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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1708.04665 | Daniela P\'erez | Gustavo E. Romero | Bunge on gravitational waves | 6 pages, accepted for publication in Foundations of Science | null | null | null | gr-qc physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I discuss the recent claims made by Mario Bunge on the philosophical
implications of the discovery of gravitational waves. I think that Bunge is
right when he points out that the detection implies the materiality of
spacetime, but I reject his identification of spacetime with the gravitational
field. I show that Bunge's analysis of the spacetime inside a hollow sphere is
defective, but this in no way affects his main claim.
| [
{
"created": "Tue, 15 Aug 2017 20:11:57 GMT",
"version": "v1"
}
] | 2017-08-17 | [
[
"Romero",
"Gustavo E.",
""
]
] | I discuss the recent claims made by Mario Bunge on the philosophical implications of the discovery of gravitational waves. I think that Bunge is right when he points out that the detection implies the materiality of spacetime, but I reject his identification of spacetime with the gravitational field. I show that Bunge's analysis of the spacetime inside a hollow sphere is defective, but this in no way affects his main claim. |
gr-qc/0108005 | Geoffery Ericksson | Geoffery Ericksson and Susan M. Scott | Isotropic singularities in shear-free perfect fluid cosmologies | 21 pages, 1 figure | Gen.Rel.Grav. 32 (2000) 425-443 | 10.1023/A:1001968015342 | null | gr-qc | null | We investigate barotropic perfect fluid cosmologies which admit an isotropic
singularity. From the General Vorticity Result of Scott, it is known that these
cosmologies must be irrotational. In this paper we prove, using two different
methods, that if we make the additional assumption that the perfect fluid is
shear-free, then the fluid flow must be geodesic. This then implies that the
only shear-free, barotropic, perfect fluid cosmologies which admit an isotropic
singularity are the FRW models.
| [
{
"created": "Thu, 2 Aug 2001 07:53:26 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Ericksson",
"Geoffery",
""
],
[
"Scott",
"Susan M.",
""
]
] | We investigate barotropic perfect fluid cosmologies which admit an isotropic singularity. From the General Vorticity Result of Scott, it is known that these cosmologies must be irrotational. In this paper we prove, using two different methods, that if we make the additional assumption that the perfect fluid is shear-free, then the fluid flow must be geodesic. This then implies that the only shear-free, barotropic, perfect fluid cosmologies which admit an isotropic singularity are the FRW models. |
2308.01575 | Rui-Hui Lin | Rui-Hui Lin, Rui Jiang and Xiang-Hua Zhai | Quasinormal modes of the spherical bumblebee black holes with a global
monopole | accepted by Eur. Phys. J. C | null | 10.1140/epjc/s10052-023-11899-9 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The bumblebee model is an extension of the Einstein-Maxwell theory that
allows for the spontaneous breaking of the Lorentz symmetry of the spacetime.
In this paper, we study the quasinormal modes of the spherical black holes in
this model that are characterized by a global monopole. We analyze the two
cases with a vanishing cosmological constant or a negative one (the anti-de
Sitter case). We find that the black holes are stable under the perturbation of
a massless scalar field. However, both the Lorentz symmetry breaking and the
global monopole have notable impacts on the evolution of the perturbation. The
Lorentz symmetry breaking may prolong or shorten the decay of the perturbation
according to the sign of the breaking parameter. The global monopole, on the
other hand, has different effects depending on whether a nonzero cosmological
constant presences: it reduces the damping of the perturbations for the case
with a vanishing cosmological constant, but has little influence for the
anti-de Sitter case.
| [
{
"created": "Thu, 3 Aug 2023 07:22:31 GMT",
"version": "v1"
}
] | 2023-12-19 | [
[
"Lin",
"Rui-Hui",
""
],
[
"Jiang",
"Rui",
""
],
[
"Zhai",
"Xiang-Hua",
""
]
] | The bumblebee model is an extension of the Einstein-Maxwell theory that allows for the spontaneous breaking of the Lorentz symmetry of the spacetime. In this paper, we study the quasinormal modes of the spherical black holes in this model that are characterized by a global monopole. We analyze the two cases with a vanishing cosmological constant or a negative one (the anti-de Sitter case). We find that the black holes are stable under the perturbation of a massless scalar field. However, both the Lorentz symmetry breaking and the global monopole have notable impacts on the evolution of the perturbation. The Lorentz symmetry breaking may prolong or shorten the decay of the perturbation according to the sign of the breaking parameter. The global monopole, on the other hand, has different effects depending on whether a nonzero cosmological constant presences: it reduces the damping of the perturbations for the case with a vanishing cosmological constant, but has little influence for the anti-de Sitter case. |
gr-qc/0205080 | Cuauhtemoc Campuzano Vargas | Alberto A. Garcia and Cuauhtemoc Campuzano | On Conformally Flat Stationary Axisymmetric Spacetimes | RevTex4, 5 pages | Phys.Rev.D66:124018,2002; Erratum-ibid.D68:049901,2003 | 10.1103/PhysRevD.66.124018 10.1103/PhysRevD.68.049901 | null | gr-qc | null | It is shown that within conformally flat stationary axisymmetric spacetimes,
besides of the static family, there exists a new class of metrics, which is
always stationary and axisymmetric. All these spacetimes, the static and the
stationary ones, are endowed with an arbitrary function depending on the two
non--Killingian coordinates. The explicit form of this function can be
determined once the coupled matter, i.e., the energy--momentum tensor is given.
One might hope possible extensions of this result to black holes on two--branes
in four dimensions.
| [
{
"created": "Fri, 17 May 2002 23:31:41 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Garcia",
"Alberto A.",
""
],
[
"Campuzano",
"Cuauhtemoc",
""
]
] | It is shown that within conformally flat stationary axisymmetric spacetimes, besides of the static family, there exists a new class of metrics, which is always stationary and axisymmetric. All these spacetimes, the static and the stationary ones, are endowed with an arbitrary function depending on the two non--Killingian coordinates. The explicit form of this function can be determined once the coupled matter, i.e., the energy--momentum tensor is given. One might hope possible extensions of this result to black holes on two--branes in four dimensions. |
1207.2442 | Eric G. Adelberger | T. A. Wagner, S. Schlamminger, J. H. Gundlach and E. G. Adelberger | Torsion-balance tests of the weak equivalence principle | 17 pages, 9 figures (in press Classical Quantum Gravity 2012) | null | 10.1088/0264-9381/29/18/184002 | null | gr-qc hep-ex | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We briefly summarize motivations for testing the weak equivalence principle
and then review recent torsion-balance results that compare the differential
accelerations of beryllium-aluminum and beryllium-titanium test body pairs with
precisions at the part in $10^{13}$ level. We discuss some implications of
these results for the gravitational properties of antimatter and dark matter,
and speculate about the prospects for further improvements in experimental
sensitivity.
| [
{
"created": "Tue, 10 Jul 2012 18:51:17 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Wagner",
"T. A.",
""
],
[
"Schlamminger",
"S.",
""
],
[
"Gundlach",
"J. H.",
""
],
[
"Adelberger",
"E. G.",
""
]
] | We briefly summarize motivations for testing the weak equivalence principle and then review recent torsion-balance results that compare the differential accelerations of beryllium-aluminum and beryllium-titanium test body pairs with precisions at the part in $10^{13}$ level. We discuss some implications of these results for the gravitational properties of antimatter and dark matter, and speculate about the prospects for further improvements in experimental sensitivity. |
2012.01073 | Francois Larrouturou | Antonio De Felice, Fran\c{c}ois Larrouturou, Shinji Mukohyama, Michele
Oliosi | Minimal Theory of Bigravity: construction and cosmology | 23 pages | JCAP04(2021)015 | 10.1088/1475-7516/2021/04/015 | YITP-20-157, IPMU20-0126 | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | Following the path of minimalism in alternative theories of gravity, we
construct the "Minimal Theory of Bigravity" (MTBG), a theory of two interacting
spin-2 fields that propagates only four local degrees of freedom instead of the
usual seven ones and that allows for the same homogeneous and isotropic
cosmological solutions as in Hassan-Rosen bigravity (HRBG). Starting from a
precursor theory that propagates six local degrees of freedom, we carefully
choose additional constraints to eliminate two of them to construct the theory.
Investigating the cosmology of MTBG, we find that it accommodates two different
branches of homogeneous and isotropic background solutions, equivalent on-shell
to the two branches that are present in HRBG. Those branches in MTBG differ
however from the HRBG ones at the perturbative level, are both perfectly
healthy and do not exhibit strong coupling issues nor ghost instabilities. In
the so-called self-accelerating branch, characterized by the presence of an
effective cosmological constant, the scalar and vector sectors are the same as
in General Relativity (GR). In the so-called normal branch, the scalar sector
exhibits non-trivial phenomenology, while its vector sector remains the same as
in GR. In both branches, the tensor sector exhibits the usual HRBG features: an
effective mass term and oscillations of the gravitons. Therefore MTBG provides
a stable nonlinear completion of the cosmology in HRBG.
| [
{
"created": "Wed, 2 Dec 2020 10:39:32 GMT",
"version": "v1"
}
] | 2021-05-26 | [
[
"De Felice",
"Antonio",
""
],
[
"Larrouturou",
"François",
""
],
[
"Mukohyama",
"Shinji",
""
],
[
"Oliosi",
"Michele",
""
]
] | Following the path of minimalism in alternative theories of gravity, we construct the "Minimal Theory of Bigravity" (MTBG), a theory of two interacting spin-2 fields that propagates only four local degrees of freedom instead of the usual seven ones and that allows for the same homogeneous and isotropic cosmological solutions as in Hassan-Rosen bigravity (HRBG). Starting from a precursor theory that propagates six local degrees of freedom, we carefully choose additional constraints to eliminate two of them to construct the theory. Investigating the cosmology of MTBG, we find that it accommodates two different branches of homogeneous and isotropic background solutions, equivalent on-shell to the two branches that are present in HRBG. Those branches in MTBG differ however from the HRBG ones at the perturbative level, are both perfectly healthy and do not exhibit strong coupling issues nor ghost instabilities. In the so-called self-accelerating branch, characterized by the presence of an effective cosmological constant, the scalar and vector sectors are the same as in General Relativity (GR). In the so-called normal branch, the scalar sector exhibits non-trivial phenomenology, while its vector sector remains the same as in GR. In both branches, the tensor sector exhibits the usual HRBG features: an effective mass term and oscillations of the gravitons. Therefore MTBG provides a stable nonlinear completion of the cosmology in HRBG. |
1909.09173 | Giacomo Rosati | Salvatore Mignemi, Giacomo Rosati | Physical velocity of particles in relativistic curved momentum space | null | null | 10.1142/S0217732320501801 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show in general that for a relativistic theory with curved momentum space,
i.e.~a theory with deformed relativistic symmetries, the physical velocity of
particles coincides with their group velocity. This clarifies a long-standing
question about the discrepancy between coordinate and group velocity for this
kind of theories. The first evidence that this was the case had been obtained
at linear order in the deformation parameter in Phys.Lett.B700(2011)150 for the
specific case of $\kappa$-momentum space. The proof was based on the recent
understanding of how relative locality affects these scenarios. We here rely
again on a careful implementation of relative locality effects, and obtain our
result for a generic (relativistic) curved momentum space framework at all
orders in the deformation/curvature parameter. We also discuss the validity of
this result when the deformation depends on the coordinates as well as on the
momenta.
| [
{
"created": "Thu, 19 Sep 2019 18:01:43 GMT",
"version": "v1"
}
] | 2020-08-26 | [
[
"Mignemi",
"Salvatore",
""
],
[
"Rosati",
"Giacomo",
""
]
] | We show in general that for a relativistic theory with curved momentum space, i.e.~a theory with deformed relativistic symmetries, the physical velocity of particles coincides with their group velocity. This clarifies a long-standing question about the discrepancy between coordinate and group velocity for this kind of theories. The first evidence that this was the case had been obtained at linear order in the deformation parameter in Phys.Lett.B700(2011)150 for the specific case of $\kappa$-momentum space. The proof was based on the recent understanding of how relative locality affects these scenarios. We here rely again on a careful implementation of relative locality effects, and obtain our result for a generic (relativistic) curved momentum space framework at all orders in the deformation/curvature parameter. We also discuss the validity of this result when the deformation depends on the coordinates as well as on the momenta. |
2001.09003 | Alexander Lukyanenko | Natalia Gorobey and Alexander Lukyanenko | Time and Observables in Covariant Quantum Theory | 6 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A modification of the covariant theory is proposed in which the self-energy
of the system, corresponding to time-like degrees of freedom in the
configuration space, preserves the classical law of change in quantum theory.
As a result, proper time in covariant quantum theory takes on a dynamic
meaning. As applications of the new formalism, a modification of the
relativistic quantum mechanics of a scalar particle and a homogeneous model of
the universe is considered.
| [
{
"created": "Wed, 22 Jan 2020 16:35:12 GMT",
"version": "v1"
}
] | 2020-01-27 | [
[
"Gorobey",
"Natalia",
""
],
[
"Lukyanenko",
"Alexander",
""
]
] | A modification of the covariant theory is proposed in which the self-energy of the system, corresponding to time-like degrees of freedom in the configuration space, preserves the classical law of change in quantum theory. As a result, proper time in covariant quantum theory takes on a dynamic meaning. As applications of the new formalism, a modification of the relativistic quantum mechanics of a scalar particle and a homogeneous model of the universe is considered. |
gr-qc/0610117 | Yanbei Chen | Kentaro Somiya, Keisuke Goda, Yanbei Chen and Eugeniy E. Mikhailov | Isolation of gravitational waves from displacement noise and utility of
a time-delay device | 10 pages, 12 figures, a proceeding for the Spanish Relativity Meeting
ERE 2006 | J.Phys.Conf.Ser.66:012053,2007 | 10.1088/1742-6596/66/1/012053 | null | gr-qc | null | Interferometers with kilometer-scale arms have been built for
gravitational-wave detections on the ground; ones with much longer arms are
being planned for space-based detection. One fundamental motivation for long
baseline interferometry is from displacement noise. In general, the longer the
arm length L, the larger the motion the gravitational-wave induces on the test
masses, until L becomes comparable to the gravitational wavelength. Recently,
schemes have been invented, in which displacement noises can be evaded by
employing differences between the influence of test-mass motions and that of
gravitational waves on light propagation. However, in these schemes, such
differences only becomes significant when L approaches the gravitational
wavelength, and shot-noise limited sensitivity becomes worse than that of
conventional configurations by a factor of at least (f L/c)^(-2), for f<c/L.
Such a factor, although can be overcome theoretically by employing high optical
powers, makes these schemes quite impractical. In this paper, we explore the
use of time delay in displacement-noise-free interferometers, which can improve
their shot-noise-limited sensitivity at low frequencies, to a factor of (f
L/c)^(-1) of the shot-noise-limited sensitivity of conventional configurations.
| [
{
"created": "Wed, 25 Oct 2006 16:12:35 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jan 2007 12:27:44 GMT",
"version": "v2"
}
] | 2020-07-06 | [
[
"Somiya",
"Kentaro",
""
],
[
"Goda",
"Keisuke",
""
],
[
"Chen",
"Yanbei",
""
],
[
"Mikhailov",
"Eugeniy E.",
""
]
] | Interferometers with kilometer-scale arms have been built for gravitational-wave detections on the ground; ones with much longer arms are being planned for space-based detection. One fundamental motivation for long baseline interferometry is from displacement noise. In general, the longer the arm length L, the larger the motion the gravitational-wave induces on the test masses, until L becomes comparable to the gravitational wavelength. Recently, schemes have been invented, in which displacement noises can be evaded by employing differences between the influence of test-mass motions and that of gravitational waves on light propagation. However, in these schemes, such differences only becomes significant when L approaches the gravitational wavelength, and shot-noise limited sensitivity becomes worse than that of conventional configurations by a factor of at least (f L/c)^(-2), for f<c/L. Such a factor, although can be overcome theoretically by employing high optical powers, makes these schemes quite impractical. In this paper, we explore the use of time delay in displacement-noise-free interferometers, which can improve their shot-noise-limited sensitivity at low frequencies, to a factor of (f L/c)^(-1) of the shot-noise-limited sensitivity of conventional configurations. |
1806.06539 | Alfredo Lopez Ortega | D. V. Gomez-Navarro, A. Lopez-Ortega | Electromagnetic quasinormal modes of five-dimensional topological black
holes | 16 pages. Already published in Revista Mexicana de Fisica | Revista Mexicana de Fisica 63 (2017) 541-548 | null | https://rmf.smf.mx/ojs/index.php/rmf/article/view/378/223 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate exactly the QNF of the vector type and scalar type
electromagnetic fields propagating on a family of five-dimensional topological
black holes. To get a discrete spectrum of quasinormal frequencies for the
scalar type electromagnetic field we find that it is necessary to change the
boundary condition usually imposed at the asymptotic region. Furthermore for
the vector type electromagnetic field we impose the usual boundary condition at
the asymptotic region and we discuss the existence of unstable quasinormal
modes in the five-dimensional topological black holes.
| [
{
"created": "Mon, 18 Jun 2018 07:59:57 GMT",
"version": "v1"
}
] | 2023-06-06 | [
[
"Gomez-Navarro",
"D. V.",
""
],
[
"Lopez-Ortega",
"A.",
""
]
] | We calculate exactly the QNF of the vector type and scalar type electromagnetic fields propagating on a family of five-dimensional topological black holes. To get a discrete spectrum of quasinormal frequencies for the scalar type electromagnetic field we find that it is necessary to change the boundary condition usually imposed at the asymptotic region. Furthermore for the vector type electromagnetic field we impose the usual boundary condition at the asymptotic region and we discuss the existence of unstable quasinormal modes in the five-dimensional topological black holes. |
0710.5135 | Michael Martin Nieto | Michael Martin Nieto | New Horizons and the Onset of the Pioneer Anomaly | 7 pages 2 figures Revision includes final corrections for publication | Phys.Lett.B659:483-485,2008 | 10.1016/j.physletb.2007.11.067 | LA-UR-07-7264 | gr-qc | null | Analysis of the radio tracking data from the Pioneer 10/11 spacecraft at
distances between about 20 - 70 AU from the Sun has indicated the presence of
an unmodeled, small, constant, Doppler blue shift which can be interpreted as a
constant acceleration of a_P= (8.74 \pm 1.33) \times 10^{-8} cm/s^2 directed
approximately towards the Sun. In addition, there is early (roughly modeled)
data from as close in as 5 AU which indicates there may have been an onset of
the anomaly near Saturn. We observe that the data now arriving from the New
Horizons mission to Pluto and the Kuiper Belt could allow a relatively easy,
direct experimental test of whether this onset is associated with distance from
the Sun (being, for example, an effect of drag on dark matter). We strongly
urge that this test be done.
| [
{
"created": "Fri, 26 Oct 2007 16:23:15 GMT",
"version": "v1"
},
{
"created": "Sat, 5 Jan 2008 19:11:34 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Nieto",
"Michael Martin",
""
]
] | Analysis of the radio tracking data from the Pioneer 10/11 spacecraft at distances between about 20 - 70 AU from the Sun has indicated the presence of an unmodeled, small, constant, Doppler blue shift which can be interpreted as a constant acceleration of a_P= (8.74 \pm 1.33) \times 10^{-8} cm/s^2 directed approximately towards the Sun. In addition, there is early (roughly modeled) data from as close in as 5 AU which indicates there may have been an onset of the anomaly near Saturn. We observe that the data now arriving from the New Horizons mission to Pluto and the Kuiper Belt could allow a relatively easy, direct experimental test of whether this onset is associated with distance from the Sun (being, for example, an effect of drag on dark matter). We strongly urge that this test be done. |
1003.5836 | Pac\^ome Delva Dr. | P. Delva, U. Kostic and A. Cadez | Numerical modeling of a Global Navigation Satellite System in a general
relativistic framework | 17 pages, 11 figures | null | 10.1016/j.asr.2010.07.007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we model a Global Navigation Satellite System (GNSS) in a
Schwarzschild space-time, as a first approximation of the relativistic geometry
around the Earth. The closed time-like and scattering light-like geodesics are
obtained analytically, describing respectively trajectories of satellites and
electromagnetic signals. We implement an algorithm to calculate Schwarzschild
coordinates of a GNSS user who receives proper times sent by four satellites,
knowing their orbital parameters; the inverse procedure is implemented to check
for consistency. The constellation of satellites therefore realizes a
geocentric inertial reference system with no \emph{a priori} realization of a
terrestrial reference frame. We show that the calculation is very fast and
could be implemented in a real GNSS, as an alternative to usual post-Newtonian
corrections. Effects of non-gravitational perturbations on positioning errors
are assessed, and methods to reduce them are sketched. In particular,
inter-links between satellites could greatly enhance stability and accuracy of
the positioning system.
| [
{
"created": "Tue, 30 Mar 2010 15:04:06 GMT",
"version": "v1"
}
] | 2015-05-18 | [
[
"Delva",
"P.",
""
],
[
"Kostic",
"U.",
""
],
[
"Cadez",
"A.",
""
]
] | In this article we model a Global Navigation Satellite System (GNSS) in a Schwarzschild space-time, as a first approximation of the relativistic geometry around the Earth. The closed time-like and scattering light-like geodesics are obtained analytically, describing respectively trajectories of satellites and electromagnetic signals. We implement an algorithm to calculate Schwarzschild coordinates of a GNSS user who receives proper times sent by four satellites, knowing their orbital parameters; the inverse procedure is implemented to check for consistency. The constellation of satellites therefore realizes a geocentric inertial reference system with no \emph{a priori} realization of a terrestrial reference frame. We show that the calculation is very fast and could be implemented in a real GNSS, as an alternative to usual post-Newtonian corrections. Effects of non-gravitational perturbations on positioning errors are assessed, and methods to reduce them are sketched. In particular, inter-links between satellites could greatly enhance stability and accuracy of the positioning system. |
1004.3654 | Bijan Saha | Yu.P. Rybakov, G.N. Shikin, Yu.A. Popov and Bijan Saha | Electromagnetic field with induced massive term: Case with scalar field | 8 Pages | Central European Journal of Physics, 9(5), (2011) 1165 - 1172 | 10.2478/s11534-011-0033-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider an interacting system of massless scalar and electromagnetic
field, with the Lagrangian explicitly depending on the electromagnetic
potentials, i.e., interaction with broken gauge invariance. The Lagrangian for
interaction is chosen in such a way that the electromagnetic field equation
acquires an additional term, which in some cases is proportional to the vector
potential of the electromagnetic field. This equation can be interpreted as the
equation of motion of photon with induced nonzero rest-mass. This system of
interacting fields is considered within the scope of Bianchi type-I (BI)
cosmological model. It is shown that, as a result of interaction the
electromagnetic field vanishes at $t \to \infty$ and the isotropization process
of the expansion takes place.
| [
{
"created": "Wed, 21 Apr 2010 09:06:40 GMT",
"version": "v1"
}
] | 2015-05-01 | [
[
"Rybakov",
"Yu. P.",
""
],
[
"Shikin",
"G. N.",
""
],
[
"Popov",
"Yu. A.",
""
],
[
"Saha",
"Bijan",
""
]
] | We consider an interacting system of massless scalar and electromagnetic field, with the Lagrangian explicitly depending on the electromagnetic potentials, i.e., interaction with broken gauge invariance. The Lagrangian for interaction is chosen in such a way that the electromagnetic field equation acquires an additional term, which in some cases is proportional to the vector potential of the electromagnetic field. This equation can be interpreted as the equation of motion of photon with induced nonzero rest-mass. This system of interacting fields is considered within the scope of Bianchi type-I (BI) cosmological model. It is shown that, as a result of interaction the electromagnetic field vanishes at $t \to \infty$ and the isotropization process of the expansion takes place. |
1512.03462 | Giulia Gubitosi | Leonardo Barcaroli and Giulia Gubitosi | Kinematics of particles with quantum de Sitter symmetries | null | Phys. Rev. D 93, 124063 (2016) | 10.1103/PhysRevD.93.124063 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first detailed study of the kinematics of free relativistic
particles whose symmetries are described by a quantum deformation of the de
Sitter algebra, known as $q$-de Sitter Hopf algebra. The quantum deformation
parameter is a function of the Planck length $\ell$ and the de Sitter radius
$H^{-1}$, such that when the Planck length vanishes, the algebra reduces to the
de Sitter algebra, while when the de Sitter radius is sent to infinity one
recovers the $\kappa$-Poincar\'e Hopf algebra. In the first limit the picture
is that of a particle with trivial momentum space geometry moving on de Sitter
spacetime, in the second one the picture is that of a particle with de Sitter
momentum space geometry moving on Minkowski spacetime. When both the Planck
length and the inverse of the de Sitter radius are non-zero, effects due to
spacetime curvature and non-trivial momentum space geometry are both present
and affect each other. The particles' motion is then described in a full phase
space picture. We find that redshift effects that are usually associated to
spacetime curvature become energy-dependent. Also, the energy dependence of
particles' travel times that is usually associated to momentum space
non-trivial properties is modified in a curvature-dependent way.
| [
{
"created": "Thu, 10 Dec 2015 22:01:56 GMT",
"version": "v1"
}
] | 2016-06-29 | [
[
"Barcaroli",
"Leonardo",
""
],
[
"Gubitosi",
"Giulia",
""
]
] | We present the first detailed study of the kinematics of free relativistic particles whose symmetries are described by a quantum deformation of the de Sitter algebra, known as $q$-de Sitter Hopf algebra. The quantum deformation parameter is a function of the Planck length $\ell$ and the de Sitter radius $H^{-1}$, such that when the Planck length vanishes, the algebra reduces to the de Sitter algebra, while when the de Sitter radius is sent to infinity one recovers the $\kappa$-Poincar\'e Hopf algebra. In the first limit the picture is that of a particle with trivial momentum space geometry moving on de Sitter spacetime, in the second one the picture is that of a particle with de Sitter momentum space geometry moving on Minkowski spacetime. When both the Planck length and the inverse of the de Sitter radius are non-zero, effects due to spacetime curvature and non-trivial momentum space geometry are both present and affect each other. The particles' motion is then described in a full phase space picture. We find that redshift effects that are usually associated to spacetime curvature become energy-dependent. Also, the energy dependence of particles' travel times that is usually associated to momentum space non-trivial properties is modified in a curvature-dependent way. |
0710.2666 | Hamid Reza Sepangi | M. Heydari-Fard and H. R. Sepangi | Generalized Chaplygin gas as geometrical dark energy | 11 pages, 3 figures, to appear in PRD | Phys.Rev.D76:104009,2007 | 10.1103/PhysRevD.76.104009 | null | gr-qc | null | The generalized Chaplygin gas provides an interesting candidate for the
present accelerated expansion of the universe. We explore a geometrical
explanation for the generalized Chaplygin gas within the context of brane world
theories where matter fields are confined to the brane by means of the action
of a confining potential. We obtain the modified Friedmann equations,
deceleration parameter and age of the universe in this scenario and show that
they are consistent with the present observational data.
| [
{
"created": "Sun, 14 Oct 2007 14:16:47 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Nov 2007 05:37:42 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Heydari-Fard",
"M.",
""
],
[
"Sepangi",
"H. R.",
""
]
] | The generalized Chaplygin gas provides an interesting candidate for the present accelerated expansion of the universe. We explore a geometrical explanation for the generalized Chaplygin gas within the context of brane world theories where matter fields are confined to the brane by means of the action of a confining potential. We obtain the modified Friedmann equations, deceleration parameter and age of the universe in this scenario and show that they are consistent with the present observational data. |
gr-qc/0512002 | Daniele Oriti | Etera R. Livine and Daniele Oriti | Coupling of spacetime atoms and spin foam renormalisation from group
field theory | RevTeX, 18 pages, no figures | JHEP 0702:092,2007 | 10.1088/1126-6708/2007/02/092 | null | gr-qc | null | We study the issue of coupling among 4-simplices in the context of spin foam
models obtained from a group field theory formalism. We construct a
generalisation of the Barrett-Crane model in which an additional coupling
between the normals to tetrahedra, as defined in different 4-simplices that
share them, is present. This is realised through an extension of the usual
field over the group manifold to a five argument one. We define a specific
model in which this coupling is parametrised by an additional real parameter
that allows to tune the degree of locality of the resulting model,
interpolating between the usual Barrett-Crane model and a flat BF-type one.
Moreover, we define a further extension of the group field theory formalism in
which the coupling parameter enters as a new variable of the field, and the
action presents derivative terms that lead to modified classical equations of
motion. Finally, we discuss the issue of renormalisation of spin foam models,
and how the new coupled model can be of help regarding this.
| [
{
"created": "Wed, 30 Nov 2005 22:19:36 GMT",
"version": "v1"
}
] | 2010-10-27 | [
[
"Livine",
"Etera R.",
""
],
[
"Oriti",
"Daniele",
""
]
] | We study the issue of coupling among 4-simplices in the context of spin foam models obtained from a group field theory formalism. We construct a generalisation of the Barrett-Crane model in which an additional coupling between the normals to tetrahedra, as defined in different 4-simplices that share them, is present. This is realised through an extension of the usual field over the group manifold to a five argument one. We define a specific model in which this coupling is parametrised by an additional real parameter that allows to tune the degree of locality of the resulting model, interpolating between the usual Barrett-Crane model and a flat BF-type one. Moreover, we define a further extension of the group field theory formalism in which the coupling parameter enters as a new variable of the field, and the action presents derivative terms that lead to modified classical equations of motion. Finally, we discuss the issue of renormalisation of spin foam models, and how the new coupled model can be of help regarding this. |
2206.00428 | Parth Bambhaniya | Vishva Patel, Kauntey Acharya, Parth Bambhaniya, Pankaj S. Joshi | Rotational energy extraction from the Kerr black hole's mimickers | 16 pages, 23 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, the Penrose process is being used to extract rotational energy
from regular black holes. Initially, we consider the rotating Simpson-Visser
regular spacetime which describes the class of geometries of the Kerr black
hole's mimickers. The Penrose process is then studied through conformally
transformed rotating singular and regular black hole solutions. These both
Simpson-Visser and conformally transformed geometries depend on mass, spin, and
an additional regularisation parameter $l$. In both cases, we investigate how
the spin and regularisation parameter $l$ affects the configuration of an
ergoregion and event horizons. Surprisingly, we find that the energy extraction
efficiency from the event horizon surface is not dependent on the
regularisation parameter $l$ in the Simpson-Visser regular spacetimes and hence
it does not vary from the Kerr black hole case. While, in the conformally
transformed singular and regular black holes, we obtain the efficiency rate of
extracted energies are extremely high compared to the Kerr black hole scenario.
This distinct signature of the conformally transformed singular and regular
black holes would be useful to distinguish them from the Kerr black hole in
observation.
| [
{
"created": "Wed, 1 Jun 2022 12:07:59 GMT",
"version": "v1"
}
] | 2022-06-02 | [
[
"Patel",
"Vishva",
""
],
[
"Acharya",
"Kauntey",
""
],
[
"Bambhaniya",
"Parth",
""
],
[
"Joshi",
"Pankaj S.",
""
]
] | In this paper, the Penrose process is being used to extract rotational energy from regular black holes. Initially, we consider the rotating Simpson-Visser regular spacetime which describes the class of geometries of the Kerr black hole's mimickers. The Penrose process is then studied through conformally transformed rotating singular and regular black hole solutions. These both Simpson-Visser and conformally transformed geometries depend on mass, spin, and an additional regularisation parameter $l$. In both cases, we investigate how the spin and regularisation parameter $l$ affects the configuration of an ergoregion and event horizons. Surprisingly, we find that the energy extraction efficiency from the event horizon surface is not dependent on the regularisation parameter $l$ in the Simpson-Visser regular spacetimes and hence it does not vary from the Kerr black hole case. While, in the conformally transformed singular and regular black holes, we obtain the efficiency rate of extracted energies are extremely high compared to the Kerr black hole scenario. This distinct signature of the conformally transformed singular and regular black holes would be useful to distinguish them from the Kerr black hole in observation. |
1811.02467 | Chunshan Lin | Chunshan Lin | The Self-consistent Matter Coupling of a Class of Minimally Modified
Gravity Theories | 11 pages, version accepted by JCAP | JCAP05(2019)037 | 10.1088/1475-7516/2019/05/037 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The self-consistent matter coupling is found in a broad class of minimally
modified gravity theories which was discovered recently. All constraints in the
theories remain first class and thus a graviton has only 2 local degrees of
freedom. The cosmological solution of one of the examples in this class, the
so-called square root gravity, exhibits a singularity freeness at high energy
limit. At low energy limit, the theory smoothly connects to GR. A general
feature of the theories in this class, with the self-consistent matter coupling
discovered in our current work, is the non-trivial interaction among different
components of matter sector. We have also checked the Hamiltonian structure of
a scalar QED coupling to the square root gravity in the same manner. All
constraints in the theory are first class too and thus the local U(1) gauge
symmetry in scalar QED is preserved.
| [
{
"created": "Tue, 6 Nov 2018 16:18:48 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Nov 2018 18:00:29 GMT",
"version": "v2"
},
{
"created": "Thu, 10 Jan 2019 22:13:20 GMT",
"version": "v3"
},
{
"created": "Thu, 23 May 2019 08:47:31 GMT",
"version": "v4"
}
] | 2019-05-24 | [
[
"Lin",
"Chunshan",
""
]
] | The self-consistent matter coupling is found in a broad class of minimally modified gravity theories which was discovered recently. All constraints in the theories remain first class and thus a graviton has only 2 local degrees of freedom. The cosmological solution of one of the examples in this class, the so-called square root gravity, exhibits a singularity freeness at high energy limit. At low energy limit, the theory smoothly connects to GR. A general feature of the theories in this class, with the self-consistent matter coupling discovered in our current work, is the non-trivial interaction among different components of matter sector. We have also checked the Hamiltonian structure of a scalar QED coupling to the square root gravity in the same manner. All constraints in the theory are first class too and thus the local U(1) gauge symmetry in scalar QED is preserved. |
2311.13497 | Jose Luis Hernandez-Pastora | J.L.Hern\'andez-Pastora | Gravitational fields of axially symmetric compact objects in 5D
space-time-matter gravity | 20 pages. No figures. General Relativity and Gravitation (2024) 56:23 | General Relativity and Gravitation 56: 23 (2024) | 10.1007/s10714-024-03210-2 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the standard Einstein's theory the exterior gravitational field of any
static and axially symmetric stellar object can be described by means of a
single function from which we obtain a metric into a four-dimensional
space-time. In this work we present a generalization of those so called Weyl
solutions to a space-time-matter metric in a five-dimensional manifold within a
non-compactified Kaluza-Klein theory of gravity. The arising field equations
reduce to those of vacuum Einstein's gravity when the metric function
associated to the fifth dimension is considered to be constant. The calculation
of the geodesics allows to identify the existence or not of different
behaviours of test particles, in orbits on a constant plane, between the two
metrics. In addition, static solutions on the hypersurface orthogonal to the
added dimension but with time dependence in the five-dimensional metric are
also obtained. The consequences on the variation of the rest mass, if the fifth
dimension is identified with it, are studied.
| [
{
"created": "Wed, 22 Nov 2023 16:15:00 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Feb 2024 10:25:29 GMT",
"version": "v2"
}
] | 2024-02-19 | [
[
"Hernández-Pastora",
"J. L.",
""
]
] | In the standard Einstein's theory the exterior gravitational field of any static and axially symmetric stellar object can be described by means of a single function from which we obtain a metric into a four-dimensional space-time. In this work we present a generalization of those so called Weyl solutions to a space-time-matter metric in a five-dimensional manifold within a non-compactified Kaluza-Klein theory of gravity. The arising field equations reduce to those of vacuum Einstein's gravity when the metric function associated to the fifth dimension is considered to be constant. The calculation of the geodesics allows to identify the existence or not of different behaviours of test particles, in orbits on a constant plane, between the two metrics. In addition, static solutions on the hypersurface orthogonal to the added dimension but with time dependence in the five-dimensional metric are also obtained. The consequences on the variation of the rest mass, if the fifth dimension is identified with it, are studied. |
gr-qc/9611018 | Shiekh Anwar | A. Akhundov, S. Bellucci, A. Shiekh | Gravitational interaction to one loop in effective quantum gravity | 9 pages, LaTeX, 7 Postscript figures, replaced with minor changes to
the abstract and end of section 4 | Phys.Lett. B395 (1997) 16-23 | 10.1016/S0370-2693(96)01694-2 | LNF-96/058 (P) | gr-qc hep-ph hep-th | null | We carry out the first step of a program conceived, in order to build a
realistic model, having the particle spectrum of the standard model and
renormalized masses, interaction terms and couplings, etc. which include the
class of quantum gravity corrections, obtained by handling gravity as an
effective theory. This provides an adequate picture at low energies, i.e. much
less than the scale of strong gravity (the Planck mass). Hence our results are
valid, irrespectively of any proposal for the full quantum gravity as a
fundamental theory. We consider only non-analytic contributions to the one-loop
scattering matrix elements, which provide the dominant quantum effect at long
distance. These contributions are finite and independent from the finite value
of the renormalization counter terms of the effective lagrangian. We calculate
the interaction of two heavy scalar particles, i.e. close to rest, due to the
effective quantum gravity to the one loop order and compare with similar
results in the literature.
| [
{
"created": "Thu, 7 Nov 1996 14:45:56 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Nov 1996 16:10:40 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Akhundov",
"A.",
""
],
[
"Bellucci",
"S.",
""
],
[
"Shiekh",
"A.",
""
]
] | We carry out the first step of a program conceived, in order to build a realistic model, having the particle spectrum of the standard model and renormalized masses, interaction terms and couplings, etc. which include the class of quantum gravity corrections, obtained by handling gravity as an effective theory. This provides an adequate picture at low energies, i.e. much less than the scale of strong gravity (the Planck mass). Hence our results are valid, irrespectively of any proposal for the full quantum gravity as a fundamental theory. We consider only non-analytic contributions to the one-loop scattering matrix elements, which provide the dominant quantum effect at long distance. These contributions are finite and independent from the finite value of the renormalization counter terms of the effective lagrangian. We calculate the interaction of two heavy scalar particles, i.e. close to rest, due to the effective quantum gravity to the one loop order and compare with similar results in the literature. |
1611.08783 | Chen Songbai | Songbai Chen, Shangyun Wang, Yang Huang, Jiliang Jing, Shiliang Wang | Strong gravitational lensing for the photons coupled to Weyl tensor in a
Kerr black hole spacetime | 28 pages, 15 figures, Accepted by PRD for publication. arXiv admin
note: text overlap with arXiv:1502.01088 | Phys. Rev. D 95, 104017 (2017) | 10.1103/PhysRevD.95.104017 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present firstly equation of motion for the photon coupled to Weyl tensor
in a Kerr black hole spacetime and then study further the corresponding strong
gravitational lensing. We find that black hole rotation makes propagation of
the coupled photons more complicated, which brings some new features for
physical quantities including the marginally circular photon orbit, the
deflection angle, the observational gravitational lensing variables and the
time delay between two relativistic images. There is a critical value of the
coupling parameter for existence of the marginally circular photon orbit
outside the event horizon, which depends on the rotation parameter of black
hole and the polarization direction of photons. As the value of coupling
parameter is near the critical value, we find that the marginally circular
photon orbit for the retrograde photon increases with the rotation parameter,
which modifies a common feature of the marginally circular photon orbit in a
rotating black hole spacetime since it always decreases monotonously with the
rotation parameter in the case without Weyl coupling. Combining with the
supermassive central object in our Galaxy, we estimated the observables
including time delays between the relativistic images in the strong
gravitational lensing as the photons couple to Weyl tensor.
| [
{
"created": "Sun, 27 Nov 2016 04:33:33 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Apr 2017 02:33:48 GMT",
"version": "v2"
}
] | 2017-05-19 | [
[
"Chen",
"Songbai",
""
],
[
"Wang",
"Shangyun",
""
],
[
"Huang",
"Yang",
""
],
[
"Jing",
"Jiliang",
""
],
[
"Wang",
"Shiliang",
""
]
] | We present firstly equation of motion for the photon coupled to Weyl tensor in a Kerr black hole spacetime and then study further the corresponding strong gravitational lensing. We find that black hole rotation makes propagation of the coupled photons more complicated, which brings some new features for physical quantities including the marginally circular photon orbit, the deflection angle, the observational gravitational lensing variables and the time delay between two relativistic images. There is a critical value of the coupling parameter for existence of the marginally circular photon orbit outside the event horizon, which depends on the rotation parameter of black hole and the polarization direction of photons. As the value of coupling parameter is near the critical value, we find that the marginally circular photon orbit for the retrograde photon increases with the rotation parameter, which modifies a common feature of the marginally circular photon orbit in a rotating black hole spacetime since it always decreases monotonously with the rotation parameter in the case without Weyl coupling. Combining with the supermassive central object in our Galaxy, we estimated the observables including time delays between the relativistic images in the strong gravitational lensing as the photons couple to Weyl tensor. |
1507.00378 | Stoytcho Yazadjiev | Daniela D. Doneva, Stoytcho S. Yazadjiev, Kostas D. Kokkotas | The I-Q relations for rapidly rotating neutron stars in $f(R)$ gravity | 8 pages, one figure | Phys. Rev. D 92, 064015 (2015) | 10.1103/PhysRevD.92.064015 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present paper we study the behavior of the normalized $I$-$Q$ relation
for neutron stars in a particular class of $f(R)$ theories of gravity, namely
the $R^2$ gravity that is one of the most natural and simplest extensions of
general relativity in the strong field regime. We study both the slowly and
rapidly rotating cases. The results show that the $I$-$Q$ relation remain
nearly equation of state independent for fixed values of the normalized
rotational parameter, but the deviations from universality can be a little bit
larger compared to the general relativistic case. What is the most interesting
in our studies, is that the differences with the pure Einstein's theory can be
large reaching above 20\%. This is qualitative different from the majority of
alternative theories of gravity, where the normalized $I$-$Q$ relations are
almost indistinguishable from the general relativistic case, and can lead to
observational constraints on the $f(R)$ theories in the future.
| [
{
"created": "Wed, 1 Jul 2015 21:38:01 GMT",
"version": "v1"
}
] | 2015-09-16 | [
[
"Doneva",
"Daniela D.",
""
],
[
"Yazadjiev",
"Stoytcho S.",
""
],
[
"Kokkotas",
"Kostas D.",
""
]
] | In the present paper we study the behavior of the normalized $I$-$Q$ relation for neutron stars in a particular class of $f(R)$ theories of gravity, namely the $R^2$ gravity that is one of the most natural and simplest extensions of general relativity in the strong field regime. We study both the slowly and rapidly rotating cases. The results show that the $I$-$Q$ relation remain nearly equation of state independent for fixed values of the normalized rotational parameter, but the deviations from universality can be a little bit larger compared to the general relativistic case. What is the most interesting in our studies, is that the differences with the pure Einstein's theory can be large reaching above 20\%. This is qualitative different from the majority of alternative theories of gravity, where the normalized $I$-$Q$ relations are almost indistinguishable from the general relativistic case, and can lead to observational constraints on the $f(R)$ theories in the future. |
1412.4220 | Sabine Hossenfelder | S. Hossenfelder | Analog Systems for Gravity Duals | replaced with published version | Phys. Rev. D 91, 124064 (2015) | 10.1103/PhysRevD.91.124064 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that analog gravity systems exist for charged, planar black holes in
asymptotic Anti-de Sitter space. These black holes have been employed to
describe, via the gauge-gravity duality, strongly coupled condensed matter
systems on the boundary of AdS-space. The analog gravity system is a different
condensed matter system that, in a suitable limit, describes the same bulk
physics as the theory on the AdS boundary. This combination of the
gauge-gravity duality and analog gravity therefore suggests a duality between
different condensed matter systems.
| [
{
"created": "Sat, 13 Dec 2014 10:08:58 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jun 2015 13:54:39 GMT",
"version": "v2"
}
] | 2015-06-30 | [
[
"Hossenfelder",
"S.",
""
]
] | We show that analog gravity systems exist for charged, planar black holes in asymptotic Anti-de Sitter space. These black holes have been employed to describe, via the gauge-gravity duality, strongly coupled condensed matter systems on the boundary of AdS-space. The analog gravity system is a different condensed matter system that, in a suitable limit, describes the same bulk physics as the theory on the AdS boundary. This combination of the gauge-gravity duality and analog gravity therefore suggests a duality between different condensed matter systems. |
gr-qc/0307067 | Carlos Palenzuela | C.Bona, T.Ledvinka, C.Palenzuela and M. Zacek | A symmetry-breaking mechanism for the Z4 general-covariant evolution
system | figures added, text changed, accepted in PRD | Phys.Rev. D69 (2004) 064036 | 10.1103/PhysRevD.69.064036 | null | gr-qc | null | The general-covariant Z4 formalism is further analyzed. The gauge conditions
are generalized with a view to Numerical Relativity applications and the
conditions for obtaining strongly hyperbolic evolution systems are given both
at the first and the second order levels. A symmetry-breaking mechanism is
proposed that allows one, when applied in a partial way, to recover previously
proposed strongly hyperbolic formalisms, like the BSSN and the Bona-Mass\'o
ones. When applied in its full form, the symmetry breaking mechanism allows one
to recover the full five-parameter family of first order KST systems. Numerical
codes based in the proposed formalisms are tested. A robust stability test is
provided by evolving random noise data around Minkowski space-time. A strong
field test is provided by the collapse of a periodic background of plane
gravitational waves, as described by the Gowdy metric.
| [
{
"created": "Tue, 15 Jul 2003 09:58:03 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Jul 2003 12:05:42 GMT",
"version": "v2"
},
{
"created": "Mon, 22 Mar 2004 10:36:05 GMT",
"version": "v3"
}
] | 2009-11-10 | [
[
"Bona",
"C.",
""
],
[
"Ledvinka",
"T.",
""
],
[
"Palenzuela",
"C.",
""
],
[
"Zacek",
"M.",
""
]
] | The general-covariant Z4 formalism is further analyzed. The gauge conditions are generalized with a view to Numerical Relativity applications and the conditions for obtaining strongly hyperbolic evolution systems are given both at the first and the second order levels. A symmetry-breaking mechanism is proposed that allows one, when applied in a partial way, to recover previously proposed strongly hyperbolic formalisms, like the BSSN and the Bona-Mass\'o ones. When applied in its full form, the symmetry breaking mechanism allows one to recover the full five-parameter family of first order KST systems. Numerical codes based in the proposed formalisms are tested. A robust stability test is provided by evolving random noise data around Minkowski space-time. A strong field test is provided by the collapse of a periodic background of plane gravitational waves, as described by the Gowdy metric. |
2206.01150 | Theodoros Papanikolaou | Shreya Banerjee, Theodoros Papanikolaou, Emmanuel N. Saridakis | Constraining $F(R)$ bouncing cosmologies with primordial black holes | To appear in Phys.Rev.D | null | 10.1103/PhysRevD.106.124012 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The phenomenology of primordial black hole (PBH) physics and the associated
PBH abundance constraints, can be used in order to probe the physics of the
early Universe. In this work, we investigate the PBH formation during the
standard radiation-dominated era by studying the effect of an early F(R)
modified gravity phase with a bouncing behavior which is introduced to avoid
the initial spacetime singularity problem. In particular, we calculate the
energy density power spectrum at horizon crossing time and then we extract the
PBH abundance in the context of peak theory as a function of the parameter
$\alpha$ of our $F(R)$ gravity bouncing model at hand. Interestingly, we find
that in order to avoid GW overproduction from an early PBH dominated era before
Big Bang Nucleosynthesis (BBN), $\alpha$ should lie within the range
$\alpha\leq 10^{-19}M^2_\mathrm{Pl}$. This constraint can be translated to a
constraint on the energy scale at the onset of the Hot Big Bang (HBB) phase,
$H_\mathrm{RD}\sim \sqrt{\alpha}/2$ which can be recast as $H_\mathrm{RD}<
10^{-10}M_\mathrm{Pl}$.
| [
{
"created": "Thu, 2 Jun 2022 17:05:13 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Aug 2022 10:00:03 GMT",
"version": "v2"
},
{
"created": "Tue, 15 Nov 2022 17:19:59 GMT",
"version": "v3"
}
] | 2022-12-21 | [
[
"Banerjee",
"Shreya",
""
],
[
"Papanikolaou",
"Theodoros",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] | The phenomenology of primordial black hole (PBH) physics and the associated PBH abundance constraints, can be used in order to probe the physics of the early Universe. In this work, we investigate the PBH formation during the standard radiation-dominated era by studying the effect of an early F(R) modified gravity phase with a bouncing behavior which is introduced to avoid the initial spacetime singularity problem. In particular, we calculate the energy density power spectrum at horizon crossing time and then we extract the PBH abundance in the context of peak theory as a function of the parameter $\alpha$ of our $F(R)$ gravity bouncing model at hand. Interestingly, we find that in order to avoid GW overproduction from an early PBH dominated era before Big Bang Nucleosynthesis (BBN), $\alpha$ should lie within the range $\alpha\leq 10^{-19}M^2_\mathrm{Pl}$. This constraint can be translated to a constraint on the energy scale at the onset of the Hot Big Bang (HBB) phase, $H_\mathrm{RD}\sim \sqrt{\alpha}/2$ which can be recast as $H_\mathrm{RD}< 10^{-10}M_\mathrm{Pl}$. |
2105.07827 | Claus Kiefer | Claus Kiefer and Hermann Nicolai | The impact of Friedmann's work on cosmology | 4 pages, invited contribution to "Mathematicians from Saint
Petersburg and their theorems", ed. by Nikita Kalinin, v2: references added | null | null | null | gr-qc physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a brief review of Friedmann's impact on cosmology from a
historical and a physical perspective.
| [
{
"created": "Mon, 17 May 2021 13:36:47 GMT",
"version": "v1"
},
{
"created": "Tue, 25 May 2021 08:28:40 GMT",
"version": "v2"
}
] | 2021-05-26 | [
[
"Kiefer",
"Claus",
""
],
[
"Nicolai",
"Hermann",
""
]
] | We present a brief review of Friedmann's impact on cosmology from a historical and a physical perspective. |
2101.12391 | Durmus Demir | Durmus Demir | Emergent Gravity as the Eraser of Anomalous Gauge Boson Masses, and
QFT-GR Concord | 22 pages, 3 tables; to appear in General Relativity and Gravitation | Gen. Relativ. Gravit. 53, 22 (2021) | 10.1007/s10714-021-02797-0 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the same base setup as Sakharov's induced gravity, we investigate
emergence of gravity in effective quantum field theories (QFT), with particular
emphasis on the gauge sector in which gauge bosons acquire anomalous masses in
proportion to the ultraviolet cutoff $\Lambda_\wp$. Drawing on the fact that
$\Lambda_\wp^2$ corrections explicitly break the gauge and Poincare symmetries,
we find that it is possible to map $\Lambda_\wp^2$ to spacetime curvature as a
covariance relation and we find also that this map erases the anomalous gauge
boson masses. The resulting framework describes gravity by the general
relativity (GR) and matter by the QFT itself with $\log\Lambda_\wp$ corrections
(dimensional regularization). This QFT-GR concord predicts existence of new
physics beyond the Standard Model such that the new physics can be a
weakly-interacting or even a non-interacting sector comprising the dark matter,
dark energy and possibly more. The concord has consequential implications for
collider, astrophysical and cosmological phenomena.
| [
{
"created": "Fri, 29 Jan 2021 04:05:16 GMT",
"version": "v1"
}
] | 2021-02-24 | [
[
"Demir",
"Durmus",
""
]
] | In the same base setup as Sakharov's induced gravity, we investigate emergence of gravity in effective quantum field theories (QFT), with particular emphasis on the gauge sector in which gauge bosons acquire anomalous masses in proportion to the ultraviolet cutoff $\Lambda_\wp$. Drawing on the fact that $\Lambda_\wp^2$ corrections explicitly break the gauge and Poincare symmetries, we find that it is possible to map $\Lambda_\wp^2$ to spacetime curvature as a covariance relation and we find also that this map erases the anomalous gauge boson masses. The resulting framework describes gravity by the general relativity (GR) and matter by the QFT itself with $\log\Lambda_\wp$ corrections (dimensional regularization). This QFT-GR concord predicts existence of new physics beyond the Standard Model such that the new physics can be a weakly-interacting or even a non-interacting sector comprising the dark matter, dark energy and possibly more. The concord has consequential implications for collider, astrophysical and cosmological phenomena. |
1306.1623 | Aron Wall | Sudipta Sarkar, Aron C. Wall | Generalized second law at linear order for actions that are functions of
Lovelock densities | 19 pages, no figues, v2 references and minor comments added, v3 Ref.
4 & typos in Eq. 14, 27, 40 corrected | Phys. Rev. D 88, 044017 (2013) | 10.1103/PhysRevD.88.044017 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we consider the second law of black holes (and other causal
horizons) in theories where the gravitational action is an arbitrary function
of the Lovelock densities. We show that there exists an entropy which increases
locally, for linearized perturbations to regular Killing horizons. In addition
to a classical increase theorem, we also prove a generalized second law for
semiclassical, minimally-coupled matter fields.
| [
{
"created": "Fri, 7 Jun 2013 05:59:25 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Aug 2013 09:13:35 GMT",
"version": "v2"
},
{
"created": "Tue, 19 May 2015 21:20:54 GMT",
"version": "v3"
}
] | 2015-05-21 | [
[
"Sarkar",
"Sudipta",
""
],
[
"Wall",
"Aron C.",
""
]
] | In this article we consider the second law of black holes (and other causal horizons) in theories where the gravitational action is an arbitrary function of the Lovelock densities. We show that there exists an entropy which increases locally, for linearized perturbations to regular Killing horizons. In addition to a classical increase theorem, we also prove a generalized second law for semiclassical, minimally-coupled matter fields. |
1910.01899 | Fay\c{c}al Hammad | Fay\c{c}al Hammad and Alexandre Landry | Landau levels in a gravitational field: The Levi-Civita and Kerr
spacetimes case | 35 Pages. References, corrections and improvements added. Accepted
version for publication in EPJP | Eur. Phys. J. Plus 135, 90 (2020) | 10.1140/epjp/s13360-020-00108-1 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have recently found that the gravitational field of a static spherical
mass removes the Landau degeneracy of the energy levels of a particle moving
around the mass inside a magnetic field by splitting the energy of the Landau
orbitals. In this paper we present the second part of our investigation of the
effect of gravity on Landau levels. We examine the effect of the gravitational
fields created by an infinitely long massive cylinder and a rotating spherical
mass. In both cases, we show that the degeneracy is again removed thanks to the
splitting of the particle's orbitals. The first case would constitute an
experimental test - which is quantum mechanical in nature - of the
gravitational field of a cylinder. The approach relies on the Newtonian
approximation of the gravitational potential created by a cylinder but, in view
of self-consistency and for future higher-order approximations, the formalism
is based on the full Levi-Civita metric. The second case opens up the
possibility for a novel quantum mechanical test of the well-known rotational
frame-dragging effect of general relativity.
| [
{
"created": "Tue, 1 Oct 2019 15:01:32 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Dec 2019 10:37:49 GMT",
"version": "v2"
}
] | 2020-02-04 | [
[
"Hammad",
"Fayçal",
""
],
[
"Landry",
"Alexandre",
""
]
] | We have recently found that the gravitational field of a static spherical mass removes the Landau degeneracy of the energy levels of a particle moving around the mass inside a magnetic field by splitting the energy of the Landau orbitals. In this paper we present the second part of our investigation of the effect of gravity on Landau levels. We examine the effect of the gravitational fields created by an infinitely long massive cylinder and a rotating spherical mass. In both cases, we show that the degeneracy is again removed thanks to the splitting of the particle's orbitals. The first case would constitute an experimental test - which is quantum mechanical in nature - of the gravitational field of a cylinder. The approach relies on the Newtonian approximation of the gravitational potential created by a cylinder but, in view of self-consistency and for future higher-order approximations, the formalism is based on the full Levi-Civita metric. The second case opens up the possibility for a novel quantum mechanical test of the well-known rotational frame-dragging effect of general relativity. |
gr-qc/0506067 | James Ryan | Laurent Freidel, Daniele Oriti, James Ryan | A group field theory for 3d quantum gravity coupled to a scalar field | 11 pages, no figures, references added | null | null | null | gr-qc hep-th | null | We present a new group field theory model, generalising the Boulatov model,
which incorporates both 3-dimensional gravity and matter coupled to gravity. We
show that the Feynman diagram amplitudes of this model are given by Riemannian
quantum gravity spin foam amplitudes coupled to a scalar matter field. We
briefly discuss the features of this model and its possible generalisations.
| [
{
"created": "Fri, 10 Jun 2005 20:46:28 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Jul 2005 18:08:23 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Freidel",
"Laurent",
""
],
[
"Oriti",
"Daniele",
""
],
[
"Ryan",
"James",
""
]
] | We present a new group field theory model, generalising the Boulatov model, which incorporates both 3-dimensional gravity and matter coupled to gravity. We show that the Feynman diagram amplitudes of this model are given by Riemannian quantum gravity spin foam amplitudes coupled to a scalar matter field. We briefly discuss the features of this model and its possible generalisations. |
gr-qc/0505001 | Vladimir S. Manko | V.S. Manko and E. Ruiz | Physical interpretation of NUT solution | 7 pages, 1 figure, submitted to Classical and Quantum Gravity | Class.Quant.Grav. 22 (2005) 3555-3560 | 10.1088/0264-9381/22/17/014 | null | gr-qc | null | We show that the well-known NUT solution can be correctly interpreted as
describing the exterior field of two counter-rotating semi-infinite sources
possessing negative masses and infinite angular momenta which are attached to
the poles of a static finite rod of positive mass.
| [
{
"created": "Fri, 29 Apr 2005 22:52:42 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Manko",
"V. S.",
""
],
[
"Ruiz",
"E.",
""
]
] | We show that the well-known NUT solution can be correctly interpreted as describing the exterior field of two counter-rotating semi-infinite sources possessing negative masses and infinite angular momenta which are attached to the poles of a static finite rod of positive mass. |
1808.03200 | Claes Uggla | Claes Uggla and John Wainwright | Dynamics of cosmological perturbations at first and second order | 27 pages | Phys. Rev. D 98, 103534 (2018) | 10.1103/PhysRevD.98.103534 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we give five gauge-invariant systems of governing equations for
first and second order scalar perturbations of flat Friedmann-Lema\^{i}tre
universes that are minimal in the sense that they contain no redundant
equations or variables. We normalize the variables so that they are
dimensionless, which leads to systems of equations that are simple and
ready-to-use. We compare the properties and utility of the different systems.
For example, they serve as a starting point for finding explicit solutions for
two benchmark problems in cosmological perturbation theory at second order:
adiabatic perturbations in the super-horizon regime (the long wavelength limit)
and perturbations of $\Lambda$CDM universes. However, our framework has much
wider applicability and serves as a reference for future work in the field.
| [
{
"created": "Thu, 9 Aug 2018 15:37:07 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Jan 2019 09:49:59 GMT",
"version": "v2"
}
] | 2019-01-23 | [
[
"Uggla",
"Claes",
""
],
[
"Wainwright",
"John",
""
]
] | In this paper we give five gauge-invariant systems of governing equations for first and second order scalar perturbations of flat Friedmann-Lema\^{i}tre universes that are minimal in the sense that they contain no redundant equations or variables. We normalize the variables so that they are dimensionless, which leads to systems of equations that are simple and ready-to-use. We compare the properties and utility of the different systems. For example, they serve as a starting point for finding explicit solutions for two benchmark problems in cosmological perturbation theory at second order: adiabatic perturbations in the super-horizon regime (the long wavelength limit) and perturbations of $\Lambda$CDM universes. However, our framework has much wider applicability and serves as a reference for future work in the field. |
2008.12206 | Alan Kostelecky | Alan Kostelecky and Zonghao Li | Backgrounds in gravitational effective field theory | 36 pages two-column REVTeX | Phys. Rev. D 103, 024059 (2021) | 10.1103/PhysRevD.103.024059 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Effective field theories describing gravity coupled to matter are
investigated, allowing for operators of arbitrary mass dimension. Terms
violating local Lorentz and diffeomorphism invariance while preserving internal
gauge symmetries are included. The theoretical framework for violations of
local Lorentz and diffeomorphism invariance and associated conceptual issues
are discussed, including transformations in curved and approximately flat
spacetimes, the treatment of various types of backgrounds, the implications of
symmetry breaking, and the no-go constraints for explicit violation in Riemann
geometry. Techniques are presented for the construction of effective operators,
and the possible terms in the gravity, gauge, fermion, and scalar sectors are
classified and enumerated. Explicit expressions are obtained for terms
containing operators of mass dimension six or less in the effective action for
General Relativity coupled to the Standard Model of particle physics. Special
cases considered include Einstein-Maxwell effective field theories and the
limit with only scalar coupling constants.
| [
{
"created": "Thu, 27 Aug 2020 16:02:34 GMT",
"version": "v1"
}
] | 2021-02-03 | [
[
"Kostelecky",
"Alan",
""
],
[
"Li",
"Zonghao",
""
]
] | Effective field theories describing gravity coupled to matter are investigated, allowing for operators of arbitrary mass dimension. Terms violating local Lorentz and diffeomorphism invariance while preserving internal gauge symmetries are included. The theoretical framework for violations of local Lorentz and diffeomorphism invariance and associated conceptual issues are discussed, including transformations in curved and approximately flat spacetimes, the treatment of various types of backgrounds, the implications of symmetry breaking, and the no-go constraints for explicit violation in Riemann geometry. Techniques are presented for the construction of effective operators, and the possible terms in the gravity, gauge, fermion, and scalar sectors are classified and enumerated. Explicit expressions are obtained for terms containing operators of mass dimension six or less in the effective action for General Relativity coupled to the Standard Model of particle physics. Special cases considered include Einstein-Maxwell effective field theories and the limit with only scalar coupling constants. |
2304.01154 | Hongbo Cheng | Yuxuan Shi, Hongbo Cheng | The shadow and gamma-ray bursts of a Schwarzschild black hole in
asymptotic safety | 17 pages, 5 figures | null | null | null | gr-qc hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | We research on the neutrino pair annihilation
$\nu+\overline{\nu}\longrightarrow e^{-}+e^{+}$ around a massive source in
asymptotic safety. Since neutrinos and photons have the same geodesic equation
around black holes, we can estimate the radius where the neutrinos will be
released by obtaining a series of trajectory curves with various correction
values $\xi$. The black hole shadow radius is influenced by the correction
parameter $\xi$. The black hole shadow radius decreases with increasing the
$\xi$. The ratio $\dfrac{\dot{Q}}{\dot{Q}_{Newt}}$ corresponding to the energy
deposition per unit time over that in the Newtonian case is derived and
calculated. We find that the quantum corrections to the black hole spacetime
affect the emitted energy rate ratio for the annihilation. It is interesting
that the more considerable quantum effect reduces the ratio value slightly.
Although the energy conversion is damped because of the quantum correction, the
energy deposition rate is enough during the neutrino-antineutrino annihilation.
The corrected annihilation process can become a source of gamma ray burst. We
also investigate the derivative $\dfrac{\mathrm{d}\dot{Q}}{\mathrm{d}r}$
relating to the star's radius $r$ to show that the quantum effect for the black
hole will drop the ratio. The more manifest quantum gravity influence leads the
weaker neutrino pair annihilation.
| [
{
"created": "Fri, 31 Mar 2023 02:01:12 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Apr 2023 14:23:35 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Aug 2023 06:54:16 GMT",
"version": "v3"
},
{
"created": "Sun, 12 Nov 2023 09:26:44 GMT",
"version": "v4"
},
{
"cr... | 2024-05-24 | [
[
"Shi",
"Yuxuan",
""
],
[
"Cheng",
"Hongbo",
""
]
] | We research on the neutrino pair annihilation $\nu+\overline{\nu}\longrightarrow e^{-}+e^{+}$ around a massive source in asymptotic safety. Since neutrinos and photons have the same geodesic equation around black holes, we can estimate the radius where the neutrinos will be released by obtaining a series of trajectory curves with various correction values $\xi$. The black hole shadow radius is influenced by the correction parameter $\xi$. The black hole shadow radius decreases with increasing the $\xi$. The ratio $\dfrac{\dot{Q}}{\dot{Q}_{Newt}}$ corresponding to the energy deposition per unit time over that in the Newtonian case is derived and calculated. We find that the quantum corrections to the black hole spacetime affect the emitted energy rate ratio for the annihilation. It is interesting that the more considerable quantum effect reduces the ratio value slightly. Although the energy conversion is damped because of the quantum correction, the energy deposition rate is enough during the neutrino-antineutrino annihilation. The corrected annihilation process can become a source of gamma ray burst. We also investigate the derivative $\dfrac{\mathrm{d}\dot{Q}}{\mathrm{d}r}$ relating to the star's radius $r$ to show that the quantum effect for the black hole will drop the ratio. The more manifest quantum gravity influence leads the weaker neutrino pair annihilation. |
2204.11169 | Yaqi Zhao | Yaqi Zhao, Xin Ren, Amara Ilyas, Emmanuel N. Saridakis, Yi-Fu Cai | Quasinormal modes of black holes in f(T) gravity | 22 pages, 7 figures | JCAP10(2022)087 | 10.1088/1475-7516/2022/10/087 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the quasinormal modes (QNM) frequencies of a test massless
scalar field and an electromagnetic field around static black holes in $f(T)$
gravity. Focusing on quadratic $f(T)$ modifications, which is a good
approximation for every realistic $f(T)$ theory, we first extract the
spherically symmetric solutions using the perturbative method, imposing two
ans$\ddot{\text{a}}$tze for the metric functions, which suitably quantify the
deviation from the Schwarzschild solution. Moreover, we extract the effective
potential, and then calculate the QNM frequency of the obtained solutions.
Firstly, we numerically solve the Schr$\ddot{\text{o}}$dinger-like equation
using the discretization method, and we extract the frequency and the time
evolution of the dominant mode applying the function fit method. Secondly, we
perform a semi-analytical calculation by applying the WKB method with the Pade
approximation. We show that the results for $f(T)$ gravity are different
compared to General Relativity, and in particular we obtain a different slope
and period of the field decay behavior for different model parameter values.
Hence, under the light of gravitational-wave observations of increasing
accuracy from binary systems, the whole analysis could be used as an additional
tool to test General Relativity and examine whether torsional gravitational
modifications are possible.
| [
{
"created": "Sun, 24 Apr 2022 02:57:28 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Oct 2022 03:21:11 GMT",
"version": "v2"
}
] | 2022-10-31 | [
[
"Zhao",
"Yaqi",
""
],
[
"Ren",
"Xin",
""
],
[
"Ilyas",
"Amara",
""
],
[
"Saridakis",
"Emmanuel N.",
""
],
[
"Cai",
"Yi-Fu",
""
]
] | We calculate the quasinormal modes (QNM) frequencies of a test massless scalar field and an electromagnetic field around static black holes in $f(T)$ gravity. Focusing on quadratic $f(T)$ modifications, which is a good approximation for every realistic $f(T)$ theory, we first extract the spherically symmetric solutions using the perturbative method, imposing two ans$\ddot{\text{a}}$tze for the metric functions, which suitably quantify the deviation from the Schwarzschild solution. Moreover, we extract the effective potential, and then calculate the QNM frequency of the obtained solutions. Firstly, we numerically solve the Schr$\ddot{\text{o}}$dinger-like equation using the discretization method, and we extract the frequency and the time evolution of the dominant mode applying the function fit method. Secondly, we perform a semi-analytical calculation by applying the WKB method with the Pade approximation. We show that the results for $f(T)$ gravity are different compared to General Relativity, and in particular we obtain a different slope and period of the field decay behavior for different model parameter values. Hence, under the light of gravitational-wave observations of increasing accuracy from binary systems, the whole analysis could be used as an additional tool to test General Relativity and examine whether torsional gravitational modifications are possible. |
1109.2371 | Sushant Ghosh Prof | Sushant G. Ghosh | 5D Radiating black holes in Einstein-Yang-Mills-Gauss-Bonnet gravity | 6 RevTex Pages, Accepted in Phys. Lett. B | null | 10.1016/j.physletb.2011.08.066 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive nonstatic spherically symmetric solutions of a null fluid, in five
dimension (5D), to Einstein-Yang-Mills (EYM) equations with the coupling of
Gauss-Bonnet (GB) combination of quadratic curvature terms, namely, 5D-EYMGB
radiating black hole solution. It is shown that, in the limit, we can recover
known radiating black hole solutions. The spherically symmetric known 5D static
black hole solutions are also retrieved. The effect of the GB term and
Yang-Mills (YM) gauge charge on the structure and location of horizons, of the
5D radiating black hole, is also discussed.
| [
{
"created": "Mon, 12 Sep 2011 03:22:53 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Ghosh",
"Sushant G.",
""
]
] | We derive nonstatic spherically symmetric solutions of a null fluid, in five dimension (5D), to Einstein-Yang-Mills (EYM) equations with the coupling of Gauss-Bonnet (GB) combination of quadratic curvature terms, namely, 5D-EYMGB radiating black hole solution. It is shown that, in the limit, we can recover known radiating black hole solutions. The spherically symmetric known 5D static black hole solutions are also retrieved. The effect of the GB term and Yang-Mills (YM) gauge charge on the structure and location of horizons, of the 5D radiating black hole, is also discussed. |
1712.10177 | Athanasios Tzikas | Konstantinos F. Dialektopoulos, Antonios Nathanail and Athanasios G.
Tzikas | Cosmological production of black holes: a way to constrain alternative
theories of gravity | 10 pages, 1 figure, 1 table, version accepted for publication in
Physical Review D | Phys. Rev. D 97, 124059 (2018) | 10.1103/PhysRevD.97.124059 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Primordial black holes are considered to be pair created quantum-mechanically
during inflation. In the context of General Relativity (GR), it has been shown
that the pair creation rate is exponentially decreasing during inflation.
Specifically, tiny black holes are favored in the early universe, but they can
grow with the horizon scale, as inflation approaches its end. At the same time,
cosmological, and not only, shortcomings of GR have triggered the pursuit for a
new, alternative theory of gravity. In this paper, by using probability
amplitudes from the No Boundary Proposal (NBP), we argue that any alternative
gravity should have a black hole creation rate similar to that of GR; that is,
in the early universe the creation of small black holes is in favor, while in
the late universe larger black holes are being exponentially suppressed. As an
example, we apply this argument in $f(R)$-theories of gravity and derive a
general formula for the rate in any $f(R)$-theory with constant curvature.
Finally, we consider well known $f(R)$-models and using this formula we put
constraints in their free parameters.
| [
{
"created": "Fri, 29 Dec 2017 10:47:27 GMT",
"version": "v1"
},
{
"created": "Sun, 29 Apr 2018 15:29:04 GMT",
"version": "v2"
},
{
"created": "Fri, 8 Jun 2018 20:46:43 GMT",
"version": "v3"
}
] | 2018-06-27 | [
[
"Dialektopoulos",
"Konstantinos F.",
""
],
[
"Nathanail",
"Antonios",
""
],
[
"Tzikas",
"Athanasios G.",
""
]
] | Primordial black holes are considered to be pair created quantum-mechanically during inflation. In the context of General Relativity (GR), it has been shown that the pair creation rate is exponentially decreasing during inflation. Specifically, tiny black holes are favored in the early universe, but they can grow with the horizon scale, as inflation approaches its end. At the same time, cosmological, and not only, shortcomings of GR have triggered the pursuit for a new, alternative theory of gravity. In this paper, by using probability amplitudes from the No Boundary Proposal (NBP), we argue that any alternative gravity should have a black hole creation rate similar to that of GR; that is, in the early universe the creation of small black holes is in favor, while in the late universe larger black holes are being exponentially suppressed. As an example, we apply this argument in $f(R)$-theories of gravity and derive a general formula for the rate in any $f(R)$-theory with constant curvature. Finally, we consider well known $f(R)$-models and using this formula we put constraints in their free parameters. |
1404.6541 | Eleni-Alexandra Kontou | Eleni-Alexandra Kontou and Ken D. Olum | Quantum inequality for a scalar field with a background potential | 20 pages | Phys. Rev. D 90, 024031 (2014) | 10.1103/PhysRevD.90.024031 | null | gr-qc math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum inequalities are bounds on negative time-averages of the energy
density of a quantum field. They can be used to rule out exotic spacetimes in
general relativity. We study quantum inequalities for a scalar field with a
background potential (i.e., a mass that varies with spacetime position) in
Minkowski space. We treat the potential as a perturbation and explicitly
calculate the first-order correction to a quantum inequality with an arbitrary
sampling function, using general results of Fewster and Smith. For an arbitrary
potential, we give bounds on the correction in terms of the maximum values of
the potential and its first three derivatives. The techniques we develop here
will also be applicable to quantum inequalities in general spacetimes with
small curvature, which are necessary to rule out exotic phenomena.
| [
{
"created": "Fri, 25 Apr 2014 20:23:20 GMT",
"version": "v1"
}
] | 2014-07-16 | [
[
"Kontou",
"Eleni-Alexandra",
""
],
[
"Olum",
"Ken D.",
""
]
] | Quantum inequalities are bounds on negative time-averages of the energy density of a quantum field. They can be used to rule out exotic spacetimes in general relativity. We study quantum inequalities for a scalar field with a background potential (i.e., a mass that varies with spacetime position) in Minkowski space. We treat the potential as a perturbation and explicitly calculate the first-order correction to a quantum inequality with an arbitrary sampling function, using general results of Fewster and Smith. For an arbitrary potential, we give bounds on the correction in terms of the maximum values of the potential and its first three derivatives. The techniques we develop here will also be applicable to quantum inequalities in general spacetimes with small curvature, which are necessary to rule out exotic phenomena. |
1010.1123 | Joan Josep Ferrando | Joan J. Ferrando and Juan A. S\'aez | Obtaining the Weyl tensor from the Bel-Robinson tensor | 21 pages | Gen.Rel.Grav.42: 1469-1490,2010 | 10.1007/s10714-009-0921-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The algebraic study of the Bel-Robinson tensor proposed and initiated in a
previous work (Gen. Relativ. Gravit. {\bf 41}, see ref [11]) is achieved. The
canonical form of the different algebraic types is obtained in terms of
Bel-Robinson eigen-tensors. An algorithmic determination of the Weyl tensor
from the Bel-Robinson tensor is presented.
| [
{
"created": "Wed, 6 Oct 2010 11:11:39 GMT",
"version": "v1"
}
] | 2011-01-13 | [
[
"Ferrando",
"Joan J.",
""
],
[
"Sáez",
"Juan A.",
""
]
] | The algebraic study of the Bel-Robinson tensor proposed and initiated in a previous work (Gen. Relativ. Gravit. {\bf 41}, see ref [11]) is achieved. The canonical form of the different algebraic types is obtained in terms of Bel-Robinson eigen-tensors. An algorithmic determination of the Weyl tensor from the Bel-Robinson tensor is presented. |
gr-qc/0304024 | David R. Fiske | David R. Fiske (University of Maryland) | Toward Making the Constraint Hypersurface an Attractor in Free Evolution | 6 pages, 3 figures, 1 table. Uses REVTeX4 | Phys.Rev. D69 (2004) 047501 | 10.1103/PhysRevD.69.047501 | null | gr-qc physics.comp-ph | null | There is an abundance of empirical evidence in the numerical relativity
literature that the form in which the Einstein evolution equations are written
plays a significant role in the lifetime of numerical simulations. This paper
attempts to present a consistent framework for modifying any system of
evolution equations by adding terms that push the evolution toward the
constraint hypersurface. The method is, in principle, applicable to any system
of partial differential equations which can be divided into evolution equations
and constraints, although it is only demonstrated here through an application
to the Maxwell equations.
| [
{
"created": "Fri, 4 Apr 2003 20:57:26 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Fiske",
"David R.",
"",
"University of Maryland"
]
] | There is an abundance of empirical evidence in the numerical relativity literature that the form in which the Einstein evolution equations are written plays a significant role in the lifetime of numerical simulations. This paper attempts to present a consistent framework for modifying any system of evolution equations by adding terms that push the evolution toward the constraint hypersurface. The method is, in principle, applicable to any system of partial differential equations which can be divided into evolution equations and constraints, although it is only demonstrated here through an application to the Maxwell equations. |
gr-qc/9506022 | Larry Kidder | Lawrence E. Kidder | Coalescing binary systems of compact objects to (post)$^{5/2}-Newtonian
order. V. Spin Effects | 60 pages, revtex 3.0, 16 figures available upon request, to appear in
Physical Review D | Phys.Rev. D52 (1995) 821-847 | 10.1103/PhysRevD.52.821 | WUGRAV-94-6, NU-GR-11 | gr-qc | null | We examine the effects of spin-orbit and spin-spin coupling on the inspiral
of a coalescing binary system of spinning compact objects and on the
gravitational radiation emitted therefrom. Using a formalism developed by
Blanchet, Damour, and Iyer, we calculate the contributions due to the spins of
the bodies to the symmetric trace-free radiative multipole moments which are
used to calculate the waveform, energy loss, and angular momentum loss from the
inspiralling binary. Using equations of motion which include terms due to
spin-orbit and spin-spin coupling, we evolve the orbit of a coalescing binary
and use the orbit to calculate the emitted gravitational waveform. We find the
spins of the bodies affect the waveform in several ways: 1) The spin terms
contribute to the orbital decay of the binary, and thus to the accumulated
phase of the gravitational waveform. 2) The spins cause the orbital plane to
precess, which changes the orientation of the orbital plane with respect to an
observer, thus causing the shape of the waveform to be modulated. 3) The spins
contribute directly to the amplitude of the waveform. We discuss the size and
importance of spin effects for the case of two coalescing neutron stars, and
for the case of a neutron star orbiting a rapidly rotating $10M_\odot$ black
hole.
| [
{
"created": "Thu, 8 Jun 1995 20:24:19 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Kidder",
"Lawrence E.",
""
]
] | We examine the effects of spin-orbit and spin-spin coupling on the inspiral of a coalescing binary system of spinning compact objects and on the gravitational radiation emitted therefrom. Using a formalism developed by Blanchet, Damour, and Iyer, we calculate the contributions due to the spins of the bodies to the symmetric trace-free radiative multipole moments which are used to calculate the waveform, energy loss, and angular momentum loss from the inspiralling binary. Using equations of motion which include terms due to spin-orbit and spin-spin coupling, we evolve the orbit of a coalescing binary and use the orbit to calculate the emitted gravitational waveform. We find the spins of the bodies affect the waveform in several ways: 1) The spin terms contribute to the orbital decay of the binary, and thus to the accumulated phase of the gravitational waveform. 2) The spins cause the orbital plane to precess, which changes the orientation of the orbital plane with respect to an observer, thus causing the shape of the waveform to be modulated. 3) The spins contribute directly to the amplitude of the waveform. We discuss the size and importance of spin effects for the case of two coalescing neutron stars, and for the case of a neutron star orbiting a rapidly rotating $10M_\odot$ black hole. |
1604.04578 | Mauricio Cataldo MC | Mauricio Cataldo, Luis Liempi, Pablo Rodr\'iguez | Static spherically symmetric wormholes with isotropic pressure | 8 pages, 3 figures | Phys. Lett. B 757, 130-135 (2016) | 10.1016/j.physletb.2016.03.057 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study static spherically symmetric wormhole solutions
sustained by matter sources with isotropic pressure. We show that such
spherical wormholes do not exist in the framework of zero-tidal-force
wormholes. On the other hand, it is shown that for the often used power-law
shape function there is no spherically symmetric traversable wormholes
sustained by sources with a linear equation of state $p=\omega \rho$ for the
isotropic pressure, independently of the form of the redshift function
$\phi(r)$. We consider a solution obtained by Tolman at 1939 for describing
static spheres of isotropic fluids, and show that it also may describe wormhole
spacetimes with a power-law redshift function, which leads to a polynomial
shape function, generalizing a power-law shape function, and inducing a solid
angle deficit.
| [
{
"created": "Fri, 15 Apr 2016 17:29:02 GMT",
"version": "v1"
}
] | 2016-05-04 | [
[
"Cataldo",
"Mauricio",
""
],
[
"Liempi",
"Luis",
""
],
[
"Rodríguez",
"Pablo",
""
]
] | In this paper we study static spherically symmetric wormhole solutions sustained by matter sources with isotropic pressure. We show that such spherical wormholes do not exist in the framework of zero-tidal-force wormholes. On the other hand, it is shown that for the often used power-law shape function there is no spherically symmetric traversable wormholes sustained by sources with a linear equation of state $p=\omega \rho$ for the isotropic pressure, independently of the form of the redshift function $\phi(r)$. We consider a solution obtained by Tolman at 1939 for describing static spheres of isotropic fluids, and show that it also may describe wormhole spacetimes with a power-law redshift function, which leads to a polynomial shape function, generalizing a power-law shape function, and inducing a solid angle deficit. |
1907.00799 | Houwen Wu | Kangkai Liang, Peng Wang, Houwen Wu, Mingtao Yang | Phase Structures and Transitions of Born-Infeld Black Holes in a Grand
Canonical Ensemble | 29 pages, 22 figures. arXiv admin note: text overlap with
arXiv:1901.06216 | null | 10.1140/epjc/s10052-020-7750-z | CTP-SCU/2019004 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To make a Born-Infeld (BI) black hole thermally stable, we consider two types
of boundary conditions, i.e., the asymptotically anti-de Sitter (AdS) space and
a Dirichlet wall placed in the asymptotically flat space. The phase structures
and transitions of these two types of BI black holes, namely BI-AdS black holes
and BI black holes in a cavity, are investigated in a grand canonical ensemble,
where the temperature and the potential are fixed. For BI-AdS black holes, the
globally stable phases can be the thermal AdS space. For small values of the
potential, there is a Hawking-Page-like first order phase transition between
the BI-AdS black holes and the thermal-AdS space. However, the phase transition
becomes zeroth order when the values of the potential are large enough. For BI
black holes in a cavity, the globally stable phases can be a naked singularity
or an extremal black hole with the horizon merging with the wall, which both
are on the boundaries of the physical parameter region. The thermal flat space
is never globally preferred. Besides a first order phase transition, there is a
second order phase transition between the globally stable phases. Thus, it
shows that the phase structures and transitions of BI black holes with these
two different boundary conditions have several dissimilarities.
| [
{
"created": "Fri, 28 Jun 2019 16:17:38 GMT",
"version": "v1"
}
] | 2020-03-18 | [
[
"Liang",
"Kangkai",
""
],
[
"Wang",
"Peng",
""
],
[
"Wu",
"Houwen",
""
],
[
"Yang",
"Mingtao",
""
]
] | To make a Born-Infeld (BI) black hole thermally stable, we consider two types of boundary conditions, i.e., the asymptotically anti-de Sitter (AdS) space and a Dirichlet wall placed in the asymptotically flat space. The phase structures and transitions of these two types of BI black holes, namely BI-AdS black holes and BI black holes in a cavity, are investigated in a grand canonical ensemble, where the temperature and the potential are fixed. For BI-AdS black holes, the globally stable phases can be the thermal AdS space. For small values of the potential, there is a Hawking-Page-like first order phase transition between the BI-AdS black holes and the thermal-AdS space. However, the phase transition becomes zeroth order when the values of the potential are large enough. For BI black holes in a cavity, the globally stable phases can be a naked singularity or an extremal black hole with the horizon merging with the wall, which both are on the boundaries of the physical parameter region. The thermal flat space is never globally preferred. Besides a first order phase transition, there is a second order phase transition between the globally stable phases. Thus, it shows that the phase structures and transitions of BI black holes with these two different boundary conditions have several dissimilarities. |
gr-qc/0512105 | Mohammad Vahid Takook | Samad Behroozi, Shahriar Rouhani, Mohammad Vahid Takook and Mohammad
Reza Tanhayi | Conformally invariant wave-equations and massless fields in de Sitter
spacetime | 21 pages, LaTeX, some details added | Phys.Rev.D74:124014,2006 | 10.1103/PhysRevD.74.124014 | null | gr-qc | null | Conformally invariant wave equations in de Sitter space, for scalar and
vector fields, are introduced in the present paper. Solutions of their wave
equations and the related two-point functions, in the ambient space notation,
have been calculated. The ``Hilbert'' space structure and the field operator,
in terms of coordinate independent de Sitter plane waves, have been defined.
The construction of the paper is based on the analyticity in the complexified
pseudo-Riemanian manifold, presented first by Bros et al.. Minkowskian limits
of these functions are analyzed. The relation between the ambient space
notation and the intrinsic coordinates is then studied in the final stage.
| [
{
"created": "Mon, 19 Dec 2005 13:17:54 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Dec 2006 11:21:32 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Behroozi",
"Samad",
""
],
[
"Rouhani",
"Shahriar",
""
],
[
"Takook",
"Mohammad Vahid",
""
],
[
"Tanhayi",
"Mohammad Reza",
""
]
] | Conformally invariant wave equations in de Sitter space, for scalar and vector fields, are introduced in the present paper. Solutions of their wave equations and the related two-point functions, in the ambient space notation, have been calculated. The ``Hilbert'' space structure and the field operator, in terms of coordinate independent de Sitter plane waves, have been defined. The construction of the paper is based on the analyticity in the complexified pseudo-Riemanian manifold, presented first by Bros et al.. Minkowskian limits of these functions are analyzed. The relation between the ambient space notation and the intrinsic coordinates is then studied in the final stage. |
1802.03288 | Roberto De Pietri | Roberto De Pietri, Alessandra Feo, Jos\'e A. Font, Frank L\"offler,
Francesco Maione, Michele Pasquali and Nikolaos Stergioulas | Convective Excitation of Inertial Modes in Binary Neutron Star Mergers | 6 pages, 4 figures | Phys. Rev. Lett. 120, 221101 (2018) | 10.1103/PhysRevLett.120.221101 | LIGO-P1800025 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the first very long-term simulations (extending up to ~140 ms
after merger) of binary neutron star mergers with piecewise polytropic
equations of state and in full general relativity. Our simulations reveal that
at a time of 30-50 ms after merger, parts of the star become convectively
unstable, which triggers the excitation of inertial modes. The excited inertial
modes are sustained up to several tens of milliseconds and are potentially
observable by the planned third-generation gravitational-wave detectors at
frequencies of a few kilohertz. Since inertial modes depend on the rotation
rate of the star and they are triggered by a convective instability in the
postmerger remnant, their detection in gravitational waves will provide a
unique opportunity to probe the rotational and thermal state of the merger
remnant. In addition, our findings have implications for the long-term
evolution and stability of binary neutron star remnants
| [
{
"created": "Fri, 9 Feb 2018 14:50:10 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Jul 2018 08:12:07 GMT",
"version": "v2"
}
] | 2018-07-04 | [
[
"De Pietri",
"Roberto",
""
],
[
"Feo",
"Alessandra",
""
],
[
"Font",
"José A.",
""
],
[
"Löffler",
"Frank",
""
],
[
"Maione",
"Francesco",
""
],
[
"Pasquali",
"Michele",
""
],
[
"Stergioulas",
"Nikolaos",
"... | We present the first very long-term simulations (extending up to ~140 ms after merger) of binary neutron star mergers with piecewise polytropic equations of state and in full general relativity. Our simulations reveal that at a time of 30-50 ms after merger, parts of the star become convectively unstable, which triggers the excitation of inertial modes. The excited inertial modes are sustained up to several tens of milliseconds and are potentially observable by the planned third-generation gravitational-wave detectors at frequencies of a few kilohertz. Since inertial modes depend on the rotation rate of the star and they are triggered by a convective instability in the postmerger remnant, their detection in gravitational waves will provide a unique opportunity to probe the rotational and thermal state of the merger remnant. In addition, our findings have implications for the long-term evolution and stability of binary neutron star remnants |
gr-qc/9602003 | Jorma Louko | Jorma Louko and Stephen N. Winters-Hilt | Hamiltonian thermodynamics of the Reissner-Nordstr\"om-anti-de Sitter
black hole | 34 pages, REVTeX v3.0. (Minor corrections and presentational
revisions; added references.) | Phys.Rev.D54:2647-2663,1996 | 10.1103/PhysRevD.54.2647 | PP96--63, WISC--MILW--96--TH--11 | gr-qc hep-th | null | We consider the Hamiltonian dynamics and thermodynamics of spherically
symmetric Einstein-Maxwell spacetimes with a negative cosmological constant. We
impose boundary conditions that enforce every classical solution to be an
exterior region of a Reissner-Nordstr\"om-anti-de Sitter black hole with a
nondegenerate Killing horizon, with the spacelike hypersurfaces extending from
the horizon bifurcation two-sphere to the asymptotically anti-de Sitter
infinity. The constraints are simplified by a canonical transformation, which
generalizes that given by Kucha\v{r} in the spherically symmetric vacuum
Einstein theory, and the theory is reduced to its true dynamical degrees of
freedom. After quantization, the grand partition function of a thermodynamical
grand canonical ensemble is obtained by analytically continuing the Lorentzian
time evolution operator to imaginary time and taking the trace. A~similar
analysis under slightly modified boundary conditions leads to the partition
function of a thermodynamical canonical ensemble. The thermodynamics in each
ensemble is analyzed, and the conditions that the (grand) partition function be
dominated by a classical Euclidean black hole solution are found. When these
conditions are satisfied, we recover in particular the Bekenstein-Hawking
entropy. The limit of a vanishing cosmological constant is briefly discussed.
(This paper is dedicated to Karel Kucha\v{r} on the occasion of his sixtieth
birthday.)
| [
{
"created": "Fri, 2 Feb 1996 00:09:56 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Sep 1996 16:13:08 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Louko",
"Jorma",
""
],
[
"Winters-Hilt",
"Stephen N.",
""
]
] | We consider the Hamiltonian dynamics and thermodynamics of spherically symmetric Einstein-Maxwell spacetimes with a negative cosmological constant. We impose boundary conditions that enforce every classical solution to be an exterior region of a Reissner-Nordstr\"om-anti-de Sitter black hole with a nondegenerate Killing horizon, with the spacelike hypersurfaces extending from the horizon bifurcation two-sphere to the asymptotically anti-de Sitter infinity. The constraints are simplified by a canonical transformation, which generalizes that given by Kucha\v{r} in the spherically symmetric vacuum Einstein theory, and the theory is reduced to its true dynamical degrees of freedom. After quantization, the grand partition function of a thermodynamical grand canonical ensemble is obtained by analytically continuing the Lorentzian time evolution operator to imaginary time and taking the trace. A~similar analysis under slightly modified boundary conditions leads to the partition function of a thermodynamical canonical ensemble. The thermodynamics in each ensemble is analyzed, and the conditions that the (grand) partition function be dominated by a classical Euclidean black hole solution are found. When these conditions are satisfied, we recover in particular the Bekenstein-Hawking entropy. The limit of a vanishing cosmological constant is briefly discussed. (This paper is dedicated to Karel Kucha\v{r} on the occasion of his sixtieth birthday.) |
1807.04156 | Christopher Hilweg | Robert Beig, Piotr T. Chru\'sciel, Christopher Hilweg, Philipp
Kornreich and Philip Walther | Weakly gravitating isotropic waveguides | 35 pages, 1 figure | Class. Quantum Grav. 35 244001 (2018) | 10.1088/1361-6382/aae873 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyse the effect of post-Newtonian gravitational fields on propagation
of light in a cylindrical waveguide in both a straight configuration and a
spool configuration. We derive an equation for the dependence of the wave
vector upon the vertical location of the waveguide. It is shown that the
gravitational field produces a small shift in the wave vector, which we
determine, while the spooling creates additional modes which could perhaps be
measurable in future accurate experiments.
| [
{
"created": "Wed, 11 Jul 2018 14:30:26 GMT",
"version": "v1"
}
] | 2022-10-03 | [
[
"Beig",
"Robert",
""
],
[
"Chruściel",
"Piotr T.",
""
],
[
"Hilweg",
"Christopher",
""
],
[
"Kornreich",
"Philipp",
""
],
[
"Walther",
"Philip",
""
]
] | We analyse the effect of post-Newtonian gravitational fields on propagation of light in a cylindrical waveguide in both a straight configuration and a spool configuration. We derive an equation for the dependence of the wave vector upon the vertical location of the waveguide. It is shown that the gravitational field produces a small shift in the wave vector, which we determine, while the spooling creates additional modes which could perhaps be measurable in future accurate experiments. |
1701.02645 | Piotr Jaranowski | Thibault Damour and Piotr Jaranowski | On the four-loop static contribution to the gravitational interaction
potential of two point masses | 19 pages, 10 figures | Phys. Rev. D 95, 084005 (2017) | 10.1103/PhysRevD.95.084005 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute a subset of three, velocity-independent four-loop (and fourth
post-Newtonian) contributions to the harmonic-coordinates effective action of a
gravitationally interacting system of two point-masses. We find that, after
summing the three terms, the coefficient of the total contribution is rational,
due to a remarkable cancellation between the various occurrences of $\pi^2$.
This result, obtained by a classical field-theory calculation, corrects the
recent effective-field-theory-based calculation by Foffa et al.
[arXiv:1612.00482]. Besides showing the usefulness of the saddle-point approach
to the evaluation of the effective action, and of x-space computations, our
result brings a further confirmation of the current knowledge of the fourth
post-Newtonian effective action. We also show how the use of the generalized
Riesz formula [Phys. Rev. D 57, 7274 (1998)] allows one to analytically compute
a certain four-loop scalar master integral (represented by a four-spoked wheel
diagram) which was, so far, only numerically computed.
| [
{
"created": "Tue, 10 Jan 2017 15:46:14 GMT",
"version": "v1"
}
] | 2017-04-12 | [
[
"Damour",
"Thibault",
""
],
[
"Jaranowski",
"Piotr",
""
]
] | We compute a subset of three, velocity-independent four-loop (and fourth post-Newtonian) contributions to the harmonic-coordinates effective action of a gravitationally interacting system of two point-masses. We find that, after summing the three terms, the coefficient of the total contribution is rational, due to a remarkable cancellation between the various occurrences of $\pi^2$. This result, obtained by a classical field-theory calculation, corrects the recent effective-field-theory-based calculation by Foffa et al. [arXiv:1612.00482]. Besides showing the usefulness of the saddle-point approach to the evaluation of the effective action, and of x-space computations, our result brings a further confirmation of the current knowledge of the fourth post-Newtonian effective action. We also show how the use of the generalized Riesz formula [Phys. Rev. D 57, 7274 (1998)] allows one to analytically compute a certain four-loop scalar master integral (represented by a four-spoked wheel diagram) which was, so far, only numerically computed. |
2102.02239 | Vasilis Oikonomou | S.D. Odintsov, V.K. Oikonomou, F.P. Fronimos | Late-Time Cosmology of Scalar-Coupled $f(R, \mathcal{G})$ Gravity | CQG Accepted, abstract reduced due to arXiv limitations | null | 10.1088/1361-6382/abe24f | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work by using a numerical analysis, we investigate in a quantitative
way the late-time dynamics of scalar coupled $f(R,\mathcal{G})$ gravity.
Particularly, we consider a Gauss-Bonnet term coupled to the scalar field
coupling function $\xi(\phi)$, and we study three types of models, one with
$f(R)$ terms that are known to provide a viable late-time phenomenology, and
two Einstein-Gauss-Bonnet types of models. Our aim is to write the Friedmann
equation in terms of appropriate statefinder quantities frequently used in the
literature, and we numerically solve it by using physically motivated initial
conditions. In the case that $f(R)$ gravity terms are present, the contribution
of the Gauss-Bonnet related terms is minor, as we actually expected. This
result is robust against changes in the initial conditions of the scalar field,
and the reason is the dominating parts of the $f(R)$ gravity sector at late
times. In the Einstein-Gauss-Bonnet type of models, we examine two distinct
scenarios, firstly by choosing freely the scalar potential and the scalar
Gauss-Bonnet coupling $\xi(\phi)$, in which case the resulting phenomenology is
compatible with the latest Planck data and mimics the
$\Lambda$-Cold-Dark-Matter model. In the second case, since there is no
fundamental particle physics reason for the graviton to change its mass, we
assume that primordially the tensor perturbations propagate with the speed
equal to that of light's, and thus this constraint restricts the functional
form of the scalar coupling function $\xi(\phi)$, which must satisfy the
differential equation $\ddot{\xi}=H\dot{\xi}$.
| [
{
"created": "Wed, 3 Feb 2021 19:20:15 GMT",
"version": "v1"
}
] | 2022-07-27 | [
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
],
[
"Fronimos",
"F. P.",
""
]
] | In this work by using a numerical analysis, we investigate in a quantitative way the late-time dynamics of scalar coupled $f(R,\mathcal{G})$ gravity. Particularly, we consider a Gauss-Bonnet term coupled to the scalar field coupling function $\xi(\phi)$, and we study three types of models, one with $f(R)$ terms that are known to provide a viable late-time phenomenology, and two Einstein-Gauss-Bonnet types of models. Our aim is to write the Friedmann equation in terms of appropriate statefinder quantities frequently used in the literature, and we numerically solve it by using physically motivated initial conditions. In the case that $f(R)$ gravity terms are present, the contribution of the Gauss-Bonnet related terms is minor, as we actually expected. This result is robust against changes in the initial conditions of the scalar field, and the reason is the dominating parts of the $f(R)$ gravity sector at late times. In the Einstein-Gauss-Bonnet type of models, we examine two distinct scenarios, firstly by choosing freely the scalar potential and the scalar Gauss-Bonnet coupling $\xi(\phi)$, in which case the resulting phenomenology is compatible with the latest Planck data and mimics the $\Lambda$-Cold-Dark-Matter model. In the second case, since there is no fundamental particle physics reason for the graviton to change its mass, we assume that primordially the tensor perturbations propagate with the speed equal to that of light's, and thus this constraint restricts the functional form of the scalar coupling function $\xi(\phi)$, which must satisfy the differential equation $\ddot{\xi}=H\dot{\xi}$. |
2301.12107 | Himanshu Chaudhary | Himanshu Chaudhary, Amine Bouali, Ujjal Debnath, Tanusree Roy,
G.Mustafa | Constraints on the Parameterized Deceleration Parameter in FLRW Universe | 16 pages, 24 figures, accepted for publication in physica scripta | null | 10.1088/1402-4896/acea02 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Confirmation of accelerated expansion of the universe probed the concept of
dark energy theory, and since then, numerous models have been introduced to
explain its origin and nature. The present work is based on reconstructing dark
energy by parametrization of the deceleration parameter in the FRW universe
filled with radiation, dark matter, and dark energy. We have chosen some
well-motivated parametrized models 1-3 in an attempt to investigate the energy
density in terms of deceleration parameters by estimating the cosmological
parameters with the help of different observational datasets. Also, we have
introduced a new model 4 for the parametrization of the deceleration parameter.
Then we analyzed the cosmography parameters using the best-fit values of the
parameters. Using the information criteria, we have examined the viability of
the models.
| [
{
"created": "Sat, 28 Jan 2023 06:33:50 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Sep 2023 19:42:42 GMT",
"version": "v2"
},
{
"created": "Fri, 6 Oct 2023 07:48:35 GMT",
"version": "v3"
}
] | 2023-10-09 | [
[
"Chaudhary",
"Himanshu",
""
],
[
"Bouali",
"Amine",
""
],
[
"Debnath",
"Ujjal",
""
],
[
"Roy",
"Tanusree",
""
],
[
"Mustafa",
"G.",
""
]
] | Confirmation of accelerated expansion of the universe probed the concept of dark energy theory, and since then, numerous models have been introduced to explain its origin and nature. The present work is based on reconstructing dark energy by parametrization of the deceleration parameter in the FRW universe filled with radiation, dark matter, and dark energy. We have chosen some well-motivated parametrized models 1-3 in an attempt to investigate the energy density in terms of deceleration parameters by estimating the cosmological parameters with the help of different observational datasets. Also, we have introduced a new model 4 for the parametrization of the deceleration parameter. Then we analyzed the cosmography parameters using the best-fit values of the parameters. Using the information criteria, we have examined the viability of the models. |
0812.1298 | Marcin Kazmierczak | Marcin Ka\'zmierczak | Einstein-Cartan gravity with Holst term and fermions | 11 pages, typos corrected, final version, to appear in Phys. Rev. D | Phys.Rev.D79:064029,2009 | 10.1103/PhysRevD.79.064029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the consequences of the ambiguity of minimal coupling
procedure for Einstein-Cartan gravity with Holst term and fermions. A new
insight is provided into the nature and physical relevance of coupling
procedures considered hitherto in the context of Ashtekar-Barbero-Immirzi
formalism with fermions. The issue of physical effects of the Immirzi parameter
in semi--classical theory is reinvestigated. We argue that the conclusive
answer to the question of its measurability will not be possible until the more
fundamental problem of nonuniqueness of gravity--induced fermion interaction in
Einstein-Cartan theory is solved.
| [
{
"created": "Sat, 6 Dec 2008 17:19:05 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Jan 2009 14:15:42 GMT",
"version": "v2"
},
{
"created": "Wed, 25 Feb 2009 18:57:24 GMT",
"version": "v3"
},
{
"created": "Wed, 25 Mar 2009 17:23:24 GMT",
"version": "v4"
}
] | 2009-12-11 | [
[
"Kaźmierczak",
"Marcin",
""
]
] | We investigate the consequences of the ambiguity of minimal coupling procedure for Einstein-Cartan gravity with Holst term and fermions. A new insight is provided into the nature and physical relevance of coupling procedures considered hitherto in the context of Ashtekar-Barbero-Immirzi formalism with fermions. The issue of physical effects of the Immirzi parameter in semi--classical theory is reinvestigated. We argue that the conclusive answer to the question of its measurability will not be possible until the more fundamental problem of nonuniqueness of gravity--induced fermion interaction in Einstein-Cartan theory is solved. |
2112.09154 | Damianos Iosifidis | Damianos Iosifidis | The Full Quadratic Metric-Affine Gravity (Including Parity Odd Terms):
Exact solutions for the Affine-Connection | 20 pages, no figures. arXiv admin note: text overlap with
arXiv:2109.13293 | null | 10.1088/1361-6382/ac6058 | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | We consider the most general Quadratic Metric-Affine Gravity setup in the
presence of generic matter sources with non-vanishing hypermomentum. The
gravitational action consists of all $17$ quadratic invariants (both parity
even and odd) in torsion and non-metricity as well as their mixings, along with
the terms that are linear in the curvature namely the Ricci scalar and the
totally antisymmetric Riemann piece. Adding also a matter sector to the latter
we first obtain the field equations for the generalized quadratic Theory. Then,
using a recent Theorem, we successfully find the exact form of the affine
connection under some quite general non-degeneracy conditions. Having obtained
the exact and unique solution of the affine connection we subsequently derive
the closed forms of spacetime torsion and non-metricity and also recast the
metric field equations into a GR form with modified source terms that are
quadratic in the hypermomentum and linear in its derivatives. We also study the
vacuum quadratic Theory and prove that in this instance, or more generally for
vanishing hypermomentum, the connection becomes the Levi-Civita one. Therefore,
we also find exactly to what does the quadratic vacuum Theory correspond to.
Finally, we generalize our result even further and also discuss the physical
consequences and applications of our study.
| [
{
"created": "Thu, 16 Dec 2021 19:01:46 GMT",
"version": "v1"
}
] | 2022-05-18 | [
[
"Iosifidis",
"Damianos",
""
]
] | We consider the most general Quadratic Metric-Affine Gravity setup in the presence of generic matter sources with non-vanishing hypermomentum. The gravitational action consists of all $17$ quadratic invariants (both parity even and odd) in torsion and non-metricity as well as their mixings, along with the terms that are linear in the curvature namely the Ricci scalar and the totally antisymmetric Riemann piece. Adding also a matter sector to the latter we first obtain the field equations for the generalized quadratic Theory. Then, using a recent Theorem, we successfully find the exact form of the affine connection under some quite general non-degeneracy conditions. Having obtained the exact and unique solution of the affine connection we subsequently derive the closed forms of spacetime torsion and non-metricity and also recast the metric field equations into a GR form with modified source terms that are quadratic in the hypermomentum and linear in its derivatives. We also study the vacuum quadratic Theory and prove that in this instance, or more generally for vanishing hypermomentum, the connection becomes the Levi-Civita one. Therefore, we also find exactly to what does the quadratic vacuum Theory correspond to. Finally, we generalize our result even further and also discuss the physical consequences and applications of our study. |
gr-qc/0406111 | Josep Llosa | Josep Llosa and Daniel Soler | On the degrees of freedom of a semi-Riemannian metric | null | Class.Quant.Grav. 22 (2005) 893-908 | 10.1088/0264-9381/22/5/009 | LFM-04-03 | gr-qc | null | A semi-Riemannian metric in a n-manifold has n(n-1)/2 degrees of freedom,
i.e. as many as the number of components of a differential 2-form. We prove
that any semi-Riemannian metric can be obtained as a deformation of a constant
curvature metric, this deformation being parametrized by a 2-form
| [
{
"created": "Mon, 28 Jun 2004 09:59:18 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Llosa",
"Josep",
""
],
[
"Soler",
"Daniel",
""
]
] | A semi-Riemannian metric in a n-manifold has n(n-1)/2 degrees of freedom, i.e. as many as the number of components of a differential 2-form. We prove that any semi-Riemannian metric can be obtained as a deformation of a constant curvature metric, this deformation being parametrized by a 2-form |
2112.02114 | Lorenzo K\"uchler | Geoffrey Comp\`ere and Lorenzo K\"uchler | Asymptotically matched quasi-circular inspiral and transition-to-plunge
in the small mass ratio expansion | Minor changes. 39 pages, 4 ancillary files | SciPost Phys. 13, 043 (2022) | 10.21468/SciPostPhys.13.2.043 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the small mass ratio expansion and on the equatorial plane, the two-body
problem for point particles in general relativity admits a quasi-circular
inspiral motion followed by a transition-to-plunge motion. We first derive the
equations governing the quasi-circular inspiral in the Kerr background at
adiabatic, post-adiabatic and post-post-adiabatic orders in the slow-timescale
expansion in terms of the self-force and we highlight the structure of the
equations of motion at higher subleading orders. We derive in parallel the
equations governing the transition-to-plunge motion to any subleading order,
and demonstrate that they are governed by sourced linearized Painlev\'e
transcendental equations of the first kind. The first ten perturbative orders
do not require any further developments in self-force theory, as they are
determined by the second-order self-force. We propose a scheme that matches the
slow-timescale expansion of the inspiral with the transition-to-plunge motion
to all perturbative orders in the overlapping region exterior to the last
stable orbit where both expansions are valid. We explicitly verify the validity
of the matching conditions for a large set of coefficients involved, on the one
hand, in the adiabatic or post-adiabatic inspiral and, on the other hand, in
the leading, subleading or higher subleading transition-to-plunge motion. This
result is instrumental for deriving gravitational waveforms within the
self-force formalism beyond the innermost stable circular orbit.
| [
{
"created": "Fri, 3 Dec 2021 19:00:10 GMT",
"version": "v1"
},
{
"created": "Sun, 1 May 2022 12:31:10 GMT",
"version": "v2"
},
{
"created": "Tue, 10 May 2022 13:55:13 GMT",
"version": "v3"
},
{
"created": "Mon, 16 May 2022 08:27:21 GMT",
"version": "v4"
}
] | 2022-08-31 | [
[
"Compère",
"Geoffrey",
""
],
[
"Küchler",
"Lorenzo",
""
]
] | In the small mass ratio expansion and on the equatorial plane, the two-body problem for point particles in general relativity admits a quasi-circular inspiral motion followed by a transition-to-plunge motion. We first derive the equations governing the quasi-circular inspiral in the Kerr background at adiabatic, post-adiabatic and post-post-adiabatic orders in the slow-timescale expansion in terms of the self-force and we highlight the structure of the equations of motion at higher subleading orders. We derive in parallel the equations governing the transition-to-plunge motion to any subleading order, and demonstrate that they are governed by sourced linearized Painlev\'e transcendental equations of the first kind. The first ten perturbative orders do not require any further developments in self-force theory, as they are determined by the second-order self-force. We propose a scheme that matches the slow-timescale expansion of the inspiral with the transition-to-plunge motion to all perturbative orders in the overlapping region exterior to the last stable orbit where both expansions are valid. We explicitly verify the validity of the matching conditions for a large set of coefficients involved, on the one hand, in the adiabatic or post-adiabatic inspiral and, on the other hand, in the leading, subleading or higher subleading transition-to-plunge motion. This result is instrumental for deriving gravitational waveforms within the self-force formalism beyond the innermost stable circular orbit. |
gr-qc/0211104 | Edward Malec | Janusz Karkowski and Edward Malec | Gravitational redshifts in electromagnetic bursts occuring near
Schwarzschild horizon | 4 pages, 2 figures. To appear in the Class. Q. Grav | Class.Quant.Grav. 20 (2003) 85-92 | 10.1088/0264-9381/20/1/306 | null | gr-qc hep-th | null | It was suggested earlier that the gravitational redshift formula can be
invalid when the effect of the backscattering is strong. It is demonstrated
here numerically, for an exemplary electromagnetic pulse that is: i) initially
located very close to the horizon of a Schwarzschild black hole and ii)
strongly backscattered, that a mean frequency does not obey the standard
redshift formula. Redshifts appear to depend on the frequency and there
manifests a backscatter-induced blueshift in the outgoing radiation.
| [
{
"created": "Fri, 29 Nov 2002 12:06:41 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Karkowski",
"Janusz",
""
],
[
"Malec",
"Edward",
""
]
] | It was suggested earlier that the gravitational redshift formula can be invalid when the effect of the backscattering is strong. It is demonstrated here numerically, for an exemplary electromagnetic pulse that is: i) initially located very close to the horizon of a Schwarzschild black hole and ii) strongly backscattered, that a mean frequency does not obey the standard redshift formula. Redshifts appear to depend on the frequency and there manifests a backscatter-induced blueshift in the outgoing radiation. |
gr-qc/0605148 | Daniel Grumiller | L. Bergamin and D. Grumiller | Killing horizons kill horizon degrees | 5 pages, received honorable mention in the GRF Essay Contest 2006,
v2: version to be published in IJMPD | Int.J.Mod.Phys.D15:2279-2284,2006 | 10.1142/S0218271806009571 | MIT-CTP/3750 | gr-qc hep-th | null | Frequently it is argued that the microstates responsible for the
Bekenstein-Hawking entropy should arise from some physical degrees of freedom
located near or on the black hole horizon. In this Essay we elucidate that
instead entropy may emerge from the conversion of physical degrees of freedom,
attached to a generic boundary, into unobservable gauge degrees of freedom
attached to the horizon. By constructing the reduced phase space it can be
demonstrated that such a transmutation indeed takes place for a large class of
black holes, including Schwarzschild.
| [
{
"created": "Tue, 30 May 2006 21:20:16 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Nov 2006 15:35:40 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Bergamin",
"L.",
""
],
[
"Grumiller",
"D.",
""
]
] | Frequently it is argued that the microstates responsible for the Bekenstein-Hawking entropy should arise from some physical degrees of freedom located near or on the black hole horizon. In this Essay we elucidate that instead entropy may emerge from the conversion of physical degrees of freedom, attached to a generic boundary, into unobservable gauge degrees of freedom attached to the horizon. By constructing the reduced phase space it can be demonstrated that such a transmutation indeed takes place for a large class of black holes, including Schwarzschild. |
gr-qc/0607143 | Andrea Passamonti | Andrea Passamonti | Non-linear Oscillations of Compact Stars and Gravitational Waves | 172 pages, 32 figures, PhD thesis, University of Portsmouth | null | 10.1088/1742-6596/68/1/012052 | null | gr-qc astro-ph | null | This thesis investigates in the time domain a particular class of second
order perturbations of a perfect fluid non-rotating compact star: those arising
from the coupling between first order radial and non-radial perturbations. This
problem has been treated by developing a gauge invariant formalism based on the
2-parameter perturbation theory (Sopuerta, Bruni and Gualtieri, 2004) where the
radial and non-radial perturbations have been separately parameterized. The
non-linear perturbations obey inhomogeneous partial differential equations,
where the structure of the differential operator is given by the previous
perturbative orders and the source terms are quadratic in the first order
perturbations. In the exterior spacetime the sources vanish, thus the
gravitational wave properties are completely described by the second order
Zerilli and Regge-Wheeler functions.
As main initial configuration we have considered a first order differentially
rotating and radially pulsating star. Although at first perturbative order this
configuration does not exhibit any gravitational radiation, we have found a new
interesting gravitational signal at non-linear order, in which the radial
normal modes are precisely mirrored. In addition, a resonance effect is present
when the frequencies of the radial pulsations are close to the first axial
w-mode. Finally, we have roughly estimated the damping times of the radial
pulsations due to the non-linear gravitational emission. The coupling near the
resonance results to be a very effective mechanism for extracting energy from
the radial oscillations.
| [
{
"created": "Mon, 31 Jul 2006 17:29:56 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Passamonti",
"Andrea",
""
]
] | This thesis investigates in the time domain a particular class of second order perturbations of a perfect fluid non-rotating compact star: those arising from the coupling between first order radial and non-radial perturbations. This problem has been treated by developing a gauge invariant formalism based on the 2-parameter perturbation theory (Sopuerta, Bruni and Gualtieri, 2004) where the radial and non-radial perturbations have been separately parameterized. The non-linear perturbations obey inhomogeneous partial differential equations, where the structure of the differential operator is given by the previous perturbative orders and the source terms are quadratic in the first order perturbations. In the exterior spacetime the sources vanish, thus the gravitational wave properties are completely described by the second order Zerilli and Regge-Wheeler functions. As main initial configuration we have considered a first order differentially rotating and radially pulsating star. Although at first perturbative order this configuration does not exhibit any gravitational radiation, we have found a new interesting gravitational signal at non-linear order, in which the radial normal modes are precisely mirrored. In addition, a resonance effect is present when the frequencies of the radial pulsations are close to the first axial w-mode. Finally, we have roughly estimated the damping times of the radial pulsations due to the non-linear gravitational emission. The coupling near the resonance results to be a very effective mechanism for extracting energy from the radial oscillations. |
2208.03932 | Andres Vargas-Sanchez Mr | Andr\'es F. Vargas, Andrew Melatos | Search for continuous gravitational waves from PSR J0437$-$4715 with a
hidden Markov model in O3 LIGO data | null | Phys. Rev. D 107 (2022) 064062 | 10.1103/PhysRevD.107.064062 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Results are presented for a semi-coherent search for continuous gravitational
waves from the millisecond pulsar PSR J0437$-$4715, using a hidden Markov model
to track spin wandering, in LIGO data from the third LIGO-Virgo observing run.
This is the first search for PSR J0437$-$4715 to cover a wide frequency range
from $60$ Hz to $500$ Hz and simultanously accommodate random spin deviations
from the secular radio ephemeris. Two searches are performed with plausible
coherence times of $10$ days and $30$ days, as the frequency wandering
time-scale of the gravitational-wave-emitting quadrupole is unknown. The former
analysis yields no surviving candidates, while the latter yields five
candidates after the veto procedure. The detection statistic of each of the
five survivors is mapped as a function of sky position, in preparation for
follow-up analyses in the future, e.g. during LIGO-Virgo-KAGRA fourth observing
run.
| [
{
"created": "Mon, 8 Aug 2022 06:19:15 GMT",
"version": "v1"
}
] | 2023-05-17 | [
[
"Vargas",
"Andrés F.",
""
],
[
"Melatos",
"Andrew",
""
]
] | Results are presented for a semi-coherent search for continuous gravitational waves from the millisecond pulsar PSR J0437$-$4715, using a hidden Markov model to track spin wandering, in LIGO data from the third LIGO-Virgo observing run. This is the first search for PSR J0437$-$4715 to cover a wide frequency range from $60$ Hz to $500$ Hz and simultanously accommodate random spin deviations from the secular radio ephemeris. Two searches are performed with plausible coherence times of $10$ days and $30$ days, as the frequency wandering time-scale of the gravitational-wave-emitting quadrupole is unknown. The former analysis yields no surviving candidates, while the latter yields five candidates after the veto procedure. The detection statistic of each of the five survivors is mapped as a function of sky position, in preparation for follow-up analyses in the future, e.g. during LIGO-Virgo-KAGRA fourth observing run. |
2407.04666 | Daniela Magos | Mauricio Bellini, Juan Ignacio Musmarra and Daniela Magos | Geometric Hawking radiation of Schwarzschild Black Hole with novel
quantum algebra | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In the context of an extended General Relativity theory with boundary terms
included, we introduce a new nonlinear quantum algebra involving a quantum
differential operator, with the aim to calculate quantum geometric alterations
when a particle is created in the vicinity of a Schwarzschild black-hole by the
Hawking radiation mechanism. The boundary terms in the varied action give rise
to modifications in the geometric background, which are investigated by
analyzing the metric tensor and the Ricci curvature within the framework of a
renormalized quantum theory of gravity.
| [
{
"created": "Fri, 5 Jul 2024 17:19:45 GMT",
"version": "v1"
}
] | 2024-07-08 | [
[
"Bellini",
"Mauricio",
""
],
[
"Musmarra",
"Juan Ignacio",
""
],
[
"Magos",
"Daniela",
""
]
] | In the context of an extended General Relativity theory with boundary terms included, we introduce a new nonlinear quantum algebra involving a quantum differential operator, with the aim to calculate quantum geometric alterations when a particle is created in the vicinity of a Schwarzschild black-hole by the Hawking radiation mechanism. The boundary terms in the varied action give rise to modifications in the geometric background, which are investigated by analyzing the metric tensor and the Ricci curvature within the framework of a renormalized quantum theory of gravity. |
gr-qc/0512062 | W. F. Kao | W.F. Kao | Modified Newtonian Dynamics and Induced gravity | 8 pages, typo corrected | null | null | null | gr-qc astro-ph | null | Modified Newtonian dynamics, a successful alternative to the cosmic dark
matter model, proposes that gravitational field deviates from the Newtonian law
when the field strength $g$ is weaker than a critical value $g_0$. We will show
that the dynamics of MOND can be derived from an induced gravity model. New
dynamics is shown to be compatible with the spatial deformation of scalar
fields coupled to the system. Approximate solutions are shown explicitly for a
simple toy model.
| [
{
"created": "Sun, 11 Dec 2005 10:06:04 GMT",
"version": "v1"
},
{
"created": "Mon, 29 May 2006 19:58:49 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Kao",
"W. F.",
""
]
] | Modified Newtonian dynamics, a successful alternative to the cosmic dark matter model, proposes that gravitational field deviates from the Newtonian law when the field strength $g$ is weaker than a critical value $g_0$. We will show that the dynamics of MOND can be derived from an induced gravity model. New dynamics is shown to be compatible with the spatial deformation of scalar fields coupled to the system. Approximate solutions are shown explicitly for a simple toy model. |
gr-qc/0506132 | Christodoulakis Theodosios | T. Christodoulakis, Th. Grammenos, Ch. Helias, P.G. Kevrekidis, A.
Spanou | Decoupling of the general scalar field mode and the solution space for
Bianchi type I and V cosmologies coupled to perfect fluid sources | latex2e source file,14 pages, no figures; (v3): minor corrections, to
appear in J. Math. Phys | J.Math.Phys. 47 (2006) 042505 | 10.1063/1.2188210 | null | gr-qc | null | The scalar field degree of freedom in Einstein's plus Matter field equations
is decoupled for Bianchi type I and V general cosmological models. The source,
apart from the minimally coupled scalar field with arbitrary potential V(Phi),
is provided by a perfect fluid obeying a general equation of state p =p(rho).
The resulting ODE is, by an appropriate choice of final time gauge affiliated
to the scalar field, reduced to 1st order, and then the system is completely
integrated for arbitrary choices of the potential and the equation of state.
| [
{
"created": "Wed, 29 Jun 2005 12:13:55 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Oct 2005 13:05:21 GMT",
"version": "v2"
},
{
"created": "Fri, 24 Feb 2006 11:23:54 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Christodoulakis",
"T.",
""
],
[
"Grammenos",
"Th.",
""
],
[
"Helias",
"Ch.",
""
],
[
"Kevrekidis",
"P. G.",
""
],
[
"Spanou",
"A.",
""
]
] | The scalar field degree of freedom in Einstein's plus Matter field equations is decoupled for Bianchi type I and V general cosmological models. The source, apart from the minimally coupled scalar field with arbitrary potential V(Phi), is provided by a perfect fluid obeying a general equation of state p =p(rho). The resulting ODE is, by an appropriate choice of final time gauge affiliated to the scalar field, reduced to 1st order, and then the system is completely integrated for arbitrary choices of the potential and the equation of state. |
2104.12646 | Kallol Dey | Kallol Dey, Nikolaos Karnesis, Alexandre Toubiana, Enrico Barausse,
Natalia Korsakova, Quentin Baghi and Soumen Basak | Effect of data gaps on the detectability and parameter estimation of
massive black hole binaries with LISA | 25 pages, 14 figures. Matches version published in Physical Review D | Phys. Rev. D 104, 044035 (2021) | 10.1103/PhysRevD.104.044035 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Massive black hole binaries are expected to provide the strongest
gravitational wave signals for the Laser Interferometer Space Antenna (LISA), a
space mission targeting $\sim\,$mHz frequencies. As a result of the
technological challenges inherent in the mission's design, implementation and
long duration (4 yr nominal), the LISA data stream is expected to be affected
by relatively long gaps where no data is collected (either because of hardware
failures, or because of scheduled maintenance operations, such as re-pointing
of the antennas toward the Earth). Depending on their mass, massive black hole
binary signals may range from quasi-transient to very long lived, and it is
unclear how data gaps will impact detection and parameter estimation of these
sources. Here, we will explore this question by using state-of-the-art
astrophysical models for the population of massive black hole binaries. We will
investigate the potential detectability of MBHB signals by observing the effect
of gaps on their signal-to-noise ratios. We will also assess the effect of the
gaps on parameter estimation for these sources, using the Fisher Information
Matrix formalism as well as full Bayesian analyses. Overall, we find that the
effect of data gaps due to regular maintenance of the spacecraft is negligible,
except for systems that coalesce within such a gap. The effect of unscheduled
gaps, however, will probably be more significant than that of scheduled ones.
| [
{
"created": "Mon, 26 Apr 2021 15:16:03 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Aug 2021 17:22:53 GMT",
"version": "v2"
}
] | 2021-08-18 | [
[
"Dey",
"Kallol",
""
],
[
"Karnesis",
"Nikolaos",
""
],
[
"Toubiana",
"Alexandre",
""
],
[
"Barausse",
"Enrico",
""
],
[
"Korsakova",
"Natalia",
""
],
[
"Baghi",
"Quentin",
""
],
[
"Basak",
"Soumen",
""
]
... | Massive black hole binaries are expected to provide the strongest gravitational wave signals for the Laser Interferometer Space Antenna (LISA), a space mission targeting $\sim\,$mHz frequencies. As a result of the technological challenges inherent in the mission's design, implementation and long duration (4 yr nominal), the LISA data stream is expected to be affected by relatively long gaps where no data is collected (either because of hardware failures, or because of scheduled maintenance operations, such as re-pointing of the antennas toward the Earth). Depending on their mass, massive black hole binary signals may range from quasi-transient to very long lived, and it is unclear how data gaps will impact detection and parameter estimation of these sources. Here, we will explore this question by using state-of-the-art astrophysical models for the population of massive black hole binaries. We will investigate the potential detectability of MBHB signals by observing the effect of gaps on their signal-to-noise ratios. We will also assess the effect of the gaps on parameter estimation for these sources, using the Fisher Information Matrix formalism as well as full Bayesian analyses. Overall, we find that the effect of data gaps due to regular maintenance of the spacecraft is negligible, except for systems that coalesce within such a gap. The effect of unscheduled gaps, however, will probably be more significant than that of scheduled ones. |
1207.3361 | Shaon Ghosh | Sukanta Bose, Shaon Ghosh and Ajith Parameswaran | Systematic errors in measuring parameters of non-spinning compact binary
coalescences with post-Newtonian templates | 8 pages, 5 figures | null | 10.1088/0264-9381/27/11/114001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the astrophysical impact of inaccurate and incomplete modeling of
the gravitational waveforms from compact binary coalescences (CBCs). We do so
by the matched filtering of complete inspiral-merger-ringdown (IMR) signals
with a bank of inspiral-phase templates modeled after the 3.5 post-Newtonian
TaylorT1 approximant. The rationale for the choice of the templates is
threefold: (1) The inspiral phase of the Phenomenological signals, which are an
example of complete IMR signals, is modeled on the same TaylorT1 approximant.
(2) In the low-mass limit, where the merger and ringdown phases last much
shorter than the inspiral phase, the errors should tend to vanishingly small
values and, thus, provide an important check on the numerical aspects of our
simulations. (3) Since the binary black hole (BBH) signals are not yet known
for mass-ratios above ten and since signals from CBCs involving neutron stars
are affected by uncertainties in the knowledge of their equation of state,
inspiral templates are still in use in searches for those signals. The results
from our numerical simulations are compared with analytical calculations of the
systematic errors using the Fisher matrix on the template parameter space. We
find that the loss in signal-to-noise ratio (SNR) can be as large as 60% even
for binary black holes with component masses m1 = 13M\odot and m2 = 20M\odot.
Also, the estimated total-mass for the same pair can be off by as much as 20%.
Both of these are worse for some higher-mass combinations. Even the estimation
of the symmetric mass-ratio {\eta} suffers a nearly 20% error for this example,
and can be worse than 50% for the mass ranges studied here. These errors
significantly dominate their statistical counterparts (at a nominal SNR of 10).
It may, however, be possible to mitigate the loss in SNR by allowing for
templates with unphysical values of {\eta}.
| [
{
"created": "Fri, 13 Jul 2012 20:32:20 GMT",
"version": "v1"
}
] | 2012-07-17 | [
[
"Bose",
"Sukanta",
""
],
[
"Ghosh",
"Shaon",
""
],
[
"Parameswaran",
"Ajith",
""
]
] | We study the astrophysical impact of inaccurate and incomplete modeling of the gravitational waveforms from compact binary coalescences (CBCs). We do so by the matched filtering of complete inspiral-merger-ringdown (IMR) signals with a bank of inspiral-phase templates modeled after the 3.5 post-Newtonian TaylorT1 approximant. The rationale for the choice of the templates is threefold: (1) The inspiral phase of the Phenomenological signals, which are an example of complete IMR signals, is modeled on the same TaylorT1 approximant. (2) In the low-mass limit, where the merger and ringdown phases last much shorter than the inspiral phase, the errors should tend to vanishingly small values and, thus, provide an important check on the numerical aspects of our simulations. (3) Since the binary black hole (BBH) signals are not yet known for mass-ratios above ten and since signals from CBCs involving neutron stars are affected by uncertainties in the knowledge of their equation of state, inspiral templates are still in use in searches for those signals. The results from our numerical simulations are compared with analytical calculations of the systematic errors using the Fisher matrix on the template parameter space. We find that the loss in signal-to-noise ratio (SNR) can be as large as 60% even for binary black holes with component masses m1 = 13M\odot and m2 = 20M\odot. Also, the estimated total-mass for the same pair can be off by as much as 20%. Both of these are worse for some higher-mass combinations. Even the estimation of the symmetric mass-ratio {\eta} suffers a nearly 20% error for this example, and can be worse than 50% for the mass ranges studied here. These errors significantly dominate their statistical counterparts (at a nominal SNR of 10). It may, however, be possible to mitigate the loss in SNR by allowing for templates with unphysical values of {\eta}. |
0912.1293 | Patrick Peter | P. Peter (IAP) | Observing alternatives to inflation | 12 pages, no figure, proceedings "Workshop on Cosmic Structure and
Evolution" - Sept. 2009, Bielefeld, Germany | PoS Cosmology2009:003,2009 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the possibility that the inflationary paradigm, undoubtfully
today's best framework to understand all the present cosmological data, may
still have some viable challengers. The underlying idea for such discussions is
that although inflation already passed quite a large number of tests, indeed
enough to make it part of the so-called ``standard model'' of cosmology, it has
always been through indirect measurements: there is not a chance that we may
ever directly check its validity, and therefore, in order to assert its
factuality with increasing level of confidence, it is required that we compare
its predictions not only to observations, but also to as many contenders as
possible. Among other categories of possible models, we wish to put the
emphasis in particular on bouncing cosmologies that, however not as complete as
the inflation paradigm might be, could still represent a reasonnable way of
explaining the current data. Hopefully, future data will be able to
discriminate between these various sets of theories.
| [
{
"created": "Mon, 7 Dec 2009 17:37:48 GMT",
"version": "v1"
}
] | 2010-11-15 | [
[
"Peter",
"P.",
"",
"IAP"
]
] | We discuss the possibility that the inflationary paradigm, undoubtfully today's best framework to understand all the present cosmological data, may still have some viable challengers. The underlying idea for such discussions is that although inflation already passed quite a large number of tests, indeed enough to make it part of the so-called ``standard model'' of cosmology, it has always been through indirect measurements: there is not a chance that we may ever directly check its validity, and therefore, in order to assert its factuality with increasing level of confidence, it is required that we compare its predictions not only to observations, but also to as many contenders as possible. Among other categories of possible models, we wish to put the emphasis in particular on bouncing cosmologies that, however not as complete as the inflation paradigm might be, could still represent a reasonnable way of explaining the current data. Hopefully, future data will be able to discriminate between these various sets of theories. |
1407.2909 | Lee Smolin | Lee Smolin | Linking shape dynamics and loop quantum gravity | 12 pages, no figures, mistake fixed, other small changes | Phys. Rev. D 90, 044070 (2014) | 10.1103/PhysRevD.90.044070 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Shape dynamics is a reformulation of general relativity, locally equivalent
to Einstein's theory, in which the refoliation invariance of the older theory
is traded for local scale invariance. Shape dynamics is here derived in a
formulation related to the Ashtekar variables by beginning with a modification
of the Plebanski action. The constraints of shape dynamics and their algebra
are reproduced in terms of these new variables.
| [
{
"created": "Thu, 10 Jul 2014 19:19:49 GMT",
"version": "v1"
},
{
"created": "Wed, 24 May 2017 19:02:29 GMT",
"version": "v2"
}
] | 2017-05-26 | [
[
"Smolin",
"Lee",
""
]
] | Shape dynamics is a reformulation of general relativity, locally equivalent to Einstein's theory, in which the refoliation invariance of the older theory is traded for local scale invariance. Shape dynamics is here derived in a formulation related to the Ashtekar variables by beginning with a modification of the Plebanski action. The constraints of shape dynamics and their algebra are reproduced in terms of these new variables. |
2305.10481 | Minglei Xiao | Hao-Lin Li, Zhe Ren, Ming-Lei Xiao, Jiang-Hao Yu, Yu-Hui Zheng | On-shell Operator Construction in the Effective Field Theory of Gravity | 128 pages | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct the on-shell amplitude basis and the corresponding effective
operators for generic modified gravity theory, such as pure gravity with higher
derivatives, scalar-tensor gravity, Einstein-Yang-Mills, etc. Taking the Weyl
tensor as the building block, we utilize the Young tensor technique to obtain
independent operators, without equation of motion and total derivative
redundancies. We update our algorithm and vastly increase the speed for finding
the monomial basis (m-basis) of effective operators expressed in terms of Weyl
tensors with Lorentz indices, the familiar form for the General Relativity
community. Finally, we obtain the complete and independent amplitude and
operator basis for GRSMEFT and GRLEFT up to mass dimension 10.
| [
{
"created": "Wed, 17 May 2023 18:00:01 GMT",
"version": "v1"
}
] | 2023-05-23 | [
[
"Li",
"Hao-Lin",
""
],
[
"Ren",
"Zhe",
""
],
[
"Xiao",
"Ming-Lei",
""
],
[
"Yu",
"Jiang-Hao",
""
],
[
"Zheng",
"Yu-Hui",
""
]
] | We construct the on-shell amplitude basis and the corresponding effective operators for generic modified gravity theory, such as pure gravity with higher derivatives, scalar-tensor gravity, Einstein-Yang-Mills, etc. Taking the Weyl tensor as the building block, we utilize the Young tensor technique to obtain independent operators, without equation of motion and total derivative redundancies. We update our algorithm and vastly increase the speed for finding the monomial basis (m-basis) of effective operators expressed in terms of Weyl tensors with Lorentz indices, the familiar form for the General Relativity community. Finally, we obtain the complete and independent amplitude and operator basis for GRSMEFT and GRLEFT up to mass dimension 10. |
1104.4608 | Nathalie Deruelle | Nathalie Deruelle | Nordstrom's scalar theory of gravity and the equivalence principle | null | null | 10.1007/s10714-011-1247-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Nordstrom's theory of gravity, which describes gravity by a scalar field in
flat spacetime, is observationally ruled out. It is however the only theory of
gravity with General Relativity to obey the strong equivalence principle. I
show in this paper that this remarkable property is true beyond post-newtonian
level and can be related to the existence of a 'Nordstrom-Katz' superpotential.
| [
{
"created": "Sun, 24 Apr 2011 07:51:16 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Deruelle",
"Nathalie",
""
]
] | Nordstrom's theory of gravity, which describes gravity by a scalar field in flat spacetime, is observationally ruled out. It is however the only theory of gravity with General Relativity to obey the strong equivalence principle. I show in this paper that this remarkable property is true beyond post-newtonian level and can be related to the existence of a 'Nordstrom-Katz' superpotential. |
1402.1524 | Clifford Chafin | Clifford E Chafin | Globally Causal Solutions for Gravitational Collapse | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Through an illuminating thought experiment we demonstrate that the
nonsingular "continued collapse" picture of a black hole is the only consistent
and physical one. We provide a class exact solutions on the boundary of the
space of physical configurations. This will show that all the other known exact
solutions are unphysical near the surface of the event horizon or in the
interior. This will have important consequences for the no-hair conjecture and
the kinds of persistent fields that can emerge from a black hole as well as the
evolution during collisions and near grazing events. The interior of these
holes are characterized by a limiting degenerate metric and these regions tend
to well defined volumes and radii in contrast with what is inferred from
singular solutions. Surprisingly, these depend on past history and not simply
the mass or external fields of the body. It is shown that there is often a well
defined "hidden" flat background that can be used to equivalently reformulate
GR in terms of a classical nonlinear gravity field and gives local conservation
laws. This has implications for unification efforts and numerical approaches to
handle the degenerate metric regions reminiscent of the Rankine-Hugoniot
conditions. Possible consistency problems with current numerical approaches to
black hole dynamics are discussed.
| [
{
"created": "Thu, 6 Feb 2014 23:15:00 GMT",
"version": "v1"
}
] | 2014-02-10 | [
[
"Chafin",
"Clifford E",
""
]
] | Through an illuminating thought experiment we demonstrate that the nonsingular "continued collapse" picture of a black hole is the only consistent and physical one. We provide a class exact solutions on the boundary of the space of physical configurations. This will show that all the other known exact solutions are unphysical near the surface of the event horizon or in the interior. This will have important consequences for the no-hair conjecture and the kinds of persistent fields that can emerge from a black hole as well as the evolution during collisions and near grazing events. The interior of these holes are characterized by a limiting degenerate metric and these regions tend to well defined volumes and radii in contrast with what is inferred from singular solutions. Surprisingly, these depend on past history and not simply the mass or external fields of the body. It is shown that there is often a well defined "hidden" flat background that can be used to equivalently reformulate GR in terms of a classical nonlinear gravity field and gives local conservation laws. This has implications for unification efforts and numerical approaches to handle the degenerate metric regions reminiscent of the Rankine-Hugoniot conditions. Possible consistency problems with current numerical approaches to black hole dynamics are discussed. |
0705.4147 | Ujjal Debnath | Writambhara Chakraborty, Ujjal Debnath | Effect of Dynamical Cosmological Constant in presence of Modified
Chaplygin Gas for Accelerating Universe | 12 latex pages, 14 figures, revtex style | Astrophys.Space Sci.313:409-417,2008 | 10.1007/s10509-007-9710-6 | null | gr-qc | null | In this paper we have considered the Universe to be filled with Modified Gas
and the Cosmological Constant $\Lambda$ to be time-dependent with or without
the Gravitational Constant $G$ to be time-dependent. We have considered various
phenomenological models for $\Lambda$, viz., $\Lambda\propto\rho,
\Lambda\propto\frac{\dot{a}^{2}}{a^{2}}$ and
$\Lambda\propto\frac{\ddot{a}}{a}$. Using these models it is possible to show
the accelerated expansion of the Universe at the present epoch. Also we have
shown the natures of $G$ and $\Lambda$ over the total age of the Universe.
Using the statefinder parameters we have shown the diagramamtical
representation of the evolution of the Universe starting from radiation era to
$\Lambda$CDM model.
| [
{
"created": "Tue, 29 May 2007 06:24:14 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Chakraborty",
"Writambhara",
""
],
[
"Debnath",
"Ujjal",
""
]
] | In this paper we have considered the Universe to be filled with Modified Gas and the Cosmological Constant $\Lambda$ to be time-dependent with or without the Gravitational Constant $G$ to be time-dependent. We have considered various phenomenological models for $\Lambda$, viz., $\Lambda\propto\rho, \Lambda\propto\frac{\dot{a}^{2}}{a^{2}}$ and $\Lambda\propto\frac{\ddot{a}}{a}$. Using these models it is possible to show the accelerated expansion of the Universe at the present epoch. Also we have shown the natures of $G$ and $\Lambda$ over the total age of the Universe. Using the statefinder parameters we have shown the diagramamtical representation of the evolution of the Universe starting from radiation era to $\Lambda$CDM model. |
1605.03618 | Surajit Chattopadhyay | Surajit Chattopadhyay | Viscous extended holographic Ricci dark energy in the framework of
standard Eckart theory | 18 pages, 12 figures | Mod. Phys. Lett. A, Vol. 31, No. 36 (2016) 1650202 | 10.1142/S0217732316502023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work we report a study on the viscous extended holographic
Ricci dark energy (EHRDE) model under the assumption of existence of bulk
viscosity in the linear barotropic fluid and the EHRDE in the framework of
standard Eckart theory of relativistic irreversible thermodynamics and it has
been observed that the non-equilibrium bulk viscous pressure is significantly
smaller than the local equilibrium pressure. We have studied the equation of
state (EoS) parameter and observed that the EoS behaves like "quintom" and is
consistent with the constraints set by observational data sets from SNLS3, BAO
and Planck + WMAP9 + WiggleZ measurements in the reference S. Kumar and L. Xu,
\emph{Phys. Lett. B},\textbf{737}, 244 (2014). Analysis of statefinder
parameters has shown the possibility of attainment of $\Lambda$CDM phase under
current model and at the same time it has been pointed out that the for $z=0$
i.e. current universe, the statefinder pair is different from that of
$\Lambda$CDM and the $\Lambda$CDM can be attained in a later stage of the
universe. An analysis of stability has shown that although the viscous EHRDE
along with viscous barotropic is classically unstable in the present epoch, it
can lead to a stable universe in very late stage. Considering an universe
enveloped by event horizon we have observed validity of generalized second law
of thermodynamics.
| [
{
"created": "Thu, 5 May 2016 11:13:04 GMT",
"version": "v1"
}
] | 2016-11-03 | [
[
"Chattopadhyay",
"Surajit",
""
]
] | In the present work we report a study on the viscous extended holographic Ricci dark energy (EHRDE) model under the assumption of existence of bulk viscosity in the linear barotropic fluid and the EHRDE in the framework of standard Eckart theory of relativistic irreversible thermodynamics and it has been observed that the non-equilibrium bulk viscous pressure is significantly smaller than the local equilibrium pressure. We have studied the equation of state (EoS) parameter and observed that the EoS behaves like "quintom" and is consistent with the constraints set by observational data sets from SNLS3, BAO and Planck + WMAP9 + WiggleZ measurements in the reference S. Kumar and L. Xu, \emph{Phys. Lett. B},\textbf{737}, 244 (2014). Analysis of statefinder parameters has shown the possibility of attainment of $\Lambda$CDM phase under current model and at the same time it has been pointed out that the for $z=0$ i.e. current universe, the statefinder pair is different from that of $\Lambda$CDM and the $\Lambda$CDM can be attained in a later stage of the universe. An analysis of stability has shown that although the viscous EHRDE along with viscous barotropic is classically unstable in the present epoch, it can lead to a stable universe in very late stage. Considering an universe enveloped by event horizon we have observed validity of generalized second law of thermodynamics. |
2101.12039 | Seyed Hossein Hendi Dr. | Mehrab Momennia and Seyed Hossein Hendi | Critical Phenomena and Reentrant Phase Transition of Asymptotically
Reissner-Nordstrom Black Holes | 10 Page with 5 captioned figures. Submitted for publication | Phys. Lett. B 822 (2021) 136692 | 10.1016/j.physletb.2021.136692 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | By considering a small correction to the Maxwell field, we show that the
resultant black hole solutions (also known as the asymptotically
Reissner--Nordstr\"{o}m black holes) undergo the reentrant phase transition and
can have a novel phase behavior. We also show that such a small nonlinear
correction of the Reissner--Nordstr\"{o}m black holes has high effects on the
phase structure of the solutions. It leads to a new classification in the
canonical ensemble of extended phase space providing the values of the
nonlinearity parameter $\alpha$ being $\alpha \lesseqqgtr 4q^{2}/7$. We shall
study these three classes and investigate deviations from those of the standard
Reissner--Nordstr\"{o}m solutions. Interestingly, we find that there is the
reentrant phase transition for $\alpha <4q^{2}/7$, and for the case of $\alpha
=4q^{2}/7$ there is no phase transition below (at) the critical point. For the
last case, one finds that small and large black holes are thermodynamically
distinguishable for temperatures and pressures higher than the critical ones.
| [
{
"created": "Tue, 26 Jan 2021 21:47:26 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Feb 2021 07:16:49 GMT",
"version": "v2"
}
] | 2022-04-07 | [
[
"Momennia",
"Mehrab",
""
],
[
"Hendi",
"Seyed Hossein",
""
]
] | By considering a small correction to the Maxwell field, we show that the resultant black hole solutions (also known as the asymptotically Reissner--Nordstr\"{o}m black holes) undergo the reentrant phase transition and can have a novel phase behavior. We also show that such a small nonlinear correction of the Reissner--Nordstr\"{o}m black holes has high effects on the phase structure of the solutions. It leads to a new classification in the canonical ensemble of extended phase space providing the values of the nonlinearity parameter $\alpha$ being $\alpha \lesseqqgtr 4q^{2}/7$. We shall study these three classes and investigate deviations from those of the standard Reissner--Nordstr\"{o}m solutions. Interestingly, we find that there is the reentrant phase transition for $\alpha <4q^{2}/7$, and for the case of $\alpha =4q^{2}/7$ there is no phase transition below (at) the critical point. For the last case, one finds that small and large black holes are thermodynamically distinguishable for temperatures and pressures higher than the critical ones. |
gr-qc/9612060 | Neil John Cornish | Neil Cornish and Gary Gibbons (DAMTP Cambridge) | The tale of two centres | 20 pages, RevTeX, 7 figures included, TeX format changed | Class.Quant.Grav.14:1865-1881,1997 | 10.1088/0264-9381/14/7/020 | DAMTP-R96/59 | gr-qc chao-dyn hep-th nlin.CD | null | We study motion in the field of two fixed centres described by a family of
Einstein-dilaton-Maxwell theories. Transitions between regular and chaotic
motion are observed as the dilaton coupling is varied.
| [
{
"created": "Fri, 20 Dec 1996 15:23:20 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Dec 1996 13:07:21 GMT",
"version": "v2"
}
] | 2009-10-07 | [
[
"Cornish",
"Neil",
"",
"DAMTP Cambridge"
],
[
"Gibbons",
"Gary",
"",
"DAMTP Cambridge"
]
] | We study motion in the field of two fixed centres described by a family of Einstein-dilaton-Maxwell theories. Transitions between regular and chaotic motion are observed as the dilaton coupling is varied. |
1903.03434 | Krishnakanta Bhattacharya | Krishnakanta Bhattacharya, Sumit Dey, Bibhas Ranjan Majhi and Saurav
Samanta | A general framework to study the extremal phase transition of black
holes | 24 Pages, No figure, New comments added, To appear in Phys. Rev. D | Phys. Rev. D 99, 124047 (2019) | 10.1103/PhysRevD.99.124047 | null | gr-qc cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the universality of some features for the extremal phase
transition of black holes and unify all the approaches which have been applied
in different spacetimes. Unlike the other existing approaches where the
information of the spacetime and its dimension is directly used to get various
results, we provide a general formulation in which those results are obtained
for any arbitrary black hole spacetime having an extremal limit. Calculating
the second order moments of fluctuations of some thermodynamic quantities we
show that, the phase transition occurs only in the microcanonical ensemble.
Without considering any specific black hole we calculate the values of critical
exponents for this type of phase transition. These are shown to be in agreement
with the values obtained earlier for metric specified cases. Finally we extend
our analysis to the geometrothermodynamics (henceforth GTD) formulation. We
show that for any black hole, if there is an extremal point, the Ricci scalar
for the Ruppeiner metric must diverge at that point.
| [
{
"created": "Fri, 8 Mar 2019 13:29:52 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Jun 2019 16:28:45 GMT",
"version": "v2"
}
] | 2019-07-03 | [
[
"Bhattacharya",
"Krishnakanta",
""
],
[
"Dey",
"Sumit",
""
],
[
"Majhi",
"Bibhas Ranjan",
""
],
[
"Samanta",
"Saurav",
""
]
] | We investigate the universality of some features for the extremal phase transition of black holes and unify all the approaches which have been applied in different spacetimes. Unlike the other existing approaches where the information of the spacetime and its dimension is directly used to get various results, we provide a general formulation in which those results are obtained for any arbitrary black hole spacetime having an extremal limit. Calculating the second order moments of fluctuations of some thermodynamic quantities we show that, the phase transition occurs only in the microcanonical ensemble. Without considering any specific black hole we calculate the values of critical exponents for this type of phase transition. These are shown to be in agreement with the values obtained earlier for metric specified cases. Finally we extend our analysis to the geometrothermodynamics (henceforth GTD) formulation. We show that for any black hole, if there is an extremal point, the Ricci scalar for the Ruppeiner metric must diverge at that point. |
1707.02795 | Stefano Chinaglia | Stefano Chinaglia | A model of regular black hole satisfying the Weak Energy Condition | 15 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we discuss a star generated by some matter fluid, whose
stress-energy tensor is known. We investigate both the maximally symmetric
framework, where all the pressures are equal, and the dark energy framework,
with $P = -\rho$. We show that the first one is not able to produce a black
hole, while second one actually is. Finally, within this second framework, we
present an example of regular black hole, showing it satisfies the NEC and the
WEC.
| [
{
"created": "Mon, 10 Jul 2017 10:55:25 GMT",
"version": "v1"
}
] | 2017-07-11 | [
[
"Chinaglia",
"Stefano",
""
]
] | In this article we discuss a star generated by some matter fluid, whose stress-energy tensor is known. We investigate both the maximally symmetric framework, where all the pressures are equal, and the dark energy framework, with $P = -\rho$. We show that the first one is not able to produce a black hole, while second one actually is. Finally, within this second framework, we present an example of regular black hole, showing it satisfies the NEC and the WEC. |
2406.12558 | Shin'ichi Nojiri | Shin'ichi Nojiri and S. D. Odintsov | $F(Q)$ gravity with Gauss-Bonnet corrections: from early-time inflation
to late-time acceleration | LaTeX 20 pages, version to appear in Fortschritte der Physik -
Progress of Physics | null | null | KEK-TH-2629, KEK-Cosmo-0346 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that in the $f(Q)$ gravity with a non-metricity scalar $Q$, the
curvatures in Einstein's gravity, that is, the Riemann curvature constructed
from the standard Levi-Civita connection, could not be excluded or naturally
appear. The first observation is that even in $f(Q)$ gravity, the conservation
of the matter energy-momentum tensor is not described by the covariant
derivatives in the non-metricity gravity but that is given by the Levi-Civita
connection. The commutator of the covariant derivatives in Einstein's gravity
inevitably induces the Riemann curvature. There is no symmetry nor principle
which prohibits the Riemann curvature in non-metricity gravity. Based on this
observation, we propose and investigate $f\left(Q, \mathcal{G} \right)$ gravity
with the Gauss-Bonnet invariant $\mathcal{G}$ and its generalisations. We show
how $f\left(Q, \mathcal{G} \right)$ models realising any given the
Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) spacetime can be reconstructed.
We apply the reconstruction formalism to cosmology. Explicitly, the gravity
models which realise slow roll or constant roll inflation, dark energy epoch as
well as the unification of the inflation and dark energy are found. The
dynamical autonomous system and the gravitational wave in the theory under
investigation are discussed. It is found the condition that the de Sitter
spacetime becomes the (stable) fixed point of the system.
| [
{
"created": "Tue, 18 Jun 2024 12:34:56 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Aug 2024 01:59:03 GMT",
"version": "v2"
}
] | 2024-08-16 | [
[
"Nojiri",
"Shin'ichi",
""
],
[
"Odintsov",
"S. D.",
""
]
] | We show that in the $f(Q)$ gravity with a non-metricity scalar $Q$, the curvatures in Einstein's gravity, that is, the Riemann curvature constructed from the standard Levi-Civita connection, could not be excluded or naturally appear. The first observation is that even in $f(Q)$ gravity, the conservation of the matter energy-momentum tensor is not described by the covariant derivatives in the non-metricity gravity but that is given by the Levi-Civita connection. The commutator of the covariant derivatives in Einstein's gravity inevitably induces the Riemann curvature. There is no symmetry nor principle which prohibits the Riemann curvature in non-metricity gravity. Based on this observation, we propose and investigate $f\left(Q, \mathcal{G} \right)$ gravity with the Gauss-Bonnet invariant $\mathcal{G}$ and its generalisations. We show how $f\left(Q, \mathcal{G} \right)$ models realising any given the Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) spacetime can be reconstructed. We apply the reconstruction formalism to cosmology. Explicitly, the gravity models which realise slow roll or constant roll inflation, dark energy epoch as well as the unification of the inflation and dark energy are found. The dynamical autonomous system and the gravitational wave in the theory under investigation are discussed. It is found the condition that the de Sitter spacetime becomes the (stable) fixed point of the system. |
1709.00115 | Bruno Arderucio Costa | Bruno Arderucio-Costa, William Unruh | Model for Quantum Effects in Stellar Collapse | null | Phys. Rev. D 97, 024005 (2018) | 10.1103/PhysRevD.97.024005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a simple model for stellar collapse and evaluate the quantum
mechanical stress-energy tensor to argue that quantum effects do not play an
important role for the collapse of astrophysical objects.
| [
{
"created": "Fri, 1 Sep 2017 00:30:34 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Dec 2017 19:29:40 GMT",
"version": "v2"
}
] | 2018-01-17 | [
[
"Arderucio-Costa",
"Bruno",
""
],
[
"Unruh",
"William",
""
]
] | We present a simple model for stellar collapse and evaluate the quantum mechanical stress-energy tensor to argue that quantum effects do not play an important role for the collapse of astrophysical objects. |
1404.4479 | Alexei Zayats | Alexander B. Balakin, Ruslan K. Muharlyamov, Alexei E. Zayats | Axion-induced oscillations of cooperative electric field in a cosmic
magneto-active plasma | 7 pages, misprints corrected | Eur. Phys. J. D 68: 159, 2014 | 10.1140/epjd/e2014-50131-6 | null | gr-qc hep-th physics.plasm-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider one cosmological application of an axionic extension of the
Maxwell-Vlasov theory, which describes axionically induced oscillatory regime
in the state of global magnetic field evolving in the anisotropic expanding
(early) universe. We show that the cooperative electric field in the
relativistic plasma, being coupled to the pseudoscalar (axion) and global
magnetic fields, plays the role of a regulator in this three-level system; in
particular, the cooperative (Vlasov) electric field converts the regime of
anomalous growth of the pseudoscalar field, caused by the axion-photon coupling
at the inflationary epoch of the universe expansion, into an oscillatory regime
with finite density of relic axions. We analyze solutions to the dispersion
equations for the axionically induced cooperative oscillations of the electric
field in the relativistic plasma.
| [
{
"created": "Thu, 17 Apr 2014 10:51:28 GMT",
"version": "v1"
},
{
"created": "Mon, 26 May 2014 15:57:07 GMT",
"version": "v2"
}
] | 2014-06-26 | [
[
"Balakin",
"Alexander B.",
""
],
[
"Muharlyamov",
"Ruslan K.",
""
],
[
"Zayats",
"Alexei E.",
""
]
] | We consider one cosmological application of an axionic extension of the Maxwell-Vlasov theory, which describes axionically induced oscillatory regime in the state of global magnetic field evolving in the anisotropic expanding (early) universe. We show that the cooperative electric field in the relativistic plasma, being coupled to the pseudoscalar (axion) and global magnetic fields, plays the role of a regulator in this three-level system; in particular, the cooperative (Vlasov) electric field converts the regime of anomalous growth of the pseudoscalar field, caused by the axion-photon coupling at the inflationary epoch of the universe expansion, into an oscillatory regime with finite density of relic axions. We analyze solutions to the dispersion equations for the axionically induced cooperative oscillations of the electric field in the relativistic plasma. |
1704.08198 | Pasquale Bosso | Pasquale Bosso, Saurya Das, Robert B. Mann | Planck scale Corrections to the Harmonic Oscillator, Coherent and
Squeezed States | 15 pages, 3 figures, accepted in Physical Review D | Phys. Rev. D 96, 066008 (2017) | 10.1103/PhysRevD.96.066008 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Generalized Uncertainty Principle (GUP) is a modification of Heisenberg's
Principle predicted by several theories of Quantum Gravity. It consists of a
modified commutator between position and momentum. In this work we compute
potentially observable effects that GUP implies for the harmonic oscillator,
coherent and squeezed states in Quantum Mechanics. In particular, we rigorously
analyze the GUP-perturbed harmonic oscillator Hamiltonian, defining new
operators that act as ladder operators on the perturbed states. We use these
operators to define the new coherent and squeezed states. We comment on
potential applications.
| [
{
"created": "Wed, 26 Apr 2017 16:37:18 GMT",
"version": "v1"
},
{
"created": "Sat, 12 Aug 2017 02:44:15 GMT",
"version": "v2"
}
] | 2017-09-13 | [
[
"Bosso",
"Pasquale",
""
],
[
"Das",
"Saurya",
""
],
[
"Mann",
"Robert B.",
""
]
] | The Generalized Uncertainty Principle (GUP) is a modification of Heisenberg's Principle predicted by several theories of Quantum Gravity. It consists of a modified commutator between position and momentum. In this work we compute potentially observable effects that GUP implies for the harmonic oscillator, coherent and squeezed states in Quantum Mechanics. In particular, we rigorously analyze the GUP-perturbed harmonic oscillator Hamiltonian, defining new operators that act as ladder operators on the perturbed states. We use these operators to define the new coherent and squeezed states. We comment on potential applications. |
1812.11742 | Vardarajan Suneeta | Amruta Sadhu, Vardarajan Suneeta | Study of Semiclassical Instability of the Schwarzschild AdS Black Hole
in the Large $D$ Limit | 41 pages, cut-paste typos in pedagogical Appendix fixed, no changes
to results or in main body of paper, supercedes journal version | null | 10.1088/1361-6382/ab1d69 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the semiclassical stability of the Schwarzschild AdS black hole in
the Euclidean partition function approach. We perform this computation in the
large $D$ limit and focus on scalar perturbations. We obtain the equations for
non-spherically symmetric scalar perturbations in a simple form. For a class of
perturbations stability is demonstrated by the S-deformation method. For some
other classes we rule out unstable modes of $\mathcal{O}(D^2)$. We also analyze
the spherically symmetric perturbations and demonstrate the appearance of an
unstable mode for small black holes in the large $D$ limit. We obtain an
expression for the eigenvalue corresponding to the unstable mode to next to
leading order in a $1/D$ expansion. This result agrees with a previously
obtained numerical bound on this eigenvalue. For cosmological constant zero,
our answer matches a previous result obtained for the corresponding eigenvalue
for the $D$ dimensional Schwarzschild-Tangherlini black hole to next to leading
order in a $1/D$ expansion.
| [
{
"created": "Mon, 31 Dec 2018 09:56:57 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Apr 2019 06:17:09 GMT",
"version": "v2"
},
{
"created": "Wed, 3 Aug 2022 11:19:32 GMT",
"version": "v3"
}
] | 2022-08-04 | [
[
"Sadhu",
"Amruta",
""
],
[
"Suneeta",
"Vardarajan",
""
]
] | We analyze the semiclassical stability of the Schwarzschild AdS black hole in the Euclidean partition function approach. We perform this computation in the large $D$ limit and focus on scalar perturbations. We obtain the equations for non-spherically symmetric scalar perturbations in a simple form. For a class of perturbations stability is demonstrated by the S-deformation method. For some other classes we rule out unstable modes of $\mathcal{O}(D^2)$. We also analyze the spherically symmetric perturbations and demonstrate the appearance of an unstable mode for small black holes in the large $D$ limit. We obtain an expression for the eigenvalue corresponding to the unstable mode to next to leading order in a $1/D$ expansion. This result agrees with a previously obtained numerical bound on this eigenvalue. For cosmological constant zero, our answer matches a previous result obtained for the corresponding eigenvalue for the $D$ dimensional Schwarzschild-Tangherlini black hole to next to leading order in a $1/D$ expansion. |
gr-qc/0405078 | Y. Jack Ng | Y. Jack Ng (University of North Carolina) | Quantum Foam and Quantum Gravity Phenomenology | 29 pages, 4 figures, lectures given at the 40th Karpacz Winter School
on Theoretical Physics (Poland, Feb. 2004), submitted to Lect. Notes Phys | null | 10.1007/11377306_9 | null | gr-qc astro-ph hep-ph hep-th | null | Spacetime undergoes quantum fluctuations, giving rise to spacetime foam,
a.k.a. quantum foam. We discuss some properties of spacetime foam, and point
out the conceptual interconnections in the physics of quantum foam, black
holes, and quantum computation. We also discuss the phenomenology of quantum
foam, and conclude that it may be difficult, but by no means impossible, to
detect its tiny effects in the not-too-distant future.
| [
{
"created": "Fri, 14 May 2004 20:40:00 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Ng",
"Y. Jack",
"",
"University of North Carolina"
]
] | Spacetime undergoes quantum fluctuations, giving rise to spacetime foam, a.k.a. quantum foam. We discuss some properties of spacetime foam, and point out the conceptual interconnections in the physics of quantum foam, black holes, and quantum computation. We also discuss the phenomenology of quantum foam, and conclude that it may be difficult, but by no means impossible, to detect its tiny effects in the not-too-distant future. |
0912.3884 | Sergey Strigin | S. E. Strigin and S. P. Vyatchanin | Analysis of parametric oscillatory instability in Fabry-Perot cavity
with Gauss and Laguerre-Gauss main mode profile | 11 pages, 3 figures | Phys.Lett.A374:1101-1104,2010 | 10.1016/j.physleta.2009.12.054 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/3.0/ | We calculate the parametric instabilities in Fabry-Perot cavities of Advanced
VIRGO and LIGO interferometers with different main mode profiles. All unstable
combinations of elastic and Stokes modes both for the case with TEM00 and LG33
as a carriers are deduced.
| [
{
"created": "Sat, 19 Dec 2009 10:52:54 GMT",
"version": "v1"
}
] | 2010-04-14 | [
[
"Strigin",
"S. E.",
""
],
[
"Vyatchanin",
"S. P.",
""
]
] | We calculate the parametric instabilities in Fabry-Perot cavities of Advanced VIRGO and LIGO interferometers with different main mode profiles. All unstable combinations of elastic and Stokes modes both for the case with TEM00 and LG33 as a carriers are deduced. |
gr-qc/0111089 | Jorge Pullin | Rodolfo Gambini and Jorge Pullin | A finite spin-foam-based theory of three and four dimensional quantum
gravity | 4 pages, Revtex, 6 figures included with psfig, to appear in PRD | Phys.Rev. D66 (2002) 024020 | 10.1103/PhysRevD.66.024020 | LSU-REL-112601 | gr-qc hep-th | null | Starting from Ooguri's construction for $BF$ theory in three (and four)
dimensions, we show how to construct a well defined theory with an infinite
number of degrees of freedom. The spin network states that are kept invariant
by the evolution operators of the theory are exact solutions of the Hamiltonian
constraint of quantum gravity proposed by Thiemann. The resulting theory is the
first example of a well defined, finite, consistent, spin-foam based theory in
a situation with an infinite number of degrees of freedom. Since it solves the
quantum constraints of general relativity it is also a candidate for a theory
of quantum gravity. It is likely, however, that the solutions constructed
correspond to a spurious sector of solutions of the constraints. The richness
of the resulting theory makes it an interesting example to be analyzed by
forthcoming techniques that construct the semi-classical limit of spin network
quantum gravity.
| [
{
"created": "Mon, 26 Nov 2001 15:16:11 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Jul 2002 18:34:47 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | Starting from Ooguri's construction for $BF$ theory in three (and four) dimensions, we show how to construct a well defined theory with an infinite number of degrees of freedom. The spin network states that are kept invariant by the evolution operators of the theory are exact solutions of the Hamiltonian constraint of quantum gravity proposed by Thiemann. The resulting theory is the first example of a well defined, finite, consistent, spin-foam based theory in a situation with an infinite number of degrees of freedom. Since it solves the quantum constraints of general relativity it is also a candidate for a theory of quantum gravity. It is likely, however, that the solutions constructed correspond to a spurious sector of solutions of the constraints. The richness of the resulting theory makes it an interesting example to be analyzed by forthcoming techniques that construct the semi-classical limit of spin network quantum gravity. |
2404.09446 | Yuki Osawa | Yuki Osawa, Kuan-Nan Lin, Yasusada Nambu, Masahiro Hotta, and Pisin
Chen | The final burst of the moving mirror is unrelated to the partner mode of
analog Hawking radiation | 18 pages, 6 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Flying mirrors with appropriate trajectories have been recognized as an
analog system that mimics black hole Hawking evaporation and have been widely
investigated. It has recently been suggested that the partner mode of the
analog Hawking radiation emitted from a moving mirror would manifest itself
through a final burst when the mirror executes a sudden stop. Here we argue the
opposite via the partner formula for the moving mirror model. By expanding the
theoretical foundation of the partner formula and augmenting it with numerical
analysis, we demonstrate that the supposed final burst is induced by a shock
that requires the input of external energy, whereas the Hawking radiation
partner mode, which is associated with the zero-point vacuum fluctuations, is
not responsible for the burst.
| [
{
"created": "Mon, 15 Apr 2024 04:17:57 GMT",
"version": "v1"
}
] | 2024-04-16 | [
[
"Osawa",
"Yuki",
""
],
[
"Lin",
"Kuan-Nan",
""
],
[
"Nambu",
"Yasusada",
""
],
[
"Hotta",
"Masahiro",
""
],
[
"Chen",
"Pisin",
""
]
] | Flying mirrors with appropriate trajectories have been recognized as an analog system that mimics black hole Hawking evaporation and have been widely investigated. It has recently been suggested that the partner mode of the analog Hawking radiation emitted from a moving mirror would manifest itself through a final burst when the mirror executes a sudden stop. Here we argue the opposite via the partner formula for the moving mirror model. By expanding the theoretical foundation of the partner formula and augmenting it with numerical analysis, we demonstrate that the supposed final burst is induced by a shock that requires the input of external energy, whereas the Hawking radiation partner mode, which is associated with the zero-point vacuum fluctuations, is not responsible for the burst. |
2207.01657 | Trupti Patil | Trupti Patil and Sukanta Panda | Coupled scalar field cosmology with effects of curvature | The published version in Eur. Phys. J. Plus | Eur. Phys. J. Plus (2023) 138:583 | 10.1140/epjp/s13360-023-04192-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present study, we investigate the interaction between dark energy and
dark matter, particularly emphasizing the effects of curvature in the realm of
Friedmann-Lemaitre-Robertson-Walker (FLRW) space-time. We examine the system by
forming a dynamic set of equations for various critical points. Later, we study
their stability characteristics and show that with a suitable choice of
potential, the system gives rise to the late-time attractor (stable) solution
in the expanding environment. Lastly, we present the cosmological compatibility
of the model using the phase-space portrait tools.
| [
{
"created": "Mon, 4 Jul 2022 18:13:17 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Mar 2023 12:49:27 GMT",
"version": "v2"
},
{
"created": "Thu, 6 Jul 2023 04:06:44 GMT",
"version": "v3"
}
] | 2023-07-07 | [
[
"Patil",
"Trupti",
""
],
[
"Panda",
"Sukanta",
""
]
] | In the present study, we investigate the interaction between dark energy and dark matter, particularly emphasizing the effects of curvature in the realm of Friedmann-Lemaitre-Robertson-Walker (FLRW) space-time. We examine the system by forming a dynamic set of equations for various critical points. Later, we study their stability characteristics and show that with a suitable choice of potential, the system gives rise to the late-time attractor (stable) solution in the expanding environment. Lastly, we present the cosmological compatibility of the model using the phase-space portrait tools. |
gr-qc/0602055 | Yungui Gong | Yungui Gong and Anzhong Wang | Acceleration from M theory and Fine-tuning | 9 pages, 3 figures, use iopart, v2; references updated, accepted for
publication in Class. Quantum Grav | Class.Quant.Grav. 23 (2006) 3419-3426 | 10.1088/0264-9381/23/10/012 | null | gr-qc astro-ph hep-th | null | The compactification of M theory with time dependent hyperbolic internal
space gives an effective scalar field with exponential potential which provides
a transient acceleration in Einstein frame in four dimensions. Ordinary matter
and radiation are present in addition to the scalar field coming from
compactification. We find that we have to fine-tune the initial conditions of
the scalar field so that our Universe experiences acceleration now. During the
evolution of our Universe, the volume of the internal space increases about 12
times. The time variation of the internal space results in a large time
variation of the fine structure constant which violates the observational
constraint on the variation of the fine structure constant. The large variation
of the fine structure constant is a generic feature of transient acceleration
models.
| [
{
"created": "Tue, 14 Feb 2006 20:30:53 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Apr 2006 22:45:12 GMT",
"version": "v2"
},
{
"created": "Wed, 12 Apr 2006 04:28:40 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Gong",
"Yungui",
""
],
[
"Wang",
"Anzhong",
""
]
] | The compactification of M theory with time dependent hyperbolic internal space gives an effective scalar field with exponential potential which provides a transient acceleration in Einstein frame in four dimensions. Ordinary matter and radiation are present in addition to the scalar field coming from compactification. We find that we have to fine-tune the initial conditions of the scalar field so that our Universe experiences acceleration now. During the evolution of our Universe, the volume of the internal space increases about 12 times. The time variation of the internal space results in a large time variation of the fine structure constant which violates the observational constraint on the variation of the fine structure constant. The large variation of the fine structure constant is a generic feature of transient acceleration models. |
gr-qc/0507080 | Gary T. Horowitz | Gary T. Horowitz | Higher Dimensional Generalizations of the Kerr Black Hole | 15 pages, to appear in "Kerr Spacetime: Rotating Black Holes", eds.
S. Scott, M. Visser, and D. Wiltshire (Cambridge University Press) | null | null | null | gr-qc hep-th | null | A brief introduction is given to rotating black holes in more than four
spacetime dimensions.
| [
{
"created": "Mon, 18 Jul 2005 23:45:53 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Horowitz",
"Gary T.",
""
]
] | A brief introduction is given to rotating black holes in more than four spacetime dimensions. |
1706.01773 | Gamal G.L. Nashed | A. M. Awad, S. Capozziello and G. G. L. Nashed | $D$-dimensional charged Anti-de-Sitter black holes in $f(T)$ gravity | 11 Pages, will appear in JHEP | JHEP 07 (2017) 136 | 10.1007/JHEP07(2017)136 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a $D$-dimensional charged Anti-de-Sitter black hole solutions in
$f(T)$ gravity, where $f(T)=T+\beta T^2$ and $D \geq 4$. These solutions are
characterized by flat or cylindrical horizons. The interesting feature of these
solutions is the existence of inseparable electric monopole and quadrupole
terms in the potential which share related momenta, in contrast with most of
the known charged black hole solutions in General Relativity and its
extensions. Furthermore, these solutions have curvature singularities which are
milder than those of the known charged black hole solutions in General
Relativity and Teleparallel Gravity. This feature can be shown by calculating
some invariants of curvature and torsion tensors. Furthermore, we calculate the
total energy of these black holes using the energy-momentum tensor. Finally, we
show that these charged black hole solutions violate the first law of
thermodynamics in agreement with previous results.
| [
{
"created": "Sat, 3 Jun 2017 16:27:11 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Jul 2017 14:04:01 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Jul 2017 12:11:44 GMT",
"version": "v3"
}
] | 2017-08-01 | [
[
"Awad",
"A. M.",
""
],
[
"Capozziello",
"S.",
""
],
[
"Nashed",
"G. G. L.",
""
]
] | We present a $D$-dimensional charged Anti-de-Sitter black hole solutions in $f(T)$ gravity, where $f(T)=T+\beta T^2$ and $D \geq 4$. These solutions are characterized by flat or cylindrical horizons. The interesting feature of these solutions is the existence of inseparable electric monopole and quadrupole terms in the potential which share related momenta, in contrast with most of the known charged black hole solutions in General Relativity and its extensions. Furthermore, these solutions have curvature singularities which are milder than those of the known charged black hole solutions in General Relativity and Teleparallel Gravity. This feature can be shown by calculating some invariants of curvature and torsion tensors. Furthermore, we calculate the total energy of these black holes using the energy-momentum tensor. Finally, we show that these charged black hole solutions violate the first law of thermodynamics in agreement with previous results. |
2308.04939 | Adailton Ara\'ujo Filho | A. A. Ara\'ujo Filho | Implications of a Simpson-Visser solution in Verlinde's framework | 46 pages, 9 figures, and 9 tables -- accepted for publication in The
European physical Journal C | The European Physical Journal C, 84, 73, (2024) | 10.1140/epjc/s10052-023-12328-7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This study focuses on investigating a regular black hole within the framework
of Verlinde's emergent gravity. In particular, we explore the main aspects of
the modified Simpson--Visser solution. Our analysis reveals the presence of a
unique physical event horizon under certain conditions. Moreover, we study the
thermodynamic properties, including the Hawking temperature, the entropy, and
the heat capacity. Based on these quantities, our results indicate several
phase transitions. Geodesic trajectories for photon-like particles,
encompassing photon spheres and the formation of black hole shadows, are also
calculated to comprehend the behavior of light in the vicinity of the black
hole. Additionally, we also provide the calculation of the time delay and the
deflection angle. Corroborating our results, we include an additional
application in the context of high-energy astrophysical phenomena: neutrino
energy deposition. Finally, we investigate the quasinormal modes using
third-order WKB approximation.
| [
{
"created": "Wed, 9 Aug 2023 13:14:33 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Dec 2023 19:18:00 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Dec 2023 13:26:24 GMT",
"version": "v3"
}
] | 2024-01-24 | [
[
"Filho",
"A. A. Araújo",
""
]
] | This study focuses on investigating a regular black hole within the framework of Verlinde's emergent gravity. In particular, we explore the main aspects of the modified Simpson--Visser solution. Our analysis reveals the presence of a unique physical event horizon under certain conditions. Moreover, we study the thermodynamic properties, including the Hawking temperature, the entropy, and the heat capacity. Based on these quantities, our results indicate several phase transitions. Geodesic trajectories for photon-like particles, encompassing photon spheres and the formation of black hole shadows, are also calculated to comprehend the behavior of light in the vicinity of the black hole. Additionally, we also provide the calculation of the time delay and the deflection angle. Corroborating our results, we include an additional application in the context of high-energy astrophysical phenomena: neutrino energy deposition. Finally, we investigate the quasinormal modes using third-order WKB approximation. |
gr-qc/0103093 | Toporenskij A. V. | A.V.Toporensky | The shear dynamics in Bianchi I cosmological model on the brane | 7 pages, no figures; some comments and references added; submitted to
Class. Quant. Gravity | Class.Quant.Grav. 18 (2001) 2311-2316 | 10.1088/0264-9381/18/12/306 | null | gr-qc hep-th | null | The shear dynamics in Bianchi I cosmological model on the brane with a
perfect fluid (the equation of state is $p=(\gamma-1) \mu$) is studied. It is
shown that for $1 < \gamma < 2$ the shear parameter has maximum at some moment
during a transition period from nonstandard to standard cosmology. An exact
formula for the matter density $\mu$ in the epoch of maximum shear parameter as
a function of the equation of state is obtained.
| [
{
"created": "Mon, 26 Mar 2001 14:55:42 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Apr 2001 14:33:20 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Toporensky",
"A. V.",
""
]
] | The shear dynamics in Bianchi I cosmological model on the brane with a perfect fluid (the equation of state is $p=(\gamma-1) \mu$) is studied. It is shown that for $1 < \gamma < 2$ the shear parameter has maximum at some moment during a transition period from nonstandard to standard cosmology. An exact formula for the matter density $\mu$ in the epoch of maximum shear parameter as a function of the equation of state is obtained. |
gr-qc/9312006 | Jerzy Lewandowski | Robert Alicki, John R. Klauder and Jerzy Lewandowski | Landau Level Ground--State Degeneracy, and Its Relevance for a General
Quantization Procedure | 32, Phys. Rev. A, 48, 2538 | Phys.Rev. A48 (1993) 2538-2548 | 10.1103/PhysRevA.48.2538 | null | gr-qc hep-th | null | The quantum dynamics of a two-dimensional charged spin $1/2$ particle is
studied for general, symmetry--free curved surfaces and general, nonuniform
magnetic fields that are, when different from zero, orthogonal to the defining
two surface. Although higher Landau levels generally lose their degeneracy
under such general conditions, the lowest Landau level, the ground state,
remains degenerate. Previous discussions of this problem have had less
generality and/or used supersymmetry, or else have appealed to very general
mathematical theorems from differential geometry. In contrast our discussion
relies on simple and standard quantum mechanical concepts.
The mathematical similarity of the physical problem at hand and that of a
phase-space path integral quantization scheme of a general classical system is
emphasized. Adopting this analogy in the general case leads to a general
quantization procedure that is invariant under general coordinate
transformations-- completely unlike any of the conventional quantization
prescriptions -- and therefore generalizes the concept of quantization to new
and hitherto inaccesible situations.
In a complementary fashion , the so-obtained picture of general quantization
helps to derive useful semiclassical formulas for the Hall current in the case
of a filling factor equal to one for a general surface and magnetic field.
| [
{
"created": "Fri, 3 Dec 1993 01:45:33 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Alicki",
"Robert",
""
],
[
"Klauder",
"John R.",
""
],
[
"Lewandowski",
"Jerzy",
""
]
] | The quantum dynamics of a two-dimensional charged spin $1/2$ particle is studied for general, symmetry--free curved surfaces and general, nonuniform magnetic fields that are, when different from zero, orthogonal to the defining two surface. Although higher Landau levels generally lose their degeneracy under such general conditions, the lowest Landau level, the ground state, remains degenerate. Previous discussions of this problem have had less generality and/or used supersymmetry, or else have appealed to very general mathematical theorems from differential geometry. In contrast our discussion relies on simple and standard quantum mechanical concepts. The mathematical similarity of the physical problem at hand and that of a phase-space path integral quantization scheme of a general classical system is emphasized. Adopting this analogy in the general case leads to a general quantization procedure that is invariant under general coordinate transformations-- completely unlike any of the conventional quantization prescriptions -- and therefore generalizes the concept of quantization to new and hitherto inaccesible situations. In a complementary fashion , the so-obtained picture of general quantization helps to derive useful semiclassical formulas for the Hall current in the case of a filling factor equal to one for a general surface and magnetic field. |
1104.5290 | Tetsuyuki Yukawa | Tetsuyuki Yukawa | Birth and Growth of Two-dimensional Universe | null | null | 10.1103/PhysRevD.85.023505 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A master equation for the evolution of two-dimensional universe is derived
based on the simplicial quantum gravity regarding the evolution as the Markov
process of a space-time lattice. Three typical phases, expanding, elongating
and collapsing phase, which have been found in the numerical simulation, are
studied together with their boundaries, analytically. Asymptotic solutions of
the evolution equation for statistical quantities, such as averaged area,
boundary length, and correlation of fluctuations, are obtained for each phase
and boundary.After introducing a physical time the cosmological significance of
each phase is discussed.
| [
{
"created": "Thu, 28 Apr 2011 03:58:35 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Nov 2011 04:58:14 GMT",
"version": "v2"
}
] | 2015-05-28 | [
[
"Yukawa",
"Tetsuyuki",
""
]
] | A master equation for the evolution of two-dimensional universe is derived based on the simplicial quantum gravity regarding the evolution as the Markov process of a space-time lattice. Three typical phases, expanding, elongating and collapsing phase, which have been found in the numerical simulation, are studied together with their boundaries, analytically. Asymptotic solutions of the evolution equation for statistical quantities, such as averaged area, boundary length, and correlation of fluctuations, are obtained for each phase and boundary.After introducing a physical time the cosmological significance of each phase is discussed. |
2009.06705 | Pengzhang He | Peng-Zhang He, Qi-Qi Fan, Hao-Ran Zhang, and Jian-Bo Deng | Shadows of rotating Hayward-de Sitter black holes with astrometric
observables | 16 pages, 6 figures | null | 10.1140/epjc/s10052-020-08707-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by recent work on rotating black hole shadow [Phys. Rev. D101,
084029 (2020)], we investigate the shadow behaviors of rotating Hayward-de
Sitter black hole for static observers at a finite distance in terms of
astronomical observables. This paper uses the newly introduced distortion
parameter in [arXiv:2006.00685] to describe the shadow's shape quantitatively.
We show that the spin parameter would distort shadows and the magnetic monopole
charge would increase the degree of deformation. At the same time, the
distortion could be relieved because of the cosmological constant and the
distortion would increase with the distance from the black hole. Besides, the
spin parameter, magnetic monopole charge and cosmological constant increase
will cause the shadow to shrink.
| [
{
"created": "Tue, 8 Sep 2020 22:03:55 GMT",
"version": "v1"
}
] | 2020-12-29 | [
[
"He",
"Peng-Zhang",
""
],
[
"Fan",
"Qi-Qi",
""
],
[
"Zhang",
"Hao-Ran",
""
],
[
"Deng",
"Jian-Bo",
""
]
] | Motivated by recent work on rotating black hole shadow [Phys. Rev. D101, 084029 (2020)], we investigate the shadow behaviors of rotating Hayward-de Sitter black hole for static observers at a finite distance in terms of astronomical observables. This paper uses the newly introduced distortion parameter in [arXiv:2006.00685] to describe the shadow's shape quantitatively. We show that the spin parameter would distort shadows and the magnetic monopole charge would increase the degree of deformation. At the same time, the distortion could be relieved because of the cosmological constant and the distortion would increase with the distance from the black hole. Besides, the spin parameter, magnetic monopole charge and cosmological constant increase will cause the shadow to shrink. |
2310.02315 | Andrew Robert Clifford Spiers A R C S | Andrew Spiers, Andrea Maselli, Thomas P. Sotiriou | Measuring scalar charge with compact binaries: High accuracy modelling
with self-force | 15 pages, 0 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Using the self-force approach, we present the premier first-post-adiabatic
accuracy formalism for modelling compact binaries in theories with a massless
scalar field non-minimally coupled to gravity. We limit the binary secondary to
being a non-spinning compact body with no scalar dipole (we will address the
spinning and scalar dipole cases in an upcoming paper). By producing an ansatz
for the scalar charged point particle action, we derive first- and second-order
perturbative field equations and equations of motion for the secondary compact
object. Under our assumptions, implementing this formalism will produce
sufficiently accurate waveform templates for precision measurements of the
scalar charge of the secondary with LISA data on extreme-mass-ratio inspirals.
Our formalism is consistent with almost general scalar-tensor theories of
gravity. Implementing our formalism builds on self-force models in General
Relativity; we show the incorporation into the two-timescale formalism is
straightforward. Excitingly, implementation poses no significantly more
challenging barriers than computing first-post adiabatic waveforms in General
Relativity.
| [
{
"created": "Tue, 3 Oct 2023 18:00:05 GMT",
"version": "v1"
}
] | 2023-10-05 | [
[
"Spiers",
"Andrew",
""
],
[
"Maselli",
"Andrea",
""
],
[
"Sotiriou",
"Thomas P.",
""
]
] | Using the self-force approach, we present the premier first-post-adiabatic accuracy formalism for modelling compact binaries in theories with a massless scalar field non-minimally coupled to gravity. We limit the binary secondary to being a non-spinning compact body with no scalar dipole (we will address the spinning and scalar dipole cases in an upcoming paper). By producing an ansatz for the scalar charged point particle action, we derive first- and second-order perturbative field equations and equations of motion for the secondary compact object. Under our assumptions, implementing this formalism will produce sufficiently accurate waveform templates for precision measurements of the scalar charge of the secondary with LISA data on extreme-mass-ratio inspirals. Our formalism is consistent with almost general scalar-tensor theories of gravity. Implementing our formalism builds on self-force models in General Relativity; we show the incorporation into the two-timescale formalism is straightforward. Excitingly, implementation poses no significantly more challenging barriers than computing first-post adiabatic waveforms in General Relativity. |
gr-qc/9809026 | Adrian Kent | Adrian Kent | Quantum Histories | 19 pages, TeX with harvmac. Contribution to Proceedings of the 104th
Nobel Symposium, ``Modern Studies of Basic Quantum Concepts and Phenomena'',
Gimo, June 1997. To appear in Physica Scripta | Phys.Scripta T76 (1998) 78-84 | 10.1238/Physica.Topical.076a00078 | DAMTP-1997-117 | gr-qc hep-th quant-ph | null | There are good motivations for considering some type of quantum histories
formalism. Several possible formalisms are known, defined by different
definitions of event and by different selection criteria for sets of histories.
These formalisms have a natural interpretation, according to which nature
somehow chooses one set of histories from among those allowed, and then
randomly chooses to realise one history from that set; other interpretations
are possible, but their scientific implications are essentially the same.
The selection criteria proposed to date are reasonably natural, and certainly
raise new questions. For example, the validity of ordering inferences which we
normally take for granted --- such as that a particle in one region is
necessarily in a larger region containing it --- depends on whether or not our
history respects the criterion of ordered consistency, or merely consistency.
However, the known selection criteria, including consistency and medium
decoherence, are very weak. It is not possible to derive the predictions of
classical mechanics or Copenhagen quantum mechanics from the theories they
define, even given observational data in an extended time interval. Attempts to
refine the consistent histories approach so as to solve this problem by finding
a definition of quasiclassicality have so far not succeeded.
On the other hand, it is shown that dynamical collapse models, of the type
originally proposed by Ghirardi-Rimini-Weber, can be re-interpreted as set
selection criteria within a quantum histories framework, in which context they
appear as candidate solutions to the set selection problem. This suggests a new
route to relativistic generalisation of these models, since covariant
definitions of a quantum event are known.
| [
{
"created": "Fri, 4 Sep 1998 21:33:01 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Kent",
"Adrian",
""
]
] | There are good motivations for considering some type of quantum histories formalism. Several possible formalisms are known, defined by different definitions of event and by different selection criteria for sets of histories. These formalisms have a natural interpretation, according to which nature somehow chooses one set of histories from among those allowed, and then randomly chooses to realise one history from that set; other interpretations are possible, but their scientific implications are essentially the same. The selection criteria proposed to date are reasonably natural, and certainly raise new questions. For example, the validity of ordering inferences which we normally take for granted --- such as that a particle in one region is necessarily in a larger region containing it --- depends on whether or not our history respects the criterion of ordered consistency, or merely consistency. However, the known selection criteria, including consistency and medium decoherence, are very weak. It is not possible to derive the predictions of classical mechanics or Copenhagen quantum mechanics from the theories they define, even given observational data in an extended time interval. Attempts to refine the consistent histories approach so as to solve this problem by finding a definition of quasiclassicality have so far not succeeded. On the other hand, it is shown that dynamical collapse models, of the type originally proposed by Ghirardi-Rimini-Weber, can be re-interpreted as set selection criteria within a quantum histories framework, in which context they appear as candidate solutions to the set selection problem. This suggests a new route to relativistic generalisation of these models, since covariant definitions of a quantum event are known. |
1305.2020 | Hyeong-Chan Kim | Inyong Cho, Hyeong-Chan Kim, and Taeyoon Moon | Precursor of Inflation | 6pages, 1figure | Phys. Rev. Lett 111, 071301 (2013) | 10.1103/PhysRevLett.111.071301 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate a nonsingular initial state of the Universe which leads to
inflation naturally. The model is described by a scalar field with a quadratic
potential in Eddington-inspired Born-Infeld gravity. The curvature of this
initial state is given by the mass scale of the scalar field which is much
smaller than the Planck scale. Therefore, in this model, quantum gravity is not
necessary in understanding this pre-inflationary stage, no matter how large the
energy density becomes. The initial state in this model evolves eventually to a
long inflationary period which is similar to the usual chaotic inflation.
| [
{
"created": "Thu, 9 May 2013 07:16:38 GMT",
"version": "v1"
}
] | 2013-08-26 | [
[
"Cho",
"Inyong",
""
],
[
"Kim",
"Hyeong-Chan",
""
],
[
"Moon",
"Taeyoon",
""
]
] | We investigate a nonsingular initial state of the Universe which leads to inflation naturally. The model is described by a scalar field with a quadratic potential in Eddington-inspired Born-Infeld gravity. The curvature of this initial state is given by the mass scale of the scalar field which is much smaller than the Planck scale. Therefore, in this model, quantum gravity is not necessary in understanding this pre-inflationary stage, no matter how large the energy density becomes. The initial state in this model evolves eventually to a long inflationary period which is similar to the usual chaotic inflation. |
gr-qc/0010096 | Alexander I. Nesterov | Alexander I. Nesterov | Riemann normal coordinates, Fermi reference system and the geodesic
deviation equation | LATeX, 13 pages | Class.Quant.Grav. 16 (1999) 465-477 | 10.1088/0264-9381/16/2/011 | null | gr-qc | null | We obtain the integral formulae for computing the tetrads and metric
components in Riemann normal coordinates and Fermi coordinate system of an
observer in arbitrary motion. Our approach admits essential enlarging the range
of validity of these coordinates. The results obtained are applied to the
geodesic deviation in the field of a weak plane gravitational wave and the
computation of plane-wave metric in Fermi normal coordinates.
| [
{
"created": "Thu, 26 Oct 2000 01:59:59 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Nesterov",
"Alexander I.",
""
]
] | We obtain the integral formulae for computing the tetrads and metric components in Riemann normal coordinates and Fermi coordinate system of an observer in arbitrary motion. Our approach admits essential enlarging the range of validity of these coordinates. The results obtained are applied to the geodesic deviation in the field of a weak plane gravitational wave and the computation of plane-wave metric in Fermi normal coordinates. |
1308.3642 | Michael T. Anderson | Michael T Anderson | Local existence and uniqueness for exterior static vacuum Einstein
metrics | 5 pages | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study solutions to the static vacuum Einstein equations on exterior
domains with prescribed metric and mean curvature on the inner boundary. It is
proved that for any such boundary data near the standard round boundary data in
Euclidean space, there exists a unique AF solution to the static vacuum
equations realizing the boundary data, which is close to the standard flat
solution.
| [
{
"created": "Fri, 16 Aug 2013 14:43:06 GMT",
"version": "v1"
}
] | 2013-08-19 | [
[
"Anderson",
"Michael T",
""
]
] | We study solutions to the static vacuum Einstein equations on exterior domains with prescribed metric and mean curvature on the inner boundary. It is proved that for any such boundary data near the standard round boundary data in Euclidean space, there exists a unique AF solution to the static vacuum equations realizing the boundary data, which is close to the standard flat solution. |
1101.4684 | Pablo Laguna | Tanja Bode, Tamara Bogdanovic, Roland Haas, James Healy, Pablo Laguna
and Deirdre Shoemaker | Mergers of Supermassive Black Holes in Astrophysical Environments | 9 pages, 5 figures, 1 table, replaced with version accepted for
publication in ApJ | null | 10.1088/0004-637X/744/1/45 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Modeling the late inspiral and merger of supermassive black holes is central
to understanding accretion processes and the conditions under which
electromagnetic emission accompanies gravitational waves. We use fully general
relativistic, hydrodynamics simulations to investigate how electromagnetic
signatures correlate with black hole spins, mass ratios, and the gaseous
environment in this final phase of binary evolution. In all scenarios, we find
some form of characteristic electromagnetic variability whose pattern depends
on the spins and binary mass ratios. Binaries in hot accretion flows exhibit a
flare followed by a sudden drop in luminosity associated with the plunge and
merger, as well as quasi-periodic oscillations correlated with the
gravitational waves during the inspiral. Conversely, circumbinary disk systems
are characterized by a low luminosity of variable emission, suggesting
challenging prospects for their detection.
| [
{
"created": "Mon, 24 Jan 2011 22:54:37 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Oct 2011 16:46:41 GMT",
"version": "v2"
}
] | 2015-05-27 | [
[
"Bode",
"Tanja",
""
],
[
"Bogdanovic",
"Tamara",
""
],
[
"Haas",
"Roland",
""
],
[
"Healy",
"James",
""
],
[
"Laguna",
"Pablo",
""
],
[
"Shoemaker",
"Deirdre",
""
]
] | Modeling the late inspiral and merger of supermassive black holes is central to understanding accretion processes and the conditions under which electromagnetic emission accompanies gravitational waves. We use fully general relativistic, hydrodynamics simulations to investigate how electromagnetic signatures correlate with black hole spins, mass ratios, and the gaseous environment in this final phase of binary evolution. In all scenarios, we find some form of characteristic electromagnetic variability whose pattern depends on the spins and binary mass ratios. Binaries in hot accretion flows exhibit a flare followed by a sudden drop in luminosity associated with the plunge and merger, as well as quasi-periodic oscillations correlated with the gravitational waves during the inspiral. Conversely, circumbinary disk systems are characterized by a low luminosity of variable emission, suggesting challenging prospects for their detection. |
1901.02461 | Lorenzo Annulli | Lorenzo Annulli, Vitor Cardoso, Leonardo Gualtieri | Electromagnetism and hidden vector fields in modified gravity theories:
spontaneous and induced vectorization | 12 pages, RevTeX4. Matches published version | Phys. Rev. D 99, 044038 (2019) | 10.1103/PhysRevD.99.044038 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In general relativity, Maxwell's equations are embedded in curved spacetime
through the minimal prescription, but this could change if strong-gravity
modifications are present. We show that with a nonminimal coupling between
gravity and a massless vector field, nonperturbative effects can arise in
compact stars. We find solutions describing stars with nontrivial vector field
configurations, some of which are associated to an instability, while others
are not. The vector field can be interpreted either as the electromagnetic
field, or as a hidden vector field weakly coupled with the standard model.
| [
{
"created": "Tue, 8 Jan 2019 19:00:01 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Feb 2019 16:29:26 GMT",
"version": "v2"
}
] | 2019-02-27 | [
[
"Annulli",
"Lorenzo",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Gualtieri",
"Leonardo",
""
]
] | In general relativity, Maxwell's equations are embedded in curved spacetime through the minimal prescription, but this could change if strong-gravity modifications are present. We show that with a nonminimal coupling between gravity and a massless vector field, nonperturbative effects can arise in compact stars. We find solutions describing stars with nontrivial vector field configurations, some of which are associated to an instability, while others are not. The vector field can be interpreted either as the electromagnetic field, or as a hidden vector field weakly coupled with the standard model. |
2201.07596 | Artur Alho | Artur Alho, Woei Chet Lim, Claes Uggla | Cosmological global dynamical systems analysis | 15 pages, 5 figures | null | 10.1088/1361-6382/ac7769 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a dynamical systems formulation for models with an exponential
scalar field and matter with a linear equation of state in a spatially flat and
isotropic spacetime. In contrast to earlier work, which only considered linear
hyperbolic fixed point analysis, we do a center manifold analysis of the
non-hyperbolic fixed points associated with bifurcations. More importantly
though, we construct monotonic functions and a Dulac function. Together with
the complete local fixed point analysis this leads to proofs that describe the
entire global dynamics of these models, thereby complementing previous local
results in the literature.
| [
{
"created": "Wed, 19 Jan 2022 13:46:45 GMT",
"version": "v1"
}
] | 2022-07-13 | [
[
"Alho",
"Artur",
""
],
[
"Lim",
"Woei Chet",
""
],
[
"Uggla",
"Claes",
""
]
] | We consider a dynamical systems formulation for models with an exponential scalar field and matter with a linear equation of state in a spatially flat and isotropic spacetime. In contrast to earlier work, which only considered linear hyperbolic fixed point analysis, we do a center manifold analysis of the non-hyperbolic fixed points associated with bifurcations. More importantly though, we construct monotonic functions and a Dulac function. Together with the complete local fixed point analysis this leads to proofs that describe the entire global dynamics of these models, thereby complementing previous local results in the literature. |
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