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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9503026 | Masaru Siino | Shuxue Ding, Yasushige Maeda and Masaru Siino | Four Dimensional Quantum Topology Changes of Spacetimes | 26 pages, revtex, 13 figures. The calculation of volume and
grammatical errors are corrected | J.Math.Phys. 37 (1996) 5611-5626 | 10.1063/1.531725 | KUNS-1322; TIT/HEP-282/COSMO-52 | gr-qc hep-th | null | We investigate topology changing processes in the WKB approximation of four
dimensional quantum cosmology with a negative cosmological constant. As
Riemannian manifolds which describe quantum tunnelings of spacetime we consider
constant negative curvature solutions of the Einstein equation i.e. hyperbolic
geometries. Using four dimensional polytopes, we can explicitly construct
hyperbolic manifolds with topologically non-trivial boundaries which describe
topology changes. These instanton-like solutions are constructed out of
8-cell's, 16-cell's or 24-cell's and have several points at infinity called
cusps. The hyperbolic manifolds are non-compact because of the cusps but have
finite volumes. Then we evaluate topology change amplitudes in the WKB
approximation in terms of the volumes of these manifolds. We find that the more
complicated are the topology changes, the more likely are suppressed.
| [
{
"created": "Thu, 16 Mar 1995 07:04:37 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Apr 1996 12:20:34 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Ding",
"Shuxue",
""
],
[
"Maeda",
"Yasushige",
""
],
[
"Siino",
"Masaru",
""
]
] | We investigate topology changing processes in the WKB approximation of four dimensional quantum cosmology with a negative cosmological constant. As Riemannian manifolds which describe quantum tunnelings of spacetime we consider constant negative curvature solutions of the Einstein equation i.e. hyperbolic geometries. Using four dimensional polytopes, we can explicitly construct hyperbolic manifolds with topologically non-trivial boundaries which describe topology changes. These instanton-like solutions are constructed out of 8-cell's, 16-cell's or 24-cell's and have several points at infinity called cusps. The hyperbolic manifolds are non-compact because of the cusps but have finite volumes. Then we evaluate topology change amplitudes in the WKB approximation in terms of the volumes of these manifolds. We find that the more complicated are the topology changes, the more likely are suppressed. |
1407.5678 | Matt Visser | Petarpa Boonserm (Chulalongkorn University), Tritos Ngampitipan
(Chulalongkorn University), and Matt Visser (Victoria University of
Wellington) | Super-radiance and flux conservation | V1: 8 pages; no figures; V2: 6 references added, no physics changes,
now 9 pages | Phys. Rev. D 90, 064013 (2014) | 10.1103/PhysRevD.90.064013 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The theoretical foundations of the phenomenon known as super-radiance still
continues to attract considerable attention. Despite many valiant attempts at
pedagogically clear presentations, the effect nevertheless still continues to
generate some significant confusion. Part of the confusion arises from the fact
that super-radiance in a quantum field theory [QFT] context is not the same as
super-radiance (super-fluorescence) in some condensed matter contexts; part of
the confusion arises from traditional but sometimes awkward normalization
conventions, and part is due to sometimes unnecessary confusion between fluxes
and probabilities. We shall argue that the key point underlying the effect is
flux conservation, (and, in the presence of dissipation, a controlled amount of
flux non-conservation), and that attempting to phrase things in terms of
reflection and transmission probabilities only works in the absence of
super-radiance. To help clarify the situation we present a simple exactly
solvable toy model exhibiting both super-radiance and damping.
| [
{
"created": "Mon, 21 Jul 2014 22:22:34 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Jul 2014 07:01:28 GMT",
"version": "v2"
}
] | 2014-09-17 | [
[
"Boonserm",
"Petarpa",
"",
"Chulalongkorn University"
],
[
"Ngampitipan",
"Tritos",
"",
"Chulalongkorn University"
],
[
"Visser",
"Matt",
"",
"Victoria University of\n Wellington"
]
] | The theoretical foundations of the phenomenon known as super-radiance still continues to attract considerable attention. Despite many valiant attempts at pedagogically clear presentations, the effect nevertheless still continues to generate some significant confusion. Part of the confusion arises from the fact that super-radiance in a quantum field theory [QFT] context is not the same as super-radiance (super-fluorescence) in some condensed matter contexts; part of the confusion arises from traditional but sometimes awkward normalization conventions, and part is due to sometimes unnecessary confusion between fluxes and probabilities. We shall argue that the key point underlying the effect is flux conservation, (and, in the presence of dissipation, a controlled amount of flux non-conservation), and that attempting to phrase things in terms of reflection and transmission probabilities only works in the absence of super-radiance. To help clarify the situation we present a simple exactly solvable toy model exhibiting both super-radiance and damping. |
0904.1338 | M. Hossein Dehghani | M. H. Dehghani and N. Farhangkhah | Static and Radiating Solutions of Lovelock Gravity in the Presence of a
Perfect Fluid | 15 pages, two figures | Phys.Lett.B674:243-249, 2009 | 10.1016/j.physletb.2009.03.045 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a general solution of third order Lovelock gravity in the presence
of a specific type II perfect fluid. This solution for linear equation of
state, $p=w(\rho-4B)$ contains all the known solutions of third order Lovelock
gravity in the literature and some new static and radiating solutions for
different values of $w$ and $B$. Specially, we consider the properties of
static and radiating solutions for $w=0$ and $w=(n-2)^{-1}$ with B=0 and
$B\neq0$. These solutions are asymptotically flat for B=0, while they are
asymptotically (anti)-de Sitter for $B\neq0$. The new static solutions for
these choices of $B$ and $w$ present black holes with one or two horizons,
extreme black holes or naked singularities provided the parameters of the
solutions are chosen suitable. The static solution with $w=0$ and vanishing
geometrical mass ($m=0$) may present a black hole with two inner and outer
horizons. This is a peculiar feature of the third order Lovelock gravity, which
does not occur in lower order Lovelock gravity. We also, investigate the
properties of radiating solutions for these values of $B$ and $w$, and compare
the singularity strengths of them with the known radiating solutions of third
order Lovelock gravity.
| [
{
"created": "Wed, 8 Apr 2009 13:32:11 GMT",
"version": "v1"
}
] | 2014-11-18 | [
[
"Dehghani",
"M. H.",
""
],
[
"Farhangkhah",
"N.",
""
]
] | We present a general solution of third order Lovelock gravity in the presence of a specific type II perfect fluid. This solution for linear equation of state, $p=w(\rho-4B)$ contains all the known solutions of third order Lovelock gravity in the literature and some new static and radiating solutions for different values of $w$ and $B$. Specially, we consider the properties of static and radiating solutions for $w=0$ and $w=(n-2)^{-1}$ with B=0 and $B\neq0$. These solutions are asymptotically flat for B=0, while they are asymptotically (anti)-de Sitter for $B\neq0$. The new static solutions for these choices of $B$ and $w$ present black holes with one or two horizons, extreme black holes or naked singularities provided the parameters of the solutions are chosen suitable. The static solution with $w=0$ and vanishing geometrical mass ($m=0$) may present a black hole with two inner and outer horizons. This is a peculiar feature of the third order Lovelock gravity, which does not occur in lower order Lovelock gravity. We also, investigate the properties of radiating solutions for these values of $B$ and $w$, and compare the singularity strengths of them with the known radiating solutions of third order Lovelock gravity. |
2211.09674 | Asher Yahalom PhD | Asher Yahalom | The Primordial Particle Accelerator of the Cosmos | 28 pages, 24 figures. arXiv admin note: text overlap with
arXiv:gr-qc/0611124 | Universe 8, no. 11: 594, 2022 | 10.3390/universe8110594 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | In a previous paper we have shown that superluminal particles are allowed by
the general relativistic theory of gravity provided that the metric is locally
Euclidean. Here we calculate the probability density function of a canonical
ensemble of superluminal particles as function of temperature. This is done for
both space-times invariant under Lorentz symmetry group, and for space times
invariant under an Euclidean symmetry group. Although only the Lorentzian
metric is stable for normal matter density, an Euclidian metric can be created
under special gravitational circumstances and persist in a limited region of
space-time consisting of the very early universe which is characterized by
extremely high densities and temperatures. Superluminal particles also allow
attaining thermodynamic equilibrium at a shorter duration and also suggest a
rapid expansion of the matter density, thus making mechanism such as inflation
(which demands invoking and ad-hoc scalar field) redundant. This is in
accordance with Occam's razor.
| [
{
"created": "Tue, 15 Nov 2022 12:52:44 GMT",
"version": "v1"
}
] | 2022-11-18 | [
[
"Yahalom",
"Asher",
""
]
] | In a previous paper we have shown that superluminal particles are allowed by the general relativistic theory of gravity provided that the metric is locally Euclidean. Here we calculate the probability density function of a canonical ensemble of superluminal particles as function of temperature. This is done for both space-times invariant under Lorentz symmetry group, and for space times invariant under an Euclidean symmetry group. Although only the Lorentzian metric is stable for normal matter density, an Euclidian metric can be created under special gravitational circumstances and persist in a limited region of space-time consisting of the very early universe which is characterized by extremely high densities and temperatures. Superluminal particles also allow attaining thermodynamic equilibrium at a shorter duration and also suggest a rapid expansion of the matter density, thus making mechanism such as inflation (which demands invoking and ad-hoc scalar field) redundant. This is in accordance with Occam's razor. |
1902.05670 | J\"org Frauendiener | Boris Daszuta and J\"org Frauendiener | Numerical initial data deformation exploiting a gluing construction: I.
Exterior asymptotic Schwarzschild | null | null | 10.1088/1361-6382/ab34d8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work a new numerical technique to prepare Cauchy data for the initial
value problem (IVP) formulation of Einstein's field equations is presented.
Directly inspired by the exterior asymptotic gluing (EAG) result of Corvino
(2000) our (pseudo)-spectral scheme is demonstrated under the assumption of
axisymmetry so as to fashion composite Hamiltonian constraint satisfying
initial data featuring internal binary black holes (BBH) as glued to exterior
Schwarzschild initial data in isotropic form. The generality of the method is
illustrated in a comparison of the ADM mass of EAG initial data sets featuring
internal BBHs as modelled by Brill-Lindquist and Misner data.In contrast to the
recent work of Doulis and Rinne (2016), and Pook-Kolb and Giulini (2018) we do
not make use of the York-Lichnerowicz conformal framework to reformulate the
constraints.
| [
{
"created": "Fri, 15 Feb 2019 03:16:38 GMT",
"version": "v1"
}
] | 2019-09-04 | [
[
"Daszuta",
"Boris",
""
],
[
"Frauendiener",
"Jörg",
""
]
] | In this work a new numerical technique to prepare Cauchy data for the initial value problem (IVP) formulation of Einstein's field equations is presented. Directly inspired by the exterior asymptotic gluing (EAG) result of Corvino (2000) our (pseudo)-spectral scheme is demonstrated under the assumption of axisymmetry so as to fashion composite Hamiltonian constraint satisfying initial data featuring internal binary black holes (BBH) as glued to exterior Schwarzschild initial data in isotropic form. The generality of the method is illustrated in a comparison of the ADM mass of EAG initial data sets featuring internal BBHs as modelled by Brill-Lindquist and Misner data.In contrast to the recent work of Doulis and Rinne (2016), and Pook-Kolb and Giulini (2018) we do not make use of the York-Lichnerowicz conformal framework to reformulate the constraints. |
2202.09126 | Igor Bogush M.Sc. | Kirill Kobialko, Igor Bogush, Dmitri Gal'tsov | Slice-reducible conformal Killing tensors, photon surfaces and shadows | 44 pages, revtex4 | null | 10.1103/PhysRevD.106.024006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We generalize our recent method for constructing Killing tensors of the
second rank to conformal Killing tensors. The method is intended for foliated
spacetimes of arbitrary dimension $m$, which have a set of conformal Killing
vectors. It applies to foliations of a more general structure than in previous
literature. The basic idea is to start with reducible Killing tensors in slices
constructed from a set of conformal Killing vectors and the induced metric, and
then lift them to the whole manifold. Integrability conditions are derived that
ensure this, and a constructive lifting procedure is presented. The resulting
conformal Killing tensor may be irreducible. It is shown that subdomains of
foliation slices suitable for the method are fundamental photon surfaces if
some additional photon region inequality is satisfied. Thus our procedure also
opens the way to obtain a simple general analytical expression for the boundary
of the gravitational shadow. We apply this technique to electrovacuum, and
${\cal N}=2,\,4,\,8$ supergravity black holes, providing a new easy way to
establish the existence of exact and conformal Killing tensors.
| [
{
"created": "Fri, 18 Feb 2022 11:15:05 GMT",
"version": "v1"
}
] | 2022-07-20 | [
[
"Kobialko",
"Kirill",
""
],
[
"Bogush",
"Igor",
""
],
[
"Gal'tsov",
"Dmitri",
""
]
] | We generalize our recent method for constructing Killing tensors of the second rank to conformal Killing tensors. The method is intended for foliated spacetimes of arbitrary dimension $m$, which have a set of conformal Killing vectors. It applies to foliations of a more general structure than in previous literature. The basic idea is to start with reducible Killing tensors in slices constructed from a set of conformal Killing vectors and the induced metric, and then lift them to the whole manifold. Integrability conditions are derived that ensure this, and a constructive lifting procedure is presented. The resulting conformal Killing tensor may be irreducible. It is shown that subdomains of foliation slices suitable for the method are fundamental photon surfaces if some additional photon region inequality is satisfied. Thus our procedure also opens the way to obtain a simple general analytical expression for the boundary of the gravitational shadow. We apply this technique to electrovacuum, and ${\cal N}=2,\,4,\,8$ supergravity black holes, providing a new easy way to establish the existence of exact and conformal Killing tensors. |
gr-qc/0009059 | Sean C. Ahern | Sean C. Ahern, John W. Norbury and William J. Poyser | Graviton Production in Relativistic Heavy-Ion Collisions | 10 pages, 3 figures, accepted for publication in Physical Review D | Phys.Rev.D62:116001,2000 | 10.1103/PhysRevD.62.116001 | null | gr-qc hep-ph | null | We study the feasibility of producing the graviton of the novel Kaluza-Klein
theory in which there are d large compact dimensions in addition to the 4
dimensions of Minkowski spacetime. We calculate the cross section for producing
such a graviton in nucleus-nucleus collisions via t-channel photon-photon
fusion using the semiclassical Weizsacker-Williams method and show that it can
exceed the cross section for graviton production in electron-positron
scattering by several orders of magnitude.
| [
{
"created": "Sun, 17 Sep 2000 03:07:26 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ahern",
"Sean C.",
""
],
[
"Norbury",
"John W.",
""
],
[
"Poyser",
"William J.",
""
]
] | We study the feasibility of producing the graviton of the novel Kaluza-Klein theory in which there are d large compact dimensions in addition to the 4 dimensions of Minkowski spacetime. We calculate the cross section for producing such a graviton in nucleus-nucleus collisions via t-channel photon-photon fusion using the semiclassical Weizsacker-Williams method and show that it can exceed the cross section for graviton production in electron-positron scattering by several orders of magnitude. |
1605.02325 | Aleksander Stachowski | Marek Szydlowski, Aleksander Stachowski | Does the diffusion DM-DE interaction model solve cosmological puzzles? | 27 pages, 17 figures | Phys. Rev. D 94, 043521 (2016) | 10.1103/PhysRevD.94.043521 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study dynamics of cosmological models with diffusion effects modeling dark
matter and dark energy interactions. We show the simple model with diffusion
between the cosmological constant sector and dark matter, where the canonical
scaling law of dark matter $(\rho_{dm,0}a^{-3}(t))$ is modified by an additive
$\epsilon(t)=\gamma t a^{-3}(t)$ to the form
$\rho_{dm}=\rho_{dm,0}a^{-3}(t)+\epsilon(t)$. We reduced this model to the
autonomous dynamical system and investigate it using dynamical system methods.
This system possesses a two-dimensional invariant submanifold on which the
DM-DE interaction can be analyzed on the phase plane. The state variables are
density parameter for matter (dark and visible) and parameter $\delta$
characterizing the rate of growth of energy transfer between the dark sectors.
A corresponding dynamical system belongs to a general class of jungle type of
cosmologies represented by coupled cosmological models in a Lotka-Volterra
framework. We demonstrate that the de Sitter solution is a global attractor for
all trajectories in the phase space and there are two repellers: the
Einstein-de Sitter universe and the de Sitter universe state dominating by the
diffusion effects. We distinguish in the phase space trajectories, which become
in good agreement with the data. They should intersect a rectangle with sides
of $\Omega_{m,0}\in [0.2724, 0.3624]$, $\delta \in [0.0000, 0.0364]$ at the
95\% CL. Our model could solve some of the puzzles of the $\Lambda$CDM model,
such as the coincidence and fine-tuning problems. In the context of the
coincidence problem, our model can explain the present ratio of $\rho_{m}$ to
$\rho_{de}$, which is equal $0.4576^{+0.1109}_{-0.0831}$ at a 2$\sigma$
confidence level.
| [
{
"created": "Sun, 8 May 2016 15:35:18 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Szydlowski",
"Marek",
""
],
[
"Stachowski",
"Aleksander",
""
]
] | We study dynamics of cosmological models with diffusion effects modeling dark matter and dark energy interactions. We show the simple model with diffusion between the cosmological constant sector and dark matter, where the canonical scaling law of dark matter $(\rho_{dm,0}a^{-3}(t))$ is modified by an additive $\epsilon(t)=\gamma t a^{-3}(t)$ to the form $\rho_{dm}=\rho_{dm,0}a^{-3}(t)+\epsilon(t)$. We reduced this model to the autonomous dynamical system and investigate it using dynamical system methods. This system possesses a two-dimensional invariant submanifold on which the DM-DE interaction can be analyzed on the phase plane. The state variables are density parameter for matter (dark and visible) and parameter $\delta$ characterizing the rate of growth of energy transfer between the dark sectors. A corresponding dynamical system belongs to a general class of jungle type of cosmologies represented by coupled cosmological models in a Lotka-Volterra framework. We demonstrate that the de Sitter solution is a global attractor for all trajectories in the phase space and there are two repellers: the Einstein-de Sitter universe and the de Sitter universe state dominating by the diffusion effects. We distinguish in the phase space trajectories, which become in good agreement with the data. They should intersect a rectangle with sides of $\Omega_{m,0}\in [0.2724, 0.3624]$, $\delta \in [0.0000, 0.0364]$ at the 95\% CL. Our model could solve some of the puzzles of the $\Lambda$CDM model, such as the coincidence and fine-tuning problems. In the context of the coincidence problem, our model can explain the present ratio of $\rho_{m}$ to $\rho_{de}$, which is equal $0.4576^{+0.1109}_{-0.0831}$ at a 2$\sigma$ confidence level. |
1111.2318 | Jose Socorro Garcia | J. Socorro, Paulo A. Rodr\'iguez, Abraham Espinoza-Garc\'ia, Luis O.
Pimentel and Priscila Romero | Cosmological Bianchi Class A models in S\'aez-Ballester theory | 24 pages; ISBN: 978-953-307-626-3, InTech | Aspects of Today's Cosmology, Antonio Alfonso-Faus (Ed.), 2011,
pages 185-204 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the S\'aez-Ballester (SB) theory on anisotropic Bianchi Class A
cosmological model, with barotropic fluid and cosmological constant, using the
Hamilton or Hamilton-Jacobi approach. Contrary to claims in the specialized
literature, it is shown that the S\'aez-Ballester theory cannot provide a
realistic solution to the dark matter problem of Cosmology for the dust epoch,
without a fine tunning because the contribution of the scalar field in this
theory is equivalent to a stiff fluid (as can be seen from the energy--momentum
tensor for the scalar field), that evolves in a different way as the dust
component. To have similar contributions of the scalar component and the dust
component implies that their past values were fine tunned. So, we
reinterpreting this null result as an indication that dark matter plays a
central role in the formation of structures and galaxy evolution, having
measureable effects in the cosmic microwave bound radiation, and than this
formalism yield to this epoch as primigenius results. We do the mention that
this formalism was used recently in the so called K-essence theory applied to
dark energy problem, in place to the dark matter problem. Also, we include a
quantization procedure of the theory which can be simplified by reinterpreting
the theory in the Einstein frame, where the scalar field can be interpreted as
part of the matter content of the theory, and exact solutions to the
Wheeler-DeWitt equation are found, employing the Bianchi Class A cosmological
models.
| [
{
"created": "Wed, 9 Nov 2011 20:26:04 GMT",
"version": "v1"
}
] | 2011-11-10 | [
[
"Socorro",
"J.",
""
],
[
"Rodríguez",
"Paulo A.",
""
],
[
"Espinoza-García",
"Abraham",
""
],
[
"Pimentel",
"Luis O.",
""
],
[
"Romero",
"Priscila",
""
]
] | We use the S\'aez-Ballester (SB) theory on anisotropic Bianchi Class A cosmological model, with barotropic fluid and cosmological constant, using the Hamilton or Hamilton-Jacobi approach. Contrary to claims in the specialized literature, it is shown that the S\'aez-Ballester theory cannot provide a realistic solution to the dark matter problem of Cosmology for the dust epoch, without a fine tunning because the contribution of the scalar field in this theory is equivalent to a stiff fluid (as can be seen from the energy--momentum tensor for the scalar field), that evolves in a different way as the dust component. To have similar contributions of the scalar component and the dust component implies that their past values were fine tunned. So, we reinterpreting this null result as an indication that dark matter plays a central role in the formation of structures and galaxy evolution, having measureable effects in the cosmic microwave bound radiation, and than this formalism yield to this epoch as primigenius results. We do the mention that this formalism was used recently in the so called K-essence theory applied to dark energy problem, in place to the dark matter problem. Also, we include a quantization procedure of the theory which can be simplified by reinterpreting the theory in the Einstein frame, where the scalar field can be interpreted as part of the matter content of the theory, and exact solutions to the Wheeler-DeWitt equation are found, employing the Bianchi Class A cosmological models. |
1504.00870 | Lavinia Heisenberg | Luc Blanchet and Lavinia Heisenberg | Dark Matter via Massive (bi-)Gravity | 7 pages, references added, typos corrected, journal version | null | 10.1103/PhysRevD.91.103518 | NORDITA-2015-38 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we investigate the existence of relativistic models for dark
matter in the context of bimetric gravity, used here to reproduce the modified
Newtonian dynamics (MOND) at galactic scales. For this purpose we consider two
different species of dark matter particles that separately couple to the two
metrics of bigravity. These two sectors are linked together \textit{via} an
internal $U(1)$ vector field, and some effective composite metric built out of
the two metrics. Among possible models only certain classes of kinetic and
interaction terms are allowed without invoking ghost degrees of freedom. Along
these lines we explore the number of allowed kinetic terms in the theory and
point out the presence of ghosts in a previous model. Finally, we propose a
promising class of ghost-free candidate theories that could provide the MOND
phenomenology at galactic scales while reproducing the standard cold dark
matter (CDM) model at cosmological scales.
| [
{
"created": "Fri, 3 Apr 2015 15:56:14 GMT",
"version": "v1"
},
{
"created": "Wed, 6 May 2015 13:28:18 GMT",
"version": "v2"
}
] | 2015-06-03 | [
[
"Blanchet",
"Luc",
""
],
[
"Heisenberg",
"Lavinia",
""
]
] | In this work we investigate the existence of relativistic models for dark matter in the context of bimetric gravity, used here to reproduce the modified Newtonian dynamics (MOND) at galactic scales. For this purpose we consider two different species of dark matter particles that separately couple to the two metrics of bigravity. These two sectors are linked together \textit{via} an internal $U(1)$ vector field, and some effective composite metric built out of the two metrics. Among possible models only certain classes of kinetic and interaction terms are allowed without invoking ghost degrees of freedom. Along these lines we explore the number of allowed kinetic terms in the theory and point out the presence of ghosts in a previous model. Finally, we propose a promising class of ghost-free candidate theories that could provide the MOND phenomenology at galactic scales while reproducing the standard cold dark matter (CDM) model at cosmological scales. |
gr-qc/9901034 | Edward N. Glass | E.N. Glass and J.P. Krisch (Department of Physics, University of
Michigan, Ann Arbor, Michgan) | Two-Fluid Atmosphere for Relativistic Stars | to appear in Classical and Quantum Gravity | Class.Quant.Grav. 16 (1999) 1175-1184 | 10.1088/0264-9381/16/4/007 | null | gr-qc | null | We have extended the Vaidya radiating metric to include both a radiation
fluid and a string fluid. This paper expands our brief introduction to
extensions of the Schwarzschild vacuum which appeared in 1998 Phys. Rev. D Vol
57, R5945. Assuming diffusive transport for the string fluid, we find new
analytic solutions of Einstein's field equations.
| [
{
"created": "Wed, 13 Jan 1999 02:46:38 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Glass",
"E. N.",
"",
"Department of Physics, University of\n Michigan, Ann Arbor, Michgan"
],
[
"Krisch",
"J. P.",
"",
"Department of Physics, University of\n Michigan, Ann Arbor, Michgan"
]
] | We have extended the Vaidya radiating metric to include both a radiation fluid and a string fluid. This paper expands our brief introduction to extensions of the Schwarzschild vacuum which appeared in 1998 Phys. Rev. D Vol 57, R5945. Assuming diffusive transport for the string fluid, we find new analytic solutions of Einstein's field equations. |
gr-qc/0003057 | Thomas P. Kling | Thomas P. Kling, Ezra T. Newman, and Alejandro Perez | Comparative Studies of Lensing Methods | 23 pages, 15 figures, corrected version | Phys.Rev.D62:024025,2000; Erratum-ibid.D62:109901,2000 | 10.1103/PhysRevD.62.024025 10.1103/PhysRevD.62.109901 | null | gr-qc astro-ph | null | Predictions of the standard thin lens approximation and a new iterative
approach to gravitational lensing are compared with an ``exact'' approach in
simple test cases involving one or two lenses. We show that the thin lens and
iterative approaches are remarkably accurate in predicting time delays, source
positions and image magnifications for a single monopole lens and combinations
of two monopole lenses. In the cases studied, the iterative method provided
greater accuracy than the thin lens method. We also study the accuracy of a ``2
lens, single lens plane model,'' where two monopole lenses colinear with the
observer are modeled by a mass distribution in a single lens plane lying
between them. We see that this model can lead to large inaccuracies in
physically meaningful situations.
A previous version of this paper was published as Phys.Rev.D62, 024025,
(2000) with errors in the computation of two lens comparisons. This paper
corrects these errors and presents new conclusions which differ from the
previous version.
| [
{
"created": "Tue, 14 Mar 2000 19:06:59 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Aug 2000 15:07:48 GMT",
"version": "v2"
},
{
"created": "Tue, 26 Sep 2000 00:11:04 GMT",
"version": "v3"
}
] | 2014-11-17 | [
[
"Kling",
"Thomas P.",
""
],
[
"Newman",
"Ezra T.",
""
],
[
"Perez",
"Alejandro",
""
]
] | Predictions of the standard thin lens approximation and a new iterative approach to gravitational lensing are compared with an ``exact'' approach in simple test cases involving one or two lenses. We show that the thin lens and iterative approaches are remarkably accurate in predicting time delays, source positions and image magnifications for a single monopole lens and combinations of two monopole lenses. In the cases studied, the iterative method provided greater accuracy than the thin lens method. We also study the accuracy of a ``2 lens, single lens plane model,'' where two monopole lenses colinear with the observer are modeled by a mass distribution in a single lens plane lying between them. We see that this model can lead to large inaccuracies in physically meaningful situations. A previous version of this paper was published as Phys.Rev.D62, 024025, (2000) with errors in the computation of two lens comparisons. This paper corrects these errors and presents new conclusions which differ from the previous version. |
0903.2270 | Simone Mercuri | Simone Mercuri | A possible topological interpretation of the Barbero-Immirzi parameter | 10 pages, based on a talk given at the III Stueckelberg workshop on
Relativistic Field Theories, July 8-18, 2008, Pescara (Italy). V2: minor
corrections in section II, major corrections in section IV | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A possible topological interpretation of the Barbero-Immirzi parameter is
proposed. Classically, by generalizing the Holst action to torsional
spacetimes, we construct a precise analogy between the Barbero--Immirzi
parameter and the $\theta$-angle of Yang-Mills gauge theories, where the role
of the Pontryagin class is played by a well known topological term containing
the Holst modification, the Nieh--Yan density. Quantum mechanically, the same
analogy requires to study the large gauge sector of the theory. In particular,
it is argued that the large sector of the gauge group can be correlated with
the Nieh-Yan density, while the Barbero-Immirzi parameter plays the role of the
free angular parameter of the large gauge transformations.
| [
{
"created": "Thu, 12 Mar 2009 21:05:27 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Apr 2009 23:50:26 GMT",
"version": "v2"
}
] | 2009-04-12 | [
[
"Mercuri",
"Simone",
""
]
] | A possible topological interpretation of the Barbero-Immirzi parameter is proposed. Classically, by generalizing the Holst action to torsional spacetimes, we construct a precise analogy between the Barbero--Immirzi parameter and the $\theta$-angle of Yang-Mills gauge theories, where the role of the Pontryagin class is played by a well known topological term containing the Holst modification, the Nieh--Yan density. Quantum mechanically, the same analogy requires to study the large gauge sector of the theory. In particular, it is argued that the large sector of the gauge group can be correlated with the Nieh-Yan density, while the Barbero-Immirzi parameter plays the role of the free angular parameter of the large gauge transformations. |
gr-qc/0206064 | Saulo Carneiro | Saulo Carneiro | Holography and the Cosmic Coincidence | RevTex, 4 pages, no figures | null | null | null | gr-qc astro-ph hep-th | null | Based on an analysis of the entropy associated to the vacuum quantum
fluctuations, we show that the holographic principle, applied to the cosmic
scale, constitutes a possible explanation for the observed value of the
cosmological constant, theoretically justifying a relation proposed 35 years
ago by Zel'dovich. Furthermore, extending to the total energy density the
conjecture by Chen and Wu, concerning the dependence of the cosmological
constant on the scale factor, we show that the holographic principle may also
lie at the root of the coincidence between the matter density in the universe
and the vacuum energy density.
| [
{
"created": "Thu, 20 Jun 2002 18:27:13 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Carneiro",
"Saulo",
""
]
] | Based on an analysis of the entropy associated to the vacuum quantum fluctuations, we show that the holographic principle, applied to the cosmic scale, constitutes a possible explanation for the observed value of the cosmological constant, theoretically justifying a relation proposed 35 years ago by Zel'dovich. Furthermore, extending to the total energy density the conjecture by Chen and Wu, concerning the dependence of the cosmological constant on the scale factor, we show that the holographic principle may also lie at the root of the coincidence between the matter density in the universe and the vacuum energy density. |
2104.04995 | Sergey Yu. Vernov | Ekaterina O. Pozdeeva, Sergey Yu. Vernov | Construction of inflationary scenarios with the Gauss-Bonnet term and
nonminimal coupling | 11 pages, 5 figures, v2: minor corrections, references are added, to
appear in EPJC | Eur. Phys. J. C 81 (2021) 633 | 10.1140/epjc/s10052-021-09435-8 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Inflationary models with a scalar field nonminimally coupled both with the
Ricci scalar and with the Gauss-Bonnet term are studied. We propose the way of
generalization of inflationary scenarios with the Gauss-Bonnet term and a
scalar field minimally coupled with the Ricci scalar to the corresponding
scenarios with a scalar field nonminimally coupled with the Ricci scalar. Using
the effective potential, we construct a set of models with the same values of
the scalar spectral index $n_s$ and the amplitude of the scalar perturbations
$A_s$ and different values of the tensor-to-scalar ratio $r$.
| [
{
"created": "Sun, 11 Apr 2021 11:27:11 GMT",
"version": "v1"
},
{
"created": "Sun, 18 Jul 2021 17:27:19 GMT",
"version": "v2"
}
] | 2021-07-21 | [
[
"Pozdeeva",
"Ekaterina O.",
""
],
[
"Vernov",
"Sergey Yu.",
""
]
] | Inflationary models with a scalar field nonminimally coupled both with the Ricci scalar and with the Gauss-Bonnet term are studied. We propose the way of generalization of inflationary scenarios with the Gauss-Bonnet term and a scalar field minimally coupled with the Ricci scalar to the corresponding scenarios with a scalar field nonminimally coupled with the Ricci scalar. Using the effective potential, we construct a set of models with the same values of the scalar spectral index $n_s$ and the amplitude of the scalar perturbations $A_s$ and different values of the tensor-to-scalar ratio $r$. |
1406.3186 | Marcello Ortaggio | Marcello Ortaggio | Asymptotic behaviour of Maxwell fields in higher dimensions | 23 pages. v2: new appendix A summarizes the definitions of the Ricci
rotation coefficients; several technical details moved to new appendix B;
former footnote 8 was not precise and has been removed; added/fixed
references, typos corrected | Phys. Rev. D 90, 124020 (2014) | 10.1103/PhysRevD.90.124020 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the fall-off behaviour of test electromagnetic fields in higher
dimensions as one approaches infinity along a congruence of "expanding" null
geodesics. The considered backgrounds are Einstein spacetimes including, in
particular, (asymptotically) flat and (anti-)de Sitter spacetimes. Various
possible boundary conditions result in different characteristic fall-offs, in
which the leading component can be of any algebraic type (N, II or G). In
particular, the peeling-off of radiative fields F=Nr^{1-n/2}+Gr^{-n/2}+...
differs from the standard four-dimensional one (instead it qualitatively
resembles the recently determined behaviour of the Weyl tensor in higher
dimensions). General p-form fields are also briefly discussed. In even n
dimensions, the special case p=n/2 displays unique properties and peels off in
the "standard way" as F=Nr^{1-n/2}+IIr^{-n/2}+.... A few explicit examples are
mentioned.
| [
{
"created": "Thu, 12 Jun 2014 10:33:55 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Mar 2015 15:13:09 GMT",
"version": "v2"
}
] | 2015-03-04 | [
[
"Ortaggio",
"Marcello",
""
]
] | We study the fall-off behaviour of test electromagnetic fields in higher dimensions as one approaches infinity along a congruence of "expanding" null geodesics. The considered backgrounds are Einstein spacetimes including, in particular, (asymptotically) flat and (anti-)de Sitter spacetimes. Various possible boundary conditions result in different characteristic fall-offs, in which the leading component can be of any algebraic type (N, II or G). In particular, the peeling-off of radiative fields F=Nr^{1-n/2}+Gr^{-n/2}+... differs from the standard four-dimensional one (instead it qualitatively resembles the recently determined behaviour of the Weyl tensor in higher dimensions). General p-form fields are also briefly discussed. In even n dimensions, the special case p=n/2 displays unique properties and peels off in the "standard way" as F=Nr^{1-n/2}+IIr^{-n/2}+.... A few explicit examples are mentioned. |
1603.07281 | Otakar Svitek | T. Tahamtan and O. Svitek | Properties of Robinson--Trautman solution with scalar hair | 2 figures | Phys. Rev. D 94, 064031 (2016) | 10.1103/PhysRevD.94.064031 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | An explicit Robinson--Trautman solution with minimally coupled free scalar
field was derived and analyzed recently. It was shown that this solution
possesses a curvature singularity which is initially naked but later enveloped
by a horizon. However, this study concentrated on the general branch of the
solution where all free constants are nonzero. Interesting special cases arise
when some of the parameters are set to zero. In most of these cases the scalar
field is still present. One of the cases is a static solution which represents
a parametric limit of the Janis--Newman--Winicour scalar field spacetime.
Additionally, we provide a calculation of the Bondi mass which clarifies the
interpretation of the general solution. Finally, by a complex rotation of a
parameter describing the strength of the scalar field we obtain a dynamical
wormhole solution.
| [
{
"created": "Wed, 23 Mar 2016 17:32:29 GMT",
"version": "v1"
},
{
"created": "Fri, 6 May 2016 13:14:49 GMT",
"version": "v2"
},
{
"created": "Thu, 25 Aug 2016 11:43:25 GMT",
"version": "v3"
}
] | 2016-09-16 | [
[
"Tahamtan",
"T.",
""
],
[
"Svitek",
"O.",
""
]
] | An explicit Robinson--Trautman solution with minimally coupled free scalar field was derived and analyzed recently. It was shown that this solution possesses a curvature singularity which is initially naked but later enveloped by a horizon. However, this study concentrated on the general branch of the solution where all free constants are nonzero. Interesting special cases arise when some of the parameters are set to zero. In most of these cases the scalar field is still present. One of the cases is a static solution which represents a parametric limit of the Janis--Newman--Winicour scalar field spacetime. Additionally, we provide a calculation of the Bondi mass which clarifies the interpretation of the general solution. Finally, by a complex rotation of a parameter describing the strength of the scalar field we obtain a dynamical wormhole solution. |
2002.02688 | Dieter Van den Bleeken | Mert Ergen, Efe Hamamci and Dieter Van den Bleeken | Oddity in nonrelativistic, strong gravity | 24 pages + appendices. Version accepted for publication by EPJC.
Subsection 4.4 on possible phenomenological applications added | null | 10.1140/epjc/s10052-020-8112-6 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the presence of odd powers of the speed of light $c$ in the
covariant nonrelativistic expansion of General Relativity (GR). The term of
order $c$ in the relativistic metric is a vector potential that contributes at
leading order in this expansion and describes strong gravitational effects
outside the (post-)Newtonian regime. The nonrelativistic theory of the leading
order potentials contains the full non-linear dynamics of the stationary sector
of GR.
| [
{
"created": "Fri, 7 Feb 2020 09:49:55 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Jun 2020 10:14:17 GMT",
"version": "v2"
}
] | 2020-07-15 | [
[
"Ergen",
"Mert",
""
],
[
"Hamamci",
"Efe",
""
],
[
"Bleeken",
"Dieter Van den",
""
]
] | We consider the presence of odd powers of the speed of light $c$ in the covariant nonrelativistic expansion of General Relativity (GR). The term of order $c$ in the relativistic metric is a vector potential that contributes at leading order in this expansion and describes strong gravitational effects outside the (post-)Newtonian regime. The nonrelativistic theory of the leading order potentials contains the full non-linear dynamics of the stationary sector of GR. |
1212.5355 | Sang Pyo Kim | Sang Pyo Kim | Third Quantization and Quantum Universes | LaTex 8 pages, no figure; 9th CosPA (Cosmology and Particle
Astrophysics) Proceedings | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the third quantization of the Friedmann-Robertson-Walker cosmology
with $N$-minimal massless fields. The third quantized Hamiltonian for the WDW
equation in the minisuperspace consists of infinite number of intrinsic
time-dependent, decoupled oscillators. The Hamiltonian has a pair of invariant
operators for each universe with conserved momenta of the fields that play a
role of the annihilation and the creation operators and that construct various
quantum states for the universe. The closed universe exhibits an interesting
feature of transitions from stable states to tachyonic states depending on the
conserved momenta of the fields. In the classical forbidden unstable regime,
the quantum states have googolplex growing position and conjugate momentum
dispersions, which defy any measurements of the position of the universe.
| [
{
"created": "Fri, 21 Dec 2012 08:10:31 GMT",
"version": "v1"
}
] | 2012-12-24 | [
[
"Kim",
"Sang Pyo",
""
]
] | We study the third quantization of the Friedmann-Robertson-Walker cosmology with $N$-minimal massless fields. The third quantized Hamiltonian for the WDW equation in the minisuperspace consists of infinite number of intrinsic time-dependent, decoupled oscillators. The Hamiltonian has a pair of invariant operators for each universe with conserved momenta of the fields that play a role of the annihilation and the creation operators and that construct various quantum states for the universe. The closed universe exhibits an interesting feature of transitions from stable states to tachyonic states depending on the conserved momenta of the fields. In the classical forbidden unstable regime, the quantum states have googolplex growing position and conjugate momentum dispersions, which defy any measurements of the position of the universe. |
gr-qc/0511145 | Hideaki Kudoh | Hideaki Kudoh, Atsushi Taruya, Takashi Hiramatsu, Yoshiaki Himemoto | Detecting a gravitational-wave background with next-generation space
interferometers | 19 pages, 6 figures, references added, typos corrected | Phys.Rev. D73 (2006) 064006 | 10.1103/PhysRevD.73.064006 | null | gr-qc astro-ph | null | Future missions of gravitational-wave astronomy will be operated by
space-based interferometers, covering very wide range of frequency. Search for
stochastic gravitational-wave backgrounds (GWBs) is one of the main targets for
such missions, and we here discuss the prospects for direct measurement of
isotropic and anisotropic components of (primordial) GWBs around the frequency
0.1-10 Hz. After extending the theoretical basis for correlation analysis, we
evaluate the sensitivity and the signal-to-noise ratio for the proposed future
space interferometer missions, like Big-Bang Observer (BBO), Deci-Hertz
Interferometer Gravitational-wave Observer (DECIGO) and recently proposed
Fabry-Perot type DECIGO. The astrophysical foregrounds which are expected at
low frequency may be a big obstacle and significantly reduce the
signal-to-noise ratio of GWBs. As a result, minimum detectable amplitude may
reach h^2 \ogw = 10^{-15} \sim 10^{-16}, as long as foreground point sources
are properly subtracted. Based on correlation analysis, we also discuss
measurement of anisotropies of GWBs. As an example, the sensitivity level
required for detecting the dipole moment of GWB induced by the proper motion of
our local system is closely examined.
| [
{
"created": "Sun, 27 Nov 2005 19:24:09 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Dec 2005 15:01:06 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Kudoh",
"Hideaki",
""
],
[
"Taruya",
"Atsushi",
""
],
[
"Hiramatsu",
"Takashi",
""
],
[
"Himemoto",
"Yoshiaki",
""
]
] | Future missions of gravitational-wave astronomy will be operated by space-based interferometers, covering very wide range of frequency. Search for stochastic gravitational-wave backgrounds (GWBs) is one of the main targets for such missions, and we here discuss the prospects for direct measurement of isotropic and anisotropic components of (primordial) GWBs around the frequency 0.1-10 Hz. After extending the theoretical basis for correlation analysis, we evaluate the sensitivity and the signal-to-noise ratio for the proposed future space interferometer missions, like Big-Bang Observer (BBO), Deci-Hertz Interferometer Gravitational-wave Observer (DECIGO) and recently proposed Fabry-Perot type DECIGO. The astrophysical foregrounds which are expected at low frequency may be a big obstacle and significantly reduce the signal-to-noise ratio of GWBs. As a result, minimum detectable amplitude may reach h^2 \ogw = 10^{-15} \sim 10^{-16}, as long as foreground point sources are properly subtracted. Based on correlation analysis, we also discuss measurement of anisotropies of GWBs. As an example, the sensitivity level required for detecting the dipole moment of GWB induced by the proper motion of our local system is closely examined. |
1401.6745 | Anirban Saha Dr. | Gour Bhattacharya, Pradip Mukherjee, Anirban Saha, Amit Singha Roy | The role of potential in the ghost-condensate dark energy model | A new sub-section added, 13 pages, 3 figures, LaTex. paper thoroughly
rewritten. arXiv admin note: substantial text overlap with arXiv:1301.4746;
and text overlap with arXiv:1008.2182 by other authors | Eur.Phys.J. C75 (2015) 2, 84 | 10.1140/epjc/s10052-015-3301-4 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the ghost-condensate model of dark energy with a generic
potential term. The inclusion of the potential is shown to give greater freedom
in realising the phantom regime. The self-consistency of the analysis is
demonstrated using WMAP7+BAO+Hubble data.
| [
{
"created": "Mon, 27 Jan 2014 05:50:20 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Oct 2014 07:02:21 GMT",
"version": "v2"
},
{
"created": "Mon, 15 Dec 2014 05:57:14 GMT",
"version": "v3"
}
] | 2015-06-03 | [
[
"Bhattacharya",
"Gour",
""
],
[
"Mukherjee",
"Pradip",
""
],
[
"Saha",
"Anirban",
""
],
[
"Roy",
"Amit Singha",
""
]
] | We consider the ghost-condensate model of dark energy with a generic potential term. The inclusion of the potential is shown to give greater freedom in realising the phantom regime. The self-consistency of the analysis is demonstrated using WMAP7+BAO+Hubble data. |
1306.1801 | Michael Holst | Michael Holst, Gantumur Tsogtgerel | The Lichnerowicz equation on compact manifolds with boundary | 33 pages, no figures. Version 2 is a minor revision based on comments
received during review | null | 10.1088/0264-9381/30/20/205011 | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we initiate a systematic study of the well-posedness theory
of the Einstein constraint equations on compact manifolds with boundary. This
is an important problem in general relativity, and it is particularly important
in numerical relativity, as it arises in models of Cauchy surfaces containing
asymptotically flat ends and/or trapped surfaces. Moreover, a number of
technical obstacles that appear when developing the solution theory for open,
asymptotically Euclidean manifolds have analogues on compact manifolds with
boundary. As a first step, here we restrict ourselves to the Lichnerowicz
equation, also called the Hamiltonian constraint equation, which is the main
source of nonlinearity in the constraint system. The focus is on low regularity
data and on the interaction between different types of boundary conditions,
which has not been carefully analyzed before. In order to develop a
well-posedness theory that mirrors the existing theory for the case of closed
manifolds, we first generalize the Yamabe classification to nonsmooth metrics
on compact manifolds with boundary. We then extend a result on conformal
invariance to manifolds with boundary, and prove a uniqueness theorem. Finally,
by using the method of sub- and super-solutions (order-preserving map
iteration), we establish several existence results for a large class of
problems covering a broad parameter regime, which includes most of the cases
relevant in practice.
| [
{
"created": "Fri, 7 Jun 2013 18:16:59 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Sep 2013 04:33:20 GMT",
"version": "v2"
}
] | 2015-06-16 | [
[
"Holst",
"Michael",
""
],
[
"Tsogtgerel",
"Gantumur",
""
]
] | In this article we initiate a systematic study of the well-posedness theory of the Einstein constraint equations on compact manifolds with boundary. This is an important problem in general relativity, and it is particularly important in numerical relativity, as it arises in models of Cauchy surfaces containing asymptotically flat ends and/or trapped surfaces. Moreover, a number of technical obstacles that appear when developing the solution theory for open, asymptotically Euclidean manifolds have analogues on compact manifolds with boundary. As a first step, here we restrict ourselves to the Lichnerowicz equation, also called the Hamiltonian constraint equation, which is the main source of nonlinearity in the constraint system. The focus is on low regularity data and on the interaction between different types of boundary conditions, which has not been carefully analyzed before. In order to develop a well-posedness theory that mirrors the existing theory for the case of closed manifolds, we first generalize the Yamabe classification to nonsmooth metrics on compact manifolds with boundary. We then extend a result on conformal invariance to manifolds with boundary, and prove a uniqueness theorem. Finally, by using the method of sub- and super-solutions (order-preserving map iteration), we establish several existence results for a large class of problems covering a broad parameter regime, which includes most of the cases relevant in practice. |
1908.03814 | Richard Woodard | A. Kyriazis (U. Crete), S. P. Miao (NCKU), N. C. Tsamis (U. Crete) and
R. P. Woodard (UF) | The Inflaton Effective Potential for General $\epsilon$ | 21 pages, 9 figures, uses LaTeX 2e. Version 2 revised for
publication, including 2 new figures and 6 pages of new text to show, among
other things, that our approximations apply as well to plateau potentials | Phys. Rev. D 102, 025024 (2020) | 10.1103/PhysRevD.102.025024 | UFIFT-QG-19-05 , CCTP-2019-8 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop an analytic approximation for the coincidence limit of a massive
scalar propagator in an arbitrary spatially flat, homogeneous and isotropic
geometry. We employ this to compute the one loop corrections to the inflaton
effective potential from a quadratic coupling to a minimally coupled scalar. We
also extend the Friedmann equations to cover potentials that depend locally on
the Hubble parameter and the first slow roll parameter.
| [
{
"created": "Sat, 10 Aug 2019 21:51:06 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Jul 2020 16:53:08 GMT",
"version": "v2"
}
] | 2020-08-05 | [
[
"Kyriazis",
"A.",
"",
"U. Crete"
],
[
"Miao",
"S. P.",
"",
"NCKU"
],
[
"Tsamis",
"N. C.",
"",
"U. Crete"
],
[
"Woodard",
"R. P.",
"",
"UF"
]
] | We develop an analytic approximation for the coincidence limit of a massive scalar propagator in an arbitrary spatially flat, homogeneous and isotropic geometry. We employ this to compute the one loop corrections to the inflaton effective potential from a quadratic coupling to a minimally coupled scalar. We also extend the Friedmann equations to cover potentials that depend locally on the Hubble parameter and the first slow roll parameter. |
2004.06769 | \"Ozcan Sert | \"Ozcan Sert, Fatma \c{C}el\.ikta\c{s} | Noether Symmetry Approach to the Non-Minimally Coupled $Y(R)F^2$ Gravity | 14 pages, 2 figures | Eur. Phys. J. C 80, 653 (2020) | 10.1140/epjc/s10052-020-8237-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use Noether symmetry approach to find spherically symmetric static
solutions of the non-minimally coupled electromagnetic fields to gravity. We
construct the point-like Lagrangian under the spherical symmetry assumption.
Then we determine Noether symmetry and the corresponding conserved charge. We
derive Euler-Lagrange equations from this point-like Lagrangian and show that
these equations are same with the differential equations derived from the field
equations of the model. Also we give two new exact asymptotically flat
solutions to these equations and investigate some thermodynamic properties of
these black holes.
| [
{
"created": "Tue, 14 Apr 2020 19:35:59 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Jul 2020 03:43:44 GMT",
"version": "v2"
}
] | 2020-07-28 | [
[
"Sert",
"Özcan",
""
],
[
"Çeliktaş",
"Fatma",
""
]
] | We use Noether symmetry approach to find spherically symmetric static solutions of the non-minimally coupled electromagnetic fields to gravity. We construct the point-like Lagrangian under the spherical symmetry assumption. Then we determine Noether symmetry and the corresponding conserved charge. We derive Euler-Lagrange equations from this point-like Lagrangian and show that these equations are same with the differential equations derived from the field equations of the model. Also we give two new exact asymptotically flat solutions to these equations and investigate some thermodynamic properties of these black holes. |
gr-qc/0602004 | Brendan Foster | Brendan Z. Foster | Radiation Damping in Einstein-Aether Theory | 25 pages, 1 figure; v2: added comments and references; v3: cosmetics;
v4: corrected error in spin-1 portion of calculation; v5: fixed typos in
Eqns. (80,85) | Phys.Rev.D73:104012,2006; Erratum-ibid.D75:129904,2007 | 10.1103/PhysRevD.73.104012 10.1103/PhysRevD.75.129904 | null | gr-qc astro-ph hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work concerns the loss of energy of a material system due to
gravitational radiation in Einstein-aether theory-an alternative theory of
gravity in which the metric couples to a dynamical, timelike, unit-norm vector
field. Derived to lowest post-Newtonian order are waveforms for the metric and
vector fields far from a nearly Newtonian system and the rate of energy
radiated by the system. The expressions depend on the quadrupole moment of the
source, as in standard general relativity, but also contain monopolar and
dipolar terms. There exists a one-parameter family of Einstein-aether theories
for which only the quadrupolar contribution is present, and for which the
expression for the damping rate is identical to that of general relativity to
the order worked to here. This family cannot yet be declared observationally
viable, since effects due to the strong internal fields of bodies in the actual
systems used to test the damping rate are not included.
| [
{
"created": "Wed, 1 Feb 2006 20:50:00 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Apr 2006 19:14:41 GMT",
"version": "v2"
},
{
"created": "Thu, 4 May 2006 19:26:11 GMT",
"version": "v3"
},
{
"created": "Wed, 12 Sep 2007 09:50:06 GMT",
"version": "v4"
},
{
"created": "Tue, 23 Sep 2008 11:19:02 GMT",
"version": "v5"
}
] | 2014-11-17 | [
[
"Foster",
"Brendan Z.",
""
]
] | This work concerns the loss of energy of a material system due to gravitational radiation in Einstein-aether theory-an alternative theory of gravity in which the metric couples to a dynamical, timelike, unit-norm vector field. Derived to lowest post-Newtonian order are waveforms for the metric and vector fields far from a nearly Newtonian system and the rate of energy radiated by the system. The expressions depend on the quadrupole moment of the source, as in standard general relativity, but also contain monopolar and dipolar terms. There exists a one-parameter family of Einstein-aether theories for which only the quadrupolar contribution is present, and for which the expression for the damping rate is identical to that of general relativity to the order worked to here. This family cannot yet be declared observationally viable, since effects due to the strong internal fields of bodies in the actual systems used to test the damping rate are not included. |
0709.3947 | Jose Geraldo Pereira | R. Aldrovandi, J. P. Beltran Almeida, C. S. O. Mayor and J. G. Pereira | Lorentz transformations in de Sitter relativity | 7 pages, no figures | null | null | null | gr-qc hep-th | null | The properties of Lorentz transformations in de Sitter relativity are
studied. It is shown that, in addition to leaving invariant the velocity of
light, they also leave invariant the length-scale related to the curvature of
the de Sitter spacetime. The basic conclusion is that it is possible to have an
invariant length parameter without breaking the Lorentz symmetry. This result
may have important implications for the study of quantum kinematics, and in
particular for quantum gravity.
| [
{
"created": "Tue, 25 Sep 2007 16:34:36 GMT",
"version": "v1"
}
] | 2007-09-28 | [
[
"Aldrovandi",
"R.",
""
],
[
"Almeida",
"J. P. Beltran",
""
],
[
"Mayor",
"C. S. O.",
""
],
[
"Pereira",
"J. G.",
""
]
] | The properties of Lorentz transformations in de Sitter relativity are studied. It is shown that, in addition to leaving invariant the velocity of light, they also leave invariant the length-scale related to the curvature of the de Sitter spacetime. The basic conclusion is that it is possible to have an invariant length parameter without breaking the Lorentz symmetry. This result may have important implications for the study of quantum kinematics, and in particular for quantum gravity. |
1507.00158 | Piotr T. Chru\'sciel | Piotr T. Chru\'sciel and Paul Klinger | Vacuum space-times with controlled singularities and without symmetries | 4 pages, minor misprints corrected, added comment that the result
holds in vacuum for all values of the cosmological constant | null | 10.1103/PhysRevD.92.041501 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a family of four-dimensional vacuum space-times with
asymptotically velocity dominated singularities and without symmetries.
| [
{
"created": "Wed, 1 Jul 2015 09:27:31 GMT",
"version": "v1"
},
{
"created": "Sun, 9 Aug 2015 15:01:12 GMT",
"version": "v2"
}
] | 2015-09-02 | [
[
"Chruściel",
"Piotr T.",
""
],
[
"Klinger",
"Paul",
""
]
] | We present a family of four-dimensional vacuum space-times with asymptotically velocity dominated singularities and without symmetries. |
gr-qc/9809047 | Hongsu Kim | Hongsu Kim | Spinning BTZ Black Hole versus Kerr Black Hole : A Closer Look | 17 pages, 1 figure, Revtex, Accepted for publication in Phys. Rev. D | Phys.Rev. D59 (1999) 064002 | 10.1103/PhysRevD.59.064002 | null | gr-qc hep-th | null | By applying Newman's algorithm, the AdS_3 rotating black hole solution is
``derived'' from the nonrotating black hole solution of Banados, Teitelboim,
and Zanelli (BTZ). The rotating BTZ solution derived in this fashion is given
in ``Boyer-Lindquist-type'' coordinates whereas the form of the solution
originally given by BTZ is given in a kind of an ``unfamiliar'' coordinates
which are related to each other by a transformation of time coordinate alone.
The relative physical meaning between these two time coordinates is carefully
studied. Since the Kerr-type and Boyer-Lindquist-type coordinates for rotating
BTZ solution are newly found via Newman's algorithm, next, the transformation
to Kerr-Schild-type coordinates is looked for. Indeed, such transformation is
found to exist. And in this Kerr-Schild-type coordinates, truely maximal
extension of its global structure by analytically continuing to ``antigravity
universe'' region is carried out.
| [
{
"created": "Wed, 16 Sep 1998 02:54:03 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Nov 1998 05:47:42 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Kim",
"Hongsu",
""
]
] | By applying Newman's algorithm, the AdS_3 rotating black hole solution is ``derived'' from the nonrotating black hole solution of Banados, Teitelboim, and Zanelli (BTZ). The rotating BTZ solution derived in this fashion is given in ``Boyer-Lindquist-type'' coordinates whereas the form of the solution originally given by BTZ is given in a kind of an ``unfamiliar'' coordinates which are related to each other by a transformation of time coordinate alone. The relative physical meaning between these two time coordinates is carefully studied. Since the Kerr-type and Boyer-Lindquist-type coordinates for rotating BTZ solution are newly found via Newman's algorithm, next, the transformation to Kerr-Schild-type coordinates is looked for. Indeed, such transformation is found to exist. And in this Kerr-Schild-type coordinates, truely maximal extension of its global structure by analytically continuing to ``antigravity universe'' region is carried out. |
1502.05166 | Haidar Sheikhahmadi | Haidar Sheikhahmadi, Soheyla Ghorbani and Khaled Saaidi | Non-local scalar fields inflationary mechanism in light of Planck $2013$ | 15 pages, 5 tables | Astrophysics and Space Science (2015) 357:115 | 10.1007/s10509-015-2343-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A generalization of the canonical and non-canonical theory of inflation is
introduced in which the kinetic energy term in action is written as non-local
term. The inflationary universe within the framework of considering this
non-locality will be studied. To investigate the effects of non-locality on the
inflationary parameters we consider two well known models of inflationary
scenario includes of chaotic and exponential inflation proposals. For such
scenarios some important parameters include slow roll parameters, scalar and
tensor power spectra, spectral indices, the tensor-to-scalar ratio and so on
for both mentioned models, chaotic and exponential inflationary scenarios, will
be calculated. Also the Hamilton-Jacobi formalism, as an easiest way to study
the effect of perturbation based on e-folding number $N$, to investigate
inflationary attractors will be used. The free theoretical parameters of this
model will be compared with observations by means of Planck $2013$,
$WMAP9+eCMB+BAO+H_0$ data sets in addition to $BICEP2$ data surveying. It will
be shown that our theoretical results are in acceptable range in comparison to
observations. For instance the tensor-to-scalar ratio for exponential
potential, by considering $BICEP2$ is in best agreement in comparison with
chaotic inflation.
| [
{
"created": "Wed, 18 Feb 2015 09:40:37 GMT",
"version": "v1"
}
] | 2015-07-01 | [
[
"Sheikhahmadi",
"Haidar",
""
],
[
"Ghorbani",
"Soheyla",
""
],
[
"Saaidi",
"Khaled",
""
]
] | A generalization of the canonical and non-canonical theory of inflation is introduced in which the kinetic energy term in action is written as non-local term. The inflationary universe within the framework of considering this non-locality will be studied. To investigate the effects of non-locality on the inflationary parameters we consider two well known models of inflationary scenario includes of chaotic and exponential inflation proposals. For such scenarios some important parameters include slow roll parameters, scalar and tensor power spectra, spectral indices, the tensor-to-scalar ratio and so on for both mentioned models, chaotic and exponential inflationary scenarios, will be calculated. Also the Hamilton-Jacobi formalism, as an easiest way to study the effect of perturbation based on e-folding number $N$, to investigate inflationary attractors will be used. The free theoretical parameters of this model will be compared with observations by means of Planck $2013$, $WMAP9+eCMB+BAO+H_0$ data sets in addition to $BICEP2$ data surveying. It will be shown that our theoretical results are in acceptable range in comparison to observations. For instance the tensor-to-scalar ratio for exponential potential, by considering $BICEP2$ is in best agreement in comparison with chaotic inflation. |
1108.0288 | Mandar Patil | Mandar Patil, Pankaj S. Joshi, Masashi Kimura, Ken-ichi Nakao | Acceleration of particles and shells by Reissner-Nordstr\"{o}m naked
singularities | 13 pages, 7 figures. Significant improvement over older version.
Accepted for publication in Physical Review D | Phys. Rev. D 86, 084023 (2012) | 10.1103/PhysRevD.86.084023 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the Reissner-Nordstr\"{o}m naked singularities with a charge $Q$
larger than its mass $M$ from the perspective of the particle acceleration. We
first consider a collision between two test particles following the radial
geodesics in the Reissner-Nordstr\"{o}m naked singular geometry. An initially
radially ingoing particle turns back due to the repulsive effect of gravity in
the vicinity of naked singularity. Such a particle then collides with an
another radially ingoing particle. We show that the center of mass energy of
collision taking place at $r \approx M$ is unbound, in the limit where the
charge transcends the mass by arbitrarily small amount $0<1-M/Q\ll1$.The
acceleration process we described avoids fine tuning of the parameters of the
particle geodesics for the unbound center of mass energy of collisions and the
proper time required for the process is also finite. We show that the
coordinate time required for the trans-Plankian collision to occur around one
solar mass naked singularity is around million years while it is many orders of
magnitude larger than Hubble time in the black hole case. We then study the
collision of the neutral spherically symmetric shells made up of dust
particles. In this case, it is possible to treat the situation by exactly
taking into account the gravity due to the shells using Israel`s thin shell
formalism, and thus this treatment allows us to go beyond the test particle
approximation. The center of mass energy of collision of the shells is then
calculated in a situation analogous to the test particle case and is shown to
be bounded above. However, we find thatthe energy of a collision between two of
constituent particles of the shells at the center of mass frame can exceed the
Planck energy.
| [
{
"created": "Mon, 1 Aug 2011 11:47:54 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Sep 2012 04:06:59 GMT",
"version": "v2"
}
] | 2012-10-17 | [
[
"Patil",
"Mandar",
""
],
[
"Joshi",
"Pankaj S.",
""
],
[
"Kimura",
"Masashi",
""
],
[
"Nakao",
"Ken-ichi",
""
]
] | We explore the Reissner-Nordstr\"{o}m naked singularities with a charge $Q$ larger than its mass $M$ from the perspective of the particle acceleration. We first consider a collision between two test particles following the radial geodesics in the Reissner-Nordstr\"{o}m naked singular geometry. An initially radially ingoing particle turns back due to the repulsive effect of gravity in the vicinity of naked singularity. Such a particle then collides with an another radially ingoing particle. We show that the center of mass energy of collision taking place at $r \approx M$ is unbound, in the limit where the charge transcends the mass by arbitrarily small amount $0<1-M/Q\ll1$.The acceleration process we described avoids fine tuning of the parameters of the particle geodesics for the unbound center of mass energy of collisions and the proper time required for the process is also finite. We show that the coordinate time required for the trans-Plankian collision to occur around one solar mass naked singularity is around million years while it is many orders of magnitude larger than Hubble time in the black hole case. We then study the collision of the neutral spherically symmetric shells made up of dust particles. In this case, it is possible to treat the situation by exactly taking into account the gravity due to the shells using Israel`s thin shell formalism, and thus this treatment allows us to go beyond the test particle approximation. The center of mass energy of collision of the shells is then calculated in a situation analogous to the test particle case and is shown to be bounded above. However, we find thatthe energy of a collision between two of constituent particles of the shells at the center of mass frame can exceed the Planck energy. |
2210.01754 | Francesco Salemi | Marek J. Szczepa\'nczyk, Francesco Salemi, Sophie Bini, Tanmaya
Mishra, Gabriele Vedovato, V. Gayathri, Imre Bartos, Shubhagata Bhaumik,
Marco Drago, Odysse Halim, Claudia Lazzaro, Andrea Miani, Edoardo Milotti,
Giovanni A. Prodi, Shubhanshu Tiwari and Sergey Klimenko | Search for gravitational-wave bursts in the third Advanced LIGO-Virgo
run with coherent WaveBurst enhanced by Machine Learning | 15 pages, 7 figures | null | 10.1103/PhysRevD.107.062002 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This paper presents a search for generic short-duration gravitational-wave
(GW) transients (or GW bursts) in the data from the third observing run of
Advanced LIGO and Advanced Virgo. We use coherent WaveBurst (cWB) pipeline
enhanced with a decision-tree classification algorithm for more efficient
separation of GW signals from noise transients. The machine-learning (ML)
algorithm is trained on a representative set of noise events and a set of
simulated stochastic signals that are not correlated with any known signal
model. This training procedure preserves the model-independent nature of the
search. We demonstrate that the ML-enhanced cWB pipeline can detect GW signals
at a larger distance than previous model-independent searches. The sensitivity
improvements are achieved across the broad spectrum of simulated signals, with
the goal of testing the robustness of this model-agnostic search. At a
false-alarm rate of one event per century, the detectable signal amplitudes are
reduced up to almost an order of magnitude, most notably for the single-cycle
signal morphologies. This ML-enhanced pipeline also improves the detection
efficiency of compact binary mergers in a wide range of masses, from stellar
mass to intermediate-mass black holes, both with circular and elliptical
orbits. After excluding previously detected compact binaries, no new
gravitational-wave signals are observed for the two-fold Hanford-Livingston and
the three-fold Hanford-Livingston-Virgo detector networks. With the improved
sensitivity of the all-sky search, we obtain the most stringent constraints on
the isotropic emission of gravitational-wave energy from short-duration burst
sources.
| [
{
"created": "Tue, 4 Oct 2022 17:19:19 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Nov 2022 20:34:51 GMT",
"version": "v2"
}
] | 2023-03-15 | [
[
"Szczepańczyk",
"Marek J.",
""
],
[
"Salemi",
"Francesco",
""
],
[
"Bini",
"Sophie",
""
],
[
"Mishra",
"Tanmaya",
""
],
[
"Vedovato",
"Gabriele",
""
],
[
"Gayathri",
"V.",
""
],
[
"Bartos",
"Imre",
""
],
[
"Bhaumik",
"Shubhagata",
""
],
[
"Drago",
"Marco",
""
],
[
"Halim",
"Odysse",
""
],
[
"Lazzaro",
"Claudia",
""
],
[
"Miani",
"Andrea",
""
],
[
"Milotti",
"Edoardo",
""
],
[
"Prodi",
"Giovanni A.",
""
],
[
"Tiwari",
"Shubhanshu",
""
],
[
"Klimenko",
"Sergey",
""
]
] | This paper presents a search for generic short-duration gravitational-wave (GW) transients (or GW bursts) in the data from the third observing run of Advanced LIGO and Advanced Virgo. We use coherent WaveBurst (cWB) pipeline enhanced with a decision-tree classification algorithm for more efficient separation of GW signals from noise transients. The machine-learning (ML) algorithm is trained on a representative set of noise events and a set of simulated stochastic signals that are not correlated with any known signal model. This training procedure preserves the model-independent nature of the search. We demonstrate that the ML-enhanced cWB pipeline can detect GW signals at a larger distance than previous model-independent searches. The sensitivity improvements are achieved across the broad spectrum of simulated signals, with the goal of testing the robustness of this model-agnostic search. At a false-alarm rate of one event per century, the detectable signal amplitudes are reduced up to almost an order of magnitude, most notably for the single-cycle signal morphologies. This ML-enhanced pipeline also improves the detection efficiency of compact binary mergers in a wide range of masses, from stellar mass to intermediate-mass black holes, both with circular and elliptical orbits. After excluding previously detected compact binaries, no new gravitational-wave signals are observed for the two-fold Hanford-Livingston and the three-fold Hanford-Livingston-Virgo detector networks. With the improved sensitivity of the all-sky search, we obtain the most stringent constraints on the isotropic emission of gravitational-wave energy from short-duration burst sources. |
1607.01255 | Elias Okon | Elias Okon and Daniel Sudarsky | Black Holes, Information Loss and the Measurement Problem | 14 pages, 3 figures | null | 10.1007/s10701-016-0048-1 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The information loss paradox is often presented as an unavoidable consequence
of well-established physics. However, in order for a genuine paradox to ensue,
not-trivial assumptions about, e.g., quantum effects on spacetime, are
necessary. In this work we will be explicit about these additional, speculative
assumptions required. We will also sketch a map of the available routes to
tackle the issue, highlighting the, often overlooked, commitments demanded of
each alternative. In particular, we will display the strong link between black
holes, the issue of information loss and the measurement problem.
| [
{
"created": "Tue, 5 Jul 2016 14:07:34 GMT",
"version": "v1"
}
] | 2017-03-08 | [
[
"Okon",
"Elias",
""
],
[
"Sudarsky",
"Daniel",
""
]
] | The information loss paradox is often presented as an unavoidable consequence of well-established physics. However, in order for a genuine paradox to ensue, not-trivial assumptions about, e.g., quantum effects on spacetime, are necessary. In this work we will be explicit about these additional, speculative assumptions required. We will also sketch a map of the available routes to tackle the issue, highlighting the, often overlooked, commitments demanded of each alternative. In particular, we will display the strong link between black holes, the issue of information loss and the measurement problem. |
1801.07159 | Rom\`an R. Zapatrin | Roman Zapatrin | Timelets on causal sets | 12 pages | null | 10.13140/RG.2.2.19132.13448 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | Dual structures on causal sets called timelets are introduced, being discrete
analogs of global time coordinates. Algebraic and geometrical features of the
set of timelets on a causal set are studied. A characterization of timelets in
terms of incidence matrix of causal set is given. The connection between
timelets and preclusive coevents is established, it is shown that any timelet
has a unique decomposition over preclusive coevents. The equivalence classes of
timelets with respect to reascaling are shown to form a simplicial complex.
| [
{
"created": "Thu, 18 Jan 2018 13:50:13 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jan 2018 08:33:30 GMT",
"version": "v2"
}
] | 2018-01-26 | [
[
"Zapatrin",
"Roman",
""
]
] | Dual structures on causal sets called timelets are introduced, being discrete analogs of global time coordinates. Algebraic and geometrical features of the set of timelets on a causal set are studied. A characterization of timelets in terms of incidence matrix of causal set is given. The connection between timelets and preclusive coevents is established, it is shown that any timelet has a unique decomposition over preclusive coevents. The equivalence classes of timelets with respect to reascaling are shown to form a simplicial complex. |
1908.01691 | Mordehai Milgrom | Mordehai Milgrom | Noncovariance at low accelerations as a route to MOND | 13 pages, version accepted for publication in Phys. Rev. D | Phys. Rev. D 100, 084039 (2019) | 10.1103/PhysRevD.100.084039 | null | gr-qc astro-ph.CO astro-ph.GA hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | MOND has limelighted the fact that Newtonian dynamics (ND) and general
relativity (GR) have not been verified at accelerations below MOND's $a_0$. In
particular, we do not know that all the principles underlying ND or GR apply
below $a_0$. I discuss possible breakdown of general covariance (GC) in this
limit. This resonates well with MOND, which hinges on accelerations. Relaxing
GC affords more freedom in constructing MOND theories. I exemplify this with a
simplified theory whose gravitational Lagrangian is $\mathcal{L}_M\propto
\ell_M^{-2}\mathcal{F}(\ell_M^{2}\mathcal{R})$, where $\mathcal{R}= g^{\mu\nu}
(\Gamma^\gamma_{\mu\nu}\Gamma^\lambda_{\lambda\gamma}-\Gamma^\gamma_{\mu\lambda}
\Gamma^\lambda_{\nu\gamma})/2$. $\Gamma^\gamma_{\mu\nu}$ is the Levi-Civita
connection of a metric, $g_{\mu\nu}$, and $\ell_M=c^2/a_0$ is the MOND length.
Requiring $\mathcal{F}(z)\rightarrow z+\zeta$, for $z\gg 1$ gives GR with a
cosmological constant $\zeta c^{-4}a_0^2$ for high accelerations. In the MOND
limit $\mathcal{F}'(z\ll 1)\propto z^{1/2}$. In the nonrelativistic limit the
metric is of the form $g_{\mu\nu}\approx \eta_{\mu\nu}-2\phi\delta_{\mu\nu}$,
as in GR, but the potential $\phi$ solves a MOND, nonlinear Poisson analog.
This form of $g_{\mu\nu}$ also produces gravitational lensing as in GR only
with the MOND potential. I show that this theory is a fixed-gauge expression of
BIMOND, with the auxiliary metric constrained to be flat. The latter theory is
thus a covariantized version of the former a-la St\"{u}ckelberg. This theory is
also a special case of so-called $f(\mathcal{Q})$ theories -- aquadratic
generalizations of `symmetric, teleparallel GR', which are, in turn, also
equivalent to constrained BIMOND-type theories. (Abridged.)
| [
{
"created": "Mon, 5 Aug 2019 15:26:03 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Oct 2019 08:54:18 GMT",
"version": "v2"
}
] | 2019-10-22 | [
[
"Milgrom",
"Mordehai",
""
]
] | MOND has limelighted the fact that Newtonian dynamics (ND) and general relativity (GR) have not been verified at accelerations below MOND's $a_0$. In particular, we do not know that all the principles underlying ND or GR apply below $a_0$. I discuss possible breakdown of general covariance (GC) in this limit. This resonates well with MOND, which hinges on accelerations. Relaxing GC affords more freedom in constructing MOND theories. I exemplify this with a simplified theory whose gravitational Lagrangian is $\mathcal{L}_M\propto \ell_M^{-2}\mathcal{F}(\ell_M^{2}\mathcal{R})$, where $\mathcal{R}= g^{\mu\nu} (\Gamma^\gamma_{\mu\nu}\Gamma^\lambda_{\lambda\gamma}-\Gamma^\gamma_{\mu\lambda} \Gamma^\lambda_{\nu\gamma})/2$. $\Gamma^\gamma_{\mu\nu}$ is the Levi-Civita connection of a metric, $g_{\mu\nu}$, and $\ell_M=c^2/a_0$ is the MOND length. Requiring $\mathcal{F}(z)\rightarrow z+\zeta$, for $z\gg 1$ gives GR with a cosmological constant $\zeta c^{-4}a_0^2$ for high accelerations. In the MOND limit $\mathcal{F}'(z\ll 1)\propto z^{1/2}$. In the nonrelativistic limit the metric is of the form $g_{\mu\nu}\approx \eta_{\mu\nu}-2\phi\delta_{\mu\nu}$, as in GR, but the potential $\phi$ solves a MOND, nonlinear Poisson analog. This form of $g_{\mu\nu}$ also produces gravitational lensing as in GR only with the MOND potential. I show that this theory is a fixed-gauge expression of BIMOND, with the auxiliary metric constrained to be flat. The latter theory is thus a covariantized version of the former a-la St\"{u}ckelberg. This theory is also a special case of so-called $f(\mathcal{Q})$ theories -- aquadratic generalizations of `symmetric, teleparallel GR', which are, in turn, also equivalent to constrained BIMOND-type theories. (Abridged.) |
1604.04905 | Kirill Bronnikov | K.A. Bronnikov, Sung-Won Kim and M.V. Skvortsova | The Birkhoff theorem and string clouds | 9 two-column pages, no figures | Class. Quantum Grav. 33, 195006 (2016) | 10.1088/0264-9381/33/19/195006 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider spherically symmetric space-times in GR under the unconventional
assumptions that the spherical radius $r$ is either a constant or has a null
gradient in the $(t,x)$ subspace orthogonal to the symmetry spheres (i.e.,
$(\partial r)^2 = 0$). It is shown that solutions to the Einstein equations
with $r = \rm const$ contain an extra (fourth) spatial or temporal Killing
vector and thus satisfy the Birkhoff theorem under an additional physically
motivated condition that the lateral pressure is functionally related to the
energy density. This leads to solutions that directly generalize the
Bertotti-Robinson, Nariai and Plebanski-Hacyan solutions. Under similar
conditions, solutions with $(\partial r)^2 = 0$ but $r\ne\rm const$, supported
by an anisotropic fluid, contain a null Killing vector, which again indicates a
Birkhoff-like behavior of the system. Similar space-times supported by pure
radiation (in particular, a massless radiative scalar field) contain a null
Killing vector without additional assumptions, which leads to one more
extension of the Birkhoff theorem. Exact radial wave solutions have been found
(i) with an anisotropic fluid and (ii) with a gas of radially directed cosmic
strings (or a "string cloud") combined with pure radiation. Furthermore, it is
shown that a perfect fluid with isotropic pressure and a massive or
self-interacting scalar field cannot be sources of gravitational fields with a
null but nonzero gradient of $r$.
| [
{
"created": "Sun, 17 Apr 2016 18:29:06 GMT",
"version": "v1"
}
] | 2016-10-17 | [
[
"Bronnikov",
"K. A.",
""
],
[
"Kim",
"Sung-Won",
""
],
[
"Skvortsova",
"M. V.",
""
]
] | We consider spherically symmetric space-times in GR under the unconventional assumptions that the spherical radius $r$ is either a constant or has a null gradient in the $(t,x)$ subspace orthogonal to the symmetry spheres (i.e., $(\partial r)^2 = 0$). It is shown that solutions to the Einstein equations with $r = \rm const$ contain an extra (fourth) spatial or temporal Killing vector and thus satisfy the Birkhoff theorem under an additional physically motivated condition that the lateral pressure is functionally related to the energy density. This leads to solutions that directly generalize the Bertotti-Robinson, Nariai and Plebanski-Hacyan solutions. Under similar conditions, solutions with $(\partial r)^2 = 0$ but $r\ne\rm const$, supported by an anisotropic fluid, contain a null Killing vector, which again indicates a Birkhoff-like behavior of the system. Similar space-times supported by pure radiation (in particular, a massless radiative scalar field) contain a null Killing vector without additional assumptions, which leads to one more extension of the Birkhoff theorem. Exact radial wave solutions have been found (i) with an anisotropic fluid and (ii) with a gas of radially directed cosmic strings (or a "string cloud") combined with pure radiation. Furthermore, it is shown that a perfect fluid with isotropic pressure and a massive or self-interacting scalar field cannot be sources of gravitational fields with a null but nonzero gradient of $r$. |
2112.08951 | Dirk Puetzfeld | Peter A. Hogan, Dirk Puetzfeld | Some Gravity Waves in Isotropic Cosmologies | 12 pages | Phys. Rev. D 105, 044054 (2022) | 10.1103/PhysRevD.105.044054 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct metric perturbations of two families of isotropic expanding
universes describing gravitational waves propagating through these universes.
The waves are non--planar and owe their wave front expansion solely to the
expansion of the universes. The presence of this radiation leads to a small
perturbation of the perfect fluid matter content of the universes by the
appearance of an anisotropic stress. We then construct exact models of gravity
waves in these universes. In this case the matter content of the models
consists of the perfect fluid matter supplemented by anisotropic stress and
lightlike matter traveling with the waves. Under appropriate conditions of
approximation the lightlike matter can be neglected and the exact models
coincide with the perturbative models.
| [
{
"created": "Thu, 16 Dec 2021 15:13:26 GMT",
"version": "v1"
},
{
"created": "Sun, 27 Feb 2022 09:40:20 GMT",
"version": "v2"
}
] | 2022-03-01 | [
[
"Hogan",
"Peter A.",
""
],
[
"Puetzfeld",
"Dirk",
""
]
] | We construct metric perturbations of two families of isotropic expanding universes describing gravitational waves propagating through these universes. The waves are non--planar and owe their wave front expansion solely to the expansion of the universes. The presence of this radiation leads to a small perturbation of the perfect fluid matter content of the universes by the appearance of an anisotropic stress. We then construct exact models of gravity waves in these universes. In this case the matter content of the models consists of the perfect fluid matter supplemented by anisotropic stress and lightlike matter traveling with the waves. Under appropriate conditions of approximation the lightlike matter can be neglected and the exact models coincide with the perturbative models. |
1108.2433 | Sujitkumar Chatterjee | D. Panigrahi and S. Chatterjee | Spherically symmetric inhomogeneous model with Chaplygin gas | null | JCAP 2011 | 10.1088/1475-7516/2011/10/002 | JCAP 1110 (2011) 002 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the late time acceleration with a Chaplygin type of gas in
spherically symmetric inhomogeneous model. At the early phase we get
Einstien-deSitter type of solution generalised to inhomogeneous spacetime. But
at late stage of the evolution our solutions admit the accelerating nature of
the universe. For a large scale factor our model behaves like a ?CDM model. We
calculate the deceleration parameter for this anisotropic model, which, unlike
its homogeneous counterpart, shows that the flip is not syn- chronous occurring
early at the outer shells. This is in line with other physical processes in any
inhomogeneous models. Depending upon initial conditions our solution also gives
bouncing universe. In the absence of inhomogeneity our solution reduces to
wellknown solutions in homogeneous case. We have also calculated the effective
deceleration parameter in terms of Hubble parameter. The whole situation is
later discussed with the help of wellknown Raychaudhury equation and the
results are compared with the previous case. This work is an extension of our
recent communication where an attempt was made to see if the presence of extra
dimensions and/or inhomogeneity can trigger an inflation in a matter dominated
Lemaitre Tolman Bondi model.
| [
{
"created": "Thu, 11 Aug 2011 15:40:09 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Sep 2011 15:20:47 GMT",
"version": "v2"
}
] | 2017-02-17 | [
[
"Panigrahi",
"D.",
""
],
[
"Chatterjee",
"S.",
""
]
] | We investigate the late time acceleration with a Chaplygin type of gas in spherically symmetric inhomogeneous model. At the early phase we get Einstien-deSitter type of solution generalised to inhomogeneous spacetime. But at late stage of the evolution our solutions admit the accelerating nature of the universe. For a large scale factor our model behaves like a ?CDM model. We calculate the deceleration parameter for this anisotropic model, which, unlike its homogeneous counterpart, shows that the flip is not syn- chronous occurring early at the outer shells. This is in line with other physical processes in any inhomogeneous models. Depending upon initial conditions our solution also gives bouncing universe. In the absence of inhomogeneity our solution reduces to wellknown solutions in homogeneous case. We have also calculated the effective deceleration parameter in terms of Hubble parameter. The whole situation is later discussed with the help of wellknown Raychaudhury equation and the results are compared with the previous case. This work is an extension of our recent communication where an attempt was made to see if the presence of extra dimensions and/or inhomogeneity can trigger an inflation in a matter dominated Lemaitre Tolman Bondi model. |
1704.08036 | Marina-Aura Dariescu | Marina-Aura Dariescu, Denisa Andreea Mihu, Ciprian Dariescu | Spatially-Flat Robertson-Walker models with combined CDM and stiff
matter sources and the corresponding thermodynamics | 13 pages, 1 figure | Romanian Journal of Physics 62, 101 (2017) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present paper, we are considering a spatially-flat
Friedmann-Robertson-Walker cosmological model, fueled with stiff matter and
dust, treated as non-interacting ideal fluid sources. By solving the
corresponding Friedmann equation with a non-zero cosmological constant, we are
deriving the scale function and the fundamental cosmological parameters. Within
a thermodynamic approach, the general form of the Equation of State is
obtained, together with the explicit dependence of the energy density and
pressure on temperature.
| [
{
"created": "Wed, 26 Apr 2017 09:37:37 GMT",
"version": "v1"
}
] | 2017-04-27 | [
[
"Dariescu",
"Marina-Aura",
""
],
[
"Mihu",
"Denisa Andreea",
""
],
[
"Dariescu",
"Ciprian",
""
]
] | In the present paper, we are considering a spatially-flat Friedmann-Robertson-Walker cosmological model, fueled with stiff matter and dust, treated as non-interacting ideal fluid sources. By solving the corresponding Friedmann equation with a non-zero cosmological constant, we are deriving the scale function and the fundamental cosmological parameters. Within a thermodynamic approach, the general form of the Equation of State is obtained, together with the explicit dependence of the energy density and pressure on temperature. |
2208.00138 | Yu Han | Yu Han | Quantisation ambiguities and the effective dynamics of scalar-tensor
theories in loop quantum cosmology | 32 pages, 7 figures | Class. Quantum Grav. 39 (2022) 245009 | 10.1088/1361-6382/aca239 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hamiltonian constraint of scalar-tensor theories in the Jordan frame is
quantised using three quantisation prescriptions in loop quantum cosmology,
from which we obtain three different effective Hamiltonian constraints. The
corresponding effective equations of motion derived from these effective
Hamiltonian constraints turn out to be drastically different. The implications
of each set of effective equations of motion are discussed in detail. In the
latter half of this paper, as a concrete example, we study the effective
dynamics of a specific model with the non-minimal coupling function
$F(\phi)=1+\xi\kappa\phi^2$ and self-interacting quartic potential. Using
numerical results, we find different features for different effective dynamics.
Moreover, it is also found that the spacetime singularity is absent and the
cosmological bounce exists in each effective dynamics of this model.
| [
{
"created": "Sat, 30 Jul 2022 04:17:56 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Dec 2022 02:49:34 GMT",
"version": "v2"
}
] | 2022-12-08 | [
[
"Han",
"Yu",
""
]
] | The Hamiltonian constraint of scalar-tensor theories in the Jordan frame is quantised using three quantisation prescriptions in loop quantum cosmology, from which we obtain three different effective Hamiltonian constraints. The corresponding effective equations of motion derived from these effective Hamiltonian constraints turn out to be drastically different. The implications of each set of effective equations of motion are discussed in detail. In the latter half of this paper, as a concrete example, we study the effective dynamics of a specific model with the non-minimal coupling function $F(\phi)=1+\xi\kappa\phi^2$ and self-interacting quartic potential. Using numerical results, we find different features for different effective dynamics. Moreover, it is also found that the spacetime singularity is absent and the cosmological bounce exists in each effective dynamics of this model. |
2305.18871 | Adailton Ara\'ujo Filho | A. A. Ara\'ujo Filho, H. Hassanabadi, N. Heidari, J. Kr\'iz, S. Zare | Gravitational traces of bumblebee gravity in metric-affine formalism | 32 pages, 8 figures and 4 tables | Classical and Quantum Gravity, 41 (2024) 055003 | 10.1088/1361-6382/ad1712 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work explores various manifestations of bumblebee gravity within the
metric-affine formalism. We investigate the impact of the Lorentz violation
parameter, denoted as $X$, on the modification of the Hawking temperature. Our
calculations reveal that as $X$ increases, the values of the Hawking
temperature attenuate. To examine the behavior of massless scalar
perturbations, specifically the quasinormal modes, we employ the WKB method.
The transmission and reflection coefficients are determined through our
calculations. The outcomes indicate that a stronger Lorentz-violating parameter
results in slower damping oscillations of gravitational waves. To comprehend
the influence of the quasinormal spectrum on time-dependent scattering
phenomena, we present a detailed analysis of scalar perturbations in the
time-domain solution. Additionally, we conduct an investigation on shadows,
revealing that larger values of $X$ correspond to larger shadow radii.
Furthermore, we constrain the magnitude of the shadow radii using the EHT
horizon-scale image of $Sgr A^*$. Finally, we calculate both the time delay and
the deflection angle.
| [
{
"created": "Tue, 30 May 2023 09:05:37 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Dec 2023 20:46:21 GMT",
"version": "v2"
}
] | 2024-02-01 | [
[
"Filho",
"A. A. Araújo",
""
],
[
"Hassanabadi",
"H.",
""
],
[
"Heidari",
"N.",
""
],
[
"Kríz",
"J.",
""
],
[
"Zare",
"S.",
""
]
] | This work explores various manifestations of bumblebee gravity within the metric-affine formalism. We investigate the impact of the Lorentz violation parameter, denoted as $X$, on the modification of the Hawking temperature. Our calculations reveal that as $X$ increases, the values of the Hawking temperature attenuate. To examine the behavior of massless scalar perturbations, specifically the quasinormal modes, we employ the WKB method. The transmission and reflection coefficients are determined through our calculations. The outcomes indicate that a stronger Lorentz-violating parameter results in slower damping oscillations of gravitational waves. To comprehend the influence of the quasinormal spectrum on time-dependent scattering phenomena, we present a detailed analysis of scalar perturbations in the time-domain solution. Additionally, we conduct an investigation on shadows, revealing that larger values of $X$ correspond to larger shadow radii. Furthermore, we constrain the magnitude of the shadow radii using the EHT horizon-scale image of $Sgr A^*$. Finally, we calculate both the time delay and the deflection angle. |
gr-qc/0212028 | Stefan Hollands | Stefan Hollands | A General PCT Theorem for the Operator Product Expansion in Curved
Spacetime | 40 pages, latex, no figures | Commun.Math.Phys. 244 (2004) 209-244 | 10.1007/s00220-003-0991-5 | null | gr-qc hep-th | null | We consider the operator product expansion for quantum field theories on
general analytic 4-dimensional curved spacetimes within an axiomatic framework.
We prove under certain general, model-independent assumptions that such an
expansion necessarily has to be invariant under a simultaneous reversal of
parity, time, and charge (PCT) in the following sense: The coefficients in the
expansion of a product of fields on a curved spacetime with a given choice of
time and space orientation are equal (modulo complex conjugation) to the
coefficients for the product of the corresponding charge conjugate fields on
the spacetime with the opposite time and space orientation. We propose that
this result should be viewed as a replacement of the usual PCT theorem in
Minkowski spacetime, at least in as far as the algebraic structure of the
quantum fields at short distances is concerned.
| [
{
"created": "Fri, 6 Dec 2002 00:08:25 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Hollands",
"Stefan",
""
]
] | We consider the operator product expansion for quantum field theories on general analytic 4-dimensional curved spacetimes within an axiomatic framework. We prove under certain general, model-independent assumptions that such an expansion necessarily has to be invariant under a simultaneous reversal of parity, time, and charge (PCT) in the following sense: The coefficients in the expansion of a product of fields on a curved spacetime with a given choice of time and space orientation are equal (modulo complex conjugation) to the coefficients for the product of the corresponding charge conjugate fields on the spacetime with the opposite time and space orientation. We propose that this result should be viewed as a replacement of the usual PCT theorem in Minkowski spacetime, at least in as far as the algebraic structure of the quantum fields at short distances is concerned. |
2105.04689 | Henrique Boschi-Filho | J. P. Morais Gra\c{c}a, Eduardo Folco Capossoli, Henrique Boschi-Filho
and Iarley P. Lobo | Joule-Thomson expansion for quantum corrected AdS-Reissner-Nordstrom
black holes in Kiselev spacetime | V2: 18 pages, 7 figures. In this version, we included a discussion of
the First Law and a deduction of equations with a non-zero pressure even at
zero inversion temperature that explain our (unchanged) numerical results.
This version matches the published one in PRD | Physical Review D 107, 024045 (2023) | 10.1103/PhysRevD.107.024045 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this work we study the inversion temperature associated with the
Joule-Thomson expansion from the thermodynamics of AdS-Reissner-N\"ordstrom
black holes. We include quantum corrections in a cosmological fluid that can
describe phantom dark matter or quintessence, both in a Kiselev scenario. The
description of such physical systems involves numerical solutions and the
results are presented as temperature-pressure plots for various values of the
parameters of our model. We find non-zero minimum inversion temperatures as
well as non-zero minimum pressures depending on the values of those parameters.
Completing our study, we also find isenthalpic curves associated with black
hole fixed mass processes.
| [
{
"created": "Mon, 10 May 2021 22:08:36 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Apr 2024 22:48:47 GMT",
"version": "v2"
}
] | 2024-04-25 | [
[
"Graça",
"J. P. Morais",
""
],
[
"Capossoli",
"Eduardo Folco",
""
],
[
"Boschi-Filho",
"Henrique",
""
],
[
"Lobo",
"Iarley P.",
""
]
] | In this work we study the inversion temperature associated with the Joule-Thomson expansion from the thermodynamics of AdS-Reissner-N\"ordstrom black holes. We include quantum corrections in a cosmological fluid that can describe phantom dark matter or quintessence, both in a Kiselev scenario. The description of such physical systems involves numerical solutions and the results are presented as temperature-pressure plots for various values of the parameters of our model. We find non-zero minimum inversion temperatures as well as non-zero minimum pressures depending on the values of those parameters. Completing our study, we also find isenthalpic curves associated with black hole fixed mass processes. |
0909.0190 | Pavel Ivanov | Pavel Ivanov | On the dynamics of exotic matter: towards creation of Perpetuum Mobile
of third kind | accepted to Physics Letters B | Phys.Lett.B680:212-216,2009 | 10.1016/j.physletb.2009.08.057 | null | gr-qc astro-ph.CO hep-th physics.flu-dyn | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The one-dimensional dynamics of a classical ideal 'exotic' fluid with
equation of state $p=p(\epsilon) < 0$ violating the weak energy condition is
discussed. Under certain assumptions it is shown that the well-known
Hwa-Bjorken exact solution of one-dimensional relativistic hydrodynamics is
confined within the future/past light cone. It is also demonstrated that the
total energy of such a solution is equal to zero and that there are regions
within the light cone with negative $(-)$ and positive $(+)$ total energies.
For certain equations of state there is a continuous energy transfer from the
$(-)$-regions to the $(+)$-regions resulting in indefinite growth of energy in
the $(+)$ regions with time, which may be interpreted as action of a specific
'Perpetuum Mobile' (Perpetuum Motion). It is speculated that if it is possible
to construct a three-dimensional non-stationary flow of an exotic fluid having
a finite negative value of energy such a situation would also occur. Such a
flow may continuously transfer positive energy to gravitational waves,
resulting in a runaway. It is conjectured that theories plagued by such
solutions should be discarded as inherently unstable.
| [
{
"created": "Tue, 1 Sep 2009 14:15:54 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Ivanov",
"Pavel",
""
]
] | The one-dimensional dynamics of a classical ideal 'exotic' fluid with equation of state $p=p(\epsilon) < 0$ violating the weak energy condition is discussed. Under certain assumptions it is shown that the well-known Hwa-Bjorken exact solution of one-dimensional relativistic hydrodynamics is confined within the future/past light cone. It is also demonstrated that the total energy of such a solution is equal to zero and that there are regions within the light cone with negative $(-)$ and positive $(+)$ total energies. For certain equations of state there is a continuous energy transfer from the $(-)$-regions to the $(+)$-regions resulting in indefinite growth of energy in the $(+)$ regions with time, which may be interpreted as action of a specific 'Perpetuum Mobile' (Perpetuum Motion). It is speculated that if it is possible to construct a three-dimensional non-stationary flow of an exotic fluid having a finite negative value of energy such a situation would also occur. Such a flow may continuously transfer positive energy to gravitational waves, resulting in a runaway. It is conjectured that theories plagued by such solutions should be discarded as inherently unstable. |
gr-qc/9801074 | S. Mignemi | S. Mignemi | The dynamical structure of four-dimensional Chamseddine's gauge theory
of gravity | 14 pages, plain TeX, section 5 revised | Phys.Rev. D59 (1999) 064022 | 10.1103/PhysRevD.59.064022 | INFNCA-TH9801 | gr-qc hep-th | null | We perform the Dirac hamiltonian analysis of a four-dimensional gauge theory
of gravity with an action of topological type, which generalizes some
well-known two-dimensional models. We show that, in contrast with the
two-dimensional case, the theory has a non-vanishing number of dynamical
degrees of freedom and that its structure is very similar to higher-dimensional
Chern-Simons gravity.
| [
{
"created": "Wed, 21 Jan 1998 17:35:43 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Feb 1998 17:48:10 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Mignemi",
"S.",
""
]
] | We perform the Dirac hamiltonian analysis of a four-dimensional gauge theory of gravity with an action of topological type, which generalizes some well-known two-dimensional models. We show that, in contrast with the two-dimensional case, the theory has a non-vanishing number of dynamical degrees of freedom and that its structure is very similar to higher-dimensional Chern-Simons gravity. |
1312.5375 | Sylvain Marsat | Sylvain Marsat, Luc Blanchet, Alejandro Bohe, Guillaume Faye | Gravitational waves from spinning compact object binaries: New
post-Newtonian results | 7 pages; to appear in the proceedings of the conference HTGRG (Quy
Nhon, Vietnam, 2013) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report on recent results obtained in the post-Newtonian framework for the
modelling of the gravitational waves emitted by binary systems of spinning
compact objects (black holes and/or neutron stars). These new results are
obtained at the spin-orbit (linear-in-spin) level and solving Einstein's field
equations iteratively in harmonic coordinates as well as the multipolar
post-Newtonian formalism. The dynamics of the binary was tackled at the
next-to-next-to-leading order, corresponding to the 3.5 post-Newtonian (PN)
order for maximally spinning objects, and the result is found to be consistent
with a previously obtained reduced Hamiltonian in the ADM approach. The
corresponding contribution to the energy flux emitted by the binary was
obtained at the 3.5PN order, as well as the next-to-leading 4PN tail
contribution to this flux, an imprint of the non-linearity in the propagation
of the wave. These new terms can be used to build more accurate PN templates
for the next generation of gravitational wave detectors. We give an
illustrative estimate of the quantitative relevance of the new terms in the
orbital phasing of the binary.
| [
{
"created": "Thu, 19 Dec 2013 00:08:31 GMT",
"version": "v1"
}
] | 2013-12-20 | [
[
"Marsat",
"Sylvain",
""
],
[
"Blanchet",
"Luc",
""
],
[
"Bohe",
"Alejandro",
""
],
[
"Faye",
"Guillaume",
""
]
] | We report on recent results obtained in the post-Newtonian framework for the modelling of the gravitational waves emitted by binary systems of spinning compact objects (black holes and/or neutron stars). These new results are obtained at the spin-orbit (linear-in-spin) level and solving Einstein's field equations iteratively in harmonic coordinates as well as the multipolar post-Newtonian formalism. The dynamics of the binary was tackled at the next-to-next-to-leading order, corresponding to the 3.5 post-Newtonian (PN) order for maximally spinning objects, and the result is found to be consistent with a previously obtained reduced Hamiltonian in the ADM approach. The corresponding contribution to the energy flux emitted by the binary was obtained at the 3.5PN order, as well as the next-to-leading 4PN tail contribution to this flux, an imprint of the non-linearity in the propagation of the wave. These new terms can be used to build more accurate PN templates for the next generation of gravitational wave detectors. We give an illustrative estimate of the quantitative relevance of the new terms in the orbital phasing of the binary. |
2003.03720 | Francisco Tello Ortiz | S. K. Maurya, Abdelghani Errehymy, Ksh. Newton Singh, Francisco
Tello-Ortiz, Mohammed Daoud | A gravitational decoupling MGD model in modified $f(R,T)$ gravity theory | 3 tables, 12 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present paper is devoted to investigating the possibility of getting
stellar interiors for ultra-dense compact spherical systems portraying an
anisotropic matter distribution employing the gravitational decoupling by means
of Minimal Geometric Deformation (MGD) procedure within the modified theory of
f(R,T) gravity. According to this theory, the covariant divergence of
stress-energy tensor does not vanish, hence the movement of classical particles
does not follow geodesics resulting in an extra acceleration which suffices the
late-time acceleration of the universe without adopting to exotic matter
fields. In this regard, we have considered the algebraic function as f(R, {\rm
T})= R+2\chi T, the corresponding effective stress-energy tensor is conserved
as well as the exact solutions are derived, where $\chi$ indicates a coupling
constant. Moreover, the physical quantities associated with the new solutions
are well-behaved from the physical and mathematical point of view as well as
free of geometrical singularities, violation of the causality condition,
non-decreasing thermodynamic functions. Thereafter, the physical viability of
the obtained model is affirmed by performing several physical tests of the main
salient features such as energy density, radial, and tangential pressure,
anisotropy effect, dynamical equilibrium, energy conditions, and dynamical
stability. On the other hand, we have generated the M-R curves from our
solutions in the four different scenarios, including GR, GR+MGD, f(R,T) and
f(R,T)+MGD, and we found a perfect fit for many compact spherical objects in
these scenarios by changing the gravitational decoupling constant \alpha and
the coupling constant \chi as free parameters. The present study reveals that
the modified f(R,T) gravity through gravitational decoupling by means of MGD
method is a suitable theory to explain compact stellar spherical systems....
| [
{
"created": "Sun, 8 Mar 2020 05:07:52 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Mar 2020 20:05:15 GMT",
"version": "v2"
}
] | 2020-03-12 | [
[
"Maurya",
"S. K.",
""
],
[
"Errehymy",
"Abdelghani",
""
],
[
"Singh",
"Ksh. Newton",
""
],
[
"Tello-Ortiz",
"Francisco",
""
],
[
"Daoud",
"Mohammed",
""
]
] | The present paper is devoted to investigating the possibility of getting stellar interiors for ultra-dense compact spherical systems portraying an anisotropic matter distribution employing the gravitational decoupling by means of Minimal Geometric Deformation (MGD) procedure within the modified theory of f(R,T) gravity. According to this theory, the covariant divergence of stress-energy tensor does not vanish, hence the movement of classical particles does not follow geodesics resulting in an extra acceleration which suffices the late-time acceleration of the universe without adopting to exotic matter fields. In this regard, we have considered the algebraic function as f(R, {\rm T})= R+2\chi T, the corresponding effective stress-energy tensor is conserved as well as the exact solutions are derived, where $\chi$ indicates a coupling constant. Moreover, the physical quantities associated with the new solutions are well-behaved from the physical and mathematical point of view as well as free of geometrical singularities, violation of the causality condition, non-decreasing thermodynamic functions. Thereafter, the physical viability of the obtained model is affirmed by performing several physical tests of the main salient features such as energy density, radial, and tangential pressure, anisotropy effect, dynamical equilibrium, energy conditions, and dynamical stability. On the other hand, we have generated the M-R curves from our solutions in the four different scenarios, including GR, GR+MGD, f(R,T) and f(R,T)+MGD, and we found a perfect fit for many compact spherical objects in these scenarios by changing the gravitational decoupling constant \alpha and the coupling constant \chi as free parameters. The present study reveals that the modified f(R,T) gravity through gravitational decoupling by means of MGD method is a suitable theory to explain compact stellar spherical systems.... |
1108.3855 | J. Robel Arenas | J. Robel Arenas, J. Manuel Tejeiro | Entanglement Entropy of Black Shells | 30 pages, no figures | Nuovo Cim.B125:1223-1248,2010 | 10.1393/ncb/i2010-10922-3 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a coherent account of how the entanglement interpretation,
thermofield dynamical description and the brick wall formulations (with the
ground state correctly identified) fit into a connected and self-consistent
explanation of what Bekenstein-Hawking entropy is, and where it is located.
| [
{
"created": "Thu, 18 Aug 2011 21:01:53 GMT",
"version": "v1"
}
] | 2011-09-21 | [
[
"Arenas",
"J. Robel",
""
],
[
"Tejeiro",
"J. Manuel",
""
]
] | We present a coherent account of how the entanglement interpretation, thermofield dynamical description and the brick wall formulations (with the ground state correctly identified) fit into a connected and self-consistent explanation of what Bekenstein-Hawking entropy is, and where it is located. |
0806.2505 | Supratik Pal Dr | Supratik Pal | Brane cosmology, Weyl fluid, and density perturbations | 18 pages, 1 figure, accepted for publication in Phys.Rev.D | Phys.Rev.D78:043517,2008 | 10.1103/PhysRevD.78.043517 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a technique to study relativistic perturbations in the generalised
brane cosmological scenario, which is a generalisation of the multi-fluid
cosmological perturbations to brane cosmology. The novelty of the technique
lies in the inclusion of a radiative bulk which is responsible for bulk-brane
energy exchange, and in turn, modifies the standard perturbative analysis to a
great extent. The analysis involves a geometric fluid -- called the Weyl fluid
-- whose nature and role have been studied extensively both for the empty bulk
and the radiative bulk scenario. Subsequently, we find that this Weyl fluid can
be a possible geometric candidate for dark matter in this generalised brane
cosmological framework.
| [
{
"created": "Mon, 16 Jun 2008 07:43:16 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Jun 2008 06:20:23 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Pal",
"Supratik",
""
]
] | We develop a technique to study relativistic perturbations in the generalised brane cosmological scenario, which is a generalisation of the multi-fluid cosmological perturbations to brane cosmology. The novelty of the technique lies in the inclusion of a radiative bulk which is responsible for bulk-brane energy exchange, and in turn, modifies the standard perturbative analysis to a great extent. The analysis involves a geometric fluid -- called the Weyl fluid -- whose nature and role have been studied extensively both for the empty bulk and the radiative bulk scenario. Subsequently, we find that this Weyl fluid can be a possible geometric candidate for dark matter in this generalised brane cosmological framework. |
1408.2442 | Florent Michel | Xavier Busch, Florent Michel, Renaud Parentani | Suppression of infrared instability in trans-sonic flows by condensation
of zero-frequency short wave length phonons | Final version oublished in PRD (15 pages, 9 figures) | Phys. Rev. D 90, 105005 (2014) | 10.1103/PhysRevD.90.105005 | LPT-Orsay-15-02 | gr-qc cond-mat.quant-gas physics.flu-dyn | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the peculiar infrared instability that characterizes stationary
inhomogeneous flows when their velocity crosses the sound speed by decreasing
values. For definiteness, we work in the context of one dimensional atomic Bose
condensates. These flows are unstable under ultra low real frequency
perturbations because of the unbounded mode amplification near the sonic
horizon. This results in a condensation of low frequency phonons which produces
a spatially structured flow in the supersonic domain. Numerical simulations
reveal that this zero-frequency undulation suppresses the instability when its
spatial extension is infinite, and when its phase is near that of a "shadow
soliton" solution attached to the sonic horizon. These phenomena are akin to
the condensation of rotons in flowing superfluid helium-4 when exceeding the
Landau velocity. They also pertain to shallow water waves propagating on
transcritical flows.
| [
{
"created": "Mon, 11 Aug 2014 15:30:03 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Nov 2014 10:41:55 GMT",
"version": "v2"
},
{
"created": "Fri, 6 Feb 2015 08:14:55 GMT",
"version": "v3"
}
] | 2015-02-09 | [
[
"Busch",
"Xavier",
""
],
[
"Michel",
"Florent",
""
],
[
"Parentani",
"Renaud",
""
]
] | We analyze the peculiar infrared instability that characterizes stationary inhomogeneous flows when their velocity crosses the sound speed by decreasing values. For definiteness, we work in the context of one dimensional atomic Bose condensates. These flows are unstable under ultra low real frequency perturbations because of the unbounded mode amplification near the sonic horizon. This results in a condensation of low frequency phonons which produces a spatially structured flow in the supersonic domain. Numerical simulations reveal that this zero-frequency undulation suppresses the instability when its spatial extension is infinite, and when its phase is near that of a "shadow soliton" solution attached to the sonic horizon. These phenomena are akin to the condensation of rotons in flowing superfluid helium-4 when exceeding the Landau velocity. They also pertain to shallow water waves propagating on transcritical flows. |
1606.06098 | Jishnu Suresh | Jishnu Suresh and V. C. Kuriakose | Geometrothermodynamics of BTZ black hole in new massive gravity | 13 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1603.00981, arXiv:1605.00142 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the thermodynamics as well as thermodynamic geometry of
chargeless BTZ black hole solution in new massive gravity. Phase structure and
thermodynamic stability of the system is analyzed using the
Geometrothermodynamic approach. The phase transition between BTZ black hole
space time and thermal AdS$_{3}$ soliton is studied using the same approach and
the existence of a second order phase transition is examined.
| [
{
"created": "Mon, 20 Jun 2016 12:58:30 GMT",
"version": "v1"
}
] | 2016-06-21 | [
[
"Suresh",
"Jishnu",
""
],
[
"Kuriakose",
"V. C.",
""
]
] | We investigate the thermodynamics as well as thermodynamic geometry of chargeless BTZ black hole solution in new massive gravity. Phase structure and thermodynamic stability of the system is analyzed using the Geometrothermodynamic approach. The phase transition between BTZ black hole space time and thermal AdS$_{3}$ soliton is studied using the same approach and the existence of a second order phase transition is examined. |
1609.08166 | Peter Taylor | Peter Taylor and Cormac Breen | A Mode-Sum Prescription for Vacuum Polarization in Odd Dimensions | New references added. Minor edits | Phys. Rev. D 94, 125024 (2016) | 10.1103/PhysRevD.94.125024 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new mode-sum regularization prescription for computing the
vacuum polarization of a scalar field in static spherically-symmetric black
hole spacetimes in odd dimensions. This is the first general and systematic
approach to regularized vacuum polarization in higher dimensions. Remarkably,
the regularization parameters can be computed in closed form in arbitrary
dimensions and for arbitrary metric function $f(r)$. In fact, we show that in
spite of the increasing severity and number of the divergences to be
regularized, the method presented is mostly agnostic to the number of
dimensions. Finally, as an explicit example of our method, we show plots for
vacuum polarization in the Schwarzschild-Tangherlini spacetime for odd
$d=5,...,11$.
| [
{
"created": "Mon, 26 Sep 2016 20:00:06 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Oct 2016 12:16:43 GMT",
"version": "v2"
}
] | 2017-01-04 | [
[
"Taylor",
"Peter",
""
],
[
"Breen",
"Cormac",
""
]
] | We present a new mode-sum regularization prescription for computing the vacuum polarization of a scalar field in static spherically-symmetric black hole spacetimes in odd dimensions. This is the first general and systematic approach to regularized vacuum polarization in higher dimensions. Remarkably, the regularization parameters can be computed in closed form in arbitrary dimensions and for arbitrary metric function $f(r)$. In fact, we show that in spite of the increasing severity and number of the divergences to be regularized, the method presented is mostly agnostic to the number of dimensions. Finally, as an explicit example of our method, we show plots for vacuum polarization in the Schwarzschild-Tangherlini spacetime for odd $d=5,...,11$. |
2005.12284 | Vitor Cardoso | Vitor Cardoso, Arianna Foschi, Miguel Zilhao | Collective scalarization or tachyonization: when averaging fails | 6 pages, version to appear in Physical Review Letters | null | 10.1103/PhysRevLett.124.221104 | null | gr-qc cond-mat.other hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Certain scalar-tensor theories of gravity provide negative-energy, tachyonic
modes to a fundamental scalar inside matter, giving rise to non-perturbative
phenomena around compact stars. Studies of this and other tachyonic
instabilities always average over local matter properties. We use elementary,
flat space models to understand possible collective effects and the accuracy of
the averaging procedure. In particular, we consider bodies made of elementary
constituents which do not, in isolation, scalarize because their compactness
${\cal C}$ is too small, ${\cal C}\lesssim {\cal C}_{\rm crit}$. We show that
when the individual constituents have compactness smaller but close to the
threshold, one is able to scalarize composite bodies through collective
effects, and the compactness of the composite body can be made arbitrarily
small. On the other hand, our results suggest that when the fundamental
building blocks have very low compactness, then scalarization of the composite
body requires a global compactness ${\cal C}_{\rm global}\gtrsim {\cal C}_{\rm
crit}$. Thus, our results rule out scalarization of dilute bodies via
collective effects.
| [
{
"created": "Mon, 25 May 2020 18:00:02 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Jun 2020 15:20:16 GMT",
"version": "v2"
}
] | 2020-06-17 | [
[
"Cardoso",
"Vitor",
""
],
[
"Foschi",
"Arianna",
""
],
[
"Zilhao",
"Miguel",
""
]
] | Certain scalar-tensor theories of gravity provide negative-energy, tachyonic modes to a fundamental scalar inside matter, giving rise to non-perturbative phenomena around compact stars. Studies of this and other tachyonic instabilities always average over local matter properties. We use elementary, flat space models to understand possible collective effects and the accuracy of the averaging procedure. In particular, we consider bodies made of elementary constituents which do not, in isolation, scalarize because their compactness ${\cal C}$ is too small, ${\cal C}\lesssim {\cal C}_{\rm crit}$. We show that when the individual constituents have compactness smaller but close to the threshold, one is able to scalarize composite bodies through collective effects, and the compactness of the composite body can be made arbitrarily small. On the other hand, our results suggest that when the fundamental building blocks have very low compactness, then scalarization of the composite body requires a global compactness ${\cal C}_{\rm global}\gtrsim {\cal C}_{\rm crit}$. Thus, our results rule out scalarization of dilute bodies via collective effects. |
1711.02933 | Saskia Grunau | Saskia Grunau, Hendrik Neumann, Stephan Reimers | Geodesic motion in the five-dimensional Myers-Perry-AdS spacetime | References added, minor corrections | Phys. Rev. D 97, 044011 (2018) | 10.1103/PhysRevD.97.044011 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we study the geodesic motion of test particles and light in
the five-dimensional Myers-Perry-anti de Sitter spacetime. We derive the
equations of motion and present their solutions in terms of the Weierstra{\ss}
$\wp$-, $\sigma$- and $\zeta$-functions. With the help of parametric diagrams
and effective potentials we analyze the geodesic motion and give a list of all
possible orbit types for timelike, null and spacelike geodesics. We plot
examples of the orbits and take a look at the photon region in five dimensions.
Furthermore we study spacelike geodesics and their relation to the AdS/CFT
correspondence.
| [
{
"created": "Wed, 8 Nov 2017 13:14:42 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Feb 2018 16:31:38 GMT",
"version": "v2"
}
] | 2018-02-12 | [
[
"Grunau",
"Saskia",
""
],
[
"Neumann",
"Hendrik",
""
],
[
"Reimers",
"Stephan",
""
]
] | In this article we study the geodesic motion of test particles and light in the five-dimensional Myers-Perry-anti de Sitter spacetime. We derive the equations of motion and present their solutions in terms of the Weierstra{\ss} $\wp$-, $\sigma$- and $\zeta$-functions. With the help of parametric diagrams and effective potentials we analyze the geodesic motion and give a list of all possible orbit types for timelike, null and spacelike geodesics. We plot examples of the orbits and take a look at the photon region in five dimensions. Furthermore we study spacelike geodesics and their relation to the AdS/CFT correspondence. |
1801.08542 | Antoine Klein | Antoine Klein, Yannick Boetzel, Achamveedu Gopakumar, Philippe Jetzer,
Lorenzo de Vittori | Fourier domain gravitational waveforms for precessing eccentric binaries | 23 pages, 13 figures | Phys. Rev. D 98, 104043 (2018) | 10.1103/PhysRevD.98.104043 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We build two families of inspiral waveforms for precessing binaries on
eccentric orbits in the Fourier domain. To achieve this, we use a small
eccentricity expansion of the waveform amplitudes in order to separate the
periastron precession timescale from the orbital timescale, and use a shifted
uniform asymptotics transformation to compute the Fourier transform in the
presence of spin-induced precession. We show that the resulting waveforms can
yield a median faithfulness above 0.993 when compared to an equivalent time
domain waveform with an initial eccentricity of $e_0 \approx 0.3$. We also show
that when the spins are large, using a circular waveform can potentially lead
to significant biases in the recovery of the parameters, even when the system
has fully circularized, particularly when the accumulated number of cycles is
large. This is an effect of the residual eccentricity present when the objects
forming the binary have nonvanishing spin components in the orbital plane.
| [
{
"created": "Thu, 25 Jan 2018 19:00:02 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Nov 2018 17:23:56 GMT",
"version": "v2"
}
] | 2018-11-29 | [
[
"Klein",
"Antoine",
""
],
[
"Boetzel",
"Yannick",
""
],
[
"Gopakumar",
"Achamveedu",
""
],
[
"Jetzer",
"Philippe",
""
],
[
"de Vittori",
"Lorenzo",
""
]
] | We build two families of inspiral waveforms for precessing binaries on eccentric orbits in the Fourier domain. To achieve this, we use a small eccentricity expansion of the waveform amplitudes in order to separate the periastron precession timescale from the orbital timescale, and use a shifted uniform asymptotics transformation to compute the Fourier transform in the presence of spin-induced precession. We show that the resulting waveforms can yield a median faithfulness above 0.993 when compared to an equivalent time domain waveform with an initial eccentricity of $e_0 \approx 0.3$. We also show that when the spins are large, using a circular waveform can potentially lead to significant biases in the recovery of the parameters, even when the system has fully circularized, particularly when the accumulated number of cycles is large. This is an effect of the residual eccentricity present when the objects forming the binary have nonvanishing spin components in the orbital plane. |
2104.11362 | Takeshi Chiba | Takeshi Chiba | Spontaneous Scalarization in Scalar-Tensor Theories with Conformal
Symmetry as an Attractor | 15 pages, 7 figures, updated to match the published version | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by constant-G theory, we introduce a one-parameter family of
scalar-tensor theories as an extension of constant-G theory in which the
conformal symmetry is a cosmological attractor. Since the model has the
coupling function of negative curvature, we expect spontaneous scalarization
occurs and the parameter is constrained by pulsar-timing measurements. Modeling
neutron stars with realistic equation of states, we study the structure of
neutron stars and calculate the effective scalar coupling with the neutron star
in these theories. We find that within the parameter region where the
observational constraints are satisfied, the effective scalar coupling almost
coincides with that derived using the quadratic model with the same curvature.
This indicates that the constraints obtained by the quadratic model will be
used to limit the curvature of the coupling function universally in the future.
| [
{
"created": "Fri, 23 Apr 2021 00:52:59 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Apr 2021 12:47:11 GMT",
"version": "v2"
},
{
"created": "Tue, 12 Oct 2021 01:04:53 GMT",
"version": "v3"
},
{
"created": "Thu, 20 Jan 2022 02:43:53 GMT",
"version": "v4"
}
] | 2022-01-21 | [
[
"Chiba",
"Takeshi",
""
]
] | Motivated by constant-G theory, we introduce a one-parameter family of scalar-tensor theories as an extension of constant-G theory in which the conformal symmetry is a cosmological attractor. Since the model has the coupling function of negative curvature, we expect spontaneous scalarization occurs and the parameter is constrained by pulsar-timing measurements. Modeling neutron stars with realistic equation of states, we study the structure of neutron stars and calculate the effective scalar coupling with the neutron star in these theories. We find that within the parameter region where the observational constraints are satisfied, the effective scalar coupling almost coincides with that derived using the quadratic model with the same curvature. This indicates that the constraints obtained by the quadratic model will be used to limit the curvature of the coupling function universally in the future. |
1603.09353 | Oleg Zaslavskii | O. B. Zaslavskii | Schwarzschild black hole as particle accelerator of spinning particles | 8 pages. Typose corrected. Final version | Europhys. Lett. 114 (2016) 30003 | 10.1209/0295-5075/114/30003 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that in the Schwarzschild background there exists direct
counterpart of the Ba\~{n}ados-Silk-West effect for spinning particles. This
means that if two particles collide near the black hole horizon, their energy
in the centre of mass frame can grow unbounded. In doing so, the crucial role
is played by so-called near-critical trajectories when particle's parameters
are almost fine-tuned. Direct scenario of the collision under discussion is
possible with restriction on the energy-to-mass ratio \thinspace
$E/m<\frac{1}{2\sqrt{3}}$ only. However, if one takes into account multiple
scattering, this becomes possible for $E\geq m$ as well.
| [
{
"created": "Wed, 30 Mar 2016 20:01:05 GMT",
"version": "v1"
},
{
"created": "Fri, 13 May 2016 09:43:40 GMT",
"version": "v2"
},
{
"created": "Wed, 1 Jun 2016 20:53:25 GMT",
"version": "v3"
}
] | 2016-06-22 | [
[
"Zaslavskii",
"O. B.",
""
]
] | It is shown that in the Schwarzschild background there exists direct counterpart of the Ba\~{n}ados-Silk-West effect for spinning particles. This means that if two particles collide near the black hole horizon, their energy in the centre of mass frame can grow unbounded. In doing so, the crucial role is played by so-called near-critical trajectories when particle's parameters are almost fine-tuned. Direct scenario of the collision under discussion is possible with restriction on the energy-to-mass ratio \thinspace $E/m<\frac{1}{2\sqrt{3}}$ only. However, if one takes into account multiple scattering, this becomes possible for $E\geq m$ as well. |
gr-qc/0612005 | Daniel Sudarsky | Daniel Sudarsky | The Seeds of Cosmic structure as a door to New Physics | Prepared for the proceedings of the conference NEBXII " Recent
Developments in Gravity", Napfio Grece June 2006. LateX, 15 pages | J.Phys.Conf.Ser.68:012029,2007 | 10.1088/1742-6596/68/1/012029 | null | gr-qc | null | There is something missing in our understanding of the origin of the seeds of
Cosmic Structuture.
The fact that the fluctuation spectrum can be extracted from the inflationary
scenario through an analysis that involves quantum field theory in curved
space-time, and that it coincides with the observational data has lead to a
certain complacency in the community, which prevents the critical analysis of
the obscure spots in the derivation. The point is that the inhomogeneity and
anisotropy of our universe seem to emerge from an exactly homogeneous and
isotropic initial state through processes that do not break those symmetries.
This article gives a brief recount of the problems faced by the arguments based
on established physics, which comprise the point of view held by a large
majority of researchers in the field.
The conclusion is that we need some new physics to be able to fully address
the problem. The article then exposes one avenue that has been used to address
the central issue and elaborates on the degree to which, the new approach makes
different predictions from the standard analyses.
The approach is inspired on Penrose's proposals that Quantum Gravity might
lead to a real, dynamical collapse of the wave function, a process that we
argue has the properties needed to extract us from the theoretical impasse
described above.
| [
{
"created": "Fri, 1 Dec 2006 01:49:25 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Sudarsky",
"Daniel",
""
]
] | There is something missing in our understanding of the origin of the seeds of Cosmic Structuture. The fact that the fluctuation spectrum can be extracted from the inflationary scenario through an analysis that involves quantum field theory in curved space-time, and that it coincides with the observational data has lead to a certain complacency in the community, which prevents the critical analysis of the obscure spots in the derivation. The point is that the inhomogeneity and anisotropy of our universe seem to emerge from an exactly homogeneous and isotropic initial state through processes that do not break those symmetries. This article gives a brief recount of the problems faced by the arguments based on established physics, which comprise the point of view held by a large majority of researchers in the field. The conclusion is that we need some new physics to be able to fully address the problem. The article then exposes one avenue that has been used to address the central issue and elaborates on the degree to which, the new approach makes different predictions from the standard analyses. The approach is inspired on Penrose's proposals that Quantum Gravity might lead to a real, dynamical collapse of the wave function, a process that we argue has the properties needed to extract us from the theoretical impasse described above. |
1810.06293 | Chan Park | Chan Park | A Covariant Approach to 1+3 Formalism | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I present a covariant approach to developing 1+3 formalism without an
introduction of any basis or coordinates. In the formalism, a spacetime which
has a timelike congruence is assumed. Then, tensors are split into temporal and
spatial parts according to the tangent direction to the congruence. I make use
of the natural derivatives to define the kinematical quantities and to
investigate their properties. They are utilized in the splitting of covariant
derivatives. In this way, the Riemann curvature is split into the temporal and
spatial part, i.e. Gauss, Codazzi, and Ricci relation. Finally, the splitting
of the Einstein equation is achieved by contraction. Choosing congruence as
normal to a spacelike hypersurface, the formalism reduces to 3+1 formalism.
This approach deepens our understanding of 3+1 formalism. All these processes
are performed in a covariant manner without the complexities caused by the
introduction of a coordinate system or basis.
| [
{
"created": "Mon, 15 Oct 2018 12:06:16 GMT",
"version": "v1"
}
] | 2018-10-16 | [
[
"Park",
"Chan",
""
]
] | I present a covariant approach to developing 1+3 formalism without an introduction of any basis or coordinates. In the formalism, a spacetime which has a timelike congruence is assumed. Then, tensors are split into temporal and spatial parts according to the tangent direction to the congruence. I make use of the natural derivatives to define the kinematical quantities and to investigate their properties. They are utilized in the splitting of covariant derivatives. In this way, the Riemann curvature is split into the temporal and spatial part, i.e. Gauss, Codazzi, and Ricci relation. Finally, the splitting of the Einstein equation is achieved by contraction. Choosing congruence as normal to a spacelike hypersurface, the formalism reduces to 3+1 formalism. This approach deepens our understanding of 3+1 formalism. All these processes are performed in a covariant manner without the complexities caused by the introduction of a coordinate system or basis. |
2007.10566 | Guansheng He | Guansheng He and Wenbin Lin | Second Order Kerr-Newman Time Delay | null | Phys. Rev. D. 93, 023005 (2016) | 10.1103/PhysRevD.93.023005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The explicit form for the post-Newtonian gravitational time delay of light
signals propagating on the equatorial plane of a Kerr-Newman black hole is
derived. Based on the null geodesic in Kerr-Newman spacetime, we adopt the
iterative method to calculate the time delay. Our result reduces to the
previous formulation for Kerr black hole if we drop off the contribution from
the electrical charge. Our time-delay formula for the Reissner-Nordstr\"{o}m
geometry is different from the previous publication [Phys. Rev. D 69, 023002
(2004)], in which the largest second-order contribution to the time delay is
missing.
| [
{
"created": "Tue, 21 Jul 2020 02:21:08 GMT",
"version": "v1"
}
] | 2020-07-22 | [
[
"He",
"Guansheng",
""
],
[
"Lin",
"Wenbin",
""
]
] | The explicit form for the post-Newtonian gravitational time delay of light signals propagating on the equatorial plane of a Kerr-Newman black hole is derived. Based on the null geodesic in Kerr-Newman spacetime, we adopt the iterative method to calculate the time delay. Our result reduces to the previous formulation for Kerr black hole if we drop off the contribution from the electrical charge. Our time-delay formula for the Reissner-Nordstr\"{o}m geometry is different from the previous publication [Phys. Rev. D 69, 023002 (2004)], in which the largest second-order contribution to the time delay is missing. |
0808.1267 | Gustavo Gazzola de Lima | G. Gazzola, M. C. Nemes, W. F. Wreszinski | On the Casimir energy for a massive quantum scalar field and the
Cosmological constant | 15 pages, 2 figures, conceptually improved version, to appear in Ann.
Phys | null | 10.1016/j.aop.2009.07.001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a rigorous, regularization independent local quantum field
theoretic treatment of the Casimir effect for a quantum scalar field of mass
$\mu\ne0$ which yields closed form expressions for the energy density and
pressure. As an application we show that there exist special states of the
quantum field at fixed cosmic time, in which the expectation value of the
renormalized energy-momentum tensor is independent of the space coordinate and
is of the perfect fluid form $g_{\mu,\nu}\rho_{vac}$ with $\rho_{vac}>0$, thus
providing a quantum field theoretic foundation of the Cosmological constant.
Using some values of $\mu$ suggested in the literature for the hypothetical
axion particle, there results a model for dark energy which is consistent with
past and future evolution and is also in good agreement with experimental data.
| [
{
"created": "Fri, 8 Aug 2008 18:48:32 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Feb 2009 13:09:12 GMT",
"version": "v2"
},
{
"created": "Tue, 7 Jul 2009 13:15:15 GMT",
"version": "v3"
}
] | 2015-05-13 | [
[
"Gazzola",
"G.",
""
],
[
"Nemes",
"M. C.",
""
],
[
"Wreszinski",
"W. F.",
""
]
] | We present a rigorous, regularization independent local quantum field theoretic treatment of the Casimir effect for a quantum scalar field of mass $\mu\ne0$ which yields closed form expressions for the energy density and pressure. As an application we show that there exist special states of the quantum field at fixed cosmic time, in which the expectation value of the renormalized energy-momentum tensor is independent of the space coordinate and is of the perfect fluid form $g_{\mu,\nu}\rho_{vac}$ with $\rho_{vac}>0$, thus providing a quantum field theoretic foundation of the Cosmological constant. Using some values of $\mu$ suggested in the literature for the hypothetical axion particle, there results a model for dark energy which is consistent with past and future evolution and is also in good agreement with experimental data. |
1107.3570 | Daniel M\"uller | Daniel M\"uller | Homogeneous Solutions of Quadratic Gravity | talk presented in the 8th Friedmann Seminar, 30 May - 03 June 2011,
Rio de Janeiro, Brazil | IJMPCS, Vol. 3, 111, (2011) | 10.1142/S2010194511001206 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is believed that soon after the Planck time, Einstein's general relativity
theory should be corrected to an effective quadratic theory. In this work we
present the 3+1 decomposition for the zero vorticity case for arbitrary
spatially homogenous spaces. We specialize for the particular Bianchi $I$
diagonal case. The 3- curvature can be understood as a generalized potential,
and the Bianchi $I$ case is a limiting case where this potential is negligible
to the dynamics. The spirit should be analogous, in some sense to the BKL
solution. In this sense, a better understanding of the Bianchi $I$ case could
shed some light into the general Bianchi case.
| [
{
"created": "Mon, 18 Jul 2011 20:22:52 GMT",
"version": "v1"
}
] | 2012-02-29 | [
[
"Müller",
"Daniel",
""
]
] | It is believed that soon after the Planck time, Einstein's general relativity theory should be corrected to an effective quadratic theory. In this work we present the 3+1 decomposition for the zero vorticity case for arbitrary spatially homogenous spaces. We specialize for the particular Bianchi $I$ diagonal case. The 3- curvature can be understood as a generalized potential, and the Bianchi $I$ case is a limiting case where this potential is negligible to the dynamics. The spirit should be analogous, in some sense to the BKL solution. In this sense, a better understanding of the Bianchi $I$ case could shed some light into the general Bianchi case. |
0805.3099 | Pedro Montero | Pedro J. Montero, Jose A. Font, Masaru Shibata | NADA: A new code for studying self-gravitating tori around black holes | 18 pages, 14 figures, accepted for publication in Phys. Rev. D | Phys.Rev.D78:064037,2008 | 10.1103/PhysRevD.78.064037 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new two-dimensional numerical code called Nada designed to solve
the full Einstein equations coupled to the general relativistic hydrodynamics
equations. The code is mainly intended for studies of self-gravitating
accretion disks (or tori) around black holes, although it is also suitable for
regular spacetimes. Concerning technical aspects the Einstein equations are
formulated and solved in the code using a formulation of the standard 3+1 (ADM)
system, the so-called BSSN approach. A key feature of the code is that
derivative terms in the spacetime evolution equations are computed using a
fourth-order centered finite difference approximation in conjunction with the
Cartoon method to impose the axisymmetry condition under Cartesian coordinates
(the choice in Nada), and the puncture/moving puncture approach to carry out
black hole evolutions. Correspondingly, the general relativistic hydrodynamics
equations are written in flux-conservative form and solved with
high-resolution, shock-capturing schemes. We perform and discuss a number of
tests to assess the accuracy and expected convergence of the code, namely
(single) black hole evolutions, shock tubes, and evolutions of both spherical
and rotating relativistic stars in equilibrium, the gravitational collapse of a
spherical relativistic star leading to the formation of a black hole. In
addition, paving the way for specific applications of the code, we also present
results from fully general relativistic numerical simulations of a system
formed by a black hole surrounded by a self-gravitating torus in equilibrium.
| [
{
"created": "Tue, 20 May 2008 15:09:30 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Aug 2008 22:14:26 GMT",
"version": "v2"
}
] | 2009-02-23 | [
[
"Montero",
"Pedro J.",
""
],
[
"Font",
"Jose A.",
""
],
[
"Shibata",
"Masaru",
""
]
] | We present a new two-dimensional numerical code called Nada designed to solve the full Einstein equations coupled to the general relativistic hydrodynamics equations. The code is mainly intended for studies of self-gravitating accretion disks (or tori) around black holes, although it is also suitable for regular spacetimes. Concerning technical aspects the Einstein equations are formulated and solved in the code using a formulation of the standard 3+1 (ADM) system, the so-called BSSN approach. A key feature of the code is that derivative terms in the spacetime evolution equations are computed using a fourth-order centered finite difference approximation in conjunction with the Cartoon method to impose the axisymmetry condition under Cartesian coordinates (the choice in Nada), and the puncture/moving puncture approach to carry out black hole evolutions. Correspondingly, the general relativistic hydrodynamics equations are written in flux-conservative form and solved with high-resolution, shock-capturing schemes. We perform and discuss a number of tests to assess the accuracy and expected convergence of the code, namely (single) black hole evolutions, shock tubes, and evolutions of both spherical and rotating relativistic stars in equilibrium, the gravitational collapse of a spherical relativistic star leading to the formation of a black hole. In addition, paving the way for specific applications of the code, we also present results from fully general relativistic numerical simulations of a system formed by a black hole surrounded by a self-gravitating torus in equilibrium. |
1407.2231 | \"Ozg\"ur Akarsu | Ozgur Akarsu, Tekin Dereli, Nihan Katirci, Mikhail B. Sheftel | General solution of a cosmological model induced from higher dimensions
using a kinematical constraint | 19 pages, 19 figures, matches the version published in General
Relativity and Gravitation | Gen. Relativ. Gravit. 47 (2015) 61 | 10.1007/s10714-015-1902-8 | null | gr-qc math-ph math.MP nlin.SI | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent study Akarsu and Dereli (Gen. Relativ. Gravit. 45:1211, 2013)
discussed the dynamical reduction of a higher dimensional cosmological model
which is augmented by a kinematical constraint characterized by a single real
parameter, correlating and controlling the expansion of both the external
(physical) and internal spaces. In that paper explicit solutions were found
only for the case of three dimensional internal space ($n=3$). Here we derive a
general solution of the system using Lie group symmetry properties, in
parametric form for arbitrary number $n=1,2,3,\dots$ of internal dimensions. We
also investigate the dynamical reduction of the model as a function of cosmic
time $t$ for various values of $n$ and generate parametric plots to discuss
cosmologically relevant results.
| [
{
"created": "Tue, 8 Jul 2014 19:45:46 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Jan 2015 15:51:12 GMT",
"version": "v2"
},
{
"created": "Mon, 4 May 2015 12:05:39 GMT",
"version": "v3"
}
] | 2015-05-06 | [
[
"Akarsu",
"Ozgur",
""
],
[
"Dereli",
"Tekin",
""
],
[
"Katirci",
"Nihan",
""
],
[
"Sheftel",
"Mikhail B.",
""
]
] | In a recent study Akarsu and Dereli (Gen. Relativ. Gravit. 45:1211, 2013) discussed the dynamical reduction of a higher dimensional cosmological model which is augmented by a kinematical constraint characterized by a single real parameter, correlating and controlling the expansion of both the external (physical) and internal spaces. In that paper explicit solutions were found only for the case of three dimensional internal space ($n=3$). Here we derive a general solution of the system using Lie group symmetry properties, in parametric form for arbitrary number $n=1,2,3,\dots$ of internal dimensions. We also investigate the dynamical reduction of the model as a function of cosmic time $t$ for various values of $n$ and generate parametric plots to discuss cosmologically relevant results. |
1205.4550 | Gabor Etesi | Gabor Etesi | A proof of the Geroch-Horowitz-Penrose formulation of the strong cosmic
censor conjecture motivated by computability theory | 17pp, LaTeX, no figures. Compared with the published version
clarifications has been made in Sect. 2 | Int. Journ. Theor. Phys. 52(3), 946-960 (2013) | 10.1007/s10773-012-1407-0 | null | gr-qc cs.CC | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we present a proof of a mathematical version of the strong
cosmic censor conjecture attributed to Geroch-Horowitz and Penrose but
formulated explicitly by Wald. The proof is based on the existence of
future-inextendible causal curves in causal pasts of events on the future
Cauchy horizon in a non-globally hyperbolic space-time. By examining explicit
non-globally hyperbolic space-times we find that in case of several physically
relevant solutions these future-inextendible curves have in fact infinite
length. This way we recognize a close relationship between asymptotically flat
or anti-de Sitter, physically relevant extendible space-times and the so-called
Malament-Hogarth space-times which play a central role in recent investigations
in the theory of "gravitational computers". This motivates us to exhibit a more
sharp, more geometric formulation of the strong cosmic censor conjecture,
namely "all physically relevant, asymptotically flat or anti-de Sitter but
non-globally hyperbolic space-times are Malament-Hogarth ones".
Our observations may indicate a natural but hidden connection between the
strong cosmic censorship scenario and the Church-Turing thesis revealing an
unexpected conceptual depth beneath both conjectures.
| [
{
"created": "Mon, 21 May 2012 10:18:48 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jun 2012 08:05:23 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Feb 2013 09:02:33 GMT",
"version": "v3"
},
{
"created": "Mon, 13 Dec 2021 10:34:35 GMT",
"version": "v4"
}
] | 2021-12-14 | [
[
"Etesi",
"Gabor",
""
]
] | In this paper we present a proof of a mathematical version of the strong cosmic censor conjecture attributed to Geroch-Horowitz and Penrose but formulated explicitly by Wald. The proof is based on the existence of future-inextendible causal curves in causal pasts of events on the future Cauchy horizon in a non-globally hyperbolic space-time. By examining explicit non-globally hyperbolic space-times we find that in case of several physically relevant solutions these future-inextendible curves have in fact infinite length. This way we recognize a close relationship between asymptotically flat or anti-de Sitter, physically relevant extendible space-times and the so-called Malament-Hogarth space-times which play a central role in recent investigations in the theory of "gravitational computers". This motivates us to exhibit a more sharp, more geometric formulation of the strong cosmic censor conjecture, namely "all physically relevant, asymptotically flat or anti-de Sitter but non-globally hyperbolic space-times are Malament-Hogarth ones". Our observations may indicate a natural but hidden connection between the strong cosmic censorship scenario and the Church-Turing thesis revealing an unexpected conceptual depth beneath both conjectures. |
gr-qc/0302111 | Domenico Giulini | Domenico Giulini | Close encounters of black holes | 31 pages, 7 eps-figures | Heino Falcke and Friedrich Hehl (eds.): The Galactic Black Hole;
pp.178-206 (IOP Publishing, Bristol, 2003) | null | THEP-03/03 | gr-qc astro-ph | null | This is an introduction into the problem of how to set up black hole
initial-data for the matter-free field equations of General Relativity. The
approach is semi-pedagogical and addresses a more general audience of
astrophysicists and students with no specialized training in General Relativity
beyond that of an introductory lecture.
| [
{
"created": "Thu, 27 Feb 2003 16:51:38 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Giulini",
"Domenico",
""
]
] | This is an introduction into the problem of how to set up black hole initial-data for the matter-free field equations of General Relativity. The approach is semi-pedagogical and addresses a more general audience of astrophysicists and students with no specialized training in General Relativity beyond that of an introductory lecture. |
2011.06799 | Yasufumi Kojima | Yasufumi Kojima and Yuto Kimura | Particle acceleration driven by null electromagnetic fields near a Kerr
black hole | 11 pages, 4 figures | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Short timescale variability is often associated with a black hole system. The
consequence of an electromagnetic outflow suddenly generated near a Kerr black
hole is considered assuming that it is described by a solution of a force-free
field with a null electric current. We compute charged particle acceleration
induced by the burst field. The interaction between the particle and the field
is characterized by a large dimensionless number. We show that the particle is
instantaneously accelerated to the relativistic regime by the field with a very
large amplitude. The typical maximum energy attained by a proton for an event
near a super massive black hole is $E_{\rm max} \sim 100$ TeV, which is enough
observed high-energy flares.
| [
{
"created": "Fri, 13 Nov 2020 07:52:42 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Dec 2020 04:19:13 GMT",
"version": "v2"
}
] | 2020-12-25 | [
[
"Kojima",
"Yasufumi",
""
],
[
"Kimura",
"Yuto",
""
]
] | Short timescale variability is often associated with a black hole system. The consequence of an electromagnetic outflow suddenly generated near a Kerr black hole is considered assuming that it is described by a solution of a force-free field with a null electric current. We compute charged particle acceleration induced by the burst field. The interaction between the particle and the field is characterized by a large dimensionless number. We show that the particle is instantaneously accelerated to the relativistic regime by the field with a very large amplitude. The typical maximum energy attained by a proton for an event near a super massive black hole is $E_{\rm max} \sim 100$ TeV, which is enough observed high-energy flares. |
1412.6312 | Alex Miranda | Alex S. Miranda, Jaqueline Morgan, Vilson T. Zanchin, Alejandra Kandus | Separable wave equations for gravitoelectromagnetic perturbations of
rotating charged black strings | 37 pages; changes in the abstract, introduction and concluding
section; version to appear in Class. Quantum Grav | null | 10.1088/0264-9381/32/23/235002 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Rotating charged black strings are solutions of four-dimensional
Einstein-Maxwell equations with a negative cosmological constant and a
non-trivial topology. According to the AdS/CFT correspondence, these black
strings are dual to rotating thermal states of a strongly interacting field
theory with nonzero chemical potential that lives in a cylinder. The dynamics
of fluctuations in the field theory can be studied from the perturbation
equations for classical fields in a black-string spacetime. With this
motivation in mind, we develop here a completely gauge and tetrad invariant
perturbation approach to deal with the gravitoelectromagnetic fluctuations of
rotating charged black strings in the presence of sources. As usual, for any
charged black hole, a perturbation in the background electromagnetic field
induces a metric perturbation and vice versa. In spite of this coupling and the
non-vanishing angular momentum, we show that linearization of equations of the
Newman-Penrose formalism leads to four separated second-order complex equations
for suitable combinations of the spin coefficients, the Weyl and the Maxwell
scalars. Then, we generalize the Chandrasekhar transformation theory by the
inclusion of sources and apply it to reduce the perturbation problem to four
decoupled inhomogeneous wave equations --- a pair for each sector of
perturbations. The radial part of such wave equations can be put into
Schrodinger-like forms after Fourier transforming them with respect to time. We
find that the resulting effective potentials form two pairs of supersymmetric
partner potentials and, as a consequence, the fundamental variables of one
perturbation sector are related to the variables of the other sector. The
relevance of such a symmetry in connection to the AdS/CFT correspondence is
discussed, and future applications of the pertubation theory developed here are
outlined.
| [
{
"created": "Fri, 19 Dec 2014 12:21:21 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Sep 2015 18:51:36 GMT",
"version": "v2"
}
] | 2015-11-18 | [
[
"Miranda",
"Alex S.",
""
],
[
"Morgan",
"Jaqueline",
""
],
[
"Zanchin",
"Vilson T.",
""
],
[
"Kandus",
"Alejandra",
""
]
] | Rotating charged black strings are solutions of four-dimensional Einstein-Maxwell equations with a negative cosmological constant and a non-trivial topology. According to the AdS/CFT correspondence, these black strings are dual to rotating thermal states of a strongly interacting field theory with nonzero chemical potential that lives in a cylinder. The dynamics of fluctuations in the field theory can be studied from the perturbation equations for classical fields in a black-string spacetime. With this motivation in mind, we develop here a completely gauge and tetrad invariant perturbation approach to deal with the gravitoelectromagnetic fluctuations of rotating charged black strings in the presence of sources. As usual, for any charged black hole, a perturbation in the background electromagnetic field induces a metric perturbation and vice versa. In spite of this coupling and the non-vanishing angular momentum, we show that linearization of equations of the Newman-Penrose formalism leads to four separated second-order complex equations for suitable combinations of the spin coefficients, the Weyl and the Maxwell scalars. Then, we generalize the Chandrasekhar transformation theory by the inclusion of sources and apply it to reduce the perturbation problem to four decoupled inhomogeneous wave equations --- a pair for each sector of perturbations. The radial part of such wave equations can be put into Schrodinger-like forms after Fourier transforming them with respect to time. We find that the resulting effective potentials form two pairs of supersymmetric partner potentials and, as a consequence, the fundamental variables of one perturbation sector are related to the variables of the other sector. The relevance of such a symmetry in connection to the AdS/CFT correspondence is discussed, and future applications of the pertubation theory developed here are outlined. |
1101.3179 | Jose Luis Bl\'azquez-Salcedo | L. M. Gonz\'alez-Romero and J. L. Bl\'azquez-Salcedo | New model of relativistic slowly rotating neutron stars with surface
layer \textit{crust}: application to giant \textit{glitches} of Vela Pulsar | 4 pages, 2 figures, to appear in Proceedings of Spanish Relativity
Meeting 2010 (ERE 2010) held in Granada, Spain | J.Phys.Conf.Ser.314:012088,2011 | 10.1088/1742-6596/314/1/012088 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Introducing a surface layer of matter on the edge of a neutron star in slow
rigid rotation, we analyze, from an intrinsic point of view, the junction
conditions that must be satisfied between the interior and exterior solutions
of the Einstein equations. In our model the core-\textit{crust} transition
pressure arise as an essential parameter in the description of a configuration.
As an application of this formalism, we describe giant \textit{glitches} of the
Vela pulsar as a result of variations in the transition pressure, finding that
these small changes are compatible with the expected temperature variations of
the inner crust during \textit{glitch} time.
| [
{
"created": "Mon, 17 Jan 2011 10:53:05 GMT",
"version": "v1"
}
] | 2015-03-17 | [
[
"González-Romero",
"L. M.",
""
],
[
"Blázquez-Salcedo",
"J. L.",
""
]
] | Introducing a surface layer of matter on the edge of a neutron star in slow rigid rotation, we analyze, from an intrinsic point of view, the junction conditions that must be satisfied between the interior and exterior solutions of the Einstein equations. In our model the core-\textit{crust} transition pressure arise as an essential parameter in the description of a configuration. As an application of this formalism, we describe giant \textit{glitches} of the Vela pulsar as a result of variations in the transition pressure, finding that these small changes are compatible with the expected temperature variations of the inner crust during \textit{glitch} time. |
gr-qc/0107028 | Abel Camacho Quintana | A. Camacho (Dept. of Physics, Instituto Nacional de Investigaciones
Nucleares) | Decoherence-induced violations of Einstein equivalence principle | This essay received an ``honorable mention'' in the 2001 Essay
Competition of the Gravity Research Foundation. Accepted in International
Journal of Modern Physics D | Int.J.Mod.Phys. D10 (2001) 767-774 | 10.1142/S0218271801001542 | null | gr-qc quant-ph | null | In this essay it will be shown that Decoherence Model and Einstein
Equivalence Principle are conceptually incompatible. In other words, assuming
only the validity of the Weak Equivalence Principle the present work concludes
that we face two possibilities: (i) if Decoherence Model provides a correct
description of nature at quantum level, then there are systems which violate
Local Position Invariance, or, (ii) if all the postulates behind Einstein
Equivalence Principle are valid, even on quantum realm, then Decoherence Model
breaks down in curved spacetimes. Finally, the present results are confronted
against Schiff's conjecture.
| [
{
"created": "Mon, 9 Jul 2001 17:27:30 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Camacho",
"A.",
"",
"Dept. of Physics, Instituto Nacional de Investigaciones\n Nucleares"
]
] | In this essay it will be shown that Decoherence Model and Einstein Equivalence Principle are conceptually incompatible. In other words, assuming only the validity of the Weak Equivalence Principle the present work concludes that we face two possibilities: (i) if Decoherence Model provides a correct description of nature at quantum level, then there are systems which violate Local Position Invariance, or, (ii) if all the postulates behind Einstein Equivalence Principle are valid, even on quantum realm, then Decoherence Model breaks down in curved spacetimes. Finally, the present results are confronted against Schiff's conjecture. |
1003.2348 | David P. Rideout | Johannes Brunnemann and David Rideout | Oriented Matroids -- Combinatorial Structures Underlying Loop Quantum
Gravity | 43 pages, 26 figures, LaTeX. Version published in CQG. Typos
corrected, presentation slightly extended | Class.Quant.Grav.27:205008,2010 | 10.1088/0264-9381/27/20/205008 | pi-qf-177 | gr-qc math-ph math.CO math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze combinatorial structures which play a central role in determining
spectral properties of the volume operator in loop quantum gravity (LQG). These
structures encode geometrical information of the embedding of arbitrary valence
vertices of a graph in 3-dimensional Riemannian space, and can be represented
by sign strings containing relative orientations of embedded edges. We
demonstrate that these signature factors are a special representation of the
general mathematical concept of an oriented matroid. Moreover, we show that
oriented matroids can also be used to describe the topology (connectedness) of
directed graphs. Hence the mathematical methods developed for oriented matroids
can be applied to the difficult combinatorics of embedded graphs underlying the
construction of LQG. As a first application we revisit the analysis of [4-5],
and find that enumeration of all possible sign configurations used there is
equivalent to enumerating all realizable oriented matroids of rank 3, and thus
can be greatly simplified. We find that for 7-valent vertices having no
coplanar triples of edge tangents, the smallest non-zero eigenvalue of the
volume spectrum does not grow as one increases the maximum spin $\jmax$ at the
vertex, for any orientation of the edge tangents. This indicates that, in
contrast to the area operator, considering large $\jmax$ does not necessarily
imply large volume eigenvalues. In addition we give an outlook to possible
starting points for rewriting the combinatorics of LQG in terms of oriented
matroids.
| [
{
"created": "Thu, 11 Mar 2010 15:40:33 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Nov 2010 17:56:29 GMT",
"version": "v2"
}
] | 2010-11-22 | [
[
"Brunnemann",
"Johannes",
""
],
[
"Rideout",
"David",
""
]
] | We analyze combinatorial structures which play a central role in determining spectral properties of the volume operator in loop quantum gravity (LQG). These structures encode geometrical information of the embedding of arbitrary valence vertices of a graph in 3-dimensional Riemannian space, and can be represented by sign strings containing relative orientations of embedded edges. We demonstrate that these signature factors are a special representation of the general mathematical concept of an oriented matroid. Moreover, we show that oriented matroids can also be used to describe the topology (connectedness) of directed graphs. Hence the mathematical methods developed for oriented matroids can be applied to the difficult combinatorics of embedded graphs underlying the construction of LQG. As a first application we revisit the analysis of [4-5], and find that enumeration of all possible sign configurations used there is equivalent to enumerating all realizable oriented matroids of rank 3, and thus can be greatly simplified. We find that for 7-valent vertices having no coplanar triples of edge tangents, the smallest non-zero eigenvalue of the volume spectrum does not grow as one increases the maximum spin $\jmax$ at the vertex, for any orientation of the edge tangents. This indicates that, in contrast to the area operator, considering large $\jmax$ does not necessarily imply large volume eigenvalues. In addition we give an outlook to possible starting points for rewriting the combinatorics of LQG in terms of oriented matroids. |
1408.5344 | Emil Nissimov | Eduardo Guendelman, Ram\'on Herrera, Pedro Labra\~na, Emil Nissimov,
Svetlana Pacheva | Emergent Cosmology, Inflation and Dark Energy | v.1 14 pages, 2 figures; v.2 references and acknowledgements added;
v.3 very significant upgrade - 24 pages, change of list of authors, two new
sections, extended abstract, introduction and conclusions, additional
citations and acknowledgements; v.4 title shortened, further improvements,
version to appear in "General Relativity and Gravitation" | General Relativity and Gravitation 47 (2015) art.10 | 10.1007/s10714-015-1852-1 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new class of gravity-matter models defined in terms of two independent
non-Riemannian volume forms (alternative generally covariant integration
measure densities) on the space-time manifold are studied in some detail. These
models involve an additional $R^2$ (square of the scalar curvature) term as
well as scalar matter field potentials of appropriate form so that the
pertinent action is invariant under global Weyl-scale symmetry. Scale
invariance is spontaneously broken upon integration of the equations of motion
for the auxiliary volume-form degrees of freedom. After performing transition
to the physical Einstein frame we obtain: (i) An effective potential for the
scalar field with two flat regions which allows for a unified description of
both early universe inflation as well as of present dark energy epoch; (ii) For
a definite parameter range the model possesses a non-singular "emergent
universe" solution which describes an initial phase of evolution that precedes
the inflationary phase; (iii) For a reasonable choice of the parameters the
present model conforms to the Planck Collaboration data.
| [
{
"created": "Fri, 22 Aug 2014 16:12:20 GMT",
"version": "v1"
},
{
"created": "Sun, 31 Aug 2014 13:28:08 GMT",
"version": "v2"
},
{
"created": "Wed, 12 Nov 2014 20:55:41 GMT",
"version": "v3"
},
{
"created": "Thu, 8 Jan 2015 12:13:47 GMT",
"version": "v4"
}
] | 2015-06-22 | [
[
"Guendelman",
"Eduardo",
""
],
[
"Herrera",
"Ramón",
""
],
[
"Labraña",
"Pedro",
""
],
[
"Nissimov",
"Emil",
""
],
[
"Pacheva",
"Svetlana",
""
]
] | A new class of gravity-matter models defined in terms of two independent non-Riemannian volume forms (alternative generally covariant integration measure densities) on the space-time manifold are studied in some detail. These models involve an additional $R^2$ (square of the scalar curvature) term as well as scalar matter field potentials of appropriate form so that the pertinent action is invariant under global Weyl-scale symmetry. Scale invariance is spontaneously broken upon integration of the equations of motion for the auxiliary volume-form degrees of freedom. After performing transition to the physical Einstein frame we obtain: (i) An effective potential for the scalar field with two flat regions which allows for a unified description of both early universe inflation as well as of present dark energy epoch; (ii) For a definite parameter range the model possesses a non-singular "emergent universe" solution which describes an initial phase of evolution that precedes the inflationary phase; (iii) For a reasonable choice of the parameters the present model conforms to the Planck Collaboration data. |
2001.10633 | Adri\`a Delhom | Adria Delhom, Iarley P. Lobo, Gonzalo J. Olmo, Carlos Romero | Conformally invariant proper time with general non-metricity | 12, 2 figures, updated to match published version | null | 10.1140/epjc/s10052-020-7974-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the definition of proper time for Weyl-invariant space-times
given by Perlick naturally extends to spaces with arbitrary non-metricity. We
then discuss the relation between this generalized proper time and the
Ehlers-Pirani-Schild definition of time when there is arbitrary non-metricity.
Then we show how this generalized proper time suffers from a second clock
effect. Assuming that muons are a device to measure this proper time, we
constrain the non-metricity tensor on Earth's surface and then elaborate on the
feasibility of such assumption.
| [
{
"created": "Tue, 28 Jan 2020 23:14:01 GMT",
"version": "v1"
},
{
"created": "Wed, 13 May 2020 12:43:40 GMT",
"version": "v2"
}
] | 2020-05-14 | [
[
"Delhom",
"Adria",
""
],
[
"Lobo",
"Iarley P.",
""
],
[
"Olmo",
"Gonzalo J.",
""
],
[
"Romero",
"Carlos",
""
]
] | We show that the definition of proper time for Weyl-invariant space-times given by Perlick naturally extends to spaces with arbitrary non-metricity. We then discuss the relation between this generalized proper time and the Ehlers-Pirani-Schild definition of time when there is arbitrary non-metricity. Then we show how this generalized proper time suffers from a second clock effect. Assuming that muons are a device to measure this proper time, we constrain the non-metricity tensor on Earth's surface and then elaborate on the feasibility of such assumption. |
1111.5825 | Jamie Scott | Jay Marx, Karsten Danzmann, James Hough, Kazuaki Kuroda, David
McClelland, Benoit Mours, Sterl Phinney, Sheila Rowan, B. Sathyaprakash,
Flavio Vetrano, Stefano Vitale, Stan Whitcomb, Clifford Will (for the
Gravitational Wave International Committee) | The Gravitational Wave International Committee Roadmap: The future of
gravitational wave astronomy | 116 pages. Original document in higher resolution can be found at
https://gwic.ligo.org/roadmap/ | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave science is on the verge of direct observation of the waves
predicted by Einstein's General Theory of Relativity and opening the exciting
new field of gravitational wave astronomy. In the coming decades,
ultra-sensitive arrays of ground-based instruments and complementary
spaced-based instruments will observe the gravitational wave sky, inevitably
discovering entirely unexpected phenomena while providing new insight into many
of the most profound astrophysical phenomena known. in July 2007 the
Gravitational Wave International Committee (GWIC) initiated the development of
a strategic roadmap for the field of gravitational wave science with a 30-year
horizon. The goal of this roadmap is to serve the international gravitational
wave community and its stakeholders as a tool for the development of
capabilities and facilities needed to address the exciting scientific
opportunities on the intermediate and long-term horizons.
| [
{
"created": "Thu, 24 Nov 2011 17:53:19 GMT",
"version": "v1"
}
] | 2011-11-28 | [
[
"Marx",
"Jay",
"",
"for the\n Gravitational Wave International Committee"
],
[
"Danzmann",
"Karsten",
"",
"for the\n Gravitational Wave International Committee"
],
[
"Hough",
"James",
"",
"for the\n Gravitational Wave International Committee"
],
[
"Kuroda",
"Kazuaki",
"",
"for the\n Gravitational Wave International Committee"
],
[
"McClelland",
"David",
"",
"for the\n Gravitational Wave International Committee"
],
[
"Mours",
"Benoit",
"",
"for the\n Gravitational Wave International Committee"
],
[
"Phinney",
"Sterl",
"",
"for the\n Gravitational Wave International Committee"
],
[
"Rowan",
"Sheila",
"",
"for the\n Gravitational Wave International Committee"
],
[
"Sathyaprakash",
"B.",
"",
"for the\n Gravitational Wave International Committee"
],
[
"Vetrano",
"Flavio",
"",
"for the\n Gravitational Wave International Committee"
],
[
"Vitale",
"Stefano",
"",
"for the\n Gravitational Wave International Committee"
],
[
"Whitcomb",
"Stan",
"",
"for the\n Gravitational Wave International Committee"
],
[
"Will",
"Clifford",
"",
"for the\n Gravitational Wave International Committee"
]
] | Gravitational wave science is on the verge of direct observation of the waves predicted by Einstein's General Theory of Relativity and opening the exciting new field of gravitational wave astronomy. In the coming decades, ultra-sensitive arrays of ground-based instruments and complementary spaced-based instruments will observe the gravitational wave sky, inevitably discovering entirely unexpected phenomena while providing new insight into many of the most profound astrophysical phenomena known. in July 2007 the Gravitational Wave International Committee (GWIC) initiated the development of a strategic roadmap for the field of gravitational wave science with a 30-year horizon. The goal of this roadmap is to serve the international gravitational wave community and its stakeholders as a tool for the development of capabilities and facilities needed to address the exciting scientific opportunities on the intermediate and long-term horizons. |
gr-qc/0701024 | Amos Ori | Amos Ori | Formation of closed timelike curves in a composite vacuum/dust
asymptotically-flat spacetime | 15 pages; accepted to Phys. Rev. D (no modifications) | Phys.Rev.D76:044002,2007 | 10.1103/PhysRevD.76.044002 | null | gr-qc | null | We present a new asymptotically-flat time-machine model made solely of vacuum
and dust. The spacetime evolves from a regular spacelike initial hypersurface S
and subsequently develops closed timelike curves. The initial hypersurface S is
asymptotically flat and topologically trivial. The chronology violation occurs
in a compact manner; namely the first closed causal curves form at the boundary
of the future domain of dependence of a compact region in S (the core). This
central core is empty, and so is the external asymptotically flat region. The
intermediate region surrounding the core (the envelope) is made of dust with
positive energy density. This model trivially satisfies the weak, dominant, and
strong energy conditions. Furthermore it is governed by a well-defined system
of field equations which possesses a well-posed initial-value problem.
| [
{
"created": "Wed, 3 Jan 2007 11:26:24 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Jan 2007 10:58:00 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Jun 2007 11:16:16 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Ori",
"Amos",
""
]
] | We present a new asymptotically-flat time-machine model made solely of vacuum and dust. The spacetime evolves from a regular spacelike initial hypersurface S and subsequently develops closed timelike curves. The initial hypersurface S is asymptotically flat and topologically trivial. The chronology violation occurs in a compact manner; namely the first closed causal curves form at the boundary of the future domain of dependence of a compact region in S (the core). This central core is empty, and so is the external asymptotically flat region. The intermediate region surrounding the core (the envelope) is made of dust with positive energy density. This model trivially satisfies the weak, dominant, and strong energy conditions. Furthermore it is governed by a well-defined system of field equations which possesses a well-posed initial-value problem. |
0710.2512 | Georgii Alekseev | G.A. Alekseev | Monodromy transform approach in the theory of integrable reductions of
Einstein's field equations and some applications | 3 pages, talk given at the Eleventh Marcel Grossmann Meeting (Berlin,
July 23 - 29, 2006), submitted to MG11 Proceedings | null | 10.1142/9789812834300_0378 | null | gr-qc | null | A brief sketch of the formulation of the monodromy transform approach and
corresponding integral equation methods as well as of various applications of
this approach for solution of integrable symmetry reductions of Einstein's
field equations is presented.
| [
{
"created": "Fri, 12 Oct 2007 17:06:07 GMT",
"version": "v1"
}
] | 2016-11-15 | [
[
"Alekseev",
"G. A.",
""
]
] | A brief sketch of the formulation of the monodromy transform approach and corresponding integral equation methods as well as of various applications of this approach for solution of integrable symmetry reductions of Einstein's field equations is presented. |
1010.3865 | Christopher Berry | Christopher P. L. Berry, Jonathan R. Gair | Gravitational wave energy spectrum of a parabolic encounter | 5 pages, 3 figures. Minor changes to match published version; figure
1 corrected; references added | Phys.Rev.D82:107501,2010 | 10.1103/PhysRevD.82.107501 | null | gr-qc astro-ph.CO astro-ph.GA astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive an analytic expression for the energy spectrum of gravitational
waves from a parabolic Keplerian binary by taking the limit of the Peters and
Matthews spectrum for eccentric orbits. This demonstrates that the location of
the peak of the energy spectrum depends primarily on the orbital periapse
rather than the eccentricity. We compare this weak-field result to strong-field
calculations and find it is reasonably accurate (~10%) provided that the
azimuthal and radial orbital frequencies do not differ by more than ~10%. For
equatorial orbits in the Kerr spacetime, this corresponds to periapse radii of
rp > 20M. These results can be used to model radiation bursts from compact
objects on highly eccentric orbits about massive black holes in the local
Universe, which could be detected by LISA.
| [
{
"created": "Tue, 19 Oct 2010 11:52:30 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Nov 2010 10:48:46 GMT",
"version": "v2"
}
] | 2011-05-18 | [
[
"Berry",
"Christopher P. L.",
""
],
[
"Gair",
"Jonathan R.",
""
]
] | We derive an analytic expression for the energy spectrum of gravitational waves from a parabolic Keplerian binary by taking the limit of the Peters and Matthews spectrum for eccentric orbits. This demonstrates that the location of the peak of the energy spectrum depends primarily on the orbital periapse rather than the eccentricity. We compare this weak-field result to strong-field calculations and find it is reasonably accurate (~10%) provided that the azimuthal and radial orbital frequencies do not differ by more than ~10%. For equatorial orbits in the Kerr spacetime, this corresponds to periapse radii of rp > 20M. These results can be used to model radiation bursts from compact objects on highly eccentric orbits about massive black holes in the local Universe, which could be detected by LISA. |
2405.09495 | Marcus Hatton | Marcus J. Hatton, Ian Hawke | A dissipative extension to ideal hydrodynamics | 16 pages, 13 figures. Intention to submit to MNRAS | null | null | null | gr-qc astro-ph.HE physics.comp-ph physics.flu-dyn | http://creativecommons.org/licenses/by/4.0/ | We present a formulation of special relativistic, dissipative hydrodynamics
(SRDHD) derived from the well-established M\"uller- Israel-Stewart (MIS)
formalism using an expansion in deviations from ideal behaviour. By re-summing
the non-ideal terms, our approach extends the Euler equations of motion for an
ideal fluid through a series of additional source terms that capture the
effects of bulk viscosity, shear viscosity and heat flux. For efficiency these
additional terms are built from purely spatial derivatives of the primitive
fluid variables. The series expansion is parametrized by the dissipation
strength and timescale coefficients, and is therefore rapidly convergent near
the ideal limit. We show, using numerical simulations, that our model
reproduces the dissipative fluid behaviour of other formulations. As our
formulation is designed to avoid the numerical stiffness issues that arise in
the traditional MIS formalism for fast relaxation timescales, it is roughly an
order of magnitude faster than standard methods near the ideal limit.
| [
{
"created": "Wed, 15 May 2024 16:41:07 GMT",
"version": "v1"
}
] | 2024-05-16 | [
[
"Hatton",
"Marcus J.",
""
],
[
"Hawke",
"Ian",
""
]
] | We present a formulation of special relativistic, dissipative hydrodynamics (SRDHD) derived from the well-established M\"uller- Israel-Stewart (MIS) formalism using an expansion in deviations from ideal behaviour. By re-summing the non-ideal terms, our approach extends the Euler equations of motion for an ideal fluid through a series of additional source terms that capture the effects of bulk viscosity, shear viscosity and heat flux. For efficiency these additional terms are built from purely spatial derivatives of the primitive fluid variables. The series expansion is parametrized by the dissipation strength and timescale coefficients, and is therefore rapidly convergent near the ideal limit. We show, using numerical simulations, that our model reproduces the dissipative fluid behaviour of other formulations. As our formulation is designed to avoid the numerical stiffness issues that arise in the traditional MIS formalism for fast relaxation timescales, it is roughly an order of magnitude faster than standard methods near the ideal limit. |
1407.6292 | Nijo Varghese Dr. | Nijo Varghese and V. C. Kuriakose | Late-time evolution of Dirac field around Schwarzschild-quintessence
black hole | 10 pages, 5 figures. To appear in MPLA. arXiv admin note: text
overlap with arXiv:1210.0476 | null | 10.1142/S0217732314501132 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The late-time evolution of Dirac field around spherically symmetric black
hole surrounded by quintessece is studied numerically. Our results show, for
lower values of the quintessence state parameter \epsilon, Dirac field decays
as power-law tail but with a slower decay rate than the corresponding
Schwarzschild case. But for \epsilon<-1/3, all the \ell-poles of the Dirac
field give up the power-law decay form and relax to a constant residual field
at asymptotically late times. The value of this residual field for which the
field settles down varies on different surfaces. It has the lowest value on the
black hole event horizon, increases as the radial distance increases and
maximizes on the cosmological horizon.
| [
{
"created": "Wed, 23 Jul 2014 16:57:37 GMT",
"version": "v1"
}
] | 2014-07-24 | [
[
"Varghese",
"Nijo",
""
],
[
"Kuriakose",
"V. C.",
""
]
] | The late-time evolution of Dirac field around spherically symmetric black hole surrounded by quintessece is studied numerically. Our results show, for lower values of the quintessence state parameter \epsilon, Dirac field decays as power-law tail but with a slower decay rate than the corresponding Schwarzschild case. But for \epsilon<-1/3, all the \ell-poles of the Dirac field give up the power-law decay form and relax to a constant residual field at asymptotically late times. The value of this residual field for which the field settles down varies on different surfaces. It has the lowest value on the black hole event horizon, increases as the radial distance increases and maximizes on the cosmological horizon. |
gr-qc/0006096 | Jerome Martin | Jerome Martin, Nelson Pinto-Neto and Ivano Damiao Soares | Green Functions for Topology Change | 11 pages, 2 figures, reshaped version | JHEP 0503:060,2005 | 10.1088/1126-6708/2005/03/060 | null | gr-qc hep-th | null | We explicitly calculate the Green functions describing quantum changes of
topology in Friedman-Lemaitre-Robertson-Walker Universes whose spacelike
sections are compact but endowed with distinct topologies. The calculations are
performed using the long wavelength approximation at second order in the
gradient expansion. We argue that complex metrics are necessary in order to
obtain a non-vanishing Green functions and interpret this fact as demonstrating
that a quantum topology change can be viewed as a quantum tunneling effect. We
demonstrate that quantum topological transitions between curved hypersurfaces
are allowed whereas no transition to or from a flat section is possible,
establishing thus a selection rule. We also show that the quantum topology
changes in the direction of negatively curved hypersurfaces are strongly
enhanced as time goes on, while transitions in the opposite direction are
suppressed.
| [
{
"created": "Wed, 28 Jun 2000 09:09:01 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Aug 2003 08:21:15 GMT",
"version": "v2"
}
] | 2010-02-03 | [
[
"Martin",
"Jerome",
""
],
[
"Pinto-Neto",
"Nelson",
""
],
[
"Soares",
"Ivano Damiao",
""
]
] | We explicitly calculate the Green functions describing quantum changes of topology in Friedman-Lemaitre-Robertson-Walker Universes whose spacelike sections are compact but endowed with distinct topologies. The calculations are performed using the long wavelength approximation at second order in the gradient expansion. We argue that complex metrics are necessary in order to obtain a non-vanishing Green functions and interpret this fact as demonstrating that a quantum topology change can be viewed as a quantum tunneling effect. We demonstrate that quantum topological transitions between curved hypersurfaces are allowed whereas no transition to or from a flat section is possible, establishing thus a selection rule. We also show that the quantum topology changes in the direction of negatively curved hypersurfaces are strongly enhanced as time goes on, while transitions in the opposite direction are suppressed. |
gr-qc/9906081 | Ms. Amita Shaw | S.Biswas, A.Shaw and B.Modak | Schwinger's Result On Particle Production From Complex Paths WKB
Approximation | 14 Pages, LaTeX, no figure | Int.J.Mod.Phys. A15 (2000) 3717-3732 | 10.1142/S0217751X00001221 | null | gr-qc | null | This paper presents the derivation of Schwinger's gauge invariant result of
$Im \cal{L}_{eff}$ upto one loop approximation, for particle production in an
uniform electric field through the method of complex trajectory WKB
approximation (CWKB). The CWKB proposed by one of the author's \cite{bis:ijtp}
looks upon particle production as due to the motion of a particle in complex
space-time plane, thereby requiring tunneling paths both in space and time.
Recently \cite{srini:iucaa,srini1:iucaa} there have been some efforts to
calculate the reflection and transmission co-efficients for particle production
in uniform electric field that differ from our expressions for the same. In
this paper we clarify the confusion in this regard and establish the
correctness of CWKB.
| [
{
"created": "Fri, 18 Jun 1999 06:14:50 GMT",
"version": "v1"
}
] | 2016-12-21 | [
[
"Biswas",
"S.",
""
],
[
"Shaw",
"A.",
""
],
[
"Modak",
"B.",
""
]
] | This paper presents the derivation of Schwinger's gauge invariant result of $Im \cal{L}_{eff}$ upto one loop approximation, for particle production in an uniform electric field through the method of complex trajectory WKB approximation (CWKB). The CWKB proposed by one of the author's \cite{bis:ijtp} looks upon particle production as due to the motion of a particle in complex space-time plane, thereby requiring tunneling paths both in space and time. Recently \cite{srini:iucaa,srini1:iucaa} there have been some efforts to calculate the reflection and transmission co-efficients for particle production in uniform electric field that differ from our expressions for the same. In this paper we clarify the confusion in this regard and establish the correctness of CWKB. |
2210.05378 | Dnyaneshwar Pawar Dr | D. D. Pawar, D. K. Raut, W. D. Patil | FRW model with Two -- fluid Source in fractal cosmology | 25 pages, 16 figures | Pramana J. Phys. (2022) 96, 133 | 10.1007/s12043-022-02364-5 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Present paper deals with flat Friedmann - Robertson - Walker (FRW) model with
two - fluid source in fractal cosmology. In this model one fluid represents
matter content of the universe and another fluid is radiation field modeling
the cosmic microwave background. To get the deterministic model, we have used
the relation between pressure and density for matter through the gamma law
equation of state $p_{m} = (\gamma-1)\, \rho_{m}, \,\, 1\leq \gamma\leq2$ . The
solutions of fractal field equations are obtained in terms of Kummer's
confluent hypergeometric function of the first kind. Some physical parameters
of the models are obtained and discussed their behavior with the help of graphs
in detail.
| [
{
"created": "Sun, 9 Oct 2022 05:37:29 GMT",
"version": "v1"
}
] | 2022-10-12 | [
[
"Pawar",
"D. D.",
""
],
[
"Raut",
"D. K.",
""
],
[
"Patil",
"W. D.",
""
]
] | Present paper deals with flat Friedmann - Robertson - Walker (FRW) model with two - fluid source in fractal cosmology. In this model one fluid represents matter content of the universe and another fluid is radiation field modeling the cosmic microwave background. To get the deterministic model, we have used the relation between pressure and density for matter through the gamma law equation of state $p_{m} = (\gamma-1)\, \rho_{m}, \,\, 1\leq \gamma\leq2$ . The solutions of fractal field equations are obtained in terms of Kummer's confluent hypergeometric function of the first kind. Some physical parameters of the models are obtained and discussed their behavior with the help of graphs in detail. |
2201.05736 | Stanley Deser | S.Deser | A short pre-history of Quantum Gravity | null | null | 10.1119/5.0080405 | brx-th-6697; caltech-th-2022-001 | gr-qc physics.hist-ph | http://creativecommons.org/licenses/by/4.0/ | I describe the early, from the nineteen sixties, history of attempts at
quantizing General Relativity.
| [
{
"created": "Sat, 15 Jan 2022 02:17:33 GMT",
"version": "v1"
}
] | 2022-04-06 | [
[
"Deser",
"S.",
""
]
] | I describe the early, from the nineteen sixties, history of attempts at quantizing General Relativity. |
gr-qc/0412065 | Francisco Lobo | Francisco S. N. Lobo and Matt Visser | Linearized warp drive and the energy conditions | 6 pages, contribution to the proceedings of the Spanish Relativity
Meeting-2004 (Miraflores de la Sierra, Madrid, September 2004) | null | null | null | gr-qc | null | ''Warp drive'' spacetimes are useful as ''gedanken-experiments'' and as a
theoretician's probe of the foundations of general relativity. Applying
linearized gravity to the weak-field warp drive, i.e., for non-relativistic
warp-bubble velocities, we find that the occurrence of energy condition
violations in this class of spacetimes is generic to the form of the geometry
under consideration and is not simply a side-effect of the ''superluminal''
properties. Using the linearized construction it is now possible to compare the
warp field energy with the mass-energy of the spaceship, and applying the
''volume integral quantifier'', extremely stringent conditions on the warp
drive spacetime are found.
| [
{
"created": "Tue, 14 Dec 2004 18:13:24 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Lobo",
"Francisco S. N.",
""
],
[
"Visser",
"Matt",
""
]
] | ''Warp drive'' spacetimes are useful as ''gedanken-experiments'' and as a theoretician's probe of the foundations of general relativity. Applying linearized gravity to the weak-field warp drive, i.e., for non-relativistic warp-bubble velocities, we find that the occurrence of energy condition violations in this class of spacetimes is generic to the form of the geometry under consideration and is not simply a side-effect of the ''superluminal'' properties. Using the linearized construction it is now possible to compare the warp field energy with the mass-energy of the spaceship, and applying the ''volume integral quantifier'', extremely stringent conditions on the warp drive spacetime are found. |
1605.06315 | Andre Maeder | Andre Maeder | Scale invariant cosmology I: the vacuum and the cosmological constant | 4 pages, no figures | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The source of the acceleration of the expansion of the Universe is still
unknown. We examine some consequences of the possible scale invariance of the
empty space at large scales. The central hypothesis of this work is that, at
macroscopic and large scales where General Relativity may be applied, the empty
space in the sense it is used in the Minkowski metric, is also scale invariant.
It is shown that if this applies, the Einstein cosmological constant and the
scale factor of the scale invariant framework are related by two differential
equations.
| [
{
"created": "Thu, 19 May 2016 06:27:59 GMT",
"version": "v1"
}
] | 2016-05-25 | [
[
"Maeder",
"Andre",
""
]
] | The source of the acceleration of the expansion of the Universe is still unknown. We examine some consequences of the possible scale invariance of the empty space at large scales. The central hypothesis of this work is that, at macroscopic and large scales where General Relativity may be applied, the empty space in the sense it is used in the Minkowski metric, is also scale invariant. It is shown that if this applies, the Einstein cosmological constant and the scale factor of the scale invariant framework are related by two differential equations. |
1102.2501 | S Habib Mazharimousavi | S. Habib Mazharimousavi and M. Halilsoy | Specific dynamics for the Domain-Walls in Einstein-Maxwell-Dilaton
theory | 9 pages, 4 figures, final version to appear in Classical and Quantum
Gravity (CQG) | Class. Quantum Grav. 29 (2012) 065013 | 10.1088/0264-9381/29/6/065013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider Einstein-Maxwell-Dilaton (EMD) Lagrangian supplemented by double
Liouville potentials to enrich our system and investigate the resulting
dynamics. The general solution provides us alternative structures induced on
the 3-dimensional domain wall (DW) moving in the 4-dimensional bulk. In
particular, the local maximum in the potential suggests a maximum bounce (or
onset for a contraction phase) of the 3-dimensional Friedmann-Robertson-Walker
(FRW) universe on the DW. Depending on the choice of parameters we plot various
cases of physical interest.
| [
{
"created": "Sat, 12 Feb 2011 11:53:50 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Feb 2012 15:57:46 GMT",
"version": "v2"
}
] | 2012-03-06 | [
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Halilsoy",
"M.",
""
]
] | We consider Einstein-Maxwell-Dilaton (EMD) Lagrangian supplemented by double Liouville potentials to enrich our system and investigate the resulting dynamics. The general solution provides us alternative structures induced on the 3-dimensional domain wall (DW) moving in the 4-dimensional bulk. In particular, the local maximum in the potential suggests a maximum bounce (or onset for a contraction phase) of the 3-dimensional Friedmann-Robertson-Walker (FRW) universe on the DW. Depending on the choice of parameters we plot various cases of physical interest. |
gr-qc/9703074 | Carey Carpenter Briggs | C. C. Briggs (Penn State U.) | A General Expression for the Quartic Lovelock Tensor | PostScript file, 2 pages | null | null | null | gr-qc | null | A general expression is given for the quartic Lovelock tensor in terms of the
Riemann-Christoffel and Ricci curvature tensors and the Riemann curvature
scalar for n-dimensional differentiable manifolds having a general linear
connection. In addition, expressions are given (in the appendix) for the
coefficient of the quartic Lovelock Lagrangian as well as for lower-order
Lovelock tensors and Lovelock Lagrangian coefficients.
| [
{
"created": "Thu, 27 Mar 1997 00:18:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Briggs",
"C. C.",
"",
"Penn State U."
]
] | A general expression is given for the quartic Lovelock tensor in terms of the Riemann-Christoffel and Ricci curvature tensors and the Riemann curvature scalar for n-dimensional differentiable manifolds having a general linear connection. In addition, expressions are given (in the appendix) for the coefficient of the quartic Lovelock Lagrangian as well as for lower-order Lovelock tensors and Lovelock Lagrangian coefficients. |
gr-qc/0602022 | Jack Sarfatti | Jack Sarfatti | Emergent Gravity and Torsion: String Theory Without String Theory, Why
the Cosmic Dark Energy Is So Small | This version is the second major revision addressing several
unresolved fundamental empirical problems | null | null | null | gr-qc | null | A surprisingly simple holographic explanation for the low dark energy density
is suggested. I derive the Einstein-Cartan disclination curvature tetrads and
the physically independent dislocation torsion gap spin connections from an
"M-Matrix" of non-closed Cartan 1-forms made from 8 Goldstone phase 0-forms of
the vacuum ODLRO condensate inflation field in which the non-compact
10-parameter Poincare symmetry group is locally gauged for all invariant matter
field actions. Quantum gravity zero point vacuum fluctuations should be
renormalizable at the spin 1 tetrad level where there is a natural
scale-dependent holographic dimensionless coupling (hG/\zpf/c^3)^1/3 ~
(Bekenstein BITS)^-1/3. The spacetime tetrad rotation coefficients play the
same role as do the Lie algebra structure constants in internal symmetry spin 1
Yang-Mills local gauge theories. This suggests an intuitively pleasing natural
"organizing idea" now missing in superstring theory. It is then clear why
supersymmetry must break in order for our pocket universe to come into being
with a small w = -1 negative pressure zero point exotic vacuum dark energy
density. Just as the Michelson-Morley experiment gave a null result, this model
predicts that the Large Hadron Collider will never find any viable
on-mass-shell dark matter exotic particles able to explain Omega(DM) ~ 0.23 as
a matter of fundamental principle, neither will any other conceivable dark
matter detector because dark matter forming galactic halos et-al is entirely
virtual exotic vacuum w = - 1 with positive irreducibly random quantum zero
point pressure that mimics w = 0 CDM in its gravity lensing and all effects
that we can observe from afar.
| [
{
"created": "Tue, 7 Feb 2006 08:39:00 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Mar 2006 21:25:49 GMT",
"version": "v10"
},
{
"created": "Mon, 27 Mar 2006 05:09:30 GMT",
"version": "v11"
},
{
"created": "Tue, 18 Apr 2006 20:18:39 GMT",
"version": "v12"
},
{
"created": "Tue, 25 Apr 2006 02:32:26 GMT",
"version": "v13"
},
{
"created": "Thu, 28 Jun 2007 05:17:20 GMT",
"version": "v14"
},
{
"created": "Fri, 29 Jun 2007 04:53:43 GMT",
"version": "v15"
},
{
"created": "Mon, 2 Jul 2007 16:56:52 GMT",
"version": "v16"
},
{
"created": "Tue, 3 Jul 2007 03:12:11 GMT",
"version": "v17"
},
{
"created": "Wed, 4 Jul 2007 19:15:51 GMT",
"version": "v18"
},
{
"created": "Wed, 4 Jul 2007 20:21:49 GMT",
"version": "v19"
},
{
"created": "Sun, 19 Feb 2006 03:50:47 GMT",
"version": "v2"
},
{
"created": "Fri, 6 Jul 2007 02:21:13 GMT",
"version": "v20"
},
{
"created": "Wed, 11 Jul 2007 03:03:58 GMT",
"version": "v21"
},
{
"created": "Fri, 24 Feb 2006 20:43:34 GMT",
"version": "v3"
},
{
"created": "Wed, 8 Mar 2006 18:51:11 GMT",
"version": "v4"
},
{
"created": "Thu, 9 Mar 2006 05:17:26 GMT",
"version": "v5"
},
{
"created": "Mon, 13 Mar 2006 16:20:35 GMT",
"version": "v6"
},
{
"created": "Thu, 16 Mar 2006 04:51:26 GMT",
"version": "v7"
},
{
"created": "Mon, 20 Mar 2006 20:34:30 GMT",
"version": "v8"
},
{
"created": "Tue, 21 Mar 2006 04:13:39 GMT",
"version": "v9"
}
] | 2007-07-11 | [
[
"Sarfatti",
"Jack",
""
]
] | A surprisingly simple holographic explanation for the low dark energy density is suggested. I derive the Einstein-Cartan disclination curvature tetrads and the physically independent dislocation torsion gap spin connections from an "M-Matrix" of non-closed Cartan 1-forms made from 8 Goldstone phase 0-forms of the vacuum ODLRO condensate inflation field in which the non-compact 10-parameter Poincare symmetry group is locally gauged for all invariant matter field actions. Quantum gravity zero point vacuum fluctuations should be renormalizable at the spin 1 tetrad level where there is a natural scale-dependent holographic dimensionless coupling (hG/\zpf/c^3)^1/3 ~ (Bekenstein BITS)^-1/3. The spacetime tetrad rotation coefficients play the same role as do the Lie algebra structure constants in internal symmetry spin 1 Yang-Mills local gauge theories. This suggests an intuitively pleasing natural "organizing idea" now missing in superstring theory. It is then clear why supersymmetry must break in order for our pocket universe to come into being with a small w = -1 negative pressure zero point exotic vacuum dark energy density. Just as the Michelson-Morley experiment gave a null result, this model predicts that the Large Hadron Collider will never find any viable on-mass-shell dark matter exotic particles able to explain Omega(DM) ~ 0.23 as a matter of fundamental principle, neither will any other conceivable dark matter detector because dark matter forming galactic halos et-al is entirely virtual exotic vacuum w = - 1 with positive irreducibly random quantum zero point pressure that mimics w = 0 CDM in its gravity lensing and all effects that we can observe from afar. |
0709.0551 | Daniel Sudarsky | Yuri Bonder and Daniel Sudarsky | Quantum Gravity Phenomenology without Lorentz Invariance Violation: a
detailed proposal | LaTeX, 24 pages. To be published in Classical and Quantum Gravity | Class.Quant.Grav.25:105017,2008 | 10.1088/0264-9381/25/10/105017 | null | gr-qc hep-th | null | We describe a scheme for the exploration of quantum gravity phenomenology
focussing on effects that could be thought as arising from a fundamental
granularity of space-time. In contrast with the simplest assumptions, such
granularity is assumed to respect Lorentz Invariance but is otherwise left
unspecified. The proposal is fully observer covariant, it involves non-trivial
couplings of curvature to matter fields and leads to a well defined
phenomenology. We present the effective Hamiltonian which could be used to
analyze concrete experimental situations, some of which are briefly described,
and we shortly discuss the degree to which the present proposal is in line with
the fundamental ideas behind the equivalence principle.
| [
{
"created": "Wed, 5 Sep 2007 00:25:34 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Dec 2007 20:13:36 GMT",
"version": "v2"
},
{
"created": "Tue, 22 Apr 2008 17:18:39 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Bonder",
"Yuri",
""
],
[
"Sudarsky",
"Daniel",
""
]
] | We describe a scheme for the exploration of quantum gravity phenomenology focussing on effects that could be thought as arising from a fundamental granularity of space-time. In contrast with the simplest assumptions, such granularity is assumed to respect Lorentz Invariance but is otherwise left unspecified. The proposal is fully observer covariant, it involves non-trivial couplings of curvature to matter fields and leads to a well defined phenomenology. We present the effective Hamiltonian which could be used to analyze concrete experimental situations, some of which are briefly described, and we shortly discuss the degree to which the present proposal is in line with the fundamental ideas behind the equivalence principle. |
1803.06335 | Shinji Tsujikawa | Ryotaro Kase, Masato Minamitsuji, Shinji Tsujikawa | Black holes in quartic-order beyond-generalized Proca theories | 14 pages, 1 figure | Phys. Lett. B782 (2018) 541-550 | 10.1016/j.physletb.2018.05.078 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The generalized Proca theories with second-order equations of motion can be
healthily extended to a more general framework in which the number of
propagating degrees of freedom remains unchanged. In the presence of a
quartic-order nonminimal coupling to gravity arising in beyond-generalized
Proca theories, the speed of gravitational waves $c_t$ on the
Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological background can be equal
to that of light $c$ under a certain condition. By using this condition alone,
we show that the speed of gravitational waves in the vicinity of static and
spherically symmetric black holes is also equivalent to $c$ for the propagation
of odd-parity perturbations along both radial and angular directions. As a
by-product, the black holes arising in our beyond-generalized Proca theories
are plagued by neither ghost nor Laplacian instabilities against odd-parity
perturbations. We show the existence of both exact and numerical black hole
solutions endowed with vector hairs induced by the quartic-order coupling.
| [
{
"created": "Fri, 16 Mar 2018 17:37:35 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jun 2018 23:53:19 GMT",
"version": "v2"
}
] | 2018-06-15 | [
[
"Kase",
"Ryotaro",
""
],
[
"Minamitsuji",
"Masato",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] | The generalized Proca theories with second-order equations of motion can be healthily extended to a more general framework in which the number of propagating degrees of freedom remains unchanged. In the presence of a quartic-order nonminimal coupling to gravity arising in beyond-generalized Proca theories, the speed of gravitational waves $c_t$ on the Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological background can be equal to that of light $c$ under a certain condition. By using this condition alone, we show that the speed of gravitational waves in the vicinity of static and spherically symmetric black holes is also equivalent to $c$ for the propagation of odd-parity perturbations along both radial and angular directions. As a by-product, the black holes arising in our beyond-generalized Proca theories are plagued by neither ghost nor Laplacian instabilities against odd-parity perturbations. We show the existence of both exact and numerical black hole solutions endowed with vector hairs induced by the quartic-order coupling. |
2204.03833 | Yan Peng | Guohua Liu, Yan Peng | A no-go theorem for scalar fields with couplings from Ginzburg-Landau
models | 6 pages | null | 10.1140/epjc/s10052-022-10497-5 | null | gr-qc cond-mat.supr-con hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently Hod proved a no-go theorem that static scalar fields cannot form
spherically symmetric boson stars in the asymptotically flat background. On the
other side, scalar fields can be coupled to the gradient according to
next-to-leading order Ginzburg-Landau models. In the present work, we extend
Hod's discussions by considering couplings between static scalar fields and the
field gradient. For a non-negative coupling parameter, we show that there is no
asymptotically flat spherically symmetric boson stars made of coupled static
scalar fields.
| [
{
"created": "Fri, 8 Apr 2022 04:18:11 GMT",
"version": "v1"
}
] | 2022-07-13 | [
[
"Liu",
"Guohua",
""
],
[
"Peng",
"Yan",
""
]
] | Recently Hod proved a no-go theorem that static scalar fields cannot form spherically symmetric boson stars in the asymptotically flat background. On the other side, scalar fields can be coupled to the gradient according to next-to-leading order Ginzburg-Landau models. In the present work, we extend Hod's discussions by considering couplings between static scalar fields and the field gradient. For a non-negative coupling parameter, we show that there is no asymptotically flat spherically symmetric boson stars made of coupled static scalar fields. |
1909.11756 | Hector O. Silva | Hector O. Silva, Masato Minamitsuji | Cosmological attractors to general relativity and spontaneous
scalarization with disformal coupling | (v1) 10 pages, 2 figures. (v2) typos corrected. (v3) 11 pages, new
references, matches published version | Phys. Rev. D 100, 104012 (2019) | 10.1103/PhysRevD.100.104012 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The canonical scalar-tensor theory model which exhibits spontaneous
scalarization in the strong-gravity regime of neutron stars has long been known
to predict a cosmological evolution for the scalar field which generically
results in severe violations of present-day Solar System constraints on
deviations from general relativity. We study if this tension can be alleviated
by generalizing this model to include a disformal coupling between the scalar
field $\varphi$ and matter, where the Jordan frame metric ${\tilde g}_{\mu\nu}$
is related to the Einstein frame one $g_{\mu\nu}$ by ${\tilde
g}_{\mu\nu}=A(\varphi)^2 (g_{\mu\nu}+\Lambda\, \partial_\mu \varphi \,
\partial_\nu\varphi)$. We find that this broader theory admits a late-time
attractor mechanism towards general relativity. However, the existence of this
attractor requires a value of disformal scale of the order $\Lambda\gtrsim
H_0^{-2}$, where $H_0$ is the Hubble parameter of today, which is much larger
than the scale relevant for spontaneous scalarization of neutron stars $\Lambda
\sim R_s^{2}$ with $R_s (\sim 10^{-22} H_0^{-1})$ being the typical radius of
these stars. The large values of $\Lambda$ necessary for the attractor
mechanism (i) suppress spontaneous scalarization altogether inside neutron
stars and (ii) induce ghost instabilities on scalar field fluctuations, thus
preventing a resolution of the tension. We argue that the problem arises
because our disformal coupling involves a dimensionful parameter.
| [
{
"created": "Wed, 25 Sep 2019 20:38:45 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Sep 2019 04:10:23 GMT",
"version": "v2"
},
{
"created": "Fri, 8 Nov 2019 03:41:41 GMT",
"version": "v3"
}
] | 2019-11-11 | [
[
"Silva",
"Hector O.",
""
],
[
"Minamitsuji",
"Masato",
""
]
] | The canonical scalar-tensor theory model which exhibits spontaneous scalarization in the strong-gravity regime of neutron stars has long been known to predict a cosmological evolution for the scalar field which generically results in severe violations of present-day Solar System constraints on deviations from general relativity. We study if this tension can be alleviated by generalizing this model to include a disformal coupling between the scalar field $\varphi$ and matter, where the Jordan frame metric ${\tilde g}_{\mu\nu}$ is related to the Einstein frame one $g_{\mu\nu}$ by ${\tilde g}_{\mu\nu}=A(\varphi)^2 (g_{\mu\nu}+\Lambda\, \partial_\mu \varphi \, \partial_\nu\varphi)$. We find that this broader theory admits a late-time attractor mechanism towards general relativity. However, the existence of this attractor requires a value of disformal scale of the order $\Lambda\gtrsim H_0^{-2}$, where $H_0$ is the Hubble parameter of today, which is much larger than the scale relevant for spontaneous scalarization of neutron stars $\Lambda \sim R_s^{2}$ with $R_s (\sim 10^{-22} H_0^{-1})$ being the typical radius of these stars. The large values of $\Lambda$ necessary for the attractor mechanism (i) suppress spontaneous scalarization altogether inside neutron stars and (ii) induce ghost instabilities on scalar field fluctuations, thus preventing a resolution of the tension. We argue that the problem arises because our disformal coupling involves a dimensionful parameter. |
gr-qc/9905109 | Uwe Gunther | U. Guenther, A. Zhuk | Observable effects from extra dimensions | 4 pages, LaTeX2e | Grav.Cosmol. 5 (1999) 167-169 | null | null | gr-qc astro-ph hep-ph hep-th | null | For any multidimensional theory with compactified internal spaces, conformal
excitations of the internal space metric result in gravitational excitons in
the external spacetime. These excitations contribute either to dark matter or
to cross sections of usual particles.
| [
{
"created": "Mon, 31 May 1999 12:48:39 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Guenther",
"U.",
""
],
[
"Zhuk",
"A.",
""
]
] | For any multidimensional theory with compactified internal spaces, conformal excitations of the internal space metric result in gravitational excitons in the external spacetime. These excitations contribute either to dark matter or to cross sections of usual particles. |
1501.01953 | Alessandro Fabbri | Paul R. Anderson, Alessandro Fabbri, Roberto Balbinot | Low frequency gray-body factors and infrared divergences: rigorous
results | 41 pages, 5 figures | Phys. Rev. D 91, 064061 (2015) | 10.1103/PhysRevD.91.064061 | null | gr-qc cond-mat.quant-gas hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Formal solutions to the mode equations for both spherically symmetric black
holes and Bose-Einstein condensate acoustic black holes are obtained by writing
the spatial part of the mode equation as a linear Volterra integral equation of
the second kind. The solutions work for a massless minimally coupled scalar
field in the s-wave or zero angular momentum sector for a spherically symmetric
black hole and in the longitudinal sector of a 1D Bose-Einstein condensate
acoustic black hole. These solutions are used to obtain in a rigorous way
analytic expressions for the scattering coefficients and gray-body factors in
the zero frequency limit. They are also used to study the infrared behaviors of
the symmetric two-point function and two functions derived from it: the
point-split stress-energy tensor for the massless minimally coupled scalar
field in Schwarzschild-de Sitter spacetime and the density-density correlation
function for a Bose-Einstein condensate acoustic black hole.
| [
{
"created": "Thu, 8 Jan 2015 20:46:49 GMT",
"version": "v1"
}
] | 2015-04-08 | [
[
"Anderson",
"Paul R.",
""
],
[
"Fabbri",
"Alessandro",
""
],
[
"Balbinot",
"Roberto",
""
]
] | Formal solutions to the mode equations for both spherically symmetric black holes and Bose-Einstein condensate acoustic black holes are obtained by writing the spatial part of the mode equation as a linear Volterra integral equation of the second kind. The solutions work for a massless minimally coupled scalar field in the s-wave or zero angular momentum sector for a spherically symmetric black hole and in the longitudinal sector of a 1D Bose-Einstein condensate acoustic black hole. These solutions are used to obtain in a rigorous way analytic expressions for the scattering coefficients and gray-body factors in the zero frequency limit. They are also used to study the infrared behaviors of the symmetric two-point function and two functions derived from it: the point-split stress-energy tensor for the massless minimally coupled scalar field in Schwarzschild-de Sitter spacetime and the density-density correlation function for a Bose-Einstein condensate acoustic black hole. |
1703.10843 | Donato Bini | Donato Bini, Carmen Chicone and Bahram Mashhoon | Relativistic Tidal Acceleration of Astrophysical Jets | 26 pages, 6 figures, revtex macros used. Revised version matching the
published one. v3: typos corrected in equations (5) and (10)-(12) | Phys. Rev. D 95, 104029 (2017) | 10.1103/PhysRevD.95.104029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the framework of general relativity, we investigate the tidal
acceleration of astrophysical jets relative to the central collapsed
configuration ("Kerr source"). We neglect electromagnetic forces throughout.
The rest frame of the Kerr source is locally defined via the set of
hypothetical static observers in the spacetime exterior to the source. Relative
to such a fiducial observer fixed on the rotation axis of the Kerr source, jet
particles are tidally accelerated to almost the speed of light if their outflow
speed is above a certain threshold, given roughly by one half of the Newtonian
escape velocity at the location of the reference observer; otherwise, the
particles reach a certain height, reverse direction and fall back toward the
gravitational source.
| [
{
"created": "Fri, 31 Mar 2017 10:39:09 GMT",
"version": "v1"
},
{
"created": "Sat, 27 May 2017 10:11:26 GMT",
"version": "v2"
},
{
"created": "Mon, 28 Dec 2020 17:46:01 GMT",
"version": "v3"
}
] | 2020-12-29 | [
[
"Bini",
"Donato",
""
],
[
"Chicone",
"Carmen",
""
],
[
"Mashhoon",
"Bahram",
""
]
] | Within the framework of general relativity, we investigate the tidal acceleration of astrophysical jets relative to the central collapsed configuration ("Kerr source"). We neglect electromagnetic forces throughout. The rest frame of the Kerr source is locally defined via the set of hypothetical static observers in the spacetime exterior to the source. Relative to such a fiducial observer fixed on the rotation axis of the Kerr source, jet particles are tidally accelerated to almost the speed of light if their outflow speed is above a certain threshold, given roughly by one half of the Newtonian escape velocity at the location of the reference observer; otherwise, the particles reach a certain height, reverse direction and fall back toward the gravitational source. |
0902.3813 | Khalid Saifullah | K. Saifullah and Shair-e-Yazdan | Conformal motions in plane symmetric static spacetimes | 13 pages | Int.J.Mod.Phys.D18:71-81,2009 | 10.1142/S0218271809014340 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, conformal motions are studied in plane symmetric static
spacetimes. The general solution of conformal Killing equations and the general
form of the conformal Killing vector for these spacetimes are presented. All
possibilities for the existence of conformal motions in these spacetimes are
exhausted.
| [
{
"created": "Sun, 22 Feb 2009 18:49:43 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Apr 2009 19:53:19 GMT",
"version": "v2"
}
] | 2009-11-13 | [
[
"Saifullah",
"K.",
""
],
[
"Shair-e-Yazdan",
"",
""
]
] | In this paper, conformal motions are studied in plane symmetric static spacetimes. The general solution of conformal Killing equations and the general form of the conformal Killing vector for these spacetimes are presented. All possibilities for the existence of conformal motions in these spacetimes are exhausted. |
1404.7422 | Antoine Folacci | Andrei Belokogne and Antoine Folacci | Renormalized stress tensor for massive fields in Kerr-Newman spacetime | v2: Presentation greatly improved, discussions and references
added.v3: Matches the published version | Physical Review D 90, 044045 (2014) | 10.1103/PhysRevD.90.044045 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a four-dimensional spacetime, the DeWitt-Schwinger expansion of the
effective action associated with a massive quantum field reduces, after
renormalization and in the large mass limit, to a single term constructed from
the purely geometrical Gilkey-DeWitt coefficient $a_3$ and its metric variation
provides a good analytical approximation for the renormalized stress-energy
tensor of the quantum field. Here, from the general expression of this tensor,
we obtain analytically the renormalized stress-energy tensors of the massive
scalar field, the massive Dirac field and the Proca field in Kerr-Newman
spacetime. It should be noted that, even if, at first sight, the expressions
obtained are complicated, their structure is in fact rather simple, involving
naturally spacetime coordinates as well as the mass $M$, the charge $Q$ and the
rotation parameter $a$ of the Kerr-Newman black hole and permitting us to
recover rapidly the results already existing in the literature for the
Schwarzschild, Reissner-Nordstr\"om and Kerr black holes (and to correct them
in the latter case). In the absence of exact results in Kerr-Newman spacetime,
our approximate renormalized stress-energy tensors could be very helpful, in
particular to study the backreaction of massive quantum fields on this
spacetime or on its quasinormal modes.
| [
{
"created": "Tue, 29 Apr 2014 16:23:55 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Jul 2014 18:41:47 GMT",
"version": "v2"
},
{
"created": "Thu, 11 Sep 2014 15:22:39 GMT",
"version": "v3"
}
] | 2014-09-12 | [
[
"Belokogne",
"Andrei",
""
],
[
"Folacci",
"Antoine",
""
]
] | In a four-dimensional spacetime, the DeWitt-Schwinger expansion of the effective action associated with a massive quantum field reduces, after renormalization and in the large mass limit, to a single term constructed from the purely geometrical Gilkey-DeWitt coefficient $a_3$ and its metric variation provides a good analytical approximation for the renormalized stress-energy tensor of the quantum field. Here, from the general expression of this tensor, we obtain analytically the renormalized stress-energy tensors of the massive scalar field, the massive Dirac field and the Proca field in Kerr-Newman spacetime. It should be noted that, even if, at first sight, the expressions obtained are complicated, their structure is in fact rather simple, involving naturally spacetime coordinates as well as the mass $M$, the charge $Q$ and the rotation parameter $a$ of the Kerr-Newman black hole and permitting us to recover rapidly the results already existing in the literature for the Schwarzschild, Reissner-Nordstr\"om and Kerr black holes (and to correct them in the latter case). In the absence of exact results in Kerr-Newman spacetime, our approximate renormalized stress-energy tensors could be very helpful, in particular to study the backreaction of massive quantum fields on this spacetime or on its quasinormal modes. |
1906.07560 | Branko Dragovich | I. Dimitrijevic, B. Dragovich, A. S. Koshelev, Z. Rakic and J.
Stankovic | Cosmological Solutions of a Nonlocal Square Root Gravity | version published in Phys. Lett. B | null | 10.1016/j.physletb.2019.134848 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we consider modification of general relativity extending $R - 2
\Lambda$ by nonlocal term of the form $\sqrt{R-2\Lambda}\, \mathcal{F}(\Box)\,
\sqrt{R-2\Lambda} ,$ where $\mathcal{F}(\Box)$ is an analytic function of the
d'Alembert operator $\Box$. We have found some exact cosmological solutions of
the corresponding equations of motion without matter and with $\Lambda \neq 0$.
One of these solutions is $ a (t) = A \, t^{\frac{2}{3}} \,
e^{\frac{\Lambda}{14} t^2} ,$ which imitates properties similar to an interplay
of the dark matter and the dark energy. For this solution we calculated some
cosmological parameters which are in a good agreement with observations. This
nonlocal gravity model has not the Minkowski space solution. We also found
several conditions which function $\mathcal{F}(\Box)$ has to satisfy.
| [
{
"created": "Sun, 16 Jun 2019 19:05:34 GMT",
"version": "v1"
},
{
"created": "Sat, 31 Aug 2019 16:33:44 GMT",
"version": "v2"
}
] | 2019-09-04 | [
[
"Dimitrijevic",
"I.",
""
],
[
"Dragovich",
"B.",
""
],
[
"Koshelev",
"A. S.",
""
],
[
"Rakic",
"Z.",
""
],
[
"Stankovic",
"J.",
""
]
] | In this paper we consider modification of general relativity extending $R - 2 \Lambda$ by nonlocal term of the form $\sqrt{R-2\Lambda}\, \mathcal{F}(\Box)\, \sqrt{R-2\Lambda} ,$ where $\mathcal{F}(\Box)$ is an analytic function of the d'Alembert operator $\Box$. We have found some exact cosmological solutions of the corresponding equations of motion without matter and with $\Lambda \neq 0$. One of these solutions is $ a (t) = A \, t^{\frac{2}{3}} \, e^{\frac{\Lambda}{14} t^2} ,$ which imitates properties similar to an interplay of the dark matter and the dark energy. For this solution we calculated some cosmological parameters which are in a good agreement with observations. This nonlocal gravity model has not the Minkowski space solution. We also found several conditions which function $\mathcal{F}(\Box)$ has to satisfy. |
2004.05882 | Anton Sheykin | A. A. Sheykin, M. V. Markov, Ya. A. Fedulov and S. A. Paston | Explicit isometric embeddings of pseudo-Riemannian manifolds: ideas and
applications | 7 pages. The minor typo in eq. (10) of published version is corrected
here, minor clarifications are also made | J. Phys. Conf. Ser., Vol. 1697, 012077 (2020) | 10.1088/1742-6596/1697/1/012077 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the problem of construction of explicit isometric embeddings of
(pseudo)-Riemannian manifolds. We discuss the method which is based in the idea
that the exterior symmetry of the embedded surface and the interior symmetry of
the metric on it must be the same. In case of high enough symmetry of the
metric such method allows to transform the metric inducedness condition, which
is the one to be solved in order to construct an embedding, into a system of
ODEs. It turns out that this method can be generalized to allow the surface to
have lower symmetry as long as the above simplification occurs. This
generalization can be of use in the construction of embeddings for metrics
whose symmetry group is hard to analyze, as well for the construction of
isometrically deformed (bended) surface. We give some examples of application
of this method. In particular, we construct the embedding of spatially-flat
Friedmann model and isometric bendings of sphere, 3-sphere and squashed AdS
universe, which is connected to the Godel universe.
| [
{
"created": "Mon, 13 Apr 2020 12:02:36 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Dec 2020 10:46:01 GMT",
"version": "v2"
}
] | 2020-12-17 | [
[
"Sheykin",
"A. A.",
""
],
[
"Markov",
"M. V.",
""
],
[
"Fedulov",
"Ya. A.",
""
],
[
"Paston",
"S. A.",
""
]
] | We study the problem of construction of explicit isometric embeddings of (pseudo)-Riemannian manifolds. We discuss the method which is based in the idea that the exterior symmetry of the embedded surface and the interior symmetry of the metric on it must be the same. In case of high enough symmetry of the metric such method allows to transform the metric inducedness condition, which is the one to be solved in order to construct an embedding, into a system of ODEs. It turns out that this method can be generalized to allow the surface to have lower symmetry as long as the above simplification occurs. This generalization can be of use in the construction of embeddings for metrics whose symmetry group is hard to analyze, as well for the construction of isometrically deformed (bended) surface. We give some examples of application of this method. In particular, we construct the embedding of spatially-flat Friedmann model and isometric bendings of sphere, 3-sphere and squashed AdS universe, which is connected to the Godel universe. |
gr-qc/9409013 | Gary Horowitz | S. W. Hawking, Gary T. Horowitz, and Simon F. Ross | Entropy, Area, and Black Hole Pairs | 25 pages; DAMTP/R 94-26, UCSBTH-94-25 (minor errors and references
corrected) | Phys.Rev.D51:4302-4314,1995 | 10.1103/PhysRevD.51.4302 | null | gr-qc hep-th | null | We clarify the relation between gravitational entropy and the area of
horizons. We first show that the entropy of an extreme Reissner-Nordstr\"om
black hole is $zero$, despite the fact that its horizon has nonzero area. Next,
we consider the pair creation of extremal and nonextremal black holes. It is
shown that the action which governs the rate of this pair creation is directly
related to the area of the acceleration horizon and (in the nonextremal case)
the area of the black hole event horizon. This provides a simple explanation of
the result that the rate of pair creation of non-extreme black holes is
enhanced by precisely the black hole entropy. Finally, we discuss black hole
$annihilation$, and argue that Planck scale remnants are not sufficient to
preserve unitarity in quantum gravity.
| [
{
"created": "Thu, 8 Sep 1994 00:21:02 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Sep 1994 17:56:52 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Hawking",
"S. W.",
""
],
[
"Horowitz",
"Gary T.",
""
],
[
"Ross",
"Simon F.",
""
]
] | We clarify the relation between gravitational entropy and the area of horizons. We first show that the entropy of an extreme Reissner-Nordstr\"om black hole is $zero$, despite the fact that its horizon has nonzero area. Next, we consider the pair creation of extremal and nonextremal black holes. It is shown that the action which governs the rate of this pair creation is directly related to the area of the acceleration horizon and (in the nonextremal case) the area of the black hole event horizon. This provides a simple explanation of the result that the rate of pair creation of non-extreme black holes is enhanced by precisely the black hole entropy. Finally, we discuss black hole $annihilation$, and argue that Planck scale remnants are not sufficient to preserve unitarity in quantum gravity. |
gr-qc/0307036 | Bernd Reimann | Bernd Reimann, Bernd Bruegmann | Maximal Slicing for Puncture Evolutions of Schwarzschild and
Reissner-Nordstr\"om Black Holes | 21 pages, 9 figures, published version with changes to Sec. VII | Phys.Rev.D69:044006,2004 | 10.1103/PhysRevD.69.044006 | AEI-2003-058, CGPG-03/7-1 | gr-qc | null | We prove by explicit construction that there exists a maximal slicing of the
Schwarzschild spacetime such that the lapse has zero gradient at the puncture.
This boundary condition has been observed to hold in numerical evolutions, but
in the past it was not clear whether the numerically obtained maximal slices
exist analytically. We show that our analytical result agrees with numerical
simulation. Given the analytical form for the lapse, we can derive that at late
times the value of the lapse at the event horizon approaches the value
${3/16}\sqrt{3} \approx 0.3248$, justifying the numerical estimate of 0.3 that
has been used for black hole excision in numerical simulations. We present our
results for the non-extremal Reissner-Nordstr\"om metric, generalizing previous
constructions of maximal slices.
| [
{
"created": "Wed, 9 Jul 2003 08:29:56 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Feb 2004 17:35:02 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Reimann",
"Bernd",
""
],
[
"Bruegmann",
"Bernd",
""
]
] | We prove by explicit construction that there exists a maximal slicing of the Schwarzschild spacetime such that the lapse has zero gradient at the puncture. This boundary condition has been observed to hold in numerical evolutions, but in the past it was not clear whether the numerically obtained maximal slices exist analytically. We show that our analytical result agrees with numerical simulation. Given the analytical form for the lapse, we can derive that at late times the value of the lapse at the event horizon approaches the value ${3/16}\sqrt{3} \approx 0.3248$, justifying the numerical estimate of 0.3 that has been used for black hole excision in numerical simulations. We present our results for the non-extremal Reissner-Nordstr\"om metric, generalizing previous constructions of maximal slices. |
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