id
stringlengths 9
13
| submitter
stringlengths 1
64
⌀ | authors
stringlengths 5
22.9k
| title
stringlengths 4
245
| comments
stringlengths 1
548
⌀ | journal-ref
stringlengths 4
362
⌀ | doi
stringlengths 12
82
⌀ | report-no
stringlengths 2
281
⌀ | categories
stringclasses 793
values | license
stringclasses 9
values | orig_abstract
stringlengths 24
1.95k
| versions
listlengths 1
30
| update_date
stringlengths 10
10
| authors_parsed
listlengths 1
1.74k
| abstract
stringlengths 21
1.95k
|
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0901.1220
|
Alessandro Marini
|
M. Barucci (6 and 7), M. Bassan (2 and 3), B. Buonomo (1), G.
Cavallari (4), E. Coccia (2 and 3), S. D'Antonio (2), V. Fafone (2 and 3), C.
Ligi (1), L. Lolli (6 and 7), A. Marini (1), G. Mazzitelli (1), G. Modestino
(1), G. Pizzella (3 and 1), L. Quintieri (1), L. Risegari (6 and 7), A.
Rocchi (2), F. Ronga (1), P. Valente (5), G. Ventura (6 and 7), S.M. Vinko
(1) ((1) INFN Laboratori Nazionali di Frascati Italy, (2) INFN Sezione di
Roma2 Rome Italy, (3) Dipartimento di Fisica Univ Tor Vergata Rome Italy, (4)
CERN Geneva Switzerland, (5) INFN Sezione di Roma1 Rome Italy, (6) INFN
Sezione di Firenze Sesto Fiorentino Italy, (7) Dipartimento di Fisica Univ
Firenze Sesto Fiorentino Italy)
|
Experimental study of high energy electron interactions in a
superconducting aluminum alloy resonant bar
| null |
Phys.Lett.A373:1801-1806,2009
|
10.1016/j.physleta.2009.03.043
| null |
gr-qc physics.ins-det
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Peak amplitude measurements of the fundamental mode of oscillation of a
suspended aluminum alloy bar hit by an electron beam show that the amplitude is
enhanced by a factor ~3.5 when the material is in the superconducting state.
This result is consistent with the cosmic ray observations made by the resonant
gravitational wave detector NAUTILUS, made of the same alloy, when operated in
the superconducting state. A comparison of the experimental data with the
predictions of the model describing the underlying physical process is also
presented.
|
[
{
"created": "Fri, 9 Jan 2009 11:14:43 GMT",
"version": "v1"
}
] |
2014-11-18
|
[
[
"Barucci",
"M.",
"",
"6 and 7"
],
[
"Bassan",
"M.",
"",
"2 and 3"
],
[
"Buonomo",
"B.",
"",
"2 and 3"
],
[
"Cavallari",
"G.",
"",
"2 and 3"
],
[
"Coccia",
"E.",
"",
"2 and 3"
],
[
"D'Antonio",
"S.",
"",
"2 and 3"
],
[
"Fafone",
"V.",
"",
"2 and 3"
],
[
"Ligi",
"C.",
"",
"6 and 7"
],
[
"Lolli",
"L.",
"",
"6 and 7"
],
[
"Marini",
"A.",
"",
"3 and 1"
],
[
"Mazzitelli",
"G.",
"",
"3 and 1"
],
[
"Modestino",
"G.",
"",
"3 and 1"
],
[
"Pizzella",
"G.",
"",
"3 and 1"
],
[
"Quintieri",
"L.",
"",
"6 and 7"
],
[
"Risegari",
"L.",
"",
"6 and 7"
],
[
"Rocchi",
"A.",
"",
"6 and 7"
],
[
"Ronga",
"F.",
"",
"6 and 7"
],
[
"Valente",
"P.",
"",
"6 and 7"
],
[
"Ventura",
"G.",
"",
"6 and 7"
],
[
"Vinko",
"S. M.",
""
]
] |
Peak amplitude measurements of the fundamental mode of oscillation of a suspended aluminum alloy bar hit by an electron beam show that the amplitude is enhanced by a factor ~3.5 when the material is in the superconducting state. This result is consistent with the cosmic ray observations made by the resonant gravitational wave detector NAUTILUS, made of the same alloy, when operated in the superconducting state. A comparison of the experimental data with the predictions of the model describing the underlying physical process is also presented.
|
1607.04250
|
Jorge L. Cervantes-Cota
|
Jorge L. Cervantes-Cota, D.-E. Liebscher
|
On constructing purely affine theories with matter
|
13 pages
|
Gen. Relativ. Gravit. (2016) 48:108
|
10.1007/s10714-016-2103-9
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We explore ways to obtain the very existence of a space-time metric from an
action principle that does not refer to it a priori. Although there are reasons
to believe that only a non-local theory can viably achieve this goal, we
investigate here local theories that start with Schroedinger's purely affine
theory [21], where he gave reasons to set the metric proportional to the Ricci
curvature aposteriori. When we leave the context of unified field theory, and
we couple the non-gravitational matter using some weak equivalence principle,
we can show that the propagation of shock waves does not define a lightcone
when the purely affine theory is local and avoids the explicit use of the Ricci
tensor in realizing the weak equivalence principle. When the Ricci tensor is
substituted for the metric, the equations seem to have only a very limited set
of solutions. This backs the conviction that viable purely affine theories have
to be non-local.
|
[
{
"created": "Thu, 14 Jul 2016 19:03:47 GMT",
"version": "v1"
}
] |
2016-07-15
|
[
[
"Cervantes-Cota",
"Jorge L.",
""
],
[
"Liebscher",
"D. -E.",
""
]
] |
We explore ways to obtain the very existence of a space-time metric from an action principle that does not refer to it a priori. Although there are reasons to believe that only a non-local theory can viably achieve this goal, we investigate here local theories that start with Schroedinger's purely affine theory [21], where he gave reasons to set the metric proportional to the Ricci curvature aposteriori. When we leave the context of unified field theory, and we couple the non-gravitational matter using some weak equivalence principle, we can show that the propagation of shock waves does not define a lightcone when the purely affine theory is local and avoids the explicit use of the Ricci tensor in realizing the weak equivalence principle. When the Ricci tensor is substituted for the metric, the equations seem to have only a very limited set of solutions. This backs the conviction that viable purely affine theories have to be non-local.
|
1905.01394
|
Olivier Dore
|
Roland de Putter, Olivier Dor\'e
|
In search of an observational quantum signature of the primordial
perturbations in slow-roll and ultra slow-roll inflation
|
27 pages, 7 figures. Comments welcome
|
Phys. Rev. D 101, 043511 (2020)
|
10.1103/PhysRevD.101.043511
| null |
gr-qc astro-ph.CO quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In the standard inflationary paradigm, cosmological density perturbations are
generated as quantum fluctuations in the early Universe, but then undergo a
quantum-to-classical transition. A key role in this transition is played by
squeezing of the quantum state, which is a result of the strong suppression of
the decaying mode component of the perturbations. Motivated by ever improving
measurements of the cosmological perturbations, we ask whether there are
scenarios where this decaying mode is nevertheless still observable in the late
Universe, ideally leading to a ``smoking gun'' signature of the quantum nature
of the perturbations. We address this question by evolving the quantum state of
the perturbations from inflation into the post-inflationary Universe. After
recovering the standard result that in slow-roll (SR) inflation the decaying
mode is indeed hopelessly suppressed by the time the perturbations are observed
(by $\sim 115$ orders of magnitude), we turn to ultra slow-roll (USR)
inflation, a scenario in which the usual decaying mode actually grows on
super-horizon scales. Despite this drastic difference in the behavior of the
mode functions, we find also in USR that the late-Universe decaying mode
amplitude is dramatically suppressed, in fact by the same $\sim 115$ orders of
magnitude. We finally explain that this large suppression is a general result
that holds beyond the SR and USR scenarios considered and follows from a
modified version of Heisenberg's uncertainty principle and the observed
amplitude of the primordial power spectrum. The classical behavior of the
perturbations is thus closely related to the classical behavior of macroscopic
objects drawing an analogy with the position of a massive particle, the
curvature perturbations today have an enormous effective mass of order $m_{\rm
pl}^2/H_0^2 \sim 10^{120}$, making them highly classical.
|
[
{
"created": "Sat, 4 May 2019 00:26:18 GMT",
"version": "v1"
}
] |
2020-02-19
|
[
[
"de Putter",
"Roland",
""
],
[
"Doré",
"Olivier",
""
]
] |
In the standard inflationary paradigm, cosmological density perturbations are generated as quantum fluctuations in the early Universe, but then undergo a quantum-to-classical transition. A key role in this transition is played by squeezing of the quantum state, which is a result of the strong suppression of the decaying mode component of the perturbations. Motivated by ever improving measurements of the cosmological perturbations, we ask whether there are scenarios where this decaying mode is nevertheless still observable in the late Universe, ideally leading to a ``smoking gun'' signature of the quantum nature of the perturbations. We address this question by evolving the quantum state of the perturbations from inflation into the post-inflationary Universe. After recovering the standard result that in slow-roll (SR) inflation the decaying mode is indeed hopelessly suppressed by the time the perturbations are observed (by $\sim 115$ orders of magnitude), we turn to ultra slow-roll (USR) inflation, a scenario in which the usual decaying mode actually grows on super-horizon scales. Despite this drastic difference in the behavior of the mode functions, we find also in USR that the late-Universe decaying mode amplitude is dramatically suppressed, in fact by the same $\sim 115$ orders of magnitude. We finally explain that this large suppression is a general result that holds beyond the SR and USR scenarios considered and follows from a modified version of Heisenberg's uncertainty principle and the observed amplitude of the primordial power spectrum. The classical behavior of the perturbations is thus closely related to the classical behavior of macroscopic objects drawing an analogy with the position of a massive particle, the curvature perturbations today have an enormous effective mass of order $m_{\rm pl}^2/H_0^2 \sim 10^{120}$, making them highly classical.
|
1904.05706
|
Dennis Hansen
|
Dennis Hansen, Jelle Hartong and Niels A. Obers
|
Gravity between Newton and Einstein
|
Essay written for the Gravity Research Foundation 2019 Awards for
Essays on Gravitation; Honorable Mention
| null |
10.1142/S0218271819440103
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Statements about relativistic effects are often subtle. In this essay we will
demonstrate that the three classical tests of general relativity, namely
perihelion precession, deflection of light and gravitational redshift, are
passed perfectly by an extension of Newtonian gravity that includes
gravitational time dilation effects while retaining a non-relativistic causal
structure. This non-relativistic gravity theory arises from a covariant large
speed of light expansion of Einstein's theory of gravity that does not assume
weak fields and which admits an action principle.
|
[
{
"created": "Thu, 11 Apr 2019 14:08:07 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Jun 2019 14:17:21 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Jan 2020 10:31:02 GMT",
"version": "v3"
}
] |
2020-01-30
|
[
[
"Hansen",
"Dennis",
""
],
[
"Hartong",
"Jelle",
""
],
[
"Obers",
"Niels A.",
""
]
] |
Statements about relativistic effects are often subtle. In this essay we will demonstrate that the three classical tests of general relativity, namely perihelion precession, deflection of light and gravitational redshift, are passed perfectly by an extension of Newtonian gravity that includes gravitational time dilation effects while retaining a non-relativistic causal structure. This non-relativistic gravity theory arises from a covariant large speed of light expansion of Einstein's theory of gravity that does not assume weak fields and which admits an action principle.
|
1808.08975
|
Jo\~ao Lu\'is Rosa
|
Jo\~ao Lu\'is Rosa, Jos\'e P. S. Lemos, Francisco S. N. Lobo
|
Wormholes in generalized hybrid metric-Palatini gravity obeying the
matter null energy condition everywhere
|
12 pages, 2 figures
|
Phys. Rev. D 98, 064054 (2018)
|
10.1103/PhysRevD.98.064054
| null |
gr-qc astro-ph.HE hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Wormhole solutions in a generalized hybrid metric-Palatini matter theory,
given by a gravitational Lagrangian $f\left(R,\cal{R}\right)$, where $R$ is the
metric Ricci scalar, and $\mathcal{R}$ is a Palatini scalar curvature defined
in terms of an independent connection, and a matter Lagrangian, are found. The
solutions are worked in the scalar-tensor representation of the theory, where
the Palatini field is traded for two scalars, $\varphi$ and $\psi$, and the
gravitational term $R$ is maintained. The main interest in the solutions found
is that the matter field obeys the null energy condition (NEC) everywhere,
including the throat and up to infinity, so that there is no need for exotic
matter. The wormhole geometry with its flaring out at the throat is supported
by the higher-order curvature terms, or equivalently, by the two fundamental
scalar fields, which either way can be interpreted as a gravitational fluid.
Thus, in this theory, in building a wormhole, it is possible to exchange the
exoticity of matter by the exoticity of the gravitational sector. The specific
wormhole displayed, built to obey the matter NEC from the throat to infinity,
has three regions, namely, an interior region containing the throat, a thin
shell of matter, and a vacuum Schwarzschild anti-de Sitter (AdS) exterior. For
hybrid metric-Palatini matter theories this wormhole solution is the first
where the NEC for the matter is verified for the entire spacetime keeping the
solution under asymptotic control. The existence of this type of solutions is
in line with the idea that traversable wormholes bore by additional fundamental
gravitational fields, here disguised as scalar fields, can be found without
exotic matter. Concomitantly, the somewhat concocted architecture needed to
assemble a complete wormhole solution for the whole spacetime may imply that in
this class of theories such solutions are scarce.
|
[
{
"created": "Mon, 27 Aug 2018 18:01:56 GMT",
"version": "v1"
}
] |
2018-10-03
|
[
[
"Rosa",
"João Luís",
""
],
[
"Lemos",
"José P. S.",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] |
Wormhole solutions in a generalized hybrid metric-Palatini matter theory, given by a gravitational Lagrangian $f\left(R,\cal{R}\right)$, where $R$ is the metric Ricci scalar, and $\mathcal{R}$ is a Palatini scalar curvature defined in terms of an independent connection, and a matter Lagrangian, are found. The solutions are worked in the scalar-tensor representation of the theory, where the Palatini field is traded for two scalars, $\varphi$ and $\psi$, and the gravitational term $R$ is maintained. The main interest in the solutions found is that the matter field obeys the null energy condition (NEC) everywhere, including the throat and up to infinity, so that there is no need for exotic matter. The wormhole geometry with its flaring out at the throat is supported by the higher-order curvature terms, or equivalently, by the two fundamental scalar fields, which either way can be interpreted as a gravitational fluid. Thus, in this theory, in building a wormhole, it is possible to exchange the exoticity of matter by the exoticity of the gravitational sector. The specific wormhole displayed, built to obey the matter NEC from the throat to infinity, has three regions, namely, an interior region containing the throat, a thin shell of matter, and a vacuum Schwarzschild anti-de Sitter (AdS) exterior. For hybrid metric-Palatini matter theories this wormhole solution is the first where the NEC for the matter is verified for the entire spacetime keeping the solution under asymptotic control. The existence of this type of solutions is in line with the idea that traversable wormholes bore by additional fundamental gravitational fields, here disguised as scalar fields, can be found without exotic matter. Concomitantly, the somewhat concocted architecture needed to assemble a complete wormhole solution for the whole spacetime may imply that in this class of theories such solutions are scarce.
|
2309.03065
|
Orlando Luongo
|
Orlando Luongo, Tommaso Mengoni
|
Quasi-quintessence inflation with non-minimal coupling to curvature in
the Jordan and Einstein frames
|
28 pages, 11 figures, 4 tables
| null | null | null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We here explore a specific class of scalar field, dubbed quasi-quintessence
which exhibits characteristics akin to ordinary matter. Specifically, we
investigate under which conditions this fluid can mitigate the classical
cosmological constant problem. We remark that, assuming a phase transition, it
is possible to predict inflationary dynamics within the metastable phase
triggered by the symmetry breaking mechanism. During this phase, we study
inflationary models incorporating this cancellation mechanism for vacuum energy
within the context of quasi-quintessence. There, we introduce four novel
potentials, categorized into two main groups, \emph{i.e.}, the Starobinsky-like
and symmetry breaking paradigms. Afterwards, we consider two distinct cases,
the first without coupling with the curvature, while the second exhibiting a
Yukawa-like interacting term. Hence, we compute the inflationary dynamics
within both the Jordan and Einstein frames and discuss the objective to unify
old with chaotic inflation into a single scheme. We therefore find the
tensor-to-scalar ratio and the spectral terms and conclude that the most suited
approach involves the Starobinsky-like class of solution. Indeed, our findings
show that small field inflationary scenarios appear disfavored and propose
\emph{de facto} a novel technique to reobtain the Starobinsky potential without
passing through generalizations of Einstein's gravity. Last but not least, we
conjecture that vacuum energy may be converted into particles by virtue of the
geometric interacting term and speculate about the physics associated with the
Jordan and Einstein frames.
|
[
{
"created": "Wed, 6 Sep 2023 15:07:54 GMT",
"version": "v1"
}
] |
2023-09-07
|
[
[
"Luongo",
"Orlando",
""
],
[
"Mengoni",
"Tommaso",
""
]
] |
We here explore a specific class of scalar field, dubbed quasi-quintessence which exhibits characteristics akin to ordinary matter. Specifically, we investigate under which conditions this fluid can mitigate the classical cosmological constant problem. We remark that, assuming a phase transition, it is possible to predict inflationary dynamics within the metastable phase triggered by the symmetry breaking mechanism. During this phase, we study inflationary models incorporating this cancellation mechanism for vacuum energy within the context of quasi-quintessence. There, we introduce four novel potentials, categorized into two main groups, \emph{i.e.}, the Starobinsky-like and symmetry breaking paradigms. Afterwards, we consider two distinct cases, the first without coupling with the curvature, while the second exhibiting a Yukawa-like interacting term. Hence, we compute the inflationary dynamics within both the Jordan and Einstein frames and discuss the objective to unify old with chaotic inflation into a single scheme. We therefore find the tensor-to-scalar ratio and the spectral terms and conclude that the most suited approach involves the Starobinsky-like class of solution. Indeed, our findings show that small field inflationary scenarios appear disfavored and propose \emph{de facto} a novel technique to reobtain the Starobinsky potential without passing through generalizations of Einstein's gravity. Last but not least, we conjecture that vacuum energy may be converted into particles by virtue of the geometric interacting term and speculate about the physics associated with the Jordan and Einstein frames.
|
0908.4029
|
Wlodzimierz Piechocki
|
Przemyslaw Malkiewicz and Wlodzimierz Piechocki
|
Turning big bang into big bounce: II. Quantum dynamics
|
14 pages, no figures, version accepted for publication in Class.
Quant. Grav
|
Class.Quant.Grav.27:225018,2010
|
10.1088/0264-9381/27/22/225018
| null |
gr-qc astro-ph.CO hep-th quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We analyze the big bounce transition of the quantum FRW model in the setting
of the nonstandard loop quantum cosmology (LQC). Elementary observables are
used to quantize composite observables. The spectrum of the energy density
operator is bounded and continuous. The spectrum of the volume operator is
bounded from below and discrete. It has equally distant levels defining a
quantum of the volume. The discreteness may imply a foamy structure of
spacetime at semiclassical level which may be detected in astro-cosmo
observations. The nonstandard LQC method has a free parameter that should be
fixed in some way to specify the big bounce transition.
|
[
{
"created": "Thu, 27 Aug 2009 15:05:37 GMT",
"version": "v1"
},
{
"created": "Mon, 26 Oct 2009 09:57:41 GMT",
"version": "v2"
},
{
"created": "Wed, 10 Feb 2010 17:40:11 GMT",
"version": "v3"
},
{
"created": "Sat, 20 Mar 2010 07:35:30 GMT",
"version": "v4"
},
{
"created": "Thu, 5 Aug 2010 06:29:08 GMT",
"version": "v5"
},
{
"created": "Fri, 6 Aug 2010 07:49:18 GMT",
"version": "v6"
}
] |
2011-03-28
|
[
[
"Malkiewicz",
"Przemyslaw",
""
],
[
"Piechocki",
"Wlodzimierz",
""
]
] |
We analyze the big bounce transition of the quantum FRW model in the setting of the nonstandard loop quantum cosmology (LQC). Elementary observables are used to quantize composite observables. The spectrum of the energy density operator is bounded and continuous. The spectrum of the volume operator is bounded from below and discrete. It has equally distant levels defining a quantum of the volume. The discreteness may imply a foamy structure of spacetime at semiclassical level which may be detected in astro-cosmo observations. The nonstandard LQC method has a free parameter that should be fixed in some way to specify the big bounce transition.
|
1208.0580
|
Claudia de Rham
|
Claudia de Rham, Andrew J. Tolley and Daniel H. Wesley
|
Vainshtein Mechanism in Binary Pulsars
|
minor revisions to match published version in prd
|
Phys. Rev. D 87, 044025 (2013)
|
10.1103/PhysRevD.87.044025
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We compute the scalar gravitational radiation from a binary pulsar system in
the simplest model that exhibits the Vainshtein mechanism. The mechanism is
successful in screening the effect from scalar fields conformally coupled to
matter, although gravitational radiation is less suppressed relative to its
general relativity predictions than static fifth forces effects within the
pulsar system. This is due to a combination of two effects: firstly the
existence of monopole and dipole radiation; secondly the Vainshtein suppression
comes from the hierarchy of scales between the inverse frequency scale and the
Vainshtein radius, rather than the orbital radius of the pulsar system.
Extensions of these results will have direct relevance to infrared
modifications of gravity, such as massive gravity theories, which are known to
exhibit a Vainshtein mechanism. Generalization to Galileon models with higher
order interactions are likely to provide stronger constraints.
|
[
{
"created": "Thu, 2 Aug 2012 19:33:57 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Aug 2012 08:48:04 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Mar 2013 19:58:19 GMT",
"version": "v3"
}
] |
2013-03-14
|
[
[
"de Rham",
"Claudia",
""
],
[
"Tolley",
"Andrew J.",
""
],
[
"Wesley",
"Daniel H.",
""
]
] |
We compute the scalar gravitational radiation from a binary pulsar system in the simplest model that exhibits the Vainshtein mechanism. The mechanism is successful in screening the effect from scalar fields conformally coupled to matter, although gravitational radiation is less suppressed relative to its general relativity predictions than static fifth forces effects within the pulsar system. This is due to a combination of two effects: firstly the existence of monopole and dipole radiation; secondly the Vainshtein suppression comes from the hierarchy of scales between the inverse frequency scale and the Vainshtein radius, rather than the orbital radius of the pulsar system. Extensions of these results will have direct relevance to infrared modifications of gravity, such as massive gravity theories, which are known to exhibit a Vainshtein mechanism. Generalization to Galileon models with higher order interactions are likely to provide stronger constraints.
|
gr-qc/9411027
| null |
J. W. Moffat
|
Consistency of the Nonsymmetric Gravitational Theory
|
20 pages, plain TeX. Corrections of typographical errors
| null | null |
UTPT-94-30
|
gr-qc
| null |
A nonsymmetric gravitational theory (NGT) is presented which is free of ghost
poles, tachyons and higher-order poles and there are no problems with
asymptotic boundary conditions. An extended Birkhoff theorem is shown to hold
for the spherically symmetric solution of the field equations. A static
spherically symmetric solution in the short-range approximation, $\mu^{-1} >
2m$, is everywhere regular and does not contain a black hole event horizon.
|
[
{
"created": "Thu, 10 Nov 1994 18:16:33 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Dec 1994 22:11:21 GMT",
"version": "v2"
}
] |
2008-02-03
|
[
[
"Moffat",
"J. W.",
""
]
] |
A nonsymmetric gravitational theory (NGT) is presented which is free of ghost poles, tachyons and higher-order poles and there are no problems with asymptotic boundary conditions. An extended Birkhoff theorem is shown to hold for the spherically symmetric solution of the field equations. A static spherically symmetric solution in the short-range approximation, $\mu^{-1} > 2m$, is everywhere regular and does not contain a black hole event horizon.
|
0811.3823
|
Hamid Reza Sepangi
|
K. Atazadeh and H. R. Sepangi
|
Brans-Dicke DGP Brane Cosmology
|
12 pages, 1 figure, to appear in JCAP
|
JCAP 0901:006,2009
|
10.1088/1475-7516/2009/01/006
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider a five dimensional DGP-brane scenario endowed with a
non-minimally coupled scalar field within the context of Brans-Dicke theory.
This theory predicts that the mass appearing in the gravitational potential is
modified by the addition of the mass of the effective intrinsic curvature on
the brane. We also derive the effective four dimensional field equations on a
3+1 dimensional brane where the fifth dimension is assumed to have an orbifold
symmetry. Finally, we discuss the cosmological implications of this setup,
predicting an accelerated expanding universe with a value of the Brans-Dicke
parameter $\omega$ consistent with values resulting from the solar system
observations.
|
[
{
"created": "Mon, 24 Nov 2008 09:04:58 GMT",
"version": "v1"
}
] |
2009-11-19
|
[
[
"Atazadeh",
"K.",
""
],
[
"Sepangi",
"H. R.",
""
]
] |
We consider a five dimensional DGP-brane scenario endowed with a non-minimally coupled scalar field within the context of Brans-Dicke theory. This theory predicts that the mass appearing in the gravitational potential is modified by the addition of the mass of the effective intrinsic curvature on the brane. We also derive the effective four dimensional field equations on a 3+1 dimensional brane where the fifth dimension is assumed to have an orbifold symmetry. Finally, we discuss the cosmological implications of this setup, predicting an accelerated expanding universe with a value of the Brans-Dicke parameter $\omega$ consistent with values resulting from the solar system observations.
|
gr-qc/0310104
|
Makoto Narita
|
Makoto Narita
|
Global existence problem in $T^3$-Gowdy symmetric IIB superstring
cosmology
| null |
Class.Quant.Grav. 20 (2003) 4983-4994
|
10.1088/0264-9381/20/23/003
|
AEI-2003-083
|
gr-qc hep-th math.AP math.DG
| null |
We show global existence theorems for Gowdy symmetric spacetimes with type
IIB stringy matter. The areal and constant mean curvature time coordinates are
used. Before coming to that, it is shown that a wave map describes the
evolution of this system.
|
[
{
"created": "Wed, 22 Oct 2003 10:17:07 GMT",
"version": "v1"
}
] |
2009-11-10
|
[
[
"Narita",
"Makoto",
""
]
] |
We show global existence theorems for Gowdy symmetric spacetimes with type IIB stringy matter. The areal and constant mean curvature time coordinates are used. Before coming to that, it is shown that a wave map describes the evolution of this system.
|
gr-qc/0507098
|
Guillermo A. Mena Marugan
|
Pablo Galan and Guillermo A. Mena Marugan
|
Length Uncertainty in a Gravity's Rainbow Formalism
|
12 pages, accepted for publication in Physical Review D
|
Phys.Rev. D72 (2005) 044019
|
10.1103/PhysRevD.72.044019
| null |
gr-qc
| null |
It is commonly accepted that the combination of quantum mechanics and general
relativity gives rise to the emergence of a minimum uncertainty both in space
and time. The arguments that support this conclusion are mainly based on
perturbative approaches to the quantization, in which the gravitational
interactions of the matter content are described as corrections to a classical
background. In a recent paper, we analyzed the existence of a minimum time
uncertainty in the framework of doubly special relativity. In this framework,
the standard definition of the energy-momentum of particles is modified
appealing to possible quantum gravitational effects, which are not necessarily
perturbative. Demanding that this modification be completed into a canonical
transformation determines the implementation of doubly special relativity in
position space and leads to spacetime coordinates that depend on the
energy-momentum of the particle. In the present work, we extend our analysis to
the quantum length uncertainty. We show that, in generic cases, there actually
exists a limit in the spatial resolution, both when the quantum evolution is
described in terms of the auxiliary time corresponding to the Minkowski
background or in terms of the physical time. These two kinds of evolutions can
be understood as corresponding to perturbative and non-perturbative
descriptions, respectively. This result contrasts with that found for the time
uncertainty, which can be made to vanish in all models with unbounded physical
energy if one adheres to a non-perturbative quantization.
|
[
{
"created": "Sat, 23 Jul 2005 11:49:44 GMT",
"version": "v1"
}
] |
2009-11-11
|
[
[
"Galan",
"Pablo",
""
],
[
"Marugan",
"Guillermo A. Mena",
""
]
] |
It is commonly accepted that the combination of quantum mechanics and general relativity gives rise to the emergence of a minimum uncertainty both in space and time. The arguments that support this conclusion are mainly based on perturbative approaches to the quantization, in which the gravitational interactions of the matter content are described as corrections to a classical background. In a recent paper, we analyzed the existence of a minimum time uncertainty in the framework of doubly special relativity. In this framework, the standard definition of the energy-momentum of particles is modified appealing to possible quantum gravitational effects, which are not necessarily perturbative. Demanding that this modification be completed into a canonical transformation determines the implementation of doubly special relativity in position space and leads to spacetime coordinates that depend on the energy-momentum of the particle. In the present work, we extend our analysis to the quantum length uncertainty. We show that, in generic cases, there actually exists a limit in the spatial resolution, both when the quantum evolution is described in terms of the auxiliary time corresponding to the Minkowski background or in terms of the physical time. These two kinds of evolutions can be understood as corresponding to perturbative and non-perturbative descriptions, respectively. This result contrasts with that found for the time uncertainty, which can be made to vanish in all models with unbounded physical energy if one adheres to a non-perturbative quantization.
|
1109.1941
|
Daniela Pugliese Dr
|
D. Pugliese, G. Montani, V. Lacquaniti
|
On the electromagnetic emission from charged test particles in a five
dimensional spacetime
|
13 pages, 10 figure, to be published in European Physical Journal C.
Keywords:Kaluza Klein theory--Generalized Schwarzschild solution (GSS)--Test
particle orbits--Emission spectra
|
The European Physical Journal C - Particles And Fields. Volume 71,
Number 9, 1747-6 (2011)
|
10.1140/epjc/s10052-011-1747-6
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the motion of charged particles radially falling in a class of
static and electromagnetic-free, five-dimensional Kaluza-Klein backgrounds.
Particle dynamics in such spacetimes is explored by an approach \emph{a
l$\acute{a}$} Papapetrou. The electromagnetic radiation emitted by these
particles is studied, outlining the new features emerging in the spectra for
the five-dimensional case. A comparison with the dynamics in the four
dimensional counterpart, \textit{i.e} the Schwarzschild background, is
performed.
|
[
{
"created": "Fri, 9 Sep 2011 08:37:07 GMT",
"version": "v1"
}
] |
2012-02-07
|
[
[
"Pugliese",
"D.",
""
],
[
"Montani",
"G.",
""
],
[
"Lacquaniti",
"V.",
""
]
] |
We study the motion of charged particles radially falling in a class of static and electromagnetic-free, five-dimensional Kaluza-Klein backgrounds. Particle dynamics in such spacetimes is explored by an approach \emph{a l$\acute{a}$} Papapetrou. The electromagnetic radiation emitted by these particles is studied, outlining the new features emerging in the spectra for the five-dimensional case. A comparison with the dynamics in the four dimensional counterpart, \textit{i.e} the Schwarzschild background, is performed.
|
gr-qc/0001036
|
John E. Heighway
|
John E. Heighway
|
Towards a Deeper Understanding of General Relativity
|
15 pages, pdf. Two figures. Comments and questions welcome
| null | null | null |
gr-qc
| null |
Standard treatments of general relativity accept the gravitational slowing of
clocks as a primary phenomenon, requiring no further analysis as to cause.
Rejecting this attitude, I argue that one or more of the fundamental
"constants" governing the quantum mechanics of atoms must depend upon position
in a gravitational field. A simple relationship governing the possible
dependencies of e, h, c and m is deduced, and arguments in favor of the choice
of the electron rest mass, m, are presented. The reduction of rest mass is thus
taken to be the sole cause of clock slowing. Importantly, this dependency
implies another effect, heretofore unsuspected, namely, the gravitational
elongation of measuring rods. An alternate ("telemetric") system of measurement
is introduced, leading to a metric that is conformally related to the usual
proper metric. In terms of the new system, many otherwise puzzling phenomena
may be simply understood. In particular,the geometry of the Schwarzschild space
as described by the telemetric system differs profoundly from that described by
proper measurments, leading to a very different understanding of the structure
of black holes. The theory is extended to cosmology,leading to a remarkable
alternate view of the structure and history of the universe.
|
[
{
"created": "Wed, 12 Jan 2000 14:58:51 GMT",
"version": "v1"
},
{
"created": "Fri, 5 May 2000 21:31:21 GMT",
"version": "v2"
},
{
"created": "Wed, 5 Sep 2001 15:14:20 GMT",
"version": "v3"
},
{
"created": "Sun, 16 Sep 2001 20:12:09 GMT",
"version": "v4"
},
{
"created": "Sat, 22 Dec 2001 22:21:37 GMT",
"version": "v5"
},
{
"created": "Wed, 1 May 2002 21:24:54 GMT",
"version": "v6"
},
{
"created": "Fri, 31 May 2002 20:42:50 GMT",
"version": "v7"
}
] |
2007-05-23
|
[
[
"Heighway",
"John E.",
""
]
] |
Standard treatments of general relativity accept the gravitational slowing of clocks as a primary phenomenon, requiring no further analysis as to cause. Rejecting this attitude, I argue that one or more of the fundamental "constants" governing the quantum mechanics of atoms must depend upon position in a gravitational field. A simple relationship governing the possible dependencies of e, h, c and m is deduced, and arguments in favor of the choice of the electron rest mass, m, are presented. The reduction of rest mass is thus taken to be the sole cause of clock slowing. Importantly, this dependency implies another effect, heretofore unsuspected, namely, the gravitational elongation of measuring rods. An alternate ("telemetric") system of measurement is introduced, leading to a metric that is conformally related to the usual proper metric. In terms of the new system, many otherwise puzzling phenomena may be simply understood. In particular,the geometry of the Schwarzschild space as described by the telemetric system differs profoundly from that described by proper measurments, leading to a very different understanding of the structure of black holes. The theory is extended to cosmology,leading to a remarkable alternate view of the structure and history of the universe.
|
1005.5401
|
Catherine Williams
|
Catherine Williams
|
A black hole with no marginally trapped tube asymptotic to its event
horizon
|
12 pages; to appear in the Proceedings of the Complex Analysis &
Dynamical Systems IV Conference (Nahariya, Israel, May 2009)
| null | null | null |
gr-qc math.DG
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We construct an example of a spherically symmetric black hole interior in
which there is NO (spherically symmetric) marginally trapped tube asymptotic to
the event horizon. The construction uses a self-gravitating massive scalar
field matter model, and the key condition we impose is that the scalar field
$\phi$ be bounded below by a positive constant along the event horizon.
|
[
{
"created": "Fri, 28 May 2010 21:17:25 GMT",
"version": "v1"
}
] |
2010-06-01
|
[
[
"Williams",
"Catherine",
""
]
] |
We construct an example of a spherically symmetric black hole interior in which there is NO (spherically symmetric) marginally trapped tube asymptotic to the event horizon. The construction uses a self-gravitating massive scalar field matter model, and the key condition we impose is that the scalar field $\phi$ be bounded below by a positive constant along the event horizon.
|
0809.0617
|
Song Li
|
Song Li, Yongge Ma and Yun Chen
|
Dynamical Evolution of Interacting Modified Chaplygin Gas
|
10 pages, 6 figures, accepted for publication in Int. J. Mod. Phys. D
|
Int.J.Mod.Phys.D18:1785-1800,2009
|
10.1142/S0218271809015321
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The cosmological model of the modified Chaplygin gas interacting with cold
dark matter is studied. Our attention is focused on the final state of universe
in the model. It turns out that there exists a stable scaling solution, which
provides the possibility to alleviate the coincidence problem. In addition, we
investigate the effect of the coupling constants $c_{1}$ and $c_{2}$ on the
dynamical evolution of this model from the statefinder viewpoint. It is found
that the coupling constants play a significant role during the dynamical
evolution of the interacting MCG model. Furthermore, we can distinguish this
interacting model from other dark energy models in the $s-r$ plane.
|
[
{
"created": "Wed, 3 Sep 2008 02:37:22 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Jul 2009 13:19:45 GMT",
"version": "v2"
}
] |
2009-12-04
|
[
[
"Li",
"Song",
""
],
[
"Ma",
"Yongge",
""
],
[
"Chen",
"Yun",
""
]
] |
The cosmological model of the modified Chaplygin gas interacting with cold dark matter is studied. Our attention is focused on the final state of universe in the model. It turns out that there exists a stable scaling solution, which provides the possibility to alleviate the coincidence problem. In addition, we investigate the effect of the coupling constants $c_{1}$ and $c_{2}$ on the dynamical evolution of this model from the statefinder viewpoint. It is found that the coupling constants play a significant role during the dynamical evolution of the interacting MCG model. Furthermore, we can distinguish this interacting model from other dark energy models in the $s-r$ plane.
|
gr-qc/9711006
|
Jeong Won Ho
|
Jeongwon Ho, Won Tae Kim, and Young-Jai Park
|
Duality of Quasilocal Black Hole Thermodynamics
|
19 pages, Latex, no figures, to be published in Class. Quantum Grav.
Some minor changes, references added
|
Class.Quant.Grav. 15 (1998) 1437-1448
|
10.1088/0264-9381/15/6/003
|
SOGANG-HEP-224/97
|
gr-qc hep-th
| null |
We consider T-duality of the quasilocal black hole thermodynamics for the
three-dimensional low energy effective string theory. Quasilocal thermodynamic
variables in the first law are explicitly calculated on a general axisymmetric
three-dimensional black hole solution and corresponding dual one. Physical
meaning of the dual invariance of the black hole entropy is considered in terms
of the Euclidean path integral formulation.
|
[
{
"created": "Tue, 4 Nov 1997 07:21:38 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Apr 1998 13:44:43 GMT",
"version": "v2"
}
] |
2009-10-30
|
[
[
"Ho",
"Jeongwon",
""
],
[
"Kim",
"Won Tae",
""
],
[
"Park",
"Young-Jai",
""
]
] |
We consider T-duality of the quasilocal black hole thermodynamics for the three-dimensional low energy effective string theory. Quasilocal thermodynamic variables in the first law are explicitly calculated on a general axisymmetric three-dimensional black hole solution and corresponding dual one. Physical meaning of the dual invariance of the black hole entropy is considered in terms of the Euclidean path integral formulation.
|
2001.03440
|
Saulo Carneiro
|
C\'assio Pigozzo, Flora S. Bacelar and Saulo Carneiro
|
On the value of the Immirzi parameter and the horizon entropy
|
11 pages, 9 figures. Final version, matching that published in
Classical and Quantum Gravity
|
Class. Quant. Grav. 38 (2021) 045001
|
10.1088/1361-6382/abce6a
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In Loop Quantum Gravity (LQG) the quantisation of General Relativity leads to
precise predictions for the eigenvalues of geometrical observables like volume
and area, up to the value of the only free parameter of the theory, the
Barbero-Immirzi (BI) parameter. With the help of the eigenvalues equation for
the area operator, LQG successfully derives the Bekenstein-Hawking entropy of
large black holes with isolated horizons, fixing at this limit the BI parameter
as $\gamma \approx 0.274$. In the present paper we show some evidence that a
black hole with angular momentum $\hbar$ and Planck mass is an eigenstate of
the area operator provided that $\gamma = \sqrt{3}/6 \approx 1.05 \times
0.274$. As the black hole is extremal, there is no Hawking radiation and the
horizon is isolated. We also suggest that such a black hole can be formed in
the head-on scattering of two parallel Standard Model neutrinos in the mass
state $m_2$ (assuming $m_1 = 0$). Furthermore, we use the obtained BI parameter
to numerically compute the entropy of isolated horizons with areas ranging up
to $250\,l_P^2$, by counting the number of micro-states associated to a given
area. The resulting entropy has a leading term ${\cal S} \approx 0.25\, {\cal
A}$, in agreement to the Bekenstein-Hawking entropy. As the identification of
the above eigenstate rests on the matching between classical areas and quantum
area eigenvalues, we also present, on the basis of an effective quantum model
for the Schwarzschild black hole recently proposed by Ashtekar, Olmedo and
Singh, an expression for the quantum corrected area of isolated horizons, valid
for any black hole mass. Quantum corrections are shown to be negligible for a
Planck mass black hole, of order $10^{-3}$ relative to the classical area.
|
[
{
"created": "Fri, 10 Jan 2020 13:45:29 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Mar 2020 15:06:57 GMT",
"version": "v2"
},
{
"created": "Tue, 7 Jul 2020 14:37:26 GMT",
"version": "v3"
},
{
"created": "Sun, 29 Nov 2020 15:00:49 GMT",
"version": "v4"
}
] |
2021-01-01
|
[
[
"Pigozzo",
"Cássio",
""
],
[
"Bacelar",
"Flora S.",
""
],
[
"Carneiro",
"Saulo",
""
]
] |
In Loop Quantum Gravity (LQG) the quantisation of General Relativity leads to precise predictions for the eigenvalues of geometrical observables like volume and area, up to the value of the only free parameter of the theory, the Barbero-Immirzi (BI) parameter. With the help of the eigenvalues equation for the area operator, LQG successfully derives the Bekenstein-Hawking entropy of large black holes with isolated horizons, fixing at this limit the BI parameter as $\gamma \approx 0.274$. In the present paper we show some evidence that a black hole with angular momentum $\hbar$ and Planck mass is an eigenstate of the area operator provided that $\gamma = \sqrt{3}/6 \approx 1.05 \times 0.274$. As the black hole is extremal, there is no Hawking radiation and the horizon is isolated. We also suggest that such a black hole can be formed in the head-on scattering of two parallel Standard Model neutrinos in the mass state $m_2$ (assuming $m_1 = 0$). Furthermore, we use the obtained BI parameter to numerically compute the entropy of isolated horizons with areas ranging up to $250\,l_P^2$, by counting the number of micro-states associated to a given area. The resulting entropy has a leading term ${\cal S} \approx 0.25\, {\cal A}$, in agreement to the Bekenstein-Hawking entropy. As the identification of the above eigenstate rests on the matching between classical areas and quantum area eigenvalues, we also present, on the basis of an effective quantum model for the Schwarzschild black hole recently proposed by Ashtekar, Olmedo and Singh, an expression for the quantum corrected area of isolated horizons, valid for any black hole mass. Quantum corrections are shown to be negligible for a Planck mass black hole, of order $10^{-3}$ relative to the classical area.
|
2201.01495
|
Tanmaya Mishra
|
T. Mishra, B. O'Brien, M. Szczepanczyk, G. Vedovato, S. Bhaumik, V.
Gayathri, G. Prodi, F. Salemi, E. Milotti, I. Bartos, S. Klimenko
|
Search for binary black hole mergers in the third observing run of
Advanced LIGO-Virgo using coherent WaveBurst enhanced with machine learning
|
11 pages, 8 figures. arXiv admin note: text overlap with
arXiv:2105.04739
| null |
10.1103/PhysRevD.105.083018
|
LIGO-P2100421
|
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this work, we use the coherent WaveBurst (cWB) pipeline enhanced with
machine learning (ML) to search for binary black hole (BBH) mergers in the
Advanced LIGO-Virgo strain data from the third observing run (O3). We detect,
with equivalent or higher significance, all gravitational-wave (GW) events
previously reported by the standard cWB search for BBH mergers in the third GW
Transient Catalog (GWTC-3). The ML-enhanced cWB search identifies five
additional GW candidate events from the catalog that were previously missed by
the standard cWB search. Moreover, we identify three marginal candidate events
not listed in GWTC-3. For simulated events distributed uniformly in a fiducial
volume, we improve the detection efficiency with respect to the standard cWB
search by approximately $20\%$ for both stellar-mass and intermediate mass
black hole binary mergers, detected with a false-alarm rate less than
$1\,\mathrm{yr}^{-1}$. We show the robustness of the ML-enhanced search for
detection of generic BBH signals by reporting increased sensitivity to the
spin-precessing and eccentric BBH events as compared to the standard cWB
search. Furthermore, we compare the improvement of the ML-enhanced cWB search
for different detector networks.
|
[
{
"created": "Wed, 5 Jan 2022 08:20:02 GMT",
"version": "v1"
}
] |
2022-05-11
|
[
[
"Mishra",
"T.",
""
],
[
"O'Brien",
"B.",
""
],
[
"Szczepanczyk",
"M.",
""
],
[
"Vedovato",
"G.",
""
],
[
"Bhaumik",
"S.",
""
],
[
"Gayathri",
"V.",
""
],
[
"Prodi",
"G.",
""
],
[
"Salemi",
"F.",
""
],
[
"Milotti",
"E.",
""
],
[
"Bartos",
"I.",
""
],
[
"Klimenko",
"S.",
""
]
] |
In this work, we use the coherent WaveBurst (cWB) pipeline enhanced with machine learning (ML) to search for binary black hole (BBH) mergers in the Advanced LIGO-Virgo strain data from the third observing run (O3). We detect, with equivalent or higher significance, all gravitational-wave (GW) events previously reported by the standard cWB search for BBH mergers in the third GW Transient Catalog (GWTC-3). The ML-enhanced cWB search identifies five additional GW candidate events from the catalog that were previously missed by the standard cWB search. Moreover, we identify three marginal candidate events not listed in GWTC-3. For simulated events distributed uniformly in a fiducial volume, we improve the detection efficiency with respect to the standard cWB search by approximately $20\%$ for both stellar-mass and intermediate mass black hole binary mergers, detected with a false-alarm rate less than $1\,\mathrm{yr}^{-1}$. We show the robustness of the ML-enhanced search for detection of generic BBH signals by reporting increased sensitivity to the spin-precessing and eccentric BBH events as compared to the standard cWB search. Furthermore, we compare the improvement of the ML-enhanced cWB search for different detector networks.
|
1105.6269
|
Brahim Lamine
|
B. Lamine, J.-M. Courty, S. Reynaud, M.-T. Jaekel
|
Testing gravity law in the solar system
|
Proceedings of Journ\'ees 2010 "Syst\`emes de r\'ef\'erence
spatio-temporels", New challenges for reference systems and numerical
standards in astronomy
|
New challenges for reference systems and numerical standards in
astronomy (Observatoire de Paris, 2011) p.270-273
| null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The predictions of General relativity (GR) are in good agreement with
observations in the solar system. Nevertheless, unexpected anomalies appeared
during the last decades, along with the increasing precision of measurements.
Those anomalies are present in spacecraft tracking data (Pioneer and flyby
anomalies) as well as ephemerides. In addition, the whole theory is challenged
at galactic and cosmic scales with the dark matter and dark energy issues.
Finally, the unification in the framework of quantum field theories remains an
open question, whose solution will certainly lead to modifications of the
theory, even at large distances. As long as those "dark sides" of the universe
have no universally accepted interpretation nor are they observed through other
means than the gravitational anomalies they have been designed to cure, these
anomalies may as well be interpreted as deviations from GR. In this context,
there is a strong motivation for improved and more systematic tests of GR
inside the solar system, with the aim to bridge the gap between gravity
experiments in the solar system and observations at much larger scales. We
review a family of metric extensions of GR which preserve the equivalence
principle but modify the coupling between energy and curvature and provide a
phenomenological framework which generalizes the PPN framework and "fifth
force" extensions of GR. We briefly discuss some possible observational
consequences in connection with highly accurate ephemerides.
|
[
{
"created": "Tue, 31 May 2011 13:22:52 GMT",
"version": "v1"
}
] |
2014-09-16
|
[
[
"Lamine",
"B.",
""
],
[
"Courty",
"J. -M.",
""
],
[
"Reynaud",
"S.",
""
],
[
"Jaekel",
"M. -T.",
""
]
] |
The predictions of General relativity (GR) are in good agreement with observations in the solar system. Nevertheless, unexpected anomalies appeared during the last decades, along with the increasing precision of measurements. Those anomalies are present in spacecraft tracking data (Pioneer and flyby anomalies) as well as ephemerides. In addition, the whole theory is challenged at galactic and cosmic scales with the dark matter and dark energy issues. Finally, the unification in the framework of quantum field theories remains an open question, whose solution will certainly lead to modifications of the theory, even at large distances. As long as those "dark sides" of the universe have no universally accepted interpretation nor are they observed through other means than the gravitational anomalies they have been designed to cure, these anomalies may as well be interpreted as deviations from GR. In this context, there is a strong motivation for improved and more systematic tests of GR inside the solar system, with the aim to bridge the gap between gravity experiments in the solar system and observations at much larger scales. We review a family of metric extensions of GR which preserve the equivalence principle but modify the coupling between energy and curvature and provide a phenomenological framework which generalizes the PPN framework and "fifth force" extensions of GR. We briefly discuss some possible observational consequences in connection with highly accurate ephemerides.
|
2001.02368
|
Vipin Dubey
|
Umesh Kumar Sharma and Vipin Chandra Dubey
|
Interacting R\'enyi holographic dark energy with parametrization on the
interaction term
|
23 pages, 12 figures
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In the present work, we study the R$\acute{e}$nyi holographic dark energy
model (RHDE) in a flat FRW Universe where the infrared cut-off is taken care by
the Hubble horizon and also by taking three different parametrizations of the
interaction term between the dark matter and the dark energy. Analyzing
graphically, the behavior of some cosmological parameters in particular
deceleration parameter, equation of state (EoS) parameter, energy density
parameter and squared speed of sound, in the process of the cosmic evolution,
is found to be leading towards the late-time accelerated expansion of the RHDE
model.
|
[
{
"created": "Tue, 7 Jan 2020 12:51:29 GMT",
"version": "v1"
},
{
"created": "Sat, 28 Nov 2020 11:12:12 GMT",
"version": "v2"
}
] |
2020-12-01
|
[
[
"Sharma",
"Umesh Kumar",
""
],
[
"Dubey",
"Vipin Chandra",
""
]
] |
In the present work, we study the R$\acute{e}$nyi holographic dark energy model (RHDE) in a flat FRW Universe where the infrared cut-off is taken care by the Hubble horizon and also by taking three different parametrizations of the interaction term between the dark matter and the dark energy. Analyzing graphically, the behavior of some cosmological parameters in particular deceleration parameter, equation of state (EoS) parameter, energy density parameter and squared speed of sound, in the process of the cosmic evolution, is found to be leading towards the late-time accelerated expansion of the RHDE model.
|
2312.08508
|
Aurora Ireland
|
Aurora Ireland, Stefano Profumo, Jordan Scharnhorst
|
Gravitational Waves from Primordial Black Hole Evaporation with Large
Extra Dimensions
|
27 pages, 6 figures
| null | null | null |
gr-qc astro-ph.CO hep-ph
|
http://creativecommons.org/licenses/by/4.0/
|
The spectra of gravitational waves from black hole evaporation generically
peak at frequencies of order the Hawking temperature, making this signal
ultra-high frequency for primordial black holes evaporating in the early
universe. This motivates us to consider small black holes in theories with
large extra dimensions, for which the peak frequency can be lowered
substantially, since the true bulk Planck scale $M_*$ can be much smaller than
the effective $M_{\rm Pl}$. We study the emission of brane-localized gravitons
during the Hawking evaporation of ultra-light primordial black holes in the
context of theories with large extra dimensions, with the ultimate goal of
computing the contribution to the stochastic gravitational wave background. To
accurately model black hole evolution, we compute greybody factors for all
particle species emitted on the brane and in the bulk, presuming the majority
of emission proceeds during the Schwarzschild phase. We then compute the power
spectrum and present day spectral density parameter for brane-localized
gravitons contributing to a gravitational wave signal. We find that for an
optimal choice of parameters, the peak frequency plateaus in the sub-MHz
regime, within range of planned high-frequency gravitational wave detectors,
making this scenario a target for detection once their sensitivity exceeds
$\Delta N_{\rm eff}$ bounds.
|
[
{
"created": "Wed, 13 Dec 2023 20:45:43 GMT",
"version": "v1"
}
] |
2023-12-15
|
[
[
"Ireland",
"Aurora",
""
],
[
"Profumo",
"Stefano",
""
],
[
"Scharnhorst",
"Jordan",
""
]
] |
The spectra of gravitational waves from black hole evaporation generically peak at frequencies of order the Hawking temperature, making this signal ultra-high frequency for primordial black holes evaporating in the early universe. This motivates us to consider small black holes in theories with large extra dimensions, for which the peak frequency can be lowered substantially, since the true bulk Planck scale $M_*$ can be much smaller than the effective $M_{\rm Pl}$. We study the emission of brane-localized gravitons during the Hawking evaporation of ultra-light primordial black holes in the context of theories with large extra dimensions, with the ultimate goal of computing the contribution to the stochastic gravitational wave background. To accurately model black hole evolution, we compute greybody factors for all particle species emitted on the brane and in the bulk, presuming the majority of emission proceeds during the Schwarzschild phase. We then compute the power spectrum and present day spectral density parameter for brane-localized gravitons contributing to a gravitational wave signal. We find that for an optimal choice of parameters, the peak frequency plateaus in the sub-MHz regime, within range of planned high-frequency gravitational wave detectors, making this scenario a target for detection once their sensitivity exceeds $\Delta N_{\rm eff}$ bounds.
|
1105.3810
|
Takashi Tamaki
|
Takashi Tamaki, Nobuyuki Sakai
|
Gravitating Q-balls in the Affleck-Dine mechanism
|
5 pages, 7 figures
|
Phys.Rev.D83:084046,2011
|
10.1103/PhysRevD.83.084046
| null |
gr-qc hep-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We investigate how gravity affects "Q-balls" with the Affleck-Dine potential
$V_{AD}(\phi):=\frac{m^2}{2}\phi^2[ 1+K\ln (\frac{\phi}{M})^2]$. Contrary to
the flat case, in which equilibrium solutions exist only if $K<0$, we find
three types of gravitating solutions as follows. In the case that $K<0$,
ordinary Q-ball solutions exist; there is an upper bound of the charge due to
gravity. In the case that K=0, equilibrium solutions called (mini-)boson stars
appear due to gravity; there is an upper bound of the charge, too. In the case
that $K>0$, equilibrium solutions appear, too. In this case, these solutions
are not asymptotically flat but surrounded by Q-matter. These solutions might
be important in considering a dark matter scenario in the Affleck-Dine
mechanism.
|
[
{
"created": "Thu, 19 May 2011 08:28:18 GMT",
"version": "v1"
}
] |
2015-05-28
|
[
[
"Tamaki",
"Takashi",
""
],
[
"Sakai",
"Nobuyuki",
""
]
] |
We investigate how gravity affects "Q-balls" with the Affleck-Dine potential $V_{AD}(\phi):=\frac{m^2}{2}\phi^2[ 1+K\ln (\frac{\phi}{M})^2]$. Contrary to the flat case, in which equilibrium solutions exist only if $K<0$, we find three types of gravitating solutions as follows. In the case that $K<0$, ordinary Q-ball solutions exist; there is an upper bound of the charge due to gravity. In the case that K=0, equilibrium solutions called (mini-)boson stars appear due to gravity; there is an upper bound of the charge, too. In the case that $K>0$, equilibrium solutions appear, too. In this case, these solutions are not asymptotically flat but surrounded by Q-matter. These solutions might be important in considering a dark matter scenario in the Affleck-Dine mechanism.
|
2408.07711
|
Iv\'an De Jes\'us Cortes
|
Ricardo Rosas-Rodr\'iguez and Iv\'an Cortes-Cruz
|
Cosmological functions and their relation
| null | null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In the non-metric gravity proposed by K. Krasnov, this is a theory in which
the scalar constraint of the Ashtekar's formalism is modified in such way that
the cosmological constant is replaced by a cosmological function that depends
of the canonical variables $A_{a}{}^{i}$ and $E_{i}{}^{a}$, the General
Relativity (GR) is the particular case when the cosmological function is a
constant. Some years ago inspired by this theory Rosas-Rodr\'iguez proposed two
cosmological functions, one for the Ashtekar's formalism and the other for the
ADM formalism. In this paper we show that this cosmological functions are
related thought the three-dimensional Ricci scalar.
|
[
{
"created": "Tue, 13 Aug 2024 19:53:26 GMT",
"version": "v1"
}
] |
2024-08-16
|
[
[
"Rosas-Rodríguez",
"Ricardo",
""
],
[
"Cortes-Cruz",
"Iván",
""
]
] |
In the non-metric gravity proposed by K. Krasnov, this is a theory in which the scalar constraint of the Ashtekar's formalism is modified in such way that the cosmological constant is replaced by a cosmological function that depends of the canonical variables $A_{a}{}^{i}$ and $E_{i}{}^{a}$, the General Relativity (GR) is the particular case when the cosmological function is a constant. Some years ago inspired by this theory Rosas-Rodr\'iguez proposed two cosmological functions, one for the Ashtekar's formalism and the other for the ADM formalism. In this paper we show that this cosmological functions are related thought the three-dimensional Ricci scalar.
|
1712.08762
|
Marko Sossich
|
Sumarna Haroon, Mubasher Jamil, Kai Lin, Petar Pavlovic, Marko Sossich
and Anzhong Wang
|
The Effects of Running Gravitational Coupling On Rotating Black Holes
|
32 pages, 16 figures, to be published in EPJC
|
Eur. Phys. J. C (2018) 78:519
|
10.1140/epjc/s10052-018-5986-7
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this work we investigate the consequences of running gravitational
coupling on the properties of rotating black holes. Apart from the changes
induced in the space-time structure of such black holes, we also study the
implications to Penrose process and geodetic precession. We are motivated by
the functional form of gravitational coupling previously investigated in the
context of infra-red limit of asymptotic safe gravity theory. In this approach,
the involvement of a new parameter $\tilde{\xi}$ in this solution makes it
different from Schwarzschild black hole. The Killing horizon, event horizon and
singularity of the computed metric is then discussed. It is noticed that the
ergosphere is increased as $\tilde{\xi}$ increases. Considering the black hole
solution in equatorial plane, the geodesics of particles, both null and time
like cases, are explored. The effective potential is computed and graphically
analyzed for different values of parameter $\tilde{\xi}$. The energy extraction
from black hole is investigated via Penrose process. For the same values of
spin parameter, the numerical results suggest that the efficiency of Penrose
process is greater in quantum corrected gravity than in Kerr Black Hole. At the
end, a brief discussion on Lense-Thirring frequency is also done.
|
[
{
"created": "Sat, 23 Dec 2017 12:10:45 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Jan 2018 08:45:26 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Jun 2018 11:20:31 GMT",
"version": "v3"
}
] |
2018-06-29
|
[
[
"Haroon",
"Sumarna",
""
],
[
"Jamil",
"Mubasher",
""
],
[
"Lin",
"Kai",
""
],
[
"Pavlovic",
"Petar",
""
],
[
"Sossich",
"Marko",
""
],
[
"Wang",
"Anzhong",
""
]
] |
In this work we investigate the consequences of running gravitational coupling on the properties of rotating black holes. Apart from the changes induced in the space-time structure of such black holes, we also study the implications to Penrose process and geodetic precession. We are motivated by the functional form of gravitational coupling previously investigated in the context of infra-red limit of asymptotic safe gravity theory. In this approach, the involvement of a new parameter $\tilde{\xi}$ in this solution makes it different from Schwarzschild black hole. The Killing horizon, event horizon and singularity of the computed metric is then discussed. It is noticed that the ergosphere is increased as $\tilde{\xi}$ increases. Considering the black hole solution in equatorial plane, the geodesics of particles, both null and time like cases, are explored. The effective potential is computed and graphically analyzed for different values of parameter $\tilde{\xi}$. The energy extraction from black hole is investigated via Penrose process. For the same values of spin parameter, the numerical results suggest that the efficiency of Penrose process is greater in quantum corrected gravity than in Kerr Black Hole. At the end, a brief discussion on Lense-Thirring frequency is also done.
|
gr-qc/0403078
|
David Garfinkle
|
David Garfinkle
|
Numerical simulation of a possible counterexample to cosmic censorship
|
discussion clarified
|
Phys.Rev. D69 (2004) 124017
|
10.1103/PhysRevD.69.124017
| null |
gr-qc hep-th
| null |
A numerical simulation is presented here of the evolution of initial data of
the kind that was conjectured by Hertog, Horowitz and Maeda to be a violation
of cosmic censorship. That initial data is essentially a thick domain wall
connecting two regions of anti-deSitter space. The initial data has a free
parameter that is the initial size of the wall. The simulation shows no
violation of cosmic censorship, but rather the formation of a small black hole.
The simulation described here is for a moderate wall size and leaves open the
possibility that cosmic censorship might be violated for larger walls.
|
[
{
"created": "Wed, 17 Mar 2004 23:36:42 GMT",
"version": "v1"
},
{
"created": "Sun, 21 Mar 2004 00:59:01 GMT",
"version": "v2"
},
{
"created": "Fri, 6 Aug 2004 18:59:54 GMT",
"version": "v3"
}
] |
2009-11-10
|
[
[
"Garfinkle",
"David",
""
]
] |
A numerical simulation is presented here of the evolution of initial data of the kind that was conjectured by Hertog, Horowitz and Maeda to be a violation of cosmic censorship. That initial data is essentially a thick domain wall connecting two regions of anti-deSitter space. The initial data has a free parameter that is the initial size of the wall. The simulation shows no violation of cosmic censorship, but rather the formation of a small black hole. The simulation described here is for a moderate wall size and leaves open the possibility that cosmic censorship might be violated for larger walls.
|
0903.5311
|
Emanuele Berti
|
Emanuele Berti, Vitor Cardoso, Paolo Pani
|
Breit-Wigner resonances and the quasinormal modes of anti-de Sitter
black holes
|
5 pages, 2 tables, 3 figures
|
Phys.Rev.D79:101501,2009
|
10.1103/PhysRevD.79.101501
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The purpose of this short communication is to show that the theory of
Breit-Wigner resonances can be used as an efficient numerical tool to compute
black hole quasinormal modes. For illustration we focus on the Schwarzschild
anti-de Sitter (SAdS) spacetime. The resonance method is better suited to small
SAdS black holes than the traditional series expansion method, allowing us to
confirm that the damping timescale of small SAdS black holes for scalar and
gravitational fields is proportional to r_+^(-2l-2), where r_+ is the horizon
radius. The proportionality coefficients are in good agreement with analytic
calculations. We also examine the eikonal limit of SAdS quasinormal modes,
confirming quantitatively Festuccia and Liu's prediction of the existence of
very long-lived modes in asymptotically AdS spacetimes. Our results are
particularly relevant for the AdS/CFT correspondence, since long-lived modes
presumably dominate the decay timescale of the perturbations.
|
[
{
"created": "Mon, 30 Mar 2009 20:21:24 GMT",
"version": "v1"
}
] |
2009-07-30
|
[
[
"Berti",
"Emanuele",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Pani",
"Paolo",
""
]
] |
The purpose of this short communication is to show that the theory of Breit-Wigner resonances can be used as an efficient numerical tool to compute black hole quasinormal modes. For illustration we focus on the Schwarzschild anti-de Sitter (SAdS) spacetime. The resonance method is better suited to small SAdS black holes than the traditional series expansion method, allowing us to confirm that the damping timescale of small SAdS black holes for scalar and gravitational fields is proportional to r_+^(-2l-2), where r_+ is the horizon radius. The proportionality coefficients are in good agreement with analytic calculations. We also examine the eikonal limit of SAdS quasinormal modes, confirming quantitatively Festuccia and Liu's prediction of the existence of very long-lived modes in asymptotically AdS spacetimes. Our results are particularly relevant for the AdS/CFT correspondence, since long-lived modes presumably dominate the decay timescale of the perturbations.
|
2109.10615
|
Tsutomu Kobayashi
|
Aya Iyonaga, Tsutomu Kobayashi
|
Distinguishing modified gravity with just two tensorial degrees of
freedom from general relativity: Black holes, cosmology, and matter coupling
|
14 pages, 2 figures
| null |
10.1103/PhysRevD.104.124020
|
RUP-21-16
|
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
We consider spatially covariant modified gravity in which the would-be scalar
degree of freedom is made non-dynamical and hence there are just two tensorial
degrees of freedom, i.e., the same number of dynamical degrees of freedom as in
general relativity. Focusing on a class of such modified gravity theories
characterized by three functions of time, we discuss how modified gravity with
two tensorial degrees of freedom can be distinguished observationally or
phenomenologically from general relativity. It is checked that the theory gives
the same predictions as general relativity for weak gravitational fields and
the propagation speed of gravitational waves. We also find that there is no
modification to asymptotically flat black hole solutions. Due to a large degree
of freedom to choose the time-dependent functions in the theory, the
homogeneous and isotropic cosmological dynamics can be made close to or even
identical to that of the $\Lambda$CDM model. We investigate the behavior of
cosmological perturbations in the long and short wavelength limits and show
that in both limits the effects of modified gravity appear only through the
modification of the background evolution. Finally, it is remarked that in the
presence of a galileon field in the matter sector, the scalar degree of freedom
is revived, ruining the essential feature of the theory.
|
[
{
"created": "Wed, 22 Sep 2021 09:28:22 GMT",
"version": "v1"
}
] |
2021-12-15
|
[
[
"Iyonaga",
"Aya",
""
],
[
"Kobayashi",
"Tsutomu",
""
]
] |
We consider spatially covariant modified gravity in which the would-be scalar degree of freedom is made non-dynamical and hence there are just two tensorial degrees of freedom, i.e., the same number of dynamical degrees of freedom as in general relativity. Focusing on a class of such modified gravity theories characterized by three functions of time, we discuss how modified gravity with two tensorial degrees of freedom can be distinguished observationally or phenomenologically from general relativity. It is checked that the theory gives the same predictions as general relativity for weak gravitational fields and the propagation speed of gravitational waves. We also find that there is no modification to asymptotically flat black hole solutions. Due to a large degree of freedom to choose the time-dependent functions in the theory, the homogeneous and isotropic cosmological dynamics can be made close to or even identical to that of the $\Lambda$CDM model. We investigate the behavior of cosmological perturbations in the long and short wavelength limits and show that in both limits the effects of modified gravity appear only through the modification of the background evolution. Finally, it is remarked that in the presence of a galileon field in the matter sector, the scalar degree of freedom is revived, ruining the essential feature of the theory.
|
0905.4182
|
Masato Minamitsuji
|
Bum-Hoon Lee, Wonwoo Lee, Masato Minamitsuji
|
Domain wall universe in the Einstein-Born-Infeld theory
|
8 pages, the version to be published in PLB
|
Phys.Lett.B679:160-166,2009
|
10.1016/j.physletb.2009.07.026
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this Letter, we discuss the dynamics of a domain wall universe embedded
into the charged black hole spacetime of the Einstein-Born-Infeld (EBI) theory.
There are four kinds of possible spacetime structures, i.e., those with no
horizon, the extremal one, those with two horizons (as the
Reissner-Nordstr$\rm{\ddot o}$m black hole), and those with a single horizon
(as the Schwarzshild black hole). We derive the effective cosmological
equations on the wall. In contrast to the previous works, we take the
contribution of the electrostatic energy on the wall into account. By examining
the properties of the effective potential, we find that a bounce can always
happen outside the (outer) horizon. For larger masses of the black hole, the
height of the barrier between the horizon and bouncing point in the effective
potential becomes smaller, leading to longer time scales of bouncing process.
These results are compared with those in the previous works.
|
[
{
"created": "Tue, 26 May 2009 12:17:13 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Jun 2009 05:00:35 GMT",
"version": "v2"
},
{
"created": "Sat, 25 Jul 2009 11:57:52 GMT",
"version": "v3"
}
] |
2010-04-30
|
[
[
"Lee",
"Bum-Hoon",
""
],
[
"Lee",
"Wonwoo",
""
],
[
"Minamitsuji",
"Masato",
""
]
] |
In this Letter, we discuss the dynamics of a domain wall universe embedded into the charged black hole spacetime of the Einstein-Born-Infeld (EBI) theory. There are four kinds of possible spacetime structures, i.e., those with no horizon, the extremal one, those with two horizons (as the Reissner-Nordstr$\rm{\ddot o}$m black hole), and those with a single horizon (as the Schwarzshild black hole). We derive the effective cosmological equations on the wall. In contrast to the previous works, we take the contribution of the electrostatic energy on the wall into account. By examining the properties of the effective potential, we find that a bounce can always happen outside the (outer) horizon. For larger masses of the black hole, the height of the barrier between the horizon and bouncing point in the effective potential becomes smaller, leading to longer time scales of bouncing process. These results are compared with those in the previous works.
|
1009.5059
|
Hossein Farajollahi
|
H.Farajollahi, M.Farhoudi, A.Salehi, H.Shojaie
|
Chameleonic Generalized Brans--Dicke model and late-time acceleration
|
20 pages, 15 figures, to be published in Astrophys. Space Sci. (2011)
|
Astrophys.Space Sci.337:415-423, 2012
|
10.1007/s10509-011-0837-0
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper we consider Chameleonic Generalized Brans--Dicke Cosmology in
the framework of FRW universes. The bouncing solution and phantom crossing is
investigated for the model. Two independent cosmological tests: Cosmological
Redshift Drift (CRD) and distance modulus are applied to test the model with
the observation.
|
[
{
"created": "Sun, 26 Sep 2010 04:38:19 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Aug 2011 11:30:52 GMT",
"version": "v2"
}
] |
2012-01-20
|
[
[
"Farajollahi",
"H.",
""
],
[
"Farhoudi",
"M.",
""
],
[
"Salehi",
"A.",
""
],
[
"Shojaie",
"H.",
""
]
] |
In this paper we consider Chameleonic Generalized Brans--Dicke Cosmology in the framework of FRW universes. The bouncing solution and phantom crossing is investigated for the model. Two independent cosmological tests: Cosmological Redshift Drift (CRD) and distance modulus are applied to test the model with the observation.
|
2011.02440
|
Philip D. Mannheim
|
Asanka Amarasinghe and Philip D. Mannheim
|
Cosmological Fluctuations on the Light Cone
|
21 pages. Final version, to appear in Phys. Rev. D
|
Phys. Rev. D 103, 103517 (2021)
|
10.1103/PhysRevD.103.103517
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In studying temperature fluctuations in the cosmic microwave background
Weinberg has noted that some ease of calculation and insight can be achieved by
looking at the structure of the perturbed light cone on which the perturbed
photons propagate. In his approach Weinberg worked in a specific gauge and
specialized to fluctuations around the standard Robertson-Walker cosmological
model with vanishing spatial three-curvature. In this paper we generalize this
analysis by providing a gauge invariant treatment in which no choice of gauge
is made, and by considering geometries with non-vanishing spatial
three-curvature. By using the scalar, vector, tensor fluctuation basis we find
that the relevant gauge invariant combinations that appear in the light cone
temperature fluctuations have no explicit dependence on the spatial curvature
even if the spatial curvature of the background geometry is nonvanishing. We
find that a not previously considered, albeit not too consequential,
temperature fluctuation at the observer has to be included in order to enforce
gauge invariance. As well as working with comoving time we also work with
conformal time in which a background metric of any given spatial
three-curvature can be written as a time-dependent conformal factor (the
comoving time expansion radius as written in conformal time) times a static
Robertson-Walker geometry of the same spatial three-curvature. For temperature
fluctuations on the light cone this conformal factor drops out identically.
Thus the gauge invariant combinations that appear in the photon temperature
fluctuations have no explicit dependence on either the conformal factor or the
spatial three-curvature at all.
|
[
{
"created": "Wed, 4 Nov 2020 17:45:36 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Apr 2021 11:45:15 GMT",
"version": "v2"
}
] |
2021-05-19
|
[
[
"Amarasinghe",
"Asanka",
""
],
[
"Mannheim",
"Philip D.",
""
]
] |
In studying temperature fluctuations in the cosmic microwave background Weinberg has noted that some ease of calculation and insight can be achieved by looking at the structure of the perturbed light cone on which the perturbed photons propagate. In his approach Weinberg worked in a specific gauge and specialized to fluctuations around the standard Robertson-Walker cosmological model with vanishing spatial three-curvature. In this paper we generalize this analysis by providing a gauge invariant treatment in which no choice of gauge is made, and by considering geometries with non-vanishing spatial three-curvature. By using the scalar, vector, tensor fluctuation basis we find that the relevant gauge invariant combinations that appear in the light cone temperature fluctuations have no explicit dependence on the spatial curvature even if the spatial curvature of the background geometry is nonvanishing. We find that a not previously considered, albeit not too consequential, temperature fluctuation at the observer has to be included in order to enforce gauge invariance. As well as working with comoving time we also work with conformal time in which a background metric of any given spatial three-curvature can be written as a time-dependent conformal factor (the comoving time expansion radius as written in conformal time) times a static Robertson-Walker geometry of the same spatial three-curvature. For temperature fluctuations on the light cone this conformal factor drops out identically. Thus the gauge invariant combinations that appear in the photon temperature fluctuations have no explicit dependence on either the conformal factor or the spatial three-curvature at all.
|
gr-qc/9801027
|
Stephen M. Merkowitz
|
Stephen M. Merkowitz and Warren W. Johnson
|
Deconvolving the information from an imperfect spherical gravitational
wave antenna
|
5 pages, 2 figures, to be published in Europhysics Letters
|
Europhys.Lett. 41 (1998) 355
|
10.1209/epl/i1998-00156-5
| null |
gr-qc
| null |
We have studied the effects of imperfections in spherical gravitational wave
antenna on our ability to properly interpret the data it will produce. The
results of a numerical simulation are reported that quantitatively describe the
systematic errors resulting from imperfections in various components of the
antenna. In addition, the results of measurements on a room-temperature
prototype are presented that verify it is possible to accurately deconvolve the
data in practice.
|
[
{
"created": "Fri, 9 Jan 1998 16:15:58 GMT",
"version": "v1"
}
] |
2009-10-31
|
[
[
"Merkowitz",
"Stephen M.",
""
],
[
"Johnson",
"Warren W.",
""
]
] |
We have studied the effects of imperfections in spherical gravitational wave antenna on our ability to properly interpret the data it will produce. The results of a numerical simulation are reported that quantitatively describe the systematic errors resulting from imperfections in various components of the antenna. In addition, the results of measurements on a room-temperature prototype are presented that verify it is possible to accurately deconvolve the data in practice.
|
1501.00435
|
Giorgio Torrieri
|
Giorgio Torrieri
|
Holography in a background-independent effective theory
|
Matches published version
| null | null | null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We discuss the meaning of the strong equivalence principle when applied to a
quantum field theory. We show that, because of unitary inequivalence of
accelerated frames, the only way for the equivalence principle to apply exactly
is to add a boundary term representing the decoherence of degrees of freedom
leaving the observable region of the bulk. We formulate the constraints
necessary for the equivalence principle to hold at the level of the partition
function and argue that, when the non-unitary part is expressed as a functional
integral over the horizon, holography arises naturally as a consequence of the
equivalence principle.
|
[
{
"created": "Fri, 2 Jan 2015 16:38:56 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Mar 2015 19:50:50 GMT",
"version": "v2"
},
{
"created": "Mon, 27 Jul 2015 11:09:15 GMT",
"version": "v3"
}
] |
2015-07-28
|
[
[
"Torrieri",
"Giorgio",
""
]
] |
We discuss the meaning of the strong equivalence principle when applied to a quantum field theory. We show that, because of unitary inequivalence of accelerated frames, the only way for the equivalence principle to apply exactly is to add a boundary term representing the decoherence of degrees of freedom leaving the observable region of the bulk. We formulate the constraints necessary for the equivalence principle to hold at the level of the partition function and argue that, when the non-unitary part is expressed as a functional integral over the horizon, holography arises naturally as a consequence of the equivalence principle.
|
2010.07660
|
Sinya Aoki
|
Sinya Aoki, Tetsuya Onogi, Shuichi Yokoyama
|
Charge Conservation, Entropy Current, and Gravitation
|
14 pages, 2 figures, published version
|
International Journal of Modern Physics A Volume 36 (2021) 2150201
|
10.1142/S0217751X21502018
|
YITP-20-135, OU-HET-1076
|
gr-qc cond-mat.stat-mech hep-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We propose a new class of vector fields to construct a conserved charge in a
general field theory whose energy momentum tensor is covariantly conserved. We
show that there always exists such a vector field in a given field theory even
without global symmetry. We also argue that the conserved current constructed
from the (asymptotically) time-like vector field can be identified with the
entropy current of the system. As a piece of evidence we show that the
conserved charge defined therefrom satisfies the first law of thermodynamics
for an isotropic system with a suitable definition of temperature. We apply our
formulation to several gravitational systems such as the expanding universe,
Schwarzschild and BTZ black holes, and gravitational plane waves. We confirm
the conservation of the proposed entropy density under any homogeneous and
isotropic expansion of the universe, the precise reproduction of the
Bekenstein-Hawking entropy incorporating the first law of thermodynamics, and
the existence of gravitational plane wave carrying no charge, respectively. We
also comment on the energy conservation during gravitational collapse in simple
models.
|
[
{
"created": "Thu, 15 Oct 2020 11:00:32 GMT",
"version": "v1"
},
{
"created": "Thu, 20 May 2021 12:55:22 GMT",
"version": "v2"
},
{
"created": "Thu, 2 Dec 2021 01:20:37 GMT",
"version": "v3"
}
] |
2021-12-03
|
[
[
"Aoki",
"Sinya",
""
],
[
"Onogi",
"Tetsuya",
""
],
[
"Yokoyama",
"Shuichi",
""
]
] |
We propose a new class of vector fields to construct a conserved charge in a general field theory whose energy momentum tensor is covariantly conserved. We show that there always exists such a vector field in a given field theory even without global symmetry. We also argue that the conserved current constructed from the (asymptotically) time-like vector field can be identified with the entropy current of the system. As a piece of evidence we show that the conserved charge defined therefrom satisfies the first law of thermodynamics for an isotropic system with a suitable definition of temperature. We apply our formulation to several gravitational systems such as the expanding universe, Schwarzschild and BTZ black holes, and gravitational plane waves. We confirm the conservation of the proposed entropy density under any homogeneous and isotropic expansion of the universe, the precise reproduction of the Bekenstein-Hawking entropy incorporating the first law of thermodynamics, and the existence of gravitational plane wave carrying no charge, respectively. We also comment on the energy conservation during gravitational collapse in simple models.
|
1506.03690
|
Farruh Atamurotov
|
Farruh Atamurotov, Sushant G. Ghosh, Bobomurat Ahmedov
|
Horizon structure of rotating Einstein-Born-Infeld black holes and
shadow
|
13 pages, 12 figures
| null |
10.1140/epjc/s10052-016-4122-9
| null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We investigate the horizon structure of the rotating Einstein-Born-Infeld
solution which goes over to the Einstein-Maxwell's Kerr-Newman solution as the
Born-Infeld parameter goes to infinity ($\beta \rightarrow \infty$). We find
that for a given $\beta$, mass $M$ and charge $Q$, there exist critical
spinning parameter $a_{E}$ and $r_{H}^{E}$, which corresponds to an extremal
Einstein-Born-Infeld black hole with degenerate horizons, and $a_{E}$ decreases
and $r_{H}^{E}$ increases with increase in the Born-Infeld parameter $\beta$.
While $a<a_{E}$ describe a non-extremal Einstein-Born-Infeld black hole with
outer and inner horizons. Similarly, the effect of $\beta$ on infinite redshift
surface and in turn on ergoregion is also included. It is well known that a
black hole can cast a shadow as an optical appearance due to its strong
gravitational field. We also investigate the shadow cast by the non-rotating
($a=0$) Einstein-Born-Infeld black hole and demonstrate that the null geodesic
equations can be integrated that allows us to investigate the shadow cast by a
black hole which is found to be a dark zone covered by a circle. Interestingly,
the shadow of the Einstein-Born-Infeld black hole is slightly smaller than for
the Reissner-Nordstrom black hole. F urther, the shadow is concentric circles
whose radius decreases with increase in value of parameter $\beta$.
|
[
{
"created": "Thu, 11 Jun 2015 14:36:49 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Jun 2015 11:29:45 GMT",
"version": "v2"
}
] |
2016-06-22
|
[
[
"Atamurotov",
"Farruh",
""
],
[
"Ghosh",
"Sushant G.",
""
],
[
"Ahmedov",
"Bobomurat",
""
]
] |
We investigate the horizon structure of the rotating Einstein-Born-Infeld solution which goes over to the Einstein-Maxwell's Kerr-Newman solution as the Born-Infeld parameter goes to infinity ($\beta \rightarrow \infty$). We find that for a given $\beta$, mass $M$ and charge $Q$, there exist critical spinning parameter $a_{E}$ and $r_{H}^{E}$, which corresponds to an extremal Einstein-Born-Infeld black hole with degenerate horizons, and $a_{E}$ decreases and $r_{H}^{E}$ increases with increase in the Born-Infeld parameter $\beta$. While $a<a_{E}$ describe a non-extremal Einstein-Born-Infeld black hole with outer and inner horizons. Similarly, the effect of $\beta$ on infinite redshift surface and in turn on ergoregion is also included. It is well known that a black hole can cast a shadow as an optical appearance due to its strong gravitational field. We also investigate the shadow cast by the non-rotating ($a=0$) Einstein-Born-Infeld black hole and demonstrate that the null geodesic equations can be integrated that allows us to investigate the shadow cast by a black hole which is found to be a dark zone covered by a circle. Interestingly, the shadow of the Einstein-Born-Infeld black hole is slightly smaller than for the Reissner-Nordstrom black hole. F urther, the shadow is concentric circles whose radius decreases with increase in value of parameter $\beta$.
|
2406.07703
|
Fabiano Feleppa
|
Fabiano Feleppa, Valerio Bozza, Oleg Yu. Tsupko
|
Strong deflection limit analysis of black hole lensing in inhomogeneous
plasma
|
18 pages, 13 figures, 2 tables
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
This paper investigates gravitational lensing effects in the presence of
plasma in the strong deflection limit, which corresponds to light rays circling
around a compact object and forming higher-order images. While previous studies
of this case have predominantly focused on the deflection of light in a vacuum
or in the presence of a homogeneous plasma, this work introduces an analytical
treatment for the influence of a non-uniform plasma. After recalling the exact
expression for the deflection angle of photons in a static, asymptotically flat
and spherically symmetric spacetime filled with cold non-magnetized plasma, a
strong deflection limit analysis is presented. Particular attention is then
given to the case of a Schwarzschild spacetime, where the deflection angle of
photons for different density profiles of plasma is obtained. Moreover,
perturbative results for an arbitrary power-law radial density profile are also
presented. These formulae are then applied to the calculation of the positions
and magnifications of higher-order images, concluding that the presence of a
non-uniform plasma reduces both their angular size and their magnifications, at
least within the range of the power-law indices considered. These findings
contribute to the understanding of gravitational lensing in the presence of
plasma, offering a versatile framework applicable to various asymptotically
flat and spherically symmetric spacetimes.
|
[
{
"created": "Tue, 11 Jun 2024 20:30:14 GMT",
"version": "v1"
}
] |
2024-06-13
|
[
[
"Feleppa",
"Fabiano",
""
],
[
"Bozza",
"Valerio",
""
],
[
"Tsupko",
"Oleg Yu.",
""
]
] |
This paper investigates gravitational lensing effects in the presence of plasma in the strong deflection limit, which corresponds to light rays circling around a compact object and forming higher-order images. While previous studies of this case have predominantly focused on the deflection of light in a vacuum or in the presence of a homogeneous plasma, this work introduces an analytical treatment for the influence of a non-uniform plasma. After recalling the exact expression for the deflection angle of photons in a static, asymptotically flat and spherically symmetric spacetime filled with cold non-magnetized plasma, a strong deflection limit analysis is presented. Particular attention is then given to the case of a Schwarzschild spacetime, where the deflection angle of photons for different density profiles of plasma is obtained. Moreover, perturbative results for an arbitrary power-law radial density profile are also presented. These formulae are then applied to the calculation of the positions and magnifications of higher-order images, concluding that the presence of a non-uniform plasma reduces both their angular size and their magnifications, at least within the range of the power-law indices considered. These findings contribute to the understanding of gravitational lensing in the presence of plasma, offering a versatile framework applicable to various asymptotically flat and spherically symmetric spacetimes.
|
2006.06891
|
Euclides Silva
|
A. R. P. Moreira, J. E. G. Silva, D. F. S. Veras, and C. A. S. Almeida
|
Thick string-like braneworlds in f(T) gravity
|
25 pages, 11 figures
|
Int. Journ. Mod. Phys. D, 30, 2150047 (2021)
|
10.1142/S0218271821500474
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We propose a codimension two warped braneworld model within the teleparallel
$f(T)$ gravity. By assuming a global vortex as the source, we found a $l=0$
vortex solution that yields to a thick string-like brane. Asymptotically, the
bulk geometry converges to an $AdS_6$ spacetime whose cosmological constant is
produced by the torsion parameters. Furthermore, the torsion induces an
$AdS-dS$ transition on the exterior region. Inside the brane core, the torsion
produces an internal structure even for a single complex scalar field. As the
torsion parameters vary, the brane undergoes a phase transition leading to the
formation of ring-like structures. The bulk-brane Planck mass ration is
modified by the torsion. The analysis of the stress energy condition reveals a
splitting brane process satisfying the weak and strong energy conditions for
some values of the parameters. In addition, we investigate the behaviour of the
gravitational perturbations in this scenario. It turns out that the
gravitational spectrum has a linear behaviour for small masses and is
independent of the torsion parameters for large masses. In the bulk, the
torsion keeps a gapless non-localizable and stable tower of massive modes.
Inside the brane core the torsion produces new barriers and potential wells
leading to small amplitude massive modes and a massless mode localized around
the ring structures.
|
[
{
"created": "Fri, 12 Jun 2020 00:39:11 GMT",
"version": "v1"
}
] |
2021-04-29
|
[
[
"Moreira",
"A. R. P.",
""
],
[
"Silva",
"J. E. G.",
""
],
[
"Veras",
"D. F. S.",
""
],
[
"Almeida",
"C. A. S.",
""
]
] |
We propose a codimension two warped braneworld model within the teleparallel $f(T)$ gravity. By assuming a global vortex as the source, we found a $l=0$ vortex solution that yields to a thick string-like brane. Asymptotically, the bulk geometry converges to an $AdS_6$ spacetime whose cosmological constant is produced by the torsion parameters. Furthermore, the torsion induces an $AdS-dS$ transition on the exterior region. Inside the brane core, the torsion produces an internal structure even for a single complex scalar field. As the torsion parameters vary, the brane undergoes a phase transition leading to the formation of ring-like structures. The bulk-brane Planck mass ration is modified by the torsion. The analysis of the stress energy condition reveals a splitting brane process satisfying the weak and strong energy conditions for some values of the parameters. In addition, we investigate the behaviour of the gravitational perturbations in this scenario. It turns out that the gravitational spectrum has a linear behaviour for small masses and is independent of the torsion parameters for large masses. In the bulk, the torsion keeps a gapless non-localizable and stable tower of massive modes. Inside the brane core the torsion produces new barriers and potential wells leading to small amplitude massive modes and a massless mode localized around the ring structures.
|
gr-qc/0701027
|
Nelson Christensen
|
F. Beauville, M.-A. Bizouard, L. Blackburn, L. Bosi, L. Brocco, D.
Brown, D. Buskulic, F. Cavalier, S. Chatterji, N. Christensen, A.-C. Clapson,
S. Fairhurst, D. Grosjean, G. Guidi, P. Hello, S. Heng, M. Hewitson, E.
Katsavounidis, S. Klimenko, M. Knight, A. Lazzarini, N. Leroy, F. Marion, J.
Markowitz, C. Melachrinos, B. Mours, F. Ricci, A. Vicer\'e, I. Yakushin, M.
Zanolin
|
Detailed comparison of LIGO and Virgo Inspiral Pipelines in Preparation
for a Joint Search
|
LIGO-Virgo Working Group. Submitted to Physical Review D
|
Class.Quant.Grav.25:045001,2008
|
10.1088/0264-9381/25/4/045001
| null |
gr-qc
| null |
Presented in this paper is a detailed and direct comparison of the LIGO and
Virgo binary neutron star detection pipelines. In order to test the search
programs, numerous inspiral signals were added to 24 hours of simulated
detector data. The efficiencies of the different pipelines were tested, and
found to be comparable. Parameter estimation routines were also tested. We
demonstrate that there are definite benefits to be had if LIGO and Virgo
conduct a joint coincident analysis; these advantages include increased
detection efficiency and the providing of source sky location information.
|
[
{
"created": "Wed, 3 Jan 2007 16:26:22 GMT",
"version": "v1"
}
] |
2008-11-26
|
[
[
"Beauville",
"F.",
""
],
[
"Bizouard",
"M. -A.",
""
],
[
"Blackburn",
"L.",
""
],
[
"Bosi",
"L.",
""
],
[
"Brocco",
"L.",
""
],
[
"Brown",
"D.",
""
],
[
"Buskulic",
"D.",
""
],
[
"Cavalier",
"F.",
""
],
[
"Chatterji",
"S.",
""
],
[
"Christensen",
"N.",
""
],
[
"Clapson",
"A. -C.",
""
],
[
"Fairhurst",
"S.",
""
],
[
"Grosjean",
"D.",
""
],
[
"Guidi",
"G.",
""
],
[
"Hello",
"P.",
""
],
[
"Heng",
"S.",
""
],
[
"Hewitson",
"M.",
""
],
[
"Katsavounidis",
"E.",
""
],
[
"Klimenko",
"S.",
""
],
[
"Knight",
"M.",
""
],
[
"Lazzarini",
"A.",
""
],
[
"Leroy",
"N.",
""
],
[
"Marion",
"F.",
""
],
[
"Markowitz",
"J.",
""
],
[
"Melachrinos",
"C.",
""
],
[
"Mours",
"B.",
""
],
[
"Ricci",
"F.",
""
],
[
"Viceré",
"A.",
""
],
[
"Yakushin",
"I.",
""
],
[
"Zanolin",
"M.",
""
]
] |
Presented in this paper is a detailed and direct comparison of the LIGO and Virgo binary neutron star detection pipelines. In order to test the search programs, numerous inspiral signals were added to 24 hours of simulated detector data. The efficiencies of the different pipelines were tested, and found to be comparable. Parameter estimation routines were also tested. We demonstrate that there are definite benefits to be had if LIGO and Virgo conduct a joint coincident analysis; these advantages include increased detection efficiency and the providing of source sky location information.
|
2305.09391
|
Parthasarathi Majumdar
|
Parthasarathi Majumdar
|
A Possible Quantum Gravity Hint in Binary Black Hole Merger
|
5 Pages Revtex 4-1, 2 jpg figures, reference added. No changes in
main body of paper
|
Physics Letters B 849, 138467 (2024)
|
10.1016/j.physletb.2024.138467
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
We present a semi-rigorous justification of Bekenstein's Generalized Second
Law of Thermodynamics applicable to a universe with black holes present, based
on a generic quantum gravity formulation of a black hole spacetime, where the
bulk Hamiltonian constraint plays a central role. Specializing to Loop Quantum
Gravity, and considering the inspiral and post-ringdown stages of binary black
hole merger into a remnant black hole, we show that the Generalized Second Law
implies a lower bound on the non-perturbative LQG correction to the
Bekenstein-Hawking area law for black hole entropy. This lower bound itself is
expressed as a function of the Bekenstein-Hawking area formula for entropy.
Results of the analyses of LIGO-VIRGO-KAGRA data recently performed to verify
the Hawking Area Theorem for binary black hole merger, are shown to be entirely
consistent with this Loop Quantum Gravity-induced inequality. However, the
consistency is independent of the magnitude of the Loop Quantum Gravity
corrections to black hole entropy, depending only on the negative algebraic
sign of the quantum correction. We argue that results of alternative quantum
gravity computations of quantum black hole entropy, where the quantum entropy
exceeds the Bekenstein-Hawking value, may not share this consistency.
|
[
{
"created": "Tue, 16 May 2023 12:25:41 GMT",
"version": "v1"
},
{
"created": "Sun, 10 Sep 2023 14:35:42 GMT",
"version": "v2"
},
{
"created": "Fri, 27 Oct 2023 06:28:12 GMT",
"version": "v3"
},
{
"created": "Thu, 4 Jan 2024 06:43:08 GMT",
"version": "v4"
},
{
"created": "Fri, 5 Jan 2024 05:59:10 GMT",
"version": "v5"
}
] |
2024-04-03
|
[
[
"Majumdar",
"Parthasarathi",
""
]
] |
We present a semi-rigorous justification of Bekenstein's Generalized Second Law of Thermodynamics applicable to a universe with black holes present, based on a generic quantum gravity formulation of a black hole spacetime, where the bulk Hamiltonian constraint plays a central role. Specializing to Loop Quantum Gravity, and considering the inspiral and post-ringdown stages of binary black hole merger into a remnant black hole, we show that the Generalized Second Law implies a lower bound on the non-perturbative LQG correction to the Bekenstein-Hawking area law for black hole entropy. This lower bound itself is expressed as a function of the Bekenstein-Hawking area formula for entropy. Results of the analyses of LIGO-VIRGO-KAGRA data recently performed to verify the Hawking Area Theorem for binary black hole merger, are shown to be entirely consistent with this Loop Quantum Gravity-induced inequality. However, the consistency is independent of the magnitude of the Loop Quantum Gravity corrections to black hole entropy, depending only on the negative algebraic sign of the quantum correction. We argue that results of alternative quantum gravity computations of quantum black hole entropy, where the quantum entropy exceeds the Bekenstein-Hawking value, may not share this consistency.
|
1301.0106
|
Alan D. Rendall
|
Ho Lee and Alan D. Rendall
|
The spatially homogeneous relativistic Boltzmann equation with a hard
potential
|
21 pages
| null | null |
AEI-2013-000
|
gr-qc math.AP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we study spatially homogeneous solutions of the Boltzmann
equation in special relativity and in Robertson-Walker spacetimes. We obtain an
analogue of the Povzner inequality in the relativistic case and use it to prove
global existence theorems. We show that global solutions exist for a certain
class of collision cross sections of the hard potential type in Minkowski space
and in spatially flat Robertson-Walker spacetimes.
|
[
{
"created": "Tue, 1 Jan 2013 16:42:06 GMT",
"version": "v1"
}
] |
2013-01-03
|
[
[
"Lee",
"Ho",
""
],
[
"Rendall",
"Alan D.",
""
]
] |
In this paper, we study spatially homogeneous solutions of the Boltzmann equation in special relativity and in Robertson-Walker spacetimes. We obtain an analogue of the Povzner inequality in the relativistic case and use it to prove global existence theorems. We show that global solutions exist for a certain class of collision cross sections of the hard potential type in Minkowski space and in spatially flat Robertson-Walker spacetimes.
|
1006.5353
|
Jian-Yang Zhu
|
Li-Fang Li and Jian-Yang Zhu
|
Quantum effect on luminosity-redshift relation
|
11 pages, 3 figures; revised version
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
There are many different proposals for a theory of quantum gravity. Even
leaving aside the fundamental difference among theories such as the string
theory and the non-perturbative quantum gravity, we are still left with many
ambiguities (and/or parameters to be determined) with regard to the choice of
variables, the choice of related groups, etc. Loop quantum gravity is also in
such a state. It is interesting to search for experimental observables to
distinguish these quantum schemes. This paper investigates the loop quantum
gravity effect on luminosity-redshift relation. The quantum bounce behavior of
loop quantum cosmology is found to result in multivalued correspondence in
luminosity-redshift relation. And the detail multivalued behavior can tell the
difference of different quantum parameters. The inverse volume quantum
correction does not result in bounce behavior in this model, but affects
luminosity-redshift relation also significantly.
|
[
{
"created": "Mon, 28 Jun 2010 14:00:31 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Jul 2010 16:22:52 GMT",
"version": "v2"
}
] |
2010-07-12
|
[
[
"Li",
"Li-Fang",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] |
There are many different proposals for a theory of quantum gravity. Even leaving aside the fundamental difference among theories such as the string theory and the non-perturbative quantum gravity, we are still left with many ambiguities (and/or parameters to be determined) with regard to the choice of variables, the choice of related groups, etc. Loop quantum gravity is also in such a state. It is interesting to search for experimental observables to distinguish these quantum schemes. This paper investigates the loop quantum gravity effect on luminosity-redshift relation. The quantum bounce behavior of loop quantum cosmology is found to result in multivalued correspondence in luminosity-redshift relation. And the detail multivalued behavior can tell the difference of different quantum parameters. The inverse volume quantum correction does not result in bounce behavior in this model, but affects luminosity-redshift relation also significantly.
|
2009.08116
|
Shaoqi Hou
|
Shaoqi Hou, Pengbo Li, Hai Yu, Marek Biesiada, Xi-Long Fan, Seiji
Kawamura, Zong-Hong Zhu
|
Lensing rates of gravitational wave signals displaying beat patterns
detectable by DECIGO and B-DECIGO
|
15 pages, 7 figures. Revised based on Referee's comments
|
Phys. Rev. D 103, 044005 (2021)
|
10.1103/PhysRevD.103.044005
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The coherent nature of gravitational wave emanating from a compact binary
system makes it possible to detect some interference patterns in two (or more)
signals registered simultaneously by the detector. Gravitational lensing effect
can be used to bend trajectories of gravitational waves, which might reach the
detector at the same time. Once this happens, a beat pattern may form, and can
be used to obtain the luminosity distance of the source, the lens mass, and
cosmological parameters such as the Hubble constant. Crucial question is how
many such kind of events could be detected. In this work, we study this issue
for the future space-borne detectors: DECIGO and its downscale version,
B-DECIGO. It is found out that there can be a few tens to a few hundreds of
lensed gravitational wave events with the beat pattern observed by DECIGO and
B-DECIGO per year, depending on the evolution scenario leading to the formation
of double compact objects. In particular, black hole-black hole binaries are
dominating population of lensed sources in which beat patterns may reveal.
However, DECIGO could also register a considerable amount of lensed signals
from binary neutron stars, which might be accompanied by electromagnetic
counterparts. Our results suggest that, in the future, lensed gravitational
wave signal with the beat pattern could play an important role in cosmology and
astrophysics.
|
[
{
"created": "Thu, 17 Sep 2020 07:31:53 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Dec 2020 09:37:47 GMT",
"version": "v2"
},
{
"created": "Tue, 2 Feb 2021 01:52:12 GMT",
"version": "v3"
}
] |
2021-02-03
|
[
[
"Hou",
"Shaoqi",
""
],
[
"Li",
"Pengbo",
""
],
[
"Yu",
"Hai",
""
],
[
"Biesiada",
"Marek",
""
],
[
"Fan",
"Xi-Long",
""
],
[
"Kawamura",
"Seiji",
""
],
[
"Zhu",
"Zong-Hong",
""
]
] |
The coherent nature of gravitational wave emanating from a compact binary system makes it possible to detect some interference patterns in two (or more) signals registered simultaneously by the detector. Gravitational lensing effect can be used to bend trajectories of gravitational waves, which might reach the detector at the same time. Once this happens, a beat pattern may form, and can be used to obtain the luminosity distance of the source, the lens mass, and cosmological parameters such as the Hubble constant. Crucial question is how many such kind of events could be detected. In this work, we study this issue for the future space-borne detectors: DECIGO and its downscale version, B-DECIGO. It is found out that there can be a few tens to a few hundreds of lensed gravitational wave events with the beat pattern observed by DECIGO and B-DECIGO per year, depending on the evolution scenario leading to the formation of double compact objects. In particular, black hole-black hole binaries are dominating population of lensed sources in which beat patterns may reveal. However, DECIGO could also register a considerable amount of lensed signals from binary neutron stars, which might be accompanied by electromagnetic counterparts. Our results suggest that, in the future, lensed gravitational wave signal with the beat pattern could play an important role in cosmology and astrophysics.
|
1111.7185
|
Kentaro Somiya
|
Kentaro Somiya (for the KAGRA Collaboration)
|
Detector configuration of KAGRA - the Japanese cryogenic
gravitational-wave detector
|
Proceeding for the Amaldi conference, 2011. To be published in
Classical Quantum Gravity
|
Class.Quantum Grav. 29, 124007 (2012)
|
10.1088/0264-9381/29/12/124007
| null |
gr-qc physics.ins-det
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Construction of the Japanese second-generation gravitational-wave detector
KAGRA has been started. In the next 6 \sim 7 years, we will be able to observe
the space-time ripple from faraway galaxies. KAGRA is equipped with the latest
advanced technologies. The entire 3-km long detector is located in the
underground to be isolated from the seismic motion, the core optics are cooled
down to 20 K to reduce thermal fluctuations, and quantum non-demolition
techniques are used to decrease quantum noise. In this paper, we introduce the
detector configuration of KAGRA; its design, strategy, and downselection of
parameters.
|
[
{
"created": "Wed, 30 Nov 2011 14:35:31 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Mar 2012 19:17:06 GMT",
"version": "v2"
}
] |
2020-07-06
|
[
[
"Somiya",
"Kentaro",
"",
"for the KAGRA Collaboration"
]
] |
Construction of the Japanese second-generation gravitational-wave detector KAGRA has been started. In the next 6 \sim 7 years, we will be able to observe the space-time ripple from faraway galaxies. KAGRA is equipped with the latest advanced technologies. The entire 3-km long detector is located in the underground to be isolated from the seismic motion, the core optics are cooled down to 20 K to reduce thermal fluctuations, and quantum non-demolition techniques are used to decrease quantum noise. In this paper, we introduce the detector configuration of KAGRA; its design, strategy, and downselection of parameters.
|
1205.2680
|
Bruno Hartmann
|
Bruno Hartmann
|
Operationalization of Relativistic Motion
|
26 pages, 7 figures, introduction, technical details simplified
| null | null | null |
gr-qc physics.hist-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We demonstrate the definition of basic observables from physical operations,
the key to overcome hidden stumbling blocks and apparent paradoxes from
unscrutinized (classical) formalisms. We develop Helmholtz program of basic
measurements for relativistic motion. We define the basic observables by direct
comparison: "longer than" if one object or process covers the other. To express
the spatiotemporal order also numerically (how many times longer) we cover them
by a locally regular grid of light clocks. These are the basic physical
operations. From their interrelation we derive mathematical relations, e.g. for
different observers the formal Lorentz transformation; for accelerating
observers we reveal a measurement-methodical view on the apparent Twin paradox.
|
[
{
"created": "Fri, 11 May 2012 19:47:12 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Jan 2015 17:51:07 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Dec 2015 13:21:14 GMT",
"version": "v3"
}
] |
2015-12-04
|
[
[
"Hartmann",
"Bruno",
""
]
] |
We demonstrate the definition of basic observables from physical operations, the key to overcome hidden stumbling blocks and apparent paradoxes from unscrutinized (classical) formalisms. We develop Helmholtz program of basic measurements for relativistic motion. We define the basic observables by direct comparison: "longer than" if one object or process covers the other. To express the spatiotemporal order also numerically (how many times longer) we cover them by a locally regular grid of light clocks. These are the basic physical operations. From their interrelation we derive mathematical relations, e.g. for different observers the formal Lorentz transformation; for accelerating observers we reveal a measurement-methodical view on the apparent Twin paradox.
|
1307.7117
|
Mohammad Reza Setare
|
M. R. Setare, M. J. S. Houndjo, V. Kamali
|
Warm-polytropic inflationary universe model
|
13 pages, 1 figure
|
International Journal of Modern Physics D Vol. 22, No. 8 (2013)
1350041
|
10.1142/S0218271813500417
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In the present paper we study warm inflationary universe models in the
context of a polytropic gas. We derive the characteristics of this model in
slow-roll approximation and develop our model in two cases, 1- For a constant
dissipative parameter $\Gamma$. 2- $\Gamma$ as a function of scalar field
$\phi$. In these cases we will obtain exact solution for the scalar field and
Hubble parameter. We will also obtain explicit expressions for the
tensor-scalar ratio $R$, scalar spectrum index $n_s$ and its running
$\alpha_s$, in slow-roll approximation.
|
[
{
"created": "Tue, 2 Jul 2013 11:13:49 GMT",
"version": "v1"
}
] |
2015-06-16
|
[
[
"Setare",
"M. R.",
""
],
[
"Houndjo",
"M. J. S.",
""
],
[
"Kamali",
"V.",
""
]
] |
In the present paper we study warm inflationary universe models in the context of a polytropic gas. We derive the characteristics of this model in slow-roll approximation and develop our model in two cases, 1- For a constant dissipative parameter $\Gamma$. 2- $\Gamma$ as a function of scalar field $\phi$. In these cases we will obtain exact solution for the scalar field and Hubble parameter. We will also obtain explicit expressions for the tensor-scalar ratio $R$, scalar spectrum index $n_s$ and its running $\alpha_s$, in slow-roll approximation.
|
2305.06325
|
Quentin G. Bailey
|
Quentin G. Bailey
|
Testing Gravity in the Laboratory
|
25 pages, 6 figures, invited chapter for the book "Recent Progress on
Gravity Tests: Challenges and Future Perspectives", editors C. Bambi & A.
Cardenas-Avendano
| null | null | null |
gr-qc hep-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this chapter, we discuss recent work on precision Earth laboratory tests
of different aspects of gravity. In particular the discussion is focused on
those tests that can be used to probe hypothesis for physics beyond Newtonian
gravity and General Relativity. The latter includes tests of foundations like
local Lorentz invariance, Weak-Equivalence Principle tests, short-range gravity
tests, gravimeter-type tests, and other frontier possibilities like the
free-fall of anti-matter and searches for non-Riemann gravity effects. The
focus is on key results in theory, phenomenology, and experiment in the last
few decades. We describe the motivations for continued interest in precision
tests of gravity in the laboratory, including the possibility to search for
physics beyond General Relativity. Test frameworks for describing deviations
from General Relativity are emphasized, including ones based on effective field
theory, allowing for generic violations of Lorentz symmetry, CPT symmetry, and
diffeomorphism symmetry.
|
[
{
"created": "Wed, 10 May 2023 17:24:14 GMT",
"version": "v1"
}
] |
2023-05-11
|
[
[
"Bailey",
"Quentin G.",
""
]
] |
In this chapter, we discuss recent work on precision Earth laboratory tests of different aspects of gravity. In particular the discussion is focused on those tests that can be used to probe hypothesis for physics beyond Newtonian gravity and General Relativity. The latter includes tests of foundations like local Lorentz invariance, Weak-Equivalence Principle tests, short-range gravity tests, gravimeter-type tests, and other frontier possibilities like the free-fall of anti-matter and searches for non-Riemann gravity effects. The focus is on key results in theory, phenomenology, and experiment in the last few decades. We describe the motivations for continued interest in precision tests of gravity in the laboratory, including the possibility to search for physics beyond General Relativity. Test frameworks for describing deviations from General Relativity are emphasized, including ones based on effective field theory, allowing for generic violations of Lorentz symmetry, CPT symmetry, and diffeomorphism symmetry.
|
1506.08344
|
Allan Alinea
|
Allan L. Alinea, Takahiro Kubota, and Wade Naylor
|
Logarithmic divergences in the $k$-inflationary power spectra computed
through the uniform approximation
|
version 4 : extended Section 6 on remarks on logarithmic divergences
|
JCAP 02 (2016) 028
|
10.1088/1475-7516/2016/02/028
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We investigate a calculation method for solving the Mukhanov-Sasaki equation
in slow-roll $k$-inflation based on the uniform approximation (UA) in
conjunction with an expansion scheme for slow-roll parameters with respect to
the number of $e$-folds about the so-called \textit{turning point}. Earlier
works on this method has so far gained some promising results derived from the
approximating expressions for the power spectra among others, up to second
order with respect to the Hubble and sound flow parameters, when compared to
other semi-analytical approaches (e.g., Green's function and WKB methods).
However, a closer inspection is suggestive that there is a problem when
higher-order parts of the power spectra are considered; residual logarithmic
divergences may come out that can render the prediction physically
inconsistent. Looking at this possibility, we map out up to what order with
respect to the mentioned parameters several physical quantities can be
calculated before hitting a logarithmically divergent result. It turns out that
the power spectra are limited up to second order, the tensor-to-scalar ratio up
to third order, and the spectral indices and running converge to all orders.
This indicates that the expansion scheme is incompatible with the working
equations derived from UA for the power spectra but compatible with that of the
spectral indices. For those quantities that involve logarithmically divergent
terms in the higher-order parts, existing results in the literature for the
convergent lower-order parts calculated in the equivalent fashion should be
viewed with some caution; they do not rest on solid mathematical ground.
|
[
{
"created": "Sun, 28 Jun 2015 02:02:33 GMT",
"version": "v1"
},
{
"created": "Sun, 5 Jul 2015 01:29:54 GMT",
"version": "v2"
},
{
"created": "Sat, 7 Nov 2015 02:02:25 GMT",
"version": "v3"
},
{
"created": "Sun, 20 Dec 2015 12:51:24 GMT",
"version": "v4"
}
] |
2016-07-18
|
[
[
"Alinea",
"Allan L.",
""
],
[
"Kubota",
"Takahiro",
""
],
[
"Naylor",
"Wade",
""
]
] |
We investigate a calculation method for solving the Mukhanov-Sasaki equation in slow-roll $k$-inflation based on the uniform approximation (UA) in conjunction with an expansion scheme for slow-roll parameters with respect to the number of $e$-folds about the so-called \textit{turning point}. Earlier works on this method has so far gained some promising results derived from the approximating expressions for the power spectra among others, up to second order with respect to the Hubble and sound flow parameters, when compared to other semi-analytical approaches (e.g., Green's function and WKB methods). However, a closer inspection is suggestive that there is a problem when higher-order parts of the power spectra are considered; residual logarithmic divergences may come out that can render the prediction physically inconsistent. Looking at this possibility, we map out up to what order with respect to the mentioned parameters several physical quantities can be calculated before hitting a logarithmically divergent result. It turns out that the power spectra are limited up to second order, the tensor-to-scalar ratio up to third order, and the spectral indices and running converge to all orders. This indicates that the expansion scheme is incompatible with the working equations derived from UA for the power spectra but compatible with that of the spectral indices. For those quantities that involve logarithmically divergent terms in the higher-order parts, existing results in the literature for the convergent lower-order parts calculated in the equivalent fashion should be viewed with some caution; they do not rest on solid mathematical ground.
|
2007.15029
|
Marko Toros
|
Marko Toro\v{s}, Thomas W. van de Kamp, Ryan J. Marshman, M. S. Kim,
Anupam Mazumdar, Sougato Bose
|
Relative Acceleration Noise Mitigation for Nanocrystal Matter-wave
Interferometry: Application to Entangling Masses via Quantum Gravity
|
16 pages, 5 figures; accepted for publication in Physical Review
Research
|
Phys. Rev. Research 3, 023178 (2021)
|
10.1103/PhysRevResearch.3.023178
| null |
gr-qc hep-th quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Matter wave interferometers with large momentum transfers, irrespective of
specific implementations, will face a universal dephasing due to relative
accelerations between the interferometric mass and the associated apparatus.
Here we propose a solution that works even without actively tracking the
relative accelerations: putting both the interfering mass and its associated
apparatus in a freely falling capsule, so that the strongest inertial noise
components vanish due to the equivalence principle. In this setting, we
investigate two of the most important remaining noise sources: (a) the
non-inertial jitter of the experimental setup and (b) the gravity-gradient
noise. We show that the former can be reduced below desired values by
appropriate pressures and temperatures, while the latter can be fully mitigated
in a controlled environment. We finally apply the analysis to a recent proposal
for testing the quantum nature of gravity [S. Bose et. al. Phys. Rev. Lett 119,
240401 (2017)] through the entanglement of two masses undergoing
interferometry. We show that the relevant entanglement witnessing is feasible
with achievable levels of relative acceleration noise.
|
[
{
"created": "Wed, 29 Jul 2020 18:01:13 GMT",
"version": "v1"
},
{
"created": "Sun, 25 Apr 2021 13:22:38 GMT",
"version": "v2"
}
] |
2021-06-08
|
[
[
"Toroš",
"Marko",
""
],
[
"van de Kamp",
"Thomas W.",
""
],
[
"Marshman",
"Ryan J.",
""
],
[
"Kim",
"M. S.",
""
],
[
"Mazumdar",
"Anupam",
""
],
[
"Bose",
"Sougato",
""
]
] |
Matter wave interferometers with large momentum transfers, irrespective of specific implementations, will face a universal dephasing due to relative accelerations between the interferometric mass and the associated apparatus. Here we propose a solution that works even without actively tracking the relative accelerations: putting both the interfering mass and its associated apparatus in a freely falling capsule, so that the strongest inertial noise components vanish due to the equivalence principle. In this setting, we investigate two of the most important remaining noise sources: (a) the non-inertial jitter of the experimental setup and (b) the gravity-gradient noise. We show that the former can be reduced below desired values by appropriate pressures and temperatures, while the latter can be fully mitigated in a controlled environment. We finally apply the analysis to a recent proposal for testing the quantum nature of gravity [S. Bose et. al. Phys. Rev. Lett 119, 240401 (2017)] through the entanglement of two masses undergoing interferometry. We show that the relevant entanglement witnessing is feasible with achievable levels of relative acceleration noise.
|
gr-qc/9705004
|
Vanzo Luciano
|
L. Vanzo
|
Black holes with unusual topology
|
14 pages, standard latex, enlarged version, major conceptual changes,
more detailed calculations, new references added
|
Phys.Rev. D56 (1997) 6475-6483
|
10.1103/PhysRevD.56.6475
|
UTF 400
|
gr-qc
| null |
The Einstein's equations with a negative cosmological constant admit
solutions which are asymptotically anti-de Sitter space. Matter fields in
anti-de Sitter space can be in stable equilibrium even if the potential energy
is unbounded from below, violating the weak energy condition. Hence there is no
fundamental reason that black hole's horizons should have spherical topology.
In anti-de Sitter space the Einstein's equations admit black hole solutions
where the horizon can be a Riemann surface with genus $g$. The case $g=0$ is
the asymptotically anti-de Sitter black hole first studied by Hawking-Page,
which has spherical topology. The genus one black hole has a new free parameter
entering the metric, the conformal class to which the torus belongs. The genus
$g>1$ black hole has no other free parameters apart from the mass and the
charge. All such black holes exhibits a natural temperature which is identified
as the period of the Euclidean continuation and there is a mass formula
connecting the mass with the surface gravity and the horizon area of the black
hole. The Euclidean action and entropy are computed and used to argue that the
mass spectrum of states is positive definite.
|
[
{
"created": "Mon, 5 May 1997 12:47:33 GMT",
"version": "v1"
},
{
"created": "Tue, 6 May 1997 15:23:02 GMT",
"version": "v2"
},
{
"created": "Wed, 21 May 1997 11:23:17 GMT",
"version": "v3"
}
] |
2009-10-30
|
[
[
"Vanzo",
"L.",
""
]
] |
The Einstein's equations with a negative cosmological constant admit solutions which are asymptotically anti-de Sitter space. Matter fields in anti-de Sitter space can be in stable equilibrium even if the potential energy is unbounded from below, violating the weak energy condition. Hence there is no fundamental reason that black hole's horizons should have spherical topology. In anti-de Sitter space the Einstein's equations admit black hole solutions where the horizon can be a Riemann surface with genus $g$. The case $g=0$ is the asymptotically anti-de Sitter black hole first studied by Hawking-Page, which has spherical topology. The genus one black hole has a new free parameter entering the metric, the conformal class to which the torus belongs. The genus $g>1$ black hole has no other free parameters apart from the mass and the charge. All such black holes exhibits a natural temperature which is identified as the period of the Euclidean continuation and there is a mass formula connecting the mass with the surface gravity and the horizon area of the black hole. The Euclidean action and entropy are computed and used to argue that the mass spectrum of states is positive definite.
|
gr-qc/0406036
|
Plamen Fiziev
|
P.P. Fiziev, T.L. Bojadjiev, D.A. Georgieva
|
Novel Properties of Bound States of Klein-Gordon Equation in
Gravitational Field of Massive Point
|
10 pages, latex file, 10 figures, typos in the text and in the
figures corrected
| null | null |
SU-TH-04-06-01
|
gr-qc
| null |
We consider for the first time the solutions of Klein-Gordon equation in
gravitational field of {\em a massive} point source in GR. We examine
numerically the basic bounded quantum state and the next few states in the
discrete spectrum for different values of the orbital momentum. A novel feature
of the solutions under consideration is the essential dependence if their
physical properties on the gravitational mass defect of the point source, even
not introduced up to recently. It yields a repulsion or an attraction of the
quantum levels up to their quasi-crossing.
|
[
{
"created": "Wed, 9 Jun 2004 17:22:33 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Jun 2004 10:01:30 GMT",
"version": "v2"
},
{
"created": "Thu, 24 Jun 2004 14:02:30 GMT",
"version": "v3"
},
{
"created": "Thu, 30 Dec 2004 13:05:13 GMT",
"version": "v4"
},
{
"created": "Tue, 25 Jan 2005 12:48:00 GMT",
"version": "v5"
}
] |
2007-05-23
|
[
[
"Fiziev",
"P. P.",
""
],
[
"Bojadjiev",
"T. L.",
""
],
[
"Georgieva",
"D. A.",
""
]
] |
We consider for the first time the solutions of Klein-Gordon equation in gravitational field of {\em a massive} point source in GR. We examine numerically the basic bounded quantum state and the next few states in the discrete spectrum for different values of the orbital momentum. A novel feature of the solutions under consideration is the essential dependence if their physical properties on the gravitational mass defect of the point source, even not introduced up to recently. It yields a repulsion or an attraction of the quantum levels up to their quasi-crossing.
|
gr-qc/0306091
|
Lluis Bel
|
Ll. Bel
|
Local Cosmology
|
13 pages, Latex. Corrected typos
| null | null | null |
gr-qc
| null |
We define the concept of a Maximally symmetric osculating space-time at any
event of any given Robertson-Walker model. We use this definition in two
circumstances: i) to approximate any given cosmological model by a simpler one
sharing the same observational parameters, i.e, the speed of light, the Hubble
constant and the deceleration parameter at the time of tangency, and ii) to
shed some light on the problem of considering an eventual influence of the
overall behaviour of the Universe on localized systems at smaller scales, or
viceversa.
|
[
{
"created": "Fri, 20 Jun 2003 07:06:46 GMT",
"version": "v1"
},
{
"created": "Sun, 12 Nov 2006 09:59:33 GMT",
"version": "v2"
}
] |
2007-05-23
|
[
[
"Bel",
"Ll.",
""
]
] |
We define the concept of a Maximally symmetric osculating space-time at any event of any given Robertson-Walker model. We use this definition in two circumstances: i) to approximate any given cosmological model by a simpler one sharing the same observational parameters, i.e, the speed of light, the Hubble constant and the deceleration parameter at the time of tangency, and ii) to shed some light on the problem of considering an eventual influence of the overall behaviour of the Universe on localized systems at smaller scales, or viceversa.
|
1704.01899
|
Yungui Gong
|
Shaoqi Hou, Yungui Gong, Yunqi Liu
|
Polarizations of Gravitational Waves in Horndeski Theory
|
15 two column pages, 6 captioned figures, EPJC in press
|
Eur. Phys. J. C 78 (2018) 378
|
10.1140/epjc/s10052-018-5869-y
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We analyze the polarization content of gravitational waves in Horndeski
theory. Besides the familiar plus and cross polarizations in Einstein's General
Relativity, there is one more polarization state which is the mixture of the
transverse breathing and longitudinal polarizations.The additional mode is
excited by the massive scalar field. In the massless limit, the longitudinal
polarization disappears, while the breathing one persists. The upper bound on
the graviton mass severely constrains the amplitude of the longitudinal
polarization, which makes its detection highly unlikely by the ground-based or
space-borne interferometers in the near future. However, pulsar timing arrays
might be able to detect the polarization excited by the massive scalar field.
Since additional polarization states appear in alternative theories of gravity,
the measurement of the polarizations of gravitational waves can be used to
probe the nature of gravity. In addition to the plus and cross states, the
detection of the breathing polarization means that gravitation is mediated by
massless spin 2 and spin 0 fields, and the detection of both the breathing and
longitudinal states means that gravitation is propagated by the massless spin 2
and massive spin 0 fields.
|
[
{
"created": "Thu, 6 Apr 2017 15:53:29 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Apr 2017 12:40:37 GMT",
"version": "v2"
},
{
"created": "Mon, 23 Oct 2017 10:42:57 GMT",
"version": "v3"
},
{
"created": "Sun, 13 May 2018 02:41:02 GMT",
"version": "v4"
}
] |
2018-05-15
|
[
[
"Hou",
"Shaoqi",
""
],
[
"Gong",
"Yungui",
""
],
[
"Liu",
"Yunqi",
""
]
] |
We analyze the polarization content of gravitational waves in Horndeski theory. Besides the familiar plus and cross polarizations in Einstein's General Relativity, there is one more polarization state which is the mixture of the transverse breathing and longitudinal polarizations.The additional mode is excited by the massive scalar field. In the massless limit, the longitudinal polarization disappears, while the breathing one persists. The upper bound on the graviton mass severely constrains the amplitude of the longitudinal polarization, which makes its detection highly unlikely by the ground-based or space-borne interferometers in the near future. However, pulsar timing arrays might be able to detect the polarization excited by the massive scalar field. Since additional polarization states appear in alternative theories of gravity, the measurement of the polarizations of gravitational waves can be used to probe the nature of gravity. In addition to the plus and cross states, the detection of the breathing polarization means that gravitation is mediated by massless spin 2 and spin 0 fields, and the detection of both the breathing and longitudinal states means that gravitation is propagated by the massless spin 2 and massive spin 0 fields.
|
1302.2057
|
Jose Manuel Velhinho
|
Jeronimo Cortez, Daniel Martin-de Blas, Guillermo A. Mena Marugan,
Jose M. Velhinho
|
Quantization of the massless scalar field in de Sitter spacetime with
unitary dynamics
|
3 pages, contribution for the Proceedings of MG13, Stockholm, 2012
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We present a Fock quantization with unitary dynamics for the massless scalar
field in de Sitter spacetime.
|
[
{
"created": "Fri, 8 Feb 2013 15:02:43 GMT",
"version": "v1"
}
] |
2013-02-11
|
[
[
"Cortez",
"Jeronimo",
""
],
[
"Blas",
"Daniel Martin-de",
""
],
[
"Marugan",
"Guillermo A. Mena",
""
],
[
"Velhinho",
"Jose M.",
""
]
] |
We present a Fock quantization with unitary dynamics for the massless scalar field in de Sitter spacetime.
|
2305.08725
|
Sebastian Schuster
|
Sebastian Schuster (Charles University of Prague)
|
Frenemies with Physicality: Manufacturing Manifold Metrics
|
9 pages; Essay written for the Gravity Research Foundation 2023
Awards for Essays on Gravitation; only layout changes compared to submitted
version; comments welcome!
| null | null | null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
Physicality has the bad habit of sneaking up on unsuspecting physicists.
Unfortunately, it comes in multitudinous incarnations, which will not always
make sense in a given situation. Breaching a warp drive metric with physical
arguments is all good, but often what counts as physicality here is but a mere
mask for something else. In times of analogue space-times and quantum effects,
a more open mind is needed. Not only to avoid using a concept of physicality
out of its natural habitat, but also to find useful toy models for our enlarged
phenomenology of physics with metrics. This journey is bound to be as vexing,
confusing, and subtle as it (hopefully) will be illuminating, entertaining, and
thought-provoking.
|
[
{
"created": "Mon, 15 May 2023 15:39:10 GMT",
"version": "v1"
}
] |
2023-05-16
|
[
[
"Schuster",
"Sebastian",
"",
"Charles University of Prague"
]
] |
Physicality has the bad habit of sneaking up on unsuspecting physicists. Unfortunately, it comes in multitudinous incarnations, which will not always make sense in a given situation. Breaching a warp drive metric with physical arguments is all good, but often what counts as physicality here is but a mere mask for something else. In times of analogue space-times and quantum effects, a more open mind is needed. Not only to avoid using a concept of physicality out of its natural habitat, but also to find useful toy models for our enlarged phenomenology of physics with metrics. This journey is bound to be as vexing, confusing, and subtle as it (hopefully) will be illuminating, entertaining, and thought-provoking.
|
gr-qc/0206046
|
Hiroshi Watabe
|
Hiroshi Watabe and Takashi Torii (Waseda University)
|
Polar Perturbations of Self-gravitating Supermassive Global Monopoles
|
10 pages, 6 figures, corrected some type mistakes (already corrected
in PRD version)
|
Phys.Rev. D66 (2002) 085019
|
10.1103/PhysRevD.66.085019
|
WU-AP/149/02
|
gr-qc hep-th
| null |
Spontaneous global symmetry breaking of O(3) scalar field gives rise to
point-like topological defects, global monopoles. By taking into account
self-gravity,the qualitative feature of the global monopole solutions depends
on the vacuum expectation value v of the scalar field. When v < sqrt{1 / 8 pi},
there are global monopole solutions which have a deficit solid angle defined at
infinity. When sqrt{1 / 8 pi} <= v < sqrt{3 / 8 pi}, there are global monopole
solutions with the cosmological horizon, which we call the supermassive global
monopole. When v >= sqrt{3 / 8 pi}, there is no nontrivial solution. It was
shown that all of these solutions are stable against the spherical
perturbations. In addition to the global monopole solutions, the de Sitter
solutions exist for any value of v. They are stable against the spherical
perturbations when v <= sqrt{3 / 8 pi}, while unstable for v > sqrt{3 / 8 pi}.
We study polar perturbations of these solutions and find that all
self-gravitating global monopoles are stable even against polar perturbations,
independently of the existence of the cosmological horizon, while the de Sitter
solutions are always unstable.
|
[
{
"created": "Mon, 17 Jun 2002 14:07:35 GMT",
"version": "v1"
},
{
"created": "Fri, 2 Aug 2002 07:55:01 GMT",
"version": "v2"
},
{
"created": "Fri, 20 Sep 2002 08:37:38 GMT",
"version": "v3"
},
{
"created": "Mon, 2 Dec 2002 03:11:27 GMT",
"version": "v4"
}
] |
2009-11-07
|
[
[
"Watabe",
"Hiroshi",
"",
"Waseda University"
],
[
"Torii",
"Takashi",
"",
"Waseda University"
]
] |
Spontaneous global symmetry breaking of O(3) scalar field gives rise to point-like topological defects, global monopoles. By taking into account self-gravity,the qualitative feature of the global monopole solutions depends on the vacuum expectation value v of the scalar field. When v < sqrt{1 / 8 pi}, there are global monopole solutions which have a deficit solid angle defined at infinity. When sqrt{1 / 8 pi} <= v < sqrt{3 / 8 pi}, there are global monopole solutions with the cosmological horizon, which we call the supermassive global monopole. When v >= sqrt{3 / 8 pi}, there is no nontrivial solution. It was shown that all of these solutions are stable against the spherical perturbations. In addition to the global monopole solutions, the de Sitter solutions exist for any value of v. They are stable against the spherical perturbations when v <= sqrt{3 / 8 pi}, while unstable for v > sqrt{3 / 8 pi}. We study polar perturbations of these solutions and find that all self-gravitating global monopoles are stable even against polar perturbations, independently of the existence of the cosmological horizon, while the de Sitter solutions are always unstable.
|
gr-qc/0109055
| null |
Dhurjati Prasad Datta (North Eastern Regional Institute of Science and
Technology)
|
Time inversion, Self-similar evolution, and Issue of time
|
Latex 2e, 17 pages, no figure
| null | null | null |
gr-qc
| null |
We investigate the question, "how does time flow?" and show that time may
change by inversions as well. We discuss its implications to a simple class of
linear systems. Instead of introducing any unphysical behaviour, inversions can
lead to a new multi- time scale evolutionary path for the linear system
exhibiting late time stochastic fluctuations. We explain how stochastic
behaviour is injected into the linear system as a combined effect of an
uncertainty in the definition of inversion and the irrationality of the golden
mean number. We also give an ansatz for the nonlinear stochastic behaviour of
(fractal) time which facilitates us to estimate the late and short time limits
of a two-time correlation function relevant for the stochastic fluctuations in
linear systems. These fluctuations are shown to enjoy generic 1/f spectrum. The
implicit functional definition of the fractal time is shown to satisfy the
differential equation dx=dt. We also discuss the relevance of intrinsic time in
the present formalism, study of which is motivated by the issue of time in
quantum gravity.
|
[
{
"created": "Mon, 17 Sep 2001 12:34:52 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Datta",
"Dhurjati Prasad",
"",
"North Eastern Regional Institute of Science and\n Technology"
]
] |
We investigate the question, "how does time flow?" and show that time may change by inversions as well. We discuss its implications to a simple class of linear systems. Instead of introducing any unphysical behaviour, inversions can lead to a new multi- time scale evolutionary path for the linear system exhibiting late time stochastic fluctuations. We explain how stochastic behaviour is injected into the linear system as a combined effect of an uncertainty in the definition of inversion and the irrationality of the golden mean number. We also give an ansatz for the nonlinear stochastic behaviour of (fractal) time which facilitates us to estimate the late and short time limits of a two-time correlation function relevant for the stochastic fluctuations in linear systems. These fluctuations are shown to enjoy generic 1/f spectrum. The implicit functional definition of the fractal time is shown to satisfy the differential equation dx=dt. We also discuss the relevance of intrinsic time in the present formalism, study of which is motivated by the issue of time in quantum gravity.
|
1406.0577
|
Xin-Zhou Li
|
Hongsheng Zhang, Yapeng Hu, Xin-Zhou Li
|
Misner-Sharp Mass in $N$-dimensional $f(R)$ Gravity
|
8 pages
|
Phys. Rev. D 90, 024062, 2014
|
10.1103/PhysRevD.90.024062
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the Misner-Sharp mass for the $f(R)$ gravity in an $n$-dimensional
(n$\geq$3) spacetime which permits three-type $(n-2)$-dimensional maximally
symmetric subspace. We obtain the Misner-Sharp mass via two approaches. One is
the inverse unified first law method, and the other is the conserved charge
method by using a generalized Kodama vector. In the first approach, we assume
the unified first still holds in the $n$-dimensional $f(R)$ gravity, which
requires a quasi-local mass form (We define it as the generalized Misner-Sharp
mass). In the second approach, the conserved charge corresponding to the
generalized local Kodama vector is the generalized Misner-Sharp mass. The two
approaches are equivalent, which are bridged by a constraint. This constraint
determines the existence of a well-defined Misner-Sharp mass. As an important
special case, we present the explicit form for the static space, and we
calculate the Misner-Sharp mass for Clifton-Barrow solution as an example.
|
[
{
"created": "Tue, 3 Jun 2014 05:15:37 GMT",
"version": "v1"
}
] |
2014-11-27
|
[
[
"Zhang",
"Hongsheng",
""
],
[
"Hu",
"Yapeng",
""
],
[
"Li",
"Xin-Zhou",
""
]
] |
We study the Misner-Sharp mass for the $f(R)$ gravity in an $n$-dimensional (n$\geq$3) spacetime which permits three-type $(n-2)$-dimensional maximally symmetric subspace. We obtain the Misner-Sharp mass via two approaches. One is the inverse unified first law method, and the other is the conserved charge method by using a generalized Kodama vector. In the first approach, we assume the unified first still holds in the $n$-dimensional $f(R)$ gravity, which requires a quasi-local mass form (We define it as the generalized Misner-Sharp mass). In the second approach, the conserved charge corresponding to the generalized local Kodama vector is the generalized Misner-Sharp mass. The two approaches are equivalent, which are bridged by a constraint. This constraint determines the existence of a well-defined Misner-Sharp mass. As an important special case, we present the explicit form for the static space, and we calculate the Misner-Sharp mass for Clifton-Barrow solution as an example.
|
1101.2991
|
Peter Hogan
|
P. A. Hogan and S. O'Farrell
|
Modeling Background Radiation in Isotropic Cosmologies
|
15 pages, Latex file, accepted for publication in General Relativity
and Gravitation
|
Gen.Rel.Grav.43:1625-1638,2011
|
10.1007/s10714-011-1144-3
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Using explicit perturbations of isotropic cosmological models which describe
simple gravitational waves, an isotropic tensor having the algebraic symmetries
of the Bel-Robinson tensor is derived as a model of cosmic background
gravitational radiation and this is used to provide an answer to the question:
in what sense can an energy-momentum-stress tensor similar to that describing
the cosmic microwave background radiation (neglecting anisotropies) be
associated with an isotropic background of gravitational radiation?
|
[
{
"created": "Sat, 15 Jan 2011 14:43:20 GMT",
"version": "v1"
}
] |
2011-05-09
|
[
[
"Hogan",
"P. A.",
""
],
[
"O'Farrell",
"S.",
""
]
] |
Using explicit perturbations of isotropic cosmological models which describe simple gravitational waves, an isotropic tensor having the algebraic symmetries of the Bel-Robinson tensor is derived as a model of cosmic background gravitational radiation and this is used to provide an answer to the question: in what sense can an energy-momentum-stress tensor similar to that describing the cosmic microwave background radiation (neglecting anisotropies) be associated with an isotropic background of gravitational radiation?
|
0902.1583
|
Kentarou Tanabe
|
Kentaro Tanabe, Norihiro Tanahashi, Tetsuya Shiromizu
|
Asymptotic flatness at spatial infinity in higher dimensions
|
10 pages
|
J.Math.Phys.50:072502,2009
|
10.1063/1.3166141
| null |
gr-qc hep-th
|
http://creativecommons.org/licenses/publicdomain/
|
A definition of asymptotic flatness at spatial infinity in $d$ dimensions
($d\geq 4$) is given using the conformal completion approach. Then we discuss
asymptotic symmetry and conserved quantities. As in four dimensions, in $d$
dimensions we should impose a condition at spatial infinity that the "magnetic"
part of the $d$-dimensional Weyl tensor vanishes at faster rate than the
"electric" part does, in order to realize the Poincare symmetry as asymptotic
symmetry and construct the conserved angular momentum. However, we found that
an additional condition should be imposed in $d>4$ dimensions.
|
[
{
"created": "Tue, 10 Feb 2009 05:46:25 GMT",
"version": "v1"
}
] |
2009-11-19
|
[
[
"Tanabe",
"Kentaro",
""
],
[
"Tanahashi",
"Norihiro",
""
],
[
"Shiromizu",
"Tetsuya",
""
]
] |
A definition of asymptotic flatness at spatial infinity in $d$ dimensions ($d\geq 4$) is given using the conformal completion approach. Then we discuss asymptotic symmetry and conserved quantities. As in four dimensions, in $d$ dimensions we should impose a condition at spatial infinity that the "magnetic" part of the $d$-dimensional Weyl tensor vanishes at faster rate than the "electric" part does, in order to realize the Poincare symmetry as asymptotic symmetry and construct the conserved angular momentum. However, we found that an additional condition should be imposed in $d>4$ dimensions.
|
gr-qc/0512033
|
Carsten Schneemann
|
Sascha Husa, Carsten Schneemann, Tilman Vogel, Anil Zenginoglu
|
Hyperboloidal data and evolution
|
11 pages, 9 figures. To appear in the Proceedings of the Spanish
Relativity Meeting (ERE 2005), Oviedo, Spain, 6-10 Sept 2005
| null |
10.1063/1.2218186
|
AEI-2005-183
|
gr-qc
| null |
We discuss the hyperboloidal evolution problem in general relativity from a
numerical perspective, and present some new results. Families of initial data
which are the hyperboloidal analogue of Brill waves are constructed
numerically, and a systematic search for apparent horizons is performed.
Schwarzschild-Kruskal spacetime is discussed as a first application of
Friedrich's general conformal field equations in spherical symmetry, and the
Maxwell equations are discussed on a nontrivial background as a toy model for
continuum instabilities.
|
[
{
"created": "Tue, 6 Dec 2005 15:46:28 GMT",
"version": "v1"
}
] |
2009-11-11
|
[
[
"Husa",
"Sascha",
""
],
[
"Schneemann",
"Carsten",
""
],
[
"Vogel",
"Tilman",
""
],
[
"Zenginoglu",
"Anil",
""
]
] |
We discuss the hyperboloidal evolution problem in general relativity from a numerical perspective, and present some new results. Families of initial data which are the hyperboloidal analogue of Brill waves are constructed numerically, and a systematic search for apparent horizons is performed. Schwarzschild-Kruskal spacetime is discussed as a first application of Friedrich's general conformal field equations in spherical symmetry, and the Maxwell equations are discussed on a nontrivial background as a toy model for continuum instabilities.
|
0901.1472
|
Valeri Frolov
|
Valeri P. Frolov
|
Hidden Symmetries and Black Holes
|
13 pages, 3 figures. To appear in the proceedings of the NEB-13
conference
|
J.Phys.Conf.Ser.189:012015,2009
|
10.1088/1742-6596/189/1/012015
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The paper contains a brief review of recent results on hidden symmetries in
higher dimensional black hole spacetimes. We show how the existence of a
principal CKY tensor (that is a closed conformal Killing-Yano 2-form) allows
one to generate a `tower' of Killing-Yano and Killing tensors responsible for
hidden symmetries. These symmetries imply complete integrability of geodesic
equations and the complete separation of variables in the Hamilton-Jacobi,
Klein-Gordon, Dirac and gravitational perturbation equations in the general
Kerr-NUT-(A)dS metrics. Equations of the parallel transport of frames along
geodesics in these spacetimes are also integrable.
|
[
{
"created": "Sun, 11 Jan 2009 21:46:11 GMT",
"version": "v1"
}
] |
2009-11-05
|
[
[
"Frolov",
"Valeri P.",
""
]
] |
The paper contains a brief review of recent results on hidden symmetries in higher dimensional black hole spacetimes. We show how the existence of a principal CKY tensor (that is a closed conformal Killing-Yano 2-form) allows one to generate a `tower' of Killing-Yano and Killing tensors responsible for hidden symmetries. These symmetries imply complete integrability of geodesic equations and the complete separation of variables in the Hamilton-Jacobi, Klein-Gordon, Dirac and gravitational perturbation equations in the general Kerr-NUT-(A)dS metrics. Equations of the parallel transport of frames along geodesics in these spacetimes are also integrable.
|
gr-qc/9911097
|
Alejandro Jakubi
|
Luis P. Chimento, Alejandro S. Jakubi and Diego Pavon
|
Stable Inflationary Dissipative Cosmologies
|
13 pages, LaTeX 2.09, 1 figure. To be published in International
Journal of Modern Physics D
|
Int.J.Mod.Phys.D9:43-55,2000
|
10.1142/S0218271800000050
| null |
gr-qc
| null |
The stability of the de Sitter era of cosmic expansion in spatially curved
homogeneous isotropic universes is studied. The source of the gravitational
field is an imperfect fluid such that the parameters that characterize it may
change with time. In this way we extend our previous analysis for
spatially-flat spaces as well as the work of Barrow.
|
[
{
"created": "Thu, 25 Nov 1999 00:54:13 GMT",
"version": "v1"
}
] |
2009-10-31
|
[
[
"Chimento",
"Luis P.",
""
],
[
"Jakubi",
"Alejandro S.",
""
],
[
"Pavon",
"Diego",
""
]
] |
The stability of the de Sitter era of cosmic expansion in spatially curved homogeneous isotropic universes is studied. The source of the gravitational field is an imperfect fluid such that the parameters that characterize it may change with time. In this way we extend our previous analysis for spatially-flat spaces as well as the work of Barrow.
|
2012.14443
|
Parampreet Singh
|
Kristina Giesel, Bao-Fei Li, Parampreet Singh
|
Relating dust reference models to conventional systems in manifestly
gauge invariant perturbation theory
|
Revised version with expanded discussion, new appendix and title
change. To appear in PRD
|
Phys. Rev. D 104, 023501 (2021)
|
10.1103/PhysRevD.104.023501
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
Models with dust reference fields in relational formalism have proved useful
in understanding the construction of gauge-invariant perturbation theory to
arbitrary orders in the canonical framework. These reference fields modify the
dynamical equations for perturbation equations. However, important questions
remain open on the relation with conventional perturbation theories of inflaton
coupled to gravity and of multi-fluid systems, and on understanding
modifications in terms of physical degrees of freedom. These gaps are filled in
this manuscript for Brown-Kucha\v{r} and Gaussian dust models, both of which
involve three scalar physical degrees of freedom. We establish a relationship
of these models with conventional inflationary and multi-fluid system of
inflation and ordinary dust by introducing a set of gauge invariant variables
on the reduced phase space of the dust reference models. We find the
modifications due to dust clocks to Bardeen equation in the longitudinal gauge
and Mukhanov-Sasaki equation in the spatially-flat gauge, in terms of physical
degrees of freedom. This results in a closed system of equations for all the
degrees of freedom needed to explore the evolution of the scalar perturbations.
Our analysis shows for the first time that even for two-fluid systems, there is
a natural choice of the set of gauge invariant variables for each chosen gauge
which not only offers a direct physical interpretation but also results in
simplifications to the dynamical equations.
|
[
{
"created": "Mon, 28 Dec 2020 19:00:20 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Jun 2021 11:41:47 GMT",
"version": "v2"
}
] |
2021-07-07
|
[
[
"Giesel",
"Kristina",
""
],
[
"Li",
"Bao-Fei",
""
],
[
"Singh",
"Parampreet",
""
]
] |
Models with dust reference fields in relational formalism have proved useful in understanding the construction of gauge-invariant perturbation theory to arbitrary orders in the canonical framework. These reference fields modify the dynamical equations for perturbation equations. However, important questions remain open on the relation with conventional perturbation theories of inflaton coupled to gravity and of multi-fluid systems, and on understanding modifications in terms of physical degrees of freedom. These gaps are filled in this manuscript for Brown-Kucha\v{r} and Gaussian dust models, both of which involve three scalar physical degrees of freedom. We establish a relationship of these models with conventional inflationary and multi-fluid system of inflation and ordinary dust by introducing a set of gauge invariant variables on the reduced phase space of the dust reference models. We find the modifications due to dust clocks to Bardeen equation in the longitudinal gauge and Mukhanov-Sasaki equation in the spatially-flat gauge, in terms of physical degrees of freedom. This results in a closed system of equations for all the degrees of freedom needed to explore the evolution of the scalar perturbations. Our analysis shows for the first time that even for two-fluid systems, there is a natural choice of the set of gauge invariant variables for each chosen gauge which not only offers a direct physical interpretation but also results in simplifications to the dynamical equations.
|
1506.06152
|
Abhay Ashtekar
|
Abhay Ashtekar, B\'eatrice Bonga and Aruna Kesavan
|
Asymptotics with a positive cosmological constant: II. Linear fields on
de Sitter space-time
|
22 pages, 4 figures. Added two clarifications in section V (on the
use of the Poincar\'e patch and on the relation with Friedrich's result [19]
in full GR). We thank the referee for bringing to our attention Ref [19].
Version to appear in PRD
|
Phys. Rev. D 92, 044011 (2015)
|
10.1103/PhysRevD.92.044011
|
IGC/2015/6-5
|
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Linearized gravitational waves in de Sitter space-time are analyzed in detail
to obtain guidance for constructing the theory of gravitational radiation in
presence of a positive cosmological constant in full, nonlinear general
relativity. Specifically: i) In the exact theory, the intrinsic geometry of
$\scri$ is often assumed to be conformally flat in order to reduce the
asymptotic symmetry group from $\Diff$ to the de Sitter group. Our {results
show explicitly} that this condition is physically unreasonable; ii) We obtain
expressions of energy-momentum and angular momentum fluxes carried by
gravitational waves in terms of fields defined at $\scrip$; iii) We argue that,
although energy of linearized gravitational waves can be arbitrarily negative
in general, gravitational waves emitted by physically reasonable sources carry
positive energy; and, finally iv) We demonstrate that the flux formulas reduce
to the familiar ones in Minkowski space-time in spite of the fact that the
limit $\Lambda \to 0$ is discontinuous (since, in particular, $\scri$ changes
its space-like character to null in the limit).
|
[
{
"created": "Fri, 19 Jun 2015 20:33:05 GMT",
"version": "v1"
},
{
"created": "Sun, 19 Jul 2015 13:26:10 GMT",
"version": "v2"
}
] |
2015-09-02
|
[
[
"Ashtekar",
"Abhay",
""
],
[
"Bonga",
"Béatrice",
""
],
[
"Kesavan",
"Aruna",
""
]
] |
Linearized gravitational waves in de Sitter space-time are analyzed in detail to obtain guidance for constructing the theory of gravitational radiation in presence of a positive cosmological constant in full, nonlinear general relativity. Specifically: i) In the exact theory, the intrinsic geometry of $\scri$ is often assumed to be conformally flat in order to reduce the asymptotic symmetry group from $\Diff$ to the de Sitter group. Our {results show explicitly} that this condition is physically unreasonable; ii) We obtain expressions of energy-momentum and angular momentum fluxes carried by gravitational waves in terms of fields defined at $\scrip$; iii) We argue that, although energy of linearized gravitational waves can be arbitrarily negative in general, gravitational waves emitted by physically reasonable sources carry positive energy; and, finally iv) We demonstrate that the flux formulas reduce to the familiar ones in Minkowski space-time in spite of the fact that the limit $\Lambda \to 0$ is discontinuous (since, in particular, $\scri$ changes its space-like character to null in the limit).
|
1109.4014
|
Kumar S. Gupta
|
S. Digal, T. R. Govindarajan, Kumar S. Gupta and X. Martin
|
Phase structure of fuzzy black holes
|
18 pages, 4 figures, minor changes in the text
| null |
10.1007/JHEP01(2012)027
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Noncommutative deformations of the BTZ blackholes are described by
noncommutative cylinders. We study the scalar fields in this background. The
spectrum is studied analytically and through numerical simulations we establish
the existence of novel `stripe phases'. These are different from stripes on
Moyal spaces and stable due to topological obstruction.
|
[
{
"created": "Mon, 19 Sep 2011 12:54:35 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Jan 2012 12:54:12 GMT",
"version": "v2"
}
] |
2015-05-30
|
[
[
"Digal",
"S.",
""
],
[
"Govindarajan",
"T. R.",
""
],
[
"Gupta",
"Kumar S.",
""
],
[
"Martin",
"X.",
""
]
] |
Noncommutative deformations of the BTZ blackholes are described by noncommutative cylinders. We study the scalar fields in this background. The spectrum is studied analytically and through numerical simulations we establish the existence of novel `stripe phases'. These are different from stripes on Moyal spaces and stable due to topological obstruction.
|
1105.0147
|
Christian Corda cordac
|
Christian Corda, Herman J. Mosquera Cuesta, Roberto Lorduy G\`omez
|
High-energy scalarons in R^{2} gravity as a model for Dark Matter in
galaxies
|
25 pages. Definitive version accepted for publication in
Astroparticle Physics
|
Astropart. Phys. 35, 362-370 (2012)
|
10.1016/j.astropartphys.2011.08.009
| null |
gr-qc astro-ph.GA hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We show that in the framework of R^{2} gravity and in the linearized approach
it is possible to obtain spherically symmetric stationary states that can be
used as a model for galaxies. The model can also help to have a better
understanding on the theoretical basis of Einstein-Vlasov systems.
Specifically, we discuss, in the linearized R^{2} gravity, the solutions of a
Klein-Gordon equation for the spacetime curvature. Such solutions describe high
energy scalarons, a field that in the context of galactic dynamics can be
interpreted like the no-light-emitting galactic component. That is, these
particles can be figured out like wave-packets showing stationary solutions in
the Einstein-Vlasov system. As pertinent to the issue under analysis in this
paper, we present an analysis on the gravitational lensing phenomena within
this framework. Although the main goal of this paper is to give a potential
solution to the Dark Matter Problem within galaxies, we add a Section where we
show that an important property of the Bullet Cluster can in principle be
explained in the scenario introduced in this work. To the end, we discuss the
generic prospective to give rise to the Dark Matter component of most galaxies
within extended gravity.
|
[
{
"created": "Sun, 1 May 2011 07:09:56 GMT",
"version": "v1"
},
{
"created": "Mon, 29 Aug 2011 14:55:36 GMT",
"version": "v2"
}
] |
2011-12-13
|
[
[
"Corda",
"Christian",
""
],
[
"Cuesta",
"Herman J. Mosquera",
""
],
[
"Gòmez",
"Roberto Lorduy",
""
]
] |
We show that in the framework of R^{2} gravity and in the linearized approach it is possible to obtain spherically symmetric stationary states that can be used as a model for galaxies. The model can also help to have a better understanding on the theoretical basis of Einstein-Vlasov systems. Specifically, we discuss, in the linearized R^{2} gravity, the solutions of a Klein-Gordon equation for the spacetime curvature. Such solutions describe high energy scalarons, a field that in the context of galactic dynamics can be interpreted like the no-light-emitting galactic component. That is, these particles can be figured out like wave-packets showing stationary solutions in the Einstein-Vlasov system. As pertinent to the issue under analysis in this paper, we present an analysis on the gravitational lensing phenomena within this framework. Although the main goal of this paper is to give a potential solution to the Dark Matter Problem within galaxies, we add a Section where we show that an important property of the Bullet Cluster can in principle be explained in the scenario introduced in this work. To the end, we discuss the generic prospective to give rise to the Dark Matter component of most galaxies within extended gravity.
|
gr-qc/0404059
|
Jonathan Thornburg
|
Jonathan Thornburg
|
Black Hole Excision with Multiple Grid Patches
|
31 pages, revtex4, includes color postscript figures, mpeg movies
available at http://www.aei.mpg.de/~jthorn/research/mpe/movies/, v4 = final
version as published = v3 + correct acknowledgments + correct grid pars in
table 1
|
Class.Quant.Grav. 21 (2004) 3665-3692
|
10.1088/0264-9381/21/15/004
|
AEI-2004-032
|
gr-qc
| null |
When using black hole excision to numerically evolve a black hole spacetime
with no continuous symmetries, most 3+1 finite differencing codes use a
Cartesian grid. It's difficult to do excision on such a grid, because the
natural $r = \text{constant}$ excision surface must be approximated either by a
very different shape such as a contained cube, or by an irregular and
non-smooth "LEGO(tm) sphere" which may introduce numerical instabilities into
the evolution. In this paper I describe an alternate scheme, which uses
multiple $\{r \times (\text{angular coordinates}) \}$ grid patches, each patch
using a different (nonsingular) choice of angular coordinates. This allows
excision on a smooth $r = \text{constant}$ 2-sphere.
I discuss the key design choices in such a multiple-patch scheme, including
the choice of ghost-zone versus internal-boundary treatment of the interpatch
boundaries, the number and shape of the patches, the details of how the ghost
zones are "synchronized" by interpolation from neighboring patches, the tensor
basis for the Einstein equations in each patch, and the handling of non-tensor
field variables such as the BSSN $\tilde{\Gamma}^i$.
I present sample numerical results from a prototype implementation of this
scheme. This code simulates the time evolution of the (asymptotically flat)
spacetime around a single (excised) black hole, using 4th-order finite
differencing in space and time. Using Kerr initial data with $J/m^2 = 0.6$, I
present evolutions to $t \gtsim 1500m$. The lifetime of these evolutions
appears to be limited only by outer boundary instabilities, not by any excision
instabilities or by any problems inherent to the multiple-patch scheme.
|
[
{
"created": "Tue, 13 Apr 2004 15:59:42 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Apr 2004 15:21:40 GMT",
"version": "v2"
},
{
"created": "Thu, 3 Jun 2004 18:38:17 GMT",
"version": "v3"
},
{
"created": "Fri, 16 Jul 2004 13:58:58 GMT",
"version": "v4"
}
] |
2007-05-23
|
[
[
"Thornburg",
"Jonathan",
""
]
] |
When using black hole excision to numerically evolve a black hole spacetime with no continuous symmetries, most 3+1 finite differencing codes use a Cartesian grid. It's difficult to do excision on such a grid, because the natural $r = \text{constant}$ excision surface must be approximated either by a very different shape such as a contained cube, or by an irregular and non-smooth "LEGO(tm) sphere" which may introduce numerical instabilities into the evolution. In this paper I describe an alternate scheme, which uses multiple $\{r \times (\text{angular coordinates}) \}$ grid patches, each patch using a different (nonsingular) choice of angular coordinates. This allows excision on a smooth $r = \text{constant}$ 2-sphere. I discuss the key design choices in such a multiple-patch scheme, including the choice of ghost-zone versus internal-boundary treatment of the interpatch boundaries, the number and shape of the patches, the details of how the ghost zones are "synchronized" by interpolation from neighboring patches, the tensor basis for the Einstein equations in each patch, and the handling of non-tensor field variables such as the BSSN $\tilde{\Gamma}^i$. I present sample numerical results from a prototype implementation of this scheme. This code simulates the time evolution of the (asymptotically flat) spacetime around a single (excised) black hole, using 4th-order finite differencing in space and time. Using Kerr initial data with $J/m^2 = 0.6$, I present evolutions to $t \gtsim 1500m$. The lifetime of these evolutions appears to be limited only by outer boundary instabilities, not by any excision instabilities or by any problems inherent to the multiple-patch scheme.
|
2001.11837
|
YongJun Cao
|
Qian Moxian, Li Xi-Bin, Cao Yongjun
|
Gravitation induced shrinkage of Mercury's orbit
|
6 pages, 0 figure
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In general relativity, the Mercury's orbit becomes approximately elliptical
and the its perihelion has thus an additional advance. We demonstrate,
meanwhile, that in comparison of those given by the Newton's theory of
gravitation for the orbit of the Mercury, the circumference and the area are
reduced by $40.39$ km and $2.35\ast10^{9}$ km$^{2}$, respectively, beside the
major-axis contraction pointed out recently, and all are produced by the curved
space within the Einstein's theory of gravitation. Since the resolution power
of present astronomical distance measurement technology reaches $one$
kilometer, the shrinkage of Mercury's orbit can then be observable.
|
[
{
"created": "Fri, 31 Jan 2020 13:55:52 GMT",
"version": "v1"
}
] |
2020-02-03
|
[
[
"Moxian",
"Qian",
""
],
[
"Xi-Bin",
"Li",
""
],
[
"Yongjun",
"Cao",
""
]
] |
In general relativity, the Mercury's orbit becomes approximately elliptical and the its perihelion has thus an additional advance. We demonstrate, meanwhile, that in comparison of those given by the Newton's theory of gravitation for the orbit of the Mercury, the circumference and the area are reduced by $40.39$ km and $2.35\ast10^{9}$ km$^{2}$, respectively, beside the major-axis contraction pointed out recently, and all are produced by the curved space within the Einstein's theory of gravitation. Since the resolution power of present astronomical distance measurement technology reaches $one$ kilometer, the shrinkage of Mercury's orbit can then be observable.
|
1707.03666
|
M. Farasat Shamir
|
M. Farasat Shamir, M. Atif Fayyaz
|
Dissipative Cylindrical Collapse of a Charged Anisotropic Fluid in
$f(R)$ Gravity
|
20 pages, accepted for publication in Canadian Journal of Physics
|
Can. J. Phys. 95(2017)1278
|
10.1139/cjp-2017-0104
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
This paper is devoted to investigate the cylindrical collapse of an
anisotropic fluid in $f(R)$ gravity. For this purpose, the viscous charged
anisotropic fluid dissipating energy with heat flow and shear is assumed. We
use the perturbation scheme to develop the dynamical equations for the
variables that ultimately lead to the disturbance of the physical variables and
the Starobinksy like $f(R)$ model chosen. The evolution of the matter variables
is discussed with the help of these equations. It can be concluded that the
range of dynamic instabilities depends on the field strength, density
distribution, pressure and the curvature term of the $f(R)$ model. We find that
our results of Newtonian and post-Newtonian regimes reduce asymptotically to
general relativity solutions in the limiting case.
|
[
{
"created": "Tue, 11 Jul 2017 15:13:24 GMT",
"version": "v1"
}
] |
2017-12-07
|
[
[
"Shamir",
"M. Farasat",
""
],
[
"Fayyaz",
"M. Atif",
""
]
] |
This paper is devoted to investigate the cylindrical collapse of an anisotropic fluid in $f(R)$ gravity. For this purpose, the viscous charged anisotropic fluid dissipating energy with heat flow and shear is assumed. We use the perturbation scheme to develop the dynamical equations for the variables that ultimately lead to the disturbance of the physical variables and the Starobinksy like $f(R)$ model chosen. The evolution of the matter variables is discussed with the help of these equations. It can be concluded that the range of dynamic instabilities depends on the field strength, density distribution, pressure and the curvature term of the $f(R)$ model. We find that our results of Newtonian and post-Newtonian regimes reduce asymptotically to general relativity solutions in the limiting case.
|
1507.05216
|
Iver Brevik
|
I. Brevik, V. V. Obukhov and A. V. Timoshkin
|
Cosmological Models Coupled with Dark Matter in a Dissipative Universe
|
6 pages, no figures; to appear in Astrophysics and Space Science
| null |
10.1007/s10509-015-2451-z
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider the cosmological system with two interacting fluids: dark energy
and dark matter, in a homogeneous and isotropic universe with dissipation. The
modified gravitational equation for dark matter is solved. The analytic
representations for the Little Rip, the Pseudo Rip, and the bounce cosmology
models with dissipation are obtained in terms of the thermodynamic parameters
in the equation of state. We analyze the corrections in the energy density for
dark matter, in view of the dissipative processes and the coupling with dark
energy.
|
[
{
"created": "Sat, 18 Jul 2015 18:55:44 GMT",
"version": "v1"
}
] |
2015-08-19
|
[
[
"Brevik",
"I.",
""
],
[
"Obukhov",
"V. V.",
""
],
[
"Timoshkin",
"A. V.",
""
]
] |
We consider the cosmological system with two interacting fluids: dark energy and dark matter, in a homogeneous and isotropic universe with dissipation. The modified gravitational equation for dark matter is solved. The analytic representations for the Little Rip, the Pseudo Rip, and the bounce cosmology models with dissipation are obtained in terms of the thermodynamic parameters in the equation of state. We analyze the corrections in the energy density for dark matter, in view of the dissipative processes and the coupling with dark energy.
|
1205.2287
|
Evan Ochsner
|
Evan Ochsner and Richard O'Shaughnessy (UWM)
|
Asymptotic frame selection for binary black hole spacetimes II:
Post-Newtonian limit
|
12 pages, 4 figures
| null |
10.1103/PhysRevD.86.104037
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
One way to select a preferred frame from gravitational radiation is via the
principal axes of < L L>, an average of the action of rotation group generators
on the Weyl tensor at asymptotic infinity. In this paper we evaluate this
time-domain average for a quasicircular binary using approximate
(post-Newtonian) waveforms. For nonprecessing unequal-mass binaries, we show
the dominant eigenvector of this tensor lies along the orbital angular
momentum. For precessing binaries, this frame is not generally aligned with
either the orbital or total angular momentum, working to leading order in the
spins. The difference between these two quantities grows with time, as the
binary approaches the end of the inspiral and both precession and higher
harmonics become more significant.
|
[
{
"created": "Thu, 10 May 2012 15:01:54 GMT",
"version": "v1"
}
] |
2013-05-30
|
[
[
"Ochsner",
"Evan",
"",
"UWM"
],
[
"O'Shaughnessy",
"Richard",
"",
"UWM"
]
] |
One way to select a preferred frame from gravitational radiation is via the principal axes of < L L>, an average of the action of rotation group generators on the Weyl tensor at asymptotic infinity. In this paper we evaluate this time-domain average for a quasicircular binary using approximate (post-Newtonian) waveforms. For nonprecessing unequal-mass binaries, we show the dominant eigenvector of this tensor lies along the orbital angular momentum. For precessing binaries, this frame is not generally aligned with either the orbital or total angular momentum, working to leading order in the spins. The difference between these two quantities grows with time, as the binary approaches the end of the inspiral and both precession and higher harmonics become more significant.
|
1812.11025
|
Davood Mahdavian Yekta
|
Majid Karimabadi, S. Aliasghar Alavi, Davood Mahdavian Yekta
|
Non-commutative effects on gravitational measurements
|
21 pages, 9 figures and one table. arXiv admin note: text overlap
with arXiv:1412.6036 by other authors
|
Class.Quant.Grav. 37 (2020) 8, 085009
|
10.1088/1361-6382/ab7693
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The general theory of relativity is currently the accepted theory of gravity
and as such, a large repository of test results has been obtained since its
inception in 1915. However, in this paper we only focus on what are considered
as the main tests but in non-commutative (NC) geometries. Using the coordinate
coherent state formalism, we calculate the gravitational redshift, deflection,
and time delay of light, separately, for NC inspired Schwarzschild and
Riessner-Nordstrom black holes. We show the NC predictions have different
behavior than the general relativity. We also provide an upper bound on the NC
parameter by comparing the NC corrections with the accuracies of gravitational
measurements in the case of typical primordial black holes produced in the
early universe. In this regard, we use observational data for the scale factor
$a$ at the end of inflation to obtain physical satisfactory results.
|
[
{
"created": "Wed, 26 Dec 2018 09:53:24 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Apr 2020 10:09:49 GMT",
"version": "v2"
}
] |
2020-04-20
|
[
[
"Karimabadi",
"Majid",
""
],
[
"Alavi",
"S. Aliasghar",
""
],
[
"Yekta",
"Davood Mahdavian",
""
]
] |
The general theory of relativity is currently the accepted theory of gravity and as such, a large repository of test results has been obtained since its inception in 1915. However, in this paper we only focus on what are considered as the main tests but in non-commutative (NC) geometries. Using the coordinate coherent state formalism, we calculate the gravitational redshift, deflection, and time delay of light, separately, for NC inspired Schwarzschild and Riessner-Nordstrom black holes. We show the NC predictions have different behavior than the general relativity. We also provide an upper bound on the NC parameter by comparing the NC corrections with the accuracies of gravitational measurements in the case of typical primordial black holes produced in the early universe. In this regard, we use observational data for the scale factor $a$ at the end of inflation to obtain physical satisfactory results.
|
1509.08771
|
Victor Ars\`ene Kpadonou
|
A. V. Kpadonou, M. J. S. Houndjo, M. E. Rodrigues
|
Tolman-Oppenheimer-Volkoff Equations and their implications or the
structures of relativistic Stars in f(T) gravity
| null |
Astrophys. Space Sci. (2016) 361:244
|
10.1007/s10509-016-2805-1
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We investigate in this paper the structures of neutron and quark stars in
f(T) theory of gravity where T denotes the torsion scalar. Attention is
attached to the TOV type equations of this theory and numerical integrations of
these equations are performed with suitable EoS. We search for the deviation of
the mass-radius diagrams for power-law and exponential type correction from the
TT gravity. Our results show that for some values of the input parameters
appearing in the considered models, f(T) theory promotes more the structures of
the relativistic stars, in consistency with the observational data.
|
[
{
"created": "Sun, 27 Sep 2015 17:45:29 GMT",
"version": "v1"
}
] |
2016-11-29
|
[
[
"Kpadonou",
"A. V.",
""
],
[
"Houndjo",
"M. J. S.",
""
],
[
"Rodrigues",
"M. E.",
""
]
] |
We investigate in this paper the structures of neutron and quark stars in f(T) theory of gravity where T denotes the torsion scalar. Attention is attached to the TOV type equations of this theory and numerical integrations of these equations are performed with suitable EoS. We search for the deviation of the mass-radius diagrams for power-law and exponential type correction from the TT gravity. Our results show that for some values of the input parameters appearing in the considered models, f(T) theory promotes more the structures of the relativistic stars, in consistency with the observational data.
|
1507.01689
|
Ragavachariar Parthasarathy
|
R. Parthasarathy
|
Five dimensional Gravity and Big Bang Singularity
|
A more complete version appeared in arXiv:1702.05231
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A 5-dimensional gravity theory, motivated by the brane world picture, with
factorisable metric and with Kaluza scalar $G_{55}(r)$, is shown to give rise
to a positive contribution to the Raychaudhuri equation. This inhibits the
focusing of geodesics and possibly cause non-focusing of the geodesics. This
feature is translated into the situation in which the universe has an infinite
age and hence no beginning avoiding the big bang singularity.
|
[
{
"created": "Tue, 7 Jul 2015 07:18:09 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Feb 2018 08:43:53 GMT",
"version": "v2"
}
] |
2018-08-29
|
[
[
"Parthasarathy",
"R.",
""
]
] |
A 5-dimensional gravity theory, motivated by the brane world picture, with factorisable metric and with Kaluza scalar $G_{55}(r)$, is shown to give rise to a positive contribution to the Raychaudhuri equation. This inhibits the focusing of geodesics and possibly cause non-focusing of the geodesics. This feature is translated into the situation in which the universe has an infinite age and hence no beginning avoiding the big bang singularity.
|
0809.2911
|
Jose Geraldo Pereira
|
R. Aldrovandi, J. G. Pereira, Roldao da Rocha, K. H. Vu
|
Nonlinear Gravitational Waves: Their Form and Effects
|
15 pages, no figures. v2: presentation changes aiming at clarifying
the text; matches published version
|
Int.J.Theor.Phys.49:549-563,2010
|
10.1007/s10773-009-0236-2
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A gravitational wave must be nonlinear to be able to transport its own
source, that is, energy and momentum. A physical gravitational wave, therefore,
cannot be represented by a solution to a linear wave equation. Relying on this
property, the second-order solution describing such physical waves is obtained.
The effects they produce on free particles are found to consist of nonlinear
oscillations along the direction of propagation.
|
[
{
"created": "Wed, 17 Sep 2008 11:31:48 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Feb 2010 17:13:07 GMT",
"version": "v2"
}
] |
2010-03-02
|
[
[
"Aldrovandi",
"R.",
""
],
[
"Pereira",
"J. G.",
""
],
[
"da Rocha",
"Roldao",
""
],
[
"Vu",
"K. H.",
""
]
] |
A gravitational wave must be nonlinear to be able to transport its own source, that is, energy and momentum. A physical gravitational wave, therefore, cannot be represented by a solution to a linear wave equation. Relying on this property, the second-order solution describing such physical waves is obtained. The effects they produce on free particles are found to consist of nonlinear oscillations along the direction of propagation.
|
0902.3978
|
Emmanuil Saridakis
|
Emmanuel N. Saridakis
|
Phantom evolution in power-law potentials
|
7 pages, 3 figures, version published in Nucl. Phys. B
| null |
10.1016/j.nuclphysb.2009.04.011
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We investigate phantom models with power-law potentials and we extract the
early-time, "tracker", solutions under the assumption of matter domination.
Contrary to quintessence case, we find that energy positivity requires normal
power-law potentials instead of inverse power-law ones, with the potential
exponent being bounded by the quadratic form. In addition, we analytically
present the general cosmological solution at intermediate times, that is at low
redshifts, which is the period of the transition from matter to dark-energy
domination. The comparison with the exact evolution, arising from numerical
elaboration, shows that the tracker solution agrees with the later within 2%
for redshifts z>1.5, while the intermediate solution is accurate within 2% up
to $z\approx 0.5$.
|
[
{
"created": "Mon, 23 Feb 2009 19:32:32 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Apr 2009 23:54:16 GMT",
"version": "v2"
}
] |
2015-05-13
|
[
[
"Saridakis",
"Emmanuel N.",
""
]
] |
We investigate phantom models with power-law potentials and we extract the early-time, "tracker", solutions under the assumption of matter domination. Contrary to quintessence case, we find that energy positivity requires normal power-law potentials instead of inverse power-law ones, with the potential exponent being bounded by the quadratic form. In addition, we analytically present the general cosmological solution at intermediate times, that is at low redshifts, which is the period of the transition from matter to dark-energy domination. The comparison with the exact evolution, arising from numerical elaboration, shows that the tracker solution agrees with the later within 2% for redshifts z>1.5, while the intermediate solution is accurate within 2% up to $z\approx 0.5$.
|
1810.07607
|
Flavio Bombacigno
|
Flavio Bombacigno and Giovanni Montani
|
Implications of the Holst term in a $f(R)$ theory with torsion
|
8 pages, 4 figures, accepted for publication in Physical Review D
|
Phys. Rev. D 99, 064016 (2019)
|
10.1103/PhysRevD.99.064016
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
We analyze a modified $f(R)$ theory of gravity in the Palatini formulation,
when an Holst term endowed with a dynamical Immirzi field is included. We study
the basic features of the model, especially in view of liminating the torsion
field via the Immirzi field and the scalar-tensor degrees of freedom of the
$f(R)$ model. The main task of this study is the investigation of the
morphology of the gravitational wave polarization when their coupling to a
circle of test particles is considered. We first observe that the dynamics of
the scalar mode of the $f(R)$ Lagrangian is frozen out, since its first order
term identically vanishes. This allows a detailed characterization of the
linearized theory, which outlines the emergence of a modified Newtonian
potential in the static limit, and when time independence is relaxed a standard
gravitational wave plus the scalar wave associated to the Immirzi field.
Investigating the effect of the coupling of this scalar-tensor wave on a circle
of test particles, we arrive to define two effective gravitational
polarizations, corresponding to an equivalent phenomenological wave, whose
morphology is anomalous with respect the standard case of General Relativity.
In fact, the particle circle suffers modifications as it was subjected to
modified plus and cross modes, whose specific features depend on the model free
parameters and are, in principle, detectable via a data analysis procedure.
|
[
{
"created": "Wed, 17 Oct 2018 15:19:02 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Mar 2019 09:39:23 GMT",
"version": "v2"
}
] |
2019-03-27
|
[
[
"Bombacigno",
"Flavio",
""
],
[
"Montani",
"Giovanni",
""
]
] |
We analyze a modified $f(R)$ theory of gravity in the Palatini formulation, when an Holst term endowed with a dynamical Immirzi field is included. We study the basic features of the model, especially in view of liminating the torsion field via the Immirzi field and the scalar-tensor degrees of freedom of the $f(R)$ model. The main task of this study is the investigation of the morphology of the gravitational wave polarization when their coupling to a circle of test particles is considered. We first observe that the dynamics of the scalar mode of the $f(R)$ Lagrangian is frozen out, since its first order term identically vanishes. This allows a detailed characterization of the linearized theory, which outlines the emergence of a modified Newtonian potential in the static limit, and when time independence is relaxed a standard gravitational wave plus the scalar wave associated to the Immirzi field. Investigating the effect of the coupling of this scalar-tensor wave on a circle of test particles, we arrive to define two effective gravitational polarizations, corresponding to an equivalent phenomenological wave, whose morphology is anomalous with respect the standard case of General Relativity. In fact, the particle circle suffers modifications as it was subjected to modified plus and cross modes, whose specific features depend on the model free parameters and are, in principle, detectable via a data analysis procedure.
|
gr-qc/9711044
|
Aros Olmedo Rodrigo
|
Rodrigo M Aros and Nelson Zamorano
|
A Wormhole at the core of an infinite cosmic string
|
1 tex file and 5 eps files. To be Published in Nov. in Phys.Rev. D
|
Phys.Rev.D56:6607-6614,1997
|
10.1103/PhysRevD.56.6607
| null |
gr-qc
| null |
We study a solution of Einstein's equations that describes a straight cosmic
string with a variable angular deficit, starting with a $2 \pi$ deficit at the
core. We show that the coordinate singularity associated to this defect can be
interpreted as a traversible wormhole lodging at the the core of the string. A
negative energy density gradually decreases the angular deficit as the distance
from the core increases, ending, at radial infinity, in a Minkowski spacetime.
The negative energy density can be confined to a small transversal section of
the string by gluing to it an exterior Gott's like solution, that freezes the
angular deficit existing at the matching border. The equation of state of the
string is such that any massive particle may stay at rest anywhere in this
spacetime. In this sense this is 2+1 spacetime solution.
|
[
{
"created": "Thu, 13 Nov 1997 13:53:07 GMT",
"version": "v1"
}
] |
2014-11-17
|
[
[
"Aros",
"Rodrigo M",
""
],
[
"Zamorano",
"Nelson",
""
]
] |
We study a solution of Einstein's equations that describes a straight cosmic string with a variable angular deficit, starting with a $2 \pi$ deficit at the core. We show that the coordinate singularity associated to this defect can be interpreted as a traversible wormhole lodging at the the core of the string. A negative energy density gradually decreases the angular deficit as the distance from the core increases, ending, at radial infinity, in a Minkowski spacetime. The negative energy density can be confined to a small transversal section of the string by gluing to it an exterior Gott's like solution, that freezes the angular deficit existing at the matching border. The equation of state of the string is such that any massive particle may stay at rest anywhere in this spacetime. In this sense this is 2+1 spacetime solution.
|
2305.17453
|
N\'ickolas De Aguiar Alves
|
N\'ickolas de Aguiar Alves
|
Nonperturbative Aspects of Quantum Field Theory in Curved Spacetime
|
MSc thesis defended at the Federal University of ABC (Brazil) on 28
April 2023. xxiv + 152 pages, 22 figures
| null | null | null |
gr-qc hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
Quantum field theory in curved spacetime is perhaps the most reliable
framework in which one can investigate quantum effects in the presence of
strong gravitational fields. Nevertheless, it is often studied by means of
perturbative treatments. In this thesis, we aim at using the functional
renormalization group -- a nonperturbative realization of the renormalization
group -- as a technique to describe nonperturbative quantum phenomena in curved
spacetimes. The chosen system is an Unruh--DeWitt particle detector coupled to
a scalar quantum field. We discuss how to formulate such a system in terms of
an action and how one can compute its renormalization group flow in the case of
an inertial detector in flat spacetime, for simplicity. We learn, however, that
the results are divergent in the limit in which the detector's energy gap
vanishes. Possible workarounds are discussed at the end.
This thesis also presents a review of quantum field theory in curved
spacetimes by means of the algebraic approach, although it assumes no previous
experience with functional analysis. Hence, it fills a pedagogical gap in the
literature. Furthermore, we also review the functional renormalization group
and derive the Wetterich equation assuming a general field content that might
include both bosonic and fermionic fields. Such a derivation is also hardly
found in pedagogical introductions available in the high energy physics
literature.
|
[
{
"created": "Tue, 23 May 2023 22:34:24 GMT",
"version": "v1"
}
] |
2023-05-30
|
[
[
"Alves",
"Níckolas de Aguiar",
""
]
] |
Quantum field theory in curved spacetime is perhaps the most reliable framework in which one can investigate quantum effects in the presence of strong gravitational fields. Nevertheless, it is often studied by means of perturbative treatments. In this thesis, we aim at using the functional renormalization group -- a nonperturbative realization of the renormalization group -- as a technique to describe nonperturbative quantum phenomena in curved spacetimes. The chosen system is an Unruh--DeWitt particle detector coupled to a scalar quantum field. We discuss how to formulate such a system in terms of an action and how one can compute its renormalization group flow in the case of an inertial detector in flat spacetime, for simplicity. We learn, however, that the results are divergent in the limit in which the detector's energy gap vanishes. Possible workarounds are discussed at the end. This thesis also presents a review of quantum field theory in curved spacetimes by means of the algebraic approach, although it assumes no previous experience with functional analysis. Hence, it fills a pedagogical gap in the literature. Furthermore, we also review the functional renormalization group and derive the Wetterich equation assuming a general field content that might include both bosonic and fermionic fields. Such a derivation is also hardly found in pedagogical introductions available in the high energy physics literature.
|
0802.0637
|
Plyatsko Roman
|
Roman Plyatsko
|
Highly Relativistic Motions of Spinning Particles According to Mathisson
Equations
|
6 pages, invited paper presented at the Mathisson Conference (17-20
October2007, Warsaw), to appear in Acta Phys. Pol. B
|
Acta Phys.Polon.Supp.1:173-178,2008
| null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The physical effects following from the Mathisson equations at the highly
relativistic motions of a spinning test particle relative to a Schwarzschild
mass are discussed. The corresponding numerical estimates are presented.
|
[
{
"created": "Tue, 5 Feb 2008 15:21:55 GMT",
"version": "v1"
}
] |
2009-02-10
|
[
[
"Plyatsko",
"Roman",
""
]
] |
The physical effects following from the Mathisson equations at the highly relativistic motions of a spinning test particle relative to a Schwarzschild mass are discussed. The corresponding numerical estimates are presented.
|
gr-qc/0209115
|
Mark A. Scheel
|
Mark A. Scheel, Lawrence E. Kidder, Lee Lindblom, Harald P. Pfeiffer,
and Saul A. Teukolsky
|
Toward stable 3D numerical evolutions of black-hole spacetimes
|
4 pages, 5 figures. To appear in Phys. Rev. D. Minor additions to
text for clarification. Added short paragraph about inner boundary dependence
|
Phys.Rev. D66 (2002) 124005
|
10.1103/PhysRevD.66.124005
| null |
gr-qc
| null |
Three dimensional (3D) numerical evolutions of static black holes with
excision are presented. These evolutions extend to about 8000M, where M is the
mass of the black hole. This degree of stability is achieved by using
growth-rate estimates to guide the fine tuning of the parameters in a
multi-parameter family of symmetric hyperbolic representations of the Einstein
evolution equations. These evolutions were performed using a fixed gauge in
order to separate the intrinsic stability of the evolution equations from the
effects of stability-enhancing gauge choices.
|
[
{
"created": "Mon, 30 Sep 2002 17:28:06 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Oct 2002 15:24:18 GMT",
"version": "v2"
}
] |
2009-11-07
|
[
[
"Scheel",
"Mark A.",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Lindblom",
"Lee",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Teukolsky",
"Saul A.",
""
]
] |
Three dimensional (3D) numerical evolutions of static black holes with excision are presented. These evolutions extend to about 8000M, where M is the mass of the black hole. This degree of stability is achieved by using growth-rate estimates to guide the fine tuning of the parameters in a multi-parameter family of symmetric hyperbolic representations of the Einstein evolution equations. These evolutions were performed using a fixed gauge in order to separate the intrinsic stability of the evolution equations from the effects of stability-enhancing gauge choices.
|
gr-qc/9403059
|
Melnikov Vitaly Nikolaevich
|
A.D.Alexeev, K.A.Bronnikov, N.I.Kolosnitsyn, M.Yu.Konstantinov,
V.N.Melnikov and A.G.Radynov
|
On Possible Measurement of Gravitational Interaction Parameters on Board
a Satellite
|
(only two misprints on title page) 7 pages
| null | null |
RGA-CSVR-001/94
|
gr-qc
| null |
The recently suggested SEE (Satellite Energy Exchange) method of measuring
the gravitational constant $G$, possible equivalence principle violation
(measured by the E\"{o}tv\"{o}s parameter $\eta$) and the hypothetic 5th force
parameters $\alpha$ and $\lambda$ on board a drag-free Earth's satellite is
discussed and further developed. Various particle trajectories near a heavy
ball are numerically simulated. Some basic sources of error are analysed. The
$G$ measurement procedure is modelled by noise insertion to a ``true''
trajectory. It is concluded that the present knowledge of $G, \alpha$ (for
$\lambda \geq 1$ m) and $\eta$ can be improved by at least two orders of
magnitude.
|
[
{
"created": "Tue, 29 Mar 1994 15:24:54 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Mar 1994 15:48:17 GMT",
"version": "v2"
}
] |
2008-02-03
|
[
[
"Alexeev",
"A. D.",
""
],
[
"Bronnikov",
"K. A.",
""
],
[
"Kolosnitsyn",
"N. I.",
""
],
[
"Konstantinov",
"M. Yu.",
""
],
[
"Melnikov",
"V. N.",
""
],
[
"Radynov",
"A. G.",
""
]
] |
The recently suggested SEE (Satellite Energy Exchange) method of measuring the gravitational constant $G$, possible equivalence principle violation (measured by the E\"{o}tv\"{o}s parameter $\eta$) and the hypothetic 5th force parameters $\alpha$ and $\lambda$ on board a drag-free Earth's satellite is discussed and further developed. Various particle trajectories near a heavy ball are numerically simulated. Some basic sources of error are analysed. The $G$ measurement procedure is modelled by noise insertion to a ``true'' trajectory. It is concluded that the present knowledge of $G, \alpha$ (for $\lambda \geq 1$ m) and $\eta$ can be improved by at least two orders of magnitude.
|
gr-qc/0410054
|
Abhay Ashtekar
|
Abhay Ashtekar
|
Gravity and the Quantum
|
A general review of quantum gravity addresed non-experts. To appear
in the special issue `Space-time Hundred Years Later' of NJP; J.Pullin and R.
Price (editors). Typos and an attribution corrected; a clarification added in
section 2.C
|
New J.Phys. 7 (2005) 198
|
10.1088/1367-2630/7/1/198
|
IGPG/04/10-3
|
gr-qc
| null |
The goal of this article is to present a broad perspective on quantum gravity
for \emph{non-experts}. After a historical introduction, key physical problems
of quantum gravity are illustrated. While there are a number of interesting and
insightful approaches to address these issues, over the past two decades
sustained progress has primarily occurred in two programs: string theory and
loop quantum gravity. The first program is described in Horowitz's contribution
while my article will focus on the second. The emphasis is on underlying ideas,
conceptual issues and overall status of the program rather than mathematical
details and associated technical subtleties.
|
[
{
"created": "Wed, 13 Oct 2004 18:12:52 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Oct 2004 15:40:35 GMT",
"version": "v2"
}
] |
2009-11-10
|
[
[
"Ashtekar",
"Abhay",
""
]
] |
The goal of this article is to present a broad perspective on quantum gravity for \emph{non-experts}. After a historical introduction, key physical problems of quantum gravity are illustrated. While there are a number of interesting and insightful approaches to address these issues, over the past two decades sustained progress has primarily occurred in two programs: string theory and loop quantum gravity. The first program is described in Horowitz's contribution while my article will focus on the second. The emphasis is on underlying ideas, conceptual issues and overall status of the program rather than mathematical details and associated technical subtleties.
|
gr-qc/9410003
|
S. Husa
|
Robert Beig and Sascha Husa
|
Initial Data for General Relativity with Toroidal Conformal Symmetry
|
REVTEX, 9 pages, ESI Preprint 126
|
Phys.Rev.D50:7116-7118,1994
|
10.1103/PhysRevD.50.R7116
| null |
gr-qc
| null |
A new class of time-symmetric solutions to the initial value constraints of
vacuum General Relativity is introduced. These data are globally regular,
asymptotically flat (with possibly several asymptotic ends) and in general have
no isometries, but a $U(1)\times U(1)$ group of conformal isometries. After
decomposing the Lichnerowicz conformal factor in a double Fourier series on the
group orbits, the solutions are given in terms of a countable family of
uncoupled ODEs on the orbit space.
|
[
{
"created": "Tue, 4 Oct 1994 16:10:51 GMT",
"version": "v1"
}
] |
2009-12-30
|
[
[
"Beig",
"Robert",
""
],
[
"Husa",
"Sascha",
""
]
] |
A new class of time-symmetric solutions to the initial value constraints of vacuum General Relativity is introduced. These data are globally regular, asymptotically flat (with possibly several asymptotic ends) and in general have no isometries, but a $U(1)\times U(1)$ group of conformal isometries. After decomposing the Lichnerowicz conformal factor in a double Fourier series on the group orbits, the solutions are given in terms of a countable family of uncoupled ODEs on the orbit space.
|
gr-qc/0412139
|
Tsutomu Kobayashi
|
Tsutomu Kobayashi, Takahiro Tanaka
|
Five-dimensional black strings in Einstein-Gauss-Bonnet gravity
|
11 pages, 8 figures. v2: typos corrected. Comments, references added.
v3: references added
|
Phys.Rev. D71 (2005) 084005
|
10.1103/PhysRevD.71.084005
|
KUNS-1954
|
gr-qc hep-th
| null |
We consider black-string-type solutions in five-dimensional
Einstein-Gauss-Bonnet gravity. Numerically constructed solutions under static,
axially symmetric and translationally invariant metric ansatz are presented.
The solutions are specified by two asymptotic charges: mass of a black string
and a scalar charge associated with the radion part of the metric. Regular
black string solutions are found if and only if the two charges satisfy a
fine-tuned relation, and otherwise the spacetime develops a singular event
horizon or a naked singularity. We can also generate bubble solutions from the
black strings by using a double Wick rotation.
|
[
{
"created": "Thu, 30 Dec 2004 21:47:03 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Mar 2005 02:39:28 GMT",
"version": "v2"
},
{
"created": "Sat, 16 Apr 2005 14:28:57 GMT",
"version": "v3"
}
] |
2009-11-10
|
[
[
"Kobayashi",
"Tsutomu",
""
],
[
"Tanaka",
"Takahiro",
""
]
] |
We consider black-string-type solutions in five-dimensional Einstein-Gauss-Bonnet gravity. Numerically constructed solutions under static, axially symmetric and translationally invariant metric ansatz are presented. The solutions are specified by two asymptotic charges: mass of a black string and a scalar charge associated with the radion part of the metric. Regular black string solutions are found if and only if the two charges satisfy a fine-tuned relation, and otherwise the spacetime develops a singular event horizon or a naked singularity. We can also generate bubble solutions from the black strings by using a double Wick rotation.
|
1507.02262
|
Julio Fernando Abalos
|
Fernando Abalos, Federico Carrasco, \'Erico Goulart, Oscar Reula
|
Nonlinear electrodynamics as a symmetric hyperbolic system
| null |
Phys. Rev. D 92, 084024 (2015)
|
10.1103/PhysRevD.92.084024
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Nonlinear theories generalizing Maxwell's electromagnetism and arising from a
Lagrangian formalism have dispersion relations in which propagation planes
factor into null planes corresponding to two effective metrics which depend on
the point-wise values of the electromagnetic field. These effective Lorentzian
metrics share the null (generically two) directions of the electromagnetic
field. We show that, the theory is symmetric hyperbolic if and only if the
cones these metrics give rise to have a non-empty intersection. Namely that
there exist families of symmetrizers in the sense of Geroch which are positive
definite for all covectors in the interior of the cones intersection. Thus, for
these theories, the initial value problem is well-posed. We illustrate the
power of this approach with several nonlinear models of physical interest such
as Born-Infeld, Gauss-Bonnet and Euler-Heisenberg.
|
[
{
"created": "Wed, 8 Jul 2015 19:15:09 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Jul 2015 16:47:23 GMT",
"version": "v2"
}
] |
2015-10-14
|
[
[
"Abalos",
"Fernando",
""
],
[
"Carrasco",
"Federico",
""
],
[
"Goulart",
"Érico",
""
],
[
"Reula",
"Oscar",
""
]
] |
Nonlinear theories generalizing Maxwell's electromagnetism and arising from a Lagrangian formalism have dispersion relations in which propagation planes factor into null planes corresponding to two effective metrics which depend on the point-wise values of the electromagnetic field. These effective Lorentzian metrics share the null (generically two) directions of the electromagnetic field. We show that, the theory is symmetric hyperbolic if and only if the cones these metrics give rise to have a non-empty intersection. Namely that there exist families of symmetrizers in the sense of Geroch which are positive definite for all covectors in the interior of the cones intersection. Thus, for these theories, the initial value problem is well-posed. We illustrate the power of this approach with several nonlinear models of physical interest such as Born-Infeld, Gauss-Bonnet and Euler-Heisenberg.
|
1612.01269
|
Somenath Chakrabarty
|
Soma Mitra, Sanchita Das and Somenath Chakrabarty
|
Time Dependent Rindler Hamiltonian Eigen States in Momentum Space
|
nine pages REVTEX file with six .eps figures (included) new
conclusion is added
| null | null | null |
gr-qc astro-ph.HE quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We have developed a formalism to get the time evolution of the eigen states
of Rindler Hamiltonian in momentum space. We have shown the difficulties with
characteristic curves, and re-cast the time evolution equations in the form of
two-dimensional Laplace equation. The solutions are obtain both in polar
coordinates as well as in the Cartesian form.
|
[
{
"created": "Mon, 5 Dec 2016 08:08:30 GMT",
"version": "v1"
},
{
"created": "Sat, 31 Dec 2016 05:30:05 GMT",
"version": "v2"
},
{
"created": "Mon, 16 Jan 2017 09:57:29 GMT",
"version": "v3"
},
{
"created": "Thu, 22 Aug 2019 10:50:12 GMT",
"version": "v4"
}
] |
2019-08-23
|
[
[
"Mitra",
"Soma",
""
],
[
"Das",
"Sanchita",
""
],
[
"Chakrabarty",
"Somenath",
""
]
] |
We have developed a formalism to get the time evolution of the eigen states of Rindler Hamiltonian in momentum space. We have shown the difficulties with characteristic curves, and re-cast the time evolution equations in the form of two-dimensional Laplace equation. The solutions are obtain both in polar coordinates as well as in the Cartesian form.
|
1512.00221
|
Norbert Bodendorfer
|
Norbert Bodendorfer, Antonia Zipfel
|
On the relation between reduced quantisation and quantum reduction for
spherical symmetry in loop quantum gravity
|
35 pages; v2: journal version, minor clarifications
|
Class. Quantum Grav. 33 (2016) 155014
|
10.1088/0264-9381/33/15/155014
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Building on a recent proposal for a quantum reduction to spherical symmetry
from full loop quantum gravity, we investigate the relation between a
quantisation of spherically symmetric general relativity and a reduction at the
quantum level. To this end, we generalise the previously proposed quantum
reduction by dropping the gauge fixing condition on the radial diffeomorphisms,
thus allowing to make direct contact between previous work on reduced
quantisation. A dictionary between spherically symmetric variables and
observables with respect to the reduction constraints in the full theory is
discussed, as well as an embedding of reduced quantum states to a sub sector of
the quantum symmetry reduced full theory states. On this full theory sub
sector, the quantum algebra of the mentioned observables is computed and shown
to qualitatively reproduce the quantum algebra of the reduced variables in the
large quantum number limit for a specific choice of regularisation.
Insufficiencies in recovering the reduced algebra quantitatively from the full
theory are attributed to the oversimplified full theory quantum states we use.
|
[
{
"created": "Tue, 1 Dec 2015 10:58:08 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jul 2016 14:24:10 GMT",
"version": "v2"
}
] |
2016-07-29
|
[
[
"Bodendorfer",
"Norbert",
""
],
[
"Zipfel",
"Antonia",
""
]
] |
Building on a recent proposal for a quantum reduction to spherical symmetry from full loop quantum gravity, we investigate the relation between a quantisation of spherically symmetric general relativity and a reduction at the quantum level. To this end, we generalise the previously proposed quantum reduction by dropping the gauge fixing condition on the radial diffeomorphisms, thus allowing to make direct contact between previous work on reduced quantisation. A dictionary between spherically symmetric variables and observables with respect to the reduction constraints in the full theory is discussed, as well as an embedding of reduced quantum states to a sub sector of the quantum symmetry reduced full theory states. On this full theory sub sector, the quantum algebra of the mentioned observables is computed and shown to qualitatively reproduce the quantum algebra of the reduced variables in the large quantum number limit for a specific choice of regularisation. Insufficiencies in recovering the reduced algebra quantitatively from the full theory are attributed to the oversimplified full theory quantum states we use.
|
2211.07418
|
Hemily Gomes Marciano Fortes
|
Jos\'e Carlos Neves de Araujo, Hemily Gomes Marciano Fortes
|
Mass of compact stars in f(T) gravity
| null |
Eur. Phys. J. C 83, 376 (2023)
|
10.1140/epjc/s10052-023-11525-8
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The mass of compact objects in General Relativity (GR), which as is well
known, is obtained via the Tolman - Oppenheimer - Volkov (TOV) equations, is a
well defined quantity. However, in alternative gravity, this is not in general
the case. In the particular case of $f(T)$ gravity, where $T$ is the scalar
torsion, some authors consider that this is still an open question, since it is
not guaranteed that the same equation used in TOV GR holds. In this paper we
consider such an important issue and compare different ways to calculate the
mass of compact objects in $f(T)$ gravity. In particular, we argue that one of
them, the asymptotic mass, may be the most appropriate way to calculate mass in
this theory. We adopt realistic equations of state in all the models presented
in this article.
|
[
{
"created": "Mon, 14 Nov 2022 14:48:09 GMT",
"version": "v1"
},
{
"created": "Mon, 8 May 2023 14:15:45 GMT",
"version": "v2"
}
] |
2023-05-09
|
[
[
"de Araujo",
"José Carlos Neves",
""
],
[
"Fortes",
"Hemily Gomes Marciano",
""
]
] |
The mass of compact objects in General Relativity (GR), which as is well known, is obtained via the Tolman - Oppenheimer - Volkov (TOV) equations, is a well defined quantity. However, in alternative gravity, this is not in general the case. In the particular case of $f(T)$ gravity, where $T$ is the scalar torsion, some authors consider that this is still an open question, since it is not guaranteed that the same equation used in TOV GR holds. In this paper we consider such an important issue and compare different ways to calculate the mass of compact objects in $f(T)$ gravity. In particular, we argue that one of them, the asymptotic mass, may be the most appropriate way to calculate mass in this theory. We adopt realistic equations of state in all the models presented in this article.
|
2109.03270
|
Christopher Kauffman
|
Christopher Kauffman and Hans Lindblad
|
Global stability of Minkowski space for the
Einstein-Maxwell-Klein-Gordon system in generalized wave coordinates
|
Version 2, 63 pages. Added exposition and corrected minor errors
| null | null | null |
gr-qc math.AP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We prove global existence for Einstein's equations with a charged scalar
field for initial conditions sufficiently close to the Minkowski spacetime
without matter. The proof relies on generalized wave coordinates adapted to the
outgoing Schwarzschild light cones and the estimates for the massless
Maxwell-Klein-Gordon system, on the background of metrics asymptotically
approaching Schwarzschild at null infinity in such coordinates, by Kauffman.
The generalized wave coordinates are obtained from a change of variables,
introduced by Lindblad, to asymptotically Schwarzschild coordinates at null
infinity. The main technical advances are that the change of coordinates makes
critical components of the metric decay faster, making the quasilinear wave
operator closer to the flat wave operator, and that commuting with modified Lie
derivatives preserves the geometric null structure, improving the error terms.
This improved decay of the metric is essential for proving our stability
result, and will likely be useful in other contexts as well.
|
[
{
"created": "Tue, 7 Sep 2021 18:17:38 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Jan 2023 20:03:26 GMT",
"version": "v2"
}
] |
2023-01-18
|
[
[
"Kauffman",
"Christopher",
""
],
[
"Lindblad",
"Hans",
""
]
] |
We prove global existence for Einstein's equations with a charged scalar field for initial conditions sufficiently close to the Minkowski spacetime without matter. The proof relies on generalized wave coordinates adapted to the outgoing Schwarzschild light cones and the estimates for the massless Maxwell-Klein-Gordon system, on the background of metrics asymptotically approaching Schwarzschild at null infinity in such coordinates, by Kauffman. The generalized wave coordinates are obtained from a change of variables, introduced by Lindblad, to asymptotically Schwarzschild coordinates at null infinity. The main technical advances are that the change of coordinates makes critical components of the metric decay faster, making the quasilinear wave operator closer to the flat wave operator, and that commuting with modified Lie derivatives preserves the geometric null structure, improving the error terms. This improved decay of the metric is essential for proving our stability result, and will likely be useful in other contexts as well.
|
1307.4406
|
Shohreh Abdolrahimi
|
Shohreh Abdolrahimi and Andrey A. Shoom
|
Distorted Five-dimensional Electrically Charged Black Holes
|
39 pages, 10 figures
|
Phys. Rev. D 89, 024040 (2014)
|
10.1103/PhysRevD.89.024040
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We derive and study distorted, five-dimensional, electrically charged,
non-extremal black holes on the example of a static and "axisymmetric" black
hole distorted by external, electrically neutral matter.The solution satisfies
Einstein-Maxwell equations which admits an $\mathbb{R}^1\times U(1)\times U(1)$
isometry group. The inner horizon remains regular if the distortion fields are
finite and smooth at the outer horizon. There exists a certain duality
transformation between the inner and the outer horizon surfaces which links
surface gravity, electrostatic potential, and space-time curvature invariants
calculated at the black hole horizons. The product of the inner and outer
horizon areas depends only on the black hole's electric charge and the
geometric mean of the areas is the upper (lower) limit for the inner (outer)
horizon area. The horizon areas, electrostatic potential, and surface gravity
satisfy the Smarr formula. We formulated the zeroth and the first laws of
mechanics and thermodynamics of the distorted black hole and found a
correspondence between the global and local forms of the first law. To
illustrate the effect of distortion we consider the dipole-monopole and
quadrupole-quadrupole distortion fields. The relative change in the Kretschamnn
scalar due to the distortion is greater at the outer horizon than at the inner
one. Calculating the maximal proper time of free fall from the outer to the
inner horizons we show that the distortion can noticeably change the black hole
interior. The change depends on type and strength of distortion fields. In
particular, due to the types of distortion fields considered here the black
hole horizons can either come arbitrarily close to or move far from each other.
|
[
{
"created": "Tue, 16 Jul 2013 20:00:20 GMT",
"version": "v1"
}
] |
2014-02-05
|
[
[
"Abdolrahimi",
"Shohreh",
""
],
[
"Shoom",
"Andrey A.",
""
]
] |
We derive and study distorted, five-dimensional, electrically charged, non-extremal black holes on the example of a static and "axisymmetric" black hole distorted by external, electrically neutral matter.The solution satisfies Einstein-Maxwell equations which admits an $\mathbb{R}^1\times U(1)\times U(1)$ isometry group. The inner horizon remains regular if the distortion fields are finite and smooth at the outer horizon. There exists a certain duality transformation between the inner and the outer horizon surfaces which links surface gravity, electrostatic potential, and space-time curvature invariants calculated at the black hole horizons. The product of the inner and outer horizon areas depends only on the black hole's electric charge and the geometric mean of the areas is the upper (lower) limit for the inner (outer) horizon area. The horizon areas, electrostatic potential, and surface gravity satisfy the Smarr formula. We formulated the zeroth and the first laws of mechanics and thermodynamics of the distorted black hole and found a correspondence between the global and local forms of the first law. To illustrate the effect of distortion we consider the dipole-monopole and quadrupole-quadrupole distortion fields. The relative change in the Kretschamnn scalar due to the distortion is greater at the outer horizon than at the inner one. Calculating the maximal proper time of free fall from the outer to the inner horizons we show that the distortion can noticeably change the black hole interior. The change depends on type and strength of distortion fields. In particular, due to the types of distortion fields considered here the black hole horizons can either come arbitrarily close to or move far from each other.
|
1112.3303
|
Abel Camacho Mr.
|
J. I. Rivas, A. Camacho, and E. Goeklue
|
Bogoliubov space of a Bose--Einstein condensate and quantum spacetime
fluctuations
| null | null |
10.1088/0264-9381/29/16/165005
| null |
gr-qc cond-mat.quant-gas
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In the present work we consider the role that metric fluctuations could have
upon the properties of a Bose--Einstein condensate. In particular we consider
the Bogoliubov space associated to it and show that there are, at least, two
independent ways in which the average size of these metric fluctuations could
be, experimentally, determined. Indeed, we prove that the pressure and the
speed of sound of the ground state define an expression allowing us to
determine the average size of these fluctuations. Afterwards, an
interferometric experiment involving Bogoliubov excitations of the condensate
and the pressure (or the speed of sound of the ground state) provides a second
and independent way in which this average size could be determined,
experimentally.
|
[
{
"created": "Wed, 14 Dec 2011 18:56:51 GMT",
"version": "v1"
}
] |
2015-06-03
|
[
[
"Rivas",
"J. I.",
""
],
[
"Camacho",
"A.",
""
],
[
"Goeklue",
"E.",
""
]
] |
In the present work we consider the role that metric fluctuations could have upon the properties of a Bose--Einstein condensate. In particular we consider the Bogoliubov space associated to it and show that there are, at least, two independent ways in which the average size of these metric fluctuations could be, experimentally, determined. Indeed, we prove that the pressure and the speed of sound of the ground state define an expression allowing us to determine the average size of these fluctuations. Afterwards, an interferometric experiment involving Bogoliubov excitations of the condensate and the pressure (or the speed of sound of the ground state) provides a second and independent way in which this average size could be determined, experimentally.
|
1703.05649
|
Jose Edgar Madriz Aguilar Dr.
|
Jose Edgar Madriz Aguilar, M. Montes
|
Interacting quintessence from new formalism of gravitoelectromagnetism
formulated on a geometrical scalar-tensor gauge theory of gravity
|
6 pages, no-figures. Improved version. We have included a
quintessence model
| null | null | null |
gr-qc hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We derive an interacting quintessence model on the framework of a recently
introduced new class of geometrical scalar-tensor theories of gravity
formulated on a Weyl-Integrable geometry, where the gravitational sector is
described by both a scalar and a tensor metric field. By using a Palatini
variational principle we construct a scalar-tensor action invariant under the
Weyl symmetry group of the background geometry, which in the Einstein-Riemann
frame leads to a gravitoelectromagnetic theory. We use the gauge freedom of the
theory and the fact that the Weyl scalar field couples with matter fields to
formulate an interacting quintessential model with a non-canonical kinetic
term, where the quintessence field has a geometrical origin. Due to this
non-canonicity we obtain that the mass of the quintessence field in the past
epochs results to be small enough not to cause modifications in the baryon to
photon ratio during nucleosynthesis.
|
[
{
"created": "Thu, 16 Mar 2017 14:45:31 GMT",
"version": "v1"
},
{
"created": "Mon, 3 Jul 2017 22:57:36 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Dec 2017 22:03:12 GMT",
"version": "v3"
}
] |
2017-12-19
|
[
[
"Aguilar",
"Jose Edgar Madriz",
""
],
[
"Montes",
"M.",
""
]
] |
We derive an interacting quintessence model on the framework of a recently introduced new class of geometrical scalar-tensor theories of gravity formulated on a Weyl-Integrable geometry, where the gravitational sector is described by both a scalar and a tensor metric field. By using a Palatini variational principle we construct a scalar-tensor action invariant under the Weyl symmetry group of the background geometry, which in the Einstein-Riemann frame leads to a gravitoelectromagnetic theory. We use the gauge freedom of the theory and the fact that the Weyl scalar field couples with matter fields to formulate an interacting quintessential model with a non-canonical kinetic term, where the quintessence field has a geometrical origin. Due to this non-canonicity we obtain that the mass of the quintessence field in the past epochs results to be small enough not to cause modifications in the baryon to photon ratio during nucleosynthesis.
|
gr-qc/9304034
|
R. Beig, Univ. Wien.
|
R. Beig (Institut f\"ur Theoretische Physik Universit\"at Wien), N.
\'O Murchadha (Physics Department, University College Cork, Ireland)
|
Trapped Surfaces in Vacuum Spacetimes
|
14 pages
|
Class.Quant.Grav.11:419-430,1994
|
10.1088/0264-9381/11/2/013
|
UWThPh-1992-33
|
gr-qc
| null |
An earlier construction by the authors of sequences of globally regular,
asymptotically flat initial data for the Einstein vacuum equations containing
trapped surfaces for large values of the parameter is extended, from the time
symmetric case considered previously, to the case of maximal slices. The
resulting theorem shows rigorously that there exists a large class of initial
configurations for non-time symmetric pure gravitational waves satisfying the
assumptions of the Penrose singularity theorem and so must have a singularity
to the future.
|
[
{
"created": "Thu, 22 Apr 1993 09:24:00 GMT",
"version": "v1"
}
] |
2010-04-06
|
[
[
"Beig",
"R.",
"",
"Institut für Theoretische Physik Universität Wien"
],
[
"Murchadha",
"N. Ó",
"",
"Physics Department, University College Cork, Ireland"
]
] |
An earlier construction by the authors of sequences of globally regular, asymptotically flat initial data for the Einstein vacuum equations containing trapped surfaces for large values of the parameter is extended, from the time symmetric case considered previously, to the case of maximal slices. The resulting theorem shows rigorously that there exists a large class of initial configurations for non-time symmetric pure gravitational waves satisfying the assumptions of the Penrose singularity theorem and so must have a singularity to the future.
|
1508.07872
|
Jacek Jezierski
|
Hans-Peter Gittel, Jacek Jezierski, Jerzy Kijowski
|
On the existence of rigid spheres in four-dimensional spacetime
manifolds
|
26 pages
|
Vietnam Journal of Mathematics, 44(1), (2016) 231-249
|
10.1007/s10013-016-0185-z
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
This paper deals with the generalization of usual round spheres in the flat
Minkowski spacetime to the case of a generic four-dimensional spacetime
manifold $M$. We consider geometric properties of sphere-like submanifolds in
$M$ and introduce conditions on external curvature and torsion, which lead to a
definition of a {\em rigid sphere}. The main result is a local existence
theorem concernig such spheres. For this purpose we apply the surjective
implicit function theorem. The proof is based on a detailed analysis of the
linearized problem and leads to an eight-parameter family of solutions in case
when the metric tensor $g$ of $M$ is from a certain neighbourhood of the flat
Minkowski metric. This contribution continues the study of rigid spheres in
(Class. Quantum Grav. \textbf{30} (2013), 175010,
doi:10.1088/0264-9381/30/17/175010, 18 pp.).
|
[
{
"created": "Mon, 31 Aug 2015 15:29:36 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Oct 2016 09:31:38 GMT",
"version": "v2"
}
] |
2016-10-26
|
[
[
"Gittel",
"Hans-Peter",
""
],
[
"Jezierski",
"Jacek",
""
],
[
"Kijowski",
"Jerzy",
""
]
] |
This paper deals with the generalization of usual round spheres in the flat Minkowski spacetime to the case of a generic four-dimensional spacetime manifold $M$. We consider geometric properties of sphere-like submanifolds in $M$ and introduce conditions on external curvature and torsion, which lead to a definition of a {\em rigid sphere}. The main result is a local existence theorem concernig such spheres. For this purpose we apply the surjective implicit function theorem. The proof is based on a detailed analysis of the linearized problem and leads to an eight-parameter family of solutions in case when the metric tensor $g$ of $M$ is from a certain neighbourhood of the flat Minkowski metric. This contribution continues the study of rigid spheres in (Class. Quantum Grav. \textbf{30} (2013), 175010, doi:10.1088/0264-9381/30/17/175010, 18 pp.).
|
2304.03160
|
Gabriele Franciolini
|
G. Franciolini, F. Iacovelli, M. Mancarella, M. Maggiore, P. Pani, and
A. Riotto
|
Searching for Primordial Black Holes with the Einstein Telescope: impact
of design and systematics
|
24 pages, 13 figures
| null |
10.1103/PhysRevD.108.043506
| null |
gr-qc astro-ph.CO hep-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Primordial Black Holes (PBHs) have recently attracted much attention as they
may explain some of the LIGO/Virgo/KAGRA observations and significantly
contribute to the dark matter in our universe. The next generation of
Gravitational Wave (GW) detectors will have the unique opportunity to set
stringent bounds on this putative population of objects. Focusing on the
Einstein Telescope (ET), in this paper we analyse in detail the impact of
systematics and different detector designs on our future capability of
observing key quantities that would allow us to discover and/or constrain a
population of PBH mergers. We also perform a population analysis, with a mass
and redshift distribution compatible with the current observational bounds. Our
results indicate that ET alone can reach an exquisite level of accuracy on the
key observables considered, as well as detect up to tens of thousands of PBH
binaries per year, but for some key signatures (in particular high--redshift
sources) the cryogenic instrument optimised for low frequencies turns out to be
crucial, both for the number of observations and the error on the parameters
reconstruction. As far as the detector geometry is concerned, we find that a
network consisting of two separated L--shaped interferometers of 15 (20)~km arm
length, oriented at $45^{\circ}$ with respect to each other performs better
than a single triangular shaped instrument of 10 (15)~km arm length, for all
the metrics considered.
|
[
{
"created": "Thu, 6 Apr 2023 15:43:47 GMT",
"version": "v1"
}
] |
2023-08-16
|
[
[
"Franciolini",
"G.",
""
],
[
"Iacovelli",
"F.",
""
],
[
"Mancarella",
"M.",
""
],
[
"Maggiore",
"M.",
""
],
[
"Pani",
"P.",
""
],
[
"Riotto",
"A.",
""
]
] |
Primordial Black Holes (PBHs) have recently attracted much attention as they may explain some of the LIGO/Virgo/KAGRA observations and significantly contribute to the dark matter in our universe. The next generation of Gravitational Wave (GW) detectors will have the unique opportunity to set stringent bounds on this putative population of objects. Focusing on the Einstein Telescope (ET), in this paper we analyse in detail the impact of systematics and different detector designs on our future capability of observing key quantities that would allow us to discover and/or constrain a population of PBH mergers. We also perform a population analysis, with a mass and redshift distribution compatible with the current observational bounds. Our results indicate that ET alone can reach an exquisite level of accuracy on the key observables considered, as well as detect up to tens of thousands of PBH binaries per year, but for some key signatures (in particular high--redshift sources) the cryogenic instrument optimised for low frequencies turns out to be crucial, both for the number of observations and the error on the parameters reconstruction. As far as the detector geometry is concerned, we find that a network consisting of two separated L--shaped interferometers of 15 (20)~km arm length, oriented at $45^{\circ}$ with respect to each other performs better than a single triangular shaped instrument of 10 (15)~km arm length, for all the metrics considered.
|
2206.08469
|
Franciele Manoel Da Silva
|
F. M. da Silva, L. C. N. Santos, C. E. Mota, T. O. F. da Costa and J.
C. Fabris
|
Rapidly rotating neutron stars in $f(R,T)$ gravity
| null | null |
10.1140/epjc/s10052-023-11466-2
| null |
gr-qc astro-ph.HE
|
http://creativecommons.org/licenses/by/4.0/
|
In this work, we study the influence of $f(R,T)$ gravity on rapidly rotating
neutron stars. First we discuss the main aspects of this modified theory of
gravity where the gravitational Lagrangian is an arbitrary function of the
Ricci scalar $R$ and of the trace of the energy-momentum tensor $T$. Then we
present the basic equations for neutron stars including the equations of state
used in the present work to describe the hadronic matter. Some physical
quantities of interest are calculated such as mass-radius relations, moments of
inertia, angular momentum, and compactness. By considering four different
rotation regimes, we obtain results that indicate substantial modifications in
the physical properties of neutron stars in $f(R,T)$ gravity when compared to
those in the context of general relativity. In particular, the mass-radius
relation for sequences of stars indicates that $f(R,T)$ gravity increases the
mass and the equatorial radius of the neutron stars for stars rotating with an
angular velocity smaller than Kepler limit.
|
[
{
"created": "Thu, 16 Jun 2022 22:37:30 GMT",
"version": "v1"
}
] |
2023-05-03
|
[
[
"da Silva",
"F. M.",
""
],
[
"Santos",
"L. C. N.",
""
],
[
"Mota",
"C. E.",
""
],
[
"da Costa",
"T. O. F.",
""
],
[
"Fabris",
"J. C.",
""
]
] |
In this work, we study the influence of $f(R,T)$ gravity on rapidly rotating neutron stars. First we discuss the main aspects of this modified theory of gravity where the gravitational Lagrangian is an arbitrary function of the Ricci scalar $R$ and of the trace of the energy-momentum tensor $T$. Then we present the basic equations for neutron stars including the equations of state used in the present work to describe the hadronic matter. Some physical quantities of interest are calculated such as mass-radius relations, moments of inertia, angular momentum, and compactness. By considering four different rotation regimes, we obtain results that indicate substantial modifications in the physical properties of neutron stars in $f(R,T)$ gravity when compared to those in the context of general relativity. In particular, the mass-radius relation for sequences of stars indicates that $f(R,T)$ gravity increases the mass and the equatorial radius of the neutron stars for stars rotating with an angular velocity smaller than Kepler limit.
|
0907.5403
|
Claus Gerhardt
|
Claus Gerhardt
|
Quantum cosmological Friedman models with a Yang-Mills field and
positive energy levels
|
9 pages, v3: minor corrections to bring it in line with the published
version
|
Class.Quant.Grav.27:035007,2010
|
10.1088/0264-9381/27/3/035007
| null |
gr-qc hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We prove the existence of a spectral resolution of the Wheeler-DeWitt
equation when the matter field is provided by a Yang-Mills field, with or
without mass term, if the spatial geometry of the underlying spacetime is
homothetic to $\R[3]$. The energy levels of the resulting quantum model, i.e.,
the eigenvalues of the corresponding self-adjoint Hamiltonian with a pure point
spectrum, are strictly positive.
|
[
{
"created": "Thu, 30 Jul 2009 19:40:58 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Aug 2009 17:37:44 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Jan 2010 17:12:43 GMT",
"version": "v3"
}
] |
2010-04-30
|
[
[
"Gerhardt",
"Claus",
""
]
] |
We prove the existence of a spectral resolution of the Wheeler-DeWitt equation when the matter field is provided by a Yang-Mills field, with or without mass term, if the spatial geometry of the underlying spacetime is homothetic to $\R[3]$. The energy levels of the resulting quantum model, i.e., the eigenvalues of the corresponding self-adjoint Hamiltonian with a pure point spectrum, are strictly positive.
|
1602.04067
|
E. Kyriakopoulos
|
E. Kyriakopoulos
|
Rotating Anisotropic Fluid Solutions
| null | null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
An exact rotating anisotropic fluid solution and a family of exact rotating
anisotropic fluid solutions are presented which satisfy all energy conditions
for certain values of their parameters. The components of the Ricci tensor the
eigenvalues of this tensor and the energy-momentum tensor of the solutions are
given explicitly. All have the ring singularity of Kerr's solution and in
addition the solution one more singularity and some solutions of the family
additional singularities.The solution matches to the extremal solution of Kerr
on two surfaces, which are thin shells and for proper values of the parameters
of the solution approximate oblate spheroids. One of these surfaces has
positive surface density. The solutions of the family satisfy the matching
conditions with the solution of Kerr on two pair of surfaces, which are again
thin shells. The surface density of one pair of surfaces is given explicitly.
Also for proper values of the parameters of the solutions the surfaces of the
other pair approximate oblate spheroids.
|
[
{
"created": "Fri, 12 Feb 2016 14:35:20 GMT",
"version": "v1"
}
] |
2016-02-15
|
[
[
"Kyriakopoulos",
"E.",
""
]
] |
An exact rotating anisotropic fluid solution and a family of exact rotating anisotropic fluid solutions are presented which satisfy all energy conditions for certain values of their parameters. The components of the Ricci tensor the eigenvalues of this tensor and the energy-momentum tensor of the solutions are given explicitly. All have the ring singularity of Kerr's solution and in addition the solution one more singularity and some solutions of the family additional singularities.The solution matches to the extremal solution of Kerr on two surfaces, which are thin shells and for proper values of the parameters of the solution approximate oblate spheroids. One of these surfaces has positive surface density. The solutions of the family satisfy the matching conditions with the solution of Kerr on two pair of surfaces, which are again thin shells. The surface density of one pair of surfaces is given explicitly. Also for proper values of the parameters of the solutions the surfaces of the other pair approximate oblate spheroids.
|
0711.0669
|
Deirdre Shoemaker
|
Tanja Bode, Deirdre Shoemaker, Frank Herrmann and Ian Hinder
|
Robustness of Binary Black Hole Mergers in the Presence of Spurious
Radiation
|
12 pages, 12 figures
|
Phys.Rev.D77:044027,2008
|
10.1103/PhysRevD.77.044027
| null |
gr-qc
| null |
We present an investigation into how sensitive the last orbits and merger of
binary black hole systems are to the presence of spurious radiation in the
initial data. Our numerical experiments consist of a binary black hole system
starting the last couple of orbits before merger with additional spurious
radiation centered at the origin and fixed initial angular momentum. As the
energy in the added spurious radiation increases, the binary is invariably
hardened for the cases we tested, i.e. the merger of the two black holes is
hastened. The change in merger time becomes significant when the additional
energy provided by the spurious radiation increases the Arnowitt-Deser-Misner
(ADM) mass of the spacetime by about 1%. While the final masses of the black
holes increase due to partial absorption of the radiation, the final spins
remain constant to within our numerical accuracy. We conjecture that the
spurious radiation is primarily increasing the eccentricity of the orbit and
secondarily increasing the mass of the black holes while propagating out to
infinity.
|
[
{
"created": "Mon, 5 Nov 2007 20:41:21 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Feb 2008 20:46:15 GMT",
"version": "v2"
}
] |
2008-11-26
|
[
[
"Bode",
"Tanja",
""
],
[
"Shoemaker",
"Deirdre",
""
],
[
"Herrmann",
"Frank",
""
],
[
"Hinder",
"Ian",
""
]
] |
We present an investigation into how sensitive the last orbits and merger of binary black hole systems are to the presence of spurious radiation in the initial data. Our numerical experiments consist of a binary black hole system starting the last couple of orbits before merger with additional spurious radiation centered at the origin and fixed initial angular momentum. As the energy in the added spurious radiation increases, the binary is invariably hardened for the cases we tested, i.e. the merger of the two black holes is hastened. The change in merger time becomes significant when the additional energy provided by the spurious radiation increases the Arnowitt-Deser-Misner (ADM) mass of the spacetime by about 1%. While the final masses of the black holes increase due to partial absorption of the radiation, the final spins remain constant to within our numerical accuracy. We conjecture that the spurious radiation is primarily increasing the eccentricity of the orbit and secondarily increasing the mass of the black holes while propagating out to infinity.
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.