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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1806.04123 | Pedro Moraes | P.H.R.S. Moraes, J.D.V. Arba\~nil, G.A. Carvalho, R.V. Lobato, E.
Otoniel, R.M. Marinho Jr., M. Malheiro | Compact Astrophysical Objects in $f(R,T)$ gravity | Invited talk presented at the XIV International Workshop on Hadron
Physics, Florian\'opolis, Brazil, March 2018 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we study the hydrostatic equilibrium configuration of neutron
stars (NSs) and strange stars (SSs), whose fluid pressure is computed from the
equations of state $p=\omega\rho^{5/3}$ and $p=0.28(\rho-4{\cal B})$,
respectively, with $\omega$ and ${\cal B}$ being constants and $\rho$ the
energy density of the fluid. We also study white dwarfs (WDs) equilibrium
configurations. We start by deriving the hydrostatic equilibrium equation for
the $f(R,T)$ theory of gravity, with $R$ and $T$ standing for the Ricci scalar
and trace of the energy-momentum tensor, respectively. Such an equation is a
generalization of the one obtained from general relativity, and the latter can
be retrieved for a certain limit of the theory. For the $f(R,T)=R+2\lambda T$
functional form, with $\lambda$ being a constant, we find that some physical
properties of the stars, such as pressure, energy density, mass and radius, are
affected when $\lambda$ is changed. We show that for some particular values of
the constant $\lambda$, some observed objects that are not predicted by General
Relativity theory of gravity can be attained. Moreover, since gravitational
fields are smaller for WDs than for NSs or SSs, the scale parameter $\lambda$
used for WDs is small when compared to the values used for NSs and SSs.
| [
{
"created": "Mon, 11 Jun 2018 17:44:23 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jun 2018 10:59:21 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Jun 2018 14:45:57 GMT",
"version": "v3"
},
{
"created": "Thu, 16 Aug 2018 12:24:54 GMT",
"version": "v4"
}
] | 2018-08-17 | [
[
"Moraes",
"P. H. R. S.",
""
],
[
"Arbañil",
"J. D. V.",
""
],
[
"Carvalho",
"G. A.",
""
],
[
"Lobato",
"R. V.",
""
],
[
"Otoniel",
"E.",
""
],
[
"Marinho",
"R. M.",
"Jr."
],
[
"Malheiro",
"M.",
""
]
] | In this article we study the hydrostatic equilibrium configuration of neutron stars (NSs) and strange stars (SSs), whose fluid pressure is computed from the equations of state $p=\omega\rho^{5/3}$ and $p=0.28(\rho-4{\cal B})$, respectively, with $\omega$ and ${\cal B}$ being constants and $\rho$ the energy density of the fluid. We also study white dwarfs (WDs) equilibrium configurations. We start by deriving the hydrostatic equilibrium equation for the $f(R,T)$ theory of gravity, with $R$ and $T$ standing for the Ricci scalar and trace of the energy-momentum tensor, respectively. Such an equation is a generalization of the one obtained from general relativity, and the latter can be retrieved for a certain limit of the theory. For the $f(R,T)=R+2\lambda T$ functional form, with $\lambda$ being a constant, we find that some physical properties of the stars, such as pressure, energy density, mass and radius, are affected when $\lambda$ is changed. We show that for some particular values of the constant $\lambda$, some observed objects that are not predicted by General Relativity theory of gravity can be attained. Moreover, since gravitational fields are smaller for WDs than for NSs or SSs, the scale parameter $\lambda$ used for WDs is small when compared to the values used for NSs and SSs. |
2006.13047 | Ali \"Ovg\"un Dr. | Zonghai Li, Guodong Zhang and Ali \"Ovg\"un | Circular orbit of a particle and weak gravitational lensing | Accepted for publication in Physical Review D
(https://journals.aps.org/prd/accepted/22076Q27Da314d28369686b12569e1772f8bcf8da) | Phys. Rev. D 101, 124058 (2020) | 10.1103/PhysRevD.101.124058 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The purpose of this paper is twofold. First, we introduce a geometric
approach to study the circular orbit of a particle in static and spherically
symmetric spacetime based on Jacobi metric. Second, we apply the circular orbit
to study the weak gravitational deflection of null and time-like particles
based on Gauss-Bonnet theorem. By this way, we obtain an expression of
deflection angle and extend the study of deflection angle to asymptotically
non-flat black hole spacetimes. Some black holes as lens are considered such as
a static and spherically symmetric black hole in the conformal Weyl gravity and
a Schwarzschild-like black hole in bumblebee gravity. Our results are
consistent with the previous literature. In particular, we find that the
connection between Gaussian curvature and the radius of a circular orbit
greatly simplifies the calculation.
| [
{
"created": "Sun, 21 Jun 2020 19:53:52 GMT",
"version": "v1"
}
] | 2020-06-29 | [
[
"Li",
"Zonghai",
""
],
[
"Zhang",
"Guodong",
""
],
[
"Övgün",
"Ali",
""
]
] | The purpose of this paper is twofold. First, we introduce a geometric approach to study the circular orbit of a particle in static and spherically symmetric spacetime based on Jacobi metric. Second, we apply the circular orbit to study the weak gravitational deflection of null and time-like particles based on Gauss-Bonnet theorem. By this way, we obtain an expression of deflection angle and extend the study of deflection angle to asymptotically non-flat black hole spacetimes. Some black holes as lens are considered such as a static and spherically symmetric black hole in the conformal Weyl gravity and a Schwarzschild-like black hole in bumblebee gravity. Our results are consistent with the previous literature. In particular, we find that the connection between Gaussian curvature and the radius of a circular orbit greatly simplifies the calculation. |
2011.05697 | Katarina Martinovic | Katarina Martinovic, Patrick M. Meyers, Mairi Sakellariadou, Nelson
Christensen | Simultaneous estimation of astrophysical and cosmological stochastic
gravitational-wave backgrounds with terrestrial detectors | null | Phys. Rev. D 103, 043023 (2021) | 10.1103/PhysRevD.103.043023 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The recent Advanced LIGO and Advanced Virgo joint observing runs have not
claimed a stochastic gravitational-wave background detection, but one expects
this to change as the sensitivity of the detectors improves. The challenge of
claiming a true detection will be immediately succeeded by the difficulty of
relating the signal to the sources that contribute to it. In this paper, we
consider backgrounds that comprise compact binary coalescences and additional
cosmological sources, and we set simultaneous upper limits on these
backgrounds. We find that the Advanced LIGO, Advanced Virgo network, operating
at design sensitivity, will not allow for separation of the sources we
consider. Third generation detectors, sensitive to most individual compact
binary mergers, can reduce the astrophysical signal via subtraction of
individual sources, and potentially reveal a cosmological background. Our
Bayesian analysis shows that, assuming a detector network containing Cosmic
Explorer and Einstein Telescope and reasonable levels of individual source
subtraction, we can detect cosmological signals $\Omega_{\rm{CS}}
(25\,\rm{Hz})=4.5 \times 10^{-13}$ for cosmic strings, and $\Omega_{\rm
BPL}(25\,\rm{Hz})= 2.2 \times 10^{-13}$ for a broken power law model of an
early universe phase transition.
| [
{
"created": "Wed, 11 Nov 2020 11:06:24 GMT",
"version": "v1"
}
] | 2021-03-03 | [
[
"Martinovic",
"Katarina",
""
],
[
"Meyers",
"Patrick M.",
""
],
[
"Sakellariadou",
"Mairi",
""
],
[
"Christensen",
"Nelson",
""
]
] | The recent Advanced LIGO and Advanced Virgo joint observing runs have not claimed a stochastic gravitational-wave background detection, but one expects this to change as the sensitivity of the detectors improves. The challenge of claiming a true detection will be immediately succeeded by the difficulty of relating the signal to the sources that contribute to it. In this paper, we consider backgrounds that comprise compact binary coalescences and additional cosmological sources, and we set simultaneous upper limits on these backgrounds. We find that the Advanced LIGO, Advanced Virgo network, operating at design sensitivity, will not allow for separation of the sources we consider. Third generation detectors, sensitive to most individual compact binary mergers, can reduce the astrophysical signal via subtraction of individual sources, and potentially reveal a cosmological background. Our Bayesian analysis shows that, assuming a detector network containing Cosmic Explorer and Einstein Telescope and reasonable levels of individual source subtraction, we can detect cosmological signals $\Omega_{\rm{CS}} (25\,\rm{Hz})=4.5 \times 10^{-13}$ for cosmic strings, and $\Omega_{\rm BPL}(25\,\rm{Hz})= 2.2 \times 10^{-13}$ for a broken power law model of an early universe phase transition. |
gr-qc/0305032 | Abdelmajid EL | H. Boutaleb-Joutei (Mohamed V Universite) and A. M. Elgasmi (Hassan II
Mohammedia universite) | Four Dimensional Spherical Space-Times and String Theory | 14 pages | null | null | null | gr-qc | null | Some shortcomings in regard to our lack of conceptual understanding of string
theory are displayed and prescription to untangle them is proposed. String
theory should be a fundamental dynamics of four dimensional symmetric
space-times. Properties of the two dimensional equivalent action are studied,
in the hydrodynamic approximation. In the pressureless regime it is conformal
invariant. Correlation of our proposal to 't Hooft work on quantization of
black holes[7] and work on 2D black hole solutions established by Witten [14]
are pointed out as perspectives of the present work.
| [
{
"created": "Thu, 8 May 2003 15:17:29 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Boutaleb-Joutei",
"H.",
"",
"Mohamed V Universite"
],
[
"Elgasmi",
"A. M.",
"",
"Hassan II\n Mohammedia universite"
]
] | Some shortcomings in regard to our lack of conceptual understanding of string theory are displayed and prescription to untangle them is proposed. String theory should be a fundamental dynamics of four dimensional symmetric space-times. Properties of the two dimensional equivalent action are studied, in the hydrodynamic approximation. In the pressureless regime it is conformal invariant. Correlation of our proposal to 't Hooft work on quantization of black holes[7] and work on 2D black hole solutions established by Witten [14] are pointed out as perspectives of the present work. |
1506.03173 | Parthapratim Pradhan | Parthapratim Pradhan | Thermodynamic Product Formula for Ho\v{r}ava Lifshitz Black Hole | 7 pages Physics Letters B, 30 July 2015 | null | 10.1016/j.physletb.2015.05.054 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the thermodynamic properties of inner and outer horizons in the
background of Ho\v{r}ava Lifshitz black hole. We compute the \emph{horizon
radii product, the surface area product, the entropy product, the surface
temperature product, the Komar energy product and the specific heat product}
for both the horizons of said black hole. We show that surface area product,
entropy product and irreducible mass product are \emph{universal} quantities,
whereas the surface temperature product, Komar energy product and specific heat
product are \emph{not universal} quantities because they all are depends on
mass parameter. We also observe that the \emph{First law} of black hole
thermodynamics and \emph {Smarr-Gibbs-Duhem } relations do not hold for this
black hole. The underlying reason behind this failure due to the scale
invariance of the coupling constant. We further derive the \emph{Smarr mass
formula} and \emph{Christodolou-Ruffini mass formula} for such black hole
spacetime. Moreover we study the stability of such black hole by computing the
specific heat for both the horizons. It has been observed that under certain
condition the black hole possesses second order phase transition.
| [
{
"created": "Wed, 10 Jun 2015 05:42:51 GMT",
"version": "v1"
}
] | 2015-06-11 | [
[
"Pradhan",
"Parthapratim",
""
]
] | We examine the thermodynamic properties of inner and outer horizons in the background of Ho\v{r}ava Lifshitz black hole. We compute the \emph{horizon radii product, the surface area product, the entropy product, the surface temperature product, the Komar energy product and the specific heat product} for both the horizons of said black hole. We show that surface area product, entropy product and irreducible mass product are \emph{universal} quantities, whereas the surface temperature product, Komar energy product and specific heat product are \emph{not universal} quantities because they all are depends on mass parameter. We also observe that the \emph{First law} of black hole thermodynamics and \emph {Smarr-Gibbs-Duhem } relations do not hold for this black hole. The underlying reason behind this failure due to the scale invariance of the coupling constant. We further derive the \emph{Smarr mass formula} and \emph{Christodolou-Ruffini mass formula} for such black hole spacetime. Moreover we study the stability of such black hole by computing the specific heat for both the horizons. It has been observed that under certain condition the black hole possesses second order phase transition. |
1407.7796 | Ivan Arraut | Ivan Arraut | The Black Hole Radiation in Massive Gravity | Title changed in order to match the published version. Version
focused on the particle creation process of black-hole in massive gravity | Universe 2018, 4(2), 27 | 10.3390/universe4020027 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the Bogoliubov transformations in order to connect two different
vacuums, one~located at past infinity and another located at future infinity
around a black hole inside the scenario of the nonlinear theory of massive
gravity. The presence of the extra degrees of freedom changes the behavior of
the logarithmic singularity and, as a consequence, the relation between the two
Bogoliubov coefficients. This has an effect on the number of particles, or
equivalently, on the black hole temperature perceived by observers defining the
time arbitrarily.
| [
{
"created": "Sun, 27 Jul 2014 10:20:20 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Jul 2014 10:35:54 GMT",
"version": "v2"
},
{
"created": "Wed, 7 Feb 2018 12:19:17 GMT",
"version": "v3"
}
] | 2018-02-08 | [
[
"Arraut",
"Ivan",
""
]
] | We apply the Bogoliubov transformations in order to connect two different vacuums, one~located at past infinity and another located at future infinity around a black hole inside the scenario of the nonlinear theory of massive gravity. The presence of the extra degrees of freedom changes the behavior of the logarithmic singularity and, as a consequence, the relation between the two Bogoliubov coefficients. This has an effect on the number of particles, or equivalently, on the black hole temperature perceived by observers defining the time arbitrarily. |
1005.2319 | Adam D. Helfer | Adam D. Helfer | Comment on "Insensitivity of Hawking Radiation to an invariant
Planck-scale cutoff" | 4 pages, to appear in Phys. Rev. D., see also the reply by Agullo et
al. | Phys.Rev.D81:108501,2010 | 10.1103/PhysRevD.81.108501 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I point out that the cutoff introduced by Agullo et al.
[Phys.Rev.D80:047503,2009 arXiv:0906.5315] has little impact on the
trans-Planckian problem as it is usually understood; it excludes only a small
fraction of the problematic modes.
| [
{
"created": "Thu, 13 May 2010 13:33:05 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Helfer",
"Adam D.",
""
]
] | I point out that the cutoff introduced by Agullo et al. [Phys.Rev.D80:047503,2009 arXiv:0906.5315] has little impact on the trans-Planckian problem as it is usually understood; it excludes only a small fraction of the problematic modes. |
2210.05201 | Puxun Wu | Li-Yang Chen, Hongwei Yu and Puxun Wu | Primordial non-Guassianity in inflation with gravitationally enhanced
friction | 19 pages, 2 figures, three references added | Physical Review D 106, 063537 (2022) | 10.1103/PhysRevD.106.063537 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The gravitationally enhanced friction can reduce the speed of the inflaton to
realize an ultra-slow-roll inflation, which will amplify the curvature
perturbations. The amplified perturbations can generate a sizable amount of
primordial black holes (PBHs) and induce simultaneously a significant
background gravitational waves (SIGWs). In this paper, we investigate the
primordial non-Gaussianity of the curvature perturbations in the inflation with
gravitationally enhanced friction. We find that when the gravitationally
enhanced friction plays a role in the inflationary dynamics, the
non-Gaussianity is noticeably larger than that from the standard slow-roll
inflation. During the regime in which the power spectrum of the curvature
perturbations is around its peak, the non-Gaussianity parameter changes from
negative to positive. When the power spectrum is at its maximum, the
non-Gaussianity parameter is near zero ($\sim \mathcal{O}(0.01)$). Furthermore,
the primordial non-Gaussianity promotes the formation of PBHs, while its effect
on SIGWs is negligible.
| [
{
"created": "Tue, 11 Oct 2022 07:14:25 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Oct 2022 00:57:14 GMT",
"version": "v2"
}
] | 2022-10-27 | [
[
"Chen",
"Li-Yang",
""
],
[
"Yu",
"Hongwei",
""
],
[
"Wu",
"Puxun",
""
]
] | The gravitationally enhanced friction can reduce the speed of the inflaton to realize an ultra-slow-roll inflation, which will amplify the curvature perturbations. The amplified perturbations can generate a sizable amount of primordial black holes (PBHs) and induce simultaneously a significant background gravitational waves (SIGWs). In this paper, we investigate the primordial non-Gaussianity of the curvature perturbations in the inflation with gravitationally enhanced friction. We find that when the gravitationally enhanced friction plays a role in the inflationary dynamics, the non-Gaussianity is noticeably larger than that from the standard slow-roll inflation. During the regime in which the power spectrum of the curvature perturbations is around its peak, the non-Gaussianity parameter changes from negative to positive. When the power spectrum is at its maximum, the non-Gaussianity parameter is near zero ($\sim \mathcal{O}(0.01)$). Furthermore, the primordial non-Gaussianity promotes the formation of PBHs, while its effect on SIGWs is negligible. |
gr-qc/9810017 | Ezra T. Newman | Simonetta Frittelli, Ezra T. Newman | An Exact Universal Gravitational Lensing Equation | 12 pages, submitted to Phys. Rev. D | Phys.Rev.D59:124001,1999 | 10.1103/PhysRevD.59.124001 | null | gr-qc | null | We first define what we mean by gravitational lensing equations in a general
space-time. A set of exact relations are then derived that can be used as the
gravitational lens equations in all physical situations. The caveat is that
into these equations there must be inserted a function, a two-parameter family
of solutions to the eikonal equation, not easily obtained, that codes all the
relevant (conformal) space-time information for this lens equation
construction. Knowledge of this two-parameter family of solutions replaces
knowledge of the solutions to the geodesic equations.
The formalism is then applied to the Schwarzschild lensing problem
| [
{
"created": "Mon, 5 Oct 1998 18:46:01 GMT",
"version": "v1"
}
] | 2008-12-18 | [
[
"Frittelli",
"Simonetta",
""
],
[
"Newman",
"Ezra T.",
""
]
] | We first define what we mean by gravitational lensing equations in a general space-time. A set of exact relations are then derived that can be used as the gravitational lens equations in all physical situations. The caveat is that into these equations there must be inserted a function, a two-parameter family of solutions to the eikonal equation, not easily obtained, that codes all the relevant (conformal) space-time information for this lens equation construction. Knowledge of this two-parameter family of solutions replaces knowledge of the solutions to the geodesic equations. The formalism is then applied to the Schwarzschild lensing problem |
gr-qc/0010035 | Yoshiaki Himemoto | Yoshiaki Himemoto and Misao Sasaki | Brane-world inflation without inflaton on the brane | 10 pages, 2 figures, final version, to be published in Phys. Rev. D | Phys.Rev.D63:044015,2001 | 10.1103/PhysRevD.63.044015 | OU-TAP-144 | gr-qc astro-ph hep-th | null | Inspired by the Randall-Sundrum brane-world scenario, we investigate the
possibility of brane-world inflation driven not by an inflaton field on the
brane, but by a bulk, dilaton-like gravitational field. As a toy model for the
dilaton-like gravitational field, we consider a minimally coupled massive
scalar field in the bulk 5-dimensional spacetime, and look for a perturbative
solution in the anti-de Sitter (AdS) background. For an adequate range of the
scalar field mass, we find a unique solution that has non-trivial dependence on
the 5th dimensional coordinate and that induces slow-roll inflation on the
brane.
| [
{
"created": "Tue, 10 Oct 2000 08:40:44 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Oct 2000 13:46:50 GMT",
"version": "v2"
},
{
"created": "Wed, 15 Nov 2000 06:17:20 GMT",
"version": "v3"
},
{
"created": "Fri, 26 Jan 2001 11:38:24 GMT",
"version": "v4"
}
] | 2009-10-09 | [
[
"Himemoto",
"Yoshiaki",
""
],
[
"Sasaki",
"Misao",
""
]
] | Inspired by the Randall-Sundrum brane-world scenario, we investigate the possibility of brane-world inflation driven not by an inflaton field on the brane, but by a bulk, dilaton-like gravitational field. As a toy model for the dilaton-like gravitational field, we consider a minimally coupled massive scalar field in the bulk 5-dimensional spacetime, and look for a perturbative solution in the anti-de Sitter (AdS) background. For an adequate range of the scalar field mass, we find a unique solution that has non-trivial dependence on the 5th dimensional coordinate and that induces slow-roll inflation on the brane. |
gr-qc/0410137 | Homer G. Ellis | Homer G. Ellis | An expanding universe of spinning spheres | 8 pages, AMSTeX, 5 Encapsulated PostScript figures | null | null | null | gr-qc | null | A novel but elementary geometric construction produces on the
seven-dimensional manifold of rotated spheres in Euclidean three-space a
finslerian geometry whose geodesics are interpreted as the paths of free,
spinning, spherical particles moving through de Sitter's expanding universe. A
particle of nonzero inertial rest mass typically follows a helical track and
exhibits behavior remindful of the phenomenon of ``Zitterbewegung'' of spinning
electrons first deduced by Schroedinger from Dirac's relativistic wave
equation. Its velocity vector and its spin vector precess about the axial
direction of the helix, with their projections onto that direction at all times
parallel or at all times antiparallel. Particles of zero rest mass follow
straight tracks at the speed of light with their spin vectors parallel or
antiparallel to their velocity vectors, thereby replicating behavior of
spinning photons predicted by the quantum theory of light.
| [
{
"created": "Thu, 28 Oct 2004 06:51:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ellis",
"Homer G.",
""
]
] | A novel but elementary geometric construction produces on the seven-dimensional manifold of rotated spheres in Euclidean three-space a finslerian geometry whose geodesics are interpreted as the paths of free, spinning, spherical particles moving through de Sitter's expanding universe. A particle of nonzero inertial rest mass typically follows a helical track and exhibits behavior remindful of the phenomenon of ``Zitterbewegung'' of spinning electrons first deduced by Schroedinger from Dirac's relativistic wave equation. Its velocity vector and its spin vector precess about the axial direction of the helix, with their projections onto that direction at all times parallel or at all times antiparallel. Particles of zero rest mass follow straight tracks at the speed of light with their spin vectors parallel or antiparallel to their velocity vectors, thereby replicating behavior of spinning photons predicted by the quantum theory of light. |
1803.05301 | Emanuel Gallo | Emanuel Gallo and Osvaldo M. Moreschi | Constructing balanced equations of motion for particles in general
relativity: the null gauge case | 14 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a convenient null gauge for the construction of the balanced
equations of motion. This null gauge has the property that the asymptotic
structure is intimately related to the interior one; in particular there is a
strong connexion between the field equation and the balanced equations of
motion. We present the balanced equations of motion in second order of the
acceleration. We solve the required components of the field equation at their
respective required orders, $G^2$ and $G^3$. We indicate how this approach can
be extended to higher orders.
| [
{
"created": "Wed, 14 Mar 2018 14:22:43 GMT",
"version": "v1"
}
] | 2018-03-15 | [
[
"Gallo",
"Emanuel",
""
],
[
"Moreschi",
"Osvaldo M.",
""
]
] | We present a convenient null gauge for the construction of the balanced equations of motion. This null gauge has the property that the asymptotic structure is intimately related to the interior one; in particular there is a strong connexion between the field equation and the balanced equations of motion. We present the balanced equations of motion in second order of the acceleration. We solve the required components of the field equation at their respective required orders, $G^2$ and $G^3$. We indicate how this approach can be extended to higher orders. |
1309.0292 | Jorge P\'aramos | Orfeu Bertolami and Jorge P\'aramos | Minimal extension of General Relativity: alternative gravity model with
non-minimal coupling between matter and curvature | 24 pages, 4 figures; talk presented by one of us (O.B.) at the 9th
Winter School of Theoretical Physics - Cosmology and non-equilibrium
statistical mechanics, Ladek-Zdroj, Poland, February 10-16, 2013 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine an extension of General Relativity with an explicit non-minimal
coupling between matter and curvature. The purpose of this work is to present
an overview of the implications of the latter to various contexts, ranging from
astrophysical matter distributions to a cosmological setting. Various results
are discussed, including the impact of this non-minimal coupling on the choice
of Lagrangian density, on a mechanism to mimic galactic and cluster dark
matter, on the possibility of accounting for the accelerated expansion of the
Universe, energy density fluctuations and modifications to post-inflationary
reheating. The equivalence between a model exhibiting a non-minimal coupling
and multi-scalar-theories is also discussed.
| [
{
"created": "Mon, 2 Sep 2013 02:46:40 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Jan 2014 22:42:39 GMT",
"version": "v2"
}
] | 2014-01-20 | [
[
"Bertolami",
"Orfeu",
""
],
[
"Páramos",
"Jorge",
""
]
] | We examine an extension of General Relativity with an explicit non-minimal coupling between matter and curvature. The purpose of this work is to present an overview of the implications of the latter to various contexts, ranging from astrophysical matter distributions to a cosmological setting. Various results are discussed, including the impact of this non-minimal coupling on the choice of Lagrangian density, on a mechanism to mimic galactic and cluster dark matter, on the possibility of accounting for the accelerated expansion of the Universe, energy density fluctuations and modifications to post-inflationary reheating. The equivalence between a model exhibiting a non-minimal coupling and multi-scalar-theories is also discussed. |
1804.09624 | Shubham Maheshwari | Luca Buoninfante, Gerhard Harmsen, Shubham Maheshwari, Anupam Mazumdar | Non-singular metric for an electrically charged point-source in
ghost-free infinite derivative gravity | 11 pages, 3 figures. Version accepted for publication in PRD | Phys. Rev. D 98, 084009 (2018) | 10.1103/PhysRevD.98.084009 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we will construct a linearized metric solution for an
electrically charged system in a {\it ghost-free} infinite derivative theory of
gravity which is valid in the entire region of spacetime. We will show that the
gravitational potential for a point-charge with mass $m$ is non-singular, the
Kretschmann scalar is finite, and the metric approaches conformal-flatness in
the ultraviolet regime where the non-local gravitational interaction becomes
important. We will show that the metric potentials are bounded below one as
long as two conditions involving the mass and the electric charge are
satisfied. Furthermore, we will argue that the cosmic censorship conjecture is
not required in this case. Unlike in the case of Reissner-Nordstr\"om in
general relativity, where $|Q|\leq m/M_p$ has to be always satisfied, in {\it
ghost-free} infinite derivative gravity $|Q|>m/M_p$ is also allowed, such as
for an electron.
| [
{
"created": "Wed, 25 Apr 2018 15:25:33 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Dec 2018 17:04:08 GMT",
"version": "v2"
}
] | 2018-12-05 | [
[
"Buoninfante",
"Luca",
""
],
[
"Harmsen",
"Gerhard",
""
],
[
"Maheshwari",
"Shubham",
""
],
[
"Mazumdar",
"Anupam",
""
]
] | In this paper we will construct a linearized metric solution for an electrically charged system in a {\it ghost-free} infinite derivative theory of gravity which is valid in the entire region of spacetime. We will show that the gravitational potential for a point-charge with mass $m$ is non-singular, the Kretschmann scalar is finite, and the metric approaches conformal-flatness in the ultraviolet regime where the non-local gravitational interaction becomes important. We will show that the metric potentials are bounded below one as long as two conditions involving the mass and the electric charge are satisfied. Furthermore, we will argue that the cosmic censorship conjecture is not required in this case. Unlike in the case of Reissner-Nordstr\"om in general relativity, where $|Q|\leq m/M_p$ has to be always satisfied, in {\it ghost-free} infinite derivative gravity $|Q|>m/M_p$ is also allowed, such as for an electron. |
1312.3471 | Nikolaos Pappas | Nikolaos Pappas | A little quantum help for cosmic censorship and a step beyond all that | 6 pages, no figures, v2: 1 reference added, corrections regarding
reference details included | Adv.High Energy Phys. 2013 (2013) 236974 | 10.1155/2013/236974 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The hypothesis of cosmic censorship (CCH) plays a crucial role in classical
general relativity, namely to ensure that naked singularities would never
emerge, since it predicts that whenever a singularity is formed an event
horizon would always develop around it as well, to prevent the former from
interacting directly with the rest of the Universe. Should this not be so,
naked singularities could eventually form, in which case phenomena beyond our
understanding and ability to predict could occur, since at the vicinity of the
singularity both predictability and determinism break down even at the
classical (e.g. non-quantum) level. More than 40 years after it was proposed,
the validity of the hypothesis remains an open question. We reconsider CCH in
both its weak and strong version, concerning point-like singularities, with
respect to the provisions of Heisenberg's uncertainty principle. We argue that
the shielding of the singularities from observers at infinity by an event
horizon is also quantum mechanically favored, but ultimately it seems more
appropriate to accept that singularities never actually form in the usual
sense, thus no naked singularity danger exists in the first place.
| [
{
"created": "Thu, 12 Dec 2013 13:20:34 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Feb 2014 19:05:48 GMT",
"version": "v2"
}
] | 2017-04-26 | [
[
"Pappas",
"Nikolaos",
""
]
] | The hypothesis of cosmic censorship (CCH) plays a crucial role in classical general relativity, namely to ensure that naked singularities would never emerge, since it predicts that whenever a singularity is formed an event horizon would always develop around it as well, to prevent the former from interacting directly with the rest of the Universe. Should this not be so, naked singularities could eventually form, in which case phenomena beyond our understanding and ability to predict could occur, since at the vicinity of the singularity both predictability and determinism break down even at the classical (e.g. non-quantum) level. More than 40 years after it was proposed, the validity of the hypothesis remains an open question. We reconsider CCH in both its weak and strong version, concerning point-like singularities, with respect to the provisions of Heisenberg's uncertainty principle. We argue that the shielding of the singularities from observers at infinity by an event horizon is also quantum mechanically favored, but ultimately it seems more appropriate to accept that singularities never actually form in the usual sense, thus no naked singularity danger exists in the first place. |
1801.04219 | Ahmet Baykal | Ahmet Baykal and Tekin Dereli | Abbott-Deser energy in connection with Thirring's superpotentials | Published version, 6 pages, formatted using EPL class files | EPL 122 (2018) 50002 | 10.1209/0295-5075/122/50002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We linearize vacuum Einstein field equations with a cosmological constant
around a curved background to elaborate on the reconstruction of the
Abbott-Deser charges and incorporate a spin connection into the definition
using the algebra of differential forms on a given curved background spacetime.
| [
{
"created": "Fri, 12 Jan 2018 16:22:30 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Jul 2018 08:10:58 GMT",
"version": "v2"
}
] | 2018-07-12 | [
[
"Baykal",
"Ahmet",
""
],
[
"Dereli",
"Tekin",
""
]
] | We linearize vacuum Einstein field equations with a cosmological constant around a curved background to elaborate on the reconstruction of the Abbott-Deser charges and incorporate a spin connection into the definition using the algebra of differential forms on a given curved background spacetime. |
gr-qc/0601128 | Felix Finster | Felix Finster | The Principle of the Fermionic Projector: An Approach for Quantum
Gravity? | 18 pages, LaTeX, few typos corrected (published version) | "Quantum Gravity," B. Fauser et al. (eds.), Birkh\"auser (2006)
263-281 | null | null | gr-qc | null | In this short article we introduce the mathematical framework of the
principle of the fermionic projector and set up a variational principle in
discrete space-time. The underlying physical principles are discussed. We
outline the connection to the continuum theory and state recent results. In the
last two sections, we speculate on how it might be possible to describe quantum
gravity within this framework.
| [
{
"created": "Sun, 29 Jan 2006 17:51:59 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Dec 2006 22:11:56 GMT",
"version": "v2"
},
{
"created": "Sat, 27 Oct 2007 15:53:30 GMT",
"version": "v3"
}
] | 2012-02-15 | [
[
"Finster",
"Felix",
""
]
] | In this short article we introduce the mathematical framework of the principle of the fermionic projector and set up a variational principle in discrete space-time. The underlying physical principles are discussed. We outline the connection to the continuum theory and state recent results. In the last two sections, we speculate on how it might be possible to describe quantum gravity within this framework. |
1705.04935 | Oindrila Ganguly | Oindrila Ganguly | Acoustic superradiance in a slightly viscous fluid | 10 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The acoustic analogue of the geometry of curved spacetime realised in a
classical fluid becomes Lorentz violating in the presence of viscosity. We
study how this effective Lorentz violation affects acoustic superradiance from
the ergosphere of a rotating sonic black hole formed in such a fluid. It turns
out that Lorentz violation imposes an upper bound on frequencies of acoustic
perturbations that can get scattered from the ergosphere. Incidentally, this
upper bound is same as that on the spectrum of superradiant frequencies. This
study also reveals how superradiance is in general modified when the wave
propagates through a dispersive and dissipative medium. Our result is valid
only upto linear order in the coefficient of viscosity and is thus a first
approximation to the full solution, focussing on the key qualitative features.
| [
{
"created": "Sun, 14 May 2017 09:03:22 GMT",
"version": "v1"
}
] | 2017-05-16 | [
[
"Ganguly",
"Oindrila",
""
]
] | The acoustic analogue of the geometry of curved spacetime realised in a classical fluid becomes Lorentz violating in the presence of viscosity. We study how this effective Lorentz violation affects acoustic superradiance from the ergosphere of a rotating sonic black hole formed in such a fluid. It turns out that Lorentz violation imposes an upper bound on frequencies of acoustic perturbations that can get scattered from the ergosphere. Incidentally, this upper bound is same as that on the spectrum of superradiant frequencies. This study also reveals how superradiance is in general modified when the wave propagates through a dispersive and dissipative medium. Our result is valid only upto linear order in the coefficient of viscosity and is thus a first approximation to the full solution, focussing on the key qualitative features. |
2205.07251 | Meir Shimon | Meir Shimon | Cosmology in a locally scale invariant gravity | 8 pages. Comments are welcome | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | A `bouncing' cosmological model is proposed in the context of a
Weyl-invariant scalar-tensor (WIST) theory of gravity. In addition to being
Weyl-invariant the theory is U(1)-symmetric and has a conserved global charge.
The entire cosmic background evolution is accounted for by a complex scalar
field that evolves in the static `comoving' frame. Its (dimensional) modulus
$\chi$ regulates the dynamics of masses and the apparent space expansion.
Cosmological redshift is essentially due to the cosmic evolution of the Rydberg
constant in the comoving frame. The temporal evolution of $\chi$ is analogous
to that of a point particle in the presence of a central potential $V(\chi)$.
The scalar field sources the spacetime curvature; as such it can account for
the (cosmological) Dark Sector. An interplay between the energy density of
radiation and that of the kinetic energy associated with the phase $\alpha$ of
the scalar field (which are of opposite signs) results in a classical
non-singular stable and nearly-symmetric bouncing dynamics deep in the
radiation-dominated era. This encompasses the observed redshifting era which
preceded by a `bounce' that follows a blushifting era. The model is essentially
free of the horizon or flatness problems. Big Bang nucleosynthesis sets a lower
1-10 MeV bound on the typical energy scale at the `bounce'.
| [
{
"created": "Sun, 15 May 2022 10:30:06 GMT",
"version": "v1"
}
] | 2022-05-17 | [
[
"Shimon",
"Meir",
""
]
] | A `bouncing' cosmological model is proposed in the context of a Weyl-invariant scalar-tensor (WIST) theory of gravity. In addition to being Weyl-invariant the theory is U(1)-symmetric and has a conserved global charge. The entire cosmic background evolution is accounted for by a complex scalar field that evolves in the static `comoving' frame. Its (dimensional) modulus $\chi$ regulates the dynamics of masses and the apparent space expansion. Cosmological redshift is essentially due to the cosmic evolution of the Rydberg constant in the comoving frame. The temporal evolution of $\chi$ is analogous to that of a point particle in the presence of a central potential $V(\chi)$. The scalar field sources the spacetime curvature; as such it can account for the (cosmological) Dark Sector. An interplay between the energy density of radiation and that of the kinetic energy associated with the phase $\alpha$ of the scalar field (which are of opposite signs) results in a classical non-singular stable and nearly-symmetric bouncing dynamics deep in the radiation-dominated era. This encompasses the observed redshifting era which preceded by a `bounce' that follows a blushifting era. The model is essentially free of the horizon or flatness problems. Big Bang nucleosynthesis sets a lower 1-10 MeV bound on the typical energy scale at the `bounce'. |
0809.1373 | Lorenzo Iorio | Lorenzo Iorio | An Assessment of the Systematic Uncertainty in Present and Future Tests
of the Lense-Thirring Effect with Satellite Laser Ranging | LaTex, 19 pages, 1 figure, 12 tables. Invited and refereed
contribution to The ISSI Workshop, 6-10 October 2008, on The Nature of
Gravity Confronting Theory and Experiment in Space To appear in Space Science
Reviews | Space Sci.Rev.148: 363-381,2009 | 10.1007/s11214-008-9478-1 | null | gr-qc astro-ph physics.geo-ph physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We deal with the attempts to measure the Lense-Thirring effect with the
Satellite Laser Ranging (SLR) technique applied to the existing LAGEOS and
LAGEOS II terrestrial satellites and to the recently approved LARES
spacecraft.The first issue addressed here is: are the so far published
evaluations of the systematic uncertainty induced by the bad knowledge of the
even zonal harmonic coefficients J_L of the multipolar expansion of the Earth's
geopotential reliable and realistic?
Our answer is negative. Indeed, if the differences Delta J_L among the even
zonals estimated in different Earth's gravity field global solutions from the
dedicated GRACE mission are assumed for the uncertainties delta J_L instead of
using their covariance sigmas sigma_JL, it turns out that the systematic
uncertainty \delta\mu in the Lense-Thirring test with the nodes Omega of LAGEOS
and LAGEOS II may be up to 3 to 4 times larger than in the evaluations so far
published ($5-10%$) based on the use of the sigmas of one model at a time
separately. The second issue consists of the possibility of using a different
approach in extracting the relativistic signature of interest from the
LAGEOS-type data. The third issue is the possibility of reaching a realistic
total accuracy of 1% with LAGEOS, LAGEOS II and LARES, which should be launched
in November 2009 with a VEGA rocket. While LAGEOS and LAGEOS II fly at
altitudes of about 6000 km, LARES will be likely placed at an altitude of 1450
km. Thus, it will be sensitive to much more even zonals than LAGEOS and LAGEOS
II. Their corrupting impact has been evaluated with the standard Kaula's
approach up to degree L=60 by using Delta J_L and sigma_JL; it turns out that
it may be as large as some tens percent.
| [
{
"created": "Mon, 8 Sep 2008 19:14:01 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Dec 2008 17:36:24 GMT",
"version": "v2"
}
] | 2010-11-30 | [
[
"Iorio",
"Lorenzo",
""
]
] | We deal with the attempts to measure the Lense-Thirring effect with the Satellite Laser Ranging (SLR) technique applied to the existing LAGEOS and LAGEOS II terrestrial satellites and to the recently approved LARES spacecraft.The first issue addressed here is: are the so far published evaluations of the systematic uncertainty induced by the bad knowledge of the even zonal harmonic coefficients J_L of the multipolar expansion of the Earth's geopotential reliable and realistic? Our answer is negative. Indeed, if the differences Delta J_L among the even zonals estimated in different Earth's gravity field global solutions from the dedicated GRACE mission are assumed for the uncertainties delta J_L instead of using their covariance sigmas sigma_JL, it turns out that the systematic uncertainty \delta\mu in the Lense-Thirring test with the nodes Omega of LAGEOS and LAGEOS II may be up to 3 to 4 times larger than in the evaluations so far published ($5-10%$) based on the use of the sigmas of one model at a time separately. The second issue consists of the possibility of using a different approach in extracting the relativistic signature of interest from the LAGEOS-type data. The third issue is the possibility of reaching a realistic total accuracy of 1% with LAGEOS, LAGEOS II and LARES, which should be launched in November 2009 with a VEGA rocket. While LAGEOS and LAGEOS II fly at altitudes of about 6000 km, LARES will be likely placed at an altitude of 1450 km. Thus, it will be sensitive to much more even zonals than LAGEOS and LAGEOS II. Their corrupting impact has been evaluated with the standard Kaula's approach up to degree L=60 by using Delta J_L and sigma_JL; it turns out that it may be as large as some tens percent. |
gr-qc/0309074 | Robert Geroch | Jurgen Ehlers, Robert Geroch | Equation of Motion of Small Bodies in Relativity | 7 pages | AnnalsPhys.309:232-236,2004 | 10.1016/j.aop.2003.08.020 | null | gr-qc | null | There is proven a theorem, to the effect that a material body in general
relativity, in a certain limit of sufficiently small size and mass, moves along
a geodesic.
| [
{
"created": "Tue, 16 Sep 2003 13:48:15 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ehlers",
"Jurgen",
""
],
[
"Geroch",
"Robert",
""
]
] | There is proven a theorem, to the effect that a material body in general relativity, in a certain limit of sufficiently small size and mass, moves along a geodesic. |
2112.06691 | Nikolaos Mavromatos | Nick E. Mavromatos | Going beyond the Standard paradigm of Cosmology: Torsion, gravitational
anomalies and inflation without inflaton fields | 11 pages latex, uses PoS style, One figure incorporated. References
and one footnote [1] added, regarding conventional quantum field theoretic
derivations of running vacuum models in curved spacetime. Plenary talk at the
7th Symposium on Prospects in the Physics of Discrete Symmetries (DISCRETE
2020-2021) 29th November - 3rd December 2021, Bergen, Norway | null | null | KCL-PH-TH/2021-97 | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I review a string-inspired cosmological model, with gravitational anomalies
present at very early epochs, which includes a totally antisymmetric torsion,
that in (3+1)-dimensions is equivalent to a pseudoscalar (Kalb-Ramond,
string-model independent) axion field. Upon condensation of primordial
gravitational waves (GW), that are created at a pre-inflationary era, the model
leads to inflation of the so-called running-vacuum-model (RVM) type, which is
realised without the need for external inflaton fields, being due to the
non-linearities that characterise the gravitational theory. The model provides
an alternative to the $\Lambda$CDM paradigm, and is also capable of inducing
matter-antimatter asymmetry in the Universe, during the post-inflationary
radiation era, in models with right-handed neutrinos in their matter spectra.
The so-induced asymmetry is triggered by a Lorentz-symmetry-violating KR axion
background that is generated during the RVM-inflationary period, as a
consequence of the GW condensate. The modern era of this cosmology is argued to
be characterised by observable (RVM-type) deviations from $\Lambda$CDM, with
the potential of alleviating the observed tensions in the cosmological data.
| [
{
"created": "Mon, 13 Dec 2021 14:22:21 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Dec 2021 19:47:57 GMT",
"version": "v2"
}
] | 2021-12-30 | [
[
"Mavromatos",
"Nick E.",
""
]
] | I review a string-inspired cosmological model, with gravitational anomalies present at very early epochs, which includes a totally antisymmetric torsion, that in (3+1)-dimensions is equivalent to a pseudoscalar (Kalb-Ramond, string-model independent) axion field. Upon condensation of primordial gravitational waves (GW), that are created at a pre-inflationary era, the model leads to inflation of the so-called running-vacuum-model (RVM) type, which is realised without the need for external inflaton fields, being due to the non-linearities that characterise the gravitational theory. The model provides an alternative to the $\Lambda$CDM paradigm, and is also capable of inducing matter-antimatter asymmetry in the Universe, during the post-inflationary radiation era, in models with right-handed neutrinos in their matter spectra. The so-induced asymmetry is triggered by a Lorentz-symmetry-violating KR axion background that is generated during the RVM-inflationary period, as a consequence of the GW condensate. The modern era of this cosmology is argued to be characterised by observable (RVM-type) deviations from $\Lambda$CDM, with the potential of alleviating the observed tensions in the cosmological data. |
gr-qc/9611061 | Henning Samtleben | D. Korotkin and H. Samtleben | Poisson Realization and Quantization of the Geroch Group | 8 pages, LaTeX2e | Class.Quant.Grav.14:L151-L156,1997 | 10.1088/0264-9381/14/8/003 | DESY 96-245 | gr-qc hep-th | null | The conserved nonlocal charges generating the Geroch group with respect to
the canonical Poisson structure of the Ernst equation are found. They are shown
to build a quadratic Poisson algebra, which suggests to identify the quantum
Geroch algebra with Yangian structures.
| [
{
"created": "Tue, 26 Nov 1996 09:42:40 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Korotkin",
"D.",
""
],
[
"Samtleben",
"H.",
""
]
] | The conserved nonlocal charges generating the Geroch group with respect to the canonical Poisson structure of the Ernst equation are found. They are shown to build a quadratic Poisson algebra, which suggests to identify the quantum Geroch algebra with Yangian structures. |
2206.11530 | Jinn-Ouk Gong | Inyong Cho, Jinn-Ouk Gong, Seung Hun Oh | Second-order energy-momentum tensor of a scalar field | 12 pages | null | null | APCTP-Pre2022-013 | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We investigate the second-order effective energy-momentum tensor (2EMT)
constructed by the quadratic terms of the linear scalar cosmological
perturbations while the universe is dominated by a scalar field. We show that
2EMT is gauge dependent. We then study 2EMT in three (longitudinal, spatially
flat, and comoving) gauge conditions in the slow-roll stage of inflation. We
find that 2EMT exhibits an effective fluid of w=-1/3 on super-horizon scales in
all of those gauge conditions.
| [
{
"created": "Thu, 23 Jun 2022 08:27:02 GMT",
"version": "v1"
}
] | 2022-06-24 | [
[
"Cho",
"Inyong",
""
],
[
"Gong",
"Jinn-Ouk",
""
],
[
"Oh",
"Seung Hun",
""
]
] | We investigate the second-order effective energy-momentum tensor (2EMT) constructed by the quadratic terms of the linear scalar cosmological perturbations while the universe is dominated by a scalar field. We show that 2EMT is gauge dependent. We then study 2EMT in three (longitudinal, spatially flat, and comoving) gauge conditions in the slow-roll stage of inflation. We find that 2EMT exhibits an effective fluid of w=-1/3 on super-horizon scales in all of those gauge conditions. |
2103.15424 | Jose M. Isidro | J.M. Isidro, P. Fernandez de Cordoba, J.C. Castro-Palacio | Spherical space in the Newtonian limit: The cosmological constant | 16 pp; clarifications added | null | 10.1142/S0218271821500838 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the cosmological constant of a spherical space in the limit of
weak gravity. To this end we use a duality developed by the present authors in
a previous work. This duality allows one to treat the Newtonian cosmological
fluid as the probability fluid of a single particle in nonrelativistic quantum
mechanics. We apply this duality to the case when the spacetime manifold on
which this quantum mechanics is defined is given by
$\mathbb{R}\times\mathbb{S}^3$. Here $\mathbb{R}$ stands for the time axis and
$\mathbb{S}^3$ is a 3-dimensional sphere endowed with the standard round
metric. A quantum operator $\Lambda$ satisfying all the requirements of a
cosmological constant is identified, and the matrix representing $\Lambda$
within the Hilbert space $L^2\left(\mathbb{S}^3\right)$ of quantum states is
obtained. Numerical values for the expectation value of the operator $\Lambda$
in certain quantum states are obtained, that are in good agreement with the
experimentally measured cosmological constant.
| [
{
"created": "Mon, 29 Mar 2021 08:47:30 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Jun 2021 14:50:26 GMT",
"version": "v2"
}
] | 2021-09-22 | [
[
"Isidro",
"J. M.",
""
],
[
"de Cordoba",
"P. Fernandez",
""
],
[
"Castro-Palacio",
"J. C.",
""
]
] | We compute the cosmological constant of a spherical space in the limit of weak gravity. To this end we use a duality developed by the present authors in a previous work. This duality allows one to treat the Newtonian cosmological fluid as the probability fluid of a single particle in nonrelativistic quantum mechanics. We apply this duality to the case when the spacetime manifold on which this quantum mechanics is defined is given by $\mathbb{R}\times\mathbb{S}^3$. Here $\mathbb{R}$ stands for the time axis and $\mathbb{S}^3$ is a 3-dimensional sphere endowed with the standard round metric. A quantum operator $\Lambda$ satisfying all the requirements of a cosmological constant is identified, and the matrix representing $\Lambda$ within the Hilbert space $L^2\left(\mathbb{S}^3\right)$ of quantum states is obtained. Numerical values for the expectation value of the operator $\Lambda$ in certain quantum states are obtained, that are in good agreement with the experimentally measured cosmological constant. |
2203.15934 | Simone Mezzasoma | S. Mezzasoma, N. Yunes | Theory-agnostic framework for inspiral tests of general relativity with
higher-harmonic gravitational waves | null | null | 10.1103/PhysRevD.106.024026 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Recent gravitational wave observations show evidence for the presence of
higher harmonics, thus possibly indicating that these waves were generated in
the inspiral of compact objects with asymmetric mass ratios. Signals with
higher harmonics contain a trove of information that can lead to a better
estimation of system parameters and possibly to more stringent tests of general
relativity. Gravitational wave model that include higher harmonics, however,
have only been developed within general relativity, while models to test
theory-agnostic deviations from general relativity have been purely based on
the signal's dominant mode. We here extend the parameterized post-Einsteinian
framework to include the $\ell=2, 3$ and $4$ higher harmonics to first
post-Newtonian order, therefore providing a ready-to-use Fourier-domain
waveform model for tests of general relativity with higher harmonics. We find
that the deformations to the higher harmonics of the Fourier phase can be
easily mapped to the deformation of the dominant harmonic, while the
deformations to the higher-harmonics of the Fourier amplitude in general cannot
in a theory-agnostic way. Nonetheless, we develop a simple ansatz for the
deformations of the waveform amplitude (through a re-scaling deformation of the
time-domain amplitude) that both minimizes the number of independent amplitude
deformations parameters and captures the predictions of all known modified
theories to date.
| [
{
"created": "Tue, 29 Mar 2022 22:27:47 GMT",
"version": "v1"
}
] | 2022-07-27 | [
[
"Mezzasoma",
"S.",
""
],
[
"Yunes",
"N.",
""
]
] | Recent gravitational wave observations show evidence for the presence of higher harmonics, thus possibly indicating that these waves were generated in the inspiral of compact objects with asymmetric mass ratios. Signals with higher harmonics contain a trove of information that can lead to a better estimation of system parameters and possibly to more stringent tests of general relativity. Gravitational wave model that include higher harmonics, however, have only been developed within general relativity, while models to test theory-agnostic deviations from general relativity have been purely based on the signal's dominant mode. We here extend the parameterized post-Einsteinian framework to include the $\ell=2, 3$ and $4$ higher harmonics to first post-Newtonian order, therefore providing a ready-to-use Fourier-domain waveform model for tests of general relativity with higher harmonics. We find that the deformations to the higher harmonics of the Fourier phase can be easily mapped to the deformation of the dominant harmonic, while the deformations to the higher-harmonics of the Fourier amplitude in general cannot in a theory-agnostic way. Nonetheless, we develop a simple ansatz for the deformations of the waveform amplitude (through a re-scaling deformation of the time-domain amplitude) that both minimizes the number of independent amplitude deformations parameters and captures the predictions of all known modified theories to date. |
2107.09601 | Alexander Vikman | Alexander Vikman | Global Dynamics for Newton and Planck | Contribution to the 2021 Gravitation session of the 55th Rencontres
de Moriond | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We discuss recently introduced scale-free Einstein equations, where the
information from their trace part is lost. These equations are classically
equivalent to General Relativity, yet the Newton constant becomes a constant of
integration or a global dynamical degree of freedom. Thus, from the point of
view of standard quantization, this effective Newton constant is susceptible to
quantum fluctuations. This is similar to what happens to the cosmological
constant in the unimodular gravity where the trace part of the Einstein
equations is lost in a different way. Using analogy with the
Henneaux-Teitelboim covariant action for the unimodular gravity, we consider
different general-covariant actions resulting in these dynamics. This setup
allows one to formulate the Heisenberg uncertainty relations for the Newton
constant and canonically conjugated quantities. Unexpectedly, one of such
theories also promotes the Planck's quantum constant to a global degree of
freedom, which is subject to quantum fluctuations. Following analogy with the
unimodular gravity, we discuss non-covariant "unimatter" and "unicurvature"
gravities describing the scale-free Einstein equations. Finally, we show that
in some limit of the Yang-Mills gauge theory a "frozen" axion-like field can
emulate the gravitational Newton constant or even of the quantum Planck
constant.
| [
{
"created": "Tue, 20 Jul 2021 16:24:31 GMT",
"version": "v1"
}
] | 2021-07-21 | [
[
"Vikman",
"Alexander",
""
]
] | We discuss recently introduced scale-free Einstein equations, where the information from their trace part is lost. These equations are classically equivalent to General Relativity, yet the Newton constant becomes a constant of integration or a global dynamical degree of freedom. Thus, from the point of view of standard quantization, this effective Newton constant is susceptible to quantum fluctuations. This is similar to what happens to the cosmological constant in the unimodular gravity where the trace part of the Einstein equations is lost in a different way. Using analogy with the Henneaux-Teitelboim covariant action for the unimodular gravity, we consider different general-covariant actions resulting in these dynamics. This setup allows one to formulate the Heisenberg uncertainty relations for the Newton constant and canonically conjugated quantities. Unexpectedly, one of such theories also promotes the Planck's quantum constant to a global degree of freedom, which is subject to quantum fluctuations. Following analogy with the unimodular gravity, we discuss non-covariant "unimatter" and "unicurvature" gravities describing the scale-free Einstein equations. Finally, we show that in some limit of the Yang-Mills gauge theory a "frozen" axion-like field can emulate the gravitational Newton constant or even of the quantum Planck constant. |
1703.10061 | Rathul Nath Raveendran | Rathul Nath Raveendran, Debika Chowdhury and L. Sriramkumar | Viable tensor-to-scalar ratio in a symmetric matter bounce | v1: 39 pages, 8 figures; v2: 40 pages, 8 figures, discussions and
references added, accepted for publication in JCAP | null | 10.1088/1475-7516/2018/01/030 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Matter bounces refer to scenarios wherein the universe contracts at early
times as in a matter dominated epoch until the scale factor reaches a minimum,
after which it starts expanding. While such scenarios are known to lead to
scale invariant spectra of primordial perturbations after the bounce, the
challenge has been to construct completely symmetric bounces that lead to a
tensor-to-scalar ratio which is small enough to be consistent with the recent
cosmological data. In this work, we construct a model involving two scalar
fields (a canonical field and a non-canonical ghost field) to drive the
symmetric matter bounce and study the evolution of the scalar perturbations in
the model. If we consider the scale associated with the bounce to be of the
order of the Planck scale, the model is completely described in terms of only
one parameter, viz the value of the scale factor at the bounce. We evolve the
scalar perturbations numerically across the bounce and evaluate the scalar
power spectra after the bounce. We show that, while the scalar and tensor
perturbation spectra are scale invariant over scales of cosmological interest,
the tensor-to-scalar ratio proves to be much smaller than the current upper
bound from the observations of the cosmic microwave background anisotropies by
the Planck mission. We also support our numerical analysis with analytical
arguments.
| [
{
"created": "Tue, 28 Mar 2017 17:28:26 GMT",
"version": "v1"
},
{
"created": "Sun, 31 Dec 2017 07:36:51 GMT",
"version": "v2"
}
] | 2018-01-31 | [
[
"Raveendran",
"Rathul Nath",
""
],
[
"Chowdhury",
"Debika",
""
],
[
"Sriramkumar",
"L.",
""
]
] | Matter bounces refer to scenarios wherein the universe contracts at early times as in a matter dominated epoch until the scale factor reaches a minimum, after which it starts expanding. While such scenarios are known to lead to scale invariant spectra of primordial perturbations after the bounce, the challenge has been to construct completely symmetric bounces that lead to a tensor-to-scalar ratio which is small enough to be consistent with the recent cosmological data. In this work, we construct a model involving two scalar fields (a canonical field and a non-canonical ghost field) to drive the symmetric matter bounce and study the evolution of the scalar perturbations in the model. If we consider the scale associated with the bounce to be of the order of the Planck scale, the model is completely described in terms of only one parameter, viz the value of the scale factor at the bounce. We evolve the scalar perturbations numerically across the bounce and evaluate the scalar power spectra after the bounce. We show that, while the scalar and tensor perturbation spectra are scale invariant over scales of cosmological interest, the tensor-to-scalar ratio proves to be much smaller than the current upper bound from the observations of the cosmic microwave background anisotropies by the Planck mission. We also support our numerical analysis with analytical arguments. |
2305.06502 | Adrian Ka-Wai Chung | Adrian Ka-Wai Chung, Nicolas Yunes | Untargeted Bayesian search of anisotropic gravitational-wave backgrounds
through the analytical marginalization of the posterior | Match the published version | Phys. Rev. D 108, 043032 (2023) | 10.1103/PhysRevD.108.043032 | null | gr-qc astro-ph.IM | http://creativecommons.org/publicdomain/zero/1.0/ | We develop a method to perform an untargeted Bayesian search for anisotropic
gravitational-wave backgrounds that can efficiently and accurately reconstruct
the background intensity map. Our method employs an analytic marginalization of
the posterior of the spherical-harmonic components of the intensity map,
without assuming the background possesses any specific angular structure. The
key idea is that the likelihood function of the spherical-harmonic components
is a multivariate Gaussian when the intensity map is expressed as a linear
combination of the spherical-harmonic components and the noise is stationary
and Gaussian. If a uniform and wide prior of these spherical-harmonic
components is prescribed, the marginalized posterior and the Bayes factor can
be well approximated by a high-dimensional Gaussian integral. The analytical
marginalization allows us to regard the spherical-harmonic components of the
intensity map of the background as free parameters, and to construct their
individual marginalized posterior distribution in a reasonable time, even
though many spherical-harmonic components are required. The marginalized
posteriors can, in turn, be used to accurately construct the intensity map of
the background. By applying our method to mock data, we show that we can
recover precisely the angular structures of various simulated anisotropic
backgrounds, without assuming prior knowledge of the relation between the
spherical-harmonic components predicted by a given model. Our method allows us
to bypass the time-consuming numerical sampling of a high-dimensional
posterior, leading to a more model-independent and untargeted Bayesian
measurement of the angular structures of the gravitational-wave background.
| [
{
"created": "Thu, 11 May 2023 00:51:44 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Aug 2023 05:32:12 GMT",
"version": "v2"
}
] | 2023-09-06 | [
[
"Chung",
"Adrian Ka-Wai",
""
],
[
"Yunes",
"Nicolas",
""
]
] | We develop a method to perform an untargeted Bayesian search for anisotropic gravitational-wave backgrounds that can efficiently and accurately reconstruct the background intensity map. Our method employs an analytic marginalization of the posterior of the spherical-harmonic components of the intensity map, without assuming the background possesses any specific angular structure. The key idea is that the likelihood function of the spherical-harmonic components is a multivariate Gaussian when the intensity map is expressed as a linear combination of the spherical-harmonic components and the noise is stationary and Gaussian. If a uniform and wide prior of these spherical-harmonic components is prescribed, the marginalized posterior and the Bayes factor can be well approximated by a high-dimensional Gaussian integral. The analytical marginalization allows us to regard the spherical-harmonic components of the intensity map of the background as free parameters, and to construct their individual marginalized posterior distribution in a reasonable time, even though many spherical-harmonic components are required. The marginalized posteriors can, in turn, be used to accurately construct the intensity map of the background. By applying our method to mock data, we show that we can recover precisely the angular structures of various simulated anisotropic backgrounds, without assuming prior knowledge of the relation between the spherical-harmonic components predicted by a given model. Our method allows us to bypass the time-consuming numerical sampling of a high-dimensional posterior, leading to a more model-independent and untargeted Bayesian measurement of the angular structures of the gravitational-wave background. |
1509.08338 | Ivan Arraut | Ivan Arraut | The graviton Higgs mechanism | 5 pages, Version published in Europhysics Letters (EPL) | Europhys. Lett. 111 (2015) 61001 | 10.1209/0295-5075/111/61001 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Higgs mechanism at the graviton level formulated as a Vainshtein
mechanism in time domains implies that the extra-degrees of freedom become
relevant depending on the direction of time (frame of reference) with respect
to the preferred time direction (preferred frame) defined by the St\"uckelberg
function $T_0(r,t)$ which contains the information of the extra-degrees of
freedom of the theory. In this manuscript, I make the general definition of the
Higgs mechanism by analyzing the gauge symmetries of the action and the general
form of the vacuum solutions for the graviton field. In general, the symmetry
generators depending explicitly on the St\"uckelberg fields are broken at the
vacuum level. These broken generators, define the number of Nambu-Goldstone
bosons which will be eating up by the dynamical metric in order to become
massive.
| [
{
"created": "Fri, 25 Sep 2015 15:30:17 GMT",
"version": "v1"
}
] | 2015-10-28 | [
[
"Arraut",
"Ivan",
""
]
] | The Higgs mechanism at the graviton level formulated as a Vainshtein mechanism in time domains implies that the extra-degrees of freedom become relevant depending on the direction of time (frame of reference) with respect to the preferred time direction (preferred frame) defined by the St\"uckelberg function $T_0(r,t)$ which contains the information of the extra-degrees of freedom of the theory. In this manuscript, I make the general definition of the Higgs mechanism by analyzing the gauge symmetries of the action and the general form of the vacuum solutions for the graviton field. In general, the symmetry generators depending explicitly on the St\"uckelberg fields are broken at the vacuum level. These broken generators, define the number of Nambu-Goldstone bosons which will be eating up by the dynamical metric in order to become massive. |
2311.12259 | Anzhong Wang | Zibo Shen, Anzhong Wang, Yungui Gong, Shaoyu Yin | Analytical models of supermassive black holes in galaxies surrounded by
dark matter halos | revtex4-2, no figures. Version to appear in Phys. Lett. B 855 (2024)
138797 | Phys. Lett. B 855 (2024) 138797 | 10.1016/j.physletb.2024.138797 | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | In this Letter, we present five analytical models in closed forms, each
representing a supermassive black hole (SMBH) located at the center of a galaxy
surrounded by dark matter (DM) halo. The density profile of the halo vanishes
inside twice the Schwarzschild radius of the hole and satisfies the weak,
strong, and dominant energy conditions. The spacetime are asymptotically flat,
and the difference among the models lies in the slopes of the density profiles
in the spike and regions far from the center of the galaxy. Three of them
represent cusp models, whereas the other two represent core models. With the
well-known (generalized) Newman-Janis algorithm, rotating SMBHs with DM halos
can be easily constructed from these models.
| [
{
"created": "Tue, 21 Nov 2023 00:43:08 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Dec 2023 08:37:00 GMT",
"version": "v2"
},
{
"created": "Tue, 12 Dec 2023 04:47:37 GMT",
"version": "v3"
},
{
"created": "Sun, 17 Dec 2023 00:18:52 GMT",
"version": "v4"
},
{
"cr... | 2024-06-21 | [
[
"Shen",
"Zibo",
""
],
[
"Wang",
"Anzhong",
""
],
[
"Gong",
"Yungui",
""
],
[
"Yin",
"Shaoyu",
""
]
] | In this Letter, we present five analytical models in closed forms, each representing a supermassive black hole (SMBH) located at the center of a galaxy surrounded by dark matter (DM) halo. The density profile of the halo vanishes inside twice the Schwarzschild radius of the hole and satisfies the weak, strong, and dominant energy conditions. The spacetime are asymptotically flat, and the difference among the models lies in the slopes of the density profiles in the spike and regions far from the center of the galaxy. Three of them represent cusp models, whereas the other two represent core models. With the well-known (generalized) Newman-Janis algorithm, rotating SMBHs with DM halos can be easily constructed from these models. |
1006.4059 | Luca Rizzi | Luca Rizzi, Sergio Cacciatori, Vittorio Gorini, Alexander Kamenshchik,
Oliver F. Piattella | Dark matter effects in vacuum spacetime | 5 pages, 2 figures, expanded with comments about the exact motion and
curvature invariants | Phys.Rev.D82:027301,2010 | 10.1103/PhysRevD.82.027301 | null | gr-qc physics.gen-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze a toy model describing an empty spacetime in which the motion of a
test mass (and the trajectories of photons) evidence the presence of a
continuous and homogeneous distribution of matter; however, since the
energy-momentum tensor vanishes, no real matter or energy distribution is
present at all. Thus, a hypothetical observer will conclude that he is immersed
in some sort of dark matter, even though he has no chance to directly detect
it. This suggests yet another possibility of explaining the elusive dark matter
as a purely dynamical effect due to the curvature of spacetime.
| [
{
"created": "Mon, 21 Jun 2010 13:08:13 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Jul 2010 18:07:20 GMT",
"version": "v2"
}
] | 2014-11-21 | [
[
"Rizzi",
"Luca",
""
],
[
"Cacciatori",
"Sergio",
""
],
[
"Gorini",
"Vittorio",
""
],
[
"Kamenshchik",
"Alexander",
""
],
[
"Piattella",
"Oliver F.",
""
]
] | We analyze a toy model describing an empty spacetime in which the motion of a test mass (and the trajectories of photons) evidence the presence of a continuous and homogeneous distribution of matter; however, since the energy-momentum tensor vanishes, no real matter or energy distribution is present at all. Thus, a hypothetical observer will conclude that he is immersed in some sort of dark matter, even though he has no chance to directly detect it. This suggests yet another possibility of explaining the elusive dark matter as a purely dynamical effect due to the curvature of spacetime. |
1401.1282 | Cosimo Bambi | Zilong Li, Lingyao Kong, Cosimo Bambi | Testing the nature of the supermassive black hole candidate in SgrA*
with light curves and images of hot spots | 16 pages, 14 figures. v3: refereed version | Astrophys.J.787:152,2014 | 10.1088/0004-637X/787/2/152 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General relativity makes clear predictions about the spacetime geometry
around black holes. In the near future, new facilities will have the capability
to explore the metric around SgrA$^*$, the supermassive black hole candidate at
the Center of our Galaxy, and open a new window to test the Kerr black hole
hypothesis. In this paper, we compute light curves and images associated with
compact emission regions (hot spots) orbiting around Kerr and non-Kerr black
holes. We study how the analysis of the properties of the radiation emitted by
a hot spot can be used to test the Kerr nature of SgrA$^*$. We find that the
sole observation of the hot spot light curve can at most constrain a
combination of the black hole spin and of possible deviations from the Kerr
solution. This happens because the same orbital frequency around a Kerr black
hole can be found for a non-Kerr object with a different spin parameter. Second
order corrections in the light curve due to the background geometry are
typically too small to be identified. While the observation of the hot spot
centroid track can potentially bound possible deviations from the Kerr
solution, that is out of reach for the near future VLTI instrument GRAVITY. The
Kerr black hole hypothesis could really be tested in the case of the discovery
of a radio pulsar in a compact orbit around SgrA$^*$. Radio observations of
such a pulsar would provide precise estimates of the mass and the spin of
SgrA$^*$, and the combination of these measurements (probing the weak field)
with the hot spot light curve information (probing the strong field) may
constrain/find possible deviations from the Kerr solution with quite good
precision.
| [
{
"created": "Tue, 7 Jan 2014 06:10:12 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Mar 2014 15:26:42 GMT",
"version": "v2"
},
{
"created": "Thu, 15 May 2014 00:56:06 GMT",
"version": "v3"
}
] | 2014-05-16 | [
[
"Li",
"Zilong",
""
],
[
"Kong",
"Lingyao",
""
],
[
"Bambi",
"Cosimo",
""
]
] | General relativity makes clear predictions about the spacetime geometry around black holes. In the near future, new facilities will have the capability to explore the metric around SgrA$^*$, the supermassive black hole candidate at the Center of our Galaxy, and open a new window to test the Kerr black hole hypothesis. In this paper, we compute light curves and images associated with compact emission regions (hot spots) orbiting around Kerr and non-Kerr black holes. We study how the analysis of the properties of the radiation emitted by a hot spot can be used to test the Kerr nature of SgrA$^*$. We find that the sole observation of the hot spot light curve can at most constrain a combination of the black hole spin and of possible deviations from the Kerr solution. This happens because the same orbital frequency around a Kerr black hole can be found for a non-Kerr object with a different spin parameter. Second order corrections in the light curve due to the background geometry are typically too small to be identified. While the observation of the hot spot centroid track can potentially bound possible deviations from the Kerr solution, that is out of reach for the near future VLTI instrument GRAVITY. The Kerr black hole hypothesis could really be tested in the case of the discovery of a radio pulsar in a compact orbit around SgrA$^*$. Radio observations of such a pulsar would provide precise estimates of the mass and the spin of SgrA$^*$, and the combination of these measurements (probing the weak field) with the hot spot light curve information (probing the strong field) may constrain/find possible deviations from the Kerr solution with quite good precision. |
0804.0328 | Gerard Hooft 't | Gerard 't Hooft | A locally finite model for gravity | 26 pages, 9 figures | Found.Phys.38:733-757,2008 | 10.1007/s10701-008-9231-3 | ITP-UU-08/17, SPIN-08/16 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Matter interacting classically with gravity in 3+1 dimensions usually gives
rise to a continuum of degrees of freedom, so that, in any attempt to quantize
the theory, ultraviolet divergences are nearly inevitable. Here, we investigate
matter of a form that only displays a finite number of degrees of freedom in
compact sections of space-time. In finite domains, one has only exact, analytic
solutions. This is achieved by limiting ourselves to straight pieces of string,
surrounded by locally flat sections of space-time. Globally, however, the model
is not finite, because solutions tend to generate infinite fractals. The model
is not (yet) quantized, but could serve as an interesting setting for
analytical approaches to classical general relativity, as well as a possible
stepping stone for quantum models. Details of its properties are explained, but
some problems remain unsolved, such as a complete description of the most
violent interactions, which can become quite complex.
| [
{
"created": "Wed, 2 Apr 2008 11:11:28 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Hooft",
"Gerard 't",
""
]
] | Matter interacting classically with gravity in 3+1 dimensions usually gives rise to a continuum of degrees of freedom, so that, in any attempt to quantize the theory, ultraviolet divergences are nearly inevitable. Here, we investigate matter of a form that only displays a finite number of degrees of freedom in compact sections of space-time. In finite domains, one has only exact, analytic solutions. This is achieved by limiting ourselves to straight pieces of string, surrounded by locally flat sections of space-time. Globally, however, the model is not finite, because solutions tend to generate infinite fractals. The model is not (yet) quantized, but could serve as an interesting setting for analytical approaches to classical general relativity, as well as a possible stepping stone for quantum models. Details of its properties are explained, but some problems remain unsolved, such as a complete description of the most violent interactions, which can become quite complex. |
2312.17680 | Lionel London | Lionel London and Michelle Gurevich | Natural polynomials for Kerr quasi-normal modes | 19 pages, 7 figures | null | null | null | gr-qc math-ph math.MP math.SP | http://creativecommons.org/licenses/by/4.0/ | We present a polynomial basis that exactly tridiagonalizes Teukolsky's radial
equation for quasi-normal modes. These polynomials naturally emerge from the
radial problem, and they are "canonical" in that they possess key features of
classical polynomials. Our canonical polynomials may be constructed using
various methods, the simplest of which is the Gram-Schmidt process. In contrast
with other polynomial bases, our polynomials allow for Teukolsky's radial
equation to be represented as a simple matrix eigenvalue equation that has
well-behaved asymptotics and is free of non-physical solutions. We expect that
our polynomials will be useful for better understanding the Kerr quasinormal
modes' properties, particularly their prospective spatial completeness and
orthogonality. We show that our polynomials are closely related to the
confluent Heun and Pollaczek-Jacobi type polynomials. Consequently, our
construction of polynomials may be used to tridiagonalize other instances of
the confluent Heun equation. We apply our polynomials to a series of simple
examples, including: (1) the high accuracy numerical computation of radial
eigenvalues, (2) the evaluation and validation of quasinormal mode solutions to
Teukolsky's radial equation, and (3) the use of Schwarzschild radial functions
to represent those of Kerr. Along the way, a potentially new concept,
"confluent Heun polynomial/non-polynomial duality", is encountered and applied
to show that some quasinormal mode separation constants are well approximated
by confluent Heun polynomial eigenvalues. We briefly discuss the implications
of our results on various topics, including the prospective spatial
completeness of Kerr quasinormal modes.
| [
{
"created": "Fri, 29 Dec 2023 16:55:05 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Jan 2024 18:58:12 GMT",
"version": "v2"
}
] | 2024-01-02 | [
[
"London",
"Lionel",
""
],
[
"Gurevich",
"Michelle",
""
]
] | We present a polynomial basis that exactly tridiagonalizes Teukolsky's radial equation for quasi-normal modes. These polynomials naturally emerge from the radial problem, and they are "canonical" in that they possess key features of classical polynomials. Our canonical polynomials may be constructed using various methods, the simplest of which is the Gram-Schmidt process. In contrast with other polynomial bases, our polynomials allow for Teukolsky's radial equation to be represented as a simple matrix eigenvalue equation that has well-behaved asymptotics and is free of non-physical solutions. We expect that our polynomials will be useful for better understanding the Kerr quasinormal modes' properties, particularly their prospective spatial completeness and orthogonality. We show that our polynomials are closely related to the confluent Heun and Pollaczek-Jacobi type polynomials. Consequently, our construction of polynomials may be used to tridiagonalize other instances of the confluent Heun equation. We apply our polynomials to a series of simple examples, including: (1) the high accuracy numerical computation of radial eigenvalues, (2) the evaluation and validation of quasinormal mode solutions to Teukolsky's radial equation, and (3) the use of Schwarzschild radial functions to represent those of Kerr. Along the way, a potentially new concept, "confluent Heun polynomial/non-polynomial duality", is encountered and applied to show that some quasinormal mode separation constants are well approximated by confluent Heun polynomial eigenvalues. We briefly discuss the implications of our results on various topics, including the prospective spatial completeness of Kerr quasinormal modes. |
gr-qc/0102114 | Keith H. Lockitch | John L. Friedman, Keith H. Lockitch | Implications of the r-mode instability of rotating relativistic stars | 20 pages LaTeX2e (stylefile included), 6 eps figures. Review to
appear in the proceedings of the 9th Marcel Grossman Meeting, World
Scientific, ed. V. Gurzadyan, R. Jantzen, R. Ruffini | null | 10.1142/9789812777386_0013 | CGPG-01/3-1 | gr-qc astro-ph | null | Several recent surprises appear dramatically to have improved the likelihood
that the spin of rapidly rotating, newly formed neutron stars (and, possibly,
of old stars spun up by accretion) is limited by a nonaxisymmetric instability
driven by gravitational waves. Except for the earliest part of the spin-down,
the axial l=m=2 mode (an r-mode) dominates the instability, and the emitted
waves may be observable by detectors with the sensitivity of LIGO II. A review
of these hopeful results is followed by a discussion of constraints on the
instability set by dissipative mechanisms, including viscosity, nonlinear
saturation, and energy loss to a magnetic field driven by differential
rotation.
| [
{
"created": "Wed, 28 Feb 2001 19:10:19 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Mar 2001 20:18:45 GMT",
"version": "v2"
}
] | 2017-08-23 | [
[
"Friedman",
"John L.",
""
],
[
"Lockitch",
"Keith H.",
""
]
] | Several recent surprises appear dramatically to have improved the likelihood that the spin of rapidly rotating, newly formed neutron stars (and, possibly, of old stars spun up by accretion) is limited by a nonaxisymmetric instability driven by gravitational waves. Except for the earliest part of the spin-down, the axial l=m=2 mode (an r-mode) dominates the instability, and the emitted waves may be observable by detectors with the sensitivity of LIGO II. A review of these hopeful results is followed by a discussion of constraints on the instability set by dissipative mechanisms, including viscosity, nonlinear saturation, and energy loss to a magnetic field driven by differential rotation. |
1909.06755 | Matt Visser | Petarpa Boonserm (Chulalongkorn University, Thailand Center of
Excellence in Physics), Tritos Ngampitipan (Chandrakasem Rajabhat University,
Thailand Center of Excellence in Physics), Alex Simpson (Victoria University
of Wellington), and Matt Visser (Victoria University of Wellington) | ISCOs and OSCOs in the presence of positive cosmological constant | V1: 14 pages; V2: four references added, minor rephrasing, no change
in physics conclusions; V3: now 20 pages; four more references added; extra
discussion regarding Paczynski-Wiita potential and Jeans scale. Closely
corresponds to published version | Phys. Rev. D 101, 024050 (2020) | 10.1103/PhysRevD.101.024050 | null | gr-qc astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Normally one thinks of the observed cosmological constant as being so small
that it can be utterly neglected on typical astrophysical scales, only
affecting extremely large-scale cosmology at Gigaparsec scales. Indeed, in
those situations where the cosmological constant only has a quantitative
influence on the physics, a separation of scales argument guarantees the effect
is indeed negligible. The exception to this argument arises when the presence
of a cosmological constant qualitatively changes the physics. One example of
this phenomenon is the existence of outermost stable circular orbits (OSCOs) in
the presence of a positive cosmological constant. Remarkably the size of these
OSCOs are of a magnitude to be astrophysically interesting. For instance: for
galactic masses the OSCOs are of order the inter-galactic spacing, for galaxy
cluster masses the OSCOs are of order the size of the cluster.
| [
{
"created": "Sun, 15 Sep 2019 07:43:53 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Sep 2019 00:24:03 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Jan 2020 22:57:51 GMT",
"version": "v3"
}
] | 2020-02-05 | [
[
"Boonserm",
"Petarpa",
"",
"Chulalongkorn University, Thailand Center of\n Excellence in Physics"
],
[
"Ngampitipan",
"Tritos",
"",
"Chandrakasem Rajabhat University,\n Thailand Center of Excellence in Physics"
],
[
"Simpson",
"Alex",
"",
"Victoria Univers... | Normally one thinks of the observed cosmological constant as being so small that it can be utterly neglected on typical astrophysical scales, only affecting extremely large-scale cosmology at Gigaparsec scales. Indeed, in those situations where the cosmological constant only has a quantitative influence on the physics, a separation of scales argument guarantees the effect is indeed negligible. The exception to this argument arises when the presence of a cosmological constant qualitatively changes the physics. One example of this phenomenon is the existence of outermost stable circular orbits (OSCOs) in the presence of a positive cosmological constant. Remarkably the size of these OSCOs are of a magnitude to be astrophysically interesting. For instance: for galactic masses the OSCOs are of order the inter-galactic spacing, for galaxy cluster masses the OSCOs are of order the size of the cluster. |
gr-qc/9706018 | null | S. Deser and Orit Levin | Accelerated Detectors and Temperature in (Anti) de Sitter Spaces | Latex +2 Fig | Class.Quant.Grav.14:L163-L168,1997 | 10.1088/0264-9381/14/9/003 | BRX-TH 415 | gr-qc hep-th | null | We show, in complete accord with the usual Rindler picture, that detectors
with constant acceleration $a$ in de Sitter (dS) and Anti de Sitter (AdS)
spaces with cosmological constants $\Lambda$ measure temperatures $2\pi
T=(\Lambda/3+a^{2})^{1/2}\equiv a_{5}$, the detector "5-acceleration" in the
embedding flat 5-space. For dS, this recovers a known result; in AdS, where
$\Lambda$ is negative, the temperature is well defined down to the critical
value $a_{5}=0$, again in accord with the underlying kinematics. The existence
of a thermal spectrum is also demonstrated for a variety of candidate wave
functions in AdS backgrounds.
| [
{
"created": "Fri, 6 Jun 1997 19:45:44 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Deser",
"S.",
""
],
[
"Levin",
"Orit",
""
]
] | We show, in complete accord with the usual Rindler picture, that detectors with constant acceleration $a$ in de Sitter (dS) and Anti de Sitter (AdS) spaces with cosmological constants $\Lambda$ measure temperatures $2\pi T=(\Lambda/3+a^{2})^{1/2}\equiv a_{5}$, the detector "5-acceleration" in the embedding flat 5-space. For dS, this recovers a known result; in AdS, where $\Lambda$ is negative, the temperature is well defined down to the critical value $a_{5}=0$, again in accord with the underlying kinematics. The existence of a thermal spectrum is also demonstrated for a variety of candidate wave functions in AdS backgrounds. |
0911.5512 | Leonid V. Verozub | Leonid V. Verozub | On some fundamental problems of the theory of gravitation | 9 pages, latex | null | null | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | Cosmological observations indicate that the Einstein equation may not be
entirely correct to describe gravity.
However, numerous modifications of these equations usually do not affect
foundations of the theory. In this paper two important issue that lead to a
substantial revision of the theory are considered : 1. The significance of
relativity of space-time geometry with respect to measuring instruments for
theory of gravitation. 2. The gauge transformations of the field variables in
correct theory of gravitation.
| [
{
"created": "Sun, 29 Nov 2009 20:11:19 GMT",
"version": "v1"
}
] | 2009-12-01 | [
[
"Verozub",
"Leonid V.",
""
]
] | Cosmological observations indicate that the Einstein equation may not be entirely correct to describe gravity. However, numerous modifications of these equations usually do not affect foundations of the theory. In this paper two important issue that lead to a substantial revision of the theory are considered : 1. The significance of relativity of space-time geometry with respect to measuring instruments for theory of gravitation. 2. The gauge transformations of the field variables in correct theory of gravitation. |
1804.02902 | Furkan Semih D\"undar | Furkan Semih D\"undar, Zahra Mirzaiyan, Metin Arik | Gravitational collapse of thin shell of dust in shape dynamics | 6 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We studied the gravitational collapse of a shell of dust in shape dynamics.
We found out static and oscillatory solutions. In the large momentum limit we
found out that the shell never reaches the singularity when the momentum of the
shell is much larger than the mass of the shell in magnitude. The shell does
not reach to the origin in a finite amount of time however when the momentum of
the shell becomes comparable to minus the mass of shell, the large momentum
approximation breaks down. Therefore more detailed future works hopefully may
be able to answer the question of singularity formation in this setup.
| [
{
"created": "Mon, 9 Apr 2018 10:39:22 GMT",
"version": "v1"
}
] | 2018-04-10 | [
[
"Dündar",
"Furkan Semih",
""
],
[
"Mirzaiyan",
"Zahra",
""
],
[
"Arik",
"Metin",
""
]
] | We studied the gravitational collapse of a shell of dust in shape dynamics. We found out static and oscillatory solutions. In the large momentum limit we found out that the shell never reaches the singularity when the momentum of the shell is much larger than the mass of the shell in magnitude. The shell does not reach to the origin in a finite amount of time however when the momentum of the shell becomes comparable to minus the mass of shell, the large momentum approximation breaks down. Therefore more detailed future works hopefully may be able to answer the question of singularity formation in this setup. |
2105.07455 | Rodrigo Tenorio | Rodrigo Tenorio, LIGO Scientific Collaboration, Virgo Collaboration | An all-sky search in early O3 LIGO data for continuous
gravitational-wave signals from unknown neutron stars in binary systems | contribution to the 2021 Gravitation session of the 55th Rencontres
de Moriond | null | null | LIGO-P2100166 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a search for continuous gravitational waves emitted by neutron
stars in binary systems conducted on data from the early third observing run of
the Advanced LIGO and Advanced Virgo detectors using the semicoherent,
GPU-accelerated, BinarySkyHough pipeline. The search analyzes the most
sensitive frequency band of the LIGO detectors, 50 - 300 Hz. Binary orbital
parameters are split into four regions, comprising orbital periods of 3 - 45
days and projected semimajor axes of 2 - 40 light-seconds. No detections are
reported. We estimate the sensitivity of the search using simulated continuous
wave signals, achieving the most sensitive results to date across the analyzed
parameter space.
| [
{
"created": "Sun, 16 May 2021 15:41:30 GMT",
"version": "v1"
}
] | 2021-05-18 | [
[
"Tenorio",
"Rodrigo",
""
],
[
"Collaboration",
"LIGO Scientific",
""
],
[
"Collaboration",
"Virgo",
""
]
] | We present a search for continuous gravitational waves emitted by neutron stars in binary systems conducted on data from the early third observing run of the Advanced LIGO and Advanced Virgo detectors using the semicoherent, GPU-accelerated, BinarySkyHough pipeline. The search analyzes the most sensitive frequency band of the LIGO detectors, 50 - 300 Hz. Binary orbital parameters are split into four regions, comprising orbital periods of 3 - 45 days and projected semimajor axes of 2 - 40 light-seconds. No detections are reported. We estimate the sensitivity of the search using simulated continuous wave signals, achieving the most sensitive results to date across the analyzed parameter space. |
2403.01495 | Haximjan Abdusattar | Haximjan Abdusattar, Shi-Bei Kong, Minawar Omar, Zhong-Wen Feng | Thermodynamics of the arbitrary dimensional FRW universe: Joule-Thomson
expansion | 16 pages,15 figures | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the thermodynamics especially the Joule-Thomson
expansion of the $n$-dimensional FRW (Friedmann-Robertson-Walker) universe with
a perfect fluid. We derive the thermodynamic equations of state $P=P(V, T)$ for
the $n$-dimensional FRW universe in Einstein gravity and Einstein-Gauss-Bonnet
gravity, where the thermodynamic pressure $P$ defined by the work density $W$
of the perfect fluid, $i.e.$ $P\equiv W$. Furthermore, we present the
Joule-Thomson expansion as an application of these equations of state to
elucidate the cooling-heating properties of the $n$-dimensional FRW universe.
We determine the inversion temperature and inversion pressure in the FRW
universe with arbitrary dimensions for the first time, and illustrate the
characteristics of inversion curves and isenthalpic curves in the $T$-$P$
plane. This study offers insights into deepening our comprehension of cooling
and heating regions in the FRW universe, thereby revealing its expansion
mechanisms.
| [
{
"created": "Sun, 3 Mar 2024 12:11:21 GMT",
"version": "v1"
}
] | 2024-03-05 | [
[
"Abdusattar",
"Haximjan",
""
],
[
"Kong",
"Shi-Bei",
""
],
[
"Omar",
"Minawar",
""
],
[
"Feng",
"Zhong-Wen",
""
]
] | In this paper, we investigate the thermodynamics especially the Joule-Thomson expansion of the $n$-dimensional FRW (Friedmann-Robertson-Walker) universe with a perfect fluid. We derive the thermodynamic equations of state $P=P(V, T)$ for the $n$-dimensional FRW universe in Einstein gravity and Einstein-Gauss-Bonnet gravity, where the thermodynamic pressure $P$ defined by the work density $W$ of the perfect fluid, $i.e.$ $P\equiv W$. Furthermore, we present the Joule-Thomson expansion as an application of these equations of state to elucidate the cooling-heating properties of the $n$-dimensional FRW universe. We determine the inversion temperature and inversion pressure in the FRW universe with arbitrary dimensions for the first time, and illustrate the characteristics of inversion curves and isenthalpic curves in the $T$-$P$ plane. This study offers insights into deepening our comprehension of cooling and heating regions in the FRW universe, thereby revealing its expansion mechanisms. |
2007.07160 | Silke Weinfurtner | Cisco Gooding, Steffen Biermann, Sebastian Erne, Jorma Louko, William
G. Unruh, Joerg Schmiedmayer and Silke Weinfurtner | Interferometric Unruh detectors for Bose-Einstein condensates | 9 pages, 2 figures | Phys. Rev. Lett. 125, 213603 (2020) | 10.1103/PhysRevLett.125.213603 | null | gr-qc cond-mat.quant-gas | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Unruh effect predicts a thermal response for an accelerated detector
moving through the vacuum. Here we propose an interferometric scheme to observe
an analogue of the circular Unruh effect using a localized laser coupled to a
Bose-Einstein condensate (BEC). Quantum fluctuations in the condensate are
governed by an effective relativistic field theory, and as demonstrated, the
coupled laser field acts as an effective Unruh-DeWitt detector thereof. The
effective speed of light is lowered by 12 orders of magnitude to the sound
velocity in the BEC. For detectors traveling close to the sound speed,
observation of the Unruh effect in the analogue system becomes experimentally
feasible.
| [
{
"created": "Tue, 14 Jul 2020 16:27:55 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Dec 2020 10:19:04 GMT",
"version": "v2"
}
] | 2020-12-22 | [
[
"Gooding",
"Cisco",
""
],
[
"Biermann",
"Steffen",
""
],
[
"Erne",
"Sebastian",
""
],
[
"Louko",
"Jorma",
""
],
[
"Unruh",
"William G.",
""
],
[
"Schmiedmayer",
"Joerg",
""
],
[
"Weinfurtner",
"Silke",
""
... | The Unruh effect predicts a thermal response for an accelerated detector moving through the vacuum. Here we propose an interferometric scheme to observe an analogue of the circular Unruh effect using a localized laser coupled to a Bose-Einstein condensate (BEC). Quantum fluctuations in the condensate are governed by an effective relativistic field theory, and as demonstrated, the coupled laser field acts as an effective Unruh-DeWitt detector thereof. The effective speed of light is lowered by 12 orders of magnitude to the sound velocity in the BEC. For detectors traveling close to the sound speed, observation of the Unruh effect in the analogue system becomes experimentally feasible. |
gr-qc/9901064 | null | Ruggiero de Ritis, Giuseppe Marmo, Bruno Preziosi | A new look at relativity transformations | 19 pages, Latex, 1 figure. Gen. Rel. Grav., to be published | Gen.Rel.Grav. 31 (1999) 1501-1517 | null | null | gr-qc | null | A free system, considered to be a comparison system, allows for the notion of
objective existence and inertial frame. Transformations connecting inertial
frames are shown to be either Lorentz or generalized Galilei.
| [
{
"created": "Sat, 23 Jan 1999 11:17:35 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Ritis",
"Ruggiero",
""
],
[
"Marmo",
"Giuseppe",
""
],
[
"Preziosi",
"Bruno",
""
]
] | A free system, considered to be a comparison system, allows for the notion of objective existence and inertial frame. Transformations connecting inertial frames are shown to be either Lorentz or generalized Galilei. |
1205.1390 | Md. Rahman Atiqur | M. Atiqur Rahman, M. Ilias Hossain | Hawking Non-thermal and Thermal Radiations of Schwarzschild Anti-de
Sitter Black Hole by Hamilton-Jacobi method | 6 pages. arXiv admin note: text overlap with arXiv:hep-th/0512351 | Astrophys Space Sci 345 (2013) 325 | 10.1007/s10509-013-1391-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The massive particles tunneling method has been used to investigate the
Hawking non-thermal and purely thermal radiations of Schwarzschild Anti-de
Sitter (SAdS) black hole. Considering the spacetime background to be dynamical,
incorporate the self-gravitation effect of the emitted particles the imaginary
part of the action has been derived from Hamilton-Jacobi equation. Using the
conservation laws of energy and angular momentum we have showed that the
non-thermal and purely thermal tunneling rates are related to the change of
Bekenstein-Hawking entropy and the derived emission spectrum deviates from the
pure thermal spectrum. The result obtained for SAdS black hole is also in
accordance with Parikh and Wilczek\rq s opinion and gives a correction to the
Hawking radiation of SAdS black hole.
| [
{
"created": "Mon, 7 May 2012 13:55:36 GMT",
"version": "v1"
}
] | 2013-05-28 | [
[
"Rahman",
"M. Atiqur",
""
],
[
"Hossain",
"M. Ilias",
""
]
] | The massive particles tunneling method has been used to investigate the Hawking non-thermal and purely thermal radiations of Schwarzschild Anti-de Sitter (SAdS) black hole. Considering the spacetime background to be dynamical, incorporate the self-gravitation effect of the emitted particles the imaginary part of the action has been derived from Hamilton-Jacobi equation. Using the conservation laws of energy and angular momentum we have showed that the non-thermal and purely thermal tunneling rates are related to the change of Bekenstein-Hawking entropy and the derived emission spectrum deviates from the pure thermal spectrum. The result obtained for SAdS black hole is also in accordance with Parikh and Wilczek\rq s opinion and gives a correction to the Hawking radiation of SAdS black hole. |
1008.2787 | Georgii Alekseev | G.A. Alekseev | Comment on F.J.Ernst, V.S.Manko and E.Ruiz "On interrelations between
Sibgatullin's and Alekseev's approaches to the construction of exact
solutions of the Einstein-Maxwell equations"
(J.Phys.:Conf.Ser.229(2010)012050; arXiv:1006.5118) | 11 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The necessity of this Comment was invoked by numerous mistakes, erroneous
discussions and misleading citations curiously collected in the paper of
F.J.Ernst, V.S.Manko and E.Ruiz and concerning the interrelations between two
integral equation methods developed for solution of Einstein - Maxwell
equations more than twenty five years ago. At first, we clarify the origin of
the errors in the paper of F.J.Ernst, V.S.Manko and E.Ruiz which gave rise to
so curious authors "conclusions" as that the monodromy transform integral
equations "...are simple combinations of Sibgatullin's integral equations and
normalizing conditions..." or even that "...in the electrovac case Alekseev's
integral equations are erroneous...". In the Comment, the way of correct
derivation of Sibgatullin's reduction of the Hauser and Ernst integral
equations in the context of the monodromy transform approach is briefly
outlined. In response to various speculations and priority claims collected in
the section 3 of the F.J.Ernst, V.S.Manko and E.Ruiz paper, the concrete
references are given here to the papers which were ignored completely by these
authors and which show that the so called "extended electrovacuum N-soliton
solutions" considered by E.Ruiz, V.S. Manko and J. Martin in 1995, are not new
because all these solutions are the particular cases of a larger class of
solutions constructed much earlier in explicit (determinant) form using the
monodromy transform equations, and that the real story of construction of the
solution for superposition of fields of two Reissner - Nordstr\"om sources and
of corresponding equilibrium configurations found in our papers with V.Belinski
differs crucially from that, which one can read in the paper of F.J.Ernst,
V.S.Manko and E.Ruiz.
| [
{
"created": "Mon, 16 Aug 2010 22:51:20 GMT",
"version": "v1"
}
] | 2010-08-18 | [
[
"Alekseev",
"G. A.",
""
]
] | The necessity of this Comment was invoked by numerous mistakes, erroneous discussions and misleading citations curiously collected in the paper of F.J.Ernst, V.S.Manko and E.Ruiz and concerning the interrelations between two integral equation methods developed for solution of Einstein - Maxwell equations more than twenty five years ago. At first, we clarify the origin of the errors in the paper of F.J.Ernst, V.S.Manko and E.Ruiz which gave rise to so curious authors "conclusions" as that the monodromy transform integral equations "...are simple combinations of Sibgatullin's integral equations and normalizing conditions..." or even that "...in the electrovac case Alekseev's integral equations are erroneous...". In the Comment, the way of correct derivation of Sibgatullin's reduction of the Hauser and Ernst integral equations in the context of the monodromy transform approach is briefly outlined. In response to various speculations and priority claims collected in the section 3 of the F.J.Ernst, V.S.Manko and E.Ruiz paper, the concrete references are given here to the papers which were ignored completely by these authors and which show that the so called "extended electrovacuum N-soliton solutions" considered by E.Ruiz, V.S. Manko and J. Martin in 1995, are not new because all these solutions are the particular cases of a larger class of solutions constructed much earlier in explicit (determinant) form using the monodromy transform equations, and that the real story of construction of the solution for superposition of fields of two Reissner - Nordstr\"om sources and of corresponding equilibrium configurations found in our papers with V.Belinski differs crucially from that, which one can read in the paper of F.J.Ernst, V.S.Manko and E.Ruiz. |
2407.18973 | Mirda Wijayanto Prisma | Mirda Prisma Wijayanto, Fiki Taufik Akbar, Bobby Eka Gunara | Classical Solutions of Higher Dimensional Einstein-Maxwell-Higgs System
With Nontrivial Potential: Global Existence and Completeness | 45 pages, no figure. arXiv admin note: text overlap with
arXiv:2304.09449 | null | null | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | We study the Cauchy problem of higher dimensional Einstein-Maxwell-Higgs
system in the framework of Bondi coordinates. As a first step, the problem is
reduced to a single first-order integro-differential equation by defining a
generalized ansatz function. Then, we employ contraction mapping to show that
there exists the unique fixed point of the problem. For a given small initial
data, we prove the existence of a global classical solution. Finally, by
introducing local mass and local charge functions in higher dimensions, we also
show the completeness property of the spacetimes.
| [
{
"created": "Mon, 22 Jul 2024 12:16:04 GMT",
"version": "v1"
}
] | 2024-07-30 | [
[
"Wijayanto",
"Mirda Prisma",
""
],
[
"Akbar",
"Fiki Taufik",
""
],
[
"Gunara",
"Bobby Eka",
""
]
] | We study the Cauchy problem of higher dimensional Einstein-Maxwell-Higgs system in the framework of Bondi coordinates. As a first step, the problem is reduced to a single first-order integro-differential equation by defining a generalized ansatz function. Then, we employ contraction mapping to show that there exists the unique fixed point of the problem. For a given small initial data, we prove the existence of a global classical solution. Finally, by introducing local mass and local charge functions in higher dimensions, we also show the completeness property of the spacetimes. |
gr-qc/9603028 | Hideyuki Tagoshi | Hideyuki Tagoshi, Masaru Shibata, Takahiro Tanaka, Misao Sasaki | Post-Newtonian expansion of gravitational waves from a particle in
circular orbits around a rotating black hole: Up to $O(v^8)$ beyond the
quadrupole formula | 27 pages, revtex, 6 figures, submitted to Physical Review D | Phys.Rev.D54:1439-1459,1996 | 10.1103/PhysRevD.54.1439 | GRP-434, OU-TAP 28 | gr-qc | null | Extending a method developed by Sasaki in the Schwarzschild case and by
Shibata, Sasaki, Tagoshi, and Tanaka in the Kerr case, we calculate the
post-Newtonian expansion of the gravitational wave luminosities from a test
particle in circular orbit around a rotating black hole up to $O(v^8)$ beyond
the quadrupole formula. The orbit of a test particle is restricted on the
equatorial plane. We find that spin dependent terms appear in each
post-Newtonian order, and that at $O(v^6)$ they have a significant effect on
the orbital phase evolution of coalescing compact binaries. By comparing the
post-Newtonian formula of the luminosity with numerical results we find that,
for $30M\lesssim r \lesssim 100M$, the spin dependent terms at $O(v^6)$ and
$O(v^7)$ improve the accuracy of the post-Newtonian formula significantly, but
those at $O(v^8)$ do not improve.
| [
{
"created": "Tue, 19 Mar 1996 09:13:22 GMT",
"version": "v1"
}
] | 2009-10-09 | [
[
"Tagoshi",
"Hideyuki",
""
],
[
"Shibata",
"Masaru",
""
],
[
"Tanaka",
"Takahiro",
""
],
[
"Sasaki",
"Misao",
""
]
] | Extending a method developed by Sasaki in the Schwarzschild case and by Shibata, Sasaki, Tagoshi, and Tanaka in the Kerr case, we calculate the post-Newtonian expansion of the gravitational wave luminosities from a test particle in circular orbit around a rotating black hole up to $O(v^8)$ beyond the quadrupole formula. The orbit of a test particle is restricted on the equatorial plane. We find that spin dependent terms appear in each post-Newtonian order, and that at $O(v^6)$ they have a significant effect on the orbital phase evolution of coalescing compact binaries. By comparing the post-Newtonian formula of the luminosity with numerical results we find that, for $30M\lesssim r \lesssim 100M$, the spin dependent terms at $O(v^6)$ and $O(v^7)$ improve the accuracy of the post-Newtonian formula significantly, but those at $O(v^8)$ do not improve. |
2303.03931 | Chen Lan | Han-Wen Hu, Chen Lan and Yan-Gang Miao | A regular black hole as the final state of evolution of a singular black
hole | Final version to appear in the EPJC, 42 pages, 24 figures, references
added | Eur. Phys. J. C 83, 1047 (2023) | 10.1140/epjc/s10052-023-12228-w | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We propose a novel black hole model in which singular and regular black holes
are combined as a whole and more precisely singular and regular black holes are
regarded as different states of parameter evolution. We refer to them as
singular and regular states, respectively. Furthermore, the regular state is
depicted by the final state of parameter evolution in the model. We also
present the sources that can generate such a black hole spacetime in the
framework of $F(R)$ gravity. This theory of modified gravity is adopted because
it offers a possible resolution to a tough issue in the thermodynamics of
regular black holes, namely the discrepancy between the thermal entropy and
Wald entropy. The dynamics and thermodynamics of the novel black hole model are
also discussed when a singular state evolves into a regular state during the
change of charge or horizon radius from its initial value to its extreme value.
| [
{
"created": "Tue, 7 Mar 2023 14:38:18 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Apr 2023 00:28:42 GMT",
"version": "v2"
},
{
"created": "Tue, 2 May 2023 07:17:59 GMT",
"version": "v3"
},
{
"created": "Fri, 17 Nov 2023 02:47:15 GMT",
"version": "v4"
}
] | 2023-11-20 | [
[
"Hu",
"Han-Wen",
""
],
[
"Lan",
"Chen",
""
],
[
"Miao",
"Yan-Gang",
""
]
] | We propose a novel black hole model in which singular and regular black holes are combined as a whole and more precisely singular and regular black holes are regarded as different states of parameter evolution. We refer to them as singular and regular states, respectively. Furthermore, the regular state is depicted by the final state of parameter evolution in the model. We also present the sources that can generate such a black hole spacetime in the framework of $F(R)$ gravity. This theory of modified gravity is adopted because it offers a possible resolution to a tough issue in the thermodynamics of regular black holes, namely the discrepancy between the thermal entropy and Wald entropy. The dynamics and thermodynamics of the novel black hole model are also discussed when a singular state evolves into a regular state during the change of charge or horizon radius from its initial value to its extreme value. |
gr-qc/0109049 | Lee Samuel Finn | Lee Samuel Finn and Patrick J. Sutton | Bounding the mass of the graviton using binary pulsar observations | 16 pages, 1 figure. Added appendix on other choices for mass term | Phys.Rev.D65:044022,2002 | 10.1103/PhysRevD.65.044022 | null | gr-qc astro-ph hep-th | null | The close agreement between the predictions of dynamical general relativity
for the radiated power of a compact binary system and the observed orbital
decay of the binary pulsars PSR B1913+16 and PSR B1534+12 allows us to bound
the graviton mass to be less than 7.6 x 10^{-20} eV with 90% confidence. This
bound is the first to be obtained from dynamic, as opposed to static-field,
relativity. The resulting limit on the graviton mass is within two orders of
magnitude of that from solar system measurements, and can be expected to
improve with further observations.
| [
{
"created": "Thu, 13 Sep 2001 20:10:19 GMT",
"version": "v1"
},
{
"created": "Tue, 14 May 2002 17:34:55 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Finn",
"Lee Samuel",
""
],
[
"Sutton",
"Patrick J.",
""
]
] | The close agreement between the predictions of dynamical general relativity for the radiated power of a compact binary system and the observed orbital decay of the binary pulsars PSR B1913+16 and PSR B1534+12 allows us to bound the graviton mass to be less than 7.6 x 10^{-20} eV with 90% confidence. This bound is the first to be obtained from dynamic, as opposed to static-field, relativity. The resulting limit on the graviton mass is within two orders of magnitude of that from solar system measurements, and can be expected to improve with further observations. |
2201.11445 | Sebasti\'an Bahamonde Dr | Sebastian Bahamonde, Ludovic Ducobu, Christian Pfeifer | Scalarized Black Holes in Teleparallel Gravity | 20 pages. Matches published version in JCAP | JCAP 04 (2022) 04, 018 | 10.1088/1475-7516/2022/04/018 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes play a crucial role in the understanding of the gravitational
interaction. Through the direct observation of the shadow of a black hole by
the event horizon telescope and the detection of gravitational waves of merging
black holes we now start to have direct access to their properties and
behaviour, which means the properties and behaviour of gravity. This further
raised the demand for models to compare with those observations. In this
respect, an important question regarding black holes properties is to know if
they can support "hairs". While this is famously forbidden in general
relativity, in particular for scalar fields, by the so-called no-hair theorems,
hairy black holes have been shown to exist in several class of scalar-tensor
theories of gravity. In this article we investigate the existence of scalarized
black holes in scalar-torsion theories of gravity. On one hand, we find exact
solutions for certain choices of couplings between a scalar field and the
torsion tensor of a teleparallel connection and certain scalar field
potentials, and thus proof the existence of scalarized black holes in these
theories. On the other hand, we show that it is possible to establish
no-scalar-hair theorems similar to what is known in general relativity for
other choices of these functions.
| [
{
"created": "Thu, 27 Jan 2022 11:07:11 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Apr 2022 04:35:44 GMT",
"version": "v2"
}
] | 2022-04-19 | [
[
"Bahamonde",
"Sebastian",
""
],
[
"Ducobu",
"Ludovic",
""
],
[
"Pfeifer",
"Christian",
""
]
] | Black holes play a crucial role in the understanding of the gravitational interaction. Through the direct observation of the shadow of a black hole by the event horizon telescope and the detection of gravitational waves of merging black holes we now start to have direct access to their properties and behaviour, which means the properties and behaviour of gravity. This further raised the demand for models to compare with those observations. In this respect, an important question regarding black holes properties is to know if they can support "hairs". While this is famously forbidden in general relativity, in particular for scalar fields, by the so-called no-hair theorems, hairy black holes have been shown to exist in several class of scalar-tensor theories of gravity. In this article we investigate the existence of scalarized black holes in scalar-torsion theories of gravity. On one hand, we find exact solutions for certain choices of couplings between a scalar field and the torsion tensor of a teleparallel connection and certain scalar field potentials, and thus proof the existence of scalarized black holes in these theories. On the other hand, we show that it is possible to establish no-scalar-hair theorems similar to what is known in general relativity for other choices of these functions. |
2404.10742 | Zhong-Hao Luo | Zhong-Hao Luo, Yun-Long Zhang | Superradiant instability of area quantized Kerr black hole with discrete
reflectivity | 10 pages, 5 figures | null | null | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Ultralight bosons can condense to form the so-called bosonic clouds around
spinning black holes by superradiance instability. When quantum effects are
taken into account, the classical black holes were replaced by exotic compact
objects including area quantized black holes. In this work, we consider the
superradiant instabilities of massive scalar fields around area quantized Kerr
black hole. We introduce the reflectivity of area quantized black hole
possesses the distinct discrete feature, and the scalar fields have the
superradiant modes solution only within the specific mass range. In addition,
the area quantization may terminate the superradiance when the black hole spins
down, or even suppress the formation of the bosionic cloud.
| [
{
"created": "Tue, 16 Apr 2024 17:18:07 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Aug 2024 01:47:19 GMT",
"version": "v2"
}
] | 2024-08-13 | [
[
"Luo",
"Zhong-Hao",
""
],
[
"Zhang",
"Yun-Long",
""
]
] | Ultralight bosons can condense to form the so-called bosonic clouds around spinning black holes by superradiance instability. When quantum effects are taken into account, the classical black holes were replaced by exotic compact objects including area quantized black holes. In this work, we consider the superradiant instabilities of massive scalar fields around area quantized Kerr black hole. We introduce the reflectivity of area quantized black hole possesses the distinct discrete feature, and the scalar fields have the superradiant modes solution only within the specific mass range. In addition, the area quantization may terminate the superradiance when the black hole spins down, or even suppress the formation of the bosionic cloud. |
1203.1859 | Lorenzo Iorio | Lorenzo Iorio | Orbital effects of Lorentz-violating Standard Model Extension
gravitomagnetism around a static body: a sensitivity analysis | LaTex2e, 9 pages, no figures, 3 tables, 25 references. Typos fixed | Class. Quant. Gravit..29:175007,2012 | 10.1088/0264-9381/29/17/175007 | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analytically work out the long-term rates of change of the six osculating
Keplerian orbital elements of a test particle acted upon by the
Lorentz-violating gravitomagnetic acceleration due to a static body, as
predicted by the Standard Model Extension (SME). We neither restrict to any
specific spatial orientation for the symmetry-violating vector s nor make a
priori simplifying assumptions concerning the orbital configuration of the
perturbed test particle. Thus, our results are quite general, and can be
applied for sensitivity analyses to a variety of specific astronomical and
astrophysical scenarios. We find that, apart from the semimajor axis a, all the
other orbital elements undergo non-vanishing secular variations. By comparing
our results to the latest determinations of the supplementary advances of the
perihelia of some planets of the solar system we preliminarily obtain s_x =
(0.9 +/- 1.5) 10^-8, s_y = (-4 +/- 6) 10^-9, s_z = (0.3 +/- 1) 10^-9. Bounds
from the terrestrial LAGEOS and LAGEOS II satellites are of the order of s\sim
10^-3-10^-4.
| [
{
"created": "Thu, 8 Mar 2012 17:31:10 GMT",
"version": "v1"
},
{
"created": "Sun, 11 Mar 2012 01:07:18 GMT",
"version": "v2"
}
] | 2012-08-22 | [
[
"Iorio",
"Lorenzo",
""
]
] | We analytically work out the long-term rates of change of the six osculating Keplerian orbital elements of a test particle acted upon by the Lorentz-violating gravitomagnetic acceleration due to a static body, as predicted by the Standard Model Extension (SME). We neither restrict to any specific spatial orientation for the symmetry-violating vector s nor make a priori simplifying assumptions concerning the orbital configuration of the perturbed test particle. Thus, our results are quite general, and can be applied for sensitivity analyses to a variety of specific astronomical and astrophysical scenarios. We find that, apart from the semimajor axis a, all the other orbital elements undergo non-vanishing secular variations. By comparing our results to the latest determinations of the supplementary advances of the perihelia of some planets of the solar system we preliminarily obtain s_x = (0.9 +/- 1.5) 10^-8, s_y = (-4 +/- 6) 10^-9, s_z = (0.3 +/- 1) 10^-9. Bounds from the terrestrial LAGEOS and LAGEOS II satellites are of the order of s\sim 10^-3-10^-4. |
1610.09819 | Panagiota Kanti | Athanasios Bakopoulos and Panagiota Kanti | Novel Ansatzes and Scalar Quantities in Gravito-Electromagnetism | Latex2e file, 29 pages, comments and references added, a shortened
version to appear in General Relativity and Gravitation | null | 10.1007/s10714-017-2207-x | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we focus on the theory of Gravito-Electromagnetism (GEM) -- the
theory that describes the dynamics of the gravitational field in terms of
quantities met in Electromagnetism -- and we propose two novel forms of metric
perturbations. The first one is a generalisation of the traditional GEM ansatz,
and succeeds in reproducing the whole set of Maxwell's equations even for a
dynamical vector potential A. The second form, the so-called alternative
ansatz, goes beyond that leading to an expression for the Lorentz force that
matches the one of Electromagnetism and is free of additional terms even for a
dynamical scalar potential \Phi. In the context of the linearised theory, we
then search for scalar invariant quantities in analogy to Electromagnetism. We
define three novel, 3rd-rank gravitational tensors, and demonstrate that the
last two can be employed to construct scalar quantities that succeed in giving
results very similar to those found in Electromagnetism. Finally, the gauge
invariance of the linearised gravitational theory is studied, and shown to lead
to the gauge invariance of the GEM fields E and B for a general configuration
of the arbitrary vector involved in the coordinate transformations.
| [
{
"created": "Mon, 31 Oct 2016 08:28:02 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Mar 2017 07:55:50 GMT",
"version": "v2"
}
] | 2017-03-13 | [
[
"Bakopoulos",
"Athanasios",
""
],
[
"Kanti",
"Panagiota",
""
]
] | In this work, we focus on the theory of Gravito-Electromagnetism (GEM) -- the theory that describes the dynamics of the gravitational field in terms of quantities met in Electromagnetism -- and we propose two novel forms of metric perturbations. The first one is a generalisation of the traditional GEM ansatz, and succeeds in reproducing the whole set of Maxwell's equations even for a dynamical vector potential A. The second form, the so-called alternative ansatz, goes beyond that leading to an expression for the Lorentz force that matches the one of Electromagnetism and is free of additional terms even for a dynamical scalar potential \Phi. In the context of the linearised theory, we then search for scalar invariant quantities in analogy to Electromagnetism. We define three novel, 3rd-rank gravitational tensors, and demonstrate that the last two can be employed to construct scalar quantities that succeed in giving results very similar to those found in Electromagnetism. Finally, the gauge invariance of the linearised gravitational theory is studied, and shown to lead to the gauge invariance of the GEM fields E and B for a general configuration of the arbitrary vector involved in the coordinate transformations. |
2208.10882 | Mordehai Milgrom | Mordehai Milgrom | Broader view of bimetric MOND | 18 pages. Version matching the published one | Physical Review D 106, 084010 (2022) | 10.1103/PhysRevD.106.084010 | null | gr-qc astro-ph.CO astro-ph.GA hep-ph | http://creativecommons.org/licenses/by/4.0/ | All existing treatments of bimetric MOND (BIMOND) -- a class of relativistic
versions of MOND -- have dealt with a rather restricted sub-class: The
Lagrangian of the interaction between the gravitational degrees of freedom --
the two metrics -- is a function of a certain {\it single} scalar argument
built from the difference in connections of the two metrics. I show that the
scope of BIMOND is much richer: The two metrics can couple through several
scalars to give theories that all have a "good" nonrelativistic (NR) limit --
one that accounts correctly, a-la MOND, for the dynamics of galactic systems,
{\it including gravitational lensing}. This extended-BIMOND framework exhibits
a qualitative departure from the way we think of MOND at present, as
encapsulated, in all its aspects, by one "interpolating function" of one
acceleration variable. After deriving the general field equations, I pinpoint
the subclass of theories that satisfy the pivotal requirement of a good NR
limit. These involve three independent, quadratic scalar variables. In the NR
limit these scalars all reduce to the same acceleration scalar, and the NR
theory then does hinge on one function of a {\it a single} acceleration
variable -- representing the NR MOND "interpolating function", whose form is
largely dictated by the observed NR galactic dynamics. However, these scalars
behave differently, in different relativistic contexts. So, the full richness
of the multi-variable Lagrangian, as it enters cosmology, for example, is
hardly informed by what we learn from observations of galactic dynamics. In
this paper, I present the formalism, with some generic examples. I also
consider some cosmological solutions where the two metrics are small departures
from one Friedman-Lemaitre-Robertson-Walker metric. This may offer a framework
for describing cosmology within the extended BIMOND.
| [
{
"created": "Tue, 23 Aug 2022 11:32:09 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Sep 2022 13:00:17 GMT",
"version": "v2"
},
{
"created": "Tue, 11 Oct 2022 09:29:38 GMT",
"version": "v3"
}
] | 2022-10-12 | [
[
"Milgrom",
"Mordehai",
""
]
] | All existing treatments of bimetric MOND (BIMOND) -- a class of relativistic versions of MOND -- have dealt with a rather restricted sub-class: The Lagrangian of the interaction between the gravitational degrees of freedom -- the two metrics -- is a function of a certain {\it single} scalar argument built from the difference in connections of the two metrics. I show that the scope of BIMOND is much richer: The two metrics can couple through several scalars to give theories that all have a "good" nonrelativistic (NR) limit -- one that accounts correctly, a-la MOND, for the dynamics of galactic systems, {\it including gravitational lensing}. This extended-BIMOND framework exhibits a qualitative departure from the way we think of MOND at present, as encapsulated, in all its aspects, by one "interpolating function" of one acceleration variable. After deriving the general field equations, I pinpoint the subclass of theories that satisfy the pivotal requirement of a good NR limit. These involve three independent, quadratic scalar variables. In the NR limit these scalars all reduce to the same acceleration scalar, and the NR theory then does hinge on one function of a {\it a single} acceleration variable -- representing the NR MOND "interpolating function", whose form is largely dictated by the observed NR galactic dynamics. However, these scalars behave differently, in different relativistic contexts. So, the full richness of the multi-variable Lagrangian, as it enters cosmology, for example, is hardly informed by what we learn from observations of galactic dynamics. In this paper, I present the formalism, with some generic examples. I also consider some cosmological solutions where the two metrics are small departures from one Friedman-Lemaitre-Robertson-Walker metric. This may offer a framework for describing cosmology within the extended BIMOND. |
1109.0330 | Michael Coughlin | LIGO Scientific Collaboration, Virgo Collaboration: Michael W.
Coughlin | Noise Line Identification in LIGO S6 and Virgo VSR2 | 9 pages, 4 figures, 14th Gravitational Wave Data Analysis Workshop
(Rome, Italy) | 2010 J. Phys.: Conf. Ser. 243 012010 | 10.1088/1742-6596/243/1/012010 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An important goal for LIGO (the Laser Interferometer Gravitational-Wave
Observatory) and Virgo is to find periodic sources of gravitational waves. The
LIGO and Virgo detectors are sensitive to a variety of noise of
non-astrophysical origin, such as instrumental artifacts and environmental
disturbances. These artifacts make it difficult to know when a signal is due to
a gravitational wave or noise. A continuous wave search algorithm, Fscan, and
the calculation of the coherence between the gravitational wave channels and
auxiliary channels has been developed to identify the source of noise lines.
The programs analyze data from the gravitational wave channels as well as
environmental sensors, searching for significant lines that appear in
coincidence (using various thresholds and frequency windows) in the
gravitational wave channel as well the environmental monitors. By this method,
the source of powerful signals at specific frequencies in the gravitational
wave channel caused by noise can be determined. Examples from LIGO's sixth
science run, S6, and Virgo' second scientific run, VSR2, are presented.
| [
{
"created": "Fri, 2 Sep 2011 00:03:51 GMT",
"version": "v1"
}
] | 2012-08-27 | [
[
"LIGO Scientific Collaboration",
"",
""
],
[
"Virgo Collaboration",
"",
""
],
[
"Coughlin",
"Michael W.",
""
]
] | An important goal for LIGO (the Laser Interferometer Gravitational-Wave Observatory) and Virgo is to find periodic sources of gravitational waves. The LIGO and Virgo detectors are sensitive to a variety of noise of non-astrophysical origin, such as instrumental artifacts and environmental disturbances. These artifacts make it difficult to know when a signal is due to a gravitational wave or noise. A continuous wave search algorithm, Fscan, and the calculation of the coherence between the gravitational wave channels and auxiliary channels has been developed to identify the source of noise lines. The programs analyze data from the gravitational wave channels as well as environmental sensors, searching for significant lines that appear in coincidence (using various thresholds and frequency windows) in the gravitational wave channel as well the environmental monitors. By this method, the source of powerful signals at specific frequencies in the gravitational wave channel caused by noise can be determined. Examples from LIGO's sixth science run, S6, and Virgo' second scientific run, VSR2, are presented. |
1009.1985 | Eliu Huerta | E.A. Huerta and Jonathan R. Gair | Intermediate-mass-ratio-inspirals in the Einstein Telescope: I.
Signal-to-noise ratio calculations | 27 pages, 9 figures, v3 has an updated reference for consistency with
accepted version | Phys.Rev.D83:044020,2011 | 10.1103/PhysRevD.83.044020 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Einstein Telescope (ET) is a proposed third generation ground-based
interferometer, for which the target is a sensitivity that is a factor of ten
better than Advanced LIGO and a frequency range that extends down to about 1Hz.
ET will provide opportunities to test Einstein's theory of relativity in the
strong field and will realize precision gravitational wave astronomy with a
thousandfold increase in the expected number of events over the advanced
ground-based detectors. A design study for ET is currently underway, so it is
timely to assess the science that could be done with such an instrument. This
paper is the first in a series that will carry out a detailed study of
intermediate-mass-ratio inspirals (IMRIs) for ET. In the context of ET, an IMRI
is the inspiral of a neutron star or stellar-mass black hole into an
intermediate mass black hole (IMBH). In this paper we focus on the development
of IMRI waveform models for circular and equatorial inspirals. We consider two
approximations for the waveforms, which both incorporate the inspiral, merger
and ringdown phases in a consistent way. One approximation, valid for IMBHs of
arbitrary spin, uses the transition model of Ori and Thorne [1] to describe the
merger, and this is then matched smoothly onto a ringdown waveform. The second
approximation uses the Effective One Body (EOB) approach to model the merger
phase of the waveform and is valid for non-spinning IMBHs. In this paper, we
use both waveform models to compute signal-to-noise ratios (SNRs) for IMRI
sources detectable by ET. At a redshift of z=1, we find typical SNRs for IMRI
systems with masses 1.4+100 solar masses, 10+100 solar masses, 1.4+500 solar
masses and 10+500 solar masses of about 10-25, 40-80, 3-15 and 10-60,
respectively. We also find that the two models make predictions for
non-spinning inspirals that are consistent to about ten percent.
| [
{
"created": "Fri, 10 Sep 2010 11:34:22 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Dec 2010 17:04:06 GMT",
"version": "v2"
},
{
"created": "Fri, 11 Feb 2011 10:23:50 GMT",
"version": "v3"
}
] | 2011-02-18 | [
[
"Huerta",
"E. A.",
""
],
[
"Gair",
"Jonathan R.",
""
]
] | The Einstein Telescope (ET) is a proposed third generation ground-based interferometer, for which the target is a sensitivity that is a factor of ten better than Advanced LIGO and a frequency range that extends down to about 1Hz. ET will provide opportunities to test Einstein's theory of relativity in the strong field and will realize precision gravitational wave astronomy with a thousandfold increase in the expected number of events over the advanced ground-based detectors. A design study for ET is currently underway, so it is timely to assess the science that could be done with such an instrument. This paper is the first in a series that will carry out a detailed study of intermediate-mass-ratio inspirals (IMRIs) for ET. In the context of ET, an IMRI is the inspiral of a neutron star or stellar-mass black hole into an intermediate mass black hole (IMBH). In this paper we focus on the development of IMRI waveform models for circular and equatorial inspirals. We consider two approximations for the waveforms, which both incorporate the inspiral, merger and ringdown phases in a consistent way. One approximation, valid for IMBHs of arbitrary spin, uses the transition model of Ori and Thorne [1] to describe the merger, and this is then matched smoothly onto a ringdown waveform. The second approximation uses the Effective One Body (EOB) approach to model the merger phase of the waveform and is valid for non-spinning IMBHs. In this paper, we use both waveform models to compute signal-to-noise ratios (SNRs) for IMRI sources detectable by ET. At a redshift of z=1, we find typical SNRs for IMRI systems with masses 1.4+100 solar masses, 10+100 solar masses, 1.4+500 solar masses and 10+500 solar masses of about 10-25, 40-80, 3-15 and 10-60, respectively. We also find that the two models make predictions for non-spinning inspirals that are consistent to about ten percent. |
1205.4055 | Santanu Das | Santanu Das | Machian gravity and a cosmology without dark matter and dark energy | 12 pages | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The standard model of cosmology is based on the general theory of relativity
and demands more than 95\% of the universe to consist of dark matter and dark
energy that has no direct observational evidence till date. The foundation of
the concept these dark components are based on a fixed relation between the
strength of the gravitational field and the matter density. Alternate models
are put forward in past to explain the observations without dark components in
the universe. Though they have their own merits and draw backs. In this paper
we propose a new cosmological model based on Mach's principle. It provides a
similar cosmology as that of the standard cosmological model without any ad-hoc
dark matter or dark energy. We show that the theory naturally provides some
geometric terms that behave like dark mater and dark energy and dark radiation.
The presence of dark radiation provides new observational features in
cosmology. We show that the theory is supported by observational data from Big
Bang Nucleosynthesis and Cosmic Microwave Background, and provides an
explanations for excess number of effective neutrino species and higher Helium
mass fraction in the universe. We also calculate the best fit cosmological
parameters for our model using Planck+WP data.
| [
{
"created": "Thu, 17 May 2012 22:48:47 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Apr 2015 16:14:52 GMT",
"version": "v2"
}
] | 2015-04-13 | [
[
"Das",
"Santanu",
""
]
] | The standard model of cosmology is based on the general theory of relativity and demands more than 95\% of the universe to consist of dark matter and dark energy that has no direct observational evidence till date. The foundation of the concept these dark components are based on a fixed relation between the strength of the gravitational field and the matter density. Alternate models are put forward in past to explain the observations without dark components in the universe. Though they have their own merits and draw backs. In this paper we propose a new cosmological model based on Mach's principle. It provides a similar cosmology as that of the standard cosmological model without any ad-hoc dark matter or dark energy. We show that the theory naturally provides some geometric terms that behave like dark mater and dark energy and dark radiation. The presence of dark radiation provides new observational features in cosmology. We show that the theory is supported by observational data from Big Bang Nucleosynthesis and Cosmic Microwave Background, and provides an explanations for excess number of effective neutrino species and higher Helium mass fraction in the universe. We also calculate the best fit cosmological parameters for our model using Planck+WP data. |
gr-qc/9510005 | Kiyoshi Shiraishi | Kiyoshi Shiraishi (Akita Junior College) and Takuya Maki (Kitasato
Univ.) | Statistical Mechanics of Charged Particles in Einstein-Maxwell-Scalar
Theory | 11 pages, RevTeX3.0 | Phys.Rev.D53:3070-3073,1996 | 10.1103/PhysRevD.53.3070 | AJC-HEP-27 | gr-qc | null | We consider an $N$-body system of charged particle coupled to gravitational,
electromagnetic, and scalar fields. The metric on moduli space for the system
can be considered if a relation among the charges and mass is satisfied, which
includes the BPS relation for monopoles and the extreme condition for charged
black holes. Using the metric on moduli space in the long distance
approximation, we study the statistical mechanics of the charged particles at
low velocities. The partition function is evaluated as the leading order of the
large $d$ expansion, where $d$ is the spatial dimension of the system and will
be substituted finally as $d=3$.
| [
{
"created": "Wed, 4 Oct 1995 09:30:35 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Shiraishi",
"Kiyoshi",
"",
"Akita Junior College"
],
[
"Maki",
"Takuya",
"",
"Kitasato\n Univ."
]
] | We consider an $N$-body system of charged particle coupled to gravitational, electromagnetic, and scalar fields. The metric on moduli space for the system can be considered if a relation among the charges and mass is satisfied, which includes the BPS relation for monopoles and the extreme condition for charged black holes. Using the metric on moduli space in the long distance approximation, we study the statistical mechanics of the charged particles at low velocities. The partition function is evaluated as the leading order of the large $d$ expansion, where $d$ is the spatial dimension of the system and will be substituted finally as $d=3$. |
1902.05851 | Jose Luis Bl\'azquez-Salcedo | Jose Luis Bl\'azquez-Salcedo, Christian Knoll, Eugen Radu | Boson and Dirac stars in $D\geq 4$ dimensions | 15 pages, 4 figures | Phys.Lett. B793 (2019) 161-168 | 10.1016/j.physletb.2019.04.035 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a comparative study of spherically symmetric, localized,
particle-like solutions for spin $s=0,1/2$ and $1$ gravitating fields in a
$D$-dimensional, asymptotically flat spacetime. These fields are massive,
possessing a harmonic time dependence and no self-interaction. Special
attention is paid to the mathematical similarities and physical differences
between the bosonic and fermonic cases. We find that the generic pattern of
solutions is similar for any value of the spin $s$, depending only on the
dimensionality of spacetime, the cases $D=4,5$ being special.
| [
{
"created": "Fri, 15 Feb 2019 15:38:06 GMT",
"version": "v1"
}
] | 2020-02-26 | [
[
"Blázquez-Salcedo",
"Jose Luis",
""
],
[
"Knoll",
"Christian",
""
],
[
"Radu",
"Eugen",
""
]
] | We present a comparative study of spherically symmetric, localized, particle-like solutions for spin $s=0,1/2$ and $1$ gravitating fields in a $D$-dimensional, asymptotically flat spacetime. These fields are massive, possessing a harmonic time dependence and no self-interaction. Special attention is paid to the mathematical similarities and physical differences between the bosonic and fermonic cases. We find that the generic pattern of solutions is similar for any value of the spin $s$, depending only on the dimensionality of spacetime, the cases $D=4,5$ being special. |
2104.13760 | Ghulam Mustafa | G. Mustafa, Mushtaq Ahmad, Ali \"Ovg\"un, M. Farasat Shamir, Ibrar
Hussain | Traversable wormholes in the extended teleparallel theory of gravity
with matter coupling | 20 pages, 13 figures, submitted for publication | Fortschr. Phys. 2021, 69, 2100048 | 10.1002/prop.202100048 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This study explores the Gaussian and the Lorentzian distributed spherically
symmetric wormhole solutions in the $f(\tau, T)$ gravity. The basic idea of the
Gaussian and Lorentzian noncommutative geometries emerges as the physically
acceptable and substantial notion in quantum physics. This idea of the
noncommutative geometries with both the Gaussian and Lorentzian distributions
becomes more striking when wormhole geometries in the modified theories of
gravity are discussed. Here we consider a linear model within $f(\tau,T)$
gravity to investigate traversable wormholes. In particular, we discuss the
possible cases for the wormhole geometries using the Gaussian and the
Lorentzian noncommutative distributions to obtain the exact shape function for
them. By incorporating the particular values of the unknown parameters
involved, we discuss different properties of the new wormhole geometries
explored here. It is noted that the involved matter violates the weak energy
condition for both the cases of the noncommutative geometries, whereas there is
a possibility for a physically viable wormhole solution. By analyzing the
equilibrium condition, it is found that the acquired solutions are stable.
Furthermore, we provide the embedded diagrams for wormhole structures under
Gaussian and Lorentzian noncommutative frameworks. Moreover, we present the
critical analysis on an anisotropic pressure under the Gaussian and the
Lorentzian distributions.
| [
{
"created": "Tue, 27 Apr 2021 10:04:49 GMT",
"version": "v1"
}
] | 2023-01-31 | [
[
"Mustafa",
"G.",
""
],
[
"Ahmad",
"Mushtaq",
""
],
[
"Övgün",
"Ali",
""
],
[
"Shamir",
"M. Farasat",
""
],
[
"Hussain",
"Ibrar",
""
]
] | This study explores the Gaussian and the Lorentzian distributed spherically symmetric wormhole solutions in the $f(\tau, T)$ gravity. The basic idea of the Gaussian and Lorentzian noncommutative geometries emerges as the physically acceptable and substantial notion in quantum physics. This idea of the noncommutative geometries with both the Gaussian and Lorentzian distributions becomes more striking when wormhole geometries in the modified theories of gravity are discussed. Here we consider a linear model within $f(\tau,T)$ gravity to investigate traversable wormholes. In particular, we discuss the possible cases for the wormhole geometries using the Gaussian and the Lorentzian noncommutative distributions to obtain the exact shape function for them. By incorporating the particular values of the unknown parameters involved, we discuss different properties of the new wormhole geometries explored here. It is noted that the involved matter violates the weak energy condition for both the cases of the noncommutative geometries, whereas there is a possibility for a physically viable wormhole solution. By analyzing the equilibrium condition, it is found that the acquired solutions are stable. Furthermore, we provide the embedded diagrams for wormhole structures under Gaussian and Lorentzian noncommutative frameworks. Moreover, we present the critical analysis on an anisotropic pressure under the Gaussian and the Lorentzian distributions. |
1801.00911 | Hamidreza Saiedi | H. Saiedi | Energy Conditions in Palatini Approach to Modified $f(R)$ Gravity | null | Journal of High Energy Physics, Gravitation and Cosmology, Vol.6
No.4, (2020) | 10.4236/jhepgc.2020.64046 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we review modified $f(R)$ theories of gravity in Palatini
formalism. In this framework, , we use the Raychaudhuri's equation along with
the requirement that the gravity is attractive, which holds for any geometrical
theory of gravity to discuss the energy conditions. Then, to derive these
conditions, we obtain an expression for effective pressure and energy density
by considering FLRW metric. Energy conditions derived in Palatini version of
$f(R)$ Gravity differ from those derived in GR. We will see that the WEC (weak
energy condition) derived in Palatini formalism has exactly the same expression
in its metric approach.
| [
{
"created": "Wed, 3 Jan 2018 06:15:44 GMT",
"version": "v1"
}
] | 2021-03-02 | [
[
"Saiedi",
"H.",
""
]
] | In this paper, we review modified $f(R)$ theories of gravity in Palatini formalism. In this framework, , we use the Raychaudhuri's equation along with the requirement that the gravity is attractive, which holds for any geometrical theory of gravity to discuss the energy conditions. Then, to derive these conditions, we obtain an expression for effective pressure and energy density by considering FLRW metric. Energy conditions derived in Palatini version of $f(R)$ Gravity differ from those derived in GR. We will see that the WEC (weak energy condition) derived in Palatini formalism has exactly the same expression in its metric approach. |
0704.3769 | Matthew Glenz | Matthew M. Glenz and Koji Uryu | Circular solution of two unequal mass particles in post-Minkowski
approximation | 4 pages, 4 figures, 4/27/07 | Phys.Rev.D76:027501,2007 | 10.1103/PhysRevD.76.027501 | DPUR/TH/2 | gr-qc | null | A Fokker action for post-Minkowski approximation with the first
post-Newtonian correction is introduced in our previous paper, and a solution
for the helically symmetric circular orbit is obtained. We present supplemental
results for the circular solution of two unequal mass point-particles. Circular
solutions for selected mass ratios are found numerically, and analytic formulas
in the extreme mass ratio limit are derived. The leading terms of the analytic
formulas agree with the first post-Newtonian formulas in this limit.
| [
{
"created": "Sat, 28 Apr 2007 02:12:32 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Glenz",
"Matthew M.",
""
],
[
"Uryu",
"Koji",
""
]
] | A Fokker action for post-Minkowski approximation with the first post-Newtonian correction is introduced in our previous paper, and a solution for the helically symmetric circular orbit is obtained. We present supplemental results for the circular solution of two unequal mass point-particles. Circular solutions for selected mass ratios are found numerically, and analytic formulas in the extreme mass ratio limit are derived. The leading terms of the analytic formulas agree with the first post-Newtonian formulas in this limit. |
gr-qc/0605005 | Yaneer Bar-Yam | Yaneer Bar-Yam | ZM theory III: Classical oscillators and semi-classical Bohr-Sommerfeld
quantization | 16 pages, 1 figure | null | null | NECSI Report 2006-04-01 | gr-qc | null | We consider the description of classical oscillatory motion in ZM theory, and
explore the relationship of ZM theory to semi-classical Bohr-Sommerfeld
quantization. The treatment illustrates some features of ZM theory, especially
the inadequacies of classical and semi-classical treatments due to
non-analyticity of the mapping of classical trajectories onto the ZM clock
field. While the more complete ZM formalism is not developed here, the
non-analyticities in the classical treatment resemble issues in the comparison
of classical and quantum formalisms. We also show that semi-classical
quantization is valid for a periodic manifold in ZM theory, though the quantum
number $n=0$ is allowed, as it would be in quantum mechanics for a periodic
manifold. Still, this suggests a connection to the first-order success of Bohr
theory in describing the phenomenology of atomic quantum states. The
approximate nature of the semi-classical treatment of three dimensional atomic
orbits is, however, also apparent in relation to ZM theory. These observations
are preliminary to a discussion of ZM theory in relation to quantum mechanics
and quantum field theory in subsequent papers.
| [
{
"created": "Sun, 30 Apr 2006 18:27:11 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bar-Yam",
"Yaneer",
""
]
] | We consider the description of classical oscillatory motion in ZM theory, and explore the relationship of ZM theory to semi-classical Bohr-Sommerfeld quantization. The treatment illustrates some features of ZM theory, especially the inadequacies of classical and semi-classical treatments due to non-analyticity of the mapping of classical trajectories onto the ZM clock field. While the more complete ZM formalism is not developed here, the non-analyticities in the classical treatment resemble issues in the comparison of classical and quantum formalisms. We also show that semi-classical quantization is valid for a periodic manifold in ZM theory, though the quantum number $n=0$ is allowed, as it would be in quantum mechanics for a periodic manifold. Still, this suggests a connection to the first-order success of Bohr theory in describing the phenomenology of atomic quantum states. The approximate nature of the semi-classical treatment of three dimensional atomic orbits is, however, also apparent in relation to ZM theory. These observations are preliminary to a discussion of ZM theory in relation to quantum mechanics and quantum field theory in subsequent papers. |
1103.4937 | Massimo Villata | M. Villata | CPT symmetry and antimatter gravity in general relativity | 6 pages, to be published in EPL (http://epljournal.edpsciences.org/) | EPL (Europhysics Letters) 94 (2011) 20001 | 10.1209/0295-5075/94/20001 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational behavior of antimatter is still unknown. While we may be
confident that antimatter is self-attractive, the interaction between matter
and antimatter might be either attractive or repulsive. We investigate this
issue on theoretical grounds. Starting from the CPT invariance of physical
laws, we transform matter into antimatter in the equations of both
electrodynamics and gravitation. In the former case, the result is the
well-known change of sign of the electric charge. In the latter, we find that
the gravitational interaction between matter and antimatter is a mutual
repulsion, i.e. antigravity appears as a prediction of general relativity when
CPT is applied. This result supports cosmological models attempting to explain
the Universe accelerated expansion in terms of a matter-antimatter repulsive
interaction.
| [
{
"created": "Fri, 25 Mar 2011 10:01:48 GMT",
"version": "v1"
}
] | 2011-11-21 | [
[
"Villata",
"M.",
""
]
] | The gravitational behavior of antimatter is still unknown. While we may be confident that antimatter is self-attractive, the interaction between matter and antimatter might be either attractive or repulsive. We investigate this issue on theoretical grounds. Starting from the CPT invariance of physical laws, we transform matter into antimatter in the equations of both electrodynamics and gravitation. In the former case, the result is the well-known change of sign of the electric charge. In the latter, we find that the gravitational interaction between matter and antimatter is a mutual repulsion, i.e. antigravity appears as a prediction of general relativity when CPT is applied. This result supports cosmological models attempting to explain the Universe accelerated expansion in terms of a matter-antimatter repulsive interaction. |
1006.4152 | Nikolai V. Mitskievich | Nikolai V. Mitskievich and H\'ector Vargas-Rodr\'iguez | Rotation and pseudo-rotation | 13 pages, no figures, contains parts of the PhD Thesis of H. Vargas
Rodr\'iguez | Gen.Rel.Grav.37:781,2005 | 10.1007/s10714-005-0062-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Eigenvectors of stress-energy tensor (the source in Einstein's equations)
form privileged bases in description of the corresponding space-times. When one
or more of these vector fields are rotating (the property well determined in
differential geometry), one says that the space-time executes this rotation.
Though the rotation in its proper sense is understood as that of a timelike
congruence (vector field), the rotation of a spacelike congruence is not a less
objective property if it corresponds to a canonical proper basis built of the
just mentioned eigenvectors. In this last case, we propose to speak on
pseudo-rotation. Both properties of metric, its material sources, and
space-time symmetries are considered in this paper.
| [
{
"created": "Mon, 21 Jun 2010 19:51:13 GMT",
"version": "v1"
}
] | 2015-05-19 | [
[
"Mitskievich",
"Nikolai V.",
""
],
[
"Vargas-Rodríguez",
"Héctor",
""
]
] | Eigenvectors of stress-energy tensor (the source in Einstein's equations) form privileged bases in description of the corresponding space-times. When one or more of these vector fields are rotating (the property well determined in differential geometry), one says that the space-time executes this rotation. Though the rotation in its proper sense is understood as that of a timelike congruence (vector field), the rotation of a spacelike congruence is not a less objective property if it corresponds to a canonical proper basis built of the just mentioned eigenvectors. In this last case, we propose to speak on pseudo-rotation. Both properties of metric, its material sources, and space-time symmetries are considered in this paper. |
1307.2472 | Yurii Ignatyev | Yu.G. Ignat'ev | Cosmological evolution of the cosmological plasma with interpartial
scalar interaction. II. Formulation of mathematical model | 12 pages, 9 references | Russian Physics Journal Volume 55, Number 5 (2012), 550-560 | 10.1007/s11182-012-9847-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | On the basis of the relativistic kinetic theory the relativistic statistical
systems with scalar interaction particles are investigated. The self-consistent
system of the equations describing self-gravitating plasma with interpartial
scalar interaction is formulated, macroscopical laws of preservation are
received. The closed system of the equations describing cosmological models to
which the matter is presented by plasma with interpartial scalar interaction is
received.
| [
{
"created": "Tue, 9 Jul 2013 14:27:51 GMT",
"version": "v1"
}
] | 2013-07-10 | [
[
"Ignat'ev",
"Yu. G.",
""
]
] | On the basis of the relativistic kinetic theory the relativistic statistical systems with scalar interaction particles are investigated. The self-consistent system of the equations describing self-gravitating plasma with interpartial scalar interaction is formulated, macroscopical laws of preservation are received. The closed system of the equations describing cosmological models to which the matter is presented by plasma with interpartial scalar interaction is received. |
gr-qc/0112032 | Finn Ravndal | Finn Ravndal and Mats Sundberg | Graviton-photon conversion on spin 0 and 1/2 particles | 13 pages, LaTeX with 5 figures | Int.J.Mod.Phys. A17 (2002) 3963-3974 | 10.1142/S0217751X02010881 | null | gr-qc hep-ph | null | The differential cross-sections for scattering of gravitons into photons on
bosons and fermions are calculated in linearized quantum gravity. They are
found to be strongly peaked in the forward direction and become constant at
high energies. Numerically, they are very small as expected for such
gravitational interactions.
| [
{
"created": "Sat, 15 Dec 2001 12:49:05 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Ravndal",
"Finn",
""
],
[
"Sundberg",
"Mats",
""
]
] | The differential cross-sections for scattering of gravitons into photons on bosons and fermions are calculated in linearized quantum gravity. They are found to be strongly peaked in the forward direction and become constant at high energies. Numerically, they are very small as expected for such gravitational interactions. |
2111.14218 | Ross Greenwood | Ross N Greenwood and Anthony Aguirre | How generic is eternal inflation? | 22 pages, 8 figures. This is a preprint of an article submitted for
review and possible inclusion in the Sci special issue "Interdisciplinary
Aspects of the Multiverse Concept" | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Everlasting inflation has far-reaching implications for cosmology and the
standing of self-localizing inferences made by observers, which have been
subjects of renewed interest in light of the growing acceptance of theory
landscapes and the attendant anthropic arguments. Under what assumptions and to
what extent does inflation generically produce an eternal "multiverse," without
fine-tuning with respect to measures over the space of inflationary cosmologies
driven by a single minimally coupled scalar field? We address this and related
questions with numerical simulations of inflationary dynamics across
populations of randomly generated inflation models, instantiating a few
particular simply-defined measures.
| [
{
"created": "Sun, 28 Nov 2021 19:22:27 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Dec 2021 17:46:44 GMT",
"version": "v2"
}
] | 2021-12-28 | [
[
"Greenwood",
"Ross N",
""
],
[
"Aguirre",
"Anthony",
""
]
] | Everlasting inflation has far-reaching implications for cosmology and the standing of self-localizing inferences made by observers, which have been subjects of renewed interest in light of the growing acceptance of theory landscapes and the attendant anthropic arguments. Under what assumptions and to what extent does inflation generically produce an eternal "multiverse," without fine-tuning with respect to measures over the space of inflationary cosmologies driven by a single minimally coupled scalar field? We address this and related questions with numerical simulations of inflationary dynamics across populations of randomly generated inflation models, instantiating a few particular simply-defined measures. |
0709.0015 | Guglielmo Fucci | Guglielmo Fucci and Ivan G. Avramidi | Noncommutative Einstein Equations | 17 Pages, LaTeX, reference added | Class.Quant.Grav.25:025005,2008 | 10.1088/0264-9381/25/2/025005 | null | gr-qc | null | We study a noncommutative deformation of general relativity where the
gravitational field is described by a matrix-valued symmetric two-tensor field.
The equations of motion are derived in the framework of this new theory by
varying a diffeomorphisms and gauge invariant action constructed by using a
matrix-valued scalar curvature. Interestingly the genuine noncommutative part
of the dynamical equations is described only in terms of a particular tensor
density that vanishes identically in the commutative limit. A noncommutative
generalization of the energy-momentum tensor for the matter field is studied as
well.
| [
{
"created": "Fri, 31 Aug 2007 21:20:45 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Sep 2007 21:35:42 GMT",
"version": "v2"
}
] | 2011-02-17 | [
[
"Fucci",
"Guglielmo",
""
],
[
"Avramidi",
"Ivan G.",
""
]
] | We study a noncommutative deformation of general relativity where the gravitational field is described by a matrix-valued symmetric two-tensor field. The equations of motion are derived in the framework of this new theory by varying a diffeomorphisms and gauge invariant action constructed by using a matrix-valued scalar curvature. Interestingly the genuine noncommutative part of the dynamical equations is described only in terms of a particular tensor density that vanishes identically in the commutative limit. A noncommutative generalization of the energy-momentum tensor for the matter field is studied as well. |
2007.09089 | Pietro Dona | Pietro Dona and Simone Speziale | Asymptotics of lowest unitary SL(2,C) invariants on graphs | 40 Pages + 5 Appendices. 11 Figures. v2: Refined presentation of the
general algorithm, additional minor amendments. v3: paragraph added in
section 5 about curved embeddings | Phys. Rev. D 102, 086016 (2020) | 10.1103/PhysRevD.102.086016 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe a technique to study the asymptotics of SL(2,C) invariant tensors
associated to graphs, with unitary irreps and lowest SU(2) spins, and apply it
to the Lorentzian EPRL-KKL (Engle, Pereira, Rovelli, Livine; Kaminski,
Kieselowski, Lewandowski) model of quantum gravity. We reproduce the known
asymptotics of the 4-simplex graph with a different perspective on the
geometric variables and introduce an algorithm valid for any graph. On general
grounds, we find that critical configurations are not just Regge geometries,
but a larger set corresponding to conformal twisted geometries. These can be
either Euclidean or Lorentzian, and include curved and flat 4d polytopes as
subsets. For modular graphs, we show that multiple pairs of critical points
exist, and there exist critical configurations of mixed signature, Euclidean
and Lorentzian in different subgraphs, with no 4d embedding possible.
| [
{
"created": "Fri, 17 Jul 2020 16:09:40 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Oct 2020 12:55:46 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Jun 2021 15:09:09 GMT",
"version": "v3"
}
] | 2021-06-04 | [
[
"Dona",
"Pietro",
""
],
[
"Speziale",
"Simone",
""
]
] | We describe a technique to study the asymptotics of SL(2,C) invariant tensors associated to graphs, with unitary irreps and lowest SU(2) spins, and apply it to the Lorentzian EPRL-KKL (Engle, Pereira, Rovelli, Livine; Kaminski, Kieselowski, Lewandowski) model of quantum gravity. We reproduce the known asymptotics of the 4-simplex graph with a different perspective on the geometric variables and introduce an algorithm valid for any graph. On general grounds, we find that critical configurations are not just Regge geometries, but a larger set corresponding to conformal twisted geometries. These can be either Euclidean or Lorentzian, and include curved and flat 4d polytopes as subsets. For modular graphs, we show that multiple pairs of critical points exist, and there exist critical configurations of mixed signature, Euclidean and Lorentzian in different subgraphs, with no 4d embedding possible. |
2203.05699 | Vinod Bhardwaj Dr. | Anirudh Pradhan, Vinod Kumar Bhardwaj, Archana Dixit, Syamala
Krishnannair, | A new class of holographic dark energy models in LRS Bianchi Type-I | 19 pages, 15 figures | International Journal of Modern Physics A, Vol. 36, No. 36 (2021)
2150256 | 10.1142/S0217751X21502560 | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | In this paper, we examine the (LRS) Bianchi-type-I cosmological model with
holographic dark energy. The exact solutions to the corresponding field
equations are obtained by using generalized hybrid expansion law (HEL). The EoS
parameter $\omega$ for DE is found to be time dependent and redshift dependent
and its exiting range for derived model is agreeing well with the current
observations. Here we likewise apply two mathematical diagnostics, the
statefinder ({r, s}) and $\omega_{d}-\omega^{'}_{d}$ plane to segregate HDE
model from the $\Lambda CDM$ model. Here the $\omega_{d}-\omega^{'}_{d}$
diagnostic trajectories is the good tool to classifying the dynamical DE model.
We found that our model lies in both thawing region and freezing region. We
have also construct the potential as well as dynamics of the quintessence and
tachyon scalar field. Some physical and geometric properties of this model
along with the physical acceptability of cosmological solution have been
discussed in detail.
| [
{
"created": "Fri, 11 Mar 2022 01:13:25 GMT",
"version": "v1"
}
] | 2022-03-14 | [
[
"Pradhan",
"Anirudh",
""
],
[
"Bhardwaj",
"Vinod Kumar",
""
],
[
"Dixit",
"Archana",
""
],
[
"Krishnannair",
"Syamala",
""
]
] | In this paper, we examine the (LRS) Bianchi-type-I cosmological model with holographic dark energy. The exact solutions to the corresponding field equations are obtained by using generalized hybrid expansion law (HEL). The EoS parameter $\omega$ for DE is found to be time dependent and redshift dependent and its exiting range for derived model is agreeing well with the current observations. Here we likewise apply two mathematical diagnostics, the statefinder ({r, s}) and $\omega_{d}-\omega^{'}_{d}$ plane to segregate HDE model from the $\Lambda CDM$ model. Here the $\omega_{d}-\omega^{'}_{d}$ diagnostic trajectories is the good tool to classifying the dynamical DE model. We found that our model lies in both thawing region and freezing region. We have also construct the potential as well as dynamics of the quintessence and tachyon scalar field. Some physical and geometric properties of this model along with the physical acceptability of cosmological solution have been discussed in detail. |
2203.08228 | Stefan Ballmer | Stefan W. Ballmer, Rana Adhikari, Leonardo Badurina, Duncan A. Brown,
Swapan Chattopadhyay, Matthew Evans, Peter Fritschel, Evan Hall, Jason M.
Hogan, Karan Jani, Tim Kovachy, Kevin Kuns, Ariel Schwartzman, Daniel Sigg,
Bram Slagmolen, Salvatore Vitale, Christopher Wipf | Snowmass2021 Cosmic Frontier White Paper: Future Gravitational-Wave
Detector Facilities | 31 pages, 5 figures, contribution to Snowmass 2021 | null | null | null | gr-qc astro-ph.IM hep-ex hep-th | http://creativecommons.org/licenses/by/4.0/ | The next generation of gravitational-wave observatories can explore a wide
range of fundamental physics phenomena throughout the history of the universe.
These phenomena include access to the universe's binary black hole population
throughout cosmic time, to the universe's expansion history independent of the
cosmic distance ladders, to stochastic gravitational-waves from early-universe
phase transitions, to warped space-time in the strong-field and high-velocity
limit, to the equation of state of nuclear matter at neutron star and
post-merger densities, and to dark matter candidates through their interaction
in extreme astrophysical environments or their interaction with the detector
itself. We present the gravitational-wave detector concepts than can drive the
future of gravitational-wave astrophysics. We summarize the status of the
necessary technology, and the research needed to be able to build these
observatories in the 2030s.
| [
{
"created": "Tue, 15 Mar 2022 20:02:30 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Mar 2022 17:01:15 GMT",
"version": "v2"
}
] | 2022-03-30 | [
[
"Ballmer",
"Stefan W.",
""
],
[
"Adhikari",
"Rana",
""
],
[
"Badurina",
"Leonardo",
""
],
[
"Brown",
"Duncan A.",
""
],
[
"Chattopadhyay",
"Swapan",
""
],
[
"Evans",
"Matthew",
""
],
[
"Fritschel",
"Peter",
... | The next generation of gravitational-wave observatories can explore a wide range of fundamental physics phenomena throughout the history of the universe. These phenomena include access to the universe's binary black hole population throughout cosmic time, to the universe's expansion history independent of the cosmic distance ladders, to stochastic gravitational-waves from early-universe phase transitions, to warped space-time in the strong-field and high-velocity limit, to the equation of state of nuclear matter at neutron star and post-merger densities, and to dark matter candidates through their interaction in extreme astrophysical environments or their interaction with the detector itself. We present the gravitational-wave detector concepts than can drive the future of gravitational-wave astrophysics. We summarize the status of the necessary technology, and the research needed to be able to build these observatories in the 2030s. |
0705.2994 | Z. Ya. Turakulov | Z. Ya. Turakulov | Non-relativistic limit of the Einstein equation | 8 pages | null | null | null | gr-qc | null | In particular cases of stationary and stationary axially symmetric space-time
passage to non-relativistic limit of Einstein equation is completed. For this
end the notions of absolute space and absolute time are introduced due to
stationarity of the space-time under consideration. In this construction
absolute time is defined as a function $t$ on the space-time such that $\prt_t$
is exactly the Killing vector and the space at different moments is presented
by the surfaces $t=\con $. The space-time metric is expressed in terms of
metric of the 3-space and two potentials one of which is exactly Newtonian
gravitational potential $\Phi$, another is vector potential $\vec A$ which,
however, differs from vector potential known in classical electrodynamics. In
the first-order approximation on $\Phi/c^2$, $|\vec A|/c$ Einstein equation is
reduced to a system for these functions in which left-hand sides contain
Laplacian of the Newtonian potential, derivatives of the vector potential and
curvature of the space and the right-hand sides do 3-dimensional stress tensor
and densities of mass and energy. Subj-class: Classical Physics
| [
{
"created": "Mon, 21 May 2007 14:54:50 GMT",
"version": "v1"
},
{
"created": "Wed, 23 May 2007 06:24:44 GMT",
"version": "v2"
},
{
"created": "Sat, 26 May 2007 08:48:30 GMT",
"version": "v3"
}
] | 2007-06-13 | [
[
"Turakulov",
"Z. Ya.",
""
]
] | In particular cases of stationary and stationary axially symmetric space-time passage to non-relativistic limit of Einstein equation is completed. For this end the notions of absolute space and absolute time are introduced due to stationarity of the space-time under consideration. In this construction absolute time is defined as a function $t$ on the space-time such that $\prt_t$ is exactly the Killing vector and the space at different moments is presented by the surfaces $t=\con $. The space-time metric is expressed in terms of metric of the 3-space and two potentials one of which is exactly Newtonian gravitational potential $\Phi$, another is vector potential $\vec A$ which, however, differs from vector potential known in classical electrodynamics. In the first-order approximation on $\Phi/c^2$, $|\vec A|/c$ Einstein equation is reduced to a system for these functions in which left-hand sides contain Laplacian of the Newtonian potential, derivatives of the vector potential and curvature of the space and the right-hand sides do 3-dimensional stress tensor and densities of mass and energy. Subj-class: Classical Physics |
1502.01747 | Serguei Ossokine | Serguei Ossokine, Michael Boyle, Lawrence E. Kidder, Harald P.
Pfeiffer, Mark A.Scheel and B\'ela Szil\'agyi | Comparing Post-Newtonian and Numerical-Relativity Precession Dynamics | null | Phys. Rev. D 92, 104028 (2015) | 10.1103/PhysRevD.92.104028 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Binary black-hole systems are expected to be important sources of
gravitational waves for upcoming gravitational-wave detectors. If the spins are
not colinear with each other or with the orbital angular momentum, these
systems exhibit complicated precession dynamics that are imprinted on the
gravitational waveform. We develop a new procedure to match the precession
dynamics computed by post-Newtonian (PN) theory to those of numerical binary
black-hole simulations in full general relativity. For numerical relativity NR)
simulations lasting approximately two precession cycles, we find that the PN
and NR predictions for the directions of the orbital angular momentum and the
spins agree to better than $\sim 1^{\circ}$ with NR during the inspiral,
increasing to $5^{\circ}$ near merger. Nutation of the orbital plane on the
orbital time-scale agrees well between NR and PN, whereas nutation of the spin
direction shows qualitatively different behavior in PN and NR. We also examine
how the PN equations for precession and orbital-phase evolution converge with
PN order, and we quantify the impact of various choices for handling partially
known PN terms.
| [
{
"created": "Thu, 5 Feb 2015 22:19:37 GMT",
"version": "v1"
}
] | 2016-08-07 | [
[
"Ossokine",
"Serguei",
""
],
[
"Boyle",
"Michael",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Szilágyi",
"Béla",
""
]
] | Binary black-hole systems are expected to be important sources of gravitational waves for upcoming gravitational-wave detectors. If the spins are not colinear with each other or with the orbital angular momentum, these systems exhibit complicated precession dynamics that are imprinted on the gravitational waveform. We develop a new procedure to match the precession dynamics computed by post-Newtonian (PN) theory to those of numerical binary black-hole simulations in full general relativity. For numerical relativity NR) simulations lasting approximately two precession cycles, we find that the PN and NR predictions for the directions of the orbital angular momentum and the spins agree to better than $\sim 1^{\circ}$ with NR during the inspiral, increasing to $5^{\circ}$ near merger. Nutation of the orbital plane on the orbital time-scale agrees well between NR and PN, whereas nutation of the spin direction shows qualitatively different behavior in PN and NR. We also examine how the PN equations for precession and orbital-phase evolution converge with PN order, and we quantify the impact of various choices for handling partially known PN terms. |
0711.0313 | Alex Nielsen | Alex B. Nielsen | Black holes as local horizons | Talk presented at KPS meeting, 18th October, 2007, Jeju, Korea, 18
pages, 5 figures | null | null | null | gr-qc | null | This talk gives a brief introduction to black hole horizons and their role in
black hole thermodynamics. In particular a distinction is made between
quasi-locally defined horizons and event horizons. Currently some new
techniques have led to interesting developments and the field seems to be
growing in two distinct directions. We will show how thermodynamics can equally
well be applied to locally defined horizons and discuss some recent results.
The emphasis is on giving simple intuitive pictures and mathematical details
are largely omitted.
| [
{
"created": "Fri, 2 Nov 2007 14:02:31 GMT",
"version": "v1"
}
] | 2007-11-05 | [
[
"Nielsen",
"Alex B.",
""
]
] | This talk gives a brief introduction to black hole horizons and their role in black hole thermodynamics. In particular a distinction is made between quasi-locally defined horizons and event horizons. Currently some new techniques have led to interesting developments and the field seems to be growing in two distinct directions. We will show how thermodynamics can equally well be applied to locally defined horizons and discuss some recent results. The emphasis is on giving simple intuitive pictures and mathematical details are largely omitted. |
1510.02858 | Marius Oltean | Marius Oltean, Richard J. Epp, Paul L. McGrath, Robert B. Mann | Geoids in General Relativity: Geoid Quasilocal Frames | 24 pages, 8 figures; v2: reference added; v3: introduction clarified,
reference added | Class.Quant.Grav.33:105001,2016 | 10.1088/0264-9381/33/10/105001 | null | gr-qc astro-ph.EP hep-th physics.geo-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop, in the context of general relativity, the notion of a geoid -- a
surface of constant "gravitational potential". In particular, we show how this
idea naturally emerges as a specific choice of a previously proposed, more
general and operationally useful construction called a quasilocal frame -- that
is, a choice of a two-parameter family of timelike worldlines comprising the
worldtube boundary of the history of a finite spatial volume. We study the
geometric properties of these geoid quasilocal frames, and construct solutions
for them in some simple spacetimes. We then compare these results -- focusing
on the computationally tractable scenario of a non-rotating body with a
quadrupole perturbation -- against their counterparts in Newtonian gravity (the
setting for current applications of the geoid), and we compute
general-relativistic corrections to some measurable geometric quantities.
| [
{
"created": "Sat, 10 Oct 2015 00:29:53 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Oct 2015 11:52:23 GMT",
"version": "v2"
},
{
"created": "Mon, 30 Nov 2015 14:43:42 GMT",
"version": "v3"
}
] | 2016-06-10 | [
[
"Oltean",
"Marius",
""
],
[
"Epp",
"Richard J.",
""
],
[
"McGrath",
"Paul L.",
""
],
[
"Mann",
"Robert B.",
""
]
] | We develop, in the context of general relativity, the notion of a geoid -- a surface of constant "gravitational potential". In particular, we show how this idea naturally emerges as a specific choice of a previously proposed, more general and operationally useful construction called a quasilocal frame -- that is, a choice of a two-parameter family of timelike worldlines comprising the worldtube boundary of the history of a finite spatial volume. We study the geometric properties of these geoid quasilocal frames, and construct solutions for them in some simple spacetimes. We then compare these results -- focusing on the computationally tractable scenario of a non-rotating body with a quadrupole perturbation -- against their counterparts in Newtonian gravity (the setting for current applications of the geoid), and we compute general-relativistic corrections to some measurable geometric quantities. |
1405.7667 | Dibyendu Panigrahi DP | D Panigrahi | Thermodynamical behaviour of the Variable Chaplygin gas | 10 pages, 4 figures | International Journal of Modern Physics D, Vol. 24, No. 05,
1550030 (2015) | 10.1142/S0218271815500303 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The thermodynamical behaviour of the Variable Chaplygin gas (VCG) model is
studied, using an equation of state like $P = - \frac{B}{\rho}$, where $B =
B_{0}V^{-\frac{n}{3}}$. Here $B_{0}$ is a positive universal constant, $n$ is
also a constant and $V$ is the volume of the fluid. From the consideration of
thermodynamic stability, it is seen that only if the values of $n$ are allowed
to be negative, then $(\frac{\partial P}{\partial V})_{S} <0$ throughout the
evolution. Again thermal capacity at constant volume $c_{V}$ shows positive
expression. Using the best fit value of $ n = -3.4$ as previously found by Guo
\emph{et al} \cite{guo1} gives that the fluid is thermodynamically stable
through out the evolution. The effective equation of state for the special case
of, $n = 0$ goes to $\Lambda$CDM model. Again for $n <0$ it favours
phantom-like cosmology which is in agreement with the current SNe Ia
constraints like VCG model. The deceleration parameter is also studied in the
context of thermodynamics and the analysis shows that the \emph{flip} occurs
for the value of $ n < 4$. Finally the thermal equation of state is discussed
which is an explicit function of temperature only. It is also observed that the
third law of thermodynamics is satisfied in this model. As expected the volume
increases as temperature falls during adiabatic expansions. In this case, for $
T \rightarrow 0$, the thermal equation of state reduces to $(- 1 +
\frac{n}{6})$ which is identical with the equation of state for the case of
large volume.
| [
{
"created": "Thu, 29 May 2014 19:21:20 GMT",
"version": "v1"
},
{
"created": "Sun, 8 Feb 2015 18:58:54 GMT",
"version": "v2"
}
] | 2017-02-14 | [
[
"Panigrahi",
"D",
""
]
] | The thermodynamical behaviour of the Variable Chaplygin gas (VCG) model is studied, using an equation of state like $P = - \frac{B}{\rho}$, where $B = B_{0}V^{-\frac{n}{3}}$. Here $B_{0}$ is a positive universal constant, $n$ is also a constant and $V$ is the volume of the fluid. From the consideration of thermodynamic stability, it is seen that only if the values of $n$ are allowed to be negative, then $(\frac{\partial P}{\partial V})_{S} <0$ throughout the evolution. Again thermal capacity at constant volume $c_{V}$ shows positive expression. Using the best fit value of $ n = -3.4$ as previously found by Guo \emph{et al} \cite{guo1} gives that the fluid is thermodynamically stable through out the evolution. The effective equation of state for the special case of, $n = 0$ goes to $\Lambda$CDM model. Again for $n <0$ it favours phantom-like cosmology which is in agreement with the current SNe Ia constraints like VCG model. The deceleration parameter is also studied in the context of thermodynamics and the analysis shows that the \emph{flip} occurs for the value of $ n < 4$. Finally the thermal equation of state is discussed which is an explicit function of temperature only. It is also observed that the third law of thermodynamics is satisfied in this model. As expected the volume increases as temperature falls during adiabatic expansions. In this case, for $ T \rightarrow 0$, the thermal equation of state reduces to $(- 1 + \frac{n}{6})$ which is identical with the equation of state for the case of large volume. |
1209.2802 | Joan Sola | J. A. S. Lima, S. Basilakos, and Joan Sola | Expansion History with Decaying Vacuum: A Complete Cosmological Scenario | Accepted in MNRAS. Extended discussion, references added | null | 10.1093/mnras/stt220 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a novel cosmological scenario with the space-time emerging from a
pure initial de Sitter stage and subsequently evolving into the radiation,
matter and dark energy dominated epochs, thereby avoiding the initial
singularity and providing a complete description of the expansion history and a
natural solution to the horizon problem. The model is based on a dynamical
vacuum energy density which evolves as a power series of the Hubble rate. The
transit from the inflation into the standard radiation epoch is universal,
giving a clue for a successful description of the graceful exit. Since the
resulting late time cosmic history is very close to the concordance LCDM model,
the new unified framework embodies a more complete past cosmic evolution than
the standard cosmology.
| [
{
"created": "Thu, 13 Sep 2012 07:38:57 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Feb 2013 20:42:30 GMT",
"version": "v2"
}
] | 2015-06-11 | [
[
"Lima",
"J. A. S.",
""
],
[
"Basilakos",
"S.",
""
],
[
"Sola",
"Joan",
""
]
] | We propose a novel cosmological scenario with the space-time emerging from a pure initial de Sitter stage and subsequently evolving into the radiation, matter and dark energy dominated epochs, thereby avoiding the initial singularity and providing a complete description of the expansion history and a natural solution to the horizon problem. The model is based on a dynamical vacuum energy density which evolves as a power series of the Hubble rate. The transit from the inflation into the standard radiation epoch is universal, giving a clue for a successful description of the graceful exit. Since the resulting late time cosmic history is very close to the concordance LCDM model, the new unified framework embodies a more complete past cosmic evolution than the standard cosmology. |
1510.07051 | Kai Schwenzer | Kostas D. Kokkotas and Kai Schwenzer | R-mode astronomy | 15 pages, 6 figures, to be published in the EPJA Topical Issue on
"Exotic Matter in Neutron Stars" | null | 10.1140/epja/i2016-16038-9 | null | gr-qc astro-ph.HE astro-ph.SR nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Next generation gravitational wave detectors will start taking data in the
near future. Here we discuss the chances to detect the continuous emission from
r-mode oscillations in compact stars and study which properties of compact
stars we can infer from such novel data. In particular we show that the
combination of the gravitational wave data with electromagnetic multi-messenger
observations could give us detailed insight into compact star properties,
ranging from precise mass-radius measurements to the determination of the
equation of state and the phase structure of dense matter.
| [
{
"created": "Fri, 23 Oct 2015 20:19:54 GMT",
"version": "v1"
}
] | 2016-03-23 | [
[
"Kokkotas",
"Kostas D.",
""
],
[
"Schwenzer",
"Kai",
""
]
] | Next generation gravitational wave detectors will start taking data in the near future. Here we discuss the chances to detect the continuous emission from r-mode oscillations in compact stars and study which properties of compact stars we can infer from such novel data. In particular we show that the combination of the gravitational wave data with electromagnetic multi-messenger observations could give us detailed insight into compact star properties, ranging from precise mass-radius measurements to the determination of the equation of state and the phase structure of dense matter. |
gr-qc/0509122 | Eric Poisson | Adam Pound, Eric Poisson, and Bernhard G. Nickel | Limitations of the adiabatic approximation to the gravitational
self-force | 8 pages, 1 colour figure, final version to be published in Physical
Review D | Phys.Rev. D72 (2005) 124001 | 10.1103/PhysRevD.72.124001 | null | gr-qc | null | A small body moving in the field of a much larger black hole and subjected to
its own gravity moves on an accelerated world line in the background spacetime
of the large black hole. The acceleration is produced by the body's
gravitational self-force, which is constructed from the body's retarded
gravitational field. The adiabatic approximation to the gravitational
self-force is obtained instead from the half-retarded minus half-advanced
field; it is known to produce the same dissipative effects as the true
self-force. We argue that the adiabatic approximation is limited, because it
discards important conservative terms which lead to the secular evolution of
some orbital elements. We argue further that this secular evolution has
measurable consequences; in particular, it affects the phasing of the orbit and
the phasing of the associated gravitational wave. Our argument rests on a
simple toy model involving a point electric charge moving slowly in the weak
gravitational field of a central mass; the charge is also subjected to its
electromagnetic self-force. In this simple context the true self-force is known
explicitly and it can cleanly be separated into conservative and
radiation-reaction pieces. We observe that the conservative part of the
self-force produces a secular regression of the orbit's periapsis. We explain
how the conclusions reached on the basis of the toy model can be extended to
the gravitational self-force, and to fast motions and strong fields. While the
limitations of the adiabatic approximation are quite severe in a post-Newtonian
context in which the motion is slow and the gravitational field weak, they
appear to be less so for rapid motions and strong fields.
| [
{
"created": "Thu, 29 Sep 2005 19:48:40 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Nov 2005 19:22:42 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Pound",
"Adam",
""
],
[
"Poisson",
"Eric",
""
],
[
"Nickel",
"Bernhard G.",
""
]
] | A small body moving in the field of a much larger black hole and subjected to its own gravity moves on an accelerated world line in the background spacetime of the large black hole. The acceleration is produced by the body's gravitational self-force, which is constructed from the body's retarded gravitational field. The adiabatic approximation to the gravitational self-force is obtained instead from the half-retarded minus half-advanced field; it is known to produce the same dissipative effects as the true self-force. We argue that the adiabatic approximation is limited, because it discards important conservative terms which lead to the secular evolution of some orbital elements. We argue further that this secular evolution has measurable consequences; in particular, it affects the phasing of the orbit and the phasing of the associated gravitational wave. Our argument rests on a simple toy model involving a point electric charge moving slowly in the weak gravitational field of a central mass; the charge is also subjected to its electromagnetic self-force. In this simple context the true self-force is known explicitly and it can cleanly be separated into conservative and radiation-reaction pieces. We observe that the conservative part of the self-force produces a secular regression of the orbit's periapsis. We explain how the conclusions reached on the basis of the toy model can be extended to the gravitational self-force, and to fast motions and strong fields. While the limitations of the adiabatic approximation are quite severe in a post-Newtonian context in which the motion is slow and the gravitational field weak, they appear to be less so for rapid motions and strong fields. |
gr-qc/0001003 | Piotr Chrusciel | Piotr T. Chru\'sciel, Erwann Delay, Gregory J. Galloway and Ralph
Howard | Regularity of Horizons and The Area Theorem | final version to appear in Annales Henri Poincare, various changes as
suggested by a referee, in particular a section on Krolak's area theorems
added | Annales Henri Poincare 2 (2001) 109-178 | null | null | gr-qc | null | We prove that the area of sections of future event horizons in space-times
satisfying the null energy condition is non-decreasing towards the future under
any one of the following circumstances: 1) the horizon is future geodesically
complete; 2) the horizon is a black hole event horizon in a globally hyperbolic
space-time and there exists a conformal completion with a ``H-regular'' Scri
plus; 3) the horizon is a black hole event horizon in a space-time which has a
globally hyperbolic conformal completion. (Some related results under less
restrictive hypotheses are also established.) This extends a theorem of
Hawking, in which piecewise smoothness of the event horizon seems to have been
assumed. No assumptions about the cosmological constant or its sign are made.
We prove smoothness or analyticity of the relevant part of the event horizon
when equality in the area inequality is attained - this has applications to the
theory of stationary black holes, as well as to the structure of compact Cauchy
horizons. In the course of the proof we establish several new results
concerning the differentiability properties of horizons.
| [
{
"created": "Mon, 3 Jan 2000 17:55:04 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Nov 2000 23:07:29 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Chruściel",
"Piotr T.",
""
],
[
"Delay",
"Erwann",
""
],
[
"Galloway",
"Gregory J.",
""
],
[
"Howard",
"Ralph",
""
]
] | We prove that the area of sections of future event horizons in space-times satisfying the null energy condition is non-decreasing towards the future under any one of the following circumstances: 1) the horizon is future geodesically complete; 2) the horizon is a black hole event horizon in a globally hyperbolic space-time and there exists a conformal completion with a ``H-regular'' Scri plus; 3) the horizon is a black hole event horizon in a space-time which has a globally hyperbolic conformal completion. (Some related results under less restrictive hypotheses are also established.) This extends a theorem of Hawking, in which piecewise smoothness of the event horizon seems to have been assumed. No assumptions about the cosmological constant or its sign are made. We prove smoothness or analyticity of the relevant part of the event horizon when equality in the area inequality is attained - this has applications to the theory of stationary black holes, as well as to the structure of compact Cauchy horizons. In the course of the proof we establish several new results concerning the differentiability properties of horizons. |
2311.11311 | Tomas Andrade | Tomas Andrade, Rossella Gamba, Juan Trenado | Actively Learning Numerical Relativity | 17 pages, 12 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Data analysis of gravitational waves detected by the Ligo-Virgo-Kagra
collaboration and future observatories relies on precise modelling of the
sources. In order to build, calibrate and validate current models, we resort to
expensive simulations in Numerical Relativity (NR), the fully-fledged
simulation of Einstein's Equations. Since simulation costs and the
dimensionality of parameter space are prohibitive to perform a dense coverage,
approximate models interpolate among the available simulation data. We put
forward the technique of Gaussian Process Active Learning (GPAL), an adaptive,
data-driven protocol, for parameter space exploration and training of
gravitational wave approximants. We evaluate this proposal by studying a
computationally inexpensive scenario, in which we calibrate the approximant
TEOBResumS using the NR-informed model as a proxy for NR. In this case study,
we find that GPAL reduces the computational cost of training by a factor of 4
with respect to uniform or randomly distributed simulations. Moreover, we
consider a parallel implementation which reduces computational time, and hybrid
strategies which improve pre-calibrated models. The Gaussian Process regression
employed in this approach naturally endows the algorithm with notion of model
uncertainty. We comment on the implications of this feature for data analysis.
| [
{
"created": "Sun, 19 Nov 2023 12:25:19 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Feb 2024 08:39:28 GMT",
"version": "v2"
}
] | 2024-02-22 | [
[
"Andrade",
"Tomas",
""
],
[
"Gamba",
"Rossella",
""
],
[
"Trenado",
"Juan",
""
]
] | Data analysis of gravitational waves detected by the Ligo-Virgo-Kagra collaboration and future observatories relies on precise modelling of the sources. In order to build, calibrate and validate current models, we resort to expensive simulations in Numerical Relativity (NR), the fully-fledged simulation of Einstein's Equations. Since simulation costs and the dimensionality of parameter space are prohibitive to perform a dense coverage, approximate models interpolate among the available simulation data. We put forward the technique of Gaussian Process Active Learning (GPAL), an adaptive, data-driven protocol, for parameter space exploration and training of gravitational wave approximants. We evaluate this proposal by studying a computationally inexpensive scenario, in which we calibrate the approximant TEOBResumS using the NR-informed model as a proxy for NR. In this case study, we find that GPAL reduces the computational cost of training by a factor of 4 with respect to uniform or randomly distributed simulations. Moreover, we consider a parallel implementation which reduces computational time, and hybrid strategies which improve pre-calibrated models. The Gaussian Process regression employed in this approach naturally endows the algorithm with notion of model uncertainty. We comment on the implications of this feature for data analysis. |
1407.2067 | Sasa Ilijic | Dubravko Horvat, Sasa Ilijic, Anamarija Kirin and Zoran Narancic | Nonminimally coupled scalar field in teleparallel gravity: boson stars | LaTeX, 14 pages, 3 figures, v3: some points clarified, refs added,
matches published version | Class. Quantum Grav. 32 (2015) 035023 | 10.1088/0264-9381/32/3/035023 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the nonminimally coupled complex scalar field within the framework
of teleparallel gravity. Coupling of the field nonminimally to the torsion
scalar destroys the Lorentz invariance of the theory in the sense that the
resulting equations of motion depend on the choice of a tetrad. For the assumed
static spherically symmetric spacetime, we find a tetrad which leads to a
self-consistent set of equations, and we construct the self-gravitating
configurations of the scalar field---boson stars. The resulting configurations
develop anisotropic principal pressures and satisfy the dominant energy
condition. An interesting property of the configurations obtained with
sufficiently large field-to-torsion coupling constant is the outwardly
increasing energy density, followed by an abrupt drop towards the usual
asymptotic tail. This feature is not present in the boson stars with the field
minimally or nonminimally coupled to the curvature scalar, and therefore
appears to be a torsion--only effect.
| [
{
"created": "Tue, 8 Jul 2014 12:46:45 GMT",
"version": "v1"
},
{
"created": "Thu, 17 Jul 2014 13:40:16 GMT",
"version": "v2"
},
{
"created": "Tue, 17 Feb 2015 09:19:04 GMT",
"version": "v3"
}
] | 2015-02-18 | [
[
"Horvat",
"Dubravko",
""
],
[
"Ilijic",
"Sasa",
""
],
[
"Kirin",
"Anamarija",
""
],
[
"Narancic",
"Zoran",
""
]
] | We study the nonminimally coupled complex scalar field within the framework of teleparallel gravity. Coupling of the field nonminimally to the torsion scalar destroys the Lorentz invariance of the theory in the sense that the resulting equations of motion depend on the choice of a tetrad. For the assumed static spherically symmetric spacetime, we find a tetrad which leads to a self-consistent set of equations, and we construct the self-gravitating configurations of the scalar field---boson stars. The resulting configurations develop anisotropic principal pressures and satisfy the dominant energy condition. An interesting property of the configurations obtained with sufficiently large field-to-torsion coupling constant is the outwardly increasing energy density, followed by an abrupt drop towards the usual asymptotic tail. This feature is not present in the boson stars with the field minimally or nonminimally coupled to the curvature scalar, and therefore appears to be a torsion--only effect. |
1009.3749 | Azad Akhter Siddiqui Professor | M. Akbar and Azad A. Siddiqui | Charged Rotating BTZ Black Hole and Thermodynamic Behavior of Field
Equations at its Horizon | 12 pages, 3 figures | Phys.Lett.B656:217-220,2007 | 10.1016/j.physletb.2007.09.053 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study different cases of the charged rotating BTZ black
hole with reference to their horizons. For the existence of these cases
conditions on mass, charge and angular momentum of the black hole are obtained.
It is also shown that the Einstein field equations for the charged rotating BTZ
black hole at the horizon can be expressed as first law of thermodynamics,
$dE=TdS+\Omega dJ+\Phi dq+P_{r}dA$.
| [
{
"created": "Mon, 20 Sep 2010 09:50:31 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Akbar",
"M.",
""
],
[
"Siddiqui",
"Azad A.",
""
]
] | In this paper, we study different cases of the charged rotating BTZ black hole with reference to their horizons. For the existence of these cases conditions on mass, charge and angular momentum of the black hole are obtained. It is also shown that the Einstein field equations for the charged rotating BTZ black hole at the horizon can be expressed as first law of thermodynamics, $dE=TdS+\Omega dJ+\Phi dq+P_{r}dA$. |
1509.03624 | Masafumi Seriu | Masafumi Seriu | Influence of geometry variations on the gravitational focusing of
timelike geodesic congruences | To appear in Physical Review D | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive a set of equations describing the linear response of the
convergence properties of a geodesic congruence to arbitrary geometry
variations. It is a combination of equations describing the deviations from the
standard Raychaudhuri-type equations due to the geodesic shifts and an equation
describing the geodesic shifts due to the geometry variations. In this
framework, the geometry variations, which can be chosen arbitrarily, serve as
probes to investigate the gravitational contraction processes from various
angles.
We apply the obtained framework to the case of conformal geometry variations,
characterized by an arbitrary function $f(x)$, and see that the formulas get
simplified to a great extent. We investigate the response of the convergence
properties of geodesics in the latest phase of gravitational contractions by
restricting the class of conformal geometry variations to the one satisfying
the strong energy condition. We then find out that in the final stage, $f$ and
$ {\bf D}\cdot {\bf D} f$ control the overall contraction behavior and that the
contraction rate gets larger when $f$ is negative and $|f|$ is so large as to
overwhelm $|{\bf D} \cdot {\bf D} f|$. (Here ${\bf D} \cdot {\bf D}$ is the
Laplacian operator on the spatial hypersurfaces orthogonal to the geodesic
congruence in concern.)
To get more concrete insights, we also apply the framework to the
time-reversed Friedmann-Robertson-Walker model as the simplest case of the
singularity formations.
| [
{
"created": "Fri, 11 Sep 2015 19:52:52 GMT",
"version": "v1"
}
] | 2015-09-14 | [
[
"Seriu",
"Masafumi",
""
]
] | We derive a set of equations describing the linear response of the convergence properties of a geodesic congruence to arbitrary geometry variations. It is a combination of equations describing the deviations from the standard Raychaudhuri-type equations due to the geodesic shifts and an equation describing the geodesic shifts due to the geometry variations. In this framework, the geometry variations, which can be chosen arbitrarily, serve as probes to investigate the gravitational contraction processes from various angles. We apply the obtained framework to the case of conformal geometry variations, characterized by an arbitrary function $f(x)$, and see that the formulas get simplified to a great extent. We investigate the response of the convergence properties of geodesics in the latest phase of gravitational contractions by restricting the class of conformal geometry variations to the one satisfying the strong energy condition. We then find out that in the final stage, $f$ and $ {\bf D}\cdot {\bf D} f$ control the overall contraction behavior and that the contraction rate gets larger when $f$ is negative and $|f|$ is so large as to overwhelm $|{\bf D} \cdot {\bf D} f|$. (Here ${\bf D} \cdot {\bf D}$ is the Laplacian operator on the spatial hypersurfaces orthogonal to the geodesic congruence in concern.) To get more concrete insights, we also apply the framework to the time-reversed Friedmann-Robertson-Walker model as the simplest case of the singularity formations. |
1602.04220 | John Lombard | John Lombard | Network Gravity | Preprint: [19 pages, 19 figures]; Submitted to Phys. Rev. D for
Publication; Changes: Updated formatting, explicitly defined projection map,
updated commentary on IR divergence | Phys. Rev. D 95, 024001 (2017) | 10.1103/PhysRevD.95.024001 | null | gr-qc cond-mat.dis-nn math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce the construction of a new framework for probing discrete
emergent geometry and boundary-boundary observables based on a fundamentally
a-dimensional underlying network structure. Using a gravitationally motivated
action with Forman weighted combinatorial curvatures and simplicial volumes
relying on a decomposition of an abstract simplicial complex into realized
embeddings of proper skeletons, we demonstrate properties such as a minimal
volume-scale cutoff, the necessity of a positive-definite cosmological
constant-like term as a regulator for non-degenerate geometries, and naturally
emergent simplicial structures from Metropolis network evolution simulations
with no restrictions on attachment rules or regular building blocks. We see
emergent properties which echo results from both the spinfoam formalism and
causal dynamical triangulations in quantum gravity, and provide analytical and
numerical results to support the analogy. We conclude with a summary of open
questions and intent for future work in developing the program.
| [
{
"created": "Fri, 12 Feb 2016 21:00:01 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Jul 2016 04:05:19 GMT",
"version": "v2"
}
] | 2017-01-11 | [
[
"Lombard",
"John",
""
]
] | We introduce the construction of a new framework for probing discrete emergent geometry and boundary-boundary observables based on a fundamentally a-dimensional underlying network structure. Using a gravitationally motivated action with Forman weighted combinatorial curvatures and simplicial volumes relying on a decomposition of an abstract simplicial complex into realized embeddings of proper skeletons, we demonstrate properties such as a minimal volume-scale cutoff, the necessity of a positive-definite cosmological constant-like term as a regulator for non-degenerate geometries, and naturally emergent simplicial structures from Metropolis network evolution simulations with no restrictions on attachment rules or regular building blocks. We see emergent properties which echo results from both the spinfoam formalism and causal dynamical triangulations in quantum gravity, and provide analytical and numerical results to support the analogy. We conclude with a summary of open questions and intent for future work in developing the program. |
gr-qc/0403072 | Claudio Dappiaggi | Claudio Dappiaggi | Simplicial and asymptotical aspects of the holographic principle | PHD thesis, 130 pages, 15 figures used xy latex package | null | null | null | gr-qc hep-th math-ph math.MP | null | In this thesis, we study some aspects of a possible holographic
correspondence in two different systems: three dimensional Chern-Simons theory
and asymptotically flat space-times. In the former we use simplicial techniques
to study CS/WZW correspondence and in particular we construct the discretized
WZW partition function for SU(2) group at level 1. In the latter we outline the
main characteristics of a field theory living at null infinity invariant under
the action of the asymptotic symmetry group: the BMS group. In particular,
using fibre bundle techniques, we derive the covariant wave equations for
fields carrying BMS representations in order to investigate the nature of
boundary degrees of freedom.
| [
{
"created": "Tue, 16 Mar 2004 16:20:57 GMT",
"version": "v1"
}
] | 2009-09-29 | [
[
"Dappiaggi",
"Claudio",
""
]
] | In this thesis, we study some aspects of a possible holographic correspondence in two different systems: three dimensional Chern-Simons theory and asymptotically flat space-times. In the former we use simplicial techniques to study CS/WZW correspondence and in particular we construct the discretized WZW partition function for SU(2) group at level 1. In the latter we outline the main characteristics of a field theory living at null infinity invariant under the action of the asymptotic symmetry group: the BMS group. In particular, using fibre bundle techniques, we derive the covariant wave equations for fields carrying BMS representations in order to investigate the nature of boundary degrees of freedom. |
1704.03362 | Carlos Ruelas | Jer\'onimo Cortez, William Cuervo, Hugo A. Morales-T\'ecotl and Juan
C. Ruelas | On effective loop quantum geometry of Schwarzschild interior | 26 pages, matches the PRD published version | Phys.Rev. D95 (2017) no.6, 064041 | 10.1103/PhysRevD.95.064041 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The success of loop quantum cosmology to resolve classical singularities of
homogeneous models has led to its application to the classical Schwarszchild
black hole interior, which takes the form of a homogeneous Kantowski-Sachs
model. The first steps of this were done in pure quantum mechanical terms,
hinting at the traversable character of the would-be classical singularity, and
then others were performed using effective heuristic models capturing quantum
effects that allowed a geometrical description closer to the classical one but
avoided its singularity. However, the problem of establishing the link between
the quantum and effective descriptions was left open. In this work, we propose
to fill in this gap by considering the path-integral approach to the loop
quantization of the Kantowski-Sachs model corresponding to the Schwarzschild
black hole interior. We show that the transition amplitude can be expressed as
a path integration over the imaginary exponential of an effective action which
just coincides, under some simplifying assumptions, with the heuristic one.
Additionally, we further explore the consequences of the effective dynamics. We
prove first that such dynamics imply some rather simple bounds for phase-space
variables, and in turn, remarkably, in an analytical way, they imply that
various phase-space functions that were singular in the classical model are now
well behaved. In particular, the expansion rate, its time derivative, and the
shear become bounded, and hence the Raychaudhuri equation is finite term by
term, thus resolving the singularities of classical geodesic congruences.
Moreover, all effective scalar polynomial invariants turn out to be bounded.
| [
{
"created": "Tue, 11 Apr 2017 15:34:26 GMT",
"version": "v1"
}
] | 2017-04-19 | [
[
"Cortez",
"Jerónimo",
""
],
[
"Cuervo",
"William",
""
],
[
"Morales-Técotl",
"Hugo A.",
""
],
[
"Ruelas",
"Juan C.",
""
]
] | The success of loop quantum cosmology to resolve classical singularities of homogeneous models has led to its application to the classical Schwarszchild black hole interior, which takes the form of a homogeneous Kantowski-Sachs model. The first steps of this were done in pure quantum mechanical terms, hinting at the traversable character of the would-be classical singularity, and then others were performed using effective heuristic models capturing quantum effects that allowed a geometrical description closer to the classical one but avoided its singularity. However, the problem of establishing the link between the quantum and effective descriptions was left open. In this work, we propose to fill in this gap by considering the path-integral approach to the loop quantization of the Kantowski-Sachs model corresponding to the Schwarzschild black hole interior. We show that the transition amplitude can be expressed as a path integration over the imaginary exponential of an effective action which just coincides, under some simplifying assumptions, with the heuristic one. Additionally, we further explore the consequences of the effective dynamics. We prove first that such dynamics imply some rather simple bounds for phase-space variables, and in turn, remarkably, in an analytical way, they imply that various phase-space functions that were singular in the classical model are now well behaved. In particular, the expansion rate, its time derivative, and the shear become bounded, and hence the Raychaudhuri equation is finite term by term, thus resolving the singularities of classical geodesic congruences. Moreover, all effective scalar polynomial invariants turn out to be bounded. |
2304.06187 | George Ruppeiner | George Ruppeiner, Alexandru-Mihail Sturzu | Black hole microstructures in the extremal limit | - Added some exposition to the end of sections 3 -Updated Image
Quality in Figures 3 and 4 -Minor typographical fixes | Physical Review D 108, 086004 (2023) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The microstructure of black holes is a mystery. There is yet no resolution of
basic questions such as what the constituent particles are. We work here with
black hole thermodynamics (BHT), and the metric geometry of thermodynamics,
which connects to interparticle interactions via the invariant thermodynamic
Ricci scalar curvature $R$. $R$ may be calculated with BHT. In ordinary
thermodynamics (OT), $R$ is positive/negative for interparticle interactions
repulsive/attractive. Its magnitude is the correlation length. The basic
universality of thermodynamics leads us to expect similar relations for BHT.
Our contribution here is motivated by a physical simplification that frequently
occurs at low temperatures $T$ in OT: complicated interactions tend to freeze
out, leaving only basic quantum statistical interactions, those of ideal Fermi
or Bose gasses. Our hope is that similar simplification happens in black holes
in the extremal limit, where the BHT temperature $T \to 0$. We evaluate the
extremal $R$ for twelve BHT literature models, working with the independent
variables mass, angular momentum, charge, and the cosmological constant,
$\{M,J,Q,\Lambda\}$, respectively. We allowed only two of these variables to
fluctuate at a time, with the other two fixed. $M$ always fluctuated, either
$J$ or $Q$ fluctuated, and $\Lambda$ was always fixed. At constant average $M$,
$R$ has limiting divergence $R=c\,T^{-1}$, with the nonsingular constant $c$
depending only on $M$ and the two fixed parameters. $c$ is positive for $11/12$
of the models we examined, and negative only for the tidal charged model. The
positive sign for $R$ indicates a BHT microstructure composed of particles with
repulsive (fermionic) interactions. The limiting BHT expression for $R$
resembles that for 2D and 3D ideal Fermi gasses at constant volume, which also
have limiting divergence $R=c\,T^{-1}$, with positive $c$.
| [
{
"created": "Wed, 12 Apr 2023 23:13:01 GMT",
"version": "v1"
},
{
"created": "Tue, 30 May 2023 19:20:41 GMT",
"version": "v2"
}
] | 2023-12-12 | [
[
"Ruppeiner",
"George",
""
],
[
"Sturzu",
"Alexandru-Mihail",
""
]
] | The microstructure of black holes is a mystery. There is yet no resolution of basic questions such as what the constituent particles are. We work here with black hole thermodynamics (BHT), and the metric geometry of thermodynamics, which connects to interparticle interactions via the invariant thermodynamic Ricci scalar curvature $R$. $R$ may be calculated with BHT. In ordinary thermodynamics (OT), $R$ is positive/negative for interparticle interactions repulsive/attractive. Its magnitude is the correlation length. The basic universality of thermodynamics leads us to expect similar relations for BHT. Our contribution here is motivated by a physical simplification that frequently occurs at low temperatures $T$ in OT: complicated interactions tend to freeze out, leaving only basic quantum statistical interactions, those of ideal Fermi or Bose gasses. Our hope is that similar simplification happens in black holes in the extremal limit, where the BHT temperature $T \to 0$. We evaluate the extremal $R$ for twelve BHT literature models, working with the independent variables mass, angular momentum, charge, and the cosmological constant, $\{M,J,Q,\Lambda\}$, respectively. We allowed only two of these variables to fluctuate at a time, with the other two fixed. $M$ always fluctuated, either $J$ or $Q$ fluctuated, and $\Lambda$ was always fixed. At constant average $M$, $R$ has limiting divergence $R=c\,T^{-1}$, with the nonsingular constant $c$ depending only on $M$ and the two fixed parameters. $c$ is positive for $11/12$ of the models we examined, and negative only for the tidal charged model. The positive sign for $R$ indicates a BHT microstructure composed of particles with repulsive (fermionic) interactions. The limiting BHT expression for $R$ resembles that for 2D and 3D ideal Fermi gasses at constant volume, which also have limiting divergence $R=c\,T^{-1}$, with positive $c$. |
2312.02399 | Francesca Vidotto | Pietropaolo Frisoni, Francesco Gozzini, Francesca Vidotto | Primordial fluctuations from quantum gravity: 16-cell topological model | 17 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We present a numerical analysis of an Hartle-Hawking state for the early
universe, in the deep quantum regime, computed using the covariant Loop Quantum
Gravity formalism, in a truncation defined by 16-cell and in a simplified case
where the dynamics is defined by SU(2) BF theory. We compute mean geometry,
fluctuations and correlations. The results are consistent with the hypothesis
that refining the triangulation does not affect the global physical picture
substantially.
| [
{
"created": "Mon, 4 Dec 2023 23:53:59 GMT",
"version": "v1"
}
] | 2023-12-06 | [
[
"Frisoni",
"Pietropaolo",
""
],
[
"Gozzini",
"Francesco",
""
],
[
"Vidotto",
"Francesca",
""
]
] | We present a numerical analysis of an Hartle-Hawking state for the early universe, in the deep quantum regime, computed using the covariant Loop Quantum Gravity formalism, in a truncation defined by 16-cell and in a simplified case where the dynamics is defined by SU(2) BF theory. We compute mean geometry, fluctuations and correlations. The results are consistent with the hypothesis that refining the triangulation does not affect the global physical picture substantially. |
1109.3514 | Eduardo V. Correa Silva | G. A. Monerat, E. V. Corr\^ea Silva, C. Neves, G. Oliveira-Neto, L.G.
Rezende Rodrigues and M. Silva de Oliveira | Can noncommutativity affect the whole history of the Universe? | Substantially revised version of the manuscript. 12 pages, 8 figures.
PACS numbers: 04.20.Fy,04.40.Nr,11.10.Nx,98.80.Jk | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a classical, noncommutative (NC), Friedmann-Robertson-Walker
cosmological model. The spatial sections may have positive, negative or zero
constant curvatures. The matter content is a generic perfect fluid. The initial
noncommutativity between some canonical variables is rewritten, such that, we
end up with commutative variables and a NC parameter. Initially, we derive the
scale factor dynamic equations for the general situation, without specifying
the perfect fluid or the curvature of the spatial sections. Next, we consider
two concrete situations: a radiation perfect fluid and dust. We study all
possible scale factor behaviors, for both cases. We compare them with the
corresponding commutative cases and one with the other. We obtain, some cases,
where the NC model predicts a scale factor expansion which may describe the
present expansion of our Universe. Those cases are not present in the
corresponding commutative models. Finally, we compare our model with another NC
model, where the noncommutativity is between different canonical variables. We
show that, in general, it leads to a scale factor behavior that is different
from our model.
| [
{
"created": "Fri, 16 Sep 2011 01:45:59 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Jul 2015 19:04:46 GMT",
"version": "v2"
},
{
"created": "Thu, 11 Feb 2016 11:32:46 GMT",
"version": "v3"
}
] | 2016-02-12 | [
[
"Monerat",
"G. A.",
""
],
[
"Silva",
"E. V. Corrêa",
""
],
[
"Neves",
"C.",
""
],
[
"Oliveira-Neto",
"G.",
""
],
[
"Rodrigues",
"L. G. Rezende",
""
],
[
"de Oliveira",
"M. Silva",
""
]
] | We study a classical, noncommutative (NC), Friedmann-Robertson-Walker cosmological model. The spatial sections may have positive, negative or zero constant curvatures. The matter content is a generic perfect fluid. The initial noncommutativity between some canonical variables is rewritten, such that, we end up with commutative variables and a NC parameter. Initially, we derive the scale factor dynamic equations for the general situation, without specifying the perfect fluid or the curvature of the spatial sections. Next, we consider two concrete situations: a radiation perfect fluid and dust. We study all possible scale factor behaviors, for both cases. We compare them with the corresponding commutative cases and one with the other. We obtain, some cases, where the NC model predicts a scale factor expansion which may describe the present expansion of our Universe. Those cases are not present in the corresponding commutative models. Finally, we compare our model with another NC model, where the noncommutativity is between different canonical variables. We show that, in general, it leads to a scale factor behavior that is different from our model. |
2006.09652 | Lijing Shao | Xueli Miao, Junjie Zhao, Lijing Shao, Norbert Wex, Michael Kramer,
Bo-Qiang Ma | Tests of conservation laws in post-Newtonian gravity with binary pulsars | 14 pages, 5 figures, 4 tables; accepted by ApJ | ApJ 898 (2020) 69 | 10.3847/1538-4357/ab9dfe | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General relativity is a fully conservative theory, but there exist other
possible metric theories of gravity. We consider non-conservative ones with a
parameterized post-Newtonian (PPN) parameter, $\zeta_2$. A non-zero $\zeta_2$
induces a self-acceleration for the center of mass of an eccentric binary
pulsar system, which contributes to the second time derivative of the pulsar
spin frequency, $\ddot{\nu}$. In our work, using the method in Will (1992), we
provide an improved analysis with four well-timed, carefully-chosen binary
pulsars. In addition, we extend Will's method and derive $\zeta_2$'s effect on
the third time derivative of the spin frequency, $\dddot{\nu}$. For PSR
B1913+16, the constraint from $\dddot{\nu}$ is even tighter than that from
$\ddot{\nu}$. We combine multiple pulsars with Bayesian inference, and obtain
an upper limit, $\left|\zeta_{2}\right|<1.3\times10^{-5}$ at 95% confidence
level, assuming a flat prior in $\log_{10} \left| \zeta_{2}\right|$. It
improves the existing bound by a factor of three. Moreover, we propose an
analytical timing formalism for $\zeta_2$. Our simulated times of arrival with
simplified assumptions show binary pulsars' capability in limiting $\zeta_{2}$,
and useful clues are extracted for real data analysis in future. In particular,
we discover that for PSRs B1913+16 and J0737$-$3039A, $\dddot{\nu}$ can yield
more constraining limits than $\ddot{\nu}$.
| [
{
"created": "Wed, 17 Jun 2020 04:34:22 GMT",
"version": "v1"
}
] | 2020-07-27 | [
[
"Miao",
"Xueli",
""
],
[
"Zhao",
"Junjie",
""
],
[
"Shao",
"Lijing",
""
],
[
"Wex",
"Norbert",
""
],
[
"Kramer",
"Michael",
""
],
[
"Ma",
"Bo-Qiang",
""
]
] | General relativity is a fully conservative theory, but there exist other possible metric theories of gravity. We consider non-conservative ones with a parameterized post-Newtonian (PPN) parameter, $\zeta_2$. A non-zero $\zeta_2$ induces a self-acceleration for the center of mass of an eccentric binary pulsar system, which contributes to the second time derivative of the pulsar spin frequency, $\ddot{\nu}$. In our work, using the method in Will (1992), we provide an improved analysis with four well-timed, carefully-chosen binary pulsars. In addition, we extend Will's method and derive $\zeta_2$'s effect on the third time derivative of the spin frequency, $\dddot{\nu}$. For PSR B1913+16, the constraint from $\dddot{\nu}$ is even tighter than that from $\ddot{\nu}$. We combine multiple pulsars with Bayesian inference, and obtain an upper limit, $\left|\zeta_{2}\right|<1.3\times10^{-5}$ at 95% confidence level, assuming a flat prior in $\log_{10} \left| \zeta_{2}\right|$. It improves the existing bound by a factor of three. Moreover, we propose an analytical timing formalism for $\zeta_2$. Our simulated times of arrival with simplified assumptions show binary pulsars' capability in limiting $\zeta_{2}$, and useful clues are extracted for real data analysis in future. In particular, we discover that for PSRs B1913+16 and J0737$-$3039A, $\dddot{\nu}$ can yield more constraining limits than $\ddot{\nu}$. |
gr-qc/0203024 | Gianluca Gemme | Ph. Bernard, A. Chincarini, G. Gemme, R. Parodi and E. Picasso | A detector of gravitational waves based on coupled microwave cavities | 29 pages, 12 eps figures. Typeset by REVTeX | null | null | INFN/TC-02/03 | gr-qc | null | Since 1978 superconducting coupled cavities have been proposed as sensitive
detector of gravitational waves. The interaction of the gravitational wave with
the cavity walls, and the resulting motion, induces the transition of some
electromagnetic energy from an initially excited cavity mode to an empty one.
The energy transfer is maximum when the frequency of the wave is equal to the
frequency difference of the two cavity modes. In this paper the basic
principles of the detector are discussed. The interaction of a gravitational
wave with the cavity walls is studied in the proper reference frame of the
detector, and the coupling between two electromagnetic normal modes induced by
the wall motion is analyzed in detail. Noise sources are also considered; in
particular the noise coming from the brownian motion of the cavity walls is
analyzed. Some ideas for the developement of a realistic detector of
gravitational waves are discussed; the outline of a possible detector design
and its expected sensitivity are also shown.
| [
{
"created": "Thu, 7 Mar 2002 09:10:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bernard",
"Ph.",
""
],
[
"Chincarini",
"A.",
""
],
[
"Gemme",
"G.",
""
],
[
"Parodi",
"R.",
""
],
[
"Picasso",
"E.",
""
]
] | Since 1978 superconducting coupled cavities have been proposed as sensitive detector of gravitational waves. The interaction of the gravitational wave with the cavity walls, and the resulting motion, induces the transition of some electromagnetic energy from an initially excited cavity mode to an empty one. The energy transfer is maximum when the frequency of the wave is equal to the frequency difference of the two cavity modes. In this paper the basic principles of the detector are discussed. The interaction of a gravitational wave with the cavity walls is studied in the proper reference frame of the detector, and the coupling between two electromagnetic normal modes induced by the wall motion is analyzed in detail. Noise sources are also considered; in particular the noise coming from the brownian motion of the cavity walls is analyzed. Some ideas for the developement of a realistic detector of gravitational waves are discussed; the outline of a possible detector design and its expected sensitivity are also shown. |
1308.2104 | Andrzej Okolow | Andrzej Okolow | Variables suitable for constructing quantum states for the Teleparallel
Equivalent of General Relativity II | 35 pages, LaTeX2e | Gen. Rel. Grav. 46:1638 (2014) | 10.1007/s10714-013-1638-2 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the second (and final) part of an analysis aimed at introducing
variables which are suitable for constructing a space of quantum states for the
Teleparallel Equivalent of General Relativity. In the first part of the
analysis we introduced a family of variables on the "position" sector of the
phase space. In this paper we distinguish differentiable variables in the
family. Then we define momenta conjugate to the distinguished variables and
express constraints of the theory in terms of the variables and the momenta.
Finally, we exclude variables which generate an obstacle for further steps of
the Dirac's procedure of canonical quantization of constrained systems we are
going to apply to the theory. As a result we obtain two collections of
variables on the phase space which will be used (in a subsequent paper) to
construct the desired space of quantum states.
| [
{
"created": "Fri, 9 Aug 2013 12:17:18 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Jul 2014 15:06:14 GMT",
"version": "v2"
}
] | 2014-07-15 | [
[
"Okolow",
"Andrzej",
""
]
] | We present the second (and final) part of an analysis aimed at introducing variables which are suitable for constructing a space of quantum states for the Teleparallel Equivalent of General Relativity. In the first part of the analysis we introduced a family of variables on the "position" sector of the phase space. In this paper we distinguish differentiable variables in the family. Then we define momenta conjugate to the distinguished variables and express constraints of the theory in terms of the variables and the momenta. Finally, we exclude variables which generate an obstacle for further steps of the Dirac's procedure of canonical quantization of constrained systems we are going to apply to the theory. As a result we obtain two collections of variables on the phase space which will be used (in a subsequent paper) to construct the desired space of quantum states. |
1705.09889 | Salvador Robles-Perez | Salvador J. Robles-Perez | Observational consequences of an interacting multiverse | 8 pages, 4 figures. Proceedings of the conference given in the
Varying Constants and Fundamental Cosmology meeting (VARCOSMOFUN-16) held in
Szczecin, Poland, 12-17th September 2016 | Universe 2017, 3(2), 49 | 10.3390/universe3020049 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The observability of the multiverse is at the very root of its physical
significance as a scientific proposal. In this conference we present, within
the third quantization formalism, an interacting scheme between the wave
functions of different universes and analyze the effects of some particular
values of the coupling function. One of the main consequences of the
interaction between universes can be the appearance of a pre-inflationary stage
in the evolution of the universes that might leave observable consequences in
the properties of the CMB.
| [
{
"created": "Sun, 28 May 2017 05:14:54 GMT",
"version": "v1"
}
] | 2017-05-30 | [
[
"Robles-Perez",
"Salvador J.",
""
]
] | The observability of the multiverse is at the very root of its physical significance as a scientific proposal. In this conference we present, within the third quantization formalism, an interacting scheme between the wave functions of different universes and analyze the effects of some particular values of the coupling function. One of the main consequences of the interaction between universes can be the appearance of a pre-inflationary stage in the evolution of the universes that might leave observable consequences in the properties of the CMB. |
1503.08725 | Thibaut Josset | Goffredo Chirco, Thibaut Josset, Carlo Rovelli | Statistical mechanics of reparametrization-invariant systems. It takes
three to tango | 9 pages, 2 figures | Class. Quantum Grav. 33 (2016) 045005 | 10.1088/0264-9381/33/4/045005 | null | gr-qc cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is notoriously difficult to apply statistical mechanics to generally
covariant systems, because the notions of time, energy and equilibrium are
seriously modified in this context. We discuss the conditions under which
weaker versions of these notions can be defined, sufficient for statistical
mechanics. We focus on reparametrization-invariant systems without additional
gauges. The key is to reconstruct statistical mechanics from the ergodic
theorem. We find that a suitable split of the system into two non interacting
components is sufficient for generalizing statistical mechanics. While
equilibrium acquires sense only when the system admits a suitable split into
three weakly interacting components ---roughly: a clock and two systems among
which a generalization of energy is equi-partitioned. This allows the
application of statistical mechanics and thermodynamics as an additivity
condition of such generalized energy.
| [
{
"created": "Mon, 30 Mar 2015 16:05:51 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Jun 2016 16:14:37 GMT",
"version": "v2"
}
] | 2016-06-15 | [
[
"Chirco",
"Goffredo",
""
],
[
"Josset",
"Thibaut",
""
],
[
"Rovelli",
"Carlo",
""
]
] | It is notoriously difficult to apply statistical mechanics to generally covariant systems, because the notions of time, energy and equilibrium are seriously modified in this context. We discuss the conditions under which weaker versions of these notions can be defined, sufficient for statistical mechanics. We focus on reparametrization-invariant systems without additional gauges. The key is to reconstruct statistical mechanics from the ergodic theorem. We find that a suitable split of the system into two non interacting components is sufficient for generalizing statistical mechanics. While equilibrium acquires sense only when the system admits a suitable split into three weakly interacting components ---roughly: a clock and two systems among which a generalization of energy is equi-partitioned. This allows the application of statistical mechanics and thermodynamics as an additivity condition of such generalized energy. |
2401.09542 | Susanna Barsanti | Matteo Della Rocca, Susanna Barsanti, Leonardo Gualtieri, Andrea
Maselli | Extreme mass-ratio inspirals as probes of scalar fields: inclined
circular orbits around Kerr black holes | 12 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Extreme mass-ratio inspirals, a target source for the space-based
gravitational wave detector LISA, are a sensitive probe of fundamental scalar
fields coupled to gravity. We assess the capability of LISA to detect whether
the secondary compact object is endowed with a scalar field, in the case of
inclined orbits. We show that the imprint of the scalar field depends on the
orbital inclination, and is significantly larger for prograde orbits.
| [
{
"created": "Wed, 17 Jan 2024 19:00:06 GMT",
"version": "v1"
}
] | 2024-01-19 | [
[
"Della Rocca",
"Matteo",
""
],
[
"Barsanti",
"Susanna",
""
],
[
"Gualtieri",
"Leonardo",
""
],
[
"Maselli",
"Andrea",
""
]
] | Extreme mass-ratio inspirals, a target source for the space-based gravitational wave detector LISA, are a sensitive probe of fundamental scalar fields coupled to gravity. We assess the capability of LISA to detect whether the secondary compact object is endowed with a scalar field, in the case of inclined orbits. We show that the imprint of the scalar field depends on the orbital inclination, and is significantly larger for prograde orbits. |
2006.05086 | Soumya Chakrabarti | Soumya Chakrabarti and Jackson Levi Said | Geodesic Congruences and a Collapsing Stellar Distribution in f (T )
Theories | 12 pages, 5 Figures, Accepted for Publication in Physical Review D | null | 10.1103/PhysRevD.101.124044 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Teleparallel Gravity (TG) describes gravitation as a torsional- rather than
curvature-based effect. As in curvature-based constructions of gravity, several
different formulations can be proposed, one of which is the Teleparallel
equivalent of General Relativity (TEGR) which is dynamically equivalent to GR.
In this work, we explore the evolution of a spatially homogeneous collapsing
stellar body in the context of two important modifications to TEGR, namely f
(T) gravity which is the TG analogue of f (R) gravity, and a nonminimal
coupling with a scalar field which has become popular in TG for its effects in
cosmology. We explore the role of geodesic deviation to study the congruence of
nearby particles in lieu of the Raychaudhuri equation. We find f (T) models
that satisfy the null energy condition and describe interesting collapse
profiles. In the case of a nonminimally coupled scalar field, we also find
potential collapse models with intriguing scalar field evolution profiles.
| [
{
"created": "Tue, 9 Jun 2020 07:26:25 GMT",
"version": "v1"
}
] | 2020-07-01 | [
[
"Chakrabarti",
"Soumya",
""
],
[
"Said",
"Jackson Levi",
""
]
] | Teleparallel Gravity (TG) describes gravitation as a torsional- rather than curvature-based effect. As in curvature-based constructions of gravity, several different formulations can be proposed, one of which is the Teleparallel equivalent of General Relativity (TEGR) which is dynamically equivalent to GR. In this work, we explore the evolution of a spatially homogeneous collapsing stellar body in the context of two important modifications to TEGR, namely f (T) gravity which is the TG analogue of f (R) gravity, and a nonminimal coupling with a scalar field which has become popular in TG for its effects in cosmology. We explore the role of geodesic deviation to study the congruence of nearby particles in lieu of the Raychaudhuri equation. We find f (T) models that satisfy the null energy condition and describe interesting collapse profiles. In the case of a nonminimally coupled scalar field, we also find potential collapse models with intriguing scalar field evolution profiles. |
2407.18536 | Sumanta Chakraborty | Sumanta Chakraborty, Sk Jahanur Hoque and Amitabh Virmani | On supertranslation invariant Lorentz charges | v1, 15 pages, no figures, for the special issue QG@RRI in Gen. Rel.
Grav | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In recent papers, Fuentealba, Henneaux, and Troessaert (FHT) gave definitions
for supertranslation invariant Lorentz charges in the ADM Hamiltonian formalism
and showed that their definitions match with the Chen, Wang, Yau (CWY)
definitions of Lorentz charges at null infinity which are free from
``supertranslation ambiguities''. In this brief note, motivated by the analysis
of FHT, we write expressions for the supertranslation invariant Lorentz charges
in Beig-Schmidt variables at spacelike and timelike infinity. We present
calculations, building upon the work of Comp\`ere, Gralla, and Wei (CGW), to
show that our expressions for supertranslation invariant Lorentz charges match
the CWY definitions at null infinity.
| [
{
"created": "Fri, 26 Jul 2024 06:34:34 GMT",
"version": "v1"
}
] | 2024-07-29 | [
[
"Chakraborty",
"Sumanta",
""
],
[
"Hoque",
"Sk Jahanur",
""
],
[
"Virmani",
"Amitabh",
""
]
] | In recent papers, Fuentealba, Henneaux, and Troessaert (FHT) gave definitions for supertranslation invariant Lorentz charges in the ADM Hamiltonian formalism and showed that their definitions match with the Chen, Wang, Yau (CWY) definitions of Lorentz charges at null infinity which are free from ``supertranslation ambiguities''. In this brief note, motivated by the analysis of FHT, we write expressions for the supertranslation invariant Lorentz charges in Beig-Schmidt variables at spacelike and timelike infinity. We present calculations, building upon the work of Comp\`ere, Gralla, and Wei (CGW), to show that our expressions for supertranslation invariant Lorentz charges match the CWY definitions at null infinity. |
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