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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2405.09945 | Surajit Das | Surajit Das, Surojit Dalui and Rickmoy Samanta | Near-horizon chaos beyond Einstein gravity | 21 pages, 63 figures, 1 table | null | null | null | gr-qc hep-th nlin.CD | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate chaos in the dynamics of outgoing massless particles near the
horizon of static spherically symmetric (SSS) black holes in two well-motivated
models of $f(R)$ gravity. In both these models, we probe chaos in the particle
trajectories (under suitable harmonic confinement) in the vicinity of the black
hole horizons, for a set of initial conditions. The particle trajectories,
associated Poincar$\acute{e}$ sections, and Lyapunov exponents clearly
illustrate the role played by the black hole horizon in the growth of chaos. We
find that with increasing energy, the particle trajectories explore regions
closer to the black hole horizon, with reduced overlap between two initially
close trajectories. We demonstrate how this energy range is controlled by the
parameters of the modified gravity theory under consideration. The growth of
chaos in such a classical setting is known to respect a surface gravity bound
arising from universal aspects of particle dynamics close to the black hole
horizon [K. Hashimoto and N. Tanahashi, Phys. Rev. D 95, 024007 (2017)],
analogous to the quantum MSS bound [J. Maldacena, S.H. Shenker and D. Stanford,
JHEP 08 (2016) 106]. Interestingly, both models studied in our work respect the
bound, in contrast to some of the other models of $f(R)$ gravity in the
existing literature. The work serves as a motivation to use chaos as an
additional tool to probe Einstein gravity in the strong gravity regime in the
vicinity of black hole horizons.
| [
{
"created": "Thu, 16 May 2024 09:50:42 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Jun 2024 04:34:11 GMT",
"version": "v2"
}
] | 2024-06-21 | [
[
"Das",
"Surajit",
""
],
[
"Dalui",
"Surojit",
""
],
[
"Samanta",
"Rickmoy",
""
]
] | We investigate chaos in the dynamics of outgoing massless particles near the horizon of static spherically symmetric (SSS) black holes in two well-motivated models of $f(R)$ gravity. In both these models, we probe chaos in the particle trajectories (under suitable harmonic confinement) in the vicinity of the black hole horizons, for a set of initial conditions. The particle trajectories, associated Poincar$\acute{e}$ sections, and Lyapunov exponents clearly illustrate the role played by the black hole horizon in the growth of chaos. We find that with increasing energy, the particle trajectories explore regions closer to the black hole horizon, with reduced overlap between two initially close trajectories. We demonstrate how this energy range is controlled by the parameters of the modified gravity theory under consideration. The growth of chaos in such a classical setting is known to respect a surface gravity bound arising from universal aspects of particle dynamics close to the black hole horizon [K. Hashimoto and N. Tanahashi, Phys. Rev. D 95, 024007 (2017)], analogous to the quantum MSS bound [J. Maldacena, S.H. Shenker and D. Stanford, JHEP 08 (2016) 106]. Interestingly, both models studied in our work respect the bound, in contrast to some of the other models of $f(R)$ gravity in the existing literature. The work serves as a motivation to use chaos as an additional tool to probe Einstein gravity in the strong gravity regime in the vicinity of black hole horizons. |
0911.2841 | Lorenzo Fatibene | M. Di Mauro, L. Fatibene, M. Ferraris, M. Francaviglia | Further Extended Theories of Gravitation: Part I | 10 pages. Some refs added | Int.J.Geom.Meth.Mod.Phys.7:887-898,2010 | 10.1142/S0219887810004592 10.1142/S0219887810004609 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We shall here propose a class of relativistic theories of gravitation, based
on a foundational paper of Ehlers Pirani and Schild (EPS).All "extended
theories of gravitation" (also known as f(R) theories) in Palatini formalism
are shown to belong to this class. In a forthcoming paper we shall show that
this class of theories contains other more general examples. EPS framework
helps in the interpretation and solution of these models that however have
exotic behaviours even compared to f(R) theories.
| [
{
"created": "Sun, 15 Nov 2009 08:59:18 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jan 2010 11:18:00 GMT",
"version": "v2"
}
] | 2011-01-05 | [
[
"Di Mauro",
"M.",
""
],
[
"Fatibene",
"L.",
""
],
[
"Ferraris",
"M.",
""
],
[
"Francaviglia",
"M.",
""
]
] | We shall here propose a class of relativistic theories of gravitation, based on a foundational paper of Ehlers Pirani and Schild (EPS).All "extended theories of gravitation" (also known as f(R) theories) in Palatini formalism are shown to belong to this class. In a forthcoming paper we shall show that this class of theories contains other more general examples. EPS framework helps in the interpretation and solution of these models that however have exotic behaviours even compared to f(R) theories. |
1302.0040 | Benjamin C. Harms | Peter L. Biermann and Benjamin C. Harms | A Comprehensive Model of Dark Energy, Inflation AND Black Holes | 5 pages, contributed talk given at the 13th Marcel Grossmann Meeting,
July 2012 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive two new equations of quantum gravity and combine them with
reinterpretations of previously proposed concepts of dark energy, black holes,
inflation, the arrow of time and the energy at which rest-mass first manifests
itself into a theory which may be a first step toward a comprehensive
description of all these phenomena. The resulting theory also predicts new
tests which can be experimentally checked within a few years.
| [
{
"created": "Thu, 31 Jan 2013 23:56:14 GMT",
"version": "v1"
}
] | 2013-02-04 | [
[
"Biermann",
"Peter L.",
""
],
[
"Harms",
"Benjamin C.",
""
]
] | We derive two new equations of quantum gravity and combine them with reinterpretations of previously proposed concepts of dark energy, black holes, inflation, the arrow of time and the energy at which rest-mass first manifests itself into a theory which may be a first step toward a comprehensive description of all these phenomena. The resulting theory also predicts new tests which can be experimentally checked within a few years. |
1309.2611 | Grant Remmen | Grant N. Remmen and Sean M. Carroll | Attractor Solutions in Scalar-Field Cosmology | 14 pages, 4 figures | Phys. Rev. D 88, 083518 (2013) | 10.1103/PhysRevD.88.083518 | CALT-68-2853 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Models of cosmological scalar fields often feature "attractor solutions" to
which the system evolves for a wide range of initial conditions. There is some
tension between this well-known fact and another well-known fact: Liouville's
theorem forbids true attractor behavior in a Hamiltonian system. In universes
with vanishing spatial curvature, the field variables (\phi,\dot\phi) specify
the system completely, defining an effective phase space. We investigate
whether one can define a unique conserved measure on this effective phase
space, showing that it exists for m^2\phi^2 potentials and deriving conditions
for its existence in more general theories. We show that apparent attractors
are places where this conserved measure diverges in the (\phi,\dot\phi)
variables and suggest a physical understanding of attractor behavior that is
compatible with Liouville's theorem.
| [
{
"created": "Tue, 10 Sep 2013 18:57:42 GMT",
"version": "v1"
}
] | 2013-10-30 | [
[
"Remmen",
"Grant N.",
""
],
[
"Carroll",
"Sean M.",
""
]
] | Models of cosmological scalar fields often feature "attractor solutions" to which the system evolves for a wide range of initial conditions. There is some tension between this well-known fact and another well-known fact: Liouville's theorem forbids true attractor behavior in a Hamiltonian system. In universes with vanishing spatial curvature, the field variables (\phi,\dot\phi) specify the system completely, defining an effective phase space. We investigate whether one can define a unique conserved measure on this effective phase space, showing that it exists for m^2\phi^2 potentials and deriving conditions for its existence in more general theories. We show that apparent attractors are places where this conserved measure diverges in the (\phi,\dot\phi) variables and suggest a physical understanding of attractor behavior that is compatible with Liouville's theorem. |
2111.12563 | Adrian Boitier | Adrian Bo\^itier, Tanguy Giroud, Shubhanshu Tiwari, Philippe Jetzer | Series expansion of the overlap reduction function for scalar and vector
polarizations for gravitational wave search with pulsar timing arrays | null | null | 10.1103/PhysRevD.105.084006 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In our previous work \cite{PTA2} we calculated the overlap reduction function
for the tensor polarization without employing the short wavelength
approximation, this was done by obtaining a power series of nested sums which
is valid for all gravitational wave frequencies and pulsar distances. In this
work we generalize the power-series expansion method to vector and scalar
polarizations. We have compared our expression for the breathing and vector
modes with previous literature. We present for the first time analytic
expressions for the overlap reduction function of the longitudinal mode for all
angles between the pulsar pairs.
| [
{
"created": "Wed, 24 Nov 2021 15:35:39 GMT",
"version": "v1"
}
] | 2022-04-20 | [
[
"Boîtier",
"Adrian",
""
],
[
"Giroud",
"Tanguy",
""
],
[
"Tiwari",
"Shubhanshu",
""
],
[
"Jetzer",
"Philippe",
""
]
] | In our previous work \cite{PTA2} we calculated the overlap reduction function for the tensor polarization without employing the short wavelength approximation, this was done by obtaining a power series of nested sums which is valid for all gravitational wave frequencies and pulsar distances. In this work we generalize the power-series expansion method to vector and scalar polarizations. We have compared our expression for the breathing and vector modes with previous literature. We present for the first time analytic expressions for the overlap reduction function of the longitudinal mode for all angles between the pulsar pairs. |
1803.07171 | Salvatore Capozziello | Habib Abedi, Salvatore Capozziello, Rocco D'Agostino, and Orlando
Luongo | Effective gravitational coupling in modified teleparallel theories | 17 pages, 4 figures, accepted for publication in Physical Review D | null | 10.1103/PhysRevD.97.084008 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present study, we consider an extended form of teleparallel Lagrangian
$f(T,\phi,X)$, as function of a scalar field $\phi$, its kinetic term $X$ and
the torsion scalar $T$. We use linear perturbations to obtain the equation of
matter density perturbations on sub-Hubble scales. The gravitational coupling
is modified in scalar modes with respect to the one of General Relativity,
albeit vector modes decay and do not show any significant effects. We thus
extend these results by involving multiple scalar field models. Further, we
study conformal transformations in teleparallel gravity and we obtain the
coupling as the scalar field is non-minimally coupled to both torsion and
boundary terms. Finally, we propose the specific model $f(T,\phi,X)=T +
\partial_\mu \phi\ \partial^\mu \phi +\xi T \phi^2$. To check its goodness, we
employ the observational Hubble data, constraining the coupling constant,
$\xi$, through a Monte Carlo technique based on the Metropolis-Hastings
algorithm. Hence, fixing $\xi$ to its best-fit value got from our numerical
analysis, we calculate the growth rate of matter perturbations and we compare
our outcomes with the latest measurements and the predictions of the
$\Lambda$CDM model.
| [
{
"created": "Mon, 19 Mar 2018 21:31:34 GMT",
"version": "v1"
}
] | 2018-05-09 | [
[
"Abedi",
"Habib",
""
],
[
"Capozziello",
"Salvatore",
""
],
[
"D'Agostino",
"Rocco",
""
],
[
"Luongo",
"Orlando",
""
]
] | In the present study, we consider an extended form of teleparallel Lagrangian $f(T,\phi,X)$, as function of a scalar field $\phi$, its kinetic term $X$ and the torsion scalar $T$. We use linear perturbations to obtain the equation of matter density perturbations on sub-Hubble scales. The gravitational coupling is modified in scalar modes with respect to the one of General Relativity, albeit vector modes decay and do not show any significant effects. We thus extend these results by involving multiple scalar field models. Further, we study conformal transformations in teleparallel gravity and we obtain the coupling as the scalar field is non-minimally coupled to both torsion and boundary terms. Finally, we propose the specific model $f(T,\phi,X)=T + \partial_\mu \phi\ \partial^\mu \phi +\xi T \phi^2$. To check its goodness, we employ the observational Hubble data, constraining the coupling constant, $\xi$, through a Monte Carlo technique based on the Metropolis-Hastings algorithm. Hence, fixing $\xi$ to its best-fit value got from our numerical analysis, we calculate the growth rate of matter perturbations and we compare our outcomes with the latest measurements and the predictions of the $\Lambda$CDM model. |
gr-qc/0604066 | Kartheek Solipuram | Kartheek R Solipuram | Mathematical Analyses of an accelerating (Griffiths-Podolsky) Black Hole | 21 pages | null | null | null | gr-qc | null | An exact solution of Einsteins equations which represents a pair of
accelerating and rotating black holes was presented by J. B. Griffiths and J.
Podolsky [2]. In the paper [2] they have shown the explicit form of a spinning
C-metric starting from the Plebanski-Demianski metric, and transformed it using
NUT and angular velocity parameters in addition to the usual parameters and
thus gave a generalized form of such solutions. In the forthcoming discussion,
an attempt has been made to realize the Riemann components of the proposed
metric. Furthermore, certain optical characteristics of the metric have been
analyzed using the Newman-Penrose formalism.
| [
{
"created": "Sat, 15 Apr 2006 18:50:56 GMT",
"version": "v1"
},
{
"created": "Sun, 22 Oct 2006 13:29:54 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Solipuram",
"Kartheek R",
""
]
] | An exact solution of Einsteins equations which represents a pair of accelerating and rotating black holes was presented by J. B. Griffiths and J. Podolsky [2]. In the paper [2] they have shown the explicit form of a spinning C-metric starting from the Plebanski-Demianski metric, and transformed it using NUT and angular velocity parameters in addition to the usual parameters and thus gave a generalized form of such solutions. In the forthcoming discussion, an attempt has been made to realize the Riemann components of the proposed metric. Furthermore, certain optical characteristics of the metric have been analyzed using the Newman-Penrose formalism. |
2106.13837 | Shauvik Biswas | Shauvik Biswas | Massive Scalar Perturbation of Extremal Rotating Braneworld Black hole:
Superradiant Stability Analysis | 16 pages , 4 figures | Phys.Lett.B 820 (2021) 136597 | 10.1016/j.physletb.2021.136597 | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | We analyse the superradiant stability of braneworld extremal Kerr and
Kerr-Newman black holes under massive scalar perturbation. These black hole
solutions differ from their four dimensional counterpart by the presence of a
tidal charge, which unlike electric charge, can take both positive and negative
values and carries the signature of extra dimensions. We consider the
perturbation of the brane geometry by a massive scalar field. From the radial
equation of motion of the scalar field, we have found the effective potential
felt by the field. For superradiant stability, there should not be any trapping
well of the effective potential outside of the horizon. Using this condition we
have specified the parameter space of superradiant stability which depends on
parameters of both black hole and perturbation. In the case of Kerr-like
extremal braneworld black holes, we have obtained a bound on tidal charge for
superradiant stability under a massive scalar perturbation. Similarly, for
slowly rotating Kerr-Newman like extremal braneworld black holes, we have
obtained a lower bound of the product of mass to charge ratio of the black hole
and scalar field, for which the system is superradiantly stable.
| [
{
"created": "Fri, 25 Jun 2021 18:27:30 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Sep 2021 11:00:02 GMT",
"version": "v2"
}
] | 2021-09-02 | [
[
"Biswas",
"Shauvik",
""
]
] | We analyse the superradiant stability of braneworld extremal Kerr and Kerr-Newman black holes under massive scalar perturbation. These black hole solutions differ from their four dimensional counterpart by the presence of a tidal charge, which unlike electric charge, can take both positive and negative values and carries the signature of extra dimensions. We consider the perturbation of the brane geometry by a massive scalar field. From the radial equation of motion of the scalar field, we have found the effective potential felt by the field. For superradiant stability, there should not be any trapping well of the effective potential outside of the horizon. Using this condition we have specified the parameter space of superradiant stability which depends on parameters of both black hole and perturbation. In the case of Kerr-like extremal braneworld black holes, we have obtained a bound on tidal charge for superradiant stability under a massive scalar perturbation. Similarly, for slowly rotating Kerr-Newman like extremal braneworld black holes, we have obtained a lower bound of the product of mass to charge ratio of the black hole and scalar field, for which the system is superradiantly stable. |
gr-qc/0703002 | Kirill Krasnov | Kirill Krasnov | Non-Metric Gravity I: Field Equations | 21 pages, no figures (v2) energy conservation equation simplified,
note on reality conditions added (v3) minor changes | Class.Quant.Grav.25:025001,2008 | 10.1088/0264-9381/25/2/025001 | null | gr-qc astro-ph hep-th | null | We describe and study a certain class of modified gravity theories. Our
starting point is Plebanski formulation of gravity in terms of a triple B^i of
2-forms, a connection A^i and a ``Lagrange multiplier'' field Psi^ij. The
generalization we consider stems from presence in the action of an extra term
proportional to a scalar function of Psi^ij. As in the usual Plebanski general
relativity (GR) case, a certain metric can be constructed from B^i. However,
unlike in GR, the connection A^i no longer coincides with the self-dual part of
the metric-compatible spin-connection. Field equations of the theory are shown
to be relations between derivatives of the metric and components of field Psi,
as well as its derivatives, the later being in contrast to the GR case. The
equations are of second order in derivatives. An analog of the Bianchi identity
is still present in the theory, as well as its contracted version tantamount to
energy conservation equation.
| [
{
"created": "Thu, 1 Mar 2007 02:39:28 GMT",
"version": "v1"
},
{
"created": "Tue, 15 May 2007 03:01:08 GMT",
"version": "v2"
},
{
"created": "Tue, 16 Oct 2007 11:19:56 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Krasnov",
"Kirill",
""
]
] | We describe and study a certain class of modified gravity theories. Our starting point is Plebanski formulation of gravity in terms of a triple B^i of 2-forms, a connection A^i and a ``Lagrange multiplier'' field Psi^ij. The generalization we consider stems from presence in the action of an extra term proportional to a scalar function of Psi^ij. As in the usual Plebanski general relativity (GR) case, a certain metric can be constructed from B^i. However, unlike in GR, the connection A^i no longer coincides with the self-dual part of the metric-compatible spin-connection. Field equations of the theory are shown to be relations between derivatives of the metric and components of field Psi, as well as its derivatives, the later being in contrast to the GR case. The equations are of second order in derivatives. An analog of the Bianchi identity is still present in the theory, as well as its contracted version tantamount to energy conservation equation. |
1007.1563 | Chopin Soo | Chopin Soo, Jinsong Yang and Hoi-Lai Yu | New formulation of Horava-Lifshitz quantum gravity as a master
constraint theory | 4 pages | Phys.Lett.B701:275-278,2011 | 10.1016/j.physletb.2011.05.055 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Both projectable and non-projectable versions of Horava-Lifshitz gravity face
serious challenges. In the non-projectable version, the constraint algebra is
seemingly inconsistent. The projectable version lacks a local Hamiltonian
constraint, thus allowing for an extra scalar mode which can be problematic. A
new formulation of non-projectable Horava-Lifshitz gravity, naturally realized
as a representation of the master constraint algebra studied by loop quantum
gravity researchers, is presented. This yields a consistent canonical theory
with first class constraints. It captures the essence of Horava-Lifshitz
gravity in retaining only spatial diffeomorphisms (instead of full space-time
covariance) as the physically relevant non-trivial gauge symmetry; at the same
time the local Hamiltonian constraint needed to eliminate the extra mode is
equivalently enforced by the master constraint.
| [
{
"created": "Fri, 9 Jul 2010 11:25:18 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Jun 2011 07:46:06 GMT",
"version": "v2"
}
] | 2011-06-28 | [
[
"Soo",
"Chopin",
""
],
[
"Yang",
"Jinsong",
""
],
[
"Yu",
"Hoi-Lai",
""
]
] | Both projectable and non-projectable versions of Horava-Lifshitz gravity face serious challenges. In the non-projectable version, the constraint algebra is seemingly inconsistent. The projectable version lacks a local Hamiltonian constraint, thus allowing for an extra scalar mode which can be problematic. A new formulation of non-projectable Horava-Lifshitz gravity, naturally realized as a representation of the master constraint algebra studied by loop quantum gravity researchers, is presented. This yields a consistent canonical theory with first class constraints. It captures the essence of Horava-Lifshitz gravity in retaining only spatial diffeomorphisms (instead of full space-time covariance) as the physically relevant non-trivial gauge symmetry; at the same time the local Hamiltonian constraint needed to eliminate the extra mode is equivalently enforced by the master constraint. |
1702.07710 | Hermano Velten | Hermano Velten and Thiago R. P. Caram\^es | Cosmological inviability of $f(R,T)$ gravity | 10 pages. Version accepted for publication in PRD | Phys. Rev. D 95, 123536 (2017) | 10.1103/PhysRevD.95.123536 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Among many alternative gravitational theories to General Relativity (GR),
$f(R,T)$ gravity (where $R$ is the Ricci scalar and $T$ the trace of the
energy-momentum tensor) has been widely studied recently. By adding a matter
contribution to the gravitational Lagrangian, $f(R,T)$ theories have become an
interesting extension to GR displaying a broad phenomenology in astrophysics
and cosmology. In this paper, we discuss however the difficulties appearing in
explaining a viable and realistic cosmology within the $f(R,T)$ class of
theories. Our results challenge the viability of $f(R,T)$ as an alternative
modification of gravity.
| [
{
"created": "Fri, 24 Feb 2017 00:59:02 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Jun 2017 16:43:03 GMT",
"version": "v2"
}
] | 2017-07-05 | [
[
"Velten",
"Hermano",
""
],
[
"Caramês",
"Thiago R. P.",
""
]
] | Among many alternative gravitational theories to General Relativity (GR), $f(R,T)$ gravity (where $R$ is the Ricci scalar and $T$ the trace of the energy-momentum tensor) has been widely studied recently. By adding a matter contribution to the gravitational Lagrangian, $f(R,T)$ theories have become an interesting extension to GR displaying a broad phenomenology in astrophysics and cosmology. In this paper, we discuss however the difficulties appearing in explaining a viable and realistic cosmology within the $f(R,T)$ class of theories. Our results challenge the viability of $f(R,T)$ as an alternative modification of gravity. |
gr-qc/0212057 | P. Mitra | Tanwi Ghosh and P. Mitra | Asymptotically non-flat rotating dilaton black holes | LaTeX, 8 pages, slightly modified version to appear in Classical and
Quantum Gravity (http://www.iop.org) | Class.Quant.Grav. 20 (2003) 1403-1410 | 10.1088/0264-9381/20/7/311 | SINP/TNP/02-27 | gr-qc hep-th | null | Dilaton black hole solutions which are neither asymptotically flat nor
(anti)-de Sitter but reduce to asymptotically flat solutions in some special
limits have been known for a Liouville type dilatonic potential. It is shown
how, by solving a pair of coupled differential equations, infinitesimally small
angular momentum can be added to these static solutions to produce rotating
black hole solutions.
| [
{
"created": "Thu, 12 Dec 2002 12:24:23 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Mar 2003 06:52:20 GMT",
"version": "v2"
}
] | 2017-08-23 | [
[
"Ghosh",
"Tanwi",
""
],
[
"Mitra",
"P.",
""
]
] | Dilaton black hole solutions which are neither asymptotically flat nor (anti)-de Sitter but reduce to asymptotically flat solutions in some special limits have been known for a Liouville type dilatonic potential. It is shown how, by solving a pair of coupled differential equations, infinitesimally small angular momentum can be added to these static solutions to produce rotating black hole solutions. |
gr-qc/0307037 | James E. Lidsey | James E. Lidsey | Cosmic Dynamics of Bose-Einstein Condensates | 12 pages, no figures. Extended discussion. In Press, Classical and
Quantum Gravity | Class.Quant.Grav. 21 (2004) 777-786 | 10.1088/0264-9381/21/4/002 | null | gr-qc astro-ph cond-mat | null | A dynamical correspondence is established between positively curved,
isotropic, perfect fluid cosmologies and quasi-two-dimensional, harmonically
trapped Bose-Einstein condensates by mapping the equations of motion for both
systems onto the one-dimensional Ermakov system. Parameters that characterize
the physical properties of the condensate wavepacket, such as its width,
momentum and energy, may be identified with the scale factor, Hubble expansion
parameter and energy density of the universe, respectively. Different forms of
cosmic matter correspond to different choices for the time-dependent trapping
frequency of the condensate. The trapping frequency that mimics a
radiation-dominated universe is determined.
| [
{
"created": "Wed, 9 Jul 2003 10:24:08 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Dec 2003 15:24:13 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Lidsey",
"James E.",
""
]
] | A dynamical correspondence is established between positively curved, isotropic, perfect fluid cosmologies and quasi-two-dimensional, harmonically trapped Bose-Einstein condensates by mapping the equations of motion for both systems onto the one-dimensional Ermakov system. Parameters that characterize the physical properties of the condensate wavepacket, such as its width, momentum and energy, may be identified with the scale factor, Hubble expansion parameter and energy density of the universe, respectively. Different forms of cosmic matter correspond to different choices for the time-dependent trapping frequency of the condensate. The trapping frequency that mimics a radiation-dominated universe is determined. |
0804.3921 | Alberto Saa | Mauricio Richartz and Alberto Saa | Overspinning a nearly extreme black hole and the Weak Cosmic Censorship
conjecture | 4 pages. Final version to appear in PRD as a Rapid Communication | Phys.Rev.D78:081503,2008 | 10.1103/PhysRevD.78.081503 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit here the recent proposal for overspinning a nearly extreme black
hole by means of a quantum tunneling process. We show that electrically neutral
massless fermions evade possible back reactions effects related to
superradiance, confirming the view that it would be indeed possible to form a
naked singularity due to quantum effects.
| [
{
"created": "Thu, 24 Apr 2008 13:21:40 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Oct 2008 23:01:14 GMT",
"version": "v2"
}
] | 2008-11-07 | [
[
"Richartz",
"Mauricio",
""
],
[
"Saa",
"Alberto",
""
]
] | We revisit here the recent proposal for overspinning a nearly extreme black hole by means of a quantum tunneling process. We show that electrically neutral massless fermions evade possible back reactions effects related to superradiance, confirming the view that it would be indeed possible to form a naked singularity due to quantum effects. |
2202.00051 | Peter K.F. Kuhfittig | Peter K.F. Kuhfittig | Accounting for exotic matter and the extreme radial tension in
Morris-Thorne wormholes of embedding class one | 8 pages, no figures | Eur. Phys. J. C, vol. 81, 778 (2021) | 10.1140/epjc/s10052-021-09492-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The embedding of a curved spacetime in a higher-dimensional flat spacetime
has continued to be a topic of interest in the general theory of relativity, as
exemplified by the induced-matter theory. This paper deals with spacetimes of
embedding class one, i.e., spacetimes that can be embedded in a
five-dimensional flat spacetime. Einstein's theory allows the fifth dimension
to be either spacelike or timelike. By assuming the latter, this paper
addresses two fundamental issues concerning Morris-Thorne wormholes, the origin
of exotic matter and the frequently inexplicable enormous radial tension at the
throat.
| [
{
"created": "Mon, 31 Jan 2022 19:24:02 GMT",
"version": "v1"
}
] | 2022-02-09 | [
[
"Kuhfittig",
"Peter K. F.",
""
]
] | The embedding of a curved spacetime in a higher-dimensional flat spacetime has continued to be a topic of interest in the general theory of relativity, as exemplified by the induced-matter theory. This paper deals with spacetimes of embedding class one, i.e., spacetimes that can be embedded in a five-dimensional flat spacetime. Einstein's theory allows the fifth dimension to be either spacelike or timelike. By assuming the latter, this paper addresses two fundamental issues concerning Morris-Thorne wormholes, the origin of exotic matter and the frequently inexplicable enormous radial tension at the throat. |
gr-qc/9604011 | null | C. Bertoni, F. Finelli, G. Venturi | The Born-Oppenheimer Approach to the Matter-Gravity System and Unitarity | Latex, 12 pages. Revised version as accepted for publication by
Class. and Quant. Grav. Some points explained and misprints corrected | Class.Quant.Grav.13:2375-2384,1996 | 10.1088/0264-9381/13/9/005 | null | gr-qc | null | The Born-Oppenheimer approach to the matter-gravity system is illustrated and
the unitary evolution for matter, in the absence of phenomena such as
tunnelling or other instabilities, verified. The Born-Oppenheimer approach to
the matter-gravity system is illustrated in a simple minisuperspace model and
the corrections to quantum field theory on a semiclassical background
exhibited. Within such a context the unitary evolution for matter, in the
absence of phenomena such as tunnelling or other instabilities, is verified and
compared with the results of other approaches. Lastly the simplifications
associated with the use of adiabatic invariants to obtain the solution of the
explicitly time dependent evolution equation for matter are evidenced.
| [
{
"created": "Thu, 4 Apr 1996 13:24:35 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Jul 1996 09:12:16 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Bertoni",
"C.",
""
],
[
"Finelli",
"F.",
""
],
[
"Venturi",
"G.",
""
]
] | The Born-Oppenheimer approach to the matter-gravity system is illustrated and the unitary evolution for matter, in the absence of phenomena such as tunnelling or other instabilities, verified. The Born-Oppenheimer approach to the matter-gravity system is illustrated in a simple minisuperspace model and the corrections to quantum field theory on a semiclassical background exhibited. Within such a context the unitary evolution for matter, in the absence of phenomena such as tunnelling or other instabilities, is verified and compared with the results of other approaches. Lastly the simplifications associated with the use of adiabatic invariants to obtain the solution of the explicitly time dependent evolution equation for matter are evidenced. |
gr-qc/0611144 | Robert Mann | P.S. Farrugia, R.B. Mann and T.C. Scott | N-body Gravity and the Schroedinger Equation | 15 pages, Latex, references added, typos corrected, final version
that appears in CQG | Class.Quant.Grav.24:4647-4660,2007 | 10.1088/0264-9381/24/18/006 | null | gr-qc | null | We consider the problem of the motion of $N$ bodies in a self-gravitating
system in two spacetime dimensions. We point out that this system can be mapped
onto the quantum-mechanical problem of an N-body generalization of the problem
of the H$_{2}^{+}$ molecular ion in one dimension. The canonical gravitational
N-body formalism can be extended to include electromagnetic charges. We derive
a general algorithm for solving this problem, and show how it reduces to known
results for the 2-body and 3-body systems.
| [
{
"created": "Mon, 27 Nov 2006 20:56:33 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Sep 2007 15:31:23 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Farrugia",
"P. S.",
""
],
[
"Mann",
"R. B.",
""
],
[
"Scott",
"T. C.",
""
]
] | We consider the problem of the motion of $N$ bodies in a self-gravitating system in two spacetime dimensions. We point out that this system can be mapped onto the quantum-mechanical problem of an N-body generalization of the problem of the H$_{2}^{+}$ molecular ion in one dimension. The canonical gravitational N-body formalism can be extended to include electromagnetic charges. We derive a general algorithm for solving this problem, and show how it reduces to known results for the 2-body and 3-body systems. |
2211.13233 | Zhe Feng | Zhe Feng | Slow-roll inflation in $f\left(R, T, R_{ab}T^{ab}\right)$ gravity | 14 pages, 1 figure | null | 10.1142/S0217732324500263 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | In the framework of $f\left(R, T, R_{ab}T^{ab}\right)$ gravity theory, the
slow-roll approximation of the cosmic inflation is investigated, where $T$ is
the trace of the energy-momentum tensor $T^{ab}$, $R$ and $R_{ab}$ are the
Ricci scalar and tensor, respectively. After obtaining the equations of motion
of the gravitational field from the action principle in the spatially flat FLRW
metric, the fundamental equations of this theory are received by introducing
the inflation scalar field as the matter and taking into account only the
minimum curvature-inflation coupling term. Remarkably, after taking the
slow-roll approximation, the identical equations as in $f(R, T)$ gravity with a
$RT$ mixing term are derived. Several potentials of interest in different
domains are evaluated individually, calculating the slow-roll parameter and the
e-folding number $N$. Finally, we analyze the behavior of the inflation scalar
field under perturbation while ignoring the effect of metric perturbations.
This research complements the slow-roll inflation in the modified theory of
gravity.
| [
{
"created": "Wed, 23 Nov 2022 07:32:05 GMT",
"version": "v1"
}
] | 2024-03-18 | [
[
"Feng",
"Zhe",
""
]
] | In the framework of $f\left(R, T, R_{ab}T^{ab}\right)$ gravity theory, the slow-roll approximation of the cosmic inflation is investigated, where $T$ is the trace of the energy-momentum tensor $T^{ab}$, $R$ and $R_{ab}$ are the Ricci scalar and tensor, respectively. After obtaining the equations of motion of the gravitational field from the action principle in the spatially flat FLRW metric, the fundamental equations of this theory are received by introducing the inflation scalar field as the matter and taking into account only the minimum curvature-inflation coupling term. Remarkably, after taking the slow-roll approximation, the identical equations as in $f(R, T)$ gravity with a $RT$ mixing term are derived. Several potentials of interest in different domains are evaluated individually, calculating the slow-roll parameter and the e-folding number $N$. Finally, we analyze the behavior of the inflation scalar field under perturbation while ignoring the effect of metric perturbations. This research complements the slow-roll inflation in the modified theory of gravity. |
gr-qc/9706024 | David Langlois | David Langlois | Cosmological CMBR dipole in open universes ? | 26 pages, Latex, 6 figures, to appear in Phys. Rev. D | null | 10.1103/PhysRevD.55.7389 | 97009, Observatoire de Paris | gr-qc astro-ph | null | The observed CMBR dipole is generally interpreted as a Doppler effect arising
from the motion of the Earth relative to the CMBR frame. An alternative
interpretation, proposed in the last years, is that the dipole results from
ultra-large scale isocurvature perturbations. We examine this idea in the
context of open cosmologies and show that the isocurvature interpretation is
not valid in an open universe, unless it is extremely close to a flat universe,
$|\Omega_0 -1|< 10^{-4}$.
| [
{
"created": "Tue, 10 Jun 1997 21:27:36 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Langlois",
"David",
""
]
] | The observed CMBR dipole is generally interpreted as a Doppler effect arising from the motion of the Earth relative to the CMBR frame. An alternative interpretation, proposed in the last years, is that the dipole results from ultra-large scale isocurvature perturbations. We examine this idea in the context of open cosmologies and show that the isocurvature interpretation is not valid in an open universe, unless it is extremely close to a flat universe, $|\Omega_0 -1|< 10^{-4}$. |
1601.00631 | Salvatore Capozziello | S. Capozziello, O. Luongo, M. Paolella | Bounding $f(R)$ gravity by particle production rate | 10 pages, 3 figures, to appear in Int. Jou. Mod. Phys. D | null | 10.1142/S021827181630010X | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several models of $f(R)$ gravity have been proposed in order to address the
dark side problem in cosmology. However, these models should be constrained
also at ultraviolet scales in order to achieve some correct fundamental
interpretation. Here we analyze this possibility comparing quantum vacuum
states in given $f(R)$ cosmological backgrounds. Specifically, we compare the
Bogolubov transformations associated to different vacuum states for some $f(R)$
models. The procedure consists in fixing the $f(R)$ free parameters by
requiring that the Bogolubov coefficients can be correspondingly minimized to
be in agreement with both high redshift observations and quantum field theory
predictions. In such a way, the particle production is related to the value of
the Hubble parameter and then to the given $f(R)$ model. The approach is
developed in both metric and Palatini formalism.
| [
{
"created": "Mon, 4 Jan 2016 20:31:48 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Jan 2016 08:21:03 GMT",
"version": "v2"
}
] | 2016-03-23 | [
[
"Capozziello",
"S.",
""
],
[
"Luongo",
"O.",
""
],
[
"Paolella",
"M.",
""
]
] | Several models of $f(R)$ gravity have been proposed in order to address the dark side problem in cosmology. However, these models should be constrained also at ultraviolet scales in order to achieve some correct fundamental interpretation. Here we analyze this possibility comparing quantum vacuum states in given $f(R)$ cosmological backgrounds. Specifically, we compare the Bogolubov transformations associated to different vacuum states for some $f(R)$ models. The procedure consists in fixing the $f(R)$ free parameters by requiring that the Bogolubov coefficients can be correspondingly minimized to be in agreement with both high redshift observations and quantum field theory predictions. In such a way, the particle production is related to the value of the Hubble parameter and then to the given $f(R)$ model. The approach is developed in both metric and Palatini formalism. |
2403.17186 | Stefano Schmidt | Stefano Schmidt, Sarah Caudill, Jolien D. E. Creighton, Ryan Magee,
Leo Tsukada, Shomik Adhicary, Pratyusava Baral, Amanda Baylor, Kipp Cannon,
Bryce Cousins, Becca Ewing, Heather Fong, Richard N. George, Patrick Godwin,
Chad Hanna, Reiko Harada, Yun-Jing Huang, Rachael Huxford, Prathamesh Joshi,
James Kennington, Soichiro Kuwahara, Alvin K. Y. Li, Duncan Meacher, Cody
Messick, Soichiro Morisaki, Debnandini Mukherjee, Wanting Niu, Alex Pace,
Cort Posnansky, Anarya Ray, Surabhi Sachdev, Shio Sakon, Divya Singh, Ron
Tapia, Takuya Tsutsui, Koh Ueno, Aaron Viets, Leslie Wade and Madeline Wade | Searching for gravitational-wave signals from precessing black hole
binaries with the GstLAL pipeline | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Precession in Binary Black Holes (BBH) is caused by the failure of the Black
Hole spins to be aligned and its study can open up new perspectives in
gravitational waves (GW) astronomy, providing, among other advancements, a
precise measure of distance and an accurate characterization of the BBH spins.
However, detecting precessing signals is a highly non-trivial task, as standard
matched filtering pipelines for GW searches are built on many assumptions that
do not hold in the precessing case. This work details the upgrades made to the
GstLAL pipeline to facilitate the search for precessing BBH signals. The
implemented changes in the search statistics and in the signal consistency test
are then described in detail. The performance of the upgraded pipeline is
evaluated through two extensive searches of precessing signals, targeting two
different regions in the mass space, and the consistency of the results is
examined. Additionally, the benefits of the upgrades are assessed by comparing
the sensitive volume of the precessing searches with two corresponding
traditional aligned-spin searches. While no significant sensitivity improvement
is observed for precessing binaries with mass ratio $q\lesssim 6$, a volume
increase of up to 100\% is attainable for heavily asymmetric systems with
largely misaligned spins. Furthermore, our findings suggest that the primary
cause of degraded performance in an aligned-spin search targeting precessing
signals is not a poor signal-to-noise-ratio recovery but rather the failure of
the $\xi^2$ signal-consistency test. Our work paves the way for a large-scale
search for precessing signals, which could potentially result in exciting
future detections.
| [
{
"created": "Mon, 25 Mar 2024 20:55:13 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Jun 2024 08:31:23 GMT",
"version": "v2"
}
] | 2024-07-01 | [
[
"Schmidt",
"Stefano",
""
],
[
"Caudill",
"Sarah",
""
],
[
"Creighton",
"Jolien D. E.",
""
],
[
"Magee",
"Ryan",
""
],
[
"Tsukada",
"Leo",
""
],
[
"Adhicary",
"Shomik",
""
],
[
"Baral",
"Pratyusava",
""
],
[
"Baylor",
"Amanda",
""
],
[
"Cannon",
"Kipp",
""
],
[
"Cousins",
"Bryce",
""
],
[
"Ewing",
"Becca",
""
],
[
"Fong",
"Heather",
""
],
[
"George",
"Richard N.",
""
],
[
"Godwin",
"Patrick",
""
],
[
"Hanna",
"Chad",
""
],
[
"Harada",
"Reiko",
""
],
[
"Huang",
"Yun-Jing",
""
],
[
"Huxford",
"Rachael",
""
],
[
"Joshi",
"Prathamesh",
""
],
[
"Kennington",
"James",
""
],
[
"Kuwahara",
"Soichiro",
""
],
[
"Li",
"Alvin K. Y.",
""
],
[
"Meacher",
"Duncan",
""
],
[
"Messick",
"Cody",
""
],
[
"Morisaki",
"Soichiro",
""
],
[
"Mukherjee",
"Debnandini",
""
],
[
"Niu",
"Wanting",
""
],
[
"Pace",
"Alex",
""
],
[
"Posnansky",
"Cort",
""
],
[
"Ray",
"Anarya",
""
],
[
"Sachdev",
"Surabhi",
""
],
[
"Sakon",
"Shio",
""
],
[
"Singh",
"Divya",
""
],
[
"Tapia",
"Ron",
""
],
[
"Tsutsui",
"Takuya",
""
],
[
"Ueno",
"Koh",
""
],
[
"Viets",
"Aaron",
""
],
[
"Wade",
"Leslie",
""
],
[
"Wade",
"Madeline",
""
]
] | Precession in Binary Black Holes (BBH) is caused by the failure of the Black Hole spins to be aligned and its study can open up new perspectives in gravitational waves (GW) astronomy, providing, among other advancements, a precise measure of distance and an accurate characterization of the BBH spins. However, detecting precessing signals is a highly non-trivial task, as standard matched filtering pipelines for GW searches are built on many assumptions that do not hold in the precessing case. This work details the upgrades made to the GstLAL pipeline to facilitate the search for precessing BBH signals. The implemented changes in the search statistics and in the signal consistency test are then described in detail. The performance of the upgraded pipeline is evaluated through two extensive searches of precessing signals, targeting two different regions in the mass space, and the consistency of the results is examined. Additionally, the benefits of the upgrades are assessed by comparing the sensitive volume of the precessing searches with two corresponding traditional aligned-spin searches. While no significant sensitivity improvement is observed for precessing binaries with mass ratio $q\lesssim 6$, a volume increase of up to 100\% is attainable for heavily asymmetric systems with largely misaligned spins. Furthermore, our findings suggest that the primary cause of degraded performance in an aligned-spin search targeting precessing signals is not a poor signal-to-noise-ratio recovery but rather the failure of the $\xi^2$ signal-consistency test. Our work paves the way for a large-scale search for precessing signals, which could potentially result in exciting future detections. |
1501.07781 | Ott Vilson | Laur Jarv, Piret Kuusk, Margus Saal and Ott Vilson | Parametrizations in scalar-tensor theories of gravity and the limit of
general relativity | 14 pages | J. Phys. Conf. Ser. 532, 012011 (2014) | 10.1088/1742-6596/532/1/012011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a general scalar-tensor theory of gravity and review briefly
different forms it can be presented (different conformal frames and scalar
field parametrizations). We investigate the conditions under which its field
equations and the parametrized post-Newtonian parameters coincide with those of
general relativity. We demonstrate that these so-called limits of general
relativity are independent of the parametrization of the scalar field, although
the transformation between scalar fields may be singular at the corresponding
value of the scalar field. In particular, the limit of general relativity can
equivalently be determined and investigated in the commonly used Jordan and
Einstein frames.
| [
{
"created": "Fri, 30 Jan 2015 14:13:17 GMT",
"version": "v1"
}
] | 2015-02-02 | [
[
"Jarv",
"Laur",
""
],
[
"Kuusk",
"Piret",
""
],
[
"Saal",
"Margus",
""
],
[
"Vilson",
"Ott",
""
]
] | We consider a general scalar-tensor theory of gravity and review briefly different forms it can be presented (different conformal frames and scalar field parametrizations). We investigate the conditions under which its field equations and the parametrized post-Newtonian parameters coincide with those of general relativity. We demonstrate that these so-called limits of general relativity are independent of the parametrization of the scalar field, although the transformation between scalar fields may be singular at the corresponding value of the scalar field. In particular, the limit of general relativity can equivalently be determined and investigated in the commonly used Jordan and Einstein frames. |
1608.05948 | Oldrich Semerak | O. Semer\'ak and M. Basovn\'ik | On geometry of deformed black holes: I. Majumdar-Papapetrou binary | 18 pages, 9 figures | Physical Review D 94, 044006 (2016) | 10.1103/PhysRevD.94.044006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Although black holes are eminent manifestations of very strong gravity, the
geometry of space-time around and even inside them can be significantly
affected by additional bodies present in their surroundings. We study such an
influence within static and axially symmetric (electro-)vacuum space-times
described by exact solutions of Einstein's equations, considering
astrophysically motivated configurations (such as black holes surrounded by
rings) as well as those of pure academic interest (such as specifically "tuned"
systems of multiple black holes). The geometry is represented by the simplest
invariants determined by the metric (the lapse function) and its gradient
(gravitational acceleration), with special emphasis given to curvature (the
Kretschmann and Ricci-square scalars). These quantities are analyzed and their
level surfaces plotted both above and below the black-hole horizons, in
particular near the central singularities. Estimating that the black hole could
be most strongly affected by the other black hole, we focus, in this first
paper, on the Majumdar--Papapetrou solution for a binary black hole and compare
the deformation caused by "the other" hole (and the electrostatic field) with
that induced by rotational dragging in the well-known Kerr and Kerr--Newman
solutions.
| [
{
"created": "Sun, 21 Aug 2016 14:37:11 GMT",
"version": "v1"
}
] | 2016-08-23 | [
[
"Semerák",
"O.",
""
],
[
"Basovník",
"M.",
""
]
] | Although black holes are eminent manifestations of very strong gravity, the geometry of space-time around and even inside them can be significantly affected by additional bodies present in their surroundings. We study such an influence within static and axially symmetric (electro-)vacuum space-times described by exact solutions of Einstein's equations, considering astrophysically motivated configurations (such as black holes surrounded by rings) as well as those of pure academic interest (such as specifically "tuned" systems of multiple black holes). The geometry is represented by the simplest invariants determined by the metric (the lapse function) and its gradient (gravitational acceleration), with special emphasis given to curvature (the Kretschmann and Ricci-square scalars). These quantities are analyzed and their level surfaces plotted both above and below the black-hole horizons, in particular near the central singularities. Estimating that the black hole could be most strongly affected by the other black hole, we focus, in this first paper, on the Majumdar--Papapetrou solution for a binary black hole and compare the deformation caused by "the other" hole (and the electrostatic field) with that induced by rotational dragging in the well-known Kerr and Kerr--Newman solutions. |
2202.03230 | Jose M. Isidro | J.C. Castro-Palacio, P. Fernandez de Cordoba, R. Gallego Torrome and
J.M. Isidro | Hyperbolic space in the Newtonian limit: the cosmological constant | 12 pp; refs. added | null | 10.1142/S0218271822500729 | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | The cosmological constant and the Boltzmann entropy of a Newtonian Universe
filled with a perfect fluid are computed, under the assumption that spatial
sections are copies of 3-dimensional hyperbolic space.
| [
{
"created": "Mon, 7 Feb 2022 14:35:22 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Feb 2022 12:20:52 GMT",
"version": "v2"
}
] | 2022-09-07 | [
[
"Castro-Palacio",
"J. C.",
""
],
[
"de Cordoba",
"P. Fernandez",
""
],
[
"Torrome",
"R. Gallego",
""
],
[
"Isidro",
"J. M.",
""
]
] | The cosmological constant and the Boltzmann entropy of a Newtonian Universe filled with a perfect fluid are computed, under the assumption that spatial sections are copies of 3-dimensional hyperbolic space. |
0809.1250 | Slava G. Turyshev | Slava G. Turyshev | Relativistic gravitational deflection of light and its impact on the
modeling accuracy for the Space Interferometry Mission | revtex4, 20 pages, 9 figures, 13 tables | Astron.Lett.35:215-234,2009 | 10.1134/S106377370904001X | null | gr-qc | http://creativecommons.org/licenses/publicdomain/ | We study the impact of relativistic gravitational deflection of light on the
accuracy of future Space Interferometry Mission (SIM). We estimate the
deflection angles caused by the monopole, quadrupole and octupole components of
gravitational fields for a number of celestial bodies in the solar system. We
observe that, in many cases, the magnitude of the corresponding effects is
significantly larger than the 1 uas accuracy expected from SIM. This fact
argues for the development of a relativistic observational model for the
mission that would account for the influence of both static and time-varying
effects of gravity on light propagation. Results presented here are different
from the ones obtained elsewhere by the fact that we specifically account for
the differential nature of the future SIM astrometric measurements. We also
obtain an estimate for the accuracy of possible determination of the
Eddington's parameter \gamma via SIM global astrometric campaign; we conclude
that accuracy of ~7 x 10^{-6} is achievable via measurements of deflection of
light by solar gravity.
| [
{
"created": "Sun, 7 Sep 2008 20:50:51 GMT",
"version": "v1"
}
] | 2009-07-24 | [
[
"Turyshev",
"Slava G.",
""
]
] | We study the impact of relativistic gravitational deflection of light on the accuracy of future Space Interferometry Mission (SIM). We estimate the deflection angles caused by the monopole, quadrupole and octupole components of gravitational fields for a number of celestial bodies in the solar system. We observe that, in many cases, the magnitude of the corresponding effects is significantly larger than the 1 uas accuracy expected from SIM. This fact argues for the development of a relativistic observational model for the mission that would account for the influence of both static and time-varying effects of gravity on light propagation. Results presented here are different from the ones obtained elsewhere by the fact that we specifically account for the differential nature of the future SIM astrometric measurements. We also obtain an estimate for the accuracy of possible determination of the Eddington's parameter \gamma via SIM global astrometric campaign; we conclude that accuracy of ~7 x 10^{-6} is achievable via measurements of deflection of light by solar gravity. |
gr-qc/0507049 | Gamal Nashed G.L. | Gamal G.L. Nashed | Energy distribution of Kerr spacetime using Moller energy momentum
complex | 8 pages, Latex | Nuovo Cim. B119 (2004) 967 | 10.1393/ncb/i2004-10132-8 | null | gr-qc | null | Using the energy momentum complex given by M{\o}ller in 1978 based on the
absolute parallelism, the energy distribution in Kerr spacetime is evaluated.
The energy with this spacetime is found to be the same as it was earlier
evaluated using different definitions mainly based on the metric tensor.
| [
{
"created": "Tue, 12 Jul 2005 09:25:29 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Nashed",
"Gamal G. L.",
""
]
] | Using the energy momentum complex given by M{\o}ller in 1978 based on the absolute parallelism, the energy distribution in Kerr spacetime is evaluated. The energy with this spacetime is found to be the same as it was earlier evaluated using different definitions mainly based on the metric tensor. |
1912.11909 | Naveena Kumara A | A. Naveena Kumara, C.L. Ahmed Rizwan, Shreyas Punacha, Ajith K.M. and
Md Sabir Ali | Photon Orbits and Thermodynamic Phase Transition of Regular AdS Black
Holes | Thoroughly revised. 12 pages, 11 figures | Phys. Rev. D 102, 084059 (2020) | 10.1103/PhysRevD.102.084059 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We probe the phase structure of the regular AdS black holes using the null
geodesics. The radius of photon orbit and minimum impact parameter shows a
non-monotonous behaviour below the critical values of the temperature and the
pressure, corresponding to the phase transition in extended phase space. The
respective differences of the radius of unstable circular orbit and the minimum
impact parameter can be seen as the order parameter for the small-large black
hole phase transition, with a critical exponent $1/2$. Our study shows that
there exists a close relationship between the gravity and thermodynamics for
the regular AdS black holes.
| [
{
"created": "Thu, 26 Dec 2019 18:15:12 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Sep 2020 06:47:59 GMT",
"version": "v2"
}
] | 2020-11-04 | [
[
"Kumara",
"A. Naveena",
""
],
[
"Rizwan",
"C. L. Ahmed",
""
],
[
"Punacha",
"Shreyas",
""
],
[
"M.",
"Ajith K.",
""
],
[
"Ali",
"Md Sabir",
""
]
] | We probe the phase structure of the regular AdS black holes using the null geodesics. The radius of photon orbit and minimum impact parameter shows a non-monotonous behaviour below the critical values of the temperature and the pressure, corresponding to the phase transition in extended phase space. The respective differences of the radius of unstable circular orbit and the minimum impact parameter can be seen as the order parameter for the small-large black hole phase transition, with a critical exponent $1/2$. Our study shows that there exists a close relationship between the gravity and thermodynamics for the regular AdS black holes. |
gr-qc/0101071 | Kimberly C. B. New | Kimberly C. B. New and Joan M. Centrella | Rotational Instabilities and Centrifugal Hangup | 13 pages (includes 11 figures) and 1 separate jpeg figure; to appear
in Astrophysical Sources of Gravitational Radiation, AIP conference
proceedings, edited by Joan M. Centrella | null | 10.1063/1.1387314 | LA-UR-00-5924 | gr-qc astro-ph | null | One interesting class of gravitational radiation sources includes rapidly
rotating astrophysical objects that encounter dynamical instabilities. We have
carried out a set of simulations of rotationally induced instabilities in
differentially rotating polytropes. An $n$=1.5 polytrope with the Maclaurin
rotation law will encounter the $m$=2 bar instability at $T/|W| \gtrsim 0.27$.
Our results indicate that the remnant of this instability is a persistent
bar-like structure that emits a long-lived gravitational radiation signal.
Furthermore, dynamical instability is shown to occur in $n$=3.33 polytropes
with the $j$-constant rotation law at $T/|W| \gtrsim 0.14$. In this case, the
dominant mode of instability is $m$=1. Such instability may allow a
centrifugally-hung core to begin collapsing to neutron star densities on a
dynamical timescale. If it occurs in a supermassive star, it may produce
gravitational radiation detectable by LISA.
| [
{
"created": "Wed, 17 Jan 2001 21:39:37 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"New",
"Kimberly C. B.",
""
],
[
"Centrella",
"Joan M.",
""
]
] | One interesting class of gravitational radiation sources includes rapidly rotating astrophysical objects that encounter dynamical instabilities. We have carried out a set of simulations of rotationally induced instabilities in differentially rotating polytropes. An $n$=1.5 polytrope with the Maclaurin rotation law will encounter the $m$=2 bar instability at $T/|W| \gtrsim 0.27$. Our results indicate that the remnant of this instability is a persistent bar-like structure that emits a long-lived gravitational radiation signal. Furthermore, dynamical instability is shown to occur in $n$=3.33 polytropes with the $j$-constant rotation law at $T/|W| \gtrsim 0.14$. In this case, the dominant mode of instability is $m$=1. Such instability may allow a centrifugally-hung core to begin collapsing to neutron star densities on a dynamical timescale. If it occurs in a supermassive star, it may produce gravitational radiation detectable by LISA. |
1708.05570 | D\'aniel Barta | D\'aniel Barta | Relativistic model for cold spherical interstellar gas clouds | null | AN 334, 9, 916-919 (2013) | 10.1002/asna.201211958 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate insterstellar gas spheres by determining the metric functions,
the material distribution, and the features of particle orbits in terms of
stability and geodesics. An exact solution of the Einstein's equations for
interstellar gas clouds is derived that is compatible with the results of
recent astronomical measurements. The solution determines the distribution of
pressure and density, and it is suitable to describe the energy, speed,
trajectory, and further relevant physical features of the cloud's particles. We
describe the spacetime inside the nebula and give the density profile and the
geodesics of particles. We find that circular orbits are stable and the cloud
rotates rigidly by an angular velocity that is inversely proportional to the
radius.
| [
{
"created": "Fri, 18 Aug 2017 11:54:03 GMT",
"version": "v1"
}
] | 2017-08-21 | [
[
"Barta",
"Dániel",
""
]
] | We investigate insterstellar gas spheres by determining the metric functions, the material distribution, and the features of particle orbits in terms of stability and geodesics. An exact solution of the Einstein's equations for interstellar gas clouds is derived that is compatible with the results of recent astronomical measurements. The solution determines the distribution of pressure and density, and it is suitable to describe the energy, speed, trajectory, and further relevant physical features of the cloud's particles. We describe the spacetime inside the nebula and give the density profile and the geodesics of particles. We find that circular orbits are stable and the cloud rotates rigidly by an angular velocity that is inversely proportional to the radius. |
2302.09284 | Ettore Minguzzi | E. Minguzzi | Further observations on the definition of global hyperbolicity under low
regularity | Latex, 11 pages | Class. Quantum Grav. 40 (2023) 185001 | 10.1088/1361-6382/acdd40 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The definitions of global hyperbolicity for closed cone structures and
topological preordered spaces are known to coincide. In this work we clarify
the connection with definitions of global hyperbolicity proposed in recent
literature on Lorentzian length spaces and Lorentzian optimal transport,
suggesting possible corrections for the terminology adopted in these works. It
is found that in Kunzinger-S\"amann's Lorentzian length spaces the definition
of global hyperbolicity coincides with that valid for closed cone structures
and, more generally, for topological preordered spaces: the causal relation is
a closed order and the causally convex hull operation preserves compactness. In
particular, it is independent of the metric, chronological relation or
Lorentzian distance.
| [
{
"created": "Sat, 18 Feb 2023 10:42:16 GMT",
"version": "v1"
}
] | 2023-08-10 | [
[
"Minguzzi",
"E.",
""
]
] | The definitions of global hyperbolicity for closed cone structures and topological preordered spaces are known to coincide. In this work we clarify the connection with definitions of global hyperbolicity proposed in recent literature on Lorentzian length spaces and Lorentzian optimal transport, suggesting possible corrections for the terminology adopted in these works. It is found that in Kunzinger-S\"amann's Lorentzian length spaces the definition of global hyperbolicity coincides with that valid for closed cone structures and, more generally, for topological preordered spaces: the causal relation is a closed order and the causally convex hull operation preserves compactness. In particular, it is independent of the metric, chronological relation or Lorentzian distance. |
2408.08139 | Shu Luo | Shu Luo | The quasinormal modes, pseudospectrum and time evolution of Proca fields
in qOS-dS spacetime | 19 pages, 35 figures. arXiv admin note: text overlap with
arXiv:2401.09907 by other authors | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this study, we investigate the quasinormal modes, pseudospectrum and time
evolution of a massive vector field around a quantum corrected black hole in
de-Sitter spacetime. We start by parameterization and using orthonormal tetrads
to get the effective potential. Methodologically we use the hyperboloidal
framework together with discretizing the non-selfadjoint operator through
Chebyshev-Gauss-Labatto grid to attain the QNMs. We explore the parametric
instability of QNMs caused by quantum correction, cosmological constant and
Proca mass, and these three factors show very different influences on the QNMs'
migration flow. On the other hand, we discuss the instability of QNMs with
arbitrary-shape perturbation and the effectiveness of numerical results through
pseudospectrum. We use high frequency approximation to attain the expression of
the time domain Green function and clarify the origin of two different stages
in time evolution. Through numerical methods we confirm that no power-law late
time tail is expected, and the possible impact on time evolution caused by
quantum correction is discussed.
| [
{
"created": "Thu, 15 Aug 2024 13:14:28 GMT",
"version": "v1"
}
] | 2024-08-16 | [
[
"Luo",
"Shu",
""
]
] | In this study, we investigate the quasinormal modes, pseudospectrum and time evolution of a massive vector field around a quantum corrected black hole in de-Sitter spacetime. We start by parameterization and using orthonormal tetrads to get the effective potential. Methodologically we use the hyperboloidal framework together with discretizing the non-selfadjoint operator through Chebyshev-Gauss-Labatto grid to attain the QNMs. We explore the parametric instability of QNMs caused by quantum correction, cosmological constant and Proca mass, and these three factors show very different influences on the QNMs' migration flow. On the other hand, we discuss the instability of QNMs with arbitrary-shape perturbation and the effectiveness of numerical results through pseudospectrum. We use high frequency approximation to attain the expression of the time domain Green function and clarify the origin of two different stages in time evolution. Through numerical methods we confirm that no power-law late time tail is expected, and the possible impact on time evolution caused by quantum correction is discussed. |
2301.06124 | Yang Zhang | Xuan Ye and Yang Zhang | Maxwell field with gauge fixing term in the radiation- and
matter-dominant stages: exact solution and stress tensor | 18 pages, add references, submitted, | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the Maxwell field with a general gauge fixing (GF) term in the
radiation-dominant (RD) and matter-dominant (MD) stages of expanding Universe,
as a continuation to the previous work in de Sitter space. We derive the exact
solutions, perform the covariant canonical quantization and obtain the stress
tensor in the Gupta-Bleuler (GB) physical states, which is independent of the
GF constant and is also invariant under the quantum residual gauge
transformation. The transverse stress tensor is similar in all flat
Robertson-Walker spacetimes, and its vacuum part is $\propto k^4$
and becomes zero after the 0th-order adiabatic regularization. The
longitudinal-temporal stress tensor, in both RD and MD stages, is zero due to a
cancelation between the longitudinal and temporal parts in the GB states, and
so is the particle part of the GF stress tensor. The vacuum GF stress tensor,
in the RD stage, contains $k^4,k^2$ divergences and becomes zero by the
2nd-order regularization, however, in the MD stage, contains $k^4, k^2, k^0$
divergences and becomes zero by the 4th-order regularization. So, the order of
adequate regularization depends not only upon the type of fields, but also upon
the background spacetimes. In summary, in both the RD and MD stages, like in de
Sitter space, the total regularized vacuum stress tensor is zero, only the
transverse photon part remains, and this holds independent of the GF term.
| [
{
"created": "Sun, 15 Jan 2023 15:44:11 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Jan 2023 15:49:05 GMT",
"version": "v2"
}
] | 2023-01-23 | [
[
"Ye",
"Xuan",
""
],
[
"Zhang",
"Yang",
""
]
] | We study the Maxwell field with a general gauge fixing (GF) term in the radiation-dominant (RD) and matter-dominant (MD) stages of expanding Universe, as a continuation to the previous work in de Sitter space. We derive the exact solutions, perform the covariant canonical quantization and obtain the stress tensor in the Gupta-Bleuler (GB) physical states, which is independent of the GF constant and is also invariant under the quantum residual gauge transformation. The transverse stress tensor is similar in all flat Robertson-Walker spacetimes, and its vacuum part is $\propto k^4$ and becomes zero after the 0th-order adiabatic regularization. The longitudinal-temporal stress tensor, in both RD and MD stages, is zero due to a cancelation between the longitudinal and temporal parts in the GB states, and so is the particle part of the GF stress tensor. The vacuum GF stress tensor, in the RD stage, contains $k^4,k^2$ divergences and becomes zero by the 2nd-order regularization, however, in the MD stage, contains $k^4, k^2, k^0$ divergences and becomes zero by the 4th-order regularization. So, the order of adequate regularization depends not only upon the type of fields, but also upon the background spacetimes. In summary, in both the RD and MD stages, like in de Sitter space, the total regularized vacuum stress tensor is zero, only the transverse photon part remains, and this holds independent of the GF term. |
2205.11629 | Miguel Sabido | A. Mart\'inez-Merino and M. Sabido | Cosmology and Non-additive Entropy | & pages, no figures | null | 10.1142/S021827182250136X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Non-additive entropies have been proposed as alternatives to understanding
the thermodynamics of Black Holes. Moreover, it has been suggested that the
difficulties of quantization of gravity are an indication that gravity is an
emergent phenomenon, and therefore an entropic formulation is warranted. In
this work, we explore cosmologies that come from non-additive entropies. We
focus our study on the cosmologies derived from entropies in superstatistics.
| [
{
"created": "Mon, 23 May 2022 20:57:27 GMT",
"version": "v1"
}
] | 2023-02-22 | [
[
"Martínez-Merino",
"A.",
""
],
[
"Sabido",
"M.",
""
]
] | Non-additive entropies have been proposed as alternatives to understanding the thermodynamics of Black Holes. Moreover, it has been suggested that the difficulties of quantization of gravity are an indication that gravity is an emergent phenomenon, and therefore an entropic formulation is warranted. In this work, we explore cosmologies that come from non-additive entropies. We focus our study on the cosmologies derived from entropies in superstatistics. |
2303.07661 | Guillem Dom\`enech | Guillem Dom\`enech and Misao Sasaki | Gravitational wave hints black hole remnants as dark matter | Note on the primordial black hole remnant scenario. 3 figures | null | 10.1088/1361-6382/ace493 | YITP-23-30 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The end state of Hawking evaporation of a black hole is uncertain. Some
candidate quantum gravity theories, such as loop quantum gravity and asymptotic
safe gravity, hint towards Planck sized remnants. If so, the Universe might be
filled with remnants of tiny primordial black holes, which formed with mass
$M<10^9\,{\rm g}$. A unique scenario is the case of $M\sim 5\times10^5\,{\rm
g}$, where tiny primordial black holes reheat the universe by Hawking
evaporation and their remnants dominate the dark matter. Here, we point out
that this scenario leads to a cosmological gravitational wave signal at
frequencies $\sim 100{\rm Hz}$. Finding such a particular gravitational wave
signature with, e.g. the Einstein Telescope, would suggest black hole remnants
as dark matter.
| [
{
"created": "Tue, 14 Mar 2023 07:06:07 GMT",
"version": "v1"
}
] | 2023-08-09 | [
[
"Domènech",
"Guillem",
""
],
[
"Sasaki",
"Misao",
""
]
] | The end state of Hawking evaporation of a black hole is uncertain. Some candidate quantum gravity theories, such as loop quantum gravity and asymptotic safe gravity, hint towards Planck sized remnants. If so, the Universe might be filled with remnants of tiny primordial black holes, which formed with mass $M<10^9\,{\rm g}$. A unique scenario is the case of $M\sim 5\times10^5\,{\rm g}$, where tiny primordial black holes reheat the universe by Hawking evaporation and their remnants dominate the dark matter. Here, we point out that this scenario leads to a cosmological gravitational wave signal at frequencies $\sim 100{\rm Hz}$. Finding such a particular gravitational wave signature with, e.g. the Einstein Telescope, would suggest black hole remnants as dark matter. |
2403.18740 | Swarnim Shirke | Swarnim Shirke, Bikram Keshari Pradhan, Debarati Chatterjee, Laura
Sagunski, J\"urgen Schaffner-Bielich | Effects of Dark Matter on $f$-mode oscillations of Neutron Stars | 24 pages, 22 figures, 5 tables | null | null | LIGO-P2400135 | gr-qc astro-ph.HE hep-ph nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The aim of this study is to investigate the effect of dark matter (DM) on
$f$-mode oscillations in DM admixed neutron stars (NSs). We consider hadronic
matter modeled by the relativistic mean field model and the DM model based on
the neutron decay anomaly. We study the non-radial $f$-mode oscillations for
such DM admixed NS in a full general relativistic framework. We investigate the
impact of DM, DM self-interaction, and DM fraction on the $f$-mode
characteristics. We derive relations encoding the effect of DM on $f$-mode
parameters. We then perform a systematic study by varying all the model
parameters within their known uncertainty range and obtain a universal relation
for the DM fraction based on the total mass of the star and DM self-interaction
strength. We also perform a correlation study among model parameters and NS
observables, in particular, $f$-mode parameters. Finally, we check the $f$-mode
universal relations (URs) for the case of DM admixed NSs and demonstrate the
existence of a degeneracy between purely hadronic NSs and DM admixed NSs.
| [
{
"created": "Wed, 27 Mar 2024 16:32:34 GMT",
"version": "v1"
}
] | 2024-04-04 | [
[
"Shirke",
"Swarnim",
""
],
[
"Pradhan",
"Bikram Keshari",
""
],
[
"Chatterjee",
"Debarati",
""
],
[
"Sagunski",
"Laura",
""
],
[
"Schaffner-Bielich",
"Jürgen",
""
]
] | The aim of this study is to investigate the effect of dark matter (DM) on $f$-mode oscillations in DM admixed neutron stars (NSs). We consider hadronic matter modeled by the relativistic mean field model and the DM model based on the neutron decay anomaly. We study the non-radial $f$-mode oscillations for such DM admixed NS in a full general relativistic framework. We investigate the impact of DM, DM self-interaction, and DM fraction on the $f$-mode characteristics. We derive relations encoding the effect of DM on $f$-mode parameters. We then perform a systematic study by varying all the model parameters within their known uncertainty range and obtain a universal relation for the DM fraction based on the total mass of the star and DM self-interaction strength. We also perform a correlation study among model parameters and NS observables, in particular, $f$-mode parameters. Finally, we check the $f$-mode universal relations (URs) for the case of DM admixed NSs and demonstrate the existence of a degeneracy between purely hadronic NSs and DM admixed NSs. |
2312.13954 | Ribhu Paul | Ribhu Paul, Sumanta Chakraborty | Singularity avoidance from path integral | 21 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have demonstrated that the wave functional describing the quantum nature
of the spacetime inside the black hole horizon, vanishes near the singularity,
using the path integral formalism. This is akin to the DeWitt criterion,
applied to the interior of a Schwarzschild black hole. To achieve the same we
have expressed the interior of a Schwarzschild black hole as a Kantowski-Sachs
spacetime and have applied the minisuperspace formalism to determine an exact
form of the propagator, and hence the wave function near the singularity, using
path integral over the reduced phase space. It is to be emphasized that our
result is exact and not a saddle point approximation to the path integral.
| [
{
"created": "Thu, 21 Dec 2023 15:41:10 GMT",
"version": "v1"
}
] | 2023-12-22 | [
[
"Paul",
"Ribhu",
""
],
[
"Chakraborty",
"Sumanta",
""
]
] | We have demonstrated that the wave functional describing the quantum nature of the spacetime inside the black hole horizon, vanishes near the singularity, using the path integral formalism. This is akin to the DeWitt criterion, applied to the interior of a Schwarzschild black hole. To achieve the same we have expressed the interior of a Schwarzschild black hole as a Kantowski-Sachs spacetime and have applied the minisuperspace formalism to determine an exact form of the propagator, and hence the wave function near the singularity, using path integral over the reduced phase space. It is to be emphasized that our result is exact and not a saddle point approximation to the path integral. |
1209.4698 | Myungseok Eune | Myungseok Eune, Bogeun Gwak, Wontae Kim | Local thermodynamics of KS black hole | 12 pages, 5 figures, final version, To be published in Physics
Letters B | Phys. Lett. B 718 (2013) 1505-1509 | 10.1016/j.physletb.2012.12.018 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the thermodynamics of the KS black hole which is an asymptotically
flat solution of the HL gravity. In particular, we introduce a cavity to
describe the thermodynamics at a finite isothermal surface on general ground
and to get a well-defined thermodynamics. We show that there exists a locally
stable small black hole which tunnels to the hot flat space below the critical
temperature and to the large black hole above the critical temperature.
Moreover, it turns out that the remnant decays into the vacuum through a
quantum tunneling.
| [
{
"created": "Fri, 21 Sep 2012 04:07:51 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Dec 2012 05:05:38 GMT",
"version": "v2"
}
] | 2013-01-18 | [
[
"Eune",
"Myungseok",
""
],
[
"Gwak",
"Bogeun",
""
],
[
"Kim",
"Wontae",
""
]
] | We study the thermodynamics of the KS black hole which is an asymptotically flat solution of the HL gravity. In particular, we introduce a cavity to describe the thermodynamics at a finite isothermal surface on general ground and to get a well-defined thermodynamics. We show that there exists a locally stable small black hole which tunnels to the hot flat space below the critical temperature and to the large black hole above the critical temperature. Moreover, it turns out that the remnant decays into the vacuum through a quantum tunneling. |
gr-qc/9605037 | Robin W. Tucker | J Schray, T Dray, C A Manogue, R W Tucker, C Wang | The Construction of Spinor Fields on Manifolds with Smooth Degenerate
Metrics | 24 pages, LaTeX (RevTeX 3.0, no figures), To appear in J. Math. Phys | J.Math.Phys. 37 (1996) 3882-3896 | 10.1063/1.531607 | null | gr-qc | null | We examine some of the subtleties inherent in formulating a theory of spinors
on a manifold with a smooth degenerate metric. We concentrate on the case where
the metric is singular on a hypersurface that partitions the manifold into
Lorentzian and Euclidean domains. We introduce the notion of a complex spinor
fibration to make precise the meaning of continuity of a spinor field and give
an expression for the components of a local spinor connection that is valid in
the absence of a frame of local orthonormal vectors. These considerations
enable one to construct a Dirac equation for the discussion of the behavior of
spinors in the vicinity of the metric degeneracy. We conclude that the theory
contains more freedom than the spacetime Dirac theory and we discuss some of
the implications of this for the continuity of conserved currents.
| [
{
"created": "Fri, 17 May 1996 13:17:30 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Schray",
"J",
""
],
[
"Dray",
"T",
""
],
[
"Manogue",
"C A",
""
],
[
"Tucker",
"R W",
""
],
[
"Wang",
"C",
""
]
] | We examine some of the subtleties inherent in formulating a theory of spinors on a manifold with a smooth degenerate metric. We concentrate on the case where the metric is singular on a hypersurface that partitions the manifold into Lorentzian and Euclidean domains. We introduce the notion of a complex spinor fibration to make precise the meaning of continuity of a spinor field and give an expression for the components of a local spinor connection that is valid in the absence of a frame of local orthonormal vectors. These considerations enable one to construct a Dirac equation for the discussion of the behavior of spinors in the vicinity of the metric degeneracy. We conclude that the theory contains more freedom than the spacetime Dirac theory and we discuss some of the implications of this for the continuity of conserved currents. |
1312.4625 | Jun-Qi Guo | Jun-Qi Guo, Daoyan Wang, Andrei V. Frolov | Spherical collapse in f(R) gravity and the
Belinskii-Khalatnikov-Lifshitz conjecture | Results in the Jordan frame and for the Starobinsky model are added,
see Sections V and VI. 27 pages, 14 figures | Phys. Rev. D 90, 024017 (2014) | 10.1103/PhysRevD.90.024017 | SCG-2013-08 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spherical scalar collapse in f(R) gravity is studied numerically in
double-null coordinates in the Einstein frame. Dynamics in the vicinity of the
singularity of the formed black hole is examined via mesh refinement and
asymptotic analysis. Before the collapse, the scalar degree of freedom f' is
coupled to a physical scalar field, and general relativity is restored. During
the collapse, the major energy of the physical scalar field moves to the
center. As a result, f' loses the coupling and becomes light, and gravity
transits from general relativity to f(R) gravity. Due to strong gravity from
the singularity and the low mass of f', f' will cross the minimum of the
potential and approach zero. Therefore, the dynamical solution is significantly
different from the static solution of the black hole in f(R) gravity---it is
not the de Sitter-Schwarzschild solution as one might have expected. f' tries
to suppress the evolution of the physical scalar field, which is a dark energy
effect. As the singularity is approached, metric terms are dominant over other
terms. The Kasner solution for spherical scalar collapse in f(R) theory is
obtained and confirmed by numerical results. These results support the
Belinskii-Khalatnikov-Lifshitz conjecture well.
| [
{
"created": "Tue, 17 Dec 2013 03:32:55 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Feb 2014 19:14:17 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Mar 2014 22:38:27 GMT",
"version": "v3"
},
{
"created": "Mon, 14 Jul 2014 19:11:05 GMT",
"version": "v4"
}
] | 2014-07-15 | [
[
"Guo",
"Jun-Qi",
""
],
[
"Wang",
"Daoyan",
""
],
[
"Frolov",
"Andrei V.",
""
]
] | Spherical scalar collapse in f(R) gravity is studied numerically in double-null coordinates in the Einstein frame. Dynamics in the vicinity of the singularity of the formed black hole is examined via mesh refinement and asymptotic analysis. Before the collapse, the scalar degree of freedom f' is coupled to a physical scalar field, and general relativity is restored. During the collapse, the major energy of the physical scalar field moves to the center. As a result, f' loses the coupling and becomes light, and gravity transits from general relativity to f(R) gravity. Due to strong gravity from the singularity and the low mass of f', f' will cross the minimum of the potential and approach zero. Therefore, the dynamical solution is significantly different from the static solution of the black hole in f(R) gravity---it is not the de Sitter-Schwarzschild solution as one might have expected. f' tries to suppress the evolution of the physical scalar field, which is a dark energy effect. As the singularity is approached, metric terms are dominant over other terms. The Kasner solution for spherical scalar collapse in f(R) theory is obtained and confirmed by numerical results. These results support the Belinskii-Khalatnikov-Lifshitz conjecture well. |
gr-qc/9509029 | null | Arthur M. Aslanyan | Gauge Fields with Quasinilpotent Gauge Group | 4 pages | null | null | -95-09 | gr-qc | null | We investigate non-linear generalization of Maxwell theory of electromagnetic
field keeping the gauge invariance of Lagrangian. New theory, which is standard
Yang-Mills theory, is based on Harmonic Oscillator HO(4,R) gauge group. It's a
solvable Lie group with nilpotent normal subgroup of codimension 1. We write
down the Yang-Mills equation and point out their pecularities and connection
with standard Maxwell theory.
| [
{
"created": "Mon, 18 Sep 1995 17:12:52 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Aslanyan",
"Arthur M.",
""
]
] | We investigate non-linear generalization of Maxwell theory of electromagnetic field keeping the gauge invariance of Lagrangian. New theory, which is standard Yang-Mills theory, is based on Harmonic Oscillator HO(4,R) gauge group. It's a solvable Lie group with nilpotent normal subgroup of codimension 1. We write down the Yang-Mills equation and point out their pecularities and connection with standard Maxwell theory. |
1209.1876 | James Kentosh | J. Kentosh and M. Mohageg | Reply to Comment on "Global positioning system test of the local
position invariance of Planck's constant" | 3 pages, no figures | Phys. Rev. Lett. 109, 068902 (2012) | 10.1103/PhysRevLett.109.068902 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We reply to a Comment [Berengut and Flambaum, Phys. Rev. Lett. 109, 068901
(2012), arXiv:1203.5592] on our recent Letter [Kentosh and Mohageg, Phys. Rev.
Lett. 108, 110801 (2012), arXiv:1203.0102]. The Comment objects to our work
partly because $h$ has dimensions and therefore measuring any variation of it
is meaningless. We reply that the relevance of dimensions in the study of
fundamental constants has been the subject of some debate. We also note that
our model differs from the one normally used to compare hydrogen masers and
cryogenic optical resonators. Ours is based on a different treatment of proper
length and energy to conform to general relativity. We also enclose in an
Appendix our transmittal to the editors of Physical Review Letters.
| [
{
"created": "Mon, 10 Sep 2012 03:57:38 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Kentosh",
"J.",
""
],
[
"Mohageg",
"M.",
""
]
] | We reply to a Comment [Berengut and Flambaum, Phys. Rev. Lett. 109, 068901 (2012), arXiv:1203.5592] on our recent Letter [Kentosh and Mohageg, Phys. Rev. Lett. 108, 110801 (2012), arXiv:1203.0102]. The Comment objects to our work partly because $h$ has dimensions and therefore measuring any variation of it is meaningless. We reply that the relevance of dimensions in the study of fundamental constants has been the subject of some debate. We also note that our model differs from the one normally used to compare hydrogen masers and cryogenic optical resonators. Ours is based on a different treatment of proper length and energy to conform to general relativity. We also enclose in an Appendix our transmittal to the editors of Physical Review Letters. |
gr-qc/0405031 | Christopher Wainwright | Chris Wainwright and Ruth M. Williams | Area Regge Calculus and Discontinuous Metrics | 18 pages, 1 figure | Class.Quant.Grav. 21 (2004) 4865-4880 | 10.1088/0264-9381/21/21/008 | DAMTP-2004-43 | gr-qc | null | Taking the triangle areas as independent variables in the theory of Regge
calculus can lead to ambiguities in the edge lengths, which can be interpreted
as discontinuities in the metric. We construct solutions to area Regge calculus
using a triangulated lattice and find that on a spacelike hypersurface no such
discontinuity can arise. On a null hypersurface however, we can have such a
situation and the resulting metric can be interpreted as a so-called refractive
wave.
| [
{
"created": "Thu, 6 May 2004 16:13:21 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Wainwright",
"Chris",
""
],
[
"Williams",
"Ruth M.",
""
]
] | Taking the triangle areas as independent variables in the theory of Regge calculus can lead to ambiguities in the edge lengths, which can be interpreted as discontinuities in the metric. We construct solutions to area Regge calculus using a triangulated lattice and find that on a spacelike hypersurface no such discontinuity can arise. On a null hypersurface however, we can have such a situation and the resulting metric can be interpreted as a so-called refractive wave. |
gr-qc/9403010 | null | Alexander Vilenkin | Approaches to Quantum Cosmology | 38 pages | Phys.Rev.D50:2581-2594,1994 | 10.1103/PhysRevD.50.2581 | null | gr-qc hep-th | null | Different proposals for the wave function of the universe are analyzed, with
an emphasis on various forms of the tunneling proposal. The issues discussed
include the equivalence of the Lorentzian path integral and outgoing-wave
proposals, the definitions of the outgoing waves and of superspace boundaries,
topology change and the corresponding modification of the Wheeler-DeWitt
equation. Also discussed are the "generic" boundary conditions and the third
quantization approach.
| [
{
"created": "Wed, 2 Mar 1994 20:35:00 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Vilenkin",
"Alexander",
""
]
] | Different proposals for the wave function of the universe are analyzed, with an emphasis on various forms of the tunneling proposal. The issues discussed include the equivalence of the Lorentzian path integral and outgoing-wave proposals, the definitions of the outgoing waves and of superspace boundaries, topology change and the corresponding modification of the Wheeler-DeWitt equation. Also discussed are the "generic" boundary conditions and the third quantization approach. |
2102.06041 | Ayan Banerjee | Sudan Hansraj, Megandhren Govender, Ayan Banerjee and Njabulo Mkhize | All Conformally Flat Einstein--Gauss--Bonnet static Metrics | 23 pages, 9 figures, accepted for publication in Class.Quant.Grav | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is known that the standard Schwarzschild interior metric is conformally
flat and generates a constant density sphere in any spacetime dimension in
Einstein and Einstein--Gauss--Bonnet gravity. This motivates the questions: In
EGB does the conformal flatness criterion yield the Schwarzschild metric? Does
the assumption of constant density generate the Schwarzschild interior
spacetime? The answer to both questions turn out in the negative in general. In
the case of the constant density sphere, a generalised Schwarzschild metric
emerges. When we invoke the conformal flatness condition the Schwarschild
interior solution is obtained as one solution and another metric which does not
yield a constant density hypersphere in EGB theory is found. For the latter
solution one of the gravitational metrics is obtained explicitly while the
other is determined up to quadratures in 5 and 6 dimensions. The physical
properties of these new solutions are studied with the use of numerical methods
and a parameter space is located for which both models display pleasing
physical behaviour.
| [
{
"created": "Wed, 10 Feb 2021 09:18:40 GMT",
"version": "v1"
}
] | 2021-02-12 | [
[
"Hansraj",
"Sudan",
""
],
[
"Govender",
"Megandhren",
""
],
[
"Banerjee",
"Ayan",
""
],
[
"Mkhize",
"Njabulo",
""
]
] | It is known that the standard Schwarzschild interior metric is conformally flat and generates a constant density sphere in any spacetime dimension in Einstein and Einstein--Gauss--Bonnet gravity. This motivates the questions: In EGB does the conformal flatness criterion yield the Schwarzschild metric? Does the assumption of constant density generate the Schwarzschild interior spacetime? The answer to both questions turn out in the negative in general. In the case of the constant density sphere, a generalised Schwarzschild metric emerges. When we invoke the conformal flatness condition the Schwarschild interior solution is obtained as one solution and another metric which does not yield a constant density hypersphere in EGB theory is found. For the latter solution one of the gravitational metrics is obtained explicitly while the other is determined up to quadratures in 5 and 6 dimensions. The physical properties of these new solutions are studied with the use of numerical methods and a parameter space is located for which both models display pleasing physical behaviour. |
0909.3176 | Young-Jai Park | Yong-Wan Kim, Jaedong Choi, and Young-Jai Park | Local free-fall temperature of a RN-AdS black hole | 18 pages, 11 figures, version to appear in Int. J. Mod. Phys. A | Int.J.Mod.Phys.A25:3107-3120,2010 | 10.1142/S0217751X10049311 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the global embedding Minkowski space (GEMS) geometries of a
(3+1)-dimensional curved Reissner-Nordstr\"om(RN)-AdS black hole spacetime into
a (5+2)-dimensional flat spacetime to define a proper local temperature, which
remains finite at the event horizon, for freely falling observers outside a
static black hole. Our extended results include the known limiting cases of the
RN, Schwarzschild--AdS, and Schwarzschild black holes.
| [
{
"created": "Thu, 17 Sep 2009 10:04:32 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Sep 2009 06:13:15 GMT",
"version": "v2"
},
{
"created": "Tue, 9 Mar 2010 05:41:13 GMT",
"version": "v3"
}
] | 2014-11-20 | [
[
"Kim",
"Yong-Wan",
""
],
[
"Choi",
"Jaedong",
""
],
[
"Park",
"Young-Jai",
""
]
] | We use the global embedding Minkowski space (GEMS) geometries of a (3+1)-dimensional curved Reissner-Nordstr\"om(RN)-AdS black hole spacetime into a (5+2)-dimensional flat spacetime to define a proper local temperature, which remains finite at the event horizon, for freely falling observers outside a static black hole. Our extended results include the known limiting cases of the RN, Schwarzschild--AdS, and Schwarzschild black holes. |
gr-qc/0004030 | Jing Wang | Anupam Mazumdar and Jing Wang | A Note on Brane Inflation | 5 pages, Latex. A footnote added, new references added | Phys.Lett. B490 (2000) 251-257 | 10.1016/S0370-2693(00)00741-3 | null | gr-qc hep-ph hep-th | null | We demonstrate that there exists an inflationary solution on the positive
tension brane in the Randall-Sundrum scenario. Inflation is driven by a
slow-rolling scalar field on the brane and is achieved within the perturbative
limit of the radion field. We find that inflation on the positive tension brane
results in a slight increase in the separation between the two branes. However,
we show that the slow-roll inflation is not possible on the negative tension
brane.
| [
{
"created": "Mon, 10 Apr 2000 15:15:44 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Apr 2000 21:50:33 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Mazumdar",
"Anupam",
""
],
[
"Wang",
"Jing",
""
]
] | We demonstrate that there exists an inflationary solution on the positive tension brane in the Randall-Sundrum scenario. Inflation is driven by a slow-rolling scalar field on the brane and is achieved within the perturbative limit of the radion field. We find that inflation on the positive tension brane results in a slight increase in the separation between the two branes. However, we show that the slow-roll inflation is not possible on the negative tension brane. |
gr-qc/0101072 | Mattias Marklund | M. Bradley, G. Fodor, M. Marklund and Z. Perjes | Some results on the integrability of Einstein's field equations for
axistationary perfect fluids | 2 pages, contribution to the 9th Marcel Grossmann meeting (MG9),
Rome, July 2000 | null | 10.1142/9789812777386_0061 | null | gr-qc | null | Using an orthonormal Lorentz frame approach to axistationary perfect fluid
spacetimes, we have formulated the necessary and sufficient equations as a
first order system, and investigated the integrability conditions of this set
of equations. The integrability conditions are helpful tools when it comes to
check the consequences and/or compatibility of certain simplifying assumptions,
e.g. Petrov types. Furthermore, using this method, a relation between the fluid
shear and vorticity is found for barotropic fluids. We collect some results
concerning Petrov types, and it is found that an incompressible axistationary
perfect fluid must be of Petrov type I.
| [
{
"created": "Wed, 17 Jan 2001 16:31:04 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Bradley",
"M.",
""
],
[
"Fodor",
"G.",
""
],
[
"Marklund",
"M.",
""
],
[
"Perjes",
"Z.",
""
]
] | Using an orthonormal Lorentz frame approach to axistationary perfect fluid spacetimes, we have formulated the necessary and sufficient equations as a first order system, and investigated the integrability conditions of this set of equations. The integrability conditions are helpful tools when it comes to check the consequences and/or compatibility of certain simplifying assumptions, e.g. Petrov types. Furthermore, using this method, a relation between the fluid shear and vorticity is found for barotropic fluids. We collect some results concerning Petrov types, and it is found that an incompressible axistationary perfect fluid must be of Petrov type I. |
1011.2832 | Sushant Ghosh Prof | Sushant G. Ghosh, L. P. Singh | Gravitating magnetic monopole in Vaidya geometry | 5 RevTeX pages, no figures, minor changes, to appear in Physical
Review D | Phys.Rev.D83:067501,2011 | 10.1103/PhysRevD.83.067501 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A magnetic-monopole solution of a non-Abelian gauge theory as proposed by 't
Hooft and Polyakov is studied in the Vaidya spacetime. We find that the
solutions of Einstein equations generates a geometry of the Bonnor-Vaidya
corresponding to magnetically charged null fluid with Higgs field contributing
a cosmological term. In the absence of the scalar fields the corresponding
Wu-Yang solution of the gauge theory still generates the Bonnor-Vaidya
geometry, but with no cosmological term.
| [
{
"created": "Fri, 12 Nov 2010 05:20:18 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Mar 2011 04:33:21 GMT",
"version": "v2"
}
] | 2011-03-22 | [
[
"Ghosh",
"Sushant G.",
""
],
[
"Singh",
"L. P.",
""
]
] | A magnetic-monopole solution of a non-Abelian gauge theory as proposed by 't Hooft and Polyakov is studied in the Vaidya spacetime. We find that the solutions of Einstein equations generates a geometry of the Bonnor-Vaidya corresponding to magnetically charged null fluid with Higgs field contributing a cosmological term. In the absence of the scalar fields the corresponding Wu-Yang solution of the gauge theory still generates the Bonnor-Vaidya geometry, but with no cosmological term. |
2405.20240 | Khireddine Nouicer | Sihem zabat, Youcef Kehal and Khireddine Nouicer | Alleviating the $H_0$ and $\sigma_8$ tensions in the interacting cubic
covariant Galileon model | 35 pages, 7 figures, 5 tables | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The interaction between dark matter and dark energy has become a focal point
in contemporary cosmological research, particularly in addressing current
cosmological tensions. This study explores the cubic Galileon model's
interaction with dark matter, where the interaction potential in the dark
sector is proportional to the dark energy density of the Galileon field. By
employing dimensionless variables, we transform the field equations into an
autonomous dynamical system. We calculate the critical points of the
corresponding autonomous systems and demonstrate the existence of a stable de
Sitter epoch. Our investigation proceeds in two phases. First, we conduct a
detailed analysis of the exact interacting cubic Galileon (ICG) model, derived
from the precise solution of the equations of motion. Second, we explore an
approximate tracker solution, labeled TICG, assuming a small coupling parameter
between dark matter and dark energy. We evaluate the evolution of these models
using data from two experiments, aiming to resolve the tensions surrounding
$H_0$ and $S_8$. The analysis of the TICG model indicates a preference for a
phantom regime and provides a negative coupling parameter in the dark sector at
a $68\%$ confidence level. This model also shows that the current tensions
regarding $H_0$ and $S_8$ are alleviated. Conversely, the ICG model, despite
its preference for the phantom regime, is plagued by an excess in today's
matter density and a higher expansion rate, easing only the $H_0$ tension.
| [
{
"created": "Thu, 30 May 2024 16:44:03 GMT",
"version": "v1"
}
] | 2024-05-31 | [
[
"zabat",
"Sihem",
""
],
[
"Kehal",
"Youcef",
""
],
[
"Nouicer",
"Khireddine",
""
]
] | The interaction between dark matter and dark energy has become a focal point in contemporary cosmological research, particularly in addressing current cosmological tensions. This study explores the cubic Galileon model's interaction with dark matter, where the interaction potential in the dark sector is proportional to the dark energy density of the Galileon field. By employing dimensionless variables, we transform the field equations into an autonomous dynamical system. We calculate the critical points of the corresponding autonomous systems and demonstrate the existence of a stable de Sitter epoch. Our investigation proceeds in two phases. First, we conduct a detailed analysis of the exact interacting cubic Galileon (ICG) model, derived from the precise solution of the equations of motion. Second, we explore an approximate tracker solution, labeled TICG, assuming a small coupling parameter between dark matter and dark energy. We evaluate the evolution of these models using data from two experiments, aiming to resolve the tensions surrounding $H_0$ and $S_8$. The analysis of the TICG model indicates a preference for a phantom regime and provides a negative coupling parameter in the dark sector at a $68\%$ confidence level. This model also shows that the current tensions regarding $H_0$ and $S_8$ are alleviated. Conversely, the ICG model, despite its preference for the phantom regime, is plagued by an excess in today's matter density and a higher expansion rate, easing only the $H_0$ tension. |
2311.03093 | Jafar Khodagholizadeh | Jafar Khodagholizadeh | Constraints on Dark Energy from the Gravitational Wave Background | 24 pages. arXiv admin note: text overlap with arXiv:2208.06844 | Eur. Phys. J. C (2023) 83: 988 | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | Current observational data indicate that dark energy (DE) is a cosmological
constant without considering its conclusiveness evidence. Considering the
dynamic nature of $\Lambda$ individually as a function of time and the scale
factor, we review their effects on the gravitational waves. This article is a
continuation of the previous work \textit{JHEAp 36 (2022) 48-54}, in which DE
only was based on Hubble's parameter and/or its derivatives. For the DE model
based on the scale factor ($a^{-m}$), the results showed that the parameter $m$
is more limited as $ 2 < m \leqslant 3$ compared with the other models and due
to the small value of DE density at the early universe. It is only in the mode
$m=3$ that DE affects the low-frequency gravitational waves when its frequency
is less than the $10^{-3}$Hz in a matter-dominated epoch. The broad bound on
reducing the amplitude and the "B-B" polarization multipole coefficients, from
maximum to minimum, is for the models developed based on the Hubble parameter
function. There are primary sources of low- and very low-frequency GWs, such as
the coalescence of massive black hole binaries with $M_{bh} > 10^{3} M_{sun}$,
to determine the type of DE by mHz frequency space experiments (e.g., LISA) and
by nHz-range NANOGrav 15-year data.
| [
{
"created": "Mon, 6 Nov 2023 13:35:46 GMT",
"version": "v1"
}
] | 2023-11-07 | [
[
"Khodagholizadeh",
"Jafar",
""
]
] | Current observational data indicate that dark energy (DE) is a cosmological constant without considering its conclusiveness evidence. Considering the dynamic nature of $\Lambda$ individually as a function of time and the scale factor, we review their effects on the gravitational waves. This article is a continuation of the previous work \textit{JHEAp 36 (2022) 48-54}, in which DE only was based on Hubble's parameter and/or its derivatives. For the DE model based on the scale factor ($a^{-m}$), the results showed that the parameter $m$ is more limited as $ 2 < m \leqslant 3$ compared with the other models and due to the small value of DE density at the early universe. It is only in the mode $m=3$ that DE affects the low-frequency gravitational waves when its frequency is less than the $10^{-3}$Hz in a matter-dominated epoch. The broad bound on reducing the amplitude and the "B-B" polarization multipole coefficients, from maximum to minimum, is for the models developed based on the Hubble parameter function. There are primary sources of low- and very low-frequency GWs, such as the coalescence of massive black hole binaries with $M_{bh} > 10^{3} M_{sun}$, to determine the type of DE by mHz frequency space experiments (e.g., LISA) and by nHz-range NANOGrav 15-year data. |
0906.4428 | John J. Oh | John J. Oh and Chanyong Park | Gravitational Collapse of the Shells with the Smeared Gravitational
Source in Noncommutative Geometry | 16 pages, LateX, 9 figures, Title changed in this published version | JHEP 1003:086,2010 | 10.1007/JHEP03(2010)086 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the formation of the (noncommutative) Schwarzschild black hole from
collapsing shell {of the} generalized matters containing polytropic and
Chaplygin gas. We show that this collapsing shell depending on various
parameters forms either a black hole or a naked singular shell with the help of
the pressure.Furthermore, by considering the smeared gravitational sources, we
investigate the noncommutative black holes formation. Though this mild
noncommutative correction of matters cannot ultimately resolve the emergence of
the naked singularity, we show that in some parameter region the collapsing
shell evolves to a noncommutative black hole before becoming a naked singular
shell.
| [
{
"created": "Wed, 24 Jun 2009 09:03:57 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Apr 2010 06:36:03 GMT",
"version": "v2"
}
] | 2010-05-12 | [
[
"Oh",
"John J.",
""
],
[
"Park",
"Chanyong",
""
]
] | We study the formation of the (noncommutative) Schwarzschild black hole from collapsing shell {of the} generalized matters containing polytropic and Chaplygin gas. We show that this collapsing shell depending on various parameters forms either a black hole or a naked singular shell with the help of the pressure.Furthermore, by considering the smeared gravitational sources, we investigate the noncommutative black holes formation. Though this mild noncommutative correction of matters cannot ultimately resolve the emergence of the naked singularity, we show that in some parameter region the collapsing shell evolves to a noncommutative black hole before becoming a naked singular shell. |
gr-qc/0302074 | Paulo M. S\' a | Paulo M. S\'a | Polytropic stars in three-dimensional spacetime | 3 pages, revtex | Phys.Lett. B467 (1999) 40 | 10.1016/S0370-2693(99)01181-8 | null | gr-qc | null | We investigate three-dimensional perfect fluid stars with polytropic equation
of state, matched to the exterior three-dimensional black hole geometry of
Banados, Teitelboim and Zanelli. A new class of exact solutions for a generic
polytropic index is found and analysed.
| [
{
"created": "Tue, 18 Feb 2003 16:03:07 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Sá",
"Paulo M.",
""
]
] | We investigate three-dimensional perfect fluid stars with polytropic equation of state, matched to the exterior three-dimensional black hole geometry of Banados, Teitelboim and Zanelli. A new class of exact solutions for a generic polytropic index is found and analysed. |
1901.07104 | Leonardo Chataignier | Leonardo Chataignier | Gauge Fixing and the Semiclassical Interpretation of Quantum Cosmology | 32+13 pages, no figures. v2: updated references, minor typos
corrected, conceptual clarifications added, published in Zeitschrift f\"ur
Naturforschung A | Z. Naturforsch. A 74 (2019) 1069 | 10.1515/zna-2019-0223 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We make a critical review of the semiclassical interpretation of quantum
cosmology and emphasise that it is not necessary to consider that a concept of
time emerges only when the gravitational field is (semi)classical. We show that
the usual results of the semiclassical interpretation, and its generalisation
known as the Born-Oppenheimer approach to quantum cosmology, can be obtained by
gauge fixing, both at the classical and quantum levels. By `gauge fixing' we
mean a particular choice of the time coordinate, which determines the arbitrary
Lagrange multiplier that appears in Hamilton's equations. In the quantum
theory, we adopt a tentative definition of the (Klein-Gordon) inner product,
which is positive definite for solutions of the quantum constraint equation
found via an iterative procedure that corresponds to a weak coupling expansion
in powers of the inverse Planck mass. We conclude that the wave function should
be interpreted as a state vector for both gravitational and matter degrees of
freedom, the dynamics of which is unitary with respect to the chosen inner
product and time variable.
| [
{
"created": "Mon, 21 Jan 2019 22:29:23 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Aug 2019 00:00:14 GMT",
"version": "v2"
}
] | 2019-12-10 | [
[
"Chataignier",
"Leonardo",
""
]
] | We make a critical review of the semiclassical interpretation of quantum cosmology and emphasise that it is not necessary to consider that a concept of time emerges only when the gravitational field is (semi)classical. We show that the usual results of the semiclassical interpretation, and its generalisation known as the Born-Oppenheimer approach to quantum cosmology, can be obtained by gauge fixing, both at the classical and quantum levels. By `gauge fixing' we mean a particular choice of the time coordinate, which determines the arbitrary Lagrange multiplier that appears in Hamilton's equations. In the quantum theory, we adopt a tentative definition of the (Klein-Gordon) inner product, which is positive definite for solutions of the quantum constraint equation found via an iterative procedure that corresponds to a weak coupling expansion in powers of the inverse Planck mass. We conclude that the wave function should be interpreted as a state vector for both gravitational and matter degrees of freedom, the dynamics of which is unitary with respect to the chosen inner product and time variable. |
gr-qc/0203003 | Adrian Ottewill | P.C.W. Davies and Adrian C. Ottewill | Detection of negative energy: 4-dimensional examples | 10 pages, 7 figures | Phys.Rev. D65 (2002) 104014 | 10.1103/PhysRevD.65.104014 | null | gr-qc | null | We study the response of switched particle detectors to static negative
energy densities and negative energy fluxes. It is demonstrated how the
switching leads to excitation even in the vacuum and how negative energy can
lead to a suppression of this excitation. We obtain quantum inequalities on the
detection similar to those obtained for the energy density by Ford and
co-workers and in an `operational' context by Helfer. We revisit the question
`Is there a quantum equivalence principle?' in terms of our model. Finally, we
briefly address the issue of negative energy and the second law of
thermodynamics.
| [
{
"created": "Fri, 1 Mar 2002 12:44:14 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Davies",
"P. C. W.",
""
],
[
"Ottewill",
"Adrian C.",
""
]
] | We study the response of switched particle detectors to static negative energy densities and negative energy fluxes. It is demonstrated how the switching leads to excitation even in the vacuum and how negative energy can lead to a suppression of this excitation. We obtain quantum inequalities on the detection similar to those obtained for the energy density by Ford and co-workers and in an `operational' context by Helfer. We revisit the question `Is there a quantum equivalence principle?' in terms of our model. Finally, we briefly address the issue of negative energy and the second law of thermodynamics. |
2404.02129 | David Wiltshire | David L. Wiltshire | Solution to the cosmological constant problem | 8 pages, 3 figures, Essay for the Gravity Research Foundation 2024 | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | I propose an observationally and theoretically consistent resolution of the
cosmological constant problem: $\Lambda$ is a counterterm -- with a running
coupling -- that balances the monopole celestial sky average of the kinetic
energy of expansion of inhomogeneously distributed `small' cosmic voids. No
other dark energy source is required. This solution relies on the first
investigation of void statistics in cosmological simulations in full general
relativity (arXiv:2403.15134). Results are consistent with parameters of the
Timescape model of cosmological backreaction. Crucially, dynamical spatial
curvature arises as time-varying spatial gradients of the kinetic spatial
curvature, and depends directly on the void volume fraction. Its monopole
average generates the cosmological term. This result potentially resolves the
Hubble tension and offers new approaches to tackling other tensions and
anomalies.
| [
{
"created": "Tue, 2 Apr 2024 17:35:58 GMT",
"version": "v1"
}
] | 2024-04-03 | [
[
"Wiltshire",
"David L.",
""
]
] | I propose an observationally and theoretically consistent resolution of the cosmological constant problem: $\Lambda$ is a counterterm -- with a running coupling -- that balances the monopole celestial sky average of the kinetic energy of expansion of inhomogeneously distributed `small' cosmic voids. No other dark energy source is required. This solution relies on the first investigation of void statistics in cosmological simulations in full general relativity (arXiv:2403.15134). Results are consistent with parameters of the Timescape model of cosmological backreaction. Crucially, dynamical spatial curvature arises as time-varying spatial gradients of the kinetic spatial curvature, and depends directly on the void volume fraction. Its monopole average generates the cosmological term. This result potentially resolves the Hubble tension and offers new approaches to tackling other tensions and anomalies. |
2003.12291 | Rahul Kumar | Sushant G. Ghosh and Rahul Kumar | Generating black holes in $4D$ Einstein-Gauss-Bonnet gravity | 12 pages and 1 table. Minor typos corrected and accepted in Classical
Quantum Gravity | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In recent times there is a surge of interest in constructing
Einstein-Gauss-Bonnet (EGB) gravity, in the limit $D \to 4 $, of the
$D$-dimensional EGB gravity. Interestingly, the static spherically symmetric
solutions in the various proposed $D \to 4 $ regularized EGB gravities
coincide, and incidentally some other theories also admit the same solution. We
prove a theorem that characterizes a large family of nonstatic or radiating
spherically symmetric solutions to the $4D$ EGB gravity, representing, in
general, spherically symmetric Type II fluid. An extension of the theorem,
given without proof as being similar to the original theorem, generates static
spherically symmetric black hole solutions of the theory. It not only enables
us to identify available known black hole solutions as particular cases but
also to generate several new solutions of the $4D$ EGB gravity.
| [
{
"created": "Fri, 27 Mar 2020 09:17:23 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Oct 2020 15:10:46 GMT",
"version": "v2"
},
{
"created": "Sun, 18 Oct 2020 07:00:57 GMT",
"version": "v3"
}
] | 2020-10-20 | [
[
"Ghosh",
"Sushant G.",
""
],
[
"Kumar",
"Rahul",
""
]
] | In recent times there is a surge of interest in constructing Einstein-Gauss-Bonnet (EGB) gravity, in the limit $D \to 4 $, of the $D$-dimensional EGB gravity. Interestingly, the static spherically symmetric solutions in the various proposed $D \to 4 $ regularized EGB gravities coincide, and incidentally some other theories also admit the same solution. We prove a theorem that characterizes a large family of nonstatic or radiating spherically symmetric solutions to the $4D$ EGB gravity, representing, in general, spherically symmetric Type II fluid. An extension of the theorem, given without proof as being similar to the original theorem, generates static spherically symmetric black hole solutions of the theory. It not only enables us to identify available known black hole solutions as particular cases but also to generate several new solutions of the $4D$ EGB gravity. |
gr-qc/0702069 | John J. Oh | Seungjoon Hyun, Jaehoon Jeong, Wontae Kim, John J. Oh | Formation of Five-Dimensional String Solutions from the Gravitational
Collapse | 17 pages, 10 figures, LaTeX, to appear in Class. Quant. Grav., a
appendix and some discussions added, title changed | Class.Quant.Grav.24:3465-3478,2007 | 10.1088/0264-9381/24/13/020 | null | gr-qc hep-th | null | We study the formation of five-dimensional string solutions including the
Gregory-Laflamme (GL) black string, the Kaluza-Klein (KK) bubble, and the
geometry with a naked singularity from the gravitational collapse. The interior
solutions of five-dimensional Einstein equations describe collapsing
non-isotropic matter clouds. It is shown that the matter cloud always forms the
GL black string solution while the KK bubble solution cannot be formed. The
numerical study seems to suggest that the collapsing matter forms the
geometries with timelike naked curvature singularities, which should be taken
cautiously as the general relativity is not reliable in the strong curvature
regime.
| [
{
"created": "Tue, 13 Feb 2007 02:12:12 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Mar 2007 07:32:52 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Jun 2007 03:10:04 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Hyun",
"Seungjoon",
""
],
[
"Jeong",
"Jaehoon",
""
],
[
"Kim",
"Wontae",
""
],
[
"Oh",
"John J.",
""
]
] | We study the formation of five-dimensional string solutions including the Gregory-Laflamme (GL) black string, the Kaluza-Klein (KK) bubble, and the geometry with a naked singularity from the gravitational collapse. The interior solutions of five-dimensional Einstein equations describe collapsing non-isotropic matter clouds. It is shown that the matter cloud always forms the GL black string solution while the KK bubble solution cannot be formed. The numerical study seems to suggest that the collapsing matter forms the geometries with timelike naked curvature singularities, which should be taken cautiously as the general relativity is not reliable in the strong curvature regime. |
gr-qc/0601107 | Volodymyr Pelykh | Volodymyr Pelykh | Comment on "Self-dual teleparallel formulation of general relativity and
the positive energy theorem" G. Y. Chee | 3 pages | Phys.Rev.D72:108502,2005 | 10.1103/PhysRevD.72.108502 | null | gr-qc | null | We give a correct tensor proof of the positive energy problem for the case
including momentum on basis of conditions of existence of the two-to-one
correspondence between the Sen-Witten spinor field and the Sen-Witten
orthonormal frame. These conditions were obtained in our previous publications,
but true significance of our works was not estimated properly by G.Y.Chee, and
these were not correct quoted in his publication. On other hand, the main
result of our work is key argument in favour of geometrical nature of the
Sen-Witten spinor field.
| [
{
"created": "Wed, 25 Jan 2006 15:32:00 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Pelykh",
"Volodymyr",
""
]
] | We give a correct tensor proof of the positive energy problem for the case including momentum on basis of conditions of existence of the two-to-one correspondence between the Sen-Witten spinor field and the Sen-Witten orthonormal frame. These conditions were obtained in our previous publications, but true significance of our works was not estimated properly by G.Y.Chee, and these were not correct quoted in his publication. On other hand, the main result of our work is key argument in favour of geometrical nature of the Sen-Witten spinor field. |
1801.00009 | Hong Lu | Wei-Jian Geng, Shou-Long Li, H. Lu and Hao Wei | Godel Metrics with Chronology Protection in Horndeski Gravities | Latex, 11 pages, references added | null | 10.1016/j.physletb.2018.02.075 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | G\"odel universe, one of the most interesting exact solutions predicted by
General Relativity, describes a homogeneous rotating universe containing naked
closed time-like curves (CTCs). It was shown that such CTCs are the consequence
of the null energy condition in General Relativity. In this paper, we show that
the G\"odel-type metrics with chronology protection can emerge in
Einstein-Horndeski gravity. We construct such exact solutions also in
Einstein-Horndeski-Maxwell and Einstein-Horndeski-Proca theories.
| [
{
"created": "Fri, 29 Dec 2017 19:00:02 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jan 2018 15:18:06 GMT",
"version": "v2"
}
] | 2018-03-14 | [
[
"Geng",
"Wei-Jian",
""
],
[
"Li",
"Shou-Long",
""
],
[
"Lu",
"H.",
""
],
[
"Wei",
"Hao",
""
]
] | G\"odel universe, one of the most interesting exact solutions predicted by General Relativity, describes a homogeneous rotating universe containing naked closed time-like curves (CTCs). It was shown that such CTCs are the consequence of the null energy condition in General Relativity. In this paper, we show that the G\"odel-type metrics with chronology protection can emerge in Einstein-Horndeski gravity. We construct such exact solutions also in Einstein-Horndeski-Maxwell and Einstein-Horndeski-Proca theories. |
gr-qc/0002032 | Norbert Wex | N. Wex (MPIfR, Bonn) | Small-eccentricity binary pulsars and relativistic gravity | 4 pages, to be published in Proc. of IAU Colloq. 177, "Pulsar
Astronomy - 2000 and Beyond", eds. M. Kramer, N. Wex & R. Wielebinski | null | null | null | gr-qc | null | Small-eccentricity binary pulsars with white dwarf companions provide
excellent test laboratories for various effects predicted by alternative
theories of gravity, in particular tests for the emission of gravitational
dipole radiation and the existence of gravitational Stark effects. We will
present new limits to these effects. The statistical analysis presented here,
for the first time, takes appropriately care of selection effects.
| [
{
"created": "Mon, 7 Feb 2000 21:38:58 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Wex",
"N.",
"",
"MPIfR, Bonn"
]
] | Small-eccentricity binary pulsars with white dwarf companions provide excellent test laboratories for various effects predicted by alternative theories of gravity, in particular tests for the emission of gravitational dipole radiation and the existence of gravitational Stark effects. We will present new limits to these effects. The statistical analysis presented here, for the first time, takes appropriately care of selection effects. |
2204.05712 | Subenoy Chakraborty | A. Bose, S. Chakraborty | Does fractal Universe favour warm inflation: Observational support? | null | Nucl. Phys. B 978, 115767 (2022) | 10.1016/j.nuclphysb.2022.115767 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present work examines the possibility of warm inflationary paradigm in
the modified gravity theory with fractal geometry. By choosing the normal fluid
as radiation fluid and the effective fluid (with the extra term in modified
field equation) as the inflaton field both strong and weak dissipative regimes
have been studied using slow roll approximation with quasi-stable criteria for
radiation. Finally, using the Planck data set, the present model has been
analyzed for various choices of the fractal function and the dissipation
parameter.
| [
{
"created": "Tue, 12 Apr 2022 11:14:19 GMT",
"version": "v1"
}
] | 2022-04-14 | [
[
"Bose",
"A.",
""
],
[
"Chakraborty",
"S.",
""
]
] | The present work examines the possibility of warm inflationary paradigm in the modified gravity theory with fractal geometry. By choosing the normal fluid as radiation fluid and the effective fluid (with the extra term in modified field equation) as the inflaton field both strong and weak dissipative regimes have been studied using slow roll approximation with quasi-stable criteria for radiation. Finally, using the Planck data set, the present model has been analyzed for various choices of the fractal function and the dissipation parameter. |
1711.10618 | Alberto Escalante | Alberto Escalante (1), Melissa Rodr\'iguez-Z\'arate (2) ((1) Puebla
U., Inst. Fis., (2) Puebla U., Mexico) | Canonical and Symplectic analysis of actions describing linearized
gravity | null | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By using the canonical and symplectic approaches an (nonstandard) alternative
action describing linearized gravity is studied. We identify the complete set
of Dirac's constraints, the counting of physical degrees of freedom is
performed and the Dirac brackets are constructed. Furthermore, the symplectic
analysis is developed which includes the complete set of Faddeev-Jackiw
constraints and a symplectic tensor; from that symplectic matrix we show that
the generalized Faddeev-Jackiw brackets and the Dirac ones coincide to each
other. With all these results at hand, we prove that the number of physical
degrees of freedom are eight, thus, we conclude that the theory does not
describe the dynamics of linearized gravity. In addition, we also develop the
symplectic analysis of standard linearized gravity and we compare the results
for both standard and nonstandard theories. Finally we present some remarks and
conclusions.
| [
{
"created": "Tue, 28 Nov 2017 23:46:10 GMT",
"version": "v1"
}
] | 2017-11-30 | [
[
"Escalante",
"Alberto",
""
],
[
"Rodríguez-Zárate",
"Melissa",
""
]
] | By using the canonical and symplectic approaches an (nonstandard) alternative action describing linearized gravity is studied. We identify the complete set of Dirac's constraints, the counting of physical degrees of freedom is performed and the Dirac brackets are constructed. Furthermore, the symplectic analysis is developed which includes the complete set of Faddeev-Jackiw constraints and a symplectic tensor; from that symplectic matrix we show that the generalized Faddeev-Jackiw brackets and the Dirac ones coincide to each other. With all these results at hand, we prove that the number of physical degrees of freedom are eight, thus, we conclude that the theory does not describe the dynamics of linearized gravity. In addition, we also develop the symplectic analysis of standard linearized gravity and we compare the results for both standard and nonstandard theories. Finally we present some remarks and conclusions. |
1906.05455 | Hector O. Silva | Kostas Glampedakis and Hector O. Silva | Eikonal quasinormal modes of black holes beyond General Relativity | 12 pages, 1 figure. Updated to match the published version and it
includes a more rigorous implementation of the eikonal approximation | Phys. Rev. D 100, 044040 (2019) | 10.1103/PhysRevD.100.044040 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Much of our physical intuition about black hole quasinormal modes in general
relativity comes from the eikonal/geometric optics approximation. According to
the well-established eikonal model, the fundamental quasinormal mode represents
wavepackets orbiting in the vicinity of the black hole's geodesic photon ring,
slowly peeling off towards the event horizon and infinity. Besides its strength
as a "visualisation" tool, the eikonal approximation also provides a simple
quantitative method for calculating the mode frequency, in close agreement with
rigorous numerical results. In this paper we move away from Einstein's theory
and its garden-variety black holes and go on to consider spherically symmetric
black holes in modified theories of gravity through the lens of the eikonal
approximation. The quasinormal modes of such black holes are typically
described by a set of coupled wave equations for the various field degrees of
freedom. Considering a general, theory-agnostic, system of two equations for
two perturbed fields, we derive eikonal formulae for the complex fundamental
quasinormal mode frequency. In addition we show that the eikonal modes can be
related to the extremum of an effective potential and its associated "photon
ring". As an application of our results we consider a specific example of a
modified theory of gravity with known black hole quasinormal modes and find
that these are well approximated by the eikonal formulae.
| [
{
"created": "Thu, 13 Jun 2019 02:10:59 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Aug 2019 19:40:41 GMT",
"version": "v2"
}
] | 2019-08-28 | [
[
"Glampedakis",
"Kostas",
""
],
[
"Silva",
"Hector O.",
""
]
] | Much of our physical intuition about black hole quasinormal modes in general relativity comes from the eikonal/geometric optics approximation. According to the well-established eikonal model, the fundamental quasinormal mode represents wavepackets orbiting in the vicinity of the black hole's geodesic photon ring, slowly peeling off towards the event horizon and infinity. Besides its strength as a "visualisation" tool, the eikonal approximation also provides a simple quantitative method for calculating the mode frequency, in close agreement with rigorous numerical results. In this paper we move away from Einstein's theory and its garden-variety black holes and go on to consider spherically symmetric black holes in modified theories of gravity through the lens of the eikonal approximation. The quasinormal modes of such black holes are typically described by a set of coupled wave equations for the various field degrees of freedom. Considering a general, theory-agnostic, system of two equations for two perturbed fields, we derive eikonal formulae for the complex fundamental quasinormal mode frequency. In addition we show that the eikonal modes can be related to the extremum of an effective potential and its associated "photon ring". As an application of our results we consider a specific example of a modified theory of gravity with known black hole quasinormal modes and find that these are well approximated by the eikonal formulae. |
gr-qc/9310032 | Max Tegmark | Max Tegmark | Apparent wave function collapse caused by scattering | Final published version. 20 pages, Plain TeX, no figures. Online at
http://astro.berkeley.edu/~max/collapse.html (faster from the US), from
http://www.mpa-garching.mpg.de/~max/collapse.html (faster from Europe) or
from max@mppmu.mpg.de | Found. Phys. Lett., 6, 571-590 (1993) | 10.1007/BF00662807 | null | gr-qc | null | Some experimental implications of the recent progress on wave function
collapse are calculated. Exact results are derived for the center-of-mass wave
function collapse caused by random scatterings and applied to a range of
specific examples. The results show that recently proposed experiments to
measure the GRW effect are likely to fail, since the effect of naturally
occurring scatterings is of the same form as the GRW effect but generally much
stronger. The same goes for attempts to measure the collapse caused by quantum
gravity as suggested by Hawking and others. The results also indicate that
macroscopic systems tend to be found in states with (Delta-x)(Delta-p) =
hbar/sqrt(2), but microscopic systems in highly tiltedly squeezed states with
(Delta-x)(Delta-p) >> hbar.
| [
{
"created": "Mon, 25 Oct 1993 06:47:37 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Mar 1996 16:23:32 GMT",
"version": "v2"
}
] | 2009-10-22 | [
[
"Tegmark",
"Max",
""
]
] | Some experimental implications of the recent progress on wave function collapse are calculated. Exact results are derived for the center-of-mass wave function collapse caused by random scatterings and applied to a range of specific examples. The results show that recently proposed experiments to measure the GRW effect are likely to fail, since the effect of naturally occurring scatterings is of the same form as the GRW effect but generally much stronger. The same goes for attempts to measure the collapse caused by quantum gravity as suggested by Hawking and others. The results also indicate that macroscopic systems tend to be found in states with (Delta-x)(Delta-p) = hbar/sqrt(2), but microscopic systems in highly tiltedly squeezed states with (Delta-x)(Delta-p) >> hbar. |
2108.02974 | Lijing Shao | Ziming Wang, Lijing Shao, Chang Liu | New limits on the Lorentz/CPT symmetry through fifty gravitational-wave
events | 7 pages, 2 figures, 2 tables; accepted by ApJ | ApJ 921 (2021) 158 | 10.3847/1538-4357/ac223c | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Lorentz invariance plays a fundamental role in modern physics. However, tiny
violations of the Lorentz invariance may arise in some candidate quantum
gravity theories. Prominent signatures of the gravitational Lorentz invariance
violation (gLIV) include anisotropy, dispersion, and birefringence in the
dispersion relation of gravitational waves (GWs). Using a total of 50 GW events
in the GW transient catalogs GWTC-1 and GWTC-2, we perform an analysis on the
anisotropic birefringence phenomenon. The use of multiple events allows us to
completely break the degeneracy among gLIV coefficients and globally constrain
the coefficient space. Compared to previous results at mass dimensions 5 and 6
for the Lorentz-violating operators, we tighten the global limits of 34
coefficients by factors ranging from $2$ to $7$.
| [
{
"created": "Fri, 6 Aug 2021 06:59:26 GMT",
"version": "v1"
},
{
"created": "Sat, 28 Aug 2021 06:16:18 GMT",
"version": "v2"
}
] | 2021-11-12 | [
[
"Wang",
"Ziming",
""
],
[
"Shao",
"Lijing",
""
],
[
"Liu",
"Chang",
""
]
] | Lorentz invariance plays a fundamental role in modern physics. However, tiny violations of the Lorentz invariance may arise in some candidate quantum gravity theories. Prominent signatures of the gravitational Lorentz invariance violation (gLIV) include anisotropy, dispersion, and birefringence in the dispersion relation of gravitational waves (GWs). Using a total of 50 GW events in the GW transient catalogs GWTC-1 and GWTC-2, we perform an analysis on the anisotropic birefringence phenomenon. The use of multiple events allows us to completely break the degeneracy among gLIV coefficients and globally constrain the coefficient space. Compared to previous results at mass dimensions 5 and 6 for the Lorentz-violating operators, we tighten the global limits of 34 coefficients by factors ranging from $2$ to $7$. |
gr-qc/0302058 | Kouji Nakamura | Kouji Nakamura, Ken-ichi Nakao, and Takeshi Mishima | Hoop Conjecture and Black Holes on a Brane | 7 pages, 1 figure, To be published in Progress of Theoretical Physics
Supplement No. 148 "Brane World: New Perspective in Cosmology" | Prog.Theor.Phys.Suppl.148:291-297,2003 | 10.1143/PTPS.148.291 | NAOJ-Th-Ap 2002, No.14 | gr-qc astro-ph hep-ph hep-th | null | The initial data of gravity for a cylindrical matter distribution confined to
a brane are studied in the framework of the single-brane Randall-Sundrum
scenario. In this scenario, the 5-dimensional nature of gravity appears in the
short-range gravitational interaction. We find that a sufficiently thin
configuration of matter leads to the formation of a marginal surface, even if
the configuration is infinitely long. This implies that the hoop conjecture
proposed by Thorne does not hold on the brane: Even if a mass $M$ does not
become compacted into a region whose circumference ${\cal C}$ in every
direction satisfies ${\cal C}> 4\pi GM$, black holes with horizons can form in
the Randall-Sundrum scenario.
| [
{
"created": "Fri, 14 Feb 2003 06:22:11 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Nakamura",
"Kouji",
""
],
[
"Nakao",
"Ken-ichi",
""
],
[
"Mishima",
"Takeshi",
""
]
] | The initial data of gravity for a cylindrical matter distribution confined to a brane are studied in the framework of the single-brane Randall-Sundrum scenario. In this scenario, the 5-dimensional nature of gravity appears in the short-range gravitational interaction. We find that a sufficiently thin configuration of matter leads to the formation of a marginal surface, even if the configuration is infinitely long. This implies that the hoop conjecture proposed by Thorne does not hold on the brane: Even if a mass $M$ does not become compacted into a region whose circumference ${\cal C}$ in every direction satisfies ${\cal C}> 4\pi GM$, black holes with horizons can form in the Randall-Sundrum scenario. |
gr-qc/0312055 | Campo David | David Campo and Renaud Parentani | Space-time correlations in inflationary spectra, a wave packet analysis | revised version, accepted for publication in PRD ; the
complementarity and the usefullness of wave packet analysis have been
emphasized ; 32 pages, 6 figures | Phys.Rev. D70 (2004) 105020 | 10.1103/PhysRevD.70.105020 | null | gr-qc astro-ph hep-th | null | The inflationary mechanism of mode amplification predicts that the state of
each mode with a given wave vector is correlated to that of its partner mode
with the opposite vector. This implies nonlocal correlations which leave their
imprint on temperature anisotropies in the cosmic microwave background. Their
spatial properties are best revealed by using local wave packets. This analysis
shows that all density fluctuations giving rise the large scale structures
originate in pairs which are born near the reheating. In fact each local
density fluctuation is paired with an oppositely moving partner with opposite
amplitude. To obtain these results we first apply a ``wave packet
transformation'' with respect to one argument of the two point correlation
function. A finer understanding of the correlations is then reached by making
use of coherent states. The knowledge of the velocity field is required to
extract the contribution of a single pair of wave packets. Otherwise, there is
a two-folded degeneracy which gives three aligned wave packets arising from two
pairs. The applicability of these methods to observational data is briefly
discussed.
| [
{
"created": "Tue, 9 Dec 2003 17:01:55 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Jul 2004 14:26:22 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Campo",
"David",
""
],
[
"Parentani",
"Renaud",
""
]
] | The inflationary mechanism of mode amplification predicts that the state of each mode with a given wave vector is correlated to that of its partner mode with the opposite vector. This implies nonlocal correlations which leave their imprint on temperature anisotropies in the cosmic microwave background. Their spatial properties are best revealed by using local wave packets. This analysis shows that all density fluctuations giving rise the large scale structures originate in pairs which are born near the reheating. In fact each local density fluctuation is paired with an oppositely moving partner with opposite amplitude. To obtain these results we first apply a ``wave packet transformation'' with respect to one argument of the two point correlation function. A finer understanding of the correlations is then reached by making use of coherent states. The knowledge of the velocity field is required to extract the contribution of a single pair of wave packets. Otherwise, there is a two-folded degeneracy which gives three aligned wave packets arising from two pairs. The applicability of these methods to observational data is briefly discussed. |
gr-qc/0304084 | Harihar Behera | Harihar Behera and P. C. Naik | Gravitomagnetic Moments and Dynamics of Dirac's (spin 1/2) fermions in
flat space-time Maxwellian Gravity | 27 pages | Int.J.Mod.Phys. A19 (2004) 4207-4230 | 10.1142/S0217751X04017768 | null | gr-qc | null | The gravitational effects in the relativistic quantum mechanics are
investigated in a relativistically derived version of Heaviside's speculative
Gravity (in flat space-time) named here as Maxwellian Gravity. The standard
Dirac's approach to the intrinsic spin in the fields of Maxwellian Gravity
yields the gravitomagnetic moment of a Dirac (spin 1/2) particle exactly equals
to its intrinsic spin. Violation of The Equivalence Principle (both at
classical and quantum mechanical level) in the relativistic domain has also
been reported in this work.
| [
{
"created": "Tue, 22 Apr 2003 18:53:28 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Apr 2003 20:04:19 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Behera",
"Harihar",
""
],
[
"Naik",
"P. C.",
""
]
] | The gravitational effects in the relativistic quantum mechanics are investigated in a relativistically derived version of Heaviside's speculative Gravity (in flat space-time) named here as Maxwellian Gravity. The standard Dirac's approach to the intrinsic spin in the fields of Maxwellian Gravity yields the gravitomagnetic moment of a Dirac (spin 1/2) particle exactly equals to its intrinsic spin. Violation of The Equivalence Principle (both at classical and quantum mechanical level) in the relativistic domain has also been reported in this work. |
1109.6140 | Walter Simon | Walter Simon | Bounds on area and charge for marginally trapped surfaces with
cosmological constant | minor corrections to previous version and to published version | 2012 Class. Quantum Grav. 29 062001 | 10.1088/0264-9381/29/6/062001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We sharpen the known inequalities $A \Lambda \le 4\pi (1-g)$ and $A\ge 4\pi
Q^2$ between the area $A$ and the electric charge $Q$ of a stable marginally
outer trapped surface (MOTS) of genus g in the presence of a cosmological
constant $\Lambda$. In particular, instead of requiring stability we include
the principal eigenvalue $\lambda$ of the stability operator. For $\Lambda^{*}
= \Lambda + \lambda > 0$ we obtain a lower and an upper bound for $ \Lambda^{*}
A$ in terms of $ \Lambda^{*} Q^2$ as well as the upper bound $ Q \le
1/(2\sqrt{\Lambda^{*}})$ for the charge, which reduces to $ Q \le
1/(2\sqrt{\Lambda})$ in the stable case $\lambda \ge 0$. For $\Lambda^{*} < 0$
there remains only a lower bound on $A$. In the spherically symmetric, static,
stable case one of the area inequalities is saturated iff the surface gravity
vanishes. We also discuss implications of our inequalities for "jumps" and
mergers of charged MOTS.
| [
{
"created": "Wed, 28 Sep 2011 09:26:23 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Dec 2011 16:37:51 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Dec 2011 11:44:55 GMT",
"version": "v3"
},
{
"created": "Mon, 9 Jan 2012 11:29:17 GMT",
"version": "v4"
},
{
"created": "Thu, 3 May 2012 09:24:00 GMT",
"version": "v5"
}
] | 2012-05-04 | [
[
"Simon",
"Walter",
""
]
] | We sharpen the known inequalities $A \Lambda \le 4\pi (1-g)$ and $A\ge 4\pi Q^2$ between the area $A$ and the electric charge $Q$ of a stable marginally outer trapped surface (MOTS) of genus g in the presence of a cosmological constant $\Lambda$. In particular, instead of requiring stability we include the principal eigenvalue $\lambda$ of the stability operator. For $\Lambda^{*} = \Lambda + \lambda > 0$ we obtain a lower and an upper bound for $ \Lambda^{*} A$ in terms of $ \Lambda^{*} Q^2$ as well as the upper bound $ Q \le 1/(2\sqrt{\Lambda^{*}})$ for the charge, which reduces to $ Q \le 1/(2\sqrt{\Lambda})$ in the stable case $\lambda \ge 0$. For $\Lambda^{*} < 0$ there remains only a lower bound on $A$. In the spherically symmetric, static, stable case one of the area inequalities is saturated iff the surface gravity vanishes. We also discuss implications of our inequalities for "jumps" and mergers of charged MOTS. |
1911.04438 | Eric Ling | Eric Ling | Aspects of $C^0$ causal theory | 40 pages, 6 figures. v2: references fixed and proof of prop 3.7
fixed. v3: added acknowledgement to Mittag-Leffler program. v4: to appear in
GRG | null | 10.1007/s10714-020-02708-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper serves as an introduction to $C^0$ causal theory. We focus on
those parts of the theory which have proven useful for establishing spacetime
inextendibility results in low regularity -- a question which is motivated by
the strong cosmic censorship conjecture in general relativity. This paper is
self-contained; prior knowledge of causal theory is not assumed.
| [
{
"created": "Mon, 11 Nov 2019 18:31:16 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Nov 2019 16:10:52 GMT",
"version": "v2"
},
{
"created": "Mon, 2 Dec 2019 13:50:34 GMT",
"version": "v3"
},
{
"created": "Tue, 2 Jun 2020 12:32:56 GMT",
"version": "v4"
}
] | 2020-06-17 | [
[
"Ling",
"Eric",
""
]
] | This paper serves as an introduction to $C^0$ causal theory. We focus on those parts of the theory which have proven useful for establishing spacetime inextendibility results in low regularity -- a question which is motivated by the strong cosmic censorship conjecture in general relativity. This paper is self-contained; prior knowledge of causal theory is not assumed. |
gr-qc/0305074 | Allan Joseph Medved | Gilad Gour and A.J.M. Medved | Questions of Stability near Black Hole Critical Points | 10 pages, Revtex | Phys.Rev. D68 (2003) 067501 | 10.1103/PhysRevD.68.067501 | null | gr-qc hep-th | null | In this letter, we discuss how thermal fluctuations can effect the stability
of (generally) charged black holes when close to certain critical points. Our
novel treatment utilizes the black hole area spectrum (which is, for
definiteness, taken to be evenly spaced) and makes an important distinction
between fixed and fluctuating charge systems (with these being modeled,
respectively, as a canonical and grand canonical ensemble.) The discussion
begins with a summary of a recent technical paper [gr-qc/0305018]. We then go
on to consider the issue of stability when the system approaches the critical
points of interest. These include the $d$-dimensional analogue of the
Hawking-Page phase transition, a phase transition that is relevant to
Reissner-Nordstrom black holes and various extremal-limiting cases.
| [
{
"created": "Mon, 19 May 2003 23:54:36 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Gour",
"Gilad",
""
],
[
"Medved",
"A. J. M.",
""
]
] | In this letter, we discuss how thermal fluctuations can effect the stability of (generally) charged black holes when close to certain critical points. Our novel treatment utilizes the black hole area spectrum (which is, for definiteness, taken to be evenly spaced) and makes an important distinction between fixed and fluctuating charge systems (with these being modeled, respectively, as a canonical and grand canonical ensemble.) The discussion begins with a summary of a recent technical paper [gr-qc/0305018]. We then go on to consider the issue of stability when the system approaches the critical points of interest. These include the $d$-dimensional analogue of the Hawking-Page phase transition, a phase transition that is relevant to Reissner-Nordstrom black holes and various extremal-limiting cases. |
gr-qc/0207040 | Luis Herrera | L. Herrera, J. Martin and J. Ospino | Anisotropic geodesic fluid spheres in general relativity | 13 pages Latex, three ps. figures, to appear in J. Math. Physics | J.Math.Phys. 43 (2002) 4889-4897 | 10.1063/1.1505985 | null | gr-qc | null | It is shown that unlike the perfect fluid case, anisotropic fluids (principal
stresses unequal) may be geodesic, without this implying the vanishing of
(spatial) pressure gradients. Then the condition of vanishing four acceleration
is integrated in non-comoving coordinates. The resulting models are necessarily
dynamic, and the mass function is expressed in terms of the fluid velocity as
measured by a locally Minkowskian observer. An explicit example is worked out.
| [
{
"created": "Tue, 9 Jul 2002 16:04:10 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Herrera",
"L.",
""
],
[
"Martin",
"J.",
""
],
[
"Ospino",
"J.",
""
]
] | It is shown that unlike the perfect fluid case, anisotropic fluids (principal stresses unequal) may be geodesic, without this implying the vanishing of (spatial) pressure gradients. Then the condition of vanishing four acceleration is integrated in non-comoving coordinates. The resulting models are necessarily dynamic, and the mass function is expressed in terms of the fluid velocity as measured by a locally Minkowskian observer. An explicit example is worked out. |
2107.01937 | Francisco Lobo | Tiberiu Harko, Francisco S. N. Lobo, Emmanuel N. Saridakis | Gravitationally Induced Particle Production through a Nonminimal
Torsion-Matter Coupling | 24 pages, 3 figures. Invited contribution to the Special Issue
"Teleparallel Gravity: Foundations and Observational Constraints". Matches
published version | Universe 2021, 7(7), 227 | 10.3390/universe7070227 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the possibility of gravitationally generated particle
production via the mechanism of nonminimal torsion--matter coupling. An
intriguing feature of this theory is that the divergence of the matter
energy--momentum tensor does not vanish identically. We explore the physical
and cosmological implications of the nonconservation of the energy--momentum
tensor by using the formalism of irreversible thermodynamics of open systems in
the presence of matter creation/annihilation. The particle creation rates,
pressure, and the expression of the comoving entropy are obtained in a
covariant formulation and discussed in detail. Applied together with the
gravitational field equations, the thermodynamics of open systems lead to a
generalization of the standard $\Lambda$CDM cosmological paradigm, in which the
particle creation rates and pressures are effectively considered as components
of the cosmological fluid energy--momentum tensor. We consider specific models,
and we show that cosmology with a torsion--matter coupling can almost perfectly
reproduce the $\Lambda$CDM scenario, while it additionally gives rise to
particle creation rates, creation pressures, and entropy generation through
gravitational matter production in both low and high redshift limits.
| [
{
"created": "Mon, 5 Jul 2021 11:08:53 GMT",
"version": "v1"
}
] | 2021-07-06 | [
[
"Harko",
"Tiberiu",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] | We investigate the possibility of gravitationally generated particle production via the mechanism of nonminimal torsion--matter coupling. An intriguing feature of this theory is that the divergence of the matter energy--momentum tensor does not vanish identically. We explore the physical and cosmological implications of the nonconservation of the energy--momentum tensor by using the formalism of irreversible thermodynamics of open systems in the presence of matter creation/annihilation. The particle creation rates, pressure, and the expression of the comoving entropy are obtained in a covariant formulation and discussed in detail. Applied together with the gravitational field equations, the thermodynamics of open systems lead to a generalization of the standard $\Lambda$CDM cosmological paradigm, in which the particle creation rates and pressures are effectively considered as components of the cosmological fluid energy--momentum tensor. We consider specific models, and we show that cosmology with a torsion--matter coupling can almost perfectly reproduce the $\Lambda$CDM scenario, while it additionally gives rise to particle creation rates, creation pressures, and entropy generation through gravitational matter production in both low and high redshift limits. |
gr-qc/9209003 | Geza Ful{\o}p | G\'eza F\"ul\"op | Transformations and BRST-Charges in 2+1 Dimensional Gravitation | 10 pages | Mod.Phys.Lett.A7:3495-3502,1992 | 10.1142/S0217732392002901 | report G\"oteborg ITP 92-39 | gr-qc hep-th | null | Canonical transformations relating the variables of the ADM-, Ashtekar's and
Witten's formulations of gravity are computed in 2+1~dimensions. Three
different forms of the BRST-charge are given in the 2+1 dimensional Ashtekar
formalism, two of them using Ashtekar's form of the constraints and one of them
using the forms suggested by Witten. The BRST-charges are of different rank.
| [
{
"created": "Tue, 8 Sep 1992 13:34:59 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Fülöp",
"Géza",
""
]
] | Canonical transformations relating the variables of the ADM-, Ashtekar's and Witten's formulations of gravity are computed in 2+1~dimensions. Three different forms of the BRST-charge are given in the 2+1 dimensional Ashtekar formalism, two of them using Ashtekar's form of the constraints and one of them using the forms suggested by Witten. The BRST-charges are of different rank. |
gr-qc/0508117 | Tonatiuh Matos | Tonatiuh Matos and Dario Nunez | Rotating Scalar Field Wormhole | Sign of the exponential in equation (10) has been changed. Some typos
corrected | Class.Quant.Grav. 23 (2006) 4485-4496 | 10.1088/0264-9381/23/13/012 | CIEA 22/08/05 | gr-qc hep-th | null | We derive an exact solution to the Einstein's equations with a stress-energy
tensor corresponding to an opposite-sign scalar field, and show that such a
solution describes the internal region of a rotating wormhole. We also derive
an static wormhole asymptotically flat solution and match them on both regions,
thus obtaining an analytic solution for the complete space-time. We explore
some of the features of these solutions.
| [
{
"created": "Mon, 29 Aug 2005 05:27:21 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Sep 2005 05:20:38 GMT",
"version": "v2"
},
{
"created": "Mon, 24 Apr 2006 19:50:59 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Matos",
"Tonatiuh",
""
],
[
"Nunez",
"Dario",
""
]
] | We derive an exact solution to the Einstein's equations with a stress-energy tensor corresponding to an opposite-sign scalar field, and show that such a solution describes the internal region of a rotating wormhole. We also derive an static wormhole asymptotically flat solution and match them on both regions, thus obtaining an analytic solution for the complete space-time. We explore some of the features of these solutions. |
2202.11328 | Magd Elias Kahil | Magd E. Kahil | Motion of Poly-vectors in Fractal Clifford Spaces | 9 TeX pages | MSA University Engineering Journal Vol 1 issue 2 ,2022 | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | Fractal Clifford Spaces (FCS) may be considered as a challenging approach to
the unification of micro-physics and macro-physics. Trajectories of these
manifolds are described by different poly-vectors describing paths and their
deviation equations for not only to test particles but also for charged,
rotating and rotating charged objects. Due to relaxing the condition of
differentiability for all extended objects in the manifold. In this approach, a
specialized Bazanski Lagrangian will be discussed to describe the fractal
version of extended objects in a fractal space-time.
| [
{
"created": "Wed, 23 Feb 2022 06:58:34 GMT",
"version": "v1"
}
] | 2022-04-13 | [
[
"Kahil",
"Magd E.",
""
]
] | Fractal Clifford Spaces (FCS) may be considered as a challenging approach to the unification of micro-physics and macro-physics. Trajectories of these manifolds are described by different poly-vectors describing paths and their deviation equations for not only to test particles but also for charged, rotating and rotating charged objects. Due to relaxing the condition of differentiability for all extended objects in the manifold. In this approach, a specialized Bazanski Lagrangian will be discussed to describe the fractal version of extended objects in a fractal space-time. |
2211.10167 | Suraj Maurya | Suraj Maurya, Sashideep Gutti and Rahul Nigam | Effects of charge on the interior volume of BTZ black holes | 11 pages, 5 figures | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this article we extend the variational technique for maximal volume
estimation of a black hole developed by Christodoulou and Rovelli (CR) to the
case of a charged BTZ black hole in 2+1 dimensions. The technique involves a
study of the equation of motion of a hypothetical particle moving in an
auxiliary manifold defined by spacetime variables. We then compare this
estimation with the volume computed using maximization method and extrinsic
curvature method. The charge Q of the black hole appears as a log term in the
metric and hence an analytical solution for the volume does not exist. So first
we compute the steady state radius and the volume for limiting case when the
charge Q is very small i.e. Q << 1 and then carry out a numerical analysis to
solve for the volume for more generic values of the charge. We find that the
volume grows monotonically with the advance time. We further investigate the
functional behaviour of the entropy of a massless scalar field living on the
maximal hypersurface of a near extremal black hole. We show that this volume
entropy exhibits a very different functional form compared to the horizon
entropy.
| [
{
"created": "Fri, 18 Nov 2022 11:26:38 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Nov 2022 13:35:54 GMT",
"version": "v2"
}
] | 2024-07-02 | [
[
"Maurya",
"Suraj",
""
],
[
"Gutti",
"Sashideep",
""
],
[
"Nigam",
"Rahul",
""
]
] | In this article we extend the variational technique for maximal volume estimation of a black hole developed by Christodoulou and Rovelli (CR) to the case of a charged BTZ black hole in 2+1 dimensions. The technique involves a study of the equation of motion of a hypothetical particle moving in an auxiliary manifold defined by spacetime variables. We then compare this estimation with the volume computed using maximization method and extrinsic curvature method. The charge Q of the black hole appears as a log term in the metric and hence an analytical solution for the volume does not exist. So first we compute the steady state radius and the volume for limiting case when the charge Q is very small i.e. Q << 1 and then carry out a numerical analysis to solve for the volume for more generic values of the charge. We find that the volume grows monotonically with the advance time. We further investigate the functional behaviour of the entropy of a massless scalar field living on the maximal hypersurface of a near extremal black hole. We show that this volume entropy exhibits a very different functional form compared to the horizon entropy. |
0804.0169 | Jose M. Isidro | J.M. Isidro, J.L. Gonzalez-Santander, P. Fernandez de Cordoba | A note on the quantum of time | 4 pages, some refs added | Mod.Phys.Lett.A23:1161-1165,2008 | 10.1142/S0217732308027126 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum mechanics rests on the assumption that time is a classical variable.
As such, classical time is assumed to be measurable with infinite accuracy.
However, all real clocks are subject to quantum fluctuations, which leads to
the existence of a nonzero uncertainty in the time variable. The existence of a
quantum of time modifies the Heisenberg evolution equation for observables. In
this letter we propose and analyse a generalisation of Heisenberg's equation
for observables evolving in real time (the time variable measured by real
clocks), that takes the existence of a quantum of time into account. This
generalisation of Heisenberg's equation turns out to be a delay-differential
equation.
| [
{
"created": "Tue, 1 Apr 2008 13:37:39 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Apr 2008 13:53:42 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Isidro",
"J. M.",
""
],
[
"Gonzalez-Santander",
"J. L.",
""
],
[
"de Cordoba",
"P. Fernandez",
""
]
] | Quantum mechanics rests on the assumption that time is a classical variable. As such, classical time is assumed to be measurable with infinite accuracy. However, all real clocks are subject to quantum fluctuations, which leads to the existence of a nonzero uncertainty in the time variable. The existence of a quantum of time modifies the Heisenberg evolution equation for observables. In this letter we propose and analyse a generalisation of Heisenberg's equation for observables evolving in real time (the time variable measured by real clocks), that takes the existence of a quantum of time into account. This generalisation of Heisenberg's equation turns out to be a delay-differential equation. |
2308.06731 | Shin'ichi Nojiri | Shin'ichi Nojiri and Sergei. D. Odintsov | Propagation Speed of Gravitational Wave in
Scalar--Einstein--Gauss-Bonnet Gravity | LaTeX, 12 pages, to appear in Nuclear Physics B | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The propagation speed of the gravitational wave in
scalar--Einstein--Gauss-Bonnet (sEGB) gravity is generally different from that
of light. Using differential equation conditions for the speed of gravitational
waves to coincide with the light speed in the expanding universe, we
constructed a general class of sEGB gravities where this condition is satisfied
and realistic inflation occurs. It is demonstrated that the condition that the
speed of gravitational wave coincides with that of the light in the
Friedmann-Lema\^{i}tre-Robertson-Walker (FRLW) universe is always different
from the condition for gravitational wave speed in the sEGB black hole
background. Moreover, it is shown that when gravitational wave speed in sEGB
black hole is equal to the speed of light the black hole spacetime geometry is
changing too so that formally there is no solution for such sEGB black hole.
This may indicate that sEGB black holes hardly can be considered as realistic
black holes unless some reasonable scenario to make gravitational wave speed to
be equal to that of light is proposed, at least asymptotically.
| [
{
"created": "Sun, 13 Aug 2023 09:27:35 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Aug 2023 17:20:44 GMT",
"version": "v2"
},
{
"created": "Sat, 2 Sep 2023 07:17:39 GMT",
"version": "v3"
},
{
"created": "Mon, 11 Dec 2023 01:02:55 GMT",
"version": "v4"
}
] | 2023-12-12 | [
[
"Nojiri",
"Shin'ichi",
""
],
[
"Odintsov",
"Sergei. D.",
""
]
] | The propagation speed of the gravitational wave in scalar--Einstein--Gauss-Bonnet (sEGB) gravity is generally different from that of light. Using differential equation conditions for the speed of gravitational waves to coincide with the light speed in the expanding universe, we constructed a general class of sEGB gravities where this condition is satisfied and realistic inflation occurs. It is demonstrated that the condition that the speed of gravitational wave coincides with that of the light in the Friedmann-Lema\^{i}tre-Robertson-Walker (FRLW) universe is always different from the condition for gravitational wave speed in the sEGB black hole background. Moreover, it is shown that when gravitational wave speed in sEGB black hole is equal to the speed of light the black hole spacetime geometry is changing too so that formally there is no solution for such sEGB black hole. This may indicate that sEGB black holes hardly can be considered as realistic black holes unless some reasonable scenario to make gravitational wave speed to be equal to that of light is proposed, at least asymptotically. |
gr-qc/9801026 | Sergei Odintsov | L.N. Granda and S.D. Odintsov | Effective average action and nonperturbative renormalization group
equation in higher derivative quantum gravity | Latex file, 10 pages, to appear in Grav.and Cosm.,v.4,1998 | Grav.Cosmol. 4 (1998) 85-95 | null | null | gr-qc | null | We study the exact renormalization group (RG) in $R^2$-gravity in the
effective average action formalism using the background field method. The
truncated evolution equation (where truncation is made to low-derivatives
functionals space) for such a theory in a de Sitter background leads to a set
of nonperturbative RG equations for cosmological and gravitational coupling
constants. The gauge dependence problem is solved by working in the physical
Landau-De Witt gauge corresponding to gauge-fixing independent effective
action. Approximate solution of nonperturbative RG equations reveals the
appearence of antiscreening or screening behaviour of Newtonian coupling,
depending on the higher-derivatives coupling constants. The existence of
unstable
UV fixed points is also mentioned.
| [
{
"created": "Fri, 9 Jan 1998 15:25:05 GMT",
"version": "v1"
},
{
"created": "Wed, 27 May 1998 02:10:51 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Granda",
"L. N.",
""
],
[
"Odintsov",
"S. D.",
""
]
] | We study the exact renormalization group (RG) in $R^2$-gravity in the effective average action formalism using the background field method. The truncated evolution equation (where truncation is made to low-derivatives functionals space) for such a theory in a de Sitter background leads to a set of nonperturbative RG equations for cosmological and gravitational coupling constants. The gauge dependence problem is solved by working in the physical Landau-De Witt gauge corresponding to gauge-fixing independent effective action. Approximate solution of nonperturbative RG equations reveals the appearence of antiscreening or screening behaviour of Newtonian coupling, depending on the higher-derivatives coupling constants. The existence of unstable UV fixed points is also mentioned. |
1409.5695 | Israel Quiros | Israel Quiros | On a symmetry relating gravity with antigravity | 9 pages, no figures. This is a sequel to the earlier paper
arXiv:gr-qc/0411064. A section on the normalized gravitational charge added.
Physical discussion enriched | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I investigate the impact of a "would be" fundamental symmetry of the laws of
nature under the interchange of gravity and antigravity, on the understanding
of negative energies in general relativity. For this purpose a toy model that
is based on Einstein-Hilbert gravity with two minimally coupled
self-interacting scalar fields is explored, where the second (exotic) scalar
field with negative energy density may be regarded, alternatively, as an
antigravitating field with positive energy. Spontaneous breakdown of reflection
symmetry is then considered in order to discuss the implications the proposed
"would be" fundamental symmetry might have for the vanishing of the
cosmological constant. A possible connection of the gravity-antigravity
symmetry with the so called quintom field is also explored.
| [
{
"created": "Thu, 18 Sep 2014 18:24:26 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Oct 2014 01:21:53 GMT",
"version": "v2"
}
] | 2014-10-03 | [
[
"Quiros",
"Israel",
""
]
] | I investigate the impact of a "would be" fundamental symmetry of the laws of nature under the interchange of gravity and antigravity, on the understanding of negative energies in general relativity. For this purpose a toy model that is based on Einstein-Hilbert gravity with two minimally coupled self-interacting scalar fields is explored, where the second (exotic) scalar field with negative energy density may be regarded, alternatively, as an antigravitating field with positive energy. Spontaneous breakdown of reflection symmetry is then considered in order to discuss the implications the proposed "would be" fundamental symmetry might have for the vanishing of the cosmological constant. A possible connection of the gravity-antigravity symmetry with the so called quintom field is also explored. |
gr-qc/0103087 | Peter Dunsby | Deon Solomons, Peter Dunsby and George Ellis | Bounce behaviour in Kantowski-Sachs and Bianchi Cosmologies | Matches published version | Class.Quant.Grav.23:6585-6597,2006 | 10.1088/0264-9381/23/23/001 | null | gr-qc | null | Many cosmological scenarios envisage either a bounce of the universe at early
times, or collapse of matter locally to form a black hole which re-expands into
a new expanding universe region. Energy conditions preclude this happening for
ordinary matter in general relativistic universes, but scalar or dilatonic
fields can violate some of these conditions, and so could possibly provide
bounce behaviour. In this paper we show that such bounces cannot occur in
Kantowski-Sachs models without violating the {\it reality condition}
$\dot{\phi}^2\geq 0$. This also holds true for other isotropic spatially
homogenous Bianchi models, with the exception of closed
Friedmann-Robertson-Walker and Bianchi IX models; bounce behaviour violates the
{\em weak energy condition} $\rho\geq 0$ and $\rho+p\geq 0$. We turn to the
Randall-Sundrum type braneworld scenario for a possible resolution of this
problem.
| [
{
"created": "Fri, 23 Mar 2001 12:22:29 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Nov 2006 12:54:09 GMT",
"version": "v2"
}
] | 2010-05-28 | [
[
"Solomons",
"Deon",
""
],
[
"Dunsby",
"Peter",
""
],
[
"Ellis",
"George",
""
]
] | Many cosmological scenarios envisage either a bounce of the universe at early times, or collapse of matter locally to form a black hole which re-expands into a new expanding universe region. Energy conditions preclude this happening for ordinary matter in general relativistic universes, but scalar or dilatonic fields can violate some of these conditions, and so could possibly provide bounce behaviour. In this paper we show that such bounces cannot occur in Kantowski-Sachs models without violating the {\it reality condition} $\dot{\phi}^2\geq 0$. This also holds true for other isotropic spatially homogenous Bianchi models, with the exception of closed Friedmann-Robertson-Walker and Bianchi IX models; bounce behaviour violates the {\em weak energy condition} $\rho\geq 0$ and $\rho+p\geq 0$. We turn to the Randall-Sundrum type braneworld scenario for a possible resolution of this problem. |
1502.03880 | Y. M. Cho | Masakatsu Kenmoku and Y. M. Cho | Bargmann-Wigner Formulation and Superradiance Problem of Bosons and
Fermions in Kerr Space-time | null | Int. J. Mod. Phys. Lett. A 30, 1550052 (2015) | 10.1142/S0217751X15500529 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The superradiance phenomena of massive bosons and fermions in the Kerr
spacetime are studied in the Bargmann-Wigner formulation. In case of bi-spinor,
the four independent components spinors correspond to the four bosonic freedom:
one scalar and three vectors uniquely. The consistent description of the
Bargmann-Wigner equations between fermions and bosons shows that the
superradiance of the type with positive energy $(0<\omega)$ and negative
momentum near horizon $(p_{\rm H}<0)$ is shown not to occur. On the other hand,
the superradiance of the type with negative energy $(\omega<0)$ and positive
momentum near horizon $(0<p_{\rm H})$ is still possible for both scalar bosons
and spinor fermions.
| [
{
"created": "Fri, 13 Feb 2015 03:45:23 GMT",
"version": "v1"
}
] | 2018-03-22 | [
[
"Kenmoku",
"Masakatsu",
""
],
[
"Cho",
"Y. M.",
""
]
] | The superradiance phenomena of massive bosons and fermions in the Kerr spacetime are studied in the Bargmann-Wigner formulation. In case of bi-spinor, the four independent components spinors correspond to the four bosonic freedom: one scalar and three vectors uniquely. The consistent description of the Bargmann-Wigner equations between fermions and bosons shows that the superradiance of the type with positive energy $(0<\omega)$ and negative momentum near horizon $(p_{\rm H}<0)$ is shown not to occur. On the other hand, the superradiance of the type with negative energy $(\omega<0)$ and positive momentum near horizon $(0<p_{\rm H})$ is still possible for both scalar bosons and spinor fermions. |
1702.07346 | Singh Ibungochouba Telem | T. Ibungochouba Singh | Quantum Radiation Properties of General Nonstationary Black Hole | Accepted in Advances in High Energy Physics, Hindawi Publishing
Corporation | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the generalized tortoise coordinate transformations the quantum
radiation properties of Klein-Gordon scalar particles, Maxwell's
electromagnetic field equations and Dirac equations are investigated in general
non-stationary black hole. The locations of the event horizon and the Hawking
temperature depend on both time and angles. A new extra coupling effect is
observed in the thermal radiation spectrum of Maxwell's equations and Dirac
equations which is absent in the thermal radiation spectrum of scalar
particles. We also observe that the chemical potential derived from scalar
particles is equal to the highest energy of the negative energy state of the
scalar particle in the non-thermal radiation in general non-stationary black
hole. Applying generalized tortoise coordinate transformation a constant term
$\xi$ is produced in the expression of thermal radiation in general
non-stationary black hole. It indicates that generalized tortoise coordinate
transformation is more accurate and reliable in the study of thermal radiation
of black hole.
| [
{
"created": "Thu, 23 Feb 2017 10:10:17 GMT",
"version": "v1"
}
] | 2017-02-27 | [
[
"Singh",
"T. Ibungochouba",
""
]
] | Using the generalized tortoise coordinate transformations the quantum radiation properties of Klein-Gordon scalar particles, Maxwell's electromagnetic field equations and Dirac equations are investigated in general non-stationary black hole. The locations of the event horizon and the Hawking temperature depend on both time and angles. A new extra coupling effect is observed in the thermal radiation spectrum of Maxwell's equations and Dirac equations which is absent in the thermal radiation spectrum of scalar particles. We also observe that the chemical potential derived from scalar particles is equal to the highest energy of the negative energy state of the scalar particle in the non-thermal radiation in general non-stationary black hole. Applying generalized tortoise coordinate transformation a constant term $\xi$ is produced in the expression of thermal radiation in general non-stationary black hole. It indicates that generalized tortoise coordinate transformation is more accurate and reliable in the study of thermal radiation of black hole. |
2407.13820 | Emanuele Panella | Jonathan Oppenheim, Emanuele Panella and Andrew Pontzen | Emergence of phantom cold dark matter from spacetime diffusion | 21 pages + appendix | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A way to reconcile general relativity and quantum field theory without
quantising the geometry is to demand the metric evolve stochastically. In this
article, we explore the consequences of such a proposal at early cosmological
times. We find the stochastic evolution results in the spatial metric diffusing
away from its deterministic value, generating phantom cold dark matter (CDM).
It is produced primarily at the end of the inflationary phase of the Universe's
evolution, with a statistical distribution that depends on the specifics of the
early-times cosmological model. We find the energy density of this phantom cold
dark matter is positive on average, a necessary condition to reproduce the
cosmological phenomenology of CDM, although further work is required to
calculate its mean density and spatial distribution. If the density is
cosmologically significant, phantom dark matter acts on the geometry in a way
that is indistinguishable from conventional CDM. As such, it has the potential
to reproduce phenomenology such as structure formation, lensing, and galactic
rotation curves. We conclude by discussing the possibility of testing hybrid
theories of gravity by combining measurements of the Cosmic Microwave
Background with tabletop experiments.
| [
{
"created": "Thu, 18 Jul 2024 18:00:02 GMT",
"version": "v1"
}
] | 2024-07-22 | [
[
"Oppenheim",
"Jonathan",
""
],
[
"Panella",
"Emanuele",
""
],
[
"Pontzen",
"Andrew",
""
]
] | A way to reconcile general relativity and quantum field theory without quantising the geometry is to demand the metric evolve stochastically. In this article, we explore the consequences of such a proposal at early cosmological times. We find the stochastic evolution results in the spatial metric diffusing away from its deterministic value, generating phantom cold dark matter (CDM). It is produced primarily at the end of the inflationary phase of the Universe's evolution, with a statistical distribution that depends on the specifics of the early-times cosmological model. We find the energy density of this phantom cold dark matter is positive on average, a necessary condition to reproduce the cosmological phenomenology of CDM, although further work is required to calculate its mean density and spatial distribution. If the density is cosmologically significant, phantom dark matter acts on the geometry in a way that is indistinguishable from conventional CDM. As such, it has the potential to reproduce phenomenology such as structure formation, lensing, and galactic rotation curves. We conclude by discussing the possibility of testing hybrid theories of gravity by combining measurements of the Cosmic Microwave Background with tabletop experiments. |
gr-qc/9907073 | Valeri Frolov | V. Frolov and D. Singh | Quantum Effects in the Presence of Expanding Semi-Transparent Spherical
Mirrors | 28 pages, Paper is slightly reorganized, additional references are
added | Class.Quant.Grav. 16 (1999) 3693-3716 | 10.1088/0264-9381/16/11/315 | null | gr-qc hep-ph hep-th quant-ph | null | We study quantum effects in the presence of a spherical semi-transparent
mirror or a system of two concentric mirrors which expand with a constant
acceleration in a flat D-dimensional spacetime. Using the Euclidean approach,
we obtain expressions for fluctuations and the renormalized value of
stress-energy tensor for a scalar non-minimally coupled massless field.
Explicit expressions are obtained for the energy fluxes at the null infinity
generated by such mirrors in the physical spacetime and their properties are
discussed.
| [
{
"created": "Fri, 23 Jul 1999 19:45:17 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Sep 1999 21:25:27 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Frolov",
"V.",
""
],
[
"Singh",
"D.",
""
]
] | We study quantum effects in the presence of a spherical semi-transparent mirror or a system of two concentric mirrors which expand with a constant acceleration in a flat D-dimensional spacetime. Using the Euclidean approach, we obtain expressions for fluctuations and the renormalized value of stress-energy tensor for a scalar non-minimally coupled massless field. Explicit expressions are obtained for the energy fluxes at the null infinity generated by such mirrors in the physical spacetime and their properties are discussed. |
gr-qc/0703013 | Joachim Schr\"oter | Joachim Schr\"oter | A New Formulation of General Relativity - Part I: Pre-Radar Charts as
Generating Functions for Metric and Velocity | 23 pages, 1 figure | null | null | null | gr-qc | null | In this paper (Part I of a series of three papers) an axiomatic formulation
of GR is given, here use is made of the concept of pre-radar charts. These
charts have "infinitesimally" the same properties as the true radar charts used
in space-time theory. Their existence in GR has far-reaching consequences which
are discussed throughout the papers. For the sake of simplicity and convenience
I consider only such material systems the state of which is defined by a
velocity field, a mass density and a temperature field. But the main results
hold also for more complex systems. It follows from the axiomatics that the
pre-radar charts define an atlas for the space-time manifold and that, in
addition, they generate the metric, the velocity field and the displacement of
the matter. Therefore, they are called generating functions. They act like
"potentials". At the end of the paper it is shown that the existence of
pre-radar charts allows to simplify the original axiomatics drasticly. But the
two versions of GR are equivalent.
| [
{
"created": "Fri, 2 Mar 2007 14:50:48 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Schröter",
"Joachim",
""
]
] | In this paper (Part I of a series of three papers) an axiomatic formulation of GR is given, here use is made of the concept of pre-radar charts. These charts have "infinitesimally" the same properties as the true radar charts used in space-time theory. Their existence in GR has far-reaching consequences which are discussed throughout the papers. For the sake of simplicity and convenience I consider only such material systems the state of which is defined by a velocity field, a mass density and a temperature field. But the main results hold also for more complex systems. It follows from the axiomatics that the pre-radar charts define an atlas for the space-time manifold and that, in addition, they generate the metric, the velocity field and the displacement of the matter. Therefore, they are called generating functions. They act like "potentials". At the end of the paper it is shown that the existence of pre-radar charts allows to simplify the original axiomatics drasticly. But the two versions of GR are equivalent. |
2308.05392 | Farux Abdulxamidov | Farrux Abdulxamidov, Javlon Rayimbaev, Ahmadjon Abdujabbarov, and
Zden\v{e}k Stuchl\'ik | Spinning magnetized particles orbiting magnetized Schwarzschild black
holes | 13 pages, 9 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A way to test electromagnetic field and spacetime properties around black
holes is by considering the dynamics of test particles. In fact, in real
astrophysical scenarios, it is hard to determine spacetime geometry which is
dominating due to degeneracy gravitational effects in parameters of gravity
theories. In this work, we study for the first time the dynamics of spinning
particles that have magnetic dipole moments around Schwarzschild black holes
immersed in an external asymptotically uniform magnetic field using the
Mathisson-Papapetrou-Dixon (MPD) equation. There are two combined interactions:
gravitational interaction between the spin of the particle and
(electro)magnetic interaction between the external magnetic field and the
magnetic dipole moment of the particle to be taken into account. First, we
derive the effective potential of the test spinning magnetized particles in
motion around the black hole. We also study the combined effects of spin and
magnetic interactions on innermost stable circular orbits (ISCOs), the energy,
and angular momentum of the particles at ISCO together with superluminal
bounds. We investigated the collision of the particles and evaluated the
center-of-mass energy in the collisions. Finally, we consider various cases in
which neutron stars and rotating stellar mass black holes can be treated as
spinning magnetized particles, evaluating the effects of the spin and magnetic
moment of objects around supermassive and intermediate-mass black holes.
| [
{
"created": "Thu, 10 Aug 2023 07:13:12 GMT",
"version": "v1"
}
] | 2023-08-11 | [
[
"Abdulxamidov",
"Farrux",
""
],
[
"Rayimbaev",
"Javlon",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
],
[
"Stuchlík",
"Zdeněk",
""
]
] | A way to test electromagnetic field and spacetime properties around black holes is by considering the dynamics of test particles. In fact, in real astrophysical scenarios, it is hard to determine spacetime geometry which is dominating due to degeneracy gravitational effects in parameters of gravity theories. In this work, we study for the first time the dynamics of spinning particles that have magnetic dipole moments around Schwarzschild black holes immersed in an external asymptotically uniform magnetic field using the Mathisson-Papapetrou-Dixon (MPD) equation. There are two combined interactions: gravitational interaction between the spin of the particle and (electro)magnetic interaction between the external magnetic field and the magnetic dipole moment of the particle to be taken into account. First, we derive the effective potential of the test spinning magnetized particles in motion around the black hole. We also study the combined effects of spin and magnetic interactions on innermost stable circular orbits (ISCOs), the energy, and angular momentum of the particles at ISCO together with superluminal bounds. We investigated the collision of the particles and evaluated the center-of-mass energy in the collisions. Finally, we consider various cases in which neutron stars and rotating stellar mass black holes can be treated as spinning magnetized particles, evaluating the effects of the spin and magnetic moment of objects around supermassive and intermediate-mass black holes. |
1604.00246 | Kentaro Takami | Luciano Rezzolla and Kentaro Takami | Gravitational-wave signal from binary neutron stars: a systematic
analysis of the spectral properties | 20 pages, 11 figures, 2 tables; Minor revisions, matches accepted
version on PRD | Phys. Rev. D 93, 124051 (2016) | 10.1103/PhysRevD.93.124051 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A number of works have shown that important information on the equation of
state of matter at nuclear density can be extracted from the gravitational
waves emitted by merging neutron-star binaries. We present a comprehensive
analysis of the gravitational-wave signal emitted during the inspiral, merger
and post-merger of 56 neutron-star binaries. This sample of binaries, arguably
the largest studied to date with realistic equations of state, spans across six
different nuclear-physics equations of state and ten masses, allowing us to
sharpen a number of results recently obtained on the spectral properties of the
gravitational-wave signal. Overall we find that: (i) for binaries with masses
differing no more than $20\%$, the frequency at gravitational-wave amplitude's
maximum is related quasi-universally with the tidal deformability of the two
stars; (ii) the spectral properties vary during the post-merger phase, with a
transient phase lasting a few millisecond after the merger and followed by a
quasi-stationary phase; (iii) when distinguishing the spectral peaks between
these two phases, a number of ambiguities in the identification of the peaks
disappear, leaving a simple and robust picture; (iv) using properly identified
frequencies, quasi-universal relations are found between the spectral features
and the properties of the neutron stars; (v) for the most salient peaks
analytic fitting functions can be obtained in terms of the stellar tidal
deformability or compactness. Altogether, these results support the idea that
the equation of state of nuclear matter can be constrained tightly when a
signal in gravitational waves from binary neutron stars is detected.
| [
{
"created": "Fri, 1 Apr 2016 13:55:19 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Jun 2016 08:27:21 GMT",
"version": "v2"
}
] | 2016-06-29 | [
[
"Rezzolla",
"Luciano",
""
],
[
"Takami",
"Kentaro",
""
]
] | A number of works have shown that important information on the equation of state of matter at nuclear density can be extracted from the gravitational waves emitted by merging neutron-star binaries. We present a comprehensive analysis of the gravitational-wave signal emitted during the inspiral, merger and post-merger of 56 neutron-star binaries. This sample of binaries, arguably the largest studied to date with realistic equations of state, spans across six different nuclear-physics equations of state and ten masses, allowing us to sharpen a number of results recently obtained on the spectral properties of the gravitational-wave signal. Overall we find that: (i) for binaries with masses differing no more than $20\%$, the frequency at gravitational-wave amplitude's maximum is related quasi-universally with the tidal deformability of the two stars; (ii) the spectral properties vary during the post-merger phase, with a transient phase lasting a few millisecond after the merger and followed by a quasi-stationary phase; (iii) when distinguishing the spectral peaks between these two phases, a number of ambiguities in the identification of the peaks disappear, leaving a simple and robust picture; (iv) using properly identified frequencies, quasi-universal relations are found between the spectral features and the properties of the neutron stars; (v) for the most salient peaks analytic fitting functions can be obtained in terms of the stellar tidal deformability or compactness. Altogether, these results support the idea that the equation of state of nuclear matter can be constrained tightly when a signal in gravitational waves from binary neutron stars is detected. |
gr-qc/9805019 | Sean Hayward | Sean A. Hayward | Dynamic wormholes | 5 revtex pages, 4 eps figures. Minor change which did not reach
publishers | Int.J.Mod.Phys. D8 (1999) 373-382 | 10.1142/S0218271899000286 | null | gr-qc | null | A new framework is proposed for general dynamic wormholes, unifying them with
black holes. Both are generically defined locally by outer trapping horizons,
temporal for wormholes and spatial or null for black and white holes. Thus
wormhole horizons are two-way traversible, while black-hole and white-hole
horizons are only one-way traversible. It follows from the Einstein equation
that the null energy condition is violated everywhere on a generic wormhole
horizon. It is suggested that quantum inequalities constraining negative energy
break down at such horizons. Wormhole dynamics can be developed as for
black-hole dynamics, including a reversed second law and a first law involving
a definition of wormhole surface gravity. Since the causal nature of a horizon
can change, being spatial under positive energy and temporal under sufficient
negative energy, black holes and wormholes are interconvertible. In particular,
if a wormhole's negative-energy source fails, it may collapse into a black
hole. Conversely, irradiating a black-hole horizon with negative energy could
convert it into a wormhole horizon. This also suggests a possible final state
of black-hole evaporation: a stationary wormhole. The new framework allows a
fully dynamical description of the operation of a wormhole for practical
transport, including the back-reaction of the transported matter on the
wormhole. As an example of a matter model, a Klein-Gordon field with negative
gravitational coupling is a source for a static wormhole of Morris & Thorne.
| [
{
"created": "Thu, 7 May 1998 08:25:37 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Dec 1998 08:04:48 GMT",
"version": "v2"
},
{
"created": "Fri, 14 Apr 2000 17:41:03 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Hayward",
"Sean A.",
""
]
] | A new framework is proposed for general dynamic wormholes, unifying them with black holes. Both are generically defined locally by outer trapping horizons, temporal for wormholes and spatial or null for black and white holes. Thus wormhole horizons are two-way traversible, while black-hole and white-hole horizons are only one-way traversible. It follows from the Einstein equation that the null energy condition is violated everywhere on a generic wormhole horizon. It is suggested that quantum inequalities constraining negative energy break down at such horizons. Wormhole dynamics can be developed as for black-hole dynamics, including a reversed second law and a first law involving a definition of wormhole surface gravity. Since the causal nature of a horizon can change, being spatial under positive energy and temporal under sufficient negative energy, black holes and wormholes are interconvertible. In particular, if a wormhole's negative-energy source fails, it may collapse into a black hole. Conversely, irradiating a black-hole horizon with negative energy could convert it into a wormhole horizon. This also suggests a possible final state of black-hole evaporation: a stationary wormhole. The new framework allows a fully dynamical description of the operation of a wormhole for practical transport, including the back-reaction of the transported matter on the wormhole. As an example of a matter model, a Klein-Gordon field with negative gravitational coupling is a source for a static wormhole of Morris & Thorne. |
2306.01927 | Kuantay Boshkayev | Kuantay Boshkayev, Gulnara Suliyeva, Vladimir Ivashchuk, Ainur
Urazalina | Circular geodesics in the field of double-charged dilatonic black holes | 12 pages, 13 figures, 2 tables | Eur. Phys. J. C 84, 19 (2024) | 10.1140/epjc/s10052-023-12337-6 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | A non-extreme dilatonic charged (by two ``color electric'' charges) black
hole solution is examined within a four-dimensional gravity model that
incorporates two scalar (dilaton) fields and two Abelian vector fields. The
scalar and vector fields interact through exponential terms containing two
dilatonic coupling vectors. The solution is characterized by a dimensionless
parameter $a$ $(0 < a < 2)$, which is a specific function of dilatonic coupling
vectors. The paper presents solutions for timelike and null circular geodesics
that may play a crucial role in different astrophysical scenarios, including
quasinormal modes of various test fields in the eikonal approximation. For $a =
1/2, 1, 3/2, 2$, the radii of the innermost stable circular orbit are presented
and analyzed.
| [
{
"created": "Fri, 2 Jun 2023 21:48:36 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jan 2024 17:38:44 GMT",
"version": "v2"
}
] | 2024-01-10 | [
[
"Boshkayev",
"Kuantay",
""
],
[
"Suliyeva",
"Gulnara",
""
],
[
"Ivashchuk",
"Vladimir",
""
],
[
"Urazalina",
"Ainur",
""
]
] | A non-extreme dilatonic charged (by two ``color electric'' charges) black hole solution is examined within a four-dimensional gravity model that incorporates two scalar (dilaton) fields and two Abelian vector fields. The scalar and vector fields interact through exponential terms containing two dilatonic coupling vectors. The solution is characterized by a dimensionless parameter $a$ $(0 < a < 2)$, which is a specific function of dilatonic coupling vectors. The paper presents solutions for timelike and null circular geodesics that may play a crucial role in different astrophysical scenarios, including quasinormal modes of various test fields in the eikonal approximation. For $a = 1/2, 1, 3/2, 2$, the radii of the innermost stable circular orbit are presented and analyzed. |
2006.06291 | Jose M. Isidro | J.C. Castro-Palacio, P. Fernandez de Cordoba, J.M. Isidro | The cosmological constant of emergent spacetime in the Newtonian
approximation | 11 pages; refs. added | null | 10.1142/S0218271820500935 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a simple quantum-mechanical estimate of the cosmological constant
of a Newtonian Universe. We first mimic the dynamics of a Newtonian spacetime
by means of a nonrelativistic quantum mechanics for the matter contents of the
Universe (baryonic and dark) within a fixed (i.e., nondynamical) Euclidean
spacetime. Then we identify an operator that plays, on the matter states, a
role analogous to that played by the cosmological constant. Finally we prove
that there exists a quantum state for the matter fields, in which the above
mentioned operator has an expectation value equal to the cosmological constant
of the given Newtonian Universe.
| [
{
"created": "Thu, 11 Jun 2020 09:56:31 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Jun 2020 13:24:45 GMT",
"version": "v2"
}
] | 2020-12-02 | [
[
"Castro-Palacio",
"J. C.",
""
],
[
"de Cordoba",
"P. Fernandez",
""
],
[
"Isidro",
"J. M.",
""
]
] | We present a simple quantum-mechanical estimate of the cosmological constant of a Newtonian Universe. We first mimic the dynamics of a Newtonian spacetime by means of a nonrelativistic quantum mechanics for the matter contents of the Universe (baryonic and dark) within a fixed (i.e., nondynamical) Euclidean spacetime. Then we identify an operator that plays, on the matter states, a role analogous to that played by the cosmological constant. Finally we prove that there exists a quantum state for the matter fields, in which the above mentioned operator has an expectation value equal to the cosmological constant of the given Newtonian Universe. |
gr-qc/9909050 | Nils Andersson | Nils Andersson and Kostas Glampedakis | A superradiance resonance cavity outside rapidly rotating black holes | 4 pages, 2 postscript figures | Phys.Rev.Lett. 84 (2000) 4537-4540 | 10.1103/PhysRevLett.84.4537 | null | gr-qc | null | We discuss the late-time behaviour of a dynamically perturbed Kerr black
hole. We present analytic results for near extreme Kerr black holes that show
that the large number of virtually undamped quasinormal modes that exist for
nonzero values of the azimuthal eigenvalue m combine in such a way that the
field oscillates with an amplitude that decays as 1/t at late times. This
prediction is verified using numerical time-evolutions of the Teukolsky
equation. We argue that the observed behaviour may be relevant for
astrophysical black holes, and that it can be understood in terms of the
presence of a ``superradiance resonance cavity'' immediately outside the black
hole.
| [
{
"created": "Thu, 16 Sep 1999 09:21:32 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Andersson",
"Nils",
""
],
[
"Glampedakis",
"Kostas",
""
]
] | We discuss the late-time behaviour of a dynamically perturbed Kerr black hole. We present analytic results for near extreme Kerr black holes that show that the large number of virtually undamped quasinormal modes that exist for nonzero values of the azimuthal eigenvalue m combine in such a way that the field oscillates with an amplitude that decays as 1/t at late times. This prediction is verified using numerical time-evolutions of the Teukolsky equation. We argue that the observed behaviour may be relevant for astrophysical black holes, and that it can be understood in terms of the presence of a ``superradiance resonance cavity'' immediately outside the black hole. |
gr-qc/0610048 | Ingunn Kathrine Wehus | Ingunn Kathrine Wehus and Finn Ravndal | Gravity coupled to a scalar field in extra dimensions | v2, 10 pages, minor change, two more references, published version.
Extended version of talk given at ERE2006, Palma de Mallorca, Spain, Sept.
4-8, 2006 | J.Phys.Conf.Ser.66:012024,2007 | 10.1088/1742-6596/66/1/012024 | null | gr-qc | null | In d+1 dimensions we solve the equations of motion for the case of gravity
minimally or conformally coupled to a scalar field. For the minimally coupled
system the equations can either be solved directly or by transforming vacuum
solutions, as shown before in 3+1 dimensions by Buchdahl. In d+1 dimensions the
solutions have been previously found directly by Xanthopoulos and Zannias. Here
we first rederive these earlier results, and then extend Buchdahl's method of
transforming vacuum solutions to d+1 dimensions. We also review the conformal
coupling case, in which d+1 dimensional solutions can be found by extending
Bekenstein's method of conformal transformation of the minimal coupling
solution. Combining the extended versions of Buchdahl transformations and
Bekenstein transformations we can in arbitrary dimensions always generate
solutions of both the minimal and the conformal equations from known vacuum
solutions.
| [
{
"created": "Tue, 10 Oct 2006 19:05:11 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Jun 2007 23:57:03 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Wehus",
"Ingunn Kathrine",
""
],
[
"Ravndal",
"Finn",
""
]
] | In d+1 dimensions we solve the equations of motion for the case of gravity minimally or conformally coupled to a scalar field. For the minimally coupled system the equations can either be solved directly or by transforming vacuum solutions, as shown before in 3+1 dimensions by Buchdahl. In d+1 dimensions the solutions have been previously found directly by Xanthopoulos and Zannias. Here we first rederive these earlier results, and then extend Buchdahl's method of transforming vacuum solutions to d+1 dimensions. We also review the conformal coupling case, in which d+1 dimensional solutions can be found by extending Bekenstein's method of conformal transformation of the minimal coupling solution. Combining the extended versions of Buchdahl transformations and Bekenstein transformations we can in arbitrary dimensions always generate solutions of both the minimal and the conformal equations from known vacuum solutions. |
1711.11244 | Vivek Venkatraman Krishnan | V. Venkatraman Krishnan, W. van Straten, P. A. Rosado, M. Bailes, E.
F. Keane, R. Bhat, C. Flynn | Strong field tests of gravity with PSR J1141-6545 | 4 pages, 1 figure, IAU 337 symposium on Pulsar Astrophysics: The Next
Fifty Years | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The initial results from timing observations of PSR J1141-6545, a
relativistic pulsar white-dwarf binary system, are presented. Predictions from
the timing baseline hint at the most stringent test of gravity by an asymmetric
binary yet. The timing precision has been hindered by the dramatic variations
of the pulse profile due to geodetic precession, a pulsar glitch and red timing
noise. Methods to overcome such timing irregularities are briefly presented
along with preliminary results from the test of the General Theory of
Relativity (GR) from this pulsar
| [
{
"created": "Thu, 30 Nov 2017 05:48:37 GMT",
"version": "v1"
}
] | 2017-12-01 | [
[
"Krishnan",
"V. Venkatraman",
""
],
[
"van Straten",
"W.",
""
],
[
"Rosado",
"P. A.",
""
],
[
"Bailes",
"M.",
""
],
[
"Keane",
"E. F.",
""
],
[
"Bhat",
"R.",
""
],
[
"Flynn",
"C.",
""
]
] | The initial results from timing observations of PSR J1141-6545, a relativistic pulsar white-dwarf binary system, are presented. Predictions from the timing baseline hint at the most stringent test of gravity by an asymmetric binary yet. The timing precision has been hindered by the dramatic variations of the pulse profile due to geodetic precession, a pulsar glitch and red timing noise. Methods to overcome such timing irregularities are briefly presented along with preliminary results from the test of the General Theory of Relativity (GR) from this pulsar |
gr-qc/9706020 | B. Linet | B. Boisseau, B. Linet | Dynamics of a self-gravitating thin string in scalar-tensor theories of
gravitation | 10 pages, latex, no figures | Class.Quant.Grav. 14 (1997) 3063-3071 | 10.1088/0264-9381/14/11/008 | null | gr-qc | null | We examine the dynamics of a self-gravitating string in the scalar-tensor
theories of gravitation by considering a thin tube of matter to describe it.
For a class of solutions, we obtain in the generic case that the extrinsic
curvature of the world sheet of the central line is null in the limit where the
radius of the string tends to zero. However, if we impose a specific constraint
on the behaviour of the solution then we find that only the mean curvature of
the world sheet of the central line vanishes which is just the Nambu-Goto
dynamics. This analysis can include the massless dilatonic theories of gravity.
| [
{
"created": "Mon, 9 Jun 1997 10:16:29 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Boisseau",
"B.",
""
],
[
"Linet",
"B.",
""
]
] | We examine the dynamics of a self-gravitating string in the scalar-tensor theories of gravitation by considering a thin tube of matter to describe it. For a class of solutions, we obtain in the generic case that the extrinsic curvature of the world sheet of the central line is null in the limit where the radius of the string tends to zero. However, if we impose a specific constraint on the behaviour of the solution then we find that only the mean curvature of the world sheet of the central line vanishes which is just the Nambu-Goto dynamics. This analysis can include the massless dilatonic theories of gravity. |
1310.6728 | Edward Wilson-Ewing | Parampreet Singh, Edward Wilson-Ewing | Quantization ambiguities and bounds on geometric scalars in anisotropic
loop quantum cosmology | 34 pages, v2: minor changes | Class.Quant.Grav.31:035010,2014 | 10.1088/0264-9381/31/3/035010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study quantization ambiguities in loop quantum cosmology that arise for
space-times with non-zero spatial curvature and anisotropies. Motivated by
lessons from different possible loop quantizations of the closed
Friedmann-Lemaitre-Robertson-Walker cosmology, we find that using open
holonomies of the extrinsic curvature, which due to gauge-fixing can be treated
as a connection, leads to the same quantum geometry effects that are found in
spatially flat cosmologies. More specifically, in contrast to the quantization
based on open holonomies of the Ashtekar-Barbero connection, the expansion and
shear scalars in the effective theories of the Bianchi type II and Bianchi type
IX models have upper bounds, and these are in exact agreement with the bounds
found in the effective theories of the Friedmann-Lemaitre-Robertson-Walker and
Bianchi type I models in loop quantum cosmology. We also comment on some
ambiguities present in the definition of inverse triad operators and their
role.
| [
{
"created": "Thu, 24 Oct 2013 19:49:08 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Jan 2014 15:31:52 GMT",
"version": "v2"
}
] | 2015-06-17 | [
[
"Singh",
"Parampreet",
""
],
[
"Wilson-Ewing",
"Edward",
""
]
] | We study quantization ambiguities in loop quantum cosmology that arise for space-times with non-zero spatial curvature and anisotropies. Motivated by lessons from different possible loop quantizations of the closed Friedmann-Lemaitre-Robertson-Walker cosmology, we find that using open holonomies of the extrinsic curvature, which due to gauge-fixing can be treated as a connection, leads to the same quantum geometry effects that are found in spatially flat cosmologies. More specifically, in contrast to the quantization based on open holonomies of the Ashtekar-Barbero connection, the expansion and shear scalars in the effective theories of the Bianchi type II and Bianchi type IX models have upper bounds, and these are in exact agreement with the bounds found in the effective theories of the Friedmann-Lemaitre-Robertson-Walker and Bianchi type I models in loop quantum cosmology. We also comment on some ambiguities present in the definition of inverse triad operators and their role. |
gr-qc/0009070 | hamid Reza Sepangi | M. Mohseni and H. R. Sepangi | Gravitational waves and spinning test particles | 11 pages, one eps figure, to appear in Class. Quantum Grav | Class.Quant.Grav. 17 (2000) 4615-4625 | 10.1088/0264-9381/17/22/302 | null | gr-qc astro-ph hep-th | null | The motion of a classical spinning test particle in the field of a weak plane
gravitational wave is studied. It is found that the characteristic dimensions
of the particle's orbit is sensitive to the ratio of the spin to the mass of
the particle. The results are compared with the corresponding motion of a
particle without spin.
| [
{
"created": "Wed, 20 Sep 2000 06:28:35 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Mohseni",
"M.",
""
],
[
"Sepangi",
"H. R.",
""
]
] | The motion of a classical spinning test particle in the field of a weak plane gravitational wave is studied. It is found that the characteristic dimensions of the particle's orbit is sensitive to the ratio of the spin to the mass of the particle. The results are compared with the corresponding motion of a particle without spin. |
2010.02279 | Charis Anastopoulos | Charis Anastopoulos and Ntina Savvidou | Classification theorem and properties of singular solutions to the
Tolman-Oppenheimer-Volkoff equation | 32 pages, 7 figures. Small revisions, some explanations added; to
appear in CQG | null | 10.1088/1361-6382/abdf26 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Tolman-Oppenheimer-Volkoff (TOV) equation admits singular solutions in
addition to regular ones. Here, we prove the following theorem. For any
equation of state that (i) is obtained from an entropy function, (ii) has
positive pressure and (iii) satisfies the dominant energy condition, the TOV
equation can be integrated from a boundary inwards to the center. Hence,
thermodynamic consistency of the EoS precludes pathological solutions, in which
the integration terminates at finite radius (because of horizons, or
divergences / zeroes of energy density). At the center, the mass function
either vanishes (regular solutions) or it is negative (singular solutions). For
singular solutions, the metric at the center is locally isomorphic to
negative-mass Schwarzschild spacetime. This means that matter is stabilized
because the singularity is strongly repulsive. We show that singular solutions
are causally well behaved: they are bounded-acceleration complete, and they are
conformal to a globally hyperbolic spacetime with boundary. Finally, we show
how to modify unphysical equations of state in order to obtain non-pathological
solutions, and we undertake a preliminary investigation of dynamical stability
for singular solutions.
| [
{
"created": "Mon, 5 Oct 2020 18:38:22 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Jan 2021 15:23:05 GMT",
"version": "v2"
}
] | 2021-06-09 | [
[
"Anastopoulos",
"Charis",
""
],
[
"Savvidou",
"Ntina",
""
]
] | The Tolman-Oppenheimer-Volkoff (TOV) equation admits singular solutions in addition to regular ones. Here, we prove the following theorem. For any equation of state that (i) is obtained from an entropy function, (ii) has positive pressure and (iii) satisfies the dominant energy condition, the TOV equation can be integrated from a boundary inwards to the center. Hence, thermodynamic consistency of the EoS precludes pathological solutions, in which the integration terminates at finite radius (because of horizons, or divergences / zeroes of energy density). At the center, the mass function either vanishes (regular solutions) or it is negative (singular solutions). For singular solutions, the metric at the center is locally isomorphic to negative-mass Schwarzschild spacetime. This means that matter is stabilized because the singularity is strongly repulsive. We show that singular solutions are causally well behaved: they are bounded-acceleration complete, and they are conformal to a globally hyperbolic spacetime with boundary. Finally, we show how to modify unphysical equations of state in order to obtain non-pathological solutions, and we undertake a preliminary investigation of dynamical stability for singular solutions. |
gr-qc/0206063 | null | Marek A. Abramowicz and Wlodek Kluzniak | Epicyclic orbital oscillations in Newton's and Einstein's dynamics | 8 pages | Gen.Rel.Grav. 35 (2003) 69-77 | 10.1023/A:1021354928292 | null | gr-qc astro-ph | null | We apply Feynman's principle, ``The same equations have the same solutions'',
to Kepler's problem and show that Newton's dynamics in a properly curved 3-D
space is identical with that described by Einstein's theory in the 3-D optical
geometry of Schwarzschild's spacetime. For this reason, rather unexpectedly,
Newton's formulae for Kepler's problem, in the case of nearly circular motion
in a static, spherically spherical gravitational potential accurately describe
strong field general relativistic effects, in particular vanishing of the
radial epicyclic frequency at the marginally stable orbit.
| [
{
"created": "Thu, 20 Jun 2002 17:25:27 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Abramowicz",
"Marek A.",
""
],
[
"Kluzniak",
"Wlodek",
""
]
] | We apply Feynman's principle, ``The same equations have the same solutions'', to Kepler's problem and show that Newton's dynamics in a properly curved 3-D space is identical with that described by Einstein's theory in the 3-D optical geometry of Schwarzschild's spacetime. For this reason, rather unexpectedly, Newton's formulae for Kepler's problem, in the case of nearly circular motion in a static, spherically spherical gravitational potential accurately describe strong field general relativistic effects, in particular vanishing of the radial epicyclic frequency at the marginally stable orbit. |
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