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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1301.2570
|
Genly Le\'on
|
Dagoberto Escobar (Camaguey U.), Carlos R. Fadragas (Havana, Central
de Las Villas U.), Genly Leon (Valparaiso U., Catolica) and Yoelsy Leyva
(Valparaiso U., Catolica & Guanajuato U.)
|
Asymptotic behavior of a scalar field with an arbitrary potential
trapped on a Randall-Sundrum's braneworld: the effect of a negative dark
radiation term on a Bianchi I brane
|
32 pages, 14 figures. Title has been changed, sections have been
reordered, discussion has been improved, several references added. The final
publication is available at link.springer.com
|
Astrophysics and Space Science, Springer Netherlands, 2013, 1-28
|
10.1007/s10509-013-1650-8
| null |
gr-qc astro-ph.CO hep-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this work we present a phase space analysis of a quintessence field and a
perfect fluid trapped in a Randall-Sundrum's Braneworld of type 2. We consider
a homogeneous but anisotropic Bianchi I brane geometry. Moreover, we consider
the effect of the projection of the five dimensional Weyl tensor onto the
three-brane in the form of a negative Dark Radiation term. For the treatment of
the potential we use the "Method of $f$-devisers" that allows investigating
arbitrary potentials in a phase space. We present general conditions on the
potential in order to obtain the stability of standard 4D and non-standard 5D
de Sitter solutions, and we provide the stability conditions for both scalar
field-matter scaling solutions, scalar field-dark radiation solutions and
scalar field-dominated solutions. We find that the shear-dominated solutions
are unstable (particularly, contracting shear-dominated solutions are of saddle
type). As a main difference with our previous work, the traditionally
ever-expanding models could potentially re-collapse due to the negativity of
the dark radiation. Additionally, our system admits a large class of static
solutions that are of saddle type. These kinds of solutions are important at
intermediate stages in the evolution of the universe, since they allow the
transition from contracting to expanding models and viceversa. New features of
our scenario are the existence of a bounce and a turnaround, which lead to
cyclic behavior, that are not allowed in Bianchi I branes with positive dark
radiation term. Finally, as specific examples we consider the potentials
$V\propto\sinh^{-\alpha}(\beta\phi)$ and $V\propto\left[\cosh\left(\xi\phi
\right)-1\right]$ which have simple $f$-devisers.
|
[
{
"created": "Fri, 11 Jan 2013 18:33:20 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Oct 2013 19:07:17 GMT",
"version": "v2"
}
] |
2013-10-31
|
[
[
"Escobar",
"Dagoberto",
"",
"Camaguey U."
],
[
"Fadragas",
"Carlos R.",
"",
"Havana, Central\n de Las Villas U."
],
[
"Leon",
"Genly",
"",
"Valparaiso U., Catolica"
],
[
"Leyva",
"Yoelsy",
"",
"Valparaiso U., Catolica & Guanajuato U."
]
] |
In this work we present a phase space analysis of a quintessence field and a perfect fluid trapped in a Randall-Sundrum's Braneworld of type 2. We consider a homogeneous but anisotropic Bianchi I brane geometry. Moreover, we consider the effect of the projection of the five dimensional Weyl tensor onto the three-brane in the form of a negative Dark Radiation term. For the treatment of the potential we use the "Method of $f$-devisers" that allows investigating arbitrary potentials in a phase space. We present general conditions on the potential in order to obtain the stability of standard 4D and non-standard 5D de Sitter solutions, and we provide the stability conditions for both scalar field-matter scaling solutions, scalar field-dark radiation solutions and scalar field-dominated solutions. We find that the shear-dominated solutions are unstable (particularly, contracting shear-dominated solutions are of saddle type). As a main difference with our previous work, the traditionally ever-expanding models could potentially re-collapse due to the negativity of the dark radiation. Additionally, our system admits a large class of static solutions that are of saddle type. These kinds of solutions are important at intermediate stages in the evolution of the universe, since they allow the transition from contracting to expanding models and viceversa. New features of our scenario are the existence of a bounce and a turnaround, which lead to cyclic behavior, that are not allowed in Bianchi I branes with positive dark radiation term. Finally, as specific examples we consider the potentials $V\propto\sinh^{-\alpha}(\beta\phi)$ and $V\propto\left[\cosh\left(\xi\phi \right)-1\right]$ which have simple $f$-devisers.
|
2105.09304
|
Junpei Harada
|
Junpei Harada
|
Emergence of the Cotton tensor for describing gravity
|
5 pages, 1 figure, accepted for publication as a Letter in PRD, v2:
typos corrected
|
Phys. Rev. D 103, L121502 (2021)
|
10.1103/PhysRevD.103.L121502
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
It is shown that the Cotton tensor can describe the effects of gravity beyond
general relativity. Any solution of the Einstein equations with or without the
cosmological constant satisfies the field equations described by the Cotton
tensor. It implies that the cosmological constant is an integration constant. A
vacuum of a theory is represented by the vanishing of the Cotton tensor, rather
than the vanishing of the Ricci tensor. An exact Schwarzschild-like solution
for a static and spherically symmetric source is discovered. Although the field
equations involve the third order of derivative, it is found that they reduce
to the second-order differential equations due to a variational principle.
|
[
{
"created": "Tue, 18 May 2021 00:00:59 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Jun 2021 03:30:09 GMT",
"version": "v2"
}
] |
2021-06-23
|
[
[
"Harada",
"Junpei",
""
]
] |
It is shown that the Cotton tensor can describe the effects of gravity beyond general relativity. Any solution of the Einstein equations with or without the cosmological constant satisfies the field equations described by the Cotton tensor. It implies that the cosmological constant is an integration constant. A vacuum of a theory is represented by the vanishing of the Cotton tensor, rather than the vanishing of the Ricci tensor. An exact Schwarzschild-like solution for a static and spherically symmetric source is discovered. Although the field equations involve the third order of derivative, it is found that they reduce to the second-order differential equations due to a variational principle.
|
1209.6191
|
Chandra Prakash Singh
|
C.P. Singh, Vijay Singh
|
Some Exact Solutions of Magnetized viscous model in String Cosmology
|
18 pages, 4 figures, paper has been revised
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we study anisotropic Bianchi-V universe with magnetic field
and bulk viscous fluid in string cosmology. Exact solutions of the field
equations are obtained by using the equation of state for a cloud of strings,
and a relationship between bulk viscous coefficient and scalar expansion. The
bulk viscous coefficient is assumed to be inversely proportional to the
expansion scalar. It is interesting to examine the effects of magnetized bulk
viscous string model in early and late stages of the evolution of the universe.
This paper presents the different string models like geometrical (Nambu
string), Takabayashi (p-string) and Reddy string models by taking certain
physical conditions. We discuss the nature of the classical potential for
viscous fluid with and without magnetic field. We find that the introduction of
bulk viscosity with and without magnetic field results in rapid change in
density parameters and in the classical potential. The presence of bulk
viscosity prevents the universe to be empty in its future evolution. The other
physical and geometrical aspects of each string model are discussed in detail.
|
[
{
"created": "Thu, 27 Sep 2012 11:33:50 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Nov 2012 09:25:17 GMT",
"version": "v2"
}
] |
2012-11-28
|
[
[
"Singh",
"C. P.",
""
],
[
"Singh",
"Vijay",
""
]
] |
In this paper, we study anisotropic Bianchi-V universe with magnetic field and bulk viscous fluid in string cosmology. Exact solutions of the field equations are obtained by using the equation of state for a cloud of strings, and a relationship between bulk viscous coefficient and scalar expansion. The bulk viscous coefficient is assumed to be inversely proportional to the expansion scalar. It is interesting to examine the effects of magnetized bulk viscous string model in early and late stages of the evolution of the universe. This paper presents the different string models like geometrical (Nambu string), Takabayashi (p-string) and Reddy string models by taking certain physical conditions. We discuss the nature of the classical potential for viscous fluid with and without magnetic field. We find that the introduction of bulk viscosity with and without magnetic field results in rapid change in density parameters and in the classical potential. The presence of bulk viscosity prevents the universe to be empty in its future evolution. The other physical and geometrical aspects of each string model are discussed in detail.
|
gr-qc/0504146
|
Bahram Mashhoon
|
C. Chicone, B. Mashhoon and B. Punsly
|
Relativistic Motion of Spinning Particles in a Gravitational Field
|
12 pages, 2 figures, v2: a few minor typos corrected, accepted for
publication in Phys. Lett. A
|
Phys.Lett.A343:1-7,2005
|
10.1016/j.physleta.2005.05.072
| null |
gr-qc astro-ph
| null |
The relative motion of a classical relativistic spinning test particle is
studied with respect to a nearby free test particle in the gravitational field
of a rotating source. The effects of the spin-curvature coupling force are
elucidated and the implications of the results for the motion of rotating
plasma clumps in astrophysical jets are discussed.
|
[
{
"created": "Fri, 29 Apr 2005 18:29:21 GMT",
"version": "v1"
},
{
"created": "Tue, 24 May 2005 20:22:49 GMT",
"version": "v2"
}
] |
2011-07-19
|
[
[
"Chicone",
"C.",
""
],
[
"Mashhoon",
"B.",
""
],
[
"Punsly",
"B.",
""
]
] |
The relative motion of a classical relativistic spinning test particle is studied with respect to a nearby free test particle in the gravitational field of a rotating source. The effects of the spin-curvature coupling force are elucidated and the implications of the results for the motion of rotating plasma clumps in astrophysical jets are discussed.
|
gr-qc/0201002
|
Dr Simon Brian Davis
|
Simon Davis and Hugh Luckock
|
The quantum theory of a quadratic gravity action for heterotic strings
|
12 pages. Renormalizability properties of the action are clarified
and a third-order differential equation for the wave function $\Psi$ with a
dependence on the potential $V(\Phi)$ is included
|
Gen.Rel.Grav. 34 (2002) 1751-1765
| null |
University of Sydney Report 2001-17
|
gr-qc
| null |
The wave function for the quadratic gravity theory derived from the heterotic
string effective action is deduced to first order in ${{e^{-\Phi}}\over
{g_4^2}}$ by solving a perturbed second-order Wheeler-DeWitt equation, assuming
that the potential is slowly varying with respect to $\Phi$. Predictions for
inflation based on the solution to the second-order Wheeler-DeWitt equation
continue to hold for this theory. It is shown how formal expressions for the
average paths in minisuperspace $\{< a(t) >, < \Phi(t)> \}$ determine the
shifts from the classical solutions to $a_{cl}(t)$ and $\Phi_{cl}(t)$, which
occur only at third order in the expansion of the integrals representing the
expectation values.
|
[
{
"created": "Mon, 31 Dec 2001 21:57:05 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Feb 2002 17:41:21 GMT",
"version": "v2"
}
] |
2007-05-23
|
[
[
"Davis",
"Simon",
""
],
[
"Luckock",
"Hugh",
""
]
] |
The wave function for the quadratic gravity theory derived from the heterotic string effective action is deduced to first order in ${{e^{-\Phi}}\over {g_4^2}}$ by solving a perturbed second-order Wheeler-DeWitt equation, assuming that the potential is slowly varying with respect to $\Phi$. Predictions for inflation based on the solution to the second-order Wheeler-DeWitt equation continue to hold for this theory. It is shown how formal expressions for the average paths in minisuperspace $\{< a(t) >, < \Phi(t)> \}$ determine the shifts from the classical solutions to $a_{cl}(t)$ and $\Phi_{cl}(t)$, which occur only at third order in the expansion of the integrals representing the expectation values.
|
1409.3146
|
Angnis Schmidt-May
|
Angnis Schmidt-May
|
Mass eigenstates in bimetric theory with matter coupling
|
Latex, 22 pages, new section 4.2.1 included, v3 matches published
version
|
JCAP 01 (2015) 039
|
10.1088/1475-7516/2015/01/039
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper we study the ghost-free bimetric action extended by a recently
proposed coupling to matter through a composite metric. The equations of motion
for this theory are derived using a method which avoids varying the square-root
matrix that appears in the matter coupling. We make an ansatz for which the
metrics are proportional to each other and find that it can solve the equations
provided that one parameter in the action is fixed. In this case, the
proportional metrics as well as the effective metric that couples to matter
solve Einstein's equations of general relativity including a matter source.
Around these backgrounds we derive the quadratic action for perturbations,
diagonalized into a massive and a massless spin-2 fluctuation. We find that
only the massless spin-2 mode interacts with matter; a result which is
independent of the remaining parameters of the theory.
|
[
{
"created": "Tue, 9 Sep 2014 16:14:25 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Sep 2014 08:23:56 GMT",
"version": "v2"
},
{
"created": "Fri, 30 Jan 2015 10:23:49 GMT",
"version": "v3"
}
] |
2015-02-17
|
[
[
"Schmidt-May",
"Angnis",
""
]
] |
In this paper we study the ghost-free bimetric action extended by a recently proposed coupling to matter through a composite metric. The equations of motion for this theory are derived using a method which avoids varying the square-root matrix that appears in the matter coupling. We make an ansatz for which the metrics are proportional to each other and find that it can solve the equations provided that one parameter in the action is fixed. In this case, the proportional metrics as well as the effective metric that couples to matter solve Einstein's equations of general relativity including a matter source. Around these backgrounds we derive the quadratic action for perturbations, diagonalized into a massive and a massless spin-2 fluctuation. We find that only the massless spin-2 mode interacts with matter; a result which is independent of the remaining parameters of the theory.
|
1707.00273
|
Anupam Mazumdar
|
Alexey S. Koshelev and Anupam Mazumdar
|
Do massive compact objects without event horizon exist in infinite
derivative gravity?
|
5 pages, Accepted version for the journal
| null |
10.1103/PhysRevD.96.084069
| null |
gr-qc astro-ph.GA hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Einstein's General theory of relativity is plagued by cosmological and
blackhole type singularities Recently, it has been shown that infinite
derivative, ghost free, gravity can yield non-singular cosmological and
mini-blackhole solutions. In particular, the theory possesses a {\it mass-gap}
determined by the scale of new physics. We will use this property to argue that
it is possible to form a non-singular super-massive compact objects without
having any event horizon in this class of theories.
|
[
{
"created": "Sun, 2 Jul 2017 10:14:14 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Oct 2017 13:55:05 GMT",
"version": "v2"
}
] |
2017-11-22
|
[
[
"Koshelev",
"Alexey S.",
""
],
[
"Mazumdar",
"Anupam",
""
]
] |
Einstein's General theory of relativity is plagued by cosmological and blackhole type singularities Recently, it has been shown that infinite derivative, ghost free, gravity can yield non-singular cosmological and mini-blackhole solutions. In particular, the theory possesses a {\it mass-gap} determined by the scale of new physics. We will use this property to argue that it is possible to form a non-singular super-massive compact objects without having any event horizon in this class of theories.
|
gr-qc/0010002
|
Katsuhito Yasuno
|
Katsuhito Yasuno, Tatsuhiko Koike and Masaru Siino
|
Thurston's Geometrization Conjecture and cosmological models
|
18 pages, no figures, LaTex 2e, IOP style, Submitted to Class.
Quantum Grav
|
Class.Quant.Grav. 18 (2001) 1405-1420
|
10.1088/0264-9381/18/8/301
| null |
gr-qc
| null |
We investigate a class of spatially compact inhomogeneous spacetimes.
Motivated by Thurston's Geometrization Conjecture, we give a formulation for
constructing spatially compact composite spacetimes as solutions for the
Einstein equations. Such composite spacetimes are built from the spatially
compact locally homogeneous vacuum spacetimes which have two commuting Killing
vectors by gluing them through a timelike hypersurface admitting a homogeneous
spatial slice spanned by the commuting Killing vectors. Topology of the spatial
section of the timelike boundary is taken to be the torus. We also assume that
the matter which will arise from the gluing is compressed on the boundary, i.e.
we take the thin-shell approximation. By solving the junction conditions, we
can see dynamical behavior of the connected (composite) spacetime. The
Teichm\"uller deformation of the torus also can be obtained. We apply our
formalism to a concrete model. The relation to the torus sum of 3-manifolds and
the difficulty of this problem are also discussed.
|
[
{
"created": "Sun, 1 Oct 2000 16:47:35 GMT",
"version": "v1"
}
] |
2009-10-31
|
[
[
"Yasuno",
"Katsuhito",
""
],
[
"Koike",
"Tatsuhiko",
""
],
[
"Siino",
"Masaru",
""
]
] |
We investigate a class of spatially compact inhomogeneous spacetimes. Motivated by Thurston's Geometrization Conjecture, we give a formulation for constructing spatially compact composite spacetimes as solutions for the Einstein equations. Such composite spacetimes are built from the spatially compact locally homogeneous vacuum spacetimes which have two commuting Killing vectors by gluing them through a timelike hypersurface admitting a homogeneous spatial slice spanned by the commuting Killing vectors. Topology of the spatial section of the timelike boundary is taken to be the torus. We also assume that the matter which will arise from the gluing is compressed on the boundary, i.e. we take the thin-shell approximation. By solving the junction conditions, we can see dynamical behavior of the connected (composite) spacetime. The Teichm\"uller deformation of the torus also can be obtained. We apply our formalism to a concrete model. The relation to the torus sum of 3-manifolds and the difficulty of this problem are also discussed.
|
2010.13480
|
Johannes M\"unch
|
Johannes M\"unch
|
Effective Quantum Dust Collapse via Surface Matching
|
40 pages, 23 figures. Version accepted for publication in CQG. Minor
changes, clarifications added
| null |
10.1088/1361-6382/ac103e
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The fate of matter forming a black hole is still an open problem, although
models of quantum gravity corrected black holes are available. In loop quantum
gravity (LQG) models were presented, which resolve the classical singularity in
the centre of the black hole by means of a black-to-white hole transition, but
neglect the collapse process. The situation is similar in other quantum gravity
approaches, where eternal non-singular models are available. In this paper, a
strategy is presented to generalise these eternal models to dynamical collapse
models by surface matching. Assuming 1) the validity of a static quantum black
hole spacetime outside the collapsing matter, 2) homogeneity of the collapsing
matter, and 3) differentiability at the surface of the matter fixes the
dynamics of the spacetime uniquely. It is argued that these assumptions
resemble a collapse of pressure-less dust and thus generalises the
Oppenheimer-Snyder-Datt model, although no precise model of the matter has to
be assumed. Hawking radiation is systematically neglected in this approach. The
junction conditions and the spacetime dynamics are discussed generically for
bouncing black hole spacetimes, as proposed by LQG, although the scheme is
approach independent. Further, the equations are explicitly solved for the
recent model [1] and a global spacetime picture of the collapse is achieved.
The causal structure is discussed in detail and the Penrose diagram is
constructed. The trajectory of the collapsing matter is completely constructed
from an inside and outside observer point of view. The general analysis shows
that the matter is collapsing and re-expanding and crosses the Penrose diagram
diagonally. This way the infinite tower of Penrose diagrams, as proposed by
several LQG models, is generically not cut out. Questions about different
timescales of the collapse for in- and outside observers can be answered.
|
[
{
"created": "Mon, 26 Oct 2020 10:57:18 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Aug 2021 11:35:32 GMT",
"version": "v2"
}
] |
2021-08-17
|
[
[
"Münch",
"Johannes",
""
]
] |
The fate of matter forming a black hole is still an open problem, although models of quantum gravity corrected black holes are available. In loop quantum gravity (LQG) models were presented, which resolve the classical singularity in the centre of the black hole by means of a black-to-white hole transition, but neglect the collapse process. The situation is similar in other quantum gravity approaches, where eternal non-singular models are available. In this paper, a strategy is presented to generalise these eternal models to dynamical collapse models by surface matching. Assuming 1) the validity of a static quantum black hole spacetime outside the collapsing matter, 2) homogeneity of the collapsing matter, and 3) differentiability at the surface of the matter fixes the dynamics of the spacetime uniquely. It is argued that these assumptions resemble a collapse of pressure-less dust and thus generalises the Oppenheimer-Snyder-Datt model, although no precise model of the matter has to be assumed. Hawking radiation is systematically neglected in this approach. The junction conditions and the spacetime dynamics are discussed generically for bouncing black hole spacetimes, as proposed by LQG, although the scheme is approach independent. Further, the equations are explicitly solved for the recent model [1] and a global spacetime picture of the collapse is achieved. The causal structure is discussed in detail and the Penrose diagram is constructed. The trajectory of the collapsing matter is completely constructed from an inside and outside observer point of view. The general analysis shows that the matter is collapsing and re-expanding and crosses the Penrose diagram diagonally. This way the infinite tower of Penrose diagrams, as proposed by several LQG models, is generically not cut out. Questions about different timescales of the collapse for in- and outside observers can be answered.
|
1308.0687
|
Julian Rennert
|
Julian Rennert, David Sloan
|
Anisotropic Spinfoam Cosmology
|
31 pages, 1 figure, v2: substantial improvements. references added.
journal version
|
Class. Quantum Grav. 31 (2014) 015017
|
10.1088/0264-9381/31/1/015017
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The dynamics of a homogeneous, anisotropic universe are investigated within
the context of spinfoam cosmology. Transition amplitudes are calculated for a
graph consisting of a single node and three links - the `Daisy graph' - probing
the behaviour a classical Bianchi I spacetime. It is shown further how the use
of such single node graphs gives rise to a simplification of states such that
all orders in the spin expansion can be calculated, indicating that it is the
vertex expansion that contains information about quantum dynamics.
|
[
{
"created": "Sat, 3 Aug 2013 11:59:36 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Nov 2013 18:40:01 GMT",
"version": "v2"
}
] |
2013-11-21
|
[
[
"Rennert",
"Julian",
""
],
[
"Sloan",
"David",
""
]
] |
The dynamics of a homogeneous, anisotropic universe are investigated within the context of spinfoam cosmology. Transition amplitudes are calculated for a graph consisting of a single node and three links - the `Daisy graph' - probing the behaviour a classical Bianchi I spacetime. It is shown further how the use of such single node graphs gives rise to a simplification of states such that all orders in the spin expansion can be calculated, indicating that it is the vertex expansion that contains information about quantum dynamics.
|
1504.05789
|
Lorenzo Iorio
|
Lorenzo Iorio
|
Editorial for the Special Issue 100 Years of Chronogeometrodynamics: The
Status of the Einstein's Theory of Gravitation in Its Centennial Year
|
LaTex2e, 41 pages, no figures, no tables, 314 references,
peer-reviewed. Accepted for publication in Universe
|
Universe 1:38 2015
|
10.3390/universe1010038
| null |
gr-qc astro-ph.CO physics.hist-ph physics.space-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The present Editorial introduces the Special Issue dedicated by the journal
Universe to the General Theory of Relativity, the beautiful theory of
gravitation of Einstein, a century after its birth. It reviews some of its key
features in a historical perspective, and, in welcoming distinguished
researchers from all over the world to contribute it, some of the main topics
at the forefront of the current research are outlined.
|
[
{
"created": "Tue, 21 Apr 2015 12:24:32 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Apr 2015 19:28:32 GMT",
"version": "v2"
}
] |
2015-04-24
|
[
[
"Iorio",
"Lorenzo",
""
]
] |
The present Editorial introduces the Special Issue dedicated by the journal Universe to the General Theory of Relativity, the beautiful theory of gravitation of Einstein, a century after its birth. It reviews some of its key features in a historical perspective, and, in welcoming distinguished researchers from all over the world to contribute it, some of the main topics at the forefront of the current research are outlined.
|
gr-qc/0210012
|
Thomas W. Baumgarte
|
Nicholas D. Lyford, Thomas W. Baumgarte and Stuart L. Shapiro
|
Effects of Differential Rotation on the Maximum Mass of Neutron Stars
|
6 pages, to appear in ApJ
|
Astrophys.J.583:410-415,2003
|
10.1086/345350
| null |
gr-qc astro-ph
| null |
The merger of binary neutron stars is likely to lead to differentially
rotating remnants. In this paper we numerically construct models of
differentially rotating neutron stars in general relativity and determine their
maximum allowed mass. We model the stars adopting a polytropic equation of
state and tabulate maximum allowed masses as a function of differential
rotation and stiffness of the equation of state. We also provide a crude
argument that yields a qualitative estimate of the effect of stiffness and
differential rotation on the maximum allowed mass.
|
[
{
"created": "Thu, 3 Oct 2002 20:06:31 GMT",
"version": "v1"
}
] |
2014-11-17
|
[
[
"Lyford",
"Nicholas D.",
""
],
[
"Baumgarte",
"Thomas W.",
""
],
[
"Shapiro",
"Stuart L.",
""
]
] |
The merger of binary neutron stars is likely to lead to differentially rotating remnants. In this paper we numerically construct models of differentially rotating neutron stars in general relativity and determine their maximum allowed mass. We model the stars adopting a polytropic equation of state and tabulate maximum allowed masses as a function of differential rotation and stiffness of the equation of state. We also provide a crude argument that yields a qualitative estimate of the effect of stiffness and differential rotation on the maximum allowed mass.
|
2008.13308
|
Matt Visser
|
Thomas Berry (Victoria University of Wellington), Alex Simpson
(Victoria University of Wellington), and Matt Visser (Victoria University of
Wellington)
|
Photon spheres, ISCOs, and OSCOs: Astrophysical observables for regular
black holes with asymptotically Minkowski cores
|
V1: 24 pages. 6 figures. V2: Two references added; one reference
updated; no physics changes
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Classical black holes contain a singularity at their core. This has prompted
various researchers to propose a multitude of modified spacetimes that mimic
the physically observable characteristics of classical black holes as best as
possible, but that crucially do not contain singularities at their cores. Due
to recent advances in near-horizon astronomy, the ability to observationally
distinguish between a classical black hole and a potential black hole mimicker
is becoming increasingly feasible. Herein, we calculate some physically
observable quantities for a recently proposed regular black hole with an
asymptotically Minkowski core -- the radius of the photon sphere and the
extremal stable timelike circular orbit (ESCO). The manner in which the photon
sphere and ESCO relate to the presence (or absence) of horizons is much more
complex than for the Schwarzschild black hole. We find situations in which
photon spheres can approach arbitrarily close to (near extremal) horizons,
situations in which some photon spheres become stable, and situations in which
the locations of both photon spheres and ESCOs become multi-valued, with both
ISCOs (innermost stable circular orbits) and OSCOs (outermost stable circular
orbits). This provides an extremely rich phenomenology of potential
astrophysical interest.
|
[
{
"created": "Mon, 31 Aug 2020 01:03:36 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Sep 2020 07:33:07 GMT",
"version": "v2"
}
] |
2020-09-08
|
[
[
"Berry",
"Thomas",
"",
"Victoria University of Wellington"
],
[
"Simpson",
"Alex",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of\n Wellington"
]
] |
Classical black holes contain a singularity at their core. This has prompted various researchers to propose a multitude of modified spacetimes that mimic the physically observable characteristics of classical black holes as best as possible, but that crucially do not contain singularities at their cores. Due to recent advances in near-horizon astronomy, the ability to observationally distinguish between a classical black hole and a potential black hole mimicker is becoming increasingly feasible. Herein, we calculate some physically observable quantities for a recently proposed regular black hole with an asymptotically Minkowski core -- the radius of the photon sphere and the extremal stable timelike circular orbit (ESCO). The manner in which the photon sphere and ESCO relate to the presence (or absence) of horizons is much more complex than for the Schwarzschild black hole. We find situations in which photon spheres can approach arbitrarily close to (near extremal) horizons, situations in which some photon spheres become stable, and situations in which the locations of both photon spheres and ESCOs become multi-valued, with both ISCOs (innermost stable circular orbits) and OSCOs (outermost stable circular orbits). This provides an extremely rich phenomenology of potential astrophysical interest.
|
2309.06232
|
Jo\~ao Lu\'is Rosa
|
Jo\~ao Lu\'is Rosa, Tom Zlosnik
|
Dynamical system analysis of cosmological evolution in the Aether scalar
tensor theory
|
18 pages, 8 figures
|
Phys. Rev. D 109, 024018 (2024)
|
10.1103/PhysRevD.109.024018
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The Aether Scalar Tensor (AeST) theory is an extension of General Relativity
(GR), proposed for addressing galactic and cosmological observations without
dark matter.The action for the theory includes a function that can currently
only be constrained by phenomenological considerations. In antecedent work,
forms of this function were considered that led to an effective fluid
contribution to the cosmological evolution equations that approximated that of
dust more and more closely at late cosmic times. In this work we consider an
alternative set of functions that most closely approximate dust at the earliest
cosmic times and where deviations from dust-like behaviour gradually emerge
with time. We use the dynamical system formalism to analyze example models from
both possible sets of functions, introducing a complete set of dynamical
variables describing the spacetime curvature, energy density parameters of
different matter components, and AeST scalar field, and obtain the dynamical
equations describing cosmological evolution. The cosmological phase space is
found to feature invariant submanifolds associated to the absence of the matter
components, as well as equilibrium states associated with well-known
cosmological behaviors e.g. matter, radiation, and cosmological constant
dominated epochs. A full numerical integration of the dynamical system is
performed for the models and it is shown that each can closely approximate the
$\Lambda \mathrm{CDM}$ model at the level of the cosmic background.
Generalizations of the models are considered and it is shown that the new
models likely can simultaneously replicate the cosmological successes of cold
dark matter whilst satisfying constraints on the theory from the weak-field
quasistatic regime.
|
[
{
"created": "Tue, 12 Sep 2023 13:50:04 GMT",
"version": "v1"
}
] |
2024-01-18
|
[
[
"Rosa",
"João Luís",
""
],
[
"Zlosnik",
"Tom",
""
]
] |
The Aether Scalar Tensor (AeST) theory is an extension of General Relativity (GR), proposed for addressing galactic and cosmological observations without dark matter.The action for the theory includes a function that can currently only be constrained by phenomenological considerations. In antecedent work, forms of this function were considered that led to an effective fluid contribution to the cosmological evolution equations that approximated that of dust more and more closely at late cosmic times. In this work we consider an alternative set of functions that most closely approximate dust at the earliest cosmic times and where deviations from dust-like behaviour gradually emerge with time. We use the dynamical system formalism to analyze example models from both possible sets of functions, introducing a complete set of dynamical variables describing the spacetime curvature, energy density parameters of different matter components, and AeST scalar field, and obtain the dynamical equations describing cosmological evolution. The cosmological phase space is found to feature invariant submanifolds associated to the absence of the matter components, as well as equilibrium states associated with well-known cosmological behaviors e.g. matter, radiation, and cosmological constant dominated epochs. A full numerical integration of the dynamical system is performed for the models and it is shown that each can closely approximate the $\Lambda \mathrm{CDM}$ model at the level of the cosmic background. Generalizations of the models are considered and it is shown that the new models likely can simultaneously replicate the cosmological successes of cold dark matter whilst satisfying constraints on the theory from the weak-field quasistatic regime.
|
1002.4246
|
Dong-han Yeom
|
Dong-il Hwang, Dong-han Yeom
|
Responses of the Brans-Dicke field due to gravitational collapses
|
28 pages, 14 figures
|
Class.Quant.Grav.27:205002,2010
|
10.1088/0264-9381/27/20/205002
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study responses of the Brans-Dicke field due to gravitational collapses of
scalar field pulses using numerical simulations. Double-null formalism is
employed to implement the numerical simulations. If we supply a scalar field
pulse, it will asymptotically form a black hole via dynamical interactions of
the Brans-Dicke field. Hence, we can observe the responses of the Brans-Dicke
field by two different regions. First, we observe the late time behaviors after
the gravitational collapse, which include formations of a singularity and an
apparent horizon. Second, we observe the fully dynamical behaviors during the
gravitational collapse and view the energy-momentum tensor components. For the
late time behaviors, if the Brans-Dicke coupling is greater (or smaller) than
-1.5, the Brans-Dicke field decreases (or increases) during the gravitational
collapse. Since the Brans-Dicke field should be relaxed to the asymptotic value
with the elapse of time, the final apparent horizon becomes time-like (or
space-like). For the dynamical behaviors, we observed the energy-momentum
tensors around $\omega$ ~ -1.5. If the Brans-Dicke coupling is greater than
-1.5, the $T_{uu}$ component can be negative at the outside of the black hole.
This can allow an instantaneous inflating region during the gravitational
collapse. If the Brans-Dicke coupling is less than -1.5, the oscillation of the
$T_{vv}$ component allows the apparent horizon to shrink. This allows a
combination that violates weak cosmic censorship. Finally, we discuss the
implications of the violation of the null energy condition and weak cosmic
censorship.
|
[
{
"created": "Tue, 23 Feb 2010 05:37:41 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Aug 2010 07:19:16 GMT",
"version": "v2"
}
] |
2015-05-18
|
[
[
"Hwang",
"Dong-il",
""
],
[
"Yeom",
"Dong-han",
""
]
] |
We study responses of the Brans-Dicke field due to gravitational collapses of scalar field pulses using numerical simulations. Double-null formalism is employed to implement the numerical simulations. If we supply a scalar field pulse, it will asymptotically form a black hole via dynamical interactions of the Brans-Dicke field. Hence, we can observe the responses of the Brans-Dicke field by two different regions. First, we observe the late time behaviors after the gravitational collapse, which include formations of a singularity and an apparent horizon. Second, we observe the fully dynamical behaviors during the gravitational collapse and view the energy-momentum tensor components. For the late time behaviors, if the Brans-Dicke coupling is greater (or smaller) than -1.5, the Brans-Dicke field decreases (or increases) during the gravitational collapse. Since the Brans-Dicke field should be relaxed to the asymptotic value with the elapse of time, the final apparent horizon becomes time-like (or space-like). For the dynamical behaviors, we observed the energy-momentum tensors around $\omega$ ~ -1.5. If the Brans-Dicke coupling is greater than -1.5, the $T_{uu}$ component can be negative at the outside of the black hole. This can allow an instantaneous inflating region during the gravitational collapse. If the Brans-Dicke coupling is less than -1.5, the oscillation of the $T_{vv}$ component allows the apparent horizon to shrink. This allows a combination that violates weak cosmic censorship. Finally, we discuss the implications of the violation of the null energy condition and weak cosmic censorship.
|
2207.00226
|
Indranil Chakraborty
|
Indranil Chakraborty, Soumya Bhattacharya, Sumanta Chakraborty
|
Gravitational wave memory in wormhole spacetimes
|
Some additions and clarifications, matches with the published version
in Phys. Rev. D
|
Phys. Rev. D 106, 104057, 2022
|
10.1103/PhysRevD.106.104057
| null |
gr-qc hep-th
|
http://creativecommons.org/publicdomain/zero/1.0/
|
Gravitational wave memory is studied in the context of a certain class of
braneworld wormholes. Unlike other wormhole geometries, this novel class of
wormholes do not require any exotic matter fields for its traversability.
First, we study geodesics in this wormhole spacetime, in the presence of a
gravitational wave pulse. The resulting evolution of the geodesic separation
shows the presence of displacement and velocity memory effects. Motivated by
the same, we study the memory effects at null infinity using the Bondi-Sachs
formalism, adapted for braneworld wormhole. Our analysis provides a non-trivial
change of the Bondi mass after the passage of a burst of gravitational
radiation and hence manifests the memory effect at null infinity. In both of
these exercises, the presence of extra dimension and the wormhole nature of the
spacetime geometry gets imprinted in the memory effect. Since future
gravitational wave detectors will be able to probe the memory effect, the
present work provides another avenue to search for compact objects other than
black holes.
|
[
{
"created": "Fri, 1 Jul 2022 06:39:42 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Nov 2022 15:26:40 GMT",
"version": "v2"
}
] |
2022-12-02
|
[
[
"Chakraborty",
"Indranil",
""
],
[
"Bhattacharya",
"Soumya",
""
],
[
"Chakraborty",
"Sumanta",
""
]
] |
Gravitational wave memory is studied in the context of a certain class of braneworld wormholes. Unlike other wormhole geometries, this novel class of wormholes do not require any exotic matter fields for its traversability. First, we study geodesics in this wormhole spacetime, in the presence of a gravitational wave pulse. The resulting evolution of the geodesic separation shows the presence of displacement and velocity memory effects. Motivated by the same, we study the memory effects at null infinity using the Bondi-Sachs formalism, adapted for braneworld wormhole. Our analysis provides a non-trivial change of the Bondi mass after the passage of a burst of gravitational radiation and hence manifests the memory effect at null infinity. In both of these exercises, the presence of extra dimension and the wormhole nature of the spacetime geometry gets imprinted in the memory effect. Since future gravitational wave detectors will be able to probe the memory effect, the present work provides another avenue to search for compact objects other than black holes.
|
1601.05386
|
Istvan Racz
|
Istv\'an R\'acz and Jeffrey Winicour
|
On solving the constraints by integrating a strongly hyperbolic system
|
16 pages, no figures, typos corrected
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
It was shown recently that the constraints on the initial data for Einstein's
equations may be posed as an evolutionary problem [9]. In one of the proposed
two methods the constraints can be replaced by a first order symmetrizable
hyperbolic system and a subsidiary algebraic relation. Here, by assuming that
the initial data surface is smoothly foliated by a one-parameter family of
topological two-spheres, the basic variables are recast in terms of
spin-weighted fields. This allows one to replace all the angular derivatives in
the evolutionary system by the Newman-Penrose $\eth$ and $\bar{\eth}$ operators
which, in turn, opens up a new avenue to solve the constraints by integrating
the resulting system using suitable numerical schemes. In particular, by
replacing the $\eth$ and $\bar{\eth}$ operators either by a finite difference
or by a pseudo-spectral representation or by applying a spectral decomposition
in terms of spin-weighted spherical harmonics, the evolutionary equations may
be put into the form of a coupled system of non-linear ordinary differential
equations.
|
[
{
"created": "Wed, 20 Jan 2016 19:46:10 GMT",
"version": "v1"
},
{
"created": "Sat, 6 Feb 2016 22:49:16 GMT",
"version": "v2"
}
] |
2016-02-09
|
[
[
"Rácz",
"István",
""
],
[
"Winicour",
"Jeffrey",
""
]
] |
It was shown recently that the constraints on the initial data for Einstein's equations may be posed as an evolutionary problem [9]. In one of the proposed two methods the constraints can be replaced by a first order symmetrizable hyperbolic system and a subsidiary algebraic relation. Here, by assuming that the initial data surface is smoothly foliated by a one-parameter family of topological two-spheres, the basic variables are recast in terms of spin-weighted fields. This allows one to replace all the angular derivatives in the evolutionary system by the Newman-Penrose $\eth$ and $\bar{\eth}$ operators which, in turn, opens up a new avenue to solve the constraints by integrating the resulting system using suitable numerical schemes. In particular, by replacing the $\eth$ and $\bar{\eth}$ operators either by a finite difference or by a pseudo-spectral representation or by applying a spectral decomposition in terms of spin-weighted spherical harmonics, the evolutionary equations may be put into the form of a coupled system of non-linear ordinary differential equations.
|
1206.3807
|
Kristina Giesel
|
Kristina Giesel, Thomas Thiemann
|
Scalar Material Reference Systems and Loop Quantum Gravity
|
28 pages, some references were corrected
|
2015 Class. Quantum Grav. 32 135015
|
10.1088/0264-9381/32/13/135015
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In the past, the possibility to employ (scalar) material reference systems in
order to describe classical and quantum gravity directly in terms of gauge
invariant (Dirac) observables has been emphasised frequently. This idea has
been picked up more recently in Loop Quantum Gravity (LQG) with the aim to
perform a reduced phase space quantisation of the theory thus possibly avoiding
problems with the (Dirac) operator constraint quantisation method for
constrained system. In this work, we review the models that have been studied
on the classical and/or the quantum level and parametrise the space of theories
so far considered. We then describe the quantum theory of a model that, to the
best of our knowledge, so far has only been considered classically. This model
could arguably called the optimal one in this class of models considered as it
displays the simplest possible true Hamiltonian while at the same time reducing
all constraints of General Relativity.
|
[
{
"created": "Sun, 17 Jun 2012 23:32:50 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Jun 2012 22:04:07 GMT",
"version": "v2"
}
] |
2022-12-05
|
[
[
"Giesel",
"Kristina",
""
],
[
"Thiemann",
"Thomas",
""
]
] |
In the past, the possibility to employ (scalar) material reference systems in order to describe classical and quantum gravity directly in terms of gauge invariant (Dirac) observables has been emphasised frequently. This idea has been picked up more recently in Loop Quantum Gravity (LQG) with the aim to perform a reduced phase space quantisation of the theory thus possibly avoiding problems with the (Dirac) operator constraint quantisation method for constrained system. In this work, we review the models that have been studied on the classical and/or the quantum level and parametrise the space of theories so far considered. We then describe the quantum theory of a model that, to the best of our knowledge, so far has only been considered classically. This model could arguably called the optimal one in this class of models considered as it displays the simplest possible true Hamiltonian while at the same time reducing all constraints of General Relativity.
|
gr-qc/0309093
|
Stephane Fay
|
Stephane Fay
|
Exact solutions of the Hyperextended Scalar Tensor theory with potential
in the Bianchi type I model
|
13 pages, 1 figure
|
Class. Quant Grav., Vol 18, 1, 2001
| null | null |
gr-qc
| null |
The Hyperextended Scalar Tensor theory with a potential is defined by three
free functions: the gravitational function, the Brans-Dicke coupling function
and the potential. Starting from the expression of the 3-volume and the
potential as function of the proper time, we determine the exact solutions of
this theory. We study two important cases corresponding to power and
exponential laws for the 3-volume and the potential.
|
[
{
"created": "Fri, 19 Sep 2003 12:06:07 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Fay",
"Stephane",
""
]
] |
The Hyperextended Scalar Tensor theory with a potential is defined by three free functions: the gravitational function, the Brans-Dicke coupling function and the potential. Starting from the expression of the 3-volume and the potential as function of the proper time, we determine the exact solutions of this theory. We study two important cases corresponding to power and exponential laws for the 3-volume and the potential.
|
1811.03209
|
Sreenath Kizhakkumpurath Manikandan
|
Sreenath K. Manikandan and Andrew N. Jordan
|
Bosons falling into a black hole: A superfluid analogue
|
11 pages, 4 figures
|
Phys. Rev. D 98, 124043 (2018)
|
10.1103/PhysRevD.98.124043
| null |
gr-qc cond-mat.quant-gas quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We propose an analogy between the quantum physics of a black hole in its late
stages of the evaporation process and a superfluid Bose Einstein Condensate
(BEC), based on the Horowitz and Maldacena quantum final state projection model
[JHEP 2004(02), 008]. The superfluid region is considered to be analogous to
the interior of a black hole, and the normal fluid/superfluid interface is
compared to the event horizon of a black hole. We theoretically investigate the
possibility of recovering the wavefunction of particles incident on a
superfluid BEC from the normal fluid, facilitated by the mode conversion
processes occurring at the normal fluid/superfluid BEC interface. We also study
how the correlations of an infalling mode with an external memory system can be
preserved in the process, similar to Hayden and Preskill's "information mirror"
model for a black hole [JHEP 2007(09), 120]. Based on these analogies, we
conjecture that the quantum state of bosons entering a black hole in its final
state is the superfluid quantum ground state of interacting bosons. Our analogy
suggests that the wavefunction of bosons falling into a black hole can be
recovered from the outgoing Hawking modes. In the particular case when a
hole-like quasiparticle (a density dip) is incident on the superfluid BEC
causing the superfluid to shrink in size, our model indicates that the
evaporation is unitary.
|
[
{
"created": "Thu, 8 Nov 2018 01:25:27 GMT",
"version": "v1"
}
] |
2019-01-02
|
[
[
"Manikandan",
"Sreenath K.",
""
],
[
"Jordan",
"Andrew N.",
""
]
] |
We propose an analogy between the quantum physics of a black hole in its late stages of the evaporation process and a superfluid Bose Einstein Condensate (BEC), based on the Horowitz and Maldacena quantum final state projection model [JHEP 2004(02), 008]. The superfluid region is considered to be analogous to the interior of a black hole, and the normal fluid/superfluid interface is compared to the event horizon of a black hole. We theoretically investigate the possibility of recovering the wavefunction of particles incident on a superfluid BEC from the normal fluid, facilitated by the mode conversion processes occurring at the normal fluid/superfluid BEC interface. We also study how the correlations of an infalling mode with an external memory system can be preserved in the process, similar to Hayden and Preskill's "information mirror" model for a black hole [JHEP 2007(09), 120]. Based on these analogies, we conjecture that the quantum state of bosons entering a black hole in its final state is the superfluid quantum ground state of interacting bosons. Our analogy suggests that the wavefunction of bosons falling into a black hole can be recovered from the outgoing Hawking modes. In the particular case when a hole-like quasiparticle (a density dip) is incident on the superfluid BEC causing the superfluid to shrink in size, our model indicates that the evaporation is unitary.
|
gr-qc/9906057
|
Motomu Tsuda
|
Motomu Tsuda
|
Generalized Lagrangian of N = 1 supergravity and its canonical
constraints with the real Ashtekar variable
|
17 pages, LATEX
|
Phys.Rev. D61 (2000) 024025
|
10.1103/PhysRevD.61.024025
|
STUPP-99-157
|
gr-qc
| null |
We generalize the Lagrangian of N = 1 supergravity (SUGRA) by using an
arbitrary parameter $\xi$, which corresponds to the inverse of Barbero's
parameter $\beta$. This generalized Lagrangian involves the chiral one as a
special case of the value $\xi = \pm i$. We show that the generalized
Lagrangian gives the canonical formulation of N = 1 SUGRA with the real
Ashtekar variable after the 3+1 decomposition of spacetime. This canonical
formulation is also derived from those of the usual N = 1 SUGRA by performing
Barbero's type canonical transformation with an arbitrary parameter $\beta
(=\xi^{-1})$. We give some comments on the canonical formulation of the theory.
|
[
{
"created": "Wed, 16 Jun 1999 06:21:30 GMT",
"version": "v1"
}
] |
2009-10-31
|
[
[
"Tsuda",
"Motomu",
""
]
] |
We generalize the Lagrangian of N = 1 supergravity (SUGRA) by using an arbitrary parameter $\xi$, which corresponds to the inverse of Barbero's parameter $\beta$. This generalized Lagrangian involves the chiral one as a special case of the value $\xi = \pm i$. We show that the generalized Lagrangian gives the canonical formulation of N = 1 SUGRA with the real Ashtekar variable after the 3+1 decomposition of spacetime. This canonical formulation is also derived from those of the usual N = 1 SUGRA by performing Barbero's type canonical transformation with an arbitrary parameter $\beta (=\xi^{-1})$. We give some comments on the canonical formulation of the theory.
|
1911.13031
|
Adrien Bourgoin
|
Adrien Bourgoin
|
General expansion of time transfer functions in optical spacetime
| null |
Phys. Rev. D 101, 064035 (2020)
|
10.1103/PhysRevD.101.064035
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
When dealing with highly accurate modeling of time and frequency transfers
into arbitrarily moving dielectrics medium, it may be convenient to work with
Gordon's optical spacetime metric rather than the usual physical spacetime
metric. Additionally, an accurate modeling of the geodesic evolution of
observable quantities (e.g., the range and the Doppler) requires us to know the
reception or the emission time transfer functions. In the physical spacetime,
these functions can be derived to any post-Minkowskian orders through a
recursive procedure. In this work, we show that the time transfer functions can
be determined to any order in Gordon's optical spacetime as well. The exact
integral forms of the gravitational, the refractive, and the coupling
contributions are recursively derived. The expression of the time transfer
function is given within the post-linear approximation assuming a stationary
optical spacetime covered with geocentric celestial reference system
coordinates. The light-dragging effect due to the steady rotation of the
neutral atmosphere of the Earth is found to be at the threshold of visibility
in many experiments involving accurate modeling of the time and frequency
transfers.
|
[
{
"created": "Fri, 29 Nov 2019 10:09:17 GMT",
"version": "v1"
},
{
"created": "Sat, 29 Feb 2020 11:18:44 GMT",
"version": "v2"
}
] |
2020-03-25
|
[
[
"Bourgoin",
"Adrien",
""
]
] |
When dealing with highly accurate modeling of time and frequency transfers into arbitrarily moving dielectrics medium, it may be convenient to work with Gordon's optical spacetime metric rather than the usual physical spacetime metric. Additionally, an accurate modeling of the geodesic evolution of observable quantities (e.g., the range and the Doppler) requires us to know the reception or the emission time transfer functions. In the physical spacetime, these functions can be derived to any post-Minkowskian orders through a recursive procedure. In this work, we show that the time transfer functions can be determined to any order in Gordon's optical spacetime as well. The exact integral forms of the gravitational, the refractive, and the coupling contributions are recursively derived. The expression of the time transfer function is given within the post-linear approximation assuming a stationary optical spacetime covered with geocentric celestial reference system coordinates. The light-dragging effect due to the steady rotation of the neutral atmosphere of the Earth is found to be at the threshold of visibility in many experiments involving accurate modeling of the time and frequency transfers.
|
2201.09902
|
Sebastian Steinhaus
|
Courtney Allen and Florian Girelli and Sebastian Steinhaus
|
Numerical evaluation of spin foam amplitudes beyond simplices
|
23 pages, 17 figures, v2: added references to code and dataset
|
Phys.Rev.D 105 (2022) 6, 066003
|
10.1103/PhysRevD.105.066003
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We present the first numerical calculation of the 4D Euclidean spin foam
vertex amplitude for vertices with hypercubic combinatorics. Concretely, we
compute the amplitude for coherent boundary data peaked on cuboid and frustum
shapes. We present the numerical algorithms to explicitly compute the vertex
amplitude and compare the results in different cases to the semi-classical
approximation of the amplitude. Overall we find good qualitative agreement of
the amplitudes and evidence of convergence of the asymptotic formula to the
full amplitude already at fairly small spins, yet also differences in the
frequency of oscillations and a phase shift absent in the 4-simplex case.
However, due to rapidly growing numerical costs, we cannot reach sufficiently
high spins to prove agreement of both amplitudes. Lastly, this setup allows us
to explore non-uniform vertex amplitudes, where some representations are small
while others are large; we find indications that scenarios might exist in which
the semi-classical amplitude is a valid approximation even if some spins remain
small. This suggests that the transition of the quantum to the semi-classical
regime (for a single vertex amplitude) is intricate.
|
[
{
"created": "Mon, 24 Jan 2022 19:00:11 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Feb 2022 13:45:40 GMT",
"version": "v2"
}
] |
2022-03-16
|
[
[
"Allen",
"Courtney",
""
],
[
"Girelli",
"Florian",
""
],
[
"Steinhaus",
"Sebastian",
""
]
] |
We present the first numerical calculation of the 4D Euclidean spin foam vertex amplitude for vertices with hypercubic combinatorics. Concretely, we compute the amplitude for coherent boundary data peaked on cuboid and frustum shapes. We present the numerical algorithms to explicitly compute the vertex amplitude and compare the results in different cases to the semi-classical approximation of the amplitude. Overall we find good qualitative agreement of the amplitudes and evidence of convergence of the asymptotic formula to the full amplitude already at fairly small spins, yet also differences in the frequency of oscillations and a phase shift absent in the 4-simplex case. However, due to rapidly growing numerical costs, we cannot reach sufficiently high spins to prove agreement of both amplitudes. Lastly, this setup allows us to explore non-uniform vertex amplitudes, where some representations are small while others are large; we find indications that scenarios might exist in which the semi-classical amplitude is a valid approximation even if some spins remain small. This suggests that the transition of the quantum to the semi-classical regime (for a single vertex amplitude) is intricate.
|
1310.7454
|
Katherine Grover
|
K. Grover, S. Fairhurst, B. F. Farr, I. Mandel, C. Rodriguez, T.
Sidery, and A. Vecchio
|
Comparison of Gravitational Wave Detector Network Sky Localization
Approximations
|
11 pages, 7 Figures
| null |
10.1103/PhysRevD.89.042004
| null |
gr-qc astro-ph.IM
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Gravitational waves emitted during compact binary coalescences are a
promising source for gravitational-wave detector networks. The accuracy with
which the location of the source on the sky can be inferred from gravitational
wave data is a limiting factor for several potential scientific goals of
gravitational-wave astronomy, including multi-messenger observations. Various
methods have been used to estimate the ability of a proposed network to
localize sources. Here we compare two techniques for predicting the uncertainty
of sky localization -- timing triangulation and the Fisher information matrix
approximations -- with Bayesian inference on the full, coherent data set. We
find that timing triangulation alone tends to over-estimate the uncertainty in
sky localization by a median factor of $4$ for a set of signals from
non-spinning compact object binaries ranging up to a total mass of $20
M_\odot$, and the over-estimation increases with the mass of the system. We
find that average predictions can be brought to better agreement by the
inclusion of phase consistency information in timing-triangulation techniques.
However, even after corrections, these techniques can yield significantly
different results to the full analysis on specific mock signals. Thus, while
the approximate techniques may be useful in providing rapid, large scale
estimates of network localization capability, the fully coherent Bayesian
analysis gives more robust results for individual signals, particularly in the
presence of detector noise.
|
[
{
"created": "Mon, 28 Oct 2013 15:16:42 GMT",
"version": "v1"
}
] |
2015-06-17
|
[
[
"Grover",
"K.",
""
],
[
"Fairhurst",
"S.",
""
],
[
"Farr",
"B. F.",
""
],
[
"Mandel",
"I.",
""
],
[
"Rodriguez",
"C.",
""
],
[
"Sidery",
"T.",
""
],
[
"Vecchio",
"A.",
""
]
] |
Gravitational waves emitted during compact binary coalescences are a promising source for gravitational-wave detector networks. The accuracy with which the location of the source on the sky can be inferred from gravitational wave data is a limiting factor for several potential scientific goals of gravitational-wave astronomy, including multi-messenger observations. Various methods have been used to estimate the ability of a proposed network to localize sources. Here we compare two techniques for predicting the uncertainty of sky localization -- timing triangulation and the Fisher information matrix approximations -- with Bayesian inference on the full, coherent data set. We find that timing triangulation alone tends to over-estimate the uncertainty in sky localization by a median factor of $4$ for a set of signals from non-spinning compact object binaries ranging up to a total mass of $20 M_\odot$, and the over-estimation increases with the mass of the system. We find that average predictions can be brought to better agreement by the inclusion of phase consistency information in timing-triangulation techniques. However, even after corrections, these techniques can yield significantly different results to the full analysis on specific mock signals. Thus, while the approximate techniques may be useful in providing rapid, large scale estimates of network localization capability, the fully coherent Bayesian analysis gives more robust results for individual signals, particularly in the presence of detector noise.
|
gr-qc/9409018
|
Lau Yun-kau
|
Y.K.Lau
|
How Objective is Black Hole Entropy?
|
Latex file, 10 pages
| null | null | null |
gr-qc
| null |
The objectivity of black hole entropy is discussed in the particular case of
a Schwarzchild black hole. Using Jaynes' maximum entropy formalism and
Euclidean path integral evaluation of partition function, it is argued that in
the semiclassical limit when the fluctutation of metric is neglected, the black
hole entropy of a Schwarzchild black hole is equal to the maximal information
entropy of an observer whose sole knowledge of the black hole is its mass.
Black hole entropy becomes a measure of number of its internal mass eigenstates
in accordance with the Boltzmann principle only in the limit of negligible
relative mass fluctutation. {}From the information theoretic perspective, the
example of a Schwarzchild black hole seems to suggest that black hole entropy
is no different from ordinary thermodynamic entropy. It is a property of the
experimental data of a black hole, rather than being an intrinsic physical
property of a black hole itself independent of any observer. However, it is
still weakly objective in the sense that different observers given the same set
of data of a black hole will measure the same maximal information entropy.
|
[
{
"created": "Sat, 10 Sep 1994 16:26:15 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Lau",
"Y. K.",
""
]
] |
The objectivity of black hole entropy is discussed in the particular case of a Schwarzchild black hole. Using Jaynes' maximum entropy formalism and Euclidean path integral evaluation of partition function, it is argued that in the semiclassical limit when the fluctutation of metric is neglected, the black hole entropy of a Schwarzchild black hole is equal to the maximal information entropy of an observer whose sole knowledge of the black hole is its mass. Black hole entropy becomes a measure of number of its internal mass eigenstates in accordance with the Boltzmann principle only in the limit of negligible relative mass fluctutation. {}From the information theoretic perspective, the example of a Schwarzchild black hole seems to suggest that black hole entropy is no different from ordinary thermodynamic entropy. It is a property of the experimental data of a black hole, rather than being an intrinsic physical property of a black hole itself independent of any observer. However, it is still weakly objective in the sense that different observers given the same set of data of a black hole will measure the same maximal information entropy.
|
1206.1408
|
Mustapha Azreg-A\"inou
|
Mustapha Azreg-A\"inou
|
Rotation and twist regular modes for trapped ghosts
|
11 pages, 3 figures; General Relativity and Gravitation - 2012
| null |
10.1007/s10714-012-1390-z
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A parameter-independent notion of stationary slow motion is formulated then
applied to the case of stationary rotation of massless trapped ghosts. The
excitations correspond to a rotation mode with angular momentum $J\neq 0$ and
twist modes. It is found that the rotation mode, which has no parity, causes
excess in the angular velocity of dragged distant coordinate frames in one
sheet of the wormhole while in the other sheet the angular velocity of the
ghosts is that of rotating stars: $2J/r^3$. As to the twist modes, which all
have parity, they cause excess in the angular velocity of one of the throat's
poles with respect to the other.
|
[
{
"created": "Thu, 7 Jun 2012 07:05:35 GMT",
"version": "v1"
}
] |
2012-06-08
|
[
[
"Azreg-Aïnou",
"Mustapha",
""
]
] |
A parameter-independent notion of stationary slow motion is formulated then applied to the case of stationary rotation of massless trapped ghosts. The excitations correspond to a rotation mode with angular momentum $J\neq 0$ and twist modes. It is found that the rotation mode, which has no parity, causes excess in the angular velocity of dragged distant coordinate frames in one sheet of the wormhole while in the other sheet the angular velocity of the ghosts is that of rotating stars: $2J/r^3$. As to the twist modes, which all have parity, they cause excess in the angular velocity of one of the throat's poles with respect to the other.
|
2007.13206
|
Fay Dowker
|
Fay Dowker
|
Boundary contributions in the causal set action
|
21 pages, 4 figures. Second version with arXiv reference added and
typos corrected
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Evidence is provided for a conjecture that, in the continuum limit, the mean
of the causal set action of a causal set sprinkled into a globally hyperbolic
Lorentzian spacetime, M, of finite volume equals the Einstein Hilbert action of
M plus the volume of the co-dimension 2 intersection of the future boundary
with the past boundary. We give the heuristic argument for this conjecture and
analyse some examples in 2 dimensions and one example in 4 dimensions.
|
[
{
"created": "Sun, 26 Jul 2020 20:05:41 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Jul 2020 08:31:48 GMT",
"version": "v2"
}
] |
2020-07-29
|
[
[
"Dowker",
"Fay",
""
]
] |
Evidence is provided for a conjecture that, in the continuum limit, the mean of the causal set action of a causal set sprinkled into a globally hyperbolic Lorentzian spacetime, M, of finite volume equals the Einstein Hilbert action of M plus the volume of the co-dimension 2 intersection of the future boundary with the past boundary. We give the heuristic argument for this conjecture and analyse some examples in 2 dimensions and one example in 4 dimensions.
|
gr-qc/9907035
|
Zhang Yuan-zhong
|
Ke-Jian Jin, Yuan-Zhong Zhang, and Zong-Hong Zhu
|
Gravitational Lensing Effects of Fermion-Fermion Stars: I. Strong Field
Case
|
7 pages, LaTex and PostScript; 4 figures, PostScript
|
Phys.Lett. A264 (2000) 335-340
|
10.1016/S0375-9601(99)00830-0
| null |
gr-qc
| null |
We investigate a two-component model for gravitational lenses, i.e., the
fermion-fermion star as a dark matter self-gravitating system made from two
kinds of fermions with different masses. We calculate the deflection angles
varying from arcseconds to even degrees. There is one Einstein ring. In
particular, we find three radial critical curves for radial magnifications and
four or five images of a point source. These are different from the case of the
one-component model such as the fermion stars and boson stars. This is due to
the fermion-fermion star being a two-component concentric sphere. Our results
suggest that any possible observations of the number of images more than 3
could imply a polytropic distribution of the mass inside the lens in the
universe.
|
[
{
"created": "Thu, 8 Jul 1999 11:30:29 GMT",
"version": "v1"
}
] |
2009-10-31
|
[
[
"Jin",
"Ke-Jian",
""
],
[
"Zhang",
"Yuan-Zhong",
""
],
[
"Zhu",
"Zong-Hong",
""
]
] |
We investigate a two-component model for gravitational lenses, i.e., the fermion-fermion star as a dark matter self-gravitating system made from two kinds of fermions with different masses. We calculate the deflection angles varying from arcseconds to even degrees. There is one Einstein ring. In particular, we find three radial critical curves for radial magnifications and four or five images of a point source. These are different from the case of the one-component model such as the fermion stars and boson stars. This is due to the fermion-fermion star being a two-component concentric sphere. Our results suggest that any possible observations of the number of images more than 3 could imply a polytropic distribution of the mass inside the lens in the universe.
|
2302.05704
|
Prosenjit Paul
|
Prosenjit Paul, S. I. Kruglov
|
Thermodynamics of BTZ Black Holes in Nonlinear Electrodynamics
|
12 pages, 14 figures, Published in Indian Journal of Physics
|
Indian Journal of Physics 98, (2024)
|
10.1007/s12648-023-02946-y
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We investigate electrically charged black holes in $(2+1)$ dimensional
gravity coupled to nonlinear electrodynamics (NED). The metric function $f(r)$
is depicted, showing that there can be one or two horizons. We study black hole
thermodynamics in extended phase space. The cosmological constant played the
role of thermodynamics pressure. Electrostatic potential, vacuum polarization,
internal energy, Helmholtz and Gibbs free energies as functions of black hole
horizon and Hawking temperature were analysed. The global stability of the
black hole is discussed. The specific heat and local thermodynamic stability of
black holes are studied. Finally, the Van der Walls behaviour of the black
holes is investigated.
|
[
{
"created": "Sat, 11 Feb 2023 14:36:32 GMT",
"version": "v1"
},
{
"created": "Sat, 23 Sep 2023 06:54:30 GMT",
"version": "v2"
}
] |
2024-07-02
|
[
[
"Paul",
"Prosenjit",
""
],
[
"Kruglov",
"S. I.",
""
]
] |
We investigate electrically charged black holes in $(2+1)$ dimensional gravity coupled to nonlinear electrodynamics (NED). The metric function $f(r)$ is depicted, showing that there can be one or two horizons. We study black hole thermodynamics in extended phase space. The cosmological constant played the role of thermodynamics pressure. Electrostatic potential, vacuum polarization, internal energy, Helmholtz and Gibbs free energies as functions of black hole horizon and Hawking temperature were analysed. The global stability of the black hole is discussed. The specific heat and local thermodynamic stability of black holes are studied. Finally, the Van der Walls behaviour of the black holes is investigated.
|
2305.01676
|
Jerome Quintin
|
Ghazal Geshnizjani, Eric Ling, Jerome Quintin
|
On the initial singularity and extendibility of flat quasi-de Sitter
spacetimes
|
62 pages, 6 figures; v2: minor corrections and references added,
matches published version
|
J. High Energ. Phys. 2023, 182 (2023)
|
10.1007/JHEP10(2023)182
|
CPH-GEOTOP-DNRF151; CF21-0680
|
gr-qc hep-th math-ph math.DG math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Inflationary spacetimes have been argued to be past geodesically incomplete
in many situations. However, whether the geodesic incompleteness implies the
existence of an initial spacetime curvature singularity or whether the
spacetime may be extended (potentially into another phase of the universe) is
generally unknown. Both questions have important physical implications. In this
paper, we take a closer look at the geometrical structure of inflationary
spacetimes and investigate these very questions. We first classify which past
inflationary histories have a scalar curvature singularity and which might be
extendible and/or non-singular in homogeneous and isotropic cosmology with flat
spatial sections. Then, we derive rigorous extendibility criteria of various
regularity classes for quasi-de Sitter spacetimes that evolve from infinite
proper time in the past. Finally, we show that beyond homogeneity and isotropy,
special continuous extensions respecting the Einstein field equations with a
perfect fluid must have the equation of state of a de Sitter universe
asymptotically. An interpretation of our results is that past-eternal
inflationary scenarios are most likely physically singular, except in
situations with very special initial conditions.
|
[
{
"created": "Tue, 2 May 2023 18:00:00 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Nov 2023 14:20:55 GMT",
"version": "v2"
}
] |
2023-11-02
|
[
[
"Geshnizjani",
"Ghazal",
""
],
[
"Ling",
"Eric",
""
],
[
"Quintin",
"Jerome",
""
]
] |
Inflationary spacetimes have been argued to be past geodesically incomplete in many situations. However, whether the geodesic incompleteness implies the existence of an initial spacetime curvature singularity or whether the spacetime may be extended (potentially into another phase of the universe) is generally unknown. Both questions have important physical implications. In this paper, we take a closer look at the geometrical structure of inflationary spacetimes and investigate these very questions. We first classify which past inflationary histories have a scalar curvature singularity and which might be extendible and/or non-singular in homogeneous and isotropic cosmology with flat spatial sections. Then, we derive rigorous extendibility criteria of various regularity classes for quasi-de Sitter spacetimes that evolve from infinite proper time in the past. Finally, we show that beyond homogeneity and isotropy, special continuous extensions respecting the Einstein field equations with a perfect fluid must have the equation of state of a de Sitter universe asymptotically. An interpretation of our results is that past-eternal inflationary scenarios are most likely physically singular, except in situations with very special initial conditions.
|
2402.08937
|
Jorge Gigante Valcarcel
|
Sebastian Bahamonde, Jorge Gigante Valcarcel
|
Stability of Poincar\'e gauge theory with cubic order invariants
|
16 pages, minor changes, references added. It matches the version
published in PRD
|
Phys. Rev. D 109 (2024) 10, 104075
|
10.1103/PhysRevD.109.104075
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We analyse the stability of the vector and axial sectors of Poincar\'e gauge
theory around general backgrounds in the presence of cubic order invariants
defined from the curvature and torsion tensors, showing how the latter can in
fact cancel out well-known instabilities arising from the quadratic curvature
invariants of the theory and accordingly help in the construction of healthy
models with both curvature and torsion. For this task, we introduce the most
general parity preserving cubic Lagrangian with mixing terms of the curvature
and torsion tensors, and find the relations of its coefficients to avoid a
pathological behaviour from the vector and axial modes of torsion. As a result,
on top of the gravitational constant of General Relativity and the mass
parameters of torsion, our action contains 23 additional coupling constants
controlling the dynamics of this field. As in the quadratic Poincar\'e gauge
theory, we show that a further restriction on the cubic part of the action
allows the existence of Reissner-Nordstr\"om-like black hole solutions with
dynamical torsion.
|
[
{
"created": "Wed, 14 Feb 2024 04:42:19 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Jun 2024 20:03:28 GMT",
"version": "v2"
}
] |
2024-06-05
|
[
[
"Bahamonde",
"Sebastian",
""
],
[
"Valcarcel",
"Jorge Gigante",
""
]
] |
We analyse the stability of the vector and axial sectors of Poincar\'e gauge theory around general backgrounds in the presence of cubic order invariants defined from the curvature and torsion tensors, showing how the latter can in fact cancel out well-known instabilities arising from the quadratic curvature invariants of the theory and accordingly help in the construction of healthy models with both curvature and torsion. For this task, we introduce the most general parity preserving cubic Lagrangian with mixing terms of the curvature and torsion tensors, and find the relations of its coefficients to avoid a pathological behaviour from the vector and axial modes of torsion. As a result, on top of the gravitational constant of General Relativity and the mass parameters of torsion, our action contains 23 additional coupling constants controlling the dynamics of this field. As in the quadratic Poincar\'e gauge theory, we show that a further restriction on the cubic part of the action allows the existence of Reissner-Nordstr\"om-like black hole solutions with dynamical torsion.
|
1505.01285
|
Dirk Puetzfeld
|
Dirk Puetzfeld, Yuri N. Obukhov
|
Equivalence principle in scalar-tensor gravity
|
5 pages, RevTex format
|
Phys. Rev. D 92, 081502 (2015)
|
10.1103/PhysRevD.92.081502
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We present a direct confirmation of the validity of the equivalence principle
for unstructured test bodies in scalar tensor gravity. Our analysis is
complementary to previous approaches and valid for a large class of
scalar-tensor theories of gravitation. A covariant approach is used to derive
the equations of motion in a systematic way and allows for the experimental
test of scalar-tensor theories by means of extended test bodies.
|
[
{
"created": "Wed, 6 May 2015 08:51:13 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Oct 2015 18:38:45 GMT",
"version": "v2"
}
] |
2015-10-21
|
[
[
"Puetzfeld",
"Dirk",
""
],
[
"Obukhov",
"Yuri N.",
""
]
] |
We present a direct confirmation of the validity of the equivalence principle for unstructured test bodies in scalar tensor gravity. Our analysis is complementary to previous approaches and valid for a large class of scalar-tensor theories of gravitation. A covariant approach is used to derive the equations of motion in a systematic way and allows for the experimental test of scalar-tensor theories by means of extended test bodies.
|
gr-qc/0701175
|
Jian-Yang Zhu
|
Jian-Zhen Chen and Jian-Yang Zhu
|
Self-organized critical behavior: the evolution of frozen spin networks
model in quantum gravity
|
5 pages, 5 figures
|
Int.J.Mod.Phys.A23:3891-3899,2008
|
10.1142/S0217751X0804041X
| null |
gr-qc
| null |
In quantum gravity, we study the evolution of a two-dimensional planar open
frozen spin network, in which the color (i.e. the twice spin of an edge)
labeling edge changes but the underlying graph remains fixed. The mainly
considered evolution rule, the random edge model, is depending on choosing an
edge randomly and changing the color of it by an even integer. Since the change
of color generally violate the gauge invariance conditions imposed on the
system, detailed propagation rule is needed and it can be defined in many ways.
Here, we provided one new propagation rule, in which the involved even integer
is not a constant one as in previous works, but changeable with certain
probability. In random edge model, we do find the evolution of the system under
the propagation rule exhibits power-law behavior, which is suggestive of the
self-organized criticality (SOC), and it is the first time to verify the SOC
behavior in such evolution model for the frozen spin network. Furthermore, the
increase of the average color of the spin network in time can show the nature
of inflation for the universe.
|
[
{
"created": "Wed, 31 Jan 2007 17:00:02 GMT",
"version": "v1"
}
] |
2009-01-06
|
[
[
"Chen",
"Jian-Zhen",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] |
In quantum gravity, we study the evolution of a two-dimensional planar open frozen spin network, in which the color (i.e. the twice spin of an edge) labeling edge changes but the underlying graph remains fixed. The mainly considered evolution rule, the random edge model, is depending on choosing an edge randomly and changing the color of it by an even integer. Since the change of color generally violate the gauge invariance conditions imposed on the system, detailed propagation rule is needed and it can be defined in many ways. Here, we provided one new propagation rule, in which the involved even integer is not a constant one as in previous works, but changeable with certain probability. In random edge model, we do find the evolution of the system under the propagation rule exhibits power-law behavior, which is suggestive of the self-organized criticality (SOC), and it is the first time to verify the SOC behavior in such evolution model for the frozen spin network. Furthermore, the increase of the average color of the spin network in time can show the nature of inflation for the universe.
|
1503.04659
|
Mariafelicia De Laurentis Professor
|
Mariafelicia De Laurentis, Mariacristina Paolella, Salvatore
Capozziello
|
Cosmological inflation in $F(R,\mathcal{G})$ gravity
|
9 pages, 5 figures, to be published in Phys. Rev. D
| null |
10.1103/PhysRevD.91.083531
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Cosmological inflation is discussed in the framework of $F(R,{\cal G})$
gravity where $F$ is a generic function of the curvature scalar $R$ and the
Gauss-Bonnet topological invariant $\cal G$. The main feature that emerges in
this analysis is the fact that this kind of theory can exhaust all the
curvature budget related to curvature invariants without considering
derivatives of $R,$ $R_{\mu\nu}$, $R^{\lambda}_{\sigma\mu\nu}$ etc. in the
action. Cosmological dynamics results driven by two effective masses (lenghts)
related to the $R$ scalaron and the $\cal G$ scalaron working respectively at
early and very early epochs of cosmic evolution. In this sense, a double
inflationary scenario naturally emerges.
|
[
{
"created": "Thu, 12 Mar 2015 10:03:09 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Apr 2015 09:13:08 GMT",
"version": "v2"
}
] |
2015-06-24
|
[
[
"De Laurentis",
"Mariafelicia",
""
],
[
"Paolella",
"Mariacristina",
""
],
[
"Capozziello",
"Salvatore",
""
]
] |
Cosmological inflation is discussed in the framework of $F(R,{\cal G})$ gravity where $F$ is a generic function of the curvature scalar $R$ and the Gauss-Bonnet topological invariant $\cal G$. The main feature that emerges in this analysis is the fact that this kind of theory can exhaust all the curvature budget related to curvature invariants without considering derivatives of $R,$ $R_{\mu\nu}$, $R^{\lambda}_{\sigma\mu\nu}$ etc. in the action. Cosmological dynamics results driven by two effective masses (lenghts) related to the $R$ scalaron and the $\cal G$ scalaron working respectively at early and very early epochs of cosmic evolution. In this sense, a double inflationary scenario naturally emerges.
|
1109.6649
|
Mayeul Arminjon
|
Mayeul Arminjon and Frank Reifler
|
Classical-quantum correspondence and wave packet solutions of the Dirac
equation in a curved spacetime
|
13 pages (standard 12pt). Text of a talk given at the "Geometry,
Integrability & Quantization" Conference, Varna (Bulgaria), June 2011
|
J. of Geometry & Symmetry in Physics 24 (2011) pp. 77-88
| null | null |
gr-qc math-ph math.MP quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The idea of wave mechanics leads naturally to assume the well-known relation
$E=\hbar \omega $ in the specific form $H=\hbar W$, where $H$ is the classical
Hamiltonian of a particle and $W$ is the dispersion relation of the sought-for
wave equation. We derive the expression of $H$ in a curved spacetime with an
electromagnetic field. Then we derive the Dirac equation from factorizing the
polynomial dispersion equation corresponding with $H$. Conversely, summarizing
a recent work, we implement the geometrical optics approximation into a
canonical form of the Dirac Lagrangian. Euler-Lagrange equations are thus
obtained for the amplitude and phase of the wave function. From them, one is
led to define a 4-velocity field which obeys exactly the classical equation of
motion. The complete de Broglie relations are then derived exact equations.
|
[
{
"created": "Thu, 29 Sep 2011 13:20:19 GMT",
"version": "v1"
}
] |
2012-07-19
|
[
[
"Arminjon",
"Mayeul",
""
],
[
"Reifler",
"Frank",
""
]
] |
The idea of wave mechanics leads naturally to assume the well-known relation $E=\hbar \omega $ in the specific form $H=\hbar W$, where $H$ is the classical Hamiltonian of a particle and $W$ is the dispersion relation of the sought-for wave equation. We derive the expression of $H$ in a curved spacetime with an electromagnetic field. Then we derive the Dirac equation from factorizing the polynomial dispersion equation corresponding with $H$. Conversely, summarizing a recent work, we implement the geometrical optics approximation into a canonical form of the Dirac Lagrangian. Euler-Lagrange equations are thus obtained for the amplitude and phase of the wave function. From them, one is led to define a 4-velocity field which obeys exactly the classical equation of motion. The complete de Broglie relations are then derived exact equations.
|
2006.04892
|
Piero Nicolini
|
Bernard Carr, Heather Mentzer, Jonas Mureika, Piero Nicolini
|
Self-complete and GUP-Modified Charged and Spinning Black Holes
|
18 pages, 10 figures: v2: minor corrections
|
Eur. Phys. J. C (2020) 80:1166
|
10.1140/epjc/s10052-020-08706-0
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We explore some implications of our previous proposal, motivated in part by
the Generalised Uncertainty Principle (GUP) and the possibility that black
holes have quantum mechanical hair that the ADM mass of a system has the form
$M + \beta M_\mathrm{Pl}^2/(2M)$, where $M$ is the bare mass, $M_\mathrm{Pl}$
is the Planck mass and $\beta$ is a positive constant. This also suggests some
connection between black holes and elementary particles and supports the
suggestion that gravity is self-complete. We extend our model to charged and
rotating black holes, since this is clearly relevant to elementary particles.
The standard Reissner-Nordstr\"om and Kerr solutions include zero-temperature
states, representing the smallest possible black holes, and already exhibit
features of the GUP-modified Schwarzschild solution. However, interesting new
features arise if the charged and rotating solutions are themselves
GUP-modified. In particular, there is an interesting transition below some
value of $\beta$ from the GUP solutions (spanning both super-Planckian and
sub-Planckian regimes) to separated super-Planckian and sub-Planckian
solutions. Equivalently, for a given value of $\beta$, there is a critical
value of the charge and spin above which the solutions bifurcate into
sub-Planckian and super-Planckian phases, separated by a mass gap in which no
black holes can form.
|
[
{
"created": "Mon, 8 Jun 2020 19:24:31 GMT",
"version": "v1"
},
{
"created": "Sat, 19 Dec 2020 14:17:36 GMT",
"version": "v2"
}
] |
2020-12-22
|
[
[
"Carr",
"Bernard",
""
],
[
"Mentzer",
"Heather",
""
],
[
"Mureika",
"Jonas",
""
],
[
"Nicolini",
"Piero",
""
]
] |
We explore some implications of our previous proposal, motivated in part by the Generalised Uncertainty Principle (GUP) and the possibility that black holes have quantum mechanical hair that the ADM mass of a system has the form $M + \beta M_\mathrm{Pl}^2/(2M)$, where $M$ is the bare mass, $M_\mathrm{Pl}$ is the Planck mass and $\beta$ is a positive constant. This also suggests some connection between black holes and elementary particles and supports the suggestion that gravity is self-complete. We extend our model to charged and rotating black holes, since this is clearly relevant to elementary particles. The standard Reissner-Nordstr\"om and Kerr solutions include zero-temperature states, representing the smallest possible black holes, and already exhibit features of the GUP-modified Schwarzschild solution. However, interesting new features arise if the charged and rotating solutions are themselves GUP-modified. In particular, there is an interesting transition below some value of $\beta$ from the GUP solutions (spanning both super-Planckian and sub-Planckian regimes) to separated super-Planckian and sub-Planckian solutions. Equivalently, for a given value of $\beta$, there is a critical value of the charge and spin above which the solutions bifurcate into sub-Planckian and super-Planckian phases, separated by a mass gap in which no black holes can form.
|
gr-qc/0103049
|
Ettore Minguzzi
|
E. Minguzzi
|
On the Conventionality of Simultaneity
|
17 pages, 3 figures, LaTeX. v3: Final version, accepted for
publication in the April issue of Found. Phys. Lett
|
Found.Phys.Lett. 15 (2002) 153-169
|
10.1023/A:1020900108093
| null |
gr-qc
| null |
Starting from the experimental fact that light propagates over a closed path
at speed c (L/c law), we show to what extent the isotropy of the speed of light
can be considered a matter of convention. We prove the consistence of
anisotropic and inhomogenous conventions, limiting the allowed possibilities.
All conventions lead to the same physical theory even if its formulation can
change in form. The mathematics involved is that of gauge theories and the
choice of a simultaneity convention is interpreted as a choice of the gauge.
Moreover we prove that a Euclidean space where the L/c law holds, gives rise to
a spacetime with Minkowskian causal structure, and we exploit the consequences
for the causal approach to the conventionality of simultaneity.
|
[
{
"created": "Wed, 14 Mar 2001 20:58:54 GMT",
"version": "v1"
},
{
"created": "Sat, 5 May 2001 22:34:12 GMT",
"version": "v2"
},
{
"created": "Wed, 13 Feb 2002 17:56:16 GMT",
"version": "v3"
}
] |
2007-05-23
|
[
[
"Minguzzi",
"E.",
""
]
] |
Starting from the experimental fact that light propagates over a closed path at speed c (L/c law), we show to what extent the isotropy of the speed of light can be considered a matter of convention. We prove the consistence of anisotropic and inhomogenous conventions, limiting the allowed possibilities. All conventions lead to the same physical theory even if its formulation can change in form. The mathematics involved is that of gauge theories and the choice of a simultaneity convention is interpreted as a choice of the gauge. Moreover we prove that a Euclidean space where the L/c law holds, gives rise to a spacetime with Minkowskian causal structure, and we exploit the consequences for the causal approach to the conventionality of simultaneity.
|
gr-qc/9809080
|
Renato Klippert Barcellos
|
R. Klippert, V.A. De Lorenci (EFEI/Itajuba) M. Novello, J.M. Salim
(CBPF)
|
On the self-consistence of electrodynamics in the early universe
|
10 pages, LaTeX2e with ws-p9-75x6-50.cls (included), improved version
presented in the IX Marcel Grossmann Meeting on General Relativity (Italy,
July 2000) Journal-refby: proceedings of IX Marcel Grossmann Meeting, part C,
1987 V.G. Gurzadyan, R.T. Jantzen and R. Ruffini editors, World Scientific,
Singapore, 2002. web version at http://141.108.24.15:8000/publish (search on
klippert)
| null | null | null |
gr-qc
| null |
The issue of a self-consistent solution of Maxwell-Einstein equations
achieves a very simple form when all quantum effects are neglected but a weak
vacuum polarization due to an external magnetic field is taken into account.
From a semi-classical point of view this means to deal with an appropriate
limit of the one-loop effective Lagrangian for electrodynamics. When the
corresponding stress-energy tensor is considered as a source of the
gravitational field a surprisingly bouncing behavior is obtained. The present
toy model leads to important new features which should have taken place in the
early universe.
|
[
{
"created": "Mon, 28 Sep 1998 22:32:48 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Mar 2002 19:02:27 GMT",
"version": "v2"
}
] |
2007-05-23
|
[
[
"Klippert",
"R.",
"",
"EFEI/Itajuba"
],
[
"De Lorenci",
"V. A.",
"",
"EFEI/Itajuba"
],
[
"Novello",
"M.",
"",
"CBPF"
],
[
"Salim",
"J. M.",
"",
"CBPF"
]
] |
The issue of a self-consistent solution of Maxwell-Einstein equations achieves a very simple form when all quantum effects are neglected but a weak vacuum polarization due to an external magnetic field is taken into account. From a semi-classical point of view this means to deal with an appropriate limit of the one-loop effective Lagrangian for electrodynamics. When the corresponding stress-energy tensor is considered as a source of the gravitational field a surprisingly bouncing behavior is obtained. The present toy model leads to important new features which should have taken place in the early universe.
|
1410.3852
|
Tyson Littenberg
|
Tyson B. Littenberg and Neil J. Cornish
|
BayesLine: Bayesian Inference for Spectral Estimation of Gravitational
Wave Detector Noise
|
17 pages, 10 figures
|
Phys. Rev. D 91, 084034 (2015)
|
10.1103/PhysRevD.91.084034
| null |
gr-qc astro-ph.HE astro-ph.IM
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Gravitational wave data from ground-based detectors is dominated by
instrument noise. Signals will be comparatively weak, and our understanding of
the noise will influence detection confidence and signal characterization.
Mis-modeled noise can produce large systematic biases in both model selection
and parameter estimation. Here we introduce a multi-component, variable
dimension, parameterized model to describe the Gaussian-noise power spectrum
for data from ground-based gravitational wave interferometers. Called
BayesLine, the algorithm models the noise power spectral density using cubic
splines for smoothly varying broad-band noise and Lorentzians for narrow-band
line features in the spectrum. We describe the algorithm and demonstrate its
performance on data from the fifth and sixth LIGO science runs. Once fully
integrated into LIGO/Virgo data analysis software, BayesLine will produce
accurate spectral estimation and provide a means for marginalizing inferences
drawn from the data over all plausible noise spectra.
|
[
{
"created": "Tue, 14 Oct 2014 20:22:22 GMT",
"version": "v1"
}
] |
2015-04-22
|
[
[
"Littenberg",
"Tyson B.",
""
],
[
"Cornish",
"Neil J.",
""
]
] |
Gravitational wave data from ground-based detectors is dominated by instrument noise. Signals will be comparatively weak, and our understanding of the noise will influence detection confidence and signal characterization. Mis-modeled noise can produce large systematic biases in both model selection and parameter estimation. Here we introduce a multi-component, variable dimension, parameterized model to describe the Gaussian-noise power spectrum for data from ground-based gravitational wave interferometers. Called BayesLine, the algorithm models the noise power spectral density using cubic splines for smoothly varying broad-band noise and Lorentzians for narrow-band line features in the spectrum. We describe the algorithm and demonstrate its performance on data from the fifth and sixth LIGO science runs. Once fully integrated into LIGO/Virgo data analysis software, BayesLine will produce accurate spectral estimation and provide a means for marginalizing inferences drawn from the data over all plausible noise spectra.
|
gr-qc/0307066
|
J. Fernando Barbero G.
|
J. Fernando Barbero G. and Eduardo J. S. Villase\~nor
|
Lorentz Violations and Euclidean Signature Metrics
|
4 pages. Minor changes. Added references. Accepted for publication in
Physical Review D
|
Phys.Rev. D68 (2003) 087501
|
10.1103/PhysRevD.68.087501
| null |
gr-qc
| null |
We show that the families of effective actions considered by Jacobson et al.
to study Lorentz invariance violations contain a class of models that represent
pure General Relativity with Euclidean signature. We also point out that some
members of this family of actions preserve Lorentz invariance in a generalized
sense.
|
[
{
"created": "Tue, 15 Jul 2003 06:38:01 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Aug 2003 11:08:32 GMT",
"version": "v2"
}
] |
2009-11-10
|
[
[
"G.",
"J. Fernando Barbero",
""
],
[
"Villaseñor",
"Eduardo J. S.",
""
]
] |
We show that the families of effective actions considered by Jacobson et al. to study Lorentz invariance violations contain a class of models that represent pure General Relativity with Euclidean signature. We also point out that some members of this family of actions preserve Lorentz invariance in a generalized sense.
|
1803.08630
|
Ronaldo Vieira Lobato
|
Ronaldo V. Lobato, G. A. Carvalho, A. G. Martins, P. H. R. S. Moraes
|
Energy nonconservation as a link between $f(R,T)$ gravity and
noncommutative quantum theory
|
Accepted version
| null |
10.1140/epjp/i2019-12638-6
| null |
gr-qc hep-th math-ph math.MP
|
http://creativecommons.org/licenses/by-nc-sa/4.0/
|
$f(R,T)$ gravity was proposed as an extension of the $f(R)$ theories,
containing not just geometrical correction terms to the General Relativity
equations, but also material correction terms, dependent on the trace of the
energy-momentum tensor $T$. These material extra terms prevent the
energy-momentum tensor of the theory to be conserved, even in a flat
background. Energy nonconservation is a prediction of quantum theory with
time-space noncommutativity. If time is considered as an operator and there are
compact spatial coordinates which do not commute with time, then the time
evolution gets quantized and energy conservation can be violated. In the
present work we construct a model in a 5-dimensional flat spacetime consisting
of 3 commutative spatial dimensions and 1 compact spatial dimension whose
coordinate does not commute with time. We show that energy flows from the
3-dimensional commutative slice into the compact extra dimension (and
vice-versa), so that conservation of energy is restored. In this model the
energy flux is proportional to the energy density of the matter content,
leading to a differential equation for $f(R,T)$, thus providing a physical
criterion to restrict the functional form of $f(R,T)$. We solve this equation
and analyze the behavior of its solution in a spherically symmetric context.
|
[
{
"created": "Fri, 23 Mar 2018 01:28:28 GMT",
"version": "v1"
},
{
"created": "Sat, 29 Dec 2018 14:22:35 GMT",
"version": "v2"
}
] |
2019-05-17
|
[
[
"Lobato",
"Ronaldo V.",
""
],
[
"Carvalho",
"G. A.",
""
],
[
"Martins",
"A. G.",
""
],
[
"Moraes",
"P. H. R. S.",
""
]
] |
$f(R,T)$ gravity was proposed as an extension of the $f(R)$ theories, containing not just geometrical correction terms to the General Relativity equations, but also material correction terms, dependent on the trace of the energy-momentum tensor $T$. These material extra terms prevent the energy-momentum tensor of the theory to be conserved, even in a flat background. Energy nonconservation is a prediction of quantum theory with time-space noncommutativity. If time is considered as an operator and there are compact spatial coordinates which do not commute with time, then the time evolution gets quantized and energy conservation can be violated. In the present work we construct a model in a 5-dimensional flat spacetime consisting of 3 commutative spatial dimensions and 1 compact spatial dimension whose coordinate does not commute with time. We show that energy flows from the 3-dimensional commutative slice into the compact extra dimension (and vice-versa), so that conservation of energy is restored. In this model the energy flux is proportional to the energy density of the matter content, leading to a differential equation for $f(R,T)$, thus providing a physical criterion to restrict the functional form of $f(R,T)$. We solve this equation and analyze the behavior of its solution in a spherically symmetric context.
|
1708.06245
|
Muhammad Sharif
|
M. Sharif and Rubab Manzoor
|
Stability of Oscillating Gaseous Masses in Massive Brans-Dicke Gravity
|
31 pages, 11 figures, to appear in IJMPD
|
Int. J. Mod. Phys. D 27(2018)1750172
|
10.1142/S0218271817501723
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
This paper explores the instability of gaseous masses for the radial
oscillations in post-Newtonian correction of massive Brans-Dicke gravity. For
this purpose, we derive linearized perturbed equation of motion through
Lagrangian radial perturbation which leads to the condition of marginal
stability. We discuss radius of instability of different polytropic structures
in terms of the Schwarzschild radius. It is concluded that our results provide
a wide range of difference with those in general relativity and Brans-Dicke
gravity.
|
[
{
"created": "Fri, 18 Aug 2017 05:06:58 GMT",
"version": "v1"
}
] |
2018-01-10
|
[
[
"Sharif",
"M.",
""
],
[
"Manzoor",
"Rubab",
""
]
] |
This paper explores the instability of gaseous masses for the radial oscillations in post-Newtonian correction of massive Brans-Dicke gravity. For this purpose, we derive linearized perturbed equation of motion through Lagrangian radial perturbation which leads to the condition of marginal stability. We discuss radius of instability of different polytropic structures in terms of the Schwarzschild radius. It is concluded that our results provide a wide range of difference with those in general relativity and Brans-Dicke gravity.
|
gr-qc/0312045
|
David Coule
|
D.H. Coule
|
Contrasting Quantum Cosmologies
|
21 pages, dispute with astro-ph/0311015 addressed
| null | null | null |
gr-qc
| null |
We compare the recent loop quantum cosmology approach of Bojowald and
co-workers with earlier quantum cosmological schemes. Because the weak-energy
condition can now be violated at short distances, and not necessarily with a
high energy density, a number of possible instabilities are suggested: flat
space unstable to expansion or baby universe production. Or else a Machian type
principle is required to prevent such behaviour. Allowing a bounce to prevent
an approaching singularity seems incompatible with other standard notions
concerning the arrow of time and unitarity.
Preventing rapid oscillations in the wavefunction appears in conflict with
more general scalar-tensor gravity.
Other approaches such as ``creation from nothing'' or from some quiescent
state, static or time machine, are also assessed on grounds of naturalness and
fine tuning.
|
[
{
"created": "Mon, 8 Dec 2003 18:23:47 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Dec 2003 16:25:30 GMT",
"version": "v2"
},
{
"created": "Fri, 6 Feb 2004 15:38:21 GMT",
"version": "v3"
}
] |
2016-08-31
|
[
[
"Coule",
"D. H.",
""
]
] |
We compare the recent loop quantum cosmology approach of Bojowald and co-workers with earlier quantum cosmological schemes. Because the weak-energy condition can now be violated at short distances, and not necessarily with a high energy density, a number of possible instabilities are suggested: flat space unstable to expansion or baby universe production. Or else a Machian type principle is required to prevent such behaviour. Allowing a bounce to prevent an approaching singularity seems incompatible with other standard notions concerning the arrow of time and unitarity. Preventing rapid oscillations in the wavefunction appears in conflict with more general scalar-tensor gravity. Other approaches such as ``creation from nothing'' or from some quiescent state, static or time machine, are also assessed on grounds of naturalness and fine tuning.
|
1007.1162
|
Fabio Duvan Lora Clavijo Mr.
|
F. D. Lora-Clavijo, A. Cruz-Osorio and F. S. Guzm\'an
|
Evolution of a mass-less test scalar field on Boson Stars space-times
|
9 pages, 15 eps figures, revtex4
|
Phys.Rev.D82:023005,2010
|
10.1103/PhysRevD.82.023005
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We numerically solve the mass-less test scalar field equation on the
space-time background of boson stars and black holes. In order to do so, we use
a numerical domain that contains future null infinity. We achieve this
construction using a scri-fixing conformal compactification technique based on
hyperboloidal constant mean curvature foliations of the space-time and solve
the conformally invariant wave equation. We present two results: the scalar
field shows oscillations of the quasi- normal-mode type found for black holes
only for boson star configurations that are compact, and no signs of tail decay
is found in the parameter space we explored. Even though our results do not
correspond to the master equation of perturbations of boson star solutions,
they indicate that the parameter space of boson stars as black hole mimickers
is restricted to compact configurations.
|
[
{
"created": "Wed, 7 Jul 2010 15:14:22 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Jul 2010 21:49:51 GMT",
"version": "v2"
}
] |
2010-08-12
|
[
[
"Lora-Clavijo",
"F. D.",
""
],
[
"Cruz-Osorio",
"A.",
""
],
[
"Guzmán",
"F. S.",
""
]
] |
We numerically solve the mass-less test scalar field equation on the space-time background of boson stars and black holes. In order to do so, we use a numerical domain that contains future null infinity. We achieve this construction using a scri-fixing conformal compactification technique based on hyperboloidal constant mean curvature foliations of the space-time and solve the conformally invariant wave equation. We present two results: the scalar field shows oscillations of the quasi- normal-mode type found for black holes only for boson star configurations that are compact, and no signs of tail decay is found in the parameter space we explored. Even though our results do not correspond to the master equation of perturbations of boson star solutions, they indicate that the parameter space of boson stars as black hole mimickers is restricted to compact configurations.
|
1309.7427
|
Michael Maziashvili
|
Alain R. P. Dirkes, Michael Maziashvili and Zurab K. Silagadze
|
Black hole remnants due to Planck-length deformed QFT
|
18 pages, published version
|
Int. J. Mod. Phys. D25, 1650015 (2016)
|
10.1142/S0218271816500152
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
It was argued in a number of papers that the gravitational potential
calculated by using the modified QFT that follows from the Planck-length
deformed uncertainty relation implies the existence of black-hole remnants of
the order of the Planck-mass. Usually this sort of QFTs are endowed with two
specific features, the modified dispersion relation, which is universal, and
the concept of minimum length, which, however, is not universal. While the
emergence of the minimum-length most readily leads to the idea of the black
hole remnants, here we examine the behaviour of the potential that follows from
the Planck-length deformed QFT in absence of the minimum length and show that
it might also lead to the formation of the Planck mass black holes in some
particular cases. The calculations are made for higher-dimensional case as
well. Such black hole remnants might be considered as a possible candidates for
the dark-matter.
|
[
{
"created": "Sat, 28 Sep 2013 05:07:00 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Nov 2015 12:14:54 GMT",
"version": "v2"
}
] |
2015-11-25
|
[
[
"Dirkes",
"Alain R. P.",
""
],
[
"Maziashvili",
"Michael",
""
],
[
"Silagadze",
"Zurab K.",
""
]
] |
It was argued in a number of papers that the gravitational potential calculated by using the modified QFT that follows from the Planck-length deformed uncertainty relation implies the existence of black-hole remnants of the order of the Planck-mass. Usually this sort of QFTs are endowed with two specific features, the modified dispersion relation, which is universal, and the concept of minimum length, which, however, is not universal. While the emergence of the minimum-length most readily leads to the idea of the black hole remnants, here we examine the behaviour of the potential that follows from the Planck-length deformed QFT in absence of the minimum length and show that it might also lead to the formation of the Planck mass black holes in some particular cases. The calculations are made for higher-dimensional case as well. Such black hole remnants might be considered as a possible candidates for the dark-matter.
|
gr-qc/9210017
|
Wai Suen
|
Ian H. Redmount and Wai-Mo Suen
|
Is Quantum Spacetime Foam Unstable?
|
15 pages
|
Phys.Rev.D47:2163-2167,1993
|
10.1103/PhysRevD.47.R2163
|
WUGRAV-92-10
|
gr-qc
| null |
A very simple wormhole geometry is considered as a model of a mode of
topological fluctutation in Planck-scale spacetime foam. Quantum dynamics of
the hole reduces to quantum mechanics of one variable, throat radius, and
admits a WKB analysis. The hole is quantum-mechanically unstable: It has no
bound states. Wormhole wave functions must eventually leak to large radii. This
suggests that stability considerations along these lines may place strong
constraints on the nature and even the existence of spacetime foam.
|
[
{
"created": "Wed, 28 Oct 1992 23:12:54 GMT",
"version": "v1"
}
] |
2010-01-06
|
[
[
"Redmount",
"Ian H.",
""
],
[
"Suen",
"Wai-Mo",
""
]
] |
A very simple wormhole geometry is considered as a model of a mode of topological fluctutation in Planck-scale spacetime foam. Quantum dynamics of the hole reduces to quantum mechanics of one variable, throat radius, and admits a WKB analysis. The hole is quantum-mechanically unstable: It has no bound states. Wormhole wave functions must eventually leak to large radii. This suggests that stability considerations along these lines may place strong constraints on the nature and even the existence of spacetime foam.
|
2202.08999
|
Naoki Sato
|
Naoki Sato
|
Hydrodynamic derivation of the Schr\"odinger equation and spacetime
curvature of a quantum particle
|
16 pages
| null | null | null |
gr-qc math-ph math.MP quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We report a hydrodynamic derivation of the Schr\"odinger equation. The
derivation only assumes that spin represents the angular momentum associated
with the rotation of a charged fluid within a massive particle. The rotation
velocity can be evaluated through the current density of the fourth Maxwell
equation, leading to a quantum correction of the classical fluid energy. The
Schr\"odinger equation then follows in Madelung form by application of the
Poisson operator of the Euler equations for an ideal fluid to the total fluid
energy including the quantum effect of internal spin. The hydrodynamic
representation is then used to obtain the stress-energy-momentum tensor for a
quantum particle. We find that the trace of the quantum modification to the
stress-energy-momentum tensor expresses the energy density of an oscillator
with frequency given by the vorticity of the internal rotation velocity.
Finally, the stress-energy-momentum tensor is used to determine the
relationship between the Ricci scalar curvature arising from the Einstein field
equations and the fluid density associated with the hydrodynamic representation
of the quantum particle in a static spherically symmetric configuration.
|
[
{
"created": "Fri, 18 Feb 2022 03:08:49 GMT",
"version": "v1"
}
] |
2022-02-21
|
[
[
"Sato",
"Naoki",
""
]
] |
We report a hydrodynamic derivation of the Schr\"odinger equation. The derivation only assumes that spin represents the angular momentum associated with the rotation of a charged fluid within a massive particle. The rotation velocity can be evaluated through the current density of the fourth Maxwell equation, leading to a quantum correction of the classical fluid energy. The Schr\"odinger equation then follows in Madelung form by application of the Poisson operator of the Euler equations for an ideal fluid to the total fluid energy including the quantum effect of internal spin. The hydrodynamic representation is then used to obtain the stress-energy-momentum tensor for a quantum particle. We find that the trace of the quantum modification to the stress-energy-momentum tensor expresses the energy density of an oscillator with frequency given by the vorticity of the internal rotation velocity. Finally, the stress-energy-momentum tensor is used to determine the relationship between the Ricci scalar curvature arising from the Einstein field equations and the fluid density associated with the hydrodynamic representation of the quantum particle in a static spherically symmetric configuration.
|
2111.15448
|
Fay\c{c}al Hammad
|
Fay\c{c}al Hammad, Alexandre Landry, Parvaneh Sadeghi
|
Spin-1/2 particles under the influence of a uniform magnetic field in
the interior Schwarzschild solution
|
18+5 pages, no figures. This paper is published in the Special Issue
of the Journal Universe: Feature Papers - Compact Objects
|
Universe 7(12), 467 (2021)
|
10.3390/universe7120467
| null |
gr-qc quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The relativistic wave equation for spin-1/2 particles in the interior
Schwarzschild solution in the presence of a uniform magnetic field is obtained.
The fully relativistic regime is considered, and the energy levels occupied by
the particles are derived as functions of the magnetic field, the radius of the
massive sphere and the total mass of the latter. As no assumption is made on
the relative strengths of the particles' interaction with the gravitational and
magnetic fields, the relevance of our results to the physics of the interior of
neutron stars, where both the gravitational and the magnetic fields are very
intense, is discussed.
|
[
{
"created": "Tue, 30 Nov 2021 14:46:00 GMT",
"version": "v1"
}
] |
2021-12-01
|
[
[
"Hammad",
"Fayçal",
""
],
[
"Landry",
"Alexandre",
""
],
[
"Sadeghi",
"Parvaneh",
""
]
] |
The relativistic wave equation for spin-1/2 particles in the interior Schwarzschild solution in the presence of a uniform magnetic field is obtained. The fully relativistic regime is considered, and the energy levels occupied by the particles are derived as functions of the magnetic field, the radius of the massive sphere and the total mass of the latter. As no assumption is made on the relative strengths of the particles' interaction with the gravitational and magnetic fields, the relevance of our results to the physics of the interior of neutron stars, where both the gravitational and the magnetic fields are very intense, is discussed.
|
gr-qc/0608123
|
Zhao Ren
|
Zhao Ren, Li Huai-Fan, Zhang Sheng-Li
|
Canonical Entropy of charged black hole
|
9 pages
| null | null | null |
gr-qc
| null |
Recently, Hawking radiation of the black hole has been studied by using the
tunnel effect method. It is found that the radiation spectrum of the black hole
is not a strictly pure thermal spectrum. How does the departure from pure
thermal spectrum affect the entropy? This is a very interesting problem. In
this paper, we calculate the partition function through energy spectrum
obtained by using the tunnel effect. From the relation between the partition
function and canonical entropy, we can derive the entropy of charged black
hole. In our calculation, we consider not only the correction to the black hole
entropy due to fluctuation of energy, but also the effect of the change in the
black hole charges on entropy. There is not any assumption. This makes our
result more reliable.
|
[
{
"created": "Tue, 29 Aug 2006 02:26:10 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Ren",
"Zhao",
""
],
[
"Huai-Fan",
"Li",
""
],
[
"Sheng-Li",
"Zhang",
""
]
] |
Recently, Hawking radiation of the black hole has been studied by using the tunnel effect method. It is found that the radiation spectrum of the black hole is not a strictly pure thermal spectrum. How does the departure from pure thermal spectrum affect the entropy? This is a very interesting problem. In this paper, we calculate the partition function through energy spectrum obtained by using the tunnel effect. From the relation between the partition function and canonical entropy, we can derive the entropy of charged black hole. In our calculation, we consider not only the correction to the black hole entropy due to fluctuation of energy, but also the effect of the change in the black hole charges on entropy. There is not any assumption. This makes our result more reliable.
|
gr-qc/0111005
|
Roland Oechslin
|
Roland Oechslin, Stephan Rosswog, Friederich-Karl Thielemann
|
Conformally Flat Smoothed Particle Hydrodynamics: Application to Neutron
Star Mergers
|
23 pages, 12 figures. Accepted for publication in Phys. Rev. D. v3:
Final Version
|
Phys.Rev. D65 (2002) 103005
|
10.1103/PhysRevD.65.103005
| null |
gr-qc astro-ph
| null |
We present a new 3D SPH code which solves the general relativistic field +
hydrodynamics equations in the conformally flat approximation. Several test
cases are considered to test different aspects of the code. We finally apply
then the code to the coalescence of a neutron star binary system. The neutron
stars are modeled by a polytropic equation of state (EoS) with adiabatic
indices $\Gamma=2.0$, $\Gamma=2.6$ and $\Gamma=3.0$. We calculate the
gravitational wave signals, luminosities and frequency spectra by employing the
quadrupole approximation for emission and back reaction in the slow motion
limit. In addition, we consider the amount of ejected mass.
|
[
{
"created": "Fri, 2 Nov 2001 17:48:18 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Nov 2001 18:25:16 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Feb 2002 09:26:59 GMT",
"version": "v3"
}
] |
2009-11-07
|
[
[
"Oechslin",
"Roland",
""
],
[
"Rosswog",
"Stephan",
""
],
[
"Thielemann",
"Friederich-Karl",
""
]
] |
We present a new 3D SPH code which solves the general relativistic field + hydrodynamics equations in the conformally flat approximation. Several test cases are considered to test different aspects of the code. We finally apply then the code to the coalescence of a neutron star binary system. The neutron stars are modeled by a polytropic equation of state (EoS) with adiabatic indices $\Gamma=2.0$, $\Gamma=2.6$ and $\Gamma=3.0$. We calculate the gravitational wave signals, luminosities and frequency spectra by employing the quadrupole approximation for emission and back reaction in the slow motion limit. In addition, we consider the amount of ejected mass.
|
1810.07443
|
Edward Porter
|
Yann Bouffanais and Edward K. Porter
|
Bayesian inference for binary neutron star inspirals using a Hamiltonian
Monte Carlo Algorithm
|
16 pages, 8 figures. Submitted to PRD
|
Phys. Rev. D 100, 104023 (2019)
|
10.1103/PhysRevD.100.104023
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The coalescence of binary neutron stars are one of the main sources of
gravitational waves for ground-based gravitational wave detectors. As Bayesian
inference for binary neutron stars is computationally expensive, more efficient
and faster converging algorithms are always needed. In this work, we conduct a
feasibility study using a Hamiltonian Monte Carlo algorithm (HMC). The HMC is a
sampling algorithm that takes advantage of gradient information from the
geometry of the parameter space to efficiently sample from the posterior
distribution, allowing the algorithm to avoid the random-walk behaviour
commonly associated with stochastic samplers. As well as tuning the algorithm's
free parameters specifically for gravitational wave astronomy, we introduce a
method for approximating the gradients of the log-likelihood that reduces the
runtime for a $10^6$ trajectory run from ten weeks, using numerical derivatives
along the Hamiltonian trajectories, to one day, in the case of non-spinning
neutron stars. Testing our algorithm against a set of neutron star binaries
using a detector network composed of Advanced LIGO and Advanced Virgo at
optimal design, we demonstrate that not only is our algorithm more efficient
than a standard sampler, but a $10^6$ trajectory HMC produces an effective
sample size on the order of $10^4 - 10^5$ statistically independent samples.
|
[
{
"created": "Wed, 17 Oct 2018 09:20:50 GMT",
"version": "v1"
}
] |
2019-11-20
|
[
[
"Bouffanais",
"Yann",
""
],
[
"Porter",
"Edward K.",
""
]
] |
The coalescence of binary neutron stars are one of the main sources of gravitational waves for ground-based gravitational wave detectors. As Bayesian inference for binary neutron stars is computationally expensive, more efficient and faster converging algorithms are always needed. In this work, we conduct a feasibility study using a Hamiltonian Monte Carlo algorithm (HMC). The HMC is a sampling algorithm that takes advantage of gradient information from the geometry of the parameter space to efficiently sample from the posterior distribution, allowing the algorithm to avoid the random-walk behaviour commonly associated with stochastic samplers. As well as tuning the algorithm's free parameters specifically for gravitational wave astronomy, we introduce a method for approximating the gradients of the log-likelihood that reduces the runtime for a $10^6$ trajectory run from ten weeks, using numerical derivatives along the Hamiltonian trajectories, to one day, in the case of non-spinning neutron stars. Testing our algorithm against a set of neutron star binaries using a detector network composed of Advanced LIGO and Advanced Virgo at optimal design, we demonstrate that not only is our algorithm more efficient than a standard sampler, but a $10^6$ trajectory HMC produces an effective sample size on the order of $10^4 - 10^5$ statistically independent samples.
|
gr-qc/9503058
|
Rainer Mueller
|
Juergen Audretsch and Rainer Mueller
|
Radiative energy shifts of accelerated atoms
|
12 pages, Latex, 1 figure as uuencoded eps file, shorter version will
appear in Phys. Rev. A
| null |
10.1103/PhysRevA.52.629
| null |
gr-qc hep-th quant-ph
| null |
We consider the influence of acceleration on the radiative energy shifts of
atoms in Minkowski space. We study a two-level atom coupled to a scalar quantum
field. Using a Heisenberg picture approach, we are able to separate the
contributions of vacuum fluctuations and radiation reaction to the Lamb shift
of the two-level atom. The resulting energy shifts for the special case of a
uniformly accelerated atom are then compared with those of an atom at rest.
|
[
{
"created": "Wed, 29 Mar 1995 15:59:10 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Mar 1995 07:22:28 GMT",
"version": "v2"
}
] |
2009-10-28
|
[
[
"Audretsch",
"Juergen",
""
],
[
"Mueller",
"Rainer",
""
]
] |
We consider the influence of acceleration on the radiative energy shifts of atoms in Minkowski space. We study a two-level atom coupled to a scalar quantum field. Using a Heisenberg picture approach, we are able to separate the contributions of vacuum fluctuations and radiation reaction to the Lamb shift of the two-level atom. The resulting energy shifts for the special case of a uniformly accelerated atom are then compared with those of an atom at rest.
|
1401.7639
|
Mohamad Atazadeh
|
K. Atazadeh
|
Stability of the Einstein static universe in Einstein-Cartan theory
|
5 pages, 1 figure, to appear in JCAP
|
JCAP06(2014)020
|
10.1088/1475-7516/2014/06/020
| null |
gr-qc hep-th
|
http://creativecommons.org/licenses/by-nc-sa/3.0/
|
The existence and stability of the Einstein static solution have been built
in the Einstein-Cartan gravity. We show that this solution in the presence of
perfect fluid with spin density satisfying the Weyssenhoff restriction is
cyclically stable around a center equilibrium point. Thus, study of this
solution is interesting because it supports non-singular emergent cosmological
models in which the early universe oscillates indeterminately about an initial
Einstein static solution and is thus past eternal.
|
[
{
"created": "Wed, 29 Jan 2014 19:54:19 GMT",
"version": "v1"
},
{
"created": "Tue, 27 May 2014 06:56:45 GMT",
"version": "v2"
}
] |
2014-06-11
|
[
[
"Atazadeh",
"K.",
""
]
] |
The existence and stability of the Einstein static solution have been built in the Einstein-Cartan gravity. We show that this solution in the presence of perfect fluid with spin density satisfying the Weyssenhoff restriction is cyclically stable around a center equilibrium point. Thus, study of this solution is interesting because it supports non-singular emergent cosmological models in which the early universe oscillates indeterminately about an initial Einstein static solution and is thus past eternal.
|
1503.03755
|
Ignacio F. Ranea-Sandoval
|
Ignacio F. Ranea-Sandoval and H\'ector Vucetich
|
Scalar Resonances in Axially Symmetric Spacetimes
|
International Journal of Modern Physics D, in press
| null |
10.1142/S0218271815500376
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study properties of resonant solutions to the scalar wave equation in
several axially symmetric spacetimes. We prove that non-axial resonant modes do
not exist neither in the Lanczos dust cylinder, the $(2+1)$ extreme BTZ
spacetime nor in a class of simple rotating wormhole solutions. Moreover, we
find unstable solutions to the wave equation in the Lanczos dust cylinder and
in the $r^2 <0$ region of the extreme $(2+1)$ BTZ spacetime, two solutions that
possess closed timelike curves. Similarities with previous results obtained for
the Kerr spacetime are explored.
|
[
{
"created": "Thu, 12 Mar 2015 14:54:42 GMT",
"version": "v1"
}
] |
2015-03-13
|
[
[
"Ranea-Sandoval",
"Ignacio F.",
""
],
[
"Vucetich",
"Héctor",
""
]
] |
We study properties of resonant solutions to the scalar wave equation in several axially symmetric spacetimes. We prove that non-axial resonant modes do not exist neither in the Lanczos dust cylinder, the $(2+1)$ extreme BTZ spacetime nor in a class of simple rotating wormhole solutions. Moreover, we find unstable solutions to the wave equation in the Lanczos dust cylinder and in the $r^2 <0$ region of the extreme $(2+1)$ BTZ spacetime, two solutions that possess closed timelike curves. Similarities with previous results obtained for the Kerr spacetime are explored.
|
2404.13981
|
Leandros Perivolaropoulos
|
Eleonora Di Valentino, Leandros Perivolaropoulos and Jackson Levi Said
|
Special Issue on Modified Gravity Approaches to the Tensions of
$\Lambda$CDM: Goals and Highlights
|
6 pages no figures Published in Universe in the Special Issue
"Modified Gravity Approaches to the Tensions of $\Lambda$CDM" (
https://www.mdpi.com/journal/universe/special_issues/Gravit )
| null |
10.3390/universe10040184
| null |
gr-qc hep-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The Special Issue on "Modified Gravity Approaches to the Tensions of
$\Lambda$CDM"} in the Universe journal tackles significant challenges faced by
the $\Lambda$CDM model, including discrepancies in the Hubble constant, growth
rate of structures, and cosmological anisotropies. These issues suggest
foundational cracks in the model, raising questions about the validity of
General Relativity, dark energy, and cosmological principles at large scales.
This collection brings together leading researchers to delve into Modified
Gravity theories as potential solutions. Covering approaches from Scalar-Tensor
theories to $f(R,T)$ gravity and beyond, each contribution presents innovative
research aimed at addressing the limitations of the $\Lambda$CDM model. This
Special Issue not only highlights the theoretical and empirical strengths of
Modified Gravity models but also opens avenues for future investigations,
emphasizing the synergy between theoretical advancements and observational
evidence to deepen our cosmological understanding.
|
[
{
"created": "Mon, 22 Apr 2024 08:43:39 GMT",
"version": "v1"
}
] |
2024-04-23
|
[
[
"Di Valentino",
"Eleonora",
""
],
[
"Perivolaropoulos",
"Leandros",
""
],
[
"Said",
"Jackson Levi",
""
]
] |
The Special Issue on "Modified Gravity Approaches to the Tensions of $\Lambda$CDM"} in the Universe journal tackles significant challenges faced by the $\Lambda$CDM model, including discrepancies in the Hubble constant, growth rate of structures, and cosmological anisotropies. These issues suggest foundational cracks in the model, raising questions about the validity of General Relativity, dark energy, and cosmological principles at large scales. This collection brings together leading researchers to delve into Modified Gravity theories as potential solutions. Covering approaches from Scalar-Tensor theories to $f(R,T)$ gravity and beyond, each contribution presents innovative research aimed at addressing the limitations of the $\Lambda$CDM model. This Special Issue not only highlights the theoretical and empirical strengths of Modified Gravity models but also opens avenues for future investigations, emphasizing the synergy between theoretical advancements and observational evidence to deepen our cosmological understanding.
|
2406.11095
|
Nicolas Lecoeur
|
Nicolas Lecoeur
|
Exact black hole solutions in scalar-tensor theories
|
PhD thesis. Chaps. 1-3: previously known results, organized to
introduce the subject of closed-form black hole solutions in scalar-tensor
theories. Chaps. 4-6: results obtained during the thesis. Results of Sec. 5.3
(diagonal Kaluza-Klein reduction of arbitrary Lovelock theory) are completely
new (i.e. unpublished). Other results of Chaps. 4-6 based on various
publications made during the thesis
| null | null | null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
General Relativity allows for a unique black hole solution, characterized by
its mass M, angular momentum J, and electric charge Q. Black holes in General
Relativity are thus said to have no hair, that is, no other independent
physical quantity (no-hair theorem). Despite the numerous successes of General
Relativity, some limitations remain, like the central singularity possessed by
black holes, where the curvature of spacetime becomes infinite. Modified
theories of gravity try to solve some of these shortcomings. This thesis tests
the no-hair theorem in a popular modification of gravity, called scalar-tensor
theories, where a unique degree of freedom (a scalar field) is added on top of
the usual metric of spacetime of General Relativity. Using various symmetries,
new black holes, called hairy black holes, are obtained. Some of them evade
strongly the no-hair theorem, being characterized by a new quantity (primary
scalar hair), distinct from M, J or Q. An interesting progress is also
achieved, since in certain cases, the usual singularity disappears: the
curvature of spacetime remains bounded even at the core of the black hole.
Moreover, theoretical links are established between scalar-tensor theories
(which take place in the usual four dimensions of spacetime), and theories of
gravity in higher dimensions, by Kaluza-Klein reduction. Finally, certain
particular properties of scalar-tensor theories enable to transform initial
black hole solutions into other solutions with very distinct geometry, like
wormholes or non-stationary black holes.
|
[
{
"created": "Sun, 16 Jun 2024 22:52:16 GMT",
"version": "v1"
}
] |
2024-06-18
|
[
[
"Lecoeur",
"Nicolas",
""
]
] |
General Relativity allows for a unique black hole solution, characterized by its mass M, angular momentum J, and electric charge Q. Black holes in General Relativity are thus said to have no hair, that is, no other independent physical quantity (no-hair theorem). Despite the numerous successes of General Relativity, some limitations remain, like the central singularity possessed by black holes, where the curvature of spacetime becomes infinite. Modified theories of gravity try to solve some of these shortcomings. This thesis tests the no-hair theorem in a popular modification of gravity, called scalar-tensor theories, where a unique degree of freedom (a scalar field) is added on top of the usual metric of spacetime of General Relativity. Using various symmetries, new black holes, called hairy black holes, are obtained. Some of them evade strongly the no-hair theorem, being characterized by a new quantity (primary scalar hair), distinct from M, J or Q. An interesting progress is also achieved, since in certain cases, the usual singularity disappears: the curvature of spacetime remains bounded even at the core of the black hole. Moreover, theoretical links are established between scalar-tensor theories (which take place in the usual four dimensions of spacetime), and theories of gravity in higher dimensions, by Kaluza-Klein reduction. Finally, certain particular properties of scalar-tensor theories enable to transform initial black hole solutions into other solutions with very distinct geometry, like wormholes or non-stationary black holes.
|
1803.09958
|
Daniela Pugliese Dr
|
D. Pugliese and Z. Stuchlik
|
Proto-jets configurations in RADs orbiting a Kerr SMBH: symmetries and
limiting surfaces
|
13 pages, double column, 4 figures multi-panels To appear in Class.
Quantum Grav. https://doi.org/10.1088/1361-6382/aab99d
| null |
10.1088/1361-6382/aab99d
| null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Ringed accretion disks (RADs) are agglomerations of perfect-fluid tori
orbiting around a single central attractor that could arise during complex
matter inflows in active galactic nuclei. We focus our analysis to
axi-symmetric accretion tori orbiting in the equatorial plane of a supermassive
Kerr black hole; equilibrium configurations, possible instabilities, and
evolutionary sequences of RADs were discussed in our previous works. In the
present work we discuss special instabilities related to open equipotential
surfaces governing the material funnels emerging at various regions of the
RADs, being located between two or more individual toroidal configurations of
the agglomerate. These open structures could be associated to proto-jets.
Boundary limiting surfaces are highlighted, connecting the emergency of the
jet-like instabilities with the black hole dimensionless spin. These
instabilities are observationally significant for active galactic nuclei, being
related to outflows of matter in jets emerging from more than one torus of RADs
orbiting around supermassive black holes.
|
[
{
"created": "Tue, 27 Mar 2018 08:43:34 GMT",
"version": "v1"
}
] |
2018-05-02
|
[
[
"Pugliese",
"D.",
""
],
[
"Stuchlik",
"Z.",
""
]
] |
Ringed accretion disks (RADs) are agglomerations of perfect-fluid tori orbiting around a single central attractor that could arise during complex matter inflows in active galactic nuclei. We focus our analysis to axi-symmetric accretion tori orbiting in the equatorial plane of a supermassive Kerr black hole; equilibrium configurations, possible instabilities, and evolutionary sequences of RADs were discussed in our previous works. In the present work we discuss special instabilities related to open equipotential surfaces governing the material funnels emerging at various regions of the RADs, being located between two or more individual toroidal configurations of the agglomerate. These open structures could be associated to proto-jets. Boundary limiting surfaces are highlighted, connecting the emergency of the jet-like instabilities with the black hole dimensionless spin. These instabilities are observationally significant for active galactic nuclei, being related to outflows of matter in jets emerging from more than one torus of RADs orbiting around supermassive black holes.
|
1505.05113
|
Pedro Moraes
|
D. Momeni, P.H.R.S. Moraes, H. Gholizade and R. Myrzakulov
|
Mimetic Compact Stars
|
14 pages, 8 figures, Accepted for publication in International
Journal of Geometrical Methods in Modern Physics
| null |
10.1142/S0219887818500913
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Modified gravity models have been constantly proposed with the purpose of
evading some standard gravity shortcomings. Recently proposed by A.H.
Chamseddine and V. Mukhanov, the Mimetic Gravity arises as an optimistic
alternative. Our purpose in this work is to derive Tolman-Oppenheimer-Volkoff
equations and solutions for such a gravity theory. We solve them numerically
for quark star and neutron star cases. The results are carefully discussed.
|
[
{
"created": "Tue, 19 May 2015 18:35:38 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Jan 2018 16:59:38 GMT",
"version": "v2"
}
] |
2018-02-07
|
[
[
"Momeni",
"D.",
""
],
[
"Moraes",
"P. H. R. S.",
""
],
[
"Gholizade",
"H.",
""
],
[
"Myrzakulov",
"R.",
""
]
] |
Modified gravity models have been constantly proposed with the purpose of evading some standard gravity shortcomings. Recently proposed by A.H. Chamseddine and V. Mukhanov, the Mimetic Gravity arises as an optimistic alternative. Our purpose in this work is to derive Tolman-Oppenheimer-Volkoff equations and solutions for such a gravity theory. We solve them numerically for quark star and neutron star cases. The results are carefully discussed.
|
1708.03592
|
Alexander Myagky
|
Andrey N. Makarenko and Alexander N. Myagky
|
The Asymptotic Behavior of Bouncing Cosmological Models in
$F(\mathcal{G})$ Gravity Theory
|
11 pages. arXiv admin note: substantial text overlap with
arXiv:1403.3242
|
Int.J.Geom.Meth.Mod.Phys. 14 (2017) 1750148
|
10.1142/S0219887817501481
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We reconstruct $F(\mathcal{G})$ gravity theory with an exponential scale
factor to realize the bouncing behavior in the early universe and examine the
asymptotic behaviour of late-time solutions in this model. We propose an
approach to the construction of asymptotic expansions of solutions of the
Friedmann equations on the basis of Puiseux series.
|
[
{
"created": "Thu, 10 Aug 2017 15:20:24 GMT",
"version": "v1"
}
] |
2017-11-15
|
[
[
"Makarenko",
"Andrey N.",
""
],
[
"Myagky",
"Alexander N.",
""
]
] |
We reconstruct $F(\mathcal{G})$ gravity theory with an exponential scale factor to realize the bouncing behavior in the early universe and examine the asymptotic behaviour of late-time solutions in this model. We propose an approach to the construction of asymptotic expansions of solutions of the Friedmann equations on the basis of Puiseux series.
|
1209.3371
|
Gonzalo Olmo
|
J. Martinez-Asencio, Gonzalo J. Olmo, D. Rubiera-Garcia
|
Black hole formation from a null fluid in extended Palatini gravity
|
8 pages, double column (revtex4-1), 4 figures
| null |
10.1103/PhysRevD.86.104010
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the formation and perturbation of black holes by null fluxes of
neutral matter in a quadratic extension of General Relativity formulated a la
Palatini. Working in a spherically symmetric space-time, we obtain an exact
analytical solution for the metric that extends the usual Vaidya-type solution
to this type of theories. We find that the resulting space-time is formally
that of a Reissner-Nordstrom black hole but with an effective charge term
carrying the wrong sign in front of it. This effective charge is directly
related to the luminosity function of the radiation stream. When the ingoing
flux vanishes, the charge term disappears and the space-time relaxes to that of
a Schwarzschild black hole. We provide two examples that illustrate the
formation of a black hole from Minkowski space and the perturbation by a finite
pulse of radiation of an existing Schwarzschild black hole.
|
[
{
"created": "Sat, 15 Sep 2012 08:23:14 GMT",
"version": "v1"
}
] |
2015-06-11
|
[
[
"Martinez-Asencio",
"J.",
""
],
[
"Olmo",
"Gonzalo J.",
""
],
[
"Rubiera-Garcia",
"D.",
""
]
] |
We study the formation and perturbation of black holes by null fluxes of neutral matter in a quadratic extension of General Relativity formulated a la Palatini. Working in a spherically symmetric space-time, we obtain an exact analytical solution for the metric that extends the usual Vaidya-type solution to this type of theories. We find that the resulting space-time is formally that of a Reissner-Nordstrom black hole but with an effective charge term carrying the wrong sign in front of it. This effective charge is directly related to the luminosity function of the radiation stream. When the ingoing flux vanishes, the charge term disappears and the space-time relaxes to that of a Schwarzschild black hole. We provide two examples that illustrate the formation of a black hole from Minkowski space and the perturbation by a finite pulse of radiation of an existing Schwarzschild black hole.
|
2304.05870
|
Luis Herrera
|
L. Herrera
|
Complexity and simplicity of self-gravitating fluids
|
30 pages Latex (Revtex-4). Invited chapter for the edited book New
Frontiers in Gravitational Collapse and Spacetime Singularities (Eds. P.
Joshi and D. Malafarina, Springer Singapore), expected in 2023
| null | null | null |
gr-qc astro-ph.CO
|
http://creativecommons.org/licenses/by/4.0/
|
We review a recently proposed definition of complexity of the structure of
self--gravitating fluids \cite{ch1}, and the criterium to define the simplest
mode of their evolution. We analyze the origin of these concepts and their
possible applications in the study of gravitation collapse. We start by
considering the static spherically symmetric case, extending next the study to
static axially symmetric case. Afterward we consider the non--static
spherically symmetric case. Two possible modes of evolution are proposed to be
the simplest one. One is the homologous conditio,, however, as was shown later
on, it may be useful to relax this last condition to enlarge the set of
possible solutions, by adopting the so-called quasi-homologous condition. As
another example of symmetry, we consider fluids endowed with hyperbolical
symmetry. Exact solutions for static fluid distributions satisfying the
condition of minimal complexity are presented.. An extension of the complexity
factor to the vacuum solutions of the Einstein equations represented by the
Bondi metric is discussed. A complexity hierarchy is established in this case,
ranging from the Minkowski spacetime (the simplest one) to gravitationally
radiating systems (the most complex). Finally we propose a list of questions
which, we believe, deserve to be treated in the future
|
[
{
"created": "Wed, 12 Apr 2023 13:59:39 GMT",
"version": "v1"
}
] |
2023-04-13
|
[
[
"Herrera",
"L.",
""
]
] |
We review a recently proposed definition of complexity of the structure of self--gravitating fluids \cite{ch1}, and the criterium to define the simplest mode of their evolution. We analyze the origin of these concepts and their possible applications in the study of gravitation collapse. We start by considering the static spherically symmetric case, extending next the study to static axially symmetric case. Afterward we consider the non--static spherically symmetric case. Two possible modes of evolution are proposed to be the simplest one. One is the homologous conditio,, however, as was shown later on, it may be useful to relax this last condition to enlarge the set of possible solutions, by adopting the so-called quasi-homologous condition. As another example of symmetry, we consider fluids endowed with hyperbolical symmetry. Exact solutions for static fluid distributions satisfying the condition of minimal complexity are presented.. An extension of the complexity factor to the vacuum solutions of the Einstein equations represented by the Bondi metric is discussed. A complexity hierarchy is established in this case, ranging from the Minkowski spacetime (the simplest one) to gravitationally radiating systems (the most complex). Finally we propose a list of questions which, we believe, deserve to be treated in the future
|
gr-qc/0611007
|
Edward Anderson
|
Edward Anderson
|
Emergent Semiclassical Time in Quantum Gravity. I. Mechanical Models
|
References Updated
|
Class.Quant.Grav.24:2935-2978,2007
|
10.1088/0264-9381/24/11/011
| null |
gr-qc
| null |
Strategies intended to resolve the problem of time in quantum gravity by
means of emergent or hidden timefunctions are considered in the arena of
relational particle toy models. In situations with `heavy' and `light' degrees
of freedom, two notions of emergent semiclassical WKB time emerge; these are
furthermore equivalent to two notions of emergent classical
`Leibniz--Mach--Barbour' time. I futhermore study the semiclassical approach,
in a geometric phase formalism, extended to include linear constraints, and
with particular care to make explicit those approximations and assumptions
used. I propose a new iterative scheme for this in the cosmologically-motivated
case with one heavy degree of freedom. I find that the usual semiclassical
quantum cosmology emergence of time comes hand in hand with the emergence of
other qualitatively significant terms, including back-reactions on the heavy
subsystem and second time derivatives. I illustrate my analysis by taking it
further for relational particle models with linearly-coupled harmonic
oscillator potentials. As these examples are exactly soluble by means outside
the semiclassical approach, they are additionally useful for testing the
justifiability of some of the approximations and assumptions habitually made in
the semiclassical approach to quantum cosmology. Finally, I contrast the
emergent semiclassical timefunction with its hidden dilational Euler time
counterpart.
|
[
{
"created": "Wed, 1 Nov 2006 23:57:01 GMT",
"version": "v1"
},
{
"created": "Sun, 4 Nov 2007 03:45:26 GMT",
"version": "v2"
}
] |
2010-10-27
|
[
[
"Anderson",
"Edward",
""
]
] |
Strategies intended to resolve the problem of time in quantum gravity by means of emergent or hidden timefunctions are considered in the arena of relational particle toy models. In situations with `heavy' and `light' degrees of freedom, two notions of emergent semiclassical WKB time emerge; these are furthermore equivalent to two notions of emergent classical `Leibniz--Mach--Barbour' time. I futhermore study the semiclassical approach, in a geometric phase formalism, extended to include linear constraints, and with particular care to make explicit those approximations and assumptions used. I propose a new iterative scheme for this in the cosmologically-motivated case with one heavy degree of freedom. I find that the usual semiclassical quantum cosmology emergence of time comes hand in hand with the emergence of other qualitatively significant terms, including back-reactions on the heavy subsystem and second time derivatives. I illustrate my analysis by taking it further for relational particle models with linearly-coupled harmonic oscillator potentials. As these examples are exactly soluble by means outside the semiclassical approach, they are additionally useful for testing the justifiability of some of the approximations and assumptions habitually made in the semiclassical approach to quantum cosmology. Finally, I contrast the emergent semiclassical timefunction with its hidden dilational Euler time counterpart.
|
1903.10907
|
Amir Hadi Ziaie
|
Mohammad Reza Mehdizadeh and Amir Hadi Ziaie
|
Traversable wormholes in Einsteinian cubic gravity
|
20 pages and 7 figures
|
Mod. Phys. Lett. A, 35, No. 6, 2050017 (2020)
|
10.1142/S0217732320500170
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In the present work we investigate wormhole configurations described by a
constant redshift function in Einstein-Cubic gravity ({{\sf ECG}}). We derive
analytical wormhole geometries by assuming a particular equation of state
({{\sf EoS}}) and investigate the possibility that these solutions satisfy the
standard energy conditions. We introduce exact asymptotically flat and anti-de
Sitter (AdS) spacetimes that admit traversable wormholes. These solutions are
obtained by imposing suitable values for the parameters of the theory so that
the resulted geometries satisfy the weak energy condition ({\sf WEC}) in the
vicinity of the throat, due to the presence of higher-order curvature terms.
Moreover, we find that AdS solutions satisfy the {\sf WEC} throughout the
spacetime. A description of the geodesic motion of timelike and null particles
is presented for the obtained wormhole solutions. Also, using gravitational
lensing effects, observational features of the wormhole structure are
discussed.
|
[
{
"created": "Sun, 24 Mar 2019 10:15:59 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Oct 2019 04:43:07 GMT",
"version": "v2"
}
] |
2020-03-05
|
[
[
"Mehdizadeh",
"Mohammad Reza",
""
],
[
"Ziaie",
"Amir Hadi",
""
]
] |
In the present work we investigate wormhole configurations described by a constant redshift function in Einstein-Cubic gravity ({{\sf ECG}}). We derive analytical wormhole geometries by assuming a particular equation of state ({{\sf EoS}}) and investigate the possibility that these solutions satisfy the standard energy conditions. We introduce exact asymptotically flat and anti-de Sitter (AdS) spacetimes that admit traversable wormholes. These solutions are obtained by imposing suitable values for the parameters of the theory so that the resulted geometries satisfy the weak energy condition ({\sf WEC}) in the vicinity of the throat, due to the presence of higher-order curvature terms. Moreover, we find that AdS solutions satisfy the {\sf WEC} throughout the spacetime. A description of the geodesic motion of timelike and null particles is presented for the obtained wormhole solutions. Also, using gravitational lensing effects, observational features of the wormhole structure are discussed.
|
gr-qc/9805094
|
J. A. Valiente Kroon
|
J.A. Valiente Kroon
|
Conserved Quantities for Polyhomogeneous Space-Times
|
21 pages, LaTex, to be published in CQG
|
Class.Quant.Grav. 15 (1998) 2479-2491
|
10.1088/0264-9381/15/8/023
| null |
gr-qc
| null |
The existence of conserved quantities with a structure similar to the
Newman-Penrose quantities in a polyhomogeneous space-time is addressed. The
most general form for the initial data formally consistent with the
polyhomogeneous setting is found. The subsequent study is done for those
polyhomogeneous space-times where the leading term of the shear contains no
logarithmic terms. It is found that for these space-times the original NP
quantities cease to be constants, but it is still possible to construct a set
of other 10 quantities that are constant. From these quantities it is possible
to obtain as a particular case a conserved quantity found by Chrusciel et al.
|
[
{
"created": "Wed, 27 May 1998 10:24:48 GMT",
"version": "v1"
}
] |
2009-10-31
|
[
[
"Kroon",
"J. A. Valiente",
""
]
] |
The existence of conserved quantities with a structure similar to the Newman-Penrose quantities in a polyhomogeneous space-time is addressed. The most general form for the initial data formally consistent with the polyhomogeneous setting is found. The subsequent study is done for those polyhomogeneous space-times where the leading term of the shear contains no logarithmic terms. It is found that for these space-times the original NP quantities cease to be constants, but it is still possible to construct a set of other 10 quantities that are constant. From these quantities it is possible to obtain as a particular case a conserved quantity found by Chrusciel et al.
|
gr-qc/0408058
|
Peng Wang
|
Peng Wang, Gilberto M. Kremer, Daniele S. M. Alves, Xin-He Meng
|
A Note on Energy-Momentum Conservation in Palatini Formulation of L(R)
Gravity
|
7 pages
|
Gen.Rel.Grav. 38 (2006) 517-521
|
10.1007/s10714-006-0238-9
| null |
gr-qc
| null |
By establishing that Palatini formulation of $L(R)$ gravity is equivalent to
$\omega=-3/2$ Brans-Dicke theory, we show that energy-momentum tensor is
covariantly conserved in this type of modified gravity theory.
|
[
{
"created": "Wed, 18 Aug 2004 10:41:03 GMT",
"version": "v1"
}
] |
2015-06-25
|
[
[
"Wang",
"Peng",
""
],
[
"Kremer",
"Gilberto M.",
""
],
[
"Alves",
"Daniele S. M.",
""
],
[
"Meng",
"Xin-He",
""
]
] |
By establishing that Palatini formulation of $L(R)$ gravity is equivalent to $\omega=-3/2$ Brans-Dicke theory, we show that energy-momentum tensor is covariantly conserved in this type of modified gravity theory.
|
1903.00391
|
A. Emrah Y\"ukselci
|
A. Sava\c{s} Arapo\u{g}lu and K. Yavuz Ek\c{s}i and A. Emrah
Y\"ukselci
|
Neutron Star Structure in the Presence of Nonminimally Coupled Scalar
Fields
|
17 pages, 4 figures; PRD printed
|
Phys. Rev. D 99, 064055 (2019)
|
10.1103/PhysRevD.99.064055
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the structure of neutron stars in scalar-tensor theories for the
nonminimal coupling of the form $(1+\kappa \xi \phi^{2})\cal R$. We solve the
hydrostatic equilibrium equations for two different types of scalar field
potentials and three different equations of state representative of different
degrees of stiffness. We obtain the mass-radius relations of the configurations
and determine the allowed ranges for the term $\xi\phi^2$ at the center of the
star and spatial infinity based on the measured maximum value of the mass for
neutron stars and the recent constraints on the radius coming from
gravitational wave observations. Thus we manage to limit the deviation of the
model from general relativity. We examine the possible constraints on the
parameters of the model and compare the obtained restrictions with the ones
inferred from other cosmological probes that give the allowed ranges for the
coupling constant only. In the case of the Higgs-like potential, we also find
that the central value for the scalar field cannot be chosen arbitrarily but it
depends on the vacuum expectation value of the field. Finally, we discuss the
effect of the scalar field potential on the mass and the radius of the star by
comparing the results obtained for the cases considered here.
|
[
{
"created": "Fri, 1 Mar 2019 16:25:46 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Apr 2019 15:12:43 GMT",
"version": "v2"
}
] |
2019-04-02
|
[
[
"Arapoğlu",
"A. Savaş",
""
],
[
"Ekşi",
"K. Yavuz",
""
],
[
"Yükselci",
"A. Emrah",
""
]
] |
We study the structure of neutron stars in scalar-tensor theories for the nonminimal coupling of the form $(1+\kappa \xi \phi^{2})\cal R$. We solve the hydrostatic equilibrium equations for two different types of scalar field potentials and three different equations of state representative of different degrees of stiffness. We obtain the mass-radius relations of the configurations and determine the allowed ranges for the term $\xi\phi^2$ at the center of the star and spatial infinity based on the measured maximum value of the mass for neutron stars and the recent constraints on the radius coming from gravitational wave observations. Thus we manage to limit the deviation of the model from general relativity. We examine the possible constraints on the parameters of the model and compare the obtained restrictions with the ones inferred from other cosmological probes that give the allowed ranges for the coupling constant only. In the case of the Higgs-like potential, we also find that the central value for the scalar field cannot be chosen arbitrarily but it depends on the vacuum expectation value of the field. Finally, we discuss the effect of the scalar field potential on the mass and the radius of the star by comparing the results obtained for the cases considered here.
|
2108.02331
|
Yitian Chen
|
Yitian Chen, Nils Deppe, Lawrence E. Kidder, Saul A. Teukolsky
|
Efficient simulations of high-spin black holes with a new gauge
|
17 pages, 11 figures, 3 tables
|
Phys. Rev. D 104, 084046 (2021)
|
10.1103/PhysRevD.104.084046
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We present a new choice of initial data for binary black hole simulations
that significantly improves the efficiency of high-spin simulations. We use
spherical Kerr-Schild coordinates, where the horizon of a rotating black hole
is spherical, for each black hole. The superposed spherical Kerr-Schild initial
data reduce the runtime by a factor of 2 compared to standard superposed
Kerr-Schild for an intermediate resolution spin-0.99 binary-black-hole
simulation. We also explore the possibility of delaying the transition from the
initial data gauge to the evolution gauge, which produces an additional
speed-up of 1.3.
|
[
{
"created": "Thu, 5 Aug 2021 01:23:17 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Oct 2021 15:30:18 GMT",
"version": "v2"
}
] |
2021-10-15
|
[
[
"Chen",
"Yitian",
""
],
[
"Deppe",
"Nils",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Teukolsky",
"Saul A.",
""
]
] |
We present a new choice of initial data for binary black hole simulations that significantly improves the efficiency of high-spin simulations. We use spherical Kerr-Schild coordinates, where the horizon of a rotating black hole is spherical, for each black hole. The superposed spherical Kerr-Schild initial data reduce the runtime by a factor of 2 compared to standard superposed Kerr-Schild for an intermediate resolution spin-0.99 binary-black-hole simulation. We also explore the possibility of delaying the transition from the initial data gauge to the evolution gauge, which produces an additional speed-up of 1.3.
|
1406.3040
|
Ioannis Gkigkitzis Dr.
|
Ioannis Haranas, Ioannis Gkigkitzis
|
Bekenstein Bound of Information Number N and its Relation to
Cosmological Parameters in a Universe with and without Cosmological Constant
|
Bekenstein bound, cosmological constant, information, nats, entropy,
mass of the universe, self-gravitating systems, Calogero's conjecture
|
Modern Physics Letters A, 28, 1350077 (2013)
|
10.1142/S0217732313500776
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Bekenstein has obtained is an upper limit on the entropy S, and from that, an
information number bound N is deduced. In other words, this is the information
contained within a given finite region of space that includes a finite amount
of energy. Similarly, this can be thought as the maximum amount of information
required to perfectly describe a given physical system down to its quantum
level. If the energy and the region of space are finite then the number of
information N required in describing the physical system is also finite. In
this short letter two information number bounds are derived and compared for
two types of universe. First, a universe without a cosmological constant lamda
and second a universe with a cosmological constant lamda are investigated. This
is achieved with the derivation of two different relations that connect the
Hubble constant and cosmological constants to the number of information N. We
find that the number of information N involved in a the two universes are
identical or
N1=N2, and that the total mass of the universe scales as the square root of
the information number N, containing an information number N of the order of
10E+122. Finally, we expressed Calogero quantization action as a function of
the number of information N. We also have found that in self gravitating
systems the number of information N in nats is the ratio of the total kinetic
to total thermal energy of the system.
|
[
{
"created": "Mon, 9 Jun 2014 15:34:12 GMT",
"version": "v1"
}
] |
2014-06-13
|
[
[
"Haranas",
"Ioannis",
""
],
[
"Gkigkitzis",
"Ioannis",
""
]
] |
Bekenstein has obtained is an upper limit on the entropy S, and from that, an information number bound N is deduced. In other words, this is the information contained within a given finite region of space that includes a finite amount of energy. Similarly, this can be thought as the maximum amount of information required to perfectly describe a given physical system down to its quantum level. If the energy and the region of space are finite then the number of information N required in describing the physical system is also finite. In this short letter two information number bounds are derived and compared for two types of universe. First, a universe without a cosmological constant lamda and second a universe with a cosmological constant lamda are investigated. This is achieved with the derivation of two different relations that connect the Hubble constant and cosmological constants to the number of information N. We find that the number of information N involved in a the two universes are identical or N1=N2, and that the total mass of the universe scales as the square root of the information number N, containing an information number N of the order of 10E+122. Finally, we expressed Calogero quantization action as a function of the number of information N. We also have found that in self gravitating systems the number of information N in nats is the ratio of the total kinetic to total thermal energy of the system.
|
1504.03544
|
Asrin Abdolmaleki
|
A. Abdolmaleki, T. Najafi
|
Generalized second law of thermodynamics on the apparent horizon in
modified Gauss-Bonnet gravity
|
21 pages, 18 figures
|
IJMPD 25, 3 (2016)
|
10.1142/S0218271816500401
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Modified gravity and generalized second law (GSL) of thermodynamics are
interesting topics in the modern cosmology. In this regard, we investigate the
GSL of gravitational thermodynamics in the framework of modified Gauss-Bonnet
gravity or f(G)-gravity. We consider a spatially FRW universe filled with the
matter and radiation enclosed by the dynamical apparent horizon with the
Hawking temperature. For two viable f(G) models, we first numerically solve the
set of differential equations governing the dynamics of f(G)-gravity. Then, we
obtain the evolutions of the Hubble parameter, the Gauss-Bonnet curvature
invariant term, the density and equation of state parameters as well as the
deceleration parameter. In addition, we check the energy conditions for both
models and finally examine the validity of the GSL. For the selected f(G)
models, we conclude that both models have a stable de Sitter attractor. The
equation of state parameters behave quite similar to those of the LCDM model in
the radiation/matter dominated epochs, then they enter the phantom region
before reaching the de Sitter attractor with w=-1. The deceleration parameter
starts from the radiation/matter dominated eras, then transits from a cosmic
deceleration to acceleration and finally approaches a de Sitter regime at late
times, as expected. Furthermore, the GSL is respected for both models during
the standard radiation/matter dominated epochs. Thereafter when the universe
becomes accelerating, the GSL is violated in some ranges of scale factor. At
late times, the evolution of the GSL predicts an adiabatic behavior for the
accelerated expansion of the universe.
|
[
{
"created": "Sat, 11 Apr 2015 09:10:47 GMT",
"version": "v1"
}
] |
2016-11-22
|
[
[
"Abdolmaleki",
"A.",
""
],
[
"Najafi",
"T.",
""
]
] |
Modified gravity and generalized second law (GSL) of thermodynamics are interesting topics in the modern cosmology. In this regard, we investigate the GSL of gravitational thermodynamics in the framework of modified Gauss-Bonnet gravity or f(G)-gravity. We consider a spatially FRW universe filled with the matter and radiation enclosed by the dynamical apparent horizon with the Hawking temperature. For two viable f(G) models, we first numerically solve the set of differential equations governing the dynamics of f(G)-gravity. Then, we obtain the evolutions of the Hubble parameter, the Gauss-Bonnet curvature invariant term, the density and equation of state parameters as well as the deceleration parameter. In addition, we check the energy conditions for both models and finally examine the validity of the GSL. For the selected f(G) models, we conclude that both models have a stable de Sitter attractor. The equation of state parameters behave quite similar to those of the LCDM model in the radiation/matter dominated epochs, then they enter the phantom region before reaching the de Sitter attractor with w=-1. The deceleration parameter starts from the radiation/matter dominated eras, then transits from a cosmic deceleration to acceleration and finally approaches a de Sitter regime at late times, as expected. Furthermore, the GSL is respected for both models during the standard radiation/matter dominated epochs. Thereafter when the universe becomes accelerating, the GSL is violated in some ranges of scale factor. At late times, the evolution of the GSL predicts an adiabatic behavior for the accelerated expansion of the universe.
|
0711.4767
|
Ulf Leonhardt
|
Germain Rousseaux, Christian Mathis, Philippe Maissa, Thomas G.
Philbin, and Ulf Leonhardt
|
Observation of negative-frequency waves in a water tank: A classical
analogue to the Hawking effect?
| null |
NewJ.Phys.10:053015,2008
|
10.1088/1367-2630/10/5/053015
| null |
gr-qc
| null |
The conversion of positive-frequency waves into negative-frequency waves at
the event horizon is the mechanism at the heart of the Hawking radiation of
black holes. In black-hole analogues, horizons are formed for waves propagating
in a medium against the current when and where the flow exceeds the wave
velocity. We report on the first direct observation of negative-frequency waves
converted from positive-frequency waves in a moving medium. The measured degree
of mode conversion is significantly higher than expected from theory.
|
[
{
"created": "Thu, 29 Nov 2007 16:33:08 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Jan 2008 15:36:58 GMT",
"version": "v2"
},
{
"created": "Sat, 1 Mar 2008 11:52:39 GMT",
"version": "v3"
}
] |
2008-11-26
|
[
[
"Rousseaux",
"Germain",
""
],
[
"Mathis",
"Christian",
""
],
[
"Maissa",
"Philippe",
""
],
[
"Philbin",
"Thomas G.",
""
],
[
"Leonhardt",
"Ulf",
""
]
] |
The conversion of positive-frequency waves into negative-frequency waves at the event horizon is the mechanism at the heart of the Hawking radiation of black holes. In black-hole analogues, horizons are formed for waves propagating in a medium against the current when and where the flow exceeds the wave velocity. We report on the first direct observation of negative-frequency waves converted from positive-frequency waves in a moving medium. The measured degree of mode conversion is significantly higher than expected from theory.
|
1506.06400
|
Spyros Alexakis
|
Spyros Alexakis
|
The Penrose inequality on perturbations of the Schwarzschild exterior
|
50 pages, 2 figures
| null | null | null |
gr-qc math.AP math.DG
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We prove a version the Penrose inequality for black hole space-times which
are perturbations of the Schwarzschild exterior in a slab around a null
hypersurface $\underline{\mathcal{N}}_0$. $\underline{\mathcal{N}}_0$
terminates at past null infinity $\mathcal{I}^-$ and
$\mathcal{S}_0:=\partial\underline{\mathcal{N}}_0$ is chosen to be a marginally
outer trapped sphere. We show that the area of $\mathcal{S}_0$ yields a lower
bound for the Bondi energy of sections of past null infinity, thus also for the
total ADM energy. Our argument is perturbative, and rests on suitably deforming
the initial null hypersurface $\underline{\mathcal{N}}_0$ to one for which the
natural "luminosity" foliation originally introduced by Hawking yields a
monotonically increasing Hawking mass, and for which the leaves of this
foliation become asymptotically round. It is to ensure the latter (essential)
property that we perform the deformation of the initial nullhypersurface
$\underline{\mathcal{N}}_0$.
|
[
{
"created": "Sun, 21 Jun 2015 18:52:47 GMT",
"version": "v1"
}
] |
2015-06-23
|
[
[
"Alexakis",
"Spyros",
""
]
] |
We prove a version the Penrose inequality for black hole space-times which are perturbations of the Schwarzschild exterior in a slab around a null hypersurface $\underline{\mathcal{N}}_0$. $\underline{\mathcal{N}}_0$ terminates at past null infinity $\mathcal{I}^-$ and $\mathcal{S}_0:=\partial\underline{\mathcal{N}}_0$ is chosen to be a marginally outer trapped sphere. We show that the area of $\mathcal{S}_0$ yields a lower bound for the Bondi energy of sections of past null infinity, thus also for the total ADM energy. Our argument is perturbative, and rests on suitably deforming the initial null hypersurface $\underline{\mathcal{N}}_0$ to one for which the natural "luminosity" foliation originally introduced by Hawking yields a monotonically increasing Hawking mass, and for which the leaves of this foliation become asymptotically round. It is to ensure the latter (essential) property that we perform the deformation of the initial nullhypersurface $\underline{\mathcal{N}}_0$.
|
gr-qc/0604018
|
Moh'd Qusailah Mr
|
K.G. Arun, B.R. Iyer, M.S.S. Qusailah, B.S. Sathyaprakash
|
Testing post-Newtonian theory with gravitational wave observations
|
9 pages, 2 figures
|
Class.Quant.Grav.23:L37-L43,2006
|
10.1088/0264-9381/23/9/L01
| null |
gr-qc astro-ph
| null |
The Laser Interferometric Space Antenna (LISA) will observe supermassive
black hole binary mergers with amplitude signal-to-noise ratio of several
thousands. We investigate the extent to which such observations afford
high-precision tests of Einstein's gravity. We show that LISA provides a unique
opportunity to probe the non-linear structure of post-Newtonian theory both in
the context of general relativity and its alternatives.
|
[
{
"created": "Wed, 5 Apr 2006 12:23:02 GMT",
"version": "v1"
}
] |
2010-11-05
|
[
[
"Arun",
"K. G.",
""
],
[
"Iyer",
"B. R.",
""
],
[
"Qusailah",
"M. S. S.",
""
],
[
"Sathyaprakash",
"B. S.",
""
]
] |
The Laser Interferometric Space Antenna (LISA) will observe supermassive black hole binary mergers with amplitude signal-to-noise ratio of several thousands. We investigate the extent to which such observations afford high-precision tests of Einstein's gravity. We show that LISA provides a unique opportunity to probe the non-linear structure of post-Newtonian theory both in the context of general relativity and its alternatives.
|
1407.5662
|
Davood Momeni Dr
|
Davood Momeni, Aziza Altaibayeva, Ratbay Myrzakulov
|
New Modified Mimetic Gravity
|
Revised version, Accepted in "International Journal of Geometric
Methods in Modern Physics"
|
Int. J. Geom. Methods Mod. Phys. 11, 1450091 (2014)
|
10.1142/S0219887814500911
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A modified Mimetic gravity (MMG) is proposed as a generalization of general
relativity. The model contain a physical metric which is function of an
auxiliary (unphysical) metric and a Lyra's metric. We construct different kinds
of conformally invariant models in different levels of the expansion parameter
$\lambda$. This model phenomenologically has been extended to higher order
forms. Cosmology of a certain class of such models has been investigated in
details. A cosmological solution has been proposed in inhomogeneous form of
scalar field. For homogenous case, energy conditions are widely investigated.
We have shown that the system evaluated at intervals shorter than a certain
time $T_c$ meets all the energy conditions.
|
[
{
"created": "Mon, 21 Jul 2014 20:41:03 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Aug 2014 13:00:39 GMT",
"version": "v2"
}
] |
2015-04-07
|
[
[
"Momeni",
"Davood",
""
],
[
"Altaibayeva",
"Aziza",
""
],
[
"Myrzakulov",
"Ratbay",
""
]
] |
A modified Mimetic gravity (MMG) is proposed as a generalization of general relativity. The model contain a physical metric which is function of an auxiliary (unphysical) metric and a Lyra's metric. We construct different kinds of conformally invariant models in different levels of the expansion parameter $\lambda$. This model phenomenologically has been extended to higher order forms. Cosmology of a certain class of such models has been investigated in details. A cosmological solution has been proposed in inhomogeneous form of scalar field. For homogenous case, energy conditions are widely investigated. We have shown that the system evaluated at intervals shorter than a certain time $T_c$ meets all the energy conditions.
|
1012.2861
|
Dmitri Gal'tsov
|
Dmitry V. Gal'tsov and Evgeny A. Davydov
|
Cosmological models with gauge fields
|
Talk at the Int. Conf. "Gauge Fields. Yesterday, Today, Tomorrow"
dedicated the 70-th anniversary of A. A. Slavnov, MIAN, Moscow, January
19-24, 2010, to be published in the Proceedings
|
Proceedings of the Steklov Institute of Mathematics, 2011, Vol.
272, pp. 119-140
| null | null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We discuss cosmological models involving homogeneous and isotropic Yang-Mills
(YM) fields. Such models were proposed recently as an alternative to scalar
models of cosmic acceleration. There exists a unique SU(2) YM configuration
(generalizable to larger gauge groups) whose energy-momentum tensor is
homogeneous and isotropic in space. It is parameterized by a single scalar
field with a quatric potential. In the case of the closed universe the coupled
YM -- doublet Higgs system admits homogeneous and isotropic configurations too.
While pure Einstein-Yang-Mills (EYM) cosmology with the standard conformally
invariant YM action gives rise to the hot universe, Einstein-Yang-Mills-Higgs
(EYMH) cosmology has a variety of regimes which include inflationary stages,
bounces, and exhibits global cycling behavior reminiscent of the Multiverse
developed in time. We also discuss other mechanisms of conformal symmetry
breaking such as string-inspired Born-Infeld (BI) modification of the YM action
or field-theoretical quantum corrections.
|
[
{
"created": "Mon, 13 Dec 2010 20:59:47 GMT",
"version": "v1"
}
] |
2011-03-22
|
[
[
"Gal'tsov",
"Dmitry V.",
""
],
[
"Davydov",
"Evgeny A.",
""
]
] |
We discuss cosmological models involving homogeneous and isotropic Yang-Mills (YM) fields. Such models were proposed recently as an alternative to scalar models of cosmic acceleration. There exists a unique SU(2) YM configuration (generalizable to larger gauge groups) whose energy-momentum tensor is homogeneous and isotropic in space. It is parameterized by a single scalar field with a quatric potential. In the case of the closed universe the coupled YM -- doublet Higgs system admits homogeneous and isotropic configurations too. While pure Einstein-Yang-Mills (EYM) cosmology with the standard conformally invariant YM action gives rise to the hot universe, Einstein-Yang-Mills-Higgs (EYMH) cosmology has a variety of regimes which include inflationary stages, bounces, and exhibits global cycling behavior reminiscent of the Multiverse developed in time. We also discuss other mechanisms of conformal symmetry breaking such as string-inspired Born-Infeld (BI) modification of the YM action or field-theoretical quantum corrections.
|
2208.02761
|
Piyabut Burikham
|
Supakchai Ponglertsakul, Piyabut Burikham, Sitthichai Pinkanjanarod
|
Normal and Quasinormal Modes of Holographic Multiquark Star
|
9 pages, 8 figures
| null |
10.1103/PhysRevD.107.023020
| null |
gr-qc astro-ph.SR hep-ph
|
http://creativecommons.org/licenses/by/4.0/
|
The quadrupole normal-mode oscillation frequency $f_{n}$ of multiquark star
are computed for $n=1-5$. At the transition from low to high density multiquark
in the core region, the first 2 modes jump to larger values, a distinctive
signature of the presence of the high-density core. When the star oscillation
couples with spacetime, gravitational waves~(GW) will be generated and the star
will undergo damped oscillation. The quasinormal modes~(QNMs) of the
oscillation are computed using two methods, direct scan and WKB, for QNMs with
small and large imaginary parts respectively. The small imaginary QNMs have
frequencies $1.5-2.6$ kHz and damping times $0.19-1.7$ secs for multiquark star
with mass $M=0.6-2.1 M_{\odot}$~(solar mass). The WKB QNMs with large imaginary
parts have frequencies $5.98-9.81$ kHz and damping times $0.13-0.46$ ms for
$M\simeq 0.3-2.1 M_{\odot}$. They are found to be the fluid $f-$modes and
spacetime curvature $w-$modes respectively.
|
[
{
"created": "Thu, 4 Aug 2022 16:39:12 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Jan 2023 15:28:47 GMT",
"version": "v2"
}
] |
2023-02-08
|
[
[
"Ponglertsakul",
"Supakchai",
""
],
[
"Burikham",
"Piyabut",
""
],
[
"Pinkanjanarod",
"Sitthichai",
""
]
] |
The quadrupole normal-mode oscillation frequency $f_{n}$ of multiquark star are computed for $n=1-5$. At the transition from low to high density multiquark in the core region, the first 2 modes jump to larger values, a distinctive signature of the presence of the high-density core. When the star oscillation couples with spacetime, gravitational waves~(GW) will be generated and the star will undergo damped oscillation. The quasinormal modes~(QNMs) of the oscillation are computed using two methods, direct scan and WKB, for QNMs with small and large imaginary parts respectively. The small imaginary QNMs have frequencies $1.5-2.6$ kHz and damping times $0.19-1.7$ secs for multiquark star with mass $M=0.6-2.1 M_{\odot}$~(solar mass). The WKB QNMs with large imaginary parts have frequencies $5.98-9.81$ kHz and damping times $0.13-0.46$ ms for $M\simeq 0.3-2.1 M_{\odot}$. They are found to be the fluid $f-$modes and spacetime curvature $w-$modes respectively.
|
gr-qc/0202068
|
Shatskiy Alexandr
|
A. A. Shatskiy
|
Axial Magnetostatics of a Ring Current in a Kerr Field
|
10 pages, 1 figures
|
Journal of Experimental and Theoretical Physics, Vol. 93, No. 5,
2001, Received March 28, 2001
| null | null |
gr-qc
| null |
The electromagnetic fields generated by a ring current around a Kerr black
hole have been found. The acceleration of a charged particle by a force
electric field along the rotation axis is investigated in the constructed
model, as applied to the astrophysics of quasars.
|
[
{
"created": "Tue, 19 Feb 2002 10:38:25 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Feb 2002 14:54:33 GMT",
"version": "v2"
}
] |
2007-05-23
|
[
[
"Shatskiy",
"A. A.",
""
]
] |
The electromagnetic fields generated by a ring current around a Kerr black hole have been found. The acceleration of a charged particle by a force electric field along the rotation axis is investigated in the constructed model, as applied to the astrophysics of quasars.
|
1702.05889
|
Junji Jia
|
Junji Jia, Jiawei Liu, Xionghui Liu, Zhongyou Mo, Xiankai Pang,
Yaoguang Wang, Nan Yang
|
Existence and stability of circular orbits in general static and
spherically symmetric spacetimes
|
17 pages, no figure; references adjusted; error corrected
| null |
10.1007/s10714-017-2337-1
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The existence and stability of circular orbits (CO) in static and spherically
symmetric (SSS) spacetime are important because of their practical and
potential usefulness. In this paper, using the fixed point method, we first
prove a necessary and sufficient condition on the metric function for the
existence of timelike COs in SSS spacetimes. After analyzing the asymptotic
behavior of the metric, we then show that asymptotic flat SSS spacetime that
corresponds to a negative Newtonian potential at large $r$ will always allow
the existence of CO. The stability of the CO in a general SSS spacetime is then
studied using the Lyapunov exponent method. Two sufficient conditions on the
(in)stability of the COs are obtained. For null geodesics, a sufficient
condition on the metric function for the (in)stability of null CO is also
obtained. We then illustrate one powerful application of these results by
showing that an SU(2) Yang-Mills-Einstein SSS spacetime whose metric function
is not known, will allow the existence of timelike COs. We also used our
results to assert the existence and (in)stabilities of a number of known SSS
metrics.
|
[
{
"created": "Mon, 20 Feb 2017 08:12:19 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Mar 2017 05:33:54 GMT",
"version": "v2"
},
{
"created": "Sat, 15 Apr 2017 11:30:26 GMT",
"version": "v3"
}
] |
2018-02-14
|
[
[
"Jia",
"Junji",
""
],
[
"Liu",
"Jiawei",
""
],
[
"Liu",
"Xionghui",
""
],
[
"Mo",
"Zhongyou",
""
],
[
"Pang",
"Xiankai",
""
],
[
"Wang",
"Yaoguang",
""
],
[
"Yang",
"Nan",
""
]
] |
The existence and stability of circular orbits (CO) in static and spherically symmetric (SSS) spacetime are important because of their practical and potential usefulness. In this paper, using the fixed point method, we first prove a necessary and sufficient condition on the metric function for the existence of timelike COs in SSS spacetimes. After analyzing the asymptotic behavior of the metric, we then show that asymptotic flat SSS spacetime that corresponds to a negative Newtonian potential at large $r$ will always allow the existence of CO. The stability of the CO in a general SSS spacetime is then studied using the Lyapunov exponent method. Two sufficient conditions on the (in)stability of the COs are obtained. For null geodesics, a sufficient condition on the metric function for the (in)stability of null CO is also obtained. We then illustrate one powerful application of these results by showing that an SU(2) Yang-Mills-Einstein SSS spacetime whose metric function is not known, will allow the existence of timelike COs. We also used our results to assert the existence and (in)stabilities of a number of known SSS metrics.
|
0709.4538
|
Ujjal Debnath
|
Ujjal Debnath, Narayan Chandra Chakraborty and Subenoy Chakraborty
|
Gravitational Collapse in Higher Dimensional Husain Space-Time
|
12 latex pages, No figure, RevTex style
|
Gen.Rel.Grav.40:749-763,2008
|
10.1007/s10714-007-0525-0
| null |
gr-qc
| null |
We investigate exact solution in higher dimensional Husain model for a null
fluid source with pressure $p$ and density $\rho$ are related by the following
relations (i) $p=k\rho$, (ii) $p=k\rho-\frac{B(v)}{\rho^{\alpha}}$ (variable
modified Chaplygin) and (iii) $p=k\rho^{\alpha}$ (polytropic). We have studied
the nature of singularity in gravitational collapse for the above equations of
state and also for different choices of the of the parameters $k$ and $B$
namely, (i) $k=0$, $B=$ constant (generalized Chaplygin), (ii) $B=$ constant
(modified Chaplygin). It is found that the nature of singularity is independent
of these choices of different equation of state except for variable Chaplygin
model. Choices of various parameters are shown in tabular form. Finally,
matching of Szekeres model with exterior Husain space-time is done.
|
[
{
"created": "Fri, 28 Sep 2007 06:03:31 GMT",
"version": "v1"
}
] |
2008-11-26
|
[
[
"Debnath",
"Ujjal",
""
],
[
"Chakraborty",
"Narayan Chandra",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] |
We investigate exact solution in higher dimensional Husain model for a null fluid source with pressure $p$ and density $\rho$ are related by the following relations (i) $p=k\rho$, (ii) $p=k\rho-\frac{B(v)}{\rho^{\alpha}}$ (variable modified Chaplygin) and (iii) $p=k\rho^{\alpha}$ (polytropic). We have studied the nature of singularity in gravitational collapse for the above equations of state and also for different choices of the of the parameters $k$ and $B$ namely, (i) $k=0$, $B=$ constant (generalized Chaplygin), (ii) $B=$ constant (modified Chaplygin). It is found that the nature of singularity is independent of these choices of different equation of state except for variable Chaplygin model. Choices of various parameters are shown in tabular form. Finally, matching of Szekeres model with exterior Husain space-time is done.
|
gr-qc/9703009
|
Henning Wissowski
|
H. Wissowski and H.A. Kastrup
|
Back Reaction and Semiclassical Approximation of cosmological models
coupled to matter
|
4 pages, Latex, to appear in: Proceedings of the Second Meeting on
constrained Dynamics and Quantum Gravity (Santa Margherita Ligure 1996)
|
Nucl.Phys.Proc.Suppl.57:299-302,1997
|
10.1016/S0920-5632(97)00394-0
|
PITHA 97/14
|
gr-qc
| null |
Bianchi -I, -III, and FRW type models minimally coupled to a massive
spatially homogeneous scalar field (i.e. a particle) are studied in the
framework of semiclassical quantum gravity. In a first step we discuss the
solutions of the corresponding equation for a Schr\"odinger particle
propagating on a classical background. The back reaction of the Schr\"odinger
particle on the classical metric is calculated by means of the Wigner function
and by means of the expectation value of the energy-momentum-tensor of the
field as a source. Both methods in general lead to different results.
|
[
{
"created": "Tue, 4 Mar 1997 15:03:56 GMT",
"version": "v1"
}
] |
2008-11-26
|
[
[
"Wissowski",
"H.",
""
],
[
"Kastrup",
"H. A.",
""
]
] |
Bianchi -I, -III, and FRW type models minimally coupled to a massive spatially homogeneous scalar field (i.e. a particle) are studied in the framework of semiclassical quantum gravity. In a first step we discuss the solutions of the corresponding equation for a Schr\"odinger particle propagating on a classical background. The back reaction of the Schr\"odinger particle on the classical metric is calculated by means of the Wigner function and by means of the expectation value of the energy-momentum-tensor of the field as a source. Both methods in general lead to different results.
|
1606.01011
|
Michael Coughlin
|
Michael W. Coughlin, Nelson L. Christensen, Rosario De Rosa, Irene
Fiori, Mark Go{\l}kowski, Melissa Guidry, Jan Harms, Jerzy Kubisz, Andrzej
Kulak, Janusz Mlynarczyk, Federico Paoletti, Eric Thrane
|
Subtraction of correlated noise in global networks of gravitational-wave
interferometers
| null | null |
10.1088/0264-9381/33/22/224003
| null |
gr-qc astro-ph.IM physics.ins-det
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The recent discovery of merging black holes suggests that a stochastic
gravitational-wave background is within reach of the advanced detector network
operating at design sensitivity. However, correlated magnetic noise from
Schumann resonances threatens to contaminate observation of a stochastic
background. In this paper, we report on the first effort to eliminate
intercontinental correlated noise from Schumann resonances using Wiener
filtering. Using magnetometers as proxies for gravitational-wave detectors, we
demonstrate as much as a factor of two reduction in the coherence between
magnetometers on different continents. While much work remains to be done, our
results constitute a proof-of-principle and motivate follow-up studies with a
dedicated array of magnetometers.
|
[
{
"created": "Fri, 3 Jun 2016 09:07:45 GMT",
"version": "v1"
}
] |
2016-11-23
|
[
[
"Coughlin",
"Michael W.",
""
],
[
"Christensen",
"Nelson L.",
""
],
[
"De Rosa",
"Rosario",
""
],
[
"Fiori",
"Irene",
""
],
[
"Gołkowski",
"Mark",
""
],
[
"Guidry",
"Melissa",
""
],
[
"Harms",
"Jan",
""
],
[
"Kubisz",
"Jerzy",
""
],
[
"Kulak",
"Andrzej",
""
],
[
"Mlynarczyk",
"Janusz",
""
],
[
"Paoletti",
"Federico",
""
],
[
"Thrane",
"Eric",
""
]
] |
The recent discovery of merging black holes suggests that a stochastic gravitational-wave background is within reach of the advanced detector network operating at design sensitivity. However, correlated magnetic noise from Schumann resonances threatens to contaminate observation of a stochastic background. In this paper, we report on the first effort to eliminate intercontinental correlated noise from Schumann resonances using Wiener filtering. Using magnetometers as proxies for gravitational-wave detectors, we demonstrate as much as a factor of two reduction in the coherence between magnetometers on different continents. While much work remains to be done, our results constitute a proof-of-principle and motivate follow-up studies with a dedicated array of magnetometers.
|
gr-qc/0401054
|
Giovanni Montani
|
G. Aprea, G. Montani, R. Ruffini
|
Test particles behavior in the framework of a lagrangian geometric
theory with propagating torsion
|
12 pages, no figures, to appear on Int. Journ. Mod. Phys.D
|
Int.J.Mod.Phys. D12 (2003) 1875-1888
|
10.1142/S0218271803003888
| null |
gr-qc astro-ph
| null |
Working in the lagrangian framework, we develop a geometric theory in vacuum
with propagating torsion; the antisymmetric and trace parts of the torsion
tensor, considered as derived from local potential fields, are taken and, using
the minimal action principle, their field equations are calculated. Actually
these will show themselves to be just equations for propagating waves giving
torsion a behavior similar to that of metric which, as known, propagates
through gravitational waves. Then we establish a principle of minimal
substitution to derive test particles equation of motion, obtaining, as result,
that they move along autoparallels. We then calculate the analogous of the
geodesic deviation for these trajectories and analyze their behavior in the
nonrelativistic limit, showing that the torsion trace potential $\phi$ has a
phenomenology which is indistinguishable from that of the gravitational
newtonian field; in this way we also give a reason for why there have never
been evidence for it.
|
[
{
"created": "Tue, 13 Jan 2004 11:42:51 GMT",
"version": "v1"
}
] |
2009-11-10
|
[
[
"Aprea",
"G.",
""
],
[
"Montani",
"G.",
""
],
[
"Ruffini",
"R.",
""
]
] |
Working in the lagrangian framework, we develop a geometric theory in vacuum with propagating torsion; the antisymmetric and trace parts of the torsion tensor, considered as derived from local potential fields, are taken and, using the minimal action principle, their field equations are calculated. Actually these will show themselves to be just equations for propagating waves giving torsion a behavior similar to that of metric which, as known, propagates through gravitational waves. Then we establish a principle of minimal substitution to derive test particles equation of motion, obtaining, as result, that they move along autoparallels. We then calculate the analogous of the geodesic deviation for these trajectories and analyze their behavior in the nonrelativistic limit, showing that the torsion trace potential $\phi$ has a phenomenology which is indistinguishable from that of the gravitational newtonian field; in this way we also give a reason for why there have never been evidence for it.
|
gr-qc/0307077
|
Giovanni Montani
|
Giovanni Montani, Remo Ruffini and Roustam Zalaletdinov
|
The Gravitational Polarization in General Relativity: Solution to
Szekeres' Model of Quadrupole Polarization
|
22 pages, no figures, to appear on Class. Quantum Grav
|
Class.Quant.Grav. 20 (2003) 4195-4212
|
10.1088/0264-9381/20/19/305
| null |
gr-qc
| null |
A model for the static weak-field macroscopic medium is analyzed and the
equation for the macroscopic gravitational potential is derived. This is a
biharmonic equation which is a non-trivial generalization of the Poisson
equation of Newtonian gravity. In case of the strong gravitational quadrupole
polarization it essentially holds inside a macroscopic matter source. Outside
the source the gravitational potential fades away exponentially. The equation
is equivalent to a system of the Poisson equation and the nonhomogeneous
modified Helmholtz equations. The general solution to this system is obtained
by using Green's function method and it does not have a limit to Newtonian
gravity. In case of the insignificant gravitational quadrupole polarization the
equation for macroscopic gravitational potential becomes the Poisson equation
with the matter density renormalized by the factor including the value of the
quadrupole gravitational polarization of the source. The general solution to
this equation obtained by using Green's function method has a limit to
Newtonian gravity.
|
[
{
"created": "Wed, 16 Jul 2003 10:02:15 GMT",
"version": "v1"
}
] |
2009-11-10
|
[
[
"Montani",
"Giovanni",
""
],
[
"Ruffini",
"Remo",
""
],
[
"Zalaletdinov",
"Roustam",
""
]
] |
A model for the static weak-field macroscopic medium is analyzed and the equation for the macroscopic gravitational potential is derived. This is a biharmonic equation which is a non-trivial generalization of the Poisson equation of Newtonian gravity. In case of the strong gravitational quadrupole polarization it essentially holds inside a macroscopic matter source. Outside the source the gravitational potential fades away exponentially. The equation is equivalent to a system of the Poisson equation and the nonhomogeneous modified Helmholtz equations. The general solution to this system is obtained by using Green's function method and it does not have a limit to Newtonian gravity. In case of the insignificant gravitational quadrupole polarization the equation for macroscopic gravitational potential becomes the Poisson equation with the matter density renormalized by the factor including the value of the quadrupole gravitational polarization of the source. The general solution to this equation obtained by using Green's function method has a limit to Newtonian gravity.
|
gr-qc/0301099
|
Robert Mann
|
F.J. Burnell, J.J. Malecki, R.B. Mann and T. Ohta
|
Chaos in an Exact Relativistic 3-body Self-Gravitating System
|
latex, 65 pages, 36 figures, high-resolution figures available upon
request
|
Phys.Rev. E69 (2004) 016214
|
10.1103/PhysRevE.69.016214
|
WATPHYS-TH03/01
|
gr-qc
| null |
We consider the problem of three body motion for a relativistic
one-dimensional self-gravitating system. After describing the canonical
decomposition of the action, we find an exact expression for the 3-body
Hamiltonian, implicitly determined in terms of the four coordinate and momentum
degrees of freedom in the system. Non-relativistically these degrees of freedom
can be rewritten in terms of a single particle moving in a two-dimensional
hexagonal well. We find the exact relativistic generalization of this
potential, along with its post-Newtonian approximation. We then specialize to
the equal mass case and numerically solve the equations of motion that follow
from the Hamiltonian. Working in hexagonal-well coordinates, we obtaining
orbits in both the hexagonal and 3-body representations of the system, and plot
the Poincare sections as a function of the relativistic energy parameter $\eta
$. We find two broad categories of periodic and quasi-periodic motions that we
refer to as the annulus and pretzel patterns, as well as a set of chaotic
motions that appear in the region of phase-space between these two types.
Despite the high degree of non-linearity in the relativistic system, we find
that the the global structure of its phase space remains qualitatively the same
as its non-relativisitic counterpart for all values of $\eta $ that we could
study. However the relativistic system has a weaker symmetry and so its
Poincare section develops an asymmetric distortion that increases with
increasing $\eta $. For the post-Newtonian system we find that it experiences a
KAM breakdown for $\eta \simeq 0.26$: above which the near integrable regions
degenerate into chaos.
|
[
{
"created": "Thu, 23 Jan 2003 23:45:04 GMT",
"version": "v1"
}
] |
2009-11-10
|
[
[
"Burnell",
"F. J.",
""
],
[
"Malecki",
"J. J.",
""
],
[
"Mann",
"R. B.",
""
],
[
"Ohta",
"T.",
""
]
] |
We consider the problem of three body motion for a relativistic one-dimensional self-gravitating system. After describing the canonical decomposition of the action, we find an exact expression for the 3-body Hamiltonian, implicitly determined in terms of the four coordinate and momentum degrees of freedom in the system. Non-relativistically these degrees of freedom can be rewritten in terms of a single particle moving in a two-dimensional hexagonal well. We find the exact relativistic generalization of this potential, along with its post-Newtonian approximation. We then specialize to the equal mass case and numerically solve the equations of motion that follow from the Hamiltonian. Working in hexagonal-well coordinates, we obtaining orbits in both the hexagonal and 3-body representations of the system, and plot the Poincare sections as a function of the relativistic energy parameter $\eta $. We find two broad categories of periodic and quasi-periodic motions that we refer to as the annulus and pretzel patterns, as well as a set of chaotic motions that appear in the region of phase-space between these two types. Despite the high degree of non-linearity in the relativistic system, we find that the the global structure of its phase space remains qualitatively the same as its non-relativisitic counterpart for all values of $\eta $ that we could study. However the relativistic system has a weaker symmetry and so its Poincare section develops an asymmetric distortion that increases with increasing $\eta $. For the post-Newtonian system we find that it experiences a KAM breakdown for $\eta \simeq 0.26$: above which the near integrable regions degenerate into chaos.
|
gr-qc/0512051
|
Bijan Saha
|
Bijan Saha, Victor Rikhvitsky and Mihai Visinescu
|
Bel-Robinson tensor and dominant energy property in the Bianchi type I
Universe
|
15 pages, revised version, no figures
|
Mod.Phys.Lett. A21 (2006) 847-862
|
10.1142/S0217732306020196
| null |
gr-qc
| null |
Within the framework of Bianchi type-I space-time we study the Bel-Robinson
tensor and its impact on the evolution of the Universe. We use different
definitions of the Bel-Robinson tensor existing in the literature and compare
the results. Finally we investigate the so called "dominant super-energy
property" for the Bel-Robinson tensor as a generalization of the usual dominant
energy condition for energy momentum tensors.
Keywords: Bianchi type I model, super-energy tensors
Pacs: 03.65.Pm and 04.20.Ha
|
[
{
"created": "Thu, 8 Dec 2005 13:23:54 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Dec 2005 12:22:01 GMT",
"version": "v2"
},
{
"created": "Wed, 15 Feb 2006 11:29:02 GMT",
"version": "v3"
}
] |
2015-05-01
|
[
[
"Saha",
"Bijan",
""
],
[
"Rikhvitsky",
"Victor",
""
],
[
"Visinescu",
"Mihai",
""
]
] |
Within the framework of Bianchi type-I space-time we study the Bel-Robinson tensor and its impact on the evolution of the Universe. We use different definitions of the Bel-Robinson tensor existing in the literature and compare the results. Finally we investigate the so called "dominant super-energy property" for the Bel-Robinson tensor as a generalization of the usual dominant energy condition for energy momentum tensors. Keywords: Bianchi type I model, super-energy tensors Pacs: 03.65.Pm and 04.20.Ha
|
1409.6406
|
Ivan Agullo
|
Ivan Agullo, Aitor Landete, Jose Navarro-Salas
|
Electric-magnetic duality and renormalization in curved spacetimes
|
7 pages, 0 figures, Published version
|
Phys.Rev. D90 (2014) 12, 124067
|
10.1103/PhysRevD.90.124067
|
LSU-REL-092314
|
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We point out that the duality symmetry of free electromagnetism does not hold
in the quantum theory if an arbitrary classical gravitational background is
present. The symmetry breaks in the process of renormalization, as also happens
with conformal invariance. We show that a similar duality-anomaly appears for a
massless scalar field in $1+1$ dimensions.
|
[
{
"created": "Tue, 23 Sep 2014 04:14:59 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Dec 2014 03:18:33 GMT",
"version": "v2"
}
] |
2015-06-22
|
[
[
"Agullo",
"Ivan",
""
],
[
"Landete",
"Aitor",
""
],
[
"Navarro-Salas",
"Jose",
""
]
] |
We point out that the duality symmetry of free electromagnetism does not hold in the quantum theory if an arbitrary classical gravitational background is present. The symmetry breaks in the process of renormalization, as also happens with conformal invariance. We show that a similar duality-anomaly appears for a massless scalar field in $1+1$ dimensions.
|
2202.02303
|
Pedro Mario Ca\~nate Casseres
|
Pedro Ca\~nate
|
Black bounces as magnetically charged phantom regular black holes in
Einstein-nonlinear electrodynamics gravity coupled to a self-interacting
scalar field
|
21 pages, 0 figures
| null |
10.1103/PhysRevD.106.024031
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The "black-bounce" spacetime geometries, were recently proposed in [A.
Simpson, M. Visser, JCAP 02 (2019) 042] as regular black holes that bouncing
into a future incarnation of the universe. In this work we will present several
black-bounce exact solutions of General Relativity. Among them is a novel type
of black-bounce solutions, which in contrast of the Simpson-Visser type [A.
Simpson, M. Visser, JCAP 02 (2019) 042], do not have the Ellis wormhole metric
as a particular case. The source of these solutions are linear superposition of
phantom scalar fields and nonlinear electromagnetic fields.
|
[
{
"created": "Fri, 4 Feb 2022 18:40:41 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Feb 2022 19:54:41 GMT",
"version": "v2"
},
{
"created": "Thu, 28 Jul 2022 01:32:21 GMT",
"version": "v3"
}
] |
2022-07-29
|
[
[
"Cañate",
"Pedro",
""
]
] |
The "black-bounce" spacetime geometries, were recently proposed in [A. Simpson, M. Visser, JCAP 02 (2019) 042] as regular black holes that bouncing into a future incarnation of the universe. In this work we will present several black-bounce exact solutions of General Relativity. Among them is a novel type of black-bounce solutions, which in contrast of the Simpson-Visser type [A. Simpson, M. Visser, JCAP 02 (2019) 042], do not have the Ellis wormhole metric as a particular case. The source of these solutions are linear superposition of phantom scalar fields and nonlinear electromagnetic fields.
|
1204.5948
|
Craig J. Hogan
|
Craig J. Hogan
|
A Model of Macroscopic Geometrical Uncertainty
|
14 pages, 3 figures
| null | null |
FERMILAB-PUB-12-044-A
|
gr-qc hep-th quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A model quantum system is proposed to describe position states of a massive
body in flat space on large scales, excluding all standard quantum and
gravitational degrees of freedom. The model is based on standard quantum spin
commutators, with operators interpreted as positions instead of spin, and a
Planck-scale length $\ell_P$ in place of Planck's constant $\hbar$. The algebra
is used to derive a new quantum geometrical uncertainty in direction, with
variance given by $\langle \Delta \theta^2\rangle = \ell_P/L$ at separation
$L$, that dominates over standard quantum position uncertainty for bodies
greater than the Planck mass. The system is discrete and holographic, and
agrees with gravitational entropy if the commutator coefficient takes the exact
value $\ell_P= l_P/\sqrt{4\pi}$, where $l_P\equiv \sqrt{\hbar G/c^3}$ denotes
the standard Planck length. A physical interpretation is proposed that connects
the operators with properties of classical position in the macroscopic limit:
Approximate locality and causality emerge in macroscopic systems if position
states of multiple bodies are entangled by proximity. This interpretation
predicts coherent directional fluctuations with variance $\langle \Delta
\theta^2\rangle $ on timescale $\tau \approx L/c$ that lead to precisely
predictable correlations in signals between adjacent interferometers. It is
argued that such a signal could provide compelling evidence of Planck scale
quantum geometry, even in the absence of a complete dynamical or fundamental
theory.
|
[
{
"created": "Wed, 25 Apr 2012 16:45:26 GMT",
"version": "v1"
},
{
"created": "Sat, 16 Mar 2013 17:07:34 GMT",
"version": "v10"
},
{
"created": "Sun, 24 Mar 2013 20:06:22 GMT",
"version": "v11"
},
{
"created": "Tue, 9 Apr 2013 20:20:42 GMT",
"version": "v12"
},
{
"created": "Thu, 30 May 2013 16:13:36 GMT",
"version": "v13"
},
{
"created": "Mon, 8 Jul 2013 21:42:28 GMT",
"version": "v14"
},
{
"created": "Tue, 13 Aug 2013 17:48:47 GMT",
"version": "v15"
},
{
"created": "Wed, 20 Nov 2013 17:01:59 GMT",
"version": "v16"
},
{
"created": "Mon, 30 Dec 2013 17:45:53 GMT",
"version": "v17"
},
{
"created": "Thu, 16 Jan 2014 21:48:16 GMT",
"version": "v18"
},
{
"created": "Tue, 11 Mar 2014 15:47:23 GMT",
"version": "v19"
},
{
"created": "Wed, 23 May 2012 21:54:41 GMT",
"version": "v2"
},
{
"created": "Mon, 24 Mar 2014 01:16:57 GMT",
"version": "v20"
},
{
"created": "Tue, 3 Jun 2014 00:04:24 GMT",
"version": "v21"
},
{
"created": "Thu, 21 Aug 2014 23:09:47 GMT",
"version": "v22"
},
{
"created": "Thu, 4 Dec 2014 19:51:30 GMT",
"version": "v23"
},
{
"created": "Tue, 26 Jun 2012 20:45:53 GMT",
"version": "v3"
},
{
"created": "Fri, 17 Aug 2012 22:22:25 GMT",
"version": "v4"
},
{
"created": "Fri, 28 Sep 2012 17:53:57 GMT",
"version": "v5"
},
{
"created": "Mon, 31 Dec 2012 17:25:47 GMT",
"version": "v6"
},
{
"created": "Thu, 31 Jan 2013 19:41:41 GMT",
"version": "v7"
},
{
"created": "Thu, 28 Feb 2013 16:18:31 GMT",
"version": "v8"
},
{
"created": "Mon, 11 Mar 2013 19:37:10 GMT",
"version": "v9"
}
] |
2014-12-05
|
[
[
"Hogan",
"Craig J.",
""
]
] |
A model quantum system is proposed to describe position states of a massive body in flat space on large scales, excluding all standard quantum and gravitational degrees of freedom. The model is based on standard quantum spin commutators, with operators interpreted as positions instead of spin, and a Planck-scale length $\ell_P$ in place of Planck's constant $\hbar$. The algebra is used to derive a new quantum geometrical uncertainty in direction, with variance given by $\langle \Delta \theta^2\rangle = \ell_P/L$ at separation $L$, that dominates over standard quantum position uncertainty for bodies greater than the Planck mass. The system is discrete and holographic, and agrees with gravitational entropy if the commutator coefficient takes the exact value $\ell_P= l_P/\sqrt{4\pi}$, where $l_P\equiv \sqrt{\hbar G/c^3}$ denotes the standard Planck length. A physical interpretation is proposed that connects the operators with properties of classical position in the macroscopic limit: Approximate locality and causality emerge in macroscopic systems if position states of multiple bodies are entangled by proximity. This interpretation predicts coherent directional fluctuations with variance $\langle \Delta \theta^2\rangle $ on timescale $\tau \approx L/c$ that lead to precisely predictable correlations in signals between adjacent interferometers. It is argued that such a signal could provide compelling evidence of Planck scale quantum geometry, even in the absence of a complete dynamical or fundamental theory.
|
1201.2054
|
Jose Luis Jaramillo
|
Jos\'e Luis Jaramillo
|
Area inequalities for stable marginally trapped surfaces
|
22 pages, no figures; Contribution to the proceedings volume of the
VI International Meeting on Lorentzian Geometry, GELOGRA'11, Granada, Spain,
6-9 September 2011
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We discuss a family of inequalities involving the area, angular momentum and
charges of stably outermost marginally trapped surfaces in generic non-vacuum
dynamical spacetimes, with non-negative cosmological constant and matter
sources satisfying the dominant energy condition. These inequalities provide
lower bounds for the area of spatial sections of dynamical trapping horizons,
namely hypersurfaces offering quasi-local models of black hole horizons. In
particular, these inequalities represent particular examples of the extension
to a Lorentzian setting of tools employed in the discussion of minimal surfaces
in Riemannian contexts.
|
[
{
"created": "Tue, 10 Jan 2012 13:51:18 GMT",
"version": "v1"
}
] |
2012-01-11
|
[
[
"Jaramillo",
"José Luis",
""
]
] |
We discuss a family of inequalities involving the area, angular momentum and charges of stably outermost marginally trapped surfaces in generic non-vacuum dynamical spacetimes, with non-negative cosmological constant and matter sources satisfying the dominant energy condition. These inequalities provide lower bounds for the area of spatial sections of dynamical trapping horizons, namely hypersurfaces offering quasi-local models of black hole horizons. In particular, these inequalities represent particular examples of the extension to a Lorentzian setting of tools employed in the discussion of minimal surfaces in Riemannian contexts.
|
2307.01919
|
Bobur Turimov
|
Bobur Turimov and Shuhrat Hayitov
|
Black Holes as a Collider of High Energy Particles
|
3 pages, 3 figures
| null | null | null |
gr-qc astro-ph.HE
|
http://creativecommons.org/licenses/by/4.0/
|
According to the Banados-Silk-West (BSW) process, rotating black holes can
act as particle colliders capable of achieving arbitrarily high center-of-mass
energy (CME), provided that a specific angular momentum of one of the particles
is present. In this discussion, we demonstrate that both Kerr black holes and
Schwarzschild black holes could serve as potential sources of high-energy
particles in the polar region.
|
[
{
"created": "Tue, 4 Jul 2023 21:04:56 GMT",
"version": "v1"
}
] |
2023-07-06
|
[
[
"Turimov",
"Bobur",
""
],
[
"Hayitov",
"Shuhrat",
""
]
] |
According to the Banados-Silk-West (BSW) process, rotating black holes can act as particle colliders capable of achieving arbitrarily high center-of-mass energy (CME), provided that a specific angular momentum of one of the particles is present. In this discussion, we demonstrate that both Kerr black holes and Schwarzschild black holes could serve as potential sources of high-energy particles in the polar region.
|
1509.08804
|
Roberto De Pietri
|
Roberto De Pietri, Alessandra Feo, Francesco Maione, Frank L\"offler
|
Modeling Equal and Unequal Mass Binary Neutron Star Mergers Using Public
Codes
|
References and figures updated
|
Phys. Rev. D 93, 064047 (2016)
|
10.1103/PhysRevD.93.064047
| null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We present three-dimensional simulations of the dynamics of binary neutron
star (BNS) mergers from the late stage of the inspiral process up to $\sim 20$
ms after the system has merged, either to form a hyper-massive neutron star
(NS) or a rotating black hole (BH). We investigate five equal-mass models of
total gravitational mass $2.207$, $2.373$, $2.537$, $2.697$ and $2.854
M_\odot$, respectively, and four unequal mass models with
$M_{\mathrm{ADM}}\simeq 2.53\ M_\odot$ and $q\simeq 0.94$, $0.88$, $0.82$, and
$0.77$ (where $q = M^{(1)}/M^{(2)}$ is the mass ratio). We use a semi-realistic
equation of state (EOS) namely, the seven-segment piece-wise polytropic SLyPP
with a thermal component given by $\Gamma_{th} = 1.8$. We have also compared
the resulting dynamics (for one model) using both, the BSSN-NOK and CCZ4
methods for the evolution of the gravitational sector, and also different
reconstruction methods for the matter sector, namely PPM, WENO and MP5. Our
results show agreement and high resolution, but superiority of BSSN-NOK
supplemented by WENO reconstruction at lower resolutions.
One of the important characteristics of the present investigation is that,
for the first time, this has been done using only publicly available open
source software, in particular, the Einstein Toolkit code deployed for the
dynamical evolution and the LORENE code for the generation of the initial
models. All of the source code and parameters used for the simulations have
been made publicly available. This not only makes it possible to re-run and
re-analyze our data; it also enables others to directly build upon this work
for future research.
|
[
{
"created": "Tue, 29 Sep 2015 15:31:01 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Oct 2015 15:32:00 GMT",
"version": "v2"
},
{
"created": "Sat, 13 Feb 2016 09:05:39 GMT",
"version": "v3"
}
] |
2016-03-30
|
[
[
"De Pietri",
"Roberto",
""
],
[
"Feo",
"Alessandra",
""
],
[
"Maione",
"Francesco",
""
],
[
"Löffler",
"Frank",
""
]
] |
We present three-dimensional simulations of the dynamics of binary neutron star (BNS) mergers from the late stage of the inspiral process up to $\sim 20$ ms after the system has merged, either to form a hyper-massive neutron star (NS) or a rotating black hole (BH). We investigate five equal-mass models of total gravitational mass $2.207$, $2.373$, $2.537$, $2.697$ and $2.854 M_\odot$, respectively, and four unequal mass models with $M_{\mathrm{ADM}}\simeq 2.53\ M_\odot$ and $q\simeq 0.94$, $0.88$, $0.82$, and $0.77$ (where $q = M^{(1)}/M^{(2)}$ is the mass ratio). We use a semi-realistic equation of state (EOS) namely, the seven-segment piece-wise polytropic SLyPP with a thermal component given by $\Gamma_{th} = 1.8$. We have also compared the resulting dynamics (for one model) using both, the BSSN-NOK and CCZ4 methods for the evolution of the gravitational sector, and also different reconstruction methods for the matter sector, namely PPM, WENO and MP5. Our results show agreement and high resolution, but superiority of BSSN-NOK supplemented by WENO reconstruction at lower resolutions. One of the important characteristics of the present investigation is that, for the first time, this has been done using only publicly available open source software, in particular, the Einstein Toolkit code deployed for the dynamical evolution and the LORENE code for the generation of the initial models. All of the source code and parameters used for the simulations have been made publicly available. This not only makes it possible to re-run and re-analyze our data; it also enables others to directly build upon this work for future research.
|
1910.08368
|
Kangujam Priyokumar Singh
|
Kangujam Priyokumar Singh, Mahbubur Rahman Mollah, Rajshekhar Roy
Baruah and Meher Daimary
|
Interaction of Bianchi Type-I Anisotropic Cloud String Cosmological
Model Universe with Electromagnetic Field
|
This manuscript contains 15 pages and 4 figures. arXiv admin note:
text overlap with arXiv:1909.11444
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Here, we have investigated the interaction of Bianchi type I anisotropic
cloud string cosmological model universe with electromagnetic field in the
context of general relativity. In this paper, the energy momentum tensor is
assumed to be the sum of the rest energy density and string tension density
with an electromagnetic field. To obtain exact solutions of Einstein field
equations, we take average scale factor as an integrating function of time.
Also, the dynamics and significance of various physical parameters of model are
discussed.
|
[
{
"created": "Tue, 15 Oct 2019 10:53:54 GMT",
"version": "v1"
}
] |
2019-10-21
|
[
[
"Singh",
"Kangujam Priyokumar",
""
],
[
"Mollah",
"Mahbubur Rahman",
""
],
[
"Baruah",
"Rajshekhar Roy",
""
],
[
"Daimary",
"Meher",
""
]
] |
Here, we have investigated the interaction of Bianchi type I anisotropic cloud string cosmological model universe with electromagnetic field in the context of general relativity. In this paper, the energy momentum tensor is assumed to be the sum of the rest energy density and string tension density with an electromagnetic field. To obtain exact solutions of Einstein field equations, we take average scale factor as an integrating function of time. Also, the dynamics and significance of various physical parameters of model are discussed.
|
2105.05059
|
Fulvio Melia
|
Fulvio Melia
|
Classicalization of Quantum Fluctuations at the Planck Scale in the
R_h=ct Universe
|
14 pages, 2 figures. Accepted for publication in PLB
|
PLB 818 (2021) 136362, 11pp
|
10.1016/j.physletb.2021.136362
| null |
gr-qc astro-ph.CO hep-ph quant-ph
|
http://creativecommons.org/licenses/by/4.0/
|
The quantum to classical transition of fluctuations in the early universe is
still not completely understood. Some headway has been made incorporating the
effects of decoherence and the squeezing of states, though the methods and
procedures continue to be challenged. But new developments in the analysis of
the most recent Planck data suggest that the primordial power spectrum has a
cutoff associated with the very first quantum fluctuation to have emerged into
the semi-classical universe from the Planck domain at about the Planck time. In
this paper, we examine the implications of this result on the question of
classicalization, and demonstrate that the birth of quantum fluctuations at the
Planck scale would have been a `process' supplanting the need for a
`measurement' in quantum mechanics. Emerging with a single wavenumber, these
fluctuations would have avoided the interference between different degrees of
freedom in a superposed state. Moreover, the implied scalar-field potential had
an equation-of-state consistent with the zero active mass condition in general
relativity, allowing the quantum fluctuations to emerge in their ground state
with a time-independent frequency. They were therefore effectively quantum
harmonic oscillators with classical correlations in phase space from the very
beginning.
|
[
{
"created": "Mon, 10 May 2021 15:13:50 GMT",
"version": "v1"
}
] |
2021-05-24
|
[
[
"Melia",
"Fulvio",
""
]
] |
The quantum to classical transition of fluctuations in the early universe is still not completely understood. Some headway has been made incorporating the effects of decoherence and the squeezing of states, though the methods and procedures continue to be challenged. But new developments in the analysis of the most recent Planck data suggest that the primordial power spectrum has a cutoff associated with the very first quantum fluctuation to have emerged into the semi-classical universe from the Planck domain at about the Planck time. In this paper, we examine the implications of this result on the question of classicalization, and demonstrate that the birth of quantum fluctuations at the Planck scale would have been a `process' supplanting the need for a `measurement' in quantum mechanics. Emerging with a single wavenumber, these fluctuations would have avoided the interference between different degrees of freedom in a superposed state. Moreover, the implied scalar-field potential had an equation-of-state consistent with the zero active mass condition in general relativity, allowing the quantum fluctuations to emerge in their ground state with a time-independent frequency. They were therefore effectively quantum harmonic oscillators with classical correlations in phase space from the very beginning.
|
1404.6443
|
Ahmadjon Abdujabbarov
|
Bobir Toshmatov, Bobomurat Ahmedov, Ahmadjon Abdujabbarov, Zdenek
Stuchlik
|
Rotating Regular Black Hole Solution
|
7 pages, 6 figures, accepted for publication in Physical Review D
| null |
10.1103/PhysRevD.89.104017
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Based on the Newman-Janis algorithm the Ayon-Beato-Garcia spacetime metric of
the regular spherically symmetric, static and charged black hole has been
converted into rotational form. It is shown that the derived solution for
rotating regular black hole is regular and the critical value of the electric
charge $Q$ for which two horizons merge into one sufficiently decreases in the
presence of nonvanishing angular momentum $a$ of the black hole.
|
[
{
"created": "Thu, 24 Apr 2014 06:33:51 GMT",
"version": "v1"
}
] |
2015-06-19
|
[
[
"Toshmatov",
"Bobir",
""
],
[
"Ahmedov",
"Bobomurat",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
],
[
"Stuchlik",
"Zdenek",
""
]
] |
Based on the Newman-Janis algorithm the Ayon-Beato-Garcia spacetime metric of the regular spherically symmetric, static and charged black hole has been converted into rotational form. It is shown that the derived solution for rotating regular black hole is regular and the critical value of the electric charge $Q$ for which two horizons merge into one sufficiently decreases in the presence of nonvanishing angular momentum $a$ of the black hole.
|
2006.01172
|
Anna Ijjas
|
William G. Cook, Iryna A. Glushchenko, Anna Ijjas, Frans Pretorius and
Paul J. Steinhardt
|
Supersmoothing through Slow Contraction
|
6 pages, 3 figures
|
Phys. Lett. B 808 (2020) 135690
|
10.1016/j.physletb.2020.135690
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Performing a fully non-perturbative analysis using the tools of numerical
general relativity, we demonstrate that a period of slow contraction is a
`supersmoothing' cosmological phase that homogenizes, isotropizes and flattens
the universe both classically and quantum mechanically and can do so far more
robustly and rapidly than had been realized in earlier studies.
|
[
{
"created": "Mon, 1 Jun 2020 18:04:28 GMT",
"version": "v1"
}
] |
2020-08-19
|
[
[
"Cook",
"William G.",
""
],
[
"Glushchenko",
"Iryna A.",
""
],
[
"Ijjas",
"Anna",
""
],
[
"Pretorius",
"Frans",
""
],
[
"Steinhardt",
"Paul J.",
""
]
] |
Performing a fully non-perturbative analysis using the tools of numerical general relativity, we demonstrate that a period of slow contraction is a `supersmoothing' cosmological phase that homogenizes, isotropizes and flattens the universe both classically and quantum mechanically and can do so far more robustly and rapidly than had been realized in earlier studies.
|
1905.06856
|
Mohd Shahalam
|
M. Shahalam, R. Myrzakulov, Maxim Yu. Khlopov
|
Late time evolution of a nonminimally coupled scalar field system
|
9 pages, 3 caption figures
|
Gen. Relativ. Gravit. (2019) 51:125
|
10.1007/s10714-019-2610-6
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We revisit the dynamics of a nonminimally coupled scalar field model in case
of $F(\phi)R$ coupling with $F(\phi)= 1-\xi\phi^2 $, and the potentials
$V(\phi) = V_0 (1+ \phi^p)^2$, $V(\phi)= V_0 e^{\lambda \phi^2}$. We use an
autonomous system to bring out new asymptotic regimes, and find stable
de-Sitter solution. Under the chosen functional form of $F(\phi)$ and steep
exponential potentials, a true de-Sitter solution is trivially satisfied for
which the equation of state $w_{\phi}\simeq -1$, the effective gravitational
constant $G_{eff}$ and field $\phi$ are constant that has been missed in the
power law case and our previous study.
|
[
{
"created": "Wed, 15 May 2019 06:38:48 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Sep 2019 04:25:23 GMT",
"version": "v2"
}
] |
2019-10-02
|
[
[
"Shahalam",
"M.",
""
],
[
"Myrzakulov",
"R.",
""
],
[
"Khlopov",
"Maxim Yu.",
""
]
] |
We revisit the dynamics of a nonminimally coupled scalar field model in case of $F(\phi)R$ coupling with $F(\phi)= 1-\xi\phi^2 $, and the potentials $V(\phi) = V_0 (1+ \phi^p)^2$, $V(\phi)= V_0 e^{\lambda \phi^2}$. We use an autonomous system to bring out new asymptotic regimes, and find stable de-Sitter solution. Under the chosen functional form of $F(\phi)$ and steep exponential potentials, a true de-Sitter solution is trivially satisfied for which the equation of state $w_{\phi}\simeq -1$, the effective gravitational constant $G_{eff}$ and field $\phi$ are constant that has been missed in the power law case and our previous study.
|
1907.06880
|
Luis Granda
|
L. N. Granda
|
Finite scale factor and future singularities
|
24 pages, 3 figures
|
Astrophys.Space Sci. 364 (2019) no.4, 61
|
10.1007/s10509-019-3549-5
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The main characteristic of the dark energy is its negative pressure. In a
homogeneous and isotropic FRW background, we consider several models for the
dark energy fluid, which lead to finite time future singularities of the type
I-IV, by introducing the pressure density as a function of the scale factor.
This approach gives acceptable behavior of the dark energy equation of state.
We give various numerical examples of models with type I-IV singularities, that
show very similar late time behavior, making it difficult to determine the type
of singularity that would take place in the future.
|
[
{
"created": "Tue, 16 Jul 2019 07:59:49 GMT",
"version": "v1"
}
] |
2019-07-17
|
[
[
"Granda",
"L. N.",
""
]
] |
The main characteristic of the dark energy is its negative pressure. In a homogeneous and isotropic FRW background, we consider several models for the dark energy fluid, which lead to finite time future singularities of the type I-IV, by introducing the pressure density as a function of the scale factor. This approach gives acceptable behavior of the dark energy equation of state. We give various numerical examples of models with type I-IV singularities, that show very similar late time behavior, making it difficult to determine the type of singularity that would take place in the future.
|
2301.05679
|
Antonio Enea Romano
|
Antonio Enea Romano
|
Effective speed of cosmological perturbations
|
The first version of this paper was submitted to JCAP on February 7th
2023, and the first report was received on January 14th 2024. This is a
revised version based on the first referee report
|
Phys.Dark Univ. 45 (2024) 101549
|
10.1016/j.dark.2024.101549
| null |
gr-qc astro-ph.CO hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
We derive an effective equation and action for comoving curvature
perturbations and gravitational waves (GWs) in terms of a time, momentum and
polarization dependent effective speed, encoding the effects of the interaction
among metric perturbations or with other fields, such as dark energy and dark
matter. The structure of the effective actions and equations is the same for
scalar and tensor perturbations, and the effective actions can be written as
the Klein-Gordon action in terms of an appropriately defined effective metric,
dependent on the effective speed. The effective action reproduces, and
generalizes to higher order in perturbations, results obtained for GWs in the
effective field theory of inflation and dark energy, or for curvature
perturbations in systems with multiple scalar fields, encoding in the effective
speed the effects of both entropy and anisotropy. The effective approach can
also be applied to the solutions of theories with field equations different
from the Einstein equations, by defining an appropriate effective
energy-momentum tensor. As an example, we show that for a minimally coupled
scalar field in general relativity, the effective speeds of curvature
perturbations and gravitational waves are frequency and polarization dependent,
due to their coupling in the action beyond the quadratic order.
|
[
{
"created": "Fri, 13 Jan 2023 17:56:52 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Feb 2024 18:51:33 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Jun 2024 14:37:09 GMT",
"version": "v3"
}
] |
2024-06-21
|
[
[
"Romano",
"Antonio Enea",
""
]
] |
We derive an effective equation and action for comoving curvature perturbations and gravitational waves (GWs) in terms of a time, momentum and polarization dependent effective speed, encoding the effects of the interaction among metric perturbations or with other fields, such as dark energy and dark matter. The structure of the effective actions and equations is the same for scalar and tensor perturbations, and the effective actions can be written as the Klein-Gordon action in terms of an appropriately defined effective metric, dependent on the effective speed. The effective action reproduces, and generalizes to higher order in perturbations, results obtained for GWs in the effective field theory of inflation and dark energy, or for curvature perturbations in systems with multiple scalar fields, encoding in the effective speed the effects of both entropy and anisotropy. The effective approach can also be applied to the solutions of theories with field equations different from the Einstein equations, by defining an appropriate effective energy-momentum tensor. As an example, we show that for a minimally coupled scalar field in general relativity, the effective speeds of curvature perturbations and gravitational waves are frequency and polarization dependent, due to their coupling in the action beyond the quadratic order.
|
1802.02574
|
Piotr Bargiela
|
Piotr Bargiela
|
Transport of the light polarization in the weak gravitational wave
background
|
3 pages, REVTeX
| null | null | null |
gr-qc physics.optics
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The influence of the weak gravitational wave on the light polarization is
considered. Oscillations in the direction of the polarization vector is found.
|
[
{
"created": "Wed, 7 Feb 2018 15:40:08 GMT",
"version": "v1"
}
] |
2018-02-09
|
[
[
"Bargiela",
"Piotr",
""
]
] |
The influence of the weak gravitational wave on the light polarization is considered. Oscillations in the direction of the polarization vector is found.
|
1909.12846
|
Ollie Burke
|
Ollie Burke, Jonathan R. Gair and Joan Sim\'on
|
Transition from Inspiral to Plunge: A Complete Near-Extremal Trajectory
and Associated Waveform
|
25 pages, 7 figures, 1 Table. Accepted for publication in Phys. Rev.
D
|
Phys. Rev. D 101, 064026 (2020)
|
10.1103/PhysRevD.101.064026
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We extend the Ori and Thorne (OT) procedure to compute the transition from an
adiabatic inspiral into a geodesic plunge for any spin, with emphasis on
near-extremal ones. Our analysis revisits the validity of the approximations
made in OT. In particular, we discuss possible effects coming from eccentricity
and non-geodesic past-history of the orbital evolution. We find three different
scaling regimes according to whether the mass ratio is much smaller, of the
same order or much larger than the near extremal parameter describing how fast
the primary black hole rotates. Eccentricity and non-geodesic past-history
corrections are always sub-leading, indicating that the quasi-circular
approximation applies throughout the transition regime. However, we show that
the OT assumption that the energy and angular momentum evolve linearly with
proper time must be modified in the near-extremal regime. Using our transition
equations, we describe an algorithm to compute the full worldline in proper
time for an extreme mass ratio inspiral (EMRI) and the resultant gravitational
waveform in the high spin limit.
|
[
{
"created": "Fri, 27 Sep 2019 18:00:03 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Feb 2020 10:25:18 GMT",
"version": "v2"
}
] |
2020-03-18
|
[
[
"Burke",
"Ollie",
""
],
[
"Gair",
"Jonathan R.",
""
],
[
"Simón",
"Joan",
""
]
] |
We extend the Ori and Thorne (OT) procedure to compute the transition from an adiabatic inspiral into a geodesic plunge for any spin, with emphasis on near-extremal ones. Our analysis revisits the validity of the approximations made in OT. In particular, we discuss possible effects coming from eccentricity and non-geodesic past-history of the orbital evolution. We find three different scaling regimes according to whether the mass ratio is much smaller, of the same order or much larger than the near extremal parameter describing how fast the primary black hole rotates. Eccentricity and non-geodesic past-history corrections are always sub-leading, indicating that the quasi-circular approximation applies throughout the transition regime. However, we show that the OT assumption that the energy and angular momentum evolve linearly with proper time must be modified in the near-extremal regime. Using our transition equations, we describe an algorithm to compute the full worldline in proper time for an extreme mass ratio inspiral (EMRI) and the resultant gravitational waveform in the high spin limit.
|
2107.13436
|
Sanjar Shaymatov
|
Javlon Rayimbaev, Sanjar Shaymatov, Mubasher Jamil
|
Dynamics of particles and epicyclic motions around
Schwarzschild-de-Sitter black hole in perfect fluid dark matter
|
12 pages, 11 figures. Accepted for publication in Eur. Phys. J. C
|
Eur. Phys. J. C (2021) 81: 699
|
10.1140/epjc/s10052-021-09488-9
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper we investigate circular orbits for test particles around
Schwarzschild-de Sitter (dS) black hole surrounded by perfect fluid dark
matter. We determine the region of circular orbits bounded by innermost and
outermost stable circular orbits. We show that the impact of the perfect fluid
dark matter shrinks the region where circular orbits can exist as the values of
both innermost and outermost stable circular orbits decrease. We find that for
specific lower and upper values of dark matter parameter there exist double
matching values for inner and outermost stable circular orbits. It turns out
that the gravitational attraction due to the dark matter contribution dominates
over cosmological repulsion. This gives rise to a remarkable result in the
Schwarzschild-dS black hole surrounded by dark matter field in contrast to the
Schwarzschild-dS metric. Finally, we study epicyclic motion and its frequencies
with their applications to twin peak quasi-periodic oscillations (QPO) for
various models. We find corresponding values of the black hole parameters which
could best fit and explain the observed twin peak QPO object GRS 1915+109 from
microquasars.
|
[
{
"created": "Wed, 28 Jul 2021 15:30:37 GMT",
"version": "v1"
}
] |
2021-08-09
|
[
[
"Rayimbaev",
"Javlon",
""
],
[
"Shaymatov",
"Sanjar",
""
],
[
"Jamil",
"Mubasher",
""
]
] |
In this paper we investigate circular orbits for test particles around Schwarzschild-de Sitter (dS) black hole surrounded by perfect fluid dark matter. We determine the region of circular orbits bounded by innermost and outermost stable circular orbits. We show that the impact of the perfect fluid dark matter shrinks the region where circular orbits can exist as the values of both innermost and outermost stable circular orbits decrease. We find that for specific lower and upper values of dark matter parameter there exist double matching values for inner and outermost stable circular orbits. It turns out that the gravitational attraction due to the dark matter contribution dominates over cosmological repulsion. This gives rise to a remarkable result in the Schwarzschild-dS black hole surrounded by dark matter field in contrast to the Schwarzschild-dS metric. Finally, we study epicyclic motion and its frequencies with their applications to twin peak quasi-periodic oscillations (QPO) for various models. We find corresponding values of the black hole parameters which could best fit and explain the observed twin peak QPO object GRS 1915+109 from microquasars.
|
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