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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1012.1409 | Kouji Nakamura | Kouji Nakamura | Construction of gauge-invariant variables for linear-order metric
perturbations on some background spacetimes | 4 pages, no figure, Prepared for the proceedings of 20th Workshop On
General Relativity and Gravitation (Sept. 21 - Sept. 25, (2010), YITP Kyoto
University, Japan) | null | null | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gauge-invariant treatments of general-relativistic higher-order perturbations
on generic background spacetime is proposed. We show the fact that the
linear-order metric perturbation is decomposed into gauge-invariant and
gauge-variant parts, which was the important premise of this general framework.
This means that the development the higher-order gauge-invariant perturbation
theory on generic background spacetime is possible.
| [
{
"created": "Tue, 7 Dec 2010 06:29:40 GMT",
"version": "v1"
}
] | 2015-03-17 | [
[
"Nakamura",
"Kouji",
""
]
] | Gauge-invariant treatments of general-relativistic higher-order perturbations on generic background spacetime is proposed. We show the fact that the linear-order metric perturbation is decomposed into gauge-invariant and gauge-variant parts, which was the important premise of this general framework. This means that the development the higher-order gauge-invariant perturbation theory on generic background spacetime is possible. |
1710.10588 | David Benisty | David Benisty and Eduardo I. Guendelman | A transition between bouncing hyper-inflation to {\Lambda}CDM from
diffusive scalar fields | Updated version, before acceptance for publication | null | 10.1142/S0217751X18501191 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the history of the universe from a possible big bang or a bounce
into a late period of a unified interacting dark energy - dark matter model.
The model is based on the Two Measures Theories (T.M.T.) which introduces a
metric independent volume element and this allows us to construct a unification
of dark energy and dark matter. A generalization of the T.M.T. gives a
diffusive non-conservative stress energy momentum tensor in addition to the
conserved stress energy tensor which appear in Einstein equations. These leads
to a formulation of interacting DE-DM dust models in the form of a diffusive
type interacting Unified Dark Energy and Dark Matter scenario. The deviation
from $\Lambda$CDM is determined by the diffusion constant $C_2$. For $C_2=0$
the model is indistinguishable from $\Lambda$CDM. Numerical solutions of the
theories show that in some $C_2 \neq 0$ the evolution of the early universe is
governed by Stiff equation of state or the universe bounces to hyper inflation.
But all of those solutions have a final transition to $\Lambda$CDM as a stable
fixed point for the late universe.
| [
{
"created": "Sun, 29 Oct 2017 10:03:17 GMT",
"version": "v1"
},
{
"created": "Tue, 22 May 2018 14:54:30 GMT",
"version": "v2"
},
{
"created": "Tue, 10 Jul 2018 17:13:36 GMT",
"version": "v3"
}
] | 2018-07-30 | [
[
"Benisty",
"David",
""
],
[
"Guendelman",
"Eduardo I.",
""
]
] | We consider the history of the universe from a possible big bang or a bounce into a late period of a unified interacting dark energy - dark matter model. The model is based on the Two Measures Theories (T.M.T.) which introduces a metric independent volume element and this allows us to construct a unification of dark energy and dark matter. A generalization of the T.M.T. gives a diffusive non-conservative stress energy momentum tensor in addition to the conserved stress energy tensor which appear in Einstein equations. These leads to a formulation of interacting DE-DM dust models in the form of a diffusive type interacting Unified Dark Energy and Dark Matter scenario. The deviation from $\Lambda$CDM is determined by the diffusion constant $C_2$. For $C_2=0$ the model is indistinguishable from $\Lambda$CDM. Numerical solutions of the theories show that in some $C_2 \neq 0$ the evolution of the early universe is governed by Stiff equation of state or the universe bounces to hyper inflation. But all of those solutions have a final transition to $\Lambda$CDM as a stable fixed point for the late universe. |
1403.4393 | Orfeu Bertolami | Orfeu Bertolami, Riccardo March and Jorge P\'aramos | A perturbative approach for the study of compatibility between
nonminimally coupled gravity and Solar System experiments | 4 pages. Talk delivered by one of us (RM) at the International
Conference on Mathematical Modeling in Physical Sciences, Prague, Czech
Republic, 1-5 September, 2013 | null | 10.1088/1742-6596/490/1/012239 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a framework for constraining a certain class of theories of
nonminimally coupled (NMC) gravity with Solar System observations.
| [
{
"created": "Tue, 18 Mar 2014 10:19:50 GMT",
"version": "v1"
}
] | 2015-06-19 | [
[
"Bertolami",
"Orfeu",
""
],
[
"March",
"Riccardo",
""
],
[
"Páramos",
"Jorge",
""
]
] | We develop a framework for constraining a certain class of theories of nonminimally coupled (NMC) gravity with Solar System observations. |
gr-qc/9906089 | Brendan S. Guilfoyle | Brendan S. Guilfoyle | Interior Weyl-type Solutions of the Einstein-Maxwell Field Equations | 21 pages, RevTex, to appear in General Relativity and Gravitation | Gen.Rel.Grav. 31 (1999) 1645-1673 | 10.1023/A:1026706031676 | null | gr-qc | null | Static solutions of the electro-gravitational field equations exhibiting a
functional relationship between the electric and gravitational potentials are
studied. General results for these metrics are presented which extend previous
work of Majumdar. In particular, it is shown that for any solution of the field
equations exhibiting such a Weyl-type relationship, there exists a relationship
between the matter density, the electric field density and the charge density.
It is also found that the Majumdar condition can hold for a bounded perfect
fluid only if the matter pressure vanishes (that is, charged dust). By
restricting to spherically symmetric distributions of charged matter, a number
of exact solutions are presented in closed form which generalise the
Schwarzschild interior solution. Some of these solutions exhibit functional
relations between the electric and gravitational potentials different to the
quadratic one of Weyl. All the non-dust solutions are well-behaved and, by
matching them to the Reissner-Nordstr\"{o}m solution, all of the constants of
integration are identified in terms of the total mass, total charge and radius
of the source. This is done in detail for a number of specific examples. These
are also shown to satisfy the weak and strong energy conditions and many other
regularity and energy conditions that may be required of any physically
reasonable matter distribution.
| [
{
"created": "Tue, 22 Jun 1999 10:08:46 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Guilfoyle",
"Brendan S.",
""
]
] | Static solutions of the electro-gravitational field equations exhibiting a functional relationship between the electric and gravitational potentials are studied. General results for these metrics are presented which extend previous work of Majumdar. In particular, it is shown that for any solution of the field equations exhibiting such a Weyl-type relationship, there exists a relationship between the matter density, the electric field density and the charge density. It is also found that the Majumdar condition can hold for a bounded perfect fluid only if the matter pressure vanishes (that is, charged dust). By restricting to spherically symmetric distributions of charged matter, a number of exact solutions are presented in closed form which generalise the Schwarzschild interior solution. Some of these solutions exhibit functional relations between the electric and gravitational potentials different to the quadratic one of Weyl. All the non-dust solutions are well-behaved and, by matching them to the Reissner-Nordstr\"{o}m solution, all of the constants of integration are identified in terms of the total mass, total charge and radius of the source. This is done in detail for a number of specific examples. These are also shown to satisfy the weak and strong energy conditions and many other regularity and energy conditions that may be required of any physically reasonable matter distribution. |
1210.5182 | Silke Weinfurtner | Silke Weinfurtner, Gemma De las Cuevas, Miguel Angel Martin-Delgado
and Hans J. Briegel | Reducing Spacetime to Binary Information | 5 pages main text, 6 pages supplementary information, 7 figures | Journal of Physics A: Mathematical and Theoretical, Volume 47,
Number 9, Published 17 February 2014 | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new description of discrete space-time in 1+1 dimensions in
terms of a set of elementary geometrical units that represent its independent
classical degrees of freedom. This is achieved by means of a binary encoding
that is ergodic in the class of space-time manifolds respecting coordinate
invariance of general relativity. Space-time fluctuations can be represented in
a classical lattice gas model whose Boltzmann weights are constructed with the
discretized form of the Einstein-Hilbert action. Within this framework, it is
possible to compute basic quantities such as the Ricci curvature tensor and the
Einstein equations, and to evaluate the path integral of discrete gravity. The
description as a lattice gas model also provides a novel way of quantization
and, at the same time, to quantum simulation of fluctuating space-time.
| [
{
"created": "Thu, 18 Oct 2012 16:44:24 GMT",
"version": "v1"
}
] | 2018-01-30 | [
[
"Weinfurtner",
"Silke",
""
],
[
"Cuevas",
"Gemma De las",
""
],
[
"Martin-Delgado",
"Miguel Angel",
""
],
[
"Briegel",
"Hans J.",
""
]
] | We present a new description of discrete space-time in 1+1 dimensions in terms of a set of elementary geometrical units that represent its independent classical degrees of freedom. This is achieved by means of a binary encoding that is ergodic in the class of space-time manifolds respecting coordinate invariance of general relativity. Space-time fluctuations can be represented in a classical lattice gas model whose Boltzmann weights are constructed with the discretized form of the Einstein-Hilbert action. Within this framework, it is possible to compute basic quantities such as the Ricci curvature tensor and the Einstein equations, and to evaluate the path integral of discrete gravity. The description as a lattice gas model also provides a novel way of quantization and, at the same time, to quantum simulation of fluctuating space-time. |
1004.4620 | Paul R. Anderson | Jason D. Bates, Paul R. Anderson | Effects of Quantized Scalar Fields in Cosmological Spacetimes with Big
Rip Singularities | PRD version. References added. Several minor corrections and changes.
22 pages, 3 figures | Phys.Rev.D82:024018,2010 | 10.1103/PhysRevD.82.024018 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Effects of quantized free scalar fields in cosmological spacetimes with Big
Rip singularities are investigated. The energy densities for these fields are
computed at late times when the expansion is very rapid. For the massless
minimally coupled field it is shown that an attractor state exists in the sense
that, for a large class of states, the energy density of the field
asymptotically approaches the energy density it would have if it was in the
attractor state. Results of numerical computations of the energy density for
the massless minimally coupled field and for massive fields with minimal and
conformal coupling to the scalar curvature are presented. For the massive
fields the energy density is seen to always asymptotically approach that of the
corresponding massless field. The question of whether the energy densities of
quantized fields can be large enough for backreaction effects to remove the Big
Rip singularity is addressed.
| [
{
"created": "Mon, 26 Apr 2010 19:47:53 GMT",
"version": "v1"
},
{
"created": "Tue, 11 May 2010 18:16:07 GMT",
"version": "v2"
},
{
"created": "Fri, 22 Apr 2011 20:39:33 GMT",
"version": "v3"
}
] | 2011-04-26 | [
[
"Bates",
"Jason D.",
""
],
[
"Anderson",
"Paul R.",
""
]
] | Effects of quantized free scalar fields in cosmological spacetimes with Big Rip singularities are investigated. The energy densities for these fields are computed at late times when the expansion is very rapid. For the massless minimally coupled field it is shown that an attractor state exists in the sense that, for a large class of states, the energy density of the field asymptotically approaches the energy density it would have if it was in the attractor state. Results of numerical computations of the energy density for the massless minimally coupled field and for massive fields with minimal and conformal coupling to the scalar curvature are presented. For the massive fields the energy density is seen to always asymptotically approach that of the corresponding massless field. The question of whether the energy densities of quantized fields can be large enough for backreaction effects to remove the Big Rip singularity is addressed. |
2206.12083 | Soumya Mohanty | Xue-Hao Zhang, Shao-Dong Zhao, Soumya D. Mohanty, Yu-Xiao Liu | Resolving Galactic binaries using a network of space-borne gravitational
wave detectors | 13 pages, 5 figures | null | 10.1103/PhysRevD.106.102004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Extracting gravitational wave (GW) signals from individual Galactic binaries
(GBs) against their self-generated confusion noise is a key data analysis
challenge for space-borne detectors operating in the $\approx 0.1$ mHz to
$\approx 10$ mHz range. Given the likely prospect that there will be multiple
such detectors, namely LISA, Taiji, and Tianqin, with overlapping operational
periods in the next decade, it is important to examine the extent to which the
joint analysis of their data can benefit GB resolution and parameter
estimation. To investigate this, we use realistic simulated LISA and Taiji data
containing the set of $30\times 10^6$ GBs used in the first LISA data challenge
(Radler), and an iterative source extraction method called GBSIEVER introduced
in an earlier work. We find that a coherent network analysis of LISA-Taiji data
boosts the number of confirmed sources by $\approx 75\%$ over that from a
single detector. The residual after subtracting out the reported sources from
the data of any one of the detectors is much closer to the confusion noise
expected from an ideal, but infeasible, multisource resolution method that
perfectly removes all sources above a given signal-to-noise ratio threshold.
While parameter estimation for sources common to both the single detector and
network improves broadly in line with the enhanced signal to noise ratio of GW
sources in the latter, deviation from the scaling of error variance predicted
by Fisher information analysis is observed for a subset of the parameters.
| [
{
"created": "Fri, 24 Jun 2022 05:23:01 GMT",
"version": "v1"
}
] | 2022-11-30 | [
[
"Zhang",
"Xue-Hao",
""
],
[
"Zhao",
"Shao-Dong",
""
],
[
"Mohanty",
"Soumya D.",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | Extracting gravitational wave (GW) signals from individual Galactic binaries (GBs) against their self-generated confusion noise is a key data analysis challenge for space-borne detectors operating in the $\approx 0.1$ mHz to $\approx 10$ mHz range. Given the likely prospect that there will be multiple such detectors, namely LISA, Taiji, and Tianqin, with overlapping operational periods in the next decade, it is important to examine the extent to which the joint analysis of their data can benefit GB resolution and parameter estimation. To investigate this, we use realistic simulated LISA and Taiji data containing the set of $30\times 10^6$ GBs used in the first LISA data challenge (Radler), and an iterative source extraction method called GBSIEVER introduced in an earlier work. We find that a coherent network analysis of LISA-Taiji data boosts the number of confirmed sources by $\approx 75\%$ over that from a single detector. The residual after subtracting out the reported sources from the data of any one of the detectors is much closer to the confusion noise expected from an ideal, but infeasible, multisource resolution method that perfectly removes all sources above a given signal-to-noise ratio threshold. While parameter estimation for sources common to both the single detector and network improves broadly in line with the enhanced signal to noise ratio of GW sources in the latter, deviation from the scaling of error variance predicted by Fisher information analysis is observed for a subset of the parameters. |
1505.06996 | Lorenzo Iorio | Lorenzo Iorio, Ninfa Radicella, Matteo Luca Ruggiero | Constraining f(T) gravity in the Solar System | LaTex2e, 16 pages, 2 figures, no tables. Accepted for publication in
Journal of Cosmology and Astroparticle Physics (JCAP). arXiv admin note: text
overlap with arXiv:1501.02198 | JCAP08(2015)021 | 10.1088/1475-7516/2015/08/021 | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of $f(T)$ theories of gravity, we solve the field equations
for $f(T)=T+\alpha T^{n}$, in the weak-field approximation and for spherical
symmetry spacetime. Since $f(T)=T$ corresponds to Teleparallel Gravity, which
is equivalent to General Relativity, the non linearity of the Lagrangian are
expected to produce perturbations of the general relativistic solutions,
parameterized by $\alpha$. Hence, we use the $f(T)$ solutions to model the
gravitational field of the Sun, and exploit data from accurate tracking of
spacecrafts orbiting Mercury and Saturn to infer preliminary insights on what
could be obtained about the model parameter $\alpha$ and the cosmological
constant $\Lambda$. It turns out that improvements of about one-three orders
with respect to the present-day constraints in the literature of magnitude seem
possible.
| [
{
"created": "Sun, 24 May 2015 15:28:42 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Jul 2015 08:05:46 GMT",
"version": "v2"
}
] | 2015-08-13 | [
[
"Iorio",
"Lorenzo",
""
],
[
"Radicella",
"Ninfa",
""
],
[
"Ruggiero",
"Matteo Luca",
""
]
] | In the framework of $f(T)$ theories of gravity, we solve the field equations for $f(T)=T+\alpha T^{n}$, in the weak-field approximation and for spherical symmetry spacetime. Since $f(T)=T$ corresponds to Teleparallel Gravity, which is equivalent to General Relativity, the non linearity of the Lagrangian are expected to produce perturbations of the general relativistic solutions, parameterized by $\alpha$. Hence, we use the $f(T)$ solutions to model the gravitational field of the Sun, and exploit data from accurate tracking of spacecrafts orbiting Mercury and Saturn to infer preliminary insights on what could be obtained about the model parameter $\alpha$ and the cosmological constant $\Lambda$. It turns out that improvements of about one-three orders with respect to the present-day constraints in the literature of magnitude seem possible. |
0808.3482 | Chen Songbai | Songbai Chen, Bin Wang, Jiliang Jing | Dynamics of interacting dark energy model in Einstein and Loop Quantum
Cosmology | 16 pages, 4 figures, references added, accepted by Phys. Rev. D | Phys.Rev.D78:123503,2008 | 10.1103/PhysRevD.78.123503 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the background dynamics when dark energy is coupled to dark
matter in the universe described by Einstein cosmology and Loop Quantum
Cosmology. We introduce a new general form of dark sector coupling, which
presents us a more complicated dynamical phase space. Differences in the phase
space in obtaining the accelerated scaling attractor in Einstein cosmology and
Loop Quantum Cosmology are disclosed.
| [
{
"created": "Tue, 26 Aug 2008 10:40:44 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Nov 2008 01:57:01 GMT",
"version": "v2"
}
] | 2008-12-18 | [
[
"Chen",
"Songbai",
""
],
[
"Wang",
"Bin",
""
],
[
"Jing",
"Jiliang",
""
]
] | We investigate the background dynamics when dark energy is coupled to dark matter in the universe described by Einstein cosmology and Loop Quantum Cosmology. We introduce a new general form of dark sector coupling, which presents us a more complicated dynamical phase space. Differences in the phase space in obtaining the accelerated scaling attractor in Einstein cosmology and Loop Quantum Cosmology are disclosed. |
2008.09115 | Mubasher Jamil | Kimet Jusufi, Mustapha Azreg-A\"inou, Mubasher Jamil, Tao Zhu | Constraining the Generalized Uncertainty Principle Through Black Hole
Shadow and Quasiperiodic Oscillations | 14 pages, 10 captioned figures, 4 tables | IJGMMP Volume No. 19, Issue No. 05, Article No. 2250068, Year 2022 | 10.1142/S0219887822500682 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we study the effect of the Generalized Uncertainty Principle
(GUP) on the shadow of GUP-modified Kerr black hole and the correspondence
between the shadow radius and the real part of the quasinormal modes (QNMs). We
find that the shadow curvature radius of the GUP-modfied Kerr black hole is
bigger compared to the Kerr vacuum solution and increases linearly
monotonically with the increase of the GUP parameter. We then investigate the
characteristic points of intrinsic curvature of the shadow from a topological
point of view to calculate the the angular size for these curvature radii of
the shadow. To this end, we have used the EHT data for the M87* black hole to
constrain the upper limits of the GUP parameter red and our result is
$\beta<10^{95}$. Finally, we have explored the connection between the shadow
radius and the scalar/electromagnetic/gravitational QNMs. The GUP-modified Kerr
black hole is also used to provide perfect curve fitting of the particle
oscillation upper and lower frequencies to the observed frequencies for three
microquasars and to restrict the values of the correction parameter in the
metric of the modified black hole to very reasonable bound $\beta<10^{77}$.
| [
{
"created": "Thu, 20 Aug 2020 12:01:48 GMT",
"version": "v1"
},
{
"created": "Sun, 21 Mar 2021 04:42:03 GMT",
"version": "v2"
}
] | 2022-04-11 | [
[
"Jusufi",
"Kimet",
""
],
[
"Azreg-Aïnou",
"Mustapha",
""
],
[
"Jamil",
"Mubasher",
""
],
[
"Zhu",
"Tao",
""
]
] | In this paper we study the effect of the Generalized Uncertainty Principle (GUP) on the shadow of GUP-modified Kerr black hole and the correspondence between the shadow radius and the real part of the quasinormal modes (QNMs). We find that the shadow curvature radius of the GUP-modfied Kerr black hole is bigger compared to the Kerr vacuum solution and increases linearly monotonically with the increase of the GUP parameter. We then investigate the characteristic points of intrinsic curvature of the shadow from a topological point of view to calculate the the angular size for these curvature radii of the shadow. To this end, we have used the EHT data for the M87* black hole to constrain the upper limits of the GUP parameter red and our result is $\beta<10^{95}$. Finally, we have explored the connection between the shadow radius and the scalar/electromagnetic/gravitational QNMs. The GUP-modified Kerr black hole is also used to provide perfect curve fitting of the particle oscillation upper and lower frequencies to the observed frequencies for three microquasars and to restrict the values of the correction parameter in the metric of the modified black hole to very reasonable bound $\beta<10^{77}$. |
2406.11582 | Adailton Ara\'ujo Filho | A. A. Ara\'ujo Filho | Antisymmetric tensor influence on charged black hole lensing phenomena
and time delay | 24 pages and 6 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we investigate the gravitational lensing of a charged black
hole (spherically symmetric) within the context of Lorentz violation triggered
by an antisymmetric tensor field. Our calculations consider two different
scenarios: the weak and strong deflection limits. For the weak deflection
limit, we employ the Gauss-Bonnet theorem to obtain our results. In the strong
deflection limit, we utilize the Tsukamoto methodology, which provides
measurable outcomes such as relativistic image positions and magnifications.
Applying the latter methodology, we analyze the gravitational lensing by
Sagittarius $A^{*}$ and derive the related observables, which are expressed as
functions of the Lorentz violation parameter. Finally, the time delay is
addrressed as well.
| [
{
"created": "Mon, 17 Jun 2024 14:24:40 GMT",
"version": "v1"
}
] | 2024-06-18 | [
[
"Filho",
"A. A. Araújo",
""
]
] | In this work, we investigate the gravitational lensing of a charged black hole (spherically symmetric) within the context of Lorentz violation triggered by an antisymmetric tensor field. Our calculations consider two different scenarios: the weak and strong deflection limits. For the weak deflection limit, we employ the Gauss-Bonnet theorem to obtain our results. In the strong deflection limit, we utilize the Tsukamoto methodology, which provides measurable outcomes such as relativistic image positions and magnifications. Applying the latter methodology, we analyze the gravitational lensing by Sagittarius $A^{*}$ and derive the related observables, which are expressed as functions of the Lorentz violation parameter. Finally, the time delay is addrressed as well. |
1908.07160 | Tousif Islam | Tousif Islam and Koushik Dutta | Modified Gravity Theories in Light of the Anomalous Velocity Dispersion
of NGC1052-DF2 | 7 pages, 6 figures; matches the published version | Phys. Rev. D 100, 104049 (2019) | 10.1103/PhysRevD.100.104049 | null | gr-qc astro-ph.CO astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent observations of ultra-dwarf galaxy NGC1052-DF2 started an interesting
discussion between dark matter hypothesis and modified gravity theories.
Reported low velocity dispersion (< 10.5 km/s at 90% confidence level) derived
from the kinematic data of 10 globular clusters in the galaxy points towards an
extraordinarily low dynamical mass ($\sim$ $3.4 \times 10^{8} M_{\odot}$) which
is of the same order of the luminous mass ($\sim$ $2.0 \times 10^{8}
M_{\odot}$) in the galaxy. This has been interpreted as the first evidence of a
galaxy `without Dark Matter'. It has been argued that dark matter is not
necessarily coupled to the the baryonic mass on the galactic scale and poses a
challenge to modified gravity theories. We explore the dynamics of NGC1052-DF2
within the context of four popular alternative theories of gravity [Modified
Newtonian Dynamcies (MOND), Weyl Conformal gravity, Modified gravity
(MOG)/Scalar-Tensor-Vector Gravity (STVG) and Verlinde's Emergent gravity] and
present the analysis of detailed radial variation of the velocity dispersion.
We demonstrate that the dispersion data of NGC1052-DF2 is fully consistent with
modified gravity paradigm (as well as with general relativity without dark
matter). We reach similar conclusion for the ultra-dwarf NGC1052-DF4 which has
been claimed to be the second candidate for galaxies `without Dark Matter'.
| [
{
"created": "Tue, 20 Aug 2019 04:24:38 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Dec 2019 06:50:42 GMT",
"version": "v2"
}
] | 2019-12-10 | [
[
"Islam",
"Tousif",
""
],
[
"Dutta",
"Koushik",
""
]
] | Recent observations of ultra-dwarf galaxy NGC1052-DF2 started an interesting discussion between dark matter hypothesis and modified gravity theories. Reported low velocity dispersion (< 10.5 km/s at 90% confidence level) derived from the kinematic data of 10 globular clusters in the galaxy points towards an extraordinarily low dynamical mass ($\sim$ $3.4 \times 10^{8} M_{\odot}$) which is of the same order of the luminous mass ($\sim$ $2.0 \times 10^{8} M_{\odot}$) in the galaxy. This has been interpreted as the first evidence of a galaxy `without Dark Matter'. It has been argued that dark matter is not necessarily coupled to the the baryonic mass on the galactic scale and poses a challenge to modified gravity theories. We explore the dynamics of NGC1052-DF2 within the context of four popular alternative theories of gravity [Modified Newtonian Dynamcies (MOND), Weyl Conformal gravity, Modified gravity (MOG)/Scalar-Tensor-Vector Gravity (STVG) and Verlinde's Emergent gravity] and present the analysis of detailed radial variation of the velocity dispersion. We demonstrate that the dispersion data of NGC1052-DF2 is fully consistent with modified gravity paradigm (as well as with general relativity without dark matter). We reach similar conclusion for the ultra-dwarf NGC1052-DF4 which has been claimed to be the second candidate for galaxies `without Dark Matter'. |
1307.0753 | Lorenzo Iorio | Lorenzo Iorio, Matteo Luca Ruggiero, Christian Corda | Novel considerations about the error budget of the LAGEOS-based tests of
frame-dragging with GRACE geopotential models | LaTex2e, 18 pages, 2 tables, no figures. Version matching the
published one | Acta Astronaut.91:141-148,2013 | 10.1016/j.actaastro.2013.06.002 | null | gr-qc astro-ph.EP physics.geo-ph physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A realistic assessment of the uncertainties in the even zonals of a given
geopotential model must be made by directly comparing its coefficients with
those of a wholly independent solution of superior formal accuracy. Otherwise,
a favorable selective bias is introduced in the evaluation of the total error
budget of the LAGEOS-based Lense-Thirring tests yielding likely too optimistic
figures for it. By applying a novel approach which recently appeared in the
literature, the second (L = 4) and the third (L = 6) even zonals turn out to be
uncertain at a 2-3 10^-11 (L = 4) and 3-4 10^-11 (L = 6) level, respectively,
yielding a total gravitational error of about 27-28%, with an upper bound of
37-39%. The results by Ries et al. themselves yield an upper bound for it of
about 33%. The low-degree even zonals are not exclusively determined from the
GRACE Satellite-to-Satellite Tracking (SST) range since they affect it with
long-period, secular-like signatures over orbital arcs longer than one orbital
period: GRACE SST is not accurately sensitive to such signals. Conversely,
general relativity affects it with short-period effects as well. Thus, the
issue of the a priori "imprinting" of general relativity itself in the
GRACE-based models used so far remains open.
| [
{
"created": "Sun, 30 Jun 2013 21:25:35 GMT",
"version": "v1"
}
] | 2013-07-03 | [
[
"Iorio",
"Lorenzo",
""
],
[
"Ruggiero",
"Matteo Luca",
""
],
[
"Corda",
"Christian",
""
]
] | A realistic assessment of the uncertainties in the even zonals of a given geopotential model must be made by directly comparing its coefficients with those of a wholly independent solution of superior formal accuracy. Otherwise, a favorable selective bias is introduced in the evaluation of the total error budget of the LAGEOS-based Lense-Thirring tests yielding likely too optimistic figures for it. By applying a novel approach which recently appeared in the literature, the second (L = 4) and the third (L = 6) even zonals turn out to be uncertain at a 2-3 10^-11 (L = 4) and 3-4 10^-11 (L = 6) level, respectively, yielding a total gravitational error of about 27-28%, with an upper bound of 37-39%. The results by Ries et al. themselves yield an upper bound for it of about 33%. The low-degree even zonals are not exclusively determined from the GRACE Satellite-to-Satellite Tracking (SST) range since they affect it with long-period, secular-like signatures over orbital arcs longer than one orbital period: GRACE SST is not accurately sensitive to such signals. Conversely, general relativity affects it with short-period effects as well. Thus, the issue of the a priori "imprinting" of general relativity itself in the GRACE-based models used so far remains open. |
1911.04937 | Ernesto Nungesser | Ho Lee, Ernesto Nungesser, Paul Tod | On the future of solutions to the massless Einstein-Vlasov system in a
Bianchi I cosmology | 11 pages. In this version V2 errata corrected (in particular decay
rates of anisotropy) and references added | Gen Relativ Gravit 52, 48 (2020) | 10.1007/s10714-020-02699-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that massless solutions to the Einstein-Vlasov system in a Bianchi I
space-time with small anisotropy, i.e. small shear and small trace-free part of
the spatial energy momentum tensor, tend to a radiation fluid in an Einstein-de
Sitter space-time with the anisotropy $\Sigma^a_b\Sigma^b_a$ and $\tilde{w}^i_j
\tilde{w}^j_i$ decaying as $O(t^{-\frac12})$.
| [
{
"created": "Tue, 12 Nov 2019 15:40:00 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Feb 2020 10:10:56 GMT",
"version": "v2"
}
] | 2024-06-18 | [
[
"Lee",
"Ho",
""
],
[
"Nungesser",
"Ernesto",
""
],
[
"Tod",
"Paul",
""
]
] | We show that massless solutions to the Einstein-Vlasov system in a Bianchi I space-time with small anisotropy, i.e. small shear and small trace-free part of the spatial energy momentum tensor, tend to a radiation fluid in an Einstein-de Sitter space-time with the anisotropy $\Sigma^a_b\Sigma^b_a$ and $\tilde{w}^i_j \tilde{w}^j_i$ decaying as $O(t^{-\frac12})$. |
1709.07087 | Fran\c{c}ois Rondeau | Fran\c{c}ois Rondeau and Baojiu Li | Equivalence of cosmological observables in conformally related scalar
tensor theories | 25 pages, 1 figure | Phys. Rev. D 96, 124009 (2017) | 10.1103/PhysRevD.96.124009 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scalar tensor theories can be expressed in different frames, such as the
commonly-used Einstein and Jordan frames, and it is generally accepted that
cosmological observables are the same in these frames. We revisit this by
making a detailed side-by-side comparison of the quantities and equations in
two conformally related frames, from the actions and fully covariant field
equations to the linearised equations in both real and Fourier spaces. This
confirms that the field and conservation equations are equivalent in the two
frames, in the sense that we can always re-express equations in one frame using
relevant transformations of variables to derive the corresponding equations in
the other. We show, with both analytical derivation and a numerical example,
that the line-of-sight integration to calculate CMB temperature anisotropies
can be done using either Einstein frame or Jordan frame quantities, and the
results are identical, provided the correct redshift is used in the Einstein
frame ($1+z\neq1/a$).
| [
{
"created": "Wed, 20 Sep 2017 21:17:28 GMT",
"version": "v1"
}
] | 2017-12-20 | [
[
"Rondeau",
"François",
""
],
[
"Li",
"Baojiu",
""
]
] | Scalar tensor theories can be expressed in different frames, such as the commonly-used Einstein and Jordan frames, and it is generally accepted that cosmological observables are the same in these frames. We revisit this by making a detailed side-by-side comparison of the quantities and equations in two conformally related frames, from the actions and fully covariant field equations to the linearised equations in both real and Fourier spaces. This confirms that the field and conservation equations are equivalent in the two frames, in the sense that we can always re-express equations in one frame using relevant transformations of variables to derive the corresponding equations in the other. We show, with both analytical derivation and a numerical example, that the line-of-sight integration to calculate CMB temperature anisotropies can be done using either Einstein frame or Jordan frame quantities, and the results are identical, provided the correct redshift is used in the Einstein frame ($1+z\neq1/a$). |
2301.09437 | Boris Kolev | Boris Kolev (LMPS), Rodrigue Desmorat (LMPS) | Souriau's Relativistic general covariant formulation of hyperelasticity
revisited | null | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present and modernize Souriau's 1958 geometric framework for Relativistic
continuous media, and enlighten the necessary and the ad hoc modeling choices
made since, focusing as much as possible on the Continuum Mechanics point of
view. We describe the general covariant formulation of Hyperelasticity in
General Relativity, and then in the particular case of a static spacetime.
Finally, we apply this formalism for the Schwarzschild's metric, and recover
the Classical Galilean Hyperelasticity with gravity, as the Newton-Cartan
infinite light speed limit of this formulation.
| [
{
"created": "Fri, 20 Jan 2023 15:28:38 GMT",
"version": "v1"
}
] | 2023-01-24 | [
[
"Kolev",
"Boris",
"",
"LMPS"
],
[
"Desmorat",
"Rodrigue",
"",
"LMPS"
]
] | We present and modernize Souriau's 1958 geometric framework for Relativistic continuous media, and enlighten the necessary and the ad hoc modeling choices made since, focusing as much as possible on the Continuum Mechanics point of view. We describe the general covariant formulation of Hyperelasticity in General Relativity, and then in the particular case of a static spacetime. Finally, we apply this formalism for the Schwarzschild's metric, and recover the Classical Galilean Hyperelasticity with gravity, as the Newton-Cartan infinite light speed limit of this formulation. |
0811.4609 | Maria Emilia Guimaraes | M. C. B. Abdalla (IFT/Unesp), M. E. X. Guimaraes (IF/Uff) and J. M.
Hoff da Silva (IFT/Unesp) | Brane-Wor(l)ds within Brans-Dicke Gravity | 10 pages. Invited contribution to the Special Issue "The Problems of
Modern Cosmology", on the occasion of Prof. S. D. Odintsov's 50th birthday | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review some recent results obtained from the application of the
Gauss-Codazzi formalism to brane-worlds models in the Brans-Dicke gravity. The
cases of 4-branes embedded in a six-dimensional with and without
$\mathbb{Z}_{2}$ symmetry are both analyzed.
| [
{
"created": "Thu, 27 Nov 2008 19:14:25 GMT",
"version": "v1"
}
] | 2008-12-31 | [
[
"Abdalla",
"M. C. B.",
"",
"IFT/Unesp"
],
[
"Guimaraes",
"M. E. X.",
"",
"IF/Uff"
],
[
"da Silva",
"J. M. Hoff",
"",
"IFT/Unesp"
]
] | We review some recent results obtained from the application of the Gauss-Codazzi formalism to brane-worlds models in the Brans-Dicke gravity. The cases of 4-branes embedded in a six-dimensional with and without $\mathbb{Z}_{2}$ symmetry are both analyzed. |
1805.07126 | Piero Nicolini | Ricardo Gallego Torrom\'e and Piero Nicolini | Theories with maximal acceleration | 20 pages, invited review for International Journal of Modern Physics
A (World Scientific); v2 with an updated reference list; v3 updated version
accepted for publication | Int. J. Mod. Phys. A 33 (2018) 1830019 (17 pages) | 10.1142/S0217751X18300193 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Maximal accelerations are related to the existence of a minimal time for a
given physical system. Such a minimal time can be either an intrinsic time
scale of the system or connected to a quantum gravity induced ultraviolet cut
off. In this paper we pedagogically introduce the four major formulations for
kinematics accounting for a maximal acceleration. Some phenomenological
repercussion are offered as hints for future investigations.
| [
{
"created": "Fri, 18 May 2018 10:16:08 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Jun 2018 15:35:33 GMT",
"version": "v2"
},
{
"created": "Thu, 2 Aug 2018 12:46:44 GMT",
"version": "v3"
}
] | 2018-08-09 | [
[
"Torromé",
"Ricardo Gallego",
""
],
[
"Nicolini",
"Piero",
""
]
] | Maximal accelerations are related to the existence of a minimal time for a given physical system. Such a minimal time can be either an intrinsic time scale of the system or connected to a quantum gravity induced ultraviolet cut off. In this paper we pedagogically introduce the four major formulations for kinematics accounting for a maximal acceleration. Some phenomenological repercussion are offered as hints for future investigations. |
0809.5223 | Chris Messenger | C. Messenger, R. Prix, M. A. Papa | Random template banks and relaxed lattice coverings | 13 pages, 10 figures, submitted to PRD | Phys.Rev.D79:104017,2009 | 10.1103/PhysRevD.79.104017 | LIGO-P080090-01-Z | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Template-based searches for gravitational waves are often limited by the
computational cost associated with searching large parameter spaces. The study
of efficient template banks, in the sense of using the smallest number of
templates, is therefore of great practical interest. The "traditional" approach
to template-bank construction requires every point in parameter space to be
covered by at least one template, which rapidly becomes inefficient at higher
dimensions. Here we study an alternative approach, where any point in parameter
space is covered only with a given probability < 1. We find that by giving up
complete coverage in this way, large reductions in the number of templates are
possible, especially at higher dimensions. The prime examples studied here are
"random template banks", in which templates are placed randomly with uniform
probability over the parameter space. In addition to its obvious simplicity,
this method turns out to be surprisingly efficient. We analyze the statistical
properties of such random template banks, and compare their efficiency to
traditional lattice coverings. We further study "relaxed" lattice coverings
(using Zn and An* lattices), which similarly cover any signal location only
with probability < 1. The relaxed An* lattice is found to yield the most
efficient template banks at low dimensions (n < 10), while random template
banks increasingly outperform any other method at higher dimensions.
| [
{
"created": "Tue, 30 Sep 2008 15:15:59 GMT",
"version": "v1"
}
] | 2010-04-15 | [
[
"Messenger",
"C.",
""
],
[
"Prix",
"R.",
""
],
[
"Papa",
"M. A.",
""
]
] | Template-based searches for gravitational waves are often limited by the computational cost associated with searching large parameter spaces. The study of efficient template banks, in the sense of using the smallest number of templates, is therefore of great practical interest. The "traditional" approach to template-bank construction requires every point in parameter space to be covered by at least one template, which rapidly becomes inefficient at higher dimensions. Here we study an alternative approach, where any point in parameter space is covered only with a given probability < 1. We find that by giving up complete coverage in this way, large reductions in the number of templates are possible, especially at higher dimensions. The prime examples studied here are "random template banks", in which templates are placed randomly with uniform probability over the parameter space. In addition to its obvious simplicity, this method turns out to be surprisingly efficient. We analyze the statistical properties of such random template banks, and compare their efficiency to traditional lattice coverings. We further study "relaxed" lattice coverings (using Zn and An* lattices), which similarly cover any signal location only with probability < 1. The relaxed An* lattice is found to yield the most efficient template banks at low dimensions (n < 10), while random template banks increasingly outperform any other method at higher dimensions. |
1908.05337 | Sergio Vitorino Borba Gon\c{c}alves | G. A. Monerat, C. G. M. Santos, F. G. Alvarenga, S. V. B.
Gon\c{c}alves, R. Fracalossi, E. V. Corr\^ea Silva, G. Oliveira-Neto | Quantum Cosmology with many fluids and the choice of cosmological time | 26 pages, 25 figures, 2 tables | Brazilian Journal of Physics, 2019 | 10.1007/s13538-019-00720-2 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | In this work we propose the quantization of a cosmological model describing
the primordial universe filled with five barotropic fluids, namely: radiation,
dust, vacuum, cosmic strings and domain walls. We intend to identify which
fluid is best suited to provide phenomenologically the temporal variable in
accordance with the observable universe. Through the Galerkin spectral method
and the finite difference method in the Crank-Nicolson scheme (vacuum case),
the quantum cosmological solutions are obtained and compared. We, also, compare
the quantum cosmological solutions with the corresponding classical ones. The
vacuum case is especially interesting because it provides a tunneling
transition mechanism from the quantum to the classical phase and the
possibility of calculating quantum tunneling probabilities.
| [
{
"created": "Wed, 14 Aug 2019 20:26:12 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Dec 2019 14:52:15 GMT",
"version": "v2"
}
] | 2019-12-04 | [
[
"Monerat",
"G. A.",
""
],
[
"Santos",
"C. G. M.",
""
],
[
"Alvarenga",
"F. G.",
""
],
[
"Gonçalves",
"S. V. B.",
""
],
[
"Fracalossi",
"R.",
""
],
[
"Silva",
"E. V. Corrêa",
""
],
[
"Oliveira-Neto",
"G.",
""
]
] | In this work we propose the quantization of a cosmological model describing the primordial universe filled with five barotropic fluids, namely: radiation, dust, vacuum, cosmic strings and domain walls. We intend to identify which fluid is best suited to provide phenomenologically the temporal variable in accordance with the observable universe. Through the Galerkin spectral method and the finite difference method in the Crank-Nicolson scheme (vacuum case), the quantum cosmological solutions are obtained and compared. We, also, compare the quantum cosmological solutions with the corresponding classical ones. The vacuum case is especially interesting because it provides a tunneling transition mechanism from the quantum to the classical phase and the possibility of calculating quantum tunneling probabilities. |
1006.1794 | Hedvika Kadlecova | Hedvika Kadlecova, Pavel Krtous | Gyratons on Melvin spacetime | 15 pages, no figures, journal version extended by appendices B and C | Phys.Rev.D82:044041,2010 | 10.1103/PhysRevD.82.044041 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present and analyze new exact gyraton solutions of algebraic type II on a
background which is static, cylindrically symmetric Melvin universe of type D.
For a vanishing electromagnetic field it reduces to previously studied gyratons
on Minkowski background. We demonstrate that the solutions are member of a more
general family of the Kundt spacetimes. We show that the Einstein equations
reduce to a set of mostly linear equations on a transverse 2-space and we
discuss the properties of polynomial scalar curvature invariants which are
generally non-constant but unaffected by the presence of gyratons.
| [
{
"created": "Wed, 9 Jun 2010 13:16:57 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Jul 2010 12:18:39 GMT",
"version": "v2"
},
{
"created": "Thu, 2 Sep 2010 10:06:47 GMT",
"version": "v3"
}
] | 2010-09-03 | [
[
"Kadlecova",
"Hedvika",
""
],
[
"Krtous",
"Pavel",
""
]
] | We present and analyze new exact gyraton solutions of algebraic type II on a background which is static, cylindrically symmetric Melvin universe of type D. For a vanishing electromagnetic field it reduces to previously studied gyratons on Minkowski background. We demonstrate that the solutions are member of a more general family of the Kundt spacetimes. We show that the Einstein equations reduce to a set of mostly linear equations on a transverse 2-space and we discuss the properties of polynomial scalar curvature invariants which are generally non-constant but unaffected by the presence of gyratons. |
2302.12256 | Angela Chen | Angela Chen | Generalized Unruh effect: A potential resolution to the black hole
information paradox | 27 pages, 6 figures, accepted by PRD | null | 10.1103/PhysRevD.107.056014 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We generalize the vacuum-Unruh effect to arbitrary excited states in the Fock
space and find that the Unruh mode at the horizon induces coherent excitation
on the canonical background ensemble measured by an accelerated observer. When
there is only one type of Unruh mode in the system, for example, the ones
outgoing from a black hole horizon, the mapping from an arbitrary density
matrix on the maximal foliation to a vector space spanned by the pseudo-thermal
density matrix on the partitioned spacetime wedge is one-to-one. Hence we
propose that the information of the particles that are inside a collapsing
shell, thus inside the asymptotic black hole horizon is at least partially
retrievable by measuring the deviation of the Hawking radiation from the black
body radiation spectrum. This work shows that the long-standing black hole
information confusion might come from overlooking the possibility that the
information could be preserved much better than we have expected in a seemingly
non-unitary process when the partitions of the system are strongly entangled.
| [
{
"created": "Thu, 23 Feb 2023 07:20:14 GMT",
"version": "v1"
}
] | 2023-03-29 | [
[
"Chen",
"Angela",
""
]
] | We generalize the vacuum-Unruh effect to arbitrary excited states in the Fock space and find that the Unruh mode at the horizon induces coherent excitation on the canonical background ensemble measured by an accelerated observer. When there is only one type of Unruh mode in the system, for example, the ones outgoing from a black hole horizon, the mapping from an arbitrary density matrix on the maximal foliation to a vector space spanned by the pseudo-thermal density matrix on the partitioned spacetime wedge is one-to-one. Hence we propose that the information of the particles that are inside a collapsing shell, thus inside the asymptotic black hole horizon is at least partially retrievable by measuring the deviation of the Hawking radiation from the black body radiation spectrum. This work shows that the long-standing black hole information confusion might come from overlooking the possibility that the information could be preserved much better than we have expected in a seemingly non-unitary process when the partitions of the system are strongly entangled. |
2101.11153 | Maria Okounkova | Maria Okounkova, Will M. Farr, Maximiliano Isi, Leo C. Stein | Constraining gravitational wave amplitude birefringence and Chern-Simons
gravity with GWTC-2 | Updated to match published version, 8 pages (+6 pages of appendices),
7 figures | Phys. Rev. D 106, 044067 (2022) | 10.1103/PhysRevD.106.044067 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | We perform a new test of general relativity (GR) with signals from GWTC-2,
the LIGO and Virgo catalog of gravitational wave detections. We search for the
presence of amplitude birefringence, in which left versus right circularly
polarized modes of gravitational waves are exponentially enhanced and
suppressed during propagation. Such an effect is present in various beyond-GR
theories but is absent in GR. We constrain the amount of amplitude
birefringence consistent with the data through an opacity parameter $\kappa$,
which we bound to be $\kappa \lesssim 0.74 \textrm{ Gpc}^{-1}$. We then use
these theory-agnostic results to constrain Chern-Simons gravity, a beyond-GR
theory with motivations in quantum gravity. We bound the canonical Chern-Simons
lengthscale to be $\ell_0 \lesssim 1.0 \times 10^3$ km, improving on previous
long-distance measurement results by a factor of two.
| [
{
"created": "Wed, 27 Jan 2021 01:17:06 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Oct 2022 18:31:33 GMT",
"version": "v2"
}
] | 2022-10-07 | [
[
"Okounkova",
"Maria",
""
],
[
"Farr",
"Will M.",
""
],
[
"Isi",
"Maximiliano",
""
],
[
"Stein",
"Leo C.",
""
]
] | We perform a new test of general relativity (GR) with signals from GWTC-2, the LIGO and Virgo catalog of gravitational wave detections. We search for the presence of amplitude birefringence, in which left versus right circularly polarized modes of gravitational waves are exponentially enhanced and suppressed during propagation. Such an effect is present in various beyond-GR theories but is absent in GR. We constrain the amount of amplitude birefringence consistent with the data through an opacity parameter $\kappa$, which we bound to be $\kappa \lesssim 0.74 \textrm{ Gpc}^{-1}$. We then use these theory-agnostic results to constrain Chern-Simons gravity, a beyond-GR theory with motivations in quantum gravity. We bound the canonical Chern-Simons lengthscale to be $\ell_0 \lesssim 1.0 \times 10^3$ km, improving on previous long-distance measurement results by a factor of two. |
1309.3905 | Viacheslav Emelyanov | Slava Emelyanov | Freely-moving observer in (quasi) anti de Sitter space | typos fixed, reference added, minor corrections | Phys. Rev. D 90, 044039 (2014) | 10.1103/PhysRevD.90.044039 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A quantum scalar field in anti de Sitter space is considered in two
coordinate systems: static and FRW-like ones. It is shown that quantum vacua
corresponding to each of these coordinatizations are not unitary equivalent. A
choice of a physical ground state between these vacua is discussed under
different setups.
| [
{
"created": "Mon, 16 Sep 2013 11:27:30 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Oct 2013 20:07:32 GMT",
"version": "v2"
}
] | 2014-08-20 | [
[
"Emelyanov",
"Slava",
""
]
] | A quantum scalar field in anti de Sitter space is considered in two coordinate systems: static and FRW-like ones. It is shown that quantum vacua corresponding to each of these coordinatizations are not unitary equivalent. A choice of a physical ground state between these vacua is discussed under different setups. |
1811.00382 | Ghulam Abbas | G. Abbas and M. Tahir | Models of Anisotropic Self-Gravitating Source in Einstein-Gauss-Bonnet
Gravity | 20 pages,16 Figures, Title Changed, Major revision included,accepted
version to appear in Adv.High Energy Physics | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we have studied gravitational collapse and expansion of
non-static anisotropic fluid in $5D$ Einstein Gauss-Bonnet gravity. For this
purpose, the field equations have been modeled and evaluated for the given
source and geometry. The two metric functions have been expressed in terms of
parametric form of third metric function. We have examined the range of
parameter $\beta$ (appearing in the form of metric functions) for which
$\Theta$ the expansion scalar becomes positive/negative leads to
expansion/collapse of the source. The trapped surface condition has been
explored by using definition of Misner-Sharp mass and auxiliary solutions. The
auxiliary solutions of the field equations involve a single function which
generates two types of anisotropic solutions. Each solution can be represented
in term of arbitrary function of time, this function has been chosen
arbitrarily to fit the different astrophysical time profiles. The existing
solutions forecast gravitational expansion and collapse depending on the choice
of initial data. In this case, it has been investigated wall to wall collapse
of spherical source. The dynamics of the spherical source has been observed
graphically with the effects of Gauss-Bonnet coupling term $\alpha$ in the case
of collapse and expansion. The energy conditions are satisfied for the specific
values of parameters in the both solutions, this implies that the solutions are
physically acceptable.
| [
{
"created": "Sat, 27 Oct 2018 07:37:00 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Dec 2018 12:19:00 GMT",
"version": "v2"
}
] | 2018-12-19 | [
[
"Abbas",
"G.",
""
],
[
"Tahir",
"M.",
""
]
] | In this paper, we have studied gravitational collapse and expansion of non-static anisotropic fluid in $5D$ Einstein Gauss-Bonnet gravity. For this purpose, the field equations have been modeled and evaluated for the given source and geometry. The two metric functions have been expressed in terms of parametric form of third metric function. We have examined the range of parameter $\beta$ (appearing in the form of metric functions) for which $\Theta$ the expansion scalar becomes positive/negative leads to expansion/collapse of the source. The trapped surface condition has been explored by using definition of Misner-Sharp mass and auxiliary solutions. The auxiliary solutions of the field equations involve a single function which generates two types of anisotropic solutions. Each solution can be represented in term of arbitrary function of time, this function has been chosen arbitrarily to fit the different astrophysical time profiles. The existing solutions forecast gravitational expansion and collapse depending on the choice of initial data. In this case, it has been investigated wall to wall collapse of spherical source. The dynamics of the spherical source has been observed graphically with the effects of Gauss-Bonnet coupling term $\alpha$ in the case of collapse and expansion. The energy conditions are satisfied for the specific values of parameters in the both solutions, this implies that the solutions are physically acceptable. |
gr-qc/9601050 | Kiyoshi Ezawa | Kiyoshi Ezawa | Nonperturbative solutions for canonical quantum gravity: an overview | 78 pages Latex, four figures included as eps-files.(References added,
some minor changes made in subsections 1.4, 3.2 and 7.3.) | Phys.Rept. 286 (1997) 271-348 | 10.1016/S0370-1573(96)00051-8 | null | gr-qc | null | In this paper we will make a survey of solutions to the Wheeler-Dewitt
equation which have been found up to now in Ashtekar's formulation for
canonical quantum gravity. Roughly speaking they are classified into two
categories, namely, Wilson-loop solutions and topological solutions. While the
program of finding solutions which are composed of Wilson loops is still in its
infancy, it is expected to be developed in the near future. Topological
solutions are the only solutions at present which we can give their
interpretation in terms of spacetime geometry. While the analysis made here is
formal in the sense that we do not deal with rigorously regularized constraint
equations, these topological solutions are expected to exist even in the fully
regularized theory and they are considered to yield vacuum states of quantum
gravity. We also make an attempt to review the spin network states as
intuitively as possible. In particular, the explicit formulae for two kinds of
measures on the space of spin network states are given.
| [
{
"created": "Wed, 31 Jan 1996 13:36:34 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Feb 1996 04:07:53 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Ezawa",
"Kiyoshi",
""
]
] | In this paper we will make a survey of solutions to the Wheeler-Dewitt equation which have been found up to now in Ashtekar's formulation for canonical quantum gravity. Roughly speaking they are classified into two categories, namely, Wilson-loop solutions and topological solutions. While the program of finding solutions which are composed of Wilson loops is still in its infancy, it is expected to be developed in the near future. Topological solutions are the only solutions at present which we can give their interpretation in terms of spacetime geometry. While the analysis made here is formal in the sense that we do not deal with rigorously regularized constraint equations, these topological solutions are expected to exist even in the fully regularized theory and they are considered to yield vacuum states of quantum gravity. We also make an attempt to review the spin network states as intuitively as possible. In particular, the explicit formulae for two kinds of measures on the space of spin network states are given. |
2202.12665 | Jorge Ovalle | J. Ovalle, E. Contreras, Z. Stuchlik | Energy exchange between relativistic fluids: the polytropic case | 10 pages, 12 figures | null | 10.1140/epjc/s10052-022-10168-5 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We present a simple, analytic and straightforward method to elucidate the
effects produced by polytropic fluids on any other gravitational source, no
matter its nature, for static and spherically symmetric spacetimes. As a direct
application, we study the interaction between polytropes and perfect fluids
coexisting inside a self-gravitating stellar object
| [
{
"created": "Fri, 25 Feb 2022 12:49:13 GMT",
"version": "v1"
}
] | 2022-03-30 | [
[
"Ovalle",
"J.",
""
],
[
"Contreras",
"E.",
""
],
[
"Stuchlik",
"Z.",
""
]
] | We present a simple, analytic and straightforward method to elucidate the effects produced by polytropic fluids on any other gravitational source, no matter its nature, for static and spherically symmetric spacetimes. As a direct application, we study the interaction between polytropes and perfect fluids coexisting inside a self-gravitating stellar object |
2306.16647 | Shuichi Yokoyama | Shuichi Yokoyama | Relativistic Hydrostatic Structure Equations and Analytic Multilayer
Stellar Model | 1+27 pages, 2 figures, v2: minor modifications, a new subsection of
analytic multilayer solar model with 2 figures, references added, v3: minor
corrections, discussion improved | null | null | null | gr-qc astro-ph.HE astro-ph.SR hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | The relativistic extension of the classic stellar structure equations is
investigated. It is pointed out that the Tolman-Oppenheimer-Volkov (TOV)
equation with the gradient equation for local gravitational mass can be made
complete as a closed set of differential equations by adding that for the
Tolman temperature with one equation of state, and the set is proposed as the
relativistic hydrostatic structure equations. The exact forms of the
relativistic Poisson equation and the steady-state heat conduction equation in
the curved spacetime are derived. The application to an ideal gas of particles
with the conserved particle number current leads to a strong prediction that
the heat capacity ratio almost becomes one in any Newtonian convection zone
such as the solar surface. The steady-state heat conduction equation is solved
exactly in the system and thermodynamic observables exhibit the power law
behavior, which implies the possibility for the system to be a new model of
stellar corona and a flaw in the earlier one obtained by using the
non-relativistic stellar structure equations. The mixture with another ideal
gas yields multilayer structure to a stellar model, in which classic stellar
structure equations are reproduced and analytic multilayer structure of
luminous stars including the Sun is revealed in suitable approximation.
| [
{
"created": "Thu, 29 Jun 2023 03:16:26 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Jul 2023 10:41:44 GMT",
"version": "v2"
},
{
"created": "Sun, 13 Aug 2023 15:13:52 GMT",
"version": "v3"
}
] | 2023-08-22 | [
[
"Yokoyama",
"Shuichi",
""
]
] | The relativistic extension of the classic stellar structure equations is investigated. It is pointed out that the Tolman-Oppenheimer-Volkov (TOV) equation with the gradient equation for local gravitational mass can be made complete as a closed set of differential equations by adding that for the Tolman temperature with one equation of state, and the set is proposed as the relativistic hydrostatic structure equations. The exact forms of the relativistic Poisson equation and the steady-state heat conduction equation in the curved spacetime are derived. The application to an ideal gas of particles with the conserved particle number current leads to a strong prediction that the heat capacity ratio almost becomes one in any Newtonian convection zone such as the solar surface. The steady-state heat conduction equation is solved exactly in the system and thermodynamic observables exhibit the power law behavior, which implies the possibility for the system to be a new model of stellar corona and a flaw in the earlier one obtained by using the non-relativistic stellar structure equations. The mixture with another ideal gas yields multilayer structure to a stellar model, in which classic stellar structure equations are reproduced and analytic multilayer structure of luminous stars including the Sun is revealed in suitable approximation. |
gr-qc/9704041 | Guillermo Mena | Guillermo A. Mena Marugan (IMAFF, CSIC, Madrid) | Canonical Quantization of the Gowdy Model | 13 pages, Revtex | Phys.Rev. D56 (1997) 908-919 | 10.1103/PhysRevD.56.908 | null | gr-qc | null | The family of Gowdy universes with the spatial topology of a three-torus is
studied both classically and quantum mechanically. Starting with the Ashtekar
formulation of Lorentzian general relativity, we introduce a gauge fixing
procedure to remove almost all of the non-physical degrees of freedom. In this
way, we arrive at a reduced model that is subject only to one homogeneous
constraint. The phase space of this model is described by means of a canonical
set of elementary variables. These are two real, homogeneous variables and the
Fourier coefficients for four real fields that are periodic in the angular
coordinate which does not correspond to a Killing field of the Gowdy
spacetimes. We also obtain the explicit expressions for the line element and
reduced Hamiltonian. We then proceed to quantize the system by representing the
elementary variables as linear operators acting on a vector space of analytic
functionals. The inner product on that space is selected by imposing Lorentzian
reality conditions. We find the quantum states annihilated by the operator that
represents the homogeneous constraint of the model and construct with them the
Hilbert space of physical states. Finally, we derive the general form of the
quantum observables of the model.
| [
{
"created": "Tue, 15 Apr 1997 09:05:24 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Marugan",
"Guillermo A. Mena",
"",
"IMAFF, CSIC, Madrid"
]
] | The family of Gowdy universes with the spatial topology of a three-torus is studied both classically and quantum mechanically. Starting with the Ashtekar formulation of Lorentzian general relativity, we introduce a gauge fixing procedure to remove almost all of the non-physical degrees of freedom. In this way, we arrive at a reduced model that is subject only to one homogeneous constraint. The phase space of this model is described by means of a canonical set of elementary variables. These are two real, homogeneous variables and the Fourier coefficients for four real fields that are periodic in the angular coordinate which does not correspond to a Killing field of the Gowdy spacetimes. We also obtain the explicit expressions for the line element and reduced Hamiltonian. We then proceed to quantize the system by representing the elementary variables as linear operators acting on a vector space of analytic functionals. The inner product on that space is selected by imposing Lorentzian reality conditions. We find the quantum states annihilated by the operator that represents the homogeneous constraint of the model and construct with them the Hilbert space of physical states. Finally, we derive the general form of the quantum observables of the model. |
2008.00746 | Nikolaos Dimakis | N. Dimakis, T. Pailas, A. Paliathanasis, G. Leon, Petros A. Terzis and
T. Christodoulakis | Quantization of Einstein-aether Scalar field Cosmology | 10 pages, no figures, Latex2e source file, version accepted in EPJC | null | 10.1140/epjc/s10052-021-08933-z | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present, for the first time, the quantization process for the
Einstein-aether scalar field cosmology. We consider a cosmological theory
proposed as a Lorentz violating inflationary model, where the aether and scalar
fields interact through the assumption that the aether action constants are
ultra-local functions of the scalar field. For this specific theory there is a
valid minisuperspace description which we use to quantize. For a particular
relation between the two free functions entering the reduced Lagrangian the
solution to the Wheeler-DeWitt equation as also the generic classical solution
are presented for any given arbitrary potential function.
| [
{
"created": "Mon, 3 Aug 2020 09:58:46 GMT",
"version": "v1"
},
{
"created": "Sun, 31 Jan 2021 04:44:41 GMT",
"version": "v2"
}
] | 2021-03-17 | [
[
"Dimakis",
"N.",
""
],
[
"Pailas",
"T.",
""
],
[
"Paliathanasis",
"A.",
""
],
[
"Leon",
"G.",
""
],
[
"Terzis",
"Petros A.",
""
],
[
"Christodoulakis",
"T.",
""
]
] | We present, for the first time, the quantization process for the Einstein-aether scalar field cosmology. We consider a cosmological theory proposed as a Lorentz violating inflationary model, where the aether and scalar fields interact through the assumption that the aether action constants are ultra-local functions of the scalar field. For this specific theory there is a valid minisuperspace description which we use to quantize. For a particular relation between the two free functions entering the reduced Lagrangian the solution to the Wheeler-DeWitt equation as also the generic classical solution are presented for any given arbitrary potential function. |
gr-qc/0312084 | Docteur Philippe Grandclement | Philippe Grandclement, Mia Ihm, Vassiliki Kalogera, Krzystof
Belczynski | Searching for Gravitational Waves from the Inspiral of Precessing Binary
Systems: Astrophysical Expectations and Detection Efficiency of "Spiky''
Templates | 7 fig., accepted by Phys. Rev. D Minor modifications | Phys.Rev. D69 (2004) 102002 | 10.1103/PhysRevD.69.102002 | null | gr-qc astro-ph | null | Relativistic spin-orbit and spin-spin couplings has been shown to modify the
gravitational waveforms expected from inspiraling binaries with a black hole
and a neutron star. As a result inspiral signals may be missed due to
significant losses in signal-to-noise ratio, if precession effects are ignored
in gravitational-wave searches. We examine the sensitivity of the anticipated
loss of signal-to-noise ratio on two factors: the accuracy of the precessing
waveforms adopted as the true signals and the expected distributions of
spin-orbit tilt angles, given the current understanding of their physical
origin. We find that the results obtained using signals generated by
approximate techniques are in good agreement with the ones obtained by
integrating the 2PN equations. This shows that a complete account of all
high-order post-Newtonian effects is usually not necessary for the
determination of detection efficiencies. Based on our current astrophysical
expectations, large tilt angles are not favored and as a result the decrease in
detection rate varies rather slowly with respect to the black hole spin
magnitude and is within 20--30% of the maximum possible values.
| [
{
"created": "Thu, 18 Dec 2003 10:06:44 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Apr 2004 13:48:45 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Grandclement",
"Philippe",
""
],
[
"Ihm",
"Mia",
""
],
[
"Kalogera",
"Vassiliki",
""
],
[
"Belczynski",
"Krzystof",
""
]
] | Relativistic spin-orbit and spin-spin couplings has been shown to modify the gravitational waveforms expected from inspiraling binaries with a black hole and a neutron star. As a result inspiral signals may be missed due to significant losses in signal-to-noise ratio, if precession effects are ignored in gravitational-wave searches. We examine the sensitivity of the anticipated loss of signal-to-noise ratio on two factors: the accuracy of the precessing waveforms adopted as the true signals and the expected distributions of spin-orbit tilt angles, given the current understanding of their physical origin. We find that the results obtained using signals generated by approximate techniques are in good agreement with the ones obtained by integrating the 2PN equations. This shows that a complete account of all high-order post-Newtonian effects is usually not necessary for the determination of detection efficiencies. Based on our current astrophysical expectations, large tilt angles are not favored and as a result the decrease in detection rate varies rather slowly with respect to the black hole spin magnitude and is within 20--30% of the maximum possible values. |
gr-qc/9811033 | Ilja Schmelzer | Ilja Schmelzer | A Metric Theory of Gravity with Condensed Matter Interpretation | 11 pages Latex, no figures | null | null | WIAS preprint No. 447 (ISSN 0946-8633) | gr-qc | null | We define a metric theory of gravity with preferred Newtonian frame
(X^i(x),T(x)) by
L = L_{GR}
+ \Xi g^{mn}\delta_{ij}X^i_{,m}X^j_{,n}
- \Upsilon g^{mn}T_{,m}T_{,n}
It allows a condensed matter interpretation which generalizes LET to gravity.
The \Xi-term influences the age of the universe. \Upsilon>0 allows to avoid
big bang singularity and black hole horizon formation. This solves the horizon
problem without inflation. An atomic hypothesis solves the ultraviolet problem
by explicit regularization. We give a prediction about cutoff length.
| [
{
"created": "Wed, 11 Nov 1998 13:18:04 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Nov 1998 11:51:03 GMT",
"version": "v2"
},
{
"created": "Mon, 16 Nov 1998 12:32:27 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Schmelzer",
"Ilja",
""
]
] | We define a metric theory of gravity with preferred Newtonian frame (X^i(x),T(x)) by L = L_{GR} + \Xi g^{mn}\delta_{ij}X^i_{,m}X^j_{,n} - \Upsilon g^{mn}T_{,m}T_{,n} It allows a condensed matter interpretation which generalizes LET to gravity. The \Xi-term influences the age of the universe. \Upsilon>0 allows to avoid big bang singularity and black hole horizon formation. This solves the horizon problem without inflation. An atomic hypothesis solves the ultraviolet problem by explicit regularization. We give a prediction about cutoff length. |
1608.01284 | Rhondale Tso | Rhondale Tso, Maximiliano Isi, Yanbei Chen, and Leo Stein | Modeling the Dispersion and Polarization Content of Gravitational Waves
for Tests of General Relativity | 4 pages, Presented at the Seventh Meeting on CPT and Lorentz
Symmetry, Bloomington, Indiana, June 20-24, 2016 | null | 10.1142/9789813148505_0052 | LIGO-P1600232 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a generic, phenomenological approach to modifying the dispersion
of gravitational waves, independent of corrections to the generation mechanism.
This model-independent approach encapsulates all previously proposed
parametrizations, including Lorentz violation in the Standard-Model Extension,
and provides a roadmap for additional theories. Furthermore, we present a
general approach to include modulations to the gravitational-wave polarization
content. The framework developed here can be implemented in existing data
analysis pipelines for future gravitational-wave observation runs.
| [
{
"created": "Wed, 3 Aug 2016 18:49:20 GMT",
"version": "v1"
}
] | 2017-05-31 | [
[
"Tso",
"Rhondale",
""
],
[
"Isi",
"Maximiliano",
""
],
[
"Chen",
"Yanbei",
""
],
[
"Stein",
"Leo",
""
]
] | We propose a generic, phenomenological approach to modifying the dispersion of gravitational waves, independent of corrections to the generation mechanism. This model-independent approach encapsulates all previously proposed parametrizations, including Lorentz violation in the Standard-Model Extension, and provides a roadmap for additional theories. Furthermore, we present a general approach to include modulations to the gravitational-wave polarization content. The framework developed here can be implemented in existing data analysis pipelines for future gravitational-wave observation runs. |
2011.02317 | Carlos Ortiz | C. Ortiz | Surface Tension: Accelerated Expansion, Coincidence Problem & Hubble
Tension | 15 pages, 5 figures, IJMPD Accepted | null | 10.1142/S0218271820501151 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we give a physical explanation to the accelerated expansion of
the Universe, alleviating the tension between the discrepancy of Hubble
constant measurements. By the Euler Cauchy stress principle, we identify a
controversy on the lack of consideration of the surface forces contemplated in
the study of the expansion of the Universe. We distinguish a new effect that
modifies the spacetime fabric by means of the energy conservation equation. The
resulting dynamical equations from the proposed hypothesis are contrasted to
several testable astrophysical predictions. This paper also explains why we
have not found any particle or fluid responsible for dark energy and clarifies
the Cosmological Coincidence Problem. These explanations are achieved without
assuming the existence of exotic matter of unphysical meaning or having to
modify the Einstein's Field Equations.
| [
{
"created": "Mon, 2 Nov 2020 23:44:18 GMT",
"version": "v1"
}
] | 2021-02-17 | [
[
"Ortiz",
"C.",
""
]
] | In this paper we give a physical explanation to the accelerated expansion of the Universe, alleviating the tension between the discrepancy of Hubble constant measurements. By the Euler Cauchy stress principle, we identify a controversy on the lack of consideration of the surface forces contemplated in the study of the expansion of the Universe. We distinguish a new effect that modifies the spacetime fabric by means of the energy conservation equation. The resulting dynamical equations from the proposed hypothesis are contrasted to several testable astrophysical predictions. This paper also explains why we have not found any particle or fluid responsible for dark energy and clarifies the Cosmological Coincidence Problem. These explanations are achieved without assuming the existence of exotic matter of unphysical meaning or having to modify the Einstein's Field Equations. |
gr-qc/0106091 | Daniele Oriti | Daniele Oriti | Spacetime geometry from algebra: spin foam models for non-perturbative
quantum gravity | 68 pages, 16 figures, LaTex; v2: minor changes; v3: several points
clarified, references added; to appear in Rep. Prog. Phys | Rept.Prog.Phys.64:1703-1756,2001 | 10.1088/0034-4885/64/12/203 | DAMTP-2001-86 | gr-qc hep-th | null | This is an introduction to spin foam models for non-perturbative quantum
gravity, an approach that lies at the point of convergence of many different
research areas, including loop quantum gravity, topological quantum field
theories, path integral quantum gravity, lattice field theory, matrix models,
category theory, statistical mechanics. We describe the general formalism and
ideas of spin foam models, the picture of quantum geometry emerging from them,
and give a review of the results obtained so far, in both the Euclidean and
Lorentzian case. We focus in particular on the Barrett-Crane model for
4-dimensional quantum gravity.
| [
{
"created": "Thu, 28 Jun 2001 15:52:35 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Jul 2001 13:45:11 GMT",
"version": "v2"
},
{
"created": "Mon, 15 Oct 2001 17:51:08 GMT",
"version": "v3"
}
] | 2011-02-16 | [
[
"Oriti",
"Daniele",
""
]
] | This is an introduction to spin foam models for non-perturbative quantum gravity, an approach that lies at the point of convergence of many different research areas, including loop quantum gravity, topological quantum field theories, path integral quantum gravity, lattice field theory, matrix models, category theory, statistical mechanics. We describe the general formalism and ideas of spin foam models, the picture of quantum geometry emerging from them, and give a review of the results obtained so far, in both the Euclidean and Lorentzian case. We focus in particular on the Barrett-Crane model for 4-dimensional quantum gravity. |
2207.03799 | Maykoll Reyes | J. M. Carmona, J. L. Cort\'es, J. J. Relancio, M. A. Reyes | Time delays, choice of energy-momentum variables and relative locality
in doubly special relativity | 14 pages | null | 10.1103/PhysRevD.106.064045 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Doubly Special Relativity (DSR) theories consider (quantum-gravity motivated)
deformations of the symmetries of special relativity compatible with a
relativity principle. The existence of time delays for massless particles, one
of their proposed phenomenological consequences, is a delicate question, since,
contrary to what happens with Lorentz Invariance Violation (LIV) scenarios,
they are not simply determined by the modification in the particle dispersion
relation. While some studies of DSR assert the existence of photon time delays,
in this paper we generalize a recently proposed model for time delay studies in
DSR and show that the existence of photon time delays does not necessarily
follow from a DSR scenario, determining in which cases this is so. Moreover, we
clarify long-standing questions about the arbitrariness in the choice of the
energy-momentum labels and the independence of the time delay on this choice,
as well as on the consistency of its calculation with the relative locality
paradigm of DSR theories. Finally, we show that the result for time delays is
reproduced in models that consider propagation in a noncommutative spacetime.
| [
{
"created": "Fri, 8 Jul 2022 10:08:33 GMT",
"version": "v1"
}
] | 2022-10-12 | [
[
"Carmona",
"J. M.",
""
],
[
"Cortés",
"J. L.",
""
],
[
"Relancio",
"J. J.",
""
],
[
"Reyes",
"M. A.",
""
]
] | Doubly Special Relativity (DSR) theories consider (quantum-gravity motivated) deformations of the symmetries of special relativity compatible with a relativity principle. The existence of time delays for massless particles, one of their proposed phenomenological consequences, is a delicate question, since, contrary to what happens with Lorentz Invariance Violation (LIV) scenarios, they are not simply determined by the modification in the particle dispersion relation. While some studies of DSR assert the existence of photon time delays, in this paper we generalize a recently proposed model for time delay studies in DSR and show that the existence of photon time delays does not necessarily follow from a DSR scenario, determining in which cases this is so. Moreover, we clarify long-standing questions about the arbitrariness in the choice of the energy-momentum labels and the independence of the time delay on this choice, as well as on the consistency of its calculation with the relative locality paradigm of DSR theories. Finally, we show that the result for time delays is reproduced in models that consider propagation in a noncommutative spacetime. |
gr-qc/0309112 | Vitor Cardoso | Vitor Cardoso, Jose' P. S. Lemos, Shijun Yoshida | Quasinormal modes of Schwarzschild black holes in four and higher
dimensions | 12 pages, 5 figures, RevTeX4. v2. Typos corrected, references added | Phys.Rev. D69 (2004) 044004 | 10.1103/PhysRevD.69.044004 | null | gr-qc astro-ph hep-ph hep-th | null | We make a thorough investigation of the asymptotic quasinormal modes of the
four and five-dimensional Schwarzschild black hole for scalar, electromagnetic
and gravitational perturbations. Our numerical results give full support to all
the analytical predictions by Motl and Neitzke, for the leading term. We also
compute the first order corrections analytically, by extending to higher
dimensions, previous work of Musiri and Siopsis, and find excellent agreement
with the numerical results. For generic spacetime dimension number D the
first-order corrections go as $\frac{1}{n^{(D-3)/(D-2)}}$. This means that
there is a more rapid convergence to the asymptotic value for the five
dimensional case than for the four dimensional case, as we also show
numerically.
| [
{
"created": "Tue, 23 Sep 2003 13:47:33 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Sep 2003 17:01:58 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Cardoso",
"Vitor",
""
],
[
"Lemos",
"Jose' P. S.",
""
],
[
"Yoshida",
"Shijun",
""
]
] | We make a thorough investigation of the asymptotic quasinormal modes of the four and five-dimensional Schwarzschild black hole for scalar, electromagnetic and gravitational perturbations. Our numerical results give full support to all the analytical predictions by Motl and Neitzke, for the leading term. We also compute the first order corrections analytically, by extending to higher dimensions, previous work of Musiri and Siopsis, and find excellent agreement with the numerical results. For generic spacetime dimension number D the first-order corrections go as $\frac{1}{n^{(D-3)/(D-2)}}$. This means that there is a more rapid convergence to the asymptotic value for the five dimensional case than for the four dimensional case, as we also show numerically. |
0709.1512 | Luciano Iess | B. Bertotti, N. Ashby, L. Iess | The effect of the motion of the Sun on the light-time in interplanetary
relativistic experiments | Final version accepted by Classical and Quantum Gravity (8 Jan. 2008) | Class. Quantum Grav. 25 045013 | 10.1088/0264-9381/25/4/045013 | null | gr-qc physics.gen-ph | null | In 2002 a measurement of the effect of solar gravity upon the phase of
coherent microwave beams passing near the Sun has been carried out with the
Cassini mission, allowing a very accurate measurement of the PPN parameter
$\gamma$. The data have been analyzed with NASA's Orbit Determination Program
(ODP) in the Barycentric Celestial Reference System, in which the Sun moves
around the centre of mass of the solar system with a velocity $v_\odot$ of
about 10 m/sec; the question arises, what correction this implies for the
predicted phase shift. After a review of the way the ODP works, we set the
problem in the framework of Lorentz (and Galilean) transformations and evaluate
the correction; it is several orders of magnitude below our experimental
accuracy. We also discuss a recent paper \cite{kopeikin07}, which claims wrong
and much larger corrections, and clarify the reasons for the discrepancy.
| [
{
"created": "Tue, 11 Sep 2007 00:27:05 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Sep 2007 15:13:54 GMT",
"version": "v2"
},
{
"created": "Thu, 27 Sep 2007 11:02:31 GMT",
"version": "v3"
},
{
"created": "Sat, 27 Oct 2007 10:28:11 GMT",
"version": "v4"
},
{
"created": "Sat, 12 Jan 2008 17:34:57 GMT",
"version": "v5"
}
] | 2009-02-01 | [
[
"Bertotti",
"B.",
""
],
[
"Ashby",
"N.",
""
],
[
"Iess",
"L.",
""
]
] | In 2002 a measurement of the effect of solar gravity upon the phase of coherent microwave beams passing near the Sun has been carried out with the Cassini mission, allowing a very accurate measurement of the PPN parameter $\gamma$. The data have been analyzed with NASA's Orbit Determination Program (ODP) in the Barycentric Celestial Reference System, in which the Sun moves around the centre of mass of the solar system with a velocity $v_\odot$ of about 10 m/sec; the question arises, what correction this implies for the predicted phase shift. After a review of the way the ODP works, we set the problem in the framework of Lorentz (and Galilean) transformations and evaluate the correction; it is several orders of magnitude below our experimental accuracy. We also discuss a recent paper \cite{kopeikin07}, which claims wrong and much larger corrections, and clarify the reasons for the discrepancy. |
0801.1150 | Chunnong Zhao | C. Zhao, L. Ju, Y. Fan, S. Gras. B. J. J. Slagmolen, H. Miao, P.
Barriga D.G. Blair, D. J. Hosken, A. F. Brooks, P. J. Veitch, D. Mudge, J.
Munch | Observation of Three Mode Parametric Interactions in Long Optical
Cavities | 10 pages and 5 figures | null | 10.1103/PhysRevA.78.023807 | null | gr-qc | null | We report the first observation of three-mode opto-acoustic parametric
interactions of the type predicted to cause parametric instabilities in an 80 m
long, high optical power cavity that uses suspended sapphire mirrors. Resonant
interaction occurs between two distinct optical modes and an acoustic mode of
one mirror when the difference in frequency between the two optical cavity
modes is close to the frequency of the acoustic mode. Experimental results
validate the theory of parametric instability in high power optical cavities.
| [
{
"created": "Tue, 8 Jan 2008 03:07:03 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Zhao",
"C.",
""
],
[
"Ju",
"L.",
""
],
[
"Fan",
"Y.",
""
],
[
"Slagmolen",
"S. Gras. B. J. J.",
""
],
[
"Miao",
"H.",
""
],
[
"Blair",
"P. Barriga D. G.",
""
],
[
"Hosken",
"D. J.",
""
],
[
"Brooks",
"A. F.",
""
],
[
"Veitch",
"P. J.",
""
],
[
"Mudge",
"D.",
""
],
[
"Munch",
"J.",
""
]
] | We report the first observation of three-mode opto-acoustic parametric interactions of the type predicted to cause parametric instabilities in an 80 m long, high optical power cavity that uses suspended sapphire mirrors. Resonant interaction occurs between two distinct optical modes and an acoustic mode of one mirror when the difference in frequency between the two optical cavity modes is close to the frequency of the acoustic mode. Experimental results validate the theory of parametric instability in high power optical cavities. |
2009.03404 | Mohsen Fathi | Mohsen Fathi, Marco Olivares, J.R. Villanueva | Gravitational Rutherford scattering of electrically charged particles
from a charged Weyl black hole | 23 pages, 9 figures | Eur. Phys. J. Plus 136:420 (2021) | 10.1140/epjp/s13360-021-01441-9 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Considering electrically charged test particles, we continue our study of the
exterior dynamics of a charged Weyl black hole which has been previously
investigated regarding the motion of mass-less and (neutral) massive particles.
In this paper, the deflecting trajectories of charged particles are designated
as being gravitationally Rutherford-scattered and detailed discussions of
angular and radial particle motions are presented.
| [
{
"created": "Mon, 7 Sep 2020 20:25:35 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Nov 2020 22:41:31 GMT",
"version": "v2"
},
{
"created": "Wed, 14 Apr 2021 17:09:42 GMT",
"version": "v3"
}
] | 2021-04-27 | [
[
"Fathi",
"Mohsen",
""
],
[
"Olivares",
"Marco",
""
],
[
"Villanueva",
"J. R.",
""
]
] | Considering electrically charged test particles, we continue our study of the exterior dynamics of a charged Weyl black hole which has been previously investigated regarding the motion of mass-less and (neutral) massive particles. In this paper, the deflecting trajectories of charged particles are designated as being gravitationally Rutherford-scattered and detailed discussions of angular and radial particle motions are presented. |
1304.3176 | Richard O'Shaughnessy | (1) Larne Pekowsky, (2) Richard O'Shaughnessy, (1) Jim Healy, (1)
Deirdre Shoemaker ((1) Center for Relativistic Astrophysics, Georgia Tech,
(2) Center for Gravitation and Cosmology, University of Wisconsin-Milwaukee) | Comparing gravitational waves from nonprecessing and precessing black
hole binaries in the corotating frame | Submitted to PRD; v2 corrects mass scales; v3 repairs and improves
fig 2 and count | null | 10.1103/PhysRevD.88.024040 | LIGO DCC P1300057 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Previous analytic and numerical calculations suggest that, at each instant,
the emission from a precessing black hole binary closely resembles the emission
from a nonprecessing analog. In this paper we quantitatively explore the
validity and limitations of that correspondence, extracting the radiation from
a large collection of roughly two hundred generic black hole binary merger
simulations both in the simulation frame and in a corotating frame that tracks
precession. To a first approximation, the corotating-frame waveforms resemble
nonprecessing analogs, based on similarity over a band-limited frequency
interval defined using a fiducial detector (here, advanced LIGO) and the
source's total mass $M$. By restricting attention to masses $M\in 100, 1000
M_\odot$, we insure our comparisons are sensitive only to our simulated
late-time inspiral, merger, and ringdown signals. In this mass region, every
one of our precessing simulations can be fit by some physically similar member
of the \texttt{IMRPhenomB} phenomenological waveform family to better than 95%;
most fit significantly better. The best-fit parameters at low and high mass
correspond to natural physical limits: the pre-merger orbit and post-merger
perturbed black hole. Our results suggest that physically-motivated synthetic
signals can be derived by viewing radiation from suitable nonprecessing
binaries in a suitable nonintertial reference frame. While a good first
approximation, precessing systems have degrees of freedom (i.e., the transverse
spins) which a nonprecessing simulation cannot reproduce. We quantify the
extent to which these missing degrees of freedom limit the utility of synthetic
precessing signals for detection and parameter estimation.
| [
{
"created": "Thu, 11 Apr 2013 01:11:07 GMT",
"version": "v1"
},
{
"created": "Fri, 24 May 2013 19:05:07 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Jul 2013 20:12:20 GMT",
"version": "v3"
}
] | 2013-08-09 | [
[
"Pekowsky",
"Larne",
""
],
[
"O'Shaughnessy",
"Richard",
""
],
[
"Healy",
"Jim",
""
],
[
"Shoemaker",
"Deirdre",
""
]
] | Previous analytic and numerical calculations suggest that, at each instant, the emission from a precessing black hole binary closely resembles the emission from a nonprecessing analog. In this paper we quantitatively explore the validity and limitations of that correspondence, extracting the radiation from a large collection of roughly two hundred generic black hole binary merger simulations both in the simulation frame and in a corotating frame that tracks precession. To a first approximation, the corotating-frame waveforms resemble nonprecessing analogs, based on similarity over a band-limited frequency interval defined using a fiducial detector (here, advanced LIGO) and the source's total mass $M$. By restricting attention to masses $M\in 100, 1000 M_\odot$, we insure our comparisons are sensitive only to our simulated late-time inspiral, merger, and ringdown signals. In this mass region, every one of our precessing simulations can be fit by some physically similar member of the \texttt{IMRPhenomB} phenomenological waveform family to better than 95%; most fit significantly better. The best-fit parameters at low and high mass correspond to natural physical limits: the pre-merger orbit and post-merger perturbed black hole. Our results suggest that physically-motivated synthetic signals can be derived by viewing radiation from suitable nonprecessing binaries in a suitable nonintertial reference frame. While a good first approximation, precessing systems have degrees of freedom (i.e., the transverse spins) which a nonprecessing simulation cannot reproduce. We quantify the extent to which these missing degrees of freedom limit the utility of synthetic precessing signals for detection and parameter estimation. |
1705.07544 | Anzhong Wang | Tao Zhu, Anzhong Wang, Gerald Cleaver, Klaus Kirsten and Qin Sheng | Pre-inflationary universe in loop quantum cosmology | revtex4, 23 figures, and 5 tables. Some typos were corrected. Phys.
Rev. D 96, 083520 (2017) | Phys. Rev. D 96, 083520 (2017) | 10.1103/PhysRevD.96.083520 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The evolutions of the flat FLRW universe and its linear perturbations are
studied systematically in the dressed metric approach of LQC. When it is
dominated by the kinetic energy of the inflaton at the quantum bounce, the
evolution of the background can be divided into three different phases prior to
the preheating, {\em bouncing, transition and slow-roll inflation}. During the
bouncing phase, the evolution is independent of not only the initial
conditions, but also the inflationary potentials. In particular, the expansion
factor can be well described by the same exact solution in all the cases
considered. In contrast, in the potential dominated case such a universality is
lost. It is because of this universality that the linear perturbations are also
independent of the inflationary models and obtained exactly. During the
transition phase, the evolutions of the background and its linear perturbations
are found explicitly, and then matched to the ones given in the other two
phases. Hence, once the initial conditions are imposed, the linear scalar and
tensor perturbations will be uniquely determined. Considering two different
sets of initial conditions, one imposed during the contracting phase and the
other at the bounce, we calculate the Bogoliubov coefficients and find that the
two sets yield the same results and all lead to particle creations at the onset
of the inflation. Due to the pre-inflationary dynamics, the scalar and tensor
power spectra become scale-dependent. Comparing with the Planck 2015 data, we
find constraints on the total e-folds that the universe must have expanded
since the bounce, in order to be consistent with current observations.
| [
{
"created": "Mon, 22 May 2017 03:03:16 GMT",
"version": "v1"
},
{
"created": "Sun, 4 Jun 2017 00:52:02 GMT",
"version": "v2"
},
{
"created": "Thu, 21 Sep 2017 01:44:14 GMT",
"version": "v3"
},
{
"created": "Tue, 24 Oct 2017 15:17:31 GMT",
"version": "v4"
}
] | 2017-10-25 | [
[
"Zhu",
"Tao",
""
],
[
"Wang",
"Anzhong",
""
],
[
"Cleaver",
"Gerald",
""
],
[
"Kirsten",
"Klaus",
""
],
[
"Sheng",
"Qin",
""
]
] | The evolutions of the flat FLRW universe and its linear perturbations are studied systematically in the dressed metric approach of LQC. When it is dominated by the kinetic energy of the inflaton at the quantum bounce, the evolution of the background can be divided into three different phases prior to the preheating, {\em bouncing, transition and slow-roll inflation}. During the bouncing phase, the evolution is independent of not only the initial conditions, but also the inflationary potentials. In particular, the expansion factor can be well described by the same exact solution in all the cases considered. In contrast, in the potential dominated case such a universality is lost. It is because of this universality that the linear perturbations are also independent of the inflationary models and obtained exactly. During the transition phase, the evolutions of the background and its linear perturbations are found explicitly, and then matched to the ones given in the other two phases. Hence, once the initial conditions are imposed, the linear scalar and tensor perturbations will be uniquely determined. Considering two different sets of initial conditions, one imposed during the contracting phase and the other at the bounce, we calculate the Bogoliubov coefficients and find that the two sets yield the same results and all lead to particle creations at the onset of the inflation. Due to the pre-inflationary dynamics, the scalar and tensor power spectra become scale-dependent. Comparing with the Planck 2015 data, we find constraints on the total e-folds that the universe must have expanded since the bounce, in order to be consistent with current observations. |
1107.1336 | Parthasarathi Mitra | Bhramar Chatterjee and P. Mitra | Regularizing tunnelling calculations of Hawking temperature | 4 pages; expanded | Gen. Rel. Grav. 44 (2012) 2365 | 10.1007/s10714-012-1396-6 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Attempts to understand Hawking radiation as tunnelling across a black hole
horizon require the consideration of singular integrals. Although Schwarzschild
coordinates lead to the standard Hawking temperature, isotropic radial
coordinates may appear to produce an incorrect value. It is demonstrated here
how the proper regularization of singular integrals leads to the standard
temperature for the isotropic radial coordinates as well as for other smooth
transformations of the radial variable, which of course describe the same black
hole.
| [
{
"created": "Thu, 7 Jul 2011 10:18:28 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Jul 2011 09:12:25 GMT",
"version": "v2"
},
{
"created": "Fri, 1 Jun 2012 06:25:19 GMT",
"version": "v3"
}
] | 2014-05-22 | [
[
"Chatterjee",
"Bhramar",
""
],
[
"Mitra",
"P.",
""
]
] | Attempts to understand Hawking radiation as tunnelling across a black hole horizon require the consideration of singular integrals. Although Schwarzschild coordinates lead to the standard Hawking temperature, isotropic radial coordinates may appear to produce an incorrect value. It is demonstrated here how the proper regularization of singular integrals leads to the standard temperature for the isotropic radial coordinates as well as for other smooth transformations of the radial variable, which of course describe the same black hole. |
1806.05042 | Ghulam Abbas | G. Abbas and H. Nazar | Complexity Factor For Static Anisotropic Self-Gravitating Source in
$f(R)$ Gravity | 16 pages, no figure accepted for publication in EPJC | Eur. Phys. J. C (2018) 78:510 | 10.1140/epjc/s10052-018-5973-z | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent paper, Herrera \cite{2} (L. Herrera: Phys. Rev. D97,
044010(2018)) have proposed a new definition of complexity for static
self-gravitating fluid in General Relativity. In the present article, we
implement this definition of complexity for static self-gravitating fluid to
case of $f(R)$ gravity. Here, we found that in the frame of $f(R)$ gravity the
definition of complexity proposed by Herrera, entirely based on the quantity
known as complexity factor which appears in the orthogonal splitting of the
curvature tensor. It has been observed that fluid spheres possessing homogenous
energy density profile and isotropic pressure are capable to diminish their the
complexity factor. We are interested to see the effects of $f(R)$ term on
complexity factor of the self-gravitating object. The gravitating source with
inhomogeneous energy density and anisotropic pressure have maximum value of
complexity. Further, such fluids may have zero complexity factor if the effects
of inhomogeneity in energy density and anisotropic pressure cancel the effects
of each other in the presence of $f(R)$ dark source term. Also, we have found
some interior exact solutions of modified $f(R)$ field equations satisfying
complexity criterium and some applications of this newly concept to the study
of structure of compact objects are discussed in detail. It is interesting to
note that previous results about the complexity for static self-gravitating
fluid in General Relativity can be recovered from our analysis if $f(R)=R$,
which General Relativistic limit of $f(R)$ gravity. Some future research
directions have been mentioned in the end of the summary.
| [
{
"created": "Mon, 11 Jun 2018 09:55:38 GMT",
"version": "v1"
}
] | 2018-10-30 | [
[
"Abbas",
"G.",
""
],
[
"Nazar",
"H.",
""
]
] | In a recent paper, Herrera \cite{2} (L. Herrera: Phys. Rev. D97, 044010(2018)) have proposed a new definition of complexity for static self-gravitating fluid in General Relativity. In the present article, we implement this definition of complexity for static self-gravitating fluid to case of $f(R)$ gravity. Here, we found that in the frame of $f(R)$ gravity the definition of complexity proposed by Herrera, entirely based on the quantity known as complexity factor which appears in the orthogonal splitting of the curvature tensor. It has been observed that fluid spheres possessing homogenous energy density profile and isotropic pressure are capable to diminish their the complexity factor. We are interested to see the effects of $f(R)$ term on complexity factor of the self-gravitating object. The gravitating source with inhomogeneous energy density and anisotropic pressure have maximum value of complexity. Further, such fluids may have zero complexity factor if the effects of inhomogeneity in energy density and anisotropic pressure cancel the effects of each other in the presence of $f(R)$ dark source term. Also, we have found some interior exact solutions of modified $f(R)$ field equations satisfying complexity criterium and some applications of this newly concept to the study of structure of compact objects are discussed in detail. It is interesting to note that previous results about the complexity for static self-gravitating fluid in General Relativity can be recovered from our analysis if $f(R)=R$, which General Relativistic limit of $f(R)$ gravity. Some future research directions have been mentioned in the end of the summary. |
gr-qc/0505141 | Arunava Bhadra Dr. | Arunava Bhadra, and Kabita Sarkar | On static spherically symmetric solutions of the vacuum Brans-Dicke
theory | 15 pages, To be published in Gen. Rel. and Grav, typos in references
corrected | Gen.Rel.Grav.37:2189-2199,2005 | 10.1007/s10714-005-0181-1 | null | gr-qc | null | It is shown that among the four classes of the static spherically symmetric
solution of the vacuum Brans-Dicke theory of gravity only two are really
independent. Further by matching exterior and interior (due to physically
reasonable spherically symmetric matter source) scalar fields it is found that
only Brans class I solution with certain restriction on solution parameters may
represent exterior metric for a nonsingular massive object. The physical
viability of the black hole nature of the solution is investigated. It is
concluded that no physical black hole solution different from the Schwarzschild
black hole is available in the Brans-Dicke theory.
| [
{
"created": "Mon, 30 May 2005 17:32:48 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Feb 2006 07:47:35 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Bhadra",
"Arunava",
""
],
[
"Sarkar",
"Kabita",
""
]
] | It is shown that among the four classes of the static spherically symmetric solution of the vacuum Brans-Dicke theory of gravity only two are really independent. Further by matching exterior and interior (due to physically reasonable spherically symmetric matter source) scalar fields it is found that only Brans class I solution with certain restriction on solution parameters may represent exterior metric for a nonsingular massive object. The physical viability of the black hole nature of the solution is investigated. It is concluded that no physical black hole solution different from the Schwarzschild black hole is available in the Brans-Dicke theory. |
2309.06022 | Naosad Alam | Naosad Alam, Subrata Pal, A. Rahmansyah, A. Sulaksono | Impact of modified gravity theory on neutron star and nuclear matter
properties | 16 pages, 9 figures, Version to appear in PRD | null | null | null | gr-qc nucl-th | http://creativecommons.org/licenses/by/4.0/ | New observational data, measured with a high degree of accuracy, of compact
isolated neutron stars and binary stars in gravitational wave remnants have the
potential to explore the strong field gravity. Within the framework of
energy-momentum squared gravity (EMSG) theory we study its impact on several
properties of neutron stars and plausible modifications from the predictions of
general relativity. Based on a representative set of relativistic nuclear mean
field models, non-relativistic Skyrme-Hartree-Fock models and microscopic
calculations, we show deviations of neutron star mass-radius sequence in EMSG
theory as compared to general relativity. The variation in the effective
nuclear equation of state in EMSG, results in distinct magnitudes in the
reduced pressure, speed of sound, and maximum compactness at the center of
neutron stars. We perform extensive correlation analysis of the nuclear model
parameters with the neutron star observables in light of the new observational
bounds. Perceptible modifications in the correlations are found in the models
of gravity that provide different estimates of the slope and curvature of
nuclear matter symmetry energy. The available neutron star data however do not
impose stringent enough constraints for clear evidence of deviations from
general relativity.
| [
{
"created": "Tue, 12 Sep 2023 07:47:49 GMT",
"version": "v1"
},
{
"created": "Mon, 5 Feb 2024 08:13:01 GMT",
"version": "v2"
}
] | 2024-02-06 | [
[
"Alam",
"Naosad",
""
],
[
"Pal",
"Subrata",
""
],
[
"Rahmansyah",
"A.",
""
],
[
"Sulaksono",
"A.",
""
]
] | New observational data, measured with a high degree of accuracy, of compact isolated neutron stars and binary stars in gravitational wave remnants have the potential to explore the strong field gravity. Within the framework of energy-momentum squared gravity (EMSG) theory we study its impact on several properties of neutron stars and plausible modifications from the predictions of general relativity. Based on a representative set of relativistic nuclear mean field models, non-relativistic Skyrme-Hartree-Fock models and microscopic calculations, we show deviations of neutron star mass-radius sequence in EMSG theory as compared to general relativity. The variation in the effective nuclear equation of state in EMSG, results in distinct magnitudes in the reduced pressure, speed of sound, and maximum compactness at the center of neutron stars. We perform extensive correlation analysis of the nuclear model parameters with the neutron star observables in light of the new observational bounds. Perceptible modifications in the correlations are found in the models of gravity that provide different estimates of the slope and curvature of nuclear matter symmetry energy. The available neutron star data however do not impose stringent enough constraints for clear evidence of deviations from general relativity. |
1111.0638 | Miguel Campiglia | Miguel Campiglia | Polymer representations and geometric quantization | 15 pages | null | null | IGC-11/10-2 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Polymer representations of the Weyl algebra of linear systems provide the
simplest analogues of the representation used in loop quantum gravity. The
construction of these representations is algebraic, based on the
Gelfand-Naimark-Segal construction. Is it possible to understand these
representations from a Geometric Quantization point of view? We address this
question for the case of a two dimensional phase space.
| [
{
"created": "Wed, 2 Nov 2011 20:02:26 GMT",
"version": "v1"
}
] | 2011-11-04 | [
[
"Campiglia",
"Miguel",
""
]
] | Polymer representations of the Weyl algebra of linear systems provide the simplest analogues of the representation used in loop quantum gravity. The construction of these representations is algebraic, based on the Gelfand-Naimark-Segal construction. Is it possible to understand these representations from a Geometric Quantization point of view? We address this question for the case of a two dimensional phase space. |
1804.07264 | Kazumasa Okabayashi | Kei-ichi Maeda, Kazumasa Okabayashi, Hirotada Okawa | Maximal Efficiency of Collisional Penrose Process with Spinning
Particles | 17 pages, 1 table, 17 figures; published version | Phys. Rev. D 98, 064027 (2018) | 10.1103/PhysRevD.98.064027 | WU-AP/1803/18 | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze collisional Penrose process of spinning test particles in an
extreme Kerr black hole. We consider that two particles plunge into the black
hole from infinity and collide near the black hole. For the collision of two
massive particles, if the spins of particles are $s_1 \approx 0.01379\mu M$ and
$s_2 \approx -0.2709\mu M$, we obtain the maximal efficiency is about
$\eta_{max} = (\text{extracted energy})=(\text{input energy}) \approx 15.01$,
which is more than twice as large as the case of the collision of non-spinning
particles ($\eta_{max} \approx 6.32$). We also evaluate the collision of a
massless particle without spin and a massive particle with spin (Compton
scattering), in which we find the maximal efficiency is $\eta_{max} \approx
26.85$ when $s_2 \approx -0.2709\mu M$, which should be compared with
$\eta_{max} \approx 13.93$ for the nonspinning case.
| [
{
"created": "Thu, 19 Apr 2018 16:35:11 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Sep 2018 21:09:55 GMT",
"version": "v2"
}
] | 2018-09-26 | [
[
"Maeda",
"Kei-ichi",
""
],
[
"Okabayashi",
"Kazumasa",
""
],
[
"Okawa",
"Hirotada",
""
]
] | We analyze collisional Penrose process of spinning test particles in an extreme Kerr black hole. We consider that two particles plunge into the black hole from infinity and collide near the black hole. For the collision of two massive particles, if the spins of particles are $s_1 \approx 0.01379\mu M$ and $s_2 \approx -0.2709\mu M$, we obtain the maximal efficiency is about $\eta_{max} = (\text{extracted energy})=(\text{input energy}) \approx 15.01$, which is more than twice as large as the case of the collision of non-spinning particles ($\eta_{max} \approx 6.32$). We also evaluate the collision of a massless particle without spin and a massive particle with spin (Compton scattering), in which we find the maximal efficiency is $\eta_{max} \approx 26.85$ when $s_2 \approx -0.2709\mu M$, which should be compared with $\eta_{max} \approx 13.93$ for the nonspinning case. |
1808.00632 | Shaoqi Hou | Yungui Gong, Shaoqi Hou, Eleftherios Papantonopoulos, Dimitrios
Tzortzis | Gravitational waves and the polarizations in Ho\v{r}ava gravity after
GW170817 | 24 pages, 4 figures | Phys. Rev. D 98, 104017 (2018) | 10.1103/PhysRevD.98.104017 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational waves of Ho\v{r}ava gravity, their polarization states and
their possible observational signatures are discussed. Using the
gauge-invariant variable formalism, we found the three polarization modes in
Ho\v{r}ava gravity excited by the three physical degrees of freedom contained
in this theory. In particular, the scalar degree of freedom excites a mix of
the transverse breathing and the longitudinal polarizations. The constraints
from the previous experimental observations are taken into account, especially
including the speed bound from the observations of GW170817 and GRB 170817A. It
was found that Ho\v{r}ava theory is highly constrained. Within the
experimentally allowed parametric space, we studied whether the pulsar timing
arrays and the Gaia mission can be used to distinguish the different
polarizations. After calculating the cross-correlation functions between the
redshifts of photons and the astrometric positions of stars, one concludes that
it is possible to tell whether there exits the scalar polarization using pulsar
timing arrays and the Gaia mission.
| [
{
"created": "Thu, 2 Aug 2018 02:01:11 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Aug 2018 00:56:05 GMT",
"version": "v2"
},
{
"created": "Thu, 15 Nov 2018 00:56:13 GMT",
"version": "v3"
}
] | 2018-11-16 | [
[
"Gong",
"Yungui",
""
],
[
"Hou",
"Shaoqi",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
],
[
"Tzortzis",
"Dimitrios",
""
]
] | The gravitational waves of Ho\v{r}ava gravity, their polarization states and their possible observational signatures are discussed. Using the gauge-invariant variable formalism, we found the three polarization modes in Ho\v{r}ava gravity excited by the three physical degrees of freedom contained in this theory. In particular, the scalar degree of freedom excites a mix of the transverse breathing and the longitudinal polarizations. The constraints from the previous experimental observations are taken into account, especially including the speed bound from the observations of GW170817 and GRB 170817A. It was found that Ho\v{r}ava theory is highly constrained. Within the experimentally allowed parametric space, we studied whether the pulsar timing arrays and the Gaia mission can be used to distinguish the different polarizations. After calculating the cross-correlation functions between the redshifts of photons and the astrometric positions of stars, one concludes that it is possible to tell whether there exits the scalar polarization using pulsar timing arrays and the Gaia mission. |
1902.01865 | Kyriakos Destounis | Hang Liu, Ziyu Tang, Kyriakos Destounis, Bin Wang, Eleftherios
Papantonopoulos, Hongbao Zhang | Strong Cosmic Censorship in higher-dimensional Reissner-Nordstr\"{o}m-de
Sitter spacetime | 15 pages, 1 figure, matches published version | J. High Energ. Phys. (2019) 2019: 187 | 10.1007/JHEP03(2019)187 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It was recently shown that Strong Cosmic Censorship might be violated for
near-extremally-charged black holes in 4-dimensional de Sitter space under
scalar perturbations. Here, we extend the study of neutral massless scalar
perturbations in higher dimensions and discuss the dimensional influence on the
validity of Strong Cosmic Censorship hypothesis. By giving an elaborate
description of neutral massless scalar perturbations of
Reissner-Nordstr\"{o}m-de Sitter black holes in $d=4,5$ and $6$ dimensions we
conclude that Strong Cosmic Censorship is violated near extremality.
| [
{
"created": "Tue, 5 Feb 2019 19:00:02 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Apr 2019 13:16:47 GMT",
"version": "v2"
}
] | 2019-04-02 | [
[
"Liu",
"Hang",
""
],
[
"Tang",
"Ziyu",
""
],
[
"Destounis",
"Kyriakos",
""
],
[
"Wang",
"Bin",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
],
[
"Zhang",
"Hongbao",
""
]
] | It was recently shown that Strong Cosmic Censorship might be violated for near-extremally-charged black holes in 4-dimensional de Sitter space under scalar perturbations. Here, we extend the study of neutral massless scalar perturbations in higher dimensions and discuss the dimensional influence on the validity of Strong Cosmic Censorship hypothesis. By giving an elaborate description of neutral massless scalar perturbations of Reissner-Nordstr\"{o}m-de Sitter black holes in $d=4,5$ and $6$ dimensions we conclude that Strong Cosmic Censorship is violated near extremality. |
1109.0676 | Sumanta Chakraborty | Sumanta Chakraborty and Subenoy Chakraborty | Trajectory around a spherically symmetric non-rotating black hole | 13 pages, 6 figures | Can.j. phys. 89: 689-695(2011) | 10.1139/p11-032 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Trajectory of a test particle or a photon around a general spherical black
hole is studied and bending of light trajectory is investigated.
Pseudo-Newtonian gravitational potential describing the gravitational field of
the black hole is determined and is compared with the related effective
potential for test particle motion. As an example, results are presented for
Reissner-Nordstr\"{o}m black hole.
| [
{
"created": "Sun, 4 Sep 2011 06:17:17 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Chakraborty",
"Sumanta",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | Trajectory of a test particle or a photon around a general spherical black hole is studied and bending of light trajectory is investigated. Pseudo-Newtonian gravitational potential describing the gravitational field of the black hole is determined and is compared with the related effective potential for test particle motion. As an example, results are presented for Reissner-Nordstr\"{o}m black hole. |
0907.0671 | Deirdre Shoemaker | James Healy, Janna Levin and Deirdre Shoemaker | Zoom-Whirl Orbits in Black Hole Binaries | Replaced with published version | Phys.Rev.Lett.103:131101,2009 | 10.1103/PhysRevLett.103.131101 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Zoom-whirl behavior has the reputation of being a rare phenomenon. The
concern has been that gravitational radiation would drain angular momentum so
rapidly that generic orbits would circularize before zoom-whirl behavior could
play out, and only rare highly tuned orbits would retain their imprint. Using
full numerical relativity, we catch zoom-whirl behavior despite dissipation.
The larger the mass ratio, the longer the pair can spend in orbit before
merging and therefore the more zooms and whirls seen. Larger spins also enhance
zoom-whirliness. An important implication is that these eccentric orbits can
merge during a whirl phase, before enough angular momentum has been lost to
truly circularize the orbit. Waveforms will be modulated by the harmonics of
zoom-whirls, showing quiet phases during zooms and louder glitches during
whirls.
| [
{
"created": "Fri, 3 Jul 2009 19:08:53 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Sep 2009 18:37:37 GMT",
"version": "v2"
}
] | 2009-10-29 | [
[
"Healy",
"James",
""
],
[
"Levin",
"Janna",
""
],
[
"Shoemaker",
"Deirdre",
""
]
] | Zoom-whirl behavior has the reputation of being a rare phenomenon. The concern has been that gravitational radiation would drain angular momentum so rapidly that generic orbits would circularize before zoom-whirl behavior could play out, and only rare highly tuned orbits would retain their imprint. Using full numerical relativity, we catch zoom-whirl behavior despite dissipation. The larger the mass ratio, the longer the pair can spend in orbit before merging and therefore the more zooms and whirls seen. Larger spins also enhance zoom-whirliness. An important implication is that these eccentric orbits can merge during a whirl phase, before enough angular momentum has been lost to truly circularize the orbit. Waveforms will be modulated by the harmonics of zoom-whirls, showing quiet phases during zooms and louder glitches during whirls. |
2307.04237 | Partha Pratim Nath | Partha Pratim Nath, Debojit Sarma | Study of exponential wormhole metric in $f(R)$ gravity | V2 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we have studied an "exponential form" of spacetime metric:
\begin{equation*} ds^2 = -e^{-\frac{2m}{r}}dt^2 +e^{\frac{2m}{r}}dr^2 +
e^{\frac{2m}{r}}[r^2 d\theta^2 + r^2 \sin^2\theta d\phi^2] \end{equation*} in
some of the viable $f(R)$ gravity models, viz. exponential gravity model,
Starobinsky gravity model, Tsujikawa model and Gogoi-Goswami f(R) gravity
model. Here we have calculated the parameters including energy density,
tangential and radial pressure for these corresponding models of $f(R)$
gravity. Subsequently we have investigated the energy conditions viz. null
energy condition(NEC), weak energy condition(WEC) and strong energy
condition(SEC) for the considered models. We have also explained the suitable
conditions of energy for these models by related plots.
| [
{
"created": "Sun, 9 Jul 2023 17:53:37 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Jul 2023 15:48:40 GMT",
"version": "v2"
}
] | 2023-07-18 | [
[
"Nath",
"Partha Pratim",
""
],
[
"Sarma",
"Debojit",
""
]
] | In this work, we have studied an "exponential form" of spacetime metric: \begin{equation*} ds^2 = -e^{-\frac{2m}{r}}dt^2 +e^{\frac{2m}{r}}dr^2 + e^{\frac{2m}{r}}[r^2 d\theta^2 + r^2 \sin^2\theta d\phi^2] \end{equation*} in some of the viable $f(R)$ gravity models, viz. exponential gravity model, Starobinsky gravity model, Tsujikawa model and Gogoi-Goswami f(R) gravity model. Here we have calculated the parameters including energy density, tangential and radial pressure for these corresponding models of $f(R)$ gravity. Subsequently we have investigated the energy conditions viz. null energy condition(NEC), weak energy condition(WEC) and strong energy condition(SEC) for the considered models. We have also explained the suitable conditions of energy for these models by related plots. |
0710.4425 | Carles Bona | C. Bona and Dana Alic | Gauge and constraint degrees of freedom: from analytical to numerical
approximations in General Relativity | Talk given at the Spanish Relativity Meeting, Tenerife, September
2007 | null | 10.1051/eas:0830006 | null | gr-qc | null | The harmonic formulation of Einstein's field equations is considered, where
the gauge conditions are introduced as dynamical constraints. The difference
between the fully constrained approach (used in analytical approximations) and
the free evolution one (used in most numerical approximations) is pointed out.
As a generalization, quasi-stationary gauge conditions are also discussed,
including numerical experiments with the gauge-waves testbed. The complementary
3+1 approach is also considered, where constraints are related instead with
energy and momentum first integrals and the gauge must be provided separately.
The relationship between the two formalisms is discussed in a more general
framework (Z4 formalism). Different strategies in black hole simulations follow
when introducing singularity avoidance as a requirement. More flexible
quasi-stationary gauge conditions are proposed in this context, which can be
seen as generalizations of the current 'freezing shift' prescriptions.
| [
{
"created": "Wed, 24 Oct 2007 10:22:23 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Bona",
"C.",
""
],
[
"Alic",
"Dana",
""
]
] | The harmonic formulation of Einstein's field equations is considered, where the gauge conditions are introduced as dynamical constraints. The difference between the fully constrained approach (used in analytical approximations) and the free evolution one (used in most numerical approximations) is pointed out. As a generalization, quasi-stationary gauge conditions are also discussed, including numerical experiments with the gauge-waves testbed. The complementary 3+1 approach is also considered, where constraints are related instead with energy and momentum first integrals and the gauge must be provided separately. The relationship between the two formalisms is discussed in a more general framework (Z4 formalism). Different strategies in black hole simulations follow when introducing singularity avoidance as a requirement. More flexible quasi-stationary gauge conditions are proposed in this context, which can be seen as generalizations of the current 'freezing shift' prescriptions. |
2212.06794 | Sarbari Guha Dr. | Sucheta Datta, Sarbari Guha and Deeshani Mitra | Memory Effect of Plane Gravitational Wave Pulses | The paper is being rewritten to give a completely new look and will
be uploaded as a fresh manuscript | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | A gravitational wave pulse, while passing through spacetime, brings about a
change in the relative separation between free particles. This `memory effect'
serves as one of the signatures of gravitational waves. In this paper, we
consider some viable pulse profiles which are not yet analyzed by others (e.g.,
$u^{-4}$, $u^{-2}$, $ \frac{c}{(u^2 + au +b)^2} $), and examine the memory
effect produced by these wave pulses in pp-wave spacetime. We choose to work in
the Brinkmann coordinates to solve the geodesic equations. From the plots of
the corresponding analytical solutions, we observe a non-zero separation
between a pair of geodesics in each case, after the pulse dies out. The
displacement memory effect either increases or decreases monotonically, whereas
the velocity memory effect reaches saturation after an initial rise or drop.
| [
{
"created": "Tue, 13 Dec 2022 18:20:26 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jul 2023 07:08:06 GMT",
"version": "v2"
}
] | 2023-07-13 | [
[
"Datta",
"Sucheta",
""
],
[
"Guha",
"Sarbari",
""
],
[
"Mitra",
"Deeshani",
""
]
] | A gravitational wave pulse, while passing through spacetime, brings about a change in the relative separation between free particles. This `memory effect' serves as one of the signatures of gravitational waves. In this paper, we consider some viable pulse profiles which are not yet analyzed by others (e.g., $u^{-4}$, $u^{-2}$, $ \frac{c}{(u^2 + au +b)^2} $), and examine the memory effect produced by these wave pulses in pp-wave spacetime. We choose to work in the Brinkmann coordinates to solve the geodesic equations. From the plots of the corresponding analytical solutions, we observe a non-zero separation between a pair of geodesics in each case, after the pulse dies out. The displacement memory effect either increases or decreases monotonically, whereas the velocity memory effect reaches saturation after an initial rise or drop. |
gr-qc/0504050 | Frederique Marion | L.Blackburn, F.Beauville, M.-A.Bizouard, L.Bosi, P.Brady, L.Brocco,
D.Brown, D.Buskulic, S.Chatterji, N.Christensen, A.-C.Clapson, S.Fairhurst,
D.Grosjean, G.Guidi, P.Hello, E.Katsavounidis, M.Knight, A.Lazzarini,
F.Marion, B.Mours, F.Ricci, A.Vicere', M.Zanolin (The joint LIGO/Virgo
working group) | A First Comparison Between LIGO and Virgo Inspiral Search Pipelines | GWDAW-9 proceedings | Class.Quant.Grav. 22 (2005) S1149-S1158 | null | null | gr-qc | null | This article reports on a project that is the first step the LIGO Scientific
Collaboration and the Virgo Collaboration have taken to prepare for the mutual
search for inspiral signals. The project involved comparing the analysis
pipelines of the two collaborations on data sets prepared by both sides,
containing simulated noise and injected events. The ability of the pipelines to
detect the injected events was checked, and a first comparison of how the
parameters of the events were recovered has been completed.
| [
{
"created": "Tue, 12 Apr 2005 14:02:32 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Blackburn",
"L.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Beauville",
"F.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Bizouard",
"M. -A.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Bosi",
"L.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Brady",
"P.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Brocco",
"L.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Brown",
"D.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Buskulic",
"D.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Chatterji",
"S.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Christensen",
"N.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Clapson",
"A. -C.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Fairhurst",
"S.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Grosjean",
"D.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Guidi",
"G.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Hello",
"P.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Katsavounidis",
"E.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Knight",
"M.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Lazzarini",
"A.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Marion",
"F.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Mours",
"B.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Ricci",
"F.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Vicere'",
"A.",
"",
"The joint LIGO/Virgo\n working group"
],
[
"Zanolin",
"M.",
"",
"The joint LIGO/Virgo\n working group"
]
] | This article reports on a project that is the first step the LIGO Scientific Collaboration and the Virgo Collaboration have taken to prepare for the mutual search for inspiral signals. The project involved comparing the analysis pipelines of the two collaborations on data sets prepared by both sides, containing simulated noise and injected events. The ability of the pipelines to detect the injected events was checked, and a first comparison of how the parameters of the events were recovered has been completed. |
0712.1089 | Ibrar Hussain | Ibrar Hussain, Fazal M. Mahomed and Asghar Qadir | Second-Order Approximate Symmetries of the Geodesic Equations for the
Reissner-Nordstr\"om Metric and Re-Scaling of Energy of a Test Particle | This is a contribution to the Proc. of the Seventh International
Conference ''Symmetry in Nonlinear Mathematical Physics'' (June 24-30, 2007,
Kyiv, Ukraine), published in SIGMA (Symmetry, Integrability and Geometry:
Methods and Applications) at http://www.emis.de/journals/SIGMA/ | SIGMA 3:115,2007 | 10.3842/SIGMA.2007.115 | null | gr-qc nlin.SI | null | Following the use of approximate symmetries for the Schwarzschild spacetime
by A.H. Kara, F.M. Mahomed and A. Qadir (Nonlinear Dynam., to appear), we have
investigated the exact and approximate symmetries of the system of geodesic
equations for the Reissner-Nordstr\"om spacetime (RN). For this purpose we are
forced to use second order approximate symmetries. It is shown that in the
second-order approximation, energy must be rescaled for the RN metric. The
implications of this rescaling are discussed.
| [
{
"created": "Fri, 7 Dec 2007 08:16:34 GMT",
"version": "v1"
}
] | 2008-12-19 | [
[
"Hussain",
"Ibrar",
""
],
[
"Mahomed",
"Fazal M.",
""
],
[
"Qadir",
"Asghar",
""
]
] | Following the use of approximate symmetries for the Schwarzschild spacetime by A.H. Kara, F.M. Mahomed and A. Qadir (Nonlinear Dynam., to appear), we have investigated the exact and approximate symmetries of the system of geodesic equations for the Reissner-Nordstr\"om spacetime (RN). For this purpose we are forced to use second order approximate symmetries. It is shown that in the second-order approximation, energy must be rescaled for the RN metric. The implications of this rescaling are discussed. |
0812.1348 | Salvatore Capozziello | S. Bellucci, S. Capozziello, M. De Laurentis, V. Faraoni | Position and frequency shifts induced by massive modes of the
gravitational wave background in alternative gravity | 9 pages, 1 figure | Phys.Rev.D79:104004,2009 | 10.1103/PhysRevD.79.104004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Alternative theories of gravity predict the presence of massive scalar,
vector, and tensor gravitational wave modes in addition to the standard
massless spin~2 graviton of general relativity. The deflection and frequency
shift effects on light from distant sources propagating through a stochastic
background of gravitational waves, containing such modes, differ from their
counterparts in general relativity. Such effects are considered as a possible
signature for alternative gravity in attempts to detect deviations from
Einstein's gravity by astrophysical means.
| [
{
"created": "Sun, 7 Dec 2008 13:53:18 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Apr 2009 09:50:37 GMT",
"version": "v2"
}
] | 2009-10-29 | [
[
"Bellucci",
"S.",
""
],
[
"Capozziello",
"S.",
""
],
[
"De Laurentis",
"M.",
""
],
[
"Faraoni",
"V.",
""
]
] | Alternative theories of gravity predict the presence of massive scalar, vector, and tensor gravitational wave modes in addition to the standard massless spin~2 graviton of general relativity. The deflection and frequency shift effects on light from distant sources propagating through a stochastic background of gravitational waves, containing such modes, differ from their counterparts in general relativity. Such effects are considered as a possible signature for alternative gravity in attempts to detect deviations from Einstein's gravity by astrophysical means. |
2312.00607 | Yurii Ignat'ev | Yu.G. Ignat'ev | Formation of supermassive nuclei of Black holes in the early Universe by
the mechanism of scalar-gravitational instability. III. Large scale picture | 9 pages, 4 figures, 21 references | Gravit. Cosmol. 2024, 30, 141-148 | 10.1134/S0202289324700038 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The dependence of the parameters of the evolution of scalarly charged Black
Holes (BHs) in the early Universe on the parameters of field-theoretic theories
of interaction, the influence of the geometric factor of the structure of the
relative position of BHs on the limitation of their maximum mass are studied,
the problem of the metric of a scalarly charged BH in a medium of expanding
scalarly charged matter is discussed, the expression is obtained for the
macroscopic cosmological constant at late stages of expansion, generated by
quadratic fluctuations of the metric, connecting the value of the cosmological
constant with the BH masses and their concentration. Keywords: scalarly charged
plasma, cosmological model, Higgs scalar field, gravitational stability,
spherical perturbations, black hole formation, effective cosmological constant.
| [
{
"created": "Fri, 1 Dec 2023 14:14:10 GMT",
"version": "v1"
}
] | 2024-04-11 | [
[
"Ignat'ev",
"Yu. G.",
""
]
] | The dependence of the parameters of the evolution of scalarly charged Black Holes (BHs) in the early Universe on the parameters of field-theoretic theories of interaction, the influence of the geometric factor of the structure of the relative position of BHs on the limitation of their maximum mass are studied, the problem of the metric of a scalarly charged BH in a medium of expanding scalarly charged matter is discussed, the expression is obtained for the macroscopic cosmological constant at late stages of expansion, generated by quadratic fluctuations of the metric, connecting the value of the cosmological constant with the BH masses and their concentration. Keywords: scalarly charged plasma, cosmological model, Higgs scalar field, gravitational stability, spherical perturbations, black hole formation, effective cosmological constant. |
gr-qc/0306057 | Archana Pai | A. Pai, K. Rajesh Nayak, S. V. Dhurandhar and J-Y. Vinet | Time Delay Interferometry and LISA Optimal Sensitivity | LaTeX, 6 pages, 4 figures, To appear in Proceedings of XXXVIIIth
Recontres de Moriond: Gravitational Waves and Experimental Gravity | null | null | null | gr-qc | null | The sensitivity of LISA depends on the suppression of several noise sources;
dominant one is laser frequency noise. It has been shown that the six Doppler
data streams obtained from three space-crafts can be appropriately time delayed
and optimally combined to cancel this laser frequency noise. We show that the
optimal data combinations when operated in a network mode improves the
sensitivity over Michelson ranging from 40 % to 100 %. In this article, we
summarize these results. We further show that the residual laser noise in the
optimal data combination due to typical arm-length inaccuracy of 200 m is much
below the level of optical path and the proof mass noises.
| [
{
"created": "Fri, 13 Jun 2003 10:04:37 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Pai",
"A.",
""
],
[
"Nayak",
"K. Rajesh",
""
],
[
"Dhurandhar",
"S. V.",
""
],
[
"Vinet",
"J-Y.",
""
]
] | The sensitivity of LISA depends on the suppression of several noise sources; dominant one is laser frequency noise. It has been shown that the six Doppler data streams obtained from three space-crafts can be appropriately time delayed and optimally combined to cancel this laser frequency noise. We show that the optimal data combinations when operated in a network mode improves the sensitivity over Michelson ranging from 40 % to 100 %. In this article, we summarize these results. We further show that the residual laser noise in the optimal data combination due to typical arm-length inaccuracy of 200 m is much below the level of optical path and the proof mass noises. |
1005.5589 | Subenoy Chakraborty | Nairwita Mazumder, Subenoy Chakraborty | Generalized Second Law of Thermodynamics on the Event Horizon for
Interacting Dark Energy | 8 pages, 2 figures | null | 10.1007/s10773-011-0884-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Here we are trying to find the conditions for the validity of the generalized
second law of thermodynamics (GSLT) assuming the first law of thermodynamics on
the event horizon in both cases when the FRW universe is filled with
interacting two fluid system- one in the form of cold dark matter and the other
is either holographic dark energy or new age graphic dark energy. Using the
recent observational data we have found that GSLT holds both in quintessence
era as well as in phantom era for new age graphic model while for holographic
dark energy GSLT is valid only in phantom era.
| [
{
"created": "Mon, 31 May 2010 05:49:41 GMT",
"version": "v1"
}
] | 2015-05-19 | [
[
"Mazumder",
"Nairwita",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | Here we are trying to find the conditions for the validity of the generalized second law of thermodynamics (GSLT) assuming the first law of thermodynamics on the event horizon in both cases when the FRW universe is filled with interacting two fluid system- one in the form of cold dark matter and the other is either holographic dark energy or new age graphic dark energy. Using the recent observational data we have found that GSLT holds both in quintessence era as well as in phantom era for new age graphic model while for holographic dark energy GSLT is valid only in phantom era. |
gr-qc/0405126 | Gaurav Khanna | Daniel Cartin, Gaurav Khanna, Martin Bojowald | Generating function techniques for loop quantum cosmology | 22 pages, 5 figures; version to appear in CQG | Class.Quant.Grav.21:4495,2004 | 10.1088/0264-9381/21/18/014 | null | gr-qc hep-th | null | Loop quantum cosmology leads to a difference equation for the wave function
of a universe, which in general has solutions changing rapidly even when the
volume changes only slightly. For a semiclassical regime such small-scale
oscillations must be suppressed, by choosing the parameters of the solution
appropriately. For anisotropic models this is not possible to do numerically by
trial and error; instead, it is shown here for the Bianchi I LRS model how this
can be done analytically, using generating function techniques. Those
techniques can also be applied to more complicated models, and the results
gained allow conclusions about initial value problems for other systems.
| [
{
"created": "Wed, 26 May 2004 02:44:08 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Aug 2004 13:47:05 GMT",
"version": "v2"
}
] | 2009-03-24 | [
[
"Cartin",
"Daniel",
""
],
[
"Khanna",
"Gaurav",
""
],
[
"Bojowald",
"Martin",
""
]
] | Loop quantum cosmology leads to a difference equation for the wave function of a universe, which in general has solutions changing rapidly even when the volume changes only slightly. For a semiclassical regime such small-scale oscillations must be suppressed, by choosing the parameters of the solution appropriately. For anisotropic models this is not possible to do numerically by trial and error; instead, it is shown here for the Bianchi I LRS model how this can be done analytically, using generating function techniques. Those techniques can also be applied to more complicated models, and the results gained allow conclusions about initial value problems for other systems. |
0905.4832 | Olivier Rabaste | Olivier Rabaste, Eric Chassande-Mottin and Archana Pai | Sparse sky grid for the coherent detection of gravitational wave bursts | 20 pages,8 figures, submitted to CQG | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational wave detectors currently in operation perform the analysis
of their scientific data jointly. Concerning the search for bursting sources,
coherent data analysis methods have been shown to be more efficient. In the
coherent approach, the data collected by the detectors are time-shifted and
linearly combined so that the signatures received by each detector add up
constructively (thus improving the resulting signal-to-noise ratio). This
operation has to be performed over a sky grid (which determines the sky
locations to be searched). A limitation of those pipelines is their large
computing cost. One of the available degrees of freedom to reduce the cost is
the choice of the sky grid. Ideally, the sky sampling scheme should adapt the
angular resolution associated with the considered gravitational wave detector
network. As the geometry of detector network is not regular (the detectors are
not equally spaced and oriented), the angular resolution varies largely
depending on the sky location. We propose here a procedure which designs sky
grids that permit a complete sky coverage with a minimum number of vertices and
thus adapt the local resolution.
| [
{
"created": "Fri, 29 May 2009 11:17:40 GMT",
"version": "v1"
}
] | 2009-06-01 | [
[
"Rabaste",
"Olivier",
""
],
[
"Chassande-Mottin",
"Eric",
""
],
[
"Pai",
"Archana",
""
]
] | The gravitational wave detectors currently in operation perform the analysis of their scientific data jointly. Concerning the search for bursting sources, coherent data analysis methods have been shown to be more efficient. In the coherent approach, the data collected by the detectors are time-shifted and linearly combined so that the signatures received by each detector add up constructively (thus improving the resulting signal-to-noise ratio). This operation has to be performed over a sky grid (which determines the sky locations to be searched). A limitation of those pipelines is their large computing cost. One of the available degrees of freedom to reduce the cost is the choice of the sky grid. Ideally, the sky sampling scheme should adapt the angular resolution associated with the considered gravitational wave detector network. As the geometry of detector network is not regular (the detectors are not equally spaced and oriented), the angular resolution varies largely depending on the sky location. We propose here a procedure which designs sky grids that permit a complete sky coverage with a minimum number of vertices and thus adapt the local resolution. |
1411.2030 | Lucien Heurtier | Harold Erbin and Lucien Heurtier | Five-dimensional Janis-Newman algorithm | 27 pages | Class.Quant.Grav. 32 (2015) 16, 165004 | 10.1088/0264-9381/32/16/165004 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Janis-Newman algorithm has been shown to be successful in finding new
sta- tionary solutions of four-dimensional gravity. Attempts for a
generalization to higher dimensions have already been found for the restricted
cases with only one angular mo- mentum. In this paper we propose an extension
of this algorithm to five dimensions with two angular momenta - using the
prescription of G. Giampieri - through two specific examples, that are the
Myers-Perry and BMPV black holes. We also discuss possible enlargements of our
prescriptions to other dimensions and maximal number of angular momenta, and
show how dimensions higher than six appear to be much more challenging to treat
within this framework. Nonetheless this general algorithm provides a
unification of the formulation in d = 3, 4, 5 of the Janis-Newman algorithm,
from which which expose several examples including the BTZ black hole.
| [
{
"created": "Fri, 7 Nov 2014 21:00:04 GMT",
"version": "v1"
},
{
"created": "Tue, 27 Oct 2015 18:14:52 GMT",
"version": "v2"
}
] | 2015-10-28 | [
[
"Erbin",
"Harold",
""
],
[
"Heurtier",
"Lucien",
""
]
] | The Janis-Newman algorithm has been shown to be successful in finding new sta- tionary solutions of four-dimensional gravity. Attempts for a generalization to higher dimensions have already been found for the restricted cases with only one angular mo- mentum. In this paper we propose an extension of this algorithm to five dimensions with two angular momenta - using the prescription of G. Giampieri - through two specific examples, that are the Myers-Perry and BMPV black holes. We also discuss possible enlargements of our prescriptions to other dimensions and maximal number of angular momenta, and show how dimensions higher than six appear to be much more challenging to treat within this framework. Nonetheless this general algorithm provides a unification of the formulation in d = 3, 4, 5 of the Janis-Newman algorithm, from which which expose several examples including the BTZ black hole. |
1507.03420 | Nematollah Riazi | Nematollah Riazi, S. Sedigheh Hashemi, S. Naseh Sajadi and S. Shahrokh
Assyaee | Exact Anisotropic Solutions of the Generalized TOV Equation | 14 pages, 9 figures | null | 10.1139/cjp-2016-0365 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore gravitating relativistic spheres composed of an anisotropic,
barotropic uid. We assume a bi-polytropic equation of state which has a linear
and a power-law terms. The generalized Tolman-Oppenheimer-Volkoff (TOV)
equation which describes the hydrostatic equilibrium is obtained. The full
system of equations are solved for solutions which are regular at the origin
and asymptotically flat. Conditions for the appearance of horizon and a basic
treatment of stability are also discussed.
| [
{
"created": "Mon, 13 Jul 2015 12:25:23 GMT",
"version": "v1"
}
] | 2016-11-03 | [
[
"Riazi",
"Nematollah",
""
],
[
"Hashemi",
"S. Sedigheh",
""
],
[
"Sajadi",
"S. Naseh",
""
],
[
"Assyaee",
"S. Shahrokh",
""
]
] | We explore gravitating relativistic spheres composed of an anisotropic, barotropic uid. We assume a bi-polytropic equation of state which has a linear and a power-law terms. The generalized Tolman-Oppenheimer-Volkoff (TOV) equation which describes the hydrostatic equilibrium is obtained. The full system of equations are solved for solutions which are regular at the origin and asymptotically flat. Conditions for the appearance of horizon and a basic treatment of stability are also discussed. |
gr-qc/0303073 | Martin Bojowald | Martin Bojowald | Homogeneous Loop Quantum Cosmology | 25 pages, 3 figures | Class.Quant.Grav.20:2595-2615,2003 | 10.1088/0264-9381/20/13/310 | CGPG-03/3-5 | gr-qc hep-th | null | Loop quantum cosmological methods are extended to homogeneous models in
diagonalized form. It is shown that the diagonalization leads to a
simplification of the volume operator such that its spectrum can be determined
explicitly. This allows the calculation of composite operators, most
importantly the Hamiltonian constraint. As an application the dynamics of the
Bianchi I model is studied and it is shown that its loop quantization is free
of singularities.
| [
{
"created": "Wed, 19 Mar 2003 18:44:54 GMT",
"version": "v1"
}
] | 2011-05-05 | [
[
"Bojowald",
"Martin",
""
]
] | Loop quantum cosmological methods are extended to homogeneous models in diagonalized form. It is shown that the diagonalization leads to a simplification of the volume operator such that its spectrum can be determined explicitly. This allows the calculation of composite operators, most importantly the Hamiltonian constraint. As an application the dynamics of the Bianchi I model is studied and it is shown that its loop quantization is free of singularities. |
gr-qc/0005131 | Luis J. Garay | L. J. Garay, J. R. Anglin, J. I. Cirac, and P. Zoller | Sonic black holes in dilute Bose-Einstein condensates | RevTeX, 14 pages, 5 figures | Phys.Rev.A63:023611,2001 | 10.1103/PhysRevA.63.023611 | null | gr-qc cond-mat | null | The sonic analog of a gravitational black hole in dilute-gas Bose-Einstein
condensates is investigated. It is shown that there exist both dynamically
stable and unstable configurations which, in the hydrodynamic limit, exhibit a
behavior completely analogous to that of gravitational black holes. The
dynamical instabilities involve creation of quasiparticle pairs in positive and
negative energy states. We illustrate these features in two qualitatively
different one-dimensional models, namely, a long, thin condensate with an
outcoupler laser beam providing an ``atom sink,'' and a tight ring-shaped
condensate. We have also simulated the creation of a stable sonic black hole by
solving the Gross-Pitaevskii equation numerically for a condensate subject to a
trapping potential which is adiabatically deformed. A sonic black hole could in
this way be created experimentally with state-of-the-art or planned technology.
| [
{
"created": "Wed, 31 May 2000 09:12:40 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Jan 2001 15:15:43 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Garay",
"L. J.",
""
],
[
"Anglin",
"J. R.",
""
],
[
"Cirac",
"J. I.",
""
],
[
"Zoller",
"P.",
""
]
] | The sonic analog of a gravitational black hole in dilute-gas Bose-Einstein condensates is investigated. It is shown that there exist both dynamically stable and unstable configurations which, in the hydrodynamic limit, exhibit a behavior completely analogous to that of gravitational black holes. The dynamical instabilities involve creation of quasiparticle pairs in positive and negative energy states. We illustrate these features in two qualitatively different one-dimensional models, namely, a long, thin condensate with an outcoupler laser beam providing an ``atom sink,'' and a tight ring-shaped condensate. We have also simulated the creation of a stable sonic black hole by solving the Gross-Pitaevskii equation numerically for a condensate subject to a trapping potential which is adiabatically deformed. A sonic black hole could in this way be created experimentally with state-of-the-art or planned technology. |
1502.05042 | Gary Gibbons | Shouxin Chen, Gary W. Gibbons, and Yisong Yang | Explicit Integration of Friedmann's Equation with Nonlinear Equations of
State | 43 pages no figures | null | 10.1088/1475-7516/2015/05/020 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is a continuation of our earlier study on the integrability of the
Friedmann equations in the light of the Chebyshev theorem. Our main focus will
be on a series of important, yet not previously touched, problems when the
equation of state for the perfect-fluid universe is nonlinear. These include
the generalized Chaplygin gas, two-term energy density, trinomial Friedmann,
Born--Infeld, and two-fluid models. We show that some of these may be
integrated using Chebyshev's result while other are out of reach by the theorem
but may be integrated explicitly by other methods. With the explicit
integration, we are able to understand exactly the roles of the physical
parameters in various models play in the cosmological evolution. For example,
in the Chaplygin gas universe, it is seen that, as far as there is a tiny
presence of nonlinear matter, linear matter makes contribution to the dark
matter, which becomes significant near the phantom divide line. The Friedmann
equations also arise in areas of physics not directly related to cosmology. We
provide some examples ranging from geometric optics and central orbits to soap
films and the shape of glaciated valleys to which our results may be applied.
| [
{
"created": "Tue, 17 Feb 2015 18:10:09 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Mar 2015 10:00:32 GMT",
"version": "v2"
}
] | 2015-05-27 | [
[
"Chen",
"Shouxin",
""
],
[
"Gibbons",
"Gary W.",
""
],
[
"Yang",
"Yisong",
""
]
] | This paper is a continuation of our earlier study on the integrability of the Friedmann equations in the light of the Chebyshev theorem. Our main focus will be on a series of important, yet not previously touched, problems when the equation of state for the perfect-fluid universe is nonlinear. These include the generalized Chaplygin gas, two-term energy density, trinomial Friedmann, Born--Infeld, and two-fluid models. We show that some of these may be integrated using Chebyshev's result while other are out of reach by the theorem but may be integrated explicitly by other methods. With the explicit integration, we are able to understand exactly the roles of the physical parameters in various models play in the cosmological evolution. For example, in the Chaplygin gas universe, it is seen that, as far as there is a tiny presence of nonlinear matter, linear matter makes contribution to the dark matter, which becomes significant near the phantom divide line. The Friedmann equations also arise in areas of physics not directly related to cosmology. We provide some examples ranging from geometric optics and central orbits to soap films and the shape of glaciated valleys to which our results may be applied. |
0709.1928 | Jose Navarro | Jose Navarro, Juan B. Sancho | On the naturalness of Einstein's equation | 12 pages, added references, corrected typos | J Geom. Phys. 58, 8 (2008) 1007-1014 | 10.1016/j.geomphys.2008.03.007 | null | gr-qc math.DG | null | We compute all 2-covariant tensors naturally constructed from a
semiriemannian metric which are divergence-free and have weight greater than
-2.
As a consequence, it follows a characterization of the Einstein tensor as the
only, up to a constant factor, 2-covariant tensor naturally constructed from a
semiriemannian metric which is divergence-free and has weight 0 (i.e., is
independent of the unit of scale). Since these two conditions are also
satisfied by the energy-momentum tensor of a relativistic space-time, we
discuss in detail how these theorems lead to the field equation of General
Relativity.
| [
{
"created": "Wed, 12 Sep 2007 16:33:26 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Oct 2007 09:39:41 GMT",
"version": "v2"
}
] | 2009-05-27 | [
[
"Navarro",
"Jose",
""
],
[
"Sancho",
"Juan B.",
""
]
] | We compute all 2-covariant tensors naturally constructed from a semiriemannian metric which are divergence-free and have weight greater than -2. As a consequence, it follows a characterization of the Einstein tensor as the only, up to a constant factor, 2-covariant tensor naturally constructed from a semiriemannian metric which is divergence-free and has weight 0 (i.e., is independent of the unit of scale). Since these two conditions are also satisfied by the energy-momentum tensor of a relativistic space-time, we discuss in detail how these theorems lead to the field equation of General Relativity. |
1906.06161 | Pac\^ome Delva Dr. | P. Delva, N. Puchades, E. Sch\"onemann, F. Dilssner, C. Courde, S.
Bertone, F. Gonzalez, A. Hees, Ch. Le Poncin-Lafitte, F. Meynadier, R.
Prieto-Cerdeira, B. Sohet, J. Ventura-Traveset, P. Wolf | Testing the gravitational redshift with Galileo satellites | 8 pages, proceedings of the "Rencontres de Moriond - Gravitation",
23-30 March 2019, La Thuile, Italy | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the results of the analysis of the GREAT (Galileo gravitational
Redshift test with Eccentric sATellites) experiment from SYRTE (Observatoire de
Paris), funded by the European Space Agency. An elliptic orbit induces a
periodic modulation of the fractional frequency difference between a ground
clock and the satellite clock, while the good stability of Galileo clocks
allows to test this periodic modulation to a high level of accuracy. Galileo
satellites GSAT0201 and GSAT0202, with their large eccentricity and on-board
H-maser clocks, are perfect candidates to perform this test. By analyzing 1008
days of eccentric Galileo satellites data we measure the fractional deviation
of the gravitational redshift from the prediction by general relativity to be
$(+0.19 \pm 2.48)\times10^{-5}$ at 1 sigma, improving the best previous test by
Gravity Probe A by a factor~5.6. Moreover, we apply the exact same analysis to
two almost circular Galileo satellites, in order to show the robustness of the
method. By analyzing 899 days of circular Galileo satellites data we measure
the fractional deviation of the gravitational redshift from the prediction by
general relativity to be $(+0.29 \pm 2.00)\times10^{-2}$ at 1 sigma.
| [
{
"created": "Fri, 14 Jun 2019 12:27:51 GMT",
"version": "v1"
}
] | 2019-06-17 | [
[
"Delva",
"P.",
""
],
[
"Puchades",
"N.",
""
],
[
"Schönemann",
"E.",
""
],
[
"Dilssner",
"F.",
""
],
[
"Courde",
"C.",
""
],
[
"Bertone",
"S.",
""
],
[
"Gonzalez",
"F.",
""
],
[
"Hees",
"A.",
""
],
[
"Poncin-Lafitte",
"Ch. Le",
""
],
[
"Meynadier",
"F.",
""
],
[
"Prieto-Cerdeira",
"R.",
""
],
[
"Sohet",
"B.",
""
],
[
"Ventura-Traveset",
"J.",
""
],
[
"Wolf",
"P.",
""
]
] | We present the results of the analysis of the GREAT (Galileo gravitational Redshift test with Eccentric sATellites) experiment from SYRTE (Observatoire de Paris), funded by the European Space Agency. An elliptic orbit induces a periodic modulation of the fractional frequency difference between a ground clock and the satellite clock, while the good stability of Galileo clocks allows to test this periodic modulation to a high level of accuracy. Galileo satellites GSAT0201 and GSAT0202, with their large eccentricity and on-board H-maser clocks, are perfect candidates to perform this test. By analyzing 1008 days of eccentric Galileo satellites data we measure the fractional deviation of the gravitational redshift from the prediction by general relativity to be $(+0.19 \pm 2.48)\times10^{-5}$ at 1 sigma, improving the best previous test by Gravity Probe A by a factor~5.6. Moreover, we apply the exact same analysis to two almost circular Galileo satellites, in order to show the robustness of the method. By analyzing 899 days of circular Galileo satellites data we measure the fractional deviation of the gravitational redshift from the prediction by general relativity to be $(+0.29 \pm 2.00)\times10^{-2}$ at 1 sigma. |
2408.06896 | Yurii Ignat'ev | Yu. G. Ignat'ev | Evolution of plane perturbations in the cosmological environment of the
Higgs scalar field and an ideal scalar charged fluid | 26 pages, 24 figures, 26 references | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A phenomenological model of an ideal fluid with a scalar charge is
formulated, on the basis of which a model with a neutral fluid and a
vacuum-field model with rules of transition between them are constructed. A
qualitative analysis of the obtained dynamic systems is carried out and
numerical cosmological models based on these systems are constructed. A
mathematical model of plane longitudinal scalar-gravitational perturbations of
the Friedmann ideal charged fluid with Higgs interaction is formulated. It is
shown that in the absence of fluid, i.e., in the vacuum-field model,
gravitational perturbations do not arise. Perturbations of the scalar field are
possible only in those cases when in the unperturbed state the cosmological
system is at singular points. For these cases, exact solutions of the field
equation are found, expressed in Bessel functions of the first and second kind
and describing damped oscillations in the case of a stable unperturbed state
and growing oscillations in the case of an unstable unperturbed state. The WKB
theory of plane scalar-gravitational perturbations is constructed: dispersion
equations are obtained in general form and solved for a neutral fluid. In this
case, expressions are obtained for the local frequency and growth increment of
oscillations, as well as the integral increment. It is shown that only free
wave regimes or growing standing oscillations are possible during the
evolution. Perturbations in the WKB approximation in a neutral fluid are
studied and it is shown that local formulas for the evolution of perturbations
correspond to the model of the 1985 article by M.Yu. The times of the beginning
and end of the instability phase are determined and it is shown that
instability can develop only at the unstable inflationary stage of the
expansion of the Universe.
| [
{
"created": "Tue, 13 Aug 2024 13:44:09 GMT",
"version": "v1"
}
] | 2024-08-14 | [
[
"Ignat'ev",
"Yu. G.",
""
]
] | A phenomenological model of an ideal fluid with a scalar charge is formulated, on the basis of which a model with a neutral fluid and a vacuum-field model with rules of transition between them are constructed. A qualitative analysis of the obtained dynamic systems is carried out and numerical cosmological models based on these systems are constructed. A mathematical model of plane longitudinal scalar-gravitational perturbations of the Friedmann ideal charged fluid with Higgs interaction is formulated. It is shown that in the absence of fluid, i.e., in the vacuum-field model, gravitational perturbations do not arise. Perturbations of the scalar field are possible only in those cases when in the unperturbed state the cosmological system is at singular points. For these cases, exact solutions of the field equation are found, expressed in Bessel functions of the first and second kind and describing damped oscillations in the case of a stable unperturbed state and growing oscillations in the case of an unstable unperturbed state. The WKB theory of plane scalar-gravitational perturbations is constructed: dispersion equations are obtained in general form and solved for a neutral fluid. In this case, expressions are obtained for the local frequency and growth increment of oscillations, as well as the integral increment. It is shown that only free wave regimes or growing standing oscillations are possible during the evolution. Perturbations in the WKB approximation in a neutral fluid are studied and it is shown that local formulas for the evolution of perturbations correspond to the model of the 1985 article by M.Yu. The times of the beginning and end of the instability phase are determined and it is shown that instability can develop only at the unstable inflationary stage of the expansion of the Universe. |
1607.08427 | Donato Bini | Donato Bini, Andrea Geralico, Robert T. Jantzen | Gyroscope precession along bound equatorial plane orbits around a Kerr
black hole | 16 pages; revtex macros; 3 eps figures | Phys. Rev. D 94, 064066 (2016) | 10.1103/PhysRevD.94.064066 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The precession of a test gyroscope along stable bound equatorial plane orbits
around a Kerr black hole is analyzed and the precession angular velocity of the
gyro's parallel transported spin vector and the increment in precession angle
after one orbital period is evaluated. The parallel transported Marck frame
which enters this discussion is shown to have an elegant geometrical
explanation in terms of the electric and magnetic parts of the Killing-Yano
2-form and a Wigner rotation effect.
| [
{
"created": "Thu, 28 Jul 2016 12:33:11 GMT",
"version": "v1"
}
] | 2016-09-28 | [
[
"Bini",
"Donato",
""
],
[
"Geralico",
"Andrea",
""
],
[
"Jantzen",
"Robert T.",
""
]
] | The precession of a test gyroscope along stable bound equatorial plane orbits around a Kerr black hole is analyzed and the precession angular velocity of the gyro's parallel transported spin vector and the increment in precession angle after one orbital period is evaluated. The parallel transported Marck frame which enters this discussion is shown to have an elegant geometrical explanation in terms of the electric and magnetic parts of the Killing-Yano 2-form and a Wigner rotation effect. |
2305.00277 | Vikash Kumar Ojha | V K Ojha, Adithya A Rao, S D Pathak | Interacting tachyonic scalar field II | 19 pages, 5 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The existence of dark energy is essential to explain the cosmic accelerated
expansion. We consider a homogenous interacting tachyonic scalar field as a
possible candidate for the dynamical dark energy. The interaction between the
tachyonic field and matter can be gauged to be linear in the energy density of
matter (or the tachyonic field) and Hubble's parameter. We estimate the rate of
expansion, the age of the universe, the evolution of energy density of matter
and tachyonic field, and the coupling strength of the interaction for a
spatially flat ($k=0$) universe. We observed that the upper limit of coupling
strength is 1, and it is the same whether the interaction term depends on the
energy density of matter or the energy density of tachyonic scalar field.
| [
{
"created": "Sat, 29 Apr 2023 15:26:56 GMT",
"version": "v1"
}
] | 2023-05-02 | [
[
"Ojha",
"V K",
""
],
[
"Rao",
"Adithya A",
""
],
[
"Pathak",
"S D",
""
]
] | The existence of dark energy is essential to explain the cosmic accelerated expansion. We consider a homogenous interacting tachyonic scalar field as a possible candidate for the dynamical dark energy. The interaction between the tachyonic field and matter can be gauged to be linear in the energy density of matter (or the tachyonic field) and Hubble's parameter. We estimate the rate of expansion, the age of the universe, the evolution of energy density of matter and tachyonic field, and the coupling strength of the interaction for a spatially flat ($k=0$) universe. We observed that the upper limit of coupling strength is 1, and it is the same whether the interaction term depends on the energy density of matter or the energy density of tachyonic scalar field. |
2305.00074 | Shao-Jiang Wang | Rong-Gen Cai, Shao-Jiang Wang, Zi-Yan Yuwen | Hydrodynamic sound shell model | v1, 5 pages (3 figures) + 1 appendix (5 figures); v2, to match the
published version in Physical Review D as a Letter | Phys. Rev. D 108 (2023) L021502 | 10.1103/PhysRevD.108.L021502 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For a cosmological first-order phase transition in the early Universe, the
associated stochastic gravitational wave background is usually dominated by
sound waves from plasma fluid motions, which have been analytically modeled as
a random superposition of freely propagating sound shells but with the force by
the scalar field that produces the self-similar profile removed. In this
Letter, we propose a new analytic sound shell model by focusing on the forced
propagating contribution from the initial collision stage of sound shells when
their self-similar profiles are still maintained by the moving bubble walls. We
reproduce the causal $k^3$ scaling in the infrared consistent with numerical
simulations, and also recover the broad dome in the power spectrum first
observed in numerical simulations. The total sound waves should contain both
contributions from forced collisions and free propagation of sound shells at
early and late stages of the phase transition, respectively.
| [
{
"created": "Fri, 28 Apr 2023 19:59:25 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Jul 2023 14:51:53 GMT",
"version": "v2"
}
] | 2023-07-18 | [
[
"Cai",
"Rong-Gen",
""
],
[
"Wang",
"Shao-Jiang",
""
],
[
"Yuwen",
"Zi-Yan",
""
]
] | For a cosmological first-order phase transition in the early Universe, the associated stochastic gravitational wave background is usually dominated by sound waves from plasma fluid motions, which have been analytically modeled as a random superposition of freely propagating sound shells but with the force by the scalar field that produces the self-similar profile removed. In this Letter, we propose a new analytic sound shell model by focusing on the forced propagating contribution from the initial collision stage of sound shells when their self-similar profiles are still maintained by the moving bubble walls. We reproduce the causal $k^3$ scaling in the infrared consistent with numerical simulations, and also recover the broad dome in the power spectrum first observed in numerical simulations. The total sound waves should contain both contributions from forced collisions and free propagation of sound shells at early and late stages of the phase transition, respectively. |
gr-qc/0701020 | Remo Garattini | Remo Garattini, Francisco S. N. Lobo | Self sustained phantom wormholes in semi-classical gravity | Uses RevTeX 4. 10 pages. V2: clarifying comments and references added | Class.Quant.Grav.24:2401-2413,2007 | 10.1088/0264-9381/24/9/016 | null | gr-qc astro-ph hep-th | null | A possible candidate for the late time accelerated expanding Universe is
phantom energy, which possesses rather bizarre properties, such as the
prediction of a Big Rip singularity and the violation of the null energy
condition. The latter is a fundamental ingredient of traversable wormholes, and
it has been shown that phantom energy may indeed sustain these exotic
geometries. Inspired by the evolving dark energy parameter crossing the phantom
divide, we consider in this work a varying equation of state parameter
dependent on the radial coordinate, i.e., $\omega(r)=p(r)/\rho(r)$. We shall
impose that phantom energy is concentrated in the neighborhood of the throat,
to ensure the flaring out condition, and several models are analyzed. We shall
also consider the possibility that these phantom wormholes be sustained by
their own quantum fluctuations. The energy density of the graviton one loop
contribution to a classical energy in a phantom wormhole background and the
finite one loop energy density are considered as a self-consistent source for
these wormhole geometries. The latter semi-classical approach prohibits
solutions with a constant equation of state parameter, which further motivates
the imposition of a radial dependent parameter, $\omega(r)$, and only permits
solutions with a steep positive slope proportional to the radial derivative of
the equation of state parameter, evaluated at the throat. The size of the
wormhole throat as a function of the relevant parameters is also explored.
| [
{
"created": "Tue, 2 Jan 2007 16:57:51 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jun 2007 15:02:25 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Garattini",
"Remo",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] | A possible candidate for the late time accelerated expanding Universe is phantom energy, which possesses rather bizarre properties, such as the prediction of a Big Rip singularity and the violation of the null energy condition. The latter is a fundamental ingredient of traversable wormholes, and it has been shown that phantom energy may indeed sustain these exotic geometries. Inspired by the evolving dark energy parameter crossing the phantom divide, we consider in this work a varying equation of state parameter dependent on the radial coordinate, i.e., $\omega(r)=p(r)/\rho(r)$. We shall impose that phantom energy is concentrated in the neighborhood of the throat, to ensure the flaring out condition, and several models are analyzed. We shall also consider the possibility that these phantom wormholes be sustained by their own quantum fluctuations. The energy density of the graviton one loop contribution to a classical energy in a phantom wormhole background and the finite one loop energy density are considered as a self-consistent source for these wormhole geometries. The latter semi-classical approach prohibits solutions with a constant equation of state parameter, which further motivates the imposition of a radial dependent parameter, $\omega(r)$, and only permits solutions with a steep positive slope proportional to the radial derivative of the equation of state parameter, evaluated at the throat. The size of the wormhole throat as a function of the relevant parameters is also explored. |
gr-qc/0108026 | Bernhard Haisch | Alfonso Rueda, Bernard Haisch and Roh Tung | Gravity and the Quantum Vacuum Inertia Hypothesis. I. Formalized
Groundwork for Extension to Gravity | 12 pages, no figures | null | null | null | gr-qc | null | It has been shown [1,2] that the electromagnetic quantum vacuum makes a
contribution to the inertial mass, $m_i$, in the sense that at least part of
the inertial force of opposition to acceleration, or inertia reaction force,
springs from the electromagnetic quantum vacuum. As experienced in a Rindler
constant acceleration frame the electromagnetic quantum vacuum mainfests an
energy-momentum flux which we call the Rindler flux (RF). The RF, and its
relative, Unruh-Davies radiation, both stem from event-horizon effects in
accelerating reference frames. The force of radiation pressure produced by the
RF proves to be proportional to the acceleration of the reference frame, which
leads to the hypothesis that at least part of the inertia of an object should
be due to the interaction of its quarks and electrons with the RF. We
demonstrate that this quantum vacuum inertia hypothesis is consistent with
general relativity (GR) and that it answers a fundamental question left open
within GR, viz. is there a physical mechanism that generates the reaction force
known as weight when a specific non-geodesic motion is imposed on an object?
The quantum vacuum inertia hypothesis provides such a mechanism, since by
assuming the Einstein principle of local Lorentz-invariance (LLI), we can
immediately show that the same RF arises due to curved spacetime geometry as
for acceleration in flat spactime. Thus the previously derived expression for
the inertial mass contribution from the electromagnetic quantum vacuum field is
exactly equal to the corresponding contribution to the gravitational mass,
$m_g$. Therefore, within the electromagnetic quantum vacuum viewpoint proposed
in [1,2], the Newtonian weak equivalence principle, $m_i=m_g$, ensues in a
straightforward manner.
| [
{
"created": "Thu, 9 Aug 2001 18:25:35 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Rueda",
"Alfonso",
""
],
[
"Haisch",
"Bernard",
""
],
[
"Tung",
"Roh",
""
]
] | It has been shown [1,2] that the electromagnetic quantum vacuum makes a contribution to the inertial mass, $m_i$, in the sense that at least part of the inertial force of opposition to acceleration, or inertia reaction force, springs from the electromagnetic quantum vacuum. As experienced in a Rindler constant acceleration frame the electromagnetic quantum vacuum mainfests an energy-momentum flux which we call the Rindler flux (RF). The RF, and its relative, Unruh-Davies radiation, both stem from event-horizon effects in accelerating reference frames. The force of radiation pressure produced by the RF proves to be proportional to the acceleration of the reference frame, which leads to the hypothesis that at least part of the inertia of an object should be due to the interaction of its quarks and electrons with the RF. We demonstrate that this quantum vacuum inertia hypothesis is consistent with general relativity (GR) and that it answers a fundamental question left open within GR, viz. is there a physical mechanism that generates the reaction force known as weight when a specific non-geodesic motion is imposed on an object? The quantum vacuum inertia hypothesis provides such a mechanism, since by assuming the Einstein principle of local Lorentz-invariance (LLI), we can immediately show that the same RF arises due to curved spacetime geometry as for acceleration in flat spactime. Thus the previously derived expression for the inertial mass contribution from the electromagnetic quantum vacuum field is exactly equal to the corresponding contribution to the gravitational mass, $m_g$. Therefore, within the electromagnetic quantum vacuum viewpoint proposed in [1,2], the Newtonian weak equivalence principle, $m_i=m_g$, ensues in a straightforward manner. |
2303.07262 | Antoine Rignon-Bret | Antoine Rignon-Bret | Second law from the Noether current on null hypersurfaces | Accepted in Phys.Rev.D. Clarifications added, some parts have been
cleaned up | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | I study the balance law equation of surface charges in the presence of
background fields. The construction allows a unified description of Noether's
theorem for both global and local symmetries. From the balance law associated
with some of these symmetries, I will discuss generalizations of Wald's Noether
entropy formula and general entropy balance laws on null hypersurfaces based on
the null energy conditions, interpreted as an entropy creation term. The
entropy is generally the so-called improved Noether charge, a quantity that has
recently been investigated by many authors, associated to null future-pointing
diffeomorphisms. These local and dynamical definitions of entropy on the black
hole horizon differ from the Bekenstein-Hawking entropy through terms
proportional to the first derivative of the area along the null geodesics. Two
different definitions of the dynamical entropy are identified, deduced from
gravity symplectic potentials providing a suitable notion of gravitational flux
which vanish on non-expanding horizons. The first one is proposed as a
definition of the entropy for dynamical black holes by Wald and Zhang, and it
satisfies the physical process first law locally. The second one vanishes on
any cross section of Minkowski's light cone. I study general properties of its
balance law. In particular, I look at first order perturbations around a non
expanding horizon. Furthermore, I show that the dynamical entropy increases on
the event horizon formed by a spherical symmetric collapse between the two
stationary states of vanishing flux, i.e the initial flat light cone and the
final stationary black hole. I compare this process to a phase transition, in
which the symmetry group of the stationary black hole phase is enlarged by the
supertranslations.
| [
{
"created": "Mon, 13 Mar 2023 16:42:26 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Apr 2023 18:11:55 GMT",
"version": "v2"
},
{
"created": "Mon, 24 Apr 2023 09:01:53 GMT",
"version": "v3"
},
{
"created": "Sat, 12 Aug 2023 15:43:18 GMT",
"version": "v4"
},
{
"created": "Mon, 4 Sep 2023 22:02:42 GMT",
"version": "v5"
}
] | 2023-09-06 | [
[
"Rignon-Bret",
"Antoine",
""
]
] | I study the balance law equation of surface charges in the presence of background fields. The construction allows a unified description of Noether's theorem for both global and local symmetries. From the balance law associated with some of these symmetries, I will discuss generalizations of Wald's Noether entropy formula and general entropy balance laws on null hypersurfaces based on the null energy conditions, interpreted as an entropy creation term. The entropy is generally the so-called improved Noether charge, a quantity that has recently been investigated by many authors, associated to null future-pointing diffeomorphisms. These local and dynamical definitions of entropy on the black hole horizon differ from the Bekenstein-Hawking entropy through terms proportional to the first derivative of the area along the null geodesics. Two different definitions of the dynamical entropy are identified, deduced from gravity symplectic potentials providing a suitable notion of gravitational flux which vanish on non-expanding horizons. The first one is proposed as a definition of the entropy for dynamical black holes by Wald and Zhang, and it satisfies the physical process first law locally. The second one vanishes on any cross section of Minkowski's light cone. I study general properties of its balance law. In particular, I look at first order perturbations around a non expanding horizon. Furthermore, I show that the dynamical entropy increases on the event horizon formed by a spherical symmetric collapse between the two stationary states of vanishing flux, i.e the initial flat light cone and the final stationary black hole. I compare this process to a phase transition, in which the symmetry group of the stationary black hole phase is enlarged by the supertranslations. |
1502.02340 | Liancheng Wang | Liancheng Wang, Feng He and Xiangyun Fu | BSW process of the slowly evaporating charged black hole | 9 pages, no figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the BSW process of the slowly evaporating charged
black hole. It can be found that the BSW process will also arise near black
hole horizon when the evaporation of charged black hole is very slow. But now
the background black hole does not have to be an extremal black hole, and it
will be approximately an extremal black hole unless it is nearly a huge
stationary black hole.
| [
{
"created": "Mon, 9 Feb 2015 02:58:50 GMT",
"version": "v1"
}
] | 2015-02-10 | [
[
"Wang",
"Liancheng",
""
],
[
"He",
"Feng",
""
],
[
"Fu",
"Xiangyun",
""
]
] | In this paper, we study the BSW process of the slowly evaporating charged black hole. It can be found that the BSW process will also arise near black hole horizon when the evaporation of charged black hole is very slow. But now the background black hole does not have to be an extremal black hole, and it will be approximately an extremal black hole unless it is nearly a huge stationary black hole. |
1410.8534 | Richard Brito | Emanuele Berti, Richard Brito, Vitor Cardoso | Ultra-high-energy debris from the collisional Penrose process | 5 pages, 7 figures. v2: Unabridged version of the Letter in press in
PRL. This arXiv version contains supplemental material in response to
http://arxiv.org/abs/1501.01984 | Phys. Rev. Lett. 114, 251103 (2015) | 10.1103/PhysRevLett.114.251103 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Soon after the discovery of the Kerr metric, Penrose realized that
superradiance can be exploited to extract energy from black holes. The original
idea (involving the breakup of a single particle) yields only modest energy
gains. A variant of the Penrose process consists of particle collisions in the
ergoregion. The collisional Penrose process has been explored recently in the
context of dark matter searches, with the conclusion that the ratio $\eta$
between the energy of post-collision particles detected at infinity and the
energy of the colliding particles should be modest ($\eta \lesssim 1.5$).
Schnittman has shown that these studies underestimated the maximum efficiency
by about one order of magnitude (i.e., $\eta \lesssim 15$). In this work we
show that particle collisions in the vicinity of rapidly rotating black holes
can produce high-energy ejecta and result in high efficiencies under much more
generic conditions. The astrophysical likelihood of these events deserves
further scrutiny, but our study hints at the tantalizing possibility that the
collisional Penrose process may power gamma rays and ultra-high-energy cosmic
rays.
| [
{
"created": "Thu, 30 Oct 2014 20:00:12 GMT",
"version": "v1"
},
{
"created": "Mon, 18 May 2015 16:39:38 GMT",
"version": "v2"
}
] | 2015-07-01 | [
[
"Berti",
"Emanuele",
""
],
[
"Brito",
"Richard",
""
],
[
"Cardoso",
"Vitor",
""
]
] | Soon after the discovery of the Kerr metric, Penrose realized that superradiance can be exploited to extract energy from black holes. The original idea (involving the breakup of a single particle) yields only modest energy gains. A variant of the Penrose process consists of particle collisions in the ergoregion. The collisional Penrose process has been explored recently in the context of dark matter searches, with the conclusion that the ratio $\eta$ between the energy of post-collision particles detected at infinity and the energy of the colliding particles should be modest ($\eta \lesssim 1.5$). Schnittman has shown that these studies underestimated the maximum efficiency by about one order of magnitude (i.e., $\eta \lesssim 15$). In this work we show that particle collisions in the vicinity of rapidly rotating black holes can produce high-energy ejecta and result in high efficiencies under much more generic conditions. The astrophysical likelihood of these events deserves further scrutiny, but our study hints at the tantalizing possibility that the collisional Penrose process may power gamma rays and ultra-high-energy cosmic rays. |
gr-qc/0606135 | Janusz Karkowski | Janusz Karkowski | Boosted Kerr black hole | 18 pages, 6 figures | Acta Phys.Polon. B37 (2006) 2571-2586 | null | null | gr-qc | null | Initial data for boosted Kerr black hole are constructed in an axially
symmetric case. Momentum and hamiltonian constraints are solved numerically
using finite element method (FEM) algorithms. Both Bowen-York and puncture
boundary conditions are adopted and appropriate results are compared. Past and
future apparent horizons are also found numerically and the Penrose inequality
is tested in detail.
| [
{
"created": "Fri, 30 Jun 2006 16:31:02 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Karkowski",
"Janusz",
""
]
] | Initial data for boosted Kerr black hole are constructed in an axially symmetric case. Momentum and hamiltonian constraints are solved numerically using finite element method (FEM) algorithms. Both Bowen-York and puncture boundary conditions are adopted and appropriate results are compared. Past and future apparent horizons are also found numerically and the Penrose inequality is tested in detail. |
1604.06312 | Devin Hansen | Devin Hansen, David Kubiznak, Robert B. Mann | Criticality and Surface Tension in Rotating Horizon Thermodynamics | 10 pages, 4 figures. Appendix added, final version | null | 10.1088/0264-9381/33/16/165005 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a modified horizon thermodynamics and the associated criticality for
rotating black hole spacetimes. Namely, we show that under a virtual
displacement of the black hole horizon accompanied by an independent variation
of the rotation parameter, the radial Einstein equation takes a form of a
"cohomogeneity two" horizon first law, $dE=TdS+\Omega dJ-\sigma dA$, where $E$
and $J$ are the horizon energy (an analogue of the Misner-Sharp mass) and the
horizon angular momentum, $\Omega$ is the horizon angular velocity, $A$ is the
horizon area, and $\sigma$ is the surface tension induced by the matter fields.
For fixed angular momentum, the above equation simplifies and the more familiar
(cohomogeneity one) horizon first law $dE=TdS-PdV$ is obtained, where $P$ is
the pressure of matter fields and $V$ is the horizon volume. A universal
equation of state is obtained in each case and the corresponding critical
behavior is studied.
| [
{
"created": "Thu, 21 Apr 2016 14:02:49 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Aug 2016 16:19:38 GMT",
"version": "v2"
}
] | 2016-08-31 | [
[
"Hansen",
"Devin",
""
],
[
"Kubiznak",
"David",
""
],
[
"Mann",
"Robert B.",
""
]
] | We study a modified horizon thermodynamics and the associated criticality for rotating black hole spacetimes. Namely, we show that under a virtual displacement of the black hole horizon accompanied by an independent variation of the rotation parameter, the radial Einstein equation takes a form of a "cohomogeneity two" horizon first law, $dE=TdS+\Omega dJ-\sigma dA$, where $E$ and $J$ are the horizon energy (an analogue of the Misner-Sharp mass) and the horizon angular momentum, $\Omega$ is the horizon angular velocity, $A$ is the horizon area, and $\sigma$ is the surface tension induced by the matter fields. For fixed angular momentum, the above equation simplifies and the more familiar (cohomogeneity one) horizon first law $dE=TdS-PdV$ is obtained, where $P$ is the pressure of matter fields and $V$ is the horizon volume. A universal equation of state is obtained in each case and the corresponding critical behavior is studied. |
gr-qc/9805076 | Michael P. Grady | Michael Grady | Universe as a Phase Boundary in a Four-Dimensional Euclidean Space | 7 pages, Latex, no figures. Many arguments substantially expanded,
new introduction | null | null | SUNY-FRE-98-08 | gr-qc astro-ph hep-th quant-ph | null | It is proposed that space is a four-dimensional Euclidean space with
universal time. Originally this space was filled with a uniform substance,
pictured as a liquid, which at some time became supercooled. Our universe began
as a nucleation event initiating a liquid to solid transition. The universe we
inhabit and are directly aware of consists of only the three-dimensional
expanding phase boundary. Random energy transfers to the boundary from thermal
fluctuations in the adjacent bulk phases are interpreted by us as quantum
fluctuations. Fermionic matter is modeled as screw dislocations; gauge bosons
as phonons. Minkowski space emerges dynamically through redefining local time
to be proportional to the spatial coordinate perpendicular to the boundary.
Other features include a geometrical quantum gravitational theory, and an
explanation of quantum measurement.
| [
{
"created": "Wed, 20 May 1998 01:47:31 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Jun 1998 20:06:00 GMT",
"version": "v2"
},
{
"created": "Thu, 19 Nov 1998 16:07:14 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Grady",
"Michael",
""
]
] | It is proposed that space is a four-dimensional Euclidean space with universal time. Originally this space was filled with a uniform substance, pictured as a liquid, which at some time became supercooled. Our universe began as a nucleation event initiating a liquid to solid transition. The universe we inhabit and are directly aware of consists of only the three-dimensional expanding phase boundary. Random energy transfers to the boundary from thermal fluctuations in the adjacent bulk phases are interpreted by us as quantum fluctuations. Fermionic matter is modeled as screw dislocations; gauge bosons as phonons. Minkowski space emerges dynamically through redefining local time to be proportional to the spatial coordinate perpendicular to the boundary. Other features include a geometrical quantum gravitational theory, and an explanation of quantum measurement. |
gr-qc/9710118 | Guido Cognola | Guido Cognola | Thermodynamics of scalar fields in Kerr's geometry | 7 pages, LaTex, (revised version-last section modified) | Phys.Rev. D57 (1998) 6292-6296 | 10.1103/PhysRevD.57.6292 | University of Trento, UTF 403 | gr-qc | null | The one-loop contributions to the entropy for a massive scalar field in a
Kerr black hole are investigated using an approximation of the metric, which,
after a conformal transformation, permits to work in a Rindler-like spacetime.
Of course, as for the Schwarzschild case, the entropy is divergent in the
proximity of the event horizon.
| [
{
"created": "Tue, 28 Oct 1997 09:15:15 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Oct 1997 07:42:29 GMT",
"version": "v2"
},
{
"created": "Thu, 22 Jan 1998 16:38:13 GMT",
"version": "v3"
}
] | 2009-10-30 | [
[
"Cognola",
"Guido",
""
]
] | The one-loop contributions to the entropy for a massive scalar field in a Kerr black hole are investigated using an approximation of the metric, which, after a conformal transformation, permits to work in a Rindler-like spacetime. Of course, as for the Schwarzschild case, the entropy is divergent in the proximity of the event horizon. |
1308.3077 | Luis Nunez A | L. Becerra, H. Hernandez, L. A. Nunez | Quasi-static thermal evolution of compact objects | 28 pages, 8 figures. Some typos and misplaced equations corrected.
Quasi-local equation of state re-interpretation assumed and two new
references included | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study under what conditions the thermal peeling is present for dissipative
local and quasi-local anisotropic spherical matter configurations. The thermal
peeling occurs when different signs in the velocity of fluid elements appears,
giving rise to the splitting of the matter configuration. The evolution is
considered in the quasi-static approximation and the matter contents are
radiant, anisotropic (unequal stresses) spherical local and quasi-local fluids.
The heat flux and the associated temperature profiles are described by causal
thermodynamics consistent with this approximation. It is found some particular,
local and quasi-local equation of state for ultra-dense matter configurations
exhibit thermal peeling when most of the radiated energy is concentrated at the
middle of the distribution. This effect, which appears to be associated with
extreme astrophysical scenarios (highly relativistic and very luminous
gravitational system expelling its outer mass shells), is very sensible to
energy flux profile and to the shape of the luminosity emitted by the compact
object.
| [
{
"created": "Wed, 14 Aug 2013 10:15:11 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Aug 2013 09:49:53 GMT",
"version": "v2"
},
{
"created": "Sun, 22 Jun 2014 21:55:32 GMT",
"version": "v3"
}
] | 2014-06-24 | [
[
"Becerra",
"L.",
""
],
[
"Hernandez",
"H.",
""
],
[
"Nunez",
"L. A.",
""
]
] | We study under what conditions the thermal peeling is present for dissipative local and quasi-local anisotropic spherical matter configurations. The thermal peeling occurs when different signs in the velocity of fluid elements appears, giving rise to the splitting of the matter configuration. The evolution is considered in the quasi-static approximation and the matter contents are radiant, anisotropic (unequal stresses) spherical local and quasi-local fluids. The heat flux and the associated temperature profiles are described by causal thermodynamics consistent with this approximation. It is found some particular, local and quasi-local equation of state for ultra-dense matter configurations exhibit thermal peeling when most of the radiated energy is concentrated at the middle of the distribution. This effect, which appears to be associated with extreme astrophysical scenarios (highly relativistic and very luminous gravitational system expelling its outer mass shells), is very sensible to energy flux profile and to the shape of the luminosity emitted by the compact object. |
1412.4665 | Michael Coughlin | Michael Coughlin, Patrick Meyers, Eric Thrane, Jialun Luo, Nelson
Christensen | The detectability of eccentric compact binary coalescences with advanced
gravitational-wave detectors | null | null | 10.1103/PhysRevD.91.063004 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Compact binary coalescences are a promising source of gravitational waves for
second-generation interferometric gravitational-wave detectors such as advanced
LIGO and advanced Virgo. While most binaries are expected to possess circular
orbits, some may be eccentric, for example, if they are formed through
dynamical capture. Eccentric orbits can create difficulty for matched filtering
searches due to the challenges of creating effective template banks to detect
these signals. In previous work, we showed how seedless clustering can be used
to detect low-mass ($M_\text{total}\leq10M_\odot$) compact binary coalescences
for both spinning and eccentric systems, assuming a circular post-Newtonian
expansion. Here, we describe a parameterization that is designed to maximize
sensitivity to low-eccentricity ($0\leq\epsilon\leq0.6$) systems, derived from
the analytic equations. We show that this parameterization provides a robust
and computationally efficient method for detecting eccentric low-mass compact
binaries. Based on these results, we conclude that advanced detectors will have
a chance of detecting eccentric binaries if optimistic models prove true.
However, a null observation is unlikely to firmly rule out models of eccentric
binary populations.
| [
{
"created": "Mon, 15 Dec 2014 16:38:38 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Dec 2014 14:33:56 GMT",
"version": "v2"
},
{
"created": "Wed, 17 Dec 2014 13:57:43 GMT",
"version": "v3"
},
{
"created": "Thu, 18 Dec 2014 02:45:05 GMT",
"version": "v4"
},
{
"created": "Fri, 19 Dec 2014 03:35:05 GMT",
"version": "v5"
}
] | 2015-06-23 | [
[
"Coughlin",
"Michael",
""
],
[
"Meyers",
"Patrick",
""
],
[
"Thrane",
"Eric",
""
],
[
"Luo",
"Jialun",
""
],
[
"Christensen",
"Nelson",
""
]
] | Compact binary coalescences are a promising source of gravitational waves for second-generation interferometric gravitational-wave detectors such as advanced LIGO and advanced Virgo. While most binaries are expected to possess circular orbits, some may be eccentric, for example, if they are formed through dynamical capture. Eccentric orbits can create difficulty for matched filtering searches due to the challenges of creating effective template banks to detect these signals. In previous work, we showed how seedless clustering can be used to detect low-mass ($M_\text{total}\leq10M_\odot$) compact binary coalescences for both spinning and eccentric systems, assuming a circular post-Newtonian expansion. Here, we describe a parameterization that is designed to maximize sensitivity to low-eccentricity ($0\leq\epsilon\leq0.6$) systems, derived from the analytic equations. We show that this parameterization provides a robust and computationally efficient method for detecting eccentric low-mass compact binaries. Based on these results, we conclude that advanced detectors will have a chance of detecting eccentric binaries if optimistic models prove true. However, a null observation is unlikely to firmly rule out models of eccentric binary populations. |
2011.03973 | Masataka Tsuchiya | Masataka Tsuchiya, Tsuyoshi Houri, Chul-Moon Yoo | The First Order Symmetry Operator on Gravitational Perturbations in the
5-dimensional Myers-Perry Spacetime with Equal Angular Momenta | 37 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been revealed that the first order symmetry operator for the
linearized Einstein equation on a vacuum spacetime can be constructed from a
Killing-Yano 3-form. This might be used to construct all or part of solutions
to the field equation. In this paper, we perform a mode decomposition of a
metric perturbation on the Schwarzschild spacetime and the Myers-Perry
spacetime with equal angular momenta in 5 dimensions, and investigate the
action of the symmetry operator on specific modes concretely. We show that on
such spacetimes, there is no transition between the modes of a metric
perturbation by the action of the symmetry operator, and it ends up being the
linear combination of the infinitesimal transformations of isometry.
| [
{
"created": "Sun, 8 Nov 2020 12:53:53 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Feb 2021 08:41:14 GMT",
"version": "v2"
}
] | 2021-02-03 | [
[
"Tsuchiya",
"Masataka",
""
],
[
"Houri",
"Tsuyoshi",
""
],
[
"Yoo",
"Chul-Moon",
""
]
] | It has been revealed that the first order symmetry operator for the linearized Einstein equation on a vacuum spacetime can be constructed from a Killing-Yano 3-form. This might be used to construct all or part of solutions to the field equation. In this paper, we perform a mode decomposition of a metric perturbation on the Schwarzschild spacetime and the Myers-Perry spacetime with equal angular momenta in 5 dimensions, and investigate the action of the symmetry operator on specific modes concretely. We show that on such spacetimes, there is no transition between the modes of a metric perturbation by the action of the symmetry operator, and it ends up being the linear combination of the infinitesimal transformations of isometry. |
1011.5628 | Eugenio Bianchi | Eugenio Bianchi | Black Hole Entropy, Loop Gravity, and Polymer Physics | 13 pages, 2 figures | Class.Quant.Grav.28:114006,2011 | 10.1088/0264-9381/28/11/114006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Loop Gravity provides a microscopic derivation of Black Hole entropy. In this
paper, I show that the microstates counted admit a semiclassical description in
terms of shapes of a tessellated horizon. The counting of microstates and the
computation of the entropy can be done via a mapping to an equivalent
statistical mechanical problem: the counting of conformations of a closed
polymer chain. This correspondence suggests a number of intriguing relations
between the thermodynamics of Black Holes and the physics of polymers.
| [
{
"created": "Thu, 25 Nov 2010 13:53:14 GMT",
"version": "v1"
}
] | 2011-07-28 | [
[
"Bianchi",
"Eugenio",
""
]
] | Loop Gravity provides a microscopic derivation of Black Hole entropy. In this paper, I show that the microstates counted admit a semiclassical description in terms of shapes of a tessellated horizon. The counting of microstates and the computation of the entropy can be done via a mapping to an equivalent statistical mechanical problem: the counting of conformations of a closed polymer chain. This correspondence suggests a number of intriguing relations between the thermodynamics of Black Holes and the physics of polymers. |
1905.09502 | Alexander Zhuk | Maxim Eingorn, A. Emrah Yukselci and Alexander Zhuk | Effect of the spatial curvature of the Universe on the form of the
gravitational potential | v2 (matching the publication in European Physical Journal C) = v1 +
minor changes + new Refs.; 8 pages, 3 figures | Eur. Phys. J. C 79, 655 (2019) | 10.1140/epjc/s10052-019-7169-6 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the cosmic screening approach, we obtain the exact formulas for the
velocity-independent gravitational potentials produced by matter in the form of
discrete sources distributed in the open and closed Universes. These formulas
demonstrate that spatial curvature of the Universe considerably affect the form
of the potentials and forces. While in the open Universe the gravitational
force undergoes exponential suppression at cosmological distances, in the
closed Universe the force induced by an individual mass is equal to zero at the
antipodal point with respect to this mass. The derived formulas are applicable
for investigations of the motion of astrophysical objects (e.g., galaxies) in
the open and closed Universes, and for simulations of the large scale structure
formation.
| [
{
"created": "Thu, 23 May 2019 07:12:52 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jul 2019 19:16:52 GMT",
"version": "v2"
}
] | 2019-08-13 | [
[
"Eingorn",
"Maxim",
""
],
[
"Yukselci",
"A. Emrah",
""
],
[
"Zhuk",
"Alexander",
""
]
] | Within the cosmic screening approach, we obtain the exact formulas for the velocity-independent gravitational potentials produced by matter in the form of discrete sources distributed in the open and closed Universes. These formulas demonstrate that spatial curvature of the Universe considerably affect the form of the potentials and forces. While in the open Universe the gravitational force undergoes exponential suppression at cosmological distances, in the closed Universe the force induced by an individual mass is equal to zero at the antipodal point with respect to this mass. The derived formulas are applicable for investigations of the motion of astrophysical objects (e.g., galaxies) in the open and closed Universes, and for simulations of the large scale structure formation. |
1806.06453 | Ali \"Ovg\"un Dr. | Ali \"Ovg\"un, \.Izzet Sakall{\i} and Joel Saavedra | Weak gravitational lensing by Kerr-MOG Black Hole and Gauss-Bonnet
theorem | 9 pages, 3 Figures. Accepted for publication in Annals of Physics | Annals of Physics 411 (2019) 167978 | 10.1016/j.aop.2019.167978 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The deflection angle of Kerr-MOG black holes is studied for different values
of the parameter in modified gravity (MOG). To this end, we employ the
Gauss-Bonnet theorem, which was first studied by Gibbons and Werner and then
extended by Ono, Ishihara and Asada, who use a generalized optical metric where
the deflection of light for an observer and source at finite distance. By using
this method, we study the weak gravitational lensing by Kerr-MOG black hole.
Our computations show that with an increase in the MOG parameter ($\alpha$),
the deflection angle becomes significantly larger than that of Kerr black hole.
The results obtained show that MOG effect could be taken into account in the
gravitational lensing experiments.
| [
{
"created": "Sun, 17 Jun 2018 21:48:13 GMT",
"version": "v1"
},
{
"created": "Sun, 4 Aug 2019 07:46:43 GMT",
"version": "v2"
}
] | 2019-10-29 | [
[
"Övgün",
"Ali",
""
],
[
"Sakallı",
"İzzet",
""
],
[
"Saavedra",
"Joel",
""
]
] | The deflection angle of Kerr-MOG black holes is studied for different values of the parameter in modified gravity (MOG). To this end, we employ the Gauss-Bonnet theorem, which was first studied by Gibbons and Werner and then extended by Ono, Ishihara and Asada, who use a generalized optical metric where the deflection of light for an observer and source at finite distance. By using this method, we study the weak gravitational lensing by Kerr-MOG black hole. Our computations show that with an increase in the MOG parameter ($\alpha$), the deflection angle becomes significantly larger than that of Kerr black hole. The results obtained show that MOG effect could be taken into account in the gravitational lensing experiments. |
gr-qc/0410023 | Reinhard Prix | Reinhard Prix, Jerome Novak, G.L. Comer | Relativistic numerical models for stationary superfluid Neutron Stars | 18 pages, 9 figures, RevTex4; to appear in Phys.Rev.D; v2: improved
figures, more discussion of physical results | Phys.Rev. D71 (2005) 043005 | 10.1103/PhysRevD.71.043005 | null | gr-qc astro-ph | null | We have developed a theoretical model and a numerical code for stationary
rotating superfluid neutron stars in full general relativity. The underlying
two-fluid model is based on Carter's covariant multi-fluid hydrodynamic
formalism. The two fluids, representing the superfluid neutrons on one hand,
and the protons and electrons on the other, are restricted to uniform rotation
around a common axis, but are allowed to have different rotation rates. We have
performed extensive tests of the numerical code, including quantitative
comparisons to previous approximative results for these models. The results
presented here are the first ``exact'' calculations of such models in the sense
that no approximations (other than that inherent in a discretized numerical
treatment) are used. Using this code we reconfirm the existence of
prolate-oblate shaped configurations. We studied the dependency of the Kepler
rotation limit and of the mass-density relation on the relative rotation rate.
We further demonstrate how one can simulate a (albeit fluid) neutron-star
``crust'' by letting one fluid extend further outwards than the other, which
results in interesting cases where the Kepler limit is actually determined by
the outermost but slower fluid.
| [
{
"created": "Tue, 5 Oct 2004 21:49:57 GMT",
"version": "v1"
},
{
"created": "Sun, 6 Feb 2005 09:40:04 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Prix",
"Reinhard",
""
],
[
"Novak",
"Jerome",
""
],
[
"Comer",
"G. L.",
""
]
] | We have developed a theoretical model and a numerical code for stationary rotating superfluid neutron stars in full general relativity. The underlying two-fluid model is based on Carter's covariant multi-fluid hydrodynamic formalism. The two fluids, representing the superfluid neutrons on one hand, and the protons and electrons on the other, are restricted to uniform rotation around a common axis, but are allowed to have different rotation rates. We have performed extensive tests of the numerical code, including quantitative comparisons to previous approximative results for these models. The results presented here are the first ``exact'' calculations of such models in the sense that no approximations (other than that inherent in a discretized numerical treatment) are used. Using this code we reconfirm the existence of prolate-oblate shaped configurations. We studied the dependency of the Kepler rotation limit and of the mass-density relation on the relative rotation rate. We further demonstrate how one can simulate a (albeit fluid) neutron-star ``crust'' by letting one fluid extend further outwards than the other, which results in interesting cases where the Kepler limit is actually determined by the outermost but slower fluid. |
2305.19062 | Saddam Hussain | Saddam Hussain, Anirban Chatterjee, Kaushik Bhattacharya | Dynamical stability in models where dark matter and dark energy are
non-minimally coupled to curvature | 26 pages, 12 figures, 7 tables; Accepted for the publication in
Physical Review D | PhysRevD. 108 (2023) 103502 | 10.1103/PhysRevD.108.103502 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | This work explores the dynamical stability of cosmological models where dark
matter and dark energy can non-minimally couple to spacetime (scalar)
curvature. Two different scenarios are presented here. In the initial case,
only dark matter sector is coupled to curvature in the presence of a
quintessence scalar field. In the second case both dark matter and the
quintessence field are coupled to curvature. It is shown that one can get an
accelerating expansion phase of the universe in both the cases. The nature of
the fixed points show that there can be stable or unstable phases where the
curvature coupling vanishes and dark energy and dark matter evolve
independently. On the other hand there can be stable accelerating expansion
phases where both the components are coupled to curvature.
| [
{
"created": "Tue, 30 May 2023 14:25:46 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Oct 2023 20:19:54 GMT",
"version": "v2"
}
] | 2023-11-07 | [
[
"Hussain",
"Saddam",
""
],
[
"Chatterjee",
"Anirban",
""
],
[
"Bhattacharya",
"Kaushik",
""
]
] | This work explores the dynamical stability of cosmological models where dark matter and dark energy can non-minimally couple to spacetime (scalar) curvature. Two different scenarios are presented here. In the initial case, only dark matter sector is coupled to curvature in the presence of a quintessence scalar field. In the second case both dark matter and the quintessence field are coupled to curvature. It is shown that one can get an accelerating expansion phase of the universe in both the cases. The nature of the fixed points show that there can be stable or unstable phases where the curvature coupling vanishes and dark energy and dark matter evolve independently. On the other hand there can be stable accelerating expansion phases where both the components are coupled to curvature. |
0806.1591 | Sascha Husa | Stanislav Babak, Mark Hannam, Sascha Husa, Bernard Schutz | Resolving Super Massive Black Holes with LISA | 4 pages, 1 figure | null | null | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the angular resolution of the gravitational wave detector LISA and
show that numerical relativity can drastically improve the accuracy of position
location for coalescing Super Massive Black Hole (SMBH) binaries. For systems
with total redshifted mass above $10^7 M_{\odot}$, LISA will mainly see the
merger and ring-down of the gravitational wave (GW) signal, which can now be
computed numerically using the full Einstein equations. Using numerical
waveforms that also include about ten GW cycles of inspiral, we improve
inspiral-only position estimates by an order of magnitude. We show that LISA
localizes half of all such systems at $z=1$ to better than 3 arcminutes and the
best 20% to within one arcminute. This will give excellent prospects for
identifying the host galaxy.
| [
{
"created": "Tue, 10 Jun 2008 15:47:58 GMT",
"version": "v1"
}
] | 2008-06-15 | [
[
"Babak",
"Stanislav",
""
],
[
"Hannam",
"Mark",
""
],
[
"Husa",
"Sascha",
""
],
[
"Schutz",
"Bernard",
""
]
] | We study the angular resolution of the gravitational wave detector LISA and show that numerical relativity can drastically improve the accuracy of position location for coalescing Super Massive Black Hole (SMBH) binaries. For systems with total redshifted mass above $10^7 M_{\odot}$, LISA will mainly see the merger and ring-down of the gravitational wave (GW) signal, which can now be computed numerically using the full Einstein equations. Using numerical waveforms that also include about ten GW cycles of inspiral, we improve inspiral-only position estimates by an order of magnitude. We show that LISA localizes half of all such systems at $z=1$ to better than 3 arcminutes and the best 20% to within one arcminute. This will give excellent prospects for identifying the host galaxy. |
1202.1793 | Wytler Cordeiro dos Santos | Wytler Cordeiro dos Santos | The presence of Primordial Gravitational Waves in the Cosmic Microwave
Background | 7 pages, 1 figure | null | null | null | gr-qc astro-ph.CO astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The General Relativity affirms that any field is a source of gravitational
field, thus one should affirm that the energy of Cosmic Microwave Background
(CMB) generated primordial gravitational waves. The present article shows that
a gravitational wave with dimensionless amplitude $\sim 10^{-5}$ and large wave
length $\sim 10$ megaparsecs shifts temperature of CMB radiation about of a
part in $10^{5}$.
| [
{
"created": "Wed, 8 Feb 2012 18:42:52 GMT",
"version": "v1"
},
{
"created": "Sun, 13 May 2012 00:04:02 GMT",
"version": "v2"
}
] | 2012-05-15 | [
[
"Santos",
"Wytler Cordeiro dos",
""
]
] | The General Relativity affirms that any field is a source of gravitational field, thus one should affirm that the energy of Cosmic Microwave Background (CMB) generated primordial gravitational waves. The present article shows that a gravitational wave with dimensionless amplitude $\sim 10^{-5}$ and large wave length $\sim 10$ megaparsecs shifts temperature of CMB radiation about of a part in $10^{5}$. |
2205.09272 | PanPan Wang | Yu Hu, Pan-Pan Wang, Yu-Jie Tan, and Cheng-Gang Shao | Full analytic expression of overlap reduction function for gravitational
wave background with pulsar timing arrays | null | null | 10.1103/PhysRevD.106.024005 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Pulsar timing array (PTA) is expected to detect gravitational wave background
(GWB) in the nanohertz band within the next decade. This provides an
opportunity to test the gravity theory and cosmology. A typical data analysis
method to detect GWB is cross-correlation analysis. The overlap reduction
function (ORF) plays an important role in the correlation data analysis of GWB.
The present approach to dealing with the intricate integration in ORF is to use
short-wave approximation to drop out the tricky terms. In this paper, we
provide the full analytic expression of the ORF for PTA without any
approximation for all possible polarizations allowed by modifications of
general relativity. Compared with the numerical simulation and short-wave
approximation, our results are more efficient and widely applicable. Especially
for the scalar-longitudinal mode where the short-wave approximation is not
available, our analytical expression is particularly significant.
| [
{
"created": "Thu, 19 May 2022 01:21:56 GMT",
"version": "v1"
}
] | 2022-07-20 | [
[
"Hu",
"Yu",
""
],
[
"Wang",
"Pan-Pan",
""
],
[
"Tan",
"Yu-Jie",
""
],
[
"Shao",
"Cheng-Gang",
""
]
] | Pulsar timing array (PTA) is expected to detect gravitational wave background (GWB) in the nanohertz band within the next decade. This provides an opportunity to test the gravity theory and cosmology. A typical data analysis method to detect GWB is cross-correlation analysis. The overlap reduction function (ORF) plays an important role in the correlation data analysis of GWB. The present approach to dealing with the intricate integration in ORF is to use short-wave approximation to drop out the tricky terms. In this paper, we provide the full analytic expression of the ORF for PTA without any approximation for all possible polarizations allowed by modifications of general relativity. Compared with the numerical simulation and short-wave approximation, our results are more efficient and widely applicable. Especially for the scalar-longitudinal mode where the short-wave approximation is not available, our analytical expression is particularly significant. |
1704.06290 | Pablo Guilleminot | Pablo Guilleminot, Rodrigo Olea and Alexander N. Petrov | Constant curvature black holes in Einstein AdS gravity: conserved
quantities | 20 pages, no figures | null | 10.1103/PhysRevD.95.124039 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study physical properties of constant curvature black holes (CCBHs) in
Einstein anti-de Sitter (AdS) gravity. These objects, which are locally AdS
throughout the space, are constructed from identifications of global AdS
spacetime, in a similar fashion as Banados-Teitelboim-Zanelli (BTZ) black hole
in three dimensions. We find that, in dimensions equal or greater than four,
CCBHs have zero mass and angular momentum. Only in odd dimensions we are able
to associate a nonvanishing conserved quantity to these solutions, which
corresponds to the vacuum (Casimir) energy of the spacetime.
| [
{
"created": "Thu, 20 Apr 2017 18:20:35 GMT",
"version": "v1"
}
] | 2017-08-02 | [
[
"Guilleminot",
"Pablo",
""
],
[
"Olea",
"Rodrigo",
""
],
[
"Petrov",
"Alexander N.",
""
]
] | We study physical properties of constant curvature black holes (CCBHs) in Einstein anti-de Sitter (AdS) gravity. These objects, which are locally AdS throughout the space, are constructed from identifications of global AdS spacetime, in a similar fashion as Banados-Teitelboim-Zanelli (BTZ) black hole in three dimensions. We find that, in dimensions equal or greater than four, CCBHs have zero mass and angular momentum. Only in odd dimensions we are able to associate a nonvanishing conserved quantity to these solutions, which corresponds to the vacuum (Casimir) energy of the spacetime. |
2003.00590 | Ivan Kolar | Ivan Kolar, Anupam Mazumdar | Hamiltonian for scalar field model of infinite derivative gravity | 13 pages | Phys. Rev. D 101, 124028 (2020) | 10.1103/PhysRevD.101.124028 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Theories with an infinite number of derivatives are described by non-local
Lagrangians for which the standard Hamiltonian formalism cannot be applied.
Hamiltonians of special types of non-local theories can be constructed by means
of the (1+1)-dimensional Hamiltonian formalism. In this paper, we consider a
simple scalar field model inspired by the infinite derivative gravity and study
its reduced phase space by using this formalism. Assuming the expansion of the
solutions in the coupling constant, we compute the perturbative Hamiltonian and
the symplectic 2-form. We also discuss an example of a theory leading to an
infinite-dimensional reduced phase space for a different choice of the form
factor.
| [
{
"created": "Sun, 1 Mar 2020 21:25:36 GMT",
"version": "v1"
}
] | 2020-06-16 | [
[
"Kolar",
"Ivan",
""
],
[
"Mazumdar",
"Anupam",
""
]
] | Theories with an infinite number of derivatives are described by non-local Lagrangians for which the standard Hamiltonian formalism cannot be applied. Hamiltonians of special types of non-local theories can be constructed by means of the (1+1)-dimensional Hamiltonian formalism. In this paper, we consider a simple scalar field model inspired by the infinite derivative gravity and study its reduced phase space by using this formalism. Assuming the expansion of the solutions in the coupling constant, we compute the perturbative Hamiltonian and the symplectic 2-form. We also discuss an example of a theory leading to an infinite-dimensional reduced phase space for a different choice of the form factor. |
0705.1080 | Chiang-Mei Chen | Chiang-Mei Chen, Jian-Liang Liu, James M. Nester | Quasi-local energy for cosmological models | Contributed to International Symposium on Cosmology and Particle
Astrophysics (CosPA 2006), Taipei, Taiwan, 15-17 Nov 2006 | Mod.Phys.Lett.A22:2039-2046,2007 | 10.1142/S0217732307025285 | null | gr-qc | null | First we briefly review our covariant Hamiltonian approach to quasi-local
energy, noting that the Hamiltonian-boundary-term quasi-local energy
expressions depend on the chosen boundary conditions and reference
configuration. Then we present the quasi-local energy values resulting from the
formalism applied to homogeneous Bianchi cosmologies. Finally we consider the
quasi-local energies of the FRW cosmologies. Our results do not agree with
certain widely accepted quasi-local criteria.
| [
{
"created": "Tue, 8 May 2007 12:42:33 GMT",
"version": "v1"
},
{
"created": "Tue, 15 May 2007 23:46:19 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Chen",
"Chiang-Mei",
""
],
[
"Liu",
"Jian-Liang",
""
],
[
"Nester",
"James M.",
""
]
] | First we briefly review our covariant Hamiltonian approach to quasi-local energy, noting that the Hamiltonian-boundary-term quasi-local energy expressions depend on the chosen boundary conditions and reference configuration. Then we present the quasi-local energy values resulting from the formalism applied to homogeneous Bianchi cosmologies. Finally we consider the quasi-local energies of the FRW cosmologies. Our results do not agree with certain widely accepted quasi-local criteria. |
2004.00888 | Lavinia Heisenberg | Fabio D'Ambrosio, Mudit Garg, Lavinia Heisenberg | Non-linear extension of non-metricity scalar for MOND | 6 pages | null | 10.1016/j.physletb.2020.135970 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | General Relativity enjoys the freedom of different geometrical
interpretations in terms of curvature, torsion or non-metricity. Within this
geometrical trinity, a simpler geometrical formulation of General Relativity
manifests itself in the latter, where gravity is entirely attributed to
non-metricity. In this Letter, we consider non-linear extensions of Coincident
General Relativity $f(\mathring{\mathbb{Q}})$ for phenomenological applications
on both cosmological as well as galactic scales. The theory not only delivers
dark energy on large scales but also recovers MOND on galactic scales, together
with implications for the early universe cosmology. To the best of our
knowledge, this represents the first relativistic, covariant, and ghost-free
hybrid-formulation of MOND which recovers both, General Relativity and MOND in
the appropriate limits and reconciles expected cosmological behavior. We
further illustrate that previous bimetric formulations of MOND generically
suffer from ghost instabilities and $f(\mathring{\mathbb{Q}})$ crystalizes as a
unique ghost-free theory.
| [
{
"created": "Thu, 2 Apr 2020 09:09:43 GMT",
"version": "v1"
}
] | 2020-12-30 | [
[
"D'Ambrosio",
"Fabio",
""
],
[
"Garg",
"Mudit",
""
],
[
"Heisenberg",
"Lavinia",
""
]
] | General Relativity enjoys the freedom of different geometrical interpretations in terms of curvature, torsion or non-metricity. Within this geometrical trinity, a simpler geometrical formulation of General Relativity manifests itself in the latter, where gravity is entirely attributed to non-metricity. In this Letter, we consider non-linear extensions of Coincident General Relativity $f(\mathring{\mathbb{Q}})$ for phenomenological applications on both cosmological as well as galactic scales. The theory not only delivers dark energy on large scales but also recovers MOND on galactic scales, together with implications for the early universe cosmology. To the best of our knowledge, this represents the first relativistic, covariant, and ghost-free hybrid-formulation of MOND which recovers both, General Relativity and MOND in the appropriate limits and reconciles expected cosmological behavior. We further illustrate that previous bimetric formulations of MOND generically suffer from ghost instabilities and $f(\mathring{\mathbb{Q}})$ crystalizes as a unique ghost-free theory. |
gr-qc/0303088 | Marije Ljolje | Marije Ljolje | On the Lorentz Invariant Gravitation Field Theory | 10 pages, 49 equations | null | null | null | gr-qc | null | The theory of gravitation field within the special theory of relativity is
analyzed.
| [
{
"created": "Sun, 23 Mar 2003 12:13:50 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ljolje",
"Marije",
""
]
] | The theory of gravitation field within the special theory of relativity is analyzed. |
1809.01401 | Vaibhav Tiwari | Vaibhav Tiwari, Stephen Fairhurst and Mark Hannam | Constraining black-hole spins with gravitational wave observations | null | null | 10.3847/1538-4357/aae8df | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The observation of gravitational-wave signals from merging black-hole
binaries enables direct measurement of the properties of the black holes. An
individual observation allows measurement of the black-hole masses, but only
limited information about either the magnitude or orientation of the black hole
spins is available, primarily due to the degeneracy between measurements of
spin and binary mass ratio. Using the first six black-hole merger observations,
we are able to constrain the distribution of black-hole spins. We perform model
selection between a set of models with different spin population models
combined with a power-law mass distribution to make inferences about the spin
distribution. We assume a fixed power-law mass distribution on the black holes,
which is supported by the data and provides a realistic distribution of binary
mass-ratio. This allows us to accurately account for selection effects due to
variations in the signal amplitude with spin magnitude, and provides an
improved inference on the spin distribution. We conclude that the first six
LIGO and Virgo observations (Abbott et al. 2016a, 2017a,b,c) disfavour highly
spinning black holes against low spins by an odds-ratio of 15:1; thus providing
strong constraints on spin magnitudes from gravitational-wave observations.
Furthermore, we are able to rule out a population of binaries with completely
aligned spins, even when the spins of the individual black holes are low, at an
odds ratio of 22,000:1, significantly strengthening earlier evidence against
aligned spins (Farr et al. 2017). These results provide important information
that will aid in our understanding on the formation processes of black-holes.
| [
{
"created": "Wed, 5 Sep 2018 09:30:25 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Oct 2018 12:37:48 GMT",
"version": "v2"
}
] | 2018-12-12 | [
[
"Tiwari",
"Vaibhav",
""
],
[
"Fairhurst",
"Stephen",
""
],
[
"Hannam",
"Mark",
""
]
] | The observation of gravitational-wave signals from merging black-hole binaries enables direct measurement of the properties of the black holes. An individual observation allows measurement of the black-hole masses, but only limited information about either the magnitude or orientation of the black hole spins is available, primarily due to the degeneracy between measurements of spin and binary mass ratio. Using the first six black-hole merger observations, we are able to constrain the distribution of black-hole spins. We perform model selection between a set of models with different spin population models combined with a power-law mass distribution to make inferences about the spin distribution. We assume a fixed power-law mass distribution on the black holes, which is supported by the data and provides a realistic distribution of binary mass-ratio. This allows us to accurately account for selection effects due to variations in the signal amplitude with spin magnitude, and provides an improved inference on the spin distribution. We conclude that the first six LIGO and Virgo observations (Abbott et al. 2016a, 2017a,b,c) disfavour highly spinning black holes against low spins by an odds-ratio of 15:1; thus providing strong constraints on spin magnitudes from gravitational-wave observations. Furthermore, we are able to rule out a population of binaries with completely aligned spins, even when the spins of the individual black holes are low, at an odds ratio of 22,000:1, significantly strengthening earlier evidence against aligned spins (Farr et al. 2017). These results provide important information that will aid in our understanding on the formation processes of black-holes. |
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