$ between high- and low-redshift measurements.
|
[
{
"created": "Mon, 20 Apr 2020 15:35:26 GMT",
"version": "v1"
},
{
"created": "Sun, 27 Sep 2020 07:40:54 GMT",
"version": "v2"
}
] |
2020-09-29
|
[
[
"De Felice",
"Antonio",
""
],
[
"Nakamura",
"Shintaro",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] |
We study a coupled dark energy scenario in which a massive vector field $A_{\mu}$ with broken $U(1)$ gauge symmetry interacts with the four-velocity $u_c^{\mu}$ of cold dark matter (CDM) through the scalar product $Z=-u_c^{\mu} A_{\mu}$. This new coupling corresponds to the momentum transfer, so that the background vector and CDM continuity equations do not have explicit interacting terms analogous to the energy exchange. Hence the observational preference of uncoupled generalized Proca theories over the $\Lambda$CDM model can be still maintained at the background level. Meanwhile, the same coupling strongly affects the evolution of cosmological perturbations. While the effective sound speed of CDM vanishes, the propagation speed and no-ghost condition of a longitudinal scalar of $A_{\mu}$ and the CDM no-ghost condition are subject to nontrivial modifications by the $Z$ dependence in the Lagrangian. We propose a concrete dark energy model and show that the gravitational interaction on scales relevant to the linear growth of large-scale structures can be smaller than the Newton constant at low redshifts. This leads to the suppression of growth rates of both CDM and total matter density perturbations, so our model allows an interesting possibility for reducing the tension of matter density contrast $\sigma_8$ between high- and low-redshift measurements.
|
2209.02330
|
Davide Batic
|
Davide Batic, Joud Mojahed Faraji, Marek Nowakowski
|
Possible Connection between Dark Matter and Supermassive Black Holes
|
23 pages, 19 figures, 13 tables
|
The European Physical Journal C volume 82, Article number: 759
(2022)
|
10.1140/epjc/s10052-022-10731-0
| null |
gr-qc
|
http://creativecommons.org/licenses/by-nc-sa/4.0/
|
Dark Matter (DM) is usually studied in connection with rotational curves in
the outskirts of the galaxies. However, the role of DM might be different in
the galactic bulges and centers where Supermassive Black Holes (SMBHs) dominate
the gravitational interaction. Indeed, given the fact that DM is the dominant
matter species in the Universe, it is natural to assume a close connection
between DM and SMBHs. Here we probe into this possibility by constructing
stable objects with fuzzy mass distributions based on standard DM profiles.
These astrophysical objects come out in three types: a fuzzy droplet without
horizon and fuzzy Black Holes (BHs) with one or two horizons. We emphasize that
all objects are solutions of Einstein equations. Their effective potentials
which govern the motion of a test body, can display a reasonable similarity to
the effective potential of a Schwarzschild BH at the galactic center.
Therefore, some of our solutions could, in principle, replace the standard
BH-picture of the galactic center and, at the same time, have the advantage
that they have been composed of the main matter ingredient of the Universe.
|
[
{
"created": "Tue, 6 Sep 2022 09:39:15 GMT",
"version": "v1"
}
] |
2022-09-07
|
[
[
"Batic",
"Davide",
""
],
[
"Faraji",
"Joud Mojahed",
""
],
[
"Nowakowski",
"Marek",
""
]
] |
Dark Matter (DM) is usually studied in connection with rotational curves in the outskirts of the galaxies. However, the role of DM might be different in the galactic bulges and centers where Supermassive Black Holes (SMBHs) dominate the gravitational interaction. Indeed, given the fact that DM is the dominant matter species in the Universe, it is natural to assume a close connection between DM and SMBHs. Here we probe into this possibility by constructing stable objects with fuzzy mass distributions based on standard DM profiles. These astrophysical objects come out in three types: a fuzzy droplet without horizon and fuzzy Black Holes (BHs) with one or two horizons. We emphasize that all objects are solutions of Einstein equations. Their effective potentials which govern the motion of a test body, can display a reasonable similarity to the effective potential of a Schwarzschild BH at the galactic center. Therefore, some of our solutions could, in principle, replace the standard BH-picture of the galactic center and, at the same time, have the advantage that they have been composed of the main matter ingredient of the Universe.
|
0908.2895
|
Haryanto Siahaan
|
Haryanto M. Siahaan and Triyanta
|
Semiclassical Methods for Hawking Radiation from a Vaidya Black Hole
|
REVTeX 4, 11 pages, no figures, accepted for publication in IJMPA;
v2: eq.5 is corrected
|
Int.J.Mod.Phys.A25:145-153,2010
|
10.1142/S0217751X1004749X
| null |
gr-qc hep-th
|
http://creativecommons.org/licenses/by/3.0/
|
We derive the general form of Hawking temperature for Vaidya black hole in
the tunneling pictures. This kind of black hole is regarded as the description
of a more realistic one since it's time dependent decreasing mass due to the
evaporation process. Clearly, the temperature would be time dependent as our
findings. We use the semiclassical methods, namely radial null geodesic and
complex paths methods. Both methods are found to give the same results. Then,
we discuss the possible form of corresponding entropy.
|
[
{
"created": "Thu, 20 Aug 2009 10:10:21 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Jun 2011 15:36:45 GMT",
"version": "v2"
}
] |
2011-06-27
|
[
[
"Siahaan",
"Haryanto M.",
""
],
[
"Triyanta",
"",
""
]
] |
We derive the general form of Hawking temperature for Vaidya black hole in the tunneling pictures. This kind of black hole is regarded as the description of a more realistic one since it's time dependent decreasing mass due to the evaporation process. Clearly, the temperature would be time dependent as our findings. We use the semiclassical methods, namely radial null geodesic and complex paths methods. Both methods are found to give the same results. Then, we discuss the possible form of corresponding entropy.
|
1807.11779
|
James Read
|
James Read and Nicholas Teh
|
The Teleparallel Equivalent of Newton-Cartan Gravity
|
7 pages, forthcoming in Classical and Quantum Gravity (letters)
| null |
10.1088/1361-6382/aad70d
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We construct a notion of teleparallelization for Newton-Cartan theory, and
show that the teleparallel equivalent of this theory is Newtonian gravity;
furthermore, we show that this result is consistent with teleparallelization in
general relativity, and can be obtained by null-reducing the teleparallel
equivalent of a five-dimensional gravitational wave solution. This work thus
strengthens substantially the connections between four theories: Newton-Cartan
theory, Newtonian gravitation theory, general relativity, and teleparallel
gravity.
|
[
{
"created": "Tue, 31 Jul 2018 12:05:01 GMT",
"version": "v1"
}
] |
2018-08-29
|
[
[
"Read",
"James",
""
],
[
"Teh",
"Nicholas",
""
]
] |
We construct a notion of teleparallelization for Newton-Cartan theory, and show that the teleparallel equivalent of this theory is Newtonian gravity; furthermore, we show that this result is consistent with teleparallelization in general relativity, and can be obtained by null-reducing the teleparallel equivalent of a five-dimensional gravitational wave solution. This work thus strengthens substantially the connections between four theories: Newton-Cartan theory, Newtonian gravitation theory, general relativity, and teleparallel gravity.
|
1111.2177
|
Zhoujian Cao Dr
|
Zhoujian Cao, David Hilditch
|
Numerical stability of the Z4c formulation of general relativity
|
submitted to PRD
|
Phys. Rev. D 85, 124032 (2012)
|
10.1103/PhysRevD.85.124032
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study numerical stability of different approaches to the discretization of
a conformal decomposition of the Z4 formulation of general relativity. We
demonstrate that in the linear, constant coefficient regime a novel
discretization for tensors is formally numerically stable with a method of
lines time-integrator. We then perform a full set of apples with apples tests
on the non-linear system, and thus present numerical evidence that both the new
and standard discretizations are, in some sense, numerically stable in the
non-linear regime. The results of the Z4c numerical tests are compared with
those of BSSNOK evolutions. We typically do not employ the Z4c constraint
damping scheme and find that in the robust stability and gauge wave tests the
Z4c evolutions result in lower constraint violation at the same resolution as
the BSSNOK evolutions. In the gauge wave tests we find that the Z4c evolutions
maintain the desired convergence factor over many more light-crossing times
than the BSSNOK tests. The difference in the remaining tests is marginal.
|
[
{
"created": "Wed, 9 Nov 2011 11:33:57 GMT",
"version": "v1"
}
] |
2013-01-08
|
[
[
"Cao",
"Zhoujian",
""
],
[
"Hilditch",
"David",
""
]
] |
We study numerical stability of different approaches to the discretization of a conformal decomposition of the Z4 formulation of general relativity. We demonstrate that in the linear, constant coefficient regime a novel discretization for tensors is formally numerically stable with a method of lines time-integrator. We then perform a full set of apples with apples tests on the non-linear system, and thus present numerical evidence that both the new and standard discretizations are, in some sense, numerically stable in the non-linear regime. The results of the Z4c numerical tests are compared with those of BSSNOK evolutions. We typically do not employ the Z4c constraint damping scheme and find that in the robust stability and gauge wave tests the Z4c evolutions result in lower constraint violation at the same resolution as the BSSNOK evolutions. In the gauge wave tests we find that the Z4c evolutions maintain the desired convergence factor over many more light-crossing times than the BSSNOK tests. The difference in the remaining tests is marginal.
|
gr-qc/0111083
|
Guest User
|
G. S. Khadekar and Shilpa Samdurkar (Nagpur University, Nagpur, India)
|
Multidimensional Homogeneous Cosmological Models in Wesson Theory of
Gravitation
|
latex 4 pages, no figure
| null | null | null |
gr-qc
| null |
Higher dimensional solutions are obtained for a homogeneous, spatially
isotropic cosmological model in Wesson theory of gravitation. Some cosmological
parameter are also calculated for this model.
|
[
{
"created": "Sun, 25 Nov 2001 18:35:57 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Nov 2001 18:03:34 GMT",
"version": "v2"
}
] |
2007-05-23
|
[
[
"Khadekar",
"G. S.",
"",
"Nagpur University, Nagpur, India"
],
[
"Samdurkar",
"Shilpa",
"",
"Nagpur University, Nagpur, India"
]
] |
Higher dimensional solutions are obtained for a homogeneous, spatially isotropic cosmological model in Wesson theory of gravitation. Some cosmological parameter are also calculated for this model.
|
2308.00111
|
Marcell Howard
|
Tatsuya Daniel, Marcell Howard, and Morgane K\"onig
|
An SZ-Like Effect on Cosmological Gravitational Wave Backgrounds
|
29 pages, 3 figures, Submitted to JCAP; Updated draft commensurate
with published version: 30 pages, 3 figures
|
JCAP12(2023)041
|
10.1088/1475-7516/2023/12/041
| null |
gr-qc astro-ph.CO hep-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Cosmological gravitational wave backgrounds (CGWBs) are the conglomeration of
unresolved gravitational wave signals from early Universe sources, which make
them a promising tool for cosmologists. Because gravitons decouple from the
cosmic plasma early on, one can consider interactions between gravitons and any
particle species that were present in the very early Universe. We show that
analogous to the cosmic microwave background, elastic scattering on any
cosmological background will induce small distortions in its energy density
spectrum. We then quantify the magnitude of these spin-dependent spectral
distortions when attributed to the dark matter in the early Universe. Lastly,
we give estimates for potentially measurable distortions on CGWBs due to
gravitational scattering by primordial black holes.
|
[
{
"created": "Mon, 31 Jul 2023 19:30:53 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Dec 2023 04:07:27 GMT",
"version": "v2"
}
] |
2023-12-27
|
[
[
"Daniel",
"Tatsuya",
""
],
[
"Howard",
"Marcell",
""
],
[
"König",
"Morgane",
""
]
] |
Cosmological gravitational wave backgrounds (CGWBs) are the conglomeration of unresolved gravitational wave signals from early Universe sources, which make them a promising tool for cosmologists. Because gravitons decouple from the cosmic plasma early on, one can consider interactions between gravitons and any particle species that were present in the very early Universe. We show that analogous to the cosmic microwave background, elastic scattering on any cosmological background will induce small distortions in its energy density spectrum. We then quantify the magnitude of these spin-dependent spectral distortions when attributed to the dark matter in the early Universe. Lastly, we give estimates for potentially measurable distortions on CGWBs due to gravitational scattering by primordial black holes.
|
gr-qc/9611044
|
Max Banados
|
Maximo Banados and Andres Gomberoff
|
Black Hole Entropy in the Chern-Simons Formulation of 2+1 Gravity
|
6 pages, RevTeX, minor changes. Old title "Some remarks on Carlip's
derivation of the 2+1 black hole entropy". Version to appear in Phys. Rev. D
|
Phys.Rev.D55:6162-6167,1997
|
10.1103/PhysRevD.55.6162
| null |
gr-qc hep-th
| null |
We examine Carlip's derivation of the 2+1 Minkowskian black hole entropy. A
simplified derivation of the boundary action -valid for any value of the level
k- is given.
|
[
{
"created": "Thu, 14 Nov 1996 21:32:08 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Jan 1997 19:04:09 GMT",
"version": "v2"
}
] |
2011-09-09
|
[
[
"Banados",
"Maximo",
""
],
[
"Gomberoff",
"Andres",
""
]
] |
We examine Carlip's derivation of the 2+1 Minkowskian black hole entropy. A simplified derivation of the boundary action -valid for any value of the level k- is given.
|
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