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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2301.11304 | Antonio Enea Romano | Antonio Enea Romano, Sergio A. Vallejo-Pe\~na | Gravitoelectromagnetic quadrirefringence | Published version | Physics of the Dark Universe , Volume 44, May 2024, 101492 | 10.1016/j.dark.2024.101492 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We develop an effective approach for the study of the interaction of
gravitational waves (GWs) and electromagnetic waves (EMWs), showing that
quadrirefringence can be produced, a phenomenon consisting in a frequency and
polarization dependency of the speed of the different polarizations of GWs and
EMWs, which is also inducing a frequency and polarization dependent
modification of the GW-EMW luminosity distance ratio. Quadrirefringence can be
due to the GW-EMW interaction in the source or during the propagation from the
source to the observer. In the first case the astrophysical properties of the
source can induce a unique characteristic imprint on GWs and EMWs for each
source, the rainbow of binaries, while the effect on the propagation from the
source could be used to probe the large scale electromagnetic field using GWs.
Numerical general relativistic magnetohydrodynamic (GRMHD) simulations can be
used to obtain precise theoretical predictions for different binary systems
with large electromagnetic and gravitational fields, such as binary neutron
stars.
| [
{
"created": "Thu, 26 Jan 2023 18:43:09 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Feb 2024 22:10:35 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Apr 2024 21:19:51 GMT",
"version": "v3"
}
] | 2024-04-10 | [
[
"Romano",
"Antonio Enea",
""
],
[
"Vallejo-Peña",
"Sergio A.",
""
]
] | We develop an effective approach for the study of the interaction of gravitational waves (GWs) and electromagnetic waves (EMWs), showing that quadrirefringence can be produced, a phenomenon consisting in a frequency and polarization dependency of the speed of the different polarizations of GWs and EMWs, which is also inducing a frequency and polarization dependent modification of the GW-EMW luminosity distance ratio. Quadrirefringence can be due to the GW-EMW interaction in the source or during the propagation from the source to the observer. In the first case the astrophysical properties of the source can induce a unique characteristic imprint on GWs and EMWs for each source, the rainbow of binaries, while the effect on the propagation from the source could be used to probe the large scale electromagnetic field using GWs. Numerical general relativistic magnetohydrodynamic (GRMHD) simulations can be used to obtain precise theoretical predictions for different binary systems with large electromagnetic and gravitational fields, such as binary neutron stars. |
1301.3113 | Lorenzo Sindoni | Antonio Pittelli and Lorenzo Sindoni | New coherent states and modified heat equations | 7 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We clarify the relations between certain new coherent states for loop quantum
gravity and the analytically continued heat kernel coherent states,
highlighting the underlying general construction, the presence of a modified
heat equation as well as the way in which the properties of the heat kernels
are automatically inherited by these new states.
| [
{
"created": "Mon, 14 Jan 2013 20:25:43 GMT",
"version": "v1"
}
] | 2013-01-15 | [
[
"Pittelli",
"Antonio",
""
],
[
"Sindoni",
"Lorenzo",
""
]
] | We clarify the relations between certain new coherent states for loop quantum gravity and the analytically continued heat kernel coherent states, highlighting the underlying general construction, the presence of a modified heat equation as well as the way in which the properties of the heat kernels are automatically inherited by these new states. |
1911.12374 | Sunny Vagnozzi | Sunny Vagnozzi, Luca Visinelli, Olga Mena, David F. Mota | Do we have any hope of detecting scattering between dark energy and
baryons through cosmology? | 15 pages, 7 figures. Title changed, minor modifications added
comments on non-linearities. Version accepted for publication in MNRAS | Mon. Not. Roy. Astron. Soc. 493 (2020) 1139 | 10.1093/mnras/staa311 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the possibility that dark energy and baryons might scatter off
each other. The type of interaction we consider leads to a pure momentum
exchange, and does not affect the background evolution of the expansion
history. We parametrize this interaction in an effective way at the level of
Boltzmann equations. We compute the effect of dark energy-baryon scattering on
cosmological observables, focusing on the Cosmic Microwave Background (CMB)
temperature anisotropy power spectrum and the matter power spectrum.
Surprisingly, we find that even huge dark energy-baryon cross-sections
$\sigma_{xb} \sim {\cal O}({\rm b})$, which are generically excluded by
non-cosmological probes such as collider searches or precision gravity tests,
only leave an insignificant imprint on the observables considered. In the case
of the CMB temperature power spectrum, the only imprint consists in a
sub-percent enhancement or depletion of power (depending whether or not the
dark energy equation of state lies above or below $-1$) at very low multipoles,
which is thus swamped by cosmic variance. These effects are explained in terms
of differences in how gravitational potentials decay in the presence of a dark
energy-baryon scattering, which ultimately lead to an increase or decrease in
the late-time integrated Sachs-Wolfe power. Even smaller related effects are
imprinted on the matter power spectrum. The imprints on the CMB are not
expected to be degenerate with the effects due to altering the dark energy
sound speed. We conclude that, while strongly appealing, the prospects for a
direct detection of dark energy through cosmology do not seem feasible when
considering realistic dark energy-baryon cross-sections. As a caveat, our
results hold to linear order in perturbation theory.
| [
{
"created": "Wed, 27 Nov 2019 19:00:12 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Jan 2020 15:30:38 GMT",
"version": "v2"
}
] | 2020-02-24 | [
[
"Vagnozzi",
"Sunny",
""
],
[
"Visinelli",
"Luca",
""
],
[
"Mena",
"Olga",
""
],
[
"Mota",
"David F.",
""
]
] | We consider the possibility that dark energy and baryons might scatter off each other. The type of interaction we consider leads to a pure momentum exchange, and does not affect the background evolution of the expansion history. We parametrize this interaction in an effective way at the level of Boltzmann equations. We compute the effect of dark energy-baryon scattering on cosmological observables, focusing on the Cosmic Microwave Background (CMB) temperature anisotropy power spectrum and the matter power spectrum. Surprisingly, we find that even huge dark energy-baryon cross-sections $\sigma_{xb} \sim {\cal O}({\rm b})$, which are generically excluded by non-cosmological probes such as collider searches or precision gravity tests, only leave an insignificant imprint on the observables considered. In the case of the CMB temperature power spectrum, the only imprint consists in a sub-percent enhancement or depletion of power (depending whether or not the dark energy equation of state lies above or below $-1$) at very low multipoles, which is thus swamped by cosmic variance. These effects are explained in terms of differences in how gravitational potentials decay in the presence of a dark energy-baryon scattering, which ultimately lead to an increase or decrease in the late-time integrated Sachs-Wolfe power. Even smaller related effects are imprinted on the matter power spectrum. The imprints on the CMB are not expected to be degenerate with the effects due to altering the dark energy sound speed. We conclude that, while strongly appealing, the prospects for a direct detection of dark energy through cosmology do not seem feasible when considering realistic dark energy-baryon cross-sections. As a caveat, our results hold to linear order in perturbation theory. |
1610.01799 | Henrik Nersisyan | Henrik Nersisyan, Yashar Akrami, Luca Amendola, Tomi S. Koivisto,
Javier Rubio, Adam R. Solomon | Instabilities in tensorial nonlocal gravity | 10 pages, 2 figures. v2: version published in PRD | Phys. Rev. D 95, 043539 (2017) | 10.1103/PhysRevD.95.043539 | NORDITA-2016-102 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the cosmological implications of nonlocal modifications of general
relativity containing tensorial structures. Assuming the presence of standard
radiation- and matter-dominated eras, we show that, except in very particular
cases, the nonlocal terms contribute a rapidly growing energy density. These
models therefore generically do not have a stable cosmological evolution.
| [
{
"created": "Thu, 6 Oct 2016 09:55:55 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Feb 2017 11:42:54 GMT",
"version": "v2"
}
] | 2017-03-01 | [
[
"Nersisyan",
"Henrik",
""
],
[
"Akrami",
"Yashar",
""
],
[
"Amendola",
"Luca",
""
],
[
"Koivisto",
"Tomi S.",
""
],
[
"Rubio",
"Javier",
""
],
[
"Solomon",
"Adam R.",
""
]
] | We discuss the cosmological implications of nonlocal modifications of general relativity containing tensorial structures. Assuming the presence of standard radiation- and matter-dominated eras, we show that, except in very particular cases, the nonlocal terms contribute a rapidly growing energy density. These models therefore generically do not have a stable cosmological evolution. |
gr-qc/0212063 | Nicos Pelavas | A. Coley (1), R. Milson (1), N. Pelavas (1), V. Pravda (2), A.
Pravdov\'a (2), R. Zalaletdinov (1) ((1) Dalhousie University, Halifax, (2)
Mathematical Institute, Prague) | Generalizations of pp-wave spacetimes in higher dimensions | 5 pages, RevTex, to appear in Physical Review D | Phys.Rev.D67:104020,2003 | 10.1103/PhysRevD.67.104020 | null | gr-qc hep-th | null | We shall investigate $D$-dimensional Lorentzian spacetimes in which all of
the scalar invariants constructed from the Riemann tensor and its covariant
derivatives are zero. These spacetimes are higher-dimensional generalizations
of $D$-dimensional pp-wave spacetimes, which have been of interest recently in
the context of string theory in curved backgrounds in higher dimensions.
| [
{
"created": "Fri, 13 Dec 2002 22:50:42 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Mar 2003 18:23:18 GMT",
"version": "v2"
}
] | 2016-08-16 | [
[
"Coley",
"A.",
""
],
[
"Milson",
"R.",
""
],
[
"Pelavas",
"N.",
""
],
[
"Pravda",
"V.",
""
],
[
"Pravdová",
"A.",
""
],
[
"Zalaletdinov",
"R.",
""
]
] | We shall investigate $D$-dimensional Lorentzian spacetimes in which all of the scalar invariants constructed from the Riemann tensor and its covariant derivatives are zero. These spacetimes are higher-dimensional generalizations of $D$-dimensional pp-wave spacetimes, which have been of interest recently in the context of string theory in curved backgrounds in higher dimensions. |
1809.03884 | Beatriz Elizaga Navascu\'es | Beatriz Elizaga Navascu\'es and Guillermo A. Mena Marug\'an | Perturbations in Quantum Cosmology: The Continuum Limit in Fourier Space | 12 pages | Phys. Rev. D 98, 103522 (2018) | 10.1103/PhysRevD.98.103522 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the passage to a continuum limit of the mode spectrum of
primordial perturbations around flat cosmological spacetimes in Quantum
Cosmology, showing that this limit can be reached even if one starts by
considering a finite fiducial cell as spatial slice. Whereas the resulting
system can be described in an invariant way under changes of the fiducial
volume using appropriate variables, both for the background cosmology and the
perturbations, obtaining in this way a discrete mode spectrum owing to the
compactness of the fiducial cell, we show that the desired continuum limit for
the perturbations can still be established by means of scaling transformations
of the physical volume when this volume grows unboundedly. These
transformations lead to a model with a continuum of modes and independent of
any scale of reference for the physical volume. For the sake of comparison, we
also consider an alternative road to the continuum in Fourier space that has
been employed in geometrodynamics and is based on the use of scaling
transformations of the fiducial volume, together with variables that are
independent of them.
| [
{
"created": "Tue, 11 Sep 2018 13:40:04 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Nov 2021 02:24:48 GMT",
"version": "v2"
}
] | 2021-11-04 | [
[
"Navascués",
"Beatriz Elizaga",
""
],
[
"Marugán",
"Guillermo A. Mena",
""
]
] | We analyze the passage to a continuum limit of the mode spectrum of primordial perturbations around flat cosmological spacetimes in Quantum Cosmology, showing that this limit can be reached even if one starts by considering a finite fiducial cell as spatial slice. Whereas the resulting system can be described in an invariant way under changes of the fiducial volume using appropriate variables, both for the background cosmology and the perturbations, obtaining in this way a discrete mode spectrum owing to the compactness of the fiducial cell, we show that the desired continuum limit for the perturbations can still be established by means of scaling transformations of the physical volume when this volume grows unboundedly. These transformations lead to a model with a continuum of modes and independent of any scale of reference for the physical volume. For the sake of comparison, we also consider an alternative road to the continuum in Fourier space that has been employed in geometrodynamics and is based on the use of scaling transformations of the fiducial volume, together with variables that are independent of them. |
0912.5097 | Igor Rodnianski | S. Klainerman, I. Rodnianski | On the formation of trapped surfaces | null | null | null | null | gr-qc math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In a recent important breakthrough D. Christodoulou has solved a long
standing problem of General Relativity of evolutionary formation of trapped
surfaces in the Einstein-vacuum space-times. He has identified an open set of
regular initial conditions on an outgoing null hypersurface (both finite and at
past null infinity) leading to a formation a trapped surface in the
corresponding vacuum space-time to the future of the initial outgoing
hypersurface and another incoming null hypersurface with the prescribed
Minkowskian data.
In this paper we give a simpler proof for a finite problem by enlarging the
admissible set of initial conditions and, consistent with this, relaxing the
corresponding propagation estimates just enough that a trapped surface still
forms. We also reduce the number of derivatives needed in the argument from two
derivatives of the curvature to just one. More importantly, the proof, which
can be easily localized with respect to angular sectors, has the potential for
further developments.
| [
{
"created": "Tue, 29 Dec 2009 00:09:57 GMT",
"version": "v1"
}
] | 2009-12-31 | [
[
"Klainerman",
"S.",
""
],
[
"Rodnianski",
"I.",
""
]
] | In a recent important breakthrough D. Christodoulou has solved a long standing problem of General Relativity of evolutionary formation of trapped surfaces in the Einstein-vacuum space-times. He has identified an open set of regular initial conditions on an outgoing null hypersurface (both finite and at past null infinity) leading to a formation a trapped surface in the corresponding vacuum space-time to the future of the initial outgoing hypersurface and another incoming null hypersurface with the prescribed Minkowskian data. In this paper we give a simpler proof for a finite problem by enlarging the admissible set of initial conditions and, consistent with this, relaxing the corresponding propagation estimates just enough that a trapped surface still forms. We also reduce the number of derivatives needed in the argument from two derivatives of the curvature to just one. More importantly, the proof, which can be easily localized with respect to angular sectors, has the potential for further developments. |
0805.4294 | Rajesh R. Parwani | Le-Huy Nguyen and Rajesh R. Parwani | Nonlinear Quantum Cosmology | Final Journal version: Further clarification in Introduction and
Conclusion. references added. figures same as in version 1 | Gen.Rel.Grav.41:2543-2560,2009 | 10.1007/s10714-009-0779-9 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the effects of an information-theoretically motivated nonlinear
correction to the Wheeler-deWitt equation in the minisuperspace scheme for
flat, $k=0$, Friedmann-Robertson-Walker (FRW) universes. When the only matter
is a cosmological constant, the nonlinearity can provide a barrier that screens
the original Big Bang, leading to the quantum creation of a universe through
tunneling just as in the $k=1$ case. When the matter is instead a free massless
scalar field, the nonlinearity can again prevent a contracting classical
universe from reaching zero size by creating a bounce. Our studies here are
self-consistent to leading order in perturbation theory for the nonlinear
effects.
| [
{
"created": "Wed, 28 May 2008 09:41:21 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Oct 2008 06:49:10 GMT",
"version": "v2"
},
{
"created": "Tue, 17 Feb 2009 07:09:52 GMT",
"version": "v3"
}
] | 2014-11-18 | [
[
"Nguyen",
"Le-Huy",
""
],
[
"Parwani",
"Rajesh R.",
""
]
] | We study the effects of an information-theoretically motivated nonlinear correction to the Wheeler-deWitt equation in the minisuperspace scheme for flat, $k=0$, Friedmann-Robertson-Walker (FRW) universes. When the only matter is a cosmological constant, the nonlinearity can provide a barrier that screens the original Big Bang, leading to the quantum creation of a universe through tunneling just as in the $k=1$ case. When the matter is instead a free massless scalar field, the nonlinearity can again prevent a contracting classical universe from reaching zero size by creating a bounce. Our studies here are self-consistent to leading order in perturbation theory for the nonlinear effects. |
1707.05724 | Andrea Addazi AndAdd | Andrea Addazi | Evaporation/Antievaporation and energy conditions in alternative gravity | null | null | 10.1142/S0217751X18500306 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the evaporation and antievaporation instabilities of Nariai
solution in extended theories of gravity. These phenomena were explicitly shown
in several different extensions of General Relativity, suggesting that a
universal cause is behind them. We show that evaporation and antievaporation
are originated from deformations of energy conditions on the Nariai horizon.
Energy conditions get new contributions from the extra propagating degrees of
freedom, which can provide extra focalizing or antifocalizing terms in the
Raychanduri equation. We also show two explicit examples in $f(R)$-gravity and
Gauss-Bonnet gravity.
| [
{
"created": "Tue, 18 Jul 2017 16:14:19 GMT",
"version": "v1"
}
] | 2018-02-28 | [
[
"Addazi",
"Andrea",
""
]
] | We discuss the evaporation and antievaporation instabilities of Nariai solution in extended theories of gravity. These phenomena were explicitly shown in several different extensions of General Relativity, suggesting that a universal cause is behind them. We show that evaporation and antievaporation are originated from deformations of energy conditions on the Nariai horizon. Energy conditions get new contributions from the extra propagating degrees of freedom, which can provide extra focalizing or antifocalizing terms in the Raychanduri equation. We also show two explicit examples in $f(R)$-gravity and Gauss-Bonnet gravity. |
gr-qc/9605049 | Patricio Salgado Areas | Mauricio Cataldo (Universidad del Bio-Bio, Chile), Patricio Salgado
(Universidad de Concepcion, Chile) | Static Einstein-Maxwell Solutions in 2+1 dimensions | 8 pages, LaTeX, no figures, to appear in Physical Review D | null | 10.1103/PhysRevD.54.2971 | null | gr-qc | null | We obtain the Einstein-Maxwell equations for (2+1)-dimensional static
space-time, which are invariant under the transformation
$q_0=i\,q_2,q_2=i\,q_0,\alpha \rightleftharpoons \gamma$. It is shown that the
magnetic solution obtained with the help of the procedure used in
Ref.~\cite{Cataldo}, can be obtained from the static BTZ solution using an
appropriate transformation. Superpositions of a perfect fluid and an electric
or a magnetic field are separately studied and their corresponding solutions
found.
| [
{
"created": "Wed, 22 May 1996 11:22:26 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Cataldo",
"Mauricio",
"",
"Universidad del Bio-Bio, Chile"
],
[
"Salgado",
"Patricio",
"",
"Universidad de Concepcion, Chile"
]
] | We obtain the Einstein-Maxwell equations for (2+1)-dimensional static space-time, which are invariant under the transformation $q_0=i\,q_2,q_2=i\,q_0,\alpha \rightleftharpoons \gamma$. It is shown that the magnetic solution obtained with the help of the procedure used in Ref.~\cite{Cataldo}, can be obtained from the static BTZ solution using an appropriate transformation. Superpositions of a perfect fluid and an electric or a magnetic field are separately studied and their corresponding solutions found. |
2002.07588 | Subhajyoti Pal Mr. | Subhajyoti Pal, Subenoy Chakraborty | Dynamical System Analysis of a Three Fluid Cosmological Model : An
Invariant Manifold approach | 26 pages, 8 figures, 16 tables | Eur.Phys.J.C79(2019)no.4, 362 | 10.1140/epjc/s10052-019-6875-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present paper considers a three-fluid cosmological model consisting of
noninteracting dark matter, dark energy and baryonic matter in the background
of the Friedmann- Robertson- Walker- Lemaitre flat spacetime. It has been
assumed that the dark matter takes the form of dust whereas the dark energy is
a quintessence (real) scalar field with exponential potential. It has been
further assumed that the baryonic matter is a perfect fluid with barotropic
equation of states. The field equations for this model takes the form of an
autonomous dynamical system after some suitable changes of variables. Then a
complete stability analysis is done considering all possible parameter (the
adiabatic index of the baryonic matter and the parameter arising from the dark
energy potential) values and for both the cases of hyperbolic and
non-hyperbolic critical points. For non-hyperbolic critical points, the
invariant manifold theory (center manifold approach) is applied. Finally
various topologically different phase planes and vector field diagrams are
produced and the cosmological interpretation of this model is presented.
| [
{
"created": "Mon, 17 Feb 2020 10:07:23 GMT",
"version": "v1"
}
] | 2020-02-19 | [
[
"Pal",
"Subhajyoti",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | The present paper considers a three-fluid cosmological model consisting of noninteracting dark matter, dark energy and baryonic matter in the background of the Friedmann- Robertson- Walker- Lemaitre flat spacetime. It has been assumed that the dark matter takes the form of dust whereas the dark energy is a quintessence (real) scalar field with exponential potential. It has been further assumed that the baryonic matter is a perfect fluid with barotropic equation of states. The field equations for this model takes the form of an autonomous dynamical system after some suitable changes of variables. Then a complete stability analysis is done considering all possible parameter (the adiabatic index of the baryonic matter and the parameter arising from the dark energy potential) values and for both the cases of hyperbolic and non-hyperbolic critical points. For non-hyperbolic critical points, the invariant manifold theory (center manifold approach) is applied. Finally various topologically different phase planes and vector field diagrams are produced and the cosmological interpretation of this model is presented. |
1909.13688 | Thiago Pereira | Thiago S. Pereira, Cyril Pitrou | Bianchi spacetimes as super-curvature modes around isotropic cosmologies | 32 pages and 1 figure | Phys. Rev. D 100, 123534 (2019) | 10.1103/PhysRevD.100.123534 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A powerful result in theoretical cosmology states that a subset of
anisotropic Bianchi models can be seen as the homogeneous limit of (standard)
linear cosmological perturbations. Such models are precisely those leading to
Friedmann spacetimes in the limit of zero anisotropy. Building on previous
works, we give a comprehensive exposition of this result, and perform the
detailed identification between anisotropic degrees of freedom and their
corresponding scalar, vector, and tensor perturbations of standard perturbation
theory. In particular, we find that anisotropic models very close to open
(i.e., negatively curved) Friedmann spaces correspond to some type of
super-curvature perturbations. As a consequence, provided anisotropy is mild,
its effects on all types of cosmological observables can always be computed as
simple extensions of the standard techniques used in relativistic perturbation
theory around Friedmann models. This fact opens the possibility to consistently
constrain, for all cosmological observables, the presence of large scale
anisotropies on the top of the stochastic fluctuations.
| [
{
"created": "Mon, 30 Sep 2019 13:33:35 GMT",
"version": "v1"
}
] | 2019-12-25 | [
[
"Pereira",
"Thiago S.",
""
],
[
"Pitrou",
"Cyril",
""
]
] | A powerful result in theoretical cosmology states that a subset of anisotropic Bianchi models can be seen as the homogeneous limit of (standard) linear cosmological perturbations. Such models are precisely those leading to Friedmann spacetimes in the limit of zero anisotropy. Building on previous works, we give a comprehensive exposition of this result, and perform the detailed identification between anisotropic degrees of freedom and their corresponding scalar, vector, and tensor perturbations of standard perturbation theory. In particular, we find that anisotropic models very close to open (i.e., negatively curved) Friedmann spaces correspond to some type of super-curvature perturbations. As a consequence, provided anisotropy is mild, its effects on all types of cosmological observables can always be computed as simple extensions of the standard techniques used in relativistic perturbation theory around Friedmann models. This fact opens the possibility to consistently constrain, for all cosmological observables, the presence of large scale anisotropies on the top of the stochastic fluctuations. |
2304.13263 | Ruanjing Zhang | Ruanjing Zhang and Jiliang Jing and Zhipeng Peng and Qihong Huang | Strong gravitational lensing of rotating regular black holes in
non-minimally coupled Einstein-Yang-Mills theory | null | Chinese Physics C Vol. 47, No. 10 (2023) 105105 | 10.1088/1674-1137/acf489 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The strong gravitational lensing of a regular and rotating magnetic black
hole in non-minimally coupled Einstein-Yang-Mills theory is studied. We find
that, with the increase of any characteristic parameters of this black hole,
such as the rotating parameter, magnetic charge and EYM parameter, the angular
image position and relative magnification decrease while deflection angle and
image separation increase. The results will degenerate to that of the Kerr
case, R-N case with magnetic charge and Schwarzschild case when we take some
specific values for the black hole parameters. The results also show that, due
to the small influence of magnetic charge and Einstein-Yang-Mills parameters,
it is difficult for current astronomical instruments to tell this black hole
apart from a General Relativity one.
| [
{
"created": "Wed, 26 Apr 2023 03:36:24 GMT",
"version": "v1"
},
{
"created": "Mon, 8 May 2023 09:15:32 GMT",
"version": "v2"
}
] | 2023-10-16 | [
[
"Zhang",
"Ruanjing",
""
],
[
"Jing",
"Jiliang",
""
],
[
"Peng",
"Zhipeng",
""
],
[
"Huang",
"Qihong",
""
]
] | The strong gravitational lensing of a regular and rotating magnetic black hole in non-minimally coupled Einstein-Yang-Mills theory is studied. We find that, with the increase of any characteristic parameters of this black hole, such as the rotating parameter, magnetic charge and EYM parameter, the angular image position and relative magnification decrease while deflection angle and image separation increase. The results will degenerate to that of the Kerr case, R-N case with magnetic charge and Schwarzschild case when we take some specific values for the black hole parameters. The results also show that, due to the small influence of magnetic charge and Einstein-Yang-Mills parameters, it is difficult for current astronomical instruments to tell this black hole apart from a General Relativity one. |
2105.07695 | H. B. Benaoum | H. B. Benaoum and A. Ovgun | Matter-antimatter asymmetry induced by non-linear electrodynamics | To appear in Classical and Quantum Gravity; 12 pages; dedicated to
Andrei Sakharov on the occasion of his 100th birthday | Class. Quantum Grav. 38 135019 (2021) | 10.1088/1361-6382/abfd90 | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | In this work, we propose an economical model to address some open
cosmological problems such as the absence of the initial cosmological
singularity, an early acceleration of the Universe and the generation of
matter-antimatter asymmetry. The model is based on a scenario in which the
early Universe consists of a non-linear electrodynamics fields. It is found
that the non-linear electrodynamics model has an equation of state
$p=\frac{1}{3} \rho - \frac{4}{3} \beta \rho^{1+\alpha}$ which shows that the
Universe undergoes an early epoch acceleration to a radiation era given by $p
=\frac{1}{3} \rho$. We show that the singularities in the energy density,
pressure and curvature are absent at early stages. In our scenario, the baryon
asymmetry is generated by the non-linearity parameter $\beta$. Additionally, we
calculate the resulting baryon asymmetry and discuss how a successful
gravitational baryogenesis is obtained for different values of the model's
parameter space.
| [
{
"created": "Mon, 17 May 2021 09:31:07 GMT",
"version": "v1"
}
] | 2021-06-10 | [
[
"Benaoum",
"H. B.",
""
],
[
"Ovgun",
"A.",
""
]
] | In this work, we propose an economical model to address some open cosmological problems such as the absence of the initial cosmological singularity, an early acceleration of the Universe and the generation of matter-antimatter asymmetry. The model is based on a scenario in which the early Universe consists of a non-linear electrodynamics fields. It is found that the non-linear electrodynamics model has an equation of state $p=\frac{1}{3} \rho - \frac{4}{3} \beta \rho^{1+\alpha}$ which shows that the Universe undergoes an early epoch acceleration to a radiation era given by $p =\frac{1}{3} \rho$. We show that the singularities in the energy density, pressure and curvature are absent at early stages. In our scenario, the baryon asymmetry is generated by the non-linearity parameter $\beta$. Additionally, we calculate the resulting baryon asymmetry and discuss how a successful gravitational baryogenesis is obtained for different values of the model's parameter space. |
gr-qc/0702141 | Niklas Rohr | J. Mark Heinzle, Claes Uggla, Niklas Rohr | The cosmological billiard attractor | 88 pages, 18 figures | Adv.Theor.Math.Phys.13:293-407,2009 | null | null | gr-qc | null | This article is devoted to a study of the asymptotic dynamics of generic
solutions of the Einstein vacuum equations toward a generic spacelike
singularity. Starting from fundamental assumptions about the nature of generic
spacelike singularities we derive in a step-by-step manner the cosmological
billiard conjecture: we show that the generic asymptotic dynamics of solutions
is represented by (randomized) sequences of heteroclinic orbits on the
`billiard attractor'. Our analysis rests on two pillars: (i) a dynamical
systems formulation based on the conformal Hubble-normalized orthonormal frame
approach expressed in an Iwasawa frame; (ii) stochastic methods and the
interplay between genericity and stochasticity. Our work generalizes and
improves the level of rigor of previous work by Belinskii, Khalatnikov, and
Lifshitz; furthermore, we establish that our approach and the Hamiltonian
approach to `cosmological billiards', as elaborated by Damour, Hennaux, and
Nicolai, can be viewed as yielding `dual' representations of the asymptotic
dynamics.
| [
{
"created": "Tue, 27 Feb 2007 12:30:37 GMT",
"version": "v1"
}
] | 2009-03-19 | [
[
"Heinzle",
"J. Mark",
""
],
[
"Uggla",
"Claes",
""
],
[
"Rohr",
"Niklas",
""
]
] | This article is devoted to a study of the asymptotic dynamics of generic solutions of the Einstein vacuum equations toward a generic spacelike singularity. Starting from fundamental assumptions about the nature of generic spacelike singularities we derive in a step-by-step manner the cosmological billiard conjecture: we show that the generic asymptotic dynamics of solutions is represented by (randomized) sequences of heteroclinic orbits on the `billiard attractor'. Our analysis rests on two pillars: (i) a dynamical systems formulation based on the conformal Hubble-normalized orthonormal frame approach expressed in an Iwasawa frame; (ii) stochastic methods and the interplay between genericity and stochasticity. Our work generalizes and improves the level of rigor of previous work by Belinskii, Khalatnikov, and Lifshitz; furthermore, we establish that our approach and the Hamiltonian approach to `cosmological billiards', as elaborated by Damour, Hennaux, and Nicolai, can be viewed as yielding `dual' representations of the asymptotic dynamics. |
1409.1503 | Burkhard Kleihaus | Burkhard Kleihaus and Jutta Kunz | Rotating Ellis Wormholes in Four Dimensions | 9 pages, 3 figures | Phys. Rev. D90 (2014) 121503(R) | 10.1103/PhysRevD.90.121503 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present rotating wormhole solutions in General Relativity, which are
supported by a phantom scalar field. These solutions evolve from the static
Ellis wormhole, when the throat is set into rotation. As the rotational
velocity increases, the throat deforms until at a maximal value of the
rotational velocity, an extremal Kerr solution is encountered. The rotating
wormholes attain a finite mass and quadrupole moment. They exhibit ergospheres
and possess bound orbits.
| [
{
"created": "Thu, 4 Sep 2014 17:39:59 GMT",
"version": "v1"
}
] | 2014-12-31 | [
[
"Kleihaus",
"Burkhard",
""
],
[
"Kunz",
"Jutta",
""
]
] | We present rotating wormhole solutions in General Relativity, which are supported by a phantom scalar field. These solutions evolve from the static Ellis wormhole, when the throat is set into rotation. As the rotational velocity increases, the throat deforms until at a maximal value of the rotational velocity, an extremal Kerr solution is encountered. The rotating wormholes attain a finite mass and quadrupole moment. They exhibit ergospheres and possess bound orbits. |
2207.08780 | Wenbin Lin | Jie Li, Bo Yang, Wenbin Lin | The quasi-Keplerian motion in the regular Bardeen spacetime | 12 pages, 1 figure. arXiv admin note: substantial text overlap with
arXiv:2202.08264 | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The second post-Newtonian solution for the quasi-Keplerian motion of a test
particle in the gravitational field of regular Bardeen black hole is derived.
The solution is formulated in terms of the test particle's orbital energy and
angular momentum, as well as the mass and magnetic charge of the Bardeen black
hole. The leading effects of the magnetic charge on the test particle's orbit
and motion including perihelion precession are displayed explicitly. In
particular, it is shown that to the second post-Newtonian order the magnetic
charge does not affect the test particle's orbital period.
| [
{
"created": "Mon, 4 Jul 2022 17:31:00 GMT",
"version": "v1"
}
] | 2022-07-19 | [
[
"Li",
"Jie",
""
],
[
"Yang",
"Bo",
""
],
[
"Lin",
"Wenbin",
""
]
] | The second post-Newtonian solution for the quasi-Keplerian motion of a test particle in the gravitational field of regular Bardeen black hole is derived. The solution is formulated in terms of the test particle's orbital energy and angular momentum, as well as the mass and magnetic charge of the Bardeen black hole. The leading effects of the magnetic charge on the test particle's orbit and motion including perihelion precession are displayed explicitly. In particular, it is shown that to the second post-Newtonian order the magnetic charge does not affect the test particle's orbital period. |
1602.00682 | Pitayuth Wongjun | Pitayuth Wongjun | Perfect fluid in Lagrangian formulation due to generalized three-form
field | 21 pages, no figure, V2 minor corrected and added a subsection, V3
typos corrected, published version | Phys. Rev. D 96, 023516 (2017) | 10.1103/PhysRevD.96.023516 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A Lagrangian formulation of perfect fluid due to a noncanonical three-form
field is investigated. The thermodynamic quantities such as energy density,
pressure and the four velocity are obtained and then analyzed by comparing with
the k-essence scalar field. The nonrelativistic matter due to the generalized
three-form field with the equation of state parameter being zero is realized
while it might not be possible for the k-essence scalar field. We also found
that nonadiabatic pressure perturbations can be possibly generated. The fluid
dynamics of the perfect fluid due to the three-form field corresponds to the
system in which the number of particles is not conserved. We argue that it is
interesting to use this three-form field to represent the dark matter for the
classical interaction theory between dark matter and dark energy.
| [
{
"created": "Sun, 31 Jan 2016 09:08:42 GMT",
"version": "v1"
},
{
"created": "Sat, 1 Apr 2017 08:20:00 GMT",
"version": "v2"
},
{
"created": "Wed, 19 Jul 2017 08:08:35 GMT",
"version": "v3"
}
] | 2017-07-26 | [
[
"Wongjun",
"Pitayuth",
""
]
] | A Lagrangian formulation of perfect fluid due to a noncanonical three-form field is investigated. The thermodynamic quantities such as energy density, pressure and the four velocity are obtained and then analyzed by comparing with the k-essence scalar field. The nonrelativistic matter due to the generalized three-form field with the equation of state parameter being zero is realized while it might not be possible for the k-essence scalar field. We also found that nonadiabatic pressure perturbations can be possibly generated. The fluid dynamics of the perfect fluid due to the three-form field corresponds to the system in which the number of particles is not conserved. We argue that it is interesting to use this three-form field to represent the dark matter for the classical interaction theory between dark matter and dark energy. |
1406.1658 | Alexis Helou | Pierre Bin\'etruy and Alexis Helou | The Apparent Universe | 16 pages, 1 figure | null | 10.1088/0264-9381/32/20/205006 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We exploit the parallel between dynamical black holes and cosmological
spacetimes to describe the evolution of Friedmann-Lema\^itre-Robertson-Walker
universes from the point of view of an observer in terms of the dynamics of the
apparent horizon. Using the Hayward-Kodama formalism of dynamical black holes,
we clarify the role of the Clausius relation to derive the Friedmann equations
for a universe, in the spirit of Jacobson's work on the thermodynamics of
spacetime. We also show how dynamics at the horizon naturally leads to the
quantum-mechanical process of Hawking radiation. We comment on the connection
of this work with recent ideas to consider our observable Universe as a
Bose-Einstein condensate and on the corresponding role of vacuum energy.
| [
{
"created": "Fri, 6 Jun 2014 12:28:10 GMT",
"version": "v1"
}
] | 2015-10-07 | [
[
"Binétruy",
"Pierre",
""
],
[
"Helou",
"Alexis",
""
]
] | We exploit the parallel between dynamical black holes and cosmological spacetimes to describe the evolution of Friedmann-Lema\^itre-Robertson-Walker universes from the point of view of an observer in terms of the dynamics of the apparent horizon. Using the Hayward-Kodama formalism of dynamical black holes, we clarify the role of the Clausius relation to derive the Friedmann equations for a universe, in the spirit of Jacobson's work on the thermodynamics of spacetime. We also show how dynamics at the horizon naturally leads to the quantum-mechanical process of Hawking radiation. We comment on the connection of this work with recent ideas to consider our observable Universe as a Bose-Einstein condensate and on the corresponding role of vacuum energy. |
gr-qc/0703106 | Aseem Paranjape | Aseem Paranjape, T. P. Singh | The Spatial Averaging Limit of Covariant Macroscopic Gravity - Scalar
Corrections to the Cosmological Equations | 18 pages, no figures, revtex4; v2 - minor clarifications added; v3 -
minor changes in presentation to improve clarity, reference added, to appear
in Phys. Rev. D | Phys.Rev.D76:044006,2007 | 10.1103/PhysRevD.76.044006 | null | gr-qc astro-ph hep-th | null | It is known that any explicit averaging scheme of the type essential for
describing the large scale behaviour of the Universe, must necessarily yield
corrections to the Einstein equations applied in the Cosmological setting. The
question of whether or not the resulting corrections to the Einstein equations
are significant, is still a subject of debate, partly due to possible
ambiguities in the averaging schemes available. In particular, it has been
argued in the literature that the effects of averaging could be gauge
artifacts. We apply the formalism of Zalaletdinov's Macroscopic Gravity (MG)
which is a fully covariant and nonperturbative averaging scheme, in an attempt
to construct gauge independent corrections to the standard
Friedmann-Lemaitre-Robertson-Walker (FLRW) equations. We find that whereas one
cannot escape the problem of dependence on \emph{one} gauge choice -- which is
inherent in the assumption of large scale homogeneity and isotropy -- it is
however possible to construct \emph{spacetime scalar} corrections to the
standard FLRW equations. This partially addresses the criticism concerning the
corrections being gauge artifacts. For a particular initial choice of gauge
which simplifies the formalism, we explicitly construct these scalars in terms
of the underlying inhomogeneous geometry, and incidentally demonstrate that the
formal structure of the corrections with this gauge choice is identical to that
of analogous corrections derived by Buchert in the context of spatial averaging
of scalars.
| [
{
"created": "Wed, 21 Mar 2007 10:18:41 GMT",
"version": "v1"
},
{
"created": "Sun, 8 Apr 2007 06:08:58 GMT",
"version": "v2"
},
{
"created": "Sat, 23 Jun 2007 13:08:09 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Paranjape",
"Aseem",
""
],
[
"Singh",
"T. P.",
""
]
] | It is known that any explicit averaging scheme of the type essential for describing the large scale behaviour of the Universe, must necessarily yield corrections to the Einstein equations applied in the Cosmological setting. The question of whether or not the resulting corrections to the Einstein equations are significant, is still a subject of debate, partly due to possible ambiguities in the averaging schemes available. In particular, it has been argued in the literature that the effects of averaging could be gauge artifacts. We apply the formalism of Zalaletdinov's Macroscopic Gravity (MG) which is a fully covariant and nonperturbative averaging scheme, in an attempt to construct gauge independent corrections to the standard Friedmann-Lemaitre-Robertson-Walker (FLRW) equations. We find that whereas one cannot escape the problem of dependence on \emph{one} gauge choice -- which is inherent in the assumption of large scale homogeneity and isotropy -- it is however possible to construct \emph{spacetime scalar} corrections to the standard FLRW equations. This partially addresses the criticism concerning the corrections being gauge artifacts. For a particular initial choice of gauge which simplifies the formalism, we explicitly construct these scalars in terms of the underlying inhomogeneous geometry, and incidentally demonstrate that the formal structure of the corrections with this gauge choice is identical to that of analogous corrections derived by Buchert in the context of spatial averaging of scalars. |
gr-qc/0411038 | Christine C\'ordula Dantas | Christine C. Dantas | A Note on the Integral Formulation of Einstein's Equations Induced on a
Braneworld | 10 pages, no figures, accepted for publication in the General
Relativity and Gravitation Journal | Gen.Rel.Grav. 37 (2005) 959-965 | 10.1007/s10714-005-0078-z | null | gr-qc astro-ph | null | We revisit the integral formulation (or Green's function approach) of
Einstein's equations in the context of braneworlds. The integral formulation
has been proposed independently by several authors in the past, based on the
assumption that it is possible to give a reinterpretation of the local metric
field in curved spacetimes as an integral expression involving sources and
boundary conditions. This allows one to separate source-generated and
source-free contributions to the metric field. As a consequence, an exact
meaning to Mach's Principle can be achieved in the sense that only
source-generated (matter fields) contributions to the metric are allowed for;
universes which do not obey this condition would be non-Machian. In this paper,
we revisit this idea concentrating on a Randall-Sundrum-type model with a
non-trivial cosmology on the brane. We argue that the role of the surface term
(the source-free contribution) in the braneworld scenario may be quite subtler
than in the 4D formulation. This may pose, for instance, an interesting issue
to the cosmological constant problem.
| [
{
"created": "Mon, 8 Nov 2004 19:06:35 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Dantas",
"Christine C.",
""
]
] | We revisit the integral formulation (or Green's function approach) of Einstein's equations in the context of braneworlds. The integral formulation has been proposed independently by several authors in the past, based on the assumption that it is possible to give a reinterpretation of the local metric field in curved spacetimes as an integral expression involving sources and boundary conditions. This allows one to separate source-generated and source-free contributions to the metric field. As a consequence, an exact meaning to Mach's Principle can be achieved in the sense that only source-generated (matter fields) contributions to the metric are allowed for; universes which do not obey this condition would be non-Machian. In this paper, we revisit this idea concentrating on a Randall-Sundrum-type model with a non-trivial cosmology on the brane. We argue that the role of the surface term (the source-free contribution) in the braneworld scenario may be quite subtler than in the 4D formulation. This may pose, for instance, an interesting issue to the cosmological constant problem. |
2304.04801 | Davide Gerosa | Davide Gerosa, Giulia Fumagalli, Matthew Mould, Giovanni Cavallotto,
Diego Padilla Monroy, Daria Gangardt, Viola De Renzis | Efficient multi-timescale dynamics of precessing black-hole binaries | Code available at https://github.com/dgerosa/precession | Phys. Rev. D 108, 024042 (2023) | 10.1103/PhysRevD.108.024042 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present analytical and numerical progress on black-hole binary spin
precession at second post-Newtonian order using multi-timescale methods. In
addition to the commonly used effective spin which acts as a constant of
motion, we exploit the weighted spin difference and show that such
reparametrization cures the coordinate singularity that affected the previous
formulation for the case of equal-mass binaries. The dynamics on the precession
timescale is written down in closed form in both coprecessing and inertial
frames. Radiation reaction can then be introduced in a quasi-adiabatic fashion
such that, at least for binaries on quasi-circular orbits, gravitational
inspirals reduce to solving a single ordinary differential equation. We provide
a broad review of the resulting phenomenology and rewrite the relevant physics
in terms of the newly adopted parametrization. This includes the spin-orbit
resonances, the up-down instability, spin propagation at past time infinity,
and new precession estimators to be used in gravitational-wave astronomy. Our
findings are implemented in version 2 of the public Python module PRECESSION.
Performing a precession-averaged post-Newtonian evolution from/to arbitrarily
large separation takes $\lesssim 0.1$ s on a single off-the-shelf processor - a
50x speedup compared to our previous implementation. This allows for a wide
variety of applications including propagating gravitational-wave posterior
samples as well as population-synthesis predictions of astrophysical nature.
| [
{
"created": "Mon, 10 Apr 2023 18:21:11 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jul 2023 12:14:40 GMT",
"version": "v2"
}
] | 2023-07-26 | [
[
"Gerosa",
"Davide",
""
],
[
"Fumagalli",
"Giulia",
""
],
[
"Mould",
"Matthew",
""
],
[
"Cavallotto",
"Giovanni",
""
],
[
"Monroy",
"Diego Padilla",
""
],
[
"Gangardt",
"Daria",
""
],
[
"De Renzis",
"Viola",
... | We present analytical and numerical progress on black-hole binary spin precession at second post-Newtonian order using multi-timescale methods. In addition to the commonly used effective spin which acts as a constant of motion, we exploit the weighted spin difference and show that such reparametrization cures the coordinate singularity that affected the previous formulation for the case of equal-mass binaries. The dynamics on the precession timescale is written down in closed form in both coprecessing and inertial frames. Radiation reaction can then be introduced in a quasi-adiabatic fashion such that, at least for binaries on quasi-circular orbits, gravitational inspirals reduce to solving a single ordinary differential equation. We provide a broad review of the resulting phenomenology and rewrite the relevant physics in terms of the newly adopted parametrization. This includes the spin-orbit resonances, the up-down instability, spin propagation at past time infinity, and new precession estimators to be used in gravitational-wave astronomy. Our findings are implemented in version 2 of the public Python module PRECESSION. Performing a precession-averaged post-Newtonian evolution from/to arbitrarily large separation takes $\lesssim 0.1$ s on a single off-the-shelf processor - a 50x speedup compared to our previous implementation. This allows for a wide variety of applications including propagating gravitational-wave posterior samples as well as population-synthesis predictions of astrophysical nature. |
gr-qc/9803063 | Mahmut Hortacsu | M. Horta\c{c}su | Vacuum fluctuations for spherical gravitational impulsive waves | Class. Quantum Grav. 13(1996) 2683-2691 | Class.Quant.Grav. 13 (1996) 2683-2691 | 10.1088/0264-9381/13/10/008 | null | gr-qc | null | We propose a method for calculating vacuum fluctuations on the background of
a spherical impulsive gravitational wave which results in a finite expression
for the vacuum expectation value of the stress-energy tensor. The method is
based on first including a cosmological constant as an auxiliary constant. We
show that the result for the vacuum expectation value of the stress-energy
tensor in second-order perturbation theory is finite if both the cosmological
constant and the infrared parameter tend to zero at the same rate.
| [
{
"created": "Wed, 18 Mar 1998 13:40:13 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Apr 1998 17:18:33 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Hortaçsu",
"M.",
""
]
] | We propose a method for calculating vacuum fluctuations on the background of a spherical impulsive gravitational wave which results in a finite expression for the vacuum expectation value of the stress-energy tensor. The method is based on first including a cosmological constant as an auxiliary constant. We show that the result for the vacuum expectation value of the stress-energy tensor in second-order perturbation theory is finite if both the cosmological constant and the infrared parameter tend to zero at the same rate. |
1005.0716 | Molin Liu | Molin Liu, Benhai Yu, Fei Yu, Yuanxing Gui | The Fourth Gravity Test and Quintessence Matter Field | 9 pages, 1 figure, Eur. Phys. J. C in press | Eur.Phys.J.C67:507-512,2010 | 10.1140/epjc/s10052-010-1321-7 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | After the previous work on gravitational frequency shift, light deflection
(arXiv:1003.5296) and perihelion advance (arXiv:0812.2332), we calculate
carefully the fourth gravity test, i.e. radar echo delay in a central gravity
field surrounded by static free quintessence matter, in this paper. Through the
Lagrangian method, we find the influence of the quintessence matter on the time
delay of null particle is presence by means of an additional integral term.
When the quintessence field vanishes, it reduces to the usual Schwarzschild
case naturally. Meanwhile, we also use the data of the Viking lander from the
Mars and Cassini spacecraft to Saturn to constrain the quintessence field. For
the Viking case, the field parameter $\alpha$ is under the order of $10^{-9}$.
However, $\alpha$ is under $10^{-18}$ for the Cassini case.
| [
{
"created": "Wed, 5 May 2010 10:27:54 GMT",
"version": "v1"
}
] | 2014-11-21 | [
[
"Liu",
"Molin",
""
],
[
"Yu",
"Benhai",
""
],
[
"Yu",
"Fei",
""
],
[
"Gui",
"Yuanxing",
""
]
] | After the previous work on gravitational frequency shift, light deflection (arXiv:1003.5296) and perihelion advance (arXiv:0812.2332), we calculate carefully the fourth gravity test, i.e. radar echo delay in a central gravity field surrounded by static free quintessence matter, in this paper. Through the Lagrangian method, we find the influence of the quintessence matter on the time delay of null particle is presence by means of an additional integral term. When the quintessence field vanishes, it reduces to the usual Schwarzschild case naturally. Meanwhile, we also use the data of the Viking lander from the Mars and Cassini spacecraft to Saturn to constrain the quintessence field. For the Viking case, the field parameter $\alpha$ is under the order of $10^{-9}$. However, $\alpha$ is under $10^{-18}$ for the Cassini case. |
2207.07652 | Sankarsan Tarai | A.Y. Shaikh, Sankarsan Tarai, S.K. Tripathy, B.Mishra | Bouncing cosmological model with general relativistic hydrodynamics in
extended gravity | 10 pages, 9 figures, Accepted version IJGMMP | IGGMMP, 19(12), 2250193 (2022) | 10.1142/S0219887822501936 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, in an extended theory of gravity, we have presented bouncing
cosmological model at the backdrop of an isotropic, homogeneous space-time, in
presence of general relativistic hydrodynamics (GRH). The scale factor has been
chosen in such a manner that with appropriate normalization, the quintom
bouncing scenario can be assessed. Accordingly, the bounce occurs at $t=0$ and
the corresponding Hubble parameter vanishes at the bounce epoch. The equation
of state (EoS) parameter and the energy conditions of the model have been
analysed. The violation of strong energy condition further supports the
behaviour of extended gravity. As the bouncing cosmology suffers with
instability, this model also shows the similar behaviour.
| [
{
"created": "Fri, 15 Jul 2022 05:11:59 GMT",
"version": "v1"
}
] | 2023-03-29 | [
[
"Shaikh",
"A. Y.",
""
],
[
"Tarai",
"Sankarsan",
""
],
[
"Tripathy",
"S. K.",
""
],
[
"Mishra",
"B.",
""
]
] | In this paper, in an extended theory of gravity, we have presented bouncing cosmological model at the backdrop of an isotropic, homogeneous space-time, in presence of general relativistic hydrodynamics (GRH). The scale factor has been chosen in such a manner that with appropriate normalization, the quintom bouncing scenario can be assessed. Accordingly, the bounce occurs at $t=0$ and the corresponding Hubble parameter vanishes at the bounce epoch. The equation of state (EoS) parameter and the energy conditions of the model have been analysed. The violation of strong energy condition further supports the behaviour of extended gravity. As the bouncing cosmology suffers with instability, this model also shows the similar behaviour. |
1106.2408 | Valeria Kagramanova | Victor Enolski, Betti Hartmann, Valeria Kagramanova, Jutta Kunz, Claus
L\"ammerzahl, Parinya Sirimachan | Hyperelliptic integrals and Ho\v{r}ava-Lifshitz black hole space-times | 34 pages, 3 figures, 1 table; We extended the sections 'Introduction'
and 'Conclusions and Outlook' and made some cosmetic changes throughout the
article. The article is accepted for publication in JMP. arXiv admin note:
text overlap with arXiv:1011.6459 | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The description of many dynamical problems like the particle motion in higher
dimensional spherically and axially symmetric space-times is reduced to the
inversion of hyperelliptic integrals of all three kinds. The result of the
inversion is defined locally, using the algebro-geometric techniques of the
standard Jacobi inversion problem and the foregoing restriction to the
$\theta$-divisor. For a representation of the hyperelliptic functions the
Klein--Weierstra{\ss} multivariable $\sigma$-function is introduced. It is
shown that all parameters needed for the calculations like period matrices and
abelian images of branch points can be expressed in terms of the periods of
holomorphic differentials and $\theta$-constants. The cases of genus two, three
and four are considered in detail. The method is exemplified by the particle
motion associated with genus one elliptic and genus three hyperelliptic curves.
Applications are for instance solutions to the geodesic equations in the
space-times of static, spherically symmetric Ho\v{r}ava-Lifshitz black holes.
| [
{
"created": "Mon, 13 Jun 2011 10:20:22 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Dec 2011 19:22:22 GMT",
"version": "v2"
}
] | 2011-12-22 | [
[
"Enolski",
"Victor",
""
],
[
"Hartmann",
"Betti",
""
],
[
"Kagramanova",
"Valeria",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Lämmerzahl",
"Claus",
""
],
[
"Sirimachan",
"Parinya",
""
]
] | The description of many dynamical problems like the particle motion in higher dimensional spherically and axially symmetric space-times is reduced to the inversion of hyperelliptic integrals of all three kinds. The result of the inversion is defined locally, using the algebro-geometric techniques of the standard Jacobi inversion problem and the foregoing restriction to the $\theta$-divisor. For a representation of the hyperelliptic functions the Klein--Weierstra{\ss} multivariable $\sigma$-function is introduced. It is shown that all parameters needed for the calculations like period matrices and abelian images of branch points can be expressed in terms of the periods of holomorphic differentials and $\theta$-constants. The cases of genus two, three and four are considered in detail. The method is exemplified by the particle motion associated with genus one elliptic and genus three hyperelliptic curves. Applications are for instance solutions to the geodesic equations in the space-times of static, spherically symmetric Ho\v{r}ava-Lifshitz black holes. |
0912.0554 | Chun-Yen Lin | Chun-Yen Lin | Emergence of General Relativity from Loop Quantum Gravity | 83 pages MikteX file with 3 pdf figures. Ph.D. Thesis. Using
arbitrary real Immirzi parameter and recovering the symmetry algebra, this
work is significantly improved from its previous version. Details of the
model are also given in the content | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A model is proposed to demonstrate that classical general relativity can
emerge from loop quantum gravity, in a relational description of gravitational
field in terms of coordinates given by matter. Local Dirac observables and
coherent states are defined to explore physical content of the model.
Expectation values of commutators between the observables for the coherent
states recover the four-dimensional diffeomorphism algebra and the large-scale
dynamics of the gravitational field relative to the matter coordinates. Both
results conform with general relativity up to calculable corrections near
singularities.
| [
{
"created": "Thu, 3 Dec 2009 00:13:02 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Mar 2011 05:01:23 GMT",
"version": "v2"
}
] | 2011-03-29 | [
[
"Lin",
"Chun-Yen",
""
]
] | A model is proposed to demonstrate that classical general relativity can emerge from loop quantum gravity, in a relational description of gravitational field in terms of coordinates given by matter. Local Dirac observables and coherent states are defined to explore physical content of the model. Expectation values of commutators between the observables for the coherent states recover the four-dimensional diffeomorphism algebra and the large-scale dynamics of the gravitational field relative to the matter coordinates. Both results conform with general relativity up to calculable corrections near singularities. |
1205.0279 | Boris Altshuler | Boris L. Altshuler | Mach's Principle selects 4 space-time dimensions | 15 pages | null | 10.1103/PhysRevD.86.044006 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Bi-tensor kernel in integral form of Einstein equations realizing Mach's idea
of non-existence of empty space-times is taken as an inverse of differential
operator ("Mach operator") defined conventionally as a second variation of
Einstein's gravity Action over contravariant components of metric tensor. The
choice of transverse gauge condition used in this definition does not influence
results of the paper since only transverse and traceless tensor modes written
on different background space-times are studied. Presence of ghosts among modes
of Mach operator invalidates the integral formulation of Einstein equations.
And the demand of absence of these ghosts proves to be a selection rule for
dimensionality of the background space-time. In particular Mach operator
written on De Sitter background or on the background of so called "Einstein
Universe" does not possess tensor ghosts only in 4-dimensions. The similar
demand gives non-trivial formula for dimensionalities of subspaces of the
Freund-Rubin background.
| [
{
"created": "Mon, 30 Apr 2012 15:00:47 GMT",
"version": "v1"
}
] | 2013-05-30 | [
[
"Altshuler",
"Boris L.",
""
]
] | Bi-tensor kernel in integral form of Einstein equations realizing Mach's idea of non-existence of empty space-times is taken as an inverse of differential operator ("Mach operator") defined conventionally as a second variation of Einstein's gravity Action over contravariant components of metric tensor. The choice of transverse gauge condition used in this definition does not influence results of the paper since only transverse and traceless tensor modes written on different background space-times are studied. Presence of ghosts among modes of Mach operator invalidates the integral formulation of Einstein equations. And the demand of absence of these ghosts proves to be a selection rule for dimensionality of the background space-time. In particular Mach operator written on De Sitter background or on the background of so called "Einstein Universe" does not possess tensor ghosts only in 4-dimensions. The similar demand gives non-trivial formula for dimensionalities of subspaces of the Freund-Rubin background. |
1507.08166 | Zhoujian Cao Dr | Chung-Chin Tsai, Zhoujian Cao, Chun-Yu Lin, Hwei-Jang Yo | Pseudotensor applied to Numerical Relativity in Calculating Global
Quantities | 15 pages, 4 figures. This work is dedicated to the General Relativity
special issue | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we apply the Landau-Lifshitz pseudotensor flux formalism to the
calculation of the total mass and the total angular momentum during the
evolution of a binary black hole system. We also compare its performance with
the traditional integrations for the global quantities. It shows that the
advantage of the pseudotensor flux formalism is the smoothness of the numerical
value of the global quantities, especially of the total angular momentum.
Although the convergence behavior of the global quantities with the
pseudotensor flux method is only comparable with the ones with the traditional
method, the smoothness of its numerical value allows using a larger radius for
surface integration to obtain more accurate result.
| [
{
"created": "Wed, 29 Jul 2015 14:45:07 GMT",
"version": "v1"
}
] | 2015-07-30 | [
[
"Tsai",
"Chung-Chin",
""
],
[
"Cao",
"Zhoujian",
""
],
[
"Lin",
"Chun-Yu",
""
],
[
"Yo",
"Hwei-Jang",
""
]
] | In this work we apply the Landau-Lifshitz pseudotensor flux formalism to the calculation of the total mass and the total angular momentum during the evolution of a binary black hole system. We also compare its performance with the traditional integrations for the global quantities. It shows that the advantage of the pseudotensor flux formalism is the smoothness of the numerical value of the global quantities, especially of the total angular momentum. Although the convergence behavior of the global quantities with the pseudotensor flux method is only comparable with the ones with the traditional method, the smoothness of its numerical value allows using a larger radius for surface integration to obtain more accurate result. |
1107.2109 | Qasem Exirifard | Qasem Exirifard | GravitoMagnetic Force in Modified Newtonian Dynamics | 30 pages, 3 figures | JCAP08(2013)046 | 10.1088/1475-7516/2013/08/046 | IPM/P-2011/061 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce the Gauge Vector-Tensor (GVT) theory by extending the AQUAL's
approach to the GravitoElectroMagnetism (GEM) approximation of gravity. GVT is
a generally covariant theory of gravity composed of a pseudo Riemannian metric
and two U(1) gauge connections that reproduces MOND in the limit of very weak
gravitational fields while remains consistent with the Einstein-Hilbert gravity
in the limit of strong and Newtonian gravitational fields. GVT also provides a
simple framework to study the GEM approximation to gravity. We illustrate that
the gravitomagnetic force at the edge of a galaxy can be in accord with either
GVT or \Lambda CDM but not both. We also study the physics of the GVT theory
around the gravitational saddle point of the Sun and Jupiter system. We notice
that the conclusive refusal of the GVT theory demands measuring either both of
the gravitoelectric and gravitomagnetic fields inside the Sun-Jupiter MOND
window, or the gravitoelectric field inside two different solar GVT MOND
windows. The GVT theory, however, will be favored by observing an anomaly in
the gravitoelectric field inside a single MOND window.
| [
{
"created": "Sat, 9 Jul 2011 09:18:37 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Jul 2011 09:29:15 GMT",
"version": "v2"
},
{
"created": "Wed, 31 Aug 2011 14:54:46 GMT",
"version": "v3"
},
{
"created": "Thu, 20 Oct 2011 17:44:46 GMT",
"version": "v4"
},
{
"cr... | 2013-08-28 | [
[
"Exirifard",
"Qasem",
""
]
] | We introduce the Gauge Vector-Tensor (GVT) theory by extending the AQUAL's approach to the GravitoElectroMagnetism (GEM) approximation of gravity. GVT is a generally covariant theory of gravity composed of a pseudo Riemannian metric and two U(1) gauge connections that reproduces MOND in the limit of very weak gravitational fields while remains consistent with the Einstein-Hilbert gravity in the limit of strong and Newtonian gravitational fields. GVT also provides a simple framework to study the GEM approximation to gravity. We illustrate that the gravitomagnetic force at the edge of a galaxy can be in accord with either GVT or \Lambda CDM but not both. We also study the physics of the GVT theory around the gravitational saddle point of the Sun and Jupiter system. We notice that the conclusive refusal of the GVT theory demands measuring either both of the gravitoelectric and gravitomagnetic fields inside the Sun-Jupiter MOND window, or the gravitoelectric field inside two different solar GVT MOND windows. The GVT theory, however, will be favored by observing an anomaly in the gravitoelectric field inside a single MOND window. |
1210.7248 | Asieh Karami | Alejandro Corichi, Asieh Karami, Edison Montoya | Loop Quantum Cosmology: Anisotropy and singularity resolution | 12 pages, 4 figures, To appear in the Proceedings of the Relativity
and Gravitation 100 Years after Einstein in Prague; Addition of comments and
references | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this contribution we consider the issue of singularity resolution within
loop quantum cosmology (LQC) for different homogeneous models. We present
results of numerical evolutions of effective equations for both isotropic as
well as anisotropic cosmologies, with and without spatial curvature. To address
the issue of singularity resolution we examine the time evolution of
geometrical and curvature invariants that yield information about the
semiclassical spacetime geometry. We discuss generic behavior found for a
variety of initial conditions. Finally, we show that the modifications which
come from Loop Quantum Cosmology imply a non-chaotic effective behavior in the
vacuum Bianchi IX model.
| [
{
"created": "Fri, 26 Oct 2012 20:23:12 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Dec 2012 04:30:41 GMT",
"version": "v2"
}
] | 2012-12-04 | [
[
"Corichi",
"Alejandro",
""
],
[
"Karami",
"Asieh",
""
],
[
"Montoya",
"Edison",
""
]
] | In this contribution we consider the issue of singularity resolution within loop quantum cosmology (LQC) for different homogeneous models. We present results of numerical evolutions of effective equations for both isotropic as well as anisotropic cosmologies, with and without spatial curvature. To address the issue of singularity resolution we examine the time evolution of geometrical and curvature invariants that yield information about the semiclassical spacetime geometry. We discuss generic behavior found for a variety of initial conditions. Finally, we show that the modifications which come from Loop Quantum Cosmology imply a non-chaotic effective behavior in the vacuum Bianchi IX model. |
1806.00818 | Martin Reiris | Mart\'in Reiris Ithurralde | A classification theorem for static vacuum black holes. Part I: the
study of the lapse | 32 pages, 6 figures | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The celebrated uniqueness's theorem of the Schwarzschild solution by Israel,
Robinson et al, and Bunting/Masood-ul-Alam, asserts that the only
asymptotically flat static solution of the vacuum Einstein equations with
compact but non-necessarily connected horizon is Schwarzschild. Between this
article and its sequel we extend this result by proving a classification
theorem for all (metrically complete) solutions of the static vacuum Einstein
equations with compact but non-necessarily connected horizon without making any
further assumption on the topology or the asymptotic. It is shown that any such
solution is either: (i) a Boost, (ii) a Schwarzschild black hole, or (iii) is
of Myers/Korotkin-Nicolai type, that is, it has the same topology and Kasner
asymptotic as the Myers/Korotkin-Nicolai black holes. In a broad sense, the
theorem classifies all the static vacuum black holes in 3+1-dimensions. In this
Part I we use introduce techniques in conformal geometry and comparison
geometry \'a la Bakry-\'Emery to prove that vacuum static black holes have only
one end, and, furthermore, that the lapse is bounded away from zero at
infinity. The techniques have interest in themselves and could be applied in
other contexts as well, for instance to study higher-dimensional static black
holes.
| [
{
"created": "Sun, 3 Jun 2018 15:54:38 GMT",
"version": "v1"
}
] | 2018-06-05 | [
[
"Ithurralde",
"Martín Reiris",
""
]
] | The celebrated uniqueness's theorem of the Schwarzschild solution by Israel, Robinson et al, and Bunting/Masood-ul-Alam, asserts that the only asymptotically flat static solution of the vacuum Einstein equations with compact but non-necessarily connected horizon is Schwarzschild. Between this article and its sequel we extend this result by proving a classification theorem for all (metrically complete) solutions of the static vacuum Einstein equations with compact but non-necessarily connected horizon without making any further assumption on the topology or the asymptotic. It is shown that any such solution is either: (i) a Boost, (ii) a Schwarzschild black hole, or (iii) is of Myers/Korotkin-Nicolai type, that is, it has the same topology and Kasner asymptotic as the Myers/Korotkin-Nicolai black holes. In a broad sense, the theorem classifies all the static vacuum black holes in 3+1-dimensions. In this Part I we use introduce techniques in conformal geometry and comparison geometry \'a la Bakry-\'Emery to prove that vacuum static black holes have only one end, and, furthermore, that the lapse is bounded away from zero at infinity. The techniques have interest in themselves and could be applied in other contexts as well, for instance to study higher-dimensional static black holes. |
1503.06231 | Arvin Ravanpak | Arvin Ravanpak and Fahimeh Salmeh | Logamediate Inflation by Tachyon Field | 13 pages, 4 figures | Phys.Rev.D 89, 063504 (2014) | 10.1103/PhysRevD.89.063504 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A logamediate inflationary model in the presence of the tachyon scalar field
will be studied. Considering slow-roll inflation, the equations of motion of
the universe and the tachyon field will be derived. In the context of
perturbation theory, some important perturbation parameters will be obtained
and using numerical calculations the consistency of our model with
observational data will be illustrated.
| [
{
"created": "Fri, 20 Mar 2015 21:08:34 GMT",
"version": "v1"
}
] | 2015-06-24 | [
[
"Ravanpak",
"Arvin",
""
],
[
"Salmeh",
"Fahimeh",
""
]
] | A logamediate inflationary model in the presence of the tachyon scalar field will be studied. Considering slow-roll inflation, the equations of motion of the universe and the tachyon field will be derived. In the context of perturbation theory, some important perturbation parameters will be obtained and using numerical calculations the consistency of our model with observational data will be illustrated. |
gr-qc/9710092 | Kirill Bronnikov | K. A. Bronnikov, C. P. Constantinidis, R. L. Evangelista and J. C.
Fabris | Cold black holes in scalar-tensor theories | 9 pages, Latex, submitted to Int. J. Mod. Phys. D | null | null | UFES-DF-001/97 | gr-qc | null | We study the possible existence of black holes in scalar-tensor theories of
gravity in four dimensions. Their existence is verified for anomalous versions
of these theories, with a negative kinetic term in the Lagrangian. The Hawking
temperature T_H of these holes is zero, while the horizon area is (in most
cases) infinite. It is shown that an infinite value of T_H can occur only at a
curvature singularity rather than a horizon. As a special case, the Brans-Dicke
theory is studied in more detail, and two kinds of infinite-area black holes
are revealed, with finite and infinite proper time needed for an infalling
particle to reach the horizon.
| [
{
"created": "Mon, 20 Oct 1997 13:21:35 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bronnikov",
"K. A.",
""
],
[
"Constantinidis",
"C. P.",
""
],
[
"Evangelista",
"R. L.",
""
],
[
"Fabris",
"J. C.",
""
]
] | We study the possible existence of black holes in scalar-tensor theories of gravity in four dimensions. Their existence is verified for anomalous versions of these theories, with a negative kinetic term in the Lagrangian. The Hawking temperature T_H of these holes is zero, while the horizon area is (in most cases) infinite. It is shown that an infinite value of T_H can occur only at a curvature singularity rather than a horizon. As a special case, the Brans-Dicke theory is studied in more detail, and two kinds of infinite-area black holes are revealed, with finite and infinite proper time needed for an infalling particle to reach the horizon. |
gr-qc/0508094 | Firmin Oliveira | Firmin J. Oliveira (Joint Astronomy Centre, Hilo, Hawai`i, U.S.A.) | Quantized Intrinsic Redshift in Cosmological General Relativity | 9 pages | null | null | null | gr-qc | null | There are now several analyses reporting quantized differences in the
redshifts between pairs of galaxies. In the simplest cases, these differential
redshifts are found to be harmonics of fundamental periods of approximately 72
km/s and 37.5 km/s. In this paper a wave equation is derived based on
cosmological general relativity, which is a space-velocity theory of the
expanding Universe. The wave equation is approximated to first order and
comparisons are made between the quantized solutions and the reported
observations.
| [
{
"created": "Tue, 23 Aug 2005 05:57:42 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Oliveira",
"Firmin J.",
"",
"Joint Astronomy Centre, Hilo, Hawai`i, U.S.A."
]
] | There are now several analyses reporting quantized differences in the redshifts between pairs of galaxies. In the simplest cases, these differential redshifts are found to be harmonics of fundamental periods of approximately 72 km/s and 37.5 km/s. In this paper a wave equation is derived based on cosmological general relativity, which is a space-velocity theory of the expanding Universe. The wave equation is approximated to first order and comparisons are made between the quantized solutions and the reported observations. |
2309.07228 | Gregorio Carullo | Gregorio Carullo, Simone Albanesi, Alessandro Nagar, Rossella Gamba,
Sebastiano Bernuzzi, Tomas Andrade and Juan Trenado | Unveiling the merger structure of black hole binaries in generic planar
orbits | v2: extended to spinning case. Matches journal version; v3: fix
formatting issue in Suppl. Mat | Phys. Rev. Lett. 132, 101401 (2024) | 10.1103/PhysRevLett.132.101401 | VIR-0804A-23 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The precise modeling of binary black hole coalescences in generic planar
orbits is a crucial step to disentangle dynamical and isolated binary formation
channels through gravitational-wave observations. The merger regime of such
coalescences exhibits a significantly higher complexity compared to the
quasicircular case, and cannot be readily described through standard
parameterizations in terms of eccentricity and anomaly. In the spirit of the
Effective One Body formalism, we build on the study of the test-mass limit, and
introduce a new modelling strategy to describe the general-relativistic
dynamics of two-body systems in generic orbits. This is achieved through
gauge-invariant combinations of the binary energy and angular momentum, such as
a dynamical "impact parameter" at merger. These variables reveal simple
"quasi-universal" structures of the pivotal merger parameters, allowing to
build an accurate analytical representation of generic (bounded and
dynamically-bounded) orbital configurations. We demonstrate the validity of
these analytical relations using 311 numerical simulations of bounded
noncircular binaries with progenitors from the RIT and SXS catalogs, together
with a custom dataset of dynamical captures generated using the Einstein
Toolkit, and test-mass data in bound orbits. Our modeling strategy lays the
foundations of accurate and complete waveform models for systems in arbitrary
orbits, bolstering observational explorations of dynamical formation scenarios
and the discovery of new classes of gravitational wave sources.
| [
{
"created": "Wed, 13 Sep 2023 18:01:41 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Apr 2024 03:09:48 GMT",
"version": "v2"
},
{
"created": "Thu, 25 Apr 2024 16:42:41 GMT",
"version": "v3"
}
] | 2024-04-26 | [
[
"Carullo",
"Gregorio",
""
],
[
"Albanesi",
"Simone",
""
],
[
"Nagar",
"Alessandro",
""
],
[
"Gamba",
"Rossella",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Andrade",
"Tomas",
""
],
[
"Trenado",
"Juan",
""
... | The precise modeling of binary black hole coalescences in generic planar orbits is a crucial step to disentangle dynamical and isolated binary formation channels through gravitational-wave observations. The merger regime of such coalescences exhibits a significantly higher complexity compared to the quasicircular case, and cannot be readily described through standard parameterizations in terms of eccentricity and anomaly. In the spirit of the Effective One Body formalism, we build on the study of the test-mass limit, and introduce a new modelling strategy to describe the general-relativistic dynamics of two-body systems in generic orbits. This is achieved through gauge-invariant combinations of the binary energy and angular momentum, such as a dynamical "impact parameter" at merger. These variables reveal simple "quasi-universal" structures of the pivotal merger parameters, allowing to build an accurate analytical representation of generic (bounded and dynamically-bounded) orbital configurations. We demonstrate the validity of these analytical relations using 311 numerical simulations of bounded noncircular binaries with progenitors from the RIT and SXS catalogs, together with a custom dataset of dynamical captures generated using the Einstein Toolkit, and test-mass data in bound orbits. Our modeling strategy lays the foundations of accurate and complete waveform models for systems in arbitrary orbits, bolstering observational explorations of dynamical formation scenarios and the discovery of new classes of gravitational wave sources. |
2003.14107 | Rittick Roy | Rittick Roy and Sayan Chakrabarti | A study on black hole shadows in asymptotically de Sitter spacetimes | Minor clarifications added and grammatical mistakes corrected,
version accepted for publication in Physical Review D | Phys. Rev. D 102, 024059 (2020) | 10.1103/PhysRevD.102.024059 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Previous works on black hole shadows have been primarily focused on studying
shadows in asymptotically flat and anti-de Sitter space times. In the present
work, we find general expressions for asymptotically de Sitter black hole
shadow as seen by static and comoving observers, for any spherically symmetric
black hole solution, in any space time dimension in generic theories of
gravity. As test cases, we use the derived general expressions to study the
shadow of three different black hole solutions: the four dimensional
Reissner-Nordstr\"{o}m de Sitter black hole, the recently proposed four
dimensional Gauss Bonnet de Sitter black hole and the five dimensional Gauss
Bonnet de Sitter black hole.
| [
{
"created": "Tue, 31 Mar 2020 11:27:32 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Apr 2020 10:12:56 GMT",
"version": "v2"
},
{
"created": "Thu, 9 Jul 2020 10:36:57 GMT",
"version": "v3"
}
] | 2020-07-29 | [
[
"Roy",
"Rittick",
""
],
[
"Chakrabarti",
"Sayan",
""
]
] | Previous works on black hole shadows have been primarily focused on studying shadows in asymptotically flat and anti-de Sitter space times. In the present work, we find general expressions for asymptotically de Sitter black hole shadow as seen by static and comoving observers, for any spherically symmetric black hole solution, in any space time dimension in generic theories of gravity. As test cases, we use the derived general expressions to study the shadow of three different black hole solutions: the four dimensional Reissner-Nordstr\"{o}m de Sitter black hole, the recently proposed four dimensional Gauss Bonnet de Sitter black hole and the five dimensional Gauss Bonnet de Sitter black hole. |
1605.01983 | Soichiro Morisaki | Soichiro Morisaki, Jun'ichi Yokoyama, Kazunari Eda and Yousuke Itoh | Toward the detection of gravitational waves under non-Gaussian noises
II. Independent Component Analysis | 19 pages, 5 figures; Minor changes, accepted for publication in the
Proc. Jpn. Acad., Ser. B | null | 10.2183/pjab.92.336 | RESCEU-18/16 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a new analysis method to deal with stationary non-Gaussian
noises in gravitational wave detectors in terms of the independent component
analysis. First, we consider the simplest case where the detector outputs are
linear combinations of the inputs, consisting of signals and various noises,
and show that this method may be helpful to increase the signal-to-noise ratio.
Next, we take into account the time delay between the inputs and the outputs.
Finally, we extend our method to nonlinearly correlated noises and show that
our method can identify the coupling coefficients and remove non-Gaussian
noises. Although we focus on gravitational wave data analysis, our methods are
applicable to the detection of any signals under non-Gaussian noises.
| [
{
"created": "Fri, 6 May 2016 16:03:12 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Aug 2016 05:43:33 GMT",
"version": "v2"
}
] | 2016-11-03 | [
[
"Morisaki",
"Soichiro",
""
],
[
"Yokoyama",
"Jun'ichi",
""
],
[
"Eda",
"Kazunari",
""
],
[
"Itoh",
"Yousuke",
""
]
] | We introduce a new analysis method to deal with stationary non-Gaussian noises in gravitational wave detectors in terms of the independent component analysis. First, we consider the simplest case where the detector outputs are linear combinations of the inputs, consisting of signals and various noises, and show that this method may be helpful to increase the signal-to-noise ratio. Next, we take into account the time delay between the inputs and the outputs. Finally, we extend our method to nonlinearly correlated noises and show that our method can identify the coupling coefficients and remove non-Gaussian noises. Although we focus on gravitational wave data analysis, our methods are applicable to the detection of any signals under non-Gaussian noises. |
1302.2336 | Mairi Sakellariadou | Gaetano Lambiase, Mairi Sakellariadou, Antonio Stabile | Constraints on NonCommutative Spectral Action from Gravity Probe B and
Torsion Balance Experiments | 12 pages | JCAP12(2013)020 | 10.1088/1475-7516/2013/12/020 | KCL-PH-TH/2013-7 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Noncommutative spectral geometry offers a purely geometric explanation for
the standard model of strong and electroweak interactions, including a
geometric explanation for the origin of the Higgs field. Within this framework,
the gravitational, the electroweak and the strong forces are all described as
purely gravitational forces on a unified noncommutative space-time. In this
study, we infer a constraint on one of the three free parameters of the model,
namely the one characterising the coupling constants at unification, by
linearising the field equations in the limit of weak gravitational fields
generated by a rotating gravitational source, and by making use of recent
experimental data. In particular, using data obtained by Gravity Probe B, we
set a lower bound on the Weyl term appearing in the noncommutative spectral
action, namely $\beta \gtrsim 10^{-6}$m$^{-1}$. This constraint becomes
stronger once we use results from torsion balance experiments, leading to
$\beta \gtrsim 10^{4}$m$^{-1}$. The latter is much stronger than any constraint
imposed so far to curvature squared terms.
| [
{
"created": "Sun, 10 Feb 2013 15:22:29 GMT",
"version": "v1"
},
{
"created": "Wed, 11 Dec 2013 20:05:33 GMT",
"version": "v2"
}
] | 2015-06-15 | [
[
"Lambiase",
"Gaetano",
""
],
[
"Sakellariadou",
"Mairi",
""
],
[
"Stabile",
"Antonio",
""
]
] | Noncommutative spectral geometry offers a purely geometric explanation for the standard model of strong and electroweak interactions, including a geometric explanation for the origin of the Higgs field. Within this framework, the gravitational, the electroweak and the strong forces are all described as purely gravitational forces on a unified noncommutative space-time. In this study, we infer a constraint on one of the three free parameters of the model, namely the one characterising the coupling constants at unification, by linearising the field equations in the limit of weak gravitational fields generated by a rotating gravitational source, and by making use of recent experimental data. In particular, using data obtained by Gravity Probe B, we set a lower bound on the Weyl term appearing in the noncommutative spectral action, namely $\beta \gtrsim 10^{-6}$m$^{-1}$. This constraint becomes stronger once we use results from torsion balance experiments, leading to $\beta \gtrsim 10^{4}$m$^{-1}$. The latter is much stronger than any constraint imposed so far to curvature squared terms. |
1910.10353 | Shiyang Hu | Shiyang Hu, Xin Wu, Guoqing Huang and Enwei Liang | A novel energy-conserving scheme for eight-dimensional systems | 17 pages, 6 figures | null | 10.3847/1538-4357/ab5061 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We design a novel, exactly energy-conserving implicit non-symplectic
integration method for an eight-dimensional Hamiltonian system with four
degrees of freedom. In our algorithm, each partial derivative of the
Hamiltonian with respect to one of phase-space variables is discretized by the
average of eight Hamiltonian difference terms. Such a discretization form is a
second-order approximation to the Hamiltonian gradient. It is shown numerically
via simulations of an FPU-$\beta$ system and a post-Newtonian conservative
system of compact binaries with one body spinning that the newly proposed
method has extremely good energy-conserving performance, compared to the
Runge-Kutta, implicit midpoint symplectic method and extended phase-space
explicit symplectic-like integrators. The new method is advantageous over very
long times and for large time steps compared to state-of-the-art Runge-Kutta
method in the accuracy of numerical solutions. Although such an
energy-conserving integrator exhibits a higher computational cost than any one
of the other three algorithms, the superior results justify its use for
satisfying some specific purposes on the preservation of energies in numerical
simulations with much longer times, e.g. obtaining a high enough accuracy of
the semimajor axis in a Keplerian problem in the Solar System or accurately
grasping the frequency of a gravitational wave from a circular orbit in a
post-Newtonian system of compact binaries. The new integrator will be
potentially applied to model time-varying external electromagnetic fields or
time-dependent spacetimes.
| [
{
"created": "Wed, 23 Oct 2019 05:07:23 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Dec 2019 06:17:38 GMT",
"version": "v2"
}
] | 2019-12-30 | [
[
"Hu",
"Shiyang",
""
],
[
"Wu",
"Xin",
""
],
[
"Huang",
"Guoqing",
""
],
[
"Liang",
"Enwei",
""
]
] | We design a novel, exactly energy-conserving implicit non-symplectic integration method for an eight-dimensional Hamiltonian system with four degrees of freedom. In our algorithm, each partial derivative of the Hamiltonian with respect to one of phase-space variables is discretized by the average of eight Hamiltonian difference terms. Such a discretization form is a second-order approximation to the Hamiltonian gradient. It is shown numerically via simulations of an FPU-$\beta$ system and a post-Newtonian conservative system of compact binaries with one body spinning that the newly proposed method has extremely good energy-conserving performance, compared to the Runge-Kutta, implicit midpoint symplectic method and extended phase-space explicit symplectic-like integrators. The new method is advantageous over very long times and for large time steps compared to state-of-the-art Runge-Kutta method in the accuracy of numerical solutions. Although such an energy-conserving integrator exhibits a higher computational cost than any one of the other three algorithms, the superior results justify its use for satisfying some specific purposes on the preservation of energies in numerical simulations with much longer times, e.g. obtaining a high enough accuracy of the semimajor axis in a Keplerian problem in the Solar System or accurately grasping the frequency of a gravitational wave from a circular orbit in a post-Newtonian system of compact binaries. The new integrator will be potentially applied to model time-varying external electromagnetic fields or time-dependent spacetimes. |
2309.02946 | Alejandro Estrada | Alejandro Estrada and Leon Escobar-Diaz | Numerical Construction of initial data sets for inhomogeneous
cosmological space-times with spatial topology of $\mathbb{T}^3$ | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this work, we numerically construct initial data sets for cosmological
space-times with a spatial topology of $\mathbb{T}^3$, which are generally
inhomogeneous. To do so, we implement a pseudo-spectral approach based on the
discrete Fourier transform for numerically solving Einstein's constraint
equations in an algebraic-hyperbolic form. We explore the advantages and
disadvantages of this method by comparing the numerical solutions with known
analytical initial data sets. Furthermore, we obtain new families of initial
data sets numerically for different configurations of the boundary values of
certain geometric variables.
| [
{
"created": "Wed, 6 Sep 2023 12:25:40 GMT",
"version": "v1"
}
] | 2023-09-07 | [
[
"Estrada",
"Alejandro",
""
],
[
"Escobar-Diaz",
"Leon",
""
]
] | In this work, we numerically construct initial data sets for cosmological space-times with a spatial topology of $\mathbb{T}^3$, which are generally inhomogeneous. To do so, we implement a pseudo-spectral approach based on the discrete Fourier transform for numerically solving Einstein's constraint equations in an algebraic-hyperbolic form. We explore the advantages and disadvantages of this method by comparing the numerical solutions with known analytical initial data sets. Furthermore, we obtain new families of initial data sets numerically for different configurations of the boundary values of certain geometric variables. |
1410.0665 | Eleni-Alexandra Kontou | Eleni-Alexandra Kontou and Ken D. Olum | Quantum inequality in spacetimes with small curvature | 21 pages | Phys. Rev. D 91, 104005 (2015) | 10.1103/PhysRevD.91.104005 | null | gr-qc math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum inequalities bound the extent to which weighted time averages of the
renormalized energy density of a quantum field can be negative. They have
mostly been proved in flat spacetime, but we need curved-spacetime inequalities
to disprove the existence of exotic phenomena, such as closed timelike curves.
In this work we derive such an inequality for a minimally-coupled scalar field
on a geodesic in a spacetime with small curvature, working to first order in
the Ricci tensor and its derivatives. Since only the Ricci tensor enters, there
are no first-order corrections to the flat-space quantum inequalities on paths
which do not encounter any matter or energy.
| [
{
"created": "Thu, 2 Oct 2014 19:49:31 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Oct 2014 16:27:45 GMT",
"version": "v2"
}
] | 2015-05-13 | [
[
"Kontou",
"Eleni-Alexandra",
""
],
[
"Olum",
"Ken D.",
""
]
] | Quantum inequalities bound the extent to which weighted time averages of the renormalized energy density of a quantum field can be negative. They have mostly been proved in flat spacetime, but we need curved-spacetime inequalities to disprove the existence of exotic phenomena, such as closed timelike curves. In this work we derive such an inequality for a minimally-coupled scalar field on a geodesic in a spacetime with small curvature, working to first order in the Ricci tensor and its derivatives. Since only the Ricci tensor enters, there are no first-order corrections to the flat-space quantum inequalities on paths which do not encounter any matter or energy. |
2111.00665 | Hiroki Matsui | Hiroki Matsui, Shinji Mukohyama, Atsushi Naruko | DeWitt boundary condition is consistent in Ho\v{r}ava-Lifshitz quantum
gravity | 7 pages, v2: final published version | Physics Letters B 833 (2022) 137340 | 10.1016/j.physletb.2022.137340 | YITP-21-128, IPMU21-0072 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In quantum cosmology the DeWitt boundary condition is a proposal to set the
wave function of the universe to vanish at the classical big-bang singularity.
In this Letter, we show that in many gravitational theories including general
relativity, the DeWitt wave function does not take a desired form once tensor
perturbations around a homogeneous and isotropic closed universe are taken into
account: anisotropies and inhomogeneities due to the perturbations are not
suppressed near the classical singularity. We then show that
Ho\v{r}ava-Lifshitz gravity provides a satisfactory DeWitt wave function. In
particular, in the limit of $z=3$ anisotropic scaling, we find an exact
analytic expression for the DeWitt wave function of the universe with
scale-invariant perturbations. In general cases with relevant deformations, we
show that the DeWitt wave function can be systematically expanded around the
classical big-bang singularity with perturbations under control.
| [
{
"created": "Mon, 1 Nov 2021 02:41:13 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Aug 2022 03:58:31 GMT",
"version": "v2"
}
] | 2022-08-08 | [
[
"Matsui",
"Hiroki",
""
],
[
"Mukohyama",
"Shinji",
""
],
[
"Naruko",
"Atsushi",
""
]
] | In quantum cosmology the DeWitt boundary condition is a proposal to set the wave function of the universe to vanish at the classical big-bang singularity. In this Letter, we show that in many gravitational theories including general relativity, the DeWitt wave function does not take a desired form once tensor perturbations around a homogeneous and isotropic closed universe are taken into account: anisotropies and inhomogeneities due to the perturbations are not suppressed near the classical singularity. We then show that Ho\v{r}ava-Lifshitz gravity provides a satisfactory DeWitt wave function. In particular, in the limit of $z=3$ anisotropic scaling, we find an exact analytic expression for the DeWitt wave function of the universe with scale-invariant perturbations. In general cases with relevant deformations, we show that the DeWitt wave function can be systematically expanded around the classical big-bang singularity with perturbations under control. |
1904.02747 | Rainer Verch | Rainer Verch | The D-CTC condition in quantum field theory | Contribution for the proceedings of the conference "Progress and
Visions in Quantum Theory in View of Gravity", Leipzig, 01-05 Oct 2018. 12
pages, 3 figures | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A condition proposed by David Deutsch to describe analogues of processes in
the presence of closed timelike curves (D-CTC condition) in bipartite quantum
systems is investigated within the framework of local relativistic quantum
field theory. The main result is that in relativistic quantum field theory on
spacetimes where closed timelike curves are absent, the D-CTC condition can
nevertheless be fulfilled to arbitrary precision, under very general,
model-independent conditions. Therefore, the D-CTC condition should not be
taken as characteristic for quantum processes in the presence of closed
timelike curves in the sense of general relativity. This report is a very
condensed extract of the publication J. Tolksdorf, R. Verch, Commun. Math.
Phys. 357 (2018) 319-351. A new result showing that the D-CTC condition can be
approximately fulfilled by entangled states is also presented.
| [
{
"created": "Thu, 4 Apr 2019 18:56:34 GMT",
"version": "v1"
}
] | 2019-04-08 | [
[
"Verch",
"Rainer",
""
]
] | A condition proposed by David Deutsch to describe analogues of processes in the presence of closed timelike curves (D-CTC condition) in bipartite quantum systems is investigated within the framework of local relativistic quantum field theory. The main result is that in relativistic quantum field theory on spacetimes where closed timelike curves are absent, the D-CTC condition can nevertheless be fulfilled to arbitrary precision, under very general, model-independent conditions. Therefore, the D-CTC condition should not be taken as characteristic for quantum processes in the presence of closed timelike curves in the sense of general relativity. This report is a very condensed extract of the publication J. Tolksdorf, R. Verch, Commun. Math. Phys. 357 (2018) 319-351. A new result showing that the D-CTC condition can be approximately fulfilled by entangled states is also presented. |
2210.17504 | Di Wu | Di Wu, Shuang-Qing Wu | Revisiting mass formulas of the four-dimensional
Reissner-Nordstr\"{o}m-NUT-AdS solutions in a different metric form | 14 pages, match with the published version in PLB | Phys. Lett. B 846 (2023) 138227 | 10.1016/j.physletb.2023.138227 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Recently, the so-called ``consistent thermodynamics'' of the Lorentzian
Reissner-Nordstr\"{o}m (RN)-NUT-AdS$_4$ spacetimes has been pursued by a lot of
efforts via different means. Among these attempts, we had proposed a novel idea
that ``The NUT charge is a thermodynamical multihair" to successfully tackle
with the subject. In this paper, we will adopt this strategy to reconsider the
mass formulas of the RN-NUT-AdS$_4$ solutions but written in an alternative
form, which had not been studied before in any existing literature and might be
a most appropriate ansatz for the higher dimensional multiply NUTty-charged AdS
spacetimes without any constraint condition. Here, we shall discuss the
Christodoulou-Ruffini-like squared mass formula and the first law as well as
the Bekenstein-Smarr mass formula by introducing the secondary hair $J_n = Mn$.
For the sake of generality, we have introduced a dimensionless constant $w$
into the constant factor $\Xi$ in the solution expression so that when $w = 1$,
all obtained results can reproduce those delivered in our previous work.
| [
{
"created": "Mon, 31 Oct 2022 17:29:30 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Mar 2023 11:48:41 GMT",
"version": "v2"
},
{
"created": "Fri, 29 Sep 2023 13:20:23 GMT",
"version": "v3"
},
{
"created": "Thu, 12 Oct 2023 01:03:45 GMT",
"version": "v4"
}
] | 2023-10-13 | [
[
"Wu",
"Di",
""
],
[
"Wu",
"Shuang-Qing",
""
]
] | Recently, the so-called ``consistent thermodynamics'' of the Lorentzian Reissner-Nordstr\"{o}m (RN)-NUT-AdS$_4$ spacetimes has been pursued by a lot of efforts via different means. Among these attempts, we had proposed a novel idea that ``The NUT charge is a thermodynamical multihair" to successfully tackle with the subject. In this paper, we will adopt this strategy to reconsider the mass formulas of the RN-NUT-AdS$_4$ solutions but written in an alternative form, which had not been studied before in any existing literature and might be a most appropriate ansatz for the higher dimensional multiply NUTty-charged AdS spacetimes without any constraint condition. Here, we shall discuss the Christodoulou-Ruffini-like squared mass formula and the first law as well as the Bekenstein-Smarr mass formula by introducing the secondary hair $J_n = Mn$. For the sake of generality, we have introduced a dimensionless constant $w$ into the constant factor $\Xi$ in the solution expression so that when $w = 1$, all obtained results can reproduce those delivered in our previous work. |
0706.0132 | Marcus Werner | M. C. Werner, A. O. Petters | Magnification relations for Kerr lensing and testing Cosmic Censorship | 13 pages, version 2: references added, minor changes. To appear in
Phys. Rev. D | Phys.Rev.D76:064024,2007 | 10.1103/PhysRevD.76.064024 | null | gr-qc astro-ph | null | A Kerr black hole with mass parameter m and angular momentum parameter a
acting as a gravitational lens gives rise to two images in the weak field
limit. We study the corresponding magnification relations, namely the signed
and absolute magnification sums and the centroid up to post-Newtonian order. We
show that there are post-Newtonian corrections to the total absolute
magnification and centroid proportional to a/m, which is in contrast to the
spherically symmetric case where such corrections vanish. Hence we also propose
a new set of lensing observables for the two images involving these
corrections, which should allow measuring a/m with gravitational lensing. In
fact, the resolution capabilities needed to observe this for the Galactic black
hole should in principle be accessible to current and near-future
instrumentation. Since a/m >1 indicates a naked singularity, a most interesting
application would be a test of the Cosmic Censorship conjecture. The technique
used to derive the image properties is based on the degeneracy of the Kerr lens
and a suitably displaced Schwarzschild lens at post-Newtonian order. A simple
physical explanation for this degeneracy is also given.
| [
{
"created": "Fri, 1 Jun 2007 12:15:06 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Aug 2007 10:23:00 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Werner",
"M. C.",
""
],
[
"Petters",
"A. O.",
""
]
] | A Kerr black hole with mass parameter m and angular momentum parameter a acting as a gravitational lens gives rise to two images in the weak field limit. We study the corresponding magnification relations, namely the signed and absolute magnification sums and the centroid up to post-Newtonian order. We show that there are post-Newtonian corrections to the total absolute magnification and centroid proportional to a/m, which is in contrast to the spherically symmetric case where such corrections vanish. Hence we also propose a new set of lensing observables for the two images involving these corrections, which should allow measuring a/m with gravitational lensing. In fact, the resolution capabilities needed to observe this for the Galactic black hole should in principle be accessible to current and near-future instrumentation. Since a/m >1 indicates a naked singularity, a most interesting application would be a test of the Cosmic Censorship conjecture. The technique used to derive the image properties is based on the degeneracy of the Kerr lens and a suitably displaced Schwarzschild lens at post-Newtonian order. A simple physical explanation for this degeneracy is also given. |
1102.3474 | Abhay Ashtekar | Abhay Ashtekar, Adam Henderson and David Sloan | A Hamiltonian Formulation of the BKL Conjecture | 26 pages, 3 figures. Two references added. Minor typos corrected. To
appear in PRD | Phys.Rev.D83:084024,2011 | 10.1103/PhysRevD.83.084024 | IGC-11/02-5 | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Belinskii, Khalatnikov and Lifshitz conjecture \cite{bkl1} posits that on
approach to a space-like singularity in general relativity the dynamics are
well approximated by `ignoring spatial derivatives in favor of time
derivatives.' In \cite{ahs1} we examined this idea from within a Hamiltonian
framework and provided a new formulation of the conjecture in terms of
variables well suited to loop quantum gravity. We now present the details of
the analytical part of that investigation. While our motivation came from
quantum considerations, thanks to some of its new features, our formulation
should be useful also for future analytical and numerical investigations within
general relativity.
| [
{
"created": "Thu, 17 Feb 2011 02:09:59 GMT",
"version": "v1"
},
{
"created": "Sat, 12 Mar 2011 16:47:48 GMT",
"version": "v2"
}
] | 2011-05-10 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Henderson",
"Adam",
""
],
[
"Sloan",
"David",
""
]
] | The Belinskii, Khalatnikov and Lifshitz conjecture \cite{bkl1} posits that on approach to a space-like singularity in general relativity the dynamics are well approximated by `ignoring spatial derivatives in favor of time derivatives.' In \cite{ahs1} we examined this idea from within a Hamiltonian framework and provided a new formulation of the conjecture in terms of variables well suited to loop quantum gravity. We now present the details of the analytical part of that investigation. While our motivation came from quantum considerations, thanks to some of its new features, our formulation should be useful also for future analytical and numerical investigations within general relativity. |
2107.06101 | Paolo Maraner | Paolo Maraner | Electromagnetic and gravitational interactions from Lagrangian mechanics | 27 pages | Annals of Physics 431 (2021) 168548 | 10.1016/j.aop.2021.168548 | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Background fields of electromagnetic and gravitational type emerge in the low
kinetic energy limit of any regular Lagrangian system and, in particular, in
the corresponding limit of any spacetime theory in which the free motion of
test particles is described by an unspecified regular Lagrangian.
Electromagnetic and gravitational type interactions are therefore a universal
feature of low kinetic energy Lagrangian systems. These background interactions
can be consistently turned into dynamic Einstein-Maxwell fields by promoting
the Lagrangian function to a dynamic scalar field on the tangent bundle of the
configuration space. Accordingly, Einstein-Maxwell theory can be deduced from
the assumption that the motion of elementary test particles in spacetime is
described by Lagrangian mechanics. For higher kinetic energy-type values,
identified with the square of the invariant mass of the particle, the
Lagrangian induces higher rank interactions that seem however too weak to have
been detected in spacetime physics, but which might prove relevant at the
Planck scale.
| [
{
"created": "Sun, 11 Jul 2021 15:45:56 GMT",
"version": "v1"
}
] | 2021-07-14 | [
[
"Maraner",
"Paolo",
""
]
] | Background fields of electromagnetic and gravitational type emerge in the low kinetic energy limit of any regular Lagrangian system and, in particular, in the corresponding limit of any spacetime theory in which the free motion of test particles is described by an unspecified regular Lagrangian. Electromagnetic and gravitational type interactions are therefore a universal feature of low kinetic energy Lagrangian systems. These background interactions can be consistently turned into dynamic Einstein-Maxwell fields by promoting the Lagrangian function to a dynamic scalar field on the tangent bundle of the configuration space. Accordingly, Einstein-Maxwell theory can be deduced from the assumption that the motion of elementary test particles in spacetime is described by Lagrangian mechanics. For higher kinetic energy-type values, identified with the square of the invariant mass of the particle, the Lagrangian induces higher rank interactions that seem however too weak to have been detected in spacetime physics, but which might prove relevant at the Planck scale. |
2009.12874 | Genly Le\'on | Andronikos Paliathanasis (DUT, Durban and Chile Austral U., Valdivia),
Genly Leon (Catolica del Norte U.) | Dynamics of a two scalar field cosmological model with phantom terms | 16 pages, 11 compound figures | Class. Quantum Grav. 38 075013 (2021) | 10.1088/1361-6382/abe2d7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a detailed analysis on the dynamics of a Chiral-like cosmological
model where the scalar fields can have negative kinetic terms. In particular,
we study the asymptotic dynamics for the gravitational field equations for four
different models in a spatially flat
Friedmann--Lema\^{\i}tre--Robertson--Walker background space. When one of the
scalar fields is phantom, we calculated that the cosmological fluid can evolves
such that the parameter for the equation of state crosses twice the phantom
divide line without the appearance of ghosts. Moreover, the cosmological
viability of these four models is discussed.
| [
{
"created": "Sun, 27 Sep 2020 15:36:19 GMT",
"version": "v1"
}
] | 2021-06-08 | [
[
"Paliathanasis",
"Andronikos",
"",
"DUT, Durban and Chile Austral U., Valdivia"
],
[
"Leon",
"Genly",
"",
"Catolica del Norte U."
]
] | We perform a detailed analysis on the dynamics of a Chiral-like cosmological model where the scalar fields can have negative kinetic terms. In particular, we study the asymptotic dynamics for the gravitational field equations for four different models in a spatially flat Friedmann--Lema\^{\i}tre--Robertson--Walker background space. When one of the scalar fields is phantom, we calculated that the cosmological fluid can evolves such that the parameter for the equation of state crosses twice the phantom divide line without the appearance of ghosts. Moreover, the cosmological viability of these four models is discussed. |
2102.02426 | Angel Rincon | Angel Rincon, Ernesto Contreras, Pedro Bargue\~no, Benjamin Koch and
Grigoris Panotopoulos | Four dimensional Einstein-power-Maxwell black hole solutions in
scale-dependent gravity | 12 pages, 2 figures, accepted for publication in Phys. Dark Univ | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present work, we extend and generalize our previous work regarding the
scale dependence applied to black holes in the presence of non-linear
electrodynamics [1]. The starting point for this study is the
Einstein-power-Maxwell theory with a vanishing cosmological constant in (3+1)
dimensions, assuming a scale dependence of both the gravitational and the
electromagnetic coupling. We further examine the corresponding thermodynamic
properties and how these quantities experience deviations from their classical
counterparts. We solve the effective Einstein's field equations using the "null
energy condition" to obtain analytical solutions. The implications of quantum
corrections are also briefly discussed. Finally, we analyze our solutions and
compare them to related results in the literature.
| [
{
"created": "Thu, 4 Feb 2021 05:56:14 GMT",
"version": "v1"
}
] | 2021-02-05 | [
[
"Rincon",
"Angel",
""
],
[
"Contreras",
"Ernesto",
""
],
[
"Bargueño",
"Pedro",
""
],
[
"Koch",
"Benjamin",
""
],
[
"Panotopoulos",
"Grigoris",
""
]
] | In the present work, we extend and generalize our previous work regarding the scale dependence applied to black holes in the presence of non-linear electrodynamics [1]. The starting point for this study is the Einstein-power-Maxwell theory with a vanishing cosmological constant in (3+1) dimensions, assuming a scale dependence of both the gravitational and the electromagnetic coupling. We further examine the corresponding thermodynamic properties and how these quantities experience deviations from their classical counterparts. We solve the effective Einstein's field equations using the "null energy condition" to obtain analytical solutions. The implications of quantum corrections are also briefly discussed. Finally, we analyze our solutions and compare them to related results in the literature. |
gr-qc/9612037 | Lawrence C. Shepley | J.M. Pons, D.C. Salisbury, L.C. Shepley | Gauge transformations in the Lagrangian and Hamiltonian formalisms of
generally covariant theories | 12 pages, no figures; REVTeX; uses multicol,fancyheadings,eqsecnum;
to appear in Phys. Rev. D | null | 10.1103/PhysRevD.55.658 | null | gr-qc math-ph math.MP | null | We study spacetime diffeomorphisms in Hamiltonian and Lagrangian formalisms
of generally covariant systems. We show that the gauge group for such a system
is characterized by having generators which are projectable under the Legendre
map. The gauge group is found to be much larger than the original group of
spacetime diffeomorphisms, since its generators must depend on the lapse
function and shift vector of the spacetime metric in a given coordinate patch.
Our results are generalizations of earlier results by Salisbury and
Sundermeyer. They arise in a natural way from using the requirement of
equivalence between Lagrangian and Hamiltonian formulations of the system, and
they are new in that the symmetries are realized on the full set of phase space
variables. The generators are displayed explicitly and are applied to the
relativistic string and to general relativity.
| [
{
"created": "Sun, 15 Dec 1996 20:08:40 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Pons",
"J. M.",
""
],
[
"Salisbury",
"D. C.",
""
],
[
"Shepley",
"L. C.",
""
]
] | We study spacetime diffeomorphisms in Hamiltonian and Lagrangian formalisms of generally covariant systems. We show that the gauge group for such a system is characterized by having generators which are projectable under the Legendre map. The gauge group is found to be much larger than the original group of spacetime diffeomorphisms, since its generators must depend on the lapse function and shift vector of the spacetime metric in a given coordinate patch. Our results are generalizations of earlier results by Salisbury and Sundermeyer. They arise in a natural way from using the requirement of equivalence between Lagrangian and Hamiltonian formulations of the system, and they are new in that the symmetries are realized on the full set of phase space variables. The generators are displayed explicitly and are applied to the relativistic string and to general relativity. |
1109.1730 | Bin Wang | Jian-Hua He, Bin Wang, Elcio Abdalla | Deep connection between f(R) gravity and the interacting dark sector
model | 9 pages, 2 figures, revised version, accepted for publication in
Phys. Rev. D | null | 10.1103/PhysRevD.84.123526 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the conformal equivalence between the $f(R)$ gravity and the
interacting dark sector model. We review the well-known result that the
conformal transformation physically corresponds to the mass dilation which
marks the strength of interaction between dark sectors. Instead of modeling
f(R) gravity in the Jordan frame, we construct the $f(R)$ gravity in terms of
mass dilation function in the Einstein frame. We find that the condition to
keep $f(R)$ gravity consistent with CMB observations ensures the energy flow
from dark energy to dark matter in the corresponding interacting model, which
meets the requirement to alleviate the coincidence problem in the Einstein
framework.
| [
{
"created": "Thu, 8 Sep 2011 14:39:51 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Nov 2011 10:30:48 GMT",
"version": "v2"
}
] | 2013-05-29 | [
[
"He",
"Jian-Hua",
""
],
[
"Wang",
"Bin",
""
],
[
"Abdalla",
"Elcio",
""
]
] | We examine the conformal equivalence between the $f(R)$ gravity and the interacting dark sector model. We review the well-known result that the conformal transformation physically corresponds to the mass dilation which marks the strength of interaction between dark sectors. Instead of modeling f(R) gravity in the Jordan frame, we construct the $f(R)$ gravity in terms of mass dilation function in the Einstein frame. We find that the condition to keep $f(R)$ gravity consistent with CMB observations ensures the energy flow from dark energy to dark matter in the corresponding interacting model, which meets the requirement to alleviate the coincidence problem in the Einstein framework. |
1510.06557 | Hao Xu | Hao Xu and Zhen-Ming Xu | Maxwell's equal area law for Lovelock Thermodynamics | 16 pages, 10 figures. V2: minor corrections and new references. V3:
more discussion about the relationship between latent heat and temperature
added. Accepted by IJMPD | Int. J. Mod. Phys. D 26 (2017) 1750037 | 10.1142/S0218271817500377 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the construction of Maxwell's equal area law for the Guass-Bonnet
AdS black holes in $d=5,6$ and third order Lovelock AdS black holes in $d=7,8$.
The equal area law can be used to find the number and location of the points of
intersection in the plots of Gibbs free energy, so that we can get the
thermodynamically preferred solution which corresponds to the first order phase
transition. We obtain the radius of the small and large black holes in the
phase transition which share the same Gibbs free energy. The case with two
critical points is explored in much more details. The latent heat is also
studied.
| [
{
"created": "Thu, 22 Oct 2015 09:47:38 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Jan 2016 14:01:35 GMT",
"version": "v2"
},
{
"created": "Mon, 22 Aug 2016 15:44:00 GMT",
"version": "v3"
}
] | 2016-10-12 | [
[
"Xu",
"Hao",
""
],
[
"Xu",
"Zhen-Ming",
""
]
] | We present the construction of Maxwell's equal area law for the Guass-Bonnet AdS black holes in $d=5,6$ and third order Lovelock AdS black holes in $d=7,8$. The equal area law can be used to find the number and location of the points of intersection in the plots of Gibbs free energy, so that we can get the thermodynamically preferred solution which corresponds to the first order phase transition. We obtain the radius of the small and large black holes in the phase transition which share the same Gibbs free energy. The case with two critical points is explored in much more details. The latent heat is also studied. |
0804.2103 | Theocharis Apostolatos | Ioannis Deligiannis, Theocharis A. Apostolatos | Minimizing the kinematical effects on LISA's performance | 14 pages, 3 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | Proper tuning of the orbital characteristics of the three spacecrafts that
constitute the usual triangular configuration of the space-borne
gravitational-wave detector LISA, could minimize the breathing mode of its
arm-lengths. Since the three spacecrafts form three pairs of interferometric
arms, we have the freedom to minimize whichever combination of arm-length
variations that might be useful in signal analysis. Thus for any kind of time
delay interferometry (TDI), that is chosen to be used in analysing the data,
the optimal orbital characteristics could be chosen accordingly, so as to
enhance the performance of the gravitational wave detector.
| [
{
"created": "Mon, 14 Apr 2008 15:02:58 GMT",
"version": "v1"
}
] | 2008-04-15 | [
[
"Deligiannis",
"Ioannis",
""
],
[
"Apostolatos",
"Theocharis A.",
""
]
] | Proper tuning of the orbital characteristics of the three spacecrafts that constitute the usual triangular configuration of the space-borne gravitational-wave detector LISA, could minimize the breathing mode of its arm-lengths. Since the three spacecrafts form three pairs of interferometric arms, we have the freedom to minimize whichever combination of arm-length variations that might be useful in signal analysis. Thus for any kind of time delay interferometry (TDI), that is chosen to be used in analysing the data, the optimal orbital characteristics could be chosen accordingly, so as to enhance the performance of the gravitational wave detector. |
1901.02953 | Carlos A. R. Herdeiro | Carlos A. R. Herdeiro, Eugen Radu | Black hole scalarisation from the breakdown of scale-invariance | 27 pages, 11 figures | Phys. Rev. D 99, 084039 (2019) | 10.1103/PhysRevD.99.084039 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Electro-vacuum black holes are scale-invariant; their energy-momentum tensor
is traceless. Quantum corrections of various sorts, however, can often produce
a trace anomaly and a breakdown of scale-invariance. The (quantum-corrected)
black hole solutions of the corresponding gravitational effective field theory
(EFT) have a non-vanishing Ricci scalar. Then, the presence of a scalar field
with the standard non-minimal coupling $\xi \phi^2 R$ naturally triggers a
spontaneous scalarisation of the corresponding black holes. This scalarisation
phenomenon occurs for an (infinite) discrete set of $\xi$. We illustrate the
occurrence of this phenomenon for two examples of static, spherically
symmetric, asymptotically flat black hole solution of EFTs. In one example the
trace anomaly comes from the matter sector -- a novel, closed form,
generalisation of the Reissner-Nordstr\"om solution with an $F^4$ correction --
whereas in the other example it comes from the geometry sector -- a
noncommutative geometry generalization of the Schwarzschild black hole. For
comparison, we also consider the scalarisation of a black hole surrounded by
(non-conformally invariant) classical matter (Einstein-Maxwell-dilaton black
holes). We find that the scalarised solutions are, generically, entropically
favoured.
| [
{
"created": "Wed, 9 Jan 2019 22:24:30 GMT",
"version": "v1"
}
] | 2019-04-24 | [
[
"Herdeiro",
"Carlos A. R.",
""
],
[
"Radu",
"Eugen",
""
]
] | Electro-vacuum black holes are scale-invariant; their energy-momentum tensor is traceless. Quantum corrections of various sorts, however, can often produce a trace anomaly and a breakdown of scale-invariance. The (quantum-corrected) black hole solutions of the corresponding gravitational effective field theory (EFT) have a non-vanishing Ricci scalar. Then, the presence of a scalar field with the standard non-minimal coupling $\xi \phi^2 R$ naturally triggers a spontaneous scalarisation of the corresponding black holes. This scalarisation phenomenon occurs for an (infinite) discrete set of $\xi$. We illustrate the occurrence of this phenomenon for two examples of static, spherically symmetric, asymptotically flat black hole solution of EFTs. In one example the trace anomaly comes from the matter sector -- a novel, closed form, generalisation of the Reissner-Nordstr\"om solution with an $F^4$ correction -- whereas in the other example it comes from the geometry sector -- a noncommutative geometry generalization of the Schwarzschild black hole. For comparison, we also consider the scalarisation of a black hole surrounded by (non-conformally invariant) classical matter (Einstein-Maxwell-dilaton black holes). We find that the scalarised solutions are, generically, entropically favoured. |
1111.3565 | Danny Kermode | Danny Kermode, Dan Vollick | Gravitational Geons on the Brane | 14 pages with 9 figures. To appear in General Relativity and
Gravitation | null | 10.1007/s10714-011-1259-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we examine the possibility of static, spherically symmetric
gravitational geons on a 3 dimensional brane embedded in a 4+1 dimensional
space-time. We choose a specific g_tt for the brane-world space-time metric. We
then calculate g_rr analytically in the weak field limit and numerically for
stronger fields. We show that the induced field equations on the brane do admit
gravitational geon solutions.
| [
{
"created": "Tue, 15 Nov 2011 16:11:54 GMT",
"version": "v1"
}
] | 2015-06-03 | [
[
"Kermode",
"Danny",
""
],
[
"Vollick",
"Dan",
""
]
] | In this paper, we examine the possibility of static, spherically symmetric gravitational geons on a 3 dimensional brane embedded in a 4+1 dimensional space-time. We choose a specific g_tt for the brane-world space-time metric. We then calculate g_rr analytically in the weak field limit and numerically for stronger fields. We show that the induced field equations on the brane do admit gravitational geon solutions. |
1107.1569 | Eugeny Babichev | Eugeny Babichev, Cedric Deffayet, Gilles Esposito-Farese | Constraints on Shift-Symmetric Scalar-Tensor Theories with a Vainshtein
Mechanism from Bounds on the Time Variation of G | RevTeX4 format; v.2: 5 pages, title changed, matches published
version | Phys. Rev. Lett. 107, 251102 (2011) | 10.1103/PhysRevLett.107.251102 | LPT-Orsay 11-111 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the current bounds on the time variation of the Newton constant
G can put severe constraints on many interesting scalar-tensor theories which
possess a shift symmetry and a nonminimal matter-scalar coupling. This
includes, in particular, Galileon-like models with a Vainshtein screening
mechanism. We underline that this mechanism, if efficient to hide the effects
of the scalar field at short distance and in the static approximation, can in
general not alter the cosmological time evolution of the scalar field. This
results in a locally measured time variation of G which is too large when the
matter-scalar coupling is of order one.
| [
{
"created": "Fri, 8 Jul 2011 07:31:46 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Jan 2012 14:03:05 GMT",
"version": "v2"
}
] | 2012-01-18 | [
[
"Babichev",
"Eugeny",
""
],
[
"Deffayet",
"Cedric",
""
],
[
"Esposito-Farese",
"Gilles",
""
]
] | We show that the current bounds on the time variation of the Newton constant G can put severe constraints on many interesting scalar-tensor theories which possess a shift symmetry and a nonminimal matter-scalar coupling. This includes, in particular, Galileon-like models with a Vainshtein screening mechanism. We underline that this mechanism, if efficient to hide the effects of the scalar field at short distance and in the static approximation, can in general not alter the cosmological time evolution of the scalar field. This results in a locally measured time variation of G which is too large when the matter-scalar coupling is of order one. |
gr-qc/0604022 | Matyas Vasuth | M\'aty\'as Vas\'uth and Bal\'azs Mik\'oczi | Self interaction of spins in binary systems | 6 pages, Proceedings of the Albert Einstein Century International
Conference, Paris, France, 18-22 July, 2005 | null | 10.1063/1.2399660 | null | gr-qc | null | Beyond point mass effects various contributions add to the radiative
evolution of compact binaries. We present all the terms up to the second
post-Newtonian order contributing to the rate of increase of gravitational wave
frequency and the number of gravitational wave cycles left until the final
coalescence for binary systems with spin, mass quadrupole and magnetic dipole
moments, moving on circular orbit. We evaluate these contributions for some
famous or typical compact binaries and show that the terms representing the
self interaction of individual spins, given for the first time here, are
commensurable with the proper spin-spin contributions for the recently
discovered double pulsar J0737-3039.
| [
{
"created": "Wed, 5 Apr 2006 19:18:10 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Vasúth",
"Mátyás",
""
],
[
"Mikóczi",
"Balázs",
""
]
] | Beyond point mass effects various contributions add to the radiative evolution of compact binaries. We present all the terms up to the second post-Newtonian order contributing to the rate of increase of gravitational wave frequency and the number of gravitational wave cycles left until the final coalescence for binary systems with spin, mass quadrupole and magnetic dipole moments, moving on circular orbit. We evaluate these contributions for some famous or typical compact binaries and show that the terms representing the self interaction of individual spins, given for the first time here, are commensurable with the proper spin-spin contributions for the recently discovered double pulsar J0737-3039. |
1810.00436 | Mark Bugden | Mark Bugden, Claudio Paganini | The $\Lambda$ to zero limit of spacetimes and its physical
interpretation | null | null | 10.1088/1361-6382/aaff0d | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the $\Lambda \to 0$ behaviour of Schwarzschild-de Sitter spacetime
and show, according to Geroch's notion of spacetime limits, that it converges
to the Schwarzschild spacetime. We use an embedding into $AdS_3$ to illustrate
and quantify this limiting behaviour. We use these quantitative observations to
establish a hierarchy of validity between the Einstein-de Sitter equations and
the Einstein equations (and therefore in a weak field limit also Newton's
equations), analogous to the quantum-classical limit when taking $\hbar \to 0$.
| [
{
"created": "Sun, 30 Sep 2018 18:21:18 GMT",
"version": "v1"
}
] | 2019-02-13 | [
[
"Bugden",
"Mark",
""
],
[
"Paganini",
"Claudio",
""
]
] | We study the $\Lambda \to 0$ behaviour of Schwarzschild-de Sitter spacetime and show, according to Geroch's notion of spacetime limits, that it converges to the Schwarzschild spacetime. We use an embedding into $AdS_3$ to illustrate and quantify this limiting behaviour. We use these quantitative observations to establish a hierarchy of validity between the Einstein-de Sitter equations and the Einstein equations (and therefore in a weak field limit also Newton's equations), analogous to the quantum-classical limit when taking $\hbar \to 0$. |
1909.07602 | Andronikos Paliathanasis | Andronikos Paliathanasis | Symmetry Analysis In Inflationary Cosmology | 7 pages, no figures, published on the proceedings of "Modern
Treatment of Symmetries Differential Equations and Applications, Suranaree
University of Technology, Thailand (2019) | AIP Conference Proceedings 2153, 020015 (2019) | 10.1063/1.5125080 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We approach the cosmological inflation thought symmetries of differential
equations. We consider the general inflaton field in a homogeneous
Friedmann--Lema\^{\i}tre--Robertson--Walker spacetime and with the use of
conformal transformations we are able to write the generic algebraic solution
for the field equations. We put emphasis on the inflationary models and we show
how we can construct new inflationary models from already known models by using
symmetry transformations.
| [
{
"created": "Tue, 17 Sep 2019 05:47:48 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Oct 2019 07:07:58 GMT",
"version": "v2"
}
] | 2019-10-02 | [
[
"Paliathanasis",
"Andronikos",
""
]
] | We approach the cosmological inflation thought symmetries of differential equations. We consider the general inflaton field in a homogeneous Friedmann--Lema\^{\i}tre--Robertson--Walker spacetime and with the use of conformal transformations we are able to write the generic algebraic solution for the field equations. We put emphasis on the inflationary models and we show how we can construct new inflationary models from already known models by using symmetry transformations. |
2305.14400 | Gopi Kant Goswami Dr | Anirudh Pradhan, Gopikant Goswami, Syamala Krishnannair | The Reconstruction of Constant Jerk Parameter with $f(R,T)$ Gravity in
Bianchi-I spacetime | 19 pages, 19 figures. The European Physical Journal Plus. 2023. arXiv
admin note: text overlap with arXiv:2303.14136 | null | 10.1140/epjp/s13360-023-04057-3 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We have developed a Bianchi I cosmological model of the universe in $f(R,T)$
gravity theory which fit good with the present day scenario of accelerating
universe. The model displays transition from deceleration in the past to the
acceleration at the present. As in the $\Lambda$CDM model, we have defined the
three energy parameters $\Omega_m$, $\Omega_{\mu}$ and $\Omega_{\sigma}$ such
that $\Omega_m$ + $\Omega_{\mu}$ + $\Omega_{\sigma}$ = 1. The parameter
$\Omega_m$ is the matter energy density (baryons + dark matter), $\Omega_{\mu}$
is the energy density associated with the Ricci scalar $R$ and the trace $T$ of
the energy momentum tensor and $\Omega_{\sigma}$ is the energy density
associated with the anisotropy of the universe. We shall call $\Omega_{\mu}$
dominant over the other two due to its higher value. We find that the
$\Omega_{\mu}$ and the other two in the ratio 3:1. 46 Hubble OHD data set is
used to estimate present values of Hubble $H_0$, deceleration $q_0$ and jerk
$j$ parameters. 1$\sigma$, 2$\sigma$ and 3$\sigma$ contour region plots for the
estimated values of parameters are presented. 580 SNIa supernova distance
modulus data set and 66 pantheon SNIa data which include high red shift data in
the range $0\leq z\leq 2.36$ have been used to draw error bar plots and
likelihood probability curves for distance modulus and apparent magnitude of
SNIa supernova's. We have calculated the pressures and densities associated
with the two matter densities, viz., $p_{\mu}$, $\rho_{\mu}$, $p_m$ and
$\rho_m$, respectively. The present age of the universe as per our model is
also evaluated and it is found at par with the present observed values.
| [
{
"created": "Tue, 23 May 2023 09:08:35 GMT",
"version": "v1"
}
] | 2023-05-25 | [
[
"Pradhan",
"Anirudh",
""
],
[
"Goswami",
"Gopikant",
""
],
[
"Krishnannair",
"Syamala",
""
]
] | We have developed a Bianchi I cosmological model of the universe in $f(R,T)$ gravity theory which fit good with the present day scenario of accelerating universe. The model displays transition from deceleration in the past to the acceleration at the present. As in the $\Lambda$CDM model, we have defined the three energy parameters $\Omega_m$, $\Omega_{\mu}$ and $\Omega_{\sigma}$ such that $\Omega_m$ + $\Omega_{\mu}$ + $\Omega_{\sigma}$ = 1. The parameter $\Omega_m$ is the matter energy density (baryons + dark matter), $\Omega_{\mu}$ is the energy density associated with the Ricci scalar $R$ and the trace $T$ of the energy momentum tensor and $\Omega_{\sigma}$ is the energy density associated with the anisotropy of the universe. We shall call $\Omega_{\mu}$ dominant over the other two due to its higher value. We find that the $\Omega_{\mu}$ and the other two in the ratio 3:1. 46 Hubble OHD data set is used to estimate present values of Hubble $H_0$, deceleration $q_0$ and jerk $j$ parameters. 1$\sigma$, 2$\sigma$ and 3$\sigma$ contour region plots for the estimated values of parameters are presented. 580 SNIa supernova distance modulus data set and 66 pantheon SNIa data which include high red shift data in the range $0\leq z\leq 2.36$ have been used to draw error bar plots and likelihood probability curves for distance modulus and apparent magnitude of SNIa supernova's. We have calculated the pressures and densities associated with the two matter densities, viz., $p_{\mu}$, $\rho_{\mu}$, $p_m$ and $\rho_m$, respectively. The present age of the universe as per our model is also evaluated and it is found at par with the present observed values. |
2209.12291 | Akash Kumar Mishra | Rajes Ghosh, Mostafizur Rahman, Akash K Mishra | Regularized Stable Kerr Black Hole: Cosmic Censorships, Shadow and
Quasi-Normal Modes | 11 pages, 5 figures, 1 table, Journal Version | Eur. Phys. J. C 83, 91 (2023) | 10.1140/epjc/s10052-023-11252-0 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black hole solutions in general relativity come with pathologies such as
singularity and mass inflation instability, which are believed to be cured by a
yet-to-be-found quantum theory of gravity. Without such consistent description,
one may model theory-agnostic phenomenological black holes that bypass the
aforesaid issues. These so-called regular black holes are extensively studied
in the literature using parameterized modifications over the black hole
solutions of general relativity. However, since there exist several ways to
model such black holes, it is important to study the consistency and viability
of these solutions from both theoretical and observational perspectives. In
this work, we consider a recently proposed model of regularized stable rotating
black holes having two extra parameters in addition to the mass and spin of a
Kerr solution. We start by computing their quasi-normal modes under scalar
perturbation and investigate the impact of those additional parameters on black
hole stability. In the second part, we study the shadow structures of these
regularized black holes and obtain stringent bounds on the parameter space
requiring consistency with Event Horizon Telescope observations of $M87^*$ and
$Sgr\, A^*$ shadows.
| [
{
"created": "Sun, 25 Sep 2022 18:31:16 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Feb 2023 13:18:56 GMT",
"version": "v2"
}
] | 2023-02-14 | [
[
"Ghosh",
"Rajes",
""
],
[
"Rahman",
"Mostafizur",
""
],
[
"Mishra",
"Akash K",
""
]
] | Black hole solutions in general relativity come with pathologies such as singularity and mass inflation instability, which are believed to be cured by a yet-to-be-found quantum theory of gravity. Without such consistent description, one may model theory-agnostic phenomenological black holes that bypass the aforesaid issues. These so-called regular black holes are extensively studied in the literature using parameterized modifications over the black hole solutions of general relativity. However, since there exist several ways to model such black holes, it is important to study the consistency and viability of these solutions from both theoretical and observational perspectives. In this work, we consider a recently proposed model of regularized stable rotating black holes having two extra parameters in addition to the mass and spin of a Kerr solution. We start by computing their quasi-normal modes under scalar perturbation and investigate the impact of those additional parameters on black hole stability. In the second part, we study the shadow structures of these regularized black holes and obtain stringent bounds on the parameter space requiring consistency with Event Horizon Telescope observations of $M87^*$ and $Sgr\, A^*$ shadows. |
1810.01047 | Michele Oliosi | Katsuki Aoki, Antonio De Felice, Chunshan Lin, Shinji Mukohyama,
Michele Oliosi | Phenomenology in type-I minimally modified gravity | 14 pages, 1 figure, updated to match the version to appear in JCAP | null | 10.1088/1475-7516/2019/01/017 | WU-AP/1806/18, YITP-18-108, IPMU18-0158 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study cosmology in a class of minimally modified gravity (MMG) with two
local gravitational degrees of freedom. We classify modified gravity theories
into type-I and type-II: theories of type-I have an Einstein frame and can be
recast by change of variables as general relativity (GR) with a non-minimal
matter coupling, while theories of type-II have no Einstein frame. Considering
a canonical transformation of the lapse, the 3-dimensional induced metric and
their conjugate momenta we generate type-I MMG. We then show that
phenomenological deviations from GR, such as the speed of gravitational waves
$c_T$ and the effective gravitational constant for scalar perturbations $G_{\rm
eff}$, are characterized by two functions of an auxiliary variable. We study
the phenomenology of several models all having $c_T=1$. We obtain a scenario
with $c_T=1$ in which the effective equation-of-state parameter of dark energy
is different from $-1$ even though the cosmic acceleration is caused by a bare
cosmological constant, and we find that it is possible to reconstruct the
theory on choosing a selected time-evolution for the effective dark energy
component.
| [
{
"created": "Tue, 2 Oct 2018 03:07:23 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Oct 2018 12:15:34 GMT",
"version": "v2"
},
{
"created": "Fri, 4 Jan 2019 14:00:35 GMT",
"version": "v3"
}
] | 2019-01-16 | [
[
"Aoki",
"Katsuki",
""
],
[
"De Felice",
"Antonio",
""
],
[
"Lin",
"Chunshan",
""
],
[
"Mukohyama",
"Shinji",
""
],
[
"Oliosi",
"Michele",
""
]
] | We study cosmology in a class of minimally modified gravity (MMG) with two local gravitational degrees of freedom. We classify modified gravity theories into type-I and type-II: theories of type-I have an Einstein frame and can be recast by change of variables as general relativity (GR) with a non-minimal matter coupling, while theories of type-II have no Einstein frame. Considering a canonical transformation of the lapse, the 3-dimensional induced metric and their conjugate momenta we generate type-I MMG. We then show that phenomenological deviations from GR, such as the speed of gravitational waves $c_T$ and the effective gravitational constant for scalar perturbations $G_{\rm eff}$, are characterized by two functions of an auxiliary variable. We study the phenomenology of several models all having $c_T=1$. We obtain a scenario with $c_T=1$ in which the effective equation-of-state parameter of dark energy is different from $-1$ even though the cosmic acceleration is caused by a bare cosmological constant, and we find that it is possible to reconstruct the theory on choosing a selected time-evolution for the effective dark energy component. |
1202.0839 | Michele Vallisneri | Pau Amaro-Seoane, Sofiane Aoudia, Stanislav Babak, Pierre Bin\'etruy,
Emanuele Berti, Alejandro Boh\'e, Chiara Caprini, Monica Colpi, Neil J.
Cornish, Karsten Danzmann, Jean-Fran\c{c}ois Dufaux, Jonathan Gair, Oliver
Jennrich, Philippe Jetzer, Antoine Klein, Ryan N. Lang, Alberto Lobo, Tyson
Littenberg, Sean T. McWilliams, Gijs Nelemans, Antoine Petiteau, Edward K.
Porter, Bernard F. Schutz, Alberto Sesana, Robin Stebbins, Tim Sumner,
Michele Vallisneri, Stefano Vitale, Marta Volonteri, and Henry Ward | Low-frequency gravitational-wave science with eLISA/NGO | 20 pages, 8 figures, proceedings of the 9th Amaldi Conference on
Gravitational Waves. Final journal version. For a longer exposition of the
eLISA science case, see http://arxiv.org/abs/1201.3621 | Pau Amaro-Seoane et al 2012 Class. Quantum Grav. 29 124016 | 10.1088/0264-9381/29/12/124016 | null | gr-qc astro-ph.CO astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the expected science performance of the New Gravitational-Wave
Observatory (NGO, a.k.a. eLISA), a mission under study by the European Space
Agency for launch in the early 2020s. eLISA will survey the low-frequency
gravitational-wave sky (from 0.1 mHz to 1 Hz), detecting and characterizing a
broad variety of systems and events throughout the Universe, including the
coalescences of massive black holes brought together by galaxy mergers; the
inspirals of stellar-mass black holes and compact stars into central galactic
black holes; several millions of ultracompact binaries, both detached and mass
transferring, in the Galaxy; and possibly unforeseen sources such as the relic
gravitational-wave radiation from the early Universe. eLISA's high
signal-to-noise measurements will provide new insight into the structure and
history of the Universe, and they will test general relativity in its
strong-field dynamical regime.
| [
{
"created": "Fri, 3 Feb 2012 22:46:24 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Sep 2012 20:19:16 GMT",
"version": "v2"
}
] | 2015-03-20 | [
[
"Amaro-Seoane",
"Pau",
""
],
[
"Aoudia",
"Sofiane",
""
],
[
"Babak",
"Stanislav",
""
],
[
"Binétruy",
"Pierre",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Bohé",
"Alejandro",
""
],
[
"Caprini",
"Chiara",
""
],... | We review the expected science performance of the New Gravitational-Wave Observatory (NGO, a.k.a. eLISA), a mission under study by the European Space Agency for launch in the early 2020s. eLISA will survey the low-frequency gravitational-wave sky (from 0.1 mHz to 1 Hz), detecting and characterizing a broad variety of systems and events throughout the Universe, including the coalescences of massive black holes brought together by galaxy mergers; the inspirals of stellar-mass black holes and compact stars into central galactic black holes; several millions of ultracompact binaries, both detached and mass transferring, in the Galaxy; and possibly unforeseen sources such as the relic gravitational-wave radiation from the early Universe. eLISA's high signal-to-noise measurements will provide new insight into the structure and history of the Universe, and they will test general relativity in its strong-field dynamical regime. |
gr-qc/9311021 | Thomas Thiemann | T. Thiemann | A completely solvable model with an infinite number of Dirac observables
for a real sector of complexified Ashtekar gravity | 31 pages (Latex), Preprint PITHA 93-33, August 93 | null | null | null | gr-qc | null | We introduce a reduced model for a real sector of complexified Ashtekar
gravity that does not correspond to a subset of Einstein's gravity but for
which the programme of canonical quantization can be carried out completely,
both, via the reduced phase space approach or along the lines of the algebraic
quantization programme.\\ This model stands in a certain correspondence to the
frequently treated cylindrically symmetric waves.\\ In contrast to other models
that have been looked at up to now in terms of the new variables the reduced
phase space is infinite dimensional while the scalar constraint is genuinely
bilinear in the momenta.\\ The infinite number of Dirac observables can be
expressed in compact and explicit form in terms of the original phase space
variables.\\ They turn out, as expected, to be non-local and form naturally a
set of countable cardinality.
| [
{
"created": "Thu, 11 Nov 1993 23:25:07 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Thiemann",
"T.",
""
]
] | We introduce a reduced model for a real sector of complexified Ashtekar gravity that does not correspond to a subset of Einstein's gravity but for which the programme of canonical quantization can be carried out completely, both, via the reduced phase space approach or along the lines of the algebraic quantization programme.\\ This model stands in a certain correspondence to the frequently treated cylindrically symmetric waves.\\ In contrast to other models that have been looked at up to now in terms of the new variables the reduced phase space is infinite dimensional while the scalar constraint is genuinely bilinear in the momenta.\\ The infinite number of Dirac observables can be expressed in compact and explicit form in terms of the original phase space variables.\\ They turn out, as expected, to be non-local and form naturally a set of countable cardinality. |
gr-qc/0211052 | Antonio F. Ranada | Antonio F. Ranada | The Pioneer riddle, the quantum vacuum and the acceleration of light | 11 pages, no figures | Europhys.Lett.63:653-659,2003 | 10.1209/epl/i2003-00587-x | null | gr-qc astro-ph hep-th | null | It is shown that the same phenomenological Newtonian model recently proposed
by the author to explain the cosmological evolution of the fine structure
constant suggests furthermore an explanation of the unmodelled acceleration
$a_P\simeq 8.5\times 10^{-10}m/s^2$ of the Pioneer 10/11 spaceships reported by
Anderson {\em et al} in 1998. In the view presented here, it is argued that the
permittivity and permeability of empty space are decreasing adiabatically, and
the light is accelerating therefore, as a consequence of the progressive
attenuation of the quantum vacuum due to the combined effect of its
gravitational interaction with all the expanding universe and the fourth
Heisenberg relation. It is suggested that the spaceships do not have any extra
acceleration (but follow the unchanged Newton laws), the observed effect being
due to an adiabatic acceleration of the light equal to $a_P$, which has the
same observational radio signature as the anomalous acceleration of the
Pioneers.
| [
{
"created": "Wed, 13 Nov 2002 16:23:40 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Nov 2002 13:25:13 GMT",
"version": "v2"
},
{
"created": "Wed, 25 Jun 2003 17:25:12 GMT",
"version": "v3"
}
] | 2010-12-17 | [
[
"Ranada",
"Antonio F.",
""
]
] | It is shown that the same phenomenological Newtonian model recently proposed by the author to explain the cosmological evolution of the fine structure constant suggests furthermore an explanation of the unmodelled acceleration $a_P\simeq 8.5\times 10^{-10}m/s^2$ of the Pioneer 10/11 spaceships reported by Anderson {\em et al} in 1998. In the view presented here, it is argued that the permittivity and permeability of empty space are decreasing adiabatically, and the light is accelerating therefore, as a consequence of the progressive attenuation of the quantum vacuum due to the combined effect of its gravitational interaction with all the expanding universe and the fourth Heisenberg relation. It is suggested that the spaceships do not have any extra acceleration (but follow the unchanged Newton laws), the observed effect being due to an adiabatic acceleration of the light equal to $a_P$, which has the same observational radio signature as the anomalous acceleration of the Pioneers. |
2108.06874 | R. R. Cuzinatto | S. G. Vilhena, L. G. Medeiros, R. R. Cuzinatto | Gravitational waves in higher-order $R^{2}$ gravity | 37 pages plus appendices and references (single-column REVTeX file),
4 figures; v2: references added; v3: matches the published version; v4: typo
affecting the value of the E\"ot-Wash experiment constraint corrected
(results unchanged) | Physical Review D 104,084061 (2021) | 10.1103/PhysRevD.104.084061 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a comprehensive study of gravitational waves in the context of the
higher-order quadratic scalar curvature gravity, which encompasses the ordinary
Einstein-Hilbert term in the action plus an $R^{2}$ contribution and a term of
the type $R\square R$. The main focus is on gravitational waves emitted by
binary systems such as binary black holes and binary pulsars in the
approximation of circular orbits and nonrelativistic motion. The waveform of
higher-order gravitational waves from binary black holes is constructed and
compared with the waveform predicted by standard general relativity; we
conclude that the merger occurs earlier in our model than what would be
expected from GR. The decreasing rate of the orbital period in binary pulsars
is used to constrain the coupling parameters of our higher-order $R^{2}$
gravity; this is done with Hulse-Taylor binary pulsar data leading to
$\kappa_{0}^{-1}\lesssim1.1\times10^{16}\,\text{m}^{2}$, where
$\kappa_{0}^{-1}$ is the coupling constant for the $R^{2}$ contribution.
| [
{
"created": "Mon, 16 Aug 2021 03:17:16 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Aug 2021 03:40:30 GMT",
"version": "v2"
},
{
"created": "Thu, 4 Nov 2021 20:38:58 GMT",
"version": "v3"
},
{
"created": "Sat, 3 Dec 2022 02:26:01 GMT",
"version": "v4"
}
] | 2022-12-06 | [
[
"Vilhena",
"S. G.",
""
],
[
"Medeiros",
"L. G.",
""
],
[
"Cuzinatto",
"R. R.",
""
]
] | We perform a comprehensive study of gravitational waves in the context of the higher-order quadratic scalar curvature gravity, which encompasses the ordinary Einstein-Hilbert term in the action plus an $R^{2}$ contribution and a term of the type $R\square R$. The main focus is on gravitational waves emitted by binary systems such as binary black holes and binary pulsars in the approximation of circular orbits and nonrelativistic motion. The waveform of higher-order gravitational waves from binary black holes is constructed and compared with the waveform predicted by standard general relativity; we conclude that the merger occurs earlier in our model than what would be expected from GR. The decreasing rate of the orbital period in binary pulsars is used to constrain the coupling parameters of our higher-order $R^{2}$ gravity; this is done with Hulse-Taylor binary pulsar data leading to $\kappa_{0}^{-1}\lesssim1.1\times10^{16}\,\text{m}^{2}$, where $\kappa_{0}^{-1}$ is the coupling constant for the $R^{2}$ contribution. |
2306.15277 | Xiaolin Liu | Xiaolin Liu, Zhoujian Cao and Lijing Shao | Upgraded waveform model of eccentric binary black hole based on
effective-one-body-numerical-relativity for spin-aligned binary black holes | 15 pages, 10 figures | International Journal of Modern Physics D VOL. 32, NO. 04 (2023) | 10.1142/S0218271823500153 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Effective one body numerical relativity waveform models for spin aligned
binary black holes (SEOBNR) are based on the effective one body theoretical
framework and numerical relativity simulation results. SEOBNR models have
evolved through version 1 to version 4. We recently extended SEOBNRv1 model to
SEOBNRE (Effective One Body Numerical Relativity waveform models for Spin
aligned binary black holes along Eccentric orbit) model which is also valid for
spin aligned binary black hole coalescence along eccentric orbit. In this paper
we update our previous SEOBNRE model to make it consistent to SEOBNRv4 which is
the most widely used SEOBNR waveform model. This upgraded SEOBNRE model
improves accuracy compared to previous SEOBNRE model, especially for highly
spinning black holes. For spin aligned binary black holes with mass ratio
$1\leq q\lesssim10$, dimensionless spin $-0.9\lesssim\chi\lesssim0.995$ and
orbital eccentricity $0\leq e_0\lesssim0.6$ at reference frequency $Mf_0=0.002$
($M$ is the total mass of the binary black hole, $f_0\approx 40\frac{10{\rm
M}_\odot}{M}$Hz), the upgraded SEOBNRE model can always fit numerical
relativity waveform better than 98.2\%. For most cases the fitting factor can
even be better than 99\%.
| [
{
"created": "Tue, 27 Jun 2023 08:07:11 GMT",
"version": "v1"
}
] | 2023-06-28 | [
[
"Liu",
"Xiaolin",
""
],
[
"Cao",
"Zhoujian",
""
],
[
"Shao",
"Lijing",
""
]
] | Effective one body numerical relativity waveform models for spin aligned binary black holes (SEOBNR) are based on the effective one body theoretical framework and numerical relativity simulation results. SEOBNR models have evolved through version 1 to version 4. We recently extended SEOBNRv1 model to SEOBNRE (Effective One Body Numerical Relativity waveform models for Spin aligned binary black holes along Eccentric orbit) model which is also valid for spin aligned binary black hole coalescence along eccentric orbit. In this paper we update our previous SEOBNRE model to make it consistent to SEOBNRv4 which is the most widely used SEOBNR waveform model. This upgraded SEOBNRE model improves accuracy compared to previous SEOBNRE model, especially for highly spinning black holes. For spin aligned binary black holes with mass ratio $1\leq q\lesssim10$, dimensionless spin $-0.9\lesssim\chi\lesssim0.995$ and orbital eccentricity $0\leq e_0\lesssim0.6$ at reference frequency $Mf_0=0.002$ ($M$ is the total mass of the binary black hole, $f_0\approx 40\frac{10{\rm M}_\odot}{M}$Hz), the upgraded SEOBNRE model can always fit numerical relativity waveform better than 98.2\%. For most cases the fitting factor can even be better than 99\%. |
2311.17462 | Shahar Hod | Shahar Hod | Lower bound on the radii of light rings in traceless black-hole
spacetimes | 10 pages | Journal of High Energy Physics 12, 178 (2023) | null | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | Photonspheres, curved hypersurfaces on which massless particles can perform
closed geodesic motions around highly compact objects, are an integral part of
generic black-hole spacetimes. In the present compact paper we prove, using
analytical techniques, that the innermost light rings of spherically symmetric
hairy black-hole spacetimes whose external matter fields are characterized by a
traceless energy-momentum tensor cannot be located arbitrarily close to the
central black hole. In particular, we reveal the physically interesting fact
that the non-linearly coupled Einstein-matter field equations set the lower
bound $r_{\gamma}\geq {6\over5}r_{\text{H}}$ on the radii of traceless
black-hole photonspheres, where $r_{\text{H}}$ is the radius of the outermost
black-hole horizon.
| [
{
"created": "Wed, 29 Nov 2023 09:06:00 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Dec 2023 17:30:01 GMT",
"version": "v2"
}
] | 2024-01-01 | [
[
"Hod",
"Shahar",
""
]
] | Photonspheres, curved hypersurfaces on which massless particles can perform closed geodesic motions around highly compact objects, are an integral part of generic black-hole spacetimes. In the present compact paper we prove, using analytical techniques, that the innermost light rings of spherically symmetric hairy black-hole spacetimes whose external matter fields are characterized by a traceless energy-momentum tensor cannot be located arbitrarily close to the central black hole. In particular, we reveal the physically interesting fact that the non-linearly coupled Einstein-matter field equations set the lower bound $r_{\gamma}\geq {6\over5}r_{\text{H}}$ on the radii of traceless black-hole photonspheres, where $r_{\text{H}}$ is the radius of the outermost black-hole horizon. |
1803.08815 | Salvatore Capozziello | Salvatore Capozziello, Shin'ichi Nojiri, Sergei D. Odintsov | The role of energy conditions in $f(R)$ cosmology | 13 pages, to be published in Physics Letters B | null | 10.1016/j.physletb.2018.03.064 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Energy conditions can play an important role in defining the cosmological
evolution. Specifically acceleration/deceleration of cosmic fluid, as well as
the emergence of Big Rip singularities, can be related to the constraints
imposed by the energy conditions. Here we discuss this issue for $f(R)$ gravity
considering also conformal transformations. Cosmological solutions and
equations of state can be classified according to energy conditions. The
qualitative change of some energy conditions for transformations from the
Jordan frame to the Einstein frame is also observed.
| [
{
"created": "Fri, 23 Mar 2018 14:30:03 GMT",
"version": "v1"
}
] | 2018-05-09 | [
[
"Capozziello",
"Salvatore",
""
],
[
"Nojiri",
"Shin'ichi",
""
],
[
"Odintsov",
"Sergei D.",
""
]
] | Energy conditions can play an important role in defining the cosmological evolution. Specifically acceleration/deceleration of cosmic fluid, as well as the emergence of Big Rip singularities, can be related to the constraints imposed by the energy conditions. Here we discuss this issue for $f(R)$ gravity considering also conformal transformations. Cosmological solutions and equations of state can be classified according to energy conditions. The qualitative change of some energy conditions for transformations from the Jordan frame to the Einstein frame is also observed. |
1709.05081 | Fairoos C | C. Fairoos, Avirup Ghosh, Sudipta Sarkar | Massless charged particles: Cosmic censorship, and Third law of Black
Hole Mechanics | 12 pages, 9 figures, Minor changes in the reference section | Phys. Rev. D 96, 084013 (2017) | 10.1103/PhysRevD.96.084013 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The formulation of the laws of black hole mechanics assumes the stability of
black holes under perturbations in accordance with the "cosmic censorship
hypothesis"(CCH). CCH prohibits the formation of a naked singularity by a
physical process from a regular black hole solution with an event horizon.
Earlier studies show that naked singularities can indeed be formed leading to
the violation of CCH if a near-extremal black hole is injected with massive
charged particles and the back reaction effects are neglected. We investigate
the validity of CCH by considering the infall of charged massless particles as
well as a charged null shell. We also discuss the issue of third law of black
hole mechanics in the presence of null charged particles by considering various
possibilities.
| [
{
"created": "Fri, 15 Sep 2017 07:22:38 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Oct 2017 05:59:51 GMT",
"version": "v2"
}
] | 2017-10-13 | [
[
"Fairoos",
"C.",
""
],
[
"Ghosh",
"Avirup",
""
],
[
"Sarkar",
"Sudipta",
""
]
] | The formulation of the laws of black hole mechanics assumes the stability of black holes under perturbations in accordance with the "cosmic censorship hypothesis"(CCH). CCH prohibits the formation of a naked singularity by a physical process from a regular black hole solution with an event horizon. Earlier studies show that naked singularities can indeed be formed leading to the violation of CCH if a near-extremal black hole is injected with massive charged particles and the back reaction effects are neglected. We investigate the validity of CCH by considering the infall of charged massless particles as well as a charged null shell. We also discuss the issue of third law of black hole mechanics in the presence of null charged particles by considering various possibilities. |
2311.16936 | Saeed Ullah Khan | Saeed Ullah Khan, Javlon Rayimbaev and Zdenek Stuchl\'ik | Charged particle motion and acceleration around Kerr-MOG black hole | 15 Pages, 8 Figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | One of the most important issues in relativistic astrophysics is to explain
the origin mechanisms of (ultra)high energy charged particle components of
cosmic rays. Black holes (BHs) being huge reservoirs of (gravitational) energy
can be candidates for such particle sources. The main idea of this work is to
study the effects of scalar-tensor-vector gravity (STVG) on particle
acceleration by examining charged particle dynamics and their acceleration
through the magnetic Penrose process (MPP) near magnetized Kerr-MOG BHs. First,
we study the horizon structure of the BH. Also, we study the effective
potential to gain insight into the stability of circular orbits. Our results
show that the magnetic field can extend the region of stable circular orbits,
whereas the STVG parameter reduces the {instability} of the circular orbit. The
motion of charged particles around the magnetized BH reveals various feasible
regimes of the ionized Keplerian disk behavior. Thus, from the examination of
particle trajectories we observe that at fixed values of other parameters, the
Schwarzschild BH captures the test particle; in the case of Kerr BH, the test
particle escapes to infinity or is captured by the BH, while in Kerr-MOG BH,
the test particle is trapped in some region around BH and starts orbiting it.
On investigating the MPP, we found that with increasing magnetic field, the
behavior of orbits becomes more chaotic. As a result, the particle escapes to
infinity more quickly.
| [
{
"created": "Tue, 28 Nov 2023 16:37:29 GMT",
"version": "v1"
},
{
"created": "Tue, 16 Apr 2024 08:05:50 GMT",
"version": "v2"
}
] | 2024-04-17 | [
[
"Khan",
"Saeed Ullah",
""
],
[
"Rayimbaev",
"Javlon",
""
],
[
"Stuchlík",
"Zdenek",
""
]
] | One of the most important issues in relativistic astrophysics is to explain the origin mechanisms of (ultra)high energy charged particle components of cosmic rays. Black holes (BHs) being huge reservoirs of (gravitational) energy can be candidates for such particle sources. The main idea of this work is to study the effects of scalar-tensor-vector gravity (STVG) on particle acceleration by examining charged particle dynamics and their acceleration through the magnetic Penrose process (MPP) near magnetized Kerr-MOG BHs. First, we study the horizon structure of the BH. Also, we study the effective potential to gain insight into the stability of circular orbits. Our results show that the magnetic field can extend the region of stable circular orbits, whereas the STVG parameter reduces the {instability} of the circular orbit. The motion of charged particles around the magnetized BH reveals various feasible regimes of the ionized Keplerian disk behavior. Thus, from the examination of particle trajectories we observe that at fixed values of other parameters, the Schwarzschild BH captures the test particle; in the case of Kerr BH, the test particle escapes to infinity or is captured by the BH, while in Kerr-MOG BH, the test particle is trapped in some region around BH and starts orbiting it. On investigating the MPP, we found that with increasing magnetic field, the behavior of orbits becomes more chaotic. As a result, the particle escapes to infinity more quickly. |
2212.00591 | Salvador Mengual Sendra | Salvador Mengual, Joan Josep Ferrando and Juan Antonio S\'aez | Hydrodynamic approach to the Synge gas | 11 pages, 1 figure | Phys. Rev. D 106 (2022) 124032 | 10.1103/PhysRevD.106.124032 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The necessary and sufficient conditions for a perfect energy tensor to
describe the energy evolutions of a monoatomic relativistic Synge gas are
obtained. Then, a Rainich-like theory for the Einstein-Synge solutions can be
constructed. Equations of state approximating that of a Synge gas at low or at
high temperatures, or in the entire domain of applicability, are analyzed from
a hydrodynamic point of view.
| [
{
"created": "Thu, 1 Dec 2022 15:29:02 GMT",
"version": "v1"
}
] | 2022-12-23 | [
[
"Mengual",
"Salvador",
""
],
[
"Ferrando",
"Joan Josep",
""
],
[
"Sáez",
"Juan Antonio",
""
]
] | The necessary and sufficient conditions for a perfect energy tensor to describe the energy evolutions of a monoatomic relativistic Synge gas are obtained. Then, a Rainich-like theory for the Einstein-Synge solutions can be constructed. Equations of state approximating that of a Synge gas at low or at high temperatures, or in the entire domain of applicability, are analyzed from a hydrodynamic point of view. |
gr-qc/0404112 | Claus Gerhardt | Claus Gerhardt | The inverse mean curvature flow in Robertson-Walker spaces and its
application to cosmology | 9 pages, a pdf version can also be retrieved from
http://www.math.uni-heidelberg.de/studinfo/gerhardt/rw.pdf and bibtex data
from http://www.math.uni-heidelberg.de/studinfo/gerhardt/bibtexcgrw.html, v2:
typos corrected | Methods Appl.Anal. 13 (2006) 19-28 | null | null | gr-qc hep-th math.DG | null | We consider the inverse mean curvature flow in Robertson-Walker spacetimes
that satisfy the Einstein equations and have a big crunch singularity and prove
that under natural conditions the rescaled inverse mean curvature flow provides
a smooth transition from big crunch to big bang. We also construct an example
showing that in general the transition flow is only of class $C^3$.
| [
{
"created": "Tue, 27 Apr 2004 17:03:27 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Apr 2004 10:14:37 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Gerhardt",
"Claus",
""
]
] | We consider the inverse mean curvature flow in Robertson-Walker spacetimes that satisfy the Einstein equations and have a big crunch singularity and prove that under natural conditions the rescaled inverse mean curvature flow provides a smooth transition from big crunch to big bang. We also construct an example showing that in general the transition flow is only of class $C^3$. |
1610.09391 | Grant Meadors | Grant David Meadors, Evan Goetz, Keith Riles, Teviet Creighton,
Florent Robinet | Searches for continuous gravitational waves from Scorpius X-1 and XTE
J1751-305 in LIGO's sixth science run | 14 pages, 6 figures | Physical Review D 95, 042005 (2017) | 10.1103/PhysRevD.95.042005 | LIGO P1500039 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scorpius X-1 (Sco X-1) and X-ray transient (XTE) J1751-305 are Low-Mass X-ray
Binaries (LMXBs) that may emit continuous gravitational waves detectable in the
band of ground-based interferometric observatories. Neutron stars in LMXBs
could reach a torque-balance steady-state equilibrium in which angular momentum
addition from infalling matter from the binary companion is balanced by angular
momentum loss, conceivably due to gravitational-wave emission. Torque-balance
predicts a scale for detectable gravitational-wave strain based on observed
X-ray flux. This paper describes a search for Sco X-1 and XTE J1751-305 in LIGO
Science Run 6 data using the TwoSpect algorithm, based on searching for orbital
modulations in the frequency domain. While no detections are claimed, upper
limits on continuous gravitational-wave emission from Sco X-1 are obtained,
spanning gravitational-wave frequencies from 40 to 2040 Hz and projected
semi-major axes from 0.90 to 1.98 light-seconds. These upper limits are
injection validated, equal any previous set in initial LIGO data, and extend
over a broader parameter range. At optimal strain sensitivity, achieved at 165
Hz, the 95% confidence level random-polarization upper limit on dimensionless
strain $h_0$ is approximately $1.8 \times 10^{-24}$. Closest approach to the
torque-balance limit, within a factor of 27, is also at 165 Hz. These are the
first upper limits known to date on $r$-mode emission from this XTE source.
Upper limits are set in particular narrow frequency bands of interest for
J1751-305. The TwoSpect method will be used in upcoming searches of Advanced
LIGO and Virgo data.
| [
{
"created": "Fri, 28 Oct 2016 20:22:27 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Feb 2017 15:49:48 GMT",
"version": "v2"
}
] | 2017-02-24 | [
[
"Meadors",
"Grant David",
""
],
[
"Goetz",
"Evan",
""
],
[
"Riles",
"Keith",
""
],
[
"Creighton",
"Teviet",
""
],
[
"Robinet",
"Florent",
""
]
] | Scorpius X-1 (Sco X-1) and X-ray transient (XTE) J1751-305 are Low-Mass X-ray Binaries (LMXBs) that may emit continuous gravitational waves detectable in the band of ground-based interferometric observatories. Neutron stars in LMXBs could reach a torque-balance steady-state equilibrium in which angular momentum addition from infalling matter from the binary companion is balanced by angular momentum loss, conceivably due to gravitational-wave emission. Torque-balance predicts a scale for detectable gravitational-wave strain based on observed X-ray flux. This paper describes a search for Sco X-1 and XTE J1751-305 in LIGO Science Run 6 data using the TwoSpect algorithm, based on searching for orbital modulations in the frequency domain. While no detections are claimed, upper limits on continuous gravitational-wave emission from Sco X-1 are obtained, spanning gravitational-wave frequencies from 40 to 2040 Hz and projected semi-major axes from 0.90 to 1.98 light-seconds. These upper limits are injection validated, equal any previous set in initial LIGO data, and extend over a broader parameter range. At optimal strain sensitivity, achieved at 165 Hz, the 95% confidence level random-polarization upper limit on dimensionless strain $h_0$ is approximately $1.8 \times 10^{-24}$. Closest approach to the torque-balance limit, within a factor of 27, is also at 165 Hz. These are the first upper limits known to date on $r$-mode emission from this XTE source. Upper limits are set in particular narrow frequency bands of interest for J1751-305. The TwoSpect method will be used in upcoming searches of Advanced LIGO and Virgo data. |
1504.08209 | Carlos A. R. Herdeiro | Carlos A. R. Herdeiro, Eugen Radu | Asymptotically flat black holes with scalar hair: a review | 35 pages, 1 table, to appear in a special volume of the IJMPD,
dedicated to the VII Black Holes Workshop, Aveiro, Portugal, 18-19 December
2014; v2. Minor corrections | null | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the status of black hole solutions with non-trivial scalar fields
but no gauge fields, in four dimensional asymptotically flat space-times,
reviewing both classical results and recent developments. We start by providing
a simple illustration on the physical difference between black holes in
electro-vacuum and scalar-vacuum. Next, we review no-scalar-hair theorems. In
particular, we detail an influential theorem by Bekenstein and stress three key
assumptions: 1) the type of scalar field equation; 2) the spacetime symmetry
inheritance by the scalar field; 3) an energy condition. Then, we list regular
(on and outside the horizon), asymptotically flat BH solutions with scalar
hair, organizing them by the assumption which is violated in each case and
distinguishing primary from secondary hair. We provide a table summary of the
state of the art.
| [
{
"created": "Thu, 30 Apr 2015 13:10:22 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Dec 2018 23:14:31 GMT",
"version": "v2"
}
] | 2018-12-20 | [
[
"Herdeiro",
"Carlos A. R.",
""
],
[
"Radu",
"Eugen",
""
]
] | We consider the status of black hole solutions with non-trivial scalar fields but no gauge fields, in four dimensional asymptotically flat space-times, reviewing both classical results and recent developments. We start by providing a simple illustration on the physical difference between black holes in electro-vacuum and scalar-vacuum. Next, we review no-scalar-hair theorems. In particular, we detail an influential theorem by Bekenstein and stress three key assumptions: 1) the type of scalar field equation; 2) the spacetime symmetry inheritance by the scalar field; 3) an energy condition. Then, we list regular (on and outside the horizon), asymptotically flat BH solutions with scalar hair, organizing them by the assumption which is violated in each case and distinguishing primary from secondary hair. We provide a table summary of the state of the art. |
2008.13554 | Ryuichi Fujita | Ryuichi Fujita and Masaru Shibata | Extreme mass ratio inspirals on the equatorial plane in the adiabatic
order | 18 pages, 18 figures, published in Phys. Rev. D, supplementary data
files available at https://sites.google.com/view/bhpc1996/home | Phys. Rev. D 102, 064005 (2020) | 10.1103/PhysRevD.102.064005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute gravitational waves from inspiraling stellar-mass compact objects
on the equatorial plane of a massive spinning black hole (BH). Our inspiral
orbits are computed by taking into account the adiabatic change of orbital
parameters due to gravitational radiation in the lowest order in mass ratio. We
employ an interpolation method to compute the adiabatic change at arbitrary
points inside the region of orbital parameter space computed in advance. Using
the obtained inspiral orbits and associated gravitational waves, we compute
power spectra of gravitational waves and the signal-to-noise ratio (SNR) for
several values of the BH spin, the masses of the binary, and the initial
orbital eccentricity during a hypothetical three-yrs LISA observation before
final plunge. We find that (i) the SNR increases as the BH spin and the mass of
the compact object increase for the BH mass $M \agt 10^6M_\odot$, (ii) the SNR
has a maximum for $M \approx 10^6M_\odot$, and (iii) the SNR increases as the
initial eccentricity increases for $M=10^6M_\odot$. We also show that
incorporating the contribution from the higher multipole modes of gravitational
waves is crucial for enhancing the detection rate.
| [
{
"created": "Mon, 31 Aug 2020 12:39:01 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Sep 2020 11:44:46 GMT",
"version": "v2"
}
] | 2020-09-10 | [
[
"Fujita",
"Ryuichi",
""
],
[
"Shibata",
"Masaru",
""
]
] | We compute gravitational waves from inspiraling stellar-mass compact objects on the equatorial plane of a massive spinning black hole (BH). Our inspiral orbits are computed by taking into account the adiabatic change of orbital parameters due to gravitational radiation in the lowest order in mass ratio. We employ an interpolation method to compute the adiabatic change at arbitrary points inside the region of orbital parameter space computed in advance. Using the obtained inspiral orbits and associated gravitational waves, we compute power spectra of gravitational waves and the signal-to-noise ratio (SNR) for several values of the BH spin, the masses of the binary, and the initial orbital eccentricity during a hypothetical three-yrs LISA observation before final plunge. We find that (i) the SNR increases as the BH spin and the mass of the compact object increase for the BH mass $M \agt 10^6M_\odot$, (ii) the SNR has a maximum for $M \approx 10^6M_\odot$, and (iii) the SNR increases as the initial eccentricity increases for $M=10^6M_\odot$. We also show that incorporating the contribution from the higher multipole modes of gravitational waves is crucial for enhancing the detection rate. |
1703.06331 | Nishanth Abu Gudapati | Nishanth Gudapati | On 3+1 Lorentzian Einstein Manifolds with One Rotational Isometry | null | Gen Relativ Gravit (2018) 50: 93 | 10.1007/s10714-018-2404-2 | null | gr-qc math.AP math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider 3+1 rotationally symmetric Lorentzian Einstein spacetime
manifolds with $\Lambda >0$ and reduce the equations to 2+1 Einstein equations
coupled to `shifted' wave maps. Subsequently, we prove various (explicit)
positive mass-energy theorems. No smallness is assumed.
| [
{
"created": "Sat, 18 Mar 2017 18:24:43 GMT",
"version": "v1"
}
] | 2018-07-23 | [
[
"Gudapati",
"Nishanth",
""
]
] | We consider 3+1 rotationally symmetric Lorentzian Einstein spacetime manifolds with $\Lambda >0$ and reduce the equations to 2+1 Einstein equations coupled to `shifted' wave maps. Subsequently, we prove various (explicit) positive mass-energy theorems. No smallness is assumed. |
gr-qc/0511159 | Vitaly Vanchurin | Vitaly Vanchurin, Ken D. Olum and Alexander Vilenkin | Scaling of cosmic string loops | Added discussion of gravitational wave bounds; other minor changes | Phys.Rev. D74 (2006) 063527 | 10.1103/PhysRevD.74.063527 | null | gr-qc astro-ph hep-ph hep-th | null | We study the spectrum of loops as a part of a complete network of cosmic
strings in flat spacetime. After a long transient regime, characterized by
production of small loops at the scale of the initial conditions, it appears
that a true scaling regime takes over. In this final regime the characteristic
length of loops scales as $0.1 t$, in contrast to earlier simulations which
found tiny loops. We expect the expanding-universe behavior to be qualitatively
similar. The large loop sizes have important cosmological implications. In
particular, the nucleosynthesis bound becomes $G\mu \lesssim 10^{-7}$, much
tighter than before.
| [
{
"created": "Tue, 29 Nov 2005 23:39:00 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Dec 2005 21:39:18 GMT",
"version": "v2"
},
{
"created": "Mon, 24 Apr 2006 19:07:35 GMT",
"version": "v3"
},
{
"created": "Tue, 20 Jun 2006 16:19:09 GMT",
"version": "v4"
}
] | 2009-11-11 | [
[
"Vanchurin",
"Vitaly",
""
],
[
"Olum",
"Ken D.",
""
],
[
"Vilenkin",
"Alexander",
""
]
] | We study the spectrum of loops as a part of a complete network of cosmic strings in flat spacetime. After a long transient regime, characterized by production of small loops at the scale of the initial conditions, it appears that a true scaling regime takes over. In this final regime the characteristic length of loops scales as $0.1 t$, in contrast to earlier simulations which found tiny loops. We expect the expanding-universe behavior to be qualitatively similar. The large loop sizes have important cosmological implications. In particular, the nucleosynthesis bound becomes $G\mu \lesssim 10^{-7}$, much tighter than before. |
gr-qc/0403035 | Jose A. Gonzalez | Miguel Alcubierre, Jose A. Gonzalez and Marcelo Salgado | Dynamical evolution of unstable self-gravitating scalar solitons | 11 pages, 16 figures, submitted to Phys. Rev. D | Phys.Rev. D70 (2004) 064016 | 10.1103/PhysRevD.70.064016 | null | gr-qc | null | Recently, static and spherically symmetric configurations of globally regular
self-gravitating scalar solitons were found. These configurations are unstable
with respect to radial linear perturbations. In this paper we study the
dynamical evolution of such configurations and show that, depending on the sign
of the initial perturbation, the solitons either collapse to a Schwarzschild
black hole or else ``explode'' into an outward moving domain wall.
| [
{
"created": "Mon, 8 Mar 2004 23:30:13 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Alcubierre",
"Miguel",
""
],
[
"Gonzalez",
"Jose A.",
""
],
[
"Salgado",
"Marcelo",
""
]
] | Recently, static and spherically symmetric configurations of globally regular self-gravitating scalar solitons were found. These configurations are unstable with respect to radial linear perturbations. In this paper we study the dynamical evolution of such configurations and show that, depending on the sign of the initial perturbation, the solitons either collapse to a Schwarzschild black hole or else ``explode'' into an outward moving domain wall. |
gr-qc/0309095 | Stephane Fay | Stephane Fay | Isotropisation of the minimally coupled scalar-tensor theory with a
massive scalar field and a perfect fluid in the Bianchi type I model | 13 pages | Class. Quant. Grav., Vol 19, 2, 2002 | null | null | gr-qc | null | We look for necessary conditions such that minimally coupled scalar-tensor
theory with a massive scalar field and a perfect fluid in the Bianchi type I
model isotropises. Then we derive the dynamical asymptotical properties of the
Universe.
| [
{
"created": "Fri, 19 Sep 2003 12:23:04 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Fay",
"Stephane",
""
]
] | We look for necessary conditions such that minimally coupled scalar-tensor theory with a massive scalar field and a perfect fluid in the Bianchi type I model isotropises. Then we derive the dynamical asymptotical properties of the Universe. |
gr-qc/9910041 | S. Mignemi | S. Mignemi | Primary scalar hair in dilatonic theories with modulus fields | 15 pages, plain TeX | Phys.Rev. D62 (2000) 024014 | 10.1103/PhysRevD.62.024014 | INFNCA-TH9908 | gr-qc | null | We study the general spherical symmetric solutions of dilaton-modulus gravity
non-minimally coupled to a Maxwell field, using methods from the theory of
dynamical systems. We show that the solutions can be classified by the mass,
the electric charge, and a third parameter which we argue can be related to a
scalar charge. The global properties of the solutions are discussed.
| [
{
"created": "Tue, 12 Oct 1999 15:03:12 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Mignemi",
"S.",
""
]
] | We study the general spherical symmetric solutions of dilaton-modulus gravity non-minimally coupled to a Maxwell field, using methods from the theory of dynamical systems. We show that the solutions can be classified by the mass, the electric charge, and a third parameter which we argue can be related to a scalar charge. The global properties of the solutions are discussed. |
0807.0214 | Tomas Ledvinka | Tomas Ledvinka, Gerhard Schaefer and Jiri Bicak | Relativistic Closed-Form Hamiltonian for Many-Body Gravitating Systems
in the Post-Minkowskian Approximation | 4 pages | Phys.Rev.Lett.100:251101,2008 | 10.1103/PhysRevLett.100.251101 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hamiltonian for a system of relativistic bodies interacting by their
gravitational field is found in the post-Minkowskian approximation, including
all terms linear in the gravitational constant. It is given in a surprisingly
simple closed form as a function of canonical variables describing the bodies
only. The field is eliminated by solving inhomogeneous wave equations, applying
transverse-traceless projections, and using the Routh functional. By including
all special relativistic effects our Hamiltonian extends the results described
in classical textbooks of theoretical physics. As an application, the
scattering of relativistic objects is considered.
| [
{
"created": "Tue, 1 Jul 2008 18:36:08 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ledvinka",
"Tomas",
""
],
[
"Schaefer",
"Gerhard",
""
],
[
"Bicak",
"Jiri",
""
]
] | The Hamiltonian for a system of relativistic bodies interacting by their gravitational field is found in the post-Minkowskian approximation, including all terms linear in the gravitational constant. It is given in a surprisingly simple closed form as a function of canonical variables describing the bodies only. The field is eliminated by solving inhomogeneous wave equations, applying transverse-traceless projections, and using the Routh functional. By including all special relativistic effects our Hamiltonian extends the results described in classical textbooks of theoretical physics. As an application, the scattering of relativistic objects is considered. |
0908.2771 | Mark Durkee | Mark Durkee and Harvey S. Reall | A higher-dimensional generalization of the geodesic part of the
Goldberg-Sachs theorem | 16 pages | Class. Quantum Grav. 26 (2009) 245005 | 10.1088/0264-9381/26/24/245005 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In more than four spacetime dimensions, a multiple Weyl-aligned null
direction (WAND) need not be geodesic. It is proved that any higher-dimensional
Einstein spacetime admitting a non-geodesic multiple WAND also admits a
geodesic multiple WAND. All five-dimensional Einstein spacetimes admitting a
non-geodesic multiple WAND are determined.
| [
{
"created": "Wed, 19 Aug 2009 15:27:04 GMT",
"version": "v1"
}
] | 2010-01-04 | [
[
"Durkee",
"Mark",
""
],
[
"Reall",
"Harvey S.",
""
]
] | In more than four spacetime dimensions, a multiple Weyl-aligned null direction (WAND) need not be geodesic. It is proved that any higher-dimensional Einstein spacetime admitting a non-geodesic multiple WAND also admits a geodesic multiple WAND. All five-dimensional Einstein spacetimes admitting a non-geodesic multiple WAND are determined. |
1402.2514 | Antonin Coutant | Antonin Coutant and Renaud Parentani | Hawking radiation with dispersion: The broadened horizon paradigm | 6 pages, 4 figures, published version | Phys. Rev. D 90, 121501 (2014) | 10.1103/PhysRevD.90.121501 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | To identify what replaces the key notion of black hole horizon when working
with theories which break Lorentz invariance at high energy, we study the modes
responsible for the Hawking effect in the presence of high frequency
dispersion. We show that they are regularized across the horizon over a short
length which only depends on the scale of dispersion and the surface gravity.
Moreover, outside this width, short and long wavelength modes no longer mix.
These results can be used to show that the spectrum is hardly modified by
dispersion as long as the background geometry does not vary significantly over
this length. For relevant frequencies, the regularization differs from the
usual WKB resolution of wave singularity near a turning point.
| [
{
"created": "Tue, 11 Feb 2014 15:03:50 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Nov 2014 08:55:37 GMT",
"version": "v2"
}
] | 2014-12-10 | [
[
"Coutant",
"Antonin",
""
],
[
"Parentani",
"Renaud",
""
]
] | To identify what replaces the key notion of black hole horizon when working with theories which break Lorentz invariance at high energy, we study the modes responsible for the Hawking effect in the presence of high frequency dispersion. We show that they are regularized across the horizon over a short length which only depends on the scale of dispersion and the surface gravity. Moreover, outside this width, short and long wavelength modes no longer mix. These results can be used to show that the spectrum is hardly modified by dispersion as long as the background geometry does not vary significantly over this length. For relevant frequencies, the regularization differs from the usual WKB resolution of wave singularity near a turning point. |
gr-qc/0503073 | Fabrizio Canfora | F. Canfora and G. Vilasi | Does the Holographic Principle determine the Gravitational Interaction? | 12 pages, no figures, added references | Phys.Lett. B614 (2005) 131-139 | 10.1016/j.physletb.2005.04.013 | null | gr-qc astro-ph hep-th | null | It is likely that the holographic principle will be a consequence of the
would be theory of quantum gravity. Thus, it is interesting to try to go in the
opposite direction: can the holographic principle fix the gravitational
interaction? It is shown that the classical gravitational interaction is well
inside the set of potentials allowed by the holographic principle. Computations
clarify which role such a principle could have in lowering the value of the
cosmological constant computed in QFT to the observed one.
| [
{
"created": "Thu, 17 Mar 2005 08:38:02 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Mar 2005 08:24:20 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Canfora",
"F.",
""
],
[
"Vilasi",
"G.",
""
]
] | It is likely that the holographic principle will be a consequence of the would be theory of quantum gravity. Thus, it is interesting to try to go in the opposite direction: can the holographic principle fix the gravitational interaction? It is shown that the classical gravitational interaction is well inside the set of potentials allowed by the holographic principle. Computations clarify which role such a principle could have in lowering the value of the cosmological constant computed in QFT to the observed one. |
1801.08402 | A. Emrah Y\"ukselci | A. Sava\c{s} Arapo\u{g}lu, Ezgi Canay, A. Emrah Y\"ukselci | Dynamical System Analysis of a Five-Dimensional Cosmological Model | 14 pages, 2 figures; matches the published version | Astrophys Space Sci (2018) 363: 215 | 10.1007/s10509-018-3436-5 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A five-dimensional cosmological model including a single perfect fluid is
studied in the framework of dynamical system analysis. All the critical points
of the system with their stability properties are listed and some
representative phase diagrams are explicitly shown. It is found that the
stabilization of the extra dimension is possible and the observed flatness of
the three-dimensional space is provided for certain ranges of the equation of
state parameter of the fluid during the evolution of the universe. The model
suggested here can be considered as a simplified model for examining the
possible effects of the extra dimensions in the early universe.
| [
{
"created": "Thu, 25 Jan 2018 14:01:18 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Feb 2020 11:55:54 GMT",
"version": "v2"
}
] | 2020-02-17 | [
[
"Arapoğlu",
"A. Savaş",
""
],
[
"Canay",
"Ezgi",
""
],
[
"Yükselci",
"A. Emrah",
""
]
] | A five-dimensional cosmological model including a single perfect fluid is studied in the framework of dynamical system analysis. All the critical points of the system with their stability properties are listed and some representative phase diagrams are explicitly shown. It is found that the stabilization of the extra dimension is possible and the observed flatness of the three-dimensional space is provided for certain ranges of the equation of state parameter of the fluid during the evolution of the universe. The model suggested here can be considered as a simplified model for examining the possible effects of the extra dimensions in the early universe. |
2306.17185 | Yurii Ignat'ev | Yu.G. Ignat'ev | Evolution of spherical perturbations in the cosmological environment of
degenerate scalarly charged fermions with the Higgs scalar interaction | 24 pages, 9 figures, 31 references | Theoretical and Mathematic Physics 215 (2023) 862 | 10.1134/S0040577923060089 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A mathematical model is constructed for the evolution of spherical
perturbations in a cosmological one-component statistical system of completely
degenerate scalarly charged fermions with a scalar Higgs interaction. A
complete system of self-consistent equations for small perturbations describing
the evolution of spherical perturbations is constructed. Singular parts in
perturbation modes corresponding to point mass and scalar charge are singled
out. Systems of ordinary differential equations are obtained that describe the
evolution of the mass and charge of a singular source, and systems of partial
differential equations that describe the evolution of non-singular parts of
perturbations. In this case, the coefficients of partial differential equations
are described by solutions of evolutionary equations for mass and charge. The
problem of spatially localized perturbations for solutions polynomial in the
radial coordinate is reduced to a recurrent system of ordinary linear
differential equations for the coefficients of these polynomials. The
properties of solutions in the case of cubic polynomials are studied, in
particular, it is shown that the radii of localization of gravitational and
scalar perturbations coincide and evolve in proportion to the scale factor.
Numerical modeling of the evolution of perturbations was carried out, in
particular, it confirmed the exponential growth of the central mass of the
perturbation, and also revealed the oscillatory nature of the evolution of the
scalar charge. Keywords: scalar charged plasma, cosmological model, scalar
Higgs field, gravitational instability, spherical perturbations.
| [
{
"created": "Thu, 22 Jun 2023 21:32:54 GMT",
"version": "v1"
}
] | 2023-07-03 | [
[
"Ignat'ev",
"Yu. G.",
""
]
] | A mathematical model is constructed for the evolution of spherical perturbations in a cosmological one-component statistical system of completely degenerate scalarly charged fermions with a scalar Higgs interaction. A complete system of self-consistent equations for small perturbations describing the evolution of spherical perturbations is constructed. Singular parts in perturbation modes corresponding to point mass and scalar charge are singled out. Systems of ordinary differential equations are obtained that describe the evolution of the mass and charge of a singular source, and systems of partial differential equations that describe the evolution of non-singular parts of perturbations. In this case, the coefficients of partial differential equations are described by solutions of evolutionary equations for mass and charge. The problem of spatially localized perturbations for solutions polynomial in the radial coordinate is reduced to a recurrent system of ordinary linear differential equations for the coefficients of these polynomials. The properties of solutions in the case of cubic polynomials are studied, in particular, it is shown that the radii of localization of gravitational and scalar perturbations coincide and evolve in proportion to the scale factor. Numerical modeling of the evolution of perturbations was carried out, in particular, it confirmed the exponential growth of the central mass of the perturbation, and also revealed the oscillatory nature of the evolution of the scalar charge. Keywords: scalar charged plasma, cosmological model, scalar Higgs field, gravitational instability, spherical perturbations. |
gr-qc/9601011 | Jose Antonio Zapata | Henri Waelbroeck (Instituto de Ciencias Nucleares, UNAM, Mexico) and
Jose A. Zapata (Center for Gravitational Physics and Geometry, PennState,
USA) | $2+1$ Covariant Lattice Theory and t'Hooft's Formulation | 10 pages of text. One figure available from J.A. Zapata upon request | Class.Quant.Grav. 13 (1996) 1761-1768 | 10.1088/0264-9381/13/7/009 | CGPG-96/1-2 | gr-qc | null | We show that 't Hooft's representation of (2+1)-dimensional gravity in terms
of flat polygonal tiles is closely related to a gauge-fixed version of the
covariant Hamiltonian lattice theory. 't Hooft's gauge is remarkable in that it
leads to a Hamiltonian which is a linear sum of vertex Hamiltonians, each of
which is defined modulo $2 \pi$. A cyclic Hamiltonian implies that ``time'' is
quantized. However, it turns out that this Hamiltonian is {\it constrained}. If
one chooses an internal time and solves this constraint for the ``physical
Hamiltonian'', the result is not a cyclic function. Even if one quantizes {\it
a la Dirac}, the ``internal time'' observable does not acquire a discrete
spectrum. We also show that in Euclidean 3-d lattice gravity, ``space'' can be
either discrete or continuous depending on the choice of quantization. Finally,
we propose a generalization of 't Hooft's gauge for Hamiltonian lattice
formulations of topological gravity dimension 4.
| [
{
"created": "Tue, 9 Jan 1996 19:17:19 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Waelbroeck",
"Henri",
"",
"Instituto de Ciencias Nucleares, UNAM, Mexico"
],
[
"Zapata",
"Jose A.",
"",
"Center for Gravitational Physics and Geometry, PennState,\n USA"
]
] | We show that 't Hooft's representation of (2+1)-dimensional gravity in terms of flat polygonal tiles is closely related to a gauge-fixed version of the covariant Hamiltonian lattice theory. 't Hooft's gauge is remarkable in that it leads to a Hamiltonian which is a linear sum of vertex Hamiltonians, each of which is defined modulo $2 \pi$. A cyclic Hamiltonian implies that ``time'' is quantized. However, it turns out that this Hamiltonian is {\it constrained}. If one chooses an internal time and solves this constraint for the ``physical Hamiltonian'', the result is not a cyclic function. Even if one quantizes {\it a la Dirac}, the ``internal time'' observable does not acquire a discrete spectrum. We also show that in Euclidean 3-d lattice gravity, ``space'' can be either discrete or continuous depending on the choice of quantization. Finally, we propose a generalization of 't Hooft's gauge for Hamiltonian lattice formulations of topological gravity dimension 4. |
1803.03873 | Felipe Asenjo | Sergio A. Hojman and Felipe A. Asenjo | Non--geodesic circular motion of massive spinning test bodies | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent interest on studying possible violations of the Equivalence Principle
has led to the development of space satellite missions testing it for bodies
moving on circular orbits around Earth. This experiment establishes that the
validity of the Equivalence Principle is independent of the composition of
bodies. However, the internal degrees of freedom of the bodies (such as spin)
were not taken into account. In this work, it is shown exactly that the
circular orbit motion of test bodies does present a departure from geodesic
motion when spin effects are not negligible. Using a Lagrangian theory for
spinning massive bodies, an exact solution for their circular motion is found
showing that the non--geodesic behavior manifests through different tangential
velocities of the test bodies, depending on the orientation of its spin with
respect to the total angular momentum of the satellite. Besides, for circular
orbits, spinning test bodies present no tangential acceleration. We estimate
the difference of the two possible tangential velocities for the case of
circular motion of spinning test bodies orbiting Earth.
| [
{
"created": "Sun, 11 Mar 2018 01:11:33 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Oct 2018 14:33:09 GMT",
"version": "v2"
}
] | 2018-10-04 | [
[
"Hojman",
"Sergio A.",
""
],
[
"Asenjo",
"Felipe A.",
""
]
] | Recent interest on studying possible violations of the Equivalence Principle has led to the development of space satellite missions testing it for bodies moving on circular orbits around Earth. This experiment establishes that the validity of the Equivalence Principle is independent of the composition of bodies. However, the internal degrees of freedom of the bodies (such as spin) were not taken into account. In this work, it is shown exactly that the circular orbit motion of test bodies does present a departure from geodesic motion when spin effects are not negligible. Using a Lagrangian theory for spinning massive bodies, an exact solution for their circular motion is found showing that the non--geodesic behavior manifests through different tangential velocities of the test bodies, depending on the orientation of its spin with respect to the total angular momentum of the satellite. Besides, for circular orbits, spinning test bodies present no tangential acceleration. We estimate the difference of the two possible tangential velocities for the case of circular motion of spinning test bodies orbiting Earth. |
1011.4948 | Veronika E. Hubeny | Veronika E. Hubeny | The Fluid/Gravity Correspondence: a new perspective on the Membrane
Paradigm | 20 pages, 4 figures, Contribution (plenary lecture) to the
Proceedings of the 19th International Conference on General Relativity and
Gravitation, Mexico City, July 5-9, 2010 v2: reference added + minor changes,
as in the published CQG version | Class.Quant.Grav.28:114007,2011 | 10.1088/0264-9381/28/11/114007 | null | gr-qc hep-th physics.flu-dyn | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This talk gives an overview of the recently-formulated Fluid/Gravity
correspondence, which was developed in the context of gauge/gravity duality.
Mathematically, it posits that Einstein's equations (with negative cosmological
constant) in d+1 dimensions capture the (generalized) Navier-Stokes equations
in d dimensions. Given an arbitrary fluid dynamical solution, we can
systematically construct a corresponding asymptotically AdS black hole
spacetime with a regular horizon whose properties mimic that of the fluid flow.
Apart from an overview of this construction, we describe some of its
applications. The presentation is intended for a broad audience of relativists,
and does not assume prior knowledge of string theory or gauge/gravity duality.
| [
{
"created": "Mon, 22 Nov 2010 21:01:02 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Feb 2011 10:22:54 GMT",
"version": "v2"
}
] | 2011-07-19 | [
[
"Hubeny",
"Veronika E.",
""
]
] | This talk gives an overview of the recently-formulated Fluid/Gravity correspondence, which was developed in the context of gauge/gravity duality. Mathematically, it posits that Einstein's equations (with negative cosmological constant) in d+1 dimensions capture the (generalized) Navier-Stokes equations in d dimensions. Given an arbitrary fluid dynamical solution, we can systematically construct a corresponding asymptotically AdS black hole spacetime with a regular horizon whose properties mimic that of the fluid flow. Apart from an overview of this construction, we describe some of its applications. The presentation is intended for a broad audience of relativists, and does not assume prior knowledge of string theory or gauge/gravity duality. |
gr-qc/0303004 | W. A. van Leeuwen | P.G. Miedema, W.A. van Leeuwen | Density Perturbations in the Early Universe | Conclusions unchanged. Rewritten to make all details clear.
References added. Criticism to former gauge-invariant theories removed. Title
changed. 49 pages, 2 tables, no figures | null | null | null | gr-qc astro-ph | null | We propose a way to construct manifestly gauge independent quantities out of
the gauge dependent quantities occurring in the linearized Einstein equations.
Thereupon, we show that these gauge-invariant combinations can be identified
with measurable perturbations to the particle and energy densities.
In the radiation-dominated era we find, for small-scale perturbations,
acoustic waves with an increasing amplitude, while standard treatments predict
acoustic waves with a decaying amplitude. For large-scale perturbations we find
exactly the same growth rates as in the standard literature.
When considering the non-relativistic limit of the linearized Einstein
equations we find the Poisson equation.
It is shown, using the linearized Einstein equations, that the usual
Newtonian treatment of density perturbations does not describe the evolution of
density perturbations.
| [
{
"created": "Sat, 1 Mar 2003 20:37:25 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Apr 2004 13:09:31 GMT",
"version": "v2"
},
{
"created": "Mon, 1 Nov 2004 20:54:56 GMT",
"version": "v3"
},
{
"created": "Sun, 6 Nov 2005 14:13:01 GMT",
"version": "v4"
}
] | 2007-05-23 | [
[
"Miedema",
"P. G.",
""
],
[
"van Leeuwen",
"W. A.",
""
]
] | We propose a way to construct manifestly gauge independent quantities out of the gauge dependent quantities occurring in the linearized Einstein equations. Thereupon, we show that these gauge-invariant combinations can be identified with measurable perturbations to the particle and energy densities. In the radiation-dominated era we find, for small-scale perturbations, acoustic waves with an increasing amplitude, while standard treatments predict acoustic waves with a decaying amplitude. For large-scale perturbations we find exactly the same growth rates as in the standard literature. When considering the non-relativistic limit of the linearized Einstein equations we find the Poisson equation. It is shown, using the linearized Einstein equations, that the usual Newtonian treatment of density perturbations does not describe the evolution of density perturbations. |
0707.2153 | Thomas Buchert | Thomas Buchert | Dark Energy from structure: a status report | Invited Review for a special Gen. Rel. Grav. issue on Dark Energy, 59
pages, 2 figures; matches published version | Gen.Rel.Grav.40:467-527,2008 | 10.1007/s10714-007-0554-8 | null | gr-qc astro-ph hep-th | null | The effective evolution of an inhomogeneous universe model in any theory of
gravitation may be described in terms of spatially averaged variables. In
Einstein's theory, restricting attention to scalar variables, this evolution
can be modeled by solutions of a set of Friedmann equations for an effective
volume scale factor, with matter and backreaction source terms. The latter can
be represented by an effective scalar field (`morphon field') modeling Dark
Energy.
The present work provides an overview over the Dark Energy debate in
connection with the impact of inhomogeneities, and formulates strategies for a
comprehensive quantitative evaluation of backreaction effects both in
theoretical and observational cosmology. We recall the basic steps of a
description of backreaction effects in relativistic cosmology that lead to
refurnishing the standard cosmological equations, but also lay down a number of
challenges and unresolved issues in connection with their observational
interpretation.
The present status of this subject is intermediate: we have a good
qualitative understanding of backreaction effects pointing to a global
instability of the standard model of cosmology; exact solutions and
perturbative results modeling this instability lie in the right sector to
explain Dark Energy from inhomogeneities. It is fair to say that, even if
backreaction effects turn out to be less important than anticipated by some
researchers, the concordance high-precision cosmology, the architecture of
current N-body simulations, as well as standard perturbative approaches may all
fall short in correctly describing the Late Universe.
| [
{
"created": "Sat, 14 Jul 2007 14:23:00 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Sep 2007 10:56:21 GMT",
"version": "v2"
},
{
"created": "Mon, 3 Dec 2007 15:16:22 GMT",
"version": "v3"
}
] | 2010-04-06 | [
[
"Buchert",
"Thomas",
""
]
] | The effective evolution of an inhomogeneous universe model in any theory of gravitation may be described in terms of spatially averaged variables. In Einstein's theory, restricting attention to scalar variables, this evolution can be modeled by solutions of a set of Friedmann equations for an effective volume scale factor, with matter and backreaction source terms. The latter can be represented by an effective scalar field (`morphon field') modeling Dark Energy. The present work provides an overview over the Dark Energy debate in connection with the impact of inhomogeneities, and formulates strategies for a comprehensive quantitative evaluation of backreaction effects both in theoretical and observational cosmology. We recall the basic steps of a description of backreaction effects in relativistic cosmology that lead to refurnishing the standard cosmological equations, but also lay down a number of challenges and unresolved issues in connection with their observational interpretation. The present status of this subject is intermediate: we have a good qualitative understanding of backreaction effects pointing to a global instability of the standard model of cosmology; exact solutions and perturbative results modeling this instability lie in the right sector to explain Dark Energy from inhomogeneities. It is fair to say that, even if backreaction effects turn out to be less important than anticipated by some researchers, the concordance high-precision cosmology, the architecture of current N-body simulations, as well as standard perturbative approaches may all fall short in correctly describing the Late Universe. |
gr-qc/0702070 | John W. Moffat | J. W. Moffat | Non-Singular Spherically Symmetric Solution in Einstein-Scalar-Tensor
Gravity | 13 pages, 6 figures, LaTex file. Revised manuscript. Additional minor
revisions | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A static spherically symmetric metric in Einstein-scalar-tensor gravity
theory with a scalar field potential $V[\phi]$ is non-singular for all real
values of the coordinates. It does not have a black hole event horizon and
there is no essential singularity at the origin of coordinates. The weak energy
condition $\rho_\phi > 0$ fails to be satisfied for $r\lesssim 1.3r_S$ (where
$r_S$ is the Schwarzschild radius) but the strong energy condition
$\rho_\phi+3p_\phi > 0$ is satisfied. The classical Einstein-scalar-tensor
solution is regular everywhere in spacetime without a black hole event horizon.
However, the violation of the weak energy condition may signal the need for
quantum physics anti-gravity as $r\to 0$. The non-singular static spherically
symmetric solution is stable against the addition of ordinary matter.
| [
{
"created": "Tue, 13 Feb 2007 15:37:30 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Mar 2007 09:03:13 GMT",
"version": "v2"
},
{
"created": "Wed, 28 Nov 2007 19:56:23 GMT",
"version": "v3"
},
{
"created": "Wed, 11 Jun 2008 15:30:56 GMT",
"version": "v4"
}
] | 2008-06-11 | [
[
"Moffat",
"J. W.",
""
]
] | A static spherically symmetric metric in Einstein-scalar-tensor gravity theory with a scalar field potential $V[\phi]$ is non-singular for all real values of the coordinates. It does not have a black hole event horizon and there is no essential singularity at the origin of coordinates. The weak energy condition $\rho_\phi > 0$ fails to be satisfied for $r\lesssim 1.3r_S$ (where $r_S$ is the Schwarzschild radius) but the strong energy condition $\rho_\phi+3p_\phi > 0$ is satisfied. The classical Einstein-scalar-tensor solution is regular everywhere in spacetime without a black hole event horizon. However, the violation of the weak energy condition may signal the need for quantum physics anti-gravity as $r\to 0$. The non-singular static spherically symmetric solution is stable against the addition of ordinary matter. |
1006.3428 | Dr. Bikash Chandra Paul | B. C. Paul (North Bengal University) | Holographic Dark Energy Model with Modified Variable Chaplygin Gas | 17 pages, 1 fig | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this letter we consider a correspondence between holographic dark energy
and variable modified Chaplygin gas to obtain a holographic dark energy model
of the universe. The corresponding potential of the scalar field has been
reconstructed which describes the modified variable Chaplygin gas. The
stability of the holographic dark energy in this case is also discussed.
| [
{
"created": "Thu, 17 Jun 2010 10:59:06 GMT",
"version": "v1"
}
] | 2010-06-18 | [
[
"Paul",
"B. C.",
"",
"North Bengal University"
]
] | In this letter we consider a correspondence between holographic dark energy and variable modified Chaplygin gas to obtain a holographic dark energy model of the universe. The corresponding potential of the scalar field has been reconstructed which describes the modified variable Chaplygin gas. The stability of the holographic dark energy in this case is also discussed. |
2203.07125 | Alfredo D. Miravet | Alfredo D. Miravet and Antonio L. Maroto | Vector dark radiation and gravitational-wave polarization | 15 pages, 8 figures. Matches version published in JCAP | null | 10.1088/1475-7516/2022/09/014 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider conformal vector models which could play the role of a
cosmological dark radiation component. We analyse the propagation of
gravitational waves in the presence of this vector background and find a
suppression in the tensor transfer function at large scales. We also find that
although the cosmological background metric is isotropic, anisotropies are
imprinted in the tensor power spectrum. In addition, the presence of the
background vector fields induces a net polarization of the gravitational wave
background and, for certain configurations of the vector field, a linear to
circular polarization conversion. We also show that this kind of effects are
also present for vector models with more general potential terms.
| [
{
"created": "Mon, 14 Mar 2022 14:19:25 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Sep 2022 09:27:16 GMT",
"version": "v2"
}
] | 2022-09-14 | [
[
"Miravet",
"Alfredo D.",
""
],
[
"Maroto",
"Antonio L.",
""
]
] | We consider conformal vector models which could play the role of a cosmological dark radiation component. We analyse the propagation of gravitational waves in the presence of this vector background and find a suppression in the tensor transfer function at large scales. We also find that although the cosmological background metric is isotropic, anisotropies are imprinted in the tensor power spectrum. In addition, the presence of the background vector fields induces a net polarization of the gravitational wave background and, for certain configurations of the vector field, a linear to circular polarization conversion. We also show that this kind of effects are also present for vector models with more general potential terms. |
1105.1172 | Miguel Pino Rozas | M\'aximo Ba\~nados, Andr\'es Gomberoff, Miguel Pino | The bigravity black hole and its thermodynamics | 14 pages, 9 figures | null | 10.1103/PhysRevD.84.104028 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We argue that the Isham-Storey exact solution to bigravity does not describe
black holes because the horizon is a singular surface. However, this is not a
generic property of bigravity, but a property of a particular potential. More
general potentials do accept regular black holes. For regular black holes, we
compute the total energy and thermodynamical parameters. Phase transitions
occur for certain critical temperatures. We also find a novel region on phase
space describing up to 4 allowed states for a given temperature.
| [
{
"created": "Thu, 5 May 2011 20:58:40 GMT",
"version": "v1"
},
{
"created": "Tue, 17 May 2011 19:09:02 GMT",
"version": "v2"
},
{
"created": "Tue, 4 Oct 2011 21:03:27 GMT",
"version": "v3"
}
] | 2015-03-19 | [
[
"Bañados",
"Máximo",
""
],
[
"Gomberoff",
"Andrés",
""
],
[
"Pino",
"Miguel",
""
]
] | We argue that the Isham-Storey exact solution to bigravity does not describe black holes because the horizon is a singular surface. However, this is not a generic property of bigravity, but a property of a particular potential. More general potentials do accept regular black holes. For regular black holes, we compute the total energy and thermodynamical parameters. Phase transitions occur for certain critical temperatures. We also find a novel region on phase space describing up to 4 allowed states for a given temperature. |
2306.14273 | Dhruba Jyoti Gogoi Dr. | Dhruba Jyoti Gogoi, Jyatsnasree Bora, M. Koussour and Yassine Sekhmani | Quasinormal Modes and Optical Properties of 4-D black holes in Einstein
Power-Yang-Mills Gravity | 13 pages, 9 figures | Annals of Physics 458, 169447 (2023) | 10.1016/j.aop.2023.169447 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | This paper explores the impact of the Yang-Mills charge parameter and the
exponent term on a $4$D black hole solution in the Einstein Power-Yang-Mills
theory. Through an investigation of the massless scalar quasinormal mode
spectrum, black hole shadow, and emission rate, we have determined that the
effects of these two parameters are opposite. Specifically, the Yang-Mills
charge parameter causes an increase in the real quasinormal frequencies with a
correspondingly smaller damping rate. It also results in a smaller black hole
shadow and a lower evaporation rate.
| [
{
"created": "Sun, 25 Jun 2023 15:49:27 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Sep 2023 18:16:16 GMT",
"version": "v2"
}
] | 2023-09-06 | [
[
"Gogoi",
"Dhruba Jyoti",
""
],
[
"Bora",
"Jyatsnasree",
""
],
[
"Koussour",
"M.",
""
],
[
"Sekhmani",
"Yassine",
""
]
] | This paper explores the impact of the Yang-Mills charge parameter and the exponent term on a $4$D black hole solution in the Einstein Power-Yang-Mills theory. Through an investigation of the massless scalar quasinormal mode spectrum, black hole shadow, and emission rate, we have determined that the effects of these two parameters are opposite. Specifically, the Yang-Mills charge parameter causes an increase in the real quasinormal frequencies with a correspondingly smaller damping rate. It also results in a smaller black hole shadow and a lower evaporation rate. |
2408.06915 | Allan Alinea | Allan L. Alinea and Joshwa DJ. Ordonez | On the KG-constrained Bekenstein's disformal transformation of the
Einstein-Hilbert action | 12 pages | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Motivated by an inclination for symmetry and possible extension of the
General Theory of Relativity within the framework of Scalar Theory, we
investigate the Bekenstein's disformal transformation of the Einstein-Hilbert
action. Owing to the complicated combinations of second order metric
derivatives encoded in the Ricci scalar of the action, such a transformation
yields an unwieldy expression. To `tame' the transformed action, we exploit the
conformal-disformal (KG) constraint previously discovered in the study of the
invariance of the massless Klein-Gordon equation under disformal
transformation. The result upon its application is a surprisingly much more
concise and simple action in four spacetime dimensions containing three out of
four sub-Lagrangians found in the Horndeski action, and three beyond-Horndeski
terms. The latter group of terms may be attributed to the kinetic dependence of
the conformal and disformal factors in the Bekenstein's disformal
transformation. This is consistent with a related study on the special
disformal transformation of the Einstein-Hilbert action where no such
beyond-Horndeski terms are found to exist. Going down to three dimensions, we
find a relatively simpler resulting action but the signature of three three
`extraneous' terms remains. Remarkably, we find in two dimensions the
Einstein-Hilbert action to be invariant under the KG-constrained Bekenstein's
disformal transformation.
| [
{
"created": "Tue, 13 Aug 2024 14:06:56 GMT",
"version": "v1"
}
] | 2024-08-14 | [
[
"Alinea",
"Allan L.",
""
],
[
"Ordonez",
"Joshwa DJ.",
""
]
] | Motivated by an inclination for symmetry and possible extension of the General Theory of Relativity within the framework of Scalar Theory, we investigate the Bekenstein's disformal transformation of the Einstein-Hilbert action. Owing to the complicated combinations of second order metric derivatives encoded in the Ricci scalar of the action, such a transformation yields an unwieldy expression. To `tame' the transformed action, we exploit the conformal-disformal (KG) constraint previously discovered in the study of the invariance of the massless Klein-Gordon equation under disformal transformation. The result upon its application is a surprisingly much more concise and simple action in four spacetime dimensions containing three out of four sub-Lagrangians found in the Horndeski action, and three beyond-Horndeski terms. The latter group of terms may be attributed to the kinetic dependence of the conformal and disformal factors in the Bekenstein's disformal transformation. This is consistent with a related study on the special disformal transformation of the Einstein-Hilbert action where no such beyond-Horndeski terms are found to exist. Going down to three dimensions, we find a relatively simpler resulting action but the signature of three three `extraneous' terms remains. Remarkably, we find in two dimensions the Einstein-Hilbert action to be invariant under the KG-constrained Bekenstein's disformal transformation. |
1703.05295 | Christian Corda Prof. | Germano Resconi, Ignazio Licata and Christian Corda | Gravity with torsion in non-conservative Maxwell-like gauge approach | 13 pages, accepted for publication in International Journal of
Geometric Methods in Modern Physics | Int. J. Geom. Methods Mod. Phys. 14, 1750110 (2017) | 10.1142/S0219887817501109 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we take into consideration a generalization of Gauge Theories
based on the analysis of the structural characteristics of Maxwell theory,
which can be considered as the prototype of such kind of theories
(Maxwell-like). Such class of theories is based on few principles related to
different orders of commutators between covariant derivatives. Their physical
meaning is very simple, and lies in stating that the local transformations of a
suitable substratum (the space-time or a particular phase space) and the
imposed constraints define a "compensative mechanism" or the "interaction" we
want to characterize. After a mathematical introduction, we apply this approach
to a modified theory of gravity, in which the algebra of operators of covariant
derivatives leads to an additional term in the equation of motion associated
with the non-conservation of the energy-moment tensor. This offers the
possibility to include, without ad hoc physical assumptions and directly from
the formalism, new forms of coupling between matter and energy and the
expression of the mixing between gravity and torsion.
| [
{
"created": "Wed, 15 Mar 2017 17:53:46 GMT",
"version": "v1"
}
] | 2017-04-03 | [
[
"Resconi",
"Germano",
""
],
[
"Licata",
"Ignazio",
""
],
[
"Corda",
"Christian",
""
]
] | In this work we take into consideration a generalization of Gauge Theories based on the analysis of the structural characteristics of Maxwell theory, which can be considered as the prototype of such kind of theories (Maxwell-like). Such class of theories is based on few principles related to different orders of commutators between covariant derivatives. Their physical meaning is very simple, and lies in stating that the local transformations of a suitable substratum (the space-time or a particular phase space) and the imposed constraints define a "compensative mechanism" or the "interaction" we want to characterize. After a mathematical introduction, we apply this approach to a modified theory of gravity, in which the algebra of operators of covariant derivatives leads to an additional term in the equation of motion associated with the non-conservation of the energy-moment tensor. This offers the possibility to include, without ad hoc physical assumptions and directly from the formalism, new forms of coupling between matter and energy and the expression of the mixing between gravity and torsion. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.