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Basic datasets from which other combined datasets are formed.
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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0606094
|
Eric Poisson
|
Brent Preston and Eric Poisson
|
A light-cone gauge for black-hole perturbation theory
|
12 pages
|
Phys.Rev. D74 (2006) 064010
|
10.1103/PhysRevD.74.064010
| null |
gr-qc
| null |
The geometrical meaning of the Eddington-Finkelstein coordinates of
Schwarzschild spacetime is well understood: (i) the advanced-time coordinate v
is constant on incoming light cones that converge toward r=0, (ii) the angles
theta and phi are constant on the null generators of each light cone, (iii) the
radial coordinate r is an affine-parameter distance along each generator, and
(iv) r is an areal radius, in the sense that 4 pi r^2 is the area of each
two-surface (v,r) = constant. The light-cone gauge of black-hole perturbation
theory, which is formulated in this paper, places conditions on a perturbation
of the Schwarzschild metric that ensure that properties (i)--(iii) of the
coordinates are preserved in the perturbed spacetime. Property (iv) is lost in
general, but it is retained in exceptional situations that are identified in
this paper. Unlike other popular choices of gauge, the light-cone gauge
produces a perturbed metric that is expressed in a meaningful coordinate
system; this is a considerable asset that greatly facilitates the task of
extracting physical consequences. We illustrate the use of the light-cone gauge
by calculating the metric of a black hole immersed in a uniform magnetic field.
We construct a three-parameter family of solutions to the perturbative
Einstein-Maxwell equations and argue that it is applicable to a broader range
of physical situations than the exact, two-parameter Schwarzschild-Melvin
family.
|
[
{
"created": "Wed, 21 Jun 2006 20:39:16 GMT",
"version": "v1"
}
] |
2009-11-11
|
[
[
"Preston",
"Brent",
""
],
[
"Poisson",
"Eric",
""
]
] |
The geometrical meaning of the Eddington-Finkelstein coordinates of Schwarzschild spacetime is well understood: (i) the advanced-time coordinate v is constant on incoming light cones that converge toward r=0, (ii) the angles theta and phi are constant on the null generators of each light cone, (iii) the radial coordinate r is an affine-parameter distance along each generator, and (iv) r is an areal radius, in the sense that 4 pi r^2 is the area of each two-surface (v,r) = constant. The light-cone gauge of black-hole perturbation theory, which is formulated in this paper, places conditions on a perturbation of the Schwarzschild metric that ensure that properties (i)--(iii) of the coordinates are preserved in the perturbed spacetime. Property (iv) is lost in general, but it is retained in exceptional situations that are identified in this paper. Unlike other popular choices of gauge, the light-cone gauge produces a perturbed metric that is expressed in a meaningful coordinate system; this is a considerable asset that greatly facilitates the task of extracting physical consequences. We illustrate the use of the light-cone gauge by calculating the metric of a black hole immersed in a uniform magnetic field. We construct a three-parameter family of solutions to the perturbative Einstein-Maxwell equations and argue that it is applicable to a broader range of physical situations than the exact, two-parameter Schwarzschild-Melvin family.
|
1702.05201
|
Yen-Kheng Lim
|
Yen-Kheng Lim
|
Cohomogeneity-1 solutions in Einstein-Maxwell-dilaton gravity
|
Typos corrected, 20 pages, no figures
|
Phys. Rev. D 95, 104008 (2017)
|
10.1103/PhysRevD.95.104008
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The field equations for Einstein-Maxwell-dilaton gravity in $D$ dimensions
are reduced to an effective one-dimensional system under the influence of
exponential potentials. Various cases where exact solutions can be found are
explored. With this procedure, we present interesting solutions such as a
one-parameter generalisation of the dilaton-Melvin spacetime and a
three-parameter solution that interpolates between the Reissner-Nordstr\"{o}m
and Bertotti-Robinson solution. This procedure also allows simple, alternative
derivations of known solutions such as the Lifshitz spacetime and the planar
Anti-de Sitter naked singularity. In the latter case, the metric is cast in a
simpler form which reveals the presence of an additional curvature singularity.
|
[
{
"created": "Fri, 17 Feb 2017 01:17:13 GMT",
"version": "v1"
},
{
"created": "Tue, 9 May 2017 00:37:09 GMT",
"version": "v2"
}
] |
2017-05-10
|
[
[
"Lim",
"Yen-Kheng",
""
]
] |
The field equations for Einstein-Maxwell-dilaton gravity in $D$ dimensions are reduced to an effective one-dimensional system under the influence of exponential potentials. Various cases where exact solutions can be found are explored. With this procedure, we present interesting solutions such as a one-parameter generalisation of the dilaton-Melvin spacetime and a three-parameter solution that interpolates between the Reissner-Nordstr\"{o}m and Bertotti-Robinson solution. This procedure also allows simple, alternative derivations of known solutions such as the Lifshitz spacetime and the planar Anti-de Sitter naked singularity. In the latter case, the metric is cast in a simpler form which reveals the presence of an additional curvature singularity.
|
0708.1169
|
Sebastian Szybka
|
Piotr T. Chru\'sciel, Sebastian J. Szybka
|
On the Ernst electro-vacuum equations and ergosurfaces
|
15 pages, no figures, minor changes
|
ActaPhys.Polon.B39:59-74,2008
| null | null |
gr-qc
| null |
The question of smoothness at the ergosurface of the space-time metric
constructed out of solutions (E,phi) of the Ernst electro-vacuum equations is
considered. We prove smoothness of those ergosurfaces at which Re(E) provides
the dominant contribution to f=-(Re(E)+|phi|^2) at the zero-level-set of f.
Some partial results are obtained in the remaining cases: in particular we give
examples of leading-order solutions with singular isolated "ergocircles".
|
[
{
"created": "Thu, 9 Aug 2007 19:32:19 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Nov 2007 09:51:24 GMT",
"version": "v2"
}
] |
2008-11-26
|
[
[
"Chruściel",
"Piotr T.",
""
],
[
"Szybka",
"Sebastian J.",
""
]
] |
The question of smoothness at the ergosurface of the space-time metric constructed out of solutions (E,phi) of the Ernst electro-vacuum equations is considered. We prove smoothness of those ergosurfaces at which Re(E) provides the dominant contribution to f=-(Re(E)+|phi|^2) at the zero-level-set of f. Some partial results are obtained in the remaining cases: in particular we give examples of leading-order solutions with singular isolated "ergocircles".
|
0905.4121
|
Albert Tarantola
|
Bartolome Coll and Albert Tarantola
|
Using pulsars to define space-time coordinates
| null | null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Fully relativistic coordinates have been proposed for (relativistically)
running a "GPS" system. These coordinates are the arrival times of the light
signals emitted by four "satellites" (clocks). Replacing the signals emitted by
four controlled clocks by the signals emitted by four pulsars defines a
coordinate system with lower accuracy, but valid across the whole Solar System.
We here precisely define this new coordinate system, by choosing four
particular pulsars and a particular event as the origin of the coordinates.
|
[
{
"created": "Tue, 26 May 2009 06:19:45 GMT",
"version": "v1"
}
] |
2009-05-27
|
[
[
"Coll",
"Bartolome",
""
],
[
"Tarantola",
"Albert",
""
]
] |
Fully relativistic coordinates have been proposed for (relativistically) running a "GPS" system. These coordinates are the arrival times of the light signals emitted by four "satellites" (clocks). Replacing the signals emitted by four controlled clocks by the signals emitted by four pulsars defines a coordinate system with lower accuracy, but valid across the whole Solar System. We here precisely define this new coordinate system, by choosing four particular pulsars and a particular event as the origin of the coordinates.
|
gr-qc/0701074
|
H Mohseni Sadjadi
|
H. Mohseni Sadjadi
|
Particle vs. future event horizon in interacting holographic dark energy
model
|
12 pages, 2 figures, references added, abstract changed, typos
corrected. To be published in JCAP
|
JCAP 0702:026,2007
|
10.1088/1475-7516/2007/02/026
| null |
gr-qc astro-ph
| null |
By choosing the future event horizon as the horizon of the flat FLRW
universe, we show that although the interacting holographic dark energy model
is able to explain the phantom divide line crossing, but the thermodynamics
second law is not respected in this model. We show that if one takes the
particle event horizon as the horizon of the universe, besides describing
$\omega=-1$ crossing in a consistent way with thermodynamics second law, he is
able to determine appropriately the ratio of dark matter to dark energy density
at transition time. In this approach, after the first transition from
quintessence to phantom, there is another transition from phantom to
quintessence phase which avoids the big rip singularity.
|
[
{
"created": "Sun, 14 Jan 2007 08:36:39 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Jan 2007 21:16:31 GMT",
"version": "v2"
},
{
"created": "Wed, 7 Feb 2007 07:10:53 GMT",
"version": "v3"
}
] |
2010-10-27
|
[
[
"Sadjadi",
"H. Mohseni",
""
]
] |
By choosing the future event horizon as the horizon of the flat FLRW universe, we show that although the interacting holographic dark energy model is able to explain the phantom divide line crossing, but the thermodynamics second law is not respected in this model. We show that if one takes the particle event horizon as the horizon of the universe, besides describing $\omega=-1$ crossing in a consistent way with thermodynamics second law, he is able to determine appropriately the ratio of dark matter to dark energy density at transition time. In this approach, after the first transition from quintessence to phantom, there is another transition from phantom to quintessence phase which avoids the big rip singularity.
|
gr-qc/0108011
|
SG Ghosh
|
S G Ghosh (Science College, Nagpur, India) and A Beesham (University
of Zululand, RSA)
|
Higher dimensional inhomogeneous dust collapse and cosmic censorship
|
15 pages, LaTeX, 1 figure, 2 tables
|
Phys.Rev. D64 (2001) 124005
|
10.1103/PhysRevD.64.124005
| null |
gr-qc
| null |
We investigate the occurrence and nature of a naked singularity in the
gravitational collapse of an inhomogeneous dust cloud described by higher
dimensional Tolman-Bondi space-times. The naked singularities are found to be
gravitationally strong in the sense of Tipler. Higher dimensions seem to favour
black holes rather than naked singularities.
|
[
{
"created": "Fri, 3 Aug 2001 06:45:39 GMT",
"version": "v1"
}
] |
2009-11-07
|
[
[
"Ghosh",
"S G",
"",
"Science College, Nagpur, India"
],
[
"Beesham",
"A",
"",
"University\n of Zululand, RSA"
]
] |
We investigate the occurrence and nature of a naked singularity in the gravitational collapse of an inhomogeneous dust cloud described by higher dimensional Tolman-Bondi space-times. The naked singularities are found to be gravitationally strong in the sense of Tipler. Higher dimensions seem to favour black holes rather than naked singularities.
|
0708.2378
|
Glenn Barnich
|
Glenn Barnich and Geoffrey Compere
|
Surface charge algebra in gauge theories and thermodynamic integrability
|
40 pages Latex file, published version
|
J.Math.Phys.49:042901,2008
|
10.1063/1.2889721
|
ULB-TH/06-30
|
gr-qc hep-th
| null |
Surface charges and their algebra in interacting Lagrangian gauge field
theories are investigated by using techniques from the variational calculus. In
the case of exact solutions and symmetries, the surface charges are interpreted
as a Pfaff system. Integrability is governed by Frobenius' theorem and the
charges associated with the derived symmetry algebra are shown to vanish. In
the asymptotic context, we provide a generalized covariant derivation of the
result that the representation of the asymptotic symmetry algebra through
charges may be centrally extended. Finally, we make contact with Hamiltonian
and with covariant phase space methods.
|
[
{
"created": "Fri, 17 Aug 2007 15:40:13 GMT",
"version": "v1"
},
{
"created": "Sun, 18 May 2008 22:41:25 GMT",
"version": "v2"
}
] |
2008-11-26
|
[
[
"Barnich",
"Glenn",
""
],
[
"Compere",
"Geoffrey",
""
]
] |
Surface charges and their algebra in interacting Lagrangian gauge field theories are investigated by using techniques from the variational calculus. In the case of exact solutions and symmetries, the surface charges are interpreted as a Pfaff system. Integrability is governed by Frobenius' theorem and the charges associated with the derived symmetry algebra are shown to vanish. In the asymptotic context, we provide a generalized covariant derivation of the result that the representation of the asymptotic symmetry algebra through charges may be centrally extended. Finally, we make contact with Hamiltonian and with covariant phase space methods.
|
2108.00175
|
Mehdi Shokri
|
Mehdi Shokri, Mohammad Reza Setare, Salvatore Capozziello and Jafar
Sadeghi
|
Constant-roll $f(R)$ inflation compared with Cosmic Microwave Background
anisotropies and swampland criteria
|
16 pages, 5 figures
| null | null | null |
gr-qc astro-ph.CO
|
http://creativecommons.org/publicdomain/zero/1.0/
|
Inflationary models derived from $f(R)$ gravity, where the scalaron rolls
down with a constant rate from the top to the minimum of the effective
potential, are considered. Specifically, we take into account three $f(R)$
models \textit{i.e.}\,Starobinsky $R^{2}$, $R^{2p}$ and the logarithmic
corrected models. We compare the inflationary parameters derived from the
models with the observational data of CMB anisotropies \textit{i.e.} the Planck
and Keck/array datasets in order to find observational constraints on the
parameters space. We find that although our $f(R)$ constant-roll models for
$\gamma=0$ show observationally acceptable values of $r$, they do not predict
favoured values of the spectral index. In particular, we have $n_{s}>1$ for the
Starobinsky $R^{2}$ and $R^{2p}$ models and $0.996<n_{s}<0.999$ for logarithmic
model. Finally, we study the models from the point of view of Weak Gravity
Conjecture adopting the swampland criteria.
|
[
{
"created": "Sat, 31 Jul 2021 08:10:03 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Aug 2021 05:05:03 GMT",
"version": "v2"
}
] |
2021-08-16
|
[
[
"Shokri",
"Mehdi",
""
],
[
"Setare",
"Mohammad Reza",
""
],
[
"Capozziello",
"Salvatore",
""
],
[
"Sadeghi",
"Jafar",
""
]
] |
Inflationary models derived from $f(R)$ gravity, where the scalaron rolls down with a constant rate from the top to the minimum of the effective potential, are considered. Specifically, we take into account three $f(R)$ models \textit{i.e.}\,Starobinsky $R^{2}$, $R^{2p}$ and the logarithmic corrected models. We compare the inflationary parameters derived from the models with the observational data of CMB anisotropies \textit{i.e.} the Planck and Keck/array datasets in order to find observational constraints on the parameters space. We find that although our $f(R)$ constant-roll models for $\gamma=0$ show observationally acceptable values of $r$, they do not predict favoured values of the spectral index. In particular, we have $n_{s}>1$ for the Starobinsky $R^{2}$ and $R^{2p}$ models and $0.996<n_{s}<0.999$ for logarithmic model. Finally, we study the models from the point of view of Weak Gravity Conjecture adopting the swampland criteria.
|
gr-qc/0108054
|
Louis Scheffer
|
Louis K. Scheffer
|
A Conventional Physics Explanation for the Anomalous Acceleration of
Pioneer 10/11
|
LaTex; 5 pages, 2 figures, to be submitted to PRL
| null | null | null |
gr-qc astro-ph
| null |
Anderson, et al., find the measured trajectories of Pioneer 10 and 11
spacecraft deviate from the trajectories computed from known forces acting on
them. This unmodelled acceleration can be accounted for by non-isotropic
radiation of spacecraft heat. Various forms of non-isotropic radiation were
proposed by Katz, Murphy, and Scheffer, but Anderson, et al. felt that none of
these could explain the observed effect. This paper calculates the known
effects in more detail and considers new sources of radiation, all based on
spacecraft construction. These effects are then modelled over the duration of
the experiment. The model provides a reasonable fit to the acceleration from
its appearance at a heliocentric distance of 5 AU to the last measurement at 71
AU, but overpredicts by 9% the decrease in acceleration between intervals I and
III of the Pioneer 10 observations. (For comparison, the two different
measurements of the effect (SIGMA and CHASMP) themselves differ by 4% in
interval III.) In any case, by accounting for the bulk of the acceleration, the
proposed mechanism makes it much more likely that the entire effect can be
explained without the need for new physics.
|
[
{
"created": "Wed, 22 Aug 2001 22:19:11 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Scheffer",
"Louis K.",
""
]
] |
Anderson, et al., find the measured trajectories of Pioneer 10 and 11 spacecraft deviate from the trajectories computed from known forces acting on them. This unmodelled acceleration can be accounted for by non-isotropic radiation of spacecraft heat. Various forms of non-isotropic radiation were proposed by Katz, Murphy, and Scheffer, but Anderson, et al. felt that none of these could explain the observed effect. This paper calculates the known effects in more detail and considers new sources of radiation, all based on spacecraft construction. These effects are then modelled over the duration of the experiment. The model provides a reasonable fit to the acceleration from its appearance at a heliocentric distance of 5 AU to the last measurement at 71 AU, but overpredicts by 9% the decrease in acceleration between intervals I and III of the Pioneer 10 observations. (For comparison, the two different measurements of the effect (SIGMA and CHASMP) themselves differ by 4% in interval III.) In any case, by accounting for the bulk of the acceleration, the proposed mechanism makes it much more likely that the entire effect can be explained without the need for new physics.
|
gr-qc/0512058
|
Tatyana P. Shestakova
|
T. P. Shestakova
|
Changing the Hilbert space structure as a consequence of gauge
transformations in "extended phase space" version of quantum geometrodynamics
|
12 pages, 2 figures, talk presented at the International Conference
"Physical Interpretations of Relativity Theory - PIRT-2005" (Bauman
University, Moscow, July 2005)
|
Physical Interpretations of Relativity Theory: Proceedings of
International Meeting (Moscow, 4 - 7 July 2005), eds by M. C. Duffy, V. O.
Gladyshev, A. N. Morozov and P. Rowlands, Moscow, 2005, P. 26 - 34
| null | null |
gr-qc
| null |
In the earlier works on quantum geometrodynamics in extended phase space it
has been argued that a wave function of the Universe should satisfy a
Schrodinger equation. Its form, as well as a measure in Schrodinger scalar
product, depends on a gauge condition (a chosen reference frame). It is known
that the geometry of an appropriate Hilbert space is determined by introducing
the scalar product, so the Hilbert space structure turns out to be in a large
degree depending on a chosen gauge condition. In the present work we analyse
this issue from the viewpoint of the path integral approach. We consider how
the gauge condition changes as a result of gauge transformations. In this
respect, three kinds of gauge transformations can be singled out: Firstly,
there are residual gauge transformations, which do not change the gauge
condition. The second kind is the transformations whose parameters can be
related by homotopy. Then the change of gauge condition could be described by
smoothly changing function. In particular, in this context time dependent
gauges could be discussed. We also suggest that this kind of gauge
transformations leads to a smooth changing of solutions to the Schrodinger
equation. The third kind of the transformations includes those whose parameters
belong to different homotopy classes. They are of the most interest from the
viewpoint of changing the Hilbert space structure. In this case the gauge
condition and the very form of the Schrodinger equation would change in
discrete steps when we pass from a spacetime region with one gauge condition to
another region with another gauge condition. In conclusion we discuss the
relation between quantum gravity and fundamental problems of ordinary quantum
mechanics.
|
[
{
"created": "Fri, 9 Dec 2005 11:52:22 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Shestakova",
"T. P.",
""
]
] |
In the earlier works on quantum geometrodynamics in extended phase space it has been argued that a wave function of the Universe should satisfy a Schrodinger equation. Its form, as well as a measure in Schrodinger scalar product, depends on a gauge condition (a chosen reference frame). It is known that the geometry of an appropriate Hilbert space is determined by introducing the scalar product, so the Hilbert space structure turns out to be in a large degree depending on a chosen gauge condition. In the present work we analyse this issue from the viewpoint of the path integral approach. We consider how the gauge condition changes as a result of gauge transformations. In this respect, three kinds of gauge transformations can be singled out: Firstly, there are residual gauge transformations, which do not change the gauge condition. The second kind is the transformations whose parameters can be related by homotopy. Then the change of gauge condition could be described by smoothly changing function. In particular, in this context time dependent gauges could be discussed. We also suggest that this kind of gauge transformations leads to a smooth changing of solutions to the Schrodinger equation. The third kind of the transformations includes those whose parameters belong to different homotopy classes. They are of the most interest from the viewpoint of changing the Hilbert space structure. In this case the gauge condition and the very form of the Schrodinger equation would change in discrete steps when we pass from a spacetime region with one gauge condition to another region with another gauge condition. In conclusion we discuss the relation between quantum gravity and fundamental problems of ordinary quantum mechanics.
|
1406.4118
|
Farook Rahaman
|
Farook Rahaman, Koushik Chakraborty, P.K.F. Kuhfittig, G. C. Shit,
Mosiur Rahman
|
A new deterministic model of strange stars
|
one new figures and minor revisions have been done. To appear in
Eur.Phys.J.C
| null |
10.1140/epjc/s10052-014-3126-6
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The observed evidence for the existence of strange stars and the concomitant
observed masses and radii are used to derive an interpolation formula for the
mass as a function of the radial coordinate. The resulting general mass
function becomes an effective model for a strange star. The analysis is based
on the MIT bag model and yields the energy density, as well as the radial and
transverse pressures. Using the interpolation function for the mass, it is
shown that a mass-radius relation due to Buchdahl is satisfied in our model. We
find the surface redshift ($Z$) corresponding to the compactness of the stars.
Finally, from our results, we predict some characteristics of a strange star of
radius 9.9 km.
|
[
{
"created": "Fri, 13 Jun 2014 05:21:52 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Oct 2014 12:32:23 GMT",
"version": "v2"
}
] |
2015-06-22
|
[
[
"Rahaman",
"Farook",
""
],
[
"Chakraborty",
"Koushik",
""
],
[
"Kuhfittig",
"P. K. F.",
""
],
[
"Shit",
"G. C.",
""
],
[
"Rahman",
"Mosiur",
""
]
] |
The observed evidence for the existence of strange stars and the concomitant observed masses and radii are used to derive an interpolation formula for the mass as a function of the radial coordinate. The resulting general mass function becomes an effective model for a strange star. The analysis is based on the MIT bag model and yields the energy density, as well as the radial and transverse pressures. Using the interpolation function for the mass, it is shown that a mass-radius relation due to Buchdahl is satisfied in our model. We find the surface redshift ($Z$) corresponding to the compactness of the stars. Finally, from our results, we predict some characteristics of a strange star of radius 9.9 km.
|
gr-qc/9911051
|
Esposito Giampiero
|
Giampiero Esposito
|
Complex Geometry of Nature and General Relativity
|
229 pages, plain Tex
| null | null |
DSF preprint 99/38
|
gr-qc
| null |
An attempt is made of giving a self-contained introduction to holomorphic
ideas in general relativity, following work over the last thirty years by
several authors. The main topics are complex manifolds, spinor and twistor
methods, heaven spaces.
|
[
{
"created": "Mon, 15 Nov 1999 11:06:50 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Esposito",
"Giampiero",
""
]
] |
An attempt is made of giving a self-contained introduction to holomorphic ideas in general relativity, following work over the last thirty years by several authors. The main topics are complex manifolds, spinor and twistor methods, heaven spaces.
|
gr-qc/0601112
|
Hakan Andreasson
|
Hakan Andreasson, Gerhard Rein
|
A numerical investigation of the stability of steady states and critical
phenomena for the spherically symmetric Einstein-Vlasov system
|
29 pages, 10 figures
|
Class.Quant.Grav. 23 (2006) 3659-3678
|
10.1088/0264-9381/23/11/001
| null |
gr-qc
| null |
The stability features of steady states of the spherically symmetric
Einstein-Vlasov system are investigated numerically. We find support for the
conjecture by Zeldovich and Novikov that the binding energy maximum along a
steady state sequence signals the onset of instability, a conjecture which we
extend to and confirm for non-isotropic states. The sign of the binding energy
of a solution turns out to be relevant for its time evolution in general. We
relate the stability properties to the question of universality in critical
collapse and find that for Vlasov matter universality does not seem to hold.
|
[
{
"created": "Thu, 26 Jan 2006 15:09:46 GMT",
"version": "v1"
}
] |
2009-11-11
|
[
[
"Andreasson",
"Hakan",
""
],
[
"Rein",
"Gerhard",
""
]
] |
The stability features of steady states of the spherically symmetric Einstein-Vlasov system are investigated numerically. We find support for the conjecture by Zeldovich and Novikov that the binding energy maximum along a steady state sequence signals the onset of instability, a conjecture which we extend to and confirm for non-isotropic states. The sign of the binding energy of a solution turns out to be relevant for its time evolution in general. We relate the stability properties to the question of universality in critical collapse and find that for Vlasov matter universality does not seem to hold.
|
2207.10717
|
Hemwati Nandan
|
Shubham Kala, Hemwati Nandan and Prateek Sharma
|
Shadow and weak gravitational lensing of a rotating regular black hole
in a non-minimally coupled Einstein-Yang-Mills theory in the presence of
plasma
| null |
Eur. Phys. J. Plus (2022)
|
10.1140/epjp/s13360-022-02634-6
| null |
gr-qc
|
http://creativecommons.org/licenses/by-sa/4.0/
|
The null geodesics of the regular and rotating magnetically charged black
hole in a non-minimally coupled Einstein-Yang-Mills theory surrounded by a
plasma medium is studied. The effect of magnetic charge and Yang-Mills
parameter on the effective potential and radius of photon orbits has
investigated. We then study the shadow of a regular and rotating magnetically
charged black hole along with the observables in presence of the plasma medium.
The presence of plasma medium affects the apparent size of the shadow of a
regular rotating black hole in comparison to vacuum case. Variation of shadow
radius and deformation parameter with Yang-Mills and plasma parameter has
examined. Furthermore, the deflection angle of the massless test particles in
weak field approximation around this black hole spacetime in presence of
homogeneous plasma medium is also investigated. Finally, we have compared the
obtained results with Kerr-Newman and Schwarzschild black hole solutions in
general relativity (GR).
|
[
{
"created": "Thu, 21 Jul 2022 19:12:44 GMT",
"version": "v1"
}
] |
2022-07-25
|
[
[
"Kala",
"Shubham",
""
],
[
"Nandan",
"Hemwati",
""
],
[
"Sharma",
"Prateek",
""
]
] |
The null geodesics of the regular and rotating magnetically charged black hole in a non-minimally coupled Einstein-Yang-Mills theory surrounded by a plasma medium is studied. The effect of magnetic charge and Yang-Mills parameter on the effective potential and radius of photon orbits has investigated. We then study the shadow of a regular and rotating magnetically charged black hole along with the observables in presence of the plasma medium. The presence of plasma medium affects the apparent size of the shadow of a regular rotating black hole in comparison to vacuum case. Variation of shadow radius and deformation parameter with Yang-Mills and plasma parameter has examined. Furthermore, the deflection angle of the massless test particles in weak field approximation around this black hole spacetime in presence of homogeneous plasma medium is also investigated. Finally, we have compared the obtained results with Kerr-Newman and Schwarzschild black hole solutions in general relativity (GR).
|
gr-qc/0410098
|
Donato Bini
|
D. Bini, C. Cherubini, B. Mashhoon
|
Inertial effects of an accelerating black hole
|
Proceedings of the XVI Conference of the Italian Society for General
Relativity and Gravitation (SIGRAV), Vietri (SA), September 13-16, 2004.
Prepared using revtex4 macros
|
AIP Conference Proc. 751 (2005) 37-45.
|
10.1063/1.1891528
| null |
gr-qc astro-ph
| null |
We consider the static vacuum C metric that represents the gravitational
field of a black hole of mass $m$ undergoing uniform translational acceleration
$A$ such that $mA<1/(3\sqrt{3})$. The influence of the inertial acceleration on
the exterior perturbations of this background are investigated. In particular,
we find no evidence for a direct spin-acceleration coupling.
|
[
{
"created": "Wed, 20 Oct 2004 08:35:35 GMT",
"version": "v1"
}
] |
2009-11-10
|
[
[
"Bini",
"D.",
""
],
[
"Cherubini",
"C.",
""
],
[
"Mashhoon",
"B.",
""
]
] |
We consider the static vacuum C metric that represents the gravitational field of a black hole of mass $m$ undergoing uniform translational acceleration $A$ such that $mA<1/(3\sqrt{3})$. The influence of the inertial acceleration on the exterior perturbations of this background are investigated. In particular, we find no evidence for a direct spin-acceleration coupling.
|
2006.03940
|
Badri Krishnan
|
Daniel Pook-Kolb, Ofek Birnholtz, Jose Luis Jaramillo, Badri Krishnan
and Erik Schnetter
|
Horizons in a binary black hole merger II: Fluxes, multipole moments and
stability
|
25 pages, 19 figures
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study in detail the dynamics and stability of marginally trapped surfaces
during a binary black hole merger. This is the second in a two-part study. The
first part studied the basic geometric aspects of the world tubes traced out by
the marginal surfaces and the status of the area increase law. Here we continue
and study the dynamics of the horizons during the merger, again for the head-on
collision of two non-spinning black holes. In particular we follow the spectrum
of the stability operator during the course of the merger for all the horizons
present in the problem and implement systematic spectrum statistics for its
analysis. We also study more physical aspects of the merger, namely the fluxes
of energy which cross the horizon and cause the area to change. We construct a
natural coordinate system on the horizon and decompose the various fields
appearing in the flux, primarily the shear of the outgoing null normal, in spin
weighted spherical harmonics. For each of the modes we extract the decay rates
as the final black hole approaches equilibrium. The late part of the decay is
consistent with the expected quasi-normal mode frequencies, while the early
part displays a much steeper fall-off. Similarly, we calculate the decay of the
horizon multipole moments, again finding two different regimes. Finally,
seeking an explanation for this behavior, motivated by the membrane paradigm
interpretation, we attempt to identify the different dynamical timescales of
the area increase. This leads to the definition of a ``slowness parameter'' for
predicting the onset of transition from a faster to a slower decay.
|
[
{
"created": "Sat, 6 Jun 2020 18:56:25 GMT",
"version": "v1"
}
] |
2020-06-09
|
[
[
"Pook-Kolb",
"Daniel",
""
],
[
"Birnholtz",
"Ofek",
""
],
[
"Jaramillo",
"Jose Luis",
""
],
[
"Krishnan",
"Badri",
""
],
[
"Schnetter",
"Erik",
""
]
] |
We study in detail the dynamics and stability of marginally trapped surfaces during a binary black hole merger. This is the second in a two-part study. The first part studied the basic geometric aspects of the world tubes traced out by the marginal surfaces and the status of the area increase law. Here we continue and study the dynamics of the horizons during the merger, again for the head-on collision of two non-spinning black holes. In particular we follow the spectrum of the stability operator during the course of the merger for all the horizons present in the problem and implement systematic spectrum statistics for its analysis. We also study more physical aspects of the merger, namely the fluxes of energy which cross the horizon and cause the area to change. We construct a natural coordinate system on the horizon and decompose the various fields appearing in the flux, primarily the shear of the outgoing null normal, in spin weighted spherical harmonics. For each of the modes we extract the decay rates as the final black hole approaches equilibrium. The late part of the decay is consistent with the expected quasi-normal mode frequencies, while the early part displays a much steeper fall-off. Similarly, we calculate the decay of the horizon multipole moments, again finding two different regimes. Finally, seeking an explanation for this behavior, motivated by the membrane paradigm interpretation, we attempt to identify the different dynamical timescales of the area increase. This leads to the definition of a ``slowness parameter'' for predicting the onset of transition from a faster to a slower decay.
|
gr-qc/0610098
|
Palash Baran Pal
|
Jos\'e F. Nieves and Palash B. Pal
|
Comment on ``Can gravity distinguish between Dirac and Majorana
neutrinos?''
|
1 page, Revtex, no figure
|
Phys.Rev.Lett.98:069001,2007
|
10.1103/PhysRevLett.98.069001
|
SINP/TNP/06-28
|
gr-qc
| null |
This is a comment on the paper gr-qc/0605153, by Singh, Mobed and Papini.
|
[
{
"created": "Fri, 20 Oct 2006 05:06:14 GMT",
"version": "v1"
}
] |
2008-11-26
|
[
[
"Nieves",
"José F.",
""
],
[
"Pal",
"Palash B.",
""
]
] |
This is a comment on the paper gr-qc/0605153, by Singh, Mobed and Papini.
|
gr-qc/0402023
|
D.V. Ahluwalia-Khalilova
|
D. V. Ahluwalia-Khalilova
|
Special relativity with two invariant scales: Motivation, Fermions,
Bosons, Locality, and Critique
|
Int. J. Mod. Phys. D (in press). Extended version of a set of two
informal lectures given in "La Sapienza" (Rome, May 2001)
|
Int.J.Mod.Phys.D13:335-346,2004
|
10.1142/S0218271804004633
|
CIU-002
|
gr-qc hep-th nucl-th
| null |
We present a Master equation for description of fermions and bosons for
special relativities with two invariant scales, SR2, (c and lambda_P). We
introduce canonically-conjugate variables (chi^0, chi) to (epsilon, pi) of
Judes-Visser. Together, they bring in a formal element of linearity and
locality in an otherwise non-linear and non-local theory. Special relativities
with two invariant scales provide all corrections, say, to the standard model
of the high energy physics, in terms of one fundamental constant, lambda_P. It
is emphasized that spacetime of special relativities with two invariant scales
carries an intrinsic quantum-gravitational character. In an addenda, we also
comment on the physical importance of a phase factor that the whole literature
on the subject has missed and present a brief critique of SR2. In addition, we
remark that the most natural and physically viable SR2 shall require
momentum-space and spacetime to be non-commutative with the non-commutativity
determined by the spin content and C, P, and T properties of the examined
representation space. Therefore, in a physically successful SR2, the notion of
spacetime is expected to be deeply intertwined with specific properties of the
test particle.
|
[
{
"created": "Wed, 4 Feb 2004 18:57:41 GMT",
"version": "v1"
}
] |
2008-11-26
|
[
[
"Ahluwalia-Khalilova",
"D. V.",
""
]
] |
We present a Master equation for description of fermions and bosons for special relativities with two invariant scales, SR2, (c and lambda_P). We introduce canonically-conjugate variables (chi^0, chi) to (epsilon, pi) of Judes-Visser. Together, they bring in a formal element of linearity and locality in an otherwise non-linear and non-local theory. Special relativities with two invariant scales provide all corrections, say, to the standard model of the high energy physics, in terms of one fundamental constant, lambda_P. It is emphasized that spacetime of special relativities with two invariant scales carries an intrinsic quantum-gravitational character. In an addenda, we also comment on the physical importance of a phase factor that the whole literature on the subject has missed and present a brief critique of SR2. In addition, we remark that the most natural and physically viable SR2 shall require momentum-space and spacetime to be non-commutative with the non-commutativity determined by the spin content and C, P, and T properties of the examined representation space. Therefore, in a physically successful SR2, the notion of spacetime is expected to be deeply intertwined with specific properties of the test particle.
|
1804.02842
|
Ion I. Cotaescu
|
Ion I. Cotaescu
|
Propagators of the Dirac fermions in de Sitter expanding universe
|
14 pages, no figures
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The propagators of the Dirac fermions are studied in the configuration
representation on the expanding portion of the $(1+3)$-dimensional de Sitter
spacetime considering a fixed vacuum of Bunch-Davies type. In this
representation the method of Koksma and Prokopec [J. F. Koksma and T. Prokopec,
Class. Quant. Grav. {\bf 26}, 125003 (2009)] is applied recovering thus the
form of the propagators in the massive case but obtaining a new result for the
left-handed massless fermions (neutrinos).
|
[
{
"created": "Mon, 9 Apr 2018 06:49:25 GMT",
"version": "v1"
},
{
"created": "Mon, 30 Apr 2018 15:03:50 GMT",
"version": "v2"
},
{
"created": "Tue, 1 May 2018 06:33:15 GMT",
"version": "v3"
},
{
"created": "Thu, 23 Aug 2018 12:55:24 GMT",
"version": "v4"
},
{
"created": "Mon, 3 Sep 2018 17:57:19 GMT",
"version": "v5"
},
{
"created": "Tue, 18 Sep 2018 13:11:49 GMT",
"version": "v6"
},
{
"created": "Wed, 19 Sep 2018 17:00:29 GMT",
"version": "v7"
}
] |
2018-09-20
|
[
[
"Cotaescu",
"Ion I.",
""
]
] |
The propagators of the Dirac fermions are studied in the configuration representation on the expanding portion of the $(1+3)$-dimensional de Sitter spacetime considering a fixed vacuum of Bunch-Davies type. In this representation the method of Koksma and Prokopec [J. F. Koksma and T. Prokopec, Class. Quant. Grav. {\bf 26}, 125003 (2009)] is applied recovering thus the form of the propagators in the massive case but obtaining a new result for the left-handed massless fermions (neutrinos).
|
2102.06433
|
Bahram Mashhoon
|
Bahram Mashhoon
|
Gravitomagnetic Stern--Gerlach Force
|
20 pages; v2: minor improvements; v3: references added; v4:
references [47] and [62] updated
|
Entropy 23, 445 (2021)
|
10.3390/e23040445
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
A heuristic description of the spin-rotation-gravity coupling is presented
and the implications of the corresponding gravitomagnetic Stern--Gerlach force
are briefly mentioned. It is shown, within the framework of linearized general
relativity, that the gravitomagnetic Stern--Gerlach force reduces in the
appropriate correspondence limit to the classical Mathisson spin-curvature
force.
|
[
{
"created": "Fri, 12 Feb 2021 10:28:29 GMT",
"version": "v1"
},
{
"created": "Sat, 27 Feb 2021 08:34:27 GMT",
"version": "v2"
},
{
"created": "Sun, 21 Mar 2021 14:29:57 GMT",
"version": "v3"
},
{
"created": "Fri, 9 Apr 2021 18:11:22 GMT",
"version": "v4"
}
] |
2021-04-21
|
[
[
"Mashhoon",
"Bahram",
""
]
] |
A heuristic description of the spin-rotation-gravity coupling is presented and the implications of the corresponding gravitomagnetic Stern--Gerlach force are briefly mentioned. It is shown, within the framework of linearized general relativity, that the gravitomagnetic Stern--Gerlach force reduces in the appropriate correspondence limit to the classical Mathisson spin-curvature force.
|
1901.10285
|
Sebastian Szybka
|
Sebastian J. Szybka, Adam Cie\'slik
|
Standing waves in general relativity
|
9 pages
|
Phys. Rev. D 100, 064025 (2019)
|
10.1103/PhysRevD.100.064025
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We propose a covariant definition of standing gravitational waves in general
relativity.
|
[
{
"created": "Tue, 29 Jan 2019 13:49:06 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Sep 2019 08:38:06 GMT",
"version": "v2"
}
] |
2019-09-27
|
[
[
"Szybka",
"Sebastian J.",
""
],
[
"Cieślik",
"Adam",
""
]
] |
We propose a covariant definition of standing gravitational waves in general relativity.
|
1403.0371
|
Cosimo Bambi
|
Naoki Tsukamoto, Zilong Li, Cosimo Bambi
|
Constraining the spin and the deformation parameters from the black hole
shadow
|
1+18 pages, 11 figures. v2: a few typos corrected
|
JCAP 1406:043,2014
|
10.1088/1475-7516/2014/06/043
| null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Within 5-10 years, very-long baseline interferometry (VLBI) facilities will
be able to directly image the accretion flow around SgrA$^*$, the super-massive
black hole candidate at the center of the Galaxy, and observe the black hole
"shadow". In 4-dimensional general relativity, the no-hair theorem asserts that
uncharged black holes are described by the Kerr solution and are completely
specified by their mass $M$ and by their spin parameter $a$. In this paper, we
explore the possibility of distinguishing Kerr and Bardeen black holes from
their shadow. In Hioki & Maeda (2009), under the assumption that the background
geometry is described by the Kerr solution, the authors proposed an algorithm
to estimate the value of $a/M$ by measuring the distortion parameter $\delta$,
an observable quantity that characterizes the shape of the shadow. Here, we try
to extend their approach. Since the Hioki-Maeda distortion parameter is
degenerate with respect to the spin and possible deviations from the Kerr
solution, one has to measure another quantity to test the Kerr black hole
hypothesis. We study a few possibilities. We find that it is extremely
difficult to distinguish Kerr and Bardeen black holes from the sole observation
of the shadow, and out of reach for the near future. The combination of the
measurement of the shadow with possible accurate radio observations of a pulsar
in a compact orbit around SgrA$^*$ could be a more promising strategy to verify
the Kerr black hole paradigm.
|
[
{
"created": "Mon, 3 Mar 2014 10:24:41 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Jun 2014 14:24:30 GMT",
"version": "v2"
}
] |
2014-06-19
|
[
[
"Tsukamoto",
"Naoki",
""
],
[
"Li",
"Zilong",
""
],
[
"Bambi",
"Cosimo",
""
]
] |
Within 5-10 years, very-long baseline interferometry (VLBI) facilities will be able to directly image the accretion flow around SgrA$^*$, the super-massive black hole candidate at the center of the Galaxy, and observe the black hole "shadow". In 4-dimensional general relativity, the no-hair theorem asserts that uncharged black holes are described by the Kerr solution and are completely specified by their mass $M$ and by their spin parameter $a$. In this paper, we explore the possibility of distinguishing Kerr and Bardeen black holes from their shadow. In Hioki & Maeda (2009), under the assumption that the background geometry is described by the Kerr solution, the authors proposed an algorithm to estimate the value of $a/M$ by measuring the distortion parameter $\delta$, an observable quantity that characterizes the shape of the shadow. Here, we try to extend their approach. Since the Hioki-Maeda distortion parameter is degenerate with respect to the spin and possible deviations from the Kerr solution, one has to measure another quantity to test the Kerr black hole hypothesis. We study a few possibilities. We find that it is extremely difficult to distinguish Kerr and Bardeen black holes from the sole observation of the shadow, and out of reach for the near future. The combination of the measurement of the shadow with possible accurate radio observations of a pulsar in a compact orbit around SgrA$^*$ could be a more promising strategy to verify the Kerr black hole paradigm.
|
1107.5979
|
Mariano Cadoni
|
Mariano Cadoni, Salvatore Mignemi and Matteo Serra
|
Exact solutions with AdS asymptotics of Einstein and Einstein-Maxwell
gravity minimally coupled to a scalar field
|
Some references added
| null |
10.1103/PhysRevD.84.084046
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We propose a general method for solving exactly the static field equations of
Einstein and Einstein-Maxwell gravity minimally coupled to a scalar field. Our
method starts from an ansatz for the scalar field profile, and determines,
together with the metric functions, the corresponding form of the scalar
self-interaction potential. Using this method we prove a new no-hair theorem
about the existence of hairy black-hole and black-brane solutions and derive
broad classes of static solutions with radial symmetry of the theory, which may
play an important role in applications of the AdS/CFT correspondence to
condensed matter and strongly coupled QFTs. These solutions include: 1) four-
or generic $(d+2)$-dimensional solutions with planar, spherical or hyperbolic
horizon topology; 2) solutions with AdS, domain wall and Lifshitz asymptotics;
3) solutions interpolating between an AdS spacetime in the asymptotic region
and a domain wall or conformal Lifshitz spacetime in the near-horizon region.
|
[
{
"created": "Fri, 29 Jul 2011 14:17:28 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Aug 2011 14:16:35 GMT",
"version": "v2"
}
] |
2013-05-29
|
[
[
"Cadoni",
"Mariano",
""
],
[
"Mignemi",
"Salvatore",
""
],
[
"Serra",
"Matteo",
""
]
] |
We propose a general method for solving exactly the static field equations of Einstein and Einstein-Maxwell gravity minimally coupled to a scalar field. Our method starts from an ansatz for the scalar field profile, and determines, together with the metric functions, the corresponding form of the scalar self-interaction potential. Using this method we prove a new no-hair theorem about the existence of hairy black-hole and black-brane solutions and derive broad classes of static solutions with radial symmetry of the theory, which may play an important role in applications of the AdS/CFT correspondence to condensed matter and strongly coupled QFTs. These solutions include: 1) four- or generic $(d+2)$-dimensional solutions with planar, spherical or hyperbolic horizon topology; 2) solutions with AdS, domain wall and Lifshitz asymptotics; 3) solutions interpolating between an AdS spacetime in the asymptotic region and a domain wall or conformal Lifshitz spacetime in the near-horizon region.
|
1412.8470
|
Mark D. Roberts
|
Mark D. Roberts
|
Hybrid imploding scalar and ads spacetime
|
size increased from 3 pages to 10 pages
| null |
10.1016/j.physletb.2019.06.024
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A solution to the massless scalar cosmological constant field equations is
presented. The solution has imploding scalar and parts of anti-deSitter or
deSitter spacetime as limiting cases. Some of the solutions properties are
discussed however not much can be said because of the contrasting properties of
imploding scalar and deSitter spacetimes.
|
[
{
"created": "Mon, 29 Dec 2014 14:51:28 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Feb 2015 15:32:59 GMT",
"version": "v2"
},
{
"created": "Sat, 27 Jul 2019 15:01:24 GMT",
"version": "v3"
}
] |
2019-07-30
|
[
[
"Roberts",
"Mark D.",
""
]
] |
A solution to the massless scalar cosmological constant field equations is presented. The solution has imploding scalar and parts of anti-deSitter or deSitter spacetime as limiting cases. Some of the solutions properties are discussed however not much can be said because of the contrasting properties of imploding scalar and deSitter spacetimes.
|
0710.0258
|
D\"orte Hansen
|
D\"orte Hansen
|
Next to leading order gravitational wave emission and dynamical
evolution of compact binary systems with spin
|
typos corrected; version submitted to Class. Quant. Grav
|
Class.Quant.Grav.25:165011,2008
|
10.1088/0264-9381/25/16/165011
| null |
gr-qc
| null |
Compact binary systems with spinning components are considered. Finite size
effects due to rotational deformation are taken into account. The dynamical
evolution and next to leading order gravitational wave forms are calculated,
taking into account the orbital motion up to the first post-Newtonian
approximation.
|
[
{
"created": "Mon, 1 Oct 2007 10:19:32 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Nov 2007 17:00:45 GMT",
"version": "v2"
}
] |
2008-11-26
|
[
[
"Hansen",
"Dörte",
""
]
] |
Compact binary systems with spinning components are considered. Finite size effects due to rotational deformation are taken into account. The dynamical evolution and next to leading order gravitational wave forms are calculated, taking into account the orbital motion up to the first post-Newtonian approximation.
|
1611.01435
|
Wolfgang Muschik
|
Wolfgang Muschik
|
A modified Belinfante/Rosenfeld Procedure for Testing the Compatibility
of General-Covariant Continuum Physics and General Relativity Theory
| null | null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Creating a modified Belinfante/Rosenfeld procedure, Mathisson-Papapetrou-like
equations are derived by which a comparison of General-Covariant Continuum
Physics with General Relativity Theory becomes possible.
|
[
{
"created": "Fri, 4 Nov 2016 16:11:45 GMT",
"version": "v1"
}
] |
2016-11-07
|
[
[
"Muschik",
"Wolfgang",
""
]
] |
Creating a modified Belinfante/Rosenfeld procedure, Mathisson-Papapetrou-like equations are derived by which a comparison of General-Covariant Continuum Physics with General Relativity Theory becomes possible.
|
1702.02314
|
Sergey Yu. Vernov
|
Alexander Yu. Kamenshchik, Ekaterina O. Pozdeeva, Sergey Yu. Vernov,
Alessandro Tronconi, Giovanni Venturi
|
Bianchi-I cosmological model and crossing singularities
|
11 pages, v2: accepted for publication in Phys. Rev. D
|
Phys. Rev. D 95, 083503 (2017)
|
10.1103/PhysRevD.95.083503
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider a rather simple method for the description of the Big Bang - Big
Crunch cosmological singularity crossing. For the flat Friedmann universe this
method gives the same results as more complicated methods, using Weyl symmetry
or the transitions between the Jordan and Einstein frames. It is then easily
generalized for the case of a Bianchi-I anisotropic universe. We also present
early-time and late-time asymptotic solutions for a Bianchi-I universe, filled
with a conformally coupled massless scalar field.
|
[
{
"created": "Wed, 8 Feb 2017 07:50:16 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Mar 2017 12:28:39 GMT",
"version": "v2"
}
] |
2017-04-12
|
[
[
"Kamenshchik",
"Alexander Yu.",
""
],
[
"Pozdeeva",
"Ekaterina O.",
""
],
[
"Vernov",
"Sergey Yu.",
""
],
[
"Tronconi",
"Alessandro",
""
],
[
"Venturi",
"Giovanni",
""
]
] |
We consider a rather simple method for the description of the Big Bang - Big Crunch cosmological singularity crossing. For the flat Friedmann universe this method gives the same results as more complicated methods, using Weyl symmetry or the transitions between the Jordan and Einstein frames. It is then easily generalized for the case of a Bianchi-I anisotropic universe. We also present early-time and late-time asymptotic solutions for a Bianchi-I universe, filled with a conformally coupled massless scalar field.
|
1808.09099
|
Fabio Biancalana
|
Charles W. Robson, Leone Di Mauro Villari and Fabio Biancalana
|
Universal quantum Hawking evaporation of integrable two-dimensional
solitons
| null | null |
10.1088/1367-2630/ab1bf5
| null |
gr-qc hep-th nlin.PS nlin.SI physics.optics quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We show that any soliton solution of an arbitrary two-dimensional integrable
equation has the potential to eventually evaporate and emit the exact analogue
of Hawking radiation from black holes. From the AKNS matrix formulation of
integrability, we show that it is possible to associate a real spacetime metric
tensor which defines a curved surface, perceived by the classical and quantum
fluctuations propagating on the soliton. By defining proper scalar invariants
of the associated Riemannian geometry, and introducing the conformal anomaly,
we are able to determine the Hawking temperatures and entropies of the
fundamental solitons of the nonlinear Schroedinger, KdV and sine-Gordon
equations. The mechanism advanced here is simple, completely universal and can
be applied to all integrable equations in two dimensions, and is easily
applicable to a large class of black holes of any dimensionality, opening up
totally new windows on the quantum mechanics of solitons and their deep
connections with black hole physics.
|
[
{
"created": "Mon, 27 Aug 2018 09:04:11 GMT",
"version": "v1"
}
] |
2019-09-04
|
[
[
"Robson",
"Charles W.",
""
],
[
"Villari",
"Leone Di Mauro",
""
],
[
"Biancalana",
"Fabio",
""
]
] |
We show that any soliton solution of an arbitrary two-dimensional integrable equation has the potential to eventually evaporate and emit the exact analogue of Hawking radiation from black holes. From the AKNS matrix formulation of integrability, we show that it is possible to associate a real spacetime metric tensor which defines a curved surface, perceived by the classical and quantum fluctuations propagating on the soliton. By defining proper scalar invariants of the associated Riemannian geometry, and introducing the conformal anomaly, we are able to determine the Hawking temperatures and entropies of the fundamental solitons of the nonlinear Schroedinger, KdV and sine-Gordon equations. The mechanism advanced here is simple, completely universal and can be applied to all integrable equations in two dimensions, and is easily applicable to a large class of black holes of any dimensionality, opening up totally new windows on the quantum mechanics of solitons and their deep connections with black hole physics.
|
gr-qc/9307008
| null |
C.Barrabes, B.Boisseau and M.Sakellariadou
|
Gravitational Effects on Domain Walls with Curvature Correction
| null |
Phys.Rev. D49 (1994) 2734-2739
|
10.1103/PhysRevD.49.2734
| null |
gr-qc
| null |
We derive the effective action for a domain wall with small thickness in
curved spacetime and show that, apart from the Nambu term, it includes a
contribution proportional to the induced curvature. We then use this action to
study the dynamics of a spherical thick bubble of false vacuum (de Sitter)
surrounded by an infinite region of true vacuum (Schwarzschild).
|
[
{
"created": "Fri, 9 Jul 1993 19:27:31 GMT",
"version": "v1"
}
] |
2009-10-22
|
[
[
"Barrabes",
"C.",
""
],
[
"Boisseau",
"B.",
""
],
[
"Sakellariadou",
"M.",
""
]
] |
We derive the effective action for a domain wall with small thickness in curved spacetime and show that, apart from the Nambu term, it includes a contribution proportional to the induced curvature. We then use this action to study the dynamics of a spherical thick bubble of false vacuum (de Sitter) surrounded by an infinite region of true vacuum (Schwarzschild).
|
1402.6452
|
Lijing Shao
|
Lijing Shao
|
Tests of local Lorentz invariance violation of gravity in the standard
model extension with pulsars
|
minor modification; published in Physical Review Letters
|
Physical Review Letters 112 (2014) 111103
|
10.1103/PhysRevLett.112.111103
| null |
gr-qc astro-ph.HE hep-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Standard-model extension (SME) is an effective field theory introducing all
possible Lorentz-violating (LV) operators to the standard model (SM) and
general relativity (GR). In the pure-gravity sector of minimal SME (mSME), nine
coefficients describe dominant observable deviations from GR. We systematically
implemented twenty-seven tests from thirteen pulsar systems to tightly
constrain eight linear combinations of these coefficients with extensive Monte
Carlo simulations. It constitutes the first detailed and systematic test of the
pure-gravity sector of mSME with the state-of-the-art pulsar observations. No
deviation from GR was detected. The limits of LV coefficients are expressed in
the canonical Sun-centered celestial-equatorial frame for convenience of
further studies. They are all improved by significant factors of tens to
hundreds with existing ones. As a consequence, Einstein's equivalence principle
is verified substantially further by pulsar experiments in terms of local
Lorentz invariance in gravity.
|
[
{
"created": "Wed, 26 Feb 2014 08:36:36 GMT",
"version": "v1"
},
{
"created": "Sun, 23 Mar 2014 01:46:29 GMT",
"version": "v2"
}
] |
2014-03-25
|
[
[
"Shao",
"Lijing",
""
]
] |
Standard-model extension (SME) is an effective field theory introducing all possible Lorentz-violating (LV) operators to the standard model (SM) and general relativity (GR). In the pure-gravity sector of minimal SME (mSME), nine coefficients describe dominant observable deviations from GR. We systematically implemented twenty-seven tests from thirteen pulsar systems to tightly constrain eight linear combinations of these coefficients with extensive Monte Carlo simulations. It constitutes the first detailed and systematic test of the pure-gravity sector of mSME with the state-of-the-art pulsar observations. No deviation from GR was detected. The limits of LV coefficients are expressed in the canonical Sun-centered celestial-equatorial frame for convenience of further studies. They are all improved by significant factors of tens to hundreds with existing ones. As a consequence, Einstein's equivalence principle is verified substantially further by pulsar experiments in terms of local Lorentz invariance in gravity.
|
2105.07956
|
Carlos A. S. Almeida
|
R. Oliveira, D. M. Dantas, and C. A. S. Almeida
|
Quasinormal frequencies for a black hole in a bumblebee gravity
|
12 pages, 10 figures
| null |
10.1209/0295-5075/ac130c
| null |
gr-qc hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
After recent observational events like the LIGO-Virgo detections of
gravitational waves and the shadow image of M87* supermassive black hole by
Event Horizon Telescope (EHT), the theoretical study of black holes was
significantly improved. Quantities as quasinormal frequencies, shadows, and
light deflection become more important to analyze black hole models. In this
context, an interesting scenario to study is a black hole in the bumblebee
gravity. The bumblebee vector field imposes a spontaneous symmetry breaking
that allows the field to acquire a vacuum expectation value that generates
Lorentz-Violating (LV) into the black hole. In order to compute the quasinormal
modes (QNMs) via the WKB method, we obtain the Reege-Wheeler's equation with a
bell-shaped potential for this black hole. Both QNMs, the scalar and tensorial
modes, are computed for the black hole in the bumblebee scenario. Moreover, the
stability of the Schwarzschild-like solution and some bounds to LV parameters
are analyzed.
|
[
{
"created": "Thu, 13 May 2021 23:14:19 GMT",
"version": "v1"
}
] |
2021-09-22
|
[
[
"Oliveira",
"R.",
""
],
[
"Dantas",
"D. M.",
""
],
[
"Almeida",
"C. A. S.",
""
]
] |
After recent observational events like the LIGO-Virgo detections of gravitational waves and the shadow image of M87* supermassive black hole by Event Horizon Telescope (EHT), the theoretical study of black holes was significantly improved. Quantities as quasinormal frequencies, shadows, and light deflection become more important to analyze black hole models. In this context, an interesting scenario to study is a black hole in the bumblebee gravity. The bumblebee vector field imposes a spontaneous symmetry breaking that allows the field to acquire a vacuum expectation value that generates Lorentz-Violating (LV) into the black hole. In order to compute the quasinormal modes (QNMs) via the WKB method, we obtain the Reege-Wheeler's equation with a bell-shaped potential for this black hole. Both QNMs, the scalar and tensorial modes, are computed for the black hole in the bumblebee scenario. Moreover, the stability of the Schwarzschild-like solution and some bounds to LV parameters are analyzed.
|
1903.06951
|
Ian Vega
|
Karlo de Leon, Ian Vega
|
Weak gravitational lensing by two-power-law densities using the
Gauss-Bonnet theorem
|
11 pages, 3 figures
|
Phys. Rev. D 99, 124007 (2019)
|
10.1103/PhysRevD.99.124007
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the weak-field deflection of light by mass distributions described
by two-power-law densities $\rho(R)=\rho_0 R^{-\alpha}(R+1)^{\beta-\alpha}$,
where $\alpha$ and $\beta$ are non-negative integers. New analytic expressions
of deflection angles are obtained via the application of the Gauss-Bonnet
theorem to a chosen surface on the optical manifold. Some of the well-known
models of this two-power law form are the Navarro-Frenk-White (NFW) model
$(\alpha,\beta)=(1,3)$, Hernquist $(1,4)$, Jaffe $(2,4)$, and the singular
isothermal sphere $(2,2)$. The calculated deflection angles for Hernquist and
NFW agrees with that of Keeton and Bartelmann, respectively. The limiting
values of these deflection angles (at zero or infinite impact parameter) are
either vanishing or similar to the deflection due to a singular isothermal
sphere. We show that these behaviors can be attributed to the topological
properties of the optical manifold, thus extending the pioneering insight of
Werner and Gibbons to a broader class of mass densities.
|
[
{
"created": "Sat, 16 Mar 2019 16:07:18 GMT",
"version": "v1"
}
] |
2019-06-19
|
[
[
"de Leon",
"Karlo",
""
],
[
"Vega",
"Ian",
""
]
] |
We study the weak-field deflection of light by mass distributions described by two-power-law densities $\rho(R)=\rho_0 R^{-\alpha}(R+1)^{\beta-\alpha}$, where $\alpha$ and $\beta$ are non-negative integers. New analytic expressions of deflection angles are obtained via the application of the Gauss-Bonnet theorem to a chosen surface on the optical manifold. Some of the well-known models of this two-power law form are the Navarro-Frenk-White (NFW) model $(\alpha,\beta)=(1,3)$, Hernquist $(1,4)$, Jaffe $(2,4)$, and the singular isothermal sphere $(2,2)$. The calculated deflection angles for Hernquist and NFW agrees with that of Keeton and Bartelmann, respectively. The limiting values of these deflection angles (at zero or infinite impact parameter) are either vanishing or similar to the deflection due to a singular isothermal sphere. We show that these behaviors can be attributed to the topological properties of the optical manifold, thus extending the pioneering insight of Werner and Gibbons to a broader class of mass densities.
|
2004.15002
|
Romain Ruzziconi
|
Glenn Barnich, Pujian Mao, Romain Ruzziconi
|
Conserved currents in the Palatini formulation of general relativity
|
12 Pages
|
PoS (CORFU2019) 171
|
10.22323/1.376.0171
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We derive the expressions for the local, on-shell closed co-dimension 2 forms
in the Palatini formulation of general relativity and explicitly show their
on-shell equivalence to those of the metric formulation. When compared to other
first order formulations, two subtleties have to be addressed during the
construction: off-shell non-metricity and the fact that the transformation of
the connection under infinitesimal diffeomorphisms involves second order
derivatives of the associated vector fields.
|
[
{
"created": "Thu, 30 Apr 2020 17:48:21 GMT",
"version": "v1"
}
] |
2020-08-21
|
[
[
"Barnich",
"Glenn",
""
],
[
"Mao",
"Pujian",
""
],
[
"Ruzziconi",
"Romain",
""
]
] |
We derive the expressions for the local, on-shell closed co-dimension 2 forms in the Palatini formulation of general relativity and explicitly show their on-shell equivalence to those of the metric formulation. When compared to other first order formulations, two subtleties have to be addressed during the construction: off-shell non-metricity and the fact that the transformation of the connection under infinitesimal diffeomorphisms involves second order derivatives of the associated vector fields.
|
0804.3840
|
Kouji Nakamura
|
Kouji Nakamura
|
Perturbations of Matter Fields in the Second-order Gauge-invariant
Cosmological Perturbation Theory
|
(v1) 76 pages, no figure; (v2) minor revision, typos are corrected,
references are added; (v3) Title is changed, Compactified into 55 pages,
Comment on the comparison with the other work is added; (v4)typos are
corrected
|
Phys.Rev.D80:124021,2009
|
10.1103/PhysRevD.80.124021
| null |
gr-qc astro-ph hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Some formulae for the perturbations of the matter fields are summarized
within the framework of the second-order gauge-invariant cosmological
perturbation theory in a four dimensional homogeneous isotropic universe, which
is developed in the papers [K.Nakamura, Prog.Theor.Phys., 117 (2007), 17.]. We
derive the formulae for the perturbations of the energy momentum tensors and
equations of motion for a perfect fluid, an imperfect fluid, and a signle
scalar field, and show that all equations are derived in terms of
gauge-invariant variables without any gauge fixing.
|
[
{
"created": "Thu, 24 Apr 2008 05:27:31 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Jul 2008 06:51:49 GMT",
"version": "v2"
},
{
"created": "Wed, 31 Dec 2008 06:48:10 GMT",
"version": "v3"
},
{
"created": "Sat, 3 Jan 2009 05:50:35 GMT",
"version": "v4"
}
] |
2009-12-30
|
[
[
"Nakamura",
"Kouji",
""
]
] |
Some formulae for the perturbations of the matter fields are summarized within the framework of the second-order gauge-invariant cosmological perturbation theory in a four dimensional homogeneous isotropic universe, which is developed in the papers [K.Nakamura, Prog.Theor.Phys., 117 (2007), 17.]. We derive the formulae for the perturbations of the energy momentum tensors and equations of motion for a perfect fluid, an imperfect fluid, and a signle scalar field, and show that all equations are derived in terms of gauge-invariant variables without any gauge fixing.
|
1310.1963
|
Emil Mottola
|
Paul R. Anderson (Wake Forest Univ.) and Emil Mottola (Los Alamos
National Laboratory)
|
Quantum Vacuum Instability of 'Eternal' de Sitter Space
|
47 pages, 11 figures
|
Phys. Rev. D 89, 104039 (2014)
|
10.1103/PhysRevD.89.104039
|
LA-UR-13-26990
|
gr-qc astro-ph.CO hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The Euclidean or Bunch-Davies O(4,1) invariant 'vacuum' state of quantum
fields in global de Sitter space is shown to be unstable to small
perturbations, even for a massive free field with no self-interactions. There
are perturbations of this state with arbitrarily small energy density at early
times that is exponentially blueshifted in the contracting phase of 'eternal'
de Sitter space, and becomes large enough to disturb the classical geometry
through the semiclassical Einstein eqs. at later times. In the closely
analogous case of a constant, uniform electric field, a time symmetric state
equivalent to the de Sitter invariant one is constructed, which is also not a
stable vacuum state under perturbations. The role of a quantum anomaly in the
growth of perturbations and symmetry breaking is emphasized in both cases. In
de Sitter space, the same results are obtained either directly from the
renormalized stress tensor of a massive scalar field, or for massless conformal
fields of any spin, more directly from the effective action and stress tensor
associated with the conformal trace anomaly. The anomaly stress tensor shows
that states invariant under the O(4) subgroup of the de Sitter group are also
unstable to perturbations of lower spatial symmetry, implying that both the
O(4,1) isometry group and its O(4) subgroup are broken by quantum fluctuations.
Consequences of this result for cosmology and the problem of vacuum energy are
discussed.
|
[
{
"created": "Mon, 7 Oct 2013 22:05:35 GMT",
"version": "v1"
}
] |
2014-05-28
|
[
[
"Anderson",
"Paul R.",
"",
"Wake Forest Univ."
],
[
"Mottola",
"Emil",
"",
"Los Alamos\n National Laboratory"
]
] |
The Euclidean or Bunch-Davies O(4,1) invariant 'vacuum' state of quantum fields in global de Sitter space is shown to be unstable to small perturbations, even for a massive free field with no self-interactions. There are perturbations of this state with arbitrarily small energy density at early times that is exponentially blueshifted in the contracting phase of 'eternal' de Sitter space, and becomes large enough to disturb the classical geometry through the semiclassical Einstein eqs. at later times. In the closely analogous case of a constant, uniform electric field, a time symmetric state equivalent to the de Sitter invariant one is constructed, which is also not a stable vacuum state under perturbations. The role of a quantum anomaly in the growth of perturbations and symmetry breaking is emphasized in both cases. In de Sitter space, the same results are obtained either directly from the renormalized stress tensor of a massive scalar field, or for massless conformal fields of any spin, more directly from the effective action and stress tensor associated with the conformal trace anomaly. The anomaly stress tensor shows that states invariant under the O(4) subgroup of the de Sitter group are also unstable to perturbations of lower spatial symmetry, implying that both the O(4,1) isometry group and its O(4) subgroup are broken by quantum fluctuations. Consequences of this result for cosmology and the problem of vacuum energy are discussed.
|
1309.4836
|
Yusuke Sakakibara
|
Y. Sakakibara, N. Kimura, T. Suzuki, K. Yamamoto, D. Chen, S. Koike,
C. Tokoku, T. Uchiyama, M. Ohashi and K. Kuroda
|
A Study of Cooling Time Reduction of Interferometric Cryogenic
Gravitational Wave Detectors Using a High-Emissivity Coating
|
8 pages, 9 figures, Proceedings of CEC/ICMC 2013
| null |
10.1063/1.4860839
| null |
gr-qc astro-ph.IM physics.ins-det
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In interferometric cryogenic gravitational wave detectors, there are plans to
cool mirrors and their suspension systems (payloads) in order to reduce thermal
noise, that is, one of the fundamental noise sources. Because of the large
payload masses (several hundred kg in total) and their thermal isolation, a
cooling time of several months is required. Our calculation shows that a
high-emissivity coating (e.g. a diamond-like carbon (DLC) coating) can reduce
the cooling time effectively by enhancing radiation heat transfer. Here, we
have experimentally verified the effect of the DLC coating on the reduction of
the cooling time.
|
[
{
"created": "Thu, 19 Sep 2013 02:12:48 GMT",
"version": "v1"
}
] |
2014-03-05
|
[
[
"Sakakibara",
"Y.",
""
],
[
"Kimura",
"N.",
""
],
[
"Suzuki",
"T.",
""
],
[
"Yamamoto",
"K.",
""
],
[
"Chen",
"D.",
""
],
[
"Koike",
"S.",
""
],
[
"Tokoku",
"C.",
""
],
[
"Uchiyama",
"T.",
""
],
[
"Ohashi",
"M.",
""
],
[
"Kuroda",
"K.",
""
]
] |
In interferometric cryogenic gravitational wave detectors, there are plans to cool mirrors and their suspension systems (payloads) in order to reduce thermal noise, that is, one of the fundamental noise sources. Because of the large payload masses (several hundred kg in total) and their thermal isolation, a cooling time of several months is required. Our calculation shows that a high-emissivity coating (e.g. a diamond-like carbon (DLC) coating) can reduce the cooling time effectively by enhancing radiation heat transfer. Here, we have experimentally verified the effect of the DLC coating on the reduction of the cooling time.
|
2002.00437
|
Maxim Eingorn
|
Ezgi Canay, Maxim Eingorn
|
Duel of cosmological screening lengths
|
17 pages, one nice figure
|
Physics of the Dark Universe 29, 100565 (2020)
|
10.1016/j.dark.2020.100565
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Two distinct perturbative approaches have been recently formulated within
General Relativity, arguing for the screening of gravity in the $\Lambda$CDM
Universe. In this paper we compare them and show that the offered screening
concepts, each characterized by its own interaction range, can peacefully
coexist. Accordingly, we advance a united scheme, determining the gravitational
potential at all scales, including regions of nonlinear density contrasts, by
means of a simple Helmholtz equation with the effective cosmological screening
length. In addition, we claim that cosmic structures may not grow at distances
above this Yukawa range and confront its current value with dimensions of the
largest known objects in the Universe.
|
[
{
"created": "Sun, 2 Feb 2020 17:47:00 GMT",
"version": "v1"
}
] |
2020-04-30
|
[
[
"Canay",
"Ezgi",
""
],
[
"Eingorn",
"Maxim",
""
]
] |
Two distinct perturbative approaches have been recently formulated within General Relativity, arguing for the screening of gravity in the $\Lambda$CDM Universe. In this paper we compare them and show that the offered screening concepts, each characterized by its own interaction range, can peacefully coexist. Accordingly, we advance a united scheme, determining the gravitational potential at all scales, including regions of nonlinear density contrasts, by means of a simple Helmholtz equation with the effective cosmological screening length. In addition, we claim that cosmic structures may not grow at distances above this Yukawa range and confront its current value with dimensions of the largest known objects in the Universe.
|
1703.03295
|
Swagat Saurav Mishra
|
Swagat S. Mishra, Varun Sahni and Yuri Shtanov
|
Sourcing Dark Matter and Dark Energy from $\alpha$-attractors
|
43 pages, 22 figures, Some clarifications and an additional
reference. Main results unchanged. Accepted for publication in JCAP
|
JCAP 06 (2017) 045
|
10.1088/1475-7516/2017/06/045
| null |
gr-qc astro-ph.CO hep-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Recently, Kallosh and Linde have drawn attention to a new family of
superconformal inflationary potentials, subsequently called
$\alpha$-attractors. The $\alpha$-attractor family can interpolate between a
large class of inflationary models. It also has an important theoretical
underpinning within the framework of supergravity. We demonstrate that the
$\alpha$-attractors have an even wider appeal since they may describe dark
matter and perhaps even dark energy. The dark matter associated with the
$\alpha$-attractors, which we call $\alpha$-dark matter ($\alpha$DM), shares
many of the attractive features of fuzzy dark matter, with $V(\varphi) =
\frac{1}{2}m^2\varphi^2$, while having none of its drawbacks. Like fuzzy dark
matter, $\alpha$DM can have a large Jeans length which could resolve the
cusp-core and substructure problems faced by standard cold dark matter.
$\alpha$DM also has an appealing tracker property which enables it to converge
to the late-time dark matter asymptote, $\langle w\rangle \simeq 0$, from a
wide range of initial conditions. It thus avoids the enormous fine-tuning
problems faced by the $m^2\varphi^2$ potential in describing dark matter.
|
[
{
"created": "Tue, 7 Mar 2017 19:00:59 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Mar 2017 05:05:12 GMT",
"version": "v2"
},
{
"created": "Fri, 16 Jun 2017 06:32:51 GMT",
"version": "v3"
}
] |
2018-10-26
|
[
[
"Mishra",
"Swagat S.",
""
],
[
"Sahni",
"Varun",
""
],
[
"Shtanov",
"Yuri",
""
]
] |
Recently, Kallosh and Linde have drawn attention to a new family of superconformal inflationary potentials, subsequently called $\alpha$-attractors. The $\alpha$-attractor family can interpolate between a large class of inflationary models. It also has an important theoretical underpinning within the framework of supergravity. We demonstrate that the $\alpha$-attractors have an even wider appeal since they may describe dark matter and perhaps even dark energy. The dark matter associated with the $\alpha$-attractors, which we call $\alpha$-dark matter ($\alpha$DM), shares many of the attractive features of fuzzy dark matter, with $V(\varphi) = \frac{1}{2}m^2\varphi^2$, while having none of its drawbacks. Like fuzzy dark matter, $\alpha$DM can have a large Jeans length which could resolve the cusp-core and substructure problems faced by standard cold dark matter. $\alpha$DM also has an appealing tracker property which enables it to converge to the late-time dark matter asymptote, $\langle w\rangle \simeq 0$, from a wide range of initial conditions. It thus avoids the enormous fine-tuning problems faced by the $m^2\varphi^2$ potential in describing dark matter.
|
gr-qc/9504004
|
Ted Jacobson
|
Ted Jacobson
|
Thermodynamics of Spacetime: The Einstein Equation of State
|
8 pages, 1 figure. Revised version has core unchanged but paper
rewritten and expanded to clarify the reasoning and to emphasize some points.
One figure added
|
Phys.Rev.Lett.75:1260-1263,1995
|
10.1103/PhysRevLett.75.1260
|
UMDGR-95-114
|
gr-qc hep-th
| null |
The Einstein equation is derived from the proportionality of entropy and
horizon area together with the fundamental relation $\delta Q=TdS$ connecting
heat, entropy, and temperature. The key idea is to demand that this relation
hold for all the local Rindler causal horizons through each spacetime point,
with $\delta Q$ and $T$ interpreted as the energy flux and Unruh temperature
seen by an accelerated observer just inside the horizon. This requires that
gravitational lensing by matter energy distorts the causal structure of
spacetime in just such a way that the Einstein equation holds. Viewed in this
way, the Einstein equation is an equation of state. This perspective suggests
that it may be no more appropriate to canonically quantize the Einstein
equation than it would be to quantize the wave equation for sound in air.
|
[
{
"created": "Tue, 4 Apr 1995 18:54:14 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Jun 1995 17:47:58 GMT",
"version": "v2"
}
] |
2010-11-01
|
[
[
"Jacobson",
"Ted",
""
]
] |
The Einstein equation is derived from the proportionality of entropy and horizon area together with the fundamental relation $\delta Q=TdS$ connecting heat, entropy, and temperature. The key idea is to demand that this relation hold for all the local Rindler causal horizons through each spacetime point, with $\delta Q$ and $T$ interpreted as the energy flux and Unruh temperature seen by an accelerated observer just inside the horizon. This requires that gravitational lensing by matter energy distorts the causal structure of spacetime in just such a way that the Einstein equation holds. Viewed in this way, the Einstein equation is an equation of state. This perspective suggests that it may be no more appropriate to canonically quantize the Einstein equation than it would be to quantize the wave equation for sound in air.
|
0910.0335
|
Vladimir S. Manko
|
V.S. Manko and E. Ruiz
|
Schwarzschild black hole levitating in the hyperextreme Kerr field
|
6 pages, 1 figure; improved version
|
Gen. Rel. Grav. 44: 2891-2899, 2012
|
10.1007/s10714-012-1429-1
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The equilibrium configurations between a Schwarzschild black hole and a
hyperextreme Kerr object are shown to be described by a three-parameter
subfamily of the extended double-Kerr solution. For this subfamily, its Ernst
potential and corresponding metric functions, we provide a physical
representation which employs as arbitrary parameters the individual Komar
masses and relative coordinate distance between the sources. The calculation of
horizon's local angular velocity induced in the Schwarzschild black hole by the
Kerr constituent yields a simple expression inversely proportional to the
square of the distance parameter.
|
[
{
"created": "Fri, 2 Oct 2009 07:04:38 GMT",
"version": "v1"
},
{
"created": "Thu, 5 Nov 2015 06:33:06 GMT",
"version": "v2"
}
] |
2015-11-06
|
[
[
"Manko",
"V. S.",
""
],
[
"Ruiz",
"E.",
""
]
] |
The equilibrium configurations between a Schwarzschild black hole and a hyperextreme Kerr object are shown to be described by a three-parameter subfamily of the extended double-Kerr solution. For this subfamily, its Ernst potential and corresponding metric functions, we provide a physical representation which employs as arbitrary parameters the individual Komar masses and relative coordinate distance between the sources. The calculation of horizon's local angular velocity induced in the Schwarzschild black hole by the Kerr constituent yields a simple expression inversely proportional to the square of the distance parameter.
|
1706.07482
|
Abhay Ashtekar
|
Abhay Ashtekar
|
Implications of a positive cosmological constant for general relativity
|
A Key Issues Review, Commissioned by Rep. Prog. Phys. 12 pages, 3
figures
|
Rep. Prog. Phys. 80, 102901 (2017)
|
10.1088/1361-6633/aa7bb1
| null |
gr-qc hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Most of the literature on general relativity over the last century assumes
that the cosmological constant $\Lambda$ is zero. However, by now independent
observations have led to a consensus that the dynamics of the universe is best
described by Einstein's equations with a small but positive $\Lambda$.
Interestingly, this requires a drastic revision of conceptual frameworks
commonly used in general relativity, \emph{no matter how small $\Lambda$ is.}
We first explain why, and then summarize the current status of generalizations
of these frameworks to include a positive $\Lambda$, focusing on gravitational
waves.
|
[
{
"created": "Thu, 22 Jun 2017 20:37:33 GMT",
"version": "v1"
}
] |
2021-04-02
|
[
[
"Ashtekar",
"Abhay",
""
]
] |
Most of the literature on general relativity over the last century assumes that the cosmological constant $\Lambda$ is zero. However, by now independent observations have led to a consensus that the dynamics of the universe is best described by Einstein's equations with a small but positive $\Lambda$. Interestingly, this requires a drastic revision of conceptual frameworks commonly used in general relativity, \emph{no matter how small $\Lambda$ is.} We first explain why, and then summarize the current status of generalizations of these frameworks to include a positive $\Lambda$, focusing on gravitational waves.
|
gr-qc/9506031
|
Marcelo Jose Reboucas
|
J. Santos, M.J. Reboucas, A.F.F. Teixeira
|
Classification of Second Order Symmetric Tensors in 5-Dimensional
Kaluza-Klein-Type Theories
|
22 pages, To appear in J. Math. Phys 36 (1995)
|
J.Math.Phys. 36 (1995) 3074-3084
|
10.1063/1.531013
|
CBPF-NF-052/94
|
gr-qc astro-ph
| null |
An algebraic classification of second order symmetric tensors in
5-dimensional Kaluza-Klein-type Lorentzian spaces is presented by using Jordan
matrices. We show that the possible Segre types are $[1,1111]$, [2111], [311],
[z,\bar{z},111], and the degeneracies thereof. A set of canonical forms for
each Segre type is found. The possible continuous groups of symmetry for each
canonical form are also studied.
|
[
{
"created": "Sat, 17 Jun 1995 01:51:15 GMT",
"version": "v1"
}
] |
2015-06-25
|
[
[
"Santos",
"J.",
""
],
[
"Reboucas",
"M. J.",
""
],
[
"Teixeira",
"A. F. F.",
""
]
] |
An algebraic classification of second order symmetric tensors in 5-dimensional Kaluza-Klein-type Lorentzian spaces is presented by using Jordan matrices. We show that the possible Segre types are $[1,1111]$, [2111], [311], [z,\bar{z},111], and the degeneracies thereof. A set of canonical forms for each Segre type is found. The possible continuous groups of symmetry for each canonical form are also studied.
|
gr-qc/9909088
|
Iver H. Brevik
|
I. Brevik and A. G. Fr{\o}seth
|
Energy Production in the Formation of a Finite Thickness Cosmic String
|
20 pages, LaTeX, no figures
|
Phys.Rev.D61:085011,2000
|
10.1103/PhysRevD.61.085011
| null |
gr-qc
| null |
The classical electromagnetic modes outside a long, straight, superconducting
cosmic string are calculated, assuming the string to be surrounded by a
superconducting cylindric surface of radius R. Thereafter, by use of a
Bogoliubov-type argument, the electromagnetic energy W produced per unit length
in the lowest two modes is calculated when the string is formed "suddenly". The
essential new element in the present analysis as compared with prior work of
Parker [Phys. Rev. Lett. {\bf 59}, 1369 (1987)] and Brevik and Toverud [Phys.
Rev. D {\bf 51}, 691 (1995)], is that the radius {\it a} of the string is
assumed finite, thus necessitating Neumann functions to be included in the
fundamental modes. We find that the theory is changed significantly: W is now
strongly concentrated in the lowest mode $(m,s)=(0,1)$, whereas the
proportionality $W \propto (G\mu /t)^2$ that is characteristic for zero-width
strings is found in the next mode (1,1). Here G is the gravitational constant,
$\mu$ the string mass per unit length, and t the GUT time.
|
[
{
"created": "Wed, 29 Sep 1999 15:32:45 GMT",
"version": "v1"
}
] |
2009-01-14
|
[
[
"Brevik",
"I.",
""
],
[
"Frøseth",
"A. G.",
""
]
] |
The classical electromagnetic modes outside a long, straight, superconducting cosmic string are calculated, assuming the string to be surrounded by a superconducting cylindric surface of radius R. Thereafter, by use of a Bogoliubov-type argument, the electromagnetic energy W produced per unit length in the lowest two modes is calculated when the string is formed "suddenly". The essential new element in the present analysis as compared with prior work of Parker [Phys. Rev. Lett. {\bf 59}, 1369 (1987)] and Brevik and Toverud [Phys. Rev. D {\bf 51}, 691 (1995)], is that the radius {\it a} of the string is assumed finite, thus necessitating Neumann functions to be included in the fundamental modes. We find that the theory is changed significantly: W is now strongly concentrated in the lowest mode $(m,s)=(0,1)$, whereas the proportionality $W \propto (G\mu /t)^2$ that is characteristic for zero-width strings is found in the next mode (1,1). Here G is the gravitational constant, $\mu$ the string mass per unit length, and t the GUT time.
|
2303.06239
|
Chengcheng Liu
|
Chengcheng Liu, Shahn Majid
|
Quantum Kaluza-Klein theory with $M_2(\mathbb{C})$
| null |
JHEP 09 (2023) 102
|
10.1007/JHEP09(2023)102
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Following steps analogous to classical Kaluza-Klein theory, we solve for the
quantum Riemannian geometry on $C^\infty(M)\otimes M_2(\mathbb{C})$ in terms of
classical Riemannian geometry on a smooth manifold $M$, a finite quantum
geometry on the algebra $M_2(\mathbb{C})$ of $2\times 2$ matrices, and a
quantum metric cross term. Fixing a standard form of quantum metric on
$M_2(\mathbb{C})$, we show that this cross term data amounts in the simplest
case to a 1-form $A_\mu$ on $M$, which we regard as like a gauge-fixed
background field. We show in this case that a real scalar field on the product
algebra with its noncommutative Laplacian decomposes on $M$ into two real
neutral fields and one complex charged field minimally coupled to $A_\mu$. We
show further that the quantum Ricci scalar on the product decomposes into a
classical Ricci scalar on $M$, the Ricci scalar on $M_2(\mathbb{C})$, the
Maxwell action $||F||^2$ of $A$ and a higher order $||A.F||^2$ term. Another
solution of the QRG on the product has $A=0$ and a dynamical real scalar field
$\phi$ on $M$ which imparts mass-splitting to some of the components of a
scalar field on the product as in previous work.
|
[
{
"created": "Fri, 10 Mar 2023 23:09:22 GMT",
"version": "v1"
}
] |
2023-11-03
|
[
[
"Liu",
"Chengcheng",
""
],
[
"Majid",
"Shahn",
""
]
] |
Following steps analogous to classical Kaluza-Klein theory, we solve for the quantum Riemannian geometry on $C^\infty(M)\otimes M_2(\mathbb{C})$ in terms of classical Riemannian geometry on a smooth manifold $M$, a finite quantum geometry on the algebra $M_2(\mathbb{C})$ of $2\times 2$ matrices, and a quantum metric cross term. Fixing a standard form of quantum metric on $M_2(\mathbb{C})$, we show that this cross term data amounts in the simplest case to a 1-form $A_\mu$ on $M$, which we regard as like a gauge-fixed background field. We show in this case that a real scalar field on the product algebra with its noncommutative Laplacian decomposes on $M$ into two real neutral fields and one complex charged field minimally coupled to $A_\mu$. We show further that the quantum Ricci scalar on the product decomposes into a classical Ricci scalar on $M$, the Ricci scalar on $M_2(\mathbb{C})$, the Maxwell action $||F||^2$ of $A$ and a higher order $||A.F||^2$ term. Another solution of the QRG on the product has $A=0$ and a dynamical real scalar field $\phi$ on $M$ which imparts mass-splitting to some of the components of a scalar field on the product as in previous work.
|
1005.3722
|
George Gillies
|
Alvin J. Sanders and George T. Gillies
|
Precise Gravitational Tests via the SEE Mission: A Proposal for
Space-Based Measurements
|
Presented at the 2004 Pescara Meeting on Tests of the Equivalence
Principle
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The objective of a SEE mission is to support development of unification
theory by carrying out sensitive gravitational tests capable of determining
whether various alternative theories are compatible with nature. Gravitation is
a key "missing link" in unification theory. Nearly all unification theories
incorporate gravity at a fundamental level, and therefore precise measurements
of gravitational forces will place important constraints on unification
theories. Ground-based gravitational measurements to the accuracy required are
impossible due to the many sources of noise present in the terrestrial
environment. The proposed space-based Satellite Energy Exchange (SEE) mission
will measure several important parameters to an accuracy between 100 and 10,000
times better than current or planned measurement capabilities. It will test for
time variation of the gravitational "constant" G and for violations of the weak
equivalence principle (WEP) and the inverse-square-law (ISL), and it will
determine G. It is well-known that the discovery of breakdowns in WEP or ISL
and the possible determination of a time-varying G would have significant
consequences on virtually all aspects of unification theory.
|
[
{
"created": "Thu, 20 May 2010 14:53:58 GMT",
"version": "v1"
}
] |
2010-05-21
|
[
[
"Sanders",
"Alvin J.",
""
],
[
"Gillies",
"George T.",
""
]
] |
The objective of a SEE mission is to support development of unification theory by carrying out sensitive gravitational tests capable of determining whether various alternative theories are compatible with nature. Gravitation is a key "missing link" in unification theory. Nearly all unification theories incorporate gravity at a fundamental level, and therefore precise measurements of gravitational forces will place important constraints on unification theories. Ground-based gravitational measurements to the accuracy required are impossible due to the many sources of noise present in the terrestrial environment. The proposed space-based Satellite Energy Exchange (SEE) mission will measure several important parameters to an accuracy between 100 and 10,000 times better than current or planned measurement capabilities. It will test for time variation of the gravitational "constant" G and for violations of the weak equivalence principle (WEP) and the inverse-square-law (ISL), and it will determine G. It is well-known that the discovery of breakdowns in WEP or ISL and the possible determination of a time-varying G would have significant consequences on virtually all aspects of unification theory.
|
0901.4629
|
Ujjal Debnath
|
Surajit Chattopadhyay and Ujjal Debnath
|
Tachyonic field interacting with Scalar (Phantom) Field
|
7 LateX pages, 16 figures, RevTeX style
|
Braz.J.Phys.39:86-91,2009
| null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this letter, we have considered the universe is filled with the mixture of
tachyonic field and scalar or phantom field. If the tachyonic field interacts
with scalar or phantom field, the interaction term decays with time and the
energy for scalar field is transferred to tachyonic field or the energy for
phantom field is transferred to tachyonic field. The tachyonic field and scalar
field potentials always decrease, but phantom field potential always increases.
|
[
{
"created": "Thu, 29 Jan 2009 09:33:08 GMT",
"version": "v1"
}
] |
2009-04-24
|
[
[
"Chattopadhyay",
"Surajit",
""
],
[
"Debnath",
"Ujjal",
""
]
] |
In this letter, we have considered the universe is filled with the mixture of tachyonic field and scalar or phantom field. If the tachyonic field interacts with scalar or phantom field, the interaction term decays with time and the energy for scalar field is transferred to tachyonic field or the energy for phantom field is transferred to tachyonic field. The tachyonic field and scalar field potentials always decrease, but phantom field potential always increases.
|
gr-qc/0203085
|
Harald P. Pfeiffer
|
Harald P. Pfeiffer, Gregory B. Cook, Saul A. Teukolsky
|
Comparing initial-data sets for binary black holes
|
18 pages, 12 figures, accepted for publication in Phys. Rev. D
|
Phys.Rev. D66 (2002) 024047
|
10.1103/PhysRevD.66.024047
| null |
gr-qc
| null |
We compare the results of constructing binary black hole initial data with
three different decompositions of the constraint equations of general
relativity. For each decomposition we compute the initial data using a
superposition of two Kerr-Schild black holes to fix the freely specifiable
data. We find that these initial-data sets differ significantly, with the ADM
energy varying by as much as 5% of the total mass. We find that all
initial-data sets currently used for evolutions might contain unphysical
gravitational radiation of the order of several percent of the total mass. This
is comparable to the amount of gravitational-wave energy observed during the
evolved collision. More astrophysically realistic initial data will require
more careful choices of the freely specifiable data and boundary conditions for
both the metric and extrinsic curvature. However, we find that the choice of
extrinsic curvature affects the resulting data sets more strongly than the
choice of conformal metric.
|
[
{
"created": "Mon, 25 Mar 2002 21:35:36 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Jun 2002 21:41:26 GMT",
"version": "v2"
}
] |
2009-11-07
|
[
[
"Pfeiffer",
"Harald P.",
""
],
[
"Cook",
"Gregory B.",
""
],
[
"Teukolsky",
"Saul A.",
""
]
] |
We compare the results of constructing binary black hole initial data with three different decompositions of the constraint equations of general relativity. For each decomposition we compute the initial data using a superposition of two Kerr-Schild black holes to fix the freely specifiable data. We find that these initial-data sets differ significantly, with the ADM energy varying by as much as 5% of the total mass. We find that all initial-data sets currently used for evolutions might contain unphysical gravitational radiation of the order of several percent of the total mass. This is comparable to the amount of gravitational-wave energy observed during the evolved collision. More astrophysically realistic initial data will require more careful choices of the freely specifiable data and boundary conditions for both the metric and extrinsic curvature. However, we find that the choice of extrinsic curvature affects the resulting data sets more strongly than the choice of conformal metric.
|
1704.08570
|
Jiri Podolsky
|
Jiri Podolsky, Robert Svarc, Roland Steinbauer, Clemens S\"amann
|
Penrose junction conditions extended: impulsive waves with gyratons
|
15 pages, 2 figures
|
Phys. Rev. D 96, 064043 (2017)
|
10.1103/PhysRevD.96.064043
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We generalize the classical junction conditions for constructing impulsive
gravitational waves by the Penrose "cut and paste" method. Specifically, we
study nonexpanding impulses which propagate in spaces of constant curvature
with any value of the cosmological constant (that is Minkowski, de Sitter, or
anti-de Sitter universes) when additional off-diagonal metric components are
present. Such components encode a possible angular momentum of the
ultra-relativistic source of the impulsive wave - the so called gyraton. We
explicitly derive and analyze a specific transformation that relates the
distributional form of the metric to a new form which is (Lipschitz)
continuous. Such a transformation automatically implies an extended version of
the Penrose junction conditions. It turns out that the conditions for
identifying points of the background spacetime across the impulse are the same
as in the original Penrose "cut and paste" construction, but their derivatives
now directly represent the influence of the gyraton on the axial motion of test
particles. Our results apply both for vacuum and nonvacuum solutions of
Einstein's field equations, and can also be extended to other theories of
gravity.
|
[
{
"created": "Thu, 27 Apr 2017 13:47:46 GMT",
"version": "v1"
}
] |
2017-10-04
|
[
[
"Podolsky",
"Jiri",
""
],
[
"Svarc",
"Robert",
""
],
[
"Steinbauer",
"Roland",
""
],
[
"Sämann",
"Clemens",
""
]
] |
We generalize the classical junction conditions for constructing impulsive gravitational waves by the Penrose "cut and paste" method. Specifically, we study nonexpanding impulses which propagate in spaces of constant curvature with any value of the cosmological constant (that is Minkowski, de Sitter, or anti-de Sitter universes) when additional off-diagonal metric components are present. Such components encode a possible angular momentum of the ultra-relativistic source of the impulsive wave - the so called gyraton. We explicitly derive and analyze a specific transformation that relates the distributional form of the metric to a new form which is (Lipschitz) continuous. Such a transformation automatically implies an extended version of the Penrose junction conditions. It turns out that the conditions for identifying points of the background spacetime across the impulse are the same as in the original Penrose "cut and paste" construction, but their derivatives now directly represent the influence of the gyraton on the axial motion of test particles. Our results apply both for vacuum and nonvacuum solutions of Einstein's field equations, and can also be extended to other theories of gravity.
|
gr-qc/0504043
|
Leonardo Modesto
|
Leonardo Modesto
|
Quantum Gravitational Collapse
|
13 pages, LaTeX
| null | null | null |
gr-qc
| null |
We apply the recent results in Loop Quantum Cosmology and in the resolution
of Black Hole singularity to the gravitational collapse of a star. We study the
dynamic of the space time in the interior of the Schwarzschild radius. In
particular in our simple model we obtain the evolution of the matter inside the
star and of the gravity outside the region where the matter is present. The
boundary condition identify an unique time inside and outside the region where
the matter is present. We consider a star during the collapse in the particular
case in which inside the collapsing star we take null pressure, homogeneity and
isotropy. The space-time outside the matter is homogeneous and anisotropic. We
show that the space time is singularity free and that we can extend dynamically
the space-time beyond the classical singularity.
|
[
{
"created": "Sun, 10 Apr 2005 12:36:18 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Modesto",
"Leonardo",
""
]
] |
We apply the recent results in Loop Quantum Cosmology and in the resolution of Black Hole singularity to the gravitational collapse of a star. We study the dynamic of the space time in the interior of the Schwarzschild radius. In particular in our simple model we obtain the evolution of the matter inside the star and of the gravity outside the region where the matter is present. The boundary condition identify an unique time inside and outside the region where the matter is present. We consider a star during the collapse in the particular case in which inside the collapsing star we take null pressure, homogeneity and isotropy. The space-time outside the matter is homogeneous and anisotropic. We show that the space time is singularity free and that we can extend dynamically the space-time beyond the classical singularity.
|
1102.0907
|
Dana Levanony
|
Dana Levanony and Amos Ori
|
Extended time-travelling objects in Misner space
|
accepted for publication in Physical Review D
|
Phys.Rev.D83:044043,2011
|
10.1103/PhysRevD.83.044043
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Misner space is a two-dimensional (2D) locally-flat spacetime which elegantly
demonstrates the emergence of closed timelike curves from causally well-behaved
initial conditions. Here we explore the motion of rigid extended objects in
this time-machine spacetime. This kind of 2D time-travel is found to be risky
due to inevitable self-collisions (i.e. collisions of the object with itself).
However, in a straightforward four-dimensional generalization of Misner space
(a physically more relevant spacetime obviously), we find a wide range of
"safe" time-travel orbits free of any self-collisions.
|
[
{
"created": "Fri, 4 Feb 2011 13:25:49 GMT",
"version": "v1"
}
] |
2011-03-23
|
[
[
"Levanony",
"Dana",
""
],
[
"Ori",
"Amos",
""
]
] |
Misner space is a two-dimensional (2D) locally-flat spacetime which elegantly demonstrates the emergence of closed timelike curves from causally well-behaved initial conditions. Here we explore the motion of rigid extended objects in this time-machine spacetime. This kind of 2D time-travel is found to be risky due to inevitable self-collisions (i.e. collisions of the object with itself). However, in a straightforward four-dimensional generalization of Misner space (a physically more relevant spacetime obviously), we find a wide range of "safe" time-travel orbits free of any self-collisions.
|
0811.4055
|
Wolf-Dieter Reinhard Stein
|
W.-D. R. Stein
|
An Alternative to Kaluza
|
4 pages
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In Kaluza derived theories the electromagnetic potential is interpreted as a
part of the metric in a higher dimensional theory of gravity. Here we present a
more Yang-Mills like unification of classical electromagnetism and gravity
within five dimensions, where the electromagnetic potential is related to the
connecion and the field strength to the curvature. In addition some aspects of
a quantum theory can be described in the context of the Gauss-Bonnet-Chern
Theorem. This approach offers new coupling mechanisms between gravity and
electromagnetism.
|
[
{
"created": "Tue, 25 Nov 2008 11:13:41 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Dec 2008 10:59:37 GMT",
"version": "v2"
}
] |
2008-12-04
|
[
[
"Stein",
"W. -D. R.",
""
]
] |
In Kaluza derived theories the electromagnetic potential is interpreted as a part of the metric in a higher dimensional theory of gravity. Here we present a more Yang-Mills like unification of classical electromagnetism and gravity within five dimensions, where the electromagnetic potential is related to the connecion and the field strength to the curvature. In addition some aspects of a quantum theory can be described in the context of the Gauss-Bonnet-Chern Theorem. This approach offers new coupling mechanisms between gravity and electromagnetism.
|
2106.04870
|
Malik Al Matwi
|
Malik Matwi
|
Spin current in BF theory
|
23 pages, accepted for publication on Physics
|
Physics 2021, 3(2), 427-448
|
10.3390/physics3020029
| null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
In this paper, we introduce a current which we call spin current
corresponding to the variation of the matter action in BF theory with respect
to the spin connection $A$ which takes values in Lie algebra
$\mathfrak{so}(3,\mathbb{C})$ in self-dual formalism. For keeping the
constraint $DB^i=0$ satisfied, we suggest adding a new term to the BF
Lagrangian using a new field $\psi^i$ which can be used for calculating the
spin current. We derive the equations of motion and discuss the solutions. We
will see that the solutions of that equations do not require a specific metric
on the manifold $M$, we just need to know the symmetry of the system and the
information about the spin current. Finally we find the solutions in a
spherical and cylindrical symmetric systems.
|
[
{
"created": "Wed, 9 Jun 2021 07:52:23 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Jul 2021 13:36:57 GMT",
"version": "v2"
}
] |
2021-07-02
|
[
[
"Matwi",
"Malik",
""
]
] |
In this paper, we introduce a current which we call spin current corresponding to the variation of the matter action in BF theory with respect to the spin connection $A$ which takes values in Lie algebra $\mathfrak{so}(3,\mathbb{C})$ in self-dual formalism. For keeping the constraint $DB^i=0$ satisfied, we suggest adding a new term to the BF Lagrangian using a new field $\psi^i$ which can be used for calculating the spin current. We derive the equations of motion and discuss the solutions. We will see that the solutions of that equations do not require a specific metric on the manifold $M$, we just need to know the symmetry of the system and the information about the spin current. Finally we find the solutions in a spherical and cylindrical symmetric systems.
|
1607.04962
|
Daniel Litim
|
Kevin Falls, Daniel F. Litim, Kostas Nikolakopoulos, and Christoph
Rahmede
|
On de Sitter solutions in asymptotically safe $f(R)$ theories
|
27 pages, 11 figures, 3 tables. v2: explanations added, to appear
with CQG
| null |
10.1088/1361-6382/aac440
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The availability of scaling solutions in renormalisation group improved
versions of cosmology are investigated in the high-energy limit. We adopt
$f(R)$-type models of quantum gravity which display an interacting ultraviolet
fixed point at shortest distances. Expanding the gravitational fixed point
action to very high order in the curvature scalar, we detect a
convergence-limiting singularity in the complex field plane. Resummation
techniques including Pad\'e approximants as well as infinite order
approximations of the effective action are used to maximise the domain of
validity. We find that the theory displays near de Sitter solutions as well as
an anti-de Sitter solution in the UV whereas real de Sitter solutions, for
small curvature, appear to be absent. The significance of our results for
inflation, and implications for more general models of quantum gravity are
discussed.
|
[
{
"created": "Mon, 18 Jul 2016 07:32:41 GMT",
"version": "v1"
},
{
"created": "Tue, 15 May 2018 10:28:21 GMT",
"version": "v2"
}
] |
2018-05-16
|
[
[
"Falls",
"Kevin",
""
],
[
"Litim",
"Daniel F.",
""
],
[
"Nikolakopoulos",
"Kostas",
""
],
[
"Rahmede",
"Christoph",
""
]
] |
The availability of scaling solutions in renormalisation group improved versions of cosmology are investigated in the high-energy limit. We adopt $f(R)$-type models of quantum gravity which display an interacting ultraviolet fixed point at shortest distances. Expanding the gravitational fixed point action to very high order in the curvature scalar, we detect a convergence-limiting singularity in the complex field plane. Resummation techniques including Pad\'e approximants as well as infinite order approximations of the effective action are used to maximise the domain of validity. We find that the theory displays near de Sitter solutions as well as an anti-de Sitter solution in the UV whereas real de Sitter solutions, for small curvature, appear to be absent. The significance of our results for inflation, and implications for more general models of quantum gravity are discussed.
|
1905.10087
|
Vladimir S. Manko
|
V.S. Manko, E. Ruiz, M.B. Sadovnikova
|
Binary systems of recoiling extreme Kerr black holes
|
12 pages, 7 figures
| null |
10.1016/j.physletb.2019.07.011
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In the present paper the repulsion of two extreme Kerr black holes arising
from their spin-spin interaction is analyzed within the framework of special
subfamilies of the well-known Kinnersley-Chitre solution. The binary
configurations of both equal and nonequal extreme repelling black holes are
considered.
|
[
{
"created": "Fri, 24 May 2019 08:30:31 GMT",
"version": "v1"
}
] |
2019-09-04
|
[
[
"Manko",
"V. S.",
""
],
[
"Ruiz",
"E.",
""
],
[
"Sadovnikova",
"M. B.",
""
]
] |
In the present paper the repulsion of two extreme Kerr black holes arising from their spin-spin interaction is analyzed within the framework of special subfamilies of the well-known Kinnersley-Chitre solution. The binary configurations of both equal and nonequal extreme repelling black holes are considered.
|
1701.00017
|
Y. Jack Ng
|
Y. Jack Ng
|
Quantum Foam, Gravitational Thermodynamics, and the Dark Sector
|
13 pages, 6 figures, to appear in the Proceedings of IARD 2016 (in
Journal of Physics: Conference Series), for a short version of this article,
see "Holographic theory of gravity and cosmology" (arXiv:1610.06236)
| null |
10.1088/1742-6596/845/1/012001
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We use two simple independent gedankan experiments to show that the
holographic principle can be understood intuitively as having its origin in the
quantum fluctuations of spacetime. Applied to cosmology, this consideration
leads to a dynamical cosmological constant of the observed magnitude, a result
that can also be obtained for the present and recent cosmic eras by using
unimodular gravity and causal set theory. Next we generalize the concept of
gravitational thermodynamics to a spacetime with positive cosmological constant
(like ours) to reveal the natural emergence, in galactic dynamics, of a
critical acceleration parameter related to the cosmological constant. We are
then led to construct a phenomenological model of dark matter which we call
"modified dark matter" (MDM) in which the dark matter density profile depends
on both the cosmological constant and ordinary matter. We provide observational
tests of MDM by fitting the rotation curves to a sample of 30 local spiral
galaxies with a single free parameter and by showing that the dynamical and
observed masses agree in a sample of 93 galactic clusters. We also give a brief
discussion of the possibility that quanta of both dark energy and dark matter
are non-local, obeying quantum Boltzmann statistics (also called infinite
statistics) as described by a curious average of the bosonic and fermionic
algebras. If such a scenario is correct, we can expect some novel particle
phenomenology involving dark matter interactions. This may explain why so far
no dark matter detection experiments have been able to claim convincingly to
have detected dark matter.
|
[
{
"created": "Fri, 30 Dec 2016 21:27:32 GMT",
"version": "v1"
}
] |
2017-06-28
|
[
[
"Ng",
"Y. Jack",
""
]
] |
We use two simple independent gedankan experiments to show that the holographic principle can be understood intuitively as having its origin in the quantum fluctuations of spacetime. Applied to cosmology, this consideration leads to a dynamical cosmological constant of the observed magnitude, a result that can also be obtained for the present and recent cosmic eras by using unimodular gravity and causal set theory. Next we generalize the concept of gravitational thermodynamics to a spacetime with positive cosmological constant (like ours) to reveal the natural emergence, in galactic dynamics, of a critical acceleration parameter related to the cosmological constant. We are then led to construct a phenomenological model of dark matter which we call "modified dark matter" (MDM) in which the dark matter density profile depends on both the cosmological constant and ordinary matter. We provide observational tests of MDM by fitting the rotation curves to a sample of 30 local spiral galaxies with a single free parameter and by showing that the dynamical and observed masses agree in a sample of 93 galactic clusters. We also give a brief discussion of the possibility that quanta of both dark energy and dark matter are non-local, obeying quantum Boltzmann statistics (also called infinite statistics) as described by a curious average of the bosonic and fermionic algebras. If such a scenario is correct, we can expect some novel particle phenomenology involving dark matter interactions. This may explain why so far no dark matter detection experiments have been able to claim convincingly to have detected dark matter.
|
gr-qc/0310044
|
Theodore A. Jacobson
|
Christopher Eling and Ted Jacobson
|
Static post-Newtonian equivalence of GR and gravity with a dynamical
preferred frame
|
13 pages; v.2: minor editing, signs corrected, version to appear in
PRD; v. 3: signs corrected in eqn (3)
|
Phys.Rev. D69 (2004) 064005
|
10.1103/PhysRevD.69.064005
| null |
gr-qc astro-ph hep-th
| null |
A generally covariant extension of general relativity (GR) in which a
dynamical unit timelike vector field is coupled to the metric is studied in the
asymptotic weak field limit of spherically symmetric static solutions. The two
post-Newtonian parameters known as the Eddington-Robertson-Schiff parameters
are found to be identical to those in the case of pure GR, except for some
non-generic values of the coefficients in the Lagrangian.
|
[
{
"created": "Tue, 7 Oct 2003 16:19:16 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Jan 2004 15:34:19 GMT",
"version": "v2"
},
{
"created": "Sat, 28 Feb 2004 16:26:39 GMT",
"version": "v3"
}
] |
2009-11-10
|
[
[
"Eling",
"Christopher",
""
],
[
"Jacobson",
"Ted",
""
]
] |
A generally covariant extension of general relativity (GR) in which a dynamical unit timelike vector field is coupled to the metric is studied in the asymptotic weak field limit of spherically symmetric static solutions. The two post-Newtonian parameters known as the Eddington-Robertson-Schiff parameters are found to be identical to those in the case of pure GR, except for some non-generic values of the coefficients in the Lagrangian.
|
gr-qc/0507063
|
Francisco Lobo
|
Francisco S. N. Lobo, Paulo Crawford
|
Stability analysis of dynamic thin shells
|
19 pages, 11 figures, LaTeX2e, IOP style files. V2: Comments and
references added. This version to appear in Classical and Quantum Gravity
|
Class.Quant.Grav. 22 (2005) 4869-4886
|
10.1088/0264-9381/22/22/012
| null |
gr-qc astro-ph hep-th
| null |
We analyze the stability of generic spherically symmetric thin shells to
linearized perturbations around static solutions. We include the momentum flux
term in the conservation identity, deduced from the ''ADM'' constraint and the
Lanczos equations. Following the Ishak-Lake analysis, we deduce a master
equation which dictates the stable equilibrium configurations. Considering the
transparency condition, we study the stability of thin shells around black
holes, showing that our analysis is in agreement with previous results.
Applying the analysis to traversable wormhole geometries, by considering
specific choices for the form function, we deduce stability regions, and find
that the latter may be significantly increased by considering appropriate
choices for the redshift function.
|
[
{
"created": "Thu, 14 Jul 2005 16:27:16 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Oct 2005 22:16:38 GMT",
"version": "v2"
}
] |
2009-11-11
|
[
[
"Lobo",
"Francisco S. N.",
""
],
[
"Crawford",
"Paulo",
""
]
] |
We analyze the stability of generic spherically symmetric thin shells to linearized perturbations around static solutions. We include the momentum flux term in the conservation identity, deduced from the ''ADM'' constraint and the Lanczos equations. Following the Ishak-Lake analysis, we deduce a master equation which dictates the stable equilibrium configurations. Considering the transparency condition, we study the stability of thin shells around black holes, showing that our analysis is in agreement with previous results. Applying the analysis to traversable wormhole geometries, by considering specific choices for the form function, we deduce stability regions, and find that the latter may be significantly increased by considering appropriate choices for the redshift function.
|
1706.00431
|
Robert R. Caldwell
|
R. R. Caldwell, C. Devulder, N. A. Maksimova
|
Gravitational Wave -- Gauge Field Dynamics
|
Awarded Fifth Prize in 2017 Gravity Research Foundation Essay Contest
| null |
10.1142/S0218271817420056
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The dynamics of a gravitational wave propagating through a cosmic gauge field
are dramatically different than in vacuum. We show that a gravitational wave
acquires an effective mass, is birefringent, and its normal modes are a linear
combination of gravitational waves and gauge field excitations, leading to the
phenomenon of gravitational wave -- gauge field oscillations. These surprising
results provide insight into gravitational phenomena and may suggest new
approaches to a theory of quantum gravity.
|
[
{
"created": "Thu, 1 Jun 2017 18:00:02 GMT",
"version": "v1"
}
] |
2017-11-22
|
[
[
"Caldwell",
"R. R.",
""
],
[
"Devulder",
"C.",
""
],
[
"Maksimova",
"N. A.",
""
]
] |
The dynamics of a gravitational wave propagating through a cosmic gauge field are dramatically different than in vacuum. We show that a gravitational wave acquires an effective mass, is birefringent, and its normal modes are a linear combination of gravitational waves and gauge field excitations, leading to the phenomenon of gravitational wave -- gauge field oscillations. These surprising results provide insight into gravitational phenomena and may suggest new approaches to a theory of quantum gravity.
|
2205.04773
|
Aditya Sharma
|
Aditya Sharma, Kinjal Banerjee, Jishnu Bhattacharyya
|
de Sitterization via Kerr-Schild
|
Publication details updated. Results are unchanged
|
2022, Physical Review D
|
10.1103/PhysRevD.106.063518
|
Vol. 106, No.6
|
gr-qc hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Spatially homogeneous cosmological spacetimes, evolving in the presence of a
positive cosmological constant and matter satisfying some reasonable energy
conditions, typically approach the de Sitter geometry asymptotically (at least
locally). In this work, we propose an alternate way to characterize this
phenomena. We focus on a subset of such models admitting a generalized
Kerr-Schild representation. We argue that the functions which define such a
representation can be chosen, such that, their asymptotic behavior make the
evolution towards the de Sitter spacetime manifest through the representation.
We verify our claim for the Kantowski-Sachs family of cosmological spacetimes.
|
[
{
"created": "Tue, 10 May 2022 09:51:08 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Sep 2022 06:43:14 GMT",
"version": "v2"
}
] |
2022-09-20
|
[
[
"Sharma",
"Aditya",
""
],
[
"Banerjee",
"Kinjal",
""
],
[
"Bhattacharyya",
"Jishnu",
""
]
] |
Spatially homogeneous cosmological spacetimes, evolving in the presence of a positive cosmological constant and matter satisfying some reasonable energy conditions, typically approach the de Sitter geometry asymptotically (at least locally). In this work, we propose an alternate way to characterize this phenomena. We focus on a subset of such models admitting a generalized Kerr-Schild representation. We argue that the functions which define such a representation can be chosen, such that, their asymptotic behavior make the evolution towards the de Sitter spacetime manifest through the representation. We verify our claim for the Kantowski-Sachs family of cosmological spacetimes.
|
1412.4761
|
Stephen Green
|
Alex Buchel, Stephen R. Green, Luis Lehner, Steven L. Liebling
|
Conserved quantities and dual turbulent cascades in Anti-de Sitter
spacetime
|
9 pages, 2 figures; V2: minor updates; V3: updates to match version
accepted for publication
|
Phys. Rev. D 91, 064026 (2015)
|
10.1103/PhysRevD.91.064026
| null |
gr-qc hep-th nlin.CD
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider the dynamics of a spherically symmetric massless scalar field
coupled to general relativity in Anti--de Sitter spacetime in the
small-amplitude limit. Within the context of our previously developed two time
framework (TTF) to study the leading self-gravitating effects, we demonstrate
the existence of two new conserved quantities in addition to the known total
energy $E$ of the modes: The particle number $N$ and Hamiltonian $H$ of our TTF
system. Simultaneous conservation of $E$ and $N$ implies that weak turbulent
processes undergo dual cascades (direct cascade of $E$ and inverse cascade of
$N$ or vice versa). This partially explains the observed dynamics of 2-mode
initial data. In addition, conservation of $E$ and $N$ limits the region of
phase space that can be explored within the TTF approximation and in particular
rules out equipartion of energy among the modes for general initial data.
Finally, we discuss possible effects of conservation of $N$ and $E$ on late
time dynamics.
|
[
{
"created": "Mon, 15 Dec 2014 20:54:34 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Dec 2014 21:49:41 GMT",
"version": "v2"
},
{
"created": "Tue, 17 Feb 2015 16:26:19 GMT",
"version": "v3"
}
] |
2015-03-18
|
[
[
"Buchel",
"Alex",
""
],
[
"Green",
"Stephen R.",
""
],
[
"Lehner",
"Luis",
""
],
[
"Liebling",
"Steven L.",
""
]
] |
We consider the dynamics of a spherically symmetric massless scalar field coupled to general relativity in Anti--de Sitter spacetime in the small-amplitude limit. Within the context of our previously developed two time framework (TTF) to study the leading self-gravitating effects, we demonstrate the existence of two new conserved quantities in addition to the known total energy $E$ of the modes: The particle number $N$ and Hamiltonian $H$ of our TTF system. Simultaneous conservation of $E$ and $N$ implies that weak turbulent processes undergo dual cascades (direct cascade of $E$ and inverse cascade of $N$ or vice versa). This partially explains the observed dynamics of 2-mode initial data. In addition, conservation of $E$ and $N$ limits the region of phase space that can be explored within the TTF approximation and in particular rules out equipartion of energy among the modes for general initial data. Finally, we discuss possible effects of conservation of $N$ and $E$ on late time dynamics.
|
0907.3838
|
Yousef Bisabr
|
Yousef Bisabr
|
Solar System Constraints on a Cosmologically Viable $f(R)$ Theory
|
10 pages, no figure, Accepted for publication in Physics Letters B
|
Phys.Lett.B683:96-100,2010
|
10.1016/j.physletb.2009.11.062
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Recently, a model $f(R)$ theory is proposed \cite{recent} which is
cosmologically viable and distinguishable from $\Lambda$CDM. We use chameleon
mechanism to investigate viability of the model in terms of Solar System
experiments.
|
[
{
"created": "Wed, 22 Jul 2009 13:15:12 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Dec 2009 16:46:45 GMT",
"version": "v2"
}
] |
2010-01-15
|
[
[
"Bisabr",
"Yousef",
""
]
] |
Recently, a model $f(R)$ theory is proposed \cite{recent} which is cosmologically viable and distinguishable from $\Lambda$CDM. We use chameleon mechanism to investigate viability of the model in terms of Solar System experiments.
|
gr-qc/9712046
|
Spiros Cotsakis
|
S. Cotsakis (Department of Mathematics, University of the Aegean)
|
Mathematical problems in higher order gravity and cosmology
|
3 pages, LaTeX, talk presented at the Eighth Marcel Grossmann
Meeting, Jerousalem, June 22--27, 1997
| null | null | null |
gr-qc
| null |
We discuss the issue of motivating the analysis of higher order gravity
theories and their cosmologies and introduce a rule which states that these
theories may be considered as a vehicle for testing whether certain properties
may be of relevance to quantum theory. We discuss the physicality issue arising
as a consequence of the conformal transformation theorem, the question of
formulating a consistent first order formalism of such theories and also the
isotropization problem for a class of generalized cosmologies. We point out
that this field may have an important role to play in clarifying issues arising
also in general relativity.
|
[
{
"created": "Wed, 10 Dec 1997 14:46:34 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Cotsakis",
"S.",
"",
"Department of Mathematics, University of the Aegean"
]
] |
We discuss the issue of motivating the analysis of higher order gravity theories and their cosmologies and introduce a rule which states that these theories may be considered as a vehicle for testing whether certain properties may be of relevance to quantum theory. We discuss the physicality issue arising as a consequence of the conformal transformation theorem, the question of formulating a consistent first order formalism of such theories and also the isotropization problem for a class of generalized cosmologies. We point out that this field may have an important role to play in clarifying issues arising also in general relativity.
|
1610.03400
|
Yong Cai
|
Yong Cai, Youping Wan, Hai-Guang Li, Taotao Qiu, and Yun-Song Piao
|
The Effective Field Theory of nonsingular cosmology
|
21 pages, 2 figures, published in JHEP
|
JHEP01(2017)090
|
10.1007/JHEP01(2017)090
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we explore the nonsingular cosmology within the framework of
the Effective Field Theory(EFT) of cosmological perturbations. Due to the
recently proved no-go theorem, any nonsingular cosmological models based on the
cubic Galileon suffer from pathologies. We show how the EFT could help us
clarify the origin of the no-go theorem, and offer us solutions to break the
no-go. Particularly, we point out that the gradient instability can be removed
by using some spatial derivative operators in EFT. Based on the EFT
description, we obtain a realistic healthy nonsingular cosmological model, and
show the perturbation spectrum can be consistent with the observations.
|
[
{
"created": "Tue, 11 Oct 2016 15:50:49 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Oct 2016 13:32:23 GMT",
"version": "v2"
},
{
"created": "Sun, 22 Jan 2017 14:30:03 GMT",
"version": "v3"
}
] |
2017-01-24
|
[
[
"Cai",
"Yong",
""
],
[
"Wan",
"Youping",
""
],
[
"Li",
"Hai-Guang",
""
],
[
"Qiu",
"Taotao",
""
],
[
"Piao",
"Yun-Song",
""
]
] |
In this paper, we explore the nonsingular cosmology within the framework of the Effective Field Theory(EFT) of cosmological perturbations. Due to the recently proved no-go theorem, any nonsingular cosmological models based on the cubic Galileon suffer from pathologies. We show how the EFT could help us clarify the origin of the no-go theorem, and offer us solutions to break the no-go. Particularly, we point out that the gradient instability can be removed by using some spatial derivative operators in EFT. Based on the EFT description, we obtain a realistic healthy nonsingular cosmological model, and show the perturbation spectrum can be consistent with the observations.
|
1006.4439
|
Shahar Hod
|
Shahar Hod
|
Relaxation dynamics of charged gravitational collapse
|
5 pages
|
Phys.Lett.A374:2901,2010
|
10.1016/j.physleta.2010.05.052
| null |
gr-qc astro-ph.HE hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study analytically the relaxation dynamics of charged test fields left
outside a newly born charged black hole. In particular, we obtain a simple
analytic expression for the fundamental quasinormal resonances of near-extremal
Reissner-Nordstr\"om black holes. The formula is expressed in terms of the
black-hole physical parameters: $\omega=q\Phi-i2\pi T_{BH}(n+{1 \over 2})$,
where $T_{BH}$ and $\Phi$ are the temperature and electric potential of the
black hole, and $q$ is the charge of the field.
|
[
{
"created": "Wed, 23 Jun 2010 07:48:53 GMT",
"version": "v1"
}
] |
2011-04-07
|
[
[
"Hod",
"Shahar",
""
]
] |
We study analytically the relaxation dynamics of charged test fields left outside a newly born charged black hole. In particular, we obtain a simple analytic expression for the fundamental quasinormal resonances of near-extremal Reissner-Nordstr\"om black holes. The formula is expressed in terms of the black-hole physical parameters: $\omega=q\Phi-i2\pi T_{BH}(n+{1 \over 2})$, where $T_{BH}$ and $\Phi$ are the temperature and electric potential of the black hole, and $q$ is the charge of the field.
|
1404.4491
|
Rabin Banerjee
|
Rabin Banerjee, Arpita Mitra, Pradip Mukherjee
|
A new formulation of non-relativistic diffeomorphism invariance
|
minor changes, new reference added, to appear in PLB
| null |
10.1016/j.physletb.2014.09.004
| null |
gr-qc cond-mat.other hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We provide a new formulation of nonrelativistic diffeomorphism invariance. It
is generated by localising the usual global Galilean Symmetry. The
correspondence with the type of diffeomorphism invariant models currently in
vogue in the theory of fractional quantum Hall effect has been discussed. Our
construction is shown to open up a general approach of model building in
theoretical condensed matter physics. Also, this formulation has the capacity
of obtaining Newton - Cartan geometry from the gauge procedure.
|
[
{
"created": "Thu, 17 Apr 2014 11:18:52 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Sep 2014 07:23:17 GMT",
"version": "v2"
},
{
"created": "Thu, 4 Sep 2014 09:56:51 GMT",
"version": "v3"
}
] |
2015-06-19
|
[
[
"Banerjee",
"Rabin",
""
],
[
"Mitra",
"Arpita",
""
],
[
"Mukherjee",
"Pradip",
""
]
] |
We provide a new formulation of nonrelativistic diffeomorphism invariance. It is generated by localising the usual global Galilean Symmetry. The correspondence with the type of diffeomorphism invariant models currently in vogue in the theory of fractional quantum Hall effect has been discussed. Our construction is shown to open up a general approach of model building in theoretical condensed matter physics. Also, this formulation has the capacity of obtaining Newton - Cartan geometry from the gauge procedure.
|
gr-qc/9905054
|
Kleidis Kostas
|
K. Kleidis, H. Varvoglis and D. B. Papadopoulos
|
Parametric resonant acceleration of particles by gravitational waves
|
LaTeX file, 16 pages
|
Class.Quant.Grav. 13 (1996) 2547-2562
|
10.1088/0264-9381/13/9/018
| null |
gr-qc
| null |
We study the resonant interaction of charged particles with a gravitational
wave propagating in the non-empty interstellar space in the presence of a
uniform magnetic field. It is found that this interaction can be cast in the
form of a parametric resonance problem which, besides the main resonance,
allows for the existence of many secondary ones. Each of them is associated
with a non-zero resonant width, depending on the amplitude of the wave and the
energy density of the interstellar plasma. Numerical estimates of the
particles' energisation and the ensuing damping of the wave are given.
|
[
{
"created": "Mon, 17 May 1999 08:03:55 GMT",
"version": "v1"
}
] |
2009-10-31
|
[
[
"Kleidis",
"K.",
""
],
[
"Varvoglis",
"H.",
""
],
[
"Papadopoulos",
"D. B.",
""
]
] |
We study the resonant interaction of charged particles with a gravitational wave propagating in the non-empty interstellar space in the presence of a uniform magnetic field. It is found that this interaction can be cast in the form of a parametric resonance problem which, besides the main resonance, allows for the existence of many secondary ones. Each of them is associated with a non-zero resonant width, depending on the amplitude of the wave and the energy density of the interstellar plasma. Numerical estimates of the particles' energisation and the ensuing damping of the wave are given.
|
gr-qc/9903029
|
Ion Cotaescu
|
Ion I. Cot\u{a}escu (The West University of Timi\c{s}oara, Romania)
|
Comment on the quantum modes of the scalar field on AdS_{d+1} spacetime
|
8 pages, Latex
| null | null | null |
gr-qc
| null |
The problem of the quantum modes of the scalar free field on anti-de Sitter
backgrounds with an arbitrary number of space dimensions is considered. It is
shown that this problem can be solved by using the same quantum numbers as
those of the nonrelativistic oscillator and two parameters which give the
energy quanta and respectively the ground state energy. This last one is known
to be just the conformal dimension of the boundary field theory of the AdS/CFT
conjecture.
|
[
{
"created": "Mon, 8 Mar 1999 13:33:10 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Cotăescu",
"Ion I.",
"",
"The West University of Timişoara, Romania"
]
] |
The problem of the quantum modes of the scalar free field on anti-de Sitter backgrounds with an arbitrary number of space dimensions is considered. It is shown that this problem can be solved by using the same quantum numbers as those of the nonrelativistic oscillator and two parameters which give the energy quanta and respectively the ground state energy. This last one is known to be just the conformal dimension of the boundary field theory of the AdS/CFT conjecture.
|
1907.10059
|
Shammi Tahura
|
Shammi Tahura, Kent Yagi, Zack Carson
|
Testing Gravity with Gravitational Waves from Binary Black Hole Mergers:
Contributions from Amplitude Corrections
|
v2: The third author has been added, which was accidentally missed in
the first submission; v3: matches the published version
|
Phys. Rev. D 100, 104001 (2019)
|
10.1103/PhysRevD.100.104001
| null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The detection of gravitational waves has offered us the opportunity to
explore the dynamical and strong-field regime of gravity. Because matched
filtering is more sensitive to variations in the gravitational waveform phase
than the amplitude, many tests of gravity with gravitational waves have been
carried out using only the former. Such studies cannot probe the
non-Einsteinian effects that may enter only in the amplitude. Besides, if not
accommodated in the waveform template, a non-Einsteinian effect in the
amplitude may induce systematic errors on other parameters such as the
luminosity distance. In this paper, we derive constraints on a few modified
theories of gravity (Einstein-dilaton-Gauss-Bonnet gravity, scalar-tensor
theories, and varying-$G$ theories), incorporating both phase and amplitude
corrections. We follow the model-independent approach of the parametrized
post-Einsteinian formalism. We perform Fisher analyses with Monte-Carlo
simulations using the LIGO/Virgo posterior samples. We find that the
contributions from amplitude corrections can be comparable to the ones from the
phase corrections in case of massive binaries like GW150914. Also, constraints
derived by incorporating both phase and amplitude corrections differ from the
ones with phase corrections only by 4% at most, which supports many of the
previous studies that only considered corrections in the phase. We further
derive reliable constraints on the time-evolution of a scalar field in a
scalar-tensor theory for the first time with gravitational waves.
|
[
{
"created": "Tue, 23 Jul 2019 16:28:53 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jul 2019 16:17:39 GMT",
"version": "v2"
},
{
"created": "Sun, 29 Dec 2019 22:40:54 GMT",
"version": "v3"
}
] |
2020-01-01
|
[
[
"Tahura",
"Shammi",
""
],
[
"Yagi",
"Kent",
""
],
[
"Carson",
"Zack",
""
]
] |
The detection of gravitational waves has offered us the opportunity to explore the dynamical and strong-field regime of gravity. Because matched filtering is more sensitive to variations in the gravitational waveform phase than the amplitude, many tests of gravity with gravitational waves have been carried out using only the former. Such studies cannot probe the non-Einsteinian effects that may enter only in the amplitude. Besides, if not accommodated in the waveform template, a non-Einsteinian effect in the amplitude may induce systematic errors on other parameters such as the luminosity distance. In this paper, we derive constraints on a few modified theories of gravity (Einstein-dilaton-Gauss-Bonnet gravity, scalar-tensor theories, and varying-$G$ theories), incorporating both phase and amplitude corrections. We follow the model-independent approach of the parametrized post-Einsteinian formalism. We perform Fisher analyses with Monte-Carlo simulations using the LIGO/Virgo posterior samples. We find that the contributions from amplitude corrections can be comparable to the ones from the phase corrections in case of massive binaries like GW150914. Also, constraints derived by incorporating both phase and amplitude corrections differ from the ones with phase corrections only by 4% at most, which supports many of the previous studies that only considered corrections in the phase. We further derive reliable constraints on the time-evolution of a scalar field in a scalar-tensor theory for the first time with gravitational waves.
|
1605.08420
|
Avneet Singh
|
Avneet Singh
|
Gravitational wave transient signal emission via Ekman pumping in
neutron stars during post-glitch relaxation phase
|
24 pages, 11 figures; v1: initial submission; v2: internal review;
v3: journal review; v4: copyedited version; v5-6: minor typos corrected and
references updated; v7 (final): corrections in metadata
|
Phys. Rev. D 95, 024022 (2017)
|
10.1103/PhysRevD.95.024022
|
LIGO Document LIGO-P1600091
|
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Glitches in the rotational frequency of a spinning neutron star could be
promising sources of gravitational wave signals lasting between a few
microseconds to a few weeks. The emitted signals and their properties depend
upon the internal properties of the neutron star. In neutron stars, the most
important physical properties of the fluid core are the viscosity of the fluid,
the stratification of flow in the equilibrium state and the adiabatic sound
speed. Such models were previously studied by van Eysden and Melatos [73] and
Bennett et al. [26] following simple assumptions on all contributing factors,
in which the post-glitch relaxation phase could be driven by the well-known
process of Ekman pumping [76, 17]. We explore the hydrodynamic properties of
the flow of fluid during this phase following more relaxed assumptions on the
stratification of flow and the pressure-density gradients within the neutron
star than previously studied. We calculate the time-scales of duration as well
as the amplitudes of the resulting gravitational wave signals, and we detail
their dependence on the physical properties of the fluid core. We find that it
is possible for the neutron star to emit gravitational wave signals in a wide
range of decay time-scales and within the detection sensitivity of aLIGO for
selected domains of physical parameters.
|
[
{
"created": "Thu, 26 May 2016 19:27:59 GMT",
"version": "v1"
},
{
"created": "Sun, 29 May 2016 20:43:10 GMT",
"version": "v2"
},
{
"created": "Mon, 5 Sep 2016 13:00:48 GMT",
"version": "v3"
},
{
"created": "Wed, 21 Dec 2016 12:47:00 GMT",
"version": "v4"
},
{
"created": "Tue, 19 Sep 2017 13:44:33 GMT",
"version": "v5"
},
{
"created": "Sun, 8 Oct 2017 22:47:27 GMT",
"version": "v6"
},
{
"created": "Tue, 10 Oct 2017 00:47:31 GMT",
"version": "v7"
}
] |
2017-10-11
|
[
[
"Singh",
"Avneet",
""
]
] |
Glitches in the rotational frequency of a spinning neutron star could be promising sources of gravitational wave signals lasting between a few microseconds to a few weeks. The emitted signals and their properties depend upon the internal properties of the neutron star. In neutron stars, the most important physical properties of the fluid core are the viscosity of the fluid, the stratification of flow in the equilibrium state and the adiabatic sound speed. Such models were previously studied by van Eysden and Melatos [73] and Bennett et al. [26] following simple assumptions on all contributing factors, in which the post-glitch relaxation phase could be driven by the well-known process of Ekman pumping [76, 17]. We explore the hydrodynamic properties of the flow of fluid during this phase following more relaxed assumptions on the stratification of flow and the pressure-density gradients within the neutron star than previously studied. We calculate the time-scales of duration as well as the amplitudes of the resulting gravitational wave signals, and we detail their dependence on the physical properties of the fluid core. We find that it is possible for the neutron star to emit gravitational wave signals in a wide range of decay time-scales and within the detection sensitivity of aLIGO for selected domains of physical parameters.
|
1607.07312
|
Krzysztof A. Meissner
|
Krzysztof A. Meissner and Hermann Nicolai
|
Conformal Anomalies and Gravitational Waves
|
4 pages
| null |
10.1016/j.physletb.2017.06.031
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We argue that the presence of conformal anomalies in gravitational theories
can lead to observable modifications to Einstein's equations via the induced
anomalous effective actions, whose non-localities can overwhelm the smallness
of the Planck scale. The fact that no such effects have been seen in recent
cosmological or gravitational wave observations therefore imposes strong
restrictions on the field content of possible extensions of Einstein's theory:
all viable theories should have vanishing conformal anomalies. We then show
that a complete cancellation of conformal anomalies in D=4 for both the $C^2$
invariant and the Euler (Gauss-Bonnet) invariant can only be achieved for
N-extended supergravities with $N \geq 5$, as well as for M theory compactified
to four dimensions.
|
[
{
"created": "Mon, 25 Jul 2016 15:18:06 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Aug 2016 16:12:31 GMT",
"version": "v2"
}
] |
2017-06-21
|
[
[
"Meissner",
"Krzysztof A.",
""
],
[
"Nicolai",
"Hermann",
""
]
] |
We argue that the presence of conformal anomalies in gravitational theories can lead to observable modifications to Einstein's equations via the induced anomalous effective actions, whose non-localities can overwhelm the smallness of the Planck scale. The fact that no such effects have been seen in recent cosmological or gravitational wave observations therefore imposes strong restrictions on the field content of possible extensions of Einstein's theory: all viable theories should have vanishing conformal anomalies. We then show that a complete cancellation of conformal anomalies in D=4 for both the $C^2$ invariant and the Euler (Gauss-Bonnet) invariant can only be achieved for N-extended supergravities with $N \geq 5$, as well as for M theory compactified to four dimensions.
|
gr-qc/9404008
|
Paulo Rodrigues Lima Vargas Moniz
|
A.D.Y. Cheng, P.D. D'Eath and P.R.L.V. Moniz
|
Quantization of the Bianchi type-IX model in supergravity with a
cosmological constant
|
17 pages report DAMTP R93/35
|
Phys.Rev. D49 (1994) 5246-5251
|
10.1103/PhysRevD.49.5246
| null |
gr-qc
| null |
Diagonal Bianchi type-IX models are studied in the quantum theory of $ N = 1
$ supergravity with a cosmological constant. It is shown, by imposing the
supersymmetry and Lorentz quantum constraints, that there are no physical
quantum states in this model. The $ k = + 1 $ Friedmann model in supergravity
with cosmological constant does admit quantum states. However, the Bianchi
type-IX model provides a better guide to the behaviour of a generic state,
since more gravitino modes are available to be excited. These results indicate
that there may be no physical quantum states in the full theory of $ N = 1 $
supergravity with a non-zero cosmological constant. are available to be
excited. These results indicate that there may be no physical quantum states in
the full theory of $ N = 1 $ supergravity with a non-zero cosmological
constant.
|
[
{
"created": "Wed, 6 Apr 1994 16:15:54 GMT",
"version": "v1"
}
] |
2009-10-22
|
[
[
"Cheng",
"A. D. Y.",
""
],
[
"D'Eath",
"P. D.",
""
],
[
"Moniz",
"P. R. L. V.",
""
]
] |
Diagonal Bianchi type-IX models are studied in the quantum theory of $ N = 1 $ supergravity with a cosmological constant. It is shown, by imposing the supersymmetry and Lorentz quantum constraints, that there are no physical quantum states in this model. The $ k = + 1 $ Friedmann model in supergravity with cosmological constant does admit quantum states. However, the Bianchi type-IX model provides a better guide to the behaviour of a generic state, since more gravitino modes are available to be excited. These results indicate that there may be no physical quantum states in the full theory of $ N = 1 $ supergravity with a non-zero cosmological constant. are available to be excited. These results indicate that there may be no physical quantum states in the full theory of $ N = 1 $ supergravity with a non-zero cosmological constant.
|
1106.5543
|
Carlos Augusto Romero Filho
|
C. Romero, J. B. Fonseca-Neto and M. L. Pucheu
|
General Relativity and Weyl Frames
|
Talk presented at the 8th Alexander Friedmann International Seminar
on General Relativity and Gravitation (Rio de Janeiro - 2011)
| null |
10.1142/S2010194511001115
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We present the general theory of relativity in the language of a
non-Riemannian geometry, namely, Weyl geometry. We show that the new
mathematical formalism may lead to different pictures of the same gravitational
phenomena, by making use of the concept of Weyl frames. We show that, in this
formalism, it is possible to construct a scalar-tensor gravitational theory
that is invariant with respect to the so-called Weyl tranformations and reduces
to general relativity in a particular frame, the Riemann frame. In this
approach the Weyl geometry plays a fundamental role since it appears as the
natural geometrical setting of the theory when viewed in an arbitrary frame.
Our starting point is to build an action that is manifestly invariant with
respect to Weyl transformations. When this action is expressed in more familiar
terms of Riemannian geometry we find that the theory has some similarities with
Brans-Dicke theory of gravity. We illustrate this point with an example in
which a known Brans-Dicke vacuum solution may appear when reinterpreted in a
particular Weyl frame.
|
[
{
"created": "Tue, 28 Jun 2011 00:25:27 GMT",
"version": "v1"
}
] |
2015-05-28
|
[
[
"Romero",
"C.",
""
],
[
"Fonseca-Neto",
"J. B.",
""
],
[
"Pucheu",
"M. L.",
""
]
] |
We present the general theory of relativity in the language of a non-Riemannian geometry, namely, Weyl geometry. We show that the new mathematical formalism may lead to different pictures of the same gravitational phenomena, by making use of the concept of Weyl frames. We show that, in this formalism, it is possible to construct a scalar-tensor gravitational theory that is invariant with respect to the so-called Weyl tranformations and reduces to general relativity in a particular frame, the Riemann frame. In this approach the Weyl geometry plays a fundamental role since it appears as the natural geometrical setting of the theory when viewed in an arbitrary frame. Our starting point is to build an action that is manifestly invariant with respect to Weyl transformations. When this action is expressed in more familiar terms of Riemannian geometry we find that the theory has some similarities with Brans-Dicke theory of gravity. We illustrate this point with an example in which a known Brans-Dicke vacuum solution may appear when reinterpreted in a particular Weyl frame.
|
2301.09797
|
Yusuke Manita
|
Yusuke Manita, Sirachak Panpanich and Rampei Kimura
|
Viable massive gravity without nonlinear screening
|
8 pages
| null | null |
KUNS-2951
|
gr-qc astro-ph.CO hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
We study nonlinear effects of perturbations around a cosmological background
in projected massive gravity, which admits self-accelerating solutions in an
open FLRW universe. Using the zero-curvature scaling limit, we derive nonlinear
equations containing all the relevant terms on subhorizon scales. We find that
the solution for a scalar graviton vanishes completely for all scales, which
agrees with the linear perturbation analysis in the previous study. In
addition, the effects on the gravitational potential due to the next order
perturbation are strongly suppressed within the horizon. Therefore, a screening
mechanism is no longer needed for consistency with solar-system experiments in
the projected massive gravity.
|
[
{
"created": "Tue, 24 Jan 2023 03:19:39 GMT",
"version": "v1"
}
] |
2023-01-25
|
[
[
"Manita",
"Yusuke",
""
],
[
"Panpanich",
"Sirachak",
""
],
[
"Kimura",
"Rampei",
""
]
] |
We study nonlinear effects of perturbations around a cosmological background in projected massive gravity, which admits self-accelerating solutions in an open FLRW universe. Using the zero-curvature scaling limit, we derive nonlinear equations containing all the relevant terms on subhorizon scales. We find that the solution for a scalar graviton vanishes completely for all scales, which agrees with the linear perturbation analysis in the previous study. In addition, the effects on the gravitational potential due to the next order perturbation are strongly suppressed within the horizon. Therefore, a screening mechanism is no longer needed for consistency with solar-system experiments in the projected massive gravity.
|
gr-qc/9506009
|
Imtjj51
|
F.J.de Urries and J.Julve
|
Degrees of Freedom of Arbitrarily Higher-Derivative Field Theories
|
24 pages, plain TEX
| null | null |
preprint IMAFF-95/36
|
gr-qc hep-th
| null |
As an example of what happens with physically relevant theories like
effective gravity, we consider the covariant relativistic theory of a scalar
field of arbitrarily higher differential order. A procedure based on the
Legendre transformation and suitable field redefinitions allows to recast it as
a theory of second order with one explicit independent field for each degree of
freedom. The physical and ghost fields are then apparent. The full (classical)
equivalence of both Higher and Lower Derivative versions is shown. An artifact
of the method is the appearance of irrelevant spurious fields which are devoid
of any dynamical content.
|
[
{
"created": "Mon, 5 Jun 1995 17:16:43 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Jun 1995 14:30:58 GMT",
"version": "v2"
}
] |
2008-02-03
|
[
[
"de Urries",
"F. J.",
""
],
[
"Julve",
"J.",
""
]
] |
As an example of what happens with physically relevant theories like effective gravity, we consider the covariant relativistic theory of a scalar field of arbitrarily higher differential order. A procedure based on the Legendre transformation and suitable field redefinitions allows to recast it as a theory of second order with one explicit independent field for each degree of freedom. The physical and ghost fields are then apparent. The full (classical) equivalence of both Higher and Lower Derivative versions is shown. An artifact of the method is the appearance of irrelevant spurious fields which are devoid of any dynamical content.
|
gr-qc/9905073
|
Bodo Geyer
|
Bodo Geyer, Sergei D. Odintsov and Sergio Zerbini
|
Inflationary Brans-Dicke Quantum Universe
|
10 pages, 3 additional references
|
Phys.Lett.B460:58-62,1999
|
10.1016/S0370-2693(99)00751-0
| null |
gr-qc hep-th
| null |
The formulation of Brans-Dicke (BD) gravity with matter in the Einstein frame
is realized as Einstein gravity with dilaton and dilaton coupled matter. We
calculate the one-loop 4d anomaly-induced effective action due to N dilaton-
coupled massless fermions on the time-dependent conformally flat background
with non-trivial dilaton. Using that complete effective action the
(fourth-order) quantum corrected equations of motion are derived. One special
solution of these equations representing an inflationary Universe (with
exponential scale factor) and (much slower) expanding BD dilaton is given.
Similarly, the 2d quantum BD Universe with time-dependent dilaton is
constructed. In the last case the dynamics is completely due to quantum
effects.
|
[
{
"created": "Thu, 20 May 1999 10:39:20 GMT",
"version": "v1"
},
{
"created": "Wed, 26 May 1999 13:34:34 GMT",
"version": "v2"
}
] |
2009-09-17
|
[
[
"Geyer",
"Bodo",
""
],
[
"Odintsov",
"Sergei D.",
""
],
[
"Zerbini",
"Sergio",
""
]
] |
The formulation of Brans-Dicke (BD) gravity with matter in the Einstein frame is realized as Einstein gravity with dilaton and dilaton coupled matter. We calculate the one-loop 4d anomaly-induced effective action due to N dilaton- coupled massless fermions on the time-dependent conformally flat background with non-trivial dilaton. Using that complete effective action the (fourth-order) quantum corrected equations of motion are derived. One special solution of these equations representing an inflationary Universe (with exponential scale factor) and (much slower) expanding BD dilaton is given. Similarly, the 2d quantum BD Universe with time-dependent dilaton is constructed. In the last case the dynamics is completely due to quantum effects.
|
1503.07581
|
Bertrand Chauvineau
|
Bertrand Chauvineau, Davi C. Rodrigues, J\'ulio C. Fabris
|
Scalar-tensor theories with an external scalar
|
21 pages, 3 figures, revtex To appear in General Relativity and
Gravitation
| null |
10.1007/s10714-016-2075-9
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Scalar-tensor (ST) gravity is considered in the case where the scalar is an
external field. We show that General Relativity (GR) and usual ST gravity are
particular cases of the External Scalar-Tensor (EST) gravity. It is shown with
a particular cosmological example that it is possible to join a part of a GR
solution to a part of a ST one such that the complete solution neither belongs
to GR nor to ST, but fully satisfies the EST field equations. We argue that
external fields may effectively work as a type of screening mechanism for ST
theories.
|
[
{
"created": "Wed, 25 Mar 2015 23:44:36 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Jan 2016 12:19:06 GMT",
"version": "v2"
},
{
"created": "Mon, 23 May 2016 16:28:55 GMT",
"version": "v3"
}
] |
2016-06-08
|
[
[
"Chauvineau",
"Bertrand",
""
],
[
"Rodrigues",
"Davi C.",
""
],
[
"Fabris",
"Júlio C.",
""
]
] |
Scalar-tensor (ST) gravity is considered in the case where the scalar is an external field. We show that General Relativity (GR) and usual ST gravity are particular cases of the External Scalar-Tensor (EST) gravity. It is shown with a particular cosmological example that it is possible to join a part of a GR solution to a part of a ST one such that the complete solution neither belongs to GR nor to ST, but fully satisfies the EST field equations. We argue that external fields may effectively work as a type of screening mechanism for ST theories.
|
1110.0173
|
Paulo Pitanga
|
P. Pitanga
|
G\"odel's universe and the chronology protection conjecture
|
Added references; conclusions enlarged
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We present a solution for the geodesic motion in G\"odel's universe that
provides a particular proof of Hawking's chronology protection conjecture in
three-dimensional gravity theory. The solution is based upon the fact that the
group of the automorphisms of the Heisenberg motion group H1\timesU(1), modulo
discrete sub-group Z, act isometrically on the boundary of the hyperbolic
three-dimensional manifold. Closed timelike curves do not exist due to the
presence of a closed Cauchy-Riemann surface for chronology protection, with two
mirror symmetric sets of helicoidal self-similar modules inside. The present
solution is isometrically equivalent to a cylindrical gravitational
monochromatic wave front.
|
[
{
"created": "Sun, 2 Oct 2011 11:50:02 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Oct 2011 13:03:28 GMT",
"version": "v2"
},
{
"created": "Tue, 11 Oct 2011 23:05:36 GMT",
"version": "v3"
},
{
"created": "Mon, 17 Oct 2011 16:13:46 GMT",
"version": "v4"
},
{
"created": "Wed, 26 Oct 2011 14:46:31 GMT",
"version": "v5"
}
] |
2015-03-19
|
[
[
"Pitanga",
"P.",
""
]
] |
We present a solution for the geodesic motion in G\"odel's universe that provides a particular proof of Hawking's chronology protection conjecture in three-dimensional gravity theory. The solution is based upon the fact that the group of the automorphisms of the Heisenberg motion group H1\timesU(1), modulo discrete sub-group Z, act isometrically on the boundary of the hyperbolic three-dimensional manifold. Closed timelike curves do not exist due to the presence of a closed Cauchy-Riemann surface for chronology protection, with two mirror symmetric sets of helicoidal self-similar modules inside. The present solution is isometrically equivalent to a cylindrical gravitational monochromatic wave front.
|
gr-qc/0307112
|
Jeff Murugan
|
George F.R. Ellis, Jeff Murugan and Christos G. Tsagas
|
The Emergent Universe: An Explicit Construction
|
10 pages, 6 eps figures, revtex4. Discussion on initial conditions
improved and typos corrected. This version to appear in Classical and Quantum
Gravity
|
Class.Quant.Grav.21:233-250,2004
|
10.1088/0264-9381/21/1/016
| null |
gr-qc astro-ph
| null |
We provide a realisation of a singularity-free inflationary universe in the
form of a simple cosmological model dominated at early times by a single
minimally coupled scalar field with a physically based potential. The universe
starts asymptotically from an initial Einstein static state, which may be large
enough to avoid the quantum gravity regime. It enters an expanding phase that
leads to inflation followed by reheating and a standard hot Big Bang evolution.
We discuss the basic characteristics of this Emergent model and show that none
is at odds with current observations.
|
[
{
"created": "Mon, 28 Jul 2003 12:45:14 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Nov 2003 20:21:12 GMT",
"version": "v2"
}
] |
2008-11-26
|
[
[
"Ellis",
"George F. R.",
""
],
[
"Murugan",
"Jeff",
""
],
[
"Tsagas",
"Christos G.",
""
]
] |
We provide a realisation of a singularity-free inflationary universe in the form of a simple cosmological model dominated at early times by a single minimally coupled scalar field with a physically based potential. The universe starts asymptotically from an initial Einstein static state, which may be large enough to avoid the quantum gravity regime. It enters an expanding phase that leads to inflation followed by reheating and a standard hot Big Bang evolution. We discuss the basic characteristics of this Emergent model and show that none is at odds with current observations.
|
0904.1715
|
Chris Van Den Broeck
|
Chris Van Den Broeck, Duncan A. Brown, Thomas Cokelaer, Ian Harry,
Gareth Jones, B.S. Sathyaprakash, Hideyuki Tagoshi, and Hirotaka Takahashi
|
Template banks to search for compact binaries with spinning components
in gravitational wave data
|
11 pages, 3 figures
|
Phys.Rev.D80:024009,2009
|
10.1103/PhysRevD.80.024009
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Gravitational waves from coalescing compact binaries are one of the most
promising sources for detectors such as LIGO, Virgo and GEO600. If the
components of the binary posess significant angular momentum (spin), as is
likely to be the case if one component is a black hole, spin-induced precession
of a binary's orbital plane causes modulation of the gravitational-wave
amplitude and phase. If the templates used in a matched-filter search do not
accurately model these effects then the sensitivity, and hence the detection
rate, will be reduced. We investigate the ability of several search pipelines
to detect gravitational waves from compact binaries with spin. We use the
post-Newtonian approximation to model the inspiral phase of the signal and
construct two new template banks using the phenomenological waveforms of
Buonanno, Chen and Vallisneri. We compare the performance of these template
banks to that of banks constructed using the stationary phase approximation to
the non-spinning post-Newtonian inspiral waveform currently used by LIGO and
Virgo in the search for compact binary coalescence. We find that, at the same
false alarm rate, a search pipeline using phenomenological templates is no more
effective than a pipeline which uses non-spinning templates. We recommend the
continued use of the non-spinning stationary phase template bank until the
false alarm rate associated with templates which include spin effects can be
substantially reduced.
|
[
{
"created": "Fri, 10 Apr 2009 18:08:31 GMT",
"version": "v1"
}
] |
2009-09-02
|
[
[
"Broeck",
"Chris Van Den",
""
],
[
"Brown",
"Duncan A.",
""
],
[
"Cokelaer",
"Thomas",
""
],
[
"Harry",
"Ian",
""
],
[
"Jones",
"Gareth",
""
],
[
"Sathyaprakash",
"B. S.",
""
],
[
"Tagoshi",
"Hideyuki",
""
],
[
"Takahashi",
"Hirotaka",
""
]
] |
Gravitational waves from coalescing compact binaries are one of the most promising sources for detectors such as LIGO, Virgo and GEO600. If the components of the binary posess significant angular momentum (spin), as is likely to be the case if one component is a black hole, spin-induced precession of a binary's orbital plane causes modulation of the gravitational-wave amplitude and phase. If the templates used in a matched-filter search do not accurately model these effects then the sensitivity, and hence the detection rate, will be reduced. We investigate the ability of several search pipelines to detect gravitational waves from compact binaries with spin. We use the post-Newtonian approximation to model the inspiral phase of the signal and construct two new template banks using the phenomenological waveforms of Buonanno, Chen and Vallisneri. We compare the performance of these template banks to that of banks constructed using the stationary phase approximation to the non-spinning post-Newtonian inspiral waveform currently used by LIGO and Virgo in the search for compact binary coalescence. We find that, at the same false alarm rate, a search pipeline using phenomenological templates is no more effective than a pipeline which uses non-spinning templates. We recommend the continued use of the non-spinning stationary phase template bank until the false alarm rate associated with templates which include spin effects can be substantially reduced.
|
gr-qc/0403104
|
Zet Gheorghe
|
G. Zet, C. D. Oprisan, S. Babeti
|
Solutions without singularities in gauge theory of gravitation
|
9 pages, no figures
|
Int.J.Mod.Phys. C15 (2004) 1031-1038
|
10.1142/S0129183104006443
| null |
gr-qc
| null |
A de-Sitter gauge theory of the gravitational field is developed using a
spherical symmetric Minkowski space-time as base manifold. The gravitational
field is described by gauge potentials and the mathematical structure of the
underlying space-time is not affected by physical events. The field equations
are written and their solutions without singularities are obtained by imposing
some constraints on the invariants of the model. An example of such a solution
is given and its dependence on the cosmological constant is studied. A
comparison with results obtained in General Relativity theory is also
presented.
Keywords: gauge theory, gravitation, singularity, computer algebra
|
[
{
"created": "Thu, 25 Mar 2004 12:57:10 GMT",
"version": "v1"
}
] |
2009-11-10
|
[
[
"Zet",
"G.",
""
],
[
"Oprisan",
"C. D.",
""
],
[
"Babeti",
"S.",
""
]
] |
A de-Sitter gauge theory of the gravitational field is developed using a spherical symmetric Minkowski space-time as base manifold. The gravitational field is described by gauge potentials and the mathematical structure of the underlying space-time is not affected by physical events. The field equations are written and their solutions without singularities are obtained by imposing some constraints on the invariants of the model. An example of such a solution is given and its dependence on the cosmological constant is studied. A comparison with results obtained in General Relativity theory is also presented. Keywords: gauge theory, gravitation, singularity, computer algebra
|
gr-qc/0012014
|
B. S. Sathyaprakash
|
B.S. Sathyaprakash
|
The gravitational wave symphony of the Universe
|
Proceedings of the International Conference on Gravitation and
Cosmology, held at IIT Kharagpur, Jan 2000 (to appear in Pramana J. Phys.)
|
Pramana 56:457-475,2001
|
10.1007/s12043-001-0096-7
| null |
gr-qc
| null |
The new millennium will see the upcoming of several ground-based
interferometric gravitational wave antennas. Within the next decade a
space-based antenna may also begin to observe the distant Universe. These
gravitational wave detectors will together operate as a network taking data
continuously for several years, watching the transient and continuous phenomena
occurring in the deep cores of astronomical objects and dense environs of the
early Universe where gravity was extremely strong and highly non-linear. The
network will listen to the waves from rapidly spinning non-axisymmetric neutron
stars, normal modes of black holes, binary black hole inspiral and merger,
phase transitions in the early Universe, quantum fluctuations resulting in a
characteristic background in the early Universe. The gravitational wave
antennas will open a new window to observe the dark Universe unreachable via
other channels of astronomical observations.
|
[
{
"created": "Mon, 4 Dec 2000 22:58:19 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Jul 2002 21:58:38 GMT",
"version": "v2"
}
] |
2009-10-31
|
[
[
"Sathyaprakash",
"B. S.",
""
]
] |
The new millennium will see the upcoming of several ground-based interferometric gravitational wave antennas. Within the next decade a space-based antenna may also begin to observe the distant Universe. These gravitational wave detectors will together operate as a network taking data continuously for several years, watching the transient and continuous phenomena occurring in the deep cores of astronomical objects and dense environs of the early Universe where gravity was extremely strong and highly non-linear. The network will listen to the waves from rapidly spinning non-axisymmetric neutron stars, normal modes of black holes, binary black hole inspiral and merger, phase transitions in the early Universe, quantum fluctuations resulting in a characteristic background in the early Universe. The gravitational wave antennas will open a new window to observe the dark Universe unreachable via other channels of astronomical observations.
|
1901.04658
|
Hayato Motohashi
|
Hayato Motohashi, Masato Minamitsuji
|
Exact black hole solutions in shift-symmetric quadratic degenerate
higher-order scalar-tensor theories
|
15 pages; reference added; matches published version
|
Phys. Rev. D 99, 064040 (2019)
|
10.1103/PhysRevD.99.064040
|
YITP-19-01
|
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We find various exact black hole solutions in the shift-symmetric subclass of
the quadratic degenerate higher-order scalar-tensor (DHOST) theories with
linearly time dependent scalar field whose kinetic term is constant. The exact
solutions are the Schwarzschild and Schwarzschild-(anti-)de Sitter solutions,
and the Schwarzschild-type solution with a deficit solid angle, which are
accompanied by nontrivial scalar field regular at the black hole event horizon.
We derive the conditions for the coupling functions in the DHOST Lagrangian
that allow the exact solutions, clarify their compatibility with the degeneracy
conditions, and provide general form of coupling functions as well as simple
models that satisfy the conditions.
|
[
{
"created": "Tue, 15 Jan 2019 04:45:44 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Jan 2019 08:23:49 GMT",
"version": "v2"
},
{
"created": "Wed, 10 Apr 2019 12:50:41 GMT",
"version": "v3"
}
] |
2019-04-11
|
[
[
"Motohashi",
"Hayato",
""
],
[
"Minamitsuji",
"Masato",
""
]
] |
We find various exact black hole solutions in the shift-symmetric subclass of the quadratic degenerate higher-order scalar-tensor (DHOST) theories with linearly time dependent scalar field whose kinetic term is constant. The exact solutions are the Schwarzschild and Schwarzschild-(anti-)de Sitter solutions, and the Schwarzschild-type solution with a deficit solid angle, which are accompanied by nontrivial scalar field regular at the black hole event horizon. We derive the conditions for the coupling functions in the DHOST Lagrangian that allow the exact solutions, clarify their compatibility with the degeneracy conditions, and provide general form of coupling functions as well as simple models that satisfy the conditions.
|
1703.02372
|
Kimet Jusufi
|
Kimet Jusufi, Ali Ovgun, Gordana Apostolovska
|
Tunneling of Massive/Massless Bosons From the Apparent Horizon of FRW
Universe
|
7 pages, accepted for publication in Advances in High Energy Physics
|
Advances in High Energy Physics, vol. 2017, Article ID 8798657, 7
pages, 2017
|
10.1155/2017/8798657
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this article we investigate the Hawking radiation of vector particles from
the apparent horizon of a Friedmann-Robertson-Walker (FRW) universe in the
framework of quantum tunneling method. Furthermore we use Proca equation, a
relativistic wave equation for a massive/massless spin-1 particle (massless
$\gamma$ photons, weak massive $W^{\pm}$ and $Z^{0}$ bosons, strong massless
gluons and $\rho$ and $\omega$ mesons) together with a Painlev\'{e} spacetime
metric for the FRW universe. We solve the Proca equation via Hamilton-Jacobi
(HJ) equation and the WKB approximation method. We recover the same result for
the Hawking temperature associated with vector particles as in the case of
scalar and Dirac particles tunnelled from outside to the inside of the apparent
horizon in a FRW universe.
|
[
{
"created": "Tue, 7 Mar 2017 13:36:33 GMT",
"version": "v1"
},
{
"created": "Mon, 22 May 2017 16:34:02 GMT",
"version": "v2"
}
] |
2017-07-04
|
[
[
"Jusufi",
"Kimet",
""
],
[
"Ovgun",
"Ali",
""
],
[
"Apostolovska",
"Gordana",
""
]
] |
In this article we investigate the Hawking radiation of vector particles from the apparent horizon of a Friedmann-Robertson-Walker (FRW) universe in the framework of quantum tunneling method. Furthermore we use Proca equation, a relativistic wave equation for a massive/massless spin-1 particle (massless $\gamma$ photons, weak massive $W^{\pm}$ and $Z^{0}$ bosons, strong massless gluons and $\rho$ and $\omega$ mesons) together with a Painlev\'{e} spacetime metric for the FRW universe. We solve the Proca equation via Hamilton-Jacobi (HJ) equation and the WKB approximation method. We recover the same result for the Hawking temperature associated with vector particles as in the case of scalar and Dirac particles tunnelled from outside to the inside of the apparent horizon in a FRW universe.
|
2207.02835
|
Dipayan Mukherjee
|
Dipayan Mukherjee, H. K. Jassal, Kinjalk Lochan
|
Bouncing and collapsing universes dual to late-time cosmological models
|
36 pages, 12 figures, minor changes
|
Eur. Phys. J. C 84, 318 (2024)
|
10.1140/epjc/s10052-024-12673-1
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We use the Jordan frame-Einstein frame correspondence to explore dual
universes with contrasting cosmological evolutions. We study the mapping
between Einstein and Jordan frames where the Einstein frame universe describes
the late-time evolution of the physical universe, which is driven by dark
energy and non-relativistic matter. The Brans-Dicke theory of gravity is
considered to be the dual scalar-tensor theory in the Jordan frame. We show
that an Einstein frame universe, with cosmological evolution of the
$\Lambda$CDM model, always corresponds to a bouncing Jordan frame universe
governed by a Brans-Dicke theory. On the other hand, quintessence models of
dark energy with non-relativistic matter component are shown to be always dual
to a Brans-Dicke Jordan frame with a turn-around, i.e., a bounce or a collapse.
The evolution of the equation of state of the quintessence field determines
whether the turn-around is a bounce or a collapse. The point of the Jordan
frame turn-around for all the cases can be tuned anywhere by choosing an
appropriate Brans-Dicke parameter. This essentially leads to alternative
descriptions of the late-time evolution of the physical universe, in terms of
bouncing or collapsing Brans-Dicke universes in the Jordan frame. Therefore,the
effect of dark energy can equivalently be seen as collapse of space in a
conformally connected universe. We further study the stability of such
conformal maps against linear perturbations. The effective bouncing and
collapsing descriptions of the current accelerating universe may have
interesting implications for the evolutions of perturbations and quantum
fluctuations in the cosmological background.
|
[
{
"created": "Wed, 6 Jul 2022 17:47:38 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Jul 2022 05:56:12 GMT",
"version": "v2"
},
{
"created": "Sun, 25 Dec 2022 12:47:57 GMT",
"version": "v3"
},
{
"created": "Wed, 27 Mar 2024 15:23:54 GMT",
"version": "v4"
}
] |
2024-03-28
|
[
[
"Mukherjee",
"Dipayan",
""
],
[
"Jassal",
"H. K.",
""
],
[
"Lochan",
"Kinjalk",
""
]
] |
We use the Jordan frame-Einstein frame correspondence to explore dual universes with contrasting cosmological evolutions. We study the mapping between Einstein and Jordan frames where the Einstein frame universe describes the late-time evolution of the physical universe, which is driven by dark energy and non-relativistic matter. The Brans-Dicke theory of gravity is considered to be the dual scalar-tensor theory in the Jordan frame. We show that an Einstein frame universe, with cosmological evolution of the $\Lambda$CDM model, always corresponds to a bouncing Jordan frame universe governed by a Brans-Dicke theory. On the other hand, quintessence models of dark energy with non-relativistic matter component are shown to be always dual to a Brans-Dicke Jordan frame with a turn-around, i.e., a bounce or a collapse. The evolution of the equation of state of the quintessence field determines whether the turn-around is a bounce or a collapse. The point of the Jordan frame turn-around for all the cases can be tuned anywhere by choosing an appropriate Brans-Dicke parameter. This essentially leads to alternative descriptions of the late-time evolution of the physical universe, in terms of bouncing or collapsing Brans-Dicke universes in the Jordan frame. Therefore,the effect of dark energy can equivalently be seen as collapse of space in a conformally connected universe. We further study the stability of such conformal maps against linear perturbations. The effective bouncing and collapsing descriptions of the current accelerating universe may have interesting implications for the evolutions of perturbations and quantum fluctuations in the cosmological background.
|
1904.08012
|
Antony Speranza
|
Antony J. Speranza
|
Geometrical tools for embedding fields, submanifolds, and foliations
|
43 + 18 pages, 2 figures, v2: updated discussion of normal bundle
topology, references added
| null | null | null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Embedding fields provide a way of coupling a background structure to a theory
while preserving diffeomorphism-invariance. Examples of such background
structures include embedded submanifolds, such as branes; boundaries of local
subregions, such as the Ryu-Takayanagi surface in holography; and foliations,
which appear in fluid dynamics and force-free electrodynamics. This work
presents a systematic framework for computing geometric properties of these
background structures in the embedding field description. An overview of the
local geometric quantities associated with a foliation is given, including a
review of the Gauss, Codazzi, and Ricci-Voss equations, which relate the
geometry of the foliation to the ambient curvature. Generalizations of these
equations for curvature in the nonintegrable normal directions are derived.
Particular care is given to the question of which objects are well-defined for
single submanifolds, and which depend on the structure of the foliation away
from a submanifold. Variational formulas are provided for the geometric
quantities, which involve contributions both from the variation of the
embedding map as well as variations of the ambient metric. As an application of
these variational formulas, a derivation is given of the Jacobi equation,
describing perturbations of extremal area surfaces of arbitrary codimension.
The embedding field formalism is also applied to the problem of classifying
boundary conditions for general relativity in a finite subregion that lead to
integrable Hamiltonians. The framework developed in this paper will provide a
useful set of tools for future analyses of brane dynamics, fluid mechanics, and
edge modes for finite subregions of diffeomorphism-invariant theories.
|
[
{
"created": "Tue, 16 Apr 2019 23:22:25 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Apr 2019 03:38:30 GMT",
"version": "v2"
}
] |
2019-04-29
|
[
[
"Speranza",
"Antony J.",
""
]
] |
Embedding fields provide a way of coupling a background structure to a theory while preserving diffeomorphism-invariance. Examples of such background structures include embedded submanifolds, such as branes; boundaries of local subregions, such as the Ryu-Takayanagi surface in holography; and foliations, which appear in fluid dynamics and force-free electrodynamics. This work presents a systematic framework for computing geometric properties of these background structures in the embedding field description. An overview of the local geometric quantities associated with a foliation is given, including a review of the Gauss, Codazzi, and Ricci-Voss equations, which relate the geometry of the foliation to the ambient curvature. Generalizations of these equations for curvature in the nonintegrable normal directions are derived. Particular care is given to the question of which objects are well-defined for single submanifolds, and which depend on the structure of the foliation away from a submanifold. Variational formulas are provided for the geometric quantities, which involve contributions both from the variation of the embedding map as well as variations of the ambient metric. As an application of these variational formulas, a derivation is given of the Jacobi equation, describing perturbations of extremal area surfaces of arbitrary codimension. The embedding field formalism is also applied to the problem of classifying boundary conditions for general relativity in a finite subregion that lead to integrable Hamiltonians. The framework developed in this paper will provide a useful set of tools for future analyses of brane dynamics, fluid mechanics, and edge modes for finite subregions of diffeomorphism-invariant theories.
|
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