id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9408014 | Robert H. Gowdy | Robert H. Gowdy | Affine projection tensor geometry: Lie derivatives and isometries | 23 pages RevTeX | J.Math.Phys. 36 (1995) 1882-1907; Erratum-ibid. 36 (1995) 5200 | 10.1063/1.531092 | null | gr-qc | null | The generalized projection-tensor geometry introduced in an earlier paper is
extended. A compact notation for families of projected objects is introduced
and used to summarize the results of the previous paper and obtain fully
projected decompositions of Lie derivatives of the projection tensor field, the
metric and the projected parts of the metric. These results are applied to the
analysis of spacetimes with isometries. The familiar cases of spacetimes with
isotropic group orbits --- cosmological models and spherical symmetry --- are
discussed as illustrations of the results.
| [
{
"created": "Wed, 10 Aug 1994 18:10:21 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Gowdy",
"Robert H.",
""
]
] | The generalized projection-tensor geometry introduced in an earlier paper is extended. A compact notation for families of projected objects is introduced and used to summarize the results of the previous paper and obtain fully projected decompositions of Lie derivatives of the projection tensor field, the metric and the projected parts of the metric. These results are applied to the analysis of spacetimes with isometries. The familiar cases of spacetimes with isotropic group orbits --- cosmological models and spherical symmetry --- are discussed as illustrations of the results. |
1110.3422 | Yousef Bisabr | Yousef Bisabr (Farzan-nahad) | The Coincidence Problem in Holographic f(R) Gravity | 10 pages, no figures | Phys. Scr. 84, 035901 (2011) | 10.1088/0031-8949/84/03/035901 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well-known that $f(R)$ gravity models formulated in Einstein conformal
frame are equivalent to Einstein gravity together with a minimally coupled
scalar field. In this case, the scalar field couples with the matter sector and
the coupling term is given by the conformal factor. We apply the holographic
principle to such interacting models. In a spatially flat universe, we show
that the Einstein frame representation of $f(R)$ models leads to a constant
ratio of energy densities of dark matter to dark energy.
| [
{
"created": "Sat, 15 Oct 2011 15:56:50 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Bisabr",
"Yousef",
"",
"Farzan-nahad"
]
] | It is well-known that $f(R)$ gravity models formulated in Einstein conformal frame are equivalent to Einstein gravity together with a minimally coupled scalar field. In this case, the scalar field couples with the matter sector and the coupling term is given by the conformal factor. We apply the holographic principle to such interacting models. In a spatially flat universe, we show that the Einstein frame representation of $f(R)$ models leads to a constant ratio of energy densities of dark matter to dark energy. |
1610.09846 | Tim-Torben Paetz | Marc Mars, Tim-Torben Paetz, Jos\'e M. M. Senovilla | Classification of Kerr-de Sitter-like spacetimes with conformally flat
Scri | 63 pages | null | 10.1088/1361-6382/aa5dc2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide a classification of $\Lambda>0$-vacuum spacetimes which admit a
Killing vector field with respect to which the associated "Mars-Simon tensor"
(MST) vanishes and having a conformally flat $\mathcal{J}^-$ (or
$\mathcal{J}^+$). To that end, we also give a complete classification of
conformal Killing vector fields on the $3$-sphere $\mathbb{S}^3$ up to M\"obius
transformations shedding light on the two fundamental constants that
characterize the family of Kerr-de Sitter-like spacetimes, which turn out to be
well-defined geometrical invariants. The topology of $\mathcal{J}$ is
determined in every case, and a characterization result at $\mathcal{J}$ of the
Kerr-de Sitter family presented.
| [
{
"created": "Mon, 31 Oct 2016 10:02:13 GMT",
"version": "v1"
}
] | 2017-04-19 | [
[
"Mars",
"Marc",
""
],
[
"Paetz",
"Tim-Torben",
""
],
[
"Senovilla",
"José M. M.",
""
]
] | We provide a classification of $\Lambda>0$-vacuum spacetimes which admit a Killing vector field with respect to which the associated "Mars-Simon tensor" (MST) vanishes and having a conformally flat $\mathcal{J}^-$ (or $\mathcal{J}^+$). To that end, we also give a complete classification of conformal Killing vector fields on the $3$-sphere $\mathbb{S}^3$ up to M\"obius transformations shedding light on the two fundamental constants that characterize the family of Kerr-de Sitter-like spacetimes, which turn out to be well-defined geometrical invariants. The topology of $\mathcal{J}$ is determined in every case, and a characterization result at $\mathcal{J}$ of the Kerr-de Sitter family presented. |
2107.10217 | Ivan Agullo | Ivan Agullo, Anthony J. Brady and Dimitrios Kranas | Stimulating the Quantum Aspects of an Optical Analog White-Black Hole | 6 pages + supplemental material. 6 figures | null | 10.1103/PhysRevLett.128.091301 | null | gr-qc cond-mat.quant-gas hep-th quant-ph | http://creativecommons.org/licenses/by-nc-nd/4.0/ | This work introduces a synergistic combination of analytical methods and
numerical simulations to study the propagation of weak wave-packet modes in an
optical medium containing the analog of a pair white-black hole. We apply our
tools to analyze several aspects of the evolution, such as (i) the region of
the parameter space where the analogy with the Hawking effect is on firm ground
and (ii) the influence that ambient thermal noise and detector inefficiencies
have on the observability of the Hawking effect. We find that aspects of the
Hawking effect that are of quantum origin, such as quantum entanglement, are
extremely fragile to the influence of inefficiencies and noise. We propose a
protocol to amplify and observe these quantum aspects, based on seeding the
process with a single-mode squeezed input.
| [
{
"created": "Wed, 21 Jul 2021 17:16:37 GMT",
"version": "v1"
}
] | 2022-03-24 | [
[
"Agullo",
"Ivan",
""
],
[
"Brady",
"Anthony J.",
""
],
[
"Kranas",
"Dimitrios",
""
]
] | This work introduces a synergistic combination of analytical methods and numerical simulations to study the propagation of weak wave-packet modes in an optical medium containing the analog of a pair white-black hole. We apply our tools to analyze several aspects of the evolution, such as (i) the region of the parameter space where the analogy with the Hawking effect is on firm ground and (ii) the influence that ambient thermal noise and detector inefficiencies have on the observability of the Hawking effect. We find that aspects of the Hawking effect that are of quantum origin, such as quantum entanglement, are extremely fragile to the influence of inefficiencies and noise. We propose a protocol to amplify and observe these quantum aspects, based on seeding the process with a single-mode squeezed input. |
1305.3683 | Roberto A. Sussman | Roberto A Sussman | Invariant characterization of the growing and decaying density modes in
LTB dust models | Final version accepted for publication in Classical and Quantum
Gravity. 34 pages, 6 figures and 4 tables, IOP LaTeX format | Classical and Quantum Gravity 30 235001 (2013) | 10.1088/0264-9381/30/23/235001 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain covariant expressions that generalize the growing and decaying
density modes of linear perturbation theory of dust sources by means of the
exact density perturbation from the formalism of quasi--local scalars
associated to weighed proper volume averages in LTB dust models. The relation
between these density modes and theoretical properties of generic LTB models is
thoroughly studied by looking at the evolution of the models through a
dynamical system whose phase space is parametrized by variables directly
related to the modes themselves. The conditions for absence of shell crossings,
as well as sign conditions on the modes, become interrelated fluid flow
preserved constraints that define phase space invariant subspaces. In the
general case (both density modes being nonzero) the evolution of phase space
trajectories exhibits the expected dominance of the decaying/growing in the
early/late evolution times defined by past/future attractors characterized by
asymptotic density inhomogeneity. In particular, the growing mode is also
dominant for collapsing layers that terminate in a future attractor associated
with a "Big Crunch" singularity, which is qualitatively different from the past
attractor marking the "Big Bang". Suppression of the decaying mode modifies the
early time evolution, with phase space trajectories emerging from an
Einstein--de Sitter past attractor associated with homogeneous conditions.
Suppression of the growing mode modifies the late time evolution as phase space
trajectories terminate in future attractors associated with homogeneous states.
General results are obtained relating the signs of the density modes and the
type of asymptotic density profile (clump or void). A critical review is given
of previous attempts in the literature to define these density modes for LTB
models.
| [
{
"created": "Thu, 16 May 2013 04:55:34 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Sep 2013 23:29:28 GMT",
"version": "v2"
}
] | 2015-06-15 | [
[
"Sussman",
"Roberto A",
""
]
] | We obtain covariant expressions that generalize the growing and decaying density modes of linear perturbation theory of dust sources by means of the exact density perturbation from the formalism of quasi--local scalars associated to weighed proper volume averages in LTB dust models. The relation between these density modes and theoretical properties of generic LTB models is thoroughly studied by looking at the evolution of the models through a dynamical system whose phase space is parametrized by variables directly related to the modes themselves. The conditions for absence of shell crossings, as well as sign conditions on the modes, become interrelated fluid flow preserved constraints that define phase space invariant subspaces. In the general case (both density modes being nonzero) the evolution of phase space trajectories exhibits the expected dominance of the decaying/growing in the early/late evolution times defined by past/future attractors characterized by asymptotic density inhomogeneity. In particular, the growing mode is also dominant for collapsing layers that terminate in a future attractor associated with a "Big Crunch" singularity, which is qualitatively different from the past attractor marking the "Big Bang". Suppression of the decaying mode modifies the early time evolution, with phase space trajectories emerging from an Einstein--de Sitter past attractor associated with homogeneous conditions. Suppression of the growing mode modifies the late time evolution as phase space trajectories terminate in future attractors associated with homogeneous states. General results are obtained relating the signs of the density modes and the type of asymptotic density profile (clump or void). A critical review is given of previous attempts in the literature to define these density modes for LTB models. |
2303.00117 | Giulia Maniccia | Giulia Maniccia, Giovanni Montani, Leonardo Torcellini | Study of the Inflationary Spectrum in the Presence of Quantum Gravity
Corrections | 24 pages. Discussion expanded and references added; matches the
published version | Universe 2023, 9(4), 169 | 10.3390/universe9040169 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | After a brief review of the different approaches to predict the possible
quantum gravity corrections to quantum field theory, we discuss in some detail
the formulation based on a Gaussian reference frame fixing. Then, we implement
this scenario to the determination of the inflationary spectrum of primordial
perturbations. We consider the quantization of an inhomogeneous free massless
scalar field on a quasi-classical isotropic Universe, developing a WKB
expansion of the dynamics at the next order in the Planckian parameter, with
respect to the one at which standard QFT emerges. The quantum gravity
corrections to the scale invariant spectrum are discussed in a specific
primordial cosmological setting and then in a general minisuperspace formalism,
showing that there is no mode-dependent effect and thus the scale invariant
inflationary spectrum is preserved. Such result is discussed in connection to
the absence of a matter backreaction on the gravitational background in the
considered paradigm.
| [
{
"created": "Tue, 28 Feb 2023 22:37:12 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Mar 2023 13:41:25 GMT",
"version": "v2"
}
] | 2023-06-12 | [
[
"Maniccia",
"Giulia",
""
],
[
"Montani",
"Giovanni",
""
],
[
"Torcellini",
"Leonardo",
""
]
] | After a brief review of the different approaches to predict the possible quantum gravity corrections to quantum field theory, we discuss in some detail the formulation based on a Gaussian reference frame fixing. Then, we implement this scenario to the determination of the inflationary spectrum of primordial perturbations. We consider the quantization of an inhomogeneous free massless scalar field on a quasi-classical isotropic Universe, developing a WKB expansion of the dynamics at the next order in the Planckian parameter, with respect to the one at which standard QFT emerges. The quantum gravity corrections to the scale invariant spectrum are discussed in a specific primordial cosmological setting and then in a general minisuperspace formalism, showing that there is no mode-dependent effect and thus the scale invariant inflationary spectrum is preserved. Such result is discussed in connection to the absence of a matter backreaction on the gravitational background in the considered paradigm. |
0706.3770 | Z. Ya. Turakulov | A.T. Muminov, Z.Ya. Turakulov | Motion of a Vector Particle in a Curved Space-time. IV. Asymptotical
shape of caustic | 6 pages | Mod.Phys.Lett.A22:1091-1096,2007 | 10.1142/S0217732307023407 | null | gr-qc | null | The studies of influence of spin on a photon motion in a Schwartzschild
spacetime is continued. In the previous paper [2] the first order correction to
the geodesic motion is reduced to a non-uniform linear ordinary differential
equation and the equation obtained has been solved by the standard method of
integration of the Green function. If each photon draws a world line specified
by this solution then light rays from infinitely distant source form a caustic
which does not appear without the spin-gravity interaction. The goal of the
present work is to obtain explicit form of caustic.
| [
{
"created": "Tue, 26 Jun 2007 08:07:10 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Muminov",
"A. T.",
""
],
[
"Turakulov",
"Z. Ya.",
""
]
] | The studies of influence of spin on a photon motion in a Schwartzschild spacetime is continued. In the previous paper [2] the first order correction to the geodesic motion is reduced to a non-uniform linear ordinary differential equation and the equation obtained has been solved by the standard method of integration of the Green function. If each photon draws a world line specified by this solution then light rays from infinitely distant source form a caustic which does not appear without the spin-gravity interaction. The goal of the present work is to obtain explicit form of caustic. |
2406.04787 | Hai-Li Li | Zhijun Song, Huajie Gong, Hai-Li Li, Guoyang Fu, Li-Gang Zhu, Jian-Pin
Wu | Quasinormal modes and ringdown waveform of the Frolov black hole | 15 pages, 7 figures; accepted for publication in Communications in
Theoretical Physics | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the scalar perturbation over the Frolov black
hole (BH), which is a regular BH induced by the quantum gravity effect. The
quasinormal frequencies (QNFs) of scalar field always consistently reside in
the lower half-plane, and its time-domain evolution demonstrates a decaying
behavior, with the late-time tail exhibiting a power-law pattern. These
observations collectively suggest the stability of the Frolov BH against scalar
perturbation. Additionally, our study reveals that quantum gravity effects lead
to slower decay modes. For the case of the angular quantum number $l=0$, the
oscillation exhibits non-monotonic behavior with the quantum gravity parameter
$\alpha_0$. However, once $l\geq 1$, the angular quantum number surpasses the
influence of the quantum gravity effect.
| [
{
"created": "Fri, 7 Jun 2024 09:37:03 GMT",
"version": "v1"
}
] | 2024-06-10 | [
[
"Song",
"Zhijun",
""
],
[
"Gong",
"Huajie",
""
],
[
"Li",
"Hai-Li",
""
],
[
"Fu",
"Guoyang",
""
],
[
"Zhu",
"Li-Gang",
""
],
[
"Wu",
"Jian-Pin",
""
]
] | In this paper, we investigate the scalar perturbation over the Frolov black hole (BH), which is a regular BH induced by the quantum gravity effect. The quasinormal frequencies (QNFs) of scalar field always consistently reside in the lower half-plane, and its time-domain evolution demonstrates a decaying behavior, with the late-time tail exhibiting a power-law pattern. These observations collectively suggest the stability of the Frolov BH against scalar perturbation. Additionally, our study reveals that quantum gravity effects lead to slower decay modes. For the case of the angular quantum number $l=0$, the oscillation exhibits non-monotonic behavior with the quantum gravity parameter $\alpha_0$. However, once $l\geq 1$, the angular quantum number surpasses the influence of the quantum gravity effect. |
1312.0703 | Hyeong-Chan Kim | Hyeong-Chan Kim | Origin of the universe: A hint from Eddington-inspired Born-Infeld
gravity | Proceedings for IK13. 6 pages,1 figure | null | 10.3938/jkps.65.840 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the `initial state' of an anisotropic universe in Eddington-inspired
Born-Infeld gravity filled with a scalar field, whose potential has various
forms. With this purpose, the evolution of a spatially-flat, homogeneous
anisotropic Kasner universe is studied. We find an exact evolution of universe
for each scalar potential by imposing a maximal pressure condition. The
solution is shown to describe the initial state of the universe. The state is
regular if the scalar potential increases not faster than the quadratic power
for large field values. We also show that the anisotropy does not raise any
defect in early universe contrary to the case of general relativity.
| [
{
"created": "Tue, 3 Dec 2013 05:49:08 GMT",
"version": "v1"
}
] | 2015-06-18 | [
[
"Kim",
"Hyeong-Chan",
""
]
] | We study the `initial state' of an anisotropic universe in Eddington-inspired Born-Infeld gravity filled with a scalar field, whose potential has various forms. With this purpose, the evolution of a spatially-flat, homogeneous anisotropic Kasner universe is studied. We find an exact evolution of universe for each scalar potential by imposing a maximal pressure condition. The solution is shown to describe the initial state of the universe. The state is regular if the scalar potential increases not faster than the quadratic power for large field values. We also show that the anisotropy does not raise any defect in early universe contrary to the case of general relativity. |
1005.2682 | T. P. Singh | T. P. Singh | The connection between `emergence of time from quantum gravity' and
`dynamical collapse of the wave-function in quantum mechanics' | 6 pages. References updated. To appear in Int. J. Mod. Phys. D
[special issue] | Int.J.Mod.Phys.D19:2265-2269,2010 | 10.1142/S0218271810018335 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There are various reasons to believe that quantum theory could be an emergent
phenomenon. Trace Dynamics is an underlying classical dynamics of non-commuting
matrices, from which quantum theory and classical mechanics have been shown to
emerge, in the thermodynamic approximation. However, the time that is used to
describe evolution in quantum theory is an external classical time, and is in
turn expected to be an emergent feature - a relic of an underlying theory of
quantum gravity. In this essay we borrow ideas from Trace Dynamics to show that
classical time is a thermodynamic approximation to an operator time in quantum
gravitational physics. This prediction will be put to test by ongoing
laboratory experiments attempting to construct superposed states of macroscopic
objects.
| [
{
"created": "Sat, 15 May 2010 15:07:44 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Oct 2010 17:32:57 GMT",
"version": "v2"
}
] | 2011-01-25 | [
[
"Singh",
"T. P.",
""
]
] | There are various reasons to believe that quantum theory could be an emergent phenomenon. Trace Dynamics is an underlying classical dynamics of non-commuting matrices, from which quantum theory and classical mechanics have been shown to emerge, in the thermodynamic approximation. However, the time that is used to describe evolution in quantum theory is an external classical time, and is in turn expected to be an emergent feature - a relic of an underlying theory of quantum gravity. In this essay we borrow ideas from Trace Dynamics to show that classical time is a thermodynamic approximation to an operator time in quantum gravitational physics. This prediction will be put to test by ongoing laboratory experiments attempting to construct superposed states of macroscopic objects. |
2006.09148 | S K Narasimhamurthy | H. M. Manjunatha, S. K. Narasimhamurthy, Z. Nekouee | The gravitational field of the SdS space-time | 11 pages, 6 figures | Int. J. Geom. Methods Mod. Phys. 17, 2050069 (2020) | 10.1142/S0219887820500693 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The goal of this paper is to study SdS space-time and its gravitational field
with consideration of the canonical form and invariants of the curvature
tensor. The characteristic of $\lambda$-tensor identifies the type of
gravitational field. Gaussian curvature quantities enunciated in terms of
curvature invariants.
| [
{
"created": "Sun, 14 Jun 2020 12:09:23 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Jun 2020 11:05:30 GMT",
"version": "v2"
}
] | 2020-06-18 | [
[
"Manjunatha",
"H. M.",
""
],
[
"Narasimhamurthy",
"S. K.",
""
],
[
"Nekouee",
"Z.",
""
]
] | The goal of this paper is to study SdS space-time and its gravitational field with consideration of the canonical form and invariants of the curvature tensor. The characteristic of $\lambda$-tensor identifies the type of gravitational field. Gaussian curvature quantities enunciated in terms of curvature invariants. |
gr-qc/9808011 | Desmond Johnston | P. Bialas, Z. Burda and D. Johnston | Phase diagram of the mean field model of simplicial gravity | 15 pages, 5 figures | Nucl.Phys. B542 (1999) 413-424 | 10.1016/S0550-3213(98)00842-6 | HWM98-27 | gr-qc cond-mat.stat-mech hep-lat | null | We discuss the phase diagram of the balls in boxes model, with a varying
number of boxes. The model can be regarded as a mean-field model of simplicial
gravity. We analyse in detail the case of weights of the form $p(q) =
q^{-\beta}$, which correspond to the measure term introduced in the simplicial
quantum gravity simulations. The system has two phases~: {\em elongated} ({\em
fluid}) and {\em crumpled}. For $\beta\in (2,\infty)$ the transition between
these two phases is first order, while for $\beta \in (1,2]$ it is continuous.
The transition becomes softer when $\beta$ approaches unity and eventually
disappears at $\beta=1$. We then generalise the discussion to an arbitrary set
of weights. Finally, we show that if one introduces an additional kinematic
bound on the average density of balls per box then a new {\em condensed} phase
appears in the phase diagram. It bears some similarity to the {\em crinkled}
phase of simplicial gravity discussed recently in models of gravity interacting
with matter fields.
| [
{
"created": "Tue, 4 Aug 1998 14:45:55 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Bialas",
"P.",
""
],
[
"Burda",
"Z.",
""
],
[
"Johnston",
"D.",
""
]
] | We discuss the phase diagram of the balls in boxes model, with a varying number of boxes. The model can be regarded as a mean-field model of simplicial gravity. We analyse in detail the case of weights of the form $p(q) = q^{-\beta}$, which correspond to the measure term introduced in the simplicial quantum gravity simulations. The system has two phases~: {\em elongated} ({\em fluid}) and {\em crumpled}. For $\beta\in (2,\infty)$ the transition between these two phases is first order, while for $\beta \in (1,2]$ it is continuous. The transition becomes softer when $\beta$ approaches unity and eventually disappears at $\beta=1$. We then generalise the discussion to an arbitrary set of weights. Finally, we show that if one introduces an additional kinematic bound on the average density of balls per box then a new {\em condensed} phase appears in the phase diagram. It bears some similarity to the {\em crinkled} phase of simplicial gravity discussed recently in models of gravity interacting with matter fields. |
1410.6480 | Juri Smirnov | Juri Smirnov | Gauge-Invariant Average of Einstein Equations for finite Volumes | 14 pages, 2 figures, resolves problem of gauge dependence | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For the study of cosmological backreacktion an avaragng procedure is
required. In this work a covariant and gauge invariant averaging formalism for
finite volumes will be developed. This averaging will be applied to the scalar
parts of Einstein's equations. For this purpose dust as a physical laboratory
will be coupled to the gravitating system. The goal is to study the deviation
from the homogeneous universe and the impact of this deviation on the dynamics
of our universe. Fields of physical observers are included in the studied
system and used to construct a reference frame to perform the averaging without
a formal gauge fixing. The derived equations resolve the question whether
backreaction is gauge dependent.
| [
{
"created": "Thu, 23 Oct 2014 20:00:04 GMT",
"version": "v1"
}
] | 2014-10-27 | [
[
"Smirnov",
"Juri",
""
]
] | For the study of cosmological backreacktion an avaragng procedure is required. In this work a covariant and gauge invariant averaging formalism for finite volumes will be developed. This averaging will be applied to the scalar parts of Einstein's equations. For this purpose dust as a physical laboratory will be coupled to the gravitating system. The goal is to study the deviation from the homogeneous universe and the impact of this deviation on the dynamics of our universe. Fields of physical observers are included in the studied system and used to construct a reference frame to perform the averaging without a formal gauge fixing. The derived equations resolve the question whether backreaction is gauge dependent. |
1404.5284 | Martin Bojowald | Martin Bojowald | Fluctuation energies in quantum cosmology | 35 pages, 6 figures | Phys. Rev. D 89, 124031 (2014) | 10.1103/PhysRevD.89.124031 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum fluctuations or other moments of a state contribute to energy
expectation values and can imply interesting physical effects. In quantum
cosmology, they turn out to be important for a discussion of density bounds and
instabilities of initial-value problems in the presence of signature change in
loop-quantized models. This article provides an effective description of these
issues, accompanied by a comparison with existing numerical results and an
extension to squeezed states. The comparison confirms that canonical effective
methods are well-suited for computations of properties of physical states. As a
side product, an example is found for a simple state in which quantum
fluctuations can cancel holonomy modifications of loop quantum cosmology.
| [
{
"created": "Mon, 21 Apr 2014 19:44:04 GMT",
"version": "v1"
}
] | 2014-07-02 | [
[
"Bojowald",
"Martin",
""
]
] | Quantum fluctuations or other moments of a state contribute to energy expectation values and can imply interesting physical effects. In quantum cosmology, they turn out to be important for a discussion of density bounds and instabilities of initial-value problems in the presence of signature change in loop-quantized models. This article provides an effective description of these issues, accompanied by a comparison with existing numerical results and an extension to squeezed states. The comparison confirms that canonical effective methods are well-suited for computations of properties of physical states. As a side product, an example is found for a simple state in which quantum fluctuations can cancel holonomy modifications of loop quantum cosmology. |
1307.1683 | Istvan Racz | Istv\'an R\'acz | Stationary Black Holes as Holographs II | 35 pages, substantially extended introduction, added references,
conclusions unchanged, to appear in CQG | Class. Quantum Grav. 31 035006 2014 | 10.1088/0264-9381/31/3/035006 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Smooth four-dimensional electrovac spacetimes in Einstein's theory are
considered each possessing a pair of null hypersurfaces, $H_1$ and $H_2$,
generated by expansion and shear free geodesically complete null congruences
such that they intersect on a two-dimensional spacelike surface, $Z=H_1\cap
H_2$. By making use of a combination of the Newman-Penrose formalism and the
null characteristic initial value problem it is shown that both the spacetime
geometry and the electromagnetic field are uniquely determined, in the domain
of dependence of $H_1\cup H_2$ once a complex vector field $\xi^A$ (determining
the metric induced on $Z$), the $\tau$ spin coefficient and the $\phi_1$
electromagnetic potential are specified on $Z$. The existence of a Killing
vector field---with respect to which the null hypersurfaces $H_1$ and $H_2$
comprise a bifurcate type Killing horizon---is also justified in the domain of
dependence of $H_1\cup H_2$. Since, in general, the freely specifiable data on
$Z$ do not have any sort of symmetry the corresponding spacetimes do not
possess any symmetry in addition to the horizon Killing vector field. Thereby,
they comprise the class of generic `stationary' distorted electrovac black hole
spacetimes. It is also shown that there are stationary distorted electrovac
black hole configurations such that parallelly propagated curvature blow up
occurs both to the future and to the past ends of some of the null generators
of their bifurcate Killing horizon, and also that this behavior is universal.
In particular, it is shown that, in the space of vacuum solutions to Einstein's
equations, in an arbitrarily small neighborhood of the Schwarzschild solution
this type of distorted vacuum black hole configurations always exist. A short
discussion on the relation of these results and some of the recent claims on
the instability of extremal black holes is also given.
| [
{
"created": "Fri, 5 Jul 2013 18:15:13 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Nov 2013 08:31:31 GMT",
"version": "v2"
}
] | 2015-01-16 | [
[
"Rácz",
"István",
""
]
] | Smooth four-dimensional electrovac spacetimes in Einstein's theory are considered each possessing a pair of null hypersurfaces, $H_1$ and $H_2$, generated by expansion and shear free geodesically complete null congruences such that they intersect on a two-dimensional spacelike surface, $Z=H_1\cap H_2$. By making use of a combination of the Newman-Penrose formalism and the null characteristic initial value problem it is shown that both the spacetime geometry and the electromagnetic field are uniquely determined, in the domain of dependence of $H_1\cup H_2$ once a complex vector field $\xi^A$ (determining the metric induced on $Z$), the $\tau$ spin coefficient and the $\phi_1$ electromagnetic potential are specified on $Z$. The existence of a Killing vector field---with respect to which the null hypersurfaces $H_1$ and $H_2$ comprise a bifurcate type Killing horizon---is also justified in the domain of dependence of $H_1\cup H_2$. Since, in general, the freely specifiable data on $Z$ do not have any sort of symmetry the corresponding spacetimes do not possess any symmetry in addition to the horizon Killing vector field. Thereby, they comprise the class of generic `stationary' distorted electrovac black hole spacetimes. It is also shown that there are stationary distorted electrovac black hole configurations such that parallelly propagated curvature blow up occurs both to the future and to the past ends of some of the null generators of their bifurcate Killing horizon, and also that this behavior is universal. In particular, it is shown that, in the space of vacuum solutions to Einstein's equations, in an arbitrarily small neighborhood of the Schwarzschild solution this type of distorted vacuum black hole configurations always exist. A short discussion on the relation of these results and some of the recent claims on the instability of extremal black holes is also given. |
1601.02171 | Kent Yagi | Kent Yagi and Nicolas Yunes | I-Love-Q Relations: From Compact Stars to Black Holes | 36 pages, 10 figures; minor modifications, typos corrected; published
in CQG | Class. Quant. Grav. 33, 095005 (2016) | 10.1088/0264-9381/33/9/095005 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The relations between most observables associated with a compact star, such
as the mass and radius of a neutron star or a quark star, typically depend
strongly on their unknown internal structure. The I-Love-Q relations (between
the moment of inertia, the tidal deformability and the quadrupole moment) are
however approximately insensitive to this structure. These relations become
exact for stationary black holes in General Relativity as shown by the no-hair
theorems. In this paper, we take the first steps toward studying how the
approximate I-Love-Q relations become exact in the limit as compact stars
become black holes. To do so, we consider a toy model, i.e. incompressible
stars with anisotropic pressure, which allows us to model an equilibrium
sequence of stars with their compactness approaching the black hole limit
arbitrarily closely. We extract the I-Love-Q trio by numerically constructing
such a sequence in the slow-rotation and small-tide approximations. We find
that the I-Love-Q relations approach the black hole limit in a nontrivial way,
with the quadrupole moment and the tidal deformability changing sign as the
compactness and the amount of anisotropy are increased. Generalizing Maclaurin
spheroids to anisotropic stars, we show that the multipole moments also change
sign in the Newtonian limit as the amount of anisotropy is increased. We also
prove analytically that the stellar moment of inertia reaches the black hole
limit as the compactness reaches the black hole value in the strongly
anisotropic limit. Modeling the black hole limit through a sequence of
anisotropic stars, however, fails when considering other theories of gravity.
We calculate the scalar dipole charge and the moment of inertia in a
parity-violating modified theory and find that these quantities do not tend to
their black hole counterparts as the anisotropic stellar sequence approaches
the black hole limit.
| [
{
"created": "Sun, 10 Jan 2016 01:50:49 GMT",
"version": "v1"
},
{
"created": "Thu, 26 May 2016 18:02:42 GMT",
"version": "v2"
}
] | 2016-05-27 | [
[
"Yagi",
"Kent",
""
],
[
"Yunes",
"Nicolas",
""
]
] | The relations between most observables associated with a compact star, such as the mass and radius of a neutron star or a quark star, typically depend strongly on their unknown internal structure. The I-Love-Q relations (between the moment of inertia, the tidal deformability and the quadrupole moment) are however approximately insensitive to this structure. These relations become exact for stationary black holes in General Relativity as shown by the no-hair theorems. In this paper, we take the first steps toward studying how the approximate I-Love-Q relations become exact in the limit as compact stars become black holes. To do so, we consider a toy model, i.e. incompressible stars with anisotropic pressure, which allows us to model an equilibrium sequence of stars with their compactness approaching the black hole limit arbitrarily closely. We extract the I-Love-Q trio by numerically constructing such a sequence in the slow-rotation and small-tide approximations. We find that the I-Love-Q relations approach the black hole limit in a nontrivial way, with the quadrupole moment and the tidal deformability changing sign as the compactness and the amount of anisotropy are increased. Generalizing Maclaurin spheroids to anisotropic stars, we show that the multipole moments also change sign in the Newtonian limit as the amount of anisotropy is increased. We also prove analytically that the stellar moment of inertia reaches the black hole limit as the compactness reaches the black hole value in the strongly anisotropic limit. Modeling the black hole limit through a sequence of anisotropic stars, however, fails when considering other theories of gravity. We calculate the scalar dipole charge and the moment of inertia in a parity-violating modified theory and find that these quantities do not tend to their black hole counterparts as the anisotropic stellar sequence approaches the black hole limit. |
1611.05295 | Sergiu I. Vacaru | Marcelo M. Amaral, Raymond Aschheim, Lauren\c{t}iu Bubuianu, Klee
Irwin, Sergiu I. Vacaru, Daniel Woolridge | Anamorphic Quasiperiodic Universes in Modified and Einstein Gravity with
Loop Quantum Gravity Corrections | latex2e, 11pt, 32 pages, v3 accepted to CQG with a new Appendix and
minor modifications following referee's requests | Class. Quantum Grav. 34 (2017) 185002 | 10.1088/1361-6382/aa828a | null | gr-qc astro-ph.CO math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The goal of this work is to elaborate on new geometric methods of
constructing exact and parametric quasiperiodic solutions for anamorphic
cosmology models in modified gravity theories, MGTs, and general relativity,
GR. There exist previously studied generic off-diagonal and diagonalizable
cosmological metrics encoding gravitational and matter fields with quasicrystal
like structures, QC, and holonomy corrections from loop quantum gravity, LQG.
We apply the anholonomic frame deformation method, AFDM, in order to decouple
the (modified) gravitational and matter field equations in general form. This
allows us to find integral varieties of cosmological solutions determined by
generating functions, effective sources, integration functions and constants.
The coefficients of metrics and connections for such cosmological
configurations depend, in general, on all spacetime coordinates and can be
chosen to generate observable (quasi)-periodic/ aperiodic/ fractal / stochastic
/ (super) cluster / filament / polymer like (continuous, stochastic, fractal
and/or discrete structures) in MGTs and/or GR. In this work, we study new
classes of solutions for anamorphic cosmology with LQG holonomy corrections.
Such solutions are characterized by nonlinear symmetries of generating
functions for generic off--diagonal cosmological metrics and generalized
connections, with possible nonholonomic constraints to Levi-Civita
configurations and diagonalizable metrics depending only on a time like
coordinate. We argue that anamorphic quasiperiodic cosmological models
integrate the concept of quantum discrete spacetime, with certain gravitational
QC-like vacuum and nonvacuum structures. And, that of a contracting universe
that homogenizes, isotropizes and flattens without introducing initial
conditions or multiverse problems.
| [
{
"created": "Mon, 7 Nov 2016 11:59:11 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Jul 2017 02:38:39 GMT",
"version": "v2"
},
{
"created": "Sat, 5 Aug 2017 03:38:45 GMT",
"version": "v3"
}
] | 2017-10-24 | [
[
"Amaral",
"Marcelo M.",
""
],
[
"Aschheim",
"Raymond",
""
],
[
"Bubuianu",
"Laurenţiu",
""
],
[
"Irwin",
"Klee",
""
],
[
"Vacaru",
"Sergiu I.",
""
],
[
"Woolridge",
"Daniel",
""
]
] | The goal of this work is to elaborate on new geometric methods of constructing exact and parametric quasiperiodic solutions for anamorphic cosmology models in modified gravity theories, MGTs, and general relativity, GR. There exist previously studied generic off-diagonal and diagonalizable cosmological metrics encoding gravitational and matter fields with quasicrystal like structures, QC, and holonomy corrections from loop quantum gravity, LQG. We apply the anholonomic frame deformation method, AFDM, in order to decouple the (modified) gravitational and matter field equations in general form. This allows us to find integral varieties of cosmological solutions determined by generating functions, effective sources, integration functions and constants. The coefficients of metrics and connections for such cosmological configurations depend, in general, on all spacetime coordinates and can be chosen to generate observable (quasi)-periodic/ aperiodic/ fractal / stochastic / (super) cluster / filament / polymer like (continuous, stochastic, fractal and/or discrete structures) in MGTs and/or GR. In this work, we study new classes of solutions for anamorphic cosmology with LQG holonomy corrections. Such solutions are characterized by nonlinear symmetries of generating functions for generic off--diagonal cosmological metrics and generalized connections, with possible nonholonomic constraints to Levi-Civita configurations and diagonalizable metrics depending only on a time like coordinate. We argue that anamorphic quasiperiodic cosmological models integrate the concept of quantum discrete spacetime, with certain gravitational QC-like vacuum and nonvacuum structures. And, that of a contracting universe that homogenizes, isotropizes and flattens without introducing initial conditions or multiverse problems. |
1909.00168 | Tobias Reinhart | Tobias Reinhart and Nils Alex | Covariant Constructive Gravity | 6 pages. Prepared for Proceedings of the Fifteenth Marcel Grossmann
meeting (Rome, 1-7 July 2018), Session AT5, Constructive Gravity | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a method of constructing perturbative equations of motion for the
geometric background of any given tensorial field theory. Requiring invariance
of the gravitational dynamics under spacetime diffeomorphisms leads to a PDE
system for the gravitational Lagrangian that can be solved by means of a power
series ansatz. Furthermore, in each order we pose conditions on the causality
of the gravitational equations, that ensure coevolution of the matter fields
and the gravitational background is possible, i.e. gravitational equations and
matter equations share the same initial data hypersurfaces.
| [
{
"created": "Sat, 31 Aug 2019 08:49:38 GMT",
"version": "v1"
}
] | 2019-09-04 | [
[
"Reinhart",
"Tobias",
""
],
[
"Alex",
"Nils",
""
]
] | We present a method of constructing perturbative equations of motion for the geometric background of any given tensorial field theory. Requiring invariance of the gravitational dynamics under spacetime diffeomorphisms leads to a PDE system for the gravitational Lagrangian that can be solved by means of a power series ansatz. Furthermore, in each order we pose conditions on the causality of the gravitational equations, that ensure coevolution of the matter fields and the gravitational background is possible, i.e. gravitational equations and matter equations share the same initial data hypersurfaces. |
2202.04467 | Juan M. Z\'arate Pretel | Juan M. Z. Pretel and Sergio B. Duarte | Anisotropic quark stars in $f(R)= R^{1+\epsilon}$ gravity | 10 pages, 4 figures, some references added, new figure added,
accepted for publication in Classical and Quantum Gravity | Class. Quantum Grav. 39 (2022) 155003 | 10.1088/1361-6382/ac7a88 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the metric formalism of $f(R)$ theories of gravity, where $R$ is the
Ricci scalar, we study the hydrostatic equilibrium structure of compact stars
with the inclusion of anisotropic pressure. In particular, we focus on the
$f(R)= R^{1+\epsilon}$ model and we examine small deviations from General
Relativity (GR) for $\vert \epsilon \vert \ll 1$. A suitable definition of mass
function is explicitly formulated from the field equations and the value of the
Ricci scalar at the center of each star is chosen such that it satisfies the
asymptotic flatness requirement. We find that both the mass and the radius of a
compact star are larger with respect to the general relativistic counterpart.
Furthermore, we remark that the substantial changes due to anisotropy occur
mainly in the high-central-density region.
| [
{
"created": "Wed, 9 Feb 2022 13:53:01 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Jun 2022 02:26:28 GMT",
"version": "v2"
}
] | 2022-07-11 | [
[
"Pretel",
"Juan M. Z.",
""
],
[
"Duarte",
"Sergio B.",
""
]
] | Within the metric formalism of $f(R)$ theories of gravity, where $R$ is the Ricci scalar, we study the hydrostatic equilibrium structure of compact stars with the inclusion of anisotropic pressure. In particular, we focus on the $f(R)= R^{1+\epsilon}$ model and we examine small deviations from General Relativity (GR) for $\vert \epsilon \vert \ll 1$. A suitable definition of mass function is explicitly formulated from the field equations and the value of the Ricci scalar at the center of each star is chosen such that it satisfies the asymptotic flatness requirement. We find that both the mass and the radius of a compact star are larger with respect to the general relativistic counterpart. Furthermore, we remark that the substantial changes due to anisotropy occur mainly in the high-central-density region. |
1301.4532 | Sourav Bhattacharya | Sourav Bhattacharya and Amitabha Lahiri | Mass function and particle creation in Schwarzschild-de Sitter spacetime | v3, 16pp; added references and discussions, typo corrected; accepted
in Eur. Phys. J. C | null | 10.1140/epjc/s10052-013-2673-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a mass or energy function for the non-Nariai class
Schwarzschild-de Sitter black hole spacetime in the region between the black
hole and the cosmological event horizons. The mass function is local, positive
definite, continuous and increases monotonically with the radial distance from
the black hole event horizon. We derive the Smarr formula using this mass
function, and demonstrate that the mass function reproduces the two-temperature
Schwarzschild-de Sitter black hole thermodynamics, along with a term
corresponding to the negative pressure due to positive cosmological constant.
We further give a field theoretic derivation of the particle creation by both
the horizons and discuss its connection with the mass function.
| [
{
"created": "Sat, 19 Jan 2013 05:13:05 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Oct 2013 09:07:26 GMT",
"version": "v2"
},
{
"created": "Thu, 5 Dec 2013 12:57:43 GMT",
"version": "v3"
}
] | 2015-06-12 | [
[
"Bhattacharya",
"Sourav",
""
],
[
"Lahiri",
"Amitabha",
""
]
] | We construct a mass or energy function for the non-Nariai class Schwarzschild-de Sitter black hole spacetime in the region between the black hole and the cosmological event horizons. The mass function is local, positive definite, continuous and increases monotonically with the radial distance from the black hole event horizon. We derive the Smarr formula using this mass function, and demonstrate that the mass function reproduces the two-temperature Schwarzschild-de Sitter black hole thermodynamics, along with a term corresponding to the negative pressure due to positive cosmological constant. We further give a field theoretic derivation of the particle creation by both the horizons and discuss its connection with the mass function. |
2011.04911 | Gabriele Umberto Varieschi | Gabriele U. Varieschi | Newtonian Fractional-Dimension Gravity and Rotationally Supported
Galaxies | 19 pages, including 6 figures. Third paper on NFDG. Added Appendix A,
references, and other minor changes and corrections. Final version to be
published in the Monthly Notices of the Royal Astronomical Society, Oxford
Academic. arXiv admin note: text overlap with arXiv:2008.04737 | null | 10.1093/mnras/stab433 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We continue our analysis of Newtonian Fractional-Dimension Gravity, an
extension of the standard laws of Newtonian gravity to lower dimensional spaces
including those with fractional (i.e., non-integer) dimension. We apply our
model to three rotationally supported galaxies: NGC 7814 (Bulge-Dominated
Spiral), NGC 6503 (Disk-Dominated Spiral), and NGC 3741 (Gas-Dominated Dwarf).
As was done in the general cases of spherically-symmetric and
axially-symmetric structures, which were studied in previous work on the
subject, we examine a possible connection between our model and Modified
Newtonian Dynamics, a leading alternative gravity model which explains the
observed properties of these galaxies without requiring the Dark Matter
hypothesis.
In our model, the MOND acceleration constant $a_{0} \simeq 1.2 \times
10^{-10}\mbox{m}\thinspace \mbox{s}^{ -2}$ can be related to a natural scale
length $l_{0}$, namely $a_{0} \approx GM/l_{0}^{2}$ for a galaxy of mass $M$.
Also, the empirical Radial Acceleration Relation, connecting the observed
radial acceleration $g_{obs}$ with the baryonic one $g_{bar}$, can be explained
in terms of a variable local dimension $D$. As an example of this methodology,
we provide detailed rotation curve fits for the three galaxies mentioned above.
| [
{
"created": "Mon, 9 Nov 2020 07:03:30 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Feb 2021 02:23:23 GMT",
"version": "v2"
}
] | 2021-02-24 | [
[
"Varieschi",
"Gabriele U.",
""
]
] | We continue our analysis of Newtonian Fractional-Dimension Gravity, an extension of the standard laws of Newtonian gravity to lower dimensional spaces including those with fractional (i.e., non-integer) dimension. We apply our model to three rotationally supported galaxies: NGC 7814 (Bulge-Dominated Spiral), NGC 6503 (Disk-Dominated Spiral), and NGC 3741 (Gas-Dominated Dwarf). As was done in the general cases of spherically-symmetric and axially-symmetric structures, which were studied in previous work on the subject, we examine a possible connection between our model and Modified Newtonian Dynamics, a leading alternative gravity model which explains the observed properties of these galaxies without requiring the Dark Matter hypothesis. In our model, the MOND acceleration constant $a_{0} \simeq 1.2 \times 10^{-10}\mbox{m}\thinspace \mbox{s}^{ -2}$ can be related to a natural scale length $l_{0}$, namely $a_{0} \approx GM/l_{0}^{2}$ for a galaxy of mass $M$. Also, the empirical Radial Acceleration Relation, connecting the observed radial acceleration $g_{obs}$ with the baryonic one $g_{bar}$, can be explained in terms of a variable local dimension $D$. As an example of this methodology, we provide detailed rotation curve fits for the three galaxies mentioned above. |
2012.14418 | Micha{\l} Eckstein | Erik Aurell, Micha{\l} Eckstein, Pawe{\l} Horodecki | Quantum information in Hawking radiation | 13 pages, 1 figure. Version published in JCAP | JCAP01(2022)014 | 10.1088/1475-7516/2022/01/014 | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | In 1974 Steven Hawking showed that black holes emit thermal radiation, which
eventually causes them to evaporate. The problem of the fate of information in
this process is known as the "black hole information paradox". Two main types
of resolution postulate either a fundamental loss of information in Nature --
hence the breakdown of quantum mechanics -- or some sort of new physics, e.g.
quantum gravity, which guarantee the global preservation of unitarity. Here we
explore the second possibility with the help of recent developments in
continuous-variable quantum information. Concretely, we employ the solution to
the Gaussian quantum marginal problem to show that the thermality of all
individual Hawking modes is consistent with a global pure state of the
radiation. Surprisingly, we find out that the mods of radiation of an
astrophysical black hole are thermal until the very last burst. In contrast,
the single-mode thermality of Hawking radiation originating from microscopic
black holes, expected to evaporate through several quanta, is not excluded,
though there are constraints on modes' frequencies. Our result paves the way
towards a systematic study of multi-mode correlations in Hawking radiation.
| [
{
"created": "Mon, 28 Dec 2020 18:55:15 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Feb 2022 10:32:07 GMT",
"version": "v2"
}
] | 2022-02-09 | [
[
"Aurell",
"Erik",
""
],
[
"Eckstein",
"Michał",
""
],
[
"Horodecki",
"Paweł",
""
]
] | In 1974 Steven Hawking showed that black holes emit thermal radiation, which eventually causes them to evaporate. The problem of the fate of information in this process is known as the "black hole information paradox". Two main types of resolution postulate either a fundamental loss of information in Nature -- hence the breakdown of quantum mechanics -- or some sort of new physics, e.g. quantum gravity, which guarantee the global preservation of unitarity. Here we explore the second possibility with the help of recent developments in continuous-variable quantum information. Concretely, we employ the solution to the Gaussian quantum marginal problem to show that the thermality of all individual Hawking modes is consistent with a global pure state of the radiation. Surprisingly, we find out that the mods of radiation of an astrophysical black hole are thermal until the very last burst. In contrast, the single-mode thermality of Hawking radiation originating from microscopic black holes, expected to evaporate through several quanta, is not excluded, though there are constraints on modes' frequencies. Our result paves the way towards a systematic study of multi-mode correlations in Hawking radiation. |
1209.2346 | Mir Faizal | Mir Faizal | Super-Group Field Cosmology | 14 pages, 0 figures, accepted for publication in Class. Quant. Grav | Class. Quant. Grav. 29: 215009, 2012 | 10.1088/0264-9381/29/21/215009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we construct a model for group field cosmology. The classical
equations of motion for the non-interactive part of this model generate the
Hamiltonian constraint of loop quantum gravity for a homogeneous isotropic
universe filled with a scalar matter field. The interactions represent topology
changing processes that occurs due to joining and splitting of universes. These
universes in the multiverse are assumed to obey both bosonic and fermionic
statistics, and so a supersymmetric multiverse is constructed using superspace
formalism. We also introduce gauge symmetry in this model. The supersymmetry
and gauge symmetry are introduced at the level of third quantized fields, and
not the second quantized ones. This is the first time that supersymmetry has
been discussed at the level of third quantized fields.
| [
{
"created": "Tue, 11 Sep 2012 15:21:44 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Sep 2012 10:09:04 GMT",
"version": "v2"
}
] | 2015-06-11 | [
[
"Faizal",
"Mir",
""
]
] | In this paper we construct a model for group field cosmology. The classical equations of motion for the non-interactive part of this model generate the Hamiltonian constraint of loop quantum gravity for a homogeneous isotropic universe filled with a scalar matter field. The interactions represent topology changing processes that occurs due to joining and splitting of universes. These universes in the multiverse are assumed to obey both bosonic and fermionic statistics, and so a supersymmetric multiverse is constructed using superspace formalism. We also introduce gauge symmetry in this model. The supersymmetry and gauge symmetry are introduced at the level of third quantized fields, and not the second quantized ones. This is the first time that supersymmetry has been discussed at the level of third quantized fields. |
gr-qc/0606127 | Mark Rupright | Mark E. Rupright | Spherical Harmonic Amplitudes From Grid Data | 14 pages, 4 figures | null | null | null | gr-qc physics.comp-ph | null | The problem of resolving spherical harmonic components from numerical data
defined on a rectangular grid has many applications, particularly for the
problem of gravitational radiation extraction. A novel method due to Misner
improves on traditional techniques by avoiding the need to cover the sphere
with a coordinate system appropriate to the grid geometry. This paper will
discuss Misner's method and suggest how it can be improved by exploiting local
regression techniques.
| [
{
"created": "Thu, 29 Jun 2006 15:32:34 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Rupright",
"Mark E.",
""
]
] | The problem of resolving spherical harmonic components from numerical data defined on a rectangular grid has many applications, particularly for the problem of gravitational radiation extraction. A novel method due to Misner improves on traditional techniques by avoiding the need to cover the sphere with a coordinate system appropriate to the grid geometry. This paper will discuss Misner's method and suggest how it can be improved by exploiting local regression techniques. |
2208.06259 | Gregory B. Cook | Daniel J. Vickers and Gregory B. Cook | Understanding solutions of the angular Teukolsky equation in the prolate
asymptotic limit | 34 pages, 30 figures, 16 tables : fixed typos and other minor errors | Phys. Rev. D 106, 104037 (2022) | 10.1103/PhysRevD.106.104037 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Solutions to the Angular Teukolsky Equation have been used to solve various
applied problems in physics and are extremely important to black-hole physics,
particularly in computing quasinormal modes and in the extreme-mass-ratio
inspiral problem. The eigenfunctions of this equation, known as spin-weighted
spheroidal functions, are essentially generalizations of both the spin-weighted
spherical harmonics and the scalar spheroidal harmonics. While the latter
functions are quite well understood analytically, the spin-weighted spheroidal
harmonics are only known analytically in the spherical and oblate asymptotic
limits. Attempts to understand them in the prolate asymptotic limit have met
limited success. Here, we make use of a high-accuracy numerical solution scheme
to extensively explore the space of possible prolate solutions and extract
analytic asymptotic expansions for the eigenvalues in the prolate asymptotic
limit. Somewhat surprisingly, we find two classes of asymptotic behavior. The
behavior of one class, referred to as "normal", is in agreement with the
leading-order behavior derived analytically in prior work. The second class of
solutions was not previously predicted, but solutions in this class are
responsible for unexplained behavior seen in previous numerical prolate
solutions during the transition to asymptotic behavior. The behavior of
solutions in this "anomalous" class is more complicated than that of solutions
in the normal class, with the anomalous class separating into different types
based on the behavior of the eigenvalues at different asymptotic orders. We
explore the question of when anomalous solutions appear and find necessary, but
not sufficient conditions for their existence. It is our hope that this
extensive numerical investigation of the prolate solutions will inspire and
inform new analytic investigations into these important functions.
| [
{
"created": "Fri, 12 Aug 2022 13:12:47 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Nov 2022 16:38:19 GMT",
"version": "v2"
}
] | 2022-11-18 | [
[
"Vickers",
"Daniel J.",
""
],
[
"Cook",
"Gregory B.",
""
]
] | Solutions to the Angular Teukolsky Equation have been used to solve various applied problems in physics and are extremely important to black-hole physics, particularly in computing quasinormal modes and in the extreme-mass-ratio inspiral problem. The eigenfunctions of this equation, known as spin-weighted spheroidal functions, are essentially generalizations of both the spin-weighted spherical harmonics and the scalar spheroidal harmonics. While the latter functions are quite well understood analytically, the spin-weighted spheroidal harmonics are only known analytically in the spherical and oblate asymptotic limits. Attempts to understand them in the prolate asymptotic limit have met limited success. Here, we make use of a high-accuracy numerical solution scheme to extensively explore the space of possible prolate solutions and extract analytic asymptotic expansions for the eigenvalues in the prolate asymptotic limit. Somewhat surprisingly, we find two classes of asymptotic behavior. The behavior of one class, referred to as "normal", is in agreement with the leading-order behavior derived analytically in prior work. The second class of solutions was not previously predicted, but solutions in this class are responsible for unexplained behavior seen in previous numerical prolate solutions during the transition to asymptotic behavior. The behavior of solutions in this "anomalous" class is more complicated than that of solutions in the normal class, with the anomalous class separating into different types based on the behavior of the eigenvalues at different asymptotic orders. We explore the question of when anomalous solutions appear and find necessary, but not sufficient conditions for their existence. It is our hope that this extensive numerical investigation of the prolate solutions will inspire and inform new analytic investigations into these important functions. |
1408.0860 | Ryan Lang | Ryan N. Lang | Gravitational radiation from compact binaries in scalar-tensor gravity | 7 pages, submitted to the proceedings of the 10th International LISA
Symposium | null | 10.1088/1742-6596/610/1/012045 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General relativity (GR) has been extensively tested in the solar system and
in binary pulsars, but never in the strong-field, dynamical regime. Soon,
gravitational-wave (GW) detectors like Advanced LIGO and eLISA will be able to
probe this regime by measuring GWs from inspiraling and merging compact
binaries. One particularly interesting alternative to GR is scalar-tensor
gravity. We present progress in the calculation of second post-Newtonian (2PN)
gravitational waveforms for inspiraling compact binaries in a general class of
scalar-tensor theories. The waveforms are constructed using a standard GR
method known as "direct integration of the relaxed Einstein equations,"
appropriately adapted to the scalar-tensor case. We find that differences from
general relativity can be characterized by a reasonably small number of
parameters. Among the differences are new hereditary terms which depend on the
past history of the source. In one special case, binary black hole systems, we
find that the waveform is indistinguishable from that of general relativity. In
another, mixed black hole-neutron star systems, all differences from GR can be
characterized by only a single parameter.
| [
{
"created": "Tue, 5 Aug 2014 04:21:55 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Lang",
"Ryan N.",
""
]
] | General relativity (GR) has been extensively tested in the solar system and in binary pulsars, but never in the strong-field, dynamical regime. Soon, gravitational-wave (GW) detectors like Advanced LIGO and eLISA will be able to probe this regime by measuring GWs from inspiraling and merging compact binaries. One particularly interesting alternative to GR is scalar-tensor gravity. We present progress in the calculation of second post-Newtonian (2PN) gravitational waveforms for inspiraling compact binaries in a general class of scalar-tensor theories. The waveforms are constructed using a standard GR method known as "direct integration of the relaxed Einstein equations," appropriately adapted to the scalar-tensor case. We find that differences from general relativity can be characterized by a reasonably small number of parameters. Among the differences are new hereditary terms which depend on the past history of the source. In one special case, binary black hole systems, we find that the waveform is indistinguishable from that of general relativity. In another, mixed black hole-neutron star systems, all differences from GR can be characterized by only a single parameter. |
2012.13828 | Alireza Olamaei | A. Bazrafshan and A. R. Olamaei | Surface Terms of Quintic Quasitopological Gravity and Thermodynamics of
Quasi-Topological Magnetic Brane Coupled to Nonlinear Electrodynamics | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For the the quintic quasitopological action which has no well-defined
variational principle, we introduced a surface term that for a spacetime with
flat boundaries make the action well-defined. Moreover, we investigated the
numerical solutions of the above-mentioned gravity coupled to the nonlinear
logarithmic and exponential electrodynamics. It has no horizon and curvature
except one conical singularity at $r=0$ with a deficit angle $\delta\phi$. Also
we found the counterterm which removes non-logarithmic divergences for the
static quintic quasitopological gravity. Using this counterterm one can
calculate a finite action and conserved quantities for the quintic
quasitopological gravity.
| [
{
"created": "Sat, 26 Dec 2020 23:00:27 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Dec 2020 20:57:22 GMT",
"version": "v2"
},
{
"created": "Tue, 18 May 2021 02:23:58 GMT",
"version": "v3"
},
{
"created": "Fri, 12 Nov 2021 19:10:29 GMT",
"version": "v4"
},
{
"created": "Mon, 22 Nov 2021 17:11:43 GMT",
"version": "v5"
}
] | 2021-11-23 | [
[
"Bazrafshan",
"A.",
""
],
[
"Olamaei",
"A. R.",
""
]
] | For the the quintic quasitopological action which has no well-defined variational principle, we introduced a surface term that for a spacetime with flat boundaries make the action well-defined. Moreover, we investigated the numerical solutions of the above-mentioned gravity coupled to the nonlinear logarithmic and exponential electrodynamics. It has no horizon and curvature except one conical singularity at $r=0$ with a deficit angle $\delta\phi$. Also we found the counterterm which removes non-logarithmic divergences for the static quintic quasitopological gravity. Using this counterterm one can calculate a finite action and conserved quantities for the quintic quasitopological gravity. |
0903.4342 | Tomasz Konopka | Tomasz Konopka | Matter in Toy Dynamical Geometries | 8 pages, 1 figure, paper presented at DICE 2008 | J.Phys.Conf.Ser.174:012051,2009 | 10.1088/1742-6596/174/1/012051 | ITP-UU-08/13, SPIN-08/12 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the objectives of theories describing quantum dynamical geometry is to
compute expectation values of geometrical observables. The results of such
computations can be affected by whether or not matter is taken into account. It
is thus important to understand to what extent and to what effect matter can
affect dynamical geometries. Using a simple model, it is shown that matter can
effectively mold a geometry into an isotropic configuration. Implications for
"atomistic" models of quantum geometry are briefly discussed.
| [
{
"created": "Wed, 25 Mar 2009 14:06:02 GMT",
"version": "v1"
}
] | 2009-07-24 | [
[
"Konopka",
"Tomasz",
""
]
] | One of the objectives of theories describing quantum dynamical geometry is to compute expectation values of geometrical observables. The results of such computations can be affected by whether or not matter is taken into account. It is thus important to understand to what extent and to what effect matter can affect dynamical geometries. Using a simple model, it is shown that matter can effectively mold a geometry into an isotropic configuration. Implications for "atomistic" models of quantum geometry are briefly discussed. |
gr-qc/0305055 | Joao Magueijo | Joao Magueijo and Lee Smolin | Gravity's Rainbow | Version to be published in Classical and Quantum Gravity | Class.Quant.Grav. 21 (2004) 1725-1736 | 10.1088/0264-9381/21/7/001 | null | gr-qc | null | Non-linear special relativity (or doubly special relativity) is a simple
framework for encoding properties of flat quantum space-time. In this paper we
show how this formalism may be generalized to incorporate curvature (leading to
what might be called ``doubly general relativity''). We first propose a dual to
non-linear realizations of relativity in momentum space, and show that for such
a dual the space-time invariant is an energy-dependent metric. This leads to an
energy-dependent connection and curvature, and a simple modification to
Einstein's equations. We then examine solutions to these equations. We find the
counterpart to the cosmological metric, and show how cosmologies based upon our
theory of gravity may solve the ``horizon problem''. We discuss the
Schwarzchild solution, examining the conditions for which the horizon is energy
dependent. We finally find the weak field limit.
| [
{
"created": "Wed, 14 May 2003 16:16:20 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Feb 2004 19:17:10 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Magueijo",
"Joao",
""
],
[
"Smolin",
"Lee",
""
]
] | Non-linear special relativity (or doubly special relativity) is a simple framework for encoding properties of flat quantum space-time. In this paper we show how this formalism may be generalized to incorporate curvature (leading to what might be called ``doubly general relativity''). We first propose a dual to non-linear realizations of relativity in momentum space, and show that for such a dual the space-time invariant is an energy-dependent metric. This leads to an energy-dependent connection and curvature, and a simple modification to Einstein's equations. We then examine solutions to these equations. We find the counterpart to the cosmological metric, and show how cosmologies based upon our theory of gravity may solve the ``horizon problem''. We discuss the Schwarzchild solution, examining the conditions for which the horizon is energy dependent. We finally find the weak field limit. |
1201.4742 | Ilya Kirnos Vasilyevich | A. N. Makarenko, V. V. Obukhov, I. V. Kirnos | From Big to Little Rip in modified F(R,G) gravity | 15 pages, 7 figures | null | 10.1007/s10509-012-1240-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the cosmological reconstruction in modified Gauss-Bonnet (GB)
gravity. It is demonstrated that the modified GB gravity may describe the most
interesting features of late-time cosmology. We derive explicit form of
effective phantom cosmological models ending by the finite-time future
singularity (Big Rip) and without singularities in the future (Little Rip).
| [
{
"created": "Mon, 23 Jan 2012 15:26:37 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jan 2012 09:54:14 GMT",
"version": "v2"
}
] | 2015-06-03 | [
[
"Makarenko",
"A. N.",
""
],
[
"Obukhov",
"V. V.",
""
],
[
"Kirnos",
"I. V.",
""
]
] | We discuss the cosmological reconstruction in modified Gauss-Bonnet (GB) gravity. It is demonstrated that the modified GB gravity may describe the most interesting features of late-time cosmology. We derive explicit form of effective phantom cosmological models ending by the finite-time future singularity (Big Rip) and without singularities in the future (Little Rip). |
gr-qc/0204023 | Richard Drociuk | Richard Drociuk | Cosmic Force | 13 pages | null | null | null | gr-qc | null | The determination of the geodesics in Scharzschild black hole and de Sitter
space.
| [
{
"created": "Fri, 5 Apr 2002 02:07:54 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Drociuk",
"Richard",
""
]
] | The determination of the geodesics in Scharzschild black hole and de Sitter space. |
2303.18026 | Maarten van de Meent | Maarten van de Meent, Alessandra Buonanno, Deyan P. Mihaylov, Serguei
Ossokine, Lorenzo Pompili, Niels Warburton, Adam Pound, Barry Wardell, Leanne
Durkan, Jeremy Miller | Enhancing the SEOBNRv5 effective-one-body waveform model with
second-order gravitational self-force fluxes | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We leverage recent breakthrough calculations using second-order gravitational
self-force (2GSF) theory to improve both the gravitational-mode amplitudes and
radiation-reaction force in effective-one-body~(EOB) waveform models. We
achieve this by introducing new calibration parameters in the SEOBNRv5HM mode
amplitudes, and matching them to the newly available 2GSF energy-flux
multipolar data for quasicircular nonspinning binary black holes. We find that
this significantly improves the SEOBNRv5HM energy flux, when compared to
numerical-relativity (NR) simulations of binary black holes with mass ratios
between 1:1 and 1:20. Moreover, we find that, once the conservative part of the
SEOBNRv5 dynamics is calibrated, the SEOBNRv5HM waveform model with 2GSF
information reproduces the binding energy of NR simulations more accurately,
providing a powerful check of the consistency and naturalness of the EOB
approach. While we only include nonspinning 2GSF information, the more accurate
binding energy and energy flux carry over to the SEOBNRv5 waveform models for
spinning binary black holes. Thus, our results improve the latest generation of
SEOBNR waveform models (i.e., SEOBNRv5), which has been recently completed for
use in the upcoming fourth observing (O4) run of the LIGO-Virgo-KAGRA
Collaboration.
| [
{
"created": "Fri, 31 Mar 2023 13:04:45 GMT",
"version": "v1"
}
] | 2023-04-03 | [
[
"van de Meent",
"Maarten",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Mihaylov",
"Deyan P.",
""
],
[
"Ossokine",
"Serguei",
""
],
[
"Pompili",
"Lorenzo",
""
],
[
"Warburton",
"Niels",
""
],
[
"Pound",
"Adam",
""
],
[
"Wardell",
"Barry",
""
],
[
"Durkan",
"Leanne",
""
],
[
"Miller",
"Jeremy",
""
]
] | We leverage recent breakthrough calculations using second-order gravitational self-force (2GSF) theory to improve both the gravitational-mode amplitudes and radiation-reaction force in effective-one-body~(EOB) waveform models. We achieve this by introducing new calibration parameters in the SEOBNRv5HM mode amplitudes, and matching them to the newly available 2GSF energy-flux multipolar data for quasicircular nonspinning binary black holes. We find that this significantly improves the SEOBNRv5HM energy flux, when compared to numerical-relativity (NR) simulations of binary black holes with mass ratios between 1:1 and 1:20. Moreover, we find that, once the conservative part of the SEOBNRv5 dynamics is calibrated, the SEOBNRv5HM waveform model with 2GSF information reproduces the binding energy of NR simulations more accurately, providing a powerful check of the consistency and naturalness of the EOB approach. While we only include nonspinning 2GSF information, the more accurate binding energy and energy flux carry over to the SEOBNRv5 waveform models for spinning binary black holes. Thus, our results improve the latest generation of SEOBNR waveform models (i.e., SEOBNRv5), which has been recently completed for use in the upcoming fourth observing (O4) run of the LIGO-Virgo-KAGRA Collaboration. |
gr-qc/9906104 | Hans Kastrup | H.A. Kastrup (RWTH Aachen, Germany) | Schwarzschild Black Hole Quantum Statistics from Z(2) Orientation
Degrees of Freedom and its Relations to Ising Droplet Nucleation | 29 pages, Latex; version to appear in Annalen der Physik (Leipzig)
(Refs. added, a few text improvements, no changes of results) | Annalen Phys. 9 (2000) 503-522 | 10.1002/1521-3889(200007)9:7<503::AID-ANDP503>3.0.CO;2-L | PITHA 99/18 | gr-qc cond-mat.stat-mech hep-th | null | Generalizing previous quantum gravity results for Schwarzschild black holes
from 4 to D > 3 space-time dimensions yields an energy spectrum E_n = alpha
n^{(D-3)/(D-2)} E_P, n=1,2,..., alpha = O(1), where E_P is the Planck energy in
that space-time. This spectrum means that the quantized area A_{D-2}(n) of the
D-2 dimensional horizon has universally the form A_{D-2} = n a_{D-2}, where
a_{D-2} is essentially the (D-2)th power of the D-dimensional Planck length.
Assuming that the basic area quantum has a Z(2)-degeneracy according to its two
possible orientation degrees of freedom implies a degeneracy d_n = 2^n for the
n-th level. The energy spectrum with such a degeneracy leads to a quantum
canonical partition function which is the same as the classical grand canonical
partition function of a primitive Ising droplet nucleation model for 1st-order
phase transitions in D-2 spatial dimensions. The analogy to this model suggests
that E_n represents the surface energy of a "droplet" of n horizon quanta.
Exploiting the well-known properties of the so-called critical droplets of that
model immediately leads to the Hawking temperature and the Bekenstein-Hawking
entropy of Schwarzschild black holes. The values of temperature and entropy
appear closely related to the imaginary part of the partition function which
describes metastable states
| [
{
"created": "Thu, 24 Jun 1999 18:03:45 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Aug 1999 15:24:02 GMT",
"version": "v2"
},
{
"created": "Thu, 4 May 2000 14:44:58 GMT",
"version": "v3"
}
] | 2017-09-27 | [
[
"Kastrup",
"H. A.",
"",
"RWTH Aachen, Germany"
]
] | Generalizing previous quantum gravity results for Schwarzschild black holes from 4 to D > 3 space-time dimensions yields an energy spectrum E_n = alpha n^{(D-3)/(D-2)} E_P, n=1,2,..., alpha = O(1), where E_P is the Planck energy in that space-time. This spectrum means that the quantized area A_{D-2}(n) of the D-2 dimensional horizon has universally the form A_{D-2} = n a_{D-2}, where a_{D-2} is essentially the (D-2)th power of the D-dimensional Planck length. Assuming that the basic area quantum has a Z(2)-degeneracy according to its two possible orientation degrees of freedom implies a degeneracy d_n = 2^n for the n-th level. The energy spectrum with such a degeneracy leads to a quantum canonical partition function which is the same as the classical grand canonical partition function of a primitive Ising droplet nucleation model for 1st-order phase transitions in D-2 spatial dimensions. The analogy to this model suggests that E_n represents the surface energy of a "droplet" of n horizon quanta. Exploiting the well-known properties of the so-called critical droplets of that model immediately leads to the Hawking temperature and the Bekenstein-Hawking entropy of Schwarzschild black holes. The values of temperature and entropy appear closely related to the imaginary part of the partition function which describes metastable states |
gr-qc/9508031 | Amitabha Lahiri | E.J.Copeland and Amitabha Lahiri (University of Sussex) | How is a Closed String Loop like a Black Hole? | 6 pages, uses harvmac | Class.Quant.Grav.12:L113-L118,1995 | 10.1088/0264-9381/12/12/002 | SUSX-TH-95/33 | gr-qc hep-th | null | We demonstrate that under plausible assumptions the entropy and temperature
associated with the small oscillations on a circular loop of radius $R$ and a
black hole of mass $M=R/2G$ are identical.
| [
{
"created": "Mon, 14 Aug 1995 15:48:51 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Copeland",
"E. J.",
"",
"University of Sussex"
],
[
"Lahiri",
"Amitabha",
"",
"University of Sussex"
]
] | We demonstrate that under plausible assumptions the entropy and temperature associated with the small oscillations on a circular loop of radius $R$ and a black hole of mass $M=R/2G$ are identical. |
1410.6183 | Oscar Castillo Felisola Dr. | Oscar Castillo-Felisola and Aureliano Skirzewski | A polynomial model of purely affine gravity | 13 pages. V3: Corresponds to the published version | Rev. Mex. Fis. 61 (2015) 6, 421 | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a purely affine gravitational model in four dimensions built up
entirely on the bases of full diffeomorphism invariance, and power- counting
renormalizability. We show that its non-relativistic limit around a homogeneous
and isotropic spacetime yields to a Newtonian gravity.
| [
{
"created": "Wed, 22 Oct 2014 20:43:18 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Feb 2015 19:48:57 GMT",
"version": "v2"
},
{
"created": "Mon, 4 Jul 2016 15:30:02 GMT",
"version": "v3"
}
] | 2016-07-05 | [
[
"Castillo-Felisola",
"Oscar",
""
],
[
"Skirzewski",
"Aureliano",
""
]
] | We present a purely affine gravitational model in four dimensions built up entirely on the bases of full diffeomorphism invariance, and power- counting renormalizability. We show that its non-relativistic limit around a homogeneous and isotropic spacetime yields to a Newtonian gravity. |
gr-qc/0411126 | Krzysztof Bolejko | Krzysztof Bolejko, Andrzej Krasinski, Charles Hellaby | Formation of voids in the Universe within the Lemaitre-Tolman model | MN2e LaTeX style file, 17 pages, 16 figures, 22 figure files;
replecement has minor changes in references | Mon.Not.Roy.Astron.Soc.362:213-228,2005 | 10.1111/j.1365-2966.2005.09292.x | null | gr-qc astro-ph | null | We develop models of void formation starting from a small initial fluctuation
at recombination and growing to a realistic present day density profile in
agreement with observations of voids. The model construction is an extension of
previously developed algorithms for finding a Lemaitre-Tolman metric that
evolves between two profiles of either density or velocity specified at two
times. Of the 4 profiles of concern -- those of density and velocity at
recombination and at the present day -- two can be specified and the other two
follow from the derived model. We find that, in order to reproduce the
present-day void density profiles, the initial velocity profile is more
important than the initial density profile. Extrapolation of current CMB
observations to the scales relevant to proto-voids is very uncertain. Even so,
we find that it is very difficult to make both the initial density and velocity
fluctuation amplitudes small enough, and still obtain a realistic void by
today.
| [
{
"created": "Fri, 26 Nov 2004 14:19:43 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Nov 2004 12:44:08 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Bolejko",
"Krzysztof",
""
],
[
"Krasinski",
"Andrzej",
""
],
[
"Hellaby",
"Charles",
""
]
] | We develop models of void formation starting from a small initial fluctuation at recombination and growing to a realistic present day density profile in agreement with observations of voids. The model construction is an extension of previously developed algorithms for finding a Lemaitre-Tolman metric that evolves between two profiles of either density or velocity specified at two times. Of the 4 profiles of concern -- those of density and velocity at recombination and at the present day -- two can be specified and the other two follow from the derived model. We find that, in order to reproduce the present-day void density profiles, the initial velocity profile is more important than the initial density profile. Extrapolation of current CMB observations to the scales relevant to proto-voids is very uncertain. Even so, we find that it is very difficult to make both the initial density and velocity fluctuation amplitudes small enough, and still obtain a realistic void by today. |
0711.2543 | Ramin Nowbakht Ghalati | R. N. Ghalati, D. G. C. McKeon | A Canonical Analysis of the First Order Einstein-Hilbert Action | null | null | null | UWO-TH-07/17 | gr-qc hep-th | null | The Dirac constraint formalism is applied to the d(d>2) dimensional
Einstein-Hilbert action when written in first order form, using the metric
density and affine connection as independent fields. Field equations not
involving time derivatives are not used to eliminate fields. Primary, secondary
and tertiary constraints arise, leaving d(d-3) degrees of freedom in phase
space. The Poisson Bracket algebra of these constraints is given.
| [
{
"created": "Fri, 16 Nov 2007 01:47:40 GMT",
"version": "v1"
}
] | 2007-11-19 | [
[
"Ghalati",
"R. N.",
""
],
[
"McKeon",
"D. G. C.",
""
]
] | The Dirac constraint formalism is applied to the d(d>2) dimensional Einstein-Hilbert action when written in first order form, using the metric density and affine connection as independent fields. Field equations not involving time derivatives are not used to eliminate fields. Primary, secondary and tertiary constraints arise, leaving d(d-3) degrees of freedom in phase space. The Poisson Bracket algebra of these constraints is given. |
1306.3028 | Jia-An Lu | Jia-An Lu, Chao-Guang Huang | Kaluza--Klein-type models of de Sitter and Poincar\'e gauge theories of
gravity | 21 pages | Class. Quantum Grav. 2013 30 145004 | 10.1088/0264-9381/30/14/145004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct Kaluza--Klein-type models with a de Sitter or Minkowski bundle
in the de Sitter or Poincar\'e gauge theory of gravity, respectively. A
manifestly gauge-invariant formalism has been given. The gravitational dynamics
is constructed by the geometry of the de Sitter or Minkowski bundle and a
global section which plays an important role in the gauge-invariant formalism.
Unlike the old Kaluza--Klein-type models of gauge theory of gravity, a suitable
cosmological term can be obtained in the Lagrangian of our models and the
models in the spin-current-free and torsion-free limit will come back to
general relativity with a corresponding cosmological term. We also generalize
the results to the case with a variable cosmological term.
| [
{
"created": "Thu, 13 Jun 2013 05:44:12 GMT",
"version": "v1"
}
] | 2013-06-14 | [
[
"Lu",
"Jia-An",
""
],
[
"Huang",
"Chao-Guang",
""
]
] | We construct Kaluza--Klein-type models with a de Sitter or Minkowski bundle in the de Sitter or Poincar\'e gauge theory of gravity, respectively. A manifestly gauge-invariant formalism has been given. The gravitational dynamics is constructed by the geometry of the de Sitter or Minkowski bundle and a global section which plays an important role in the gauge-invariant formalism. Unlike the old Kaluza--Klein-type models of gauge theory of gravity, a suitable cosmological term can be obtained in the Lagrangian of our models and the models in the spin-current-free and torsion-free limit will come back to general relativity with a corresponding cosmological term. We also generalize the results to the case with a variable cosmological term. |
0707.2854 | Francesco Cianfrani dr | Francesco Cianfrani, Giovanni Montani | Boost invariance of the gravitational field dynamics: quantization
without time gauge | 9 pages, accepted for publication on Classical and Quantum Gravity | Class.Quant.Grav.24:4161-4168,2007 | 10.1088/0264-9381/24/16/011 | null | gr-qc | null | We perform a canonical quantization of gravity in a second-order formulation,
taking as configuration variables those describing a 4-bein, not adapted to the
space-time splitting. We outline how, neither if we fix the Lorentz frame
before quantizing, nor if we perform no gauge fixing at all, is invariance
under boost transformations affected by the quantization.
| [
{
"created": "Thu, 19 Jul 2007 09:14:55 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Cianfrani",
"Francesco",
""
],
[
"Montani",
"Giovanni",
""
]
] | We perform a canonical quantization of gravity in a second-order formulation, taking as configuration variables those describing a 4-bein, not adapted to the space-time splitting. We outline how, neither if we fix the Lorentz frame before quantizing, nor if we perform no gauge fixing at all, is invariance under boost transformations affected by the quantization. |
gr-qc/0111054 | Serguei Krasnikov | S. Krasnikov | No time machines in classical general relativity | A corrigendum (to be published in CQG) has been added to correct an
important mistake in the definition of locality | Class.Quant.Grav. 19 (2002) 4109 | 10.1088/0264-9381/19/15/316 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Irrespective of local conditions imposed on the metric, any extendible
spacetime U has a maximal extension containing no closed causal curves outside
the chronological past of U. We prove this fact and interpret it as
impossibility (in classical general relativity) of the time machines, insofar
as the latter are defined to be causality-violating regions created by human
beings (as opposed to those appearing spontaneously).
| [
{
"created": "Sat, 17 Nov 2001 01:25:13 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Mar 2002 11:55:10 GMT",
"version": "v2"
},
{
"created": "Sun, 4 Aug 2002 13:55:06 GMT",
"version": "v3"
},
{
"created": "Thu, 13 Feb 2014 09:34:11 GMT",
"version": "v4"
}
] | 2014-02-14 | [
[
"Krasnikov",
"S.",
""
]
] | Irrespective of local conditions imposed on the metric, any extendible spacetime U has a maximal extension containing no closed causal curves outside the chronological past of U. We prove this fact and interpret it as impossibility (in classical general relativity) of the time machines, insofar as the latter are defined to be causality-violating regions created by human beings (as opposed to those appearing spontaneously). |
gr-qc/9503056 | Guillermo Mena | Nenad Manojlovic and Guillermo A. Mena Marugan | CANONICAL QUANTIZATION OF THE BELINSKII-ZAKHAROV ONE-SOLITON SOLUTIONS | 27 pages, latex, no figures. | Int.J.Mod.Phys.D4:749-766,1995 | 10.1142/S0218271895000508 | IMAFF-RC-03-95 | gr-qc | null | We apply the algebraic quantization programme proposed by Ashtekar to the
analysis of the Belinski\v{\i}-Zakharov classical spacetimes, obtained from the
Kasner metrics by means of a generalized soliton transformation. When the
solitonic parameters associated with this transformation are frozen, the
resulting Belinski\v{\i}-Zakharov metrics provide the set of classical
solutions to a gravitational minisuperspace model whose Einstein equations
reduce to the dynamical equations generated by a homogeneous Hamiltonian
constraint and to a couple of second-class constraints. The reduced phase space
of such a model has the symplectic structure of the cotangent bundle over
$I\!\!\!\,R^+\times I\!\!\!\,R^+$. In this reduced phase space, we find a
complete set of real observables which form a Lie algebra under Poisson
brackets. The quantization of the gravitational model is then carried out by
constructing an irreducible unitary representation of that algebra of
observables. Finally, we show that the quantum theory obtained in this way is
unitarily equivalent to that which describes the quantum dynamics of the Kasner
model.
| [
{
"created": "Wed, 29 Mar 1995 13:30:20 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Manojlovic",
"Nenad",
""
],
[
"Marugan",
"Guillermo A. Mena",
""
]
] | We apply the algebraic quantization programme proposed by Ashtekar to the analysis of the Belinski\v{\i}-Zakharov classical spacetimes, obtained from the Kasner metrics by means of a generalized soliton transformation. When the solitonic parameters associated with this transformation are frozen, the resulting Belinski\v{\i}-Zakharov metrics provide the set of classical solutions to a gravitational minisuperspace model whose Einstein equations reduce to the dynamical equations generated by a homogeneous Hamiltonian constraint and to a couple of second-class constraints. The reduced phase space of such a model has the symplectic structure of the cotangent bundle over $I\!\!\!\,R^+\times I\!\!\!\,R^+$. In this reduced phase space, we find a complete set of real observables which form a Lie algebra under Poisson brackets. The quantization of the gravitational model is then carried out by constructing an irreducible unitary representation of that algebra of observables. Finally, we show that the quantum theory obtained in this way is unitarily equivalent to that which describes the quantum dynamics of the Kasner model. |
2008.13201 | Tanmoy Paul | S. D. Odintsov, V. K. Oikonomou, Tanmoy Paul | Bottom-up reconstruction of non-singular bounce in F(R) gravity from
observational indices | Nuclear Physics B accepted | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the bottom-up reconstruction technique in the context of bouncing
cosmology in F(R) gravity, where the starting point is a suitable ansatz of
observable quantity (like spectral index or tensor to scalar ratio) rather than
a priori form of Hubble parameter. In inflationary scenario, the slow roll
conditions are assumed to hold true, and thus the observational indices have
general expressions in terms of the slow-roll parameters, as for example the
tensor to scalar ratio in F(R) inflation can be expressed as $r =
48\epsilon_F^2$ with $\epsilon_F = -\frac{1}{H_F^2}\frac{dH_F}{dt_F}$ and
$H_F$, $t_F$ are the Hubble parameter, cosmic time respectively. However, in
the bouncing cosmology (say in F(R) gravity theory), the slow-roll conditions
are not satisfied, in general, and thus the observable quantities do not have
any general expressions that will hold true irrespective of the form of F(R).
Thus, in order to apply the bottom-up reconstruction procedure in F(R) bouncing
model, we use the conformal correspondence between F(R) and scalar-tensor model
where the conformal factor in the present context is chosen in a way such that
it leads to an inflationary scenario in the scalar-tensor frame. Due to the
reason that the scalar and tensor perturbations remain invariant under
conformal transformation, the observable viability of the scalar-tensor
inflationary model confirms the viability of the conformally connected F(R)
bouncing model. Motivated by these arguments, here we construct a viable
non-singular bounce in F(R) gravity directly from the observable indices of the
corresponding scalar-tensor inflationary model.
| [
{
"created": "Sun, 30 Aug 2020 15:45:06 GMT",
"version": "v1"
}
] | 2020-09-01 | [
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
],
[
"Paul",
"Tanmoy",
""
]
] | We apply the bottom-up reconstruction technique in the context of bouncing cosmology in F(R) gravity, where the starting point is a suitable ansatz of observable quantity (like spectral index or tensor to scalar ratio) rather than a priori form of Hubble parameter. In inflationary scenario, the slow roll conditions are assumed to hold true, and thus the observational indices have general expressions in terms of the slow-roll parameters, as for example the tensor to scalar ratio in F(R) inflation can be expressed as $r = 48\epsilon_F^2$ with $\epsilon_F = -\frac{1}{H_F^2}\frac{dH_F}{dt_F}$ and $H_F$, $t_F$ are the Hubble parameter, cosmic time respectively. However, in the bouncing cosmology (say in F(R) gravity theory), the slow-roll conditions are not satisfied, in general, and thus the observable quantities do not have any general expressions that will hold true irrespective of the form of F(R). Thus, in order to apply the bottom-up reconstruction procedure in F(R) bouncing model, we use the conformal correspondence between F(R) and scalar-tensor model where the conformal factor in the present context is chosen in a way such that it leads to an inflationary scenario in the scalar-tensor frame. Due to the reason that the scalar and tensor perturbations remain invariant under conformal transformation, the observable viability of the scalar-tensor inflationary model confirms the viability of the conformally connected F(R) bouncing model. Motivated by these arguments, here we construct a viable non-singular bounce in F(R) gravity directly from the observable indices of the corresponding scalar-tensor inflationary model. |
1104.3484 | Lucila Kraiselburd | Lucila Kraiselburd, Marcelo Miller Bertolami, Pablo Sisterna and
H\'ector Vucetich | Energy production in varying {\alpha} theories | null | Astronomy & Astrophysics 529 (2011) 125 | 10.1051/0004-6361/201015970 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Aims. On the basis the theoretical model proposed by Bekenstein for
{\alpha}'s variation, we analyze the equations that describe the energy
exchange between matter and both the electromagnetic and the scalar fields.
Methods. We determine how the energy flow of the material is modified by the
presence of a scalar field. We estimate the total magnetic energy of matter
from the "sum rules techniques". We compare the results with data obtained from
the thermal evolution of the Earth and other planets. Results. We obtain
stringent upper limits to the variations in {\alpha} that are comparable with
those obtained from atomic clock frequency variations. Conclusions. Our
constraints imply that the fundamental length scale of Bekenstein's theory "lB"
cannot be larger than Planck's length "lP".
| [
{
"created": "Mon, 18 Apr 2011 13:51:07 GMT",
"version": "v1"
}
] | 2011-04-19 | [
[
"Kraiselburd",
"Lucila",
""
],
[
"Bertolami",
"Marcelo Miller",
""
],
[
"Sisterna",
"Pablo",
""
],
[
"Vucetich",
"Héctor",
""
]
] | Aims. On the basis the theoretical model proposed by Bekenstein for {\alpha}'s variation, we analyze the equations that describe the energy exchange between matter and both the electromagnetic and the scalar fields. Methods. We determine how the energy flow of the material is modified by the presence of a scalar field. We estimate the total magnetic energy of matter from the "sum rules techniques". We compare the results with data obtained from the thermal evolution of the Earth and other planets. Results. We obtain stringent upper limits to the variations in {\alpha} that are comparable with those obtained from atomic clock frequency variations. Conclusions. Our constraints imply that the fundamental length scale of Bekenstein's theory "lB" cannot be larger than Planck's length "lP". |
gr-qc/0101095 | Claus Laemmerzahl | Claus L\"ammerzahl and Christian J. Bord\'e | Testing the Dirac equation | 11 pages. to appear in: C. L\"ammerzahl, C.W.F. Everitt, and F.W.
Hehl (eds.): Gyros, Clocks, Interferometers...: Testing Relativistic Gravity
in Space, Lecture Notes in Physics 562, Springer 2001 | Lect.Notes Phys. 562 (2001) 463-478 | 10.1007/3-540-40988-2_24 | null | gr-qc | null | The dynamical equations which are basic for the description of the dynamics
of quantum felds in arbitrary space--time geometries, can be derived from the
requirements of a unique deterministic evolution of the quantum fields, the
superposition principle, a finite propagation speed, and probability
conservation. We suggest and describe observations and experiments which are
able to test the unique deterministic evolution and analyze given experimental
data from which restrictions of anomalous terms violating this basic principle
can be concluded. One important point is, that such anomalous terms are
predicted from loop gravity as well as from string theories. Most accurate data
can be obtained from future astrophysical observations. Also, laboratory tests
like spectroscopy give constraints on the anomalous terms.
| [
{
"created": "Wed, 24 Jan 2001 13:36:12 GMT",
"version": "v1"
}
] | 2016-12-07 | [
[
"Lämmerzahl",
"Claus",
""
],
[
"Bordé",
"Christian J.",
""
]
] | The dynamical equations which are basic for the description of the dynamics of quantum felds in arbitrary space--time geometries, can be derived from the requirements of a unique deterministic evolution of the quantum fields, the superposition principle, a finite propagation speed, and probability conservation. We suggest and describe observations and experiments which are able to test the unique deterministic evolution and analyze given experimental data from which restrictions of anomalous terms violating this basic principle can be concluded. One important point is, that such anomalous terms are predicted from loop gravity as well as from string theories. Most accurate data can be obtained from future astrophysical observations. Also, laboratory tests like spectroscopy give constraints on the anomalous terms. |
2209.02559 | Aofei Sang | Aofei Sang, Ming Zhang, Shao-Wen Wei and Jie Jiang | Splitting the Echoes of Black Holes in Einstein-nonlinear Electrodynamic
Theories | 7 pages, 6 figures, and 1 table; reference added, title changed | Eur.Phys.J.C 83 (2023) 4, 291 | 10.1140/epjc/s10052-023-11448-4 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | Black hole echo is an important observable that can help us better understand
gravitational theories. We present that the non-linear electrodynamic black
holes can admit the multi-peak effective potential for the scalar
perturbations, which can give rise to the echoes. After choosing suitable
parameters, the effective potential can exhibit a structure with more than two
peaks. Putting the initial wave packet released outside the peaks, we find that
the time-domain profile of the echo will split when the peaks of the effective
potential change from two to three. This is a phenomenon of black hole echo and
it might be possible to determine the geometric structure of the black hole
according to this phenomenon through gravitational wave detection.
| [
{
"created": "Tue, 6 Sep 2022 15:11:01 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Oct 2022 08:15:10 GMT",
"version": "v2"
}
] | 2023-04-19 | [
[
"Sang",
"Aofei",
""
],
[
"Zhang",
"Ming",
""
],
[
"Wei",
"Shao-Wen",
""
],
[
"Jiang",
"Jie",
""
]
] | Black hole echo is an important observable that can help us better understand gravitational theories. We present that the non-linear electrodynamic black holes can admit the multi-peak effective potential for the scalar perturbations, which can give rise to the echoes. After choosing suitable parameters, the effective potential can exhibit a structure with more than two peaks. Putting the initial wave packet released outside the peaks, we find that the time-domain profile of the echo will split when the peaks of the effective potential change from two to three. This is a phenomenon of black hole echo and it might be possible to determine the geometric structure of the black hole according to this phenomenon through gravitational wave detection. |
1507.00680 | Andrea Maselli | Andrea Maselli, Paolo Pani, Leonardo Gualtieri and Valeria Ferrari | Rotating black holes in Einstein-Dilaton-Gauss-Bonnet gravity with
finite coupling | Minor bug fixed in the supplementary mathematica notebook | Phys. Rev. D 92, 083014 (2015) | 10.1103/PhysRevD.92.083014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Among various strong-curvature extensions to General Relativity,
Einstein-Dilaton-Gauss-Bonnet gravity stands out as the only nontrivial theory
containing quadratic curvature corrections while being free from the
Ostrogradsky instability to any order in the coupling parameter. We derive an
approximate stationary and axisymmetric black-hole solution of this
gravitational theory in closed form, which is quadratic in the black-hole spin
angular momentum and of seventh order in the coupling parameter of the theory.
This extends previous work that obtained the corrections to the metric only at
the leading order in the coupling parameter, and allows us to consider values
of the coupling parameter close to the maximum permitted by theoretical
constraints. We compute some geometrical properties of this solution, such as
the dilaton charge, the moment of inertia and the quadrupole moment, and its
geodesic structure, including the innermost-stable circular orbit and the
epicyclic frequencies for massive particles. The latter represent a valuable
tool to test General Relativity against strong-curvature corrections through
observations of the electromagnetic spectrum of accreting black holes.
| [
{
"created": "Thu, 2 Jul 2015 18:09:34 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Oct 2015 12:56:19 GMT",
"version": "v2"
},
{
"created": "Fri, 2 Mar 2018 06:23:07 GMT",
"version": "v3"
}
] | 2018-03-05 | [
[
"Maselli",
"Andrea",
""
],
[
"Pani",
"Paolo",
""
],
[
"Gualtieri",
"Leonardo",
""
],
[
"Ferrari",
"Valeria",
""
]
] | Among various strong-curvature extensions to General Relativity, Einstein-Dilaton-Gauss-Bonnet gravity stands out as the only nontrivial theory containing quadratic curvature corrections while being free from the Ostrogradsky instability to any order in the coupling parameter. We derive an approximate stationary and axisymmetric black-hole solution of this gravitational theory in closed form, which is quadratic in the black-hole spin angular momentum and of seventh order in the coupling parameter of the theory. This extends previous work that obtained the corrections to the metric only at the leading order in the coupling parameter, and allows us to consider values of the coupling parameter close to the maximum permitted by theoretical constraints. We compute some geometrical properties of this solution, such as the dilaton charge, the moment of inertia and the quadrupole moment, and its geodesic structure, including the innermost-stable circular orbit and the epicyclic frequencies for massive particles. The latter represent a valuable tool to test General Relativity against strong-curvature corrections through observations of the electromagnetic spectrum of accreting black holes. |
1812.06373 | Miguel Cruz | Miguel Cruz and Samuel Lepe | Modeling holographic dark energy with particle and future horizons | 19 pages, no figures. To appear in Nuclear Physics B | Nucl. Phys. B 956, 115017 (2020) | 10.1016/j.nuclphysb.2020.115017 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we explore some cosmological properties coming from the particle
and future horizons when are considered as candidates to model the dark energy
sector within a holographic context in a flat
Friedmann-Lemaitre-Robertson-Walker universe; we focus on some thermodynamics
characteristics of the resulting dark energy scenario. Within the interacting
scheme for cosmological fluids we obtain that in the dark sector, the dark
energy fluid will always have negative entropy production and additionally, the
positivity for the entropy and temperature can not be guaranteed
simultaneously; this result holds for both horizons. However, this last issue
can be solved if chemical potential is introduced in the thermodynamics
description. For the non interacting approach, we obtain similar results as
those of the single fluid description for the entropy behavior. We also find
that the model admits a genuine big rip singularity when the dark energy
density is sketched by the future horizon, in consequence the resulting
parameter state can cross to the phantom regime. For the particle horizon case
the cosmological fluid can emulate ordinary matter and the coincidence
parameter has a decreasing behavior when the future horizon is elected.
| [
{
"created": "Sun, 16 Dec 2018 01:38:52 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Jan 2019 21:15:48 GMT",
"version": "v2"
},
{
"created": "Fri, 22 Nov 2019 21:18:24 GMT",
"version": "v3"
},
{
"created": "Wed, 8 Apr 2020 23:12:17 GMT",
"version": "v4"
}
] | 2020-04-29 | [
[
"Cruz",
"Miguel",
""
],
[
"Lepe",
"Samuel",
""
]
] | In this work we explore some cosmological properties coming from the particle and future horizons when are considered as candidates to model the dark energy sector within a holographic context in a flat Friedmann-Lemaitre-Robertson-Walker universe; we focus on some thermodynamics characteristics of the resulting dark energy scenario. Within the interacting scheme for cosmological fluids we obtain that in the dark sector, the dark energy fluid will always have negative entropy production and additionally, the positivity for the entropy and temperature can not be guaranteed simultaneously; this result holds for both horizons. However, this last issue can be solved if chemical potential is introduced in the thermodynamics description. For the non interacting approach, we obtain similar results as those of the single fluid description for the entropy behavior. We also find that the model admits a genuine big rip singularity when the dark energy density is sketched by the future horizon, in consequence the resulting parameter state can cross to the phantom regime. For the particle horizon case the cosmological fluid can emulate ordinary matter and the coincidence parameter has a decreasing behavior when the future horizon is elected. |
2001.02025 | Bobby Eka Gunara | Bobby E. Gunara, Mulyanto, Rahmat H. Alineng, Fiki T. Akbar, and Hadi
Susanto | Static Spacetimes In Higher Dimensional Scalar-Torsion Theories With
Non-Minimal Derivative Coupling | Major revision: 28 pages, some authors added and reordered, no
figure, some sections added and updated. Comments are welcome | null | null | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we consider a class of static spacetimes in higher dimensional
($D \ge 4$) scalar-torsion theories with non-minimal derivative coupling and
the scalar potential turned on. The spacetime is conformal to a product space
of a two-surface and a $(D-2)$-dimensional submanifold. Analyzing the equations
of motion in the theory we find that the $(D-2)$-dimensional submanifold has to
admit constant triplet structures in which the torsion scalar is one of them.
This implies that these equations of motion can be simplified into a single
highly non-linear ordinary differential equation called the master equation.
Then, we show that in this case the solution admits at least a naked
singularity at the origin which is not a black hole. In the asymptotic region,
the spacetimes converge to spaces of constant scalar curvature which are
generally not Einstein. We also use perturbative method to linearize the master
equation and construct the first order solutions. At the end, we establish the
analysis of local-global existences of the master equation and then, prove the
non-existence of regular global solutions.
| [
{
"created": "Tue, 7 Jan 2020 13:36:37 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Nov 2022 22:50:32 GMT",
"version": "v2"
}
] | 2022-11-28 | [
[
"Gunara",
"Bobby E.",
""
],
[
"Mulyanto",
"",
""
],
[
"Alineng",
"Rahmat H.",
""
],
[
"Akbar",
"Fiki T.",
""
],
[
"Susanto",
"Hadi",
""
]
] | In this paper we consider a class of static spacetimes in higher dimensional ($D \ge 4$) scalar-torsion theories with non-minimal derivative coupling and the scalar potential turned on. The spacetime is conformal to a product space of a two-surface and a $(D-2)$-dimensional submanifold. Analyzing the equations of motion in the theory we find that the $(D-2)$-dimensional submanifold has to admit constant triplet structures in which the torsion scalar is one of them. This implies that these equations of motion can be simplified into a single highly non-linear ordinary differential equation called the master equation. Then, we show that in this case the solution admits at least a naked singularity at the origin which is not a black hole. In the asymptotic region, the spacetimes converge to spaces of constant scalar curvature which are generally not Einstein. We also use perturbative method to linearize the master equation and construct the first order solutions. At the end, we establish the analysis of local-global existences of the master equation and then, prove the non-existence of regular global solutions. |
1505.05021 | Joao Magueijo | Michele Arzano, Giulia Gubitosi, Joao Magueijo and Giovanni
Amelino-Camelia | Vacuum fluctuations in theories with deformed dispersion relations | References added. Version to appear in Phys. Rev. D | null | null | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine vacuum fluctuations in theories with modified dispersion relations
which represent dimensional reduction at high energies. By changing units of
energy and momentum we can obtain a description rendering the dispersion
relations undeformed and transferring all the non-trivial effects to the
integration measure in momentum space. Using this description we propose a
general quantization procedure, which should be applicable whether or not the
theory explicitly introduces a preferred frame. Based on this scheme we
evaluate the power spectrum of quantum vacuum fluctuations. We find that in
{\it all} theories which run to 2 dimensions in the ultraviolet the vacuum
fluctuations, in the ultraviolet regime, are scale-invariant. This is true in
flat space but also for "inside the horizon" modes in an expanding universe. We
spell out the conditions upon the gravity theory for this scale-invariance to
be preserved as the modes are frozen-in outside the horizon. We also digress on
the meaning of dimensionality (in momentum and position space) and suggest that
the spectral index could itself provide an operational definition of
dimensionality.
| [
{
"created": "Tue, 19 May 2015 14:43:38 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Jun 2015 19:56:18 GMT",
"version": "v2"
}
] | 2015-06-16 | [
[
"Arzano",
"Michele",
""
],
[
"Gubitosi",
"Giulia",
""
],
[
"Magueijo",
"Joao",
""
],
[
"Amelino-Camelia",
"Giovanni",
""
]
] | We examine vacuum fluctuations in theories with modified dispersion relations which represent dimensional reduction at high energies. By changing units of energy and momentum we can obtain a description rendering the dispersion relations undeformed and transferring all the non-trivial effects to the integration measure in momentum space. Using this description we propose a general quantization procedure, which should be applicable whether or not the theory explicitly introduces a preferred frame. Based on this scheme we evaluate the power spectrum of quantum vacuum fluctuations. We find that in {\it all} theories which run to 2 dimensions in the ultraviolet the vacuum fluctuations, in the ultraviolet regime, are scale-invariant. This is true in flat space but also for "inside the horizon" modes in an expanding universe. We spell out the conditions upon the gravity theory for this scale-invariance to be preserved as the modes are frozen-in outside the horizon. We also digress on the meaning of dimensionality (in momentum and position space) and suggest that the spectral index could itself provide an operational definition of dimensionality. |
2303.02111 | Daniel Mayerson | Seppe Staelens, Daniel R. Mayerson, Fabio Bacchini, Bart Ripperda,
Lorenzo K\"uchler | Black Hole Photon Rings Beyond General Relativity | 31 pages + appendices; 20 figures | null | 10.1103/PhysRevD.107.124026 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate whether photon ring observations in black hole imaging are
able to distinguish between the Kerr black hole in general relativity and
alternative black holes that deviate from Kerr. Certain aspects of photon rings
have been argued to be robust observables in Very-Long-Baseline Interferometry
(VLBI) black hole observations which carry imprints of the underlying
spacetime. The photon ring shape, as well as its Lyapunov exponent (which
encodes the narrowing of successive photon subrings), are detailed probes of
the underlying geometry; measurements thereof have been argued to provide a
strong null test of general relativity and the Kerr metric. However, a more
complicated question is whether such observations of the photon ring properties
can distinguish between Kerr and alternative black holes. We provide a first
answer to this question by calculating photon rings of the Johannsen,
Rasheed-Larsen, and Manko-Novikov black holes. We find that large deviations
from Kerr and large observer inclinations are needed to obtain measurable
differences in the photon ring shape. In other words, the Kerr photon ring
shape appears to be the universal shape even for deviating black holes at low
inclinations. On the other hand, the Lyapunov exponent shows more marked
variations for deviations from the Kerr metric. Our analysis lays out the
groundwork to determine deviations from the Kerr spacetime in photon rings that
are potentially detectable by future observing missions.
| [
{
"created": "Fri, 3 Mar 2023 17:53:15 GMT",
"version": "v1"
}
] | 2023-06-28 | [
[
"Staelens",
"Seppe",
""
],
[
"Mayerson",
"Daniel R.",
""
],
[
"Bacchini",
"Fabio",
""
],
[
"Ripperda",
"Bart",
""
],
[
"Küchler",
"Lorenzo",
""
]
] | We investigate whether photon ring observations in black hole imaging are able to distinguish between the Kerr black hole in general relativity and alternative black holes that deviate from Kerr. Certain aspects of photon rings have been argued to be robust observables in Very-Long-Baseline Interferometry (VLBI) black hole observations which carry imprints of the underlying spacetime. The photon ring shape, as well as its Lyapunov exponent (which encodes the narrowing of successive photon subrings), are detailed probes of the underlying geometry; measurements thereof have been argued to provide a strong null test of general relativity and the Kerr metric. However, a more complicated question is whether such observations of the photon ring properties can distinguish between Kerr and alternative black holes. We provide a first answer to this question by calculating photon rings of the Johannsen, Rasheed-Larsen, and Manko-Novikov black holes. We find that large deviations from Kerr and large observer inclinations are needed to obtain measurable differences in the photon ring shape. In other words, the Kerr photon ring shape appears to be the universal shape even for deviating black holes at low inclinations. On the other hand, the Lyapunov exponent shows more marked variations for deviations from the Kerr metric. Our analysis lays out the groundwork to determine deviations from the Kerr spacetime in photon rings that are potentially detectable by future observing missions. |
gr-qc/0609122 | Alejandro Corichi | Alejandro Corichi, Jacobo Diaz-Polo and Enrique Fernandez-Borja | Black hole entropy quantization | 4 pages, 4 figures. Version to be published in PRL | Phys.Rev.Lett.98:181301,2007 | 10.1103/PhysRevLett.98.181301 | null | gr-qc hep-th | null | Ever since the pioneer works of Bekenstein and Hawking, black hole entropy
has been known to have a quantum origin. Furthermore, it has long been argued
by Bekenstein that entropy should be quantized in discrete (equidistant) steps
given its identification with horizon area in (semi-)classical general
relativity and the properties of area as an adiabatic invariant. This lead to
the suggestion that black hole area should also be quantized in equidistant
steps to account for the discrete black hole entropy. Here we shall show that
loop quantum gravity, in which area is {\it not} quantized in equidistant steps
can nevertheless be consistent with Bekenstein's equidistant entropy proposal
in a subtle way. For that we perform a detailed analysis of the number of
microstates compatible with a given area and show consistency with the
Bekenstein framework when an oscillatory behavior in the entropy-area relation
is properly interpreted.
| [
{
"created": "Tue, 26 Sep 2006 23:54:19 GMT",
"version": "v1"
},
{
"created": "Tue, 1 May 2007 22:15:32 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Corichi",
"Alejandro",
""
],
[
"Diaz-Polo",
"Jacobo",
""
],
[
"Fernandez-Borja",
"Enrique",
""
]
] | Ever since the pioneer works of Bekenstein and Hawking, black hole entropy has been known to have a quantum origin. Furthermore, it has long been argued by Bekenstein that entropy should be quantized in discrete (equidistant) steps given its identification with horizon area in (semi-)classical general relativity and the properties of area as an adiabatic invariant. This lead to the suggestion that black hole area should also be quantized in equidistant steps to account for the discrete black hole entropy. Here we shall show that loop quantum gravity, in which area is {\it not} quantized in equidistant steps can nevertheless be consistent with Bekenstein's equidistant entropy proposal in a subtle way. For that we perform a detailed analysis of the number of microstates compatible with a given area and show consistency with the Bekenstein framework when an oscillatory behavior in the entropy-area relation is properly interpreted. |
1408.5126 | Hassan Murad | Mohammad Hassan Murad, Saba Fatema | Some new Wyman-Adler type static relativistic charged anisotropic fluid
spheres compatible to self-bound stellar modeling | 17 pages, 9 figures, 4 tables. Some corrections have been made | null | null | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | In this work some families of relativistic anisotropic charged fluid spheres
have been obtained by solving Einstein-Maxwell field equations with preferred
form of one of the metric potentials, a suitable forms of electric charge
distribution and pressure anisotropy functions. The resulting equation of state
(EOS) of the matter distribution has been obtained. Physical analysis shows
that the relativistic stellar structure for matter distribution obtained in
this work may reasonably model an electrically charged compact star whose
energy density associated with the electric fields is on the same order of
magnitude as the energy density of fluid matter itself (e.g. electrically
charged bare strange stars). These models permit a simple method of
systematically fixing bounds on the maximum possible mass of cold compact
electrically charged self-bound stars. It has been demonstrated numerically
that the maximum compactness and mass increase in the presence of electric
field and anisotropic pressures. Based on the analytic model developed in this
present work, the values of the relevant physical quantities have been
calculated by assuming the estimated masses and radii of some well known
potential strange star candidates like PSR J1614-2230, PSR J1903+327, Vela X-1,
and 4U 1820-30.
| [
{
"created": "Thu, 21 Aug 2014 06:58:40 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Sep 2014 05:55:06 GMT",
"version": "v2"
}
] | 2014-09-02 | [
[
"Murad",
"Mohammad Hassan",
""
],
[
"Fatema",
"Saba",
""
]
] | In this work some families of relativistic anisotropic charged fluid spheres have been obtained by solving Einstein-Maxwell field equations with preferred form of one of the metric potentials, a suitable forms of electric charge distribution and pressure anisotropy functions. The resulting equation of state (EOS) of the matter distribution has been obtained. Physical analysis shows that the relativistic stellar structure for matter distribution obtained in this work may reasonably model an electrically charged compact star whose energy density associated with the electric fields is on the same order of magnitude as the energy density of fluid matter itself (e.g. electrically charged bare strange stars). These models permit a simple method of systematically fixing bounds on the maximum possible mass of cold compact electrically charged self-bound stars. It has been demonstrated numerically that the maximum compactness and mass increase in the presence of electric field and anisotropic pressures. Based on the analytic model developed in this present work, the values of the relevant physical quantities have been calculated by assuming the estimated masses and radii of some well known potential strange star candidates like PSR J1614-2230, PSR J1903+327, Vela X-1, and 4U 1820-30. |
1212.6289 | Hideyoshi Arakida | Hideyoshi Arakida | Note on the perihelion/periastron advance due to cosmological constant | 8 pages, 1 figure, accepted for publication in International Journal
of Theoretical Physics | null | 10.1007/s10773-012-1458-2 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We will comment on the perihelion/periastron advance of celestial bodies due
to the cosmological constant $\Lambda$. It is well known that the cosmological
constant $\Lambda$ causes the perihelion/periastron shift; however, there seems
to still exist a discrepancy among the various derived precession formulae. We
will point out that the expression $\Delta \omega_{\Lambda} = (\pi c^2 \Lambda
a^3/(GM))\sqrt{1 - e^2}$ is the general formula for any orbital eccentricity
$e$ and the expression $\Delta \omega_{\Lambda} = (\pi c^2 \Lambda a^3/(GM))(1
- e^2)^3$ comes from the nearly circular ($e \ll 1$) approximation.
| [
{
"created": "Thu, 27 Dec 2012 01:44:24 GMT",
"version": "v1"
}
] | 2013-01-01 | [
[
"Arakida",
"Hideyoshi",
""
]
] | We will comment on the perihelion/periastron advance of celestial bodies due to the cosmological constant $\Lambda$. It is well known that the cosmological constant $\Lambda$ causes the perihelion/periastron shift; however, there seems to still exist a discrepancy among the various derived precession formulae. We will point out that the expression $\Delta \omega_{\Lambda} = (\pi c^2 \Lambda a^3/(GM))\sqrt{1 - e^2}$ is the general formula for any orbital eccentricity $e$ and the expression $\Delta \omega_{\Lambda} = (\pi c^2 \Lambda a^3/(GM))(1 - e^2)^3$ comes from the nearly circular ($e \ll 1$) approximation. |
2210.17462 | Maciej Maliborski | Piotr Bizo\'n and Maciej Maliborski | Comment on a regular black hole with Yang-Mills hair | 5 pages, 1 figure | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We comment upon a black hole with Yang-Mills hair presented in a recent
preprint by Chen, Du, and Yau.
| [
{
"created": "Mon, 31 Oct 2022 16:40:34 GMT",
"version": "v1"
}
] | 2022-11-01 | [
[
"Bizoń",
"Piotr",
""
],
[
"Maliborski",
"Maciej",
""
]
] | We comment upon a black hole with Yang-Mills hair presented in a recent preprint by Chen, Du, and Yau. |
gr-qc/9301020 | Domenico Giulini | Domenico Giulini | On the configuration space topology in general relativity | Plain-Tex, 33 pages, no figures, Freiburg THEP-92/32 | Helv.Phys.Acta 68 (1995) 86-111 | null | null | gr-qc | null | The configuration-space topology in canonical General Relativity depends on
the choice of the initial data 3-manifold. If the latter is represented as a
connected sum of prime 3-manifolds, the topology receives contributions from
all configuration spaces associated to each individual prime factor. There are
by now strong results available concerning the diffeomorphism group of prime
3-manifolds which are exploited to examine the topology of the configuration
spaces in terms of their homotopy groups. We explicitly show how to obtain
these for the class of homogeneous spherical primes, and communicate the
results for all other known primes except the non-sufficiently large ones of
infinite fundamental group.
| [
{
"created": "Mon, 25 Jan 1993 18:26:03 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Giulini",
"Domenico",
""
]
] | The configuration-space topology in canonical General Relativity depends on the choice of the initial data 3-manifold. If the latter is represented as a connected sum of prime 3-manifolds, the topology receives contributions from all configuration spaces associated to each individual prime factor. There are by now strong results available concerning the diffeomorphism group of prime 3-manifolds which are exploited to examine the topology of the configuration spaces in terms of their homotopy groups. We explicitly show how to obtain these for the class of homogeneous spherical primes, and communicate the results for all other known primes except the non-sufficiently large ones of infinite fundamental group. |
2010.15818 | Conor O'Toole | Conor O'Toole, Adrian Ottewill, Barry Wardell | Characteristic formulation of the Regge-Wheeler and Zerilli Green
functions | v2. Added computation of gravitational flux. Added Zerilli Green
function. Corrected typos, updated figures. 11 pages, 8 figures | Phys. Rev. D 103, 124022 (2021) | 10.1103/PhysRevD.103.124022 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a characteristic initial value approach to calculating the Green
function of the Regge-Wheeler and Zerilli equations. We combine well-known
numerical methods with newly derived initial data to obtain a scheme which can
in principle be generalised to any desired order of convergence. We demonstrate
the approach with implementations up to sixth-order in the grid spacing. By
combining the results of our numerical code with late-time tail expansions and
methods of subtracting the direct part of the Green function, we show that the
scalar self-force in Schwarzschild spacetime can be computed to better accuracy
than previous Green-function based approaches. We also demonstrate agreement
with frequency-domain methods for computing the Green function in the
gravitational case. Finally, we apply the Regge-Wheeler and Zerilli Green
functions to the computation of the gravitational energy flux.
| [
{
"created": "Thu, 29 Oct 2020 17:53:32 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Mar 2021 18:25:33 GMT",
"version": "v2"
}
] | 2021-06-16 | [
[
"O'Toole",
"Conor",
""
],
[
"Ottewill",
"Adrian",
""
],
[
"Wardell",
"Barry",
""
]
] | We present a characteristic initial value approach to calculating the Green function of the Regge-Wheeler and Zerilli equations. We combine well-known numerical methods with newly derived initial data to obtain a scheme which can in principle be generalised to any desired order of convergence. We demonstrate the approach with implementations up to sixth-order in the grid spacing. By combining the results of our numerical code with late-time tail expansions and methods of subtracting the direct part of the Green function, we show that the scalar self-force in Schwarzschild spacetime can be computed to better accuracy than previous Green-function based approaches. We also demonstrate agreement with frequency-domain methods for computing the Green function in the gravitational case. Finally, we apply the Regge-Wheeler and Zerilli Green functions to the computation of the gravitational energy flux. |
0810.4492 | Louis Crane | Louis Crane | Model Categories and Quantum Gravity | 19 pages latex | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a mathematically concrete way of modelling the suggestion that in
quantum gravity the spacetime disappears, replacing it with a discrete
approximation to the causal path space described as an object in a model
category. One of the versions of our models appears as a thickening of
spacetime, which we interpret as a formulation of relational geometry. Avenues
toward constructing an actual quantum theory of gravity on our models are given
a preliminary exploration.
| [
{
"created": "Fri, 24 Oct 2008 15:49:21 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Oct 2008 13:32:44 GMT",
"version": "v2"
}
] | 2008-10-27 | [
[
"Crane",
"Louis",
""
]
] | We propose a mathematically concrete way of modelling the suggestion that in quantum gravity the spacetime disappears, replacing it with a discrete approximation to the causal path space described as an object in a model category. One of the versions of our models appears as a thickening of spacetime, which we interpret as a formulation of relational geometry. Avenues toward constructing an actual quantum theory of gravity on our models are given a preliminary exploration. |
1403.2767 | Raisa Galimova | Raisa Galimova | BKL conjecture in Bianchi VIII and IX with the ultrarelativistic fluid | 60 pages. arXiv admin note: text overlap with arXiv:1005.4908 by
other authors | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We rigorously verify that in the spatially homogeneous spacetimes (Bianchi
VIII and IX), the presence of matter does not affect the oscillatory behavior
of the solutions to the Einstein field equations as first conjectured by
Belinski, Khalatnikov, and Lifshitz (BKL) in 1970. This paper is an extension
of the paper by Reiterer and Trubowitz (arXiv 1005.4908) and uses the same
formalism. We use the ultrarelativistic equation of state.
| [
{
"created": "Tue, 11 Mar 2014 21:53:59 GMT",
"version": "v1"
}
] | 2014-03-13 | [
[
"Galimova",
"Raisa",
""
]
] | We rigorously verify that in the spatially homogeneous spacetimes (Bianchi VIII and IX), the presence of matter does not affect the oscillatory behavior of the solutions to the Einstein field equations as first conjectured by Belinski, Khalatnikov, and Lifshitz (BKL) in 1970. This paper is an extension of the paper by Reiterer and Trubowitz (arXiv 1005.4908) and uses the same formalism. We use the ultrarelativistic equation of state. |
gr-qc/0506068 | Diego Meschini | Diego Meschini, Markku Lehto | Is empty spacetime a physical thing? | 21 pages, Latex. v2: Section 5 expanded | Found.Phys. 36 (2006) 1193-1216 | 10.1007/s10701-006-9058-8 | null | gr-qc | null | This article deals with empty spacetime and the question of its physical
reality. By "empty spacetime" we mean a collection of bare spacetime points,
the remains of ridding spacetime of all matter and fields. We ask whether these
geometric objects--themselves intrinsic to the concept of field--might be
observable through some physical test. By taking quantum-mechanical notions
into account, we challenge the negative conclusion drawn from the
diffeomorphism invariance postulate of general relativity, and we propose new
foundational ideas regarding the possible observation--as well as conceptual
overthrow--of this geometric ether.
| [
{
"created": "Sat, 11 Jun 2005 12:15:44 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Oct 2005 16:02:44 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Meschini",
"Diego",
""
],
[
"Lehto",
"Markku",
""
]
] | This article deals with empty spacetime and the question of its physical reality. By "empty spacetime" we mean a collection of bare spacetime points, the remains of ridding spacetime of all matter and fields. We ask whether these geometric objects--themselves intrinsic to the concept of field--might be observable through some physical test. By taking quantum-mechanical notions into account, we challenge the negative conclusion drawn from the diffeomorphism invariance postulate of general relativity, and we propose new foundational ideas regarding the possible observation--as well as conceptual overthrow--of this geometric ether. |
1312.5332 | Claude Warnick | Gustav H. Holzegel and Claude M. Warnick | The Einstein-Klein-Gordon-AdS system for general boundary conditions | 42 pages; V2 Typos corrected | null | null | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct unique local solutions for the spherically-symmetric
Einstein-Klein-Gordon-AdS system subject to a large class of initial and
boundary conditions including some considered in the context of the AdS-CFT
correspondence. The proof relies on estimates developed for the linear wave
equation by the second author and involves a careful renormalization of the
dynamical variables, including a renormalization of the well-known Hawking
mass. For some of the boundary conditions considered this system is expected to
exhibit rich global dynamics, including the existence of hairy black holes. The
present paper furnishes a starting point for such global investigations.
| [
{
"created": "Wed, 18 Dec 2013 21:00:19 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Jul 2014 13:15:08 GMT",
"version": "v2"
}
] | 2014-07-29 | [
[
"Holzegel",
"Gustav H.",
""
],
[
"Warnick",
"Claude M.",
""
]
] | We construct unique local solutions for the spherically-symmetric Einstein-Klein-Gordon-AdS system subject to a large class of initial and boundary conditions including some considered in the context of the AdS-CFT correspondence. The proof relies on estimates developed for the linear wave equation by the second author and involves a careful renormalization of the dynamical variables, including a renormalization of the well-known Hawking mass. For some of the boundary conditions considered this system is expected to exhibit rich global dynamics, including the existence of hairy black holes. The present paper furnishes a starting point for such global investigations. |
1307.1439 | Ranjan Sharma | Ranjan Sharma and B. S. Ratanpal | Relativistic stellar model admitting a quadratic equation of state | Accepted for publication in Int. J. Mod. Phys. D | Int. J. Mod. Phys. D, v. 22, p. 1350074, 2013 | 10.1142/S0218271813500740 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A class of solutions describing the interior of a static spherically
symmetric compact anisotropic star is reported. The analytic solution has been
obtained by utilizing the Finch and Skea ({\it Class. Quant. Grav.} {\bf 6}
(1989) 467) ansatz for the metric potential $g_{rr}$ which has a clear
geometric interpretation for the associated background space-time. Based on
physical grounds appropriate bounds on the model parameters have been obtained
and it has been shown that the model admits an equation of state (EOS) which is
quadratic in nature.
| [
{
"created": "Tue, 2 Jul 2013 04:53:29 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Sharma",
"Ranjan",
""
],
[
"Ratanpal",
"B. S.",
""
]
] | A class of solutions describing the interior of a static spherically symmetric compact anisotropic star is reported. The analytic solution has been obtained by utilizing the Finch and Skea ({\it Class. Quant. Grav.} {\bf 6} (1989) 467) ansatz for the metric potential $g_{rr}$ which has a clear geometric interpretation for the associated background space-time. Based on physical grounds appropriate bounds on the model parameters have been obtained and it has been shown that the model admits an equation of state (EOS) which is quadratic in nature. |
1701.04957 | Li Zhao | Tao-Tao Sui, Li Zhao, Yu-Peng Zhang, Qun-Ying Xie | Localization and mass spectra of various matter fields on Weyl thin
brane | 15 pages, 11 figures, 1 table | Eur.Phys.J.C77 (2017) no.6, 411 | 10.1140/epjc/s10052-017-4922-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been shown that the thin brane model in a five-dimensional Weyl
gravity can deal with the wrong-signed Friedmann-like equation in the
Randall--Sundrum-1 (RS1) model. In the Weyl brane model, there are also two
branes with opposite brane tensions, but the four-dimensional graviton (the
gravity zero mode) is localized near the negative tension brane, while our
four-dimensional universe is localized on the positive tension brane. In this
paper, we consider the mass spectra of various bulk matter fields (i.e.,
scalar, vector, and fermion fields) on the Weyl brane. It is shown that the
zero modes of those matter fields can be localized on the positive tension
brane under some conditions. The mass spectra of the bulk matter fields are
equidistant for the higher excited states, and relatively sparse for the lower
excited states. The size of the extra dimension determines the gap of the mass
spectra. We also consider the correction to the Newtonian potential in this
model and it is proportional to $1/r^{3}$.
| [
{
"created": "Wed, 18 Jan 2017 05:54:47 GMT",
"version": "v1"
},
{
"created": "Sun, 9 Jul 2017 13:54:36 GMT",
"version": "v2"
}
] | 2017-07-11 | [
[
"Sui",
"Tao-Tao",
""
],
[
"Zhao",
"Li",
""
],
[
"Zhang",
"Yu-Peng",
""
],
[
"Xie",
"Qun-Ying",
""
]
] | It has been shown that the thin brane model in a five-dimensional Weyl gravity can deal with the wrong-signed Friedmann-like equation in the Randall--Sundrum-1 (RS1) model. In the Weyl brane model, there are also two branes with opposite brane tensions, but the four-dimensional graviton (the gravity zero mode) is localized near the negative tension brane, while our four-dimensional universe is localized on the positive tension brane. In this paper, we consider the mass spectra of various bulk matter fields (i.e., scalar, vector, and fermion fields) on the Weyl brane. It is shown that the zero modes of those matter fields can be localized on the positive tension brane under some conditions. The mass spectra of the bulk matter fields are equidistant for the higher excited states, and relatively sparse for the lower excited states. The size of the extra dimension determines the gap of the mass spectra. We also consider the correction to the Newtonian potential in this model and it is proportional to $1/r^{3}$. |
2405.04062 | Sebastian Garcia-Saenz | Sebastian Garcia-Saenz, Junjie Hua, Yunke Zhao | Geodesic completeness, cosmological bounces and inflation | 5 pages | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The question of geodesic completeness of cosmological spacetimes has recently
received renewed scrutiny. A particularly interesting result is the observation
that the well-known Borde-Guth-Vilenkin (BGV) theorem may misdiagnose
geodesically complete cosmologies. We propose a simple amendment to the BGV
theorem which addresses such loopholes while retaining much of its generality.
We give straightforward proofs of some recently offered conjectures concerning
(generalized) Friedmann-Lema\^itre-Robertson-Walker spacetimes: geodesic
completeness implies (i) the existence of a bounce, loitering phase or an
emergent cosmology, and (ii) a phase of accelerated expansion with strictly
increasing Hubble rate. Our results are purely kinematic and do not assume
general relativity or energy conditions.
| [
{
"created": "Tue, 7 May 2024 07:09:00 GMT",
"version": "v1"
}
] | 2024-05-08 | [
[
"Garcia-Saenz",
"Sebastian",
""
],
[
"Hua",
"Junjie",
""
],
[
"Zhao",
"Yunke",
""
]
] | The question of geodesic completeness of cosmological spacetimes has recently received renewed scrutiny. A particularly interesting result is the observation that the well-known Borde-Guth-Vilenkin (BGV) theorem may misdiagnose geodesically complete cosmologies. We propose a simple amendment to the BGV theorem which addresses such loopholes while retaining much of its generality. We give straightforward proofs of some recently offered conjectures concerning (generalized) Friedmann-Lema\^itre-Robertson-Walker spacetimes: geodesic completeness implies (i) the existence of a bounce, loitering phase or an emergent cosmology, and (ii) a phase of accelerated expansion with strictly increasing Hubble rate. Our results are purely kinematic and do not assume general relativity or energy conditions. |
2301.04342 | Telem Ibungochouba Singh | Yenshembam Priyobarta Singh, Telem Ibungochouba Singh | Massive vector particle tunneling from Kerr-Newman-de Sitter black hole
under generalized uncertainty principle | null | null | null | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | The quantum tunneling of charged massive vector boson particles across the
event horizon of Kerr-Newman-de Sitter black hole is investigated under the
influence of quantum gravity effects. The modified Hawking temperatures and
heat capacities across the event horizon of KNdS black hole are derived in
3-dimensional and 4-dimensional frame dragging coordinates. It is found that
due to quantum gravity effects the modified Hawking temperatures and heat
capacities depend on the mass and angular momentum of the emitted vector boson
particles. For 3-dimensional KNdS black hole, the modified Hawking temperature
is lower than the original Hawking temperature but the modified heat capacity
is higher than the original heat capacity due to quantum gravity effects. In
the case of 4-dimensional KNdS black hole, the modified Hawking temperature and
heat capacity are lower or greater than the original Hawking temperature and
heat capacity depending upon the choices of black hole parameters due to
quantum gravity effects. We also discuss the remnant and graphical analysis of
the modified Hawking temperatures and heat capacities.
| [
{
"created": "Wed, 11 Jan 2023 07:37:32 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Mar 2023 05:59:39 GMT",
"version": "v2"
}
] | 2023-03-29 | [
[
"Singh",
"Yenshembam Priyobarta",
""
],
[
"Singh",
"Telem Ibungochouba",
""
]
] | The quantum tunneling of charged massive vector boson particles across the event horizon of Kerr-Newman-de Sitter black hole is investigated under the influence of quantum gravity effects. The modified Hawking temperatures and heat capacities across the event horizon of KNdS black hole are derived in 3-dimensional and 4-dimensional frame dragging coordinates. It is found that due to quantum gravity effects the modified Hawking temperatures and heat capacities depend on the mass and angular momentum of the emitted vector boson particles. For 3-dimensional KNdS black hole, the modified Hawking temperature is lower than the original Hawking temperature but the modified heat capacity is higher than the original heat capacity due to quantum gravity effects. In the case of 4-dimensional KNdS black hole, the modified Hawking temperature and heat capacity are lower or greater than the original Hawking temperature and heat capacity depending upon the choices of black hole parameters due to quantum gravity effects. We also discuss the remnant and graphical analysis of the modified Hawking temperatures and heat capacities. |
2209.08056 | Torsten Asselmeyer-Maluga | Torsten Asselmeyer-Maluga, Jerzy Krol and Alissa Wilms | Big Bang and Topology | 20 pages, no figures | Symmetry 14(9):1887; September 2022 | 10.3390/sym14091887 | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | In this paper we discuss the initial state of the universe at the Big Bang.
By using ideas of Freedman in the proof of the disk embedding theorem for
4-manifolds, we describe the corresponding spacetime as gravitational
instanton. The spatial space is a fractal space (wild embedded 3-sphere). Then
we construct the quantum state from this fractal space. This quantum state is
part of the string algebra of Ocneanu. There is a link to the Jones polynomial
and to Witten's topological field theory. Using this link, we are able to
determine the physical theory (action) to be the Chern-Simons functional. The
gauge fixing of this action determines the foliation of the spacetime and as
well the smoothness properties. Finally, we determine the quantum symmetry of
the quantum state to be the enveloped Lie algebra $U_{q}(sl_{2}(\mathbb{C}))$
where $q$ is the 4th root of unity.
| [
{
"created": "Wed, 14 Sep 2022 18:19:05 GMT",
"version": "v1"
}
] | 2022-09-19 | [
[
"Asselmeyer-Maluga",
"Torsten",
""
],
[
"Krol",
"Jerzy",
""
],
[
"Wilms",
"Alissa",
""
]
] | In this paper we discuss the initial state of the universe at the Big Bang. By using ideas of Freedman in the proof of the disk embedding theorem for 4-manifolds, we describe the corresponding spacetime as gravitational instanton. The spatial space is a fractal space (wild embedded 3-sphere). Then we construct the quantum state from this fractal space. This quantum state is part of the string algebra of Ocneanu. There is a link to the Jones polynomial and to Witten's topological field theory. Using this link, we are able to determine the physical theory (action) to be the Chern-Simons functional. The gauge fixing of this action determines the foliation of the spacetime and as well the smoothness properties. Finally, we determine the quantum symmetry of the quantum state to be the enveloped Lie algebra $U_{q}(sl_{2}(\mathbb{C}))$ where $q$ is the 4th root of unity. |
gr-qc/0502048 | John W. Barrett | John W. Barrett | Feynman diagams coupled to three-dimensional quantum gravity | 7 pages. v2: minor corrections, added ref | Class.Quant.Grav. 23 (2006) 137-142 | 10.1088/0264-9381/23/1/008 | null | gr-qc hep-th | null | A framework for quantum field theory coupled to three-dimensional quantum
gravity is proposed. The coupling with quantum gravity regulates the Feynman
diagrams. One recovers the usual Feynman amplitudes in the limit as the
cosmological constant tends to zero.
| [
{
"created": "Thu, 10 Feb 2005 20:11:54 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Feb 2005 15:01:29 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Barrett",
"John W.",
""
]
] | A framework for quantum field theory coupled to three-dimensional quantum gravity is proposed. The coupling with quantum gravity regulates the Feynman diagrams. One recovers the usual Feynman amplitudes in the limit as the cosmological constant tends to zero. |
2407.18993 | Achintya Sajeendran | Achintya Sajeendran and Timothy C. Ralph | Controlled closed timelike geodesics in a rotating Alcubierre spacetime | 9 pages, 8 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present two modifications to the rotating Alcubierre metric [1], which was
shown to permit closed timelike curves (CTCs). We find that if the rotation
rate of the spacetime is made spatially dependent, in certain cases there exist
simple approximate timelike geodesics that are also CTCs, provided that the
velocity of the warp bubble varies slowly. The second modification is
essentially the original Alcubierre metric [ 2 ] with a periodic boundary,
resulting in a cylindrical spacetime which can also be related to the rotating
Alcubierre metric. Furthermore, this spacetime contains simple exact timelike
geodesics that are also CTCs. In both modifications, the CTC geodesics that we
have found allow for a simple model of a particle interacting with a CTC for a
finite proper time interval, entering and exiting in chronology-respecting
space. Given the simplicity of both of these exotic spacetimes, despite their
questionable physical realisability, we suggest that they may be useful in
studies of quantum fields near CTCs.
| [
{
"created": "Fri, 26 Jul 2024 02:53:13 GMT",
"version": "v1"
}
] | 2024-07-30 | [
[
"Sajeendran",
"Achintya",
""
],
[
"Ralph",
"Timothy C.",
""
]
] | We present two modifications to the rotating Alcubierre metric [1], which was shown to permit closed timelike curves (CTCs). We find that if the rotation rate of the spacetime is made spatially dependent, in certain cases there exist simple approximate timelike geodesics that are also CTCs, provided that the velocity of the warp bubble varies slowly. The second modification is essentially the original Alcubierre metric [ 2 ] with a periodic boundary, resulting in a cylindrical spacetime which can also be related to the rotating Alcubierre metric. Furthermore, this spacetime contains simple exact timelike geodesics that are also CTCs. In both modifications, the CTC geodesics that we have found allow for a simple model of a particle interacting with a CTC for a finite proper time interval, entering and exiting in chronology-respecting space. Given the simplicity of both of these exotic spacetimes, despite their questionable physical realisability, we suggest that they may be useful in studies of quantum fields near CTCs. |
1203.3652 | Charles Hellaby | Charles Hellaby | A New Type of Exact Arbitrarily Inhomogeneous Cosmology: Evolution of
Deceleration in the Flat Homogeneous-On-Average Case | JCAP Latex, 14pp, 2 figures(2nd with 5 plots), 4 tables | Journal of Cosmology and Astroparticle Physics, JCAP01(2012)043 | 10.1088/1475-7516/2012/01/043 | uct-cosmology-2012-03-16 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new method for constructing exact inhomogeneous universes is presented,
that allows variation in 3 dimensions. The resulting spacetime may be
statistically uniform on average, or have random, non-repeating variation. The
construction utilises the Darmois junction conditions to join many different
component spacetime regions. In the initial simple example given, the component
parts are spatially flat and uniform, but much more general combinations should
be possible. Further inhomogeneity may be added via swiss cheese vacuoles and
inhomogeneous metrics. This model is used to explore the proposal, that
observers are located in bound, non-expanding regions, while the universe is
actually in the process of becoming void dominated, and thus its average
expansion rate is increasing. The model confirms qualitatively that the faster
expanding components come to dominate the average, and that inhomogeneity
results in average parameters which evolve differently from those of any one
component, but more realistic modelling of the effect will need this
construction to be generalised.
| [
{
"created": "Fri, 16 Mar 2012 09:55:36 GMT",
"version": "v1"
}
] | 2012-03-19 | [
[
"Hellaby",
"Charles",
""
]
] | A new method for constructing exact inhomogeneous universes is presented, that allows variation in 3 dimensions. The resulting spacetime may be statistically uniform on average, or have random, non-repeating variation. The construction utilises the Darmois junction conditions to join many different component spacetime regions. In the initial simple example given, the component parts are spatially flat and uniform, but much more general combinations should be possible. Further inhomogeneity may be added via swiss cheese vacuoles and inhomogeneous metrics. This model is used to explore the proposal, that observers are located in bound, non-expanding regions, while the universe is actually in the process of becoming void dominated, and thus its average expansion rate is increasing. The model confirms qualitatively that the faster expanding components come to dominate the average, and that inhomogeneity results in average parameters which evolve differently from those of any one component, but more realistic modelling of the effect will need this construction to be generalised. |
0711.0042 | Alexandru Ionescu | Alexandru D. Ionescu and Sergiu Klainerman | Uniqueness results for ill posed characteristic problems in curved
space-times | Various corrections | Commun.Math.Phys.285:873-900,2009 | 10.1007/s00220-008-0650-y | null | gr-qc math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove two uniqueness theorems for solutions of linear and nonlinear wave
equations; the first theorem is in the Minkowski space while the second is in
the domain of outer communication of a Kerr black hole. Both theorems concern
ill posed Cauchy problems on smooth, bifurcate, characteristic hypersurfaces.
In the case of the Kerr space-time this hypersurface is the event horizon of
the black hole.
| [
{
"created": "Wed, 31 Oct 2007 23:57:48 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Jul 2008 21:24:11 GMT",
"version": "v2"
}
] | 2009-01-19 | [
[
"Ionescu",
"Alexandru D.",
""
],
[
"Klainerman",
"Sergiu",
""
]
] | We prove two uniqueness theorems for solutions of linear and nonlinear wave equations; the first theorem is in the Minkowski space while the second is in the domain of outer communication of a Kerr black hole. Both theorems concern ill posed Cauchy problems on smooth, bifurcate, characteristic hypersurfaces. In the case of the Kerr space-time this hypersurface is the event horizon of the black hole. |
2206.12731 | Valeri Frolov P | Valeri P. Frolov and Alex Koek | Gravitational lensing, memory and the Penrose limit | 14 pages, 5 figures. 2 new references are added | null | 10.1103/PhysRevD.106.064026 | Alberta Thy 4-22 | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper, we discuss the gravitational field of ultrarelativistic
extended spinning objects. For this purpose, we use a solution of the
linearized gravitational equations obtained in the frame where such an object
is translationally at rest, and boost this solution close to the speed of
light. In order to obtain a regular limiting metric for non-spinning matter, it
is sufficient to keep the energy of the boosted body fixed. This process is
known as the Penrose limit. We demonstrate that in the presence of rotation, an
additional rescaling is required for the angular momentum density components in
the directions orthogonal to the boost. As a result of the Lorentz contraction,
the thickness of the body in the direction of the boost shrinks. The body takes
the form of a pancake, and its gravitational field is localized in the null
plane. We discuss light and particle scattering in this gravitational field,
and calculate the scattering parameters associated with the gravitational
memory effect. We also show that by taking the inverse of the Penrose
transform, one can use the obtained scattering map to study the gravitational
lensing effect in the rest frame of a massive spinning object.
| [
{
"created": "Sat, 25 Jun 2022 21:03:58 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Aug 2022 18:37:21 GMT",
"version": "v2"
}
] | 2022-10-05 | [
[
"Frolov",
"Valeri P.",
""
],
[
"Koek",
"Alex",
""
]
] | In this paper, we discuss the gravitational field of ultrarelativistic extended spinning objects. For this purpose, we use a solution of the linearized gravitational equations obtained in the frame where such an object is translationally at rest, and boost this solution close to the speed of light. In order to obtain a regular limiting metric for non-spinning matter, it is sufficient to keep the energy of the boosted body fixed. This process is known as the Penrose limit. We demonstrate that in the presence of rotation, an additional rescaling is required for the angular momentum density components in the directions orthogonal to the boost. As a result of the Lorentz contraction, the thickness of the body in the direction of the boost shrinks. The body takes the form of a pancake, and its gravitational field is localized in the null plane. We discuss light and particle scattering in this gravitational field, and calculate the scattering parameters associated with the gravitational memory effect. We also show that by taking the inverse of the Penrose transform, one can use the obtained scattering map to study the gravitational lensing effect in the rest frame of a massive spinning object. |
2112.03019 | Slava G. Turyshev | Slava G. Turyshev, Viktor T. Toth | Navigating stellar wobbles for imaging with the solar gravitational lens | 28 pages, 16 figures | Phys. Rev. D 105, 044012 (2022) | 10.1103/PhysRevD.105.044012 | null | gr-qc astro-ph.EP astro-ph.GA astro-ph.IM astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The solar gravitational lens (SGL) offers unique capabilities for
high-resolution imaging of faint, distant objects, such as exoplanets. In the
near future, a spacecraft carrying a meter-class telescope with a solar
coronagraph would be placed in the focal region of the SGL. That region begins
at ~547 astronomical units from the Sun and occupies the vicinity of the
target-specific primary optical axis - the line that connects the center of the
target and that of the Sun. This axis undergoes complex motion as the exoplanet
orbits its host star, as that star moves with respect to the Sun, and even as
the Sun itself moves with respect to the solar system's barycenter due to the
gravitational pull of planets in our solar system. An image of an extended
object is projected by the SGL into an image plane and moves within that plane,
responding to the motion of the optical axis. To sample the image, a telescope
must follow the projection with precise knowledge of its own position with
respect to the image. We consider the dominant motions that determine the
position of the focal line as a function of time. We evaluate the needed
navigational capability for the telescope to conduct a multiyear exoplanet
imaging mission. We show that even in a rather conservative case, when an
Earth-like exoplanet is in our stellar neighborhood at $\sim10$ light years,
the motion of the image is characterized by a small total acceleration $\sim
6.1\,\mu {\rm m/s}^2$ that is driven primarily by the orbital motion of the
exoplanet and by the reflex motion of our Sun. We discuss how the amplified
light of the host star allows establishing a local reference frame thus
relaxing navigational requirements. We conclude that the required navigation in
the SGL's focal region, although complex, can be accurately modeled and a $\sim
10$-year imaging mission is achievable with the already available propulsion
technology.
| [
{
"created": "Mon, 6 Dec 2021 13:21:57 GMT",
"version": "v1"
}
] | 2022-02-09 | [
[
"Turyshev",
"Slava G.",
""
],
[
"Toth",
"Viktor T.",
""
]
] | The solar gravitational lens (SGL) offers unique capabilities for high-resolution imaging of faint, distant objects, such as exoplanets. In the near future, a spacecraft carrying a meter-class telescope with a solar coronagraph would be placed in the focal region of the SGL. That region begins at ~547 astronomical units from the Sun and occupies the vicinity of the target-specific primary optical axis - the line that connects the center of the target and that of the Sun. This axis undergoes complex motion as the exoplanet orbits its host star, as that star moves with respect to the Sun, and even as the Sun itself moves with respect to the solar system's barycenter due to the gravitational pull of planets in our solar system. An image of an extended object is projected by the SGL into an image plane and moves within that plane, responding to the motion of the optical axis. To sample the image, a telescope must follow the projection with precise knowledge of its own position with respect to the image. We consider the dominant motions that determine the position of the focal line as a function of time. We evaluate the needed navigational capability for the telescope to conduct a multiyear exoplanet imaging mission. We show that even in a rather conservative case, when an Earth-like exoplanet is in our stellar neighborhood at $\sim10$ light years, the motion of the image is characterized by a small total acceleration $\sim 6.1\,\mu {\rm m/s}^2$ that is driven primarily by the orbital motion of the exoplanet and by the reflex motion of our Sun. We discuss how the amplified light of the host star allows establishing a local reference frame thus relaxing navigational requirements. We conclude that the required navigation in the SGL's focal region, although complex, can be accurately modeled and a $\sim 10$-year imaging mission is achievable with the already available propulsion technology. |
2111.10077 | Omar Mustafa | Omar Mustafa | Confined Klein-Gordon oscillators in Minkowski spacetime and a
pseudo-Minkowski spacetime with a space-like dislocation: PDM KG-oscillators,
isospectrality and invariance | 17 pages, 3 Figures | Ann. Phys. 446 (2022) 169124 | 10.1016/j.aop.2022.169124 | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | We revisit the a confined (in a Cornell-type Lorentz scalar potential)
KG-oscillator in Minkowski spacetime with space-like dislocation background. We
show that the effect of space-like dislocation is to shift the energy levels
along the dislocation parameter axis, and consequently energy levels crossings
are unavoidable. We report some KG-particles in a pseudo-Minkowski spacetime
with space-like dislocation that admit isospectrality and invariance with the
confined KG-oscillator in Minkowski spacetime with space-like dislocation. An
alternative PDM setting for the KG-particles (relativistic particles in
general) is introduced. We discuss the effects of space-like dislocation and
PDM settings on the confined KG-oscillators in Minkowski spacetime with
space-like dislocation. Three confined PDM KG-oscillators are discussed as
illustrative examples, (i) a PDM KG-oscillator from a dimensionless scalar
multiplier $g\left( r\right) =\, exp(2\alpha r^2)\geq0,\, \alpha\,\geq 0$, (ii)
a PDM KG-oscillator from a power law type dimensionless scalar multiplier
$g\left( r\right) =Ar^{\sigma }\geq0$, and (iii) a PDM KG-oscillator in a
Cornnell-type confinement with a dimensionless scalar multiplier $g\left(
r\right) =\exp \left( \xi r\right)\geq0$
| [
{
"created": "Fri, 19 Nov 2021 07:40:32 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Jan 2022 09:39:25 GMT",
"version": "v2"
},
{
"created": "Thu, 31 Mar 2022 07:54:06 GMT",
"version": "v3"
},
{
"created": "Fri, 5 Aug 2022 11:48:58 GMT",
"version": "v4"
},
{
"created": "Thu, 15 Sep 2022 10:01:35 GMT",
"version": "v5"
}
] | 2023-04-17 | [
[
"Mustafa",
"Omar",
""
]
] | We revisit the a confined (in a Cornell-type Lorentz scalar potential) KG-oscillator in Minkowski spacetime with space-like dislocation background. We show that the effect of space-like dislocation is to shift the energy levels along the dislocation parameter axis, and consequently energy levels crossings are unavoidable. We report some KG-particles in a pseudo-Minkowski spacetime with space-like dislocation that admit isospectrality and invariance with the confined KG-oscillator in Minkowski spacetime with space-like dislocation. An alternative PDM setting for the KG-particles (relativistic particles in general) is introduced. We discuss the effects of space-like dislocation and PDM settings on the confined KG-oscillators in Minkowski spacetime with space-like dislocation. Three confined PDM KG-oscillators are discussed as illustrative examples, (i) a PDM KG-oscillator from a dimensionless scalar multiplier $g\left( r\right) =\, exp(2\alpha r^2)\geq0,\, \alpha\,\geq 0$, (ii) a PDM KG-oscillator from a power law type dimensionless scalar multiplier $g\left( r\right) =Ar^{\sigma }\geq0$, and (iii) a PDM KG-oscillator in a Cornnell-type confinement with a dimensionless scalar multiplier $g\left( r\right) =\exp \left( \xi r\right)\geq0$ |
2204.09006 | Hemwati Nandan | Shobhit Giri, Hemwati Nandan, Lokesh Kumar Joshi, Sunil D. Maharaj | Geodesic stability and quasinormal modes of non-commutative
Schwarzschild black hole employing Lyapunov exponent | null | Eur. Phys. J. Plus 137:181 (2022) | 10.1140/epjp/s13360-022-02403-5 | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We study the dynamics of test particle and stability of circular geodesics in
the gravitational field of a non-commutative geometry inspired Schwarzschild
black hole spacetime (NCSBH). The coordinate time Lyapunov exponent
($\lambda_{c}$) is crucial to investigate the stability of equatorial circular
geodesics of massive and massless test particles. The stability or instability
of circular orbits are discussed by analysing the variation of Lyapunov
exponent with radius of these orbits for different values of non-commutative
parameter ($\alpha$). In the case of null circular orbits, the instability
exponent is calculated and presented to discuss the instability of null
circular orbits. Further, by relating parameters corresponding to null circular
geodesics (i.e. angular frequency and Lyapunov exponent), the quasinormal modes
(QNMs) for a massless scalar field perturbation in the eikonal approximation
are evaluated, and also visualised by relating the real and imaginary parts.
The nature of scalar field potential, by varying the non-commutative parameter
($\alpha$) and angular momentum of perturbation ($l$), are also observed and
discussed.
| [
{
"created": "Tue, 19 Apr 2022 17:03:50 GMT",
"version": "v1"
}
] | 2022-04-20 | [
[
"Giri",
"Shobhit",
""
],
[
"Nandan",
"Hemwati",
""
],
[
"Joshi",
"Lokesh Kumar",
""
],
[
"Maharaj",
"Sunil D.",
""
]
] | We study the dynamics of test particle and stability of circular geodesics in the gravitational field of a non-commutative geometry inspired Schwarzschild black hole spacetime (NCSBH). The coordinate time Lyapunov exponent ($\lambda_{c}$) is crucial to investigate the stability of equatorial circular geodesics of massive and massless test particles. The stability or instability of circular orbits are discussed by analysing the variation of Lyapunov exponent with radius of these orbits for different values of non-commutative parameter ($\alpha$). In the case of null circular orbits, the instability exponent is calculated and presented to discuss the instability of null circular orbits. Further, by relating parameters corresponding to null circular geodesics (i.e. angular frequency and Lyapunov exponent), the quasinormal modes (QNMs) for a massless scalar field perturbation in the eikonal approximation are evaluated, and also visualised by relating the real and imaginary parts. The nature of scalar field potential, by varying the non-commutative parameter ($\alpha$) and angular momentum of perturbation ($l$), are also observed and discussed. |
gr-qc/9210019 | Wai Suen | Ian H. Redmount and Wai-Mo Suen | Path integration in relativistic quantum mechanics | 14 pages | Int. J. Mod. Phys. A8 (1993) 1629-1636 | 10.1142/S0217751X93000667 | null | gr-qc | null | The simple physics of a free particle reveals important features of the
path-integral formulation of relativistic quantum theories. The exact
quantum-mechanical propagator is calculated here for a particle described by
the simple relativistic action proportional to its proper time. This propagator
is nonvanishing outside the light cone, implying that spacelike trajectories
must be included in the path integral. The propagator matches the WKB
approximation to the corresponding configuration-space path integral far from
the light cone; outside the light cone that approximation consists of the
contribution from a single spacelike geodesic. This propagator also has the
unusual property that its short-time limit does not coincide with the WKB
approximation, making the construction of a concrete skeletonized version of
the path integral more complicated than in nonrelativistic theory.
| [
{
"created": "Wed, 28 Oct 1992 23:15:19 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Redmount",
"Ian H.",
""
],
[
"Suen",
"Wai-Mo",
""
]
] | The simple physics of a free particle reveals important features of the path-integral formulation of relativistic quantum theories. The exact quantum-mechanical propagator is calculated here for a particle described by the simple relativistic action proportional to its proper time. This propagator is nonvanishing outside the light cone, implying that spacelike trajectories must be included in the path integral. The propagator matches the WKB approximation to the corresponding configuration-space path integral far from the light cone; outside the light cone that approximation consists of the contribution from a single spacelike geodesic. This propagator also has the unusual property that its short-time limit does not coincide with the WKB approximation, making the construction of a concrete skeletonized version of the path integral more complicated than in nonrelativistic theory. |
1510.00790 | Ali Tofighi | A. Tofighi, M. Moazzen, and A. Farokhtabar | Vacuum Expectation Value Profiles of the Bulk Scalar Field in the
Generalized Randall-Sundrum Model | arXiv admin note: text overlap with arXiv:0809.4102, arXiv:1102.1970
by other authors | Adv. High. Ener. Phys. Vol 2015, 590980 (2015) | null | null | gr-qc hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | In the generalized Randall-Sundrum warped brane-world model the cosmological
constant induced on the visible brane can be positive or negative. In this
paper we investigate profiles of vacuum expectation value of the bulk scalar
field under general Dirichlet andNeumann boundary conditions in the generalized
warped brane-worldmodel.We showthat the VEVprofiles generally depend on the
value of the brane cosmological constant. We find that the VEV profiles of the
bulk scalar field for a visible brane with negative cosmological constant and
positive tension are quite distinct fromthose of Randall-Sundrum model. In
addition we show that the VEV profiles for a visible brane with large positive
cosmological constant are also different from those of the Randall- Sundrum
model.We also verify that Goldberger andWise mechanism can work under nonzero
Dirichlet boundary conditions in the generalized Randall-Sundrum model.
| [
{
"created": "Sat, 3 Oct 2015 07:52:56 GMT",
"version": "v1"
}
] | 2015-10-06 | [
[
"Tofighi",
"A.",
""
],
[
"Moazzen",
"M.",
""
],
[
"Farokhtabar",
"A.",
""
]
] | In the generalized Randall-Sundrum warped brane-world model the cosmological constant induced on the visible brane can be positive or negative. In this paper we investigate profiles of vacuum expectation value of the bulk scalar field under general Dirichlet andNeumann boundary conditions in the generalized warped brane-worldmodel.We showthat the VEVprofiles generally depend on the value of the brane cosmological constant. We find that the VEV profiles of the bulk scalar field for a visible brane with negative cosmological constant and positive tension are quite distinct fromthose of Randall-Sundrum model. In addition we show that the VEV profiles for a visible brane with large positive cosmological constant are also different from those of the Randall- Sundrum model.We also verify that Goldberger andWise mechanism can work under nonzero Dirichlet boundary conditions in the generalized Randall-Sundrum model. |
gr-qc/0001045 | Young-Jai Park | Yong-Wan Kim, Young-Jai Park, and Kwang-Sup Soh | Reissner-Nordstr\"om-AdS black hole in the GEMS approach | 15 pages, 1 figure, latex, to appear in Phys. Rev. D | Phys.Rev.D62:104020,2000 | 10.1103/PhysRevD.62.104020 | SOGANG-HEP 264/99, SNUTP 99-057 | gr-qc | null | We obtain a (5+2)-dimensional global flat embedding of the (3+1)-dimensional
curved RN-AdS space. Our results include the various limiting cases of global
embedding Minkowski space (GEMS) geometries of the RN, Schwarzschild-AdS in
(5+2)-dimensions, Schwarzschild in (5+1)-dimensions, purely charged space, and
universal covering space of AdS in (4+1)-dimensions, through the successive
truncation procedure of parameters in the original curved space.
| [
{
"created": "Sun, 16 Jan 2000 05:20:13 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Aug 2000 08:34:07 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Kim",
"Yong-Wan",
""
],
[
"Park",
"Young-Jai",
""
],
[
"Soh",
"Kwang-Sup",
""
]
] | We obtain a (5+2)-dimensional global flat embedding of the (3+1)-dimensional curved RN-AdS space. Our results include the various limiting cases of global embedding Minkowski space (GEMS) geometries of the RN, Schwarzschild-AdS in (5+2)-dimensions, Schwarzschild in (5+1)-dimensions, purely charged space, and universal covering space of AdS in (4+1)-dimensions, through the successive truncation procedure of parameters in the original curved space. |
1412.3858 | Davide Batic | D. Batic, S. Nelson, M. Nowakowski | Light on curved backgrounds | 34 pages, 10 figures | null | 10.1103/PhysRevD.91.104015 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the motion of light on different spacetime manifolds by
calculating the deflection angle, lensing properties and by probing into the
possibility of bound states. The metrics in which we examine the light motion
include, among other, a general relativistic Dark Matter metric, a dirty Black
Hole and a Worm Hole metric, the last two inspired by non-commutative geometry.
The lensing in a Holographic Screen metric is discussed in detail. We study
also the bending of light around naked singularities like, e.g., the
Janis-Newman-Winicour metric and include other cases. A generic property of
light behaviour in these exotic metrics is pointed out. For the standard metric
like the Schwarzschild and Schwarzschild-de Sitter cases we improve the
accuracy of the lensing results for the weak and strong regime.
| [
{
"created": "Thu, 11 Dec 2014 23:06:14 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Batic",
"D.",
""
],
[
"Nelson",
"S.",
""
],
[
"Nowakowski",
"M.",
""
]
] | We consider the motion of light on different spacetime manifolds by calculating the deflection angle, lensing properties and by probing into the possibility of bound states. The metrics in which we examine the light motion include, among other, a general relativistic Dark Matter metric, a dirty Black Hole and a Worm Hole metric, the last two inspired by non-commutative geometry. The lensing in a Holographic Screen metric is discussed in detail. We study also the bending of light around naked singularities like, e.g., the Janis-Newman-Winicour metric and include other cases. A generic property of light behaviour in these exotic metrics is pointed out. For the standard metric like the Schwarzschild and Schwarzschild-de Sitter cases we improve the accuracy of the lensing results for the weak and strong regime. |
gr-qc/0001076 | Boris Grobov | A.K.Guts, A.A.Zvyagintsev | Interpretation of intuitionistic solution of the vacuum Einstein
equations in smooth topos | 9 pages, LaTeX2e | null | null | null | gr-qc | null | The topos theory is a theory which is used for deciding a number of problems
of theory of relativity, gravitation and quantum physics. In the article
spherically symmetric solution of the vacuum Einstein equations in the
Intuitionistic theory of Gravitation at different stages of smooth topos ${\bf
Set}^{\bf L_{op}}$ is considered. Infinitesimal "weak" gravitational field can
be strong at some stagies, for which we have the additional dimensions. For
example, the cosmological constant is not constant with respect to additional
dimensions. Signature of space-time metric can depend of density of vacuum and
cosmological constant.
| [
{
"created": "Mon, 24 Jan 2000 18:16:31 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Guts",
"A. K.",
""
],
[
"Zvyagintsev",
"A. A.",
""
]
] | The topos theory is a theory which is used for deciding a number of problems of theory of relativity, gravitation and quantum physics. In the article spherically symmetric solution of the vacuum Einstein equations in the Intuitionistic theory of Gravitation at different stages of smooth topos ${\bf Set}^{\bf L_{op}}$ is considered. Infinitesimal "weak" gravitational field can be strong at some stagies, for which we have the additional dimensions. For example, the cosmological constant is not constant with respect to additional dimensions. Signature of space-time metric can depend of density of vacuum and cosmological constant. |
gr-qc/9912120 | Carey Carpenter Briggs | C. C. Briggs | A Possible Theoretical Basis for Propulsive Force Generation by Both
Conventional and Unconventional Means | 10 pages | null | null | null | gr-qc | null | A possible theoretical basis is given for propulsive force generation by both
conventional and unconventional means.
| [
{
"created": "Fri, 31 Dec 1999 21:52:48 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Apr 2000 02:13:44 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Briggs",
"C. C.",
""
]
] | A possible theoretical basis is given for propulsive force generation by both conventional and unconventional means. |
2208.14117 | Avneet Singh | Avneet Singh and Maria Alessandra Papa | Opportunistic search for continuous gravitational waves from compact
objects in long-period binaries | 4 pages, 4 figures, v1: initial submit, v2: correction in figure 4,
v3: submitted to ApJ, v4: final accepted version, v5: published version (ApJ) | The Astrophysical Journal (ApJ), Volume 943, Number 2, 2023 | 10.3847/1538-4357/acaf80 | null | gr-qc astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Most all-sky searches for continuous gravitational waves assume the source to
be isolated. In this paper, we allow for an unknown companion object in a
long-period orbit and opportunistically use previous results from an all-sky
search for isolated sources to constrain the continuous gravitational wave
amplitude over a large and unexplored range of binary orbital parameters
without explicitly performing a dedicated search for binary systems. The
resulting limits are significantly more constraining than any existing upper
limit for unknown binary systems, albeit the latter apply to different orbital
parameter ranges that are computationally much costlier to explore.
| [
{
"created": "Tue, 30 Aug 2022 10:05:14 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Sep 2022 07:00:13 GMT",
"version": "v2"
},
{
"created": "Tue, 1 Nov 2022 09:20:44 GMT",
"version": "v3"
},
{
"created": "Fri, 6 Jan 2023 22:18:55 GMT",
"version": "v4"
},
{
"created": "Thu, 23 Mar 2023 09:05:14 GMT",
"version": "v5"
}
] | 2023-03-24 | [
[
"Singh",
"Avneet",
""
],
[
"Papa",
"Maria Alessandra",
""
]
] | Most all-sky searches for continuous gravitational waves assume the source to be isolated. In this paper, we allow for an unknown companion object in a long-period orbit and opportunistically use previous results from an all-sky search for isolated sources to constrain the continuous gravitational wave amplitude over a large and unexplored range of binary orbital parameters without explicitly performing a dedicated search for binary systems. The resulting limits are significantly more constraining than any existing upper limit for unknown binary systems, albeit the latter apply to different orbital parameter ranges that are computationally much costlier to explore. |
gr-qc/0212053 | Kenneth Nordtvedt | Kenneth Nordtvedt (Northwest Analysis) | The special relativistic equivalence principle: gravity theory's
foundation | 22 pages, 5 figures, PCTex32 v3.4 | null | null | null | gr-qc | null | On incorporating special relativity theory into an extended equivalence
principle, post-Newtonian gravitational phenomena beyond that originally
predicted by Einstein are predicted (required), such as geodetic and
gravitomagnetic precessions of local inertial frames, and precession of
Mercury's orbital perihelion. Why were not these phenomena predicted in the
years 1907-1911? The unique 1/c^2 order dynamical equations for clock rates and
motion of both bodies and light in local gravity are derived which guarantee
fulfillment of the special relativistic equivalence principle.
| [
{
"created": "Wed, 11 Dec 2002 22:18:33 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Nordtvedt",
"Kenneth",
"",
"Northwest Analysis"
]
] | On incorporating special relativity theory into an extended equivalence principle, post-Newtonian gravitational phenomena beyond that originally predicted by Einstein are predicted (required), such as geodetic and gravitomagnetic precessions of local inertial frames, and precession of Mercury's orbital perihelion. Why were not these phenomena predicted in the years 1907-1911? The unique 1/c^2 order dynamical equations for clock rates and motion of both bodies and light in local gravity are derived which guarantee fulfillment of the special relativistic equivalence principle. |
gr-qc/0105063 | Samir Mathur | Sumit R. Das and Samir D. Mathur | The Quantum Physics of Black Holes: Results from String Theory | 49 pages, Latex, 4 figures, (Review article) | Ann.Rev.Nucl.Part.Sci. 50 (2000) 153-206 | 10.1146/annurev.nucl.50.1.153 | OHSTPY-HEP-T-01-015 | gr-qc hep-th | null | We review recent progress in our understanding of the physics of black holes.
In particular, we discuss the ideas from string theory that explain the entropy
of black holes from a counting of microstates of the hole, and the related
derivation of unitary Hawking radiation from such holes.
| [
{
"created": "Thu, 17 May 2001 22:07:47 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Das",
"Sumit R.",
""
],
[
"Mathur",
"Samir D.",
""
]
] | We review recent progress in our understanding of the physics of black holes. In particular, we discuss the ideas from string theory that explain the entropy of black holes from a counting of microstates of the hole, and the related derivation of unitary Hawking radiation from such holes. |
gr-qc/9609059 | Karen Camarda | P. Anninos, K. Camarda, J. Libson, J. Mass\'o, E. Seidel, W.-M. Suen | Finding Apparent Horizons in Dynamic 3D Numerical Spacetimes | 19 pages, 13 figures, LaTex, to appear in Phys. Rev. D. Minor changes
made | Phys.Rev. D58 (1998) 024003 | 10.1103/PhysRevD.58.024003 | AEI-018 | gr-qc | null | We have developed a general method for finding apparent horizons in 3D
numerical relativity. Instead of solving for the partial differential equation
describing the location of the apparent horizons, we expand the closed 2D
surfaces in terms of symmetric trace--free tensors and solve for the expansion
coefficients using a minimization procedure. Our method is applied to a number
of different spacetimes, including numerically constructed spacetimes
containing highly distorted axisymmetric black holes in spherical coordinates,
and 3D rotating, and colliding black holes in Cartesian coordinates.
| [
{
"created": "Wed, 25 Sep 1996 13:16:14 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Apr 1997 19:19:15 GMT",
"version": "v2"
},
{
"created": "Wed, 20 May 1998 14:53:29 GMT",
"version": "v3"
}
] | 2016-08-15 | [
[
"Anninos",
"P.",
""
],
[
"Camarda",
"K.",
""
],
[
"Libson",
"J.",
""
],
[
"Massó",
"J.",
""
],
[
"Seidel",
"E.",
""
],
[
"Suen",
"W. -M.",
""
]
] | We have developed a general method for finding apparent horizons in 3D numerical relativity. Instead of solving for the partial differential equation describing the location of the apparent horizons, we expand the closed 2D surfaces in terms of symmetric trace--free tensors and solve for the expansion coefficients using a minimization procedure. Our method is applied to a number of different spacetimes, including numerically constructed spacetimes containing highly distorted axisymmetric black holes in spherical coordinates, and 3D rotating, and colliding black holes in Cartesian coordinates. |
gr-qc/0206008 | Badri Krishnan | Olaf Dreyer, Badri Krishnan, Eric Schnetter, Deirdre Shoemaker | Introduction to Isolated Horizons in Numerical Relativity | 14 pages, revtex4, 7 figures. Final PRD version | Phys.Rev.D67:024018,2003 | 10.1103/PhysRevD.67.024018 | null | gr-qc | null | We present a coordinate-independent method for extracting mass (M) and
angular momentum (J) of a black hole in numerical simulations. This method,
based on the isolated horizon framework, is applicable both at late times when
the black hole has reached equilibrium, and at early times when the black holes
are widely separated. We show how J and M can be determined in numerical
simulations in terms of only those quantities which are intrinsic to the
apparent horizon. We also present a numerical method for finding the rotational
symmetry vector field (required to calculate J) on the horizon.
| [
{
"created": "Mon, 3 Jun 2002 16:57:37 GMT",
"version": "v1"
},
{
"created": "Sun, 11 Jan 2004 16:51:37 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Dreyer",
"Olaf",
""
],
[
"Krishnan",
"Badri",
""
],
[
"Schnetter",
"Eric",
""
],
[
"Shoemaker",
"Deirdre",
""
]
] | We present a coordinate-independent method for extracting mass (M) and angular momentum (J) of a black hole in numerical simulations. This method, based on the isolated horizon framework, is applicable both at late times when the black hole has reached equilibrium, and at early times when the black holes are widely separated. We show how J and M can be determined in numerical simulations in terms of only those quantities which are intrinsic to the apparent horizon. We also present a numerical method for finding the rotational symmetry vector field (required to calculate J) on the horizon. |
1608.06246 | Saeed Rastgoo | Alejandro Corichi, Javier Olmedo, Saeed Rastgoo | Callan-Giddings-Harvey-Strominger vacuum in loop quantum gravity and
singularity resolution | 24 pages, 1 figure; v2: matches the PRD published version, titled
modified according to the published version, a few typos corrected and a
short comment regarding refined algebraic quantization added | Phys. Rev. D 94, 084050 (2016) | 10.1103/PhysRevD.94.084050 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study here a complete quantization of a Callan-Giddings-Harvey-Strominger
(CGHS) vacuum model following loop quantum gravity techniques. Concretely, we
adopt a formulation of the model in terms of a set of new variables that
resemble the ones commonly employed in spherically symmetric loop quantum
gravity. The classical theory consists of two pairs of canonical variables plus
a scalar and diffeomorphism (first class) constraints. We consider a suitable
redefinition of the Hamiltonian constraint such that the new constraint algebra
(with structure constants) is well adapted to the Dirac quantization approach.
For it, we adopt a polymeric representation for both the geometry and the
dilaton field. On the one hand, we find a suitable invariant domain of the
scalar constraint operator, and we construct explicitly its solution space.
There, the eigenvalues of the dilaton and the metric operators cannot vanish
locally, allowing us to conclude that singular geometries are ruled out in the
quantum theory. On the other hand, the physical Hilbert space is constructed
out of them, after group averaging the previous states with the diffeomorphism
constraint. In turn, we identify the standard observable corresponding to the
mass of the black hole at the boundary, in agreement with the classical theory.
We also construct an additional observable on the bulk associated with the
square of the dilaton field, with no direct classical analog.
| [
{
"created": "Mon, 22 Aug 2016 18:07:06 GMT",
"version": "v1"
},
{
"created": "Sat, 29 Oct 2016 00:04:14 GMT",
"version": "v2"
}
] | 2016-11-02 | [
[
"Corichi",
"Alejandro",
""
],
[
"Olmedo",
"Javier",
""
],
[
"Rastgoo",
"Saeed",
""
]
] | We study here a complete quantization of a Callan-Giddings-Harvey-Strominger (CGHS) vacuum model following loop quantum gravity techniques. Concretely, we adopt a formulation of the model in terms of a set of new variables that resemble the ones commonly employed in spherically symmetric loop quantum gravity. The classical theory consists of two pairs of canonical variables plus a scalar and diffeomorphism (first class) constraints. We consider a suitable redefinition of the Hamiltonian constraint such that the new constraint algebra (with structure constants) is well adapted to the Dirac quantization approach. For it, we adopt a polymeric representation for both the geometry and the dilaton field. On the one hand, we find a suitable invariant domain of the scalar constraint operator, and we construct explicitly its solution space. There, the eigenvalues of the dilaton and the metric operators cannot vanish locally, allowing us to conclude that singular geometries are ruled out in the quantum theory. On the other hand, the physical Hilbert space is constructed out of them, after group averaging the previous states with the diffeomorphism constraint. In turn, we identify the standard observable corresponding to the mass of the black hole at the boundary, in agreement with the classical theory. We also construct an additional observable on the bulk associated with the square of the dilaton field, with no direct classical analog. |
1111.0026 | Reinoud Slagter | Reinoud Jan Slagter, Derk Masselink | Warped Angle-deficit of a 5 Dimensional Cosmic String | 6 pages, 6 figures; plus-minus sign added in solution Eq.40;
correction of numbering of equations | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/3.0/ | We present a cosmic string on a warped five dimensional space time in
Einstein-Yang-Mills theory. Four-dimensional cosmic strings show some serious
problems concerning the mechanism of string smoothing related to the string
mass per unit length, $G\mu \approx 10^{-6}$. A warped cosmic string could
overcome this problem and also the superstring requirement that $G\mu$ must be
of order 1, which is far above observational bounds. Also the absence of
observational evidence of axially symmetric lensing effect caused by cosmic
strings could be explained by the warped cosmic string model we present: the
angle deficit of the string is warped down to unobservable value in the brane,
compared to its value in the bulk. It turns out that only for negative
cosmological constant, a consistent numerical solution of the model is
possible.
| [
{
"created": "Mon, 31 Oct 2011 20:44:00 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Nov 2011 22:40:24 GMT",
"version": "v2"
},
{
"created": "Fri, 11 Nov 2011 16:50:14 GMT",
"version": "v3"
}
] | 2011-11-14 | [
[
"Slagter",
"Reinoud Jan",
""
],
[
"Masselink",
"Derk",
""
]
] | We present a cosmic string on a warped five dimensional space time in Einstein-Yang-Mills theory. Four-dimensional cosmic strings show some serious problems concerning the mechanism of string smoothing related to the string mass per unit length, $G\mu \approx 10^{-6}$. A warped cosmic string could overcome this problem and also the superstring requirement that $G\mu$ must be of order 1, which is far above observational bounds. Also the absence of observational evidence of axially symmetric lensing effect caused by cosmic strings could be explained by the warped cosmic string model we present: the angle deficit of the string is warped down to unobservable value in the brane, compared to its value in the bulk. It turns out that only for negative cosmological constant, a consistent numerical solution of the model is possible. |
2302.07799 | Jose Socorro Garcia | J. Socorro and J. Juan Rosales | Quantum fractionary cosmology: K-essence theory | 26 pages, 21 figures, We have add references and substantial changes,
version published in Universe Journal | Universe 2023, 9, 185 | 10.3390/universe9040185 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | Using a particular form of the quantum K-essence scalar field, we show that
in the quantum formalism, a fractional differential equation in the scalar
field variable, for some epochs in the Friedmann-Lema\^itre-Robertson-Walker
(FLRW) model (radiation and inflation-like epochs, for example), appears
naturally. In the classical analysis, the kinetic energy of scalar fields can
falsify the standard matter in the sense that we obtain the time behavior for
the scale factor in all scenarios of our Universe by using the Hamiltonian
formalism, where the results are analogous to those obtained by an algebraic
procedure in the Einstein field equations with standard matter. In the case of
the quantum Wheeler-DeWitt (WDW) equation for the scalar field $\phi$, a
fractional differential equation of order $\beta=\frac{2\alpha}{2\alpha-1}$ is
obtained. This fractional equation belongs to different intervals, depending on
the value of the barotropic parameter; that is to say, when $ \omega_X \in
[0,1]$, the order belongs to the interval $1\leq \beta \leq 2$, and when $
\omega_X \in [-1,0)$, the order belongs to the interval $0< \beta \leq 1$. The
corresponding quantum solutions are also given.
| [
{
"created": "Wed, 15 Feb 2023 17:32:46 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Apr 2023 14:33:03 GMT",
"version": "v2"
}
] | 2023-04-14 | [
[
"Socorro",
"J.",
""
],
[
"Rosales",
"J. Juan",
""
]
] | Using a particular form of the quantum K-essence scalar field, we show that in the quantum formalism, a fractional differential equation in the scalar field variable, for some epochs in the Friedmann-Lema\^itre-Robertson-Walker (FLRW) model (radiation and inflation-like epochs, for example), appears naturally. In the classical analysis, the kinetic energy of scalar fields can falsify the standard matter in the sense that we obtain the time behavior for the scale factor in all scenarios of our Universe by using the Hamiltonian formalism, where the results are analogous to those obtained by an algebraic procedure in the Einstein field equations with standard matter. In the case of the quantum Wheeler-DeWitt (WDW) equation for the scalar field $\phi$, a fractional differential equation of order $\beta=\frac{2\alpha}{2\alpha-1}$ is obtained. This fractional equation belongs to different intervals, depending on the value of the barotropic parameter; that is to say, when $ \omega_X \in [0,1]$, the order belongs to the interval $1\leq \beta \leq 2$, and when $ \omega_X \in [-1,0)$, the order belongs to the interval $0< \beta \leq 1$. The corresponding quantum solutions are also given. |
2311.15944 | Antonio Tedesco | Antonio Tedesco, Antonio Capolupo, Gaetano Lambiase | Relativistic periastron advance beyond Einstein theory: analytical
solution with applications | 22 pages, 10 figures, 5 tables | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find a new solution to calculate the orbital periastron advance of a test
body subject to a central gravitational force field, for relativistic theories
and models beyond Einstein. This analitycal formula has general validity that
includes all the post-Newtonian (PN) contributions to the dynamics and is
useful for high-precision gravitational tests. The solution is directly
applicable to corrective potentials of various forms, without the need for
numerical integration. Later, we apply it to the Scalar Tensor Fourth Order
Gravity (STFOG) and NonCommutative Geometry, providing corrections to the
Newtonian potential of Yukawa-like form $V(r)=\alpha \frac{e^{-\beta r}}{r}$,
and we conduct the first analysis involving all the PN terms for these
theories. The same work is performed with a Schwarzschild geometry perturbed by
a Quintessence Field, leading to a power-law potential $V(r)=\alpha_q {r}^q$.
Finally, by using astrometric data of the Solar System planetary precessions
and those of S2 star around Sgr A*, we infer new theoretical constraints and
improvements in the bounds for $\beta$. The resulting simulated orbits turn out
to be compatible with General Relativity.
| [
{
"created": "Mon, 27 Nov 2023 15:51:03 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Dec 2023 13:47:39 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Mar 2024 22:08:55 GMT",
"version": "v3"
},
{
"created": "Sat, 15 Jun 2024 11:41:41 GMT",
"version": "v4"
}
] | 2024-06-18 | [
[
"Tedesco",
"Antonio",
""
],
[
"Capolupo",
"Antonio",
""
],
[
"Lambiase",
"Gaetano",
""
]
] | We find a new solution to calculate the orbital periastron advance of a test body subject to a central gravitational force field, for relativistic theories and models beyond Einstein. This analitycal formula has general validity that includes all the post-Newtonian (PN) contributions to the dynamics and is useful for high-precision gravitational tests. The solution is directly applicable to corrective potentials of various forms, without the need for numerical integration. Later, we apply it to the Scalar Tensor Fourth Order Gravity (STFOG) and NonCommutative Geometry, providing corrections to the Newtonian potential of Yukawa-like form $V(r)=\alpha \frac{e^{-\beta r}}{r}$, and we conduct the first analysis involving all the PN terms for these theories. The same work is performed with a Schwarzschild geometry perturbed by a Quintessence Field, leading to a power-law potential $V(r)=\alpha_q {r}^q$. Finally, by using astrometric data of the Solar System planetary precessions and those of S2 star around Sgr A*, we infer new theoretical constraints and improvements in the bounds for $\beta$. The resulting simulated orbits turn out to be compatible with General Relativity. |
2112.05608 | Maciej Kolanowski | Abhay Ashtekar, Neev Khera, Maciej Kolanowski and Jerzy Lewandowski | Charges and Fluxes on (Perturbed) Non-expanding Horizons | 36 pages, 1 figure. Two clarifications and a reference added. Version
to appear in JHEP | null | 10.1007/JHEP02(2022)066 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a companion paper we showed that the symmetry group $\mathfrak{G}$ of
non-expanding horizons (NEHs) is a 1-dimensional extension of the
Bondi-Metzner-Sachs group $\mathfrak{G}$ at $\mathcal{I}^{+}$. For each
infinitesimal generator of $\mathfrak{G}$, we now define a charge and a flux on
NEHs as well as perturbed NEHs. The procedure uses the covariant phase space
framework in presence of internal null boundaries $\mathcal{N}$. However,
$\mathcal{N}$ is required to be an NEH or a perturbed NEH. Consequently,
charges and fluxes associated with generators of $\mathfrak{G}$ are free of
physically unsatisfactory features that can arise if $\mathcal{N}$ is allowed
to be a general null boundary. In particular, all fluxes vanish if
$\mathcal{N}$ is an NEH, just as one would hope; and fluxes associated with
symmetries representing `time-translations' are positive definite on perturbed
NEHs. These results hold for zero as well as non-zero cosmological constant. In
the asymptotically flat case, as noted in \cite{akkl1}, $\mathcal{I}^\pm$ are
NEHs in the conformally completed space-time but with an extra structure that
reduces $\mathfrak{G}$ to $\mathfrak{B}$. The flux expressions at $\mathcal{N}$
reflect this synergy between NEHs and $\mathcal{I}^{+}$. In a forthcoming
paper, this close relation between NEHs and $\mathcal{I}^{+}$ will be used to
develop gravitational wave tomography, enabling one to deduce horizon dynamics
directly from the waveforms at $\mathcal{I}^{+}$.
| [
{
"created": "Fri, 10 Dec 2021 15:40:51 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Jan 2022 23:08:53 GMT",
"version": "v2"
}
] | 2022-03-02 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Khera",
"Neev",
""
],
[
"Kolanowski",
"Maciej",
""
],
[
"Lewandowski",
"Jerzy",
""
]
] | In a companion paper we showed that the symmetry group $\mathfrak{G}$ of non-expanding horizons (NEHs) is a 1-dimensional extension of the Bondi-Metzner-Sachs group $\mathfrak{G}$ at $\mathcal{I}^{+}$. For each infinitesimal generator of $\mathfrak{G}$, we now define a charge and a flux on NEHs as well as perturbed NEHs. The procedure uses the covariant phase space framework in presence of internal null boundaries $\mathcal{N}$. However, $\mathcal{N}$ is required to be an NEH or a perturbed NEH. Consequently, charges and fluxes associated with generators of $\mathfrak{G}$ are free of physically unsatisfactory features that can arise if $\mathcal{N}$ is allowed to be a general null boundary. In particular, all fluxes vanish if $\mathcal{N}$ is an NEH, just as one would hope; and fluxes associated with symmetries representing `time-translations' are positive definite on perturbed NEHs. These results hold for zero as well as non-zero cosmological constant. In the asymptotically flat case, as noted in \cite{akkl1}, $\mathcal{I}^\pm$ are NEHs in the conformally completed space-time but with an extra structure that reduces $\mathfrak{G}$ to $\mathfrak{B}$. The flux expressions at $\mathcal{N}$ reflect this synergy between NEHs and $\mathcal{I}^{+}$. In a forthcoming paper, this close relation between NEHs and $\mathcal{I}^{+}$ will be used to develop gravitational wave tomography, enabling one to deduce horizon dynamics directly from the waveforms at $\mathcal{I}^{+}$. |
gr-qc/0209017 | Jorge Pullin | Gioel Calabrese, Jorge Pullin, Oscar Reula, Olivier Sarbach, Manuel
Tiglio | Well posed constraint-preserving boundary conditions for the linearized
Einstein equations | 15 pages, RevTeX, no figures | Commun.Math.Phys.240:377-395,2003 | 10.1007/s00220-003-0889-2 | LSU-REL-090502 | gr-qc | null | In the Cauchy problem of general relativity one considers initial data that
satisfies certain constraints. The evolution equations guarantee that the
evolved variables will satisfy the constraints at later instants of time. This
is only true within the domain of dependence of the initial data. If one wishes
to consider situations where the evolutions are studied for longer intervals
than the size of the domain of dependence, as is usually the case in three
dimensional numerical relativity, one needs to give boundary data. The boundary
data should be specified in such a way that the constraints are satisfied
everywhere, at all times. In this paper we address this problem for the case of
general relativity linearized around Minkowski space using the generalized
Einstein-Christoffel symmetric hyperbolic system of evolution equations. We
study the evolution equations for the constraints, specify boundary conditions
for them that make them well posed and further choose these boundary conditions
in such a way that the evolution equations for the metric variables are also
well posed. We also consider the case of a manifold with a non-smooth boundary,
as is the usual case of the cubic boxes commonly used in numerical relativity.
The techniques discussed should be applicable to more general cases, as
linearizations around more complicated backgrounds, and may be used to
establish well posedness in the full non-linear case.
| [
{
"created": "Thu, 5 Sep 2002 20:55:39 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Calabrese",
"Gioel",
""
],
[
"Pullin",
"Jorge",
""
],
[
"Reula",
"Oscar",
""
],
[
"Sarbach",
"Olivier",
""
],
[
"Tiglio",
"Manuel",
""
]
] | In the Cauchy problem of general relativity one considers initial data that satisfies certain constraints. The evolution equations guarantee that the evolved variables will satisfy the constraints at later instants of time. This is only true within the domain of dependence of the initial data. If one wishes to consider situations where the evolutions are studied for longer intervals than the size of the domain of dependence, as is usually the case in three dimensional numerical relativity, one needs to give boundary data. The boundary data should be specified in such a way that the constraints are satisfied everywhere, at all times. In this paper we address this problem for the case of general relativity linearized around Minkowski space using the generalized Einstein-Christoffel symmetric hyperbolic system of evolution equations. We study the evolution equations for the constraints, specify boundary conditions for them that make them well posed and further choose these boundary conditions in such a way that the evolution equations for the metric variables are also well posed. We also consider the case of a manifold with a non-smooth boundary, as is the usual case of the cubic boxes commonly used in numerical relativity. The techniques discussed should be applicable to more general cases, as linearizations around more complicated backgrounds, and may be used to establish well posedness in the full non-linear case. |
gr-qc/0506013 | Marc Mars | Lars Andersson, Marc Mars, Walter Simon | Local existence of dynamical and trapping horizons | 4 pages, 1 figure, minor changes | Phys.Rev.Lett. 95 (2005) 111102 | 10.1103/PhysRevLett.95.111102 | null | gr-qc | null | Given a spacelike foliation of a spacetime and a marginally outer trapped
surface S on some initial leaf, we prove that under a suitable stability
condition S is contained in a ``horizon'', i.e. a smooth 3-surface foliated by
marginally outer trapped slices which lie in the leaves of the given foliation.
We also show that under rather weak energy conditions this horizon must be
either achronal or spacelike everywhere. Furthermore, we discuss the relation
between ``bounding'' and ``stability'' properties of marginally outer trapped
surfaces.
| [
{
"created": "Thu, 2 Jun 2005 15:07:54 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Jun 2005 16:57:19 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Andersson",
"Lars",
""
],
[
"Mars",
"Marc",
""
],
[
"Simon",
"Walter",
""
]
] | Given a spacelike foliation of a spacetime and a marginally outer trapped surface S on some initial leaf, we prove that under a suitable stability condition S is contained in a ``horizon'', i.e. a smooth 3-surface foliated by marginally outer trapped slices which lie in the leaves of the given foliation. We also show that under rather weak energy conditions this horizon must be either achronal or spacelike everywhere. Furthermore, we discuss the relation between ``bounding'' and ``stability'' properties of marginally outer trapped surfaces. |
1803.11422 | Rajibul Shaikh | Rajibul Shaikh (TIFR Mumbai, India) | Shadows of rotating wormholes | 22 pages, 6 figures, revised version, published in Phys. Rev. D | Phys. Rev. D 98, 024044 (2018) | 10.1103/PhysRevD.98.024044 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study shadows cast by a certain class of rotating wormholes and point out
the crucial role of a rotating wormhole throat in the formation of a shadow.
Overlooking this crucial role of a wormhole throat has resulted incomplete
results in the previous studies on shadows of the same class of rotating
wormholes. We explore the dependence of the shadows on the spin of the
wormholes. We compare our results with that of the Kerr black hole. With
increasing values of the spin, the shapes of the wormhole shadows start
deviating considerably from that of the black hole. Such considerable
deviation, if detected in future observations, may possibly indicate the
presence of a wormhole. In other words, the results obtained here indicate
that, through the observations of their shadows, the wormholes which are
considered in this work and have reasonable spin, can be distinguished from a
black hole.
| [
{
"created": "Fri, 30 Mar 2018 11:33:01 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Jul 2018 15:31:25 GMT",
"version": "v2"
}
] | 2018-07-31 | [
[
"Shaikh",
"Rajibul",
"",
"TIFR Mumbai, India"
]
] | We study shadows cast by a certain class of rotating wormholes and point out the crucial role of a rotating wormhole throat in the formation of a shadow. Overlooking this crucial role of a wormhole throat has resulted incomplete results in the previous studies on shadows of the same class of rotating wormholes. We explore the dependence of the shadows on the spin of the wormholes. We compare our results with that of the Kerr black hole. With increasing values of the spin, the shapes of the wormhole shadows start deviating considerably from that of the black hole. Such considerable deviation, if detected in future observations, may possibly indicate the presence of a wormhole. In other words, the results obtained here indicate that, through the observations of their shadows, the wormholes which are considered in this work and have reasonable spin, can be distinguished from a black hole. |
2010.02102 | Ujjal Debnath | Ujjal Debnath | Thermodynamics of FRW Universe: Heat Engine | 6 pages, no figures | Published in Physics Letters B 810, 135807 (2020) | 10.1016/j.physletb.2020.135807 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We assume the non-flat Friedmann-Robertson-Walker (FRW) Universe as a
thermodynamical system. We assume the cosmological horizon as a inner trapping
horizon which is treated as dynamical apparent horizon of FRW Universe. We
write the dynamical apparent horizon radius and temperature on the apparent
horizon. We assume that the fluid pressure as thermodynamical pressure of the
system. Using Hayward's unified first law, Clausius relation and Friedmann
equations with cosmological constant, we obtain the entropy on the apparent
horizon. We assume that the cosmological constant provides the thermodynamic
pressure of the system. We obtain the entropy, surface area, volume,
temperature, Gibb's Helmholtz's free energies, specific heat capacity of the
FRW Universe due to the thermodynamic system. We study the Joule-Thomson
expansion of the FRW Universe and by evaluating the positive sign of
Joule-Thomson coefficient, we determine that the FRW Universe obeys the cooling
nature. We also find the inversion temperature and inversion pressure. Next we
demonstrate the thermodynamical FRW Universe as heat engine. For Carnot cycle,
we obtain the work done and the maximum efficiency. Also for new engine, we
study the work done and its efficiency.
| [
{
"created": "Fri, 2 Oct 2020 17:08:12 GMT",
"version": "v1"
}
] | 2020-10-06 | [
[
"Debnath",
"Ujjal",
""
]
] | We assume the non-flat Friedmann-Robertson-Walker (FRW) Universe as a thermodynamical system. We assume the cosmological horizon as a inner trapping horizon which is treated as dynamical apparent horizon of FRW Universe. We write the dynamical apparent horizon radius and temperature on the apparent horizon. We assume that the fluid pressure as thermodynamical pressure of the system. Using Hayward's unified first law, Clausius relation and Friedmann equations with cosmological constant, we obtain the entropy on the apparent horizon. We assume that the cosmological constant provides the thermodynamic pressure of the system. We obtain the entropy, surface area, volume, temperature, Gibb's Helmholtz's free energies, specific heat capacity of the FRW Universe due to the thermodynamic system. We study the Joule-Thomson expansion of the FRW Universe and by evaluating the positive sign of Joule-Thomson coefficient, we determine that the FRW Universe obeys the cooling nature. We also find the inversion temperature and inversion pressure. Next we demonstrate the thermodynamical FRW Universe as heat engine. For Carnot cycle, we obtain the work done and the maximum efficiency. Also for new engine, we study the work done and its efficiency. |
1609.00879 | Abhishek Majhi | Abhishek Majhi | Conformal blocks on a 2-sphere with indistinguishable punctures and
implications on black hole entropy | 5 pages, published version | Physics Letters B 762 (2016) 243-246 | 10.1016/j.physletb.2016.09.037 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dimensionality of the Hilbert space of a Chern-Simons theory on a 3-fold,
in the presence of Wilson lines carrying spin representations, had been counted
by using its link with the Wess-Zumino theory, with level $k$, on the 2-sphere
with points (to be called punctures) marked by the piercing of the
corresponding Wilson lines and carrying the respective spin representations. It
is shown, in the weak coupling (large $k$) limit, the formula decouples into
two characteristically distinct parts; one mimics the dimensionality of the
Hilbert space of a collection of non-interacting spin systems and the other is
an effective overall correction contributed by all the punctures. The exact
formula yield from this counting has been shown earlier to have resulted from
the consideration of the punctures to be distinguishable. We investigate the
same counting problem by considering the punctures to be indistinguishable.
Although the full formula remains undiscovered, nonetheless, we are able to
impose the relevant statistics for indistinguishable punctures in the
approximate formula resulting from the weak coupling limit. As an implication
of this counting, in the context of its relation to that of black hole entropy
calculation in quantum geometric approach, we are able to show that the
logarithmic area correction, with a coefficient of $-3/2$, that results in this
method of entropy calculation, in independent of whether the punctures are
distinguishable or not.
| [
{
"created": "Sun, 4 Sep 2016 00:18:39 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Oct 2016 02:01:11 GMT",
"version": "v2"
}
] | 2016-10-07 | [
[
"Majhi",
"Abhishek",
""
]
] | The dimensionality of the Hilbert space of a Chern-Simons theory on a 3-fold, in the presence of Wilson lines carrying spin representations, had been counted by using its link with the Wess-Zumino theory, with level $k$, on the 2-sphere with points (to be called punctures) marked by the piercing of the corresponding Wilson lines and carrying the respective spin representations. It is shown, in the weak coupling (large $k$) limit, the formula decouples into two characteristically distinct parts; one mimics the dimensionality of the Hilbert space of a collection of non-interacting spin systems and the other is an effective overall correction contributed by all the punctures. The exact formula yield from this counting has been shown earlier to have resulted from the consideration of the punctures to be distinguishable. We investigate the same counting problem by considering the punctures to be indistinguishable. Although the full formula remains undiscovered, nonetheless, we are able to impose the relevant statistics for indistinguishable punctures in the approximate formula resulting from the weak coupling limit. As an implication of this counting, in the context of its relation to that of black hole entropy calculation in quantum geometric approach, we are able to show that the logarithmic area correction, with a coefficient of $-3/2$, that results in this method of entropy calculation, in independent of whether the punctures are distinguishable or not. |
1407.1457 | M. B. Paranjape | Saoussen Mbarek, M. B. Paranjape | Negative mass bubbles in de Sitter space-time | 4 pages, 5 figures | Phys. Rev. D 90, 101502(R), 2014 | 10.1103/PhysRevD.90.101502 | UdeM-GPP-TH-14-235 | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the possibility of the existence of negative mass bubbles within a
de Sitter space-time background with matter content corresponding to a perfect
fluid. It is shown that there exist configurations of the perfect fluid, that
everywhere satisfy the dominant energy condition, the Einstein equations and
the equations of hydrostatic equilibrium, however asymptotically approach the
exact solution of Schwarzschid-de Sitter space-time with a negative mass.
| [
{
"created": "Sun, 6 Jul 2014 05:17:15 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Nov 2014 03:17:15 GMT",
"version": "v2"
}
] | 2014-11-21 | [
[
"Mbarek",
"Saoussen",
""
],
[
"Paranjape",
"M. B.",
""
]
] | We study the possibility of the existence of negative mass bubbles within a de Sitter space-time background with matter content corresponding to a perfect fluid. It is shown that there exist configurations of the perfect fluid, that everywhere satisfy the dominant energy condition, the Einstein equations and the equations of hydrostatic equilibrium, however asymptotically approach the exact solution of Schwarzschid-de Sitter space-time with a negative mass. |
gr-qc/0703111 | Ying Shao | Ying Shao, Yuanxing Gui | Statefinder Parameters for Tachyon Dark Energy Model | 5 pages, 5 figures, accepted by MPLA | Mod.Phys.Lett.A23:65-71,2008 | 10.1142/S0217732308023499 | null | gr-qc | null | In this paper we study the statefinder parameters for the tachyon dark energy
model. There are two kinds of stable attractor solutions in this model. The
statefinder diagrams characterize the properties of the tachyon dark energy
model. Our results show that the evolving trajectories of the attractor
solutions lie in the total region and pass through the LCDM fixed point, which
is different from other dark energy model.
| [
{
"created": "Thu, 22 Mar 2007 05:07:12 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Shao",
"Ying",
""
],
[
"Gui",
"Yuanxing",
""
]
] | In this paper we study the statefinder parameters for the tachyon dark energy model. There are two kinds of stable attractor solutions in this model. The statefinder diagrams characterize the properties of the tachyon dark energy model. Our results show that the evolving trajectories of the attractor solutions lie in the total region and pass through the LCDM fixed point, which is different from other dark energy model. |
gr-qc/9706025 | Patricio Anibal Letelier | P.S. Letelier and W. M. Vieira | Chaos in black holes surrounded by gravitational waves | 15 pages, LaTex. | Class.Quant.Grav. 14 (1997) 1249-1257 | 10.1088/0264-9381/14/5/026 | null | gr-qc chao-dyn nlin.CD | null | The occurrence of chaos for test particles moving around Schwarzschild black
holes perturbed by a special class of gravitational waves is studied in the
context of the Melnikov method. The explicit integration of the equations of
motion for the homoclinic orbit is used to reduce the application of this
method to the study of simple graphics.
| [
{
"created": "Tue, 10 Jun 1997 14:22:18 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Letelier",
"P. S.",
""
],
[
"Vieira",
"W. M.",
""
]
] | The occurrence of chaos for test particles moving around Schwarzschild black holes perturbed by a special class of gravitational waves is studied in the context of the Melnikov method. The explicit integration of the equations of motion for the homoclinic orbit is used to reduce the application of this method to the study of simple graphics. |
1004.3661 | Patrik Sandin | Sigbjorn Hervik, Woei Chet Lim, Patrik Sandin, Claes Uggla | Future asymptotics of tilted Bianchi type II cosmologies | 15 pages | Class. Quantum Grav. 27 185006 (2010) | 10.1088/0264-9381/27/18/185006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the future asymptotics of spatially homogeneous
Bianchi type II cosmologies with a tilted perfect fluid with a linear equation
of state. By means of Hamiltonian methods we first find a monotone function for
a special tilted case, which subsequently allows us to construct a new set of
monotone functions for the general tilted type II cosmologies. In the context
of a new partially gauge invariant dynamical system, this then leads to a proof
for a theorem that for the first time gives a complete description of the
future asymptotic states of the general tilted Bianchi type II models. The
generality of our arguments suggests how one can produce monotone functions
that are useful for determining the asymptotics of other tilted perfect fluid
cosmologies, as well as for other sources.
| [
{
"created": "Wed, 21 Apr 2010 09:29:40 GMT",
"version": "v1"
}
] | 2011-12-08 | [
[
"Hervik",
"Sigbjorn",
""
],
[
"Lim",
"Woei Chet",
""
],
[
"Sandin",
"Patrik",
""
],
[
"Uggla",
"Claes",
""
]
] | In this paper we study the future asymptotics of spatially homogeneous Bianchi type II cosmologies with a tilted perfect fluid with a linear equation of state. By means of Hamiltonian methods we first find a monotone function for a special tilted case, which subsequently allows us to construct a new set of monotone functions for the general tilted type II cosmologies. In the context of a new partially gauge invariant dynamical system, this then leads to a proof for a theorem that for the first time gives a complete description of the future asymptotic states of the general tilted Bianchi type II models. The generality of our arguments suggests how one can produce monotone functions that are useful for determining the asymptotics of other tilted perfect fluid cosmologies, as well as for other sources. |
gr-qc/0103003 | A. Miyazaki | A. Miyazaki | Varying Cosmological Constant and the Machian Solution in the
Generalized Scalar-Tensor Theory | 10 pages, LaTeX2e | null | null | null | gr-qc | null | The cosmological constant $(1/2)\lambda_{1}\phi_{, \mu}\phi ^{, \mu}/\phi
^{2}$ is introduced to the generalized scalar-tensor theory of gravitation with
the coupling function $\omega (\phi)=\eta /(\xi -2)$ and the Machian
cosmological solution satisfying $\phi =O(\rho /\omega)$ is discussed for the
homogeneous and isotropic universe with a perfect fluid (with negative
pressure). We require the closed model and the negative coupling function for
the attractive gravitational force. The constraint $% \omega (\phi)<-3/2$ for
$0\leqq \xi <2$ leads to $\eta >3$. If $\lambda_{1}<0$ and $0\leqq -\eta
/\lambda_{1}<2$, the universe shows the slowly accelerating expansion. The
coupling function diverges to $-\infty $ and the scalar field $\phi $ converges
to $G_{\infty}^{-1}$ when $\xi \to 2$ ($t\to +\infty $). The cosmological
constant decays in proportion to $t^{-2}$. Thus the Machian cosmological model
approaches to the Friedmann universe in general relativity with $\ddot{a}=0$,
$\lambda =0$, and $p=-\rho /3$ as $t\to +\infty $. General relativity is
locally valid enough at present.
| [
{
"created": "Thu, 1 Mar 2001 15:08:11 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Miyazaki",
"A.",
""
]
] | The cosmological constant $(1/2)\lambda_{1}\phi_{, \mu}\phi ^{, \mu}/\phi ^{2}$ is introduced to the generalized scalar-tensor theory of gravitation with the coupling function $\omega (\phi)=\eta /(\xi -2)$ and the Machian cosmological solution satisfying $\phi =O(\rho /\omega)$ is discussed for the homogeneous and isotropic universe with a perfect fluid (with negative pressure). We require the closed model and the negative coupling function for the attractive gravitational force. The constraint $% \omega (\phi)<-3/2$ for $0\leqq \xi <2$ leads to $\eta >3$. If $\lambda_{1}<0$ and $0\leqq -\eta /\lambda_{1}<2$, the universe shows the slowly accelerating expansion. The coupling function diverges to $-\infty $ and the scalar field $\phi $ converges to $G_{\infty}^{-1}$ when $\xi \to 2$ ($t\to +\infty $). The cosmological constant decays in proportion to $t^{-2}$. Thus the Machian cosmological model approaches to the Friedmann universe in general relativity with $\ddot{a}=0$, $\lambda =0$, and $p=-\rho /3$ as $t\to +\infty $. General relativity is locally valid enough at present. |
2009.00160 | Kiyoshi Shiraishi | Nahomi Kan and Kiyoshi Shiraishi | Calculations in induced gravity from higher-derivative field theories | 19 pages, no figure | Int. J. Mod. Phys. A37 (2022) 06, 2250028 | 10.1142/S0217751X22500282 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we investigate Einstein's gravity induced from
higher-derivative scalar field theories. We develop an approach utilizing an
effective theory of multiple fields for the higher-derivative theory. The
expressions for induced cosmological constant and the induced gravitational
constant are obtained in the present scenario of induced gravity in D
dimensions. We also show that finite values for the induced constants can be
extracted in certain infinite-derivative theories.
| [
{
"created": "Tue, 1 Sep 2020 00:57:10 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Oct 2020 08:37:52 GMT",
"version": "v2"
},
{
"created": "Sat, 5 Dec 2020 05:48:01 GMT",
"version": "v3"
},
{
"created": "Tue, 23 Feb 2021 07:47:04 GMT",
"version": "v4"
},
{
"created": "Thu, 8 Apr 2021 04:00:06 GMT",
"version": "v5"
},
{
"created": "Mon, 13 Dec 2021 00:42:00 GMT",
"version": "v6"
},
{
"created": "Thu, 20 Jan 2022 01:42:12 GMT",
"version": "v7"
},
{
"created": "Sat, 26 Mar 2022 04:46:58 GMT",
"version": "v8"
}
] | 2022-03-29 | [
[
"Kan",
"Nahomi",
""
],
[
"Shiraishi",
"Kiyoshi",
""
]
] | In this paper, we investigate Einstein's gravity induced from higher-derivative scalar field theories. We develop an approach utilizing an effective theory of multiple fields for the higher-derivative theory. The expressions for induced cosmological constant and the induced gravitational constant are obtained in the present scenario of induced gravity in D dimensions. We also show that finite values for the induced constants can be extracted in certain infinite-derivative theories. |
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