id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1702.00306 | Artur Alho | Artur Alho, Claes Uggla | Inflationary $\alpha$-attractor cosmology: A global dynamical systems
perspective | 15 pages, 11 figures. Matches published version | Phys. Rev. D 95, 083517 (2017) | 10.1103/PhysRevD.95.083517 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study flat FLRW $\alpha$-attractor $\mathrm{E}$- and $\mathrm{T}$-models
by introducing a dynamical systems framework that yields regularized
unconstrained field equations on two-dimensional compact state spaces. This
results in both illustrative figures and a complete description of the entire
solution spaces of these models, including asymptotics. In particular, it is
shown that observational viability, which requires a sufficient number of
$e$-folds, is associated with a solution given by a one-dimensional center
manifold of a past asymptotic de Sitter state, where the center manifold
structure also explains why nearby solutions are attracted to this
`inflationary attractor solution.' A center manifold expansion yields a
description of the inflationary regime with arbitrary analytic accuracy, where
the slow-roll approximation asymptotically describes the tangency condition of
the center manifold at the asymptotic de Sitter state.
| [
{
"created": "Wed, 1 Feb 2017 15:13:28 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Apr 2017 11:47:41 GMT",
"version": "v2"
}
] | 2017-04-26 | [
[
"Alho",
"Artur",
""
],
[
"Uggla",
"Claes",
""
]
] | We study flat FLRW $\alpha$-attractor $\mathrm{E}$- and $\mathrm{T}$-models by introducing a dynamical systems framework that yields regularized unconstrained field equations on two-dimensional compact state spaces. This results in both illustrative figures and a complete description of the entire solution spaces of these models, including asymptotics. In particular, it is shown that observational viability, which requires a sufficient number of $e$-folds, is associated with a solution given by a one-dimensional center manifold of a past asymptotic de Sitter state, where the center manifold structure also explains why nearby solutions are attracted to this `inflationary attractor solution.' A center manifold expansion yields a description of the inflationary regime with arbitrary analytic accuracy, where the slow-roll approximation asymptotically describes the tangency condition of the center manifold at the asymptotic de Sitter state. |
gr-qc/0205067 | Simon Judes | Simon Judes, Matt Visser | Conservation Laws in Doubly Special Relativity | V2: Extensive revisions: merged with gr-qc/0205093, new author added,
references added, discussion amplified. 4 pages, revtex4; V3: Revised in
response to referee comments; no physics changes; version to appear in
Physical Review D | Phys.Rev.D68:045001,2003 | 10.1103/PhysRevD.68.045001 | null | gr-qc astro-ph hep-ph | null | Motivated by various theoretical arguments that the Planck energy (Ep - 10^19
GeV) - should herald departures from Lorentz invariance, and the possibility of
testing these expectations in the not too distant future, two so-called "Doubly
Special Relativity" theories have been suggested -- the first by
Amelino-Camelia (DSR1) and the second by Smolin and Magueijo (DSR2). These
theories contain two fundamental scales -- the speed of light and an energy
usually taken to be Ep. The symmetry group is still the Lorentz group, but in
both cases acting nonlinearly on the energy-momentum sector. Accordingly, since
energy and momentum are no longer additive quantities, finding their values for
composite systems (and hence finding the correct conservation laws) is a
nontrivial matter. Ultimately it is these possible deviations from simple
linearly realized relativistic kinematics that provide the most promising
observational signal for empirically testing these models. Various
investigations have narrowed the conservation laws down to two possibilities
per DSR theory. We derive unique exact results for the energy-momentum of
composite systems in both DSR1 and DSR2, and indicate the general strategy for
arbitrary nonlinear realizations of the Lorentz group.
| [
{
"created": "Thu, 16 May 2002 09:52:04 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Jun 2002 08:06:37 GMT",
"version": "v2"
},
{
"created": "Fri, 16 May 2003 19:24:24 GMT",
"version": "v3"
}
] | 2011-06-15 | [
[
"Judes",
"Simon",
""
],
[
"Visser",
"Matt",
""
]
] | Motivated by various theoretical arguments that the Planck energy (Ep - 10^19 GeV) - should herald departures from Lorentz invariance, and the possibility of testing these expectations in the not too distant future, two so-called "Doubly Special Relativity" theories have been suggested -- the first by Amelino-Camelia (DSR1) and the second by Smolin and Magueijo (DSR2). These theories contain two fundamental scales -- the speed of light and an energy usually taken to be Ep. The symmetry group is still the Lorentz group, but in both cases acting nonlinearly on the energy-momentum sector. Accordingly, since energy and momentum are no longer additive quantities, finding their values for composite systems (and hence finding the correct conservation laws) is a nontrivial matter. Ultimately it is these possible deviations from simple linearly realized relativistic kinematics that provide the most promising observational signal for empirically testing these models. Various investigations have narrowed the conservation laws down to two possibilities per DSR theory. We derive unique exact results for the energy-momentum of composite systems in both DSR1 and DSR2, and indicate the general strategy for arbitrary nonlinear realizations of the Lorentz group. |
1810.00423 | Shirin Khodabakhshi | Sh. Khodabakhshi (Tehran U.), M. Farhang (Shahid Beheshti U.), A.
Shojai (Tehran U.), M. S. Esmaeilian (Shahid Beheshti U.), R. Moti (Ferdowsi
U.) | Observational assessment of the viability of de Sitter-G\"odel-de Sitter
phase transition | null | Gen.Rel.Grav. 54 (2022) 160 | 10.1007/s10714-022-03046-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | de Sitter--G\"odel--de Sitter phase transition(dGd) is a possible geometrical
phase transition in the very early universe. It induces fluctuations with
possibly observable traces on matter and radiation fields. Here we present a
simulation based on dGd to investigate possible perturbations which could be
along with the standard inflationary fluctuations in the cosmic microwave
background (CMB) and distribution of the large-scale structure. The power
spectrum of perturbations is characterized by a parameter pair, labeled here as
($p_1, p_2$). With {\it Planck} observations we find
$p_1=0.008^{+0.003}_{-0.008}$ and $p_2= 0.002^{+0.001}_{-0.002}$ consistent
with pure inflationary power spectrum and no hint for the dGd transition. Also,
it is estimated future large-scale surveys such as Euclid and SKA can further
tighten the constraints up to an order of magnitude and probe the physics of
the early universe with much higher precision.
| [
{
"created": "Sun, 30 Sep 2018 17:15:13 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Aug 2019 22:26:03 GMT",
"version": "v2"
},
{
"created": "Thu, 21 Oct 2021 18:28:02 GMT",
"version": "v3"
},
{
"created": "Tue, 23 Nov 2021 15:43:05 GMT",
"version": "v4"
},
{
"c... | 2022-12-19 | [
[
"Khodabakhshi",
"Sh.",
"",
"Tehran U."
],
[
"Farhang",
"M.",
"",
"Shahid Beheshti U."
],
[
"Shojai",
"A.",
"",
"Tehran U."
],
[
"Esmaeilian",
"M. S.",
"",
"Shahid Beheshti U."
],
[
"Moti",
"R.",
"",
"Ferdowsi\n U."
... | de Sitter--G\"odel--de Sitter phase transition(dGd) is a possible geometrical phase transition in the very early universe. It induces fluctuations with possibly observable traces on matter and radiation fields. Here we present a simulation based on dGd to investigate possible perturbations which could be along with the standard inflationary fluctuations in the cosmic microwave background (CMB) and distribution of the large-scale structure. The power spectrum of perturbations is characterized by a parameter pair, labeled here as ($p_1, p_2$). With {\it Planck} observations we find $p_1=0.008^{+0.003}_{-0.008}$ and $p_2= 0.002^{+0.001}_{-0.002}$ consistent with pure inflationary power spectrum and no hint for the dGd transition. Also, it is estimated future large-scale surveys such as Euclid and SKA can further tighten the constraints up to an order of magnitude and probe the physics of the early universe with much higher precision. |
1907.08957 | David McNutt | D. McNutt, A. Coley, L. Wylleman, S. Hervik | Locally Boost Isotropic Spacetimes and the Type ${\bf D}^k$ Condition | 25 pages | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the class of locally boost isotropic spacetimes in arbitrary
dimension. For any spacetime with boost isotropy, the corresponding curvature
tensor and all of its covariant derivatives must be simultaneously of alignment
type ${\bf D}$ relative to some common null frame. Such spacetimes are known as
type ${\bf D}^k$ spacetimes and are contained within the subclass of degenerate
Kundt spacetimes. Although, these spacetimes are $\mathcal{I}$-degenerate, it
is possible to distinguish any two type ${\bf D}^k$ spacetimes, as the
curvature tensor and its covariant derivatives can be characterized by the set
of scalar polynomial curvature invariants for any type ${\bf D}^k$ spacetime.
In this paper we find all type ${\bf D}^k$ spacetimes by identifying degenerate
Kundt metrics that are of type ${\bf D}^k$ and determining the precise
conditions on the metric functions.
| [
{
"created": "Sun, 21 Jul 2019 11:24:39 GMT",
"version": "v1"
}
] | 2019-07-23 | [
[
"McNutt",
"D.",
""
],
[
"Coley",
"A.",
""
],
[
"Wylleman",
"L.",
""
],
[
"Hervik",
"S.",
""
]
] | We consider the class of locally boost isotropic spacetimes in arbitrary dimension. For any spacetime with boost isotropy, the corresponding curvature tensor and all of its covariant derivatives must be simultaneously of alignment type ${\bf D}$ relative to some common null frame. Such spacetimes are known as type ${\bf D}^k$ spacetimes and are contained within the subclass of degenerate Kundt spacetimes. Although, these spacetimes are $\mathcal{I}$-degenerate, it is possible to distinguish any two type ${\bf D}^k$ spacetimes, as the curvature tensor and its covariant derivatives can be characterized by the set of scalar polynomial curvature invariants for any type ${\bf D}^k$ spacetime. In this paper we find all type ${\bf D}^k$ spacetimes by identifying degenerate Kundt metrics that are of type ${\bf D}^k$ and determining the precise conditions on the metric functions. |
2107.01146 | Ernesto Contreras | A. Ramos, C. Arias, R. \'Avalos, E. Contreras | Geodesic motion around hairy black holes | null | Annals Phys. 431, 168557 (2021) | 10.1016/j.aop.2021.168557 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent paper (Phys. Dark Univ. {\bf 31}, 100744 (2021)) it has been
obtained new static black hole solutions with primary hairs by the
Gravitational Decoupling. In this work we either study the geodesic motion of
massive and massless particles around those solutions and restrict the values
of the primary hairs by observational data. In particular, we obtain the
effective potential, the innermost stable circular orbits, the marginally
bounded orbit, and the periastron advance for time--like geodesics. In order to
restrict the values taken by the primary hairs we explore their relationship
with the rotation parameter of the Kerr black hole giving the same innermost
stable circular orbit radius and give the numerical values for the supermassive
black holes at Ark 564 and NGC 1365. The photon sphere and the impact parameter
associated to null geodesics are also discussed.
| [
{
"created": "Fri, 2 Jul 2021 15:43:07 GMT",
"version": "v1"
}
] | 2021-07-14 | [
[
"Ramos",
"A.",
""
],
[
"Arias",
"C.",
""
],
[
"Ávalos",
"R.",
""
],
[
"Contreras",
"E.",
""
]
] | In a recent paper (Phys. Dark Univ. {\bf 31}, 100744 (2021)) it has been obtained new static black hole solutions with primary hairs by the Gravitational Decoupling. In this work we either study the geodesic motion of massive and massless particles around those solutions and restrict the values of the primary hairs by observational data. In particular, we obtain the effective potential, the innermost stable circular orbits, the marginally bounded orbit, and the periastron advance for time--like geodesics. In order to restrict the values taken by the primary hairs we explore their relationship with the rotation parameter of the Kerr black hole giving the same innermost stable circular orbit radius and give the numerical values for the supermassive black holes at Ark 564 and NGC 1365. The photon sphere and the impact parameter associated to null geodesics are also discussed. |
2004.00770 | Jing-Bo Wang | Jingbo Wang | Hawking Radiation Is Pure | Essay written for the Gravity Research Foundation 2020 Awards for
Essays on Gravitation | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Information loss paradox is still a challenging problem in theoretical
physics. In this essay, for statics BTZ black holes and Schwarzschild black
holes, we propose a simple solution based on the similarity between black holes
and topological insulators. That is, the Hawking radiation is pure due to the
entanglement between the left-moving sector and right-moving sector of the
Hawking radiation. And this entanglement may be detected in an analogue black
hole in the near future.
| [
{
"created": "Thu, 2 Apr 2020 01:49:52 GMT",
"version": "v1"
}
] | 2020-04-03 | [
[
"Wang",
"Jingbo",
""
]
] | Information loss paradox is still a challenging problem in theoretical physics. In this essay, for statics BTZ black holes and Schwarzschild black holes, we propose a simple solution based on the similarity between black holes and topological insulators. That is, the Hawking radiation is pure due to the entanglement between the left-moving sector and right-moving sector of the Hawking radiation. And this entanglement may be detected in an analogue black hole in the near future. |
2309.01760 | Chiranjeeb Singha | Chiranjeeb Singha, Shauvik Biswas | Galactic Pure Lovelock Blackholes: Geometry, stability, and Hawking
temperature | 19 pages, 3 figures | Phys.Rev.D 109 (2024) 2, 024043 | 10.1103/PhysRevD.109.024043 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this article, we will first-time model galactic black holes in pure
Lovelock gravity. Even though working with higher spacetime dimensions, we
assume (implicitly) the Hernquist-type mass profile for the galaxy in such a
way that the horizon structure of a pure LoveLock black hole remains intact. In
this way, we will model the galactic pure Lovelock black hole with arbitrary
dimension ($d$) and order ($N$). Then, we will specialize this technique for
critical dimension $d=3N+1$. We want to see how the galactic parameters affect
the time domain single, quasinormal modes, photon sphere, innermost stable
circular orbits (ISCO), and shadow radius. The time domain signal may allow us
to identify the galactic parameters as well as to distinguish them from their
isolated pure Lovelock counterparts if it is observed in future generations of
gravitational wave measurements. We also calculate Hawking temperature for the
same setup and want to see how Hawking's temperature will be affected due to
the presence of a galaxy. It shows that the presence of a galactic halo can
quench Hawking temperature.
| [
{
"created": "Mon, 4 Sep 2023 18:37:39 GMT",
"version": "v1"
},
{
"created": "Sun, 19 May 2024 11:31:37 GMT",
"version": "v2"
}
] | 2024-05-21 | [
[
"Singha",
"Chiranjeeb",
""
],
[
"Biswas",
"Shauvik",
""
]
] | In this article, we will first-time model galactic black holes in pure Lovelock gravity. Even though working with higher spacetime dimensions, we assume (implicitly) the Hernquist-type mass profile for the galaxy in such a way that the horizon structure of a pure LoveLock black hole remains intact. In this way, we will model the galactic pure Lovelock black hole with arbitrary dimension ($d$) and order ($N$). Then, we will specialize this technique for critical dimension $d=3N+1$. We want to see how the galactic parameters affect the time domain single, quasinormal modes, photon sphere, innermost stable circular orbits (ISCO), and shadow radius. The time domain signal may allow us to identify the galactic parameters as well as to distinguish them from their isolated pure Lovelock counterparts if it is observed in future generations of gravitational wave measurements. We also calculate Hawking temperature for the same setup and want to see how Hawking's temperature will be affected due to the presence of a galaxy. It shows that the presence of a galactic halo can quench Hawking temperature. |
gr-qc/0402006 | Orfeu Bertolami | Orfeu Bertolami | Translational Invariance and Noncommutative Field Theories | 10 pages; Invited talk at the Qauntum Gravity Phenomenology section
of the Tenth Marcel Grossmann Meeting on General Relativity, Rio de Janeiro,
Brazil, 20-26 July, 2003 | null | 10.1142/9789812704030_0284 | null | gr-qc | null | Implications of noncommutative field theories with commutator of the
coordinates of the form $[x^{\mu},x^{\nu}]=i \Lambda_{\quad \omega}^{\mu
\nu}x^{\omega}$with nilpotent structure constants are investigated. It is shown
that a free quantum field theory is not affected by noncommutativity, but that
invariance under translations is broken and hence the energy-momentum
conservation is not respected. The new energy-momentum law is expressed by a
Poincar\'e-invariant equation and the resulting kinematics is developed and
applied to the astrophysical puzzle related with the observed violation of the
GZK cutoff.
| [
{
"created": "Mon, 2 Feb 2004 14:41:12 GMT",
"version": "v1"
}
] | 2016-11-09 | [
[
"Bertolami",
"Orfeu",
""
]
] | Implications of noncommutative field theories with commutator of the coordinates of the form $[x^{\mu},x^{\nu}]=i \Lambda_{\quad \omega}^{\mu \nu}x^{\omega}$with nilpotent structure constants are investigated. It is shown that a free quantum field theory is not affected by noncommutativity, but that invariance under translations is broken and hence the energy-momentum conservation is not respected. The new energy-momentum law is expressed by a Poincar\'e-invariant equation and the resulting kinematics is developed and applied to the astrophysical puzzle related with the observed violation of the GZK cutoff. |
2002.01974 | Gil de Oliveira-Neto | G. A. Monerat, C. G. M. Santos, G. Oliveira-Neto, E. V. Corr\^ea Silva
and L. G. Ferreira Filho | The dynamics of the early universe in a model with radiation and a
generalized Chaplygin gas | In that new version, we removed a section and four figures. It has,
now, 30 pages and 13 figures | The European Physical Journal Plus volume 136, Article number: 34
(2021) | 10.1140/epjp/s13360-020-00996-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The early universe is modeled through the quantization of a
Friedmann-Robertson-Walker model with positive curvature of the spatial
hypersurfaces. In this model, the universe is filled by two fluids: radiation
and a generalized Chaplygin gas. The quantization of this model is made
following the prescriptions due to J. A. Wheeler and B. DeWitt. Using the
Schutz's formalism, the time notion is recovered and the Wheeler-DeWitt
equation transforms into a time dependent Schr\"{o}dinger equation, which rules
the dynamics of the early universe, under the action of an effective potential
$V_{eff}$. That potential, depends on three parameters. Depending on the values
of these parameters, $V_{eff}$ may have two different shapes. $V_{eff}(a)$ may
have the shape of a barrier or the shape of a well followed by a barrier. We
solve, numerically, the appropriate time dependent Schr\"{o}dinger equation and
obtain the time evolution of an initial wave function, for both cases. These
wave functions satisfy suitable boundary conditions. For both shapes of
$V_{eff}$, we compute the tunneling probability, which is a function of the
mean kinetic energy associated to the radiation energy $E_m$ and of the three
parameters of the generalized Chaplygin gas: $\alpha$, $A$ and $B$. The
tunneling probabilities, for both shapes of $V_{eff}$, indicates that the
universe should nucleate with the highest possible values of $E_m$, $\alpha$,
$A$ and $B$. Finally, we study the classical universe evolution after the
wavefunction has tunneled $V_{eff}$. The calculations show that the universe
may emerge from the Planck era in an inflationary phase.
| [
{
"created": "Wed, 5 Feb 2020 19:54:38 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Jul 2020 21:25:11 GMT",
"version": "v2"
},
{
"created": "Sat, 14 Nov 2020 15:14:42 GMT",
"version": "v3"
}
] | 2021-01-26 | [
[
"Monerat",
"G. A.",
""
],
[
"Santos",
"C. G. M.",
""
],
[
"Oliveira-Neto",
"G.",
""
],
[
"Silva",
"E. V. Corrêa",
""
],
[
"Filho",
"L. G. Ferreira",
""
]
] | The early universe is modeled through the quantization of a Friedmann-Robertson-Walker model with positive curvature of the spatial hypersurfaces. In this model, the universe is filled by two fluids: radiation and a generalized Chaplygin gas. The quantization of this model is made following the prescriptions due to J. A. Wheeler and B. DeWitt. Using the Schutz's formalism, the time notion is recovered and the Wheeler-DeWitt equation transforms into a time dependent Schr\"{o}dinger equation, which rules the dynamics of the early universe, under the action of an effective potential $V_{eff}$. That potential, depends on three parameters. Depending on the values of these parameters, $V_{eff}$ may have two different shapes. $V_{eff}(a)$ may have the shape of a barrier or the shape of a well followed by a barrier. We solve, numerically, the appropriate time dependent Schr\"{o}dinger equation and obtain the time evolution of an initial wave function, for both cases. These wave functions satisfy suitable boundary conditions. For both shapes of $V_{eff}$, we compute the tunneling probability, which is a function of the mean kinetic energy associated to the radiation energy $E_m$ and of the three parameters of the generalized Chaplygin gas: $\alpha$, $A$ and $B$. The tunneling probabilities, for both shapes of $V_{eff}$, indicates that the universe should nucleate with the highest possible values of $E_m$, $\alpha$, $A$ and $B$. Finally, we study the classical universe evolution after the wavefunction has tunneled $V_{eff}$. The calculations show that the universe may emerge from the Planck era in an inflationary phase. |
2104.11705 | Mohammed Khalil | Mohammed Khalil, Alessandra Buonanno, Jan Steinhoff, Justin Vines | Radiation-reaction force and multipolar waveforms for eccentric,
spin-aligned binaries in the effective-one-body formalism | 27 pages. v2: fixed typos, matches published version | Phys. Rev. D 104, 024046 (2021) | 10.1103/PhysRevD.104.024046 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | While most binary inspirals are expected to have circularized before they
enter the LIGO/Virgo frequency band, a small fraction of those binaries could
have non-negligible orbital eccentricity depending on their formation channel.
Hence, it is important to accurately model eccentricity effects in waveform
models used to detect those binaries, infer their properties, and shed light on
their astrophysical environment. We develop a multipolar effective-one-body
(EOB) eccentric waveform model for compact binaries whose components have spins
aligned or anti-aligned with the orbital angular momentum. The waveform model
contains eccentricity effects in the radiation-reaction force and gravitational
modes through second post-Newtonian (PN) order, including tail effects, and
spin-orbit and spin-spin couplings. We recast the PN-expanded, eccentric
radiation-reaction force and modes in factorized form so that the newly derived
terms can be directly included in the state-of-the-art, quasi-circular--orbit
EOB model currently used in LIGO/Virgo analyses (i.e., the SEOBNRv4HM model).
| [
{
"created": "Fri, 23 Apr 2021 16:48:42 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Jul 2021 22:21:41 GMT",
"version": "v2"
}
] | 2021-07-21 | [
[
"Khalil",
"Mohammed",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Steinhoff",
"Jan",
""
],
[
"Vines",
"Justin",
""
]
] | While most binary inspirals are expected to have circularized before they enter the LIGO/Virgo frequency band, a small fraction of those binaries could have non-negligible orbital eccentricity depending on their formation channel. Hence, it is important to accurately model eccentricity effects in waveform models used to detect those binaries, infer their properties, and shed light on their astrophysical environment. We develop a multipolar effective-one-body (EOB) eccentric waveform model for compact binaries whose components have spins aligned or anti-aligned with the orbital angular momentum. The waveform model contains eccentricity effects in the radiation-reaction force and gravitational modes through second post-Newtonian (PN) order, including tail effects, and spin-orbit and spin-spin couplings. We recast the PN-expanded, eccentric radiation-reaction force and modes in factorized form so that the newly derived terms can be directly included in the state-of-the-art, quasi-circular--orbit EOB model currently used in LIGO/Virgo analyses (i.e., the SEOBNRv4HM model). |
2211.05145 | Niklas Becker | Niklas Becker, Laura Sagunski | Comparing Accretion Disks and Dark Matter Spikes in Intermediate Mass
Ratio Inspirals | 16 pages, 8 figures. Submitted to PRD. Code available online at
http://github.com/DMGW-Goethe/imripy | null | 10.1103/PhysRevD.107.083003 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | Intermediate Mass Ratio Inspirals (IMRIs) will be observable with space-based
gravitational wave detectors such as the Laser Interferometer Space Antenna
(LISA). To this end, the environmental effects in such systems have to be
modeled and understood. These effects can include (baryonic) accretion disks
and dark matter (DM) overdensities, so called spikes. For the first time, we
model an IMRI system with both an accretion disk and a DM spike present and
compare their effects on the inspiral and the emitted gravitational wave
signal. We study the eccentricity evolution, employ the braking index and
derive the dephasing index, which turn out to be complementary observational
signatures. They allow us to disentangle the accretion disk and DM spike
effects in the IMRI system.
| [
{
"created": "Wed, 9 Nov 2022 19:00:07 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Mar 2023 14:51:47 GMT",
"version": "v2"
}
] | 2023-04-19 | [
[
"Becker",
"Niklas",
""
],
[
"Sagunski",
"Laura",
""
]
] | Intermediate Mass Ratio Inspirals (IMRIs) will be observable with space-based gravitational wave detectors such as the Laser Interferometer Space Antenna (LISA). To this end, the environmental effects in such systems have to be modeled and understood. These effects can include (baryonic) accretion disks and dark matter (DM) overdensities, so called spikes. For the first time, we model an IMRI system with both an accretion disk and a DM spike present and compare their effects on the inspiral and the emitted gravitational wave signal. We study the eccentricity evolution, employ the braking index and derive the dephasing index, which turn out to be complementary observational signatures. They allow us to disentangle the accretion disk and DM spike effects in the IMRI system. |
gr-qc/0608138 | Archana Pai | Archana Pai | Optimal Source Tracking and Beaming of LISA | 8 pages, 9 figures. To appear in the proceedings of Sixth
International LISA Symposium | null | 10.1063/1.2405088 | null | gr-qc | null | We revisit the directionally optimal data streams of LISA first introduced in
Nayak etal. It was shown that by using appropriate choice of Time delay
interferometric (TDI) combinations, a monochromatic fixed source in the
barycentric frame can be optimally tracked in the LISA frame. In this work, we
study the beaming properties of these optimal streams. We show that all the
three streams V+, Vx and Vo with maximum, minimum and zero directional SNR
respectively are highly beamed. We study in detail the frequency dependence of
the beaming.
| [
{
"created": "Thu, 31 Aug 2006 10:29:40 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Pai",
"Archana",
""
]
] | We revisit the directionally optimal data streams of LISA first introduced in Nayak etal. It was shown that by using appropriate choice of Time delay interferometric (TDI) combinations, a monochromatic fixed source in the barycentric frame can be optimally tracked in the LISA frame. In this work, we study the beaming properties of these optimal streams. We show that all the three streams V+, Vx and Vo with maximum, minimum and zero directional SNR respectively are highly beamed. We study in detail the frequency dependence of the beaming. |
2209.12058 | Alexander Zhidenko | R. A. Konoplya and A. Zhidenko | Nonoscillatory gravitational quasinormal modes and telling tails for
Schwarzschild-de Sitter black holes | 8 pages, 3 figures | Phys. Rev. D 106, 124004 (2022) | 10.1103/PhysRevD.106.124004 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the quasinormal spectrum of gravitational perturbations of
Schwarzschild - de Sitter black holes contains a new branch of purely imaginary
modes. These modes are not algebraically special and we showed that the sum of
them form the well-known in the literature exponential asymptotic tail. When
the ratio of the event horizon radius to the cosmological horizon vanishes,
these quasinormal modes approach modes of empty de Sitter spacetime. Thus, the
spectrum consists of the two branches: Schwarzschild branch deformed by the
cosmological constant and de Sitter branch deformed by the black hole mass.
While the de Sitter branch contains purely imaginary modes only, the
oscillatory modes (with nonzero real part) of the Schwarzschild branch can also
become purely imaginary for some values of the cosmological constant, for which
they approach the algebraically special mode.
| [
{
"created": "Sat, 24 Sep 2022 17:56:38 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Dec 2022 15:30:33 GMT",
"version": "v2"
}
] | 2022-12-05 | [
[
"Konoplya",
"R. A.",
""
],
[
"Zhidenko",
"A.",
""
]
] | We show that the quasinormal spectrum of gravitational perturbations of Schwarzschild - de Sitter black holes contains a new branch of purely imaginary modes. These modes are not algebraically special and we showed that the sum of them form the well-known in the literature exponential asymptotic tail. When the ratio of the event horizon radius to the cosmological horizon vanishes, these quasinormal modes approach modes of empty de Sitter spacetime. Thus, the spectrum consists of the two branches: Schwarzschild branch deformed by the cosmological constant and de Sitter branch deformed by the black hole mass. While the de Sitter branch contains purely imaginary modes only, the oscillatory modes (with nonzero real part) of the Schwarzschild branch can also become purely imaginary for some values of the cosmological constant, for which they approach the algebraically special mode. |
gr-qc/0703022 | Norbert Van den Bergh | B. Bastiaensen, H. R. Karimian, N. Van den Bergh and L. Wylleman | Purely radiative perfect fluids | 12 pages, minor grammatical changes | Class.Quant.Grav.24:3211-3220,2007 | 10.1088/0264-9381/24/13/005 | null | gr-qc | null | We study `purely radiative' (div E = div H = 0) and geodesic perfect fluids
with non-constant pressure and show that the Bianchi class A perfect fluids can
be uniquely characterized --modulo the class of purely electric and
(pseudo-)spherically symmetric universes-- as those models for which the
magnetic and electric part of the Weyl tensor and the shear are simultaneously
diagonalizable. For the case of constant pressure the same conclusion holds
provided one also assumes that the fluid is irrotational.
| [
{
"created": "Sun, 4 Mar 2007 16:30:48 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Mar 2007 10:12:45 GMT",
"version": "v2"
},
{
"created": "Tue, 8 May 2007 07:15:28 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Bastiaensen",
"B.",
""
],
[
"Karimian",
"H. R.",
""
],
[
"Bergh",
"N. Van den",
""
],
[
"Wylleman",
"L.",
""
]
] | We study `purely radiative' (div E = div H = 0) and geodesic perfect fluids with non-constant pressure and show that the Bianchi class A perfect fluids can be uniquely characterized --modulo the class of purely electric and (pseudo-)spherically symmetric universes-- as those models for which the magnetic and electric part of the Weyl tensor and the shear are simultaneously diagonalizable. For the case of constant pressure the same conclusion holds provided one also assumes that the fluid is irrotational. |
1311.4273 | Ayaka Shoda | Ayaka Shoda, Masaki Ando, Koji Ishidoshiro, Kenshi Okada, Wataru
Kokuyama, Yoichi Aso, Kimio Tsubono | Search for a Stochastic Gravitational-wave Background using a pair of
Torsion-bar Antennas | 5 pages, 4 figures | Phys. Rev. D 89, 027101 (2014) | 10.1103/PhysRevD.89.027101 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have set a new upper limit on the stochastic gravitational wave background
(SGWB) using two prototype Torsion-bar Antennas (TOBAs). TOBA is a
low-frequency gravitational-wave detector with bar-shaped test masses rotated
by the tidal force of gravitational waves. As a result of simultaneous 7-hour
observations with TOBAs in Tokyo and Kyoto in Japan, our upper limit with a
confidence level of 95% is $\Omega_{\rm gw}h_0^2 < 1.9 \times 10^{17}$ at 0.035
- 0.830 Hz, where $h_{0}$ is the Hubble constant in units of 100 km/s/Mpc and
$\Omega_{\rm gw}$ is the gravitational wave energy density per logarithmic
frequency interval in units of the closure density. We successfully updated the
upper limit and extended the explored frequency band.
| [
{
"created": "Mon, 18 Nov 2013 05:57:46 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Jan 2014 02:41:36 GMT",
"version": "v2"
}
] | 2014-01-28 | [
[
"Shoda",
"Ayaka",
""
],
[
"Ando",
"Masaki",
""
],
[
"Ishidoshiro",
"Koji",
""
],
[
"Okada",
"Kenshi",
""
],
[
"Kokuyama",
"Wataru",
""
],
[
"Aso",
"Yoichi",
""
],
[
"Tsubono",
"Kimio",
""
]
] | We have set a new upper limit on the stochastic gravitational wave background (SGWB) using two prototype Torsion-bar Antennas (TOBAs). TOBA is a low-frequency gravitational-wave detector with bar-shaped test masses rotated by the tidal force of gravitational waves. As a result of simultaneous 7-hour observations with TOBAs in Tokyo and Kyoto in Japan, our upper limit with a confidence level of 95% is $\Omega_{\rm gw}h_0^2 < 1.9 \times 10^{17}$ at 0.035 - 0.830 Hz, where $h_{0}$ is the Hubble constant in units of 100 km/s/Mpc and $\Omega_{\rm gw}$ is the gravitational wave energy density per logarithmic frequency interval in units of the closure density. We successfully updated the upper limit and extended the explored frequency band. |
1707.02764 | Igor Nikitin | Igor Nikitin | Wormhole solutions of RDM model | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The model of a spiral galaxy with radially directed flows of dark matter is
extended by exotic matter, in a form of a perfect fluid with a linear
anisotropic equation of state. The exotic matter is collected in the minimum of
gravitational potential and opens a wormhole in the center of the galaxy. The
flows of dark matter pass through the wormhole and form a mirror galaxy on the
other side. The influence of model parameters to the shape of solution is
studied, a solution matching parameters of Milky Way galaxy is computed.
| [
{
"created": "Mon, 10 Jul 2017 09:19:16 GMT",
"version": "v1"
}
] | 2017-07-11 | [
[
"Nikitin",
"Igor",
""
]
] | The model of a spiral galaxy with radially directed flows of dark matter is extended by exotic matter, in a form of a perfect fluid with a linear anisotropic equation of state. The exotic matter is collected in the minimum of gravitational potential and opens a wormhole in the center of the galaxy. The flows of dark matter pass through the wormhole and form a mirror galaxy on the other side. The influence of model parameters to the shape of solution is studied, a solution matching parameters of Milky Way galaxy is computed. |
gr-qc/0305018 | Allan Joseph Medved | Gilad Gour and A.J.M. Medved | Thermal Fluctuations and Black Hole Entropy | 25 pages, Revtex; references added and corrected, and some minor
changes | Class.Quant.Grav. 20 (2003) 3307-3326 | 10.1088/0264-9381/20/15/303 | null | gr-qc hep-th | null | In this paper, we consider the effect of thermal fluctuations on the entropy
of both neutral and charged black holes. We emphasize the distinction between
fixed and fluctuating charge systems; using a canonical ensemble to describe
the former and a grand canonical ensemble to study the latter. Our novel
approach is based on the philosophy that the black hole quantum spectrum is an
essential component in any such calculation. For definiteness, we employ a
uniformly spaced area spectrum, which has been advocated by Bekenstein and
others in the literature. The generic results are applied to some specific
models; in particular, various limiting cases of an (arbitrary-dimensional)
AdS-Reissner-Nordstrom black hole. We find that the leading-order quantum
correction to the entropy can consistently be expressed as the logarithm of the
classical quantity. For a small AdS curvature parameter and zero net charge, it
is shown that, independent of the dimension, the logarithmic prefactor is +1/2
when the charge is fixed but +1 when the charge is fluctuating.We also
demonstrate that, in the grand canonical framework, the fluctuations in the
charge are large, $\Delta Q\sim\Delta A\sim S_{BH}^{1/2}$, even when $<Q> =0$.
A further implication of this framework is that an asymptotically flat,
non-extremal black hole can never achieve a state of thermal equilibrium.
| [
{
"created": "Mon, 5 May 2003 19:56:10 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Jun 2003 23:22:10 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Gour",
"Gilad",
""
],
[
"Medved",
"A. J. M.",
""
]
] | In this paper, we consider the effect of thermal fluctuations on the entropy of both neutral and charged black holes. We emphasize the distinction between fixed and fluctuating charge systems; using a canonical ensemble to describe the former and a grand canonical ensemble to study the latter. Our novel approach is based on the philosophy that the black hole quantum spectrum is an essential component in any such calculation. For definiteness, we employ a uniformly spaced area spectrum, which has been advocated by Bekenstein and others in the literature. The generic results are applied to some specific models; in particular, various limiting cases of an (arbitrary-dimensional) AdS-Reissner-Nordstrom black hole. We find that the leading-order quantum correction to the entropy can consistently be expressed as the logarithm of the classical quantity. For a small AdS curvature parameter and zero net charge, it is shown that, independent of the dimension, the logarithmic prefactor is +1/2 when the charge is fixed but +1 when the charge is fluctuating.We also demonstrate that, in the grand canonical framework, the fluctuations in the charge are large, $\Delta Q\sim\Delta A\sim S_{BH}^{1/2}$, even when $<Q> =0$. A further implication of this framework is that an asymptotically flat, non-extremal black hole can never achieve a state of thermal equilibrium. |
1910.09363 | Jeff Steinhauer | Victor I. Kolobov, Katrine Golubkov, Juan Ram\'on Mu\~noz de Nova, and
Jeff Steinhauer | Spontaneous Hawking radiation and beyond: Observing the time evolution
of an analogue black hole | null | Nature Phys. 17, 362-367 (2021) | 10.1038/s41567-020-01076-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We observe the time dependence of the Hawking radiation in an analogue black
hole. Soon after the formation of the horizon, there is little or no Hawking
radiation. The Hawking radiation then ramps up during approximately one period
of oscillation, until it reaches the quantity expected for spontaneous
emission. This is similar to a black hole created from gravitational collapse.
The spectrum remains approximately constant at the spontaneous level for some
time, similar to a stationary black hole. An inner horizon then forms, in
analogy with a charged black hole. The inner horizon causes stimulated Hawking
radiation. Both types of stimulation predicted by Ted Jacobson and coworkers
likely contribute, but the monochromatic stimulation probably contributes more
than does the black-hole lasing.
| [
{
"created": "Mon, 21 Oct 2019 13:34:29 GMT",
"version": "v1"
}
] | 2021-11-02 | [
[
"Kolobov",
"Victor I.",
""
],
[
"Golubkov",
"Katrine",
""
],
[
"de Nova",
"Juan Ramón Muñoz",
""
],
[
"Steinhauer",
"Jeff",
""
]
] | We observe the time dependence of the Hawking radiation in an analogue black hole. Soon after the formation of the horizon, there is little or no Hawking radiation. The Hawking radiation then ramps up during approximately one period of oscillation, until it reaches the quantity expected for spontaneous emission. This is similar to a black hole created from gravitational collapse. The spectrum remains approximately constant at the spontaneous level for some time, similar to a stationary black hole. An inner horizon then forms, in analogy with a charged black hole. The inner horizon causes stimulated Hawking radiation. Both types of stimulation predicted by Ted Jacobson and coworkers likely contribute, but the monochromatic stimulation probably contributes more than does the black-hole lasing. |
gr-qc/0005056 | Lawrence E. Kidder | Lawrence E. Kidder, Mark A. Scheel, Saul A. Teukolsky, Eric D. Carlson
and Gregory B. Cook | Black hole evolution by spectral methods | 20 pages, 17 figures, submitted to PRD | Phys.Rev. D62 (2000) 084032 | 10.1103/PhysRevD.62.084032 | null | gr-qc | null | Current methods of evolving a spacetime containing one or more black holes
are plagued by instabilities that prohibit long-term evolution. Some of these
instabilities may be due to the numerical method used, traditionally finite
differencing. In this paper, we explore the use of a pseudospectral collocation
(PSC) method for the evolution of a spherically symmetric black hole spacetime
in one dimension using a hyperbolic formulation of Einstein's equations. We
demonstrate that our PSC method is able to evolve a spherically symmetric black
hole spacetime forever without enforcing constraints, even if we add dynamics
via a Klein-Gordon scalar field. We find that, in contrast to
finite-differencing methods, black hole excision is a trivial operation using
PSC applied to a hyperbolic formulation of Einstein's equations. We discuss the
extension of this method to three spatial dimensions.
| [
{
"created": "Mon, 15 May 2000 18:52:53 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Kidder",
"Lawrence E.",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Teukolsky",
"Saul A.",
""
],
[
"Carlson",
"Eric D.",
""
],
[
"Cook",
"Gregory B.",
""
]
] | Current methods of evolving a spacetime containing one or more black holes are plagued by instabilities that prohibit long-term evolution. Some of these instabilities may be due to the numerical method used, traditionally finite differencing. In this paper, we explore the use of a pseudospectral collocation (PSC) method for the evolution of a spherically symmetric black hole spacetime in one dimension using a hyperbolic formulation of Einstein's equations. We demonstrate that our PSC method is able to evolve a spherically symmetric black hole spacetime forever without enforcing constraints, even if we add dynamics via a Klein-Gordon scalar field. We find that, in contrast to finite-differencing methods, black hole excision is a trivial operation using PSC applied to a hyperbolic formulation of Einstein's equations. We discuss the extension of this method to three spatial dimensions. |
gr-qc/0207012 | D. F. Mota | John D. Barrow and David F. Mota | Qualitative Analysis of Universes with Varying Alpha | 26 pages, 6 figures | Class.Quant.Grav. 19 (2002) 6197-6212 | 10.1088/0264-9381/19/23/317 | DAMTP-2002-80 | gr-qc astro-ph hep-ph | null | Assuming a Friedmann universe which evolves with a power-law scale factor,
$a=t^{n}$, we analyse the phase space of the system of equations that describes
a time-varying fine structure 'constant', $\alpha$, in the
Bekenstein-Sandvik-Barrow-Magueijo generalisation of general relativity. We
have classified all the possible behaviours of $\alpha (t)$ in ever-expanding
universes with different $n$ and find new exact solutions for $\alpha (t)$. We
find the attractors points in the phase space for all $n$. In general, $\alpha
$ will be a non-decreasing function of time that increases logarithmically in
time during a period when the expansion is dust dominated ($n=2/3$), but
becomes constant when $n>2/3$. This includes the case of negative-curvature
domination ($n=1$). $\alpha $ also tends rapidly to a constant when the
expansion scale factor increases exponentially. A general set of conditions is
established for $\alpha $ to become asymptotically constant at late times in an
expanding universe.
| [
{
"created": "Tue, 2 Jul 2002 12:28:18 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Barrow",
"John D.",
""
],
[
"Mota",
"David F.",
""
]
] | Assuming a Friedmann universe which evolves with a power-law scale factor, $a=t^{n}$, we analyse the phase space of the system of equations that describes a time-varying fine structure 'constant', $\alpha$, in the Bekenstein-Sandvik-Barrow-Magueijo generalisation of general relativity. We have classified all the possible behaviours of $\alpha (t)$ in ever-expanding universes with different $n$ and find new exact solutions for $\alpha (t)$. We find the attractors points in the phase space for all $n$. In general, $\alpha $ will be a non-decreasing function of time that increases logarithmically in time during a period when the expansion is dust dominated ($n=2/3$), but becomes constant when $n>2/3$. This includes the case of negative-curvature domination ($n=1$). $\alpha $ also tends rapidly to a constant when the expansion scale factor increases exponentially. A general set of conditions is established for $\alpha $ to become asymptotically constant at late times in an expanding universe. |
1604.07428 | Wolfgang Wieland | Wolfgang Wieland | Quasi-local gravitational angular momentum and centre of mass from
generalised Witten equations | 26 pages, one figure | Gen. Rel. Grav. 49 (2017) | 10.1007/s10714-017-2200-4 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Witten's proof for the positivity of the ADM mass gives a definition of
energy in terms of three-surface spinors. In this paper, we give a
generalisation for the remaining six Poincar\'e charges at spacelike infinity,
which are the angular momentum and centre of mass. The construction improves on
certain three-surface spinor equations introduced by Shaw. We solve these
equations asymptotically obtaining the ten Poincar\'e charges as integrals over
the Nester--Witten two-form. We point out that the defining differential
equations can be extended to three-surfaces of arbitrary signature and we study
them on the entire boundary of a compact four-dimensional region of spacetime.
The resulting quasi-local expressions for energy and angular momentum are
integrals over a two-dimensional cross-section of the boundary. For any two
consecutive such cross-sections, conservation laws are derived that determine
the influx (outflow) of matter and gravitational radiation.
| [
{
"created": "Mon, 25 Apr 2016 20:14:27 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Feb 2017 23:04:26 GMT",
"version": "v2"
}
] | 2017-02-14 | [
[
"Wieland",
"Wolfgang",
""
]
] | Witten's proof for the positivity of the ADM mass gives a definition of energy in terms of three-surface spinors. In this paper, we give a generalisation for the remaining six Poincar\'e charges at spacelike infinity, which are the angular momentum and centre of mass. The construction improves on certain three-surface spinor equations introduced by Shaw. We solve these equations asymptotically obtaining the ten Poincar\'e charges as integrals over the Nester--Witten two-form. We point out that the defining differential equations can be extended to three-surfaces of arbitrary signature and we study them on the entire boundary of a compact four-dimensional region of spacetime. The resulting quasi-local expressions for energy and angular momentum are integrals over a two-dimensional cross-section of the boundary. For any two consecutive such cross-sections, conservation laws are derived that determine the influx (outflow) of matter and gravitational radiation. |
1005.4201 | Puxun Wu | Kaituo Zhang, Puxun Wu, Hongwei Yu | The stability of Einstein static universe in the DGP braneworld | 10 pages, 2 figures, to appear in PLB | Phys.Lett.B690:229-232,2010 | 10.1016/j.physletb.2010.05.040 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/3.0/ | The stability of an Einstein static universe in the DGP braneworld scenario
is studied in this paper. Two separate branches denoted by $\epsilon=\pm1$ of
the DGP model are analyzed. Assuming the existence of a perfect fluid with a
constant equation of state, $w$, in the universe, we find that, for the branch
with $\epsilon=1$, there is no a stable Einstein static solution, while, for
the case with $\epsilon=-1$, the Einstein static universe exists and it is
stable when $-1<w<-1/3$. Thus, the universe can stay at this stable state
past-eternally and may undergo a series of infinite, non-singular oscillations.
Therefore, the big bang singularity problem in the standard cosmological model
can be resolved.
| [
{
"created": "Sun, 23 May 2010 13:37:25 GMT",
"version": "v1"
},
{
"created": "Wed, 26 May 2010 11:21:17 GMT",
"version": "v2"
},
{
"created": "Tue, 15 Jun 2010 23:37:27 GMT",
"version": "v3"
}
] | 2014-11-21 | [
[
"Zhang",
"Kaituo",
""
],
[
"Wu",
"Puxun",
""
],
[
"Yu",
"Hongwei",
""
]
] | The stability of an Einstein static universe in the DGP braneworld scenario is studied in this paper. Two separate branches denoted by $\epsilon=\pm1$ of the DGP model are analyzed. Assuming the existence of a perfect fluid with a constant equation of state, $w$, in the universe, we find that, for the branch with $\epsilon=1$, there is no a stable Einstein static solution, while, for the case with $\epsilon=-1$, the Einstein static universe exists and it is stable when $-1<w<-1/3$. Thus, the universe can stay at this stable state past-eternally and may undergo a series of infinite, non-singular oscillations. Therefore, the big bang singularity problem in the standard cosmological model can be resolved. |
2104.02011 | Konstantin Eder | Konstantin Eder, Hanno Sahlmann | Holst-MacDowell-Mansouri action for (extended) supergravity with
boundaries and super Chern-Simons theory | v2: published version, 40 pages | J. High Energ. Phys. 2021, 71 (2021) | 10.1007/JHEP07(2021)071 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, the Cartan geometric approach toward (extended) supergravity
in the presence of boundaries will be discussed. In particular, based on new
developments in this field, we will derive the Holst variant of the
MacDowell-Mansouri action for $\mathcal{N}=1$ and $\mathcal{N}=2$ pure AdS
supergravity in $D=4$ for arbitrary Barbero-Immirzi parameters. This action
turns out to play a crucial role in context of boundaries in the framework of
supergravity if one imposes supersymmetry invariance at the boundary. For the
$\mathcal{N}=2$ case, it follows that this amounts to the introduction of a
$\theta$-topological term to the Yang-Mills sector which explicitly depends on
the Barbero-Immirzi parameter. This shows the close connection between this
parameter and the $\theta$-ambiguity of gauge theory. We will also discuss the
chiral limit of the theory, which turns out to possess some very special
properties such as the manifest invariance of the resulting action under an
enlarged gauge symmetry. Moreover, we will show that demanding supersymmetry
invariance at the boundary yields a unique boundary term corresponding to a
super Chern-Simons theory with $\mathrm{OSp}(\mathcal{N}|2)$ gauge group. In
this context, we will also derive boundary conditions that couple boundary and
bulk degrees of freedom and show equivalence to the results found in the
D'Auria-Fr\'e approach in context of the non-chiral theory. These results
provide a step towards of quantum description of supersymmetric black holes in
the framework of loop quantum gravity.
| [
{
"created": "Mon, 5 Apr 2021 17:00:04 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Jul 2021 07:55:39 GMT",
"version": "v2"
}
] | 2021-07-15 | [
[
"Eder",
"Konstantin",
""
],
[
"Sahlmann",
"Hanno",
""
]
] | In this article, the Cartan geometric approach toward (extended) supergravity in the presence of boundaries will be discussed. In particular, based on new developments in this field, we will derive the Holst variant of the MacDowell-Mansouri action for $\mathcal{N}=1$ and $\mathcal{N}=2$ pure AdS supergravity in $D=4$ for arbitrary Barbero-Immirzi parameters. This action turns out to play a crucial role in context of boundaries in the framework of supergravity if one imposes supersymmetry invariance at the boundary. For the $\mathcal{N}=2$ case, it follows that this amounts to the introduction of a $\theta$-topological term to the Yang-Mills sector which explicitly depends on the Barbero-Immirzi parameter. This shows the close connection between this parameter and the $\theta$-ambiguity of gauge theory. We will also discuss the chiral limit of the theory, which turns out to possess some very special properties such as the manifest invariance of the resulting action under an enlarged gauge symmetry. Moreover, we will show that demanding supersymmetry invariance at the boundary yields a unique boundary term corresponding to a super Chern-Simons theory with $\mathrm{OSp}(\mathcal{N}|2)$ gauge group. In this context, we will also derive boundary conditions that couple boundary and bulk degrees of freedom and show equivalence to the results found in the D'Auria-Fr\'e approach in context of the non-chiral theory. These results provide a step towards of quantum description of supersymmetric black holes in the framework of loop quantum gravity. |
gr-qc/9804075 | Sanjay Jhingan | P. S. Joshi and I. H. Dwivedi | Initial data and the end state of spherically symmetric gravitational
collapse | Ordinary Tex file, 31 pages no figures | Class.Quant.Grav. 16 (1999) 41-59 | 10.1088/0264-9381/16/1/003 | null | gr-qc | null | Generalizing earlier results on the initial data and the final fate of dust
collapse, we study here the relevance of the initial state of a spherically
symmetric matter cloud towards determining its end state in the course of a
continuing gravitational collapse. It is shown that given an arbitrary regular
distribution of matter at the initial epoch, there always exists an evolution
from this initial data which would result either in a black hole or a naked
singularity depending on the allowed choice of free functions available in the
solution. It follows that given any initial density and pressure profiles for
the cloud, there is a non-zero measure set of configurations leading either to
black holes or naked singularities, subject to the usual energy conditions
ensuring the positivity of energy density. We also characterize here wide new
families of black hole solutions resulting from spherically symmetric collapse
without requiring the cosmic censorship assumption.
| [
{
"created": "Tue, 28 Apr 1998 06:28:35 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Joshi",
"P. S.",
""
],
[
"Dwivedi",
"I. H.",
""
]
] | Generalizing earlier results on the initial data and the final fate of dust collapse, we study here the relevance of the initial state of a spherically symmetric matter cloud towards determining its end state in the course of a continuing gravitational collapse. It is shown that given an arbitrary regular distribution of matter at the initial epoch, there always exists an evolution from this initial data which would result either in a black hole or a naked singularity depending on the allowed choice of free functions available in the solution. It follows that given any initial density and pressure profiles for the cloud, there is a non-zero measure set of configurations leading either to black holes or naked singularities, subject to the usual energy conditions ensuring the positivity of energy density. We also characterize here wide new families of black hole solutions resulting from spherically symmetric collapse without requiring the cosmic censorship assumption. |
0910.1631 | Hans Westman F | Hans F. Westman | A First-Principles Implementation of Scale Invariance Using Best
Matching | 11 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a first-principles implementation of spatial scale invariance as a
local gauge symmetry in geometry dynamics using the method of best matching .
In addition to the 3-metric, the proposed scale invariant theory also contains
a 3-vector potential $A_k$ as a dynamical variable. Although some of the
mathematics is similar to Weyl's ingenious but physically questionable theory,
the equations of motion of this new theory are second order in
time-derivatives. Thereby we avoid the problems associated with fourth order
time derivatives that plague Weyl's original theory. It is tempting to try to
interpret the vector potential $A_k$ as the electromagnetic field. We exhibit
four independent reasons for not giving into this temptation. A more likely
possibility is that it can play the role of "dark matter". Indeed, as noted in
scale invariance seems to play a role in the MOND phenomenology. Spatial
boundary conditions are derived from the free-endpoint variation method and a
preliminary analysis of the constraints and their propagation in the
Hamiltonian formulation is presented.
| [
{
"created": "Thu, 8 Oct 2009 23:36:59 GMT",
"version": "v1"
}
] | 2009-10-12 | [
[
"Westman",
"Hans F.",
""
]
] | We present a first-principles implementation of spatial scale invariance as a local gauge symmetry in geometry dynamics using the method of best matching . In addition to the 3-metric, the proposed scale invariant theory also contains a 3-vector potential $A_k$ as a dynamical variable. Although some of the mathematics is similar to Weyl's ingenious but physically questionable theory, the equations of motion of this new theory are second order in time-derivatives. Thereby we avoid the problems associated with fourth order time derivatives that plague Weyl's original theory. It is tempting to try to interpret the vector potential $A_k$ as the electromagnetic field. We exhibit four independent reasons for not giving into this temptation. A more likely possibility is that it can play the role of "dark matter". Indeed, as noted in scale invariance seems to play a role in the MOND phenomenology. Spatial boundary conditions are derived from the free-endpoint variation method and a preliminary analysis of the constraints and their propagation in the Hamiltonian formulation is presented. |
gr-qc/0412041 | Zhong Chao Wu | Zhong Chao Wu | Creation of Kerr-de Sitter Black Hole in All Dimensions | 7 pages | Phys.Lett. B613 (2005) 1-4 | null | null | gr-qc astro-ph hep-th | null | We discuss the quantum creation scenario of a Kerr-de Sitter black hole in
all dimensions. We show that its relative creation probability is the
exponential to the entropy of the black hole, using a topological argument. The
action of the regular Euclidean instanton can be calculated in the same way.
| [
{
"created": "Thu, 9 Dec 2004 13:44:05 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Apr 2005 20:12:56 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Wu",
"Zhong Chao",
""
]
] | We discuss the quantum creation scenario of a Kerr-de Sitter black hole in all dimensions. We show that its relative creation probability is the exponential to the entropy of the black hole, using a topological argument. The action of the regular Euclidean instanton can be calculated in the same way. |
gr-qc/9801089 | Jacek Gruszczak | Jacek Gruszczak | Gravitational Conical Bremsstrahlung and Differential Structures | 3 pages, LaTeX, mprocl.sty, to appear in the Proceedings of the 8th
Marcel Grossman Meeting, Jerusalem, June 1997 (World Scientific, Singapore) | null | null | null | gr-qc | null | Differential properties of a spin 2 boson field $\psi_{\mu\nu}$ describing
propagation of gravitational perturbations on a straight cosmic string's
space-time background are studied by means of methods of the differential
spaces theory. It is shown that this field is a smooth one in the interior of
cosmic string's space-time and looses this property at the singular boundary
except for cosmic string space-times with the following deficits of angle:
$\Delta=2\pi (1-1/n) $, $n=1,2,...$. A relationship between smoothness of
$\psi_{\mu\nu}$ at the singularity and the gravitational conical bremsstrahlung
effect is discussed. A physical interpretation of the smoothness notion is
given. It is also argued that the assumption of smoothness of $\psi_{\mu\nu}$
at the singularity plays an equivalent role to the Aliev and Gal'tsov
"quantization" condition.
| [
{
"created": "Tue, 27 Jan 1998 11:21:37 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gruszczak",
"Jacek",
""
]
] | Differential properties of a spin 2 boson field $\psi_{\mu\nu}$ describing propagation of gravitational perturbations on a straight cosmic string's space-time background are studied by means of methods of the differential spaces theory. It is shown that this field is a smooth one in the interior of cosmic string's space-time and looses this property at the singular boundary except for cosmic string space-times with the following deficits of angle: $\Delta=2\pi (1-1/n) $, $n=1,2,...$. A relationship between smoothness of $\psi_{\mu\nu}$ at the singularity and the gravitational conical bremsstrahlung effect is discussed. A physical interpretation of the smoothness notion is given. It is also argued that the assumption of smoothness of $\psi_{\mu\nu}$ at the singularity plays an equivalent role to the Aliev and Gal'tsov "quantization" condition. |
gr-qc/0011059 | null | O. Gron, S. Hervik | Gravitational Entropy and Quantum Cosmology | 20 pages, 7 ps figures | Class.Quant.Grav. 18 (2001) 601-618 | 10.1088/0264-9381/18/4/303 | null | gr-qc | null | We investigate the evolution of different measures of ``Gravitational
Entropy'' in Bianchi type I and Lema\^itre-Tolman universe models.
A new quantity behaving in accordance with the second law of thermodynamics
is introduced. We then go on and investigate whether a quantum calculation of
initial conditions for the universe based upon the Wheeler-DeWitt equation
supports Penrose's Weyl Curvature Conjecture, according to which the Ricci part
of the curvature dominates over the Weyl part at the initial singularity of the
universe. The theory is applied to the Bianchi type I universe models with dust
and a cosmological constant and to the Lema\^itre-Tolman universe models. We
investigate two different versions of the conjecture. First we investigate a
local version which fails to support the conjecture. Thereafter we construct a
non-local entity which shows more promising behaviour concerning the
conjecture.
| [
{
"created": "Fri, 17 Nov 2000 07:33:03 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Feb 2001 08:40:46 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Gron",
"O.",
""
],
[
"Hervik",
"S.",
""
]
] | We investigate the evolution of different measures of ``Gravitational Entropy'' in Bianchi type I and Lema\^itre-Tolman universe models. A new quantity behaving in accordance with the second law of thermodynamics is introduced. We then go on and investigate whether a quantum calculation of initial conditions for the universe based upon the Wheeler-DeWitt equation supports Penrose's Weyl Curvature Conjecture, according to which the Ricci part of the curvature dominates over the Weyl part at the initial singularity of the universe. The theory is applied to the Bianchi type I universe models with dust and a cosmological constant and to the Lema\^itre-Tolman universe models. We investigate two different versions of the conjecture. First we investigate a local version which fails to support the conjecture. Thereafter we construct a non-local entity which shows more promising behaviour concerning the conjecture. |
gr-qc/9406007 | Neil Cornish | N. J. Cornish and J. W. Moffat | Non-Singular Gravity Without Black Holes | 26 pages, UTPT-94-08 | J.Math.Phys.35:6628-6643,1994 | 10.1063/1.530697 | null | gr-qc | null | A non-singular, static spherically symmetric solution to the nonsymmetric
gravitational and electromagnetic theory field equations is derived, which
depends on the four parameters m, l^2, Q and s, where m is the mass, Q is the
electric charge, l^2 is the NGT charge of a body and s is a dimensionless
constant. The electromagnetic field invariants are also singularity-free, so
that it is possible to construct regular particle-like solutions in the theory.
All the curvature invariants are finite, there are no null surfaces in the
spacetime and there are no black holes. A new stable, superdense object (SDO)
replaces black holes.
| [
{
"created": "Fri, 3 Jun 1994 23:28:04 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Cornish",
"N. J.",
""
],
[
"Moffat",
"J. W.",
""
]
] | A non-singular, static spherically symmetric solution to the nonsymmetric gravitational and electromagnetic theory field equations is derived, which depends on the four parameters m, l^2, Q and s, where m is the mass, Q is the electric charge, l^2 is the NGT charge of a body and s is a dimensionless constant. The electromagnetic field invariants are also singularity-free, so that it is possible to construct regular particle-like solutions in the theory. All the curvature invariants are finite, there are no null surfaces in the spacetime and there are no black holes. A new stable, superdense object (SDO) replaces black holes. |
1907.04982 | Masaki Yamada | Jeong-Pyong Hong, Motoo Suzuki, Masaki Yamada | Charged black holes in non-linear Q-clouds with O(3) symmetry | 6 pages, 5 figures; v2: minor revision, added a comment on no-hair
theorem by Mayo and Bekenstein | null | 10.1016/j.physletb.2020.135324 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct charged soliton solutions around spherical charged black holes
with no angular momentum in asymptotically flat spacetime. These solutions are
non-linear generalizations of charged scalar clouds, dubbed Q-ball hair or
Q-clouds, and they do not contradict the non-existence theorem for free
(linear) scalar clouds around charged black holes. These solutions are the
first examples of O(3) solutions for Q-clouds around a non-extremal and
non-rotating BH in the Abelian gauge theory. We show that a solution exists
with an infinitely short hair in the limit of extremal black holes. We discuss
the evolution of scalar hair in a system with fixed total charge and describe
how the existence of Q-clouds is related to the weak-gravity conjecture. The
reason that the no-hair theorem by Mayo and Bekenstein cannot be applied to the
massive scalar field is also discussed.
| [
{
"created": "Thu, 11 Jul 2019 03:23:17 GMT",
"version": "v1"
},
{
"created": "Sun, 9 Feb 2020 02:51:35 GMT",
"version": "v2"
}
] | 2020-03-18 | [
[
"Hong",
"Jeong-Pyong",
""
],
[
"Suzuki",
"Motoo",
""
],
[
"Yamada",
"Masaki",
""
]
] | We construct charged soliton solutions around spherical charged black holes with no angular momentum in asymptotically flat spacetime. These solutions are non-linear generalizations of charged scalar clouds, dubbed Q-ball hair or Q-clouds, and they do not contradict the non-existence theorem for free (linear) scalar clouds around charged black holes. These solutions are the first examples of O(3) solutions for Q-clouds around a non-extremal and non-rotating BH in the Abelian gauge theory. We show that a solution exists with an infinitely short hair in the limit of extremal black holes. We discuss the evolution of scalar hair in a system with fixed total charge and describe how the existence of Q-clouds is related to the weak-gravity conjecture. The reason that the no-hair theorem by Mayo and Bekenstein cannot be applied to the massive scalar field is also discussed. |
1907.04747 | Quentin Baghi | Quentin Baghi, Ira Thorpe, Jacob Slutsky, John Baker, Tito Dal Canton,
Natalia Korsakova, Nikos Karnesis | Gravitational-wave parameter estimation with gaps in LISA: a Bayesian
data augmentation method | 18 pages, 7 figures, accepted for publication in Phys. Rev. D | null | 10.1103/PhysRevD.100.022003 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By listening to gravity in the low frequency band, between 0.1 mHz and 1 Hz,
the future space-based gravitational-wave observatory LISA will be able to
detect tens of thousands of astrophysical sources from cosmic dawn to the
present. The detection and characterization of all resolvable sources is a
challenge in itself, but LISA data analysis will be further complicated by
interruptions occurring in the interferometric measurements. These
interruptions will be due to various causes occurring at various rates, such as
laser frequency switches, high-gain antenna re-pointing, orbit corrections, or
even unplanned random events. Extracting long-lasting gravitational-wave
signals from gapped data raises problems such as noise leakage and increased
computational complexity. We address these issues by using Bayesian data
augmentation, a method that reintroduces the missing data as auxiliary
variables in the sampling of the posterior distribution of astrophysical
parameters. This provides a statistically consistent way to handle gaps while
improving the sampling efficiency and mitigating leakage effects. We apply the
method to the estimation of galactic binaries parameters with different gap
patterns, and we compare the results to the case of complete data.
| [
{
"created": "Wed, 10 Jul 2019 14:23:27 GMT",
"version": "v1"
}
] | 2019-07-24 | [
[
"Baghi",
"Quentin",
""
],
[
"Thorpe",
"Ira",
""
],
[
"Slutsky",
"Jacob",
""
],
[
"Baker",
"John",
""
],
[
"Canton",
"Tito Dal",
""
],
[
"Korsakova",
"Natalia",
""
],
[
"Karnesis",
"Nikos",
""
]
] | By listening to gravity in the low frequency band, between 0.1 mHz and 1 Hz, the future space-based gravitational-wave observatory LISA will be able to detect tens of thousands of astrophysical sources from cosmic dawn to the present. The detection and characterization of all resolvable sources is a challenge in itself, but LISA data analysis will be further complicated by interruptions occurring in the interferometric measurements. These interruptions will be due to various causes occurring at various rates, such as laser frequency switches, high-gain antenna re-pointing, orbit corrections, or even unplanned random events. Extracting long-lasting gravitational-wave signals from gapped data raises problems such as noise leakage and increased computational complexity. We address these issues by using Bayesian data augmentation, a method that reintroduces the missing data as auxiliary variables in the sampling of the posterior distribution of astrophysical parameters. This provides a statistically consistent way to handle gaps while improving the sampling efficiency and mitigating leakage effects. We apply the method to the estimation of galactic binaries parameters with different gap patterns, and we compare the results to the case of complete data. |
gr-qc/0410045 | Xian-Hui Ge | Xian-Hui Ge and You-Gen Shen | Entropy in the NUT-Kerr-Newman Black Holes Due to an Arbitrary Spin
Field | null | Class.Quant.Grav.20:3593-3602,2003 | 10.1088/0264-9381/20/16/305 | null | gr-qc | null | Membrane method is used to compute the entropy of the NUT-Kerr-Newman black
holes. It is found that even though the Euler characteristic is greater than
two, the Bekenstein-Hawking area law is still satisfied. The formula $S=\chi
A/8$ relating the entropy and the Euler characteristic becomes inapplicable for
non-extreme four dimensional NUT-Kerr-Newman black holes.
| [
{
"created": "Sat, 9 Oct 2004 07:13:20 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Ge",
"Xian-Hui",
""
],
[
"Shen",
"You-Gen",
""
]
] | Membrane method is used to compute the entropy of the NUT-Kerr-Newman black holes. It is found that even though the Euler characteristic is greater than two, the Bekenstein-Hawking area law is still satisfied. The formula $S=\chi A/8$ relating the entropy and the Euler characteristic becomes inapplicable for non-extreme four dimensional NUT-Kerr-Newman black holes. |
2104.07523 | Jianping Hu | Jian-Ping Hu, Li-Li Shi, Yu Zhang, Peng-Fei Duan | Analytical time-like geodesics in modified Hayward black hole space-time | 13 pages, 8 figures | ASTROPHYS SPACE SCI, 2018, 363, 199 | 10.1007/s10509-018-3423-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The properties of modified Hayward black hole space-time can be investigated
through analyzing the particle geodesics. By means of a detailed analysis of
the corresponding effective potentials for a massive particle, we find all
possible orbits which are allowed by the energy levels. The trajectories of
orbits are plotted by solving the equation of orbital motion numerically. We
conclude that whether there is an escape orbit is associated with $b$ (angular
momentum). The properties of orbital motion are related to $b$, $\alpha$
($\alpha$ is associated with the time delay) and $\beta$ ($\beta$ is related to
1-loop quantum corrections). There are no escape orbits when $b$ $<$ $4.016M$,
$\alpha$ = 0.50 and $\beta$ = 1.00. For fixed $\alpha$ = 0.50 and $\beta$ =
1.00, if $b$ $<$ $3.493M$, there only exist unstable orbits. Comparing with the
regular Hayward black hole, we go for a reasonable speculation by mean of the
existing calculating results that the introduction of the modified term makes
the radius of the innermost circular orbit (ISCO) and the corresponding angular
momentum larger.
| [
{
"created": "Thu, 15 Apr 2021 15:21:17 GMT",
"version": "v1"
}
] | 2021-04-16 | [
[
"Hu",
"Jian-Ping",
""
],
[
"Shi",
"Li-Li",
""
],
[
"Zhang",
"Yu",
""
],
[
"Duan",
"Peng-Fei",
""
]
] | The properties of modified Hayward black hole space-time can be investigated through analyzing the particle geodesics. By means of a detailed analysis of the corresponding effective potentials for a massive particle, we find all possible orbits which are allowed by the energy levels. The trajectories of orbits are plotted by solving the equation of orbital motion numerically. We conclude that whether there is an escape orbit is associated with $b$ (angular momentum). The properties of orbital motion are related to $b$, $\alpha$ ($\alpha$ is associated with the time delay) and $\beta$ ($\beta$ is related to 1-loop quantum corrections). There are no escape orbits when $b$ $<$ $4.016M$, $\alpha$ = 0.50 and $\beta$ = 1.00. For fixed $\alpha$ = 0.50 and $\beta$ = 1.00, if $b$ $<$ $3.493M$, there only exist unstable orbits. Comparing with the regular Hayward black hole, we go for a reasonable speculation by mean of the existing calculating results that the introduction of the modified term makes the radius of the innermost circular orbit (ISCO) and the corresponding angular momentum larger. |
2012.12742 | Tanmoy Paul | Kazuharu Bamba, E. Elizalde, S. D. Odintsov, Tanmoy Paul | Inflationary magnetogenesis with reheating phase from higher curvature
coupling | JCAP accepted..(Two sections added in the revised version -
"Curvature perturbation induced from EM field" and "Constraints from
Schwinger backreaction") | null | 10.1088/1475-7516/2021/04/009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the generation of magnetic fields from inflation, which occurs
via breakdown of the conformal invariance of the electromagnetic (EM) field,
when coupled with the Ricci scalar and the Gauss-Bonnet invariant. For the case
of instantaneous reheating, the resulting strength of the magnetic field at
present is too small and violates the observational constraints. However, the
problem is solved provided there is a reheating phase with a non-zero e-fold
number. During reheating, the energy density of the magnetic field is seen to
evolve as $(a^3H)^{-2}$ and, after that, as $a^{-4}$ up to the present epoch
(here $a$ is the scale factor and $H$ the Hubble parameter). It is found that
this reheating phase -- characterized by a certain e-fold number, a constant
value of the equation of state parameter, and a given reheating temperature --
renders the magnetogenesis model compatible with the observational constraints.
The model provides, in turn, a viable way of constraining the reheating
equation of state parameter, from data analysis of the cosmic microwave
background radiation. Moreover we discuss the Schwinger backreaction in the
present context and determine the necessary constraints on the reheating
equation of state parameter.
| [
{
"created": "Wed, 23 Dec 2020 15:24:26 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Feb 2021 16:09:55 GMT",
"version": "v2"
}
] | 2021-04-14 | [
[
"Bamba",
"Kazuharu",
""
],
[
"Elizalde",
"E.",
""
],
[
"Odintsov",
"S. D.",
""
],
[
"Paul",
"Tanmoy",
""
]
] | We investigate the generation of magnetic fields from inflation, which occurs via breakdown of the conformal invariance of the electromagnetic (EM) field, when coupled with the Ricci scalar and the Gauss-Bonnet invariant. For the case of instantaneous reheating, the resulting strength of the magnetic field at present is too small and violates the observational constraints. However, the problem is solved provided there is a reheating phase with a non-zero e-fold number. During reheating, the energy density of the magnetic field is seen to evolve as $(a^3H)^{-2}$ and, after that, as $a^{-4}$ up to the present epoch (here $a$ is the scale factor and $H$ the Hubble parameter). It is found that this reheating phase -- characterized by a certain e-fold number, a constant value of the equation of state parameter, and a given reheating temperature -- renders the magnetogenesis model compatible with the observational constraints. The model provides, in turn, a viable way of constraining the reheating equation of state parameter, from data analysis of the cosmic microwave background radiation. Moreover we discuss the Schwinger backreaction in the present context and determine the necessary constraints on the reheating equation of state parameter. |
1412.5160 | Alfredo Iorio | Alfredo Iorio | Graphene and Black Holes: novel materials to reach the unreachable | 3 pages; invited to talk to the workshop "New Frontiers in Multiscale
Modelling of Advanced Materials", ECT*, Trento, June 17-20, 2014; to appear
in Frontiers in Materials | Front. Mater. 1 (2015) 36 | 10.3389/fmats.2014.00036 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The case for a dedicated laboratory, to test hep-th models on analogue
systems, is briefly made. The focus is on graphene.
| [
{
"created": "Mon, 15 Dec 2014 11:45:27 GMT",
"version": "v1"
}
] | 2015-02-02 | [
[
"Iorio",
"Alfredo",
""
]
] | The case for a dedicated laboratory, to test hep-th models on analogue systems, is briefly made. The focus is on graphene. |
1511.05700 | Rituparno Goswami | Rituparno Goswami, George F. R. Ellis | 4-dimensional spacetimes from 2-dimensional conformal null data | 7 pages, 2 Figures, Revtex4, Title changed, To appear in Classical
and Quantum Gravity | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we investigate whether the holographic principle proposed in
string theory has a classical counterpart in general relativity theory. We show
that there is a partial correspondence: at least in the case of vacuum Petrov
type D spacetimes that admit a non-trivial Killing tensor, which encompass all
the astrophysical black hole spacetimes, there exists a one to one
correspondence between gravity in bulk and a two dimensional classical
conformal scalar field on a null boundary.
| [
{
"created": "Wed, 18 Nov 2015 09:19:02 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Feb 2017 07:21:17 GMT",
"version": "v2"
}
] | 2017-02-03 | [
[
"Goswami",
"Rituparno",
""
],
[
"Ellis",
"George F. R.",
""
]
] | In this paper we investigate whether the holographic principle proposed in string theory has a classical counterpart in general relativity theory. We show that there is a partial correspondence: at least in the case of vacuum Petrov type D spacetimes that admit a non-trivial Killing tensor, which encompass all the astrophysical black hole spacetimes, there exists a one to one correspondence between gravity in bulk and a two dimensional classical conformal scalar field on a null boundary. |
2303.08548 | Pantelis Apostolopoulos | Pantelis S. Apostolopoulos and Christos Tsipogiannis | Conformal Symmetries of the Strumia and Tetradis Metric | 4 pages, Presented at the 2nd Electronic Conference on Universe, 16
February 2 March 2023, published version | Phys. Sci. Forum 2023, 7, 46 | 10.3390/ECU2023-14100 | null | gr-qc hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | In a recent paper, a new conformally flat metric was introduced, describing
an expanding scalar field in a spherically symmetric geometry. The spacetime
can be interpreted as a Schwarzschild-like model with an apparent horizon
surrounding the curvature singularity. For the above metric, we present the
complete conformal Lie algebra consisting of a six-dimensional subalgebra of
isometries (Killing Vector Fields or KVFs) and nine proper conformal vector
fields (CVFs). An interesting aspect of our findings is that there exists a
gradient (proper) conformal symmetry (i.e., its bivector vanishes) which
verifies the importance of gradient symmetries in constructing viable
cosmological models. In addition, the 9-dimensional conformal algebra implies
the existence of constants of motion along null geodesics that allow us to
determine the complete solution of null geodesic equations.
| [
{
"created": "Wed, 15 Mar 2023 12:03:03 GMT",
"version": "v1"
}
] | 2023-03-16 | [
[
"Apostolopoulos",
"Pantelis S.",
""
],
[
"Tsipogiannis",
"Christos",
""
]
] | In a recent paper, a new conformally flat metric was introduced, describing an expanding scalar field in a spherically symmetric geometry. The spacetime can be interpreted as a Schwarzschild-like model with an apparent horizon surrounding the curvature singularity. For the above metric, we present the complete conformal Lie algebra consisting of a six-dimensional subalgebra of isometries (Killing Vector Fields or KVFs) and nine proper conformal vector fields (CVFs). An interesting aspect of our findings is that there exists a gradient (proper) conformal symmetry (i.e., its bivector vanishes) which verifies the importance of gradient symmetries in constructing viable cosmological models. In addition, the 9-dimensional conformal algebra implies the existence of constants of motion along null geodesics that allow us to determine the complete solution of null geodesic equations. |
2305.15437 | Abdel Nasser Tawfik | Antonio Pasqua (University of Trieste, Italy), Surajit Chattopadhyay
(Amity University, India), Irina Radinschi (Gheorghe Asach Technical
University, Romania), Azzah Aziz Alshehri (University of Hafr Al Batin, KSA),
Abdel Nasser Tawfik (Future University in Egypt, Cairo) | Reconstruction schemes of scalar field models for the Power Law Entropy
Corrected Holographic Dark Energy model with Ricci scalar cut-off | 57 pages, 0 figure, Submitted to IJMPD. arXiv admin note: text
overlap with arXiv:gr-qc/0609115 by other authors | null | null | ECTP-2023-10 and WLCAPP-2023-10 and FUE-2023-10 | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this work, we examine the cosmological characteristics of the Power Law
Entropy Corrected Holographic Dark Energy (PLECHDE) model with infrared (IR)
cut-off, which is determined by the curvature parameter $k$, the time
derivative of $H$, and the average radius of the Ricci scalar curvature $R$,
which varies with the Hubble parameter $H$ squared. We obtain the deceleration
parameter $q$ and the Equation of State (EoS) parameter of Dark Energy (DE)
$\omega_D$. Additionally, we derive the Hubble parameter $H$ and the scale
factor $a$ expressions as functions of the cosmic time $t$. Additionally, we
examine the limiting scenario that pertains to a flat Dark Dominated Universe.
Furthermore, we establish a correspondence between the DE model considered and
some scalar fields, in particular the Generalized Chaplygin Gas, the Modified
Chaplygin Gas, the Modified Variable Chaplygin Gas, the New Modified Chaplygin
Gas, the Viscous Generalized Chaplygin Gas, the Dirac-Born-Infeld, the
Yang-Mills, and the Non Linear Electrodynamics scalar field models.
| [
{
"created": "Tue, 23 May 2023 15:08:55 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Jan 2024 17:13:55 GMT",
"version": "v2"
}
] | 2024-01-02 | [
[
"Pasqua",
"Antonio",
"",
"University of Trieste, Italy"
],
[
"Chattopadhyay",
"Surajit",
"",
"Amity University, India"
],
[
"Radinschi",
"Irina",
"",
"Gheorghe Asach Technical\n University, Romania"
],
[
"Alshehri",
"Azzah Aziz",
"",
"Un... | In this work, we examine the cosmological characteristics of the Power Law Entropy Corrected Holographic Dark Energy (PLECHDE) model with infrared (IR) cut-off, which is determined by the curvature parameter $k$, the time derivative of $H$, and the average radius of the Ricci scalar curvature $R$, which varies with the Hubble parameter $H$ squared. We obtain the deceleration parameter $q$ and the Equation of State (EoS) parameter of Dark Energy (DE) $\omega_D$. Additionally, we derive the Hubble parameter $H$ and the scale factor $a$ expressions as functions of the cosmic time $t$. Additionally, we examine the limiting scenario that pertains to a flat Dark Dominated Universe. Furthermore, we establish a correspondence between the DE model considered and some scalar fields, in particular the Generalized Chaplygin Gas, the Modified Chaplygin Gas, the Modified Variable Chaplygin Gas, the New Modified Chaplygin Gas, the Viscous Generalized Chaplygin Gas, the Dirac-Born-Infeld, the Yang-Mills, and the Non Linear Electrodynamics scalar field models. |
gr-qc/0009037 | Ghanashyam Date | G. Date | Notes on Isolated Horizons | 45 pages, Latex, no figures. Explained approach better. To appear in
Class. Quant. Grav | Class.Quant.Grav.17:5025-5046,2000 | 10.1088/0264-9381/17/24/307 | IMSc/2000/09/52 | gr-qc hep-th | null | A general analysis for characterizing and classifying `isolated horizons' is
presented in terms of null tetrads and spin coefficients. The freely
specifiable spin coefficients corresponding to isolated horizons are identified
and specific symmetry classes are enumerated. For isolated horizons admitting
at least one spatial isometry, a standard set of spherical coordinates are
introduced and associated metric is obtained. An angular momentum is also
defined.
| [
{
"created": "Tue, 12 Sep 2000 05:26:03 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Sep 2000 04:13:09 GMT",
"version": "v2"
},
{
"created": "Sun, 19 Nov 2000 11:31:47 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Date",
"G.",
""
]
] | A general analysis for characterizing and classifying `isolated horizons' is presented in terms of null tetrads and spin coefficients. The freely specifiable spin coefficients corresponding to isolated horizons are identified and specific symmetry classes are enumerated. For isolated horizons admitting at least one spatial isometry, a standard set of spherical coordinates are introduced and associated metric is obtained. An angular momentum is also defined. |
gr-qc/0109067 | Margarita Tchitchikina | O.A.Khrustalev, M.V.Tchitchikina (Moscow State University) | Quantum Gravity on the Classical Background: Group Analysis, Part I | 17 pages | null | null | null | gr-qc | null | Quantization of gravitational field in the neighbourhood of exact solution of
Einstein equation is considered. The method of Bogoliubov group variables is
used.
| [
{
"created": "Wed, 19 Sep 2001 13:30:01 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Khrustalev",
"O. A.",
"",
"Moscow State University"
],
[
"Tchitchikina",
"M. V.",
"",
"Moscow State University"
]
] | Quantization of gravitational field in the neighbourhood of exact solution of Einstein equation is considered. The method of Bogoliubov group variables is used. |
2406.07105 | Dionysios Kokkinos | Dionysios Kokkinos, Taxiarchis Papakostas | The Study of the Canonical forms of Killing tensor in vacuum with
{\Lambda} | 27 pages, | null | null | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | This paper is the initial part of a comprehensive study of spacetimes that
admit the canonical forms of Killing tensor in General Relativity. Our scope is
to derive either new exact solutions of Einstein's equations or to determine
the hidden symmetries of the already known ones. In this preliminary work we
first introduce the canonical forms of Killing tensor. Subsequently, we employ
the integrability conditions of each canonical form along with the Einstein
field equations (in vacuum with {\Lambda}) and the Bianchi identities in an
attempt to create a solvable yet overdetermined system of equations. Finally,
we obtain multiple special algebraic solutions according to the Petrov
classification (D, III, N, O). The latter becomes possible since our analysis
is embodied with the usage of the Newman-Penrose formalism of null tetrads.
| [
{
"created": "Tue, 11 Jun 2024 09:44:22 GMT",
"version": "v1"
}
] | 2024-06-12 | [
[
"Kokkinos",
"Dionysios",
""
],
[
"Papakostas",
"Taxiarchis",
""
]
] | This paper is the initial part of a comprehensive study of spacetimes that admit the canonical forms of Killing tensor in General Relativity. Our scope is to derive either new exact solutions of Einstein's equations or to determine the hidden symmetries of the already known ones. In this preliminary work we first introduce the canonical forms of Killing tensor. Subsequently, we employ the integrability conditions of each canonical form along with the Einstein field equations (in vacuum with {\Lambda}) and the Bianchi identities in an attempt to create a solvable yet overdetermined system of equations. Finally, we obtain multiple special algebraic solutions according to the Petrov classification (D, III, N, O). The latter becomes possible since our analysis is embodied with the usage of the Newman-Penrose formalism of null tetrads. |
gr-qc/0110005 | Jose Lages | A. Berard, J. Lages and H. Mohrbach | Restoration of Angular Lie Algebra Symmetries from a Covariant
Hamiltonian | null | null | null | null | gr-qc hep-th math-ph math.MP physics.class-ph | null | The sO(3) and the Lorentz algebra symmetries breaking with gauge curvatures
are studied by means of a covariant Hamiltonian. The restoration of these
algebra symmetries in flat and curved spaces is performed and led to the
apparition of a monopole field. Then in the context of the Lorentz algebra we
consider an application to the gravitoelectromagnetism theory. In this last
case a qualitative relation giving a mass spectrum for dyons is established.
| [
{
"created": "Mon, 1 Oct 2001 16:42:51 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Berard",
"A.",
""
],
[
"Lages",
"J.",
""
],
[
"Mohrbach",
"H.",
""
]
] | The sO(3) and the Lorentz algebra symmetries breaking with gauge curvatures are studied by means of a covariant Hamiltonian. The restoration of these algebra symmetries in flat and curved spaces is performed and led to the apparition of a monopole field. Then in the context of the Lorentz algebra we consider an application to the gravitoelectromagnetism theory. In this last case a qualitative relation giving a mass spectrum for dyons is established. |
2211.06435 | Anarya Ray | Anarya Ray and Michael Camilo and Jolien Creighton and Shaon Ghosh and
Soichiro Morisaki | Rapid Hierarchical Inference of Neutron Star Equation of State from
multiple Gravitational Wave Observations of Binary Neutron Star Coalescences | null | Phys.Rev. D 107, 043035 (2023) | 10.1103/PhysRevD.107.043035 | LIGO-P2200301 | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Bayesian hierarchical inference of phenomenological parameterized neutron
star equations of state (EoS) from multiple gravitational wave observations of
binary neutron star mergers is of fundamental importance in improving our
understanding of neutron star structure, the general properties of matter at
supra nuclear densities and the strong nuclear force. However, such an analysis
is computationally costly as it is unable to re-use single-event EoS agnostic
parameter estimation runs that are carried out regardless for generating
gravitational wave transient catalogs. With the number of events expected to be
observable during the 4th observing run (O4) of LIGO/Virgo/KAGRA, this problem
can only be expected to worsen. We develop a novel and robust algorithm for
rapid and computationally cheap hierarchical inference of parameterized EoSs
from gravitational wave data which re-uses single event EoS agnostic parameter
estimation samples to significantly reduce computational cost. We efficiently
include a priori knowledge of neutron star physics as Bayesian priors on the
EoS parameters. The high speed and low computational cost of our method allow
for efficient re-computation of EoS inference every time a new binary neutron
star event is discovered or whenever new observations and theoretical
discoveries change the prior on EoS parameters. We test our method on both real
and simulated gravitational wave data to demonstrate its accuracy. We show that
our computationally cheap method produces EoS constraints that are completely
consistent with existing analysis for real data, the chosen fiducial EoS for
simulated data. Armed with our fast analysis scheme, we also study the
variability of EoS constraints with binary neutron star properties for sets of
simulated events drawn in different signal-to-noise ratio and mass ranges.
| [
{
"created": "Fri, 11 Nov 2022 19:00:04 GMT",
"version": "v1"
}
] | 2023-03-08 | [
[
"Ray",
"Anarya",
""
],
[
"Camilo",
"Michael",
""
],
[
"Creighton",
"Jolien",
""
],
[
"Ghosh",
"Shaon",
""
],
[
"Morisaki",
"Soichiro",
""
]
] | Bayesian hierarchical inference of phenomenological parameterized neutron star equations of state (EoS) from multiple gravitational wave observations of binary neutron star mergers is of fundamental importance in improving our understanding of neutron star structure, the general properties of matter at supra nuclear densities and the strong nuclear force. However, such an analysis is computationally costly as it is unable to re-use single-event EoS agnostic parameter estimation runs that are carried out regardless for generating gravitational wave transient catalogs. With the number of events expected to be observable during the 4th observing run (O4) of LIGO/Virgo/KAGRA, this problem can only be expected to worsen. We develop a novel and robust algorithm for rapid and computationally cheap hierarchical inference of parameterized EoSs from gravitational wave data which re-uses single event EoS agnostic parameter estimation samples to significantly reduce computational cost. We efficiently include a priori knowledge of neutron star physics as Bayesian priors on the EoS parameters. The high speed and low computational cost of our method allow for efficient re-computation of EoS inference every time a new binary neutron star event is discovered or whenever new observations and theoretical discoveries change the prior on EoS parameters. We test our method on both real and simulated gravitational wave data to demonstrate its accuracy. We show that our computationally cheap method produces EoS constraints that are completely consistent with existing analysis for real data, the chosen fiducial EoS for simulated data. Armed with our fast analysis scheme, we also study the variability of EoS constraints with binary neutron star properties for sets of simulated events drawn in different signal-to-noise ratio and mass ranges. |
1805.01705 | Titus K Mathew | Krishna P B and Titus K Mathew | Entropy Maximization in the Emergent Gravity Paradigm | 22 pages | Phys. Rev. D 99, 023535 (2019) | 10.1103/PhysRevD.99.023535 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The accelerated expansion of the universe can be interpreted as a quest for
satisfying holographic equipartition. It can be expressed by a simple law,
$\Delta V = \Delta t\left(N_{surf}- N_{bulk}\right)$ which leads to the
standard Friedmann equation. This novel idea suggested by Padmanabhan in the
context of general relativity has been generalized by Cai and Yang et al. to
Gauss-Bonnet and Lovelock gravities for a spatially flat universe in different
methods. We investigate the consistency of these generalizations with the
constraints imposed by the maximum entropy principle. Interestingly, both these
generalizations imply entropy maximization even if their basic assumptions are
different. Further, we analyze the consistency of Verlinde's emergent gravity
with the maximum entropy principle in the cosmological context. In particular,
we consider the generalization suggested by Shu and Gong, in which an energy
flux through the horizon is assumed, in addition. Even though the conceptual
formulations are different, these two emergent perspectives of gravity
describes a universe which behaves as an ordinary macroscopic system. Our
results provide further support to the emergent gravity paradigm.
| [
{
"created": "Fri, 4 May 2018 10:40:44 GMT",
"version": "v1"
},
{
"created": "Mon, 21 May 2018 16:56:22 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Feb 2019 12:37:33 GMT",
"version": "v3"
}
] | 2019-02-06 | [
[
"B",
"Krishna P",
""
],
[
"Mathew",
"Titus K",
""
]
] | The accelerated expansion of the universe can be interpreted as a quest for satisfying holographic equipartition. It can be expressed by a simple law, $\Delta V = \Delta t\left(N_{surf}- N_{bulk}\right)$ which leads to the standard Friedmann equation. This novel idea suggested by Padmanabhan in the context of general relativity has been generalized by Cai and Yang et al. to Gauss-Bonnet and Lovelock gravities for a spatially flat universe in different methods. We investigate the consistency of these generalizations with the constraints imposed by the maximum entropy principle. Interestingly, both these generalizations imply entropy maximization even if their basic assumptions are different. Further, we analyze the consistency of Verlinde's emergent gravity with the maximum entropy principle in the cosmological context. In particular, we consider the generalization suggested by Shu and Gong, in which an energy flux through the horizon is assumed, in addition. Even though the conceptual formulations are different, these two emergent perspectives of gravity describes a universe which behaves as an ordinary macroscopic system. Our results provide further support to the emergent gravity paradigm. |
1202.5039 | Sergei Alexandrov | Sergei Alexandrov | Degenerate Plebanski Sector and Spin Foam Quantization | 34 pages; changes in the abstract and introduction, a few references
added | Class.Quant.Grav. 29 (2012) 145018 | 10.1088/0264-9381/29/14/145018 | L2C:12-013 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the degenerate sector of Spin(4) Plebanski formulation of
four-dimensional gravity is exactly solvable and describes covariantly embedded
SU(2) BF theory. This fact ensures that its spin foam quantization is given by
the SU(2) Crane-Yetter model and allows to test various approaches of imposing
the simplicity constraints. Our analysis strongly suggests that restricting
representations and intertwiners in the state sum for Spin(4) BF theory is not
sufficient to get the correct vertex amplitude. Instead, for a general theory
of Plebanski type, we propose a quantization procedure which is by construction
equivalent to the canonical path integral quantization and, being applied to
our model, reproduces the SU(2) Crane-Yetter state sum. A characteristic
feature of this procedure is the use of secondary second class constraints on
an equal footing with the primary simplicity constraints, which leads to a new
formula for the vertex amplitude.
| [
{
"created": "Wed, 22 Feb 2012 21:02:07 GMT",
"version": "v1"
},
{
"created": "Fri, 18 May 2012 00:27:18 GMT",
"version": "v2"
}
] | 2012-10-12 | [
[
"Alexandrov",
"Sergei",
""
]
] | We show that the degenerate sector of Spin(4) Plebanski formulation of four-dimensional gravity is exactly solvable and describes covariantly embedded SU(2) BF theory. This fact ensures that its spin foam quantization is given by the SU(2) Crane-Yetter model and allows to test various approaches of imposing the simplicity constraints. Our analysis strongly suggests that restricting representations and intertwiners in the state sum for Spin(4) BF theory is not sufficient to get the correct vertex amplitude. Instead, for a general theory of Plebanski type, we propose a quantization procedure which is by construction equivalent to the canonical path integral quantization and, being applied to our model, reproduces the SU(2) Crane-Yetter state sum. A characteristic feature of this procedure is the use of secondary second class constraints on an equal footing with the primary simplicity constraints, which leads to a new formula for the vertex amplitude. |
gr-qc/9902045 | Domenico Giulini | Domenico Giulini and Donald Marolf | A Uniqueness Theorem for Constraint Quantization | 23 pages, RevTeX, further comments and references added (May 26. '99) | Class.Quant.Grav. 16 (1999) 2489-2505 | 10.1088/0264-9381/16/7/322 | ZU-TH-99/2 and SU-GP-99/1-1 | gr-qc hep-th quant-ph | null | This work addresses certain ambiguities in the Dirac approach to constrained
systems. Specifically, we investigate the space of so-called ``rigging maps''
associated with Refined Algebraic Quantization, a particular realization of the
Dirac scheme. Our main result is to provide a condition under which the rigging
map is unique, in which case we also show that it is given by group averaging
techniques. Our results comprise all cases where the gauge group is a
finite-dimensional Lie group.
| [
{
"created": "Mon, 15 Feb 1999 13:26:58 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Jun 1999 16:30:13 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Giulini",
"Domenico",
""
],
[
"Marolf",
"Donald",
""
]
] | This work addresses certain ambiguities in the Dirac approach to constrained systems. Specifically, we investigate the space of so-called ``rigging maps'' associated with Refined Algebraic Quantization, a particular realization of the Dirac scheme. Our main result is to provide a condition under which the rigging map is unique, in which case we also show that it is given by group averaging techniques. Our results comprise all cases where the gauge group is a finite-dimensional Lie group. |
2103.10960 | Taishi Ikeda | Taishi Ikeda, Massimo Bianchi, Dario Consoli, Alfredo Grillo, Jos\`e
Francisco Morales, Paolo Pani, Guilherme Raposo | Black-hole microstate spectroscopy: ringdown, quasinormal modes, and
echoes | Published version, 22 pages, 10 figures, Movies are available in
https://web.uniroma1.it/gmunu/fuzzballs-multipole-moments-and-ringdown | Phys. Rev. D 104, 066021 (2021) | 10.1103/PhysRevD.104.066021 | null | gr-qc astro-ph.HE hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | Deep conceptual problems associated with classical black holes can be
addressed in string theory by the ``fuzzball'' paradigm, which provides a
microscopic description of a black hole in terms of a thermodynamically large
number of regular, horizonless, geometries with much less symmetry than the
corresponding black hole. Motivated by the tantalizing possibility to observe
quantum gravity signatures near astrophysical compact objects in this scenario,
we perform the first $3+1$ numerical simulations of a scalar field propagating
on a large class of multicenter geometries with no spatial isometries arising
from ${\cal N}=2$ four-dimensional supergravity. We identify the prompt
response to the perturbation and the ringdown modes associated with the photon
sphere, which are similar to the black-hole case, and the appearance of echoes
at later time, which is a smoking gun of some structure at the horizon scale
and of the regular interior of these solutions. The response is in agreement
with an analytical model based on geodesic motion in these complicated
geometries. Our results provide the first numerical evidence for the dynamical
linear stability of fuzzballs, and pave the way for an accurate discrimination
between fuzzballs and black holes using gravitational-wave spectroscopy.
| [
{
"created": "Fri, 19 Mar 2021 18:00:04 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Sep 2021 08:10:34 GMT",
"version": "v2"
}
] | 2021-09-29 | [
[
"Ikeda",
"Taishi",
""
],
[
"Bianchi",
"Massimo",
""
],
[
"Consoli",
"Dario",
""
],
[
"Grillo",
"Alfredo",
""
],
[
"Morales",
"Josè Francisco",
""
],
[
"Pani",
"Paolo",
""
],
[
"Raposo",
"Guilherme",
""
]
... | Deep conceptual problems associated with classical black holes can be addressed in string theory by the ``fuzzball'' paradigm, which provides a microscopic description of a black hole in terms of a thermodynamically large number of regular, horizonless, geometries with much less symmetry than the corresponding black hole. Motivated by the tantalizing possibility to observe quantum gravity signatures near astrophysical compact objects in this scenario, we perform the first $3+1$ numerical simulations of a scalar field propagating on a large class of multicenter geometries with no spatial isometries arising from ${\cal N}=2$ four-dimensional supergravity. We identify the prompt response to the perturbation and the ringdown modes associated with the photon sphere, which are similar to the black-hole case, and the appearance of echoes at later time, which is a smoking gun of some structure at the horizon scale and of the regular interior of these solutions. The response is in agreement with an analytical model based on geodesic motion in these complicated geometries. Our results provide the first numerical evidence for the dynamical linear stability of fuzzballs, and pave the way for an accurate discrimination between fuzzballs and black holes using gravitational-wave spectroscopy. |
1511.02291 | William Huanshan Chuang | William Chuang | An Invariant Between Hyperbolic Surfaces and Lattice Spin Models | null | null | null | null | gr-qc cond-mat.stat-mech | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this succinct note, it is showed that a partition function of equivalent
classes of hyperbolic surfaces can be connected to an Ising model located on
the boundary of the Poincare disc, as hinted by Poincare's Uniformization
theorem and Patterson-Sullivan's Theorem.
Keywords: Hyperbolic spaces, Schottky groups, Ising models, locations of
Lee-Yang Zeros, non-trivial zeros of Riemann zeta function, phase transition,
and quantum chaos.
| [
{
"created": "Sat, 7 Nov 2015 03:18:35 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Apr 2016 05:43:23 GMT",
"version": "v2"
},
{
"created": "Mon, 30 Jul 2018 23:01:59 GMT",
"version": "v3"
},
{
"created": "Tue, 15 Jan 2019 07:53:12 GMT",
"version": "v4"
},
{
"cr... | 2023-08-29 | [
[
"Chuang",
"William",
""
]
] | In this succinct note, it is showed that a partition function of equivalent classes of hyperbolic surfaces can be connected to an Ising model located on the boundary of the Poincare disc, as hinted by Poincare's Uniformization theorem and Patterson-Sullivan's Theorem. Keywords: Hyperbolic spaces, Schottky groups, Ising models, locations of Lee-Yang Zeros, non-trivial zeros of Riemann zeta function, phase transition, and quantum chaos. |
2305.10739 | Sangmin Lee | Hojin Lee, Sangmin Lee | Poincar\'e invariance of spinning binary dynamics in the
post-Minkowskian Hamiltonian approach | 33 pages; v2. references added, minor corrections | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We initiate the construction of the global Poincar\'e algebra generators in
the context of the post-Minkowskian Hamiltonian formulation of gravitating
binary dynamics in isotropic coordinates that is partly inspired by scattering
amplitudes. At the first post-Minkowskian (1PM) order, we write down the
Hamiltonian in a form valid in an arbitrary inertial frame. Then we construct
the boost generator at the same order which uniquely solves all the equations
required by the Poincar\'e algebra. Our results are linear in Newton's constant
but exact in velocities and spins, including all spin multiple moments. We also
compute the generators of canonical transformations that proves the equivalence
between our new generators and the corresponding generators in the ADM
coordinates up to the second post-Newtonian (2PN) order.
| [
{
"created": "Thu, 18 May 2023 06:17:51 GMT",
"version": "v1"
},
{
"created": "Sat, 3 Jun 2023 06:30:36 GMT",
"version": "v2"
}
] | 2023-06-06 | [
[
"Lee",
"Hojin",
""
],
[
"Lee",
"Sangmin",
""
]
] | We initiate the construction of the global Poincar\'e algebra generators in the context of the post-Minkowskian Hamiltonian formulation of gravitating binary dynamics in isotropic coordinates that is partly inspired by scattering amplitudes. At the first post-Minkowskian (1PM) order, we write down the Hamiltonian in a form valid in an arbitrary inertial frame. Then we construct the boost generator at the same order which uniquely solves all the equations required by the Poincar\'e algebra. Our results are linear in Newton's constant but exact in velocities and spins, including all spin multiple moments. We also compute the generators of canonical transformations that proves the equivalence between our new generators and the corresponding generators in the ADM coordinates up to the second post-Newtonian (2PN) order. |
1406.5559 | David Garfinkle | David Garfinkle and Istvan Racz | Resolving a gravitational wave memory paradox | null | null | 10.1007/s10714-015-1924-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Two different approaches to gravitational perturbation theory appear to give
two different answers for the properties of gravitational wave memory. We show
that this contradiction is only apparent and the two approaches actually agree.
| [
{
"created": "Fri, 20 Jun 2014 23:47:49 GMT",
"version": "v1"
}
] | 2015-07-15 | [
[
"Garfinkle",
"David",
""
],
[
"Racz",
"Istvan",
""
]
] | Two different approaches to gravitational perturbation theory appear to give two different answers for the properties of gravitational wave memory. We show that this contradiction is only apparent and the two approaches actually agree. |
1510.00814 | Xun Xue | Yiwei Wu, Xun Xue, Lixiang Yang, Tzu-Chiang Yuan | The Effective Gravitational Theory at Large Scale with Lorentz Violation | 5 pages | null | null | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dipole anomaly in the power spectrum of CMB may indicate that the Lorentz
boost invarianc is violated at cosmic scale. We assume that the Lorentz
symmetry is violated partly from the scale of galaxy. We employ the symmetry of
very special relativity as an example to illustrate the Lorentz violation
effect by constructing the corresponding gauge theories as the effective
gravitational theory at the large scale. We find the common feather of these
gravitation models is the non-triviality of spacetime torsion and contorsion
even if the matter source is of only scalar matter. The presence of non-trivial
contorsion contributes an effective enenrgy-momentum distribution which may
account for part of dark matter effect.
| [
{
"created": "Sat, 3 Oct 2015 13:04:22 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Oct 2015 13:09:01 GMT",
"version": "v2"
},
{
"created": "Sun, 18 Oct 2015 00:03:27 GMT",
"version": "v3"
}
] | 2015-10-20 | [
[
"Wu",
"Yiwei",
""
],
[
"Xue",
"Xun",
""
],
[
"Yang",
"Lixiang",
""
],
[
"Yuan",
"Tzu-Chiang",
""
]
] | The dipole anomaly in the power spectrum of CMB may indicate that the Lorentz boost invarianc is violated at cosmic scale. We assume that the Lorentz symmetry is violated partly from the scale of galaxy. We employ the symmetry of very special relativity as an example to illustrate the Lorentz violation effect by constructing the corresponding gauge theories as the effective gravitational theory at the large scale. We find the common feather of these gravitation models is the non-triviality of spacetime torsion and contorsion even if the matter source is of only scalar matter. The presence of non-trivial contorsion contributes an effective enenrgy-momentum distribution which may account for part of dark matter effect. |
1207.6028 | Jorge Pullin | Rodolfo Gambini and Jorge Pullin | Spherically symmetric gravity coupled to a scalar field with a local
Hamiltonian: the complete initial-boundary value problem using metric
variables | 6 pages, 1 figure | null | 10.1088/0264-9381/30/2/025012 | LSU-REL-072412 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss a gauge fixing of gravity coupled to a scalar field in spherical
symmetry such that the Hamiltonian is an integral over space of a local
density. In a previous paper we had presented it using Ashtekar's new
variables. Here we study it in metric variables. We specify completely the
initial-boundary value problem for ingoing Gaussian pulses.
| [
{
"created": "Wed, 25 Jul 2012 15:32:18 GMT",
"version": "v1"
}
] | 2015-06-05 | [
[
"Gambini",
"Rodolfo",
""
],
[
"Pullin",
"Jorge",
""
]
] | We discuss a gauge fixing of gravity coupled to a scalar field in spherical symmetry such that the Hamiltonian is an integral over space of a local density. In a previous paper we had presented it using Ashtekar's new variables. Here we study it in metric variables. We specify completely the initial-boundary value problem for ingoing Gaussian pulses. |
gr-qc/0511044 | Yasunari Kurita | Yasunari Kurita, Ken-ichi Nakao | Naked singularity resolution in cylindrical collapse | 17 pages, no figure | Phys.Rev. D73 (2006) 064022 | 10.1103/PhysRevD.73.064022 | OCU-PHYS-236, AP-GR-28, YITP-06-03 | gr-qc | null | In this paper, we study the gravitational collapse of null dust in the
cylindrically symmetric spacetime. The naked singularity necessarily forms at
the symmetry axis. We consider the situation in which null dust is emitted
again from the naked singularity formed by the collapsed null dust and
investigate the back-reaction by this emission for the naked singularity. We
show a very peculiar but physically important case in which the same amount of
null dust as that of the collapsed one is emitted from the naked singularity as
soon as the ingoing null dust hits the symmetry axis and forms the naked
singularity. In this case, although this naked singularity satisfies the strong
curvature condition by Kr\'{o}lak (limiting focusing condition), geodesics
which hit the singularity can be extended uniquely across the singularity.
Therefore we may say that the collapsing null dust passes through the
singularity formed by itself and then leaves for infinity. Finally the
singularity completely disappears and the flat spacetime remains.
| [
{
"created": "Wed, 9 Nov 2005 06:25:25 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Feb 2006 09:40:34 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Kurita",
"Yasunari",
""
],
[
"Nakao",
"Ken-ichi",
""
]
] | In this paper, we study the gravitational collapse of null dust in the cylindrically symmetric spacetime. The naked singularity necessarily forms at the symmetry axis. We consider the situation in which null dust is emitted again from the naked singularity formed by the collapsed null dust and investigate the back-reaction by this emission for the naked singularity. We show a very peculiar but physically important case in which the same amount of null dust as that of the collapsed one is emitted from the naked singularity as soon as the ingoing null dust hits the symmetry axis and forms the naked singularity. In this case, although this naked singularity satisfies the strong curvature condition by Kr\'{o}lak (limiting focusing condition), geodesics which hit the singularity can be extended uniquely across the singularity. Therefore we may say that the collapsing null dust passes through the singularity formed by itself and then leaves for infinity. Finally the singularity completely disappears and the flat spacetime remains. |
2407.06238 | Mohamed Ibrahim Nouh | Mohamed S. Aboueisha, A. S. Saad, Mohamed I. Nouh, Tarek M. Kamel, M.
M. Beheary and Kamel A. K. Gadallah | Stability Analysis Of Fractional Relativistic Polytropes | null | Physica Scripta, 99, 075052, 2024 | 10.1088/1402-4896/ad59df | null | gr-qc astro-ph.HE astro-ph.SR | http://creativecommons.org/licenses/by/4.0/ | In astrophysics, the gravitational stability of a self-gravitating polytropic
fluid sphere is an intriguing subject, especially when trying to comprehend the
genesis and development of celestial bodies like planets and stars. This
stability is the sphere's capacity to stay in balance in the face of
disruptions. We utilize fractional calculus to explore self-gravitating,
hydrostatic spheres governed by a polytropic equation of state
\P=K\rho^{1+1/n}. We focus on structures with polytropic indices ranging from 1
to 3 and consider relativistic and fractional parameters, denoted by \sigma and
\alpha, respectively. The stability of these relativistic polytropes is
evaluated using the critical point method, which is associated with the
energetic principles developed in 1964 by Tooper. This approach enables us to
pinpoint the critical mass and radius at which where polytropic spheres shift
from stable to unstable states. The results highlight the critical relativistic
parameter where the polytrope's mass peaks, signaling the onset of radial
instability. For polytropic indices of 1, 1.5, 2, and 3 with a fractional
parameter \alpha, we observe stable relativistic polytropes for \sigma values
below the critical thresholds of \sigma= 0.42, 0.20, 0.10, and 0.0,
respectively. Conversely, instability emerges as \sigma surpasses these
critical values. Our comprehensive calculations reveal that the critical
relativistic value (\sigma_{CR}) for the onset of instability tends to increase
as the fractional parameter {\alpha} decreases.
| [
{
"created": "Sun, 7 Jul 2024 20:07:50 GMT",
"version": "v1"
}
] | 2024-07-10 | [
[
"Aboueisha",
"Mohamed S.",
""
],
[
"Saad",
"A. S.",
""
],
[
"Nouh",
"Mohamed I.",
""
],
[
"Kamel",
"Tarek M.",
""
],
[
"Beheary",
"M. M.",
""
],
[
"Gadallah",
"Kamel A. K.",
""
]
] | In astrophysics, the gravitational stability of a self-gravitating polytropic fluid sphere is an intriguing subject, especially when trying to comprehend the genesis and development of celestial bodies like planets and stars. This stability is the sphere's capacity to stay in balance in the face of disruptions. We utilize fractional calculus to explore self-gravitating, hydrostatic spheres governed by a polytropic equation of state \P=K\rho^{1+1/n}. We focus on structures with polytropic indices ranging from 1 to 3 and consider relativistic and fractional parameters, denoted by \sigma and \alpha, respectively. The stability of these relativistic polytropes is evaluated using the critical point method, which is associated with the energetic principles developed in 1964 by Tooper. This approach enables us to pinpoint the critical mass and radius at which where polytropic spheres shift from stable to unstable states. The results highlight the critical relativistic parameter where the polytrope's mass peaks, signaling the onset of radial instability. For polytropic indices of 1, 1.5, 2, and 3 with a fractional parameter \alpha, we observe stable relativistic polytropes for \sigma values below the critical thresholds of \sigma= 0.42, 0.20, 0.10, and 0.0, respectively. Conversely, instability emerges as \sigma surpasses these critical values. Our comprehensive calculations reveal that the critical relativistic value (\sigma_{CR}) for the onset of instability tends to increase as the fractional parameter {\alpha} decreases. |
2303.08960 | Anish Agashe | Anish Agashe | Kinematics in Metric-Affine Geometry | Matches the published version | Phys. Scr. 98 105210 (2023) | 10.1088/1402-4896/acf5ac | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In a given geometry, the kinematics of a congruence of curves is described by
a set of three quantities called expansion, rotation, and shear. The equations
governing the evolution of these quantities are referred to as kinematic
equations. In this paper, the kinematics of congruence of curves in a
metric-affine geometry are analysed. Without assuming an underlying theory of
gravity, we derive a generalised form of the evolution equations for expansion,
namely, Raychaudhuri equation (timelike congruences) and Sachs optical equation
(null congruences). The evolution equations for rotation and shear of both
timelike and null congruences are also derived. Generalising the deviation
equation, we find that torsion and non-metricity contribute to a relative
acceleration between neighbouring curves. We briefly discuss the interpretation
of the expansion scalars and derive an equation governing angular diameter
distances. The effects of torsion and non-metricity on the distances are found
to be dependent on which curves are chosen as photon trajectories. We also show
that the rotation of a hypersurface orthogonal congruence (timelike or null) is
a purely non-Riemannian feature.
| [
{
"created": "Wed, 15 Mar 2023 22:15:39 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Sep 2023 15:21:22 GMT",
"version": "v2"
}
] | 2023-09-12 | [
[
"Agashe",
"Anish",
""
]
] | In a given geometry, the kinematics of a congruence of curves is described by a set of three quantities called expansion, rotation, and shear. The equations governing the evolution of these quantities are referred to as kinematic equations. In this paper, the kinematics of congruence of curves in a metric-affine geometry are analysed. Without assuming an underlying theory of gravity, we derive a generalised form of the evolution equations for expansion, namely, Raychaudhuri equation (timelike congruences) and Sachs optical equation (null congruences). The evolution equations for rotation and shear of both timelike and null congruences are also derived. Generalising the deviation equation, we find that torsion and non-metricity contribute to a relative acceleration between neighbouring curves. We briefly discuss the interpretation of the expansion scalars and derive an equation governing angular diameter distances. The effects of torsion and non-metricity on the distances are found to be dependent on which curves are chosen as photon trajectories. We also show that the rotation of a hypersurface orthogonal congruence (timelike or null) is a purely non-Riemannian feature. |
gr-qc/9901046 | null | T. Damour (IHES) | The theoretical significance of G | 6 pages, Revtex, contribution to the Cavendish bicentennial
conference, to appear in Measurement, Science and Technology, minor changes
in the references | Measur.Sci.Tech.10:467-469,1999 | 10.1088/0957-0233/10/6/309 | IHES/P/99/1 | gr-qc | null | The quantization of gravity, and its unification with the other interactions,
is one of the greatest challenges of theoretical physics. Current ideas suggest
that the value of G might be related to the other fundamental constants of
physics, and that gravity might be richer than the standard Newton-Einstein
description. This gives added significance to measurements of G and to
Cavendish-type experiments.
| [
{
"created": "Fri, 15 Jan 1999 17:39:13 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Jan 1999 11:31:26 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Damour",
"T.",
"",
"IHES"
]
] | The quantization of gravity, and its unification with the other interactions, is one of the greatest challenges of theoretical physics. Current ideas suggest that the value of G might be related to the other fundamental constants of physics, and that gravity might be richer than the standard Newton-Einstein description. This gives added significance to measurements of G and to Cavendish-type experiments. |
1803.05310 | Hossein Mohseni Sadjadi | H. Mohseni Sadjadi | Cosmic acceleration in screening hybrid quintessence model | 18 pages, 5 figures, references updated | Phys. Dark Univ. 22 (2018) 101 | 10.1016/j.dark.2018.10.003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A formalism for the appearance of dark energy in the matter dominated era,
leading to a persistent de Sitter expansion at the late time is proposed. Our
framework is a hybrid quintessence model with a non-minimal coupling to the
Ricci scalar. Coupling to the curvature triggers the dark energy evolution,
while the coupling of scalar fields drives this evolution to a de Sitter stable
fixed point. These occur via successive $Z_2$ symmetry breakings.
| [
{
"created": "Mon, 12 Mar 2018 13:12:56 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Oct 2018 08:03:06 GMT",
"version": "v2"
},
{
"created": "Wed, 28 Nov 2018 07:01:32 GMT",
"version": "v3"
}
] | 2018-11-29 | [
[
"Sadjadi",
"H. Mohseni",
""
]
] | A formalism for the appearance of dark energy in the matter dominated era, leading to a persistent de Sitter expansion at the late time is proposed. Our framework is a hybrid quintessence model with a non-minimal coupling to the Ricci scalar. Coupling to the curvature triggers the dark energy evolution, while the coupling of scalar fields drives this evolution to a de Sitter stable fixed point. These occur via successive $Z_2$ symmetry breakings. |
gr-qc/0610083 | Harry I. Ringermacher | Harry I. Ringermacher, Lawrence R. Mead | Are Dark Matter and Dark Energy the Residue of the Expansion-Reaction to
the Big Bang ? | null | null | null | null | gr-qc astro-ph | null | We derive the phenomenological Milgrom square-law acceleration, describing
the apparent behavior of dark matter, as the reaction to the Big Bang from a
model based on the Lorentz-Dirac equation of motion traditionally describing
radiation reaction in electromagnetism but proven applicable to expansion
reaction in cosmology. The model is applied within the Robertson-Walker
hypersphere, and suggests that the Hubble expansion exactly cancels the
classical reaction imparted to matter following the Big Bang, leaving behind a
residue proportional to the square of the acceleration. The model further
suggests that the energy density associated with the reaction acceleration is
precisely the critical density for flattening the universe thus providing a
potential explanation of dark energy as well. A test of this model is proposed.
| [
{
"created": "Mon, 16 Oct 2006 21:14:45 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ringermacher",
"Harry I.",
""
],
[
"Mead",
"Lawrence R.",
""
]
] | We derive the phenomenological Milgrom square-law acceleration, describing the apparent behavior of dark matter, as the reaction to the Big Bang from a model based on the Lorentz-Dirac equation of motion traditionally describing radiation reaction in electromagnetism but proven applicable to expansion reaction in cosmology. The model is applied within the Robertson-Walker hypersphere, and suggests that the Hubble expansion exactly cancels the classical reaction imparted to matter following the Big Bang, leaving behind a residue proportional to the square of the acceleration. The model further suggests that the energy density associated with the reaction acceleration is precisely the critical density for flattening the universe thus providing a potential explanation of dark energy as well. A test of this model is proposed. |
gr-qc/9901011 | Mohammad Nouri-Zonoz | Mohammad Nouri-Zonoz | Gravoelectromagnetic approach to the gravitational Faraday rotation in
stationary spacetimes | 13 pages including one figure. Latex. Section 6 has been removed and
included in the conclusion section. Some typos has been corrected and new
reference has been added | Phys.Rev.D60:024013,1999 | 10.1103/PhysRevD.60.024013 | IUCAA-1/99 | gr-qc | null | Using the 1+3 formulation of stationary spacetimes we show, in the context of
gravoelectromagnetism, that the plane of the polarization of light rays passing
close to a black hole undergoes a rotation. We show that this rotation has the
same integral form as the usual Faraday effect, i.e. it is proportional to the
integral of the component of the gravomagnetic field along the propagation
path. We apply this integral formula to calculate the Faraday rotation induced
by the Kerr and NUT spaces using the quasi-Maxwell form of the vacuum Einstein
equations.
| [
{
"created": "Wed, 6 Jan 1999 05:16:34 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Apr 1999 08:31:49 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Nouri-Zonoz",
"Mohammad",
""
]
] | Using the 1+3 formulation of stationary spacetimes we show, in the context of gravoelectromagnetism, that the plane of the polarization of light rays passing close to a black hole undergoes a rotation. We show that this rotation has the same integral form as the usual Faraday effect, i.e. it is proportional to the integral of the component of the gravomagnetic field along the propagation path. We apply this integral formula to calculate the Faraday rotation induced by the Kerr and NUT spaces using the quasi-Maxwell form of the vacuum Einstein equations. |
2011.11948 | Davide Gerosa | Davide Gerosa, Matthew Mould, Daria Gangardt, Patricia Schmidt,
Geraint Pratten, Lucy M. Thomas | A generalized precession parameter $\chi_\mathrm{p}$ to interpret
gravitational-wave data | 12 pages, 6 figures, 1 table. Published in PRD. Software available at
https://github.com/dgerosa/generalizedchip | Phys. Rev. D 103, 064067 (2021) | 10.1103/PhysRevD.103.064067 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Originally designed for waveform approximants, the effective precession
parameter $\chi_\mathrm{p}$ is the most commonly used quantity to characterize
spin-precession effects in gravitational-wave observations of black-hole binary
coalescences. We point out that the current definition of $\chi_\mathrm{p}$
retains some, but not all, variations taking place on the precession timescale.
We rectify this inconsistency and propose more general definitions that either
fully consider or fully average those oscillations. Our generalized parameter
$\chi_\mathrm{p}\in[0,2]$ presents an exclusive region $\chi_\mathrm{p}>1$ that
can only be populated by binaries with two precessing spins. We apply our
prescriptions to current LIGO/Virgo events and find that posterior
distributions of $\chi_\mathrm{p}$ tend to show longer tails at larger values.
This appears to be a generic feature, implying that (i) current
$\chi_\mathrm{p}$ measurement errors might be underestimated, but also that
(ii) evidence for spin precession in current data might be stronger than
previously inferred. Among the gravitational-wave events released to date, that
which shows the most striking behavior is GW190521.
| [
{
"created": "Tue, 24 Nov 2020 08:04:48 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Mar 2021 14:38:54 GMT",
"version": "v2"
}
] | 2021-03-26 | [
[
"Gerosa",
"Davide",
""
],
[
"Mould",
"Matthew",
""
],
[
"Gangardt",
"Daria",
""
],
[
"Schmidt",
"Patricia",
""
],
[
"Pratten",
"Geraint",
""
],
[
"Thomas",
"Lucy M.",
""
]
] | Originally designed for waveform approximants, the effective precession parameter $\chi_\mathrm{p}$ is the most commonly used quantity to characterize spin-precession effects in gravitational-wave observations of black-hole binary coalescences. We point out that the current definition of $\chi_\mathrm{p}$ retains some, but not all, variations taking place on the precession timescale. We rectify this inconsistency and propose more general definitions that either fully consider or fully average those oscillations. Our generalized parameter $\chi_\mathrm{p}\in[0,2]$ presents an exclusive region $\chi_\mathrm{p}>1$ that can only be populated by binaries with two precessing spins. We apply our prescriptions to current LIGO/Virgo events and find that posterior distributions of $\chi_\mathrm{p}$ tend to show longer tails at larger values. This appears to be a generic feature, implying that (i) current $\chi_\mathrm{p}$ measurement errors might be underestimated, but also that (ii) evidence for spin precession in current data might be stronger than previously inferred. Among the gravitational-wave events released to date, that which shows the most striking behavior is GW190521. |
gr-qc/0401057 | Sang Pyo Kim | Sang Pyo Kim (Kunsan Nat'l Univ.), Don N. Page (Univ. Alberta) | Remarks on Schwinger Pair Production by Charged Black Holes | RevTex 19 Pages; Proceedings of the 8th Italian-Korean Symposium on
Relativistic Astrophysics, Pescara, Italy, 2003 | Nuovo Cim. B120 (2005) 1193-1208 | 10.1393/ncb/i2005-10148-6 | null | gr-qc | null | We introduce a canonical method for pair production by electromagnetic
fields. The canonical method in the space-dependent gauge provides
pair-production rate even for inhomogeneous fields. Further, the instanton
action including all corrections leads to an accurate formula for the
pair-production rate. We discuss various aspects of the canonical method and
clarify terminology for pair production. We study pair production by charged
black holes first by finding states of the field equation that describe pair
production and then by applying the canonical method.
| [
{
"created": "Tue, 13 Jan 2004 19:51:58 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Kim",
"Sang Pyo",
"",
"Kunsan Nat'l Univ."
],
[
"Page",
"Don N.",
"",
"Univ. Alberta"
]
] | We introduce a canonical method for pair production by electromagnetic fields. The canonical method in the space-dependent gauge provides pair-production rate even for inhomogeneous fields. Further, the instanton action including all corrections leads to an accurate formula for the pair-production rate. We discuss various aspects of the canonical method and clarify terminology for pair production. We study pair production by charged black holes first by finding states of the field equation that describe pair production and then by applying the canonical method. |
gr-qc/9905011 | Jerry B. Griffiths | Rong-Gen Cai and J. B. Griffiths | Null particle solutions in three-dimensional (anti-) de Sitter spaces | 11 pages, LaTeX, To appear in J. Math. Phys | J.Math.Phys. 40 (1999) 3465-3475 | 10.1063/1.532900 | null | gr-qc | null | We obtain a class of exact solutions representing null particles moving in
three-dimensional (anti-) de Sitter spaces by boosting the corresponding static
point source solutions given by Deser and Jackiw. In de Sitter space the
resulting solution describes two null particles moving on the (circular)
cosmological horizon, while in anti-de Sitter space it describes a single null
particle propagating from one side of the universe to the other. We also boost
the BTZ black hole solution to the ultrarelativistic limit and obtain the
solution for a spinning null particle moving in anti-de Sitter space. We find
that the ultrarelativistic geometry of the black hole is exactly the same as
that resulting from boosting the Deser-Jackiw solution when the angular
momentum of the hole vanishes. A general class of solutions is also obtained
which represents several null particles propagating in the Deser-Jackiw
background. The differences between the three-dimensional and four-dimensional
cases are also discussed.
| [
{
"created": "Tue, 4 May 1999 14:06:15 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Cai",
"Rong-Gen",
""
],
[
"Griffiths",
"J. B.",
""
]
] | We obtain a class of exact solutions representing null particles moving in three-dimensional (anti-) de Sitter spaces by boosting the corresponding static point source solutions given by Deser and Jackiw. In de Sitter space the resulting solution describes two null particles moving on the (circular) cosmological horizon, while in anti-de Sitter space it describes a single null particle propagating from one side of the universe to the other. We also boost the BTZ black hole solution to the ultrarelativistic limit and obtain the solution for a spinning null particle moving in anti-de Sitter space. We find that the ultrarelativistic geometry of the black hole is exactly the same as that resulting from boosting the Deser-Jackiw solution when the angular momentum of the hole vanishes. A general class of solutions is also obtained which represents several null particles propagating in the Deser-Jackiw background. The differences between the three-dimensional and four-dimensional cases are also discussed. |
1504.05839 | Yungui Gong | Nan Yang, Qin Fei, Qing Gao and Yungui Gong | Inflationary models with non-minimally derivative coupling | v2: add the general formulae without taking the high friction limit,
accepted for publication in CQG | Class. Quantum Grav. 33 (2016) 205001 | 10.1088/0264-9381/33/20/205001 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the general formulae for the the scalar and tensor spectral tilts
to the second order for the inflationary models with non-minimally derivative
coupling without taking the high friction limit. The non-minimally kinetic
coupling to Einstein tensor brings the energy scale in the inflationary models
down to be sub-Planckian. In the high friction limit, the Lyth bound is
modified with an extra suppression factor, so that the field excursion of the
inflaton is sub-Planckian. The inflationary models with non-minimally
derivative coupling are more consistent with observations in the high friction
limit. In particular, with the help of the non-minimally derivative coupling,
the quartic power law potential is consistent with the observational constraint
at 95\% CL.
| [
{
"created": "Wed, 22 Apr 2015 14:58:03 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Sep 2016 13:31:05 GMT",
"version": "v2"
}
] | 2017-02-08 | [
[
"Yang",
"Nan",
""
],
[
"Fei",
"Qin",
""
],
[
"Gao",
"Qing",
""
],
[
"Gong",
"Yungui",
""
]
] | We derive the general formulae for the the scalar and tensor spectral tilts to the second order for the inflationary models with non-minimally derivative coupling without taking the high friction limit. The non-minimally kinetic coupling to Einstein tensor brings the energy scale in the inflationary models down to be sub-Planckian. In the high friction limit, the Lyth bound is modified with an extra suppression factor, so that the field excursion of the inflaton is sub-Planckian. The inflationary models with non-minimally derivative coupling are more consistent with observations in the high friction limit. In particular, with the help of the non-minimally derivative coupling, the quartic power law potential is consistent with the observational constraint at 95\% CL. |
1607.03540 | Luca Baiotti | Luca Baiotti and Luciano Rezzolla | Binary neutron-star mergers: a review of Einstein's richest laboratory | 106 pages; invited review from Reports on Progress of Physics; small
changes, matches version to be published | 2017 Rep. Prog. Phys. 80 096901 | 10.1088/1361-6633/aa67bb | null | gr-qc astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The merger of binary neutron-stars systems combines in a single process:
extreme gravity, copious emission of gravitational waves, complex microphysics,
and electromagnetic processes that can lead to astrophysical signatures
observable at the largest redshifts. We review here the recent progress in
understanding what could be considered Einstein's richest laboratory,
highlighting in particular the numerous significant advances of the last
decade. Although special attention is paid to the status of models, techniques,
and results for fully general-relativistic dynamical simulations, a review is
also offered on initial data and advanced simulations with approximate
treatments of gravity. Finally, we review the considerable amount of work
carried out on the post-merger phase, including: black-hole formation, torus
accretion onto the merged compact object, connection with gamma-ray burst
engines, ejected material, and its nucleosynthesis.
| [
{
"created": "Tue, 12 Jul 2016 23:03:39 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Mar 2017 21:26:33 GMT",
"version": "v2"
}
] | 2018-02-21 | [
[
"Baiotti",
"Luca",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | The merger of binary neutron-stars systems combines in a single process: extreme gravity, copious emission of gravitational waves, complex microphysics, and electromagnetic processes that can lead to astrophysical signatures observable at the largest redshifts. We review here the recent progress in understanding what could be considered Einstein's richest laboratory, highlighting in particular the numerous significant advances of the last decade. Although special attention is paid to the status of models, techniques, and results for fully general-relativistic dynamical simulations, a review is also offered on initial data and advanced simulations with approximate treatments of gravity. Finally, we review the considerable amount of work carried out on the post-merger phase, including: black-hole formation, torus accretion onto the merged compact object, connection with gamma-ray burst engines, ejected material, and its nucleosynthesis. |
1908.07227 | Troels Harmark | Gianluca Grignani, Troels Harmark and Marta Orselli | Force-free electrodynamics near rotation axis of a Kerr black hole | 10 pages. v3: Discussion of the outer light surface expanded
considerably. Assumptions are clarified | null | 10.1088/1361-6382/ab7ac7 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Despite their potential importance for understanding astrophysical jets,
physically realistic exact solutions for magnetospheres around Kerr black holes
have not been found, even in the force-free approximation. Instead approximate
analytical solutions such as the Blandford-Znajek (split-)monopole, as well as
numerical solutions, have been constructed. In this paper we consider a new
approach to the analysis and construction of such magnetospheres. We consider
force-free electrodynamics close to the rotation axis of a magnetosphere
surrounding a Kerr black hole assuming axisymmetry. This is the region where
the force-free approximation should work the best, and where the jets are
located. We perform a systematic study of the asymptotic region with
(split-)monopole, paraboloidal and vertical asymptotic behaviors. Imposing
asymptotics similar to a (split-)monopole, we find under certain assumptions
that demanding regularity at the rotation axis and the event horizon restricts
solutions of the stream equation so much that it is not possible for a solution
to be continuously connected to the static (split-)monopole around the
Schwarzschild black hole in the limit where the rotation goes to zero. On the
one hand, this result provides independent evidence to the issues discovered
with the asymptotics of the Blandford-Znajek (split-)monopole in Ref. [1]. On
the other hand, we also point out possible caveats in our arguments that one
could conceivably exploit to amend the perturbative construction of the
Blandford-Znajek (split-)monopole.
| [
{
"created": "Tue, 20 Aug 2019 08:55:49 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Nov 2019 12:18:04 GMT",
"version": "v2"
},
{
"created": "Thu, 30 Jan 2020 13:37:52 GMT",
"version": "v3"
}
] | 2020-06-17 | [
[
"Grignani",
"Gianluca",
""
],
[
"Harmark",
"Troels",
""
],
[
"Orselli",
"Marta",
""
]
] | Despite their potential importance for understanding astrophysical jets, physically realistic exact solutions for magnetospheres around Kerr black holes have not been found, even in the force-free approximation. Instead approximate analytical solutions such as the Blandford-Znajek (split-)monopole, as well as numerical solutions, have been constructed. In this paper we consider a new approach to the analysis and construction of such magnetospheres. We consider force-free electrodynamics close to the rotation axis of a magnetosphere surrounding a Kerr black hole assuming axisymmetry. This is the region where the force-free approximation should work the best, and where the jets are located. We perform a systematic study of the asymptotic region with (split-)monopole, paraboloidal and vertical asymptotic behaviors. Imposing asymptotics similar to a (split-)monopole, we find under certain assumptions that demanding regularity at the rotation axis and the event horizon restricts solutions of the stream equation so much that it is not possible for a solution to be continuously connected to the static (split-)monopole around the Schwarzschild black hole in the limit where the rotation goes to zero. On the one hand, this result provides independent evidence to the issues discovered with the asymptotics of the Blandford-Znajek (split-)monopole in Ref. [1]. On the other hand, we also point out possible caveats in our arguments that one could conceivably exploit to amend the perturbative construction of the Blandford-Znajek (split-)monopole. |
1306.4616 | Eugen Radu | Burkhard Kleihaus, Jutta Kunz, Eugen Radu and Bintoro Subagyo | Axially symmetric static scalar solitons and black holes with scalar
hair | 8 pages, 3 figures | null | 10.1016/j.physletb.2013.07.051 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct static, asymptotically flat black hole solutions with scalar
hair. They evade the no-hair theorems by having a scalar potential which is not
strictly positive. By including an azimuthal winding number in the scalar field
ansatz, we find hairy black hole solutions which are static but axially
symmetric only. These solutions possess a globally regular limit, describing
scalar solitons. A branch of axially symmetric black holes is found to possess
a positive specific heat.
| [
{
"created": "Wed, 19 Jun 2013 17:01:22 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Radu",
"Eugen",
""
],
[
"Subagyo",
"Bintoro",
""
]
] | We construct static, asymptotically flat black hole solutions with scalar hair. They evade the no-hair theorems by having a scalar potential which is not strictly positive. By including an azimuthal winding number in the scalar field ansatz, we find hairy black hole solutions which are static but axially symmetric only. These solutions possess a globally regular limit, describing scalar solitons. A branch of axially symmetric black holes is found to possess a positive specific heat. |
0805.4614 | Hongbao Zhang | Song He and Hongbao Zhang | A covariant entropy bound conjecture on the dynamical horizon | JHEP style, 9 pages, 1 figure, honorable mention award received from
Gravity Research Foundation for 2008 Essay Competition | Int.J.Mod.Phys.D17:2467-2474,2009 | 10.1142/S0218271808014163 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As a compelling pattern for the holographic principle, our covariant entropy
bound conjecture is proposed for more general dynamical horizons. Then we apply
our conjecture to $\Lambda$CDM cosmological models, where we find it imposes a
novel upper bound $10^{-90}$ on the cosmological constant for our own universe
by taking into account the dominant entropy contribution from super-massive
black holes, which thus provides an alternative macroscopic perspective to
understand the longstanding cosmological constant problem. As an intriguing
implication of this conjecture, we also discuss the possible profound relation
between the present cosmological constant, the origin of mass, and the
anthropic principle.
| [
{
"created": "Thu, 29 May 2008 19:53:57 GMT",
"version": "v1"
},
{
"created": "Thu, 29 May 2008 20:04:48 GMT",
"version": "v2"
}
] | 2009-03-20 | [
[
"He",
"Song",
""
],
[
"Zhang",
"Hongbao",
""
]
] | As a compelling pattern for the holographic principle, our covariant entropy bound conjecture is proposed for more general dynamical horizons. Then we apply our conjecture to $\Lambda$CDM cosmological models, where we find it imposes a novel upper bound $10^{-90}$ on the cosmological constant for our own universe by taking into account the dominant entropy contribution from super-massive black holes, which thus provides an alternative macroscopic perspective to understand the longstanding cosmological constant problem. As an intriguing implication of this conjecture, we also discuss the possible profound relation between the present cosmological constant, the origin of mass, and the anthropic principle. |
2205.01363 | Genly Le\'on | Genly Leon, A. Paliathanasis and P.G.L. Leach | New analytic solutions in $f\left( R\right) $-Cosmology from
Painlev\'{e} analysis | 16 pages, no figures | Math. Meth. Appl. Sci. (2024), 1-9 | 10.1002/mma.9921 | null | gr-qc math-ph math.MP nlin.SI | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the singularity analysis, we investigate the integrability properties
and existence of analytic solutions in $f\left( R\right)$-cosmology.
Specifically, for some power-law $f\left( R\right) $-theories of particular
interest, we apply the ARS algorithm to prove if the field equations possess
the Painlev\'{e} property. Constraints for the free parameters of the power-law
models are derived, and new analytic solutions are derived, expressed in terms
of Laurent expansions.
| [
{
"created": "Tue, 3 May 2022 08:23:47 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Mar 2024 03:30:38 GMT",
"version": "v2"
}
] | 2024-03-27 | [
[
"Leon",
"Genly",
""
],
[
"Paliathanasis",
"A.",
""
],
[
"Leach",
"P. G. L.",
""
]
] | Using the singularity analysis, we investigate the integrability properties and existence of analytic solutions in $f\left( R\right)$-cosmology. Specifically, for some power-law $f\left( R\right) $-theories of particular interest, we apply the ARS algorithm to prove if the field equations possess the Painlev\'{e} property. Constraints for the free parameters of the power-law models are derived, and new analytic solutions are derived, expressed in terms of Laurent expansions. |
2209.12692 | Naeem Ahmad Pundeer | Musavvir Ali, Mohammad Salman, Farook Rahaman and Naeem Ahmad Pundeer | On some properties of M-projective curvature tensor in spacetime of
general relativity | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we investigate the connection between the M-projective
curvature tensor and other tensors. Also, we obtain the divergence of
M-projective curvature tensor. A symmetry of spacetime known as M-projective
collineation has been presented, and it has been possible to determine the
conditions under which the general relativity spacetimes can admit such
collineations.
| [
{
"created": "Fri, 23 Sep 2022 12:50:48 GMT",
"version": "v1"
},
{
"created": "Fri, 26 May 2023 11:48:56 GMT",
"version": "v2"
}
] | 2023-05-29 | [
[
"Ali",
"Musavvir",
""
],
[
"Salman",
"Mohammad",
""
],
[
"Rahaman",
"Farook",
""
],
[
"Pundeer",
"Naeem Ahmad",
""
]
] | In this paper, we investigate the connection between the M-projective curvature tensor and other tensors. Also, we obtain the divergence of M-projective curvature tensor. A symmetry of spacetime known as M-projective collineation has been presented, and it has been possible to determine the conditions under which the general relativity spacetimes can admit such collineations. |
1412.3434 | Andrzej G\"orlich | Jan Ambj{\o}rn, Andrzej G\"orlich, Jerzy Jurkiewicz, Hongguang Zhang | The spectral dimension in 2D CDT gravity coupled to scalar fields | 13 pages, 8 figures | null | 10.1142/S0217732315500777 | null | gr-qc hep-lat hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Causal Dynamical Triangulations (CDT) provide a non-perturbative formulation
of Quantum Gravity assuming the existence of a global time foliation. In our
earlier study we analyzed the effect of including $d$ copies of a massless
scalar field in the two-dimensional CDT model with imaginary time. For $d > 1$
we observed the formation of a "blob", somewhat similar to that observed in
four-dimensional CDT without matter. In the two-dimensional case the "blob" has
a Hausdorff dimension $D_H=3$. In this paper we study the spectral dimension
$D_S$ of the two-dimensional CDT-universe, both for $d = 0$ (pure gravity) and
$d = 4$. We show that in both cases the spectral dimension is consistent with
$D_S = 2$.
| [
{
"created": "Wed, 10 Dec 2014 20:08:50 GMT",
"version": "v1"
}
] | 2015-04-15 | [
[
"Ambjørn",
"Jan",
""
],
[
"Görlich",
"Andrzej",
""
],
[
"Jurkiewicz",
"Jerzy",
""
],
[
"Zhang",
"Hongguang",
""
]
] | Causal Dynamical Triangulations (CDT) provide a non-perturbative formulation of Quantum Gravity assuming the existence of a global time foliation. In our earlier study we analyzed the effect of including $d$ copies of a massless scalar field in the two-dimensional CDT model with imaginary time. For $d > 1$ we observed the formation of a "blob", somewhat similar to that observed in four-dimensional CDT without matter. In the two-dimensional case the "blob" has a Hausdorff dimension $D_H=3$. In this paper we study the spectral dimension $D_S$ of the two-dimensional CDT-universe, both for $d = 0$ (pure gravity) and $d = 4$. We show that in both cases the spectral dimension is consistent with $D_S = 2$. |
1801.09630 | Parampreet Singh | Kristina Giesel, Adrian Herzog, Parampreet Singh | Gauge invariant variables for cosmological perturbation theory using
geometrical clocks | Discussion expanded, references added. To appear in Classical and
Quantum Gravity | null | 10.1088/1361-6382/aacda2 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the extended ADM-phase space formulation in the canonical framework we
analyze the relationship between various gauge choices made in cosmological
perturbation theory and the choice of geometrical clocks in the relational
formalism. We show that various gauge invariant variables obtained in the
conventional analysis of cosmological perturbation theory correspond to Dirac
observables tied to a specific choice of geometrical clocks. As examples, we
show that the Bardeen potentials and the Mukhanov-Sasaki variable emerge
naturally in our analysis as observables when gauge fixing conditions are
determined via clocks in the Hamiltonian framework. Similarly other gauge
invariant variables for various gauges can be systematically obtained. We
demonstrate this by analyzing five common gauge choices: longitudinal,
spatially flat, uniform field, synchronous and comoving gauge. For all these,
we apply the observable map in the context of the relational formalism and
obtain the corresponding Dirac observables associated with these choices of
clocks. At the linear order, our analysis generalizes the existing results in
canonical cosmological perturbation theory twofold. On the one hand we can
include also gauges that can only be analyzed in the context of the extended
ADM-phase space and furthermore, we obtain a set of natural gauge invariant
variables, namely the Dirac observables, for each considered choice of gauge
conditions. Our analysis provides insights on which clocks should be used to
extract the relevant natural physical observables both at the classical and
quantum level. We also discuss how to generalize our analysis in a
straightforward way to higher orders in the perturbation theory to understand
gauge conditions and the construction of gauge invariant quantities beyond
linear order.
| [
{
"created": "Mon, 29 Jan 2018 17:11:47 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Mar 2018 14:56:19 GMT",
"version": "v2"
},
{
"created": "Tue, 19 Jun 2018 00:04:13 GMT",
"version": "v3"
}
] | 2018-07-25 | [
[
"Giesel",
"Kristina",
""
],
[
"Herzog",
"Adrian",
""
],
[
"Singh",
"Parampreet",
""
]
] | Using the extended ADM-phase space formulation in the canonical framework we analyze the relationship between various gauge choices made in cosmological perturbation theory and the choice of geometrical clocks in the relational formalism. We show that various gauge invariant variables obtained in the conventional analysis of cosmological perturbation theory correspond to Dirac observables tied to a specific choice of geometrical clocks. As examples, we show that the Bardeen potentials and the Mukhanov-Sasaki variable emerge naturally in our analysis as observables when gauge fixing conditions are determined via clocks in the Hamiltonian framework. Similarly other gauge invariant variables for various gauges can be systematically obtained. We demonstrate this by analyzing five common gauge choices: longitudinal, spatially flat, uniform field, synchronous and comoving gauge. For all these, we apply the observable map in the context of the relational formalism and obtain the corresponding Dirac observables associated with these choices of clocks. At the linear order, our analysis generalizes the existing results in canonical cosmological perturbation theory twofold. On the one hand we can include also gauges that can only be analyzed in the context of the extended ADM-phase space and furthermore, we obtain a set of natural gauge invariant variables, namely the Dirac observables, for each considered choice of gauge conditions. Our analysis provides insights on which clocks should be used to extract the relevant natural physical observables both at the classical and quantum level. We also discuss how to generalize our analysis in a straightforward way to higher orders in the perturbation theory to understand gauge conditions and the construction of gauge invariant quantities beyond linear order. |
2206.02140 | Qing Gao | Qing Gao | Constraint on the mass of graviton with gravitational waves | 23 pages, 3 tables, 4 figures. Minor changes to match the version
published on SCPMA(SCIENCE CHINA Physics, Mechanics & Astronomy) | Sci.China Phys.Mech.Astron. 66 (2023) 2, 220411 | 10.1007/s11433-022-1971-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the effects of the mass of graviton on both the waveform of
gravitational waves and the antenna response to gravitational waves. We find
the effect on the response function is negligible for small mass. By using the
Fisher matrix method, we make parameter estimations with space-based
gravitational wave detectors for massive black hole binaries in massive gravity
theory. The wavelength of massive graviton is constrained to be
$\lambda_g\gtrsim 10^{17}$ m and the mass is constrained to be $m_g\lesssim
10^{-60}$ kg by one year's observation of massive black hole binaries with
space-based gravitational wave detectors.
| [
{
"created": "Sun, 5 Jun 2022 09:58:27 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Nov 2022 08:54:22 GMT",
"version": "v2"
}
] | 2022-11-28 | [
[
"Gao",
"Qing",
""
]
] | We consider the effects of the mass of graviton on both the waveform of gravitational waves and the antenna response to gravitational waves. We find the effect on the response function is negligible for small mass. By using the Fisher matrix method, we make parameter estimations with space-based gravitational wave detectors for massive black hole binaries in massive gravity theory. The wavelength of massive graviton is constrained to be $\lambda_g\gtrsim 10^{17}$ m and the mass is constrained to be $m_g\lesssim 10^{-60}$ kg by one year's observation of massive black hole binaries with space-based gravitational wave detectors. |
gr-qc/9404047 | Viqar Husain | Viqar Husain | Radiation collapse and gravitational waves in three dimensions | 9 pages (RevTeX) 1 figure upon request, Alberta-Thy-12-94 | Phys.Rev.D50:2361-2363,1994 | 10.1103/PhysRevD.50.R2361 | null | gr-qc | null | Two non-static solutions for three dimensional gravity coupled to matter
fields are given. One describes the collapse of radiation that results in a
black hole. This is the three dimensional analog of the Vaidya metric, and is
used to construct a model for mass inflation. The other describes plane
gravitational waves for coupling to a massless scalar field.
| [
{
"created": "Tue, 26 Apr 1994 03:23:30 GMT",
"version": "v1"
}
] | 2009-12-30 | [
[
"Husain",
"Viqar",
""
]
] | Two non-static solutions for three dimensional gravity coupled to matter fields are given. One describes the collapse of radiation that results in a black hole. This is the three dimensional analog of the Vaidya metric, and is used to construct a model for mass inflation. The other describes plane gravitational waves for coupling to a massless scalar field. |
gr-qc/9912078 | Tekin Dereli | Tekin Dereli (METU,Ankara), Yuri N. Obukhov (Moscow State Univ.) | Massless scalar fields and topological black holes | 15 pages, LATEX, no figures. (To appear in Phys. Rev. D) | Phys.Rev. D61 (2000) 084015 | 10.1103/PhysRevD.61.084015 | null | gr-qc | null | The exact static solutions in the higher dimensional Einstein-Maxwell-Klein-
Gordon theory are investigated. With the help of the methods developed for the
effective dilaton type gauge gravity models in two dimensions, we find new
spherically and hyperbolically symmetric solutions which generalize the four
dimensional configurations of Dereli-Eris. We show that, like in four
dimensions, the non-trivial scalar field yields, in general, a naked
singularity. The new solutions are compared with the higher dimensional
Brans-Dicke black hole type solutions.
| [
{
"created": "Sat, 18 Dec 1999 11:39:42 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Dereli",
"Tekin",
"",
"METU,Ankara"
],
[
"Obukhov",
"Yuri N.",
"",
"Moscow State Univ."
]
] | The exact static solutions in the higher dimensional Einstein-Maxwell-Klein- Gordon theory are investigated. With the help of the methods developed for the effective dilaton type gauge gravity models in two dimensions, we find new spherically and hyperbolically symmetric solutions which generalize the four dimensional configurations of Dereli-Eris. We show that, like in four dimensions, the non-trivial scalar field yields, in general, a naked singularity. The new solutions are compared with the higher dimensional Brans-Dicke black hole type solutions. |
1607.03508 | Florencia Anabella Teppa Pannia | F. A. Teppa Pannia, F. Garc\'ia, S. E. Perez Bergliaffa, M. Orellana,
G. E. Romero | Structure of Compact Stars in R-squared Palatini Gravity | 9 pages, 5 figures. Accepted for publication in General Relativity
and Gravitation | null | 10.1007/s10714-016-2182-7 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyse configurations of compact stars in the so-called R-squared gravity
in the Palatini formalism. Using a realistic equation of state we show that the
mass-radius configurations are lighter than their counterparts in General
Relativity. We also obtain the internal profiles, which run in strong
correlation with the derivatives of the equation of state, leading to regions
where the mass parameter decreases with the radial coordinate in a
counter-intuitive way. In order to analyse such correlation, we introduce a
parametrisation of the equation of state given by multiple polytropes, which
allows us to explicitly control its derivatives. We show that, even in a
limiting case where hard phase transitions in matter are allowed, the internal
profile of the mass parameter still presents strange features and the
calculated M-R configurations also yield NSs lighter than those obtained in
General Relativity.
| [
{
"created": "Fri, 1 Jul 2016 13:11:42 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Dec 2016 17:23:55 GMT",
"version": "v2"
}
] | 2016-12-28 | [
[
"Pannia",
"F. A. Teppa",
""
],
[
"García",
"F.",
""
],
[
"Bergliaffa",
"S. E. Perez",
""
],
[
"Orellana",
"M.",
""
],
[
"Romero",
"G. E.",
""
]
] | We analyse configurations of compact stars in the so-called R-squared gravity in the Palatini formalism. Using a realistic equation of state we show that the mass-radius configurations are lighter than their counterparts in General Relativity. We also obtain the internal profiles, which run in strong correlation with the derivatives of the equation of state, leading to regions where the mass parameter decreases with the radial coordinate in a counter-intuitive way. In order to analyse such correlation, we introduce a parametrisation of the equation of state given by multiple polytropes, which allows us to explicitly control its derivatives. We show that, even in a limiting case where hard phase transitions in matter are allowed, the internal profile of the mass parameter still presents strange features and the calculated M-R configurations also yield NSs lighter than those obtained in General Relativity. |
1310.7250 | Farhad Darabi | M. R. Setare and F. Darabi | Polytropic inspired inflation | 8 pages | CHINESE JOURNAL OF PHYSICS VOL. 51, NO. 3, 2013, 427 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the chaotic inflation in the context of a gravity theory where the
Friedman equation is modified, inspired by the polytropic gas equation of
state. It is seen that in the $n=1$ case for the polytropic index the inflaton
field at the end of inflation $\phi_e$, depends on the Planck mass, while for
$n\neq1$ it generally depends on the polytropic constant and mass of the
inflaton field.
| [
{
"created": "Sun, 27 Oct 2013 20:52:00 GMT",
"version": "v1"
}
] | 2013-10-29 | [
[
"Setare",
"M. R.",
""
],
[
"Darabi",
"F.",
""
]
] | We study the chaotic inflation in the context of a gravity theory where the Friedman equation is modified, inspired by the polytropic gas equation of state. It is seen that in the $n=1$ case for the polytropic index the inflaton field at the end of inflation $\phi_e$, depends on the Planck mass, while for $n\neq1$ it generally depends on the polytropic constant and mass of the inflaton field. |
gr-qc/9702044 | Henrique Oliveira | H. P. de Oliveira, I. Damiao Soares and T. J. Stuchi | Chaos in Anisotropic Pre-Inflationary Universes | 14 pages, figures available under request. submitted to Physical
Review D | Phys.Rev. D56 (1997) 730-740 | 10.1103/PhysRevD.56.730 | null | gr-qc | null | We study the dynamics of anisotropic Bianchi type-IX models with matter and
cosmological constant. The models can be thought as describing the role of
anisotropy in the early stages of inflation. The concurrence of the
cosmological constant and anisotropy are sufficient to produce a chaotic
dynamics in the gravitational degrees of freedom, connected to the presence of
a critical point of saddle-center type in the phase space of the system. The
invariant character of chaos is guaranteed by the topology of the cylinders
emanating from unstable periodic orbits in the neighborhood of the
saddle-center. We discuss a possible mechanism for amplification of specific
wavelengths of inhomogeneous fluctuations in the models. A geometrical
interpretation is given for Wald's inequality in terms of invariant tori and
their destruction by increasing values of the cosmological constant.
| [
{
"created": "Fri, 21 Feb 1997 20:44:13 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"de Oliveira",
"H. P.",
""
],
[
"Soares",
"I. Damiao",
""
],
[
"Stuchi",
"T. J.",
""
]
] | We study the dynamics of anisotropic Bianchi type-IX models with matter and cosmological constant. The models can be thought as describing the role of anisotropy in the early stages of inflation. The concurrence of the cosmological constant and anisotropy are sufficient to produce a chaotic dynamics in the gravitational degrees of freedom, connected to the presence of a critical point of saddle-center type in the phase space of the system. The invariant character of chaos is guaranteed by the topology of the cylinders emanating from unstable periodic orbits in the neighborhood of the saddle-center. We discuss a possible mechanism for amplification of specific wavelengths of inhomogeneous fluctuations in the models. A geometrical interpretation is given for Wald's inequality in terms of invariant tori and their destruction by increasing values of the cosmological constant. |
1304.0550 | Eddy Sham | Y.-H. Sham, P. T. Leung, and L.-M. Lin | Compact stars in Eddington-inspired Born-Infeld gravity: Anomalies
associated with phase transitions | 8 pages, 2 figures | Physical Review D 87, 061503(R) (2013) | 10.1103/PhysRevD.87.061503 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study how generic phase transitions taking place in compact stars
constructed in the framework of the Eddington-inspired Born-Infeld (EiBI)
gravity can lead to anomalous behavior of these stars. For the case with
first-order phase transitions, compact stars in EiBI gravity with a positive
coupling parameter $\kappa $ exhibit a finite region with constant pressure,
which is absent in general relativity. However, for the case with a negative
$\kappa $, an equilibrium stellar configuration cannot be constructed. Hence,
EiBI gravity seems to impose stricter constraints on the microphysics of
stellar matter. Besides, in the presence of spatial discontinuities in the
sound speed $c_s$ due to phase transitions, the Ricci scalar is spatially
discontinuous and contains $\delta$-function singularities proportional to the
jump in $c_s^2$ acquired in the associated phase transition.
| [
{
"created": "Tue, 2 Apr 2013 07:51:35 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Apr 2013 07:56:24 GMT",
"version": "v2"
}
] | 2015-06-15 | [
[
"Sham",
"Y. -H.",
""
],
[
"Leung",
"P. T.",
""
],
[
"Lin",
"L. -M.",
""
]
] | We study how generic phase transitions taking place in compact stars constructed in the framework of the Eddington-inspired Born-Infeld (EiBI) gravity can lead to anomalous behavior of these stars. For the case with first-order phase transitions, compact stars in EiBI gravity with a positive coupling parameter $\kappa $ exhibit a finite region with constant pressure, which is absent in general relativity. However, for the case with a negative $\kappa $, an equilibrium stellar configuration cannot be constructed. Hence, EiBI gravity seems to impose stricter constraints on the microphysics of stellar matter. Besides, in the presence of spatial discontinuities in the sound speed $c_s$ due to phase transitions, the Ricci scalar is spatially discontinuous and contains $\delta$-function singularities proportional to the jump in $c_s^2$ acquired in the associated phase transition. |
2210.15433 | Gopi Kant Goswami Dr | Anirudh Pradhan, Gopikant Goswami, Rita Rani, Aroonkumar Beesham | An f(R,T) Gravity Based FLRW Model and Observational Constraints | 19 pages, 8 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We attempt to construct a Friedmann-Lemaitre-Robertson-Walker(FLRW)
cosmological model in $f(R, T)$ gravity which exhibits a phase transition from
deceleration to acceleration at present. We take $f(R,T) = R + 2 \lambda T$,
$\lambda$ being an arbitrary constant. In our model, the $\lambda$ parameter
develops a negative pressure in the universe whose Equation of state is
parameterized. The present values of model parameters such as density, Hubble,
deceleration, Equation of state, and $\lambda$ are estimated statistically by
using the Chi-Square test. For this, we have used three different types of
observational data sets: the $46$ Hubble parameter data set, the SNeIa $715$
data sets of distance modulus, and the 66 Pantheon data set (the latest
compilation of SNeIa 40 bined plus 26 high red shift apparent magnitude $m_b$
data set in the red shift ranges from $0.014 \leq z \leq 2.26 $). We have
calculated the transitional red shift and time. The estimated results for the
present values of various model parameters are found as per expectations and
surveys. Interestingly, we get the present value of the density $\rho_0$,
$\simeq 1.5 \rho_c $. The critical density is estimated as $\rho_c\simeq 1.88 ~
h_0^2~10^{-29}~gm/cm^3 $ in the literature. The higher value of the present
density is attributed to the presence of some additional energies in the
universe apart from baryon energy. We have examined the behavior of the
pressure in our model. It is negative and produces acceleration in the
universe. Its present value is obtained as $p_0 \simeq - 0.7 \rho_0$.
| [
{
"created": "Wed, 26 Oct 2022 13:55:34 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Dec 2022 16:33:59 GMT",
"version": "v2"
},
{
"created": "Fri, 2 Jun 2023 17:46:32 GMT",
"version": "v3"
}
] | 2023-06-05 | [
[
"Pradhan",
"Anirudh",
""
],
[
"Goswami",
"Gopikant",
""
],
[
"Rani",
"Rita",
""
],
[
"Beesham",
"Aroonkumar",
""
]
] | We attempt to construct a Friedmann-Lemaitre-Robertson-Walker(FLRW) cosmological model in $f(R, T)$ gravity which exhibits a phase transition from deceleration to acceleration at present. We take $f(R,T) = R + 2 \lambda T$, $\lambda$ being an arbitrary constant. In our model, the $\lambda$ parameter develops a negative pressure in the universe whose Equation of state is parameterized. The present values of model parameters such as density, Hubble, deceleration, Equation of state, and $\lambda$ are estimated statistically by using the Chi-Square test. For this, we have used three different types of observational data sets: the $46$ Hubble parameter data set, the SNeIa $715$ data sets of distance modulus, and the 66 Pantheon data set (the latest compilation of SNeIa 40 bined plus 26 high red shift apparent magnitude $m_b$ data set in the red shift ranges from $0.014 \leq z \leq 2.26 $). We have calculated the transitional red shift and time. The estimated results for the present values of various model parameters are found as per expectations and surveys. Interestingly, we get the present value of the density $\rho_0$, $\simeq 1.5 \rho_c $. The critical density is estimated as $\rho_c\simeq 1.88 ~ h_0^2~10^{-29}~gm/cm^3 $ in the literature. The higher value of the present density is attributed to the presence of some additional energies in the universe apart from baryon energy. We have examined the behavior of the pressure in our model. It is negative and produces acceleration in the universe. Its present value is obtained as $p_0 \simeq - 0.7 \rho_0$. |
1511.00231 | Wei-Tou Ni | Kazuaki Kuroda, Wei-Tou Ni and Wei-Ping Pan | Gravitational waves: Classification, Methods of detection,
Sensitivities, and Sources | 38 pages, 4 figures, 6 tables. Chapter 10 in One Hundred Years of
General Relativity: From Genesis and Empirical Foundations to Gravitational
Waves, Cosmology and Quantum Gravity, ed.W.-T. Ni (World Scientific,
Singapore, 2015); Int. J. Mod. Phys. D, to be published | Int. J. Mod. Phys. D, Vol. 24, No. 14 (2015) 1530031 | 10.1142/S0218271815300311 | null | gr-qc astro-ph.CO astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | After giving a brief introduction and presenting a complete classification of
gravitational waves (GWs) according to their frequencies, we review and
summarize the detection methods, the sensitivities, and the sources. We notice
that real-time detections are possible above 300 pHz. Below 300 pHz, the
detections are possible on GW imprints or indirectly. We are on the verge of
detection. The progress in this field will be promising and thriving. We will
see improvement of a few orders to several orders of magnitude in the GW
detection sensitivities over all frequency bands in the next hundred years.
| [
{
"created": "Sun, 1 Nov 2015 11:31:31 GMT",
"version": "v1"
}
] | 2016-02-03 | [
[
"Kuroda",
"Kazuaki",
""
],
[
"Ni",
"Wei-Tou",
""
],
[
"Pan",
"Wei-Ping",
""
]
] | After giving a brief introduction and presenting a complete classification of gravitational waves (GWs) according to their frequencies, we review and summarize the detection methods, the sensitivities, and the sources. We notice that real-time detections are possible above 300 pHz. Below 300 pHz, the detections are possible on GW imprints or indirectly. We are on the verge of detection. The progress in this field will be promising and thriving. We will see improvement of a few orders to several orders of magnitude in the GW detection sensitivities over all frequency bands in the next hundred years. |
1203.0112 | Dong-han Yeom | Dong-il Hwang, Bum-Hoon Lee, Hanno Sahlmann, Dong-han Yeom | The no-boundary measure in string theory: Applications to moduli
stabilization, flux compactification, and cosmic landscape | 27 pages, 8 figures | Class.Quant.Grav.29:175001,2012 | 10.1088/0264-9381/29/17/175001 | APCTP Pre2012-003 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the no-boundary measure in the context of moduli
stabilization. To this end, we first show that for exponential potentials,
there are no classical histories once the slope exceeds a critical value. We
also investigate the probability distributions given by the no-boundary wave
function near maxima of the potential. These results are then applied to a
simple model that compactifies 6D to 4D (HBSV model) with fluxes. We find that
the no-boundary wave function effectively stabilizes the moduli of the model.
Moreover, we find the a priori probability for the cosmological constant in
this model. We find that a negative value is preferred, and a vanishing
cosmological constant is not distinguished by the probability measure. We also
discuss the application to the cosmic landscape. Our preliminary arguments
indicate that the probability of obtaining anti de Sitter space is vastly
greater than for de Sitter.
| [
{
"created": "Thu, 1 Mar 2012 08:11:08 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Aug 2012 03:21:42 GMT",
"version": "v2"
}
] | 2015-06-04 | [
[
"Hwang",
"Dong-il",
""
],
[
"Lee",
"Bum-Hoon",
""
],
[
"Sahlmann",
"Hanno",
""
],
[
"Yeom",
"Dong-han",
""
]
] | We investigate the no-boundary measure in the context of moduli stabilization. To this end, we first show that for exponential potentials, there are no classical histories once the slope exceeds a critical value. We also investigate the probability distributions given by the no-boundary wave function near maxima of the potential. These results are then applied to a simple model that compactifies 6D to 4D (HBSV model) with fluxes. We find that the no-boundary wave function effectively stabilizes the moduli of the model. Moreover, we find the a priori probability for the cosmological constant in this model. We find that a negative value is preferred, and a vanishing cosmological constant is not distinguished by the probability measure. We also discuss the application to the cosmic landscape. Our preliminary arguments indicate that the probability of obtaining anti de Sitter space is vastly greater than for de Sitter. |
1505.00541 | Patrick Das Gupta | Patrick Das Gupta | Gravity, Bose-Einstein Condensates and Gross-Pitaevskii Equation | This paper was presented at the Discussion Meeting on Quantum
Measurements, I.I.Sc., Bangalore, in 2014 | Current Science, Volume 109, pp. 1946-1950 (2015) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore the effect of mutual gravitational interaction between ultra-cold
gas atoms on the dynamics of Bose-Einstein condensates (BEC). Small amplitude
oscillation of BEC is studied by applying variational technique to reduce the
Gross-Pitaevskii equation, with gravity included, to the equation of motion of
a particle moving in a potential. According to our analysis, if the s-wave
scattering length can be tuned to zero using Feshbach resonance for future BEC
with occupation numbers as high as $\approx 10^{20}$, there exists a critical
ground state occupation number above which the BEC is unstable, provided that
its constituents interact with a $1/r^3 $ gravity at short scales.
| [
{
"created": "Mon, 4 May 2015 08:00:21 GMT",
"version": "v1"
}
] | 2018-12-27 | [
[
"Gupta",
"Patrick Das",
""
]
] | We explore the effect of mutual gravitational interaction between ultra-cold gas atoms on the dynamics of Bose-Einstein condensates (BEC). Small amplitude oscillation of BEC is studied by applying variational technique to reduce the Gross-Pitaevskii equation, with gravity included, to the equation of motion of a particle moving in a potential. According to our analysis, if the s-wave scattering length can be tuned to zero using Feshbach resonance for future BEC with occupation numbers as high as $\approx 10^{20}$, there exists a critical ground state occupation number above which the BEC is unstable, provided that its constituents interact with a $1/r^3 $ gravity at short scales. |
1603.08798 | Abdul Jawad | Abdul Jawad, Amara Ilyas and Shamaila Rani | Dynamics of Modified Chaplygin Gas Inflation on the Brane with Bulk
Viscous Pressure | 21 pages, 8 figures | Int. J. Mod. Phys. D 26 (2017) 1750031 | 10.1142/S0218271817500316 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the role of bulk viscous pressure on the warm inflationary
modified Chaplygin gas in brane-world framework in the presence of standard
scalar field. We assume the intermediate inflationary scenario in strong
dissipative regime and constructed the inflaton, potential, entropy density,
slow-roll parameters, scalar and tensor power spectra, scalar spectral index
and tensor-to-scalar ratio. We develop various trajectories such as $n_s - N$,
$n_s - r$ and $n_s - \alpha_s$ (where $n_s$ is the spectral index, $\alpha_s$
is the running of spectral index, $N$ is the number of e-folds and $r$ is
tensor-to-scalar ratio) for variable as well as constant dissipation and bulk
viscous coefficients at high dissipative regime. It is interesting to remark
here that our results of these parameters are compatible with recent
observational data such as WMAP $7+9$, BICEP$2$ and Planck data.
| [
{
"created": "Tue, 29 Mar 2016 14:59:12 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Mar 2016 11:09:27 GMT",
"version": "v2"
},
{
"created": "Sun, 14 Aug 2016 13:50:24 GMT",
"version": "v3"
},
{
"created": "Tue, 1 Nov 2016 09:00:17 GMT",
"version": "v4"
}
] | 2017-02-22 | [
[
"Jawad",
"Abdul",
""
],
[
"Ilyas",
"Amara",
""
],
[
"Rani",
"Shamaila",
""
]
] | We investigate the role of bulk viscous pressure on the warm inflationary modified Chaplygin gas in brane-world framework in the presence of standard scalar field. We assume the intermediate inflationary scenario in strong dissipative regime and constructed the inflaton, potential, entropy density, slow-roll parameters, scalar and tensor power spectra, scalar spectral index and tensor-to-scalar ratio. We develop various trajectories such as $n_s - N$, $n_s - r$ and $n_s - \alpha_s$ (where $n_s$ is the spectral index, $\alpha_s$ is the running of spectral index, $N$ is the number of e-folds and $r$ is tensor-to-scalar ratio) for variable as well as constant dissipation and bulk viscous coefficients at high dissipative regime. It is interesting to remark here that our results of these parameters are compatible with recent observational data such as WMAP $7+9$, BICEP$2$ and Planck data. |
2110.10917 | Masaya Amo | Masaya Amo, Tetsuya Shiromizu, Keisuke Izumi, Hirotaka Yoshino,
Yoshimune Tomikawa | Asymptotic behavior of null geodesics near future null infinity II:
curvatures, photon surface and dynamically transversely trapping surface | 17 pages, no figures, published version | Phys. Rev. D 105, 064074 (2022) | 10.1103/PhysRevD.105.064074 | YITP-21-103, KOBE-COSMO-21-15, OCU-PHYS-550, AP-GR-174 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Bearing in mind our previous study on asymptotic behavior of null geodesics
near future null infinity, we analyze the behavior of geometrical quantities
such as a certain extrinsic curvature and Riemann tensor in the Bondi
coordinates. In the sense of asymptotics, the condition for an $r$-constant
hypersurface to be a photon surface is shown to be controlled by a key quantity
that determines the fate of photons initially emitted in angular directions. As
a consequence, in four dimensions, such a non-expanding photon surface can be
realized even near future null infinity in the presence of enormous energy flux
for a short period of time. By contrast, in higher-dimensional cases, no such a
photon surface can exist. This result also implies that the dynamically
transversely trapping surface, which is proposed as an extension of a photon
surface, can have an arbitrarily large radius in four dimensions.
| [
{
"created": "Thu, 21 Oct 2021 06:15:08 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Apr 2022 10:59:47 GMT",
"version": "v2"
}
] | 2022-04-04 | [
[
"Amo",
"Masaya",
""
],
[
"Shiromizu",
"Tetsuya",
""
],
[
"Izumi",
"Keisuke",
""
],
[
"Yoshino",
"Hirotaka",
""
],
[
"Tomikawa",
"Yoshimune",
""
]
] | Bearing in mind our previous study on asymptotic behavior of null geodesics near future null infinity, we analyze the behavior of geometrical quantities such as a certain extrinsic curvature and Riemann tensor in the Bondi coordinates. In the sense of asymptotics, the condition for an $r$-constant hypersurface to be a photon surface is shown to be controlled by a key quantity that determines the fate of photons initially emitted in angular directions. As a consequence, in four dimensions, such a non-expanding photon surface can be realized even near future null infinity in the presence of enormous energy flux for a short period of time. By contrast, in higher-dimensional cases, no such a photon surface can exist. This result also implies that the dynamically transversely trapping surface, which is proposed as an extension of a photon surface, can have an arbitrarily large radius in four dimensions. |
1306.5410 | Richard Woodard | S. P. Miao (National Cheng Kung U.), P. J. Mora (U. Florida), N. C.
Tsamis (U. Crete) and R. P. Woodard (U. Florida) | The Perils of Analytic Continuation | 40 pages, 2 figures (6 figure files), uses LaTeX2e, Version 2
expanded to 43 pages, principally in section 3 to show that even the closed
coordinate mode sums break de Sitter invariance and that claims to the
contrary are based upon the (admitted) use of negative normed states | Phys. Rev. D 89, 104004 (2014) | 10.1103/PhysRevD.89.104004 | UFIFT-QG-13-03 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A nice paper by Morrison demonstrates the recent convergence of opinion that
has taken place concerning the graviton propagator on de Sitter background. We
here discuss the few points which remain under dispute. First, the inevitable
decay of tachyonic scalars really does result in their 2-point functions
breaking de Sitter invariance. This is obscured by analytic continuation
techniques which produce formal solutions to the propagator equation that are
not propagators. Second, Morrison's de Sitter invariant solution for the spin
two sector of the graviton propagator involves derivatives of the scalar
propagator at $M^2 = 0$, where it is not meromorphic unless de Sitter breaking
is permitted. Third, de Sitter breaking does not require zero modes. Fourth,
the ambiguity Morrison claims in the equation for the spin two structure
function is fixed by requiring it to derive from a mode sum. Fifth, Morrison's
spin two sector is not "physically equivalent" to ours because their
coincidence limits differ. Finally, it is only the noninvariant propagator that
gets the time independence and scale invariance of the tensor power spectrum
correctly.
| [
{
"created": "Sun, 23 Jun 2013 14:03:50 GMT",
"version": "v1"
},
{
"created": "Thu, 8 May 2014 07:43:46 GMT",
"version": "v2"
}
] | 2014-05-09 | [
[
"Miao",
"S. P.",
"",
"National Cheng Kung U."
],
[
"Mora",
"P. J.",
"",
"U. Florida"
],
[
"Tsamis",
"N. C.",
"",
"U. Crete"
],
[
"Woodard",
"R. P.",
"",
"U. Florida"
]
] | A nice paper by Morrison demonstrates the recent convergence of opinion that has taken place concerning the graviton propagator on de Sitter background. We here discuss the few points which remain under dispute. First, the inevitable decay of tachyonic scalars really does result in their 2-point functions breaking de Sitter invariance. This is obscured by analytic continuation techniques which produce formal solutions to the propagator equation that are not propagators. Second, Morrison's de Sitter invariant solution for the spin two sector of the graviton propagator involves derivatives of the scalar propagator at $M^2 = 0$, where it is not meromorphic unless de Sitter breaking is permitted. Third, de Sitter breaking does not require zero modes. Fourth, the ambiguity Morrison claims in the equation for the spin two structure function is fixed by requiring it to derive from a mode sum. Fifth, Morrison's spin two sector is not "physically equivalent" to ours because their coincidence limits differ. Finally, it is only the noninvariant propagator that gets the time independence and scale invariance of the tensor power spectrum correctly. |
gr-qc/0107014 | Martin Tajmar | C.J. de Matos, M. Tajmar | Gravitational Poynting Vector and Gravitational Larmor Theorem in
Rotating Bodies with Angular Acceleration | null | null | null | null | gr-qc | null | The gravitational Poynting vector provides a mechanism for the transfer of
gravitational energy to a system of falling objects. In the following we will
show that the gravitational poynting vector together with the gravitational
Larmor theorem also provides a mechanism to explain how massive bodies acquire
rotational kinetic energy when external mechanical forces are applied on them.
| [
{
"created": "Wed, 4 Jul 2001 07:33:08 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Matos",
"C. J.",
""
],
[
"Tajmar",
"M.",
""
]
] | The gravitational Poynting vector provides a mechanism for the transfer of gravitational energy to a system of falling objects. In the following we will show that the gravitational poynting vector together with the gravitational Larmor theorem also provides a mechanism to explain how massive bodies acquire rotational kinetic energy when external mechanical forces are applied on them. |
1901.08499 | Rudolf Baier | Rudolf Baier | On gravitational spherical collapse without spacetime singularity | 13 pages, 5 figures | null | null | BI-TP 2019/02 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This note discusses possible quantum effects in the context of homogeneous
flat FLRW and inhomogeneous LTB gravitational spherical collapse, which lead to
bounce solutions.
| [
{
"created": "Tue, 22 Jan 2019 14:21:45 GMT",
"version": "v1"
}
] | 2019-01-25 | [
[
"Baier",
"Rudolf",
""
]
] | This note discusses possible quantum effects in the context of homogeneous flat FLRW and inhomogeneous LTB gravitational spherical collapse, which lead to bounce solutions. |
1808.07987 | Sebastian Schuster | Sebastian Schuster (Victoria University of Wellington) and Matt Visser
(Victoria University of Wellington) | Electromagnetic analogue space-times, analytically and algebraically | 27 pages, 11 figures, 1 table; v2: Now 35 pages, improved discussion,
minor corrections, no physics changes, matched to published version | Classical and Quantum Gravity 36, 134004 (2019) | 10.1088/1361-6382/ab2159 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | While quantum field theory could more aptly be called the "quantum field
framework" $-$ as it encompasses a vast variety of varying concepts and
theories $-$ in comparison, relativity, both special and general, is more
commonly portrayed as less of a "general framework". Viewed from this
perspective, the paradigm of "analogue space-times" is to promote the specific
theory of general relativity (Einstein gravity) to a framework which covers
relativistic phenomena at large. Ultimately, this then also gives rise to new
proposals for experiments in the laboratory, as it allows one to move general
features of the "relativistic framework" from general relativity to entirely
new fields. This allows experiments looking into analogies of currently
unobservable phenomena of general relativity proper. The only requirement for
this to work is the presence of a notion of an upper limit for propagation
speeds in this new field. Systems of such a kind abound in physics, as all
hyperbolic wave equations fulfil this requirement.
Consequently, models for analogue space-times can be found aplenty. We shall
demonstrate this here in two separate analogue space-time models, both taken
from electrodynamics in continuous media. First of all, one can distinguish
between analytic analogue models (where the analogy is based on some specific
hyperbolic differential equation), on the one hand, and algebraic models (where
the analogy is fashioned from the more or less explicit appearance of a metric
tensor), on the other hand. Yet this distinction is more than just a matter of
taste: The analogue space-time model's nature will also determine which
physical concepts from general relativity can be taken easily into an
experimental context. Examples of this will the main aim of this paper, and the
Hawking effect in one of the two models considered the example of most
immediate experimental interest.
| [
{
"created": "Fri, 24 Aug 2018 02:56:57 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Jun 2019 15:36:12 GMT",
"version": "v2"
}
] | 2019-06-27 | [
[
"Schuster",
"Sebastian",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | While quantum field theory could more aptly be called the "quantum field framework" $-$ as it encompasses a vast variety of varying concepts and theories $-$ in comparison, relativity, both special and general, is more commonly portrayed as less of a "general framework". Viewed from this perspective, the paradigm of "analogue space-times" is to promote the specific theory of general relativity (Einstein gravity) to a framework which covers relativistic phenomena at large. Ultimately, this then also gives rise to new proposals for experiments in the laboratory, as it allows one to move general features of the "relativistic framework" from general relativity to entirely new fields. This allows experiments looking into analogies of currently unobservable phenomena of general relativity proper. The only requirement for this to work is the presence of a notion of an upper limit for propagation speeds in this new field. Systems of such a kind abound in physics, as all hyperbolic wave equations fulfil this requirement. Consequently, models for analogue space-times can be found aplenty. We shall demonstrate this here in two separate analogue space-time models, both taken from electrodynamics in continuous media. First of all, one can distinguish between analytic analogue models (where the analogy is based on some specific hyperbolic differential equation), on the one hand, and algebraic models (where the analogy is fashioned from the more or less explicit appearance of a metric tensor), on the other hand. Yet this distinction is more than just a matter of taste: The analogue space-time model's nature will also determine which physical concepts from general relativity can be taken easily into an experimental context. Examples of this will the main aim of this paper, and the Hawking effect in one of the two models considered the example of most immediate experimental interest. |
1709.09193 | Swagat Saurav Mishra | Satadru Bag, Swagat S. Mishra and Varun Sahni | New tracker models of dark energy | 24 pages, 16 figures, matches published version in JCAP | JCAP 08 (2018) 009 | 10.1088/1475-7516/2018/08/009 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a new class of dark energy (DE) models which behave like
cosmological trackers at early times. These models are based on the
$\alpha$-attractor set of potentials, originally discussed in the context of
inflation. The new models allow the current acceleration of the universe to be
reached from a wide class of initial conditions. Prominent examples of this
class of models are the potentials $\coth\varphi$ and $\cosh\varphi$. A
remarkable feature of this new class of models is that they lead to large
enough negative values of the equation of state at the present epoch,
consistent with the observations of accelerated expansion of the universe, from
a very large initial basin of attraction. They therefore avoid the fine tuning
problem which afflicts many models of DE.
| [
{
"created": "Tue, 26 Sep 2017 18:01:44 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Sep 2017 15:33:24 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Jun 2018 11:31:36 GMT",
"version": "v3"
},
{
"created": "Wed, 15 Aug 2018 05:57:22 GMT",
"version": "v4"
}
] | 2018-08-16 | [
[
"Bag",
"Satadru",
""
],
[
"Mishra",
"Swagat S.",
""
],
[
"Sahni",
"Varun",
""
]
] | We describe a new class of dark energy (DE) models which behave like cosmological trackers at early times. These models are based on the $\alpha$-attractor set of potentials, originally discussed in the context of inflation. The new models allow the current acceleration of the universe to be reached from a wide class of initial conditions. Prominent examples of this class of models are the potentials $\coth\varphi$ and $\cosh\varphi$. A remarkable feature of this new class of models is that they lead to large enough negative values of the equation of state at the present epoch, consistent with the observations of accelerated expansion of the universe, from a very large initial basin of attraction. They therefore avoid the fine tuning problem which afflicts many models of DE. |
2304.09482 | Olivier Minazzoli | Olivier Minazzoli | Standard quantum field theory from entangled relativity | Contribution to the 2023 Gravitation session of the 57th Rencontres
de Moriond
(https://moriond.in2p3.fr/2023/Gravitation/gravitation-agenda.html) | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Despite its non-linear form, entangled relativity possesses both general
relativity and standard quantum field theory in a specific (but generic) limit.
On one side it means that the theory is consistent with our current
understanding of elementary physics. But on the other side it means that our
current understanding might actually just be approximately valid: and this,
surprisingly, goes for both \textit{general relativity} and standard quantum
field theory together.
| [
{
"created": "Wed, 19 Apr 2023 08:07:04 GMT",
"version": "v1"
}
] | 2023-04-20 | [
[
"Minazzoli",
"Olivier",
""
]
] | Despite its non-linear form, entangled relativity possesses both general relativity and standard quantum field theory in a specific (but generic) limit. On one side it means that the theory is consistent with our current understanding of elementary physics. But on the other side it means that our current understanding might actually just be approximately valid: and this, surprisingly, goes for both \textit{general relativity} and standard quantum field theory together. |
2101.07638 | Tomi Koivisto | Tomi Koivisto, Luxi Zheng | Scale-invariant cosmology in de Sitter gauge theory | 9 pages, 0 figures | Phys. Rev. D 103, 124063 (2021) | 10.1103/PhysRevD.103.124063 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | The Planck mass and the cosmological constant determine the minimum and the
maximum distances in the physical universe. A relativistic theory that takes
into account a fundamental distance limit $\ell$ on par with the fundamental
speed limit $c$, is based on the de Sitter extension of the Lorentz symmetry.
This article proposes a new de Sitter gauge theory of gravity which allows the
consistent cosmological evolution of the $\ell$. The theory is locally
equivalent to Dirac's scale-invariant version of general relativity, and
suggests a novel non-singular extension of cosmology.
| [
{
"created": "Tue, 19 Jan 2021 14:28:21 GMT",
"version": "v1"
}
] | 2021-07-07 | [
[
"Koivisto",
"Tomi",
""
],
[
"Zheng",
"Luxi",
""
]
] | The Planck mass and the cosmological constant determine the minimum and the maximum distances in the physical universe. A relativistic theory that takes into account a fundamental distance limit $\ell$ on par with the fundamental speed limit $c$, is based on the de Sitter extension of the Lorentz symmetry. This article proposes a new de Sitter gauge theory of gravity which allows the consistent cosmological evolution of the $\ell$. The theory is locally equivalent to Dirac's scale-invariant version of general relativity, and suggests a novel non-singular extension of cosmology. |
gr-qc/9811067 | Eduardo Sergio Santini | N. Pinto-Neto and E. Sergio Santini | Must Quantum Spacetimes Be Euclidean? | 42 pages LaTeX, last version with minor corrections, being the most
importants on pages 0, 6, 11, 21, 23, and 30 . The new title does not change
our conclusions | Phys. Rev. D 59, 123517 (1999) | 10.1103/PhysRevD.59.123517 | null | gr-qc | null | The Bohm-de Broglie interpretation of quantum mechanics is applied to
canonical quantum cosmology. It is shown that, irrespective of any
regularization or choice of factor ordering of the Wheeler-DeWitt equation, the
unique relevant quantum effect which does not break spacetime is the change of
its signature from lorentzian to euclidean. The other quantum effects are
either trivial or break the four-geometry of spacetime. A Bohm-de Broglie
picture of a quantum geometrodynamics is constructed, which allows the
investigation of these latter structures. For instance, it is shown that any
real solution of the Wheeler-De Witt equation yields a generate four-geometry
compatible with the strong gravity limit of General Relativity and the Carroll
group. Due to the more detailed description of quantum geometrodynamics given
by the Bohm-de Broglie interpretation, some new boundary conditions on
solutions of the Wheeler-DeWitt equation must be imposed in order to preserve
consistency of this finer view.
| [
{
"created": "Thu, 19 Nov 1998 16:34:09 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Nov 1998 17:51:57 GMT",
"version": "v2"
}
] | 2016-08-25 | [
[
"Pinto-Neto",
"N.",
""
],
[
"Santini",
"E. Sergio",
""
]
] | The Bohm-de Broglie interpretation of quantum mechanics is applied to canonical quantum cosmology. It is shown that, irrespective of any regularization or choice of factor ordering of the Wheeler-DeWitt equation, the unique relevant quantum effect which does not break spacetime is the change of its signature from lorentzian to euclidean. The other quantum effects are either trivial or break the four-geometry of spacetime. A Bohm-de Broglie picture of a quantum geometrodynamics is constructed, which allows the investigation of these latter structures. For instance, it is shown that any real solution of the Wheeler-De Witt equation yields a generate four-geometry compatible with the strong gravity limit of General Relativity and the Carroll group. Due to the more detailed description of quantum geometrodynamics given by the Bohm-de Broglie interpretation, some new boundary conditions on solutions of the Wheeler-DeWitt equation must be imposed in order to preserve consistency of this finer view. |
2212.09499 | Zeeshan Gul | M. Sharif and M. Zeeshan Gul | Noether Symmetries and Some Exact Solutions in $f(R, T^{2})$ Theory | Accepted | null | 10.1134/S106377612303007X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main objective of this article is to examine some physically viable
solutions through the Noether symmetry technique in $f(R, T^{2})$ theory. For
this purpose, we assume a generalized anisotropic and homogenous spacetime that
yields distinct cosmic models. In order to investigate Noether equations,
symmetry generators and conserved quantities, we use a specific model of this
modified theory. We find exact solutions and examine the behavior of various
cosmological quantities. It is found the behavior these quantities is
consistent with current observations indicating that this theory describes the
cosmic accelerated expansion. We conclude that generators of Noether symmetry
and conserved quantities exist in this theory.
| [
{
"created": "Fri, 16 Dec 2022 03:23:45 GMT",
"version": "v1"
}
] | 2023-06-14 | [
[
"Sharif",
"M.",
""
],
[
"Gul",
"M. Zeeshan",
""
]
] | The main objective of this article is to examine some physically viable solutions through the Noether symmetry technique in $f(R, T^{2})$ theory. For this purpose, we assume a generalized anisotropic and homogenous spacetime that yields distinct cosmic models. In order to investigate Noether equations, symmetry generators and conserved quantities, we use a specific model of this modified theory. We find exact solutions and examine the behavior of various cosmological quantities. It is found the behavior these quantities is consistent with current observations indicating that this theory describes the cosmic accelerated expansion. We conclude that generators of Noether symmetry and conserved quantities exist in this theory. |
2003.11754 | Sanjay Siwach | Dharm Veer Singh and Sanjay Siwach | Thermodynamics and P-v criticality of Bardeen-AdS Black Hole in 4-D
Einstein-Gauss-Bonnet Gravity | 12 pages, 5 figures, minor changes, references added | null | 10.1016/j.physletb.2020.135658 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the Gauss-Bonnet corrected Bardeen black hole solution in 4-D AdS
space-time. The solution is obtained by the limiting procedure adopted by
Glavan and Lin in 4-D Einstein-Gauss-Bonnet gravity. The general form of first
law of black hole thermodynamics is utilized to calculate various
thermodynamics variables. The solution exhibit P-v criticality and belong to
the universality class of van-der Waals fluid. The effect of Gauss-Bonnet
coupling is investigated on critical parameters and inversion temperature.
| [
{
"created": "Thu, 26 Mar 2020 06:14:04 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Apr 2020 05:51:01 GMT",
"version": "v2"
}
] | 2020-08-05 | [
[
"Singh",
"Dharm Veer",
""
],
[
"Siwach",
"Sanjay",
""
]
] | We consider the Gauss-Bonnet corrected Bardeen black hole solution in 4-D AdS space-time. The solution is obtained by the limiting procedure adopted by Glavan and Lin in 4-D Einstein-Gauss-Bonnet gravity. The general form of first law of black hole thermodynamics is utilized to calculate various thermodynamics variables. The solution exhibit P-v criticality and belong to the universality class of van-der Waals fluid. The effect of Gauss-Bonnet coupling is investigated on critical parameters and inversion temperature. |
1908.06743 | Sarbari Guha Dr. | Sucheta Datta and Sarbari Guha | Propagation of Gravitational Waves in Anisotropic Universe | 14 pages, no figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have considered a toy model of an anisotropic universe and
studied the propagation of gravitational waves in such a universe. The
consideration of this toy model simplifies the analysis and helps us to
illustrate the effects of anisotropy. Incorporating linear perturbations on
this anisotropic background, we have considered the synchronous, transverse,
traceless gauge conditions and evaluated the perturbations of the Ricci tensor.
The energy-momentum tensor is that of a perfect fluid, for which the Einstein's
field equations are determined in presence of perturbations. We arrive at the
set of linearised Einstein's equations explicitly and find solutions for
gravitational waves propagating along the direction of anisotropy. We also
study the propagation along a direction perpendicular to the direction of
anisotropy. Subsequently we have validated the assumption of the tracelessness
of the linear perturbations. Finally we determine the amount of tidal
acceleration caused by the propagation of gravitational waves in this
background spacetime.
| [
{
"created": "Wed, 14 Aug 2019 16:02:24 GMT",
"version": "v1"
}
] | 2019-08-20 | [
[
"Datta",
"Sucheta",
""
],
[
"Guha",
"Sarbari",
""
]
] | In this paper, we have considered a toy model of an anisotropic universe and studied the propagation of gravitational waves in such a universe. The consideration of this toy model simplifies the analysis and helps us to illustrate the effects of anisotropy. Incorporating linear perturbations on this anisotropic background, we have considered the synchronous, transverse, traceless gauge conditions and evaluated the perturbations of the Ricci tensor. The energy-momentum tensor is that of a perfect fluid, for which the Einstein's field equations are determined in presence of perturbations. We arrive at the set of linearised Einstein's equations explicitly and find solutions for gravitational waves propagating along the direction of anisotropy. We also study the propagation along a direction perpendicular to the direction of anisotropy. Subsequently we have validated the assumption of the tracelessness of the linear perturbations. Finally we determine the amount of tidal acceleration caused by the propagation of gravitational waves in this background spacetime. |
1709.10341 | Sergey Mirzoyan | V. G. Gurzadyan, I. Ciufolini, A.Paolozzi, A.L. Kashin, H.G.
Khachatryan, S. Mirzoyan and G. Sindoni | Satellites testing general relativity: residuals versus perturbations | 7 pages 3 figures | IJMPD, 26 (2017) 1741020 | 10.1142/S0218271817410206 | null | gr-qc astro-ph.EP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Laser ranging satellites have proved their efficiency for high precision
testing of the effect of frame-dragging, one of remarkable predictions of the
General Relativity. The analysis of the randomness properties of the residuals
of LAGEOS and LAGEOS 2 satellites reveals the role of the thermal thrust --
Yarkovsky effect -- on the satellite which was in the orbit for longer period
(LAGEOS). We also compute Earth's tidal modes affecting the satellite LARES.
The recently obtained 5\% accuracy limit reached for the frame dragging effect
based on the 3.5 year data of LARES analysed together with those of LAGEOS
satellites and using the Earth gravity model of GRACE satellite, is also
represented.
| [
{
"created": "Thu, 28 Sep 2017 05:35:09 GMT",
"version": "v1"
}
] | 2017-10-04 | [
[
"Gurzadyan",
"V. G.",
""
],
[
"Ciufolini",
"I.",
""
],
[
"Paolozzi",
"A.",
""
],
[
"Kashin",
"A. L.",
""
],
[
"Khachatryan",
"H. G.",
""
],
[
"Mirzoyan",
"S.",
""
],
[
"Sindoni",
"G.",
""
]
] | Laser ranging satellites have proved their efficiency for high precision testing of the effect of frame-dragging, one of remarkable predictions of the General Relativity. The analysis of the randomness properties of the residuals of LAGEOS and LAGEOS 2 satellites reveals the role of the thermal thrust -- Yarkovsky effect -- on the satellite which was in the orbit for longer period (LAGEOS). We also compute Earth's tidal modes affecting the satellite LARES. The recently obtained 5\% accuracy limit reached for the frame dragging effect based on the 3.5 year data of LARES analysed together with those of LAGEOS satellites and using the Earth gravity model of GRACE satellite, is also represented. |
gr-qc/0703124 | Bijan Saha | Bijan Saha | Interacting spinor and scalar fields in Bianchi type-I Universe filled
with viscous fluid: exact and numerical solutions | 18 pages, 6 figures | Gravitation & Cosmology, 15(4), (2009) 353 - 361 | 10.1134/S0202289309040112 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a self-consistent system of spinor and scalar fields within the
framework of a Bianchi type I gravitational field filled with viscous fluid in
presence of a $\Lambda$ term. Exact self-consistent solutions to the
corresponding spinor, scalar and BI gravitational field equations are obtained
in terms of $\tau$, where $\tau$ is the volume scale of BI universe. System of
equations for $\tau$ and $\ve$, where $\ve$ is the energy of the viscous fluid,
is deduced. Some special cases allowing exact solutions are thoroughly studied.
| [
{
"created": "Mon, 26 Mar 2007 12:12:24 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Jun 2008 10:58:24 GMT",
"version": "v2"
}
] | 2019-04-22 | [
[
"Saha",
"Bijan",
""
]
] | We consider a self-consistent system of spinor and scalar fields within the framework of a Bianchi type I gravitational field filled with viscous fluid in presence of a $\Lambda$ term. Exact self-consistent solutions to the corresponding spinor, scalar and BI gravitational field equations are obtained in terms of $\tau$, where $\tau$ is the volume scale of BI universe. System of equations for $\tau$ and $\ve$, where $\ve$ is the energy of the viscous fluid, is deduced. Some special cases allowing exact solutions are thoroughly studied. |
1704.07366 | Sumanta Chakraborty | Sumanta Chakraborty | Field equations for Lovelock gravity: An alternative route | Invited Article; 11 pages, no figures | Adv. High Energy Phys. 6509045 (2018) | 10.1155/2018/6509045 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an alternative derivation of the gravitational field equations for
Lovelock gravity starting from the Newton's law, which is closer in spirit to
the thermodynamic description of gravity. As a warm up exercise, we have
explicitly demonstrated that projecting the Riemann curvature tensor
appropriately and taking a cue from Poisson's equation, the Einstein's
equations immediately follow. The above derivation naturally generalizes to
Lovelock gravity theories where an appropriate curvature tensor satisfying the
symmetries as well as the Bianchi derivative properties of the Riemann tensor
has to be used. Interestingly, in the above derivation, the thermodynamic route
to gravitational field equations, suited for null hypersurfaces, emerge quiet
naturally.
| [
{
"created": "Sat, 22 Apr 2017 05:34:15 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Apr 2018 00:37:23 GMT",
"version": "v2"
}
] | 2018-04-23 | [
[
"Chakraborty",
"Sumanta",
""
]
] | We present an alternative derivation of the gravitational field equations for Lovelock gravity starting from the Newton's law, which is closer in spirit to the thermodynamic description of gravity. As a warm up exercise, we have explicitly demonstrated that projecting the Riemann curvature tensor appropriately and taking a cue from Poisson's equation, the Einstein's equations immediately follow. The above derivation naturally generalizes to Lovelock gravity theories where an appropriate curvature tensor satisfying the symmetries as well as the Bianchi derivative properties of the Riemann tensor has to be used. Interestingly, in the above derivation, the thermodynamic route to gravitational field equations, suited for null hypersurfaces, emerge quiet naturally. |
2301.02216 | Riasat Ali | Riasat Ali, Zunaira Akhtar, Rimsha Babar, G. Mustafa and Xia Tiecheng | Logarithm Corrections and Thermodynamics for Horndeski gravity like
Black Holes | 14 Pages, 9 figures, Published in New Astronomy | New Astronomy Vol. 100, May 2023, 101976 | 10.1016/j.newast.2022.101976 | null | gr-qc math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | In this paper, we compute the Hawking temperature by applying quantum
tunneling approach for the Horndeski like black holes. We utilize the
semi-classical phenomenon and WKB approximation to the Lagrangian field
equation involving generalized uncertainty principle (GUP) and compute the
tunneling rate as well as Hawking temperature. For the zero gravity parameter,
we obtain results consistent without correction parameter or original
tunneling. Moreover, we study the thermal fluctuations of the considered
geometry and examine the stable state of the system by heat capacity technique.
We also investigate the behaviour of thermodynamic quantities under the
influence of thermal fluctuations. We observe from the graphical analysis, the
corresponding system is thermodynamically stable with these correction terms.
| [
{
"created": "Thu, 5 Jan 2023 18:38:06 GMT",
"version": "v1"
}
] | 2023-01-06 | [
[
"Ali",
"Riasat",
""
],
[
"Akhtar",
"Zunaira",
""
],
[
"Babar",
"Rimsha",
""
],
[
"Mustafa",
"G.",
""
],
[
"Tiecheng",
"Xia",
""
]
] | In this paper, we compute the Hawking temperature by applying quantum tunneling approach for the Horndeski like black holes. We utilize the semi-classical phenomenon and WKB approximation to the Lagrangian field equation involving generalized uncertainty principle (GUP) and compute the tunneling rate as well as Hawking temperature. For the zero gravity parameter, we obtain results consistent without correction parameter or original tunneling. Moreover, we study the thermal fluctuations of the considered geometry and examine the stable state of the system by heat capacity technique. We also investigate the behaviour of thermodynamic quantities under the influence of thermal fluctuations. We observe from the graphical analysis, the corresponding system is thermodynamically stable with these correction terms. |
gr-qc/0408044 | Edward Malec | Edward Malec and Niall \'O Murchadha | The Jang equation, apparent horizons, and the Penrose inequality | minor misprints corrected | Class.Quant.Grav. 21 (2004) 5777-5788 | 10.1088/0264-9381/21/24/007 | null | gr-qc | null | The Jang equation in the spherically symmetric case reduces to a first order
equation. This permits an easy analysis of the role apparent horizons play in
the (non)existence of solutions. We demonstrate that the proposed derivation of
the Penrose inequality based on the Jang equation cannot work in the
spherically symmetric case. Thus it is fruitless to apply this method, as it
stands, to the general case. We show also that those analytic criteria for the
formation of horizons that are based on the use of the Jang equation are of
limited validity for the proof of the trapped surface conjecture.
| [
{
"created": "Mon, 16 Aug 2004 06:49:49 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Dec 2004 11:44:14 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Malec",
"Edward",
""
],
[
"Murchadha",
"Niall Ó",
""
]
] | The Jang equation in the spherically symmetric case reduces to a first order equation. This permits an easy analysis of the role apparent horizons play in the (non)existence of solutions. We demonstrate that the proposed derivation of the Penrose inequality based on the Jang equation cannot work in the spherically symmetric case. Thus it is fruitless to apply this method, as it stands, to the general case. We show also that those analytic criteria for the formation of horizons that are based on the use of the Jang equation are of limited validity for the proof of the trapped surface conjecture. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.