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1905.13542 | Dimitris Moustos | Benito A. Ju\'arez-Aubry, Dimitris Moustos | Asymptotic states for stationary Unruh-DeWitt detectors | 19 pages, 2 figures, Updated to match the published version | Phys. Rev. D 100, 025018 (2019) | 10.1103/PhysRevD.100.025018 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the late-time asymptotic state of a stationary Unruh-DeWitt detector
interacting with a field in a thermal state. We work in an open system
framework, where the field plays the role of an environment for the detector.
The long-time interaction between the detector and the field is modelled with
the aid of a one-parameter family of switching functions that turn on and off
the interaction Hamiltonian between the two subsystems, such that the long-time
interaction limit is reached as the family parameter goes to infinity. In such
limit, we show that if the field is in a Kubo-Martin-Schwinger (KMS) state and
the detector is stationary with respect to the notion of positive frequency of
the field, in the Born-Markov approximation, the asymptotic state of the
detector is a Gibbs state at the KMS temperature. We then relax the KMS
condition for the field state, and require only that a frequency-dependent
version of the detailed balance condition for the Wightman function pulled back
to the detector worldline hold, in the sense that the inverse temperature
appearing in the detailed balance relation need not be constant. In this
setting, we show that the late-time asymptotic state of the detector has the
form of a thermal density matrix, but with a frequency-dependent temperature.
We present examples of these results, which include the classical Unruh effect
and idealised Hawking radiation (for fields in the HHI state), and also the
study of the late-time behaviour of detectors following stationary "cusped" and
circular motions in Minkowski space interacting with a massless Klein-Gordon
field in the Minkowski vacuum. In the cusped motion case, a
frequency-dependent, effective temperature for the asymptotic late-time
detector state is obtained analytically. In the circular motion case, such
effective temperature is obtained numerically.
| [
{
"created": "Fri, 31 May 2019 12:13:09 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Aug 2019 13:54:38 GMT",
"version": "v2"
}
] | 2019-08-07 | [
[
"Juárez-Aubry",
"Benito A.",
""
],
[
"Moustos",
"Dimitris",
""
]
] | We study the late-time asymptotic state of a stationary Unruh-DeWitt detector interacting with a field in a thermal state. We work in an open system framework, where the field plays the role of an environment for the detector. The long-time interaction between the detector and the field is modelled with the aid of a one-parameter family of switching functions that turn on and off the interaction Hamiltonian between the two subsystems, such that the long-time interaction limit is reached as the family parameter goes to infinity. In such limit, we show that if the field is in a Kubo-Martin-Schwinger (KMS) state and the detector is stationary with respect to the notion of positive frequency of the field, in the Born-Markov approximation, the asymptotic state of the detector is a Gibbs state at the KMS temperature. We then relax the KMS condition for the field state, and require only that a frequency-dependent version of the detailed balance condition for the Wightman function pulled back to the detector worldline hold, in the sense that the inverse temperature appearing in the detailed balance relation need not be constant. In this setting, we show that the late-time asymptotic state of the detector has the form of a thermal density matrix, but with a frequency-dependent temperature. We present examples of these results, which include the classical Unruh effect and idealised Hawking radiation (for fields in the HHI state), and also the study of the late-time behaviour of detectors following stationary "cusped" and circular motions in Minkowski space interacting with a massless Klein-Gordon field in the Minkowski vacuum. In the cusped motion case, a frequency-dependent, effective temperature for the asymptotic late-time detector state is obtained analytically. In the circular motion case, such effective temperature is obtained numerically. |
2108.09567 | Marc Rodoreda | Dom\`enec Espriu and Marc Rodoreda | Effect of the cosmological parameters on gravitational waves: general
analysis | null | null | 10.1088/1361-6382/ac33bc | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Some time ago it was pointed out that the presence of cosmological components
could affect the propagation of gravitational waves (GW) beyond the usual
cosmological redshift and that such effects might be observable in pulsar
timing arrays. These analyses were done at leading order in the Hubble constant
$H_0$, which is proportional to $\Lambda^{1/2}$ and $\rho_i^{1/2}$ ($\rho_i$
being the various cosmological fluid densities). In this work, we study in
detail the propagation of metric perturbations on a Schwarzschild-de Sitter
(SdS) background, close to the place where GW are produced, and obtain
solutions that incorporate corrections linear in $\rho_i$ and $\Lambda$. At the
next-to-leading order the corrections do not appear in the form of $H_0$ thus
lifting the degeneracy among the various cosmological components. We also
determine the leading corrections proportional to the mass of the final object;
they are very small for the distances considered in pulsar timing arrays but
may be of relevance in other cases. When transformed into comoving coordinates,
the ones used in cosmological measurements, this SdS solution does satisfy the
perturbation equations in a Friedmann-Lema\^itre-Robertson-Walker metric up to
and including $\Lambda^{3/2}$ terms. This analysis is then extended to the
other cosmological fluids, allowing us to consider GW sources in the Gpc range.
Finally, we investigate the influence of these corrections in pulsar timing
arrays observations.
| [
{
"created": "Sat, 21 Aug 2021 19:30:37 GMT",
"version": "v1"
}
] | 2021-12-22 | [
[
"Espriu",
"Domènec",
""
],
[
"Rodoreda",
"Marc",
""
]
] | Some time ago it was pointed out that the presence of cosmological components could affect the propagation of gravitational waves (GW) beyond the usual cosmological redshift and that such effects might be observable in pulsar timing arrays. These analyses were done at leading order in the Hubble constant $H_0$, which is proportional to $\Lambda^{1/2}$ and $\rho_i^{1/2}$ ($\rho_i$ being the various cosmological fluid densities). In this work, we study in detail the propagation of metric perturbations on a Schwarzschild-de Sitter (SdS) background, close to the place where GW are produced, and obtain solutions that incorporate corrections linear in $\rho_i$ and $\Lambda$. At the next-to-leading order the corrections do not appear in the form of $H_0$ thus lifting the degeneracy among the various cosmological components. We also determine the leading corrections proportional to the mass of the final object; they are very small for the distances considered in pulsar timing arrays but may be of relevance in other cases. When transformed into comoving coordinates, the ones used in cosmological measurements, this SdS solution does satisfy the perturbation equations in a Friedmann-Lema\^itre-Robertson-Walker metric up to and including $\Lambda^{3/2}$ terms. This analysis is then extended to the other cosmological fluids, allowing us to consider GW sources in the Gpc range. Finally, we investigate the influence of these corrections in pulsar timing arrays observations. |
2207.11454 | Ashutosh Singh Dr | Ashutosh Singh and Anirudh Pradhan | Cosmic acceleration and ekpyrotic bounce with Chameleon field | 11 Pages | Int. J. Geom. Method Mod. Phys. 19 2250216 (2022) | 10.1142/S0219887822502164 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, we explore the homogeneous and isotropic flat
Friedmann-Robertson-Walker (FRW) model in Chameleon cosmology. By considering a
non-minimal coupling between the scalar field and matter, we present a
non-singular bouncing cosmological scenario of the universe. The universe
initially exhibits the ekpyrotic phase during the contracting era, undergoes a
non-singular bounce, and then in expanding era, it smoothly transits to the
decelerating era having matter and radiation dominated phases. Further, this
decelerating era is smoothly connected to the late-time dark energy-dominated
era of the present epoch. We use numerical solution techniques to solve
non-minimally coupled gravity equations for understanding the evolution of
scalar field along with other quantities like effective potential in the model.
The model thus unifies an ekpyrotic, non-singular, asymmetric bounce with the
dark energy era of the present epoch. We study the evolution of bouncing model
and confront the model with observational results on the equation of state
parameter by constraining the model parameters.
| [
{
"created": "Sat, 23 Jul 2022 08:06:45 GMT",
"version": "v1"
}
] | 2022-12-06 | [
[
"Singh",
"Ashutosh",
""
],
[
"Pradhan",
"Anirudh",
""
]
] | In this article, we explore the homogeneous and isotropic flat Friedmann-Robertson-Walker (FRW) model in Chameleon cosmology. By considering a non-minimal coupling between the scalar field and matter, we present a non-singular bouncing cosmological scenario of the universe. The universe initially exhibits the ekpyrotic phase during the contracting era, undergoes a non-singular bounce, and then in expanding era, it smoothly transits to the decelerating era having matter and radiation dominated phases. Further, this decelerating era is smoothly connected to the late-time dark energy-dominated era of the present epoch. We use numerical solution techniques to solve non-minimally coupled gravity equations for understanding the evolution of scalar field along with other quantities like effective potential in the model. The model thus unifies an ekpyrotic, non-singular, asymmetric bounce with the dark energy era of the present epoch. We study the evolution of bouncing model and confront the model with observational results on the equation of state parameter by constraining the model parameters. |
1510.05400 | Antonio C. Guti\'errez-Pi\~neres | Antonio C. Guti\'errez-Pi\~neres and Abra\~ao J. S. Capistrano | Motion of test particles in a magnetized conformastatic background | Submitted to the proceeding of MG14 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A class of exact conformastatic solutions of the Einstein-Maxwell field
equations is presented in which the gravitational and electromagnetic
potentials are completely determined by a harmonic function only. The motion of
test particles is investigated in the background of a space-time characterized
by this class of solutions. We focus on the study of circular stable and
unstable orbits obtained by taking account particular harmonic functions
defining the gravitational potential. We show that is possible to have
repulsive force generated by the charge distribution of the source. As the
space-time here considered is singularity free we conclude that this phenomena
is not exclusive to the case of naked singularities. Additionally, we obtain an
expression for the perihelion advance of the test particles in a general
magnetized conformastatic space-time.
| [
{
"created": "Mon, 19 Oct 2015 09:19:32 GMT",
"version": "v1"
}
] | 2015-10-20 | [
[
"Gutiérrez-Piñeres",
"Antonio C.",
""
],
[
"Capistrano",
"Abraão J. S.",
""
]
] | A class of exact conformastatic solutions of the Einstein-Maxwell field equations is presented in which the gravitational and electromagnetic potentials are completely determined by a harmonic function only. The motion of test particles is investigated in the background of a space-time characterized by this class of solutions. We focus on the study of circular stable and unstable orbits obtained by taking account particular harmonic functions defining the gravitational potential. We show that is possible to have repulsive force generated by the charge distribution of the source. As the space-time here considered is singularity free we conclude that this phenomena is not exclusive to the case of naked singularities. Additionally, we obtain an expression for the perihelion advance of the test particles in a general magnetized conformastatic space-time. |
1902.07917 | Daniela Pugliese Dr | D. Pugliese and H. Quevedo | Disclosing connections between black holes and naked singularities:
Horizon remnants, Killing throats and bottlenecks | 33 pages, 32 multi-panels figures, 3 Tables | null | 10.1140/epjc/s10052-019-6725-4 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the properties of black holes and naked singularities by considering
stationary observers and light surfaces in Kerr spacetimes. We reconsider the
notion of Killing horizons from a special perspective by exploring the entire
family of Kerr metrics. To this end, we introduce the concepts of extended
plane, Killing throats and bottlenecks for weak (slowly spinning) naked
singularities. Killing bottlenecks (or horizon remnants in analogy with the
corresponding definition of throats in black holes) are restrictions of the
Killing throats appearing in special classes of slowly spinning naked
singularities. Killing bottlenecks appear in association with the concept of
pre-horizon regime introduced in [1, 2]. In the extended plane of the Kerr
spacetime, we introduce particular sets, metric bundles, of metric tensors
which allow us to reinterpret the concept of horizon and to find connections
between black holes and naked singularities throughout the horizons. To
evaluate the effects of frame-dragging on the formation and structure of
Killing bottlenecks and horizons in the extended plane, we consider also the
Kerr-Newman and the Reissner-Norstrom spacetimes. We argue that these results
might be significant for the comprehension of processes that lead to the
formation and eventually destruction of Killing horizons.
| [
{
"created": "Thu, 21 Feb 2019 08:53:15 GMT",
"version": "v1"
}
] | 2019-03-27 | [
[
"Pugliese",
"D.",
""
],
[
"Quevedo",
"H.",
""
]
] | We study the properties of black holes and naked singularities by considering stationary observers and light surfaces in Kerr spacetimes. We reconsider the notion of Killing horizons from a special perspective by exploring the entire family of Kerr metrics. To this end, we introduce the concepts of extended plane, Killing throats and bottlenecks for weak (slowly spinning) naked singularities. Killing bottlenecks (or horizon remnants in analogy with the corresponding definition of throats in black holes) are restrictions of the Killing throats appearing in special classes of slowly spinning naked singularities. Killing bottlenecks appear in association with the concept of pre-horizon regime introduced in [1, 2]. In the extended plane of the Kerr spacetime, we introduce particular sets, metric bundles, of metric tensors which allow us to reinterpret the concept of horizon and to find connections between black holes and naked singularities throughout the horizons. To evaluate the effects of frame-dragging on the formation and structure of Killing bottlenecks and horizons in the extended plane, we consider also the Kerr-Newman and the Reissner-Norstrom spacetimes. We argue that these results might be significant for the comprehension of processes that lead to the formation and eventually destruction of Killing horizons. |
1905.11525 | Salah Haggag | Salah Haggag, Samy A. Abdel-Hafeez, Moutaz Ramadan | A Closed Universe with Maximum Life-Time | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A closed universe with maximum life-time is constructed using optimal
control. Einstein's field equations are used with varying cosmological
"constant". The second time derivative of the Hubble parameter acts as the
control function in the optimal control model.
| [
{
"created": "Mon, 27 May 2019 21:55:36 GMT",
"version": "v1"
}
] | 2019-05-29 | [
[
"Haggag",
"Salah",
""
],
[
"Abdel-Hafeez",
"Samy A.",
""
],
[
"Ramadan",
"Moutaz",
""
]
] | A closed universe with maximum life-time is constructed using optimal control. Einstein's field equations are used with varying cosmological "constant". The second time derivative of the Hubble parameter acts as the control function in the optimal control model. |
1503.04113 | Diego Pavon | Rafael C. Nunes and Diego Pav\'on | Phantom behavior via cosmological creation of particles | 20 pages, 6 eps figures, to be published in the Physical Review D | null | 10.1103/PhysRevD.91.063526 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent determinations of the equation of state of dark energy hint that this
may well be of the phantom type, i.e., $w_{de} < -1$. If confirmed by future
experiments, this would strongly point to the existence of fields that violate
the dominant energy condition, which are known to present serious theoretical
difficulties. This paper presents an alternative to this possibility, namely,
that the measured equation of state, $w_{de}$, is in reality an effective one,
the equation of state of the quantum vacuum, $w_{\Lambda} = -1$, plus the
negative equation of state, $w_{c}$, associated to the production of particles
by the gravitational field acting on the vacuum. To illustrate this, three
phenomenological models are proposed and constrained with recent observational
data.
| [
{
"created": "Fri, 13 Mar 2015 15:41:46 GMT",
"version": "v1"
}
] | 2015-06-24 | [
[
"Nunes",
"Rafael C.",
""
],
[
"Pavón",
"Diego",
""
]
] | Recent determinations of the equation of state of dark energy hint that this may well be of the phantom type, i.e., $w_{de} < -1$. If confirmed by future experiments, this would strongly point to the existence of fields that violate the dominant energy condition, which are known to present serious theoretical difficulties. This paper presents an alternative to this possibility, namely, that the measured equation of state, $w_{de}$, is in reality an effective one, the equation of state of the quantum vacuum, $w_{\Lambda} = -1$, plus the negative equation of state, $w_{c}$, associated to the production of particles by the gravitational field acting on the vacuum. To illustrate this, three phenomenological models are proposed and constrained with recent observational data. |
2101.09697 | Arthur Suvorov Dr. | Arthur G. Suvorov and Sebastian H. V\"olkel | Exact theory for the Rezzolla-Zhidenko metric and self-consistent
calculation of quasinormal modes | 11 pages, 4 figures, 2 tables. Minor updates to match PRD version | null | 10.1103/PhysRevD.103.044027 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A covariant, scalar-tensor gravity is constructed such that the static,
spherically symmetric Rezzolla-Zhidenko metric is an exact solution to the
theory. The equations describing gravitational perturbations of this spacetime,
which represents a generic black hole possessing an arbitrary number of hairs,
can then be derived. This allows for a self-consistent study of the associated
quasinormal modes. It is shown that mode spectra are tied to not only the
non-Einstein parameters in the metric but also to those that appear at the
level of the action, and that different branches of the exact theory can, in
some cases, predict significantly different oscillation frequencies and damping
times. For choices which make the theory appear more like general relativity in
some precise sense, we find that a nontrivial Rezzolla-Zhidenko parameter space
is permissible under current constraints on fundamental ringdown modes observed
by Advanced LIGO.
| [
{
"created": "Sun, 24 Jan 2021 12:16:24 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Feb 2021 11:58:35 GMT",
"version": "v2"
}
] | 2021-02-24 | [
[
"Suvorov",
"Arthur G.",
""
],
[
"Völkel",
"Sebastian H.",
""
]
] | A covariant, scalar-tensor gravity is constructed such that the static, spherically symmetric Rezzolla-Zhidenko metric is an exact solution to the theory. The equations describing gravitational perturbations of this spacetime, which represents a generic black hole possessing an arbitrary number of hairs, can then be derived. This allows for a self-consistent study of the associated quasinormal modes. It is shown that mode spectra are tied to not only the non-Einstein parameters in the metric but also to those that appear at the level of the action, and that different branches of the exact theory can, in some cases, predict significantly different oscillation frequencies and damping times. For choices which make the theory appear more like general relativity in some precise sense, we find that a nontrivial Rezzolla-Zhidenko parameter space is permissible under current constraints on fundamental ringdown modes observed by Advanced LIGO. |
2312.01980 | Clemens S\"amann | Clemens S\"amann, Benedict Schinnerl, Roland Steinbauer, Robert
\v{S}varc | Cut-and-paste for impulsive gravitational waves with $\Lambda$: The
mathematical analysis | 26 pages | Lett. Math. Phys. Volume 114, article number 58 (2024) | 10.1007/s11005-024-01804-0 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Impulsive gravitational waves are theoretical models of short but violent
bursts of gravitational radiation. They are commonly described by two distinct
spacetime metrics, one of local Lipschitz regularity, the other one even
distributional. These two metrics are thought to be `physically equivalent'
since they can be formally related by a `discontinuous coordinate
transformation'. In this paper we provide a mathematical analysis of this issue
for the entire class of nonexpanding impulsive gravitational waves propagating
in a background spacetime of constant curvature. We devise a natural geometric
regularisation procedure to show that the notorious change of variables arises
as the distributional limit of a family of smooth coordinate transformations.
In other words, we establish that both spacetimes arise as distributional
limits of a smooth sandwich wave taken in different coordinate systems which
are diffeomorphically related.
| [
{
"created": "Mon, 4 Dec 2023 15:49:12 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Apr 2024 21:52:58 GMT",
"version": "v2"
}
] | 2024-04-26 | [
[
"Sämann",
"Clemens",
""
],
[
"Schinnerl",
"Benedict",
""
],
[
"Steinbauer",
"Roland",
""
],
[
"Švarc",
"Robert",
""
]
] | Impulsive gravitational waves are theoretical models of short but violent bursts of gravitational radiation. They are commonly described by two distinct spacetime metrics, one of local Lipschitz regularity, the other one even distributional. These two metrics are thought to be `physically equivalent' since they can be formally related by a `discontinuous coordinate transformation'. In this paper we provide a mathematical analysis of this issue for the entire class of nonexpanding impulsive gravitational waves propagating in a background spacetime of constant curvature. We devise a natural geometric regularisation procedure to show that the notorious change of variables arises as the distributional limit of a family of smooth coordinate transformations. In other words, we establish that both spacetimes arise as distributional limits of a smooth sandwich wave taken in different coordinate systems which are diffeomorphically related. |
1406.2451 | Lorenzo Iorio | Lorenzo Iorio | Orbital motions as gradiometers for post-Newtonian tidal effects | LaTex2e, 20 pages, no figures, 3 tables. Accepted for publication in
Frontiers in Astronomy and Space Sciences - Cosmology | Front. Astron. Space Sci. 1:3 2014 | 10.3389/fspas.2014.00003 | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The direct long-term changes occurring in the orbital dynamics of a local
gravitationally bound binary system $S$ due to the post-Newtonian tidal
acceleration caused by an external massive source are investigated. A class of
systems made of a test particle $m$ rapidly orbiting with orbital frequency
$n_{\rm b}$ an astronomical body of mass $M$ which, in turn, slowly revolves
around a distant object of mass $M^{'}$ with orbital frequency $n_{\rm
b}^{'}\ll n_{\rm b}$ is considered. The characteristic frequencies of the
non-Keplerian orbital variations of $m$ and of $M$ itself are assumed to be
negligible with respect to both $n_{\rm b}$ and $n_{\rm b}^{'}$. General
expressions for the resulting Newtonian and post-Newtonian tidal orbital shifts
of $m$ are obtained. The future missions BepiColombo and JUICE to Mercury and
Ganymede, respectively, are considered in view of a possible detection. The
largest effects, of the order of $\approx 0.1-0.5$ milliarcseconds per year
(mas yr$^{-1}$), occur for the Ganymede orbiter of the JUICE mission. Although
future improvements in spacecraft tracking and orbit determination might,
perhaps, reach the required sensitivity, the systematic bias represented by the
other known orbital perturbations of both Newtonian and post-Newtonian origin
would be overwhelming. The realization of a dedicated artificial mini-planetary
system to be carried onboard and Earth-orbiting spacecraft is considered as
well. Post-Newtonian tidal precessions as large as $\approx 1-10^2$ mas
yr$^{-1}$ could be obtained, but the quite larger Newtonian tidal effects would
be a major source of systematic bias because of the present-day percent
uncertainty in the product of the Earth's mass times the Newtonian
gravitational parameter.
| [
{
"created": "Tue, 10 Jun 2014 07:49:43 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Jul 2014 07:04:21 GMT",
"version": "v2"
},
{
"created": "Thu, 31 Jul 2014 13:58:59 GMT",
"version": "v3"
}
] | 2014-08-15 | [
[
"Iorio",
"Lorenzo",
""
]
] | The direct long-term changes occurring in the orbital dynamics of a local gravitationally bound binary system $S$ due to the post-Newtonian tidal acceleration caused by an external massive source are investigated. A class of systems made of a test particle $m$ rapidly orbiting with orbital frequency $n_{\rm b}$ an astronomical body of mass $M$ which, in turn, slowly revolves around a distant object of mass $M^{'}$ with orbital frequency $n_{\rm b}^{'}\ll n_{\rm b}$ is considered. The characteristic frequencies of the non-Keplerian orbital variations of $m$ and of $M$ itself are assumed to be negligible with respect to both $n_{\rm b}$ and $n_{\rm b}^{'}$. General expressions for the resulting Newtonian and post-Newtonian tidal orbital shifts of $m$ are obtained. The future missions BepiColombo and JUICE to Mercury and Ganymede, respectively, are considered in view of a possible detection. The largest effects, of the order of $\approx 0.1-0.5$ milliarcseconds per year (mas yr$^{-1}$), occur for the Ganymede orbiter of the JUICE mission. Although future improvements in spacecraft tracking and orbit determination might, perhaps, reach the required sensitivity, the systematic bias represented by the other known orbital perturbations of both Newtonian and post-Newtonian origin would be overwhelming. The realization of a dedicated artificial mini-planetary system to be carried onboard and Earth-orbiting spacecraft is considered as well. Post-Newtonian tidal precessions as large as $\approx 1-10^2$ mas yr$^{-1}$ could be obtained, but the quite larger Newtonian tidal effects would be a major source of systematic bias because of the present-day percent uncertainty in the product of the Earth's mass times the Newtonian gravitational parameter. |
1910.12873 | Alexandru Lupsasca | Samuel E. Gralla, Alexandru Lupsasca | Lensing by Kerr Black Holes | 28 pages, 9 figures. v2: minor edits, matches published version | Phys. Rev. D 101, 044031 (2020) | 10.1103/PhysRevD.101.044031 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Interpreting horizon-scale observations of astrophysical black holes demands
a general understanding of null geodesics in the Kerr spacetime. These may be
divided into two classes: "direct" rays that primarily determine the
observational appearance of a given source, and highly bent rays that produce a
nested sequence of exponentially demagnified images of the main emission: the
so-called "photon ring". We develop heuristics that characterize the direct
rays and study the highly bent geodesics analytically. We define three critical
parameters $\gamma$, $\delta$, and $\tau$ that respectively control the
demagnification, rotation, and time delay of successive images of the source,
thereby providing an analytic theory of the photon ring. These observable
parameters encode universal effects of general relativity, independent of the
details of the emitting matter.
| [
{
"created": "Mon, 28 Oct 2019 18:00:01 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Feb 2020 22:45:43 GMT",
"version": "v2"
}
] | 2020-02-18 | [
[
"Gralla",
"Samuel E.",
""
],
[
"Lupsasca",
"Alexandru",
""
]
] | Interpreting horizon-scale observations of astrophysical black holes demands a general understanding of null geodesics in the Kerr spacetime. These may be divided into two classes: "direct" rays that primarily determine the observational appearance of a given source, and highly bent rays that produce a nested sequence of exponentially demagnified images of the main emission: the so-called "photon ring". We develop heuristics that characterize the direct rays and study the highly bent geodesics analytically. We define three critical parameters $\gamma$, $\delta$, and $\tau$ that respectively control the demagnification, rotation, and time delay of successive images of the source, thereby providing an analytic theory of the photon ring. These observable parameters encode universal effects of general relativity, independent of the details of the emitting matter. |
1708.00941 | Henri Roesch | Hubert L. Bray and Henri P. Roesch | Null Geometry and the Penrose Conjecture | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we survey recent progress on the Null Penrose Conjecture,
including a proof of the conjecture for smooth null cones that are foliated by
doubly convex spheres.
| [
{
"created": "Wed, 2 Aug 2017 21:43:32 GMT",
"version": "v1"
}
] | 2017-08-04 | [
[
"Bray",
"Hubert L.",
""
],
[
"Roesch",
"Henri P.",
""
]
] | In this paper, we survey recent progress on the Null Penrose Conjecture, including a proof of the conjecture for smooth null cones that are foliated by doubly convex spheres. |
1801.08358 | Luis Herrera | L. Herrera | New definition of complexity for self-gravitating fluid distributions:
The spherically symmetric, static case | 10 pages Revtex. Typos corrected. Published in Phys.Rev.D | Phys. Rev. D97, 044010 (2018) | 10.1103/PhysRevD.97.044010 | null | gr-qc physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We put forward a new definition of complexity, for static and spherically
symmetric self--gravitating systems, based on a quantity, hereafter referred to
as complexity factor, that appears in the orthogonal splitting of the Riemann
tensor, in the context of general relativity. We start by assuming that the
homogeneous (in the energy density) fluid, with isotropic pressure is endowed
with minimal complexity. For this kind of fluid distribution, the value of
complexity factor is zero. So, the rationale behind our proposal for the
definition of complexity factor stems from the fact that it measures the
departure, in the value of the active gravitational mass (Tolman mass), with
respect to its value for a zero complexity system. Such departure is produced
by a specific combination of energy density inhomogeneity and pressure
anisotropy. Thus, zero complexity factor may also be found in self--gravitating
systems with inhomogeneous energy density and anisotropic pressure, provided
the effects of these two factors, on the complexity factor, cancel each other.
Some exact interior solutions to the Einstein equations satisfying the zero
complexity criterium are found, and prospective applications of this newly
defined concept, to the study of the structure and evolution of compact
objects, are discussed.
| [
{
"created": "Thu, 25 Jan 2018 11:23:55 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Feb 2018 09:29:22 GMT",
"version": "v2"
}
] | 2018-03-14 | [
[
"Herrera",
"L.",
""
]
] | We put forward a new definition of complexity, for static and spherically symmetric self--gravitating systems, based on a quantity, hereafter referred to as complexity factor, that appears in the orthogonal splitting of the Riemann tensor, in the context of general relativity. We start by assuming that the homogeneous (in the energy density) fluid, with isotropic pressure is endowed with minimal complexity. For this kind of fluid distribution, the value of complexity factor is zero. So, the rationale behind our proposal for the definition of complexity factor stems from the fact that it measures the departure, in the value of the active gravitational mass (Tolman mass), with respect to its value for a zero complexity system. Such departure is produced by a specific combination of energy density inhomogeneity and pressure anisotropy. Thus, zero complexity factor may also be found in self--gravitating systems with inhomogeneous energy density and anisotropic pressure, provided the effects of these two factors, on the complexity factor, cancel each other. Some exact interior solutions to the Einstein equations satisfying the zero complexity criterium are found, and prospective applications of this newly defined concept, to the study of the structure and evolution of compact objects, are discussed. |
1007.3851 | Paul Reska | Tomislav Prokopec, Paul Reska | Scalar cosmological perturbations from inflationary black holes | 41 pages, 11 figures, published version | JCAP 1103:050,2011 | 10.1088/1475-7516/2011/03/050 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the correction to the scale invariant power spectrum of a scalar
field on de Sitter space from small black holes that formed during a
pre-inflationary matter dominated era. The formation probability of such black
holes is estimated from primordial Gaussian density fluctuations. We determine
the correction to the spectrum by first deriving the Keldysh propagator for a
massless scalar field on Schwarzschild-de Sitter space. Our results suggest
that the effect is strong enough to be tested -- and possibly even ruled out --
by observations.
| [
{
"created": "Thu, 22 Jul 2010 10:40:09 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Mar 2011 16:47:22 GMT",
"version": "v2"
}
] | 2011-04-01 | [
[
"Prokopec",
"Tomislav",
""
],
[
"Reska",
"Paul",
""
]
] | We study the correction to the scale invariant power spectrum of a scalar field on de Sitter space from small black holes that formed during a pre-inflationary matter dominated era. The formation probability of such black holes is estimated from primordial Gaussian density fluctuations. We determine the correction to the spectrum by first deriving the Keldysh propagator for a massless scalar field on Schwarzschild-de Sitter space. Our results suggest that the effect is strong enough to be tested -- and possibly even ruled out -- by observations. |
1302.1399 | Sourav Bhattacharya | Sourav Bhattacharya | Black holes and the positive cosmological constant | 171pp, 1 figure; PhD thesis submitted to Jadavpur University,
Kolkata, from S.N. Bose National Centre for Basic Sciences, Kolkata;
Supervisor-Prof. Amitabha Lahiri | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We address some aspects of black hole spacetimes endowed with a positive
cosmological constant, i.e. black holes located inside a cosmological event
horizon. First we establish a general criterion for existence of cosmological
event horizons. Using the geometrical set up built for this, we study classical
black hole no hair theorems for both static and stationary axisymmetric
spacetimes. We discuss cosmic Nielsen-Olesen strings as hair in
Schwarzschild-de Sitter spacetime. We also give a general calculation for
particle creation by a Killing horizon using complex path analysis and using
this we study particle creation in Schwarzschild-de Sitter spacetime by both
black hole and the cosmological event horizons.
| [
{
"created": "Wed, 6 Feb 2013 15:08:45 GMT",
"version": "v1"
}
] | 2013-02-07 | [
[
"Bhattacharya",
"Sourav",
""
]
] | We address some aspects of black hole spacetimes endowed with a positive cosmological constant, i.e. black holes located inside a cosmological event horizon. First we establish a general criterion for existence of cosmological event horizons. Using the geometrical set up built for this, we study classical black hole no hair theorems for both static and stationary axisymmetric spacetimes. We discuss cosmic Nielsen-Olesen strings as hair in Schwarzschild-de Sitter spacetime. We also give a general calculation for particle creation by a Killing horizon using complex path analysis and using this we study particle creation in Schwarzschild-de Sitter spacetime by both black hole and the cosmological event horizons. |
2303.01737 | Muhammad Sharif | M. Sharif and Arooj Fatima | Traversable Wormhole Solutions admitting Karmarkar Condition in $f(R,T)$
Theory | 25 pages, 7 figures | Eur. Phys. J. Plus 138(2023)196 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we evaluate traversable wormhole solutions through Karmarkar
condition in $f(R,T)$ theory, where $T$ is the trace of the energy-momentum
tensor and $R$ represents the Ricci scalar. We develop a wormhole shape
function for the static traversable wormhole geometry by using the embedding
class-I technique. The resulting shape function is used to construct wormhole
geometry that fulfills all the necessary conditions and joins the two
asymptotically flat regions of the spacetime. We investigate the existence of
viable traversable wormhole solutions for anisotropic matter configuration and
examine the stable state of these solutions for different $f(R,T)$ gravity
models. We analyze the graphical behavior of null energy bound to examine the
presence of physically viable wormhole geometry. It is found that viable and
stable traversable wormhole solutions exist in this modified theory of gravity.
| [
{
"created": "Fri, 3 Mar 2023 06:41:50 GMT",
"version": "v1"
}
] | 2023-03-06 | [
[
"Sharif",
"M.",
""
],
[
"Fatima",
"Arooj",
""
]
] | In this paper, we evaluate traversable wormhole solutions through Karmarkar condition in $f(R,T)$ theory, where $T$ is the trace of the energy-momentum tensor and $R$ represents the Ricci scalar. We develop a wormhole shape function for the static traversable wormhole geometry by using the embedding class-I technique. The resulting shape function is used to construct wormhole geometry that fulfills all the necessary conditions and joins the two asymptotically flat regions of the spacetime. We investigate the existence of viable traversable wormhole solutions for anisotropic matter configuration and examine the stable state of these solutions for different $f(R,T)$ gravity models. We analyze the graphical behavior of null energy bound to examine the presence of physically viable wormhole geometry. It is found that viable and stable traversable wormhole solutions exist in this modified theory of gravity. |
1407.2013 | Francisco Lobo | Tiberiu Harko, Francisco S. N. Lobo | Generalized curvature-matter couplings in modified gravity | 55 pages, to appear as a review paper in a Special Issue of Galaxies:
"Beyond Standard Gravity and Cosmology". V2: minor corrections and references
added. Matches published version | Galaxies 2 (2014) 3, 410-465 | 10.3390/galaxies2030410 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we review a plethora of modified theories of gravity with
generalized curvature-matter couplings. The explicit nonminimal couplings, for
instance, between an arbitrary function of the scalar curvature $R$ and the
Lagrangian density of matter, induces a non-vanishing covariant derivative of
the energy-momentum tensor, implying non-geodesic motion and consequently leads
to the appearance of an extra force. Applied to the cosmological context, these
curvature-matter couplings lead to interesting phenomenology, where one can
obtain a unified description of the cosmological epochs. We also consider the
possibility that the behavior of the galactic flat rotation curves can be
explained in the framework of the curvature-matter coupling models, where the
extra-terms in the gravitational field equations modify the equations of motion
of test particles, and induce a supplementary gravitational interaction. In
addition to this, these models are extremely useful for describing dark
energy-dark matter interactions, and for explaining the late-time cosmic
acceleration.
| [
{
"created": "Tue, 8 Jul 2014 09:40:01 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Jul 2014 09:28:47 GMT",
"version": "v2"
}
] | 2014-07-29 | [
[
"Harko",
"Tiberiu",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] | In this work, we review a plethora of modified theories of gravity with generalized curvature-matter couplings. The explicit nonminimal couplings, for instance, between an arbitrary function of the scalar curvature $R$ and the Lagrangian density of matter, induces a non-vanishing covariant derivative of the energy-momentum tensor, implying non-geodesic motion and consequently leads to the appearance of an extra force. Applied to the cosmological context, these curvature-matter couplings lead to interesting phenomenology, where one can obtain a unified description of the cosmological epochs. We also consider the possibility that the behavior of the galactic flat rotation curves can be explained in the framework of the curvature-matter coupling models, where the extra-terms in the gravitational field equations modify the equations of motion of test particles, and induce a supplementary gravitational interaction. In addition to this, these models are extremely useful for describing dark energy-dark matter interactions, and for explaining the late-time cosmic acceleration. |
2010.16276 | Yuri Obukhov | Yuri N. Obukhov | Parity violation in Poincar\'e gauge gravity | 27 pages, Revtex style, minor corrections, references added,
contribution to Proceedings of Teleparallel Gravity Workshop Tartu 2020 in
Special Issue of International Journal of Geometric Methods in Modern Physics | null | 10.1142/S0219887821500225 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyse the parity violation issue in the Poincar\'e gauge theory of
gravity for the two classes of models which are built as natural extensions of
the Einstein-Cartan theory. The conservation laws of the matter currents are
revisited and we clarify the derivation of the effective Einstein field
equation and the structure of the effective energy-momentum current for
arbitrary matter sources.
| [
{
"created": "Fri, 30 Oct 2020 13:53:19 GMT",
"version": "v1"
},
{
"created": "Sat, 21 Nov 2020 14:10:47 GMT",
"version": "v2"
}
] | 2020-11-24 | [
[
"Obukhov",
"Yuri N.",
""
]
] | We analyse the parity violation issue in the Poincar\'e gauge theory of gravity for the two classes of models which are built as natural extensions of the Einstein-Cartan theory. The conservation laws of the matter currents are revisited and we clarify the derivation of the effective Einstein field equation and the structure of the effective energy-momentum current for arbitrary matter sources. |
gr-qc/9208001 | null | Jonathan J. Halliwell | The Interpretation of Quantum Cosmological Models | 18 pages | null | null | CTP preprint 2130 (July 1992) | gr-qc hep-th | null | We consider the problem of extracting physical predictions from the wave
function of the universe in quantum cosmological models. We state the features
of quantum cosmology an interpretational scheme should confront. We discuss the
Everett interpretation, and extensions of it, and their application to quantum
cosmology. We review the steps that are normally taken in the process of
extracting predictions from solutions to the Wheeler-DeWitt equation for
quantum cosmological models. Some difficulties and their possible resolution
are discussed. We conclude that the usual wave function-based approach admits
at best a rather heuristic interpretation, although it may in the future be
justified by appeal to the decoherent histories approach.
| [
{
"created": "Wed, 5 Aug 1992 15:30:31 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Halliwell",
"Jonathan J.",
""
]
] | We consider the problem of extracting physical predictions from the wave function of the universe in quantum cosmological models. We state the features of quantum cosmology an interpretational scheme should confront. We discuss the Everett interpretation, and extensions of it, and their application to quantum cosmology. We review the steps that are normally taken in the process of extracting predictions from solutions to the Wheeler-DeWitt equation for quantum cosmological models. Some difficulties and their possible resolution are discussed. We conclude that the usual wave function-based approach admits at best a rather heuristic interpretation, although it may in the future be justified by appeal to the decoherent histories approach. |
gr-qc/0306124 | Gyula Bene | Ga'bor Helesfai and Gyula Bene (Institute for Theoretical Physics,
Eo"tvo"s University, Budapest) | A numerical study of spectral properties of the area operator in loop
quantum gravity | LaTeX, 9 pages, 4 figures | null | null | null | gr-qc | null | The lowest 37000 eigenvalues of the area operator in loop quantum gravity is
calculated and studied numerically. We obtain an asymptotical formula for the
eigenvalues as a function of their sequential number. The multiplicity of the
lowest few hundred eigenvalues is also determined and the smoothed spectral
density is calculated. The spectral density is presented for various number of
vertices, edges and SU(2) representations. A scaling form of spectral density
is found, being a power law for one vertex, while following an exponential for
several vertices. The latter case is explained on the basis of the one vertex
spectral density.
| [
{
"created": "Mon, 30 Jun 2003 08:44:23 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Helesfai",
"Ga'bor",
"",
"Institute for Theoretical Physics,\n Eo\"tvo\"s University, Budapest"
],
[
"Bene",
"Gyula",
"",
"Institute for Theoretical Physics,\n Eo\"tvo\"s University, Budapest"
]
] | The lowest 37000 eigenvalues of the area operator in loop quantum gravity is calculated and studied numerically. We obtain an asymptotical formula for the eigenvalues as a function of their sequential number. The multiplicity of the lowest few hundred eigenvalues is also determined and the smoothed spectral density is calculated. The spectral density is presented for various number of vertices, edges and SU(2) representations. A scaling form of spectral density is found, being a power law for one vertex, while following an exponential for several vertices. The latter case is explained on the basis of the one vertex spectral density. |
1112.5559 | Nobuyuki Sakai | Nobuyuki Sakai, Takashi Tamaki | What happens to Q-balls if $Q$ is so large? | 9 pages, 10 figures, results for large $\kappa$ added, to appear in
PRD | null | 10.1103/PhysRevD.85.104008 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the system of a gravitating Q-ball, there is a maximum charge $Q_{{\rm
max}}$ inevitably, while in flat spacetime there is no upper bound on $Q$ in
typical models such as the Affleck-Dine model. Theoretically the charge $Q$ is
a free parameter, and phenomenologically it could increase by charge
accumulation. We address a question of what happens to Q-balls if $Q$ is close
to $Q_{{\rm max}}$. First, without specifying a model, we show analytically
that inflation cannot take place in the core of a Q-ball, contrary to the claim
of previous work. Next, for the Affleck-Dine model, we analyze perturbation of
equilibrium solutions with $Q\approx Q_{{\rm max}}$ by numerical analysis of
dynamical field equations. We find that the extremal solution with $Q=Q_{{\rm
max}}$ and unstable solutions around it are "critical solutions", which means
the threshold of black-hole formation.
| [
{
"created": "Fri, 23 Dec 2011 11:33:24 GMT",
"version": "v1"
},
{
"created": "Sun, 29 Apr 2012 13:06:21 GMT",
"version": "v2"
}
] | 2013-05-30 | [
[
"Sakai",
"Nobuyuki",
""
],
[
"Tamaki",
"Takashi",
""
]
] | In the system of a gravitating Q-ball, there is a maximum charge $Q_{{\rm max}}$ inevitably, while in flat spacetime there is no upper bound on $Q$ in typical models such as the Affleck-Dine model. Theoretically the charge $Q$ is a free parameter, and phenomenologically it could increase by charge accumulation. We address a question of what happens to Q-balls if $Q$ is close to $Q_{{\rm max}}$. First, without specifying a model, we show analytically that inflation cannot take place in the core of a Q-ball, contrary to the claim of previous work. Next, for the Affleck-Dine model, we analyze perturbation of equilibrium solutions with $Q\approx Q_{{\rm max}}$ by numerical analysis of dynamical field equations. We find that the extremal solution with $Q=Q_{{\rm max}}$ and unstable solutions around it are "critical solutions", which means the threshold of black-hole formation. |
1908.10377 | Leo Stein | Leo C. Stein | qnm: A Python package for calculating Kerr quasinormal modes, separation
constants, and spherical-spheroidal mixing coefficients | 3 pages, 0 figures. Matches version accepted by the Journal of Open
Source Software. The source repository: https://github.com/duetosymmetry/qnm
, PyPI entry: https://pypi.org/project/qnm/ , documentation:
https://qnm.readthedocs.io . Suggestions and pull requests welcome | J. Open Source Softw., 4(42), 1683 (2019) | 10.21105/joss.01683 | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | $\mathtt{qnm}$ is an open-source Python package for computing the Kerr
quasinormal mode frequencies, angular separation constants, and
spherical-spheroidal mixing coefficients. The $\mathtt{qnm}$ package includes a
Leaver solver with the Cook-Zalutskiy spectral approach to the angular sector,
and a caching mechanism to avoid repeating calculations. We provide a large
cache of low $\ell, m, n$ modes, which can be downloaded and installed with a
single function call, and interpolated to provide good initial guess for
root-polishing at new values of spin.
| [
{
"created": "Tue, 27 Aug 2019 18:00:03 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Oct 2019 19:24:39 GMT",
"version": "v2"
}
] | 2019-10-03 | [
[
"Stein",
"Leo C.",
""
]
] | $\mathtt{qnm}$ is an open-source Python package for computing the Kerr quasinormal mode frequencies, angular separation constants, and spherical-spheroidal mixing coefficients. The $\mathtt{qnm}$ package includes a Leaver solver with the Cook-Zalutskiy spectral approach to the angular sector, and a caching mechanism to avoid repeating calculations. We provide a large cache of low $\ell, m, n$ modes, which can be downloaded and installed with a single function call, and interpolated to provide good initial guess for root-polishing at new values of spin. |
1702.03832 | Xavier Calmet | Xavier Calmet and Iber\^e Kuntz | What is modified gravity and how to differentiate it from particle dark
matter? | 12 pages | Eur. Phys. J. C, 77 2 (2017) 132 | 10.1140/epjc/s10052-017-4695-y | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An obvious criterion to classify theories of modified gravity is to identify
their gravitational degrees of freedom and their coupling to the metric and the
matter sector. Using this simple idea, we show that any theory which depends on
the curvature invariants is equivalent to general relativity in the presence of
new fields that are gravitationally coupled to the energy-momentum tensor. We
show that they can be shifted into a new energy-momentum tensor. There is no a
priori reason to identify these new fields as gravitational degrees of freedom
or matter fields. This leads to an equivalence between dark matter particles
gravitationally coupled to the standard model fields and modified gravity
theories designed to account for the dark matter phenomenon. Due to this
ambiguity, it is impossible to differentiate experimentally between these
theories and any attempt of doing so should be classified as a mere
interpretation of the same phenomenon.
| [
{
"created": "Fri, 10 Feb 2017 13:17:05 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Feb 2017 20:06:21 GMT",
"version": "v2"
}
] | 2017-03-01 | [
[
"Calmet",
"Xavier",
""
],
[
"Kuntz",
"Iberê",
""
]
] | An obvious criterion to classify theories of modified gravity is to identify their gravitational degrees of freedom and their coupling to the metric and the matter sector. Using this simple idea, we show that any theory which depends on the curvature invariants is equivalent to general relativity in the presence of new fields that are gravitationally coupled to the energy-momentum tensor. We show that they can be shifted into a new energy-momentum tensor. There is no a priori reason to identify these new fields as gravitational degrees of freedom or matter fields. This leads to an equivalence between dark matter particles gravitationally coupled to the standard model fields and modified gravity theories designed to account for the dark matter phenomenon. Due to this ambiguity, it is impossible to differentiate experimentally between these theories and any attempt of doing so should be classified as a mere interpretation of the same phenomenon. |
gr-qc/0401025 | Claudio Benedito Silva Furtado | Claudio Furtado, A. M. de M. Carvalho, L. C. Garcia de Andrade, F.
Moraes | Holonomy, Aharonov-Bohm effect and phonon scattering in superfluids | 15 pages, Revtex4 | null | null | null | gr-qc | null | In this article we discuss the analogy between superfluids and a spinning
thick cosmic string. We use the geometrical approach to obtain the geometrical
phases for a phonon in the presence of a vortex. We use loop variables for a
geometric description of Aharonov-Bohm effect in these systems. We use holonomy
transformations to characterize globally the "space-time" of a vortex and in
this point of view we study the gravitational analog of the Aharonov-Bohm
effect in this system. We demonstrate that in the general case the
Aharonov-Bohm effect has a contribution both from the rotational and the
translational holonomy. We study also Berrys quantum phase for phonons in this
systems.
| [
{
"created": "Thu, 8 Jan 2004 10:56:27 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Furtado",
"Claudio",
""
],
[
"Carvalho",
"A. M. de M.",
""
],
[
"de Andrade",
"L. C. Garcia",
""
],
[
"Moraes",
"F.",
""
]
] | In this article we discuss the analogy between superfluids and a spinning thick cosmic string. We use the geometrical approach to obtain the geometrical phases for a phonon in the presence of a vortex. We use loop variables for a geometric description of Aharonov-Bohm effect in these systems. We use holonomy transformations to characterize globally the "space-time" of a vortex and in this point of view we study the gravitational analog of the Aharonov-Bohm effect in this system. We demonstrate that in the general case the Aharonov-Bohm effect has a contribution both from the rotational and the translational holonomy. We study also Berrys quantum phase for phonons in this systems. |
0707.4026 | Theodore A. Jacobson | Ted Jacobson | Renormalization and black hole entropy in Loop Quantum Gravity | 8 pages; v2: references added, typos corrected, version to appear in
CQG | Class.Quant.Grav.24:4875-4879,2007 | 10.1088/0264-9381/24/18/N02 | null | gr-qc hep-th | null | Microscopic state counting for a black hole in Loop Quantum Gravity yields a
result proportional to horizon area, and inversely proportional to Newton's
constant and the Immirzi parameter. It is argued here that before this result
can be compared to the Bekenstein-Hawking entropy of a macroscopic black hole,
the scale dependence of both Newton's constant and the area must be accounted
for. The two entropies could then agree for any value of the Immirzi parameter,
if a certain renormalization property holds.
| [
{
"created": "Thu, 26 Jul 2007 23:33:10 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Aug 2007 02:11:25 GMT",
"version": "v2"
}
] | 2010-10-27 | [
[
"Jacobson",
"Ted",
""
]
] | Microscopic state counting for a black hole in Loop Quantum Gravity yields a result proportional to horizon area, and inversely proportional to Newton's constant and the Immirzi parameter. It is argued here that before this result can be compared to the Bekenstein-Hawking entropy of a macroscopic black hole, the scale dependence of both Newton's constant and the area must be accounted for. The two entropies could then agree for any value of the Immirzi parameter, if a certain renormalization property holds. |
gr-qc/0506082 | Iosif Khriplovich | I.B. Khriplovich | Quantized Black Holes, Their Spectrum and Radiation | 15 pages, content of few talks given at conferences this summer | Phys.Atom.Nucl.71:671-680,2008 | 10.1134/S1063778808040078 | null | gr-qc hep-th | null | Under quite natural general assumptions, the following results are obtained.
The maximum entropy of a quantized surface is demonstrated to be proportional
to the surface area in the classical limit. The general structure of the
horizon spectrum is found. The discrete spectrum of thermal radiation of a
black hole Under quite natural general assumptions, the following results are
obtained. The maximum entropy of a quantized surface is demonstrated to be
proportional to the surface area in the classical limit. The general structure
of the horizon spectrum is found. The discrete spectrum of thermal radiation of
a black hole fits the Wien profile. The natural widths of the lines are much
smaller than the distances between them. The total intensity of the thermal
radiation is estimated.
In the special case of loop quantum gravity, the value of the Barbero --
Immirzi parameter is found. Different values for this parameter, obtained under
additional assumption that the horizon is described by a U(1) Chern -- Simons
theory, are demonstrated to be in conflict with the firmly established
holographic bound.
| [
{
"created": "Wed, 15 Jun 2005 06:02:41 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Khriplovich",
"I. B.",
""
]
] | Under quite natural general assumptions, the following results are obtained. The maximum entropy of a quantized surface is demonstrated to be proportional to the surface area in the classical limit. The general structure of the horizon spectrum is found. The discrete spectrum of thermal radiation of a black hole Under quite natural general assumptions, the following results are obtained. The maximum entropy of a quantized surface is demonstrated to be proportional to the surface area in the classical limit. The general structure of the horizon spectrum is found. The discrete spectrum of thermal radiation of a black hole fits the Wien profile. The natural widths of the lines are much smaller than the distances between them. The total intensity of the thermal radiation is estimated. In the special case of loop quantum gravity, the value of the Barbero -- Immirzi parameter is found. Different values for this parameter, obtained under additional assumption that the horizon is described by a U(1) Chern -- Simons theory, are demonstrated to be in conflict with the firmly established holographic bound. |
0810.1961 | Barry Wardell | Adrian C. Ottewill and Barry Wardell | Quasi-local contribution to the scalar self-force: Non-geodesic Motion | 11 pages, 1 figure, corrected typo in Eq. 2.8 | Phys.Rev.D79:024031,2009 | 10.1103/PhysRevD.79.024031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend our previous calculation of the quasi-local contribution to the
self-force on a scalar particle to general (not necessarily geodesic) motion in
a general spacetime. In addition to the general case and the case of a particle
at rest in a stationary spacetime, we consider as examples a particle held at
rest in Reissner-Nordstrom and Kerr-Newman space-times. This allows us to most
easily analyse the effect of non-geodesic motion on our previous results and
also allows for comparison to existing results for Schwarzschild spacetime.
| [
{
"created": "Fri, 10 Oct 2008 22:12:16 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Nov 2008 17:19:18 GMT",
"version": "v2"
},
{
"created": "Sun, 1 Feb 2009 00:02:04 GMT",
"version": "v3"
},
{
"created": "Mon, 16 Jan 2012 14:34:54 GMT",
"version": "v4"
}
] | 2012-01-17 | [
[
"Ottewill",
"Adrian C.",
""
],
[
"Wardell",
"Barry",
""
]
] | We extend our previous calculation of the quasi-local contribution to the self-force on a scalar particle to general (not necessarily geodesic) motion in a general spacetime. In addition to the general case and the case of a particle at rest in a stationary spacetime, we consider as examples a particle held at rest in Reissner-Nordstrom and Kerr-Newman space-times. This allows us to most easily analyse the effect of non-geodesic motion on our previous results and also allows for comparison to existing results for Schwarzschild spacetime. |
2106.10235 | Shao-Jiang Wang | Ligong Bian, Rong-Gen Cai, Shuo Cao, Zhoujian Cao, He Gao, Zong-Kuan
Guo, Kejia Lee, Di Li, Jing Liu, Youjun Lu, Shi Pi, Jian-Min Wang, Shao-Jiang
Wang, Yan Wang, Tao Yang, Xing-Yu Yang, Shenghua Yu, Xin Zhang | The Gravitational-Wave Physics II: Progress | v1, 93 pages, 18 figures, prepared as a status review of project
report for Sci. China Phys. Mech. Astron.; v2, 95 pages, minor revision,
references added, accepted for publication in Sci. China Phys. Mech. Astron;
v3, to match the published version | Sci. China Phys. Mech. Astron. 64, 120401 (2021) | 10.1007/s11433-021-1781-x | null | gr-qc astro-ph.CO astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been a half-decade since the first direct detection of gravitational
waves, which signifies the coming of the era of the gravitational-wave
astronomy and gravitational-wave cosmology. The increasing number of the
detected gravitational-wave events has revealed the promising capability of
constraining various aspects of cosmology, astronomy, and gravity. Due to the
limited space in this review article, we will briefly summarize the recent
progress over the past five years, but with a special focus on some of our own
work for the Key Project ``Physics associated with the gravitational waves''
supported by the National Natural Science Foundation of China. In particular,
(1) we have presented the mechanism of the gravitational-wave production during
some physical processes of the early Universe, such as inflation, preheating
and phase transition, and the cosmological implications of gravitational-wave
measurements; (2) we have put constraints on the neutron star maximum mass
according to GW170817 observations; (3) we have developed a numerical
relativity algorithm based on the finite element method and a waveform model
for the binary black hole coalescence along an eccentric orbit.
| [
{
"created": "Thu, 17 Jun 2021 04:05:58 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Sep 2021 14:59:23 GMT",
"version": "v2"
},
{
"created": "Wed, 3 Nov 2021 08:53:42 GMT",
"version": "v3"
}
] | 2021-11-04 | [
[
"Bian",
"Ligong",
""
],
[
"Cai",
"Rong-Gen",
""
],
[
"Cao",
"Shuo",
""
],
[
"Cao",
"Zhoujian",
""
],
[
"Gao",
"He",
""
],
[
"Guo",
"Zong-Kuan",
""
],
[
"Lee",
"Kejia",
""
],
[
"Li",
"Di",
""
],
[
"Liu",
"Jing",
""
],
[
"Lu",
"Youjun",
""
],
[
"Pi",
"Shi",
""
],
[
"Wang",
"Jian-Min",
""
],
[
"Wang",
"Shao-Jiang",
""
],
[
"Wang",
"Yan",
""
],
[
"Yang",
"Tao",
""
],
[
"Yang",
"Xing-Yu",
""
],
[
"Yu",
"Shenghua",
""
],
[
"Zhang",
"Xin",
""
]
] | It has been a half-decade since the first direct detection of gravitational waves, which signifies the coming of the era of the gravitational-wave astronomy and gravitational-wave cosmology. The increasing number of the detected gravitational-wave events has revealed the promising capability of constraining various aspects of cosmology, astronomy, and gravity. Due to the limited space in this review article, we will briefly summarize the recent progress over the past five years, but with a special focus on some of our own work for the Key Project ``Physics associated with the gravitational waves'' supported by the National Natural Science Foundation of China. In particular, (1) we have presented the mechanism of the gravitational-wave production during some physical processes of the early Universe, such as inflation, preheating and phase transition, and the cosmological implications of gravitational-wave measurements; (2) we have put constraints on the neutron star maximum mass according to GW170817 observations; (3) we have developed a numerical relativity algorithm based on the finite element method and a waveform model for the binary black hole coalescence along an eccentric orbit. |
2308.12669 | Giuseppe Gaetano Luciano Dr | Giuseppe Gaetano Luciano and Emmanuel Saridakis | $P-v$ criticalities, phase transitions and geometrothermodynamics of
charged AdS black holes from Kaniadakis statistics | 15 pages, 11 labelled figures, comments are welcome | null | null | null | gr-qc cond-mat.stat-mech hep-th | http://creativecommons.org/licenses/by/4.0/ | Boltzmann entropy-based thermodynamics of charged anti-de Sitter (AdS) black
holes has been shown to exhibit physically interesting features, such as $P-V$
criticalities and van der Waals-like phase transitions. In this work we extend
the study of these critical phenomena to Kaniadakis theory, which is a
non-extensive generalization of the classical statistical mechanics
incorporating relativity. By applying the typical framework of condensed-matter
physics, we analyze the impact of Kaniadakis entropy onto the equation of
state, the Gibbs free energy and the critical exponents of AdS black holes in
the extended phase space. Additionally, we investigate the underlying
micro-structure of black holes in Ruppeiner geometry, which reveals appreciable
deviations of the nature of the particle interactions from the standard
behavior. Our analysis opens up new perspectives on the understanding of black
hole thermodynamics in a relativistic statistical framework, highlighting the
role of non-extensive corrections in the AdS black holes/van der Waals fluids
dual picture.
| [
{
"created": "Thu, 24 Aug 2023 09:20:10 GMT",
"version": "v1"
}
] | 2023-08-25 | [
[
"Luciano",
"Giuseppe Gaetano",
""
],
[
"Saridakis",
"Emmanuel",
""
]
] | Boltzmann entropy-based thermodynamics of charged anti-de Sitter (AdS) black holes has been shown to exhibit physically interesting features, such as $P-V$ criticalities and van der Waals-like phase transitions. In this work we extend the study of these critical phenomena to Kaniadakis theory, which is a non-extensive generalization of the classical statistical mechanics incorporating relativity. By applying the typical framework of condensed-matter physics, we analyze the impact of Kaniadakis entropy onto the equation of state, the Gibbs free energy and the critical exponents of AdS black holes in the extended phase space. Additionally, we investigate the underlying micro-structure of black holes in Ruppeiner geometry, which reveals appreciable deviations of the nature of the particle interactions from the standard behavior. Our analysis opens up new perspectives on the understanding of black hole thermodynamics in a relativistic statistical framework, highlighting the role of non-extensive corrections in the AdS black holes/van der Waals fluids dual picture. |
gr-qc/9606077 | Thibault Damour | Thibault Damour | Theoretical aspects of gravitational radiation | 14 pages, Latex, uses sprocl.sty, to appear in the Proceedings of
GR14, eds M. Francaviglia et al, World Scientific | null | null | IHES/P/95/101 | gr-qc | null | A central problem in gravitational wave research is the {\it generation
problem}, i.e., the problem of relating the outgoing gravitational wave field
to the structure and motion of the material source. This problem has become, in
recent years, of increased interest in view of the development of a worldwide
network of gravitational wave detectors. We review recent progress in {\it
analytical} methods of tackling the gravitational wave generation problem. In
particular, we describe recent work in an approach which consists of matching a
post-Newtonian expansion of the metric near the material source with a
multipolar-post-Minkowskian expansion of the external metric. The results of
such analytical methods are important notably for providing accurate
theoretical predictions for the most promising targets of the LIGO/VIRGO
interferometric network: the ``chirp'' gravitational waveforms emitted during
the radiation-reaction-driven inspiral of binary systems of compact objects
(neutron stars or black holes).
| [
{
"created": "Thu, 27 Jun 1996 17:19:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Damour",
"Thibault",
""
]
] | A central problem in gravitational wave research is the {\it generation problem}, i.e., the problem of relating the outgoing gravitational wave field to the structure and motion of the material source. This problem has become, in recent years, of increased interest in view of the development of a worldwide network of gravitational wave detectors. We review recent progress in {\it analytical} methods of tackling the gravitational wave generation problem. In particular, we describe recent work in an approach which consists of matching a post-Newtonian expansion of the metric near the material source with a multipolar-post-Minkowskian expansion of the external metric. The results of such analytical methods are important notably for providing accurate theoretical predictions for the most promising targets of the LIGO/VIRGO interferometric network: the ``chirp'' gravitational waveforms emitted during the radiation-reaction-driven inspiral of binary systems of compact objects (neutron stars or black holes). |
1803.11094 | Eleni-Alexandra Kontou | Peter J. Brown, Christopher J. Fewster, Eleni-Alexandra Kontou | A singularity theorem for Einstein-Klein-Gordon theory | 19 pages | null | 10.1007/s10714-018-2446-5 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hawking's singularity theorem concerns matter obeying the strong energy
condition (SEC), which means that all observers experience a nonnegative
effective energy density (EED), thereby guaranteeing the timelike convergence
property. However, there are models that do not satisfy the SEC and therefore
lie outside the scope of Hawking's hypotheses, an important example being the
massive Klein-Gordon field. Here we derive lower bounds on local averages of
the EED for solutions to the Klein-Gordon equation, allowing nonzero mass and
nonminimal coupling to the scalar curvature. The averages are taken along
timelike geodesics or over spacetime volumes, and our bounds are valid for a
range of coupling constants including both minimal and conformal coupling.
Using methods developed by Fewster and Galloway, these lower bounds are applied
to prove a Hawking-type singularity theorem for solutions to the
Einstein-Klein-Gordon theory, asserting that solutions with sufficient initial
contraction at a compact Cauchy surface will be future timelike geodesically
incomplete.
| [
{
"created": "Thu, 29 Mar 2018 14:29:41 GMT",
"version": "v1"
}
] | 2018-09-19 | [
[
"Brown",
"Peter J.",
""
],
[
"Fewster",
"Christopher J.",
""
],
[
"Kontou",
"Eleni-Alexandra",
""
]
] | Hawking's singularity theorem concerns matter obeying the strong energy condition (SEC), which means that all observers experience a nonnegative effective energy density (EED), thereby guaranteeing the timelike convergence property. However, there are models that do not satisfy the SEC and therefore lie outside the scope of Hawking's hypotheses, an important example being the massive Klein-Gordon field. Here we derive lower bounds on local averages of the EED for solutions to the Klein-Gordon equation, allowing nonzero mass and nonminimal coupling to the scalar curvature. The averages are taken along timelike geodesics or over spacetime volumes, and our bounds are valid for a range of coupling constants including both minimal and conformal coupling. Using methods developed by Fewster and Galloway, these lower bounds are applied to prove a Hawking-type singularity theorem for solutions to the Einstein-Klein-Gordon theory, asserting that solutions with sufficient initial contraction at a compact Cauchy surface will be future timelike geodesically incomplete. |
1106.2709 | Derek Lee | Derek Lee | Scattering of massive scalars by Schwarzschild black holes | 8 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Klein-Gordon equation for the wave function of a single massive scalar is
written in spherical and parabolic coordinates in the presence of a
Schwarzschild background, and some semi-classical techniques for deriving
asymptotic results are considered. In addition to the well-known logarithmic
phase shift due to the tortoise radial coordinate, it is found that there is a
mass-dependent logarithmic phase shift at infinity. This is found to be
necessary to match the Newtonian cross-section in the non-relativistic limit.
Finally, by imposing suitable boundary conditions near the horizon, the phase
shift is calculated.
| [
{
"created": "Tue, 14 Jun 2011 13:29:19 GMT",
"version": "v1"
}
] | 2011-06-15 | [
[
"Lee",
"Derek",
""
]
] | The Klein-Gordon equation for the wave function of a single massive scalar is written in spherical and parabolic coordinates in the presence of a Schwarzschild background, and some semi-classical techniques for deriving asymptotic results are considered. In addition to the well-known logarithmic phase shift due to the tortoise radial coordinate, it is found that there is a mass-dependent logarithmic phase shift at infinity. This is found to be necessary to match the Newtonian cross-section in the non-relativistic limit. Finally, by imposing suitable boundary conditions near the horizon, the phase shift is calculated. |
2105.11965 | Rabin Banerjee | Rabin Banerjee | Covariant Formulation of the Newton-Hooke Particle and its Canonical
Analysis | 21 pages, No figures, Accepted in Physical Review D | Phys. Rev. D 103, 125009 (2021) | 10.1103/PhysRevD.103.125009 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A covariant formulation for the Newton-Hooke particle is presented by
following an algorithm developed by us \cite{BMM1, BMM2, BMM3}. It naturally
leads to a coupling with the Newton-Cartan geometry. From this result we
provide an understanding of gravitation in a Newtonian geometric background.
Using Dirac's constrained analysis a canonical formulation for the Newton-Hooke
covariant action is done in both gauge independent and gauge fixed approaches.
While the former helps in identifying the various symmetries of the model, the
latter is able to define the physical variables. From this analysis a path to
canonical quantisation is traced and the Schroedinger equation is derived which
is shown to satisfy various consistency checks. Some consequences of this
equation are briefly mentioned.
| [
{
"created": "Mon, 24 May 2021 06:23:45 GMT",
"version": "v1"
}
] | 2021-06-16 | [
[
"Banerjee",
"Rabin",
""
]
] | A covariant formulation for the Newton-Hooke particle is presented by following an algorithm developed by us \cite{BMM1, BMM2, BMM3}. It naturally leads to a coupling with the Newton-Cartan geometry. From this result we provide an understanding of gravitation in a Newtonian geometric background. Using Dirac's constrained analysis a canonical formulation for the Newton-Hooke covariant action is done in both gauge independent and gauge fixed approaches. While the former helps in identifying the various symmetries of the model, the latter is able to define the physical variables. From this analysis a path to canonical quantisation is traced and the Schroedinger equation is derived which is shown to satisfy various consistency checks. Some consequences of this equation are briefly mentioned. |
gr-qc/9406013 | Takashi Torii | Takashi Torii, Kei-ichi Maeda and Takashi Tachizawa | Non-Abelian Black Holes and Catastrophe Theory I : Neutral Type | 27pages, LaTex style, WU-AP/39/94. Figures are available (hard
copies) upon requests [64L514@cfi.waseda.ac.jp (T.Torii)] | Phys.Rev. D51 (1995) 1510-1524 | 10.1103/PhysRevD.51.1510 | null | gr-qc | null | We re-analyze the globally neutral non-Abelian black holes and present a
unified picture, classifying them into two types; Type I (black holes with
massless non-Abelian field) and Type II (black holes with ``massive"
non-Abelian field). For the Type II, there are two branches: The black hole in
the high-entropy branch is ``stable" and almost neutral, while that in the low
entropy branch, which is similar to the Type I, is unstable and locally
charged. To analyze their stabilities, we adopt the catastrophe theoretic
method, which reveals us a universal picture of stability of the black holes.
It is shown that the isolated Type II black hole has a fold catastrophe
structure.
In a heat bath system, the Type I black hole shows a cusp catastrophe, while
the Type II has both fold and cusp catastrophe.
| [
{
"created": "Wed, 8 Jun 1994 03:39:33 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Torii",
"Takashi",
""
],
[
"Maeda",
"Kei-ichi",
""
],
[
"Tachizawa",
"Takashi",
""
]
] | We re-analyze the globally neutral non-Abelian black holes and present a unified picture, classifying them into two types; Type I (black holes with massless non-Abelian field) and Type II (black holes with ``massive" non-Abelian field). For the Type II, there are two branches: The black hole in the high-entropy branch is ``stable" and almost neutral, while that in the low entropy branch, which is similar to the Type I, is unstable and locally charged. To analyze their stabilities, we adopt the catastrophe theoretic method, which reveals us a universal picture of stability of the black holes. It is shown that the isolated Type II black hole has a fold catastrophe structure. In a heat bath system, the Type I black hole shows a cusp catastrophe, while the Type II has both fold and cusp catastrophe. |
1810.06446 | Miloslav Svec | Miloslav Svec | Quantum Structure of Spacetime and Its Entropy in a Cyclic Universe with
Negative Curvature II: Data Analysis and Results | 29 pages, 8 Figures, 12 Tables; Table caption of the Table IV and the
equation (9.1) corrected; change in the address | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the Part I of this work we show that Friedmann equations and the
thermodynamical Gibbs-Duhem relation determine a general form of the Hubble
function called Model E which predicts a dynamical Dark Energy and Dark Matter
with equations of state w_0=-1 and w_M=0, respectively. We identify Dark Energy
and Dark Matter with Space. General theory of relativity asserts that Space is
gravitational fields. We propose the Space has a specific quantum structure:
entangled Space quanta form Dark Energy, non-entangled ones form Dark Matter.
We identify Dark Matter and Dark Energy as the gravitational fields generated
by Fisher information metric from the probability distributions p and q of the
entropies carried by their quanta, respectively. This model of the quantum
structure of the spacetime determines a specific form of the dynamical terms of
Dark Energy and Dark Matter and predicts the existence of a new "residual"
matter term with equation of state w_r=-1/3. This term plays a role of a
curvature term in the Hubble function with negative curvature k=-1. Its
consistency with the curvature term in the Robertson-Walker metric then
predicts a positive present curvature density \Omega_{c,0} which places
constraints on the cosmological parameters. In this work we test these
predictions in fits to the Hubble data and angular diameter distance data. The
fits confirm all predictions and support our model of the quantum structure of
the spacetime.
| [
{
"created": "Mon, 15 Oct 2018 15:06:40 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Nov 2018 12:49:58 GMT",
"version": "v2"
}
] | 2018-11-21 | [
[
"Svec",
"Miloslav",
""
]
] | In the Part I of this work we show that Friedmann equations and the thermodynamical Gibbs-Duhem relation determine a general form of the Hubble function called Model E which predicts a dynamical Dark Energy and Dark Matter with equations of state w_0=-1 and w_M=0, respectively. We identify Dark Energy and Dark Matter with Space. General theory of relativity asserts that Space is gravitational fields. We propose the Space has a specific quantum structure: entangled Space quanta form Dark Energy, non-entangled ones form Dark Matter. We identify Dark Matter and Dark Energy as the gravitational fields generated by Fisher information metric from the probability distributions p and q of the entropies carried by their quanta, respectively. This model of the quantum structure of the spacetime determines a specific form of the dynamical terms of Dark Energy and Dark Matter and predicts the existence of a new "residual" matter term with equation of state w_r=-1/3. This term plays a role of a curvature term in the Hubble function with negative curvature k=-1. Its consistency with the curvature term in the Robertson-Walker metric then predicts a positive present curvature density \Omega_{c,0} which places constraints on the cosmological parameters. In this work we test these predictions in fits to the Hubble data and angular diameter distance data. The fits confirm all predictions and support our model of the quantum structure of the spacetime. |
1503.02433 | Behrouz Mirza | Mohammad Bagher Jahani Poshteh, Behrouz Mirza, Fatemeh Oboudiat | Generalized Ehrenfest's Equations and phase transition in Black Holes | 6 pages | IJMPD Vol. 24, No. 3 (2015) 1550029 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We generalize Ehrenfest's equations to systems having two work terms, i.e.
systems with three degrees of freedom. For black holes with two work terms we
obtain nine equations instead of two to be satisfied at the critical point of a
second order phase transition. We finally generalize this method to a system
with an arbitrary number of degrees of freedom and found there is
$\frac{N(N+1)^{2}}{2}$ equations to be satisfied at the point of a second order
phase transition where $N$ is number of work terms in the first law of
thermodynamics.
| [
{
"created": "Mon, 9 Mar 2015 11:36:43 GMT",
"version": "v1"
}
] | 2015-03-10 | [
[
"Poshteh",
"Mohammad Bagher Jahani",
""
],
[
"Mirza",
"Behrouz",
""
],
[
"Oboudiat",
"Fatemeh",
""
]
] | We generalize Ehrenfest's equations to systems having two work terms, i.e. systems with three degrees of freedom. For black holes with two work terms we obtain nine equations instead of two to be satisfied at the critical point of a second order phase transition. We finally generalize this method to a system with an arbitrary number of degrees of freedom and found there is $\frac{N(N+1)^{2}}{2}$ equations to be satisfied at the point of a second order phase transition where $N$ is number of work terms in the first law of thermodynamics. |
2209.02426 | Maria Petronikolou | Shreya Banerjee, Maria Petronikolou and Emmanuel N. Saridakis | Alleviating $H_0$ Tension with New Gravitational Scalar Tensor Theories | 9 pages, 7 figures, version to appear in Phys.Rev.D | null | 10.1103/PhysRevD.108.024012 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the cosmological applications of new gravitational
scalar-tensor theories and we analyze them in the light of $H_0$ tension. In
these theories the Lagrangian contains the Ricci scalar and its first and
second derivatives in a specific combination that makes them free of ghosts,
thus corresponding to healthy bi-scalar extensions of general relativity. We
examine two specific models, and for particular choices of the model parameters
we find that the effect of the additional terms is negligible at high
redshifts, obtaining a coincidence with $\Lambda$CDM cosmology, however as time
passes the deviation increases and thus at low redshifts the Hubble parameter
acquires increased values ($H_0\approx 74 km/s/Mpc$) in a controlled way. The
mechanism behind this behavior is the fact that the effective dark-energy
equation-of-state parameter exhibits phantom behavior, which implies faster
expansion, which is one of the theoretical requirements that are capable of
alleviating the $H_0$ tension. Lastly, we confront the models with Cosmic
Chronometer (CC) data showing full agreement within 1$\sigma$ confidence level.
| [
{
"created": "Tue, 6 Sep 2022 11:49:31 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Jun 2023 14:49:20 GMT",
"version": "v2"
}
] | 2023-07-19 | [
[
"Banerjee",
"Shreya",
""
],
[
"Petronikolou",
"Maria",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] | We investigate the cosmological applications of new gravitational scalar-tensor theories and we analyze them in the light of $H_0$ tension. In these theories the Lagrangian contains the Ricci scalar and its first and second derivatives in a specific combination that makes them free of ghosts, thus corresponding to healthy bi-scalar extensions of general relativity. We examine two specific models, and for particular choices of the model parameters we find that the effect of the additional terms is negligible at high redshifts, obtaining a coincidence with $\Lambda$CDM cosmology, however as time passes the deviation increases and thus at low redshifts the Hubble parameter acquires increased values ($H_0\approx 74 km/s/Mpc$) in a controlled way. The mechanism behind this behavior is the fact that the effective dark-energy equation-of-state parameter exhibits phantom behavior, which implies faster expansion, which is one of the theoretical requirements that are capable of alleviating the $H_0$ tension. Lastly, we confront the models with Cosmic Chronometer (CC) data showing full agreement within 1$\sigma$ confidence level. |
2006.09716 | Dirk Puetzfeld | Gerald Neumann, Dirk Puetzfeld, Guillermo F. Rubilar | Extended gravitational clock compass: new exact solutions and
simulations | 20 pages, 18 figures | Phys. Rev. D 102, 044027 (2020) | 10.1103/PhysRevD.102.044027 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By extending the framework of the gravitational clock compass we show how a
suitably prepared set of clocks can be used to extract information about the
gravitational field in the context of General Relativity. Conceptual
differences between the extended and the standard clock compass are
highlighted. Particular attention is paid to the influence of kinematic
quantities on the measurement process and the setup of the compass.
Additionally, we present results of simulations of the inference process for
the acceleration and the curvature components. Several examples of different
strategies for the computation of the posterior probability distributions of
the curvature components are discussed. This allows us to anticipate the
precision with which physical quantities could be determined in a realistic
measurement.
| [
{
"created": "Wed, 17 Jun 2020 08:30:57 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Aug 2020 09:00:04 GMT",
"version": "v2"
}
] | 2020-08-21 | [
[
"Neumann",
"Gerald",
""
],
[
"Puetzfeld",
"Dirk",
""
],
[
"Rubilar",
"Guillermo F.",
""
]
] | By extending the framework of the gravitational clock compass we show how a suitably prepared set of clocks can be used to extract information about the gravitational field in the context of General Relativity. Conceptual differences between the extended and the standard clock compass are highlighted. Particular attention is paid to the influence of kinematic quantities on the measurement process and the setup of the compass. Additionally, we present results of simulations of the inference process for the acceleration and the curvature components. Several examples of different strategies for the computation of the posterior probability distributions of the curvature components are discussed. This allows us to anticipate the precision with which physical quantities could be determined in a realistic measurement. |
1901.09899 | Francisco Jos\'e Maldonado Torralba | J.A.R. Cembranos, J. Gigante Valcarcel, F.J. Maldonado Torralba | Non-geodesic incompleteness in Poincar\'e gauge gravity | 9 pages, 2 figures. Invited article for the Special Issue of Entropy
"Modified Gravity: From Black Holes Entropy to Current Cosmology II". arXiv
admin note: text overlap with arXiv:1609.07814 | Entropy 2019, 21(3), 280 | 10.3390/e21030280 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we review the study of singularities in Poincar\'e gauge
theories of gravity. Since one of the most recent studies uses the appearance
of black hole regions of arbitrary dimension as an indicator of singular
behaviour, we also give some explicit examples of these structures and study
how particles behave around them.
| [
{
"created": "Sun, 27 Jan 2019 15:24:58 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Mar 2019 10:30:52 GMT",
"version": "v2"
}
] | 2019-03-21 | [
[
"Cembranos",
"J. A. R.",
""
],
[
"Valcarcel",
"J. Gigante",
""
],
[
"Torralba",
"F. J. Maldonado",
""
]
] | In this work we review the study of singularities in Poincar\'e gauge theories of gravity. Since one of the most recent studies uses the appearance of black hole regions of arbitrary dimension as an indicator of singular behaviour, we also give some explicit examples of these structures and study how particles behave around them. |
gr-qc/9501023 | null | Dieter R. Brill (University of Maryland) | Black Hole Collisions, Analytic Continuation, and Cosmic Censorship | Misprints corrected, some Figures (LaTeX picture environment) made
even more beautiful, References added. This is the text of lectures at the
First Samos Meeting on Cosmology Geometry and Relativity, to appear in
Springer Lecture Notes in Physics. | null | null | UMD PP 95-88 | gr-qc | null | Exact solutions of the Einstein-Maxwell equations that describe moving black
holes in a cosmological setting are discussed with the aim of discovering the
global structure and testing cosmic censorship. Continuation beyond the
horizons present in these solutions is necessary in order to identify the
global structure. Therefore the possibilities and methods of analytic extension
of geometries are briefly reviewed. The global structure of the
Reissner-Nordstr\"om-de Sitter geometry is found by these methods. When several
black holes are present, the exact solution is no longer everywhere analytic,
but less smooth extensions satisfying the Einstein equations everywhere are
possible. Some of these provide counterexamples to cosmic censorship.
| [
{
"created": "Fri, 20 Jan 1995 17:45:27 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Mar 1995 22:47:44 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Brill",
"Dieter R.",
"",
"University of Maryland"
]
] | Exact solutions of the Einstein-Maxwell equations that describe moving black holes in a cosmological setting are discussed with the aim of discovering the global structure and testing cosmic censorship. Continuation beyond the horizons present in these solutions is necessary in order to identify the global structure. Therefore the possibilities and methods of analytic extension of geometries are briefly reviewed. The global structure of the Reissner-Nordstr\"om-de Sitter geometry is found by these methods. When several black holes are present, the exact solution is no longer everywhere analytic, but less smooth extensions satisfying the Einstein equations everywhere are possible. Some of these provide counterexamples to cosmic censorship. |
1810.06193 | I-Ching Yang | I-Ching Yang | The energy of the universe in the Bianchi type-II cosmological model | 8 pages | null | 10.1142/S021773231950192X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To investigate the energy of Bianchi type-II cosmological model, I used the
energy-momentum complexes of Einstein and M{\o}ller and obtained the zero total
energy in these two prescriptions. This result reinforces the viewpoint of
Albrow and Tryon that the universe must have a zero net value for all conserved
quantities and be equivalent to the previous works of Nester et al. and Aydogdu
et al.
| [
{
"created": "Mon, 15 Oct 2018 06:24:14 GMT",
"version": "v1"
}
] | 2019-08-21 | [
[
"Yang",
"I-Ching",
""
]
] | To investigate the energy of Bianchi type-II cosmological model, I used the energy-momentum complexes of Einstein and M{\o}ller and obtained the zero total energy in these two prescriptions. This result reinforces the viewpoint of Albrow and Tryon that the universe must have a zero net value for all conserved quantities and be equivalent to the previous works of Nester et al. and Aydogdu et al. |
2006.03771 | Chengjie Fu | Chengjie Fu, Jing Liu, Tao Zhu, Hongwei Yu, Puxun Wu | Resonance instability of primordial gravitational waves during inflation
in Chern-Simons gravity | 16 pages, 4 figures | Eur. Phys. J. C 81 (2021) 3, 204 | 10.1140/epjc/s10052-021-09001-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate axion inflation where the gravitational Chern-Simons term is
coupled to a periodic function of the inflaton. We find that tensor
perturbations with different polarizations are amplified in different ways by
the Chern-Simons coupling. Depending on the model parameters, the resonance
amplification results in a parity-violating peak or a board plateau in the
energy spectrum of gravitational waves, and the sharp cutoff in the infrared
region constitutes a characteristic distinguishable from stochastic
gravitational wave backgrounds produced by matter fields in Einstein gravity.
| [
{
"created": "Sat, 6 Jun 2020 03:32:07 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Jun 2020 02:11:37 GMT",
"version": "v2"
},
{
"created": "Sat, 25 Jul 2020 10:25:26 GMT",
"version": "v3"
},
{
"created": "Mon, 8 Mar 2021 05:02:12 GMT",
"version": "v4"
}
] | 2021-03-09 | [
[
"Fu",
"Chengjie",
""
],
[
"Liu",
"Jing",
""
],
[
"Zhu",
"Tao",
""
],
[
"Yu",
"Hongwei",
""
],
[
"Wu",
"Puxun",
""
]
] | We investigate axion inflation where the gravitational Chern-Simons term is coupled to a periodic function of the inflaton. We find that tensor perturbations with different polarizations are amplified in different ways by the Chern-Simons coupling. Depending on the model parameters, the resonance amplification results in a parity-violating peak or a board plateau in the energy spectrum of gravitational waves, and the sharp cutoff in the infrared region constitutes a characteristic distinguishable from stochastic gravitational wave backgrounds produced by matter fields in Einstein gravity. |
0912.2447 | B. V. Ivanov | B.V.Ivanov | The fundamental spherically symmetric fluid model | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that an effective anisotropic spherically symmetric fluid model
with heat flow can absorb the addition to a perfect fluid of pressure
anisotropy, heat flow, bulk and shear viscosity, electric field and null fluid.
| [
{
"created": "Sat, 12 Dec 2009 19:16:01 GMT",
"version": "v1"
}
] | 2009-12-15 | [
[
"Ivanov",
"B. V.",
""
]
] | It is shown that an effective anisotropic spherically symmetric fluid model with heat flow can absorb the addition to a perfect fluid of pressure anisotropy, heat flow, bulk and shear viscosity, electric field and null fluid. |
gr-qc/0508110 | Frans Pretorius | Frans Pretorius and Matthew W. Choptuik | Adaptive Mesh Refinement for Coupled Elliptic-Hyperbolic Systems | 31 pages, 15 figures; replaced with published version | J.Comput.Phys. 218 (2006) 246-274 | 10.1016/j.jcp.2006.02.011 | null | gr-qc | null | We present a modification to the Berger and Oliger adaptive mesh refinement
algorithm designed to solve systems of coupled, non-linear, hyperbolic and
elliptic partial differential equations. Such systems typically arise during
constrained evolution of the field equations of general relativity. The novel
aspect of this algorithm is a technique of "extrapolation and delayed solution"
used to deal with the non-local nature of the solution of the elliptic
equations, driven by dynamical sources, within the usual Berger and Oliger
time-stepping framework. We show empirical results demonstrating the
effectiveness of this technique in axisymmetric gravitational collapse
simulations. We also describe several other details of the code, including
truncation error estimation using a self-shadow hierarchy, and the
refinement-boundary interpolation operators that are used to help suppress
spurious high-frequency solution components ("noise").
| [
{
"created": "Sun, 28 Aug 2005 19:46:50 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Aug 2006 13:41:43 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Pretorius",
"Frans",
""
],
[
"Choptuik",
"Matthew W.",
""
]
] | We present a modification to the Berger and Oliger adaptive mesh refinement algorithm designed to solve systems of coupled, non-linear, hyperbolic and elliptic partial differential equations. Such systems typically arise during constrained evolution of the field equations of general relativity. The novel aspect of this algorithm is a technique of "extrapolation and delayed solution" used to deal with the non-local nature of the solution of the elliptic equations, driven by dynamical sources, within the usual Berger and Oliger time-stepping framework. We show empirical results demonstrating the effectiveness of this technique in axisymmetric gravitational collapse simulations. We also describe several other details of the code, including truncation error estimation using a self-shadow hierarchy, and the refinement-boundary interpolation operators that are used to help suppress spurious high-frequency solution components ("noise"). |
1108.0832 | Carlo Rovelli | Carlo Rovelli | On the structure of a background independent quantum theory: Hamilton
function, transition amplitudes, classical limit and continuous limit | 7 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hamilton function is a powerful tool for studying the classical limit of
quantum systems, which remains meaningful in background-independent systems. In
quantum gravity, it clarifies the physical interpretation of the transitions
amplitudes and their truncations.
| [
{
"created": "Wed, 3 Aug 2011 12:41:08 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Aug 2011 10:20:25 GMT",
"version": "v2"
}
] | 2011-08-05 | [
[
"Rovelli",
"Carlo",
""
]
] | The Hamilton function is a powerful tool for studying the classical limit of quantum systems, which remains meaningful in background-independent systems. In quantum gravity, it clarifies the physical interpretation of the transitions amplitudes and their truncations. |
1603.05689 | David Kubiznak | Devin Hansen, David Kubiznak, Robert B. Mann | Universality of P-V Criticality in Horizon Thermodynamics | 11 pages, 5 figures | null | 10.1007/JHEP01(2017)047 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study P-V criticality of black holes in Lovelock gravities in the context
of horizon thermodynamics. The corresponding first law of horizon
thermodynamics emerges as one of the Einstein-Lovelock equations and assumes
the universal (independent of matter content) form dE=TdS-PdV, where P is
identified with the total pressure of all matter in the spacetime (including a
cosmological constant Lambda if present). We compare this approach to recent
advances in extended phase space thermodynamics of asymptotically AdS black
holes where the "standard" first law of black hole thermodynamics is extended
to include a pressure-volume term, where the pressure is entirely due to the
(variable) cosmological constant. We show that both approaches are quite
different in interpretation. Provided there is sufficient non-linearity in the
gravitational sector, we find that horizon thermodynamics admits the same
interesting black hole phase behaviour seen in the extended case, such as a
Hawking-Page transition, Van der Waals like behaviour, and the presence of a
triple point. We also formulate the Smarr formula in horizon thermodynamics and
discuss the interpretation of the quantity E appearing in the horizon first
law.
| [
{
"created": "Thu, 17 Mar 2016 21:08:05 GMT",
"version": "v1"
}
] | 2017-02-01 | [
[
"Hansen",
"Devin",
""
],
[
"Kubiznak",
"David",
""
],
[
"Mann",
"Robert B.",
""
]
] | We study P-V criticality of black holes in Lovelock gravities in the context of horizon thermodynamics. The corresponding first law of horizon thermodynamics emerges as one of the Einstein-Lovelock equations and assumes the universal (independent of matter content) form dE=TdS-PdV, where P is identified with the total pressure of all matter in the spacetime (including a cosmological constant Lambda if present). We compare this approach to recent advances in extended phase space thermodynamics of asymptotically AdS black holes where the "standard" first law of black hole thermodynamics is extended to include a pressure-volume term, where the pressure is entirely due to the (variable) cosmological constant. We show that both approaches are quite different in interpretation. Provided there is sufficient non-linearity in the gravitational sector, we find that horizon thermodynamics admits the same interesting black hole phase behaviour seen in the extended case, such as a Hawking-Page transition, Van der Waals like behaviour, and the presence of a triple point. We also formulate the Smarr formula in horizon thermodynamics and discuss the interpretation of the quantity E appearing in the horizon first law. |
gr-qc/0512044 | Michael Maziashvili | M. T. Makhviladze, M. A. Maziashvili and D. V. Nozadze | GUP in presence of extra dimensions and lifetime of mini black holes | 4 pages | null | null | null | gr-qc | null | Based on the general considerations of quantum mechanics and gravity the
generalized uncertainty principle (GUP) is determined in higher-dimensional
case and on the brane, respectively. The result is used to evaluate the effect
of GUP on the dynamics of evaporation and lifetime of mini black holes in the
brane-world models.
| [
{
"created": "Wed, 7 Dec 2005 08:24:12 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Dec 2005 13:09:00 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Makhviladze",
"M. T.",
""
],
[
"Maziashvili",
"M. A.",
""
],
[
"Nozadze",
"D. V.",
""
]
] | Based on the general considerations of quantum mechanics and gravity the generalized uncertainty principle (GUP) is determined in higher-dimensional case and on the brane, respectively. The result is used to evaluate the effect of GUP on the dynamics of evaporation and lifetime of mini black holes in the brane-world models. |
2307.13380 | Soichiro Morisaki | Soichiro Morisaki, Rory Smith, Leo Tsukada, Surabhi Sachdev, Simon
Stevenson, Colm Talbot, Aaron Zimmerman | Rapid localization and inference on compact binary coalescences with the
Advanced LIGO-Virgo-KAGRA gravitational-wave detector network | 19 pages, 9 figures | null | null | null | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a rapid parameter estimation framework for compact binary
coalescence (CBC) signals observed by the LIGO-Virgo-KAGRA (LVK) detector
network. The goal of our framework is to enable optimal source localization of
binary neutron star (BNS) signals in low latency, as well as improve the
overall scalability of full CBC parameter estimation analyses. Our framework is
based on the reduced order quadrature (ROQ) technique, and resolves its
shortcomings by utilizing multiple ROQ bases in a single parameter estimation
run. We have also developed sets of compact ROQ bases for various waveform
models, IMRPhenomD, IMRPhenomPv2, IMRPhenomPv2$\_$NRTidalv2, and IMRPhenomXPHM.
We benchmark our framework with hundreds of simulated observations of BNS
signals by the LIGO-Virgo detector network, and demonstrate that it provides
accurate and unbiased estimates on BNS source location, with a median analysis
time of $6$ minutes. The median searched area is reduced by around 30$\%$
compared to estimates produced by BAYESTAR: from $21.8\,\mathrm{deg^2}$ to
$16.6\,\mathrm{deg^2}$. Our framework also enables detailed parameter
estimation taking into account gravitational-wave higher multipole moments, the
tidal deformation of colliding objects, and detector calibration errors of
amplitude and phase with the time scale of hours. Our rapid parameter
estimation technique has been implemented in one of the LVK parameter
estimation engines, BILBY, and is being employed by the automated parameter
estimation analysis of the LVK alert system.
| [
{
"created": "Tue, 25 Jul 2023 10:01:38 GMT",
"version": "v1"
}
] | 2023-07-26 | [
[
"Morisaki",
"Soichiro",
""
],
[
"Smith",
"Rory",
""
],
[
"Tsukada",
"Leo",
""
],
[
"Sachdev",
"Surabhi",
""
],
[
"Stevenson",
"Simon",
""
],
[
"Talbot",
"Colm",
""
],
[
"Zimmerman",
"Aaron",
""
]
] | We present a rapid parameter estimation framework for compact binary coalescence (CBC) signals observed by the LIGO-Virgo-KAGRA (LVK) detector network. The goal of our framework is to enable optimal source localization of binary neutron star (BNS) signals in low latency, as well as improve the overall scalability of full CBC parameter estimation analyses. Our framework is based on the reduced order quadrature (ROQ) technique, and resolves its shortcomings by utilizing multiple ROQ bases in a single parameter estimation run. We have also developed sets of compact ROQ bases for various waveform models, IMRPhenomD, IMRPhenomPv2, IMRPhenomPv2$\_$NRTidalv2, and IMRPhenomXPHM. We benchmark our framework with hundreds of simulated observations of BNS signals by the LIGO-Virgo detector network, and demonstrate that it provides accurate and unbiased estimates on BNS source location, with a median analysis time of $6$ minutes. The median searched area is reduced by around 30$\%$ compared to estimates produced by BAYESTAR: from $21.8\,\mathrm{deg^2}$ to $16.6\,\mathrm{deg^2}$. Our framework also enables detailed parameter estimation taking into account gravitational-wave higher multipole moments, the tidal deformation of colliding objects, and detector calibration errors of amplitude and phase with the time scale of hours. Our rapid parameter estimation technique has been implemented in one of the LVK parameter estimation engines, BILBY, and is being employed by the automated parameter estimation analysis of the LVK alert system. |
gr-qc/9808067 | Rong Gen Cai | Rong-Gen Cai, Kwang-Sup Soh (SNU) | Topological black holes in the dimensionally continued gravity | Revtex, 20 Pages, no figures, minor modification and two references
added | Phys.Rev.D59:044013,1999 | 10.1103/PhysRevD.59.044013 | null | gr-qc | null | We investigate the topological black holes in a special class of Lovelock
gravity. In the odd dimensions, the action is the Chern-Simons form for the
anti-de Sitter group. In the even dimensions, it is the Euler density
constructed with the Lorentz part of the anti-de Sitter curvature tensor. The
Lovelock coefficients are reduced to two independent parameters: cosmological
constant and gravitational constant. The event horizons of these topological
black holes may have constant positive, zero or negative curvature. Their
thermodynamics is analyzed and electrically charged topological black holes are
also considered. We emphasize the differences due to the different curvatures
of event horizons. As a comparison, we also discuss the topological black holes
in the higher dimensional Einstein-Maxwell theory with a negative cosmological
constant.
| [
{
"created": "Tue, 25 Aug 1998 13:32:24 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Aug 1998 10:42:12 GMT",
"version": "v2"
}
] | 2009-07-09 | [
[
"Cai",
"Rong-Gen",
"",
"SNU"
],
[
"Soh",
"Kwang-Sup",
"",
"SNU"
]
] | We investigate the topological black holes in a special class of Lovelock gravity. In the odd dimensions, the action is the Chern-Simons form for the anti-de Sitter group. In the even dimensions, it is the Euler density constructed with the Lorentz part of the anti-de Sitter curvature tensor. The Lovelock coefficients are reduced to two independent parameters: cosmological constant and gravitational constant. The event horizons of these topological black holes may have constant positive, zero or negative curvature. Their thermodynamics is analyzed and electrically charged topological black holes are also considered. We emphasize the differences due to the different curvatures of event horizons. As a comparison, we also discuss the topological black holes in the higher dimensional Einstein-Maxwell theory with a negative cosmological constant. |
1204.4339 | John Baez | John C. Baez and Derek K. Wise | Teleparallel Gravity as a Higher Gauge Theory | 36 pages; v3: minor corrections | Communications in Mathematical Physics, Vol. 333 No. 1 (2015),
153-186 | 10.1007/s00220-014-2178-7 | null | gr-qc math.CT math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that general relativity can be viewed as a higher gauge theory
involving a categorical group, or 2-group, called the teleparallel 2-group. On
any semi-Riemannian manifold M, we first construct a principal 2-bundle with
the Poincare 2-group as its structure 2-group. Any flat metric-preserving
connection on M gives a flat 2-connection on this 2-bundle, and the key
ingredient of this 2-connection is the torsion. Conversely, every flat strict
2-connection on this 2-bundle arises in this way if M is simply connected and
has vanishing 2nd deRham cohomology. Extending from the Poincare 2-group to the
teleparallel 2-group, a 2-connection includes an additional piece: a coframe
field. Taking advantage of the teleparallel reformulation of general
relativity, which uses a coframe field, a flat connection and its torsion, this
lets us rewrite general relativity as a theory with a 2-connection for the
teleparallel 2-group as its only field.
| [
{
"created": "Thu, 19 Apr 2012 12:48:47 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Jun 2012 12:16:14 GMT",
"version": "v2"
},
{
"created": "Thu, 17 Jul 2014 02:26:04 GMT",
"version": "v3"
}
] | 2017-08-22 | [
[
"Baez",
"John C.",
""
],
[
"Wise",
"Derek K.",
""
]
] | We show that general relativity can be viewed as a higher gauge theory involving a categorical group, or 2-group, called the teleparallel 2-group. On any semi-Riemannian manifold M, we first construct a principal 2-bundle with the Poincare 2-group as its structure 2-group. Any flat metric-preserving connection on M gives a flat 2-connection on this 2-bundle, and the key ingredient of this 2-connection is the torsion. Conversely, every flat strict 2-connection on this 2-bundle arises in this way if M is simply connected and has vanishing 2nd deRham cohomology. Extending from the Poincare 2-group to the teleparallel 2-group, a 2-connection includes an additional piece: a coframe field. Taking advantage of the teleparallel reformulation of general relativity, which uses a coframe field, a flat connection and its torsion, this lets us rewrite general relativity as a theory with a 2-connection for the teleparallel 2-group as its only field. |
gr-qc/0001022 | Victor Flambaum | V. V. Flambaum and J. C. Berengut | Atom made from charged elementary black hole | 22 pages, 4 figures | Phys.Rev.D63:084010,2001 | 10.1103/PhysRevD.63.084010 | null | gr-qc astro-ph hep-th physics.atom-ph | null | It is believed that there may have been a large number of black holes formed
in the very early universe. These would have quantised masses. A charged
``elementary black hole'' (with the minimum possible mass) can capture
electrons, protons and other charged particles to form a ``black hole atom''.
We find the spectrum of such an object with a view to laboratory and
astronomical observation of them, and estimate the lifetime of the bound
states. There is no limit to the charge of the black hole, which gives us the
possibility of observing Z>137 bound states and transitions at the lower
continuum. Negatively charged black holes can capture protons. For Z>1, the
orbiting protons will coalesce to form a nucleus (after beta-decay of some
protons to neutrons), with a stability curve different to that of free nuclei.
In this system there is also the distinct possibility of single quark capture.
This leads to the formation of a coloured black hole that plays the role of an
extremely heavy quark interacting strongly with the other two quarks. Finally
we consider atoms formed with much larger black holes.
| [
{
"created": "Mon, 10 Jan 2000 21:38:49 GMT",
"version": "v1"
}
] | 2009-08-18 | [
[
"Flambaum",
"V. V.",
""
],
[
"Berengut",
"J. C.",
""
]
] | It is believed that there may have been a large number of black holes formed in the very early universe. These would have quantised masses. A charged ``elementary black hole'' (with the minimum possible mass) can capture electrons, protons and other charged particles to form a ``black hole atom''. We find the spectrum of such an object with a view to laboratory and astronomical observation of them, and estimate the lifetime of the bound states. There is no limit to the charge of the black hole, which gives us the possibility of observing Z>137 bound states and transitions at the lower continuum. Negatively charged black holes can capture protons. For Z>1, the orbiting protons will coalesce to form a nucleus (after beta-decay of some protons to neutrons), with a stability curve different to that of free nuclei. In this system there is also the distinct possibility of single quark capture. This leads to the formation of a coloured black hole that plays the role of an extremely heavy quark interacting strongly with the other two quarks. Finally we consider atoms formed with much larger black holes. |
1110.4051 | Sebastian Steinhaus | Sebastian Steinhaus | Perfect discretization of path integrals | 4 pages, 1 figure, based on a talk given at Loops '11, Madrid, to
appear in Journal of Physics: Conference Series (JPCS) | J. Phys.: Conf. Ser. 360 012025 (2012) | 10.1088/1742-6596/360/1/012025 | null | gr-qc hep-lat | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In order to obtain a well-defined path integral one often employs
discretizations. In the case of General Relativity these generically break
diffeomorphism symmetry, which has severe consequences since these symmetries
determine the dynamics of the corresponding system.
In this article we consider the path integral of reparametrization invariant
systems as a toy example and present an improvement procedure for the
discretized propagator. Fixed points and convergence of the procedure are
discussed. Furthermore we show that a reparametrization invariant path integral
implies discretization independence and acts as a projector onto physical
states.
| [
{
"created": "Tue, 18 Oct 2011 17:03:02 GMT",
"version": "v1"
}
] | 2012-05-24 | [
[
"Steinhaus",
"Sebastian",
""
]
] | In order to obtain a well-defined path integral one often employs discretizations. In the case of General Relativity these generically break diffeomorphism symmetry, which has severe consequences since these symmetries determine the dynamics of the corresponding system. In this article we consider the path integral of reparametrization invariant systems as a toy example and present an improvement procedure for the discretized propagator. Fixed points and convergence of the procedure are discussed. Furthermore we show that a reparametrization invariant path integral implies discretization independence and acts as a projector onto physical states. |
gr-qc/0312078 | Jiliang Jing | Jiliang Jing | Can the "brick wall" model present the same results in different
coordinate representations? | 8 pages, Phys. Rev. D in press | Phys.Rev. D69 (2004) 024011 | 10.1103/PhysRevD.69.024011 | null | gr-qc astro-ph hep-th | null | By using the 't Hooft's "brick wall" model and the Pauli-Villars
regularization scheme we calculate the statistical-mechanical entropies arising
from the quantum scalar field in different coordinate settings, such as the
Painlev\'{e} and Lemaitre coordinates. At first glance, it seems that the
entropies would be different from that in the standard Schwarzschild coordinate
since the metrics in both the Painlev\'{e} and Lemaitre coordinates do not
possess the singularity at the event horizon as that in the Schwarzschild-like
coordinate. However, after an exact calculation we find that, up to the
subleading correction, the statistical-mechanical entropies in these
coordinates are equivalent to that in the Schwarzschild-like coordinate. The
result is not only valid for black holes and de Sitter spaces, but also for the
case that the quantum field exerts back reaction on the gravitational field
provided that the back reaction does not alter the symmetry of the spacetime.
| [
{
"created": "Wed, 17 Dec 2003 14:22:05 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Jing",
"Jiliang",
""
]
] | By using the 't Hooft's "brick wall" model and the Pauli-Villars regularization scheme we calculate the statistical-mechanical entropies arising from the quantum scalar field in different coordinate settings, such as the Painlev\'{e} and Lemaitre coordinates. At first glance, it seems that the entropies would be different from that in the standard Schwarzschild coordinate since the metrics in both the Painlev\'{e} and Lemaitre coordinates do not possess the singularity at the event horizon as that in the Schwarzschild-like coordinate. However, after an exact calculation we find that, up to the subleading correction, the statistical-mechanical entropies in these coordinates are equivalent to that in the Schwarzschild-like coordinate. The result is not only valid for black holes and de Sitter spaces, but also for the case that the quantum field exerts back reaction on the gravitational field provided that the back reaction does not alter the symmetry of the spacetime. |
2006.10077 | Andrey Shoom A | Andrey A. Shoom | Gravitational Faraday and Spin-Hall Effects of Light | 11 pages | Phys. Rev. D 104, 084007 (2021) | 10.1103/PhysRevD.104.084007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational Faraday and its dual spin-Hall effects of light arise in
space-times of non-zero angular momentum. These effects were studied in
stationary, asymptotically flat space-times. Here we study these effects in
arbitrary, non-stationary, asymptotically flat space-times. These effects arise
due to interaction between light polarisation and space-time angular momentum.
As a result of such interaction, the phase velocity of left- and right-handed
circularly polarised light becomes different, that results in the gravitational
Faraday effect. This difference implies different dynamics of these components,
that begin to propagate along different paths\textemdash the gravitational
spin-Hall effect of light. Due to this effect, the gravitational field splits a
multicomponent beam of unpolarized light and produces polarized gravitational
rainbow. The component separation is an accumulative effect observed in long
range asymptotics. To study this effect, we construct uniform eikonal expansion
and derive dynamical equation describing this effect. To analyse the dynamical
equation, we present it in the local space and time decomposition form. The
spatial part of the equation presented in the related optical metric is
analogous to the dynamical equation of a charged particle moving in magnetic
field under influence of the Coriolis force.
| [
{
"created": "Wed, 17 Jun 2020 18:01:13 GMT",
"version": "v1"
}
] | 2021-10-04 | [
[
"Shoom",
"Andrey A.",
""
]
] | The gravitational Faraday and its dual spin-Hall effects of light arise in space-times of non-zero angular momentum. These effects were studied in stationary, asymptotically flat space-times. Here we study these effects in arbitrary, non-stationary, asymptotically flat space-times. These effects arise due to interaction between light polarisation and space-time angular momentum. As a result of such interaction, the phase velocity of left- and right-handed circularly polarised light becomes different, that results in the gravitational Faraday effect. This difference implies different dynamics of these components, that begin to propagate along different paths\textemdash the gravitational spin-Hall effect of light. Due to this effect, the gravitational field splits a multicomponent beam of unpolarized light and produces polarized gravitational rainbow. The component separation is an accumulative effect observed in long range asymptotics. To study this effect, we construct uniform eikonal expansion and derive dynamical equation describing this effect. To analyse the dynamical equation, we present it in the local space and time decomposition form. The spatial part of the equation presented in the related optical metric is analogous to the dynamical equation of a charged particle moving in magnetic field under influence of the Coriolis force. |
1612.00482 | Riccardo Sturani | Stefano Foffa (Geneva U., Dept. Theor. Phys. and Geneva U., CAP),
Pierpaolo Mastrolia (Padua U. and INFN, Padua), Riccardo Sturani (IIP,
Natal), Christian Sturm (Wurzburg U.) | Effective field theory approach to the gravitational two-body dynamics,
at fourth post-Newtonian order and quintic in the Newton constant | Version accepted for publication in Phys. Rev. D. Appendix C added
with details of amplitude computations | Phys. Rev. D 95, 104009 (2017) | 10.1103/PhysRevD.95.104009 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Working within the post-Newtonian (PN) approximation to General Relativity,
we use the effective field theory (EFT) framework to study the conservative
dynamics of the two-body motion at fourth PN order, at fifth order in the
Newton constant. This is one of the missing pieces preventing the computation
of the full Lagrangian at fourth PN order using EFT methods. We exploit the
analogy between diagrams in the EFT gravitational theory and 2-point functions
in massless gauge theory, to address the calculation of 4-loop amplitudes by
means of standard multi-loop diagrammatic techniques. For those terms which can
be directly compared, our result confirms the findings of previous studies,
performed using different methods.
| [
{
"created": "Thu, 1 Dec 2016 21:41:14 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Jan 2017 22:35:24 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Mar 2017 12:42:56 GMT",
"version": "v3"
}
] | 2017-05-17 | [
[
"Foffa",
"Stefano",
"",
"Geneva U., Dept. Theor. Phys. and Geneva U., CAP"
],
[
"Mastrolia",
"Pierpaolo",
"",
"Padua U. and INFN, Padua"
],
[
"Sturani",
"Riccardo",
"",
"IIP,\n Natal"
],
[
"Sturm",
"Christian",
"",
"Wurzburg U."
]
] | Working within the post-Newtonian (PN) approximation to General Relativity, we use the effective field theory (EFT) framework to study the conservative dynamics of the two-body motion at fourth PN order, at fifth order in the Newton constant. This is one of the missing pieces preventing the computation of the full Lagrangian at fourth PN order using EFT methods. We exploit the analogy between diagrams in the EFT gravitational theory and 2-point functions in massless gauge theory, to address the calculation of 4-loop amplitudes by means of standard multi-loop diagrammatic techniques. For those terms which can be directly compared, our result confirms the findings of previous studies, performed using different methods. |
1409.3395 | Christian Marinoni | Christian Marinoni and Heinrich Steigerwald (Aix-Marseille University) | On the dynamical emergence of de Sitter spacetime | 17 pages, 2 figures | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present and discuss an asynchronous coordinate system covering de Sitter
spacetime, notably in a complete way in 1+1 dimensions. The new coordinates
have several interesting cosmological properties: the worldlines of comoving
($x^i=const$) observers are geodesics, cosmic time is finite in the past, and
the coordinates asymptotically tend to that of a flat Robertson & Walker model
at large times. This analysis also provides an argument in favor of the natural
emergence of an equation of state of the type $p=-\rho$ in the context of the
standard cosmological model.
| [
{
"created": "Thu, 11 Sep 2014 11:24:40 GMT",
"version": "v1"
}
] | 2014-09-12 | [
[
"Marinoni",
"Christian",
"",
"Aix-Marseille University"
],
[
"Steigerwald",
"Heinrich",
"",
"Aix-Marseille University"
]
] | We present and discuss an asynchronous coordinate system covering de Sitter spacetime, notably in a complete way in 1+1 dimensions. The new coordinates have several interesting cosmological properties: the worldlines of comoving ($x^i=const$) observers are geodesics, cosmic time is finite in the past, and the coordinates asymptotically tend to that of a flat Robertson & Walker model at large times. This analysis also provides an argument in favor of the natural emergence of an equation of state of the type $p=-\rho$ in the context of the standard cosmological model. |
1701.00037 | Harold Erbin | Harold Erbin | Janis-Newman algorithm: generating rotating and NUT charged black holes | 68 pages, invited review for Universe; v2: sec. 1-4, 6 and app. B
match published version, sec. 5, 7, 8 and app. A, C are specific to arxiv
version | Universe 2017, 3(1), 19 | 10.3390/universe3010019 | LPTENS/17/02 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this review we present the most general form of the Janis--Newman
algorithm. This extension allows to generate configurations which contain all
bosonic fields with spin less than or equal to two (real and complex scalar
fields, gauge fields, metric field) and with five of the six parameters of the
Pleba\'nski-Demia\'nski metric (mass, electric charge, magnetic charge, NUT
charge and angular momentum). Several examples are included to illustrate the
algorithm. We also discuss the extension of the algorithm to other dimensions.
| [
{
"created": "Sat, 31 Dec 2016 00:20:31 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Mar 2017 15:35:44 GMT",
"version": "v2"
}
] | 2017-03-08 | [
[
"Erbin",
"Harold",
""
]
] | In this review we present the most general form of the Janis--Newman algorithm. This extension allows to generate configurations which contain all bosonic fields with spin less than or equal to two (real and complex scalar fields, gauge fields, metric field) and with five of the six parameters of the Pleba\'nski-Demia\'nski metric (mass, electric charge, magnetic charge, NUT charge and angular momentum). Several examples are included to illustrate the algorithm. We also discuss the extension of the algorithm to other dimensions. |
1710.04544 | Ivan De Martino | Ivan De Martino, Antonio Capolupo | Kinetic theory of Jean Instability in Eddington-inspired Born-Infield
gravity | 6 pages, 3 figures. Accepted for publication in EPJC | Eur. Phys. J. C (2017) 77: 715 | 10.1140/epjc/s10052-017-5300-0 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the stability of self-gravitating systems which dynamics is
investigated using the collisionless Boltzmann equation, and the modified
Poisson equation of Eddington-inspired Born-Infield gravity. These equations
provide a description of the Jeans paradigm used to determine the critical
scale above which such systems collapse. At equilibrium, the systems are
described using the time-independent Maxwell- Boltzmann distribution function
$f_0(v)$. Considering small perturbations to this equilibrium state, we obtain
a modified dispersion relation, and we find a new characteristic scale length.
Our results indicate that the dynamics of the self-gravitating astrophysical
systems can be fully addressed in the Eddington-inspired Born-Infield gravity.
The latter modifies the Jeans instability in high densities environments while
its effects become negligible in the star formation regions.
| [
{
"created": "Thu, 12 Oct 2017 14:37:43 GMT",
"version": "v1"
}
] | 2017-10-31 | [
[
"De Martino",
"Ivan",
""
],
[
"Capolupo",
"Antonio",
""
]
] | We analyze the stability of self-gravitating systems which dynamics is investigated using the collisionless Boltzmann equation, and the modified Poisson equation of Eddington-inspired Born-Infield gravity. These equations provide a description of the Jeans paradigm used to determine the critical scale above which such systems collapse. At equilibrium, the systems are described using the time-independent Maxwell- Boltzmann distribution function $f_0(v)$. Considering small perturbations to this equilibrium state, we obtain a modified dispersion relation, and we find a new characteristic scale length. Our results indicate that the dynamics of the self-gravitating astrophysical systems can be fully addressed in the Eddington-inspired Born-Infield gravity. The latter modifies the Jeans instability in high densities environments while its effects become negligible in the star formation regions. |
1612.07077 | Janusz Garecki Prof | Janusz Garecki | Do gravitational waves carry energy-momentum? A reappraisal | 7 pages, no figures, Revtex 4, lecture delivered on Conference
"Varcosmofun'16", Szczecin, 12-17 September 2016, Szczecin, Poland, EU. arXiv
admin note: text overlap with arXiv:1306.5121, arXiv:1209.4807 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | After direct detection gravitational radiation in 2015 many authors are
publishing remakes of their old articles about this radiation. I decided to
follow this line in my Lecture delivered at the Conference "Varcosmofun'16"
(12-17 September 2016, Szczecin, Poland, EU). Namely, I have presented at this
Conference an updated summary of my past articles on gravitational radiation.
As a base for my presentation I have used mainly the article published in 2002
in Annalen der Physik \cite{Gar3} and the articles \cite{Gar4}.
In these past articles I have showed that the real gravitational waves which
possess a non-vanishing Riemann tensor always carry energy-momentum (and also
angular momentum). Our proof have used canonical superenergy and supermomentum
tensor for gravitational field in former articles and the averaged relative
energy-momentum tensor in latter. In this article we confine to the
energy-momentum only.
| [
{
"created": "Wed, 21 Dec 2016 12:39:19 GMT",
"version": "v1"
}
] | 2016-12-22 | [
[
"Garecki",
"Janusz",
""
]
] | After direct detection gravitational radiation in 2015 many authors are publishing remakes of their old articles about this radiation. I decided to follow this line in my Lecture delivered at the Conference "Varcosmofun'16" (12-17 September 2016, Szczecin, Poland, EU). Namely, I have presented at this Conference an updated summary of my past articles on gravitational radiation. As a base for my presentation I have used mainly the article published in 2002 in Annalen der Physik \cite{Gar3} and the articles \cite{Gar4}. In these past articles I have showed that the real gravitational waves which possess a non-vanishing Riemann tensor always carry energy-momentum (and also angular momentum). Our proof have used canonical superenergy and supermomentum tensor for gravitational field in former articles and the averaged relative energy-momentum tensor in latter. In this article we confine to the energy-momentum only. |
gr-qc/0701100 | Mark J. Hadley | Mark J Hadley | Classical Dark Matter | 5 pages | null | null | null | gr-qc | null | Classical particle-like solutions of field equations such as general
relativity, could account for dark matter. Such particles would not interact
quantum mechanically and would have negligible interactions apart from
gravitation. As a relic from the big bang, they would be a candidate for cold
dark matter consistent with observations.
| [
{
"created": "Wed, 17 Jan 2007 17:26:36 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hadley",
"Mark J",
""
]
] | Classical particle-like solutions of field equations such as general relativity, could account for dark matter. Such particles would not interact quantum mechanically and would have negligible interactions apart from gravitation. As a relic from the big bang, they would be a candidate for cold dark matter consistent with observations. |
1212.2901 | David Hilditch | David Hilditch, Sebastiano Bernuzzi, Marcus Thierfelder, Zhoujian Cao,
Wolfgang Tichy and Bernd Bruegmann | Compact binary evolutions with the Z4c formulation | null | Phys. Rev. D 88, 084057 (2013) | 10.1103/PhysRevD.88.084057 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Numerical relativity simulations of compact binaries with the Z4c and BSSNOK
formulations are compared. The Z4c formulation is advantageous in every case
considered. In simulations of non-vacuum spacetimes the constraint violations
due to truncation errors are between one and three orders of magnitude lower in
the Z4c evolutions. Improvements are also found in the accuracy of the computed
gravitational radiation. For equal-mass irrotational binary neutron star
evolutions we find that the absolute errors in phase and amplitude of the
waveforms can be up to a factor of four smaller. The quality of the Z4c
numerical data is also demonstrated by a remarkably accurate computation of the
ADM mass from surface integrals. For equal-mass non-spinning binary puncture
black hole evolutions we find that the absolute errors in phase and amplitude
of the waveforms can be up to a factor of two smaller. In the same evolutions
we find that away from the punctures the Hamiltonian constraint violation is
reduced by between one and two orders of magnitude. Furthermore, the utility of
gravitational radiation controlling, constraint preserving boundary conditions
for the Z4c formulation is demonstrated. The evolution of spacetimes containing
a single compact object confirm earlier results in spherical symmetry. The
boundary conditions avoid spurious and non-convergent effects present in high
resolution runs with either formulation with a more naive boundary treatment.
We conclude that Z4c is preferable to BSSNOK for the numerical solution of the
3+1 Einstein equations with the puncture gauge.
| [
{
"created": "Wed, 12 Dec 2012 17:44:15 GMT",
"version": "v1"
}
] | 2013-11-05 | [
[
"Hilditch",
"David",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Thierfelder",
"Marcus",
""
],
[
"Cao",
"Zhoujian",
""
],
[
"Tichy",
"Wolfgang",
""
],
[
"Bruegmann",
"Bernd",
""
]
] | Numerical relativity simulations of compact binaries with the Z4c and BSSNOK formulations are compared. The Z4c formulation is advantageous in every case considered. In simulations of non-vacuum spacetimes the constraint violations due to truncation errors are between one and three orders of magnitude lower in the Z4c evolutions. Improvements are also found in the accuracy of the computed gravitational radiation. For equal-mass irrotational binary neutron star evolutions we find that the absolute errors in phase and amplitude of the waveforms can be up to a factor of four smaller. The quality of the Z4c numerical data is also demonstrated by a remarkably accurate computation of the ADM mass from surface integrals. For equal-mass non-spinning binary puncture black hole evolutions we find that the absolute errors in phase and amplitude of the waveforms can be up to a factor of two smaller. In the same evolutions we find that away from the punctures the Hamiltonian constraint violation is reduced by between one and two orders of magnitude. Furthermore, the utility of gravitational radiation controlling, constraint preserving boundary conditions for the Z4c formulation is demonstrated. The evolution of spacetimes containing a single compact object confirm earlier results in spherical symmetry. The boundary conditions avoid spurious and non-convergent effects present in high resolution runs with either formulation with a more naive boundary treatment. We conclude that Z4c is preferable to BSSNOK for the numerical solution of the 3+1 Einstein equations with the puncture gauge. |
0803.3204 | Carsten Busch | C. Busch | The semiclassical stability of de Sitter spacetime | 47 pages, 3 figures | null | null | DESY 92-131, ITP-UH 9/92 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | de Sitter spacetime and Bunch-Davies vacuum are a solution to the
semiclassical Einstein-Schroedinger equations describing the evolution of
spacetime geometry and a massive scalar quantum field with arbitrary coupling
to curvature. The stability of this solution is proven by calculating the
renormalized energy momentum tensor expectation value for small spatially
homogeneous deviations from the de Sitter - Bunch-Davies system and solving the
linearized backreaction problem. A renormalization scheme is developed. All
momentum integrations are carried out analytically. The general solution is
given in terms of its Laplace transform. It contains only two artificial
instabilities: a constant gauge mode and an instability on the Planck time
scale lying outside of the scope of our semiclassical theory.
| [
{
"created": "Fri, 21 Mar 2008 18:30:16 GMT",
"version": "v1"
}
] | 2008-03-24 | [
[
"Busch",
"C.",
""
]
] | de Sitter spacetime and Bunch-Davies vacuum are a solution to the semiclassical Einstein-Schroedinger equations describing the evolution of spacetime geometry and a massive scalar quantum field with arbitrary coupling to curvature. The stability of this solution is proven by calculating the renormalized energy momentum tensor expectation value for small spatially homogeneous deviations from the de Sitter - Bunch-Davies system and solving the linearized backreaction problem. A renormalization scheme is developed. All momentum integrations are carried out analytically. The general solution is given in terms of its Laplace transform. It contains only two artificial instabilities: a constant gauge mode and an instability on the Planck time scale lying outside of the scope of our semiclassical theory. |
1507.03175 | V H Satheeshkumar | V. H. Satheeshkumar | Aspects of Black Holes in Gravitational Theories with Broken Lorentz and
Diffeomorphism Symmetries | XIV+147 pages, 19 figures, PhD Thesis, Baylor University | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | Since Stephen Hawking discovered that black holes emit thermal radiation,
black holes have become the theoretical laboratories for testing our ideas on
quantum gravity. This dissertation is devoted to the study of singularities,
the formation of black holes by gravitational collapse and the global structure
of spacetime. All our investigations are in the context of a recently proposed
approach to quantum gravity, which breaks Lorentz and diffeomorphism symmetries
at very high energies.
| [
{
"created": "Sun, 12 Jul 2015 01:11:40 GMT",
"version": "v1"
}
] | 2015-07-14 | [
[
"Satheeshkumar",
"V. H.",
""
]
] | Since Stephen Hawking discovered that black holes emit thermal radiation, black holes have become the theoretical laboratories for testing our ideas on quantum gravity. This dissertation is devoted to the study of singularities, the formation of black holes by gravitational collapse and the global structure of spacetime. All our investigations are in the context of a recently proposed approach to quantum gravity, which breaks Lorentz and diffeomorphism symmetries at very high energies. |
0901.3264 | Mattias N. R. Wohlfarth | Raffaele Punzi, Frederic P. Schuller, Mattias N.R. Wohlfarth | Massive motion in Brans-Dicke geometry and beyond | 12 pages | null | 10.1103/PhysRevD.79.124025 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravity theories that can be viewed as dynamics for area metric manifolds,
for which Brans-Dicke theory presents a recently studied example, require for
their physical interpretation the identification of the distinguished curves
that serve as the trajectories of light and massive matter. Complementing
previous results on the propagation of light, we study effective massive point
particle motion. We show that the relevant geometrical structure is a special
Finsler norm determined by the area metric, and that massive point particles
follow Finsler geodesics.
| [
{
"created": "Wed, 21 Jan 2009 12:57:08 GMT",
"version": "v1"
}
] | 2013-05-29 | [
[
"Punzi",
"Raffaele",
""
],
[
"Schuller",
"Frederic P.",
""
],
[
"Wohlfarth",
"Mattias N. R.",
""
]
] | Gravity theories that can be viewed as dynamics for area metric manifolds, for which Brans-Dicke theory presents a recently studied example, require for their physical interpretation the identification of the distinguished curves that serve as the trajectories of light and massive matter. Complementing previous results on the propagation of light, we study effective massive point particle motion. We show that the relevant geometrical structure is a special Finsler norm determined by the area metric, and that massive point particles follow Finsler geodesics. |
2310.00030 | Sanjay Mandal | Sanjay Mandal, Sneha Pradhan, P.K. Sahoo, and Tiberiu Harko | Cosmological observational constraints on the power law $f(Q)$ type
modified gravity theory | EPJC published version | Eur. Phys. J. C (2023) 83:1141 | 10.1140/epjc/s10052-023-12339-4 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In modern cosmology, the curiosity of ultimately understanding the nature of
the dark energy controlling the recent acceleration of the Universe motivates
us to explore its properties by using some novel approaches. In this work, to
explore the properties of dark energy we adopt the modified $f(Q)$ gravity
theory, where the non-metricity scalar $Q$, emerging from Weyl geometry, plays
the dynamical role. For the function $f(Q)$ we adopt the functional form
$f(Q)=Q+ 6\gamma\,H_0^2(Q/Q_0)^n$, where $n,\, \gamma,\, H_0$ and $Q_0$ are
constants. Then, we test our constructed model against the various
observational datasets, such as the Hubble, and the Pantheon+SHOES samples, and
their combined sample, through the Markov Chain Monte Carlo (MCMC) statistical
analysis. We also employ the parameter estimation technique to constrain the
free parameters of the model. In addition, we use the constrained values of the
model parameters to explore a few implications of the cosmological model. A
detailed comparison of the predictions of our model with the $\Lambda$CDM model
is also performed. In particular, we discuss in detail some cosmographic
parameters, like the deceleration, the jerk, and the snap parameters, as well
as the behavior of the dark energy and matter energy densities to see the
evolution of various energy/matter profiles. The $Om$ diagnostics is also
presented to test the dark energy nature of our model, as compared to the
standard $\Lambda$CDM paradigm. Our findings show that the considered version
of the non-metric $f(Q)$ type modified gravity theory, despite some differences
with respect to the $\Lambda$CDM paradigm, can still explain the current
observational results on the cosmological parameters, and provide a convincing
and consistent account for the accelerating expansion of the Universe.
| [
{
"created": "Fri, 29 Sep 2023 04:56:29 GMT",
"version": "v1"
},
{
"created": "Sat, 16 Dec 2023 08:25:33 GMT",
"version": "v2"
}
] | 2023-12-19 | [
[
"Mandal",
"Sanjay",
""
],
[
"Pradhan",
"Sneha",
""
],
[
"Sahoo",
"P. K.",
""
],
[
"Harko",
"Tiberiu",
""
]
] | In modern cosmology, the curiosity of ultimately understanding the nature of the dark energy controlling the recent acceleration of the Universe motivates us to explore its properties by using some novel approaches. In this work, to explore the properties of dark energy we adopt the modified $f(Q)$ gravity theory, where the non-metricity scalar $Q$, emerging from Weyl geometry, plays the dynamical role. For the function $f(Q)$ we adopt the functional form $f(Q)=Q+ 6\gamma\,H_0^2(Q/Q_0)^n$, where $n,\, \gamma,\, H_0$ and $Q_0$ are constants. Then, we test our constructed model against the various observational datasets, such as the Hubble, and the Pantheon+SHOES samples, and their combined sample, through the Markov Chain Monte Carlo (MCMC) statistical analysis. We also employ the parameter estimation technique to constrain the free parameters of the model. In addition, we use the constrained values of the model parameters to explore a few implications of the cosmological model. A detailed comparison of the predictions of our model with the $\Lambda$CDM model is also performed. In particular, we discuss in detail some cosmographic parameters, like the deceleration, the jerk, and the snap parameters, as well as the behavior of the dark energy and matter energy densities to see the evolution of various energy/matter profiles. The $Om$ diagnostics is also presented to test the dark energy nature of our model, as compared to the standard $\Lambda$CDM paradigm. Our findings show that the considered version of the non-metric $f(Q)$ type modified gravity theory, despite some differences with respect to the $\Lambda$CDM paradigm, can still explain the current observational results on the cosmological parameters, and provide a convincing and consistent account for the accelerating expansion of the Universe. |
1806.10031 | Oscar Lasso Andino | Oscar Lasso Andino | RG-2 flow, mass and entropy | Typos corrected, references added | Class. Quantum Grav. 36 065011 (2019) | 10.1088/1361-6382/ab05f6 | IFT-UAM/CSIC-18-063 | gr-qc math.DG | http://creativecommons.org/licenses/by-nc-sa/4.0/ | The RG-2 flow is the two-loop approximation for the world-sheet non-linear
sigma model renormalization group flow. The first truncation of the flow is the
well known Ricci flow, at two loops higher order curvature terms appear,
changing almost completely the behaviour of the evolution equation. In this
article we study the RG-2 flow in the context of general relativity. Contrary
to what happens with the Ricci flow the RG-2 flow theory has not been studied
exhaustively, and from a mathematical point of view there are big differences
between both flows. Considering a time symmetric foliation of an asymptotically
flat spacetime, we show that the area $A$ of a closed two dimensional surface
$S$ is monotonous under the RG-2 flow, refining and extending the previous
results already known for the Ricci flow. We show that the inequality that
relates the area of the surface $S$ and the Hawking mass, already found for the
Ricci flow, is still satisfied when we make evolve the area under the new flow.
Finally, we discuss about Perelman`s $W$-entropy for the RG-2 flow and the
physically motivated path towards the gradient formulation of the RG-2 flow.
| [
{
"created": "Tue, 26 Jun 2018 14:46:48 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Jul 2018 15:16:15 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Mar 2019 17:08:59 GMT",
"version": "v3"
}
] | 2019-03-12 | [
[
"Andino",
"Oscar Lasso",
""
]
] | The RG-2 flow is the two-loop approximation for the world-sheet non-linear sigma model renormalization group flow. The first truncation of the flow is the well known Ricci flow, at two loops higher order curvature terms appear, changing almost completely the behaviour of the evolution equation. In this article we study the RG-2 flow in the context of general relativity. Contrary to what happens with the Ricci flow the RG-2 flow theory has not been studied exhaustively, and from a mathematical point of view there are big differences between both flows. Considering a time symmetric foliation of an asymptotically flat spacetime, we show that the area $A$ of a closed two dimensional surface $S$ is monotonous under the RG-2 flow, refining and extending the previous results already known for the Ricci flow. We show that the inequality that relates the area of the surface $S$ and the Hawking mass, already found for the Ricci flow, is still satisfied when we make evolve the area under the new flow. Finally, we discuss about Perelman`s $W$-entropy for the RG-2 flow and the physically motivated path towards the gradient formulation of the RG-2 flow. |
1708.06763 | Michael Florian Wondrak | Michael Florian Wondrak, Marcus Bleicher, Piero Nicolini | Black Holes and High Energy Physics: From Astrophysics to Large Extra
Dimensions | 15 pages, 5 figures. Version to appear in the "Walter Greiner
Memorial Volume" by World Scientific | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Up to now, Einstein's general theory of relativity has passed all
experimental tests. But yet we know that it is not a fundamental theory and
that it is incompatible with quantum theory. While several extended and
improved gravitational theories on classical and quantum level are nowadays
available, it is a great challenge to find experimental setups to check their
signatures.
We discuss recent developments in direct observation of black holes
comprising gravitational waves from black hole mergers, radio interferometry
images of black hole shadows, and Hawking radiation of black holes in particle
accelerators. These investigations cover the full black hole mass range from
microscopic to stellar and supermassive black holes. We comment on the
associated strong-field tests of Einstein's general theory of relativity and
implications for quantum gravity.
Special emphasis lies upon the physics of large extra dimensions and black
hole evaporation, the existence of a minimal black hole mass, and the cross
sections of higher-dimensional black holes. We complete this short review with
the latest experimental constraints at the Large Hadron Collider.
| [
{
"created": "Tue, 22 Aug 2017 18:00:03 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Nov 2017 22:32:35 GMT",
"version": "v2"
}
] | 2017-11-28 | [
[
"Wondrak",
"Michael Florian",
""
],
[
"Bleicher",
"Marcus",
""
],
[
"Nicolini",
"Piero",
""
]
] | Up to now, Einstein's general theory of relativity has passed all experimental tests. But yet we know that it is not a fundamental theory and that it is incompatible with quantum theory. While several extended and improved gravitational theories on classical and quantum level are nowadays available, it is a great challenge to find experimental setups to check their signatures. We discuss recent developments in direct observation of black holes comprising gravitational waves from black hole mergers, radio interferometry images of black hole shadows, and Hawking radiation of black holes in particle accelerators. These investigations cover the full black hole mass range from microscopic to stellar and supermassive black holes. We comment on the associated strong-field tests of Einstein's general theory of relativity and implications for quantum gravity. Special emphasis lies upon the physics of large extra dimensions and black hole evaporation, the existence of a minimal black hole mass, and the cross sections of higher-dimensional black holes. We complete this short review with the latest experimental constraints at the Large Hadron Collider. |
0710.1378 | Raymond Chiao Y. | Raymond Y. Chiao | Generation and detection of gravitational waves at microwave frequencies
by means of a superconducting two-body system | 12 pages, 3 figures, 'Time and Matter' conference,10-09a-07 version
with acknowledgments added, and with the mention of linear induction
generator added on page 3, and entangled states on pages 9 and 10 | null | null | null | gr-qc | null | The 2-body system of a superconducting sphere levitated in the magnetic field
generated by a persistent current in a superconducting ring, can possibly
convert gravitational waves into electromagnetic waves, and vice versa.
Faraday's law of induction implies that the time-varying distance between the
sphere and the ring caused by the tidal force of an incident gravitational wave
induces time-varying electrical currents, which are the source of an
electromagnetic wave at the same frequency as the incident gravitational wave.
At sufficiently low temperatures, the internal degrees of freedom of the
superconductors are frozen out because of the superconducting energy gap, and
only external degrees of freedom, which are coupled to the radiation fields,
remain. Hence this wave-conversion process is loss-free and therefore
efficient, and by time-reversal symmetry, so is the reverse process. A
Hertz-like experiment at microwave frequencies should therefore be practical to
perform. This would open up observations of the gravitational-wave analog of
the Cosmic Microwave Background from the extremely early Big Bang, and also
communications directly through the interior of the Earth.
| [
{
"created": "Mon, 8 Oct 2007 08:25:36 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Oct 2007 23:25:29 GMT",
"version": "v2"
},
{
"created": "Tue, 23 Oct 2007 23:54:43 GMT",
"version": "v3"
},
{
"created": "Sun, 28 Oct 2007 22:30:04 GMT",
"version": "v4"
}
] | 2007-10-29 | [
[
"Chiao",
"Raymond Y.",
""
]
] | The 2-body system of a superconducting sphere levitated in the magnetic field generated by a persistent current in a superconducting ring, can possibly convert gravitational waves into electromagnetic waves, and vice versa. Faraday's law of induction implies that the time-varying distance between the sphere and the ring caused by the tidal force of an incident gravitational wave induces time-varying electrical currents, which are the source of an electromagnetic wave at the same frequency as the incident gravitational wave. At sufficiently low temperatures, the internal degrees of freedom of the superconductors are frozen out because of the superconducting energy gap, and only external degrees of freedom, which are coupled to the radiation fields, remain. Hence this wave-conversion process is loss-free and therefore efficient, and by time-reversal symmetry, so is the reverse process. A Hertz-like experiment at microwave frequencies should therefore be practical to perform. This would open up observations of the gravitational-wave analog of the Cosmic Microwave Background from the extremely early Big Bang, and also communications directly through the interior of the Earth. |
2406.02454 | Rajes Ghosh | Rajes Ghosh, Kabir Chakravarti | Parameterized Non-circular Deviation from the Kerr Paradigm and Its
Observational Signatures: Extreme Mass Ratio Inspirals and Lense-Thirring
Effect | Revised version for journal submission, 15 pages, 3 figures, 2 tables | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent gravitational wave observations and shadow imaging have demonstrated
the astonishing consistency of the Kerr paradigm despite all the special
symmetries assumed in deriving the Kerr metric. Hence, it is crucial to test
the presence of these symmetries in astrophysical scenarios and constraint
possible deviations from them, especially in strong field regimes. With this
motivation, the present work aims to investigate the theoretical consequences
and observational signatures of non-circularity in a unified theory-agnostic
manner. For this purpose, we construct a general non-circular metric with a
small parameterized deviation from Kerr. This metric preserves the other
properties of Kerr, such as stationarity, axisymmetry, asymptotic flatness, and
the equatorial reflection symmetry. Apart from the resulting mathematical
simplifications, this assumption is crucial to disentangle the consequences of
relaxing circularity from other properties. Then, after discussing various
novel theoretical consequences, we perform a detailed analysis of extreme mass
ratio inspirals and Lense-Thirring precession in the context of this newly
constructed metric. Our study clearly shows the promising prospects of
detecting and constraining even a slight non-circular deviation from the Kerr
paradigm using the future gravitational wave observations by the Laser
Interferometer Space Antenna.
| [
{
"created": "Tue, 4 Jun 2024 16:20:14 GMT",
"version": "v1"
},
{
"created": "Sun, 9 Jun 2024 08:10:04 GMT",
"version": "v2"
}
] | 2024-06-11 | [
[
"Ghosh",
"Rajes",
""
],
[
"Chakravarti",
"Kabir",
""
]
] | Recent gravitational wave observations and shadow imaging have demonstrated the astonishing consistency of the Kerr paradigm despite all the special symmetries assumed in deriving the Kerr metric. Hence, it is crucial to test the presence of these symmetries in astrophysical scenarios and constraint possible deviations from them, especially in strong field regimes. With this motivation, the present work aims to investigate the theoretical consequences and observational signatures of non-circularity in a unified theory-agnostic manner. For this purpose, we construct a general non-circular metric with a small parameterized deviation from Kerr. This metric preserves the other properties of Kerr, such as stationarity, axisymmetry, asymptotic flatness, and the equatorial reflection symmetry. Apart from the resulting mathematical simplifications, this assumption is crucial to disentangle the consequences of relaxing circularity from other properties. Then, after discussing various novel theoretical consequences, we perform a detailed analysis of extreme mass ratio inspirals and Lense-Thirring precession in the context of this newly constructed metric. Our study clearly shows the promising prospects of detecting and constraining even a slight non-circular deviation from the Kerr paradigm using the future gravitational wave observations by the Laser Interferometer Space Antenna. |
gr-qc/9402004 | null | Giorgio Immirzi | Regge calculus and Ashtekar variables | 10 pages, uses harvmac. DFUPG 83/94 | Class.Quant.Grav.11:1971-1980,1994 | 10.1088/0264-9381/11/8/005 | null | gr-qc | null | Spacetime discretized in simplexes, as proposed in the pioneer work of Regge,
is described in terms of selfdual variables. In particular, we elucidate the
"kinematic" structure of the initial value problem, in which 3--space is
divided into flat tetrahedra, paying particular attention to the role played by
the reality condition for the Ashtekar variables. An attempt is made to write
down the vector and scalar constraints of the theory in a simple and
potentially useful way.
| [
{
"created": "Wed, 2 Feb 1994 12:38:12 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Immirzi",
"Giorgio",
""
]
] | Spacetime discretized in simplexes, as proposed in the pioneer work of Regge, is described in terms of selfdual variables. In particular, we elucidate the "kinematic" structure of the initial value problem, in which 3--space is divided into flat tetrahedra, paying particular attention to the role played by the reality condition for the Ashtekar variables. An attempt is made to write down the vector and scalar constraints of the theory in a simple and potentially useful way. |
2301.02579 | Vaibhav Kalvakota | Vaibhav Kalvakota | Singularities from Hyperentropic regions using the Quantum Expansion | 4 pages, Revtex file | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A recent paper \cite{Bousso:2022cun} put forward a theorem showing that
hyperentropic surface would result in incomplete null generators for a null
hypersurface emanating from the surface provided it satisfies the null
curvature condition and the spacetime is globally hyperbolic. In this paper, we
will put forward a version of this theorem using the quantum expansion in place
of the classical expansion, and we will discuss the quantum focusing conjecture
in this regard.
| [
{
"created": "Fri, 6 Jan 2023 16:18:49 GMT",
"version": "v1"
}
] | 2023-01-09 | [
[
"Kalvakota",
"Vaibhav",
""
]
] | A recent paper \cite{Bousso:2022cun} put forward a theorem showing that hyperentropic surface would result in incomplete null generators for a null hypersurface emanating from the surface provided it satisfies the null curvature condition and the spacetime is globally hyperbolic. In this paper, we will put forward a version of this theorem using the quantum expansion in place of the classical expansion, and we will discuss the quantum focusing conjecture in this regard. |
2011.10234 | Yasutaka Koga | Yasutaka Koga, Takahisa Igata, Keisuke Nakashi | Photon surfaces in less symmetric spacetimes | 21 pages, no figure | Phys. Rev. D 103, 044003 (2021) | 10.1103/PhysRevD.103.044003 | RUP-20-34; KEK-Cosmo-0268; KEK-TH-2280 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate photon surfaces and their stability in a less symmetric
spacetime, a general static warped product with a warping function acting on a
Riemannian submanifold of codimension two. We find a one-dimensional
pseudopotential that gives photon surfaces as its extrema regardless of the
spatial symmetry of the submanifold. The maxima and minima correspond to
unstable and stable photon surfaces, respectively. It is analogous to the
potential giving null circular orbits in a spherically symmetric spacetime. We
also see that photon surfaces indeed exist for the spacetimes which are
solutions to the Einstein equation. The parameter values for which the photon
surfaces exist are specified. As we show finally, the pseudopotential arises
due to the separability of the null geodesic equation, and the separability
comes from the existence of a Killing tensor in the spacetime. The result leads
to the conclusion that photon surfaces may exist even in a less symmetric
spacetime if the spacetime admits a Killing tensor.
| [
{
"created": "Fri, 20 Nov 2020 06:47:09 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Feb 2021 10:03:19 GMT",
"version": "v2"
}
] | 2021-02-10 | [
[
"Koga",
"Yasutaka",
""
],
[
"Igata",
"Takahisa",
""
],
[
"Nakashi",
"Keisuke",
""
]
] | We investigate photon surfaces and their stability in a less symmetric spacetime, a general static warped product with a warping function acting on a Riemannian submanifold of codimension two. We find a one-dimensional pseudopotential that gives photon surfaces as its extrema regardless of the spatial symmetry of the submanifold. The maxima and minima correspond to unstable and stable photon surfaces, respectively. It is analogous to the potential giving null circular orbits in a spherically symmetric spacetime. We also see that photon surfaces indeed exist for the spacetimes which are solutions to the Einstein equation. The parameter values for which the photon surfaces exist are specified. As we show finally, the pseudopotential arises due to the separability of the null geodesic equation, and the separability comes from the existence of a Killing tensor in the spacetime. The result leads to the conclusion that photon surfaces may exist even in a less symmetric spacetime if the spacetime admits a Killing tensor. |
1207.6055 | Volker Schlue | Volker Schlue | Global results for linear waves on expanding Kerr and Schwarzschild de
Sitter cosmologies | Substantially extended results for Kerr de Sitter backgrounds, and
more general expanding cosmologies without symmetries (Section 5);
applications to Klein-Gordon equations added (Section 7); Introduction
(Section 2.3.2) and references updated; 45 pages, 7 figures | Commun. Math. Phys. 334, 977-1023 (2015) | 10.1007/s00220-014-2154-2 | null | gr-qc math.AP math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this global study of solutions to the linear wave equation on
Schwarzschild de Sitter spacetimes we attend to the cosmological region of
spacetime which is bounded in the past by cosmological horizons and to the
future by a spacelike hypersurface at infinity. We prove an energy estimate
capturing the expansion of that region which combined with earlier results for
the static region yields a global boundedness result for linear waves. It
asserts that a general finite energy solution to the global initial value
problem has a limit on the future boundary at infinity that can be viewed as a
function on the standard cylinder with finite energy, and that moreover any
decay along the cosmological horizon is inherited along the future boundary. In
particular, we exhibit an explicit nonvanishing quantity on the future boundary
of the spacetime consistent with our expectations for the nonlinear stability
problem. Our results apply to a large class of expanding cosmologies near the
Schwarzschild de Sitter geometry, in particular subextremal Kerr de Sitter
spacetimes.
| [
{
"created": "Wed, 25 Jul 2012 16:57:45 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Nov 2013 20:34:45 GMT",
"version": "v2"
}
] | 2021-08-16 | [
[
"Schlue",
"Volker",
""
]
] | In this global study of solutions to the linear wave equation on Schwarzschild de Sitter spacetimes we attend to the cosmological region of spacetime which is bounded in the past by cosmological horizons and to the future by a spacelike hypersurface at infinity. We prove an energy estimate capturing the expansion of that region which combined with earlier results for the static region yields a global boundedness result for linear waves. It asserts that a general finite energy solution to the global initial value problem has a limit on the future boundary at infinity that can be viewed as a function on the standard cylinder with finite energy, and that moreover any decay along the cosmological horizon is inherited along the future boundary. In particular, we exhibit an explicit nonvanishing quantity on the future boundary of the spacetime consistent with our expectations for the nonlinear stability problem. Our results apply to a large class of expanding cosmologies near the Schwarzschild de Sitter geometry, in particular subextremal Kerr de Sitter spacetimes. |
0905.3492 | Luca Bombelli | Luca Bombelli, Alejandro Corichi, Oliver Winkler | Semiclassical Quantum Gravity: Obtaining Manifolds from Graphs | 16 pages, 5 figures | Class.Quant.Grav.26:245012,2009 | 10.1088/0264-9381/26/24/245012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We address the "inverse problem" for discrete geometry, which consists in
determining whether, given a discrete structure of a type that does not in
general imply geometrical information or even a topology, one can associate
with it a unique manifold in an appropriate sense, and constructing the
manifold when it exists. This problem arises in a variety of approaches to
quantum gravity that assume a discrete structure at the fundamental level; the
present work is motivated by the semiclassical sector of loop quantum gravity,
so we will take the discrete structure to be a graph and the manifold to be a
spatial slice in spacetime. We identify a class of graphs, those whose vertices
have a fixed valence, for which such a construction can be specified. We define
a procedure designed to produce a cell complex from a graph and show that, for
graphs with which it can be carried out to completion, the resulting cell
complex is in fact a PL-manifold. Graphs of our class for which the procedure
cannot be completed either do not arise as edge graphs of manifold cell
decompositions, or can be seen as cell decompositions of manifolds with
structure at small scales (in terms of the cell spacing). We also comment
briefly on how one can extend our procedure to more general graphs.
| [
{
"created": "Thu, 21 May 2009 14:09:39 GMT",
"version": "v1"
}
] | 2010-04-30 | [
[
"Bombelli",
"Luca",
""
],
[
"Corichi",
"Alejandro",
""
],
[
"Winkler",
"Oliver",
""
]
] | We address the "inverse problem" for discrete geometry, which consists in determining whether, given a discrete structure of a type that does not in general imply geometrical information or even a topology, one can associate with it a unique manifold in an appropriate sense, and constructing the manifold when it exists. This problem arises in a variety of approaches to quantum gravity that assume a discrete structure at the fundamental level; the present work is motivated by the semiclassical sector of loop quantum gravity, so we will take the discrete structure to be a graph and the manifold to be a spatial slice in spacetime. We identify a class of graphs, those whose vertices have a fixed valence, for which such a construction can be specified. We define a procedure designed to produce a cell complex from a graph and show that, for graphs with which it can be carried out to completion, the resulting cell complex is in fact a PL-manifold. Graphs of our class for which the procedure cannot be completed either do not arise as edge graphs of manifold cell decompositions, or can be seen as cell decompositions of manifolds with structure at small scales (in terms of the cell spacing). We also comment briefly on how one can extend our procedure to more general graphs. |
gr-qc/9509001 | Shiho Kobayashi | Akio Hosoya and Shiho Kobayashi | Anderson Localization in the Sky and Cosmological Magnetic Field | 13 pages, latex, epsfj, 3 figures | Phys.Rev. D54 (1996) 4738-4743 | 10.1103/PhysRevD.54.4738 | TIT/HEP-298/COSMO-57 | gr-qc astro-ph cond-mat | null | We discuss the Anderson localization of electromagnetic fields in the
fluctuating plasma induced by the gravitational density perturbation before the
recombination time of the Universe. Randomly distributed localized coherent
electromagnetic fields emerge in the thermal equilibrium before the
recombination time. We argue that the localized coherent electric fields
eventually produce cosmological magnetic fields after the decoupling time.
| [
{
"created": "Fri, 1 Sep 1995 12:59:18 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Hosoya",
"Akio",
""
],
[
"Kobayashi",
"Shiho",
""
]
] | We discuss the Anderson localization of electromagnetic fields in the fluctuating plasma induced by the gravitational density perturbation before the recombination time of the Universe. Randomly distributed localized coherent electromagnetic fields emerge in the thermal equilibrium before the recombination time. We argue that the localized coherent electric fields eventually produce cosmological magnetic fields after the decoupling time. |
gr-qc/0503048 | Etienne Takou | N. Noutchegueme, D. Dongo and E. Takou | Global existence of solutions for the relativistic Boltzmann equation
with arbitrarily large initial data on a Bianchi type I space-time | 17 pages | Gen.Rel.Grav. 37 (2005) 2047-2062 | 10.1007/s10714-005-0179-8 | null | gr-qc | null | We prove, for the relativistic Boltzmann equation on a Bianchi type I
space-time, a global existence and uniqueness theorem, for arbitrarily large
initial data.
| [
{
"created": "Fri, 11 Mar 2005 09:54:57 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Noutchegueme",
"N.",
""
],
[
"Dongo",
"D.",
""
],
[
"Takou",
"E.",
""
]
] | We prove, for the relativistic Boltzmann equation on a Bianchi type I space-time, a global existence and uniqueness theorem, for arbitrarily large initial data. |
1908.10600 | Jinsong Yang | Jinsong Yang, Yongge Ma | Consistency check on the fundamental and alternative flux operators in
loop quantum gravity | 12 pages, 4 figures; minor updates | Chin. Phys. C 43, 103106 (2019) | 10.1088/1674-1137/43/10/103106 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There are different constructions of the flux of triad in loop quantum
gravity, namely the fundamental and alternative flux operators. In parallel to
the consistency check on the two versions of operator by the algebraic calculus
in the literature, we check their consistency by the graphical calculus. Our
calculation based on the original Brink graphical method is obviously simpler
than the algebraic calculation. It turns out that our consistency check fixes
the regulating factor $\kappa_{\rm reg}$ of the Ashtekar-Lewandowski volume
operator as $\frac12$, which corrects its previous value in the literature.
| [
{
"created": "Wed, 28 Aug 2019 08:56:36 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Nov 2019 11:51:35 GMT",
"version": "v2"
}
] | 2019-11-06 | [
[
"Yang",
"Jinsong",
""
],
[
"Ma",
"Yongge",
""
]
] | There are different constructions of the flux of triad in loop quantum gravity, namely the fundamental and alternative flux operators. In parallel to the consistency check on the two versions of operator by the algebraic calculus in the literature, we check their consistency by the graphical calculus. Our calculation based on the original Brink graphical method is obviously simpler than the algebraic calculation. It turns out that our consistency check fixes the regulating factor $\kappa_{\rm reg}$ of the Ashtekar-Lewandowski volume operator as $\frac12$, which corrects its previous value in the literature. |
gr-qc/9809081 | Grigori Volovik | G.E. Volovik | Energy-momentum tensor of quasiparticles in the effective gravity in
superfluids | Latex file, 19 pages, discussion is extended and includes the global
and local thermodynamic equilibrium in the presence of event horizon | null | null | null | gr-qc | null | The problem of the energy-momentum conservation for matter in the
gravitational field is discussed on the example of the effective gravity, which
arises in superfluids. The "gravitational" field experienced by the
relativistic-like massless quasiparticles which form the "matter" (phonons in
superfluid 4He and low-energy fermions in superfluid 3He-A), is induced by the
flow of the superfluid "vacuum". It appears that the energy-momentum
conservation law for quasiparticles, has the covariant form
T^{\mu}_{\nu;\mu}=0. "Pseudotensor" of the energy-momentum for the
"gravitational field" (superfluid condensate) appears to depend on "matter". In
the presence of the stationary "gravitational" (superfluid) field the real
thermodynamic temperature T is constant in the true dissipationless equilibrium
state with no entropy production, while the "relativistic" temperature
T/\sqrt{g_{00}} is space dependent in agreement with Tolman's law. In the
presence of the event horizon the true dissipationless equilibrium state does
not exist. The quasiequilibrium dissipative motion across the horizon is
considered. The inflationary stage of the expansion of the Universe can be
modelled using the expanding Bose-condendsate.
| [
{
"created": "Tue, 29 Sep 1998 06:40:36 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Oct 1998 14:30:28 GMT",
"version": "v2"
},
{
"created": "Tue, 13 Oct 1998 06:23:36 GMT",
"version": "v3"
},
{
"created": "Sun, 25 Oct 1998 11:56:25 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Volovik",
"G. E.",
""
]
] | The problem of the energy-momentum conservation for matter in the gravitational field is discussed on the example of the effective gravity, which arises in superfluids. The "gravitational" field experienced by the relativistic-like massless quasiparticles which form the "matter" (phonons in superfluid 4He and low-energy fermions in superfluid 3He-A), is induced by the flow of the superfluid "vacuum". It appears that the energy-momentum conservation law for quasiparticles, has the covariant form T^{\mu}_{\nu;\mu}=0. "Pseudotensor" of the energy-momentum for the "gravitational field" (superfluid condensate) appears to depend on "matter". In the presence of the stationary "gravitational" (superfluid) field the real thermodynamic temperature T is constant in the true dissipationless equilibrium state with no entropy production, while the "relativistic" temperature T/\sqrt{g_{00}} is space dependent in agreement with Tolman's law. In the presence of the event horizon the true dissipationless equilibrium state does not exist. The quasiequilibrium dissipative motion across the horizon is considered. The inflationary stage of the expansion of the Universe can be modelled using the expanding Bose-condendsate. |
1910.01872 | Xiangdong Zhang | Yunlong Liu and Xiangdong Zhang | Maximal efficiency of the collisional Penrose process with spinning
particles in Kerr-Sen black hole | 20 pages, 17 figures. Published version | Eur. Phys. J. C (2020) 80: 31 | 10.1140/epjc/s10052-019-7605-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the collision of two uncharged spinning particles around an extreme
Kerr-Sen black hole and calculate the maximal efficiency of the energy
extraction from the Kerr-Sen black hole via super Penrose process. We consider
the collision of two massive particles as well as collision of a massless
particle with a massive particle. For all the cases, we find that the maximum
efficiency decreases as the Kerr-Sen black hole's parameter($b=1-a$) increases.
| [
{
"created": "Fri, 4 Oct 2019 11:12:34 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Jan 2020 07:35:11 GMT",
"version": "v2"
}
] | 2020-01-29 | [
[
"Liu",
"Yunlong",
""
],
[
"Zhang",
"Xiangdong",
""
]
] | We study the collision of two uncharged spinning particles around an extreme Kerr-Sen black hole and calculate the maximal efficiency of the energy extraction from the Kerr-Sen black hole via super Penrose process. We consider the collision of two massive particles as well as collision of a massless particle with a massive particle. For all the cases, we find that the maximum efficiency decreases as the Kerr-Sen black hole's parameter($b=1-a$) increases. |
2106.08679 | Antonio C. Guti\'errez-Pi\~neres | Antonio Calixto Guti\'errez-Pi\~neres and Hernando Quevedo | Darmois matching and $C^3$ matching | Replaced with the version matching the published one in CQG | null | 10.1088/1361-6382/ac45dc | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We apply the Darmois and the $C^3$ matching conditions to three different
spherically symmetric spacetimes. The exterior spacetime is described by the
Schwarzschild vacuum solution whereas for the interior counterpart we choose
different perfect fluid solutions with the same symmetry. We show that Darmois
matching conditions are satisfied in all three cases whereas the $C^3$
conditions are not fulfilled. We argue that this difference is due to a
non-physical behavior of the pressure on the matching surface.
| [
{
"created": "Wed, 16 Jun 2021 10:33:14 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Oct 2021 05:01:18 GMT",
"version": "v2"
},
{
"created": "Fri, 21 Jan 2022 23:27:24 GMT",
"version": "v3"
}
] | 2022-01-25 | [
[
"Gutiérrez-Piñeres",
"Antonio Calixto",
""
],
[
"Quevedo",
"Hernando",
""
]
] | We apply the Darmois and the $C^3$ matching conditions to three different spherically symmetric spacetimes. The exterior spacetime is described by the Schwarzschild vacuum solution whereas for the interior counterpart we choose different perfect fluid solutions with the same symmetry. We show that Darmois matching conditions are satisfied in all three cases whereas the $C^3$ conditions are not fulfilled. We argue that this difference is due to a non-physical behavior of the pressure on the matching surface. |
2406.04525 | Naritaka Oshita | Naritaka Oshita, Kazufumi Takahashi, Shinji Mukohyama | (In)stability of the black hole greybody factors and ringdowns against a
small-bump correction | 14 pages, 4 figures | null | null | YITP-24-69, IPMU24-0025, RIKEN-iTHEMS-Report-24 | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | Recently, it has been proposed that the black hole greybody factors can be
important to model ringdown spectral amplitudes. We study the stability of
greybody factors against a small-bump correction in the perturbation equation.
We find (I) that the greybody factor is stable in the frequency region relevant
to ringdown and (II) that it is destabilized at higher frequencies, especially
for a sharper bump correction. This behavior is similar to the case of higher
overtones, which is also very sensitive to a small correction. We clarify this
(in)stability with the WKB analysis. As the greybody factor is stable at the
frequency region relevant to the main part of ringdown, we conclude that the
greybody factor is suitable to model ringdown amplitude. In order to
investigate a bump correction in a self-consistent manner, we consider the
small-bump correction that can be realized in the general framework of
effective field theory of black hole perturbations.
| [
{
"created": "Thu, 6 Jun 2024 21:51:21 GMT",
"version": "v1"
}
] | 2024-06-10 | [
[
"Oshita",
"Naritaka",
""
],
[
"Takahashi",
"Kazufumi",
""
],
[
"Mukohyama",
"Shinji",
""
]
] | Recently, it has been proposed that the black hole greybody factors can be important to model ringdown spectral amplitudes. We study the stability of greybody factors against a small-bump correction in the perturbation equation. We find (I) that the greybody factor is stable in the frequency region relevant to ringdown and (II) that it is destabilized at higher frequencies, especially for a sharper bump correction. This behavior is similar to the case of higher overtones, which is also very sensitive to a small correction. We clarify this (in)stability with the WKB analysis. As the greybody factor is stable at the frequency region relevant to the main part of ringdown, we conclude that the greybody factor is suitable to model ringdown amplitude. In order to investigate a bump correction in a self-consistent manner, we consider the small-bump correction that can be realized in the general framework of effective field theory of black hole perturbations. |
gr-qc/0310097 | Matt Visser | A. J. M. Medved, Damien Martin, and Matt Visser | Dirty black holes: Quasinormal modes for "squeezed" horizons | 15 pages, uses iopart.cls and setstack.sty V2: Two references added.
Also, the appendix now relates our computation of the Regge-Wheeler potential
for gravity in a generic "dirty" black hole to the results of Karlovini
[gr-qc/0111066] | Class.Quant.Grav. 21 (2004) 2393-2405 | 10.1088/0264-9381/21/9/013 | null | gr-qc hep-th | null | We consider the quasinormal modes for a class of black hole spacetimes that,
informally speaking, contain a closely ``squeezed'' pair of horizons. (This
scenario, where the relevant observer is presumed to be ``trapped'' between the
horizons, is operationally distinct from near-extremal black holes with an
external observer.) It is shown, by analytical means, that the spacing of the
quasinormal frequencies equals the surface gravity at the squeezed horizons.
Moreover, we can calculate the real part of these frequencies provided that the
horizons are sufficiently close together (but not necessarily degenerate or
even ``nearly degenerate''). The novelty of our analysis (which extends a
model-specific treatment by Cardoso and Lemos) is that we consider ``dirty''
black holes; that is, the observable portion of the (static and spherically
symmetric) spacetime is allowed to contain an arbitrary distribution of matter.
| [
{
"created": "Mon, 20 Oct 2003 01:54:42 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Oct 2003 02:53:40 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Medved",
"A. J. M.",
""
],
[
"Martin",
"Damien",
""
],
[
"Visser",
"Matt",
""
]
] | We consider the quasinormal modes for a class of black hole spacetimes that, informally speaking, contain a closely ``squeezed'' pair of horizons. (This scenario, where the relevant observer is presumed to be ``trapped'' between the horizons, is operationally distinct from near-extremal black holes with an external observer.) It is shown, by analytical means, that the spacing of the quasinormal frequencies equals the surface gravity at the squeezed horizons. Moreover, we can calculate the real part of these frequencies provided that the horizons are sufficiently close together (but not necessarily degenerate or even ``nearly degenerate''). The novelty of our analysis (which extends a model-specific treatment by Cardoso and Lemos) is that we consider ``dirty'' black holes; that is, the observable portion of the (static and spherically symmetric) spacetime is allowed to contain an arbitrary distribution of matter. |
0705.2255 | Mamdouh Wanas | M.I. Wanas | Torsion Energy | 7 pages, LaTeX file | null | null | null | gr-qc hep-th math.DG | null | In the present work, torsion energy is defined. Its law of conservation is
given. It is shown that this type of energy gives rise to a repulsive force
which can be used to interpret supernovae type Ia observations, and
consequently the accelerating expansion of the Universe. This interpretation is
a pure geometric one and is a direct application of the geometrization
philosophy. Torsion energy can also be used to solve other problems of General
Relativity especially the singularity problem.
| [
{
"created": "Tue, 15 May 2007 23:11:03 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Wanas",
"M. I.",
""
]
] | In the present work, torsion energy is defined. Its law of conservation is given. It is shown that this type of energy gives rise to a repulsive force which can be used to interpret supernovae type Ia observations, and consequently the accelerating expansion of the Universe. This interpretation is a pure geometric one and is a direct application of the geometrization philosophy. Torsion energy can also be used to solve other problems of General Relativity especially the singularity problem. |
gr-qc/9610039 | Joa Centrella | Xing Zhuge, Joan M. Centrella, and Stephen L. W. McMillan (Drexel
University) | Gravitational Radiation from the Coalescence of Binary Neutron Stars:
Effects Due to the Equation of State, Spin, and Mass Ratio | 39 pages, uses Latex 2.09. To be published in the Dec. 15, 1996 issue
of Physical Review D. 16 Figures (bitmapped). Originals available in
compressed Postscript format at ftp://zonker.drexel.edu/papers/PAPER2/ | Phys.Rev.D54:7261-7277,1996 | 10.1103/PhysRevD.54.7261 | null | gr-qc astro-ph | null | We calculate the gravitational radiation produced by the coalescence of
inspiraling binary neutron stars in the Newtonian regime using 3-dimensional
numerical simulations. The stars are modeled as polytropes and start out in the
point-mass regime at wide separation. The hydrodynamic integration is performed
using smooth particle hydrodynamics (SPH) with Newtonian gravity, and the
gravitational radiation is calculated using the quadrupole approximation. We
have run a number of simulations varying the neutron star radii, equations of
state, spins, and mass ratio. The resulting gravitational waveforms and spectra
are rich in information about the hydrodynamics of coalescence, and show
characteristic dependence on GM/Rc^2, the equation of state, and the mass
ratio.
| [
{
"created": "Thu, 17 Oct 1996 17:35:12 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Zhuge",
"Xing",
"",
"Drexel\n University"
],
[
"Centrella",
"Joan M.",
"",
"Drexel\n University"
],
[
"McMillan",
"Stephen L. W.",
"",
"Drexel\n University"
]
] | We calculate the gravitational radiation produced by the coalescence of inspiraling binary neutron stars in the Newtonian regime using 3-dimensional numerical simulations. The stars are modeled as polytropes and start out in the point-mass regime at wide separation. The hydrodynamic integration is performed using smooth particle hydrodynamics (SPH) with Newtonian gravity, and the gravitational radiation is calculated using the quadrupole approximation. We have run a number of simulations varying the neutron star radii, equations of state, spins, and mass ratio. The resulting gravitational waveforms and spectra are rich in information about the hydrodynamics of coalescence, and show characteristic dependence on GM/Rc^2, the equation of state, and the mass ratio. |
1603.01611 | Ratbay Myrzakulov | Aizhan Myrzakul and Ratbay Myrzakulov | On the Hojman conservation quantities in FRW Cosmology | 24 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work we investigate the Hojman symmetry in FRW cosmology. In
particular, we use the Hojman symmetry to find conserved quantities of
particular cosmological models. Next, we study the Hojman symmetry in the
scalar-tensor cosmology and find corresponding exact forms of integrals of
motion. Finally, the formalism of the Hojman symmetry is extended to dynamical
systems with the higher-order equations of motion.
| [
{
"created": "Mon, 7 Mar 2016 17:25:50 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Mar 2016 17:25:25 GMT",
"version": "v2"
}
] | 2016-03-15 | [
[
"Myrzakul",
"Aizhan",
""
],
[
"Myrzakulov",
"Ratbay",
""
]
] | In the present work we investigate the Hojman symmetry in FRW cosmology. In particular, we use the Hojman symmetry to find conserved quantities of particular cosmological models. Next, we study the Hojman symmetry in the scalar-tensor cosmology and find corresponding exact forms of integrals of motion. Finally, the formalism of the Hojman symmetry is extended to dynamical systems with the higher-order equations of motion. |
gr-qc/0505155 | Marek Szydlowski | Orest Hrycyna and Marek Szydlowski | Different faces of chaos in FRW models with scalar fields -- geometrical
point of view | Revtex4, 10 pages, 16 figures | Chaos Solitons & Fractals 28 (2006) 1252-1270 | 10.1016/j.chaos.2005.08.187 | null | gr-qc | null | FRW cosmologies with conformally coupled scalar fields are investigated in a
geometrical way by the means of geodesics of the Jacobi metric. In this model
of dynamics, trajectories in the configuration space are represented by
geodesics. Because of the singular nature of the Jacobi metric on the boundary
set $\partial\mathcal{D}$ of the domain of admissible motion, the geodesics
change the cone sectors several times (or an infinite number of times) in the
neighborhood of the singular set $\partial\mathcal{D}$. We show that this
singular set contains interesting information about the dynamical complexity of
the model. Firstly, this set can be used as a Poincar{\'e} surface for
construction of Poincar{\'e} sections, and the trajectories then have the
recurrence property. We also investigate the distribution of the intersection
points. Secondly, the full classification of periodic orbits in the
configuration space is performed and existence of UPO is demonstrated. Our
general conclusion is that, although the presented model leads to several
complications, like divergence of curvature invariants as a measure of
sensitive dependence on initial conditions, some global results can be obtained
and some additional physical insight is gained from using the conformal Jacobi
metric. We also study the complex behavior of trajectories in terms of symbolic
dynamics.
| [
{
"created": "Tue, 31 May 2005 06:59:15 GMT",
"version": "v1"
}
] | 2007-06-14 | [
[
"Hrycyna",
"Orest",
""
],
[
"Szydlowski",
"Marek",
""
]
] | FRW cosmologies with conformally coupled scalar fields are investigated in a geometrical way by the means of geodesics of the Jacobi metric. In this model of dynamics, trajectories in the configuration space are represented by geodesics. Because of the singular nature of the Jacobi metric on the boundary set $\partial\mathcal{D}$ of the domain of admissible motion, the geodesics change the cone sectors several times (or an infinite number of times) in the neighborhood of the singular set $\partial\mathcal{D}$. We show that this singular set contains interesting information about the dynamical complexity of the model. Firstly, this set can be used as a Poincar{\'e} surface for construction of Poincar{\'e} sections, and the trajectories then have the recurrence property. We also investigate the distribution of the intersection points. Secondly, the full classification of periodic orbits in the configuration space is performed and existence of UPO is demonstrated. Our general conclusion is that, although the presented model leads to several complications, like divergence of curvature invariants as a measure of sensitive dependence on initial conditions, some global results can be obtained and some additional physical insight is gained from using the conformal Jacobi metric. We also study the complex behavior of trajectories in terms of symbolic dynamics. |
1110.4185 | Sandipan Sengupta | Sandipan Sengupta | SU(2) gauge theory of gravity with topological invariants | Based on a talk at Loops-11, Madrid, Spain; To appear in Journal of
Physics: Conference Series | 2012 J. Phys.: Conf. Ser. 360 012024 | 10.1088/1742-6596/360/1/012024 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The most general gravity Lagrangian in four dimensions contains three
topological densities, namely Nieh-Yan, Pontryagin and Euler, in addition to
the Hilbert-Palatini term. We set up a Hamiltonian formulation based on this
Lagrangian. The resulting canonical theory depends on three parameters which
are coefficients of these terms and is shown to admit a real SU(2) gauge
theoretic interpretation with a set of seven first-class constraints. Thus, in
addition to the Newton's constant, the theory of gravity contains three
(topological) coupling constants, which might have non-trivial imports in the
quantum theory.
| [
{
"created": "Wed, 19 Oct 2011 05:26:29 GMT",
"version": "v1"
}
] | 2012-06-01 | [
[
"Sengupta",
"Sandipan",
""
]
] | The most general gravity Lagrangian in four dimensions contains three topological densities, namely Nieh-Yan, Pontryagin and Euler, in addition to the Hilbert-Palatini term. We set up a Hamiltonian formulation based on this Lagrangian. The resulting canonical theory depends on three parameters which are coefficients of these terms and is shown to admit a real SU(2) gauge theoretic interpretation with a set of seven first-class constraints. Thus, in addition to the Newton's constant, the theory of gravity contains three (topological) coupling constants, which might have non-trivial imports in the quantum theory. |
gr-qc/0002005 | D. V. Ahluwalia | D. V. Ahluwalia | Wave-Particle duality at the Planck scale: Freezing of neutrino
oscillations | Published version | Phys.Lett.A275:31-35,2000 | 10.1016/S0375-9601(00)00578-8 | EdeFUAZ/ISGBG-02 | gr-qc astro-ph hep-ph hep-th quant-ph | null | A gravitationally-induced modification to de Broglie wave-particle duality is
presented. At Planck scale, the gravitationally-modified matter wavelength
saturates to a few times the Planck length in a momentum independent manner. In
certain frameworks, this circumstance freezes neutrino oscillations in the
Planck realm. This effect is apart, and beyond, the gravitational red-shift. A
conclusion is drawn that in a complete theory of quantum gravity the notions of
``quantum'' and ``gravity'' shall carry new meanings -- meanings, that are yet
to be deciphered from theory and observations in their entirety.
| [
{
"created": "Tue, 1 Feb 2000 22:29:32 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Aug 2000 18:53:42 GMT",
"version": "v2"
},
{
"created": "Sat, 30 Dec 2000 19:16:57 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Ahluwalia",
"D. V.",
""
]
] | A gravitationally-induced modification to de Broglie wave-particle duality is presented. At Planck scale, the gravitationally-modified matter wavelength saturates to a few times the Planck length in a momentum independent manner. In certain frameworks, this circumstance freezes neutrino oscillations in the Planck realm. This effect is apart, and beyond, the gravitational red-shift. A conclusion is drawn that in a complete theory of quantum gravity the notions of ``quantum'' and ``gravity'' shall carry new meanings -- meanings, that are yet to be deciphered from theory and observations in their entirety. |
gr-qc/9411053 | Haret Rosu | H.C. Rosu | Remarks on the frequency spectra of some fundamental quantum effects | 6 pages, LaTex | Nuovo Cimento B 114 (January 1999) 107-112 | null | null | gr-qc quant-ph | null | Short remarks on the problem of assigning frequency spectra to Casimir,
sonoluminescence, Hawking, Unruh, and quantum optical squeezing effects are
presented
| [
{
"created": "Mon, 21 Nov 1994 03:15:00 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Dec 1997 17:53:57 GMT",
"version": "v2"
},
{
"created": "Mon, 26 Apr 1999 15:46:32 GMT",
"version": "v3"
}
] | 2008-02-03 | [
[
"Rosu",
"H. C.",
""
]
] | Short remarks on the problem of assigning frequency spectra to Casimir, sonoluminescence, Hawking, Unruh, and quantum optical squeezing effects are presented |
0812.4033 | Claudio Dappiaggi | Claudio Dappiaggi, Valter Moretti, Nicola Pinamonti | Distinguished quantum states in a class of cosmological spacetimes and
their Hadamard property | 41 pages | null | 10.1063/1.3122770 | Desy 08-199, ESI 2088, UTM 726, ZMP-HH/08-21 | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent paper, we proved that a large class of spacetimes, not
necessarily homogeneous or isotropous and relevant at a cosmological level,
possesses a preferred codimension one submanifold, i.e., the past cosmological
horizon, on which it is possible to encode the information of a scalar field
theory living in the bulk. Such bulk-to-boundary reconstruction procedure
entails the identification of a preferred quasifree algebraic state for the
bulk theory, enjoying remarkable properties concerning invariance under
isometries (if any) of the bulk and energy positivity, and reducing to
well-known vacua in standard situations. In this paper, specialising to open
FRW models, we extend previously obtained results and we prove that the
preferred state is of Hadamard form, hence the backreaction on the metric is
finite and the state can be used as a starting point for renormalisation
procedures. That state could play a distinguished role in the discussion of the
evolution of scalar fluctuations of the metric, an analysis often performed in
the development of any model describing the dynamic of an early Universe which
undergoes an inflationary phase of rapid expansion in the past.
| [
{
"created": "Sun, 21 Dec 2008 17:46:23 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Dappiaggi",
"Claudio",
""
],
[
"Moretti",
"Valter",
""
],
[
"Pinamonti",
"Nicola",
""
]
] | In a recent paper, we proved that a large class of spacetimes, not necessarily homogeneous or isotropous and relevant at a cosmological level, possesses a preferred codimension one submanifold, i.e., the past cosmological horizon, on which it is possible to encode the information of a scalar field theory living in the bulk. Such bulk-to-boundary reconstruction procedure entails the identification of a preferred quasifree algebraic state for the bulk theory, enjoying remarkable properties concerning invariance under isometries (if any) of the bulk and energy positivity, and reducing to well-known vacua in standard situations. In this paper, specialising to open FRW models, we extend previously obtained results and we prove that the preferred state is of Hadamard form, hence the backreaction on the metric is finite and the state can be used as a starting point for renormalisation procedures. That state could play a distinguished role in the discussion of the evolution of scalar fluctuations of the metric, an analysis often performed in the development of any model describing the dynamic of an early Universe which undergoes an inflationary phase of rapid expansion in the past. |
2004.14863 | Nihan Kat{\i}rc{\i} | Ozgur Akarsu, Nihan Katirci, Anjan A. Sen, J. Alberto Vazquez | Scalar field emulator via anisotropically deformed vacuum energy:
Application to dark energy | 7 pages, 1 figure, 2 tables | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a generalization of the usual vacuum energy, called `deformed
vacuum energy', which yields anisotropic pressure whilst preserving zero
inertial mass density. It couples to the shear scalar in a unique way, such
that they together emulate the canonical scalar field with an arbitrary
potential. This opens up a new avenue by reconsidering cosmologies based on
canonical scalar fields, along with a bonus that the kinetic term of the scalar
field is replaced by an observable, the shear scalar. We further elaborate the
aspects of this approach in the context of dark energy.
| [
{
"created": "Wed, 29 Apr 2020 15:48:13 GMT",
"version": "v1"
}
] | 2020-05-01 | [
[
"Akarsu",
"Ozgur",
""
],
[
"Katirci",
"Nihan",
""
],
[
"Sen",
"Anjan A.",
""
],
[
"Vazquez",
"J. Alberto",
""
]
] | We introduce a generalization of the usual vacuum energy, called `deformed vacuum energy', which yields anisotropic pressure whilst preserving zero inertial mass density. It couples to the shear scalar in a unique way, such that they together emulate the canonical scalar field with an arbitrary potential. This opens up a new avenue by reconsidering cosmologies based on canonical scalar fields, along with a bonus that the kinetic term of the scalar field is replaced by an observable, the shear scalar. We further elaborate the aspects of this approach in the context of dark energy. |
1905.00834 | Francisco Linares | Francisco X. Linares Cede\~no, Ariadna Montiel, Juan Carlos Hidalgo,
Gabriel Germ\'an | Bayesian evidence for $\alpha$-attractor dark energy models | 18 pages, 3 figures, 6 tables. Final version accepted for publication
in JCAP | null | 10.1088/1475-7516/2019/08/002 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dark energy models with tracker properties have gained attention due to the
large range of initial conditions leading to the current value of the dark
energy density parameter. A well-motivated family of these models are the
so-called $\alpha$-attractors, which show the late time behavior of a
cosmological constant. In the present paper we perform a model-selection
analysis of a variety of $\alpha$-attractor potentials in comparison with a
non-flat $\Lambda$CDM model. Specifically, we compute the Bayes Factor for the
L-Model, the Oscillatory Tracker Model, the Recliner Model, and the Starobinsky
Model, while considering the non-flat $\Lambda$CDM as the base model. Each
model is tested through a Bayesian analysis using observations relevant to the
current accelerated expansion: we employ the latest SNe Ia data, combined with
cosmic clocks, the latest BOSS release of BAO data, and the Planck Compressed
2018 data. The produced Markov Chains for each model are further compared
through a Bayesian evidence analysis. From the latter we conclude that the
Oscillatory Tracker Model is preferred by data (even if weakly) over the
non-flat $\Lambda$CDM model. Our results also suggest at the L-model is the
least favoured version of the $\alpha$-attractor models considered.
| [
{
"created": "Thu, 2 May 2019 16:20:28 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Jul 2019 13:45:44 GMT",
"version": "v2"
}
] | 2019-08-07 | [
[
"Cedeño",
"Francisco X. Linares",
""
],
[
"Montiel",
"Ariadna",
""
],
[
"Hidalgo",
"Juan Carlos",
""
],
[
"Germán",
"Gabriel",
""
]
] | Dark energy models with tracker properties have gained attention due to the large range of initial conditions leading to the current value of the dark energy density parameter. A well-motivated family of these models are the so-called $\alpha$-attractors, which show the late time behavior of a cosmological constant. In the present paper we perform a model-selection analysis of a variety of $\alpha$-attractor potentials in comparison with a non-flat $\Lambda$CDM model. Specifically, we compute the Bayes Factor for the L-Model, the Oscillatory Tracker Model, the Recliner Model, and the Starobinsky Model, while considering the non-flat $\Lambda$CDM as the base model. Each model is tested through a Bayesian analysis using observations relevant to the current accelerated expansion: we employ the latest SNe Ia data, combined with cosmic clocks, the latest BOSS release of BAO data, and the Planck Compressed 2018 data. The produced Markov Chains for each model are further compared through a Bayesian evidence analysis. From the latter we conclude that the Oscillatory Tracker Model is preferred by data (even if weakly) over the non-flat $\Lambda$CDM model. Our results also suggest at the L-model is the least favoured version of the $\alpha$-attractor models considered. |
gr-qc/9612058 | Alexandre Filippov | A.T.Filippov (JINR, Dubna, Russia) | Integrable 1+1 dimensional gravity models | 10 pages, Latex; submitted to Proc. of the International Workshop
`Classical and Quantum Integrable Systems', Dubna, July 1996; to be published
in Intern. Journ. Mod. Phys. A | Int.J.Mod.Phys.A12:13-22,1997 | 10.1142/S0217751X97000037 | null | gr-qc | null | Integrable models of dilaton gravity coupled to electromagnetic and scalar
matter fields in dimensions 1+1 and 0+1 are briefly reviewed. The 1+1
dimensional integrable models are either solved in terms of explicit
quadratures or reduced to the classically integrable Liouville equation. The
0+1 dimensional integrable models emerge as sectors in generally non integrable
1+1 dimensional models and can be solved in terms of explicit quadratures. The
Hamiltonian formulation and the problem of quantizing are briefly discussed.
Applications to gravity in any space - time dimension are outlined and a
generalization of the so called `no - hair' theorem is proven using local
properties of the Lagrange equations for a rather general 1+1 dimensional
dilaton gravity coupled to matter. This report is based on the paper
hep-th/9605008 but some simplifications, corrections and new results are added.
| [
{
"created": "Fri, 20 Dec 1996 12:46:32 GMT",
"version": "v1"
}
] | 2011-04-15 | [
[
"Filippov",
"A. T.",
"",
"JINR, Dubna, Russia"
]
] | Integrable models of dilaton gravity coupled to electromagnetic and scalar matter fields in dimensions 1+1 and 0+1 are briefly reviewed. The 1+1 dimensional integrable models are either solved in terms of explicit quadratures or reduced to the classically integrable Liouville equation. The 0+1 dimensional integrable models emerge as sectors in generally non integrable 1+1 dimensional models and can be solved in terms of explicit quadratures. The Hamiltonian formulation and the problem of quantizing are briefly discussed. Applications to gravity in any space - time dimension are outlined and a generalization of the so called `no - hair' theorem is proven using local properties of the Lagrange equations for a rather general 1+1 dimensional dilaton gravity coupled to matter. This report is based on the paper hep-th/9605008 but some simplifications, corrections and new results are added. |
gr-qc/0109090 | Ramin G. Daghigh | R. G. Daghigh and J. I. Kapusta | High Temperature Matter and Gamma Ray Spectra from Microscopic Black
Holes | 33 pages, 13 figures, to be submitted to PRD | Phys.Rev. D65 (2002) 064028 | 10.1103/PhysRevD.65.064028 | null | gr-qc astro-ph | null | The relativistic viscous fluid equations describing the outflow of high
temperature matter created via Hawking radiation from microscopic black holes
are solved numerically for a realistic equation of state. We focus on black
holes with initial temperatures greater than 100 GeV and lifetimes less than 6
days. The spectra of direct photons and photons from $\pi^0$ decay are
calculated for energies greater than 1 GeV. We calculate the diffuse gamma ray
spectrum from black holes distributed in our galactic halo. However, the most
promising route for their observation is to search for point sources emitting
gamma rays of ever-increasing energy.
| [
{
"created": "Thu, 27 Sep 2001 18:38:00 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Daghigh",
"R. G.",
""
],
[
"Kapusta",
"J. I.",
""
]
] | The relativistic viscous fluid equations describing the outflow of high temperature matter created via Hawking radiation from microscopic black holes are solved numerically for a realistic equation of state. We focus on black holes with initial temperatures greater than 100 GeV and lifetimes less than 6 days. The spectra of direct photons and photons from $\pi^0$ decay are calculated for energies greater than 1 GeV. We calculate the diffuse gamma ray spectrum from black holes distributed in our galactic halo. However, the most promising route for their observation is to search for point sources emitting gamma rays of ever-increasing energy. |
1503.03240 | Norman G\"urlebeck | Norman G\"urlebeck | No-hair theorem for Black Holes in Astrophysical Environments | 5 pages, to appear in Phys. Rev. Lett | null | 10.1103/PhysRevLett.114.151102 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | According to the no-hair theorem, static black holes are described by a
Schwarzschild spacetime provided there are no other sources of the
gravitational field. This requirement, however, is in astrophysical realistic
scenarios often violated, e.g., if the black hole is part of a binary system or
if it is surrounded by an accretion disk. In these cases, the black hole is
distorted due to tidal forces. Nonetheless, the subsequent formulation of the
no-hair theorem holds: The contribution of the distorted black hole to the
multipole moments that describe the gravitational field close to infinity and,
thus, all sources is that of a Schwarzschild black hole. It still has no hair.
This implies that there is no multipole moment induced in the black hole and
that its second Love numbers, which measure some aspects of the distortion,
vanish as was already shown in approximations to general relativity. But here
we prove this property for astrophysical relevant black holes in full general
relativity.
| [
{
"created": "Wed, 11 Mar 2015 09:40:25 GMT",
"version": "v1"
}
] | 2015-06-24 | [
[
"Gürlebeck",
"Norman",
""
]
] | According to the no-hair theorem, static black holes are described by a Schwarzschild spacetime provided there are no other sources of the gravitational field. This requirement, however, is in astrophysical realistic scenarios often violated, e.g., if the black hole is part of a binary system or if it is surrounded by an accretion disk. In these cases, the black hole is distorted due to tidal forces. Nonetheless, the subsequent formulation of the no-hair theorem holds: The contribution of the distorted black hole to the multipole moments that describe the gravitational field close to infinity and, thus, all sources is that of a Schwarzschild black hole. It still has no hair. This implies that there is no multipole moment induced in the black hole and that its second Love numbers, which measure some aspects of the distortion, vanish as was already shown in approximations to general relativity. But here we prove this property for astrophysical relevant black holes in full general relativity. |
gr-qc/0603105 | Brien C. Nolan | Brien C. Nolan | Bounds for scalar waves on self-similar naked-singularity backgrounds | 16 pages, 1 figure. Published version | Class.Quant.Grav. 23 (2006) 4523-4538 | 10.1088/0264-9381/23/13/015 | null | gr-qc | null | The stability of naked singularities in self-similar collapse is probed using
scalar waves. It is shown that the multipoles of a minimally coupled massless
scalar field propagating on a spherically symmetric self-similar background
spacetime admitting a naked singularity maintain finite $L^2$ norm as they
impinge on the Cauchy horizon. It is also shown that each multipole obeys a
pointwise bound at the horizon, as does its locally observed energy density.
$L^2$ and pointwise bounds are also obtained for the multipoles of a minimally
coupled massive scalar wave packet.
| [
{
"created": "Tue, 28 Mar 2006 11:39:58 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Mar 2006 08:55:06 GMT",
"version": "v2"
},
{
"created": "Mon, 19 Jun 2006 08:15:23 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Nolan",
"Brien C.",
""
]
] | The stability of naked singularities in self-similar collapse is probed using scalar waves. It is shown that the multipoles of a minimally coupled massless scalar field propagating on a spherically symmetric self-similar background spacetime admitting a naked singularity maintain finite $L^2$ norm as they impinge on the Cauchy horizon. It is also shown that each multipole obeys a pointwise bound at the horizon, as does its locally observed energy density. $L^2$ and pointwise bounds are also obtained for the multipoles of a minimally coupled massive scalar wave packet. |
1407.8529 | Jose Manuel Torres | Miguel Alcubierre and Jose M. Torres | Constraint preserving boundary conditions for the
Baumgarte-Shapiro-Shibata-Nakamura formulation in spherical symmetry | 15 pages, 12 figures, to be published in Classical and Quantum
Gravity | null | 10.1088/0264-9381/32/3/035006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a set of constraint preserving boundary conditions for the
Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formulation of the Einstein evolution
equations in spherical symmetry, based on its hyperbolic structure. While the
outgoing eigenfields are left to propagate freely off the numerical grid,
boundary conditions are set to enforce that the incoming eigenfields don't
introduce spurious reflections and, more importantly, that there are no fields
introduced at the boundary that violate the constraint equations. In order to
do this we adopt two different approaches to set boundary conditions for the
extrinsic curvature, by expressing either the radial or the time derivative of
its associated outgoing eigenfield in terms of the constraints. We find that
these boundary conditions are very robust in practice, allowing us to perform
long lasting evolutions that remain accurate and stable, and that converge to a
solution that satisfies the constraints all the way to the boundary.
| [
{
"created": "Thu, 31 Jul 2014 18:59:30 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Nov 2014 18:40:04 GMT",
"version": "v2"
}
] | 2015-06-22 | [
[
"Alcubierre",
"Miguel",
""
],
[
"Torres",
"Jose M.",
""
]
] | We introduce a set of constraint preserving boundary conditions for the Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formulation of the Einstein evolution equations in spherical symmetry, based on its hyperbolic structure. While the outgoing eigenfields are left to propagate freely off the numerical grid, boundary conditions are set to enforce that the incoming eigenfields don't introduce spurious reflections and, more importantly, that there are no fields introduced at the boundary that violate the constraint equations. In order to do this we adopt two different approaches to set boundary conditions for the extrinsic curvature, by expressing either the radial or the time derivative of its associated outgoing eigenfield in terms of the constraints. We find that these boundary conditions are very robust in practice, allowing us to perform long lasting evolutions that remain accurate and stable, and that converge to a solution that satisfies the constraints all the way to the boundary. |
1701.06899 | Adel Awad | Adel Awad and Gamal Nashed | Generalized teleparallel cosmology and initial singularity crossing | added few references and corrected some typos | null | 10.1088/1475-7516/2017/02/046 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a class of cosmological solutions for a generalized teleparallel
gravity with, $f(T)=T+\tilde{\alpha}(-T)^n$, where $\tilde{\alpha}$ is some
parameter and $n$ is an integer or half-integer. Choosing $\tilde{\alpha} \sim
G^{n-1}$, where $G$ is the gravitational constant, and working with an equation
of state $p=w\, \rho$, one obtains a cosmological solution with multiple
branches. The dynamics of the solution describes standard cosmology at late
times, but the higher-torsion correction changes the nature of the initial
singularity from big bang to a sudden singularity. The milder behavior of the
sudden singularity enables us to extend timelike or lightlike curves, through
joining two disconnected branches of solution at the singularity, leaving the
singularity traversable. We show that this extension is consistent with the
field equations through checking the known junction conditions for generalized
teleparallel gravity. This suggests that these solutions describe a contracting
phase a prior to the expanding phase of the universe.
| [
{
"created": "Thu, 19 Jan 2017 17:39:34 GMT",
"version": "v1"
},
{
"created": "Sun, 12 Feb 2017 00:01:22 GMT",
"version": "v2"
}
] | 2017-03-08 | [
[
"Awad",
"Adel",
""
],
[
"Nashed",
"Gamal",
""
]
] | We present a class of cosmological solutions for a generalized teleparallel gravity with, $f(T)=T+\tilde{\alpha}(-T)^n$, where $\tilde{\alpha}$ is some parameter and $n$ is an integer or half-integer. Choosing $\tilde{\alpha} \sim G^{n-1}$, where $G$ is the gravitational constant, and working with an equation of state $p=w\, \rho$, one obtains a cosmological solution with multiple branches. The dynamics of the solution describes standard cosmology at late times, but the higher-torsion correction changes the nature of the initial singularity from big bang to a sudden singularity. The milder behavior of the sudden singularity enables us to extend timelike or lightlike curves, through joining two disconnected branches of solution at the singularity, leaving the singularity traversable. We show that this extension is consistent with the field equations through checking the known junction conditions for generalized teleparallel gravity. This suggests that these solutions describe a contracting phase a prior to the expanding phase of the universe. |
1205.0733 | Edward Wilson-Ewing | Carlo Rovelli, Edward Wilson-Ewing | Discrete Symmetries in Covariant LQG | 8 pages, v2: Minor changes | Phys.Rev.D86:064002,2012 | 10.1103/PhysRevD.86.064002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study time-reversal and parity ---on the physical manifold and in internal
space--- in covariant loop gravity. We consider a minor modification of the
Holst action which makes it transform coherently under such transformations.
The classical theory is not affected but the quantum theory is slightly
different. In particular, the simplicity constraints are slightly modified and
this restricts orientation flips in a spinfoam to occur only across degenerate
regions, thus reducing the sources of potential divergences.
| [
{
"created": "Thu, 3 May 2012 15:19:24 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Jul 2012 13:05:01 GMT",
"version": "v2"
}
] | 2013-05-30 | [
[
"Rovelli",
"Carlo",
""
],
[
"Wilson-Ewing",
"Edward",
""
]
] | We study time-reversal and parity ---on the physical manifold and in internal space--- in covariant loop gravity. We consider a minor modification of the Holst action which makes it transform coherently under such transformations. The classical theory is not affected but the quantum theory is slightly different. In particular, the simplicity constraints are slightly modified and this restricts orientation flips in a spinfoam to occur only across degenerate regions, thus reducing the sources of potential divergences. |
1511.08645 | Eduardo Guendelman I | Eduardo I. Guendelman and Ramon Herrera | Curvaton reheating in a Scale Invariant Two Measures Theory | 26 pages, published in Gen.Rel.Grav. arXiv admin note: text overlap
with arXiv:1408.5344 | Gen.Rel.Grav. 48:3 (2016) | 10.1007/s10714-015-1999-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The curvaton reheating mechanism in a Scale Invariant Two Measures Theory
defined in terms of two independent non-Riemannian volume forms (alternative
generally covariant integration measure densities) on the space-time manifold
which are metric independent is studied. The model involves two scalar matter
fields, a dilaton, that transforms under scale transformations and it will be
used also as the inflaton of the model and another scalar, which does not
transform under scale transformations and which will play the role of a
curvaton field. Potentials of appropriate form so that the pertinent action is
invariant under global Weyl-scale symmetry are introduced. Scale invariance is
spontaneously broken upon integration of the equations of motion. After
performing transition to the physical Einstein frame we obtain: (i) For given
value of the curvaton field an effective potential for the scalar field with
two flat regions for the dilaton which allows for a unified description of both
early universe inflation as well as of present dark energy epoch;(iii) In the
phase corresponding to the early universe, the curvaton has a constant mass and
can oscillate decoupled from the dilaton and that can be responsible for both
reheating and perturbations in the theory. In this framework, we obtain some
interesting constraints on different parameters that appear in our model;
(iii) For a definite parameter range the model possesses a non-singular
"emergent universe" solution which describes an initial phase of evolution that
precedes the inflationary phase. Finally we discuss generalizations of the
model, through the effect of higher curvature terms, where inflaton and
curvaton can have coupled oscillations.
| [
{
"created": "Fri, 27 Nov 2015 12:35:23 GMT",
"version": "v1"
}
] | 2015-11-30 | [
[
"Guendelman",
"Eduardo I.",
""
],
[
"Herrera",
"Ramon",
""
]
] | The curvaton reheating mechanism in a Scale Invariant Two Measures Theory defined in terms of two independent non-Riemannian volume forms (alternative generally covariant integration measure densities) on the space-time manifold which are metric independent is studied. The model involves two scalar matter fields, a dilaton, that transforms under scale transformations and it will be used also as the inflaton of the model and another scalar, which does not transform under scale transformations and which will play the role of a curvaton field. Potentials of appropriate form so that the pertinent action is invariant under global Weyl-scale symmetry are introduced. Scale invariance is spontaneously broken upon integration of the equations of motion. After performing transition to the physical Einstein frame we obtain: (i) For given value of the curvaton field an effective potential for the scalar field with two flat regions for the dilaton which allows for a unified description of both early universe inflation as well as of present dark energy epoch;(iii) In the phase corresponding to the early universe, the curvaton has a constant mass and can oscillate decoupled from the dilaton and that can be responsible for both reheating and perturbations in the theory. In this framework, we obtain some interesting constraints on different parameters that appear in our model; (iii) For a definite parameter range the model possesses a non-singular "emergent universe" solution which describes an initial phase of evolution that precedes the inflationary phase. Finally we discuss generalizations of the model, through the effect of higher curvature terms, where inflaton and curvaton can have coupled oscillations. |
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