id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9607030 | G. Kunstatter | A. Barvinsky (Lebedev Physics Institute) and G. Kunstatter (University
of Winnipeg) | Mass Spectrum for Black Holes in Generic 2-D Dilaton Gravity | 6 pages, Latex | null | null | null | gr-qc | null | Two arguments for the quantization of entropy for black holes in generic 2-D
dilaton gravity are summarized. The first argument is based on reduced
quantization of the only physical observables in the theory, namely the black
hole mass and its conjugate momentum, the Killing time separation. The second
one uses the exact physical mass eigenstates for Euclidean black holes found
via Dirac quantization. Both methods give the same spectrum: the black hole
entropy must be quantized $S= 2\pi n/G$.
| [
{
"created": "Fri, 12 Jul 1996 20:26:41 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Barvinsky",
"A.",
"",
"Lebedev Physics Institute"
],
[
"Kunstatter",
"G.",
"",
"University\n of Winnipeg"
]
] | Two arguments for the quantization of entropy for black holes in generic 2-D dilaton gravity are summarized. The first argument is based on reduced quantization of the only physical observables in the theory, namely the black hole mass and its conjugate momentum, the Killing time separation. The second one uses the exact physical mass eigenstates for Euclidean black holes found via Dirac quantization. Both methods give the same spectrum: the black hole entropy must be quantized $S= 2\pi n/G$. |
0812.3462 | Tomohiro Harada | Tomohiro Harada, Ken-ichi Nakao and Brien C. Nolan | Einstein-Rosen waves and the self-similarity hypothesis in cylindrical
symmetry | 21 pages, 10 figure files, revised version, accepted for publication
in Physical Review D, minor correction, erratum added | Phys.Rev.D80:024025,2009; Erratum-ibid.D80:109903,2009 | 10.1103/PhysRevD.80.024025 10.1103/PhysRevD.80.109903 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The self-similarity hypothesis claims that in classical general relativity,
spherically symmetric solutions may naturally evolve to a self-similar form in
certain circumstances. In this context, the validity of the corresponding
hypothesis in nonspherical geometry is very interesting as there may exist
gravitational waves. We investigate self-similar vacuum solutions to the
Einstein equation in the so-called whole-cylinder symmetry. We find that those
solutions are reduced to part of the Minkowski spacetime with a regular or
conically singular axis and with trivial or nontrivial topology if the
homothetic vector is orthogonal to the cylinders of symmetry. These solutions
are analogous to the Milne universe, but only in the direction parallel to the
axis. Using these solutions, we discuss the nonuniqueness (and nonvanishing
nature) of C energy and the existence of a cylindrical trapping horizon in
Minkowski spacetime. Then, as we generalize the analysis, we find a
two-parameter family of self-similar vacuum solutions, where the homothetic
vector is not orthogonal to the cylinders in general. The family includes the
Minkowski, the Kasner and the cylindrical Milne solutions. The obtained
solutions describe the interior to the exploding (imploding) shell of
gravitational waves or the collapse (explosion) of gravitational waves
involving singularities from nonsingular initial data in general. Since recent
numerical simulations strongly suggest that one of these solutions may describe
the asymptotic behavior of gravitational waves from the collapse of a dust
cylinder, this means that the self-similarity hypothesis is naturally
generalized to cylindrical symmetry.
| [
{
"created": "Thu, 18 Dec 2008 05:38:53 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jun 2009 07:09:11 GMT",
"version": "v2"
},
{
"created": "Sun, 19 Jul 2009 06:27:53 GMT",
"version": "v3"
},
{
"created": "Sun, 22 Nov 2009 07:10:31 GMT",
"version": "v4"
}
] | 2014-11-18 | [
[
"Harada",
"Tomohiro",
""
],
[
"Nakao",
"Ken-ichi",
""
],
[
"Nolan",
"Brien C.",
""
]
] | The self-similarity hypothesis claims that in classical general relativity, spherically symmetric solutions may naturally evolve to a self-similar form in certain circumstances. In this context, the validity of the corresponding hypothesis in nonspherical geometry is very interesting as there may exist gravitational waves. We investigate self-similar vacuum solutions to the Einstein equation in the so-called whole-cylinder symmetry. We find that those solutions are reduced to part of the Minkowski spacetime with a regular or conically singular axis and with trivial or nontrivial topology if the homothetic vector is orthogonal to the cylinders of symmetry. These solutions are analogous to the Milne universe, but only in the direction parallel to the axis. Using these solutions, we discuss the nonuniqueness (and nonvanishing nature) of C energy and the existence of a cylindrical trapping horizon in Minkowski spacetime. Then, as we generalize the analysis, we find a two-parameter family of self-similar vacuum solutions, where the homothetic vector is not orthogonal to the cylinders in general. The family includes the Minkowski, the Kasner and the cylindrical Milne solutions. The obtained solutions describe the interior to the exploding (imploding) shell of gravitational waves or the collapse (explosion) of gravitational waves involving singularities from nonsingular initial data in general. Since recent numerical simulations strongly suggest that one of these solutions may describe the asymptotic behavior of gravitational waves from the collapse of a dust cylinder, this means that the self-similarity hypothesis is naturally generalized to cylindrical symmetry. |
2207.08199 | Krishnakanta Bhattacharya | Krishnakanta Bhattacharya | A novel probe of Einstein-Hilbert action: Dynamic upgradation of metric
parameters | 28 Pages, To appear in GERG (in the memorial volume for Prof. Thanu
Padmanabhan) | Gen. Rel. Grav. 54, 81 (2022) | 10.1007/s10714-022-02958-9 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Einstein-Hilbert (EH) action is peculiar in many ways. Some of the
Peculiar features have already been highlighted in literature. In the present
article, we have discussed some peculiar features of EH action which has not
been discussed earlier. It is well-known that there are several ways of
decomposing the EH action into the bulk and the surface part with different
underlying motivations. We provide a review on all of these decompositions.
Then, we attempt to study the static coordinate as a limiting case of a
time-dependent coordinate via dynamic upgradation of the constant metric
parameters. Firstly, we study the consequences when the constant parameters,
present in a static and spherically symmetric (SSS) metric, are promoted to the
time dependent variables, which allows us to incorporate the time-dependence in
the static coordinate. We find that, in every sets of decomposition, the
expression of the bulk term remains invariant, whereas the surface term changes
by a total derivative term. Finally, when we obliterate the time dependence of
the metric parameters, we find that the expression of the Ricci-scalar (or the
EH action) does not go back to its original value. Instead, we find that the
curvature becomes singular on the horizon, which implies a topological change
from the original spacetime.
| [
{
"created": "Sun, 17 Jul 2022 15:09:13 GMT",
"version": "v1"
}
] | 2022-08-05 | [
[
"Bhattacharya",
"Krishnakanta",
""
]
] | The Einstein-Hilbert (EH) action is peculiar in many ways. Some of the Peculiar features have already been highlighted in literature. In the present article, we have discussed some peculiar features of EH action which has not been discussed earlier. It is well-known that there are several ways of decomposing the EH action into the bulk and the surface part with different underlying motivations. We provide a review on all of these decompositions. Then, we attempt to study the static coordinate as a limiting case of a time-dependent coordinate via dynamic upgradation of the constant metric parameters. Firstly, we study the consequences when the constant parameters, present in a static and spherically symmetric (SSS) metric, are promoted to the time dependent variables, which allows us to incorporate the time-dependence in the static coordinate. We find that, in every sets of decomposition, the expression of the bulk term remains invariant, whereas the surface term changes by a total derivative term. Finally, when we obliterate the time dependence of the metric parameters, we find that the expression of the Ricci-scalar (or the EH action) does not go back to its original value. Instead, we find that the curvature becomes singular on the horizon, which implies a topological change from the original spacetime. |
1210.1566 | Gabor Kunstatter | Gabor Kunstatter, Hideki Maeda and Tim Taves | Hamiltonian dynamics of Lovelock black holes with spherical symmetry | 53 pages, including two major appendices; some typos fixed; version
published in CQG | Class.Quant.Grav. 30 (2013) 065002 | 10.1088/0264-9381/30/6/065002 | CECS-PHY-12/08 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider spherically symmetric black holes in generic Lovelock gravity.
Using geometrodynamical variables we do a complete Hamiltonian analysis,
including derivation of the super-Hamiltonian and super-momentum constraints
and verification of suitable boundary conditions for asymptotically flat black
holes. Our analysis leads to a remarkably simple fully reduced Hamiltonian for
the vacuum gravitational sector that provides the starting point for the
quantization of Lovelock block holes. Finally, we derive the completely reduced
equations of motion for the collapse of a spherically symmetric charged,
self-gravitating complex scalar field in generalized flat slice
(Painlev\'{e}-Gullstrand) coordinates.
| [
{
"created": "Thu, 4 Oct 2012 19:59:08 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Oct 2012 14:14:30 GMT",
"version": "v2"
},
{
"created": "Mon, 4 Feb 2013 01:53:28 GMT",
"version": "v3"
}
] | 2014-08-13 | [
[
"Kunstatter",
"Gabor",
""
],
[
"Maeda",
"Hideki",
""
],
[
"Taves",
"Tim",
""
]
] | We consider spherically symmetric black holes in generic Lovelock gravity. Using geometrodynamical variables we do a complete Hamiltonian analysis, including derivation of the super-Hamiltonian and super-momentum constraints and verification of suitable boundary conditions for asymptotically flat black holes. Our analysis leads to a remarkably simple fully reduced Hamiltonian for the vacuum gravitational sector that provides the starting point for the quantization of Lovelock block holes. Finally, we derive the completely reduced equations of motion for the collapse of a spherically symmetric charged, self-gravitating complex scalar field in generalized flat slice (Painlev\'{e}-Gullstrand) coordinates. |
1106.0970 | Mustapha Azreg-A\"inou | Mustapha Azreg-A\"inou | Comment on `Spinning loop black holes' [arXiv:1006.0232] | 2 pages, 1 figure | Class. Quantum Grav. 28 (2011) 148001 (2pp) | 10.1088/0264-9381/28/14/148001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the derivations and conclusions made in Caravelli and Modesto (2010
\textit{Class. Quantum Grav.} \textbf{27} 245022, arXiv:1006.0232) and show
that most of the analysis performed there is not valid.
| [
{
"created": "Mon, 6 Jun 2011 06:42:46 GMT",
"version": "v1"
}
] | 2011-06-07 | [
[
"Azreg-Aïnou",
"Mustapha",
""
]
] | We review the derivations and conclusions made in Caravelli and Modesto (2010 \textit{Class. Quantum Grav.} \textbf{27} 245022, arXiv:1006.0232) and show that most of the analysis performed there is not valid. |
2208.07379 | Macarena Lagos | Macarena Lagos and Lam Hui | Generation and propagation of nonlinear quasi-normal modes of a
Schwarzschild black hole | Version accepted in PRD | null | 10.1103/PhysRevD.107.044040 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the analysis of a binary black hole coalescence, it is necessary to
include gravitational self-interactions in order to describe the transition of
the gravitational wave signal from the merger to the ringdown stage. In this
paper we study the phenomenology of the generation and propagation of
nonlinearities in the ringdown of a Schwarzschild black hole, using
second-order perturbation theory. Following earlier work, we show that the
Green's function and its causal structure determines how both first-order and
second-order perturbations are generated, and hence highlight that both of
these solutions share some physical properties. In particular, we discuss the
sense in which both linear and quadratic quasi-normal modes (QNMs) are
generated in the vicinity of the peak of the gravitational potential barrier
(loosely referred to as the light ring). Among the second-order perturbations,
there are solutions with linear QNM frequencies (whose amplitudes are thus
renormalized from their linear values), as well as quadratic QNM frequencies
with a distinct spectrum. Moreover, we show using a WKB analysis that, in the
eikonal limit, waves generated inside the light ring propagate towards the
black hole horizon, and only waves generated outside propagate towards an
asymptotic observer. These results might be relevant for recent discussions on
the validity of perturbation theory close to the merger. Finally, we argue that
even if nonlinearities are small, quadratic QNMs may be detectable and would
likely be useful for improving ringdown models of higher angular harmonics and
future tests of gravity.
| [
{
"created": "Mon, 15 Aug 2022 18:00:03 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Jan 2023 14:56:19 GMT",
"version": "v2"
}
] | 2023-03-08 | [
[
"Lagos",
"Macarena",
""
],
[
"Hui",
"Lam",
""
]
] | In the analysis of a binary black hole coalescence, it is necessary to include gravitational self-interactions in order to describe the transition of the gravitational wave signal from the merger to the ringdown stage. In this paper we study the phenomenology of the generation and propagation of nonlinearities in the ringdown of a Schwarzschild black hole, using second-order perturbation theory. Following earlier work, we show that the Green's function and its causal structure determines how both first-order and second-order perturbations are generated, and hence highlight that both of these solutions share some physical properties. In particular, we discuss the sense in which both linear and quadratic quasi-normal modes (QNMs) are generated in the vicinity of the peak of the gravitational potential barrier (loosely referred to as the light ring). Among the second-order perturbations, there are solutions with linear QNM frequencies (whose amplitudes are thus renormalized from their linear values), as well as quadratic QNM frequencies with a distinct spectrum. Moreover, we show using a WKB analysis that, in the eikonal limit, waves generated inside the light ring propagate towards the black hole horizon, and only waves generated outside propagate towards an asymptotic observer. These results might be relevant for recent discussions on the validity of perturbation theory close to the merger. Finally, we argue that even if nonlinearities are small, quadratic QNMs may be detectable and would likely be useful for improving ringdown models of higher angular harmonics and future tests of gravity. |
0901.1121 | Tomas Liko | Tomas Liko | Isolated horizons, p-form matter fields, topology and the
black-hole/string correspondence principle | 11 pages; v2: figure added; references added; v3: introduction
shortened; to appear in Physical Review D; v4: typos corrected | Phys.Rev.D79:084038,2009 | 10.1103/PhysRevD.79.084038 | IGC-09/1-2 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the mechanics of D-dimensional isolated horizons (IHs) for Einstein
gravity in the presence of arbitrary p-form matter fields. This generalizes the
analysis of Copsey and Horowitz to non-stationary spacetimes and therefore the
local first law to include non-monopolar (dipole) charges. The only requirement
for the local first law to hold is that the action has to be differentiable.
The resulting conserved charges are all intrinsic to the horizon and are
independent of the topology of the horizon cross sections. We explicitly
calculate the local charges for five-dimensional black holes and black rings
that are relevant within the context of superstring theory. We conclude with
some comments on the black-hole/string correspondence principle and argue that
IHs (or some other quasilocal variant) should play a fundamental role in
superstring theory.
| [
{
"created": "Thu, 8 Jan 2009 20:08:44 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Feb 2009 20:16:50 GMT",
"version": "v2"
},
{
"created": "Sat, 7 Mar 2009 00:25:11 GMT",
"version": "v3"
},
{
"created": "Wed, 25 Mar 2009 16:06:34 GMT",
"version": "v4"
}
] | 2009-04-29 | [
[
"Liko",
"Tomas",
""
]
] | We study the mechanics of D-dimensional isolated horizons (IHs) for Einstein gravity in the presence of arbitrary p-form matter fields. This generalizes the analysis of Copsey and Horowitz to non-stationary spacetimes and therefore the local first law to include non-monopolar (dipole) charges. The only requirement for the local first law to hold is that the action has to be differentiable. The resulting conserved charges are all intrinsic to the horizon and are independent of the topology of the horizon cross sections. We explicitly calculate the local charges for five-dimensional black holes and black rings that are relevant within the context of superstring theory. We conclude with some comments on the black-hole/string correspondence principle and argue that IHs (or some other quasilocal variant) should play a fundamental role in superstring theory. |
2101.03360 | Zaza Osmanov | G. Butbaia and Z.N. Osmanov | Fluid Dynamics in the Ellis Wormhole | 12 pages, 7 figures | null | 10.1142/S0218271821500723 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | In the Ellis wormhole metrics we study characteristics of fluid dynamics and
the properties of linear sound waves. By implying the energy-momentum equation
and the continuity equation in the general relativistic manner we examine the
flow dynamics and solve the corresponding equations for a relatively simple
case - radial flow. To study the linear sound waves the equations governing the
mentioned physical system are linearized and solved and interesting
characteristic properties are found.
| [
{
"created": "Sat, 9 Jan 2021 13:50:46 GMT",
"version": "v1"
}
] | 2021-08-25 | [
[
"Butbaia",
"G.",
""
],
[
"Osmanov",
"Z. N.",
""
]
] | In the Ellis wormhole metrics we study characteristics of fluid dynamics and the properties of linear sound waves. By implying the energy-momentum equation and the continuity equation in the general relativistic manner we examine the flow dynamics and solve the corresponding equations for a relatively simple case - radial flow. To study the linear sound waves the equations governing the mentioned physical system are linearized and solved and interesting characteristic properties are found. |
2212.14396 | Hongguang Liu | Pietro Dona, Muxin Han, Hongguang Liu | Spinfoams and high performance computing | 33 pages, 11 figures. Invited chapter for the book "Handbook of
Quantum Gravity" (Eds. C. Bambi, L. Modesto and I.L. Shapiro, Springer
Singapore, expected in 2023) | Bambi, C., Modesto, L., Shapiro, I. (eds) Handbook of Quantum
Gravity. Springer, Singapore 2023 | 10.1007/978-981-19-3079-9_100-1 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Numerical methods are a powerful tool for doing calculations in spinfoam
theory. We review the major frameworks available, their definition, and various
applications. We start from $\texttt{sl2cfoam-next}$, the state-of-the-art
library to efficiently compute EPRL spin foam amplitudes based on the booster
decomposition. We also review two alternative approaches based on the
integration representation of the spinfoam amplitude: Firstly, the numerical
computations of the complex critical points discover the curved geometries from
the spinfoam amplitude and provides important evidence of resolving the
flatness problem in the spinfoam theory. Lastly, we review the numerical
estimation of observable expectation values based on the Lefschetz thimble and
Markov-Chain Monte Carlo method, with the EPRL spinfoam propagator as an
example.
| [
{
"created": "Thu, 29 Dec 2022 17:58:31 GMT",
"version": "v1"
}
] | 2023-09-12 | [
[
"Dona",
"Pietro",
""
],
[
"Han",
"Muxin",
""
],
[
"Liu",
"Hongguang",
""
]
] | Numerical methods are a powerful tool for doing calculations in spinfoam theory. We review the major frameworks available, their definition, and various applications. We start from $\texttt{sl2cfoam-next}$, the state-of-the-art library to efficiently compute EPRL spin foam amplitudes based on the booster decomposition. We also review two alternative approaches based on the integration representation of the spinfoam amplitude: Firstly, the numerical computations of the complex critical points discover the curved geometries from the spinfoam amplitude and provides important evidence of resolving the flatness problem in the spinfoam theory. Lastly, we review the numerical estimation of observable expectation values based on the Lefschetz thimble and Markov-Chain Monte Carlo method, with the EPRL spinfoam propagator as an example. |
2010.09751 | Wei Wei | Wei Wei, E. A. Huerta | Deep learning for gravitational wave forecasting of neutron star mergers | 10 pages, 4 figures | Physics Letters B 816 (2021) 136185 | 10.1016/j.physletb.2021.136185 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce deep learning time-series forecasting for gravitational wave
detection of binary neutron star mergers. This method enables the
identification of these signals in real advanced LIGO data up to 30 seconds
before merger. When applied to GW170817, our deep learning forecasting method
identifies the presence of this gravitational wave signal 10 seconds before
merger. This novel approach requires a single GPU for inference, and may be
used as part of an early warning system for time-sensitive multi-messenger
searches.
| [
{
"created": "Mon, 19 Oct 2020 18:00:39 GMT",
"version": "v1"
}
] | 2021-03-09 | [
[
"Wei",
"Wei",
""
],
[
"Huerta",
"E. A.",
""
]
] | We introduce deep learning time-series forecasting for gravitational wave detection of binary neutron star mergers. This method enables the identification of these signals in real advanced LIGO data up to 30 seconds before merger. When applied to GW170817, our deep learning forecasting method identifies the presence of this gravitational wave signal 10 seconds before merger. This novel approach requires a single GPU for inference, and may be used as part of an early warning system for time-sensitive multi-messenger searches. |
gr-qc/9912012 | Martin Rainer | Martin Rainer | Multidimensional Sigma-Model with Black Holes and p-Branes | 10 pages, latex & AMS symb., presented at ERE 99 (Bilbao) | null | null | null | gr-qc | null | The bosonic content of string theory in curved background of multidimensional
structure with p-branes has a systematic geometrical description as an
effective sigma-model of gravity in lower dimension (say 3+1) with additional
interacting dilatonic and p-brane fields. If the target-space is locally
symmetric, solutions with intersecting p-branes can be found. Some static
solutions are p-brane generalizations of black holes (including the standard
Reissner-Nordstr"om class), which allow the prediction of detectable features
of the higher-dimensional p-brane geometry via scaling properties of black hole
thermal properties. E.g. the Hawking temperature T_H depends critically on the
p-brane intersection topology.
| [
{
"created": "Thu, 2 Dec 1999 16:48:43 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Rainer",
"Martin",
""
]
] | The bosonic content of string theory in curved background of multidimensional structure with p-branes has a systematic geometrical description as an effective sigma-model of gravity in lower dimension (say 3+1) with additional interacting dilatonic and p-brane fields. If the target-space is locally symmetric, solutions with intersecting p-branes can be found. Some static solutions are p-brane generalizations of black holes (including the standard Reissner-Nordstr"om class), which allow the prediction of detectable features of the higher-dimensional p-brane geometry via scaling properties of black hole thermal properties. E.g. the Hawking temperature T_H depends critically on the p-brane intersection topology. |
1006.5039 | Alfredo Lopez Ortega | A. Lopez-Ortega | Entropy spectrum of the D-dimensional massless topological black hole | 6 pages | Gen.Rel.Grav.42:2939-2945,2010 | 10.1007/s10714-010-1049-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | There are exact solutions to Einstein's equations with negative cosmological
constant that represent black holes whose event horizons are manifolds of
negative curvature, the so-called topological black holes. Among these
solutions there is one, the massless topological black hole, whose mass is
equal to zero. Hod proposes that in the semiclassical limit the asymptotic
quasinormal frequencies determine the entropy spectrum of the black holes.
Taking into account this proposal, we calculate the entropy spectrum of the
massless topological black hole and we compare with the results on the entropy
spectra of other topological black holes.
| [
{
"created": "Fri, 25 Jun 2010 18:45:21 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Jun 2010 01:32:42 GMT",
"version": "v2"
}
] | 2010-11-09 | [
[
"Lopez-Ortega",
"A.",
""
]
] | There are exact solutions to Einstein's equations with negative cosmological constant that represent black holes whose event horizons are manifolds of negative curvature, the so-called topological black holes. Among these solutions there is one, the massless topological black hole, whose mass is equal to zero. Hod proposes that in the semiclassical limit the asymptotic quasinormal frequencies determine the entropy spectrum of the black holes. Taking into account this proposal, we calculate the entropy spectrum of the massless topological black hole and we compare with the results on the entropy spectra of other topological black holes. |
1708.02035 | Vladimir Khatsymovsky | V.M. Khatsymovsky | First order discrete Faddeev gravity at the strongly varying fields | 15 pages | Mod. Phys. Lett. A, Vol. 32, No. 35 (2017) 1750181 | 10.1142/S0217732317501814 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the Faddeev formulation of general relativity (GR), which can be
characterized by a kind of $d$-dimensional tetrad (typically $d$=10) and a
non-Riemannian connection. This theory is invariant w. r. t. the global, but
not local, rotations in the $d$-dimensional space. There can be configurations
with a smooth or flat metric, but with the tetrad that changes abruptly at
small distances, a kind of "antiferromagnetic" structure.
Previously, we discussed a first order representation for the Faddeev
gravity, which uses the orthogonal connection in the $d$-dimensional space as
an independent variable. Using the discrete form of this formulation, we
considered the spectrum of (elementary) area. This spectrum turns out to be
physically reasonable just on a classical background with large connection like
rotations by $\pi$, that is, with such an "antiferromagnetic" structure.
In the discrete first order Faddeev gravity, we consider such a structure
with periodic cells and large connection and strongly changing tetrad field
inside the cell. We show that this system in the continuum limit reduces to a
generalization of the Faddeev system. The action is a sum of related actions of
the Faddeev type and is still reduced to the GR action.
| [
{
"created": "Mon, 7 Aug 2017 08:36:27 GMT",
"version": "v1"
}
] | 2017-11-09 | [
[
"Khatsymovsky",
"V. M.",
""
]
] | We consider the Faddeev formulation of general relativity (GR), which can be characterized by a kind of $d$-dimensional tetrad (typically $d$=10) and a non-Riemannian connection. This theory is invariant w. r. t. the global, but not local, rotations in the $d$-dimensional space. There can be configurations with a smooth or flat metric, but with the tetrad that changes abruptly at small distances, a kind of "antiferromagnetic" structure. Previously, we discussed a first order representation for the Faddeev gravity, which uses the orthogonal connection in the $d$-dimensional space as an independent variable. Using the discrete form of this formulation, we considered the spectrum of (elementary) area. This spectrum turns out to be physically reasonable just on a classical background with large connection like rotations by $\pi$, that is, with such an "antiferromagnetic" structure. In the discrete first order Faddeev gravity, we consider such a structure with periodic cells and large connection and strongly changing tetrad field inside the cell. We show that this system in the continuum limit reduces to a generalization of the Faddeev system. The action is a sum of related actions of the Faddeev type and is still reduced to the GR action. |
2205.02675 | Nicholas Loutrel | Nicholas Loutrel and Nicolas Yunes | Parity Violation in Spin-Precessing Binaries: Gravitational Waves from
the Inspiral of Black Holes in Dynamical Chern-Simons Gravity | 32 pages, 4 figures, published version | Phys. Rev. D 106, 064009 (2022) | 10.1103/PhysRevD.106.064009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spin precession in compact binaries is intricately tuned to the multipole
structure of the underlying bodies. For black holes, violations of the no-hair
theorems induced by modifications to general relativity correct the precession
dynamics, which in turn imprints onto the amplitude and phase modulations of
the gravitational waves emitted by the binary. Recently, the spin precession
equations were derived up to second order in spin for dynamical Chern-Simons
gravity, a parity violating modified theory of gravity. We here solve these
equations and construct, for the first time, analytic expressions for the time-
and frequency-domain gravitational waves emitted in the quasi-circular inspiral
of spin-precessing black hole binaries in a modified theory of gravity using
the post-Newtonian approximation. Working within the small coupling
approximation and using multiple scale analysis, we show that the corrections
to the nutation phase enter at relative 1PN order, and the corrections to the
precession angle and Thomas phase enter at relative 0PN order. Making use of
the stationary phase approximation and shifted uniform asymptotics, we find
that the Fourier phase of the waveform is characterized by three modifications,
two due to the back-reaction of the precession dynamics onto the spin-orbit and
spin-spin couplings that enter at 1.5PN and 2PN orders, and a 2PN modification
due to the emission of dipole radiation. We also find that back-reaction of the
precession dynamics forces the dCS corrections to the Fourier amplitude to
enter at 0PN order, as opposed to 2PN order, as expected for spin-aligned
binaries. Our work lays the first foundational stones to build an
inspiral-merger-ringdown phenomenological model for spin-precessing binaries in
a modified theory of gravity.
| [
{
"created": "Thu, 5 May 2022 14:30:27 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Sep 2022 10:00:20 GMT",
"version": "v2"
}
] | 2022-09-08 | [
[
"Loutrel",
"Nicholas",
""
],
[
"Yunes",
"Nicolas",
""
]
] | Spin precession in compact binaries is intricately tuned to the multipole structure of the underlying bodies. For black holes, violations of the no-hair theorems induced by modifications to general relativity correct the precession dynamics, which in turn imprints onto the amplitude and phase modulations of the gravitational waves emitted by the binary. Recently, the spin precession equations were derived up to second order in spin for dynamical Chern-Simons gravity, a parity violating modified theory of gravity. We here solve these equations and construct, for the first time, analytic expressions for the time- and frequency-domain gravitational waves emitted in the quasi-circular inspiral of spin-precessing black hole binaries in a modified theory of gravity using the post-Newtonian approximation. Working within the small coupling approximation and using multiple scale analysis, we show that the corrections to the nutation phase enter at relative 1PN order, and the corrections to the precession angle and Thomas phase enter at relative 0PN order. Making use of the stationary phase approximation and shifted uniform asymptotics, we find that the Fourier phase of the waveform is characterized by three modifications, two due to the back-reaction of the precession dynamics onto the spin-orbit and spin-spin couplings that enter at 1.5PN and 2PN orders, and a 2PN modification due to the emission of dipole radiation. We also find that back-reaction of the precession dynamics forces the dCS corrections to the Fourier amplitude to enter at 0PN order, as opposed to 2PN order, as expected for spin-aligned binaries. Our work lays the first foundational stones to build an inspiral-merger-ringdown phenomenological model for spin-precessing binaries in a modified theory of gravity. |
2401.06424 | Salvatore Capozziello | Salvatore Capozziello, Maurizio Capriolo, Shin'ichi Nojiri | Gravitational waves in $f(Q)$ non-metric gravity via geodesic deviation | 21 pages, accepted for publication in Phys. Lett. B | null | null | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | We investigate gravitational waves in the $f(Q)$ gravity, i.e., a geometric
theory of gravity described by a non-metric compatible connection, free from
torsion and curvature, known as symmetric-teleparallel gravity. We show that
$f(Q)$ gravity exhibits only two massless and tensor modes. Their polarizations
are transverse with helicity equal to two, exactly reproducing the plus and
cross tensor modes typical of General Relativity. In order to analyze these
gravitational waves, we first obtain the deviation equation of two trajectories
followed by nearby freely falling point-like particles and we find it to
coincide with the geodesic deviation of General Relativity. This is because the
energy-momentum tensor of matter and field equations are Levi-Civita
covariantly conserved and, therefore, free structure-less particles follow,
also in $f(Q)$ gravity, the General Relativity geodesics. Equivalently, it is
possible to show that the curves are solutions of a force equation, where an
extra force term of geometric origin, due to non-metricity, modifies the
autoparallel curves with respect to the non-metric connection. In summary,
gravitational waves produced in non-metricity-based $f(Q)$ gravity behave as
those in torsion-based $f(T)$ gravity and it is not possible to distinguish
them from those of General Relativity only by wave polarization measurements.
This shows that the situation is different with respect to the curvature-based
$f(R)$ gravity where an additional scalar mode is always present for $f(R)\neq
R$.
| [
{
"created": "Fri, 12 Jan 2024 07:41:18 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Feb 2024 09:17:44 GMT",
"version": "v2"
}
] | 2024-02-02 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Capriolo",
"Maurizio",
""
],
[
"Nojiri",
"Shin'ichi",
""
]
] | We investigate gravitational waves in the $f(Q)$ gravity, i.e., a geometric theory of gravity described by a non-metric compatible connection, free from torsion and curvature, known as symmetric-teleparallel gravity. We show that $f(Q)$ gravity exhibits only two massless and tensor modes. Their polarizations are transverse with helicity equal to two, exactly reproducing the plus and cross tensor modes typical of General Relativity. In order to analyze these gravitational waves, we first obtain the deviation equation of two trajectories followed by nearby freely falling point-like particles and we find it to coincide with the geodesic deviation of General Relativity. This is because the energy-momentum tensor of matter and field equations are Levi-Civita covariantly conserved and, therefore, free structure-less particles follow, also in $f(Q)$ gravity, the General Relativity geodesics. Equivalently, it is possible to show that the curves are solutions of a force equation, where an extra force term of geometric origin, due to non-metricity, modifies the autoparallel curves with respect to the non-metric connection. In summary, gravitational waves produced in non-metricity-based $f(Q)$ gravity behave as those in torsion-based $f(T)$ gravity and it is not possible to distinguish them from those of General Relativity only by wave polarization measurements. This shows that the situation is different with respect to the curvature-based $f(R)$ gravity where an additional scalar mode is always present for $f(R)\neq R$. |
0902.0928 | Xin Zhang | Xin Zhang, Jingfei Zhang, Jinglei Cui, Li Zhang | Chaplygin inflation in loop quantum cosmology | 6 pages, accepted for publication in Mod. Phys. Lett. A | Mod.Phys.Lett.A24:1763-1773,2009 | 10.1142/S0217732309030436 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we discuss the inflationary universe in the context of a
Chaplygin gas equation of state within the framework of the effective theory of
loop quantum cosmology. Under the slow-roll approximation, we calculate the
primordial perturbations for this model. We give the general expressions of the
scalar spectral index, its running, and the tensor-to-scalar ratio, etc. For
the chaotic inflation with a quadratic potential, using the WMAP 5-year
results, we determine the parameters of the Chaplygin inflation model in loop
quantum cosmology. The results are consistent with the WMAP observations.
| [
{
"created": "Thu, 5 Feb 2009 15:33:16 GMT",
"version": "v1"
}
] | 2009-08-20 | [
[
"Zhang",
"Xin",
""
],
[
"Zhang",
"Jingfei",
""
],
[
"Cui",
"Jinglei",
""
],
[
"Zhang",
"Li",
""
]
] | In this paper we discuss the inflationary universe in the context of a Chaplygin gas equation of state within the framework of the effective theory of loop quantum cosmology. Under the slow-roll approximation, we calculate the primordial perturbations for this model. We give the general expressions of the scalar spectral index, its running, and the tensor-to-scalar ratio, etc. For the chaotic inflation with a quadratic potential, using the WMAP 5-year results, we determine the parameters of the Chaplygin inflation model in loop quantum cosmology. The results are consistent with the WMAP observations. |
gr-qc/0510018 | Sanjeev Dhurandhar | Bhim Prasad Sarmah, S.K. Banerjee, S.V. Dhurandhar and J.V. Narlikar | On searches for gravitational waves from mini creation event by laser
interferometric detectors | null | Mon.Not.Roy.Astron.Soc.369:89-96,2006 | 10.1111/j.1365-2966.2006.10262.x | null | gr-qc | null | As an alternative view to the standard big bang cosmology the quasi-steady
state cosmology(QSSC) argues that the universe was not created in a single
great explosion; it neither had a beginning nor will it ever come to an end.
The creation of new matter in the universe is a regular feature occurring
through finite explosive events. Each creation event is called a mini-bang or,
a mini creation event(MCE). Gravitational waves are expected to be generated
due to any anisotropy present in this process of creation. Mini creation event
ejecting matter in two oppositely directed jets is thus a source of
gravitational waves which can in principle be detected by laser interferometric
detectors. In the present work we consider the gravitational waveforms
propagated by linear jets and then estimate the response of laser
interferometric detectors like LIGO and LISA.
| [
{
"created": "Wed, 5 Oct 2005 11:56:22 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Sarmah",
"Bhim Prasad",
""
],
[
"Banerjee",
"S. K.",
""
],
[
"Dhurandhar",
"S. V.",
""
],
[
"Narlikar",
"J. V.",
""
]
] | As an alternative view to the standard big bang cosmology the quasi-steady state cosmology(QSSC) argues that the universe was not created in a single great explosion; it neither had a beginning nor will it ever come to an end. The creation of new matter in the universe is a regular feature occurring through finite explosive events. Each creation event is called a mini-bang or, a mini creation event(MCE). Gravitational waves are expected to be generated due to any anisotropy present in this process of creation. Mini creation event ejecting matter in two oppositely directed jets is thus a source of gravitational waves which can in principle be detected by laser interferometric detectors. In the present work we consider the gravitational waveforms propagated by linear jets and then estimate the response of laser interferometric detectors like LIGO and LISA. |
1503.00932 | Theodosios Christodoulakis | Petros A. Terzis, N. Dimakis, T. Christodoulakis, A. Paliathanasis, M.
Tsamparlis | Variational Contact Symmetries of Constraint Lagrangians | LaTex2e source file, 20 pages, no figures | null | 10.1016/j.geomphys.2015.12.003 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The investigation of contact symmetries of re--parametrization invariant
Lagrangians of finite degrees of freedom and quadratic in the velocities is
presented. The main concern of the paper is those symmetry generators which
depend linearly in the velocities. A natural extension of the symmetry
generator along the lapse function $N(t)$, with the appropriate extension of
the dependence in $\dot{N}(t)$ of the gauge function, is assumed; this action
yields new results. The central finding is that the integrals of motion are
either linear or quadratic in velocities and are generated, respectively by the
conformal Killing vector fields and the conformal Killing tensors of the
configuration space metric deduced from the kinetic part of the Lagrangian
(with appropriate conformal factors). The freedom of re--parametrization allows
one to appropriately scale $N(t)$, so that the potential becomes constant; in
this case the integrals of motion can be constructed from the Killing fields
and Killing tensors of the scaled metric. A rather interesting result is the
non--necessity of the gauge function in Noether's theorem due to the presence
of the Hamiltonian constraint
| [
{
"created": "Tue, 3 Mar 2015 13:15:05 GMT",
"version": "v1"
}
] | 2016-02-17 | [
[
"Terzis",
"Petros A.",
""
],
[
"Dimakis",
"N.",
""
],
[
"Christodoulakis",
"T.",
""
],
[
"Paliathanasis",
"A.",
""
],
[
"Tsamparlis",
"M.",
""
]
] | The investigation of contact symmetries of re--parametrization invariant Lagrangians of finite degrees of freedom and quadratic in the velocities is presented. The main concern of the paper is those symmetry generators which depend linearly in the velocities. A natural extension of the symmetry generator along the lapse function $N(t)$, with the appropriate extension of the dependence in $\dot{N}(t)$ of the gauge function, is assumed; this action yields new results. The central finding is that the integrals of motion are either linear or quadratic in velocities and are generated, respectively by the conformal Killing vector fields and the conformal Killing tensors of the configuration space metric deduced from the kinetic part of the Lagrangian (with appropriate conformal factors). The freedom of re--parametrization allows one to appropriately scale $N(t)$, so that the potential becomes constant; in this case the integrals of motion can be constructed from the Killing fields and Killing tensors of the scaled metric. A rather interesting result is the non--necessity of the gauge function in Noether's theorem due to the presence of the Hamiltonian constraint |
1701.08224 | Carlos Augusto Romero Filho | R. Avalos, F. Dahia, C. Romero | On the embedding of Weyl manifolds | 31 pages, Journal of Mathematical Physics, Volume 58, Issue 1 (2017) | null | 10.1063/1.4973751 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the possibility of extending different versions of the
Campbell-Magaard theorem, which have already been established in the context of
semi-Riemannian geometry, to the context of Weyl's geometry. We show that some
of the known results can be naturally extended to the new geometric scenario,
although new difficulties arise. In pursuit of solving the embedding problem we
have obtained some no-go theorems. We also highlight some of the difficulties
that appear in the embedding problem, which are typical of the Weylian
character of the geometry. The establishing of these new results may be viewed
as part of a program that highlights the possible significance of embedding
theorems of increasing degrees of generality in the context of modern
higher-dimensional space-time theories.
| [
{
"created": "Fri, 27 Jan 2017 23:58:30 GMT",
"version": "v1"
}
] | 2017-01-31 | [
[
"Avalos",
"R.",
""
],
[
"Dahia",
"F.",
""
],
[
"Romero",
"C.",
""
]
] | We discuss the possibility of extending different versions of the Campbell-Magaard theorem, which have already been established in the context of semi-Riemannian geometry, to the context of Weyl's geometry. We show that some of the known results can be naturally extended to the new geometric scenario, although new difficulties arise. In pursuit of solving the embedding problem we have obtained some no-go theorems. We also highlight some of the difficulties that appear in the embedding problem, which are typical of the Weylian character of the geometry. The establishing of these new results may be viewed as part of a program that highlights the possible significance of embedding theorems of increasing degrees of generality in the context of modern higher-dimensional space-time theories. |
gr-qc/0308009 | Sergio Dain | Sergio Dain | Trapped surfaces as boundaries for the constraint equations | 26 pages, 2 figures references updated, minor corrections | Class.Quant.Grav. 21 (2004) 555-574; Class.Quant.Grav. 22 (2005)
769-770 | 10.1088/0264-9381/22/4/C01 | null | gr-qc | null | Trapped surfaces are studied as inner boundary for the Einstein vacuum
constraint equations. The trapped surface condition can be written as a non
linear boundary condition for these equations. Under appropriate assumptions,
we prove existence and uniqueness of solutions in the exterior region for this
boundary value problem. We also discuss the relevance of this result for the
study of black holes collisions.
| [
{
"created": "Mon, 4 Aug 2003 14:21:07 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Nov 2003 09:52:20 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Dain",
"Sergio",
""
]
] | Trapped surfaces are studied as inner boundary for the Einstein vacuum constraint equations. The trapped surface condition can be written as a non linear boundary condition for these equations. Under appropriate assumptions, we prove existence and uniqueness of solutions in the exterior region for this boundary value problem. We also discuss the relevance of this result for the study of black holes collisions. |
2406.10782 | Wei-Liang Qian | Guan-Ru Li, Wei-Liang Qian, Ramin G. Daghigh | On bifurcation and spectral instability of asymptotic quasinormal modes
in the modified P\"oschl-Teller effective potential | 41 pages, 7 figures, and 2 tables | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The P\"ochl-Teller effective potential mimics an asymptotically de Sitter
black hole bounded by an event horizon and a cosmological one. Owing to the
benefit of being analytically soluble, the asymptotic quasinormal modes in the
modified P\"oschl-Teller potential have been extensively explored in the
literature by various authors, and the results bear distinct features.
Specifically, for small discontinuities placed at the potential's peak, Skakala
and Visser showed that the resulting modes lie primarily along the imaginary
frequency axis, in line with the numerical results encountered for most black
hole metrics. However, it was also suggested that under ultraviolet
perturbations, asymptotic modes are expected to lie parallel to the real axis,
closely intervening with recent developments on spectral instability. In this
work, by numerical and semi-analytical approaches, we aim to resolve the above
apparent ambiguity. The numerical scheme is based on an improved version of the
matrix method, which is implemented in compactified hyperboloidal coordinates
on the Chebyshev grid. It is demonstrated that both asymptotic behaviors indeed
agree with the numerical findings, which is somewhat to one's surprise.
Specifically, we report the emergence of a novel branch of purely imaginary
modes originating from a bifurcation in the asymptotic quasinormal mode
spectrum. Moreover, we demonstrate how the bifurcation and asymptotic modes
evolve as the discontinuity moves away from the potential's peak, furnishing a
dynamic picture as the spectral instability unfolds. It is further argued that
they can be partly attributed to the observed parity-dependent deviations
occurring for the low-lying perturbed modes of the original P\"oschl-Teller
effective potential.
| [
{
"created": "Sun, 16 Jun 2024 02:39:39 GMT",
"version": "v1"
}
] | 2024-06-18 | [
[
"Li",
"Guan-Ru",
""
],
[
"Qian",
"Wei-Liang",
""
],
[
"Daghigh",
"Ramin G.",
""
]
] | The P\"ochl-Teller effective potential mimics an asymptotically de Sitter black hole bounded by an event horizon and a cosmological one. Owing to the benefit of being analytically soluble, the asymptotic quasinormal modes in the modified P\"oschl-Teller potential have been extensively explored in the literature by various authors, and the results bear distinct features. Specifically, for small discontinuities placed at the potential's peak, Skakala and Visser showed that the resulting modes lie primarily along the imaginary frequency axis, in line with the numerical results encountered for most black hole metrics. However, it was also suggested that under ultraviolet perturbations, asymptotic modes are expected to lie parallel to the real axis, closely intervening with recent developments on spectral instability. In this work, by numerical and semi-analytical approaches, we aim to resolve the above apparent ambiguity. The numerical scheme is based on an improved version of the matrix method, which is implemented in compactified hyperboloidal coordinates on the Chebyshev grid. It is demonstrated that both asymptotic behaviors indeed agree with the numerical findings, which is somewhat to one's surprise. Specifically, we report the emergence of a novel branch of purely imaginary modes originating from a bifurcation in the asymptotic quasinormal mode spectrum. Moreover, we demonstrate how the bifurcation and asymptotic modes evolve as the discontinuity moves away from the potential's peak, furnishing a dynamic picture as the spectral instability unfolds. It is further argued that they can be partly attributed to the observed parity-dependent deviations occurring for the low-lying perturbed modes of the original P\"oschl-Teller effective potential. |
2104.03753 | Sergei Alexandrov | Sergei Alexandrov, Simone Speziale, Tom Zlosnik | Canonical structure of minimal varying $\Lambda$ theories | 38 pages | null | 10.1088/1361-6382/ac1852 | L2C:21-030 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Minimal varying $\Lambda$ theories are defined by an action built from the
Einstein-Cartan-Holst first order action for gravity with the cosmological
constant $\Lambda$ as an independent scalar field, and supplemented by the
Euler and Pontryagin densities multiplied by $1/\Lambda$. We identify the
canonical structure of these theories which turn out to represent an example of
irregular systems. We find five degrees of freedom on generic backgrounds and
for generic values of parameters, whereas if the parameters satisfy a certain
condition (which includes the most commonly considered Euler case) only three
degrees of freedom remain. On de Sitter-like backgrounds the canonical
structure changes, and due to an emergent conformal symmetry one degree of
freedom drops from the spectrum. We also analyze the self-dual case with an
holomorphic action depending only on the self-dual part of the connection. In
this case we find two (complex) degrees of freedom, and further discuss the
Kodama state, the restriction to de Sitter background and the effect of reality
conditions.
| [
{
"created": "Thu, 8 Apr 2021 13:15:08 GMT",
"version": "v1"
}
] | 2021-08-03 | [
[
"Alexandrov",
"Sergei",
""
],
[
"Speziale",
"Simone",
""
],
[
"Zlosnik",
"Tom",
""
]
] | Minimal varying $\Lambda$ theories are defined by an action built from the Einstein-Cartan-Holst first order action for gravity with the cosmological constant $\Lambda$ as an independent scalar field, and supplemented by the Euler and Pontryagin densities multiplied by $1/\Lambda$. We identify the canonical structure of these theories which turn out to represent an example of irregular systems. We find five degrees of freedom on generic backgrounds and for generic values of parameters, whereas if the parameters satisfy a certain condition (which includes the most commonly considered Euler case) only three degrees of freedom remain. On de Sitter-like backgrounds the canonical structure changes, and due to an emergent conformal symmetry one degree of freedom drops from the spectrum. We also analyze the self-dual case with an holomorphic action depending only on the self-dual part of the connection. In this case we find two (complex) degrees of freedom, and further discuss the Kodama state, the restriction to de Sitter background and the effect of reality conditions. |
gr-qc/0403101 | Chiang-Mei Chen | James M. Nester, Fei-Hong Ho and Chiang-Mei Chen | Quasilocal Center-of-Mass for Teleparallel Gravity | 12 pages, to appear in the proceedings of the 10th Marcel Grossman
meeting (Rio de Janeiro, 2003) | null | 10.1142/9789812704030_0138 | null | gr-qc | null | Asymptotically flat gravitating systems have 10 conserved quantities, which
lack proper local densities. It has been hoped that the teleparallel equivalent
of Einstein's GR (TEGR, aka GR${}_{||}$) could solve this gravitational
energy-momentum localization problem. Meanwhile a new idea: quasilocal
quantities, has come into favor. The earlier quasilocal investigations focused
on energy-momentum. Recently we considered quasilocal angular momentum for the
teleparallel theory and found that the popular expression (unlike our
``covariant-symplectic'' one) gives the correct result only in a certain frame.
We now report that the center-of-mass moment, which has largely been neglected,
gives an even stronger requirement. We found (independent of the frame gauge)
that our ``covariant symplectic'' Hamiltonian-boundary-term quasilocal
expression succeeds for all the quasilocal quantities, while the usual
expression cannot give the desired center-of-mass moment. We also conclude,
contrary to hopes, that the teleparallel formulation appears to have no
advantage over GR with regard to localization.
| [
{
"created": "Thu, 25 Mar 2004 10:42:06 GMT",
"version": "v1"
}
] | 2016-11-09 | [
[
"Nester",
"James M.",
""
],
[
"Ho",
"Fei-Hong",
""
],
[
"Chen",
"Chiang-Mei",
""
]
] | Asymptotically flat gravitating systems have 10 conserved quantities, which lack proper local densities. It has been hoped that the teleparallel equivalent of Einstein's GR (TEGR, aka GR${}_{||}$) could solve this gravitational energy-momentum localization problem. Meanwhile a new idea: quasilocal quantities, has come into favor. The earlier quasilocal investigations focused on energy-momentum. Recently we considered quasilocal angular momentum for the teleparallel theory and found that the popular expression (unlike our ``covariant-symplectic'' one) gives the correct result only in a certain frame. We now report that the center-of-mass moment, which has largely been neglected, gives an even stronger requirement. We found (independent of the frame gauge) that our ``covariant symplectic'' Hamiltonian-boundary-term quasilocal expression succeeds for all the quasilocal quantities, while the usual expression cannot give the desired center-of-mass moment. We also conclude, contrary to hopes, that the teleparallel formulation appears to have no advantage over GR with regard to localization. |
1903.07934 | Kourosh Nozari | Kourosh Nozari and Parham Dehghani | The role of an invariant IR cutoff in late time cosmological dynamics | 13 pages, one figure, accepted for publication in Phys. Lett. B | null | 10.1016/j.physletb.2019.03.032 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the role of an invariant infra-red cutoff in the late time
cosmological dynamics. This low energy cutoff originates from the existence of
a minimal measurable uncertainty as a result of the curvature of background
manifold, and can be encoded in an extended uncertainty relation. Inspired by
black hole entropy-area relation, we extend the analysis to the thermodynamics
of apparent horizon of the universe. By treating both the Newtonian and general
relativistic cosmologies, we show that the contribution of infra-red cutoff in
the equations of dynamics can be interpreted as an effective fluid which is
capable of explaining late time cosmic speed up and even transition to a
phantom phase of expansion. We use the latest observational data from
PLANCK2018 to constrain the parameter of an extended uncertainty relation.
| [
{
"created": "Tue, 19 Mar 2019 10:59:05 GMT",
"version": "v1"
}
] | 2019-05-01 | [
[
"Nozari",
"Kourosh",
""
],
[
"Dehghani",
"Parham",
""
]
] | We study the role of an invariant infra-red cutoff in the late time cosmological dynamics. This low energy cutoff originates from the existence of a minimal measurable uncertainty as a result of the curvature of background manifold, and can be encoded in an extended uncertainty relation. Inspired by black hole entropy-area relation, we extend the analysis to the thermodynamics of apparent horizon of the universe. By treating both the Newtonian and general relativistic cosmologies, we show that the contribution of infra-red cutoff in the equations of dynamics can be interpreted as an effective fluid which is capable of explaining late time cosmic speed up and even transition to a phantom phase of expansion. We use the latest observational data from PLANCK2018 to constrain the parameter of an extended uncertainty relation. |
2001.03571 | Maria Okounkova | Maria Okounkova | Numerical relativity simulation of GW150914 in Einstein dilaton
Gauss-Bonnet gravity | 6 pages, 5 figures | Phys. Rev. D 102, 084046 (2020) | 10.1103/PhysRevD.102.084046 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A present challenge in testing general relativity (GR) with binary black hole
gravitational wave detections is the inability to perform model-dependent tests
due to the lack of merger waveforms in beyond-GR theories. In this study, we
produce the first numerical relativity binary black hole gravitational waveform
in Einstein dilaton Gauss-Bonnet (EDGB) gravity, a higher-curvature theory of
gravity with motivations in string theory. We evolve a binary black hole system
in order-reduced EDGB gravity, with parameters consistent with GW150914. We
focus on the merger portion of the waveform, due to the presence of secular
growth in the inspiral phase. We compute mismatches with the corresponding
general relativity merger waveform, finding that from a post-inspiral-only
analysis, we can constrain the EDGB lengthscale to be
$\sqrt{\alpha_\mathrm{GB}} \lesssim 11$ km.
| [
{
"created": "Fri, 10 Jan 2020 17:33:45 GMT",
"version": "v1"
}
] | 2020-11-04 | [
[
"Okounkova",
"Maria",
""
]
] | A present challenge in testing general relativity (GR) with binary black hole gravitational wave detections is the inability to perform model-dependent tests due to the lack of merger waveforms in beyond-GR theories. In this study, we produce the first numerical relativity binary black hole gravitational waveform in Einstein dilaton Gauss-Bonnet (EDGB) gravity, a higher-curvature theory of gravity with motivations in string theory. We evolve a binary black hole system in order-reduced EDGB gravity, with parameters consistent with GW150914. We focus on the merger portion of the waveform, due to the presence of secular growth in the inspiral phase. We compute mismatches with the corresponding general relativity merger waveform, finding that from a post-inspiral-only analysis, we can constrain the EDGB lengthscale to be $\sqrt{\alpha_\mathrm{GB}} \lesssim 11$ km. |
0904.1190 | K G Arun | K G Arun, Clifford M Will | Bounding the mass of the graviton with gravitational waves: Effect of
higher harmonics in gravitational waveform templates | 12 pages, 4 figures. Minor changes to the text and the plots. Matches
the published CQG version | Class.Quant.Grav.26:155002,2009 | 10.1088/0264-9381/26/15/155002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Observations by laser interferometric detectors of gravitational waves from
inspiraling compact binary systems can be used to search for a dependence of
the waves' propagation speed on wavelength, and thereby to bound the mass or
Compton wavelength of a putative graviton. We study the effect of including
higher harmonics, as well as their post-Newtonian amplitude corrections, in the
template gravitational waveforms employed in the process of parameter
estimation using matched filtering. We consider the bounds that could be
achieved using advanced LIGO, a proposed third generation instrument called
Einstein Telescope, and the proposed space interferometer LISA. We find that in
all cases, the bounds on the graviton Compton wavelength are improved by almost
an order of magnitude for higher masses when amplitude corrections are
included.
| [
{
"created": "Tue, 7 Apr 2009 18:16:19 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Jul 2009 19:55:41 GMT",
"version": "v2"
}
] | 2009-07-22 | [
[
"Arun",
"K G",
""
],
[
"Will",
"Clifford M",
""
]
] | Observations by laser interferometric detectors of gravitational waves from inspiraling compact binary systems can be used to search for a dependence of the waves' propagation speed on wavelength, and thereby to bound the mass or Compton wavelength of a putative graviton. We study the effect of including higher harmonics, as well as their post-Newtonian amplitude corrections, in the template gravitational waveforms employed in the process of parameter estimation using matched filtering. We consider the bounds that could be achieved using advanced LIGO, a proposed third generation instrument called Einstein Telescope, and the proposed space interferometer LISA. We find that in all cases, the bounds on the graviton Compton wavelength are improved by almost an order of magnitude for higher masses when amplitude corrections are included. |
2005.12410 | Sanjar Shaymatov | Sanjar Shaymatov, Jaroslav Vrba, Daniele Malafarina, Bobomurat
Ahmedov, Zden\v{e}k Stuchl\'ik | Charged particle and epicyclic motions around $4D$ Einstein-Gauss-Bonnet
black hole immersed in an external magnetic field | 36 pages, 8 figures, 1 table | Physics of the Dark Universe 30, 100648 (2020) | 10.1016/j.dark.2020.100648 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate particle motion in the vicinity of a $4D$
Einstein-Gauss-Bonnet (EGB) black hole immersed in external asymptotically
uniform magnetic field. It is well known that magnetic fields can strongly
affect charged particle motion in the black hole vicinity due to the Lorenz
force. We find that the presence of the Gauss-Bonnet (GB) coupling gives rise
to a similar effect, reducing the radius of the innermost stable circular orbit
(ISCO) with respect to the purely relativistic Schwarzschild black hole.
Further, we consider particle collisions in the black hole vicinity to
determine the center of mass energy and show that this energy increases with
respect to the Schwarzschild case due to the effect of the GB term. Finally, we
consider epicyclic motion and its frequencies and resonance as a mean to test
the predictions of the model against astrophysical observations. In particular
we test which values of the parameters of the theory best fit the 3:2 resonance
of high-frequency quasi-periodic oscillations in three low-mass X-ray binaries.
| [
{
"created": "Mon, 25 May 2020 21:22:16 GMT",
"version": "v1"
},
{
"created": "Thu, 28 May 2020 14:42:20 GMT",
"version": "v2"
},
{
"created": "Thu, 2 Jul 2020 14:21:05 GMT",
"version": "v3"
}
] | 2020-07-03 | [
[
"Shaymatov",
"Sanjar",
""
],
[
"Vrba",
"Jaroslav",
""
],
[
"Malafarina",
"Daniele",
""
],
[
"Ahmedov",
"Bobomurat",
""
],
[
"Stuchlík",
"Zdeněk",
""
]
] | We investigate particle motion in the vicinity of a $4D$ Einstein-Gauss-Bonnet (EGB) black hole immersed in external asymptotically uniform magnetic field. It is well known that magnetic fields can strongly affect charged particle motion in the black hole vicinity due to the Lorenz force. We find that the presence of the Gauss-Bonnet (GB) coupling gives rise to a similar effect, reducing the radius of the innermost stable circular orbit (ISCO) with respect to the purely relativistic Schwarzschild black hole. Further, we consider particle collisions in the black hole vicinity to determine the center of mass energy and show that this energy increases with respect to the Schwarzschild case due to the effect of the GB term. Finally, we consider epicyclic motion and its frequencies and resonance as a mean to test the predictions of the model against astrophysical observations. In particular we test which values of the parameters of the theory best fit the 3:2 resonance of high-frequency quasi-periodic oscillations in three low-mass X-ray binaries. |
1606.08980 | Kiyoshi Shiraishi | Nahomi Kan (NIT, Gifu College), Takuya Maki (Japan Women's College of
Physical Education) and Kiyoshi Shiraishi (Yamaguchi University) | GR-GSG Hybrid Gravity | 21 pages, 10 figures. Reference added | Phys. Rev. D 94, 084001 (2016) | 10.1103/PhysRevD.94.084001 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a model of gravity in which a General Relativity metric tensor and
an effective metric generated from a single scalar formulated in Geometric
Scalar Gravity are mixed. We show that the model yields the exact Schwarzschild
solution, along with accelerating behavior of scale factors in cosmological
solutions.
| [
{
"created": "Wed, 29 Jun 2016 07:01:49 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Jul 2016 09:20:02 GMT",
"version": "v2"
}
] | 2016-10-12 | [
[
"Kan",
"Nahomi",
"",
"NIT, Gifu College"
],
[
"Maki",
"Takuya",
"",
"Japan Women's College of\n Physical Education"
],
[
"Shiraishi",
"Kiyoshi",
"",
"Yamaguchi University"
]
] | We propose a model of gravity in which a General Relativity metric tensor and an effective metric generated from a single scalar formulated in Geometric Scalar Gravity are mixed. We show that the model yields the exact Schwarzschild solution, along with accelerating behavior of scale factors in cosmological solutions. |
2011.05542 | Yan-Gang Miao | Xin-Chang Cai, Yan-Gang Miao | High-dimensional Schwarzschild black holes in scalar-tensor-vector
gravity theory | v1: 18 pages, 6 figures, 4 tables; v2: clarifications and references
added; v3: 19 pages, final version to appear in European Physical Journal C | European Physical Journal C 81, 559 (2021) | 10.1140/epjc/s10052-021-09351-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain a high-dimensional Schwarzschild black hole solution in the
scalar-tensor-vector gravity (STVG), and then analyze the influence of
parameter $\alpha$ associated with a deviation of the STVG theory from General
Relativity on event horizons and Hawking temperature. We calculate the
quasinormal mode frequencies of massless scalar field perturbations for the
high-dimensional Schwarzschild STVG black hole by using the sixth-order WKB
approximation method and the unstable null geodesic method in the eikonal
limit. The results show that the increase of parameter $\alpha$ makes the
scalar waves decay slowly, while the increase of the spacetime dimension makes
the scalar waves decay fast. In addition, we study the influence of parameter
$\alpha$ on the shadow radius of this high-dimensional Schwarzschild STVG black
hole and find that the increase of parameter $\alpha$ makes the black hole
shadow radius increase, but the increase of the spacetime dimension makes the
black hole shadow radius decrease. Finally, we investigate the energy emission
rate of the high-dimensional Schwarzschild STVG black hole, and find that the
increase of parameter $\alpha$ makes the evaporation process slow, while the
increase of the spacetime dimension makes the process fast.
| [
{
"created": "Wed, 11 Nov 2020 04:46:59 GMT",
"version": "v1"
},
{
"created": "Sat, 12 Dec 2020 14:10:38 GMT",
"version": "v2"
},
{
"created": "Mon, 21 Jun 2021 00:41:34 GMT",
"version": "v3"
}
] | 2021-07-05 | [
[
"Cai",
"Xin-Chang",
""
],
[
"Miao",
"Yan-Gang",
""
]
] | We obtain a high-dimensional Schwarzschild black hole solution in the scalar-tensor-vector gravity (STVG), and then analyze the influence of parameter $\alpha$ associated with a deviation of the STVG theory from General Relativity on event horizons and Hawking temperature. We calculate the quasinormal mode frequencies of massless scalar field perturbations for the high-dimensional Schwarzschild STVG black hole by using the sixth-order WKB approximation method and the unstable null geodesic method in the eikonal limit. The results show that the increase of parameter $\alpha$ makes the scalar waves decay slowly, while the increase of the spacetime dimension makes the scalar waves decay fast. In addition, we study the influence of parameter $\alpha$ on the shadow radius of this high-dimensional Schwarzschild STVG black hole and find that the increase of parameter $\alpha$ makes the black hole shadow radius increase, but the increase of the spacetime dimension makes the black hole shadow radius decrease. Finally, we investigate the energy emission rate of the high-dimensional Schwarzschild STVG black hole, and find that the increase of parameter $\alpha$ makes the evaporation process slow, while the increase of the spacetime dimension makes the process fast. |
2308.04713 | Mudassar Sabir | Arshad Ali, Ya-Peng Hu, Mudassar Sabir, Taotao Sui | On the gauge dependence of scalar induced secondary gravitational waves
during radiation and matter domination eras | 19 pages, 6 figures, SCPMA in press | Sci.China Phys.Mech.Astron. 66 (2023) 290411 | 10.1007/s11433-022-2118-5 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We revisit the vital issue of gauge dependence in the scalar-induced
secondary gravitational waves (SIGWs), focusing on the radiation domination
(RD) and matter domination (MD) eras. The energy density spectrum is the main
physical observable in such induced gravitational waves. For various gauge
choices, there has been a divergence in the energy density,
$\Omega_{\text{GW}}$, of SIGWs. We calculate SIGWs in different gauges to
quantify this divergence to address the gauge-dependent problem. In our
previous studies, we had found that the energy density diverges in the
polynomial power of conformal time (e.g., $\eta^6$ in uniform density gauge).
We try to fix this discrepancy by adding a counter-term that removes the
fictitious terms in secondary tensor perturbations. We graphically compare the
calculations in various gauges and also comment on the physical origin of the
observed gauge dependence.
| [
{
"created": "Wed, 9 Aug 2023 05:11:53 GMT",
"version": "v1"
}
] | 2023-08-10 | [
[
"Ali",
"Arshad",
""
],
[
"Hu",
"Ya-Peng",
""
],
[
"Sabir",
"Mudassar",
""
],
[
"Sui",
"Taotao",
""
]
] | We revisit the vital issue of gauge dependence in the scalar-induced secondary gravitational waves (SIGWs), focusing on the radiation domination (RD) and matter domination (MD) eras. The energy density spectrum is the main physical observable in such induced gravitational waves. For various gauge choices, there has been a divergence in the energy density, $\Omega_{\text{GW}}$, of SIGWs. We calculate SIGWs in different gauges to quantify this divergence to address the gauge-dependent problem. In our previous studies, we had found that the energy density diverges in the polynomial power of conformal time (e.g., $\eta^6$ in uniform density gauge). We try to fix this discrepancy by adding a counter-term that removes the fictitious terms in secondary tensor perturbations. We graphically compare the calculations in various gauges and also comment on the physical origin of the observed gauge dependence. |
2009.09820 | Andras Laszlo | Andras Laszlo and Zoltan Zimboras | Clarification on theoretical predictions for general relativistic
effects in frozen spin storage rings | Contribution to Gribov-90 memorial volume | Gribov-90 Memorial Volume (2021) | 10.1142/9789811238406_0016 | null | gr-qc hep-ex hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Electromagnetic moments of particles carry important information on their
internal structure, as well as on the structure of the effective Lagrangian
describing their underlying field theory. One of the cleanest observable of
such kind is the electric dipole moment (EDM), since Standard Model estimates
would imply very small, much less then 10^-30 ecm value for that quantity,
whereas several Beyond Standard Model (BSM) theories happen to predict of the
order of 10^-28 ecm EDM for elementary or hadronic particles. So far, precision
EDM upper bounds are mainly available for neutrons via cold neutron
experiments, and indirect measurements for electrons. Therefore, in the recent
year there has been a growing interest for direct measurement of EDM for
charged particles, such as electrons, protons, muons or light nuclei. Such
measurements become possible in relativistic storage rings, called frozen spin
storage rings. Many environmental factors give systematic backgrounds to the
EDM signal, including General Relativity (GR), due to the gravitational field
of the Earth. It turns out that, depending of the experimental scenario, the GR
effect can be well above the planned EDM sensitivity. Therefore, it is both of
concern as a source of systematics, as well as it can serve as a spin-off
experiment for an independent test of GR. There are a handful of theoretical
papers quantifying the GR systematics, delivering slightly different results.
The aim of this paper is to clarify these claims, eventually try to reconcile
these predictions, and to deduce their experimental implications. The closing
section of the paper quantifies the field imperfection systematic error
cancellation in the case of a so-called doubly-frozen spin storage ring
setting, in the idealized axial symmetric limit.
| [
{
"created": "Mon, 21 Sep 2020 12:46:04 GMT",
"version": "v1"
}
] | 2021-06-01 | [
[
"Laszlo",
"Andras",
""
],
[
"Zimboras",
"Zoltan",
""
]
] | Electromagnetic moments of particles carry important information on their internal structure, as well as on the structure of the effective Lagrangian describing their underlying field theory. One of the cleanest observable of such kind is the electric dipole moment (EDM), since Standard Model estimates would imply very small, much less then 10^-30 ecm value for that quantity, whereas several Beyond Standard Model (BSM) theories happen to predict of the order of 10^-28 ecm EDM for elementary or hadronic particles. So far, precision EDM upper bounds are mainly available for neutrons via cold neutron experiments, and indirect measurements for electrons. Therefore, in the recent year there has been a growing interest for direct measurement of EDM for charged particles, such as electrons, protons, muons or light nuclei. Such measurements become possible in relativistic storage rings, called frozen spin storage rings. Many environmental factors give systematic backgrounds to the EDM signal, including General Relativity (GR), due to the gravitational field of the Earth. It turns out that, depending of the experimental scenario, the GR effect can be well above the planned EDM sensitivity. Therefore, it is both of concern as a source of systematics, as well as it can serve as a spin-off experiment for an independent test of GR. There are a handful of theoretical papers quantifying the GR systematics, delivering slightly different results. The aim of this paper is to clarify these claims, eventually try to reconcile these predictions, and to deduce their experimental implications. The closing section of the paper quantifies the field imperfection systematic error cancellation in the case of a so-called doubly-frozen spin storage ring setting, in the idealized axial symmetric limit. |
2201.07693 | Martin Bojowald | Martin Bojowald | Abelianized structures in spherically symmetric hypersurface
deformations | 14 pages, v2: title change and more focused on hypersurface
deformations | Universe 8 (2022) 184 | 10.3390/universe8030184 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In canonical gravity, general covariance is implemented by
hypersurface-deformation symmetries on phase space. The different versions of
hypersurface deformations required for full covariance have complicated
interplays with one another, governed by non-Abelian brackets with structure
functions. For spherically symmetric space-times, it is possible to identify a
certain Abelian substructure within general hypersurface deformations, which
suggests a simplified realization as a Lie algebra. The generators of this
substructure can be quantized more easily than full hypersurface deformations,
but the symmetries they generate do not directly correspond to hypersurface
deformations. The availability of consistent quantizations therefore does not
guarantee general covariance or a meaningful quantum notion thereof. In
addition to placing the Abelian substructure within the full context of
spherically symmetric hypersurface deformation, this paper points out several
subtleties relevant for attempted applications in quantized space-time
structures. In particular, it follows that recent constructions by Gambini,
Olmedo and Pullin in an Abelianized setting fail to address the covariance
crisis of loop quantum gravity.
| [
{
"created": "Wed, 19 Jan 2022 16:24:23 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Mar 2022 17:57:42 GMT",
"version": "v2"
}
] | 2022-05-25 | [
[
"Bojowald",
"Martin",
""
]
] | In canonical gravity, general covariance is implemented by hypersurface-deformation symmetries on phase space. The different versions of hypersurface deformations required for full covariance have complicated interplays with one another, governed by non-Abelian brackets with structure functions. For spherically symmetric space-times, it is possible to identify a certain Abelian substructure within general hypersurface deformations, which suggests a simplified realization as a Lie algebra. The generators of this substructure can be quantized more easily than full hypersurface deformations, but the symmetries they generate do not directly correspond to hypersurface deformations. The availability of consistent quantizations therefore does not guarantee general covariance or a meaningful quantum notion thereof. In addition to placing the Abelian substructure within the full context of spherically symmetric hypersurface deformation, this paper points out several subtleties relevant for attempted applications in quantized space-time structures. In particular, it follows that recent constructions by Gambini, Olmedo and Pullin in an Abelianized setting fail to address the covariance crisis of loop quantum gravity. |
2105.07573 | Juan M. Z\'arate Pretel | Juan M. Z. Pretel, Sergio E. Jor\'as, Ribamar R. R. Reis and Jos\'e D.
V. Arba\~nil | Neutron stars in $f(R,T)$ gravity with conserved energy-momentum tensor:
Hydrostatic equilibrium and asteroseismology | 21 pages, 8 figures | JCAP 08 (2021) 055 | 10.1088/1475-7516/2021/08/055 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the equilibrium and radial stability of spherically symmetric
relativistic stars, considering a polytropic equation of state (EoS), within
the framework of $f(R,T)$ gravity with a conservative energy-momentum tensor.
Both modified stellar structure equations and Chandrasekhar's pulsation
equations are derived for the $f(R,T)= R+ h(T)$ gravity model, where the
function $h(T)$ assumes a specific form in order to safeguard the conservation
equation for the energy-momentum tensor. The neutron star properties, such as
radius, mass, binding energy and oscillation spectrum are studied in detail.
Our results show that a cusp -- which signals the appearance of instability --
is formed when the binding energy is plotted as a function of the compact star
proper mass. We find that the squared frequency of the fundamental vibration
mode passes through zero at the central-density value corresponding to such a
cusp where the binding energy is a minimum.
| [
{
"created": "Mon, 17 May 2021 01:46:12 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Aug 2021 09:04:51 GMT",
"version": "v2"
}
] | 2021-08-26 | [
[
"Pretel",
"Juan M. Z.",
""
],
[
"Jorás",
"Sergio E.",
""
],
[
"Reis",
"Ribamar R. R.",
""
],
[
"Arbañil",
"José D. V.",
""
]
] | We investigate the equilibrium and radial stability of spherically symmetric relativistic stars, considering a polytropic equation of state (EoS), within the framework of $f(R,T)$ gravity with a conservative energy-momentum tensor. Both modified stellar structure equations and Chandrasekhar's pulsation equations are derived for the $f(R,T)= R+ h(T)$ gravity model, where the function $h(T)$ assumes a specific form in order to safeguard the conservation equation for the energy-momentum tensor. The neutron star properties, such as radius, mass, binding energy and oscillation spectrum are studied in detail. Our results show that a cusp -- which signals the appearance of instability -- is formed when the binding energy is plotted as a function of the compact star proper mass. We find that the squared frequency of the fundamental vibration mode passes through zero at the central-density value corresponding to such a cusp where the binding energy is a minimum. |
2404.18608 | P. B. Covas | P. B. Covas, R. Prix, J. Martins | A new framework to follow up candidates from continuous
gravitational-wave searches | 16 pages, 13 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Searches for continuous gravitational waves from unknown neutron stars are
limited in sensitivity due to their high computational cost. For this reason,
developing new methods or improving existing ones can increase the probability
of making a detection. In this paper we present a new framework that uses MCMC
or nested sampling methods to follow-up candidates of continuous
gravitational-wave searches. This framework aims to go beyond the capabilities
of PYFSTAT (which is limited to the PTEMCEE sampler), by allowing a flexible
choice of sampling algorithm (using BILBY as a wrapper) and multi-dimensional
correlated prior distributions. We show that MCMC and nested sampling methods
can recover the maximum posterior point for much bigger parameter-space regions
than previously thought (including for sources in binary systems), and we
present tests that examine the capabilities of the new framework: a comparison
between the DYNESTY, NESSAI, and PTEMCEE samplers, the usage of correlated
priors, and its improved computational cost.
| [
{
"created": "Mon, 29 Apr 2024 11:22:45 GMT",
"version": "v1"
}
] | 2024-04-30 | [
[
"Covas",
"P. B.",
""
],
[
"Prix",
"R.",
""
],
[
"Martins",
"J.",
""
]
] | Searches for continuous gravitational waves from unknown neutron stars are limited in sensitivity due to their high computational cost. For this reason, developing new methods or improving existing ones can increase the probability of making a detection. In this paper we present a new framework that uses MCMC or nested sampling methods to follow-up candidates of continuous gravitational-wave searches. This framework aims to go beyond the capabilities of PYFSTAT (which is limited to the PTEMCEE sampler), by allowing a flexible choice of sampling algorithm (using BILBY as a wrapper) and multi-dimensional correlated prior distributions. We show that MCMC and nested sampling methods can recover the maximum posterior point for much bigger parameter-space regions than previously thought (including for sources in binary systems), and we present tests that examine the capabilities of the new framework: a comparison between the DYNESTY, NESSAI, and PTEMCEE samplers, the usage of correlated priors, and its improved computational cost. |
2107.00010 | Scott Melville | Anne-Christine Davis and Scott Melville | Scalar Fields Near Compact Objects: Resummation versus UV Completion | 34+12 pages, 6 figures | null | 10.1088/1475-7516/2021/11/012 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Low-energy effective field theories containing a light scalar field are used
extensively in cosmology, but often there is a tension between embedding such
theories in a healthy UV completion and achieving a phenomenologically viable
screening mechanism in the IR. Here, we identify the range of interaction
couplings which allow for a smooth resummation of classical non-linearities
(necessary for kinetic/Vainshtein-type screening), and compare this with the
range allowed by unitarity, causality and locality in the underlying UV theory.
The latter region is identified using positivity bounds on the $2\to2$
scattering amplitude, and in particular by considering scattering about a
non-trivial background for the scalar we are able to place constraints on
interactions at all orders in the field (beyond quartic order). We identify two
classes of theories can both exhibit screening and satisfy existing positivity
bounds, namely scalar-tensor theories of $P(X)$ or quartic Horndeski type in
which the leading interaction contains an odd power of $X$. Finally, for the
quartic DBI Galileon (equivalent to a disformally coupled scalar in the
Einstein frame), the analogous resummation can be performed near two-body
systems and imposing positivity constraints introduces a non-perturbative
ambiguity in the screened scalar profile. These results will guide future
searches for UV complete models which exhibit screening of fifth forces in the
IR.
| [
{
"created": "Wed, 30 Jun 2021 18:00:01 GMT",
"version": "v1"
}
] | 2021-11-17 | [
[
"Davis",
"Anne-Christine",
""
],
[
"Melville",
"Scott",
""
]
] | Low-energy effective field theories containing a light scalar field are used extensively in cosmology, but often there is a tension between embedding such theories in a healthy UV completion and achieving a phenomenologically viable screening mechanism in the IR. Here, we identify the range of interaction couplings which allow for a smooth resummation of classical non-linearities (necessary for kinetic/Vainshtein-type screening), and compare this with the range allowed by unitarity, causality and locality in the underlying UV theory. The latter region is identified using positivity bounds on the $2\to2$ scattering amplitude, and in particular by considering scattering about a non-trivial background for the scalar we are able to place constraints on interactions at all orders in the field (beyond quartic order). We identify two classes of theories can both exhibit screening and satisfy existing positivity bounds, namely scalar-tensor theories of $P(X)$ or quartic Horndeski type in which the leading interaction contains an odd power of $X$. Finally, for the quartic DBI Galileon (equivalent to a disformally coupled scalar in the Einstein frame), the analogous resummation can be performed near two-body systems and imposing positivity constraints introduces a non-perturbative ambiguity in the screened scalar profile. These results will guide future searches for UV complete models which exhibit screening of fifth forces in the IR. |
2103.02688 | Jo\~ao Cavedagne Lobato | Jo\~ao C. Lobato, Isabela S. Matos, Lucas T. Santana, Ribamar R. R.
Reis and Maur\'icio O. Calv\~ao | Influence of gravitational waves upon light. Part II. Electric field
propagation and interference pattern in a gravitational wave detector | 23 pages, 2 figures, 1 table. To be submitted to JCAP | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this second article of the series, we apply our recently derived equation
for the electric field propagation along light rays [arXiv:2004.03496], valid
on the electromagnetic geometrical optics limit, to the special case of a toy
interferometer used to detect gravitational waves in a flat background. Such an
equation shows that, assuming the detector is in the transverse-traceless
frame, which has a local shearing relative motion due to the gravitational wave
perturbations, the electric field does not propagate as in an inertial
reference frame in Minkowski spacetime. We present the electric field at the
end of the interferometric process, for arbitrary arm configurations with
respect to the plane gravitational wave packet propagation direction. Then, for
normal incidence, we compute the interference pattern and, in addition to the
usual term associated with the difference in path traveled by light in the
arms, we deduce two new contributions to the final intensity, arising from: (i)
the round-trip electromagnetic frequency shift and (ii) the divergence of the
light beam. Their quantitative relevance is compared to the traditional
contribution and shown to be typically negligible due to the geometrical optics
regime of light. Moreover, a non-parallel transport of the polarization vector
takes place, in general, because of the gravitational wave, a feature which
could generate further contributions. However, we conclude that for the normal
incidence case such vector is parallel transported, preventing this kind of
correction.
| [
{
"created": "Wed, 3 Mar 2021 21:10:56 GMT",
"version": "v1"
}
] | 2021-03-05 | [
[
"Lobato",
"João C.",
""
],
[
"Matos",
"Isabela S.",
""
],
[
"Santana",
"Lucas T.",
""
],
[
"Reis",
"Ribamar R. R.",
""
],
[
"Calvão",
"Maurício O.",
""
]
] | In this second article of the series, we apply our recently derived equation for the electric field propagation along light rays [arXiv:2004.03496], valid on the electromagnetic geometrical optics limit, to the special case of a toy interferometer used to detect gravitational waves in a flat background. Such an equation shows that, assuming the detector is in the transverse-traceless frame, which has a local shearing relative motion due to the gravitational wave perturbations, the electric field does not propagate as in an inertial reference frame in Minkowski spacetime. We present the electric field at the end of the interferometric process, for arbitrary arm configurations with respect to the plane gravitational wave packet propagation direction. Then, for normal incidence, we compute the interference pattern and, in addition to the usual term associated with the difference in path traveled by light in the arms, we deduce two new contributions to the final intensity, arising from: (i) the round-trip electromagnetic frequency shift and (ii) the divergence of the light beam. Their quantitative relevance is compared to the traditional contribution and shown to be typically negligible due to the geometrical optics regime of light. Moreover, a non-parallel transport of the polarization vector takes place, in general, because of the gravitational wave, a feature which could generate further contributions. However, we conclude that for the normal incidence case such vector is parallel transported, preventing this kind of correction. |
1506.04252 | Richard Woodard | R. P. Woodard (University of Florida) | Some Inconvenient Truths | 14 pages, uses LaTeX2e | null | null | UFIFT-QG-15-04 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A recent paper by Fr\"ob employs the linearized Weyl-Weyl correlator to
construct the tensor power spectrum. Although his purpose was to argue that
infrared divergences and secular growth in the graviton propagator are gauge
artefacts, a closer examination of the problem leads to the opposite
conclusion. The analogies with the BMS symmetries of graviton scattering on a
flat background, and with the Aharonov-Bohm effect of quantum mechanics,
suggest that de Sitter breaking secular growth is likely to be observable in
graviton loop effects. And a recent result for the vacuum polarization does
seem to show it.
| [
{
"created": "Sat, 13 Jun 2015 11:16:41 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Woodard",
"R. P.",
"",
"University of Florida"
]
] | A recent paper by Fr\"ob employs the linearized Weyl-Weyl correlator to construct the tensor power spectrum. Although his purpose was to argue that infrared divergences and secular growth in the graviton propagator are gauge artefacts, a closer examination of the problem leads to the opposite conclusion. The analogies with the BMS symmetries of graviton scattering on a flat background, and with the Aharonov-Bohm effect of quantum mechanics, suggest that de Sitter breaking secular growth is likely to be observable in graviton loop effects. And a recent result for the vacuum polarization does seem to show it. |
1810.02581 | LSC P&P Committee | The LIGO Scientific Collaboration and the Virgo Collaboration: B. P.
Abbott, R. Abbott, T. D. Abbott, F. Acernese, K. Ackley, C. Adams, T. Adams,
P. Addesso, R. X. Adhikari, V. B. Adya, C. Affeldt, B. Agarwal, M. Agathos,
K. Agatsuma, N. Aggarwal, O. D. Aguiar, L. Aiello, A. Ain, P. Ajith, B.
Allen, G. Allen, A. Allocca, M. A. Aloy, P. A. Altin, A. Amato, A. Ananyeva,
S. B. Anderson, W. G. Anderson, S. V. Angelova, S. Antier, S. Appert, K.
Arai, M. C. Araya, J. S. Areeda, M. Ar\`ene, N. Arnaud, S. Ascenzi, G.
Ashton, M. Ast, S. M. Aston, P. Astone, D. V. Atallah, F. Aubin, P. Aufmuth,
C. Aulbert, K. AultONeal, C. Austin, A. Avila-Alvarez, S. Babak, P. Bacon, F.
Badaracco, M. K. M. Bader, S. Bae, P. T. Baker, F. Baldaccini, G. Ballardin,
S. W. Ballmer, S. Banagiri, J. C. Barayoga, S. E. Barclay, B. C. Barish, D.
Barker, K. Barkett, S. Barnum, F. Barone, B. Barr, L. Barsotti, M. Barsuglia,
D. Barta, J. Bartlett, I. Bartos, R. Bassiri, A. Basti, J. C. Batch, M.
Bawaj, J. C. Bayley, M. Bazzan, B. B\'ecsy, C. Beer, M. Bejger, I. Belahcene,
A. S. Bell, D. Beniwal, M. Bensch, B. K. Berger, G. Bergmann, S. Bernuzzi, J.
J. Bero, C. P. L. Berry, D. Bersanetti, A. Bertolini, J. Betzwieser, R.
Bhandare, I. A. Bilenko, S. A. Bilgili, G. Billingsley, C. R. Billman, J.
Birch, R. Birney, O. Birnholtz, S. Biscans, S. Biscoveanu, A. Bisht, M.
Bitossi, M. A. Bizouard, J. K. Blackburn, J. Blackman, C. D. Blair, D. G.
Blair, R. M. Blair, S. Bloemen, O. Bock, N. Bode, M. Boer, Y. Boetzel, G.
Bogaert, A. Bohe, F. Bondu, E. Bonilla, R. Bonnand, P. Booker, B. A. Boom, C.
D. Booth, R. Bork, V. Boschi, S. Bose, K. Bossie, V. Bossilkov, J. Bosveld,
Y. Bouffanais, A. Bozzi, C. Bradaschia, P. R. Brady, A. Bramley, M.
Branchesi, J. E. Brau, T. Briant, F. Brighenti, A. Brillet, M. Brinkmann, V.
Brisson, P. Brockill, A. F. Brooks, D. D. Brown, S. Brunett, C. C. Buchanan,
A. Buikema, T. Bulik, H. J. Bulten, A. Buonanno, D. Buskulic, C. Buy, R. L.
Byer, M. Cabero, L. Cadonati, G. Cagnoli, C. Cahillane, J. Calder\'on
Bustillo, T. A. Callister, E. Calloni, J. B. Camp, M. Canepa, P. Canizares,
K. C. Cannon, H. Cao, J. Cao, C. D. Capano, E. Capocasa, F. Carbognani, S.
Caride, M. F. Carney, J. Casanueva Diaz, C. Casentini, S. Caudill, M.
Cavagli\`a, F. Cavalier, R. Cavalieri, G. Cella, C. B. Cepeda, P.
Cerd\'a-Dur\'an, G. Cerretani, E. Cesarini, O. Chaibi, S. J. Chamberlin, M.
Chan, S. Chao, P. Charlton, E. Chase, E. Chassande-Mottin, D. Chatterjee, B.
D. Cheeseboro, H. Y. Chen, X. Chen, Y. Chen, H.-P. Cheng, H. Y. Chia, A.
Chincarini, A. Chiummo, T. Chmiel, H. S. Cho, M. Cho, J. H. Chow, N.
Christensen, Q. Chu, A. J. K. Chua, S. Chua, K. W. Chung, S. Chung, G. Ciani,
A. A. Ciobanu, R. Ciolfi, F. Cipriano, C. E. Cirelli, A. Cirone, F. Clara, J.
A. Clark, P. Clearwater, F. Cleva, C. Cocchieri, E. Coccia, P.-F. Cohadon, D.
Cohen, A. Colla, C. G. Collette, C. Collins, L. R. Cominsky, M. Constancio
Jr., L. Conti, S. J. Cooper, P. Corban, T. R. Corbitt, I. Cordero-Carri\'on,
K. R. Corley, N. Cornish, A. Corsi, S. Cortese, C. A. Costa, R. Cotesta, M.
W. Coughlin, S. B. Coughlin, J.-P. Coulon, S. T. Countryman, P. Couvares, P.
B. Covas, E. E. Cowan, D. M. Coward, M. J. Cowart, D. C. Coyne, R. Coyne, J.
D. E. Creighton, T. D. Creighton, J. Cripe, S. G. Crowder, T. J. Cullen, A.
Cumming, L. Cunningham, E. Cuoco, T. Dal Canton, G. D\'alya, S. L.
Danilishin, S. D'Antonio, K. Danzmann, A. Dasgupta, C. F. Da Silva Costa, V.
Dattilo, I. Dave, M. Davier, D. Davis, E. J. Daw, B. Day, D. DeBra, M.
Deenadayalan, J. Degallaix, M. De Laurentis, S. Del\'eglise, W. Del Pozzo, N.
Demos, T. Denker, T. Dent, R. De Pietri, J. Derby, V. Dergachev, R. De Rosa,
C. De Rossi, R. DeSalvo, O. de Varona, S. Dhurandhar, M. C. D\'iaz, L. Di
Fiore, M. Di Giovanni, T. Di Girolamo, A. Di Lieto, B. Ding, S. Di Pace, I.
Di Palma, F. Di Renzo, A. Dmitriev, Z. Doctor, V. Dolique, F. Donovan, K. L.
Dooley, S. Doravari, I. Dorrington, M. Dovale \'Alvarez, T. P. Downes, M.
Drago, C. Dreissigacker, J. C. Driggers, Z. Du, P. Dupej, S. E. Dwyer, P. J.
Easter, T. B. Edo, M. C. Edwards, A. Effler, P. Ehrens, J. Eichholz, S. S.
Eikenberry, M. Eisenmann, R. A. Eisenstein, R. C. Essick, H. Estelles, D.
Estevez, Z. B. Etienne, T. Etzel, M. Evans, T. M. Evans, V. Fafone, H. Fair,
S. Fairhurst, X. Fan, S. Farinon, B. Farr, W. M. Farr, E. J. Fauchon-Jones,
M. Favata, M. Fays, C. Fee, H. Fehrmann, J. Feicht, M. M. Fejer, F. Feng, A.
Fernandez-Galiana, I. Ferrante, E. C. Ferreira, F. Ferrini, F. Fidecaro, I.
Fiori, D. Fiorucci, M. Fishbach, R. P. Fisher, J. M. Fishner, M. Fitz-Axen,
R. Flaminio, M. Fletcher, H. Fong, J. A. Font, P. W. F. Forsyth, S. S.
Forsyth, J.-D. Fournier, S. Frasca, F. Frasconi, Z. Frei, A. Freise, R. Frey,
V. Frey, P. Fritschel, V. V. Frolov, P. Fulda, M. Fyffe, H. A. Gabbard, B. U.
Gadre, S. M. Gaebel, J. R. Gair, L. Gammaitoni, M. R. Ganija, S. G. Gaonkar,
A. Garcia, C. Garc\'ia-Quir\'os, F. Garufi, B. Gateley, S. Gaudio, G. Gaur,
V. Gayathri, G. Gemme, E. Genin, A. Gennai, D. George, J. George, L. Gergely,
V. Germain, S. Ghonge, Abhirup Ghosh, Archisman Ghosh, S. Ghosh, B.
Giacomazzo, J. A. Giaime, K. D. Giardina, A. Giazotto, K. Gill, G. Giordano,
L. Glover, E. Goetz, R. Goetz, B. Goncharov, G. Gonz\'alez, J. M. Gonzalez
Castro, A. Gopakumar, M. L. Gorodetsky, S. E. Gossan, M. Gosselin, R. Gouaty,
A. Grado, C. Graef, M. Granata, A. Grant, S. Gras, C. Gray, G. Greco, A. C.
Green, R. Green, E. M. Gretarsson, P. Groot, H. Grote, S. Grunewald, P.
Gruning, G. M. Guidi, H. K. Gulati, X. Guo, A. Gupta, M. K. Gupta, K. E.
Gushwa, E. K. Gustafson, R. Gustafson, O. Halim, B. R. Hall, E. D. Hall, E.
Z. Hamilton, H. F. Hamilton, G. Hammond, M. Haney, M. M. Hanke, J. Hanks, C.
Hanna, M. D. Hannam, O. A. Hannuksela, J. Hanson, T. Hardwick, J. Harms, G.
M. Harry, I. W. Harry, M. J. Hart, C.-J. Haster, K. Haughian, J. Healy, A.
Heidmann, M. C. Heintze, H. Heitmann, P. Hello, G. Hemming, M. Hendry, I. S.
Heng, J. Hennig, A. W. Heptonstall, F. J. Hernandez, M. Heurs, S. Hild, T.
Hinderer, D. Hoak, S. Hochheim, D. Hofman, N. A. Holland, K. Holt, D. E.
Holz, P. Hopkins, C. Horst, J. Hough, E. A. Houston, E. J. Howell, A. Hreibi,
E. A. Huerta, D. Huet, B. Hughey, M. Hulko, S. Husa, S. H. Huttner, T.
Huynh-Dinh, A. Iess, N. Indik, C. Ingram, R. Inta, G. Intini, H. N. Isa,
J.-M. Isac, M. Isi, B. R. Iyer, K. Izumi, T. Jacqmin, K. Jani, P. Jaranowski,
D. S. Johnson, W. W. Johnson, D. I. Jones, R. Jones, R. J. G. Jonker, L. Ju,
J. Junker, C. V. Kalaghatgi, V. Kalogera, B. Kamai, S. Kandhasamy, G. Kang,
J. B. Kanner, S. J. Kapadia, S. Karki, K. S. Karvinen, W. Kastaun, M.
Kasprzack, M. Katolik, S. Katsanevas, E. Katsavounidis, W. Katzman, S.
Kaufer, K. Kawabe, N. V. Keerthana, F. K\'ef\'elian, D. Keitel, A. J.
Kemball, R. Kennedy, J. S. Key, F. Y. Khalili, B. Khamesra, H. Khan, I. Khan,
S. Khan, Z. Khan, E. A. Khazanov, N. Kijbunchoo, Chunglee Kim, J. C. Kim, K.
Kim, W. Kim, W. S. Kim, Y.-M. Kim, E. J. King, P. J. King, M. Kinley-Hanlon,
R. Kirchhoff, J. S. Kissel, L. Kleybolte, S. Klimenko, T. D. Knowles, P.
Koch, S. M. Koehlenbeck, S. Koley, V. Kondrashov, A. Kontos, M. Korobko, W.
Z. Korth, I. Kowalska, D. B. Kozak, C. Kr\"amer, V. Kringel, B. Krishnan, A.
Kr\'olak, G. Kuehn, P. Kumar, R. Kumar, S. Kumar, L. Kuo, A. Kutynia, S.
Kwang, B. D. Lackey, K. H. Lai, M. Landry, R. N. Lang, J. Lange, B. Lantz, R.
K. Lanza, A. Lartaux-Vollard, P. D. Lasky, M. Laxen, A. Lazzarini, C.
Lazzaro, P. Leaci, S. Leavey, C. H. Lee, H. K. Lee, H. M. Lee, H. W. Lee, K.
Lee, J. Lehmann, A. Lenon, M. Leonardi, N. Leroy, N. Letendre, Y. Levin, J.
Li, T. G. F. Li, X. Li, S. D. Linker, T. B. Littenberg, J. Liu, X. Liu, R. K.
L. Lo, N. A. Lockerbie, L. T. London, A. Longo, M. Lorenzini, V. Loriette, M.
Lormand, G. Losurdo, J. D. Lough, C. O. Lousto, G. Lovelace, H. L\"uck, D.
Lumaca, A. P. Lundgren, R. Lynch, Y. Ma, R. Macas, S. Macfoy, B.
Machenschalk, M. MacInnis, D. M. Macleod, I. Maga\~na Hernandez, F.
Maga\~na-Sandoval, L. Maga\~na Zertuche, R. M. Magee, E. Majorana, I.
Maksimovic, N. Man, V. Mandic, V. Mangano, G. L. Mansell, M. Manske, M.
Mantovani, F. Marchesoni, F. Marion, S. M\'arka, Z. M\'arka, C. Markakis, A.
S. Markosyan, A. Markowitz, E. Maros, A. Marquina, F. Martelli, L.
Martellini, I. W. Martin, R. M. Martin, D. V. Martynov, K. Mason, E. Massera,
A. Masserot, T. J. Massinger, M. Masso-Reid, S. Mastrogiovanni, A. Matas, F.
Matichard, L. Matone, N. Mavalvala, N. Mazumder, J. J. McCann, R. McCarthy,
D. E. McClelland, S. McCormick, L. McCuller, S. C. McGuire, J. McIver, D. J.
McManus, T. McRae, S. T. McWilliams, D. Meacher, G. D. Meadors, M. Mehmet, J.
Meidam, E. Mejuto-Villa, A. Melatos, G. Mendell, D. Mendoza-Gandara, R. A.
Mercer, L. Mereni, E. L. Merilh, M. Merzougui, S. Meshkov, C. Messenger, C.
Messick, R. Metzdorff, P. M. Meyers, H. Miao, C. Michel, H. Middleton, E. E.
Mikhailov, L. Milano, A. L. Miller, A. Miller, B. B. Miller, J. Miller, M.
Millhouse, J. Mills, M. C. Milovich-Goff, O. Minazzoli, Y. Minenkov, J. Ming,
C. Mishra, S. Mitra, V. P. Mitrofanov, G. Mitselmakher, R. Mittleman, D.
Moffa, K. Mogushi, M. Mohan, S. R. P. Mohapatra, M. Montani, C. J. Moore, D.
Moraru, G. Moreno, S. Morisaki, B. Mours, C. M. Mow-Lowry, G. Mueller, A. W.
Muir, Arunava Mukherjee, D. Mukherjee, S. Mukherjee, N. Mukund, A. Mullavey,
J. Munch, E. A. Mu\~niz, M. Muratore, P. G. Murray, A. Nagar, K. Napier, I.
Nardecchia, L. Naticchioni, R. K. Nayak, J. Neilson, G. Nelemans, T. J. N.
Nelson, M. Nery, A. Neunzert, L. Nevin, J. M. Newport, K. Y. Ng, S. Ng, P.
Nguyen, T. T. Nguyen, D. Nichols, A. B. Nielsen, S. Nissanke, A. Nitz, F.
Nocera, D. Nolting, C. North, L. K. Nuttall, M. Obergaulinger, J. Oberling,
B. D. O'Brien, G. D. O'Dea, G. H. Ogin, J. J. Oh, S. H. Oh, F. Ohme, H. Ohta,
M. A. Okada, M. Oliver, P. Oppermann, Richard J. Oram, B. O'Reilly, R.
Ormiston, L. F. Ortega, R. O'Shaughnessy, S. Ossokine, D. J. Ottaway, H.
Overmier, B. J. Owen, A. E. Pace, G. Pagano, J. Page, M. A. Page, A. Pai, S.
A. Pai, J. R. Palamos, O. Palashov, C. Palomba, A. Pal-Singh, Howard Pan,
Huang-Wei Pan, B. Pang, P. T. H. Pang, C. Pankow, F. Pannarale, B. C. Pant,
F. Paoletti, A. Paoli, M. A. Papa, A. Parida, W. Parker, D. Pascucci, A.
Pasqualetti, R. Passaquieti, D. Passuello, M. Patil, B. Patricelli, B. L.
Pearlstone, C. Pedersen, M. Pedraza, R. Pedurand, L. Pekowsky, A. Pele, S.
Penn, C. J. Perez, A. Perreca, L. M. Perri, H. P. Pfeiffer, M. Phelps, K. S.
Phukon, O. J. Piccinni, M. Pichot, F. Piergiovanni, V. Pierro, G. Pillant, L.
Pinard, I. M. Pinto, M. Pirello, M. Pitkin, R. Poggiani, P. Popolizio, E. K.
Porter, L. Possenti, A. Post, J. Powell, J. Prasad, J. W. W. Pratt, G.
Pratten, V. Predoi, T. Prestegard, M. Principe, S. Privitera, G. A. Prodi, L.
G. Prokhorov, O. Puncken, M. Punturo, P. Puppo, M. P\"urrer, H. Qi, V.
Quetschke, E. A. Quintero, R. Quitzow-James, F. J. Raab, D. S. Rabeling, H.
Radkins, P. Raffai, S. Raja, C. Rajan, B. Rajbhandari, M. Rakhmanov, K. E.
Ramirez, A. Ramos-Buades, Javed Rana, P. Rapagnani, V. Raymond, M. Razzano,
J. Read, T. Regimbau, L. Rei, S. Reid, D. H. Reitze, W. Ren, F. Ricci, P. M.
Ricker, K. Riles, M. Rizzo, N. A. Robertson, R. Robie, F. Robinet, T. Robson,
A. Rocchi, L. Rolland, J. G. Rollins, V. J. Roma, R. Romano, C. L. Romel, J.
H. Romie, D. Rosi\'nska, M. P. Ross, S. Rowan, A. R\"udiger, P. Ruggi, G.
Rutins, K. Ryan, S. Sachdev, T. Sadecki, M. Sakellariadou, L. Salconi, M.
Saleem, F. Salemi, A. Samajdar, L. Sammut, L. M. Sampson, E. J. Sanchez, L.
E. Sanchez, N. Sanchis-Gual, V. Sandberg, J. R. Sanders, N. Sarin, B.
Sassolas, B. S. Sathyaprakash, P. R. Saulson, O. Sauter, R. L. Savage, A.
Sawadsky, P. Schale, M. Scheel, J. Scheuer, P. Schmidt, R. Schnabel, R. M. S.
Schofield, A. Sch\"onbeck, E. Schreiber, D. Schuette, B. W. Schulte, B. F.
Schutz, S. G. Schwalbe, J. Scott, S. M. Scott, E. Seidel, D. Sellers, A. S.
Sengupta, D. Sentenac, V. Sequino, A. Sergeev, Y. Setyawati, D. A. Shaddock,
T. J. Shaffer, A. A. Shah, M. S. Shahriar, M. B. Shaner, L. Shao, B. Shapiro,
P. Shawhan, H. Shen, D. H. Shoemaker, D. M. Shoemaker, K. Siellez, X.
Siemens, M. Sieniawska, D. Sigg, A. D. Silva, L. P. Singer, A. Singh, A.
Singhal, A. M. Sintes, B. J. J. Slagmolen, T. J. Slaven-Blair, B. Smith, J.
R. Smith, R. J. E. Smith, S. Somala, E. J. Son, B. Sorazu, F. Sorrentino, T.
Souradeep, A. P. Spencer, A. K. Srivastava, K. Staats, M. Steinke, J.
Steinlechner, S. Steinlechner, D. Steinmeyer, B. Steltner, S. P. Stevenson,
D. Stocks, R. Stone, D. J. Stops, K. A. Strain, G. Stratta, S. E. Strigin, A.
Strunk, R. Sturani, A. L. Stuver, T. Z. Summerscales, L. Sun, S. Sunil, J.
Suresh, P. J. Sutton, B. L. Swinkels, M. J. Szczepa\'nczyk, M. Tacca, S. C.
Tait, C. Talbot, D. Talukder, D. B. Tanner, M. T\'apai, A. Taracchini, J. D.
Tasson, J. A. Taylor, R. Taylor, S. V. Tewari, T. Theeg, F. Thies, E. G.
Thomas, M. Thomas, P. Thomas, K. A. Thorne, E. Thrane, S. Tiwari, V. Tiwari,
K. V. Tokmakov, K. Toland, M. Tonelli, Z. Tornasi, A. Torres-Forn\'e, C. I.
Torrie, D. T\"oyr\"a, F. Travasso, G. Traylor, J. Trinastic, M. C. Tringali,
L. Trozzo, K. W. Tsang, M. Tse, R. Tso, D. Tsuna, L. Tsukada, D. Tuyenbayev,
K. Ueno, D. Ugolini, A. L. Urban, S. A. Usman, H. Vahlbruch, G. Vajente, G.
Valdes, N. van Bakel, M. van Beuzekom, J. F. J. van den Brand, C. Van Den
Broeck, D. C. Vander-Hyde, L. van der Schaaf, J. V. van Heijningen, A. A. van
Veggel, M. Vardaro, V. Varma, S. Vass, M. Vas\'uth, A. Vecchio, G. Vedovato,
J. Veitch, P. J. Veitch, K. Venkateswara, G. Venugopalan, D. Verkindt, F.
Vetrano, A. Vicer\'e, A. D. Viets, S. Vinciguerra, D. J. Vine, J.-Y. Vinet,
S. Vitale, T. Vo, H. Vocca, C. Vorvick, S. P. Vyatchanin, A. R. Wade, L. E.
Wade, M. Wade, R. Walet, M. Walker, L. Wallace, S. Walsh, G. Wang, H. Wang,
J. Z. Wang, W. H. Wang, Y. F. Wang, R. L. Ward, J. Warner, M. Was, J. Watchi,
B. Weaver, L.-W. Wei, M. Weinert, A. J. Weinstein, R. Weiss, F. Wellmann, L.
Wen, E. K. Wessel, P. We{\ss}els, J. Westerweck, K. Wette, J. T. Whelan, B.
F. Whiting, C. Whittle, D. Wilken, D. Williams, R. D. Williams, A. R.
Williamson, J. L. Willis, B. Willke, M. H. Wimmer, W. Winkler, C. C. Wipf, H.
Wittel, G. Woan, J. Woehler, J. K. Wofford, W. K. Wong, J. Worden, J. L.
Wright, D. S. Wu, D. M. Wysocki, S. Xiao, W. Yam, H. Yamamoto, C. C. Yancey,
L. Yang, M. J. Yap, M. Yazback, Hang Yu, Haocun Yu, M. Yvert, A. Zadro\.zny,
M. Zanolin, T. Zelenova, J.-P. Zendri, M. Zevin, J. Zhang, L. Zhang, M.
Zhang, T. Zhang, Y.-H. Zhang, C. Zhao, M. Zhou, Z. Zhou, S. J. Zhu, X. J.
Zhu, A. B. Zimmermann, M. E. Zucker, J. Zweizig | Search for gravitational waves from a long-lived remnant of the binary
neutron star merger GW170817 | main paper: 9 pages and 3 figures; total with appendices: 24 pages
and 9 figures. Full UL tables available as MRT ancillary files | The Astrophysical Journal 875:160 (2019) | 10.3847/1538-4357/ab0f3d | LIGO-P1800195 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One unanswered question about the binary neutron star coalescence GW170817 is
the nature of its post-merger remnant. A previous search for post-merger
gravitational waves targeted high-frequency signals from a possible neutron
star remnant with a maximum signal duration of 500 s. Here we revisit the
neutron star remnant scenario with a focus on longer signal durations up until
the end of the Second Advanced LIGO-Virgo Observing run, 8.5 days after the
coalescence of GW170817. The main physical scenario for such emission is the
power-law spindown of a massive magnetar-like remnant. We use four independent
search algorithms with varying degrees of restrictiveness on the signal
waveformand different ways of dealing with noise artefacts. In agreement with
theoretical estimates, we find no significant signal candidates. Through
simulated signals, we quantify that with the current detector sensitivity,
nowhere in the studied parameter space are we sensitive to a signal from more
than 1 Mpc away, compared to the actual distance of 40 Mpc. This study however
serves as a prototype for post-merger analyses in future observing runs with
expected higher sensitivity.
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"Ackley",
"K.",
... | One unanswered question about the binary neutron star coalescence GW170817 is the nature of its post-merger remnant. A previous search for post-merger gravitational waves targeted high-frequency signals from a possible neutron star remnant with a maximum signal duration of 500 s. Here we revisit the neutron star remnant scenario with a focus on longer signal durations up until the end of the Second Advanced LIGO-Virgo Observing run, 8.5 days after the coalescence of GW170817. The main physical scenario for such emission is the power-law spindown of a massive magnetar-like remnant. We use four independent search algorithms with varying degrees of restrictiveness on the signal waveformand different ways of dealing with noise artefacts. In agreement with theoretical estimates, we find no significant signal candidates. Through simulated signals, we quantify that with the current detector sensitivity, nowhere in the studied parameter space are we sensitive to a signal from more than 1 Mpc away, compared to the actual distance of 40 Mpc. This study however serves as a prototype for post-merger analyses in future observing runs with expected higher sensitivity. |
gr-qc/9403038 | Sherry Robinson | Abhay Ashtekar | Overview and Outlook | 33 pages, plain TEX, CGPG-94/1-1 | null | 10.1007/3-540-58339-4_24 | null | gr-qc | null | This report is based on the talk given by the author in the concluding
session of the workshop on Canonical Methods in Classical and Quantum General
Relativity, held a Bad-Honef, Germany, in September 93. It contains an
assessment of the canonical approach in general, an overview of recent
developments within the canonical approach based on connections and loops, and
some suggestions for future work.
| [
{
"created": "Fri, 18 Mar 1994 20:59:19 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Ashtekar",
"Abhay",
""
]
] | This report is based on the talk given by the author in the concluding session of the workshop on Canonical Methods in Classical and Quantum General Relativity, held a Bad-Honef, Germany, in September 93. It contains an assessment of the canonical approach in general, an overview of recent developments within the canonical approach based on connections and loops, and some suggestions for future work. |
gr-qc/9607018 | Kim Sang Pyo | Sang Pyo Kim, Sung Ku Kim, Kwang-Sup Soh, Jae Hyung Yee | The Effect of Brick Walls on the Black Hole Radiation | 8 pages, no figures, Revtex | J.KoreanPhys.Soc.31:357-359,1997 | null | SNUTP 96-069, YUMS 96-15 | gr-qc | null | In order to understand the physical effect of the brick wall boundary
condition, we compute the distribution of the zero-point energy of the massless
scalar fields minimally coupled to the Schwarzschild and Reissner-Nordstr\"{o}m
black hole backgrounds. We find that the black hole radiation spectrum depends
on the positions of the brick wall and the observer, and reveals the
interference effect due to the reflected field by the brick wall.
| [
{
"created": "Sun, 7 Jul 1996 13:46:32 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kim",
"Sang Pyo",
""
],
[
"Kim",
"Sung Ku",
""
],
[
"Soh",
"Kwang-Sup",
""
],
[
"Yee",
"Jae Hyung",
""
]
] | In order to understand the physical effect of the brick wall boundary condition, we compute the distribution of the zero-point energy of the massless scalar fields minimally coupled to the Schwarzschild and Reissner-Nordstr\"{o}m black hole backgrounds. We find that the black hole radiation spectrum depends on the positions of the brick wall and the observer, and reveals the interference effect due to the reflected field by the brick wall. |
1108.3254 | William Joseph Weber | R. Dolesi, M. Hueller, D. Nicolodi, D. Tombolato, S. Vitale, P. J.
Wass, W. J. Weber, M. Evans, P. Fritschel, R. Weiss, J. H. Gundlach, C. A.
Hagedorn, S. Schlamminger, G. Ciani, and A. Cavalleri | Brownian force noise from molecular collisions and the sensitivity of
advanced gravitational wave observatories | 13 pages with 9 figures (fixed typos found in proofs) | Physical Review D 84, 063007 (2011) | 10.1103/PhysRevD.84.063007 | null | gr-qc astro-ph.IM physics.ins-det | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an analysis of Brownian force noise from residual gas damping of
reference test masses as a fundamental sensitivity limit in small force
experiments. The resulting acceleration noise increases significantly when the
distance of the test mass to the surrounding experimental apparatus is smaller
than the dimension of the test mass itself. For the Advanced LIGO
interferometric gravitational wave observatory, where the relevant test mass is
a suspended 340 mm diameter cylindrical end mirror, the force noise power is
increased by roughly a factor 40 by the presence of a similarly shaped reaction
mass at a nominal separation of 5 mm. The force noise, of order 20 fN\rthz\ for
$2 \times 10^{-6}$ Pa of residual H$_2$ gas, rivals quantum optical
fluctuations as the dominant noise source between 10 and 30 Hz. We present here
a numerical and analytical analysis for the gas damping force noise for
Advanced LIGO, backed up by experimental evidence from several recent
measurements. Finally, we discuss the impact of residual gas damping on the
gravitational wave sensitivity and possible mitigation strategies.
| [
{
"created": "Tue, 16 Aug 2011 14:41:53 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Sep 2011 15:02:59 GMT",
"version": "v2"
}
] | 2015-03-19 | [
[
"Dolesi",
"R.",
""
],
[
"Hueller",
"M.",
""
],
[
"Nicolodi",
"D.",
""
],
[
"Tombolato",
"D.",
""
],
[
"Vitale",
"S.",
""
],
[
"Wass",
"P. J.",
""
],
[
"Weber",
"W. J.",
""
],
[
"Evans",
"M.",
... | We present an analysis of Brownian force noise from residual gas damping of reference test masses as a fundamental sensitivity limit in small force experiments. The resulting acceleration noise increases significantly when the distance of the test mass to the surrounding experimental apparatus is smaller than the dimension of the test mass itself. For the Advanced LIGO interferometric gravitational wave observatory, where the relevant test mass is a suspended 340 mm diameter cylindrical end mirror, the force noise power is increased by roughly a factor 40 by the presence of a similarly shaped reaction mass at a nominal separation of 5 mm. The force noise, of order 20 fN\rthz\ for $2 \times 10^{-6}$ Pa of residual H$_2$ gas, rivals quantum optical fluctuations as the dominant noise source between 10 and 30 Hz. We present here a numerical and analytical analysis for the gas damping force noise for Advanced LIGO, backed up by experimental evidence from several recent measurements. Finally, we discuss the impact of residual gas damping on the gravitational wave sensitivity and possible mitigation strategies. |
gr-qc/0209039 | Massimo Tinto | Thomas A. Prince, Massimo Tinto, Shane L. Larson, and J.W. Armstrong | The LISA Optimal Sensitivity | Equation (20) of the previous version contained a typographical
error, which now has been corrected. The final results of the paper are
unchanged | Phys.Rev. D66 (2002) 122002 | 10.1103/PhysRevD.66.122002 | null | gr-qc | null | The multiple Doppler readouts available on the Laser Interferometer Space
Antenna (LISA) permit simultaneous formation of several interferometric
observables. All these observables are independent of laser frequency
fluctuations and have different couplings to gravitational waves and to the
various LISA instrumental noises. Within the functional space of
interferometric combinations LISA will be able to synthesize, we have
identified a triplet of interferometric combinations that show optimally
combined sensitivity. As an application of the method, we computed the
sensitivity improvement for sinusoidal sources in the nominal, equal-arm LISA
configuration. In the part of the Fourier band where the period of the wave is
longer than the typical light travel-time across LISA, the sensitivity gain
over a single Michelson interferometer is equal to $\sqrt{2}$. In the mid-band
region, where the LISA Michelson combination has its best sensitivity, the
improvement over the Michelson sensitivity is slightly better than $\sqrt{2}$,
and the frequency band of best sensitivity is broadened. For frequencies
greater than the reciprocal of the light travel-time, the sensitivity
improvement is oscillatory and $\sim \sqrt{3}$, but can be greater than
$\sqrt{3}$ near frequencies that are integer multiples of the inverse of the
one-way light travel-time in the LISA arm.
| [
{
"created": "Thu, 12 Sep 2002 06:45:36 GMT",
"version": "v1"
},
{
"created": "Wed, 4 Jun 2003 05:04:15 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Prince",
"Thomas A.",
""
],
[
"Tinto",
"Massimo",
""
],
[
"Larson",
"Shane L.",
""
],
[
"Armstrong",
"J. W.",
""
]
] | The multiple Doppler readouts available on the Laser Interferometer Space Antenna (LISA) permit simultaneous formation of several interferometric observables. All these observables are independent of laser frequency fluctuations and have different couplings to gravitational waves and to the various LISA instrumental noises. Within the functional space of interferometric combinations LISA will be able to synthesize, we have identified a triplet of interferometric combinations that show optimally combined sensitivity. As an application of the method, we computed the sensitivity improvement for sinusoidal sources in the nominal, equal-arm LISA configuration. In the part of the Fourier band where the period of the wave is longer than the typical light travel-time across LISA, the sensitivity gain over a single Michelson interferometer is equal to $\sqrt{2}$. In the mid-band region, where the LISA Michelson combination has its best sensitivity, the improvement over the Michelson sensitivity is slightly better than $\sqrt{2}$, and the frequency band of best sensitivity is broadened. For frequencies greater than the reciprocal of the light travel-time, the sensitivity improvement is oscillatory and $\sim \sqrt{3}$, but can be greater than $\sqrt{3}$ near frequencies that are integer multiples of the inverse of the one-way light travel-time in the LISA arm. |
1405.2824 | Tiberiu Harko | Tiberiu Harko, Chun Sing Leung, Gabriela Mocanu | Generalized Langevin equation with colored noise description of the
stochastic oscillations of accretion disks | 17 pages, 10 figures, accepted for publication in EPJC | Eur. Phys. J. C (2014) 74:2900 | 10.1140/epjc/s10052-014-2900-9 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a description of the stochastic oscillations of the general
relativistic accretion disks around compact astrophysical objects interacting
with their external medium based on a generalized Langevin equation with
colored noise, which accounts for the general memory and retarded effects of
the frictional force, and on the fluctuation-dissipation theorem. The presence
of the memory effects influences the response of the disk to external random
interactions, and modifies the dynamical behavior of the disk, as well as the
energy dissipation processes. The generalized Langevin equation of the motion
of the disk in the vertical direction is studied numerically, and the vertical
displacements, velocities and luminosities of the stochastically perturbed
disks are explicitly obtained for both the Schwarzschild and the Kerr cases.
The Power Spectral Distribution (PSD) of the disk luminosity is also obtained.
As a possible astrophysical application of the formalism we investigate the
possibility that the Intra Day Variability (IDV) of the Active Galactic Nuclei
(AGN) may be due to the stochastic disk instabilities. The perturbations due to
colored/nontrivially correlated noise induce a complicated disk dynamics, which
could explain some astrophysical observational features related to disk
variability.
| [
{
"created": "Mon, 12 May 2014 16:28:49 GMT",
"version": "v1"
}
] | 2015-06-19 | [
[
"Harko",
"Tiberiu",
""
],
[
"Leung",
"Chun Sing",
""
],
[
"Mocanu",
"Gabriela",
""
]
] | We consider a description of the stochastic oscillations of the general relativistic accretion disks around compact astrophysical objects interacting with their external medium based on a generalized Langevin equation with colored noise, which accounts for the general memory and retarded effects of the frictional force, and on the fluctuation-dissipation theorem. The presence of the memory effects influences the response of the disk to external random interactions, and modifies the dynamical behavior of the disk, as well as the energy dissipation processes. The generalized Langevin equation of the motion of the disk in the vertical direction is studied numerically, and the vertical displacements, velocities and luminosities of the stochastically perturbed disks are explicitly obtained for both the Schwarzschild and the Kerr cases. The Power Spectral Distribution (PSD) of the disk luminosity is also obtained. As a possible astrophysical application of the formalism we investigate the possibility that the Intra Day Variability (IDV) of the Active Galactic Nuclei (AGN) may be due to the stochastic disk instabilities. The perturbations due to colored/nontrivially correlated noise induce a complicated disk dynamics, which could explain some astrophysical observational features related to disk variability. |
2305.17307 | Sijie Gao | Minghao Xia and Sijie Gao | General Proof of the Tolman law | 4 pages, no figure | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Tolman proposed that the proper temper $T$ of a static self-gravitating fluid
in thermodynamic equilibrium satisfies the relation $\chi T=constant$, where
$\chi$ is the redshift factor of the spacetime. The Tolman law has been proven
for radiation in stationary spacetimes and for perfect fluids in stationary,
asymototically flat and axisymmetric spacetimes. It is unclear whether the
proof can be extended to more general cases. In this paper, we prove that under
some reasonable conditions, the Tolman law always holds for a perfect fluid in
a stationary spacetime. The key assumption in our proof is that the particle
number density $n$ can not be determined by the energy density $\rho$ and
pressure $p$ via the equations of state. This is true for many known fluids
with the equation of state $p=p(\rho)$. Then, by requiring that the total
entropy of the fluid is an extremum for the variation of $n$ with a fixed
metric, we prove the Tolman law. In our proof, only the conservations of stress
energy and the total particle number are used, and no field equations are
involved. Our work suggests that the Tolman law holds for a generic perfect
fluid in a stationary spacetime, even beyond general relativity.
| [
{
"created": "Fri, 26 May 2023 23:51:30 GMT",
"version": "v1"
}
] | 2023-05-30 | [
[
"Xia",
"Minghao",
""
],
[
"Gao",
"Sijie",
""
]
] | Tolman proposed that the proper temper $T$ of a static self-gravitating fluid in thermodynamic equilibrium satisfies the relation $\chi T=constant$, where $\chi$ is the redshift factor of the spacetime. The Tolman law has been proven for radiation in stationary spacetimes and for perfect fluids in stationary, asymototically flat and axisymmetric spacetimes. It is unclear whether the proof can be extended to more general cases. In this paper, we prove that under some reasonable conditions, the Tolman law always holds for a perfect fluid in a stationary spacetime. The key assumption in our proof is that the particle number density $n$ can not be determined by the energy density $\rho$ and pressure $p$ via the equations of state. This is true for many known fluids with the equation of state $p=p(\rho)$. Then, by requiring that the total entropy of the fluid is an extremum for the variation of $n$ with a fixed metric, we prove the Tolman law. In our proof, only the conservations of stress energy and the total particle number are used, and no field equations are involved. Our work suggests that the Tolman law holds for a generic perfect fluid in a stationary spacetime, even beyond general relativity. |
2405.16689 | Tuan Do | Tuan Q. Do | A note on the area of event horizon of Kleinian black hole | 8 pages, 3 figures. Comments are welcome | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We point out that the area of event horizon of Kleinian black hole is
infinite due to the fact that its event horizon is not a sphere but a
hyperboloid. Therefore, the usual interpretations of Schwarzschild black hole
might not be applicable to the Kleinian black hole.
| [
{
"created": "Sun, 26 May 2024 20:50:29 GMT",
"version": "v1"
}
] | 2024-05-28 | [
[
"Do",
"Tuan Q.",
""
]
] | We point out that the area of event horizon of Kleinian black hole is infinite due to the fact that its event horizon is not a sphere but a hyperboloid. Therefore, the usual interpretations of Schwarzschild black hole might not be applicable to the Kleinian black hole. |
1112.2829 | Mohamed Ahmed | M. A. Ahmed | On f(R) theories in two-dimensional spacetime | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In recent years, theories in which the Einstien-Hilbert lagrangian is
replaced by a function f(R) of the Ricci Scalar have been extensively studied
in four-dimensional spacetime. In this work we carry out an analysis of such
theories in two-dimensional spacetime with focus on cosmological implications.
Solutions to the cosmological field equations are obtained and their properties
are analysed. Inflationary solutions are also obtained and discussed.
Quantization is then carried out, the Wheeler-DeWitt equation is set up and its
exact solutions obtained.
| [
{
"created": "Tue, 13 Dec 2011 09:26:33 GMT",
"version": "v1"
}
] | 2011-12-14 | [
[
"Ahmed",
"M. A.",
""
]
] | In recent years, theories in which the Einstien-Hilbert lagrangian is replaced by a function f(R) of the Ricci Scalar have been extensively studied in four-dimensional spacetime. In this work we carry out an analysis of such theories in two-dimensional spacetime with focus on cosmological implications. Solutions to the cosmological field equations are obtained and their properties are analysed. Inflationary solutions are also obtained and discussed. Quantization is then carried out, the Wheeler-DeWitt equation is set up and its exact solutions obtained. |
1702.02787 | Titus K Mathew | Krishna P B and Titus K Mathew | Holographic equipartition and the maximization of entropy | 16 pages, 4 figures | Phys. Rev. D 96, 063513 (2017) | 10.1103/PhysRevD.96.063513 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | \begin{abstract} The accelerated expansion of the universe can be interpreted
as a tendency to satisfy the holographic equipartition. It can be expressed by
a simple law, $\Delta V = \Delta t\left(N_{surf}-\epsilon N_{bulk}\right),$
where $V$ is the Hubble volume in Plank units, $t$ is the cosmic time plank
units and $N_{surf/bulk}$ is the degrees of freedom on the horizon/bulk of the
universe. We show that this holographic equipartition law effectively implies
the maximization of entropy. In the cosmological context, a system that obeys
the holographic equipartition law behaves as an ordinary macroscopic system
that proceeds to an equilibrium state of maximum entropy. We consider the
standard $\Lambda$CDM model of the universe and have shown that it is
consistent with the holographic equipartition law. Analyzing the entropy
evolution we find that it also proceeds to an equilibrium state of maximum
entropy.
| [
{
"created": "Thu, 9 Feb 2017 11:31:30 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Aug 2017 13:22:59 GMT",
"version": "v2"
}
] | 2017-09-20 | [
[
"B",
"Krishna P",
""
],
[
"Mathew",
"Titus K",
""
]
] | \begin{abstract} The accelerated expansion of the universe can be interpreted as a tendency to satisfy the holographic equipartition. It can be expressed by a simple law, $\Delta V = \Delta t\left(N_{surf}-\epsilon N_{bulk}\right),$ where $V$ is the Hubble volume in Plank units, $t$ is the cosmic time plank units and $N_{surf/bulk}$ is the degrees of freedom on the horizon/bulk of the universe. We show that this holographic equipartition law effectively implies the maximization of entropy. In the cosmological context, a system that obeys the holographic equipartition law behaves as an ordinary macroscopic system that proceeds to an equilibrium state of maximum entropy. We consider the standard $\Lambda$CDM model of the universe and have shown that it is consistent with the holographic equipartition law. Analyzing the entropy evolution we find that it also proceeds to an equilibrium state of maximum entropy. |
1703.01158 | Markus B. Fr\"ob | Markus B. Fr\"ob, Thomas-Paul Hack, Atsushi Higuchi | Compactly supported linearised observables in single-field inflation | 33 pages, new section on the relation between our compactly supported
observables and the scalar and tensor power spectra, agrees with published
version up to appendix E | JCAP 07 (2017) 043 | 10.1088/1475-7516/2017/07/043 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the gauge-invariant observables constructed by smearing the
graviton and inflaton fields by compactly supported tensors at linear order in
general single-field inflation. These observables correspond to gauge-invariant
quantities that can be measured locally. In particular, we show that these
observables are equivalent to (smeared) local gauge-invariant observables such
as the linearised Weyl tensor, which have better infrared properties than the
graviton and inflaton fields. Special cases include the equivalence between the
compactly supported gauge-invariant graviton observable and the smeared
linearised Weyl tensor in Minkowski and de Sitter spaces. Our results indicate
that the infrared divergences in the tensor and scalar perturbations in
single-field inflation have the same status as in de Sitter space and are both
a gauge artefact, in a certain technical sense, at tree level.
| [
{
"created": "Fri, 3 Mar 2017 13:52:41 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Aug 2017 13:54:55 GMT",
"version": "v2"
}
] | 2017-09-01 | [
[
"Fröb",
"Markus B.",
""
],
[
"Hack",
"Thomas-Paul",
""
],
[
"Higuchi",
"Atsushi",
""
]
] | We investigate the gauge-invariant observables constructed by smearing the graviton and inflaton fields by compactly supported tensors at linear order in general single-field inflation. These observables correspond to gauge-invariant quantities that can be measured locally. In particular, we show that these observables are equivalent to (smeared) local gauge-invariant observables such as the linearised Weyl tensor, which have better infrared properties than the graviton and inflaton fields. Special cases include the equivalence between the compactly supported gauge-invariant graviton observable and the smeared linearised Weyl tensor in Minkowski and de Sitter spaces. Our results indicate that the infrared divergences in the tensor and scalar perturbations in single-field inflation have the same status as in de Sitter space and are both a gauge artefact, in a certain technical sense, at tree level. |
1211.4586 | Sam Dolan Dr | Sam R. Dolan and Leor Barack | Self-force via $m$-mode regularization and 2+1D evolution: III.
Gravitational field on Schwarzschild spacetime | 56 pages, 17 figures | Phys.Rev.D87,084066(2013) | 10.1103/PhysRevD.87.084066 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is the third in a series of papers aimed at developing a practical
time-domain method for self-force calculations in Kerr spacetime. The key
elements of the method are (i) removal of a singular part of the perturbation
field with a suitable analytic "puncture", (ii) decomposition of the
perturbation equations in azimuthal ($m$-)modes, taking advantage of the axial
symmetry of the Kerr background, (iii) numerical evolution of the individual
$m$-modes in 2+1-dimensions with a finite difference scheme, and (iv)
reconstruction of the local self-force from the mode sum. Here we report a
first implementation of the method to compute the gravitational self-force. We
work in the Lorenz gauge, solving directly for the metric perturbation in
2+1-dimensions. The modes $m=0,1$ contain nonradiative pieces, whose
time-domain evolution is hampered by certain gauge instabilities. We study this
problem in detail and propose ways around it. In the current work we use the
Schwarzschild geometry as a platform for development; in a forthcoming
paper---the fourth in the series---we apply our method to the gravitational
self-force in Kerr geometry.
| [
{
"created": "Mon, 19 Nov 2012 21:01:15 GMT",
"version": "v1"
}
] | 2013-05-13 | [
[
"Dolan",
"Sam R.",
""
],
[
"Barack",
"Leor",
""
]
] | This is the third in a series of papers aimed at developing a practical time-domain method for self-force calculations in Kerr spacetime. The key elements of the method are (i) removal of a singular part of the perturbation field with a suitable analytic "puncture", (ii) decomposition of the perturbation equations in azimuthal ($m$-)modes, taking advantage of the axial symmetry of the Kerr background, (iii) numerical evolution of the individual $m$-modes in 2+1-dimensions with a finite difference scheme, and (iv) reconstruction of the local self-force from the mode sum. Here we report a first implementation of the method to compute the gravitational self-force. We work in the Lorenz gauge, solving directly for the metric perturbation in 2+1-dimensions. The modes $m=0,1$ contain nonradiative pieces, whose time-domain evolution is hampered by certain gauge instabilities. We study this problem in detail and propose ways around it. In the current work we use the Schwarzschild geometry as a platform for development; in a forthcoming paper---the fourth in the series---we apply our method to the gravitational self-force in Kerr geometry. |
2111.14809 | Fred Tomlinson | Fred Tomlinson | Five-dimensional electrostatic black holes in a background field | 21 pages | null | 10.1088/1361-6382/ac5814 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider $5$ dimensional electrostatic solutions to Einstein-Maxwell
gravity with $2$ commuting spacelike Killing fields. Taking two distinct
reductions from $5$ dimensions to a $3$ dimensional base space, we write the
Einstein-Maxwell equations using some axially symmetric functions on
$\mathbb{R}^3$. These equations can be viewed as arising from a harmonic map
coupled to 3-dimensional gravity with the isometries of the target space of
this map revealing a hidden $SL(2,\mathbb{R})$ symmetry of this sector of the
theory. Depending on the choice of reduction this symmetry then gives rise to
two different 1-parameter families of transformations corresponding to either
charging a black hole or immersing it in a background electric field. We use
these transformations to charge a static black Saturn and a static $L(n,1)$
black lens spacetime and by tuning the strength of the external field, we cure
the conical singularities to give new regular solutions. Notably the
electrified black lens generated is the first example of a regular black lens
in Einstein-Maxwell gravity with topologically trivial asymptotics.
| [
{
"created": "Mon, 29 Nov 2021 18:55:14 GMT",
"version": "v1"
}
] | 2022-06-22 | [
[
"Tomlinson",
"Fred",
""
]
] | We consider $5$ dimensional electrostatic solutions to Einstein-Maxwell gravity with $2$ commuting spacelike Killing fields. Taking two distinct reductions from $5$ dimensions to a $3$ dimensional base space, we write the Einstein-Maxwell equations using some axially symmetric functions on $\mathbb{R}^3$. These equations can be viewed as arising from a harmonic map coupled to 3-dimensional gravity with the isometries of the target space of this map revealing a hidden $SL(2,\mathbb{R})$ symmetry of this sector of the theory. Depending on the choice of reduction this symmetry then gives rise to two different 1-parameter families of transformations corresponding to either charging a black hole or immersing it in a background electric field. We use these transformations to charge a static black Saturn and a static $L(n,1)$ black lens spacetime and by tuning the strength of the external field, we cure the conical singularities to give new regular solutions. Notably the electrified black lens generated is the first example of a regular black lens in Einstein-Maxwell gravity with topologically trivial asymptotics. |
gr-qc/0604070 | Mikhail Kalinin | M.I. Kalinin and V.N. Melnikov | On the cosmological constant in quantum cosmology | This paper was published originally in "Problems of Gravitational
Theory and Particle Theory", VNIIFTRI Proceedings, Moscow, 1972. v. 16(46),
pp. 43-48 (in Russian). The English version was published in the journal
"Gravitation & Cosmology" in 2003 | Grav.Cosmol.9:227-228,2003 | null | null | gr-qc | null | Quantization of a dust-like closed isotropic cosmological model with a
cosmological constant is realized by the method of B. DeWitt \cite{1}. It is
shown that such quantization leads to interesting results, in particular, to a
finite lifetime of the system, and appearance of the Universe in our world as
penetration via the barrier. These purely quantum effects appear when
$\Lambda>0$.
| [
{
"created": "Mon, 17 Apr 2006 09:12:28 GMT",
"version": "v1"
}
] | 2009-09-25 | [
[
"Kalinin",
"M. I.",
""
],
[
"Melnikov",
"V. N.",
""
]
] | Quantization of a dust-like closed isotropic cosmological model with a cosmological constant is realized by the method of B. DeWitt \cite{1}. It is shown that such quantization leads to interesting results, in particular, to a finite lifetime of the system, and appearance of the Universe in our world as penetration via the barrier. These purely quantum effects appear when $\Lambda>0$. |
2008.04951 | Andre Landulfo | Joao Lucas Miqueleto and Andre G. S. Landulfo | Exact Renormalization Group, Entanglement Entropy, and Black Hole
Entropy | 13 pages, 1 figure | Phys. Rev. D 103, 045012 (2021) | 10.1103/PhysRevD.103.045012 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The study of black hole physics revealed a fundamental connection between
thermodynamics, quantum mechanics, and gravity. Today, it is known that black
holes are thermodynamical objects with well-defined temperature and entropy.
Although black hole radiance gives us the mechanism from which we can associate
a well-defined temperature to the black hole, the origin of its entropy remains
a mystery. Here we investigate how the quantum fluctuations from the fields
that render the black hole its temperature contribute to its entropy. By using
the exact renormalization group equation for a self-interacting real scalar
field in a spacetime possessing a bifurcate Killing horizon, we find the
renormalization group flow of the total gravitational entropy. We show that
throughout the flow one can split the quantum field contribution to the entropy
into a part coming from the entanglement between field degrees of freedom
inside and outside the horizon and a part due to the quantum corrections to the
Wald entropy coming from the Noether charge. The renormalized black hole
entropy is shown to be constant throughout the flow while the balance between
the effective black hole entropy at low energies and the infra-red entanglement
entropy changes. A similar conclusion is valid for the Wald entropy part of the
total entropy. Additionally, our calculations show that there is no mismatch
between the renormalization of the coupling constants coming from the effective
action or the gravitational entropy, solving an apparent "puzzle" that appeared
to exist for interacting fields.
| [
{
"created": "Tue, 11 Aug 2020 18:34:45 GMT",
"version": "v1"
}
] | 2021-02-24 | [
[
"Miqueleto",
"Joao Lucas",
""
],
[
"Landulfo",
"Andre G. S.",
""
]
] | The study of black hole physics revealed a fundamental connection between thermodynamics, quantum mechanics, and gravity. Today, it is known that black holes are thermodynamical objects with well-defined temperature and entropy. Although black hole radiance gives us the mechanism from which we can associate a well-defined temperature to the black hole, the origin of its entropy remains a mystery. Here we investigate how the quantum fluctuations from the fields that render the black hole its temperature contribute to its entropy. By using the exact renormalization group equation for a self-interacting real scalar field in a spacetime possessing a bifurcate Killing horizon, we find the renormalization group flow of the total gravitational entropy. We show that throughout the flow one can split the quantum field contribution to the entropy into a part coming from the entanglement between field degrees of freedom inside and outside the horizon and a part due to the quantum corrections to the Wald entropy coming from the Noether charge. The renormalized black hole entropy is shown to be constant throughout the flow while the balance between the effective black hole entropy at low energies and the infra-red entanglement entropy changes. A similar conclusion is valid for the Wald entropy part of the total entropy. Additionally, our calculations show that there is no mismatch between the renormalization of the coupling constants coming from the effective action or the gravitational entropy, solving an apparent "puzzle" that appeared to exist for interacting fields. |
gr-qc/0109066 | Margarita Tchitchikina | O.A.Khrustalev, M.V.Tchitchikina (Moscow State University) | Quantum Gravity on the Classical Background: Group Analysis, Part II | 10 pages | null | null | null | gr-qc | null | Quantization of gravitational field in the neighbourhood of arbitrary
nontrivial solution of Einstein equations is considered, the 2nd order of
perturbation theory is calculated. The expression for quantum corrections of
the field operator and explicit view of Hamiltonian are represented.
| [
{
"created": "Wed, 19 Sep 2001 14:06:23 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Khrustalev",
"O. A.",
"",
"Moscow State University"
],
[
"Tchitchikina",
"M. V.",
"",
"Moscow State University"
]
] | Quantization of gravitational field in the neighbourhood of arbitrary nontrivial solution of Einstein equations is considered, the 2nd order of perturbation theory is calculated. The expression for quantum corrections of the field operator and explicit view of Hamiltonian are represented. |
gr-qc/9702053 | Alexander L. Gromov | Alexander Gromov (St-Petersburg State Thechnical University, Russia)
V. Perepelovsky (St-Petersburg ElectroTechnical University, Russia) | Quasi-Two-Dimentional Modeling of the Self Gravitating Gas | LaTeX,6 pages,Invited talk at the Cosmion'94 Int. Conf. 1994;
Published in: Cosmoparticle physics. 1. Proceedings of 1 International
conference on cosmoparticle physics "Cosmion-94", dedicated to 80 Anniversary
of Ya.B.Zedovich and 5 Memorial of A.D.Sakharov. Eds M.Yu.Khlopov,
M.E.Prokhorov, A.A.Starobinsky, J.Tran Thanh Van, Editions Frontieres, 1996.
p.p.203 - 206 | null | null | IRB-StP-GR-120696 | gr-qc | null | The quasi-two-dimensional modeling of the small adiabatic perturbation on the
background of the stationary configuration of the selfgravitating gas with the
weak transverse nonhomogeneity approximation is presented. The space periodic
character of the solution of this system is proofed.
| [
{
"created": "Tue, 25 Feb 1997 10:11:40 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gromov",
"Alexander",
"",
"St-Petersburg State Thechnical University, Russia"
],
[
"Perepelovsky",
"V.",
"",
"St-Petersburg ElectroTechnical University, Russia"
]
] | The quasi-two-dimensional modeling of the small adiabatic perturbation on the background of the stationary configuration of the selfgravitating gas with the weak transverse nonhomogeneity approximation is presented. The space periodic character of the solution of this system is proofed. |
gr-qc/0203043 | Victor Tapia | Victor Tapia | The number of tensor differential invariants of a Riemannian metric | LaTeX, 5 pages | null | null | null | gr-qc | null | We determine the number of functionally independent components of tensors
involving higher-order derivatives of a Riemannian metric.
| [
{
"created": "Tue, 12 Mar 2002 21:33:36 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Tapia",
"Victor",
""
]
] | We determine the number of functionally independent components of tensors involving higher-order derivatives of a Riemannian metric. |
gr-qc/9703020 | Kirill A. Bronnikov | Kirill A. Bronnikov | Extra Dimensions, Nonminimal Couplings, Horizons and Wormholes | 6 pages, Latex | Grav.Cosmol. 2 (1996) 221-226 | null | RGS-VNIIMS-96/06 | gr-qc | null | Static, spherically symmetric configurations of gravity with nonminimally
coupled scalar fields are considered in D-dimensional space-times in the
framework of generalized scalar-tensor theories. We seek special cases when the
system has no naked singularity but instead forms either a black hole, or a
wormhole. General conditions when this is possible are formulated. In
particlar, some such special cases are indicated for multidimensional
Brans-Dicke theory and for linear, massless, nonminimally coupled scalar
fields. It is shown that in the Brans-Dicke theory the only black-hole solution
corresponds to D=4 and the coupling constant \omega< -2, and there is a
wormhole solution for \omega=0. For linear scalar fields it is shown that the
only black-hole solution is the well-known one (D=4, a black hole with scalar
charge), while the known 4-dimensional wormhole solution is generalized to
systems with conformal coupling in arbitrary dimension.
| [
{
"created": "Fri, 7 Mar 1997 06:43:27 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bronnikov",
"Kirill A.",
""
]
] | Static, spherically symmetric configurations of gravity with nonminimally coupled scalar fields are considered in D-dimensional space-times in the framework of generalized scalar-tensor theories. We seek special cases when the system has no naked singularity but instead forms either a black hole, or a wormhole. General conditions when this is possible are formulated. In particlar, some such special cases are indicated for multidimensional Brans-Dicke theory and for linear, massless, nonminimally coupled scalar fields. It is shown that in the Brans-Dicke theory the only black-hole solution corresponds to D=4 and the coupling constant \omega< -2, and there is a wormhole solution for \omega=0. For linear scalar fields it is shown that the only black-hole solution is the well-known one (D=4, a black hole with scalar charge), while the known 4-dimensional wormhole solution is generalized to systems with conformal coupling in arbitrary dimension. |
0907.1556 | Ayan Chatterjee | Ayan Chatterjee | Entropy of Black Holes in N=2 Supergravity | 21 Pages, major revision, results unchanged | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the techniques of isolated horizon formalism, we construct the space of
solutions of asymptotically flat extremal black holes in N=2 pure supergravity
in 4 dimensions. We prove the laws of black hole mechanics. Further,
restricting to constant area phase space, we show that the spherical horizons
admits a U(1) Chern- Simons theory. Standard way of quantizing this topological
theory and counting states confirms that entropy is indeed proportional to the
area of horizon.
| [
{
"created": "Thu, 9 Jul 2009 14:30:25 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Dec 2009 17:04:36 GMT",
"version": "v2"
}
] | 2009-12-03 | [
[
"Chatterjee",
"Ayan",
""
]
] | Using the techniques of isolated horizon formalism, we construct the space of solutions of asymptotically flat extremal black holes in N=2 pure supergravity in 4 dimensions. We prove the laws of black hole mechanics. Further, restricting to constant area phase space, we show that the spherical horizons admits a U(1) Chern- Simons theory. Standard way of quantizing this topological theory and counting states confirms that entropy is indeed proportional to the area of horizon. |
gr-qc/9903015 | Roberto B. Salgado | Roberto B. Salgado (Syracuse University) | Some Identities for the Quantum Measure and its Generalizations | (v1) 19 pages, LaTeX. (v2) 18 pages, LaTeX: minor corrections,
simplified proof of lemma 3 | Mod.Phys.Lett. A17 (2002) 711-728 | 10.1142/S0217732302007041 | SU-GP-99/3-1 | gr-qc hep-th math.RA quant-ph | null | After a brief review of classical probability theory (measure theory), we
present an observation (due to Sorkin) concerning an aspect of probability in
quantum mechanics. Following Sorkin, we introduce a generalized measure theory
based on a hierarchy of ``sum-rules.'' The first sum-rule yields classical
probability theory, and the second yields a generalized probability theory that
includes quantum mechanics as a special case. We present some algebraic
relations involving these sum-rules. This may be useful for the study of the
higher-order sum-rules and possible generalizations of quantum mechanics. We
conclude with some open questions and suggestions for further work.
| [
{
"created": "Thu, 4 Mar 1999 23:11:27 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Jun 2002 02:54:37 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Salgado",
"Roberto B.",
"",
"Syracuse University"
]
] | After a brief review of classical probability theory (measure theory), we present an observation (due to Sorkin) concerning an aspect of probability in quantum mechanics. Following Sorkin, we introduce a generalized measure theory based on a hierarchy of ``sum-rules.'' The first sum-rule yields classical probability theory, and the second yields a generalized probability theory that includes quantum mechanics as a special case. We present some algebraic relations involving these sum-rules. This may be useful for the study of the higher-order sum-rules and possible generalizations of quantum mechanics. We conclude with some open questions and suggestions for further work. |
1607.00651 | Oleg Zaslavskii | O. B. Zaslavskii | Maximum efficiency of the collisional Penrose process | 18 pages. Typos corrected. Title somewhat modified according to
suggestions of editors of PRD | Phys. Rev. D 94, 064048 (2016) | 10.1103/PhysRevD.94.064048 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider collision of two particles that move in the equatorial plane near
a general stationary rotating axially symmetric extremal black hole. One of
particles is critical (with fine-tuned parameters) and moves in the outward
direction. The second particle (usual, not fine-tuned) comes from infinity. We
examine the efficiency $\eta $ of the collisional Penrose process. There are
two relevant cases here: (i) a particle falling into a black hole after
collision is heavy, (ii) it has a finite mass. We show that the maximum of
$\eta $ in case (ii) is less or equal to that in case (i). It is argued that
for superheavy particles, the bound applies to nonequatorial motion as well. As
an example, we analyze collision in the Kerr-Newman background. When the bound
is the same for processes (i) and (ii), $\eta =3$ for this metric. For the Kerr
black hole, recent results in literature are reproduced.
| [
{
"created": "Sun, 3 Jul 2016 16:01:44 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Sep 2016 15:24:53 GMT",
"version": "v2"
}
] | 2016-09-28 | [
[
"Zaslavskii",
"O. B.",
""
]
] | We consider collision of two particles that move in the equatorial plane near a general stationary rotating axially symmetric extremal black hole. One of particles is critical (with fine-tuned parameters) and moves in the outward direction. The second particle (usual, not fine-tuned) comes from infinity. We examine the efficiency $\eta $ of the collisional Penrose process. There are two relevant cases here: (i) a particle falling into a black hole after collision is heavy, (ii) it has a finite mass. We show that the maximum of $\eta $ in case (ii) is less or equal to that in case (i). It is argued that for superheavy particles, the bound applies to nonequatorial motion as well. As an example, we analyze collision in the Kerr-Newman background. When the bound is the same for processes (i) and (ii), $\eta =3$ for this metric. For the Kerr black hole, recent results in literature are reproduced. |
1812.05204 | Shinji Tsujikawa | Noemi Frusciante, Ryotaro Kase, Kazuya Koyama, Shinji Tsujikawa,
Daniele Vernieri | Tracker and scaling solutions in DHOST theories | 12 pages | Phys. Lett. B790 (2019) 167-175 | 10.1016/j.physletb.2019.01.009 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In quadratic-order degenerate higher-order scalar-tensor (DHOST) theories
compatible with gravitational-wave constraints, we derive the most general
Lagrangian allowing for tracker solutions characterized by $\dot{\phi}/H^p={\rm
constant}$, where $\dot{\phi}$ is the time derivative of a scalar field $\phi$,
$H$ is the Hubble expansion rate, and $p$ is a constant. While the tracker is
present up to the cubic-order Horndeski Lagrangian $L=c_2X-c_3X^{(p-1)/(2p)}
\square \phi$, where $c_2, c_3$ are constants and $X$ is the kinetic energy of
$\phi$, the DHOST interaction breaks this structure for $p \neq 1$. Even in the
latter case, however, there exists an approximate tracker solution in the early
cosmological epoch with the nearly constant field equation of state
$w_{\phi}=-1-2p\dot{H}/(3H^2)$. The scaling solution, which corresponds to
$p=1$, is the unique case in which all the terms in the field density
$\rho_{\phi}$ and the pressure $P_{\phi}$ obey the scaling relation
$\rho_{\phi} \propto P_{\phi} \propto H^2$. Extending the analysis to the
coupled DHOST theories with the field-dependent coupling $Q(\phi)$ between the
scalar field and matter, we show that the scaling solution exists for
$Q(\phi)=1/(\mu_1 \phi+\mu_2)$, where $\mu_1$ and $\mu_2$ are constants. For
the constant $Q$, i.e., $\mu_1=0$, we derive fixed points of the dynamical
system by using the general Lagrangian with scaling solutions. This result can
be applied to the model construction of late-time cosmic acceleration preceded
by the scaling $\phi$-matter-dominated epoch.
| [
{
"created": "Thu, 13 Dec 2018 00:07:14 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Jan 2019 13:00:47 GMT",
"version": "v2"
}
] | 2019-01-30 | [
[
"Frusciante",
"Noemi",
""
],
[
"Kase",
"Ryotaro",
""
],
[
"Koyama",
"Kazuya",
""
],
[
"Tsujikawa",
"Shinji",
""
],
[
"Vernieri",
"Daniele",
""
]
] | In quadratic-order degenerate higher-order scalar-tensor (DHOST) theories compatible with gravitational-wave constraints, we derive the most general Lagrangian allowing for tracker solutions characterized by $\dot{\phi}/H^p={\rm constant}$, where $\dot{\phi}$ is the time derivative of a scalar field $\phi$, $H$ is the Hubble expansion rate, and $p$ is a constant. While the tracker is present up to the cubic-order Horndeski Lagrangian $L=c_2X-c_3X^{(p-1)/(2p)} \square \phi$, where $c_2, c_3$ are constants and $X$ is the kinetic energy of $\phi$, the DHOST interaction breaks this structure for $p \neq 1$. Even in the latter case, however, there exists an approximate tracker solution in the early cosmological epoch with the nearly constant field equation of state $w_{\phi}=-1-2p\dot{H}/(3H^2)$. The scaling solution, which corresponds to $p=1$, is the unique case in which all the terms in the field density $\rho_{\phi}$ and the pressure $P_{\phi}$ obey the scaling relation $\rho_{\phi} \propto P_{\phi} \propto H^2$. Extending the analysis to the coupled DHOST theories with the field-dependent coupling $Q(\phi)$ between the scalar field and matter, we show that the scaling solution exists for $Q(\phi)=1/(\mu_1 \phi+\mu_2)$, where $\mu_1$ and $\mu_2$ are constants. For the constant $Q$, i.e., $\mu_1=0$, we derive fixed points of the dynamical system by using the general Lagrangian with scaling solutions. This result can be applied to the model construction of late-time cosmic acceleration preceded by the scaling $\phi$-matter-dominated epoch. |
2102.13427 | Takahisa Igata | Takahisa Igata, Kazunori Kohri, Kota Ogasawara | Photon emission from inside the innermost stable circular orbit | 21 pages, 9 figures; v2: published version | Phys. Rev. D 103, 104028 (2021) | 10.1103/PhysRevD.103.104028 | KEK-Cosmo-0273, KEK-TH-2305, KUNS-2858 | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a situation where a light source orbiting the innermost stable
circular orbit (ISCO) of the Kerr black hole is gently falling from the
marginally stable orbit due to an infinitesimal perturbation. Assuming that the
light source emits photons isotropically, we show that the last radius at which
more than 50\% of emitted photons can escape to infinity is approximately
halfway between the ISCO radius and the event horizon radius. To evaluate them,
we determine emitter orbits from the vicinity of the ISCO, which are uniquely
specified for each black hole spin, and identify the conditions for a photon to
escape from any point on the equatorial plane of the Kerr spacetime to infinity
by specifying regions in the two-dimensional photon impact parameter space
completely. We further show that the proper motion of the emitter affects the
photon escape probability and blueshifts the energy of emitted photons.
| [
{
"created": "Fri, 26 Feb 2021 12:29:04 GMT",
"version": "v1"
},
{
"created": "Tue, 18 May 2021 03:12:17 GMT",
"version": "v2"
}
] | 2021-05-19 | [
[
"Igata",
"Takahisa",
""
],
[
"Kohri",
"Kazunori",
""
],
[
"Ogasawara",
"Kota",
""
]
] | We consider a situation where a light source orbiting the innermost stable circular orbit (ISCO) of the Kerr black hole is gently falling from the marginally stable orbit due to an infinitesimal perturbation. Assuming that the light source emits photons isotropically, we show that the last radius at which more than 50\% of emitted photons can escape to infinity is approximately halfway between the ISCO radius and the event horizon radius. To evaluate them, we determine emitter orbits from the vicinity of the ISCO, which are uniquely specified for each black hole spin, and identify the conditions for a photon to escape from any point on the equatorial plane of the Kerr spacetime to infinity by specifying regions in the two-dimensional photon impact parameter space completely. We further show that the proper motion of the emitter affects the photon escape probability and blueshifts the energy of emitted photons. |
2010.10847 | Vinod Bhardwaj Dr. | Archana Dixit, Vinod Kumar Bhardwaj, Anirudh Pradhan | RHDE models in FRW Universe with two IR cut-offs with redshift
parametrization | 13 pages, 11 figures, 2 tables | The European Physical Journal Plus, Vol. 135, Issue 10, October
(2020) Article No. 831 (13 pages) | 10.1140/epjp/s13360-020-00850-6 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this manuscript, we have researched the cosmic expansion phenomenon in
flat FRW Universe through the interaction of the recently proposed
R$\grave{e}$nyi holographic dark energy (RHDE). For this reason, we assumed
Hubble (H) and Granda--Oliveros (GO) horizons as IR cut-off in the framework of
$f(R, T)$ gravity. With this choice for IR cut-off, we can obtain some
important cosmological quantities such as the equation of state $\omega_{_T}$,
energy density $\rho_{_T}$, density parameter $\Omega_{_T}$, and pressure
$p_{_T}$, which are the function of the redshift $z$. It is observed that in
both IR cut-offs the EoS parameter displays quintom-like behaviour for three
different values of $\delta$. Here we plot these parameters versus redshift $z$
and discuss the consistency of the recent findings. Next, we explore the
$\omega_{_T}$-$\omega_{_T}^{'}$ plane and the stability analysis of the dark
energy model by a perturbation method. Our findings demonstrate that the
Universe is an accelerating model of rapid growth that is explained by quintom
like behaviour.Hence the feasibility of the RHDE model with Hubble and GO
cut-off is supported by our model. The results indicate that the IR cut-offs
play a significant role in the understanding of the dynamics of the universe.
| [
{
"created": "Wed, 21 Oct 2020 09:13:29 GMT",
"version": "v1"
}
] | 2021-08-02 | [
[
"Dixit",
"Archana",
""
],
[
"Bhardwaj",
"Vinod Kumar",
""
],
[
"Pradhan",
"Anirudh",
""
]
] | In this manuscript, we have researched the cosmic expansion phenomenon in flat FRW Universe through the interaction of the recently proposed R$\grave{e}$nyi holographic dark energy (RHDE). For this reason, we assumed Hubble (H) and Granda--Oliveros (GO) horizons as IR cut-off in the framework of $f(R, T)$ gravity. With this choice for IR cut-off, we can obtain some important cosmological quantities such as the equation of state $\omega_{_T}$, energy density $\rho_{_T}$, density parameter $\Omega_{_T}$, and pressure $p_{_T}$, which are the function of the redshift $z$. It is observed that in both IR cut-offs the EoS parameter displays quintom-like behaviour for three different values of $\delta$. Here we plot these parameters versus redshift $z$ and discuss the consistency of the recent findings. Next, we explore the $\omega_{_T}$-$\omega_{_T}^{'}$ plane and the stability analysis of the dark energy model by a perturbation method. Our findings demonstrate that the Universe is an accelerating model of rapid growth that is explained by quintom like behaviour.Hence the feasibility of the RHDE model with Hubble and GO cut-off is supported by our model. The results indicate that the IR cut-offs play a significant role in the understanding of the dynamics of the universe. |
1002.4115 | Jiri Podolsky | J. B. Griffiths, J. Podolsky | The Linet-Tian solution with a positive cosmological constant in four
and higher dimensions | 6 pages, 1 figure. To appear in Phys. Rev. D | Phys.Rev.D81:064015,2010 | 10.1103/PhysRevD.81.064015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The static, apparently cylindrically symmetric vacuum solution of Linet and
Tian for the case of a positive cosmological constant $\Lambda$ is shown to
have toroidal symmetry and, besides $\Lambda$, to include three arbitrary
parameters. It possesses two curvature singularities, of which one can be
removed by matching it across a toroidal surface to a corresponding region of
the dust-filled Einstein static universe. In four dimensions, this clarifies
the geometrical properties, the coordinate ranges and the meaning of the
parameters in this solution. Some other properties and limiting cases of this
space-time are described. Its generalisation to any higher number of dimensions
is also explicitly given.
| [
{
"created": "Mon, 22 Feb 2010 13:47:23 GMT",
"version": "v1"
}
] | 2010-12-23 | [
[
"Griffiths",
"J. B.",
""
],
[
"Podolsky",
"J.",
""
]
] | The static, apparently cylindrically symmetric vacuum solution of Linet and Tian for the case of a positive cosmological constant $\Lambda$ is shown to have toroidal symmetry and, besides $\Lambda$, to include three arbitrary parameters. It possesses two curvature singularities, of which one can be removed by matching it across a toroidal surface to a corresponding region of the dust-filled Einstein static universe. In four dimensions, this clarifies the geometrical properties, the coordinate ranges and the meaning of the parameters in this solution. Some other properties and limiting cases of this space-time are described. Its generalisation to any higher number of dimensions is also explicitly given. |
2211.09497 | Mokhtar Adda-Bedia | Mokhtar Adda-Bedia and Eytan Katzav | Kaluza-Klein Dimensional Reduction From Elasticity Theory of Crumpled
Paper | null | null | null | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | During the last century, two independent theories using the concept of
dimensional reduction have been developed independently. The first, known as
F\"oppl-von K\`arm\`an theory, uses Riemannian geometry and continuum mechanics
to study the shaping of thin elastic structures which could become as complex
as crumpled paper. The second one, known as Kaluza-Klein theory, uses
Minkowskian geometry and general relativity to unify fundamental interactions
and gravity under the same formalism. Here we draw a parallel between these two
theories in an attempt to use concepts from elasticity theory of plates to
recover the Einstein-Maxwell equations. We argue that Kaluza-Klein theory
belongs to the same conceptual group of theories as three-dimensional
elasticity, which upon dimensional reduction leads to the F\"oppl-von
K\`arm\`an theory of two-dimensional elastic plates. We exploit this analogy to
develop an alternative Kaluza-Klein formalism in the framework of elasticity
theory in which the gravitational and electromagnetic fields are respectively
associated with stretching-like and bending-like deformations. We show that our
approach of dimensional reduction allows us to retrieve the Lagrangian
densities of both gravitational, electromagnetic and Dirac spinors fields as
well as the Lagrangian densities of mass and charge sources.
| [
{
"created": "Thu, 17 Nov 2022 12:42:09 GMT",
"version": "v1"
}
] | 2022-11-18 | [
[
"Adda-Bedia",
"Mokhtar",
""
],
[
"Katzav",
"Eytan",
""
]
] | During the last century, two independent theories using the concept of dimensional reduction have been developed independently. The first, known as F\"oppl-von K\`arm\`an theory, uses Riemannian geometry and continuum mechanics to study the shaping of thin elastic structures which could become as complex as crumpled paper. The second one, known as Kaluza-Klein theory, uses Minkowskian geometry and general relativity to unify fundamental interactions and gravity under the same formalism. Here we draw a parallel between these two theories in an attempt to use concepts from elasticity theory of plates to recover the Einstein-Maxwell equations. We argue that Kaluza-Klein theory belongs to the same conceptual group of theories as three-dimensional elasticity, which upon dimensional reduction leads to the F\"oppl-von K\`arm\`an theory of two-dimensional elastic plates. We exploit this analogy to develop an alternative Kaluza-Klein formalism in the framework of elasticity theory in which the gravitational and electromagnetic fields are respectively associated with stretching-like and bending-like deformations. We show that our approach of dimensional reduction allows us to retrieve the Lagrangian densities of both gravitational, electromagnetic and Dirac spinors fields as well as the Lagrangian densities of mass and charge sources. |
gr-qc/9807039 | Ali Nayeri | Ali Nayeri and T. Padmanabhan (IUCAA) | A possible Newtonian interpretation of relativistic cosmological
perturbation theory | 7 pages, 2 postscript figures, title was corrected | null | null | IUCAA-25/98 | gr-qc astro-ph | null | Cosmological perturbations with wavelengths smaller than Hubble radius can be
handled in the context of Newtonian theory with very high accuracy. The
application of this Newtonian approximation, however, is restricted to
nonrelativistic matter and cannot be used for relativistic matter. Recently, by
modifying the continuity equation, Lima, et. al., extended the domain of
applicability of Newtonian cosmology to radiation dominated phase. We adopted
this continuity equation to re-examine linear cosmological perturbation theory
for a two fluid universe with uniform pressure. We study the evolution
equations for density contrasts and their validity in different epochs and on
scales larger than Hubble radius and compare the results with the full
relativistic approach. The comparison shows the high accuracy of this
approximation.
| [
{
"created": "Thu, 16 Jul 1998 10:06:03 GMT",
"version": "v1"
},
{
"created": "Sat, 18 Jul 1998 05:54:56 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Nayeri",
"Ali",
"",
"IUCAA"
],
[
"Padmanabhan",
"T.",
"",
"IUCAA"
]
] | Cosmological perturbations with wavelengths smaller than Hubble radius can be handled in the context of Newtonian theory with very high accuracy. The application of this Newtonian approximation, however, is restricted to nonrelativistic matter and cannot be used for relativistic matter. Recently, by modifying the continuity equation, Lima, et. al., extended the domain of applicability of Newtonian cosmology to radiation dominated phase. We adopted this continuity equation to re-examine linear cosmological perturbation theory for a two fluid universe with uniform pressure. We study the evolution equations for density contrasts and their validity in different epochs and on scales larger than Hubble radius and compare the results with the full relativistic approach. The comparison shows the high accuracy of this approximation. |
1303.1256 | Subir Ghosh | Subir Ghosh (Indian Statistical Institute) | Quantum Gravity Effects in Geodesic Motion and Predictions of
Equivalence Principle Violation | Title changed, Universality of Free Fall expt. added, references
added, modified version, to appear in CQG | null | 10.1088/0264-9381/31/2/025025 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the Equivalence Principle (EP) is violated by Quantum Gravity
(QG) effects. The predicted violations are compared to experimental
observations for Gravitational Redshift, Law of Reciprocal Action and
Universality of Free Fall. This allows us to derive explicit bounds for
$\beta$ - the QG scale.
In our approach, there appears a deviation in the geodesic motion of a
particle. This deviation is induced by a non-commutative spacetime, consistent
with a Generalized Uncertainty Principle (GUP). GUP admits the presence of a
minimum length scale, that is advocated by QG theories. Remarkably, the GUP
induced corrections are quite robust since the bound on $\beta$ obtained by us,
{\it{in General Relativity scenario in an essentially classical setting}} of
modified geodesic motion, is closely comparable to similar bounds in recent
literature \cite{vag}. The latter are computed in purely {\it{quantum}} physics
domain in {\it{flat}} spacetime.
| [
{
"created": "Wed, 6 Mar 2013 06:29:40 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Mar 2013 12:01:06 GMT",
"version": "v2"
},
{
"created": "Tue, 26 Nov 2013 19:15:19 GMT",
"version": "v3"
}
] | 2015-06-15 | [
[
"Ghosh",
"Subir",
"",
"Indian Statistical Institute"
]
] | We show that the Equivalence Principle (EP) is violated by Quantum Gravity (QG) effects. The predicted violations are compared to experimental observations for Gravitational Redshift, Law of Reciprocal Action and Universality of Free Fall. This allows us to derive explicit bounds for $\beta$ - the QG scale. In our approach, there appears a deviation in the geodesic motion of a particle. This deviation is induced by a non-commutative spacetime, consistent with a Generalized Uncertainty Principle (GUP). GUP admits the presence of a minimum length scale, that is advocated by QG theories. Remarkably, the GUP induced corrections are quite robust since the bound on $\beta$ obtained by us, {\it{in General Relativity scenario in an essentially classical setting}} of modified geodesic motion, is closely comparable to similar bounds in recent literature \cite{vag}. The latter are computed in purely {\it{quantum}} physics domain in {\it{flat}} spacetime. |
1006.3927 | Xiang-Song Chen | Xiang-Song Chen and Ben-Chao Zhu | The true radiation gauge for gravity | 11 pages, no figure; significant revision, showing how the TT gauge
can be adapted in the presence of source | Phys.Rev.D83:061501,2011 | 10.1103/PhysRevD.83.061501 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Corresponding to the similarity between the Lorentz gauge $\partial_\mu
A^\mu=0$ in electrodynamics and $g^{\mu\nu}\Gamma^\rho_{\mu\nu}=0$ in gravity,
we show that the counterpart of the radiation gauge $\partial_iA^i=0$ is
$g^{ij}\Gamma^\rho_{ij}=0$, in stead of other forms as discussed before.
Particularly: 1) at least for a weak field, $g^{ij}\Gamma^\rho_{ij}=0$ fixes
the gauge completely and picks out exactly the two physical components of the
gravitational field; 2) like $A^0$, the non-dynamical components $h_{0\mu}$ are
solved instantaneously; 3) gravitational radiation is generated by the
"transverse" part of the energy-momentum tensor, similar to the transverse
current $\vec J_\perp$. This true" radiation gauge $g^{ij}\Gamma^\rho_{ij}=0$
is especially pertinent for studying gravitational energy, such as the energy
flow in gravitational radiation. It agrees with the transverse-traceless (TT)
gauge for a pure wave, and reveals remarkably how the TT gauge can be adapted
in the presence of source.
| [
{
"created": "Sun, 20 Jun 2010 11:22:44 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Jun 2010 07:58:42 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Jan 2011 15:06:14 GMT",
"version": "v3"
}
] | 2011-03-21 | [
[
"Chen",
"Xiang-Song",
""
],
[
"Zhu",
"Ben-Chao",
""
]
] | Corresponding to the similarity between the Lorentz gauge $\partial_\mu A^\mu=0$ in electrodynamics and $g^{\mu\nu}\Gamma^\rho_{\mu\nu}=0$ in gravity, we show that the counterpart of the radiation gauge $\partial_iA^i=0$ is $g^{ij}\Gamma^\rho_{ij}=0$, in stead of other forms as discussed before. Particularly: 1) at least for a weak field, $g^{ij}\Gamma^\rho_{ij}=0$ fixes the gauge completely and picks out exactly the two physical components of the gravitational field; 2) like $A^0$, the non-dynamical components $h_{0\mu}$ are solved instantaneously; 3) gravitational radiation is generated by the "transverse" part of the energy-momentum tensor, similar to the transverse current $\vec J_\perp$. This true" radiation gauge $g^{ij}\Gamma^\rho_{ij}=0$ is especially pertinent for studying gravitational energy, such as the energy flow in gravitational radiation. It agrees with the transverse-traceless (TT) gauge for a pure wave, and reveals remarkably how the TT gauge can be adapted in the presence of source. |
2007.13600 | Fabio Duvan Lora Clavijo Mr. | J. A. Arrieta-Villamizar, J. M. Vel\'asquez-Cadavid, O. M. Pimentel,
F. D. Lora-Clavijo, A. C. Guti\'errez-Pi\~neres | Shadows around the q-metric | Pages 20, 32 figures. Accepted for publication in Classical and
Quantum Gravity (CQG) | null | 10.1088/1361-6382/abc223 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One crucial problem in relativistic astrophysics is that of the nature of
black hole candidates. It is usually assumed that astrophysical black holes are
described by the Schwarzschild or Kerr space-times; however, there is no direct
evidence to assert this. Moreover, there are various solutions in general
relativity that can be alternatives to black holes, usually called black hole
mimickers. In this work, we study the shadow produced by a compact object
described by the q-metric, which is the simplest static and axially symmetric
solution of Einstein equations with a non-vanishing quadrupole moment. This
particular spacetime has the property of containing an independent parameter
$q$, which is related to the compact object deformation. The solution
corresponds to naked singularities for some specific values of this parameter.
Additionally, we analyze the eigenvalues of the Riemann tensor using the
$SO(3,C)$ representation, which allows us to find, in an invariant way, regions
where there may be repulsive effects. Furthermore, we numerically solve the
motion equations to show the shadow, the Einstein ring, and the gravitational
lensing to establish a possible signature of such repulsive effects. We found
that as $q$ is smaller, the Einstein ring decreases, but the shape is the same
as the Schwarzschild black hole case. However, for values of $q$ lower or equal
than $-0.5$, repulsive gravitational effects appear in the gravitational
lensing close to the compact object, where a strong dependence of the system to
the initial conditions seems to take place.
| [
{
"created": "Mon, 27 Jul 2020 14:33:24 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Nov 2020 20:48:04 GMT",
"version": "v2"
}
] | 2020-11-05 | [
[
"Arrieta-Villamizar",
"J. A.",
""
],
[
"Velásquez-Cadavid",
"J. M.",
""
],
[
"Pimentel",
"O. M.",
""
],
[
"Lora-Clavijo",
"F. D.",
""
],
[
"Gutiérrez-Piñeres",
"A. C.",
""
]
] | One crucial problem in relativistic astrophysics is that of the nature of black hole candidates. It is usually assumed that astrophysical black holes are described by the Schwarzschild or Kerr space-times; however, there is no direct evidence to assert this. Moreover, there are various solutions in general relativity that can be alternatives to black holes, usually called black hole mimickers. In this work, we study the shadow produced by a compact object described by the q-metric, which is the simplest static and axially symmetric solution of Einstein equations with a non-vanishing quadrupole moment. This particular spacetime has the property of containing an independent parameter $q$, which is related to the compact object deformation. The solution corresponds to naked singularities for some specific values of this parameter. Additionally, we analyze the eigenvalues of the Riemann tensor using the $SO(3,C)$ representation, which allows us to find, in an invariant way, regions where there may be repulsive effects. Furthermore, we numerically solve the motion equations to show the shadow, the Einstein ring, and the gravitational lensing to establish a possible signature of such repulsive effects. We found that as $q$ is smaller, the Einstein ring decreases, but the shape is the same as the Schwarzschild black hole case. However, for values of $q$ lower or equal than $-0.5$, repulsive gravitational effects appear in the gravitational lensing close to the compact object, where a strong dependence of the system to the initial conditions seems to take place. |
1206.6736 | Thomas Cailleteau Mr | Thomas Cailleteau, Aurelien Barrau, Julien Grain and Francesca Vidotto | Consistency of holonomy-corrected scalar, vector and tensor
perturbations in Loop Quantum Cosmology | 5 pages | Phys. Rev. D 86, 087301 (2012) | 10.1103/PhysRevD.86.087301 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Loop Quantum Cosmology yields two kinds of quantum corrections to the
effective equations of motion for cosmological perturbations. Here we focus on
the holonomy kind and we study the problem of the closure of the resulting
algebra of constraints. Up to now, tensor, vector and scalar perturbations were
studied independently, leading to different algebras of constraints. The
structures of the related algebras were imposed by the requirement of anomaly
freedom. In this article we show that the algebra can be modified by a very
simple quantum correction, holding for all types of perturbations. This
demonstrates the consistency of the theory and shows that lessons from the
study of scalar perturbations should be taken into account when studying tensor
modes. The Mukhanov-Sasaki equations of motion are similarly modified by a
simple term.
| [
{
"created": "Thu, 28 Jun 2012 15:46:14 GMT",
"version": "v1"
}
] | 2012-11-01 | [
[
"Cailleteau",
"Thomas",
""
],
[
"Barrau",
"Aurelien",
""
],
[
"Grain",
"Julien",
""
],
[
"Vidotto",
"Francesca",
""
]
] | Loop Quantum Cosmology yields two kinds of quantum corrections to the effective equations of motion for cosmological perturbations. Here we focus on the holonomy kind and we study the problem of the closure of the resulting algebra of constraints. Up to now, tensor, vector and scalar perturbations were studied independently, leading to different algebras of constraints. The structures of the related algebras were imposed by the requirement of anomaly freedom. In this article we show that the algebra can be modified by a very simple quantum correction, holding for all types of perturbations. This demonstrates the consistency of the theory and shows that lessons from the study of scalar perturbations should be taken into account when studying tensor modes. The Mukhanov-Sasaki equations of motion are similarly modified by a simple term. |
gr-qc/0105004 | Pal G. Molnar | Pal G. Molnar | Electrostatic boundary value problems in the Schwarzschild background | 18 pages, no figures, uses iopart.sty | Class.Quant.Grav.18:1853-1869,2001 | 10.1088/0264-9381/18/10/304 | null | gr-qc astro-ph | null | The electrostatic potential of any test charge distribution in Schwarzschild
space with boundary values is derived. We calculate the Green's function,
generalize the second Green's identity for p-forms and find the general
solution. Boundary value problems are solved. With a multipole expansion the
asymptotic property for the field of any charge distribution is derived. It is
shown that one produces a Reissner--Nordstrom black hole if one lowers a test
charge distribution slowly toward the horizon. The symmetry of the distribution
is not important. All the multipole moments fade away except the monopole. A
calculation of the gravitationally induced electrostatic self-force on a
pointlike test charge distribution held stationary outside the black hole is
presented.
| [
{
"created": "Wed, 2 May 2001 11:01:55 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Molnar",
"Pal G.",
""
]
] | The electrostatic potential of any test charge distribution in Schwarzschild space with boundary values is derived. We calculate the Green's function, generalize the second Green's identity for p-forms and find the general solution. Boundary value problems are solved. With a multipole expansion the asymptotic property for the field of any charge distribution is derived. It is shown that one produces a Reissner--Nordstrom black hole if one lowers a test charge distribution slowly toward the horizon. The symmetry of the distribution is not important. All the multipole moments fade away except the monopole. A calculation of the gravitationally induced electrostatic self-force on a pointlike test charge distribution held stationary outside the black hole is presented. |
gr-qc/0402050 | Miguel Lorente | M. Lorente, P. Kramer | Tensor and spin representations of SO(4) and discrete quantum gravity | LaTeX, 18 pages, 1 eps figure. Communication presented to the
International Symposium Symmetries in Science XIII, July 2003, Bregenz. To be
published by Kluwer | null | 10.1007/1-4020-2634-X_18 | null | gr-qc | null | Starting from the defining transformations of complex matrices for the SO(4)
group, we construct the fundamental representation and the tensor and spinor
representations of the group SO(4). Given the commutation relations for the
corresponding algebra, the unitary representations of the group in terms of the
generalized Euler angles are constructed. These mathematical results help us to
a more complete description of the Barrett-Crane model in Quantum Gravity. In
particular a complete realization of the weight function for the partition
function is given and a new geometrical itnerpretation of the asymptotic limit
for the Regge action is presented.
| [
{
"created": "Wed, 11 Feb 2004 10:17:50 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Feb 2004 10:32:52 GMT",
"version": "v2"
},
{
"created": "Tue, 24 Feb 2004 18:31:36 GMT",
"version": "v3"
},
{
"created": "Wed, 25 Feb 2004 10:30:15 GMT",
"version": "v4"
}
] | 2015-06-25 | [
[
"Lorente",
"M.",
""
],
[
"Kramer",
"P.",
""
]
] | Starting from the defining transformations of complex matrices for the SO(4) group, we construct the fundamental representation and the tensor and spinor representations of the group SO(4). Given the commutation relations for the corresponding algebra, the unitary representations of the group in terms of the generalized Euler angles are constructed. These mathematical results help us to a more complete description of the Barrett-Crane model in Quantum Gravity. In particular a complete realization of the weight function for the partition function is given and a new geometrical itnerpretation of the asymptotic limit for the Regge action is presented. |
2401.09907 | Liang-Bi Wu | Li-Ming Cao, Jia-Ning Chen, Liang-Bi Wu, Libo Xie and Yu-Sen Zhou | The pseudospectrum and spectrum (in)stability of quantum corrected
Schwarzschild black hole | 23 pages, 10 figures. This manuscript has been accepted for
publication as a regular article in SCPMA | null | null | ICTS-USTC/PCFT-24-03 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this study, we investigate the pseudospectrum and spectrum (in)stability
of quantum corrected Schwarzschild black hole. Methodologically, we use the
hyperboloidal framework to cast the quasinormal mode (QNM) problem into an
eigenvalue problem associated with a non-selfadjoint operator, and then the
spectrum and pseudospectrum are depicted. Besides, the invariant subspace
method is exploited to improve the computational efficiency for pseudospectrum.
The investigation into the spectrum (in)stability entails two main aspects. On
the one hand, we calculate the spectra of the quantum corrected black hole,
then by the means of the migration ratio, the impact of the quantum correction
effect on the Schwarzschild black hole has been studied. The results indicate
that the so-called ``migration ratio instability" will occur for small black
holes with small angular momentum number l. In the eikonal limit, the migration
ratios remain the same for each overtone. On the other hand, we study the
spectrum (in)stability of the quantum corrected black hole by directly adding
some particular perturbations into the effective potential, where perturbations
are located at the event horizon and null infinity, respectively. There are two
interesting observations under the same perturbation energy norm. First,
perturbations at infinity are more capable of generating spectrum instability
than those at the event horizon. Second, we find that the peak distribution can
lead to the instability of QNM spectrum more efficiently than the average
distribution.
| [
{
"created": "Thu, 18 Jan 2024 11:41:40 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Jan 2024 10:48:08 GMT",
"version": "v2"
},
{
"created": "Thu, 13 Jun 2024 05:26:54 GMT",
"version": "v3"
}
] | 2024-06-14 | [
[
"Cao",
"Li-Ming",
""
],
[
"Chen",
"Jia-Ning",
""
],
[
"Wu",
"Liang-Bi",
""
],
[
"Xie",
"Libo",
""
],
[
"Zhou",
"Yu-Sen",
""
]
] | In this study, we investigate the pseudospectrum and spectrum (in)stability of quantum corrected Schwarzschild black hole. Methodologically, we use the hyperboloidal framework to cast the quasinormal mode (QNM) problem into an eigenvalue problem associated with a non-selfadjoint operator, and then the spectrum and pseudospectrum are depicted. Besides, the invariant subspace method is exploited to improve the computational efficiency for pseudospectrum. The investigation into the spectrum (in)stability entails two main aspects. On the one hand, we calculate the spectra of the quantum corrected black hole, then by the means of the migration ratio, the impact of the quantum correction effect on the Schwarzschild black hole has been studied. The results indicate that the so-called ``migration ratio instability" will occur for small black holes with small angular momentum number l. In the eikonal limit, the migration ratios remain the same for each overtone. On the other hand, we study the spectrum (in)stability of the quantum corrected black hole by directly adding some particular perturbations into the effective potential, where perturbations are located at the event horizon and null infinity, respectively. There are two interesting observations under the same perturbation energy norm. First, perturbations at infinity are more capable of generating spectrum instability than those at the event horizon. Second, we find that the peak distribution can lead to the instability of QNM spectrum more efficiently than the average distribution. |
gr-qc/0206052 | Charles Hellaby | Charles Hellaby and Andrzej Krasinski | You Can't Get Through Szekeres Wormholes - or - Regularity, Topology and
Causality in Quasi-Spherical Szekeres Models | zip file with LaTeX text + 6 figures (.eps & .ps). 47 pages. Second
replacement corrects some minor errors and typos. (First replacement prints
better on US letter size paper.) | Phys.Rev.D66:084011,2002 | 10.1103/PhysRevD.66.084011 | UCT-cosmology0201 | gr-qc | null | The spherically symmetric dust model of Lemaitre-Tolman can describe
wormholes, but the causal communication between the two asymptotic regions
through the neck is even less than in the vacuum
(Schwarzschild-Kruskal-Szekeres) case. We investigate the anisotropic
generalisation of the wormhole topology in the Szekeres model. The function
E(r, p, q) describes the deviation from spherical symmetry if \partial_r E \neq
0, but this requires the mass to be increasing with radius, \partial_r M > 0,
i.e. non-zero density. We investigate the geometrical relations between the
mass dipole and the locii of apparent horizon and of shell-crossings. We
present the various conditions that ensure physically reasonable
quasi-spherical models, including a regular origin, regular maxima and minima
in the spatial sections, and the absence of shell-crossings. We show that
physically reasonable values of \partial_r E \neq 0 cannot compensate for the
effects of \partial_r M > 0 in any direction, so that communication through the
neck is still worse than the vacuum.
We also show that a handle topology cannot be created by identifying
hypersufaces in the two asymptotic regions on either side of a wormhole, unless
a surface layer is allowed at the junction. This impossibility includes the
Schwarzschild-Kruskal-Szekeres case.
| [
{
"created": "Tue, 18 Jun 2002 13:27:29 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Jun 2002 15:41:44 GMT",
"version": "v2"
},
{
"created": "Thu, 20 Jun 2002 15:52:13 GMT",
"version": "v3"
},
{
"created": "Tue, 27 Aug 2002 14:52:31 GMT",
"version": "v4"
}
] | 2016-08-31 | [
[
"Hellaby",
"Charles",
""
],
[
"Krasinski",
"Andrzej",
""
]
] | The spherically symmetric dust model of Lemaitre-Tolman can describe wormholes, but the causal communication between the two asymptotic regions through the neck is even less than in the vacuum (Schwarzschild-Kruskal-Szekeres) case. We investigate the anisotropic generalisation of the wormhole topology in the Szekeres model. The function E(r, p, q) describes the deviation from spherical symmetry if \partial_r E \neq 0, but this requires the mass to be increasing with radius, \partial_r M > 0, i.e. non-zero density. We investigate the geometrical relations between the mass dipole and the locii of apparent horizon and of shell-crossings. We present the various conditions that ensure physically reasonable quasi-spherical models, including a regular origin, regular maxima and minima in the spatial sections, and the absence of shell-crossings. We show that physically reasonable values of \partial_r E \neq 0 cannot compensate for the effects of \partial_r M > 0 in any direction, so that communication through the neck is still worse than the vacuum. We also show that a handle topology cannot be created by identifying hypersufaces in the two asymptotic regions on either side of a wormhole, unless a surface layer is allowed at the junction. This impossibility includes the Schwarzschild-Kruskal-Szekeres case. |
2112.00497 | Andronikos Paliathanasis | Andronikos Paliathanasis | Dynamical analysis and cosmological evolution in Weyl integrable gravity | 17 pages, no figures | Universe 2021, 7(12), 468 | 10.3390/universe7120468 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate the cosmological evolution for the physical parameters in Weyl
integrable gravity in a Friedmann--Lema\^{\i}tre--Robertson--Walker universe
with zero spatially curvature. For the matter component, we assume that it is
an ideal gas, and of the Chaplygin gas. From the Weyl integrable gravity a
scalar field is introduced by a geometric approach which provides an
interaction with the matter component. We calculate the stationary points for
the field equations and we study their stability properties. Furthermore, we
solve the inverse problem for the case of an ideal gas and prove that the
gravitational field equations can follow from the variation of a Lagrangian
function. Finally, variational symmetries are applied for the construction of
analytic and exact solutions.
| [
{
"created": "Wed, 1 Dec 2021 13:48:07 GMT",
"version": "v1"
}
] | 2021-12-02 | [
[
"Paliathanasis",
"Andronikos",
""
]
] | We investigate the cosmological evolution for the physical parameters in Weyl integrable gravity in a Friedmann--Lema\^{\i}tre--Robertson--Walker universe with zero spatially curvature. For the matter component, we assume that it is an ideal gas, and of the Chaplygin gas. From the Weyl integrable gravity a scalar field is introduced by a geometric approach which provides an interaction with the matter component. We calculate the stationary points for the field equations and we study their stability properties. Furthermore, we solve the inverse problem for the case of an ideal gas and prove that the gravitational field equations can follow from the variation of a Lagrangian function. Finally, variational symmetries are applied for the construction of analytic and exact solutions. |
gr-qc/9906007 | Jose Socorro Garcia Diaz | Alfredo Mac\'ias and Jos\'e Socorro | Generalized Reissner-Nordstr\"om solution in Metric-Affine Gravity | 13 pages, Revtex, to appear in Class. Quantum Grav | Class.Quant.Grav. 16 (1999) 2323-2333 | 10.1088/0264-9381/16/7/312 | IFUG-99-10 | gr-qc | null | We present the generalized Reissner-Nordstr\"om solution of the field
equations of metric-affine gravity (MAG), endowed with electric and magnetic
charges, as well as with gravito-electric and gravito-magnetic charges and a
cosmological constant term. Moreover, the case $M=e_o$, i.e. mass equal to
electric charge and $\lambda=0$, corresponds to an electrically and
magnetically charged monopole. Also further multipole solutions are obtained.
The charge assignments of the solutions is discussed.
| [
{
"created": "Wed, 2 Jun 1999 14:26:13 GMT",
"version": "v1"
}
] | 2016-08-15 | [
[
"Macías",
"Alfredo",
""
],
[
"Socorro",
"José",
""
]
] | We present the generalized Reissner-Nordstr\"om solution of the field equations of metric-affine gravity (MAG), endowed with electric and magnetic charges, as well as with gravito-electric and gravito-magnetic charges and a cosmological constant term. Moreover, the case $M=e_o$, i.e. mass equal to electric charge and $\lambda=0$, corresponds to an electrically and magnetically charged monopole. Also further multipole solutions are obtained. The charge assignments of the solutions is discussed. |
0810.1714 | Carlo Rovelli | Claudio Perini, Carlo Rovelli, Simone Speziale | Self-energy and vertex radiative corrections in LQG | 11 pages, 3 figures | Phys.Lett.B682:78-84,2009 | 10.1016/j.physletb.2009.10.076 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the elementary radiative-correction terms in loop quantum
gravity. These are a two-vertex "elementary bubble" and a five-vertex "ball";
they correspond to the one-loop self-energy and the one-loop vertex correction
of ordinary quantum field theory. We compute their naive degree of (infrared)
divergence.
| [
{
"created": "Thu, 9 Oct 2008 18:32:50 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Oct 2008 07:51:25 GMT",
"version": "v2"
}
] | 2009-11-18 | [
[
"Perini",
"Claudio",
""
],
[
"Rovelli",
"Carlo",
""
],
[
"Speziale",
"Simone",
""
]
] | We consider the elementary radiative-correction terms in loop quantum gravity. These are a two-vertex "elementary bubble" and a five-vertex "ball"; they correspond to the one-loop self-energy and the one-loop vertex correction of ordinary quantum field theory. We compute their naive degree of (infrared) divergence. |
1108.4110 | Sunil Maharaj | K. Komathiraj, S. D. Maharaj | A class of charged relativistic spheres | 11 pages, To appear in Mathematical and Computational Applications | Mathematical and Computational Applications 15: 665-673, 2010 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find a new class of exact solutions to the Einstein-Maxwell equations
which can be used to model the interior of charged relativistic objects. These
solutions can be written in terms of special functions in general; for
particular parameter values it is possible to find solutions in terms of
elementary functions. Our results contain models found previously for uncharged
neutron stars and charged isotropic spheres.
| [
{
"created": "Sat, 20 Aug 2011 11:17:46 GMT",
"version": "v1"
}
] | 2013-01-01 | [
[
"Komathiraj",
"K.",
""
],
[
"Maharaj",
"S. D.",
""
]
] | We find a new class of exact solutions to the Einstein-Maxwell equations which can be used to model the interior of charged relativistic objects. These solutions can be written in terms of special functions in general; for particular parameter values it is possible to find solutions in terms of elementary functions. Our results contain models found previously for uncharged neutron stars and charged isotropic spheres. |
gr-qc/0203079 | R. Aldrovandi | R. Aldrovandi, J. Gariel and G. Marcilhacy | On the pre-nucleosynthesis cosmological period | standard LateX, 28 pages (no figures) | null | null | IFT-P 018/2002 | gr-qc | null | Physics, as known from our local, around--earth experience, meets some of its
applicability limits at the time just preceding the period of primeval
nucleosynthesis. Attention is focussed here on the effects of the nucleon size.
Radiation--belonging nucleons are found to produce an extremely high pressure
at kT of the order of some tens or hundreds of MeV. Quark deconfinement at
higher energies would not change the results.
| [
{
"created": "Fri, 22 Mar 2002 17:16:11 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Aldrovandi",
"R.",
""
],
[
"Gariel",
"J.",
""
],
[
"Marcilhacy",
"G.",
""
]
] | Physics, as known from our local, around--earth experience, meets some of its applicability limits at the time just preceding the period of primeval nucleosynthesis. Attention is focussed here on the effects of the nucleon size. Radiation--belonging nucleons are found to produce an extremely high pressure at kT of the order of some tens or hundreds of MeV. Quark deconfinement at higher energies would not change the results. |
1808.06974 | Killian Martineau | Killian Martineau | Detailed background dynamics and trans-planckian effects in loop quantum
cosmology | 4 pages, 2 figures, Proceedings of the 15th Marcel Grossmann Meeting
- MG15, July 1-7 2018, University of Rome "La Sapienza" | null | 10.1142/9789811258251_0302 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmology appears as the most promising way to test and constrain quantum
gravity theories. Loop quantum gravity is among the most advanced attempts to
perform a non-perturbative quantization of general relativity. Its cosmological
counterpart, loop quantum cosmology, has clear predictions both for the
cosmological background and for the perturbations. In particular, the initial
Big Bang singularity is replaced by a bounce due to quantum geometry effects.
In this proceeding I will focus on new results obtained in loop quantum
cosmology: i) the prediction of the duration of inflation as a function of all
the unknown parameters of the model and ii) new primordial power spectra
obtained with modified dispersion relations accounting for trans-planckian
effects.
| [
{
"created": "Tue, 21 Aug 2018 15:46:44 GMT",
"version": "v1"
}
] | 2023-06-27 | [
[
"Martineau",
"Killian",
""
]
] | Cosmology appears as the most promising way to test and constrain quantum gravity theories. Loop quantum gravity is among the most advanced attempts to perform a non-perturbative quantization of general relativity. Its cosmological counterpart, loop quantum cosmology, has clear predictions both for the cosmological background and for the perturbations. In particular, the initial Big Bang singularity is replaced by a bounce due to quantum geometry effects. In this proceeding I will focus on new results obtained in loop quantum cosmology: i) the prediction of the duration of inflation as a function of all the unknown parameters of the model and ii) new primordial power spectra obtained with modified dispersion relations accounting for trans-planckian effects. |
2003.10284 | Daniela Doneva | Daniela D. Doneva, Stoytcho S. Yazadjiev | Relativistic stars in 4D Einstein-Gauss-Bonnet gravity | 9 pages, 3 figures | null | 10.1088/1475-7516/2021/05/024 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present paper we investigate the structure of relativistic stars in 4D
Einstein-Gauss-Bonnet gravity. The mass-radius relations are obtained for
realistic hadronic and for strange quark star equations of state, and for a
wide range of the Gauss-Bonnet coupling parameter $\alpha$. Even though the
deviations from general relativity for nonzero values of $\alpha$ can be large
enough, they are still comparable with the variations due to different modern
realistic equations of state if we restrict ourselves to moderate value of
$\alpha$. That is why the current observations of the neutron star masses and
radii alone can not impose stringent constraints on the value of the parameter
$\alpha$. Nevertheless some rough constraints on $\alpha$ can be put. The
existence of stable stellar mass black holes imposes $\sqrt{\alpha}\lesssim 2.6
{\rm km}$ for $\alpha>0$ while the requirement that the maximum neutron star
mass should be greater than two solar masses gives $\sqrt{|\alpha|}\lesssim 3.9
{\rm km}$ for $\alpha<0$. We also present an exact solution describing the
structure of relativistic stars with uniform energy density in 4D
Einstein-Gauss-Bonnet gravity.
| [
{
"created": "Mon, 23 Mar 2020 14:04:18 GMT",
"version": "v1"
}
] | 2021-05-19 | [
[
"Doneva",
"Daniela D.",
""
],
[
"Yazadjiev",
"Stoytcho S.",
""
]
] | In the present paper we investigate the structure of relativistic stars in 4D Einstein-Gauss-Bonnet gravity. The mass-radius relations are obtained for realistic hadronic and for strange quark star equations of state, and for a wide range of the Gauss-Bonnet coupling parameter $\alpha$. Even though the deviations from general relativity for nonzero values of $\alpha$ can be large enough, they are still comparable with the variations due to different modern realistic equations of state if we restrict ourselves to moderate value of $\alpha$. That is why the current observations of the neutron star masses and radii alone can not impose stringent constraints on the value of the parameter $\alpha$. Nevertheless some rough constraints on $\alpha$ can be put. The existence of stable stellar mass black holes imposes $\sqrt{\alpha}\lesssim 2.6 {\rm km}$ for $\alpha>0$ while the requirement that the maximum neutron star mass should be greater than two solar masses gives $\sqrt{|\alpha|}\lesssim 3.9 {\rm km}$ for $\alpha<0$. We also present an exact solution describing the structure of relativistic stars with uniform energy density in 4D Einstein-Gauss-Bonnet gravity. |
gr-qc/0406093 | Jiri Podolsky | Otakar Svitek and Jiri Podolsky | The Efroimsky formalism adapted to high-frequency perturbations | 7 pages, to appear in Class. Quantum Grav | Class.Quant.Grav. 21 (2004) 3579-3586 | 10.1088/0264-9381/21/14/017 | null | gr-qc | null | The Efroimsky perturbation scheme for consistent treatment of gravitational
waves and their influence on the background is summarized and compared with
classical Isaacson's high-frequency approach. We demonstrate that the Efroimsky
method in its present form is not compatible with the Isaacson limit of
high-frequency gravitational waves, and we propose its natural generalization
to resolve this drawback.
| [
{
"created": "Wed, 23 Jun 2004 15:46:52 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Svitek",
"Otakar",
""
],
[
"Podolsky",
"Jiri",
""
]
] | The Efroimsky perturbation scheme for consistent treatment of gravitational waves and their influence on the background is summarized and compared with classical Isaacson's high-frequency approach. We demonstrate that the Efroimsky method in its present form is not compatible with the Isaacson limit of high-frequency gravitational waves, and we propose its natural generalization to resolve this drawback. |
0811.0985 | Christian Corda | Christian Corda | A longitudinal component in massive gravitational waves arising from a
bimetric theory of gravity | Published in Astroparticle Physics | Astropart.Phys.28:247-250,2007 | 10.1016/j.astropartphys.2007.05.009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | After a brief review of the work of de Paula, Miranda and Marinho on massive
gravitational waves arising from a bimetric theory of gravity, in this paper it
is shown that the presence of the mass generates a longi- tudinal component in
a particular polarization of the wave. The effect of this polarization on test
masses is performed using the geodesic deviation. A the end of this paper the
detectability of this particular polarization is also discussed, showing that
its angular dependence could, in princi- ple, discriminate such polarization
with respect the two ones of general relativity, if present or future detectors
will achieve a high sensitivity.
| [
{
"created": "Thu, 6 Nov 2008 16:24:10 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Corda",
"Christian",
""
]
] | After a brief review of the work of de Paula, Miranda and Marinho on massive gravitational waves arising from a bimetric theory of gravity, in this paper it is shown that the presence of the mass generates a longi- tudinal component in a particular polarization of the wave. The effect of this polarization on test masses is performed using the geodesic deviation. A the end of this paper the detectability of this particular polarization is also discussed, showing that its angular dependence could, in princi- ple, discriminate such polarization with respect the two ones of general relativity, if present or future detectors will achieve a high sensitivity. |
2406.08831 | Diego S\'aez-Chill\'on G\'omez | Sergei D. Odintsov, Diego S\'aez-Chill\'on G\'omez and German S.
Sharov | Exponential gravity with logarithmic corrections in the presence of
axion dark matter | 12 pages, 3 figures. To be published in Phys. Dark Univ | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An exponential modified gravity with additional logarithmic corrections is
considered with the presence of an axion-like scalar field in the role of dark
matter. Axion fields are thought to become important at late-times when the
axion-like scalar field oscillates around its vacuum expectation value,
mimicking dark matter behaviour. The model is compared with the usual
pressureless fluid description of dark matter. Both models are tested with
observational data including some of the latest sources, providing similar fits
in comparison with the $\Lambda$CDM model. Despite results are not
statistically relevant to rule out any model, the number of free parameters
still favours $\Lambda$CDM model, as shown by computing the goodness of the
fits.
| [
{
"created": "Thu, 13 Jun 2024 05:53:36 GMT",
"version": "v1"
}
] | 2024-06-14 | [
[
"Odintsov",
"Sergei D.",
""
],
[
"Gómez",
"Diego Sáez-Chillón",
""
],
[
"Sharov",
"German S.",
""
]
] | An exponential modified gravity with additional logarithmic corrections is considered with the presence of an axion-like scalar field in the role of dark matter. Axion fields are thought to become important at late-times when the axion-like scalar field oscillates around its vacuum expectation value, mimicking dark matter behaviour. The model is compared with the usual pressureless fluid description of dark matter. Both models are tested with observational data including some of the latest sources, providing similar fits in comparison with the $\Lambda$CDM model. Despite results are not statistically relevant to rule out any model, the number of free parameters still favours $\Lambda$CDM model, as shown by computing the goodness of the fits. |
gr-qc/0307095 | Yuki Uchida | Daisuke Ida and Yuki Uchida | Stationary Einstein-Maxwell fields in arbitrary dimensions | 26 pages | Phys.Rev. D68 (2003) 104014 | 10.1103/PhysRevD.68.104014 | null | gr-qc | null | The Einstein-Maxwell equations in D-dimensions admitting (D-3) commuting
Killing vector fields have been investigated. The existence of the electric,
magnetic and twist potentials have been proved. The system is formulated as the
harmonic map coupled to gravity on three-dimensional base space generalizing
the Ernst system in the four-dimensional stationary Einstein-Maxwell theory.
Some classes of the new exact solutions have been provided, which include the
electro-magnetic generalization of the Myers-Perry solution, which describes
the rotating black hole immersed in a magnetic universe, and the static charged
black ring solution.
| [
{
"created": "Tue, 22 Jul 2003 09:54:56 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Ida",
"Daisuke",
""
],
[
"Uchida",
"Yuki",
""
]
] | The Einstein-Maxwell equations in D-dimensions admitting (D-3) commuting Killing vector fields have been investigated. The existence of the electric, magnetic and twist potentials have been proved. The system is formulated as the harmonic map coupled to gravity on three-dimensional base space generalizing the Ernst system in the four-dimensional stationary Einstein-Maxwell theory. Some classes of the new exact solutions have been provided, which include the electro-magnetic generalization of the Myers-Perry solution, which describes the rotating black hole immersed in a magnetic universe, and the static charged black ring solution. |
0907.2114 | Alexander A. Chernitskii | Alexander A. Chernitskii | On unification of gravitation and electromagnetism in the framework of a
general-relativistic approach | 3 pages, Talk given at the International Conference RUSGRAV-13, June
23-28, 2008, PFUR, Moscow | Grav.Cosmol.15:151-153,2009 | 10.1134/S0202289309020091 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the unification problem for the gravitational and electromagnetic
interactions and its possible solution on the basis of the existence of an
effective Riemannian space in nonlinear electrodynamics
| [
{
"created": "Mon, 13 Jul 2009 08:44:59 GMT",
"version": "v1"
}
] | 2010-12-15 | [
[
"Chernitskii",
"Alexander A.",
""
]
] | We consider the unification problem for the gravitational and electromagnetic interactions and its possible solution on the basis of the existence of an effective Riemannian space in nonlinear electrodynamics |
2402.07036 | Jonathan Holland | Jonathan Holland and George Sparling | Sachs equations and plane waves, I: Rosen universes | null | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article, the first in a series, analyzes the general theory of plane
wave spacetimes. Following Dmitri Aleekseevsky, these are defined as spacetimes
admitting a group of dilations leaving invariant a smooth curve. If this curve
is specified as part of the structure, the spacetime is termed a Penrose limit,
whose theory was developed first by Roger Penrose. The main result is that
every plane wave is a Rosen universe, a generalization of the smooth metrics of
Albert Einstein and Nathan Rosen, allowing for certain isolated co-ordinate
singularities; the latter are characterized. We conclude with an extended
example, using the techniques developed in the article to associate a vacuum
plane wave in four dimensions to any hyperbolic billiard trajectory.
| [
{
"created": "Sat, 10 Feb 2024 20:21:35 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Apr 2024 10:51:39 GMT",
"version": "v2"
}
] | 2024-04-10 | [
[
"Holland",
"Jonathan",
""
],
[
"Sparling",
"George",
""
]
] | This article, the first in a series, analyzes the general theory of plane wave spacetimes. Following Dmitri Aleekseevsky, these are defined as spacetimes admitting a group of dilations leaving invariant a smooth curve. If this curve is specified as part of the structure, the spacetime is termed a Penrose limit, whose theory was developed first by Roger Penrose. The main result is that every plane wave is a Rosen universe, a generalization of the smooth metrics of Albert Einstein and Nathan Rosen, allowing for certain isolated co-ordinate singularities; the latter are characterized. We conclude with an extended example, using the techniques developed in the article to associate a vacuum plane wave in four dimensions to any hyperbolic billiard trajectory. |
1908.09286 | Kiyoshi Shiraishi | Nahomi Kan, Masashi Kuniyasu, Kiyoshi Shiraishi, Kohjiroh Takimoto | Equivalent Hamiltonian approach to quantum cosmology of integrable
models | 25 pages, 22 figures. Final version | Class. Quant. Grav. 37 (2020) 10, 105002 | 10.1088/1361-6382/ab8602 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose an approach to quantum cosmology of integrable models. To analyze
the models with two dynamical variables, we introduce equivalent Hamiltonians
in reduced phase spaces, which are obtained with the aid of the Faddeev--Jackiw
method. Quantum dynamics of the models can be studied by using the equivalent
Hamiltonians with various techniques.
| [
{
"created": "Sun, 25 Aug 2019 09:15:32 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Sep 2019 08:52:12 GMT",
"version": "v2"
},
{
"created": "Wed, 6 Nov 2019 01:25:28 GMT",
"version": "v3"
},
{
"created": "Mon, 3 Feb 2020 08:27:11 GMT",
"version": "v4"
},
{
"cre... | 2020-05-11 | [
[
"Kan",
"Nahomi",
""
],
[
"Kuniyasu",
"Masashi",
""
],
[
"Shiraishi",
"Kiyoshi",
""
],
[
"Takimoto",
"Kohjiroh",
""
]
] | We propose an approach to quantum cosmology of integrable models. To analyze the models with two dynamical variables, we introduce equivalent Hamiltonians in reduced phase spaces, which are obtained with the aid of the Faddeev--Jackiw method. Quantum dynamics of the models can be studied by using the equivalent Hamiltonians with various techniques. |
2402.15354 | Krishnendu De Dr. | Krishnendu De, Uday Chand De and Ljubica Velimirovic | Some curvature properties of perfect fluid spacetimes | null | Quaestiones Mathematicae (2023) | 10.2989/16073606.2023.2255933 | null | gr-qc math.DG | http://creativecommons.org/licenses/by/4.0/ | In this paper we assume that a perfect fluid is the source of the
gravitational field while analyzing the solutions to the Einstein field
equations.
| [
{
"created": "Fri, 23 Feb 2024 14:40:04 GMT",
"version": "v1"
}
] | 2024-02-26 | [
[
"De",
"Krishnendu",
""
],
[
"De",
"Uday Chand",
""
],
[
"Velimirovic",
"Ljubica",
""
]
] | In this paper we assume that a perfect fluid is the source of the gravitational field while analyzing the solutions to the Einstein field equations. |
1901.11506 | Wu-Sheng Dai | Wen-Du Li and Wu-Sheng Dai | Geodesic dual spacetime | null | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A duality between spacetime manifolds, the geodesic duality, is introduced.
Two manifolds are geodesic dual, if the transformation between their metrics is
also the transformation between their geodesics. That is, the transformation
that transforms the metric to the metric of the dual manifold is also the
transformation that transforms the geodesic to the geodesic of the dual
manifold. On the contrary, for nondual spacetime manifolds, a geodesic is no
longer a geodesic after the transformation between the metrics. We give a
general result of the duality between spacetime manifolds with diagonal
metrics. The geodesic duality of spherically symmetric spacetime are discussed
for illustrating the concept. The geodesic dual spacetime of the Schwarzschild
spacetime and the geodesic dual spacetime of the Reissner-Nordstr\"om spacetime
are presented.
| [
{
"created": "Thu, 31 Jan 2019 18:11:59 GMT",
"version": "v1"
}
] | 2019-02-01 | [
[
"Li",
"Wen-Du",
""
],
[
"Dai",
"Wu-Sheng",
""
]
] | A duality between spacetime manifolds, the geodesic duality, is introduced. Two manifolds are geodesic dual, if the transformation between their metrics is also the transformation between their geodesics. That is, the transformation that transforms the metric to the metric of the dual manifold is also the transformation that transforms the geodesic to the geodesic of the dual manifold. On the contrary, for nondual spacetime manifolds, a geodesic is no longer a geodesic after the transformation between the metrics. We give a general result of the duality between spacetime manifolds with diagonal metrics. The geodesic duality of spherically symmetric spacetime are discussed for illustrating the concept. The geodesic dual spacetime of the Schwarzschild spacetime and the geodesic dual spacetime of the Reissner-Nordstr\"om spacetime are presented. |
gr-qc/9503025 | Joan Masso | Peter Anninos, Karen Camarda, Joan Masso, Edward Seidel, Wai-Mo Suen,
John Towns | Three dimensional numerical relativity: the evolution of black holes | 35 pages, LaTeX with RevTeX 3.0 macros. 27 postscript figures taking
7 MB of space, uuencoded and gz-compressed into a 2MB uufile. Also available
at http://jean-luc.ncsa.uiuc.edu/Papers/ and mpeg simulations at
http://jean-luc.ncsa.uiuc.edu/Movies/ Submitted to Physical Review D | Phys.Rev. D52 (1995) 2059-2082 | 10.1103/PhysRevD.52.2059 | WUGRAV-95-4 | gr-qc | null | We report on a new 3D numerical code designed to solve the Einstein equations
for general vacuum spacetimes. This code is based on the standard 3+1 approach
using cartesian coordinates. We discuss the numerical techniques used in
developing this code, and its performance on massively parallel and vector
supercomputers. As a test case, we present evolutions for the first 3D black
hole spacetimes. We identify a number of difficulties in evolving 3D black
holes and suggest approaches to overcome them. We show how special treatment of
the conformal factor can lead to more accurate evolution, and discuss
techniques we developed to handle black hole spacetimes in the absence of
symmetries. Many different slicing conditions are tested, including geodesic,
maximal, and various algebraic conditions on the lapse. With current
resolutions, limited by computer memory sizes, we show that with certain lapse
conditions we can evolve the black hole to about $t=50M$, where $M$ is the
black hole mass. Comparisons are made with results obtained by evolving
spherical initial black hole data sets with a 1D spherically symmetric code. We
also demonstrate that an ``apparent horizon locking shift'' can be used to
prevent the development of large gradients in the metric functions that result
from singularity avoiding time slicings. We compute the mass of the apparent
horizon in these spacetimes, and find that in many cases it can be conserved to
within about 5\% throughout the evolution with our techniques and current
resolution.
| [
{
"created": "Wed, 15 Mar 1995 00:04:38 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Anninos",
"Peter",
""
],
[
"Camarda",
"Karen",
""
],
[
"Masso",
"Joan",
""
],
[
"Seidel",
"Edward",
""
],
[
"Suen",
"Wai-Mo",
""
],
[
"Towns",
"John",
""
]
] | We report on a new 3D numerical code designed to solve the Einstein equations for general vacuum spacetimes. This code is based on the standard 3+1 approach using cartesian coordinates. We discuss the numerical techniques used in developing this code, and its performance on massively parallel and vector supercomputers. As a test case, we present evolutions for the first 3D black hole spacetimes. We identify a number of difficulties in evolving 3D black holes and suggest approaches to overcome them. We show how special treatment of the conformal factor can lead to more accurate evolution, and discuss techniques we developed to handle black hole spacetimes in the absence of symmetries. Many different slicing conditions are tested, including geodesic, maximal, and various algebraic conditions on the lapse. With current resolutions, limited by computer memory sizes, we show that with certain lapse conditions we can evolve the black hole to about $t=50M$, where $M$ is the black hole mass. Comparisons are made with results obtained by evolving spherical initial black hole data sets with a 1D spherically symmetric code. We also demonstrate that an ``apparent horizon locking shift'' can be used to prevent the development of large gradients in the metric functions that result from singularity avoiding time slicings. We compute the mass of the apparent horizon in these spacetimes, and find that in many cases it can be conserved to within about 5\% throughout the evolution with our techniques and current resolution. |
1609.07322 | Timothy Walton | Robin W. Tucker and Timothy J. Walton | On Gravitational Chirality as the Genesis of Astrophysical Jets | 16 pages, 10 figures; Updated version accepted by CQG | null | 10.1088/1361-6382/aa5325 | null | gr-qc astro-ph.GA physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been suggested that single and double jets observed emanating from
certain astrophysical objects may have a purely gravitational origin. We
discuss new classes of plane-fronted and pulsed gravitational wave solutions to
the equation for perturbations of Ricci-flat spacetimes around Minkowski
metrics, as models for the genesis of such phenomena. These solutions are
classified in terms of their chirality and generate a family of non-stationary
spacetime metrics. Particular members of these families are used as backgrounds
in analysing time-like solutions to the geodesic equation for test particles.
They are found numerically to exhibit both single and double jet-like features
with dimensionless aspect ratios suggesting that it may be profitable to
include such backgrounds in simulations of astrophysical jet dynamics from
rotating accretion discs involving electromagnetic fields.
| [
{
"created": "Fri, 23 Sep 2016 11:35:04 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Dec 2016 11:12:58 GMT",
"version": "v2"
}
] | 2017-01-18 | [
[
"Tucker",
"Robin W.",
""
],
[
"Walton",
"Timothy J.",
""
]
] | It has been suggested that single and double jets observed emanating from certain astrophysical objects may have a purely gravitational origin. We discuss new classes of plane-fronted and pulsed gravitational wave solutions to the equation for perturbations of Ricci-flat spacetimes around Minkowski metrics, as models for the genesis of such phenomena. These solutions are classified in terms of their chirality and generate a family of non-stationary spacetime metrics. Particular members of these families are used as backgrounds in analysing time-like solutions to the geodesic equation for test particles. They are found numerically to exhibit both single and double jet-like features with dimensionless aspect ratios suggesting that it may be profitable to include such backgrounds in simulations of astrophysical jet dynamics from rotating accretion discs involving electromagnetic fields. |
1107.3210 | Sigbjorn Hervik | Sigbjorn Hervik | All metrics have curvature tensors characterised by its invariants as a
limit: the \epsilon-property | 6 pages | Class.Quant.Grav.28:157001,2011 | 10.1088/0264-9381/28/15/157001 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove a generalisation of the $\epsilon$-property, namely that for any
dimension and signature, a metric which is not characterised by its polynomial
scalar curvature invariants, there is a frame such that the components of the
curvature tensors can be arbitrary close to a certain "background". This
"background" is defined by its curvature tensors: it is characterised by its
curvature tensors and has the same polynomial curvature invariants as the
original metric.
| [
{
"created": "Sat, 16 Jul 2011 08:47:14 GMT",
"version": "v1"
}
] | 2011-07-19 | [
[
"Hervik",
"Sigbjorn",
""
]
] | We prove a generalisation of the $\epsilon$-property, namely that for any dimension and signature, a metric which is not characterised by its polynomial scalar curvature invariants, there is a frame such that the components of the curvature tensors can be arbitrary close to a certain "background". This "background" is defined by its curvature tensors: it is characterised by its curvature tensors and has the same polynomial curvature invariants as the original metric. |
gr-qc/0402121 | Gavriel Segre Dr. | Gavriel Segre | The role of Topology in the classical geometric theories of gravitation | null | null | null | null | gr-qc math-ph math.MP | null | I withdraw the previous version of the paper since it contains conceptual and
mathematical mistakes. I will soon replace it with a radically revised version.
| [
{
"created": "Fri, 27 Feb 2004 19:09:10 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Mar 2004 18:54:14 GMT",
"version": "v2"
},
{
"created": "Fri, 30 Jul 2004 13:52:56 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Segre",
"Gavriel",
""
]
] | I withdraw the previous version of the paper since it contains conceptual and mathematical mistakes. I will soon replace it with a radically revised version. |
1502.07508 | Marcello Ortaggio | Marcello Ortaggio, Alena Pravdov\'a | Asymptotic properties of gravitational and electromagnetic fields in
higher dimensions | 6 pages; summary of (parts of) arXiv:1403.7559 and arXiv:1406.3186.
Proceedings of Spanish Relativity Meeting ERE 2014: Almost 100 years after
Einstein Revolution, Valencia, September 1-5, 2014
(http://www.uv.es/ere2014/) | null | 10.1088/1742-6596/600/1/012052 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We summarize the fall-off of electromagnetic and gravitational fields in n>5
dimensional Ricci-flat spacetimes along an asympotically expanding non-singular
geodesic null congruence.
| [
{
"created": "Thu, 26 Feb 2015 11:20:47 GMT",
"version": "v1"
}
] | 2015-05-20 | [
[
"Ortaggio",
"Marcello",
""
],
[
"Pravdová",
"Alena",
""
]
] | We summarize the fall-off of electromagnetic and gravitational fields in n>5 dimensional Ricci-flat spacetimes along an asympotically expanding non-singular geodesic null congruence. |
1301.4891 | Mohammad Reza Setare | M. R. Setare, N. Mohammadipour | Can $f(T)$ gravity theories mimic $\Lambda$CDM cosmic history | 15 pages, 1 figure, accepted for publication in JCAP | JCAP01(2013)015, doi:10.1088/1475-7516/2013/01/015 | 10.1088/1475-7516/2013/01/015 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently the teleparallel Lagrangian density described by the torsion scalar
T has been extended to a function of T. The $f(T)$ modified teleparallel
gravity has been proposed as the natural gravitational alternative for dark
energy to explain the late time acceleration of the universe. In order to
reconstruct the function $f(T)$ by demanding a background $\Lambda$CDM
cosmology we assume that, (i) the background cosmic history provided by the
flat $\Lambda$CDM (the radiation ere with $\omega_{eff}=1/3$, matter and de
Sitter eras with $\omega_{eff}=0$ and $\omega_{eff}=-1$, respectively) (ii) the
radiation dominate in the radiation era with $\Omega_{0r}=1$ and the matter
dominate during the matter phases when $\Omega_{0m}=1$. We find the
cosmological dynamical system which can obey the $\Lambda$CDM cosmic history.
In each era, we find a critical lines that, the radiation dominated and the
matter dominated are one points of them in the radiation and matter phases,
respectively. Also, we drive the cosmologically viability condition for these
models. We investigate the stability condition with respect to the homogeneous
scalar perturbations in each era and we obtain the stability conditions for the
fixed points in each eras. Finally, we reconstruct the function $f(T)$ which
mimics cosmic expansion history.
| [
{
"created": "Sat, 12 Jan 2013 06:52:21 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Setare",
"M. R.",
""
],
[
"Mohammadipour",
"N.",
""
]
] | Recently the teleparallel Lagrangian density described by the torsion scalar T has been extended to a function of T. The $f(T)$ modified teleparallel gravity has been proposed as the natural gravitational alternative for dark energy to explain the late time acceleration of the universe. In order to reconstruct the function $f(T)$ by demanding a background $\Lambda$CDM cosmology we assume that, (i) the background cosmic history provided by the flat $\Lambda$CDM (the radiation ere with $\omega_{eff}=1/3$, matter and de Sitter eras with $\omega_{eff}=0$ and $\omega_{eff}=-1$, respectively) (ii) the radiation dominate in the radiation era with $\Omega_{0r}=1$ and the matter dominate during the matter phases when $\Omega_{0m}=1$. We find the cosmological dynamical system which can obey the $\Lambda$CDM cosmic history. In each era, we find a critical lines that, the radiation dominated and the matter dominated are one points of them in the radiation and matter phases, respectively. Also, we drive the cosmologically viability condition for these models. We investigate the stability condition with respect to the homogeneous scalar perturbations in each era and we obtain the stability conditions for the fixed points in each eras. Finally, we reconstruct the function $f(T)$ which mimics cosmic expansion history. |
gr-qc/0105045 | Alan D. Rendall | Markus Kunze and Alan D. Rendall | Simplified models of electromagnetic and gravitational radiation damping | null | Class.Quant.Grav. 18 (2001) 3573-3588 | 10.1088/0264-9381/18/17/311 | AEI-2001-051 | gr-qc | null | In previous work the authors analysed the global properties of an approximate
model of radiation damping for charged particles. This work is put into context
and related to the original motivation of understanding approximations used in
the study of gravitational radiation damping. It is examined to what extent the
results obtained previously depend on the particular model chosen. Comparisons
are made with other models for gravitational and electromagnetic fields. The
relation of the kinetic model for which theorems were proved to certain
many-particle models with radiation damping is exhibited.
| [
{
"created": "Mon, 14 May 2001 13:27:40 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Kunze",
"Markus",
""
],
[
"Rendall",
"Alan D.",
""
]
] | In previous work the authors analysed the global properties of an approximate model of radiation damping for charged particles. This work is put into context and related to the original motivation of understanding approximations used in the study of gravitational radiation damping. It is examined to what extent the results obtained previously depend on the particular model chosen. Comparisons are made with other models for gravitational and electromagnetic fields. The relation of the kinetic model for which theorems were proved to certain many-particle models with radiation damping is exhibited. |
gr-qc/0511143 | Pedro Marronetti | Pedro Marronetti | Momentum constraint relaxation | 17 pages, 10 figures. New numerical tests and references added. More
detailed description of the algorithms are provided. Final published version | Class.Quant.Grav. 23 (2006) 2681-2696 | 10.1088/0264-9381/23/7/027 | null | gr-qc astro-ph | null | Full relativistic simulations in three dimensions invariably develop runaway
modes that grow exponentially and are accompanied by violations of the
Hamiltonian and momentum constraints. Recently, we introduced a numerical
method (Hamiltonian relaxation) that greatly reduces the Hamiltonian constraint
violation and helps improve the quality of the numerical model. We present here
a method that controls the violation of the momentum constraint. The method is
based on the addition of a longitudinal component to the traceless extrinsic
curvature generated by a vector potential w_i, as outlined by York. The
components of w_i are relaxed to solve approximately the momentum constraint
equations, pushing slowly the evolution toward the space of solutions of the
constraint equations. We test this method with simulations of binary neutron
stars in circular orbits and show that effectively controls the growth of the
aforementioned violations. We also show that a full numerical enforcement of
the constraints, as opposed to the gentle correction of the momentum relaxation
scheme, results in the development of instabilities that stop the runs shortly.
| [
{
"created": "Sun, 27 Nov 2005 15:24:35 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Mar 2006 15:49:44 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Marronetti",
"Pedro",
""
]
] | Full relativistic simulations in three dimensions invariably develop runaway modes that grow exponentially and are accompanied by violations of the Hamiltonian and momentum constraints. Recently, we introduced a numerical method (Hamiltonian relaxation) that greatly reduces the Hamiltonian constraint violation and helps improve the quality of the numerical model. We present here a method that controls the violation of the momentum constraint. The method is based on the addition of a longitudinal component to the traceless extrinsic curvature generated by a vector potential w_i, as outlined by York. The components of w_i are relaxed to solve approximately the momentum constraint equations, pushing slowly the evolution toward the space of solutions of the constraint equations. We test this method with simulations of binary neutron stars in circular orbits and show that effectively controls the growth of the aforementioned violations. We also show that a full numerical enforcement of the constraints, as opposed to the gentle correction of the momentum relaxation scheme, results in the development of instabilities that stop the runs shortly. |
2012.05714 | Qudsia Gani | M. Hameeda, Q. Gani, B. Pourhassan, M.C.Rocca | Boltzmann and Tsallis statistical approaches to study Quantum
corrections at large distances and clustering of galaxies | 34 pages, 9 Figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Gravity is so different from other fundamental forces that it is now
essentially treated as a non-fundamental force of entropic origin. A number of
good studies have been carried out in this direction. Quantum gravity has also
significantly improved our understanding by combining gravity well with quantum
physics. However, there are still many impediments to our understanding
especially in the limits of extreme. The effects of quantum gravity start
appearing on the scene at Planck length which is the smallest length in nature
idealized so far. While as this study incorporates a model which is valid for
potential energy corrections at small distances but we have also given a bold
try to use it confidently for the corrections at very large distances as well.
The model uses two techniques namely Boltzmann and Tsallis statistical
approaches to explore the thermodynamics within the ambit of brane world model
giving its further modified version. We have computed partition function by
using both Boltzmann and Tsallis statistical approaches and then used it to
study thermodynamics of the brane world model. We have analyzed both
analytically and graphically, the thermodynamic quantities like Helmholtz free
energy and specific heat. The thermodynamic stability of the model is also
discussed depending on the number of galaxies.
| [
{
"created": "Wed, 9 Dec 2020 07:26:04 GMT",
"version": "v1"
}
] | 2020-12-11 | [
[
"Hameeda",
"M.",
""
],
[
"Gani",
"Q.",
""
],
[
"Pourhassan",
"B.",
""
],
[
"Rocca",
"M. C.",
""
]
] | Gravity is so different from other fundamental forces that it is now essentially treated as a non-fundamental force of entropic origin. A number of good studies have been carried out in this direction. Quantum gravity has also significantly improved our understanding by combining gravity well with quantum physics. However, there are still many impediments to our understanding especially in the limits of extreme. The effects of quantum gravity start appearing on the scene at Planck length which is the smallest length in nature idealized so far. While as this study incorporates a model which is valid for potential energy corrections at small distances but we have also given a bold try to use it confidently for the corrections at very large distances as well. The model uses two techniques namely Boltzmann and Tsallis statistical approaches to explore the thermodynamics within the ambit of brane world model giving its further modified version. We have computed partition function by using both Boltzmann and Tsallis statistical approaches and then used it to study thermodynamics of the brane world model. We have analyzed both analytically and graphically, the thermodynamic quantities like Helmholtz free energy and specific heat. The thermodynamic stability of the model is also discussed depending on the number of galaxies. |
1404.3582 | Victor Berezin | Victor Berezin | On the phenomenological description of particle creation and its
influence on the space-time metrics | 8 pages. To be publishe in the Proceedings of the "RUSGRAV"
Conference, Kazan' June 30 -July 5, 2014 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The method is proposed for the phenomenological description of particle
creation by external fields (in the presence of gravitational field or without
it). It is shown that, despite the appearance of the non-dynamical degrees of
freedom, such as the number density and four-velocities of particles at the
moment of creation (and corresponding Lagrange multipliers) the theory is
complete and self-consistent. It appears that the very existence of particle
creation processes requires the non-zero trace anomaly of the external quantum
field under consideration.
| [
{
"created": "Mon, 14 Apr 2014 13:55:50 GMT",
"version": "v1"
}
] | 2014-04-15 | [
[
"Berezin",
"Victor",
""
]
] | The method is proposed for the phenomenological description of particle creation by external fields (in the presence of gravitational field or without it). It is shown that, despite the appearance of the non-dynamical degrees of freedom, such as the number density and four-velocities of particles at the moment of creation (and corresponding Lagrange multipliers) the theory is complete and self-consistent. It appears that the very existence of particle creation processes requires the non-zero trace anomaly of the external quantum field under consideration. |
gr-qc/9403036 | null | I. G. Avramidi | Covariant methods for calculating the low-energy effective action in
quantum field theory and quantum gravity | 48 pages, plain TeX, University of Greifswald, EMA-MAT-1994-2 | null | null | null | gr-qc hep-th | null | We continue the development of the effective covariant methods for
calculating the heat kernel and the one-loop effective action in quantum field
theory and quantum gravity. The status of the low-energy approximation in
quantum gauge theories and quantum gravity is discussed in detail on the basis
of analyzing the local Schwinger - De Witt expansion. It is argued that the
low-energy limit, when defined in a covariant way, should be related to
background fields with covariantly constant curvature, gauge field strength and
potential. Some new approaches for calculating the low-energy heat kernel
assuming a covariantly constant background are proposed. The one-loop
low-energy effective action in Yang-Mills theory in flat space with arbitrary
compact simple gauge group and arbitrary matter on a covariantly constant
background is calculated. The stability problem of the chromomagnetic
(Savvidy-type) vacuum is analyzed. It is shown, that this type of vacuum
structure can be stable only in the case when more than one background
chromomagnetic fields are present and the values of these fields differ not
greatly from each other.This is possible only in space-times of dimension not
less than five $d\geq 5$.
| [
{
"created": "Fri, 18 Mar 1994 18:31:18 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Avramidi",
"I. G.",
""
]
] | We continue the development of the effective covariant methods for calculating the heat kernel and the one-loop effective action in quantum field theory and quantum gravity. The status of the low-energy approximation in quantum gauge theories and quantum gravity is discussed in detail on the basis of analyzing the local Schwinger - De Witt expansion. It is argued that the low-energy limit, when defined in a covariant way, should be related to background fields with covariantly constant curvature, gauge field strength and potential. Some new approaches for calculating the low-energy heat kernel assuming a covariantly constant background are proposed. The one-loop low-energy effective action in Yang-Mills theory in flat space with arbitrary compact simple gauge group and arbitrary matter on a covariantly constant background is calculated. The stability problem of the chromomagnetic (Savvidy-type) vacuum is analyzed. It is shown, that this type of vacuum structure can be stable only in the case when more than one background chromomagnetic fields are present and the values of these fields differ not greatly from each other.This is possible only in space-times of dimension not less than five $d\geq 5$. |
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