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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1101.5756
|
Vjacheslav Dorofeev
|
V. Yu. Dorofeev
|
Model of the electro-weak, gravitational and strong interactions in the
O-theory
|
21 pages
| null | null | null |
gr-qc nucl-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Based on the matrix representation of octonion algebra, supplied with
specific multiplication rule, the model of electroweak and gravitational
interactions is built up. While electroweak interaction in this model is
induced by charged W-bosons, other two forces appear to have slightly more
complicated nature. Gravitational interaction coincides in the model with
dipole interaction of a pair of charged bosons. The dipole consists of a
charged vector bosons pair from the major octonion algebra fields. When the
charged dipole pair interacts with the neutral bosons pair from the major
octonion algebra fields, the charged bosons pair misses its mass. The drop in
mass leads to appearance of far-ranging forces of gravitational interaction.
Finally, strong interaction appears in the model as internal gravitational
solution of 'black whole' type with the peculiar 'gravitational' constant. The
solution is a product of interaction of major vector fields pair with charged
W-bosons pair. It is inferred from the model that the state space is
ten-dimensional. The space is built as a module of the matrix representation of
octonion algebra over the particles field (O-module). Similarly to the Standard
Weinberg-Salam theory, the particle mass here appears as the product of
interaction of massless spinor fields and Higgs field from O-module
representation.
|
[
{
"created": "Sun, 30 Jan 2011 10:04:34 GMT",
"version": "v1"
}
] |
2011-02-01
|
[
[
"Dorofeev",
"V. Yu.",
""
]
] |
Based on the matrix representation of octonion algebra, supplied with specific multiplication rule, the model of electroweak and gravitational interactions is built up. While electroweak interaction in this model is induced by charged W-bosons, other two forces appear to have slightly more complicated nature. Gravitational interaction coincides in the model with dipole interaction of a pair of charged bosons. The dipole consists of a charged vector bosons pair from the major octonion algebra fields. When the charged dipole pair interacts with the neutral bosons pair from the major octonion algebra fields, the charged bosons pair misses its mass. The drop in mass leads to appearance of far-ranging forces of gravitational interaction. Finally, strong interaction appears in the model as internal gravitational solution of 'black whole' type with the peculiar 'gravitational' constant. The solution is a product of interaction of major vector fields pair with charged W-bosons pair. It is inferred from the model that the state space is ten-dimensional. The space is built as a module of the matrix representation of octonion algebra over the particles field (O-module). Similarly to the Standard Weinberg-Salam theory, the particle mass here appears as the product of interaction of massless spinor fields and Higgs field from O-module representation.
|
gr-qc/9607010
|
Takashi Hara
|
Takashi Hara (Tokyo Institute of Technology), Tatsuhiko Koike (Keio
University), and Satoshi Adachi (Tokyo Institute of Technology)
|
Renormalization group and critical behaviour in gravitational collapse
|
ReVTeX, 42 pages with 8 embedded PS figures using "boxedeps.tex."
This is a replacement, which (1) presents more straightforward presentation
by sending some detailed "proofs" into the appendices, (2) corrects some
minor errors in the first version
| null | null | null |
gr-qc
| null |
We present a general framework for understanding and analyzing critical
behaviour in gravitational collapse. We adopt the method of renormalization
group, which has the following advantages. (1) It provides a natural
explanation for various types of universality and scaling observed in numerical
studies. In particular, universality in initial data space and universality for
different models are understood in a unified way. (2) It enables us to perform
a detailed analysis of time evolution beyond linear perturbation, by providing
rigorous controls on nonlinear terms. Under physically reasonable assumptions
we prove: (1) Uniqueness of the relevant mode around a fixed point implies
universality in initial data space. (2) The critical exponent $\beta_{BH}$ and
the unique positive eigenvalue $\kappa$ of the relevant mode is exactly related
by $\beta_{BH} = \beta /\kappa$, where $\beta$ is a scaling exponent. (3) The
above (1) and (2) hold also for discretely self-similar case (replacing ``fixed
point'' with ``limit cycle''). (4) Universality for diffent models holds under
a certain condition.
According to the framework, we carry out a rather complete (though not
mathematically rigorous) analysis for perfect fluids with pressure proportional
to density, in a wide range of the adiabatic index $\gamma$. The uniqueness of
the relevant mode around a fixed point is established by Lyapunov analyses.
This shows that the critical phenomena occurs not only for the radiation fluid
but also for perfect fluids with $1 < \gamma \lesssim 1.88$. The accurate
values of critical exponents are calculated for the models.
|
[
{
"created": "Thu, 4 Jul 1996 11:24:18 GMT",
"version": "v1"
},
{
"created": "Wed, 28 May 1997 10:09:36 GMT",
"version": "v2"
}
] |
2016-08-31
|
[
[
"Hara",
"Takashi",
"",
"Tokyo Institute of Technology"
],
[
"Koike",
"Tatsuhiko",
"",
"Keio\n University"
],
[
"Adachi",
"Satoshi",
"",
"Tokyo Institute of Technology"
]
] |
We present a general framework for understanding and analyzing critical behaviour in gravitational collapse. We adopt the method of renormalization group, which has the following advantages. (1) It provides a natural explanation for various types of universality and scaling observed in numerical studies. In particular, universality in initial data space and universality for different models are understood in a unified way. (2) It enables us to perform a detailed analysis of time evolution beyond linear perturbation, by providing rigorous controls on nonlinear terms. Under physically reasonable assumptions we prove: (1) Uniqueness of the relevant mode around a fixed point implies universality in initial data space. (2) The critical exponent $\beta_{BH}$ and the unique positive eigenvalue $\kappa$ of the relevant mode is exactly related by $\beta_{BH} = \beta /\kappa$, where $\beta$ is a scaling exponent. (3) The above (1) and (2) hold also for discretely self-similar case (replacing ``fixed point'' with ``limit cycle''). (4) Universality for diffent models holds under a certain condition. According to the framework, we carry out a rather complete (though not mathematically rigorous) analysis for perfect fluids with pressure proportional to density, in a wide range of the adiabatic index $\gamma$. The uniqueness of the relevant mode around a fixed point is established by Lyapunov analyses. This shows that the critical phenomena occurs not only for the radiation fluid but also for perfect fluids with $1 < \gamma \lesssim 1.88$. The accurate values of critical exponents are calculated for the models.
|
1409.3743
|
Wen-Biao Han
|
Michael H. Soffel, Wen-Biao Han
|
The gravitational time delay in the field of a slowly moving body with
arbitrary multipoles
|
9 pages, no figures
|
Physics Letters A 379, 233-236 (2015)
|
10.1016/j.physleta.2014.11.047
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We calculate the time delay of light in the gravitational field of a slowly
moving body with arbitrary multipoles (mass and spin multipole moments) by the
Time-Transfer-Function (TTF) formalism. The parameters we use, first introduced
by Kopeikin for a gravitational source at rest, make the integration of the TTF
very elegant and simple. Results completely coincide with expressions from the
literature. The results for a moving body (with constant velocity) with
complete multipole-structure are new, according to our knowledge.
|
[
{
"created": "Fri, 12 Sep 2014 14:17:02 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Dec 2014 22:03:21 GMT",
"version": "v2"
}
] |
2014-12-30
|
[
[
"Soffel",
"Michael H.",
""
],
[
"Han",
"Wen-Biao",
""
]
] |
We calculate the time delay of light in the gravitational field of a slowly moving body with arbitrary multipoles (mass and spin multipole moments) by the Time-Transfer-Function (TTF) formalism. The parameters we use, first introduced by Kopeikin for a gravitational source at rest, make the integration of the TTF very elegant and simple. Results completely coincide with expressions from the literature. The results for a moving body (with constant velocity) with complete multipole-structure are new, according to our knowledge.
|
0908.4178
|
Luca Fabbri
|
Luca Fabbri
|
Geometrical Properties and Propagation for the Proca Field Theory
|
6 pages
|
Annales Fond.Broglie 36:19-28,2011
| null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider the Proca field with dynamical term given by the exterior
derivative with respect to the most general connection; the most general Proca
field equations are given, and a discussion about the propagation and the
geometrical properties are presented: it is shown that this generalization is
inconsistent. So the standard theory is already the most general Proca Theory
possible.
|
[
{
"created": "Fri, 28 Aug 2009 10:18:07 GMT",
"version": "v1"
}
] |
2012-12-06
|
[
[
"Fabbri",
"Luca",
""
]
] |
We consider the Proca field with dynamical term given by the exterior derivative with respect to the most general connection; the most general Proca field equations are given, and a discussion about the propagation and the geometrical properties are presented: it is shown that this generalization is inconsistent. So the standard theory is already the most general Proca Theory possible.
|
0708.3820
|
Elizabeth Winstanley
|
Elizabeth Winstanley and Phil M. Young
|
Vacuum polarization for lukewarm black holes
|
19 pages, 9 figures, revtex4. Minor changes only, accepted for
publication in Physical Review D
|
Phys.Rev.D77:024008,2008
|
10.1103/PhysRevD.77.024008
| null |
gr-qc
| null |
We compute the renormalized expectation value of the square of a quantum
scalar field on a Reissner-Nordstrom-de Sitter black hole in which the
temperatures of the event and cosmological horizons are equal (`lukewarm' black
hole). Our numerical calculations for a thermal state at the same temperature
as the two horizons indicate that this renormalized expectation value is
regular on both the event and cosmological horizons. We are able to show
analytically, using an approximation for the field modes near the horizons,
that this is indeed the case.
|
[
{
"created": "Tue, 28 Aug 2007 17:11:28 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Dec 2007 10:20:22 GMT",
"version": "v2"
}
] |
2008-11-26
|
[
[
"Winstanley",
"Elizabeth",
""
],
[
"Young",
"Phil M.",
""
]
] |
We compute the renormalized expectation value of the square of a quantum scalar field on a Reissner-Nordstrom-de Sitter black hole in which the temperatures of the event and cosmological horizons are equal (`lukewarm' black hole). Our numerical calculations for a thermal state at the same temperature as the two horizons indicate that this renormalized expectation value is regular on both the event and cosmological horizons. We are able to show analytically, using an approximation for the field modes near the horizons, that this is indeed the case.
|
1906.01978
|
Zbigniew Haba
|
Z. Haba
|
Conformally flat travelling plane wave solutions of Einstein equations
|
substantially changed version,18 pages
|
Int.Journ.Geometric Methods in Mod.Phys.17(2020)2050015
|
10.1142/S0219887820500152
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We discuss conformally flat plane wave solutions of Einstein equations
depending on the plane wave phase $\xi=\omega\tau-{\bf qx}$, where $\tau$ is
the conformal time. We show that ideal fluid Einstein equations and scalar
fields with exponential self-interaction have solutions of this form. We
consider in more detail the source depending on $\xi$ with $\omega=\vert{\bf
q}\vert$ describing models of a massless scalar field, electromagnetic field
and relativistic particles with space-time depending mass density. We obtain
explicit conformally flat metrics solving Einstein equations with such a source
of the energy-momentum.
|
[
{
"created": "Wed, 5 Jun 2019 12:32:09 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Sep 2019 17:38:14 GMT",
"version": "v2"
},
{
"created": "Thu, 26 Sep 2019 19:08:09 GMT",
"version": "v3"
}
] |
2020-02-26
|
[
[
"Haba",
"Z.",
""
]
] |
We discuss conformally flat plane wave solutions of Einstein equations depending on the plane wave phase $\xi=\omega\tau-{\bf qx}$, where $\tau$ is the conformal time. We show that ideal fluid Einstein equations and scalar fields with exponential self-interaction have solutions of this form. We consider in more detail the source depending on $\xi$ with $\omega=\vert{\bf q}\vert$ describing models of a massless scalar field, electromagnetic field and relativistic particles with space-time depending mass density. We obtain explicit conformally flat metrics solving Einstein equations with such a source of the energy-momentum.
|
gr-qc/9902050
|
Garcia
|
L.C.Garcia de Andrade
|
Gravitational field of global monopoles in Einstein-Cartan gravity
|
Latex file 5 Kb
| null | null | null |
gr-qc
| null |
The gravitational weak field of a global monopole in the Einstein-Cartan
theory of gravity is investigated.To obtain this solution we assume that Cartan
torsion takes the form of the Newtonian gravitational potential.From the
geodesics it is possible to show that the torsionic monopole produces a
repulsive gravitational force.
|
[
{
"created": "Wed, 17 Feb 1999 23:06:02 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"de Andrade",
"L. C. Garcia",
""
]
] |
The gravitational weak field of a global monopole in the Einstein-Cartan theory of gravity is investigated.To obtain this solution we assume that Cartan torsion takes the form of the Newtonian gravitational potential.From the geodesics it is possible to show that the torsionic monopole produces a repulsive gravitational force.
|
gr-qc/9808075
|
Anjan Ananda Sen.
|
A.A.Sen
|
Superconducting cosmic string in Brans-Dicke theory
|
Revised, Connection of Dilaton gravity with Brans-Dicke theory has
been included, Accepted for publication in Phys.Rev.D
|
Phys.Rev. D60 (1999) 067501
|
10.1103/PhysRevD.60.067501
| null |
gr-qc
| null |
In the present work, the gravitational field of superconducting cosmic string
has been investigated in the context of Brans-Dicke theory of gravity. We have
presented two kind of solutions for the spacetime in the far field zone of the
string. When the B-D scalar field is switched off, one of the solutions reduces
to the solution earlier obtained by Moss and Poletti in General Relativity.
|
[
{
"created": "Thu, 27 Aug 1998 14:51:49 GMT",
"version": "v1"
},
{
"created": "Tue, 25 May 1999 07:46:22 GMT",
"version": "v2"
}
] |
2009-10-31
|
[
[
"Sen",
"A. A.",
""
]
] |
In the present work, the gravitational field of superconducting cosmic string has been investigated in the context of Brans-Dicke theory of gravity. We have presented two kind of solutions for the spacetime in the far field zone of the string. When the B-D scalar field is switched off, one of the solutions reduces to the solution earlier obtained by Moss and Poletti in General Relativity.
|
gr-qc/0102015
|
Novak
|
Jerome Novak
|
Numerical Relativity CM1-a and CM1-b sessions
|
Summary of the "Numerical Relativity" session of the 9th Marcel
Grossman Meeting, held in Rome, July 2000. 8 pages, no figures, uses World
Scientific Latex style file (included)
| null |
10.1142/9789812777386_0362
| null |
gr-qc
| null |
Numerical Relativity is concerned with solving the Einstein equations, as
well as any field or matter equations on curved space-time, by means of
computer calculations. The methods developed for this purpose up to now, as
well as the addressed physical problems are getting more numerous every day.
This is a brief summary of the presentations which have been given during the
9th Marcel Grossman meeting, which took place in Rome, from 2nd to 8th of July
2000. Many different fields have been addressed, from pure numerics and applied
mathematics to neutron star properties and gravitational wave astronomy.
|
[
{
"created": "Mon, 5 Feb 2001 09:15:39 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Feb 2001 12:50:12 GMT",
"version": "v2"
}
] |
2017-08-23
|
[
[
"Novak",
"Jerome",
""
]
] |
Numerical Relativity is concerned with solving the Einstein equations, as well as any field or matter equations on curved space-time, by means of computer calculations. The methods developed for this purpose up to now, as well as the addressed physical problems are getting more numerous every day. This is a brief summary of the presentations which have been given during the 9th Marcel Grossman meeting, which took place in Rome, from 2nd to 8th of July 2000. Many different fields have been addressed, from pure numerics and applied mathematics to neutron star properties and gravitational wave astronomy.
|
gr-qc/9912040
|
Tetsuya Shiromizu
|
Tetsuya Shiromizu (Cambridge) and Uchida Gen (Osaka)
|
A Probe Particle in Kerr-Newman-deSitter Cosmos
|
7 pages, Classical and Quantum Gravity accepted
|
Class.Quant.Grav.17:1361-1368,2000
|
10.1088/0264-9381/17/6/303
|
DAMTP-1999-100;UTAP-354;RESCEU-46/99
|
gr-qc astro-ph hep-th
| null |
We consider the force acting on a spinning charged test particle (probe
particle) with the mass m and the charge q in slow rotating the
Kerr-Newman-deSitter(KNdS) black hole with the mass M and the charge Q. We
consider the case which the spin vector of the probe particle is parallel to
the angular momentum vector of the KNdS space-time. We take account of the
gravitational spin-spin interaction under the slow rotating limit of the KNdS
space-time. When Q=M and q=m, we show that the force balance holds including
the spin-spin interaction and the motion is approximately same as that of a
particle in the deSitter space-time. This force cancellation suggests the
possibility of the existence of an exact solution of spinning multi-KNdS black
hole.
|
[
{
"created": "Fri, 10 Dec 1999 14:58:18 GMT",
"version": "v1"
}
] |
2010-11-19
|
[
[
"Shiromizu",
"Tetsuya",
"",
"Cambridge"
],
[
"Gen",
"Uchida",
"",
"Osaka"
]
] |
We consider the force acting on a spinning charged test particle (probe particle) with the mass m and the charge q in slow rotating the Kerr-Newman-deSitter(KNdS) black hole with the mass M and the charge Q. We consider the case which the spin vector of the probe particle is parallel to the angular momentum vector of the KNdS space-time. We take account of the gravitational spin-spin interaction under the slow rotating limit of the KNdS space-time. When Q=M and q=m, we show that the force balance holds including the spin-spin interaction and the motion is approximately same as that of a particle in the deSitter space-time. This force cancellation suggests the possibility of the existence of an exact solution of spinning multi-KNdS black hole.
|
1908.10817
|
Pierre-Henri Chavanis
|
Pierre-Henri Chavanis
|
Statistical mechanics of self-gravitating systems in general relativity:
II. The classical Boltzmann gas
| null |
Eur. Phys. J. Plus, 135, 310 (2020)
| null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the statistical mechanics of classical self-gravitating systems
confined within a box of radius $R$ in general relativity. It has been found
that the caloric curve $T_{\infty}(E)$ has the form of a double spiral whose
shape depends on the compactness parameter $\nu=GNm/Rc^2$. The double spiral
shrinks as $\nu$ increases and finally disappears when $\nu_{\rm max}=0.1764$.
Therefore, general relativistic effects render the system more unstable. On the
other hand, the cold spiral and the hot spiral move away from each other as
$\nu$ decreases. Using a normalization $\Lambda=-ER/GN^2m^2$ and $\eta=GNm^2/R
k_B T_{\infty}$ appropriate to the nonrelativistic limit, and considering
$\nu\rightarrow 0$, the hot spiral goes to infinity and the caloric curve tends
towards a limit curve (determined by the Emden equation) exhibiting a single
cold spiral, as found in former works. Using another normalization ${\cal
M}=GM/Rc^2$ and ${\cal B}={Rc^4}/{GNk_B T_{\infty}}$ appropriate to the
ultrarelativistic limit, and considering $\nu\rightarrow 0$, the cold spiral
goes to infinity and the caloric curve tends towards a limit curve (determined
by the general relativistic Emden equation) exhibiting a single hot spiral.
This result is new. We discuss the analogies and the differences between this
asymptotic caloric curve and the caloric curve of the self-gravitating
black-body radiation. Finally, we compare box-confined isothermal models with
heavily truncated isothermal distributions in Newtonian gravity and general
relativity.
|
[
{
"created": "Wed, 28 Aug 2019 16:36:58 GMT",
"version": "v1"
}
] |
2020-12-24
|
[
[
"Chavanis",
"Pierre-Henri",
""
]
] |
We study the statistical mechanics of classical self-gravitating systems confined within a box of radius $R$ in general relativity. It has been found that the caloric curve $T_{\infty}(E)$ has the form of a double spiral whose shape depends on the compactness parameter $\nu=GNm/Rc^2$. The double spiral shrinks as $\nu$ increases and finally disappears when $\nu_{\rm max}=0.1764$. Therefore, general relativistic effects render the system more unstable. On the other hand, the cold spiral and the hot spiral move away from each other as $\nu$ decreases. Using a normalization $\Lambda=-ER/GN^2m^2$ and $\eta=GNm^2/R k_B T_{\infty}$ appropriate to the nonrelativistic limit, and considering $\nu\rightarrow 0$, the hot spiral goes to infinity and the caloric curve tends towards a limit curve (determined by the Emden equation) exhibiting a single cold spiral, as found in former works. Using another normalization ${\cal M}=GM/Rc^2$ and ${\cal B}={Rc^4}/{GNk_B T_{\infty}}$ appropriate to the ultrarelativistic limit, and considering $\nu\rightarrow 0$, the cold spiral goes to infinity and the caloric curve tends towards a limit curve (determined by the general relativistic Emden equation) exhibiting a single hot spiral. This result is new. We discuss the analogies and the differences between this asymptotic caloric curve and the caloric curve of the self-gravitating black-body radiation. Finally, we compare box-confined isothermal models with heavily truncated isothermal distributions in Newtonian gravity and general relativity.
|
0705.2659
|
Theophanes Grammenos
|
I. Radinschi, Th. Grammenos
|
Moeller's Energy-Momentum Complex for a Spacetime Geometry on a
Noncommutative Curved D3-Brane
|
12 pages
|
Int.J.Theor.Phys.47:1363-1372,2008
|
10.1007/s10773-007-9578-9
| null |
gr-qc
| null |
Moeller's energy-momentum complex is employed in order to determine the
energy and momentum distributions for a spacetime described by a "generalized
Schwarzschild" geometry in (3+1)-dimensions on a noncommutative curved D3-brane
in an effective, open bosonic string theory. The geometry considered is
obtained by an effective theory of gravity coupled with a nonlinear
electromagnetic field and depends only on the generalized (effective) mass and
charge which incorporate corrections of first order in the noncommutativity
parameter.
|
[
{
"created": "Fri, 18 May 2007 08:57:50 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Sep 2007 15:50:51 GMT",
"version": "v2"
}
] |
2008-11-26
|
[
[
"Radinschi",
"I.",
""
],
[
"Grammenos",
"Th.",
""
]
] |
Moeller's energy-momentum complex is employed in order to determine the energy and momentum distributions for a spacetime described by a "generalized Schwarzschild" geometry in (3+1)-dimensions on a noncommutative curved D3-brane in an effective, open bosonic string theory. The geometry considered is obtained by an effective theory of gravity coupled with a nonlinear electromagnetic field and depends only on the generalized (effective) mass and charge which incorporate corrections of first order in the noncommutativity parameter.
|
1404.1910
|
Suresh Kumar
|
Suresh Kumar
|
Probing the matter and dark energy sources in a viable Big Rip model of
the Universe
|
8 pages, 2 tables, 4 figures; Minor additions in the running text;
Matches the version published in Mod. Phys. Lett. A
|
Modern Physics Letters A 29 (2014) 1450119
|
10.1142/S0217732314501193
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Chevallier-Polarski-Linder (CPL) parametrization for the equation of state of
dark energy in terms of cosmic redshift or scale factor have been frequently
studied in the literature. In this study, we consider cosmic time based CPL
parametrization for the equation of state parameter of the effective cosmic
fluid that fills the fabric of spatially flat and homogeneous Robertson-Walker
spacetime in general relativity. The model exhibits two worthy features: (i) It
fits the observational data from the latest $H(z)$ and Union 2.1 SN Ia
compilations matching the success of $\Lambda$CDM model. (ii) It describes the
evolution of the Universe from the matter-dominated phase to the recent
accelerating phase similar to the $\Lambda$CDM model but leads to Big Rip end
of the Universe contrary to the everlasting de Sitter expansion in the
$\Lambda$CDM model. We investigate the matter and dark energy sources in the
model, in particular, behavior of the dynamical dark energy responsible for the
Big Rip end of Universe.
|
[
{
"created": "Mon, 7 Apr 2014 13:42:37 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Aug 2014 14:01:10 GMT",
"version": "v2"
}
] |
2014-08-27
|
[
[
"Kumar",
"Suresh",
""
]
] |
Chevallier-Polarski-Linder (CPL) parametrization for the equation of state of dark energy in terms of cosmic redshift or scale factor have been frequently studied in the literature. In this study, we consider cosmic time based CPL parametrization for the equation of state parameter of the effective cosmic fluid that fills the fabric of spatially flat and homogeneous Robertson-Walker spacetime in general relativity. The model exhibits two worthy features: (i) It fits the observational data from the latest $H(z)$ and Union 2.1 SN Ia compilations matching the success of $\Lambda$CDM model. (ii) It describes the evolution of the Universe from the matter-dominated phase to the recent accelerating phase similar to the $\Lambda$CDM model but leads to Big Rip end of the Universe contrary to the everlasting de Sitter expansion in the $\Lambda$CDM model. We investigate the matter and dark energy sources in the model, in particular, behavior of the dynamical dark energy responsible for the Big Rip end of Universe.
|
2106.13548
|
Deyou Chen
|
Chuanhong Gao, Deyou Chen, Chengye Yu
|
Quasinormal modes and the correspondence with shadow in a charged black
hole in presence of quintessence
|
There was an error in section 3
| null | null | null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
In this paper, we investigate the photon sphere, shadow radius and
quasinormal modes of a charged black hole in presence of quintessence. The
result shows that the shadow radius decreases with the increase of the electric
charge. The quasinormal modes are derived by the sixth WKB approximation method
and shadow radius, respectively. For the fixed electric charge and multipole
number, the values of the real and imaginary parts of the quasinormal modes
decrease with the increase of the quintessence charge. When the value of the
multipole number is large, the quasinormal modes derived by the two methods are
consistent, which shows the correspondence between the quasinormal modes in the
eikonal limit and shadow. When the value of the multipole number is small, the
quasinormal modes obtained by the two methods are also in good agreement.
|
[
{
"created": "Fri, 25 Jun 2021 10:51:06 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Jul 2021 08:19:19 GMT",
"version": "v2"
},
{
"created": "Tue, 27 Jul 2021 03:13:27 GMT",
"version": "v3"
},
{
"created": "Mon, 18 Oct 2021 07:03:50 GMT",
"version": "v4"
}
] |
2021-10-19
|
[
[
"Gao",
"Chuanhong",
""
],
[
"Chen",
"Deyou",
""
],
[
"Yu",
"Chengye",
""
]
] |
In this paper, we investigate the photon sphere, shadow radius and quasinormal modes of a charged black hole in presence of quintessence. The result shows that the shadow radius decreases with the increase of the electric charge. The quasinormal modes are derived by the sixth WKB approximation method and shadow radius, respectively. For the fixed electric charge and multipole number, the values of the real and imaginary parts of the quasinormal modes decrease with the increase of the quintessence charge. When the value of the multipole number is large, the quasinormal modes derived by the two methods are consistent, which shows the correspondence between the quasinormal modes in the eikonal limit and shadow. When the value of the multipole number is small, the quasinormal modes obtained by the two methods are also in good agreement.
|
gr-qc/0108066
|
L. C. Garcia de Andrade
|
L.C.Garcia de Andrade
|
Spherically symmetric Weitzenb\"{o}ck defect solution of Einstein field
equation
|
Latex file
| null | null | null |
gr-qc
| null |
A new class of spacetime defect solutions of Einstein Field equations of
Edelen's direct Poincar\'{e} Gauge Field theory without biaxial symmetry is
presented. The interior solution describes a core of defects where curvature
vanishes and Cartan torsion is nonvanishing. Outside the core (in vacuum) the
solution represents a spacetime with vanishing curvature and torsion describing
a nontrivial topological defect solution of Einstein equations of gravity. Our
solution corresponds to a very weak strenght of Tachyons can be found far away
from the core defect.
|
[
{
"created": "Sat, 25 Aug 2001 21:15:45 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"de Andrade",
"L. C. Garcia",
""
]
] |
A new class of spacetime defect solutions of Einstein Field equations of Edelen's direct Poincar\'{e} Gauge Field theory without biaxial symmetry is presented. The interior solution describes a core of defects where curvature vanishes and Cartan torsion is nonvanishing. Outside the core (in vacuum) the solution represents a spacetime with vanishing curvature and torsion describing a nontrivial topological defect solution of Einstein equations of gravity. Our solution corresponds to a very weak strenght of Tachyons can be found far away from the core defect.
|
gr-qc/9712009
|
Heller Michal
|
M. Heller, W. Sasin
|
Towards Noncommutative Quantization of Gravity
|
25 pages, latex, no figures
| null |
10.1063/1.532186
|
CGC-97-05
|
gr-qc
| null |
We propose a mathematical structure, based on a noncommutative geometry,
which combines essential aspects of general relativity and quantum mechanics,
and leads to correct "limiting cases" of both these theories. We quantize a
groupoid constructed on space-time rather than space-time itself. Both space
and time emerge in the transition process to the commutative case. Our approach
clearly suggests that quantum gravitational observables should be looked for
among correlations of distant phenomena rather than among local effects. A toy
model is computed (based on a finite group) which predicts the value of
"cosmological constants" (in the quantum sector) which vanish when going to the
standard space-time physics.
|
[
{
"created": "Mon, 1 Dec 1997 22:24:17 GMT",
"version": "v1"
}
] |
2009-10-30
|
[
[
"Heller",
"M.",
""
],
[
"Sasin",
"W.",
""
]
] |
We propose a mathematical structure, based on a noncommutative geometry, which combines essential aspects of general relativity and quantum mechanics, and leads to correct "limiting cases" of both these theories. We quantize a groupoid constructed on space-time rather than space-time itself. Both space and time emerge in the transition process to the commutative case. Our approach clearly suggests that quantum gravitational observables should be looked for among correlations of distant phenomena rather than among local effects. A toy model is computed (based on a finite group) which predicts the value of "cosmological constants" (in the quantum sector) which vanish when going to the standard space-time physics.
|
gr-qc/9901079
|
Neil G. Turok
|
Neil Turok
|
Stability of Flat Space to Singular Instantons
|
9 pages, RevTex file, including two postscript figure files. Minor
typos corrected, figure improved
|
Phys.Lett. B458 (1999) 202-208
|
10.1016/S0370-2693(99)00587-0
| null |
gr-qc astro-ph hep-th
| null |
Hawking and the author have proposed a class of singular, finite action
instantons for defining the initial conditions for inflation. Vilenkin has
argued they are unacceptable. He exhibited an analogous class of asymptotically
flat instantons which on the face of it lead to an instability of Minkowski
space. However, all these instantons must be defined by introducing a
constraint into the path integral, which is then integrated over. I show that
with a careful definition these instantons do not possess a negative mode.
Infinite flat space is therefore stable against decay via singular instantons.
|
[
{
"created": "Wed, 27 Jan 1999 21:39:18 GMT",
"version": "v1"
},
{
"created": "Sun, 31 Jan 1999 01:05:19 GMT",
"version": "v2"
},
{
"created": "Thu, 4 Feb 1999 09:59:40 GMT",
"version": "v3"
}
] |
2009-10-31
|
[
[
"Turok",
"Neil",
""
]
] |
Hawking and the author have proposed a class of singular, finite action instantons for defining the initial conditions for inflation. Vilenkin has argued they are unacceptable. He exhibited an analogous class of asymptotically flat instantons which on the face of it lead to an instability of Minkowski space. However, all these instantons must be defined by introducing a constraint into the path integral, which is then integrated over. I show that with a careful definition these instantons do not possess a negative mode. Infinite flat space is therefore stable against decay via singular instantons.
|
0912.3165
|
T. Padmanabhan
|
T. Padmanabhan
|
Equipartition of energy in the horizon degrees of freedom and the
emergence of gravity
|
ver 1: six pages; ver. 2: some algebraic details and discussion added
for greater conceptual clarity; seven pages
|
Mod.Phys.Lett.A25:1129-1136,2010
|
10.1142/S021773231003313X
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
It is possible to provide a physical interpretation for the field equations
of gravity based on a thermodynamical perspective. The virtual degrees of
freedom associated with the horizons perceived by the local Rindler observers,
play a crucial role in this approach. In this context, the relation S=E/2T
between the entropy (S), active gravitational mass (E) and temperature (T) -
obtained previously in gr-qc/0308070 [CQG, 21, 4485 (2004)] - can be
reinterpreted as the law of equipartition E = (1/2) nkT where n=A/L_P^2 is the
number (density) of microscopic horizon degrees of freedom. Conversely, one can
use the equipartition argument to provide a thermodynamic interpretation of
even non-relativistic gravity. These results emphasize the intrinsic quantum
nature of all gravitational phenomena and diminishes the distinction between
thermal phenomena associated with local Rindler horizons and the usual
thermodynamics of macroscopic bodies in non-inertial frames. Just like the
original thermodynamic interpretation, these results also hold for a wide class
of gravitational theories like the Lanczos-Lovelock models.
|
[
{
"created": "Wed, 16 Dec 2009 15:36:40 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Dec 2009 08:52:12 GMT",
"version": "v2"
}
] |
2010-05-12
|
[
[
"Padmanabhan",
"T.",
""
]
] |
It is possible to provide a physical interpretation for the field equations of gravity based on a thermodynamical perspective. The virtual degrees of freedom associated with the horizons perceived by the local Rindler observers, play a crucial role in this approach. In this context, the relation S=E/2T between the entropy (S), active gravitational mass (E) and temperature (T) - obtained previously in gr-qc/0308070 [CQG, 21, 4485 (2004)] - can be reinterpreted as the law of equipartition E = (1/2) nkT where n=A/L_P^2 is the number (density) of microscopic horizon degrees of freedom. Conversely, one can use the equipartition argument to provide a thermodynamic interpretation of even non-relativistic gravity. These results emphasize the intrinsic quantum nature of all gravitational phenomena and diminishes the distinction between thermal phenomena associated with local Rindler horizons and the usual thermodynamics of macroscopic bodies in non-inertial frames. Just like the original thermodynamic interpretation, these results also hold for a wide class of gravitational theories like the Lanczos-Lovelock models.
|
1001.0756
|
Yuri Pavlov
|
A. A. Grib, Yu. V. Pavlov
|
On particle collisions in the gravitational field of the Kerr black hole
|
LaTeX, 7 pages, 2 figures
|
Astropart. Phys.34:581-586, 2011
|
10.1016/j.astropartphys.2010.12.005
| null |
gr-qc astro-ph.HE hep-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Scattering of particles in the gravitational field of Kerr black holes is
considered. It is shown that scattering energy of particles in the centre of
mass system can obtain very large values not only for extremal black holes but
also for nonextremal ones existing in Nature. This can be used for explanation
of still unresolved problem of the origin of ultrahigh energy cosmic rays
observed in Auger experiment. Extraction of energy after the collision is
investigated. It is shown that due to the Penrose process the energy of the
particle escaping the hole at infinity can be large. Contradictions in the
problem of getting high energetic particles escaping the black hole are
resolved.
|
[
{
"created": "Tue, 5 Jan 2010 20:03:06 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Jan 2011 22:23:52 GMT",
"version": "v2"
}
] |
2011-02-01
|
[
[
"Grib",
"A. A.",
""
],
[
"Pavlov",
"Yu. V.",
""
]
] |
Scattering of particles in the gravitational field of Kerr black holes is considered. It is shown that scattering energy of particles in the centre of mass system can obtain very large values not only for extremal black holes but also for nonextremal ones existing in Nature. This can be used for explanation of still unresolved problem of the origin of ultrahigh energy cosmic rays observed in Auger experiment. Extraction of energy after the collision is investigated. It is shown that due to the Penrose process the energy of the particle escaping the hole at infinity can be large. Contradictions in the problem of getting high energetic particles escaping the black hole are resolved.
|
1808.02963
|
Tony Rothman
|
Tony Rothman, Mariam Campbell, Rituparno Goswami, George F.R. Ellis
|
Direct Detection of Universal Expansion by Holonomy in the McVittie
Spacetime
|
10 pages, 5 figures. This version corrects an error in the previous
version and is as will appear in PRD but with updated figures
|
Phys. Rev. D 99, 024033 (2019)
|
10.1103/PhysRevD.99.024033
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In general relativity the parallel transfer of a vector around a closed curve
in spacetime, or along two curves which together form a closed loop, usually
results in a nonzero deficit angle between the vector's initial and final
positions. We show that such holonomy in the McVittie spacetime, which
represents a gravitating object imbedded in an expanding universe, can in
principle be used to directly detect the expansion of the universe, for example
by measuring changes in the components of a gyroscopic spin axis. Although such
changes are of course small, they are large enough (\D S \sim 10^{-7}) that
they could conceivably be measured if the real universe behaved like the
McVittie spacetime. The real problem is that virialization will lead to domains
decoupled from the global expansion on a scale much larger than that of the
solar system, making such an experiment infeasible probably even in principle.
Nevertheless the effect is of interest in relation to ongoing discussions,
dating back at least to Einstein and Straus, which concern the relationship
between the expansion of the universe and local systems.
|
[
{
"created": "Wed, 8 Aug 2018 23:22:50 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Aug 2018 15:39:48 GMT",
"version": "v2"
},
{
"created": "Sun, 16 Sep 2018 11:54:56 GMT",
"version": "v3"
},
{
"created": "Thu, 10 Jan 2019 14:48:35 GMT",
"version": "v4"
}
] |
2019-01-30
|
[
[
"Rothman",
"Tony",
""
],
[
"Campbell",
"Mariam",
""
],
[
"Goswami",
"Rituparno",
""
],
[
"Ellis",
"George F. R.",
""
]
] |
In general relativity the parallel transfer of a vector around a closed curve in spacetime, or along two curves which together form a closed loop, usually results in a nonzero deficit angle between the vector's initial and final positions. We show that such holonomy in the McVittie spacetime, which represents a gravitating object imbedded in an expanding universe, can in principle be used to directly detect the expansion of the universe, for example by measuring changes in the components of a gyroscopic spin axis. Although such changes are of course small, they are large enough (\D S \sim 10^{-7}) that they could conceivably be measured if the real universe behaved like the McVittie spacetime. The real problem is that virialization will lead to domains decoupled from the global expansion on a scale much larger than that of the solar system, making such an experiment infeasible probably even in principle. Nevertheless the effect is of interest in relation to ongoing discussions, dating back at least to Einstein and Straus, which concern the relationship between the expansion of the universe and local systems.
|
2309.10830
|
Bivudutta Mishra Dr.
|
Santosh V. Lohakare, S.K. Maurya, Ksh. Newton Singh, B.Mishra,
Abdelghani Errehymy
|
Influence of three parameters on maximum mass and stability of strange
star under linear $f(Q)-$action
|
18 pages, 18 figures, Accepted version Monthly Notices of Royal
Astronomical Society
|
MNRAS, 526, 2023, 3796-3814
|
10.1093/mnras/stad2861
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
This study simulates strange stars in $f(Q)$ gravity with an additional
source under an electric field using gravitational decoupling and the complete
Gravitational Decoupling (CGD) technique. By employing the Tolman ansatz and
the MIT bag model equation of state (EOS), we explore bounded star
configurations derived from the $\theta_0^0 = \rho$ and $\theta_1^1 = p_r$
sectors within the CGD formalism. Our models are subjected to physical
viability tests, and we analyze the impact of anisotropy and the electric
charge parameter $E_0$ as well as the coupling parameters $\alpha$ and
$\beta_1$. Comparisons are made with observational constraints, including
GW190814, neutron stars PSR J1614-2230, PSR J1903+6620, Cen X-3 and LMC X-4.
Notably, we achieve the presence of a lower "\textit{mass gap}" component by
adjusting parameters $\alpha$ and $\beta_1$. Our models exhibit well-behaved
mass profiles, internal regularity, and stability, with the absence of
gravitational collapse verified through the Buchdahl--Andr\'{e}asson's limit.
In addition, we present a detailed physical analysis based on three parameters,
$\alpha$ (decoupling strength), $\beta_1$ ($f(Q)$--coupling) and $Q$ (surface
charge). This study provides insights into the behavior of compact objects in
$f(Q)$ gravity and expands our understanding of strange star configurations
within this framework.
|
[
{
"created": "Sat, 16 Sep 2023 14:23:48 GMT",
"version": "v1"
}
] |
2024-03-21
|
[
[
"Lohakare",
"Santosh V.",
""
],
[
"Maurya",
"S. K.",
""
],
[
"Singh",
"Ksh. Newton",
""
],
[
"Mishra",
"B.",
""
],
[
"Errehymy",
"Abdelghani",
""
]
] |
This study simulates strange stars in $f(Q)$ gravity with an additional source under an electric field using gravitational decoupling and the complete Gravitational Decoupling (CGD) technique. By employing the Tolman ansatz and the MIT bag model equation of state (EOS), we explore bounded star configurations derived from the $\theta_0^0 = \rho$ and $\theta_1^1 = p_r$ sectors within the CGD formalism. Our models are subjected to physical viability tests, and we analyze the impact of anisotropy and the electric charge parameter $E_0$ as well as the coupling parameters $\alpha$ and $\beta_1$. Comparisons are made with observational constraints, including GW190814, neutron stars PSR J1614-2230, PSR J1903+6620, Cen X-3 and LMC X-4. Notably, we achieve the presence of a lower "\textit{mass gap}" component by adjusting parameters $\alpha$ and $\beta_1$. Our models exhibit well-behaved mass profiles, internal regularity, and stability, with the absence of gravitational collapse verified through the Buchdahl--Andr\'{e}asson's limit. In addition, we present a detailed physical analysis based on three parameters, $\alpha$ (decoupling strength), $\beta_1$ ($f(Q)$--coupling) and $Q$ (surface charge). This study provides insights into the behavior of compact objects in $f(Q)$ gravity and expands our understanding of strange star configurations within this framework.
|
1811.00762
|
Chul-Moon Yoo
|
Chul-Moon Yoo and Taishi Ikeda and Hirotada Okawa
|
Gravitational Collapse of a Massless Scalar Field in a Periodic Box
|
17 pages, 18 figures
| null |
10.1088/1361-6382/ab06e2
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Gravitational collapse of a massless scalar field with the periodic boundary
condition in a cubic box is reported. This system can be regarded as a lattice
universe model. We construct the initial data for a Gaussian like profile of
the scalar field taking the integrability condition associated with the
periodic boundary condition into account. For a large initial amplitude, a
black hole is formed after a certain period of time. While the scalar field
spreads out in the whole region for a small initial amplitude. It is shown that
the expansion law in a late time approaches to that of the radiation dominated
universe and the matter dominated universe for the small and large initial
amplitude cases, respectively. For the large initial amplitude case, the
horizon is initially a past outer trapping horizon, whose area decreases with
time, and after a certain period of time, it turns to a future outer trapping
horizon with the increasing area.
|
[
{
"created": "Fri, 2 Nov 2018 07:33:06 GMT",
"version": "v1"
},
{
"created": "Wed, 16 Jan 2019 04:32:20 GMT",
"version": "v2"
}
] |
2019-05-22
|
[
[
"Yoo",
"Chul-Moon",
""
],
[
"Ikeda",
"Taishi",
""
],
[
"Okawa",
"Hirotada",
""
]
] |
Gravitational collapse of a massless scalar field with the periodic boundary condition in a cubic box is reported. This system can be regarded as a lattice universe model. We construct the initial data for a Gaussian like profile of the scalar field taking the integrability condition associated with the periodic boundary condition into account. For a large initial amplitude, a black hole is formed after a certain period of time. While the scalar field spreads out in the whole region for a small initial amplitude. It is shown that the expansion law in a late time approaches to that of the radiation dominated universe and the matter dominated universe for the small and large initial amplitude cases, respectively. For the large initial amplitude case, the horizon is initially a past outer trapping horizon, whose area decreases with time, and after a certain period of time, it turns to a future outer trapping horizon with the increasing area.
|
1210.8138
|
Martin Bojowald
|
Martin Bojowald, Alexander L. Chinchilli, Christine C. Dantas, Matthew
Jaffe and David Simpson
|
Non-linear (loop) quantum cosmology
|
20 pages
|
Phys. Rev. D 86 (2012) 124027
|
10.1103/PhysRevD.86.124027
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Inhomogeneous quantum cosmology is modeled as a dynamical system of discrete
patches, whose interacting many-body equations can be mapped to a non-linear
minisuperspace equation by methods analogous to Bose-Einstein condensation.
Complicated gravitational dynamics can therefore be described by
more-manageable equations for finitely many degrees of freedom, for which
powerful solution procedures are available, including effective equations. The
specific form of non-linear and non-local equations suggests new questions for
mathematical and computational investigations, and general properties of
non-linear wave equations lead to several new options for physical effects and
tests of the consistency of loop quantum gravity. In particular, our quantum
cosmological methods show how sizeable quantum corrections in a low-curvature
universe can arise from tiny local contributions adding up coherently in large
regions.
|
[
{
"created": "Tue, 30 Oct 2012 19:50:35 GMT",
"version": "v1"
}
] |
2012-12-18
|
[
[
"Bojowald",
"Martin",
""
],
[
"Chinchilli",
"Alexander L.",
""
],
[
"Dantas",
"Christine C.",
""
],
[
"Jaffe",
"Matthew",
""
],
[
"Simpson",
"David",
""
]
] |
Inhomogeneous quantum cosmology is modeled as a dynamical system of discrete patches, whose interacting many-body equations can be mapped to a non-linear minisuperspace equation by methods analogous to Bose-Einstein condensation. Complicated gravitational dynamics can therefore be described by more-manageable equations for finitely many degrees of freedom, for which powerful solution procedures are available, including effective equations. The specific form of non-linear and non-local equations suggests new questions for mathematical and computational investigations, and general properties of non-linear wave equations lead to several new options for physical effects and tests of the consistency of loop quantum gravity. In particular, our quantum cosmological methods show how sizeable quantum corrections in a low-curvature universe can arise from tiny local contributions adding up coherently in large regions.
|
gr-qc/9605029
|
Neil Cornish
|
Neil J. Cornish (Cambridge Uni.), Janna J. Levin (UC, Berkeley)
|
The mixmaster universe is chaotic
|
4 pages, RevTeX, 3 figures included. New presentation, same results
|
Phys.Rev.Lett. 78 (1997) 998-1001
|
10.1103/PhysRevLett.78.998
|
UM-P-96/33, CfPA-96-TH-10
|
gr-qc astro-ph chao-dyn nlin.CD
| null |
For the past decade there has been a considerable debate about the existence
of chaos in the mixmaster cosmological model. The debate has been hampered by
the coordinate, or observer dependence of standard chaotic indicators such as
Lyapanov exponents. Here we use coordinate independent, fractal methods to show
the mixmaster universe is indeed chaotic.
|
[
{
"created": "Thu, 16 May 1996 11:15:51 GMT",
"version": "v1"
},
{
"created": "Fri, 17 May 1996 07:52:36 GMT",
"version": "v2"
},
{
"created": "Tue, 5 Nov 1996 18:10:39 GMT",
"version": "v3"
}
] |
2009-10-28
|
[
[
"Cornish",
"Neil J.",
"",
"Cambridge Uni."
],
[
"Levin",
"Janna J.",
"",
"UC, Berkeley"
]
] |
For the past decade there has been a considerable debate about the existence of chaos in the mixmaster cosmological model. The debate has been hampered by the coordinate, or observer dependence of standard chaotic indicators such as Lyapanov exponents. Here we use coordinate independent, fractal methods to show the mixmaster universe is indeed chaotic.
|
1811.06947
|
Yu Shi
|
Yue Dai, Yu Shi
|
Kinetic Spin Decoherence in a Gravitational Field
|
10 pages
| null |
10.1142/S0218271819501049
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider a wave packet of a spin-1/2 particle in a gravitational field,
the effect of which can be described in terms of a succession of local inertial
frames. It is shown that integrating out of the momentum yields a spin mixed
state, with the entropy dependent on the deviation of metric from the flat
spacetime. The decoherence occurs even if the particle is static in the
gravitational field.
|
[
{
"created": "Fri, 16 Nov 2018 18:00:16 GMT",
"version": "v1"
}
] |
2019-06-26
|
[
[
"Dai",
"Yue",
""
],
[
"Shi",
"Yu",
""
]
] |
We consider a wave packet of a spin-1/2 particle in a gravitational field, the effect of which can be described in terms of a succession of local inertial frames. It is shown that integrating out of the momentum yields a spin mixed state, with the entropy dependent on the deviation of metric from the flat spacetime. The decoherence occurs even if the particle is static in the gravitational field.
|
2112.04393
|
Vincenzo Pierro prof.
|
Vincenzo Pierro, Vincenzo Fiumara, and Francesco Chiadini
|
Optimal Design of Coatings for Mirrors of Gravitational Wave Detectors:
Analytic Turbo Solution via Herpin Equivalent Layers
|
accepted for publication in "Gravitational Wave Observatory: The
Realm of Applied Science" special issue of Applied Science
| null |
10.3390/app112411669
| null |
gr-qc astro-ph.IM math.OC physics.optics
|
http://creativecommons.org/licenses/by-nc-nd/4.0/
|
In this paper, an analytical solution to the problem of optimal dielectric
coating design of mirrors for gravitational wave detectors is found. The
technique used to solve this problem is based on Herpin's equivalent layers,
which provide a simple, constructive, and analytical solution. The performance
of the Herpin-type design exceeds that of the periodic design and is almost
equal to the performance of the numerical, non-constructive optimized design
obtained by brute force. Note that the existence of explicit analytic
constructive solutions of a constrained optimization problem is not guaranteed
in general, when such a solution is found, we speak of turbo optimal solutions.
|
[
{
"created": "Wed, 8 Dec 2021 16:41:09 GMT",
"version": "v1"
}
] |
2021-12-14
|
[
[
"Pierro",
"Vincenzo",
""
],
[
"Fiumara",
"Vincenzo",
""
],
[
"Chiadini",
"Francesco",
""
]
] |
In this paper, an analytical solution to the problem of optimal dielectric coating design of mirrors for gravitational wave detectors is found. The technique used to solve this problem is based on Herpin's equivalent layers, which provide a simple, constructive, and analytical solution. The performance of the Herpin-type design exceeds that of the periodic design and is almost equal to the performance of the numerical, non-constructive optimized design obtained by brute force. Note that the existence of explicit analytic constructive solutions of a constrained optimization problem is not guaranteed in general, when such a solution is found, we speak of turbo optimal solutions.
|
1907.07961
|
Yeinzon Rodriguez Garcia
|
L. Gabriel Gomez (1), Yeinzon Rodriguez (1,2,3) ((1) Universidad
Industrial de Santander, (2) Universidad Antonio Narino, (3) The Abdus Salam
International Centre for Theoretical Physics)
|
Stability Conditions in the Generalized SU(2) Proca Theory
|
LaTeX file in RevTex 4.1 style, 8 pages in double column, 5 figures.
v2: minor changes. Version accepted for publication in Physical Review D. v3:
proofreading corrections implemented
|
Phys. Rev. D 100, 084048 (2019)
|
10.1103/PhysRevD.100.084048
|
PI/UAN-2019-651FT
|
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Under the same spirit of the Galileon-Horndeski theories and their more
modern extensions, the generalized SU(2) Proca theory was built by demanding
that its action may be free of the Ostrogradski's instability. Nevertheless,
the theory must also be free of other instability problems in order to ensure
its viability. As a first approach to address this issue, we concentrate on a
quite general variant of the theory and investigate the general conditions for
the absence of ghost and gradient instabilities in the tensor sector without
the need for resolving the dynamical background. The phenomenological interest
of this approach as well as of the variant investigated lies on the possibility
of building cosmological models driven solely by non-Abelian vector fields that
may account for a successful description of both the early inflation and the
late-time accelerated expansion of the universe.
|
[
{
"created": "Thu, 18 Jul 2019 10:11:56 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Oct 2019 04:11:55 GMT",
"version": "v2"
},
{
"created": "Tue, 15 Oct 2019 13:29:42 GMT",
"version": "v3"
}
] |
2019-10-30
|
[
[
"Gomez",
"L. Gabriel",
""
],
[
"Rodriguez",
"Yeinzon",
""
]
] |
Under the same spirit of the Galileon-Horndeski theories and their more modern extensions, the generalized SU(2) Proca theory was built by demanding that its action may be free of the Ostrogradski's instability. Nevertheless, the theory must also be free of other instability problems in order to ensure its viability. As a first approach to address this issue, we concentrate on a quite general variant of the theory and investigate the general conditions for the absence of ghost and gradient instabilities in the tensor sector without the need for resolving the dynamical background. The phenomenological interest of this approach as well as of the variant investigated lies on the possibility of building cosmological models driven solely by non-Abelian vector fields that may account for a successful description of both the early inflation and the late-time accelerated expansion of the universe.
|
0707.2775
|
Stefan Hollands
|
Stefan Hollands and Stoytcho Yazadjiev
|
Uniqueness theorem for 5-dimensional black holes with two axial Killing
fields
|
Latex, 21pp, no figures. v2: technical assumption added, extended
discussion of orbit space, results unchanged but sharpened
|
Commun.Math.Phys.283:749-768,2008
|
10.1007/s00220-008-0516-3
| null |
gr-qc
| null |
We show that two stationary, asymptotically flat vacuum black holes in 5
dimensions with two commuting axial symmetries are identical if and only if
their masses, angular momenta, and their ``rod structures'' coincide. We also
show that the horizon must be topologically either a 3-sphere, a ring, or a
Lens-space. Our argument is a generalization of constructions of Morisawa and
Ida (based in turn on key work of Maison) who considered the spherical case,
combined with basic arguments concerning the nature of the factor manifold of
symmetry orbits.
|
[
{
"created": "Wed, 18 Jul 2007 17:55:29 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Sep 2007 09:07:53 GMT",
"version": "v2"
}
] |
2008-11-26
|
[
[
"Hollands",
"Stefan",
""
],
[
"Yazadjiev",
"Stoytcho",
""
]
] |
We show that two stationary, asymptotically flat vacuum black holes in 5 dimensions with two commuting axial symmetries are identical if and only if their masses, angular momenta, and their ``rod structures'' coincide. We also show that the horizon must be topologically either a 3-sphere, a ring, or a Lens-space. Our argument is a generalization of constructions of Morisawa and Ida (based in turn on key work of Maison) who considered the spherical case, combined with basic arguments concerning the nature of the factor manifold of symmetry orbits.
|
2110.02757
|
Jen-Tsung Hsiang
|
Jen-Tsung Hsiang and Bei-Lok Hu
|
Intrinsic Entropy of Squeezed Quantum Fields and Nonequilibrium Quantum
Dynamics of Cosmological Perturbations
|
45 pages, 2 figures
|
Entropy 23, 1544 (2021)
|
10.3390/e23111544
| null |
gr-qc hep-th quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Density contrasts in the universe are governed by scalar cosmological
perturbations which, when expressed in terms of gauge-invariant variables,
contain a classical component from scalar metric perturbations and a quantum
component from inflaton field fluctuations. It has long been known that the
effect of cosmological expansion on a quantum field amounts to squeezing. Thus
the entropy of cosmological perturbations can be studied by treating them in
the framework of squeezed quantum systems. Entropy of a free quantum field is a
seemingly simple yet subtle issue. In this paper, as different from previous
treatments, we tackle this issue with a fully developed nonequilibrium quantum
field theory formalism for such systems. We compute the covariance matrix
elements of the parametric quantum field and solve for the evolution of the
density matrix elements and the Wigner functions, and, from them, derive the
von Neumann entropy. We then show explicitly why the entropy for the squeezed
yet closed system is zero, but is proportional to the particle number produced
upon coarse-graining out the correlation between the particle pairs. We also
construct the bridge between our quantum field-theoretic results and those
using probability distribution of classical stochastic fields by earlier
authors. From this we can see the clear advantages of the quantum
field-theoretical approach over the stochastic classical field treatment since
the latter misses out in some important quantum properties, such as
entanglement and coherence, of the quantum field.
|
[
{
"created": "Wed, 6 Oct 2021 13:43:00 GMT",
"version": "v1"
}
] |
2022-01-11
|
[
[
"Hsiang",
"Jen-Tsung",
""
],
[
"Hu",
"Bei-Lok",
""
]
] |
Density contrasts in the universe are governed by scalar cosmological perturbations which, when expressed in terms of gauge-invariant variables, contain a classical component from scalar metric perturbations and a quantum component from inflaton field fluctuations. It has long been known that the effect of cosmological expansion on a quantum field amounts to squeezing. Thus the entropy of cosmological perturbations can be studied by treating them in the framework of squeezed quantum systems. Entropy of a free quantum field is a seemingly simple yet subtle issue. In this paper, as different from previous treatments, we tackle this issue with a fully developed nonequilibrium quantum field theory formalism for such systems. We compute the covariance matrix elements of the parametric quantum field and solve for the evolution of the density matrix elements and the Wigner functions, and, from them, derive the von Neumann entropy. We then show explicitly why the entropy for the squeezed yet closed system is zero, but is proportional to the particle number produced upon coarse-graining out the correlation between the particle pairs. We also construct the bridge between our quantum field-theoretic results and those using probability distribution of classical stochastic fields by earlier authors. From this we can see the clear advantages of the quantum field-theoretical approach over the stochastic classical field treatment since the latter misses out in some important quantum properties, such as entanglement and coherence, of the quantum field.
|
2310.03555
|
Anna Puecher
|
Anna Puecher, Anuradha Samajdar, Gregory Ashton, Chris Van Den Broeck,
Tim Dietrich
|
Comparing gravitational waveform models for binary black hole mergers
through a hypermodels approach
| null | null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The inference of source parameters from gravitational-wave signals relies on
theoretical models that describe the emitted waveform. Different model
assumptions on which the computation of these models is based could lead to
biases in the analysis of gravitational-wave data. In this work, we sample
directly on four state-of-the-art binary black hole waveform models from
different families, in order to investigate these systematic biases from the 13
heaviest gravitational-wave sources with moderate to high signal-to-noise
ratios in the third Gravitational-Wave Transient Catalog (GWTC- 3). All models
include spin-precession as well as higher-order modes. Using the "hypermodels"
technique, we treat the waveform models as one of the sampled parameters,
therefore directly getting the odds ratio of one waveform model over another
from a single parameter estimation run. From the joint odds ratio over all 13
sources, we find the model NRSur7dq4 to be favoured over SEOBNRv4PHM, with an
odds ratio of 29.43; IMRPhenomXPHM and IMRPhenomTPHM have an odds ratio,
respectively, of 4.70 and 5.09 over SEOBNRv4PHM. However, this result is mainly
determined by three events that show a strong preference for some of the models
and that are all affected by possible data quality issues. If we do not
consider these potentially problematic events, the odds ratio do not exhibit a
significant preference for any of the models. Although further work studying a
larger set of signals will be needed for robust quantitative results, the
presented method highlights one possible avenue for future waveform model
development.
|
[
{
"created": "Thu, 5 Oct 2023 14:08:11 GMT",
"version": "v1"
}
] |
2023-10-06
|
[
[
"Puecher",
"Anna",
""
],
[
"Samajdar",
"Anuradha",
""
],
[
"Ashton",
"Gregory",
""
],
[
"Broeck",
"Chris Van Den",
""
],
[
"Dietrich",
"Tim",
""
]
] |
The inference of source parameters from gravitational-wave signals relies on theoretical models that describe the emitted waveform. Different model assumptions on which the computation of these models is based could lead to biases in the analysis of gravitational-wave data. In this work, we sample directly on four state-of-the-art binary black hole waveform models from different families, in order to investigate these systematic biases from the 13 heaviest gravitational-wave sources with moderate to high signal-to-noise ratios in the third Gravitational-Wave Transient Catalog (GWTC- 3). All models include spin-precession as well as higher-order modes. Using the "hypermodels" technique, we treat the waveform models as one of the sampled parameters, therefore directly getting the odds ratio of one waveform model over another from a single parameter estimation run. From the joint odds ratio over all 13 sources, we find the model NRSur7dq4 to be favoured over SEOBNRv4PHM, with an odds ratio of 29.43; IMRPhenomXPHM and IMRPhenomTPHM have an odds ratio, respectively, of 4.70 and 5.09 over SEOBNRv4PHM. However, this result is mainly determined by three events that show a strong preference for some of the models and that are all affected by possible data quality issues. If we do not consider these potentially problematic events, the odds ratio do not exhibit a significant preference for any of the models. Although further work studying a larger set of signals will be needed for robust quantitative results, the presented method highlights one possible avenue for future waveform model development.
|
1712.07592
|
Jackson Levi Said
|
Jackson Levi Said
|
Reconstruction from scalar-tensor theory and the inhomogeneous equation
of state in f(T) Gravity
|
9 pages
|
Said, J.L. Eur. Phys. J. C (2017) 77: 883
|
10.1140/epjc/s10052-017-5460-y
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
General relativity (GR) characterizes gravity as a geometric properly
exhibited as curvature on spacetime. Teleprallelism describes gravity through
torsional properties, and can reproduce GR at the level of equations. Similar
to f(R) gravity, on taking a generalization, f(T) gravity can produce various
modifications its gravitational mechanism. The resulting field equations are
inherently distinct to f(R) gravity in that they are second order. In the
present work, f(T) gravity is examined in the cosmological context with a
number of solutions reconstructed by means of an auxiliary scalar field. To do
this, various forms of the Hubble parameter are considered with an f(T)
lagrangian emerging for each instance. In addition, the inhomogeneous equation
of state (EoS) is investigated with a particular Hubble parameter model used to
show how this can be used to reconstruct the f(T) lagrangian. Observationally,
both the auxiliary scalar field or exotic terms in the FRW field equations give
the same results, meaning that the variation in the Hubble parameter may be
interpreted as the need to reformulate gravity in some way as is done in f(T)
gravity.
|
[
{
"created": "Tue, 19 Dec 2017 14:23:42 GMT",
"version": "v1"
}
] |
2017-12-21
|
[
[
"Said",
"Jackson Levi",
""
]
] |
General relativity (GR) characterizes gravity as a geometric properly exhibited as curvature on spacetime. Teleprallelism describes gravity through torsional properties, and can reproduce GR at the level of equations. Similar to f(R) gravity, on taking a generalization, f(T) gravity can produce various modifications its gravitational mechanism. The resulting field equations are inherently distinct to f(R) gravity in that they are second order. In the present work, f(T) gravity is examined in the cosmological context with a number of solutions reconstructed by means of an auxiliary scalar field. To do this, various forms of the Hubble parameter are considered with an f(T) lagrangian emerging for each instance. In addition, the inhomogeneous equation of state (EoS) is investigated with a particular Hubble parameter model used to show how this can be used to reconstruct the f(T) lagrangian. Observationally, both the auxiliary scalar field or exotic terms in the FRW field equations give the same results, meaning that the variation in the Hubble parameter may be interpreted as the need to reformulate gravity in some way as is done in f(T) gravity.
|
gr-qc/9902070
|
Martin Goliath
|
B. J. Carr, A. A. Coley, M. Goliath, U. S. Nilsson and C. Uggla
|
The state space and physical interpretation of self-similar spherically
symmetric perfect-fluid models
|
24 pages, 12 figures
|
Class.Quant.Grav.18:303-324,2001
|
10.1088/0264-9381/18/2/309
| null |
gr-qc
| null |
The purpose of this paper is to further investigate the solution space of
self-similar spherically symmetric perfect-fluid models and gain deeper
understanding of the physical aspects of these solutions. We achieve this by
combining the state space description of the homothetic approach with the use
of the physically interesting quantities arising in the comoving approach. We
focus on three types of models. First, we consider models that are natural
inhomogeneous generalizations of the Friedmann Universe; such models are
asymptotically Friedmann in their past and evolve fluctuations in the energy
density at later times. Second, we consider so-called quasi-static models. This
class includes models that undergo self-similar gravitational collapse and is
important for studying the formation of naked singularities. If naked
singularities do form, they have profound implications for the predictability
of general relativity as a theory. Third, we consider a new class of
asymptotically Minkowski self-similar spacetimes, emphasizing that some of them
are associated with the self-similar solutions associated with the critical
behaviour observed in recent gravitational collapse calculations.
|
[
{
"created": "Tue, 23 Feb 1999 11:01:02 GMT",
"version": "v1"
},
{
"created": "Wed, 19 Jul 2000 14:16:08 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Aug 2000 13:25:36 GMT",
"version": "v3"
}
] |
2008-11-26
|
[
[
"Carr",
"B. J.",
""
],
[
"Coley",
"A. A.",
""
],
[
"Goliath",
"M.",
""
],
[
"Nilsson",
"U. S.",
""
],
[
"Uggla",
"C.",
""
]
] |
The purpose of this paper is to further investigate the solution space of self-similar spherically symmetric perfect-fluid models and gain deeper understanding of the physical aspects of these solutions. We achieve this by combining the state space description of the homothetic approach with the use of the physically interesting quantities arising in the comoving approach. We focus on three types of models. First, we consider models that are natural inhomogeneous generalizations of the Friedmann Universe; such models are asymptotically Friedmann in their past and evolve fluctuations in the energy density at later times. Second, we consider so-called quasi-static models. This class includes models that undergo self-similar gravitational collapse and is important for studying the formation of naked singularities. If naked singularities do form, they have profound implications for the predictability of general relativity as a theory. Third, we consider a new class of asymptotically Minkowski self-similar spacetimes, emphasizing that some of them are associated with the self-similar solutions associated with the critical behaviour observed in recent gravitational collapse calculations.
|
0802.1798
|
T. Padmanabhan
|
T. Padmanabhan
|
Emergent gravity and Dark Energy
|
26 pages; no figures; standard latex
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
This is an invited contribution to be included in a multi-authored book on
"Dark Energy", to be edited by Pilar Ruiz-Lapuente and published by Cambridge
University Press.
|
[
{
"created": "Wed, 13 Feb 2008 10:45:05 GMT",
"version": "v1"
}
] |
2008-02-14
|
[
[
"Padmanabhan",
"T.",
""
]
] |
This is an invited contribution to be included in a multi-authored book on "Dark Energy", to be edited by Pilar Ruiz-Lapuente and published by Cambridge University Press.
|
2007.12184
|
Michael Kavic
|
John H. Simonetti, Michael J. Kavic, Djordje Minic, Dejan Stojkovic
and De-Chang Dai
|
A sensitive search for wormholes
|
6 pages, 1 figure
|
Phys. Rev. D 104, 081502 (2021)
|
10.1103/PhysRevD.104.L081502
| null |
gr-qc astro-ph.HE hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The realm of strong classical gravity and perhaps even quantum gravity are
waiting to be explored. In this letter we consider the recently detected triple
system composed of two stars and a non-accreting black hole. Using published
observations of this system we conduct the most sensitive test to date for
whether the black hole is actually a wormhole by looking for orbital
perturbations due to an object on the other side of the wormhole. The mass
limit obtained on the perturber is $\sim4$ orders of magnitude better than for
observations of S2 orbiting the supermassive black hole at Sgr A*. We also
consider how observations of a pulsar could test for whether the black hole in
a pulsar-black hole binary is a wormhole. A pulsar in a similar orbit to S2
would be $\sim10$ orders of magnitude more sensitive than observations of S2.
For a nominal pulsar-black hole binary of stellar masses, with orbital size
similar to that of the Hulse-Taylor binary pulsar, one year of observations
could set a mass limit on a perturber that is $\sim6$ orders of magnitude
better than observations of a pulsar around Sgr~A*. A range of limits between
the pulsar-Sgr~A* and Hulse-Taylor cases could be obtained for a possible
population of pulsar-black hole binaries that may exist near the galactic
center.
|
[
{
"created": "Thu, 23 Jul 2020 18:00:01 GMT",
"version": "v1"
}
] |
2021-10-13
|
[
[
"Simonetti",
"John H.",
""
],
[
"Kavic",
"Michael J.",
""
],
[
"Minic",
"Djordje",
""
],
[
"Stojkovic",
"Dejan",
""
],
[
"Dai",
"De-Chang",
""
]
] |
The realm of strong classical gravity and perhaps even quantum gravity are waiting to be explored. In this letter we consider the recently detected triple system composed of two stars and a non-accreting black hole. Using published observations of this system we conduct the most sensitive test to date for whether the black hole is actually a wormhole by looking for orbital perturbations due to an object on the other side of the wormhole. The mass limit obtained on the perturber is $\sim4$ orders of magnitude better than for observations of S2 orbiting the supermassive black hole at Sgr A*. We also consider how observations of a pulsar could test for whether the black hole in a pulsar-black hole binary is a wormhole. A pulsar in a similar orbit to S2 would be $\sim10$ orders of magnitude more sensitive than observations of S2. For a nominal pulsar-black hole binary of stellar masses, with orbital size similar to that of the Hulse-Taylor binary pulsar, one year of observations could set a mass limit on a perturber that is $\sim6$ orders of magnitude better than observations of a pulsar around Sgr~A*. A range of limits between the pulsar-Sgr~A* and Hulse-Taylor cases could be obtained for a possible population of pulsar-black hole binaries that may exist near the galactic center.
|
2012.06902
|
Riccardo Falcone
|
Riccardo Falcone, Daniela D. Doneva, Kostas D. Kokkotas, Stoytcho S.
Yazadjiev
|
Non-linear stability of soliton solutions for massive
tensor-multi-scalar-theories
| null |
Phys. Rev. D 104, 064045 (2021)
|
10.1103/PhysRevD.104.064045
| null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The aim of this paper is to study the stability of soliton-like static
solutions via non-linear simulations in the context of a special class of
massive tensor-multi-scalar-theories of gravity whose target space metric
admits Killing field(s) with a periodic flow. We focused on the case with two
scalar fields and maximally symmetric target space metric, as the simplest
configuration where solitonic solutions can exist. In the limit of zero
curvature of the target space $\kappa = 0$ these solutions reduce to the
standard boson stars, while for $\kappa \ne 0$ significant deviations can be
observed, both qualitative and quantitative. By evolving these solitonic
solutions in time, we show that they are stable for low values of the central
scalar field $\psi_c$ while instability kicks in with the increase of $\psi_c$.
Specifically, in the stable region, the models oscillate with a characteristic
frequency related to the fundamental mode. Such frequency tends to zero with
the approach of the unstable models and eventually becomes imaginary when the
solitonic solutions lose stability. As expected from the study of the
equilibrium models, the change of stability occurs exactly at the maximum mass
point, which was checked numerically with a very good accuracy.
|
[
{
"created": "Sat, 12 Dec 2020 20:12:26 GMT",
"version": "v1"
}
] |
2021-09-22
|
[
[
"Falcone",
"Riccardo",
""
],
[
"Doneva",
"Daniela D.",
""
],
[
"Kokkotas",
"Kostas D.",
""
],
[
"Yazadjiev",
"Stoytcho S.",
""
]
] |
The aim of this paper is to study the stability of soliton-like static solutions via non-linear simulations in the context of a special class of massive tensor-multi-scalar-theories of gravity whose target space metric admits Killing field(s) with a periodic flow. We focused on the case with two scalar fields and maximally symmetric target space metric, as the simplest configuration where solitonic solutions can exist. In the limit of zero curvature of the target space $\kappa = 0$ these solutions reduce to the standard boson stars, while for $\kappa \ne 0$ significant deviations can be observed, both qualitative and quantitative. By evolving these solitonic solutions in time, we show that they are stable for low values of the central scalar field $\psi_c$ while instability kicks in with the increase of $\psi_c$. Specifically, in the stable region, the models oscillate with a characteristic frequency related to the fundamental mode. Such frequency tends to zero with the approach of the unstable models and eventually becomes imaginary when the solitonic solutions lose stability. As expected from the study of the equilibrium models, the change of stability occurs exactly at the maximum mass point, which was checked numerically with a very good accuracy.
|
2105.04726
|
Yong Tang
|
Yong Tang, Yue-Liang Wu
|
On Conformal Transformation with Multiple Scalar Fields and Geometric
Property of Field Space with Einstein-like Solutions
|
1+17 pages, 1 table
|
Phys. Rev. D 104, 064042 (2021)
|
10.1103/PhysRevD.104.064042
| null |
gr-qc astro-ph.CO hep-ph
|
http://creativecommons.org/licenses/by/4.0/
|
Multiple scalar fields appear in vast modern particle physics and gravity
models. When they couple to gravity non-minimally, conformal transformation is
utilized to bring the theory into Einstein frame. However, the kinetic terms of
scalar fields are usually not canonical, which makes analytic treatment
difficult. Here we investigate under what conditions the theories can be
transformed to the quasi-canonical form, in which case the effective metric
tensor in field space is conformally flat. We solve the relevant nonlinear
partial differential equations for arbitrary number of scalar fields and
present several solutions that may be useful for future phenomenological model
building, including the $\sigma$-model with a particular non-minimal coupling.
We also find conformal flatness can always be achieved in some modified gravity
theories, for example, Starobinsky model.
|
[
{
"created": "Tue, 11 May 2021 00:45:53 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Jul 2021 09:12:57 GMT",
"version": "v2"
}
] |
2021-09-22
|
[
[
"Tang",
"Yong",
""
],
[
"Wu",
"Yue-Liang",
""
]
] |
Multiple scalar fields appear in vast modern particle physics and gravity models. When they couple to gravity non-minimally, conformal transformation is utilized to bring the theory into Einstein frame. However, the kinetic terms of scalar fields are usually not canonical, which makes analytic treatment difficult. Here we investigate under what conditions the theories can be transformed to the quasi-canonical form, in which case the effective metric tensor in field space is conformally flat. We solve the relevant nonlinear partial differential equations for arbitrary number of scalar fields and present several solutions that may be useful for future phenomenological model building, including the $\sigma$-model with a particular non-minimal coupling. We also find conformal flatness can always be achieved in some modified gravity theories, for example, Starobinsky model.
|
2010.09716
|
Sunandan Gangopadhyay
|
Rituparna Mandal, Sunandan Gangopadhyay, Amitabha Lahiri
|
Cosmology with modified continuity equation in asymptotically safe
gravity
|
25 pages Latex, some References added
|
The European Physical Journal Plus 137 (2022) 10, 1110
| null | null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study FLRW cosmology, taking into account quantum gravitational
corrections in the formalism of the exact renormalization group flow of the
effective action for gravity. We calculate the quantum corrected scale factor,
energy density, and entropy production at late times, taking different cut-off
functions. Our approach differs from previous ones in the way energy-momentum
conservation is imposed -- we include the running Newton constant $G(k)$ in the
definition of energy-momentum tensor, keeping in mind the covariant
conservation identity of the Einstein tensor. The quantum corrections obtained
in this approach are different from what are found by letting the conservation
equation remain the same as for a scale-independent Newton constant. We also
find that for a specific choice of the cut-off scale, the quantum corrected
behaviour of the Newton constant and the cosmological constant lead to a
bouncing emergent universe solution.
|
[
{
"created": "Mon, 19 Oct 2020 06:06:25 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Dec 2020 08:27:05 GMT",
"version": "v2"
},
{
"created": "Mon, 22 Feb 2021 04:27:31 GMT",
"version": "v3"
}
] |
2022-10-26
|
[
[
"Mandal",
"Rituparna",
""
],
[
"Gangopadhyay",
"Sunandan",
""
],
[
"Lahiri",
"Amitabha",
""
]
] |
We study FLRW cosmology, taking into account quantum gravitational corrections in the formalism of the exact renormalization group flow of the effective action for gravity. We calculate the quantum corrected scale factor, energy density, and entropy production at late times, taking different cut-off functions. Our approach differs from previous ones in the way energy-momentum conservation is imposed -- we include the running Newton constant $G(k)$ in the definition of energy-momentum tensor, keeping in mind the covariant conservation identity of the Einstein tensor. The quantum corrections obtained in this approach are different from what are found by letting the conservation equation remain the same as for a scale-independent Newton constant. We also find that for a specific choice of the cut-off scale, the quantum corrected behaviour of the Newton constant and the cosmological constant lead to a bouncing emergent universe solution.
|
gr-qc/0308074
|
Johan Noldus
|
Johan Noldus
|
A Lorentzian Gromov-Hausdoff notion of distance
|
20 pages, 0 figures, submitted to Classical and quantum gravity,
seriously improved presentation
|
Class.Quant.Grav. 21 (2004) 839-850
|
10.1088/0264-9381/21/4/007
| null |
gr-qc math.MG
| null |
This paper is the first of three in which I study the moduli space of
isometry classes of (compact) globally hyperbolic spacetimes (with boundary). I
introduce a notion of Gromov-Hausdorff distance which makes this moduli space
into a metric space. Further properties of this metric space are studied in the
next papers. The importance of the work can be situated in fields such as
cosmology, quantum gravity and - for the mathematicians - global Lorentzian
geometry.
|
[
{
"created": "Fri, 22 Aug 2003 19:19:52 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Aug 2003 00:57:24 GMT",
"version": "v2"
},
{
"created": "Tue, 18 Nov 2003 09:44:28 GMT",
"version": "v3"
}
] |
2009-11-10
|
[
[
"Noldus",
"Johan",
""
]
] |
This paper is the first of three in which I study the moduli space of isometry classes of (compact) globally hyperbolic spacetimes (with boundary). I introduce a notion of Gromov-Hausdorff distance which makes this moduli space into a metric space. Further properties of this metric space are studied in the next papers. The importance of the work can be situated in fields such as cosmology, quantum gravity and - for the mathematicians - global Lorentzian geometry.
|
1108.4578
|
Diana Kaminski
|
Diana Kaminski
|
AQV II. A new formulation of the Weyl C*-algebra
|
71 pages, 10 figures
| null | null | null |
gr-qc math-ph math.MP quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this article a new formulation of the Weyl C*-algebra, which has been
invented by Fleischhack, in terms of C*-dynamical systems is presented. The
quantum configuration variables are given by the holonomies along paths in a
graph. Functions depending on these quantum variables form the analytic
holonomy C*-algebra. Each classical flux variable is quantised as an element of
a flux group associated to a certain surface set and a graph. The quantised
spatial diffeomorphisms are elements of the group of bisections of a finite
graph system. Then different actions of the flux group associated to surfaces
and the group of bisections on the analytic holonomy C*-algebra are studied.
The Weyl C*-algebra for surfaces is generated by unitary operators, which
implements the group-valued quantum flux operators, and certain functions
depending on holonomies along paths that satisfy canonical commutation
relations. Furthermore there is a unique pure state on the commutative Weyl
C*-algebra for surfaces, which is a path- or graph-diffeomorphism invariant.
|
[
{
"created": "Fri, 19 Aug 2011 16:52:40 GMT",
"version": "v1"
}
] |
2011-08-24
|
[
[
"Kaminski",
"Diana",
""
]
] |
In this article a new formulation of the Weyl C*-algebra, which has been invented by Fleischhack, in terms of C*-dynamical systems is presented. The quantum configuration variables are given by the holonomies along paths in a graph. Functions depending on these quantum variables form the analytic holonomy C*-algebra. Each classical flux variable is quantised as an element of a flux group associated to a certain surface set and a graph. The quantised spatial diffeomorphisms are elements of the group of bisections of a finite graph system. Then different actions of the flux group associated to surfaces and the group of bisections on the analytic holonomy C*-algebra are studied. The Weyl C*-algebra for surfaces is generated by unitary operators, which implements the group-valued quantum flux operators, and certain functions depending on holonomies along paths that satisfy canonical commutation relations. Furthermore there is a unique pure state on the commutative Weyl C*-algebra for surfaces, which is a path- or graph-diffeomorphism invariant.
|
gr-qc/0105114
|
Christophe Grojean
|
C. Csaki, J. Erlich, C. Grojean
|
The Cosmological Constant Problem in Brane--Worlds and Gravitational
Lorentz Violations
|
First Award in the 2001 Annual Essay Competition of the Gravity
Research Foundation
|
Gen.Rel.Grav.33:1921-1928,2001
|
10.1023/A:1013094709013
| null |
gr-qc astro-ph hep-ph hep-th
| null |
Brane worlds are theories with extra spatial dimensions in which ordinary
matter is localized on a (3+1) dimensional submanifold. Such theories could
have interesting consequences for particle physics and gravitational physics.
In this essay we concentrate on the cosmological constant (CC) problem in the
context of brane worlds. We show how extra-dimensional scenarios may violate
Lorentz invariance in the gravity sector of the effective 4D theory, while
particle physics remains unaffected. In such theories the usual no-go theorems
for adjustment of the CC do not apply, and we indicate a possible explanation
of the smallness of the CC. Lorentz violating effects would manifest themselves
in gravitational waves travelling with a speed different from light, which can
be searched for in gravitational wave experiments.
|
[
{
"created": "Wed, 30 May 2001 02:01:52 GMT",
"version": "v1"
}
] |
2009-09-17
|
[
[
"Csaki",
"C.",
""
],
[
"Erlich",
"J.",
""
],
[
"Grojean",
"C.",
""
]
] |
Brane worlds are theories with extra spatial dimensions in which ordinary matter is localized on a (3+1) dimensional submanifold. Such theories could have interesting consequences for particle physics and gravitational physics. In this essay we concentrate on the cosmological constant (CC) problem in the context of brane worlds. We show how extra-dimensional scenarios may violate Lorentz invariance in the gravity sector of the effective 4D theory, while particle physics remains unaffected. In such theories the usual no-go theorems for adjustment of the CC do not apply, and we indicate a possible explanation of the smallness of the CC. Lorentz violating effects would manifest themselves in gravitational waves travelling with a speed different from light, which can be searched for in gravitational wave experiments.
|
1605.08901
|
Carlos A. R. Herdeiro
|
Yves Brihaye, Carlos Herdeiro, Eugen Radu
|
Inside black holes with synchronized hair
|
15 pages, 4 figures
| null |
10.1016/j.physletb.2016.06.078
| null |
gr-qc astro-ph.HE hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Recently, various examples of asymptotically flat, rotating black holes (BHs)
with synchronized hair have been explicitly constructed, including Kerr BHs
with scalar or Proca hair, and Myers-Perry BHs with scalar hair and a mass gap,
showing there is a general mechanism at work. All these solutions have been
found numerically, integrating the fully non-linear field equations of motion
from the event horizon outwards. Here, we address the spacetime geometry of
these solutions inside the event horizon. Firstly, we provide arguments, within
linear theory, that there is no regular inner horizon for these solutions.
Then, we address this question fully non-linearly, using as a tractable model
five dimensional, equal spinning, Myers-Perry hairy BHs. We find that, for
non-extremal solutions: $(1)$ the inside spacetime geometry in the vicinity of
the event horizon is smooth and the equations of motion can be integrated
inwards; $(2)$ before an inner horizon is reached, the spacetime curvature
grows (apparently) without bound. In all cases, our results suggest the absence
of a smooth Cauchy horizon, beyond which the metric can be extended, for hairy
BHs with synchronized hair.
|
[
{
"created": "Sat, 28 May 2016 15:02:33 GMT",
"version": "v1"
}
] |
2016-08-03
|
[
[
"Brihaye",
"Yves",
""
],
[
"Herdeiro",
"Carlos",
""
],
[
"Radu",
"Eugen",
""
]
] |
Recently, various examples of asymptotically flat, rotating black holes (BHs) with synchronized hair have been explicitly constructed, including Kerr BHs with scalar or Proca hair, and Myers-Perry BHs with scalar hair and a mass gap, showing there is a general mechanism at work. All these solutions have been found numerically, integrating the fully non-linear field equations of motion from the event horizon outwards. Here, we address the spacetime geometry of these solutions inside the event horizon. Firstly, we provide arguments, within linear theory, that there is no regular inner horizon for these solutions. Then, we address this question fully non-linearly, using as a tractable model five dimensional, equal spinning, Myers-Perry hairy BHs. We find that, for non-extremal solutions: $(1)$ the inside spacetime geometry in the vicinity of the event horizon is smooth and the equations of motion can be integrated inwards; $(2)$ before an inner horizon is reached, the spacetime curvature grows (apparently) without bound. In all cases, our results suggest the absence of a smooth Cauchy horizon, beyond which the metric can be extended, for hairy BHs with synchronized hair.
|
gr-qc/0012011
|
Sawa Manoff
|
S. Manoff, B. Dimitrov
|
On the existence of a gyroscope in spaces with affine connections and
metrics
|
12 pages, RevTex
|
Gen.Rel.Grav. 35 (2003) 25-33
|
10.1023/A:1021346626475
| null |
gr-qc
| null |
Conditions for the existence of a gyroscope in spaces with affine connections
and metrics are found. They appear as special types of Fermi-Walker transports
for vector fields, lying in a subspace, orthogonal to the velocity vector field
of an observer.
PACS numbers: 04.20Cv, 04.90.+e, 04.50.+h, 02.40.Ky
|
[
{
"created": "Mon, 4 Dec 2000 12:19:18 GMT",
"version": "v1"
}
] |
2015-06-25
|
[
[
"Manoff",
"S.",
""
],
[
"Dimitrov",
"B.",
""
]
] |
Conditions for the existence of a gyroscope in spaces with affine connections and metrics are found. They appear as special types of Fermi-Walker transports for vector fields, lying in a subspace, orthogonal to the velocity vector field of an observer. PACS numbers: 04.20Cv, 04.90.+e, 04.50.+h, 02.40.Ky
|
2104.07686
|
Marco Astorino
|
Marco Astorino, Adriano Vigan\`o
|
Binary black hole system at equilibrium
|
8 pages, 2 figures, Mathematica worksheet included in the arXiv
files, v2: typos corrected, references added
|
Phys.Lett.B 820 (2021) 136506
|
10.1016/j.physletb.2021.136506
|
IFUM-1090-FT
|
gr-qc astro-ph.HE hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
An exact and analytical solution of four dimensional vacuum General
Relativity representing a system of two static black holes at equilibrium is
presented. The metric is completely regular outside the event horizons, both
from curvature and conical singularities. The balance between the two
Schwarzschild sources is granted by an external gravitational field, without
the need of extra matter fields besides gravity, nor strings or struts. The
geometry of the solution is analysed. The Smarr law, the first and the second
law of black hole thermodynamics are discussed.
|
[
{
"created": "Thu, 15 Apr 2021 18:00:06 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Jun 2021 17:01:08 GMT",
"version": "v2"
}
] |
2023-08-22
|
[
[
"Astorino",
"Marco",
""
],
[
"Viganò",
"Adriano",
""
]
] |
An exact and analytical solution of four dimensional vacuum General Relativity representing a system of two static black holes at equilibrium is presented. The metric is completely regular outside the event horizons, both from curvature and conical singularities. The balance between the two Schwarzschild sources is granted by an external gravitational field, without the need of extra matter fields besides gravity, nor strings or struts. The geometry of the solution is analysed. The Smarr law, the first and the second law of black hole thermodynamics are discussed.
|
gr-qc/0211064
|
Nicolas Arnaud
|
Nicolas Arnaud, Matteo Barsuglia, Marie-Anne Bizouard, Violette
Brisson, Fabien Cavalier, Michel Davier, Patrice Hello, Stephane Kreckelbergh
and Edward K. Porter
|
An elliptical tiling method to generate a 2-dimensional set of templates
for gravitational wave search
|
Accepted in PRD
|
Phys.Rev. D67 (2003) 102003
|
10.1103/PhysRevD.67.102003
| null |
gr-qc
| null |
Searching for a signal depending on unknown parameters in a noisy background
with matched filtering techniques always requires an analysis of the data with
several templates in parallel in order to ensure a proper match between the
filter and the real waveform. The key feature of such an implementation is the
design of the filter bank which must be small to limit the computational cost
while keeping the detection efficiency as high as possible. This paper presents
a geometrical method which allows one to cover the corresponding physical
parameter space by a set of ellipses, each of them being associated to a given
template. After the description of the main characteristics of the algorithm,
the method is applied in the field of gravitational wave (GW) data analysis,
for the search of damped sine signals. Such waveforms are expected to be
produced during the de-excitation phase of black holes -- the so-called
'ringdown' signals -- and are also encountered in some numerically computed
supernova signals.
|
[
{
"created": "Mon, 18 Nov 2002 19:22:04 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Jan 2003 07:59:10 GMT",
"version": "v2"
}
] |
2009-11-07
|
[
[
"Arnaud",
"Nicolas",
""
],
[
"Barsuglia",
"Matteo",
""
],
[
"Bizouard",
"Marie-Anne",
""
],
[
"Brisson",
"Violette",
""
],
[
"Cavalier",
"Fabien",
""
],
[
"Davier",
"Michel",
""
],
[
"Hello",
"Patrice",
""
],
[
"Kreckelbergh",
"Stephane",
""
],
[
"Porter",
"Edward K.",
""
]
] |
Searching for a signal depending on unknown parameters in a noisy background with matched filtering techniques always requires an analysis of the data with several templates in parallel in order to ensure a proper match between the filter and the real waveform. The key feature of such an implementation is the design of the filter bank which must be small to limit the computational cost while keeping the detection efficiency as high as possible. This paper presents a geometrical method which allows one to cover the corresponding physical parameter space by a set of ellipses, each of them being associated to a given template. After the description of the main characteristics of the algorithm, the method is applied in the field of gravitational wave (GW) data analysis, for the search of damped sine signals. Such waveforms are expected to be produced during the de-excitation phase of black holes -- the so-called 'ringdown' signals -- and are also encountered in some numerically computed supernova signals.
|
2108.00896
|
Paul Lageyre
|
Paul Lageyre, Xavier Ribeyre, Emmanuel D'Humieres
|
Gravitational influence of high power laser pulses
| null | null |
10.1103/PhysRevD.105.104052
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The study of the generation of metric perturbation in the laboratory presents
an opportunity to observe and understand more easily the mechanisms at work in
gravitation. The present study will focus on the metric perturbation generated
by a light pulse, as it could be generated by a current ultra-high power laser.
Although of very small magnitude, the potential thus generated has advantages
over that generated by mass acceleration, such as the absence of noise due to
non uniform acceleration or the ability to scale up the experiment. It is
indeed easier to scale up an electromagnetic oscillation compared to a
mechanical oscillator, which must either be made with a large accelerated mass
or a lot of small masses, all in sync, which acceleration must furthermore be
quadripolar. Generation of metric deformation by laser could therefore prove
useful in the long-term establishment of a laboratory experiment for the
generation and detection of gravitational waves.
|
[
{
"created": "Fri, 30 Jul 2021 12:40:21 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Mar 2022 20:06:46 GMT",
"version": "v2"
},
{
"created": "Thu, 31 Mar 2022 18:49:22 GMT",
"version": "v3"
}
] |
2022-06-08
|
[
[
"Lageyre",
"Paul",
""
],
[
"Ribeyre",
"Xavier",
""
],
[
"D'Humieres",
"Emmanuel",
""
]
] |
The study of the generation of metric perturbation in the laboratory presents an opportunity to observe and understand more easily the mechanisms at work in gravitation. The present study will focus on the metric perturbation generated by a light pulse, as it could be generated by a current ultra-high power laser. Although of very small magnitude, the potential thus generated has advantages over that generated by mass acceleration, such as the absence of noise due to non uniform acceleration or the ability to scale up the experiment. It is indeed easier to scale up an electromagnetic oscillation compared to a mechanical oscillator, which must either be made with a large accelerated mass or a lot of small masses, all in sync, which acceleration must furthermore be quadripolar. Generation of metric deformation by laser could therefore prove useful in the long-term establishment of a laboratory experiment for the generation and detection of gravitational waves.
|
1906.11572
|
D. Ghilencea
|
D. M. Ghilencea
|
Weyl $R^2$ inflation with an emergent Planck scale
|
v3: 14 pages; Section 4 and references added
|
JHEP10(2019)209
|
10.1007/JHEP10(2019)209
| null |
gr-qc astro-ph.CO hep-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study inflation in Weyl gravity. The original Weyl quadratic gravity,
based on Weyl conformal geometry, is a theory invariant under Weyl symmetry of
(gauged) local scale transformations. In this theory Planck scale ($M$) emerges
as the scale where this symmetry is broken spontaneously by a geometric
Stueckelberg mechanism, to Einstein-Proca action for the Weyl "photon" (of mass
near $M$). With this action as a "low energy" broken phase of Weyl gravity,
century-old criticisms of the latter (due to non-metricity) are avoided. In
this context, inflation with field values above $M$ is natural, since this is
just a phase transition scale from Weyl gravity (geometry) to Einstein gravity
(Riemannian geometry), where the massive Weyl photon decouples. We show that
inflation in Weyl gravity coupled to a scalar field has results close to those
in Starobinsky model (recovered for vanishing non-minimal coupling), with a
mildly smaller tensor-to-scalar ratio ($r$). Weyl gravity predicts a specific,
narrow range $0.00257 \leq r\leq 0.00303$, for a spectral index $n_s$ within
experimental bounds at $68\%$CL and e-folds number $N=60$. This range of values
will soon be reached by CMB experiments and provides a test of Weyl gravity.
Unlike in the Starobinsky model, the prediction for $(r, n_s)$ is not affected
by unknown higher dimensional curvature operators (suppressed by some large
mass scale) since these are forbidden by the Weyl gauge symmetry.
|
[
{
"created": "Thu, 27 Jun 2019 11:58:21 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Jul 2019 08:51:06 GMT",
"version": "v2"
},
{
"created": "Mon, 30 Sep 2019 13:24:17 GMT",
"version": "v3"
}
] |
2020-01-08
|
[
[
"Ghilencea",
"D. M.",
""
]
] |
We study inflation in Weyl gravity. The original Weyl quadratic gravity, based on Weyl conformal geometry, is a theory invariant under Weyl symmetry of (gauged) local scale transformations. In this theory Planck scale ($M$) emerges as the scale where this symmetry is broken spontaneously by a geometric Stueckelberg mechanism, to Einstein-Proca action for the Weyl "photon" (of mass near $M$). With this action as a "low energy" broken phase of Weyl gravity, century-old criticisms of the latter (due to non-metricity) are avoided. In this context, inflation with field values above $M$ is natural, since this is just a phase transition scale from Weyl gravity (geometry) to Einstein gravity (Riemannian geometry), where the massive Weyl photon decouples. We show that inflation in Weyl gravity coupled to a scalar field has results close to those in Starobinsky model (recovered for vanishing non-minimal coupling), with a mildly smaller tensor-to-scalar ratio ($r$). Weyl gravity predicts a specific, narrow range $0.00257 \leq r\leq 0.00303$, for a spectral index $n_s$ within experimental bounds at $68\%$CL and e-folds number $N=60$. This range of values will soon be reached by CMB experiments and provides a test of Weyl gravity. Unlike in the Starobinsky model, the prediction for $(r, n_s)$ is not affected by unknown higher dimensional curvature operators (suppressed by some large mass scale) since these are forbidden by the Weyl gauge symmetry.
|
1901.00869
|
Wei Wei
|
Wei Wei and E. A. Huerta
|
Gravitational Wave Denoising of Binary Black Hole Mergers with Deep
Learning
|
26 pages, 10 figures. v2: new results for denoising and deglitching
included, as well as denoising of spin-precessing binary black hole signals
embedded in real advanced LIGO data. Accepted to Physics Letters B
|
Physics Letters B 800 (2020) 135081
|
10.1016/j.physletb.2019.135081
| null |
gr-qc astro-ph.IM physics.data-an
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Gravitational wave detection requires an in-depth understanding of the
physical properties of gravitational wave signals, and the noise from which
they are extracted. Understanding the statistical properties of noise is a
complex endeavor, particularly in realistic detection scenarios. In this
article we demonstrate that deep learning can handle the non-Gaussian and
non-stationary nature of gravitational wave data, and showcase its application
to denoise the gravitational wave signals generated by the binary black hole
mergers GW150914, GW170104, GW170608 and GW170814 from advanced LIGO noise. To
exhibit the accuracy of this methodology, we compute the overlap between the
time-series signals produced by our denoising algorithm, and the numerical
relativity templates that are expected to describe these gravitational wave
sources, finding overlaps ${\cal{O}}\gtrsim0.99$. We also show that our deep
learning algorithm is capable of removing noise anomalies from numerical
relativity signals that we inject in real advanced LIGO data. We discuss the
implications of these results for the characterization of gravitational wave
signals.
|
[
{
"created": "Thu, 3 Jan 2019 19:00:05 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Dec 2019 20:00:48 GMT",
"version": "v2"
}
] |
2019-12-05
|
[
[
"Wei",
"Wei",
""
],
[
"Huerta",
"E. A.",
""
]
] |
Gravitational wave detection requires an in-depth understanding of the physical properties of gravitational wave signals, and the noise from which they are extracted. Understanding the statistical properties of noise is a complex endeavor, particularly in realistic detection scenarios. In this article we demonstrate that deep learning can handle the non-Gaussian and non-stationary nature of gravitational wave data, and showcase its application to denoise the gravitational wave signals generated by the binary black hole mergers GW150914, GW170104, GW170608 and GW170814 from advanced LIGO noise. To exhibit the accuracy of this methodology, we compute the overlap between the time-series signals produced by our denoising algorithm, and the numerical relativity templates that are expected to describe these gravitational wave sources, finding overlaps ${\cal{O}}\gtrsim0.99$. We also show that our deep learning algorithm is capable of removing noise anomalies from numerical relativity signals that we inject in real advanced LIGO data. We discuss the implications of these results for the characterization of gravitational wave signals.
|
1609.08580
|
Sabir Ramazanov Dr.
|
Eugeny Babichev and Sabir Ramazanov
|
Gravitational focusing of Imperfect Dark Matter
|
34 pages, 1 figure. Clarifications and references added. Matches
published version
|
Phys. Rev. D 95, 024025 (2017)
|
10.1103/PhysRevD.95.024025
|
LPT-Orsay-17-02
|
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Motivated by the projectable Horava--Lifshitz model/mimetic matter scenario,
we consider a particular modification of standard gravity, which manifests as
an imperfect low pressure fluid. While practically indistinguishable from a
collection of non-relativistic weakly interacting particles on cosmological
scales, it leaves drastically different signatures in the Solar system. The
main effect stems from gravitational focusing of the flow of Imperfect Dark
Matter passing near the Sun. This entails strong amplification of Imperfect
Dark Matter energy density compared to its average value in the surrounding
halo. The enhancement is many orders of magnitude larger than in the case of
Cold Dark Matter, provoking deviations of the metric in the second order in the
Newtonian potential. Effects of gravitational focusing are prominent enough to
substantially affect the planetary dynamics. Using the existing bound on the
PPN parameter $\beta_{PPN}$, we deduce a stringent constraint on the unique
constant of the model.
|
[
{
"created": "Tue, 27 Sep 2016 19:01:22 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Oct 2016 15:13:10 GMT",
"version": "v2"
},
{
"created": "Tue, 24 Jan 2017 15:17:24 GMT",
"version": "v3"
}
] |
2017-01-25
|
[
[
"Babichev",
"Eugeny",
""
],
[
"Ramazanov",
"Sabir",
""
]
] |
Motivated by the projectable Horava--Lifshitz model/mimetic matter scenario, we consider a particular modification of standard gravity, which manifests as an imperfect low pressure fluid. While practically indistinguishable from a collection of non-relativistic weakly interacting particles on cosmological scales, it leaves drastically different signatures in the Solar system. The main effect stems from gravitational focusing of the flow of Imperfect Dark Matter passing near the Sun. This entails strong amplification of Imperfect Dark Matter energy density compared to its average value in the surrounding halo. The enhancement is many orders of magnitude larger than in the case of Cold Dark Matter, provoking deviations of the metric in the second order in the Newtonian potential. Effects of gravitational focusing are prominent enough to substantially affect the planetary dynamics. Using the existing bound on the PPN parameter $\beta_{PPN}$, we deduce a stringent constraint on the unique constant of the model.
|
0804.4067
|
Mattias N. R. Wohlfarth
|
Raffaele Punzi, Frederic P. Schuller, Mattias N.R. Wohlfarth
|
Brans-Dicke geometry
|
8 pages, v2 with additional comment and references
|
Phys.Lett.B670:161-164,2008
|
10.1016/j.physletb.2008.10.046
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We reveal the non-metric geometry underlying omega-->0 Brans-Dicke theory by
unifying the metric and scalar field into a single geometric structure. Taking
this structure seriously as the geometry to which matter universally couples,
we show that the theory is fully consistent with solar system tests. This is in
striking constrast with the standard metric coupling, which grossly violates
post-Newtonian experimental constraints.
|
[
{
"created": "Fri, 25 Apr 2008 09:12:37 GMT",
"version": "v1"
},
{
"created": "Fri, 9 May 2008 08:52:07 GMT",
"version": "v2"
}
] |
2008-12-18
|
[
[
"Punzi",
"Raffaele",
""
],
[
"Schuller",
"Frederic P.",
""
],
[
"Wohlfarth",
"Mattias N. R.",
""
]
] |
We reveal the non-metric geometry underlying omega-->0 Brans-Dicke theory by unifying the metric and scalar field into a single geometric structure. Taking this structure seriously as the geometry to which matter universally couples, we show that the theory is fully consistent with solar system tests. This is in striking constrast with the standard metric coupling, which grossly violates post-Newtonian experimental constraints.
|
1612.06718
|
Vladimir Kassandrov
|
Vladimir V. Kassandrov, Joseph A. Rizcallah
|
Maxwell, Yang-Mills, Weyl and eikonal fields defined by any null
shear-free congruence
|
18 pages, 2 figures. Partly reproduces the old (unpublished) preprint
arXiv:gr-qc/0012109
|
International Journal of Geometrical Methods in Modern Physics,
Vol.14 (2017), 1750031 (22 pp.)
|
10.1142/S0219887817500311
| null |
gr-qc hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We show that (specifically scaled) equations of shear-free null geodesic
congruences on the Minkowski space-time possess intrinsic self-dual, restricted
gauge and algebraic structures. The complex eikonal, Weyl 2-spinor,
$SL(2,\mathbb C)$ Yang-Mills and complex Maxwell fields, the latter produced by
integer-valued electric charges ("elementary" for the Kerr-like congruences),
can all be explicitly associated with any shear-free null geodesic congruence.
Using twistor variables, we derive the general solution of the equations of the
shear-free null geodesic congruence (as a modification of the Kerr theorem) and
analyze the corresponding "particle-like" field distributions, with bounded
singularities of the associated physical fields. These can be obtained in a
straightforward algebraic way and exhibit non-trivial collective dynamics
simulating physical interactions
|
[
{
"created": "Mon, 19 Dec 2016 19:32:53 GMT",
"version": "v1"
}
] |
2017-01-01
|
[
[
"Kassandrov",
"Vladimir V.",
""
],
[
"Rizcallah",
"Joseph A.",
""
]
] |
We show that (specifically scaled) equations of shear-free null geodesic congruences on the Minkowski space-time possess intrinsic self-dual, restricted gauge and algebraic structures. The complex eikonal, Weyl 2-spinor, $SL(2,\mathbb C)$ Yang-Mills and complex Maxwell fields, the latter produced by integer-valued electric charges ("elementary" for the Kerr-like congruences), can all be explicitly associated with any shear-free null geodesic congruence. Using twistor variables, we derive the general solution of the equations of the shear-free null geodesic congruence (as a modification of the Kerr theorem) and analyze the corresponding "particle-like" field distributions, with bounded singularities of the associated physical fields. These can be obtained in a straightforward algebraic way and exhibit non-trivial collective dynamics simulating physical interactions
|
1502.07245
|
Piotr Jaranowski
|
Thibault Damour, Piotr Jaranowski, Gerhard Sch\"afer
|
Fourth post-Newtonian effective one-body dynamics
|
Minor amendments added; misprints removed; identical with published
version; 18 pages, 1 figure
|
Phys. Rev. D 91, 084024 (2015)
|
10.1103/PhysRevD.91.084024
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The conservative dynamics of gravitationally interacting two-point-mass
systems has been recently determined at the fourth post-Newtonian (4PN)
approximation [T.Damour, P.Jaranowski, and G.Sch\"afer, Phys. Rev. D 89, 064058
(2014)], and found to be nonlocal in time. We show how to transcribe this
dynamics within the effective one-body (EOB) formalism. To achieve this EOB
transcription, we develop a new strategy involving the
(infinite-)order-reduction of a nonlocal dynamics to an ordinary action-angle
Hamiltonian. Our final, equivalent EOB dynamics comprises two (local) radial
potentials, $A(r)$ and $\bar{D}(r)$, and a nongeodesic mass-shell contribution
$Q(r,p_r)$ given by an infinite series of even powers of the radial momentum
$p_r$. Using an effective action technique, we complete our 4PN-level results
by deriving two different, higher-order conservative contributions linked to
tail-transported hereditary effects: the 5PN-level EOB logarithmic terms, as
well as the 5.5PN-level, half-integral terms. We compare our improved
analytical knowledge to previous, numerical gravitational-self-force
computation of precession effects.
|
[
{
"created": "Wed, 25 Feb 2015 17:06:00 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Apr 2015 13:01:56 GMT",
"version": "v2"
}
] |
2015-05-01
|
[
[
"Damour",
"Thibault",
""
],
[
"Jaranowski",
"Piotr",
""
],
[
"Schäfer",
"Gerhard",
""
]
] |
The conservative dynamics of gravitationally interacting two-point-mass systems has been recently determined at the fourth post-Newtonian (4PN) approximation [T.Damour, P.Jaranowski, and G.Sch\"afer, Phys. Rev. D 89, 064058 (2014)], and found to be nonlocal in time. We show how to transcribe this dynamics within the effective one-body (EOB) formalism. To achieve this EOB transcription, we develop a new strategy involving the (infinite-)order-reduction of a nonlocal dynamics to an ordinary action-angle Hamiltonian. Our final, equivalent EOB dynamics comprises two (local) radial potentials, $A(r)$ and $\bar{D}(r)$, and a nongeodesic mass-shell contribution $Q(r,p_r)$ given by an infinite series of even powers of the radial momentum $p_r$. Using an effective action technique, we complete our 4PN-level results by deriving two different, higher-order conservative contributions linked to tail-transported hereditary effects: the 5PN-level EOB logarithmic terms, as well as the 5.5PN-level, half-integral terms. We compare our improved analytical knowledge to previous, numerical gravitational-self-force computation of precession effects.
|
1609.07225
|
Vishal Baibhav
|
Vishal Baibhav and Debaprasad Maity
|
Boson Stars in Higher Derivative Gravity
| null |
Phys. Rev. D 95, 024027 (2017)
|
10.1103/PhysRevD.95.024027
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we have constructed Boson star (BS) solutions in four
dimensional scalar-Gauss-Bonnet (sGB) theory. In order to have non-trivial
effect from Gauss-Bonnet term, we invoked non-minimal coupling between a
complex scalar field and the Gauss-Bonnet term with a coupling parameter,
$\alpha$. We show that the scalar field can no longer take arbitrary value at
the center of the star. Furthermore, boson-stars in our higher derivative
theory turn out to be slightly massive but much more compact than those in the
usual Einstein's gravity. Interestingly, we found that for $\alpha<-0.4$ and
$\alpha>0.8$, binding energy for all possible boson stars is always negative.
This implies that these stars are intrinsically stable against the decay by
dispersion. We also present the mass-radius and mass-frequency curves for
boson-star and compare them with other compact objects in gravity models
derived from Gauss-Bonnet term.
|
[
{
"created": "Fri, 23 Sep 2016 04:07:39 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Oct 2016 00:17:00 GMT",
"version": "v2"
}
] |
2017-01-25
|
[
[
"Baibhav",
"Vishal",
""
],
[
"Maity",
"Debaprasad",
""
]
] |
In this paper, we have constructed Boson star (BS) solutions in four dimensional scalar-Gauss-Bonnet (sGB) theory. In order to have non-trivial effect from Gauss-Bonnet term, we invoked non-minimal coupling between a complex scalar field and the Gauss-Bonnet term with a coupling parameter, $\alpha$. We show that the scalar field can no longer take arbitrary value at the center of the star. Furthermore, boson-stars in our higher derivative theory turn out to be slightly massive but much more compact than those in the usual Einstein's gravity. Interestingly, we found that for $\alpha<-0.4$ and $\alpha>0.8$, binding energy for all possible boson stars is always negative. This implies that these stars are intrinsically stable against the decay by dispersion. We also present the mass-radius and mass-frequency curves for boson-star and compare them with other compact objects in gravity models derived from Gauss-Bonnet term.
|
0901.3971
|
David Kofro\v{n}
|
Jiri Bicak, David Kofron
|
The Newtonian limit of spacetimes for accelerated particles and black
holes
| null |
Gen. Relat. Gravit. 41(1), 153-172 (2009)
|
10.1007/s10714-008-0662-0
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Solutions of vacuum Einstein's field equations describing uniformly
accelerated particles or black holes belong to the class of boost-rotation
symmetric spacetimes. They are the only explicit solutions known which
represent moving finite objects. Their Newtonian limit is analyzed using the
Ehlers frame theory. Generic spacetimes with axial and boost symmetries are
first studied from the Newtonian perspective. The results are then illustrated
by specific examples such as C-metric, Bonnor-Swaminarayan solutions,
self-accelerating "dipole particles", and generalized boost-rotation symmetric
solutions describing freely falling particles in an external field. In contrast
to some previous discussions, our results are physically plausible in the sense
that the Newtonian limit corresponds to the fields of classical point masses
accelerated uniformly in classical mechanics. This corroborates the physical
significance of the boost-rotation symmetric spacetimes.
|
[
{
"created": "Mon, 26 Jan 2009 11:05:26 GMT",
"version": "v1"
}
] |
2009-01-27
|
[
[
"Bicak",
"Jiri",
""
],
[
"Kofron",
"David",
""
]
] |
Solutions of vacuum Einstein's field equations describing uniformly accelerated particles or black holes belong to the class of boost-rotation symmetric spacetimes. They are the only explicit solutions known which represent moving finite objects. Their Newtonian limit is analyzed using the Ehlers frame theory. Generic spacetimes with axial and boost symmetries are first studied from the Newtonian perspective. The results are then illustrated by specific examples such as C-metric, Bonnor-Swaminarayan solutions, self-accelerating "dipole particles", and generalized boost-rotation symmetric solutions describing freely falling particles in an external field. In contrast to some previous discussions, our results are physically plausible in the sense that the Newtonian limit corresponds to the fields of classical point masses accelerated uniformly in classical mechanics. This corroborates the physical significance of the boost-rotation symmetric spacetimes.
|
0806.4102
|
Valerio Bozza
|
V. Bozza
|
Optical caustics of Kerr spacetime: the full structure
|
20 pages, 21 figures
|
Phys.Rev.D78:063014,2008
|
10.1103/PhysRevD.78.063014
| null |
gr-qc astro-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We present an exhaustive numerical investigation of the optical caustics in
gravitational lensing by a spinning black hole for an observer at infinity.
Besides the primary caustic, we examine higher order caustics, formed by
photons performing one or several loops around the black hole. Our
investigation covers the whole parameter space, including the black hole spin,
its inclination with respect to the line of sight, the source distance, and the
caustic order. By comparing our results with the available analytical
approximations, we find perfect agreement in their respective domains of
validity. We then prove that all caustics maintain their shape (a tube with
astroidal cross-section) in the entire parameter space without suffering any
transitions to different caustic shapes. For nearly extremal spin, however,
higher order caustics grow so large that their cross-sections at fixed radii
wind several times around the black hole. As a consequence, for each caustic
order, the number of images ranges from 2 to 2(n+1), where n is the number of
loops spanned by the caustic. As for the critical curves, we note that for high
values of the spin they develop a small dip on the side corresponding to
prograde orbits.
|
[
{
"created": "Wed, 25 Jun 2008 14:07:10 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Oct 2008 16:48:01 GMT",
"version": "v2"
}
] |
2008-11-26
|
[
[
"Bozza",
"V.",
""
]
] |
We present an exhaustive numerical investigation of the optical caustics in gravitational lensing by a spinning black hole for an observer at infinity. Besides the primary caustic, we examine higher order caustics, formed by photons performing one or several loops around the black hole. Our investigation covers the whole parameter space, including the black hole spin, its inclination with respect to the line of sight, the source distance, and the caustic order. By comparing our results with the available analytical approximations, we find perfect agreement in their respective domains of validity. We then prove that all caustics maintain their shape (a tube with astroidal cross-section) in the entire parameter space without suffering any transitions to different caustic shapes. For nearly extremal spin, however, higher order caustics grow so large that their cross-sections at fixed radii wind several times around the black hole. As a consequence, for each caustic order, the number of images ranges from 2 to 2(n+1), where n is the number of loops spanned by the caustic. As for the critical curves, we note that for high values of the spin they develop a small dip on the side corresponding to prograde orbits.
|
gr-qc/0009022
|
Pavel Klepac
|
P. Klepac, J. Horsky
|
Cylindrically symmetric perfect-fluid universes
|
LaTeX, 9 pages
|
Class.Quant.Grav. 17 (2000) 2547
|
10.1088/0264-9381/17/13/308
| null |
gr-qc
| null |
The aim of this paper is to examine some obtained exact solutions of the
Einstein-Maxwell equations, especially their properties from a chronological
point of view. Each our spacetime is stationary cylindrically symmetric and it
is filled up with an perfect fluid that is electrically charged. There are two
classes of solutions and examples of each of them are investigated. We give
examples of the first class both for the vanishing as well as for the
non-vanishing Lorentz force.
|
[
{
"created": "Thu, 7 Sep 2000 16:45:11 GMT",
"version": "v1"
}
] |
2009-10-31
|
[
[
"Klepac",
"P.",
""
],
[
"Horsky",
"J.",
""
]
] |
The aim of this paper is to examine some obtained exact solutions of the Einstein-Maxwell equations, especially their properties from a chronological point of view. Each our spacetime is stationary cylindrically symmetric and it is filled up with an perfect fluid that is electrically charged. There are two classes of solutions and examples of each of them are investigated. We give examples of the first class both for the vanishing as well as for the non-vanishing Lorentz force.
|
gr-qc/9710033
|
Herbert Liebl
|
W. Kummer, H. Liebl (Vienna, Tech. U.), D.V. Vassilevich (St.
Petersburg University)
|
Exact Path Integral Quantization of 2-D Dilaton Gravity
|
3 pages, LaTeX, requires mprocl.sty available at
http://shemesh.fiz.huji.ac.il/MG8/submission.html , talk presented at the 8th
Marcel Grossmann conference (MG8)
| null | null | null |
gr-qc
| null |
We demonstrate that in the absence of `matter' fields to all orders of
perturbation theory and for all 2D dilaton theories the quantum effective
action coincides with the classical one. This resolves the apparent
contradiction between the well established results of Dirac quantization and
perturbative (path-integral) approaches which seemed to yield non-trivial
quantum corrections. For the Jackiw--Teitelboim (JT) model, our result is even
extended to the situation when a matter field is present.
|
[
{
"created": "Mon, 6 Oct 1997 14:55:07 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Kummer",
"W.",
"",
"Vienna, Tech. U."
],
[
"Liebl",
"H.",
"",
"Vienna, Tech. U."
],
[
"Vassilevich",
"D. V.",
"",
"St.\n Petersburg University"
]
] |
We demonstrate that in the absence of `matter' fields to all orders of perturbation theory and for all 2D dilaton theories the quantum effective action coincides with the classical one. This resolves the apparent contradiction between the well established results of Dirac quantization and perturbative (path-integral) approaches which seemed to yield non-trivial quantum corrections. For the Jackiw--Teitelboim (JT) model, our result is even extended to the situation when a matter field is present.
|
1604.08332
|
Jie-Xiong Mo
|
Jie-Xiong Mo, Gu-Qiang Li, Ze-Tao Lin and Xiao-Xiong Zeng
|
Revisiting van der Waals like behavior of f(R) AdS black holes via the
two point correlation function
|
Revised version. Match the published version. 14pages,5figures
|
Nuclear Physics B 918 (2017)11-22
|
10.1016/j.nuclphysb.2017.02.015
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Van der Waals like behavior of $f(R)$ AdS black holes is revisited via two
point correlation function, which is dual to the geodesic length in the bulk.
The equation of motion constrained by the boundary condition is solved
numerically and both the effect of boundary region size and $f(R)$ gravity are
probed. Moreover, an analogous specific heat related to $\delta L$ is
introduced. It is shown that the $T-\delta L$ graphs of $f(R)$ AdS black holes
exhibit reverse van der Waals like behavior just as the $T-S$ graphs do. Free
energy analysis is carried out to determine the first order phase transition
temperature $T_*$ and the unstable branch in $T-\delta L$ curve is removed by a
bar $T=T_*$. It is shown that the first order phase transition temperature is
the same at least to the order of $10^{-10}$ for different choices of the
parameter $b$ although the values of free energy vary with $b$. Our result
further supports the former finding that charged $f(R)$ AdS black holes behave
much like RN-AdS black holes. We also check the analogous equal area law
numerically and find that the relative errors for both the cases $\theta_0=0.1$
and $\theta_0=0.2$ are small enough. The fitting functions between $ \log\mid T
-T_c\mid$ and $\log\mid\delta L-\delta L_c\mid $ for both cases are also
obtained. It is shown that the slope is around 3, implying that the critical
exponent is about $2/3$. This result is in accordance with those in former
literatures of specific heat related to the thermal entropy or entanglement
entropy.
|
[
{
"created": "Thu, 28 Apr 2016 07:38:23 GMT",
"version": "v1"
},
{
"created": "Wed, 4 May 2016 02:41:24 GMT",
"version": "v2"
},
{
"created": "Thu, 9 Mar 2017 06:16:56 GMT",
"version": "v3"
}
] |
2017-03-10
|
[
[
"Mo",
"Jie-Xiong",
""
],
[
"Li",
"Gu-Qiang",
""
],
[
"Lin",
"Ze-Tao",
""
],
[
"Zeng",
"Xiao-Xiong",
""
]
] |
Van der Waals like behavior of $f(R)$ AdS black holes is revisited via two point correlation function, which is dual to the geodesic length in the bulk. The equation of motion constrained by the boundary condition is solved numerically and both the effect of boundary region size and $f(R)$ gravity are probed. Moreover, an analogous specific heat related to $\delta L$ is introduced. It is shown that the $T-\delta L$ graphs of $f(R)$ AdS black holes exhibit reverse van der Waals like behavior just as the $T-S$ graphs do. Free energy analysis is carried out to determine the first order phase transition temperature $T_*$ and the unstable branch in $T-\delta L$ curve is removed by a bar $T=T_*$. It is shown that the first order phase transition temperature is the same at least to the order of $10^{-10}$ for different choices of the parameter $b$ although the values of free energy vary with $b$. Our result further supports the former finding that charged $f(R)$ AdS black holes behave much like RN-AdS black holes. We also check the analogous equal area law numerically and find that the relative errors for both the cases $\theta_0=0.1$ and $\theta_0=0.2$ are small enough. The fitting functions between $ \log\mid T -T_c\mid$ and $\log\mid\delta L-\delta L_c\mid $ for both cases are also obtained. It is shown that the slope is around 3, implying that the critical exponent is about $2/3$. This result is in accordance with those in former literatures of specific heat related to the thermal entropy or entanglement entropy.
|
2312.02492
|
Gaurav Gadbail
|
Gaurav N. Gadbail, Avik De, P.K. Sahoo
|
Cosmological reconstruction and $\Lambda$CDM universe in $f(Q,C)$
gravity
|
EPJC published version
|
Eur. Phys. J. C 83,1099 (2023)
|
10.1140/epjc/s10052-023-12288-y
| null |
gr-qc hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
Symmetric Teleparallel Gravity allows for the reformulation of gravity in the
form of nonmetricity by vanishing the contorsion term in the generic affine
connection. Our focus is on investigating a recently proposed extension of this
theory in which the Lagrangian has the form $f(Q,C)$ by incorporating the
boundary term $C$. In this work, we first use a reconstruction approach in
$f(Q,C)$ gravity that might admit the $\Lambda$CDM expansion history.
Furthermore, we perform a novel approach for cosmological reconstruction of
$f(Q,C)$ gravity in terms of e-folding, and it shows how any FLRW cosmology can
arise from a specific $f(Q,C)$ gravity. A variety of instances are provided
using this approach in which $f(Q, C)$ gravity is reconstructed to yield the
well-known cosmic evolution: $\Lambda$CDM era, acceleration/deceleration era
which is equivalent to the presence of phantom and non-phantom matter,
late-time acceleration with the crossing of phantom-divide line and transient
phantom era.
|
[
{
"created": "Tue, 5 Dec 2023 04:49:01 GMT",
"version": "v1"
}
] |
2023-12-06
|
[
[
"Gadbail",
"Gaurav N.",
""
],
[
"De",
"Avik",
""
],
[
"Sahoo",
"P. K.",
""
]
] |
Symmetric Teleparallel Gravity allows for the reformulation of gravity in the form of nonmetricity by vanishing the contorsion term in the generic affine connection. Our focus is on investigating a recently proposed extension of this theory in which the Lagrangian has the form $f(Q,C)$ by incorporating the boundary term $C$. In this work, we first use a reconstruction approach in $f(Q,C)$ gravity that might admit the $\Lambda$CDM expansion history. Furthermore, we perform a novel approach for cosmological reconstruction of $f(Q,C)$ gravity in terms of e-folding, and it shows how any FLRW cosmology can arise from a specific $f(Q,C)$ gravity. A variety of instances are provided using this approach in which $f(Q, C)$ gravity is reconstructed to yield the well-known cosmic evolution: $\Lambda$CDM era, acceleration/deceleration era which is equivalent to the presence of phantom and non-phantom matter, late-time acceleration with the crossing of phantom-divide line and transient phantom era.
|
1503.06768
|
Stephen Appleby
|
Stephen Appleby
|
Self Tuning Scalar Fields in Spherically Symmetric Spacetimes
| null | null |
10.1088/1475-7516/2015/05/009
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We search for self tuning solutions to the Einstein-scalar field equations
for the simplest class of `Fab-Four' models with constant potentials. We first
review the conditions under which self tuning occurs in a cosmological
spacetime, and by introducing a small modification to the original theory -
introducing the second and third Galileon terms - show how one can obtain de
Sitter states where the expansion rate is independent of the vacuum energy. We
then consider whether the same self tuning mechanism can persist in a
spherically symmetric inhomogeneous spacetime. We show that there are no
asymptotically flat solutions to the field equations in which the vacuum energy
is screened, other than the trivial one (Minkowski space). We then consider the
possibility of constructing Schwarzschild de Sitter spacetimes for the modified
Fab Four plus Galileon theory. We argue that the only model that can
successfully screen the vacuum energy in both an FLRW and Schwarzschild de
Sitter spacetime is one containing `John' $\sim G^{\mu}{}_{\nu}
\partial_{\mu}\phi\partial^{\nu}\phi$ and a canonical kinetic term $\sim
\partial_{\alpha}\phi \partial^{\alpha}\phi$. This behaviour was first observed
in (Babichev&Charmousis,2013). The screening mechanism, which requires
redundancy of the scalar field equation in the `vacuum', fails for the `Paul'
term in an inhomogeneous spacetime.
|
[
{
"created": "Thu, 19 Mar 2015 03:10:36 GMT",
"version": "v1"
}
] |
2015-05-20
|
[
[
"Appleby",
"Stephen",
""
]
] |
We search for self tuning solutions to the Einstein-scalar field equations for the simplest class of `Fab-Four' models with constant potentials. We first review the conditions under which self tuning occurs in a cosmological spacetime, and by introducing a small modification to the original theory - introducing the second and third Galileon terms - show how one can obtain de Sitter states where the expansion rate is independent of the vacuum energy. We then consider whether the same self tuning mechanism can persist in a spherically symmetric inhomogeneous spacetime. We show that there are no asymptotically flat solutions to the field equations in which the vacuum energy is screened, other than the trivial one (Minkowski space). We then consider the possibility of constructing Schwarzschild de Sitter spacetimes for the modified Fab Four plus Galileon theory. We argue that the only model that can successfully screen the vacuum energy in both an FLRW and Schwarzschild de Sitter spacetime is one containing `John' $\sim G^{\mu}{}_{\nu} \partial_{\mu}\phi\partial^{\nu}\phi$ and a canonical kinetic term $\sim \partial_{\alpha}\phi \partial^{\alpha}\phi$. This behaviour was first observed in (Babichev&Charmousis,2013). The screening mechanism, which requires redundancy of the scalar field equation in the `vacuum', fails for the `Paul' term in an inhomogeneous spacetime.
|
gr-qc/9301022
|
Marco
|
M. Cavaglia' V. de Alfaro and F. de Felice
|
An Anisotropic Wormhole:TUNNELLING in Time and Space
|
PLAIN-TEX, 16 pages (4 figures not included), Report DFTT 2/93
|
Phys.Rev. D49 (1994) 6493-6499
|
10.1103/PhysRevD.49.6493
| null |
gr-qc
| null |
We discuss the structure of a gravitational euclidean instanton obtained
through coupling of gravity to electromagnetism. Its topology at fixed $t$ is
$S^1\times S^2$. This euclidean solution can be interpreted as a tunnelling to
a hyperbolic space (baby universe) at $t=0$ or alternatively as a static
wormhole that joins the two asymptotically flat spaces of a
Reissner--Nordstr\"om type solution with $M=0$.
|
[
{
"created": "Wed, 27 Jan 1993 17:12:57 GMT",
"version": "v1"
}
] |
2009-10-22
|
[
[
"de Alfaro",
"M. Cavaglia' V.",
""
],
[
"de Felice",
"F.",
""
]
] |
We discuss the structure of a gravitational euclidean instanton obtained through coupling of gravity to electromagnetism. Its topology at fixed $t$ is $S^1\times S^2$. This euclidean solution can be interpreted as a tunnelling to a hyperbolic space (baby universe) at $t=0$ or alternatively as a static wormhole that joins the two asymptotically flat spaces of a Reissner--Nordstr\"om type solution with $M=0$.
|
1502.03957
|
Vee-Liem Saw
|
Vee-Liem Saw
|
Constructing vacuum spacetimes by generating manifolds of revolution
around a curve
|
27 pages, 3 figures. v4: The vacuum solutions containing closed
timelike curves are discussed. Accepted by Classical and Quantum Gravity
|
Classical and Quantum Gravity, 33, 065006, 2016
|
10.1088/0264-9381/33/6/065006
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We develop a general perturbative analysis on vacuum spacetimes which can be
constructed by generating manifolds of revolution around a curve, and apply it
to the Schwarzschild metric. The following different perturbations are carried
out separately: 1) Non-rotating 2-spheres are added along a plane curve
slightly deviated from the ``Schwarzschild line''; 2) General non-rotating
topological 2-spheres are added along the ``Schwarzschild line'' 3)
Slow-rotating 2-spheres are added along the ``Schwarzschild line''. For (1), we
obtain the first order vacuum solution and show that no higher order solution
exists. This linearised vacuum solution turns out however to be just a gauge
transformation of the Schwarzschild metric. For (2), we solve the general
linearised vacuum equations under several special cases. In particular, there
exist linearised vacuum solutions with signature-changing metrics that contain
closed timelike curves (though these do not correspond to adding topological
2-spheres). For (3), we find that the first order vacuum solution is equivalent
to the slowly rotating Kerr metric. This is hence a much simpler and
geometrically insightful derivation as compared to the gravitomagnetic one,
where this rotating-shells construction is a direct manifestation of the
frame-dragging phenomenon. We also show that the full Kerr however, cannot be
obtained via adding rotating ellipsoids.
|
[
{
"created": "Fri, 13 Feb 2015 12:11:16 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Apr 2015 09:23:47 GMT",
"version": "v2"
},
{
"created": "Tue, 23 Jun 2015 08:16:38 GMT",
"version": "v3"
},
{
"created": "Wed, 25 Nov 2015 11:31:01 GMT",
"version": "v4"
}
] |
2016-02-25
|
[
[
"Saw",
"Vee-Liem",
""
]
] |
We develop a general perturbative analysis on vacuum spacetimes which can be constructed by generating manifolds of revolution around a curve, and apply it to the Schwarzschild metric. The following different perturbations are carried out separately: 1) Non-rotating 2-spheres are added along a plane curve slightly deviated from the ``Schwarzschild line''; 2) General non-rotating topological 2-spheres are added along the ``Schwarzschild line'' 3) Slow-rotating 2-spheres are added along the ``Schwarzschild line''. For (1), we obtain the first order vacuum solution and show that no higher order solution exists. This linearised vacuum solution turns out however to be just a gauge transformation of the Schwarzschild metric. For (2), we solve the general linearised vacuum equations under several special cases. In particular, there exist linearised vacuum solutions with signature-changing metrics that contain closed timelike curves (though these do not correspond to adding topological 2-spheres). For (3), we find that the first order vacuum solution is equivalent to the slowly rotating Kerr metric. This is hence a much simpler and geometrically insightful derivation as compared to the gravitomagnetic one, where this rotating-shells construction is a direct manifestation of the frame-dragging phenomenon. We also show that the full Kerr however, cannot be obtained via adding rotating ellipsoids.
|
1902.01504
|
Omar Gallegos
|
Omar Gallegos and Tonatiuh Matos
|
Weak gravitational quantum effects in boson particles
|
19 pages
|
General Relativity and Gravitation 53, 50 (2021)
|
10.1007/s10714-021-02810-6
| null |
gr-qc
|
http://creativecommons.org/publicdomain/zero/1.0/
|
We rewrite the Klein-Gordon (KG) equation in an arbitrary space-time
transforming it into a generalized Schr\"odinger equation. Then we take the
weak field limit and show that this equation has some differences with the
traditional Schr\"odinger equation plus a gravitational field. Thus, this
procedure shows that the Schr\"odinger equation derived in a covariant manner
is different from the traditional one. With this new Schr\"odinger equation, we
study the KG equation in a Newtonian space-time to describe the behavior of a
scalar particle in an inertial system. We give some examples where it is
possible to study the energy levels, effective potential and the wave function
of the systems, these results contain the gravitational effects due to the
curvature of space-time. We show that it is possible to verify experimentally
these effects in a laboratory using non-inertial reference frames.
|
[
{
"created": "Tue, 5 Feb 2019 00:48:30 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Jun 2019 05:32:54 GMT",
"version": "v2"
},
{
"created": "Thu, 7 May 2020 06:32:08 GMT",
"version": "v3"
},
{
"created": "Wed, 28 Apr 2021 00:43:12 GMT",
"version": "v4"
}
] |
2021-04-30
|
[
[
"Gallegos",
"Omar",
""
],
[
"Matos",
"Tonatiuh",
""
]
] |
We rewrite the Klein-Gordon (KG) equation in an arbitrary space-time transforming it into a generalized Schr\"odinger equation. Then we take the weak field limit and show that this equation has some differences with the traditional Schr\"odinger equation plus a gravitational field. Thus, this procedure shows that the Schr\"odinger equation derived in a covariant manner is different from the traditional one. With this new Schr\"odinger equation, we study the KG equation in a Newtonian space-time to describe the behavior of a scalar particle in an inertial system. We give some examples where it is possible to study the energy levels, effective potential and the wave function of the systems, these results contain the gravitational effects due to the curvature of space-time. We show that it is possible to verify experimentally these effects in a laboratory using non-inertial reference frames.
|
gr-qc/0306004
|
W. F. Kao
|
W.F. Kao and Chopin Soo
|
A note on 4-dimensional traversable wormholes and energy conditions in
higher dimensions
|
4 pages
| null | null | null |
gr-qc
| null |
We show explicitly that traversable wormholes requiring exotic matter in
4-dimensions nevertheless have acceptable stress-tensors obeying reasonable
energy conditions in higher dimensions if the wormholes are regarded as being
embedded in higher dimensional space-times satisfying Einstein's field
equations. From the 4-dimensional perspective, the existence of higher
dimensions may thus facilitate wormhole and time-machine constructions through
access to "exotic matter".
|
[
{
"created": "Mon, 2 Jun 2003 11:12:07 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Kao",
"W. F.",
""
],
[
"Soo",
"Chopin",
""
]
] |
We show explicitly that traversable wormholes requiring exotic matter in 4-dimensions nevertheless have acceptable stress-tensors obeying reasonable energy conditions in higher dimensions if the wormholes are regarded as being embedded in higher dimensional space-times satisfying Einstein's field equations. From the 4-dimensional perspective, the existence of higher dimensions may thus facilitate wormhole and time-machine constructions through access to "exotic matter".
|
1901.11268
|
Arkadiusz B{\l}aut
|
Arkadiusz B{\l}aut
|
Angular and frequency response of the gravitational wave interferometers
in the metric theories of gravity
|
18 pages, 10 figures
|
Physical Review D 85, 043005 (2012)
|
10.1103/PhysRevD.85.043005
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We analyze detector responses of gravitational wave detectors for
gravitational waves with arbitrary polarizations predicted in the metric
theories of gravity. We present the general formulas for the frequency
responses valid in various interferometric arrangements including Michelson,
Delay-Line and Fabry-Perot detectors. We analyze the angular and frequency
behavior and the sensitivity patterns of the responses for each polarization
mode.
|
[
{
"created": "Thu, 31 Jan 2019 08:42:47 GMT",
"version": "v1"
}
] |
2019-02-06
|
[
[
"Błaut",
"Arkadiusz",
""
]
] |
We analyze detector responses of gravitational wave detectors for gravitational waves with arbitrary polarizations predicted in the metric theories of gravity. We present the general formulas for the frequency responses valid in various interferometric arrangements including Michelson, Delay-Line and Fabry-Perot detectors. We analyze the angular and frequency behavior and the sensitivity patterns of the responses for each polarization mode.
|
gr-qc/0109025
|
Sergio M. C. V. Goncalves
|
Sergio M. C. V. Goncalves (Caltech)
|
Strong curvature singularities in quasispherical asymptotically de
Sitter dust collapse
|
16 pages, LaTeX, uses IOP package, 2 eps figures; accepted for
publication in Class. Quantum Grav
|
Class.Quant.Grav. 18 (2001) 4517-4530
|
10.1088/0264-9381/18/21/309
| null |
gr-qc
| null |
We study the occurrence, visibility, and curvature strength of singularities
in dust-containing Szekeres spacetimes (which possess no Killing vectors) with
a positive cosmological constant. We find that such singularities can be
locally naked, Tipler strong, and develop from a non-zero-measure set of
regular initial data. When examined along timelike geodesics, the singularity's
curvature strength is found to be independent of the initial data.
|
[
{
"created": "Thu, 6 Sep 2001 16:04:50 GMT",
"version": "v1"
}
] |
2009-11-07
|
[
[
"Goncalves",
"Sergio M. C. V.",
"",
"Caltech"
]
] |
We study the occurrence, visibility, and curvature strength of singularities in dust-containing Szekeres spacetimes (which possess no Killing vectors) with a positive cosmological constant. We find that such singularities can be locally naked, Tipler strong, and develop from a non-zero-measure set of regular initial data. When examined along timelike geodesics, the singularity's curvature strength is found to be independent of the initial data.
|
2403.02373
|
Beyhan Pulice
|
Beyhan Puli\c{c}e, Reggie C. Pantig, Ali \"Ovg\"un, Durmu\c{s} Demir
|
Asymptotically-Flat Black Hole Solutions in Symmergent Gravity
|
20 pages, 10 figures. Accepted for publication in Fortschritte der
Physik. Dedicated to Durmu\c{s} Demir (1967-2024), our supervisor, candid
friend, and guiding light. His unwavering supports always led our way
|
Fortsch.Phys.(2024)
|
10.1002/prop.202300138
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Symmergent gravity is an emergent gravity model with an $R+R^2$ curvature
sector and an extended particle sector having new particles beyond the known
ones. With constant scalar curvature, asymptotically flat black hole solutions
are known to have no sensitivity to the quadratic curvature term (coefficient
of $R^2$). With variable scalar curvature, however, asymptotically-flat
symmergent black hole solutions turn out to explicitly depend on the quadratic
curvature term. In the present work, we construct asymptotically-flat
symmergent black holes with variable scalar curvature and use its evaporation,
shadow, and deflection angle to constrain the symmergent gravity parameters.
Concerning their evaporation, we find that the new particles predicted by
symmergent gravity, even if they do not interact with the known particles, can
enhance the black hole evaporation rate. Concerning their shadow, we show that
statistically significant symmergent effects are reached at the $2\,\sigma$
level for the observational data of the Event Horizon Telescope (EHT) on the
Sagittarius A* supermassive black hole. Concerning their weak deflection angle,
we reveal discernible features for the boson-fermion number differences,
particularly at large impact parameters. These findings hold the potential to
serve as theoretical predictions for future observations and investigations on
black hole properties.
|
[
{
"created": "Mon, 4 Mar 2024 18:52:27 GMT",
"version": "v1"
}
] |
2024-03-06
|
[
[
"Puliçe",
"Beyhan",
""
],
[
"Pantig",
"Reggie C.",
""
],
[
"Övgün",
"Ali",
""
],
[
"Demir",
"Durmuş",
""
]
] |
Symmergent gravity is an emergent gravity model with an $R+R^2$ curvature sector and an extended particle sector having new particles beyond the known ones. With constant scalar curvature, asymptotically flat black hole solutions are known to have no sensitivity to the quadratic curvature term (coefficient of $R^2$). With variable scalar curvature, however, asymptotically-flat symmergent black hole solutions turn out to explicitly depend on the quadratic curvature term. In the present work, we construct asymptotically-flat symmergent black holes with variable scalar curvature and use its evaporation, shadow, and deflection angle to constrain the symmergent gravity parameters. Concerning their evaporation, we find that the new particles predicted by symmergent gravity, even if they do not interact with the known particles, can enhance the black hole evaporation rate. Concerning their shadow, we show that statistically significant symmergent effects are reached at the $2\,\sigma$ level for the observational data of the Event Horizon Telescope (EHT) on the Sagittarius A* supermassive black hole. Concerning their weak deflection angle, we reveal discernible features for the boson-fermion number differences, particularly at large impact parameters. These findings hold the potential to serve as theoretical predictions for future observations and investigations on black hole properties.
|
1605.00123
|
Caio Macedo
|
Caio F. B. Macedo, Lu\'is C. B. Crispino, Ednilton S. de Oliveira
|
Scalar waves in regular Bardeen black holes: Scattering, absorption and
quasinormal modes
|
To appear in a Special Issue of the IJMPD on Selected Papers of the
III Amazonian Symposium on Physics (Eds. C. Herdeiro, E. Berti, V. Cardoso,
L. C. Crispino, L. Gualtieri and U. Sperhake). 10 pages, 4 figures
| null |
10.1142/S021827181641008X
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We discuss the phenomenology of massless scalar fields around a regular
Bardeen black hole, namely absorption cross section, scattering cross section
and quasinormal modes. We compare the Bardeen and Reissner-Nordstr\"om black
holes, showing limiting cases for which their properties are similar.
|
[
{
"created": "Sat, 30 Apr 2016 15:22:09 GMT",
"version": "v1"
}
] |
2016-08-17
|
[
[
"Macedo",
"Caio F. B.",
""
],
[
"Crispino",
"Luís C. B.",
""
],
[
"de Oliveira",
"Ednilton S.",
""
]
] |
We discuss the phenomenology of massless scalar fields around a regular Bardeen black hole, namely absorption cross section, scattering cross section and quasinormal modes. We compare the Bardeen and Reissner-Nordstr\"om black holes, showing limiting cases for which their properties are similar.
|
1501.00486
|
Ujjal Debnath
|
Ujjal Debnath and Mubasher Jamil
|
Spherical Top-Hat Collapse of Viscous Modified Chaplygin Gas in
Einstein's Gravity and Loop Quantum Cosmology
|
7 pages, 14 figures. arXiv admin note: text overlap with
arXiv:1401.1270, arXiv:1110.6205 by other authors
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this work, we focus on the collapse of a spherically symmetric
perturbation, with a classical top-hat profile, to study the nonlinear
evolution of only viscous modified Chaplygin gas (VMCG) perturbations in
Einstein's gravity as well as in loop quantum Cosmology (LQC). In the perturbed
region, we have investigated the natures of equation of state parameter, square
speed of sound and another perturbed quantities. The results have been analyzed
by numerical and graphical investigations.
|
[
{
"created": "Sat, 3 Jan 2015 06:29:29 GMT",
"version": "v1"
}
] |
2015-01-06
|
[
[
"Debnath",
"Ujjal",
""
],
[
"Jamil",
"Mubasher",
""
]
] |
In this work, we focus on the collapse of a spherically symmetric perturbation, with a classical top-hat profile, to study the nonlinear evolution of only viscous modified Chaplygin gas (VMCG) perturbations in Einstein's gravity as well as in loop quantum Cosmology (LQC). In the perturbed region, we have investigated the natures of equation of state parameter, square speed of sound and another perturbed quantities. The results have been analyzed by numerical and graphical investigations.
|
1509.03267
|
Manuel Rodrigues
|
Ednaldo L. B. Junior and Manuel E. Rodrigues
|
Generalized Teleparallel Theory
|
15 pages. arXiv admin note: text overlap with arXiv:1503.07427,
arXiv:1503.07857
|
Eur. Phys. J. C (2016) 76:376
|
10.1140/epjc/s10052-016-4220-8
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We construct a theory in which the gravitational interaction is described
only by torsion, but that generalizes the Teleparallel Theory still keeping the
invariance of local Lorentz transformations in one particular case. We show
that our theory falls, to a certain limit of a real parameter, in the
$f(\bar{R})$ Gravity or, to another limit of the same real parameter, in a
modified $f(T)$ Gravity, interpolating between these two theories and still can
fall on several other theories. We explicitly show the equivalence with
$f(\bar{R})$ Gravity for cases of Friedmann-Lemaitre-Robertson-Walker flat
metric for diagonal tetrads, and a metric with spherical symmetry for diagonal
and non-diagonal tetrads. We do still four applications, one in the
reconstruction of the de Sitter universe cosmological model, for obtaining a
static spherically symmetric solution type-de Sitter for a perfect fluid, for
evolution of the state parameter $\omega_{DE}$ and for the thermodynamics to
the apparent horizon.
|
[
{
"created": "Fri, 4 Sep 2015 00:50:40 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Jul 2016 16:28:40 GMT",
"version": "v2"
}
] |
2016-07-07
|
[
[
"Junior",
"Ednaldo L. B.",
""
],
[
"Rodrigues",
"Manuel E.",
""
]
] |
We construct a theory in which the gravitational interaction is described only by torsion, but that generalizes the Teleparallel Theory still keeping the invariance of local Lorentz transformations in one particular case. We show that our theory falls, to a certain limit of a real parameter, in the $f(\bar{R})$ Gravity or, to another limit of the same real parameter, in a modified $f(T)$ Gravity, interpolating between these two theories and still can fall on several other theories. We explicitly show the equivalence with $f(\bar{R})$ Gravity for cases of Friedmann-Lemaitre-Robertson-Walker flat metric for diagonal tetrads, and a metric with spherical symmetry for diagonal and non-diagonal tetrads. We do still four applications, one in the reconstruction of the de Sitter universe cosmological model, for obtaining a static spherically symmetric solution type-de Sitter for a perfect fluid, for evolution of the state parameter $\omega_{DE}$ and for the thermodynamics to the apparent horizon.
|
1708.06255
|
Jorge Noronha
|
Fabio S. Bemfica (Rio Grande do Norte U.), Marcelo M. Disconzi
(Vanderbilt U.), Jorge Noronha (Sao Paulo U.)
|
Causality and existence of solutions of relativistic viscous fluid
dynamics with gravity
|
33 pages, 5 figures. Substantial improvements were made: the new
conformal tensor is now derived from kinetic theory; the causality and
well-posedness theorems now hold under more general conditions on the
transport coefficients; further discussion and applications have also been
included; new references were added
|
Phys. Rev. D 98, 104064 (2018)
|
10.1103/PhysRevD.98.104064
| null |
gr-qc hep-ph hep-th math-ph math.MP nucl-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A new approach is described to help improve the foundations of relativistic
viscous fluid dynamics and its coupling to general relativity. Focusing on
neutral conformal fluids constructed solely in terms of hydrodynamic variables,
we derive the most general viscous energy-momentum tensor yielding equations of
motion of second order in the derivatives, which is shown to provide a novel
type of generalization of the relativistic Navier-Stokes equations for which
causality holds. We show how this energy-momentum tensor may be derived from
conformal kinetic theory. We rigorously prove existence, uniqueness, and
causality of solutions of this theory (in the full nonlinear regime) both in a
Minkowski background and also when the fluid is dynamically coupled to
Einstein's equations. Linearized disturbances around equilibrium in Minkowski
spacetime are stable in this causal theory. A numerical study reveals the
presence of an out-of-equilibrium hydrodynamic attractor for a rapidly
expanding fluid. Further properties are also studied and a brief discussion of
how this approach can be generalized to non-conformal fluids is presented.
|
[
{
"created": "Fri, 18 Aug 2017 16:54:29 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Aug 2018 07:43:26 GMT",
"version": "v2"
}
] |
2018-12-05
|
[
[
"Bemfica",
"Fabio S.",
"",
"Rio Grande do Norte U."
],
[
"Disconzi",
"Marcelo M.",
"",
"Vanderbilt U."
],
[
"Noronha",
"Jorge",
"",
"Sao Paulo U."
]
] |
A new approach is described to help improve the foundations of relativistic viscous fluid dynamics and its coupling to general relativity. Focusing on neutral conformal fluids constructed solely in terms of hydrodynamic variables, we derive the most general viscous energy-momentum tensor yielding equations of motion of second order in the derivatives, which is shown to provide a novel type of generalization of the relativistic Navier-Stokes equations for which causality holds. We show how this energy-momentum tensor may be derived from conformal kinetic theory. We rigorously prove existence, uniqueness, and causality of solutions of this theory (in the full nonlinear regime) both in a Minkowski background and also when the fluid is dynamically coupled to Einstein's equations. Linearized disturbances around equilibrium in Minkowski spacetime are stable in this causal theory. A numerical study reveals the presence of an out-of-equilibrium hydrodynamic attractor for a rapidly expanding fluid. Further properties are also studied and a brief discussion of how this approach can be generalized to non-conformal fluids is presented.
|
gr-qc/0508051
|
Eugen Radu
|
Eugen Radu
|
On a Petrov-type D homogeneous solution
|
20 pages, TeX file
|
Int.J.Mod.Phys. A21 (2006) 4355-4372
|
10.1142/S0217751X06032484
| null |
gr-qc
| null |
We present a new two-parameter family of solutions of Einstein gravity with
negative cosmological constant in 2+1 dimensions. These solutions are obtained
by squashing the anti-de Sitter geometry along one direction and posses four
Killing vectors. Global properties as well as the four dimensional
generalization are discussed, followed by the investigation of the geodesic
motion. A simple global embedding of these spaces as the intersection of four
quadratic surfaces in a seven dimensional space is obtained. We argue also that
these geometries describe the boundary of a four dimensional nutty-bubble
solution and are relevant in the context of AdS/CFT correspondence.
|
[
{
"created": "Fri, 12 Aug 2005 09:05:37 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Aug 2005 15:30:54 GMT",
"version": "v2"
}
] |
2009-11-11
|
[
[
"Radu",
"Eugen",
""
]
] |
We present a new two-parameter family of solutions of Einstein gravity with negative cosmological constant in 2+1 dimensions. These solutions are obtained by squashing the anti-de Sitter geometry along one direction and posses four Killing vectors. Global properties as well as the four dimensional generalization are discussed, followed by the investigation of the geodesic motion. A simple global embedding of these spaces as the intersection of four quadratic surfaces in a seven dimensional space is obtained. We argue also that these geometries describe the boundary of a four dimensional nutty-bubble solution and are relevant in the context of AdS/CFT correspondence.
|
1011.2595
|
Zou De Cheng
|
Decheng Zou, Ruihong Yue and Zhanying Yang
|
Thermodynamics of third order Lovelock anti-de Sitter black holes
revisited
|
15 pages, 22 figures
|
Commun.Theor.Phys.55:449-456,2011
|
10.1088/0253-6102/55/3/16
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We compute the mass and the temperature of third order Lovelock black holes
with negative Gauss-Bonnet coefficient $\alpha_2<0$ in anti-de Sitter space and
perform the stability analysis of topological black holes. When $k=-1$, the
third order Lovelock black holes are thermodynamically stable for the whole
range $r_+$. When $k=1$, we found that the black hole has an intermediate
unstable phase for $D=7$. In eight dimensional spacetimes, however, a new phase
of thermodynamically unstable small black holes appears if the coefficient
$\tilde{\alpha}$ is under a critical value. For $D\geq 9$, black holes have
similar the distributions of thermodynamically stable regions to the case where
the coefficient $\tilde{\alpha}$ is under a critical value for $D=8$. It is
worth to mention that all the thermodynamic and conserved quantities of the
black holes with flat horizon don't depend on the Lovelock coefficients and are
the same as those of black holes in general gravity.
|
[
{
"created": "Thu, 11 Nov 2010 08:56:16 GMT",
"version": "v1"
}
] |
2011-05-18
|
[
[
"Zou",
"Decheng",
""
],
[
"Yue",
"Ruihong",
""
],
[
"Yang",
"Zhanying",
""
]
] |
We compute the mass and the temperature of third order Lovelock black holes with negative Gauss-Bonnet coefficient $\alpha_2<0$ in anti-de Sitter space and perform the stability analysis of topological black holes. When $k=-1$, the third order Lovelock black holes are thermodynamically stable for the whole range $r_+$. When $k=1$, we found that the black hole has an intermediate unstable phase for $D=7$. In eight dimensional spacetimes, however, a new phase of thermodynamically unstable small black holes appears if the coefficient $\tilde{\alpha}$ is under a critical value. For $D\geq 9$, black holes have similar the distributions of thermodynamically stable regions to the case where the coefficient $\tilde{\alpha}$ is under a critical value for $D=8$. It is worth to mention that all the thermodynamic and conserved quantities of the black holes with flat horizon don't depend on the Lovelock coefficients and are the same as those of black holes in general gravity.
|
1407.2350
|
Leo Stein
|
Leo C. Stein
|
Rapidly rotating black holes in dynamical Chern-Simons gravity:
Decoupling limit solutions and breakdown
|
8 pages, 4 figures; matches version appearing in PRD
|
Phys. Rev. D 90, 044061 (2014)
|
10.1103/PhysRevD.90.044061
| null |
gr-qc astro-ph.HE hep-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Rapidly rotating black holes are a prime arena for understanding corrections
to Einstein's theory of general relativity (GR). We construct solutions for
rapidly rotating black holes in dynamical Chern-Simons (dCS) gravity, a useful
and motivated example of a post-GR correction. We treat dCS as an effective
theory and thus work in the decoupling limit, where we apply a perturbation
scheme using the Kerr metric as the background solution. Using the solutions to
the scalar field and the trace of the metric perturbation, we determine the
regime of validity of our perturbative approach. We find that the maximal spin
limit may be divergent, and the decoupling limit is strongly restricted for
rapid rotation. Rapidly-rotating stellar-mass BHs can potentially be used to
place strong bounds on the coupling parameter $\ell$ of dCS. In order for the
black hole observed in GRO J1655-40 to be within the decoupling limit we need
$\ell \lesssim 22$ km, a value 7 orders of magnitude smaller than present Solar
System bounds on dynamical Chern-Simons gravity.
|
[
{
"created": "Wed, 9 Jul 2014 04:41:53 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Aug 2014 14:54:28 GMT",
"version": "v2"
}
] |
2014-08-25
|
[
[
"Stein",
"Leo C.",
""
]
] |
Rapidly rotating black holes are a prime arena for understanding corrections to Einstein's theory of general relativity (GR). We construct solutions for rapidly rotating black holes in dynamical Chern-Simons (dCS) gravity, a useful and motivated example of a post-GR correction. We treat dCS as an effective theory and thus work in the decoupling limit, where we apply a perturbation scheme using the Kerr metric as the background solution. Using the solutions to the scalar field and the trace of the metric perturbation, we determine the regime of validity of our perturbative approach. We find that the maximal spin limit may be divergent, and the decoupling limit is strongly restricted for rapid rotation. Rapidly-rotating stellar-mass BHs can potentially be used to place strong bounds on the coupling parameter $\ell$ of dCS. In order for the black hole observed in GRO J1655-40 to be within the decoupling limit we need $\ell \lesssim 22$ km, a value 7 orders of magnitude smaller than present Solar System bounds on dynamical Chern-Simons gravity.
|
2111.12858
|
Xi-Long Fan
|
Xi-Long Fan
|
Tests of interaction of gravitational waves with detectors
|
5 pages, 2 figure
| null | null | null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The various materials of test masses, and the difference of arm lengths of
global ground-based gravitational-wave interferometer detectors offer a unique
approach to test Newton's second law, weak equivalence principle, and Einstein
equivalence principle with dynamical space-time effects in terms of the
interaction of gravitational waves with detectors. We proposed a novel test
strategy for the interaction between gravitational waves and detectors, which
is independent of particular gravitation theory. A new population level of the
Fisher-Matrix approach for multiple sources and multiple detectors case is
formalized to evaluate the prospects for a binary neutron star and binary black
hole coalescences. Through a generalized detector response, we found more
sources could break the parameter degeneracy and one could constrain the
interaction and gravitational-inertial mass ratio parameters with the standard
deviation $\ls 1\%$ with about 10 compact binary coalescence sources with
future third-generation detectors network.
|
[
{
"created": "Thu, 25 Nov 2021 00:53:44 GMT",
"version": "v1"
}
] |
2021-11-29
|
[
[
"Fan",
"Xi-Long",
""
]
] |
The various materials of test masses, and the difference of arm lengths of global ground-based gravitational-wave interferometer detectors offer a unique approach to test Newton's second law, weak equivalence principle, and Einstein equivalence principle with dynamical space-time effects in terms of the interaction of gravitational waves with detectors. We proposed a novel test strategy for the interaction between gravitational waves and detectors, which is independent of particular gravitation theory. A new population level of the Fisher-Matrix approach for multiple sources and multiple detectors case is formalized to evaluate the prospects for a binary neutron star and binary black hole coalescences. Through a generalized detector response, we found more sources could break the parameter degeneracy and one could constrain the interaction and gravitational-inertial mass ratio parameters with the standard deviation $\ls 1\%$ with about 10 compact binary coalescence sources with future third-generation detectors network.
|
gr-qc/0201086
|
Ulrich Sperhake
|
Ulrich Sperhake
|
Non-linear numerical Schemes in General Relativity
|
217 pages, 65 figures, PhD thesis, University of Southampton
| null | null | null |
gr-qc
| null |
This thesis describes the application of numerical techniques to solve
Einstein's field equations in three distinct cases. First we present the first
long-term stable second order convergent Cauchy characteristic matching code in
cylindrical symmetry including both gravitational degrees of freedom. Compared
with previous work we achieve a substantial simplification of the evolution
equations as well as the relations at the interface by factoring out the
z-Killing direction via the Geroch decomposition in both the Cauchy and the
characteristic region. In the second part we numerically solve the equations
for static and dynamic cosmic strings of infinite length coupled to gravity and
provide the first fully non-linear evolutions of cosmic strings in curved
spacetimes. The inclusion of null infinity as part of the numerical grid allows
us to apply suitable boundary conditions on the metric and the matter fields to
suppress unphysical divergent solutions. The code is used to study the
interaction between a Weber-Wheeler pulse of gravitational radiation with an
initially static string. In the final part of the thesis we probe a new
numerical approach for highly accurate evolutions of non-linear neutron star
oscillations in the case of radial oscillations of spherically symmetric stars.
For this purpose we view the evolution of the physical quantities as deviations
from a static equilibrium configuration and reformulate the equations in a
fully non-linear perturbative form. The high accuracy of the new scheme enables
us to study the non-linear coupling of eigenmodes over a wide range of initial
amplitudes.
|
[
{
"created": "Fri, 25 Jan 2002 20:16:18 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Sperhake",
"Ulrich",
""
]
] |
This thesis describes the application of numerical techniques to solve Einstein's field equations in three distinct cases. First we present the first long-term stable second order convergent Cauchy characteristic matching code in cylindrical symmetry including both gravitational degrees of freedom. Compared with previous work we achieve a substantial simplification of the evolution equations as well as the relations at the interface by factoring out the z-Killing direction via the Geroch decomposition in both the Cauchy and the characteristic region. In the second part we numerically solve the equations for static and dynamic cosmic strings of infinite length coupled to gravity and provide the first fully non-linear evolutions of cosmic strings in curved spacetimes. The inclusion of null infinity as part of the numerical grid allows us to apply suitable boundary conditions on the metric and the matter fields to suppress unphysical divergent solutions. The code is used to study the interaction between a Weber-Wheeler pulse of gravitational radiation with an initially static string. In the final part of the thesis we probe a new numerical approach for highly accurate evolutions of non-linear neutron star oscillations in the case of radial oscillations of spherically symmetric stars. For this purpose we view the evolution of the physical quantities as deviations from a static equilibrium configuration and reformulate the equations in a fully non-linear perturbative form. The high accuracy of the new scheme enables us to study the non-linear coupling of eigenmodes over a wide range of initial amplitudes.
|
1008.3261
|
Vladimir Dzhunushaliev
|
Vladimir Dzhunushaliev
|
Stochastic Einstein equations
|
5 pages
|
IJGMMP, Vol. 8, No. 6 (2011) 1189-1195
|
10.1142/S0219887811005671
| null |
gr-qc hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Stochastic Einstein equations are considered when 3D space metric
$\gamma_{ij}$ are stochastic functions. The probability density for the
stochastic quantities is connected with the Perelman's entropy functional. As
an example, the Friedman Universe is considered. It is shown that for the
Friedman Universe the dynamical evolution is not changed. The connection
between general relativity and Ricci flows is discussed.
|
[
{
"created": "Thu, 19 Aug 2010 10:18:27 GMT",
"version": "v1"
}
] |
2015-05-19
|
[
[
"Dzhunushaliev",
"Vladimir",
""
]
] |
Stochastic Einstein equations are considered when 3D space metric $\gamma_{ij}$ are stochastic functions. The probability density for the stochastic quantities is connected with the Perelman's entropy functional. As an example, the Friedman Universe is considered. It is shown that for the Friedman Universe the dynamical evolution is not changed. The connection between general relativity and Ricci flows is discussed.
|
2010.06645
|
Jungjoon Leo Kim
|
J. Leo Kim, Ghazal Geshnizjani
|
Spectrum of Cuscuton Bounce
|
Version matches JCAP publication
|
JCAP03(2021)104
|
10.1088/1475-7516/2021/03/104
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
It has been recently shown that a cosmological bounce model based on Cuscuton
gravity does not have any ghosts or curvature instabilities. We explore whether
Cuscuton bounce can provide an alternative to inflation for generating near
scale-invariant scalar perturbations. While a single field Cuscuton bounce
generically produces a strongly blue power spectrum (for a variety of
initial/boundary conditions), we demonstrate that scale invariant entropy modes
can be generated in a spectator field that starts in adiabatic vacuum, and is
kinetically coupled to the primary field. Furthermore, our solution has no
singularity, nor requires an ad hoc matching condition. We also study the
generation of tensor modes (or gravitational waves) in Cuscuton bounce and show
that while they are stable, similar to other bounce models, the produced
spectrum is strongly blue and unobservable.
|
[
{
"created": "Tue, 13 Oct 2020 19:27:14 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Apr 2021 18:15:00 GMT",
"version": "v2"
}
] |
2021-04-19
|
[
[
"Kim",
"J. Leo",
""
],
[
"Geshnizjani",
"Ghazal",
""
]
] |
It has been recently shown that a cosmological bounce model based on Cuscuton gravity does not have any ghosts or curvature instabilities. We explore whether Cuscuton bounce can provide an alternative to inflation for generating near scale-invariant scalar perturbations. While a single field Cuscuton bounce generically produces a strongly blue power spectrum (for a variety of initial/boundary conditions), we demonstrate that scale invariant entropy modes can be generated in a spectator field that starts in adiabatic vacuum, and is kinetically coupled to the primary field. Furthermore, our solution has no singularity, nor requires an ad hoc matching condition. We also study the generation of tensor modes (or gravitational waves) in Cuscuton bounce and show that while they are stable, similar to other bounce models, the produced spectrum is strongly blue and unobservable.
|
2305.07444
|
Kajol Paithankar
|
Kajol Paithankar and Sanved Kolekar
|
Black hole shadow and acceleration bounds for spherically symmetric
spacetimes
|
27 pages, no figures, new section added, Accepted for publication in
PRD
| null | null | null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We explore an interesting connection between black hole shadow parameters and
the acceleration bounds for radial linear uniformly accelerated (LUA)
trajectories in static spherically symmetric black hole spacetime geometries of
the Schwarzschild type. For an incoming radial LUA trajectory to escape back to
infinity, there exists a bound on its magnitude of acceleration and the
distance of closest approach from the event horizon of the black hole. We
calculate these bounds and the shadow parameters, namely the photon sphere
radius and the shadow radius, explicitly for specific black hole solutions in
$d$-dimensional Einstein's theory of gravity, in pure Lovelock theory of
gravity and in the $\mathcal{F}(R)$ theory of gravity. We find that for a
particular boundary data, the photon sphere radius $r_{ph}$ is equal to the
bound on radius of closest approach $r_b$ of the incoming radial LUA trajectory
while the shadow radius $r_{sh}$ is equal to the inverse magnitude of the
acceleration bound $|a|_b$ for the LUA trajectory to turn back to infinity.
Using the effective potential technique, we further show that the same
relations are valid in any theory of gravity for static spherically symmetric
black hole geometries of the Schwarzschild type. Investigating the trajectories
in a more general class of static spherically symmetric black hole spacetimes,
we find that the two relations are valid separately for two different choices
of boundary data.
|
[
{
"created": "Fri, 12 May 2023 13:03:59 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Nov 2023 10:04:58 GMT",
"version": "v2"
}
] |
2023-11-06
|
[
[
"Paithankar",
"Kajol",
""
],
[
"Kolekar",
"Sanved",
""
]
] |
We explore an interesting connection between black hole shadow parameters and the acceleration bounds for radial linear uniformly accelerated (LUA) trajectories in static spherically symmetric black hole spacetime geometries of the Schwarzschild type. For an incoming radial LUA trajectory to escape back to infinity, there exists a bound on its magnitude of acceleration and the distance of closest approach from the event horizon of the black hole. We calculate these bounds and the shadow parameters, namely the photon sphere radius and the shadow radius, explicitly for specific black hole solutions in $d$-dimensional Einstein's theory of gravity, in pure Lovelock theory of gravity and in the $\mathcal{F}(R)$ theory of gravity. We find that for a particular boundary data, the photon sphere radius $r_{ph}$ is equal to the bound on radius of closest approach $r_b$ of the incoming radial LUA trajectory while the shadow radius $r_{sh}$ is equal to the inverse magnitude of the acceleration bound $|a|_b$ for the LUA trajectory to turn back to infinity. Using the effective potential technique, we further show that the same relations are valid in any theory of gravity for static spherically symmetric black hole geometries of the Schwarzschild type. Investigating the trajectories in a more general class of static spherically symmetric black hole spacetimes, we find that the two relations are valid separately for two different choices of boundary data.
|
gr-qc/0006097
|
Sayan Kar
|
Sayan Kar, Parthasarathi Majumdar, Soumitra Sengupta, Aninda Sinha
|
Does a Kalb-Ramond field make spacetime optically active
|
Revised version with several additions and deletions
|
Eur.Phys.J.C23:357-361,2002
|
10.1007/s100520100872
| null |
gr-qc hep-th
| null |
A spacetime with torsion produced by a Kalb-Ramond field coupled
gravitationally to the Maxwell field, in accordance with a recent proposal by
two of us (PM and SS), is argued to lead to an optical activity in synchrotron
radiation from cosmologically distant radio sources. We suggest that this could
qualitatively explain observational data from a large number of radio sources
displaying such polarization asymmetry (after eliminating effects of Faraday
rotation due to magnetized galactic plasma). Possible implications for
heterotic string theory are also outlined.
|
[
{
"created": "Wed, 28 Jun 2000 10:16:08 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Sep 2000 09:57:01 GMT",
"version": "v2"
}
] |
2011-09-13
|
[
[
"Kar",
"Sayan",
""
],
[
"Majumdar",
"Parthasarathi",
""
],
[
"Sengupta",
"Soumitra",
""
],
[
"Sinha",
"Aninda",
""
]
] |
A spacetime with torsion produced by a Kalb-Ramond field coupled gravitationally to the Maxwell field, in accordance with a recent proposal by two of us (PM and SS), is argued to lead to an optical activity in synchrotron radiation from cosmologically distant radio sources. We suggest that this could qualitatively explain observational data from a large number of radio sources displaying such polarization asymmetry (after eliminating effects of Faraday rotation due to magnetized galactic plasma). Possible implications for heterotic string theory are also outlined.
|
1508.06755
|
Gary Gibbons
|
G. W. Gibbons
|
The Jacobi-metric for timelike geodesics in static spacetimes
|
one reference added
| null |
10.1088/0264-9381/33/2/025004
| null |
gr-qc hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
It is shown that the free motion of massive particles moving in static
spacetimes are given by the geodesics of an energy-dependent Riemannian metric
on the spatial sections analogous to Jacobi's metric in classical dynamics. In
the massless limit Jacobi's metric coincides with the energy independent Fermat
or optical metric. For stationary metrics, it is known that the motion of
massless particles is given by the geodesics of an energy independent
Finslerian metric of Randers type. The motion of massive particles is governed
by neither a Riemannian nor a Finslerian metric. The properies of the Jacobi
metric for massive particles moving outside the horizon of a Schwarschild black
hole are described. By constrast with the massless case, the Gaussian curvature
of the equatorial sections is not always negative.
|
[
{
"created": "Thu, 27 Aug 2015 08:55:56 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Sep 2015 07:35:51 GMT",
"version": "v2"
}
] |
2016-01-13
|
[
[
"Gibbons",
"G. W.",
""
]
] |
It is shown that the free motion of massive particles moving in static spacetimes are given by the geodesics of an energy-dependent Riemannian metric on the spatial sections analogous to Jacobi's metric in classical dynamics. In the massless limit Jacobi's metric coincides with the energy independent Fermat or optical metric. For stationary metrics, it is known that the motion of massless particles is given by the geodesics of an energy independent Finslerian metric of Randers type. The motion of massive particles is governed by neither a Riemannian nor a Finslerian metric. The properies of the Jacobi metric for massive particles moving outside the horizon of a Schwarschild black hole are described. By constrast with the massless case, the Gaussian curvature of the equatorial sections is not always negative.
|
1905.08043
|
Sumanta Chakraborty
|
Indrani Banerjee, Sumanta Chakraborty and Soumitra SenGupta
|
Decoding signatures of extra dimensions and estimating spin of quasars
from the continuum spectrum
|
References Updated, Published Version, 32 pages, 4 figures, 1 Table
|
Phys. Rev. D 100, 044045 (2019)
|
10.1103/PhysRevD.100.044045
| null |
gr-qc astro-ph.HE hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Continuum spectrum emitted by the accretion disk around quasars hold a wealth
of information regarding the strong gravitational field produced by the massive
central object. Such strong gravity regime is often expected to exhibit
deviations from general relativity (GR) which may manifest through the presence
of extra dimensions. Higher dimensions, which serve as the corner stone for
string theory and M-theory can act as promising alternatives to dark matter and
dark energy with interesting implications in inflationary cosmology,
gravitational waves and collider physics. Therefore it is instructive to
investigate the effect of more than four spacetime dimensions on the black hole
continuum spectrum which provide an effective astrophysical probe to the strong
gravity regime. To explore such a scenario, we compute the optical luminosity
emitted by a thin accretion disk around a rotating supermassive black hole
albeit in the presence of extra dimensions. The background metric resembles the
Kerr-Newman spacetime in GR where the tidal charge parameter inherited from
extra dimensions can also assume negative signature. The theoretical luminosity
computed in such a background is contrasted with optical observations of eighty
quasars. The difference between the theoretical and observed luminosity for
these quasars is used to infer the most favoured choice of the rotation
parameter for each quasar and the tidal charge parameter. This has been
achieved by minimizing/maximizing several error estimators, e.g., chi-squared,
Nash-Sutcliffe efficiency, index of agreement etc. Intriguingly, all of them
favour a negative value for the tidal charge parameter, a characteristic
signature of extra dimensions. Thus accretion disk does provide a significant
possibility of exploring the existence of extra dimensions through its close
correspondence with the strong gravity regime.
|
[
{
"created": "Mon, 20 May 2019 12:35:24 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Aug 2019 04:51:54 GMT",
"version": "v2"
}
] |
2019-08-30
|
[
[
"Banerjee",
"Indrani",
""
],
[
"Chakraborty",
"Sumanta",
""
],
[
"SenGupta",
"Soumitra",
""
]
] |
Continuum spectrum emitted by the accretion disk around quasars hold a wealth of information regarding the strong gravitational field produced by the massive central object. Such strong gravity regime is often expected to exhibit deviations from general relativity (GR) which may manifest through the presence of extra dimensions. Higher dimensions, which serve as the corner stone for string theory and M-theory can act as promising alternatives to dark matter and dark energy with interesting implications in inflationary cosmology, gravitational waves and collider physics. Therefore it is instructive to investigate the effect of more than four spacetime dimensions on the black hole continuum spectrum which provide an effective astrophysical probe to the strong gravity regime. To explore such a scenario, we compute the optical luminosity emitted by a thin accretion disk around a rotating supermassive black hole albeit in the presence of extra dimensions. The background metric resembles the Kerr-Newman spacetime in GR where the tidal charge parameter inherited from extra dimensions can also assume negative signature. The theoretical luminosity computed in such a background is contrasted with optical observations of eighty quasars. The difference between the theoretical and observed luminosity for these quasars is used to infer the most favoured choice of the rotation parameter for each quasar and the tidal charge parameter. This has been achieved by minimizing/maximizing several error estimators, e.g., chi-squared, Nash-Sutcliffe efficiency, index of agreement etc. Intriguingly, all of them favour a negative value for the tidal charge parameter, a characteristic signature of extra dimensions. Thus accretion disk does provide a significant possibility of exploring the existence of extra dimensions through its close correspondence with the strong gravity regime.
|
2111.09457
|
Vasilis Oikonomou
|
S. Nojiri, S.D. Odintsov, V.K. Oikonomou, Arkady A. Popov
|
Ghost-free $F\left( R,\mathcal{G} \right)$ Gravity
|
NPB Accepted
| null | null | null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this work we shall address the ghost issue of $F\left( R,\mathcal{G}
\right)$ gravity, which is known to be plagued with ghost degrees of freedom.
These ghosts occur due to the presence of higher than two derivatives in the
field equations, and can arise even when considering cosmological
perturbations, where superluminal modes may arise in the theory. If we consider
the quantum theory, the ghosts generate the negative norm states, which give
the negative probabilities, and therefore the ghosts are physically
inconsistent. Motivated by the importance of $F\left( R,\mathcal{G} \right)$
gravity for providing viable inflationary and dark energy phenomenologies, in
this work we shall provide a technique that can render $F\left( R,\mathcal{G}
\right)$ gravity theories free from ghost degrees of freedom. This will be done
by introducing two auxiliary scalar fields, and by employing the Lagrange
multiplier technique, the theory is ghost free in the Einstein frame. Also the
framework can be viewed as a reconstruction technique and can be used as a
method in order to realize several cosmological evolutions of interest. We
demonstrate how we can realize several cosmologically interesting
phenomenologies by using the reconstruction technique.
|
[
{
"created": "Thu, 18 Nov 2021 00:22:08 GMT",
"version": "v1"
}
] |
2021-11-19
|
[
[
"Nojiri",
"S.",
""
],
[
"Odintsov",
"S. D.",
""
],
[
"Oikonomou",
"V. K.",
""
],
[
"Popov",
"Arkady A.",
""
]
] |
In this work we shall address the ghost issue of $F\left( R,\mathcal{G} \right)$ gravity, which is known to be plagued with ghost degrees of freedom. These ghosts occur due to the presence of higher than two derivatives in the field equations, and can arise even when considering cosmological perturbations, where superluminal modes may arise in the theory. If we consider the quantum theory, the ghosts generate the negative norm states, which give the negative probabilities, and therefore the ghosts are physically inconsistent. Motivated by the importance of $F\left( R,\mathcal{G} \right)$ gravity for providing viable inflationary and dark energy phenomenologies, in this work we shall provide a technique that can render $F\left( R,\mathcal{G} \right)$ gravity theories free from ghost degrees of freedom. This will be done by introducing two auxiliary scalar fields, and by employing the Lagrange multiplier technique, the theory is ghost free in the Einstein frame. Also the framework can be viewed as a reconstruction technique and can be used as a method in order to realize several cosmological evolutions of interest. We demonstrate how we can realize several cosmologically interesting phenomenologies by using the reconstruction technique.
|
1303.1705
|
Alikram Aliev
|
Alikram N. Aliev and Goksel Daylan Esmer
|
Hidden Symmetries and Geodesics of Kerr spacetime in Kaluza-Klein Theory
|
25 pages, 5 figures; REVTeX
| null |
10.1103/PhysRevD.87.084022
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The Kerr spacetime in Kaluza-Klein theory describes a rotating black hole in
four dimensions from the Kaluza-Klein point of view and involves the signature
of an extra dimension that shows up through the appearance of the electric and
dilaton charges. In this paper, we study the separability properties of the
Hamilton-Jacobi equation for geodesics and the associated hidden symmetries in
the spacetime of the Kerr-Kaluza-Klein black hole. We show that the complete
separation of variables occurs only for massless geodesics, implying the
existence of hidden symmetries generated by a second rank conformal Killing
tensor. Employing a simple procedure built up on an "effective" metric, which
is conformally related to the original spacetime metric and admits a complete
separability structure, we construct the explicit expression for the conformal
Killing tensor. Next, we study the properties of the geodesic motion in the
equatorial plane, focusing on the cases of static and rotating Kaluza-Klein
black holes separately. In both cases, we obtain the defining equations for the
boundaries of the regions of existence, boundedness and stability of the
circular orbits as well as the analytical formulas for the orbital frequency,
the radial and vertical epicyclic frequencies of the geodesic motion.
Performing a detailed numerical analysis of these equations and frequencies, we
show that the physical effect of the extra dimension amounts to the significant
enlarging of the regions of existence, boundedness and stability towards the
event horizon, regardless of the classes of orbits.
|
[
{
"created": "Thu, 7 Mar 2013 14:48:14 GMT",
"version": "v1"
}
] |
2015-06-15
|
[
[
"Aliev",
"Alikram N.",
""
],
[
"Esmer",
"Goksel Daylan",
""
]
] |
The Kerr spacetime in Kaluza-Klein theory describes a rotating black hole in four dimensions from the Kaluza-Klein point of view and involves the signature of an extra dimension that shows up through the appearance of the electric and dilaton charges. In this paper, we study the separability properties of the Hamilton-Jacobi equation for geodesics and the associated hidden symmetries in the spacetime of the Kerr-Kaluza-Klein black hole. We show that the complete separation of variables occurs only for massless geodesics, implying the existence of hidden symmetries generated by a second rank conformal Killing tensor. Employing a simple procedure built up on an "effective" metric, which is conformally related to the original spacetime metric and admits a complete separability structure, we construct the explicit expression for the conformal Killing tensor. Next, we study the properties of the geodesic motion in the equatorial plane, focusing on the cases of static and rotating Kaluza-Klein black holes separately. In both cases, we obtain the defining equations for the boundaries of the regions of existence, boundedness and stability of the circular orbits as well as the analytical formulas for the orbital frequency, the radial and vertical epicyclic frequencies of the geodesic motion. Performing a detailed numerical analysis of these equations and frequencies, we show that the physical effect of the extra dimension amounts to the significant enlarging of the regions of existence, boundedness and stability towards the event horizon, regardless of the classes of orbits.
|
gr-qc/0605006
|
Joseph Henson
|
Luca Bombelli, Joe Henson and Rafael D. Sorkin
|
Discreteness without symmetry breaking: a theorem
|
7 pages, laTeX
|
Mod.Phys.Lett.A24:2579-2587,2009
|
10.1142/S0217732309031958
| null |
gr-qc
| null |
This paper concerns sprinklings into Minkowski space (Poisson processes). It
proves that there exists no equivariant measurable map from sprinklings to
spacetime directions (even locally). Therefore, if a discrete structure is
associated to a sprinkling in an intrinsic manner, then the structure will not
pick out a preferred frame, locally or globally. This implies that the
discreteness of a sprinkled causal set will not give rise to ``Lorentz
breaking'' effects like modified dispersion relations. Another consequence is
that there is no way to associate a finite-valency graph to a sprinkling
consistently with Lorentz invariance.
|
[
{
"created": "Mon, 1 May 2006 09:48:36 GMT",
"version": "v1"
}
] |
2009-11-09
|
[
[
"Bombelli",
"Luca",
""
],
[
"Henson",
"Joe",
""
],
[
"Sorkin",
"Rafael D.",
""
]
] |
This paper concerns sprinklings into Minkowski space (Poisson processes). It proves that there exists no equivariant measurable map from sprinklings to spacetime directions (even locally). Therefore, if a discrete structure is associated to a sprinkling in an intrinsic manner, then the structure will not pick out a preferred frame, locally or globally. This implies that the discreteness of a sprinkled causal set will not give rise to ``Lorentz breaking'' effects like modified dispersion relations. Another consequence is that there is no way to associate a finite-valency graph to a sprinkling consistently with Lorentz invariance.
|
1806.10526
|
Marcus Khuri
|
Edward T. Bryden, Marcus A. Khuri, Benjamin D. Sokolowsky
|
The Positive Mass Theorem with Angular Momentum and Charge for Manifolds
with Boundary
| null |
J. Math. Phys., 60 (2019), no. 5, 052501, 10 pp
|
10.1063/1.5070080
| null |
gr-qc math-ph math.DG math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Motivated by the cosmic censorship conjecture in mathematical relativity, we
establish the precise mass lower bound for an asymptotically flat Riemannian
3-manifold with nonnegative scalar curvature and minimal surface boundary, in
terms of angular momentum and charge. In particular this result does not
require the restrictive assumptions of simple connectivity and completeness,
which are undesirable from both a mathematical and physical perspective.
|
[
{
"created": "Wed, 27 Jun 2018 15:15:15 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Jan 2021 04:35:36 GMT",
"version": "v2"
}
] |
2021-01-26
|
[
[
"Bryden",
"Edward T.",
""
],
[
"Khuri",
"Marcus A.",
""
],
[
"Sokolowsky",
"Benjamin D.",
""
]
] |
Motivated by the cosmic censorship conjecture in mathematical relativity, we establish the precise mass lower bound for an asymptotically flat Riemannian 3-manifold with nonnegative scalar curvature and minimal surface boundary, in terms of angular momentum and charge. In particular this result does not require the restrictive assumptions of simple connectivity and completeness, which are undesirable from both a mathematical and physical perspective.
|
2104.04442
|
Nan Jiang
|
Nan Jiang and Kent Yagi
|
Probing modified gravitational-wave propagation through tidal
measurements of binary neutron star mergers
|
14 pages, 12 figures
|
Phys. Rev. D 103, 124047 (2021)
|
10.1103/PhysRevD.103.124047
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
Gravitational-wave sources can serve as standard sirens to probe cosmology by
measuring their luminosity distance and redshift. Such standard sirens are also
useful to probe theories beyond general relativity with a modified
gravitational-wave propagation. Many of previous studies on the latter assume
multi-messenger observations so that the luminosity distance can be measured
with gravitational waves while the redshift is obtained by identifying sources'
host galaxies from electromagnetic counterparts. Given that gravitational-wave
events of binary neutron star coalescences with associated electromagnetic
counterpart detections are expected to be rather rare, it is important to
examine the possibility of using standard sirens with gravitational-wave
observations alone to probe gravity. In this paper, we achieve this by
extracting the redshift from the tidal measurement of binary neutron stars that
was originally proposed within the context of gravitational-wave cosmology
(another approach is to correlate "dark sirens" with galaxy catalogs that we do
not consider here). We consider not only observations with ground-based
detectors (e.g. Einstein Telescope) but also multi-band observations between
ground-based and space-based (e.g. DECIGO) interferometers. We find that such
multi-band observations with the tidal information can constrain a parametric
non-Einsteinian deviation in the luminosity distance (due to the modified
friction in the gravitational wave evolution) more stringently than the case
with electromagnetic counterparts by a factor of a few. We also map the
above-projected constraints on the parametric deviation to those on specific
theories and phenomenological models beyond general relativity to put the
former into context.
|
[
{
"created": "Fri, 9 Apr 2021 15:43:22 GMT",
"version": "v1"
}
] |
2021-06-30
|
[
[
"Jiang",
"Nan",
""
],
[
"Yagi",
"Kent",
""
]
] |
Gravitational-wave sources can serve as standard sirens to probe cosmology by measuring their luminosity distance and redshift. Such standard sirens are also useful to probe theories beyond general relativity with a modified gravitational-wave propagation. Many of previous studies on the latter assume multi-messenger observations so that the luminosity distance can be measured with gravitational waves while the redshift is obtained by identifying sources' host galaxies from electromagnetic counterparts. Given that gravitational-wave events of binary neutron star coalescences with associated electromagnetic counterpart detections are expected to be rather rare, it is important to examine the possibility of using standard sirens with gravitational-wave observations alone to probe gravity. In this paper, we achieve this by extracting the redshift from the tidal measurement of binary neutron stars that was originally proposed within the context of gravitational-wave cosmology (another approach is to correlate "dark sirens" with galaxy catalogs that we do not consider here). We consider not only observations with ground-based detectors (e.g. Einstein Telescope) but also multi-band observations between ground-based and space-based (e.g. DECIGO) interferometers. We find that such multi-band observations with the tidal information can constrain a parametric non-Einsteinian deviation in the luminosity distance (due to the modified friction in the gravitational wave evolution) more stringently than the case with electromagnetic counterparts by a factor of a few. We also map the above-projected constraints on the parametric deviation to those on specific theories and phenomenological models beyond general relativity to put the former into context.
|
0706.0260
|
Gamal Nashed G.L.
|
Gamal Gergess Lamee Nashed
|
Charged Axially Symmetric Solution and Energy in Teleparallel Theory
Equivalent to General Relativity
|
15 pages, Latex
|
Eur.Phys.J.C49:851-857,2007
|
10.1140/epjc/s10052-006-0154-x
| null |
gr-qc
| null |
An exact charged solution with axial symmetry is obtained in the teleparallel
equivalent of general relativity (TEGR). The associated metric has the
structure function $G(\xi)=1-{\xi}^2-2mA{\xi}^3-q^2A^2{\xi}^4$. The fourth
order nature of the structure function can make calculations cumbersome. Using
a coordinate transformation we get a tetrad whose metric has the structure
function in a factorisable form $(1-{\xi}^2)(1+r_{+}A\xi)(1+r_{-}A\xi)$ with
$r_{\pm}$ as the horizons of Reissner-Nordstr$\ddot{o}$m space-time. This new
form has the advantage that its roots are now trivial to write down. Then, we
study the singularities of this space-time. Using another coordinate
transformation, we obtain a tetrad field. Its associated metric yields the
Reissner-Nordstr$\ddot{o}$m black hole. In Calculating the energy content of
this tetrad field using the gravitational energy-momentum, we find that the
resulting form depends on the radial coordinate! Using the regularized
expression of the gravitational energy-momentum in the teleparallel equivalent
of general relativity we get a consistent value for the energy.
|
[
{
"created": "Sat, 2 Jun 2007 09:57:08 GMT",
"version": "v1"
}
] |
2008-11-26
|
[
[
"Nashed",
"Gamal Gergess Lamee",
""
]
] |
An exact charged solution with axial symmetry is obtained in the teleparallel equivalent of general relativity (TEGR). The associated metric has the structure function $G(\xi)=1-{\xi}^2-2mA{\xi}^3-q^2A^2{\xi}^4$. The fourth order nature of the structure function can make calculations cumbersome. Using a coordinate transformation we get a tetrad whose metric has the structure function in a factorisable form $(1-{\xi}^2)(1+r_{+}A\xi)(1+r_{-}A\xi)$ with $r_{\pm}$ as the horizons of Reissner-Nordstr$\ddot{o}$m space-time. This new form has the advantage that its roots are now trivial to write down. Then, we study the singularities of this space-time. Using another coordinate transformation, we obtain a tetrad field. Its associated metric yields the Reissner-Nordstr$\ddot{o}$m black hole. In Calculating the energy content of this tetrad field using the gravitational energy-momentum, we find that the resulting form depends on the radial coordinate! Using the regularized expression of the gravitational energy-momentum in the teleparallel equivalent of general relativity we get a consistent value for the energy.
|
gr-qc/0006074
|
Hagen Kleinert
|
Hagen Kleinert, Hans-J\"urgen Schmidt
|
Cosmology with Curvature-Saturated Gravitational Lagrangian R/\sqrt{1 +
l^4 R^2}
|
Author Information under
http://www.physik.fu-berlin.de/~kleinert/institution.html . Latest update of
paper (including all PS fonts) at
http://www.physik.fu-berlin.de/~kleinert/kleiner_re311/preprint.html
|
Gen.Rel.Grav. 34 (2002) 1295-1318
| null | null |
gr-qc
| null |
We argue that the Lagrangian for gravity should remain bounded at large
curvature, and interpolate between the weak-field tested Einstein-Hilbert
Lagrangian L_EH = R /16 pi G and a pure cosmological constant for large R with
the curvature-saturated ansatz L_cs=L_EH/ \sqrt{1+l^4 R^2}, where l is a length
parameter expected to be a few orders of magnitude above the Planck length. The
curvature-dependent effective gravitational constant defined by dL/dR = 1/16 pi
G_eff is G_eff = G \sqrt{1+l^4 R^2}^{3}, and tends to infinity for large $R$,
in contrast to most other approaches where G_eff-> 0. The theory possesses
neither ghosts nor tachyons. In a curvature-saturated cosmology, the
coordinates with ds^2 = a^2 [da^2/B(a) - dx^2 - dy^2- dz^2] are most convenient
since the curvature scalar becomes a linear function of $B(a)$. Solutions with
a big-bang singularity have a much milder behavior of the curvature than in
Einstein's theory. In synchronized time, the metric is given by ds^2 = dt^2 -
t^{6/5(dx^2 + dy^2+ dz^2). On the technical side we show that two different
conformal transformations make L_cs asymptotically equivalent to the
Gurovich-ansatz L= | R |^{4/3} on the one hand, and to Einstein's theory with a
minimally coupled scalar field with self-interaction on the other.
|
[
{
"created": "Wed, 21 Jun 2000 06:25:18 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Sep 2000 06:57:16 GMT",
"version": "v2"
}
] |
2007-05-23
|
[
[
"Kleinert",
"Hagen",
""
],
[
"Schmidt",
"Hans-Jürgen",
""
]
] |
We argue that the Lagrangian for gravity should remain bounded at large curvature, and interpolate between the weak-field tested Einstein-Hilbert Lagrangian L_EH = R /16 pi G and a pure cosmological constant for large R with the curvature-saturated ansatz L_cs=L_EH/ \sqrt{1+l^4 R^2}, where l is a length parameter expected to be a few orders of magnitude above the Planck length. The curvature-dependent effective gravitational constant defined by dL/dR = 1/16 pi G_eff is G_eff = G \sqrt{1+l^4 R^2}^{3}, and tends to infinity for large $R$, in contrast to most other approaches where G_eff-> 0. The theory possesses neither ghosts nor tachyons. In a curvature-saturated cosmology, the coordinates with ds^2 = a^2 [da^2/B(a) - dx^2 - dy^2- dz^2] are most convenient since the curvature scalar becomes a linear function of $B(a)$. Solutions with a big-bang singularity have a much milder behavior of the curvature than in Einstein's theory. In synchronized time, the metric is given by ds^2 = dt^2 - t^{6/5(dx^2 + dy^2+ dz^2). On the technical side we show that two different conformal transformations make L_cs asymptotically equivalent to the Gurovich-ansatz L= | R |^{4/3} on the one hand, and to Einstein's theory with a minimally coupled scalar field with self-interaction on the other.
|
gr-qc/0406003
|
Olivier Sarbach
|
Horst Beyer and Olivier Sarbach
|
On the well posedness of the Baumgarte-Shapiro-Shibata-Nakamura
formulation of Einstein's field equations
| null |
Phys.Rev.D70:104004,2004
|
10.1103/PhysRevD.70.104004
| null |
gr-qc
| null |
We give a well posed initial value formulation of the
Baumgarte-Shapiro-Shibata-Nakamura form of Einstein's equations with gauge
conditions given by a Bona-Masso like slicing condition for the lapse and a
frozen shift. This is achieved by introducing extra variables and recasting the
evolution equations into a first order symmetric hyperbolic system. We also
consider the presence of artificial boundaries and derive a set of boundary
conditions that guarantee that the resulting initial-boundary value problem is
well posed, though not necessarily compatible with the constraints. In the case
of dynamical gauge conditions for the lapse and shift we obtain a class of
evolution equations which are strongly hyperbolic and so yield well posed
initial value formulations.
|
[
{
"created": "Tue, 1 Jun 2004 19:39:45 GMT",
"version": "v1"
}
] |
2009-01-09
|
[
[
"Beyer",
"Horst",
""
],
[
"Sarbach",
"Olivier",
""
]
] |
We give a well posed initial value formulation of the Baumgarte-Shapiro-Shibata-Nakamura form of Einstein's equations with gauge conditions given by a Bona-Masso like slicing condition for the lapse and a frozen shift. This is achieved by introducing extra variables and recasting the evolution equations into a first order symmetric hyperbolic system. We also consider the presence of artificial boundaries and derive a set of boundary conditions that guarantee that the resulting initial-boundary value problem is well posed, though not necessarily compatible with the constraints. In the case of dynamical gauge conditions for the lapse and shift we obtain a class of evolution equations which are strongly hyperbolic and so yield well posed initial value formulations.
|
gr-qc/9410038
|
Bronnikov Kirill Alexandrovich
|
K.A.Bronnikov and V.N.Melnikov
|
Vacuum Weyl Cosmologies in D Dimensions
|
6 pages, LaTeX
| null | null |
RGS-CSVR-013/94
|
gr-qc
| null |
Vacuum cosmological models are considered in the context of a
multidimensional theory of gravity with integrable Weyl geometry. A family of
exact solutions with a chain of internal spaces is obtained. Models with one
internal space are considered in more detail; nonsingular models are selected.
|
[
{
"created": "Tue, 25 Oct 1994 12:51:03 GMT",
"version": "v1"
}
] |
2016-08-31
|
[
[
"Bronnikov",
"K. A.",
""
],
[
"Melnikov",
"V. N.",
""
]
] |
Vacuum cosmological models are considered in the context of a multidimensional theory of gravity with integrable Weyl geometry. A family of exact solutions with a chain of internal spaces is obtained. Models with one internal space are considered in more detail; nonsingular models are selected.
|
2306.17296
|
Hossein Ghaffarnejad
|
Hossein Ghaffarnejad and Elham Ghasemi
|
Thermodynamic phase transition of modified Anti-de Sitter
Reissner-Nordstr\"{o}m black holes with generalized gauge invariant
Einstein-Maxwell gravity
|
44 pages, 1 table and 4 figure
| null | null | null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We generalize the Einstein Maxwell gravity by an additional term which is
made by contraction of the Ricci tensor and the electromagnetic antisymmetric
Maxwell tensor field, to study thermodynamic of a modified
Reissner-Nordstr\"{o}m (RN) black hole. Our motivation in use of this exotic
form of the gravity theory instead of the ordinary EM gravity is based on
influence of cosmic magnetic field throughout the spacetime as inevitable
effect at duration of cosmic inflation. While in ordinary models of
inflationary cosmology the dark energy sector is just considered. Dynamical
field equations are nonlinear and so they have not exact analytic solutions in
general form. On the other side to find equation of state of a back hole by
horizon equation we need an analytic form of the metric field solutions. Hence
we use dynamical system approach to obtain analytic metric solutions near the
critical points of secular equation of the corresponding Jacobi matrix. we
investigated stabilization situations of the obtained metric fields and finding
equations of state of modified RN AdS black hole, the Hawking temperature and
possibility of phase transitions.
|
[
{
"created": "Thu, 22 Jun 2023 13:02:35 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jan 2024 12:50:35 GMT",
"version": "v2"
}
] |
2024-01-24
|
[
[
"Ghaffarnejad",
"Hossein",
""
],
[
"Ghasemi",
"Elham",
""
]
] |
We generalize the Einstein Maxwell gravity by an additional term which is made by contraction of the Ricci tensor and the electromagnetic antisymmetric Maxwell tensor field, to study thermodynamic of a modified Reissner-Nordstr\"{o}m (RN) black hole. Our motivation in use of this exotic form of the gravity theory instead of the ordinary EM gravity is based on influence of cosmic magnetic field throughout the spacetime as inevitable effect at duration of cosmic inflation. While in ordinary models of inflationary cosmology the dark energy sector is just considered. Dynamical field equations are nonlinear and so they have not exact analytic solutions in general form. On the other side to find equation of state of a back hole by horizon equation we need an analytic form of the metric field solutions. Hence we use dynamical system approach to obtain analytic metric solutions near the critical points of secular equation of the corresponding Jacobi matrix. we investigated stabilization situations of the obtained metric fields and finding equations of state of modified RN AdS black hole, the Hawking temperature and possibility of phase transitions.
|
2106.10291
|
Antoine Klein
|
Antoine Klein
|
EFPE: Efficient fully precessing eccentric gravitational waveforms for
binaries with long inspirals
|
18 pages, 3 tables, 4 figures
| null | null | null |
gr-qc astro-ph.HE
|
http://creativecommons.org/licenses/by/4.0/
|
In this paper, we derive a set of equations of motions for binaries on
eccentric orbits undergoing spin-induced precession that can efficiently be
integrated on the radiation-reaction timescale. We find a family of solutions
with a computation cost improved by a factor $10$ - $50$ down to $\sim 10$ ms
per waveform evaluation compared to waveforms obtained by directly integrating
the precession equations, that maintain a mismatch of the order $10^{-4}$ -
$10^{-6}$ for waveforms lasting a million orbital cycles and a thousand
spin-induced precession cycles. We express it in terms of parameters that make
the solution regular in the equal-mass limit, thus bypassing a problem of
previous similar solutions. We point to ways in which the solution presented in
this paper can be perturbed to take into account effects such as general
quadrupole momenta and post-Newtonian corrections to the precession equations.
This new waveform, with its improved efficiency and its accuracy, makes
possible Bayesian parameter estimation using the full spin and eccentricity
parameter volume for long lasting inspiralling signals such as stellar-origin
black hole binaries observed by LISA.
|
[
{
"created": "Fri, 18 Jun 2021 18:00:04 GMT",
"version": "v1"
}
] |
2021-06-22
|
[
[
"Klein",
"Antoine",
""
]
] |
In this paper, we derive a set of equations of motions for binaries on eccentric orbits undergoing spin-induced precession that can efficiently be integrated on the radiation-reaction timescale. We find a family of solutions with a computation cost improved by a factor $10$ - $50$ down to $\sim 10$ ms per waveform evaluation compared to waveforms obtained by directly integrating the precession equations, that maintain a mismatch of the order $10^{-4}$ - $10^{-6}$ for waveforms lasting a million orbital cycles and a thousand spin-induced precession cycles. We express it in terms of parameters that make the solution regular in the equal-mass limit, thus bypassing a problem of previous similar solutions. We point to ways in which the solution presented in this paper can be perturbed to take into account effects such as general quadrupole momenta and post-Newtonian corrections to the precession equations. This new waveform, with its improved efficiency and its accuracy, makes possible Bayesian parameter estimation using the full spin and eccentricity parameter volume for long lasting inspiralling signals such as stellar-origin black hole binaries observed by LISA.
|
1708.00166
|
Zhoujian Cao Dr
|
Zhoujian Cao and Wen-Biao Han
|
A waveform model for eccentric binary black hole based on
effective-one-body-numerical-relativity (EOBNR) formalism
| null |
PRD 96, 044028 (2017)
|
10.1103/PhysRevD.96.044028
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Binary black hole systems are among the most important sources for
gravitational wave detection. And also they are good objects for theoretical
research for general relativity. Gravitational waveform template is important
to data analysis. Effective-one-body-numerical-relativity (EOBNR) model has
played an essential role in the LIGO data analysis. For future space-based
gravitational wave detection, many binary systems will admit somewhat orbit
eccentricity. At the same time the eccentric binary is also an interesting
topic for theoretical study in general relativity. In this paper we construct
the first eccentric binary waveform model based on
effective-one-body-numerical-relativity framework. Our basic assumption in the
model construction is that the involved eccentricity is small. We have compared
our eccentric EOBNR model to the circular one used in LIGO data analysis. We
have also tested our eccentric EOBNR model against to another recently proposed
eccentric binary waveform model; against to numerical relativity simulation
results; and against to perturbation approximation results for extreme mass
ratio binary systems. Compared to numerical relativity simulations with
eccentricity as large as about 0.2, the overlap factor for our eccentric EOBNR
model is better than 0.98 for all tested cases including spinless binary and
spinning binary; equal mass binary and unequal mass binary. Hopefully our
eccentric model can be the start point to develop a faithful template for
future space-based gravitational wave detectors.
|
[
{
"created": "Tue, 1 Aug 2017 05:23:50 GMT",
"version": "v1"
}
] |
2017-08-30
|
[
[
"Cao",
"Zhoujian",
""
],
[
"Han",
"Wen-Biao",
""
]
] |
Binary black hole systems are among the most important sources for gravitational wave detection. And also they are good objects for theoretical research for general relativity. Gravitational waveform template is important to data analysis. Effective-one-body-numerical-relativity (EOBNR) model has played an essential role in the LIGO data analysis. For future space-based gravitational wave detection, many binary systems will admit somewhat orbit eccentricity. At the same time the eccentric binary is also an interesting topic for theoretical study in general relativity. In this paper we construct the first eccentric binary waveform model based on effective-one-body-numerical-relativity framework. Our basic assumption in the model construction is that the involved eccentricity is small. We have compared our eccentric EOBNR model to the circular one used in LIGO data analysis. We have also tested our eccentric EOBNR model against to another recently proposed eccentric binary waveform model; against to numerical relativity simulation results; and against to perturbation approximation results for extreme mass ratio binary systems. Compared to numerical relativity simulations with eccentricity as large as about 0.2, the overlap factor for our eccentric EOBNR model is better than 0.98 for all tested cases including spinless binary and spinning binary; equal mass binary and unequal mass binary. Hopefully our eccentric model can be the start point to develop a faithful template for future space-based gravitational wave detectors.
|
1306.2549
|
Eva Hackmann
|
Alberto Garc\'ia, Eva Hackmann, Jutta Kunz, Claus L\"ammerzahl,
Alfredo Mac\'ias
|
Motion of test particles in a regular black hole space--time
|
23 pages, 10 Figures; revised to match published version
|
J.Math.Phys. 56, 032501 (2015)
|
10.1063/1.4913882
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider the motion of test particles in the regular black hole space-time
given by Ay\'{o}n-Beato and Garc\'{\i}a in Phys. Rev. Lett. 80:5056 (1998). The
complete set of orbits for neutral and weakly charged test particles is
discussed, including for neutral particles the extreme and over-extreme metric.
We also derive the analytical solutions for the equation of motion of neutral
test particles in a parametric form and consider a post-Schwarzschild expansion
of the periastron shift to second order in the charge.
|
[
{
"created": "Tue, 11 Jun 2013 15:16:12 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Jul 2013 08:32:27 GMT",
"version": "v2"
},
{
"created": "Fri, 8 Nov 2013 16:50:53 GMT",
"version": "v3"
},
{
"created": "Wed, 27 May 2015 09:39:51 GMT",
"version": "v4"
}
] |
2015-05-28
|
[
[
"García",
"Alberto",
""
],
[
"Hackmann",
"Eva",
""
],
[
"Kunz",
"Jutta",
""
],
[
"Lämmerzahl",
"Claus",
""
],
[
"Macías",
"Alfredo",
""
]
] |
We consider the motion of test particles in the regular black hole space-time given by Ay\'{o}n-Beato and Garc\'{\i}a in Phys. Rev. Lett. 80:5056 (1998). The complete set of orbits for neutral and weakly charged test particles is discussed, including for neutral particles the extreme and over-extreme metric. We also derive the analytical solutions for the equation of motion of neutral test particles in a parametric form and consider a post-Schwarzschild expansion of the periastron shift to second order in the charge.
|
1201.2588
|
Francesco Cianfrani dr
|
Francesco Cianfrani, Andrea Marchini and Giovanni Montani
|
The picture of the Bianchi I model via gauge fixing in Loop Quantum
Gravity
|
6 pages
|
Europhys. Lett., 99, 10003(2012)
|
10.1209/0295-5075/99/10003
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The implications of the SU(2) gauge fixing associated with the choice of
invariant triads in Loop Quantum Cosmology are discussed for a Bianchi I model.
In particular, via the analysis of Dirac brackets, it is outlined how the
holonomy-flux algebra coincides with the one of Loop Quantum Gravity if paths
are parallel to fiducial vectors only. This way the quantization procedure for
the Bianchi I model is performed by applying the techniques developed in Loop
Quantum Gravity but restricting the admissible paths. Furthermore, the local
character retained by the reduced variables provides a relic diffeomorphisms
constraint, whose imposition implies homogeneity on a quantum level. The
resulting picture for the fundamental spatial manifold is that of a cubical
knot with attached SU(2) irreducible representations. The discretization of
geometric operators is outlined and a new perspective for the super-Hamiltonian
regularization in Loop Quantum Cosmology is proposed.
|
[
{
"created": "Thu, 12 Jan 2012 15:22:23 GMT",
"version": "v1"
}
] |
2015-06-03
|
[
[
"Cianfrani",
"Francesco",
""
],
[
"Marchini",
"Andrea",
""
],
[
"Montani",
"Giovanni",
""
]
] |
The implications of the SU(2) gauge fixing associated with the choice of invariant triads in Loop Quantum Cosmology are discussed for a Bianchi I model. In particular, via the analysis of Dirac brackets, it is outlined how the holonomy-flux algebra coincides with the one of Loop Quantum Gravity if paths are parallel to fiducial vectors only. This way the quantization procedure for the Bianchi I model is performed by applying the techniques developed in Loop Quantum Gravity but restricting the admissible paths. Furthermore, the local character retained by the reduced variables provides a relic diffeomorphisms constraint, whose imposition implies homogeneity on a quantum level. The resulting picture for the fundamental spatial manifold is that of a cubical knot with attached SU(2) irreducible representations. The discretization of geometric operators is outlined and a new perspective for the super-Hamiltonian regularization in Loop Quantum Cosmology is proposed.
|
1509.02740
|
Valentin Kuzmichev
|
V. E. Kuzmichev, V. V. Kuzmichev (Bogolyubov Institute for Theoretical
Physics)
|
Comparative description of the evolving universe in classical and
quantum geometrodynamics
|
17 pages, v.2: Sect. 2 and 6 are revised, v.3: Sect. 2 is
supplemented, new references are added
| null | null | null |
gr-qc astro-ph.CO quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The description of the universe evolving in time according to general
relativity is given in comparison with the quantum description of the same
universe in terms of semiclassical wave functions. The spacetime geometry is
determined by the Robertson-Walker metric. It is shown that the main equation
of the quantum geometrodynamics is reduced to the non-linear Hamilton-Jacobi
equation. Its non-linearity is caused by a new source of the gravitational
field, which has a purely quantum dynamical nature, and is additional to
ordinary matter sources. In the semiclassical approximation, the non-linear
equation of motion is linearized and reduces to the Friedmann equation with the
additional quantum source of gravity (or anti-gravity) in the form of the stiff
Zel'dovich matter. The semiclassical wave functions of the universe, in which
different types of matter-energies dominate, are obtained. As examples, the
cases of the domination of radiation, barotropic fluid, or new quantum
matter-energy are discussed. The probability of the transition from the quantum
state, where radiation dominates into the state, in which barotropic fluid in
the form of dust is dominant, is calculated. This probability has the same
order of magnitude as the matter density contrast in the era of
matter-radiation equality.
|
[
{
"created": "Wed, 9 Sep 2015 12:05:49 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Oct 2015 09:48:14 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Dec 2015 15:29:38 GMT",
"version": "v3"
}
] |
2015-12-09
|
[
[
"Kuzmichev",
"V. E.",
"",
"Bogolyubov Institute for Theoretical\n Physics"
],
[
"Kuzmichev",
"V. V.",
"",
"Bogolyubov Institute for Theoretical\n Physics"
]
] |
The description of the universe evolving in time according to general relativity is given in comparison with the quantum description of the same universe in terms of semiclassical wave functions. The spacetime geometry is determined by the Robertson-Walker metric. It is shown that the main equation of the quantum geometrodynamics is reduced to the non-linear Hamilton-Jacobi equation. Its non-linearity is caused by a new source of the gravitational field, which has a purely quantum dynamical nature, and is additional to ordinary matter sources. In the semiclassical approximation, the non-linear equation of motion is linearized and reduces to the Friedmann equation with the additional quantum source of gravity (or anti-gravity) in the form of the stiff Zel'dovich matter. The semiclassical wave functions of the universe, in which different types of matter-energies dominate, are obtained. As examples, the cases of the domination of radiation, barotropic fluid, or new quantum matter-energy are discussed. The probability of the transition from the quantum state, where radiation dominates into the state, in which barotropic fluid in the form of dust is dominant, is calculated. This probability has the same order of magnitude as the matter density contrast in the era of matter-radiation equality.
|
gr-qc/0304069
|
Bahram Mashhoon
|
John C. Hauck and Bahram Mashhoon
|
Electromagnetic Waves in a Rotating Frame of Reference
|
LaTeX file, 2 PS figures, 18 pages, a few minor corrections, accepted
for publication in Annalen der Physik, in press
|
Annalen Phys. 12 (2003) 275-288
|
10.1002/andp.200310011
| null |
gr-qc astro-ph
| null |
We discuss the electromagnetic measurements of rotating observers and study
the propagation of electromagnetic waves in a uniformly rotating frame of
reference. The phenomenon of helicity-rotation coupling is elucidated and some
of the observational consequences of the coupling of the spin of a particle
with the rotation of a gravitational source are briefly examined.
|
[
{
"created": "Sun, 20 Apr 2003 00:19:49 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Jun 2003 00:20:31 GMT",
"version": "v2"
}
] |
2009-11-10
|
[
[
"Hauck",
"John C.",
""
],
[
"Mashhoon",
"Bahram",
""
]
] |
We discuss the electromagnetic measurements of rotating observers and study the propagation of electromagnetic waves in a uniformly rotating frame of reference. The phenomenon of helicity-rotation coupling is elucidated and some of the observational consequences of the coupling of the spin of a particle with the rotation of a gravitational source are briefly examined.
|
1806.07246
|
Mohsen Khodadi
|
Mohsen Khodadi and Kourosh Nozari
|
Non-singular model universe from a perfect fluid scalar-metric cosmology
|
19 pages, 7 figures, 2 tables, To be published in GERG
|
Gen.Rel.Grav. (2018) 50:88
|
10.1007/s10714-018-2405-1
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
To seek for a singularity free model universe from a perfect fluid
scalar-metric cosmology, we work in the "\emph{Emergent Cosmology}" (EC)
paradigm which is a non-singular alternative for cosmological inflation. By
using two methods including Linear Stability Theory and Effective Potential
Formalism, we perform a classical analysis on the possible static solutions
(that are called usually as Einstein Static Universes (ESU)in literature) in
order to study EC paradigm in a FRW background. Our model contains a kinetic
term of the scalar field minimally coupled to the background geometry without a
potential term. The matter content of the model consists of a perfect fluid
plus a cosmological constant $\Lambda$ as a separate source. In the framework
of a local dynamical system analysis, we show that in the absence or presence
of $\Lambda$, depending on some adopted values for the free parameters of the
underlying cosmological model with flat and non-flat spatial geometries, one
gets some static solutions which are viable under classical linear
perturbations. By extending our study to a global dynamical system analysis, we
show that in the presence of $\Lambda$ with non-flat spatial geometries there
is a future global de Sitter attractor in this model. Following the second
method, we derive a new static solution that represents a stable ESU but this
time without dependence on the free parameters of the cosmological model at
hand. As a whole, our analysis suggests the possibility of graceful realization
of a non-singular EC paradigm (i.e. leaving the initial static phase and
entering the inflation period as the universe is evolving) through either
preserving or violation of the strong energy condition.
|
[
{
"created": "Sat, 16 Jun 2018 07:23:41 GMT",
"version": "v1"
}
] |
2018-06-26
|
[
[
"Khodadi",
"Mohsen",
""
],
[
"Nozari",
"Kourosh",
""
]
] |
To seek for a singularity free model universe from a perfect fluid scalar-metric cosmology, we work in the "\emph{Emergent Cosmology}" (EC) paradigm which is a non-singular alternative for cosmological inflation. By using two methods including Linear Stability Theory and Effective Potential Formalism, we perform a classical analysis on the possible static solutions (that are called usually as Einstein Static Universes (ESU)in literature) in order to study EC paradigm in a FRW background. Our model contains a kinetic term of the scalar field minimally coupled to the background geometry without a potential term. The matter content of the model consists of a perfect fluid plus a cosmological constant $\Lambda$ as a separate source. In the framework of a local dynamical system analysis, we show that in the absence or presence of $\Lambda$, depending on some adopted values for the free parameters of the underlying cosmological model with flat and non-flat spatial geometries, one gets some static solutions which are viable under classical linear perturbations. By extending our study to a global dynamical system analysis, we show that in the presence of $\Lambda$ with non-flat spatial geometries there is a future global de Sitter attractor in this model. Following the second method, we derive a new static solution that represents a stable ESU but this time without dependence on the free parameters of the cosmological model at hand. As a whole, our analysis suggests the possibility of graceful realization of a non-singular EC paradigm (i.e. leaving the initial static phase and entering the inflation period as the universe is evolving) through either preserving or violation of the strong energy condition.
|
gr-qc/0610045
|
Daniel Pollack
|
Yvonne Choquet-Bruhat, James Isenberg and Daniel Pollack
|
The constraint equations for the Einstein-scalar field system on compact
manifolds
|
Minor changes, final version. To appear: Classical and Quantum
Gravity
|
Class.Quant.Grav.24:809-828,2007
|
10.1088/0264-9381/24/4/004
| null |
gr-qc math.AP math.DG
| null |
We study the constraint equations for the Einstein-scalar field system on
compact manifolds. Using the conformal method we reformulate these equations as
a determined system of nonlinear partial differential equations. By introducing
a new conformal invariant, which is sensitive to the presence of the initial
data for the scalar field, we are able to divide the set of free conformal data
into subclasses depending on the possible signs for the coefficients of terms
in the resulting Einstein-scalar field Lichnerowicz equation. For many of these
subclasses we determine whether or not a solution exists. In contrast to other
well studied field theories, there are certain cases, depending on the mean
curvature and the potential of the scalar field, for which we are unable to
resolve the question of existence of a solution. We consider this system in
such generality so as to include the vacuum constraint equations with an
arbitrary cosmological constant, the Yamabe equation and even (all cases of)
the prescribed scalar curvature problem as special cases.
|
[
{
"created": "Tue, 10 Oct 2006 14:40:37 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Dec 2006 19:20:13 GMT",
"version": "v2"
}
] |
2008-11-26
|
[
[
"Choquet-Bruhat",
"Yvonne",
""
],
[
"Isenberg",
"James",
""
],
[
"Pollack",
"Daniel",
""
]
] |
We study the constraint equations for the Einstein-scalar field system on compact manifolds. Using the conformal method we reformulate these equations as a determined system of nonlinear partial differential equations. By introducing a new conformal invariant, which is sensitive to the presence of the initial data for the scalar field, we are able to divide the set of free conformal data into subclasses depending on the possible signs for the coefficients of terms in the resulting Einstein-scalar field Lichnerowicz equation. For many of these subclasses we determine whether or not a solution exists. In contrast to other well studied field theories, there are certain cases, depending on the mean curvature and the potential of the scalar field, for which we are unable to resolve the question of existence of a solution. We consider this system in such generality so as to include the vacuum constraint equations with an arbitrary cosmological constant, the Yamabe equation and even (all cases of) the prescribed scalar curvature problem as special cases.
|
gr-qc/0501103
|
Patricio S. Letelier
|
D. Vogt and P.S. Letelier
|
New Models of General Relativistic Static Thick Disks
|
27 pages, 14 figures
|
Phys.Rev. D71 (2005) 084030
|
10.1103/PhysRevD.71.084030
| null |
gr-qc astro-ph
| null |
New families of exact general relativistic thick disks are constructed using
the ``displace, cut, fill and reflect'' method. A class of functions used to
``fill'' the disks is derived imposing conditions on the first and second
derivatives to generate physically acceptable disks. The analysis of the
function's curvature further restrict the ranges of the free parameters that
allow phisically acceptable disks. Then this class of functions together with
the Schwarzschild metric is employed to construct thick disks in isotropic,
Weyl and Schwarzschild canonical coordinates. In these last coordinates an
additional function must be added to one of the metric coefficients to generate
exact disks. Disks in isotropic and Weyl coordinates satisfy all energy
conditions, but those in Schwarzschild canonical coordinates do not satisfy the
dominant energy condition.
|
[
{
"created": "Mon, 31 Jan 2005 14:14:38 GMT",
"version": "v1"
}
] |
2009-11-11
|
[
[
"Vogt",
"D.",
""
],
[
"Letelier",
"P. S.",
""
]
] |
New families of exact general relativistic thick disks are constructed using the ``displace, cut, fill and reflect'' method. A class of functions used to ``fill'' the disks is derived imposing conditions on the first and second derivatives to generate physically acceptable disks. The analysis of the function's curvature further restrict the ranges of the free parameters that allow phisically acceptable disks. Then this class of functions together with the Schwarzschild metric is employed to construct thick disks in isotropic, Weyl and Schwarzschild canonical coordinates. In these last coordinates an additional function must be added to one of the metric coefficients to generate exact disks. Disks in isotropic and Weyl coordinates satisfy all energy conditions, but those in Schwarzschild canonical coordinates do not satisfy the dominant energy condition.
|
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