id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0211105 | Reinhard Prix | R. Prix, J. Novak and G.L. Comer | Stationary structure of relativistic superfluid neutron stars | 5 pages, 2 figures. Conference proceedings for the 26th Spanish
Relativity Meeting (ERE 2002), Menorca, Spain, 22-24 Sept. 2002 | null | null | null | gr-qc astro-ph | null | We describe recent progress in the numerical study of the structure of
rapidly rotating superfluid neutron star models in full general relativity. The
superfluid neutron star is described by a model of two interpenetrating and
interacting fluids, one representing the superfluid neutrons and the second
consisting of the remaining charged particles (protons, electrons, muons). We
consider general stationary configurations where the two fluids can have
different rotation rates around a common rotation axis. The previously
discovered existence of configurations with one fluid in a prolate shape is
confirmed.
| [
{
"created": "Fri, 29 Nov 2002 14:27:05 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Prix",
"R.",
""
],
[
"Novak",
"J.",
""
],
[
"Comer",
"G. L.",
""
]
] | We describe recent progress in the numerical study of the structure of rapidly rotating superfluid neutron star models in full general relativity. The superfluid neutron star is described by a model of two interpenetrating and interacting fluids, one representing the superfluid neutrons and the second consisting of the remaining charged particles (protons, electrons, muons). We consider general stationary configurations where the two fluids can have different rotation rates around a common rotation axis. The previously discovered existence of configurations with one fluid in a prolate shape is confirmed. |
0904.1363 | Hamid Reza Sepangi | A. Borzou and H. R. Sepangi | Unification of gravity and electromagnetism revisited | 10 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the context of a $5D$ space-time, we construct a unified theory of
gravity and electromagnetism from which the Einstein field equations and
Maxwell equations emerge, with homogenous Maxwell equations appearing
naturally. We also introduce a well-defined five dimensional energy-momentum
tensor consistent with our unification scheme. A correction term appears in
Maxwell equations which can be used to explain the recently discovered galactic
magnetic fields.
| [
{
"created": "Wed, 8 Apr 2009 15:15:55 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Nov 2009 09:24:46 GMT",
"version": "v2"
},
{
"created": "Wed, 16 Jun 2010 08:30:42 GMT",
"version": "v3"
}
] | 2010-06-17 | [
[
"Borzou",
"A.",
""
],
[
"Sepangi",
"H. R.",
""
]
] | Within the context of a $5D$ space-time, we construct a unified theory of gravity and electromagnetism from which the Einstein field equations and Maxwell equations emerge, with homogenous Maxwell equations appearing naturally. We also introduce a well-defined five dimensional energy-momentum tensor consistent with our unification scheme. A correction term appears in Maxwell equations which can be used to explain the recently discovered galactic magnetic fields. |
1901.09946 | Arkadiusz B{\l}aut | Arkadiusz B{\l}aut | Laser interferometer response to scalar massive gravitational waves | 13 pages, 2 figures | Phys. Rev. D 92, 063013, 2015 | 10.1103/PhysRevD.92.063013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the response of the gravitational wave detector to a scalar
massive plane gravitational wave. We give the compact form of the response and
discuss its angular and frequency characteristics. The derivations is carried
out in the conformal and the synchronous gauges and the equivalence of the two
approaches is shown. In the case of the massive Brans-Dicke theory we solve the
linearized vacuum field equations in the two gauges as well.
| [
{
"created": "Mon, 28 Jan 2019 19:07:37 GMT",
"version": "v1"
}
] | 2019-02-06 | [
[
"Błaut",
"Arkadiusz",
""
]
] | We analyze the response of the gravitational wave detector to a scalar massive plane gravitational wave. We give the compact form of the response and discuss its angular and frequency characteristics. The derivations is carried out in the conformal and the synchronous gauges and the equivalence of the two approaches is shown. In the case of the massive Brans-Dicke theory we solve the linearized vacuum field equations in the two gauges as well. |
1707.05268 | Sylvia Zhu | Sylvia J. Zhu, Maria Alessandra Papa, Sin\'ead Walsh | A new veto for continuous gravitational wave searches | 10 pages, 6 figures, 2 tables | Phys. Rev. D 96, 124007 (2017) | 10.1103/PhysRevD.96.124007 | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | We present a new veto procedure to distinguish between continuous
gravitational wave (CW) signals and the detector artifacts that can mimic their
behavior. The veto procedure exploits the fact that a long-lasting coherent
disturbance is less likely than a real signal to exhibit a Doppler modulation
of astrophysical origin. Therefore, in the presence of an outlier from a
search, we perform a multi-step search around the frequency of the outlier with
the Doppler modulation turned off (DM-off), and compare these results with the
results from the original (DM-on) search. If the results from the DM-off search
are more significant than those from the DM-on search, the outlier is most
likely due to an artifact rather than a signal. We tune the veto procedure so
that it has a very low false dismissal rate. With this veto, we are able to
identify as coherent disturbances >99.9% of the 6349 candidates from the recent
all-sky low-frequency Einstein@Home search on the data from the Advanced LIGO
O1 observing run [1]. We present the details of each identified disturbance in
the Appendix.
| [
{
"created": "Mon, 17 Jul 2017 16:25:43 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Sep 2017 15:17:31 GMT",
"version": "v2"
}
] | 2017-12-13 | [
[
"Zhu",
"Sylvia J.",
""
],
[
"Papa",
"Maria Alessandra",
""
],
[
"Walsh",
"Sinéad",
""
]
] | We present a new veto procedure to distinguish between continuous gravitational wave (CW) signals and the detector artifacts that can mimic their behavior. The veto procedure exploits the fact that a long-lasting coherent disturbance is less likely than a real signal to exhibit a Doppler modulation of astrophysical origin. Therefore, in the presence of an outlier from a search, we perform a multi-step search around the frequency of the outlier with the Doppler modulation turned off (DM-off), and compare these results with the results from the original (DM-on) search. If the results from the DM-off search are more significant than those from the DM-on search, the outlier is most likely due to an artifact rather than a signal. We tune the veto procedure so that it has a very low false dismissal rate. With this veto, we are able to identify as coherent disturbances >99.9% of the 6349 candidates from the recent all-sky low-frequency Einstein@Home search on the data from the Advanced LIGO O1 observing run [1]. We present the details of each identified disturbance in the Appendix. |
1511.05439 | Francesco Becattini | F. Becattini, E. Grossi (University of Florence) | Quantum relativistic fluid at global thermodynamic equilibrium in curved
spacetime | 5 pages | null | null | null | gr-qc hep-th nucl-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new approach to the problem of the thermodynamical equilibrium
of a quantum relativistic fluid in a curved spacetime in the limit of small
curvature. We calculate the mean value of local operators by expanding the
four-temperature Killing vector field in Riemann normal coordinates about the
same spacetime point and we derive corrections with respect to the flat
spacetime expressions. Thereby, we clarify the origin of the terms proportional
to Riemann and Ricci tensors introduced in general hydrodynamic expansion of
the stress-energy tensor.
| [
{
"created": "Tue, 17 Nov 2015 15:36:20 GMT",
"version": "v1"
}
] | 2015-11-18 | [
[
"Becattini",
"F.",
"",
"University of Florence"
],
[
"Grossi",
"E.",
"",
"University of Florence"
]
] | We present a new approach to the problem of the thermodynamical equilibrium of a quantum relativistic fluid in a curved spacetime in the limit of small curvature. We calculate the mean value of local operators by expanding the four-temperature Killing vector field in Riemann normal coordinates about the same spacetime point and we derive corrections with respect to the flat spacetime expressions. Thereby, we clarify the origin of the terms proportional to Riemann and Ricci tensors introduced in general hydrodynamic expansion of the stress-energy tensor. |
2311.07671 | Hideki Maeda | Hideki Maeda and Jiri Podolsky | Charged rotating BTZ solution revisited: New coordinates and algebraic
classifications | 31 pages, no figure, 1 table; v2, final version to appear in
Classical and Quantum Gravity | Class.Quant.Grav. 41 (2024) 11, 115012 | 10.1088/1361-6382/ad422d | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the charged rotating Ba\~nados-Teitelboim-Zanelli (BTZ) solution
in the three-dimensional Einstein-Maxwell-$\Lambda$ system. After the erroneous
announcement of its discovery at the end of the original BTZ paper in 1992, the
solution was first obtained by Cl\'ement in the paper published in 1996 by
coordinate transformations from the charged non-rotating BTZ solution. While
Cl\'ement's form of the solution is valid only for ${\Lambda<0}$, we present a
new form for a wider range of $\Lambda$ by uniform scaling transformations and
a reparametrization. We also introduce new coordinates corresponding to the
Doran coordinates in the Kerr spacetime, in which the metric and also its
inverse are regular at the Killing horizon, and described by elementary
functions. Lastly, we show that (i) the algebraic Cotton type of the spacetime
is type III on the Killing horizon and type I away from the horizon, and (ii)
the energy-momentum tensor for the Maxwell field is of the Hawking-Ellis type I
everywhere.
| [
{
"created": "Mon, 13 Nov 2023 19:00:59 GMT",
"version": "v1"
},
{
"created": "Wed, 1 May 2024 00:33:27 GMT",
"version": "v2"
}
] | 2024-05-10 | [
[
"Maeda",
"Hideki",
""
],
[
"Podolsky",
"Jiri",
""
]
] | We revisit the charged rotating Ba\~nados-Teitelboim-Zanelli (BTZ) solution in the three-dimensional Einstein-Maxwell-$\Lambda$ system. After the erroneous announcement of its discovery at the end of the original BTZ paper in 1992, the solution was first obtained by Cl\'ement in the paper published in 1996 by coordinate transformations from the charged non-rotating BTZ solution. While Cl\'ement's form of the solution is valid only for ${\Lambda<0}$, we present a new form for a wider range of $\Lambda$ by uniform scaling transformations and a reparametrization. We also introduce new coordinates corresponding to the Doran coordinates in the Kerr spacetime, in which the metric and also its inverse are regular at the Killing horizon, and described by elementary functions. Lastly, we show that (i) the algebraic Cotton type of the spacetime is type III on the Killing horizon and type I away from the horizon, and (ii) the energy-momentum tensor for the Maxwell field is of the Hawking-Ellis type I everywhere. |
gr-qc/9904031 | Carlos F. Sopuerta | M.A.G. Bonilla and C.F. Sopuerta | Super-energy tensor for space-times with vanishing scalar curvature | 13 pages, LaTeX 2.09. To be published in Journal of Mathematical
Physics | J.Math.Phys. 40 (1999) 3053-3062 | 10.1063/1.532743 | null | gr-qc | null | A four-index tensor is constructed with terms both quadratic in the Riemann
tensor and linear in its second derivatives, which has zero divergence for
space-times with vanishing scalar curvature. This tensor reduces in vacuum to
the Bel-Robinson tensor. Furthermore, the completely timelike component
referred to any observer is positive, and zero if and only if the space-time is
flat (excluding some unphysical space-times). We also show that this tensor is
the unique that can be constructed with these properties. Such a tensor does
not exist for general gravitational fields. Finally, we study this tensor in
several examples: the Friedmann-Lema\^{\i}tre-Robertson-Walker space-times
filled with radiation, the plane-fronted gravitational waves, and the Vaidya
radiating metric.
| [
{
"created": "Wed, 14 Apr 1999 09:10:44 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Bonilla",
"M. A. G.",
""
],
[
"Sopuerta",
"C. F.",
""
]
] | A four-index tensor is constructed with terms both quadratic in the Riemann tensor and linear in its second derivatives, which has zero divergence for space-times with vanishing scalar curvature. This tensor reduces in vacuum to the Bel-Robinson tensor. Furthermore, the completely timelike component referred to any observer is positive, and zero if and only if the space-time is flat (excluding some unphysical space-times). We also show that this tensor is the unique that can be constructed with these properties. Such a tensor does not exist for general gravitational fields. Finally, we study this tensor in several examples: the Friedmann-Lema\^{\i}tre-Robertson-Walker space-times filled with radiation, the plane-fronted gravitational waves, and the Vaidya radiating metric. |
2104.00485 | Seth Asante | Seth K. Asante, Bianca Dittrich, Jos\'e Padua-Arguelles | Effective Spin Foam Models for Lorentzian Quantum Gravity | 34 pages, 15 figures (Accepted to Classical and Quantum Gravity
Journal) | null | 10.1088/1361-6382/ac1b44 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Making the Lorentzian path integral for quantum gravity well-defined and
computable has been a long standing challenge. In this work we adopt the
recently proposed effective spin foam models to the Lorentzian case. This
defines a path integral over discrete Lorentzian quantum geometric
configurations, which include metric and torsion degrees of freedom. The
torsion degrees of freedom arise due to an anomaly, which is parametrized by
the Barbero--Immirzi parameter. Requiring a semi-classical regime constrains
this parameter, but the precise bound has to be determined by probing the
dynamics. The effective models provide the computationally most efficient spin
foam models yet, which allows us to perform first tests for determining the
semi-classical regime. This includes explorations specific to the Lorentzian
case, e.g. investigating quantum geometries with null lengths and null areas as
well as geometries that describe a change of spatial topology.
| [
{
"created": "Thu, 1 Apr 2021 14:13:31 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Aug 2021 19:31:19 GMT",
"version": "v2"
}
] | 2021-09-22 | [
[
"Asante",
"Seth K.",
""
],
[
"Dittrich",
"Bianca",
""
],
[
"Padua-Arguelles",
"José",
""
]
] | Making the Lorentzian path integral for quantum gravity well-defined and computable has been a long standing challenge. In this work we adopt the recently proposed effective spin foam models to the Lorentzian case. This defines a path integral over discrete Lorentzian quantum geometric configurations, which include metric and torsion degrees of freedom. The torsion degrees of freedom arise due to an anomaly, which is parametrized by the Barbero--Immirzi parameter. Requiring a semi-classical regime constrains this parameter, but the precise bound has to be determined by probing the dynamics. The effective models provide the computationally most efficient spin foam models yet, which allows us to perform first tests for determining the semi-classical regime. This includes explorations specific to the Lorentzian case, e.g. investigating quantum geometries with null lengths and null areas as well as geometries that describe a change of spatial topology. |
2406.02466 | Katy Clough Dr | Katy Clough, Tim Dietrich and Sebastian Khan | What no one has seen before: gravitational waveforms from warp drive
collapse | 12 pages, 6 figures, plus appendix. Comments welcome! | null | 10.33232/001c.121868 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Despite originating in science fiction, warp drives have a concrete
description in general relativity, with Alcubierre first proposing a spacetime
metric that supported faster-than-light travel. Whilst there are numerous
practical barriers to their implementation in real life, including a
requirement for negative energy, computationally, one can simulate their
evolution in time given an equation of state describing the matter. In this
work, we study the signatures arising from a warp drive "containment failure",
assuming a stiff equation of state for the fluid. We compute the emitted
gravitational-wave signal and track the energy fluxes of the fluid. Apart from
its rather speculative application to the search for extraterrestrial life in
gravitational-wave detector data, this work is interesting as a study of the
dynamical evolution and stability of spacetimes that violate the null energy
condition. Our work highlights the importance of exploring strange new
spacetimes, to (boldly) simulate what no one has seen before.
| [
{
"created": "Tue, 4 Jun 2024 16:34:41 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Jul 2024 09:22:40 GMT",
"version": "v2"
}
] | 2024-08-02 | [
[
"Clough",
"Katy",
""
],
[
"Dietrich",
"Tim",
""
],
[
"Khan",
"Sebastian",
""
]
] | Despite originating in science fiction, warp drives have a concrete description in general relativity, with Alcubierre first proposing a spacetime metric that supported faster-than-light travel. Whilst there are numerous practical barriers to their implementation in real life, including a requirement for negative energy, computationally, one can simulate their evolution in time given an equation of state describing the matter. In this work, we study the signatures arising from a warp drive "containment failure", assuming a stiff equation of state for the fluid. We compute the emitted gravitational-wave signal and track the energy fluxes of the fluid. Apart from its rather speculative application to the search for extraterrestrial life in gravitational-wave detector data, this work is interesting as a study of the dynamical evolution and stability of spacetimes that violate the null energy condition. Our work highlights the importance of exploring strange new spacetimes, to (boldly) simulate what no one has seen before. |
gr-qc/0306001 | Carsten Gundlach | C. Gundlach and J. M. Martin-Garcia | Kinematics of discretely self-similar spherically symmetric spacetimes | RevTex, 11 pages, 7 eps figures | null | 10.1103/PhysRevD.68.064019 | null | gr-qc | null | We summarize the consequences of the twin assumptions of (discrete)
self-similarity and spherical symmetry for the global structure of a spacetime.
All such spacetimes can be constructed from two building blocks, the "fan" and
"splash". Each building block contains one radial null geodesic that is
invariant under the self-similarity (self-similarity horizon).
| [
{
"created": "Sat, 31 May 2003 20:51:55 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Gundlach",
"C.",
""
],
[
"Martin-Garcia",
"J. M.",
""
]
] | We summarize the consequences of the twin assumptions of (discrete) self-similarity and spherical symmetry for the global structure of a spacetime. All such spacetimes can be constructed from two building blocks, the "fan" and "splash". Each building block contains one radial null geodesic that is invariant under the self-similarity (self-similarity horizon). |
1911.01739 | Behnam Pourhassan | Mir Hameeda, Behnam Pourhassan, Mir Faizal, C. P. Masroor, Rizwan Ul
Haq Ansari, P. K. Suresh | Modified Theory of Gravity and Clustering of Multi-Component System of
Galaxies | Published by EPJC including 5 figures | Eur. Phys. J. C (2019) 79:769 | 10.1140/epjc/s10052-019-7281-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we analyze the clustering of galaxies using a modified theory
of gravity, in which the field content of general relativity has been be
increased. This increasing in the field content of general relativity changes
the large distance behavior of the theory, and in weak field approximation, it
will also modify the large distance behavior of Newtonian potential. So, we
will analyzing the clustering of multi-component system of galaxies interacting
through this modified Newtonian potential. We will obtain the partition
function for this multi-component system, and study the thermodynamics of this
system. So, we will analyze the effects of the large distance modification to
the Newtonian potential on Helmholtz free energy, internal energy, entropy,
pressure and chemical potential of this system. We obtain also the modified
distribution function and the modified clustering parameter for this system,
and hence observe the effect of large distance modification of Newtonian
potential on clustering of galaxies.
| [
{
"created": "Tue, 5 Nov 2019 12:17:34 GMT",
"version": "v1"
}
] | 2019-11-06 | [
[
"Hameeda",
"Mir",
""
],
[
"Pourhassan",
"Behnam",
""
],
[
"Faizal",
"Mir",
""
],
[
"Masroor",
"C. P.",
""
],
[
"Ansari",
"Rizwan Ul Haq",
""
],
[
"Suresh",
"P. K.",
""
]
] | In this paper, we analyze the clustering of galaxies using a modified theory of gravity, in which the field content of general relativity has been be increased. This increasing in the field content of general relativity changes the large distance behavior of the theory, and in weak field approximation, it will also modify the large distance behavior of Newtonian potential. So, we will analyzing the clustering of multi-component system of galaxies interacting through this modified Newtonian potential. We will obtain the partition function for this multi-component system, and study the thermodynamics of this system. So, we will analyze the effects of the large distance modification to the Newtonian potential on Helmholtz free energy, internal energy, entropy, pressure and chemical potential of this system. We obtain also the modified distribution function and the modified clustering parameter for this system, and hence observe the effect of large distance modification of Newtonian potential on clustering of galaxies. |
2308.15995 | Maria Caruana | Salvatore Capozziello, Maria Caruana, Gabriel Farrugia, Jackson Levi
Said, Joseph Sultana | Cosmic Growth in $f(T)$ Teleparallel Gravity | null | null | 10.1007/s10714-024-03204-0 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | Physical evolution of cosmological models can be tested by using expansion
data, while growth history of these models is capable of testing dynamics of
the inhomogeneous parts of energy density. The growth factor, as well as its
growth index, gives a clear indication of the performance of cosmological
models in the regime of structure formation of early Universe. In this work, we
explore the growth index in several leading $f(T)$ cosmological models, based
on a specific class of teleparallel gravity theories. These have become
prominent in the literature and lead to other formulations of teleparallel
gravity. Here we adopt a generalized approach by obtaining the M\'{e}sz\'{a}ros
equation without immediately imposing the subhorizon limit, because this
assumption could lead to over-simplification. This approach gives avenue to
study at which $k$ modes the subhorizon limit starts to apply. We obtain
numerical results for the growth factor and growth index for a variety of data
set combinations for each $f(T)$ model.
| [
{
"created": "Wed, 30 Aug 2023 12:35:50 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Sep 2023 09:11:08 GMT",
"version": "v2"
}
] | 2024-02-20 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Caruana",
"Maria",
""
],
[
"Farrugia",
"Gabriel",
""
],
[
"Said",
"Jackson Levi",
""
],
[
"Sultana",
"Joseph",
""
]
] | Physical evolution of cosmological models can be tested by using expansion data, while growth history of these models is capable of testing dynamics of the inhomogeneous parts of energy density. The growth factor, as well as its growth index, gives a clear indication of the performance of cosmological models in the regime of structure formation of early Universe. In this work, we explore the growth index in several leading $f(T)$ cosmological models, based on a specific class of teleparallel gravity theories. These have become prominent in the literature and lead to other formulations of teleparallel gravity. Here we adopt a generalized approach by obtaining the M\'{e}sz\'{a}ros equation without immediately imposing the subhorizon limit, because this assumption could lead to over-simplification. This approach gives avenue to study at which $k$ modes the subhorizon limit starts to apply. We obtain numerical results for the growth factor and growth index for a variety of data set combinations for each $f(T)$ model. |
1009.0320 | Fredy Dubeibe | Jos\'e D. Sanabria-G\'omez, Jos\'e L. Hern\'andez-Pastora and F. L.
Dubeibe | Innermost stable circular orbits around magnetized rotating massive
stars | 8 pages, 3 figures | Phys.Rev.D82:124014,2010 | 10.1103/PhysRevD.82.124014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In 1998, Shibata and Sasaki [Phys. Rev. D 58, 104011 (1998)] presented an
approximate analytical formula for the radius of the innermost stable circular
orbit (ISCO) of a neutral test particle around a massive, rotating and deformed
source. In the present paper, we generalize their expression by including the
magnetic dipole moment. We show that our approximate analytical formulas are
accurate enough by comparing them with the six-parametric exact solution
calculated by Pach\'on et. al. [Phys. Rev. D 73, 104038 (2006)] along with the
numerical data presented by Berti and Stergioulas [MNRAS 350, 1416 (2004)] for
realistic neutron stars. As a main result, we find that in general, the radius
at ISCO exhibits a decreasing behavior with increasing magnetic field. However,
for magnetic fields below 100GT the variation of the radius at ISCO is
negligible and hence the non-magnetized approximate expression can be used. In
addition, we derive approximate analytical formulas for angular velocity,
energy and angular momentum of the test particle at ISCO.
| [
{
"created": "Thu, 2 Sep 2010 03:17:23 GMT",
"version": "v1"
}
] | 2016-08-30 | [
[
"Sanabria-Gómez",
"José D.",
""
],
[
"Hernández-Pastora",
"José L.",
""
],
[
"Dubeibe",
"F. L.",
""
]
] | In 1998, Shibata and Sasaki [Phys. Rev. D 58, 104011 (1998)] presented an approximate analytical formula for the radius of the innermost stable circular orbit (ISCO) of a neutral test particle around a massive, rotating and deformed source. In the present paper, we generalize their expression by including the magnetic dipole moment. We show that our approximate analytical formulas are accurate enough by comparing them with the six-parametric exact solution calculated by Pach\'on et. al. [Phys. Rev. D 73, 104038 (2006)] along with the numerical data presented by Berti and Stergioulas [MNRAS 350, 1416 (2004)] for realistic neutron stars. As a main result, we find that in general, the radius at ISCO exhibits a decreasing behavior with increasing magnetic field. However, for magnetic fields below 100GT the variation of the radius at ISCO is negligible and hence the non-magnetized approximate expression can be used. In addition, we derive approximate analytical formulas for angular velocity, energy and angular momentum of the test particle at ISCO. |
gr-qc/9709026 | Thomas Baumgarte | T. W. Baumgarte, G. B. Cook, M. A. Scheel, S. L. Shapiro and S. A.
Teukolsky | General Relativistic Models of Binary Neutron Stars in Quasiequilibrium | 14 pages, 8 figures, RevTeX | Phys. Rev. D 57, 7299 (1998) | 10.1103/PhysRevD.57.7299 | null | gr-qc astro-ph | null | We perform fully relativistic calculations of binary neutron stars in
corotating, circular orbit. While Newtonian gravity allows for a strict
equilibrium, a relativistic binary system emits gravitational radiation,
causing the system to lose energy and slowly spiral inwards. However, since
inspiral occurs on a time scale much longer than the orbital period, we can
treat the binary to be in quasiequilibrium. In this approximation, we integrate
a subset of the Einstein equations coupled to the relativistic equation of
hydrostatic equilibrium to solve the initial value problem for binaries of
arbitrary separation. We adopt a polytropic equation of state to determine the
structure and maximum mass of neutron stars in close binaries for polytropic
indices n=1, 1.5 and 2. We construct sequences of constant rest-mass and locate
turning points along energy equilibrium curves to identify the onset of orbital
instability. In particular, we locate the innermost stable circular orbit
(ISCO) and its angular velocity. We construct the first contact binary systems
in full general relativity. These arise whenever the equation of state is
sufficiently soft >= 1.5. A radial stability analysis reveals no tendency for
neutron stars in close binaries to collapse to black holes prior to merger.
| [
{
"created": "Thu, 11 Sep 1997 22:22:30 GMT",
"version": "v1"
}
] | 2016-08-25 | [
[
"Baumgarte",
"T. W.",
""
],
[
"Cook",
"G. B.",
""
],
[
"Scheel",
"M. A.",
""
],
[
"Shapiro",
"S. L.",
""
],
[
"Teukolsky",
"S. A.",
""
]
] | We perform fully relativistic calculations of binary neutron stars in corotating, circular orbit. While Newtonian gravity allows for a strict equilibrium, a relativistic binary system emits gravitational radiation, causing the system to lose energy and slowly spiral inwards. However, since inspiral occurs on a time scale much longer than the orbital period, we can treat the binary to be in quasiequilibrium. In this approximation, we integrate a subset of the Einstein equations coupled to the relativistic equation of hydrostatic equilibrium to solve the initial value problem for binaries of arbitrary separation. We adopt a polytropic equation of state to determine the structure and maximum mass of neutron stars in close binaries for polytropic indices n=1, 1.5 and 2. We construct sequences of constant rest-mass and locate turning points along energy equilibrium curves to identify the onset of orbital instability. In particular, we locate the innermost stable circular orbit (ISCO) and its angular velocity. We construct the first contact binary systems in full general relativity. These arise whenever the equation of state is sufficiently soft >= 1.5. A radial stability analysis reveals no tendency for neutron stars in close binaries to collapse to black holes prior to merger. |
0802.1298 | Gao Changjun | Changjun Gao, Xuelei Chen, Valerio Faraoni, You-Gen Shen | Does the mass of a black hole decrease due to the accretion of phantom
energy | 12 pages, 5 figures. PRD accepted | Phys.Rev.D78:024008,2008 | 10.1103/PhysRevD.78.024008 | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | According to Babichev et al., the accretion of a phantom test fluid onto a
Schwarzschild black hole will induce the mass of the black hole to decrease,
however the backreaction was ignored in their calculation. Using new exact
solutions describing black holes in a background Friedmann-Robertson-Walker
universe, we find that the physical black hole mass may instead increase due to
the accretion of phantom energy. If this is the case, and the future universe
is dominated by phantom dark energy, the black hole apparent horizon and the
cosmic apparent horizon will eventually coincide and, after that, the black
hole singularity will become naked in finite comoving time before the Big Rip
occurs, violating the Cosmic Censorship Conjecture.
| [
{
"created": "Sun, 10 Feb 2008 01:46:47 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Jun 2008 01:46:00 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Gao",
"Changjun",
""
],
[
"Chen",
"Xuelei",
""
],
[
"Faraoni",
"Valerio",
""
],
[
"Shen",
"You-Gen",
""
]
] | According to Babichev et al., the accretion of a phantom test fluid onto a Schwarzschild black hole will induce the mass of the black hole to decrease, however the backreaction was ignored in their calculation. Using new exact solutions describing black holes in a background Friedmann-Robertson-Walker universe, we find that the physical black hole mass may instead increase due to the accretion of phantom energy. If this is the case, and the future universe is dominated by phantom dark energy, the black hole apparent horizon and the cosmic apparent horizon will eventually coincide and, after that, the black hole singularity will become naked in finite comoving time before the Big Rip occurs, violating the Cosmic Censorship Conjecture. |
0812.2214 | Leonardo Modesto | Leonardo Modesto | Fractal Structure of Loop Quantum Gravity | 5 pages, 5 figures | Class.Quant.Grav.26:242002,2009 | 10.1088/0264-9381/26/24/242002 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we have calculated the spectral dimension of loop quantum
gravity (LQG) using simple arguments coming from the area spectrum at different
length scales. We have obtained that the spectral dimension of the spatial
section runs from 2 to 3, across a 1.5 phase, when the energy of a probe scalar
field decrees from high to low energy. We have calculated the spectral
dimension of the space-time also using results from spin-foam models, obtaining
a 2-dimensional effective manifold at hight energy. Our result is consistent
with other two approach to non perturbative quantum gravity: causal dynamical
triangulation and asymptotic safety quantum gravity.
| [
{
"created": "Thu, 11 Dec 2008 18:43:44 GMT",
"version": "v1"
}
] | 2010-01-30 | [
[
"Modesto",
"Leonardo",
""
]
] | In this paper we have calculated the spectral dimension of loop quantum gravity (LQG) using simple arguments coming from the area spectrum at different length scales. We have obtained that the spectral dimension of the spatial section runs from 2 to 3, across a 1.5 phase, when the energy of a probe scalar field decrees from high to low energy. We have calculated the spectral dimension of the space-time also using results from spin-foam models, obtaining a 2-dimensional effective manifold at hight energy. Our result is consistent with other two approach to non perturbative quantum gravity: causal dynamical triangulation and asymptotic safety quantum gravity. |
1112.3770 | Alexander Shatskiy Dr. | Darya Tretyakova, Alexander Shatskiy, Igor Novikov and Stanislav
Alexeyev | Non-singular Brans-Dicke cosmology with cosmological constant | 12 pages, 1 figure | null | 10.1103/PhysRevD.85.124059 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider Brans-Dicke cosmology with cosmological constant with negative w
parameter and an arbitrary (in general non-vanishing) scale factor at the Big
Bang. The field equations describe the flat universe, current observational
values for Hubble constant H and deceleration parameter q play a role of
initial conditions. In order to solve field equations we adopt the approach of
Uehara and Kim (1982). They considered only positive values of w, hence our
solution is a new one and has not been described in their paper. Our main
result is that unlike the standard cosmology the scale factor may not vanish in
it's evolution back in time. In other words our model displays a cosmological
bounce and avoids the initial singularity. The formula for the scale factor,
leading to the bounce, is only valid for the dust-filled universe and hence
cannot be adequate for the hot stage in the early universe when the bounce
happens. So, the results of this paper are only qualitative in nature and must
be used to obtain initial values for the hot stage of the unverse when one
considers the evolution back in time.
| [
{
"created": "Fri, 16 Dec 2011 11:53:54 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Jan 2012 08:09:00 GMT",
"version": "v2"
}
] | 2015-06-03 | [
[
"Tretyakova",
"Darya",
""
],
[
"Shatskiy",
"Alexander",
""
],
[
"Novikov",
"Igor",
""
],
[
"Alexeyev",
"Stanislav",
""
]
] | We consider Brans-Dicke cosmology with cosmological constant with negative w parameter and an arbitrary (in general non-vanishing) scale factor at the Big Bang. The field equations describe the flat universe, current observational values for Hubble constant H and deceleration parameter q play a role of initial conditions. In order to solve field equations we adopt the approach of Uehara and Kim (1982). They considered only positive values of w, hence our solution is a new one and has not been described in their paper. Our main result is that unlike the standard cosmology the scale factor may not vanish in it's evolution back in time. In other words our model displays a cosmological bounce and avoids the initial singularity. The formula for the scale factor, leading to the bounce, is only valid for the dust-filled universe and hence cannot be adequate for the hot stage in the early universe when the bounce happens. So, the results of this paper are only qualitative in nature and must be used to obtain initial values for the hot stage of the unverse when one considers the evolution back in time. |
1901.00937 | David Anderson | David Anderson, Nicol\'as Yunes | Scalar Charges and Scaling Relations in Massless Scalar-Tensor Theories | 25 pages, 10 figures, Submitted to CQG | null | 10.1088/1361-6382/ab2eda | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The timing of binary pulsars allows us to place some of the tightest
constraints on modified theories of gravity. Perhaps some of the most
interesting and well-motivated extensions to General Relativity are
scalar-tensor theories, in which gravity is mediated by the metric tensor and a
scalar field. These theories predict large deviations from General Relativity
in the presence of neutron stars through a phenomenon known as scalarization.
Neutron stars in scalar-tensor theories develop scalar charges, which directly
enter the timing model for binary pulsars. In this paper, we calculate and
tabulate these scalar charges in two popular, massless scalar tensor theories
for a collection of neutron star equations of state that are compatible with
constraints placed by the recent, gravitational wave observations of a binary
neutron star coalescence. We then study these scalar charges and explore
analytic scaling relations that allow us to predict their value in a large
region of parameter space. Our results allow for the quick evaluation of the
scalar charge in a large region of scalar-tensor theory parameter space, which
has applications for gravitational wave tests of scalar-tensor theories, as
well as binary pulsar experiments.
| [
{
"created": "Thu, 3 Jan 2019 23:01:24 GMT",
"version": "v1"
}
] | 2019-09-04 | [
[
"Anderson",
"David",
""
],
[
"Yunes",
"Nicolás",
""
]
] | The timing of binary pulsars allows us to place some of the tightest constraints on modified theories of gravity. Perhaps some of the most interesting and well-motivated extensions to General Relativity are scalar-tensor theories, in which gravity is mediated by the metric tensor and a scalar field. These theories predict large deviations from General Relativity in the presence of neutron stars through a phenomenon known as scalarization. Neutron stars in scalar-tensor theories develop scalar charges, which directly enter the timing model for binary pulsars. In this paper, we calculate and tabulate these scalar charges in two popular, massless scalar tensor theories for a collection of neutron star equations of state that are compatible with constraints placed by the recent, gravitational wave observations of a binary neutron star coalescence. We then study these scalar charges and explore analytic scaling relations that allow us to predict their value in a large region of parameter space. Our results allow for the quick evaluation of the scalar charge in a large region of scalar-tensor theory parameter space, which has applications for gravitational wave tests of scalar-tensor theories, as well as binary pulsar experiments. |
1903.01502 | Mattia Scomparin | Mattia Scomparin and Simone Vazzoler | Damping of cosmological tensor modes in Horndeski theories after
GW170817 | 16 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This paper investigates the propagation of cosmological gravitational waves
interacting with free-streaming neutrinos within the context of Horndeski
theories of gravity constrained by the detection of GW170817. We apply the
theory of cosmological perturbations to explicitly derive the
Einstein-Boltzmann equation for the damped propagation of first-order
transverse traceless gravitational waves. In contrast to general relativity, we
argue that modified gravity can give rise to non-vanishing free-streaming
damping effects during the cosmological matter dominated era. We also provide
an analytic formula for the main multipole order with which modified gravity
and free-streaming neutrinos damp the variety of tensor correlation functions
of the cosmic microwave background.
| [
{
"created": "Mon, 4 Mar 2019 19:39:59 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Apr 2019 19:19:04 GMT",
"version": "v2"
}
] | 2019-04-19 | [
[
"Scomparin",
"Mattia",
""
],
[
"Vazzoler",
"Simone",
""
]
] | This paper investigates the propagation of cosmological gravitational waves interacting with free-streaming neutrinos within the context of Horndeski theories of gravity constrained by the detection of GW170817. We apply the theory of cosmological perturbations to explicitly derive the Einstein-Boltzmann equation for the damped propagation of first-order transverse traceless gravitational waves. In contrast to general relativity, we argue that modified gravity can give rise to non-vanishing free-streaming damping effects during the cosmological matter dominated era. We also provide an analytic formula for the main multipole order with which modified gravity and free-streaming neutrinos damp the variety of tensor correlation functions of the cosmic microwave background. |
1703.06215 | Yerko V\'asquez | P. A. Gonz\'alez, R. A. Konoplya, Yerko V\'asquez | Quasinormal modes of a scalar field in the Einstein--Gauss--Bonnet-AdS
black hole background: Perturbative and non-perturbative branches | 9 pages, 5 figures, matches version published in PRD | Phys. Rev. D 95, 124012 (2017) | 10.1103/PhysRevD.95.124012 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has recently been found that quasinormal modes of asymptotically anti-de
Sitter (AdS) black holes in theories with higher curvature corrections may help
to describe the regime of intermediate 't Hooft coupling in the dual field
theory. Here, we consider quasinormal modes of a scalar field in the background
of spherical Gauss--Bonnet--anti-de Sitter (AdS) black holes. In general, the
eigenvalues of wave equations are found here numerically, but at a fixed
Gauss-Bonnet constant $\alpha = R^2/2$ (where $R$ is the AdS radius), an exact
solution of the scalar field equation has been obtained. Remarkably, the purely
imaginary modes, which are usually appropriate only to some gravitational
perturbations, were found here even for a test scalar field. These purely
imaginary modes of the Einstein--Gauss--Bonnet theory do not have the
Einsteinian limits, because their damping rates grow, when $\alpha$ is
decreasing. Thus, these modes are nonperturbative in $\alpha$. The real
oscillation frequencies of the perturbative branch are linearly related to
their Schwarzschild-AdS limits $Re (\omega_{GB}) = Re (\omega_{SAdS}) (1+ K(D)
(\alpha/R^2))$, where $D$ is the number of spacetime dimensions. Comparison of
the analytical formula with the frequencies found by the shooting method allows
us to test the latter. In addition, we found exact solutions to the master
equations for gravitational perturbations at $\alpha=R^2/2$ and observed that
for the scalar type of gravitational perturbations an eikonal instability
develops.
| [
{
"created": "Fri, 17 Mar 2017 23:29:44 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Mar 2017 02:28:46 GMT",
"version": "v2"
},
{
"created": "Thu, 8 Jun 2017 00:36:34 GMT",
"version": "v3"
}
] | 2017-06-14 | [
[
"González",
"P. A.",
""
],
[
"Konoplya",
"R. A.",
""
],
[
"Vásquez",
"Yerko",
""
]
] | It has recently been found that quasinormal modes of asymptotically anti-de Sitter (AdS) black holes in theories with higher curvature corrections may help to describe the regime of intermediate 't Hooft coupling in the dual field theory. Here, we consider quasinormal modes of a scalar field in the background of spherical Gauss--Bonnet--anti-de Sitter (AdS) black holes. In general, the eigenvalues of wave equations are found here numerically, but at a fixed Gauss-Bonnet constant $\alpha = R^2/2$ (where $R$ is the AdS radius), an exact solution of the scalar field equation has been obtained. Remarkably, the purely imaginary modes, which are usually appropriate only to some gravitational perturbations, were found here even for a test scalar field. These purely imaginary modes of the Einstein--Gauss--Bonnet theory do not have the Einsteinian limits, because their damping rates grow, when $\alpha$ is decreasing. Thus, these modes are nonperturbative in $\alpha$. The real oscillation frequencies of the perturbative branch are linearly related to their Schwarzschild-AdS limits $Re (\omega_{GB}) = Re (\omega_{SAdS}) (1+ K(D) (\alpha/R^2))$, where $D$ is the number of spacetime dimensions. Comparison of the analytical formula with the frequencies found by the shooting method allows us to test the latter. In addition, we found exact solutions to the master equations for gravitational perturbations at $\alpha=R^2/2$ and observed that for the scalar type of gravitational perturbations an eikonal instability develops. |
2312.11692 | Bilel Hamil | R.Oubagha, B. Hamil, M. Merad, B. C. L\"utf\"uo\u{g}lu | Van der Waals black holes in rainbow gravity | 7 figures, 16 pages | Int. J. Mod. Phys. A 39(04), 2450023 (2024) | 10.1142/S0217751X24500234 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, Rajagapol et al presented an asymptotically AdS black hole metric
whose thermodynamics qualitatively mimics the behavior of the Van der Waals
fluid by treating the cosmological constant as a thermodynamic pressure. In
some studies in the literature, authors have discussed the effects of deformed
algebras such as generalized and extended uncertainty principles on the thermal
quantities of these black holes. In this manuscript, we considered another
deformation, the rainbow gravity formalism, and we investigated its impact on
the Van der Waal black hole thermodynamics. To this end, we first generated the
modified lapse and mass functions, and then we derived the modified thermal
quantities such as thermodynamic volume, Hawking temperature, entropy, and
specific heat functions. Finally, we explored the thermodynamics of a black
hole, which mimics the thermodynamics of an ideal gas, under the influence of
the rainbow gravity formalism.
| [
{
"created": "Mon, 18 Dec 2023 20:31:47 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Apr 2024 20:11:32 GMT",
"version": "v2"
}
] | 2024-04-12 | [
[
"Oubagha",
"R.",
""
],
[
"Hamil",
"B.",
""
],
[
"Merad",
"M.",
""
],
[
"Lütfüoğlu",
"B. C.",
""
]
] | Recently, Rajagapol et al presented an asymptotically AdS black hole metric whose thermodynamics qualitatively mimics the behavior of the Van der Waals fluid by treating the cosmological constant as a thermodynamic pressure. In some studies in the literature, authors have discussed the effects of deformed algebras such as generalized and extended uncertainty principles on the thermal quantities of these black holes. In this manuscript, we considered another deformation, the rainbow gravity formalism, and we investigated its impact on the Van der Waal black hole thermodynamics. To this end, we first generated the modified lapse and mass functions, and then we derived the modified thermal quantities such as thermodynamic volume, Hawking temperature, entropy, and specific heat functions. Finally, we explored the thermodynamics of a black hole, which mimics the thermodynamics of an ideal gas, under the influence of the rainbow gravity formalism. |
2204.09855 | Jonathan Luk | Jonathan Luk and Georgios Moschidis | On the non-existence of trapped surfaces under low-regularity bounds | 20 pages. 2 figures; minor corrections; published version | null | null | null | gr-qc math.AP math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The emergence of trapped surfaces in solutions to the Einstein field
equations is intimately tied to the well-posedness properties of the
corresponding Cauchy problem in the low regularity regime. In this paper, we
study the question of existence of trapped surfaces already at the level of the
initial hypersurface when the scale invariant size of the Cauchy data is
assumed to be bounded. Our main theorem states that no trapped surfaces can
exist initially when the Cauchy data are close to the data induced on a
spacelike hypersurface of Minkowski spacetime (not necessarily a flat
hyperplane) in the Besov $B^{3/2}_{2,1}$ norm. We also discuss the question of
extending the above result to the case when merely smallness in $H^{3/2}$ is
assumed.
| [
{
"created": "Thu, 21 Apr 2022 02:48:52 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Jun 2023 22:35:12 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Jun 2024 20:06:43 GMT",
"version": "v3"
}
] | 2024-06-21 | [
[
"Luk",
"Jonathan",
""
],
[
"Moschidis",
"Georgios",
""
]
] | The emergence of trapped surfaces in solutions to the Einstein field equations is intimately tied to the well-posedness properties of the corresponding Cauchy problem in the low regularity regime. In this paper, we study the question of existence of trapped surfaces already at the level of the initial hypersurface when the scale invariant size of the Cauchy data is assumed to be bounded. Our main theorem states that no trapped surfaces can exist initially when the Cauchy data are close to the data induced on a spacelike hypersurface of Minkowski spacetime (not necessarily a flat hyperplane) in the Besov $B^{3/2}_{2,1}$ norm. We also discuss the question of extending the above result to the case when merely smallness in $H^{3/2}$ is assumed. |
2105.13886 | Antonio Pereira Jr | Gustavo P. de Brito, Oleg Melichev, Roberto Percacci, Antonio D.
Pereira | Can quantum fluctuations differentiate between standard and unimodular
gravity? | 14 pages + appendices and references | null | 10.1007/JHEP12(2021)090 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We formally prove the existence of a quantization procedure that makes the
path integral of a general diffeomorphism-invariant theory of gravity, with
fixed total spacetime volume, equivalent to that of its unimodular version.
This is achieved by means of a partial gauge fixing of diffeomorphisms together
with a careful definition of the unimodular measure. The statement holds also
in the presence of matter. As an explicit example, we consider scalar-tensor
theories and compute the corresponding logarithmic divergences in both
settings. In spite of significant differences in the coupling of the scalar
field to gravity, the results are equivalent for all couplings, including
non-minimal ones.
| [
{
"created": "Thu, 27 May 2021 13:49:17 GMT",
"version": "v1"
}
] | 2022-01-05 | [
[
"de Brito",
"Gustavo P.",
""
],
[
"Melichev",
"Oleg",
""
],
[
"Percacci",
"Roberto",
""
],
[
"Pereira",
"Antonio D.",
""
]
] | We formally prove the existence of a quantization procedure that makes the path integral of a general diffeomorphism-invariant theory of gravity, with fixed total spacetime volume, equivalent to that of its unimodular version. This is achieved by means of a partial gauge fixing of diffeomorphisms together with a careful definition of the unimodular measure. The statement holds also in the presence of matter. As an explicit example, we consider scalar-tensor theories and compute the corresponding logarithmic divergences in both settings. In spite of significant differences in the coupling of the scalar field to gravity, the results are equivalent for all couplings, including non-minimal ones. |
1002.4120 | Nima Khosravi | Nima Khosravi | Self-Relative (or Machian) Information: Entropy-Area Relation | null | Phys.Lett.B695:343-349,2011 | 10.1016/j.physletb.2010.11.008 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The entropy-area relation of black holes is one of the important results of
theoretical physics. It is one of the few relations that is used to test
theories of quantum gravity in the absence of any experimental evidence. It
states that $4 \times \ell_P^2$ is the fundamental area that holds \textit{one}
bit of information. Consequently, a question arises: why $4 \times \ell_P^2$
and not $1 \times \ell_P^2$ is the fundamental holder of \textit{one} bit of
information? In any case it seems the latter choice is more natural. We show
that this question can be answered with a more explicit counting of the
independent states of a black hole. To do this we introduce a method of
counting which we name self-relative information. It says that a bit alone does
not have any information unless it is considered near other bits. Utilizing
this approach we obtain the correct entropy-area relation for black holes with
$1 \times \ell_P^2$ as the fundamental holder of \textit{one} bit of
information. This method also predicts, naturally, the existence of logarithmic
corrections to the entropy-area relation.
| [
{
"created": "Mon, 22 Feb 2010 14:08:45 GMT",
"version": "v1"
}
] | 2011-01-27 | [
[
"Khosravi",
"Nima",
""
]
] | The entropy-area relation of black holes is one of the important results of theoretical physics. It is one of the few relations that is used to test theories of quantum gravity in the absence of any experimental evidence. It states that $4 \times \ell_P^2$ is the fundamental area that holds \textit{one} bit of information. Consequently, a question arises: why $4 \times \ell_P^2$ and not $1 \times \ell_P^2$ is the fundamental holder of \textit{one} bit of information? In any case it seems the latter choice is more natural. We show that this question can be answered with a more explicit counting of the independent states of a black hole. To do this we introduce a method of counting which we name self-relative information. It says that a bit alone does not have any information unless it is considered near other bits. Utilizing this approach we obtain the correct entropy-area relation for black holes with $1 \times \ell_P^2$ as the fundamental holder of \textit{one} bit of information. This method also predicts, naturally, the existence of logarithmic corrections to the entropy-area relation. |
1705.05977 | Jiliang Jing | Xiongjun Fang, Xiaokai He, Jiliang Jing | Consistency between dynamical and thermodynamical stabilities for
perfect fluid in $f(R)$ theories | 18pages | Eur. Phys. J. C (2018) 78:623 | 10.1140/epjc/s10052-018-6053-0 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the stability criterions for perfect fluid in $f(R)$ theories
which is an important generalization of general relativity. Firstly, using
Wald's general variation principle, we recast Seifert's work and obtain the
dynamical stability criterion. Then using our generalized thermodynamical
criterion, we obtain the concrete expressions of the criterion. We show that
the dynamical stability criterion is exactly the same as the thermodynamical
stability criterion. This result suggests that there is an inherent connection
between the thermodynamics and gravity in $f(R)$ theories. It should be pointed
out that using the thermodynamical method to determine the stability for
perfect fluid is simpler and more directly than the dynamical method.
| [
{
"created": "Wed, 17 May 2017 01:49:10 GMT",
"version": "v1"
},
{
"created": "Wed, 24 May 2017 01:16:42 GMT",
"version": "v2"
}
] | 2018-08-29 | [
[
"Fang",
"Xiongjun",
""
],
[
"He",
"Xiaokai",
""
],
[
"Jing",
"Jiliang",
""
]
] | We investigate the stability criterions for perfect fluid in $f(R)$ theories which is an important generalization of general relativity. Firstly, using Wald's general variation principle, we recast Seifert's work and obtain the dynamical stability criterion. Then using our generalized thermodynamical criterion, we obtain the concrete expressions of the criterion. We show that the dynamical stability criterion is exactly the same as the thermodynamical stability criterion. This result suggests that there is an inherent connection between the thermodynamics and gravity in $f(R)$ theories. It should be pointed out that using the thermodynamical method to determine the stability for perfect fluid is simpler and more directly than the dynamical method. |
2303.04076 | Nasr Ahmed | Nasr Ahmed and Tarek M. Kamel | Investigating the hyperbolic and hybrid scalar field cosmologies with
varying cosmological constant in $f(R,T)$ gravity | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This paper investigated two scalar field cosmological models in $f(R,T)$
gravity with cosmic transit and varying cosmological constant $\Lambda(t)$.The
cosmological constant tends to have a tiny positive value in the current
epoch.The scalar field pressure $p_{\phi}$ shows a sign reversal for a normal
scalar field. For the phantom field, the scalar potential $V(\phi)$ is negative
and the energy density $\rho_{\phi}=E_k+V$ takes negative values when the
equation of state parameter $\omega_{\phi}$ is less than $-1$. While the weak
energy condition WEC implies that the total energy density
$\rho=\sum_i\rho_i\geq 0$, we still can have a negative $\rho$ term as long as
the total $\rho$ is positive. In the current work we argue that the WEC,
$\rho=\sum_i \rho_i \geq 0$ and $p_i+\rho_i \geq 0$, is not violated but with
an instability for the second model at late-times. For a scalar field $\phi$,
The condition $\rho_{\phi}+p_{\phi}=\rho_{\phi} (1+\omega_{\phi})=2E_k\geq 0$
allows for $\rho_{\phi}<0$ if $\omega_{\phi}<-1$. The causality and energy
conditions have been discussed for both models.
The cosmology in both models was studied using a given function $a(t)$
derived from the desired cosmic behavior, which is the opposite of the
traditional view.
| [
{
"created": "Sat, 4 Mar 2023 07:55:15 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Mar 2023 10:59:28 GMT",
"version": "v2"
},
{
"created": "Mon, 21 Aug 2023 15:45:05 GMT",
"version": "v3"
},
{
"created": "Sun, 29 Oct 2023 16:27:35 GMT",
"version": "v4"
},
{
"cre... | 2024-07-12 | [
[
"Ahmed",
"Nasr",
""
],
[
"Kamel",
"Tarek M.",
""
]
] | This paper investigated two scalar field cosmological models in $f(R,T)$ gravity with cosmic transit and varying cosmological constant $\Lambda(t)$.The cosmological constant tends to have a tiny positive value in the current epoch.The scalar field pressure $p_{\phi}$ shows a sign reversal for a normal scalar field. For the phantom field, the scalar potential $V(\phi)$ is negative and the energy density $\rho_{\phi}=E_k+V$ takes negative values when the equation of state parameter $\omega_{\phi}$ is less than $-1$. While the weak energy condition WEC implies that the total energy density $\rho=\sum_i\rho_i\geq 0$, we still can have a negative $\rho$ term as long as the total $\rho$ is positive. In the current work we argue that the WEC, $\rho=\sum_i \rho_i \geq 0$ and $p_i+\rho_i \geq 0$, is not violated but with an instability for the second model at late-times. For a scalar field $\phi$, The condition $\rho_{\phi}+p_{\phi}=\rho_{\phi} (1+\omega_{\phi})=2E_k\geq 0$ allows for $\rho_{\phi}<0$ if $\omega_{\phi}<-1$. The causality and energy conditions have been discussed for both models. The cosmology in both models was studied using a given function $a(t)$ derived from the desired cosmic behavior, which is the opposite of the traditional view. |
1505.03034 | Saibal Ray | Dibyendu Shee, Farook Rahaman, B.K. Guha and Saibal Ray | Anisotropic stars with non-static conformal symmetry | 18 pages, 14 figures | null | 10.1007/s10509-016-2753-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have proposed a model for relativistic compact star with anisotropy and
analytically obtained exact spherically symmetric solutions describing the
interior of the dense star admitting non-static conformal symmetry. Several
features of the solutions including drawbacks of the model have been explored
and discussed. For this purpose we have provided the energy conditions,
TOV-equations and other physical requirements and thus thoroughly investigated
stability, mass-radius relation and surface redshift of the model. It is
observed that most of the features are well matched with the compact stars,
like quark/strange stars.
| [
{
"created": "Mon, 11 May 2015 12:05:14 GMT",
"version": "v1"
}
] | 2016-04-27 | [
[
"Shee",
"Dibyendu",
""
],
[
"Rahaman",
"Farook",
""
],
[
"Guha",
"B. K.",
""
],
[
"Ray",
"Saibal",
""
]
] | We have proposed a model for relativistic compact star with anisotropy and analytically obtained exact spherically symmetric solutions describing the interior of the dense star admitting non-static conformal symmetry. Several features of the solutions including drawbacks of the model have been explored and discussed. For this purpose we have provided the energy conditions, TOV-equations and other physical requirements and thus thoroughly investigated stability, mass-radius relation and surface redshift of the model. It is observed that most of the features are well matched with the compact stars, like quark/strange stars. |
1403.3335 | Markus B. Fr\"ob | Markus B. Fr\"ob, Albert Roura, Enric Verdaguer | Riemann correlator in de Sitter including loop corrections from
conformal fields | 44 pages, 2 figures, matches published version | JCAP 07 (2014) 048 | 10.1088/1475-7516/2014/07/048 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Riemann correlator with appropriately raised indices characterizes in a
gauge-invariant way the quantum metric fluctuations around de Sitter spacetime
including loop corrections from matter fields. Specializing to conformal fields
and employing a method that selects the de Sitter-invariant vacuum in the
Poincar\'e patch, we obtain the exact result for the Riemann correlator through
order $H^4/m_\mathrm{p}^4$. The result is expressed in a manifestly de
Sitter-invariant form in terms of maximally symmetric bitensors. Its behavior
for both short and long distances (sub- and superhorizon scales) is analyzed in
detail. Furthermore, by carefully taking the flat-space limit, the explicit
result for the Riemann correlator for metric fluctuations around Minkowki
spacetime is also obtained. Although the main focus is on free scalar fields
(our calculation corresponds then to one-loop order in the matter fields), the
result for general conformal field theories is also derived.
| [
{
"created": "Thu, 13 Mar 2014 17:27:01 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Jul 2014 15:57:51 GMT",
"version": "v2"
}
] | 2014-08-01 | [
[
"Fröb",
"Markus B.",
""
],
[
"Roura",
"Albert",
""
],
[
"Verdaguer",
"Enric",
""
]
] | The Riemann correlator with appropriately raised indices characterizes in a gauge-invariant way the quantum metric fluctuations around de Sitter spacetime including loop corrections from matter fields. Specializing to conformal fields and employing a method that selects the de Sitter-invariant vacuum in the Poincar\'e patch, we obtain the exact result for the Riemann correlator through order $H^4/m_\mathrm{p}^4$. The result is expressed in a manifestly de Sitter-invariant form in terms of maximally symmetric bitensors. Its behavior for both short and long distances (sub- and superhorizon scales) is analyzed in detail. Furthermore, by carefully taking the flat-space limit, the explicit result for the Riemann correlator for metric fluctuations around Minkowki spacetime is also obtained. Although the main focus is on free scalar fields (our calculation corresponds then to one-loop order in the matter fields), the result for general conformal field theories is also derived. |
1405.6702 | Behrooz Malekolkalami | Behrooz Malekolkalami, Awat Lotfi | Intrinsic Gravitomagnetism and Non-commutative effects | 9 pages, 1 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The two equations of motion for a test particle are compared with each other.
One is in the Non commutative space involving a static rigid sphere (as a
source of central force) and the other is in the usual space involving a slowly
stationary rotating sphere. The comparison tells us that, the effects of Non
commutativity is analogous to gravitational effects of rotation of the sphere.
That is, non commutativity imitates the effects of the intrinsic
gravitomagnetic field of the sphere.
| [
{
"created": "Sat, 24 May 2014 18:14:27 GMT",
"version": "v1"
}
] | 2014-05-28 | [
[
"Malekolkalami",
"Behrooz",
""
],
[
"Lotfi",
"Awat",
""
]
] | The two equations of motion for a test particle are compared with each other. One is in the Non commutative space involving a static rigid sphere (as a source of central force) and the other is in the usual space involving a slowly stationary rotating sphere. The comparison tells us that, the effects of Non commutativity is analogous to gravitational effects of rotation of the sphere. That is, non commutativity imitates the effects of the intrinsic gravitomagnetic field of the sphere. |
gr-qc/0410125 | Viqar Husain | Viqar Husain and Oliver Winkler | Quantum resolution of black hole singularities | 5 pages, version to appear in CQG | Class.Quant.Grav.22:L127-L134,2005 | 10.1088/0264-9381/22/21/L01 | null | gr-qc hep-th | null | We study the classical and quantum theory of spherically symmetric spacetimes
with scalar field coupling in general relativity. We utilise the canonical
formalism of geometrodynamics adapted to the Painleve-Gullstrand coordinates,
and present a new quantisation of the resulting field theory. We give an
explicit construction of operators that capture curvature properties of the
spacetime and use these to show that the black hole curvature singularity is
avoided in the quantum theory.
| [
{
"created": "Tue, 26 Oct 2004 15:33:34 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Jan 2005 14:57:45 GMT",
"version": "v2"
},
{
"created": "Tue, 27 Sep 2005 18:10:52 GMT",
"version": "v3"
}
] | 2010-11-19 | [
[
"Husain",
"Viqar",
""
],
[
"Winkler",
"Oliver",
""
]
] | We study the classical and quantum theory of spherically symmetric spacetimes with scalar field coupling in general relativity. We utilise the canonical formalism of geometrodynamics adapted to the Painleve-Gullstrand coordinates, and present a new quantisation of the resulting field theory. We give an explicit construction of operators that capture curvature properties of the spacetime and use these to show that the black hole curvature singularity is avoided in the quantum theory. |
0903.1134 | David Brizuela | David Brizuela, Jose M. Martin-Garcia, Manuel Tiglio | A complete gauge-invariant formalism for arbitrary second-order
perturbations of a Schwarzschild black hole | 14 pages | Phys.Rev.D80:024021,2009 | 10.1103/PhysRevD.80.024021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using recently developed efficient symbolic manipulations tools, we present a
general gauge-invariant formalism to study arbitrary radiative $(l\geq 2)$
second-order perturbations of a Schwarzschild black hole. In particular, we
construct the second order Zerilli and Regge-Wheeler equations under the
presence of any two first-order modes, reconstruct the perturbed metric in
terms of the master scalars, and compute the radiated energy at null infinity.
The results of this paper enable systematic studies of generic second order
perturbations of the Schwarzschild spacetime. In particular, studies of
mode-mode coupling and non-linear effects in gravitational radiation, the
second-order stability of the Schwarzschild spacetime, or the geometry of the
black hole horizon.
| [
{
"created": "Fri, 6 Mar 2009 11:40:30 GMT",
"version": "v1"
}
] | 2009-09-02 | [
[
"Brizuela",
"David",
""
],
[
"Martin-Garcia",
"Jose M.",
""
],
[
"Tiglio",
"Manuel",
""
]
] | Using recently developed efficient symbolic manipulations tools, we present a general gauge-invariant formalism to study arbitrary radiative $(l\geq 2)$ second-order perturbations of a Schwarzschild black hole. In particular, we construct the second order Zerilli and Regge-Wheeler equations under the presence of any two first-order modes, reconstruct the perturbed metric in terms of the master scalars, and compute the radiated energy at null infinity. The results of this paper enable systematic studies of generic second order perturbations of the Schwarzschild spacetime. In particular, studies of mode-mode coupling and non-linear effects in gravitational radiation, the second-order stability of the Schwarzschild spacetime, or the geometry of the black hole horizon. |
1910.03616 | Marco de Cesare | Marco de Cesare, Edward Wilson-Ewing | A generalized Kasner transition for bouncing Bianchi I models in
modified gravity theories | 28 pages, 2 figures; v2: references added; accepted for publication
in JCAP | JCAP12(2019)039 | 10.1088/1475-7516/2019/12/039 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive transition rules for Kasner exponents in bouncing Bianchi I models
with generic perfect fluid matter fields for a broad class of modified gravity
theories where cosmological singularities are resolved and replaced by a
non-singular bounce. This is a generalization of results obtained previously in
limiting curvature mimetic gravity and loop quantum cosmology. A geometric
interpretation is provided for the transition rule as a linear map in the
Kasner plane. We show that the general evolution of anisotropies in a Bianchi I
universe -- including during the bounce phase -- is equivalent to the motion of
a point particle on a sphere, where the sphere is the one-point
compactification of the Kasner plane. In addition, we study the evolution of
anisotropies in a large family of bouncing Bianchi I space-times. We also
present a novel explicit solution to the Einstein equations for a Bianchi I
universe with ekpyrotic matter with a constant equation of state $\omega=3$.
| [
{
"created": "Tue, 8 Oct 2019 18:07:52 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Dec 2019 15:02:48 GMT",
"version": "v2"
}
] | 2019-12-12 | [
[
"de Cesare",
"Marco",
""
],
[
"Wilson-Ewing",
"Edward",
""
]
] | We derive transition rules for Kasner exponents in bouncing Bianchi I models with generic perfect fluid matter fields for a broad class of modified gravity theories where cosmological singularities are resolved and replaced by a non-singular bounce. This is a generalization of results obtained previously in limiting curvature mimetic gravity and loop quantum cosmology. A geometric interpretation is provided for the transition rule as a linear map in the Kasner plane. We show that the general evolution of anisotropies in a Bianchi I universe -- including during the bounce phase -- is equivalent to the motion of a point particle on a sphere, where the sphere is the one-point compactification of the Kasner plane. In addition, we study the evolution of anisotropies in a large family of bouncing Bianchi I space-times. We also present a novel explicit solution to the Einstein equations for a Bianchi I universe with ekpyrotic matter with a constant equation of state $\omega=3$. |
1011.3467 | Bijunath Patla | Robert D. Reasenberg, Enrico C. Lorenzini, Biju R. Patla, James D.
Phillips, Eugeniu E. Popescu, Emanuele Rocco, and Rajesh Thapa | A quick test of the WEP enabled by a sounding rocket | 10 pages, 2 figures, To be submitted to: Classical and Quantum
Gravity | Class.Quant.Grav.28:094014,2011 | 10.1088/0264-9381/28/9/094014 | null | gr-qc | http://creativecommons.org/licenses/publicdomain/ | We describe SR-POEM, a Galilean test of the weak equivalence principle, which
is to be conducted during the free fall portion of a sounding rocket flight.
This test of a single pair of substances is aimed at a measurement uncertainty
of \sigma(\eta) < 10-16 after averaging the results of eight separate drops,
each of 40 s duration. The weak equivalence principle measurement is made with
a set of four laser gauges that are expected to achieve 0.1 pm/\sqrt{Hz}. We
address the two sources of systematic error that are currently of greatest
concern, magnetic force and electrostatic (patch effect) force on the test mass
assemblies. The discovery of a violation (\eta \not= 0) would have profound
implications for physics, astrophysics and cosmology.
| [
{
"created": "Mon, 15 Nov 2010 18:09:19 GMT",
"version": "v1"
}
] | 2011-05-25 | [
[
"Reasenberg",
"Robert D.",
""
],
[
"Lorenzini",
"Enrico C.",
""
],
[
"Patla",
"Biju R.",
""
],
[
"Phillips",
"James D.",
""
],
[
"Popescu",
"Eugeniu E.",
""
],
[
"Rocco",
"Emanuele",
""
],
[
"Thapa",
"Rajesh",
... | We describe SR-POEM, a Galilean test of the weak equivalence principle, which is to be conducted during the free fall portion of a sounding rocket flight. This test of a single pair of substances is aimed at a measurement uncertainty of \sigma(\eta) < 10-16 after averaging the results of eight separate drops, each of 40 s duration. The weak equivalence principle measurement is made with a set of four laser gauges that are expected to achieve 0.1 pm/\sqrt{Hz}. We address the two sources of systematic error that are currently of greatest concern, magnetic force and electrostatic (patch effect) force on the test mass assemblies. The discovery of a violation (\eta \not= 0) would have profound implications for physics, astrophysics and cosmology. |
2203.14468 | Dana Jones | Dana Jones, Ling Sun, Julian Carlin, Liam Dunn, Meg Millhouse, Hannah
Middleton, Patrick Meyers, Patrick Clearwater, Deeksha Beniwal, Lucy Strang,
Andr\'es Vargas, Andrew Melatos | Validating continuous gravitational-wave candidates from a semicoherent
search using Doppler modulation and an effective point spread function | 24 pages, 15 figures | null | 10.1103/PhysRevD.106.123011 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following up large numbers of candidates in continuous gravitational wave
searches presents a challenge, particularly in regard to computational power
and the time required to manually scrutinize each of the candidates. It is
important to design and test good follow-up procedures that are safe (i.e.,
minimize false dismissals) and computationally efficient across many search
configurations. We investigate two follow-up procedures, or "vetoes," both of
which exploit the Doppler modulation predicted in astrophysical signals. In
particular, we introduce the concept of using an effective point spread
function as part of our veto criteria. We take advantage of a well-established
semicoherent search algorithm based on a hidden Markov model to study various
search configurations and to generalize the veto criteria by considering the
overall veto performance in terms of efficiency and safety. The results can
serve as a guideline for follow-up studies in future continuous gravitational
wave searches using a hidden Markov model algorithm. The results also apply
qualitatively to other semicoherent search algorithms.
| [
{
"created": "Mon, 28 Mar 2022 03:16:47 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Nov 2022 00:18:18 GMT",
"version": "v2"
}
] | 2022-12-28 | [
[
"Jones",
"Dana",
""
],
[
"Sun",
"Ling",
""
],
[
"Carlin",
"Julian",
""
],
[
"Dunn",
"Liam",
""
],
[
"Millhouse",
"Meg",
""
],
[
"Middleton",
"Hannah",
""
],
[
"Meyers",
"Patrick",
""
],
[
"Clearwate... | Following up large numbers of candidates in continuous gravitational wave searches presents a challenge, particularly in regard to computational power and the time required to manually scrutinize each of the candidates. It is important to design and test good follow-up procedures that are safe (i.e., minimize false dismissals) and computationally efficient across many search configurations. We investigate two follow-up procedures, or "vetoes," both of which exploit the Doppler modulation predicted in astrophysical signals. In particular, we introduce the concept of using an effective point spread function as part of our veto criteria. We take advantage of a well-established semicoherent search algorithm based on a hidden Markov model to study various search configurations and to generalize the veto criteria by considering the overall veto performance in terms of efficiency and safety. The results can serve as a guideline for follow-up studies in future continuous gravitational wave searches using a hidden Markov model algorithm. The results also apply qualitatively to other semicoherent search algorithms. |
gr-qc/0410089 | Edward Glass | E.N. Glass and J.P. Krisch | Spinning Up Asymptotically Flat Spacetimes | Class. Quantum Grav. (to appear) | Class.Quant.Grav.21:5543-5554,2004 | 10.1088/0264-9381/21/23/015 | null | gr-qc | null | We present a method for constructing stationary, asymptotically flat,
rotating solutions of Einstein's field equations. One of the spun-up solutions
has quasilocal mass but no global mass. It has an ergosphere but no event
horizon. The angular momentum is constant everywhere beyond the ergosphere. The
energy-momentum content of this solution can be interpreted as a rotating
string-fluid.
| [
{
"created": "Tue, 19 Oct 2004 03:13:49 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Glass",
"E. N.",
""
],
[
"Krisch",
"J. P.",
""
]
] | We present a method for constructing stationary, asymptotically flat, rotating solutions of Einstein's field equations. One of the spun-up solutions has quasilocal mass but no global mass. It has an ergosphere but no event horizon. The angular momentum is constant everywhere beyond the ergosphere. The energy-momentum content of this solution can be interpreted as a rotating string-fluid. |
1301.1658 | Aur\'elien Hees | A. Hees, B. Lamine, S. Reynaud, M.-T. Jaekel, C. Le Poncin-Lafitte, V.
Lainey, A. F\"uzfa, J.-M. Courty, V. Dehant, P. Wolf | Simulations of Solar System observations in alternative theories of
gravity | 3 pages, 1 figure, proceedings of 13th Marcel Grossmann Meeting, v2:
minor changes | The Thirteenth Marcel Grossmann Meeting (World Scientific, 2015)
pp. 2357-2359 | 10.1142/9789814623995_0440 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this communication, we focus on the possibility to test General Relativity
(GR) with radioscience experiments. We present simulations of observables
performed in alternative theories of gravity using a software that simulates
Range/Doppler signals directly from the space time metric. This software allows
one to get the order of magnitude and the signature of the modifications
induced by an alternative theory of gravity on radioscience signals. As
examples, we present some simulations for the Cassini mission in
Post-Einsteinian gravity (PEG) and with Standard Model Extension (SME).
| [
{
"created": "Tue, 8 Jan 2013 20:11:21 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Jan 2013 16:29:43 GMT",
"version": "v2"
},
{
"created": "Wed, 27 Feb 2013 18:18:30 GMT",
"version": "v3"
}
] | 2015-03-11 | [
[
"Hees",
"A.",
""
],
[
"Lamine",
"B.",
""
],
[
"Reynaud",
"S.",
""
],
[
"Jaekel",
"M. -T.",
""
],
[
"Poncin-Lafitte",
"C. Le",
""
],
[
"Lainey",
"V.",
""
],
[
"Füzfa",
"A.",
""
],
[
"Courty",
"J.... | In this communication, we focus on the possibility to test General Relativity (GR) with radioscience experiments. We present simulations of observables performed in alternative theories of gravity using a software that simulates Range/Doppler signals directly from the space time metric. This software allows one to get the order of magnitude and the signature of the modifications induced by an alternative theory of gravity on radioscience signals. As examples, we present some simulations for the Cassini mission in Post-Einsteinian gravity (PEG) and with Standard Model Extension (SME). |
2205.11727 | Carlos Albertho Benavides-Gallego | Farrux Abdulxamidov, Carlos A. Benavides-Gallego, Wen-Biao Han, Javlon
Rayimbaev, Ahmadjon Abdujabbarov | Spinning test particle motion around a rotating wormhole | 20 pages, 16 figures | Phys.Rev.D 106 (2022) 2, 024012 | 10.1103/PhysRevD.106.024012 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this work, we investigated the motion of spinning test particles around a
rotating wormhole, extending, in this way, the previous work of
Benavides-Gallego et al. in [Phys. Rev. D 101, no.12, 124024] to the general
case. Using the Mathisson-Papapetrous-Dixon equations, we study the effective
potential, circular orbits, and the innermost stable circular orbit (ISCO) of
spinning test particles. We found that both the particle and wormhole spins
affect the location of the ISCO significantly. On the other hand, Similar to
the non-rotating case, we also found two possible configurations in the
effective potential: plus and minus. Furthermore, the minimum value of the
effective potential is not at the throat due to its spin, in contrast to the
motion of the non-spinning test particles in a non-rotating wormhole, where the
effective potential is symmetric, and its minimum value is at the throat. In
the case of the ISCO, we found that it increases as the spin of the wormhole a
increases, in contrast to black holes where the presence of spin decreases the
value of the ISCO. Finally, since the dynamical four-momentum and kinematical
four-velocity of the spinning particle are not always parallel, we consider the
superluminal bound, finding that the allowed values of s change as the
wormhole's spin a increases.
| [
{
"created": "Tue, 24 May 2022 02:27:53 GMT",
"version": "v1"
}
] | 2022-07-13 | [
[
"Abdulxamidov",
"Farrux",
""
],
[
"Benavides-Gallego",
"Carlos A.",
""
],
[
"Han",
"Wen-Biao",
""
],
[
"Rayimbaev",
"Javlon",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
]
] | In this work, we investigated the motion of spinning test particles around a rotating wormhole, extending, in this way, the previous work of Benavides-Gallego et al. in [Phys. Rev. D 101, no.12, 124024] to the general case. Using the Mathisson-Papapetrous-Dixon equations, we study the effective potential, circular orbits, and the innermost stable circular orbit (ISCO) of spinning test particles. We found that both the particle and wormhole spins affect the location of the ISCO significantly. On the other hand, Similar to the non-rotating case, we also found two possible configurations in the effective potential: plus and minus. Furthermore, the minimum value of the effective potential is not at the throat due to its spin, in contrast to the motion of the non-spinning test particles in a non-rotating wormhole, where the effective potential is symmetric, and its minimum value is at the throat. In the case of the ISCO, we found that it increases as the spin of the wormhole a increases, in contrast to black holes where the presence of spin decreases the value of the ISCO. Finally, since the dynamical four-momentum and kinematical four-velocity of the spinning particle are not always parallel, we consider the superluminal bound, finding that the allowed values of s change as the wormhole's spin a increases. |
2305.11416 | Dnyaneshwar Tadas | A. Y. Shaikh, D. P. Tadas, S. D. Katore | An Oscillating Holographic Dark Energy in $f(R)$ Gravity | 14 Pages, 10 Figures | Bulg. J. Phys. vol.50 no.2 (2023), pp. 190-205 | 10.55318/bgjp.2023.50.2.190 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article, we investigated a Locally Rotationally Symmetric (LRS)
Bianchi-II cosmological model with matter and Holographic Dark Energy (HDE) in
the context of $f(R)$ theory of gravity. In order to find exact solutions to
the field equations, we assumed that the Shear scalar $(\sigma)$ is
proportional to Expansion scalar $(\theta)$. For HDE, it is observed that the
Equation of state (EoS) parameter $ \omega_{\Lambda} $ has an oscillating
nature and lies in $[-0.778,\, 1.016].$ Also, we have studied the validity of
energy conditions and shows that Null Energy Condition (NEC) is violated near
the bouncing points. Moreover, we analysed the physical and geometrical aspects
of the investigated model.
Keywords: Holographic dark energy, LRS Bianchi-II, $f(R)$ gravity.
| [
{
"created": "Fri, 19 May 2023 03:58:18 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Jun 2023 02:32:14 GMT",
"version": "v2"
}
] | 2023-07-03 | [
[
"Shaikh",
"A. Y.",
""
],
[
"Tadas",
"D. P.",
""
],
[
"Katore",
"S. D.",
""
]
] | In this article, we investigated a Locally Rotationally Symmetric (LRS) Bianchi-II cosmological model with matter and Holographic Dark Energy (HDE) in the context of $f(R)$ theory of gravity. In order to find exact solutions to the field equations, we assumed that the Shear scalar $(\sigma)$ is proportional to Expansion scalar $(\theta)$. For HDE, it is observed that the Equation of state (EoS) parameter $ \omega_{\Lambda} $ has an oscillating nature and lies in $[-0.778,\, 1.016].$ Also, we have studied the validity of energy conditions and shows that Null Energy Condition (NEC) is violated near the bouncing points. Moreover, we analysed the physical and geometrical aspects of the investigated model. Keywords: Holographic dark energy, LRS Bianchi-II, $f(R)$ gravity. |
gr-qc/9705028 | Keisuke Taniguchi | Masaru Shibata and Keisuke Taniguchi | Solving the Darwin problem in the first post-Newtonian approximation of
general relativity: compressible model | 28 pages, revtex, 9 figures(eps), accepted for publication in Phys.
Rev. D | Phys.Rev. D56 (1997) 811-825 | 10.1103/PhysRevD.56.811 | OU-TAP 58, KUNS 1434 | gr-qc | null | Using the ellipsoidal model for the density configuration, we calculate the
equilibrium sequence of the corotating binary stars of the polytropic equation
of state in the first post-Newtonian approximation of general relativity. After
we calibrate this model by comparing with previous numerical results, we
perform the stability analysis by calculating the energy and the angular
momentum of the system as a function of the orbital separation. We find that
the orbital angular velocity at the energy and/or momentum minimum increases
with the increase of the compactness of each star, and this fact holds
irrespective of the polytropic index. These features agree with those in
previous numerical works. We also show that due to the influence of the tidal
field from the companion star, the central density of each star slightly
decreases.
| [
{
"created": "Tue, 13 May 1997 10:55:30 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Shibata",
"Masaru",
""
],
[
"Taniguchi",
"Keisuke",
""
]
] | Using the ellipsoidal model for the density configuration, we calculate the equilibrium sequence of the corotating binary stars of the polytropic equation of state in the first post-Newtonian approximation of general relativity. After we calibrate this model by comparing with previous numerical results, we perform the stability analysis by calculating the energy and the angular momentum of the system as a function of the orbital separation. We find that the orbital angular velocity at the energy and/or momentum minimum increases with the increase of the compactness of each star, and this fact holds irrespective of the polytropic index. These features agree with those in previous numerical works. We also show that due to the influence of the tidal field from the companion star, the central density of each star slightly decreases. |
1706.00678 | Qing Yang | Qing Yang, Li-Wei Ji, Bin Hu, Zhou-Jian Cao, Rong-Gen Cai | An axion-like scalar field environment effect on binary black hole
merger | 14 pages, 12 figures | null | 10.1088/1674-4527/18/6/65 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Environment, such as the accretion disk, could modify the signal of the
gravitational wave from the astrophysical black hole binaries. In this article,
we model the matter field around the intermediate-mass binary black holes by
means of an axion-like scalar field and investigate their joint evolution. In
details, we consider the equal mass binary black holes surrounded by a shell of
axion-like scalar field both in spherical symmetric and non-spherical symmetric
cases, and with different strength of the scalar field. Our result shows that
the environmental scalar field could essentially modify the dynamics. Firstly,
in the spherical symmetric case, with increasing of the scalar field strength,
the number of circular orbit of the binary black hole is reduced. It means that
the scalar field could significantly accelerate the merger process. Secondly,
once the scalar field strength exceeds certain critical value, the scalar field
could collapse into a third black hole with its mass being larger than the
binary. Consequently, the new black hole collapsed from the environmental
scalar field could accrete the binary promptly and the binary collides head-on
between each other. In this process, there is almost no any quadrupole signal
produced, namely the gravitational wave is greatly suppressed. Thirdly, when
the scalar field strength is relatively smaller than the critical value, the
black hole orbit could develop eccentricity through the accretion of the scalar
field. Fourthly, during the initial stage of the inspire, the gravitational
attractive force from the axion-like scalar field could induce a sudden turn in
the binary orbits, hence result in a transient wiggle in the gravitational
waveform. Finally, in the non-spherical case, the scalar field could
gravitationally attract the binary moving toward the mass center of the scalar
field and slow down the merger process.
| [
{
"created": "Thu, 1 Jun 2017 04:29:27 GMT",
"version": "v1"
}
] | 2018-06-13 | [
[
"Yang",
"Qing",
""
],
[
"Ji",
"Li-Wei",
""
],
[
"Hu",
"Bin",
""
],
[
"Cao",
"Zhou-Jian",
""
],
[
"Cai",
"Rong-Gen",
""
]
] | Environment, such as the accretion disk, could modify the signal of the gravitational wave from the astrophysical black hole binaries. In this article, we model the matter field around the intermediate-mass binary black holes by means of an axion-like scalar field and investigate their joint evolution. In details, we consider the equal mass binary black holes surrounded by a shell of axion-like scalar field both in spherical symmetric and non-spherical symmetric cases, and with different strength of the scalar field. Our result shows that the environmental scalar field could essentially modify the dynamics. Firstly, in the spherical symmetric case, with increasing of the scalar field strength, the number of circular orbit of the binary black hole is reduced. It means that the scalar field could significantly accelerate the merger process. Secondly, once the scalar field strength exceeds certain critical value, the scalar field could collapse into a third black hole with its mass being larger than the binary. Consequently, the new black hole collapsed from the environmental scalar field could accrete the binary promptly and the binary collides head-on between each other. In this process, there is almost no any quadrupole signal produced, namely the gravitational wave is greatly suppressed. Thirdly, when the scalar field strength is relatively smaller than the critical value, the black hole orbit could develop eccentricity through the accretion of the scalar field. Fourthly, during the initial stage of the inspire, the gravitational attractive force from the axion-like scalar field could induce a sudden turn in the binary orbits, hence result in a transient wiggle in the gravitational waveform. Finally, in the non-spherical case, the scalar field could gravitationally attract the binary moving toward the mass center of the scalar field and slow down the merger process. |
gr-qc/0608103 | Sanjeev Dhurandhar | Himan Mukhopadhyay, Norichica Sago, Hideyuki Tagoshi, Sanjeev
Dhurandhar, Hirotaka Takahashi & Nobuyuki Kanda | Detecting gravitational waves from inspiraling binaries with a network
of detectors : coherent versus coincident strategies | 18 pages, 10 figures, typo corrected | Phys.Rev. D74 (2006) 083005 | 10.1103/PhysRevD.74.083005 | null | gr-qc | null | We compare two strategies of multi-detector detection of compact binary
inspiral signals, namely, the coincidence and the coherent. For simplicity we
consider here two identical detectors having the same power spectral density of
noise, that of initial LIGO, located in the same place and having the same
orientation. We consider the cases of independent noise as well as that of
correlated noise. The coincident strategy involves separately making two
candidate event lists, one for each detector, and from these choosing those
pairs of events from the two lists which lie within a suitable parameter
window, which then are called as coincidence detections. The coherent strategy
on the other hand involves combining the data phase coherently, so as to obtain
a single network statistic which is then compared with a single threshold. Here
we attempt to shed light on the question as to which strategy is better. We
compare the performances of the two methods by plotting the Receiver Operating
Characteristics (ROC) for the two strategies. Several of the results are
obtained analytically in order to gain insight. Further we perform numerical
simulations in order to determine certain parameters in the analytic formulae
and thus obtain the final complete results. We consider here several cases from
the relatively simple to the astrophysically more relevant in order to
establish our results. The bottom line is that the coherent strategy although
more computationally expensive in general than the coincidence strategy, is
superior to the coincidence strategy - considerably less false dismissal
probability for the same false alarm probability in the viable false alarm
regime.
| [
{
"created": "Tue, 22 Aug 2006 10:07:17 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Mukhopadhyay",
"Himan",
""
],
[
"Sago",
"Norichica",
""
],
[
"Tagoshi",
"Hideyuki",
""
],
[
"Dhurandhar",
"Sanjeev",
""
],
[
"Takahashi",
"Hirotaka",
""
],
[
"Kanda",
"Nobuyuki",
""
]
] | We compare two strategies of multi-detector detection of compact binary inspiral signals, namely, the coincidence and the coherent. For simplicity we consider here two identical detectors having the same power spectral density of noise, that of initial LIGO, located in the same place and having the same orientation. We consider the cases of independent noise as well as that of correlated noise. The coincident strategy involves separately making two candidate event lists, one for each detector, and from these choosing those pairs of events from the two lists which lie within a suitable parameter window, which then are called as coincidence detections. The coherent strategy on the other hand involves combining the data phase coherently, so as to obtain a single network statistic which is then compared with a single threshold. Here we attempt to shed light on the question as to which strategy is better. We compare the performances of the two methods by plotting the Receiver Operating Characteristics (ROC) for the two strategies. Several of the results are obtained analytically in order to gain insight. Further we perform numerical simulations in order to determine certain parameters in the analytic formulae and thus obtain the final complete results. We consider here several cases from the relatively simple to the astrophysically more relevant in order to establish our results. The bottom line is that the coherent strategy although more computationally expensive in general than the coincidence strategy, is superior to the coincidence strategy - considerably less false dismissal probability for the same false alarm probability in the viable false alarm regime. |
0712.0238 | Salvatore Capozziello | S. Capozziello, C. Stornaiolo | Space-time deformations as extended conformal transformations | 9 pages | Int.J.Geom.Meth.Mod.Phys.05:185-195,2008 | 10.1142/S0219887808002709 | null | gr-qc | null | A definition of space-time metric deformations on an $n$-dimensional manifold
is given. We show that such deformations can be regarded as extended conformal
transformations. In particular, their features can be related to the
perturbation theory giving a natural picture by which gravitational waves are
described by small deformations of the metric. As further result, deformations
can be related to approximate Killing vectors (approximate symmetries) by which
it is possible to parameterize the deformed region of a given manifold. The
perspectives and some possible physical applications of such an approach are
discussed.
| [
{
"created": "Mon, 3 Dec 2007 09:39:58 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Capozziello",
"S.",
""
],
[
"Stornaiolo",
"C.",
""
]
] | A definition of space-time metric deformations on an $n$-dimensional manifold is given. We show that such deformations can be regarded as extended conformal transformations. In particular, their features can be related to the perturbation theory giving a natural picture by which gravitational waves are described by small deformations of the metric. As further result, deformations can be related to approximate Killing vectors (approximate symmetries) by which it is possible to parameterize the deformed region of a given manifold. The perspectives and some possible physical applications of such an approach are discussed. |
2401.06467 | Sreejith Nair | Sreejith Nair, Sumanta Chakraborty and Sudipta Sarkar | Asymptotically de-Sitter black holes have non-zero tidal Love numbers | 18 pages | Phys.Rev.D 109 (2024) 6, 064025 | 10.1103/PhysRevD.109.064025 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Love numbers of compact objects quantify their tidal deformability against
external perturbations. It is expected that Love numbers of asymptotically flat
black holes (BHs) in General Relativity are identically zero. We show that
quite contrary to common expectations, the tidal Love numbers of asymptotically
de Sitter black holes are non-zero.
| [
{
"created": "Fri, 12 Jan 2024 09:26:59 GMT",
"version": "v1"
}
] | 2024-05-09 | [
[
"Nair",
"Sreejith",
""
],
[
"Chakraborty",
"Sumanta",
""
],
[
"Sarkar",
"Sudipta",
""
]
] | Love numbers of compact objects quantify their tidal deformability against external perturbations. It is expected that Love numbers of asymptotically flat black holes (BHs) in General Relativity are identically zero. We show that quite contrary to common expectations, the tidal Love numbers of asymptotically de Sitter black holes are non-zero. |
1906.06254 | Khalykbek Yelshibekov | Khalykbek Yelshibekov | A modification to the mirror trajectory corresponding to shell collapse | 43 pages, 12 figures, this BSc thesis is almost exclusively drawn
from arXiv:1611.00809 and arXiv:1801.08020. arXiv admin note: substantial
text overlap with arXiv:hep-th/9302096, arXiv:hep-th/9403108 by other authors | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The well-known moving mirror trajectory corresponding to black hole shell
collapse scenario (BHC) appears to produce an infinite amount of energy. By
changing the final velocity of the BHC mirror from the speed of light to a free
variable $\xi$ a new mirror trajectory was found. This modified BHC mirror
produces finite energy and emits thermal radiation. In the limit of $\xi \to c$
the BHC mirror is restored. In this thesis, the energy and particle production
of the modified BHC mirror, as well as the correlations in its radiation, are
presented.
| [
{
"created": "Wed, 22 May 2019 13:35:55 GMT",
"version": "v1"
}
] | 2019-06-17 | [
[
"Yelshibekov",
"Khalykbek",
""
]
] | The well-known moving mirror trajectory corresponding to black hole shell collapse scenario (BHC) appears to produce an infinite amount of energy. By changing the final velocity of the BHC mirror from the speed of light to a free variable $\xi$ a new mirror trajectory was found. This modified BHC mirror produces finite energy and emits thermal radiation. In the limit of $\xi \to c$ the BHC mirror is restored. In this thesis, the energy and particle production of the modified BHC mirror, as well as the correlations in its radiation, are presented. |
1404.2382 | Ilya Mandel | Ilya Mandel, Christopher P L Berry, Frank Ohme, Stephen Fairhurst,
Will M Farr | Parameter estimation on compact binary coalescences with abruptly
terminating gravitational waveforms | Very minor changes to match published version | Class. Quantum Grav 31, 155005 (2014) | 10.1088/0264-9381/31/15/155005 | null | gr-qc astro-ph.HE physics.data-an | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational-wave astronomy seeks to extract information about astrophysical
systems from the gravitational-wave signals they emit. For coalescing
compact-binary sources this requires accurate model templates for the inspiral
and, potentially, the subsequent merger and ringdown. Models with
frequency-domain waveforms that terminate abruptly in the sensitive band of the
detector are often used for parameter-estimation studies. We show that the
abrupt waveform termination contains significant information that affects
parameter-estimation accuracy. If the sharp cutoff is not physically motivated,
this extra information can lead to misleadingly good accuracy claims. We also
show that using waveforms with a cutoff as templates to recover complete
signals can lead to biases in parameter estimates. We evaluate when the
information content in the cutoff is likely to be important in both cases. We
also point out that the standard Fisher matrix formalism, frequently employed
for approximately predicting parameter-estimation accuracy, cannot properly
incorporate an abrupt cutoff that is present in both signals and templates;
this observation explains some previously unexpected results found in the
literature. These effects emphasize the importance of using complete waveforms
with accurate merger and ringdown phases for parameter estimation.
| [
{
"created": "Wed, 9 Apr 2014 07:22:29 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Jul 2014 01:25:36 GMT",
"version": "v2"
}
] | 2014-07-24 | [
[
"Mandel",
"Ilya",
""
],
[
"Berry",
"Christopher P L",
""
],
[
"Ohme",
"Frank",
""
],
[
"Fairhurst",
"Stephen",
""
],
[
"Farr",
"Will M",
""
]
] | Gravitational-wave astronomy seeks to extract information about astrophysical systems from the gravitational-wave signals they emit. For coalescing compact-binary sources this requires accurate model templates for the inspiral and, potentially, the subsequent merger and ringdown. Models with frequency-domain waveforms that terminate abruptly in the sensitive band of the detector are often used for parameter-estimation studies. We show that the abrupt waveform termination contains significant information that affects parameter-estimation accuracy. If the sharp cutoff is not physically motivated, this extra information can lead to misleadingly good accuracy claims. We also show that using waveforms with a cutoff as templates to recover complete signals can lead to biases in parameter estimates. We evaluate when the information content in the cutoff is likely to be important in both cases. We also point out that the standard Fisher matrix formalism, frequently employed for approximately predicting parameter-estimation accuracy, cannot properly incorporate an abrupt cutoff that is present in both signals and templates; this observation explains some previously unexpected results found in the literature. These effects emphasize the importance of using complete waveforms with accurate merger and ringdown phases for parameter estimation. |
2203.12332 | Samuel Kov\'a\v{c}ik | Samuel Kov\'a\v{c}ik | Microscopic black holes as probes for quantum gravity | Corfu Summer Institute 2021 "School and Workshops on Elementary
Particle Physics and Gravity" proceedings | null | null | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | One of the main goals of contemporary theoretical physics is to find the
quantum theory of gravity. There are various working hypotheses, mostly
operating in the regime of high-energy physics well above the reach of particle
accelerators. So far, strong experimental or observational evidence to guide
the theory is missing. A possible consequence of quantum gravity and quantum
spacetime that is often discussed is the vacuum dispersion effect. In this
paper, we consider a different line of quantum space phenomenology, the
behaviour of microscopic black holes. Even though their exact nature is
unknown, some of their features are very model-independent, allowing us to draw
conclusions about their role in the current cosmological models.
| [
{
"created": "Wed, 23 Mar 2022 11:16:18 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Mar 2022 15:03:05 GMT",
"version": "v2"
}
] | 2022-04-01 | [
[
"Kováčik",
"Samuel",
""
]
] | One of the main goals of contemporary theoretical physics is to find the quantum theory of gravity. There are various working hypotheses, mostly operating in the regime of high-energy physics well above the reach of particle accelerators. So far, strong experimental or observational evidence to guide the theory is missing. A possible consequence of quantum gravity and quantum spacetime that is often discussed is the vacuum dispersion effect. In this paper, we consider a different line of quantum space phenomenology, the behaviour of microscopic black holes. Even though their exact nature is unknown, some of their features are very model-independent, allowing us to draw conclusions about their role in the current cosmological models. |
1311.6899 | Sijie Gao | Xiongjun Fang, Sijie Gao | General proof of the entropy principle for self-gravitating fluid in
static spacetimes | 11 pages, no figure. Order of the two theorems exchanged, matches
published version | Phys. Rev. D 90, 044013 (2014) | 10.1103/PhysRevD.90.044013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that for any perfect fluid in a static spacetime, if the Einstein
constraint equation is satisfied and the temperature of the fluid obeys
Tolman's law, then the other components of Einstein's equation are implied by
the assumption that the total entropy of the fluid achieves an extremum for
fixed total particle number and for all variations of metric with certain
boundary conditions. Conversely, one can show that the extrema of the total
entropy of the fluid are implied by Einstein's equation. Compared to previous
works on this issue, we do not require spherical symmetry for the spacetime.
Our results suggest a general and solid connection between thermodynamics and
general relativity.
| [
{
"created": "Wed, 27 Nov 2013 08:47:30 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Dec 2013 12:20:40 GMT",
"version": "v2"
},
{
"created": "Wed, 13 Aug 2014 14:54:40 GMT",
"version": "v3"
}
] | 2015-06-18 | [
[
"Fang",
"Xiongjun",
""
],
[
"Gao",
"Sijie",
""
]
] | We show that for any perfect fluid in a static spacetime, if the Einstein constraint equation is satisfied and the temperature of the fluid obeys Tolman's law, then the other components of Einstein's equation are implied by the assumption that the total entropy of the fluid achieves an extremum for fixed total particle number and for all variations of metric with certain boundary conditions. Conversely, one can show that the extrema of the total entropy of the fluid are implied by Einstein's equation. Compared to previous works on this issue, we do not require spherical symmetry for the spacetime. Our results suggest a general and solid connection between thermodynamics and general relativity. |
0901.3879 | Kiyoshi Shiraishi | Nahomi Kan (Yamaguchi Junior College) and Kiyoshi Shiraishi (Yamaguchi
University) | Emergent Einstein Universe under Deconstruction | 15 pages, three figures, use ptptex | Prog.Theor.Phys.121:1035-1048,2009 | 10.1143/PTP.121.1035 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study self-consistent static solutions for an Einstein universe in a
graph-based induced gravity. The one-loop quantum action is computed at finite
temperature. In particular, we demonstrate specific results for the models
based on cycle graphs.
| [
{
"created": "Sun, 25 Jan 2009 07:09:41 GMT",
"version": "v1"
}
] | 2009-08-11 | [
[
"Kan",
"Nahomi",
"",
"Yamaguchi Junior College"
],
[
"Shiraishi",
"Kiyoshi",
"",
"Yamaguchi\n University"
]
] | We study self-consistent static solutions for an Einstein universe in a graph-based induced gravity. The one-loop quantum action is computed at finite temperature. In particular, we demonstrate specific results for the models based on cycle graphs. |
gr-qc/9606090 | Thomas Thiemann | T. Thiemann | Quantum Spin Dynamics (QSD) II | 27 pages, Latex, preceded by a companion paper before this one | Class.Quant.Grav. 15 (1998) 875-905 | 10.1088/0264-9381/15/4/012 | HUTMP-96/B-352 | gr-qc hep-th | null | We continue here the analysis of the previous paper of the Wheeler-DeWitt
constraint operator for four-dimensional, Lorentzian, non-perturbative,
canonical vacuum quantum gravity in the continuum. In this paper we derive the
complete kernel, as well as a physical inner product on it, for a non-symmetric
version of the Wheeler-DeWitt operator. We then define a symmetric version of
the Wheeler-DeWitt operator. For the Euclidean Wheeler-DeWitt operator as well
as for the generator of the Wick transform from the Euclidean to the Lorentzian
regime we prove existence of self-adjoint extensions and based on these we
present a method of proof of self-adjoint extensions for the Lorentzian
operator. Finally we comment on the status of the Wick rotation transform in
the light of the present results.
| [
{
"created": "Sat, 29 Jun 1996 23:16:50 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Thiemann",
"T.",
""
]
] | We continue here the analysis of the previous paper of the Wheeler-DeWitt constraint operator for four-dimensional, Lorentzian, non-perturbative, canonical vacuum quantum gravity in the continuum. In this paper we derive the complete kernel, as well as a physical inner product on it, for a non-symmetric version of the Wheeler-DeWitt operator. We then define a symmetric version of the Wheeler-DeWitt operator. For the Euclidean Wheeler-DeWitt operator as well as for the generator of the Wick transform from the Euclidean to the Lorentzian regime we prove existence of self-adjoint extensions and based on these we present a method of proof of self-adjoint extensions for the Lorentzian operator. Finally we comment on the status of the Wick rotation transform in the light of the present results. |
gr-qc/0302063 | Alex Kaganovich | E.I. Guendelman and A.B. Kaganovich | Counter-example where cosmic time keeps its original role in quantum
cosmology | 19 pages; the talk presented to the International colloquium on the
science of time "Time and Matter" at Venice International University, Italy,
August 11-17, 2002 | null | null | null | gr-qc | null | In the minisuperspace models of quantum cosmology, the absence of time in the
Wheeler-DeWitt (constraint) equation, is the main point leading to the
generally accepted conclusion that in the quantum cosmology there is no
possibility to describe the evolution of the universe procceding in the cosmic
time (the time usually used in classical cosmology). We show that in spite of
the constraint, under the specific circumstances, the averaging of some of the
Heisenberg equations can give nontrivial additional information about explicit
time dependence of the expectation values of certain dynamical variables in
quantum cosmology. This idea is realized explicitly in a higher dimensional
model with a negative cosmological constant and dust as the sources of gravity.
When there is an anisotropy in the evolution of the universe, the above
phenomenon (i.e. explicit cosmic time dependence of certain expectation values)
appears and we find the new quantum effect which consists in "quantum
inflationary phase" for some dimensions and simultaneous "quantum deflationary
contraction" for the remaining dimensions. The expectation value of the
"volume" of the universe remains constant during this quantum
"inflation-deflation" process.
| [
{
"created": "Sun, 16 Feb 2003 14:01:46 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Guendelman",
"E. I.",
""
],
[
"Kaganovich",
"A. B.",
""
]
] | In the minisuperspace models of quantum cosmology, the absence of time in the Wheeler-DeWitt (constraint) equation, is the main point leading to the generally accepted conclusion that in the quantum cosmology there is no possibility to describe the evolution of the universe procceding in the cosmic time (the time usually used in classical cosmology). We show that in spite of the constraint, under the specific circumstances, the averaging of some of the Heisenberg equations can give nontrivial additional information about explicit time dependence of the expectation values of certain dynamical variables in quantum cosmology. This idea is realized explicitly in a higher dimensional model with a negative cosmological constant and dust as the sources of gravity. When there is an anisotropy in the evolution of the universe, the above phenomenon (i.e. explicit cosmic time dependence of certain expectation values) appears and we find the new quantum effect which consists in "quantum inflationary phase" for some dimensions and simultaneous "quantum deflationary contraction" for the remaining dimensions. The expectation value of the "volume" of the universe remains constant during this quantum "inflation-deflation" process. |
1203.5367 | James Quach Mr | James Q. Quach, Chun-Hsu Su, Andrew M. Martin and Andrew D. Greentree | Domain structures in quantum graphity | 11 pages, 12 figures | Physical Review D 86, 044001 (2012) | 10.1103/PhysRevD.86.044001 | null | gr-qc cond-mat.stat-mech | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum graphity offers the intriguing notion that space emerges in the low
energy states of the spatial degrees of freedom of a dynamical lattice. Here we
investigate metastable domain structures which are likely to exist in the low
energy phase of lattice evolution. Through an annealing process we explore the
formation of metastable defects at domain boundaries and the effects of domain
structures on the propagation of bosons. We show that these structures should
have observable background independent consequences including scattering,
double imaging, and gravitational lensing-like effects.
| [
{
"created": "Fri, 23 Mar 2012 22:40:42 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Aug 2012 08:03:04 GMT",
"version": "v2"
}
] | 2015-06-04 | [
[
"Quach",
"James Q.",
""
],
[
"Su",
"Chun-Hsu",
""
],
[
"Martin",
"Andrew M.",
""
],
[
"Greentree",
"Andrew D.",
""
]
] | Quantum graphity offers the intriguing notion that space emerges in the low energy states of the spatial degrees of freedom of a dynamical lattice. Here we investigate metastable domain structures which are likely to exist in the low energy phase of lattice evolution. Through an annealing process we explore the formation of metastable defects at domain boundaries and the effects of domain structures on the propagation of bosons. We show that these structures should have observable background independent consequences including scattering, double imaging, and gravitational lensing-like effects. |
1103.0287 | Niels Warburton | Niels Warburton, Leor Barack | Self force on a scalar charge in Kerr spacetime: eccentric equatorial
orbits | 26 pages, 9 figures. Minor typo corrected | Phys.Rev.D83:124038,2011 | 10.1103/PhysRevD.83.124038 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a numerical code for calculating the self force on a scalar charge
moving in a bound (eccentric) geodesic in the equatorial plane of a Kerr black
hole. We work in the frequency domain and make use of the method of extended
homogeneous solutions [Phys.\ Rev.\ D {\bf 78}, 084021 (2008)], in conjunction
with mode-sum regularization. Our work is part of a program to develop a
computational architecture for fast and efficient self-force calculations,
alternative to time-domain methods. We find that our frequency-domain method
outperforms existing time-domain schemes for small eccentricities, and,
remarkably, remains competitive up to eccentricities as high as $\sim 0.7$. As
an application of our code we (i) compute the conservative scalar-field
self-force correction to the innermost stable circular equatorial orbit, as a
function of the Kerr spin parameter; and (ii) calculate the variation in the
rest mass of the scalar particle along the orbit, caused by the component of
the self force tangent to the four-velocity.
| [
{
"created": "Tue, 1 Mar 2011 21:14:08 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jun 2011 12:31:26 GMT",
"version": "v2"
},
{
"created": "Thu, 26 Feb 2015 19:36:42 GMT",
"version": "v3"
}
] | 2015-02-27 | [
[
"Warburton",
"Niels",
""
],
[
"Barack",
"Leor",
""
]
] | We present a numerical code for calculating the self force on a scalar charge moving in a bound (eccentric) geodesic in the equatorial plane of a Kerr black hole. We work in the frequency domain and make use of the method of extended homogeneous solutions [Phys.\ Rev.\ D {\bf 78}, 084021 (2008)], in conjunction with mode-sum regularization. Our work is part of a program to develop a computational architecture for fast and efficient self-force calculations, alternative to time-domain methods. We find that our frequency-domain method outperforms existing time-domain schemes for small eccentricities, and, remarkably, remains competitive up to eccentricities as high as $\sim 0.7$. As an application of our code we (i) compute the conservative scalar-field self-force correction to the innermost stable circular equatorial orbit, as a function of the Kerr spin parameter; and (ii) calculate the variation in the rest mass of the scalar particle along the orbit, caused by the component of the self force tangent to the four-velocity. |
gr-qc/0601022 | Xiao Zhang | Wen-ling Huang, Xiao Zhang | On the relation between ADM and Bondi energy-momenta III -- perturbed
radiative spatial infinity | 12 pages, formulas simplified | Sci.China 50:1217-1226,2007 | 10.1007/s11425-007-0074-8 | null | gr-qc math.DG | null | In a vacuum spacetime equipped with the Bondi's radiating metric which is
asymptotically flat at spatial infinity including gravitational radiation ({\bf
Condition D}), we establish the relation between the ADM total energy-momentum
and the Bondi energy-momentum for perturbed radiative spatial infinity. The
perturbation is given by defining the "real" time the sum of the retarded time,
the Euclidean distance and certain function $f$.
| [
{
"created": "Fri, 6 Jan 2006 03:40:40 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Apr 2006 11:55:07 GMT",
"version": "v2"
},
{
"created": "Tue, 12 Sep 2006 05:10:32 GMT",
"version": "v3"
},
{
"created": "Sun, 1 Oct 2006 15:29:35 GMT",
"version": "v4"
}
] | 2015-06-25 | [
[
"Huang",
"Wen-ling",
""
],
[
"Zhang",
"Xiao",
""
]
] | In a vacuum spacetime equipped with the Bondi's radiating metric which is asymptotically flat at spatial infinity including gravitational radiation ({\bf Condition D}), we establish the relation between the ADM total energy-momentum and the Bondi energy-momentum for perturbed radiative spatial infinity. The perturbation is given by defining the "real" time the sum of the retarded time, the Euclidean distance and certain function $f$. |
2006.09399 | Shahar Hod | Shahar Hod | Onset of spontaneous scalarization in spinning Gauss-Bonnet black holes | 6 pages | Phys. Rev. D 102, 084060 (2020) | 10.1103/PhysRevD.102.084060 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has recently been proved numerically that spinning black holes in
Einstein-scalar theories which are characterized by a non-minimal negative
coupling of the scalar field to the Gauss-Bonnet invariant of the curved
spacetime may develop exponentially growing instabilities. Intriguingly, it has
been demonstrated that this tachyonic instability, which marks the onset of the
spontaneous scalarization phenomenon in the Einstein-Gauss-Bonnet-scalar
theory, characterizes spinning black holes whose dimensionless angular momentum
parameter ${\bar a}\equiv a/M$ is larger than some critical value ${\bar
a}_{\text{crit}}\simeq0.505$. In the present paper we prove, using {\it
analytical} techniques, that the critical rotation parameter which marks the
boundary between bald Kerr black holes and hairy (scalarized) spinning black
holes in the Einstein-Gauss-Bonnet-scalar theory is given by the exact
dimensionless relation ${\bar a}_{\text{crit}}={1\over 2}$.
| [
{
"created": "Tue, 16 Jun 2020 18:00:05 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Aug 2020 05:04:34 GMT",
"version": "v2"
}
] | 2020-11-04 | [
[
"Hod",
"Shahar",
""
]
] | It has recently been proved numerically that spinning black holes in Einstein-scalar theories which are characterized by a non-minimal negative coupling of the scalar field to the Gauss-Bonnet invariant of the curved spacetime may develop exponentially growing instabilities. Intriguingly, it has been demonstrated that this tachyonic instability, which marks the onset of the spontaneous scalarization phenomenon in the Einstein-Gauss-Bonnet-scalar theory, characterizes spinning black holes whose dimensionless angular momentum parameter ${\bar a}\equiv a/M$ is larger than some critical value ${\bar a}_{\text{crit}}\simeq0.505$. In the present paper we prove, using {\it analytical} techniques, that the critical rotation parameter which marks the boundary between bald Kerr black holes and hairy (scalarized) spinning black holes in the Einstein-Gauss-Bonnet-scalar theory is given by the exact dimensionless relation ${\bar a}_{\text{crit}}={1\over 2}$. |
gr-qc/0602011 | Tomislav Prokopec | Bjorn Garbrecht (University of Manchester) and Tomislav Prokopec
(Utrecht University) | Fermion Mass Generation in de Sitter Space | 17 pages, 3 figures, LaTeX | Phys.Rev. D73 (2006) 064036 | 10.1103/PhysRevD.73.064036 | null | gr-qc | null | We study the one-loop radiative corrections for massless fermions in de
Sitter space induced by a Yukawa coupling to a light, nearly minimally coupled
scalar field. We show that the fermions acquire a mass. Next we construct the
corresponding (nonlocal) effective fermionic action, which -- in contrast to
the case of a massive Dirac fermion -- preserves chirality. Nevertheless, the
resulting fermion dynamics is precisely that of a Dirac fermion with a mass
proportional to the expansion rate. Our finding supports the view that an
observer or a test particle responds to a scalar field in inflation by shifting
its energy rather than seeing a thermal bath.
| [
{
"created": "Thu, 2 Feb 2006 17:47:11 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Garbrecht",
"Bjorn",
"",
"University of Manchester"
],
[
"Prokopec",
"Tomislav",
"",
"Utrecht University"
]
] | We study the one-loop radiative corrections for massless fermions in de Sitter space induced by a Yukawa coupling to a light, nearly minimally coupled scalar field. We show that the fermions acquire a mass. Next we construct the corresponding (nonlocal) effective fermionic action, which -- in contrast to the case of a massive Dirac fermion -- preserves chirality. Nevertheless, the resulting fermion dynamics is precisely that of a Dirac fermion with a mass proportional to the expansion rate. Our finding supports the view that an observer or a test particle responds to a scalar field in inflation by shifting its energy rather than seeing a thermal bath. |
2305.13339 | Abdolhosein Khodam-Mohammadi | A. Khodam-Mohammadi and M. Monshizadeh | Exploring Modifications to FLRW Cosmology with General Entropy and
Thermodynamics: A new Approach | 12 pages. Accepted for publication in PLB (Physics letter B) | Physics Letter B 843 (2023) 138066 | 10.1016/j.physletb.2023.138066 | null | gr-qc | http://creativecommons.org/publicdomain/zero/1.0/ | The investigation of modifications to the FLRW cosmology resulting from the
consideration of a general entropy for the cosmological apparent horizon is the
subject of this study. Building upon the work of Nojiri and collaborators in
2022, who introduced a class of generalized entropies with four parameters
capable of converging to familiar entropies and addressing specific
cosmological issues, our research explores the impact of correcting the entropy
on the energy-momentum tensor of the cosmic fluid from the outset. Our
calculations demonstrate that, by employing a correction function $f(\rho)$ to
modify the energy-momentum density tensor, the entropic area law
(Bekenstein-Hawking entropy) can still be regarded as a general entropy. The
construction of the function $f(\rho)$ is facilitated through considerations of
the thermodynamics associated with the apparent horizon. Additionally, we
investigate the first and second laws of thermodynamics within this framework
and illustrate how the limitations imposed on the equation of state of the
cosmic fluid can be resolved through the incorporation of this correction
function. Finally, we compute cosmography parameters to analyze the kinematics
of the universe, with particular attention given to the notable influence of
the correction function $f(\rho)$ on these parameters. This paper provides
valuable insights into the application of general entropies to the apparent
horizon of the universe.
| [
{
"created": "Sun, 21 May 2023 06:15:19 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Jul 2023 07:51:31 GMT",
"version": "v2"
}
] | 2023-07-26 | [
[
"Khodam-Mohammadi",
"A.",
""
],
[
"Monshizadeh",
"M.",
""
]
] | The investigation of modifications to the FLRW cosmology resulting from the consideration of a general entropy for the cosmological apparent horizon is the subject of this study. Building upon the work of Nojiri and collaborators in 2022, who introduced a class of generalized entropies with four parameters capable of converging to familiar entropies and addressing specific cosmological issues, our research explores the impact of correcting the entropy on the energy-momentum tensor of the cosmic fluid from the outset. Our calculations demonstrate that, by employing a correction function $f(\rho)$ to modify the energy-momentum density tensor, the entropic area law (Bekenstein-Hawking entropy) can still be regarded as a general entropy. The construction of the function $f(\rho)$ is facilitated through considerations of the thermodynamics associated with the apparent horizon. Additionally, we investigate the first and second laws of thermodynamics within this framework and illustrate how the limitations imposed on the equation of state of the cosmic fluid can be resolved through the incorporation of this correction function. Finally, we compute cosmography parameters to analyze the kinematics of the universe, with particular attention given to the notable influence of the correction function $f(\rho)$ on these parameters. This paper provides valuable insights into the application of general entropies to the apparent horizon of the universe. |
gr-qc/0609027 | Ulrich Straumann | St. Schlamminger, E. Holzschuh, W. K\"undig, F. Nolting, R.E. Pixley,
J. Schurr, U. Straumann | A Measurement of Newton's Gravitational Constant | 26 pages, 20 figures, Accepted for publication by Phys. Rev. D | Phys.Rev.D74:082001,2006 | 10.1103/PhysRevD.74.082001 | null | gr-qc | null | A precision measurement of the gravitational constant $G$ has been made using
a beam balance. Special attention has been given to determining the
calibration, the effect of a possible nonlinearity of the balance and the
zero-point variation of the balance. The equipment, the measurements and the
analysis are described in detail. The value obtained for G is 6.674252(109)(54)
10^{-11} m3 kg-1 s-2. The relative statistical and systematic uncertainties of
this result are 16.3 10^{-6} and 8.1 10^{-6}, respectively.
| [
{
"created": "Thu, 7 Sep 2006 17:21:20 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Schlamminger",
"St.",
""
],
[
"Holzschuh",
"E.",
""
],
[
"Kündig",
"W.",
""
],
[
"Nolting",
"F.",
""
],
[
"Pixley",
"R. E.",
""
],
[
"Schurr",
"J.",
""
],
[
"Straumann",
"U.",
""
]
] | A precision measurement of the gravitational constant $G$ has been made using a beam balance. Special attention has been given to determining the calibration, the effect of a possible nonlinearity of the balance and the zero-point variation of the balance. The equipment, the measurements and the analysis are described in detail. The value obtained for G is 6.674252(109)(54) 10^{-11} m3 kg-1 s-2. The relative statistical and systematic uncertainties of this result are 16.3 10^{-6} and 8.1 10^{-6}, respectively. |
0804.4131 | Fumiko Kawazoe | Fumiko Kawazoe (1), Mitsuhiro Fukushima (2), Seiji Kawamura (2),
Volker Leonhardt (2), Osamu Miyakawa (3), Tomoko Morioka (4), Atsushi
Nishizawa (5), Shuichi Sato (2), Kentaro Somiya (6), Akio Sugamoto (1),
Toshitaka Yamazaki (2) ((1)Ochanomizu University, Tokyo, Japan, (2)National
Astronomical Observatory of Japan, Tokyo, Japan, (3) LIGO Laboratory,
California Institute of Technology, CA, USA, (4)University of Tokyo, Japan,
(5)Kyoto University, Kyoto, Japan, (6)Max-Planck-Institut fuer
Gravitationsphysik, Potsdam, Germany) | Experimental investigation of a control scheme for a zero-detuning
resonant sideband extraction interferometer for next-generation
gravitational-wave detectors | 6 pages, 9 figrues | Class.Quant.Grav.25:195008,2008 | 10.1088/0264-9381/25/19/195008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Some next-generation gravitational-wave detectors, such as the American
Advanced LIGO project and the Japanese LCGT project, plan to use power recycled
resonant sideband extraction (RSE) interferometers for their interferometer's
optical configuration. A power recycled zero-detuning (PRZD) RSE
interferometer, which is the default design for LCGT, has five main length
degrees of freedom that need to be controlled in order to operate a
gravitational-wave detector. This task is expected to be very challenging
because of the complexity of optical configuration. A new control scheme for a
PRZD RSE interferometer has been developed and tested with a prototype
interferometer. The PRZD RSE interferometer was successfully locked with the
control scheme. It is the first experimental demonstration of a PRZD RSE
interferometer with suspended test masses. The result serves as an important
step for the operation of LCGT.
| [
{
"created": "Fri, 25 Apr 2008 15:39:47 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kawazoe",
"Fumiko",
""
],
[
"Fukushima",
"Mitsuhiro",
""
],
[
"Kawamura",
"Seiji",
""
],
[
"Leonhardt",
"Volker",
""
],
[
"Miyakawa",
"Osamu",
""
],
[
"Morioka",
"Tomoko",
""
],
[
"Nishizawa",
"Atsushi",
"... | Some next-generation gravitational-wave detectors, such as the American Advanced LIGO project and the Japanese LCGT project, plan to use power recycled resonant sideband extraction (RSE) interferometers for their interferometer's optical configuration. A power recycled zero-detuning (PRZD) RSE interferometer, which is the default design for LCGT, has five main length degrees of freedom that need to be controlled in order to operate a gravitational-wave detector. This task is expected to be very challenging because of the complexity of optical configuration. A new control scheme for a PRZD RSE interferometer has been developed and tested with a prototype interferometer. The PRZD RSE interferometer was successfully locked with the control scheme. It is the first experimental demonstration of a PRZD RSE interferometer with suspended test masses. The result serves as an important step for the operation of LCGT. |
1101.2791 | Roberto Tauraso | Riccardo March, Giovanni Bellettini, Roberto Tauraso, Simone
Dell'Agnello | Constraining spacetime torsion with LAGEOS | null | null | 10.1007/s10714-011-1226-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the corrections to the orbital Lense-Thirring effect (or
frame-dragging) in the presence of spacetime torsion. We derive the equations
of motion of a test body in the gravitational field of a rotating axisymmetric
massive body, using the parametrized framework of Mao, Tegmark, Guth and Cabi.
We calculate the secular variations of the longitudes of the node and of the
pericenter. We also show how the LAser GEOdynamics Satellites (LAGEOS) can be
used to constrain torsion parameters. We report the experimental constraints
obtained using both the nodes and perigee measurements of the orbital
Lense-Thirring effect. This makes LAGEOS and Gravity Probe B (GPB)
complementary frame-dragging and torsion experiments, since they constrain
three different combinations of torsion parameters.
| [
{
"created": "Fri, 14 Jan 2011 12:45:46 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Feb 2011 14:54:58 GMT",
"version": "v2"
},
{
"created": "Tue, 12 Jul 2011 05:29:37 GMT",
"version": "v3"
}
] | 2015-05-27 | [
[
"March",
"Riccardo",
""
],
[
"Bellettini",
"Giovanni",
""
],
[
"Tauraso",
"Roberto",
""
],
[
"Dell'Agnello",
"Simone",
""
]
] | We compute the corrections to the orbital Lense-Thirring effect (or frame-dragging) in the presence of spacetime torsion. We derive the equations of motion of a test body in the gravitational field of a rotating axisymmetric massive body, using the parametrized framework of Mao, Tegmark, Guth and Cabi. We calculate the secular variations of the longitudes of the node and of the pericenter. We also show how the LAser GEOdynamics Satellites (LAGEOS) can be used to constrain torsion parameters. We report the experimental constraints obtained using both the nodes and perigee measurements of the orbital Lense-Thirring effect. This makes LAGEOS and Gravity Probe B (GPB) complementary frame-dragging and torsion experiments, since they constrain three different combinations of torsion parameters. |
gr-qc/9901059 | Chanyong Park | Chanyong Park and Sang-Jin Sin | Phases of the Brans-Dicke Cosmology with Matter | 16 pages, 5 figures, Revtex | J.Korean Phys.Soc.34:463,1999 | null | null | gr-qc hep-th | null | We study the cosmology of the Brans-Dicke theory with perfect fluid type
matter. In our previous work, we found exact solutions for any Brans-Dicke
parameter $\omega$ and for general parameter $\gamma$ of equation of state. In
this paper we further study the cosmology of these solutions by analyzing them
according to their asymptotic behaviors. The cosmology is classified into 19
phases according to the values of $\gamma$ and $\omega$. The effect of the
cosmological constant to the Brans-Dicke theory is a particular case of our
model. We give plot of time evolution of the scale factor by numerical
investigations. We also give a comparison of the solutions for the theories
with and without matter.
| [
{
"created": "Fri, 22 Jan 1999 05:55:44 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Jan 1999 02:41:10 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Park",
"Chanyong",
""
],
[
"Sin",
"Sang-Jin",
""
]
] | We study the cosmology of the Brans-Dicke theory with perfect fluid type matter. In our previous work, we found exact solutions for any Brans-Dicke parameter $\omega$ and for general parameter $\gamma$ of equation of state. In this paper we further study the cosmology of these solutions by analyzing them according to their asymptotic behaviors. The cosmology is classified into 19 phases according to the values of $\gamma$ and $\omega$. The effect of the cosmological constant to the Brans-Dicke theory is a particular case of our model. We give plot of time evolution of the scale factor by numerical investigations. We also give a comparison of the solutions for the theories with and without matter. |
2210.04837 | Gregory Horndeski | Gregory W. Horndeski | Second-Order, Biconformally Invariant Scalar-Tensor Field Theories in a
Four-Dimensional Space | 24 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper I shall consider field theories in a space of four-dimensions
which have field variables consisting of the components of a metric tensor and
scalar field. The field equations of these scalar-tensor field theories will be
derivable from a variational principle using a Lagrange scalar density which is
a concomitant of the field variables and their derivatives of arbitrary, but
finite, order. I shall consider biconformal transformations of the field
variables, which are conformal transformations which affect both the metric
tensor and scalar field. A necessary and sufficient condition will be developed
to determine when the Euler-Lagrange tensor densities are biconformally
invariant. This condition will be employed to construct all of the second-order
biconformally invariant scalar-tensor field theories in a space of
four-dimensions. It turns out that the field equations of these theories can be
derived from a linear combination of (at most) two second-order Lagrangians,
with the coefficients in that linear combination being real constants.
| [
{
"created": "Mon, 10 Oct 2022 16:50:55 GMT",
"version": "v1"
}
] | 2022-10-11 | [
[
"Horndeski",
"Gregory W.",
""
]
] | In this paper I shall consider field theories in a space of four-dimensions which have field variables consisting of the components of a metric tensor and scalar field. The field equations of these scalar-tensor field theories will be derivable from a variational principle using a Lagrange scalar density which is a concomitant of the field variables and their derivatives of arbitrary, but finite, order. I shall consider biconformal transformations of the field variables, which are conformal transformations which affect both the metric tensor and scalar field. A necessary and sufficient condition will be developed to determine when the Euler-Lagrange tensor densities are biconformally invariant. This condition will be employed to construct all of the second-order biconformally invariant scalar-tensor field theories in a space of four-dimensions. It turns out that the field equations of these theories can be derived from a linear combination of (at most) two second-order Lagrangians, with the coefficients in that linear combination being real constants. |
gr-qc/9306009 | Dominik Schwarz | Dominik J. Schwarz | Analytic Solutions for Cosmological Perturbations in Multi-Dimensional
Space-Time | 6 pages (incl. 3 figures), LaTeX (epsf), TUW-93-07, two misprints
corrected (one formula, one reference) | Int.J.Mod.Phys.D3:265-268,1994 | 10.1142/S0218271894000423 | null | gr-qc astro-ph | null | We obtain analytic solutions for the density contrast and the anisotropic
pressure in a multi-dimensional FRW cosmology with collisionless, massless
matter. These are compared with perturbations of a perfect fluid universe. To
describe the metric perturbations we use manifest gauge invariant metric
potentials. The matter perturbations are calculated by means of (automatically
gauge invariant) finite temperature field theory, instead of kinetic theory.
(Talk given at the Journ\'ees Relativistes '93, 5 -- 7 April, Brussels,
Belgium)
| [
{
"created": "Mon, 7 Jun 1993 13:55:38 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Nov 1993 15:19:17 GMT",
"version": "v2"
}
] | 2011-04-15 | [
[
"Schwarz",
"Dominik J.",
""
]
] | We obtain analytic solutions for the density contrast and the anisotropic pressure in a multi-dimensional FRW cosmology with collisionless, massless matter. These are compared with perturbations of a perfect fluid universe. To describe the metric perturbations we use manifest gauge invariant metric potentials. The matter perturbations are calculated by means of (automatically gauge invariant) finite temperature field theory, instead of kinetic theory. (Talk given at the Journ\'ees Relativistes '93, 5 -- 7 April, Brussels, Belgium) |
2109.03258 | Zonghao Li | Zonghao Li | Lorentz violation in the matter-gravity sector | Presented at the Eighth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, May 12-16, 2019 | null | null | null | gr-qc hep-ph | http://creativecommons.org/licenses/by/4.0/ | We construct the general Lorentz-violating effective field theory in curved
spacetime and the corresponding nonrelativistic Hamiltonian in the Earth's
gravitational field. Applying this general framework to three types of
experiments, free-dropping, interferometer, and bound-state experiments, we
extract first constraints on certain new coefficients in the matter-gravity
sector.
| [
{
"created": "Tue, 7 Sep 2021 18:00:53 GMT",
"version": "v1"
}
] | 2021-09-09 | [
[
"Li",
"Zonghao",
""
]
] | We construct the general Lorentz-violating effective field theory in curved spacetime and the corresponding nonrelativistic Hamiltonian in the Earth's gravitational field. Applying this general framework to three types of experiments, free-dropping, interferometer, and bound-state experiments, we extract first constraints on certain new coefficients in the matter-gravity sector. |
1504.07855 | Gilbert Weinstein | Gilbert Weinstein, Yosef Strauss, Sergey Bondarenko, Asher Yahalom,
Meir Lewkowicz, Lawrence Paul Horwitz, and Jacob Levitan | Entropy measures as geometrical tools in the study of cosmology | Final Version | Entropy 2018, 20(1), 6 | 10.3390/e20010006 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Classical chaos is often characterized as exponential divergence of nearby
trajectories. In many interesting cases these trajectories can be identified
with geodesic curves. We define here the entropy by $S = \ln \chi (x)$ with
$\chi(x)$ being the distance between two nearby geodesics. We derive an
equation for the entropy which by transformation to a Ricatti-type equation
becomes similar to the Jacobi equation. We further show that the geodesic
equation for a null geodesic in a double warped space time leads to the same
entropy equation. By applying a Robertson-Walker metric for a flat
three-dimensional Euclidian space expanding as a function of time, we again
reach the entropy equation stressing the connection between the chosen entropy
measure and time. We finally turn to the Raychaudhuri equation for expansion,
which also is a Ricatti equation similar to the transformed entropy equation.
Those Ricatti-type equations have solutions of the same form as the Jacobi
equation. The Raychaudhuri equation can be transformed to a harmonic oscillator
equation, and it has been shown that the geodesic deviation equation of Jacobi
is essentially equivalent to that of a harmonic oscillator. The Raychaudhuri
equations are strong geometrical tools in the study of General Relativity and
Cosmology. We suggest a refined entropy measure applicable in Cosmology and
defined by the average deviation of the geodesics in a congruence.
| [
{
"created": "Wed, 29 Apr 2015 13:35:07 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Dec 2017 10:49:34 GMT",
"version": "v2"
}
] | 2017-12-27 | [
[
"Weinstein",
"Gilbert",
""
],
[
"Strauss",
"Yosef",
""
],
[
"Bondarenko",
"Sergey",
""
],
[
"Yahalom",
"Asher",
""
],
[
"Lewkowicz",
"Meir",
""
],
[
"Horwitz",
"Lawrence Paul",
""
],
[
"Levitan",
"Jacob",
"... | Classical chaos is often characterized as exponential divergence of nearby trajectories. In many interesting cases these trajectories can be identified with geodesic curves. We define here the entropy by $S = \ln \chi (x)$ with $\chi(x)$ being the distance between two nearby geodesics. We derive an equation for the entropy which by transformation to a Ricatti-type equation becomes similar to the Jacobi equation. We further show that the geodesic equation for a null geodesic in a double warped space time leads to the same entropy equation. By applying a Robertson-Walker metric for a flat three-dimensional Euclidian space expanding as a function of time, we again reach the entropy equation stressing the connection between the chosen entropy measure and time. We finally turn to the Raychaudhuri equation for expansion, which also is a Ricatti equation similar to the transformed entropy equation. Those Ricatti-type equations have solutions of the same form as the Jacobi equation. The Raychaudhuri equation can be transformed to a harmonic oscillator equation, and it has been shown that the geodesic deviation equation of Jacobi is essentially equivalent to that of a harmonic oscillator. The Raychaudhuri equations are strong geometrical tools in the study of General Relativity and Cosmology. We suggest a refined entropy measure applicable in Cosmology and defined by the average deviation of the geodesics in a congruence. |
gr-qc/9907024 | Marc Toussaint | Marc Toussaint | A gauge theoretical view of the charge concept in Einstein gravity | LaTeX2e, 16 pages, 1 figure; enhanced discussion | Gen.Rel.Grav. 32 (2000) 885-896 | 10.1023/A:1001985024409 | Cologne-ThP-He2-Jul99 | gr-qc hep-th | null | We will discuss some analogies between internal gauge theories and gravity in
order to better understand the charge concept in gravity. A dimensional
analysis of gauge theories in general and a strict definition of elementary,
monopole, and topological charges are applied to electromagnetism and to
teleparallelism, a gauge theoretical formulation of Einstein gravity.
As a result we inevitably find that the gravitational coupling constant has
dimension $\hbar/l^2$, the mass parameter of a particle dimension $\hbar/l$,
and the Schwarzschild mass parameter dimension l (where l means length). These
dimensions confirm the meaning of mass as elementary and as monopole charge of
the translation group, respectively. In detail, we find that the Schwarzschild
mass parameter is a quasi-electric monopole charge of the time translation
whereas the NUT parameter is a quasi-magnetic monopole charge of the time
translation as well as a topological charge. The Kerr parameter and the
electric and magnetic charges are interpreted similarly. We conclude that each
elementary charge of a Casimir operator of the gauge group is the source of a
(quasi-electric) monopole charge of the respective Killing vector.
| [
{
"created": "Tue, 6 Jul 1999 16:09:05 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Mar 2000 10:53:28 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Toussaint",
"Marc",
""
]
] | We will discuss some analogies between internal gauge theories and gravity in order to better understand the charge concept in gravity. A dimensional analysis of gauge theories in general and a strict definition of elementary, monopole, and topological charges are applied to electromagnetism and to teleparallelism, a gauge theoretical formulation of Einstein gravity. As a result we inevitably find that the gravitational coupling constant has dimension $\hbar/l^2$, the mass parameter of a particle dimension $\hbar/l$, and the Schwarzschild mass parameter dimension l (where l means length). These dimensions confirm the meaning of mass as elementary and as monopole charge of the translation group, respectively. In detail, we find that the Schwarzschild mass parameter is a quasi-electric monopole charge of the time translation whereas the NUT parameter is a quasi-magnetic monopole charge of the time translation as well as a topological charge. The Kerr parameter and the electric and magnetic charges are interpreted similarly. We conclude that each elementary charge of a Casimir operator of the gauge group is the source of a (quasi-electric) monopole charge of the respective Killing vector. |
2302.02244 | Peter K.F. Kuhfittig | Peter K.F. Kuhfittig | Noncommutative-geometry wormholes based on the Casimir effect | 6 pages, no figures | J. High Energy Phys. Grav. Cosmol. (JHEPGC) Vol. 9, 295-300, 2023 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | While wormholes are as good a prediction of Einstein's theory as black holes,
they are subject to severe restrictions from quantum field theory. In
particular, holding a wormhole open requires a violation of the null energy
condition, calling for the existence of exotic matter. The Casimir effect has
shown that this physical requirement can be met on a small scale, thereby
solving a key conceptual problem. The Casimir effect does not, however,
guarantee that the small-scale violation is sufficient for supporting a
macroscopic wormhole. The purpose of this paper is to connect the Casimir
effect to noncommutative geometry, which also aims to accommodate small-scale
effects, the difference being that these can now be viewed as intrinsic
properties of spacetime. As a result, the noncommutative effects can be
implemented by modifying only the energy momentum tensor in the Einstein field
equations, while leaving the Einstein tensor unchanged. The wormhole can
therefore be macroscopic in spite of the small Casimir effect.
| [
{
"created": "Sat, 4 Feb 2023 21:09:38 GMT",
"version": "v1"
},
{
"created": "Mon, 22 May 2023 14:37:09 GMT",
"version": "v2"
}
] | 2023-05-23 | [
[
"Kuhfittig",
"Peter K. F.",
""
]
] | While wormholes are as good a prediction of Einstein's theory as black holes, they are subject to severe restrictions from quantum field theory. In particular, holding a wormhole open requires a violation of the null energy condition, calling for the existence of exotic matter. The Casimir effect has shown that this physical requirement can be met on a small scale, thereby solving a key conceptual problem. The Casimir effect does not, however, guarantee that the small-scale violation is sufficient for supporting a macroscopic wormhole. The purpose of this paper is to connect the Casimir effect to noncommutative geometry, which also aims to accommodate small-scale effects, the difference being that these can now be viewed as intrinsic properties of spacetime. As a result, the noncommutative effects can be implemented by modifying only the energy momentum tensor in the Einstein field equations, while leaving the Einstein tensor unchanged. The wormhole can therefore be macroscopic in spite of the small Casimir effect. |
gr-qc/9411054 | Markus Heusler | M. Heusler | A Mass Bound for Spherically Symmetric Black Hole Spacetimes | 16 pages, LATEX, no figures | Class.Quant.Grav.12:779-790,1995 | 10.1088/0264-9381/12/3/015 | null | gr-qc | null | Requiring that the matter fields are subject to the dominant energy
condition, we establish the lower bound $(4\pi)^{-1} \kappa {\cal A}$ for the
total mass $M$ of a static, spherically symmetric black hole spacetime. (${\cal
A}$ and $\kappa$ denote the area and the surface gravity of the horizon,
respectively.) Together with the fact that the Komar integral provides a simple
relation between $M - (4\pi)^{-1} \kappa A$ and the strong energy condition,
this enables us to prove that the Schwarzschild metric represents the only
static, spherically symmetric black hole solution of a selfgravitating matter
model satisfying the dominant, but violating the strong energy condition for
the timelike Killing field $K$ at every point, that is, $R(K,K) \leq 0$.
Applying this result to scalar fields, we recover the fact that the only black
hole configuration of the spherically symmetric Einstein-Higgs model with
arbitrary non-negative potential is the Schwarzschild spacetime with constant
Higgs field. In the presence of electromagnetic fields, we also derive a
stronger bound for the total mass, involving the electromagnetic potentials and
charges. Again, this estimate provides a simple tool to prove a ``no-hair''
theorem for matter fields violating the strong energy condition.
| [
{
"created": "Mon, 21 Nov 1994 16:46:01 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Heusler",
"M.",
""
]
] | Requiring that the matter fields are subject to the dominant energy condition, we establish the lower bound $(4\pi)^{-1} \kappa {\cal A}$ for the total mass $M$ of a static, spherically symmetric black hole spacetime. (${\cal A}$ and $\kappa$ denote the area and the surface gravity of the horizon, respectively.) Together with the fact that the Komar integral provides a simple relation between $M - (4\pi)^{-1} \kappa A$ and the strong energy condition, this enables us to prove that the Schwarzschild metric represents the only static, spherically symmetric black hole solution of a selfgravitating matter model satisfying the dominant, but violating the strong energy condition for the timelike Killing field $K$ at every point, that is, $R(K,K) \leq 0$. Applying this result to scalar fields, we recover the fact that the only black hole configuration of the spherically symmetric Einstein-Higgs model with arbitrary non-negative potential is the Schwarzschild spacetime with constant Higgs field. In the presence of electromagnetic fields, we also derive a stronger bound for the total mass, involving the electromagnetic potentials and charges. Again, this estimate provides a simple tool to prove a ``no-hair'' theorem for matter fields violating the strong energy condition. |
gr-qc/9405035 | Desmond McManus | Des J. Mc Manus and Alan A. Coley | Shear-free, Irrotational, Geodesic, Anisotropic Fluid Cosmologies | 13 pages LaTeX | Class.Quant.Grav.11:2045-2058,1994 | 10.1088/0264-9381/11/8/011 | null | gr-qc | null | General relativistic anisotropic fluid models whose fluid flow lines form a
shear-free, irrotational, geodesic timelike congruence are examined. These
models are of Petrov type D, and are assumed to have zero heat flux and an
anisotropic stress tensor that possesses two distinct non-zero eigenvalues.
Some general results concerning the form of the metric and the stress-tensor
for these models are established. Furthermore, if the energy density and the
isotropic pressure, as measured by a comoving observer, satisfy an equation of
state of the form $p = p(\mu)$, with $\frac{dp}{d\mu} \neq -\frac{1}{3}$, then
these spacetimes admit a foliation by spacelike hypersurfaces of constant Ricci
scalar. In addition, models for which both the energy density and the
anisotropic pressures only depend on time are investigated; both spatially
homogeneous and spatially inhomogeneous models are found. A classification of
these models is undertaken. Also, a particular class of anisotropic fluid
models which are simple generalizations of the homogeneous isotropic
cosmological models is studied.
| [
{
"created": "Mon, 16 May 1994 17:40:58 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Manus",
"Des J. Mc",
""
],
[
"Coley",
"Alan A.",
""
]
] | General relativistic anisotropic fluid models whose fluid flow lines form a shear-free, irrotational, geodesic timelike congruence are examined. These models are of Petrov type D, and are assumed to have zero heat flux and an anisotropic stress tensor that possesses two distinct non-zero eigenvalues. Some general results concerning the form of the metric and the stress-tensor for these models are established. Furthermore, if the energy density and the isotropic pressure, as measured by a comoving observer, satisfy an equation of state of the form $p = p(\mu)$, with $\frac{dp}{d\mu} \neq -\frac{1}{3}$, then these spacetimes admit a foliation by spacelike hypersurfaces of constant Ricci scalar. In addition, models for which both the energy density and the anisotropic pressures only depend on time are investigated; both spatially homogeneous and spatially inhomogeneous models are found. A classification of these models is undertaken. Also, a particular class of anisotropic fluid models which are simple generalizations of the homogeneous isotropic cosmological models is studied. |
1807.01939 | Ronaldas Macas | Francesco Pannarale, Ronaldas Macas, Patrick J. Sutton | Bayesian Inference Analysis of Unmodelled Gravitational-Wave Transients | 10 pages, 7 figures | null | 10.1088/1361-6382/aaf76d | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report the results of an in-depth analysis of the parameter estimation
capabilities of BayesWave, an algorithm for the reconstruction of
gravitational-wave signals without reference to a specific signal model. Using
binary black hole signals, we compare BayesWave's performance to the
theoretical best achievable performance in three key areas: sky localisation
accuracy, signal/noise discrimination, and waveform reconstruction accuracy.
BayesWave is most effective for signals that have very compact time-frequency
representations. For binaries, where the signal time-frequency volume decreases
with mass, we find that BayesWave's performance reaches or approaches
theoretical optimal limits for system masses above approximately 50 M_sun. For
such systems BayesWave is able to localise the source on the sky as well as
templated Bayesian analyses that rely on a precise signal model, and it is
better than timing-only triangulation in all cases. We also show that the
discrimination of signals against glitches and noise closely follow analytical
predictions, and that only a small fraction of signals are discarded as
glitches at a false alarm rate of 1/100 y. Finally, the match between
BayesWave- reconstructed signals and injected signals is broadly consistent
with first-principles estimates of the maximum possible accuracy, peaking at
about 0.95 for high mass systems and decreasing for lower-mass systems. These
results demonstrate the potential of unmodelled signal reconstruction
techniques for gravitational-wave astronomy.
| [
{
"created": "Thu, 5 Jul 2018 10:56:33 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Jul 2018 11:54:05 GMT",
"version": "v2"
},
{
"created": "Mon, 10 Sep 2018 08:45:48 GMT",
"version": "v3"
}
] | 2019-02-13 | [
[
"Pannarale",
"Francesco",
""
],
[
"Macas",
"Ronaldas",
""
],
[
"Sutton",
"Patrick J.",
""
]
] | We report the results of an in-depth analysis of the parameter estimation capabilities of BayesWave, an algorithm for the reconstruction of gravitational-wave signals without reference to a specific signal model. Using binary black hole signals, we compare BayesWave's performance to the theoretical best achievable performance in three key areas: sky localisation accuracy, signal/noise discrimination, and waveform reconstruction accuracy. BayesWave is most effective for signals that have very compact time-frequency representations. For binaries, where the signal time-frequency volume decreases with mass, we find that BayesWave's performance reaches or approaches theoretical optimal limits for system masses above approximately 50 M_sun. For such systems BayesWave is able to localise the source on the sky as well as templated Bayesian analyses that rely on a precise signal model, and it is better than timing-only triangulation in all cases. We also show that the discrimination of signals against glitches and noise closely follow analytical predictions, and that only a small fraction of signals are discarded as glitches at a false alarm rate of 1/100 y. Finally, the match between BayesWave- reconstructed signals and injected signals is broadly consistent with first-principles estimates of the maximum possible accuracy, peaking at about 0.95 for high mass systems and decreasing for lower-mass systems. These results demonstrate the potential of unmodelled signal reconstruction techniques for gravitational-wave astronomy. |
gr-qc/0102072 | Janusz Garecki | Janusz Garecki | Do gravitational waves carry energy-momentum and angular momentum? | REVTEX, 14 pages | AnnalenPhys.11:442-456,2002 | 10.1002/1521-3889(200206)11:6<442::AID-ANDP442>3.0.CO;2-A | null | gr-qc | null | In the paper we show that the real gravitational waves which have
$R_{iklm}\not= 0$ always carry energy-momentum and angular momentum. Our proof
uses canonical superenergy and supermomentum tensors for gravitational field.
| [
{
"created": "Thu, 15 Feb 2001 15:01:17 GMT",
"version": "v1"
}
] | 2017-09-27 | [
[
"Garecki",
"Janusz",
""
]
] | In the paper we show that the real gravitational waves which have $R_{iklm}\not= 0$ always carry energy-momentum and angular momentum. Our proof uses canonical superenergy and supermomentum tensors for gravitational field. |
1501.04484 | Ifra Noureen | Ifra Noureen, M. Zubair | Dynamical Instability and Expansion-free Condition in $f(R,T)$ Gravity | 22 pages | Eur. Phys. J. C (2015) 75:62 | 10.1140/epjc/s10052-015-3289-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dynamical analysis of spherically symmetric collapsing star surrounding in
locally anisotropic environment with expansion-free condition is presented in
$f(R,T)$ gravity, where $R$ corresponds to Ricci scalar and $T$ stands for the
trace of energy momentum tensor. The modified field equations and evolution
equations are reconstructed in the framework of $f(R,T)$ gravty. In order to
acquire the collapse equation we implement the perturbation on all matter
variables and dark source components comprising the viable $f(R,T)$ model. The
instability range is described in Newtonian and post-Newtonian eras by
constraining the adiabatic index $\Gamma$ to maintain viability of considered
model and stable stellar configuration.
| [
{
"created": "Mon, 19 Jan 2015 13:16:58 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Apr 2015 12:07:57 GMT",
"version": "v2"
}
] | 2015-04-21 | [
[
"Noureen",
"Ifra",
""
],
[
"Zubair",
"M.",
""
]
] | Dynamical analysis of spherically symmetric collapsing star surrounding in locally anisotropic environment with expansion-free condition is presented in $f(R,T)$ gravity, where $R$ corresponds to Ricci scalar and $T$ stands for the trace of energy momentum tensor. The modified field equations and evolution equations are reconstructed in the framework of $f(R,T)$ gravty. In order to acquire the collapse equation we implement the perturbation on all matter variables and dark source components comprising the viable $f(R,T)$ model. The instability range is described in Newtonian and post-Newtonian eras by constraining the adiabatic index $\Gamma$ to maintain viability of considered model and stable stellar configuration. |
2307.09268 | Agata Trovato | A. Trovato, \'E. Chassande-Mottin, M. Bejger, R. Flamary, N.Courty | Neural network time-series classifiers for gravitational-wave searches
in single-detector periods | 29 pages, 11 figures, submitted to CQG | Class. Quantum Grav. 41 125003 (2024) | 10.1088/1361-6382/ad40f0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The search for gravitational-wave signals is limited by non-Gaussian
transient noises that mimic astrophysical signals. Temporal coincidence between
two or more detectors is used to mitigate contamination by these instrumental
glitches. However, when a single detector is in operation, coincidence is
impossible, and other strategies have to be used. We explore the possibility of
using neural network classifiers and present the results obtained with three
types of architectures: convolutional neural network, temporal convolutional
network, and inception time. The last two architectures are specifically
designed to process time-series data. The classifiers are trained on a month of
data from the LIGO Livingston detector during the first observing run (O1) to
identify data segments that include the signature of a binary black hole
merger. Their performances are assessed and compared. We then apply trained
classifiers to the remaining three months of O1 data, focusing specifically on
single-detector times. The most promising candidate from our search is
2016-01-04 12:24:17 UTC. Although we are not able to constrain the significance
of this event to the level conventionally followed in gravitational-wave
searches, we show that the signal is compatible with the merger of two black
holes with masses $m_1 = 50.7^{+10.4}_{-8.9}\,M_{\odot}$ and $m_2 =
24.4^{+20.2}_{-9.3}\,M_{\odot}$ at the luminosity distance of $d_L =
564^{+812}_{-338}\,\mathrm{Mpc}$.
| [
{
"created": "Tue, 18 Jul 2023 13:50:23 GMT",
"version": "v1"
}
] | 2024-05-15 | [
[
"Trovato",
"A.",
""
],
[
"Chassande-Mottin",
"É.",
""
],
[
"Bejger",
"M.",
""
],
[
"Flamary",
"R.",
""
],
[
"Courty",
"N.",
""
]
] | The search for gravitational-wave signals is limited by non-Gaussian transient noises that mimic astrophysical signals. Temporal coincidence between two or more detectors is used to mitigate contamination by these instrumental glitches. However, when a single detector is in operation, coincidence is impossible, and other strategies have to be used. We explore the possibility of using neural network classifiers and present the results obtained with three types of architectures: convolutional neural network, temporal convolutional network, and inception time. The last two architectures are specifically designed to process time-series data. The classifiers are trained on a month of data from the LIGO Livingston detector during the first observing run (O1) to identify data segments that include the signature of a binary black hole merger. Their performances are assessed and compared. We then apply trained classifiers to the remaining three months of O1 data, focusing specifically on single-detector times. The most promising candidate from our search is 2016-01-04 12:24:17 UTC. Although we are not able to constrain the significance of this event to the level conventionally followed in gravitational-wave searches, we show that the signal is compatible with the merger of two black holes with masses $m_1 = 50.7^{+10.4}_{-8.9}\,M_{\odot}$ and $m_2 = 24.4^{+20.2}_{-9.3}\,M_{\odot}$ at the luminosity distance of $d_L = 564^{+812}_{-338}\,\mathrm{Mpc}$. |
gr-qc/9304031 | Juan Pablo | Juan Pablo Paz and Wojciech Hubert Zurek | Environment--Induced Decoherence, Classicality and Consistency of
Quantum Histories | 32 pages (1 figure, postcript included at the end: use epsf.tex and
follow instructions before Texing) LA-UR-93-1415 | Phys.Rev.D48:2728-2738,1993 | 10.1103/PhysRevD.48.2728 | null | gr-qc | null | We prove that for an open system, in the Markovian regime, it is always
possible to construct an infinite number of non trivial sets of histories that
exactly satisfy the probability sum rules. In spite of being perfectly
consistent, these sets manifest a very non--classical behavior: they are quite
unstable under the addition of an extra instant to the list of times defining
the history. To eliminate this feature --whose implications for the
interpretation of the formalism we discuss-- and to achieve the stability that
characterizes the quasiclassical domain, it is necessary to separate the
instants which define the history by time intervals significantly larger than
the typical decoherence time. In this case environment induced superselection
is very effective and the quasiclassical domain is characterized by histories
constructed with ``pointer projectors''.
| [
{
"created": "Tue, 20 Apr 1993 22:21:57 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Paz",
"Juan Pablo",
""
],
[
"Zurek",
"Wojciech Hubert",
""
]
] | We prove that for an open system, in the Markovian regime, it is always possible to construct an infinite number of non trivial sets of histories that exactly satisfy the probability sum rules. In spite of being perfectly consistent, these sets manifest a very non--classical behavior: they are quite unstable under the addition of an extra instant to the list of times defining the history. To eliminate this feature --whose implications for the interpretation of the formalism we discuss-- and to achieve the stability that characterizes the quasiclassical domain, it is necessary to separate the instants which define the history by time intervals significantly larger than the typical decoherence time. In this case environment induced superselection is very effective and the quasiclassical domain is characterized by histories constructed with ``pointer projectors''. |
gr-qc/9704005 | 3 | Donald E. Neville | Energy and directional signatures for plane quantized gravity waves | 54 pages; LaTex | Phys.Rev. D57 (1998) 986-1008 | 10.1103/PhysRevD.57.986 | TU-33l-97 | gr-qc | null | Solutions are constructed to the quantum constraints for planar gravity
(fields dependent on z and t only) in the Ashtekar complex connection
formalism. A number of operators are constructed and applied to the solutions.
These include the familiar ADM energy and area operators, as well as new
operators sensitive to directionality (z+ct vs. z-ct dependence). The
directionality operators are quantum analogs of the classical constraints
proposed for unidirectional plane waves by Bondi, Pirani, and Robinson (BPR).
It is argued that the quantum BPR constraints will predict unidirectionality
reliably only for solutions which are semiclassical in a certain sense. The ADM
energy and area operators are likely to have imaginary eigenvalues, unless one
either shifts to a real connection, or allows the connection to occur other
than in a holonomy. In classical theory, the area can evolve to zero. A quantum
mechanical mechanism is proposed which would prevent this collapse.
| [
{
"created": "Tue, 1 Apr 1997 19:32:23 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Neville",
"Donald E.",
""
]
] | Solutions are constructed to the quantum constraints for planar gravity (fields dependent on z and t only) in the Ashtekar complex connection formalism. A number of operators are constructed and applied to the solutions. These include the familiar ADM energy and area operators, as well as new operators sensitive to directionality (z+ct vs. z-ct dependence). The directionality operators are quantum analogs of the classical constraints proposed for unidirectional plane waves by Bondi, Pirani, and Robinson (BPR). It is argued that the quantum BPR constraints will predict unidirectionality reliably only for solutions which are semiclassical in a certain sense. The ADM energy and area operators are likely to have imaginary eigenvalues, unless one either shifts to a real connection, or allows the connection to occur other than in a holonomy. In classical theory, the area can evolve to zero. A quantum mechanical mechanism is proposed which would prevent this collapse. |
gr-qc/9910044 | Charles W. Misner | Charles W. Misner (University of Maryland) | Spherical Harmonic Decomposition on a Cubic Grid | 5 pages, LaTeX uses cjour.cls (supplied) | Class.Quant.Grav.21:S243-S248,2004 | 10.1088/0264-9381/21/3/014 | UM PP-00-032 | gr-qc | null | A method is described by which a function defined on a cubic grid (as from a
finite difference solution of a partial differential equation) can be resolved
into spherical harmonic components at some fixed radius. This has applications
to the treatment of boundary conditions imposed at radii larger than the size
of the grid, following Abrahams, Rezzola, Rupright et al.(gr-qc/9709082}. In
the method described here, the interpolation of the grid data to the
integration 2-sphere is combined in the same step as the integrations to
extract the spherical harmonic amplitudes, which become sums over grid points.
Coordinates adapted to the integration sphere are not needed.
| [
{
"created": "Tue, 12 Oct 1999 21:53:58 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Misner",
"Charles W.",
"",
"University of Maryland"
]
] | A method is described by which a function defined on a cubic grid (as from a finite difference solution of a partial differential equation) can be resolved into spherical harmonic components at some fixed radius. This has applications to the treatment of boundary conditions imposed at radii larger than the size of the grid, following Abrahams, Rezzola, Rupright et al.(gr-qc/9709082}. In the method described here, the interpolation of the grid data to the integration 2-sphere is combined in the same step as the integrations to extract the spherical harmonic amplitudes, which become sums over grid points. Coordinates adapted to the integration sphere are not needed. |
1904.11790 | J. Fernando Barbero G. | J. Fernando Barbero G., Bogar D\'iaz, Juan Margalef-Bentabol and
Eduardo J. S. Villase\~nor | Dirac's algorithm in the presence of boundaries: a practical guide to a
geometric approach | 25 pages | Classical and Quantum Gravity, 36 (2019) 205014 | 10.1088/1361-6382/ab436b | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The goal of this paper is to propose and discuss a practical way to implement
the Dirac algorithm for constrained field models defined on spatial regions
with boundaries. Our method is inspired in the geometric viewpoint developed by
Gotay, Nester, and Hinds (GNH) to deal with singular Hamiltonian systems. We
pay special attention to the specific issues raised by the presence of
boundaries and provide a number of significant examples -among them field
theories related to general relativity- to illustrate the main features of our
approach.
| [
{
"created": "Fri, 26 Apr 2019 12:13:26 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Aug 2019 08:19:41 GMT",
"version": "v2"
},
{
"created": "Mon, 30 Sep 2019 09:49:26 GMT",
"version": "v3"
}
] | 2019-10-01 | [
[
"G.",
"J. Fernando Barbero",
""
],
[
"Díaz",
"Bogar",
""
],
[
"Margalef-Bentabol",
"Juan",
""
],
[
"Villaseñor",
"Eduardo J. S.",
""
]
] | The goal of this paper is to propose and discuss a practical way to implement the Dirac algorithm for constrained field models defined on spatial regions with boundaries. Our method is inspired in the geometric viewpoint developed by Gotay, Nester, and Hinds (GNH) to deal with singular Hamiltonian systems. We pay special attention to the specific issues raised by the presence of boundaries and provide a number of significant examples -among them field theories related to general relativity- to illustrate the main features of our approach. |
gr-qc/9710031 | Eric Gourgoulhon | S. Bonazzola, E. Gourgoulhon, J.-A. Marck (DARC, CNRS, Observatoire de
Paris, France) | A relativistic formalism to compute quasi-equilibrium configurations of
non-synchronized neutron star binaries | 14 pages, 1 PostScript figure, RevTeX, accepted for publication in
Physical Review D | Phys.Rev. D56 (1997) 7740-7749 | 10.1103/PhysRevD.56.7740 | null | gr-qc astro-ph | null | A general relativistic version of the Euler equation for perfect fluid
hydrodynamics is applied to a system of two neutron stars orbiting each other.
In the quasi-equilibrium phase of the evolution of this system, a first
integral of motion can be derived for certain velocity fields of the neutron
star fluid including the (academic) case of co-rotation with respect to the
orbital motion (synchronized binaries) and the realistic case of
counter-rotation with respect to the orbital motion. The velocity field leading
to this latter configuration can be computed by solving three-dimensional
vector and scalar Poisson equations.
| [
{
"created": "Mon, 6 Oct 1997 11:20:20 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Bonazzola",
"S.",
"",
"DARC, CNRS, Observatoire de\n Paris, France"
],
[
"Gourgoulhon",
"E.",
"",
"DARC, CNRS, Observatoire de\n Paris, France"
],
[
"Marck",
"J. -A.",
"",
"DARC, CNRS, Observatoire de\n Paris, France"
]
] | A general relativistic version of the Euler equation for perfect fluid hydrodynamics is applied to a system of two neutron stars orbiting each other. In the quasi-equilibrium phase of the evolution of this system, a first integral of motion can be derived for certain velocity fields of the neutron star fluid including the (academic) case of co-rotation with respect to the orbital motion (synchronized binaries) and the realistic case of counter-rotation with respect to the orbital motion. The velocity field leading to this latter configuration can be computed by solving three-dimensional vector and scalar Poisson equations. |
1401.0895 | Behrouz Mirza | Behrouz Mirza, Fatemeh Oboudiat, Somayeh Zare | Dimension of quantum channel of radiation in pure Lovelock black holes | 6 pages | Gen Relativ Gravit (2014) 46:1652 | 10.1007/s10714-013-1652-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is known that the emission rate of entropy from a Schwarzschild black hole
is exactly the same as that of a one dimensional quantum channel \cite{Beken}.
We calculate the dimension of entropy emission from a $D$ dimensional pure
Lovelock black holes. Our results indicate that the dimension of transmission
for odd $D$ dimensional space-times is equal to $D$ and for even $D$
dimensional space-times, the dimension of quantum channel becomes $1+\epsilon
(\Lambda)$, where $ \Lambda $ is cosmological constant. It is interesting that
cosmological constant may put some constraint on dimension of quantum channel
in even dimensional space-times. The effect of Generalized Uncertainty
Principle (GUP) on the dimension of transmission of entropy for a Schwarzschild
black hole is also investigated.
| [
{
"created": "Sun, 5 Jan 2014 14:20:10 GMT",
"version": "v1"
}
] | 2014-06-10 | [
[
"Mirza",
"Behrouz",
""
],
[
"Oboudiat",
"Fatemeh",
""
],
[
"Zare",
"Somayeh",
""
]
] | It is known that the emission rate of entropy from a Schwarzschild black hole is exactly the same as that of a one dimensional quantum channel \cite{Beken}. We calculate the dimension of entropy emission from a $D$ dimensional pure Lovelock black holes. Our results indicate that the dimension of transmission for odd $D$ dimensional space-times is equal to $D$ and for even $D$ dimensional space-times, the dimension of quantum channel becomes $1+\epsilon (\Lambda)$, where $ \Lambda $ is cosmological constant. It is interesting that cosmological constant may put some constraint on dimension of quantum channel in even dimensional space-times. The effect of Generalized Uncertainty Principle (GUP) on the dimension of transmission of entropy for a Schwarzschild black hole is also investigated. |
gr-qc/0312080 | Umpei Miyamoto | Umpei Miyamoto, Tomohiro Harada | Semiclassical Instability of the Cauchy Horizon in Self-Similar Collapse | 14 pages, 4 figures, minor errors corrected and some sentences added
in the introduction, accepted for publication in Physical Review D | Phys.Rev. D69 (2004) 104005 | 10.1103/PhysRevD.69.104005 | null | gr-qc astro-ph hep-th quant-ph | null | Generic spherically symmetric self-similar collapse results in strong
naked-singularity formation. In this paper we are concerned with particle
creation during a naked-singularity formation in spherically symmetric
self-similar collapse without specifying the collapsing matter. In the generic
case, the power of particle emission is found to be proportional to the inverse
square of the remaining time to the Cauchy horizon (CH). The constant of
proportion can be arbitrarily large in the limit to marginally naked
singularity. Therefore, the unbounded power is especially striking in the case
that an event horizon is very close to the CH because the emitted energy can be
arbitrarily large in spite of a cutoff expected from quantum gravity. Above
results suggest the instability of the CH in spherically symmetric self-similar
spacetime from quantum field theory and seem to support the existence of a
semiclassical cosmic censor. The divergence of redshifts and blueshifts of
emitted particles is found to cause the divergence of power to positive or
negative infinity, depending on the coupling manner of scalar fields to
gravity. On the other hand, it is found that there is a special class of
self-similar spacetimes in which the semiclassical instability of the CH is not
efficient. The analyses in this paper are based on the geometric optics
approximation, which is justified in two dimensions but needs justification in
four dimensions.
| [
{
"created": "Wed, 17 Dec 2003 20:13:55 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Feb 2004 14:01:19 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Miyamoto",
"Umpei",
""
],
[
"Harada",
"Tomohiro",
""
]
] | Generic spherically symmetric self-similar collapse results in strong naked-singularity formation. In this paper we are concerned with particle creation during a naked-singularity formation in spherically symmetric self-similar collapse without specifying the collapsing matter. In the generic case, the power of particle emission is found to be proportional to the inverse square of the remaining time to the Cauchy horizon (CH). The constant of proportion can be arbitrarily large in the limit to marginally naked singularity. Therefore, the unbounded power is especially striking in the case that an event horizon is very close to the CH because the emitted energy can be arbitrarily large in spite of a cutoff expected from quantum gravity. Above results suggest the instability of the CH in spherically symmetric self-similar spacetime from quantum field theory and seem to support the existence of a semiclassical cosmic censor. The divergence of redshifts and blueshifts of emitted particles is found to cause the divergence of power to positive or negative infinity, depending on the coupling manner of scalar fields to gravity. On the other hand, it is found that there is a special class of self-similar spacetimes in which the semiclassical instability of the CH is not efficient. The analyses in this paper are based on the geometric optics approximation, which is justified in two dimensions but needs justification in four dimensions. |
0801.3801 | Virginia Re | AURIGA Collaboration, Virgo Collaboration | A Cross-correlation method to search for gravitational wave bursts with
AURIGA and Virgo | 11 pages, 6 figures, submitted to CQG special issue for Amaldi 7
Proceedings | Class.Quant.Grav.25:114046,2008 | 10.1088/0264-9381/25/11/114046 | null | gr-qc | null | We present a method to search for transient GWs using a network of detectors
with different spectral and directional sensitivities: the interferometer Virgo
and the bar detector AURIGA. The data analysis method is based on the
measurements of the correlated energy in the network by means of a weighted
cross-correlation. To limit the computational load, this coherent analysis step
is performed around time-frequency coincident triggers selected by an excess
power event trigger generator tuned at low thresholds. The final selection of
GW candidates is performed by a combined cut on the correlated energy and on
the significance as measured by the event trigger generator. The method has
been tested on one day of data of AURIGA and Virgo during September 2005. The
outcomes are compared to the results of a stand-alone time-frequency
coincidence search. We discuss the advantages and the limits of this approach,
in view of a possible future joint search between AURIGA and one
interferometric detector.
| [
{
"created": "Thu, 24 Jan 2008 17:03:21 GMT",
"version": "v1"
}
] | 2012-08-27 | [
[
"AURIGA Collaboration",
"",
""
],
[
"Virgo Collaboration",
"",
""
]
] | We present a method to search for transient GWs using a network of detectors with different spectral and directional sensitivities: the interferometer Virgo and the bar detector AURIGA. The data analysis method is based on the measurements of the correlated energy in the network by means of a weighted cross-correlation. To limit the computational load, this coherent analysis step is performed around time-frequency coincident triggers selected by an excess power event trigger generator tuned at low thresholds. The final selection of GW candidates is performed by a combined cut on the correlated energy and on the significance as measured by the event trigger generator. The method has been tested on one day of data of AURIGA and Virgo during September 2005. The outcomes are compared to the results of a stand-alone time-frequency coincidence search. We discuss the advantages and the limits of this approach, in view of a possible future joint search between AURIGA and one interferometric detector. |
gr-qc/0312020 | Alan D. Rendall | Alan D. Rendall | Asymptotics of solutions of the Einstein equations with positive
cosmological constant | 23 pages | Annales Henri Poincare 5 (2004) 1041-1064 | 10.1007/s00023-004-0189-1 | AEI-2003-102 | gr-qc | null | A positive cosmological constant simplifies the asymptotics of forever
expanding cosmological solutions of the Einstein equations. In this paper a
general mathematical analysis on the level of formal power series is carried
out for vacuum spacetimes of any dimension and perfect fluid spacetimes with
linear equation of state in spacetime dimension four. For equations of state
stiffer than radiation evidence for development of large gradients, analogous
to spikes in Gowdy spacetimes, is found. It is shown that any vacuum solution
satisfying minimal asymptotic conditions has a full asymptotic expansion given
by the formal series. In four spacetime dimensions, and for spatially
homogeneous spacetimes of any dimension, these minimal conditions can be
derived for appropriate initial data. Using Fuchsian methods the existence of
vacuum spacetimes with the given formal asymptotics depending on the maximal
number of free functions is shown without symmetry assumptions.
| [
{
"created": "Wed, 3 Dec 2003 11:44:46 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Rendall",
"Alan D.",
""
]
] | A positive cosmological constant simplifies the asymptotics of forever expanding cosmological solutions of the Einstein equations. In this paper a general mathematical analysis on the level of formal power series is carried out for vacuum spacetimes of any dimension and perfect fluid spacetimes with linear equation of state in spacetime dimension four. For equations of state stiffer than radiation evidence for development of large gradients, analogous to spikes in Gowdy spacetimes, is found. It is shown that any vacuum solution satisfying minimal asymptotic conditions has a full asymptotic expansion given by the formal series. In four spacetime dimensions, and for spatially homogeneous spacetimes of any dimension, these minimal conditions can be derived for appropriate initial data. Using Fuchsian methods the existence of vacuum spacetimes with the given formal asymptotics depending on the maximal number of free functions is shown without symmetry assumptions. |
0805.1900 | Francesco Cianfrani dr | F. Cianfrani, G. Montani | Synchronous Quantum Gravity | 8 pages, Proceedings of the II Stueckelberg workshop | Int.J.Mod.Phys.23:1105-1112,2008 | 10.1142/S0217751X08040007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The implications of restricting the covariance principle within a Gaussian
gauge are developed both on a classical and a quantum level. Hence, we
investigate the cosmological issues of the obtained Schr\"odinger Quantum
Gravity with respect to the asymptotically early dynamics of a generic
Universe. A dualism between time and the reference frame fixing is then
inferred.
| [
{
"created": "Tue, 13 May 2008 18:41:39 GMT",
"version": "v1"
}
] | 2009-11-13 | [
[
"Cianfrani",
"F.",
""
],
[
"Montani",
"G.",
""
]
] | The implications of restricting the covariance principle within a Gaussian gauge are developed both on a classical and a quantum level. Hence, we investigate the cosmological issues of the obtained Schr\"odinger Quantum Gravity with respect to the asymptotically early dynamics of a generic Universe. A dualism between time and the reference frame fixing is then inferred. |
gr-qc/0603093 | Grigory Volovik | G.E. Volovik | Horizons and Ergoregions in Superfluids | 21 pages, 5 Figures, JLTP style, prepared for proceedings of the
workshop "Universal features in turbulence: from quantum to cosmological
scales", December 2005, Warwick, version submitted to JLTP, discussion on
Hawking radiation extended, references added | J.LowTemp.Phys.145:337-356,2006 | 10.1007/s10909-006-9248-y | null | gr-qc cond-mat.soft hep-ph physics.flu-dyn | null | Ripplons -- gravity-capillary waves on the free surface of a liquid or at the
interfaces between two superfluids -- are the most favourable excitations for
simulation of the general-relativistic effects related to horizons and
ergoregions. The white-hole horizon for the ``relativistic'' ripplons at the
surface of the shallow liquid is easily simulated using the kitchen-bath
hydraulic jump. The same white-hole horizon is observed in quantum liquid --
superfluid 4He. The ergoregion for the ``non-relativistic'' ripplons is
generated in the experiments with two sliding 3He superfluids. The common
property experienced by all these ripplons is the Miles instability inside the
ergoregion or horizon. Because of the universality of the Miles instability,
one may expect that it could take place inside the horizon of the astrophysical
black holes, if there is a preferred reference frame which comes from the
trans-Planckian physics. If this is the case, the black hole would evapotate
much faster than due to the Hawking radiation. Hawking radiation from the
artificial black hole in terms of the quantum tunneling of phonons and ripplons
is also discussed.
| [
{
"created": "Thu, 23 Mar 2006 14:36:20 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jul 2006 14:11:11 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Aug 2006 14:21:47 GMT",
"version": "v3"
},
{
"created": "Fri, 25 Aug 2006 08:39:09 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Volovik",
"G. E.",
""
]
] | Ripplons -- gravity-capillary waves on the free surface of a liquid or at the interfaces between two superfluids -- are the most favourable excitations for simulation of the general-relativistic effects related to horizons and ergoregions. The white-hole horizon for the ``relativistic'' ripplons at the surface of the shallow liquid is easily simulated using the kitchen-bath hydraulic jump. The same white-hole horizon is observed in quantum liquid -- superfluid 4He. The ergoregion for the ``non-relativistic'' ripplons is generated in the experiments with two sliding 3He superfluids. The common property experienced by all these ripplons is the Miles instability inside the ergoregion or horizon. Because of the universality of the Miles instability, one may expect that it could take place inside the horizon of the astrophysical black holes, if there is a preferred reference frame which comes from the trans-Planckian physics. If this is the case, the black hole would evapotate much faster than due to the Hawking radiation. Hawking radiation from the artificial black hole in terms of the quantum tunneling of phonons and ripplons is also discussed. |
2210.13493 | Adrien Kuntz | Adrien Kuntz, Francesco Serra, Enrico Trincherini | Effective two-body approach to the hierarchical three-body problem:
quadrupole to 1PN | 41 pages, 3 figures | null | 10.1103/PhysRevD.107.044011 | null | gr-qc astro-ph.EP astro-ph.HE astro-ph.SR hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Many binary systems of interest for gravitational-wave astronomy are orbited
by a third distant body, which can considerably alter their relativistic
dynamics. Precision computations are needed to understand the interplay between
relativistic corrections and three-body interactions. We use an effective field
theory approach to derive the effective action describing the long time-scale
dynamics of hierarchical three-body systems up to 1PN quadrupole order. At this
level of approximation, computations are complicated by the backreaction of
small oscillations on orbital time-scales as well as deviations from the
adiabatic approximation. We address these difficulties by eliminating the fast
modes through the method of near-identity transformations. This allows us to
compute for the first time the complete expression of the 1PN quadrupole
cross-terms in generic configurations of three-body systems. We numerically
integrate the resulting equations of motion and show that 1PN quadrupole terms
can affect the long term dynamics of relativistic three-body systems.
| [
{
"created": "Mon, 24 Oct 2022 18:00:05 GMT",
"version": "v1"
}
] | 2023-02-22 | [
[
"Kuntz",
"Adrien",
""
],
[
"Serra",
"Francesco",
""
],
[
"Trincherini",
"Enrico",
""
]
] | Many binary systems of interest for gravitational-wave astronomy are orbited by a third distant body, which can considerably alter their relativistic dynamics. Precision computations are needed to understand the interplay between relativistic corrections and three-body interactions. We use an effective field theory approach to derive the effective action describing the long time-scale dynamics of hierarchical three-body systems up to 1PN quadrupole order. At this level of approximation, computations are complicated by the backreaction of small oscillations on orbital time-scales as well as deviations from the adiabatic approximation. We address these difficulties by eliminating the fast modes through the method of near-identity transformations. This allows us to compute for the first time the complete expression of the 1PN quadrupole cross-terms in generic configurations of three-body systems. We numerically integrate the resulting equations of motion and show that 1PN quadrupole terms can affect the long term dynamics of relativistic three-body systems. |
gr-qc/9904056 | N. Kumar | N. Kumar (Raman Research Institute, Bangalore, India) | Cut-off free finite zero-point vacuum energy and the cosmological
missing mass problem | 5 pages, Latex, no figures Journal ref: MNRAS | null | null | null | gr-qc | null | As the mass-energy is universally self-gravitating, the gravitational binding
energy must be subtracted self-consistently from its bare mass value so as to
give the physical gravitational mass. Such a self-consistent gravitational
self-energy correction can be made non-perturbatively by the use of a
gravitational `charging' technique, where we calculate the incremental change
$dm$ of the physical mass of the cosmological object, of size $r_o$ due to the
accretion of a bare mass $dM$, corresponding to the gravitational coupling-in
of the successive zero-point vacuum modes, i.e., of the Casimir energy, whose
bare value $\Sigma_{\bf k} \hbar ck$ is infinite. Integrating the `charging'
equation, $dm = dM - (3\alpha/5)Gm\Delta M/r_o c^2$, we get a gravitational
mass for the cosmological object that remains finite even in the limit of the
infinite zero-point vacuum energy, i.e., without any ultraviolet cut-off
imposed. Here $\alpha$ is a geometrical factor of order unity. Also, setting
$r_o = c/H$, the Hubble length, we get the corresponding cosmological density
parameter $\Omega \simeq 1$, without any adjustable parameter. The cosmological
significance of this finite and unique contribution of the otherwise infinite
zero-point vacuum energy to the density parameter can hardly be overstated.
| [
{
"created": "Thu, 22 Apr 1999 02:47:59 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Kumar",
"N.",
"",
"Raman Research Institute, Bangalore, India"
]
] | As the mass-energy is universally self-gravitating, the gravitational binding energy must be subtracted self-consistently from its bare mass value so as to give the physical gravitational mass. Such a self-consistent gravitational self-energy correction can be made non-perturbatively by the use of a gravitational `charging' technique, where we calculate the incremental change $dm$ of the physical mass of the cosmological object, of size $r_o$ due to the accretion of a bare mass $dM$, corresponding to the gravitational coupling-in of the successive zero-point vacuum modes, i.e., of the Casimir energy, whose bare value $\Sigma_{\bf k} \hbar ck$ is infinite. Integrating the `charging' equation, $dm = dM - (3\alpha/5)Gm\Delta M/r_o c^2$, we get a gravitational mass for the cosmological object that remains finite even in the limit of the infinite zero-point vacuum energy, i.e., without any ultraviolet cut-off imposed. Here $\alpha$ is a geometrical factor of order unity. Also, setting $r_o = c/H$, the Hubble length, we get the corresponding cosmological density parameter $\Omega \simeq 1$, without any adjustable parameter. The cosmological significance of this finite and unique contribution of the otherwise infinite zero-point vacuum energy to the density parameter can hardly be overstated. |
2106.01385 | Christian Pfeifer | Stefano Liberati and Christian Pfeifer and Jos\'e Javier Relancio | Exploring black holes as particle accelerators: hoop-radius, target
particles and escaping conditions | Improved and extended version of the original article, now including
a discussion of the escape conditions for the particles produced in a
collisional Penrose processes | JCAP05(2022)023 | 10.1088/1475-7516/2022/05/023 | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The possibility that rotating black holes could be natural particle
accelerators has been subject of intense debate. While it appears that for
extremal Kerr black holes arbitrarily high center of mass energies could be
achieved, several works pointed out that both theoretical as well as
astrophysical arguments would severely dampen the attainable energies. In this
work we study particle collisions near Kerr black holes, by reviewing and
extending the so far proposed scenarios. Most noticeably, we shall focus on the
recently advanced target particle scenarios which were claimed to reach
arbitrarily high energies even for Schwarzschild black holes. By implementing
the hoop conjecture we show that these scenarios involving near-horizon target
particles are in principle able to attain, sub-Planckian, but still ultra-high
center of mass energies of the order of $10^{23}-10^{25}$ eV even for
non-extremal Kerr black holes. Furthermore, analysing the properties of
particles produced in such collisions, we find that photons can escape to
infinity. However, their energy is only of the order of the energy of the
colliding particles and hence relatively low, which is the same conclusion
previously reached in the literature about the original Ba\~nados--Silk--West
process. This finding points towards a general limitation of collisional
Penrose processes, at least for what concerns their primary products.
| [
{
"created": "Wed, 2 Jun 2021 18:00:06 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Apr 2022 09:30:55 GMT",
"version": "v2"
}
] | 2022-05-24 | [
[
"Liberati",
"Stefano",
""
],
[
"Pfeifer",
"Christian",
""
],
[
"Relancio",
"José Javier",
""
]
] | The possibility that rotating black holes could be natural particle accelerators has been subject of intense debate. While it appears that for extremal Kerr black holes arbitrarily high center of mass energies could be achieved, several works pointed out that both theoretical as well as astrophysical arguments would severely dampen the attainable energies. In this work we study particle collisions near Kerr black holes, by reviewing and extending the so far proposed scenarios. Most noticeably, we shall focus on the recently advanced target particle scenarios which were claimed to reach arbitrarily high energies even for Schwarzschild black holes. By implementing the hoop conjecture we show that these scenarios involving near-horizon target particles are in principle able to attain, sub-Planckian, but still ultra-high center of mass energies of the order of $10^{23}-10^{25}$ eV even for non-extremal Kerr black holes. Furthermore, analysing the properties of particles produced in such collisions, we find that photons can escape to infinity. However, their energy is only of the order of the energy of the colliding particles and hence relatively low, which is the same conclusion previously reached in the literature about the original Ba\~nados--Silk--West process. This finding points towards a general limitation of collisional Penrose processes, at least for what concerns their primary products. |
2008.06711 | Karima Masmar | H. El Moumni, K. Masmar, Ali \"Ovg\"un | Weak Deflection angle of some classes of non-linear electrodynamics
black holes via Gauss-Bonnet Theorem | 8 pages, 2 figures | Int.J.Geom.Meth.Mod.Phys. (2022) 2250094 | 10.1142/S0219887822500943 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the gravitational lensing by some black hole classes
within the non-linear electrodynamics in weak field limits. First, we calculate
an optical geometry of the non-linear electrodynamics black hole then we use
the Gauss-Bonnet theorem for finding deflection angle in weak field limits. The
effect of non-linear electrodynamics on the deflection angle in leading order
terms is studied. Furthermore, we discuss the effects of the plasma medium on
the weak deflection angle.
| [
{
"created": "Sat, 15 Aug 2020 12:30:36 GMT",
"version": "v1"
}
] | 2022-03-22 | [
[
"Moumni",
"H. El",
""
],
[
"Masmar",
"K.",
""
],
[
"Övgün",
"Ali",
""
]
] | In this paper, we study the gravitational lensing by some black hole classes within the non-linear electrodynamics in weak field limits. First, we calculate an optical geometry of the non-linear electrodynamics black hole then we use the Gauss-Bonnet theorem for finding deflection angle in weak field limits. The effect of non-linear electrodynamics on the deflection angle in leading order terms is studied. Furthermore, we discuss the effects of the plasma medium on the weak deflection angle. |
2407.07125 | Bo Liang | Bo Liang, Minghui Du, He Wang, Yuxiang Xu, Chang Liu, Xiaotong Wei,
Peng Xu, Li-e Qiang, Ziren Luo | Rapid Parameter Estimation for Merging Massive Black Hole Binaries Using
ODE-Based Generative Models | null | null | null | null | gr-qc astro-ph.IM physics.data-an | http://creativecommons.org/licenses/by/4.0/ | Detecting the coalescences of massive black hole binaries (MBHBs) is one of
the primary targets for space-based gravitational wave observatories such as
LISA, Taiji, and Tianqin. The fast and accurate parameter estimation of merging
MBHBs is of great significance for both astrophysics and the global fitting of
all resolvable sources. However, such analyses entail significant computational
costs. To address these challenges, inspired by the latest progress in
generative models, we proposed a novel artificial intelligence (AI) based
parameter estimation method called Variance Preserving Flow Matching Posterior
Estimation (VPFMPE). Specifically, we utilize triangular interpolation to
maintain variance over time, thereby constructing a transport path for training
continuous normalization flows. Compared to the simple linear interpolation
method used in flow matching to construct the optimal transport path, our
approach better captures continuous temporal variations, making it more
suitable for the parameter estimation of MBHBs. Additionally, we creatively
introduce a parameter transformation method based on the symmetry in the
detector's response function. This transformation is integrated within VPFMPE,
allowing us to train the model using a simplified dataset, and then perform
parameter estimation on more general data, hence also acting as a crucial
factor in improving the training speed. In conclusion, for the first time,
within a comprehensive and reasonable parameter range, we have achieved a
complete and unbiased 11-dimensional rapid inference for MBHBs in the presence
of astrophysical confusion noise using ODE-based generative models. In the
experiments based on simulated data, our model produces posterior distributions
comparable to those obtained by nested sampling.
| [
{
"created": "Tue, 9 Jul 2024 07:05:53 GMT",
"version": "v1"
}
] | 2024-07-11 | [
[
"Liang",
"Bo",
""
],
[
"Du",
"Minghui",
""
],
[
"Wang",
"He",
""
],
[
"Xu",
"Yuxiang",
""
],
[
"Liu",
"Chang",
""
],
[
"Wei",
"Xiaotong",
""
],
[
"Xu",
"Peng",
""
],
[
"Qiang",
"Li-e",
""
... | Detecting the coalescences of massive black hole binaries (MBHBs) is one of the primary targets for space-based gravitational wave observatories such as LISA, Taiji, and Tianqin. The fast and accurate parameter estimation of merging MBHBs is of great significance for both astrophysics and the global fitting of all resolvable sources. However, such analyses entail significant computational costs. To address these challenges, inspired by the latest progress in generative models, we proposed a novel artificial intelligence (AI) based parameter estimation method called Variance Preserving Flow Matching Posterior Estimation (VPFMPE). Specifically, we utilize triangular interpolation to maintain variance over time, thereby constructing a transport path for training continuous normalization flows. Compared to the simple linear interpolation method used in flow matching to construct the optimal transport path, our approach better captures continuous temporal variations, making it more suitable for the parameter estimation of MBHBs. Additionally, we creatively introduce a parameter transformation method based on the symmetry in the detector's response function. This transformation is integrated within VPFMPE, allowing us to train the model using a simplified dataset, and then perform parameter estimation on more general data, hence also acting as a crucial factor in improving the training speed. In conclusion, for the first time, within a comprehensive and reasonable parameter range, we have achieved a complete and unbiased 11-dimensional rapid inference for MBHBs in the presence of astrophysical confusion noise using ODE-based generative models. In the experiments based on simulated data, our model produces posterior distributions comparable to those obtained by nested sampling. |
gr-qc/9511054 | BoB | Roberto Casadio and Giovanni Venturi (Department of Physics,
University of Bologna, and Istituto Nazionale di Fisica Nucleare, Sezione di
Bologna, Italy) | Black hole and the adiabatic phase | Plain TeX, 12 pages | Class.Quant.Grav.12:1267-1278,1995 | 10.1088/0264-9381/12/5/016 | null | gr-qc hep-th | null | An open system consisting of a scalar field bound to a Kerr black hole whose
mass ($M$) and specific angular momentum ($a$) are slowly (adiabatically)
perturbed is considered. The adiabatically induced phase and the conditions for
the validity of the adiabatic approximation are obtained. The effect of closed
cycles in parameter space ($a$, $M$ plane) on the energy levels of both stable
and unstable scalar field bound states, together with other quantities of
interest, is illustrated. Lastly it is noted that the black hole wavefunction
will acquire an equal and opposite phase to that of matter thus leading to a
change of its effective action (entropy).
| [
{
"created": "Mon, 20 Nov 1995 10:55:31 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Casadio",
"Roberto",
"",
"Department of Physics,\n University of Bologna, and Istituto Nazionale di Fisica Nucleare, Sezione di\n Bologna, Italy"
],
[
"Venturi",
"Giovanni",
"",
"Department of Physics,\n University of Bologna, and Istituto Nazionale di Fisica Nucleare, Sezi... | An open system consisting of a scalar field bound to a Kerr black hole whose mass ($M$) and specific angular momentum ($a$) are slowly (adiabatically) perturbed is considered. The adiabatically induced phase and the conditions for the validity of the adiabatic approximation are obtained. The effect of closed cycles in parameter space ($a$, $M$ plane) on the energy levels of both stable and unstable scalar field bound states, together with other quantities of interest, is illustrated. Lastly it is noted that the black hole wavefunction will acquire an equal and opposite phase to that of matter thus leading to a change of its effective action (entropy). |
2212.02530 | Alberto Diez-Tejedor | Miguel Alcubierre, Juan Barranco, Argelia Bernal, Juan Carlos
Degollado, Alberto Diez-Tejedor, Miguel Megevand, Dar\'io N\'u\~nez and
Olivier Sarbach | Boson stars and their relatives in semiclassical gravity | 21 pages, 1 figure, 3 tables. To appear in Phys. Rev. D | null | 10.1103/PhysRevD.107.045017 | null | gr-qc astro-ph.CO hep-ph | http://creativecommons.org/licenses/by/4.0/ | We construct boson star configurations in quantum field theory using the
semiclassical gravity approximation. Restricting our attention to the static
case, we show that the semiclassical Einstein-Klein-Gordon system for a {\it
single real quantum} scalar field whose state describes the excitation of $N$
{\it identical particles}, each one corresponding to a given energy level, can
be reduced to the Einstein-Klein-Gordon system for $N$ {\it complex classical}
scalar fields. Particular consideration is given to the spherically symmetric
static scenario, where energy levels are labeled by quantum numbers $n$, $\ell$
and $m$. When all particles are accommodated in the ground state $n=\ell=m=0$,
one recovers the standard static boson star solutions, that can be excited if
$n\neq 0$. On the other hand, for the case where all particles have fixed
radial and total angular momentum numbers $n$ and $\ell$, with $\ell\neq 0$,
but are homogeneously distributed with respect to their magnetic number $m$,
one obtains the $\ell$-boson stars, whereas when $\ell=m=0$ and $n$ takes
multiple values, the multi-state boson star solutions are obtained. Further
generalizations of these configurations are presented, including the
multi-$\ell$ multi-state boson stars, that constitute the most general
solutions to the $N$-particle, static, spherically symmetric, semiclassical
real Einstein-Klein-Gordon system, in which the total number of particles is
definite. In spite of the fact that the same spacetime configurations also
appear in multi-field classical theories, in semiclassical gravity they arise
naturally as the quantum fluctuations associated with the state of a single
field describing a many-body system. Our results could have potential impact on
direct detection experiments in the context of ultralight scalar field/fuzzy
dark matter candidates.
| [
{
"created": "Mon, 5 Dec 2022 19:00:08 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Feb 2023 00:48:24 GMT",
"version": "v2"
}
] | 2023-03-08 | [
[
"Alcubierre",
"Miguel",
""
],
[
"Barranco",
"Juan",
""
],
[
"Bernal",
"Argelia",
""
],
[
"Degollado",
"Juan Carlos",
""
],
[
"Diez-Tejedor",
"Alberto",
""
],
[
"Megevand",
"Miguel",
""
],
[
"Núñez",
"Darío",
... | We construct boson star configurations in quantum field theory using the semiclassical gravity approximation. Restricting our attention to the static case, we show that the semiclassical Einstein-Klein-Gordon system for a {\it single real quantum} scalar field whose state describes the excitation of $N$ {\it identical particles}, each one corresponding to a given energy level, can be reduced to the Einstein-Klein-Gordon system for $N$ {\it complex classical} scalar fields. Particular consideration is given to the spherically symmetric static scenario, where energy levels are labeled by quantum numbers $n$, $\ell$ and $m$. When all particles are accommodated in the ground state $n=\ell=m=0$, one recovers the standard static boson star solutions, that can be excited if $n\neq 0$. On the other hand, for the case where all particles have fixed radial and total angular momentum numbers $n$ and $\ell$, with $\ell\neq 0$, but are homogeneously distributed with respect to their magnetic number $m$, one obtains the $\ell$-boson stars, whereas when $\ell=m=0$ and $n$ takes multiple values, the multi-state boson star solutions are obtained. Further generalizations of these configurations are presented, including the multi-$\ell$ multi-state boson stars, that constitute the most general solutions to the $N$-particle, static, spherically symmetric, semiclassical real Einstein-Klein-Gordon system, in which the total number of particles is definite. In spite of the fact that the same spacetime configurations also appear in multi-field classical theories, in semiclassical gravity they arise naturally as the quantum fluctuations associated with the state of a single field describing a many-body system. Our results could have potential impact on direct detection experiments in the context of ultralight scalar field/fuzzy dark matter candidates. |
2008.03562 | Bikash Chandra Paul Professor | B. C. Paul | Dynamical Wormholes in Higher Dimensions and the Emergent Universe | 11 pages, 7 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Dynamical wormholes in higher dimensions which admit flat emergent universe
(EU) model is presented. The EU model is free from initial singularity with
other observed features of the universe. The basic assumption of EU model was
that the present universe emerged out from a static Einstein universe. EU model
originates from a dynamical wormhole, its throat is the seed of Einstein Static
universe. A class of cosmological solutions in a higher dimensional flat
universe is presented. A new shape function for closed universe is determined.
The non-linear equation of state (EoS) corresponds to three types of cosmic
fluids. The EoS parameters determine the cosmic fluids. The space-time
dimensions determines the rate of change of a particular fluid that varies with
the scale factor of a dynamically evolving universe with non-interacting
fluids. Considering interaction at time $t > t_0$, among the three types of
fluids it is possible to describe the observed universe satisfactorily. In a
higher dimensional universe it is found that near the throat null energy
condition (NEC) is violated, but away from the throat NEC is found to obey
admitting the observed universe for a flat case. Another interesting aspect of
the EU model is that it permits late accelerating phase. However, in asymptotic
closed or open universe, flat emergent universe can be accommodated with NEC
which is obeyed right from the throat to the present epoch. The tension at the
throat of the wormhole is estimated which is found to depend on the initial
size of the Einstein static universe and dimensions of the universe. It is
interesting to note that NEC is not violated to accommodate dynamical wormholes
for closed or open universe. Although exotic matter is required at the throat
for the flat universe, no exotic matter is required for closed or open universe
which encompass the emergent universe.
| [
{
"created": "Sat, 8 Aug 2020 17:30:43 GMT",
"version": "v1"
}
] | 2020-08-11 | [
[
"Paul",
"B. C.",
""
]
] | Dynamical wormholes in higher dimensions which admit flat emergent universe (EU) model is presented. The EU model is free from initial singularity with other observed features of the universe. The basic assumption of EU model was that the present universe emerged out from a static Einstein universe. EU model originates from a dynamical wormhole, its throat is the seed of Einstein Static universe. A class of cosmological solutions in a higher dimensional flat universe is presented. A new shape function for closed universe is determined. The non-linear equation of state (EoS) corresponds to three types of cosmic fluids. The EoS parameters determine the cosmic fluids. The space-time dimensions determines the rate of change of a particular fluid that varies with the scale factor of a dynamically evolving universe with non-interacting fluids. Considering interaction at time $t > t_0$, among the three types of fluids it is possible to describe the observed universe satisfactorily. In a higher dimensional universe it is found that near the throat null energy condition (NEC) is violated, but away from the throat NEC is found to obey admitting the observed universe for a flat case. Another interesting aspect of the EU model is that it permits late accelerating phase. However, in asymptotic closed or open universe, flat emergent universe can be accommodated with NEC which is obeyed right from the throat to the present epoch. The tension at the throat of the wormhole is estimated which is found to depend on the initial size of the Einstein static universe and dimensions of the universe. It is interesting to note that NEC is not violated to accommodate dynamical wormholes for closed or open universe. Although exotic matter is required at the throat for the flat universe, no exotic matter is required for closed or open universe which encompass the emergent universe. |
1112.3410 | Ran Li | Ran Li | Logarithmic entropy of black hole in gravity with conformal anomaly from
quantum tunneling approach | 10 pages, no figure, EPL in press | Europhys. Lett. 96 (2011) 60014 | 10.1209/0295-5075/96/60014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using quantum tunneling approach, we are able to derive the entropy with
logarithmic term of the static spherically symmetric black hole in
semi-classical Einstein equations with conformal anomaly. The results indicate
that the logarithmic correction to Bekenstein-Hawking area entropy can be well
explained by the self-gravitation.
| [
{
"created": "Thu, 15 Dec 2011 02:23:50 GMT",
"version": "v1"
}
] | 2011-12-19 | [
[
"Li",
"Ran",
""
]
] | Using quantum tunneling approach, we are able to derive the entropy with logarithmic term of the static spherically symmetric black hole in semi-classical Einstein equations with conformal anomaly. The results indicate that the logarithmic correction to Bekenstein-Hawking area entropy can be well explained by the self-gravitation. |
1003.2849 | Masato Nozawa | Kei-ichi Maeda and Masato Nozawa | Black Hole in the Expanding Universe with Arbitrary Power-Law Expansion | 22 pages, 8 figures, 1 table; v2: typos corrected, references added,
version to appear in PRD | Phys.Rev.D81:124038,2010 | 10.1103/PhysRevD.81.124038 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a time-dependent and spatially inhomogeneous solution that
interpolates the extremal Reissner-Nordstr\"om (RN) black hole and the
Friedmann-Lema\^itre-Robertson-Walker (FLRW) universe with arbitrary power-law
expansion. It is an exact solution of the $D$-dimensional
Einstein-"Maxwell"-dilaton system, where two Abelian gauge fields couple to the
dilaton with different coupling constants, and the dilaton field has a
Liouville-type exponential potential. It is shown that the system satisfies the
weak energy condition. The solution involves two harmonic functions on a
$(D-1)$-dimensional Ricci-flat base space. In the case where the harmonics have
a single-point source on the Euclidean space, we find that the spacetime
describes a spherically symmetric charged black hole in the FLRW universe,
which is characterized by three parameters: the steepness parameter of the
dilaton potential $n_T$, the U$(1)$ charge $Q$, and the "nonextremality" $\tau
$. In contrast with the extremal RN solution, the spacetime admits a
nondegenerate Killing horizon unless these parameters are finely tuned. The
global spacetime structures are discussed in detail.
| [
{
"created": "Mon, 15 Mar 2010 05:49:48 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Jun 2010 18:47:38 GMT",
"version": "v2"
}
] | 2014-11-20 | [
[
"Maeda",
"Kei-ichi",
""
],
[
"Nozawa",
"Masato",
""
]
] | We present a time-dependent and spatially inhomogeneous solution that interpolates the extremal Reissner-Nordstr\"om (RN) black hole and the Friedmann-Lema\^itre-Robertson-Walker (FLRW) universe with arbitrary power-law expansion. It is an exact solution of the $D$-dimensional Einstein-"Maxwell"-dilaton system, where two Abelian gauge fields couple to the dilaton with different coupling constants, and the dilaton field has a Liouville-type exponential potential. It is shown that the system satisfies the weak energy condition. The solution involves two harmonic functions on a $(D-1)$-dimensional Ricci-flat base space. In the case where the harmonics have a single-point source on the Euclidean space, we find that the spacetime describes a spherically symmetric charged black hole in the FLRW universe, which is characterized by three parameters: the steepness parameter of the dilaton potential $n_T$, the U$(1)$ charge $Q$, and the "nonextremality" $\tau $. In contrast with the extremal RN solution, the spacetime admits a nondegenerate Killing horizon unless these parameters are finely tuned. The global spacetime structures are discussed in detail. |
0709.1620 | Shahram Jalalzadeh | P. Pedram, S. Jalalzadeh, S. S. Gousheh | Quantum Stephani exact cosmological solutions and the selection of time
variable | 19 pages, 7 figures | Class.Quant.Grav.24:5515-5526,2007 | 10.1088/0264-9381/24/22/014 | null | gr-qc | null | We study perfect fluid Stephani quantum cosmological model. In the present
work the Schutz's variational formalism which recovers the notion of time is
applied. This gives rise to Wheeler-DeWitt equation for the scale factor. We
use the eigenfunctions in order to construct wave packets for each case. We
study the time-dependent behavior of the expectation value of the scale factor,
using many-worlds and deBroglie-Bohm interpretations of quantum mechanics.
| [
{
"created": "Tue, 11 Sep 2007 13:26:36 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Pedram",
"P.",
""
],
[
"Jalalzadeh",
"S.",
""
],
[
"Gousheh",
"S. S.",
""
]
] | We study perfect fluid Stephani quantum cosmological model. In the present work the Schutz's variational formalism which recovers the notion of time is applied. This gives rise to Wheeler-DeWitt equation for the scale factor. We use the eigenfunctions in order to construct wave packets for each case. We study the time-dependent behavior of the expectation value of the scale factor, using many-worlds and deBroglie-Bohm interpretations of quantum mechanics. |
gr-qc/0206047 | Jian-Miin Liu | Jian-Miin Liu | A test of Einstein's theory of gravitation: Velocity distribution of
low-energy particles in a spherically symmetric gravitational field | 4 pages with no figure | null | null | null | gr-qc | null | We propose a new test of Einstein's theory of gravitation. It concerns the
velocity distribution of low-energy particles in a spherically symmetric
gravitational field.
| [
{
"created": "Mon, 17 Jun 2002 20:41:17 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Liu",
"Jian-Miin",
""
]
] | We propose a new test of Einstein's theory of gravitation. It concerns the velocity distribution of low-energy particles in a spherically symmetric gravitational field. |
1407.6983 | Scott A. Hughes | Stephen O'Sullivan and Scott A. Hughes | Strong-field tidal distortions of rotating black holes: Formalism and
results for circular, equatorial orbits | 37 pages, 8 figures. Accepted for publication to Physical Review D.
This version corrects a number of typographical errors found when reviewing
the page proofs | Phys. Rev. D 90, 124039 (2014) | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Tidal coupling between members of a compact binary system can have an
interesting and important influence on that binary's dynamical inspiral. Tidal
coupling also distorts the binary's members, changing them (at lowest order)
from spheres to ellipsoids. At least in the limit of fluid bodies and Newtonian
gravity, there are simple connections between the geometry of the distorted
ellipsoid and the impact of tides on the orbit's evolution. In this paper, we
develop tools for investigating tidal distortions of rapidly rotating black
holes using techniques that are good for strong-field, fast-motion binary
orbits. We use black hole perturbation theory, so our results assume extreme
mass ratios. We develop tools to compute the distortion to a black hole's
curvature for any spin parameter, and for tidal fields arising from any bound
orbit, in the frequency domain. We also develop tools to visualize the
horizon's distortion for black hole spin $a/M \le \sqrt{3}/2$ (leaving the more
complicated $a/M > \sqrt{3}/2$ case to a future analysis). We then study how a
Kerr black hole's event horizon is distorted by a small body in a circular,
equatorial orbit. We find that the connection between the geometry of tidal
distortion and the orbit's evolution is not as simple as in the Newtonian
limit.
| [
{
"created": "Fri, 25 Jul 2014 17:36:02 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Oct 2014 16:07:51 GMT",
"version": "v2"
},
{
"created": "Fri, 28 Nov 2014 19:12:32 GMT",
"version": "v3"
}
] | 2015-12-02 | [
[
"O'Sullivan",
"Stephen",
""
],
[
"Hughes",
"Scott A.",
""
]
] | Tidal coupling between members of a compact binary system can have an interesting and important influence on that binary's dynamical inspiral. Tidal coupling also distorts the binary's members, changing them (at lowest order) from spheres to ellipsoids. At least in the limit of fluid bodies and Newtonian gravity, there are simple connections between the geometry of the distorted ellipsoid and the impact of tides on the orbit's evolution. In this paper, we develop tools for investigating tidal distortions of rapidly rotating black holes using techniques that are good for strong-field, fast-motion binary orbits. We use black hole perturbation theory, so our results assume extreme mass ratios. We develop tools to compute the distortion to a black hole's curvature for any spin parameter, and for tidal fields arising from any bound orbit, in the frequency domain. We also develop tools to visualize the horizon's distortion for black hole spin $a/M \le \sqrt{3}/2$ (leaving the more complicated $a/M > \sqrt{3}/2$ case to a future analysis). We then study how a Kerr black hole's event horizon is distorted by a small body in a circular, equatorial orbit. We find that the connection between the geometry of tidal distortion and the orbit's evolution is not as simple as in the Newtonian limit. |
2110.12457 | Stavros Venikoudis | F.P. Fronimos (Aristotle U., Thessaloniki), S.A. Venikoudis (Aristotle
U., Thessaloniki) | Inflation with exotic kinetic terms in Einstein-Chern-Simons gravity | Accepted in International Journal of Modern Physics A. arXiv admin
note: text overlap with arXiv:2107.09457 | null | 10.1142/S0217751X21502298 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | An alternative scenario about the phenomenology of primordial Universe is
k-inflation. According to this concept, inflation can be achieved by
nonstandard kinetic term of scalar field, namely the inflaton. In this project
we focus on k-essence models in the presence of a higher order and a linear
kinetic term. Furthermore, the inflationary phenomenology with a
Dirac-Born-Infeld scalar field is briefly examined, which arises from quantum
theories of gravity such as superstring theory. Our approach about the
inflationary era is that it can be described in the context of Einstein's
gravity involving quantum corrections such as the Chern-Simons string inspired
parity violating gravitational term. The equations of motion namely, the
Friedmann equation, the Raychadhuri equation and the Klein-Gordon equation for
an expanding background are extracted from the gravitational action utilizing
the variational principle. The consequential system of differential equations
with respect to Hubble's parameter and the inflaton field was quite perplexed
in order to be solved with an analytic way. Therefore, the slow-roll conditions
during inflationary era were imposed and terms with minor numerically
contribution were neglected. From the overall phenomenological analysis it is
proved that, models with exotic kinetic terms can generate viable results in
consistency with the latest Planck data. Finally, the presence of Chern-Simons
quantum corrections shifts the primordial spectral tensor index to blue. Even
though blue gravitational waves have yet to be observed, if detected,
compatibility with the aforementioned theory can be achieved.
| [
{
"created": "Sun, 24 Oct 2021 14:44:00 GMT",
"version": "v1"
}
] | 2021-12-01 | [
[
"Fronimos",
"F. P.",
"",
"Aristotle U., Thessaloniki"
],
[
"Venikoudis",
"S. A.",
"",
"Aristotle\n U., Thessaloniki"
]
] | An alternative scenario about the phenomenology of primordial Universe is k-inflation. According to this concept, inflation can be achieved by nonstandard kinetic term of scalar field, namely the inflaton. In this project we focus on k-essence models in the presence of a higher order and a linear kinetic term. Furthermore, the inflationary phenomenology with a Dirac-Born-Infeld scalar field is briefly examined, which arises from quantum theories of gravity such as superstring theory. Our approach about the inflationary era is that it can be described in the context of Einstein's gravity involving quantum corrections such as the Chern-Simons string inspired parity violating gravitational term. The equations of motion namely, the Friedmann equation, the Raychadhuri equation and the Klein-Gordon equation for an expanding background are extracted from the gravitational action utilizing the variational principle. The consequential system of differential equations with respect to Hubble's parameter and the inflaton field was quite perplexed in order to be solved with an analytic way. Therefore, the slow-roll conditions during inflationary era were imposed and terms with minor numerically contribution were neglected. From the overall phenomenological analysis it is proved that, models with exotic kinetic terms can generate viable results in consistency with the latest Planck data. Finally, the presence of Chern-Simons quantum corrections shifts the primordial spectral tensor index to blue. Even though blue gravitational waves have yet to be observed, if detected, compatibility with the aforementioned theory can be achieved. |
2312.11808 | Neil J. Cornish | Toral Gupta and Neil Cornish | Bayesian power spectral estimation of gravitational wave detector noise
revisited | 11 pages, 14 figures | null | null | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The analysis of gravitational wave interferometer data requires estimates for
the noise covariance matrix. For stationary noise, this amounts to estimating
the power spectrum. Classical methods such as Welch averaging are used in many
analyses, but this method require large stretches of ``off-source'' data, where
the assumption of stationarity may break down. For this reason, Bayesian
spectral estimates using only ``on-source'' data are becoming more widely used,
but the Bayesian approach tends to be slower, and more computationally
expensive than classical methods. Here we introduce numerous improvements in
speed and performance for the BayesWave trans-dimensional Bayesian spectral
estimation algorithm, and introduce a new, low-latency fixed dimension Bayesian
spectral estimation algorithm, FastSpec, which serves as both a starting point
for the BayesWave analysis, and as a stand-alone fast spectral estimation tool.
The performance of the Welch, BayesWave and FastSpec algorithms are compared by
applying statistical tests for normality to the whitened frequency domain data.
Bayesian spectral estimation methods are shown to significantly outperform the
classical approach.
| [
{
"created": "Tue, 19 Dec 2023 02:46:02 GMT",
"version": "v1"
},
{
"created": "Sat, 2 Mar 2024 17:26:58 GMT",
"version": "v2"
}
] | 2024-03-05 | [
[
"Gupta",
"Toral",
""
],
[
"Cornish",
"Neil",
""
]
] | The analysis of gravitational wave interferometer data requires estimates for the noise covariance matrix. For stationary noise, this amounts to estimating the power spectrum. Classical methods such as Welch averaging are used in many analyses, but this method require large stretches of ``off-source'' data, where the assumption of stationarity may break down. For this reason, Bayesian spectral estimates using only ``on-source'' data are becoming more widely used, but the Bayesian approach tends to be slower, and more computationally expensive than classical methods. Here we introduce numerous improvements in speed and performance for the BayesWave trans-dimensional Bayesian spectral estimation algorithm, and introduce a new, low-latency fixed dimension Bayesian spectral estimation algorithm, FastSpec, which serves as both a starting point for the BayesWave analysis, and as a stand-alone fast spectral estimation tool. The performance of the Welch, BayesWave and FastSpec algorithms are compared by applying statistical tests for normality to the whitened frequency domain data. Bayesian spectral estimation methods are shown to significantly outperform the classical approach. |
1903.01781 | Bijan Saha Dr. | Bijan Saha | Non-minimally coupled nonlinear spinor field in Bianchi type-I cosmology | 9 pages, 2 figures | The European Physical Journal Plus 134, 491 (2019) | 10.1140/epjp/i2019-12859-7 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the scope of Bianchi type-$I$ cosmological model we have studied the
role of spinor field in the evolution of the Universe. In doing so we have
considered the case with non-minimal coupling. It was found that the
non-diagonal components of the energy-momentum tensor of the spinor field,
hence the restrictions on the space-time geometry remain the same as in case of
minimal coupling. Since in this case the diagonal components of the
energy-momentum tensor differ, the evolution of the corresponding universe also
differs. For example, while a linear spinor field with non-minimal coupling or
nonlinear spinor field with minimal coupling give rise to open universe, a
nonlinear spinor field with non-minimal coupling with the same parameters can
generate close universe that at the beginning expands, and after attaining some
maximum value begin to contract and finally ends in a Big Crunch.
| [
{
"created": "Tue, 5 Mar 2019 12:12:44 GMT",
"version": "v1"
}
] | 2020-03-05 | [
[
"Saha",
"Bijan",
""
]
] | Within the scope of Bianchi type-$I$ cosmological model we have studied the role of spinor field in the evolution of the Universe. In doing so we have considered the case with non-minimal coupling. It was found that the non-diagonal components of the energy-momentum tensor of the spinor field, hence the restrictions on the space-time geometry remain the same as in case of minimal coupling. Since in this case the diagonal components of the energy-momentum tensor differ, the evolution of the corresponding universe also differs. For example, while a linear spinor field with non-minimal coupling or nonlinear spinor field with minimal coupling give rise to open universe, a nonlinear spinor field with non-minimal coupling with the same parameters can generate close universe that at the beginning expands, and after attaining some maximum value begin to contract and finally ends in a Big Crunch. |
1007.3670 | Salvatore Capozziello | S. Capozziello, R. Cianci, M. De Laurentis, S. Vignolo | Testing metric-affine f(R)-gravity by relic scalar gravitational waves | 12 pages, 4 figures | Eur.Phys.J.C70:341-349,2010 | 10.1140/epjc/s10052-010-1412-5 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the emergence of scalar gravitational waves in metric-affine
f(R)-gravity. Such a component allows to discriminate between metric and
metric-affine theories The intrinsic meaning of this result is that the
geodesic structure of the theory can be discriminated. We extend the formalism
of cross correlation analysis, including the additional polarization mode, and
calculate the detectable energy density of the spectrum for cosmological relic
gravitons. The possible detection of the signal is discussed against
sensitivities of VIRGO, LIGO and LISA interferometers.
| [
{
"created": "Wed, 21 Jul 2010 14:25:25 GMT",
"version": "v1"
}
] | 2011-02-09 | [
[
"Capozziello",
"S.",
""
],
[
"Cianci",
"R.",
""
],
[
"De Laurentis",
"M.",
""
],
[
"Vignolo",
"S.",
""
]
] | We discuss the emergence of scalar gravitational waves in metric-affine f(R)-gravity. Such a component allows to discriminate between metric and metric-affine theories The intrinsic meaning of this result is that the geodesic structure of the theory can be discriminated. We extend the formalism of cross correlation analysis, including the additional polarization mode, and calculate the detectable energy density of the spectrum for cosmological relic gravitons. The possible detection of the signal is discussed against sensitivities of VIRGO, LIGO and LISA interferometers. |
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