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1903.07735 | Andreas G. A. Pithis | Andreas G. A. Pithis | Aspects of quantum gravity | Ph.D. Thesis, University of London, King's College (Supervisor: Prof.
Mairi Sakellariadou), 357 pages, 51 figures; originally submitted in
September 2018; detailed abstract in the file; largely based on the
publications: arXiv:1402.2274, 1606.00352, 1607.06662, 1612.02456,
1709.00994, 1806.09961 and 1808.09765 | null | null | null | gr-qc hep-ph hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For more than 80 years theoretical physicists have been trying to develop a
theory of quantum gravity which would successfully combine the tenets of
Einstein's theory of general relativity (GR) together with those of quantum
field theory. At the current stage, there are various competing responses to
this challenge under construction. Attacking the problem of quantum gravity
from the quantum geometry perspective, where space and spacetime are discrete,
the focus of this thesis lies on the application of loop quantum gravity (LQG)
and group field theory (GFT). We employ these two closely related
nonperturbative approaches to two areas where quantum gravity effects are
broadly expected to be relevant: black holes and quantum cosmology.
Concerning black holes, apart from understanding their inner structure, a
pressing issue is to give a microscopic explanation for the phenomenon of black
hole entropy in terms of a discrete quantum geometry and relate it to the
symmetries of the horizon. Black hole models in LQG are typically constructed
via the isolated horizon boundary condition which gives rise to an effective
description of the horizon geometry in terms SU(2) Chern-Simons theory. In this
thesis we find a reinterpretation of the statistics of the horizon degrees of
freedom as those of a system of non-Abelian anyons.
As regards quantum cosmology, the challenge is to understand how the initial
singularity problem of GR can be resolved by means of the discreteness of
geometry and how a continuum spacetime can emerge from a large assembly of
geometric building blocks. Most recent research in GFT aims at deriving the
effective dynamics for condensate states directly from the microscopic GFT
quantum dynamics and subsequently to extract a cosmological interpretation from
them. In this thesis we elaborate on aspects of this approach and study
phenomenological consequences in detail.
| [
{
"created": "Mon, 18 Mar 2019 21:38:29 GMT",
"version": "v1"
}
] | 2019-03-20 | [
[
"Pithis",
"Andreas G. A.",
""
]
] | For more than 80 years theoretical physicists have been trying to develop a theory of quantum gravity which would successfully combine the tenets of Einstein's theory of general relativity (GR) together with those of quantum field theory. At the current stage, there are various competing responses to this challenge under construction. Attacking the problem of quantum gravity from the quantum geometry perspective, where space and spacetime are discrete, the focus of this thesis lies on the application of loop quantum gravity (LQG) and group field theory (GFT). We employ these two closely related nonperturbative approaches to two areas where quantum gravity effects are broadly expected to be relevant: black holes and quantum cosmology. Concerning black holes, apart from understanding their inner structure, a pressing issue is to give a microscopic explanation for the phenomenon of black hole entropy in terms of a discrete quantum geometry and relate it to the symmetries of the horizon. Black hole models in LQG are typically constructed via the isolated horizon boundary condition which gives rise to an effective description of the horizon geometry in terms SU(2) Chern-Simons theory. In this thesis we find a reinterpretation of the statistics of the horizon degrees of freedom as those of a system of non-Abelian anyons. As regards quantum cosmology, the challenge is to understand how the initial singularity problem of GR can be resolved by means of the discreteness of geometry and how a continuum spacetime can emerge from a large assembly of geometric building blocks. Most recent research in GFT aims at deriving the effective dynamics for condensate states directly from the microscopic GFT quantum dynamics and subsequently to extract a cosmological interpretation from them. In this thesis we elaborate on aspects of this approach and study phenomenological consequences in detail. |
1409.6708 | Xian Gao | Xian Gao | Hamiltonian analysis of spatially covariant gravity | v1: 17 pages; v2: 15 pages, double column, Sec.II extended, comments
added, typos corrected | Phys. Rev. D 90, 104033 (2014) | 10.1103/PhysRevD.90.104033 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform the Hamiltonian constraint analysis for a wide class of gravity
theories that are invariant under spatial diffeomorphism. With very general
setup, we show that different from the general relativity, the primary and
secondary constraints associated with the lapse function $N$ become second
class, as long as the lapse function $N$ enters the Hamiltonian nonlinearly.
This fact implies that there are three degrees of freedom are propagating, of
which two correspond to the usual tensor type transverse and traceless
gravitons, and one is the scalar type graviton. By restoring the full spacetime
diffeomorphism using the St\"{u}ckelberg trick, this type of spatially
covariant gravity theories corresponds to a large class of single field
scalar-tensor theories that possess higher order derivatives in the equations
of motion, and thus is beyond the scope of the Horndeski theory.
| [
{
"created": "Tue, 23 Sep 2014 19:28:08 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Oct 2014 19:00:24 GMT",
"version": "v2"
}
] | 2014-11-26 | [
[
"Gao",
"Xian",
""
]
] | We perform the Hamiltonian constraint analysis for a wide class of gravity theories that are invariant under spatial diffeomorphism. With very general setup, we show that different from the general relativity, the primary and secondary constraints associated with the lapse function $N$ become second class, as long as the lapse function $N$ enters the Hamiltonian nonlinearly. This fact implies that there are three degrees of freedom are propagating, of which two correspond to the usual tensor type transverse and traceless gravitons, and one is the scalar type graviton. By restoring the full spacetime diffeomorphism using the St\"{u}ckelberg trick, this type of spatially covariant gravity theories corresponds to a large class of single field scalar-tensor theories that possess higher order derivatives in the equations of motion, and thus is beyond the scope of the Horndeski theory. |
gr-qc/9607065 | Madore | J. Madore | Fuzzy Space-Time | 17 pages LaTex | null | 10.1139/cjp-75-6-385 | LPTHE Orsay 96/64 | gr-qc | null | A review is made of recent efforts to define linear connections and their
corresponding curvature within the context of noncommutative geometry. As an
application it is suggested that it is possible to identify the gravitational
field as a phenomenological manifestation of space-time commutation relations
and to thereby clarify its role as an ultraviolet regularizer.
| [
{
"created": "Fri, 26 Jul 1996 09:08:06 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Madore",
"J.",
""
]
] | A review is made of recent efforts to define linear connections and their corresponding curvature within the context of noncommutative geometry. As an application it is suggested that it is possible to identify the gravitational field as a phenomenological manifestation of space-time commutation relations and to thereby clarify its role as an ultraviolet regularizer. |
gr-qc/0503046 | Abel Camacho Mr. | Abel Camacho (Dept. Physics, Universidad Autonoma
Metropolitana--Iztapalapa) and A. Camacho-Galvan (DEP--Facultad de
Ingenieria, Universidad Nacional Autonoma de Mexico) | Quantum Measurements and the kappa--Poincare Group | Accepted in General Relativity and Gravitation. Dedicated to Alberto
Garcia on the occasion of his 60th. birthday | Gen.Rel.Grav. 37 (2005) 651-657 | 10.1007/s10714-005-0052-9 | null | gr-qc quant-ph | null | The possible description of the vacuum of quantum gravity through the so
called kappa--Poincare group is analyzed considering some of the consequences
of this symmetry in the path integral formulation of nonrelativistic quantum
theory. This study is carried out with two cases, firstly, a free particle, and
finally, the situation of a particle immersed in a homogeneous gravitational
field. It will be shown that the kappa--Poincare group implies the loss of some
of the basic properties associated to Feynman's path integral. For instance,
loss of the group characteristic related to the time dependence of the
evolution operator, or the breakdown of the composition law for amplitudes of
events occurring successively in time. Additionally some similarities between
the present idea and the so called restricted path integral formalism will be
underlined. These analogies advocate the claim that if the kappa--Poincare
group contains some of the physical information of the quantum gravity vacuum,
then this vacuum could entail decoherence. This last result will also allow us
to consider the possibility of analyzing the continuous measurement problem of
quantum theory from a group--theoretical point of view, but now taking into
account the kappa--Poincare symmetries.
| [
{
"created": "Thu, 10 Mar 2005 19:57:18 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Camacho",
"Abel",
"",
"Dept. Physics, Universidad Autonoma\n Metropolitana--Iztapalapa"
],
[
"Camacho-Galvan",
"A.",
"",
"DEP--Facultad de\n Ingenieria, Universidad Nacional Autonoma de Mexico"
]
] | The possible description of the vacuum of quantum gravity through the so called kappa--Poincare group is analyzed considering some of the consequences of this symmetry in the path integral formulation of nonrelativistic quantum theory. This study is carried out with two cases, firstly, a free particle, and finally, the situation of a particle immersed in a homogeneous gravitational field. It will be shown that the kappa--Poincare group implies the loss of some of the basic properties associated to Feynman's path integral. For instance, loss of the group characteristic related to the time dependence of the evolution operator, or the breakdown of the composition law for amplitudes of events occurring successively in time. Additionally some similarities between the present idea and the so called restricted path integral formalism will be underlined. These analogies advocate the claim that if the kappa--Poincare group contains some of the physical information of the quantum gravity vacuum, then this vacuum could entail decoherence. This last result will also allow us to consider the possibility of analyzing the continuous measurement problem of quantum theory from a group--theoretical point of view, but now taking into account the kappa--Poincare symmetries. |
0812.3936 | Marc-Thierry Jaekel | Marc-Thierry Jaekel and Serge Reynaud | Mass, inertia and gravitation | 24 pages, Proc. School on Mass, Orleans (2008) | Mass and Motion in General Relativity, L. Blanchet, A. Spallicci
and B. Whiting Eds. (Springer,2011) 491 | 10.1007/978-90-481-3015-3 | LPTENS 08/67 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss some effects induced by quantum field fluctuations on mass,
inertia and gravitation. Recalling the problem raised by vacuum field
fluctuations with respect to inertia and gravitation, we show that vacuum
energy differences, such as Casimir energy, do contribute to inertia. Mass
behaves as a quantum observable and in particular possesses quantum
fluctuations. We show that the compatibility of the quantum nature of mass with
gravitation can be ensured by conformal symmetries, which allow one to
formulate a quantum version of the equivalence principle. Finally, we consider
some corrections to the coupling between metric fields and energy-momentum
tensors induced by radiative corrections. Newton gravitation constant is
replaced by two different running coupling constants in the sectors of
traceless and traced tensors. There result metric extensions of general
relativity, which can be characterized by modified Ricci curvatures or by two
gravitation potentials. The corresponding phenomenological framework extends
the usual Parametrized Post-Newtonian one, with the ability to remain
compatible with classical tests of gravity while accounting for new features,
such as Pioneer like anomalies or anomalous light deflection.
| [
{
"created": "Mon, 22 Dec 2008 15:46:59 GMT",
"version": "v1"
}
] | 2011-01-27 | [
[
"Jaekel",
"Marc-Thierry",
""
],
[
"Reynaud",
"Serge",
""
]
] | We discuss some effects induced by quantum field fluctuations on mass, inertia and gravitation. Recalling the problem raised by vacuum field fluctuations with respect to inertia and gravitation, we show that vacuum energy differences, such as Casimir energy, do contribute to inertia. Mass behaves as a quantum observable and in particular possesses quantum fluctuations. We show that the compatibility of the quantum nature of mass with gravitation can be ensured by conformal symmetries, which allow one to formulate a quantum version of the equivalence principle. Finally, we consider some corrections to the coupling between metric fields and energy-momentum tensors induced by radiative corrections. Newton gravitation constant is replaced by two different running coupling constants in the sectors of traceless and traced tensors. There result metric extensions of general relativity, which can be characterized by modified Ricci curvatures or by two gravitation potentials. The corresponding phenomenological framework extends the usual Parametrized Post-Newtonian one, with the ability to remain compatible with classical tests of gravity while accounting for new features, such as Pioneer like anomalies or anomalous light deflection. |
1806.10408 | Vladimir S. Manko | V. S. Manko and E. Ruiz | Metric for two arbitrary Kerr sources | 12 pages, 1 figure | null | 10.1016/j.physletb.2019.05.027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The full metric describing a stationary axisymmetric system of two arbitrary
Kerr sources, black holes or hyperextreme objects, located on the symmetry axis
and kept apart in equilibrium by a massless strut is presented in a concise
explicit form involving five physical parameters. The binary system composed of
a Schwarzschild black hole and a Kerr source is a special case not covered by
the general formulas, and we elaborate the metric for this physically
interesting configuration too.
| [
{
"created": "Wed, 27 Jun 2018 10:54:09 GMT",
"version": "v1"
}
] | 2019-06-26 | [
[
"Manko",
"V. S.",
""
],
[
"Ruiz",
"E.",
""
]
] | The full metric describing a stationary axisymmetric system of two arbitrary Kerr sources, black holes or hyperextreme objects, located on the symmetry axis and kept apart in equilibrium by a massless strut is presented in a concise explicit form involving five physical parameters. The binary system composed of a Schwarzschild black hole and a Kerr source is a special case not covered by the general formulas, and we elaborate the metric for this physically interesting configuration too. |
gr-qc/9905063 | Pascual-Sanchez J.-F. | J.-F. Pascual-S\'anchez | Cosmic acceleration: Inhomogeneity versus vacuum energy | LATEX, 7 pags, no figs, Honorable Mention in the 1999 Essay
Competition of the Gravity Research Foundation | Mod.Phys.Lett. A14 (1999) 1539-1544 | 10.1142/S0217732399001632 | null | gr-qc astro-ph | null | In this essay, I present an alternative explanation for the cosmic
acceleration which appears as a consequence of recent high redshift Supernova
data. In the usual interpretation, this cosmic acceleration is explained by the
presence of a positive cosmological constant or vacuum energy, in the
background of Friedmann models. Instead, I will consider a Local Rotational
Symmetric (LRS) inhomogeneous spacetime, with a barotropic equation of state
for the cosmic matter. Within this framework the kinematical acceleration of
the cosmic fluid or, equivalently, the inhomogeneity of matter, is just the
responsible of the SNe Ia measured cosmic acceleration. Although in our model
the Cosmological Principle is relaxed, it maintains local isotropy about our
worldline in agreement with the CBR experiments.
| [
{
"created": "Tue, 18 May 1999 19:39:30 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Pascual-Sánchez",
"J. -F.",
""
]
] | In this essay, I present an alternative explanation for the cosmic acceleration which appears as a consequence of recent high redshift Supernova data. In the usual interpretation, this cosmic acceleration is explained by the presence of a positive cosmological constant or vacuum energy, in the background of Friedmann models. Instead, I will consider a Local Rotational Symmetric (LRS) inhomogeneous spacetime, with a barotropic equation of state for the cosmic matter. Within this framework the kinematical acceleration of the cosmic fluid or, equivalently, the inhomogeneity of matter, is just the responsible of the SNe Ia measured cosmic acceleration. Although in our model the Cosmological Principle is relaxed, it maintains local isotropy about our worldline in agreement with the CBR experiments. |
gr-qc/0509015 | Carles Bona | C. Bona, J. Carot and C. Palenzuela-Luque | Almost-stationary motions and gauge conditions in General Relativity | Talk presented at the Spanish Relativity Meeting, September 6-10 2005
Revised version | Phys.Rev. D72 (2005) 124010 | 10.1103/PhysRevD.72.124010 | null | gr-qc | null | An almost-stationary gauge condition is proposed with a view to Numerical
Relativity applications. The time lines are defined as the integral curves of
the timelike solutions of the harmonic almost-Killing equation. This vector
equation is derived by a variational principle, by minimizing the deviations
from isometry. The corresponding almost-stationary gauge condition allows one
to put the field equations in hyperbolic form, both in the free-evolution ADM
and in the Z4 formalisms.
| [
{
"created": "Mon, 5 Sep 2005 08:20:59 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Dec 2005 12:16:39 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Bona",
"C.",
""
],
[
"Carot",
"J.",
""
],
[
"Palenzuela-Luque",
"C.",
""
]
] | An almost-stationary gauge condition is proposed with a view to Numerical Relativity applications. The time lines are defined as the integral curves of the timelike solutions of the harmonic almost-Killing equation. This vector equation is derived by a variational principle, by minimizing the deviations from isometry. The corresponding almost-stationary gauge condition allows one to put the field equations in hyperbolic form, both in the free-evolution ADM and in the Z4 formalisms. |
2404.00090 | Veome Kapil | Veome Kapil, Luca Reali, Roberto Cotesta and Emanuele Berti | Systematic bias from waveform modeling for binary black hole populations
in next-generation gravitational wave detectors | 15 pages, 11 figures, 1 table. Matches the version published in Phys.
Rev. D 109, 104043 | Phys. Rev. D 109, 104043 (2024) | 10.1103/PhysRevD.109.104043 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Next-generation gravitational wave detectors such as the Einstein Telescope
and Cosmic Explorer will have increased sensitivity and observing volumes,
enabling unprecedented precision in parameter estimation. However, this
enhanced precision could also reveal systematic biases arising from waveform
modeling, which may impact astrophysical inference. We investigate the extent
of these biases over a year-long observing run with $10^5$ simulated binary
black hole sources using the linear signal approximation. To establish a
conservative estimate, we sample binaries from a smoothed truncated power-law
population model and compute systematic parameter biases between the
IMRPhenomXAS and IMRPhenomD waveform models. For sources with signal-to-noise
ratios above 100, we estimate statistically significant parameter biases in
$\sim 3\%-20\%$ of the events, depending on the parameter. We find that the
average mismatch between waveform models required to achieve a bias of $\leq
1\sigma$ for $99\%$ of detections with signal-to-noise ratios $\geq 100$ should
be $\mathcal{O}(10^{-5})$, or at least one order of magnitude better than
current levels of waveform accuracy.
| [
{
"created": "Fri, 29 Mar 2024 18:00:01 GMT",
"version": "v1"
},
{
"created": "Wed, 15 May 2024 17:16:59 GMT",
"version": "v2"
}
] | 2024-05-16 | [
[
"Kapil",
"Veome",
""
],
[
"Reali",
"Luca",
""
],
[
"Cotesta",
"Roberto",
""
],
[
"Berti",
"Emanuele",
""
]
] | Next-generation gravitational wave detectors such as the Einstein Telescope and Cosmic Explorer will have increased sensitivity and observing volumes, enabling unprecedented precision in parameter estimation. However, this enhanced precision could also reveal systematic biases arising from waveform modeling, which may impact astrophysical inference. We investigate the extent of these biases over a year-long observing run with $10^5$ simulated binary black hole sources using the linear signal approximation. To establish a conservative estimate, we sample binaries from a smoothed truncated power-law population model and compute systematic parameter biases between the IMRPhenomXAS and IMRPhenomD waveform models. For sources with signal-to-noise ratios above 100, we estimate statistically significant parameter biases in $\sim 3\%-20\%$ of the events, depending on the parameter. We find that the average mismatch between waveform models required to achieve a bias of $\leq 1\sigma$ for $99\%$ of detections with signal-to-noise ratios $\geq 100$ should be $\mathcal{O}(10^{-5})$, or at least one order of magnitude better than current levels of waveform accuracy. |
1109.2693 | Abdollah Refaei | A. Refaei, M V. Takook | Scalar effective action in Krein space quantization | 11 pages | Mod.Phys.Lett. A Vol. 26, No. 1 (2011) 31--41 | 10.1142/S0217732311034505 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, the \lambda\phi^4 scalar feld effective action, in the
one-loop approximation, is calculated by using the Krein space quantization. We
show that the effective action is naturally fnite and the singularity does not
appear in the theory. The physical interaction mass, the running coupling
constant and \beta-function are then calculated. The effective potential which
is calculated in the Krein space quantization is different from the usual
Hilbert space calculation, however we show that \beta-function is the same in
the two different methods.
| [
{
"created": "Tue, 13 Sep 2011 07:37:57 GMT",
"version": "v1"
}
] | 2011-09-14 | [
[
"Refaei",
"A.",
""
],
[
"Takook",
"M V.",
""
]
] | In this paper, the \lambda\phi^4 scalar feld effective action, in the one-loop approximation, is calculated by using the Krein space quantization. We show that the effective action is naturally fnite and the singularity does not appear in the theory. The physical interaction mass, the running coupling constant and \beta-function are then calculated. The effective potential which is calculated in the Krein space quantization is different from the usual Hilbert space calculation, however we show that \beta-function is the same in the two different methods. |
1608.01598 | Parthapratim Pradhan | Parthapratim Pradhan | Logarithmic Corrections to the Black Hole Entropy Product of ${\cal
H}^{\pm}$ via Cardy Formula | EPL Style, 4 pages | EPL, 116 (2016) 50002 | 10.1209/0295-5075/116/50002 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the logarithmic corrections to black hole (BH) entropy product of
${\cal H}^{\pm}$ \footnote{ ${\cal H}^{+}$ and ${\cal H}^{-}$ denote outer
(event) horizon and inner (Cauchy) horizons} by using \emph{Cardy
prescription}. We particularly apply this formula for \emph{BTZ BH}. We
speculate that the logarithmic corrections to entropy product of ${\cal
H}^{\pm}$ when computed \emph{via Cardy formula} the product should be neither
\emph{mass-independent (universal)} nor be \emph{quantized}.
| [
{
"created": "Thu, 4 Aug 2016 16:21:10 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Jan 2017 15:34:11 GMT",
"version": "v2"
}
] | 2017-01-13 | [
[
"Pradhan",
"Parthapratim",
""
]
] | We compute the logarithmic corrections to black hole (BH) entropy product of ${\cal H}^{\pm}$ \footnote{ ${\cal H}^{+}$ and ${\cal H}^{-}$ denote outer (event) horizon and inner (Cauchy) horizons} by using \emph{Cardy prescription}. We particularly apply this formula for \emph{BTZ BH}. We speculate that the logarithmic corrections to entropy product of ${\cal H}^{\pm}$ when computed \emph{via Cardy formula} the product should be neither \emph{mass-independent (universal)} nor be \emph{quantized}. |
1110.0687 | Cosimo Bambi | Cosimo Bambi | Can we constrain the maximum value for the spin parameter of the
super-massive objects in galactic nuclei without knowing their actual nature? | 5 pages, 2 figures. v2: some typos corrected | Phys.Lett.B705:5-8,2011 | 10.1016/j.physletb.2011.10.005 | IPMU11-0170; LMU-ASC-26-12 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In 4-dimensional General Relativity, black holes are described by the Kerr
solution and are subject to the bound $|a_*| \le 1$, where $a_*$ is the black
hole spin parameter. If current black hole candidates are not the black holes
predicted in General Relativity, this bound does not hold and $a_*$ might
exceed 1. In this letter, I relax the Kerr black hole hypothesis and I find
that the value of the spin parameter of the super-massive black hole candidates
in galactic nuclei cannot be higher than about 1.2. A higher spin parameter
would not be consistent with a radiative efficiency $\eta > 0.15$, as observed
at least for the most luminous AGN. While a rigorous proof is lacking, I
conjecture that the bound $|a_*| \lesssim 1.2$ is independent of the exact
nature of these objects.
| [
{
"created": "Tue, 4 Oct 2011 13:55:58 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Oct 2011 14:52:18 GMT",
"version": "v2"
}
] | 2012-04-09 | [
[
"Bambi",
"Cosimo",
""
]
] | In 4-dimensional General Relativity, black holes are described by the Kerr solution and are subject to the bound $|a_*| \le 1$, where $a_*$ is the black hole spin parameter. If current black hole candidates are not the black holes predicted in General Relativity, this bound does not hold and $a_*$ might exceed 1. In this letter, I relax the Kerr black hole hypothesis and I find that the value of the spin parameter of the super-massive black hole candidates in galactic nuclei cannot be higher than about 1.2. A higher spin parameter would not be consistent with a radiative efficiency $\eta > 0.15$, as observed at least for the most luminous AGN. While a rigorous proof is lacking, I conjecture that the bound $|a_*| \lesssim 1.2$ is independent of the exact nature of these objects. |
gr-qc/0612121 | Michael Seifert | Michael D. Seifert and Robert M. Wald | A general variational principle for spherically symmetric perturbations
in diffeomorphism covariant theories | 13 pages; submitted to Phys. Rev. D. v2: changed formatting, added
conclusion, corrected sign conventions | Phys.Rev.D75:084029,2007 | 10.1103/PhysRevD.75.084029 | null | gr-qc | null | We present a general method for the analysis of the stability of static,
spherically symmetric solutions to spherically symmetric perturbations in an
arbitrary diffeomorphism covariant Lagrangian field theory. Our method involves
fixing the gauge and solving the linearized gravitational field equations to
eliminate the metric perturbation variable in terms of the matter variables. In
a wide class of cases--which include f(R) gravity, the Einstein-aether theory
of Jacobson and Mattingly, and Bekenstein's TeVeS theory--the remaining
perturbation equations for the matter fields are second order in time. We show
how the symplectic current arising from the original Lagrangian gives rise to a
symmetric bilinear form on the variables of the reduced theory. If this
bilinear form is positive definite, it provides an inner product that puts the
equations of motion of the reduced theory into a self-adjoint form. A
variational principle can then be written down immediately, from which
stability can be tested readily. We illustrate our method in the case of
Einstein's equation with perfect fluid matter, thereby re-deriving, in a
systematic manner, Chandrasekhar's variational principle for radial
oscillations of spherically symmetric stars. In a subsequent paper, we will
apply our analysis to f(R) gravity, the Einstein-aether theory, and
Bekenstein's TeVeS theory.
| [
{
"created": "Tue, 19 Dec 2006 20:57:57 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Mar 2007 22:51:58 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Seifert",
"Michael D.",
""
],
[
"Wald",
"Robert M.",
""
]
] | We present a general method for the analysis of the stability of static, spherically symmetric solutions to spherically symmetric perturbations in an arbitrary diffeomorphism covariant Lagrangian field theory. Our method involves fixing the gauge and solving the linearized gravitational field equations to eliminate the metric perturbation variable in terms of the matter variables. In a wide class of cases--which include f(R) gravity, the Einstein-aether theory of Jacobson and Mattingly, and Bekenstein's TeVeS theory--the remaining perturbation equations for the matter fields are second order in time. We show how the symplectic current arising from the original Lagrangian gives rise to a symmetric bilinear form on the variables of the reduced theory. If this bilinear form is positive definite, it provides an inner product that puts the equations of motion of the reduced theory into a self-adjoint form. A variational principle can then be written down immediately, from which stability can be tested readily. We illustrate our method in the case of Einstein's equation with perfect fluid matter, thereby re-deriving, in a systematic manner, Chandrasekhar's variational principle for radial oscillations of spherically symmetric stars. In a subsequent paper, we will apply our analysis to f(R) gravity, the Einstein-aether theory, and Bekenstein's TeVeS theory. |
2012.10814 | Adamantia Zampeli | Adamantia Zampeli, Andronikos Paliathanasis | Quantization of inhomogeneous spacetimes with cosmological constant term | 11 pages, 2 figures | null | 10.1088/1361-6382/ac1209 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the Szekeres system with cosmological constant admits a
sufficient number of conservation laws, which allow to claim the integrability
of the system. The main novelty in this investigation is that we find that the
unique attractor of the Szekeres system is the isotropic inhomogeneous de
Sitter (-like) universe, contrary to the original system in which the
attractors describe Kantowski-Sachs (-like) spacetimes. We also study the
existence of quantum corrections and the emergence of classicality by
considering the linear and quadratic conserved quantities at the quantum level.
We perform an analysis considering different approaches, involving the Bohmian
quantum potential and a probability analysis. The result is that there are no
quantum corrections for the quadratic integrals, while there exists a linear
case for which we find quantum corrections.
| [
{
"created": "Sat, 19 Dec 2020 23:30:58 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Jun 2021 06:59:59 GMT",
"version": "v2"
}
] | 2021-08-11 | [
[
"Zampeli",
"Adamantia",
""
],
[
"Paliathanasis",
"Andronikos",
""
]
] | We show that the Szekeres system with cosmological constant admits a sufficient number of conservation laws, which allow to claim the integrability of the system. The main novelty in this investigation is that we find that the unique attractor of the Szekeres system is the isotropic inhomogeneous de Sitter (-like) universe, contrary to the original system in which the attractors describe Kantowski-Sachs (-like) spacetimes. We also study the existence of quantum corrections and the emergence of classicality by considering the linear and quadratic conserved quantities at the quantum level. We perform an analysis considering different approaches, involving the Bohmian quantum potential and a probability analysis. The result is that there are no quantum corrections for the quadratic integrals, while there exists a linear case for which we find quantum corrections. |
1004.0525 | Gabor Kunstatter | Jonathan Ziprick and Gabor Kunstatter | Quantum Corrected Spherical Collapse: A Phenomenological Framework | null | Phys.Rev.D82:044031,2010 | 10.1103/PhysRevD.82.044031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A phenomenological framework is presented for incorporating quantum gravity
motivated corrections into the dynamics of spherically symmetric collapse. The
effective equations are derived from a variational principle that guarantees
energy conservation and the existence of a Birkhoff theorem. The gravitational
potential can be chosen as a function of the areal radius to yield specific
non-singular static spherically symmetric solutions that generically have two
horizons. For a specific choice of potential the effective stress energy tensor
violates only the dominant energy condition. The violations are maximum near
the inner horizon and die off rapidly. A numerical study of the quantum
corrected collapse of a spherically symmetric scalar field in this case reveals
that the modified gravitational potential prevents the formation of a central
singularity and ultimately yields a static, mostly vacuum, spacetime with two
horizons. The matter "piles up" on the inner horizon giving rise to mass
inflation at late times. The Cauchy horizon is transformed into a null, weak
singularity, but in contrast to Einstein gravity, the absence of a central
singularity renders this null singularity stable.
| [
{
"created": "Sun, 4 Apr 2010 18:25:26 GMT",
"version": "v1"
}
] | 2015-03-14 | [
[
"Ziprick",
"Jonathan",
""
],
[
"Kunstatter",
"Gabor",
""
]
] | A phenomenological framework is presented for incorporating quantum gravity motivated corrections into the dynamics of spherically symmetric collapse. The effective equations are derived from a variational principle that guarantees energy conservation and the existence of a Birkhoff theorem. The gravitational potential can be chosen as a function of the areal radius to yield specific non-singular static spherically symmetric solutions that generically have two horizons. For a specific choice of potential the effective stress energy tensor violates only the dominant energy condition. The violations are maximum near the inner horizon and die off rapidly. A numerical study of the quantum corrected collapse of a spherically symmetric scalar field in this case reveals that the modified gravitational potential prevents the formation of a central singularity and ultimately yields a static, mostly vacuum, spacetime with two horizons. The matter "piles up" on the inner horizon giving rise to mass inflation at late times. The Cauchy horizon is transformed into a null, weak singularity, but in contrast to Einstein gravity, the absence of a central singularity renders this null singularity stable. |
2207.08809 | Nader Inan | Nader A. Inan | A new approach to detecting gravitational waves via the coupling of
gravity to the zero-point energy of the phonon modes of a superconductor | arXiv admin note: substantial text overlap with arXiv:2207.08062 | International Journal of Modern Physics D, Vol. 26, No. 12 (2017) | 10.1142/S0218271817430313 | null | gr-qc cond-mat.supr-con | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The response of a superconductor to a gravitational wave is shown to obey a
London-like constituent equation. The Cooper pairs are described by the
Ginzburg-Landau free energy density embedded in curved spacetime. The lattice
ions are modeled by quantum harmonic oscillators characterized by quasi-energy
eigenvalues. This formulation is shown to predict a dynamical Casimir effect
since the zero-point energy of the ionic lattice phonons is modulated by the
gravitational wave. It is also shown that the response to a gravitational wave
is far less for the Cooper pair density than for the ionic lattice. This
predicts a "charge separation effect" which can be used to detect the passage
of a gravitational wave.
| [
{
"created": "Sun, 17 Jul 2022 03:15:32 GMT",
"version": "v1"
}
] | 2022-07-20 | [
[
"Inan",
"Nader A.",
""
]
] | The response of a superconductor to a gravitational wave is shown to obey a London-like constituent equation. The Cooper pairs are described by the Ginzburg-Landau free energy density embedded in curved spacetime. The lattice ions are modeled by quantum harmonic oscillators characterized by quasi-energy eigenvalues. This formulation is shown to predict a dynamical Casimir effect since the zero-point energy of the ionic lattice phonons is modulated by the gravitational wave. It is also shown that the response to a gravitational wave is far less for the Cooper pair density than for the ionic lattice. This predicts a "charge separation effect" which can be used to detect the passage of a gravitational wave. |
1312.6731 | Bruno Coutinho Mundim | Bruno C. Mundim, Hiroyuki Nakano, Nicol\'as Yunes, Manuela Campanelli,
Scott C. Noble, Yosef Zlochower | Approximate black hole binary spacetime via asymptotic matching | 17 pages, 8 figures, 1 table. Appendix added to match published
version | Phys. Rev. D 89, 084008 - Published 9 April 2014 | 10.1103/PhysRevD.89.084008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a fully analytic, general relativistic, nonspinning black hole
binary spacetime that approximately solves the vacuum Einstein equations
everywhere in space and time for black holes sufficiently well separated. The
metric is constructed by asymptotically matching perturbed Schwarzschild
metrics near each black hole to a two-body post-Newtonian metric far from them,
and a two-body post-Minkowskian metric farther still. Asymptotic matching is
done without linearizing about a particular time slice, and thus it is valid
dynamically and for all times, provided the binary is sufficiently well
separated. This approximate global metric can be used for long dynamical
evolutions of relativistic magnetohydrodynamical, circumbinary disks around
inspiraling supermassive black holes to study a variety of phenomena.
| [
{
"created": "Tue, 24 Dec 2013 00:55:30 GMT",
"version": "v1"
},
{
"created": "Sat, 10 May 2014 13:23:21 GMT",
"version": "v2"
}
] | 2014-05-13 | [
[
"Mundim",
"Bruno C.",
""
],
[
"Nakano",
"Hiroyuki",
""
],
[
"Yunes",
"Nicolás",
""
],
[
"Campanelli",
"Manuela",
""
],
[
"Noble",
"Scott C.",
""
],
[
"Zlochower",
"Yosef",
""
]
] | We construct a fully analytic, general relativistic, nonspinning black hole binary spacetime that approximately solves the vacuum Einstein equations everywhere in space and time for black holes sufficiently well separated. The metric is constructed by asymptotically matching perturbed Schwarzschild metrics near each black hole to a two-body post-Newtonian metric far from them, and a two-body post-Minkowskian metric farther still. Asymptotic matching is done without linearizing about a particular time slice, and thus it is valid dynamically and for all times, provided the binary is sufficiently well separated. This approximate global metric can be used for long dynamical evolutions of relativistic magnetohydrodynamical, circumbinary disks around inspiraling supermassive black holes to study a variety of phenomena. |
2404.09698 | Dinesh Chandra Maurya | Dinesh Chandra Maurya, K. Yesmakhanova, R. Myrzakulov, G. Nugmanova | Myrzakulov $F(T,Q)$ gravity: cosmological implications and constraints | 33 pages, 11 figures. arXiv admin note: text overlap with
arXiv:2403.11604 | null | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | In this paper, we investigate some exact cosmological models in Myrzakulov
$F(T,Q)$ gravity or the Myrzakulov gravity-III (MG-III) proposed in
[arXiv:1205.5266], with observational constraints. The MG-III gravity is some
kind of unification of two known gravity theories, namely, the $F(T)$ gravity
and the $F(Q)$ gravity. The field equations of the MG-III theory are obtained
by regarding the metric tensor and the general affine connection as independent
variables. We then focus on the particular case in which the $F(T,Q)$ function
characterizing the aforementioned metric-affine models is linear that is
$F(T,Q)=\lambda T+\mu Q$. We investigate this linear case and consider a
Friedmann-Lema\^{i}tre-Robertson-Walker background to study cosmological
aspects and applications. We have obtained three exact solutions of the
modified field equations in different cases $T$ and $Q$, in the form of Hubble
function $H(t)$ and scale factor $a(t)$ and placed observational constraints on
it through the Hubble $H(z)$ datasets on it using the MCMC analysis. We have
investigated the deceleration parameter $q(z)$, effective EoS parameters and a
comparative study of all three models with $\Lambda$CDM model has been carried
out.
| [
{
"created": "Mon, 15 Apr 2024 11:59:36 GMT",
"version": "v1"
}
] | 2024-04-16 | [
[
"Maurya",
"Dinesh Chandra",
""
],
[
"Yesmakhanova",
"K.",
""
],
[
"Myrzakulov",
"R.",
""
],
[
"Nugmanova",
"G.",
""
]
] | In this paper, we investigate some exact cosmological models in Myrzakulov $F(T,Q)$ gravity or the Myrzakulov gravity-III (MG-III) proposed in [arXiv:1205.5266], with observational constraints. The MG-III gravity is some kind of unification of two known gravity theories, namely, the $F(T)$ gravity and the $F(Q)$ gravity. The field equations of the MG-III theory are obtained by regarding the metric tensor and the general affine connection as independent variables. We then focus on the particular case in which the $F(T,Q)$ function characterizing the aforementioned metric-affine models is linear that is $F(T,Q)=\lambda T+\mu Q$. We investigate this linear case and consider a Friedmann-Lema\^{i}tre-Robertson-Walker background to study cosmological aspects and applications. We have obtained three exact solutions of the modified field equations in different cases $T$ and $Q$, in the form of Hubble function $H(t)$ and scale factor $a(t)$ and placed observational constraints on it through the Hubble $H(z)$ datasets on it using the MCMC analysis. We have investigated the deceleration parameter $q(z)$, effective EoS parameters and a comparative study of all three models with $\Lambda$CDM model has been carried out. |
gr-qc/9509006 | Jun'ichi Yokoyama | Jun'ichi Yokoyama (YITP Uji Research Center, Kyoto U.) | Density Fluctuations in Inflationary Models with Multiple Scalar Fields | 17 pages, To be published in Proc. Sixth Quantum Gravity Seminar
(Moscow) | null | null | YITP/U-95-25 | gr-qc | null | Making use of the primordially isocurvature fluctuations, which are generated
in inflationary models with multiple scalar fields, we make a phenomenological
model that predicts formation of primordial black holes which can account for
the massive compact halo objects recently observed.
| [
{
"created": "Wed, 6 Sep 1995 01:39:14 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Yokoyama",
"Jun'ichi",
"",
"YITP Uji Research Center, Kyoto U."
]
] | Making use of the primordially isocurvature fluctuations, which are generated in inflationary models with multiple scalar fields, we make a phenomenological model that predicts formation of primordial black holes which can account for the massive compact halo objects recently observed. |
1002.3581 | Khalid Saifullah | M. Akbar and K. Saifullah | Quantum corrections to the entropy of charged rotating black holes | null | Eur. Phys. J. C Vol 67 (2010) 205 | 10.1140/epjc/s10052-010-1279-5 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hawking radiation from a black hole can be viewed as quantum tunneling of
particles through the event horizon. Using this approach we provide a general
framework for studying corrections to the entropy of black holes beyond
semiclassical approximations. Applying the properties of exact differentials
for three variables to the first law thermodynamics, we study charged rotating
black holes and explicitly work out the corrections to entropy and horizon area
for the Kerr-Newman and charged rotating BTZ black holes. It is shown that the
results for other geometries like the Schwarzschild, Reissner-Nordstr\"{o}m and
anti-de Sitter Schwarzschild spacetimes follow easily.
| [
{
"created": "Thu, 18 Feb 2010 17:29:25 GMT",
"version": "v1"
}
] | 2015-05-18 | [
[
"Akbar",
"M.",
""
],
[
"Saifullah",
"K.",
""
]
] | Hawking radiation from a black hole can be viewed as quantum tunneling of particles through the event horizon. Using this approach we provide a general framework for studying corrections to the entropy of black holes beyond semiclassical approximations. Applying the properties of exact differentials for three variables to the first law thermodynamics, we study charged rotating black holes and explicitly work out the corrections to entropy and horizon area for the Kerr-Newman and charged rotating BTZ black holes. It is shown that the results for other geometries like the Schwarzschild, Reissner-Nordstr\"{o}m and anti-de Sitter Schwarzschild spacetimes follow easily. |
gr-qc/0111100 | Marcelo S. Berman | Marcelo S. Berman and Luis A. Trevisan | Amplification of Gravitational Waves During Inflation in Brans-Dicke
Theory | Submtted to Physical Review D15. Date of receipt 31 August 2001 | null | null | null | gr-qc | null | We show that Gravitational Waves are exponetially amplified in the
inflationary phase in Brans-Dicke theory, so that it would be possible to
detect them and in this way verify several features of physical reality.
| [
{
"created": "Wed, 28 Nov 2001 17:07:29 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Dec 2001 14:35:47 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Berman",
"Marcelo S.",
""
],
[
"Trevisan",
"Luis A.",
""
]
] | We show that Gravitational Waves are exponetially amplified in the inflationary phase in Brans-Dicke theory, so that it would be possible to detect them and in this way verify several features of physical reality. |
gr-qc/0105094 | Christian Heinicke | Christian Heinicke, Friedrich W. Hehl (University of Cologne) | Computer algebra in gravity | 10 pages, LaTeX2e, hyperref, updated version of an article to appear
in: Computer Algebra Handbook. J. Grabmeier, E. Kaltofen, V. Weispfennig,
editors (Springer, Berlin 2001/2002) | null | null | null | gr-qc | null | We survey the application of computer algebra in the context of gravitational
theories. After some general remarks, we show of how to check the second
Bianchi-identity by means of the Reduce package Excalc. Subsequently we list
some computer algebra systems and packages relevant to applications in
gravitational physics. We conclude by presenting a couple of typical examples.
| [
{
"created": "Fri, 25 May 2001 12:34:27 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Heinicke",
"Christian",
"",
"University of Cologne"
],
[
"Hehl",
"Friedrich W.",
"",
"University of Cologne"
]
] | We survey the application of computer algebra in the context of gravitational theories. After some general remarks, we show of how to check the second Bianchi-identity by means of the Reduce package Excalc. Subsequently we list some computer algebra systems and packages relevant to applications in gravitational physics. We conclude by presenting a couple of typical examples. |
1607.02115 | Alex H. Blin | Rafael Pav\~ao, Ricardo Faleiro, Alex H. Blin, Brigitte Hiller | Entanglement of Vacuum States With the de Sitter Horizon: Consequences
on Holographic Dark Energy | changed layout style, minor typos corrected; 15 pages, 3 figures | null | null | null | gr-qc hep-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The aim of this article is to study the effect of an Event Horizon on the
entanglement of the Quantum Vacuum and how entanglement, together with the
Holographic Principle, may explain the current value of the Cosmological
Constant, in light of recent theories. Entanglement is tested for vacuum states
very near and very far from the Horizon of a de Sitter Universe, using the
Peres-Horodecki (PPT) criterion. A scalar vacuum field ($\hat{\phi}$) is
averaged inside two boxes of volume $V$ in different spatial positions such
that it acquires the structure of a bipartite Quantum Harmonic Oscillator, for
which the PPT criterion is a necessary but not sufficient condition of
separability. Entanglement is found between states obtained from boxes shaped
as spherical shells with thickness of the order of one Planck distance ($l_p$),
when one of the states is near the Horizon, and the other state is anywhere in
the Universe. Entanglement disappears when the distance of the state near the
horizon and the Horizon increases to around $5l_p$. If we consider the Horizon
not as a surface but as a spherical shell of thickness $l_p$, then this means
that there is entanglement between the states in the Horizon and the rest of
the Universe. When both states are at distances larger than $\sim 5 l_p$ from
the Horizon, no entanglement is found.
| [
{
"created": "Thu, 7 Jul 2016 18:36:41 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Jul 2016 10:24:41 GMT",
"version": "v2"
}
] | 2016-07-22 | [
[
"Pavão",
"Rafael",
""
],
[
"Faleiro",
"Ricardo",
""
],
[
"Blin",
"Alex H.",
""
],
[
"Hiller",
"Brigitte",
""
]
] | The aim of this article is to study the effect of an Event Horizon on the entanglement of the Quantum Vacuum and how entanglement, together with the Holographic Principle, may explain the current value of the Cosmological Constant, in light of recent theories. Entanglement is tested for vacuum states very near and very far from the Horizon of a de Sitter Universe, using the Peres-Horodecki (PPT) criterion. A scalar vacuum field ($\hat{\phi}$) is averaged inside two boxes of volume $V$ in different spatial positions such that it acquires the structure of a bipartite Quantum Harmonic Oscillator, for which the PPT criterion is a necessary but not sufficient condition of separability. Entanglement is found between states obtained from boxes shaped as spherical shells with thickness of the order of one Planck distance ($l_p$), when one of the states is near the Horizon, and the other state is anywhere in the Universe. Entanglement disappears when the distance of the state near the horizon and the Horizon increases to around $5l_p$. If we consider the Horizon not as a surface but as a spherical shell of thickness $l_p$, then this means that there is entanglement between the states in the Horizon and the rest of the Universe. When both states are at distances larger than $\sim 5 l_p$ from the Horizon, no entanglement is found. |
gr-qc/9809064 | null | S.Sen and N.Banerjee | On the absence of scalar hair for charged rotating blackholes in non
minimally coupled theories | Revtex style, 11 pages, major rivisions done, appendix added, title
changed | Pramana, vol.56, 487 (2001) | 10.1007/s12043-001-0098-5 | null | gr-qc | null | In this work we check the validity of the no scalar hair theorem in charged
axisymmetric stationary black holes for a wide class of scalar tensor theories.
| [
{
"created": "Wed, 23 Sep 1998 12:04:08 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Sep 1998 11:39:47 GMT",
"version": "v2"
},
{
"created": "Sat, 20 Mar 1999 13:41:39 GMT",
"version": "v3"
},
{
"created": "Thu, 31 May 2001 09:58:28 GMT",
"version": "v4"
}
] | 2015-06-25 | [
[
"Sen",
"S.",
""
],
[
"Banerjee",
"N.",
""
]
] | In this work we check the validity of the no scalar hair theorem in charged axisymmetric stationary black holes for a wide class of scalar tensor theories. |
1312.3760 | Masato Minamitsuji | Masato Minamitsuji | Braneworlds with field derivative coupling to the Einstein tensor | 18 pages, 1 figure, comments and references added, the version to
appear in Physical Review D | null | 10.1103/PhysRevD.89.064025 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the Randall-Sundrum type braneworld models in
the scalar-tensor theory with field derivative coupling to the Einstein tensor.
We first formulate the generalized junction conditions of the metric and the
scalar field on the timelike codimension-one hypersurface (=brane). With the
use of these junction conditions, we then derive the Minkowski and de Sitter
brane solutions embedded into the $Z_2$-symmetric five-dimensional anti-de
Sitter (AdS) bulk spacetime. The configuration of the scalar field depends on
the slice of the AdS spacetime. These branes are supported by the tension and
not coupled to the scalar field. The Minkowski brane solution can be obtained
when the brane tension is tuned to the bulk contributions. Once this tuning
relation is broken, the de Sitter brane solutions are obtained. The de Sitter
brane solutions have two branches. One has the smooth limit to the case where
the scalar field becomes trivial, while the other branch does not. The latter
branch has the upper bound on the brane tension, where the expansion rate
vanishes. Finally, we investigate the low energy effective gravitational theory
realized on the brane, which is given by the four-dimensional Einstein-scalar
theory with the corrections from the bulk. In the case that there is no
generation of the dark radiation from the bulk scalar field, we recover the the
four-dimensional Einstein-scalar theory.
| [
{
"created": "Fri, 13 Dec 2013 10:29:21 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Feb 2014 18:07:23 GMT",
"version": "v2"
}
] | 2015-06-18 | [
[
"Minamitsuji",
"Masato",
""
]
] | In this paper, we investigate the Randall-Sundrum type braneworld models in the scalar-tensor theory with field derivative coupling to the Einstein tensor. We first formulate the generalized junction conditions of the metric and the scalar field on the timelike codimension-one hypersurface (=brane). With the use of these junction conditions, we then derive the Minkowski and de Sitter brane solutions embedded into the $Z_2$-symmetric five-dimensional anti-de Sitter (AdS) bulk spacetime. The configuration of the scalar field depends on the slice of the AdS spacetime. These branes are supported by the tension and not coupled to the scalar field. The Minkowski brane solution can be obtained when the brane tension is tuned to the bulk contributions. Once this tuning relation is broken, the de Sitter brane solutions are obtained. The de Sitter brane solutions have two branches. One has the smooth limit to the case where the scalar field becomes trivial, while the other branch does not. The latter branch has the upper bound on the brane tension, where the expansion rate vanishes. Finally, we investigate the low energy effective gravitational theory realized on the brane, which is given by the four-dimensional Einstein-scalar theory with the corrections from the bulk. In the case that there is no generation of the dark radiation from the bulk scalar field, we recover the the four-dimensional Einstein-scalar theory. |
1502.04036 | Debottam Nandi | Debottam Nandi, S. Shankaranarayanan (IISER-TVM) | 'Constraint consistency' at all orders in Cosmological perturbation
theory | 25 pages | JCAP 1508 (2015) no.08, 050 | 10.1088/1475-7516/2015/08/050 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the equivalence of two - order-by-order Einstein's equation and
Reduced action - approaches to cosmological perturbation theory at all orders
for different models of inflation. We point out a crucial consistency check
which we refer to as 'Constraint consistency' that needs to be satisfied. We
propose a quick and efficient method to check the consistency for any model
including modified gravity models. Our analysis points out an important feature
which is crucial for inflationary model building i.e., all `constraint'
inconsistent models have higher order Ostrogradsky's instabilities but the
reverse is not true. In other words, one can have models with constraint lapse
function and shift vector, though it may have Ostrogradsky's instabilities. We
also obtain the single variable equation for non-canonical scalar field in the
limit of power-law inflation for the second-order perturbed variables.
| [
{
"created": "Thu, 12 Feb 2015 16:02:23 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Oct 2015 16:45:20 GMT",
"version": "v2"
},
{
"created": "Sat, 18 Jun 2016 13:23:08 GMT",
"version": "v3"
}
] | 2016-06-21 | [
[
"Nandi",
"Debottam",
"",
"IISER-TVM"
],
[
"Shankaranarayanan",
"S.",
"",
"IISER-TVM"
]
] | We study the equivalence of two - order-by-order Einstein's equation and Reduced action - approaches to cosmological perturbation theory at all orders for different models of inflation. We point out a crucial consistency check which we refer to as 'Constraint consistency' that needs to be satisfied. We propose a quick and efficient method to check the consistency for any model including modified gravity models. Our analysis points out an important feature which is crucial for inflationary model building i.e., all `constraint' inconsistent models have higher order Ostrogradsky's instabilities but the reverse is not true. In other words, one can have models with constraint lapse function and shift vector, though it may have Ostrogradsky's instabilities. We also obtain the single variable equation for non-canonical scalar field in the limit of power-law inflation for the second-order perturbed variables. |
1404.5729 | Aharon Davidson | Aharon Davidson and Ben Yellin | Quantum Black Hole Wave Packet: Average Area Entropy and Temperature
Dependent Width | 5 PRD pages, 1 figure; v.2 minor typo corrections | Phys. Lett. B 736, 267 (2014) | 10.1016/j.physletb.2014.07.032 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A quantum Schwarzschild black hole is described, at the mini super spacetime
level, by a non-singular wave packet composed of plane wave eigenstates of the
momentum Dirac-conjugate to the mass operator. The entropy of the mass spectrum
acquires then independent contributions from the average mass and the width.
Hence, Bekenstein's area entropy is formulated using the $\langle \text{mass}^2
\rangle$ average, leaving the $\langle \text{mass} \rangle$ average to set the
Hawking temperature. The width function peaks at the Planck scale for an
elementary (zero entropy, zero free energy) micro black hole of finite rms
size, and decreases Doppler-like towards the classical limit.
| [
{
"created": "Wed, 23 Apr 2014 07:50:05 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Jun 2014 08:45:14 GMT",
"version": "v2"
}
] | 2014-08-11 | [
[
"Davidson",
"Aharon",
""
],
[
"Yellin",
"Ben",
""
]
] | A quantum Schwarzschild black hole is described, at the mini super spacetime level, by a non-singular wave packet composed of plane wave eigenstates of the momentum Dirac-conjugate to the mass operator. The entropy of the mass spectrum acquires then independent contributions from the average mass and the width. Hence, Bekenstein's area entropy is formulated using the $\langle \text{mass}^2 \rangle$ average, leaving the $\langle \text{mass} \rangle$ average to set the Hawking temperature. The width function peaks at the Planck scale for an elementary (zero entropy, zero free energy) micro black hole of finite rms size, and decreases Doppler-like towards the classical limit. |
gr-qc/0105003 | Nematollah Riazi | N. Riazi | Spherical Structures in the Inflationary Cosmology | one figure | null | null | null | gr-qc | null | It has been suggested that wormholes and other non-trivial geometrical
structures might have been formed during the quantum cosmological era ($t\sim
10^{-43}$s). Subsequent inflation of the universe might have enlarged these
structures to macroscopic sizes. In this paper, spherical geometrical
structures in an inflationary RW background are derived from the Einstein
equations, using a constraint on the energy-momentum tensor which is an
extension of the one expected for inflation. The possibility of dynamical
wormholes and other spherical structures are explored in the framework of the
solutions.
| [
{
"created": "Wed, 2 May 2001 06:35:36 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Riazi",
"N.",
""
]
] | It has been suggested that wormholes and other non-trivial geometrical structures might have been formed during the quantum cosmological era ($t\sim 10^{-43}$s). Subsequent inflation of the universe might have enlarged these structures to macroscopic sizes. In this paper, spherical geometrical structures in an inflationary RW background are derived from the Einstein equations, using a constraint on the energy-momentum tensor which is an extension of the one expected for inflation. The possibility of dynamical wormholes and other spherical structures are explored in the framework of the solutions. |
2402.07657 | Riasat Ali | Riasat Ali, Xia Tiecheng, Rimsha Babar and Ali Ovgun | Evaluation of plasma on deflection angle and shadow by a black hole
solution immersed in perfect fluid in Rastall theory | 28 pages, 30 figures, submitted for publication | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The present study examines the gravitational deflection of particles in
curved space-times immersed in perfect fluid in the context of Rastall theory,
applying the Gibbons-Werner useful technique. In its application to integral
areas inside a four-dimensional space-time, the Gauss-Bonnet theorem studies
the computation expression of the deflection angle. The Gibbons-Werner
technique has two limitations in Rastall theory for space-times immersed in
perfect fluid: the integral region is generally infinite and the integral
complicates calculation, particularly for complex space-times and extremely
accurate solutions. An infinite region approach to Gibbons-Werner is proposed
to avoid singularity. For demonstrating the Gibbons-Werner method, we use a
complete Rastall theory framework. It studies black hole solutions like the
dust field, radiation field, quintessence field, cosmological constant field
and phantom field using the Gibbons-Werner approach. Additionally, we check the
deflection angle from these space-times under the influence of plasma.
Furthermore, we compute analytically the influence of a plasma on a black hole
shadow by using a ray-tracing approach. In the Hamiltonian equation, our model
describes the plasma, so the light ray motion equations are independent of the
plasma's velocity. It is assumed that plasma is a dispersive medium,
pressure-less and non-magnetized. We investigate the perfect fluid in Rastall
theory in further depth, where the plasma particle density corresponds to
particle accumulation. The supermassive black hole shadows are explored in the
case when plasma falls radially from infinity onto a black hole.
| [
{
"created": "Mon, 12 Feb 2024 13:59:19 GMT",
"version": "v1"
}
] | 2024-02-13 | [
[
"Ali",
"Riasat",
""
],
[
"Tiecheng",
"Xia",
""
],
[
"Babar",
"Rimsha",
""
],
[
"Ovgun",
"Ali",
""
]
] | The present study examines the gravitational deflection of particles in curved space-times immersed in perfect fluid in the context of Rastall theory, applying the Gibbons-Werner useful technique. In its application to integral areas inside a four-dimensional space-time, the Gauss-Bonnet theorem studies the computation expression of the deflection angle. The Gibbons-Werner technique has two limitations in Rastall theory for space-times immersed in perfect fluid: the integral region is generally infinite and the integral complicates calculation, particularly for complex space-times and extremely accurate solutions. An infinite region approach to Gibbons-Werner is proposed to avoid singularity. For demonstrating the Gibbons-Werner method, we use a complete Rastall theory framework. It studies black hole solutions like the dust field, radiation field, quintessence field, cosmological constant field and phantom field using the Gibbons-Werner approach. Additionally, we check the deflection angle from these space-times under the influence of plasma. Furthermore, we compute analytically the influence of a plasma on a black hole shadow by using a ray-tracing approach. In the Hamiltonian equation, our model describes the plasma, so the light ray motion equations are independent of the plasma's velocity. It is assumed that plasma is a dispersive medium, pressure-less and non-magnetized. We investigate the perfect fluid in Rastall theory in further depth, where the plasma particle density corresponds to particle accumulation. The supermassive black hole shadows are explored in the case when plasma falls radially from infinity onto a black hole. |
gr-qc/0207017 | Michael A. Ivanov | Michael A.Ivanov | A model of gravitation with global U(1)-symmetry | 7 pages | Gen.Rel.Grav. 31 (1999) 1431-1437 | 10.1023/A:1026749529917 | null | gr-qc | null | It is shown that an embedding of the general relativity $4-$space into a flat
$12-$space gives a model of gravitation with the global $U(1)-$symmetry and the
discrete $D_{1}-$one. The last one may be transformed into the $SU(2)-$symmetry
of the unified model, and the demand of independence of $U(1)-$ and
$SU(2)-$transformations leads to the estimate $\sin^{2}\theta_{min}=0,20$ where
$\theta_{min}$ is an analog of the Weinberg angle of the standard model.
| [
{
"created": "Tue, 2 Jul 2002 15:44:10 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Ivanov",
"Michael A.",
""
]
] | It is shown that an embedding of the general relativity $4-$space into a flat $12-$space gives a model of gravitation with the global $U(1)-$symmetry and the discrete $D_{1}-$one. The last one may be transformed into the $SU(2)-$symmetry of the unified model, and the demand of independence of $U(1)-$ and $SU(2)-$transformations leads to the estimate $\sin^{2}\theta_{min}=0,20$ where $\theta_{min}$ is an analog of the Weinberg angle of the standard model. |
gr-qc/9405071 | null | Sean A. Hayward | Quasi-Localisation of Bondi-Sachs Energy Loss | 13 pages | Class.Quant.Grav.11:3037-3048,1994 | 10.1088/0264-9381/11/12/017 | null | gr-qc | null | A formula is given for the variation of the Hawking energy along any
one-parameter foliation of compact spatial 2-surfaces. A surface for which one
null expansion is positive and the other negative has a preferred orientation,
with a spatial or null normal direction being called outgoing or ingoing as the
area increases or decreases respectively. A natural way to propagate such a
surface through a hypersurface is to choose the foliation such that the null
expansions are constant over each surface. For such uniformly expanding
foliations, the Hawking energy is non-decreasing in any outgoing direction, and
non-increasing in any ingoing direction, assuming the dominant energy
condition. It follows that the Hawking energy is non-negative if the foliation
is bounded at the inward end by either a point or a marginal surface, and in
the latter case satisfies the Penrose-Gibbons isoperimetric inequality. The
Bondi-Sachs energy may be expressed as a limit of the Hawking energy at
conformal infinity, and the energy-variation formula reduces at conformal
infinity to the Bondi-Sachs energy-loss formula.
| [
{
"created": "Mon, 30 May 1994 08:17:43 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Hayward",
"Sean A.",
""
]
] | A formula is given for the variation of the Hawking energy along any one-parameter foliation of compact spatial 2-surfaces. A surface for which one null expansion is positive and the other negative has a preferred orientation, with a spatial or null normal direction being called outgoing or ingoing as the area increases or decreases respectively. A natural way to propagate such a surface through a hypersurface is to choose the foliation such that the null expansions are constant over each surface. For such uniformly expanding foliations, the Hawking energy is non-decreasing in any outgoing direction, and non-increasing in any ingoing direction, assuming the dominant energy condition. It follows that the Hawking energy is non-negative if the foliation is bounded at the inward end by either a point or a marginal surface, and in the latter case satisfies the Penrose-Gibbons isoperimetric inequality. The Bondi-Sachs energy may be expressed as a limit of the Hawking energy at conformal infinity, and the energy-variation formula reduces at conformal infinity to the Bondi-Sachs energy-loss formula. |
1202.3550 | Karl Landsteiner | Karl Landsteiner | The Sound of Strongly Coupled Field Theories: Quasinormal Modes In AdS | 16 pages, 8 figures, 1 cow, Contribution to Proceedings of ERE2011,
v2: minor changes, refs added | null | 10.1063/1.4734412 | IFT-UAM/CSIC-12-17 | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The AdS/CFT correspondence has developed over the last years into a very
useful and powerful tool for studying strongly coupled field theories at finite
temperature and density. Of particular interest is the regime of near
equilibrium real time evolution that can be captured via linear response
theory. The AdS/CFT correspondence allows the calculation of retarded two point
functions of gauge invariant operators by studying fluctuations around
asymptotically AdS black holes. A major role is played by the poles of these
holographic response functions: the quasinormal frequencies. I will review the
applications of these ideas to the hydrodynamics of the strongly coupled quark
gluon plasma and the holographic realization of strongly coupled superfluids.
| [
{
"created": "Thu, 16 Feb 2012 10:00:15 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Feb 2012 11:42:57 GMT",
"version": "v2"
}
] | 2015-06-04 | [
[
"Landsteiner",
"Karl",
""
]
] | The AdS/CFT correspondence has developed over the last years into a very useful and powerful tool for studying strongly coupled field theories at finite temperature and density. Of particular interest is the regime of near equilibrium real time evolution that can be captured via linear response theory. The AdS/CFT correspondence allows the calculation of retarded two point functions of gauge invariant operators by studying fluctuations around asymptotically AdS black holes. A major role is played by the poles of these holographic response functions: the quasinormal frequencies. I will review the applications of these ideas to the hydrodynamics of the strongly coupled quark gluon plasma and the holographic realization of strongly coupled superfluids. |
1712.08680 | Nader Inan | R.Y. Chiao, J.S. Sharping, L.A. Martinez, B.S. Kang, A. Castelli, N.A.
Inan, and J.J. Thompson | Dynamical Casimir effect and the possibility of laser-like generation of
gravitational radiation | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we address the question as to whether or not measurable
sources for gravitational waves could possibly be made in the laboratory. Based
on an analogy of the dynamical Casimir effect with the stimulated emission of
radiation in the laser, our answer to this question is in the affirmative,
provided that superconducting radio-frequency cavities in fact possess high
quality factors for both electromagnetic and gravitational microwave radiation,
as one would expect due to a quantum-mechanical gravitational Meissner-like
effect. In order to characterize the response of matter to tensor gravitational
fields, we introduce a prefactor to the source term of the gravitational wave
equation, which we call the "relative gravitational permeativity" analogous to
the "relative electric permittivity" and "relative magnetic permeability" that
characterize the vector response of matter to applied fields in
electromagnetism. This allows for a possibly large quantum mechanical
enhancement of the response of a superconductor to an incident tensor
gravitational wave field. Finally, we describe our experimental work with
high-Q superconducting radio-frequency cavities, and propose a design for a
coupled-cavity system with a flexible superconducting membrane in its middle as
its amplifying element. This will then allow us to test for a Meissner-like
expulsion, and therefore reflection, of incident tensor gravitational wave
fields, and, above a certain threshold, to generate coherent gravitational
radiation via the dynamical Casimir effect.
| [
{
"created": "Fri, 22 Dec 2017 22:58:34 GMT",
"version": "v1"
}
] | 2017-12-27 | [
[
"Chiao",
"R. Y.",
""
],
[
"Sharping",
"J. S.",
""
],
[
"Martinez",
"L. A.",
""
],
[
"Kang",
"B. S.",
""
],
[
"Castelli",
"A.",
""
],
[
"Inan",
"N. A.",
""
],
[
"Thompson",
"J. J.",
""
]
] | In this paper, we address the question as to whether or not measurable sources for gravitational waves could possibly be made in the laboratory. Based on an analogy of the dynamical Casimir effect with the stimulated emission of radiation in the laser, our answer to this question is in the affirmative, provided that superconducting radio-frequency cavities in fact possess high quality factors for both electromagnetic and gravitational microwave radiation, as one would expect due to a quantum-mechanical gravitational Meissner-like effect. In order to characterize the response of matter to tensor gravitational fields, we introduce a prefactor to the source term of the gravitational wave equation, which we call the "relative gravitational permeativity" analogous to the "relative electric permittivity" and "relative magnetic permeability" that characterize the vector response of matter to applied fields in electromagnetism. This allows for a possibly large quantum mechanical enhancement of the response of a superconductor to an incident tensor gravitational wave field. Finally, we describe our experimental work with high-Q superconducting radio-frequency cavities, and propose a design for a coupled-cavity system with a flexible superconducting membrane in its middle as its amplifying element. This will then allow us to test for a Meissner-like expulsion, and therefore reflection, of incident tensor gravitational wave fields, and, above a certain threshold, to generate coherent gravitational radiation via the dynamical Casimir effect. |
2308.01056 | Martina Muratore | Martina Muratore, Jonathan Gair, Lorenzo Speri | Impact of the noise knowledge uncertainty for the science exploitation
of cosmological and astrophysical stochastic gravitational wave background
with LISA | null | null | null | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | This paper investigates the impact of a lack of knowledge of the instrumental
noise on the characterisation of stochastic gravitational wave backgrounds with
the Laser Interferometer Space Antenna (LISA). We focus on constraints on
modelled backgrounds that represent the possible backgrounds from the mergers
of binary black holes of stellar origin, from primordial black hole generation,
from non-standard inflation, and from sound wave production during cosmic fluid
phase transitions. We use splines to model generic, slowly varying,
uncertainties in the auto and cross-spectral densities of the LISA time delay
interferometry channels. We find that allowing for noise knowledge uncertainty
in this way leads to one to two orders of magnitude degradation in our ability
to constrain stochastic backgrounds, and a corresponding increase in the
background energy density required for a confident detection. We also find that
to avoid this degradation, the LISA noise would have to be known at the
sub-percent level, which is unlikely to be achievable in practice.
| [
{
"created": "Wed, 2 Aug 2023 10:07:16 GMT",
"version": "v1"
}
] | 2023-08-03 | [
[
"Muratore",
"Martina",
""
],
[
"Gair",
"Jonathan",
""
],
[
"Speri",
"Lorenzo",
""
]
] | This paper investigates the impact of a lack of knowledge of the instrumental noise on the characterisation of stochastic gravitational wave backgrounds with the Laser Interferometer Space Antenna (LISA). We focus on constraints on modelled backgrounds that represent the possible backgrounds from the mergers of binary black holes of stellar origin, from primordial black hole generation, from non-standard inflation, and from sound wave production during cosmic fluid phase transitions. We use splines to model generic, slowly varying, uncertainties in the auto and cross-spectral densities of the LISA time delay interferometry channels. We find that allowing for noise knowledge uncertainty in this way leads to one to two orders of magnitude degradation in our ability to constrain stochastic backgrounds, and a corresponding increase in the background energy density required for a confident detection. We also find that to avoid this degradation, the LISA noise would have to be known at the sub-percent level, which is unlikely to be achievable in practice. |
gr-qc/0508028 | Ezra Newman | Ezra T. Newman and Gilberto Silva-Ortigoza | Tensorial Spin-s Harmonics | null | Class.Quant.Grav. 23 (2006) 497-510 | 10.1088/0264-9381/23/2/014 | null | gr-qc | null | We show how to define and go from the spin-s spherical harmonics to the
tensorial spin-s harmonics. These quantities, which are functions on the sphere
taking values as Euclidean tensors, turn out to be extremely useful for many
calculations in General Relativity. In the calculations, products of these
functions, with their needed decompositions which are given here, often arise
naturally.
| [
{
"created": "Mon, 8 Aug 2005 18:19:22 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Newman",
"Ezra T.",
""
],
[
"Silva-Ortigoza",
"Gilberto",
""
]
] | We show how to define and go from the spin-s spherical harmonics to the tensorial spin-s harmonics. These quantities, which are functions on the sphere taking values as Euclidean tensors, turn out to be extremely useful for many calculations in General Relativity. In the calculations, products of these functions, with their needed decompositions which are given here, often arise naturally. |
2309.08071 | Arthur Suvorov Dr. | Arthur G. Suvorov and Kostas Glampedakis | Magnetic equilibria of relativistic axisymmetric stars: The impact of
flow constants | 20 pages, 6 figures. Minor changes to match published version | Phys. Rev. D 108, 084006 (2023) | 10.1103/PhysRevD.108.084006 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Symmetries and conservation laws associated with the ideal Einstein-Euler
system, for stationary and axisymmetric stars, can be utilized to define a set
of flow constants. These quantities are conserved along flow lines in the sense
that their gradients are orthogonal to the four-velocity. They are also
conserved along surfaces of constant magnetic flux, making them powerful tools
to identify general features of neutron star equilibria. One important
corollary of their existence is that mixed poloidal-toroidal fields are
inconsistent with the absence of meridional flows except in some singular
sense, a surprising but powerful result first proven by Bekenstein and Oron. In
this work, we revisit the flow constant formalism to rederive this result
together with several new ones concerning both nonlinear and perturbative
magnetic equilibria. Our investigation is supplemented by some numerical
solutions for multipolar magnetic fields on top of a Tolman-VII background,
where strict power-counting of the flow constants is used to ensure a
self-consistent treatment.
| [
{
"created": "Fri, 15 Sep 2023 00:02:36 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Oct 2023 22:53:29 GMT",
"version": "v2"
}
] | 2023-10-05 | [
[
"Suvorov",
"Arthur G.",
""
],
[
"Glampedakis",
"Kostas",
""
]
] | Symmetries and conservation laws associated with the ideal Einstein-Euler system, for stationary and axisymmetric stars, can be utilized to define a set of flow constants. These quantities are conserved along flow lines in the sense that their gradients are orthogonal to the four-velocity. They are also conserved along surfaces of constant magnetic flux, making them powerful tools to identify general features of neutron star equilibria. One important corollary of their existence is that mixed poloidal-toroidal fields are inconsistent with the absence of meridional flows except in some singular sense, a surprising but powerful result first proven by Bekenstein and Oron. In this work, we revisit the flow constant formalism to rederive this result together with several new ones concerning both nonlinear and perturbative magnetic equilibria. Our investigation is supplemented by some numerical solutions for multipolar magnetic fields on top of a Tolman-VII background, where strict power-counting of the flow constants is used to ensure a self-consistent treatment. |
1304.7730 | Francesco Caravelli | Francesco Caravelli | GEMs and amplitude bounds in the colored Boulatov model | 20 pages; 20 Figures; Style changed, discussion improved and typos
corrected, citations added; These GEMs are not related to "Global Embedding
Minkowskian spacetimes" | Journal of Theoretical and Applied Physics. 2013, 7:63 | 10.1186/2251-7235-7-63 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we construct a methodology for separating the divergencies due
to different topological manifolds dual to Feynman graphs in colored group
field theory. After having introduced the amplitude bounds using propagator
cuts, we show how Graph-Encoded-Manifolds (GEM) techniques can be used in order
to factorize divergencies related to different parts of the dual topologies of
the Feynman graphs in the general case. We show the potential of the formalism
in the case of 3-dimensional solid torii in the colored Boulatov model.
| [
{
"created": "Mon, 29 Apr 2013 18:11:27 GMT",
"version": "v1"
},
{
"created": "Sat, 11 May 2013 23:48:21 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Oct 2013 14:01:02 GMT",
"version": "v3"
},
{
"created": "Fri, 4 Oct 2013 16:39:27 GMT",
"version": "v4"
},
{
"created": "Sat, 23 Nov 2013 11:19:08 GMT",
"version": "v5"
},
{
"created": "Tue, 26 Nov 2013 08:40:30 GMT",
"version": "v6"
}
] | 2013-11-27 | [
[
"Caravelli",
"Francesco",
""
]
] | In this paper we construct a methodology for separating the divergencies due to different topological manifolds dual to Feynman graphs in colored group field theory. After having introduced the amplitude bounds using propagator cuts, we show how Graph-Encoded-Manifolds (GEM) techniques can be used in order to factorize divergencies related to different parts of the dual topologies of the Feynman graphs in the general case. We show the potential of the formalism in the case of 3-dimensional solid torii in the colored Boulatov model. |
0708.2738 | Amitabh Virmani | Aaron J. Amsel, Donald Marolf, Amitabh Virmani | The Physical Process First Law for Bifurcate Killing Horizons | 19 pages; v2: ref added, minor changes | Phys.Rev.D77:024011,2008 | 10.1103/PhysRevD.77.024011 | null | gr-qc hep-th | null | The physical process version of the first law for black holes states that the
passage of energy and angular momentum through the horizon results in a change
in area $\frac{\kappa}{8 \pi} \Delta A = \Delta E - \Omega \Delta J$, so long
as this passage is quasi-stationary. A similar physical process first law can
be derived for any bifurcate Killing horizon in any spacetime dimension $d \ge
3$ using much the same argument. However, to make this law non-trivial, one
must show that sufficiently quasi-stationary processes do in fact occur. In
particular, one must show that processes exist for which the shear and
expansion remain small, and in which no new generators are added to the
horizon. Thorne, MacDonald, and Price considered related issues when an object
falls across a d=4 black hole horizon. By generalizing their argument to
arbitrary $d \ge 3$ and to any bifurcate Killing horizon, we derive a condition
under which these effects are controlled and the first law applies. In
particular, by providing a non-trivial first law for Rindler horizons, our work
completes the parallel between the mechanics of such horizons and those of
black holes for $d \ge 3$. We also comment on the situation for d=2.
| [
{
"created": "Mon, 20 Aug 2007 21:50:07 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Oct 2007 21:00:39 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Amsel",
"Aaron J.",
""
],
[
"Marolf",
"Donald",
""
],
[
"Virmani",
"Amitabh",
""
]
] | The physical process version of the first law for black holes states that the passage of energy and angular momentum through the horizon results in a change in area $\frac{\kappa}{8 \pi} \Delta A = \Delta E - \Omega \Delta J$, so long as this passage is quasi-stationary. A similar physical process first law can be derived for any bifurcate Killing horizon in any spacetime dimension $d \ge 3$ using much the same argument. However, to make this law non-trivial, one must show that sufficiently quasi-stationary processes do in fact occur. In particular, one must show that processes exist for which the shear and expansion remain small, and in which no new generators are added to the horizon. Thorne, MacDonald, and Price considered related issues when an object falls across a d=4 black hole horizon. By generalizing their argument to arbitrary $d \ge 3$ and to any bifurcate Killing horizon, we derive a condition under which these effects are controlled and the first law applies. In particular, by providing a non-trivial first law for Rindler horizons, our work completes the parallel between the mechanics of such horizons and those of black holes for $d \ge 3$. We also comment on the situation for d=2. |
2310.03769 | Hugo L\'evy | Hugo L\'evy, Jo\"el Berg\'e, Jean-Philippe Uzan | What to expect from scalar-tensor space geodesy | 36 pages, 20 figures. Accepted for publication in PRD | null | 10.1103/PhysRevD.109.084009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scalar-tensor theories with screening mechanisms come with non-linearities
that make it difficult to study setups of complex geometry without resorting to
numerical simulations. In this article, we use the $\textit{femtoscope}$ code
that we introduced in a previous work in order to compute the fifth force
arising in the chameleon model in the Earth orbit. We go beyond published works
by introducing a departure from spherical symmetry $\unicode{x2014}$ embodied
by a mountain on an otherwise spherical Earth $\unicode{x2014}$ as well as by
implementing several atmospheric models, and quantify their combined effect on
the chameleon field. Building on the numerical results thus obtained, we
address the question of the detectability of a putative chameleon fifth force
by means of space geodesy techniques and, for the first time, quantitatively
assess the back-reaction created by the screening of a satellite itself. We
find that although the fifth force has a supposedly measurable effect on the
dynamics of an orbiting spacecraft, the imprecise knowledge of the mass
distribution inside the Earth greatly curtails the constraining power of such
space missions. Finally, we show how this degeneracy can be lifted when several
measurements are performed at different altitudes.
| [
{
"created": "Wed, 4 Oct 2023 18:03:09 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Apr 2024 07:28:29 GMT",
"version": "v2"
}
] | 2024-04-12 | [
[
"Lévy",
"Hugo",
""
],
[
"Bergé",
"Joël",
""
],
[
"Uzan",
"Jean-Philippe",
""
]
] | Scalar-tensor theories with screening mechanisms come with non-linearities that make it difficult to study setups of complex geometry without resorting to numerical simulations. In this article, we use the $\textit{femtoscope}$ code that we introduced in a previous work in order to compute the fifth force arising in the chameleon model in the Earth orbit. We go beyond published works by introducing a departure from spherical symmetry $\unicode{x2014}$ embodied by a mountain on an otherwise spherical Earth $\unicode{x2014}$ as well as by implementing several atmospheric models, and quantify their combined effect on the chameleon field. Building on the numerical results thus obtained, we address the question of the detectability of a putative chameleon fifth force by means of space geodesy techniques and, for the first time, quantitatively assess the back-reaction created by the screening of a satellite itself. We find that although the fifth force has a supposedly measurable effect on the dynamics of an orbiting spacecraft, the imprecise knowledge of the mass distribution inside the Earth greatly curtails the constraining power of such space missions. Finally, we show how this degeneracy can be lifted when several measurements are performed at different altitudes. |
1705.05304 | Mauricio Bellini | Juan Ignacio Musmarra, Mariano Anabitarte, Mauricio Bellini (IFIMAR -
CONICET & UNMdP) | Large scale solitonic back-reaction effects in pre-inflation | 9 pages, 1 figure. arXiv admin note: text overlap with
arXiv:1610.07979 | null | null | null | gr-qc hep-th physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using Relativistic Quantum Geometry (RQG), we study the emergence of
back-reaction modes with solitonic properties, on astrophysical and
cosmological scales, in a model of pre-inflation where the universe emerge from
a topological phase transition. We found that, modes of the geometrical field
that describes back-reaction effects related to larger scales (cosmological
scales), are more coherent than those related to astrophysical scales, so that
they can be considered a coarse-grained soliton.
| [
{
"created": "Mon, 15 May 2017 15:47:40 GMT",
"version": "v1"
}
] | 2017-05-18 | [
[
"Musmarra",
"Juan Ignacio",
"",
"IFIMAR -\n CONICET & UNMdP"
],
[
"Anabitarte",
"Mariano",
"",
"IFIMAR -\n CONICET & UNMdP"
],
[
"Bellini",
"Mauricio",
"",
"IFIMAR -\n CONICET & UNMdP"
]
] | Using Relativistic Quantum Geometry (RQG), we study the emergence of back-reaction modes with solitonic properties, on astrophysical and cosmological scales, in a model of pre-inflation where the universe emerge from a topological phase transition. We found that, modes of the geometrical field that describes back-reaction effects related to larger scales (cosmological scales), are more coherent than those related to astrophysical scales, so that they can be considered a coarse-grained soliton. |
1712.06504 | Eric Ling | Melanie Graf, Eric Ling | Maximizers in Lipschitz spacetimes are either timelike or null | 7 pages, 1 figure. Version 2 accepted to CQ&G | null | 10.1088/1361-6382/aab259 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that causal maximizers in $C^{0,1}$ spacetimes are either timelike
or null. This question was posed in [17] since bubbling regions in
$C^{0,\alpha}$ spacetimes ($\alpha <1$) can produce causal maximizers that
contain a segment which is timelike and a segment which is null, cf. [3]. While
$C^{0,1}$ spacetimes do not produce bubbling regions, the causal character of
maximizers for spacetimes with regularity at least $C^{0,1}$ but less than
$C^{1,1}$ was unknown until now. As an application we show that timelike
geodesically complete spacetimes are $C^{0,1}$-inextendible.
| [
{
"created": "Mon, 18 Dec 2017 16:35:24 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Feb 2018 17:37:53 GMT",
"version": "v2"
}
] | 2018-03-28 | [
[
"Graf",
"Melanie",
""
],
[
"Ling",
"Eric",
""
]
] | We prove that causal maximizers in $C^{0,1}$ spacetimes are either timelike or null. This question was posed in [17] since bubbling regions in $C^{0,\alpha}$ spacetimes ($\alpha <1$) can produce causal maximizers that contain a segment which is timelike and a segment which is null, cf. [3]. While $C^{0,1}$ spacetimes do not produce bubbling regions, the causal character of maximizers for spacetimes with regularity at least $C^{0,1}$ but less than $C^{1,1}$ was unknown until now. As an application we show that timelike geodesically complete spacetimes are $C^{0,1}$-inextendible. |
1312.2022 | Alvaro de la Cruz-Dombriz | Alvaro de la Cruz-Dombriz, Peter K. S. Dunsby, Vinicius C. Busti and
Sulona Kandhai | On tidal forces in f(R) theories of gravity | 9 pages, 2 figures | null | 10.1103/PhysRevD.89.064029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Despite the extraordinary attention that modified gravity theories have
attracted over the past decade, the geodesic deviation equation in this context
has not received proper formulation thus far. This equation provides an elegant
way to investigate the timelike, null and spacelike structure of spacetime
geometries. In this investigation we provide the full derivation of this
equation in situations where General Relativity has been extended in
Robertson-Walker background spacetimes. We find that for null geodesics the
contribution arising from the geometrical new terms is in general non-zero.
Finally we apply the results to a well known class of f(R) theories, compare
the results with General Relativity predictions and obtain the equivalent area
distance relation.
| [
{
"created": "Fri, 6 Dec 2013 21:43:32 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"de la Cruz-Dombriz",
"Alvaro",
""
],
[
"Dunsby",
"Peter K. S.",
""
],
[
"Busti",
"Vinicius C.",
""
],
[
"Kandhai",
"Sulona",
""
]
] | Despite the extraordinary attention that modified gravity theories have attracted over the past decade, the geodesic deviation equation in this context has not received proper formulation thus far. This equation provides an elegant way to investigate the timelike, null and spacelike structure of spacetime geometries. In this investigation we provide the full derivation of this equation in situations where General Relativity has been extended in Robertson-Walker background spacetimes. We find that for null geodesics the contribution arising from the geometrical new terms is in general non-zero. Finally we apply the results to a well known class of f(R) theories, compare the results with General Relativity predictions and obtain the equivalent area distance relation. |
gr-qc/0304005 | Jose Wadih Maluf | J. W. Maluf | Dirac spinor fields in the teleparallel gravity: comment on
"Metric-affine approach to teleparallel gravity" | 8 pages, Latex file, no figures, to appear in the Phys. Rev. D as a
Comment | Phys.Rev. D67 (2003) 108501 | 10.1103/PhysRevD.67.108501 | null | gr-qc | null | We show that the coupling of a Dirac spinor field with the gravitational
field in the teleparallel equivalent of general relativity is consistent. For
an arbitrary SO(3,1) connection there are two possibilities for the coupling of
the spinor field with the gravitational field. The problems of consistency
raised by Y. N. Obukhov and J. G. Pereira in the paper {\it Metric-affine
approach to teleparallel gravity} [gr-qc/0212080] take place only in the
framework of one particular coupling. By adopting an alternative coupling the
consistency problem disappears.
| [
{
"created": "Tue, 1 Apr 2003 13:01:46 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Maluf",
"J. W.",
""
]
] | We show that the coupling of a Dirac spinor field with the gravitational field in the teleparallel equivalent of general relativity is consistent. For an arbitrary SO(3,1) connection there are two possibilities for the coupling of the spinor field with the gravitational field. The problems of consistency raised by Y. N. Obukhov and J. G. Pereira in the paper {\it Metric-affine approach to teleparallel gravity} [gr-qc/0212080] take place only in the framework of one particular coupling. By adopting an alternative coupling the consistency problem disappears. |
gr-qc/0703145 | Robert Owen | Robert Owen | Constraint Damping in First-Order Evolution Systems for Numerical
Relativity | 11 pages, 5 figures | Phys.Rev.D76:044019,2007 | 10.1103/PhysRevD.76.044019 | null | gr-qc | null | A new constraint suppressing formulation of the Einstein evolution equations
is presented, generalizing the five-parameter first-order system due to Kidder,
Scheel and Teukolsky (KST). The auxiliary fields, introduced to make the KST
system first-order, are given modified evolution equations designed to drive
constraint violations toward zero. The algebraic structure of the new system is
investigated, showing that the modifications preserve the hyperbolicity of the
fundamental and constraint evolution equations. The evolution of the
constraints for pertubations of flat spacetime is completely analyzed, and all
finite-wavelength constraint modes are shown to decay exponentially when
certain adjustable parameters satisfy appropriate inequalities. Numerical
simulations of a single Schwarzschild black hole are presented, demonstrating
the effectiveness of the new constraint-damping modifications.
| [
{
"created": "Thu, 29 Mar 2007 09:49:53 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Owen",
"Robert",
""
]
] | A new constraint suppressing formulation of the Einstein evolution equations is presented, generalizing the five-parameter first-order system due to Kidder, Scheel and Teukolsky (KST). The auxiliary fields, introduced to make the KST system first-order, are given modified evolution equations designed to drive constraint violations toward zero. The algebraic structure of the new system is investigated, showing that the modifications preserve the hyperbolicity of the fundamental and constraint evolution equations. The evolution of the constraints for pertubations of flat spacetime is completely analyzed, and all finite-wavelength constraint modes are shown to decay exponentially when certain adjustable parameters satisfy appropriate inequalities. Numerical simulations of a single Schwarzschild black hole are presented, demonstrating the effectiveness of the new constraint-damping modifications. |
2112.06302 | Alberto Garcia-Diaz | Alberto A. Garcia-Diaz | Stationary Rotating Black Hole Exact Solution within Einstein--Nonlinear
Electrodynamics | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The first exact rotating charged black hole solution to the
Einstein{nonlinear electrodynamics theory is reported. It is equipped with
mass, rotation parameter, electric and magnetic charges, and three parameters
due to the electrodynamics: beta is associated to the potential vectors A{mu}
and starP{nu}, and two constants, F0 and G0, related to the presence of the
invariants F and G in the Lagrangian L(F;G). This Petrov type D solution is
characterized by the Weyl tensor eigenvalue Psi2, the Ricci tensor eigenvalue S
= 2Phi(11), and the scalar curvature R; it allows for event horizons, exhibits
a ring singularity and fulfills the energy conditions. Its Maxwell limit is the
Kerr{Newman black hole.
| [
{
"created": "Sun, 12 Dec 2021 19:15:06 GMT",
"version": "v1"
}
] | 2021-12-14 | [
[
"Garcia-Diaz",
"Alberto A.",
""
]
] | The first exact rotating charged black hole solution to the Einstein{nonlinear electrodynamics theory is reported. It is equipped with mass, rotation parameter, electric and magnetic charges, and three parameters due to the electrodynamics: beta is associated to the potential vectors A{mu} and starP{nu}, and two constants, F0 and G0, related to the presence of the invariants F and G in the Lagrangian L(F;G). This Petrov type D solution is characterized by the Weyl tensor eigenvalue Psi2, the Ricci tensor eigenvalue S = 2Phi(11), and the scalar curvature R; it allows for event horizons, exhibits a ring singularity and fulfills the energy conditions. Its Maxwell limit is the Kerr{Newman black hole. |
1104.2669 | Francisco Lobo | Tiberiu Harko, Francisco S.N. Lobo, Shin'ichi Nojiri, Sergei D.
Odintsov | f(R,T) gravity | 14 pages. V2: minor corrections, to appear in PRD | Phys.Rev.D84:024020,2011 | 10.1103/PhysRevD.84.024020 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider f(R,T) modified theories of gravity, where the gravitational
Lagrangian is given by an arbitrary function of the Ricci scalar R and of the
trace of the stress-energy tensor T. We obtain the gravitational field
equations in the metric formalism, as well as the equations of motion for test
particles, which follow from the covariant divergence of the stress-energy
tensor. Generally, the gravitational field equations depend on the nature of
the matter source. The field equations of several particular models,
corresponding to some explicit forms of the function f(R,T), are also
presented. An important case, which is analyzed in detail, is represented by
scalar field models. We write down the action and briefly consider the
cosmological implications of the $f(R,T^{\phi})$ models, where $T^{\phi}$ is
the trace of the stress-energy tensor of a self-interacting scalar field. The
equations of motion of the test particles are also obtained from a variational
principle. The motion of massive test particles is non-geodesic, and takes
place in the presence of an extra force orthogonal to the four-velocity. The
Newtonian limit of the equation of motion is further analyzed. Finally, we
provide a constraint on the magnitude of the extra-acceleration by analyzing
the perihelion precession of the planet Mercury in the framework of the present
model.
| [
{
"created": "Thu, 14 Apr 2011 05:47:38 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jun 2011 21:34:31 GMT",
"version": "v2"
}
] | 2011-07-14 | [
[
"Harko",
"Tiberiu",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Nojiri",
"Shin'ichi",
""
],
[
"Odintsov",
"Sergei D.",
""
]
] | We consider f(R,T) modified theories of gravity, where the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar R and of the trace of the stress-energy tensor T. We obtain the gravitational field equations in the metric formalism, as well as the equations of motion for test particles, which follow from the covariant divergence of the stress-energy tensor. Generally, the gravitational field equations depend on the nature of the matter source. The field equations of several particular models, corresponding to some explicit forms of the function f(R,T), are also presented. An important case, which is analyzed in detail, is represented by scalar field models. We write down the action and briefly consider the cosmological implications of the $f(R,T^{\phi})$ models, where $T^{\phi}$ is the trace of the stress-energy tensor of a self-interacting scalar field. The equations of motion of the test particles are also obtained from a variational principle. The motion of massive test particles is non-geodesic, and takes place in the presence of an extra force orthogonal to the four-velocity. The Newtonian limit of the equation of motion is further analyzed. Finally, we provide a constraint on the magnitude of the extra-acceleration by analyzing the perihelion precession of the planet Mercury in the framework of the present model. |
1907.01209 | Jing-Bo Wang | Jingbo Wang | Fractional charge of quasi-particles on the horizon of black holes | 6 pages, comments are welcome; There are some mistakes in section 2
and is replaced by arXiv:2011.05498 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the previous works, it was claimed that black holes can be considered as
topological insulators. In this paper, we will show that they are actually
fractional topological insulators. That is, the quasi-particles and quasi-holes
can have fractional charges and statistics (spins). For BTZ black hole, the
filling fraction is $v=\frac{1}{2k}$. For Kerr black hole, the filling fraction
is $v=\frac{\pi}{S}$, where $S$ is the entropy of black hole.
| [
{
"created": "Tue, 2 Jul 2019 07:33:54 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Nov 2020 08:05:25 GMT",
"version": "v2"
}
] | 2020-11-13 | [
[
"Wang",
"Jingbo",
""
]
] | In the previous works, it was claimed that black holes can be considered as topological insulators. In this paper, we will show that they are actually fractional topological insulators. That is, the quasi-particles and quasi-holes can have fractional charges and statistics (spins). For BTZ black hole, the filling fraction is $v=\frac{1}{2k}$. For Kerr black hole, the filling fraction is $v=\frac{\pi}{S}$, where $S$ is the entropy of black hole. |
1604.07604 | Waleed El Hanafy | Kazuharu Bamba, G.G.L. Nashed, W. El Hanafy and Sh.K. Ibraheem | Bounce inflation in $f(T)$ Cosmology: A unified inflaton-quintessence
field | 21 pages, 9 figures. An updated version to match the published
version. arXiv admin note: text overlap with arXiv:1509.08769 by other
authors | Phys. Rev. D 94, 083513 (2016) | 10.1103/PhysRevD.94.083513 | FU-PCG-14 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate a bounce inflation model with a graceful exit into the
Friedmann-Robertson-Walker (FRW) decelerated Universe within $f(T)$ gravity
framework, where $T$ is the torsion scalar in the teleparallelism. We study the
cosmic thermal evolution, the model predicts a supercold Universe during the
precontraction phase, which is consistent with the requirements of the
slow-roll models, while it performs a reheating period by the end of the
contraction with a maximum temperature just below the grand unified theory
(GUT) temperature. However, it matches the radiation temperature of the hot big
bang at later stages. The equation-of-state due to the effective gravitational
sector suggests that our Universe is self-accelerated by teleparallel gravity.
We assume the matter component to be a canonical scalar field. We obtain the
scalar field potential that is induced by the $f(T)$ theory. The power spectrum
of the model is nearly scale invariant. In addition, we show that the model
unifies inflaton and quintessence fields in a single model. Also, we revisited
the primordial fluctuations in $f(T)$ bounce cosmology, to study the
fluctuations that are produced at the precontraction phase.
| [
{
"created": "Tue, 26 Apr 2016 10:16:41 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Oct 2016 08:18:26 GMT",
"version": "v2"
}
] | 2016-10-13 | [
[
"Bamba",
"Kazuharu",
""
],
[
"Nashed",
"G. G. L.",
""
],
[
"Hanafy",
"W. El",
""
],
[
"Ibraheem",
"Sh. K.",
""
]
] | We investigate a bounce inflation model with a graceful exit into the Friedmann-Robertson-Walker (FRW) decelerated Universe within $f(T)$ gravity framework, where $T$ is the torsion scalar in the teleparallelism. We study the cosmic thermal evolution, the model predicts a supercold Universe during the precontraction phase, which is consistent with the requirements of the slow-roll models, while it performs a reheating period by the end of the contraction with a maximum temperature just below the grand unified theory (GUT) temperature. However, it matches the radiation temperature of the hot big bang at later stages. The equation-of-state due to the effective gravitational sector suggests that our Universe is self-accelerated by teleparallel gravity. We assume the matter component to be a canonical scalar field. We obtain the scalar field potential that is induced by the $f(T)$ theory. The power spectrum of the model is nearly scale invariant. In addition, we show that the model unifies inflaton and quintessence fields in a single model. Also, we revisited the primordial fluctuations in $f(T)$ bounce cosmology, to study the fluctuations that are produced at the precontraction phase. |
2405.03157 | Mauricio Gamonal | Eugenio Bianchi and Mauricio Gamonal | Primordial power spectrum at N3LO in effective theories of inflation | 25 pages, 4 figures, 7 tables; References added | null | null | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We develop a systematic framework to compute the primordial power spectrum up
to next-to-next-to-next to leading order (N3LO) in the Hubble-flow parameters
for a large class of effective theories of inflation. We assume that the
quadratic action for perturbations is characterized by two functions of time,
the kinetic amplitude and the speed of sound, that are independent of the
Fourier mode $k$. Using the Green's function method introduced by Stewart &
Gong and developed by Auclair & Ringeval, we determine the primordial power
spectrum, including its amplitude, spectral indices, their running and running
of their running, starting from a given generic action for perturbations. As a
check, we reproduce the state-of-the-art results for scalar and the tensor
power spectrum of the simplest "vanilla" models of single-field inflation. The
framework applies to Weinberg's effective field theory of inflation (with the
condition of no parity violation) and to effective theory of spontaneous de
Sitter-symmetry breaking. As a concrete application, we provide the expression
for the N3LO power spectrum of $R+R^2$ Starobinsky inflation, without a field
redefinition. All expressions are provided in terms of an expansion in one
single parameter, the number of inflationary e-foldings $N_\ast$. Surprisingly
we find that, compared to previous leading-order calculations, for $N_\ast =
55$ the N3LO correction results in a $7\%$ decrease of the predicted
tensor-to-scalar ratio, in addition to a deviation from the consistency
relation and a prediction of a negative running
$\alpha_\mathrm{s}=-\frac{1}{2}(n_\mathrm{s}-1)^2+\ldots$ of the scalar tilt.
These results provide precise theoretical predictions for the next generation
of CMB observations.
| [
{
"created": "Mon, 6 May 2024 04:25:55 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Aug 2024 21:05:32 GMT",
"version": "v2"
}
] | 2024-08-13 | [
[
"Bianchi",
"Eugenio",
""
],
[
"Gamonal",
"Mauricio",
""
]
] | We develop a systematic framework to compute the primordial power spectrum up to next-to-next-to-next to leading order (N3LO) in the Hubble-flow parameters for a large class of effective theories of inflation. We assume that the quadratic action for perturbations is characterized by two functions of time, the kinetic amplitude and the speed of sound, that are independent of the Fourier mode $k$. Using the Green's function method introduced by Stewart & Gong and developed by Auclair & Ringeval, we determine the primordial power spectrum, including its amplitude, spectral indices, their running and running of their running, starting from a given generic action for perturbations. As a check, we reproduce the state-of-the-art results for scalar and the tensor power spectrum of the simplest "vanilla" models of single-field inflation. The framework applies to Weinberg's effective field theory of inflation (with the condition of no parity violation) and to effective theory of spontaneous de Sitter-symmetry breaking. As a concrete application, we provide the expression for the N3LO power spectrum of $R+R^2$ Starobinsky inflation, without a field redefinition. All expressions are provided in terms of an expansion in one single parameter, the number of inflationary e-foldings $N_\ast$. Surprisingly we find that, compared to previous leading-order calculations, for $N_\ast = 55$ the N3LO correction results in a $7\%$ decrease of the predicted tensor-to-scalar ratio, in addition to a deviation from the consistency relation and a prediction of a negative running $\alpha_\mathrm{s}=-\frac{1}{2}(n_\mathrm{s}-1)^2+\ldots$ of the scalar tilt. These results provide precise theoretical predictions for the next generation of CMB observations. |
gr-qc/9511039 | Zoltan Perjes | Z. Perj\'es (KFKI Research Institute for Particle and Nuclear Physics,
Hungary), A. Kom\'arik (E\"otv\"os University, Hungary) | Perturbations of a Universe Filled with Dust and Radiation | 9 pp, typeset in latex | Int.J.Theor.Phys. 34 (1995) 2275-2284 | 10.1007/BF00673842 | null | gr-qc | null | A first-order perturbation approach to $k=0$ Friedmann cosmologies filled
with dust and radiation is developed. Adopting the coordinate gauge comoving
with the perturbed matter, and neglecting the vorticity of the radiation, a
pair of coupled equations is obtained for the trace $h$ of the metric
perturbations and for the velocity potential $v$. A power series solution with
upwards cutoff exists such that the leading terms for large values of the
dimensionless time $\xi$ agree with the relatively growing terms of the dust
solution of Sachs and Wolfe.
| [
{
"created": "Mon, 13 Nov 1995 16:20:00 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Perjés",
"Z.",
"",
"KFKI Research Institute for Particle and Nuclear Physics,\n Hungary"
],
[
"Komárik",
"A.",
"",
"Eötvös University, Hungary"
]
] | A first-order perturbation approach to $k=0$ Friedmann cosmologies filled with dust and radiation is developed. Adopting the coordinate gauge comoving with the perturbed matter, and neglecting the vorticity of the radiation, a pair of coupled equations is obtained for the trace $h$ of the metric perturbations and for the velocity potential $v$. A power series solution with upwards cutoff exists such that the leading terms for large values of the dimensionless time $\xi$ agree with the relatively growing terms of the dust solution of Sachs and Wolfe. |
gr-qc/9803053 | Lee Lindblom | Lee Lindblom, Benjamin J. Owen, Sharon M. Morsink | Gravitational Radiation Instability in Hot Young Neutron Stars | 4 Pages, 2 Figures | Phys.Rev.Lett.80:4843-4846,1998 | 10.1103/PhysRevLett.80.4843 | GRP-495 | gr-qc | null | We show that gravitational radiation drives an instability in hot young
rapidly rotating neutron stars. This instability occurs primarily in the l=2
r-mode and will carry away most of the angular momentum of a rapidly rotating
star by gravitational radiation. On the timescale needed to cool a young
neutron star to about T=10^9 K (about one year) this instability can reduce the
rotation rate of a rapidly rotating star to about 0.076\Omega_K, where \Omega_K
is the Keplerian angular velocity where mass shedding occurs. In older colder
neutron stars this instability is suppressed by viscous effects, allowing older
stars to be spun up by accretion to larger angular velocities.
| [
{
"created": "Fri, 13 Mar 1998 22:09:33 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Lindblom",
"Lee",
""
],
[
"Owen",
"Benjamin J.",
""
],
[
"Morsink",
"Sharon M.",
""
]
] | We show that gravitational radiation drives an instability in hot young rapidly rotating neutron stars. This instability occurs primarily in the l=2 r-mode and will carry away most of the angular momentum of a rapidly rotating star by gravitational radiation. On the timescale needed to cool a young neutron star to about T=10^9 K (about one year) this instability can reduce the rotation rate of a rapidly rotating star to about 0.076\Omega_K, where \Omega_K is the Keplerian angular velocity where mass shedding occurs. In older colder neutron stars this instability is suppressed by viscous effects, allowing older stars to be spun up by accretion to larger angular velocities. |
gr-qc/9703021 | Donald Marolf | James B. Hartle (Institute for Theoretical Physics, University of
California, Santa Barbara) and Donald Marolf (Department of Physics, Syracuse
University) | Comparing Formulations of Generalized Quantum Mechanics for
Reparametrization-Invariant Systems | 21 pages ReVTeX | Phys. Rev. D 56, 6247 (1997) | 10.1103/PhysRevD.56.6247 | UCSBTH-96-15, NSF-ITP-96-59 | gr-qc quant-ph | null | A class of decoherence schemes is described for implementing the principles
of generalized quantum theory in reparametrization-invariant `hyperbolic'
models such as minisuperspace quantum cosmology. The connection with
sum-over-histories constructions is exhibited and the physical equivalence or
inequivalence of different such schemes is analyzed. The discussion focuses on
comparing constructions based on the Klein-Gordon product with those based on
the induced (a.k.a. Rieffel, Refined Algebraic, Group Averaging, or Spectral
Analysis) inner product. It is shown that the Klein-Gordon and induced products
can be simply related for the models of interest. This fact is then used to
establish isomorphisms between certain decoherence schemes based on these
products.
| [
{
"created": "Fri, 7 Mar 1997 17:39:27 GMT",
"version": "v1"
}
] | 2016-08-25 | [
[
"Hartle",
"James B.",
"",
"Institute for Theoretical Physics, University of\n California, Santa Barbara"
],
[
"Marolf",
"Donald",
"",
"Department of Physics, Syracuse\n University"
]
] | A class of decoherence schemes is described for implementing the principles of generalized quantum theory in reparametrization-invariant `hyperbolic' models such as minisuperspace quantum cosmology. The connection with sum-over-histories constructions is exhibited and the physical equivalence or inequivalence of different such schemes is analyzed. The discussion focuses on comparing constructions based on the Klein-Gordon product with those based on the induced (a.k.a. Rieffel, Refined Algebraic, Group Averaging, or Spectral Analysis) inner product. It is shown that the Klein-Gordon and induced products can be simply related for the models of interest. This fact is then used to establish isomorphisms between certain decoherence schemes based on these products. |
2208.00171 | Omar Mustafa | Omar Mustafa | Klein-Gordon particles in G\"odel-type Som-Raychaudhuri cosmic string
spacetime and the phenomenon of spacetime associated degeneracies | 13 pages, no figures | Phys. Scr. 98 (2023) 015302 | 10.1088/1402-4896/aca72b | null | gr-qc math-ph math.MP quant-ph | http://creativecommons.org/licenses/by/4.0/ | We argue that only exact, comprehensive, and explicit solutions for the
fundamental models, the Klein-Gordon (KG) oscillators and the KG-Coulomb, would
help to understand the effects of gravitational fields on the dynamics of such
quantum mechanical systems. In the current methodical proposal, the effects of
the gravitational fields generated by a G\"odel-type Som-Raychaudhuri (SR)
cosmic string spacetime on KG-oscillators (KG-particles in general) are studied
and reported. In so doing, we revisit the KG-oscillators in a topologically
trivial G\"odel-type spacetime background and use textbook procedures to report
its exact solution that covers even and odd parities. Next, we discuss the
drawbacks associated with the power series expansion approach that implies the
biconfluent Heun functions/polynomials solution. We, therefore, recollect the
so called pseudo perturbative shifted L expansion technique (PSLET) as an
alternative and more sophisticated method/technique. Illustrative examples are
used: (i) a KG-oscillator in a topologically trivial G\"odel-type spacetime,
(ii) a quasi-free KG-oscillator in G\"odel SR-type cosmic string spacetime,
(iii) a KG-Coulombic particle in G\"odel SR-type cosmic string spacetime at
zero vorticity, and (iv) a massless KG-particle in G\"odel SR-type cosmic
string spacetime in a Cornell-type Lorentz scalar potential. The corresponding
exact energies are obtained from the zeroth (leading) order correction of
PSLET, where all higher order correction identically vanish. The comprehensive
exactness of the reported solutions manifestly suggest degeneracies associated
with spacetime (STAD) phenomenon.
| [
{
"created": "Sat, 30 Jul 2022 09:06:51 GMT",
"version": "v1"
}
] | 2023-04-17 | [
[
"Mustafa",
"Omar",
""
]
] | We argue that only exact, comprehensive, and explicit solutions for the fundamental models, the Klein-Gordon (KG) oscillators and the KG-Coulomb, would help to understand the effects of gravitational fields on the dynamics of such quantum mechanical systems. In the current methodical proposal, the effects of the gravitational fields generated by a G\"odel-type Som-Raychaudhuri (SR) cosmic string spacetime on KG-oscillators (KG-particles in general) are studied and reported. In so doing, we revisit the KG-oscillators in a topologically trivial G\"odel-type spacetime background and use textbook procedures to report its exact solution that covers even and odd parities. Next, we discuss the drawbacks associated with the power series expansion approach that implies the biconfluent Heun functions/polynomials solution. We, therefore, recollect the so called pseudo perturbative shifted L expansion technique (PSLET) as an alternative and more sophisticated method/technique. Illustrative examples are used: (i) a KG-oscillator in a topologically trivial G\"odel-type spacetime, (ii) a quasi-free KG-oscillator in G\"odel SR-type cosmic string spacetime, (iii) a KG-Coulombic particle in G\"odel SR-type cosmic string spacetime at zero vorticity, and (iv) a massless KG-particle in G\"odel SR-type cosmic string spacetime in a Cornell-type Lorentz scalar potential. The corresponding exact energies are obtained from the zeroth (leading) order correction of PSLET, where all higher order correction identically vanish. The comprehensive exactness of the reported solutions manifestly suggest degeneracies associated with spacetime (STAD) phenomenon. |
gr-qc/9803034 | Horst R. Beyer | Horst R. Beyer | On the Completeness of the Quasinormal Modes of the Poeschl-Teller
Potential | 22 pages, 2 figures, submitted to Comm. Math. Phys | Commun.Math.Phys. 204 (1999) 397-423 | 10.1007/s002200050651 | null | gr-qc | null | The completeness of the quasinormal modes of the wave equation with
Poeschl-Teller potential is investigated. A main result is that after a large
enough time $t_0$, the solutions of this equation corresponding to
$C^{\infty}$-data with compact support can be expanded uniformly in time with
respect to the quasinormal modes, thereby leading to absolutely convergent
series. Explicit estimates for $t_0$ depending on both the support of the data
and the point of observation are given. For the particular case of an ``early''
time and zero distance between the support of the data and observational point,
it is shown that the corresponding series is not absolutely convergent, and
hence that there is no associated sum which is independent of the order of
summation.
| [
{
"created": "Tue, 10 Mar 1998 14:11:42 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Beyer",
"Horst R.",
""
]
] | The completeness of the quasinormal modes of the wave equation with Poeschl-Teller potential is investigated. A main result is that after a large enough time $t_0$, the solutions of this equation corresponding to $C^{\infty}$-data with compact support can be expanded uniformly in time with respect to the quasinormal modes, thereby leading to absolutely convergent series. Explicit estimates for $t_0$ depending on both the support of the data and the point of observation are given. For the particular case of an ``early'' time and zero distance between the support of the data and observational point, it is shown that the corresponding series is not absolutely convergent, and hence that there is no associated sum which is independent of the order of summation. |
2010.07560 | Masato Nozawa | Masato Nozawa | Static spacetimes haunted by a phantom scalar field II: dilatonic
charged solutions | 2 figures, 1 table, 33 pages; v2: refs added, to appear in PRD | Phys. Rev. D 103, 024004 (2021) | 10.1103/PhysRevD.103.024004 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a method to generate static solutions in the Einstein-Maxwell
system with a (phantom) dilaton field in $n(\ge 4)$-dimensions, based upon the
symmetry of the target space for the nonlinear sigma model. Unlike the
conventional Einstein-Maxwell-dilaton system, there appears a critical value of
the coupling constant for a phantom dilaton field. In the noncritical case, the
target space is $\mathbb R\times {\rm SL}(2,\mathbb R)/H$ with the maximal
subgroup $H=\{{\rm SO}(2), {\rm SO}(1,1)\}$, whereas in the critical case the
target space becomes a symmetric pp-wave and the corresponding Killing vectors
form a non-semisimple algebra. In either case, we apply the formalism to charge
up the neutral solutions and show the analytical expression for dilatonic
charged versions of (i) the Fisher solution, (ii) the Gibbons solution, and
(iii) the Ellis-Bronnikov solution. We discuss global structures of these
solutions in detail. It turns out that some solutions contained in the Fisher
and Gibbons classes possess the parallelly propagated (p.p) curvature
singularities in the parameter region where all the scalar curvature invariants
remain bounded. These p.p curvature singularities are not veiled by a horizon,
thrusting them into physically untenable nakedly singular spacetimes. We also
demonstrate that the dilatonic-charged Ellis-Bronnikov solution admits a
parameter range under which the solution represents a regular wormhole
spacetime in the two-sided asymptotically flat regions.
| [
{
"created": "Thu, 15 Oct 2020 07:18:00 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jan 2021 03:12:01 GMT",
"version": "v2"
}
] | 2021-01-13 | [
[
"Nozawa",
"Masato",
""
]
] | We present a method to generate static solutions in the Einstein-Maxwell system with a (phantom) dilaton field in $n(\ge 4)$-dimensions, based upon the symmetry of the target space for the nonlinear sigma model. Unlike the conventional Einstein-Maxwell-dilaton system, there appears a critical value of the coupling constant for a phantom dilaton field. In the noncritical case, the target space is $\mathbb R\times {\rm SL}(2,\mathbb R)/H$ with the maximal subgroup $H=\{{\rm SO}(2), {\rm SO}(1,1)\}$, whereas in the critical case the target space becomes a symmetric pp-wave and the corresponding Killing vectors form a non-semisimple algebra. In either case, we apply the formalism to charge up the neutral solutions and show the analytical expression for dilatonic charged versions of (i) the Fisher solution, (ii) the Gibbons solution, and (iii) the Ellis-Bronnikov solution. We discuss global structures of these solutions in detail. It turns out that some solutions contained in the Fisher and Gibbons classes possess the parallelly propagated (p.p) curvature singularities in the parameter region where all the scalar curvature invariants remain bounded. These p.p curvature singularities are not veiled by a horizon, thrusting them into physically untenable nakedly singular spacetimes. We also demonstrate that the dilatonic-charged Ellis-Bronnikov solution admits a parameter range under which the solution represents a regular wormhole spacetime in the two-sided asymptotically flat regions. |
gr-qc/9904043 | Wai-Mo Suen | Wai-Mo Suen | Impact of a Multi-TeraFlop Machine to Gravitational Physics | Prepared for presentation at the National Computational Science
Alliance User Advisory Council Meeting at NSF, June 1998, in support of the
funding of a NSF TeraFlop computer | null | null | null | gr-qc | null | A multi-TeraFlop/TeraByte machine will enable the application of the Einstein
theory of gravity to realistic astrophysical processes. Without the
computational power, the complexity of the Einstein theory restricts most
studies based on it to the quasi static/linear near-Newtonian regime of the
theory.
The application of the Einstein theory to realistic astrophysical processes
is bound to bring deep and far-reaching scientific discoveries, and produce
results that will inspire the general public. It is an essential component in
developing the new frontier of gravitational wave astronomy - an exciting new
window to observe our universe.
The computational requirements of carrying out numerical simulations based on
the Einstein theory is discussed with an explicit example, the coalescence of a
neutron star binary.
This document is prepared for presentation at the National Computational
Science Alliance User Advisory Council Meeting at NSF, June 1998, in support of
the funding of a NSF TeraFlop computer.
| [
{
"created": "Mon, 19 Apr 1999 01:24:07 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Suen",
"Wai-Mo",
""
]
] | A multi-TeraFlop/TeraByte machine will enable the application of the Einstein theory of gravity to realistic astrophysical processes. Without the computational power, the complexity of the Einstein theory restricts most studies based on it to the quasi static/linear near-Newtonian regime of the theory. The application of the Einstein theory to realistic astrophysical processes is bound to bring deep and far-reaching scientific discoveries, and produce results that will inspire the general public. It is an essential component in developing the new frontier of gravitational wave astronomy - an exciting new window to observe our universe. The computational requirements of carrying out numerical simulations based on the Einstein theory is discussed with an explicit example, the coalescence of a neutron star binary. This document is prepared for presentation at the National Computational Science Alliance User Advisory Council Meeting at NSF, June 1998, in support of the funding of a NSF TeraFlop computer. |
0803.0376 | Alessandra Corsi | The Virgo collaboration | Search for gravitational waves associated with GRB 050915a using the
Virgo detector | 26 pages, 10 figures | Class.Quant.Grav.25:225001,2008 | 10.1088/0264-9381/25/22/225001 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of the expected association between gamma-ray bursts and
gravitational waves, we present results of an analysis aimed to search for a
burst of gravitational waves in coincidence with gamma-ray burst 050915a. This
was a long duration gamma-ray burst detected by Swift during September 2005,
when the Virgo gravitational wave detector was engaged in a commissioning run
during which the best sensitivity attained in 2005 was exhibited. This offered
the opportunity for Virgo's first search for a gravitational wave signal in
coincidence with a gamma-ray burst. The result of our study is a set of strain
amplitude upper-limits, based on the loudest event approach, for different but
quite general types of burst signal waveforms. The best upper-limit strain
amplitudes we obtain are h_{rss}=O(10^{-20})Hz^{-1/2} around 200-1500 Hz. These
upper-limits allow us to evaluate the level up to which Virgo, when reaching
nominal sensitivity, will be able to constrain the gravitational wave output
associated with a long burst. Moreover, the analysis here presented plays the
role of a prototype, crucial in defining a methodology for gamma-ray burst
triggered searches with Virgo and opening the way for future joint analyses
with LIGO.
| [
{
"created": "Tue, 4 Mar 2008 07:04:57 GMT",
"version": "v1"
}
] | 2012-08-27 | [
[
"The Virgo collaboration",
"",
""
]
] | In the framework of the expected association between gamma-ray bursts and gravitational waves, we present results of an analysis aimed to search for a burst of gravitational waves in coincidence with gamma-ray burst 050915a. This was a long duration gamma-ray burst detected by Swift during September 2005, when the Virgo gravitational wave detector was engaged in a commissioning run during which the best sensitivity attained in 2005 was exhibited. This offered the opportunity for Virgo's first search for a gravitational wave signal in coincidence with a gamma-ray burst. The result of our study is a set of strain amplitude upper-limits, based on the loudest event approach, for different but quite general types of burst signal waveforms. The best upper-limit strain amplitudes we obtain are h_{rss}=O(10^{-20})Hz^{-1/2} around 200-1500 Hz. These upper-limits allow us to evaluate the level up to which Virgo, when reaching nominal sensitivity, will be able to constrain the gravitational wave output associated with a long burst. Moreover, the analysis here presented plays the role of a prototype, crucial in defining a methodology for gamma-ray burst triggered searches with Virgo and opening the way for future joint analyses with LIGO. |
gr-qc/0202059 | Sean A. Hayward | Sean A. Hayward | Wormholes supported by pure ghost radiation | 3 revtex pages | Phys.Rev. D65 (2002) 124016 | 10.1103/PhysRevD.65.124016 | null | gr-qc | null | Traversible wormhole space-times are found as static, spherically symmetric
solutions to the Einstein equations with ingoing and outgoing pure ghost
radiation, i.e. pure radiation with negative energy density. Switching off the
radiation causes the wormhole to collapse to a Schwarzschild black hole.
| [
{
"created": "Sun, 17 Feb 2002 05:13:50 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Hayward",
"Sean A.",
""
]
] | Traversible wormhole space-times are found as static, spherically symmetric solutions to the Einstein equations with ingoing and outgoing pure ghost radiation, i.e. pure radiation with negative energy density. Switching off the radiation causes the wormhole to collapse to a Schwarzschild black hole. |
2311.10946 | Taotao Sui | Tao-Tao Sui, Zi-Liang Wang, and Wen-Di Guo | The effect of scalar hair on the charged black hole with the images from
accretions disk | 13 pages, 13figures | Eur. Phys. J. C 84, 441 (2024) | 10.1140/epjc/s10052-024-12807-5 | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | In this paper, we investigate the optical properties of a charged black hole
with scalar hair (CSH) within the context of four-dimensional
Einstein-Maxwell-Dilaton gravity. To achieve this, we consider three distinct
toy models of thin accretion disks. The presence of dilaton coupling allows us
to express both the solutions of CSH and the Reissner-Nordstr\"om (RN) black
hole in terms of their mass ($M$) and charge ($Q$). Our findings reveal
differences in the effective potentials $V_{eff}$, photon sphere radii
$r_{ph}$, and innermost stable circular orbit $r_{isco}$ between the CSH and RN
black hole cases, which become increasingly pronounced as the charge parameter
$Q$ increases. However, no noticeable distinctions are observed concerning the
critical impact parameter $b_{ph}$. When the ratio of the photon ring band and
the lensed ring band exceeds 0.1, it may suggest the presence of a charged
black hole with scalar hair. Furthermore, our results underscore the
significant influence of the charge parameter $Q$ on the brightness
distributions of the direct, lensed ring, and photon ring for three standard
emission functions. These findings emphasize the potential for distinguishing
between CSH and RN black holes through an analysis of direct intensity and peak
brightness in specific accretion disk models.
| [
{
"created": "Sat, 18 Nov 2023 02:51:12 GMT",
"version": "v1"
},
{
"created": "Mon, 6 May 2024 06:16:02 GMT",
"version": "v2"
}
] | 2024-05-07 | [
[
"Sui",
"Tao-Tao",
""
],
[
"Wang",
"Zi-Liang",
""
],
[
"Guo",
"Wen-Di",
""
]
] | In this paper, we investigate the optical properties of a charged black hole with scalar hair (CSH) within the context of four-dimensional Einstein-Maxwell-Dilaton gravity. To achieve this, we consider three distinct toy models of thin accretion disks. The presence of dilaton coupling allows us to express both the solutions of CSH and the Reissner-Nordstr\"om (RN) black hole in terms of their mass ($M$) and charge ($Q$). Our findings reveal differences in the effective potentials $V_{eff}$, photon sphere radii $r_{ph}$, and innermost stable circular orbit $r_{isco}$ between the CSH and RN black hole cases, which become increasingly pronounced as the charge parameter $Q$ increases. However, no noticeable distinctions are observed concerning the critical impact parameter $b_{ph}$. When the ratio of the photon ring band and the lensed ring band exceeds 0.1, it may suggest the presence of a charged black hole with scalar hair. Furthermore, our results underscore the significant influence of the charge parameter $Q$ on the brightness distributions of the direct, lensed ring, and photon ring for three standard emission functions. These findings emphasize the potential for distinguishing between CSH and RN black holes through an analysis of direct intensity and peak brightness in specific accretion disk models. |
1107.1464 | Tai-Zhuo Huang | Tai-Zhuo Huang, Yi Ling, Wen-Jian Pan, Yu Tian, and Xiao-Ning Wu | From Petrov-Einstein to Navier-Stokes in Spatially Curved Spacetime | 17 pages, references added, generalizing the metric form in part 3,
version published in JHEP | JHEP 1110:079,2011 | 10.1007/JHEP10(2011)079 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We generalize the framework in arXiv:1104.5502 to the case that an embedding
may have a nonvanishing intrinsic curvature. Directly employing the Brown-York
stress tensor as the fundamental variables, we study the effect of finite
perturbations of the extrinsic curvature while keeping the intrinsic metric
fixed. We show that imposing a Petrov type I condition on the hypersurface
geometry may reduce to the incompressible Navier-Stokes equation for a fluid
moving in spatially curved spacetime in the near-horizon limit.
| [
{
"created": "Thu, 7 Jul 2011 17:42:35 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Jul 2011 16:28:00 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Oct 2011 16:05:08 GMT",
"version": "v3"
}
] | 2011-10-20 | [
[
"Huang",
"Tai-Zhuo",
""
],
[
"Ling",
"Yi",
""
],
[
"Pan",
"Wen-Jian",
""
],
[
"Tian",
"Yu",
""
],
[
"Wu",
"Xiao-Ning",
""
]
] | We generalize the framework in arXiv:1104.5502 to the case that an embedding may have a nonvanishing intrinsic curvature. Directly employing the Brown-York stress tensor as the fundamental variables, we study the effect of finite perturbations of the extrinsic curvature while keeping the intrinsic metric fixed. We show that imposing a Petrov type I condition on the hypersurface geometry may reduce to the incompressible Navier-Stokes equation for a fluid moving in spatially curved spacetime in the near-horizon limit. |
1806.09616 | Utkarsh Kumar | Utkarsh Kumar and Sukanta Panda | Non-local cosmological models | null | null | 10.1088/1361-6382/ab4eb6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Nonlocal cosmological models are studied extensively in recent times because
of their interesting cosmological consequences. In this paper, we have analyzed
background cosmology on a class of non-local models which are motivated by the
perturbative nature of gravity at infrared scale. We show that inflationary
solutions are possible in all constructed non-local models. However, exit from
inflation to RD era is not possible in most of the models.
| [
{
"created": "Mon, 25 Jun 2018 13:27:16 GMT",
"version": "v1"
}
] | 2020-01-08 | [
[
"Kumar",
"Utkarsh",
""
],
[
"Panda",
"Sukanta",
""
]
] | Nonlocal cosmological models are studied extensively in recent times because of their interesting cosmological consequences. In this paper, we have analyzed background cosmology on a class of non-local models which are motivated by the perturbative nature of gravity at infrared scale. We show that inflationary solutions are possible in all constructed non-local models. However, exit from inflation to RD era is not possible in most of the models. |
gr-qc/0110054 | Jorge Pullin | Rodolfo Gambini and Jorge Pullin | Lorentz violations in canonical quantum gravity | 4 pages, Revtex. Talk given at CP01. To appear in proceedings | null | 10.1142/9789812778123_0005 | LSU-REL-101001 | gr-qc | null | This is a summary of a talk given at the CP01 meeting on possible Lorentz
anomalies in canonical quantum gravity. It briefly reviews some initial
explorations on the subject that have taken place recently, and should be only
be seen as a short pointer to the literature on the subject, mostly for
outsiders.
| [
{
"created": "Wed, 10 Oct 2001 18:06:18 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | This is a summary of a talk given at the CP01 meeting on possible Lorentz anomalies in canonical quantum gravity. It briefly reviews some initial explorations on the subject that have taken place recently, and should be only be seen as a short pointer to the literature on the subject, mostly for outsiders. |
2104.06258 | Yaser Ahmadi | Y. Ahmadi | De Sitter scalar-spinor interaction in Minkowski limit | 5 pages | International Journal of Modern Physics D, Vol. 29, No. 13,
2050092 (2020) | 10.1142/S0218271820500923 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The scalar-spinor interaction Lagrangian is presented by the Yukawa
potential. In dS ambient space formalism, the interaction Lagrangian of
scalar-spinor fields was obtained from a new transformation which is very
similar to the guage theory. The interaction of massless minimally coupled
scalar and spinor fields was investigated. The Minkowski limit of the massless
minimally coupled scalar field and massive spinor field interaction in the
ambient space formalism of de Sitter space time is calculated. The interaction
Lagrangian and massless minimally coupled scalar field in the null curvature
limit become zero and the local transformation in the null curvature limit
become a constant phase transformation and the interaction in this limit become
zero. The covariant derivative reduces to ordinary derivative too. Then we
conclude that this interaction is due to the curvature of space time and then
the massless minimally coupled scalar field may be a part of a gravitational
field.
| [
{
"created": "Sun, 4 Apr 2021 15:17:34 GMT",
"version": "v1"
}
] | 2021-04-14 | [
[
"Ahmadi",
"Y.",
""
]
] | The scalar-spinor interaction Lagrangian is presented by the Yukawa potential. In dS ambient space formalism, the interaction Lagrangian of scalar-spinor fields was obtained from a new transformation which is very similar to the guage theory. The interaction of massless minimally coupled scalar and spinor fields was investigated. The Minkowski limit of the massless minimally coupled scalar field and massive spinor field interaction in the ambient space formalism of de Sitter space time is calculated. The interaction Lagrangian and massless minimally coupled scalar field in the null curvature limit become zero and the local transformation in the null curvature limit become a constant phase transformation and the interaction in this limit become zero. The covariant derivative reduces to ordinary derivative too. Then we conclude that this interaction is due to the curvature of space time and then the massless minimally coupled scalar field may be a part of a gravitational field. |
1306.0903 | Marco Sampaio | Marco O. P. Sampaio | Radiation from a D-dimensional collision of shock waves: numerical
methods | Lecture notes from the NRHEP spring school held at IST-Lisbon, March
2013. Extra material and notebooks available online at
http://blackholes.ist.utl.pt/nrhep2/ To be published by IJMPA (V. Cardoso, L.
Gualtieri, C. Herdeiro and U. Sperhake, Eds., 2013) | null | 10.1142/S0217751X13400198 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a pedagogical introduction to the problem of evolving a head on
collision of two Aichelburg-Sexl gravitational shock waves in D-dimensions,
using perturbative techniques. We follow a constructive approach with examples,
going in some detail through: the set up of the exact initial conditions and
their properties; perturbative methods in flat space-time with Green function
solutions; and numerical strategies to evaluate the integral solutions. We also
discuss, briefly, radiation extraction methods adapted to this problem,
together with some of the results for this system.
| [
{
"created": "Tue, 4 Jun 2013 20:00:03 GMT",
"version": "v1"
}
] | 2013-09-18 | [
[
"Sampaio",
"Marco O. P.",
""
]
] | We present a pedagogical introduction to the problem of evolving a head on collision of two Aichelburg-Sexl gravitational shock waves in D-dimensions, using perturbative techniques. We follow a constructive approach with examples, going in some detail through: the set up of the exact initial conditions and their properties; perturbative methods in flat space-time with Green function solutions; and numerical strategies to evaluate the integral solutions. We also discuss, briefly, radiation extraction methods adapted to this problem, together with some of the results for this system. |
2003.14136 | Sushant Ghosh Prof | Dharm Veer Singh, Sushant G. Ghosh and Sunil D. Maharaj | Clouds of strings in $4D$ Einstein-Gauss-Bonnet black holes | 12 pages, 4 figures, 2 tables, Phys.Dark Univ. 30 (2020) 100730 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently it has been shown that the Einstein-Gauss-Bonnet (EGB) gravity, by
rescaling the coupling constant as $\alpha/(D-4)$ and taking the limit $D
\rightarrow 4$ at the level of the equations of motion, becomes nontrivially
ghost-free in $4D$ - namely the novel $4D$ EGB gravity. We present an exact
charged black hole solution to the theory surrounded by clouds of string (CS)
and also analyze their thermodynamic properties to calculate exact expressions
for the black hole mass, temperature, and entropy. Owing to the corrected black
hole due to the background CS, the thermodynamic quantities have also been
corrected except for the entropy, which remains unaffected by a CS background.
However, as a result of the novel $4D$ EGB theory, the Bekenstein-Hawking area
law turns out to be corrected by a logarithmic area term. The heat capacity
$C_+$ diverges at a critical radius $r=r_C$, where incidentally the temperature
has a maximum, and the Hawking-Page transitions even in absence of the
cosmological term and $C_+ > 0$ for $r_+ < r_C$ allowing the black hole to
become thermodynamically stable. In addition, the smaller black holes are
globally preferred with negative free energy $F_+<0$. Our solution can also be
identified as a $4D$ monopole-charged EGB black hole. We regain results of
spherically symmetric black hole solutions of general relativity and that of
novel $4D$ EGB, respectively, in the limits $\alpha \to 0$ and $a=0$.
| [
{
"created": "Tue, 31 Mar 2020 12:17:03 GMT",
"version": "v1"
},
{
"created": "Sun, 5 Apr 2020 12:11:58 GMT",
"version": "v2"
},
{
"created": "Thu, 10 Sep 2020 06:41:08 GMT",
"version": "v3"
},
{
"created": "Mon, 14 Sep 2020 11:19:17 GMT",
"version": "v4"
},
{
"created": "Fri, 9 Oct 2020 11:30:27 GMT",
"version": "v5"
},
{
"created": "Mon, 12 Oct 2020 10:04:26 GMT",
"version": "v6"
}
] | 2020-10-13 | [
[
"Singh",
"Dharm Veer",
""
],
[
"Ghosh",
"Sushant G.",
""
],
[
"Maharaj",
"Sunil D.",
""
]
] | Recently it has been shown that the Einstein-Gauss-Bonnet (EGB) gravity, by rescaling the coupling constant as $\alpha/(D-4)$ and taking the limit $D \rightarrow 4$ at the level of the equations of motion, becomes nontrivially ghost-free in $4D$ - namely the novel $4D$ EGB gravity. We present an exact charged black hole solution to the theory surrounded by clouds of string (CS) and also analyze their thermodynamic properties to calculate exact expressions for the black hole mass, temperature, and entropy. Owing to the corrected black hole due to the background CS, the thermodynamic quantities have also been corrected except for the entropy, which remains unaffected by a CS background. However, as a result of the novel $4D$ EGB theory, the Bekenstein-Hawking area law turns out to be corrected by a logarithmic area term. The heat capacity $C_+$ diverges at a critical radius $r=r_C$, where incidentally the temperature has a maximum, and the Hawking-Page transitions even in absence of the cosmological term and $C_+ > 0$ for $r_+ < r_C$ allowing the black hole to become thermodynamically stable. In addition, the smaller black holes are globally preferred with negative free energy $F_+<0$. Our solution can also be identified as a $4D$ monopole-charged EGB black hole. We regain results of spherically symmetric black hole solutions of general relativity and that of novel $4D$ EGB, respectively, in the limits $\alpha \to 0$ and $a=0$. |
2405.12640 | Han Yan | Han Yan, Xian Chen, Jinhai Zhang, Fan Zhang, Lijing Shao, Mengyao Wang | Constraining the stochastic gravitational wave background using the
future lunar seismometers | Accepted for publication in Physical Review D | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the old idea of using the moon as a resonant gravitational-wave
(GW) detector, as well as the recent updates in modeling the lunar response to
GWs, we re-evaluate the feasibility of using a network of lunar seismometers to
constrain the stochastic GW background (SGWB). In particular, using the updated
model of the lunar response, we derive the pattern functions for the two
polarizations of GW. With these pattern functions, we further calculate the
overlap reduction functions for a network of lunar seismometers, where we have
relaxed the conventional assumption that lunar seismometers are perfectly
leveled to measure only the vertical acceleration. We apply our calculation to
two future lunar projects, namely, Chang'e and the Lunar Gravitational-Wave
Antenna (LGWA). We find that the two projects could constrain the SGWB to a
level of $\Omega_{\text{GW}}^{\text{Chang'e}} < 2.4 \times 10^{2}$ and
$\Omega_{\text{GW}}^{\text{LGWA}} < 2.0 \times 10^{-10}$, respectively, which
corresponds to a signal-to-noise ratio of SNR $=3$. These results are better
than the constraints placed previously on the SGWB in the mid-frequency band
(around $10^{-3}- 10~\text{Hz}$) by various types of experiments.
| [
{
"created": "Tue, 21 May 2024 09:44:34 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jul 2024 07:41:03 GMT",
"version": "v2"
}
] | 2024-07-10 | [
[
"Yan",
"Han",
""
],
[
"Chen",
"Xian",
""
],
[
"Zhang",
"Jinhai",
""
],
[
"Zhang",
"Fan",
""
],
[
"Shao",
"Lijing",
""
],
[
"Wang",
"Mengyao",
""
]
] | Motivated by the old idea of using the moon as a resonant gravitational-wave (GW) detector, as well as the recent updates in modeling the lunar response to GWs, we re-evaluate the feasibility of using a network of lunar seismometers to constrain the stochastic GW background (SGWB). In particular, using the updated model of the lunar response, we derive the pattern functions for the two polarizations of GW. With these pattern functions, we further calculate the overlap reduction functions for a network of lunar seismometers, where we have relaxed the conventional assumption that lunar seismometers are perfectly leveled to measure only the vertical acceleration. We apply our calculation to two future lunar projects, namely, Chang'e and the Lunar Gravitational-Wave Antenna (LGWA). We find that the two projects could constrain the SGWB to a level of $\Omega_{\text{GW}}^{\text{Chang'e}} < 2.4 \times 10^{2}$ and $\Omega_{\text{GW}}^{\text{LGWA}} < 2.0 \times 10^{-10}$, respectively, which corresponds to a signal-to-noise ratio of SNR $=3$. These results are better than the constraints placed previously on the SGWB in the mid-frequency band (around $10^{-3}- 10~\text{Hz}$) by various types of experiments. |
2105.02683 | Vipin Dubey | Shikha Srivastava, Umesh Kumar Sharma, Vipin Chandra Dubey | Exploring the new Tsallis agegraphic dark energy with interaction
through statefinder | 19 pages, 14 figures | null | 10.1007/s10714-021-02818-y | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this work, we explore the recently proposed new Tsallis agegraphic dark
energy model in a flat FLRW Universe by taking the conformal time as IR cutoff
with interaction. The deceleration parameter of the interacting new Tsallis
agegraphic dark energy model provides the phase transition of the Universe from
decelerated to accelerated phase. The EoS parameter of the model shows a rich
behaviour as it can be quintessence-like or phantom-like depending on the
interaction ($b^2$) and parameter $B$. The evolutionary trajectories of the
statefinder parameters and $(\omega_D, \omega_D^{'})$ planes are plotted by
considering the initial condition $\Omega_{D}^{0} =0.73$, $H_{0}= 67$ according
to $\Lambda$CDM observational Planck 2018 data for different $b^2$ and $B$. The
model shows both quintessence and Chaplygin gas behaviour in the statefinder
$(r, s)$ and $(r, q)$ pair planes for different $b^2$ and $B$.
| [
{
"created": "Wed, 5 May 2021 14:47:18 GMT",
"version": "v1"
}
] | 2021-05-07 | [
[
"Srivastava",
"Shikha",
""
],
[
"Sharma",
"Umesh Kumar",
""
],
[
"Dubey",
"Vipin Chandra",
""
]
] | In this work, we explore the recently proposed new Tsallis agegraphic dark energy model in a flat FLRW Universe by taking the conformal time as IR cutoff with interaction. The deceleration parameter of the interacting new Tsallis agegraphic dark energy model provides the phase transition of the Universe from decelerated to accelerated phase. The EoS parameter of the model shows a rich behaviour as it can be quintessence-like or phantom-like depending on the interaction ($b^2$) and parameter $B$. The evolutionary trajectories of the statefinder parameters and $(\omega_D, \omega_D^{'})$ planes are plotted by considering the initial condition $\Omega_{D}^{0} =0.73$, $H_{0}= 67$ according to $\Lambda$CDM observational Planck 2018 data for different $b^2$ and $B$. The model shows both quintessence and Chaplygin gas behaviour in the statefinder $(r, s)$ and $(r, q)$ pair planes for different $b^2$ and $B$. |
2112.12659 | Jam Sadiq | Jam Sadiq, Thomas Dent, and Daniel Wysocki | Flexible and Fast Estimation of Binary Merger Population Distributions
with Adaptive KDE | 12 pages, 12 figures, update the paper using publically available
data for GWTC-3 BBH events to include some new results and update the peak
detection method | null | 10.1103/PhysRevD.105.123014 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The LIGO Scientific, Virgo and KAGRA Collaborations recently released the
third gravitational wave transient catalog or GWTC-3, significantly expanding
the number of gravitational wave (GW) signals. To address the -- still
uncertain -- formation channels of the source compact binaries, their
population properties must be characterized. The computational cost of the
Bayesian hierarchical methods employed thus far scales with the size of the
event catalogs, and such methods have until recently assumed fixed functional
forms for the source distribution. Here we propose a fast and flexible method
to reconstruct the population of LIGO--Virgo merging black hole (BH) binaries
without such assumptions. For sufficiently high event statistics and
sufficiently low individual event measurement error (relative to the scale of
population features) a kernel density estimator (KDE) reconstruction of the
event distribution will be accurate. We improve the accuracy and flexibility of
KDE for finite event statistics using an adaptive bandwidth KDE (awKDE). We
apply awKDE to publicly released parameter estimates for 44 significant (69) BH
binary mergers in GWTC-2 (GWTC-3), in combination with a fast polynomial fit of
search sensitivity, to obtain a non-parametric estimate of the mass
distribution, and compare to Bayesian hierarchical methods. We also demonstrate
a robust peak detection algorithm based on awKDE and use it to calculate the
significance of the apparent peak in the BH mass distribution around $35\,
M_\odot$. We find such a peak is very unlikely to have occurred if the true
distribution is a featureless power-law (significance of $3.6\sigma$ for
confident GWTC-2 BBH events, $3.0\sigma$ for confident GWTC-3 BBH events).
| [
{
"created": "Thu, 23 Dec 2021 15:51:24 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Feb 2022 10:12:45 GMT",
"version": "v2"
},
{
"created": "Wed, 25 May 2022 13:54:53 GMT",
"version": "v3"
}
] | 2022-06-29 | [
[
"Sadiq",
"Jam",
""
],
[
"Dent",
"Thomas",
""
],
[
"Wysocki",
"Daniel",
""
]
] | The LIGO Scientific, Virgo and KAGRA Collaborations recently released the third gravitational wave transient catalog or GWTC-3, significantly expanding the number of gravitational wave (GW) signals. To address the -- still uncertain -- formation channels of the source compact binaries, their population properties must be characterized. The computational cost of the Bayesian hierarchical methods employed thus far scales with the size of the event catalogs, and such methods have until recently assumed fixed functional forms for the source distribution. Here we propose a fast and flexible method to reconstruct the population of LIGO--Virgo merging black hole (BH) binaries without such assumptions. For sufficiently high event statistics and sufficiently low individual event measurement error (relative to the scale of population features) a kernel density estimator (KDE) reconstruction of the event distribution will be accurate. We improve the accuracy and flexibility of KDE for finite event statistics using an adaptive bandwidth KDE (awKDE). We apply awKDE to publicly released parameter estimates for 44 significant (69) BH binary mergers in GWTC-2 (GWTC-3), in combination with a fast polynomial fit of search sensitivity, to obtain a non-parametric estimate of the mass distribution, and compare to Bayesian hierarchical methods. We also demonstrate a robust peak detection algorithm based on awKDE and use it to calculate the significance of the apparent peak in the BH mass distribution around $35\, M_\odot$. We find such a peak is very unlikely to have occurred if the true distribution is a featureless power-law (significance of $3.6\sigma$ for confident GWTC-2 BBH events, $3.0\sigma$ for confident GWTC-3 BBH events). |
1004.5050 | Francisco Navarro-Lerida | Masoud Allahverdizadeh, Jutta Kunz, and Francisco Navarro-Lerida | Extremal Charged Rotating Black Holes in Odd Dimensions | 24 pages, 3 figures | Phys.Rev.D82:024030,2010 | 10.1103/PhysRevD.82.024030 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Employing higher order perturbation theory, we obtain charged rotating black
holes in odd dimensions, where the Einstein-Maxwell Lagrangian may be
supplemented with a Chern-Simons term. Starting from the Myers-Perry solutions,
we use the electric charge as the perturbative parameter, and focus on extremal
black holes with equal-magnitude angular momenta. For
Einstein-Maxwell-Chern-Simons theory with arbitrary Chern-Simons coupling
constant, we perform the perturbations up to third order for any odd dimension.
We discuss the physical properties of these black holes and study their
dependence on the charge. In particular, we show that the gyromagnetic ratio
$g$ of Einstein-Maxwell black holes differs from the lowest order perturbative
value $D-2$, and that the first correction term to $g/(D-2)$ is universal.
| [
{
"created": "Wed, 28 Apr 2010 14:55:26 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Allahverdizadeh",
"Masoud",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Navarro-Lerida",
"Francisco",
""
]
] | Employing higher order perturbation theory, we obtain charged rotating black holes in odd dimensions, where the Einstein-Maxwell Lagrangian may be supplemented with a Chern-Simons term. Starting from the Myers-Perry solutions, we use the electric charge as the perturbative parameter, and focus on extremal black holes with equal-magnitude angular momenta. For Einstein-Maxwell-Chern-Simons theory with arbitrary Chern-Simons coupling constant, we perform the perturbations up to third order for any odd dimension. We discuss the physical properties of these black holes and study their dependence on the charge. In particular, we show that the gyromagnetic ratio $g$ of Einstein-Maxwell black holes differs from the lowest order perturbative value $D-2$, and that the first correction term to $g/(D-2)$ is universal. |
1904.12423 | Chen Songbai | Mingzhi Wang, Songbai Chen, Jieci Wang, and Jiliang Jing | Shadow of a Schwarzschild black hole surrounded by a Bach-Weyl ring | 16 pages,8 figures, the version published in EPJC | Eur. Phys. J. C (2020) 80:110 | 10.1140/epjc/s10052-020-7641-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have studied the shadows of a Schwarzschild black hole surrounded by a
Bach-Weyl ring through the backward ray-tracing method. The presence of
Bach-Weyl ring leads to that the photon dynamical system is non-integrable and
then chaos would appear in the photon motion, which affects sharply the black
hole shadow. The size and shape the black hole shadow depend on the black hole
parameter, the Bach-Weyl ring mass and the Weyl radius between black hole and
ring. Some self-similar fractal structures also appear in the black hole
shadow, which originates from the chaotic lensing. We also study the change of
the image of Bach-Weyl ring with the ring mass and the Weyl radius. Finally, we
analyze the invariant manifolds of Lyapunov orbits near the fixed points and
discuss further the formation of the shadow of a Schwarzschild black hole with
Bach-Weyl ring.
| [
{
"created": "Mon, 29 Apr 2019 02:19:13 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Mar 2020 13:35:20 GMT",
"version": "v2"
}
] | 2020-03-19 | [
[
"Wang",
"Mingzhi",
""
],
[
"Chen",
"Songbai",
""
],
[
"Wang",
"Jieci",
""
],
[
"Jing",
"Jiliang",
""
]
] | We have studied the shadows of a Schwarzschild black hole surrounded by a Bach-Weyl ring through the backward ray-tracing method. The presence of Bach-Weyl ring leads to that the photon dynamical system is non-integrable and then chaos would appear in the photon motion, which affects sharply the black hole shadow. The size and shape the black hole shadow depend on the black hole parameter, the Bach-Weyl ring mass and the Weyl radius between black hole and ring. Some self-similar fractal structures also appear in the black hole shadow, which originates from the chaotic lensing. We also study the change of the image of Bach-Weyl ring with the ring mass and the Weyl radius. Finally, we analyze the invariant manifolds of Lyapunov orbits near the fixed points and discuss further the formation of the shadow of a Schwarzschild black hole with Bach-Weyl ring. |
2303.10356 | Klaus Morawetz | K. Morawetz | Time behaviour of Hubble parameter by torsion | null | Modern Physics Letters A (2024) | 10.1142/S0217732323501924 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | Consequences of the consistent exact solution of Einstein-Cartan equation on
the time dependence of Hubble parameter are discussed. The torsion leads to a
space and time dependent expansion parameter which results into nontrivial
windows of Hubble parameter between diverging behaviour. Only one window shows
a period of decreasing followed by increasing time dependence. Provided a known
cosmological constant and the present values of Hubble and deceleration
parameter this changing time can be given in the past as well as the ending
time of the windows or universe. The comparison with the present experimental
data allows to determine all parameters of the model. Large-scale spatial
periodic structures appear. From the metric with torsion outside matter it is
seen that torsion can feign dark matter.
| [
{
"created": "Sat, 18 Mar 2023 07:47:53 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Jun 2023 10:00:16 GMT",
"version": "v2"
},
{
"created": "Wed, 7 Feb 2024 07:48:33 GMT",
"version": "v3"
}
] | 2024-02-08 | [
[
"Morawetz",
"K.",
""
]
] | Consequences of the consistent exact solution of Einstein-Cartan equation on the time dependence of Hubble parameter are discussed. The torsion leads to a space and time dependent expansion parameter which results into nontrivial windows of Hubble parameter between diverging behaviour. Only one window shows a period of decreasing followed by increasing time dependence. Provided a known cosmological constant and the present values of Hubble and deceleration parameter this changing time can be given in the past as well as the ending time of the windows or universe. The comparison with the present experimental data allows to determine all parameters of the model. Large-scale spatial periodic structures appear. From the metric with torsion outside matter it is seen that torsion can feign dark matter. |
gr-qc/0605016 | Satheesh Kumar V H | V H Satheesh Kumar and P K Suresh | Gravitons in Kaluza-Klein Theory | 12 pages | null | null | null | gr-qc | null | This is a pedagogical introduction to original Kaluza-Klein theory and its
salient features. Most of the technical calculations are given in detail and
the nature of gravitons is discussed.
| [
{
"created": "Tue, 2 May 2006 14:39:16 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kumar",
"V H Satheesh",
""
],
[
"Suresh",
"P K",
""
]
] | This is a pedagogical introduction to original Kaluza-Klein theory and its salient features. Most of the technical calculations are given in detail and the nature of gravitons is discussed. |
1909.11749 | Edgar Gasperin | Edgar Gasperin, Shalabh Gautam, David Hilditch, Alex
Va\~n\'o-Vi\~nuales | The Hyperboloidal Numerical Evolution of a Good-Bad-Ugly Wave Equation | 11 pages, 5 figures | null | 10.1088/1361-6382/ab5f21 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One method for the numerical treatment of future null-infinity is to decouple
coordinates from the tensor basis and choose each in a careful manner. This
dual-frame approach is hampered by logarithmically divergent terms that appear
in a naive choice of evolved variables. Here we consider a system of wave
equations that satisfy the weak-null condition and serve as a model system with
similar nonlinearities to those present in the Einstein field equations in
generalized harmonic gauge. We show that these equations can be explicitly
regularized by a nonlinear change of variables. Working in spherical symmetry,
a numerical implementation of this model using compactified hyperboloidal
slices is then presented. Clean convergence is found for the regularized
system. Although more complicated, it is expected that general relativity can
be treated similarly.
| [
{
"created": "Wed, 25 Sep 2019 20:23:51 GMT",
"version": "v1"
}
] | 2020-01-29 | [
[
"Gasperin",
"Edgar",
""
],
[
"Gautam",
"Shalabh",
""
],
[
"Hilditch",
"David",
""
],
[
"Vañó-Viñuales",
"Alex",
""
]
] | One method for the numerical treatment of future null-infinity is to decouple coordinates from the tensor basis and choose each in a careful manner. This dual-frame approach is hampered by logarithmically divergent terms that appear in a naive choice of evolved variables. Here we consider a system of wave equations that satisfy the weak-null condition and serve as a model system with similar nonlinearities to those present in the Einstein field equations in generalized harmonic gauge. We show that these equations can be explicitly regularized by a nonlinear change of variables. Working in spherical symmetry, a numerical implementation of this model using compactified hyperboloidal slices is then presented. Clean convergence is found for the regularized system. Although more complicated, it is expected that general relativity can be treated similarly. |
1012.4467 | Matt Visser | Jozef Skakala (Victoria University of Wellington) and Matt Visser
(Victoria University of Wellington) | The causal structure of spacetime is a parameterized Randers geometry | 8 pages | Class.Quant.Grav.28:065007,2011 | 10.1088/0264-9381/28/6/065007 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There is a by now well-established isomorphism between stationary
4-dimensional spacetimes and 3-dimensional purely spatial Randers geometries -
these Randers geometries being a particular case of the more general class of
3-dimensional Finsler geometries. We point out that in stably causal
spacetimes, by using the (time-dependent) ADM decomposition, this result can be
extended to general non-stationary spacetimes - the causal structure (conformal
structure) of the full spacetime is completely encoded in a parameterized
(time-dependent) class of Randers spaces, which can then be used to define a
Fermat principle, and also to reconstruct the null cones and causal structure.
| [
{
"created": "Mon, 20 Dec 2010 21:00:06 GMT",
"version": "v1"
}
] | 2011-03-18 | [
[
"Skakala",
"Jozef",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | There is a by now well-established isomorphism between stationary 4-dimensional spacetimes and 3-dimensional purely spatial Randers geometries - these Randers geometries being a particular case of the more general class of 3-dimensional Finsler geometries. We point out that in stably causal spacetimes, by using the (time-dependent) ADM decomposition, this result can be extended to general non-stationary spacetimes - the causal structure (conformal structure) of the full spacetime is completely encoded in a parameterized (time-dependent) class of Randers spaces, which can then be used to define a Fermat principle, and also to reconstruct the null cones and causal structure. |
2306.05394 | Todd Fugleberg | Jesse Elder, Todd Fugleberg | Series Solution for Interaction of Scalar Plane Wave with Spatially
Decaying Gravitational Wave | 25 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we present the power series solution of the Klein-Gordon
equation in the spacetime background of a gravitational wave with amplitude
that decays with distance from the source. The resulting solution describes the
interaction of a scalar plane wave travelling in an arbitrary direction
relative to the direction of propagation of the gravitational wave. This
solution has the unexpected property that as the scalar wave approaches
collinearity with the gravitational wave there is a rapid transition in the
form of the solution. The solution in the collinear limit exhibits a resonance
phenomenon which distinguishes these results from previous analyses involving
plane gravitational wave backgrounds. We discuss in detail the similarities and
differences between the solutions for plane gravitational waves and
gravitational waves with amplitude that decreases with distance from the
source. We give an argument that this solution of the Klein-Gordon equation
only describes the interaction of a gravitational wave with a scalar wave and
that the gravitational wave will not produce a scalar waveform in a vacuum. The
interaction between the gravitational and scalar waves lead to both sinusoidal
time-dependent fluctuations in, and time-independent enhancement of, the scalar
current in the direction of the gravitational wave. Finally, we discuss the
possibility of observable effects of this interaction.
| [
{
"created": "Thu, 8 Jun 2023 17:45:55 GMT",
"version": "v1"
}
] | 2023-06-09 | [
[
"Elder",
"Jesse",
""
],
[
"Fugleberg",
"Todd",
""
]
] | In this paper we present the power series solution of the Klein-Gordon equation in the spacetime background of a gravitational wave with amplitude that decays with distance from the source. The resulting solution describes the interaction of a scalar plane wave travelling in an arbitrary direction relative to the direction of propagation of the gravitational wave. This solution has the unexpected property that as the scalar wave approaches collinearity with the gravitational wave there is a rapid transition in the form of the solution. The solution in the collinear limit exhibits a resonance phenomenon which distinguishes these results from previous analyses involving plane gravitational wave backgrounds. We discuss in detail the similarities and differences between the solutions for plane gravitational waves and gravitational waves with amplitude that decreases with distance from the source. We give an argument that this solution of the Klein-Gordon equation only describes the interaction of a gravitational wave with a scalar wave and that the gravitational wave will not produce a scalar waveform in a vacuum. The interaction between the gravitational and scalar waves lead to both sinusoidal time-dependent fluctuations in, and time-independent enhancement of, the scalar current in the direction of the gravitational wave. Finally, we discuss the possibility of observable effects of this interaction. |
gr-qc/0005075 | Yungui Gong | Yungui Gong | Brane Universe and Standard Cosmology | 5 pages, no figure | null | null | utexas-hep-00-7 | gr-qc hep-th | null | Brane cosmology takes the unconventional form $H\sim \sqrt{\rho}$. To recover
the standard cosmology, we have to assume that the matter density is much less
than the brane tension. We show that the assumption can be justified even near
the end of inflation if we fine-tune the coupling constant of the inflaton
potential. As a consequence, the standard cosmology is recovered after
inflation.
| [
{
"created": "Wed, 17 May 2000 17:14:22 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gong",
"Yungui",
""
]
] | Brane cosmology takes the unconventional form $H\sim \sqrt{\rho}$. To recover the standard cosmology, we have to assume that the matter density is much less than the brane tension. We show that the assumption can be justified even near the end of inflation if we fine-tune the coupling constant of the inflaton potential. As a consequence, the standard cosmology is recovered after inflation. |
gr-qc/0602102 | James M. Overduin | R.J. Adler, J.D. Bjorken and J.M. Overduin | Finite cosmology and a CMB cold spot | 20 pages, 12 figures | null | null | null | gr-qc astro-ph | null | The standard cosmological model posits a spatially flat universe of infinite
extent. However, no observation, even in principle, could verify that the
matter extends to infinity. In this work we model the universe as a finite
spherical ball of dust and dark energy, and obtain a lower limit estimate of
its mass and present size: the mass is at least 5 x 10^23 solar masses and the
present radius is at least 50 Gly. If we are not too far from the dust-ball
edge we might expect to see a cold spot in the cosmic microwave background, and
there might be suppression of the low multipoles in the angular power spectrum.
Thus the model may be testable, at least in principle. We also obtain and
discuss the geometry exterior to the dust ball; it is Schwarzschild-de Sitter
with a naked singularity, and provides an interesting picture of cosmogenesis.
Finally we briefly sketch how radiation and inflation eras may be incorporated
into the model.
| [
{
"created": "Fri, 24 Feb 2006 19:56:16 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Feb 2006 00:03:49 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Adler",
"R. J.",
""
],
[
"Bjorken",
"J. D.",
""
],
[
"Overduin",
"J. M.",
""
]
] | The standard cosmological model posits a spatially flat universe of infinite extent. However, no observation, even in principle, could verify that the matter extends to infinity. In this work we model the universe as a finite spherical ball of dust and dark energy, and obtain a lower limit estimate of its mass and present size: the mass is at least 5 x 10^23 solar masses and the present radius is at least 50 Gly. If we are not too far from the dust-ball edge we might expect to see a cold spot in the cosmic microwave background, and there might be suppression of the low multipoles in the angular power spectrum. Thus the model may be testable, at least in principle. We also obtain and discuss the geometry exterior to the dust ball; it is Schwarzschild-de Sitter with a naked singularity, and provides an interesting picture of cosmogenesis. Finally we briefly sketch how radiation and inflation eras may be incorporated into the model. |
1212.4357 | Alessandro Nagar | Thibault Damour, Alessandro Nagar, Sebastiano Bernuzzi | Improved effective-one-body description of coalescing nonspinning
black-hole binaries and its numerical-relativity completion | 42 pages, 22 figures. Improved version, to appear in Phys. Rev. D.
The EOB code will be freely available at eob.ihes.fr | null | 10.1103/PhysRevD.87.084035 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We improve the effective-one-body (EOB) description of nonspinning coalescing
black hole binaries by incorporating several recent analytical advances,
notably: (i) logarithmic contributions to the conservative dynamics; (ii)
resummed horizon-absorption contribution to the orbital angular momentum loss;
and (iii) a specific radial component of the radiation reaction force implied
by consistency with the azimuthal one. We then complete this analytically
improved EOB model by comparing it to accurate numerical relativity (NR)
simulations performed by the Caltech-Cornell-CITA group for mass ratios
$q=(1,2,3,4,6)$. In particular, the comparison to NR data allows us to
determine with high-accuracy ($\sim 10^{-4}$) the value of the main EOB radial
potential: $A(u;\,\nu)$, where $u=GM/(R c^2)$ is the inter-body gravitational
potential and $\nu=q/(q+1)^2$ is the symmetric mass ratio. We introduce a new
technique for extracting from NR data an intrinsic measure of the phase
evolution, ($Q_\omega(\omega)$ diagnostics). Aligning the NR-completed EOB
quadrupolar waveform and the NR one at low frequencies, we find that they keep
agreeing (in phase and amplitude) within the NR uncertainties throughout the
evolution for all mass ratios considered. We also find good agreement for
several subdominant multipoles without having to introduce and tune any extra
parameters.
| [
{
"created": "Tue, 18 Dec 2012 14:19:28 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Apr 2013 10:35:39 GMT",
"version": "v2"
}
] | 2013-04-17 | [
[
"Damour",
"Thibault",
""
],
[
"Nagar",
"Alessandro",
""
],
[
"Bernuzzi",
"Sebastiano",
""
]
] | We improve the effective-one-body (EOB) description of nonspinning coalescing black hole binaries by incorporating several recent analytical advances, notably: (i) logarithmic contributions to the conservative dynamics; (ii) resummed horizon-absorption contribution to the orbital angular momentum loss; and (iii) a specific radial component of the radiation reaction force implied by consistency with the azimuthal one. We then complete this analytically improved EOB model by comparing it to accurate numerical relativity (NR) simulations performed by the Caltech-Cornell-CITA group for mass ratios $q=(1,2,3,4,6)$. In particular, the comparison to NR data allows us to determine with high-accuracy ($\sim 10^{-4}$) the value of the main EOB radial potential: $A(u;\,\nu)$, where $u=GM/(R c^2)$ is the inter-body gravitational potential and $\nu=q/(q+1)^2$ is the symmetric mass ratio. We introduce a new technique for extracting from NR data an intrinsic measure of the phase evolution, ($Q_\omega(\omega)$ diagnostics). Aligning the NR-completed EOB quadrupolar waveform and the NR one at low frequencies, we find that they keep agreeing (in phase and amplitude) within the NR uncertainties throughout the evolution for all mass ratios considered. We also find good agreement for several subdominant multipoles without having to introduce and tune any extra parameters. |
1207.1942 | Shijun Yoshida | Shijun Yoshida, Kenta Kiuchi, Masaru Shibata | Stably stratified magnetized stars in general relativity | 18 pages, 5 figures, accepted for publication in Physical Review D | null | 10.1103/PhysRevD.86.044012 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct magnetized stars composed of a fluid stably stratified by
entropy gradients in the framework of general relativity, assuming ideal
magnetohydrodynamics and employing a barotropic equation of state. We first
revisit basic equations for describing stably-stratified stationary
axisymmetric stars containing both poloidal and toroidal magnetic fields. As
sample models, the magnetized stars considered by Ioka and Sasaki (2004),
inside which the magnetic fields are confined, are modified to the ones stably
stratified. The magnetized stars newly constructed in this study are believed
to be more stable than the existing relativistic models because they have both
poloidal and toroidal magnetic fields with comparable strength, and magnetic
buoyancy instabilities near the surface of the star, which can be stabilized by
the stratification, are suppressed.
| [
{
"created": "Mon, 9 Jul 2012 04:17:25 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Yoshida",
"Shijun",
""
],
[
"Kiuchi",
"Kenta",
""
],
[
"Shibata",
"Masaru",
""
]
] | We construct magnetized stars composed of a fluid stably stratified by entropy gradients in the framework of general relativity, assuming ideal magnetohydrodynamics and employing a barotropic equation of state. We first revisit basic equations for describing stably-stratified stationary axisymmetric stars containing both poloidal and toroidal magnetic fields. As sample models, the magnetized stars considered by Ioka and Sasaki (2004), inside which the magnetic fields are confined, are modified to the ones stably stratified. The magnetized stars newly constructed in this study are believed to be more stable than the existing relativistic models because they have both poloidal and toroidal magnetic fields with comparable strength, and magnetic buoyancy instabilities near the surface of the star, which can be stabilized by the stratification, are suppressed. |
2406.04611 | YuSen An | Quan-Xu Liu, Ya-Peng Hu, Tao-Tao Sui, Yu-Sen An | Superradiance of rotating black holes surrounded by dark matter | 14 pages, 5 figures,1 table | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In rotating black hole background surrounded by dark matter, we investigated
the super-radiant phenomenon of massive scalar field and its associated
instability.Using the method of asymptotic matching, we computed the
amplification factor of scalar wave scattering to assess the strength of
super-radiance. We discussed the influence of dark matter density on
amplification factor in this black hole background. Our result indicates that
the presence of dark matter has suppressive influence on black hole
super-radiance. We also computed the net extracted energy to further support
this result. Finally, we analyzed the super-radiant instability caused by
massive scalar field using the black hole bomb mechanism and found that the
presence of dark matter has no influence on the super-radiant instability
condition.
| [
{
"created": "Fri, 7 Jun 2024 03:38:29 GMT",
"version": "v1"
}
] | 2024-06-10 | [
[
"Liu",
"Quan-Xu",
""
],
[
"Hu",
"Ya-Peng",
""
],
[
"Sui",
"Tao-Tao",
""
],
[
"An",
"Yu-Sen",
""
]
] | In rotating black hole background surrounded by dark matter, we investigated the super-radiant phenomenon of massive scalar field and its associated instability.Using the method of asymptotic matching, we computed the amplification factor of scalar wave scattering to assess the strength of super-radiance. We discussed the influence of dark matter density on amplification factor in this black hole background. Our result indicates that the presence of dark matter has suppressive influence on black hole super-radiance. We also computed the net extracted energy to further support this result. Finally, we analyzed the super-radiant instability caused by massive scalar field using the black hole bomb mechanism and found that the presence of dark matter has no influence on the super-radiant instability condition. |
1411.5411 | Bahram Mashhoon | B. Mashhoon | Nonlocal General Relativity | 23 pages; v:2 slightly expanded version. Dedicated to the memory of
M. Hossein Partovi (1941-2014) | Galaxies 3 (2015) 1-17 | null | null | gr-qc astro-ph.GA hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A brief account of the present status of the recent nonlocal generalization
of Einstein's theory of gravitation is presented. The main physical assumptions
that underlie this theory are described. We clarify the physical meaning and
significance of Weitzenb\"ock's torsion, and emphasize its intimate
relationship with the gravitational field, characterized by the Riemannian
curvature of spacetime. In this theory, nonlocality can simulate dark matter;
in fact, in the Newtonian regime, we recover the phenomenological Tohline-Kuhn
approach to modified gravity. To account for the observational data regarding
dark matter, nonlocality is associated with a characteristic length scale of
order 1 kpc. The confrontation of nonlocal gravity with observation is briefly
discussed.
| [
{
"created": "Thu, 20 Nov 2014 01:04:25 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Dec 2014 19:56:46 GMT",
"version": "v2"
}
] | 2015-01-20 | [
[
"Mashhoon",
"B.",
""
]
] | A brief account of the present status of the recent nonlocal generalization of Einstein's theory of gravitation is presented. The main physical assumptions that underlie this theory are described. We clarify the physical meaning and significance of Weitzenb\"ock's torsion, and emphasize its intimate relationship with the gravitational field, characterized by the Riemannian curvature of spacetime. In this theory, nonlocality can simulate dark matter; in fact, in the Newtonian regime, we recover the phenomenological Tohline-Kuhn approach to modified gravity. To account for the observational data regarding dark matter, nonlocality is associated with a characteristic length scale of order 1 kpc. The confrontation of nonlocal gravity with observation is briefly discussed. |
0909.1503 | Ragab Gad | Ragab M. Gad | Axially Symmetric Cosmological Mesonic Stiff Fluid Models in Lyra's
Geometry | 13 pages, no figures, typos corrected | Canadian Journal of Physics 89:(7) 773-778 (2011) | 10.1139/p11-055 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | In this paper, we obtained a new class of axially symmetric cosmological
mesonic stiff fluid models in the context of Lyra's geometry. Expressions for
the energy, pressure and the massless scalar field are derived by considering
the time dependent displacement field. We found that the mesonic scalar field
depends on only $t$ coordinate. Some physical properties of the obtained models
are discussed.
| [
{
"created": "Tue, 8 Sep 2009 14:44:47 GMT",
"version": "v1"
},
{
"created": "Wed, 12 May 2010 12:11:16 GMT",
"version": "v2"
}
] | 2015-05-14 | [
[
"Gad",
"Ragab M.",
""
]
] | In this paper, we obtained a new class of axially symmetric cosmological mesonic stiff fluid models in the context of Lyra's geometry. Expressions for the energy, pressure and the massless scalar field are derived by considering the time dependent displacement field. We found that the mesonic scalar field depends on only $t$ coordinate. Some physical properties of the obtained models are discussed. |
1612.04320 | Shahen Hacyan | S. Hacyan | Some remarks on the Bel-Robinson tensor and gravitational radiation | new version | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The asymptotic form of the Bel-Robinson tensor in the gravitational
radiation-zone is obtained in terms of the mass quadrupole of the source. A
comparison is made with the standard formula for the gravitational power
emission. The problem of a fully covariant description of gravitational
radiation in terms of this tensor is discussed with some detail.
| [
{
"created": "Tue, 13 Dec 2016 19:05:57 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Jan 2017 18:48:32 GMT",
"version": "v2"
},
{
"created": "Thu, 16 Mar 2017 16:51:44 GMT",
"version": "v3"
}
] | 2017-03-17 | [
[
"Hacyan",
"S.",
""
]
] | The asymptotic form of the Bel-Robinson tensor in the gravitational radiation-zone is obtained in terms of the mass quadrupole of the source. A comparison is made with the standard formula for the gravitational power emission. The problem of a fully covariant description of gravitational radiation in terms of this tensor is discussed with some detail. |
2008.08450 | Kimet Jusufi | Kimet Jusufi, Mustapha Azreg-A\"inou, Mubasher Jamil, Shao-Wen Wei,
Qiang Wu, Anzhong Wang | Quasinormal modes, quasiperiodic oscillations and shadow of rotating
regular black holes in non-minimally coupled Einstein-Yang-Mills theory | 25 pages, 17 figures, 7 tables | Phys. Rev. D 103, 024013 (2021) | 10.1103/PhysRevD.103.024013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we obtain an effective metric describing a regular and rotating
magnetic black hole (BH) solution with a Yang-Mills electromagnetic source in
Einstein-Yang-Mills (EYM) theory using the Newman--Janis algorithm via the
non-complexification radial coordinate procedure. We then study the BH shadow
and the quasinormal modes (QNMs) for massless scalar and electromagnetic fields
and the quasiperiodic oscillations (QPOs). To this end, we also study the
embedding diagram for the rotating EYM BH. The energy conditions, shadow
curvature radius, topology and the dynamical evolution of scalar and
electromagnetic perturbations using the time domain integration method are
investigated. We show that the shadow radius decreases by increasing the
magnetic charge, while the real part of QNMs of scalar and electromagnetic
fields increases by increasing the magnetic charge. This result is consistent
with the inverse relation between the shadow radius and the real part of QNMs.
In addition, we have studied observational constraints on the EYM parameter
$\lambda$ via frequency analysis of QPOs and the EHT data of shadow cast by the
M87 central black hole. We also find that the decaying rate of the EYM BH is
slower than that of the neutral and ends up with a tail. We argue that the
rotating EYM black hole can be distinguished from the Kerr-Newman black hole
with a magnetic charge based on the difference between the angular diameters of
their shadows.
| [
{
"created": "Tue, 18 Aug 2020 09:32:41 GMT",
"version": "v1"
}
] | 2021-01-08 | [
[
"Jusufi",
"Kimet",
""
],
[
"Azreg-Aïnou",
"Mustapha",
""
],
[
"Jamil",
"Mubasher",
""
],
[
"Wei",
"Shao-Wen",
""
],
[
"Wu",
"Qiang",
""
],
[
"Wang",
"Anzhong",
""
]
] | In this paper we obtain an effective metric describing a regular and rotating magnetic black hole (BH) solution with a Yang-Mills electromagnetic source in Einstein-Yang-Mills (EYM) theory using the Newman--Janis algorithm via the non-complexification radial coordinate procedure. We then study the BH shadow and the quasinormal modes (QNMs) for massless scalar and electromagnetic fields and the quasiperiodic oscillations (QPOs). To this end, we also study the embedding diagram for the rotating EYM BH. The energy conditions, shadow curvature radius, topology and the dynamical evolution of scalar and electromagnetic perturbations using the time domain integration method are investigated. We show that the shadow radius decreases by increasing the magnetic charge, while the real part of QNMs of scalar and electromagnetic fields increases by increasing the magnetic charge. This result is consistent with the inverse relation between the shadow radius and the real part of QNMs. In addition, we have studied observational constraints on the EYM parameter $\lambda$ via frequency analysis of QPOs and the EHT data of shadow cast by the M87 central black hole. We also find that the decaying rate of the EYM BH is slower than that of the neutral and ends up with a tail. We argue that the rotating EYM black hole can be distinguished from the Kerr-Newman black hole with a magnetic charge based on the difference between the angular diameters of their shadows. |
0803.3447 | Charis Anastopoulos | C. Anastopoulos and B. L. Hu | Intrinsic and Fundamental Decoherence: Issues and Problems | 16 pages | Class.Quant.Grav.25:154003,2008 | 10.1088/0264-9381/25/15/154003 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the meaning of gravity-induced decoherence in quantum theory,
known as `intrinsic' or `fundamental' decoherence in the literature. We explore
a range of issues relevant to this problem, including the meaning of modified
uncertainty relations, the interpretations of the Planck scale, the distinction
between quantum and stochastic fluctuations and the role of the time variable
in quantum mechanics. We examine the specific physical assumptions that enter
into different approaches to the subject. In particular, we critique two
representative approaches that identify time fluctuations as the origin of
intrinsic or fundamental decoherence: one that models the fluctuations by
stochastic process and one that purports to derive decoherence from the quantum
fluctuations of real clocks.
| [
{
"created": "Mon, 24 Mar 2008 19:36:43 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Anastopoulos",
"C.",
""
],
[
"Hu",
"B. L.",
""
]
] | We investigate the meaning of gravity-induced decoherence in quantum theory, known as `intrinsic' or `fundamental' decoherence in the literature. We explore a range of issues relevant to this problem, including the meaning of modified uncertainty relations, the interpretations of the Planck scale, the distinction between quantum and stochastic fluctuations and the role of the time variable in quantum mechanics. We examine the specific physical assumptions that enter into different approaches to the subject. In particular, we critique two representative approaches that identify time fluctuations as the origin of intrinsic or fundamental decoherence: one that models the fluctuations by stochastic process and one that purports to derive decoherence from the quantum fluctuations of real clocks. |
gr-qc/9408011 | Marco | Marco Cavaglia` | Can the Interaction between Baby Universes Generate a Big Universe? | 4 pages, PLAIN-TEX, Ref: SISSA 104/94/A, to be published in Int. Jou.
Mod. Phys. D | Int.J.Mod.Phys. D3 (1994) 623-626 | 10.1142/S0218271894000757 | null | gr-qc | null | We explore a simple toy model of interacting universes to establish that a
small baby universe could become large ($\gg$ Planck length) if a third
quantization mechanism is taken into account.
| [
{
"created": "Tue, 9 Aug 1994 08:42:14 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Cavaglia`",
"Marco",
""
]
] | We explore a simple toy model of interacting universes to establish that a small baby universe could become large ($\gg$ Planck length) if a third quantization mechanism is taken into account. |
2005.12875 | Bo Wang | Bo Wang, Zhenyu Zhu, Ang Li, Wen Zhao | Comprehensive analysis of the tidal effect in gravitational waves and
implication for cosmology | 28 pages, 23 figures. Accepted for publication in ApJS | Astrophys. J. Suppl. S. 250, 6 (2020) | 10.3847/1538-4365/aba2f3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Detection of gravitational waves (GWs) produced by coalescence of compact
binaries provides a novel way to measure the luminosity distance of GW events.
Combining their redshift, they can act as standard sirens to constrain
cosmological parameters. For various GW detector networks in 2nd-generation
(2G), 2.5G and 3G, we comprehensively analyze the method to constrain the
equation-of-state (EOS) of binary neutron-stars (BNSs) and extract their
redshifts through the imprints of tidal effects in GW waveforms. We find for
these events, the observations of electromagnetic counterparts in low-redshift
range $z < 0.1$ are important for constraining the tidal effects. Considering
17 different EOSs of NSs or quark-stars, we find GW observations have strong
capability to determine the EOS. Applying the events as standard sirens, and
considering the constraints of NS's EOS derived from low-redshift observations
as prior, we can constrain the dark-energy EOS parameters $w_0$ and $w_a$. In
3G era, the potential constraints are $\Delta w_0\in (0.0006,0.004)$ and
$\Delta w_a\in(0.004,0.02)$, which are 1-3 orders smaller than those from
traditional methods, including Type Ia supernovas and baryon acoustic
oscillations. The constraints are also 1 order smaller than the method of GW
standard siren by fixing the redshifts through short-hard $\gamma$-ray bursts,
due to more available GW events in this method. Therefore, GW standard sirens,
based on the tidal effect measurement, provide a realizable and much more
powerful tool in cosmology.
| [
{
"created": "Tue, 26 May 2020 17:09:21 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Jun 2020 08:00:19 GMT",
"version": "v2"
},
{
"created": "Sun, 7 Jun 2020 10:28:30 GMT",
"version": "v3"
},
{
"created": "Wed, 8 Jul 2020 23:56:13 GMT",
"version": "v4"
}
] | 2020-08-28 | [
[
"Wang",
"Bo",
""
],
[
"Zhu",
"Zhenyu",
""
],
[
"Li",
"Ang",
""
],
[
"Zhao",
"Wen",
""
]
] | Detection of gravitational waves (GWs) produced by coalescence of compact binaries provides a novel way to measure the luminosity distance of GW events. Combining their redshift, they can act as standard sirens to constrain cosmological parameters. For various GW detector networks in 2nd-generation (2G), 2.5G and 3G, we comprehensively analyze the method to constrain the equation-of-state (EOS) of binary neutron-stars (BNSs) and extract their redshifts through the imprints of tidal effects in GW waveforms. We find for these events, the observations of electromagnetic counterparts in low-redshift range $z < 0.1$ are important for constraining the tidal effects. Considering 17 different EOSs of NSs or quark-stars, we find GW observations have strong capability to determine the EOS. Applying the events as standard sirens, and considering the constraints of NS's EOS derived from low-redshift observations as prior, we can constrain the dark-energy EOS parameters $w_0$ and $w_a$. In 3G era, the potential constraints are $\Delta w_0\in (0.0006,0.004)$ and $\Delta w_a\in(0.004,0.02)$, which are 1-3 orders smaller than those from traditional methods, including Type Ia supernovas and baryon acoustic oscillations. The constraints are also 1 order smaller than the method of GW standard siren by fixing the redshifts through short-hard $\gamma$-ray bursts, due to more available GW events in this method. Therefore, GW standard sirens, based on the tidal effect measurement, provide a realizable and much more powerful tool in cosmology. |
1812.07438 | Ludovic Ducobu | Y. Brihaye and L. Ducobu | Hairy black holes, boson stars and non-minimal coupling to curvature
invariants | 16 pages, 9 figures, Published version : Paper reorganized, Results
extended to discuss stability of the boson stars, Title modified | Physics Letters B, Volume 795, 10 August 2019, Pages 135-143 | 10.1016/j.physletb.2019.06.006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Einstein-Klein-Gordon Lagrangian is supplemented by a non-minimal
coupling of the scalar field to specific geometric invariants : the
Gauss-Bonnet term and the Chern-Simons term. The non-minimal coupling is chosen
as a general quadratic polynomial in the scalar field and allows - depending on
the parameters - for large families of hairy black holes to exist. These
solutions are characterized, namely, by the number of nodes of the scalar
function. The fundamental family encompasses black holes whose scalar hairs
appear spontaneously and solutions presenting shift-symmetric hairs. When
supplemented by a an appropriate potential, the model possesses both hairy
black holes and non-topological solitons : boson stars. These latter exist in
the standard Einstein-Klein-Gordon equations; it is shown that the coupling to
the Gauss-Bonnet term modifies considerably their domain of classical
stability.
| [
{
"created": "Tue, 18 Dec 2018 15:40:37 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Aug 2019 08:53:02 GMT",
"version": "v2"
}
] | 2019-08-21 | [
[
"Brihaye",
"Y.",
""
],
[
"Ducobu",
"L.",
""
]
] | The Einstein-Klein-Gordon Lagrangian is supplemented by a non-minimal coupling of the scalar field to specific geometric invariants : the Gauss-Bonnet term and the Chern-Simons term. The non-minimal coupling is chosen as a general quadratic polynomial in the scalar field and allows - depending on the parameters - for large families of hairy black holes to exist. These solutions are characterized, namely, by the number of nodes of the scalar function. The fundamental family encompasses black holes whose scalar hairs appear spontaneously and solutions presenting shift-symmetric hairs. When supplemented by a an appropriate potential, the model possesses both hairy black holes and non-topological solitons : boson stars. These latter exist in the standard Einstein-Klein-Gordon equations; it is shown that the coupling to the Gauss-Bonnet term modifies considerably their domain of classical stability. |
1806.10986 | Prasanta Char | Prasanta Char, Sayak Datta | Relativistic tidal properties of superfluid neutron stars | Accepted for publication in Physical Review D | Phys. Rev. D 98, 084010 (2018) | 10.1103/PhysRevD.98.084010 | null | gr-qc astro-ph.HE nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the tidal deformability of a superfluid neutron star. We
calculate the equilibrium structure in the general relativistic two-fluid
formalism with entrainment effect where we take neutron superfluid as one fluid
and the other fluid is comprised of protons and electrons, making it a charge
neutral fluid. We use a relativistic mean field model for the equation of state
of matter where the interaction between baryons is mediated by the exchange
$\sigma$, $\omega$ and $\rho$ mesons. Then, we study the linear, static $l=2$
perturbation on the star to compute the electric-type Love number following
Hinderer's prescription.
| [
{
"created": "Thu, 28 Jun 2018 14:12:12 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Oct 2018 12:35:50 GMT",
"version": "v2"
}
] | 2018-10-10 | [
[
"Char",
"Prasanta",
""
],
[
"Datta",
"Sayak",
""
]
] | We investigate the tidal deformability of a superfluid neutron star. We calculate the equilibrium structure in the general relativistic two-fluid formalism with entrainment effect where we take neutron superfluid as one fluid and the other fluid is comprised of protons and electrons, making it a charge neutral fluid. We use a relativistic mean field model for the equation of state of matter where the interaction between baryons is mediated by the exchange $\sigma$, $\omega$ and $\rho$ mesons. Then, we study the linear, static $l=2$ perturbation on the star to compute the electric-type Love number following Hinderer's prescription. |
1509.07357 | Amalya Khurshudyan | M. Khurshudyan, R. Myrzakulov | Late time attractors of some varying Chaplygin gas cosmological models | New section has been added. Old results have been updated. 19 pages,
4 figures | Symmetry 2021, 13(5), 769 | 10.3390/sym13050769 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The goal of this paper is to study new cosmological models where the dark
energy is a varying Chaplygin gas. This specific dark energy model with
non-linear EoS had been often discussed in modern cosmology. Contrary to
previous studies, we consider new forms of non-linear non-gravitational
interaction between dark matter and assumed dark energy models. We applied the
phase space analysis allowing understanding the late time behavior of the
models. It allows demonstrating that considered non-gravitational interactions
can solve the cosmological coincidence problem. On the other hand, we applied
Bayesian Machine Learning technique to learn the constraints on the free
parameters. In this way, we gained a better understanding of the models
providing a hint which of them can be ruled out. Moreover, the learning based
on the simulated expansion rate data shows that the models cannot solve the
$H_{0}$ tension problem.
| [
{
"created": "Sun, 20 Sep 2015 14:01:45 GMT",
"version": "v1"
},
{
"created": "Sat, 1 May 2021 11:22:22 GMT",
"version": "v2"
}
] | 2021-05-04 | [
[
"Khurshudyan",
"M.",
""
],
[
"Myrzakulov",
"R.",
""
]
] | The goal of this paper is to study new cosmological models where the dark energy is a varying Chaplygin gas. This specific dark energy model with non-linear EoS had been often discussed in modern cosmology. Contrary to previous studies, we consider new forms of non-linear non-gravitational interaction between dark matter and assumed dark energy models. We applied the phase space analysis allowing understanding the late time behavior of the models. It allows demonstrating that considered non-gravitational interactions can solve the cosmological coincidence problem. On the other hand, we applied Bayesian Machine Learning technique to learn the constraints on the free parameters. In this way, we gained a better understanding of the models providing a hint which of them can be ruled out. Moreover, the learning based on the simulated expansion rate data shows that the models cannot solve the $H_{0}$ tension problem. |
2011.09930 | Ulf Leonhardt | Ulf Leonhardt | Cosmological horizons radiate | null | Europhys. Lett. 135, 10002 (2021) | 10.1209/0295-5075/ac0ecf | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | Gibbons and Hawking [Phys. Rev. D 15, 2738 (1977)] have shown that the
horizon of de Sitter space emits radiation in the same way as the event horizon
of the black hole. But actual cosmological horizons are not event horizons,
except in de Sitter space. Nevertheless, this paper proves Gibbons' and
Hawking's radiation formula as an exact result for any flat space expanding
with strictly positive Hubble parameter. The paper gives visual and intuitive
insight into why this is the case. The paper also indicates how cosmological
horizons are related to the dynamical Casimir effect, which makes experimental
tests with laboratory analogues possible.
| [
{
"created": "Thu, 19 Nov 2020 16:12:45 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Nov 2020 14:56:59 GMT",
"version": "v2"
}
] | 2021-09-10 | [
[
"Leonhardt",
"Ulf",
""
]
] | Gibbons and Hawking [Phys. Rev. D 15, 2738 (1977)] have shown that the horizon of de Sitter space emits radiation in the same way as the event horizon of the black hole. But actual cosmological horizons are not event horizons, except in de Sitter space. Nevertheless, this paper proves Gibbons' and Hawking's radiation formula as an exact result for any flat space expanding with strictly positive Hubble parameter. The paper gives visual and intuitive insight into why this is the case. The paper also indicates how cosmological horizons are related to the dynamical Casimir effect, which makes experimental tests with laboratory analogues possible. |
gr-qc/0211003 | Djordje Minic | Vijay Balasubramanian, Jan de Boer and Djordje Minic | Holography, Time and Quantum Mechanics | Talk presented at the 3rd Sakharov International Conference on
Physics, Moscow, June 2002; to appear in the proceedings of the conference | null | null | null | gr-qc hep-th | null | In this talk we entertain the possibility that the synthesis of general
covariance and quantum mechanics requires an extension of the basic kinematical
setup of quantum mechanics. According to the holographic principle, regions of
spacetime bounded by a finite area carry finite entropy. When we in addition
assume that the origin of the entropy is a finite dimensional Hilbert space,
and apply this to cosmological solutions using a suitable notion of
complementarity, we find as a consequence that gravitational effects can lead
to dynamical variation in the dimensionality of such Hilbert spaces. This
happens generally in cosmological settings like our own universe.
| [
{
"created": "Fri, 1 Nov 2002 16:27:33 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Balasubramanian",
"Vijay",
""
],
[
"de Boer",
"Jan",
""
],
[
"Minic",
"Djordje",
""
]
] | In this talk we entertain the possibility that the synthesis of general covariance and quantum mechanics requires an extension of the basic kinematical setup of quantum mechanics. According to the holographic principle, regions of spacetime bounded by a finite area carry finite entropy. When we in addition assume that the origin of the entropy is a finite dimensional Hilbert space, and apply this to cosmological solutions using a suitable notion of complementarity, we find as a consequence that gravitational effects can lead to dynamical variation in the dimensionality of such Hilbert spaces. This happens generally in cosmological settings like our own universe. |
2004.05178 | Helvi Witek | Gast\'on Creci and Stefan Vandoren and Helvi Witek | Evolution of black hole shadows from superradiance | 22 pages, 16 figures. Updated to match published version | Phys. Rev. D 101, 124051 (2020) | 10.1103/PhysRevD.101.124051 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes have turned into cosmic laboratories to search for ultra-light
scalars by virtue of the superradiant instability. In this paper we present a
detailed study of the impact of the superradiant evolution on the black hole
shadow and investigate the exciting possibility to explore it with future
observations of Very Long Baseline Interferometry. We simulated the
superradiant evolution numerically, in the adiabatic regime, and derived
analytic approximations modelling the process. Driven by superradiance, we
evolve the black hole shadow diameter and (i) find that it can change by a few
$\mu$as, just below the current resolution of the Event Horizon Telescope,
albeit on timescales that are longer than realistic observation times; (ii)
show that the shadow diameter can either shrink or grow; and (iii) explore in
detail how the shadow's end state is determined by the initial parameters and
coupling.
| [
{
"created": "Fri, 10 Apr 2020 18:00:12 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Jul 2020 02:19:38 GMT",
"version": "v2"
}
] | 2020-07-03 | [
[
"Creci",
"Gastón",
""
],
[
"Vandoren",
"Stefan",
""
],
[
"Witek",
"Helvi",
""
]
] | Black holes have turned into cosmic laboratories to search for ultra-light scalars by virtue of the superradiant instability. In this paper we present a detailed study of the impact of the superradiant evolution on the black hole shadow and investigate the exciting possibility to explore it with future observations of Very Long Baseline Interferometry. We simulated the superradiant evolution numerically, in the adiabatic regime, and derived analytic approximations modelling the process. Driven by superradiance, we evolve the black hole shadow diameter and (i) find that it can change by a few $\mu$as, just below the current resolution of the Event Horizon Telescope, albeit on timescales that are longer than realistic observation times; (ii) show that the shadow diameter can either shrink or grow; and (iii) explore in detail how the shadow's end state is determined by the initial parameters and coupling. |
1910.05738 | Christian K\"ading | Christian K\"ading | Astro- and Quantum Physical Tests of Screened Scalar Fields | PhD thesis; 140 pages | null | null | null | gr-qc astro-ph.CO hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In general, modified gravity theories are modifications or extensions of
Einstein's general relativity. Some of them give rise to additional scalar
degrees of freedom in Nature. If these scalar fields exist and are light
enough, they should cause a gravity-like fifth force that could, in principle,
exceed gravity in its strength. However, there are tight constraints on fifth
forces from Solar System-based tests. Screening mechanisms are popular means
for avoiding these constraints by suppressing a fifth force in regions of high
environmental mass density but allowing for phenomenologically interesting
effects in environments of lower densities. In this thesis, scalar field models
with screening mechanisms will be discussed and some astro- and quantum
physical tests for their existence presented. At first, the impact of
disformally coupled symmetrons on gravitational lensing by galaxies will be
evaluated. Secondly, it will be shown how fluctuations of a chameleon scalar
field induce the open dynamics of a quantum test particle. For this, tools from
non-equilibrium quantum field theory will be introduced, developed and applied,
and a quantum master equation derived.
| [
{
"created": "Sun, 13 Oct 2019 12:20:49 GMT",
"version": "v1"
}
] | 2019-12-12 | [
[
"Käding",
"Christian",
""
]
] | In general, modified gravity theories are modifications or extensions of Einstein's general relativity. Some of them give rise to additional scalar degrees of freedom in Nature. If these scalar fields exist and are light enough, they should cause a gravity-like fifth force that could, in principle, exceed gravity in its strength. However, there are tight constraints on fifth forces from Solar System-based tests. Screening mechanisms are popular means for avoiding these constraints by suppressing a fifth force in regions of high environmental mass density but allowing for phenomenologically interesting effects in environments of lower densities. In this thesis, scalar field models with screening mechanisms will be discussed and some astro- and quantum physical tests for their existence presented. At first, the impact of disformally coupled symmetrons on gravitational lensing by galaxies will be evaluated. Secondly, it will be shown how fluctuations of a chameleon scalar field induce the open dynamics of a quantum test particle. For this, tools from non-equilibrium quantum field theory will be introduced, developed and applied, and a quantum master equation derived. |
gr-qc/0605126 | Delia Ionescu | Delia Ionescu | Comparative analysis of the electrogravitational Kepler problem in GRT
and RTG | null | International Journal of Non-Linear Mechanics, 38(2003), 1251-1268 | 10.1016/S0020-7462(02)00071-9 | null | gr-qc | null | In the framework of Einstein's General Relativity Theory and of the
Relativistic Theory of Gravitation, the equations governing the trajectories of
charged particles in the field created by a charged mass point are given. An
analysis of the shape of the trajectories in both theories is presented. The
first and the second order approximate solutions of the electrogravitational
Kepler problem are found in the two theories and the results are compared with
each other. I have pointed out the differences between the predictions in the
two theories.
| [
{
"created": "Wed, 24 May 2006 10:45:44 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Ionescu",
"Delia",
""
]
] | In the framework of Einstein's General Relativity Theory and of the Relativistic Theory of Gravitation, the equations governing the trajectories of charged particles in the field created by a charged mass point are given. An analysis of the shape of the trajectories in both theories is presented. The first and the second order approximate solutions of the electrogravitational Kepler problem are found in the two theories and the results are compared with each other. I have pointed out the differences between the predictions in the two theories. |
gr-qc/9211003 | Kay-Thomas Pirk | Kay-Thomas Pirk | Hadamard States and Adiabatic Vacua | 10pages, LaTeX (RevTeX-preprint style) | Phys.Rev. D48 (1993) 3779-3783 | 10.1103/PhysRevD.48.3779 | UMD preprint 92-239 | gr-qc hep-th | null | Reversing a slight detrimental effect of the mailer related to TeXability
| [
{
"created": "Wed, 4 Nov 1992 20:55:28 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Nov 1992 15:43:39 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Pirk",
"Kay-Thomas",
""
]
] | Reversing a slight detrimental effect of the mailer related to TeXability |
gr-qc/9710006 | Kirill Krasnov | Kirill Krasnov (PennState) | Quantum Geometry and Thermal Radiation from Black Holes | 19 pages, 4 figures, modified version to appear in Class. Quant. Grav | Class.Quant.Grav. 16 (1999) 563-578 | 10.1088/0264-9381/16/2/018 | CGPG-97/9-4 | gr-qc hep-th | null | A quantum mechanical description of black hole states proposed recently
within non-perturbative quantum gravity is used to study the emission and
absorption spectra of quantum black holes. We assume that the probability
distribution of states of the quantum black hole is given by the ``area''
canonical ensemble, in which the horizon area is used instead of energy, and
use Fermi's golden rule to find the line intensities. For a non-rotating black
hole, we study the absorption and emission of s-waves considering a special set
of emission lines. To find the line intensities we use an analogy between a
microscopic state of the black hole and a state of the gas of atoms.
| [
{
"created": "Wed, 1 Oct 1997 20:43:18 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Feb 1999 06:03:37 GMT",
"version": "v2"
}
] | 2009-10-30 | [
[
"Krasnov",
"Kirill",
"",
"PennState"
]
] | A quantum mechanical description of black hole states proposed recently within non-perturbative quantum gravity is used to study the emission and absorption spectra of quantum black holes. We assume that the probability distribution of states of the quantum black hole is given by the ``area'' canonical ensemble, in which the horizon area is used instead of energy, and use Fermi's golden rule to find the line intensities. For a non-rotating black hole, we study the absorption and emission of s-waves considering a special set of emission lines. To find the line intensities we use an analogy between a microscopic state of the black hole and a state of the gas of atoms. |
0903.4610 | Shuang-Yong Zhou | Shuang-Yong Zhou, Edmund J. Copeland, Paul M. Saffin | Cosmological Constraints on $f(G)$ Dark Energy Models | 17 pages, 3 figures; typos corrected | JCAP 0907:009,2009 | 10.1088/1475-7516/2009/07/009 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Modified gravity theories with the Gauss-Bonnet term
$G=R^2-4R^{\mu\nu}R_{\mu\nu}+R^{\mu\nu\rho\sigma}R_{\mu\nu\rho\sigma}$ have
recently gained a lot of attention as a possible explanation of dark energy. We
perform a thorough phase space analysis on the so-called $f(G)$ models, where
$f(G)$ is some general function of the Gauss-Bonnet term, and derive conditions
for the cosmological viability of $f(G)$ dark energy models. Following the
$f(R)$ case, we show that these conditions can be nicely presented as
geometrical constraints on the derivatives of $f(G)$. We find that for general
$f(G)$ models there are two kinds of stable accelerated solutions, a de Sitter
solution and a phantom-like solution. They co-exist with each other and which
solution the universe evolves to depends on the initial conditions. Finally,
several toy models of $f(G)$ dark energy are explored. Cosmologically viable
trajectories that mimic the $\Lambda$CDM model in the radiation and matter
dominated periods, but have distinctive signatures at late times, are obtained.
| [
{
"created": "Thu, 26 Mar 2009 19:28:47 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Apr 2009 15:53:42 GMT",
"version": "v2"
},
{
"created": "Thu, 30 Sep 2010 13:09:25 GMT",
"version": "v3"
}
] | 2010-10-01 | [
[
"Zhou",
"Shuang-Yong",
""
],
[
"Copeland",
"Edmund J.",
""
],
[
"Saffin",
"Paul M.",
""
]
] | Modified gravity theories with the Gauss-Bonnet term $G=R^2-4R^{\mu\nu}R_{\mu\nu}+R^{\mu\nu\rho\sigma}R_{\mu\nu\rho\sigma}$ have recently gained a lot of attention as a possible explanation of dark energy. We perform a thorough phase space analysis on the so-called $f(G)$ models, where $f(G)$ is some general function of the Gauss-Bonnet term, and derive conditions for the cosmological viability of $f(G)$ dark energy models. Following the $f(R)$ case, we show that these conditions can be nicely presented as geometrical constraints on the derivatives of $f(G)$. We find that for general $f(G)$ models there are two kinds of stable accelerated solutions, a de Sitter solution and a phantom-like solution. They co-exist with each other and which solution the universe evolves to depends on the initial conditions. Finally, several toy models of $f(G)$ dark energy are explored. Cosmologically viable trajectories that mimic the $\Lambda$CDM model in the radiation and matter dominated periods, but have distinctive signatures at late times, are obtained. |
1404.4307 | Luc Blanchet | Brett Altschul, Quentin G. Bailey, Luc Blanchet, Kai Bongs, Philippe
Bouyer, Luigi Cacciapuoti, Salvatore Capozziello, Naceur Gaaloul, Domenico
Giulini, Jonas Hartwig, Luciano Iess, Philippe Jetzer, Arnaud Landragin,
Ernst Rasel, Serge Reynaud, Stephan Schiller, Christian Schubert, Fiodor
Sorrentino, Uwe Sterr, Jay D. Tasson, Guglielmo M. Tino, Philip Tuckey, Peter
Wolf | Quantum Tests of the Einstein Equivalence Principle with the STE-QUEST
Space Mission | 27 pages, 6 figures, to appear in Advances in Space Research | Advances in Space Research, 55 (2015) 501-524 | 10.1016/j.asr.2014.07.014 | null | gr-qc astro-ph.CO quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present in detail the scientific objectives in fundamental physics of the
Space-Time Explorer and QUantum Equivalence Space Test (STE-QUEST) space
mission. STE-QUEST was pre-selected by the European Space Agency together with
four other missions for the cosmic vision M3 launch opportunity planned around
2024. It carries out tests of different aspects of the Einstein Equivalence
Principle using atomic clocks, matter wave interferometry and long distance
time/frequency links, providing fascinating science at the interface between
quantum mechanics and gravitation that cannot be achieved, at that level of
precision, in ground experiments. We especially emphasize the specific strong
interest of performing equivalence principle tests in the quantum regime, i.e.
using quantum atomic wave interferometry. Although STE-QUEST was finally not
selected in early 2014 because of budgetary and technological reasons, its
science case was very highly rated. Our aim is to expose that science to a
large audience in order to allow future projects and proposals to take
advantage of the STE-QUEST experience.
| [
{
"created": "Wed, 16 Apr 2014 16:42:31 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Sep 2014 17:11:24 GMT",
"version": "v2"
}
] | 2015-03-19 | [
[
"Altschul",
"Brett",
""
],
[
"Bailey",
"Quentin G.",
""
],
[
"Blanchet",
"Luc",
""
],
[
"Bongs",
"Kai",
""
],
[
"Bouyer",
"Philippe",
""
],
[
"Cacciapuoti",
"Luigi",
""
],
[
"Capozziello",
"Salvatore",
""
],
[
"Gaaloul",
"Naceur",
""
],
[
"Giulini",
"Domenico",
""
],
[
"Hartwig",
"Jonas",
""
],
[
"Iess",
"Luciano",
""
],
[
"Jetzer",
"Philippe",
""
],
[
"Landragin",
"Arnaud",
""
],
[
"Rasel",
"Ernst",
""
],
[
"Reynaud",
"Serge",
""
],
[
"Schiller",
"Stephan",
""
],
[
"Schubert",
"Christian",
""
],
[
"Sorrentino",
"Fiodor",
""
],
[
"Sterr",
"Uwe",
""
],
[
"Tasson",
"Jay D.",
""
],
[
"Tino",
"Guglielmo M.",
""
],
[
"Tuckey",
"Philip",
""
],
[
"Wolf",
"Peter",
""
]
] | We present in detail the scientific objectives in fundamental physics of the Space-Time Explorer and QUantum Equivalence Space Test (STE-QUEST) space mission. STE-QUEST was pre-selected by the European Space Agency together with four other missions for the cosmic vision M3 launch opportunity planned around 2024. It carries out tests of different aspects of the Einstein Equivalence Principle using atomic clocks, matter wave interferometry and long distance time/frequency links, providing fascinating science at the interface between quantum mechanics and gravitation that cannot be achieved, at that level of precision, in ground experiments. We especially emphasize the specific strong interest of performing equivalence principle tests in the quantum regime, i.e. using quantum atomic wave interferometry. Although STE-QUEST was finally not selected in early 2014 because of budgetary and technological reasons, its science case was very highly rated. Our aim is to expose that science to a large audience in order to allow future projects and proposals to take advantage of the STE-QUEST experience. |
2207.11370 | Fech Scen Khoo | Jose Luis Bl\'azquez-Salcedo, Luis Manuel Gonz\'alez-Romero, Fech Scen
Khoo, Jutta Kunz, Vincent Preut | $\phi$-modes of neutron stars in a massless scalar-tensor theory | 23 pages, 16 figures, Invited contribution to the volume
"Perturbations in Modified Gravitation and Cosmology", to appear in Frontiers
in Astronomy And Space Sciences | Front.Astron.Space Sci. 9 (2022) 1005108 | 10.3389/fspas.2022.1005108 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scalar-tensor theories allow for a rich spectrum of quasinormal modes of
neutron stars. The presence of the scalar field allows for polar monopole and
dipole radiation, as well as for additional higher multipole modes led by the
scalar field. Here we present these scalar-led $\phi$-modes for the lowest
multipoles, $l=0$, 1 and 2 for a massless scalar-tensor theory of the
Brans-Dicke type, motivated by $R^2$ theory, and compare with those of a
minimally coupled scalar field in general relativity. We consider a set of six
realistic equations of state and extract universal relations for the modes.
| [
{
"created": "Fri, 22 Jul 2022 22:54:34 GMT",
"version": "v1"
}
] | 2024-05-13 | [
[
"Blázquez-Salcedo",
"Jose Luis",
""
],
[
"González-Romero",
"Luis Manuel",
""
],
[
"Khoo",
"Fech Scen",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Preut",
"Vincent",
""
]
] | Scalar-tensor theories allow for a rich spectrum of quasinormal modes of neutron stars. The presence of the scalar field allows for polar monopole and dipole radiation, as well as for additional higher multipole modes led by the scalar field. Here we present these scalar-led $\phi$-modes for the lowest multipoles, $l=0$, 1 and 2 for a massless scalar-tensor theory of the Brans-Dicke type, motivated by $R^2$ theory, and compare with those of a minimally coupled scalar field in general relativity. We consider a set of six realistic equations of state and extract universal relations for the modes. |
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