id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1202.3131 | Yuuiti Sendouda | Nathalie Deruelle, Misao Sasaki, Yuuiti Sendouda, Ahmed Youssef | Lorentz-violating vs ghost gravitons: the example of Weyl gravity | 14 pages, 3 figures, REVTeX 4.1 | null | 10.1007/JHEP09(2012)009 | YITP-12-3 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the ghost degrees of freedom of Einstein gravity with a Weyl
term can be eliminated by a simple mechanism that invokes local Lorentz
symmetry breaking. We demonstrate how the mechanism works in a cosmological
setting. The presence of the Weyl term forces a redefinition of the quantum
vacuum state of the tensor perturbations. As a consequence the amplitude of
their spectrum blows up when the Lorentz-violating scale becomes comparable to
the Hubble radius. Such a behaviour is in sharp contrast to what happens in
standard Weyl gravity where the gravitational ghosts smoothly damp out the
spectrum of primordial gravitational waves.
| [
{
"created": "Tue, 14 Feb 2012 20:20:01 GMT",
"version": "v1"
}
] | 2015-06-04 | [
[
"Deruelle",
"Nathalie",
""
],
[
"Sasaki",
"Misao",
""
],
[
"Sendouda",
"Yuuiti",
""
],
[
"Youssef",
"Ahmed",
""
]
] | We show that the ghost degrees of freedom of Einstein gravity with a Weyl term can be eliminated by a simple mechanism that invokes local Lorentz symmetry breaking. We demonstrate how the mechanism works in a cosmological setting. The presence of the Weyl term forces a redefinition of the quantum vacuum state of the tensor perturbations. As a consequence the amplitude of their spectrum blows up when the Lorentz-violating scale becomes comparable to the Hubble radius. Such a behaviour is in sharp contrast to what happens in standard Weyl gravity where the gravitational ghosts smoothly damp out the spectrum of primordial gravitational waves. |
0705.2252 | Carlos Augusto Romero Filho | M. A. S. Cruz, F. Dahia and C. Romero | Inducing charges and currents from extra dimensions | 8 pages. Accepted for publication in Modern Physics Letters A | Mod.Phys.Lett.A23:197-203,2008 | 10.1142/S0217732308023839 | null | gr-qc | null | In a particular variant of Kaluza-Klein theory, the so-called induced-matter
theory (IMT), it is shown that any configuration of matter may be geometrically
induced from a five-dimensional vacuum space. By using a similar approach we
show that any distribution of charges and currents may also be induced from a
five-dimensional vacuum space. Whereas in the case of IMT the geometry is
Riemannian and the fundamental equations are the five-dimensional Einstein
equations in vacuum, here we consider a Minkowskian geometry and the
five-dimensional Maxwell equations in vacuum.
| [
{
"created": "Tue, 15 May 2007 22:21:11 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Cruz",
"M. A. S.",
""
],
[
"Dahia",
"F.",
""
],
[
"Romero",
"C.",
""
]
] | In a particular variant of Kaluza-Klein theory, the so-called induced-matter theory (IMT), it is shown that any configuration of matter may be geometrically induced from a five-dimensional vacuum space. By using a similar approach we show that any distribution of charges and currents may also be induced from a five-dimensional vacuum space. Whereas in the case of IMT the geometry is Riemannian and the fundamental equations are the five-dimensional Einstein equations in vacuum, here we consider a Minkowskian geometry and the five-dimensional Maxwell equations in vacuum. |
gr-qc/9704028 | Bill Hiscock | Shane L. Larson, William A. Hiscock (Montana State University) | Astrophysical Bounds on Global Strings | 14 pages, REVTeX | Phys.Rev. D56 (1997) 3242-3247 | 10.1103/PhysRevD.56.3242 | MSUPHY97.08 | gr-qc | null | Global topological defects produce nonzero stress-energy throughout
spacetime, and as a result can have observable gravitational influence on
surrounding matter. Gravitational effects of global strings are used to place
bounds on their cosmic abundance. The minimum separation between global strings
is estimated by considering the defects' contribution to the cosmological
energy density. More rigorous constraints on the abundance of global strings
are constructed by examining the tidal forces such defects will have on
observable astrophysical systems. The small number of observed tidally
disrupted systems indicates there can be very few of these objects in the
observable universe.
| [
{
"created": "Wed, 9 Apr 1997 16:03:22 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Larson",
"Shane L.",
"",
"Montana State University"
],
[
"Hiscock",
"William A.",
"",
"Montana State University"
]
] | Global topological defects produce nonzero stress-energy throughout spacetime, and as a result can have observable gravitational influence on surrounding matter. Gravitational effects of global strings are used to place bounds on their cosmic abundance. The minimum separation between global strings is estimated by considering the defects' contribution to the cosmological energy density. More rigorous constraints on the abundance of global strings are constructed by examining the tidal forces such defects will have on observable astrophysical systems. The small number of observed tidally disrupted systems indicates there can be very few of these objects in the observable universe. |
gr-qc/0011060 | Rachael M. Hawkins | Rachael M. Hawkins and James E. Lidsey | Inflation on a single brane - exact solutions | 6 pages, Revtex, In Press Phys. Rev. D | Phys.Rev.D63:041301,2001 | 10.1103/PhysRevD.63.041301 | null | gr-qc | null | Algorithms are developed for generating a class of exact braneworld
cosmologies, where a self-interacting scalar field is confined to a
positive-tension brane embedded in a bulk containing a negative cosmological
constant. It is assumed that the five-dimensional Planck scale exceeds the
brane tension but is smaller than the four-dimensional Planck mass. It is shown
that the field equations can be expressed as a first-order system. A number of
solutions to the equations of motion are found. The potential resulting in the
perfect fluid model is identified.
| [
{
"created": "Fri, 17 Nov 2000 13:10:27 GMT",
"version": "v1"
}
] | 2009-12-31 | [
[
"Hawkins",
"Rachael M.",
""
],
[
"Lidsey",
"James E.",
""
]
] | Algorithms are developed for generating a class of exact braneworld cosmologies, where a self-interacting scalar field is confined to a positive-tension brane embedded in a bulk containing a negative cosmological constant. It is assumed that the five-dimensional Planck scale exceeds the brane tension but is smaller than the four-dimensional Planck mass. It is shown that the field equations can be expressed as a first-order system. A number of solutions to the equations of motion are found. The potential resulting in the perfect fluid model is identified. |
1011.3065 | Galina L. Klimchitskaya | G. L. Klimchitskaya and C. Romero | Strengthening constraints on Yukawa-type corrections to Newtonian
gravity from measuring the Casimir force between a cylinder and a plate | 17 pages, 2 figures; to appear in Phys. Rev. D | Phys.Rev.D82:115005,2010 | 10.1103/PhysRevD.82.115005 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss possibility to obtain stronger constraints on non-Newtonian
gravity from measuring the gradient of the Casimir force between a cylinder and
a plate. Exact analytical expression for the Yukawa-type force in a
cylinder-plate configuration is obtained, as well as its asymptotic expansions.
The gravitational force is compared with the Casimir force acting between a
cylinder and a plate. Numerical computations for the prospective constraints on
non-Newtonian gravity are performed for recently proposed experiment using a
microfabricated cylinder attached to a micromachined oscillator. Specifically,
it is shown that this experiment is expected to obtain up to 70 times stronger
constraints on the Yukawa-type force, compared with the best present day
limits, over a wide interaction range from 12.5 to 630 nm.
| [
{
"created": "Fri, 12 Nov 2010 22:22:38 GMT",
"version": "v1"
}
] | 2010-12-24 | [
[
"Klimchitskaya",
"G. L.",
""
],
[
"Romero",
"C.",
""
]
] | We discuss possibility to obtain stronger constraints on non-Newtonian gravity from measuring the gradient of the Casimir force between a cylinder and a plate. Exact analytical expression for the Yukawa-type force in a cylinder-plate configuration is obtained, as well as its asymptotic expansions. The gravitational force is compared with the Casimir force acting between a cylinder and a plate. Numerical computations for the prospective constraints on non-Newtonian gravity are performed for recently proposed experiment using a microfabricated cylinder attached to a micromachined oscillator. Specifically, it is shown that this experiment is expected to obtain up to 70 times stronger constraints on the Yukawa-type force, compared with the best present day limits, over a wide interaction range from 12.5 to 630 nm. |
gr-qc/0303096 | Ruth Lazkoz | J.M. Aguirregabiria, L.P. Chimento, and Ruth Lazkoz | Anisotropy and inflation in Bianchi I brane worlds | 10 pages, improved discussion on the likeliness of
non-isotropization, completed list of references, matches version to appear
in Class. Quantum Grav | Class.Quant.Grav. 21 (2004) 823-830 | 10.1088/0264-9381/21/4/005 | null | gr-qc hep-th | null | After a more general assumption on the influence of the bulk on the brane, we
extend some conclusions by Maartens et al. and Santos et al. on the asymptotic
behavior of Bianchi I brane worlds. As a consequence of the nonlocal
anisotropic stresses induced by the bulk, in most of our models, the brane does
not isotropize and the nonlocal energy does not vanish in the limit in which
the mean radius goes to infinity. We have also found the intriguing possibility
that the inflation due to the cosmological constant might be prevented by the
interaction with the bulk. We show that the problem for the mean radius can be
completely solved in our models, which include as particular cases those in the
references above.
| [
{
"created": "Tue, 25 Mar 2003 15:15:18 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Dec 2003 13:21:49 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Aguirregabiria",
"J. M.",
""
],
[
"Chimento",
"L. P.",
""
],
[
"Lazkoz",
"Ruth",
""
]
] | After a more general assumption on the influence of the bulk on the brane, we extend some conclusions by Maartens et al. and Santos et al. on the asymptotic behavior of Bianchi I brane worlds. As a consequence of the nonlocal anisotropic stresses induced by the bulk, in most of our models, the brane does not isotropize and the nonlocal energy does not vanish in the limit in which the mean radius goes to infinity. We have also found the intriguing possibility that the inflation due to the cosmological constant might be prevented by the interaction with the bulk. We show that the problem for the mean radius can be completely solved in our models, which include as particular cases those in the references above. |
2201.04694 | Christian Pfeifer | Dagmar L\"a\"anemets, Manuel Hohmann, Christian Pfeifer | Observables from spherically symmetric modified dispersion relations | Contribution to the Special Issue of the International Journal of
Geometric Methods in Modern Physics dedicated to the conference Geometric
Foundations of Gravity 2021, journal version | Int.J.Geom.Meth.Mod.Phys. 19 (2022) 10, 2250155 | 10.1142/S0219887822501559 | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we continue the systematic study of observable effects emerging
from modified dispersion relations. We study the motion of test particles
subject to a general first order modification of the general relativistic
dispersion relation as well as subject to the $\kappa$-Poincar\'e dispersion
relation in spherical symmetry. We derive the corrections to the photon sphere,
the black hole shadow, the Shapiro delay and the light deflection and identify
the additional dependence of these observables on the photons' four momentum,
which leads to measurable effects that can be compared to experimental data.
The results presented here can be interpreted in two ways, depending on the
origin of the modified dispersion relation: on the one hand as prediction for
traces of quantum gravity, when the modified dispersion relation is induced by
phenomenological approaches to quantum gravity, on the other hand as
predictions of observables due to the presence of a medium, like a plasma,
which modifies the dispersion relation of light on curved spacetimes.
| [
{
"created": "Wed, 12 Jan 2022 20:48:14 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Aug 2022 11:40:19 GMT",
"version": "v2"
},
{
"created": "Wed, 31 Aug 2022 16:05:17 GMT",
"version": "v3"
}
] | 2022-09-01 | [
[
"Läänemets",
"Dagmar",
""
],
[
"Hohmann",
"Manuel",
""
],
[
"Pfeifer",
"Christian",
""
]
] | In this work we continue the systematic study of observable effects emerging from modified dispersion relations. We study the motion of test particles subject to a general first order modification of the general relativistic dispersion relation as well as subject to the $\kappa$-Poincar\'e dispersion relation in spherical symmetry. We derive the corrections to the photon sphere, the black hole shadow, the Shapiro delay and the light deflection and identify the additional dependence of these observables on the photons' four momentum, which leads to measurable effects that can be compared to experimental data. The results presented here can be interpreted in two ways, depending on the origin of the modified dispersion relation: on the one hand as prediction for traces of quantum gravity, when the modified dispersion relation is induced by phenomenological approaches to quantum gravity, on the other hand as predictions of observables due to the presence of a medium, like a plasma, which modifies the dispersion relation of light on curved spacetimes. |
gr-qc/0106026 | Bela Szilagyi | Bela Szilagyi, Bernd Schmidt, and Jeffrey Winicour | Boundary conditions in linearized harmonic gravity | 22 pages, 6 Postscript figures | Phys.Rev.D65:064015,2002 | 10.1103/PhysRevD.65.064015 | null | gr-qc | null | We investigate the initial-boundary value problem for linearized
gravitational theory in harmonic coordinates. Rigorous techniques for
hyperbolic systems are applied to establish well-posedness for various
reductions of the system into a set of six wave equations. The results are used
to formulate computational algorithms for Cauchy evolution in a 3-dimensional
bounded domain. Numerical codes based upon these algorithms are shown to
satisfy tests of robust stability for random constraint violating initial data
and random boundary data; and shown to give excellent performance for the
evolution of typical physical data. The results are obtained for plane
boundaries as well as piecewise cubic spherical boundaries cut out of a
Cartesian grid.
| [
{
"created": "Thu, 7 Jun 2001 15:45:37 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Nov 2001 19:24:11 GMT",
"version": "v2"
}
] | 2011-04-21 | [
[
"Szilagyi",
"Bela",
""
],
[
"Schmidt",
"Bernd",
""
],
[
"Winicour",
"Jeffrey",
""
]
] | We investigate the initial-boundary value problem for linearized gravitational theory in harmonic coordinates. Rigorous techniques for hyperbolic systems are applied to establish well-posedness for various reductions of the system into a set of six wave equations. The results are used to formulate computational algorithms for Cauchy evolution in a 3-dimensional bounded domain. Numerical codes based upon these algorithms are shown to satisfy tests of robust stability for random constraint violating initial data and random boundary data; and shown to give excellent performance for the evolution of typical physical data. The results are obtained for plane boundaries as well as piecewise cubic spherical boundaries cut out of a Cartesian grid. |
2203.12809 | Eloy Ay\'on-Beato | Eloy Ay\'on-Beato | Unveiling the electrodynamics of the first nonlinearly charged rotating
black hole | 4 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | After many years of efforts, the first nonlinearly charged rotating black
hole has been finally reported by Garcia-Diaz in two recent works. This is an
important result that was pending in General Relativity, since nonlinear
generalizations of the Kerr-Newman solution were not yet known. Unfortunately,
the Lagrangian supporting this configuration cannot be expressible in terms of
the standard invariants using elementary functions. In the present work we
circumvent this problem by using the formulations of nonlinear electrodynamics
in terms of mixed electromagnetic eigenvalues, introduced by Salazar,
Garcia-Diaz and Plebanski almost four decades ago. In doing so, we prove that
the underlying theory becomes fully determined, and hence the new found
nonlinearly charged stationary axisymmetric spacetimes correspond to exact
solutions of a well-defined self-gravitating nonlinear electrodynamics whose
fundamental structural functions are provided here.
| [
{
"created": "Thu, 24 Mar 2022 02:19:46 GMT",
"version": "v1"
}
] | 2022-03-28 | [
[
"Ayón-Beato",
"Eloy",
""
]
] | After many years of efforts, the first nonlinearly charged rotating black hole has been finally reported by Garcia-Diaz in two recent works. This is an important result that was pending in General Relativity, since nonlinear generalizations of the Kerr-Newman solution were not yet known. Unfortunately, the Lagrangian supporting this configuration cannot be expressible in terms of the standard invariants using elementary functions. In the present work we circumvent this problem by using the formulations of nonlinear electrodynamics in terms of mixed electromagnetic eigenvalues, introduced by Salazar, Garcia-Diaz and Plebanski almost four decades ago. In doing so, we prove that the underlying theory becomes fully determined, and hence the new found nonlinearly charged stationary axisymmetric spacetimes correspond to exact solutions of a well-defined self-gravitating nonlinear electrodynamics whose fundamental structural functions are provided here. |
0809.1036 | Spenta Wadia | Spenta R. Wadia | String Theory: A Framework for Quantum Gravity and Various Applications | 38 pages, 5 figures, Article for TWAS Jubilee Publication, References
and Comments added | null | null | TIFR/TH/08-32 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this semi-technical review we discuss string theory (and all that goes by
that name) as a framework for a quantum theory of gravity. This is a new
paradigm in theoretical physics that goes beyond relativistic quantum field
theory. We provide concrete evidence for this proposal. It leads to the
resolution of the ultra-violet catastrophe of Einstein's theory of general
relativity and an explanation of the Bekenstein-Hawking entropy (of a class of
black holes) in terms of Boltzmann's formula for entropy in statistical
mechanics. We discuss `the holographic principle' and its precise and
consequential formulation in the AdS/CFT correspondence of Maldacena. One
consequence of this correspondence is the ability to do strong coupling
calculations in SU(N) gauge theories in terms of semi-classical gravity. In
particular, we indicate a connection between dissipative fluid dynamics and the
dynamics of black hole horizons. We end with a discussion of elementary
particle physics and cosmology in the framework of string theory. We do not
cover all aspects of string theory and its applications to diverse areas of
physics and mathematics, but follow a few paths in a vast landscape of ideas.
(This article has been prepared for the TWAS Silver Jubilee)
| [
{
"created": "Fri, 5 Sep 2008 14:17:16 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Nov 2008 10:52:39 GMT",
"version": "v2"
}
] | 2008-11-05 | [
[
"Wadia",
"Spenta R.",
""
]
] | In this semi-technical review we discuss string theory (and all that goes by that name) as a framework for a quantum theory of gravity. This is a new paradigm in theoretical physics that goes beyond relativistic quantum field theory. We provide concrete evidence for this proposal. It leads to the resolution of the ultra-violet catastrophe of Einstein's theory of general relativity and an explanation of the Bekenstein-Hawking entropy (of a class of black holes) in terms of Boltzmann's formula for entropy in statistical mechanics. We discuss `the holographic principle' and its precise and consequential formulation in the AdS/CFT correspondence of Maldacena. One consequence of this correspondence is the ability to do strong coupling calculations in SU(N) gauge theories in terms of semi-classical gravity. In particular, we indicate a connection between dissipative fluid dynamics and the dynamics of black hole horizons. We end with a discussion of elementary particle physics and cosmology in the framework of string theory. We do not cover all aspects of string theory and its applications to diverse areas of physics and mathematics, but follow a few paths in a vast landscape of ideas. (This article has been prepared for the TWAS Silver Jubilee) |
0901.0640 | Krzysztof A. Meissner | Krzysztof A. Meissner | Horizons and the cosmological constant | 6 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new solution of the Einstein equations for the point mass immersed in the
de Sitter Universe is presented. The properties of the metric are very
different from both the Schwarzschild black hole and the de Sitter Universe: it
is everywhere smooth, light can propagate outward through the horizon, there is
an antitrapped surface enclosing the point mass and there is necessarily an
initial singularity. The solution for any positive cosmological constant is
qualitatively different from the Schwarzschild solution and is not its
continuous deformation.
| [
{
"created": "Tue, 6 Jan 2009 14:52:16 GMT",
"version": "v1"
}
] | 2009-01-07 | [
[
"Meissner",
"Krzysztof A.",
""
]
] | A new solution of the Einstein equations for the point mass immersed in the de Sitter Universe is presented. The properties of the metric are very different from both the Schwarzschild black hole and the de Sitter Universe: it is everywhere smooth, light can propagate outward through the horizon, there is an antitrapped surface enclosing the point mass and there is necessarily an initial singularity. The solution for any positive cosmological constant is qualitatively different from the Schwarzschild solution and is not its continuous deformation. |
2305.08756 | Bernardo Araneda | Bernardo Araneda | Complex conformal transformations and zero-rest-mass fields | 16 pages | null | 10.1103/PhysRevD.108.024032 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We give a simple prescription for relating different solutions to the
zero-rest-mass field equations in conformally flat space-time via complex
conformal transformations and changes in reality conditions. We give several
examples including linearized black holes. In particular, we show that the
linearized Plebanski-Demianski and Schwarzschild fields are related by a
complex translation and a complex special conformal transformation. Similar
results hold for the linearized Kerr and C-metric fields, and for a peculiar
toroidal singularity.
| [
{
"created": "Mon, 15 May 2023 16:10:35 GMT",
"version": "v1"
}
] | 2023-07-26 | [
[
"Araneda",
"Bernardo",
""
]
] | We give a simple prescription for relating different solutions to the zero-rest-mass field equations in conformally flat space-time via complex conformal transformations and changes in reality conditions. We give several examples including linearized black holes. In particular, we show that the linearized Plebanski-Demianski and Schwarzschild fields are related by a complex translation and a complex special conformal transformation. Similar results hold for the linearized Kerr and C-metric fields, and for a peculiar toroidal singularity. |
1003.0882 | Ulrich Sperhake | U.Sperhake, V.Cardoso, F.Pretorius, E.Berti, T.Hinderer, N.Yunes | Ultra-relativistic grazing collisions of black holes | Proceedings for the 12th Marcel Grossman Meeting | null | 10.1103/PhysRevD.81.104048 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study gravitational wave emission, zoom-whirl behavior and the resulting
spin of the remnant black hole in highly boosted collisions of equal-mass, non
spinning black-hole binaries with generic impact parameter.
| [
{
"created": "Wed, 3 Mar 2010 19:43:17 GMT",
"version": "v1"
}
] | 2013-05-29 | [
[
"Sperhake",
"U.",
""
],
[
"Cardoso",
"V.",
""
],
[
"Pretorius",
"F.",
""
],
[
"Berti",
"E.",
""
],
[
"Hinderer",
"T.",
""
],
[
"Yunes",
"N.",
""
]
] | We study gravitational wave emission, zoom-whirl behavior and the resulting spin of the remnant black hole in highly boosted collisions of equal-mass, non spinning black-hole binaries with generic impact parameter. |
2012.04472 | Meir Shimon | Meir Shimon | Weyl-Invariant Gravity and the Nature of Dark Matter | Matches published version | null | 10.1088/1361-6382/abeae5 | null | gr-qc astro-ph.CO astro-ph.GA hep-ph | http://creativecommons.org/licenses/by/4.0/ | The apparent missing mass in galaxies and galaxy clusters, commonly viewed as
evidence for dark matter, could possibly originate from gradients in the
gravitational coupling parameter, $G$, and active gravitational mass,
$M_{act}$, rather than hypothetical beyond-the-standard-model particles. We
argue that in (the weak field limit of) a Weyl-invariant extension of General
Relativity, one can simply affect the change $\Phi_{b}(x)\rightarrow\Phi_{b}(x)
+ \Phi_{DM}(x)$, where $\Phi_{b}$ is the baryon-sourced potential and
$\Phi_{DM}$ is the `excess' potential. This is compensated by gradients of
$GM_{act}$ and a fractional increase of $O(-4\Phi_{DM}(x))$ in the baryon
density, well below current detection thresholds on all relevant scales.
| [
{
"created": "Sun, 6 Dec 2020 11:55:50 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Apr 2022 13:56:56 GMT",
"version": "v2"
}
] | 2022-04-05 | [
[
"Shimon",
"Meir",
""
]
] | The apparent missing mass in galaxies and galaxy clusters, commonly viewed as evidence for dark matter, could possibly originate from gradients in the gravitational coupling parameter, $G$, and active gravitational mass, $M_{act}$, rather than hypothetical beyond-the-standard-model particles. We argue that in (the weak field limit of) a Weyl-invariant extension of General Relativity, one can simply affect the change $\Phi_{b}(x)\rightarrow\Phi_{b}(x) + \Phi_{DM}(x)$, where $\Phi_{b}$ is the baryon-sourced potential and $\Phi_{DM}$ is the `excess' potential. This is compensated by gradients of $GM_{act}$ and a fractional increase of $O(-4\Phi_{DM}(x))$ in the baryon density, well below current detection thresholds on all relevant scales. |
2011.10168 | R Loll | J. Brunekreef, R. Loll | Curvature profiles for quantum gravity | 30 pages, 14 figures | Phys. Rev. D 103, 026019 (2021) | 10.1103/PhysRevD.103.026019 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Building on the recently introduced notion of quantum Ricci curvature and
motivated by considerations in nonperturbative quantum gravity, we advocate a
new, global observable for curved metric spaces, the curvature profile. It is
obtained by integrating the scale-dependent, quasi-local quantum Ricci
curvature, and therefore also depends on a coarse-graining scale. To understand
how the distribution of local, Gaussian curvature is reflected in the curvature
profile, we compute it on a class of regular polygons with isolated conical
singularities. We focus on the case of the tetrahedron, for which we have a
good computational control of its geodesics, and compare its curvature profile
to that of a smooth sphere. The two are distinct, but qualitatively similar,
which confirms that the curvature profile has averaging properties which are
interesting from a quantum point of view.
| [
{
"created": "Fri, 20 Nov 2020 01:37:21 GMT",
"version": "v1"
}
] | 2021-02-03 | [
[
"Brunekreef",
"J.",
""
],
[
"Loll",
"R.",
""
]
] | Building on the recently introduced notion of quantum Ricci curvature and motivated by considerations in nonperturbative quantum gravity, we advocate a new, global observable for curved metric spaces, the curvature profile. It is obtained by integrating the scale-dependent, quasi-local quantum Ricci curvature, and therefore also depends on a coarse-graining scale. To understand how the distribution of local, Gaussian curvature is reflected in the curvature profile, we compute it on a class of regular polygons with isolated conical singularities. We focus on the case of the tetrahedron, for which we have a good computational control of its geodesics, and compare its curvature profile to that of a smooth sphere. The two are distinct, but qualitatively similar, which confirms that the curvature profile has averaging properties which are interesting from a quantum point of view. |
1706.09078 | Mark A. Scheel | Mark A. Scheel and Kip S. Thorne | Geometrodynamics: The Nonlinear Dynamics of Curved Spacetime | 12 pages, 14 figures. Published in 2014 in Uspekhi Fizicheskikh Nauk
and P N Lebedev Physics Institute of the Russian Academy of Sciences in an
issue commemorating the 100th anniversary of the birth of Y B Zeldovich | Phys.-Usp. 57 342 (2014) | 10.3367/UFNe.0184.201404b.0367 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review discoveries in the nonlinear dynamics of curved spacetime, largely
made possible by numerical solutions of Einstein's equations. We discuss
critical phenomena and self-similarity in gravitational collapse, the behavior
of spacetime curvature near singularities, the instability of black strings in
5 spacetime dimensions, and the collision of four-dimensional black holes. We
also discuss the prospects for further discoveries in geometrodynamics via
observation of gravitational waves.
| [
{
"created": "Wed, 28 Jun 2017 00:02:40 GMT",
"version": "v1"
}
] | 2017-06-29 | [
[
"Scheel",
"Mark A.",
""
],
[
"Thorne",
"Kip S.",
""
]
] | We review discoveries in the nonlinear dynamics of curved spacetime, largely made possible by numerical solutions of Einstein's equations. We discuss critical phenomena and self-similarity in gravitational collapse, the behavior of spacetime curvature near singularities, the instability of black strings in 5 spacetime dimensions, and the collision of four-dimensional black holes. We also discuss the prospects for further discoveries in geometrodynamics via observation of gravitational waves. |
gr-qc/0403068 | Sergei Kopeikin M. | Sergei Kopeikin and Igor Vlasov (University of Missouri-Columbia, USA) | Parametrized Post-Newtonian Theory of Reference Frames, Multipolar
Expansions and Equations of Motion in the N-body Problem | 121 pages, 5 figures, references added, improvements made in response
to referee's report | Phys.Rept.400:209-318,2004 | 10.1016/j.physrep.2004.08.004 | null | gr-qc astro-ph math-ph math.MP | null | We discuss a covariant generalization of the parametrized post-Newtonian
(PPN) formalism in a class of scalar-tensor theories of gravity. It includes an
exact construction of a set of global and local (Fermi-like) references frames
for an isolated N-body astronomical system as well as PPN multipolar
decomposition of gravitational field in these frames. We derive PPN equations
of translational and rotational motion of extended bodies taking into account
all gravitational multipoles and analyze the body finite-size effects in
relativistic dynamics that can be important at the latest stages of orbital
evolution of coalescing binary systems. We also reconcile the IAU 2000
resolutions on the general relativistic reference frames in the solar system
with the PPN equations of motion of the solar system bodies used in JPL
ephemerides.
| [
{
"created": "Mon, 15 Mar 2004 21:42:22 GMT",
"version": "v1"
},
{
"created": "Sun, 11 Jul 2004 17:06:10 GMT",
"version": "v2"
},
{
"created": "Wed, 24 May 2006 16:41:20 GMT",
"version": "v3"
}
] | 2009-01-14 | [
[
"Kopeikin",
"Sergei",
"",
"University of Missouri-Columbia, USA"
],
[
"Vlasov",
"Igor",
"",
"University of Missouri-Columbia, USA"
]
] | We discuss a covariant generalization of the parametrized post-Newtonian (PPN) formalism in a class of scalar-tensor theories of gravity. It includes an exact construction of a set of global and local (Fermi-like) references frames for an isolated N-body astronomical system as well as PPN multipolar decomposition of gravitational field in these frames. We derive PPN equations of translational and rotational motion of extended bodies taking into account all gravitational multipoles and analyze the body finite-size effects in relativistic dynamics that can be important at the latest stages of orbital evolution of coalescing binary systems. We also reconcile the IAU 2000 resolutions on the general relativistic reference frames in the solar system with the PPN equations of motion of the solar system bodies used in JPL ephemerides. |
2209.00341 | Mouhssine Koussour | M. Koussour, S. H. Shekh, H. Filali and M. Bennai | Barrow holographic dark energy models in $f\left( Q\right)$ symmetric
teleparallel gravity with Lambert function distribution | IJGMMP accepted version | International Journal of Geometric Methods in Modern Physics
(2022) | 10.1142/S0219887823500196 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The paper presents Barrow holographic dark energy (infrared cut-off is the
Hubble horizon) suggested by Barrow recently (Physics Letters B 808 (2020):
135643) in an anisotropic Bianchi type-I Universe within the framework of $%
f\left( Q\right) $ symmetric teleparallel gravity, where the non-metricity
scalar $Q$ is responsible for the gravitational interaction. We consider two
cases: Interacting and non-interacting models of pressureless dark matter and
Barrow holographic dark energy by solving $f\left( Q\right) $ symmetric
teleparallel field equations. To find the exact solutions of the field
equations, we assume that the time-redshift relation follows a Lambert function
distribution as $t\left( z\right) =\frac{mt_{0}}{l}g\left( z\right) $, where
$g\left( z\right) =LambertW\left[ \frac{l}{m}e^{\frac{l-\ln \left( 1+z\right)
}{m}}\right] $, $m$ and $l$ are non-negative constants and $t_{0}$ represents
the age of the Universe. Moreover, we discuss several cosmological parameters
such as energy density, equation of state (EoS) and skewness parameters,
squared sound speed, and $(\omega _{B}-\omega _{B}^{^{\prime }})$ plane.
Finally, we found the values of the deceleration parameter (DP) for the Lambert
function distribution as $q_{(z=0)}=-0.45$ and $q_{(z=-1)}=-1$ which are
consistent with recent observational data, i.e. DP evolves with cosmic time
from initial deceleration to late-time acceleration.
| [
{
"created": "Thu, 1 Sep 2022 10:18:03 GMT",
"version": "v1"
}
] | 2022-12-01 | [
[
"Koussour",
"M.",
""
],
[
"Shekh",
"S. H.",
""
],
[
"Filali",
"H.",
""
],
[
"Bennai",
"M.",
""
]
] | The paper presents Barrow holographic dark energy (infrared cut-off is the Hubble horizon) suggested by Barrow recently (Physics Letters B 808 (2020): 135643) in an anisotropic Bianchi type-I Universe within the framework of $% f\left( Q\right) $ symmetric teleparallel gravity, where the non-metricity scalar $Q$ is responsible for the gravitational interaction. We consider two cases: Interacting and non-interacting models of pressureless dark matter and Barrow holographic dark energy by solving $f\left( Q\right) $ symmetric teleparallel field equations. To find the exact solutions of the field equations, we assume that the time-redshift relation follows a Lambert function distribution as $t\left( z\right) =\frac{mt_{0}}{l}g\left( z\right) $, where $g\left( z\right) =LambertW\left[ \frac{l}{m}e^{\frac{l-\ln \left( 1+z\right) }{m}}\right] $, $m$ and $l$ are non-negative constants and $t_{0}$ represents the age of the Universe. Moreover, we discuss several cosmological parameters such as energy density, equation of state (EoS) and skewness parameters, squared sound speed, and $(\omega _{B}-\omega _{B}^{^{\prime }})$ plane. Finally, we found the values of the deceleration parameter (DP) for the Lambert function distribution as $q_{(z=0)}=-0.45$ and $q_{(z=-1)}=-1$ which are consistent with recent observational data, i.e. DP evolves with cosmic time from initial deceleration to late-time acceleration. |
2405.09471 | Luis B Castro | Luis B. Castro and Angel E. Obispo and Andr\'es G. Jir\'on | Charged scalar bosons in a Bonnor-Melvin-$\Lambda$ universe at conical
approximation | 11 pages, 5 figures | Eur. Phys. J. C 84 (2024) 536 | 10.1140/epjc/s10052-024-12911-6 | null | gr-qc hep-th math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The quantum dynamics of charged scalar bosons in a Bonnor-Melvin-$\Lambda$
universe is considered. In this study, the behavior of charged scalar bosons is
explored within the framework of the Duffin-Kemmer-Petiau (DKP) formalism.
Adopting a conical approximation ($\Lambda\ll 1$), we are considered two
scenarios for the vector potential: a linear and quadratic vector potentials.
In particular, the effects of this background in the equation of motion, phase
shift, $S$-matrix, energy spectrum and DKP spinor are analyzed and discussed.
| [
{
"created": "Wed, 15 May 2024 16:09:02 GMT",
"version": "v1"
}
] | 2024-05-30 | [
[
"Castro",
"Luis B.",
""
],
[
"Obispo",
"Angel E.",
""
],
[
"Jirón",
"Andrés G.",
""
]
] | The quantum dynamics of charged scalar bosons in a Bonnor-Melvin-$\Lambda$ universe is considered. In this study, the behavior of charged scalar bosons is explored within the framework of the Duffin-Kemmer-Petiau (DKP) formalism. Adopting a conical approximation ($\Lambda\ll 1$), we are considered two scenarios for the vector potential: a linear and quadratic vector potentials. In particular, the effects of this background in the equation of motion, phase shift, $S$-matrix, energy spectrum and DKP spinor are analyzed and discussed. |
gr-qc/9809024 | Laszlo A. Gergely | L\'aszl\'o \'A. Gergely | Spherically symmetric static solution for colliding null dust | 12 pages, 7 figures, to appear in Phys. Rev. D | Phys.Rev.D58:084030,1998 | 10.1103/PhysRevD.58.084030 | null | gr-qc | null | The Einstein equations are integrated in the presence of two (incoming and
outgoing) streams of null dust, under the assumptions of spherical symmetry and
staticity. The solution is also written in double null and radiation
coordinates and it is reinterpreted as an anisotropic fluid. Interior matching
with a static fluid and exterior matching with the Vaidya solution along null
hypersurfaces is discussed. The connection with two-dimensional dilaton gravity
is established.
| [
{
"created": "Fri, 4 Sep 1998 21:09:44 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Gergely",
"László Á.",
""
]
] | The Einstein equations are integrated in the presence of two (incoming and outgoing) streams of null dust, under the assumptions of spherical symmetry and staticity. The solution is also written in double null and radiation coordinates and it is reinterpreted as an anisotropic fluid. Interior matching with a static fluid and exterior matching with the Vaidya solution along null hypersurfaces is discussed. The connection with two-dimensional dilaton gravity is established. |
1509.08181 | Maxim Eingorn | Maxim Eingorn, Ruslan Brilenkov | Perfect fluids with $\omega=\mathrm{const}$ as sources of scalar
cosmological perturbations | 14 pages, no figures | Physics of the Dark Universe 17, 63 (2017) | 10.1016/j.dark.2017.08.003 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We make a generalization of a self-consistent first-order perturbation
scheme, being suitable for all (sub-horizon and super-horizon) scales, which
has been recently constructed for the concordance cosmological model and
discrete presentation of matter sources, to the case of extended models with
extra perfect fluids and continuous presentation. Namely, we derive a single
equation determining the scalar perturbation and covering the whole space as
well as define the corresponding universal Yukawa interaction range. We also
demonstrate explicitly that the structure growth is suppressed at distances
exceeding this fundamental range.
| [
{
"created": "Mon, 28 Sep 2015 02:51:07 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Mar 2016 18:39:05 GMT",
"version": "v2"
},
{
"created": "Fri, 8 Sep 2017 17:20:51 GMT",
"version": "v3"
}
] | 2017-09-11 | [
[
"Eingorn",
"Maxim",
""
],
[
"Brilenkov",
"Ruslan",
""
]
] | We make a generalization of a self-consistent first-order perturbation scheme, being suitable for all (sub-horizon and super-horizon) scales, which has been recently constructed for the concordance cosmological model and discrete presentation of matter sources, to the case of extended models with extra perfect fluids and continuous presentation. Namely, we derive a single equation determining the scalar perturbation and covering the whole space as well as define the corresponding universal Yukawa interaction range. We also demonstrate explicitly that the structure growth is suppressed at distances exceeding this fundamental range. |
2304.04551 | Takuya Katagiri | Takuya Katagiri, Hiroyuki Nakano, Kazuyuki Omukai | Stability of relativistic tidal response against small potential
modification | 44 pages, 19 figures, v2: minor corrections, v3: minor corrections,
accepted for publication in PRD | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | The tidal response of compact objects in an inspiraling binary system is
measured by a set of tidal Love and dissipation numbers imprinted in the
gravitational waveforms. While a four-dimensional black hole in vacuum within
General Relativity has vanishing Love numbers, a black hole in alternative
theories of gravity can acquire non-vanishing Love numbers. The dissipation
numbers may quantify Planckian corrections at the horizon scale. These
properties will allow a test of classical theories of gravity in the
strong-field regime with gravitational-wave observation. Since black holes are
not in the exact vacuum environment in astrophysical situations, the following
question arises: can the environment affect the tidal response? In this paper,
we investigate the stability of the tidal response of a Schwarzschild black
hole for frequency-dependent tidal-field perturbations against a small
modification of the background. Our analysis relies on the scattering theory,
which overcomes difficulties in computing the relativistic tidal Love numbers.
The tidal Love and dissipation numbers can be understood from the property of
sufficiently low-frequency scattering waves. We show that the tidal Love
numbers are sensitive to the property of the modification. Therefore, we need
careful consideration of the environment around the black hole in assessing the
deviation of the underlying theory of gravity from General Relativity with the
Love numbers. The modification has less impact on the dissipation numbers,
indicating that quantifying the existence of the event horizon with them is not
spoiled. We also demonstrate that in a composite system, i.e., a compact object
with environmental effects, the Love and dissipation numbers are approximately
determined by the sum of the numbers of each component.
| [
{
"created": "Mon, 10 Apr 2023 12:45:39 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Apr 2023 09:30:03 GMT",
"version": "v2"
},
{
"created": "Thu, 12 Oct 2023 14:59:57 GMT",
"version": "v3"
}
] | 2023-10-13 | [
[
"Katagiri",
"Takuya",
""
],
[
"Nakano",
"Hiroyuki",
""
],
[
"Omukai",
"Kazuyuki",
""
]
] | The tidal response of compact objects in an inspiraling binary system is measured by a set of tidal Love and dissipation numbers imprinted in the gravitational waveforms. While a four-dimensional black hole in vacuum within General Relativity has vanishing Love numbers, a black hole in alternative theories of gravity can acquire non-vanishing Love numbers. The dissipation numbers may quantify Planckian corrections at the horizon scale. These properties will allow a test of classical theories of gravity in the strong-field regime with gravitational-wave observation. Since black holes are not in the exact vacuum environment in astrophysical situations, the following question arises: can the environment affect the tidal response? In this paper, we investigate the stability of the tidal response of a Schwarzschild black hole for frequency-dependent tidal-field perturbations against a small modification of the background. Our analysis relies on the scattering theory, which overcomes difficulties in computing the relativistic tidal Love numbers. The tidal Love and dissipation numbers can be understood from the property of sufficiently low-frequency scattering waves. We show that the tidal Love numbers are sensitive to the property of the modification. Therefore, we need careful consideration of the environment around the black hole in assessing the deviation of the underlying theory of gravity from General Relativity with the Love numbers. The modification has less impact on the dissipation numbers, indicating that quantifying the existence of the event horizon with them is not spoiled. We also demonstrate that in a composite system, i.e., a compact object with environmental effects, the Love and dissipation numbers are approximately determined by the sum of the numbers of each component. |
1105.3520 | Aron Wall | Aron C. Wall | Testing the Generalized Second Law in 1+1 dimensional Conformal Vacua:
An Argument for the Causal Horizon | 19 pages, 2 figures, v2 significant additions clarifying sections 3,
5, and 6, v3 fixed typo in Eq. (35) | Phys. Rev. D 85, 024015 (2012) | 10.1103/PhysRevD.85.024015 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The anomalous conformal transformation law of the generalized entropy is
found for dilaton gravity coupled to a 1+1 conformal matter sector with central
charges $c = \tilde{c}$. (When $c \ne \tilde{c}$ the generalized entropy is not
invariant under local Lorentz boosts.) It is shown that a certain second null
derivative of the entropy, $S_\text{gen}" + (6/c)(S_\text{out}')^2$, is
primary, and therefore retains its sign under a general conformal
transformation. Consequently all conformal vacua have increasing entropy on
causal horizons. Alternative definitions of the horizon, including apparent or
dynamical horizons, can have decreasing entropy in any dimension $D \ge 2$.
This indicates that the generalized second law should be defined using the
causal horizon.
| [
{
"created": "Wed, 18 May 2011 02:59:56 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Jan 2012 03:31:00 GMT",
"version": "v2"
},
{
"created": "Fri, 4 Nov 2016 22:47:18 GMT",
"version": "v3"
}
] | 2016-11-08 | [
[
"Wall",
"Aron C.",
""
]
] | The anomalous conformal transformation law of the generalized entropy is found for dilaton gravity coupled to a 1+1 conformal matter sector with central charges $c = \tilde{c}$. (When $c \ne \tilde{c}$ the generalized entropy is not invariant under local Lorentz boosts.) It is shown that a certain second null derivative of the entropy, $S_\text{gen}" + (6/c)(S_\text{out}')^2$, is primary, and therefore retains its sign under a general conformal transformation. Consequently all conformal vacua have increasing entropy on causal horizons. Alternative definitions of the horizon, including apparent or dynamical horizons, can have decreasing entropy in any dimension $D \ge 2$. This indicates that the generalized second law should be defined using the causal horizon. |
gr-qc/0106079 | Gladush | Valentin D. Gladush | Five-dimensional general relativity and Kaluza-Klein theory | 11 pages, LaTeX | Theor.Math.Phys.136:1312-1324,2003; Teor.Mat.Fiz.136:480-495,2003 | 10.1023/A:1025655400605 | null | gr-qc | null | We consider 5D spaces which admit the most symmetric 3D subspaces. 5D vacuum
Einstein equations are constructed and 5D analog of the mass function is found.
The corresponding conservation law leads to 5D analog of Birkhoff's theorem.
Hence the cylinder condition is dynamically implemented for the considered
spaces. For some obtained metrics a period of space with respect to the fifth
coordinate was found. The problem of the dynamical degrees of freedom of the
fields system obtained in the process of dimensional reduction is discussed,
and the problem of their interpretation is considered. One can think that the
parametrization of the scalar field and 4D metric leading to the conformally
invariant 4D theory for interacting gravitational and scalar fields is most
natural and adequate.
| [
{
"created": "Tue, 26 Jun 2001 00:07:26 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Gladush",
"Valentin D.",
""
]
] | We consider 5D spaces which admit the most symmetric 3D subspaces. 5D vacuum Einstein equations are constructed and 5D analog of the mass function is found. The corresponding conservation law leads to 5D analog of Birkhoff's theorem. Hence the cylinder condition is dynamically implemented for the considered spaces. For some obtained metrics a period of space with respect to the fifth coordinate was found. The problem of the dynamical degrees of freedom of the fields system obtained in the process of dimensional reduction is discussed, and the problem of their interpretation is considered. One can think that the parametrization of the scalar field and 4D metric leading to the conformally invariant 4D theory for interacting gravitational and scalar fields is most natural and adequate. |
gr-qc/0612142 | Masaru Shibata | Masaru Shibata and Koji Uryu | Merger of black hole-neutron star binaries: nonspinning black hole case | 5 pages. Phys. Rev. D 74, 121503 (R) (2006) | Phys.Rev. D74 (2006) 121503 | 10.1103/PhysRevD.74.121503 | null | gr-qc | null | We perform a simulation for merger of a black hole (BH)-neutron star (NS)
binary in full general relativity preparing a quasicircular state as initial
condition. The BH is modeled by a moving puncture with no spin and the NS by
the $\Gamma$-law equation of state with $\Gamma=2$. Corotating velocity field
is assumed for the NS. The mass of the BH and the rest-mass of the NS are
chosen to be $\approx 3.2 M_{\odot}$ and $\approx 1.4 M_{\odot}$ with
relatively large radius of the NS $\approx 14$ km. The NS is tidally disrupted
near the innermost stable orbit but $\sim 80%$ of the material is swallowed
into the BH with small disk mass $\sim 0.3M_{\odot}$ even for such small BH
mass $\sim 3M_{\odot}$. The result indicates that the system of a BH and a
massive disk of $\sim M_{\odot}$ is not formed from nonspinning BH-NS binaries,
although a disk of mass $\sim 0.1M_{\odot}$ is a possible outcome.
| [
{
"created": "Fri, 22 Dec 2006 06:14:24 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Shibata",
"Masaru",
""
],
[
"Uryu",
"Koji",
""
]
] | We perform a simulation for merger of a black hole (BH)-neutron star (NS) binary in full general relativity preparing a quasicircular state as initial condition. The BH is modeled by a moving puncture with no spin and the NS by the $\Gamma$-law equation of state with $\Gamma=2$. Corotating velocity field is assumed for the NS. The mass of the BH and the rest-mass of the NS are chosen to be $\approx 3.2 M_{\odot}$ and $\approx 1.4 M_{\odot}$ with relatively large radius of the NS $\approx 14$ km. The NS is tidally disrupted near the innermost stable orbit but $\sim 80%$ of the material is swallowed into the BH with small disk mass $\sim 0.3M_{\odot}$ even for such small BH mass $\sim 3M_{\odot}$. The result indicates that the system of a BH and a massive disk of $\sim M_{\odot}$ is not formed from nonspinning BH-NS binaries, although a disk of mass $\sim 0.1M_{\odot}$ is a possible outcome. |
2301.00913 | Qing-Hua Zhu | Qing-Hua Zhu | Photon ring autocorrelations from gravitational fluctuations around a
black hole | v2: accepted version, 24 pages, 11 figures, 11pt | Phys. Rev. D 109, 064031 (2024) | 10.1103/PhysRevD.109.064031 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The images of supermassive black holes in M87 and our galaxy captured by the
Event Horizon Telescope (EHT) might open up a new way for exploring black hole
physics at the horizon scale. Theoretically, this could provide insights into
studying the emission sources around a black hole or the geometries of the
black hole itself. This paper investigates the two-point correlations of
intensity fluctuations on the photon ring, resulting from the existence of
shock waves or gravitational fluctuations around a black hole. Following
approaches used in the field of gravitational wave detectors, we introduce
response functions of very long baseline interferometry (VLBI) for detecting
gravitational fluctuations and study the shape of the overlap reduction
functions. It is found that the shape of the correlations here differs from
that resulting from stochastic emission sources. By providing an
order-of-magnitude estimate for the signal-to-noise ratio (SNR), we obtain
sensitivity curves for the detection of gravitational fluctuations. This might
reveal the potential for detecting gravitational fluctuations with future VLBI
observations in the LIGO frequency band.
| [
{
"created": "Tue, 3 Jan 2023 01:09:36 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Mar 2024 14:32:54 GMT",
"version": "v2"
}
] | 2024-03-15 | [
[
"Zhu",
"Qing-Hua",
""
]
] | The images of supermassive black holes in M87 and our galaxy captured by the Event Horizon Telescope (EHT) might open up a new way for exploring black hole physics at the horizon scale. Theoretically, this could provide insights into studying the emission sources around a black hole or the geometries of the black hole itself. This paper investigates the two-point correlations of intensity fluctuations on the photon ring, resulting from the existence of shock waves or gravitational fluctuations around a black hole. Following approaches used in the field of gravitational wave detectors, we introduce response functions of very long baseline interferometry (VLBI) for detecting gravitational fluctuations and study the shape of the overlap reduction functions. It is found that the shape of the correlations here differs from that resulting from stochastic emission sources. By providing an order-of-magnitude estimate for the signal-to-noise ratio (SNR), we obtain sensitivity curves for the detection of gravitational fluctuations. This might reveal the potential for detecting gravitational fluctuations with future VLBI observations in the LIGO frequency band. |
1903.10115 | Bo Wang | Yang Zhang, Xuan Ye, Bo Wang | Adiabatic regularization and Green's function of a scalar field in de
Sitter space: Positive energy spectrum and no trace anomaly | 47 Pages, 10 Figures. Accepted for publication in SCIENCE CHINA
Physics, Mechanics & Astronomy | Science China Physics, Mechanics & Astronomy 63, 250411 (2020) | 10.1007/s11433-019-1451-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the conventional adiabatic regularization the vacuum ultraviolet
divergences of a quantum field in curved spacetime are removed by subtracting
the $k$-mode of the stress tensor to the 4th-order. For a scalar field in de
Sitter space, we find that the 4th-order regularized spectral energy density is
negative. Moreover, the 2nd-order regularization for minimal coupling ($\xi=0$)
and the 0th-order regularization for conformal coupling ($\xi=\frac16$) yield a
positive and UV-convergent spectral energy density and power spectrum. The
regularized stress tensor in the vacuum is maximally symmetric and can drive
inflation, while its $k$-modes representing the primordial fluctuations are
nonuniformly distributed. Conventional regularization of a Green's function in
position space is generally plagued by a log IR divergence. Only in the
massless case with $\xi=0$ or $\frac16$, we can directly regularize the Green's
functions and obtain vanishing results that agree with the adiabatic
regularization results. In this case, the regularized power spectrum and stress
tensor are both zero, and no trace anomaly exists. To overcome the log IR
divergence problem in the massive cases with $\xi=0$ and $\frac16$, we perform
Fourier transformation of the regularized power spectra and obtain the
regularized analytical Green's functions which are IR- and UV-convergent.
| [
{
"created": "Mon, 25 Mar 2019 03:31:17 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Apr 2019 12:25:28 GMT",
"version": "v2"
},
{
"created": "Sat, 28 Sep 2019 03:13:15 GMT",
"version": "v3"
},
{
"created": "Mon, 2 Mar 2020 14:53:46 GMT",
"version": "v4"
}
] | 2020-03-03 | [
[
"Zhang",
"Yang",
""
],
[
"Ye",
"Xuan",
""
],
[
"Wang",
"Bo",
""
]
] | In the conventional adiabatic regularization the vacuum ultraviolet divergences of a quantum field in curved spacetime are removed by subtracting the $k$-mode of the stress tensor to the 4th-order. For a scalar field in de Sitter space, we find that the 4th-order regularized spectral energy density is negative. Moreover, the 2nd-order regularization for minimal coupling ($\xi=0$) and the 0th-order regularization for conformal coupling ($\xi=\frac16$) yield a positive and UV-convergent spectral energy density and power spectrum. The regularized stress tensor in the vacuum is maximally symmetric and can drive inflation, while its $k$-modes representing the primordial fluctuations are nonuniformly distributed. Conventional regularization of a Green's function in position space is generally plagued by a log IR divergence. Only in the massless case with $\xi=0$ or $\frac16$, we can directly regularize the Green's functions and obtain vanishing results that agree with the adiabatic regularization results. In this case, the regularized power spectrum and stress tensor are both zero, and no trace anomaly exists. To overcome the log IR divergence problem in the massive cases with $\xi=0$ and $\frac16$, we perform Fourier transformation of the regularized power spectra and obtain the regularized analytical Green's functions which are IR- and UV-convergent. |
1607.01961 | Ramil Izmailov | Alexander A. Potapov, Ramil N. Izmailov and Kamal K. Nandi | Mass decomposition of SLACS lens galaxies in Weyl conformal gravity | 32 pages, 4 figures, 2 tables | Phys. Rev. D 93, 124070 (2016) | 10.1103/PhysRevD.93.124070 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study here, using the Mannheim-Kazanas solution of Weyl conformal theory,
the mass decomposition in the representative subsample of $57$ early-type
elliptical lens galaxies of the SLACS on board the HST. We begin by showing
that the solution need not be an exclusive solution of conformal gravity but
can also be viewed as a solution of a class of $f(R)$ gravity theories coupled
to non-linear electrodynamics thereby rendering the ensuing results more
universal. Since lensing involves light bending, we shall first show that the
solution adds to Schwarzschild light bending caused by the luminous mass
($M_{\ast }$) a positive contribution $+\gamma R$ contrary to the previous
results in the literature, thereby resolving a long standing problem. The cause
of the error is critically examined. Applying the expressions for light bending
together with an input equating Einstein and Weyl angles, we develop a novel
algorithm for separating the luminous component from the total lens mass
(luminous+dark) within the Einstein radius. Our results indicate that the
luminous mass estimates differ from the observed total lens masses by a linear
proportionality factor. In quantitative detail, we observe that the ratios of
luminous over total lens mass ($f^{\ast }$) within the Einstein radius of
individual galaxies take on values near unity, many of which remarkably fall
inside or just marginally outside the specified error bars obtained from a
simulation based on the Bruzual-Charlot stellar population synthesis model
together with the Salpeter IMF favored on the ground of metallicity
[Grillo,2009]. We shall also calculate the average dark matter density of
individual galaxies within their respective Einstein spheres. The present
approach, being truly analytic, seems to be the first of its kind attempting to
provide a new decomposition scheme distinct from the simulational ones.
| [
{
"created": "Thu, 7 Jul 2016 11:18:11 GMT",
"version": "v1"
}
] | 2016-07-08 | [
[
"Potapov",
"Alexander A.",
""
],
[
"Izmailov",
"Ramil N.",
""
],
[
"Nandi",
"Kamal K.",
""
]
] | We study here, using the Mannheim-Kazanas solution of Weyl conformal theory, the mass decomposition in the representative subsample of $57$ early-type elliptical lens galaxies of the SLACS on board the HST. We begin by showing that the solution need not be an exclusive solution of conformal gravity but can also be viewed as a solution of a class of $f(R)$ gravity theories coupled to non-linear electrodynamics thereby rendering the ensuing results more universal. Since lensing involves light bending, we shall first show that the solution adds to Schwarzschild light bending caused by the luminous mass ($M_{\ast }$) a positive contribution $+\gamma R$ contrary to the previous results in the literature, thereby resolving a long standing problem. The cause of the error is critically examined. Applying the expressions for light bending together with an input equating Einstein and Weyl angles, we develop a novel algorithm for separating the luminous component from the total lens mass (luminous+dark) within the Einstein radius. Our results indicate that the luminous mass estimates differ from the observed total lens masses by a linear proportionality factor. In quantitative detail, we observe that the ratios of luminous over total lens mass ($f^{\ast }$) within the Einstein radius of individual galaxies take on values near unity, many of which remarkably fall inside or just marginally outside the specified error bars obtained from a simulation based on the Bruzual-Charlot stellar population synthesis model together with the Salpeter IMF favored on the ground of metallicity [Grillo,2009]. We shall also calculate the average dark matter density of individual galaxies within their respective Einstein spheres. The present approach, being truly analytic, seems to be the first of its kind attempting to provide a new decomposition scheme distinct from the simulational ones. |
gr-qc/0412003 | Chris Van Den Broeck | Abhay Ashtekar, Jonathan Engle and Chris Van Den Broeck | Quantum horizons and black hole entropy: Inclusion of distortion and
rotation | 9 pages | Class.Quant.Grav.22:L27-L34,2005 | 10.1088/0264-9381/22/4/L02 | IGPG 2004-11/9 | gr-qc hep-th | null | Equilibrium states of black holes can be modelled by isolated horizons. If
the intrinsic geometry is spherical, they are called type I while if it is
axi-symmetric, they are called type II. The detailed theory of geometry of
\emph{quantum} type I horizons and the calculation of their entropy can be
generalized to type II, thereby including arbitrary distortions and rotations.
The leading term in entropy of large horizons is again given by 1/4th of the
horizon area for the \emph{same} value of the Barbero-Immirzi parameter as in
the type I case. Ideas and constructions underlying this extension are
summarized.
| [
{
"created": "Wed, 1 Dec 2004 19:38:32 GMT",
"version": "v1"
}
] | 2010-11-05 | [
[
"Ashtekar",
"Abhay",
""
],
[
"Engle",
"Jonathan",
""
],
[
"Broeck",
"Chris Van Den",
""
]
] | Equilibrium states of black holes can be modelled by isolated horizons. If the intrinsic geometry is spherical, they are called type I while if it is axi-symmetric, they are called type II. The detailed theory of geometry of \emph{quantum} type I horizons and the calculation of their entropy can be generalized to type II, thereby including arbitrary distortions and rotations. The leading term in entropy of large horizons is again given by 1/4th of the horizon area for the \emph{same} value of the Barbero-Immirzi parameter as in the type I case. Ideas and constructions underlying this extension are summarized. |
1609.01685 | Jeremy Wachter | Jeremy M. Wachter and Ken D. Olum | Gravitational back reaction on piecewise linear cosmic string loops | 24 pages, 14 figures, updated to version accepted to PRD | Phys. Rev. D 95, 023519 (2017) | 10.1103/PhysRevD.95.023519 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We calculate the metric and affine connection due to a piecewise linear
cosmic string loop, and the effect of gravitational back reaction for the
Garfinkle-Vachaspati loop with four straight segments. As expected, back
reaction reduces the size of the loop, in accord with the energy going into
gravitational waves. The "square" (maximally symmetric) loop evaporates without
changing shape, but for all other loops in this class, the kinks become less
sharp and segments between kinks become curved. If the loop is close to the
square case, it will evaporate before its kinks are significantly changed, if
it is far from square, the opening out of the kinks is much faster than
evaporation of the loop.
| [
{
"created": "Tue, 6 Sep 2016 18:25:22 GMT",
"version": "v1"
},
{
"created": "Tue, 20 Dec 2016 20:38:52 GMT",
"version": "v2"
}
] | 2017-02-08 | [
[
"Wachter",
"Jeremy M.",
""
],
[
"Olum",
"Ken D.",
""
]
] | We calculate the metric and affine connection due to a piecewise linear cosmic string loop, and the effect of gravitational back reaction for the Garfinkle-Vachaspati loop with four straight segments. As expected, back reaction reduces the size of the loop, in accord with the energy going into gravitational waves. The "square" (maximally symmetric) loop evaporates without changing shape, but for all other loops in this class, the kinks become less sharp and segments between kinks become curved. If the loop is close to the square case, it will evaporate before its kinks are significantly changed, if it is far from square, the opening out of the kinks is much faster than evaporation of the loop. |
gr-qc/9902078 | Garcia | L.C.Garcia de Andrade | Vacuumless torsion defects | Latex file (16K),submitted to Phys.Review D | null | null | null | gr-qc | null | Vacuumless defects in space-times with torsion may be obtained from vacuum
defects in spacetimes without torsion.This idea is applied to planar domain
walls and global monopoles.In the case of domain walls exponentially decaying
Higgs type potentials are obtained.In the case of global monopoles torsion
string type singularities are obtained like the string singularities in Dirac
monopoles.
| [
{
"created": "Wed, 24 Feb 1999 17:20:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Andrade",
"L. C. Garcia",
""
]
] | Vacuumless defects in space-times with torsion may be obtained from vacuum defects in spacetimes without torsion.This idea is applied to planar domain walls and global monopoles.In the case of domain walls exponentially decaying Higgs type potentials are obtained.In the case of global monopoles torsion string type singularities are obtained like the string singularities in Dirac monopoles. |
0801.1375 | Francisco Lobo | Christian G. Boehmer, Tiberiu Harko, Francisco S.N. Lobo | Solar system tests of brane world models | 14 pages, to appear in Classical and Quantum Gravity. V2, minor
corrections and references added | Class.Quant.Grav.25:045015,2008 | 10.1088/0264-9381/25/4/045015 | null | gr-qc astro-ph hep-th | null | The classical tests of general relativity (perihelion precession, deflection
of light, and the radar echo delay) are considered for the Dadhich, Maartens,
Papadopoulos and Rezania (DMPR) solution of the spherically symmetric static
vacuum field equations in brane world models. For this solution the metric in
the vacuum exterior to a brane world star is similar to the Reissner-Nordstrom
form of classical general relativity, with the role of the charge played by the
tidal effects arising from projections of the fifth dimension. The existing
observational solar system data on the perihelion shift of Mercury, on the
light bending around the Sun (obtained using long-baseline radio
interferometry), and ranging to Mars using the Viking lander, constrain the
numerical values of the bulk tidal parameter and of the brane tension.
| [
{
"created": "Wed, 9 Jan 2008 09:04:20 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Feb 2008 15:37:24 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Boehmer",
"Christian G.",
""
],
[
"Harko",
"Tiberiu",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] | The classical tests of general relativity (perihelion precession, deflection of light, and the radar echo delay) are considered for the Dadhich, Maartens, Papadopoulos and Rezania (DMPR) solution of the spherically symmetric static vacuum field equations in brane world models. For this solution the metric in the vacuum exterior to a brane world star is similar to the Reissner-Nordstrom form of classical general relativity, with the role of the charge played by the tidal effects arising from projections of the fifth dimension. The existing observational solar system data on the perihelion shift of Mercury, on the light bending around the Sun (obtained using long-baseline radio interferometry), and ranging to Mars using the Viking lander, constrain the numerical values of the bulk tidal parameter and of the brane tension. |
gr-qc/0605136 | Marcello Ortaggio | Jiri Podolsky, Marcello Ortaggio | Robinson-Trautman spacetimes in higher dimensions | 11 pages | Class.Quant.Grav. 23 (2006) 5785-5797 | 10.1088/0264-9381/23/20/002 | null | gr-qc hep-th | null | As an extension of the Robinson-Trautman solutions of D=4 general relativity,
we investigate higher dimensional spacetimes which admit a hypersurface
orthogonal, non-shearing and expanding geodesic null congruence. Einstein's
field equations with an arbitrary cosmological constant and possibly an aligned
pure radiation are fully integrated, so that the complete family is presented
in closed explicit form. As a distinctive feature of higher dimensions, the
transverse spatial part of the general line element must be a Riemannian
Einstein space, but it is otherwise arbitrary. On the other hand, the remaining
part of the metric is - perhaps surprisingly - not so rich as in the standard
D=4 case, and the corresponding Weyl tensor is necessarily of algebraic type D.
While the general family contains (generalized) static
Schwarzschild-Kottler-Tangherlini black holes and extensions of the Vaidya
metric, there is no analogue of important solutions such as the C-metric.
| [
{
"created": "Fri, 26 May 2006 14:15:37 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Podolsky",
"Jiri",
""
],
[
"Ortaggio",
"Marcello",
""
]
] | As an extension of the Robinson-Trautman solutions of D=4 general relativity, we investigate higher dimensional spacetimes which admit a hypersurface orthogonal, non-shearing and expanding geodesic null congruence. Einstein's field equations with an arbitrary cosmological constant and possibly an aligned pure radiation are fully integrated, so that the complete family is presented in closed explicit form. As a distinctive feature of higher dimensions, the transverse spatial part of the general line element must be a Riemannian Einstein space, but it is otherwise arbitrary. On the other hand, the remaining part of the metric is - perhaps surprisingly - not so rich as in the standard D=4 case, and the corresponding Weyl tensor is necessarily of algebraic type D. While the general family contains (generalized) static Schwarzschild-Kottler-Tangherlini black holes and extensions of the Vaidya metric, there is no analogue of important solutions such as the C-metric. |
0708.3410 | Gabriel Bela Nagy | M. Holst, J. Kommemi, G. Nagy | Rough solutions of the Einstein constraint equations with nonconstant
mean curvature | 81 pages, 1 figure, Latex. Submitted for publication. Typos corrected | null | null | null | gr-qc | null | We consider the conformal decomposition of Einstein's constraint equations
introduced by Lichnerowicz and York, on a compact manifold with boundary. We
use order relations on appropriate Banach spaces to derive weak solution
generalizations of known sub- and super-solutions (barriers) for the
Hamiltonian constraint. The barriers are combined with variational methods to
establish existence of solutions to the Hamiltonian constraint in the
intersection of the space of essentially bounded functions and the Sobolev
space H1. The result is established for scalar curvature R of the background
metric having any sign; non-negative R requires additional positivity
assumptions either on the matter energy density or on the trace-free
divergence-free part of the extrinsic curvature. Although the formulation is
different, the result can be viewed as lowering the regularity of the recent
result of Maxwell on rough CMC solutions. We also establish existence of
non-CMC solutions of the Hamiltonian and momentum constraint equations. The
result is obtained using fixed-point iteration and compactness arguments
directly, rather than by building a contraction map. The non-CMC result can be
viewed as a type of extension of the regularity of the 1996 non-CMC result of
Isenberg and Moncrief to lower regularity and to scalar curvature R having any
sign.
| [
{
"created": "Fri, 24 Aug 2007 22:06:12 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Aug 2007 23:45:29 GMT",
"version": "v2"
}
] | 2007-08-28 | [
[
"Holst",
"M.",
""
],
[
"Kommemi",
"J.",
""
],
[
"Nagy",
"G.",
""
]
] | We consider the conformal decomposition of Einstein's constraint equations introduced by Lichnerowicz and York, on a compact manifold with boundary. We use order relations on appropriate Banach spaces to derive weak solution generalizations of known sub- and super-solutions (barriers) for the Hamiltonian constraint. The barriers are combined with variational methods to establish existence of solutions to the Hamiltonian constraint in the intersection of the space of essentially bounded functions and the Sobolev space H1. The result is established for scalar curvature R of the background metric having any sign; non-negative R requires additional positivity assumptions either on the matter energy density or on the trace-free divergence-free part of the extrinsic curvature. Although the formulation is different, the result can be viewed as lowering the regularity of the recent result of Maxwell on rough CMC solutions. We also establish existence of non-CMC solutions of the Hamiltonian and momentum constraint equations. The result is obtained using fixed-point iteration and compactness arguments directly, rather than by building a contraction map. The non-CMC result can be viewed as a type of extension of the regularity of the 1996 non-CMC result of Isenberg and Moncrief to lower regularity and to scalar curvature R having any sign. |
1001.3831 | Remo Garattini | Remo Garattini | Wormholes or Gravastars? | RevTeX 4, 18 pages, 2 Figs | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The one loop effective action in a Schwarzschild background is here used to
compute the Zero Point Energy (ZPE) which is compared to the same one generated
by a gravastar. We find that only when we set up a difference between ZPE in
these different background we can have an indication on which configuration is
favored. Such a ZPE difference represents the Casimir energy. It is shown that
the expression of the ZPE is equivalent to the one computed by means of a
variational approach. To handle with ZPE divergences, we use the zeta function
regularization. A renormalization procedure to remove the infinities together
with a renormalization group equation is introduced. We find that the final
configuration is dependent on the ratio between the radius of the wormhole
augmented by the "brick wall" and the radius of the gravastar.
| [
{
"created": "Thu, 21 Jan 2010 15:57:39 GMT",
"version": "v1"
}
] | 2010-01-22 | [
[
"Garattini",
"Remo",
""
]
] | The one loop effective action in a Schwarzschild background is here used to compute the Zero Point Energy (ZPE) which is compared to the same one generated by a gravastar. We find that only when we set up a difference between ZPE in these different background we can have an indication on which configuration is favored. Such a ZPE difference represents the Casimir energy. It is shown that the expression of the ZPE is equivalent to the one computed by means of a variational approach. To handle with ZPE divergences, we use the zeta function regularization. A renormalization procedure to remove the infinities together with a renormalization group equation is introduced. We find that the final configuration is dependent on the ratio between the radius of the wormhole augmented by the "brick wall" and the radius of the gravastar. |
1812.11122 | Kristina Giesel | Max Joseph Fahn, Kristina Giesel, Michael Kobler | Dynamical Properties of the Mukhanov-Sasaki Hamiltonian in the context
of adiabatic vacua and the Lewis-Riesenfeld invariant | 40 pages, 5 figures, minor changes: slightly rewrote the
introduction, extended the discussion on the infrared modes, corrected typos
and added references | Universe 2019, 5(7), 170 | 10.3390/universe5070170 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the method of the Lewis-Riesenfeld invariant to analyze the dynamical
properties of the Mukhanov-Sasaki Hamiltonian and, following this approach,
investigate whether we can obtain possible candidates for initial states in the
context of inflation considering a quasi-de Sitter spacetime. Our main interest
lies in the question to which extent these already well-established methods at
the classical and quantum level for finitely many degrees of freedom can be
generalized to field theory. As our results show, a straightforward
generalization does in general not lead to a unitary operator on Fock space
that implements the corresponding time-dependent canonical transformation
associated with the Lewis-Riesenfeld invariant. The action of this operator can
be rewritten as a time-dependent Bogoliubov transformation and we show that its
generalization to Fock space has to be chosen appropriately in order that the
Shale-Stinespring condition is not violated, where we also compare our results
to already existing ones in the literature. Furthermore, our analysis relates
the Ermakov differential equation that plays the role of an auxiliary equation,
whose solution is necessary to construct the Lewis-Riesenfeld invariant, as
well as the corresponding time-dependent canonical transformation to the
defining differential equation for adiabatic vacua. Therefore, a given solution
of the Ermakov equation directly yields a full solution to the differential
equation for adiabatic vacua involving no truncation at some adiabatic order.
As a consequence, we can interpret our result obtained here as a kind of
non-squeezed Bunch-Davies mode, where the term non-squeezed refers to a
possible residual squeezing that can be involved in the unitary operator for
certain choices of the Bogoliubov map.
| [
{
"created": "Fri, 28 Dec 2018 17:35:10 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Jan 2019 17:35:44 GMT",
"version": "v2"
},
{
"created": "Fri, 14 Jun 2019 16:55:41 GMT",
"version": "v3"
}
] | 2022-12-05 | [
[
"Fahn",
"Max Joseph",
""
],
[
"Giesel",
"Kristina",
""
],
[
"Kobler",
"Michael",
""
]
] | We use the method of the Lewis-Riesenfeld invariant to analyze the dynamical properties of the Mukhanov-Sasaki Hamiltonian and, following this approach, investigate whether we can obtain possible candidates for initial states in the context of inflation considering a quasi-de Sitter spacetime. Our main interest lies in the question to which extent these already well-established methods at the classical and quantum level for finitely many degrees of freedom can be generalized to field theory. As our results show, a straightforward generalization does in general not lead to a unitary operator on Fock space that implements the corresponding time-dependent canonical transformation associated with the Lewis-Riesenfeld invariant. The action of this operator can be rewritten as a time-dependent Bogoliubov transformation and we show that its generalization to Fock space has to be chosen appropriately in order that the Shale-Stinespring condition is not violated, where we also compare our results to already existing ones in the literature. Furthermore, our analysis relates the Ermakov differential equation that plays the role of an auxiliary equation, whose solution is necessary to construct the Lewis-Riesenfeld invariant, as well as the corresponding time-dependent canonical transformation to the defining differential equation for adiabatic vacua. Therefore, a given solution of the Ermakov equation directly yields a full solution to the differential equation for adiabatic vacua involving no truncation at some adiabatic order. As a consequence, we can interpret our result obtained here as a kind of non-squeezed Bunch-Davies mode, where the term non-squeezed refers to a possible residual squeezing that can be involved in the unitary operator for certain choices of the Bogoliubov map. |
1903.12119 | Sourabh Nampalliwar | Sourabh Nampalliwar, Shuo Xin, Shubham Srivastava, Askar B.
Abdikamalov, Dimitry Ayzenberg, Cosimo Bambi, Thomas Dauser, Javier A.
Garcia, Ashutosh Tripathi | Testing General Relativity with X-ray reflection spectroscopy: The
Konoplya-Rezzolla-Zhidenko parametrization | Minor updates. Published at Phys. Rev. D 102, 124071 (2020) | Phys. Rev. D 102, 124071 (2020) | 10.1103/PhysRevD.102.124071 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | X-ray reflection spectroscopy is a promising technique for testing general
relativity in the strong field regime, as it can be used to test the Kerr black
hole hypothesis. In this context, the parametrically deformed black hole
metrics proposed by Konoplya, Rezzolla \& Zhidenko (Phys. Rev. D93, 064015,
2016) form an important class of non-Kerr black holes. We implement this class
of black hole metrics in \textsc{relxill\_nk}, which is a framework we have
developed for testing for non-Kerr black holes using X-ray reflection
spectroscopy. We perform a qualitative analysis of the effect of the leading
order strong-field deformation parameters on typical observables like the
innermost stable circular orbits and the reflection spectra. We also present
the first X-ray constraints on some of the deformation parameters of this
metric, using \textit{Suzaku} data from the supermassive black hole in Ark~564,
and compare them with those obtained (or expected) from other observational
techniques like gravitational waves and black hole imaging.
| [
{
"created": "Thu, 28 Mar 2019 17:05:47 GMT",
"version": "v1"
},
{
"created": "Sun, 18 Oct 2020 17:26:07 GMT",
"version": "v2"
},
{
"created": "Tue, 12 Jan 2021 11:50:08 GMT",
"version": "v3"
}
] | 2021-01-13 | [
[
"Nampalliwar",
"Sourabh",
""
],
[
"Xin",
"Shuo",
""
],
[
"Srivastava",
"Shubham",
""
],
[
"Abdikamalov",
"Askar B.",
""
],
[
"Ayzenberg",
"Dimitry",
""
],
[
"Bambi",
"Cosimo",
""
],
[
"Dauser",
"Thomas",
""
],
[
"Garcia",
"Javier A.",
""
],
[
"Tripathi",
"Ashutosh",
""
]
] | X-ray reflection spectroscopy is a promising technique for testing general relativity in the strong field regime, as it can be used to test the Kerr black hole hypothesis. In this context, the parametrically deformed black hole metrics proposed by Konoplya, Rezzolla \& Zhidenko (Phys. Rev. D93, 064015, 2016) form an important class of non-Kerr black holes. We implement this class of black hole metrics in \textsc{relxill\_nk}, which is a framework we have developed for testing for non-Kerr black holes using X-ray reflection spectroscopy. We perform a qualitative analysis of the effect of the leading order strong-field deformation parameters on typical observables like the innermost stable circular orbits and the reflection spectra. We also present the first X-ray constraints on some of the deformation parameters of this metric, using \textit{Suzaku} data from the supermassive black hole in Ark~564, and compare them with those obtained (or expected) from other observational techniques like gravitational waves and black hole imaging. |
gr-qc/9909040 | Sharmanthie Fernando | Sharmanthie Fernando | Spinning Charged Solutions in 2+1 Dimensional Einstein-Maxwell-Dilaton
Gravity | 10 pages, LaTeX | Phys.Lett. B468 (1999) 201-207 | 10.1016/S0370-2693(99)01245-9 | UCTP116.99 | gr-qc hep-th | null | We report a new class of rotating charged solutions in 2+1 dimensions. These
solutions are obtained for Einstein-Maxwell gravity coupled to a dilaton field
with selfdual electromagnetic fields. The mass and the angular momentum of
these solutions computed at spatial infinity are finite. The class of solutions
considered here have naked singularities and are asymptotically flat.
| [
{
"created": "Tue, 14 Sep 1999 00:31:48 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Fernando",
"Sharmanthie",
""
]
] | We report a new class of rotating charged solutions in 2+1 dimensions. These solutions are obtained for Einstein-Maxwell gravity coupled to a dilaton field with selfdual electromagnetic fields. The mass and the angular momentum of these solutions computed at spatial infinity are finite. The class of solutions considered here have naked singularities and are asymptotically flat. |
1608.07090 | Shibei Kong | Chao-Guang Huang, Shibei Kong | Hamiltonian Analysis of 3-Dimensional Connection Dynamics in Bondi-like
Coordinates | null | Commun. Theor. Phys. 68 (2017) 227 | 10.1088/0253-6102/68/2/227 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hamiltonian analysis for a 3-dimensional connection dynamics of
$\frak{so}(1,2)$, spanned by $\{L_{-+},L_{-2},L_{+2}\}$ instead of $\{L_{01},
L_{02}, L_{12}\}$, is first conducted in a Bondi-like coordinate system.The
symmetry of the system is clearly presented. A null coframe with 3 independent
variables and 9 connection coefficients are treated as basic configuration
variables. All constraints and their consistency conditions, the solutions of
Lagrange multipliers as well as the equations of motion are presented. There is
no physical degree of freedom in the system. The Ba\~nados-Teitelboim-Zanelli
(BTZ) spacetime is discussed as an example to check the analysis. Unlike the
ADM formalism, where only non-degenerate geometries on slices are dealt with
and the Ashtekar formalism, where non-degenerate geometries on slices are
mainly concerned though the degenerate geometries may be studied as well, in
the present formalism the geometries on the slices are always degenerate though
the geometries for the spacetime are not degenerate.
| [
{
"created": "Thu, 25 Aug 2016 11:35:50 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Feb 2017 02:43:46 GMT",
"version": "v2"
},
{
"created": "Wed, 18 Jul 2018 10:14:43 GMT",
"version": "v3"
}
] | 2018-07-19 | [
[
"Huang",
"Chao-Guang",
""
],
[
"Kong",
"Shibei",
""
]
] | The Hamiltonian analysis for a 3-dimensional connection dynamics of $\frak{so}(1,2)$, spanned by $\{L_{-+},L_{-2},L_{+2}\}$ instead of $\{L_{01}, L_{02}, L_{12}\}$, is first conducted in a Bondi-like coordinate system.The symmetry of the system is clearly presented. A null coframe with 3 independent variables and 9 connection coefficients are treated as basic configuration variables. All constraints and their consistency conditions, the solutions of Lagrange multipliers as well as the equations of motion are presented. There is no physical degree of freedom in the system. The Ba\~nados-Teitelboim-Zanelli (BTZ) spacetime is discussed as an example to check the analysis. Unlike the ADM formalism, where only non-degenerate geometries on slices are dealt with and the Ashtekar formalism, where non-degenerate geometries on slices are mainly concerned though the degenerate geometries may be studied as well, in the present formalism the geometries on the slices are always degenerate though the geometries for the spacetime are not degenerate. |
2212.07323 | Lorenzo Iorio | Lorenzo Iorio | Might the 2PN perihelion precession of Mercury become measurable in the
next future? | LaTex2e, 13 pages, 1 figure, no tables. Accepted for publication in
Universe | Universe 2023, 9(1), 37 | 10.3390/universe9010037 | null | gr-qc astro-ph.EP physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Hermean average perihelion rate $\dot\omega^\mathrm{2PN}$, calculated to
the second post-Newtonian (2PN) order with the Gauss perturbing equations and
the osculating Keplerian orbital elements, ranges from $-18$ to $-4$
microarcseconds per century $\left(\mu\mathrm{as\,cty}^{-1}\right)$, depending
on the true anomaly at epoch $f_0$. It is the sum of four contributions: one of
them is the direct consequence of the 2PN acceleration entering the equations
of motion, while the other three are indirect effects of the 1PN component of
the Sun's gravitational field. An evaluation of the merely formal uncertainty
of the experimental Mercury's perihelion rate $\dot\omega_\mathrm{exp}$
recently published by the present author, based on 51 years of radiotechnical
data processed with the EPM2017 planetary ephemerides by the astronomers E.V.
Pitjeva and N.P. Pitjev, is $\sigma_{\dot\omega_\mathrm{exp}}\simeq
8\,\mu\mathrm{as\,cty}^{-1}$, corresponding to a relative accuracy of $2\times
10^{-7}$ for the combination $\left(2 + 2\gamma - \beta\right)/3$ of the PPN
parameters $\beta$ and $\gamma$ scaling the well known 1PN perihelion
precession. In fact, the realistic uncertainty may be up to $\simeq 10-50$
times larger, despite reprocessing the now available raw data of the former
MESSENGER mission with a recent improved solar corona model should ameliorate
our knowledge of the Hermean orbit. The BepiColombo spacecraft, currently en
route to Mercury, might reach a $\simeq 10^{-7}$ accuracy level in constraining
$\beta$ and $\gamma$ in an extended mission, despite $\simeq 10^{-6}$ seems
more likely according to most of the simulations currently available in the
literature. Thus, it might be that in the not too distant future it will be
necessary to include the 2PN acceleration in the Solar System's dynamics as
well.
| [
{
"created": "Wed, 14 Dec 2022 16:40:41 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Jan 2023 01:37:01 GMT",
"version": "v2"
}
] | 2023-01-05 | [
[
"Iorio",
"Lorenzo",
""
]
] | The Hermean average perihelion rate $\dot\omega^\mathrm{2PN}$, calculated to the second post-Newtonian (2PN) order with the Gauss perturbing equations and the osculating Keplerian orbital elements, ranges from $-18$ to $-4$ microarcseconds per century $\left(\mu\mathrm{as\,cty}^{-1}\right)$, depending on the true anomaly at epoch $f_0$. It is the sum of four contributions: one of them is the direct consequence of the 2PN acceleration entering the equations of motion, while the other three are indirect effects of the 1PN component of the Sun's gravitational field. An evaluation of the merely formal uncertainty of the experimental Mercury's perihelion rate $\dot\omega_\mathrm{exp}$ recently published by the present author, based on 51 years of radiotechnical data processed with the EPM2017 planetary ephemerides by the astronomers E.V. Pitjeva and N.P. Pitjev, is $\sigma_{\dot\omega_\mathrm{exp}}\simeq 8\,\mu\mathrm{as\,cty}^{-1}$, corresponding to a relative accuracy of $2\times 10^{-7}$ for the combination $\left(2 + 2\gamma - \beta\right)/3$ of the PPN parameters $\beta$ and $\gamma$ scaling the well known 1PN perihelion precession. In fact, the realistic uncertainty may be up to $\simeq 10-50$ times larger, despite reprocessing the now available raw data of the former MESSENGER mission with a recent improved solar corona model should ameliorate our knowledge of the Hermean orbit. The BepiColombo spacecraft, currently en route to Mercury, might reach a $\simeq 10^{-7}$ accuracy level in constraining $\beta$ and $\gamma$ in an extended mission, despite $\simeq 10^{-6}$ seems more likely according to most of the simulations currently available in the literature. Thus, it might be that in the not too distant future it will be necessary to include the 2PN acceleration in the Solar System's dynamics as well. |
0809.2659 | Stefan Hollands | Stefan Hollands and Akihiro Ishibashi | On the `Stationary Implies Axisymmetric' Theorem for Extremal Black
Holes in Higher Dimensions | 30pp, Latex, no figures | Commun.Math.Phys.291:403-441,2009 | 10.1007/s00220-009-0841-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | All known stationary black hole solutions in higher dimensions possess
additional rotational symmetries in addition to the stationary Killing field.
Also, for all known stationary solutions, the event horizon is a Killing
horizon, and the surface gravity is constant. In the case of non-degenerate
horizons (non-extremal black holes), a general theorem was previously
established [gr-qc/0605106] proving that these statements are in fact generally
true under the assumption that the spacetime is analytic, and that the metric
satisfies Einstein's equation. Here, we extend the analysis to the case of
degenerate (extremal) black holes. It is shown that the theorem still holds
true if the vector of angular velocities of the horizon satisfies a certain
"diophantine condition," which holds except for a set of measure zero.
| [
{
"created": "Tue, 16 Sep 2008 08:27:10 GMT",
"version": "v1"
}
] | 2009-08-18 | [
[
"Hollands",
"Stefan",
""
],
[
"Ishibashi",
"Akihiro",
""
]
] | All known stationary black hole solutions in higher dimensions possess additional rotational symmetries in addition to the stationary Killing field. Also, for all known stationary solutions, the event horizon is a Killing horizon, and the surface gravity is constant. In the case of non-degenerate horizons (non-extremal black holes), a general theorem was previously established [gr-qc/0605106] proving that these statements are in fact generally true under the assumption that the spacetime is analytic, and that the metric satisfies Einstein's equation. Here, we extend the analysis to the case of degenerate (extremal) black holes. It is shown that the theorem still holds true if the vector of angular velocities of the horizon satisfies a certain "diophantine condition," which holds except for a set of measure zero. |
1003.5215 | Jane MacGibbon | Jane H. MacGibbon | Generalized Second Law Limits on the Variation of Fundamental Constants | Twelfth Marcel Grossmann Meeting, Paris 12 - 18 July 2009; 4 pages | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The theoretical maximum time variation in the electronic charge permitted by
the Generalized Second Law of Thermodynamics applied to black holes radiating
and accreting in the cosmic microwave background matches the measured
cosmological variation in the fine structure constant claimed by Webb et al..
Such black holes cannot respond adiabatically to a varying fine structure
constant.
| [
{
"created": "Fri, 26 Mar 2010 20:00:05 GMT",
"version": "v1"
}
] | 2010-04-02 | [
[
"MacGibbon",
"Jane H.",
""
]
] | The theoretical maximum time variation in the electronic charge permitted by the Generalized Second Law of Thermodynamics applied to black holes radiating and accreting in the cosmic microwave background matches the measured cosmological variation in the fine structure constant claimed by Webb et al.. Such black holes cannot respond adiabatically to a varying fine structure constant. |
1806.08823 | Sumanta Chakraborty | Sumanta Chakraborty and Krishnamohan Parattu | Null boundary terms for Lanczos-Lovelock gravity | Editor's Choice; Published Version; 42 pages; For v4, affiliations
corrected; Erratum added for the same in the journal version | Gen. Rel. Grav. 51, 23 (2019) | 10.1007/s10714-019-2502-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive boundary terms appropriate for the general Lanczos-Lovelock action
on a null boundary, when Dirichlet boundary conditions are imposed. We believe
that these boundary terms have been derived for the first time in the
literature. In this derivation, we rely only on the structure of the boundary
variation of the action for Lanczos-Lovelock gravity. We also provide the null
boundary term for Gauss-Bonnet gravity separately.
| [
{
"created": "Fri, 22 Jun 2018 19:04:11 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Sep 2018 00:15:58 GMT",
"version": "v2"
},
{
"created": "Wed, 6 Feb 2019 00:29:14 GMT",
"version": "v3"
},
{
"created": "Tue, 26 Mar 2019 08:52:11 GMT",
"version": "v4"
}
] | 2019-03-27 | [
[
"Chakraborty",
"Sumanta",
""
],
[
"Parattu",
"Krishnamohan",
""
]
] | We derive boundary terms appropriate for the general Lanczos-Lovelock action on a null boundary, when Dirichlet boundary conditions are imposed. We believe that these boundary terms have been derived for the first time in the literature. In this derivation, we rely only on the structure of the boundary variation of the action for Lanczos-Lovelock gravity. We also provide the null boundary term for Gauss-Bonnet gravity separately. |
gr-qc/0701164 | Yosef Zlochower | Manuela Campanelli, Carlos O. Lousto, Yosef Zlochower, David Merritt | Large Merger Recoils and Spin Flips From Generic Black-Hole Binaries | 4 pages. Accepted for publication in ApJL | Astrophys.J.659:L5-L8,2007 | 10.1086/516712 | null | gr-qc astro-ph | null | We report the first results from evolutions of a generic black-hole binary,
i.e. a binary containing unequal mass black holes with misaligned spins. Our
configuration, which has a mass ratio of 2:1, consists of an initially
non-spinning hole orbiting a larger, rapidly spinning hole (specific spin a/m =
0.885), with the spin direction oriented -45 degrees with respect to the
orbital plane. We track the inspiral and merger for ~2 orbits and find that the
remnant receives a substantial kick of 454 km/s, more than twice as large as
the maximum kick from non-spinning binaries. The remnant spin direction is
flipped by 103 degrees with respect to the initial spin direction of the larger
hole. We performed a second run with anti-aligned spins, a/m = +-0.5 lying in
the orbital plane that produces a kick of 1830 km/s off the orbital plane. This
value scales to nearly 4000 km/s for maximally spinning holes. Such a large
recoil velocity opens the possibility that a merged binary can be ejected even
from the nucleus of a massive host galaxy.
| [
{
"created": "Mon, 29 Jan 2007 20:50:10 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Feb 2007 16:35:11 GMT",
"version": "v2"
},
{
"created": "Fri, 2 Mar 2007 15:14:55 GMT",
"version": "v3"
}
] | 2009-11-13 | [
[
"Campanelli",
"Manuela",
""
],
[
"Lousto",
"Carlos O.",
""
],
[
"Zlochower",
"Yosef",
""
],
[
"Merritt",
"David",
""
]
] | We report the first results from evolutions of a generic black-hole binary, i.e. a binary containing unequal mass black holes with misaligned spins. Our configuration, which has a mass ratio of 2:1, consists of an initially non-spinning hole orbiting a larger, rapidly spinning hole (specific spin a/m = 0.885), with the spin direction oriented -45 degrees with respect to the orbital plane. We track the inspiral and merger for ~2 orbits and find that the remnant receives a substantial kick of 454 km/s, more than twice as large as the maximum kick from non-spinning binaries. The remnant spin direction is flipped by 103 degrees with respect to the initial spin direction of the larger hole. We performed a second run with anti-aligned spins, a/m = +-0.5 lying in the orbital plane that produces a kick of 1830 km/s off the orbital plane. This value scales to nearly 4000 km/s for maximally spinning holes. Such a large recoil velocity opens the possibility that a merged binary can be ejected even from the nucleus of a massive host galaxy. |
2204.11616 | Rituparna Mandal | Rituparna Mandal and Sunandan Gangopadhyay | Black hole thermodynamics in asymptotically safe gravity | 18 pages, 9 figures, comments are welcome | null | 10.1007/s10714-022-03045-9 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We have investigated the black hole thermodynamics and the phase transition
for renormalized group improved asymptotically safe Schwarzschild black hole.
This geometry takes into account the quantum gravitational correction in the
running gravitational constant identifying $G(r) \equiv G(k=k(r))$. We studied
various thermodynamic quantity like the Hawking temperature, specific heat and
entropy for the general parameter $\gamma$ for quantum corrected Schwarzschild
metric. We have noticed that the coefficient of the leading quantum correction,
that is, the logarithmic correction gets affected by the presence of $\gamma$.
We further study the local temperature, thermal stability of the black hole and
the free energy considering a cavity enclosing the black hole. According to the
local specific heat, there exists three black hole states, among them the large
and tiny black hole are thermally stable states. We further investigate the
on-shell free energy and find that no Hawking-Page phase transition occurs here
unlike the ordinary Schwarzschild black hole. The black hole state always
prevails for all temperatures. Also, we have found two critical points,
$T_{c1}$ and $T_{c2}$, corresponding to the phase transition from one black
hole state to another.
| [
{
"created": "Fri, 22 Apr 2022 09:40:21 GMT",
"version": "v1"
}
] | 2022-12-21 | [
[
"Mandal",
"Rituparna",
""
],
[
"Gangopadhyay",
"Sunandan",
""
]
] | We have investigated the black hole thermodynamics and the phase transition for renormalized group improved asymptotically safe Schwarzschild black hole. This geometry takes into account the quantum gravitational correction in the running gravitational constant identifying $G(r) \equiv G(k=k(r))$. We studied various thermodynamic quantity like the Hawking temperature, specific heat and entropy for the general parameter $\gamma$ for quantum corrected Schwarzschild metric. We have noticed that the coefficient of the leading quantum correction, that is, the logarithmic correction gets affected by the presence of $\gamma$. We further study the local temperature, thermal stability of the black hole and the free energy considering a cavity enclosing the black hole. According to the local specific heat, there exists three black hole states, among them the large and tiny black hole are thermally stable states. We further investigate the on-shell free energy and find that no Hawking-Page phase transition occurs here unlike the ordinary Schwarzschild black hole. The black hole state always prevails for all temperatures. Also, we have found two critical points, $T_{c1}$ and $T_{c2}$, corresponding to the phase transition from one black hole state to another. |
0812.1981 | Franco Fiorini | Rafael Ferraro and Franco Fiorini | On Born-Infeld Gravity in Weitzenbock spacetime | 8 pages, 1 figure. Accepted for publication in Phys. Rev. D | Phys.Rev.D78:124019,2008 | 10.1103/PhysRevD.78.124019 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the Teleparallel Equivalent of General Relativity formulated in
Weitzenb\"{o}ck spacetime, we thoroughly explore a kind of Born-Infeld regular
gravity leading to second order field equations for the vielbein components. We
explicitly solve the equations of motion for two examples: the extended BTZ
black hole, which results to exist even if the cosmological constant is
positive, and a cosmological model with matter, where the scale factor results
to be well behaved, giving so a singularity-free solution.
| [
{
"created": "Wed, 10 Dec 2008 17:37:22 GMT",
"version": "v1"
}
] | 2009-01-08 | [
[
"Ferraro",
"Rafael",
""
],
[
"Fiorini",
"Franco",
""
]
] | Using the Teleparallel Equivalent of General Relativity formulated in Weitzenb\"{o}ck spacetime, we thoroughly explore a kind of Born-Infeld regular gravity leading to second order field equations for the vielbein components. We explicitly solve the equations of motion for two examples: the extended BTZ black hole, which results to exist even if the cosmological constant is positive, and a cosmological model with matter, where the scale factor results to be well behaved, giving so a singularity-free solution. |
0811.1129 | Iver Brevik | I. Brevik and O. Gorbunova | A Brief Review of the Singularities in 4D and 5D Viscous Cosmologies
Near the Future Singularity | 11 pages latex, no figures. Contribution to the anniversary volume
"The Problems of Modern Cosmology", on the occasion of the 50th birthday of
Prof. S. D. Odintsov. Editor: Prof. P. M. Lavrov, Tomsk State Pedagogical
University | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Analytic properties of physical quantities in the cosmic fluid such as energy
density \rho(t) and Hubble parameter H(t) are investigated near the future
singularity (Big Rip). Both 4D and 5D cosmologies are considered (the
Randall-Sundrum II model in the 5D case), and the fluid is assumed to possess a
bulk viscosity \zeta. We consider both Einstein gravity and modified gravity,
where in the latter case the Lagrangian contains a term R^\alpha with \alpha a
constant. If \zeta is proportional to the power (2\alpha-1) of the scalar
expansion, the fluid can pass from the quintessence region into the phantom
region as a consequence of the viscosity. A property worth noticing is that the
4D singularity on the brane becomes carried over to the bulk region.
| [
{
"created": "Fri, 7 Nov 2008 12:15:07 GMT",
"version": "v1"
}
] | 2008-11-10 | [
[
"Brevik",
"I.",
""
],
[
"Gorbunova",
"O.",
""
]
] | Analytic properties of physical quantities in the cosmic fluid such as energy density \rho(t) and Hubble parameter H(t) are investigated near the future singularity (Big Rip). Both 4D and 5D cosmologies are considered (the Randall-Sundrum II model in the 5D case), and the fluid is assumed to possess a bulk viscosity \zeta. We consider both Einstein gravity and modified gravity, where in the latter case the Lagrangian contains a term R^\alpha with \alpha a constant. If \zeta is proportional to the power (2\alpha-1) of the scalar expansion, the fluid can pass from the quintessence region into the phantom region as a consequence of the viscosity. A property worth noticing is that the 4D singularity on the brane becomes carried over to the bulk region. |
1410.2765 | Xavier Calmet | Xavier Calmet and Matthias Keller | Cosmological Evolution of Fundamental Constants: From Theory to
Experiment | Invited paper to the Special Issue: "Fundamental Constants in Physics
and Their Time Variation" (Modern Physics Letters A, Guest Ed. Joan Sol\`a) | Mod. Phys. Lett. A, Vol. 30, No. 22 (2015) 154002822 | 10.1142/S0217732315400283 | null | gr-qc astro-ph.CO physics.atom-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we discuss a possible cosmological time evolution of
fundamental constants from the theoretical and experimental point of views. On
the theoretical side, we explain that such a cosmological time evolution is
actually something very natural which can be described by mechanisms similar to
those used to explain cosmic inflation. We then discuss implications for grand
unified theories, showing that the unification condition of the gauge coupling
could evolve with cosmological time. Measurements of the electron-to-proton
mass ratio can test grand unified theories using low energy data. Following the
theoretical discussion, we review the current status of precision measurements
of fundamental constants and their potential cosmological time dependence.
| [
{
"created": "Fri, 10 Oct 2014 12:38:04 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Dec 2014 08:42:39 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Calmet",
"Xavier",
""
],
[
"Keller",
"Matthias",
""
]
] | In this paper we discuss a possible cosmological time evolution of fundamental constants from the theoretical and experimental point of views. On the theoretical side, we explain that such a cosmological time evolution is actually something very natural which can be described by mechanisms similar to those used to explain cosmic inflation. We then discuss implications for grand unified theories, showing that the unification condition of the gauge coupling could evolve with cosmological time. Measurements of the electron-to-proton mass ratio can test grand unified theories using low energy data. Following the theoretical discussion, we review the current status of precision measurements of fundamental constants and their potential cosmological time dependence. |
1707.08442 | Binaya Bishi Kumar | G. P. Singh, Binaya K. Bishi | Bulk viscous cosmological model in Brans Dicke theory with new form of
time varying deceleration parameter | 16 pages, 24 figures, Accepted in Advances in high energy physics,
2017 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this article we have presented FRW cosmological model in the framework of
Brans-Dicke theory. This paper deals with a new proposed form of deceleration
parameter and cosmological constant. The effect of bulk viscosity is also
studied in the presence of modified Chaplygin gas equation of state. Further,
we have discussed the physical behaviors of the models.
| [
{
"created": "Tue, 25 Jul 2017 15:05:18 GMT",
"version": "v1"
}
] | 2017-07-27 | [
[
"Singh",
"G. P.",
""
],
[
"Bishi",
"Binaya K.",
""
]
] | In this article we have presented FRW cosmological model in the framework of Brans-Dicke theory. This paper deals with a new proposed form of deceleration parameter and cosmological constant. The effect of bulk viscosity is also studied in the presence of modified Chaplygin gas equation of state. Further, we have discussed the physical behaviors of the models. |
1803.04106 | Jessica Santiago | Jessica Santiago (Victoria University of Wellington) and Matt Visser
(Victoria University of Wellington) | Tolman temperature gradients in a gravitational field | 9 pages | European Journal of Physics 40 #2 (2019) 025604 | 10.1088/1361-6404/aaff1c | null | gr-qc cond-mat.stat-mech | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Tolman's relation for the temperature gradient in an equilibrium
self-gravitating general relativistic fluid is broadly accepted within the
general relativity community. However, the concept of temperature gradients in
thermal equilibrium continues to cause confusion in other branches of physics,
since it contradicts naive versions of the laws of classical thermodynamics. In
this paper we discuss the crucial role of the universality of free fall, and
how thermodynamics emphasises the great distinction between gravity and other
forces. To do so we will present an argument given by Maxwell and apply it to
an electro-thermal system, concluding with an reductio ad absurdum. Among other
issues we shall show that Tolman temperature gradients could also (in
principle) have been derived circa 1905 - a decade before the development of
full general relativity.
| [
{
"created": "Mon, 12 Mar 2018 03:38:18 GMT",
"version": "v1"
}
] | 2019-03-01 | [
[
"Santiago",
"Jessica",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | Tolman's relation for the temperature gradient in an equilibrium self-gravitating general relativistic fluid is broadly accepted within the general relativity community. However, the concept of temperature gradients in thermal equilibrium continues to cause confusion in other branches of physics, since it contradicts naive versions of the laws of classical thermodynamics. In this paper we discuss the crucial role of the universality of free fall, and how thermodynamics emphasises the great distinction between gravity and other forces. To do so we will present an argument given by Maxwell and apply it to an electro-thermal system, concluding with an reductio ad absurdum. Among other issues we shall show that Tolman temperature gradients could also (in principle) have been derived circa 1905 - a decade before the development of full general relativity. |
gr-qc/9308024 | Rainer Mueller | Claus Kiefer, Rainer Mueller, and Tejinder P. Singh | Quantum Gravity and Non-unitarity in Black Hole Evaporation | 6 pages, Latex, ZU-TH 25/93 | Mod.Phys.Lett.A9:2661-2670,1994 | 10.1142/S0217732394002501 | null | gr-qc hep-th | null | We discuss the relevance of quantum gravitational corrections to the
functional Schr\"odinger equation for the information loss paradox in black
hole evaporation. These corrections are found from the Wheeler-DeWitt equation
through a semiclassical expansion scheme. The dominant contribution in the
final evaporation stage, when the black hole approaches the Planck regime, is a
term which explicitly violates unitarity in the non-gravitational sector. While
pure states remain pure, there is an increase in the degree of purity for
non-pure states in this sector. This result holds irrespective of whether full
quantum gravity respects unitarity or not.
| [
{
"created": "Mon, 23 Aug 1993 11:47:19 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Kiefer",
"Claus",
""
],
[
"Mueller",
"Rainer",
""
],
[
"Singh",
"Tejinder P.",
""
]
] | We discuss the relevance of quantum gravitational corrections to the functional Schr\"odinger equation for the information loss paradox in black hole evaporation. These corrections are found from the Wheeler-DeWitt equation through a semiclassical expansion scheme. The dominant contribution in the final evaporation stage, when the black hole approaches the Planck regime, is a term which explicitly violates unitarity in the non-gravitational sector. While pure states remain pure, there is an increase in the degree of purity for non-pure states in this sector. This result holds irrespective of whether full quantum gravity respects unitarity or not. |
1208.5327 | Kaushik Bhattacharya | Prashant Kumar, Kaushik Bhattacharya, Tapobrata Sarkar | Geodesic flows and their deformations in Bertrand spacetimes | 3 pages, 2 figures, Latex file. This is a talk given in the 13th
Marcel Grossmann meeting held in Stockholm university from 1st-7th July 2012.
The new submission is a shortened version of the previous version | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by-nc-sa/3.0/ | In this article we will discuss some features of a particular spacetime
called Bertrand space-time of Type II (BST-II). The talk discusses about the
energy conditions and the ESR parameters in this spacetime.
| [
{
"created": "Mon, 27 Aug 2012 08:33:26 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Nov 2012 13:10:37 GMT",
"version": "v2"
}
] | 2012-11-22 | [
[
"Kumar",
"Prashant",
""
],
[
"Bhattacharya",
"Kaushik",
""
],
[
"Sarkar",
"Tapobrata",
""
]
] | In this article we will discuss some features of a particular spacetime called Bertrand space-time of Type II (BST-II). The talk discusses about the energy conditions and the ESR parameters in this spacetime. |
2102.12515 | S. N Sajadi | B. Bahrami Asl, S. H. Hendi and S. N. Sajadi | Complexity Conjecture of Regular Electric Black Holes | 26 pages, 13 figures | null | 10.1103/PhysRevD.104.104034 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Recently, the action growth rate of a variety of four-dimensional regular
magnetic black holes in F frame is obtained in [1]. Here, we study the action
growth rate of a four-dimensional regular electric black hole in P frame that
is the Legendre transformation of F frame. We also investigate the action
growth rates of the Wheeler-De Witt patch for such black hole configurations at
the late time and examine the Lloyd bound on the rate of quantum computation.
We show that although the form of the Lloyd bound formula remains unaltered,
the energy modifies due to a non-vanishing trace of the energy-momentum tensor
and some extra terms may appear in the total growth action. We also investigate
the asymptotic behavior of complexity in two conjectures for static and
rotating regular black holes.
| [
{
"created": "Wed, 24 Feb 2021 19:14:04 GMT",
"version": "v1"
}
] | 2021-11-24 | [
[
"Asl",
"B. Bahrami",
""
],
[
"Hendi",
"S. H.",
""
],
[
"Sajadi",
"S. N.",
""
]
] | Recently, the action growth rate of a variety of four-dimensional regular magnetic black holes in F frame is obtained in [1]. Here, we study the action growth rate of a four-dimensional regular electric black hole in P frame that is the Legendre transformation of F frame. We also investigate the action growth rates of the Wheeler-De Witt patch for such black hole configurations at the late time and examine the Lloyd bound on the rate of quantum computation. We show that although the form of the Lloyd bound formula remains unaltered, the energy modifies due to a non-vanishing trace of the energy-momentum tensor and some extra terms may appear in the total growth action. We also investigate the asymptotic behavior of complexity in two conjectures for static and rotating regular black holes. |
gr-qc/9705058 | Luigi Mangiarotti | G.Giachetta, L.Mangiarotti, G.Sardanashvily | Universal Spin Structure in Gauge Gravitation Theory | 39 pages, LaTex | null | null | null | gr-qc dg-ga hep-th math.DG | null | Building on the universal covering group of the general linear group, we
introduce the composite spinor bundle whose subbundles are Lorentz spin
structures associated with different gravitational fields. General covariant
transformations of this composite spinor bundle are canonically defined.
| [
{
"created": "Wed, 21 May 1997 19:53:25 GMT",
"version": "v1"
}
] | 2008-02-03 | [
[
"Giachetta",
"G.",
""
],
[
"Mangiarotti",
"L.",
""
],
[
"Sardanashvily",
"G.",
""
]
] | Building on the universal covering group of the general linear group, we introduce the composite spinor bundle whose subbundles are Lorentz spin structures associated with different gravitational fields. General covariant transformations of this composite spinor bundle are canonically defined. |
gr-qc/0206037 | Thomas Thiemann | Thomas Thiemann | Complexifier Coherent States for Quantum General Relativity | Latex, 54 p., no figures | Class.Quant.Grav. 23 (2006) 2063-2118 | 10.1088/0264-9381/23/6/013 | AEI-2002-045 | gr-qc hep-th math-ph math.MP quant-ph | null | Recently, substantial amount of activity in Quantum General Relativity (QGR)
has focussed on the semiclassical analysis of the theory. In this paper we want
to comment on two such developments: 1) Polymer-like states for Maxwell theory
and linearized gravity constructed by Varadarajan which use much of the Hilbert
space machinery that has proved useful in QGR and 2) coherent states for QGR,
based on the general complexifier method, with built-in semiclassical
properties. We show the following: A) Varadarajan's states {\it are}
complexifier coherent states. This unifies all states constructed so far under
the general complexifier principle. B) Ashtekar and Lewandowski suggested a
non-Abelean generalization of Varadarajan's states to QGR which, however, are
no longer of the complexifier type. We construct a new class of non-Abelean
complexifiers which come close to the one underlying Varadarajan's
construction. C) Non-Abelean complexifiers close to Varadarajan's induce new
types of Hilbert spaces which do not support the operator algebra of QGR. The
analysis suggests that if one sticks to the present kinematical framework of
QGR and if kinematical coherent states are at all useful, then normalizable,
graph dependent states must be used which are produced by the complexifier
method as well. D) Present proposals for states with mildened graph dependence,
obtained by performing a graph average, do not approximate well coordinate
dependent observables. However, graph dependent states, whether averaged or
not, seem to be well suited for the semiclassical analysis of QGR with respect
to coordinate independent operators.
| [
{
"created": "Thu, 13 Jun 2002 11:19:34 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Thiemann",
"Thomas",
""
]
] | Recently, substantial amount of activity in Quantum General Relativity (QGR) has focussed on the semiclassical analysis of the theory. In this paper we want to comment on two such developments: 1) Polymer-like states for Maxwell theory and linearized gravity constructed by Varadarajan which use much of the Hilbert space machinery that has proved useful in QGR and 2) coherent states for QGR, based on the general complexifier method, with built-in semiclassical properties. We show the following: A) Varadarajan's states {\it are} complexifier coherent states. This unifies all states constructed so far under the general complexifier principle. B) Ashtekar and Lewandowski suggested a non-Abelean generalization of Varadarajan's states to QGR which, however, are no longer of the complexifier type. We construct a new class of non-Abelean complexifiers which come close to the one underlying Varadarajan's construction. C) Non-Abelean complexifiers close to Varadarajan's induce new types of Hilbert spaces which do not support the operator algebra of QGR. The analysis suggests that if one sticks to the present kinematical framework of QGR and if kinematical coherent states are at all useful, then normalizable, graph dependent states must be used which are produced by the complexifier method as well. D) Present proposals for states with mildened graph dependence, obtained by performing a graph average, do not approximate well coordinate dependent observables. However, graph dependent states, whether averaged or not, seem to be well suited for the semiclassical analysis of QGR with respect to coordinate independent operators. |
gr-qc/9611008 | Robert Mann | R.B. Mann and T. Ohta | Exact Solution for the Metric and the Motion of Two Bodies in (1+1)
Dimensional Gravity | 34 pages, LaTeX, 16 figures | Phys.Rev. D55 (1997) 4723-4747 | 10.1103/PhysRevD.55.4723 | WATPHYS TH-96/16 | gr-qc | null | We present the exact solution of two-body motion in (1+1) dimensional dilaton
gravity by solving the constraint equations in the canonical formalism. The
determining equation of the Hamiltonian is derived in a transcendental form and
the Hamiltonian is expressed for the system of two identical particles in terms
of the Lambert $W$ function. The $W$ function has two real branches which join
smoothly onto each other and the Hamiltonian on the principal branch reduces to
the Newtonian limit for small coupling constant. On the other branch the
Hamiltonian yields a new set of motions which can not be understood as
relativistically correcting the Newtonian motion. The explicit trajectory in
the phase space $(r, p)$ is illustrated for various values of the energy. The
analysis is extended to the case of unequal masses. The full expression of
metric tensor is given and the consistency between the solution of the metric
and the equations of motion is rigorously proved.
| [
{
"created": "Mon, 4 Nov 1996 21:27:36 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Mann",
"R. B.",
""
],
[
"Ohta",
"T.",
""
]
] | We present the exact solution of two-body motion in (1+1) dimensional dilaton gravity by solving the constraint equations in the canonical formalism. The determining equation of the Hamiltonian is derived in a transcendental form and the Hamiltonian is expressed for the system of two identical particles in terms of the Lambert $W$ function. The $W$ function has two real branches which join smoothly onto each other and the Hamiltonian on the principal branch reduces to the Newtonian limit for small coupling constant. On the other branch the Hamiltonian yields a new set of motions which can not be understood as relativistically correcting the Newtonian motion. The explicit trajectory in the phase space $(r, p)$ is illustrated for various values of the energy. The analysis is extended to the case of unequal masses. The full expression of metric tensor is given and the consistency between the solution of the metric and the equations of motion is rigorously proved. |
2404.01355 | Mrinnoy Gohain | Mrinnoy M. Gohain and Kalyan Bhuyan | Emergent Cosmology in 4D Einstein Gauss Bonnet Theory of Gravity | 12 pages, 2 figures, Accepted in Physica Scripta | Phys. Scr. 99 (2024) 075306 | 10.1088/1402-4896/ad5238 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, in an FLRW background and a perfect fluid equation of state,
we explore the possibility of the realization of an emergent scenario in a 4D
regularized extension of Einstein-Gauss-Bonnet gravity, with the field
equations particularly expressed in terms of scalar-tensor degrees of freedom.
By assuming non-zero spatial curvature ($k = \pm 1$), the stability of the
Einstein static universe (ESU) and its subsequent exit into the standard
inflationary system is tested through different approaches. In terms of
dynamical systems, a spatially closed universe rather than an open universe
shows appealing behaviour to exhibit a graceful transition from the Einstein
static universe to standard cosmological history. We found that under linear
homogeneous perturbations, for some constraints imposed on the model
parameters, the Einstein static universe is stable under those perturbations.
Moreover, it is noted that for a successful graceful transition, the equation
of state $\omega$ must satisfy the conditions $-1 < \omega <0$ and $\omega <
-1$ for closed and open universes, respectively. Also, under density
perturbations, the Einstein static universe is unstable if the fluid satisfies
the strong energy condition but is stable if it violates it, for both closed
and open universes. Furthermore, the Einstein static universe is seen to be
stable under vector perturbations and tensor perturbations, regardless of
whether the fluid obeys or violates the SEC.
| [
{
"created": "Mon, 1 Apr 2024 08:14:15 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Apr 2024 08:43:35 GMT",
"version": "v2"
},
{
"created": "Thu, 30 May 2024 15:36:10 GMT",
"version": "v3"
}
] | 2024-06-12 | [
[
"Gohain",
"Mrinnoy M.",
""
],
[
"Bhuyan",
"Kalyan",
""
]
] | In this paper, in an FLRW background and a perfect fluid equation of state, we explore the possibility of the realization of an emergent scenario in a 4D regularized extension of Einstein-Gauss-Bonnet gravity, with the field equations particularly expressed in terms of scalar-tensor degrees of freedom. By assuming non-zero spatial curvature ($k = \pm 1$), the stability of the Einstein static universe (ESU) and its subsequent exit into the standard inflationary system is tested through different approaches. In terms of dynamical systems, a spatially closed universe rather than an open universe shows appealing behaviour to exhibit a graceful transition from the Einstein static universe to standard cosmological history. We found that under linear homogeneous perturbations, for some constraints imposed on the model parameters, the Einstein static universe is stable under those perturbations. Moreover, it is noted that for a successful graceful transition, the equation of state $\omega$ must satisfy the conditions $-1 < \omega <0$ and $\omega < -1$ for closed and open universes, respectively. Also, under density perturbations, the Einstein static universe is unstable if the fluid satisfies the strong energy condition but is stable if it violates it, for both closed and open universes. Furthermore, the Einstein static universe is seen to be stable under vector perturbations and tensor perturbations, regardless of whether the fluid obeys or violates the SEC. |
1702.04973 | Claus Kiefer | Claus Kiefer and Branislav Nikolic | Conformal and Weyl-Einstein gravity: Classical geometrodynamics | 27 pages, conceptual clarifications added | Phys. Rev. D 95, 084018 (2017) | 10.1103/PhysRevD.95.084018 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new formulation for the canonical approach to conformal
(Weyl-squared) gravity and its extension by the Einstein-Hilbert term and a
nonminimally coupled scalar field. For this purpose we use a unimodular
decomposition of the three-metric and introduce unimodular-conformal canonical
variables. The important feature of this choice is that only the scale part of
the three-metric and the rescaled trace part of the extrinsic curvature change
under a conformal transformation. This significantly simplifies the constraint
analysis and manifestly reveals the conformal properties of a theory that
contains the conformally invariant Weyl-tensor term. The conformal symmetry
breaking which occurs in the presence of the Einstein-Hilbert term and a
nonconformally coupled scalar field can then be interpreted directly in terms
of this scale and this trace. We also discuss in detail the generator for the
conformal transformations. This new Hamiltonian formulation is especially
suitable for quantization, which will be the subject of a separate paper.
| [
{
"created": "Thu, 16 Feb 2017 14:13:24 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Apr 2017 15:28:14 GMT",
"version": "v2"
}
] | 2017-04-19 | [
[
"Kiefer",
"Claus",
""
],
[
"Nikolic",
"Branislav",
""
]
] | We present a new formulation for the canonical approach to conformal (Weyl-squared) gravity and its extension by the Einstein-Hilbert term and a nonminimally coupled scalar field. For this purpose we use a unimodular decomposition of the three-metric and introduce unimodular-conformal canonical variables. The important feature of this choice is that only the scale part of the three-metric and the rescaled trace part of the extrinsic curvature change under a conformal transformation. This significantly simplifies the constraint analysis and manifestly reveals the conformal properties of a theory that contains the conformally invariant Weyl-tensor term. The conformal symmetry breaking which occurs in the presence of the Einstein-Hilbert term and a nonconformally coupled scalar field can then be interpreted directly in terms of this scale and this trace. We also discuss in detail the generator for the conformal transformations. This new Hamiltonian formulation is especially suitable for quantization, which will be the subject of a separate paper. |
gr-qc/9604052 | Larry Ford | L.H. Ford and N. F. Svaiter | Gravitons and Lightcone Fluctuations II: Correlation Functions | 16 pages and two figures, uses epsf | Phys.Rev.D54:2640-2646,1996 | 10.1103/PhysRevD.54.2640 | TUTP-96-1 | gr-qc | null | A model of a fluctuating lightcone due to a bath of gravitons is further
investigated. The flight times of photons between a source and a detector may
be either longer or shorter than the light propagation time in the background
classical spacetime, and will form a Gaussian distribution centered around the
classical flight time. However, a pair of photons emitted in rapid succession
will tend to have correlated flight times. We derive and discuss a correlation
function which describes this effect. This enables us to understand more fully
the operational significance of a fluctuating lightcone. Our results may be
combined with observational data on pulsar timing to place some constraints on
the quantum state of cosmological gravitons.
| [
{
"created": "Sat, 27 Apr 1996 17:06:27 GMT",
"version": "v1"
}
] | 2011-09-09 | [
[
"Ford",
"L. H.",
""
],
[
"Svaiter",
"N. F.",
""
]
] | A model of a fluctuating lightcone due to a bath of gravitons is further investigated. The flight times of photons between a source and a detector may be either longer or shorter than the light propagation time in the background classical spacetime, and will form a Gaussian distribution centered around the classical flight time. However, a pair of photons emitted in rapid succession will tend to have correlated flight times. We derive and discuss a correlation function which describes this effect. This enables us to understand more fully the operational significance of a fluctuating lightcone. Our results may be combined with observational data on pulsar timing to place some constraints on the quantum state of cosmological gravitons. |
1805.00026 | Hideki Maeda | Hideki Maeda, Robert Svarc, Jiri Podolsky | Decreasing entropy of dynamical black holes in critical gravity | 11 pages, no figure, 2 tables; v2, revised version with more
references; v3, final version to appear in JHEP | JHEP 1806 (2018) 118 | 10.1007/JHEP06(2018)118 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Critical gravity is a quadratic curvature gravity in four dimensions which is
ghost-free around the AdS background. Constructing a Vaidya-type exact
solution, we show that the area of a black hole defined by a future outer
trapping horizon can shrink by injecting a charged null fluid with positive
energy density, so that a black hole is no more a one-way membrane even under
the null energy condition. In addition, the solution shows that the Wald-Kodama
dynamical entropy of a black hole is negative and can decrease. These
properties expose the pathological aspects of critical gravity at the
non-perturbative level.
| [
{
"created": "Mon, 30 Apr 2018 18:00:02 GMT",
"version": "v1"
},
{
"created": "Thu, 10 May 2018 12:11:24 GMT",
"version": "v2"
},
{
"created": "Thu, 28 Jun 2018 04:07:33 GMT",
"version": "v3"
}
] | 2018-08-01 | [
[
"Maeda",
"Hideki",
""
],
[
"Svarc",
"Robert",
""
],
[
"Podolsky",
"Jiri",
""
]
] | Critical gravity is a quadratic curvature gravity in four dimensions which is ghost-free around the AdS background. Constructing a Vaidya-type exact solution, we show that the area of a black hole defined by a future outer trapping horizon can shrink by injecting a charged null fluid with positive energy density, so that a black hole is no more a one-way membrane even under the null energy condition. In addition, the solution shows that the Wald-Kodama dynamical entropy of a black hole is negative and can decrease. These properties expose the pathological aspects of critical gravity at the non-perturbative level. |
2402.19397 | Lavinia Heisenberg | Fabio D'Ambrosio, Francesco Gozzini, Lavinia Heisenberg, Henri
Inchausp\'e, David Maibach, Jann Zosso | Testing gravitational waveforms in full General Relativity | 22 pages, 15 figures, Comments are welcome | null | null | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We perform a comprehensive analysis of state-of-the-art waveform models,
focusing on their predictions concerning kick velocity and inferred
gravitational wave memory. In our investigation we assess the accuracy of
waveform models using energy-momentum balance laws, which were derived in the
framework of full, non-linear General Relativity. The numerical accuracy
assessment is performed for precessing as well as non-precessing scenarios for
models belonging to the \textit{EOB}, \textit{Phenom}, and \textit{Surrogate}
families. We analyze the deviations of these models from each other and from
Numerical Relativity waveforms. Our analysis reveals statistically significant
deviations, which we trace back to inaccuracies in modelling subdominant modes
and inherent systematic errors in the chosen models. We corroborate our
findings through analytical considerations regarding the mixing of harmonic
modes in the computed kick velocities and inferred memories.
| [
{
"created": "Thu, 29 Feb 2024 17:55:26 GMT",
"version": "v1"
}
] | 2024-03-01 | [
[
"D'Ambrosio",
"Fabio",
""
],
[
"Gozzini",
"Francesco",
""
],
[
"Heisenberg",
"Lavinia",
""
],
[
"Inchauspé",
"Henri",
""
],
[
"Maibach",
"David",
""
],
[
"Zosso",
"Jann",
""
]
] | We perform a comprehensive analysis of state-of-the-art waveform models, focusing on their predictions concerning kick velocity and inferred gravitational wave memory. In our investigation we assess the accuracy of waveform models using energy-momentum balance laws, which were derived in the framework of full, non-linear General Relativity. The numerical accuracy assessment is performed for precessing as well as non-precessing scenarios for models belonging to the \textit{EOB}, \textit{Phenom}, and \textit{Surrogate} families. We analyze the deviations of these models from each other and from Numerical Relativity waveforms. Our analysis reveals statistically significant deviations, which we trace back to inaccuracies in modelling subdominant modes and inherent systematic errors in the chosen models. We corroborate our findings through analytical considerations regarding the mixing of harmonic modes in the computed kick velocities and inferred memories. |
1712.06601 | Moritz Platscher | Kevin Max, Moritz Platscher, Juri Smirnov | Decoherence of Gravitational Wave Oscillations in Bigravity | 7 pages, 2 figures; v2: extended discussion on the importance of the
Vainshtein mechanism, content matches published version | Phys. Rev. D 97, 064009 (2018) | 10.1103/PhysRevD.97.064009 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Following up on our recent study, we consider the regime of graviton masses
and gravitational wave propagation distances at which decoherence of the wave
packets plays a major role for phenomenology. This regime is of particular
interest, as it can lead to very striking phenomena of echo events in the
gravitational waves coming from coalescence events. The power of the
experimental search in this case lies in the fact that it becomes sensitive to
a large range of graviton masses, while not relying on a specific production
mechanism. We are thus able to place new relevant limits on the parameter space
of the graviton mixing angle.
| [
{
"created": "Mon, 18 Dec 2017 19:00:01 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Mar 2018 13:32:33 GMT",
"version": "v2"
}
] | 2018-03-21 | [
[
"Max",
"Kevin",
""
],
[
"Platscher",
"Moritz",
""
],
[
"Smirnov",
"Juri",
""
]
] | Following up on our recent study, we consider the regime of graviton masses and gravitational wave propagation distances at which decoherence of the wave packets plays a major role for phenomenology. This regime is of particular interest, as it can lead to very striking phenomena of echo events in the gravitational waves coming from coalescence events. The power of the experimental search in this case lies in the fact that it becomes sensitive to a large range of graviton masses, while not relying on a specific production mechanism. We are thus able to place new relevant limits on the parameter space of the graviton mixing angle. |
0810.0199 | Lorenzo Iorio | Lorenzo Iorio, Matteo Luca Ruggiero | Gravitomagnetic effects in Kerr-de Sitter space-time | Latex2e, 18 pages, 1 table, no figures. To appear in Journal of
Cosmology and Astroparticle Physics (JCAP) | JCAP03(2009)024 | 10.1088/1475-7516/2009/03/024 | null | gr-qc astro-ph hep-ph physics.space-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explicitly worked out the orbital effects induced on the trajectory of a
test particle by the the weak-field approximation of the Kerr-de Sitter metric.
It results that the node, the pericentre and the mean anomaly undergo secular
precessions proportional to k, which is a measure of the non linearity of the
theory. We used such theoretical predictions and the latest observational
determinations of the non-standard precessions of the perihelia of the inner
planets of the Solar System to put a bound on k getting k <= 10^-29 m^-2. The
node rate of the LAGEOS Earth's satellite yields k <= 10^-26 m^-2. The
periastron precession of the double pulsar PSR J0737-3039A/B allows to obtain k
<= 3 10^-21 m^-2. Interpreting k as a cosmological constant \Lambda, it turns
out that such constraints are weaker than those obtained from the
Schwarzschild-de Sitter metric.
| [
{
"created": "Wed, 1 Oct 2008 15:49:05 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Oct 2008 15:52:51 GMT",
"version": "v2"
},
{
"created": "Mon, 2 Mar 2009 09:04:37 GMT",
"version": "v3"
}
] | 2009-03-18 | [
[
"Iorio",
"Lorenzo",
""
],
[
"Ruggiero",
"Matteo Luca",
""
]
] | We explicitly worked out the orbital effects induced on the trajectory of a test particle by the the weak-field approximation of the Kerr-de Sitter metric. It results that the node, the pericentre and the mean anomaly undergo secular precessions proportional to k, which is a measure of the non linearity of the theory. We used such theoretical predictions and the latest observational determinations of the non-standard precessions of the perihelia of the inner planets of the Solar System to put a bound on k getting k <= 10^-29 m^-2. The node rate of the LAGEOS Earth's satellite yields k <= 10^-26 m^-2. The periastron precession of the double pulsar PSR J0737-3039A/B allows to obtain k <= 3 10^-21 m^-2. Interpreting k as a cosmological constant \Lambda, it turns out that such constraints are weaker than those obtained from the Schwarzschild-de Sitter metric. |
gr-qc/0504071 | Neil J. Cornish | Seth E. Timpano, Louis J. Rubbo and Neil J. Cornish | Characterizing the Galactic Gravitational Wave Background with LISA | 32 pages, 14 figures. Version to appear in PRD | Phys.Rev. D73 (2006) 122001 | 10.1103/PhysRevD.73.122001 | null | gr-qc astro-ph | null | We present a Monte Carlo simulation for the response of the Laser
Interferometer Space Antenna (LISA) to the galactic gravitational wave
background. The simulated data streams are used to estimate the number and type
of binary systems that will be individually resolved in a 1-year power
spectrum. We find that the background is highly non-Gaussian due to the
presence of individual bright sources, but once these sources are identified
and removed, the remaining signal is Gaussian. We also present a new estimate
of the confusion noise caused by unresolved sources that improves on earlier
estimates.
| [
{
"created": "Fri, 15 Apr 2005 19:30:41 GMT",
"version": "v1"
},
{
"created": "Sat, 16 Apr 2005 19:01:28 GMT",
"version": "v2"
},
{
"created": "Thu, 8 Dec 2005 04:27:34 GMT",
"version": "v3"
},
{
"created": "Fri, 7 Apr 2006 17:09:28 GMT",
"version": "v4"
}
] | 2009-11-11 | [
[
"Timpano",
"Seth E.",
""
],
[
"Rubbo",
"Louis J.",
""
],
[
"Cornish",
"Neil J.",
""
]
] | We present a Monte Carlo simulation for the response of the Laser Interferometer Space Antenna (LISA) to the galactic gravitational wave background. The simulated data streams are used to estimate the number and type of binary systems that will be individually resolved in a 1-year power spectrum. We find that the background is highly non-Gaussian due to the presence of individual bright sources, but once these sources are identified and removed, the remaining signal is Gaussian. We also present a new estimate of the confusion noise caused by unresolved sources that improves on earlier estimates. |
1802.00329 | Massimiliano Rinaldi | Marco Calz\`a, Massimiliano Rinaldi, Lorenzo Sebastiani | A special class of solutions in $F(R)$-gravity | Minor typos corrected, references added. Version accepted for
publication in the European Physical Journal C | null | 10.1140/epjc/s10052-018-5681-8 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a special class of vacuum $F(R)$-modified gravity models. The
form of their Lagrangian is such that the field equations are trivially
satisfied when the Ricci scalar is constant. There are many interesting
$F(R)$-models for inflation and dark energy that fall in this class. However,
little is known outside the domain of cosmology therefore we aim to explore the
class of solutions that are static and spherically symmetric. After some
general considerations, we investigate in more detail black hole solutions,
traversable wormhole metrics and, finally, configurations that can match the
anomalous rotation curves of galaxies.
| [
{
"created": "Wed, 31 Jan 2018 09:44:50 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Feb 2018 06:21:06 GMT",
"version": "v2"
}
] | 2018-04-04 | [
[
"Calzà",
"Marco",
""
],
[
"Rinaldi",
"Massimiliano",
""
],
[
"Sebastiani",
"Lorenzo",
""
]
] | We consider a special class of vacuum $F(R)$-modified gravity models. The form of their Lagrangian is such that the field equations are trivially satisfied when the Ricci scalar is constant. There are many interesting $F(R)$-models for inflation and dark energy that fall in this class. However, little is known outside the domain of cosmology therefore we aim to explore the class of solutions that are static and spherically symmetric. After some general considerations, we investigate in more detail black hole solutions, traversable wormhole metrics and, finally, configurations that can match the anomalous rotation curves of galaxies. |
0707.2089 | Israel Quiros | Tame Gonzalez, Israel Quiros | Exact models with non-minimal interaction between dark matter and
(either phantom or quintessence) dark energy | 15 pages, 2 eps figures. Several bibliographic references added. Some
new comments and acknowledgements also added | Class.Quant.Grav.25:175019,2008 | 10.1088/0264-9381/25/17/175019 | null | gr-qc | null | A method for deriving Friedmann-Robertson-Walker (FRW) solutions developed in
Int. J. Mod. Phys. D{\bf 5}(1996)71-84, is generalized to account for models
with non-minimal coupling between the dark energy and the dark matter. New
quintessence and phantom (flat) FRW solutions are found. Their physical
significance is discussed. Additionally, the aforementioned method is modified
so that, "coincidence free" solutions can be readily derived. Besides, we
review some aspects of the phantom barrier crossing. In this regard we present
a model which is free from the coincidence problem and, at the same time, does
the crossing of the phantom barrier $\omega=-1$ at late time. Finally, we give
additional comments on the non predictive properties of scalar field
cosmological models with or without energy transfer.
| [
{
"created": "Fri, 13 Jul 2007 20:45:19 GMT",
"version": "v1"
},
{
"created": "Mon, 14 Jan 2008 16:17:20 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Gonzalez",
"Tame",
""
],
[
"Quiros",
"Israel",
""
]
] | A method for deriving Friedmann-Robertson-Walker (FRW) solutions developed in Int. J. Mod. Phys. D{\bf 5}(1996)71-84, is generalized to account for models with non-minimal coupling between the dark energy and the dark matter. New quintessence and phantom (flat) FRW solutions are found. Their physical significance is discussed. Additionally, the aforementioned method is modified so that, "coincidence free" solutions can be readily derived. Besides, we review some aspects of the phantom barrier crossing. In this regard we present a model which is free from the coincidence problem and, at the same time, does the crossing of the phantom barrier $\omega=-1$ at late time. Finally, we give additional comments on the non predictive properties of scalar field cosmological models with or without energy transfer. |
2301.12319 | Tyler McMaken | Tyler McMaken and Andrew J.S. Hamilton | Hawking radiation inside a charged black hole | 26 pages, 8 figures, 1 appendix | Phys. Rev. D 107, 085010 (2023) | 10.1103/PhysRevD.107.085010 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Here we analyze the Hawking radiation detected by an inertial observer in an
arbitrary position in a Reissner-Nordstr\"om spacetime, with special emphasis
on the asymptotic behavior of the Hawking spectrum as an observer approaches
the inner or outer horizon. Two different methods are used to analyze the
Hawking flux: first, we calculate an effective temperature quantifying the rate
of exponential redshift experienced by an observer from an emitter's vacuum
modes, which reproduces the Hawking effect provided the redshift is
sufficiently adiabatic. Second, we compute the full Bogoliubov graybody
spectrum observed in the three regimes where the wave equation can be solved
analytically (at infinity and at the outer and inner horizons). We find that
for an observer at the event horizon, the effective Hawking temperature is
finite and becomes negative when $(Q/M)^2>8/9$, while at the inner horizon, the
effective temperature is always negative and infinite in every direction the
observer looks, coinciding with an ultraviolet-divergent spectrum.
| [
{
"created": "Sun, 29 Jan 2023 02:04:28 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Apr 2023 15:57:01 GMT",
"version": "v2"
}
] | 2023-04-14 | [
[
"McMaken",
"Tyler",
""
],
[
"Hamilton",
"Andrew J. S.",
""
]
] | Here we analyze the Hawking radiation detected by an inertial observer in an arbitrary position in a Reissner-Nordstr\"om spacetime, with special emphasis on the asymptotic behavior of the Hawking spectrum as an observer approaches the inner or outer horizon. Two different methods are used to analyze the Hawking flux: first, we calculate an effective temperature quantifying the rate of exponential redshift experienced by an observer from an emitter's vacuum modes, which reproduces the Hawking effect provided the redshift is sufficiently adiabatic. Second, we compute the full Bogoliubov graybody spectrum observed in the three regimes where the wave equation can be solved analytically (at infinity and at the outer and inner horizons). We find that for an observer at the event horizon, the effective Hawking temperature is finite and becomes negative when $(Q/M)^2>8/9$, while at the inner horizon, the effective temperature is always negative and infinite in every direction the observer looks, coinciding with an ultraviolet-divergent spectrum. |
2404.13887 | Bertrand Chauvineau | Bertrand Chauvineau, Hoang Ky Nguyen | The complete exterior spacetime of spherical Brans-Dicke stars | 1 figure. Correcting a typo in Eq (19) (an unjustified 4*pi factor
has been removed) | Phys. Lett. B 855, 138803 (2024) | 10.1016/j.physletb.2024.138803 | null | gr-qc astro-ph.HE math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the complete expression for the Brans Class I exterior spacetime
explicitly in terms of the energy and pressures profiles of a stationary
spherisymmetric gravity source. This novel and generic expression is achieved
in a parsimonious manner, requiring only a subset of the Brans-Dicke field
equation and the scalar equation. For distant orbiting test particles, this
expression promptly provides a simple, closed and exact formula of the
[textgreek]<LaTeX>\textgreek{g}</LaTeX> Eddington parameter, which reads
{\gamma}_{exact}=(({\omega}+1+({\omega}+2){\Theta})/({\omega}+2+({\omega}+1){\Theta})),
where {\Theta} is the ratio of the star's "total pressure" integral over its
energy integral. This non-perturbative result reproduces the usual
Post-Newtonian (({\omega}+1)/({\omega}+2)) expression in the case of a
"Newtonian star", in which the pressure is negligible with respect to the
energy density. Furthermore, it converges to the General Relativity value
({\gamma}_{GR}=1) as the star's equation of state approaches that of
ultra-relativistic matter (in which case {\Theta} approaches 1), a behavior
consistent with broader studies on scalar-tensor gravity. Our derivation
underscores the essence of these results involving (1) the key relevant portion
of the Brans-Dicke field equations, (2) the uniqueness of the Brans Class I
vacuum solution for the non-phantom action, viz. {\omega}>-3/2, and (3) the
involvement of only two free parameters in this solution, hence requiring two
quantities (energy and pressure integrals) of the mass source to fully
characterize the solution. From a practical standpoint, it elucidates how a
given stellar interior structure model determines the star's exterior
gravitational field and impacts the motions of light objects (such as planets
and accretion disks) orbiting it.
| [
{
"created": "Mon, 22 Apr 2024 05:23:53 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Jun 2024 14:08:26 GMT",
"version": "v2"
},
{
"created": "Thu, 27 Jun 2024 08:36:24 GMT",
"version": "v3"
}
] | 2024-06-28 | [
[
"Chauvineau",
"Bertrand",
""
],
[
"Nguyen",
"Hoang Ky",
""
]
] | We derive the complete expression for the Brans Class I exterior spacetime explicitly in terms of the energy and pressures profiles of a stationary spherisymmetric gravity source. This novel and generic expression is achieved in a parsimonious manner, requiring only a subset of the Brans-Dicke field equation and the scalar equation. For distant orbiting test particles, this expression promptly provides a simple, closed and exact formula of the [textgreek]<LaTeX>\textgreek{g}</LaTeX> Eddington parameter, which reads {\gamma}_{exact}=(({\omega}+1+({\omega}+2){\Theta})/({\omega}+2+({\omega}+1){\Theta})), where {\Theta} is the ratio of the star's "total pressure" integral over its energy integral. This non-perturbative result reproduces the usual Post-Newtonian (({\omega}+1)/({\omega}+2)) expression in the case of a "Newtonian star", in which the pressure is negligible with respect to the energy density. Furthermore, it converges to the General Relativity value ({\gamma}_{GR}=1) as the star's equation of state approaches that of ultra-relativistic matter (in which case {\Theta} approaches 1), a behavior consistent with broader studies on scalar-tensor gravity. Our derivation underscores the essence of these results involving (1) the key relevant portion of the Brans-Dicke field equations, (2) the uniqueness of the Brans Class I vacuum solution for the non-phantom action, viz. {\omega}>-3/2, and (3) the involvement of only two free parameters in this solution, hence requiring two quantities (energy and pressure integrals) of the mass source to fully characterize the solution. From a practical standpoint, it elucidates how a given stellar interior structure model determines the star's exterior gravitational field and impacts the motions of light objects (such as planets and accretion disks) orbiting it. |
1103.5543 | Barun Majumder | Barun Majumder | Quantum Scalar-metric Cosmology with Chaplygin gas | 13 pages, 6 figures | Phys.Lett.B697:101-106,2011 | 10.1016/j.physletb.2011.01.054 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A spatially flat Friedmann-Robertson-Walker(FRW) cosmological model with
generalized Chaplygin gas is studied in the context of scalar-metric
formulation of cosmology. Schutz's mechanism for the perfect fluid is applied
with generalized Chaplygin gas and the classical and quantum dynamics for this
model is studied. It is found that the only surviving matter degree of freedom
played the role of cosmic time. For the quantum mechanical description it is
possible to find the wave packet which resulted from the linear superposition
of the wave functions of the Schr\"{o}dinger-Wheeler-DeWitt(SWD) equation,
which is a consequence of the above formalism. The wave packets show two
distinct dominant peaks and propagate in the direction of increasing scale
factor. It may happen that our present universe originated from one of those
peaks. The many-world and ontological interpretation of quantum mechanics is
applied to investigate about the behaviour of the scale factor and the scalar
field(considered for this model). In both the cases the scale factor avoids
singularity and a bouncing non-singular universe is found.
| [
{
"created": "Tue, 29 Mar 2011 05:00:20 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Mar 2011 03:47:27 GMT",
"version": "v2"
}
] | 2011-06-24 | [
[
"Majumder",
"Barun",
""
]
] | A spatially flat Friedmann-Robertson-Walker(FRW) cosmological model with generalized Chaplygin gas is studied in the context of scalar-metric formulation of cosmology. Schutz's mechanism for the perfect fluid is applied with generalized Chaplygin gas and the classical and quantum dynamics for this model is studied. It is found that the only surviving matter degree of freedom played the role of cosmic time. For the quantum mechanical description it is possible to find the wave packet which resulted from the linear superposition of the wave functions of the Schr\"{o}dinger-Wheeler-DeWitt(SWD) equation, which is a consequence of the above formalism. The wave packets show two distinct dominant peaks and propagate in the direction of increasing scale factor. It may happen that our present universe originated from one of those peaks. The many-world and ontological interpretation of quantum mechanics is applied to investigate about the behaviour of the scale factor and the scalar field(considered for this model). In both the cases the scale factor avoids singularity and a bouncing non-singular universe is found. |
2001.10307 | Snehasish Bhattacharjee | Snehasish Bhattacharjee | Effects of magnetic field on the radiation pressure dominated discs
around neutron stars | 14 pages, 9 figures, accepted in Modern Physics Letters A | Modern Physics Letters A, 35 (15), 2050125 (2020) | 10.1142/S0217732320501254 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We supplement the analytic solution obtained by Matthews O. M., et. al.,
2005, MNRAS, \textbf{356}, 66 to investigate the steady-state structure of
radiation pressure dominated disc under the influence of a stellar magnetic
field which deploys a torque. The solutions converge to the non-magnetic
Shakura N. I., Sunyaev R. A., 1973, A\& A, \textbf{24}, 337 form when magnetic
field of the star tends to zero and also at large radii. Effects of varying the
mass accretion rates and the spin period of a typical neutron star on the disc
parameters are presented. We further report that the presence of a magnetic
correction term $k$ reduces the radial extent upto which radiation pressure and
electron scattering continue to be the major source of pressure and opacity
respectively. We also report that magnetic effects amplify the viscous
timescale several times in the inner disc.
| [
{
"created": "Tue, 28 Jan 2020 13:21:00 GMT",
"version": "v1"
}
] | 2020-05-26 | [
[
"Bhattacharjee",
"Snehasish",
""
]
] | We supplement the analytic solution obtained by Matthews O. M., et. al., 2005, MNRAS, \textbf{356}, 66 to investigate the steady-state structure of radiation pressure dominated disc under the influence of a stellar magnetic field which deploys a torque. The solutions converge to the non-magnetic Shakura N. I., Sunyaev R. A., 1973, A\& A, \textbf{24}, 337 form when magnetic field of the star tends to zero and also at large radii. Effects of varying the mass accretion rates and the spin period of a typical neutron star on the disc parameters are presented. We further report that the presence of a magnetic correction term $k$ reduces the radial extent upto which radiation pressure and electron scattering continue to be the major source of pressure and opacity respectively. We also report that magnetic effects amplify the viscous timescale several times in the inner disc. |
gr-qc/0412054 | Marcelo S. Berman | Marcelo Samuel Berman | Brief History of Black-Holes | 3 pages including front page.Replaced version consists of a slightly
reworded text | null | null | null | gr-qc | null | We show that the gravitational collapse of a black-hole terminates in the
birth of a white-hole, due to repulsive gravitation (antigravitation); in
particular, the infinite energy density singularity does NOT occur.
| [
{
"created": "Sun, 12 Dec 2004 14:29:30 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Dec 2004 22:43:45 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Berman",
"Marcelo Samuel",
""
]
] | We show that the gravitational collapse of a black-hole terminates in the birth of a white-hole, due to repulsive gravitation (antigravitation); in particular, the infinite energy density singularity does NOT occur. |
1612.05117 | F. S. Guzman | J. A. Gonz\'alez, F. S. Guzm\'an | Accretion of a Phantom Scalar Field by a Black Hole: restrictions on the
field distribution | 5 pages, 18 eps figures | Phys. Rev. D 94, 104012 (2016) | 10.1103/PhysRevD.94.104012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using numerical simulations we study the accretion of a phantom scalar field
into a black hole and track the black hole horizon shrinking process. We
integrate the amount of field left outside the black hole during the process in
terms of the properties of the wave packet sent toward the black hole. Our
results indicate that the accretion of thick wave packets with small wave
number is inefficient and a portion of the scalar field remains outside the
black hole.
| [
{
"created": "Thu, 15 Dec 2016 15:47:16 GMT",
"version": "v1"
}
] | 2016-12-16 | [
[
"González",
"J. A.",
""
],
[
"Guzmán",
"F. S.",
""
]
] | Using numerical simulations we study the accretion of a phantom scalar field into a black hole and track the black hole horizon shrinking process. We integrate the amount of field left outside the black hole during the process in terms of the properties of the wave packet sent toward the black hole. Our results indicate that the accretion of thick wave packets with small wave number is inefficient and a portion of the scalar field remains outside the black hole. |
1211.3448 | Peter Kazinski | P.O. Kazinski | Propagator of a scalar field on a stationary slowly varying
gravitational background | 45 pp., 1 fig; some misprints corrected, references and appendix
added; exposition improved, app. C added | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The propagator of a scalar field on a stationary slowly varying in space
gravitational background is derived retaining only the second derivatives of
the metric. The corresponding one-loop effective action is constructed. The
propagator and the effective action turn out to depend nontrivially on the
Killing vector defining the vacuum state and the Hamiltonian of a scalar field.
The Hawking particle production is described in the quasiclassical
approximation and the quasiclassical formula for the Hawking temperature is
derived. The behaviour of the Unruh detector on a curved background is
considered and the quasiclassical formula for the Unruh acceleration
determining the Unruh temperature is derived. The radiation reaction problem on
a curved background is discussed in view of the new approximate expression for
the propagator. The correction to the mass squared of a scalar particle on a
stationary gravitational background is obtained. This correction is analogous
to the quantum correction to the particle mass in a strong electromagnetic
field. For a vacuum solution to the Einstein equations, it is equal to minus
one-fourth of the free fall acceleration squared.
| [
{
"created": "Wed, 14 Nov 2012 22:25:16 GMT",
"version": "v1"
},
{
"created": "Sat, 24 Nov 2012 11:10:46 GMT",
"version": "v2"
},
{
"created": "Tue, 12 Mar 2013 17:04:19 GMT",
"version": "v3"
}
] | 2013-03-13 | [
[
"Kazinski",
"P. O.",
""
]
] | The propagator of a scalar field on a stationary slowly varying in space gravitational background is derived retaining only the second derivatives of the metric. The corresponding one-loop effective action is constructed. The propagator and the effective action turn out to depend nontrivially on the Killing vector defining the vacuum state and the Hamiltonian of a scalar field. The Hawking particle production is described in the quasiclassical approximation and the quasiclassical formula for the Hawking temperature is derived. The behaviour of the Unruh detector on a curved background is considered and the quasiclassical formula for the Unruh acceleration determining the Unruh temperature is derived. The radiation reaction problem on a curved background is discussed in view of the new approximate expression for the propagator. The correction to the mass squared of a scalar particle on a stationary gravitational background is obtained. This correction is analogous to the quantum correction to the particle mass in a strong electromagnetic field. For a vacuum solution to the Einstein equations, it is equal to minus one-fourth of the free fall acceleration squared. |
1507.05036 | Cosimo Bambi | Cosimo Bambi | Testing the Kerr Paradigm with X-ray Observations | 6 pages, 3 figures. Talk given at the "14th Marcel Grossmann Meeting"
(12-18 July 2015, Rome, Italy). To appear in the conference proceedings | null | 10.1142/9789813226609_0143 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Astrophysical black hole candidates are thought to be the Kerr black holes of
general relativity, but the actual nature of these objects has still to be
confirmed. The continuum-fitting and the iron line methods are currently the
only available techniques to probe the spacetime geometry around these bodies
and test the Kerr black hole paradigm. The continuum-fitting method is a robust
approach, but the shape of the disk's thermal spectrum is in general too simple
to measure the spin and to constrain possible deviations from the Kerr solution
at the same time. The iron line analysis is potentially a powerful technique,
but at the moment we do not have high quality data and a robust astrophysical
model.
| [
{
"created": "Fri, 17 Jul 2015 17:20:30 GMT",
"version": "v1"
}
] | 2017-12-19 | [
[
"Bambi",
"Cosimo",
""
]
] | Astrophysical black hole candidates are thought to be the Kerr black holes of general relativity, but the actual nature of these objects has still to be confirmed. The continuum-fitting and the iron line methods are currently the only available techniques to probe the spacetime geometry around these bodies and test the Kerr black hole paradigm. The continuum-fitting method is a robust approach, but the shape of the disk's thermal spectrum is in general too simple to measure the spin and to constrain possible deviations from the Kerr solution at the same time. The iron line analysis is potentially a powerful technique, but at the moment we do not have high quality data and a robust astrophysical model. |
1509.04702 | Marc Casals | Marc Casals and Adrian C. Ottewill | High-order Tail in Schwarzschild Space-time | 39 pages, 10 figures. Small improvements throughout | Phys. Rev. D 92, 124055 (2015) | 10.1103/PhysRevD.92.124055 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an analysis of the behaviour at late-times of linear field
perturbations of a Schwarzschild black hole space-time. In particular, we give
explicit analytic expressions for the field perturbations (for a specific
multipole) of general spin up to the first four orders at late times. These
expressions are valid at arbitrary radius and include, apart from the
well-known power-law tail decay at leading order ($\sim t^{-2\ell-3}$), a new
logarithmic behaviour at third leading order ($\sim t^{-2\ell-5}\ln t$). We
obtain these late-time results by developing the so-called MST formalism and by
expanding the various MST Fourier-mode quantities for small frequency. While we
give explicit expansions up to the first four leading orders (for
small-frequency for the Fourier modes, for late-time for the field
perturbation), we give a prescription for obtaining expressions to arbitrary
order within a `perturbative regime'.
| [
{
"created": "Tue, 15 Sep 2015 19:58:53 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Oct 2015 00:21:48 GMT",
"version": "v2"
}
] | 2015-12-30 | [
[
"Casals",
"Marc",
""
],
[
"Ottewill",
"Adrian C.",
""
]
] | We present an analysis of the behaviour at late-times of linear field perturbations of a Schwarzschild black hole space-time. In particular, we give explicit analytic expressions for the field perturbations (for a specific multipole) of general spin up to the first four orders at late times. These expressions are valid at arbitrary radius and include, apart from the well-known power-law tail decay at leading order ($\sim t^{-2\ell-3}$), a new logarithmic behaviour at third leading order ($\sim t^{-2\ell-5}\ln t$). We obtain these late-time results by developing the so-called MST formalism and by expanding the various MST Fourier-mode quantities for small frequency. While we give explicit expansions up to the first four leading orders (for small-frequency for the Fourier modes, for late-time for the field perturbation), we give a prescription for obtaining expressions to arbitrary order within a `perturbative regime'. |
gr-qc/9405043 | Steve Carlip | S. Carlip | Time in (2+1)-Dimensional Quantum Gravity | 5 pages, LaTeX, UCD-94-18 | null | null | null | gr-qc | null | General relativity in three spacetime dimensions is used to explore three
approaches to the ``problem of time'' in quantum gravity: the internal
Schr\"odinger approach with mean extrinsic curvature as a time variable, the
Wheeler-DeWitt equation, and covariant canonical quantization with ``evolving
constants of motion.'' (To appear in {\em Proc.\ of the Lanczos Centenary
Conference}, Raleigh, NC, December 1993.)
| [
{
"created": "Fri, 20 May 1994 23:24:24 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Carlip",
"S.",
""
]
] | General relativity in three spacetime dimensions is used to explore three approaches to the ``problem of time'' in quantum gravity: the internal Schr\"odinger approach with mean extrinsic curvature as a time variable, the Wheeler-DeWitt equation, and covariant canonical quantization with ``evolving constants of motion.'' (To appear in {\em Proc.\ of the Lanczos Centenary Conference}, Raleigh, NC, December 1993.) |
2303.07361 | Oscar J. C. Dias | Oscar J.C. Dias, Gary W. Gibbons, Jorge E. Santos and Benson Way | Static Black Binaries in de Sitter | 15 pages, 8 figures. v2: matches published version (improved
discussions and Figs. 6 and 7 added) | null | null | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | We construct the first four-dimensional multi-black hole solution of general
relativity with a positive cosmological constant. The solution consists of two
static black holes whose gravitational attraction is balanced by the cosmic
expansion. These static binaries provide the first four-dimensional example of
non-uniqueness in general relativity without matter.
| [
{
"created": "Mon, 13 Mar 2023 18:00:01 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Aug 2023 18:00:03 GMT",
"version": "v2"
}
] | 2023-08-04 | [
[
"Dias",
"Oscar J. C.",
""
],
[
"Gibbons",
"Gary W.",
""
],
[
"Santos",
"Jorge E.",
""
],
[
"Way",
"Benson",
""
]
] | We construct the first four-dimensional multi-black hole solution of general relativity with a positive cosmological constant. The solution consists of two static black holes whose gravitational attraction is balanced by the cosmic expansion. These static binaries provide the first four-dimensional example of non-uniqueness in general relativity without matter. |
2010.01490 | Xiang Liu | Xiang Liu | Primordial particles and waves in the early Universe | 5 pages, comments are welcome | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The observational evidence points to the origin of our Universe from a
big-bang explosion, the normal matter we observed can be well explained by the
particles created in the strong and weak interacting phases of the early
universe. The dark energy and dark matter, which occupy major contents of the
universe, may be created from earlier times than that of quarks. We propose
that the dark energy is an integration of the gravitational waves (GWs) in
early universe, and the dark matter is composed of x particles which are
created earlier and have much heavier mass than quarks in early universe. The x
particles may be bosons with no or little interaction with normal matter except
gravity, and they can be free particles or Bose-Einstein Condensed (BEC) matter
as the dominant matter in the galaxy clusters and galactic halos. This paper
notes as a framework of ideas need to be investigated further.
| [
{
"created": "Sun, 4 Oct 2020 06:19:11 GMT",
"version": "v1"
}
] | 2020-10-06 | [
[
"Liu",
"Xiang",
""
]
] | The observational evidence points to the origin of our Universe from a big-bang explosion, the normal matter we observed can be well explained by the particles created in the strong and weak interacting phases of the early universe. The dark energy and dark matter, which occupy major contents of the universe, may be created from earlier times than that of quarks. We propose that the dark energy is an integration of the gravitational waves (GWs) in early universe, and the dark matter is composed of x particles which are created earlier and have much heavier mass than quarks in early universe. The x particles may be bosons with no or little interaction with normal matter except gravity, and they can be free particles or Bose-Einstein Condensed (BEC) matter as the dominant matter in the galaxy clusters and galactic halos. This paper notes as a framework of ideas need to be investigated further. |
gr-qc/9603041 | null | M. Tsuda and T. Shirafuji | Supersymmetry algebra in N = 1 chiral supergravity | 10 pages, latex | Phys.Rev. D54 (1996) 2960-2963 | 10.1103/PhysRevD.54.2960 | STUPP-96-145 | gr-qc | null | We consider the supersymmetry (SUSY) transformations in the chiral Lagrangian
for $N = 1$ supergravity (SUGRA) with the complex tetrad following the method
used in the usual $N = 1$ SUGRA, and present the explicit form of the SUSY
trasformations in the first-order form. The SUSY transformations are generated
by two independent Majorana spinor parameters, which are apparently different
from the constrained parameters employed in the method of the 2-form gravity.
We also calculate the commutator algebra of the SUSY transformations on-shell.
| [
{
"created": "Mon, 25 Mar 1996 06:39:05 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Tsuda",
"M.",
""
],
[
"Shirafuji",
"T.",
""
]
] | We consider the supersymmetry (SUSY) transformations in the chiral Lagrangian for $N = 1$ supergravity (SUGRA) with the complex tetrad following the method used in the usual $N = 1$ SUGRA, and present the explicit form of the SUSY trasformations in the first-order form. The SUSY transformations are generated by two independent Majorana spinor parameters, which are apparently different from the constrained parameters employed in the method of the 2-form gravity. We also calculate the commutator algebra of the SUSY transformations on-shell. |
gr-qc/0510054 | George E. A. Matsas | Eduardo Gueron, Clovis A. S. Maia and George E. A. Matsas | "Swimming" versus "swinging" in spacetime | 4 pages (revtex), 4 figures, to appear in Physical Review D | Phys.Rev. D73 (2006) 024020 | 10.1103/PhysRevD.73.024020 | null | gr-qc astro-ph | null | Wisdom has recently unveiled a new relativistic effect, called ``spacetime
swimming'', where quasi-rigid free bodies in curved spacetimes can "speed up",
"slow down" or "deviate" their falls by performing "local" cyclic shape
deformations. We show here that for fast enough cycles this effect dominates
over a non-relativistic related one, named here ``space swinging'', where the
fall is altered through "nonlocal" cyclic deformations in Newtonian
gravitational fields. We expect, therefore, to clarify the distinction between
both effects leaving no room to controversy. Moreover, the leading contribution
to the swimming effect predicted by Wisdom is enriched with a higher order term
and the whole result is generalized to be applicable in cases where the tripod
is in large red-shift regions.
| [
{
"created": "Tue, 11 Oct 2005 12:44:17 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Jan 2006 20:35:56 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Gueron",
"Eduardo",
""
],
[
"Maia",
"Clovis A. S.",
""
],
[
"Matsas",
"George E. A.",
""
]
] | Wisdom has recently unveiled a new relativistic effect, called ``spacetime swimming'', where quasi-rigid free bodies in curved spacetimes can "speed up", "slow down" or "deviate" their falls by performing "local" cyclic shape deformations. We show here that for fast enough cycles this effect dominates over a non-relativistic related one, named here ``space swinging'', where the fall is altered through "nonlocal" cyclic deformations in Newtonian gravitational fields. We expect, therefore, to clarify the distinction between both effects leaving no room to controversy. Moreover, the leading contribution to the swimming effect predicted by Wisdom is enriched with a higher order term and the whole result is generalized to be applicable in cases where the tripod is in large red-shift regions. |
2007.10850 | Kemal Ak{\i}n | Kemal Ak{\i}n, A. Sava\c{s} Arapo\u{g}lu, A. Emrah Y\"ukselci | Formalizing Slow-roll Inflation in Scalar-Tensor Theories of Gravitation | 19 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1504.02192 | null | 10.1016/j.dark.2020.100691 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The viability of slow-roll approximation is examined by considering the
structure of phase spaces in scalar-tensor theories of gravitation and the
analysis is exemplified with a nonminimally coupled scalar field to the
spacetime curvature. The slow-roll field equations are obtained in the Jordan
frame in two ways: first using the direct generalization of the slow-roll
conditions in the minimal coupling case to nonminimal one, and second,
conformal transforming the slow-roll field equations in the Einstein frame to
the Jordan frame and then applying the generalized slow-roll conditions. Two
inflationary models governed by the potentials $V(\phi) \propto \phi^2$ and
$V(\phi) \propto \phi^4$ are considered to compare the outcomes of two methods
based on the analysis of $n_s$ and $r$ values in the light of recent
observational data.
| [
{
"created": "Sun, 19 Jul 2020 11:54:28 GMT",
"version": "v1"
}
] | 2020-07-22 | [
[
"Akın",
"Kemal",
""
],
[
"Arapoğlu",
"A. Savaş",
""
],
[
"Yükselci",
"A. Emrah",
""
]
] | The viability of slow-roll approximation is examined by considering the structure of phase spaces in scalar-tensor theories of gravitation and the analysis is exemplified with a nonminimally coupled scalar field to the spacetime curvature. The slow-roll field equations are obtained in the Jordan frame in two ways: first using the direct generalization of the slow-roll conditions in the minimal coupling case to nonminimal one, and second, conformal transforming the slow-roll field equations in the Einstein frame to the Jordan frame and then applying the generalized slow-roll conditions. Two inflationary models governed by the potentials $V(\phi) \propto \phi^2$ and $V(\phi) \propto \phi^4$ are considered to compare the outcomes of two methods based on the analysis of $n_s$ and $r$ values in the light of recent observational data. |
gr-qc/0104074 | null | S. Q. Wu and X. Cai | Extra Spin-Rotation Coupling Effect in a Radiating Kerr Space-time | Revtex, 4 pages, no figure, submitted to Phys. Rev. Lett | null | null | null | gr-qc | null | Source-less wave equations are derived for massless scalar, neutrino and
electromagnetic perturbations of a radiating Kerr space-time, and the Hawking
radiation of massless particles with spin $s =0, 1/2$ and 1 in this geometry is
investigated by using a method of the generalized tortoise coordinate
transformation. An extra interaction between the spin of particles and the
rotation of the hole displays in the thermal spectra of Hawking radiation of
massless particles with spin $s = 1/2, 1$ in the evaporating Kerr space-time.
The character of such effect is its obvious dependence on different helicity
states of particles with higher spin.
| [
{
"created": "Tue, 24 Apr 2001 03:47:19 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Wu",
"S. Q.",
""
],
[
"Cai",
"X.",
""
]
] | Source-less wave equations are derived for massless scalar, neutrino and electromagnetic perturbations of a radiating Kerr space-time, and the Hawking radiation of massless particles with spin $s =0, 1/2$ and 1 in this geometry is investigated by using a method of the generalized tortoise coordinate transformation. An extra interaction between the spin of particles and the rotation of the hole displays in the thermal spectra of Hawking radiation of massless particles with spin $s = 1/2, 1$ in the evaporating Kerr space-time. The character of such effect is its obvious dependence on different helicity states of particles with higher spin. |
2309.03565 | Xiao-Mei Kuang | Zhen-Hao Yang, Yun-He Lei, Xiao-Mei Kuang, Jian-Pin Wu | Perturbations of massless external fields in Horndeski hairy black hole | 20 pages | Eur. Phys. J. C (2024) 84:153 | 10.1140/epjc/s10052-024-12511-4 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we study the propagations of external fields in Horndeski
theory, including the scalar field, electromagnetic field and Dirac field. We
extensively explore the quasinormal frequencies, time evolution, greybody
factors and emission rates of those massless perturbing fields by solving the
corresponding master equations in the Horndeski hairy black hole. With the use
of both numerical and analytical methods, we disclose the
competitive/promotional influences of the Horndeski hair, spin and quantum
momentum number of the external fields on those phenomenal physics. Our results
show that the Horndeski hairy black hole is stable under those perturbations.
Moreover, a larger Horndeski hair could enhance the intensity of energy
emission rate for Hawking radiation of various particles, indicating that
comparing to the Schwarzschild black hole, the Horndeski hariy black hole could
have longer or shorter lifetime depending on the sign of the Horndeski hair.
| [
{
"created": "Thu, 7 Sep 2023 08:52:44 GMT",
"version": "v1"
}
] | 2024-03-26 | [
[
"Yang",
"Zhen-Hao",
""
],
[
"Lei",
"Yun-He",
""
],
[
"Kuang",
"Xiao-Mei",
""
],
[
"Wu",
"Jian-Pin",
""
]
] | In this paper, we study the propagations of external fields in Horndeski theory, including the scalar field, electromagnetic field and Dirac field. We extensively explore the quasinormal frequencies, time evolution, greybody factors and emission rates of those massless perturbing fields by solving the corresponding master equations in the Horndeski hairy black hole. With the use of both numerical and analytical methods, we disclose the competitive/promotional influences of the Horndeski hair, spin and quantum momentum number of the external fields on those phenomenal physics. Our results show that the Horndeski hairy black hole is stable under those perturbations. Moreover, a larger Horndeski hair could enhance the intensity of energy emission rate for Hawking radiation of various particles, indicating that comparing to the Schwarzschild black hole, the Horndeski hariy black hole could have longer or shorter lifetime depending on the sign of the Horndeski hair. |
2103.11245 | R. E. Kastner | R. E. Kastner | The Relativistic Transactional Interpretation and Spacetime Emergence | Excerpted material from the forthcoming 2nd edition of my book, The
Transactional Interpretation of Quantum Mechanics: A Relativistic Account
(CUP) | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the manner in which the spacetime manifold emerges from a quantum
substratum through the transactional process, in which spacetime events and
their connections are established. In this account, there is no background
spacetime as is generally assumed in physical theorizing. Instead, the usual
notion of a background spacetime is replaced by the quantum substratum,
comprising quantum systems with nonvanishing rest mass. Rest mass corresponds
to internal periodicities that function as internal clocks defining proper
times, and in turn, inertial frames that are not themselves aspects of the
spacetime manifold, but are pre-spacetime reference structures. Specific
processes in the quantum substratum serve to distinguish absolute from relative
motion.
| [
{
"created": "Sat, 20 Mar 2021 21:08:58 GMT",
"version": "v1"
}
] | 2021-03-23 | [
[
"Kastner",
"R. E.",
""
]
] | We consider the manner in which the spacetime manifold emerges from a quantum substratum through the transactional process, in which spacetime events and their connections are established. In this account, there is no background spacetime as is generally assumed in physical theorizing. Instead, the usual notion of a background spacetime is replaced by the quantum substratum, comprising quantum systems with nonvanishing rest mass. Rest mass corresponds to internal periodicities that function as internal clocks defining proper times, and in turn, inertial frames that are not themselves aspects of the spacetime manifold, but are pre-spacetime reference structures. Specific processes in the quantum substratum serve to distinguish absolute from relative motion. |
2208.02983 | Sandipan Sengupta | Sandipan Sengupta | Hamiltonian form of `Carroll' gravity | Version published in Phys. Rev. D | Phys. Rev. D 107, 024010 (2023) | 10.1103/PhysRevD.107.024010 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We develop a Hamiltonian description of the `Carroll' (Levy Leblond-Sen
Gupta) limit of gravity theory in the first-order formalism. Through a
constraint analysis, the number of local degrees of freedom are shown to be two
in this singular limit. The associated Hamiltonian constraint depends only on
the densitized triad fields and their space derivatives. We also provide a
scaling prescription within the Hilbert-Palatini theory to obtain the
first-order analogue of the `electric' limit of canonical metric gravity. The
simplicity of both these limiting Hamiltonian forms in these variables make
them interesting candidates for quantization.
| [
{
"created": "Fri, 5 Aug 2022 04:45:00 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Aug 2022 16:39:44 GMT",
"version": "v2"
},
{
"created": "Sat, 14 Jan 2023 13:33:15 GMT",
"version": "v3"
}
] | 2023-01-18 | [
[
"Sengupta",
"Sandipan",
""
]
] | We develop a Hamiltonian description of the `Carroll' (Levy Leblond-Sen Gupta) limit of gravity theory in the first-order formalism. Through a constraint analysis, the number of local degrees of freedom are shown to be two in this singular limit. The associated Hamiltonian constraint depends only on the densitized triad fields and their space derivatives. We also provide a scaling prescription within the Hilbert-Palatini theory to obtain the first-order analogue of the `electric' limit of canonical metric gravity. The simplicity of both these limiting Hamiltonian forms in these variables make them interesting candidates for quantization. |
2103.00155 | Gianmassimo Tasinato | Gianmassimo Tasinato, Alice Garoffolo, Daniele Bertacca, Sabino
Matarrese | Gravitational-wave cosmological distances in scalar-tensor theories of
gravity | 22 pages plus technical appendixes. 3 figures. V2: version published
in JCAP | null | 10.1088/1475-7516/2021/06/050 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the propagation of high-frequency gravitational waves (GW) in
scalar-tensor theories of gravity, with the aim of examining properties of
cosmological distances as inferred from GW measurements. By using symmetry
principles, we first determine the most general structure of the GW linearized
equations and of the GW energy momentum tensor, assuming that GW move with the
speed of light. Modified gravity effects are encoded in a small number of
parameters, and we study the conditions for ensuring graviton number
conservation in our covariant set-up. We then apply our general findings to the
case of GW propagating through a perturbed cosmological space-time, deriving
the expressions for the GW luminosity distance $d_L^{({\rm GW})}$ and the GW
angular distance $d_A^{({\rm GW})}$. We prove for the first time the validity
of Etherington reciprocity law $d_L^{({\rm GW})}\,=\,(1+z)^2\,d_A^{({\rm GW})}$
for a perturbed universe within a scalar-tensor framework. We find that besides
the GW luminosity distance, also the GW angular distance can be modified with
respect to General Relativity. We discuss implications of this result for
gravitational lensing, focussing on time-delays of lensed GW and lensed photons
emitted simultaneously during a multimessenger event. We explicitly show how
modified gravity effects compensate between different coefficients in the GW
time-delay formula: lensed GW arrive at the same time as their lensed
electromagnetic counterparts, in agreement with causality constraints.
| [
{
"created": "Sat, 27 Feb 2021 08:22:16 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Jun 2021 07:13:20 GMT",
"version": "v2"
}
] | 2021-07-07 | [
[
"Tasinato",
"Gianmassimo",
""
],
[
"Garoffolo",
"Alice",
""
],
[
"Bertacca",
"Daniele",
""
],
[
"Matarrese",
"Sabino",
""
]
] | We analyze the propagation of high-frequency gravitational waves (GW) in scalar-tensor theories of gravity, with the aim of examining properties of cosmological distances as inferred from GW measurements. By using symmetry principles, we first determine the most general structure of the GW linearized equations and of the GW energy momentum tensor, assuming that GW move with the speed of light. Modified gravity effects are encoded in a small number of parameters, and we study the conditions for ensuring graviton number conservation in our covariant set-up. We then apply our general findings to the case of GW propagating through a perturbed cosmological space-time, deriving the expressions for the GW luminosity distance $d_L^{({\rm GW})}$ and the GW angular distance $d_A^{({\rm GW})}$. We prove for the first time the validity of Etherington reciprocity law $d_L^{({\rm GW})}\,=\,(1+z)^2\,d_A^{({\rm GW})}$ for a perturbed universe within a scalar-tensor framework. We find that besides the GW luminosity distance, also the GW angular distance can be modified with respect to General Relativity. We discuss implications of this result for gravitational lensing, focussing on time-delays of lensed GW and lensed photons emitted simultaneously during a multimessenger event. We explicitly show how modified gravity effects compensate between different coefficients in the GW time-delay formula: lensed GW arrive at the same time as their lensed electromagnetic counterparts, in agreement with causality constraints. |
2008.13185 | Chiranjeeb Singha | Saptarshi Saha, Chiranjeeb Singha and Arpan Chatterjee | Retarded resonance Casimir-Polder interaction of a uniformly rotating
two-atom system | 8 pages, Comments are welcome | Eur. Phys. J. C 81 (2021) 3, 265 | 10.1140/epjc/s10052-021-09077-w | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | We consider here, a two-atom system is uniformly moving through a circular
ring at an ultra-relativistic speed and weakly interacting with common external
fields. The vacuum fluctuations of the quantum fields generate the entanglement
between the atoms. Hence an effective energy shift is originated, which depends
on the inter-atomic distance. This is commonly known as resonance
Casimir-Polder interaction (RCPI). It is well known that, for a linearly
accelerated system coupled with a massless scalar field, we get a thermal
response when the local inertial approximation is valid. On the contrary, the
non-thermality arises in the presence of the centripetal acceleration. We use
the quantum master equation formalism to calculate the second-order energy
shift of the entangled states in the presence of two kinds of fields. They are
the massive free scalar field and the electromagnetic vector field. For both
cases, we observe the non-thermal behavior. A unique retarded response is also
noticed in comparison to the free massless case, which can be observed via the
polarization transfer technique.
| [
{
"created": "Sun, 30 Aug 2020 14:31:59 GMT",
"version": "v1"
}
] | 2021-04-07 | [
[
"Saha",
"Saptarshi",
""
],
[
"Singha",
"Chiranjeeb",
""
],
[
"Chatterjee",
"Arpan",
""
]
] | We consider here, a two-atom system is uniformly moving through a circular ring at an ultra-relativistic speed and weakly interacting with common external fields. The vacuum fluctuations of the quantum fields generate the entanglement between the atoms. Hence an effective energy shift is originated, which depends on the inter-atomic distance. This is commonly known as resonance Casimir-Polder interaction (RCPI). It is well known that, for a linearly accelerated system coupled with a massless scalar field, we get a thermal response when the local inertial approximation is valid. On the contrary, the non-thermality arises in the presence of the centripetal acceleration. We use the quantum master equation formalism to calculate the second-order energy shift of the entangled states in the presence of two kinds of fields. They are the massive free scalar field and the electromagnetic vector field. For both cases, we observe the non-thermal behavior. A unique retarded response is also noticed in comparison to the free massless case, which can be observed via the polarization transfer technique. |
1710.07862 | Kent Yagi | Toral Gupta, Barun Majumder, Kent Yagi, Nicol\'as Yunes | I-Love-Q Relations for Neutron Stars in dynamical Chern Simons Gravity | 23 pages, 7 figures | null | 10.1088/1361-6382/aa9c68 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Neutron stars are ideal to probe, not only nuclear physics, but also
strong-field gravity. Approximate universal relations insensitive to the star's
internal structure exist among certain observables and are useful in testing
General Relativity, as they project out the uncertainties in the equation of
state. One such set of universal relations between the moment of inertia $(I)$,
the tidal Love number and the quadrupole moment $(Q)$ has been studied both in
General Relativity and in modified theories. In this paper, we study the
relations in dynamical Chern-Simons gravity, a well-motivated, parity-violating
effective field theory, extending previous work in various ways. First, we
study how projected constraints on the theory using the I-Love relation depend
on the measurement accuracy of $I$ with radio observations and that of the Love
number with gravitational-wave observations. Provided these quantities can be
measured with future observations, we find that the latter could place bounds
on dynamical Chern-Simons gravity that are six orders of magnitude stronger
than current bounds. Second, we study the I-Q and Q-Love relations in this
theory by constructing slowly-rotating neutron star solutions to quadratic
order in spin. We find that the approximate universality continues to hold in
dynamical Chern-Simons gravity, and in fact, it becomes stronger than in
General Relativity, although its existence depends on the normalization of the
dimensional coupling constant of the theory. Finally, we study the variation of
the eccentricity of isodensity contours inside a star and its relation to the
degree of universality. We find that, in most cases, the eccentricity variation
is smaller in dynamical Chern-Simons gravity than in General Relativity,
providing further support to the idea that the approximate self-similarity of
isodensity contours is responsible for universality.
| [
{
"created": "Sat, 21 Oct 2017 23:31:37 GMT",
"version": "v1"
}
] | 2017-12-27 | [
[
"Gupta",
"Toral",
""
],
[
"Majumder",
"Barun",
""
],
[
"Yagi",
"Kent",
""
],
[
"Yunes",
"Nicolás",
""
]
] | Neutron stars are ideal to probe, not only nuclear physics, but also strong-field gravity. Approximate universal relations insensitive to the star's internal structure exist among certain observables and are useful in testing General Relativity, as they project out the uncertainties in the equation of state. One such set of universal relations between the moment of inertia $(I)$, the tidal Love number and the quadrupole moment $(Q)$ has been studied both in General Relativity and in modified theories. In this paper, we study the relations in dynamical Chern-Simons gravity, a well-motivated, parity-violating effective field theory, extending previous work in various ways. First, we study how projected constraints on the theory using the I-Love relation depend on the measurement accuracy of $I$ with radio observations and that of the Love number with gravitational-wave observations. Provided these quantities can be measured with future observations, we find that the latter could place bounds on dynamical Chern-Simons gravity that are six orders of magnitude stronger than current bounds. Second, we study the I-Q and Q-Love relations in this theory by constructing slowly-rotating neutron star solutions to quadratic order in spin. We find that the approximate universality continues to hold in dynamical Chern-Simons gravity, and in fact, it becomes stronger than in General Relativity, although its existence depends on the normalization of the dimensional coupling constant of the theory. Finally, we study the variation of the eccentricity of isodensity contours inside a star and its relation to the degree of universality. We find that, in most cases, the eccentricity variation is smaller in dynamical Chern-Simons gravity than in General Relativity, providing further support to the idea that the approximate self-similarity of isodensity contours is responsible for universality. |
0807.1797 | Iver Brevik | Iver Brevik | Viscous Modified Gravity on a RS Brane Embedded in AdS5 | 12 pages, no figures; to appear in Eur. Phys. J. C | null | 10.1140/epjc/s10052-008-0678-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a modified gravity fluid on a Randall-Sundrum II brane situated
at y=0, the action containing a power \alpha of the scalar curvature. As is
known from 4D spatially flat modified gravity, the presence of a bulk viscosity
may drive the cosmic fluid into the phantom region (w < -1) and thereafter
inevitably into the Big Rip singularity, even it is initially nonviscous and
lies in the quintessence region (w > -1). The condition for this to occur is
that the bulk viscosity contains the power (2\alpha-1) of the scalar expansion.
We combine this with the 5D RS II model, and find that the Big Rip, occurring
for \alpha > 1/2, carries over to the metric for the bulk metric, |y|>0.
Actually, the scale factors on the brane and in the bulk become simply
proportional to each other.
| [
{
"created": "Fri, 11 Jul 2008 08:52:24 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Brevik",
"Iver",
""
]
] | We consider a modified gravity fluid on a Randall-Sundrum II brane situated at y=0, the action containing a power \alpha of the scalar curvature. As is known from 4D spatially flat modified gravity, the presence of a bulk viscosity may drive the cosmic fluid into the phantom region (w < -1) and thereafter inevitably into the Big Rip singularity, even it is initially nonviscous and lies in the quintessence region (w > -1). The condition for this to occur is that the bulk viscosity contains the power (2\alpha-1) of the scalar expansion. We combine this with the 5D RS II model, and find that the Big Rip, occurring for \alpha > 1/2, carries over to the metric for the bulk metric, |y|>0. Actually, the scale factors on the brane and in the bulk become simply proportional to each other. |
0705.1207 | Arunava Bhadra Dr. | A. Bhadra and S. C. Das | Comment on "On Mach's critique of Newton and Copernicus" | Six pages, to appear in AJP | Am.J.Phys.75:850-854,2007 | 10.1119/1.2716032 | null | gr-qc | null | Hartman and Nissim-Sabat have argued that Mach's idea of the relativity of
rotational motion suffers from internal inconsistencies and leads to a
contradiction that there cannot be a stationary bucket in a rotating universe.
They also claimed that non-inertial electromagnetic and stellar aberration
observations can distinguish between a rotating and a stationary universe,
whereas according to Mach there cannot be any observable way to distinguish
these two cases. We contest these objections.
| [
{
"created": "Wed, 9 May 2007 05:43:44 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Bhadra",
"A.",
""
],
[
"Das",
"S. C.",
""
]
] | Hartman and Nissim-Sabat have argued that Mach's idea of the relativity of rotational motion suffers from internal inconsistencies and leads to a contradiction that there cannot be a stationary bucket in a rotating universe. They also claimed that non-inertial electromagnetic and stellar aberration observations can distinguish between a rotating and a stationary universe, whereas according to Mach there cannot be any observable way to distinguish these two cases. We contest these objections. |
1306.3594 | Robert Mann | Andrew Laurtizen, Peter Gustainis, and Robert B. Mann | The 4-Body Problem in a (1+1)-Dimensional Self-Gravitating System | 40 pages, 23 figures, to appear in Journal of Mathematical Physics | null | null | null | gr-qc astro-ph.IM math-ph math.MP nlin.CD | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report on the results of a study of the motion of a four particle
non-relativistic one-dimensional self-gravitating system. We show that the
system can be visualized in terms of a single particle moving within a
potential whose equipotential surfaces are shaped like a box of pyramid-shaped
sides. As such this is the largest $N$-body system that can be visualized in
this way. We describe how to classify possible states of motion in terms of
Braid Group operators, generalizing this to $N$ bodies. We find that the
structure of the phase\textcolor{black}{{} space of each of these systems
yields a large variety of interesting dynamics, containing regions of
quasiperiodicity and chaos. Lyapunov exponents are calculated for many
trajectories to measure stochasticity and previously unseen phenomena in the
Lyapunov graphs are observed.
| [
{
"created": "Sat, 15 Jun 2013 17:31:16 GMT",
"version": "v1"
}
] | 2013-06-18 | [
[
"Laurtizen",
"Andrew",
""
],
[
"Gustainis",
"Peter",
""
],
[
"Mann",
"Robert B.",
""
]
] | We report on the results of a study of the motion of a four particle non-relativistic one-dimensional self-gravitating system. We show that the system can be visualized in terms of a single particle moving within a potential whose equipotential surfaces are shaped like a box of pyramid-shaped sides. As such this is the largest $N$-body system that can be visualized in this way. We describe how to classify possible states of motion in terms of Braid Group operators, generalizing this to $N$ bodies. We find that the structure of the phase\textcolor{black}{{} space of each of these systems yields a large variety of interesting dynamics, containing regions of quasiperiodicity and chaos. Lyapunov exponents are calculated for many trajectories to measure stochasticity and previously unseen phenomena in the Lyapunov graphs are observed. |
gr-qc/9711048 | Marco Spaans | Marco Spaans (Harvard CfA) | A Topological Formulation of the Standard Model | 19 pages, PS file | null | null | null | gr-qc | null | A topological theory for the interactions in Nature is presented. The theory
derives from the cyclic properties of the topological manifold Q=2T^3 + 3S^1 x
S^2 which has 23 intrinsic degrees of freedom, discrete Z_3 and Z_2 x Z_3
internal groups, an SU(5) gauge group, and an anomalous U(1) symmetry. These
properties reproduce the standard model with a stable proton, a natural place
for CP violation and doublet-triplet splitting. The equation of motion for the
unified theory is derived and leads to a Higgs field. The thermodynamic
properties of Q are discussed and yield a consistent amplitude for the cosmic
microwave background fluctuations. The manifold Q possesses internal energy
scales which are independent of the field theory defined on it, but which
constrain the predicted mass hierarchy of such theories. In particular the
electron and its neutrino are identified as ground states and their masses are
predicted. The correct masses of quarks and the CKM mixing angles can be
derived as well from these energy scales if one uses the anomalous U(1)
symmetry. Furthermore, it is shown that if the Planck scale topology of the
universe involves loops as fundamental objects, its spatial dimension is equal
to three. The existence of the prime manifold T^3=S^1 x S^1 S^1 is then
required for a dynamical universe, i.e. a universe which supports forces. Some
links with M-theory are pointed out.
| [
{
"created": "Sat, 15 Nov 1997 22:34:39 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Spaans",
"Marco",
"",
"Harvard CfA"
]
] | A topological theory for the interactions in Nature is presented. The theory derives from the cyclic properties of the topological manifold Q=2T^3 + 3S^1 x S^2 which has 23 intrinsic degrees of freedom, discrete Z_3 and Z_2 x Z_3 internal groups, an SU(5) gauge group, and an anomalous U(1) symmetry. These properties reproduce the standard model with a stable proton, a natural place for CP violation and doublet-triplet splitting. The equation of motion for the unified theory is derived and leads to a Higgs field. The thermodynamic properties of Q are discussed and yield a consistent amplitude for the cosmic microwave background fluctuations. The manifold Q possesses internal energy scales which are independent of the field theory defined on it, but which constrain the predicted mass hierarchy of such theories. In particular the electron and its neutrino are identified as ground states and their masses are predicted. The correct masses of quarks and the CKM mixing angles can be derived as well from these energy scales if one uses the anomalous U(1) symmetry. Furthermore, it is shown that if the Planck scale topology of the universe involves loops as fundamental objects, its spatial dimension is equal to three. The existence of the prime manifold T^3=S^1 x S^1 S^1 is then required for a dynamical universe, i.e. a universe which supports forces. Some links with M-theory are pointed out. |
1109.0201 | Alexander Kamenshchik | Alexander Yu. Kamenshchik and Isaak M. Khalatnikov | Some properties of the "String gas" with the equation of state $p =
-\rho/3$ | 9 pages, 1 figure | null | 10.1142/S0218271812500046 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the string gas - a perfect fluid with the equation of state $p =
-\frac13 \rho$ possesses rather interesing properties. In Friedmann universes
its presence can can change the observable topology of the space; in the
spherically symmetric spacetimes it produces rather bizzare geometries and in a
way its influence on the rotation curves mimics the dark matter effects.
| [
{
"created": "Thu, 1 Sep 2011 14:52:55 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Kamenshchik",
"Alexander Yu.",
""
],
[
"Khalatnikov",
"Isaak M.",
""
]
] | We show that the string gas - a perfect fluid with the equation of state $p = -\frac13 \rho$ possesses rather interesing properties. In Friedmann universes its presence can can change the observable topology of the space; in the spherically symmetric spacetimes it produces rather bizzare geometries and in a way its influence on the rotation curves mimics the dark matter effects. |
1003.1617 | Lorenzo Fatibene | L. Fatibene, M. Ferraris, M. Francaviglia | New Cases of Universality Theorem for Gravitational Theories | 10 pages, few typos corrected | Class.Quant.Grav.27:165021,2010 | 10.1088/0264-9381/27/16/165021 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The "Universality Theorem" for gravity shows that f(R) theories (in their
metric-affine formulation) in vacuum are dynamically equivalent to vacuum
Einstein equations with suitable cosmological constants. This holds true for a
generic (i.e. except sporadic degenerate cases) analytic function f(R) and
standard gravity without cosmological constant is reproduced if f is the
identity function (i.e. f(R)=R). The theorem is here extended introducing in
dimension 4 a 1-parameter family of invariants R' inspired by the
Barbero-Immirzi formulation of GR (which in the Euclidean sector includes also
selfdual formulation). It will be proven that f(R') theories so defined are
dynamically equivalent to the corresponding metric-affine f(R) theory. In
particular for the function f(R)=R the standard equivalence between GR and
Holst Lagrangian is obtained.
| [
{
"created": "Mon, 8 Mar 2010 13:21:38 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Mar 2010 17:19:36 GMT",
"version": "v2"
},
{
"created": "Thu, 18 Mar 2010 06:48:58 GMT",
"version": "v3"
}
] | 2014-11-20 | [
[
"Fatibene",
"L.",
""
],
[
"Ferraris",
"M.",
""
],
[
"Francaviglia",
"M.",
""
]
] | The "Universality Theorem" for gravity shows that f(R) theories (in their metric-affine formulation) in vacuum are dynamically equivalent to vacuum Einstein equations with suitable cosmological constants. This holds true for a generic (i.e. except sporadic degenerate cases) analytic function f(R) and standard gravity without cosmological constant is reproduced if f is the identity function (i.e. f(R)=R). The theorem is here extended introducing in dimension 4 a 1-parameter family of invariants R' inspired by the Barbero-Immirzi formulation of GR (which in the Euclidean sector includes also selfdual formulation). It will be proven that f(R') theories so defined are dynamically equivalent to the corresponding metric-affine f(R) theory. In particular for the function f(R)=R the standard equivalence between GR and Holst Lagrangian is obtained. |
1412.8485 | Idan Talshir | Idan Talshir | General Relativity from conservation laws without the principle of least
action | The paragraph that follows equation 2.13 needs to be checked and/or
revised and/or expanded | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove that the field equations of general relativity and other metric
theories can be derived from the conservation of energy-momentum without using
the assumption of least action principle. We show a new procedure for
perturbative derivation of symmetric pseudo-energy momentum for the gravity
field.
| [
{
"created": "Mon, 29 Dec 2014 21:07:32 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Dec 2014 07:41:11 GMT",
"version": "v2"
},
{
"created": "Wed, 4 Feb 2015 14:58:23 GMT",
"version": "v3"
},
{
"created": "Tue, 10 Feb 2015 10:19:45 GMT",
"version": "v4"
},
{
"created": "Thu, 15 Oct 2015 20:28:11 GMT",
"version": "v5"
}
] | 2015-10-19 | [
[
"Talshir",
"Idan",
""
]
] | We prove that the field equations of general relativity and other metric theories can be derived from the conservation of energy-momentum without using the assumption of least action principle. We show a new procedure for perturbative derivation of symmetric pseudo-energy momentum for the gravity field. |
1110.1967 | Plyatsko Roman | Roman Plyatsko, Oleksandr Stefanyshyn, Mykola Fenyk | Mathisson-Papapetrou-Dixon equations in the Schwarzschild and Kerr
backgrounds | 21 pages, 11 figures. arXiv admin note: substantial text overlap with
arXiv:1105.2405 | Class. Quantum Grav. 28, 195025 (2011) | 10.1088/0264-9381/28/19/195025 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new representation, which does not contain the third-order derivatives of
the coordinates, of the exact Mathisson-Papapetrou-Dixon equations, describing
the motion of a spinning test particle, is obtained under the assumption of the
Mathisson-Pirani condition in a Kerr background. For this purpose the integrals
of energy and angular momentum of the spinning particle as well as a
differential relationship following from the Mathisson-Papapetrou-Dixon
equations are used. The form of these equations is adapted for their computer
integration with the aim to investigate the influence of the spin-curvature
interaction on the particle's behavior in the gravitational field without
restrictions on its velocity and spin orientation. Some numerical examples for
a Schwarzschild background are presented.
| [
{
"created": "Mon, 10 Oct 2011 09:18:29 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Plyatsko",
"Roman",
""
],
[
"Stefanyshyn",
"Oleksandr",
""
],
[
"Fenyk",
"Mykola",
""
]
] | A new representation, which does not contain the third-order derivatives of the coordinates, of the exact Mathisson-Papapetrou-Dixon equations, describing the motion of a spinning test particle, is obtained under the assumption of the Mathisson-Pirani condition in a Kerr background. For this purpose the integrals of energy and angular momentum of the spinning particle as well as a differential relationship following from the Mathisson-Papapetrou-Dixon equations are used. The form of these equations is adapted for their computer integration with the aim to investigate the influence of the spin-curvature interaction on the particle's behavior in the gravitational field without restrictions on its velocity and spin orientation. Some numerical examples for a Schwarzschild background are presented. |
gr-qc/9812020 | Jose Wadih Maluf | J. W. Maluf and J. F. da Rocha-Neto | Static Bondi Energy in the Teleparallel Equivalent of General Relativity | 23 pages, Latex, no figures, to appear in the J. Math. Phys | J.Math.Phys. 40 (1999) 1490-1503 | 10.1063/1.532817 | null | gr-qc | null | We consider Bondi's radiating metric in the context of the teleparallel
equivalent of general relativity (TEGR). This metric describes the asymptotic
form of a radiating solution of Einstein's equations. The total gravitational
energy for this solution can be calculated by means of pseudo-tensors in the
static case. In the nonstatic case, Bondi defines the {\it mass aspect} $m(u)$,
which describes the mass of an isolated system. In this paper we express
Bondi's solution in asymptotically spherical 3+1 coordinates, not in radiation
coordinates, and obtain Bondi's energy in the static limit by means of the
expression for the gravitational energy in the framework of the TEGR. We can
either obtain the total energy or the energy inside a large (but finite)
portion of the three-dimensional spacelike hypersurface, whose boundary is far
away from the source. The relationship of the present energy expression with
Moller's energy is established.
| [
{
"created": "Sat, 5 Dec 1998 18:03:24 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Maluf",
"J. W.",
""
],
[
"da Rocha-Neto",
"J. F.",
""
]
] | We consider Bondi's radiating metric in the context of the teleparallel equivalent of general relativity (TEGR). This metric describes the asymptotic form of a radiating solution of Einstein's equations. The total gravitational energy for this solution can be calculated by means of pseudo-tensors in the static case. In the nonstatic case, Bondi defines the {\it mass aspect} $m(u)$, which describes the mass of an isolated system. In this paper we express Bondi's solution in asymptotically spherical 3+1 coordinates, not in radiation coordinates, and obtain Bondi's energy in the static limit by means of the expression for the gravitational energy in the framework of the TEGR. We can either obtain the total energy or the energy inside a large (but finite) portion of the three-dimensional spacelike hypersurface, whose boundary is far away from the source. The relationship of the present energy expression with Moller's energy is established. |
gr-qc/0512143 | Ozgur Delice | Ahmet Baykal, Ozgur Delice | Cylindrically Symmetric-Static Brans-Dicke-Maxwell Solutions | 10 pages, latex | null | null | null | gr-qc | null | We present static cylindrically symmetric electrovac solutions in the
framework of the Brans-Dicke theory and show that our solution yields some of
the well-known solutions for special values of the parameters of the resulting
metric functions.
| [
{
"created": "Fri, 23 Dec 2005 14:30:18 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Baykal",
"Ahmet",
""
],
[
"Delice",
"Ozgur",
""
]
] | We present static cylindrically symmetric electrovac solutions in the framework of the Brans-Dicke theory and show that our solution yields some of the well-known solutions for special values of the parameters of the resulting metric functions. |
1511.08752 | Tyson Littenberg | Tyson B. Littenberg, Jonah B. Kanner, Neil J. Cornish, Margaret
Millhouse | Enabling high confidence detections of gravitational-wave bursts | 15 pages, 6 figures, submitted to PRD | Phys. Rev. D 94, 044050 (2016) | 10.1103/PhysRevD.94.044050 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | With the advanced LIGO and Virgo detectors taking observations the detection
of gravitational waves is expected within the next few years. Extracting
astrophysical information from gravitational wave detections is a well-posed
problem and thoroughly studied when detailed models for the waveforms are
available. However, one motivation for the field of gravitational wave
astronomy is the potential for new discoveries. Recognizing and characterizing
unanticipated signals requires data analysis techniques which do not depend on
theoretical predictions for the gravitational waveform. Past searches for
short-duration un-modeled gravitational wave signals have been hampered by
transient noise artifacts, or "glitches," in the detectors. In some cases, even
high signal-to-noise simulated astrophysical signals have proven difficult to
distinguish from glitches, so that essentially any plausible signal could be
detected with at most 2-3 $\sigma$ level confidence. We have put forth the
BayesWave algorithm to differentiate between generic gravitational wave
transients and glitches, and to provide robust waveform reconstruction and
characterization of the astrophysical signals. Here we study BayesWave's
capabilities for rejecting glitches while assigning high confidence to
detection candidates through analytic approximations to the Bayesian evidence.
Analytic results are tested with numerical experiments by adding simulated
gravitational wave transient signals to LIGO data collected between 2009 and
2010 and found to be in good agreement.
| [
{
"created": "Fri, 27 Nov 2015 17:37:20 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Littenberg",
"Tyson B.",
""
],
[
"Kanner",
"Jonah B.",
""
],
[
"Cornish",
"Neil J.",
""
],
[
"Millhouse",
"Margaret",
""
]
] | With the advanced LIGO and Virgo detectors taking observations the detection of gravitational waves is expected within the next few years. Extracting astrophysical information from gravitational wave detections is a well-posed problem and thoroughly studied when detailed models for the waveforms are available. However, one motivation for the field of gravitational wave astronomy is the potential for new discoveries. Recognizing and characterizing unanticipated signals requires data analysis techniques which do not depend on theoretical predictions for the gravitational waveform. Past searches for short-duration un-modeled gravitational wave signals have been hampered by transient noise artifacts, or "glitches," in the detectors. In some cases, even high signal-to-noise simulated astrophysical signals have proven difficult to distinguish from glitches, so that essentially any plausible signal could be detected with at most 2-3 $\sigma$ level confidence. We have put forth the BayesWave algorithm to differentiate between generic gravitational wave transients and glitches, and to provide robust waveform reconstruction and characterization of the astrophysical signals. Here we study BayesWave's capabilities for rejecting glitches while assigning high confidence to detection candidates through analytic approximations to the Bayesian evidence. Analytic results are tested with numerical experiments by adding simulated gravitational wave transient signals to LIGO data collected between 2009 and 2010 and found to be in good agreement. |
1602.00599 | Tanja Hinderer | Tanja Hinderer, Andrea Taracchini, Francois Foucart, Alessandra
Buonanno, Jan Steinhoff, Matthew Duez, Lawrence E. Kidder, Harald P.
Pfeiffer, Mark A. Scheel, Bela Szilagyi, Kenta Hotokezaka, Koutarou Kyutoku,
Masaru Shibata, Cory W. Carpenter | Effects of neutron-star dynamic tides on gravitational waveforms within
the effective-one-body approach | null | Phys. Rev. Lett. 116, 181101 (2016) | 10.1103/PhysRevLett.116.181101 | null | gr-qc astro-ph.HE astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Extracting the unique information on ultradense nuclear matter from the
gravitational waves emitted by merging, neutron-star binaries requires robust
theoretical models of the signal. We develop a novel effective-one-body
waveform model that includes, for the first time, dynamic (instead of only
adiabatic) tides of the neutron star, as well as the merger signal for
neutron-star--black-hole binaries. We demonstrate the importance of the dynamic
tides by comparing our model against new numerical-relativity simulations of
nonspinning neutron-star--black-hole binaries spanning more than 24
gravitational-wave cycles, and to other existing numerical simulations for
double neutron-star systems. Furthermore, we derive an effective description
that makes explicit the dependence of matter effects on two key parameters:
tidal deformability and fundamental oscillation frequency.
| [
{
"created": "Mon, 1 Feb 2016 17:16:14 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Mar 2016 17:15:52 GMT",
"version": "v2"
},
{
"created": "Mon, 9 May 2016 15:16:37 GMT",
"version": "v3"
}
] | 2016-05-11 | [
[
"Hinderer",
"Tanja",
""
],
[
"Taracchini",
"Andrea",
""
],
[
"Foucart",
"Francois",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Steinhoff",
"Jan",
""
],
[
"Duez",
"Matthew",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Scheel",
"Mark A.",
""
],
[
"Szilagyi",
"Bela",
""
],
[
"Hotokezaka",
"Kenta",
""
],
[
"Kyutoku",
"Koutarou",
""
],
[
"Shibata",
"Masaru",
""
],
[
"Carpenter",
"Cory W.",
""
]
] | Extracting the unique information on ultradense nuclear matter from the gravitational waves emitted by merging, neutron-star binaries requires robust theoretical models of the signal. We develop a novel effective-one-body waveform model that includes, for the first time, dynamic (instead of only adiabatic) tides of the neutron star, as well as the merger signal for neutron-star--black-hole binaries. We demonstrate the importance of the dynamic tides by comparing our model against new numerical-relativity simulations of nonspinning neutron-star--black-hole binaries spanning more than 24 gravitational-wave cycles, and to other existing numerical simulations for double neutron-star systems. Furthermore, we derive an effective description that makes explicit the dependence of matter effects on two key parameters: tidal deformability and fundamental oscillation frequency. |
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