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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1812.06841 | Jorma Louko | Anshuman Bhardwaj, Edmund J. Copeland and Jorma Louko | Inflation in Loop Quantum Cosmology | 18 pages, 6 tables. v2: updates to match published version | Phys. Rev. D 99, 063520 (2019) | 10.1103/PhysRevD.99.063520 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a consistent analytic approach to determine the conditions under
which slow roll inflation can arise when the inflaton is the same scalar field
that is responsible for the bounce in Loop Quantum Cosmology (LQC). We find
that the requirement that the energy density of the field is fixed at the
bounce having to match a critical density has important consequences for its
future evolution. For a generic potential with a minimum, we find different
scenarios depending on the initial velocity of the field and whether it begins
life in a kinetic or potential energy dominated regime. For chaotic potentials
that start in a kinetic dominated regime, we find an initial phase of
superinflation independent of the shape of the potential followed by a damping
phase which slows the inflaton down, forcing it to turnaround and naturally
enter a phase of slow-roll inflation. If we begin in a potential energy
dominated regime, then the field undergoes a period where the corrections
present in LQC damp its evolution once again forcing it to turnaround and enter
a phase of slow roll inflation. On the other hand we show for the Starobinsky
potential that inflation never occurs when we begin in a potential dominated
regime. In fact traditional Starobinsky inflation has to start in a kinetic
energy dominated regime, with corresponding tighter constraints on the initial
value of the field for successful inflation than in the conventional case.
Comparing our analytic results to published numerical ones, we find remarkable
agreement especially when we consider the different epochs that are involved.
In particular the values of key observables obtained from the two approaches
are in excellent agreement, opening up the possibility of obtaining analytic
results for the evolution of the density perturbations in these models.
| [
{
"created": "Mon, 17 Dec 2018 15:35:33 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Nov 2019 12:48:06 GMT",
"version": "v2"
}
] | 2019-11-04 | [
[
"Bhardwaj",
"Anshuman",
""
],
[
"Copeland",
"Edmund J.",
""
],
[
"Louko",
"Jorma",
""
]
] | We develop a consistent analytic approach to determine the conditions under which slow roll inflation can arise when the inflaton is the same scalar field that is responsible for the bounce in Loop Quantum Cosmology (LQC). We find that the requirement that the energy density of the field is fixed at the bounce having to match a critical density has important consequences for its future evolution. For a generic potential with a minimum, we find different scenarios depending on the initial velocity of the field and whether it begins life in a kinetic or potential energy dominated regime. For chaotic potentials that start in a kinetic dominated regime, we find an initial phase of superinflation independent of the shape of the potential followed by a damping phase which slows the inflaton down, forcing it to turnaround and naturally enter a phase of slow-roll inflation. If we begin in a potential energy dominated regime, then the field undergoes a period where the corrections present in LQC damp its evolution once again forcing it to turnaround and enter a phase of slow roll inflation. On the other hand we show for the Starobinsky potential that inflation never occurs when we begin in a potential dominated regime. In fact traditional Starobinsky inflation has to start in a kinetic energy dominated regime, with corresponding tighter constraints on the initial value of the field for successful inflation than in the conventional case. Comparing our analytic results to published numerical ones, we find remarkable agreement especially when we consider the different epochs that are involved. In particular the values of key observables obtained from the two approaches are in excellent agreement, opening up the possibility of obtaining analytic results for the evolution of the density perturbations in these models. |
2111.11199 | Aneta Wojnar | Aleksander Kozak and Aneta Wojnar | Interiors of terrestrial planets in metric-affine gravity | 8 pages, 6 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using a semi-empirical approach we show that modified gravity affects the
internal properties of terrestrial planets, such as their physical
characteristics of a core, mantle, and core-mantle boundary. We also apply
these findings for modeling a two-layers exoplanet in Palatini $f(R)$ gravity.
| [
{
"created": "Mon, 22 Nov 2021 13:43:40 GMT",
"version": "v1"
}
] | 2021-11-23 | [
[
"Kozak",
"Aleksander",
""
],
[
"Wojnar",
"Aneta",
""
]
] | Using a semi-empirical approach we show that modified gravity affects the internal properties of terrestrial planets, such as their physical characteristics of a core, mantle, and core-mantle boundary. We also apply these findings for modeling a two-layers exoplanet in Palatini $f(R)$ gravity. |
2209.07555 | Yolbeiker Rodr\'iguez Baez | Yolbeiker Rodr\'iguez Baez and Manuel Gonzalez-Espinoza | Odd-parity perturbations in the most general scalar-vector-tensor theory | 22 pages, Mathematica Notebook, Added some comments, Published in
Classical and Quantum Gravity | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | In the context of the most general scalar-vector-tensor theory, we study the
stability of static spherically symmetric black holes under linear odd-parity
perturbations. We calculate the action to second order in the linear
perturbations to derive a master equation for these perturbations. For this
general class of models, we obtain the conditions of no-ghost and Laplacian
instability. Then, we study in detail the generalized Regge-Wheeler potential
of particular cases to find their stability conditions.
| [
{
"created": "Thu, 15 Sep 2022 18:30:22 GMT",
"version": "v1"
},
{
"created": "Tue, 4 Apr 2023 18:05:06 GMT",
"version": "v2"
}
] | 2023-04-06 | [
[
"Baez",
"Yolbeiker Rodríguez",
""
],
[
"Gonzalez-Espinoza",
"Manuel",
""
]
] | In the context of the most general scalar-vector-tensor theory, we study the stability of static spherically symmetric black holes under linear odd-parity perturbations. We calculate the action to second order in the linear perturbations to derive a master equation for these perturbations. For this general class of models, we obtain the conditions of no-ghost and Laplacian instability. Then, we study in detail the generalized Regge-Wheeler potential of particular cases to find their stability conditions. |
0708.4218 | Christian Fr{\o}nsdal | Christian Fronsdal | Reissner-Nordstrom and charged gas spheres | 19 pages, plain tex | Lett.Math.Phys.82:255-273,2007 | 10.1007/s11005-007-0203-x | null | gr-qc | null | The main point of this paper is a suggestion about the proper treatment of
the photon gas in a theory of stellar structure and other plasmas. This problem
arises in the study of polytropic gas spheres, where we have already introduced
some innovations. The main idea, already advanced in the contextof neutral,
homogeneous, polytropic stellar models, is to base the theory firmly on a
variational principle. Another essential novelty is to let mass distribution
extend to infinity, the boundary between bulk and atmosphere being defined by
an abrupt change in the polytropic index, triggered by the density. The logical
next step in this program is to include the effect of radiation, which is a
very significant complication since a full treatment would have to include an
account of ionization, thus fieldsrepresenting electrons, ions, photons,
gravitons and neutral atoms as well. In way of preparation, we consider models
that are charged but homogeneous, involving only gravity, electromagnetism and
a single scalar field that represents both the mass and the electric charge; in
short, anon-neutral plasma. While this work only represents a stage in the
development of a theory of stars, without direct application to physical
systems, it does shed some light on the meaning of the Reissner-Nordstrom
solution of the modified Einstein-Maxwell equations., with an application to a
simple system.
| [
{
"created": "Thu, 30 Aug 2007 19:29:33 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Fronsdal",
"Christian",
""
]
] | The main point of this paper is a suggestion about the proper treatment of the photon gas in a theory of stellar structure and other plasmas. This problem arises in the study of polytropic gas spheres, where we have already introduced some innovations. The main idea, already advanced in the contextof neutral, homogeneous, polytropic stellar models, is to base the theory firmly on a variational principle. Another essential novelty is to let mass distribution extend to infinity, the boundary between bulk and atmosphere being defined by an abrupt change in the polytropic index, triggered by the density. The logical next step in this program is to include the effect of radiation, which is a very significant complication since a full treatment would have to include an account of ionization, thus fieldsrepresenting electrons, ions, photons, gravitons and neutral atoms as well. In way of preparation, we consider models that are charged but homogeneous, involving only gravity, electromagnetism and a single scalar field that represents both the mass and the electric charge; in short, anon-neutral plasma. While this work only represents a stage in the development of a theory of stars, without direct application to physical systems, it does shed some light on the meaning of the Reissner-Nordstrom solution of the modified Einstein-Maxwell equations., with an application to a simple system. |
1901.01315 | Pablo Antonio Cano Molina-Ni\~nirola | Pablo A. Cano and Alejandro Ruip\'erez | Leading higher-derivative corrections to Kerr geometry | v3: The equations 4.41-4.43 for the lightring frequencies have been
amended. These formulas were incorrect in the previous versions due to an
error when translating the results to the LaTeX file (the error does not
propagate to other results). For all the rest, this version matches the one
published in JHEP | null | 10.1007/JHEP05(2019)189 | IFT-UAM/CSIC-19-2 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the most general leading-order correction to Kerr solution when
the Einstein-Hilbert action is supplemented with higher-derivative terms,
including the possibility of dynamical couplings controlled by scalars. The
model we present depends on five parameters and it contains, as particular
cases, Einstein-dilaton-Gauss-Bonnet gravity, dynamical Chern-Simons gravity
and the effective action coming from Heterotic Superstring theory. By solving
the corrected field equations, we find the modified Kerr metric that describes
rotating black holes in these theories. We express the solution as a series in
the spin parameter $\chi$, and we show that including enough terms in the
expansion we are able to describe black holes with large spin. For the
computations in the text we use an expansion up to order $\chi^{14}$, which is
accurate for $\chi<0.7$, but we provide as well a Mathematica notebook that
computes the solution at any given order. We study several properties of the
corrected black holes, such as geometry of the horizon, ergosphere, light rings
and scalar hair. Some of the corrections violate parity, and we highlight in
those cases plots of horizons and ergospheres without $\mathbb{Z}_{2}$
symmetry.
| [
{
"created": "Fri, 4 Jan 2019 21:12:12 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Jan 2019 13:21:25 GMT",
"version": "v2"
},
{
"created": "Thu, 5 Mar 2020 12:59:09 GMT",
"version": "v3"
}
] | 2020-03-06 | [
[
"Cano",
"Pablo A.",
""
],
[
"Ruipérez",
"Alejandro",
""
]
] | We compute the most general leading-order correction to Kerr solution when the Einstein-Hilbert action is supplemented with higher-derivative terms, including the possibility of dynamical couplings controlled by scalars. The model we present depends on five parameters and it contains, as particular cases, Einstein-dilaton-Gauss-Bonnet gravity, dynamical Chern-Simons gravity and the effective action coming from Heterotic Superstring theory. By solving the corrected field equations, we find the modified Kerr metric that describes rotating black holes in these theories. We express the solution as a series in the spin parameter $\chi$, and we show that including enough terms in the expansion we are able to describe black holes with large spin. For the computations in the text we use an expansion up to order $\chi^{14}$, which is accurate for $\chi<0.7$, but we provide as well a Mathematica notebook that computes the solution at any given order. We study several properties of the corrected black holes, such as geometry of the horizon, ergosphere, light rings and scalar hair. Some of the corrections violate parity, and we highlight in those cases plots of horizons and ergospheres without $\mathbb{Z}_{2}$ symmetry. |
1501.02342 | Wolfgang Muschik | Wolfgang Muschik, Horst-Heino v. Borzeszkowski | Exploitation of the Dissipation Inequality in General Relativistic
Continuum Thermodynamics | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The balance equations of energy-momentum and spin together with Einstein's
field equations are investigated by the Liu procedure to find constraints for
the constitutive equations in such a way that the Second Law is satisfied.
Special cases such as spinless systems and curvature insensitive materials are
shortly discussed.
| [
{
"created": "Sat, 10 Jan 2015 12:08:50 GMT",
"version": "v1"
}
] | 2015-01-13 | [
[
"Muschik",
"Wolfgang",
""
],
[
"Borzeszkowski",
"Horst-Heino v.",
""
]
] | The balance equations of energy-momentum and spin together with Einstein's field equations are investigated by the Liu procedure to find constraints for the constitutive equations in such a way that the Second Law is satisfied. Special cases such as spinless systems and curvature insensitive materials are shortly discussed. |
1509.04577 | Francisco Lobo | Marzieh Peyravi, Nematollah Riazi, Francisco S.N. Lobo | Thick brane solitons breaking $Z_2$ symmetry | 6 pages, 3 figures; contribution to the proceedings of the "The
Fourtheenth Marcel Grossmann Meeting on General Relativity", University of
Rome "La Sapienza", Rome, July 12-18, 2015, based on a talk delivered at the
AT2-Alternative Theories parallel session | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | New soliton solutions for thick branes in 4 + 1 dimensions are considered in
this article. In particular, brane models based on the sine-Gordon (SG),
$\varphi^{4}$ and $\varphi^{6}$ scalar fields are investigated; in some cases
$Z_{2}$ symmetry is broken. Besides, these soliton solutions are responsible
for supporting and stabilizing the thick branes. In these models, the origin of
the symmetry breaking resides in the fact that the modified scalar field
potential may have non-degenerate vacuua and these non-degenerate vacuua
determine the cosmological constant on both sides of the brane. At last, in
order to explore the particle motion in the neighborhood of the brane, the
geodesic equations along the fifth dimension are studied.
| [
{
"created": "Tue, 15 Sep 2015 14:23:57 GMT",
"version": "v1"
}
] | 2015-09-16 | [
[
"Peyravi",
"Marzieh",
""
],
[
"Riazi",
"Nematollah",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] | New soliton solutions for thick branes in 4 + 1 dimensions are considered in this article. In particular, brane models based on the sine-Gordon (SG), $\varphi^{4}$ and $\varphi^{6}$ scalar fields are investigated; in some cases $Z_{2}$ symmetry is broken. Besides, these soliton solutions are responsible for supporting and stabilizing the thick branes. In these models, the origin of the symmetry breaking resides in the fact that the modified scalar field potential may have non-degenerate vacuua and these non-degenerate vacuua determine the cosmological constant on both sides of the brane. At last, in order to explore the particle motion in the neighborhood of the brane, the geodesic equations along the fifth dimension are studied. |
gr-qc/0301079 | Jose Wadih Maluf | A. A. Sousa and J. W. Maluf | Black Holes in 2+1 Teleparallel Theories of Gravity | 20 pages, Latex file, no figures | Prog.Theor.Phys. 108 (2002) 457-470 | 10.1143/PTP.108.457 | Prog. Theor. Phys. Vol. 108, 457-470 (2002) | gr-qc | null | We apply the Hamiltonian formulation of teleparallel theories of gravity in
2+1 dimensions to a circularly symmetric geometry. We find a family of
one-parameter black hole solutions. The BTZ solution fixes the unique free
parameter of the theory. The resulting field equations coincide with the
teleparallel equivalent of Einstein's three-dimensional equations. We calculate
the gravitational energy of the black holes by means of the simple expression
that arises in the Hamiltonian formulation and conclude that the resulting
value is identical to that calculated by means of the Brown-York method.
| [
{
"created": "Tue, 21 Jan 2003 16:59:41 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Sousa",
"A. A.",
""
],
[
"Maluf",
"J. W.",
""
]
] | We apply the Hamiltonian formulation of teleparallel theories of gravity in 2+1 dimensions to a circularly symmetric geometry. We find a family of one-parameter black hole solutions. The BTZ solution fixes the unique free parameter of the theory. The resulting field equations coincide with the teleparallel equivalent of Einstein's three-dimensional equations. We calculate the gravitational energy of the black holes by means of the simple expression that arises in the Hamiltonian formulation and conclude that the resulting value is identical to that calculated by means of the Brown-York method. |
gr-qc/9508007 | Per Kraus | Per Kraus | Non-thermal aspects of black hole radiance | Princeton University thesis; 101 pages; compressed latex; 4 figures | null | null | null | gr-qc | null | The phenomenon of black hole thermodynamics raises several deep issues which
any proper theory of quantum gravity must confront: to what extent does the
inclusion of the back-reaction alter the thermal character of the radiation,
how can the entropy be understood from a microscopic standpoint, what is the
ultimate fate of an evaporating black hole, and is the outcome reconcilable
with unitary time evolution in quantum mechanics?
In the first part of this thesis, we address the issue of determining what
the actual emission spectrum from a black hole is, once the gravitational field
of the emitted quanta is included in a quantum mechanical manner. To make the
problem tractable, we employ two important approximations: we quantize only the
s-wave sector of the full theory, and we consider only single particle
emission. By proceeding in the framework of a Hamiltonian path integral
description of this system, we are able to integrate out the gravitational
field, thereby obtaining an effective action depending only on the matter
degrees of freedom. This effective action can then be second quantized in terms
of new, corrected, mode solutions thus enabling the calculation of the emission
spectrum from modified Bogoliubov coefficients. The results are particularly
interesting in the case of emission from Reissner-Nordstrom black holes, since
in the extremal limit our results are dramatically different from what a naive,
and incorrect, semi-classical calculation would yield.
The other major topic which we discuss is the dynamics of quantum fields on
background geometries which undergo quantum tunneling. An example of such a
system which has important implications for both cosmology and quantum gravity
in general, is the tunneling of a false vacuum bubble leading to the creation
| [
{
"created": "Fri, 4 Aug 1995 02:04:31 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Kraus",
"Per",
""
]
] | The phenomenon of black hole thermodynamics raises several deep issues which any proper theory of quantum gravity must confront: to what extent does the inclusion of the back-reaction alter the thermal character of the radiation, how can the entropy be understood from a microscopic standpoint, what is the ultimate fate of an evaporating black hole, and is the outcome reconcilable with unitary time evolution in quantum mechanics? In the first part of this thesis, we address the issue of determining what the actual emission spectrum from a black hole is, once the gravitational field of the emitted quanta is included in a quantum mechanical manner. To make the problem tractable, we employ two important approximations: we quantize only the s-wave sector of the full theory, and we consider only single particle emission. By proceeding in the framework of a Hamiltonian path integral description of this system, we are able to integrate out the gravitational field, thereby obtaining an effective action depending only on the matter degrees of freedom. This effective action can then be second quantized in terms of new, corrected, mode solutions thus enabling the calculation of the emission spectrum from modified Bogoliubov coefficients. The results are particularly interesting in the case of emission from Reissner-Nordstrom black holes, since in the extremal limit our results are dramatically different from what a naive, and incorrect, semi-classical calculation would yield. The other major topic which we discuss is the dynamics of quantum fields on background geometries which undergo quantum tunneling. An example of such a system which has important implications for both cosmology and quantum gravity in general, is the tunneling of a false vacuum bubble leading to the creation |
1111.5090 | Ryotaro Kase | Antonio De Felice, Ryotaro Kase, Shinji Tsujikawa | Vainshtein mechanism in second-order scalar-tensor theories | 15 pages, no figures | Phys.Rev.D85:044059, 2012 | 10.1103/PhysRevD.85.044059 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In second-order scalar-tensor theories we study how the Vainshtein mechanism
works in a spherically symmetric background with a matter source. In the
presence of the field coupling $F(\phi)=e^{-2Q\phi}$ with the Ricci scalar $R$
we generally derive the Vainshtein radius within which the General Relativistic
behavior is recovered even for the coupling $Q$ of the order of unity. Our
analysis covers the models such as the extended Galileon and Brans-Dicke
theories with a dilatonic field self-interaction. We show that, if these models
are responsible for the cosmic acceleration today, the corrections to
gravitational potentials are generally small enough to be compatible with local
gravity constraints.
| [
{
"created": "Tue, 22 Nov 2011 04:58:43 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Feb 2012 12:56:45 GMT",
"version": "v2"
}
] | 2015-06-03 | [
[
"De Felice",
"Antonio",
""
],
[
"Kase",
"Ryotaro",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] | In second-order scalar-tensor theories we study how the Vainshtein mechanism works in a spherically symmetric background with a matter source. In the presence of the field coupling $F(\phi)=e^{-2Q\phi}$ with the Ricci scalar $R$ we generally derive the Vainshtein radius within which the General Relativistic behavior is recovered even for the coupling $Q$ of the order of unity. Our analysis covers the models such as the extended Galileon and Brans-Dicke theories with a dilatonic field self-interaction. We show that, if these models are responsible for the cosmic acceleration today, the corrections to gravitational potentials are generally small enough to be compatible with local gravity constraints. |
1311.5808 | Matteo Luca Ruggiero | Matteo Luca Ruggiero | Using Ring Laser Systems to Measure Gravitomagnetic Effects on Earth | 3 pages, in "QSO astrophysics, fundamental physics, and astrometric
cosmology in the Gaia era" Porto-Portugal, June 6-9, 2011, Editors: S. Anton,
M. Crosta, M.G. Lattanzi and A. Andrei. Memorie della Societ\`a Astronomica
Italiana, Vol. 83 (2012) | Memorie della Societ\`a Astronomica Italiana, Vol. 83 (2012),
Pages 1017-1019 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitomagnetic effects originates from the rotation of the source of the
gravitational field and from the rotational features of the observers' frame.
In recent years, gravitomagnetism has been tested by means of its impact on the
precession of LAGEOS orbits and on the precession of spherical gyroscopes in
the GP-B experiment. What we suggest here is that light can be used as a probe
to test gravitomagnetic effects in an terrestrial laboratory: the proposed
detector consists of large ring-lasers arranged along three orthogonal axes.
| [
{
"created": "Fri, 22 Nov 2013 16:45:28 GMT",
"version": "v1"
}
] | 2013-12-06 | [
[
"Ruggiero",
"Matteo Luca",
""
]
] | Gravitomagnetic effects originates from the rotation of the source of the gravitational field and from the rotational features of the observers' frame. In recent years, gravitomagnetism has been tested by means of its impact on the precession of LAGEOS orbits and on the precession of spherical gyroscopes in the GP-B experiment. What we suggest here is that light can be used as a probe to test gravitomagnetic effects in an terrestrial laboratory: the proposed detector consists of large ring-lasers arranged along three orthogonal axes. |
1109.4239 | Aurelien Barrau | Aurelien Barrau, Xiangyu Cao, Jacobo Diaz-Polo, Julien Grain, Thomas
Cailleteau | Probing Loop Quantum Gravity with Evaporating Black Holes | 5 pages, 3 figures. Version accpeted by Phys. Rev. Lett | Phys. Rev. Lett. 107, 251301 (2011) | 10.1103/PhysRevLett.107.251301 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This letter aims at showing that the observation of evaporating black holes
should allow distinguishing between the usual Hawking behavior and Loop Quantum
Gravity (LQG) expectations. We present a full Monte-Carlo simulation of the
evaporation in LQG and statistical tests that discriminate between competing
models. We conclude that contrarily to what was commonly thought, the
discreteness of the area in LQG leads to characteristic features that qualify
evaporating black holes as objects that could reveal quantum gravity
footprints.
| [
{
"created": "Tue, 20 Sep 2011 08:50:24 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Dec 2011 15:43:24 GMT",
"version": "v2"
}
] | 2015-05-30 | [
[
"Barrau",
"Aurelien",
""
],
[
"Cao",
"Xiangyu",
""
],
[
"Diaz-Polo",
"Jacobo",
""
],
[
"Grain",
"Julien",
""
],
[
"Cailleteau",
"Thomas",
""
]
] | This letter aims at showing that the observation of evaporating black holes should allow distinguishing between the usual Hawking behavior and Loop Quantum Gravity (LQG) expectations. We present a full Monte-Carlo simulation of the evaporation in LQG and statistical tests that discriminate between competing models. We conclude that contrarily to what was commonly thought, the discreteness of the area in LQG leads to characteristic features that qualify evaporating black holes as objects that could reveal quantum gravity footprints. |
gr-qc/9802019 | null | Thibault Damour, Gilles Esposito-Farese | Light deflection by gravitational waves from localized sources | 12 pages, REVTeX 3.0, no figure | Phys.Rev. D58 (1998) 044003 | 10.1103/PhysRevD.58.044003 | IHES/P/98/11, CPT-98/P.3607 | gr-qc astro-ph | null | We study the deflection of light (and the redshift, or integrated time delay)
caused by the time-dependent gravitational field generated by a localized
material source lying close to the line of sight. Our calculation explicitly
takes into account the full, near-zone, plus intermediate-zone, plus wave-zone,
retarded gravitational field. Contrary to several recent claims in the
literature, we find that the deflections due to both the wave-zone 1/r
gravitational wave and the intermediate-zone 1/r^2 retarded fields vanish
exactly. The leading total time-dependent deflection caused by a localized
material source, such as a binary system, is proven to be given by the
quasi-static, near-zone quadrupolar piece of the gravitational field, and
therefore to fall off as the inverse cube of the impact parameter.
| [
{
"created": "Mon, 9 Feb 1998 14:32:45 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Damour",
"Thibault",
""
],
[
"Esposito-Farese",
"Gilles",
""
]
] | We study the deflection of light (and the redshift, or integrated time delay) caused by the time-dependent gravitational field generated by a localized material source lying close to the line of sight. Our calculation explicitly takes into account the full, near-zone, plus intermediate-zone, plus wave-zone, retarded gravitational field. Contrary to several recent claims in the literature, we find that the deflections due to both the wave-zone 1/r gravitational wave and the intermediate-zone 1/r^2 retarded fields vanish exactly. The leading total time-dependent deflection caused by a localized material source, such as a binary system, is proven to be given by the quasi-static, near-zone quadrupolar piece of the gravitational field, and therefore to fall off as the inverse cube of the impact parameter. |
0804.2163 | Antonio De Felice | Salvatore Capozziello, Antonio De Felice | f(R) cosmology by Noether's symmetry | 23 pages, uses RevTeX | JCAP 0808:016,2008 | 10.1088/1475-7516/2008/08/016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A general approach to find out exact cosmological solutions in f(R)-gravity
is discussed. Instead of taking into account phenomenological models, we
assume, as a physical criterium, the existence of Noether symmetries in the
cosmological f(R) Lagrangian. As a result, the presence of such symmetries
selects viable models and allow to solve the equations of motion. We discuss
also the case in which no Noether charge is present but general criteria can be
used to achieve solutions.
| [
{
"created": "Mon, 14 Apr 2008 14:25:16 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Jul 2008 08:53:11 GMT",
"version": "v2"
},
{
"created": "Wed, 10 Feb 2010 11:38:05 GMT",
"version": "v3"
}
] | 2010-02-10 | [
[
"Capozziello",
"Salvatore",
""
],
[
"De Felice",
"Antonio",
""
]
] | A general approach to find out exact cosmological solutions in f(R)-gravity is discussed. Instead of taking into account phenomenological models, we assume, as a physical criterium, the existence of Noether symmetries in the cosmological f(R) Lagrangian. As a result, the presence of such symmetries selects viable models and allow to solve the equations of motion. We discuss also the case in which no Noether charge is present but general criteria can be used to achieve solutions. |
1902.10269 | Hector O. Silva | Hector O. Silva, Nicol\'as Yunes | Neutron star pulse profile observations as extreme gravity probes | 7 pages, 3 figures. v2: updated title and new appendix | null | 10.1088/1361-6382/ab3560 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The x-ray emission of hot spots on the surface of neutron stars is the prime
target of the Neutron star Interior Composition Explorer (NICER). These x-ray
pulse profiles not only encode information of the bulk properties of these
stars, which teaches us about matter at supranuclear densities, but also about
the spacetime curvature around them which teaches us about relativistic
gravity. We explore the possibility of performing strong-gravity tests with
NICER observations using a recently developed pulse profile model beyond
general relativity. Our results suggest that NICER can place constraints on
deviations from general relativity due to an additional scalar degree of
freedom which are independent and competitive relative to constraints with
binary pulsar observations.
| [
{
"created": "Wed, 27 Feb 2019 00:01:58 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Aug 2019 22:24:15 GMT",
"version": "v2"
}
] | 2019-08-19 | [
[
"Silva",
"Hector O.",
""
],
[
"Yunes",
"Nicolás",
""
]
] | The x-ray emission of hot spots on the surface of neutron stars is the prime target of the Neutron star Interior Composition Explorer (NICER). These x-ray pulse profiles not only encode information of the bulk properties of these stars, which teaches us about matter at supranuclear densities, but also about the spacetime curvature around them which teaches us about relativistic gravity. We explore the possibility of performing strong-gravity tests with NICER observations using a recently developed pulse profile model beyond general relativity. Our results suggest that NICER can place constraints on deviations from general relativity due to an additional scalar degree of freedom which are independent and competitive relative to constraints with binary pulsar observations. |
2004.13010 | Hristu Culetu | Hristu Culetu | Pattern for a star filled with imperfect fluid | 9 pages, minor corrections, two refs added | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A static, spherically symmetric spacetime with negative pressures is
conjectured inside a star. The gravitational field is repulsive and so a
central singularity is avoided. The positive energy density and the pressures
of the imperfect fluid are finite everywhere. The Tolman-Komar energy of the
space is negative, as for a de Sitter geometry. From the Darmois-Israel
junction conditions on the star surface one finds the constant length $b$ from
the metric and the expression of the surface tension $\sigma$ of the thin shell
separating the interior from the Schwarzschild exterior. Some properties of the
timelike and null geodesics in the Painleve-Gullstrand coordinates are
investigated.
| [
{
"created": "Sat, 25 Apr 2020 17:03:15 GMT",
"version": "v1"
},
{
"created": "Sat, 2 May 2020 10:42:29 GMT",
"version": "v2"
}
] | 2020-05-05 | [
[
"Culetu",
"Hristu",
""
]
] | A static, spherically symmetric spacetime with negative pressures is conjectured inside a star. The gravitational field is repulsive and so a central singularity is avoided. The positive energy density and the pressures of the imperfect fluid are finite everywhere. The Tolman-Komar energy of the space is negative, as for a de Sitter geometry. From the Darmois-Israel junction conditions on the star surface one finds the constant length $b$ from the metric and the expression of the surface tension $\sigma$ of the thin shell separating the interior from the Schwarzschild exterior. Some properties of the timelike and null geodesics in the Painleve-Gullstrand coordinates are investigated. |
0712.4122 | Orfeu Bertolami | Catarina Bastos, Orfeu Bertolami, Nuno Costa Dias, Jo\~ao Nuno Prata | Phase-Space Noncommutative Quantum Cosmology | Version to match the one to appear in Phys. Rev. D. Revtex4 style | Phys.Rev.D78:023516,2008 | 10.1103/PhysRevD.78.23516 | DF/IST-8.2007 | gr-qc astro-ph hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a noncommutative extension of Quantum Cosmology and study the
Kantowski-Sachs (KS) cosmological model requiring that the two scale factors of
the KS metric, the coordinates of the system, and their conjugate canonical
momenta do not commute. Through the ADM formalism, we obtain the Wheeler-DeWitt
(WDW) equation for the noncommutative system. The Seiberg-Witten map is used to
transform the noncommutative equation into a commutative one, i.e. into an
equation with commutative variables, which depend on the noncommutative
parameters, $\theta$ and $\eta$. Numerical solutions are found both for the
classical and the quantum formulations of the system. These solutions are used
to characterize the dynamics and the state of the universe. From the classical
solutions we obtain the behavior of quantities such as the volume expansion,
the shear and the characteristic volume. However the analysis of these
quantities does not lead to any restriction on the value of the noncommutative
parameters, $\theta$ and $\eta$. On the other hand, for the quantum system, one
can obtain, via the numerical solution of the WDW equation, the wave function
of the universe both for commutative as well as for the noncommutative models.
Interestingly, we find that the existence of suitable solutions of the WDW
equation imposes bounds on the values of the noncommutative parameters.
Moreover, the noncommutativity in the momenta leads to damping of the wave
function implying that this noncommutativity can be of relevance for the
selection of possible initial states of the early universe.
| [
{
"created": "Wed, 26 Dec 2007 12:15:44 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Jul 2008 13:48:28 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Bastos",
"Catarina",
""
],
[
"Bertolami",
"Orfeu",
""
],
[
"Dias",
"Nuno Costa",
""
],
[
"Prata",
"João Nuno",
""
]
] | We present a noncommutative extension of Quantum Cosmology and study the Kantowski-Sachs (KS) cosmological model requiring that the two scale factors of the KS metric, the coordinates of the system, and their conjugate canonical momenta do not commute. Through the ADM formalism, we obtain the Wheeler-DeWitt (WDW) equation for the noncommutative system. The Seiberg-Witten map is used to transform the noncommutative equation into a commutative one, i.e. into an equation with commutative variables, which depend on the noncommutative parameters, $\theta$ and $\eta$. Numerical solutions are found both for the classical and the quantum formulations of the system. These solutions are used to characterize the dynamics and the state of the universe. From the classical solutions we obtain the behavior of quantities such as the volume expansion, the shear and the characteristic volume. However the analysis of these quantities does not lead to any restriction on the value of the noncommutative parameters, $\theta$ and $\eta$. On the other hand, for the quantum system, one can obtain, via the numerical solution of the WDW equation, the wave function of the universe both for commutative as well as for the noncommutative models. Interestingly, we find that the existence of suitable solutions of the WDW equation imposes bounds on the values of the noncommutative parameters. Moreover, the noncommutativity in the momenta leads to damping of the wave function implying that this noncommutativity can be of relevance for the selection of possible initial states of the early universe. |
2107.01845 | Haowen Zhong | Haowen Zhong, Biping Gong and Taotao Qiu | Gravitational waves from bubble collisions in FLRW spacetime | 16 pages, 8 figures; This paper has been accepted by JHEP | null | 10.1007/JHEP02(2022)077 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Stochastic gravitational wave background (SGWB) is a promising tool to probe
the very early universe where the standard model of particle physics and
cosmology are connected closely. As a possible component of SGWB, gravitational
waves (GW) from bubble collisions during the first order cosmological phase
transitions deserve comprehensive analyses. In 2017, Ryusuke Jinno and Masahiro
Takimoto proposed an elegant analysis approach to derive the analytical
expressions of energy spectra of GW from bubble collisions in Minkowski
spacetime avoiding large-scale numerical simulations for the first time[26].
However, they neglect the expansion of the universe and regard the duration of
phase transitions as infinity in their derivation which could deviate their
estimations from true values. For these two reasons, we give a new expression
of GW spectra by adopting their method, switching spacetime background to FLRW
spacetime, and considering a finite duration of phase transitions. By denoting
$\sigma$ as the fraction of the speed of phase transitions to the expansion
speed of the universe, we find when $\sigma$ is around $\mathcal{O}(10)$, the
maxima of estimated GW energy spectra drop by around 1 order of magnitude than
the results given by their previous work. Even when $\sigma=100$, the maximum
of GW energy spectrum is only $65\%$ of their previous estimation. Such a
significant decrease may bring about new challenges for the detectability of GW
from bubble collisions. Luckily, by comparing new spectra with PLI
(\textit{power-law integrated}) sensitivity curves of GW detectors, we find
that the detection prospect for GW from bubble collisions is still promising
for DECIGO, BBO, LISA, and TianQin in the foreseeable future.
| [
{
"created": "Mon, 5 Jul 2021 08:03:06 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Jul 2021 07:26:04 GMT",
"version": "v2"
},
{
"created": "Wed, 9 Feb 2022 19:56:17 GMT",
"version": "v3"
}
] | 2022-03-02 | [
[
"Zhong",
"Haowen",
""
],
[
"Gong",
"Biping",
""
],
[
"Qiu",
"Taotao",
""
]
] | Stochastic gravitational wave background (SGWB) is a promising tool to probe the very early universe where the standard model of particle physics and cosmology are connected closely. As a possible component of SGWB, gravitational waves (GW) from bubble collisions during the first order cosmological phase transitions deserve comprehensive analyses. In 2017, Ryusuke Jinno and Masahiro Takimoto proposed an elegant analysis approach to derive the analytical expressions of energy spectra of GW from bubble collisions in Minkowski spacetime avoiding large-scale numerical simulations for the first time[26]. However, they neglect the expansion of the universe and regard the duration of phase transitions as infinity in their derivation which could deviate their estimations from true values. For these two reasons, we give a new expression of GW spectra by adopting their method, switching spacetime background to FLRW spacetime, and considering a finite duration of phase transitions. By denoting $\sigma$ as the fraction of the speed of phase transitions to the expansion speed of the universe, we find when $\sigma$ is around $\mathcal{O}(10)$, the maxima of estimated GW energy spectra drop by around 1 order of magnitude than the results given by their previous work. Even when $\sigma=100$, the maximum of GW energy spectrum is only $65\%$ of their previous estimation. Such a significant decrease may bring about new challenges for the detectability of GW from bubble collisions. Luckily, by comparing new spectra with PLI (\textit{power-law integrated}) sensitivity curves of GW detectors, we find that the detection prospect for GW from bubble collisions is still promising for DECIGO, BBO, LISA, and TianQin in the foreseeable future. |
1008.0795 | Robert Ward | Massimo Granata and Christelle Buy and Robert Ward and Matteo
Barsuglia | Higher-order Laguerre-Gauss mode generation and interferometry for
gravitational wave detectors | 4 pages, 5 figures | Phys.Rev.Lett.105:231102,2010 | 10.1103/PhysRevLett.105.231102 | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report on the first experimental demonstration of higher-order
Laguerre-Gauss (LGpl) mode generation and interferometry using a method
scalable to the requirements of gravitational wave (GW) detection. GW detectors
which use higher-order LGpl modes will be less susceptible to mirror thermal
noise, which is expected to limit the sensitivity of all currently planned
terrestrial detectors. We used a diffractive optic and a mode-cleaner cavity to
convert a fundamental LG00 Gaussian beam into an LG33 mode with a purity of
98%. The ratio between the power of the LG00 mode of our laser and the power of
the LG33 transmitted by the cavity was 36%. By measuring the transmission of
our setup using the LG00, we inferred that the conversion efficiency specific
to the LG33 mode was 49%. We illuminated a Michelson interferometer with the
LG33 beam and achieved a visibility of 97%.
| [
{
"created": "Wed, 4 Aug 2010 14:48:46 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Sep 2010 12:06:01 GMT",
"version": "v2"
},
{
"created": "Wed, 8 Dec 2010 14:00:21 GMT",
"version": "v3"
}
] | 2010-12-23 | [
[
"Granata",
"Massimo",
""
],
[
"Buy",
"Christelle",
""
],
[
"Ward",
"Robert",
""
],
[
"Barsuglia",
"Matteo",
""
]
] | We report on the first experimental demonstration of higher-order Laguerre-Gauss (LGpl) mode generation and interferometry using a method scalable to the requirements of gravitational wave (GW) detection. GW detectors which use higher-order LGpl modes will be less susceptible to mirror thermal noise, which is expected to limit the sensitivity of all currently planned terrestrial detectors. We used a diffractive optic and a mode-cleaner cavity to convert a fundamental LG00 Gaussian beam into an LG33 mode with a purity of 98%. The ratio between the power of the LG00 mode of our laser and the power of the LG33 transmitted by the cavity was 36%. By measuring the transmission of our setup using the LG00, we inferred that the conversion efficiency specific to the LG33 mode was 49%. We illuminated a Michelson interferometer with the LG33 beam and achieved a visibility of 97%. |
1705.09618 | Babak Vakili | H. Ardehali, P. Pedram and B. Vakili | Classical and quantum Chaplygin gas Ho\v{r}ava-Lifshitz scalar-metric
cosmology | 17 pages, 4 figures. arXiv admin note: text overlap with
arXiv:1004.0306 | Acta Phys. Pol. B 48 (2017) 827 | 10.5506/APhysPolB.48.827 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we study the Friedmann-Robertson-Walker cosmology in which a
Chaplygin gas is coupled to a non-linear scalar field in the framework of the
Ho\v{r}ava-Lifshitz theory. In writing the action of the matter part, we use
the Schutz's formalism so that the only degree of freedom of the Chaplygin gas
plays the role of an evolutionary parameter. In a minisuperspace perspective,
we construct the Lagrangian for this model and show that in comparison with the
usual Einstein-Hilbert gravity, there are some correction terms coming from the
Ho\v{r}ava theory. In such a set-up and by using of some approximations the
classical dynamics of the model is investigated and some discussions about
their possible singularities are presented. We then deal with the quantization
of the model in the context of the Wheeler-DeWitt approach of quantum cosmology
to find the cosmological wave function. We use the resulting wave functions to
investigate the possibility of the avoidance of classical singularities due to
quantum effects.
| [
{
"created": "Thu, 25 May 2017 11:32:41 GMT",
"version": "v1"
}
] | 2017-06-27 | [
[
"Ardehali",
"H.",
""
],
[
"Pedram",
"P.",
""
],
[
"Vakili",
"B.",
""
]
] | In this work, we study the Friedmann-Robertson-Walker cosmology in which a Chaplygin gas is coupled to a non-linear scalar field in the framework of the Ho\v{r}ava-Lifshitz theory. In writing the action of the matter part, we use the Schutz's formalism so that the only degree of freedom of the Chaplygin gas plays the role of an evolutionary parameter. In a minisuperspace perspective, we construct the Lagrangian for this model and show that in comparison with the usual Einstein-Hilbert gravity, there are some correction terms coming from the Ho\v{r}ava theory. In such a set-up and by using of some approximations the classical dynamics of the model is investigated and some discussions about their possible singularities are presented. We then deal with the quantization of the model in the context of the Wheeler-DeWitt approach of quantum cosmology to find the cosmological wave function. We use the resulting wave functions to investigate the possibility of the avoidance of classical singularities due to quantum effects. |
2212.13896 | Branko Dragovich | I. Dimitrijevic, B. Dragovich, Z. Rakic and J. Stankovic | On the Schwarzschild-de Sitter metric of nonlocal de Sitter gravity | 10 pages | null | null | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | Earlier constructed a simple nonlocal de Sitter gravity model has a
cosmological solution in a very good agreement with astronomical observations.
In this paper, we continue the investigation of the nonlocal de Sitter model of
gravity, focusing on finding an appropriate solution for the Schwarzschild-de
Sitter metric. We succeeded to solve the equations of motion in a certain
approximation. The obtained approximate solution is of particular interest for
examining the possible role of non-local de Sitter gravity in describing the
effects in galactic dynamics that are usually attributed to dark matter.
| [
{
"created": "Mon, 26 Dec 2022 16:28:01 GMT",
"version": "v1"
}
] | 2022-12-29 | [
[
"Dimitrijevic",
"I.",
""
],
[
"Dragovich",
"B.",
""
],
[
"Rakic",
"Z.",
""
],
[
"Stankovic",
"J.",
""
]
] | Earlier constructed a simple nonlocal de Sitter gravity model has a cosmological solution in a very good agreement with astronomical observations. In this paper, we continue the investigation of the nonlocal de Sitter model of gravity, focusing on finding an appropriate solution for the Schwarzschild-de Sitter metric. We succeeded to solve the equations of motion in a certain approximation. The obtained approximate solution is of particular interest for examining the possible role of non-local de Sitter gravity in describing the effects in galactic dynamics that are usually attributed to dark matter. |
1302.5950 | Sean McWilliams | Sean T. McWilliams | Reply to "Comment on `Black Holes are neither Particle Accelerators nor
Dark Matter Probes' " | 2 pages, 1 figure | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We respond to a recent criticism from Zaslavskii (arXiv:1301.3429v2 [gr-qc])
of our article, which appeared in Phys. Rev. Lett. 110 011102 (2013). We
clarify the points of apparent disagreement, none of which relate to the
central result of our original paper, which is the demonstration that the
diverging center-of-masss energy of collisions in Kerr spacetime, known as the
"BSW effect", can never be observed in nature. To emphasize this result, we
present it in a more concise way which completely avoids any of the questions
brought up by Zaslavskii.
| [
{
"created": "Sun, 24 Feb 2013 20:39:12 GMT",
"version": "v1"
}
] | 2013-02-26 | [
[
"McWilliams",
"Sean T.",
""
]
] | We respond to a recent criticism from Zaslavskii (arXiv:1301.3429v2 [gr-qc]) of our article, which appeared in Phys. Rev. Lett. 110 011102 (2013). We clarify the points of apparent disagreement, none of which relate to the central result of our original paper, which is the demonstration that the diverging center-of-masss energy of collisions in Kerr spacetime, known as the "BSW effect", can never be observed in nature. To emphasize this result, we present it in a more concise way which completely avoids any of the questions brought up by Zaslavskii. |
gr-qc/0502020 | Lorenzo Iorio | Lorenzo Iorio | On the possibility of measuring the post-Newtonian gravitoelectric
correction to the orbital period of a test body in a Solar System scenario | LateX2e, 5 pages, two-column, no figures, 1 table, 22 references.
Accepted for publication in Monthly Notices of the Royal Astronomical Society
(MNRAS) | Mon.Not.Roy.Astron.Soc.359:328-333,2005 | 10.1111/j.1365-2966.2005.08912.x | null | gr-qc astro-ph | null | The possibility of measuring the post-Newtonian gravitoelectric correction to
the orbital period of a test particle freely orbiting a spherically symmetric
mass in the Solar System is analyzed. It should be possible, in principle, to
detect it for Mercury at a precision level of 10^-4. This level is mainly set
by the unavoidable systematic errors due to the mismodelling in the Keplerian
period which could not be reduced by accumulating a large number of orbital
revolutions. Future missions like Messenger and BepiColombo should allow to
improve it by increasing our knowledge of the Mercury's orbital parameters. The
observational accuracy is estimated to be 10^-4 from the knowledge of the
International Celestial Reference Frame (ICRF) axes. It could be improved by
observing as many planetary transits as possible. It is not possible to measure
such an effect in the gravitational field of the Earth by analyzing the motion
of artificial satellites or the Moon because of the unavoidable systematic
errors related to the uncertainties in the Keplerian periods. In the case of
some recently discovered exoplanets the problems come from the observational
errors which are larger than the relativistic effect.
| [
{
"created": "Sat, 5 Feb 2005 12:45:35 GMT",
"version": "v1"
}
] | 2012-07-31 | [
[
"Iorio",
"Lorenzo",
""
]
] | The possibility of measuring the post-Newtonian gravitoelectric correction to the orbital period of a test particle freely orbiting a spherically symmetric mass in the Solar System is analyzed. It should be possible, in principle, to detect it for Mercury at a precision level of 10^-4. This level is mainly set by the unavoidable systematic errors due to the mismodelling in the Keplerian period which could not be reduced by accumulating a large number of orbital revolutions. Future missions like Messenger and BepiColombo should allow to improve it by increasing our knowledge of the Mercury's orbital parameters. The observational accuracy is estimated to be 10^-4 from the knowledge of the International Celestial Reference Frame (ICRF) axes. It could be improved by observing as many planetary transits as possible. It is not possible to measure such an effect in the gravitational field of the Earth by analyzing the motion of artificial satellites or the Moon because of the unavoidable systematic errors related to the uncertainties in the Keplerian periods. In the case of some recently discovered exoplanets the problems come from the observational errors which are larger than the relativistic effect. |
gr-qc/9704034 | York Xylander | Gerhard Mack | Pushing Einstein's Principles to the Extreme | null | null | null | null | gr-qc hep-lat hep-th | null | In these lectures I propose to push Einstein's principle of coordinate
independence to the extreme in order to restrict the possible form of
fundamental equations of motion in physics. I start from nearly tautological
system theoretic axioms. They provide a minimal amount of a priori structure
which is thought to be characteristic of human thinking in general. It is shown
how formal discretizations of Maxwell and Yang Mills theory in flat space and
of general relativity in Ashtekar variables fit into this frame work.
| [
{
"created": "Mon, 14 Apr 1997 09:07:07 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Mack",
"Gerhard",
""
]
] | In these lectures I propose to push Einstein's principle of coordinate independence to the extreme in order to restrict the possible form of fundamental equations of motion in physics. I start from nearly tautological system theoretic axioms. They provide a minimal amount of a priori structure which is thought to be characteristic of human thinking in general. It is shown how formal discretizations of Maxwell and Yang Mills theory in flat space and of general relativity in Ashtekar variables fit into this frame work. |
2107.13082 | Vera Delfavero | Vera Delfavero (1), Richard O'Shaughnessy (1), Daniel Wysocki (2),
Anjali Yelikar (1) ((1) Rochester Institute of Technology, (2) University of
Wisconsin - Milwaukee) | Normal Approximate Likelihoods to Gravitational Wave Events | null | null | null | LIGO-P2100274 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational wave observations of quasicircular compact binary mergers in
principle provide an arbitrarily complex likelihood over eight independent
intrinsic parameters: the masses and spins of the two merging objects. In this
work, we demonstrate by example that a simple normal approximation over fewer
(usually, three) effective dimensions provides a very accurate representation
of the likelihood, and allows us to replicate the eight-dimensional posterior
over the mass and spin degrees of freedom. Alongside this paper, we provide the
parameters for multivariate normal fits for each event published in GWTC-1 and
GWTC-2, using the posterior samples from the catalog for each associated
release. These normal approximations provide a highly efficient way to
characterize gravitational wave observations when combining large numbers of
events.
| [
{
"created": "Tue, 27 Jul 2021 21:14:38 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Jan 2022 23:00:21 GMT",
"version": "v2"
}
] | 2022-01-05 | [
[
"Delfavero",
"Vera",
""
],
[
"O'Shaughnessy",
"Richard",
""
],
[
"Wysocki",
"Daniel",
""
],
[
"Yelikar",
"Anjali",
""
]
] | Gravitational wave observations of quasicircular compact binary mergers in principle provide an arbitrarily complex likelihood over eight independent intrinsic parameters: the masses and spins of the two merging objects. In this work, we demonstrate by example that a simple normal approximation over fewer (usually, three) effective dimensions provides a very accurate representation of the likelihood, and allows us to replicate the eight-dimensional posterior over the mass and spin degrees of freedom. Alongside this paper, we provide the parameters for multivariate normal fits for each event published in GWTC-1 and GWTC-2, using the posterior samples from the catalog for each associated release. These normal approximations provide a highly efficient way to characterize gravitational wave observations when combining large numbers of events. |
2007.01828 | C. S. Unnikrishnan | C. S. Unnikrishnan and George T. Gillies | Gravitational Wave Test of the Strong Equivalence Principle | RevTeX, 8 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Strong Equivalence Principle (SEP) holds the full essence and meaning of
the General Theory of Relativity as the nonlinear relativistic theory of
gravitation. It asserts the universal coupling of gravity to all matter and its
interactions including the gravitational interaction and the gravitational self
energy. We point out that confirming the gravitational coupling to gravitons,
and hence to the gravitational waves, is the direct test of the SEP. We show
that the near simultaneous detection of gravitational waves and gamma rays from
the merger of binary neutron stars provides a unique and the most precise test
of the SEP, better than a part in $10^{9}$, which is also the only test of the
SEP in the radiation sector.
| [
{
"created": "Thu, 2 Jul 2020 14:35:00 GMT",
"version": "v1"
}
] | 2020-07-06 | [
[
"Unnikrishnan",
"C. S.",
""
],
[
"Gillies",
"George T.",
""
]
] | The Strong Equivalence Principle (SEP) holds the full essence and meaning of the General Theory of Relativity as the nonlinear relativistic theory of gravitation. It asserts the universal coupling of gravity to all matter and its interactions including the gravitational interaction and the gravitational self energy. We point out that confirming the gravitational coupling to gravitons, and hence to the gravitational waves, is the direct test of the SEP. We show that the near simultaneous detection of gravitational waves and gamma rays from the merger of binary neutron stars provides a unique and the most precise test of the SEP, better than a part in $10^{9}$, which is also the only test of the SEP in the radiation sector. |
1609.03957 | Ramon Herrera | Ramon Herrera, Joel Saavedra and Cuauhtemoc Campuzano | Curvaton reheating in non-minimal derivative coupling to gravity: NO
models | 22 pages, 4 figures | null | 10.1007/s10714-016-2133-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The curvaton reheating mechanism in a non-minimal derivative coupling to
gravity for any non-oscillating (NO) model is studied. In this framework, we
analyze the energy density during the kinetic epoch and we find that this
energy has a complicated dependencies of the scale factor. Considering this
mechanism, we study the decay of the curvaton in two different scenarios and
also we determine the reheating temperatures. As an example the NO model, we
consider an exponential potential and we obtain the reheating temperature
indirectly from the inflation through of the number of e-folds.
| [
{
"created": "Tue, 13 Sep 2016 18:07:50 GMT",
"version": "v1"
}
] | 2016-10-05 | [
[
"Herrera",
"Ramon",
""
],
[
"Saavedra",
"Joel",
""
],
[
"Campuzano",
"Cuauhtemoc",
""
]
] | The curvaton reheating mechanism in a non-minimal derivative coupling to gravity for any non-oscillating (NO) model is studied. In this framework, we analyze the energy density during the kinetic epoch and we find that this energy has a complicated dependencies of the scale factor. Considering this mechanism, we study the decay of the curvaton in two different scenarios and also we determine the reheating temperatures. As an example the NO model, we consider an exponential potential and we obtain the reheating temperature indirectly from the inflation through of the number of e-folds. |
gr-qc/0005034 | Piotr Jaranowski | Thibault Damour, Piotr Jaranowski, and Gerhard Schaefer | On the determination of the last stable orbit for circular general
relativistic binaries at the third post-Newtonian approximation | REVTeX, 25 pages, 3 figures, submitted to Phys. Rev. D | Phys.Rev. D62 (2000) 084011 | 10.1103/PhysRevD.62.084011 | null | gr-qc | null | We discuss the analytical determination of the location of the Last Stable
Orbit (LSO) in circular general relativistic orbits of two point masses. We use
several different ``resummation methods'' (including new ones) based on the
consideration of gauge-invariant functions, and compare the results they give
at the third post-Newtonian (3PN) approximation of general relativity. Our
treatment is based on the 3PN Hamiltonian of Jaranowski and Sch\"afer. One of
the new methods we introduce is based on the consideration of the (invariant)
function linking the angular momentum and the angular frequency. We also
generalize the ``effective one-body'' approach of Buonanno and Damour by
introducing a non-minimal (i.e. ``non-geodesic'') effective dynamics at the 3PN
level. We find that the location of the LSO sensitively depends on the
(currently unknown) value of the dimensionless quantity $\oms$ which
parametrizes a certain regularization ambiguity of the 3PN dynamics. We find,
however, that all the analytical methods we use numerically agree between
themselves if the value of this parameter is $\oms\simeq-9$. This suggests that
the correct value of $\oms$ is near -9 (the precise value
$\oms^*\equiv-{47/3}+{41/64}\pi^2=-9.3439...$ seems to play a special role). If
this is the case, we then show how to further improve the analytical
determination of various LSO quantities by using a ``Shanks'' transformation to
accelerate the convergence of the successive (already resummed) PN estimates.
| [
{
"created": "Wed, 10 May 2000 17:47:24 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Damour",
"Thibault",
""
],
[
"Jaranowski",
"Piotr",
""
],
[
"Schaefer",
"Gerhard",
""
]
] | We discuss the analytical determination of the location of the Last Stable Orbit (LSO) in circular general relativistic orbits of two point masses. We use several different ``resummation methods'' (including new ones) based on the consideration of gauge-invariant functions, and compare the results they give at the third post-Newtonian (3PN) approximation of general relativity. Our treatment is based on the 3PN Hamiltonian of Jaranowski and Sch\"afer. One of the new methods we introduce is based on the consideration of the (invariant) function linking the angular momentum and the angular frequency. We also generalize the ``effective one-body'' approach of Buonanno and Damour by introducing a non-minimal (i.e. ``non-geodesic'') effective dynamics at the 3PN level. We find that the location of the LSO sensitively depends on the (currently unknown) value of the dimensionless quantity $\oms$ which parametrizes a certain regularization ambiguity of the 3PN dynamics. We find, however, that all the analytical methods we use numerically agree between themselves if the value of this parameter is $\oms\simeq-9$. This suggests that the correct value of $\oms$ is near -9 (the precise value $\oms^*\equiv-{47/3}+{41/64}\pi^2=-9.3439...$ seems to play a special role). If this is the case, we then show how to further improve the analytical determination of various LSO quantities by using a ``Shanks'' transformation to accelerate the convergence of the successive (already resummed) PN estimates. |
1606.04364 | Ahmad Sheykhi | Ahmad Sheykhi and Fatemeh Shaker | Effects of backreaction and exponential nonlinear electrodynamics on the
holographic superconductors | 17 pages | International Journal of Modern Physics D Vol. 26, No. 5 (2017)
1750050 | 10.1142/S021827181750050X | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We analytically study the properties of a $(2+1)$-dimensional $s$-wave
holographic superconductor in the presence of exponential nonlinear
electrodynamics. We consider the case in which the scalar and gauge fields back
react on the background metric. Employing the analytical Sturm-Liouville
method, we find that in the black hole background, the nonlinear
electrodynamics correction will affect the properties of the holographic
superconductors. We find that with increasing both backreaction and nonlinear
parameters, the scalar hair condensation on the boundary will develop more
difficult. We obtain the relation connecting the critical temperature with the
charge density. Our analytical results support that, even in the presence of
the nonlinear electrodynamics and backreaction, the phase transition for the
holographic superconductor still belongs to the second order and the critical
exponent of the system always takes the mean-field value $1/2$.
| [
{
"created": "Mon, 13 Jun 2016 09:05:35 GMT",
"version": "v1"
}
] | 2017-01-12 | [
[
"Sheykhi",
"Ahmad",
""
],
[
"Shaker",
"Fatemeh",
""
]
] | We analytically study the properties of a $(2+1)$-dimensional $s$-wave holographic superconductor in the presence of exponential nonlinear electrodynamics. We consider the case in which the scalar and gauge fields back react on the background metric. Employing the analytical Sturm-Liouville method, we find that in the black hole background, the nonlinear electrodynamics correction will affect the properties of the holographic superconductors. We find that with increasing both backreaction and nonlinear parameters, the scalar hair condensation on the boundary will develop more difficult. We obtain the relation connecting the critical temperature with the charge density. Our analytical results support that, even in the presence of the nonlinear electrodynamics and backreaction, the phase transition for the holographic superconductor still belongs to the second order and the critical exponent of the system always takes the mean-field value $1/2$. |
gr-qc/0205081 | Lorenzo Iorio | Lorenzo Iorio | Is it possible to improve the present LAGEOS-LAGEOS II Lense-Thirring
experiment? | LaTeX2e, 1 table, no figures, 8 pages | Classical and Quantum Gravity, vol.19, no.21, pp. 5473-5480, 2002 | 10.1088/0264-9381/19/21/312 | null | gr-qc astro-ph physics.geo-ph physics.space-ph | null | The Lense-Thirring effect is currently being measured by means of a
combination of the orbital residuals of the nodes of LAGEOS and LAGEOS II and
the perigee of LAGEOS II. The total error is of the order of 20%. The most
insidious systematic error is due to the mismodelled even zonal harmonics of
the geopotential and amounts to 12.9%, according to EGM96 model. The role and
the importance of the LAGEOS--LAGEOS II Lense--Thirring experiment is
investigated. Using other suitable combinations with orbital elements of the
other existing laser-ranged satellites does not yield significative
improvements except for one combination including the nodes of LAGEOS, LAGEOS
II and Ajisai and the perigee of LAGEOS II. The related systematic error due to
the mismodelled even zonal part of the geopotential reduces to almost 10.7%.
| [
{
"created": "Sat, 18 May 2002 08:36:14 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Jun 2002 08:43:50 GMT",
"version": "v2"
},
{
"created": "Mon, 28 Oct 2002 15:48:08 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Iorio",
"Lorenzo",
""
]
] | The Lense-Thirring effect is currently being measured by means of a combination of the orbital residuals of the nodes of LAGEOS and LAGEOS II and the perigee of LAGEOS II. The total error is of the order of 20%. The most insidious systematic error is due to the mismodelled even zonal harmonics of the geopotential and amounts to 12.9%, according to EGM96 model. The role and the importance of the LAGEOS--LAGEOS II Lense--Thirring experiment is investigated. Using other suitable combinations with orbital elements of the other existing laser-ranged satellites does not yield significative improvements except for one combination including the nodes of LAGEOS, LAGEOS II and Ajisai and the perigee of LAGEOS II. The related systematic error due to the mismodelled even zonal part of the geopotential reduces to almost 10.7%. |
2012.05548 | Gyula Fodor | Gyula Fodor, Etevaldo dos Santos Costa Filho, Betti Hartmann | Calculation of multipole moments of axistationary electrovacuum
spacetimes | 44 pages. Two Mathematica and two equivalent Maple programs are
provided as ancillary files | Phys. Rev. D 104, 064012 (2021) | 10.1103/PhysRevD.104.064012 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The multipole moments of stationary axially symmetric vacuum or electrovacuum
spacetimes can be expressed in terms of the power series expansion coefficients
of the Ernst potential on the axis. In this paper we present a simpler, more
efficient calculation of the multipole moments, applying methods introduced by
B\"ackdahl and Herberthson. For the non-vacuum electromagnetic case, our
results for the octupole and higher moments differ from the results already
published in the literature. The reason for this difference is that we correct
an earlier unnoticed mistake in the power series solution of the Ernst
equations. We also apply the presented method to directly calculate the
multipole moments of a 5-parameter charged magnetized generalization of the
Kerr and Tomimatsu-Sato exact solutions.
| [
{
"created": "Thu, 10 Dec 2020 09:40:36 GMT",
"version": "v1"
}
] | 2021-09-15 | [
[
"Fodor",
"Gyula",
""
],
[
"Filho",
"Etevaldo dos Santos Costa",
""
],
[
"Hartmann",
"Betti",
""
]
] | The multipole moments of stationary axially symmetric vacuum or electrovacuum spacetimes can be expressed in terms of the power series expansion coefficients of the Ernst potential on the axis. In this paper we present a simpler, more efficient calculation of the multipole moments, applying methods introduced by B\"ackdahl and Herberthson. For the non-vacuum electromagnetic case, our results for the octupole and higher moments differ from the results already published in the literature. The reason for this difference is that we correct an earlier unnoticed mistake in the power series solution of the Ernst equations. We also apply the presented method to directly calculate the multipole moments of a 5-parameter charged magnetized generalization of the Kerr and Tomimatsu-Sato exact solutions. |
1607.01378 | Maur\'icio Richartz | Vitor Cardoso, Antonin Coutant, Mauricio Richartz, Silke Weinfurtner | Detecting Rotational Superradiance in Fluid Laboratories | v2: title change, matches published version in PRL | Phys. Rev. Lett. 117, 271101 (2016) | 10.1103/PhysRevLett.117.271101 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Rotational superradiance was predicted theoretically decades ago, and is
chiefly responsible for a number of important effects and phenomenology in
black-hole physics. However, rotational superradiance has never been observed
experimentally. Here, with the aim of probing superradiance in the lab, we
investigate the behavior of sound and surface waves in fluids resting in a
circular basin at the center of which a rotating cylinder is placed. We show
that with a suitable choice for the material of the cylinder, surface and sound
waves are amplified. Two types of instabilities are studied: one sets in
whenever superradiant modes are confined near the rotating cylinder and the
other, which does not rely on confinement, corresponds to a local excitation of
the cylinder. Our findings are experimentally testable in existing fluid
laboratories and, hence, offer experimental exploration and comparison of
dynamical instabilities arising from rapidly rotating boundary layers in
astrophysical as well as in fluid dynamical systems.
| [
{
"created": "Tue, 5 Jul 2016 19:32:02 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Dec 2016 22:23:50 GMT",
"version": "v2"
}
] | 2017-01-02 | [
[
"Cardoso",
"Vitor",
""
],
[
"Coutant",
"Antonin",
""
],
[
"Richartz",
"Mauricio",
""
],
[
"Weinfurtner",
"Silke",
""
]
] | Rotational superradiance was predicted theoretically decades ago, and is chiefly responsible for a number of important effects and phenomenology in black-hole physics. However, rotational superradiance has never been observed experimentally. Here, with the aim of probing superradiance in the lab, we investigate the behavior of sound and surface waves in fluids resting in a circular basin at the center of which a rotating cylinder is placed. We show that with a suitable choice for the material of the cylinder, surface and sound waves are amplified. Two types of instabilities are studied: one sets in whenever superradiant modes are confined near the rotating cylinder and the other, which does not rely on confinement, corresponds to a local excitation of the cylinder. Our findings are experimentally testable in existing fluid laboratories and, hence, offer experimental exploration and comparison of dynamical instabilities arising from rapidly rotating boundary layers in astrophysical as well as in fluid dynamical systems. |
gr-qc/0610151 | Yungui Gong | Yungui Gong, Bin Wang and Anzhong Wang | Thermodynamical properties of the Universe with dark energy | two figures; v2: minor corrections and updates, JCAP in press | JCAP 0701:024,2007 | 10.1088/1475-7516/2007/01/024 | null | gr-qc astro-ph hep-th | null | We have investigated the thermodynamical properties of the Universe with dark
energy. Adopting the usual assumption in deriving the constant co-moving
entropy density that the physical volume and the temperature are independent,
we observed some strange thermodynamical behaviors. However, these strange
behaviors disappeared if we consider the realistic situation that the physical
volume and the temperature of the Universe are related. Based on the well known
correspondence between the Friedmann equation and the first law of
thermodynamics of the apparent horizon, we argued that the apparent horizon is
the physical horizon in dealing with thermodynamics problems. We have
concentrated on the volume of the Universe within the apparent horizon and
considered that the Universe is in thermal equilibrium with the Hawking
temperature on the apparent horizon. For dark energy with $w\ge -1$, the
holographic principle and the generalized second law are always respected.
| [
{
"created": "Mon, 30 Oct 2006 18:16:54 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Jan 2007 21:19:14 GMT",
"version": "v2"
}
] | 2010-10-27 | [
[
"Gong",
"Yungui",
""
],
[
"Wang",
"Bin",
""
],
[
"Wang",
"Anzhong",
""
]
] | We have investigated the thermodynamical properties of the Universe with dark energy. Adopting the usual assumption in deriving the constant co-moving entropy density that the physical volume and the temperature are independent, we observed some strange thermodynamical behaviors. However, these strange behaviors disappeared if we consider the realistic situation that the physical volume and the temperature of the Universe are related. Based on the well known correspondence between the Friedmann equation and the first law of thermodynamics of the apparent horizon, we argued that the apparent horizon is the physical horizon in dealing with thermodynamics problems. We have concentrated on the volume of the Universe within the apparent horizon and considered that the Universe is in thermal equilibrium with the Hawking temperature on the apparent horizon. For dark energy with $w\ge -1$, the holographic principle and the generalized second law are always respected. |
2010.15845 | Wei Wei | Wei Wei, Asad Khan, E. A. Huerta, Xiaobo Huang, Minyang Tian | Deep Learning Ensemble for Real-time Gravitational Wave Detection of
Spinning Binary Black Hole Mergers | 10 pages, 7 figures | Physics Letters B 812 (2021) 136029 | 10.1016/j.physletb.2020.136029 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce the use of deep learning ensembles for real-time, gravitational
wave detection of spinning binary black hole mergers. This analysis consists of
training independent neural networks that simultaneously process strain data
from multiple detectors. The output of these networks is then combined and
processed to identify significant noise triggers. We have applied this
methodology in O2 and O3 data finding that deep learning ensembles clearly
identify binary black hole mergers in open source data available at the
Gravitational-Wave Open Science Center. We have also benchmarked the
performance of this new methodology by processing 200 hours of open source,
advanced LIGO noise from August 2017. Our findings indicate that our approach
identifies real gravitational wave sources in advanced LIGO data with a false
positive rate of 1 misclassification for every 2.7 days of searched data. A
follow up of these misclassifications identified them as glitches. Our deep
learning ensemble represents the first class of neural network classifiers that
are trained with millions of modeled waveforms that describe quasi-circular,
spinning, non-precessing, binary black hole mergers. Once fully trained, our
deep learning ensemble processes advanced LIGO strain data faster than
real-time using 4 NVIDIA V100 GPUs.
| [
{
"created": "Thu, 29 Oct 2020 18:00:03 GMT",
"version": "v1"
}
] | 2020-12-21 | [
[
"Wei",
"Wei",
""
],
[
"Khan",
"Asad",
""
],
[
"Huerta",
"E. A.",
""
],
[
"Huang",
"Xiaobo",
""
],
[
"Tian",
"Minyang",
""
]
] | We introduce the use of deep learning ensembles for real-time, gravitational wave detection of spinning binary black hole mergers. This analysis consists of training independent neural networks that simultaneously process strain data from multiple detectors. The output of these networks is then combined and processed to identify significant noise triggers. We have applied this methodology in O2 and O3 data finding that deep learning ensembles clearly identify binary black hole mergers in open source data available at the Gravitational-Wave Open Science Center. We have also benchmarked the performance of this new methodology by processing 200 hours of open source, advanced LIGO noise from August 2017. Our findings indicate that our approach identifies real gravitational wave sources in advanced LIGO data with a false positive rate of 1 misclassification for every 2.7 days of searched data. A follow up of these misclassifications identified them as glitches. Our deep learning ensemble represents the first class of neural network classifiers that are trained with millions of modeled waveforms that describe quasi-circular, spinning, non-precessing, binary black hole mergers. Once fully trained, our deep learning ensemble processes advanced LIGO strain data faster than real-time using 4 NVIDIA V100 GPUs. |
1011.3281 | Emanuele Berti | Ulrich Sperhake, Emanuele Berti, Vitor Cardoso, Frans Pretorius,
Nicolas Yunes | Superkicks in ultrarelativistic encounters of spinning black holes | 10 pages, 6 figures, 2 tables | Phys.Rev.D83:024037,2011 | 10.1103/PhysRevD.83.024037 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study ultrarelativistic encounters of two spinning, equal-mass black holes
through simulations in full numerical relativity. Two initial data sequences
are studied in detail: one that leads to scattering and one that leads to a
grazing collision and merger. In all cases, the initial black hole spins lie in
the orbital plane, a configuration that leads to the so-called "superkicks". In
astrophysical, quasicircular inspirals, such kicks can be as large as ~3,000
km/s; here, we find configurations that exceed ~15,000 km/s. We find that the
maximum recoil is to a good approximation proportional to the total amount of
energy radiated in gravitational waves, but largely independent of whether a
merger occurs or not. This shows that the mechanism predominantly responsible
for the superkick is not related to merger dynamics. Rather, a consistent
explanation is that the "bobbing" motion of the orbit causes an asymmetric
beaming of the radiation produced by the in-plane orbital motion of the binary,
and the net asymmetry is balanced by a recoil. We use our results to formulate
some conjectures on the ultimate kick achievable in any black hole encounter.
| [
{
"created": "Mon, 15 Nov 2010 03:26:32 GMT",
"version": "v1"
}
] | 2011-02-28 | [
[
"Sperhake",
"Ulrich",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Pretorius",
"Frans",
""
],
[
"Yunes",
"Nicolas",
""
]
] | We study ultrarelativistic encounters of two spinning, equal-mass black holes through simulations in full numerical relativity. Two initial data sequences are studied in detail: one that leads to scattering and one that leads to a grazing collision and merger. In all cases, the initial black hole spins lie in the orbital plane, a configuration that leads to the so-called "superkicks". In astrophysical, quasicircular inspirals, such kicks can be as large as ~3,000 km/s; here, we find configurations that exceed ~15,000 km/s. We find that the maximum recoil is to a good approximation proportional to the total amount of energy radiated in gravitational waves, but largely independent of whether a merger occurs or not. This shows that the mechanism predominantly responsible for the superkick is not related to merger dynamics. Rather, a consistent explanation is that the "bobbing" motion of the orbit causes an asymmetric beaming of the radiation produced by the in-plane orbital motion of the binary, and the net asymmetry is balanced by a recoil. We use our results to formulate some conjectures on the ultimate kick achievable in any black hole encounter. |
gr-qc/0703065 | Myungseok Yoon | Wontae Kim and Myung Seok Yoon | Positive Equation-of-state Parameter in the Accelerating Dilaton
Cosmology | 9 pages, 4 figures; to appear in the Journal of Korean Physical
Society | null | 10.3938/jkps.50.941 | null | gr-qc | null | In a semiclassically quantized two-dimensional cosmological model, it can be
shown that the parameter of the equation of state for the accelerating universe
can be positive due to the negative energy density and the negative pressure,
which is a little different from the conventional wisdom that the parameter is
negative with the positivity of the energy density. Furthermore, we show that
the full parameter composed of the classical and the quantum-mechanical
contributions is positive and finite even though the partial state parameter
from the quantum-mechanical contribution is not positive definite, which means
that the state parameter is not perturbatively additive in this model.
| [
{
"created": "Mon, 12 Mar 2007 02:55:23 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Kim",
"Wontae",
""
],
[
"Yoon",
"Myung Seok",
""
]
] | In a semiclassically quantized two-dimensional cosmological model, it can be shown that the parameter of the equation of state for the accelerating universe can be positive due to the negative energy density and the negative pressure, which is a little different from the conventional wisdom that the parameter is negative with the positivity of the energy density. Furthermore, we show that the full parameter composed of the classical and the quantum-mechanical contributions is positive and finite even though the partial state parameter from the quantum-mechanical contribution is not positive definite, which means that the state parameter is not perturbatively additive in this model. |
1602.02875 | Hiroyuki Nakano | Hiroyuki Nakano, Takashi Nakamura, Takahiro Tanaka | The detection of quasinormal mode with $a/M \sim 0.95$ would prove a
sphere $99\%$ soaking in the ergoregion of the Kerr space-time | 8 pages, 5 figures, accepted for publication in PTEP (Submitted on
Jan. 19, 2016) | Prog. Theor. Exp. Phys. (2016) 031E02 | 10.1093/ptep/ptw015 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent numerical relativity simulations of mergers of binary black holes
suggest that the maximum final value of $a/M$ is $\sim 0.95$ for the
coalescence of two equal mass black holes with aligned spins of the same
magnitude $a/M=0.994$ which is close to the upper limit $a/M=0.998$ of
accretion spin-up shown by Thorne. Using the WKB method, we suggest that if
quasinormal modes with $a/M \sim 0.95$ are detected by the second generation
gravitational wave detectors, we could confirm the strong gravity space-time
based on Einstein's general relativity up to $1.33M$ which is only $\sim 1.014$
times the event horizon radius and within the ergoregion. One more message
about black hole geometry is expected here. If the quasinormal mode is
different from that of general relativity, we need to find the true theory of
gravity which deviates from general relativity only near the black hole
horizon.
| [
{
"created": "Tue, 9 Feb 2016 06:57:54 GMT",
"version": "v1"
}
] | 2016-03-29 | [
[
"Nakano",
"Hiroyuki",
""
],
[
"Nakamura",
"Takashi",
""
],
[
"Tanaka",
"Takahiro",
""
]
] | Recent numerical relativity simulations of mergers of binary black holes suggest that the maximum final value of $a/M$ is $\sim 0.95$ for the coalescence of two equal mass black holes with aligned spins of the same magnitude $a/M=0.994$ which is close to the upper limit $a/M=0.998$ of accretion spin-up shown by Thorne. Using the WKB method, we suggest that if quasinormal modes with $a/M \sim 0.95$ are detected by the second generation gravitational wave detectors, we could confirm the strong gravity space-time based on Einstein's general relativity up to $1.33M$ which is only $\sim 1.014$ times the event horizon radius and within the ergoregion. One more message about black hole geometry is expected here. If the quasinormal mode is different from that of general relativity, we need to find the true theory of gravity which deviates from general relativity only near the black hole horizon. |
1511.01260 | Li-Xin Li | Li-Xin Li | A New Unified Theory of Electromagnetic and Gravitational Interactions | 41 pages, including 1 figure and 1 table. A new section is added to
describe the relation to the Kaluza-Klein theory. Version accepted to
Frontiers of Physics | Frontiers of Physics, Volume 11, Issue 6, article id. 110402
(2016) | 10.1007/s11467-016-0588-z | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we present a new unified theory of electromagnetic and
gravitational interactions. By considering a four-dimensional spacetime as a
hypersurface embedded in a five-dimensional bulk spacetime, we derive the
complete set of field equations in the four-dimensional spacetime from the
five-dimensional Einstein field equation. Besides the Einstein field equation
in the four-dimensional spacetime, an electromagnetic field equation is
derived: $\nabla_a F^{ab}-\xi R^b_{\;\,a}A^a=-4\pi J^b$ with $\xi=-2$, where
$F^{ab}$ is the antisymmetric electromagnetic field tensor defined by the
potential vector $A^a$, $R_{ab}$ is the Ricci curvature tensor of the
hypersurface, and $J^a$ is the electric current density vector. The
electromagnetic field equation differs from the Einstein-Maxwell equation by a
curvature-coupled term $\xi R^b_{\;\,a}A^a$, whose presence addresses the
problem of incompatibility of the Einstein-Maxwell equation with a universe
containing a uniformly distributed net charge as discussed in a previous paper
by the author [L.-X. Li, Gen. Relativ. Gravit. {\bf 48}, 28 (2016)]. Hence, the
new unified theory is physically different from the Kaluza-Klein theory and its
variants where the Einstein-Maxwell equation is derived. In the
four-dimensional Einstein field equation derived in the new theory, the source
term includes the stress-energy tensor of electromagnetic fields as well as the
stress-energy tensor of other unidentified matter. Under some conditions the
unidentified matter can be interpreted as a cosmological constant in the
four-dimensional spacetime. We argue that, the electromagnetic field equation
and hence the unified theory presented in this paper can be tested in an
environment with a high mass density, e.g., inside a neutron star or a white
dwarf, and in the early epoch of the universe.
| [
{
"created": "Wed, 4 Nov 2015 09:41:56 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Mar 2016 09:13:46 GMT",
"version": "v2"
}
] | 2016-07-05 | [
[
"Li",
"Li-Xin",
""
]
] | In this paper we present a new unified theory of electromagnetic and gravitational interactions. By considering a four-dimensional spacetime as a hypersurface embedded in a five-dimensional bulk spacetime, we derive the complete set of field equations in the four-dimensional spacetime from the five-dimensional Einstein field equation. Besides the Einstein field equation in the four-dimensional spacetime, an electromagnetic field equation is derived: $\nabla_a F^{ab}-\xi R^b_{\;\,a}A^a=-4\pi J^b$ with $\xi=-2$, where $F^{ab}$ is the antisymmetric electromagnetic field tensor defined by the potential vector $A^a$, $R_{ab}$ is the Ricci curvature tensor of the hypersurface, and $J^a$ is the electric current density vector. The electromagnetic field equation differs from the Einstein-Maxwell equation by a curvature-coupled term $\xi R^b_{\;\,a}A^a$, whose presence addresses the problem of incompatibility of the Einstein-Maxwell equation with a universe containing a uniformly distributed net charge as discussed in a previous paper by the author [L.-X. Li, Gen. Relativ. Gravit. {\bf 48}, 28 (2016)]. Hence, the new unified theory is physically different from the Kaluza-Klein theory and its variants where the Einstein-Maxwell equation is derived. In the four-dimensional Einstein field equation derived in the new theory, the source term includes the stress-energy tensor of electromagnetic fields as well as the stress-energy tensor of other unidentified matter. Under some conditions the unidentified matter can be interpreted as a cosmological constant in the four-dimensional spacetime. We argue that, the electromagnetic field equation and hence the unified theory presented in this paper can be tested in an environment with a high mass density, e.g., inside a neutron star or a white dwarf, and in the early epoch of the universe. |
gr-qc/9911041 | Jose Maria Pozo | Jose M. Pozo, Josep M. Parra | Clifford Algebra Approach to Superenergy Tensors | 6 pages, LaTeX, uses ere99.sty, contribution to proceedings of ERE99,
Bilbao, Sep 7th-10th | null | null | null | gr-qc | null | Senovilla has recently defined an algebraic construction of a superenergy
tensor T{A} from any arbitrary tensor A, by structuring it as an r-fold form.
This superenergy tensor satisfies automatically the dominant superenergy
property. We present a more compact definition using the r-direct product
Clifford algebra r-Cl(p,q). This form for the superenergy tensors allows to
obtain an easy proof of the dominant superenergy property valid for any
dimension.
| [
{
"created": "Wed, 10 Nov 1999 22:55:31 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Pozo",
"Jose M.",
""
],
[
"Parra",
"Josep M.",
""
]
] | Senovilla has recently defined an algebraic construction of a superenergy tensor T{A} from any arbitrary tensor A, by structuring it as an r-fold form. This superenergy tensor satisfies automatically the dominant superenergy property. We present a more compact definition using the r-direct product Clifford algebra r-Cl(p,q). This form for the superenergy tensors allows to obtain an easy proof of the dominant superenergy property valid for any dimension. |
1212.2880 | Angelo Tartaglia | Angelo Tartaglia (Politecnico di Torino and INFN) | Experimental determination of gravitomagnetic effects by means of ring
lasers | 9 pages, 9 figures, to appear on Journal of Physics: Conference
Series in the proceedings of NEB 15 (Chanya, June 2012) | null | 10.1088/1742-6596/453/1/012019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new experiment aimed to the detection of the gravito-magnetic
Lense-Thirring effect at the surface of the Earth will be presented; the name
of the experiment is GINGER. The proposed technique is based on the behavior of
light beams in ring lasers, also known as gyrolasers. A three-dimensional array
of ringlasers will be attached to a rigid monument; each ring will have a
different orientation in space. Within the space-time of a rotating mass the
propagation of light is indeed anisotropic; part of the anisotropy is purely
kinematical (Sagnac effect), part is due to the interaction between the
gravito-electric field of the source and the kinematical motion of the observer
(de Sitter effect), finally there is a contribution from the gravito-magnetic
component of the Earth (gravito-magnetic frame dragging or Lense-Thirring
effect). In a ring laser a light beam traveling counterclockwise is superposed
to another beam traveling in the opposite sense. The anisotropy in the
propagation leads to standing waves with slightly different frequencies in the
two directions; the final effect is a beat frequency proportional to the size
of the instrument and its effective rotation rate in space, including the
gravito-magnetic drag. Current laser techniques and the performances of the
best existing ring lasers allow at the moment a sensitivity within one order of
magnitude of the required accuracy for the detection of gravito-magnetic
effects, so that the objective of GINGER is in the range of feasibility and
aims to improve the sensitivity of a couple of orders of magnitude with respect
to present. The experiment will be underground, probably in the Gran Sasso
National Laboratories in Italy, and is based on an international collaboration
among four Italian groups, the Technische Universitaet Muenchen and the
University of Canterbury in Christchurch (NZ).
| [
{
"created": "Wed, 12 Dec 2012 16:44:45 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Tartaglia",
"Angelo",
"",
"Politecnico di Torino and INFN"
]
] | A new experiment aimed to the detection of the gravito-magnetic Lense-Thirring effect at the surface of the Earth will be presented; the name of the experiment is GINGER. The proposed technique is based on the behavior of light beams in ring lasers, also known as gyrolasers. A three-dimensional array of ringlasers will be attached to a rigid monument; each ring will have a different orientation in space. Within the space-time of a rotating mass the propagation of light is indeed anisotropic; part of the anisotropy is purely kinematical (Sagnac effect), part is due to the interaction between the gravito-electric field of the source and the kinematical motion of the observer (de Sitter effect), finally there is a contribution from the gravito-magnetic component of the Earth (gravito-magnetic frame dragging or Lense-Thirring effect). In a ring laser a light beam traveling counterclockwise is superposed to another beam traveling in the opposite sense. The anisotropy in the propagation leads to standing waves with slightly different frequencies in the two directions; the final effect is a beat frequency proportional to the size of the instrument and its effective rotation rate in space, including the gravito-magnetic drag. Current laser techniques and the performances of the best existing ring lasers allow at the moment a sensitivity within one order of magnitude of the required accuracy for the detection of gravito-magnetic effects, so that the objective of GINGER is in the range of feasibility and aims to improve the sensitivity of a couple of orders of magnitude with respect to present. The experiment will be underground, probably in the Gran Sasso National Laboratories in Italy, and is based on an international collaboration among four Italian groups, the Technische Universitaet Muenchen and the University of Canterbury in Christchurch (NZ). |
2103.07266 | Sebastian V\"olkel | Sebastian H. V\"olkel, Christian J. Kr\"uger, Kostas D. Kokkotas | Bayesian Inverse Problem of Rotating Neutron Stars | Accepted for publication in PRD, 9 pages, 3 figures | null | 10.1103/PhysRevD.103.083008 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we provide a framework that connects the co-rotating and counter
rotating $f$-mode frequencies of rotating neutron stars with their stellar
structure. The accurate computation of these modes for realistic equations of
state has been presented recently and they are here used as input for a
Bayesian analysis of the inverse problem. This allows to quantitatively
reconstruct basic neutron star parameters, such as the mass, radius, rotation
rate or universal scaling parameters. We find that future observations of both
$f$-mode frequencies, in combination with a Bayesian analysis, would provide a
promising direction to solve the inverse stellar problem. We provide two
complementary approaches, one that is equation of state dependent and one that
only uses universal scaling relations. We discuss advantages and disadvantages
of each approach, such as possible bias and robustness. The focus is on
astrophysically motivated scenarios in which informed prior information on the
neutron star mass or rotation rate can be provided and study how they impact
the results.
| [
{
"created": "Thu, 11 Mar 2021 10:30:24 GMT",
"version": "v1"
}
] | 2021-04-21 | [
[
"Völkel",
"Sebastian H.",
""
],
[
"Krüger",
"Christian J.",
""
],
[
"Kokkotas",
"Kostas D.",
""
]
] | In this work we provide a framework that connects the co-rotating and counter rotating $f$-mode frequencies of rotating neutron stars with their stellar structure. The accurate computation of these modes for realistic equations of state has been presented recently and they are here used as input for a Bayesian analysis of the inverse problem. This allows to quantitatively reconstruct basic neutron star parameters, such as the mass, radius, rotation rate or universal scaling parameters. We find that future observations of both $f$-mode frequencies, in combination with a Bayesian analysis, would provide a promising direction to solve the inverse stellar problem. We provide two complementary approaches, one that is equation of state dependent and one that only uses universal scaling relations. We discuss advantages and disadvantages of each approach, such as possible bias and robustness. The focus is on astrophysically motivated scenarios in which informed prior information on the neutron star mass or rotation rate can be provided and study how they impact the results. |
gr-qc/0104102 | Jose Geraldo Pereira | V. C. de Andrade, L. C. T. Guillen, J. G. Pereira | Teleparallel Spin Connection | 2 pages, RevTeX, to appear in Phys. Rev D (Brief Report) | Phys.Rev. D64 (2001) 027502 | 10.1103/PhysRevD.64.027502 | IFT-P.031/2001 | gr-qc | null | A new expression for the spin connection of teleparallel gravity is proposed,
given by minus the contorsion tensor plus a zero connection. The corresponding
minimal coupling is covariant under local Lorentz transformation, and
equivalent to the minimal coupling prescription of general relativity. With
this coupling prescription, therefore, teleparallel gravity turns out to be
fully equivalent to general relativity, even in the presence of spinor fields.
| [
{
"created": "Mon, 30 Apr 2001 20:57:23 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"de Andrade",
"V. C.",
""
],
[
"Guillen",
"L. C. T.",
""
],
[
"Pereira",
"J. G.",
""
]
] | A new expression for the spin connection of teleparallel gravity is proposed, given by minus the contorsion tensor plus a zero connection. The corresponding minimal coupling is covariant under local Lorentz transformation, and equivalent to the minimal coupling prescription of general relativity. With this coupling prescription, therefore, teleparallel gravity turns out to be fully equivalent to general relativity, even in the presence of spinor fields. |
1306.2168 | Bijan Saha Dr. | Mohd.Zeyauddin and Bijan Saha | Bianchi type V bulk viscous cosmological models with particle creation
in General Relativity | 23 pages, 32 Figures | The European Physical Journal Plus 129 (2014) 177 | 10.1140/epjp/i2014-14177-0 | null | gr-qc physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, a spatially homogeneous and anisotropic Bianchi type V model
filled with an imperfect fluid with bulk viscosity and particle creation, is
investigated within the framework of General Relativity. Particle creation and
bulk viscosity have been considered as separate irreversible processes. The
energy- momentum tensor is modified to accommodate the viscous pressure and
creation pressure which is associated with creation of matter out of
gravitational field. Exact solutions of the field equations are obtained by
applying a special law of variation of Hubble parameter. Using this assumption,
we obtain two types of cosmological models. We find a singularity in the first
model whereas second model is non-singular. Further we separately study the
bulk viscosity and particle creation in each model considering four different
cases. The bulk viscosity coefficient $\zeta$ is obtained for Truncated, Full
Causal and Eckart theories in all cases. All physical parameters are calculated
and thoroughly discussed in both models.
| [
{
"created": "Mon, 10 Jun 2013 11:37:41 GMT",
"version": "v1"
}
] | 2015-05-01 | [
[
"Zeyauddin",
"Mohd.",
""
],
[
"Saha",
"Bijan",
""
]
] | In this paper, a spatially homogeneous and anisotropic Bianchi type V model filled with an imperfect fluid with bulk viscosity and particle creation, is investigated within the framework of General Relativity. Particle creation and bulk viscosity have been considered as separate irreversible processes. The energy- momentum tensor is modified to accommodate the viscous pressure and creation pressure which is associated with creation of matter out of gravitational field. Exact solutions of the field equations are obtained by applying a special law of variation of Hubble parameter. Using this assumption, we obtain two types of cosmological models. We find a singularity in the first model whereas second model is non-singular. Further we separately study the bulk viscosity and particle creation in each model considering four different cases. The bulk viscosity coefficient $\zeta$ is obtained for Truncated, Full Causal and Eckart theories in all cases. All physical parameters are calculated and thoroughly discussed in both models. |
1912.11667 | Sukanta Bose | William Dupree and Sukanta Bose | Multi-detector null-stream-based $\chi^2$ statistic for compact binary
coalescence searches | 14 pages, 5 figures, published in Classical and Quantum Gravity | Class. Quantum Grav. 36 (2019) 195012 | 10.1088/1361-6382/ab30cf | null | gr-qc astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a new multi-detector signal-based discriminator to improve the
sensitivity of searches for gravitational waves from compact binary
coalescences. The new statistic is the traditional $\chi^2$ computed on a
null-stream synthesized from the gravitational-wave detector strain time-series
of three detectors. This null-stream-$\chi^2$ statistic can be extended to
networks involving more than three detectors as well. The null-stream itself
was proposed as a discriminator between correlated unmodeled signals in
multiple detectors, such as arising from a common astrophysical source, and
uncorrelated noise transients. It can be useful even when the signal model is
known, such as for compact binary coalescences. The traditional $\chi^2$, on
the other hand, is an effective discriminator when the signal model is known
and lends itself to the matched-filtering technique. The latter weakens in its
effectiveness when a signal lacks enough cycles in band; this can happen for
high-mass black hole binaries. The former weakens when there are concurrent
noise transients in different detectors in the network or the detector
sensitivities are substantially different. Using simulated binary black hole
signals, noise transients and strain for Advanced LIGO (in Livingston and
Hanford) and Advanced Virgo detectors, we compare the performance of the
null-stream-$\chi^2$ statistic with that of the traditional $\chi^2$ statistic
using receiver-operating characteristics. The new statistic may form the basis
for better signal-noise discriminators in multi-detector searches in the
future.
| [
{
"created": "Wed, 25 Dec 2019 13:33:51 GMT",
"version": "v1"
}
] | 2019-12-30 | [
[
"Dupree",
"William",
""
],
[
"Bose",
"Sukanta",
""
]
] | We develop a new multi-detector signal-based discriminator to improve the sensitivity of searches for gravitational waves from compact binary coalescences. The new statistic is the traditional $\chi^2$ computed on a null-stream synthesized from the gravitational-wave detector strain time-series of three detectors. This null-stream-$\chi^2$ statistic can be extended to networks involving more than three detectors as well. The null-stream itself was proposed as a discriminator between correlated unmodeled signals in multiple detectors, such as arising from a common astrophysical source, and uncorrelated noise transients. It can be useful even when the signal model is known, such as for compact binary coalescences. The traditional $\chi^2$, on the other hand, is an effective discriminator when the signal model is known and lends itself to the matched-filtering technique. The latter weakens in its effectiveness when a signal lacks enough cycles in band; this can happen for high-mass black hole binaries. The former weakens when there are concurrent noise transients in different detectors in the network or the detector sensitivities are substantially different. Using simulated binary black hole signals, noise transients and strain for Advanced LIGO (in Livingston and Hanford) and Advanced Virgo detectors, we compare the performance of the null-stream-$\chi^2$ statistic with that of the traditional $\chi^2$ statistic using receiver-operating characteristics. The new statistic may form the basis for better signal-noise discriminators in multi-detector searches in the future. |
1911.10996 | Qingyu Gan | Qingyu Gan, Peng Wang, Houwen Wu and Haitang Yang | Strong cosmic censorship for a scalar field in an
Einstein-Maxwell-Gauss-Bonnet-de Sitter black hole | v1: 24 pages, 6 figures; v2: 24 pages, 6 figures and 1 table.
Significantly revised. Comments and references added | null | null | CTP-SCU/2019019 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been shown that the Christodoulou version of the Strong Cosmic
Censorship (SCC) conjecture can be violated for a scalar field in a
near-extremal Reissner-Nordstrom-de Sitter black hole. In this paper, we
investigate the effects of higher derivative corrections to the
Einstein-Hilbert action on the validity of SCC, by considering a neutral
massless scalar perturbation in 5- and 6-dimensional
Einstein-Maxwell-Gauss-Bonnet-de Sitter black holes. Our numerical results
exhibit that the higher derivative term plays a different role in the d = 5
case than it does in the d = 6 case. For d = 5, the SCC violation region
increases as the strength of the higher derivative term increases. For d = 6,
the SCC violation region first increases and then decreases as the higher
derivative correction becomes stronger, and SCC can always be restored for a
black hole with a fixed charge ratio when the higher derivative correction is
strong enough. Finally, we find that the C2 version of SCC is respected in the
d = 6 case, but can be violated in some near-extremal regime in the d = 5 case.
| [
{
"created": "Mon, 25 Nov 2019 15:42:20 GMT",
"version": "v1"
},
{
"created": "Sun, 1 Dec 2019 14:16:33 GMT",
"version": "v2"
}
] | 2019-12-03 | [
[
"Gan",
"Qingyu",
""
],
[
"Wang",
"Peng",
""
],
[
"Wu",
"Houwen",
""
],
[
"Yang",
"Haitang",
""
]
] | It has been shown that the Christodoulou version of the Strong Cosmic Censorship (SCC) conjecture can be violated for a scalar field in a near-extremal Reissner-Nordstrom-de Sitter black hole. In this paper, we investigate the effects of higher derivative corrections to the Einstein-Hilbert action on the validity of SCC, by considering a neutral massless scalar perturbation in 5- and 6-dimensional Einstein-Maxwell-Gauss-Bonnet-de Sitter black holes. Our numerical results exhibit that the higher derivative term plays a different role in the d = 5 case than it does in the d = 6 case. For d = 5, the SCC violation region increases as the strength of the higher derivative term increases. For d = 6, the SCC violation region first increases and then decreases as the higher derivative correction becomes stronger, and SCC can always be restored for a black hole with a fixed charge ratio when the higher derivative correction is strong enough. Finally, we find that the C2 version of SCC is respected in the d = 6 case, but can be violated in some near-extremal regime in the d = 5 case. |
2010.15771 | Ellery Ames | Ellery Ames, H\r{a}kan Andr\'easson, Oliver Rinne | Dynamics of gravitational collapse in the axisymmetric Einstein-Vlasov
system | Accepted version. 33 pages; 11 figures | null | 10.1088/1361-6382/abdd0c | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We numerically investigate the dynamics near black hole formation of
solutions to the Einstein--Vlasov system in axisymmetry. Our results are
obtained using a particle-in-cell and finite difference code based on the
$(2+1)+1$ formulation of the Einstein field equations in axisymmetry. Solutions
are launched from non-stationary initial data and exhibit type I critical
behaviour. In particular, we find lifetime scaling in solutions containing
black holes, and support that the critical solutions are stationary. Our
results contain examples of solutions that form black holes, perform damped
oscillations, and appear to disperse. We prove that complete dispersal of the
solution implies that it has nonpositive binding energy.
| [
{
"created": "Thu, 29 Oct 2020 17:15:23 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Feb 2021 00:09:25 GMT",
"version": "v2"
}
] | 2021-02-05 | [
[
"Ames",
"Ellery",
""
],
[
"Andréasson",
"Håkan",
""
],
[
"Rinne",
"Oliver",
""
]
] | We numerically investigate the dynamics near black hole formation of solutions to the Einstein--Vlasov system in axisymmetry. Our results are obtained using a particle-in-cell and finite difference code based on the $(2+1)+1$ formulation of the Einstein field equations in axisymmetry. Solutions are launched from non-stationary initial data and exhibit type I critical behaviour. In particular, we find lifetime scaling in solutions containing black holes, and support that the critical solutions are stationary. Our results contain examples of solutions that form black holes, perform damped oscillations, and appear to disperse. We prove that complete dispersal of the solution implies that it has nonpositive binding energy. |
gr-qc/0611009 | Daniel Pollack | Yvonne Choquet-Bruhat, James Isenberg and Daniel Pollack | Applications of theorems of Jean Leray to the Einstein-scalar field
equations | null | null | null | null | gr-qc math.AP math.DG | null | The Einstein-scalar field theory can be used to model gravitational physics
with scalar field matter sources. We discuss the initial value formulation of
this field theory, and show that the ideas of Leray can be used to show that
the Einstein-scalar field system of partial differential equations is
well-posed as an evolutionary system. We also show that one can generate
solutions of the Einstein-scalar field constraint equations using conformal
methods.
| [
{
"created": "Thu, 2 Nov 2006 00:24:50 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Choquet-Bruhat",
"Yvonne",
""
],
[
"Isenberg",
"James",
""
],
[
"Pollack",
"Daniel",
""
]
] | The Einstein-scalar field theory can be used to model gravitational physics with scalar field matter sources. We discuss the initial value formulation of this field theory, and show that the ideas of Leray can be used to show that the Einstein-scalar field system of partial differential equations is well-posed as an evolutionary system. We also show that one can generate solutions of the Einstein-scalar field constraint equations using conformal methods. |
gr-qc/9704033 | null | Vladimir S. Mashkevich (Institute of Physics, Kiev) | Indeterministic Quantum Gravity and Cosmology VI. Predynamical Geometry
of Spacetime Manifold, Supplementary Conditions for Metric, and CPT | 10 pages, LATEX 2.09 | null | null | IP 5/97 | gr-qc | null | This paper is a continuation of the papers [gr-qc/9409010, gr-qc/9505034,
gr-qc/9603022, gr-qc/9609035, gr-qc/9609046]. The introduction of a prior,
i.e., predynamical global geometry of spacetime manifold is substantiated, and
the geometry is specified. The manifold is an infinite four-cylinder, or tube
in the five-dimensional Euclidean space, the orthogonal section of the cylinder
being the unit three-sphere. Supplementary conditions for metric are introduced
geometrically, coordinate-independently, as opposed to coordinate conditions.
Parity and time-reversal transformations are extended to the manifold
specified. PT is equivalent to a rotation through \pi about an axis orthogonal
to the cylinder axis. CPT invariance is discussed.
Keywords: cosmic time, cosmic space, cylindrical manifold
| [
{
"created": "Sun, 13 Apr 1997 21:36:36 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Mashkevich",
"Vladimir S.",
"",
"Institute of Physics, Kiev"
]
] | This paper is a continuation of the papers [gr-qc/9409010, gr-qc/9505034, gr-qc/9603022, gr-qc/9609035, gr-qc/9609046]. The introduction of a prior, i.e., predynamical global geometry of spacetime manifold is substantiated, and the geometry is specified. The manifold is an infinite four-cylinder, or tube in the five-dimensional Euclidean space, the orthogonal section of the cylinder being the unit three-sphere. Supplementary conditions for metric are introduced geometrically, coordinate-independently, as opposed to coordinate conditions. Parity and time-reversal transformations are extended to the manifold specified. PT is equivalent to a rotation through \pi about an axis orthogonal to the cylinder axis. CPT invariance is discussed. Keywords: cosmic time, cosmic space, cylindrical manifold |
1409.0533 | Hirotada Okawa | Hirotada Okawa, Vitor Cardoso, Paolo Pani | On the nonlinear instability of confined geometries | 14 pages, 9 figures; v2:Some improvements in convergence results,
accepted for publication in Physical Review D | null | 10.1103/PhysRevD.90.104032 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The discovery of a "weakly-turbulent" instability of anti-de Sitter spacetime
supports the idea that confined fluctuations eventually collapse to black holes
and suggests that similar phenomena might be possible in asymptotically-flat
spacetime, for example in the context of spherically symmetric oscillations of
stars or nonradial pulsations of ultracompact objects. Here we present a
detailed study of the evolution of the Einstein-Klein-Gordon system in a
cavity, with different types of deformations of the spectrum, including a mass
term for the scalar and Neumann conditions at the boundary. We provide
numerical evidence that gravitational collapse always occurs, at least for
amplitudes that are three orders of magnitude smaller than Choptuik's critical
value and corresponding to more than $10^5$ reflections before collapse. The
collapse time scales as the inverse square of the initial amplitude in the
small-amplitude limit. In addition, we find that fields with nonresonant
spectrum collapse earlier than in the fully-resonant case, a result that is at
odds with the current understanding of the process. Energy is transferred
through a direct cascade to high frequencies when the spectrum is resonant, but
we observe both direct- and inverse-cascade effects for nonresonant spectra.
Our results indicate that a fully-resonant spectrum might not be a crucial
ingredient of the conjectured turbulent instability and that other mechanisms
might be relevant. We discuss how a definitive answer to this problem is
essentially impossible within the present framework.
| [
{
"created": "Mon, 1 Sep 2014 20:00:07 GMT",
"version": "v1"
},
{
"created": "Sat, 18 Oct 2014 10:44:32 GMT",
"version": "v2"
}
] | 2015-06-22 | [
[
"Okawa",
"Hirotada",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Pani",
"Paolo",
""
]
] | The discovery of a "weakly-turbulent" instability of anti-de Sitter spacetime supports the idea that confined fluctuations eventually collapse to black holes and suggests that similar phenomena might be possible in asymptotically-flat spacetime, for example in the context of spherically symmetric oscillations of stars or nonradial pulsations of ultracompact objects. Here we present a detailed study of the evolution of the Einstein-Klein-Gordon system in a cavity, with different types of deformations of the spectrum, including a mass term for the scalar and Neumann conditions at the boundary. We provide numerical evidence that gravitational collapse always occurs, at least for amplitudes that are three orders of magnitude smaller than Choptuik's critical value and corresponding to more than $10^5$ reflections before collapse. The collapse time scales as the inverse square of the initial amplitude in the small-amplitude limit. In addition, we find that fields with nonresonant spectrum collapse earlier than in the fully-resonant case, a result that is at odds with the current understanding of the process. Energy is transferred through a direct cascade to high frequencies when the spectrum is resonant, but we observe both direct- and inverse-cascade effects for nonresonant spectra. Our results indicate that a fully-resonant spectrum might not be a crucial ingredient of the conjectured turbulent instability and that other mechanisms might be relevant. We discuss how a definitive answer to this problem is essentially impossible within the present framework. |
1702.01380 | Ahmad Al-Badawi | Ahmad Al-Badawi | Behaviour of a spin-1/2 particle in Schwarzschild embedded in an
electromagnetic universe | 17 pages, 7 figures. arXiv admin note: substantial text overlap with
arXiv:1702.00368 | General Relativity and Gravitation (2018) 50:16 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Dirac equation is considered in Schwarzschild black hole immersed in an
electromagnetic universe with charge coupling. The equations of the charged
spin-1/2 particle is separated into radial and angular equations by adopting
the Newman-Penrose formalism. The angular equations obtained are similar to the
Schwarzschild geometry. For the radial equations we manage to obtain the one
dimensional Schr\"odinger-type wave equations with effective potentials. Due to
the presence of electromagnetic field from the surroundings, the interaction
with the charged spin-1/2 is considered. Finally, we study the behaviour of the
potentials by plotting them as a function of radial distance and expose the
effect of the external parameter, charge and the frequency of the particle on
them.
| [
{
"created": "Sun, 5 Feb 2017 08:41:39 GMT",
"version": "v1"
}
] | 2019-07-19 | [
[
"Al-Badawi",
"Ahmad",
""
]
] | The Dirac equation is considered in Schwarzschild black hole immersed in an electromagnetic universe with charge coupling. The equations of the charged spin-1/2 particle is separated into radial and angular equations by adopting the Newman-Penrose formalism. The angular equations obtained are similar to the Schwarzschild geometry. For the radial equations we manage to obtain the one dimensional Schr\"odinger-type wave equations with effective potentials. Due to the presence of electromagnetic field from the surroundings, the interaction with the charged spin-1/2 is considered. Finally, we study the behaviour of the potentials by plotting them as a function of radial distance and expose the effect of the external parameter, charge and the frequency of the particle on them. |
1702.02760 | Hakan Cebeci | Hakan Cebeci, N\"ulifer \"Ozdemir, Se\c{c}il \c{S}entorun | The equatorial motion of the charged test particles in
Kerr-Newman-Taub-NUT spacetime | title changed , revised version | Gen. Rel. Grav. 51 , No : 7 , 85 (2019) | 10.1007/s10714-019-2569-3 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we perform a detailed analysis of the equatorial motion of the
charged test particles in Kerr-Newman-Taub-NUT spacetime. By working out the
orbit equation in the radial direction, we examine possible orbit types. We
investigate the conditions for existence of bound orbits in
causality-preserving region as well as the conditions for existence of circular
orbits for charged and uncharged particles. We also study the effect of NUT
parameter on Newtonian orbits. Finally, we give exact analytical solutions of
equations of equatorial motion for a charged test particle.
| [
{
"created": "Thu, 9 Feb 2017 09:27:58 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jul 2017 13:31:51 GMT",
"version": "v2"
},
{
"created": "Thu, 18 Jul 2019 08:03:51 GMT",
"version": "v3"
}
] | 2019-07-19 | [
[
"Cebeci",
"Hakan",
""
],
[
"Özdemir",
"Nülifer",
""
],
[
"Şentorun",
"Seçil",
""
]
] | In this work, we perform a detailed analysis of the equatorial motion of the charged test particles in Kerr-Newman-Taub-NUT spacetime. By working out the orbit equation in the radial direction, we examine possible orbit types. We investigate the conditions for existence of bound orbits in causality-preserving region as well as the conditions for existence of circular orbits for charged and uncharged particles. We also study the effect of NUT parameter on Newtonian orbits. Finally, we give exact analytical solutions of equations of equatorial motion for a charged test particle. |
2408.06032 | Michael Ebersold | Michael Ebersold, Tania Regimbau, Nelson Christensen | Next-generation global gravitational-wave detector network: Impact of
detector orientation on compact binary coalescence and stochastic
gravitational-wave background searches | 18 pages, 14 figures, 3 tables | null | null | null | gr-qc astro-ph.CO astro-ph.HE astro-ph.IM | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Next-generation gravitational-wave detectors like the Einstein Telescope and
Cosmic Explorer, currently in their preparatory phase, have the potential to
significantly improve our understanding of astrophysics, cosmology and
fundamental physics. We examine how the arm orientations of the proposed
detectors influence the sensitivity of a combined Einstein Telescope - Cosmic
Explorer network with respect to the sensitivity to the stochastic
gravitational-wave background and compact binary coalescences, where measuring
both gravitational-wave polarizations is favorable. We present a method to
optimize the arm orientations in the network for these two targets, and also
demonstrate how to achieve a balanced configuration for both stochastic
background and compact binary coalescence searches. For five specific network
configurations, we explicitly compare the sensitivity to the stochastic
background and binary neutron star mergers. For the latter, we conduct Bayesian
parameter estimation on the extrinsic parameters of a reference binary neutron
star system to assess sky localization and distance estimation capabilities.
These are illustrated through efficiency curves showing the fraction of events
meeting sky localization and distance uncertainty criteria as a function of
redshift. Our findings suggest that globally coordinating efforts towards the
next-generation gravitational-wave detector network is advantageous.
| [
{
"created": "Mon, 12 Aug 2024 09:48:28 GMT",
"version": "v1"
}
] | 2024-08-13 | [
[
"Ebersold",
"Michael",
""
],
[
"Regimbau",
"Tania",
""
],
[
"Christensen",
"Nelson",
""
]
] | Next-generation gravitational-wave detectors like the Einstein Telescope and Cosmic Explorer, currently in their preparatory phase, have the potential to significantly improve our understanding of astrophysics, cosmology and fundamental physics. We examine how the arm orientations of the proposed detectors influence the sensitivity of a combined Einstein Telescope - Cosmic Explorer network with respect to the sensitivity to the stochastic gravitational-wave background and compact binary coalescences, where measuring both gravitational-wave polarizations is favorable. We present a method to optimize the arm orientations in the network for these two targets, and also demonstrate how to achieve a balanced configuration for both stochastic background and compact binary coalescence searches. For five specific network configurations, we explicitly compare the sensitivity to the stochastic background and binary neutron star mergers. For the latter, we conduct Bayesian parameter estimation on the extrinsic parameters of a reference binary neutron star system to assess sky localization and distance estimation capabilities. These are illustrated through efficiency curves showing the fraction of events meeting sky localization and distance uncertainty criteria as a function of redshift. Our findings suggest that globally coordinating efforts towards the next-generation gravitational-wave detector network is advantageous. |
1906.12034 | Yunho Kim | Yunho Kim, Archil Kobakhidze, and Zachary S. C. Picker | Probing Quadratic Gravity with Binary Inspirals | 9 pages. v3: Section 4 is modified, results are unaltered. v4:
Matches the journal version | null | null | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study gravitational waves generated by binary systems
within an extension of General Relativity which is described by the addition of
quadratic in curvature tensor terms to the Einstein-Hilbert action. Treating
quadratic gravity as an effective theory valid in the low energy/curvature
regime, we argue that reliable calculations can be performed in the early
inspiral phase, and furthermore, no flux of additional massive waves can be
detected. We then compute the massive dipole (-1PN) leading corrections to the
post-Newtonian (PN) expansion of the standard waveform. By confronting these
theoretical calculations with available experimental data, we constrain both
unknown parameters of quadratic gravity to be $0 \leq \gamma \, \lesssim
5.7\cdot 10^{76}$, and $-\frac{\gamma}{4} \leq \beta \, \lesssim - 4.2\cdot
10^{75}$.
| [
{
"created": "Fri, 28 Jun 2019 04:03:50 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jul 2019 04:45:04 GMT",
"version": "v2"
},
{
"created": "Mon, 16 Mar 2020 08:41:44 GMT",
"version": "v3"
},
{
"created": "Mon, 21 Jun 2021 02:59:48 GMT",
"version": "v4"
}
] | 2021-06-22 | [
[
"Kim",
"Yunho",
""
],
[
"Kobakhidze",
"Archil",
""
],
[
"Picker",
"Zachary S. C.",
""
]
] | In this paper, we study gravitational waves generated by binary systems within an extension of General Relativity which is described by the addition of quadratic in curvature tensor terms to the Einstein-Hilbert action. Treating quadratic gravity as an effective theory valid in the low energy/curvature regime, we argue that reliable calculations can be performed in the early inspiral phase, and furthermore, no flux of additional massive waves can be detected. We then compute the massive dipole (-1PN) leading corrections to the post-Newtonian (PN) expansion of the standard waveform. By confronting these theoretical calculations with available experimental data, we constrain both unknown parameters of quadratic gravity to be $0 \leq \gamma \, \lesssim 5.7\cdot 10^{76}$, and $-\frac{\gamma}{4} \leq \beta \, \lesssim - 4.2\cdot 10^{75}$. |
2310.04489 | Mark Ho-Yeuk Cheung | Mark Ho-Yeuk Cheung, Emanuele Berti, Vishal Baibhav, Roberto Cotesta | Extracting linear and nonlinear quasinormal modes from black hole merger
simulations | 38 pages, 22 figures, 2 tables. Interactive plots and code usage
examples available at https://mhycheung.github.io/jaxqualin/. The fitting
formulas in Eq. (13) have been updated to match an erratum accepted by PRD.
None of the figures are affected | Phys. Rev. D 109 (2024) 4, 044069 | 10.1103/PhysRevD.109.044069 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In general relativity, when two black holes merge they produce a rotating
(Kerr) black hole remnant. According to perturbation theory, the remnant emits
"ringdown" radiation: a superposition of exponentials with characteristic
complex frequencies that depend only on the remnant's mass and spin. While the
goal of the black hole spectroscopy program is to measure the quasinormal mode
frequencies, a knowledge of their amplitudes and phases is equally important to
determine which modes are detectable, and possibly to perform additional
consistency checks. Unlike the complex frequencies, the amplitudes and phases
depend on the properties of the binary progenitors, such as the binary mass
ratio and component spins. In this paper we develop a fitting algorithm
designed to reliably identify the modes present in numerical simulations and to
extract their amplitudes and phases. We apply the algorithm to over 500 binary
black hole simulations from the public SXS numerical relativity simulation
catalog, and we present fitting formulas for the resulting mode amplitudes and
phases as functions of the properties of the progenitors. Crucially, our
algorithm allows for the extraction of not only prograde fundamental modes and
overtones, but also retrograde modes and second-order modes. We unveil
interesting relations for the amplitude ratios of different modes. The fitting
code and interactive versions of some of the plots are publicly available. The
results presented in this paper can be updated as more and better simulations
become available.
| [
{
"created": "Fri, 6 Oct 2023 18:00:00 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Oct 2023 21:21:26 GMT",
"version": "v2"
},
{
"created": "Fri, 9 Aug 2024 23:47:29 GMT",
"version": "v3"
}
] | 2024-08-13 | [
[
"Cheung",
"Mark Ho-Yeuk",
""
],
[
"Berti",
"Emanuele",
""
],
[
"Baibhav",
"Vishal",
""
],
[
"Cotesta",
"Roberto",
""
]
] | In general relativity, when two black holes merge they produce a rotating (Kerr) black hole remnant. According to perturbation theory, the remnant emits "ringdown" radiation: a superposition of exponentials with characteristic complex frequencies that depend only on the remnant's mass and spin. While the goal of the black hole spectroscopy program is to measure the quasinormal mode frequencies, a knowledge of their amplitudes and phases is equally important to determine which modes are detectable, and possibly to perform additional consistency checks. Unlike the complex frequencies, the amplitudes and phases depend on the properties of the binary progenitors, such as the binary mass ratio and component spins. In this paper we develop a fitting algorithm designed to reliably identify the modes present in numerical simulations and to extract their amplitudes and phases. We apply the algorithm to over 500 binary black hole simulations from the public SXS numerical relativity simulation catalog, and we present fitting formulas for the resulting mode amplitudes and phases as functions of the properties of the progenitors. Crucially, our algorithm allows for the extraction of not only prograde fundamental modes and overtones, but also retrograde modes and second-order modes. We unveil interesting relations for the amplitude ratios of different modes. The fitting code and interactive versions of some of the plots are publicly available. The results presented in this paper can be updated as more and better simulations become available. |
gr-qc/0202062 | Delia Ionescu | Delia Ionescu | The Electrogravitational Field of an Electrically Charged Mass Point and
the Causality Principle in RTG | 12 pages, no figures | Theor.Math.Phys. 136 (2003) 1177-1187 | null | null | gr-qc | null | In this paper, I determine the electrogravitational field produced by a
charged mass point according to the Relativistic Theory of Gravitation. The
Causality Principle in the Relativistic Theory of Gravitation will play a very
important part in finding this field. The analytical form and the domain of
definition, i.e the gravitational radius of the obtained solution, differ from
that given by Einstein's General Relativity Theory.
| [
{
"created": "Sun, 17 Feb 2002 23:02:18 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Ionescu",
"Delia",
""
]
] | In this paper, I determine the electrogravitational field produced by a charged mass point according to the Relativistic Theory of Gravitation. The Causality Principle in the Relativistic Theory of Gravitation will play a very important part in finding this field. The analytical form and the domain of definition, i.e the gravitational radius of the obtained solution, differ from that given by Einstein's General Relativity Theory. |
gr-qc/9606033 | Leonid S. Kuzmenkov | Yu.A. Baurov (Central Scientific Research Institute of Machinery,
Moscow), A.A. Efimov and A.A. Shpitalnaya (State Astronomical Observatory of
Russian Academy of Sciences, Pulkovo) | Anisotropy of fast-going processes in the Sun and new interaction in
nature | 5 pages, revtex, 1 eps figure, in one .uue file, published in Fiz.
Mysl Ross. (in russian) | null | null | null | gr-qc astro-ph hep-ph | null | The processing of the galactic coordinates of 3543 solar flares with a
magnitude of 2 or more has shown that the distribution of these fast-going
processes on the surface of the "nonrotating" Sun is irregular and non-random
what testifies that in the near-Sun space an anisotropy takes place which
practically coincides with that predicted and obtained in laboratory
experiments and caused by existence of the intergalactic vector potential ${\bf
A_g}$.
| [
{
"created": "Fri, 14 Jun 1996 11:56:44 GMT",
"version": "v1"
}
] | 2009-09-25 | [
[
"Baurov",
"Yu. A.",
"",
"Central Scientific Research Institute of Machinery,\n Moscow"
],
[
"Efimov",
"A. A.",
"",
"State Astronomical Observatory of\n Russian Academy of Sciences, Pulkovo"
],
[
"Shpitalnaya",
"A. A.",
"",
"State Astronomical Observatory o... | The processing of the galactic coordinates of 3543 solar flares with a magnitude of 2 or more has shown that the distribution of these fast-going processes on the surface of the "nonrotating" Sun is irregular and non-random what testifies that in the near-Sun space an anisotropy takes place which practically coincides with that predicted and obtained in laboratory experiments and caused by existence of the intergalactic vector potential ${\bf A_g}$. |
0906.3847 | Sujitkumar Chatterjee | S. Chatterjee and D. Panigrahi | Dimension Driven Accelerating Universe | null | AIP Conf. Proc. - 2009,THE DARK SIDE OF THE UNIVERSE: 4th
International Workshop on the Dark Side of the Universe; Volume - 1115, pp.
335-340 | 10.1063/1.3131522 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The current acceleration of the universe leads us to investigate higher
dimensional gravity theory, which is able to explain acceleration from a
theoretical view point without the need of introducing dark energy by hand. We
argue that the terms containing higher dimensional metric coefficients produce
an extra negative pressure that apparently drives an acceleration of the 3D
space, tempting us to suggest that the accelerating universe seems to act as a
window to the existence of extra spatial dimensions. Interesting to point out
that in this case our cosmology apparently mimics the well known quintessence
scenario fuelled by a generalised Chaplygin-type of fluid where a smooth
transition from a dust dominated model to a de Sitter like one takes place.
Correspondence to models generated by a tachyonic form of matter is also
briefly discussed.
| [
{
"created": "Sun, 21 Jun 2009 06:08:05 GMT",
"version": "v1"
}
] | 2009-06-26 | [
[
"Chatterjee",
"S.",
""
],
[
"Panigrahi",
"D.",
""
]
] | The current acceleration of the universe leads us to investigate higher dimensional gravity theory, which is able to explain acceleration from a theoretical view point without the need of introducing dark energy by hand. We argue that the terms containing higher dimensional metric coefficients produce an extra negative pressure that apparently drives an acceleration of the 3D space, tempting us to suggest that the accelerating universe seems to act as a window to the existence of extra spatial dimensions. Interesting to point out that in this case our cosmology apparently mimics the well known quintessence scenario fuelled by a generalised Chaplygin-type of fluid where a smooth transition from a dust dominated model to a de Sitter like one takes place. Correspondence to models generated by a tachyonic form of matter is also briefly discussed. |
gr-qc/0002006 | Giovanni Losurdo | Giovanni Losurdo | Active controls in interferometric detectors of gravitational waves:
inertial damping of the VIRGO superattenuator | 11 pages, 9 figures. Lecture given at the "International summer
school on experimental physics of gravitational waves" - Urbino (Italy),
September 6-18, 1999 | null | 10.1142/9789812792846_0014 | null | gr-qc | null | The operation of an interferometer for gravitational waves detection requires
sophisticated feedback controls in many parts of the apparatus. The aim of this
lecture is to introduce the types of problems to be faced in this line of
research. The attention is focused on the "inertial damping" of the test mass
suspension of the VIRGO interferometer (the superattenuator): it is a
multidimensional local control aimed to reduce the residual motion of the
suspended mirror associated to the normal modes of the suspension. Its
performance is very important for the locking of the interferometer.
| [
{
"created": "Wed, 2 Feb 2000 12:51:09 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Feb 2000 15:16:05 GMT",
"version": "v2"
}
] | 2017-08-23 | [
[
"Losurdo",
"Giovanni",
""
]
] | The operation of an interferometer for gravitational waves detection requires sophisticated feedback controls in many parts of the apparatus. The aim of this lecture is to introduce the types of problems to be faced in this line of research. The attention is focused on the "inertial damping" of the test mass suspension of the VIRGO interferometer (the superattenuator): it is a multidimensional local control aimed to reduce the residual motion of the suspended mirror associated to the normal modes of the suspension. Its performance is very important for the locking of the interferometer. |
1705.02226 | Marcelo J. Reboucas | G. Otalora, M.J. Reboucas | Violation of causality in $f(T)$ gravity | 10 pages, V2: Presentation of Sec.2 improved, references added,
version published in Eur.Phys.J.C | Eur.Phys.J. C 77, 799 (2017) | 10.1140/epjc/s10052-017-5367-7 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | [Abridged] In its standard formulation, the $f(T)$ field equations are not
invariant under local Lorentz transformations, and thus the theory does not
inherit the causal structure of special relativity. A locally Lorentz covariant
$f(T)$ gravity theory has been devised recently, and this local causality
problem has been overcome. The nonlocal question, however, is left open. If
gravitation is to be described by this covariant $f(T)$ gravity theory there
are a number of issues that ought to be examined in its context, including the
question as to whether its field equations allow homogeneous G\"odel-type
solutions, which necessarily leads to violation of causality on nonlocal scale.
Here, to look into the potentialities and difficulties of the covariant $f(T)$
theories, we examine whether they admit G\"odel-type solutions. We take a
combination of a perfect fluid with electromagnetic plus a scalar field as
source, and determine a general G\"odel-type solution, which contains special
solutions in which the essential parameter of G\"odel-type geometries, $m^2$,
defines any class of homogeneous G\"odel-type geometries. We extended to the
context of covariant $f(T)$ gravity a theorem, which ensures that any
perfect-fluid homogeneous G\"odel-type solution defines the same set of G\"odel
tetrads $h_A^{~\mu}$ up to a Lorentz transformation. We also shown that the
single massless scalar field generates G\"odel-type solution with no closed
timelike curves. Even though the covariant $f(T)$ gravity restores Lorentz
covariance of the field equations and the local validity of the causality
principle, the bare existence of the G\"odel-type solutions makes apparent that
the covariant formulation of $f(T)$ gravity does not preclude non-local
violation of causality in the form of closed timelike curves.
| [
{
"created": "Thu, 4 May 2017 02:29:20 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Nov 2017 02:56:50 GMT",
"version": "v2"
}
] | 2017-11-28 | [
[
"Otalora",
"G.",
""
],
[
"Reboucas",
"M. J.",
""
]
] | [Abridged] In its standard formulation, the $f(T)$ field equations are not invariant under local Lorentz transformations, and thus the theory does not inherit the causal structure of special relativity. A locally Lorentz covariant $f(T)$ gravity theory has been devised recently, and this local causality problem has been overcome. The nonlocal question, however, is left open. If gravitation is to be described by this covariant $f(T)$ gravity theory there are a number of issues that ought to be examined in its context, including the question as to whether its field equations allow homogeneous G\"odel-type solutions, which necessarily leads to violation of causality on nonlocal scale. Here, to look into the potentialities and difficulties of the covariant $f(T)$ theories, we examine whether they admit G\"odel-type solutions. We take a combination of a perfect fluid with electromagnetic plus a scalar field as source, and determine a general G\"odel-type solution, which contains special solutions in which the essential parameter of G\"odel-type geometries, $m^2$, defines any class of homogeneous G\"odel-type geometries. We extended to the context of covariant $f(T)$ gravity a theorem, which ensures that any perfect-fluid homogeneous G\"odel-type solution defines the same set of G\"odel tetrads $h_A^{~\mu}$ up to a Lorentz transformation. We also shown that the single massless scalar field generates G\"odel-type solution with no closed timelike curves. Even though the covariant $f(T)$ gravity restores Lorentz covariance of the field equations and the local validity of the causality principle, the bare existence of the G\"odel-type solutions makes apparent that the covariant formulation of $f(T)$ gravity does not preclude non-local violation of causality in the form of closed timelike curves. |
1502.01843 | Julian Gonzalez-Ayala | Julian Gonzalez-Ayala and F. Angulo-Brown | Is the $(3+1)-d$ nature of the universe a thermodynamic necessity? | 3 pages, 5 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well established that at early times, long before the time of
radiation-matter equality, the universe could have been well described by a
spatially flat, radiation only model. In this letter we consider the whole
primeval universe as a black body radiation (BBR) system in an $n-$dimensional
Euclidean space. We propose that the $(3+1)-d$ nature of the universe could be
the result of a kind of thermodynamic selection principle stemming from the
second law of thermodynamics. In regard the three spatial dimensions we suggest
that they were chosen by means of the minimization of the Helmholtz free energy
per hypervolume unit, while the time dimension, as it is well known was the
result of the principle of increment of entropy for closed systems; that is,
the so-called arrow of time.
| [
{
"created": "Fri, 6 Feb 2015 10:18:27 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Feb 2015 18:47:39 GMT",
"version": "v2"
}
] | 2015-02-17 | [
[
"Gonzalez-Ayala",
"Julian",
""
],
[
"Angulo-Brown",
"F.",
""
]
] | It is well established that at early times, long before the time of radiation-matter equality, the universe could have been well described by a spatially flat, radiation only model. In this letter we consider the whole primeval universe as a black body radiation (BBR) system in an $n-$dimensional Euclidean space. We propose that the $(3+1)-d$ nature of the universe could be the result of a kind of thermodynamic selection principle stemming from the second law of thermodynamics. In regard the three spatial dimensions we suggest that they were chosen by means of the minimization of the Helmholtz free energy per hypervolume unit, while the time dimension, as it is well known was the result of the principle of increment of entropy for closed systems; that is, the so-called arrow of time. |
1802.04401 | Laszlo B. Szabados | L\'aszl\'o B. Szabados | On gravity's role in the genesis of rest masses of classical fields | 21 pages, 3 figures; short, journal version of arXiv:1603.06997 | General Relativity and Gravitation (2018) {\bf 50} 34 | 10.1007/s10714-018-2340-1 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that in the Einstein-conformally coupled Higgs--Maxwell system
with Friedman-Robertson-Walker symmetries the energy density of the Higgs field
has stable local minimum only if the mean curvature of the $t={\rm const}$
hypersurfaces is less than a finite critical value $\chi_c$, while for greater
mean curvature the energy density is not bounded from below. Therefore, there
are extreme gravitational situations in which even quasi-locally defined
instantaneous vacuum states of the Higgs sector cannot exist, and hence one
cannot at all define the rest mass of all the classical fields. On
hypersurfaces with mean curvature less than $\chi_c$ the energy density has the
`wine bottle' (rather than the familiar `Mexican hat') shape, and the gauge
field can get rest mass via the Brout--Englert--Higgs mechanism. The spacelike
hypersurface with the critical mean curvature represents the moment of
`genesis' of rest masses.
| [
{
"created": "Tue, 13 Feb 2018 00:03:30 GMT",
"version": "v1"
}
] | 2018-08-29 | [
[
"Szabados",
"László B.",
""
]
] | It is shown that in the Einstein-conformally coupled Higgs--Maxwell system with Friedman-Robertson-Walker symmetries the energy density of the Higgs field has stable local minimum only if the mean curvature of the $t={\rm const}$ hypersurfaces is less than a finite critical value $\chi_c$, while for greater mean curvature the energy density is not bounded from below. Therefore, there are extreme gravitational situations in which even quasi-locally defined instantaneous vacuum states of the Higgs sector cannot exist, and hence one cannot at all define the rest mass of all the classical fields. On hypersurfaces with mean curvature less than $\chi_c$ the energy density has the `wine bottle' (rather than the familiar `Mexican hat') shape, and the gauge field can get rest mass via the Brout--Englert--Higgs mechanism. The spacelike hypersurface with the critical mean curvature represents the moment of `genesis' of rest masses. |
1502.06913 | Subenoy Chakraborty | Sujay Kr. Biswas and Subenoy Chakraborty | Dynamical Systems analysis of an interacting dark energy model in the
Brane Scenario | 22 pages, 7 figures | General Relativity and Gravitation 47, 22 (2015) | 10.1007/s10714-015-1866-8 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate the background dynamics in brane cosmology when
dark energy is coupled to dark matter by a suitable interaction. Here we
consider an homogeneous and isotropic Friedmann-Robertson-Walker (FRW) brane
model and the evolution equations are reduced to an autonomous system by
suitable transformation of variables. The nature of critical points are
analyzed by evaluating the eigenvalues of linearized Jacobi matrix. Finally,
the classical stability of the model is also studied.
| [
{
"created": "Fri, 20 Feb 2015 08:28:11 GMT",
"version": "v1"
}
] | 2015-02-25 | [
[
"Biswas",
"Sujay Kr.",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | In this paper, we investigate the background dynamics in brane cosmology when dark energy is coupled to dark matter by a suitable interaction. Here we consider an homogeneous and isotropic Friedmann-Robertson-Walker (FRW) brane model and the evolution equations are reduced to an autonomous system by suitable transformation of variables. The nature of critical points are analyzed by evaluating the eigenvalues of linearized Jacobi matrix. Finally, the classical stability of the model is also studied. |
1902.10128 | Rogerio Teixeira Cavalcanti | Rogerio Teixeira Cavalcanti | Aspects of Black Hole Physics Beyond General Relativity: extra
dimensions, horizon wave function and applications | Doctoral Thesis | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work is devoted to investigate some consequences of black holes physics
beyond the domain of general relativity, mainly in effective extra dimensional
models. The investigation is carried along three gravitational effects, namely
the Hawking radiation, the strong deflection of gravitational lensing and the
formation of quantum black holes. A cosmological thick brane solution is also
investigated. Effective theories and models provide a prominent approach for
testing the limits of known theories and show what would be expected beyond
that. Based on such idea we have used effective models for finding deviations
of general relativity associated to each of the mentioned phenomena.
| [
{
"created": "Mon, 25 Feb 2019 23:20:41 GMT",
"version": "v1"
}
] | 2019-02-28 | [
[
"Cavalcanti",
"Rogerio Teixeira",
""
]
] | This work is devoted to investigate some consequences of black holes physics beyond the domain of general relativity, mainly in effective extra dimensional models. The investigation is carried along three gravitational effects, namely the Hawking radiation, the strong deflection of gravitational lensing and the formation of quantum black holes. A cosmological thick brane solution is also investigated. Effective theories and models provide a prominent approach for testing the limits of known theories and show what would be expected beyond that. Based on such idea we have used effective models for finding deviations of general relativity associated to each of the mentioned phenomena. |
1001.4157 | Khaled Saaidi | Kh. Saaidi, A. Vajdi, S. W. Rabiei, A. Aghamohammadi, H. Sheikhahmadi | Strong and weak gravitational field in $R+\mu^4/R$ gravity | 7 pages, 3 figures, to be appear in APSS | Astrophys. Space Sci (2012). 337: 739-745 | 10.1007/s10509-011-0871-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce a new approach for investigating the weak field limit of vacuum
field equations in $f(R)$ gravity and we find the weak field limit of
$f(R)=R+\mu ^4/R$ gravity. Furthermore, we study the strong gravity regime in
$R+\mu^{4}/R$ model of $f(R)$ gravity. We show the existence of strong
gravitational field in vacuum for such model.
We find out in the limit $\mu\rightarrow 0$, the weak field limit and the
strong gravitational field can be regarded as a perturbed Schwarzschild metric.
| [
{
"created": "Mon, 25 Jan 2010 15:37:55 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Jan 2012 16:55:42 GMT",
"version": "v2"
},
{
"created": "Wed, 18 Jan 2012 15:47:56 GMT",
"version": "v3"
}
] | 2014-01-14 | [
[
"Saaidi",
"Kh.",
""
],
[
"Vajdi",
"A.",
""
],
[
"Rabiei",
"S. W.",
""
],
[
"Aghamohammadi",
"A.",
""
],
[
"Sheikhahmadi",
"H.",
""
]
] | We introduce a new approach for investigating the weak field limit of vacuum field equations in $f(R)$ gravity and we find the weak field limit of $f(R)=R+\mu ^4/R$ gravity. Furthermore, we study the strong gravity regime in $R+\mu^{4}/R$ model of $f(R)$ gravity. We show the existence of strong gravitational field in vacuum for such model. We find out in the limit $\mu\rightarrow 0$, the weak field limit and the strong gravitational field can be regarded as a perturbed Schwarzschild metric. |
2212.04225 | Soham Bhattacharyya | Soham Bhattacharyya | On the equivalence between $ f\left(R\right) $ theories and Einstein
gravity | 6 pages, version as accepted in Classical and Quantum Gravity | null | 10.1088/1361-6382/acfcff | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this brief note we present a somewhat trivial result. Namely, we show that
perturbative off-shell $f(R)$-theory is equivalent to Einstein gravity, as well
as to the Brans-Dicke theory and the Einstein scalar field model. We also
discuss possible generalisation of this result to higher-order gravitational
field models.
| [
{
"created": "Thu, 8 Dec 2022 12:09:28 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Dec 2022 07:18:02 GMT",
"version": "v2"
},
{
"created": "Tue, 26 Sep 2023 05:16:42 GMT",
"version": "v3"
}
] | 2023-09-27 | [
[
"Bhattacharyya",
"Soham",
""
]
] | In this brief note we present a somewhat trivial result. Namely, we show that perturbative off-shell $f(R)$-theory is equivalent to Einstein gravity, as well as to the Brans-Dicke theory and the Einstein scalar field model. We also discuss possible generalisation of this result to higher-order gravitational field models. |
1605.01938 | Enrico Barausse | Fabian Hofmann, Enrico Barausse and Luciano Rezzolla | The final spin from binary black holes in quasi-circular orbits | 6 pages, 3 figures. Matches ApJL accepted version. Coefficients
$\epsilon_\alpha$, $\epsilon_\beta$ and $\epsilon_\gamma$ slightly changed to
reflect dataset filtered of imprecise NR data; contains comparison with newly
published NR catalog | null | 10.3847/2041-8205/825/2/L19 | null | gr-qc astro-ph.CO astro-ph.GA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We revisit the problem of predicting the spin magnitude and direction of the
black hole resulting from the merger of two black holes with arbitrary masses
and spins inspiralling in quasi-circular orbits. We do this by analyzing a
catalog of 619 recent numerical-relativity simulations collected from the
literature and spanning a large variety of initial conditions. By combining
information from the post-Newtonian approximation, the extreme mass-ratio limit
and perturbative calculations, we improve our previously proposed
phenomenological formulae for the final remnant spin. In contrast with
alternative suggestions in the literature, and in analogy with our previous
expressions, the new formula is a simple algebraic function of the initial
system parameters and is not restricted to binaries with spins
aligned/anti-aligned with the orbital angular momentum, but can be employed for
fully generic binaries. The accuracy of the new expression is significantly
improved, especially for almost extremal progenitor spins and for small mass
ratios, yielding a root-mean-square error $\sigma\approx0.002$ for
aligned/anti-aligned binaries and $\sigma\approx0.006$ for generic binaries.
Our new formula is suitable for cosmological applications and can be employed
robustly in the analysis of the gravitational waveforms from advanced
interferometric detectors.
| [
{
"created": "Fri, 6 May 2016 13:49:34 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Jun 2016 08:56:46 GMT",
"version": "v2"
}
] | 2016-07-13 | [
[
"Hofmann",
"Fabian",
""
],
[
"Barausse",
"Enrico",
""
],
[
"Rezzolla",
"Luciano",
""
]
] | We revisit the problem of predicting the spin magnitude and direction of the black hole resulting from the merger of two black holes with arbitrary masses and spins inspiralling in quasi-circular orbits. We do this by analyzing a catalog of 619 recent numerical-relativity simulations collected from the literature and spanning a large variety of initial conditions. By combining information from the post-Newtonian approximation, the extreme mass-ratio limit and perturbative calculations, we improve our previously proposed phenomenological formulae for the final remnant spin. In contrast with alternative suggestions in the literature, and in analogy with our previous expressions, the new formula is a simple algebraic function of the initial system parameters and is not restricted to binaries with spins aligned/anti-aligned with the orbital angular momentum, but can be employed for fully generic binaries. The accuracy of the new expression is significantly improved, especially for almost extremal progenitor spins and for small mass ratios, yielding a root-mean-square error $\sigma\approx0.002$ for aligned/anti-aligned binaries and $\sigma\approx0.006$ for generic binaries. Our new formula is suitable for cosmological applications and can be employed robustly in the analysis of the gravitational waveforms from advanced interferometric detectors. |
1608.04228 | Abhay Ashtekar | Abhay Ashtekar, Brajesh Gupt | Quantum Gravity in the Sky: Interplay between fundamental theory and
observations | Invited article, to appear in CQG. This paper is addressed both to
the quantum gravity and cosmology audiences. Cosmologists can focus just on
sections I, IV.C, IV.D and V without loss of continuity. 43 pages, 13
figures. Version 2 contains a few clarifications and new references,
especially to compare and contrast related results in the literature | Class. Quant. Grav. 34, 014002 (2017), (44pp) | 10.1088/1361-6382/34/1/014002 | null | gr-qc astro-ph.CO hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Observational missions have provided us with a reliable model of the
evolution of the universe starting from the last scattering surface all the way
to future infinity. Furthermore given a specific model of inflation, using
quantum field theory on curved space-times this history can be pushed
\emph{back in time} to the epoch when space-time curvature was some $10^{62}$
times that at the horizon of a solar mass black hole! However, to extend the
history further back to the Planck regime requires input from quantum gravity.
An important aspect of this input is the choice of the background quantum
geometry and of the Heisenberg state of cosmological perturbations thereon,
motivated by Planck scale physics. This paper introduces first steps in that
direction. Specifically we propose two principles that link quantum geometry
and Heisenberg uncertainties in the Planck epoch with late time physics and
explore in detail the observational consequences of the initial conditions they
select. We find that the predicted temperature-temperature (T-T) correlations
for scalar modes are indistinguishable from standard inflation at small angular
scales even though the initial conditions are now set in the deep Planck
regime. However, \emph{there is a specific power suppression at large angular
scales}. As a result, the predicted spectrum provides a better fit to the
PLANCK mission data than standard inflation, where the initial conditions are
set in the general relativity regime. Thus, our proposal brings out a deep
interplay between the ultraviolet and the infrared. Finally, the proposal also
leads to specific predictions for power suppression at large angular scales
also for the (T-E and E-E) correlations involving electric polarization. The
PLANCK team is expected to release this data in the coming year.
| [
{
"created": "Mon, 15 Aug 2016 10:44:35 GMT",
"version": "v1"
},
{
"created": "Sat, 12 Nov 2016 02:08:50 GMT",
"version": "v2"
}
] | 2017-01-19 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Gupt",
"Brajesh",
""
]
] | Observational missions have provided us with a reliable model of the evolution of the universe starting from the last scattering surface all the way to future infinity. Furthermore given a specific model of inflation, using quantum field theory on curved space-times this history can be pushed \emph{back in time} to the epoch when space-time curvature was some $10^{62}$ times that at the horizon of a solar mass black hole! However, to extend the history further back to the Planck regime requires input from quantum gravity. An important aspect of this input is the choice of the background quantum geometry and of the Heisenberg state of cosmological perturbations thereon, motivated by Planck scale physics. This paper introduces first steps in that direction. Specifically we propose two principles that link quantum geometry and Heisenberg uncertainties in the Planck epoch with late time physics and explore in detail the observational consequences of the initial conditions they select. We find that the predicted temperature-temperature (T-T) correlations for scalar modes are indistinguishable from standard inflation at small angular scales even though the initial conditions are now set in the deep Planck regime. However, \emph{there is a specific power suppression at large angular scales}. As a result, the predicted spectrum provides a better fit to the PLANCK mission data than standard inflation, where the initial conditions are set in the general relativity regime. Thus, our proposal brings out a deep interplay between the ultraviolet and the infrared. Finally, the proposal also leads to specific predictions for power suppression at large angular scales also for the (T-E and E-E) correlations involving electric polarization. The PLANCK team is expected to release this data in the coming year. |
1507.02945 | Peter K.F. Kuhfittig | Peter K.F. Kuhfittig | Wormholes admitting conformal Killing vectors and supported by
generalized Chaplygin gas | 8 pages, one figure | Eur. Phys. J. C, volume 75, 357 (2015) | 10.1140/epjc/s10052-015-3584-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | When Morris and Thorne first proposed that traversable wormholes may be
actual physical objects, they concentrated on the geometry by specifying the
shape and redshift functions. This mathematical approach necessarily raises
questins regarding the determination of the required stress-energy tensor. This
paper discusses a natural way to obtain a complete wormhole solution by
assuming that the wormhole (1) is supported by generalized Chaplygin gas and
(2) admits conformal Killing vectors.
| [
{
"created": "Fri, 10 Jul 2015 15:48:31 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Jul 2015 14:01:10 GMT",
"version": "v2"
},
{
"created": "Sat, 8 Aug 2015 15:46:25 GMT",
"version": "v3"
}
] | 2015-08-11 | [
[
"Kuhfittig",
"Peter K. F.",
""
]
] | When Morris and Thorne first proposed that traversable wormholes may be actual physical objects, they concentrated on the geometry by specifying the shape and redshift functions. This mathematical approach necessarily raises questins regarding the determination of the required stress-energy tensor. This paper discusses a natural way to obtain a complete wormhole solution by assuming that the wormhole (1) is supported by generalized Chaplygin gas and (2) admits conformal Killing vectors. |
2202.02173 | Patryk Mach | Patryk Mach and Andrzej Odrzywolek | Accretion of the relativistic Vlasov gas onto a moving Schwarzschild
black hole: Low-temperature limit and numerical aspects | Talk presented at the 7th Conference of the Polish Society on
Relativity, Lodz, Poland, September 20-23, 2021 | Acta Phys. Pol. B Proc. Suppl. 15, 1-A7 (2022) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | New developments related to our recent study of the accretion of the Vlasov
gas onto a moving Schwarzschild black hole are presented. We discuss the
low-temperature limit of the mas accretion rate and a simple Monte Carlo
simulation used to check the results obtained in this limit. We also comment on
several numerical aspects related with momentum integrals expressing the
particle density current and the particle density.
| [
{
"created": "Fri, 4 Feb 2022 15:06:05 GMT",
"version": "v1"
}
] | 2022-02-07 | [
[
"Mach",
"Patryk",
""
],
[
"Odrzywolek",
"Andrzej",
""
]
] | New developments related to our recent study of the accretion of the Vlasov gas onto a moving Schwarzschild black hole are presented. We discuss the low-temperature limit of the mas accretion rate and a simple Monte Carlo simulation used to check the results obtained in this limit. We also comment on several numerical aspects related with momentum integrals expressing the particle density current and the particle density. |
1006.2600 | Ujjal Debnath | Samarpita Bhattacharya and Ujjal Debnath | Thermodynamical Laws in Horava-Lifshitz Gravity | 7 latex pages, 7 figures | Int.J.Mod.Phys.D20:1191-1204,2011 | 10.1142/S0218271811019323 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we have investigated the validity of GSL of thermodynamics in a
universe (open, closed and flat) governed by Ho$\check{\text r}$ava-Lifshitz
gravity. If the universe contains barotropic fluid the corresponding solutions
have been obtained. The validity of GSL have been examined by two approaches:
(i) robust approach and (ii) effective approach. In robust approach, we have
considered the universe contains only matter fluid and the effect of the
gravitational sector of HL gravity was incorporated through the modified black
hole entropy on the horizon. Effective approach is that all extra information
of HL gravity into an effective dark energy fluid and so we consider the
universe contains matter fluid plus this effective fluid. This approach is
essentially same as the Einstein's gravity theory. The general prescription for
validity of GSL have been discussed. Graphically we have shown that the GSL may
be satisfied for open, closed and flat universe on the different horizons with
different conditions.
| [
{
"created": "Mon, 14 Jun 2010 06:39:08 GMT",
"version": "v1"
}
] | 2011-07-25 | [
[
"Bhattacharya",
"Samarpita",
""
],
[
"Debnath",
"Ujjal",
""
]
] | In this work, we have investigated the validity of GSL of thermodynamics in a universe (open, closed and flat) governed by Ho$\check{\text r}$ava-Lifshitz gravity. If the universe contains barotropic fluid the corresponding solutions have been obtained. The validity of GSL have been examined by two approaches: (i) robust approach and (ii) effective approach. In robust approach, we have considered the universe contains only matter fluid and the effect of the gravitational sector of HL gravity was incorporated through the modified black hole entropy on the horizon. Effective approach is that all extra information of HL gravity into an effective dark energy fluid and so we consider the universe contains matter fluid plus this effective fluid. This approach is essentially same as the Einstein's gravity theory. The general prescription for validity of GSL have been discussed. Graphically we have shown that the GSL may be satisfied for open, closed and flat universe on the different horizons with different conditions. |
1907.13311 | Cristiano Germani | Albert Escriv\`a, Cristiano Germani and Ravi K. Sheth | A universal threshold for primordial black hole formation | 5 pages and 5 figures, v3: clarifications and more numerical
evidences for the lower bound added. Version accepted in PRD | Phys. Rev. D 101, 044022 (2020) | 10.1103/PhysRevD.101.044022 | ICC-19-013 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this letter, we argue and show numerically that the threshold to form
primordial black holes from an initial spherically symmetric perturbation is,
to an excellent approximation, universal, whenever given in terms of the
compaction function averaged over a sphere of radius $r_m$, where $r_m$ is the
scale on which the compaction function is maximum. This can be understood as
the requirement that, for a black hole to form, each shell of the averaged
compaction function should have an amplitude exceeding the so-called
Harada-Yoo-Kohri limit. For a radiation dominated universe we argued, supported
by the numerical simulations, that this limit is $\delta_c = 0.40$, which is
slightly below the one quoted in the literature. Additionally, we show that the
profile dependence of the threshold for the compaction function is only
sensitive to its curvature at the maximum. We use these results to provide an
analytic formula for the threshold amplitude of the compaction function at its
maximum in terms of the normalised compaction function curvature at $r_m$.
| [
{
"created": "Wed, 31 Jul 2019 05:21:22 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Sep 2019 22:05:24 GMT",
"version": "v2"
},
{
"created": "Mon, 27 Jan 2020 10:25:09 GMT",
"version": "v3"
}
] | 2020-02-19 | [
[
"Escrivà",
"Albert",
""
],
[
"Germani",
"Cristiano",
""
],
[
"Sheth",
"Ravi K.",
""
]
] | In this letter, we argue and show numerically that the threshold to form primordial black holes from an initial spherically symmetric perturbation is, to an excellent approximation, universal, whenever given in terms of the compaction function averaged over a sphere of radius $r_m$, where $r_m$ is the scale on which the compaction function is maximum. This can be understood as the requirement that, for a black hole to form, each shell of the averaged compaction function should have an amplitude exceeding the so-called Harada-Yoo-Kohri limit. For a radiation dominated universe we argued, supported by the numerical simulations, that this limit is $\delta_c = 0.40$, which is slightly below the one quoted in the literature. Additionally, we show that the profile dependence of the threshold for the compaction function is only sensitive to its curvature at the maximum. We use these results to provide an analytic formula for the threshold amplitude of the compaction function at its maximum in terms of the normalised compaction function curvature at $r_m$. |
gr-qc/0505159 | Andrea Fuster | A. Fuster and J.W. van Holten | Type III Einstein-Yang-Mills solutions | revtex, 4 pages, minor changes, some factors and references
corrected, footnote added | Phys.Rev. D72 (2005) 024011 | 10.1103/PhysRevD.72.024011 | NIKHEF/2005-009 | gr-qc hep-th | null | We construct two distinct classes of exact type III solutions of the D=4
Einstein-Yang-Mills system. The solutions are embeddings of the non-abelian
plane waves in spacetimes in Kundt's class. Reduction of the solutions to type
N leads to generalized $pp$ and Kundt waves. The geodesic equations are briefly
discussed.
| [
{
"created": "Tue, 31 May 2005 14:23:20 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Jun 2005 15:07:59 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Fuster",
"A.",
""
],
[
"van Holten",
"J. W.",
""
]
] | We construct two distinct classes of exact type III solutions of the D=4 Einstein-Yang-Mills system. The solutions are embeddings of the non-abelian plane waves in spacetimes in Kundt's class. Reduction of the solutions to type N leads to generalized $pp$ and Kundt waves. The geodesic equations are briefly discussed. |
1604.08939 | Robert R. Caldwell | R. R. Caldwell, C. Devulder, and N. A. Maksimova | Gravitational Wave - Gauge Field Oscillations | 4 pages, 3 figures, 1 animation; replacement matches published
version | Phys. Rev. D 94, 063005 (2016) | 10.1103/PhysRevD.94.063005 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves propagating through a stationary gauge field transform
into gauge field waves and back again. When multiple families of flavor-space
locked gauge fields are present, the gravitational and gauge field waves
exhibit novel dynamics. At high frequencies, the system behaves like coupled
oscillators in which the gravitational wave is the central pacemaker. Due to
energy conservation and exchange among the oscillators, the wave amplitudes lie
on a multidimensional sphere, reminiscent of neutrino flavor oscillations. This
phenomenon has implications for cosmological scenarios based on flavor-space
locked gauge fields.
| [
{
"created": "Fri, 29 Apr 2016 19:12:39 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Jun 2017 20:05:09 GMT",
"version": "v2"
}
] | 2017-06-05 | [
[
"Caldwell",
"R. R.",
""
],
[
"Devulder",
"C.",
""
],
[
"Maksimova",
"N. A.",
""
]
] | Gravitational waves propagating through a stationary gauge field transform into gauge field waves and back again. When multiple families of flavor-space locked gauge fields are present, the gravitational and gauge field waves exhibit novel dynamics. At high frequencies, the system behaves like coupled oscillators in which the gravitational wave is the central pacemaker. Due to energy conservation and exchange among the oscillators, the wave amplitudes lie on a multidimensional sphere, reminiscent of neutrino flavor oscillations. This phenomenon has implications for cosmological scenarios based on flavor-space locked gauge fields. |
2003.13730 | Yolbeiker Rodr\'iguez Baez | Radouane Gannouji and Yolbeiker Rodr\'iguez Baez | Critical collapse in K-essence models | 19 pages, 7 figures; v2: accepted by JHEP, comments + appendix added,
references updated | J. High Energ. Phys. 2020, 132 (2020) | 10.1007/JHEP07(2020)132 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study gravitational collapse in K-essence model with shift symmetry. For
these models, we have the formation of two types of horizons, event and sonic.
For the particular case $K(X)=X+\beta X^2$ we found three different regimes. In
the weak field regime the scalar field disperses to infinity, in the very
strong regime both horizons form at the same time and finally for the
intermediate regime, the sonic horizon could form first or both horizons form
at the same time. The threshold of formation of black hole is found in the
regime where the sonic horizon forms first. We observe a universal behavior
with scaling parameter $\gamma\simeq 0.51$. Interestingly this universal
behavior is already encoded in the sonic horizon much before the black hole
forms and therefore the emergence of the event horizon.
| [
{
"created": "Mon, 30 Mar 2020 18:25:27 GMT",
"version": "v1"
},
{
"created": "Sat, 25 Jul 2020 15:28:21 GMT",
"version": "v2"
}
] | 2020-07-28 | [
[
"Gannouji",
"Radouane",
""
],
[
"Baez",
"Yolbeiker Rodríguez",
""
]
] | We study gravitational collapse in K-essence model with shift symmetry. For these models, we have the formation of two types of horizons, event and sonic. For the particular case $K(X)=X+\beta X^2$ we found three different regimes. In the weak field regime the scalar field disperses to infinity, in the very strong regime both horizons form at the same time and finally for the intermediate regime, the sonic horizon could form first or both horizons form at the same time. The threshold of formation of black hole is found in the regime where the sonic horizon forms first. We observe a universal behavior with scaling parameter $\gamma\simeq 0.51$. Interestingly this universal behavior is already encoded in the sonic horizon much before the black hole forms and therefore the emergence of the event horizon. |
1608.07118 | Jiri Podolsky | Jiri Podolsky, Robert Svarc | Algebraic classification of Robinson-Trautman spacetimes | 23 pages, no figures, slightly extended version of the Phys. Rev. D
paper | Phys. Rev. D 94, 064043 (2016) | 10.1103/PhysRevD.94.064043 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a general class of four-dimensional geometries admitting a null
vector field that has no twist and no shear but has an arbitrary expansion. We
explicitly present the Petrov classification of such Robinson-Trautman (and
Kundt) gravitational fields, based on the algebraic properties of the Weyl
tensor. In particular, we determine all algebraically special subcases when the
optically privileged null vector field is a multiple principal null direction
(PND), as well as all the cases when it remains a single PND. No field
equations are a priori applied, so that our classification scheme can be used
in any metric theory of gravity in four dimensions. In the classic Einstein
theory this reproduces previous results for vacuum spacetimes, possibly with a
cosmological constant, pure radiation and electromagnetic field, but can be
applied to an arbitrary matter content. As non-trivial explicit examples we
investigate specific algebraic properties of the Robinson-Trautman spacetimes
with a free scalar field, and also black hole spacetimes in the pure
Einstein-Weyl gravity.
| [
{
"created": "Thu, 25 Aug 2016 12:48:07 GMT",
"version": "v1"
}
] | 2017-05-08 | [
[
"Podolsky",
"Jiri",
""
],
[
"Svarc",
"Robert",
""
]
] | We consider a general class of four-dimensional geometries admitting a null vector field that has no twist and no shear but has an arbitrary expansion. We explicitly present the Petrov classification of such Robinson-Trautman (and Kundt) gravitational fields, based on the algebraic properties of the Weyl tensor. In particular, we determine all algebraically special subcases when the optically privileged null vector field is a multiple principal null direction (PND), as well as all the cases when it remains a single PND. No field equations are a priori applied, so that our classification scheme can be used in any metric theory of gravity in four dimensions. In the classic Einstein theory this reproduces previous results for vacuum spacetimes, possibly with a cosmological constant, pure radiation and electromagnetic field, but can be applied to an arbitrary matter content. As non-trivial explicit examples we investigate specific algebraic properties of the Robinson-Trautman spacetimes with a free scalar field, and also black hole spacetimes in the pure Einstein-Weyl gravity. |
2104.00195 | Carlos A. S. Almeida | A. R. P. Moreira, J. E. G. Silva and C.A.S. Almeida | Fermion localization in braneworld teleparallel f(T,B) gravity | 12 pages, 7 figures. To appear in European Physical Journal C | European Physical Journal C, 81 (2021) 298 | 10.1140/epjc/s10052-021-09106-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a spin 1/2 fermion in a thick braneworld in the context of
teleparallel $f(T, B)$ gravity. Here, $f(T,B)$ is such that
$f_1(T,B)=T+k_1B^{n_1}$ and $f_2(T,B)=B+k_2T^{n_2}$, where $n_{1,2}$ and
$k_{1,2}$ are parameters that control the influence of torsion and the boundary
term. We assume Yukawa coupling, where one scalar field is coupled to a Dirac
spinor field. We show how the $n_{1,2}$ and $k_{1,2}$ parameters control the
width of the massless Kaluza-Klein mode, the breadth of non-normalized massive
fermionic modes, and the properties of the analogue quantum-potential near the
origin.
| [
{
"created": "Thu, 1 Apr 2021 01:49:24 GMT",
"version": "v1"
}
] | 2021-04-13 | [
[
"Moreira",
"A. R. P.",
""
],
[
"Silva",
"J. E. G.",
""
],
[
"Almeida",
"C. A. S.",
""
]
] | We study a spin 1/2 fermion in a thick braneworld in the context of teleparallel $f(T, B)$ gravity. Here, $f(T,B)$ is such that $f_1(T,B)=T+k_1B^{n_1}$ and $f_2(T,B)=B+k_2T^{n_2}$, where $n_{1,2}$ and $k_{1,2}$ are parameters that control the influence of torsion and the boundary term. We assume Yukawa coupling, where one scalar field is coupled to a Dirac spinor field. We show how the $n_{1,2}$ and $k_{1,2}$ parameters control the width of the massless Kaluza-Klein mode, the breadth of non-normalized massive fermionic modes, and the properties of the analogue quantum-potential near the origin. |
2305.09157 | Umananda Dev Goswami | Nashiba Parbin, Dhruba Jyoti Gogoi and Umananda Dev Goswami | Weak gravitational lensing and shadow cast by rotating black holes in
axionic Chern-Simons theory | 18 pages and 9 figures. Published in Physics of the Dark Universe | Physics of the Dark Universe 41 (2023) 101265 | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate the impact of the axionic coupling parameter on the bending
angle of light and the shadow cast by slowly rotating black holes in
Chern-Simons modified gravity. We utilize the Ishihara \etal method to derive
the deflection angle of light for an observer and source located at finite
distances from a lens object in an asymptotically flat spacetime, using the
Gauss-Bonnet theorem. The deflection angle exhibits an increasing trend up to a
certain point, followed by a decrease as a function of the impact parameter,
with the presence of the axion matter field causing the observed increase.
Additionally, we calculate the Einstein ring radius as a direct application of
the weak deflection angle. We also investigate the effect of the axion matter
field on the time delay of light and analyze its impact on the shadow cast by
slowly rotating black holes. Our findings reveal a significant effect of the
axionic coupling parameter on the black hole's shadow.
| [
{
"created": "Tue, 16 May 2023 04:17:51 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Jun 2023 12:50:25 GMT",
"version": "v2"
}
] | 2023-06-16 | [
[
"Parbin",
"Nashiba",
""
],
[
"Gogoi",
"Dhruba Jyoti",
""
],
[
"Goswami",
"Umananda Dev",
""
]
] | We investigate the impact of the axionic coupling parameter on the bending angle of light and the shadow cast by slowly rotating black holes in Chern-Simons modified gravity. We utilize the Ishihara \etal method to derive the deflection angle of light for an observer and source located at finite distances from a lens object in an asymptotically flat spacetime, using the Gauss-Bonnet theorem. The deflection angle exhibits an increasing trend up to a certain point, followed by a decrease as a function of the impact parameter, with the presence of the axion matter field causing the observed increase. Additionally, we calculate the Einstein ring radius as a direct application of the weak deflection angle. We also investigate the effect of the axion matter field on the time delay of light and analyze its impact on the shadow cast by slowly rotating black holes. Our findings reveal a significant effect of the axionic coupling parameter on the black hole's shadow. |
2009.09527 | Gregory J. Galloway | Michael Eichmair, Gregory J. Galloway, Abra\~ao Mendes | Initial data rigidity results | 22 pages. Final version. Published in Commun. Math. Phys., vol. 386
(2021). All comments welcome | null | 10.1007/s00220-021-04033-x | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present several rigidity results for initial data sets motivated by the
positive mass theorem. An important step in our proofs here is to establish
conditions that ensure that a marginally outer trapped surface is "weakly
outermost". A rigidity result for Riemannian manifolds with a lower bound on
their scalar curvature is included as a special case.
| [
{
"created": "Sun, 20 Sep 2020 21:28:50 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Mar 2023 03:30:11 GMT",
"version": "v2"
}
] | 2023-03-07 | [
[
"Eichmair",
"Michael",
""
],
[
"Galloway",
"Gregory J.",
""
],
[
"Mendes",
"Abraão",
""
]
] | We present several rigidity results for initial data sets motivated by the positive mass theorem. An important step in our proofs here is to establish conditions that ensure that a marginally outer trapped surface is "weakly outermost". A rigidity result for Riemannian manifolds with a lower bound on their scalar curvature is included as a special case. |
gr-qc/9504027 | null | Bj{\o}rn Jensen and Ulf Lindstr\"om | Rotating Dilaton Black Holes | 11 pages, RevTex, one figure included | Phys.Rev. D52 (1995) 3543-3547 | 10.1103/PhysRevD.52.3543 | Oslo-TP 6-95 and USITP-95-05 | gr-qc hep-th | null | We consider the axially symmetric coupled system of gravitation,
electromagnetism and a dilaton field. Reducing from four to three dimensions,
the system is described by gravity coupled to a non-linear $\sigma$-model. We
find the target space isometries and use them to generate new solutions. It
seems that it is only possible to generate rotating solutions from non-rotating
ones for the special cases when the dilaton coupling parameter $a=0, \pm
\sqrt{3}$. For those particular values, the target space symmetry is enlarged.
| [
{
"created": "Wed, 19 Apr 1995 17:14:58 GMT",
"version": "v1"
}
] | 2016-08-15 | [
[
"Jensen",
"Bjørn",
""
],
[
"Lindström",
"Ulf",
""
]
] | We consider the axially symmetric coupled system of gravitation, electromagnetism and a dilaton field. Reducing from four to three dimensions, the system is described by gravity coupled to a non-linear $\sigma$-model. We find the target space isometries and use them to generate new solutions. It seems that it is only possible to generate rotating solutions from non-rotating ones for the special cases when the dilaton coupling parameter $a=0, \pm \sqrt{3}$. For those particular values, the target space symmetry is enlarged. |
0911.1811 | Shinji Tsujikawa | Antonio De Felice, David F. Mota, Shinji Tsujikawa | Matter instabilities in general Gauss-Bonnet gravity | 9 pages, 2 figures, published PRD version | Phys.Rev.D81:023532,2010 | 10.1103/PhysRevD.81.023532 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the evolution of cosmological perturbations in f(G) gravity, where
the Lagrangian is the sum of a Ricci scalar R and an arbitrary function f in
terms of a Gauss-Bonnet term G. We derive the equations for perturbations
assuming matter to be described by a perfect fluid with a constant equation of
state w. We show that density perturbations in perfect fluids exhibit negative
instabilities during both the radiation and the matter domination, irrespective
of the form of f(G). This growth of perturbations gets stronger on smaller
scales, which is difficult to be compatible with the observed galaxy spectrum
unless the deviation from General Relativity is very small. Thus f(G)
cosmological models are effectively ruled out from this Ultra-Violet
instability, even though they can be compatible with the late-time cosmic
acceleration and local gravity constraints.
| [
{
"created": "Tue, 10 Nov 2009 01:04:21 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Jan 2010 00:29:03 GMT",
"version": "v2"
},
{
"created": "Sat, 30 Jan 2010 15:02:21 GMT",
"version": "v3"
}
] | 2014-11-20 | [
[
"De Felice",
"Antonio",
""
],
[
"Mota",
"David F.",
""
],
[
"Tsujikawa",
"Shinji",
""
]
] | We study the evolution of cosmological perturbations in f(G) gravity, where the Lagrangian is the sum of a Ricci scalar R and an arbitrary function f in terms of a Gauss-Bonnet term G. We derive the equations for perturbations assuming matter to be described by a perfect fluid with a constant equation of state w. We show that density perturbations in perfect fluids exhibit negative instabilities during both the radiation and the matter domination, irrespective of the form of f(G). This growth of perturbations gets stronger on smaller scales, which is difficult to be compatible with the observed galaxy spectrum unless the deviation from General Relativity is very small. Thus f(G) cosmological models are effectively ruled out from this Ultra-Violet instability, even though they can be compatible with the late-time cosmic acceleration and local gravity constraints. |
1409.7385 | Hermano Velten | A. M. Oliveira, H. E. S. Velten, J. C. Fabris and I. G. Salako | Newtonian View of General Relativistic Stars | 6 pages, 3 figures. v2 matches accepted version (EPJC) | Eur.Phys.J. C74 (2014) 11, 3170 | 10.1140/epjc/s10052-014-3170-2 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Although general relativistic cosmological solutions, even in the presence of
pressure, can be mimicked by using neo-Newtonian hydrodynamics, it is not clear
whether there exists the same Newtonian correspondence for spherical static
configurations. General relativity solutions for stars are known as the
Tolman-Oppenheimer-Volkoff (TOV) equations. On the other hand, the Newtonian
description does not take into account the total pressure effects and therefore
can not be used in strong field regimes. We discuss how to incorporate pressure
in the stellar equilibrium equations within the neo-Newtonian framework. We
compare the Newtonian, neo-Newtonian and the full relativistic theory by
solving the equilibrium equations for both three approaches and calculating the
mass-radius diagrams for some simple neutron stars equation of state.
| [
{
"created": "Thu, 25 Sep 2014 13:09:12 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Nov 2014 09:51:52 GMT",
"version": "v2"
}
] | 2015-06-23 | [
[
"Oliveira",
"A. M.",
""
],
[
"Velten",
"H. E. S.",
""
],
[
"Fabris",
"J. C.",
""
],
[
"Salako",
"I. G.",
""
]
] | Although general relativistic cosmological solutions, even in the presence of pressure, can be mimicked by using neo-Newtonian hydrodynamics, it is not clear whether there exists the same Newtonian correspondence for spherical static configurations. General relativity solutions for stars are known as the Tolman-Oppenheimer-Volkoff (TOV) equations. On the other hand, the Newtonian description does not take into account the total pressure effects and therefore can not be used in strong field regimes. We discuss how to incorporate pressure in the stellar equilibrium equations within the neo-Newtonian framework. We compare the Newtonian, neo-Newtonian and the full relativistic theory by solving the equilibrium equations for both three approaches and calculating the mass-radius diagrams for some simple neutron stars equation of state. |
2203.02338 | Mahmut Elbistan | Mahmut Elbistan | Circularly polarized periodic gravitational wave and the Pais-Uhlenbeck
oscillator | 14 pages, version to appear in Nuclear Physics B | Nuclear Physics B 980 (2022) 115846 | 10.1016/j.nuclphysb.2022.115846 | null | gr-qc hep-th math-ph math.MP | http://creativecommons.org/licenses/by/4.0/ | The "Bargmann framework" allows us to prove the equivalence of the
Pais-Uhlenbeck oscillator with a spin-zero particle in a circularly polarized
periodic gravitational wave. Pushing forward the symmetries (which include
Carroll symmetry) of the latter, we derive conserved charges for the
Pais-Uhlenbeck oscillator.
| [
{
"created": "Fri, 4 Mar 2022 14:23:52 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Apr 2022 15:15:48 GMT",
"version": "v2"
},
{
"created": "Wed, 25 May 2022 12:47:51 GMT",
"version": "v3"
}
] | 2022-05-27 | [
[
"Elbistan",
"Mahmut",
""
]
] | The "Bargmann framework" allows us to prove the equivalence of the Pais-Uhlenbeck oscillator with a spin-zero particle in a circularly polarized periodic gravitational wave. Pushing forward the symmetries (which include Carroll symmetry) of the latter, we derive conserved charges for the Pais-Uhlenbeck oscillator. |
2012.00320 | Chen Wu | Zening Yan, Chen Wu and Wenjun Guo | Scalar field quasinormal modes of noncommutative high dimensional
Schwarzschild-Tangherlini black hole spacetime with smeared matter sources | 26 pages, 11 figures, to be appeared in Nucl. phys. B | null | 10.1016/j.nuclphysb.2020.115217 | null | gr-qc nucl-th | http://creativecommons.org/licenses/by-nc-sa/4.0/ | We investigate the massless scalar quasinormal modes (QNMs) of the
noncommutative $D$-dimensional Schwarzschild-Tangherlini black hole spacetime
in this paper. By using the Wentzel-Kramers-Brillouin (WKB) approximation
method, the asymptotic iterative method (AIM) and the inverted potential method
(IPM) method, we made a detail analysis of the massless scalar QNM frequencies
by varying the general smeared matter distribution and the allowable
characteristic parameters ($k$ and $\theta$) corresponding to different
dimensions. It is found that the nonconvergence of the high order WKB
approximation exists in the QNMs frequencies of scalar perturbation around the
noncommutative $D$-dimensional Schwarzschild black holes. We conclude that the
3rd WKB result should be more reliable than those of the high order WKB method
since our numerical results are also verified by the AIM method and the IPM
method. In the dimensional range of $4\leq D \leq7$, the scalar QNMs as a
function of the different papameters (the noncommutative parameter $\theta$,
the smeared matter distribution parameter $k$, the multipole number $l$ and the
main node number $n$) are obtained. Moreover, we study the dynamical evolution
of a scalar field in the background of the noncommutative high dimensional
Schwarzschild-Tangherlini black hole.
| [
{
"created": "Tue, 1 Dec 2020 07:52:36 GMT",
"version": "v1"
}
] | 2020-12-02 | [
[
"Yan",
"Zening",
""
],
[
"Wu",
"Chen",
""
],
[
"Guo",
"Wenjun",
""
]
] | We investigate the massless scalar quasinormal modes (QNMs) of the noncommutative $D$-dimensional Schwarzschild-Tangherlini black hole spacetime in this paper. By using the Wentzel-Kramers-Brillouin (WKB) approximation method, the asymptotic iterative method (AIM) and the inverted potential method (IPM) method, we made a detail analysis of the massless scalar QNM frequencies by varying the general smeared matter distribution and the allowable characteristic parameters ($k$ and $\theta$) corresponding to different dimensions. It is found that the nonconvergence of the high order WKB approximation exists in the QNMs frequencies of scalar perturbation around the noncommutative $D$-dimensional Schwarzschild black holes. We conclude that the 3rd WKB result should be more reliable than those of the high order WKB method since our numerical results are also verified by the AIM method and the IPM method. In the dimensional range of $4\leq D \leq7$, the scalar QNMs as a function of the different papameters (the noncommutative parameter $\theta$, the smeared matter distribution parameter $k$, the multipole number $l$ and the main node number $n$) are obtained. Moreover, we study the dynamical evolution of a scalar field in the background of the noncommutative high dimensional Schwarzschild-Tangherlini black hole. |
2310.15522 | Kenji Tsuji | Kenji Tsuji, Tomohiro Ishikawa, Kentaro Komori, Koji Nagano, Yutaro
Enomoto, Yuta Michimura, Kurumi Umemura, Ryuma Shimizu, Bin Wu, Shoki
Iwaguchi, Yuki Kawasaki, Akira Furusawa, Seiji Kawamura | Optimization of quantum noise in space gravitational-wave antenna DECIGO
with optical-spring quantum locking considering mixture of vacuum
fluctuations in homodyne detection | 12 pages, 5 figures | null | null | null | gr-qc astro-ph.IM physics.ins-det | http://creativecommons.org/licenses/by/4.0/ | Quantum locking using optical spring and homodyne detection has been devised
to reduce quantum noise that limits the sensitivity of DECIGO, a space-based
gravitational wave antenna in the frequency band around 0.1 Hz for detection of
primordial gravitational waves. The reduction in the upper limit of energy
density ${\Omega}_{\mathrm{GW}}$ from $2{\times}10^{-15}$ to
$1{\times}10^{-16}$, as inferred from recent observations, necessitates
improved sensitivity in DECIGO to meet its primary science goals. To accurately
evaluate the effectiveness of this method, this paper considers a detection
mechanism that takes into account the influence of vacuum fluctuations on
homodyne detection. In addition, an advanced signal processing method is
devised to efficiently utilize signals from each photodetector, and design
parameters for this configuration are optimized for the quantum noise. Our
results show that this method is effective in reducing quantum noise, despite
the detrimental impact of vacuum fluctuations on its sensitivity.
| [
{
"created": "Tue, 24 Oct 2023 05:04:14 GMT",
"version": "v1"
}
] | 2023-10-25 | [
[
"Tsuji",
"Kenji",
""
],
[
"Ishikawa",
"Tomohiro",
""
],
[
"Komori",
"Kentaro",
""
],
[
"Nagano",
"Koji",
""
],
[
"Enomoto",
"Yutaro",
""
],
[
"Michimura",
"Yuta",
""
],
[
"Umemura",
"Kurumi",
""
],
[
... | Quantum locking using optical spring and homodyne detection has been devised to reduce quantum noise that limits the sensitivity of DECIGO, a space-based gravitational wave antenna in the frequency band around 0.1 Hz for detection of primordial gravitational waves. The reduction in the upper limit of energy density ${\Omega}_{\mathrm{GW}}$ from $2{\times}10^{-15}$ to $1{\times}10^{-16}$, as inferred from recent observations, necessitates improved sensitivity in DECIGO to meet its primary science goals. To accurately evaluate the effectiveness of this method, this paper considers a detection mechanism that takes into account the influence of vacuum fluctuations on homodyne detection. In addition, an advanced signal processing method is devised to efficiently utilize signals from each photodetector, and design parameters for this configuration are optimized for the quantum noise. Our results show that this method is effective in reducing quantum noise, despite the detrimental impact of vacuum fluctuations on its sensitivity. |
2306.14023 | Luciano Petruzziello | Luca Buoninfante, Giuseppe Gaetano Luciano, Luciano Petruzziello and
Luca Smaldone | Neutrino decoherence and violation of the strong equivalence principle | null | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We analyze the dynamics of neutrino Gaussian wave-packets, the damping of
flavor oscillations and decoherence effects within the framework of extended
theories of gravity. In particular, we show that, when the underlying
description of the gravitational interaction admits a violation of the strong
equivalence principle, the parameter quantifying such a violation modulates the
wave-packet spreading, giving rise to potentially measurable effects in future
neutrino experiments.
| [
{
"created": "Sat, 24 Jun 2023 17:19:38 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Oct 2023 07:52:18 GMT",
"version": "v2"
}
] | 2023-10-17 | [
[
"Buoninfante",
"Luca",
""
],
[
"Luciano",
"Giuseppe Gaetano",
""
],
[
"Petruzziello",
"Luciano",
""
],
[
"Smaldone",
"Luca",
""
]
] | We analyze the dynamics of neutrino Gaussian wave-packets, the damping of flavor oscillations and decoherence effects within the framework of extended theories of gravity. In particular, we show that, when the underlying description of the gravitational interaction admits a violation of the strong equivalence principle, the parameter quantifying such a violation modulates the wave-packet spreading, giving rise to potentially measurable effects in future neutrino experiments. |
2208.03509 | Michael Zlotnikov | Michael Zlotnikov | Inflation Alternative via the Gravitational Field of a Singularity | 17 pages, 3 figures | 2024 Class. Quantum Grav | 10.1088/1361-6382/ad210d | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We explore the scenario that the observable universe emerged from the
vicinity of a negative mass ring singularity, and all content of the universe
travels at the same group velocity close to the speed of light on a geodesic
trajectory along the axis of rotation of the singularity. In appropriate
coordinate parametrization and evaluated on the trajectory, we find that the
metric tensor in the vicinity of the trajectory exhibits a conformal scale
factor $a(\eta)$ with contraction and subsequent expansion properties that
solve the horizon problem. We then introduce a static flow of gravitating
radiation along the trajectory (perturbatively with respect to the mass scale
of the singularity) to model a homogeneous radiation dominated universe.
Solving the Einstein field equations with a physically motivated ansatz of
metric perturbation then reveals that the effective conformal scale factor
indeed grows asymptotically with the same power law as expected in a
conventional radiation dominated universe.
| [
{
"created": "Sat, 6 Aug 2022 12:36:47 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jul 2023 04:20:26 GMT",
"version": "v2"
}
] | 2024-01-24 | [
[
"Zlotnikov",
"Michael",
""
]
] | We explore the scenario that the observable universe emerged from the vicinity of a negative mass ring singularity, and all content of the universe travels at the same group velocity close to the speed of light on a geodesic trajectory along the axis of rotation of the singularity. In appropriate coordinate parametrization and evaluated on the trajectory, we find that the metric tensor in the vicinity of the trajectory exhibits a conformal scale factor $a(\eta)$ with contraction and subsequent expansion properties that solve the horizon problem. We then introduce a static flow of gravitating radiation along the trajectory (perturbatively with respect to the mass scale of the singularity) to model a homogeneous radiation dominated universe. Solving the Einstein field equations with a physically motivated ansatz of metric perturbation then reveals that the effective conformal scale factor indeed grows asymptotically with the same power law as expected in a conventional radiation dominated universe. |
gr-qc/0003052 | Santiago Esteban Perez Bergliaffa | M. Novello, S. E. Perez Bergliaffa, and J. M. Salim | Singularities in General Relativity coupled to nonlinear electrodynamics | 7 pages, 6 figures. One reference added. Expression of the effective
potential corrected, without change in the conclusions | Class.Quant.Grav. 17 (2000) 3821-3832 | 10.1088/0264-9381/17/18/316 | null | gr-qc | null | We study here some consequences of the nonlinearities of the electromagnetic
field acting as a source of Einstein's equations on the propagation of photons.
We restrict to the particular case of a ``regular black hole'', and show that
there exist singularities in the effective geometry. These singularities may be
hidden behind a horizon or naked, according to the value of a parameter. Some
unusual properties of this solution are also analyzed.
| [
{
"created": "Mon, 13 Mar 2000 20:19:45 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Apr 2000 21:50:05 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Novello",
"M.",
""
],
[
"Bergliaffa",
"S. E. Perez",
""
],
[
"Salim",
"J. M.",
""
]
] | We study here some consequences of the nonlinearities of the electromagnetic field acting as a source of Einstein's equations on the propagation of photons. We restrict to the particular case of a ``regular black hole'', and show that there exist singularities in the effective geometry. These singularities may be hidden behind a horizon or naked, according to the value of a parameter. Some unusual properties of this solution are also analyzed. |
1910.13499 | F Shojai | R. Saadati, F. Shojai | Bending of light in the Universe filled with quintessential dark energy | 14 pages, Accepted for publication in Phys. Rev. D | Phys. Rev. D 100, 104041 (2019) | 10.1103/PhysRevD.100.104041 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As a local effect of dynamical dark energy, bending of light in the presence
of a spherically symmetric and static black hole surrounded by quintessence has
been studied. Having in mind recent observational data, we have treated the
problem as a deviation from Kottler space-time. This deviation is measured by a
perturbation parameter $\varepsilon$ included in the equation of state
parameter of quintessence as $\omega_q=-1+\frac{1}{3}\varepsilon$. Here, the
deflection angle is calculated and then the result is compared with
\cite{Arakida:2011th} in the limit $\varepsilon\rightarrow 0$ where the
quintessence behaves like the cosmological constant. It is shown that unlike
the cosmological constant, the effect of quintessence on the photon energy
equation can not be absorbed into the definition of impact parameter. Moreover
in this paper, we generalize the Kiselev black hole to the case that there is a
modified Chaplygin gas as the dark energy component of the universe and show
that the resulted metric can be reduced to the Kiselev metric by adjusting some
arbitrary parameters.
| [
{
"created": "Tue, 29 Oct 2019 19:49:01 GMT",
"version": "v1"
}
] | 2019-11-25 | [
[
"Saadati",
"R.",
""
],
[
"Shojai",
"F.",
""
]
] | As a local effect of dynamical dark energy, bending of light in the presence of a spherically symmetric and static black hole surrounded by quintessence has been studied. Having in mind recent observational data, we have treated the problem as a deviation from Kottler space-time. This deviation is measured by a perturbation parameter $\varepsilon$ included in the equation of state parameter of quintessence as $\omega_q=-1+\frac{1}{3}\varepsilon$. Here, the deflection angle is calculated and then the result is compared with \cite{Arakida:2011th} in the limit $\varepsilon\rightarrow 0$ where the quintessence behaves like the cosmological constant. It is shown that unlike the cosmological constant, the effect of quintessence on the photon energy equation can not be absorbed into the definition of impact parameter. Moreover in this paper, we generalize the Kiselev black hole to the case that there is a modified Chaplygin gas as the dark energy component of the universe and show that the resulted metric can be reduced to the Kiselev metric by adjusting some arbitrary parameters. |
0807.4171 | Kazuhiro Hayama | Kazuhiro Hayama, Shantanu Desai, Soumya D. Mohanty, Malik Rakhmanov,
Tiffany Summerscales, Sanichiro Yoshida | Source Tracking for Sco X-1 | Accepted for the publication in CQG | Class. Quant. Grav.25:184021, 2008 | 10.1088/0264-9381/25/18/184021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Sco X-1, the brightest low mass X-ray binary, is likely to be a source for
gravitational wave emission. In one mechanism, emission of a gravitational wave
arrests the increase in spin frequency due to the accretion torque in a low
mass X-ray binary. Since the gravitational waveform is unknown, a detection
method assuming no apriori knowledge of the signal is preferable. In this
paper, we propose to search for a gravitational wave from Sco X-1 using a {{\it
source tracking}} method based on a coherent network analysis. In the method,
we combine data from several interferometric gravitational wave detectors
taking into account of the direction to Sco X-1, and reconstruct two
polarization waveforms at the location of Sco X-1 in the sky as Sco X-1 is
moving. The source tracking method opens up the possibility of searching for a
wide variety of signals. We perform Monte Carlo simulations and show results
for bursts, modeled, short duration periodic sources using a simple excess
power and a matched filter method on the reconstructed signals.
| [
{
"created": "Fri, 25 Jul 2008 19:40:13 GMT",
"version": "v1"
}
] | 2009-02-23 | [
[
"Hayama",
"Kazuhiro",
""
],
[
"Desai",
"Shantanu",
""
],
[
"Mohanty",
"Soumya D.",
""
],
[
"Rakhmanov",
"Malik",
""
],
[
"Summerscales",
"Tiffany",
""
],
[
"Yoshida",
"Sanichiro",
""
]
] | Sco X-1, the brightest low mass X-ray binary, is likely to be a source for gravitational wave emission. In one mechanism, emission of a gravitational wave arrests the increase in spin frequency due to the accretion torque in a low mass X-ray binary. Since the gravitational waveform is unknown, a detection method assuming no apriori knowledge of the signal is preferable. In this paper, we propose to search for a gravitational wave from Sco X-1 using a {{\it source tracking}} method based on a coherent network analysis. In the method, we combine data from several interferometric gravitational wave detectors taking into account of the direction to Sco X-1, and reconstruct two polarization waveforms at the location of Sco X-1 in the sky as Sco X-1 is moving. The source tracking method opens up the possibility of searching for a wide variety of signals. We perform Monte Carlo simulations and show results for bursts, modeled, short duration periodic sources using a simple excess power and a matched filter method on the reconstructed signals. |
2103.05389 | Valerio Faraoni | Valerio Faraoni (Bishop's University) and Andrea Giusti (ETH Zurich) | Thermodynamics of scalar-tensor gravity | 5 pages. Corrected Eq. (26) describing the approach to equilibrium
and one typographical error. Matches Letter to appear in Physical Review D | Phys. Rev. D 103, 121501 (2021) | 10.1103/PhysRevD.103.L121501 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Previously, the Einstein equation has been described as an equation of state,
general relativity as the equilibrium state of gravity, and $f({\cal R})$
gravity as a non-equilibrium one. We apply Eckart's first order thermodynamics
to the effective dissipative fluid describing scalar-tensor gravity.
Surprisingly, we obtain simple expressions for the effective heat flux,
"temperature of gravity", shear and bulk viscosity, and entropy density, plus a
generalized Fourier law in a consistent Eckart thermodynamical picture.
Well-defined notions of temperature and approach to equilibrium, missing in the
current thermodynamics of spacetime scenarios, naturally emerge.
| [
{
"created": "Tue, 9 Mar 2021 12:15:33 GMT",
"version": "v1"
},
{
"created": "Sun, 9 May 2021 00:42:04 GMT",
"version": "v2"
}
] | 2021-06-09 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
],
[
"Giusti",
"Andrea",
"",
"ETH Zurich"
]
] | Previously, the Einstein equation has been described as an equation of state, general relativity as the equilibrium state of gravity, and $f({\cal R})$ gravity as a non-equilibrium one. We apply Eckart's first order thermodynamics to the effective dissipative fluid describing scalar-tensor gravity. Surprisingly, we obtain simple expressions for the effective heat flux, "temperature of gravity", shear and bulk viscosity, and entropy density, plus a generalized Fourier law in a consistent Eckart thermodynamical picture. Well-defined notions of temperature and approach to equilibrium, missing in the current thermodynamics of spacetime scenarios, naturally emerge. |
2209.07416 | Stefano Rinaldi | Stefano Rinaldi, Hannah Middleton, Walter Del Pozzo, Jonathan Gair | Bayesian analysis of systematic errors in the determination of the
constant of gravitation | 11 pages, 2 figures. Accepted for publication in EPJ C | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Measurements of the gravitational constant $G$ are notoriously difficult.
Individual state-of-the-art experiments have managed to determine the value of
$G$ with high precision: although, when considered collectively, the range in
the measured values of $G$ far exceeds individual uncertainties, suggesting the
presence of unaccounted for systematic effects.
Here, we propose a Bayesian framework to account for the presence of
systematic errors in the various measurement of $G$ while proposing a consensus
value, following two paths: a parametric approach, based on the Maximum Entropy
Principle, and a non-parametric one, the latter being a very flexible approach
not committed to any specific functional form.
With both our methods, we find that the uncertainty on this fundamental
constant, once systematics are included, is significantly larger than what
quoted in CODATA 2018. Moreover, the morphology of the non-parametric
distribution hints towards the presence of several sources of unaccounted for
systematics. In light of this, we recommend a consensus value for the
gravitational constant $G = 6.6740^{+0.0015}_{-0.0015} \times 10^{-11}\
\mathrm{m}^3\ \mathrm{kg}^{-1}\ \mathrm{s}^{-2}$.
| [
{
"created": "Thu, 15 Sep 2022 16:11:50 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Sep 2023 08:06:00 GMT",
"version": "v2"
}
] | 2023-09-26 | [
[
"Rinaldi",
"Stefano",
""
],
[
"Middleton",
"Hannah",
""
],
[
"Del Pozzo",
"Walter",
""
],
[
"Gair",
"Jonathan",
""
]
] | Measurements of the gravitational constant $G$ are notoriously difficult. Individual state-of-the-art experiments have managed to determine the value of $G$ with high precision: although, when considered collectively, the range in the measured values of $G$ far exceeds individual uncertainties, suggesting the presence of unaccounted for systematic effects. Here, we propose a Bayesian framework to account for the presence of systematic errors in the various measurement of $G$ while proposing a consensus value, following two paths: a parametric approach, based on the Maximum Entropy Principle, and a non-parametric one, the latter being a very flexible approach not committed to any specific functional form. With both our methods, we find that the uncertainty on this fundamental constant, once systematics are included, is significantly larger than what quoted in CODATA 2018. Moreover, the morphology of the non-parametric distribution hints towards the presence of several sources of unaccounted for systematics. In light of this, we recommend a consensus value for the gravitational constant $G = 6.6740^{+0.0015}_{-0.0015} \times 10^{-11}\ \mathrm{m}^3\ \mathrm{kg}^{-1}\ \mathrm{s}^{-2}$. |
2107.01083 | Thomas Celora | Thomas Celora, Nils Andersson, Ian Hawke and Gregory L. Comer | A covariant approach to relativistic large-eddy simulations: The
fibration picture | Version as published on Phys. Rev. D | Phys. Rev. D 104, 084090 (2021) | 10.1103/PhysRevD.104.084090 | null | gr-qc astro-ph.HE physics.flu-dyn | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Models of turbulent flows require the resolution of a vast range of scales,
from large eddies to small-scale features directly associated with dissipation.
As the required resolution is not within reach of large scale numerical
simulations, standard strategies involve a smoothing of the fluid dynamics,
either through time averaging or spatial filtering. These strategies raise
formal issues in general relativity, where the split between space and time is
observer dependent. To make progress, we develop a new covariant framework for
filtering/averaging based on the fibration of spacetime associated with fluid
elements and the use of Fermi coordinates to facilitate a meaningful local
analysis. We derive the resolved equations of motion, demonstrating how
"effective" dissipative terms arise because of the coarse-graining, and paying
particular attention to the thermodynamical interpretation of the resolved
quantities. Finally, as the smoothing of the fluid-dynamics inevitably leads to
a closure problem, we propose a new closure scheme inspired by recent progress
in the modelling of dissipative relativistic fluids, and crucially, demonstrate
the linear stability of the proposed model.
| [
{
"created": "Fri, 2 Jul 2021 13:51:36 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Oct 2021 10:56:36 GMT",
"version": "v2"
}
] | 2021-10-28 | [
[
"Celora",
"Thomas",
""
],
[
"Andersson",
"Nils",
""
],
[
"Hawke",
"Ian",
""
],
[
"Comer",
"Gregory L.",
""
]
] | Models of turbulent flows require the resolution of a vast range of scales, from large eddies to small-scale features directly associated with dissipation. As the required resolution is not within reach of large scale numerical simulations, standard strategies involve a smoothing of the fluid dynamics, either through time averaging or spatial filtering. These strategies raise formal issues in general relativity, where the split between space and time is observer dependent. To make progress, we develop a new covariant framework for filtering/averaging based on the fibration of spacetime associated with fluid elements and the use of Fermi coordinates to facilitate a meaningful local analysis. We derive the resolved equations of motion, demonstrating how "effective" dissipative terms arise because of the coarse-graining, and paying particular attention to the thermodynamical interpretation of the resolved quantities. Finally, as the smoothing of the fluid-dynamics inevitably leads to a closure problem, we propose a new closure scheme inspired by recent progress in the modelling of dissipative relativistic fluids, and crucially, demonstrate the linear stability of the proposed model. |
1906.04465 | Arvin Ravanpak | Arvin Ravanpak and Golnaz Farpour Fadakar | Dynamical System Analysis of Brane Induced Gravity with Tachyon Field | null | Class. Quantum Grav. 36 (2019) 235003 | 10.1088/1361-6382/ab4eec | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this manuscript we use the dynamical system approach to study the linear
dynamics of a normal DGP brane-world model with a tachyon field as the dark
energy component. Our focus is on a Gaussian tachyonic potential in which the
parameter $\lambda=-V_\phi/V^{3/2}$, goes to infinity. One of the most
important results of this study is that we find critical submanifolds which
indicate the effect of extra dimension.
| [
{
"created": "Tue, 11 Jun 2019 09:50:31 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Nov 2019 12:02:04 GMT",
"version": "v2"
}
] | 2020-01-08 | [
[
"Ravanpak",
"Arvin",
""
],
[
"Fadakar",
"Golnaz Farpour",
""
]
] | In this manuscript we use the dynamical system approach to study the linear dynamics of a normal DGP brane-world model with a tachyon field as the dark energy component. Our focus is on a Gaussian tachyonic potential in which the parameter $\lambda=-V_\phi/V^{3/2}$, goes to infinity. One of the most important results of this study is that we find critical submanifolds which indicate the effect of extra dimension. |
1404.1681 | Jun-Wang Lu | Ya-Bo Wu, Yue-Yue Zhao, Jun-Wang Lu, Xue Zhang, Cheng-Yuan Zhang,
Jia-Wei Qiao | Five-dimensional generalized $f(R)$ gravity with curvature-matter
coupling | arXiv admin note: text overlap with arXiv:0912.4581,
arXiv:gr-qc/0411066 by other authors | Eur. Phys. J . C (2014) 74 :2791 | 10.1140/epjc/s10052-014-2791-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The generalized $f(R)$ gravity with curvature-matter coupling in
five-dimensional (5D) spacetime can be established by assuming a
hypersurface-orthogonal spacelike Killing vector field of 5D spacetime, and it
can be reduced to the 4D formulism of FRW universe. This theory is quite
general and can give the corresponding results to the Einstein gravity, $f(R)$
gravity with both no-coupling and non-minimal coupling in 5D spacetime as
special cases, that is, we would give the some new results besides previous
ones given by Ref.\cite{60}. Furthermore, in order to get some insight into the
effects of this theory on the 4D spacetime, by considering a specific type of
models with $f_{1}(R)=f_{2}(R)=\alpha R^{m}$ and $B(L_{m})=L_{m}=-\rho$, we not
only discuss the constraints on the model parameters $m$, $n$, but also
illustrate the evolutionary trajectories of the scale factor $a(t)$, the
deceleration parameter $q(t)$ and the scalar field $\epsilon(t)$, $\phi(t)$ in
the reduced 4D spacetime. The research results show that this type of $f(R)$
gravity models given by us could explain the current accelerated expansion of
our universe without introducing dark energy.
| [
{
"created": "Mon, 7 Apr 2014 07:58:38 GMT",
"version": "v1"
}
] | 2014-04-22 | [
[
"Wu",
"Ya-Bo",
""
],
[
"Zhao",
"Yue-Yue",
""
],
[
"Lu",
"Jun-Wang",
""
],
[
"Zhang",
"Xue",
""
],
[
"Zhang",
"Cheng-Yuan",
""
],
[
"Qiao",
"Jia-Wei",
""
]
] | The generalized $f(R)$ gravity with curvature-matter coupling in five-dimensional (5D) spacetime can be established by assuming a hypersurface-orthogonal spacelike Killing vector field of 5D spacetime, and it can be reduced to the 4D formulism of FRW universe. This theory is quite general and can give the corresponding results to the Einstein gravity, $f(R)$ gravity with both no-coupling and non-minimal coupling in 5D spacetime as special cases, that is, we would give the some new results besides previous ones given by Ref.\cite{60}. Furthermore, in order to get some insight into the effects of this theory on the 4D spacetime, by considering a specific type of models with $f_{1}(R)=f_{2}(R)=\alpha R^{m}$ and $B(L_{m})=L_{m}=-\rho$, we not only discuss the constraints on the model parameters $m$, $n$, but also illustrate the evolutionary trajectories of the scale factor $a(t)$, the deceleration parameter $q(t)$ and the scalar field $\epsilon(t)$, $\phi(t)$ in the reduced 4D spacetime. The research results show that this type of $f(R)$ gravity models given by us could explain the current accelerated expansion of our universe without introducing dark energy. |
gr-qc/9906025 | Guendel Eduardo | E.I. Guendelman | Scale Symmetry Spontaneously Broken by Asymptotic Behavior | null | Class.Quant.Grav. 17 (2000) 361-372 | 10.1088/0264-9381/17/2/307 | null | gr-qc | null | Conserved quantities are obtained and analyzed in the new models with global
scale invariance recently proposed. Such models allow for non tivial scalar
field potentials and masses for particles, so that the scale symmetry must be
broken somehow. We get to this conclusion by showing that the infrared behavior
of the conserved currents is singular so that there are no conserved charges
associated with the global scale symmetry. The scale symmetry plays
nevertheless a crucial role in determining the structure of the theory and it
implies that in some high field regions the potentials become flat.
| [
{
"created": "Mon, 7 Jun 1999 09:34:15 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Guendelman",
"E. I.",
""
]
] | Conserved quantities are obtained and analyzed in the new models with global scale invariance recently proposed. Such models allow for non tivial scalar field potentials and masses for particles, so that the scale symmetry must be broken somehow. We get to this conclusion by showing that the infrared behavior of the conserved currents is singular so that there are no conserved charges associated with the global scale symmetry. The scale symmetry plays nevertheless a crucial role in determining the structure of the theory and it implies that in some high field regions the potentials become flat. |
1901.05953 | T. P. Singh | Tejinder P. Singh | Outline for a quantum theory of gravity | v1: 7 pages, one figure; v2: 7 pages, one figure, minor
modifications, accepted for publication in Zeitschrift f\"ur Naturforschung | Z. Naturforsch. A 74 (2019) 383 | 10.1515/zna-2019-0027 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By invoking an asymmetric metric tensor, and borrowing ideas from
non-commutative geometry, string theory, and trace dynamics, we propose an
action function for quantum gravity. The action is proportional to the four
dimensional non-commutative curvature scalar (which is torsion dependent) that
is sourced by the Nambu-Goto world-sheet action for a string, plus the
Kalb-Ramond string action. This `quantum gravity' is actually a non-commutative
{\it classical} matrix dynamics, and the only two fundamental constants in the
theory are the square of Planck length and the speed of light. By treating the
entity described by this action as a microstate, one constructs the statistical
thermodynamics of a large number of such microstates, in the spirit of trace
dynamics. Quantum field theory (and $\hbar$) and quantum general relativity
(and $G$) emerge from the underlying matrix dynamics in the thermodynamic
limit. The statistical fluctuations that are inevitably present about
equilibrium, are the source for spontaneous localisation, which drives
macroscopic quantum gravitational systems to the classical general relativistic
limit. While the mathematical formalism governing these ideas remains to be
developed, we hope here to highlight the deep connection between quantum
foundations, and the sought for quantum theory of gravity. In the sense
described in this article, ongoing experimental tests of spontaneous collapse
theories are in fact also tests of string theory!
| [
{
"created": "Thu, 17 Jan 2019 18:50:07 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Jan 2019 09:51:52 GMT",
"version": "v2"
}
] | 2019-07-01 | [
[
"Singh",
"Tejinder P.",
""
]
] | By invoking an asymmetric metric tensor, and borrowing ideas from non-commutative geometry, string theory, and trace dynamics, we propose an action function for quantum gravity. The action is proportional to the four dimensional non-commutative curvature scalar (which is torsion dependent) that is sourced by the Nambu-Goto world-sheet action for a string, plus the Kalb-Ramond string action. This `quantum gravity' is actually a non-commutative {\it classical} matrix dynamics, and the only two fundamental constants in the theory are the square of Planck length and the speed of light. By treating the entity described by this action as a microstate, one constructs the statistical thermodynamics of a large number of such microstates, in the spirit of trace dynamics. Quantum field theory (and $\hbar$) and quantum general relativity (and $G$) emerge from the underlying matrix dynamics in the thermodynamic limit. The statistical fluctuations that are inevitably present about equilibrium, are the source for spontaneous localisation, which drives macroscopic quantum gravitational systems to the classical general relativistic limit. While the mathematical formalism governing these ideas remains to be developed, we hope here to highlight the deep connection between quantum foundations, and the sought for quantum theory of gravity. In the sense described in this article, ongoing experimental tests of spontaneous collapse theories are in fact also tests of string theory! |
0712.0565 | Diego Pavon | Diego Pavon (Univ. Autonoma de Barcelona), Bin Wang (Fudan University) | Le Chatelier-Braun principle in cosmological physics | 6 pages, revtex file, no figures; version accepted for publication in
General Relativity and Gravitation | Gen.Rel.Grav.41:1-5,2009 | 10.1007/s10714-008-0656-y | null | gr-qc astro-ph hep-ph | null | Assuming that dark energy may be treated as a fluid with a well defined
temperature, close to equilibrium, we argue that if nowadays there is a
transfer of energy between dark energy and dark matter, it must be such that
the latter gains energy from the former and not the other way around.
| [
{
"created": "Tue, 4 Dec 2007 16:25:11 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Apr 2008 11:40:30 GMT",
"version": "v2"
}
] | 2009-01-16 | [
[
"Pavon",
"Diego",
"",
"Univ. Autonoma de Barcelona"
],
[
"Wang",
"Bin",
"",
"Fudan University"
]
] | Assuming that dark energy may be treated as a fluid with a well defined temperature, close to equilibrium, we argue that if nowadays there is a transfer of energy between dark energy and dark matter, it must be such that the latter gains energy from the former and not the other way around. |
2210.15597 | Thomas Pappas | Thomas D. Pappas, Camilo Posada and Zden\v{e}k Stuchl\'ik | Extended Tolman III and VII solutions in $f(\mathcal{R},T)$ gravity:
Models for neutron stars and supermassive stars | 24 pages, 20 figures, 1 table, version to match the one published in
Phys. Rev. D, corrected issue of version 2 with figures appearing in the
references section | Phys. Rev. D 106 (2022) 12, 124014 | 10.1103/PhysRevD.106.124014 | null | gr-qc astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the context of linear $f(\mathcal{R},T)=\mathcal{R}+\chi T$ gravity, where
$\mathcal{R}$ is the Ricci scalar, $T$ is the trace of the energy-momentum
tensor, and $\chi$ is a dimensionless parameter, we have obtained exact
analytical and numerical solutions for isotropic perfect-fluid spheres in
hydrostatic equilibrium. Our solutions correspond to two-parametric extensions
of the Tolman III (T-III) and Tolman VII (T-VII) models, in terms of the
compactness $\beta$ and $\chi$. By requiring configurations that exhibit
monotonically decreasing radial profiles for both the energy density and
pressure, compliance with the energy conditions, as well as subluminal speed of
sound, we have constrained the parametric space of our solutions. We have also
obtained analytically a parametric deformation of the T-VII solution that
continuously interpolates between the T-III and T-VII models for any $\chi$,
and in the appropriate limits, provides an analytic approximation for the
uniform density configuration in linear $f(\mathcal{R},T)$ gravity. Finally, by
integrating numerically the TOV equations, we have obtained a numerical
solution for the uniform-density configuration and subsequently, using the
mass-radius relations, we have obtained the maximum mass that can be supported
by such configurations. We have found that in the appropriate parametric regime
our solution is in very good agreement with the observational bounds for the
masses and radii of neutron stars.
| [
{
"created": "Thu, 27 Oct 2022 16:37:25 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Jan 2023 15:58:33 GMT",
"version": "v2"
},
{
"created": "Fri, 27 Jan 2023 15:50:28 GMT",
"version": "v3"
}
] | 2023-01-30 | [
[
"Pappas",
"Thomas D.",
""
],
[
"Posada",
"Camilo",
""
],
[
"Stuchlík",
"Zdeněk",
""
]
] | In the context of linear $f(\mathcal{R},T)=\mathcal{R}+\chi T$ gravity, where $\mathcal{R}$ is the Ricci scalar, $T$ is the trace of the energy-momentum tensor, and $\chi$ is a dimensionless parameter, we have obtained exact analytical and numerical solutions for isotropic perfect-fluid spheres in hydrostatic equilibrium. Our solutions correspond to two-parametric extensions of the Tolman III (T-III) and Tolman VII (T-VII) models, in terms of the compactness $\beta$ and $\chi$. By requiring configurations that exhibit monotonically decreasing radial profiles for both the energy density and pressure, compliance with the energy conditions, as well as subluminal speed of sound, we have constrained the parametric space of our solutions. We have also obtained analytically a parametric deformation of the T-VII solution that continuously interpolates between the T-III and T-VII models for any $\chi$, and in the appropriate limits, provides an analytic approximation for the uniform density configuration in linear $f(\mathcal{R},T)$ gravity. Finally, by integrating numerically the TOV equations, we have obtained a numerical solution for the uniform-density configuration and subsequently, using the mass-radius relations, we have obtained the maximum mass that can be supported by such configurations. We have found that in the appropriate parametric regime our solution is in very good agreement with the observational bounds for the masses and radii of neutron stars. |
1503.08973 | Bibhas Majhi Ranjan | Bibhas Ranjan Majhi | Entropy function from the gravitational surface action for an extremal
near horizon black hole | Matches with the accepted version, to appear in EPJC | Eur.Phys.J. C75 (2015) 11, 521 | 10.1140/epjc/s10052-015-3744-7 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is often argued that {\it all the information of a gravitational theory is
encoded in the surface term of the action}; which means one can find several
physical quantities just from the surface term without incorporating the bulk
part of the action. This has been observed in various instances; e.g.
derivation of the Einstein's equations, surface term calculated on the horizon
leads to entropy, etc. Here I investigate the role of it in the context of
entropy function and entropy of extremal near horizon black holes. Considering
only the Gibbons-Hawking-York (GHY) surface term to define an entropy function
for the extremal near horizon black hole solution, it is observed that the
extremization of such function leads to the exact value of the horizon entropy.
This analysis again supports the previous claim that there exists a ``{\it
holographic}'' nature in the gravitational action -- surface term contains the
information of the bulk.
| [
{
"created": "Tue, 31 Mar 2015 09:17:39 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Oct 2015 12:45:15 GMT",
"version": "v2"
}
] | 2015-11-09 | [
[
"Majhi",
"Bibhas Ranjan",
""
]
] | It is often argued that {\it all the information of a gravitational theory is encoded in the surface term of the action}; which means one can find several physical quantities just from the surface term without incorporating the bulk part of the action. This has been observed in various instances; e.g. derivation of the Einstein's equations, surface term calculated on the horizon leads to entropy, etc. Here I investigate the role of it in the context of entropy function and entropy of extremal near horizon black holes. Considering only the Gibbons-Hawking-York (GHY) surface term to define an entropy function for the extremal near horizon black hole solution, it is observed that the extremization of such function leads to the exact value of the horizon entropy. This analysis again supports the previous claim that there exists a ``{\it holographic}'' nature in the gravitational action -- surface term contains the information of the bulk. |
2007.02225 | Puxun Wu | Guoqiang Jin, Chengjie Fu, Puxun Wu, Hongwei Yu | Production of gravitational waves during preheating in the Starobinsky
inflationary model | 15 pages, 5 figures | Eur. Phys. J. C 80, 491 (2020) | 10.1140/epjc/s10052-020-8061-0 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The production of GWs during preheating in the Starobinsky model with a
nonminimally coupled auxiliary scalar field is studied through the lattice
simulation in this paper. We find that the GW spectrum $\Omega_{\rm gw}$ grows
fast with the increase of the absolute value of coupling parameter $\xi$. This
is because the resonant bands become broad with the increase of $|\xi|$. When
$\xi<0$, $\Omega_{\rm gw}$ begins to grow once the inflation ends and grows
faster than the case of $\xi>0$. $\Omega_{\rm gw}$ reaches the maximum at
$\xi=-20$ ($\xi=42$ for the case $\xi>0$) and then decreases with slight
oscillation. Furthermore we find that the GWs produced in the era of preheating
satisfy the limits from the Planck and next-generation CMB experiments.
| [
{
"created": "Sun, 5 Jul 2020 02:09:06 GMT",
"version": "v1"
}
] | 2020-07-08 | [
[
"Jin",
"Guoqiang",
""
],
[
"Fu",
"Chengjie",
""
],
[
"Wu",
"Puxun",
""
],
[
"Yu",
"Hongwei",
""
]
] | The production of GWs during preheating in the Starobinsky model with a nonminimally coupled auxiliary scalar field is studied through the lattice simulation in this paper. We find that the GW spectrum $\Omega_{\rm gw}$ grows fast with the increase of the absolute value of coupling parameter $\xi$. This is because the resonant bands become broad with the increase of $|\xi|$. When $\xi<0$, $\Omega_{\rm gw}$ begins to grow once the inflation ends and grows faster than the case of $\xi>0$. $\Omega_{\rm gw}$ reaches the maximum at $\xi=-20$ ($\xi=42$ for the case $\xi>0$) and then decreases with slight oscillation. Furthermore we find that the GWs produced in the era of preheating satisfy the limits from the Planck and next-generation CMB experiments. |
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