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/9602025 | Jaume Garriga | Jaume Garriga | Bubble fluctuations in $\Omega<1$ inflation | 17 pages, 3 figs, LaTeX, epsfig.sty, available at
ftp://ftp.ifae.es/preprint/ft/uabft387.ps | Phys.Rev. D54 (1996) 4764-4769 | 10.1103/PhysRevD.54.4764 | UAB-FT-387 | gr-qc astro-ph | null | In the context of the open inflationary universe, we calculate the amplitude
of quantum fluctuations which deform the bubble shape. These give rise to
scalar field fluctuations in the open Friedman-Robertson-Walker universe which
is contained inside the bubble. One can transform to a new gauge in which
matter looks perfectly smooth, and then the perturbations behave as tensor
modes (gravitational waves of very long wavelength). For $(1-\Omega)<<1$, where
$\Omega$ is the density parameter, the microwave temperature anisotropies
produced by these modes are of order $\delta T/T\sim H(R_0\mu l)^{-1/2}
(1-\Omega)^{l/2}$. Here, $H$ is the expansion rate during inflation, $R_0$ is
the intrinsic radius of the bubble at the time of nucleation, $\mu$ is the
bubble wall tension and $l$ labels the different multipoles ($l>1$). The
gravitational backreaction of the bubble has been ignored. In this
approximation, $G\mu R_0<<1$, and the new effect can be much larger than the
one due to ordinary gravitational waves generated during inflation (unless, of
course, $\Omega$ gets too close to one, in which case the new effect
disappears).
| [
{
"created": "Mon, 13 Feb 1995 11:56:35 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Garriga",
"Jaume",
""
]
] | In the context of the open inflationary universe, we calculate the amplitude of quantum fluctuations which deform the bubble shape. These give rise to scalar field fluctuations in the open Friedman-Robertson-Walker universe which is contained inside the bubble. One can transform to a new gauge in which matter looks perfectly smooth, and then the perturbations behave as tensor modes (gravitational waves of very long wavelength). For $(1-\Omega)<<1$, where $\Omega$ is the density parameter, the microwave temperature anisotropies produced by these modes are of order $\delta T/T\sim H(R_0\mu l)^{-1/2} (1-\Omega)^{l/2}$. Here, $H$ is the expansion rate during inflation, $R_0$ is the intrinsic radius of the bubble at the time of nucleation, $\mu$ is the bubble wall tension and $l$ labels the different multipoles ($l>1$). The gravitational backreaction of the bubble has been ignored. In this approximation, $G\mu R_0<<1$, and the new effect can be much larger than the one due to ordinary gravitational waves generated during inflation (unless, of course, $\Omega$ gets too close to one, in which case the new effect disappears). |
1408.4203 | Richard Barry | Richard A. Barry and Susan M. Scott | The Strongly Attached Point Topology of the Abstract Boundary For
Space-Time | 48 pages, 11 figures | Class. Quantum Grav. 31(12) 125004 2014 | 10.1088/0264-9381/31/12/125004 | null | gr-qc math.GN | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The abstract boundary construction of Scott and Szekeres provides a
`boundary' for any n-dimensional, paracompact, connected, Hausdorff, smooth
manifold. Singularities may then be defined as objects within this boundary. In
a previous paper by the authors, a topology referred to as the attached point
topology was defined for a manifold and its abstract boundary, thereby
providing us with a description of how the abstract boundary is related to the
underlying manifold. In this paper, a second topology, referred to as the
strongly attached point topology, is presented for the abstract boundary
construction. Whereas the abstract boundary was effectively disconnected from
the manifold in the attached point topology, it is very much connected in the
strongly attached point topology. A number of other interesting properties of
the strongly attached point topology are considered, each of which support the
idea that it is a very natural and appropriate topology for a manifold and its
abstract boundary.
| [
{
"created": "Tue, 19 Aug 2014 03:50:46 GMT",
"version": "v1"
}
] | 2014-08-20 | [
[
"Barry",
"Richard A.",
""
],
[
"Scott",
"Susan M.",
""
]
] | The abstract boundary construction of Scott and Szekeres provides a `boundary' for any n-dimensional, paracompact, connected, Hausdorff, smooth manifold. Singularities may then be defined as objects within this boundary. In a previous paper by the authors, a topology referred to as the attached point topology was defined for a manifold and its abstract boundary, thereby providing us with a description of how the abstract boundary is related to the underlying manifold. In this paper, a second topology, referred to as the strongly attached point topology, is presented for the abstract boundary construction. Whereas the abstract boundary was effectively disconnected from the manifold in the attached point topology, it is very much connected in the strongly attached point topology. A number of other interesting properties of the strongly attached point topology are considered, each of which support the idea that it is a very natural and appropriate topology for a manifold and its abstract boundary. |
0909.4039 | Gaurav Khanna | Gaurav Khanna, Justin McKennon | An exploration of CUDA and CBEA for a gravitational wave
source-modelling application | 8 pages, 4 figures, Accepted for publication in Parallel and
Distributed Computing and Systems (PDCS 2009) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we accelerate a gravitational physics numerical modelling
application using hardware accelerators -- Cell processor and Tesla CUDA GPU.
We describe these new technologies and our approach in detail, and then present
our final performance results. We obtain well over an order-of-magnitude
performance gain in our application by making use of these many-core
architectures.
| [
{
"created": "Tue, 22 Sep 2009 16:55:59 GMT",
"version": "v1"
}
] | 2009-09-23 | [
[
"Khanna",
"Gaurav",
""
],
[
"McKennon",
"Justin",
""
]
] | In this paper, we accelerate a gravitational physics numerical modelling application using hardware accelerators -- Cell processor and Tesla CUDA GPU. We describe these new technologies and our approach in detail, and then present our final performance results. We obtain well over an order-of-magnitude performance gain in our application by making use of these many-core architectures. |
1503.08751 | Mairi Sakellariadou | Gaetano Lambiase, Mairi Sakellariadou, Antonio Stabile, Arturo Stabile | Astrophysical constraints on extended gravity models | 22 pages; minor changes to match published version | JCAP 07 (2015) 003 | 10.1088/1475-7516/2015/07/003 | KCL-PH-TH/2015-16 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the propagation of gravitational waves in the context of
fourth order gravity nonminimally coupled to a massive scalar field. Using the
damping of the orbital period of coalescing stellar binary systems, we impose
constraints on the free parameters of extended gravity models. In particular,
we find that the variation of the orbital period is a function of three mass
scales which depend on the free parameters of the model under consideration; we
can constrain these mass scales from current observational data.
| [
{
"created": "Mon, 30 Mar 2015 17:24:58 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Jul 2015 17:01:26 GMT",
"version": "v2"
}
] | 2015-07-10 | [
[
"Lambiase",
"Gaetano",
""
],
[
"Sakellariadou",
"Mairi",
""
],
[
"Stabile",
"Antonio",
""
],
[
"Stabile",
"Arturo",
""
]
] | We investigate the propagation of gravitational waves in the context of fourth order gravity nonminimally coupled to a massive scalar field. Using the damping of the orbital period of coalescing stellar binary systems, we impose constraints on the free parameters of extended gravity models. In particular, we find that the variation of the orbital period is a function of three mass scales which depend on the free parameters of the model under consideration; we can constrain these mass scales from current observational data. |
1602.08583 | Winfried Zimdahl | Eddy G.Chirinos Isidro, Cristofher Zu\~niga Vargas, Winfried Zimdahl | Simple inhomogeneous cosmological (toy) models | 30 pages, 14 figures, comments and references added, accepted for
publication in JCAP | null | 10.1088/1475-7516/2016/05/003 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on the Lema\^itre-Tolman-Bondi (LTB) metric we consider two flat
inhomogeneous big-bang models. We aim at clarifying, as far as possible
analytically, basic features of the dynamics of the simplest inhomogeneous
models and to point out the potential usefulness of exact inhomogeneous
solutions as generalizations of the homogeneous configurations of the
cosmological standard model. We discuss explicitly partial successes but also
potential pitfalls of these simplest models. Although primarily seen as toy
models, the relevant free parameters are fixed by best-fit values using the
Joint Light-curve Analysis (JLA)-sample data. On the basis of a likelihood
analysis we find that a local hump with an extension of almost 2 Gpc provides a
better description of the observations than a local void for which we obtain a
best-fit scale of about 30 Mpc. Future redshift-drift measurements are
discussed as a promising tool to discriminate between inhomogeneous
configurations and the $\Lambda$CDM model.
| [
{
"created": "Sat, 27 Feb 2016 11:04:18 GMT",
"version": "v1"
},
{
"created": "Thu, 7 Apr 2016 01:21:24 GMT",
"version": "v2"
}
] | 2016-05-25 | [
[
"Isidro",
"Eddy G. Chirinos",
""
],
[
"Vargas",
"Cristofher Zuñiga",
""
],
[
"Zimdahl",
"Winfried",
""
]
] | Based on the Lema\^itre-Tolman-Bondi (LTB) metric we consider two flat inhomogeneous big-bang models. We aim at clarifying, as far as possible analytically, basic features of the dynamics of the simplest inhomogeneous models and to point out the potential usefulness of exact inhomogeneous solutions as generalizations of the homogeneous configurations of the cosmological standard model. We discuss explicitly partial successes but also potential pitfalls of these simplest models. Although primarily seen as toy models, the relevant free parameters are fixed by best-fit values using the Joint Light-curve Analysis (JLA)-sample data. On the basis of a likelihood analysis we find that a local hump with an extension of almost 2 Gpc provides a better description of the observations than a local void for which we obtain a best-fit scale of about 30 Mpc. Future redshift-drift measurements are discussed as a promising tool to discriminate between inhomogeneous configurations and the $\Lambda$CDM model. |
2104.08024 | Alkiviadis Triantafyllopoulos | Spyros Konitopoulos, Emmanuel N. Saridakis, P. C. Stavrinos and A.
Triantafyllopoulos | Dark Gravitational Sectors on a Generalized Scalar-Tensor Vector Bundle
Model and Cosmological Applications | 17 pages, 2 figures, version to appear in Phys.Rev.D | Phys. Rev. D 104, 064018 (2021) | 10.1103/PhysRevD.104.064018 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we present the foundations of generalized scalar-tensor theories
arising from vector bundle constructions, and we study the kinematic, dynamical
and cosmological consequences. In particular, over a pseudo-Riemannian
space-time base manifold, we define a fiber structure with two scalar fields.
The resulting space is a 6-dimensional vector bundle endowed with a non-linear
connection. We provide the form of the geodesics and the Raychaudhuri and
general field equations, both in Palatini and metrical method. When applied at
a cosmological framework, this novel geometrical structure induces extra terms
in the modified Friedmann equations, leading to the appearance of an effective
dark energy sector, as well as of an interaction of the dark mater sector with
the metric. We show that we can obtain the standard thermal history of the
universe, with the sequence of matter and dark-energy epochs, and furthermore
the effective dark-energy equation-of-state parameter can lie in the
quintessence or phantom regimes, or exhibit the phantom-divide crossing.
| [
{
"created": "Fri, 16 Apr 2021 10:37:19 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Aug 2021 12:33:18 GMT",
"version": "v2"
}
] | 2021-09-15 | [
[
"Konitopoulos",
"Spyros",
""
],
[
"Saridakis",
"Emmanuel N.",
""
],
[
"Stavrinos",
"P. C.",
""
],
[
"Triantafyllopoulos",
"A.",
""
]
] | In this work we present the foundations of generalized scalar-tensor theories arising from vector bundle constructions, and we study the kinematic, dynamical and cosmological consequences. In particular, over a pseudo-Riemannian space-time base manifold, we define a fiber structure with two scalar fields. The resulting space is a 6-dimensional vector bundle endowed with a non-linear connection. We provide the form of the geodesics and the Raychaudhuri and general field equations, both in Palatini and metrical method. When applied at a cosmological framework, this novel geometrical structure induces extra terms in the modified Friedmann equations, leading to the appearance of an effective dark energy sector, as well as of an interaction of the dark mater sector with the metric. We show that we can obtain the standard thermal history of the universe, with the sequence of matter and dark-energy epochs, and furthermore the effective dark-energy equation-of-state parameter can lie in the quintessence or phantom regimes, or exhibit the phantom-divide crossing. |
1404.7757 | Giulio Mazzolo | G. Mazzolo, F. Salemi, M. Drago, V. Necula, C. Pankow, G. A. Prodi, V.
Re, V. Tiwari, G. Vedovato, I. Yakushin, S. Klimenko | Prospects for intermediate mass black hole binary searches with advanced
gravitational-wave detectors | 9 pages, 4 figures, corrected the name of one author (previously
misspelled) | Phys. Rev. D 90, 063002 (2014) | 10.1103/PhysRevD.90.063002 | LIGO-P1300053 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We estimated the sensitivity of the upcoming advanced, ground-based
gravitational-wave observatories (the upgraded LIGO and Virgo and the KAGRA
interferometers) to coalescing intermediate mass black hole binaries (IMBHB).
We added waveforms modeling the gravitational radiation emitted by IMBHBs to
detectors' simulated data and searched for the injected signals with the
coherent WaveBurst algorithm. The tested binary's parameter space covers
non-spinning IMBHBs with source-frame total masses between 50 and 1050
$\text{M}_{\odot}$ and mass ratios between $1/6$ and 1$\,$. We found that
advanced detectors could be sensitive to these systems up to a range of a few
Gpc. A theoretical model was adopted to estimate the expected observation
rates, yielding up to a few tens of events per year. Thus, our results indicate
that advanced detectors will have a reasonable chance to collect the first
direct evidence for intermediate mass black holes and open a new, intriguing
channel for probing the Universe over cosmological scales.
| [
{
"created": "Wed, 30 Apr 2014 15:13:35 GMT",
"version": "v1"
},
{
"created": "Fri, 2 May 2014 07:47:30 GMT",
"version": "v2"
}
] | 2014-09-17 | [
[
"Mazzolo",
"G.",
""
],
[
"Salemi",
"F.",
""
],
[
"Drago",
"M.",
""
],
[
"Necula",
"V.",
""
],
[
"Pankow",
"C.",
""
],
[
"Prodi",
"G. A.",
""
],
[
"Re",
"V.",
""
],
[
"Tiwari",
"V.",
""
],
... | We estimated the sensitivity of the upcoming advanced, ground-based gravitational-wave observatories (the upgraded LIGO and Virgo and the KAGRA interferometers) to coalescing intermediate mass black hole binaries (IMBHB). We added waveforms modeling the gravitational radiation emitted by IMBHBs to detectors' simulated data and searched for the injected signals with the coherent WaveBurst algorithm. The tested binary's parameter space covers non-spinning IMBHBs with source-frame total masses between 50 and 1050 $\text{M}_{\odot}$ and mass ratios between $1/6$ and 1$\,$. We found that advanced detectors could be sensitive to these systems up to a range of a few Gpc. A theoretical model was adopted to estimate the expected observation rates, yielding up to a few tens of events per year. Thus, our results indicate that advanced detectors will have a reasonable chance to collect the first direct evidence for intermediate mass black holes and open a new, intriguing channel for probing the Universe over cosmological scales. |
1808.01044 | Jeferson de Oliveira | R. D. B. Fontana, Jeferson de Oliveira, A. B. Pavan | Dynamical evolution of non-minimally coupled scalar field in spherically
symmetric de Sitter spacetimes | 31 pages; 11 figures, 8 tables and typos corrected | Eur.Phys.J. C79 (2019) no.4, 338, (2019-04-13) | 10.1140/epjc/s10052-019-6831-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the dynamical behavior of a scalar field non-minimally coupled
to Einstein's tensor and Ricci scalar in geometries of asymptotically de Sitter
spacetimes. We show that the quasinormal modes remain unaffected if the scalar
field is massless and the black hole is electrically chargeless. In the massive
case, the coupling of both parameters produces a region of instability in the
spacetime determined by the geometry and field parameters. In the Schwarzschild
case, every solution for the equations of motion with $\ell>0$ has a range of
values of the coupling constant that produces unstable modes. The case $\ell=0$
is the most unstable one, with a threshold value for stability in the coupling.
For the charged black hole, the existence of a range of instability in $\eta$
is strongly related to geometry parameters presenting a region of stability
independent of the chosen parameter.
| [
{
"created": "Thu, 2 Aug 2018 23:09:03 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Apr 2019 13:14:59 GMT",
"version": "v2"
},
{
"created": "Wed, 24 Apr 2019 15:08:40 GMT",
"version": "v3"
}
] | 2019-04-25 | [
[
"Fontana",
"R. D. B.",
""
],
[
"de Oliveira",
"Jeferson",
""
],
[
"Pavan",
"A. B.",
""
]
] | We investigate the dynamical behavior of a scalar field non-minimally coupled to Einstein's tensor and Ricci scalar in geometries of asymptotically de Sitter spacetimes. We show that the quasinormal modes remain unaffected if the scalar field is massless and the black hole is electrically chargeless. In the massive case, the coupling of both parameters produces a region of instability in the spacetime determined by the geometry and field parameters. In the Schwarzschild case, every solution for the equations of motion with $\ell>0$ has a range of values of the coupling constant that produces unstable modes. The case $\ell=0$ is the most unstable one, with a threshold value for stability in the coupling. For the charged black hole, the existence of a range of instability in $\eta$ is strongly related to geometry parameters presenting a region of stability independent of the chosen parameter. |
gr-qc/9211010 | null | S. Deser | Gauge (In)variance, Mass and Parity in D=3 Revisited | 11 pages | Directions in general relativity, vol 2 (Cambridge U Press 1993) | null | BRX TH-341 | gr-qc | null | We analyze the degree of equivalence between abelian topologically massive,
gauge-invariant, vector or tensor parity doublets and their explicitly massive,
non-gauge, counterparts. We establish equivalence of field equations by
exploiting a generalized Stueckelberg invariance of the gauge systems. Although
the respective excitation spectra and induced source-source interactions are
essentially identical, there are also differences, most dramatic being those
between the Einstein limits of the interactions in the tensor case: the
doublets avoid the discontinuity (well-known from D=4) exhibited by Pauli-Fierz
theory.
| [
{
"created": "Fri, 6 Nov 1992 17:30:00 GMT",
"version": "v1"
}
] | 2009-11-19 | [
[
"Deser",
"S.",
""
]
] | We analyze the degree of equivalence between abelian topologically massive, gauge-invariant, vector or tensor parity doublets and their explicitly massive, non-gauge, counterparts. We establish equivalence of field equations by exploiting a generalized Stueckelberg invariance of the gauge systems. Although the respective excitation spectra and induced source-source interactions are essentially identical, there are also differences, most dramatic being those between the Einstein limits of the interactions in the tensor case: the doublets avoid the discontinuity (well-known from D=4) exhibited by Pauli-Fierz theory. |
gr-qc/0303023 | Ulvi Yurtsever | Ulvi Yurtsever | The Holographic Entropy Bound and Local Quantum Field Theory | 5 pages, RevTeX, 1 eps figure | Phys.Rev.Lett. 91 (2003) 041302 | 10.1103/PhysRevLett.91.041302 | null | gr-qc hep-th quant-ph | null | The maximum entropy that can be stored in a bounded region of space is in
dispute: it goes as volume, implies (non-gravitational) microphysics; it goes
as the surface area, asserts the "holographic principle." Here I show how the
holographic bound can be derived from elementary flat-spacetime quantum field
theory when the total energy of Fock states is constrained gravitationally.
This energy constraint makes the Fock space dimension (whose logarithm is the
maximum entropy) finite for both Bosons and Fermions. Despite the elementary
nature of my analysis, it results in an upper limit on entropy in remarkable
agreement with the holographic bound.
| [
{
"created": "Thu, 6 Mar 2003 12:13:10 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Yurtsever",
"Ulvi",
""
]
] | The maximum entropy that can be stored in a bounded region of space is in dispute: it goes as volume, implies (non-gravitational) microphysics; it goes as the surface area, asserts the "holographic principle." Here I show how the holographic bound can be derived from elementary flat-spacetime quantum field theory when the total energy of Fock states is constrained gravitationally. This energy constraint makes the Fock space dimension (whose logarithm is the maximum entropy) finite for both Bosons and Fermions. Despite the elementary nature of my analysis, it results in an upper limit on entropy in remarkable agreement with the holographic bound. |
2211.08137 | Zi-Yu Tang | Zi-Yu Tang, Xiao-Mei Kuang, Bin Wang, Wei-Liang Qian | Photon region and shadow of a rotating 5D black string | 17 pages, 6 figures. arXiv admin note: text overlap with
arXiv:2206.08608 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To explore the possible clues for the extra dimension from the Event Horizon
Telescope (EHT) observations, we study the shadow of the rotating 5D black
string in General Relativity (GR). Instead of investigating the shadow in the
effective 4D theory, we concern the motion of photons along the extra dimension
$z$ with a conserved momentum $P_z$, which appears as an effective mass in the
geodesic equations of photons. The existence of $P_z$ enlarges the photon
regions and the shadow of the rotating 5D black string while it has slight
impact on the distortion. The EHT observations of M87* and SgrA* can rule out
the black string model with an infinite length along the extra dimension, and
support the hypothesis that the extra dimension is compact to avoid the
Gregory-Laflamme (GL) instability, where the length of the black string/the
compact extra dimension can be constrained as $2.03125~\rm{mm} \lesssim \ell
\lesssim 2.6~\rm{mm}$ and $2.28070~\rm{mm} \lesssim \ell \lesssim 2.6~\rm{mm}$
respectively.
| [
{
"created": "Tue, 15 Nov 2022 13:45:43 GMT",
"version": "v1"
}
] | 2022-11-16 | [
[
"Tang",
"Zi-Yu",
""
],
[
"Kuang",
"Xiao-Mei",
""
],
[
"Wang",
"Bin",
""
],
[
"Qian",
"Wei-Liang",
""
]
] | To explore the possible clues for the extra dimension from the Event Horizon Telescope (EHT) observations, we study the shadow of the rotating 5D black string in General Relativity (GR). Instead of investigating the shadow in the effective 4D theory, we concern the motion of photons along the extra dimension $z$ with a conserved momentum $P_z$, which appears as an effective mass in the geodesic equations of photons. The existence of $P_z$ enlarges the photon regions and the shadow of the rotating 5D black string while it has slight impact on the distortion. The EHT observations of M87* and SgrA* can rule out the black string model with an infinite length along the extra dimension, and support the hypothesis that the extra dimension is compact to avoid the Gregory-Laflamme (GL) instability, where the length of the black string/the compact extra dimension can be constrained as $2.03125~\rm{mm} \lesssim \ell \lesssim 2.6~\rm{mm}$ and $2.28070~\rm{mm} \lesssim \ell \lesssim 2.6~\rm{mm}$ respectively. |
gr-qc/9605050 | Sumati | Rafael D. Sorkin (Syracuse U. & Mexico U., CEN), Sumati Surya
(Syracuse U.) | An Analysis of the Representations of the Mapping Class Group of a
Multi-Geon Three-Manifold | 52 pages, harvmac, 2 postscript figures, epsf required. Added an
appendix proving the semi-direct product structure of the MCG, corrected an
error in the characterization of the slide subgroup, reworded extensively.
All our analysis and conclusions remain as before | Int.J.Mod.Phys. A13 (1998) 3749-3790 | 10.1142/S0217751X98001761 | SU-GP/9601-01 | gr-qc hep-th | null | It is well known that the inequivalent unitary irreducible representations
(UIR's) of the mapping class group $G$ of a 3-manifold give rise to ``theta
sectors'' in theories of quantum gravity with fixed spatial topology. In this
paper, we study several families of UIR's of $G$ and attempt to understand the
physical implications of the resulting quantum sectors. The mapping class group
of a three-manifold which is the connected sum of $\R^3$ with a finite number
of identical irreducible primes is a semi-direct product group. Following
Mackey's theory of induced representations, we provide an analysis of the
structure of the general finite dimensional UIR of such a group. In the picture
of quantized primes as particles (topological geons), this general
group-theoretic analysis enables one to draw several interesting qualitative
conclusions about the geons' behavior in different quantum sectors, without
requiring an explicit knowledge of the UIR's corresponding to the individual
primes.
| [
{
"created": "Wed, 22 May 1996 21:39:50 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Jun 1997 00:53:13 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Sorkin",
"Rafael D.",
"",
"Syracuse U. & Mexico U., CEN"
],
[
"Surya",
"Sumati",
"",
"Syracuse U."
]
] | It is well known that the inequivalent unitary irreducible representations (UIR's) of the mapping class group $G$ of a 3-manifold give rise to ``theta sectors'' in theories of quantum gravity with fixed spatial topology. In this paper, we study several families of UIR's of $G$ and attempt to understand the physical implications of the resulting quantum sectors. The mapping class group of a three-manifold which is the connected sum of $\R^3$ with a finite number of identical irreducible primes is a semi-direct product group. Following Mackey's theory of induced representations, we provide an analysis of the structure of the general finite dimensional UIR of such a group. In the picture of quantized primes as particles (topological geons), this general group-theoretic analysis enables one to draw several interesting qualitative conclusions about the geons' behavior in different quantum sectors, without requiring an explicit knowledge of the UIR's corresponding to the individual primes. |
2303.16798 | Viktor Skoup\'y | Viktor Skoup\'y, Georgios Lukes-Gerakopoulos, Lisa V. Drummond, Scott
A. Hughes | Asymptotic gravitational-wave fluxes from a spinning test body on
generic orbits around a Kerr black hole | 19 pages, 8 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work provides gravitational wave energy and angular momentum asymptotic
fluxes from a spinning body moving on generic orbits in a Kerr spacetime up to
linear in spin approximation. To achieve this, we have developed a new
frequency domain Teukolsky equation solver that calculates asymptotic
amplitudes from generic orbits of spinning bodies with their spin aligned with
the total orbital angular momentum. However, the energy and angular momentum
fluxes from these orbits in the linear in spin approximation are appropriate
for adiabatic models of extreme mass ratio inspirals even for spins non-aligned
to the orbital angular momentum. To check the newly obtained fluxes, they were
compared with already known frequency domain results for equatorial orbits and
with results from a time domain Teukolsky equation solver called Teukode for
off-equatorial orbits. The spinning body framework of our work is based on the
Mathisson-Papapetrou-Dixon equations under the Tulczyjew-Dixon spin
supplementary condition.
| [
{
"created": "Wed, 29 Mar 2023 15:39:08 GMT",
"version": "v1"
}
] | 2023-03-30 | [
[
"Skoupý",
"Viktor",
""
],
[
"Lukes-Gerakopoulos",
"Georgios",
""
],
[
"Drummond",
"Lisa V.",
""
],
[
"Hughes",
"Scott A.",
""
]
] | This work provides gravitational wave energy and angular momentum asymptotic fluxes from a spinning body moving on generic orbits in a Kerr spacetime up to linear in spin approximation. To achieve this, we have developed a new frequency domain Teukolsky equation solver that calculates asymptotic amplitudes from generic orbits of spinning bodies with their spin aligned with the total orbital angular momentum. However, the energy and angular momentum fluxes from these orbits in the linear in spin approximation are appropriate for adiabatic models of extreme mass ratio inspirals even for spins non-aligned to the orbital angular momentum. To check the newly obtained fluxes, they were compared with already known frequency domain results for equatorial orbits and with results from a time domain Teukolsky equation solver called Teukode for off-equatorial orbits. The spinning body framework of our work is based on the Mathisson-Papapetrou-Dixon equations under the Tulczyjew-Dixon spin supplementary condition. |
2407.17568 | Erik Jensko | Erik Jensko | Spatial curvature in coincident gauge $f(Q)$ cosmology | 39 pages, 1 figure | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study the Friedmann-Lema\^{i}tre-Robertson-Walker cosmologies
with arbitrary spatial curvature for the symmetric teleparallel theories of
gravity, giving the first presentation of their coincident gauge form. Our
approach explicitly starts with the cosmological Killing vectors and constructs
the coincident gauge coordinates adapted to these Killing vectors. We then
obtain three distinct spatially flat branches and a single spatially curved
branch. Contrary to some previous claims, we show that all branches of
connection in the covariant approach can be studied in this gauge-fixed
formalism, which offers certain conceptual advantages. Interestingly, we find
that the flat and negative spatially curved solutions in $f(Q)$ gravity can be
seen as equivalent to the metric teleparallel $f(T)$ theories, demonstrating a
deeper connection between these theories. This is accomplished by studying the
connection equation of motion, which can be interpreted as a consistency
condition in the gauge-fixed approach. Finally, we discuss the role of
diffeomorphism invariance and local Lorentz invariance in these geometric
modifications of gravity.
| [
{
"created": "Wed, 24 Jul 2024 18:01:36 GMT",
"version": "v1"
}
] | 2024-07-26 | [
[
"Jensko",
"Erik",
""
]
] | In this work we study the Friedmann-Lema\^{i}tre-Robertson-Walker cosmologies with arbitrary spatial curvature for the symmetric teleparallel theories of gravity, giving the first presentation of their coincident gauge form. Our approach explicitly starts with the cosmological Killing vectors and constructs the coincident gauge coordinates adapted to these Killing vectors. We then obtain three distinct spatially flat branches and a single spatially curved branch. Contrary to some previous claims, we show that all branches of connection in the covariant approach can be studied in this gauge-fixed formalism, which offers certain conceptual advantages. Interestingly, we find that the flat and negative spatially curved solutions in $f(Q)$ gravity can be seen as equivalent to the metric teleparallel $f(T)$ theories, demonstrating a deeper connection between these theories. This is accomplished by studying the connection equation of motion, which can be interpreted as a consistency condition in the gauge-fixed approach. Finally, we discuss the role of diffeomorphism invariance and local Lorentz invariance in these geometric modifications of gravity. |
1907.05758 | Moorad Alexanian | Moorad Alexanian | Statistical Entropy of a Schwarzschild-anti-de Sitter Black Hole | null | Armenian Journal of Physics, 2019, vol. 12, issue 2, pp. 178-184 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the intrinsic entropy of a Schwarzschild black hole in an
asymptotically antide Sitter space. The statistical calculation of the entropy
is based on a model for particle structure that leads to confinement. The
constituents of the particle are distinguishable quasiparticles. The entropy
(temperature) is less (greater) than the entropy of a Schwarzschild black hole
in an asymptotically flat space. The equilibrium thermodynamic states are
described by pure states, myriotic fields, and the distinguishability of the
internal microstates may provide a solution to the black hole information
paradox by suggesting a Bose-Einstein condensate whereby the zero mass state is
a limit point (or accumulation point) of condensates on the event horizon.
| [
{
"created": "Fri, 12 Jul 2019 14:19:51 GMT",
"version": "v1"
}
] | 2019-07-15 | [
[
"Alexanian",
"Moorad",
""
]
] | We calculate the intrinsic entropy of a Schwarzschild black hole in an asymptotically antide Sitter space. The statistical calculation of the entropy is based on a model for particle structure that leads to confinement. The constituents of the particle are distinguishable quasiparticles. The entropy (temperature) is less (greater) than the entropy of a Schwarzschild black hole in an asymptotically flat space. The equilibrium thermodynamic states are described by pure states, myriotic fields, and the distinguishability of the internal microstates may provide a solution to the black hole information paradox by suggesting a Bose-Einstein condensate whereby the zero mass state is a limit point (or accumulation point) of condensates on the event horizon. |
2009.05747 | Tushar Kanti Dey | Tushar Kanti Dey and Surajit Sen | A Compendium on General Relativity for Undergraduate Students | 17 pages | Physics Education (IAPT), 36/1/8 , January - March 2020 | null | null | gr-qc physics.ed-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give a pedagogical introduction of the essential features of General
Theory of Relativity (GTR) in the format of an undergraduate (UG) project. A
set of simple MATHEMATICA code is developed which enables the UG students to
calculate the tensorial objects without prior knowledge of any package
operation. The orbit equations of light and material particle in Minkowski and
Schwarzschild spacetime are solved numerically to illustrate the crucial tests
of GTR.
| [
{
"created": "Sat, 12 Sep 2020 08:23:29 GMT",
"version": "v1"
}
] | 2020-09-15 | [
[
"Dey",
"Tushar Kanti",
""
],
[
"Sen",
"Surajit",
""
]
] | We give a pedagogical introduction of the essential features of General Theory of Relativity (GTR) in the format of an undergraduate (UG) project. A set of simple MATHEMATICA code is developed which enables the UG students to calculate the tensorial objects without prior knowledge of any package operation. The orbit equations of light and material particle in Minkowski and Schwarzschild spacetime are solved numerically to illustrate the crucial tests of GTR. |
1303.1528 | Kent Yagi | Kent Yagi and Nicolas Yunes | I-Love-Q Relations in Neutron Stars and their Applications to
Astrophysics, Gravitational Waves and Fundamental Physics | 29 pages, 16 figures; typos corrected | Phys. Rev. D 88, 023009 (2013) | 10.1103/PhysRevD.88.023009 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The exterior gravitational field of a slowly-rotating neutron star can be
characterized by its multipole moments, the first few being the neutron star
mass, moment of inertia, and quadrupole moment to quadratic order in spin. In
principle, all of these quantities depend on the neutron star's internal
structure, and thus, on unknown nuclear physics at supra-nuclear energy
densities. We here find relations between the moment of inertia, the Love
numbers and the quadrupole moment (I-Love-Q relations) that do not depend
sensitively on the neutron star's internal structure. Three important
consequences derive from these I-Love-Q relations. On an observational
astrophysics front, the measurement of a single member of the I-Love-Q trio
would automatically provide information about the other two, even when the
latter may not be observationally accessible. On a gravitational wave front,
the I-Love-Q relations break the degeneracy between the quadrupole moment and
the neutron-star spins in binary inspiral waveforms, allowing second-generation
ground-based detectors to determine the (dimensionless) averaged spin to
$\mathcal{O}(10)%$, given a sufficiently large signal-to-noise ratio detection.
On a fundamental physics front, the I-Love-Q relations allow for tests of
General Relativity in the neutron-star strong-field that are both theory- and
internal structure-independent. As an example, by combining gravitational-wave
and electromagnetic observations, one may constrain dynamical Chern-Simons
gravity in the future by more than 6 orders of magnitude more stringently than
Solar System and table-top constraints.
| [
{
"created": "Wed, 6 Mar 2013 21:00:03 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Sep 2013 03:46:03 GMT",
"version": "v2"
},
{
"created": "Thu, 30 Nov 2017 16:53:50 GMT",
"version": "v3"
}
] | 2017-12-01 | [
[
"Yagi",
"Kent",
""
],
[
"Yunes",
"Nicolas",
""
]
] | The exterior gravitational field of a slowly-rotating neutron star can be characterized by its multipole moments, the first few being the neutron star mass, moment of inertia, and quadrupole moment to quadratic order in spin. In principle, all of these quantities depend on the neutron star's internal structure, and thus, on unknown nuclear physics at supra-nuclear energy densities. We here find relations between the moment of inertia, the Love numbers and the quadrupole moment (I-Love-Q relations) that do not depend sensitively on the neutron star's internal structure. Three important consequences derive from these I-Love-Q relations. On an observational astrophysics front, the measurement of a single member of the I-Love-Q trio would automatically provide information about the other two, even when the latter may not be observationally accessible. On a gravitational wave front, the I-Love-Q relations break the degeneracy between the quadrupole moment and the neutron-star spins in binary inspiral waveforms, allowing second-generation ground-based detectors to determine the (dimensionless) averaged spin to $\mathcal{O}(10)%$, given a sufficiently large signal-to-noise ratio detection. On a fundamental physics front, the I-Love-Q relations allow for tests of General Relativity in the neutron-star strong-field that are both theory- and internal structure-independent. As an example, by combining gravitational-wave and electromagnetic observations, one may constrain dynamical Chern-Simons gravity in the future by more than 6 orders of magnitude more stringently than Solar System and table-top constraints. |
gr-qc/0608060 | Farrukh Fattoyev Jabborovich | B. J. Ahmedov, M. J. Ermamatov | Electrical Conductivity in General Relativity | 16 pages, 1 figure | Phys.Lett. 15 (2002) 137-151 | null | null | gr-qc astro-ph cond-mat.other | null | The general relativistic kinetic theory including the effect of a stationary
gravitational field is applied to the electromagnetic transport processes in
conductors. Then it is applied to derive the general relativistic Ohm's law
where the gravitomagnetic terms are incorporated. The total electric charge
quantity and charge distribution inside conductors carrying conduction current
in some relativistic cases are considered. The general relativistic Ohm's law
is applied to predict new gravitomagnetic and gyroscopic effects which can, in
principle, be used to detect the Lense-Thirring and rotational fields.
| [
{
"created": "Fri, 11 Aug 2006 16:53:50 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ahmedov",
"B. J.",
""
],
[
"Ermamatov",
"M. J.",
""
]
] | The general relativistic kinetic theory including the effect of a stationary gravitational field is applied to the electromagnetic transport processes in conductors. Then it is applied to derive the general relativistic Ohm's law where the gravitomagnetic terms are incorporated. The total electric charge quantity and charge distribution inside conductors carrying conduction current in some relativistic cases are considered. The general relativistic Ohm's law is applied to predict new gravitomagnetic and gyroscopic effects which can, in principle, be used to detect the Lense-Thirring and rotational fields. |
1609.00397 | Orr Sela | Orr Sela | Late-time decay of coupled electromagnetic and gravitational
perturbations outside an extremal charged black hole | 12 pages. Corrected typos | Phys. Rev. D 94, 084006 (2016) | 10.1103/PhysRevD.94.084006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we employ the results of a previous paper on the late-time
decay of scalar-field perturbations of an extreme Reissner-Nordstrom black
hole, in order to find the late-time decay of coupled electromagnetic and
gravitational perturbations of this black hole. We explicitly write the
late-time tails of Moncrief's gauge invariant variables and of the
perturbations of the metric tensor and the electromagnetic field tensor in the
Regge-Wheeler gauge. We discuss some of the consequences of the results and
relations to previous works.
| [
{
"created": "Thu, 1 Sep 2016 20:27:06 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Oct 2016 09:21:05 GMT",
"version": "v2"
}
] | 2016-10-14 | [
[
"Sela",
"Orr",
""
]
] | In this paper we employ the results of a previous paper on the late-time decay of scalar-field perturbations of an extreme Reissner-Nordstrom black hole, in order to find the late-time decay of coupled electromagnetic and gravitational perturbations of this black hole. We explicitly write the late-time tails of Moncrief's gauge invariant variables and of the perturbations of the metric tensor and the electromagnetic field tensor in the Regge-Wheeler gauge. We discuss some of the consequences of the results and relations to previous works. |
1402.5656 | Christian Kr\"uger | C. J. Kr\"uger, W. C. G. Ho, N. Andersson | Seismology of adolescent neutron stars: Accounting for thermal effects
and crust elasticity | 27 pages, 14 figures | Phys. Rev. D 92, 063009 (2015) | 10.1103/PhysRevD.92.063009 | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the oscillations of relativistic stars, incorporating key physics
associated with internal composition, thermal gradients and crust elasticity.
Our aim is to develop a formalism which is able to account for the
state-of-the-art understanding of the complex physics associated with these
systems. As a first step, we build models using a modern equation of state
including composition gradients and density discontinuities associated with
internal phase-transitions (like the crust-core transition and the point where
muons first appear in the core). In order to understand the nature of the
oscillation spectrum, we carry out cooling simulations to provide realistic
snapshots of the temperature distribution in the interior as the star evolves
through adolescence. The associated thermal pressure is incorporated in the
perturbation analysis, and we discuss the presence of $g$-modes arising as a
result of thermal effects. We also consider interface modes due to
phase-transitions and the gradual formation of the star's crust and the
emergence of a set of shear modes.
| [
{
"created": "Sun, 23 Feb 2014 19:32:59 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Aug 2014 12:23:17 GMT",
"version": "v2"
}
] | 2015-09-16 | [
[
"Krüger",
"C. J.",
""
],
[
"Ho",
"W. C. G.",
""
],
[
"Andersson",
"N.",
""
]
] | We study the oscillations of relativistic stars, incorporating key physics associated with internal composition, thermal gradients and crust elasticity. Our aim is to develop a formalism which is able to account for the state-of-the-art understanding of the complex physics associated with these systems. As a first step, we build models using a modern equation of state including composition gradients and density discontinuities associated with internal phase-transitions (like the crust-core transition and the point where muons first appear in the core). In order to understand the nature of the oscillation spectrum, we carry out cooling simulations to provide realistic snapshots of the temperature distribution in the interior as the star evolves through adolescence. The associated thermal pressure is incorporated in the perturbation analysis, and we discuss the presence of $g$-modes arising as a result of thermal effects. We also consider interface modes due to phase-transitions and the gradual formation of the star's crust and the emergence of a set of shear modes. |
2307.10399 | Kazuharu Bamba | Kazuharu Bamba, M. Z. Bhatti, Z. Yousaf, Z. Shoukat | Gravitational decoupling of anisotropic stars in the Brans-Dicke theory | 15 pages, 5 figures, version accepted for publication in the European
Physical Journal C | null | null | FU-PCG-120 | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Anisotropic spherically symmetric solutions within the framework of the
Brans-Dicke theory are uncovered through a unique gravitational decoupling
approach involving a minimal geometric transformation. This transformation
effectively divides the Einstein field equations into two separate systems,
resulting in the alteration of the radial metric component. The first system
encompasses the influence of the seed source, derived from the metric functions
of the isotropic Tolman IV solution. Meanwhile, the anisotropic source is
subjected to two specific constraints in order to address the second system. By
employing matching conditions to determine the unknown constants at the
boundary of the stellar object, a comprehensive examination of the internal
structure of stellar systems ensues. This investigation delves into the impact
of the decoupling parameter, the Brans-Dicke parameters, and a scalar field on
the structural characteristics of anisotropic spherically symmetric spacetimes,
all while considering the strong energy conditions.
| [
{
"created": "Tue, 18 Jul 2023 04:44:04 GMT",
"version": "v1"
},
{
"created": "Tue, 31 Oct 2023 09:41:47 GMT",
"version": "v2"
}
] | 2023-11-01 | [
[
"Bamba",
"Kazuharu",
""
],
[
"Bhatti",
"M. Z.",
""
],
[
"Yousaf",
"Z.",
""
],
[
"Shoukat",
"Z.",
""
]
] | Anisotropic spherically symmetric solutions within the framework of the Brans-Dicke theory are uncovered through a unique gravitational decoupling approach involving a minimal geometric transformation. This transformation effectively divides the Einstein field equations into two separate systems, resulting in the alteration of the radial metric component. The first system encompasses the influence of the seed source, derived from the metric functions of the isotropic Tolman IV solution. Meanwhile, the anisotropic source is subjected to two specific constraints in order to address the second system. By employing matching conditions to determine the unknown constants at the boundary of the stellar object, a comprehensive examination of the internal structure of stellar systems ensues. This investigation delves into the impact of the decoupling parameter, the Brans-Dicke parameters, and a scalar field on the structural characteristics of anisotropic spherically symmetric spacetimes, all while considering the strong energy conditions. |
2012.12032 | Liliane Biskupek | Liliane Biskupek, J\"urgen M\"uller and Jean-Marie Torre | Benefit of New High-Precision LLR Data for the Determination of
Relativistic Parameters | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Since 1969, Lunar Laser Ranging (LLR) data have been collected by various
observatories and analysed by different analysis groups. In the recent years,
observations with bigger telescopes (APOLLO) and at infra-red wavelength (OCA)
are carried out, resulting in a better distribution of precise LLR data over
the lunar orbit and the observed retro-reflectors on the Moon. This is a great
advantage for various investigations in the LLR analysis. The aim of this study
is to evaluate the benefit of the new LLR data for the determination of
relativistic parameters. Here we show current results for relativistic
parameters like a possible temporal variation of the gravitational constant
$\dot{G}/G_0 = (-5.0 \pm 9.6) \times 10^{-15} \, \mathrm{yr}^{-1}$, the
equivalence principle with $\Delta\left(m_g/m_i\right)_{\mathrm{EM}} = (-2.1
\pm 2.4)\times10^{-14}$ and the PPN parameters $\beta-1 = (6.2 \pm 7.2) \times
10^{-5}$ and $\gamma-1 = (1.7 \pm 1.6) \times 10^{-4}$. The results show a
significant improvement in the accuracy of the various parameters, mainly due
to better coverage of the lunar orbit, better distribution of measurements over
the lunar retro-reflectors, and last but not least, higher accuracy of the
data. Within the estimated accuracies, no violation of Einstein's theory is
found and the results set improved limits for the different effects.
| [
{
"created": "Tue, 22 Dec 2020 14:19:30 GMT",
"version": "v1"
}
] | 2020-12-23 | [
[
"Biskupek",
"Liliane",
""
],
[
"Müller",
"Jürgen",
""
],
[
"Torre",
"Jean-Marie",
""
]
] | Since 1969, Lunar Laser Ranging (LLR) data have been collected by various observatories and analysed by different analysis groups. In the recent years, observations with bigger telescopes (APOLLO) and at infra-red wavelength (OCA) are carried out, resulting in a better distribution of precise LLR data over the lunar orbit and the observed retro-reflectors on the Moon. This is a great advantage for various investigations in the LLR analysis. The aim of this study is to evaluate the benefit of the new LLR data for the determination of relativistic parameters. Here we show current results for relativistic parameters like a possible temporal variation of the gravitational constant $\dot{G}/G_0 = (-5.0 \pm 9.6) \times 10^{-15} \, \mathrm{yr}^{-1}$, the equivalence principle with $\Delta\left(m_g/m_i\right)_{\mathrm{EM}} = (-2.1 \pm 2.4)\times10^{-14}$ and the PPN parameters $\beta-1 = (6.2 \pm 7.2) \times 10^{-5}$ and $\gamma-1 = (1.7 \pm 1.6) \times 10^{-4}$. The results show a significant improvement in the accuracy of the various parameters, mainly due to better coverage of the lunar orbit, better distribution of measurements over the lunar retro-reflectors, and last but not least, higher accuracy of the data. Within the estimated accuracies, no violation of Einstein's theory is found and the results set improved limits for the different effects. |
1902.05530 | Vladimir Dergachev Ph.D. | Vladimir Dergachev, Maria Alessandra Papa | Sensitivity improvements in the search for periodic gravitational waves
using O1 LIGO data | Updated paper title | Phys. Rev. Lett. 123, 101101 (2019) | 10.1103/PhysRevLett.123.101101 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We demonstrate a breakthrough in the capabilities of robust, broad-parameter
space searches for continuous gravitational waves. With a large scale search
for continuous gravitational waves on the O1 LIGO data, we prove that our
Falcon search achieves the sensitivity improvements expected from the use of a
long coherence length, while maintaining the computational expense within
manageable bounds. On this data we set the most constraining upper limits in
the gravitational wave amplitude in the band 100-200 Hz. We provide full
outlier lists and upper limits near 0-spindown band suitable for analysis of
signals with small spindown such as boson condensates around black holes.
| [
{
"created": "Thu, 14 Feb 2019 18:13:19 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Apr 2019 20:56:28 GMT",
"version": "v2"
},
{
"created": "Thu, 30 May 2019 20:05:14 GMT",
"version": "v3"
},
{
"created": "Thu, 19 Sep 2019 19:20:27 GMT",
"version": "v4"
}
] | 2019-09-23 | [
[
"Dergachev",
"Vladimir",
""
],
[
"Papa",
"Maria Alessandra",
""
]
] | We demonstrate a breakthrough in the capabilities of robust, broad-parameter space searches for continuous gravitational waves. With a large scale search for continuous gravitational waves on the O1 LIGO data, we prove that our Falcon search achieves the sensitivity improvements expected from the use of a long coherence length, while maintaining the computational expense within manageable bounds. On this data we set the most constraining upper limits in the gravitational wave amplitude in the band 100-200 Hz. We provide full outlier lists and upper limits near 0-spindown band suitable for analysis of signals with small spindown such as boson condensates around black holes. |
1105.6193 | Salvatore Capozziello | S. Capozziello, G. Basini, M. De Laurentis | Deriving the mass of particles from Extended Theories of Gravity in LHC
era | 30 pages, 1 figure | null | 10.1140/epjc/s10052-011-1679-1 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive a geometrical approach to produce the mass of particles that could
be suitably tested at LHC. Starting from a 5D unification scheme, we show that
all the known interactions could be suitably deduced as an induced symmetry
breaking of the non-unitary GL(4)-group of diffeomorphisms. The deformations
inducing such a breaking act as vector bosons that, depending on the
gravitational mass states, can assume the role of interaction bosons like
gluons, electroweak bosons or photon. The further gravitational degrees of
freedom, emerging from the reduction mechanism in 4D, eliminate the hierarchy
problem since generate a cut-off comparable with electroweak one at TeV scales.
In this "economic" scheme, gravity should induce the other interactions in a
non-perturbative way.
| [
{
"created": "Tue, 31 May 2011 07:56:29 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Capozziello",
"S.",
""
],
[
"Basini",
"G.",
""
],
[
"De Laurentis",
"M.",
""
]
] | We derive a geometrical approach to produce the mass of particles that could be suitably tested at LHC. Starting from a 5D unification scheme, we show that all the known interactions could be suitably deduced as an induced symmetry breaking of the non-unitary GL(4)-group of diffeomorphisms. The deformations inducing such a breaking act as vector bosons that, depending on the gravitational mass states, can assume the role of interaction bosons like gluons, electroweak bosons or photon. The further gravitational degrees of freedom, emerging from the reduction mechanism in 4D, eliminate the hierarchy problem since generate a cut-off comparable with electroweak one at TeV scales. In this "economic" scheme, gravity should induce the other interactions in a non-perturbative way. |
1506.02858 | Matthew Wright | Matthew Wright | Buchdahl type inequalities in $d$-dimensions | 23 pages. To appear in Classical and Quantum Gravity. Matches
published version. Typos fixed, section added discussing saturation of bounds | Class. Quantum Grav. 32 (2015) 215005 | 10.1088/0264-9381/32/21/215005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spherically symmetric anisotropic static compact solutions to the Einstein
equations in dimension $d\geq4$ are considered. Various matter models are
examined and upper bounds on the ratio of the gravitational mass to the radius
in these different models are obtained. Bounds are also generalised in the
presence of a non-zero charge and a positive cosmological constant. These
bounds are then used to find the maximum of the gravitational redshift at the
surface of the object.
| [
{
"created": "Tue, 9 Jun 2015 10:48:34 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Jun 2015 16:44:09 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Sep 2015 09:22:55 GMT",
"version": "v3"
}
] | 2015-10-09 | [
[
"Wright",
"Matthew",
""
]
] | Spherically symmetric anisotropic static compact solutions to the Einstein equations in dimension $d\geq4$ are considered. Various matter models are examined and upper bounds on the ratio of the gravitational mass to the radius in these different models are obtained. Bounds are also generalised in the presence of a non-zero charge and a positive cosmological constant. These bounds are then used to find the maximum of the gravitational redshift at the surface of the object. |
gr-qc/9910082 | Daniel Cartin | Daniel Cartin | Linearized general relativity and the Lanczos potential | 5 pages, LaTeX 2e | null | null | CGPG 99/10-4 | gr-qc hep-th | null | Recently, there has been a revival of interest in the Lanczos potential of
the Weyl conformal tensor. Previous work by Novello and Neto has been done with
the linearized Lanczos potential as a model of a spin-2 field, which depends on
a massless limit of the field. In this paper, we look at an action based on a
massless potential, and show that it is classically equivalent to the
linearized regime of general relativity, without reference to a massless limit.
| [
{
"created": "Mon, 25 Oct 1999 15:22:46 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Cartin",
"Daniel",
""
]
] | Recently, there has been a revival of interest in the Lanczos potential of the Weyl conformal tensor. Previous work by Novello and Neto has been done with the linearized Lanczos potential as a model of a spin-2 field, which depends on a massless limit of the field. In this paper, we look at an action based on a massless potential, and show that it is classically equivalent to the linearized regime of general relativity, without reference to a massless limit. |
2212.06448 | Orlando Luongo | Alessio Belfiglio, Orlando Luongo, Stefano Mancini | Inflationary entanglement | 16 pages, 5 figures | Phys. Rev. D, 107, 103512 (2023) | 10.1103/PhysRevD.107.103512 | null | gr-qc astro-ph.CO hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the entanglement due to geometric corrections in particle
creation during inflation. To do so, we propose a single-field inflationary
scenario, nonminimally coupled to the scalar curvature of spacetime. We require
particle production to be purely geometric, setting to zero the Bogolubov
coefficients and computing the $S$ matrix associated to spacetime
perturbations, which are traced back to inflaton fluctuations. The
corresponding particle density leads to a nonzero entanglement entropy whose
effects are investigated at primordial time of Universe evolution. The
possibility of modeling our particle candidate in terms of dark matter is
discussed. The classical back-reaction of inhomogeneities on the homogeneous
dynamical background degrees of freedom is also studied and quantified in the
slow-roll regime.
| [
{
"created": "Tue, 13 Dec 2022 09:36:54 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Jun 2023 16:39:21 GMT",
"version": "v2"
}
] | 2023-06-05 | [
[
"Belfiglio",
"Alessio",
""
],
[
"Luongo",
"Orlando",
""
],
[
"Mancini",
"Stefano",
""
]
] | We investigate the entanglement due to geometric corrections in particle creation during inflation. To do so, we propose a single-field inflationary scenario, nonminimally coupled to the scalar curvature of spacetime. We require particle production to be purely geometric, setting to zero the Bogolubov coefficients and computing the $S$ matrix associated to spacetime perturbations, which are traced back to inflaton fluctuations. The corresponding particle density leads to a nonzero entanglement entropy whose effects are investigated at primordial time of Universe evolution. The possibility of modeling our particle candidate in terms of dark matter is discussed. The classical back-reaction of inhomogeneities on the homogeneous dynamical background degrees of freedom is also studied and quantified in the slow-roll regime. |
gr-qc/0608114 | Louis Rubbo | Louis J. Rubbo | When is Enough Good Enough in Gravitational Wave Source Modeling? | 7 pages, 2 figures, proceedings paper for the Sixth International
LISA Symposium | null | 10.1063/1.2405106 | null | gr-qc | null | A typical approach to developing an analysis algorithm for analyzing
gravitational wave data is to assume a particular waveform and use its
characteristics to formulate a detection criteria. Once a detection has been
made, the algorithm uses those same characteristics to tease out parameter
estimates from a given data set. While an obvious starting point, such an
approach is initiated by assuming a single, correct model for the waveform
regardless of the signal strength, observation length, noise, etc. This paper
introduces the method of Bayesian model selection as a way to select the most
plausible waveform model from a set of models given the data and prior
information. The discussion is done in the scientific context for the proposed
Laser Interferometer Space Antenna.
| [
{
"created": "Mon, 28 Aug 2006 17:15:35 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Rubbo",
"Louis J.",
""
]
] | A typical approach to developing an analysis algorithm for analyzing gravitational wave data is to assume a particular waveform and use its characteristics to formulate a detection criteria. Once a detection has been made, the algorithm uses those same characteristics to tease out parameter estimates from a given data set. While an obvious starting point, such an approach is initiated by assuming a single, correct model for the waveform regardless of the signal strength, observation length, noise, etc. This paper introduces the method of Bayesian model selection as a way to select the most plausible waveform model from a set of models given the data and prior information. The discussion is done in the scientific context for the proposed Laser Interferometer Space Antenna. |
gr-qc/0005114 | Tomohiro Harada | Tomohiro Harada (Waseda U.), Hideo Iguchi (Osaka U.), and Ken-ichi
Nakao (Osaka City U.) | Power, energy, and spectrum of a naked singularity explosion | 34 pages, 13 postscript figures included, to appear in Phys. Rev. D,
grammatical errors corrected | Phys.Rev. D62 (2000) 084037 | 10.1103/PhysRevD.62.084037 | WU-AP/98/00, OU-TAP 137, OCU-PHYS-174 | gr-qc astro-ph hep-th quant-ph | null | Naked singularity occurs in the gravitational collapse of an inhomogeneous
dust ball from an initial density profile which is physically reasonable. We
show that explosive radiation is emitted during the formation process of the
naked singularity. The energy flux is proportional to $(t_{\rm CH}-t)^{-3/2}$
for a minimally coupled massless scalar field, while is proportional to
$(t_{\rm CH}-t)^{-1}$ for a conformally coupled massless scalar field, where
$t_{\rm CH}-t$ is the `remained time' until the distant observer could observe
the singularity if the naked singularity was formed. As a consequence, the
radiated energy grows unboundedly for both scalar fields. The amount of the
power and the energy depends on parameters which characterize the initial
density profile but do not depend on the gravitational mass of the cloud. In
particular, there is characteristic frequency $\nu_{s}$ of singularity above
which the divergent energy is radiated. The energy flux is dominated by
particles of which the wave length is about $t_{\rm CH}-t$ at each moment. The
observed total spectrum is nonthermal, i.e., $\nu dN/d\nu \sim
(\nu/\nu_{s})^{-1}$ for $\nu>\nu_{s}$. If the naked singularity formation could
continue until a considerable fraction of the total energy of the dust cloud is
radiated, the radiated energy would reach about $10^{54}(M/M_{\odot})$ erg. The
calculations are based on the geometrical optics approximation which turns out
to be consistent as a rough order estimate. The analysis does not depend on
whether or not the naked singularity occurs in its exact meaning. This
phenomenon may provide a new candidate for a source of ultra high energy cosmic
rays or a central engine of gamma ray bursts.
| [
{
"created": "Thu, 25 May 2000 06:32:29 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jul 2000 10:26:28 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Harada",
"Tomohiro",
"",
"Waseda U."
],
[
"Iguchi",
"Hideo",
"",
"Osaka U."
],
[
"Nakao",
"Ken-ichi",
"",
"Osaka City U."
]
] | Naked singularity occurs in the gravitational collapse of an inhomogeneous dust ball from an initial density profile which is physically reasonable. We show that explosive radiation is emitted during the formation process of the naked singularity. The energy flux is proportional to $(t_{\rm CH}-t)^{-3/2}$ for a minimally coupled massless scalar field, while is proportional to $(t_{\rm CH}-t)^{-1}$ for a conformally coupled massless scalar field, where $t_{\rm CH}-t$ is the `remained time' until the distant observer could observe the singularity if the naked singularity was formed. As a consequence, the radiated energy grows unboundedly for both scalar fields. The amount of the power and the energy depends on parameters which characterize the initial density profile but do not depend on the gravitational mass of the cloud. In particular, there is characteristic frequency $\nu_{s}$ of singularity above which the divergent energy is radiated. The energy flux is dominated by particles of which the wave length is about $t_{\rm CH}-t$ at each moment. The observed total spectrum is nonthermal, i.e., $\nu dN/d\nu \sim (\nu/\nu_{s})^{-1}$ for $\nu>\nu_{s}$. If the naked singularity formation could continue until a considerable fraction of the total energy of the dust cloud is radiated, the radiated energy would reach about $10^{54}(M/M_{\odot})$ erg. The calculations are based on the geometrical optics approximation which turns out to be consistent as a rough order estimate. The analysis does not depend on whether or not the naked singularity occurs in its exact meaning. This phenomenon may provide a new candidate for a source of ultra high energy cosmic rays or a central engine of gamma ray bursts. |
2107.14618 | Mohamed Ibrahim Nouh | A. S. Saad, M. I. Nouh, A. A. Shaker and T. M. Kamel | Stability Analysis of Relativistic Polytropes | 24 pages, 6 figures | null | 10.22201/ia.01851101p.2021.57.02.13 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | A main question in astrophysics and cosmology has been the severe stability
of the astrophysical objects, whether a particular equilibrium configuration is
stable. In this article, we study the relativistic self-gravitating,
hydrostatic spheres with a polytropic equation of state , considering
structures with the polytropic indices and illustrates the results for the
relativistic parameters . We determined the critical relativistic parameter at
which the mass of the polytrope has a maximum value and represents the first
mode of radial instability. For n=1 (0.5)-2.5, stable relativistic polytropes
occur for less than the critical values 0.42, 0.20, 0.10, and 0.04
respectively, while unstable relativistic polytropes are obtained when the
relativistic parameter is greater than the same values. When n=3.0 and,
energetically unstable solutions have occurred. The results of critical values
obtained in this paper for different polytropic indices are in full agreement
with those evaluated by several authors. Comparisons between analytical and
numerical solutions of the given relativistic functions provide a maximum
relative error of order.
| [
{
"created": "Thu, 29 Jul 2021 04:09:11 GMT",
"version": "v1"
}
] | 2022-03-23 | [
[
"Saad",
"A. S.",
""
],
[
"Nouh",
"M. I.",
""
],
[
"Shaker",
"A. A.",
""
],
[
"Kamel",
"T. M.",
""
]
] | A main question in astrophysics and cosmology has been the severe stability of the astrophysical objects, whether a particular equilibrium configuration is stable. In this article, we study the relativistic self-gravitating, hydrostatic spheres with a polytropic equation of state , considering structures with the polytropic indices and illustrates the results for the relativistic parameters . We determined the critical relativistic parameter at which the mass of the polytrope has a maximum value and represents the first mode of radial instability. For n=1 (0.5)-2.5, stable relativistic polytropes occur for less than the critical values 0.42, 0.20, 0.10, and 0.04 respectively, while unstable relativistic polytropes are obtained when the relativistic parameter is greater than the same values. When n=3.0 and, energetically unstable solutions have occurred. The results of critical values obtained in this paper for different polytropic indices are in full agreement with those evaluated by several authors. Comparisons between analytical and numerical solutions of the given relativistic functions provide a maximum relative error of order. |
2309.04991 | Sayantan Dey | Sayantan Dey | Stability analysis for a cosmologically viable model of $f(R)$ gravity | 9 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In recent times, there has been an increasing interest with theories of
modified gravity as a means to gain a deeper understanding of the universe's
late-time acceleration phase. In this study we focused our attention on a
specific cosmologically viable $f(R)$ model. We performed a dynamic stability
analysis of this model, revealing that the model supports presence of just one
asymptotically stable solution which can explain the present-day acceleration
of the universe.
| [
{
"created": "Sun, 10 Sep 2023 10:53:51 GMT",
"version": "v1"
}
] | 2023-09-12 | [
[
"Dey",
"Sayantan",
""
]
] | In recent times, there has been an increasing interest with theories of modified gravity as a means to gain a deeper understanding of the universe's late-time acceleration phase. In this study we focused our attention on a specific cosmologically viable $f(R)$ model. We performed a dynamic stability analysis of this model, revealing that the model supports presence of just one asymptotically stable solution which can explain the present-day acceleration of the universe. |
1611.09970 | Hernando Quevedo | Christine Gruber and Hernando Quevedo | Geometrothermodynamic model for the evolution of the Universe | 5 latex pages | JCAP 07 (2017) 032 | 10.1088/1475-7516/2017/07/032 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the formalism of geometrothermodynamics to derive a fundamental
thermodynamic equation, we construct a cosmological model in the framework of
relativistic cosmology. In a first step, we describe a system without
thermodynamic interaction, and show it to be equivalent to the standard
$\Lambda$CDM paradigm. The second step includes thermodynamic interaction and
produces a model consistent with the main features of inflation. With the
proposed fundamental equation we are thus able to describe all the known epochs
in the evolution of our Universe, starting from the inflationary phase.
| [
{
"created": "Wed, 30 Nov 2016 02:06:56 GMT",
"version": "v1"
}
] | 2017-08-25 | [
[
"Gruber",
"Christine",
""
],
[
"Quevedo",
"Hernando",
""
]
] | Using the formalism of geometrothermodynamics to derive a fundamental thermodynamic equation, we construct a cosmological model in the framework of relativistic cosmology. In a first step, we describe a system without thermodynamic interaction, and show it to be equivalent to the standard $\Lambda$CDM paradigm. The second step includes thermodynamic interaction and produces a model consistent with the main features of inflation. With the proposed fundamental equation we are thus able to describe all the known epochs in the evolution of our Universe, starting from the inflationary phase. |
gr-qc/0305076 | Pascual-Sanchez J.-F. | J.-F. Pascual-S\'anchez, A. San Miguel, F. Vicente (Univ. de
Valladolid) | Isotropy of the velocity of light and the Sagnac effect | LaTeX, 13 pages, 3 eps figures; typos corrected, added references,
minor changes; to appear in "Relativity in Rotating Frames", ed. G. Rizzi G.
and M.L. Ruggiero, Kluwer Academic Publishers, Dordrecht (2003) | null | null | null | gr-qc physics.class-ph | null | In this paper, it is shown, using a geometrical approach, the isotropy of the
velocity of light measured in a rotating frame in Minkowski space-time, and it
is verified that this result is compatible with the Sagnac effect. Furthermore,
we find that this problem can be reduced to the solution of geodesic triangles
in a Minkowskian cylinder. A relationship between the problems established on
the cylinder and on the Minkowskian plane is obtained through a local isometry.
| [
{
"created": "Tue, 20 May 2003 12:42:51 GMT",
"version": "v1"
},
{
"created": "Thu, 22 May 2003 12:17:38 GMT",
"version": "v2"
},
{
"created": "Thu, 5 Jun 2003 12:35:00 GMT",
"version": "v3"
},
{
"created": "Tue, 10 Jun 2003 12:38:40 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Pascual-Sánchez",
"J. -F.",
"",
"Univ. de\n Valladolid"
],
[
"Miguel",
"A. San",
"",
"Univ. de\n Valladolid"
],
[
"Vicente",
"F.",
"",
"Univ. de\n Valladolid"
]
] | In this paper, it is shown, using a geometrical approach, the isotropy of the velocity of light measured in a rotating frame in Minkowski space-time, and it is verified that this result is compatible with the Sagnac effect. Furthermore, we find that this problem can be reduced to the solution of geodesic triangles in a Minkowskian cylinder. A relationship between the problems established on the cylinder and on the Minkowskian plane is obtained through a local isometry. |
2106.16114 | Sarbari Guha Dr. | Samarjit Chakraborty, Sarbari Guha, Rituparno Goswami | How appropriate are the gravitational entropy proposals for traversable
wormholes? | 29 pages, 38 figures | General Relativity and Gravitation (2022) | 10.1007/s10714-022-02934-3 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper we have examined the validity of some proposed definitions of
gravitational entropy (GE) in the context of traversable wormhole solutions of
the Einstein field equations. Here we have adopted two different proposals of
GE and checked for their applicability in the case of these wormholes. The
first one is the phenomenological approach proposed by Rudjord et al
\cite{entropy1} and expanded by Romero et al in \cite{entropy2}, which is a
purely geometric method of measuring gravitational entropy. The latter one is
the Clifton-Ellis-Tavakol (CET) proposal \cite{CET} for the gravitational
entropy which arises in relativistic thermodynamics and is based on the
Bel-Robinson tensor, which represents the effective super-energy-momentum
tensor of free gravitational fields. Considering some of the Lorentzian
traversable wormholes along with the Brill solution for NUT wormholes and the
AdS wormholes, we have evaluated the gravitational entropy for these systems.
Incidentally, the application of the CET proposal can provide unique
gravitational entropies for spacetimes of Petrov type D and N only, whereas the
geometric method can be applied to almost every kind of spacetime, although it
has no relation with thermodynamics. For any traversable wormhole to be
physically realistic, it should have a viable GE. We found that the GE
proposals do give us a consistent measure of GE in several of them. This means
that the existence of a viable gravitational entropy strictly depends on its
definition.
| [
{
"created": "Wed, 30 Jun 2021 15:10:49 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Mar 2022 18:45:56 GMT",
"version": "v2"
}
] | 2022-06-01 | [
[
"Chakraborty",
"Samarjit",
""
],
[
"Guha",
"Sarbari",
""
],
[
"Goswami",
"Rituparno",
""
]
] | In this paper we have examined the validity of some proposed definitions of gravitational entropy (GE) in the context of traversable wormhole solutions of the Einstein field equations. Here we have adopted two different proposals of GE and checked for their applicability in the case of these wormholes. The first one is the phenomenological approach proposed by Rudjord et al \cite{entropy1} and expanded by Romero et al in \cite{entropy2}, which is a purely geometric method of measuring gravitational entropy. The latter one is the Clifton-Ellis-Tavakol (CET) proposal \cite{CET} for the gravitational entropy which arises in relativistic thermodynamics and is based on the Bel-Robinson tensor, which represents the effective super-energy-momentum tensor of free gravitational fields. Considering some of the Lorentzian traversable wormholes along with the Brill solution for NUT wormholes and the AdS wormholes, we have evaluated the gravitational entropy for these systems. Incidentally, the application of the CET proposal can provide unique gravitational entropies for spacetimes of Petrov type D and N only, whereas the geometric method can be applied to almost every kind of spacetime, although it has no relation with thermodynamics. For any traversable wormhole to be physically realistic, it should have a viable GE. We found that the GE proposals do give us a consistent measure of GE in several of them. This means that the existence of a viable gravitational entropy strictly depends on its definition. |
1404.1750 | Carlo Rovelli | Seramika Ariwahjoedi, Jusak Sali Kosasih, Carlo Rovelli, Freddy P. Zen | How many quanta are there in a quantum spacetime? | 16 pages, 9 figures | null | 10.1088/0264-9381/32/16/165019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following earlier insights by Livine and Terno, we develop a technique for
describing quantum states of the gravitational field in terms of coarse grained
spin networks. We show that the number of nodes and links and the values of the
spin depend on the observables chosen for the description of the state. Hence
the question in the title of this paper is ill posed, unless further
information about what is been measured is given.
| [
{
"created": "Mon, 7 Apr 2014 11:28:37 GMT",
"version": "v1"
}
] | 2015-08-26 | [
[
"Ariwahjoedi",
"Seramika",
""
],
[
"Kosasih",
"Jusak Sali",
""
],
[
"Rovelli",
"Carlo",
""
],
[
"Zen",
"Freddy P.",
""
]
] | Following earlier insights by Livine and Terno, we develop a technique for describing quantum states of the gravitational field in terms of coarse grained spin networks. We show that the number of nodes and links and the values of the spin depend on the observables chosen for the description of the state. Hence the question in the title of this paper is ill posed, unless further information about what is been measured is given. |
gr-qc/0508096 | R\'ejean J. Dupuis | R\'ejean J. Dupuis and Graham Woan | Bayesian estimation of pulsar parameters from gravitational wave data | 9 pages, 6 figures. Accepted to Phys. Rev. D. A few small changes
from previous version | Phys.Rev. D72 (2005) 102002 | 10.1103/PhysRevD.72.102002 | null | gr-qc astro-ph | null | We present a method of searching for, and parameterizing, signals from known
radio pulsars in data from interferometric gravitational wave detectors. This
method has been applied to data from the LIGO and GEO 600 detectors to set
upper limits on the gravitational wave emission from several radio pulsars.
Here we discuss the nature of the signal and the performance of the technique
on simulated data. We show how to perform a coherent multiple detector analysis
and give some insight in the covariance between the signal parameters.
| [
{
"created": "Tue, 23 Aug 2005 15:07:42 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Oct 2005 19:06:23 GMT",
"version": "v2"
}
] | 2013-05-29 | [
[
"Dupuis",
"Réjean J.",
""
],
[
"Woan",
"Graham",
""
]
] | We present a method of searching for, and parameterizing, signals from known radio pulsars in data from interferometric gravitational wave detectors. This method has been applied to data from the LIGO and GEO 600 detectors to set upper limits on the gravitational wave emission from several radio pulsars. Here we discuss the nature of the signal and the performance of the technique on simulated data. We show how to perform a coherent multiple detector analysis and give some insight in the covariance between the signal parameters. |
2212.03168 | Marek Li\v{s}ka | Ana Alonso-Serrano, Marek Li\v{s}ka | Emergence of quadratic gravity from entanglement equilibrium | 8 pages, 1 figure. Matches the version accepted in PRD | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we derive the linearised equations of quadratic gravity from
entanglement equilibrium of local causal diamonds. Rather than starting from
the Wald entropy prescription (which depends on the gravitational Lagrangian),
we employ a model independent approach based on the logarithmic corrections to
horizon entanglement entropy. In this way, we are able to show the emergence of
linearised quadratic gravity from entanglement equilibrium without using any a
priori knowledge about gravitational dynamics. If the logarithmic correction to
entropy has a negative sign, as predicted by replica trick calculations of
entanglement entropy, we find that the quadratic gravity correction terms have
the sign necessary to avoid tachyonic instabilities of the theory.
| [
{
"created": "Tue, 6 Dec 2022 17:43:39 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Oct 2023 09:23:43 GMT",
"version": "v2"
}
] | 2023-10-17 | [
[
"Alonso-Serrano",
"Ana",
""
],
[
"Liška",
"Marek",
""
]
] | In this work, we derive the linearised equations of quadratic gravity from entanglement equilibrium of local causal diamonds. Rather than starting from the Wald entropy prescription (which depends on the gravitational Lagrangian), we employ a model independent approach based on the logarithmic corrections to horizon entanglement entropy. In this way, we are able to show the emergence of linearised quadratic gravity from entanglement equilibrium without using any a priori knowledge about gravitational dynamics. If the logarithmic correction to entropy has a negative sign, as predicted by replica trick calculations of entanglement entropy, we find that the quadratic gravity correction terms have the sign necessary to avoid tachyonic instabilities of the theory. |
gr-qc/0512073 | David D. Reid | Raluca Ilie, Gregory B. Thompson, and David D. Reid | A numerical study of the correspondence between paths in a causal set
and geodesics in the continuum | To the celebration of the 60th birthday of Rafael D. Sorkin | Class.Quant.Grav. 23 (2006) 3275-3286 | 10.1088/0264-9381/23/10/002 | null | gr-qc | null | This paper presents the results of a computational study related to the
path-geodesic correspondence in causal sets. For intervals in flat spacetimes,
and in selected curved spacetimes, we present evidence that the longest maximal
chains (the longest paths) in the corresponding causal set intervals
statistically approach the geodesic for that interval in the appropriate
continuum limit.
| [
{
"created": "Tue, 13 Dec 2005 13:19:33 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Ilie",
"Raluca",
""
],
[
"Thompson",
"Gregory B.",
""
],
[
"Reid",
"David D.",
""
]
] | This paper presents the results of a computational study related to the path-geodesic correspondence in causal sets. For intervals in flat spacetimes, and in selected curved spacetimes, we present evidence that the longest maximal chains (the longest paths) in the corresponding causal set intervals statistically approach the geodesic for that interval in the appropriate continuum limit. |
2307.07360 | Che-Yu Chen | Che-Yu Chen, Petr Kotla\v{r}\'ik | Quasinormal modes of black holes encircled by a gravitating thin disk | 14 pages, 10 figures. Matching published version | Phys. Rev. D 108 (2023) 064052 | 10.1103/PhysRevD.108.064052 | RIKEN-iTHEMS-Report-23 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The ringdown phase of gravitational waves emitted by a perturbed black hole
is described by a superposition of exponentially decaying sinusoidal modes,
called quasinormal modes (QNMs), whose frequencies depend only on the property
of the black hole geometry. The extraction of QNM frequencies of an isolated
black hole would allow for testing how well the black hole is described by
general relativity. However, astrophysical black holes are not isolated. It
remains unclear whether the extra matter surrounding the black holes such as
accretion disks would affect the validity of the black hole spectroscopy when
the gravitational effects of the disks are taken into account. In this paper,
we study the QNMs of a Schwarzschild black hole superposed with a gravitating
thin disk. Considering up to the first order of the mass ratio between the disk
and the black hole, we find that the existence of the disk would decrease the
oscillating frequency and the decay rate. In addition, within the parameter
space where the disk model can be regarded as physical, there seems to be a
universal relation that the QNM frequencies tend to obey. The relation, if it
holds generically, would assist in disentangling the QNM shifts caused by the
disk contributions from those induced by other putative effects beyond general
relativity. The QNMs in the eikonal limit, as well as their correspondence with
bound photon orbits in this model, are briefly discussed.
| [
{
"created": "Fri, 14 Jul 2023 14:05:56 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Oct 2023 15:27:55 GMT",
"version": "v2"
}
] | 2023-10-04 | [
[
"Chen",
"Che-Yu",
""
],
[
"Kotlařík",
"Petr",
""
]
] | The ringdown phase of gravitational waves emitted by a perturbed black hole is described by a superposition of exponentially decaying sinusoidal modes, called quasinormal modes (QNMs), whose frequencies depend only on the property of the black hole geometry. The extraction of QNM frequencies of an isolated black hole would allow for testing how well the black hole is described by general relativity. However, astrophysical black holes are not isolated. It remains unclear whether the extra matter surrounding the black holes such as accretion disks would affect the validity of the black hole spectroscopy when the gravitational effects of the disks are taken into account. In this paper, we study the QNMs of a Schwarzschild black hole superposed with a gravitating thin disk. Considering up to the first order of the mass ratio between the disk and the black hole, we find that the existence of the disk would decrease the oscillating frequency and the decay rate. In addition, within the parameter space where the disk model can be regarded as physical, there seems to be a universal relation that the QNM frequencies tend to obey. The relation, if it holds generically, would assist in disentangling the QNM shifts caused by the disk contributions from those induced by other putative effects beyond general relativity. The QNMs in the eikonal limit, as well as their correspondence with bound photon orbits in this model, are briefly discussed. |
gr-qc/9906068 | Carsten Gundlach | C. Gundlach and J. M. Martin-Garcia | Gauge-invariant and coordinate-independent perturbations of stellar
collapse I: the interior | 21 pages, RevTex | Phys.Rev. D61 (2000) 084024 | 10.1103/PhysRevD.61.084024 | null | gr-qc | null | Small non-spherical perturbations of a spherically symmetric but
time-dependent background spacetime can be used to model situations of
astrophysical interest, for example the production of gravitational waves in a
supernova explosion. We allow for perfect fluid matter with an arbitrary
equation of state p=p(rho,s), coupled to general relativity. Applying a general
framework proposed by Gerlach and Sengupta, we obtain covariant field
equations, in a 2+2 reduction of the spacetime, for the background and a
complete set of gauge-invariant perturbations, and then scalarize them using
the natural frame provided by the fluid. Building on previous work by Seidel,
we identify a set of true perturbation degrees of freedom admitting free
initial data for the axial and for the l>1 polar perturbations. The true
degrees of freedom are evolved among themselves by a set of coupled wave and
transport equations, while the remaining degrees of freedom can be obtained by
quadratures. The polar l=0,1 perturbations are discussed in the same framework.
They require gauge fixing and do not admit an unconstrained evolution scheme.
| [
{
"created": "Wed, 16 Jun 1999 21:56:48 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Gundlach",
"C.",
""
],
[
"Martin-Garcia",
"J. M.",
""
]
] | Small non-spherical perturbations of a spherically symmetric but time-dependent background spacetime can be used to model situations of astrophysical interest, for example the production of gravitational waves in a supernova explosion. We allow for perfect fluid matter with an arbitrary equation of state p=p(rho,s), coupled to general relativity. Applying a general framework proposed by Gerlach and Sengupta, we obtain covariant field equations, in a 2+2 reduction of the spacetime, for the background and a complete set of gauge-invariant perturbations, and then scalarize them using the natural frame provided by the fluid. Building on previous work by Seidel, we identify a set of true perturbation degrees of freedom admitting free initial data for the axial and for the l>1 polar perturbations. The true degrees of freedom are evolved among themselves by a set of coupled wave and transport equations, while the remaining degrees of freedom can be obtained by quadratures. The polar l=0,1 perturbations are discussed in the same framework. They require gauge fixing and do not admit an unconstrained evolution scheme. |
gr-qc/9708023 | null | B. L. Hu and K. Shiokawa | Wave Propagation in Stochastic Spacetimes: Localization, Amplification
and Particle Creation | 26 pages, 1 Postscript figure, submitted to Phys. Rev. D on July 29,
1997 | Phys. Rev. D 57, 3474 (1998) | 10.1103/PhysRevD.57.3474 | umdpp 97-125 | gr-qc cond-mat | null | Here we study novel effects associated with electromagnetic wave propagation
in a Robertson-Walker universe and the Schwarzschild spacetime with a small
amount of metric stochasticity. We find that localization of electromagnetic
waves occurs in a Robertson-Walker universe with time-independent metric
stochasticity, while time-dependent metric stochasticity induces exponential
instability in the particle production rate. For the Schwarzschild metric,
time-independent randomness can decrease the total luminosity of Hawking
radiation due to multiple scattering of waves outside the black hole and gives
rise to event horizon fluctuations and thus fluctuations in the Hawking
temperature.
| [
{
"created": "Tue, 12 Aug 1997 01:30:42 GMT",
"version": "v1"
}
] | 2016-08-25 | [
[
"Hu",
"B. L.",
""
],
[
"Shiokawa",
"K.",
""
]
] | Here we study novel effects associated with electromagnetic wave propagation in a Robertson-Walker universe and the Schwarzschild spacetime with a small amount of metric stochasticity. We find that localization of electromagnetic waves occurs in a Robertson-Walker universe with time-independent metric stochasticity, while time-dependent metric stochasticity induces exponential instability in the particle production rate. For the Schwarzschild metric, time-independent randomness can decrease the total luminosity of Hawking radiation due to multiple scattering of waves outside the black hole and gives rise to event horizon fluctuations and thus fluctuations in the Hawking temperature. |
1604.05415 | Edward Anderson | Edward Anderson | On Types of Observables in Constrained Theories | 12 pages, including 5 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Kuchar observables notion is shown to apply only to a limited range of
theories. Relational mechanics, slightly inhomogeneous cosmology and
supergravity are used as examples that require further notions of observables.
A suitably general notion of A-observables is then given to cover all of these
cases. `A' here stands for `algebraic substructure'; A-observables can be
defined by association with each closed algebraic substructure of a theory's
constraints. Both constrained algebraic structures and associated notions of
A-observables form bounded lattices.
| [
{
"created": "Tue, 19 Apr 2016 03:07:47 GMT",
"version": "v1"
}
] | 2016-04-20 | [
[
"Anderson",
"Edward",
""
]
] | The Kuchar observables notion is shown to apply only to a limited range of theories. Relational mechanics, slightly inhomogeneous cosmology and supergravity are used as examples that require further notions of observables. A suitably general notion of A-observables is then given to cover all of these cases. `A' here stands for `algebraic substructure'; A-observables can be defined by association with each closed algebraic substructure of a theory's constraints. Both constrained algebraic structures and associated notions of A-observables form bounded lattices. |
1311.2573 | \"Ozg\"ur Akarsu | Ozgur Akarsu, Tekin Dereli, Neslihan Oflaz | Accelerating anisotropic cosmologies in Brans-Dicke gravity coupled to a
mass-varying vector field | 15 pages, no figures and tables; matches the version published in
Classical and Quantum Gravity | Classical and Quantum Gravity 31 (2014) 045020 | 10.1088/0264-9381/31/4/045020 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The field equations of Brans-Dicke gravity coupled to a mass-varying vector
field are derived. Anisotropic cosmological solutions with a locally
rotationally symmetric Bianchi type I metric and time-dependent scalar and
electric vector fields are studied. A particular class of exact solutions for
which all the variable parameters have a power-law time dependence is given.
The universe expands with a constant expansion anisotropy within this class of
solutions. We show that the accelerating expansion is driven by the scalar
field and the electric vector field can be interpreted as an anisotropic dark
matter source.
| [
{
"created": "Mon, 11 Nov 2013 20:40:12 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Jan 2014 16:32:06 GMT",
"version": "v2"
},
{
"created": "Tue, 4 Feb 2014 13:02:52 GMT",
"version": "v3"
}
] | 2014-02-05 | [
[
"Akarsu",
"Ozgur",
""
],
[
"Dereli",
"Tekin",
""
],
[
"Oflaz",
"Neslihan",
""
]
] | The field equations of Brans-Dicke gravity coupled to a mass-varying vector field are derived. Anisotropic cosmological solutions with a locally rotationally symmetric Bianchi type I metric and time-dependent scalar and electric vector fields are studied. A particular class of exact solutions for which all the variable parameters have a power-law time dependence is given. The universe expands with a constant expansion anisotropy within this class of solutions. We show that the accelerating expansion is driven by the scalar field and the electric vector field can be interpreted as an anisotropic dark matter source. |
2108.12368 | Katerina Chatziioannou | Katerina Chatziioannou | Uncertainty limits on neutron star radius measurements with
gravitational waves | 5 pages, 3 figures, published version | null | 10.1103/PhysRevD.105.084021 | null | gr-qc astro-ph.HE nucl-th | http://creativecommons.org/licenses/by/4.0/ | Upcoming observing campaigns with improved detectors will yield numerous
detections of gravitational waves from neutron star binary inspirals. Rare loud
signals together with numerous signals of moderate strength promise stringent
constraints on the properties of neutron star matter, with a projected radius
statistical uncertainty of $50-200$m with ${\cal{O}}(2000)$ sources. Given this
precision we revisit all analysis assumptions and identify sources of
systematic errors, quantify their impact on radius extraction, and discuss
their relative importance and ways to mitigate them.
| [
{
"created": "Fri, 27 Aug 2021 16:02:48 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Apr 2022 17:18:16 GMT",
"version": "v2"
}
] | 2022-04-15 | [
[
"Chatziioannou",
"Katerina",
""
]
] | Upcoming observing campaigns with improved detectors will yield numerous detections of gravitational waves from neutron star binary inspirals. Rare loud signals together with numerous signals of moderate strength promise stringent constraints on the properties of neutron star matter, with a projected radius statistical uncertainty of $50-200$m with ${\cal{O}}(2000)$ sources. Given this precision we revisit all analysis assumptions and identify sources of systematic errors, quantify their impact on radius extraction, and discuss their relative importance and ways to mitigate them. |
2102.10479 | Shao-Jun Zhang | Shao-Jun Zhang | Massive scalar field perturbation on Kerr black holes in dynamical
Chern-Simons gravity | v1:14 pages, 4 figures;v2: minor modification, refs added. v3: minor
modification, more refs, match published version | Eur.Phys.J.C 81 (2021) 5, 441 | 10.1140/epjc/s10052-021-09249-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study massive scalar field perturbation on Kerr black holes in dynamical
Chern-Simons gravity by performing a $(2+1)$-dimensional simulation. Object
pictures of the wave dynamics in time domain are obtained. The tachyonic
instability is found to always occur for any nonzero black hole spin and any
scalar field mass as long as the coupling constant exceeds a critical value.
The presence of the mass term suppresses or even quenches the instability. The
quantitative dependence of the onset of the tachyonic instability on the
coupling constant, the scalar field mass and the black hole spin is given
numerically.
| [
{
"created": "Sun, 21 Feb 2021 00:04:12 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Mar 2021 07:10:33 GMT",
"version": "v2"
},
{
"created": "Thu, 27 May 2021 12:10:21 GMT",
"version": "v3"
}
] | 2021-05-28 | [
[
"Zhang",
"Shao-Jun",
""
]
] | We study massive scalar field perturbation on Kerr black holes in dynamical Chern-Simons gravity by performing a $(2+1)$-dimensional simulation. Object pictures of the wave dynamics in time domain are obtained. The tachyonic instability is found to always occur for any nonzero black hole spin and any scalar field mass as long as the coupling constant exceeds a critical value. The presence of the mass term suppresses or even quenches the instability. The quantitative dependence of the onset of the tachyonic instability on the coupling constant, the scalar field mass and the black hole spin is given numerically. |
2305.02726 | Serge Parnovsky | S L Parnovsky | Is the Universe anisotropic right now? Comparing the real Universe with
the Kasner's space-time | 18 pages, 2 figures | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate possible astronomical manifestations of space-time anisotropy.
The homogeneous vacuum Kasner solution was chosen as a reference anisotropic
cosmological model because there are no effects caused by inhomogeneity in this
simple model with a constant degree of anisotropy. This anisotropy cannot
become weak. The study of its geodesic structure made it possible to clarify
the properties of this space-time. It showed that the degree of manifestation
of anisotropy varies significantly depending on the travel time of the light
from the observed object. For nearby objects, for which it does not exceed half
the age of the universe, the manifestations of anisotropy are very small.
Distant objects show more pronounced manifestations, for example, in the
distribution of objects over the sky and over photometric distances. These
effects for each of the individual objects decrease with time, but in general,
the manifestations of anisotropy in the Kasner space-time remain constant due
to the fact that new sources emerging from beyond the cosmological horizon.We
analyse observable signatures of the Kasner-type anisotropy and compare it to
observations. These effects were not found in astronomical observations,
including the study of the CMB. We can assume that the Universe has always been
isotropic or almost isotropic since the recombination era. This does not
exclude the possibility of its significant anisotropy at the moment of the Big
Bang followed by rapid isotropization during the inflationary epoch.
| [
{
"created": "Thu, 4 May 2023 10:48:48 GMT",
"version": "v1"
},
{
"created": "Sun, 28 May 2023 15:49:28 GMT",
"version": "v2"
}
] | 2023-05-30 | [
[
"Parnovsky",
"S L",
""
]
] | We investigate possible astronomical manifestations of space-time anisotropy. The homogeneous vacuum Kasner solution was chosen as a reference anisotropic cosmological model because there are no effects caused by inhomogeneity in this simple model with a constant degree of anisotropy. This anisotropy cannot become weak. The study of its geodesic structure made it possible to clarify the properties of this space-time. It showed that the degree of manifestation of anisotropy varies significantly depending on the travel time of the light from the observed object. For nearby objects, for which it does not exceed half the age of the universe, the manifestations of anisotropy are very small. Distant objects show more pronounced manifestations, for example, in the distribution of objects over the sky and over photometric distances. These effects for each of the individual objects decrease with time, but in general, the manifestations of anisotropy in the Kasner space-time remain constant due to the fact that new sources emerging from beyond the cosmological horizon.We analyse observable signatures of the Kasner-type anisotropy and compare it to observations. These effects were not found in astronomical observations, including the study of the CMB. We can assume that the Universe has always been isotropic or almost isotropic since the recombination era. This does not exclude the possibility of its significant anisotropy at the moment of the Big Bang followed by rapid isotropization during the inflationary epoch. |
1011.1179 | Johannes Hartung | Johannes Hartung and Jan Steinhoff | Next-to-leading order spin-orbit and spin(a)-spin(b) Hamiltonians for n
gravitating spinning compact objects | 13 pages, 1 Mathematica source file, v2: submitted version, v3:
published version, some minor corrections | Phys.Rev.D83:044008,2011 | 10.1103/PhysRevD.83.044008 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the post-Newtonian next-to-leading order conservative spin-orbit
and spin(a)-spin(b) gravitational interaction Hamiltonians for arbitrary many
compact objects. The spin-orbit Hamiltonian completes the knowledge of
Hamiltonians up to and including 2.5PN for the general relativistic three-body
problem. The new Hamiltonians include highly nontrivial three-body
interactions, in contrast to the leading order consisting of two-body
interactions only. This may be important for the study of effects like Kozai
resonances in mergers of black holes with binary black holes.
| [
{
"created": "Thu, 4 Nov 2010 15:00:23 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Nov 2010 19:07:30 GMT",
"version": "v2"
},
{
"created": "Thu, 10 Feb 2011 15:35:10 GMT",
"version": "v3"
}
] | 2011-02-11 | [
[
"Hartung",
"Johannes",
""
],
[
"Steinhoff",
"Jan",
""
]
] | We derive the post-Newtonian next-to-leading order conservative spin-orbit and spin(a)-spin(b) gravitational interaction Hamiltonians for arbitrary many compact objects. The spin-orbit Hamiltonian completes the knowledge of Hamiltonians up to and including 2.5PN for the general relativistic three-body problem. The new Hamiltonians include highly nontrivial three-body interactions, in contrast to the leading order consisting of two-body interactions only. This may be important for the study of effects like Kozai resonances in mergers of black holes with binary black holes. |
1910.12133 | Zainab Sedaghatmanesh | Mohammad.A Ganjali, Zainab Sedaghatmanesh | Laser Interferometer in Presence of Scalar field on Gravitational Wave
Background | 20 pages, 1 figure | Class. Quantum Grav. 38 (2021) 105010 (16pp) | 10.1088/1361-6382/abdd0e | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Detection of gravitational waves (GW) opened new windows on fundamental
physics and it would be natural to search how the role of extra dimensional
effects can be traced to gravitational wave physics. In this article, we
consider a toy model of five dimensional pure gravity theory compactified on a
circle. The resulting four dimensional theory is a scalar-Maxwell theory which
is minimally coupled with gravity. By finding the equations of motion for
scalar, electric and magnetic fields , we would be able to find exact wave
solutions of coupled equations which are zero mode solutions. We also perform
perturbation in order to consider non-zero modes of electromagnetic fields .\\
Having these solutions at hand, we study the recombination of scalar-affected
electromagnetic waves (EWs) in a typical Michelson interferometer. In
particular , we obtain, up to to first order , the change of amplitude of
electromagnetic power due to presence of this scalar field which may reveal
some signals of extra dimension.
| [
{
"created": "Sat, 26 Oct 2019 20:30:17 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Nov 2020 06:56:20 GMT",
"version": "v2"
},
{
"created": "Sun, 29 Aug 2021 14:48:27 GMT",
"version": "v3"
}
] | 2021-08-31 | [
[
"Ganjali",
"Mohammad. A",
""
],
[
"Sedaghatmanesh",
"Zainab",
""
]
] | Detection of gravitational waves (GW) opened new windows on fundamental physics and it would be natural to search how the role of extra dimensional effects can be traced to gravitational wave physics. In this article, we consider a toy model of five dimensional pure gravity theory compactified on a circle. The resulting four dimensional theory is a scalar-Maxwell theory which is minimally coupled with gravity. By finding the equations of motion for scalar, electric and magnetic fields , we would be able to find exact wave solutions of coupled equations which are zero mode solutions. We also perform perturbation in order to consider non-zero modes of electromagnetic fields .\\ Having these solutions at hand, we study the recombination of scalar-affected electromagnetic waves (EWs) in a typical Michelson interferometer. In particular , we obtain, up to to first order , the change of amplitude of electromagnetic power due to presence of this scalar field which may reveal some signals of extra dimension. |
2010.09363 | Ya-Peng Hu | Ya-Peng Hu, Liang Cai, Xiao Liang, Shi-Bei Kong and Hongsheng Zhang | Divergence Behavior of Thermodynamic Curvature Scalar at Critical Point
in the Extended Phase Space of Generic Black Holes | 10 pages, no figure, version accepted by PLB | null | 10.1016/j.physletb.2021.136661 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The $P$-$V$ phase transition and critical behavior in the extended phase
space of asymptotic Anti-de Sitter (AdS) black holes have been widely
investigated, in which four critical exponents around critical point are found
to be consistent with values in the mean field theory. Recently, another
critical exponent $\nu$ related to divergent correlation length at critical
point is proposed by using thermodynamic curvature scalar $R_N$ in the charged
AdS black hole. In this paper, we develop a method to investigate the divergent
behavior of $R_N$ at critical point, and find that the divergent behavior of
$R_N$ around the critical point expresses a universal property in generic black
holes. We further directly apply this method to investigate black holes in de
Rham-Gabadadze-Tolley (dRGT) massive gravity to check this universality. Those
results shed new lights on the microscopic properties of black holes.
| [
{
"created": "Mon, 19 Oct 2020 10:03:35 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Sep 2021 15:17:54 GMT",
"version": "v2"
}
] | 2021-09-29 | [
[
"Hu",
"Ya-Peng",
""
],
[
"Cai",
"Liang",
""
],
[
"Liang",
"Xiao",
""
],
[
"Kong",
"Shi-Bei",
""
],
[
"Zhang",
"Hongsheng",
""
]
] | The $P$-$V$ phase transition and critical behavior in the extended phase space of asymptotic Anti-de Sitter (AdS) black holes have been widely investigated, in which four critical exponents around critical point are found to be consistent with values in the mean field theory. Recently, another critical exponent $\nu$ related to divergent correlation length at critical point is proposed by using thermodynamic curvature scalar $R_N$ in the charged AdS black hole. In this paper, we develop a method to investigate the divergent behavior of $R_N$ at critical point, and find that the divergent behavior of $R_N$ around the critical point expresses a universal property in generic black holes. We further directly apply this method to investigate black holes in de Rham-Gabadadze-Tolley (dRGT) massive gravity to check this universality. Those results shed new lights on the microscopic properties of black holes. |
gr-qc/0304023 | A. W. Whinnett | A. W. Whinnett | Neutron Stars in a Varying Speed of Light Theory | 15 pages, 2 figures. Added solutions with a more realistic equation
of state. To be published in PRD | Phys.Rev. D68 (2003) 024009 | 10.1103/PhysRevD.68.024009 | null | gr-qc | null | We study neutron stars in a varying speed of light (VSL) theory of gravity in
which the local speed of light depends upon the value of a scalar field $\phi$.
We find that the masses and radii of the stars are strongly dependent on the
strength of the coupling between $\phi$ and the matter field and that for
certain choices of coupling parameters, the maximum neutron star mass can be
arbitrarily small. We also discuss the phenomenon of cosmological evolution of
VSL stars (analogous to the gravitational evolution in scalar-tensor theories)
and we derive a relation showing how the fractional change in the energy of a
star is related to the change in the cosmological value of the scalar field.
| [
{
"created": "Fri, 4 Apr 2003 17:29:06 GMT",
"version": "v1"
},
{
"created": "Wed, 21 May 2003 13:18:57 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Whinnett",
"A. W.",
""
]
] | We study neutron stars in a varying speed of light (VSL) theory of gravity in which the local speed of light depends upon the value of a scalar field $\phi$. We find that the masses and radii of the stars are strongly dependent on the strength of the coupling between $\phi$ and the matter field and that for certain choices of coupling parameters, the maximum neutron star mass can be arbitrarily small. We also discuss the phenomenon of cosmological evolution of VSL stars (analogous to the gravitational evolution in scalar-tensor theories) and we derive a relation showing how the fractional change in the energy of a star is related to the change in the cosmological value of the scalar field. |
1701.02556 | Thomas M\"adler | Thomas M\"adler and Jeffrey Winicour | Radiation Memory, Boosted Schwarzschild Spacetimes and Supertranslations | matches published version | null | 10.1088/1361-6382/aa6ca8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate gravitational radiation memory and its corresponding effect on
the asymptotic symmetries of a body whose exterior is a boosted Schwarzschild
spacetime. First, in the context of linearized theory, we consider such a
Schwarzschild body which is initially at rest, then goes through a radiative
stage and finally emerges as a boosted Schwarzschild body. We show that the
proper retarded solution of the exterior Schwarzschild spacetime for this
process can be described in terms of the ingoing Kerr-Schild form of the
Schwarzschild metric for both the initial and final states. An outgoing
Kerr-Schild or time symmetric metric does not give the proper solution. The
special property of Kerr-Schild metrics that their linearized and nonlinear
forms are identical allows us to extend this result to processes in the
nonlinear regime. We then discuss how the nonlinear memory effect, and its
associated supertranslation, affect angular momentum conservation. Our approach
provides a new framework for studying nonlinear aspects of the memory effect.
| [
{
"created": "Tue, 10 Jan 2017 12:38:53 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Jan 2017 10:15:36 GMT",
"version": "v2"
},
{
"created": "Fri, 19 May 2017 15:20:04 GMT",
"version": "v3"
}
] | 2017-05-22 | [
[
"Mädler",
"Thomas",
""
],
[
"Winicour",
"Jeffrey",
""
]
] | We investigate gravitational radiation memory and its corresponding effect on the asymptotic symmetries of a body whose exterior is a boosted Schwarzschild spacetime. First, in the context of linearized theory, we consider such a Schwarzschild body which is initially at rest, then goes through a radiative stage and finally emerges as a boosted Schwarzschild body. We show that the proper retarded solution of the exterior Schwarzschild spacetime for this process can be described in terms of the ingoing Kerr-Schild form of the Schwarzschild metric for both the initial and final states. An outgoing Kerr-Schild or time symmetric metric does not give the proper solution. The special property of Kerr-Schild metrics that their linearized and nonlinear forms are identical allows us to extend this result to processes in the nonlinear regime. We then discuss how the nonlinear memory effect, and its associated supertranslation, affect angular momentum conservation. Our approach provides a new framework for studying nonlinear aspects of the memory effect. |
2101.03948 | Pravin Dahal | Pravin Kumar Dahal | Properties of space-time in the vicinity of trapped regions | 46 pages, 3 figures. Thesis submitted for the Master of Research.
Macquarie University, November 2020 | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We investigate the near horizon geometry of the simplest representative of
the class of axisymmetric space-times: the Kerr Vaidya metrics. Kerr Vaidya
metrics can be derived from the Vaidya metric by the complex coordinate
transformation suggested by Newman and Janis. We show that the energy momentum
tensor belongs to type 3 in the Segre Hawking Ellis classification but has a
special form with all Lorentz invariant eigenvalues belonging to zero. We find
a location of the apparent horizon for quasi-stationary Kerr Vaidya black
holes. The energy-momentum tensor of the Kerr Vaidya geometries violates the
null energy condition. We show that energy density, pressure, and flux for an
infalling observer are diverging in the outgoing Kerr Vaidya metric. This
firewall leads to the violation of a specific quantum energy inequality.
| [
{
"created": "Fri, 8 Jan 2021 13:41:54 GMT",
"version": "v1"
}
] | 2021-01-12 | [
[
"Dahal",
"Pravin Kumar",
""
]
] | We investigate the near horizon geometry of the simplest representative of the class of axisymmetric space-times: the Kerr Vaidya metrics. Kerr Vaidya metrics can be derived from the Vaidya metric by the complex coordinate transformation suggested by Newman and Janis. We show that the energy momentum tensor belongs to type 3 in the Segre Hawking Ellis classification but has a special form with all Lorentz invariant eigenvalues belonging to zero. We find a location of the apparent horizon for quasi-stationary Kerr Vaidya black holes. The energy-momentum tensor of the Kerr Vaidya geometries violates the null energy condition. We show that energy density, pressure, and flux for an infalling observer are diverging in the outgoing Kerr Vaidya metric. This firewall leads to the violation of a specific quantum energy inequality. |
1610.00135 | Elizabeth Winstanley | Supakchai Ponglertsakul and Elizabeth Winstanley | Effect of scalar field mass on gravitating charged scalar solitons and
black holes in a cavity | Minor changes, 7 pages, 7 figures | null | 10.1016/j.physletb.2016.10.073 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study soliton and black hole solutions of Einstein charged scalar field
theory in cavity. We examine the effect of introducing a scalar field mass on
static, spherically symmetric solutions of the field equations. We focus
particularly on the spaces of soliton and black hole solutions, as well as
studying their stability under linear, spherically symmetric perturbations of
the metric, electromagnetic field, and scalar field.
| [
{
"created": "Sat, 1 Oct 2016 13:31:48 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Nov 2016 20:57:19 GMT",
"version": "v2"
}
] | 2016-11-11 | [
[
"Ponglertsakul",
"Supakchai",
""
],
[
"Winstanley",
"Elizabeth",
""
]
] | We study soliton and black hole solutions of Einstein charged scalar field theory in cavity. We examine the effect of introducing a scalar field mass on static, spherically symmetric solutions of the field equations. We focus particularly on the spaces of soliton and black hole solutions, as well as studying their stability under linear, spherically symmetric perturbations of the metric, electromagnetic field, and scalar field. |
gr-qc/0408008 | Sean A. Hayward | Sean A. Hayward | Energy and entropy conservation for dynamical black holes | 16 revtex4 pages, 2 eps figures, expanded discussion of horizon types
and evaporating black holes | Phys.Rev.D70:104027,2004 | 10.1103/PhysRevD.70.104027 | null | gr-qc | null | The Ashtekar-Krishnan energy-balance law for dynamical horizons, expressing
the increase in mass-energy of a general black hole in terms of the infalling
matter and gravitational radiation, is expressed in terms of trapping horizons,
allowing the inclusion of null (isolated) horizons as well as spatial
(dynamical) horizons. This first law of black-hole dynamics is given in
differential and integral forms, regular in the null limit. An effective
gravitational-radiation energy tensor is obtained, providing measures of both
ingoing and outgoing, transverse and longitudinal gravitational radiation on
and near a black hole. Corresponding energy-tensor forms of the first law
involve a preferred time vector which plays the role for dynamical black holes
which the stationary Killing vector plays for stationary black holes.
Identifying an energy flux, vanishing if and only if the horizon is null,
allows a division into energy-supply and work terms, as in the first law of
thermodynamics. The energy supply can be expressed in terms of area increase
and a newly defined surface gravity, yielding a Gibbs-like equation, with a
similar form to the so-called first law for stationary black holes. A
Clausius-like relation suggests a definition of geometric entropy flux. Taking
entropy as area/4 for dynamical black holes, it is shown that geometric entropy
is conserved: the entropy of the black hole equals the geometric entropy
supplied by the infalling matter and gravitational radiation. The area or
entropy of a dynamical horizon increases by the so-called second law, not
because entropy is produced, but because black holes classically are perfect
absorbers.
| [
{
"created": "Tue, 3 Aug 2004 08:39:38 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Nov 2004 12:17:41 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Hayward",
"Sean A.",
""
]
] | The Ashtekar-Krishnan energy-balance law for dynamical horizons, expressing the increase in mass-energy of a general black hole in terms of the infalling matter and gravitational radiation, is expressed in terms of trapping horizons, allowing the inclusion of null (isolated) horizons as well as spatial (dynamical) horizons. This first law of black-hole dynamics is given in differential and integral forms, regular in the null limit. An effective gravitational-radiation energy tensor is obtained, providing measures of both ingoing and outgoing, transverse and longitudinal gravitational radiation on and near a black hole. Corresponding energy-tensor forms of the first law involve a preferred time vector which plays the role for dynamical black holes which the stationary Killing vector plays for stationary black holes. Identifying an energy flux, vanishing if and only if the horizon is null, allows a division into energy-supply and work terms, as in the first law of thermodynamics. The energy supply can be expressed in terms of area increase and a newly defined surface gravity, yielding a Gibbs-like equation, with a similar form to the so-called first law for stationary black holes. A Clausius-like relation suggests a definition of geometric entropy flux. Taking entropy as area/4 for dynamical black holes, it is shown that geometric entropy is conserved: the entropy of the black hole equals the geometric entropy supplied by the infalling matter and gravitational radiation. The area or entropy of a dynamical horizon increases by the so-called second law, not because entropy is produced, but because black holes classically are perfect absorbers. |
1806.01473 | Vitor Silveira Barroso | V. S. Barroso and J. P. M. Pitelli | Vacuum Fluctuations and Boundary Conditions in a Global Monopole | 7 pages, submitted to PRD | Phys. Rev. D 98, 065009 (2018) | 10.1103/PhysRevD.98.065009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the vacuum fluctuations of a massless scalar field $\hat{\Psi}$ on
the background of a global monopole. Due to the nontrivial topology of the
global monopole spacetime, characterized by a solid deficit angle parametrized
by $\eta^2$, we expect that $\left<\hat{\Psi}^2\right>_{\text{ren}}$ and
$\left<\hat{T}_{\mu\nu}\right>_{\text{ren}}$ are nonzero and proportional to
$\eta^2$, so that they annul in the Minkowski limit $\eta\to0$. However, due to
the naked singularity at the monopole core, the evolution of the scalar field
is not unique. In fact, they are in one to one correspondence with the boundary
conditions which turn into self-adjoint the spatial part of the wave operator.
We show that only Dirichlet boundary condition corresponds to our expectations
and gives zero contribution to the vacuum fluctuations in Minkowski limit. All
other boundary conditions give nonzero contributions in this limit due to the
nontrivial interaction between the field and the singularity.
| [
{
"created": "Tue, 5 Jun 2018 03:01:25 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Jun 2018 16:26:47 GMT",
"version": "v2"
},
{
"created": "Tue, 7 Aug 2018 13:54:46 GMT",
"version": "v3"
}
] | 2018-09-19 | [
[
"Barroso",
"V. S.",
""
],
[
"Pitelli",
"J. P. M.",
""
]
] | We study the vacuum fluctuations of a massless scalar field $\hat{\Psi}$ on the background of a global monopole. Due to the nontrivial topology of the global monopole spacetime, characterized by a solid deficit angle parametrized by $\eta^2$, we expect that $\left<\hat{\Psi}^2\right>_{\text{ren}}$ and $\left<\hat{T}_{\mu\nu}\right>_{\text{ren}}$ are nonzero and proportional to $\eta^2$, so that they annul in the Minkowski limit $\eta\to0$. However, due to the naked singularity at the monopole core, the evolution of the scalar field is not unique. In fact, they are in one to one correspondence with the boundary conditions which turn into self-adjoint the spatial part of the wave operator. We show that only Dirichlet boundary condition corresponds to our expectations and gives zero contribution to the vacuum fluctuations in Minkowski limit. All other boundary conditions give nonzero contributions in this limit due to the nontrivial interaction between the field and the singularity. |
2212.01182 | Aurelien Barrau | Maxime De Sousa, Killian Martineau, Cyril Renevey, Aur\'elien Barrau | Impact of generalized holonomy corrections on the cosmological
primordial power spectra | null | null | 10.1103/PhysRevD.107.126008 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The propagation of perturbations is studied with generalized holonomy
corrections in a fully consistent way, ensuring that the deformed algebra of
constraints remains closed. The primordial cosmological power spectra are
calculated. It is shown that, although the detailed form of the correction does
unavoidably impact the observables, the main known results of loop quantum
cosmology are robust in this respect.
| [
{
"created": "Fri, 2 Dec 2022 14:06:41 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Jun 2023 11:24:25 GMT",
"version": "v2"
}
] | 2023-06-28 | [
[
"De Sousa",
"Maxime",
""
],
[
"Martineau",
"Killian",
""
],
[
"Renevey",
"Cyril",
""
],
[
"Barrau",
"Aurélien",
""
]
] | The propagation of perturbations is studied with generalized holonomy corrections in a fully consistent way, ensuring that the deformed algebra of constraints remains closed. The primordial cosmological power spectra are calculated. It is shown that, although the detailed form of the correction does unavoidably impact the observables, the main known results of loop quantum cosmology are robust in this respect. |
1411.7326 | Kayll Lake | Kayll Lake | Central density cusps in the Lema\^{i}tre-Tolman solutions | 4 pages 1 figure revtex 4-1 updated final form to appear in Phys Rev
D | Phys. Rev. D 91, 124036 (2015) | 10.1103/PhysRevD.91.124036 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The character of the central density profile in the Lema\^{i}tre-Tolman (LT)
solutions plays a fundamental role in their application as cosmological models.
This same character is studied here for these solutions used to model complete
gravitational collapse. A necessary condition for the development of a black
hole (not even locally naked singularities) is developed. This condition allows
central density cusps, the central feature of the LT solutions when used to
match cosmological observations without invoking the cosmological constant.
| [
{
"created": "Wed, 26 Nov 2014 18:46:39 GMT",
"version": "v1"
},
{
"created": "Mon, 11 May 2015 18:07:11 GMT",
"version": "v2"
},
{
"created": "Thu, 28 May 2015 16:48:46 GMT",
"version": "v3"
}
] | 2015-06-24 | [
[
"Lake",
"Kayll",
""
]
] | The character of the central density profile in the Lema\^{i}tre-Tolman (LT) solutions plays a fundamental role in their application as cosmological models. This same character is studied here for these solutions used to model complete gravitational collapse. A necessary condition for the development of a black hole (not even locally naked singularities) is developed. This condition allows central density cusps, the central feature of the LT solutions when used to match cosmological observations without invoking the cosmological constant. |
2009.11156 | Polina Dyadina | N. Avdeev, P. Dyadina, S. Labazova | Test of hybrid metric-Palatini f(R)-gravity in binary pulsars | 12 pages, 4 figures | JETP Vol. 131, pp. 537-547 (2020) | 10.1134/S1063776120100039 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We developed the parameterized post-Keplerian formalism for hybrid
metric-Palatini $f(R)$-gravity. We obtained analytical expressions in the
generel eccentric case for four PPK parameters: $\dot\omega$, $\dot P_{\rm b}$,
$r$ and $s$. Using observational data of PSR J0737-3039 and PSR J1903+0327 we
imposed restrictions on the parameters of hybrid f(R)-gravity and showed that
this theory is not ruled out by the observations in strong field regime. In
addition we obtained predictions for masses of systems components and found
that considered astrophysical objects will be heavier than in GR.
| [
{
"created": "Wed, 23 Sep 2020 14:07:11 GMT",
"version": "v1"
}
] | 2022-10-13 | [
[
"Avdeev",
"N.",
""
],
[
"Dyadina",
"P.",
""
],
[
"Labazova",
"S.",
""
]
] | We developed the parameterized post-Keplerian formalism for hybrid metric-Palatini $f(R)$-gravity. We obtained analytical expressions in the generel eccentric case for four PPK parameters: $\dot\omega$, $\dot P_{\rm b}$, $r$ and $s$. Using observational data of PSR J0737-3039 and PSR J1903+0327 we imposed restrictions on the parameters of hybrid f(R)-gravity and showed that this theory is not ruled out by the observations in strong field regime. In addition we obtained predictions for masses of systems components and found that considered astrophysical objects will be heavier than in GR. |
1510.09048 | Satoshi Nakajima | Satoshi Nakajima | Application of covariant analytic mechanics with differential forms to
gravity with Dirac field | 14 pages, no figure | EJTP 13, 95 (2016) | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the covariant analytic mechanics with the differential forms to the
Dirac field and the gravity with the Dirac field. The covariant analytic
mechanics treats space and time on an equal footing regarding the differential
forms as the basic variables. A significant feature of the covariant analytic
mechanics is that the canonical equations, in addition to the Euler-Lagrange
equation, are not only manifestly general coordinate covariant but also gauge
covariant. Combining our study and the previous works (the scalar field, the
abelian and non-abelian gauge fields and the gravity without the Dirac field),
the applicability of the covariant analytic mechanics is checked for all
fundamental fields. We study both the first and second order formalism of the
gravitational field coupled with matters including the Dirac field. It is
suggested that gravitation theories including higher order curvatures cannot be
treated by the second order formalism in the covariant analytic mechanics.
| [
{
"created": "Fri, 30 Oct 2015 11:12:06 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Feb 2016 14:53:45 GMT",
"version": "v2"
}
] | 2016-05-25 | [
[
"Nakajima",
"Satoshi",
""
]
] | We apply the covariant analytic mechanics with the differential forms to the Dirac field and the gravity with the Dirac field. The covariant analytic mechanics treats space and time on an equal footing regarding the differential forms as the basic variables. A significant feature of the covariant analytic mechanics is that the canonical equations, in addition to the Euler-Lagrange equation, are not only manifestly general coordinate covariant but also gauge covariant. Combining our study and the previous works (the scalar field, the abelian and non-abelian gauge fields and the gravity without the Dirac field), the applicability of the covariant analytic mechanics is checked for all fundamental fields. We study both the first and second order formalism of the gravitational field coupled with matters including the Dirac field. It is suggested that gravitation theories including higher order curvatures cannot be treated by the second order formalism in the covariant analytic mechanics. |
2211.14278 | Adrien Bourgoin | Adrien Bourgoin (1 and 2), Christophe Le Poncin-Lafitte (1),
St\'ephane Mathis (2) and Marie-Christine Angonin (1) ((1) SYRTE,
Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universit\'e,
UPMC Univ. Paris 6, LNE, 61 avenue de l'Observatoire, 75014 Paris, France,
(2) D\'epartement d'Astrophysique-AIM, CEA, CNRS, Universit\'e Paris-Saclay,
Universit\'e Paris Cit\'e, 91191 Gif-sur-Yvette, France) | Gravitational waves radiated by magnetic galactic binaries and detection
by LISA | 4 pages, 1 figure, proceedings Les rencontres de Moriond | null | null | null | gr-qc astro-ph.HE astro-ph.SR hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of the future Laser Interferometer Space Antenna (LISA)
mission, galactic binary systems of white dwarfs and neutron stars will
represent the dominant source of Gravitational Waves (GWs) within the
$10^{-4}-10^{-1}\,\mathrm{Hz}$ frequency band. It is expected that LISA will
measure simultaneously, the GWs from more than ten thousands of these compact
galactic binaries. The analysis of such a superposition of signals will
represent one of the greatest challenge for the mission. Currently, in the LISA
Datacode Challenge, each galactic binary is modeled as a quasi-monochromatic
source of GWs. This corresponds to the circular motion of two point-masses at
the 2.5 post-Newtonian approximation. If this picture is expected to be an
accurate description for most of the galactic binaries that LSIA will detect,
we nevertheless expect to observe eccentric systems with complex physical
properties beyond the point-mass approximation. In this work, we investigate
how a binary system of highly magnetic objects in quasi-circular orbit could
affect the quasi-monochromatic picture of the GW signal detected by LISA. We
demonstrate that the eccentricity generates additional frequency peaks at
harmonics of the mean motion and that magnetism is responsible for shifting
each frequency peak with respect to the case without magnetism. We provide
analytical estimates and argue that LISA will be able to detect magnetism if it
can measure the main peaks at two and three times the mean motion with a
sufficient accuracy.
| [
{
"created": "Fri, 25 Nov 2022 18:23:13 GMT",
"version": "v1"
}
] | 2022-11-28 | [
[
"Bourgoin",
"Adrien",
"",
"1 and 2"
],
[
"Poncin-Lafitte",
"Christophe Le",
""
],
[
"Mathis",
"Stéphane",
""
],
[
"Angonin",
"Marie-Christine",
""
]
] | In the context of the future Laser Interferometer Space Antenna (LISA) mission, galactic binary systems of white dwarfs and neutron stars will represent the dominant source of Gravitational Waves (GWs) within the $10^{-4}-10^{-1}\,\mathrm{Hz}$ frequency band. It is expected that LISA will measure simultaneously, the GWs from more than ten thousands of these compact galactic binaries. The analysis of such a superposition of signals will represent one of the greatest challenge for the mission. Currently, in the LISA Datacode Challenge, each galactic binary is modeled as a quasi-monochromatic source of GWs. This corresponds to the circular motion of two point-masses at the 2.5 post-Newtonian approximation. If this picture is expected to be an accurate description for most of the galactic binaries that LSIA will detect, we nevertheless expect to observe eccentric systems with complex physical properties beyond the point-mass approximation. In this work, we investigate how a binary system of highly magnetic objects in quasi-circular orbit could affect the quasi-monochromatic picture of the GW signal detected by LISA. We demonstrate that the eccentricity generates additional frequency peaks at harmonics of the mean motion and that magnetism is responsible for shifting each frequency peak with respect to the case without magnetism. We provide analytical estimates and argue that LISA will be able to detect magnetism if it can measure the main peaks at two and three times the mean motion with a sufficient accuracy. |
1211.6157 | Phil Threlfall | Philip Threlfall and Susan M. Scott | The Monotonicity of the Gravitational Entropy Scalar within Quiescent
Cosmology | 19 pages, 7 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we show that Quiescent Cosmology [1, 2, 3] is consistent with
Penrose's Weyl Curvature Hypothesis and the notion of gravitational entropy
[4]. Gravitational entropy, from a conceptual point of view, acts in an
opposite fashion to the more familiar notion of entropy. A closed system of
gravitating particles will coalesce whereas a collection of gas particles will
tend to diffuse; regarding increasing entropy, these two scenarios are
identical. What has been shown previously [2, 3] is that gravitational entropy
at the initial singularity predicted by Quiescent Cosmology - the Isotropic
Past Singularity (IPS) - tends to zero. The results from this paper show that
not only is this the case but that gravitational entropy increases as this
singularity evolves.
In the first section of this paper we present relevant background information
and motivation. In the second section of this paper we present the main results
of this paper. Our third section contains a discussion of how this result will
inspire future research before we make concluding remarks in our final section.
| [
{
"created": "Mon, 26 Nov 2012 23:04:03 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Dec 2012 00:03:20 GMT",
"version": "v2"
}
] | 2012-12-18 | [
[
"Threlfall",
"Philip",
""
],
[
"Scott",
"Susan M.",
""
]
] | In this paper we show that Quiescent Cosmology [1, 2, 3] is consistent with Penrose's Weyl Curvature Hypothesis and the notion of gravitational entropy [4]. Gravitational entropy, from a conceptual point of view, acts in an opposite fashion to the more familiar notion of entropy. A closed system of gravitating particles will coalesce whereas a collection of gas particles will tend to diffuse; regarding increasing entropy, these two scenarios are identical. What has been shown previously [2, 3] is that gravitational entropy at the initial singularity predicted by Quiescent Cosmology - the Isotropic Past Singularity (IPS) - tends to zero. The results from this paper show that not only is this the case but that gravitational entropy increases as this singularity evolves. In the first section of this paper we present relevant background information and motivation. In the second section of this paper we present the main results of this paper. Our third section contains a discussion of how this result will inspire future research before we make concluding remarks in our final section. |
gr-qc/0703108 | Ezra Newman | Carlos Kozameh and Ezra T. Newman | Asymptotically Shear-free and Twist-free Null Geodesic Congruences | 10 pages | Class.Quant.Grav.24:3085-3090,2007 | 10.1088/0264-9381/24/11/019 | null | gr-qc | null | We show that, though they are rare, there are asymptotically flat space-times
that possess null geodesic congruences that are both asymptotically shear- free
and twist-free (surface forming). In particular, we display the class of
space-times that possess this property and demonstrate how these congruences
can be found. A special case within this class are the Robinson- Trautman
space-times. In addition, we show that in each case the congruence is isolated
in the sense that there are no other neighboring congruences with this dual
property.
| [
{
"created": "Wed, 21 Mar 2007 15:59:59 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kozameh",
"Carlos",
""
],
[
"Newman",
"Ezra T.",
""
]
] | We show that, though they are rare, there are asymptotically flat space-times that possess null geodesic congruences that are both asymptotically shear- free and twist-free (surface forming). In particular, we display the class of space-times that possess this property and demonstrate how these congruences can be found. A special case within this class are the Robinson- Trautman space-times. In addition, we show that in each case the congruence is isolated in the sense that there are no other neighboring congruences with this dual property. |
1110.2019 | Julian Adamek | Julian Adamek, Claudia de Rham and Ruth Durrer | Mode Spectrum of the Electromagnetic Field in Open Universe Models | 6 pages, 1 figure; v2: minor revision, appendix added, accepted for
publication in MNRAS | Mon.Not.R.Astron.Soc. 423 (2012) 2705-2710 | 10.1111/j.1365-2966.2012.21082.x | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the mode functions of the electromagnetic field on spherically
symmetric backgrounds with special attention to the subclass which allows for
the foliation as open Friedmann-Lemaitre (FL) spacetime. It is well-known that
in certain scalar field theories on open FL background there can exist
so-called supercurvature modes, their existence depending on parameters of the
theory. Looking at specific open universe models, such as open inflation and
the Milne universe, we find that no supercurvature modes are present in the
spectrum of the electromagnetic field. This excludes the possibility for
superadiabatic evolution of cosmological magnetic fields within these models
without relying on new physics or breaking the conformal invariance of
electromagnetism.
| [
{
"created": "Mon, 10 Oct 2011 12:08:14 GMT",
"version": "v1"
},
{
"created": "Thu, 3 May 2012 07:56:01 GMT",
"version": "v2"
}
] | 2012-06-21 | [
[
"Adamek",
"Julian",
""
],
[
"de Rham",
"Claudia",
""
],
[
"Durrer",
"Ruth",
""
]
] | We examine the mode functions of the electromagnetic field on spherically symmetric backgrounds with special attention to the subclass which allows for the foliation as open Friedmann-Lemaitre (FL) spacetime. It is well-known that in certain scalar field theories on open FL background there can exist so-called supercurvature modes, their existence depending on parameters of the theory. Looking at specific open universe models, such as open inflation and the Milne universe, we find that no supercurvature modes are present in the spectrum of the electromagnetic field. This excludes the possibility for superadiabatic evolution of cosmological magnetic fields within these models without relying on new physics or breaking the conformal invariance of electromagnetism. |
2108.02500 | Reginald Christian Bernardo | Reginald Christian Bernardo, Jackson Levi Said, Maria Caruana, Stephen
Appleby | Well-Tempered Minkowski Solutions in Teleparallel Horndeski Theory | 34 pages, 5 figures, v2: minor revisions, template changed, to appear
in CQG | 2022 Class. Quantum Grav. 39 015013 | 10.1088/1361-6382/ac36e4 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Well-tempering stands among the few classical methods of screening vacuum
energy to deliver a late-time, low energy vacuum state. We build on the class
of Horndeski models that admit a Minkowski vacuum state despite the presence of
an arbitrarily large vacuum energy to obtain a much larger family of models in
teleparallel Horndeski theory. We set up the routine for obtaining these models
and present a variety of cases, all of which are able to screen a natural
particle physics scale vacuum energy using degeneracy in the field equations.
We establish that well-tempering is the unique method of utilizing degeneracy
in Horndeski scalar-tensor gravity -- and its teleparallel generalisation --
that can accommodate self-tuned flat Minkowski solutions, when the explicit
scalar field dependence in the action is minimal (a tadpole and a conformal
coupling to the Ricci scalar). Finally, we study the dynamics of the
well-tempered teleparallel Galileon. We generate its phase portraits and assess
the attractor nature of the Minkowski vacuum under linear perturbations and
through a phase transition of vacuum energy.
| [
{
"created": "Thu, 5 Aug 2021 10:18:41 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Nov 2021 05:06:38 GMT",
"version": "v2"
}
] | 2021-12-13 | [
[
"Bernardo",
"Reginald Christian",
""
],
[
"Said",
"Jackson Levi",
""
],
[
"Caruana",
"Maria",
""
],
[
"Appleby",
"Stephen",
""
]
] | Well-tempering stands among the few classical methods of screening vacuum energy to deliver a late-time, low energy vacuum state. We build on the class of Horndeski models that admit a Minkowski vacuum state despite the presence of an arbitrarily large vacuum energy to obtain a much larger family of models in teleparallel Horndeski theory. We set up the routine for obtaining these models and present a variety of cases, all of which are able to screen a natural particle physics scale vacuum energy using degeneracy in the field equations. We establish that well-tempering is the unique method of utilizing degeneracy in Horndeski scalar-tensor gravity -- and its teleparallel generalisation -- that can accommodate self-tuned flat Minkowski solutions, when the explicit scalar field dependence in the action is minimal (a tadpole and a conformal coupling to the Ricci scalar). Finally, we study the dynamics of the well-tempered teleparallel Galileon. We generate its phase portraits and assess the attractor nature of the Minkowski vacuum under linear perturbations and through a phase transition of vacuum energy. |
2105.11430 | Dan A. Lee | Gregory J. Galloway and Dan A. Lee | A note on the positive mass theorem with boundary | 10 pages, Remark 6 from v2 (which is the published version) was
incorrect | Letters in Mathematical Physics, Vol 111, 111 (2021) | 10.1007/s11005-021-01449-3 | null | gr-qc math.DG | http://creativecommons.org/licenses/by-nc-nd/4.0/ | In this short note we explain how one can use established results to prove
various versions of the positive mass theorem for initial data sets with
boundary, in dimensions less than 8.
| [
{
"created": "Mon, 24 May 2021 17:39:41 GMT",
"version": "v1"
},
{
"created": "Sun, 22 Aug 2021 16:18:55 GMT",
"version": "v2"
},
{
"created": "Fri, 7 Jan 2022 19:06:04 GMT",
"version": "v3"
}
] | 2022-01-11 | [
[
"Galloway",
"Gregory J.",
""
],
[
"Lee",
"Dan A.",
""
]
] | In this short note we explain how one can use established results to prove various versions of the positive mass theorem for initial data sets with boundary, in dimensions less than 8. |
gr-qc/9704062 | Roman R. Zapatrin | R.R.Zapatrin | Finitary Algebraic Superspace | latex 2.09, no frills | Int.J.Theor.Phys. 37 (1998) 799-816 | null | IBR-MSP-970401 | gr-qc quant-ph | null | An algebraic scheme is suggested in which discretized spacetime turns out to
be a quantum observable. As an example, a toy model producing spacetimes of
four points with different topologies is presented. The possibility of
incorporating this scheme into the framework of non-commutative differential
geometry is discussed.
| [
{
"created": "Wed, 23 Apr 1997 10:04:15 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Zapatrin",
"R. R.",
""
]
] | An algebraic scheme is suggested in which discretized spacetime turns out to be a quantum observable. As an example, a toy model producing spacetimes of four points with different topologies is presented. The possibility of incorporating this scheme into the framework of non-commutative differential geometry is discussed. |
2303.07371 | Shafaq Elahi | Shafaq Gulzar Elahi and Anupam Mazumdar | Probing massless and massive gravitons via entanglement in a warped
extra dimension | Accepted for publication by Physical Review D ; Matches the journal
version | Physical Review D 108, 035018 (2023) | 10.1103/PhysRevD.108.035018 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravity's quantum nature can be probed in a laboratory by witnessing the
entanglement between the two quantum systems, which cannot be possible if
gravity is a classical entity. In this paper, we will provide a simple example
where we can probe the effects of higher dimensions, in particular, the warped
extra dimension of five-dimensional Anti-de Sitter spacetime ($\rm AdS_5$). We
assume that the two quantum harmonic oscillators are kept at a distance $d$ on
a 3-brane (our 4D world) embedded in $\rm AdS_5$, while gravity can propagate
in all five dimensions. We will compute the effective potential due to the
massless and massive gravitons propagating in the warped geometry. We will
compute the entanglement between position and momentum states for both static
and non-static cases. The entanglement enhances compared to the
four-dimensional massless graviton, and it depends now on the $\rm AdS_5$
radius. We will also show that if we would prepare non-Gaussian superposition
states, e.g. spatial superposition of masses of order $10^{-14}-10^{-15}$kg
with a superposition size of ${\cal O}(20)$ micron, we can yield larger
concurrence of order ${\cal O}(0.1)$.
| [
{
"created": "Mon, 13 Mar 2023 18:00:04 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Mar 2023 18:00:11 GMT",
"version": "v2"
},
{
"created": "Fri, 28 Jul 2023 17:51:42 GMT",
"version": "v3"
}
] | 2023-10-26 | [
[
"Elahi",
"Shafaq Gulzar",
""
],
[
"Mazumdar",
"Anupam",
""
]
] | Gravity's quantum nature can be probed in a laboratory by witnessing the entanglement between the two quantum systems, which cannot be possible if gravity is a classical entity. In this paper, we will provide a simple example where we can probe the effects of higher dimensions, in particular, the warped extra dimension of five-dimensional Anti-de Sitter spacetime ($\rm AdS_5$). We assume that the two quantum harmonic oscillators are kept at a distance $d$ on a 3-brane (our 4D world) embedded in $\rm AdS_5$, while gravity can propagate in all five dimensions. We will compute the effective potential due to the massless and massive gravitons propagating in the warped geometry. We will compute the entanglement between position and momentum states for both static and non-static cases. The entanglement enhances compared to the four-dimensional massless graviton, and it depends now on the $\rm AdS_5$ radius. We will also show that if we would prepare non-Gaussian superposition states, e.g. spatial superposition of masses of order $10^{-14}-10^{-15}$kg with a superposition size of ${\cal O}(20)$ micron, we can yield larger concurrence of order ${\cal O}(0.1)$. |
0705.0006 | Mauricio Mondragon | Mauricio Mondragon, Alejandro Perez, Carlo Rovelli | Multiple-event probability in general-relativistic quantum mechanics: a
discrete model | null | Phys.Rev.D76:064005,2007 | 10.1103/PhysRevD.76.064005 | null | gr-qc | null | We introduce a simple quantum mechanical model in which time and space are
discrete and periodic. These features avoid the complications related to
continuous-spectrum operators and infinite-norm states. The model provides a
tool for discussing the probabilistic interpretation of generally-covariant
quantum systems, without the confusion generated by spurious infinities. We use
the model to illustrate the formalism of general-relativistic quantum
mechanics, and to test the definition of multiple-event probability introduced
in a companion paper. We consider a version of the model with unitary
time-evolution and a version without unitary time-evolution
| [
{
"created": "Mon, 30 Apr 2007 20:07:22 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Mondragon",
"Mauricio",
""
],
[
"Perez",
"Alejandro",
""
],
[
"Rovelli",
"Carlo",
""
]
] | We introduce a simple quantum mechanical model in which time and space are discrete and periodic. These features avoid the complications related to continuous-spectrum operators and infinite-norm states. The model provides a tool for discussing the probabilistic interpretation of generally-covariant quantum systems, without the confusion generated by spurious infinities. We use the model to illustrate the formalism of general-relativistic quantum mechanics, and to test the definition of multiple-event probability introduced in a companion paper. We consider a version of the model with unitary time-evolution and a version without unitary time-evolution |
1906.11824 | Nikodem Poplawski | Jordan L. Cubero, Nikodem J. Pop{\l}awski | Analysis of big bounce in Einstein--Cartan cosmology | 5 pages, 3 tables, 2 figures | Class. Quantum Grav. 37, 025011 (2020) | 10.1088/1361-6382/ab5cb9 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the dynamics of a homogeneous and isotropic universe in the
Einstein--Cartan theory of gravity. The spin of fermions produces spacetime
torsion that prevents gravitational singularities and replaces the big bang
with a nonsingular big bounce. We show that a closed universe exists only when
a particular function of its scale factor and temperature is higher than some
threshold value, whereas an open and a flat universes do not have such a
restriction. We also show that a bounce of the scale factor is double: as the
temperature increases and then decreases, the scale factor decreases,
increases, decreases, and then increases.
| [
{
"created": "Thu, 27 Jun 2019 17:59:55 GMT",
"version": "v1"
}
] | 2019-12-30 | [
[
"Cubero",
"Jordan L.",
""
],
[
"Popławski",
"Nikodem J.",
""
]
] | We analyze the dynamics of a homogeneous and isotropic universe in the Einstein--Cartan theory of gravity. The spin of fermions produces spacetime torsion that prevents gravitational singularities and replaces the big bang with a nonsingular big bounce. We show that a closed universe exists only when a particular function of its scale factor and temperature is higher than some threshold value, whereas an open and a flat universes do not have such a restriction. We also show that a bounce of the scale factor is double: as the temperature increases and then decreases, the scale factor decreases, increases, decreases, and then increases. |
1605.03405 | Rampei Kimura | Rampei Kimura, Takahiro Tanaka, Kazuhiro Yamamoto, Yasuho Yamashita | Constraint on ghost-free bigravity from gravitational Cherenkov
radiation | 13 pages, 2 figures; v2 | Phys. Rev. D 94, 064059 (2016) | 10.1103/PhysRevD.94.064059 | YITP-16-60, KUNS-2626 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate gravitational Cherenkov radiation in a healthy branch of
background solutions in the ghost-free bigravity model. In this model, because
of the modification of dispersion relations, each polarization mode can possess
subluminal phase velocities, and the gravitational Cherenkov radiation could be
potentially emitted from a relativistic particle. In the present paper, we
derive conditions for the process of the gravitational Cherenkov radiation to
occur and estimate the energy emission rate for each polarization mode. We
found that the gravitational Cherenkov radiation emitted even from an ultrahigh
energy cosmic ray is sufficiently suppressed for the graviton's effective mass
less than $100\,{\rm eV}$, and the bigravity model with dark matter coupled to
the hidden metric is therefore consistent with observations of high energy
cosmic rays.
| [
{
"created": "Tue, 10 May 2016 08:05:21 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Sep 2016 04:50:35 GMT",
"version": "v2"
}
] | 2016-09-28 | [
[
"Kimura",
"Rampei",
""
],
[
"Tanaka",
"Takahiro",
""
],
[
"Yamamoto",
"Kazuhiro",
""
],
[
"Yamashita",
"Yasuho",
""
]
] | We investigate gravitational Cherenkov radiation in a healthy branch of background solutions in the ghost-free bigravity model. In this model, because of the modification of dispersion relations, each polarization mode can possess subluminal phase velocities, and the gravitational Cherenkov radiation could be potentially emitted from a relativistic particle. In the present paper, we derive conditions for the process of the gravitational Cherenkov radiation to occur and estimate the energy emission rate for each polarization mode. We found that the gravitational Cherenkov radiation emitted even from an ultrahigh energy cosmic ray is sufficiently suppressed for the graviton's effective mass less than $100\,{\rm eV}$, and the bigravity model with dark matter coupled to the hidden metric is therefore consistent with observations of high energy cosmic rays. |
2201.03959 | Davide Astesiano | Davide Astesiano | Rigid rotation in GR and a generalization of the virial theorem | 17 pages, 0 figures | null | 10.1007/s10714-022-02947-y | null | gr-qc astro-ph.GA | http://creativecommons.org/licenses/by/4.0/ | In this work we study the properties of rigidly rotating neutral dust
solutions in general relativity. This class of solutions gained relevance
recently due to applications to the dynamics of spiral galaxies. We show that
this class could be interpreted as a rigid body in general relativity and we
analyze the different properties respect to the rigidly rotating disk in
special relativity: for example, the general relativistic counterpart shows no
Doppler effect for a light signal emitted and received from any two points at
rest respect to the rigid body. This effect can be important to test the
validity of the assumed model for our galaxy. In the second part we approach
the problem from a low energy expansion perspective and we write down a
generalization of the virial theorem for stationary spacetimes. The
non-Newtonian contributions can lead to a re-weighting of dark matter in
galaxies.
| [
{
"created": "Tue, 11 Jan 2022 14:12:46 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Apr 2022 11:29:29 GMT",
"version": "v2"
},
{
"created": "Wed, 22 Jun 2022 08:11:09 GMT",
"version": "v3"
}
] | 2022-07-06 | [
[
"Astesiano",
"Davide",
""
]
] | In this work we study the properties of rigidly rotating neutral dust solutions in general relativity. This class of solutions gained relevance recently due to applications to the dynamics of spiral galaxies. We show that this class could be interpreted as a rigid body in general relativity and we analyze the different properties respect to the rigidly rotating disk in special relativity: for example, the general relativistic counterpart shows no Doppler effect for a light signal emitted and received from any two points at rest respect to the rigid body. This effect can be important to test the validity of the assumed model for our galaxy. In the second part we approach the problem from a low energy expansion perspective and we write down a generalization of the virial theorem for stationary spacetimes. The non-Newtonian contributions can lead to a re-weighting of dark matter in galaxies. |
2305.05541 | Ghulam Abbas | G. Abbas and R. H. Ali | Thermal fluctuations, quasi-normal modes and phase transition of the
charged AdS black hole with perfect fluid dark matter | 31 Pages, 41 EPS figure, accepted for Publication in EPJC | null | 10.1140/epjc/s10052-023-11580-1 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | In this paper, we study thermodynamics, thermal fluctuations, phase
transitions and the charged anti-de Sitter black hole surrounded by perfect
fluid dark matter. Large black holes are shown to be stable when subject to
thermal fluctuations, and we begin by exploring how these fluctuations affect
the uncorrected thermodynamic quantities of entropy, Helmholtz free energy,
Gibbs free energy, enthalpy specific heat, and phase transition stability. We
also discuss null geodesics and the radius of the photon sphere for the charged
AdS BH and use the radius of a photon sphere to calculate the Lyapunov exponent
and angular velocity. Exceptionally, we test the effects of various parameters
of a black hole graphically by observing the existence of the correction
parameter and the coupling parameter, which reveal the behavior of corrected
thermodynamic quantities. Lastly, we see how the system is stable (under the
effects of the dark matter parameter) by figuring out the specific heat and
Hawking temperature, which are both related to entropy.
| [
{
"created": "Sat, 6 May 2023 10:15:12 GMT",
"version": "v1"
}
] | 2023-05-31 | [
[
"Abbas",
"G.",
""
],
[
"Ali",
"R. H.",
""
]
] | In this paper, we study thermodynamics, thermal fluctuations, phase transitions and the charged anti-de Sitter black hole surrounded by perfect fluid dark matter. Large black holes are shown to be stable when subject to thermal fluctuations, and we begin by exploring how these fluctuations affect the uncorrected thermodynamic quantities of entropy, Helmholtz free energy, Gibbs free energy, enthalpy specific heat, and phase transition stability. We also discuss null geodesics and the radius of the photon sphere for the charged AdS BH and use the radius of a photon sphere to calculate the Lyapunov exponent and angular velocity. Exceptionally, we test the effects of various parameters of a black hole graphically by observing the existence of the correction parameter and the coupling parameter, which reveal the behavior of corrected thermodynamic quantities. Lastly, we see how the system is stable (under the effects of the dark matter parameter) by figuring out the specific heat and Hawking temperature, which are both related to entropy. |
2312.06590 | Alejandro C\'ardenas-Avenda\~no | Alejandro C\'ardenas-Avenda\~no and Aaron Held | A Lensing-Band Approach to Spacetime Constraints | 16 pages, 9 figures + 4 appendices and references. V2: Minor changes
to match the published version | Phys. Rev. D 109, 064052 (2024) | 10.1103/PhysRevD.109.064052 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | General relativity's prediction that all black holes are described by the
Kerr metric, irrespective of their size, can now be empirically tested using
electromagnetic observations of supermassive black holes and gravitational
waves from mergers of stellar-mass black holes. In this work, we focus on the
electromagnetic side of this test and quantify the constraining power of
very-long-baseline-interferometry (VLBI) observations of emission generated by
hot gas surrounding supermassive black holes. We demonstrate how to use lensing
bands--annular regions on the observer's screen surrounding the critical
curve--to constrain the underlying spacetime geometry. Contingent upon a
detection of a lensed VLBI feature, the resulting lensing-band framework allows
us to exclude spacetimes for which said feature cannot arise from geodesics
that traversed the equatorial plane more than once. Focusing on the first
indirect image and tests of black-hole uniqueness, we employ a parametrized
spacetime as a case study. We find that resolving geometric information that
goes beyond the apparent size of the critical curve has the potential to lift
degeneracies between different spacetime parameters. Our work thereby
quantifies a conservative estimate of the constraining power of VLBI
measurements and contributes to a larger effort to simultaneously constrain
geometry and astrophysics.
| [
{
"created": "Mon, 11 Dec 2023 18:27:05 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Mar 2024 15:17:41 GMT",
"version": "v2"
}
] | 2024-03-20 | [
[
"Cárdenas-Avendaño",
"Alejandro",
""
],
[
"Held",
"Aaron",
""
]
] | General relativity's prediction that all black holes are described by the Kerr metric, irrespective of their size, can now be empirically tested using electromagnetic observations of supermassive black holes and gravitational waves from mergers of stellar-mass black holes. In this work, we focus on the electromagnetic side of this test and quantify the constraining power of very-long-baseline-interferometry (VLBI) observations of emission generated by hot gas surrounding supermassive black holes. We demonstrate how to use lensing bands--annular regions on the observer's screen surrounding the critical curve--to constrain the underlying spacetime geometry. Contingent upon a detection of a lensed VLBI feature, the resulting lensing-band framework allows us to exclude spacetimes for which said feature cannot arise from geodesics that traversed the equatorial plane more than once. Focusing on the first indirect image and tests of black-hole uniqueness, we employ a parametrized spacetime as a case study. We find that resolving geometric information that goes beyond the apparent size of the critical curve has the potential to lift degeneracies between different spacetime parameters. Our work thereby quantifies a conservative estimate of the constraining power of VLBI measurements and contributes to a larger effort to simultaneously constrain geometry and astrophysics. |
1411.3583 | Prabir Rudra | Prabir Rudra (Indian Instt. of Engg. Sci. and tech., Pailan colg. of
Mgmt. and tech.) | Towards a possible solution for the coincidence problem: f(G) gravity as
background | 10 pages, 5 figures (Accepted for publication in Int. J. Mod. Phys.
D.). arXiv admin note: substantial text overlap with arXiv:1410.6710 | null | 10.1142/S0218271815500133 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we address the well-known cosmic coincidence problem in the
framework of the f(G) gravity. In order to achieve this, an interaction between
dark energy and dark matter is considered. A set-up is designed and a
constraint equation is obtained which generates the f(G) models that do not
suffer from the coincidence problem. Due to the absence of a universally
accepted interaction term introduced by a fundamental theory, the study is
conducted over three different forms of logically chosen interaction terms. To
illustrate the set-up three widely known models of f(G) gravity are taken into
consideration and the problem is studied under the designed set-up. The study
reveals that the popular f(G) gravity models does not approve of a satisfactory
solution of the long standing coincidence problem, thus proving to be a major
setback for them as successful models of universe. Finally, two
non-conventional models of f(G) gravity have been proposed and studied in the
framework of the designed set-up. It is seen that a complete solution of the
coincidence problem is achieved for these models. The study also reveals that
the b-interaction term is much more preferable compared to the other
interactions, due to its greater compliance with the recent observational data.
| [
{
"created": "Tue, 11 Nov 2014 06:30:45 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Rudra",
"Prabir",
"",
"Indian Instt. of Engg. Sci. and tech., Pailan colg. of\n Mgmt. and tech."
]
] | In this article we address the well-known cosmic coincidence problem in the framework of the f(G) gravity. In order to achieve this, an interaction between dark energy and dark matter is considered. A set-up is designed and a constraint equation is obtained which generates the f(G) models that do not suffer from the coincidence problem. Due to the absence of a universally accepted interaction term introduced by a fundamental theory, the study is conducted over three different forms of logically chosen interaction terms. To illustrate the set-up three widely known models of f(G) gravity are taken into consideration and the problem is studied under the designed set-up. The study reveals that the popular f(G) gravity models does not approve of a satisfactory solution of the long standing coincidence problem, thus proving to be a major setback for them as successful models of universe. Finally, two non-conventional models of f(G) gravity have been proposed and studied in the framework of the designed set-up. It is seen that a complete solution of the coincidence problem is achieved for these models. The study also reveals that the b-interaction term is much more preferable compared to the other interactions, due to its greater compliance with the recent observational data. |
1803.10719 | Katy Clough Dr | Katy Clough, Jens C. Niemeyer | On the difficulty of generating gravitational wave turbulence in the
early universe | 4 pages | null | 10.1088/1361-6382/aad7f0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A recent article by Galtier and Nazarenko [1] proposed that weakly nonlinear
gravitational waves could result in a turbulent cascade, with energy flowing
from high to low frequency modes or vice versa. This is an interesting
proposition for early universe cosmology because it could suggest some
"natural" initial conditions for the gravitational background. In this paper we
use the ADM formalism to show that, given some simple and, arguably, natural
assumptions, such initial conditions lead to expansion (or collapse) of the
spacetime on a timescale much faster than that of the turbulent cascade,
meaning that the cascade is unlikely to have sufficient time to develop under
general conditions. We suggest possible ways in which the expansion could be
mitigated to give the cascade time to develop.
| [
{
"created": "Wed, 28 Mar 2018 16:40:44 GMT",
"version": "v1"
}
] | 2018-08-29 | [
[
"Clough",
"Katy",
""
],
[
"Niemeyer",
"Jens C.",
""
]
] | A recent article by Galtier and Nazarenko [1] proposed that weakly nonlinear gravitational waves could result in a turbulent cascade, with energy flowing from high to low frequency modes or vice versa. This is an interesting proposition for early universe cosmology because it could suggest some "natural" initial conditions for the gravitational background. In this paper we use the ADM formalism to show that, given some simple and, arguably, natural assumptions, such initial conditions lead to expansion (or collapse) of the spacetime on a timescale much faster than that of the turbulent cascade, meaning that the cascade is unlikely to have sufficient time to develop under general conditions. We suggest possible ways in which the expansion could be mitigated to give the cascade time to develop. |
gr-qc/0408066 | Ishai Ben-Dov | Ishai Ben-Dov | The Penrose inequality and apparent horizons | 24 pages, 6 figures, revised for publication; revised section 6,
added footnote no. 16, typos corrected | Phys.Rev. D70 (2004) 124031 | 10.1103/PhysRevD.70.124031 | null | gr-qc | null | A spherically symmetric spacetime is presented with an initial data set that
is asymptotically flat, satisfies the dominant energy condition, and such that
on this initial data $M<\sqrt{A/16\pi}$, where M is the total (ADM) mass and A
is the area of the apparent horizon. This provides a counterexample to a
commonly stated version of the Penrose inequality, though it does not
contradict the ``true'' Penrose inequality.
| [
{
"created": "Thu, 19 Aug 2004 19:56:14 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Jan 2005 17:37:20 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Ben-Dov",
"Ishai",
""
]
] | A spherically symmetric spacetime is presented with an initial data set that is asymptotically flat, satisfies the dominant energy condition, and such that on this initial data $M<\sqrt{A/16\pi}$, where M is the total (ADM) mass and A is the area of the apparent horizon. This provides a counterexample to a commonly stated version of the Penrose inequality, though it does not contradict the ``true'' Penrose inequality. |
gr-qc/0308068 | Wataru Hikida | Wataru Hikida, Sanjay Jhingan, Hiroyuki Nakano, Norichika Sago, Misao
Sasaki, Takahiro Tanaka | A new analytical method for self-force regularization I. scalar charged
particle in Schwarzschild spacetime | 17 pages, no figure | Prog.Theor.Phys.111:821-840,2004 | 10.1143/PTP.111.821 | YITP-03-58,OCU-PHYS-204,AP-GR-13,KUNS-1866,OU-TAP-218 | gr-qc | null | We formulate a new analytical method for regularizing the self-force acting
on a particle of small mass $\mu$ orbiting a black hole of mass $M$, where
$\mu\ll M$. At first order in $\mu$, the geometry is perturbed and the motion
of the particle is affected by its self-force. The self-force, however,
diverges at the location of the particle, and hence should be regularized. It
is known that the properly regularized self-force is given by the tail part (or
the $R$-part) of the self-field, obtained by subtracting the direct part (or
the $S$-part) from the full self-field. The most successful method of
regularization proposed so far relies on the spherical harmonic decomposition
of the self-force, the so-called mode-sum regularization or mode decomposition
regularization. However, except for some special orbits, no systematic
analytical method for computing the regularized self-force has been given. In
this paper, utilizing a new decomposition of the retarded Green function in the
frequency domain, we formulate a systematic method for the computation of the
self-force. Our method relies on the post-Newtonian (PN) expansion but the
order of the expansion can be arbitrarily high. To demonstrate the essence of
our method, in this paper, we focus on a scalar charged particle on the
Schwarzschild background. The generalization to the gravitational case is
straightforward, except for some subtle issues related with the choice of gauge
(which exists irrespective of regularization methods).
| [
{
"created": "Thu, 21 Aug 2003 13:44:45 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Aug 2003 17:26:35 GMT",
"version": "v2"
},
{
"created": "Thu, 27 May 2004 05:09:53 GMT",
"version": "v3"
}
] | 2009-10-09 | [
[
"Hikida",
"Wataru",
""
],
[
"Jhingan",
"Sanjay",
""
],
[
"Nakano",
"Hiroyuki",
""
],
[
"Sago",
"Norichika",
""
],
[
"Sasaki",
"Misao",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | We formulate a new analytical method for regularizing the self-force acting on a particle of small mass $\mu$ orbiting a black hole of mass $M$, where $\mu\ll M$. At first order in $\mu$, the geometry is perturbed and the motion of the particle is affected by its self-force. The self-force, however, diverges at the location of the particle, and hence should be regularized. It is known that the properly regularized self-force is given by the tail part (or the $R$-part) of the self-field, obtained by subtracting the direct part (or the $S$-part) from the full self-field. The most successful method of regularization proposed so far relies on the spherical harmonic decomposition of the self-force, the so-called mode-sum regularization or mode decomposition regularization. However, except for some special orbits, no systematic analytical method for computing the regularized self-force has been given. In this paper, utilizing a new decomposition of the retarded Green function in the frequency domain, we formulate a systematic method for the computation of the self-force. Our method relies on the post-Newtonian (PN) expansion but the order of the expansion can be arbitrarily high. To demonstrate the essence of our method, in this paper, we focus on a scalar charged particle on the Schwarzschild background. The generalization to the gravitational case is straightforward, except for some subtle issues related with the choice of gauge (which exists irrespective of regularization methods). |
2111.05441 | Charis Anastopoulos | Charis Anastopoulos, Miles Blencowe and Bei-Lok Hu | Gravitational Decoherence in Deep Space Experiments | 7 pages. A white paper contribution to the Decadal Survey on
Biological and Physical Sciences (BPS) Research in Space 2023-2032 (BPS2023)
conducted by The National Academies of Sciences, Engineering and Medicine.
arXiv admin note: text overlap with arXiv:2111.02462 | null | null | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | Among the many worthwhile quantum experiments taking advantage of long
baselines in space, this white paper points to the far-reaching significance of
gravitational decoherence experiments. These experiments can provide clues as
to whether gravity is of a fundamental or an effective nature. They can also
discriminate between the predictions of quantum field theory in curved
spacetime, our default theory for quantum phenomena in background gravitational
fields, and other popular alternative quantum theories.
| [
{
"created": "Tue, 9 Nov 2021 22:44:15 GMT",
"version": "v1"
}
] | 2021-11-11 | [
[
"Anastopoulos",
"Charis",
""
],
[
"Blencowe",
"Miles",
""
],
[
"Hu",
"Bei-Lok",
""
]
] | Among the many worthwhile quantum experiments taking advantage of long baselines in space, this white paper points to the far-reaching significance of gravitational decoherence experiments. These experiments can provide clues as to whether gravity is of a fundamental or an effective nature. They can also discriminate between the predictions of quantum field theory in curved spacetime, our default theory for quantum phenomena in background gravitational fields, and other popular alternative quantum theories. |
gr-qc/0401047 | Kofinas Georgios | G. Kofinas and E. Papantonopoulos | Gravitational collapse in braneworld models with curvature corrections | References added | JCAP 0412 (2004) 011 | 10.1088/1475-7516/2004/12/011 | null | gr-qc astro-ph hep-th | null | We study the collapse of a homogeneous braneworld dust cloud in the context
of the various curvature correction scenarios, namely, the induced-gravity, the
Gauss-Bonnet, and the combined induced-gravity and Gauss-Bonnet. In accordance
to the Randall-Sundrum model, and contrary to four-dimensional general
relativity, we show in all cases that the exterior spacetime on the brane is
non-static.
| [
{
"created": "Mon, 12 Jan 2004 01:59:35 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Nov 2004 22:27:43 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Kofinas",
"G.",
""
],
[
"Papantonopoulos",
"E.",
""
]
] | We study the collapse of a homogeneous braneworld dust cloud in the context of the various curvature correction scenarios, namely, the induced-gravity, the Gauss-Bonnet, and the combined induced-gravity and Gauss-Bonnet. In accordance to the Randall-Sundrum model, and contrary to four-dimensional general relativity, we show in all cases that the exterior spacetime on the brane is non-static. |
gr-qc/0107086 | Giovanni Amelino-Camelia | Giovanni Amelino-Camelia | Space-time quantum solves three experimental paradoxes | LaTex, 9 pages. Typos corrected (in the version submitted yesterday
there was one type in equation and a couple of spelling typos). All aspects
of the analysis remain unchanged | Phys.Lett. B528 (2002) 181-187 | 10.1016/S0370-2693(02)01223-6 | null | gr-qc | null | I show that a Planck-scale deformation of the relativistic dispersion
relation, which has been independently considered in the quantum-gravity
literature, can explain the surprising results of three classes of experiments:
(1) observations of cosmic rays above the expected GZK limit, (2) observations
of multi-TeV photons from the BL Lac object Markarian 501, (3) studies of the
longitudinal development of the air showers produced by ultra-high-energy
hadronic particles. Experiments now in preparation, such as the ones planned
for the GLAST space telescope, will provide an independent test of this
solution of the three experimental paradoxes.
| [
{
"created": "Thu, 26 Jul 2001 17:42:26 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Jul 2001 12:27:05 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Amelino-Camelia",
"Giovanni",
""
]
] | I show that a Planck-scale deformation of the relativistic dispersion relation, which has been independently considered in the quantum-gravity literature, can explain the surprising results of three classes of experiments: (1) observations of cosmic rays above the expected GZK limit, (2) observations of multi-TeV photons from the BL Lac object Markarian 501, (3) studies of the longitudinal development of the air showers produced by ultra-high-energy hadronic particles. Experiments now in preparation, such as the ones planned for the GLAST space telescope, will provide an independent test of this solution of the three experimental paradoxes. |
1410.4567 | Shahar Hod | Shahar Hod | Resonance spectra of caged black holes | 5 pages | The European Physical Journal C 74, 3137 (2014) | 10.1140/epjc/s10052-014-3137-3 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent numerical studies of the coupled Einstein-Klein-Gordon system in a
cavity have provided compelling evidence that {\it confined} scalar fields
generically collapse to form black holes. Motivated by this intriguing
discovery, we here use analytical tools in order to study the characteristic
resonance spectra of the confined fields. These discrete resonant frequencies
are expected to dominate the late-time dynamics of the coupled
black-hole-field-cage system. We consider caged Reissner-Nordstr\"om black
holes whose confining mirrors are placed in the near-horizon region
$x_{\text{m}}\equiv (r_{\text{m}}-r_+)/r_+\ll\tau\equiv (r_+-r_-)/r_+$ (here
$r_{\text{m}}$ is the radius of the confining mirror and $r_{\pm}$ are the
radii of the black-hole horizons). We obtain a simple analytical expression for
the fundamental quasinormal resonances of the coupled black-hole-field-cage
system: $\omega_n=-i2\pi T_{\text{BH}}\cdot n[1+O(x^n_{\text{m}}/\tau^n)]$,
where $T_{\text{BH}}$ is the temperature of the caged black hole and
$n=1,2,3,...$ is the resonance parameter.
| [
{
"created": "Thu, 16 Oct 2014 20:00:11 GMT",
"version": "v1"
}
] | 2015-06-23 | [
[
"Hod",
"Shahar",
""
]
] | Recent numerical studies of the coupled Einstein-Klein-Gordon system in a cavity have provided compelling evidence that {\it confined} scalar fields generically collapse to form black holes. Motivated by this intriguing discovery, we here use analytical tools in order to study the characteristic resonance spectra of the confined fields. These discrete resonant frequencies are expected to dominate the late-time dynamics of the coupled black-hole-field-cage system. We consider caged Reissner-Nordstr\"om black holes whose confining mirrors are placed in the near-horizon region $x_{\text{m}}\equiv (r_{\text{m}}-r_+)/r_+\ll\tau\equiv (r_+-r_-)/r_+$ (here $r_{\text{m}}$ is the radius of the confining mirror and $r_{\pm}$ are the radii of the black-hole horizons). We obtain a simple analytical expression for the fundamental quasinormal resonances of the coupled black-hole-field-cage system: $\omega_n=-i2\pi T_{\text{BH}}\cdot n[1+O(x^n_{\text{m}}/\tau^n)]$, where $T_{\text{BH}}$ is the temperature of the caged black hole and $n=1,2,3,...$ is the resonance parameter. |
gr-qc/0506006 | Valery Kiselev | V.V.Kiselev | Quantum black hole and Hawking radiation at microscopic magnifying | 14 pages, iopart class, 8 eps-figures | null | null | null | gr-qc astro-ph hep-th | null | We establish a state of stopping the Hawking radiation by quantum
Schwarzschild black hole in the framework of quasi-classical thermal
quantization for particles behind the horizon. The mechanism of absorption and
radiation by the black hole is presented.
| [
{
"created": "Wed, 1 Jun 2005 06:37:20 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kiselev",
"V. V.",
""
]
] | We establish a state of stopping the Hawking radiation by quantum Schwarzschild black hole in the framework of quasi-classical thermal quantization for particles behind the horizon. The mechanism of absorption and radiation by the black hole is presented. |
1402.3009 | Edward Wilson-Ewing | Yi-Fu Cai, Edward Wilson-Ewing | Non-singular bounce scenarios in loop quantum cosmology and the
effective field description | 12 pages, 5 figures, v2: references added | JCAP03(2014)026 | 10.1088/1475-7516/2014/03/026 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A non-singular bouncing cosmology is generically obtained in loop quantum
cosmology due to non-perturbative quantum gravity effects. A similar picture
can be achieved in standard general relativity in the presence of a scalar
field with a non-standard kinetic term such that at high energy densities the
field evolves into a ghost condensate and causes a non-singular bounce. During
the bouncing phase, the perturbations can be stabilized by introducing a
Horndeski operator. Taking the matter content to be a dust field and an
ekpyrotic scalar field, we compare the dynamics in loop quantum cosmology and
in a non-singular bouncing effective field model with a non-standard kinetic
term at both the background and perturbative levels. We find that these two
settings share many important properties, including the result that they both
generate scale-invariant scalar perturbations. This shows that some quantum
gravity effects of the very early universe may be mimicked by effective field
models.
| [
{
"created": "Thu, 13 Feb 2014 00:03:07 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Mar 2014 19:25:02 GMT",
"version": "v2"
}
] | 2014-03-17 | [
[
"Cai",
"Yi-Fu",
""
],
[
"Wilson-Ewing",
"Edward",
""
]
] | A non-singular bouncing cosmology is generically obtained in loop quantum cosmology due to non-perturbative quantum gravity effects. A similar picture can be achieved in standard general relativity in the presence of a scalar field with a non-standard kinetic term such that at high energy densities the field evolves into a ghost condensate and causes a non-singular bounce. During the bouncing phase, the perturbations can be stabilized by introducing a Horndeski operator. Taking the matter content to be a dust field and an ekpyrotic scalar field, we compare the dynamics in loop quantum cosmology and in a non-singular bouncing effective field model with a non-standard kinetic term at both the background and perturbative levels. We find that these two settings share many important properties, including the result that they both generate scale-invariant scalar perturbations. This shows that some quantum gravity effects of the very early universe may be mimicked by effective field models. |
1305.0025 | Christian Boehmer | Christian G. Boehmer, Francisco S. N. Lobo, Nicola Tamanini | Einstein static Universe in hybrid metric-Palatini gravity | 10 pages, 6 figures; v2 added inhomogeneous perturbations | Phys. Rev. D 88, 104019 (2013) | 10.1103/PhysRevD.88.104019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hybrid metric-Palatini gravity is a recent and novel approach to modified
theories of gravity, which consists of adding to the metric Einstein-Hilbert
Lagrangian an f(R) term constructed a la Palatini. It was shown that the theory
passes local tests even if the scalar field is very light, and thus implies the
existence of a long-range scalar field, which is able to modify the dynamics in
galactic and cosmological scales, but leaves the Solar System unaffected. In
this work, motivated by the possibility that the Universe may have started out
in an asymptotically Einstein static state in the inflationary universe
context, we analyse the stability of the Einstein static Universe by
considering linear homogeneous perturbations in the respective dynamically
equivalent scalar-tensor representation of hybrid metric-Palatini gravity.
Considering linear homogeneous perturbations, the stability regions of the
Einstein static universe are parametrized by the first and second derivatives
of the scalar potential, and it is explicitly shown that a large class of
stable solutions exists in the respective parameter space, in the context of
hybrid metric-Palatini gravity.
| [
{
"created": "Tue, 30 Apr 2013 20:51:32 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Feb 2015 13:35:25 GMT",
"version": "v2"
}
] | 2015-02-19 | [
[
"Boehmer",
"Christian G.",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Tamanini",
"Nicola",
""
]
] | Hybrid metric-Palatini gravity is a recent and novel approach to modified theories of gravity, which consists of adding to the metric Einstein-Hilbert Lagrangian an f(R) term constructed a la Palatini. It was shown that the theory passes local tests even if the scalar field is very light, and thus implies the existence of a long-range scalar field, which is able to modify the dynamics in galactic and cosmological scales, but leaves the Solar System unaffected. In this work, motivated by the possibility that the Universe may have started out in an asymptotically Einstein static state in the inflationary universe context, we analyse the stability of the Einstein static Universe by considering linear homogeneous perturbations in the respective dynamically equivalent scalar-tensor representation of hybrid metric-Palatini gravity. Considering linear homogeneous perturbations, the stability regions of the Einstein static universe are parametrized by the first and second derivatives of the scalar potential, and it is explicitly shown that a large class of stable solutions exists in the respective parameter space, in the context of hybrid metric-Palatini gravity. |
2212.09346 | Dicong Liang | Dicong Liang, Rui Xu, Zhan-Feng Mai, Lijing Shao | Probing vector hair of black holes with extreme mass ratio inspirals | 8 pages, 4 figures | Phys. Rev. D 107 (2023) 044053 | 10.1103/PhysRevD.107.044053 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The bumblebee gravity model, with a vector field nonminimally coupled to
gravity, is a natural extension of the Einstein-Maxwell theory. In this theory,
a black hole can carry a vector hair, making the metric deviate from the
Schwarzschild metric. To investigate the detectability of the vector hair, we
consider an Extreme Mass Ratio Inspiral (EMRI) system, where a stellar-mass
black hole inspiraling into a supermassive black hole. We find that, with a
one-year observation of an EMRI by a space-based gravitational-wave detector,
we can probe the vector charge as small as $Q\sim 10^{-3}$ in the bumblebee
gravity model, which is about three orders of magnitude tighter comparing to
current EHT observations.
| [
{
"created": "Mon, 19 Dec 2022 10:23:37 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Feb 2023 01:52:30 GMT",
"version": "v2"
}
] | 2023-02-24 | [
[
"Liang",
"Dicong",
""
],
[
"Xu",
"Rui",
""
],
[
"Mai",
"Zhan-Feng",
""
],
[
"Shao",
"Lijing",
""
]
] | The bumblebee gravity model, with a vector field nonminimally coupled to gravity, is a natural extension of the Einstein-Maxwell theory. In this theory, a black hole can carry a vector hair, making the metric deviate from the Schwarzschild metric. To investigate the detectability of the vector hair, we consider an Extreme Mass Ratio Inspiral (EMRI) system, where a stellar-mass black hole inspiraling into a supermassive black hole. We find that, with a one-year observation of an EMRI by a space-based gravitational-wave detector, we can probe the vector charge as small as $Q\sim 10^{-3}$ in the bumblebee gravity model, which is about three orders of magnitude tighter comparing to current EHT observations. |
1007.1411 | Anil Yadav dr | Anil Kumar Yadav, Lallan Yadav | Bianchi Type III Anisotropic Dark Energy Models with Constant
Deceleration Parameter | 12 pages, 2 figures, Accepted version of IJTP | Int.J.Theor.Phys.50:218-227,2011 | 10.1007/s10773-010-0510-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Bianchi type III dark energy models with constant deceleration parameter
are investigated. The equation of state parameter $\omega$ is found to be time
dependent and its existing range for this model is consistent with the recent
observations of SN Ia data, SN Ia data (with CMBR anisotropy) and galaxy
clustering statistics. The physical aspect of the dark energy models are
discussed.
| [
{
"created": "Thu, 8 Jul 2010 16:11:02 GMT",
"version": "v1"
},
{
"created": "Sun, 18 Jul 2010 13:41:36 GMT",
"version": "v2"
},
{
"created": "Sat, 2 Oct 2010 04:42:42 GMT",
"version": "v3"
}
] | 2011-01-05 | [
[
"Yadav",
"Anil Kumar",
""
],
[
"Yadav",
"Lallan",
""
]
] | The Bianchi type III dark energy models with constant deceleration parameter are investigated. The equation of state parameter $\omega$ is found to be time dependent and its existing range for this model is consistent with the recent observations of SN Ia data, SN Ia data (with CMBR anisotropy) and galaxy clustering statistics. The physical aspect of the dark energy models are discussed. |
1909.13007 | Wen Zhao | Wen Zhao, Tan Liu, Linqing Wen, Tao Zhu, Anzhong Wang, Qian Hu, Cong
Zhou | Model-independent test of the parity symmetry of gravity with
gravitational waves | 9 pages,4 figs, EPJC accepted | EPJC 80, 630 (2020) | 10.1140/epjc/s10052-020-8211-4 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave (GW) data can be used to test the parity symmetry of
gravity by investigating the difference between left-hand and right-hand
circular polarization modes. In this article, we develop a method to decompose
the circular polarizations of GWs produced during the inspiralling stage of
compact binaries, with the help of stationary phase approximation. The foremost
advantage is that this method is simple, clean, independent of GW waveform, and
is applicable to the existing detector network. Applying it to the mock data,
we test the parity symmetry of gravity by constraining the velocity
birefringence of GWs. If a nearly edge-on binary neutron-stars with observed
electromagnetic counterparts at 40 Mpc is detected by the second-generation
detector network, one could derive the model-independent test on the parity
symmetry in gravity: the lower limit of the energy scale of parity violation
can be constrained within $\mathcal{O}(10^4{\rm eV})$.
| [
{
"created": "Sat, 28 Sep 2019 02:35:54 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Jul 2020 01:00:01 GMT",
"version": "v2"
}
] | 2020-07-21 | [
[
"Zhao",
"Wen",
""
],
[
"Liu",
"Tan",
""
],
[
"Wen",
"Linqing",
""
],
[
"Zhu",
"Tao",
""
],
[
"Wang",
"Anzhong",
""
],
[
"Hu",
"Qian",
""
],
[
"Zhou",
"Cong",
""
]
] | Gravitational wave (GW) data can be used to test the parity symmetry of gravity by investigating the difference between left-hand and right-hand circular polarization modes. In this article, we develop a method to decompose the circular polarizations of GWs produced during the inspiralling stage of compact binaries, with the help of stationary phase approximation. The foremost advantage is that this method is simple, clean, independent of GW waveform, and is applicable to the existing detector network. Applying it to the mock data, we test the parity symmetry of gravity by constraining the velocity birefringence of GWs. If a nearly edge-on binary neutron-stars with observed electromagnetic counterparts at 40 Mpc is detected by the second-generation detector network, one could derive the model-independent test on the parity symmetry in gravity: the lower limit of the energy scale of parity violation can be constrained within $\mathcal{O}(10^4{\rm eV})$. |
2312.12702 | Hongsheng Zhang | Chunmei Liu, Hongsheng Zhang | Black Holes and Non-perturbative Gravitational Waves in $f(R)$ Gravity | 13 pages | Eur. Phys. J. C (2023) 83:1096 | 10.1140/epjc/s10052-023-12261-9 | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | Exact solutions of spherically symmetric black hole and gravitational wave
are explored in $f(R)$ gravity in arbitrary dimension. We find two exact
solutions for the radiation and absorption of null dust. In the framework of
general relativity, the Birkhoff theorem strictly forbids the existence of
spherical gravitational waves in vacuum space. We find spherical
non-perturbative gravitational waves, which are shear-free, twist-free, but
expanding.
| [
{
"created": "Wed, 20 Dec 2023 01:58:43 GMT",
"version": "v1"
}
] | 2023-12-21 | [
[
"Liu",
"Chunmei",
""
],
[
"Zhang",
"Hongsheng",
""
]
] | Exact solutions of spherically symmetric black hole and gravitational wave are explored in $f(R)$ gravity in arbitrary dimension. We find two exact solutions for the radiation and absorption of null dust. In the framework of general relativity, the Birkhoff theorem strictly forbids the existence of spherical gravitational waves in vacuum space. We find spherical non-perturbative gravitational waves, which are shear-free, twist-free, but expanding. |
2207.10658 | Qiu Shi Wang | Qiu Shi Wang | Local Dirac energy decay in the 5D Myers-Perry geometry using an
integral spectral representation for the Dirac propagator | Minor corrections and improvements, published version, 15 pages | Classical and Quantum Gravity 39 (2022), no. 23, 235016 | 10.1088/1361-6382/ac9f9f | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | We consider the massive Dirac equation in the exterior region of the
5-dimensional Myers-Perry black hole. Using the resulting ODEs obtained from
the separation of variables of the Dirac equation, we construct an integral
spectral representation for the solution of the Cauchy problem with compactly
supported smooth initial data. We then prove that the probability of presence
of a Dirac particle to be in any compact region of space decays to zero as
$t\to\infty$, in analogy with the case of the Dirac operator in the Kerr-Newman
geometry.
| [
{
"created": "Thu, 21 Jul 2022 17:53:26 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Jul 2022 14:43:04 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Nov 2022 15:16:18 GMT",
"version": "v3"
}
] | 2022-11-22 | [
[
"Wang",
"Qiu Shi",
""
]
] | We consider the massive Dirac equation in the exterior region of the 5-dimensional Myers-Perry black hole. Using the resulting ODEs obtained from the separation of variables of the Dirac equation, we construct an integral spectral representation for the solution of the Cauchy problem with compactly supported smooth initial data. We then prove that the probability of presence of a Dirac particle to be in any compact region of space decays to zero as $t\to\infty$, in analogy with the case of the Dirac operator in the Kerr-Newman geometry. |
2404.19012 | Giulia Ventagli | Giulia Ventagli, Pedro G. S. Fernandes, Andrea Maselli, Antonio
Padilla, Thomas P. Sotiriou | Neutron stars and the cosmological constant problem | 21 pages, 15 figures | null | null | null | gr-qc astro-ph.HE hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | Phase transitions can play an important role in the cosmological constant
problem, allowing the underlying vacuum energy, and therefore the value of the
cosmological constant, to change. Deep within the core of neutron stars, the
local pressure may be sufficiently high to trigger the QCD phase transition,
thus generating a shift in the value of the cosmological constant. The
gravitational effects of such a transition should then be imprinted on the
properties of the star. Working in the framework of General Relativity, we
provide a new model of the stellar interior, allowing for a QCD and a vacuum
energy phase transition. We determine the impact of a vacuum energy jump on
mass-radius relations, tidal deformability-radius relations, I-Love-Q relations
and on the combined tidal deformability measured in neutron star binaries.
| [
{
"created": "Mon, 29 Apr 2024 18:00:14 GMT",
"version": "v1"
}
] | 2024-05-01 | [
[
"Ventagli",
"Giulia",
""
],
[
"Fernandes",
"Pedro G. S.",
""
],
[
"Maselli",
"Andrea",
""
],
[
"Padilla",
"Antonio",
""
],
[
"Sotiriou",
"Thomas P.",
""
]
] | Phase transitions can play an important role in the cosmological constant problem, allowing the underlying vacuum energy, and therefore the value of the cosmological constant, to change. Deep within the core of neutron stars, the local pressure may be sufficiently high to trigger the QCD phase transition, thus generating a shift in the value of the cosmological constant. The gravitational effects of such a transition should then be imprinted on the properties of the star. Working in the framework of General Relativity, we provide a new model of the stellar interior, allowing for a QCD and a vacuum energy phase transition. We determine the impact of a vacuum energy jump on mass-radius relations, tidal deformability-radius relations, I-Love-Q relations and on the combined tidal deformability measured in neutron star binaries. |
gr-qc/9701037 | Alexander Zhuk | A.Zhuk | Multidimensional Topological Foam | 10 pages, latex, submitted to Gravitation and Cosmology | Grav.Cosmol. 3 (1997) 24-28 | null | FUB HEP/12-96 | gr-qc | null | Multidimensional cosmological model with the topology M=RxM_1xM_2x...xM_n
where M_i (i=1,... ,n) undergo a chain splitting into arbitrary number of
compact spaces is considered. It is shown that equations of motion can be
solved exactly because they depend only on the effective curvatures and
dimensions and "forget" about inner topological structure. It is proved that
effective cosmological action for the model with n=1 in the case of infinite
splitting of the internal space coincides with the tree-level effective action
for a bosonic string.
| [
{
"created": "Wed, 15 Jan 1997 21:18:23 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Zhuk",
"A.",
""
]
] | Multidimensional cosmological model with the topology M=RxM_1xM_2x...xM_n where M_i (i=1,... ,n) undergo a chain splitting into arbitrary number of compact spaces is considered. It is shown that equations of motion can be solved exactly because they depend only on the effective curvatures and dimensions and "forget" about inner topological structure. It is proved that effective cosmological action for the model with n=1 in the case of infinite splitting of the internal space coincides with the tree-level effective action for a bosonic string. |
2304.03819 | Arad Nasiri | Santanu Das, Arad Nasiri, Yasaman K. Yazdi | Aspects of Everpresent $\Lambda$ (I): A Fluctuating Cosmological
Constant from Spacetime Discreteness | 28 pages, 10 figures | JCAP10(2023)047 | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We provide a comprehensive discussion of the Everpresent $\Lambda$
cosmological model arising from fundamental principles in causal set theory and
unimodular gravity. In this framework the value of the cosmological constant
($\Lambda$) fluctuates, in magnitude and in sign, over cosmic history. At each
epoch, $\Lambda$ stays statistically close to the inverse square root of the
spacetime volume. Since the latter is of the order of $H^2$ today, this
provides a way out of the cosmological constant puzzle without fine tuning. Our
discussion includes a review of what is known about the topic as well as new
motivations and insights supplementing the original arguments. We also study
features of a phenomenological implementation of this model, and investigate
the statistics of simulations based on it. Our results show that while the
observed values of $H_0$ and $\Omega_\Lambda^0$ are not typical outcomes of the
model, they can be achieved through a modest number of simulations. We also
confirm some expected features of $\Lambda$ based on this model, such as the
fact that it stays statistically close to the value of the total ambient energy
density (be it matter or radiation dominated), and that it is likely to change
sign roughly every Hubble timescale.
| [
{
"created": "Fri, 7 Apr 2023 19:07:42 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Feb 2024 21:05:40 GMT",
"version": "v2"
}
] | 2024-02-22 | [
[
"Das",
"Santanu",
""
],
[
"Nasiri",
"Arad",
""
],
[
"Yazdi",
"Yasaman K.",
""
]
] | We provide a comprehensive discussion of the Everpresent $\Lambda$ cosmological model arising from fundamental principles in causal set theory and unimodular gravity. In this framework the value of the cosmological constant ($\Lambda$) fluctuates, in magnitude and in sign, over cosmic history. At each epoch, $\Lambda$ stays statistically close to the inverse square root of the spacetime volume. Since the latter is of the order of $H^2$ today, this provides a way out of the cosmological constant puzzle without fine tuning. Our discussion includes a review of what is known about the topic as well as new motivations and insights supplementing the original arguments. We also study features of a phenomenological implementation of this model, and investigate the statistics of simulations based on it. Our results show that while the observed values of $H_0$ and $\Omega_\Lambda^0$ are not typical outcomes of the model, they can be achieved through a modest number of simulations. We also confirm some expected features of $\Lambda$ based on this model, such as the fact that it stays statistically close to the value of the total ambient energy density (be it matter or radiation dominated), and that it is likely to change sign roughly every Hubble timescale. |
1411.3623 | Babak Vakili | B. Malekolkalami, K. Atazadeh and B. Vakili | Late time acceleration in a non-commutative model of modified cosmology | 9 pages, no figures, typos corrected | Phys. Lett. B 739 (2014) 400 | 10.1016/j.physletb.2014.11.003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the effects of noncommutativity between the position-position,
position-momentum and momentum-momentum of a phase space corresponding to a
modified cosmological model. We show that the existence of such
noncommutativity results in a Moyal Poisson algebra between the phase space
variables in which the product law between the functions is of the kind of an
$\alpha$-deformed product. We then transform the variables in such a way that
the Poisson brackets between the dynamical variables take the form of a usual
Poisson bracket but this time with a noncommutative structure. For a power law
expression for the function of the Ricci scalar with which the action of the
gravity model is modified, the exact solutions in the commutative and
noncommutative cases are presented and compared. In terms of these solutions we
address the issue of the late time acceleration in cosmic evolution.
| [
{
"created": "Thu, 13 Nov 2014 17:31:14 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Nov 2014 15:49:38 GMT",
"version": "v2"
}
] | 2015-06-23 | [
[
"Malekolkalami",
"B.",
""
],
[
"Atazadeh",
"K.",
""
],
[
"Vakili",
"B.",
""
]
] | We investigate the effects of noncommutativity between the position-position, position-momentum and momentum-momentum of a phase space corresponding to a modified cosmological model. We show that the existence of such noncommutativity results in a Moyal Poisson algebra between the phase space variables in which the product law between the functions is of the kind of an $\alpha$-deformed product. We then transform the variables in such a way that the Poisson brackets between the dynamical variables take the form of a usual Poisson bracket but this time with a noncommutative structure. For a power law expression for the function of the Ricci scalar with which the action of the gravity model is modified, the exact solutions in the commutative and noncommutative cases are presented and compared. In terms of these solutions we address the issue of the late time acceleration in cosmic evolution. |
gr-qc/9708052 | Eduardo Gueron | Eduardo Gu\'eron and P.S. Letelier | Textures and Newtonian Gravity | 4 pages, 4 ps figures, REVTEX, accepted for publication in PRD | Phys.Rev.D56:5272-5275,1997 | 10.1103/PhysRevD.56.5272 | null | gr-qc | null | Newtonian theory is used to study the gravitational effects of a texture, in
particular the formation of massive structures.
| [
{
"created": "Thu, 21 Aug 1997 20:42:45 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Guéron",
"Eduardo",
""
],
[
"Letelier",
"P. S.",
""
]
] | Newtonian theory is used to study the gravitational effects of a texture, in particular the formation of massive structures. |
2307.10966 | Marco de Cesare | Marco de Cesare, Giulia Gubitosi | Cosmological evolution from modified Bekenstein entropy law | 14 pages, 2 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the dynamics of the homogeneous and isotropic cosmological
background in the recently proposed ``quantum phenomenological gravitational
dynamics'', characterised by logarithmic corrections to the Bekenstein entropy.
We show that the model admits a family of solutions that are self-accelerating
both at early and late times: they approach de Sitter in the future and admit a
past attractor corresponding to an inflationary acceleration era. On the other
hand, there are no solutions corresponding to a primordial bounce. We also show
that asking scalar perturbations to be unaffected by instabilities on
observable scales puts stringent constraints on the deviations from general
relativity encoded by the model.
| [
{
"created": "Thu, 20 Jul 2023 15:50:51 GMT",
"version": "v1"
}
] | 2023-07-21 | [
[
"de Cesare",
"Marco",
""
],
[
"Gubitosi",
"Giulia",
""
]
] | We study the dynamics of the homogeneous and isotropic cosmological background in the recently proposed ``quantum phenomenological gravitational dynamics'', characterised by logarithmic corrections to the Bekenstein entropy. We show that the model admits a family of solutions that are self-accelerating both at early and late times: they approach de Sitter in the future and admit a past attractor corresponding to an inflationary acceleration era. On the other hand, there are no solutions corresponding to a primordial bounce. We also show that asking scalar perturbations to be unaffected by instabilities on observable scales puts stringent constraints on the deviations from general relativity encoded by the model. |
1804.02182 | Satadal Datta | Satadal Datta | Acoustic Analogue of Gravitational Wave | null | Phys. Rev. D 98, 064049 (2018) | 10.1103/PhysRevD.98.064049 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore nonlinear perturbations in different static fluid systems. We find
that the equations, corresponding to the perturbation of the integrals of
motion, i.e; Bernoulli's constant and the mass flow rate, satisfy massless
scalar field equation in a time dependent acoustic metric. When one is
interested up to the second order behaviour of the perturbations, the emergent
time dependent acoustic metric of the system, derived from the massless scalar
field equations of the perturbations of the integrals of motion, has some
astounding similarities with the metric describing gravitational wave in
Minkowski spacetime.
| [
{
"created": "Fri, 6 Apr 2018 10:02:15 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Apr 2018 20:07:28 GMT",
"version": "v2"
}
] | 2018-10-03 | [
[
"Datta",
"Satadal",
""
]
] | We explore nonlinear perturbations in different static fluid systems. We find that the equations, corresponding to the perturbation of the integrals of motion, i.e; Bernoulli's constant and the mass flow rate, satisfy massless scalar field equation in a time dependent acoustic metric. When one is interested up to the second order behaviour of the perturbations, the emergent time dependent acoustic metric of the system, derived from the massless scalar field equations of the perturbations of the integrals of motion, has some astounding similarities with the metric describing gravitational wave in Minkowski spacetime. |
2405.12671 | Etera R. Livine | Etera R. Livine, Clara Montagnon, Naritaka Oshita, Hugo Roussille | Scalar Quasi-Normal Modes of a Loop Quantum Black Hole | 29 pages; auxiliary mathematica notebook
QNM_recursion_coefficients.nb with explicit QNM recursion relation
coefficients | null | null | YITP-24-58, RIKEN-iTHEMS-Report-24 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the Quasi-Normal Mode (QNM) frequencies for scalar perturbations
for modified Schwarzschild black holes in Loop Quantum Gravity. We study the
singularity-free polymerized metric characterised by two parameters encoding
loop quantum effects: the minimal area gap $a_0$ and the polymeric deformation
parameter $P$. We perform numerical computations using Leaver's continued
fraction method and compare our results to other semi-analytical methods and
existing literature. We study the effects on the QNM spectrum of variation of
both deformation parameters and systematically compare to the standard
Schwarzschild case. In particular we find that the scalar fundamental mode is
modified from the third decimal for values of $P$ in accordance with the most
recent astrophysical constraints. We also show that qualitative differences
arise for highly damped modes: on the one hand, a new crossing of the imaginary
axis occurs for high values of $a_0$ and, on the other hand, increasing $P$
produces a positive shift of the real part and an increase of the spacing in
imaginary part between modes.
| [
{
"created": "Tue, 21 May 2024 10:42:04 GMT",
"version": "v1"
}
] | 2024-05-22 | [
[
"Livine",
"Etera R.",
""
],
[
"Montagnon",
"Clara",
""
],
[
"Oshita",
"Naritaka",
""
],
[
"Roussille",
"Hugo",
""
]
] | We compute the Quasi-Normal Mode (QNM) frequencies for scalar perturbations for modified Schwarzschild black holes in Loop Quantum Gravity. We study the singularity-free polymerized metric characterised by two parameters encoding loop quantum effects: the minimal area gap $a_0$ and the polymeric deformation parameter $P$. We perform numerical computations using Leaver's continued fraction method and compare our results to other semi-analytical methods and existing literature. We study the effects on the QNM spectrum of variation of both deformation parameters and systematically compare to the standard Schwarzschild case. In particular we find that the scalar fundamental mode is modified from the third decimal for values of $P$ in accordance with the most recent astrophysical constraints. We also show that qualitative differences arise for highly damped modes: on the one hand, a new crossing of the imaginary axis occurs for high values of $a_0$ and, on the other hand, increasing $P$ produces a positive shift of the real part and an increase of the spacing in imaginary part between modes. |
1204.1291 | Carlos Molina Mendes | C. Molina and J. C. S. Neves | Wormholes in de Sitter branes | 10 pages, 7 figures | Physical Review D 86, 024015 (2012) | 10.1103/PhysRevD.86.024015 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we present a class of geometries which describes wormholes in a
Randall-Sundrum brane model, focusing on de Sitter backgrounds. Maximal
extensions of the solutions are constructed and their causal structures are
discussed. A perturbative analysis is developed, where matter and gravitational
perturbations are studied. Analytical results for the quasinormal spectra are
obtained and an extensive numerical survey is conducted. Our results indicate
that the wormhole geometries presented are stable.
| [
{
"created": "Thu, 5 Apr 2012 18:02:00 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Aug 2012 22:30:28 GMT",
"version": "v2"
}
] | 2012-08-06 | [
[
"Molina",
"C.",
""
],
[
"Neves",
"J. C. S.",
""
]
] | In this work we present a class of geometries which describes wormholes in a Randall-Sundrum brane model, focusing on de Sitter backgrounds. Maximal extensions of the solutions are constructed and their causal structures are discussed. A perturbative analysis is developed, where matter and gravitational perturbations are studied. Analytical results for the quasinormal spectra are obtained and an extensive numerical survey is conducted. Our results indicate that the wormhole geometries presented are stable. |
1805.09667 | David Benisty | David Benisty, Eduardo I. Guendelman | A correspondence between $1^{st}$ and $2^{nd}$ order formalism by a
metricity constraint | 5 pages. Accepted for publication in Phys Rev D | Phys. Rev. D 98, 044023 (2018) | 10.1103/PhysRevD.98.044023 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A way to obtain a correspondence between the first order and second order
formalism is studied. By introducing a Lagrange multiplier coupled to the
covariant derivative of the metric, a metricity constraint is implemented. The
new contributions which comes from the variation of the Lagrange multiplier
transforms the field equations from the first order to the second order
formalism, yet the action is formulated in the first order. In this way all the
higher derivatives terms in the second order formalism appear as derivatives of
the Lagrange multiplier. Using the same method for breaking metricity condition
and building conformal invariant theory is briefly discussed, so the method
goes beyond just the study of first order or second formulations of gravity, in
fact vast new possible theories of gravity are envisioned this way.
| [
{
"created": "Thu, 24 May 2018 13:48:16 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Jun 2018 18:18:28 GMT",
"version": "v2"
},
{
"created": "Wed, 1 Aug 2018 19:09:45 GMT",
"version": "v3"
}
] | 2018-08-22 | [
[
"Benisty",
"David",
""
],
[
"Guendelman",
"Eduardo I.",
""
]
] | A way to obtain a correspondence between the first order and second order formalism is studied. By introducing a Lagrange multiplier coupled to the covariant derivative of the metric, a metricity constraint is implemented. The new contributions which comes from the variation of the Lagrange multiplier transforms the field equations from the first order to the second order formalism, yet the action is formulated in the first order. In this way all the higher derivatives terms in the second order formalism appear as derivatives of the Lagrange multiplier. Using the same method for breaking metricity condition and building conformal invariant theory is briefly discussed, so the method goes beyond just the study of first order or second formulations of gravity, in fact vast new possible theories of gravity are envisioned this way. |
2011.06276 | Nobuyoshi Komatsu | Nobuyoshi Komatsu | Evolution of dissipative and non-dissipative universes in holographic
cosmological models with a power-law term | Final version accepted for publication in PRD. A typo is corrected.
[17 pages, 8 figures] | Phys. Rev. D 103, 023534 (2021) | 10.1103/PhysRevD.103.023534 | null | gr-qc astro-ph.CO hep-ph | http://creativecommons.org/licenses/by/4.0/ | Density perturbations related to structure formations are expected to be
different in dissipative and non-dissipative universes, even if the background
evolution of the two universes is the same. To clarify the difference between
the two universes, first-order density perturbations are studied, using two
types of holographic cosmological models. The first type is a "$\Lambda(t)$
model" similar to a time-varying $\Lambda(t)$ cosmology for the non-dissipative
universe. The second type is a "BV model" similar to a bulk viscous cosmology
for the dissipative universe. To systematically examine the two different
universes, a power-law term proportional to $H^{\alpha}$ is applied to the
$\Lambda(t)$ and BV (bulk-viscous-cosmology-like) models, assuming a flat
Friedmann--Robertson--Walker model for the late universe. Here, $H$ is the
Hubble parameter and $\alpha$ is a free parameter whose value is a real number.
The $\Lambda(t)$-$H^{\alpha}$ and BV-$H^{\alpha}$ models are used to examine
first-order density perturbations for matter, in which the background evolution
of the two models is equivalent. In addition, thermodynamic constraints on the
two models are discussed, with a focus on the maximization of entropy on the
horizon of the universe, extending previous analyses [Phys. Rev. D 100, 123545
(2019) (arXiv:1911.08306); 102, 063512 (2020) (arXiv:2006.09650)].
Consequently, the $\Lambda(t)$-$H^{\alpha}$ model for small $|\alpha|$ values
is found to be consistent with observations and satisfies the thermodynamic
constraints, compared with the BV-$H^{\alpha}$ model. The results show that the
non-dissipative universe described by the $\Lambda(t)$-$H^{\alpha}$ model
similar to lambda cold dark matter models is likely favored.
| [
{
"created": "Thu, 12 Nov 2020 09:27:03 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Jan 2021 23:25:30 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Jan 2021 23:23:42 GMT",
"version": "v3"
}
] | 2021-01-27 | [
[
"Komatsu",
"Nobuyoshi",
""
]
] | Density perturbations related to structure formations are expected to be different in dissipative and non-dissipative universes, even if the background evolution of the two universes is the same. To clarify the difference between the two universes, first-order density perturbations are studied, using two types of holographic cosmological models. The first type is a "$\Lambda(t)$ model" similar to a time-varying $\Lambda(t)$ cosmology for the non-dissipative universe. The second type is a "BV model" similar to a bulk viscous cosmology for the dissipative universe. To systematically examine the two different universes, a power-law term proportional to $H^{\alpha}$ is applied to the $\Lambda(t)$ and BV (bulk-viscous-cosmology-like) models, assuming a flat Friedmann--Robertson--Walker model for the late universe. Here, $H$ is the Hubble parameter and $\alpha$ is a free parameter whose value is a real number. The $\Lambda(t)$-$H^{\alpha}$ and BV-$H^{\alpha}$ models are used to examine first-order density perturbations for matter, in which the background evolution of the two models is equivalent. In addition, thermodynamic constraints on the two models are discussed, with a focus on the maximization of entropy on the horizon of the universe, extending previous analyses [Phys. Rev. D 100, 123545 (2019) (arXiv:1911.08306); 102, 063512 (2020) (arXiv:2006.09650)]. Consequently, the $\Lambda(t)$-$H^{\alpha}$ model for small $|\alpha|$ values is found to be consistent with observations and satisfies the thermodynamic constraints, compared with the BV-$H^{\alpha}$ model. The results show that the non-dissipative universe described by the $\Lambda(t)$-$H^{\alpha}$ model similar to lambda cold dark matter models is likely favored. |
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