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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/0604087 | Luca Lusanna | Luca Lusanna (INFN, Firenze) and Massimo Pauri (Parma Univ. and INFN,
Parma) | Explaining Leibniz-equivalence as difference of non-inertial
appearances: dis-solution of the Hole Argument and physical individuation of
point-events | 37 pages, talk at Oxford Conference on Spacetime (2004), to appear in
Studies in History and Philosophy of Modern Physics. Affiliations Corrected | null | null | null | gr-qc astro-ph hep-th | null | "The last remnant of physical objectivity of space-time" is disclosed in the
case of a continuous family of spatially non-compact models of general
relativity (GR). The {\it physical individuation} of point-events is furnished
by the intrinsic degrees of freedom of the gravitational field, (viz, the {\it
Dirac observables}) that represent - as it were - the {\it ontic} part of the
metric field. The physical role of the {\it epistemic} part (viz. the {\it
gauge} variables) is likewise clarified as emboding the unavoidable
non-inertial aspects of GR. At the end the philosophical import of the {\it
Hole Argument} is substantially weakened and in fact the Argument itself
dis-solved, while a specific four-dimensional {\it holistic and structuralist}
view of space-time, (called {\it point-structuralism}), emerges, including
elements common to the tradition of both {\it substantivalism} and {\it
relationism}. The observables of our models undergo real {\it temporal change}:
this gives new evidence to the fact that statements like the {\it frozen-time}
character of evolution, as other ontological claims about GR, are {\it model
dependent}. \medskip Forthcoming in Studies in History and Philosophy of Modern
Physics
| [
{
"created": "Thu, 20 Apr 2006 16:59:14 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Apr 2006 16:21:41 GMT",
"version": "v2"
},
{
"created": "Thu, 8 Feb 2007 16:29:28 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Lusanna",
"Luca",
"",
"INFN, Firenze"
],
[
"Pauri",
"Massimo",
"",
"Parma Univ. and INFN,\n Parma"
]
] | "The last remnant of physical objectivity of space-time" is disclosed in the case of a continuous family of spatially non-compact models of general relativity (GR). The {\it physical individuation} of point-events is furnished by the intrinsic degrees of freedom of the gravitational field, (viz, the {\it Dirac observables}) that represent - as it were - the {\it ontic} part of the metric field. The physical role of the {\it epistemic} part (viz. the {\it gauge} variables) is likewise clarified as emboding the unavoidable non-inertial aspects of GR. At the end the philosophical import of the {\it Hole Argument} is substantially weakened and in fact the Argument itself dis-solved, while a specific four-dimensional {\it holistic and structuralist} view of space-time, (called {\it point-structuralism}), emerges, including elements common to the tradition of both {\it substantivalism} and {\it relationism}. The observables of our models undergo real {\it temporal change}: this gives new evidence to the fact that statements like the {\it frozen-time} character of evolution, as other ontological claims about GR, are {\it model dependent}. \medskip Forthcoming in Studies in History and Philosophy of Modern Physics |
2005.14141 | Leonid Perlov | Leonid Perlov | Barbero-Immirzi Value from Experiment | null | Modern Physics Letters A 2021 | 10.1142/S0217732321501923 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider General Relativity as a limit case of the Scalar-Tensor theory
with Barbero-Immirzi field when the field tends to a constant. We use Shapiro
time delay experimental limit of $1/w = (2.1 \pm 2.3)10^{-5}$ provided by the
Cassini spacecraft to find the Barbero-Immirzi parameter value.
| [
{
"created": "Thu, 28 May 2020 16:47:43 GMT",
"version": "v1"
},
{
"created": "Sun, 7 Jun 2020 18:42:35 GMT",
"version": "v2"
},
{
"created": "Fri, 10 Jul 2020 04:39:23 GMT",
"version": "v3"
},
{
"created": "Mon, 26 Oct 2020 19:14:31 GMT",
"version": "v4"
},
{
"cr... | 2021-09-03 | [
[
"Perlov",
"Leonid",
""
]
] | We consider General Relativity as a limit case of the Scalar-Tensor theory with Barbero-Immirzi field when the field tends to a constant. We use Shapiro time delay experimental limit of $1/w = (2.1 \pm 2.3)10^{-5}$ provided by the Cassini spacecraft to find the Barbero-Immirzi parameter value. |
0711.4674 | Romesh K. Kaul | Romesh K. Kaul | Holst Actions for Supergravity Theories | 15 pages | Phys.Rev.D77:045030,2008 | 10.1103/PhysRevD.77.045030 | null | gr-qc hep-th | null | Holst action containing Immirzi parameter for pure gravity is generalised to
the supergravity theories. Supergravity equations of motion are not modified by
such generalisations, thus preserving supersymmetry. Dependence on the Immirzi
parameter does not emerge in the classical equations of motion. This is in
contrast with the recent observation of Perez and Rovelli for gravity action
containing original Holst term and a minimally coupled Dirac fermion where the
classical equations of motion do develop a dependence on Immirzi parameter.
| [
{
"created": "Thu, 29 Nov 2007 09:26:22 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kaul",
"Romesh K.",
""
]
] | Holst action containing Immirzi parameter for pure gravity is generalised to the supergravity theories. Supergravity equations of motion are not modified by such generalisations, thus preserving supersymmetry. Dependence on the Immirzi parameter does not emerge in the classical equations of motion. This is in contrast with the recent observation of Perez and Rovelli for gravity action containing original Holst term and a minimally coupled Dirac fermion where the classical equations of motion do develop a dependence on Immirzi parameter. |
1203.6444 | Cesar S. Lopez-Monsalvo | C. S. Lopez-Monsalvo, F. Nettel, A. Sanchez | Comment on "Geometrothermodynamics of a Charged Black Hole of String
Theory" | Comment on arXiv:1012.2070 | Brazilian Journal of Physics, 2012 | 10.1007/s13538-012-0090-1 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We comment on the conclusions found by Larra\~naga and Mojica regarding the
consistency of the Geoemtrothermodynamics programme to describe the critical
behaviour of a Gibbons-Maeda-Garfinkle-Horowitz-Strominger charged black hole.
We argue that making the appropriate choice of metric for the thermodynamic
phase space and, most importantly, considering the homogeneity of the
thermodynamic potential we obtain consistent results for such a black hole.
| [
{
"created": "Thu, 29 Mar 2012 06:50:25 GMT",
"version": "v1"
}
] | 2013-09-05 | [
[
"Lopez-Monsalvo",
"C. S.",
""
],
[
"Nettel",
"F.",
""
],
[
"Sanchez",
"A.",
""
]
] | We comment on the conclusions found by Larra\~naga and Mojica regarding the consistency of the Geoemtrothermodynamics programme to describe the critical behaviour of a Gibbons-Maeda-Garfinkle-Horowitz-Strominger charged black hole. We argue that making the appropriate choice of metric for the thermodynamic phase space and, most importantly, considering the homogeneity of the thermodynamic potential we obtain consistent results for such a black hole. |
2109.08463 | Tao Wang | Yanni Zhu, Towe Wang | Shadow of the wormholelike static aether solution | 11 pages, 4 figures, match the version published in PRD | null | 10.1103/PhysRevD.104.104052 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently, an analytical solution in Einstein-aether theory was presented
explicitly in isotropic coordinates. It is characterized by a mass parameter
$m$ and a combined coupling constant $c_{14}$. By a coordinate transformation,
we verify this solution is equivalent to the previously known static aether
solution. Assuming photons couple minimally to aether and gravity, we
investigate the photon sphere and shadow of the solution by varying $c_{14}$.
Results are compared with those of the Schwarzschild black hole.
| [
{
"created": "Fri, 17 Sep 2021 10:56:28 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Nov 2021 17:09:06 GMT",
"version": "v2"
}
] | 2021-12-01 | [
[
"Zhu",
"Yanni",
""
],
[
"Wang",
"Towe",
""
]
] | Recently, an analytical solution in Einstein-aether theory was presented explicitly in isotropic coordinates. It is characterized by a mass parameter $m$ and a combined coupling constant $c_{14}$. By a coordinate transformation, we verify this solution is equivalent to the previously known static aether solution. Assuming photons couple minimally to aether and gravity, we investigate the photon sphere and shadow of the solution by varying $c_{14}$. Results are compared with those of the Schwarzschild black hole. |
0811.1870 | Valerio Faraoni | Valerio Faraoni (Bishop's University) | Extension of the EGS theorem to metric and Palatini f(R) gravity | 10 pages, latex. Contribution to the anniversary volume "Problems of
Modern Cosmology" in honour of Prof. S.D. Odintsov to be published by Tomsk
University | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By using the equivalence between metric and Palatini f(R) (or "modified")
gravities with omega=0, -3/2 Brans-Dicke theories, it is shown that the
Ehlers-Geren-Sachs theorem of general relativity is extended to modified
gravity. In the case of metric f(R) gravity previously studied, this agrees
with previous literature.
| [
{
"created": "Wed, 12 Nov 2008 11:38:54 GMT",
"version": "v1"
}
] | 2008-11-13 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
]
] | By using the equivalence between metric and Palatini f(R) (or "modified") gravities with omega=0, -3/2 Brans-Dicke theories, it is shown that the Ehlers-Geren-Sachs theorem of general relativity is extended to modified gravity. In the case of metric f(R) gravity previously studied, this agrees with previous literature. |
1505.03770 | Thomas B\"ackdahl | Thomas B\"ackdahl and Juan A. Valiente Kroon | A formalism for the calculus of variations with spinors | 18 pages. Added diffeomorphism dependence | J. Math. Phys. 57, 022502 (2016) | 10.1063/1.4939562 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a frame and dyad gauge-independent formalism for the calculus of
variations of functionals involving spinorial objects. As part of this
formalism we define a modified variation operator which absorbs frame and spin
dyad gauge terms. This formalism is applicable to both the standard spacetime
(i.e. SL(2,C)) 2-spinors as well as to space (i.e. SU(2,C)) 2-spinors. We
compute expressions for the variations of the connection and the curvature
spinors.
| [
{
"created": "Thu, 14 May 2015 15:57:22 GMT",
"version": "v1"
},
{
"created": "Fri, 22 May 2015 15:07:04 GMT",
"version": "v2"
}
] | 2016-01-14 | [
[
"Bäckdahl",
"Thomas",
""
],
[
"Kroon",
"Juan A. Valiente",
""
]
] | We develop a frame and dyad gauge-independent formalism for the calculus of variations of functionals involving spinorial objects. As part of this formalism we define a modified variation operator which absorbs frame and spin dyad gauge terms. This formalism is applicable to both the standard spacetime (i.e. SL(2,C)) 2-spinors as well as to space (i.e. SU(2,C)) 2-spinors. We compute expressions for the variations of the connection and the curvature spinors. |
1810.09222 | Gulira Tuleganova | Alina Khaybullina, Gulira Tuleganova | Stability of Schwarzschild-$f(R)$ gravity thin-shell wormholes | 10 pages, 5 figures | null | 10.1142/S0217732319500068 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Mazharimousavi and Halilsoy [1] recently proposed wormhole solutions in
$f(R)$-gravity that satisfy energy conditions but are unstable. We show here
that stability could still be achieved for thin-shell wormholes obtained by
gluing the wormholes in $f(R)$-gravity with the exterior Schwarzschild vacuum.
Using the new geometrical constraints from thin-shell "mass" and from external
"force" developed by Garcia, Lobo and Visser, we demarcate and analyze the
stability regions.
| [
{
"created": "Mon, 22 Oct 2018 12:47:57 GMT",
"version": "v1"
}
] | 2019-02-20 | [
[
"Khaybullina",
"Alina",
""
],
[
"Tuleganova",
"Gulira",
""
]
] | Mazharimousavi and Halilsoy [1] recently proposed wormhole solutions in $f(R)$-gravity that satisfy energy conditions but are unstable. We show here that stability could still be achieved for thin-shell wormholes obtained by gluing the wormholes in $f(R)$-gravity with the exterior Schwarzschild vacuum. Using the new geometrical constraints from thin-shell "mass" and from external "force" developed by Garcia, Lobo and Visser, we demarcate and analyze the stability regions. |
1602.02453 | Nathan Johnson-McDaniel | Abhirup Ghosh, Archisman Ghosh, Nathan K. Johnson-McDaniel, Chandra
Kant Mishra, Parameswaran Ajith, Walter Del Pozzo, David A. Nichols, Yanbei
Chen, Alex B. Nielsen, Christopher P. L. Berry, Lionel London | Testing general relativity using golden black-hole binaries | 5 pages, 2 figs | Phys. Rev. D 94, 021101(R) (2016) | 10.1103/PhysRevD.94.021101 | LIGO-P1500185-v11, ICTS/2016/1 | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The coalescences of stellar-mass black-hole binaries through their inspiral,
merger, and ringdown are among the most promising sources for ground-based
gravitational-wave (GW) detectors. If a GW signal is observed with sufficient
signal-to-noise ratio, the masses and spins of the black holes can be estimated
from just the inspiral part of the signal. Using these estimates of the initial
parameters of the binary, the mass and spin of the final black hole can be
uniquely predicted making use of general-relativistic numerical simulations. In
addition, the mass and spin of the final black hole can be independently
estimated from the merger--ringdown part of the signal. If the binary black
hole dynamics is correctly described by general relativity (GR), these
independent estimates have to be consistent with each other. We present a
Bayesian implementation of such a test of general relativity, which allows us
to combine the constraints from multiple observations. Using kludge modified GR
waveforms, we demonstrate that this test can detect sufficiently large
deviations from GR, and outline the expected constraints from upcoming GW
observations using the second-generation of ground-based GW detectors.
| [
{
"created": "Mon, 8 Feb 2016 02:57:56 GMT",
"version": "v1"
},
{
"created": "Wed, 14 Sep 2016 08:32:59 GMT",
"version": "v2"
}
] | 2016-09-15 | [
[
"Ghosh",
"Abhirup",
""
],
[
"Ghosh",
"Archisman",
""
],
[
"Johnson-McDaniel",
"Nathan K.",
""
],
[
"Mishra",
"Chandra Kant",
""
],
[
"Ajith",
"Parameswaran",
""
],
[
"Del Pozzo",
"Walter",
""
],
[
"Nichols",
"D... | The coalescences of stellar-mass black-hole binaries through their inspiral, merger, and ringdown are among the most promising sources for ground-based gravitational-wave (GW) detectors. If a GW signal is observed with sufficient signal-to-noise ratio, the masses and spins of the black holes can be estimated from just the inspiral part of the signal. Using these estimates of the initial parameters of the binary, the mass and spin of the final black hole can be uniquely predicted making use of general-relativistic numerical simulations. In addition, the mass and spin of the final black hole can be independently estimated from the merger--ringdown part of the signal. If the binary black hole dynamics is correctly described by general relativity (GR), these independent estimates have to be consistent with each other. We present a Bayesian implementation of such a test of general relativity, which allows us to combine the constraints from multiple observations. Using kludge modified GR waveforms, we demonstrate that this test can detect sufficiently large deviations from GR, and outline the expected constraints from upcoming GW observations using the second-generation of ground-based GW detectors. |
gr-qc/9504006 | Guillermo Mena | Guillermo A. Mena Marugan | CANONICAL QUANTIZATION OF CYLINDRICALLY SYMMETRIC MODELS | 18 pages, latex, no figures | Phys.Rev.D53:3156-3161,1996 | 10.1103/PhysRevD.53.3156 | null | gr-qc | null | We carry out the canonical quantization of the Levi-Civit\`a family of static
and cylindrical solutions. The reduced phase space of this family of metrics is
proved to coincide with that corresponding to the Kasner model, including the
associated symplectic structures, except for that the respective domains of
definition of one of the phase space variables are not identical. Using this
result, we are able to construct a quantum model that describes spacetimes of
both the Levi-Civit\`a and the Kasner type, and in which the three-dimensional
spatial topology is not uniquely fixed. Finally, we quantize to completion the
subfamily of Levi-Civit\`a solutions which represent the exterior gravitational
field of a straight cosmic string. These solutions are conical geometries,ie,
Minkowski spacetime minus a wedge. The quantum theory obtained provides us with
predictions about the angular size of this wedge.
| [
{
"created": "Wed, 5 Apr 1995 14:00:19 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Marugan",
"Guillermo A. Mena",
""
]
] | We carry out the canonical quantization of the Levi-Civit\`a family of static and cylindrical solutions. The reduced phase space of this family of metrics is proved to coincide with that corresponding to the Kasner model, including the associated symplectic structures, except for that the respective domains of definition of one of the phase space variables are not identical. Using this result, we are able to construct a quantum model that describes spacetimes of both the Levi-Civit\`a and the Kasner type, and in which the three-dimensional spatial topology is not uniquely fixed. Finally, we quantize to completion the subfamily of Levi-Civit\`a solutions which represent the exterior gravitational field of a straight cosmic string. These solutions are conical geometries,ie, Minkowski spacetime minus a wedge. The quantum theory obtained provides us with predictions about the angular size of this wedge. |
1504.05774 | James M. Overduin | James M. Overduin | Spacetime, Spin and Gravity Probe B | To appear in a special issue of Classical and Quantum Gravity devoted
to the GP-B experiment. 13 pages, 1 figure | null | 10.1088/0264-9381/32/22/224003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is more important than ever to push experimental tests of gravitational
theory to the limits of existing technology in both range and sensitivity. This
brief review focuses on spin-based tests of General Relativity and their
implications for alternative, mostly non-metric theories of gravity motivated
by the challenge of unification with the Standard Model of particle physics.
The successful detection of geodetic precession and frame-dragging by Gravity
Probe B places new constraints on a number of these theories, and increases our
confidence in the theoretical mechanisms underpinning current ideas in
astrophysics and cosmology.
| [
{
"created": "Wed, 22 Apr 2015 13:00:14 GMT",
"version": "v1"
}
] | 2015-12-09 | [
[
"Overduin",
"James M.",
""
]
] | It is more important than ever to push experimental tests of gravitational theory to the limits of existing technology in both range and sensitivity. This brief review focuses on spin-based tests of General Relativity and their implications for alternative, mostly non-metric theories of gravity motivated by the challenge of unification with the Standard Model of particle physics. The successful detection of geodetic precession and frame-dragging by Gravity Probe B places new constraints on a number of these theories, and increases our confidence in the theoretical mechanisms underpinning current ideas in astrophysics and cosmology. |
2006.12267 | Ranjan Sharma | Ranjan Sharma, Shyam Das, Megan Govender and Dishant M. Pandya | Revisiting Vaidya-Tikekar stellar model in the linear regime | null | Annals of Physics 414 (2020) 168079 | 10.1016/j.aop.2020.168079 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain a new class of solutions by revisiting the Vaidya-Tikekar stellar
model in the linear regime. Making use of the Vaidya and Tikekar metric ansatz
[J. Astrophys. Astron. {\bf3} (1982) 325] describing the spacetime of static
spherically symmetric relativistic star composed of an anisotropic matter
distribution admitting a linear EOS, we solve the Einstein field equations and
subsequently analyze physical viability of the solution. We probe the impact of
the curvature parameter $K$ of the Vaidya-Tikekar model, which characterizes a
departure from homogeneous spherical distribution, on the mass-radius
relationship of the star. In the context of density-dependent MIT Bag models,
we show a correlation between the curvature parameter, the bag constant and
total mass and radius of some of the well-known pulsars viz., 4U 1820-30, RX
J1856-37, SAXJ 1808.4 and Her X-1. We explore the possibility of fine-tuning
these parameters based on current observational data.
| [
{
"created": "Fri, 19 Jun 2020 05:33:46 GMT",
"version": "v1"
},
{
"created": "Tue, 23 Jun 2020 16:36:30 GMT",
"version": "v2"
}
] | 2020-07-01 | [
[
"Sharma",
"Ranjan",
""
],
[
"Das",
"Shyam",
""
],
[
"Govender",
"Megan",
""
],
[
"Pandya",
"Dishant M.",
""
]
] | We obtain a new class of solutions by revisiting the Vaidya-Tikekar stellar model in the linear regime. Making use of the Vaidya and Tikekar metric ansatz [J. Astrophys. Astron. {\bf3} (1982) 325] describing the spacetime of static spherically symmetric relativistic star composed of an anisotropic matter distribution admitting a linear EOS, we solve the Einstein field equations and subsequently analyze physical viability of the solution. We probe the impact of the curvature parameter $K$ of the Vaidya-Tikekar model, which characterizes a departure from homogeneous spherical distribution, on the mass-radius relationship of the star. In the context of density-dependent MIT Bag models, we show a correlation between the curvature parameter, the bag constant and total mass and radius of some of the well-known pulsars viz., 4U 1820-30, RX J1856-37, SAXJ 1808.4 and Her X-1. We explore the possibility of fine-tuning these parameters based on current observational data. |
0910.1252 | Matthew Corne | Matthew Corne, Arkady Kheyfets, Jennifer Piasio, Chad Voegele | Binding in charged spherically symmetric objects | 11 pages, no figures | Int.J.Theor.Phys.50:2737-2747,2011 | 10.1007/s10773-011-0773-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the subject of self--binding in static, spherically symmetric
objects consisting of a charged fluid. We have shown previously that in the
case of a perfect fluid, only the localized part of the mass contributes to
gravitational self--binding of such objects and that in the limiting case of
objects comprised purely of electromagnetic mass, there is no gravitational
binding. Here, we extend this result to the more general case of an anisotropic
fluid. Our inspection of the Oppenheimer--Volkov equation allows tracking of
both gravitational and non-gravitational contributions to binding of
spherically symmetric objects and shows that those with pure electromagnetic
mass cannot exist.
| [
{
"created": "Wed, 7 Oct 2009 13:16:39 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Mar 2010 18:22:10 GMT",
"version": "v2"
},
{
"created": "Thu, 14 Oct 2010 01:43:13 GMT",
"version": "v3"
}
] | 2011-07-15 | [
[
"Corne",
"Matthew",
""
],
[
"Kheyfets",
"Arkady",
""
],
[
"Piasio",
"Jennifer",
""
],
[
"Voegele",
"Chad",
""
]
] | We consider the subject of self--binding in static, spherically symmetric objects consisting of a charged fluid. We have shown previously that in the case of a perfect fluid, only the localized part of the mass contributes to gravitational self--binding of such objects and that in the limiting case of objects comprised purely of electromagnetic mass, there is no gravitational binding. Here, we extend this result to the more general case of an anisotropic fluid. Our inspection of the Oppenheimer--Volkov equation allows tracking of both gravitational and non-gravitational contributions to binding of spherically symmetric objects and shows that those with pure electromagnetic mass cannot exist. |
gr-qc/9412046 | Franz Schunck | Fjodor V.~Kusmartsev, Eckehard W.~Mielke, Yuri N.~Obukhov, and Franz
E.~Schunck | Classification of Inflationary Einstein--Scalar--Field--Models via
Catastrophe Theory | 12 pages, REVTeX, no figures | Phys.Rev. D51 (1995) 924-927 | 10.1103/PhysRevD.51.924 | Cologne-thp-1994-H6 | gr-qc | null | Various scenarios of the initial inflation of the universe are distinguished
by the choice of a scalar field {\em potential} $U(\phi)$ which simulates a
{\it temporarily} non--vanishing {\em cosmological term}. Our new method, which
involves a reparametrization in terms of the Hubble expansion parameter $H$,
provides a classification of allowed inflationary potentials and of the
stability of the critical points. It is broad enough to embody all known {\it
exact} solutions involving one scalar field as special cases. Inflation
corresponds to the evolution of critical points of some catastrophe manifold.
The coalescence of its nondegenerate critical points with the creation of a
degenerate critical point corresponds the reheating phase of the universe. This
is illustrated by several examples.
| [
{
"created": "Fri, 16 Dec 1994 21:51:41 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"~Kusmartsev",
"Fjodor V.",
""
],
[
"~Mielke",
"Eckehard W.",
""
],
[
"~Obukhov",
"Yuri N.",
""
],
[
"~Schunck",
"Franz E.",
""
]
] | Various scenarios of the initial inflation of the universe are distinguished by the choice of a scalar field {\em potential} $U(\phi)$ which simulates a {\it temporarily} non--vanishing {\em cosmological term}. Our new method, which involves a reparametrization in terms of the Hubble expansion parameter $H$, provides a classification of allowed inflationary potentials and of the stability of the critical points. It is broad enough to embody all known {\it exact} solutions involving one scalar field as special cases. Inflation corresponds to the evolution of critical points of some catastrophe manifold. The coalescence of its nondegenerate critical points with the creation of a degenerate critical point corresponds the reheating phase of the universe. This is illustrated by several examples. |
gr-qc/9801007 | Philippe Droz-Vincent | Ph. Droz-Vincent (Universite P. et M. Curie, Paris) | Invariance of Positive-Frequency Kernels in Generalized FRW Spacetimes | 25 pages. Plain TeX file | null | null | GCR 97/12/06 | gr-qc hep-th math-ph math.MP | null | We consider the Klein-Gordon equation in FRW-like spacetimes, with compact
space sections (not necessarily isotropic neither homogeneous). The bi-scalar
kernel allowing to select the positive-frequency part of any solution is
developed on mode solutions, using the eigenfunctions of the three-dimensional
Laplacian. Of course this kernel is not unique but, except (perhaps) when the
scale factor undergoes a special law of evolution, the metric has no more
symmetries (connected with the identity) than those inherited from the space
sections. As a result, all admissible definitions of the positive-frequency
kernel are related one to another by a unitary transformation which commutes
with the connected isometries of spacetime; any such kernel is invariant under
these isometries isometries. A physical interpretation is tentatively
suggested.
| [
{
"created": "Mon, 5 Jan 1998 16:15:49 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Droz-Vincent",
"Ph.",
"",
"Universite P. et M. Curie, Paris"
]
] | We consider the Klein-Gordon equation in FRW-like spacetimes, with compact space sections (not necessarily isotropic neither homogeneous). The bi-scalar kernel allowing to select the positive-frequency part of any solution is developed on mode solutions, using the eigenfunctions of the three-dimensional Laplacian. Of course this kernel is not unique but, except (perhaps) when the scale factor undergoes a special law of evolution, the metric has no more symmetries (connected with the identity) than those inherited from the space sections. As a result, all admissible definitions of the positive-frequency kernel are related one to another by a unitary transformation which commutes with the connected isometries of spacetime; any such kernel is invariant under these isometries isometries. A physical interpretation is tentatively suggested. |
1403.6396 | Jaume Amor\'os | Jaume de Haro, Jaume Amor\'os | Viability of the matter bounce scenario in Loop Quantum Cosmology from
BICEP2 last data | 3 figures. New section added to further justify power spectrum
computations. Numerical results more thoroughly explained | JCAP08(2014)025 | 10.1088/1475-7516/2014/08/025 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The CMB map provided by the Planck project constrains the value of the ratio
of tensor-to-scalar perturbations, namely $r$, to be smaller than $0.11$ (95%
CL). This bound rules out the simplest models of inflation. However, recent
data from BICEP2 is in strong tension with this constrain, as it finds a value
$r=0.20^{+0.07}_{-0.05}$ with $r=0$ disfavored at $7.0 \sigma$, which allows
these simplest inflationary models to survive. The remarkable fact is that,
even though the BICEP2 experiment was conceived to search for evidence of
inflation, its experimental data matches correctly theoretical results coming
from the matter bounce scenario (the alternative model to the inflationary
paradigm). More precisely, most bouncing cosmologies do not pass Planck's
constrains due to the smallness of the value of the tensor/scalar ratio $r\leq
0.11$, but with new BICEP2 data some of them fit well with experimental data.
This is the case with the matter bounce scenario in the teleparallel version of
Loop Quantum Cosmology.
| [
{
"created": "Tue, 25 Mar 2014 15:43:33 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Mar 2014 18:12:44 GMT",
"version": "v2"
},
{
"created": "Wed, 2 Jul 2014 17:02:12 GMT",
"version": "v3"
}
] | 2014-08-14 | [
[
"de Haro",
"Jaume",
""
],
[
"Amorós",
"Jaume",
""
]
] | The CMB map provided by the Planck project constrains the value of the ratio of tensor-to-scalar perturbations, namely $r$, to be smaller than $0.11$ (95% CL). This bound rules out the simplest models of inflation. However, recent data from BICEP2 is in strong tension with this constrain, as it finds a value $r=0.20^{+0.07}_{-0.05}$ with $r=0$ disfavored at $7.0 \sigma$, which allows these simplest inflationary models to survive. The remarkable fact is that, even though the BICEP2 experiment was conceived to search for evidence of inflation, its experimental data matches correctly theoretical results coming from the matter bounce scenario (the alternative model to the inflationary paradigm). More precisely, most bouncing cosmologies do not pass Planck's constrains due to the smallness of the value of the tensor/scalar ratio $r\leq 0.11$, but with new BICEP2 data some of them fit well with experimental data. This is the case with the matter bounce scenario in the teleparallel version of Loop Quantum Cosmology. |
0811.0232 | Maurice H. P. M. van Putten | Maurice H.P.M. van Putten | Hyperbolic Hamiltonian equations for general relativity | Based on an invited talk at the Federation Denis Poisson (October
2008) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The 3+1 Hamiltonian formulation in the gauge $D_tN=-K$ on the lapse function
fixes the direction of time associated with the trace $K$ of the extrinsic
curvature tensor. The Hamiltonian equations hereby become hyperbolic. We study
this new system for black hole spacetimes that are asymptotically quiescent,
which introduces analyticity properties that can be exploited for numerical
calculations by compactification in spherical coordinates with complex radius
following a M\"obius transformation. Conformal flat initial data of two black
holes are hereby invariant, and correspond to a turn point in a pendulum, up
for a pair of separated black holes and down for a single black hole. Here,
Newton's law appears in the relaxation of $l=2$ deformations of semi-infinite
poloidal surface elements, defined by the moment of inertia of the binary.
| [
{
"created": "Mon, 3 Nov 2008 07:25:21 GMT",
"version": "v1"
}
] | 2008-11-04 | [
[
"van Putten",
"Maurice H. P. M.",
""
]
] | The 3+1 Hamiltonian formulation in the gauge $D_tN=-K$ on the lapse function fixes the direction of time associated with the trace $K$ of the extrinsic curvature tensor. The Hamiltonian equations hereby become hyperbolic. We study this new system for black hole spacetimes that are asymptotically quiescent, which introduces analyticity properties that can be exploited for numerical calculations by compactification in spherical coordinates with complex radius following a M\"obius transformation. Conformal flat initial data of two black holes are hereby invariant, and correspond to a turn point in a pendulum, up for a pair of separated black holes and down for a single black hole. Here, Newton's law appears in the relaxation of $l=2$ deformations of semi-infinite poloidal surface elements, defined by the moment of inertia of the binary. |
1512.05358 | Carlos A. R. Herdeiro | Nicolas Sanchis-Gual, Juan Carlos Degollado, Pedro J. Montero, Jos\'e
A. Font, Carlos Herdeiro | Explosion and final state of an unstable Reissner-Nordstrom black hole | 5 pages, 4 figures; v2: 8 pages, including Supplemental Material;
matches published version in Phys. Rev. Lett.; title changed | Phys. Rev. Lett. 116, 141101 (2016) | 10.1103/PhysRevLett.116.141101 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A Reissner-Nordstr\"om black hole (BH) is superradiantly unstable against
spherical perturbations of a charged scalar field, enclosed in a cavity, with
frequency lower than a critical value. We use numerical relativity techniques
to follow the development of this unstable system -- dubbed a charged BH bomb
-- into the non-linear regime, solving the full Einstein--Maxwell--Klein-Gordon
equations, in spherical symmetry. We show that: $i)$ the process stops before
all the charge is extracted from the BH; $ii)$ the system settles down into a
hairy BH: a charged horizon in equilibrium with a scalar field condensate,
whose phase is oscillating at the (final) critical frequency. For low scalar
field charge, $q$, the final state is approached smoothly and monotonically.
For large $q$, however, the energy extraction overshoots and an explosive
phenomenon, akin to a $bosenova$, pushes some energy back into the BH. The
charge extraction, by contrast, does not reverse.
| [
{
"created": "Wed, 16 Dec 2015 21:00:06 GMT",
"version": "v1"
},
{
"created": "Tue, 19 Apr 2016 16:40:25 GMT",
"version": "v2"
}
] | 2016-04-20 | [
[
"Sanchis-Gual",
"Nicolas",
""
],
[
"Degollado",
"Juan Carlos",
""
],
[
"Montero",
"Pedro J.",
""
],
[
"Font",
"José A.",
""
],
[
"Herdeiro",
"Carlos",
""
]
] | A Reissner-Nordstr\"om black hole (BH) is superradiantly unstable against spherical perturbations of a charged scalar field, enclosed in a cavity, with frequency lower than a critical value. We use numerical relativity techniques to follow the development of this unstable system -- dubbed a charged BH bomb -- into the non-linear regime, solving the full Einstein--Maxwell--Klein-Gordon equations, in spherical symmetry. We show that: $i)$ the process stops before all the charge is extracted from the BH; $ii)$ the system settles down into a hairy BH: a charged horizon in equilibrium with a scalar field condensate, whose phase is oscillating at the (final) critical frequency. For low scalar field charge, $q$, the final state is approached smoothly and monotonically. For large $q$, however, the energy extraction overshoots and an explosive phenomenon, akin to a $bosenova$, pushes some energy back into the BH. The charge extraction, by contrast, does not reverse. |
0712.3660 | Matej Pavsic | Matej Pavsic | Towards a New Paradigm: Relativity in Configuration Space | 15 pages; Presented at "Time and Matter 2007", 26-31 August 2007,
Bled, Slovenia | null | null | null | gr-qc | null | We consider the possibility that the basic space of physics is not spacetime,
but configuration space. We illustrate this on the example with a system of
gravitationally interacting point particles. It turns out that such system can
be described by the minimal length action in a multidimensional configuration
space C with a block diagonal metric. Allowing for more general metrics and
curvatures of C, we step beyond the ordinary general relativity in spacetime.
The latter theory is then an approximation to the general relativity in C.
Other sorts of configuration spaces can also be considered, for instance those
associated with extended objects, such as strings and branes. This enables a
deeper understanding of the geometric principle behind string theory, and an
insight on the occurrence of Yang-Mills and gravitational fields at the
`fundamental level'.
| [
{
"created": "Fri, 21 Dec 2007 12:54:18 GMT",
"version": "v1"
}
] | 2007-12-24 | [
[
"Pavsic",
"Matej",
""
]
] | We consider the possibility that the basic space of physics is not spacetime, but configuration space. We illustrate this on the example with a system of gravitationally interacting point particles. It turns out that such system can be described by the minimal length action in a multidimensional configuration space C with a block diagonal metric. Allowing for more general metrics and curvatures of C, we step beyond the ordinary general relativity in spacetime. The latter theory is then an approximation to the general relativity in C. Other sorts of configuration spaces can also be considered, for instance those associated with extended objects, such as strings and branes. This enables a deeper understanding of the geometric principle behind string theory, and an insight on the occurrence of Yang-Mills and gravitational fields at the `fundamental level'. |
2001.07052 | Edward Malec | Wojciech Kulczycki and Edward Malec | General-relativistic rotation laws in fluid tori around spinning black
holes | 6 pages | Phys. Rev. D 101, 084016 (2020) | 10.1103/PhysRevD.101.084016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We obtain rotation laws for axially symmetric, selfgravitating and stationary
fluids around spinning black holes. They reduce --- in the Newtonian limit ---
to monomial rotation curves. For spinless black hole, one obtains in the first
post-Newtonian (1PN) approximation the hitherto known results, that can be
interpreted as the geometric dragging and material antidragging. We find new
1PN effects, that are due to spins of black holes.
| [
{
"created": "Mon, 20 Jan 2020 10:53:07 GMT",
"version": "v1"
}
] | 2020-04-15 | [
[
"Kulczycki",
"Wojciech",
""
],
[
"Malec",
"Edward",
""
]
] | We obtain rotation laws for axially symmetric, selfgravitating and stationary fluids around spinning black holes. They reduce --- in the Newtonian limit --- to monomial rotation curves. For spinless black hole, one obtains in the first post-Newtonian (1PN) approximation the hitherto known results, that can be interpreted as the geometric dragging and material antidragging. We find new 1PN effects, that are due to spins of black holes. |
gr-qc/0110028 | Alan Barnes | Ugur Camci & Alan Barnes | Ricci Collineations in Friedmann-Robertson-Walker Spacetimes | 14 pages, plain TeX, no figures | Class.Quant.Grav. 19 (2002) 393-404 | null | null | gr-qc | null | Ricci collineations and Ricci inheritance collineations of
Friedmann-Robertson-Walker spacetimes are considered. When the Ricci tensor is
non-degenerate, it is shown that the spacetime always admits a fifteen
parameter group of Ricci inheritance collineations; this is the maximal
possible dimension for spacetime manifolds. The general form of the vector
generating the symmetry is exhibited. It is also shown, in the generic case,
that the group of Ricci collineations is six-dimensional and coincides with the
isometry group. In special cases the spacetime may admit either one or four
proper Ricci collineations in addition to the six isometries. These special
cases are classified and the general form of the vector fields generating the
Ricci collineations is exhibited. When the Ricci tensor is degenerate, the
groups of Ricci inheritance collineations and Ricci collineations are
infinite-dimensional. General forms for the generating vectors are obtained.
Similar results are obtained for matter collineations and matter inheritance
collineations.
| [
{
"created": "Thu, 4 Oct 2001 21:15:02 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Camci",
"Ugur",
""
],
[
"Barnes",
"Alan",
""
]
] | Ricci collineations and Ricci inheritance collineations of Friedmann-Robertson-Walker spacetimes are considered. When the Ricci tensor is non-degenerate, it is shown that the spacetime always admits a fifteen parameter group of Ricci inheritance collineations; this is the maximal possible dimension for spacetime manifolds. The general form of the vector generating the symmetry is exhibited. It is also shown, in the generic case, that the group of Ricci collineations is six-dimensional and coincides with the isometry group. In special cases the spacetime may admit either one or four proper Ricci collineations in addition to the six isometries. These special cases are classified and the general form of the vector fields generating the Ricci collineations is exhibited. When the Ricci tensor is degenerate, the groups of Ricci inheritance collineations and Ricci collineations are infinite-dimensional. General forms for the generating vectors are obtained. Similar results are obtained for matter collineations and matter inheritance collineations. |
2202.11259 | Gregory Horndeski | Gregory W. Horndeski | Reformulating Scalar-Tensor Field Theories as Scalar-Scalar Field
Theories Using a Novel Geometry | 53 pages | null | 10.1098/rsta.2021.0183 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper I shall show how the notions of Finsler geometry can be used to
construct a similar geometry using a scalar field, f, on the cotangent bundle
of a differentiable manifold M. This will enable me to use the second vertical
derivatives of f, along with the differential of a scalar field phi on M, to
construct a Lorentzian metric on M that depends upon phi. I refer to a field
theory based upon a manifold with such a Lorentzian structure as a
scalar-scalar field theory. We shall study such a field theory when f is chosen
so that the resultant metric on M has the form of a
Friedmann-Lemaitre-Robertson-Walker metric, and the Lagrangian has a
particularly simple form. It will be shown that the scalar-scalar theory
determined by this Lagrangian can generate self-inflating universes, which can
be pieced together to form multiverses with non-Hausdorff topologies, in which
the global time function multifurcates at t=0. Some of the universes in these
multiverses begin explosively, and then settle down to a period of much quieter
accelerated expansion, which can be followed by a collapse to its original
pre-expansion state. I conclude the paper with a discussion of how
probabilities can be assigned to the various universes of a multiverse. This is
accomplished by using the action of the universes, with universes having action
closer to zero being more likely than universes with large positive values for
their action. In order to assure that universe models similar to our own
universe are likely to exist I found it necessary to introduce a second scalar
field on M, and to modify the original Lagrangian. In the end my theory has
three scalar fields, two on the manifold M and one on the cotangent bundle of
M.
| [
{
"created": "Wed, 23 Feb 2022 01:24:51 GMT",
"version": "v1"
}
] | 2022-03-23 | [
[
"Horndeski",
"Gregory W.",
""
]
] | In this paper I shall show how the notions of Finsler geometry can be used to construct a similar geometry using a scalar field, f, on the cotangent bundle of a differentiable manifold M. This will enable me to use the second vertical derivatives of f, along with the differential of a scalar field phi on M, to construct a Lorentzian metric on M that depends upon phi. I refer to a field theory based upon a manifold with such a Lorentzian structure as a scalar-scalar field theory. We shall study such a field theory when f is chosen so that the resultant metric on M has the form of a Friedmann-Lemaitre-Robertson-Walker metric, and the Lagrangian has a particularly simple form. It will be shown that the scalar-scalar theory determined by this Lagrangian can generate self-inflating universes, which can be pieced together to form multiverses with non-Hausdorff topologies, in which the global time function multifurcates at t=0. Some of the universes in these multiverses begin explosively, and then settle down to a period of much quieter accelerated expansion, which can be followed by a collapse to its original pre-expansion state. I conclude the paper with a discussion of how probabilities can be assigned to the various universes of a multiverse. This is accomplished by using the action of the universes, with universes having action closer to zero being more likely than universes with large positive values for their action. In order to assure that universe models similar to our own universe are likely to exist I found it necessary to introduce a second scalar field on M, and to modify the original Lagrangian. In the end my theory has three scalar fields, two on the manifold M and one on the cotangent bundle of M. |
1205.5386 | Luca Fabbri | Luca Fabbri | Conformal Gravity with Electrodynamics for Fermion Fields and their
Symmetry Breaking Mechanism | 13 pages | Int.J.Geom.Meth.Mod.Phys.11,1450019(2014) | 10.1142/S0219887814500194 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we consider an axial torsion to build metric-compatible
connections in conformal gravity, with gauge potentials; the geometric
background is filled with Dirac spinors: scalar fields with suitable potentials
are added eventually. The system of field equations is worked out to have
torsional effects converted into spinorial self-interactions: the massless
spinors display self-interactions of a specific form that gives them the
features they have in the non-conformal theory but with the additional
character of renormalizability, and the mechanisms of generation of mass and
cosmological constants become dynamical. As a final step we will address the
cosmological constant and coincidence problems.
| [
{
"created": "Thu, 24 May 2012 09:55:43 GMT",
"version": "v1"
},
{
"created": "Tue, 15 Oct 2013 23:57:32 GMT",
"version": "v2"
}
] | 2014-03-12 | [
[
"Fabbri",
"Luca",
""
]
] | In this paper we consider an axial torsion to build metric-compatible connections in conformal gravity, with gauge potentials; the geometric background is filled with Dirac spinors: scalar fields with suitable potentials are added eventually. The system of field equations is worked out to have torsional effects converted into spinorial self-interactions: the massless spinors display self-interactions of a specific form that gives them the features they have in the non-conformal theory but with the additional character of renormalizability, and the mechanisms of generation of mass and cosmological constants become dynamical. As a final step we will address the cosmological constant and coincidence problems. |
2105.08428 | Dirk Puetzfeld | Yuri N. Obukhov, Dirk Puetzfeld | Demystifying autoparallels in alternative gravity | 4 pages | Phys. Rev. D 104, 044031 (2021) | 10.1103/PhysRevD.104.044031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Autoparallel curves along with geodesic curves can arise as trajectories of
physical test bodies. We explicitly derive autoparallels as effective
post-Riemannian geometric constructs, and at the same time we argue
\emph{against} postulating autoparallels as fundamental equations of motion for
test bodies in alternative gravity theories.
| [
{
"created": "Tue, 18 May 2021 10:35:33 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Aug 2021 07:40:58 GMT",
"version": "v2"
}
] | 2021-08-17 | [
[
"Obukhov",
"Yuri N.",
""
],
[
"Puetzfeld",
"Dirk",
""
]
] | Autoparallel curves along with geodesic curves can arise as trajectories of physical test bodies. We explicitly derive autoparallels as effective post-Riemannian geometric constructs, and at the same time we argue \emph{against} postulating autoparallels as fundamental equations of motion for test bodies in alternative gravity theories. |
2401.14209 | Jonathan Gorard | Jonathan Gorard | Computational General Relativity in the Wolfram Language using Gravitas
II: ADM Formalism and Numerical Relativity | 76 pages, 54 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is the second in a series of two articles introducing the Gravitas
computational general relativity framework, in which we now focus upon the
design and capabilities of Gravitas's numerical subsystem, including its
ability to perform general 3+1 decompositions of spacetime via the ADM
formalism, its support for the definition and construction of arbitrary Cauchy
surfaces as initial data, its support for the definition and enforcement of
arbitrary gauge and coordinate conditions, its various algorithms for ensuring
the satisfaction of the ADM Hamiltonian and momentum constraints, and its
unique adaptive refinement algorithms based on hypergraph rewriting via Wolfram
model evolution. Particular attention is paid to the seamless integration
between Gravitas's symbolic and numerical subsystems, its ability to configure,
run, analyze and visualize complex numerical relativity simulations and their
outputs within a single notebook environment, and its capabilities for handling
generic curvilinear coordinate systems and spacetimes with general (and often
highly non-trivial) topologies using its specialized and highly efficient
hypergraph-based numerical algorithms. We also provide illustrations of
Gravitas's functionality for the visualization of hypergraph geometries and
spacetime embedding diagrams, the ability for Gravitas's symbolic and numerical
subsystems to be used in concert for the extraction of gravitational wave
signals and other crucial simulation data, and Gravitas's in-built library of
standard initial data, matter distributions and gauge conditions. We conclude
by demonstrating how the numerical subsystem can be used to set up, run,
visualize and analyze a standard yet nevertheless reasonably challenging
numerical relativity test case: a binary black hole collision and merger within
a vacuum spacetime (including the extraction of its outgoing gravitational wave
profile).
| [
{
"created": "Thu, 25 Jan 2024 14:48:05 GMT",
"version": "v1"
}
] | 2024-01-26 | [
[
"Gorard",
"Jonathan",
""
]
] | This is the second in a series of two articles introducing the Gravitas computational general relativity framework, in which we now focus upon the design and capabilities of Gravitas's numerical subsystem, including its ability to perform general 3+1 decompositions of spacetime via the ADM formalism, its support for the definition and construction of arbitrary Cauchy surfaces as initial data, its support for the definition and enforcement of arbitrary gauge and coordinate conditions, its various algorithms for ensuring the satisfaction of the ADM Hamiltonian and momentum constraints, and its unique adaptive refinement algorithms based on hypergraph rewriting via Wolfram model evolution. Particular attention is paid to the seamless integration between Gravitas's symbolic and numerical subsystems, its ability to configure, run, analyze and visualize complex numerical relativity simulations and their outputs within a single notebook environment, and its capabilities for handling generic curvilinear coordinate systems and spacetimes with general (and often highly non-trivial) topologies using its specialized and highly efficient hypergraph-based numerical algorithms. We also provide illustrations of Gravitas's functionality for the visualization of hypergraph geometries and spacetime embedding diagrams, the ability for Gravitas's symbolic and numerical subsystems to be used in concert for the extraction of gravitational wave signals and other crucial simulation data, and Gravitas's in-built library of standard initial data, matter distributions and gauge conditions. We conclude by demonstrating how the numerical subsystem can be used to set up, run, visualize and analyze a standard yet nevertheless reasonably challenging numerical relativity test case: a binary black hole collision and merger within a vacuum spacetime (including the extraction of its outgoing gravitational wave profile). |
gr-qc/9503051 | Renate Loll | R. Loll (INFN, Florence) | QUANTUM ASPECTS OF 2+1 GRAVITY | 24 pages, TeX, Mar 95; contribution to the JMP special issue on
"Quantum geometry and diffeomorphism invariant quantum field theory" | J.Math.Phys.36:6494-6509,1995 | 10.1063/1.531253 | DFF 223/03/95 | gr-qc hep-th | null | We review and systematize recent attempts to canonically quantize general
relativity in 2+1 dimensions, defined on space-times $\R\times\Sigma^g$, where
$\Sigma^g$ is a compact Riemann surface of genus $g$. The emphasis is on
quantizations of the classical connection formulation, which use Wilson loops
as their basic observables, but also results from the ADM formulation are
summarized. We evaluate the progress and discuss the possible quantum
(in)equivalence of the various approaches.
| [
{
"created": "Mon, 27 Mar 1995 16:47:58 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Loll",
"R.",
"",
"INFN, Florence"
]
] | We review and systematize recent attempts to canonically quantize general relativity in 2+1 dimensions, defined on space-times $\R\times\Sigma^g$, where $\Sigma^g$ is a compact Riemann surface of genus $g$. The emphasis is on quantizations of the classical connection formulation, which use Wilson loops as their basic observables, but also results from the ADM formulation are summarized. We evaluate the progress and discuss the possible quantum (in)equivalence of the various approaches. |
0812.3062 | Wu Ning | Ning Wu | Path Integral Quantization of Quantum Gauge General Relativity | 19 pages, no figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Path integral quantization of quantum gauge general relativity is discussed
in this paper. First, we deduce the generating functional of green function
with external fields. Based on this generating functional, the propagators of
gravitational gauge field and related ghost field are deduced. Then, we
calculate Feynman rules of various interaction vertices of three or four
gravitational gauge fields and vertex between ghost field and gravitational
gauge field. Results in this paper are the bases of calculating vacuum
polarization of gravitational gauge field and vertex correction of
gravitational couplings in one loop diagram level. As we have pointed out in
previous paper, quantum gauge general relativity is perturbative
renormalizable, and a formal proof on its renormalizability is also given in
the previous paper. Next step, we will calculate one-loop and two-loop
renormalization constant, and to prove that the theory is renormalizable in
one-loop and two-loop level by direct calculations.
| [
{
"created": "Tue, 16 Dec 2008 14:05:46 GMT",
"version": "v1"
}
] | 2008-12-17 | [
[
"Wu",
"Ning",
""
]
] | Path integral quantization of quantum gauge general relativity is discussed in this paper. First, we deduce the generating functional of green function with external fields. Based on this generating functional, the propagators of gravitational gauge field and related ghost field are deduced. Then, we calculate Feynman rules of various interaction vertices of three or four gravitational gauge fields and vertex between ghost field and gravitational gauge field. Results in this paper are the bases of calculating vacuum polarization of gravitational gauge field and vertex correction of gravitational couplings in one loop diagram level. As we have pointed out in previous paper, quantum gauge general relativity is perturbative renormalizable, and a formal proof on its renormalizability is also given in the previous paper. Next step, we will calculate one-loop and two-loop renormalization constant, and to prove that the theory is renormalizable in one-loop and two-loop level by direct calculations. |
gr-qc/0305039 | Peter Diener | Peter Diener | A new general purpose event horizon finder for 3D numerical spacetimes | 18 pages, 6 figures, submitted to Classical and Quantum Gravity | Class.Quant.Grav. 20 (2003) 4901-4918 | 10.1088/0264-9381/20/22/014 | AEI-2003-043 | gr-qc | null | I present a new general purpose event horizon finder for full 3D numerical
spacetimes. It works by evolving a complete null surface backwards in time. The
null surface is described as the zero level set of a scalar function, that in
principle is defined everywhere. This description of the surface allows the
surface, trivially, to change topology, making this event horizon finder able
to handle numerical spacetimes, where two (or more) black holes merge into a
single final black hole.
| [
{
"created": "Sat, 10 May 2003 16:42:02 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Diener",
"Peter",
""
]
] | I present a new general purpose event horizon finder for full 3D numerical spacetimes. It works by evolving a complete null surface backwards in time. The null surface is described as the zero level set of a scalar function, that in principle is defined everywhere. This description of the surface allows the surface, trivially, to change topology, making this event horizon finder able to handle numerical spacetimes, where two (or more) black holes merge into a single final black hole. |
gr-qc/9609010 | Steve Detweiler | Steven Detweiler, Lee H. Brown | The Post Minkowskii Expansion of General Relativity | This revision contains improvements in the exposition of two sections
and in one appendix and also matches the published version. RevTeX, 22pp | Phys.Rev.D56:826-841,1997 | 10.1103/PhysRevD.56.826 | UF-RAP-96-13 | gr-qc | null | We describe a post-Minkowskii approximation of general relativity as a power
series expansion in G, Newton's gravitational constant. Material sources are
hidden behind boundaries, and only the vacuum Einstein equations are
considered. An iterative procedure is described which, in one complete step,
takes any approximate solution of the Einstein equations and produces a new
approximation which has the error decreased by a factor of G. Each step in the
procedure consists of three parts: first the equations of motion are used to
update the trajectories of the boundaries; then the field equations are solved
using a retarded Green's function for Minkowskii space; finally a gauge
transformation is performed which makes the geometry well behaved at future
null infinity. Differences between this approach to the Einstein equations and
similar ones are that we use a general (non-harmonic) gauge and formulate the
procedure in a constructive manner which emphasizes its suitability for
implementation on a computer.
| [
{
"created": "Tue, 3 Sep 1996 12:44:35 GMT",
"version": "v1"
},
{
"created": "Thu, 31 Jul 1997 13:03:54 GMT",
"version": "v2"
}
] | 2010-05-12 | [
[
"Detweiler",
"Steven",
""
],
[
"Brown",
"Lee H.",
""
]
] | We describe a post-Minkowskii approximation of general relativity as a power series expansion in G, Newton's gravitational constant. Material sources are hidden behind boundaries, and only the vacuum Einstein equations are considered. An iterative procedure is described which, in one complete step, takes any approximate solution of the Einstein equations and produces a new approximation which has the error decreased by a factor of G. Each step in the procedure consists of three parts: first the equations of motion are used to update the trajectories of the boundaries; then the field equations are solved using a retarded Green's function for Minkowskii space; finally a gauge transformation is performed which makes the geometry well behaved at future null infinity. Differences between this approach to the Einstein equations and similar ones are that we use a general (non-harmonic) gauge and formulate the procedure in a constructive manner which emphasizes its suitability for implementation on a computer. |
1602.08686 | Peng Wang | Jun Tao, Peng Wang, Haitang Yang | Free-fall Frame Black Hole in Gravity's Rainbow | 18 pages, 2 figures, Journal version. arXiv admin note: substantial
text overlap with arXiv:1507.03768 | Phys. Rev. D 94, 064068 (2016) | 10.1103/PhysRevD.94.064068 | CTP-SCU/2016002 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Doubly special relativity (DSR) is an effective model for encoding quantum
gravity in flat spacetime. To incorporate DSR into general relativity, one
could use "Gravity's rainbow", where the spacetime background felt by a test
particle would depend on its energy. In this scenario, one could rewrite the
rainbow metric $g_{\mu\nu}\left( E\right) $ in terms of some orthonormal frame
fields and use the modified equivalence principle to determine the energy
dependence of $g_{\mu\nu}\left( E\right) $. Obviously, the form of
$g_{\mu\nu}\left( E\right) $ depends on the choice of the orthonormal frame.
For a static black hole, there are two natural orthonormal frames, the static
one hovering above it and freely falling one along geodesics. The cases with
the static orthonormal frame have been extensively studied by many authors. The
aim of this paper is to investigate properties of rainbow black holes in the
scenario with the free-fall orthonormal frame. We first derive the metric of
rainbow black holes and their Hawking temperatures in this free-fall scenario.
Then, the thermodynamics of a rainbow Schwarzschild black hole is studied.
Finally, we use the brick wall model to compute the thermal entropy of a
massless scalar field near the horizon of a Schwarzschild rainbow black hole in
this free-fall scenario.
| [
{
"created": "Sun, 28 Feb 2016 09:11:51 GMT",
"version": "v1"
},
{
"created": "Thu, 13 Oct 2016 07:05:40 GMT",
"version": "v2"
}
] | 2016-10-14 | [
[
"Tao",
"Jun",
""
],
[
"Wang",
"Peng",
""
],
[
"Yang",
"Haitang",
""
]
] | Doubly special relativity (DSR) is an effective model for encoding quantum gravity in flat spacetime. To incorporate DSR into general relativity, one could use "Gravity's rainbow", where the spacetime background felt by a test particle would depend on its energy. In this scenario, one could rewrite the rainbow metric $g_{\mu\nu}\left( E\right) $ in terms of some orthonormal frame fields and use the modified equivalence principle to determine the energy dependence of $g_{\mu\nu}\left( E\right) $. Obviously, the form of $g_{\mu\nu}\left( E\right) $ depends on the choice of the orthonormal frame. For a static black hole, there are two natural orthonormal frames, the static one hovering above it and freely falling one along geodesics. The cases with the static orthonormal frame have been extensively studied by many authors. The aim of this paper is to investigate properties of rainbow black holes in the scenario with the free-fall orthonormal frame. We first derive the metric of rainbow black holes and their Hawking temperatures in this free-fall scenario. Then, the thermodynamics of a rainbow Schwarzschild black hole is studied. Finally, we use the brick wall model to compute the thermal entropy of a massless scalar field near the horizon of a Schwarzschild rainbow black hole in this free-fall scenario. |
gr-qc/0611025 | Jorge P\'aramos | Jorge Paramos and Orfeu Bertolami | Current tests of alternative gravity theories: the Modified Newtonian
Dynamics case | 12 pages. Talk presented by one of us (O.B.) at the Fundamental
Physics in Space section of the Comittee on Space Research, 36th. COSPAR
Scientific Assembly, Beijing, China, 16-23 July, 2006 (version with corrected
reference list) | null | null | null | gr-qc | null | We address the possibility of taking advantage of high accuracy gravitational
space experiments in the Solar System and complementary cosmological tests to
distinguish between the usual general relativistic theory from the alternative
modified Newtonian dynamics paradigm.
| [
{
"created": "Sat, 4 Nov 2006 04:35:20 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Nov 2006 11:51:27 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Paramos",
"Jorge",
""
],
[
"Bertolami",
"Orfeu",
""
]
] | We address the possibility of taking advantage of high accuracy gravitational space experiments in the Solar System and complementary cosmological tests to distinguish between the usual general relativistic theory from the alternative modified Newtonian dynamics paradigm. |
gr-qc/9710019 | Moffat | J. W. Moffat | Quantum Measurements, Nonlocality and the Arrow of Time | 8 pages. Revtex. Revised version | null | null | UTPT-97-05 | gr-qc hep-th quant-ph | null | A theory is developed which attempts to reconcile the measurements of
nonlocal quantum observables with special relativity and quantum mechanics. The
collapse of a wave function, which coincides with a nonlocal measurement by
some macroscopic measuring device, is associated with the triggering of an
absorber mechanism due to the interaction of the apparatus with the charges in
the rest of the universe. The standard retarded electromagnetic field plus
radiation damping is converted, for a short time during the collapse of the
wave function, to an advanced field plus radiation. The reversal of the arrow
of time during the wave function reduction permits communication in nonlocal
quantum experiments at the speed of light, resolving paradoxes associated with
measurements of correlated quantum states and special relativity. The absorber
mechanism and the advanced field solution are consistent with conventional
Friedmann-Robertson-Walker expanding universes.
| [
{
"created": "Thu, 2 Oct 1997 21:54:12 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Sep 1998 21:40:50 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Moffat",
"J. W.",
""
]
] | A theory is developed which attempts to reconcile the measurements of nonlocal quantum observables with special relativity and quantum mechanics. The collapse of a wave function, which coincides with a nonlocal measurement by some macroscopic measuring device, is associated with the triggering of an absorber mechanism due to the interaction of the apparatus with the charges in the rest of the universe. The standard retarded electromagnetic field plus radiation damping is converted, for a short time during the collapse of the wave function, to an advanced field plus radiation. The reversal of the arrow of time during the wave function reduction permits communication in nonlocal quantum experiments at the speed of light, resolving paradoxes associated with measurements of correlated quantum states and special relativity. The absorber mechanism and the advanced field solution are consistent with conventional Friedmann-Robertson-Walker expanding universes. |
gr-qc/9406047 | Paulo Rodrigues Lima Vargas Moniz | A.D.Y. Cheng, P.D. D'Eath and P.R.L.V. Moniz | Quantization of Bianchi Models in N=1 Supergravity with a Cosmological
Constant | 20 pages, DAMTP R94/20 | Grav.Cosmol.1:12-21,1995 | null | null | gr-qc | null | We study the quantization of some cosmological models within the theory of
N=1 supergravity with a positive cosmological constant. We find, by imposing
the supersymmetry and Lorentz constraints, that there are no physical states in
the models we have considered. For the k=1 Friedmann-Robertson-Walker model,
where the fermionic degrees of freedom of the gravitino field are very
restricted, we have found two bosonic quantum physical states, namely the
wormhole and the Hartle-Hawking state.
From the point of view of perturbation theory, it seems that the
gravitational and gravitino modes that are allowed to be excited in a
supersymmetric Bianchi-IX model contribute in such a way to forbid any physical
solutions of the quantum constraints. This suggests that in a complete
perturbation expansion we would have to conclude that the full theory of N=1
supergravity with a non-zero cosmological constant should have no physical
states.
| [
{
"created": "Tue, 28 Jun 1994 14:20:02 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jul 1994 08:45:25 GMT",
"version": "v2"
}
] | 2011-04-15 | [
[
"Cheng",
"A. D. Y.",
""
],
[
"D'Eath",
"P. D.",
""
],
[
"Moniz",
"P. R. L. V.",
""
]
] | We study the quantization of some cosmological models within the theory of N=1 supergravity with a positive cosmological constant. We find, by imposing the supersymmetry and Lorentz constraints, that there are no physical states in the models we have considered. For the k=1 Friedmann-Robertson-Walker model, where the fermionic degrees of freedom of the gravitino field are very restricted, we have found two bosonic quantum physical states, namely the wormhole and the Hartle-Hawking state. From the point of view of perturbation theory, it seems that the gravitational and gravitino modes that are allowed to be excited in a supersymmetric Bianchi-IX model contribute in such a way to forbid any physical solutions of the quantum constraints. This suggests that in a complete perturbation expansion we would have to conclude that the full theory of N=1 supergravity with a non-zero cosmological constant should have no physical states. |
2111.02817 | Anisur Rahaman | Sohan Kumar Jha, Anisur Rahaman | Lorentz violation and noncommutative effect on superradiance scattering
off Kerr-like black hole and on the shadow of it | 31 pages latex with 36 figs, modified including Superradiation
phenomena | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a Lorentz violating non-commutating Kerr-like spacetime and
studied the superradiance effect and the shadow cast by the back hole. We
extensively study the different aspects of the black hole associated with a
generalized Kerr-like spacetime metric endowed with the corrections licked with
Lorentz violation and non-commutativity effect jointly. We investigate the
superradiance effect, deviation of shape, and size of the ergosphere, energy
emission rate, and black hole shadow in this generalized situation and study
their variation taking different admissible values of Lorentz violating
parameter $l$ and non-commutative parameter $b$. The admissible range has been
determined from the observation of the Event Horizon Telescope (EHT)
collaboration concerning $M87_8$ astronomical black hole. We observe that the
superradiance phenomena has a crucially depends on the parameter $l$ and $b$
apart from its dependence on $a$ which is linked to the spin of the black hole.
We also observe that with the increase in Lorentz violating parameter $l$, the
size of the black hole shadow increases, and with the increase in the
non-commutative parameter $b$, the size of the black hole decreases. We have
made an attempt to constrain parameters $b$ of a non-commutative Kerr-like
black hole using the observation available from the EHT collaboration, in the
same way, we put constrain on the Lorentz violating parameter $l$. This study
shows that black holes associated with non-commutative Kerr-like spacetime may
be a suitable candidate for an astrophysical black hole.
| [
{
"created": "Thu, 4 Nov 2021 12:35:29 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Feb 2022 13:13:50 GMT",
"version": "v2"
},
{
"created": "Thu, 21 Apr 2022 14:52:55 GMT",
"version": "v3"
}
] | 2022-04-22 | [
[
"Jha",
"Sohan Kumar",
""
],
[
"Rahaman",
"Anisur",
""
]
] | We consider a Lorentz violating non-commutating Kerr-like spacetime and studied the superradiance effect and the shadow cast by the back hole. We extensively study the different aspects of the black hole associated with a generalized Kerr-like spacetime metric endowed with the corrections licked with Lorentz violation and non-commutativity effect jointly. We investigate the superradiance effect, deviation of shape, and size of the ergosphere, energy emission rate, and black hole shadow in this generalized situation and study their variation taking different admissible values of Lorentz violating parameter $l$ and non-commutative parameter $b$. The admissible range has been determined from the observation of the Event Horizon Telescope (EHT) collaboration concerning $M87_8$ astronomical black hole. We observe that the superradiance phenomena has a crucially depends on the parameter $l$ and $b$ apart from its dependence on $a$ which is linked to the spin of the black hole. We also observe that with the increase in Lorentz violating parameter $l$, the size of the black hole shadow increases, and with the increase in the non-commutative parameter $b$, the size of the black hole decreases. We have made an attempt to constrain parameters $b$ of a non-commutative Kerr-like black hole using the observation available from the EHT collaboration, in the same way, we put constrain on the Lorentz violating parameter $l$. This study shows that black holes associated with non-commutative Kerr-like spacetime may be a suitable candidate for an astrophysical black hole. |
1806.02186 | Luis Herrera | L. Herrera | Maxwell's Demon and the Problem of Observers in General Relativity | 6 pages Latex.1 figure. Published in the special issue of Entropy:
Selected Papers from 4th International Electronic Conference on Entropy and
Its Applications | Entropy,20,391,(2018) | 10.3390/e20050391 | null | gr-qc physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The fact that real dissipative (entropy producing) processes may be detected
by non-comoving observers (tilted), in systems that appear to be isentropic for
comoving observers, in general relativity, is explained in terms of the
information theory, analogous with the explanation of the Maxwell's demon
paradox
| [
{
"created": "Wed, 6 Jun 2018 13:53:51 GMT",
"version": "v1"
}
] | 2018-07-04 | [
[
"Herrera",
"L.",
""
]
] | The fact that real dissipative (entropy producing) processes may be detected by non-comoving observers (tilted), in systems that appear to be isentropic for comoving observers, in general relativity, is explained in terms of the information theory, analogous with the explanation of the Maxwell's demon paradox |
0801.3805 | Sam Dolan Dr | Sam R. Dolan | Scattering and absorption of gravitational plane waves by rotating black
holes | 43 pages, 17 figures. To match published version | Class.Quant.Grav.25:235002,2008 | 10.1088/0264-9381/25/23/235002 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is a study of the scattering and absorption of planar gravitational
waves by a Kerr black hole in vacuum. We apply the partial wave method to
compute cross sections for the special case of radiation incident along the
rotation axis. A catalogue of numerically-accurate cross sections is presented,
for a range of incident wavelengths $M\omega \le 4$ and rotation rates $a \le
0.999M$. Three effects are studied in detail: polarization, helicity-reversal
and glory scattering. First, a new approximation to the polarization in the
long-wavelength limit is derived. We show that black hole rotation
distinguishes between co- and counter-rotating wave helicities, leading to a
term in the cross section proportional to $a\omega$. Second, we confirm that
helicity is not conserved by the scattering process, and show that
superradiance amplifies the effect. For certain wavelengths, the back-scattered
flux is enhanced by as much as $\sim 35$ times for a rapidly-rotating hole
(e.g. for $a = 0.999M$ at $M\omega = 0.945$). Third, we observe regular glory
and spiral scattering peaks in the numerically-determined cross sections. We
show that the angular width and intensity of the peaks may be estimated via a
semi-classical approximation. We conclude with a discussion of the observable
implications of our results.
| [
{
"created": "Thu, 24 Jan 2008 17:47:07 GMT",
"version": "v1"
},
{
"created": "Mon, 12 May 2008 19:21:10 GMT",
"version": "v2"
},
{
"created": "Fri, 14 Nov 2008 14:42:23 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Dolan",
"Sam R.",
""
]
] | This is a study of the scattering and absorption of planar gravitational waves by a Kerr black hole in vacuum. We apply the partial wave method to compute cross sections for the special case of radiation incident along the rotation axis. A catalogue of numerically-accurate cross sections is presented, for a range of incident wavelengths $M\omega \le 4$ and rotation rates $a \le 0.999M$. Three effects are studied in detail: polarization, helicity-reversal and glory scattering. First, a new approximation to the polarization in the long-wavelength limit is derived. We show that black hole rotation distinguishes between co- and counter-rotating wave helicities, leading to a term in the cross section proportional to $a\omega$. Second, we confirm that helicity is not conserved by the scattering process, and show that superradiance amplifies the effect. For certain wavelengths, the back-scattered flux is enhanced by as much as $\sim 35$ times for a rapidly-rotating hole (e.g. for $a = 0.999M$ at $M\omega = 0.945$). Third, we observe regular glory and spiral scattering peaks in the numerically-determined cross sections. We show that the angular width and intensity of the peaks may be estimated via a semi-classical approximation. We conclude with a discussion of the observable implications of our results. |
1407.8165 | Lars Andersson | Lars Andersson | Self-gravitating elastic bodies | 16 pages. Based on a talk given at the 2013 WE-Heraeus seminar on
"Equations of motion in relativistic gravity" | null | 10.1007/978-3-319-18335-0_16 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Extended objects in GR are often modelled using distributional solutions of
the Einstein equations with point-like sources, or as the limit of
infinitesimally small "test" objects. In this note, I will consider models of
finite self-gravitating extended objects, which make it possible to give a
rigorous treatment of the initial value problem for (finite) extended objects.
| [
{
"created": "Wed, 30 Jul 2014 19:24:37 GMT",
"version": "v1"
}
] | 2021-04-07 | [
[
"Andersson",
"Lars",
""
]
] | Extended objects in GR are often modelled using distributional solutions of the Einstein equations with point-like sources, or as the limit of infinitesimally small "test" objects. In this note, I will consider models of finite self-gravitating extended objects, which make it possible to give a rigorous treatment of the initial value problem for (finite) extended objects. |
1211.5403 | Mikjel Thorsrud | John D. Barrow, Mikjel Thorsrud, Kei Yamamoto | Cosmologies in Horndeski's second-order vector-tensor theory | 32 pages, 11 figures, v2: refs added, minor changes. Published in
JHEP02(2013)146 | JHEP02(2013)146 | 10.1007/JHEP02(2013)146 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Horndeski derived a most general vector-tensor theory in which the vector
field respects the gauge symmetry and the resulting dynamical equations are of
second order. The action contains only one free parameter, $\lambda$, that
determines the strength of the non-minimal coupling between the gauge field and
gravity. We investigate the cosmological consequences of this action and
discuss observational constraints. For $\lambda<0$ we identify singularities
where the deceleration parameter diverges within a finite proper time. This
effectively rules out any sensible cosmological application of the theory for a
negative non-minimal coupling. We also find a range of parameter that gives a
viable cosmology and study the phenomenology for this case. Observational
constraints on the value of the coupling are rather weak since the interaction
is higher-order in space-time curvature.
| [
{
"created": "Fri, 23 Nov 2012 02:10:06 GMT",
"version": "v1"
},
{
"created": "Mon, 11 Mar 2013 09:17:43 GMT",
"version": "v2"
}
] | 2013-03-12 | [
[
"Barrow",
"John D.",
""
],
[
"Thorsrud",
"Mikjel",
""
],
[
"Yamamoto",
"Kei",
""
]
] | Horndeski derived a most general vector-tensor theory in which the vector field respects the gauge symmetry and the resulting dynamical equations are of second order. The action contains only one free parameter, $\lambda$, that determines the strength of the non-minimal coupling between the gauge field and gravity. We investigate the cosmological consequences of this action and discuss observational constraints. For $\lambda<0$ we identify singularities where the deceleration parameter diverges within a finite proper time. This effectively rules out any sensible cosmological application of the theory for a negative non-minimal coupling. We also find a range of parameter that gives a viable cosmology and study the phenomenology for this case. Observational constraints on the value of the coupling are rather weak since the interaction is higher-order in space-time curvature. |
gr-qc/0404001 | Muhammad Sharif | M. Sharif | Energy and Momentum in General Relativity | null | Nuovo Cim. B118 (2003) 669-683 | 10.1393/ncb/i2003-10053-0 | null | gr-qc | null | The energy and momentum for different cosmological models using various
prescriptions are evaluated. In particular, we have focused our attention on
the energy and momentum for gravitational waves and discuss the results. It is
concluded that there are methods which can provide physically acceptable
results.
| [
{
"created": "Wed, 31 Mar 2004 23:53:56 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Sharif",
"M.",
""
]
] | The energy and momentum for different cosmological models using various prescriptions are evaluated. In particular, we have focused our attention on the energy and momentum for gravitational waves and discuss the results. It is concluded that there are methods which can provide physically acceptable results. |
2312.01827 | Ruchi Mishra | Ruchi Mishra and W{\l}odek Klu\'zniak | Equilibrium tori orbiting Reissner-Nordstr\"om naked singularities | Published in the Proceedings of RAGtime 23-35, Z. Stuchl\'ik, G.
T\"or\"ok, V. Karas and D. Lan\v{c}ov\'a, editors, Silesian University in
Opava, 2023, pp. 151-166 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In general relativity, the asymptotically flat space-time of a charged,
spherically symmetric (non-rotating) body is described by the
Reissner-Nordstr\"om metric. This metric corresponds to a naked singularity
when the absolute value of charge, $Q$, exceeds the mass, $M$. For all
Reissner-Nordstr\"om naked singularities, there exists a zero gravity sphere
where a test particle can remain at rest. Outside that sphere gravity is
attractive, inside it gravity is repulsive. For values of $Q/M>\sqrt{9/8}$ the
angular frequency of circular test-particle orbits has a maximum at radius
$r=(4/3)\,Q^2/M$. We construct polytropic tori with uniform values of specific
angular momentum in the naked singularity regime of the Reissner-Nordstr\"om
metric, $(Q/M>1)$.
| [
{
"created": "Mon, 4 Dec 2023 11:59:47 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Jan 2024 23:42:00 GMT",
"version": "v2"
}
] | 2024-01-29 | [
[
"Mishra",
"Ruchi",
""
],
[
"Kluźniak",
"Włodek",
""
]
] | In general relativity, the asymptotically flat space-time of a charged, spherically symmetric (non-rotating) body is described by the Reissner-Nordstr\"om metric. This metric corresponds to a naked singularity when the absolute value of charge, $Q$, exceeds the mass, $M$. For all Reissner-Nordstr\"om naked singularities, there exists a zero gravity sphere where a test particle can remain at rest. Outside that sphere gravity is attractive, inside it gravity is repulsive. For values of $Q/M>\sqrt{9/8}$ the angular frequency of circular test-particle orbits has a maximum at radius $r=(4/3)\,Q^2/M$. We construct polytropic tori with uniform values of specific angular momentum in the naked singularity regime of the Reissner-Nordstr\"om metric, $(Q/M>1)$. |
gr-qc/0604102 | Pavel Krtous | Jiri Bicak | Einstein equations: exact solutions | 8 pages, published in Encyclopedia of Mathematical Physics, eds.
J.-P. Francoise, G. L. Naber and Tsou S. T., Oxford: Elsevier, 2006 (ISBN
978-0-1251-2666-3), volume 2, page 165-173. (The number of references had to
be limited, some additional references are indicated inside the text only.) | null | null | null | gr-qc astro-ph hep-th | null | In Einstein's general relativity, with its nonlinear field equations, the
discoveries and analyzes of various specific explicit solutions made a great
impact on understanding many of the unforeseen features of the theory. Some
solutions found fundamental applications in astrophysics, cosmology and, more
recently, in the developments inspired by string theory. In this short article
we survey the invariant characterization and classification of the solutions
and describe the properties and role of the most relevant classes: Minkowski,
(anti-)de Sitter spacetimes, spherical Schwarzschild and Reissner-Nordstroem
metrics, stationary axisymmetric solutions, radiative metrics describing plane
and cylindrical waves, radiative fields of uniformly accelerated sources and
Robinson-Trautman solutions. Metrics representing regions of spacetimes filled
with matter are also discussed and cosmological models are very briefly
mentioned. Some parts of the text are based on a detailed survey which appeared
in gr-qc/0004016 (see Ref. 2).
| [
{
"created": "Mon, 24 Apr 2006 07:15:30 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bicak",
"Jiri",
""
]
] | In Einstein's general relativity, with its nonlinear field equations, the discoveries and analyzes of various specific explicit solutions made a great impact on understanding many of the unforeseen features of the theory. Some solutions found fundamental applications in astrophysics, cosmology and, more recently, in the developments inspired by string theory. In this short article we survey the invariant characterization and classification of the solutions and describe the properties and role of the most relevant classes: Minkowski, (anti-)de Sitter spacetimes, spherical Schwarzschild and Reissner-Nordstroem metrics, stationary axisymmetric solutions, radiative metrics describing plane and cylindrical waves, radiative fields of uniformly accelerated sources and Robinson-Trautman solutions. Metrics representing regions of spacetimes filled with matter are also discussed and cosmological models are very briefly mentioned. Some parts of the text are based on a detailed survey which appeared in gr-qc/0004016 (see Ref. 2). |
gr-qc/9804061 | Michael Reisenberger | Michael P. Reisenberger | Classical Euclidean general relativity from ``left-handed area =
right-handed area" | 19 pages latex. No figures | null | 10.1088/0264-9381/16/4/024 | null | gr-qc | null | A classical continuum theory corresponding to Barrett and Crane's model of
Euclidean quantum gravity is presented. The fields in this classical theory are
those of SO(4) BF theory, a simple topological theory of an so(4) valued 2-form
field, $B^{IJ}_{\m\n}$, and an so(4) connection. The left handed (self-dual)
and right handed (anti-self-dual) components of $B$ define a left handed and a,
generally distinct, right handed area for each spacetime 2-surface. The theory
being presented is obtained by adding to the BF action a Lagrange multiplier
term that enforces the constraint that the left handed and the right handed
areas be equal. It is shown that Euclidean general relativity (GR) forms a
sector of the resulting theory. The remaining three sectors of the theory are
also characterized and it is shown that, except in special cases, GR canonical
initial data is sufficient to specify the GR sector as well as a specific
solution within this sector.
Finally, the path integral quantization of the theory is discussed at a
formal level and a hueristic argument is given suggesting that in the
semiclassical limit the path integral is dominated by solutions in one of the
non-GR sectors, which would mean that the theory quantized in this way is not a
quantization of GR.
| [
{
"created": "Thu, 23 Apr 1998 20:14:28 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Reisenberger",
"Michael P.",
""
]
] | A classical continuum theory corresponding to Barrett and Crane's model of Euclidean quantum gravity is presented. The fields in this classical theory are those of SO(4) BF theory, a simple topological theory of an so(4) valued 2-form field, $B^{IJ}_{\m\n}$, and an so(4) connection. The left handed (self-dual) and right handed (anti-self-dual) components of $B$ define a left handed and a, generally distinct, right handed area for each spacetime 2-surface. The theory being presented is obtained by adding to the BF action a Lagrange multiplier term that enforces the constraint that the left handed and the right handed areas be equal. It is shown that Euclidean general relativity (GR) forms a sector of the resulting theory. The remaining three sectors of the theory are also characterized and it is shown that, except in special cases, GR canonical initial data is sufficient to specify the GR sector as well as a specific solution within this sector. Finally, the path integral quantization of the theory is discussed at a formal level and a hueristic argument is given suggesting that in the semiclassical limit the path integral is dominated by solutions in one of the non-GR sectors, which would mean that the theory quantized in this way is not a quantization of GR. |
0912.2862 | Jose Manuel Velhinho | J. M. Velhinho | Groups of flux-like transformations in loop quantum gravity | 3 pages. Proceedings of the 12th Marcel Grossmann Meeting, Paris, Jul
2009. Talk based on arXiv:0804.3765 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a group of transformations in the quantum configuration space of
loop quantum gravity that contains the set of all transformations generated by
the flux variables.
| [
{
"created": "Tue, 15 Dec 2009 12:24:56 GMT",
"version": "v1"
}
] | 2009-12-16 | [
[
"Velhinho",
"J. M.",
""
]
] | We present a group of transformations in the quantum configuration space of loop quantum gravity that contains the set of all transformations generated by the flux variables. |
gr-qc/0611094 | Ujjal Debnath | Writambhara Chakraborty and Ujjal Debnath | Is Modified Chaplygin gas along with barotropic fluid responsible for
acceleration of the Universe? | RevTex style, 6 pages, 8 figures | Mod.Phys.Lett.A22:1805-1812,2007 | 10.1142/S021773230702172X | null | gr-qc | null | In this letter, we have considered a model of the universe filled with
modified Chaplygin gas and another fluid (with barotropic equation of state)
and its role in accelerating phase of the universe. We have assumed that the
mixture of these two fluid models is valid from (i) the radiation era to
$\Lambda$CDM for $-1\le\gamma\le 1$ and (ii) the radiation era to quiessence
model for $\gamma<-1$. For these two fluid models, the statefinder parameters
describe different phase of the evolution of the universe.
| [
{
"created": "Fri, 17 Nov 2006 07:25:57 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Chakraborty",
"Writambhara",
""
],
[
"Debnath",
"Ujjal",
""
]
] | In this letter, we have considered a model of the universe filled with modified Chaplygin gas and another fluid (with barotropic equation of state) and its role in accelerating phase of the universe. We have assumed that the mixture of these two fluid models is valid from (i) the radiation era to $\Lambda$CDM for $-1\le\gamma\le 1$ and (ii) the radiation era to quiessence model for $\gamma<-1$. For these two fluid models, the statefinder parameters describe different phase of the evolution of the universe. |
gr-qc/0302018 | Daniele Oriti | Etera R. Livine, Daniele Oriti | Causality in spin foam models for quantum gravity | 6 pages; uses IOP conference macros; to appear in the Proceedings of
the 15th SIGRAV Conference on General Relativity and Gravitational Physics | null | null | DAMTP-2003-10 | gr-qc | null | We describe how the Barrett-Crane spin foam model defines transition
amplitudes for quantum gravity states and how causality can be consistently
implemented in it.
| [
{
"created": "Thu, 6 Feb 2003 16:38:18 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Livine",
"Etera R.",
""
],
[
"Oriti",
"Daniele",
""
]
] | We describe how the Barrett-Crane spin foam model defines transition amplitudes for quantum gravity states and how causality can be consistently implemented in it. |
gr-qc/9309025 | Robert Caldwell | R. R. Caldwell | Green's function for gravitational waves in FRW spacetimes | 9 pages, FERMILAB-Pub-93/189-A | Phys.Rev. D48 (1993) 4688-4692 | 10.1103/PhysRevD.48.4688 | null | gr-qc astro-ph | null | A method for calculating the retarded Green's function for the gravitational
wave equation in Friedmann-Roberson-Walker spacetimes, within the formalism of
linearized Einstein gravity is developed. Hadamard's general solution to
Cauchy's problem for second-order, linear partial differential equations is
applied to the FRW gravitational wave equation. The retarded Green's function
may be calculated for any FRW spacetime, with curved or flat spatial sections,
for which the functional form of the Ricci scalar curvature $R$ is known. The
retarded Green's function for gravitational waves propagating through a
cosmological fluid composed of both radiation and dust is calculated
analytically for the first time. It is also shown that for all FRW spacetimes
in which the Ricci scalar curvatures does not vanish, $R \neq 0$, the Green's
function violates Huygens' principle; the Green's function has support inside
the light-cone due to the scatter of gravitational waves off the background
curvature.
| [
{
"created": "Fri, 24 Sep 1993 21:16:16 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Caldwell",
"R. R.",
""
]
] | A method for calculating the retarded Green's function for the gravitational wave equation in Friedmann-Roberson-Walker spacetimes, within the formalism of linearized Einstein gravity is developed. Hadamard's general solution to Cauchy's problem for second-order, linear partial differential equations is applied to the FRW gravitational wave equation. The retarded Green's function may be calculated for any FRW spacetime, with curved or flat spatial sections, for which the functional form of the Ricci scalar curvature $R$ is known. The retarded Green's function for gravitational waves propagating through a cosmological fluid composed of both radiation and dust is calculated analytically for the first time. It is also shown that for all FRW spacetimes in which the Ricci scalar curvatures does not vanish, $R \neq 0$, the Green's function violates Huygens' principle; the Green's function has support inside the light-cone due to the scatter of gravitational waves off the background curvature. |
1703.08894 | Jing-Bo Wang | Jingbo Wang and Chao-Guang Huang | The Conformal Field Theory on the Horizon of BTZ Black Hole | 7 pages | Chinese Physics C, 2018, 42(12): 123110-123110 | 10.1088/1674-1137/42/12/123110 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In three dimensional spacetime with negative cosmology constant, the general
relativity can be written as two copies of SO$(2,1)$ Chern-Simons theory. On a
manifold with boundary the Chern-Simons theory induces a conformal field
theory--WZW theory on the boundary. In this paper, it is show that with
suitable boundary condition for BTZ black hole, the WZW theory can reduce to a
massless scalar field on the horizon.
| [
{
"created": "Mon, 27 Mar 2017 01:41:27 GMT",
"version": "v1"
}
] | 2018-11-22 | [
[
"Wang",
"Jingbo",
""
],
[
"Huang",
"Chao-Guang",
""
]
] | In three dimensional spacetime with negative cosmology constant, the general relativity can be written as two copies of SO$(2,1)$ Chern-Simons theory. On a manifold with boundary the Chern-Simons theory induces a conformal field theory--WZW theory on the boundary. In this paper, it is show that with suitable boundary condition for BTZ black hole, the WZW theory can reduce to a massless scalar field on the horizon. |
gr-qc/0610156 | Christian Corda cordac | Christian Corda | Extension of the frequency-range of interferometers for the ''magnetic''
components of gravitational waves? | Accepted for the International Journal of Modern Physics A | Int.J.Mod.Phys.A22:2361-2381,2007 | 10.1142/S0217751X07036452 | null | gr-qc | null | Recently, with an enlighting treatment, Baskaran and Grishchuk have shown the
presence and importance of the so-called ``magnetic'' components of
gravitational waves (GWs), which have to be taken into account in the context
of the total response functions of interferometers for GWs propagating from
arbitrary directions. In this paper the analysis of the response functions for
the magnetic components is generalized in its full frequency dependence, while
in the work of Baskaran and Grishchuk the response functions were computed only
in the approximation of wavelength much larger than the linear dimensions of
the interferometer. It is also shown that the response functions to the
magnetic components grow at high frequencies, differently from the values of
the response functions to the well known ordinary components that decrease at
high frequencies. Thus the magnetic components could in principle become the
dominant part of the signal at high frequencies. This is important for a
potential detection of the signal at high frequencies and confirms that the
magnetic contributions must be taken into account in the data analysis. More,
the fact that the response functions of the magnetic components grow at high
frequencies shows that, in principle, the frequency-range of Earth-based
interferometers could extend to frequencies over 10000 Hz.
| [
{
"created": "Tue, 31 Oct 2006 09:25:19 GMT",
"version": "v1"
},
{
"created": "Sat, 11 Nov 2006 11:08:45 GMT",
"version": "v2"
},
{
"created": "Fri, 17 Nov 2006 11:15:20 GMT",
"version": "v3"
},
{
"created": "Mon, 15 Jan 2007 09:02:53 GMT",
"version": "v4"
},
{
"c... | 2010-10-27 | [
[
"Corda",
"Christian",
""
]
] | Recently, with an enlighting treatment, Baskaran and Grishchuk have shown the presence and importance of the so-called ``magnetic'' components of gravitational waves (GWs), which have to be taken into account in the context of the total response functions of interferometers for GWs propagating from arbitrary directions. In this paper the analysis of the response functions for the magnetic components is generalized in its full frequency dependence, while in the work of Baskaran and Grishchuk the response functions were computed only in the approximation of wavelength much larger than the linear dimensions of the interferometer. It is also shown that the response functions to the magnetic components grow at high frequencies, differently from the values of the response functions to the well known ordinary components that decrease at high frequencies. Thus the magnetic components could in principle become the dominant part of the signal at high frequencies. This is important for a potential detection of the signal at high frequencies and confirms that the magnetic contributions must be taken into account in the data analysis. More, the fact that the response functions of the magnetic components grow at high frequencies shows that, in principle, the frequency-range of Earth-based interferometers could extend to frequencies over 10000 Hz. |
2306.17130 | Heling Deng | Heling Deng, Bence B\'ecsy, Xavier Siemens, Neil J. Cornish and Dustin
R. Madison | Searching for gravitational wave burst in PTA data with piecewise linear
functions | 13 pages, 10 figures | null | null | null | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Transient gravitational waves (aka gravitational wave bursts) within the
nanohertz frequency band could be generated by a variety of astrophysical
phenomena such as the encounter of supermassive black holes, the kinks or cusps
in cosmic strings, or other as-yet-unknown physical processes. Radio-pulses
emitted from millisecond pulsars could be perturbed by passing gravitational
waves, hence the correlation of the perturbations in a pulsar timing array can
be used to detect and characterize burst signals with a duration of
$\mathcal{O}(1\text{-}10)$ years. We propose a fully Bayesian framework for the
analysis of the pulsar timing array data, where the burst waveform is
generically modeled by piecewise straight lines, and the waveform parameters in
the likelihood can be integrated out analytically. As a result, with merely
three parameters (in addition to those describing the pulsars' intrinsic and
background noise), one is able to efficiently search for the existence and the
sky location of {a burst signal}. If a signal is present, the posterior of the
waveform can be found without further Bayesian inference. We demonstrate this
model by analyzing simulated data sets containing a stochastic gravitational
wave background {and a burst signal generated by the parabolic encounter of two
supermassive black holes.
| [
{
"created": "Thu, 29 Jun 2023 17:33:57 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Jul 2023 15:00:59 GMT",
"version": "v2"
}
] | 2023-07-13 | [
[
"Deng",
"Heling",
""
],
[
"Bécsy",
"Bence",
""
],
[
"Siemens",
"Xavier",
""
],
[
"Cornish",
"Neil J.",
""
],
[
"Madison",
"Dustin R.",
""
]
] | Transient gravitational waves (aka gravitational wave bursts) within the nanohertz frequency band could be generated by a variety of astrophysical phenomena such as the encounter of supermassive black holes, the kinks or cusps in cosmic strings, or other as-yet-unknown physical processes. Radio-pulses emitted from millisecond pulsars could be perturbed by passing gravitational waves, hence the correlation of the perturbations in a pulsar timing array can be used to detect and characterize burst signals with a duration of $\mathcal{O}(1\text{-}10)$ years. We propose a fully Bayesian framework for the analysis of the pulsar timing array data, where the burst waveform is generically modeled by piecewise straight lines, and the waveform parameters in the likelihood can be integrated out analytically. As a result, with merely three parameters (in addition to those describing the pulsars' intrinsic and background noise), one is able to efficiently search for the existence and the sky location of {a burst signal}. If a signal is present, the posterior of the waveform can be found without further Bayesian inference. We demonstrate this model by analyzing simulated data sets containing a stochastic gravitational wave background {and a burst signal generated by the parabolic encounter of two supermassive black holes. |
1407.0025 | Wolfgang Wieland | Wolfgang M. Wieland | New action for simplicial gravity in four dimensions | 26 pages, 2 figures | Class. Quantum Grav. 32 (2015) 015016 | 10.1088/0264-9381/32/1/015016 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a proposal for a theory of simplicial gravity with spinors as the
fundamental configuration variables. The underlying action describes a
mechanical system with finitely many degrees of freedom, the system has a
Hamiltonian and local gauge symmetries. We will close with some comments on the
resulting quantum theory, and explain the relation to loop quantum gravity and
twisted geometries. The paper appears in parallel with an article by Cort\^es
and Smolin, who study the relevance of the model for energetic causal sets and
various other approaches to quantum gravity.
| [
{
"created": "Mon, 30 Jun 2014 20:00:27 GMT",
"version": "v1"
}
] | 2014-12-09 | [
[
"Wieland",
"Wolfgang M.",
""
]
] | We develop a proposal for a theory of simplicial gravity with spinors as the fundamental configuration variables. The underlying action describes a mechanical system with finitely many degrees of freedom, the system has a Hamiltonian and local gauge symmetries. We will close with some comments on the resulting quantum theory, and explain the relation to loop quantum gravity and twisted geometries. The paper appears in parallel with an article by Cort\^es and Smolin, who study the relevance of the model for energetic causal sets and various other approaches to quantum gravity. |
gr-qc/0412008 | Mladen Martinis Dr | Mladen Martinis and Vesna Mikuta-Martinis | Quantum Horizons and Space-Time Non-Commutativity | LaTex, 6 pages, no figures, Expanded version of a poster presented at
5 European Advanced Study Conference in Ancient Olympia, Greece, July 2004.
to appear in a special issue of IJBC | null | null | null | gr-qc | null | We study dynamics of a scalar field in the near-horizon region described by a
static Klein-Gordon operator which is the Hamiltonian of the system. The
explicite construction of a time operator near-horizon is given and its
self-adjointness discussed.
| [
{
"created": "Thu, 2 Dec 2004 18:19:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Martinis",
"Mladen",
""
],
[
"Mikuta-Martinis",
"Vesna",
""
]
] | We study dynamics of a scalar field in the near-horizon region described by a static Klein-Gordon operator which is the Hamiltonian of the system. The explicite construction of a time operator near-horizon is given and its self-adjointness discussed. |
2301.06480 | Sumati Surya | Anish Bhattacharya, Abhishek Mathur, Sumati Surya | Null Geodesics from Ladder Molecules | Contribution to the collection "Singularity theorems, causality, and
all that (SCRI21)" in the journal General Relativity and Gravitation, in
honor of Roger Penrose | null | 10.1007/s10714-023-03074-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a discrete analogue of null geodesics in causal sets that are
approximated by a region of 2d Minkowski spacetime, in the spirit of Kronheimer
and Penrose's "grids" and "beams" for an abstract causal space. The causal set
analogues are "ladder molecules", whose rungs are linked pairs of elements
corresponding loosely to Barton et al's horizon bi-atoms. In 2d a ladder
molecule traps a ribbon of null geodesics corresponding to a thickened or
fuzzed out horizon. The existence of a ladder between linked pairs of elements
in turn provides a generalisation of the horismotic relation to causal sets.
Simulations of causal sets approximated by a region of 2d Minkowski spacetime
show that ladder molecules are fairly dense in the causal set, and provide a
light-cone like grid. Moreover, similar to the uniqueness of null geodesics
between horismotically related events in the spacetime, in such causal sets
there is a unique ladder molecule between any two linked pairs which are
related by the generalised horismotic relation.
| [
{
"created": "Mon, 16 Jan 2023 15:39:03 GMT",
"version": "v1"
}
] | 2023-02-15 | [
[
"Bhattacharya",
"Anish",
""
],
[
"Mathur",
"Abhishek",
""
],
[
"Surya",
"Sumati",
""
]
] | We propose a discrete analogue of null geodesics in causal sets that are approximated by a region of 2d Minkowski spacetime, in the spirit of Kronheimer and Penrose's "grids" and "beams" for an abstract causal space. The causal set analogues are "ladder molecules", whose rungs are linked pairs of elements corresponding loosely to Barton et al's horizon bi-atoms. In 2d a ladder molecule traps a ribbon of null geodesics corresponding to a thickened or fuzzed out horizon. The existence of a ladder between linked pairs of elements in turn provides a generalisation of the horismotic relation to causal sets. Simulations of causal sets approximated by a region of 2d Minkowski spacetime show that ladder molecules are fairly dense in the causal set, and provide a light-cone like grid. Moreover, similar to the uniqueness of null geodesics between horismotically related events in the spacetime, in such causal sets there is a unique ladder molecule between any two linked pairs which are related by the generalised horismotic relation. |
gr-qc/9910098 | Nistor Nicolaevici | Nistor Nicolaevici | Quantum radiation from a partially reflecting moving mirror | 20 pages, LaTeX | Class.Quant.Grav.18:619-628,2001 | 10.1088/0264-9381/18/4/304 | null | gr-qc | null | We consider the quantum radiation from a partially reflecting moving mirror
for the massless scalar field in 1+1 Minkowski space. Partial reflectivity is
achieved by localizing a delta-type potential at the mirror's position. The
radiated flux is exactly obtained for arbitrary motions as an integral
functional of the mirror's past trajectory. Partial reflectivity corrections to
the perfect mirror result are discussed.
| [
{
"created": "Wed, 27 Oct 1999 00:33:39 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Mar 2000 23:43:19 GMT",
"version": "v2"
},
{
"created": "Wed, 29 Mar 2000 19:51:57 GMT",
"version": "v3"
}
] | 2011-07-19 | [
[
"Nicolaevici",
"Nistor",
""
]
] | We consider the quantum radiation from a partially reflecting moving mirror for the massless scalar field in 1+1 Minkowski space. Partial reflectivity is achieved by localizing a delta-type potential at the mirror's position. The radiated flux is exactly obtained for arbitrary motions as an integral functional of the mirror's past trajectory. Partial reflectivity corrections to the perfect mirror result are discussed. |
1104.3775 | Alexandre Baranov | Alexandre M.Baranov | Lightons and Helixons as Lightlike Particles in General Relativity | 8 pages, 1 figure, Journal of Siberian Federal University.
Mathematics & Physics | J.Sib.Fed.U.4:3-10,2011 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The exterior gravitational fields of the massive Schwarzschild, Kerr and NUT
particles have an algebraic type {\bfseries D} according to Petrov's algebraic
classification of the gravitational fields. A lightlike limit is input for
these particles. It is shown that under this limiting procedure the
gravitational fields of the particles are transformed into the gravitational
fields of the lightlike particles a lighton and a helixon. On the other hand
this limit can be described as a cusp catastrophe on a level of Weyl's matrix
with a change of a gravitational field symmetry of such sources. In considered
cases we have a phase gravitational transition of second kind from {\bfseries
D} type into {\bfseries N} type or {\bfseries III} type. There is a transition
of one "phase" to another. Petrov's algebraic types are the different "phases"
of the gravitational field. It is shown that the lightlike sources in General
Relativity "have no hairs".
| [
{
"created": "Tue, 19 Apr 2011 15:24:03 GMT",
"version": "v1"
}
] | 2011-05-24 | [
[
"Baranov",
"Alexandre M.",
""
]
] | The exterior gravitational fields of the massive Schwarzschild, Kerr and NUT particles have an algebraic type {\bfseries D} according to Petrov's algebraic classification of the gravitational fields. A lightlike limit is input for these particles. It is shown that under this limiting procedure the gravitational fields of the particles are transformed into the gravitational fields of the lightlike particles a lighton and a helixon. On the other hand this limit can be described as a cusp catastrophe on a level of Weyl's matrix with a change of a gravitational field symmetry of such sources. In considered cases we have a phase gravitational transition of second kind from {\bfseries D} type into {\bfseries N} type or {\bfseries III} type. There is a transition of one "phase" to another. Petrov's algebraic types are the different "phases" of the gravitational field. It is shown that the lightlike sources in General Relativity "have no hairs". |
1307.8144 | Laura Sampson | Laura Sampson, Nicolas Yunes, and Neil Cornish | A Rosetta Stone for Parameterized Tests of Gravity | 13 pages, 1 figure, 7 tables, submitted to Phys. Rev. D | null | 10.1103/PhysRevD.88.064056 | null | gr-qc astro-ph.HE hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several model-independent parameterizations of deviations from General
Relativity have been developed to test Einstein's theory. Although these
different parameterizations were developed for different gravitational
observables, they ultimately all test the same underlying physics. In this
paper, we develop connections between the parameterized post-Newtonian,
parameterized post-Keplerian, and the parameterized post-Einsteinian
frameworks, developed to carry out tests of General Relativity with Solar
System, binary pulsar, and gravitational wave observations respectively. These
connections allow us to use knowledge gained from one framework to inform and
guide tests using the others. Relating these parameterizations and combining
the results from each approach strengthens our tests of General Relativity.
| [
{
"created": "Tue, 30 Jul 2013 20:56:15 GMT",
"version": "v1"
}
] | 2015-06-16 | [
[
"Sampson",
"Laura",
""
],
[
"Yunes",
"Nicolas",
""
],
[
"Cornish",
"Neil",
""
]
] | Several model-independent parameterizations of deviations from General Relativity have been developed to test Einstein's theory. Although these different parameterizations were developed for different gravitational observables, they ultimately all test the same underlying physics. In this paper, we develop connections between the parameterized post-Newtonian, parameterized post-Keplerian, and the parameterized post-Einsteinian frameworks, developed to carry out tests of General Relativity with Solar System, binary pulsar, and gravitational wave observations respectively. These connections allow us to use knowledge gained from one framework to inform and guide tests using the others. Relating these parameterizations and combining the results from each approach strengthens our tests of General Relativity. |
2101.02958 | Sajal Mukherjee | Sajal Mukherjee and Naresh Dadhich | Pure Gauss-Bonnet NUT Black Hole Solution: I | 19 pages, 5 figures, Published in: Eur.Phys.J.C | null | 10.1140/epjc/s10052-022-10256-6 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We find a new exact $\Lambda$-vacuum solution in pure Gauss-Bonnet gravity
with NUT charge in six dimension with horizon having product topology $S^{(2)}
\times S^{(2)}$. We also discuss its horizon and singularity structure, and
consequently arrive at a parameter window for its physical viability. It should
be noted that all NUT black hole solutions in higher dimensions have product,
instead of spherical, topology. We prove, in general, that it is because of the
radial symmetry of the NUT spacetime; i.e. in higher dimensions NUT spacetime
cannot maintain radial symmetry unless horizon has $S^{(2)}$ or its product
topology. On the way we also prove a general result for spherical symmetry that
when null energy condition is satisfied, one has then only to solve a first
order equation to get a vacuum or $\Lambda$-vacuum solution.
| [
{
"created": "Fri, 8 Jan 2021 10:59:41 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Apr 2022 13:42:08 GMT",
"version": "v2"
}
] | 2022-04-13 | [
[
"Mukherjee",
"Sajal",
""
],
[
"Dadhich",
"Naresh",
""
]
] | We find a new exact $\Lambda$-vacuum solution in pure Gauss-Bonnet gravity with NUT charge in six dimension with horizon having product topology $S^{(2)} \times S^{(2)}$. We also discuss its horizon and singularity structure, and consequently arrive at a parameter window for its physical viability. It should be noted that all NUT black hole solutions in higher dimensions have product, instead of spherical, topology. We prove, in general, that it is because of the radial symmetry of the NUT spacetime; i.e. in higher dimensions NUT spacetime cannot maintain radial symmetry unless horizon has $S^{(2)}$ or its product topology. On the way we also prove a general result for spherical symmetry that when null energy condition is satisfied, one has then only to solve a first order equation to get a vacuum or $\Lambda$-vacuum solution. |
gr-qc/0211100 | Ettore Minguzzi | E. Caponio and E. Minguzzi | Solutions to the Lorentz force equation with fixed charge-to-mass ratio
in globally hyperbolic spacetimes | AMS-Latex, 9 pages | J.Geom.Phys. 49 (2004) 176-186 | 10.1016/S0393-0440(03)00073-1 | null | gr-qc | null | We extend the classical Avez-Seifert theorem to trajectories of charged test
particles with fixed charge-to-mass ratio. In particular, given two events
x_{0} and x_{1}, with x_{1} in the chronological future of x_{0}, we find an
interval I=]-R,R[ such that for any q/m in I there is a timelike connecting
solution of the Lorentz force equation. Moreover, under the assumption that
there is no null geodesic connecting x_0 and x_1, we prove that to any value of
|q/m| there correspond at least two connecting timelike solutions which
coincide only if they are geodesics.
| [
{
"created": "Thu, 28 Nov 2002 18:41:08 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Feb 2003 19:22:04 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Caponio",
"E.",
""
],
[
"Minguzzi",
"E.",
""
]
] | We extend the classical Avez-Seifert theorem to trajectories of charged test particles with fixed charge-to-mass ratio. In particular, given two events x_{0} and x_{1}, with x_{1} in the chronological future of x_{0}, we find an interval I=]-R,R[ such that for any q/m in I there is a timelike connecting solution of the Lorentz force equation. Moreover, under the assumption that there is no null geodesic connecting x_0 and x_1, we prove that to any value of |q/m| there correspond at least two connecting timelike solutions which coincide only if they are geodesics. |
2012.06356 | Francisco Lobo | Francisco Cabral, Francisco S. N. Lobo, Diego Rubiera-Garcia | Fundamental Symmetries and Spacetime Geometries in Gauge Theories of
Gravity: Prospects for Unified Field Theories | 33 pages. Invite review to the Special Issue "80 Years of Professor
Wigner's Seminal Work "On Unitary Representations of the Inhomogeneous
Lorentz Group"". Matches published version | Universe 2020, 6(12), 238 | 10.3390/universe6120238 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravity can be formulated as a gauge theory by combining symmetry principles
and geometrical methods in a consistent mathematical framework. The gauge
approach to gravity leads directly to non-Euclidean, post-Riemannian spacetime
geometries, providing the adequate formalism for metric-affine theories of
gravity with curvature, torsion and non-metricity. In this paper, we analyze
the structure of gauge theories of gravity and consider the relation between
fundamental geometrical objects and symmetry principles as well as different
spacetime paradigms. Special attention is given to Poincar\'{e} gauge theories
of gravity, their field equations and Noether conserved currents, which are the
sources of gravity. We then discuss several topics of the gauge approach to
gravitational phenomena, namely, quadratic Poincar\'{e} gauge models,
the~Einstein-Cartan-Sciama-Kibble theory, the teleparallel equivalent of
general relativity, quadratic metric-affine Lagrangians, non-Lorentzian
connections, and the breaking of Lorentz invariance in the presence of
non-metricity. We also highlight the probing of post-Riemannian geometries with
test matter. Finally, we briefly discuss some perspectives regarding the role
of both geometrical methods and symmetry principles towards unified field
theories and a new spacetime paradigm, motivated from the gauge approach to
gravity.
| [
{
"created": "Fri, 11 Dec 2020 13:55:56 GMT",
"version": "v1"
}
] | 2020-12-14 | [
[
"Cabral",
"Francisco",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Rubiera-Garcia",
"Diego",
""
]
] | Gravity can be formulated as a gauge theory by combining symmetry principles and geometrical methods in a consistent mathematical framework. The gauge approach to gravity leads directly to non-Euclidean, post-Riemannian spacetime geometries, providing the adequate formalism for metric-affine theories of gravity with curvature, torsion and non-metricity. In this paper, we analyze the structure of gauge theories of gravity and consider the relation between fundamental geometrical objects and symmetry principles as well as different spacetime paradigms. Special attention is given to Poincar\'{e} gauge theories of gravity, their field equations and Noether conserved currents, which are the sources of gravity. We then discuss several topics of the gauge approach to gravitational phenomena, namely, quadratic Poincar\'{e} gauge models, the~Einstein-Cartan-Sciama-Kibble theory, the teleparallel equivalent of general relativity, quadratic metric-affine Lagrangians, non-Lorentzian connections, and the breaking of Lorentz invariance in the presence of non-metricity. We also highlight the probing of post-Riemannian geometries with test matter. Finally, we briefly discuss some perspectives regarding the role of both geometrical methods and symmetry principles towards unified field theories and a new spacetime paradigm, motivated from the gauge approach to gravity. |
2105.12572 | Pramit Rej | Pramit Rej and Piyali Bhar | Charged strange star in $f(R,T)$ gravity with linear equation of state | 26 Pages, 10 Figures | Astrophysics and Space Science 366, 35 (2021) | 10.1007/s10509-021-03943-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Our present study involves the strange stars model in the framework of
$f(R,T)$ theory of gravitation. We have taken a linear function of the Ricci
scalar $R$ and the trace $T$ of the stress-energy tensor $T_{\mu \nu}$ for the
expression of $f(R,T)$, i.e., $f(R,T)=R+ 2 \gamma T $ to obtain the proposed
model, where $\gamma$ is a coupling constant. Moreover, to solve the
hydrostatic equilibrium equations, we consider a linear equation of state
between the radial pressure $p_r$ and matter density $\rho$ as $p_r=\alpha
\rho-\beta$, where $\alpha$ and $\beta$ are some positive constants, Both
$\alpha,\,\beta$ depend on coupling constant $\gamma$ which have been also
depicted in this paper. By employing the Krori-Barua {\em ansatz} already
reported in the literature [J. Phys. A, Math. Gen. 8:508, 1975] we have found
the solutions of the field equations in $f (R, T )$ gravity. The effect of
coupling constant $\gamma$ have been studied on the model parameters like
density, pressures, anisotropic factor, compactness, surface redshift, etc.
both numerically and graphically. A suitable range for $\gamma$ is also
obtained. The physical acceptability and stability of the stellar system have
been tested by different physical tests, e.g., the causality condition, Herrera
cracking concept, relativistic adiabatic index, energy conditions, etc. One can
regain the solutions in Einstein gravity when $\gamma\rightarrow 0$
| [
{
"created": "Tue, 25 May 2021 14:48:11 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Jun 2021 01:58:03 GMT",
"version": "v2"
}
] | 2021-06-02 | [
[
"Rej",
"Pramit",
""
],
[
"Bhar",
"Piyali",
""
]
] | Our present study involves the strange stars model in the framework of $f(R,T)$ theory of gravitation. We have taken a linear function of the Ricci scalar $R$ and the trace $T$ of the stress-energy tensor $T_{\mu \nu}$ for the expression of $f(R,T)$, i.e., $f(R,T)=R+ 2 \gamma T $ to obtain the proposed model, where $\gamma$ is a coupling constant. Moreover, to solve the hydrostatic equilibrium equations, we consider a linear equation of state between the radial pressure $p_r$ and matter density $\rho$ as $p_r=\alpha \rho-\beta$, where $\alpha$ and $\beta$ are some positive constants, Both $\alpha,\,\beta$ depend on coupling constant $\gamma$ which have been also depicted in this paper. By employing the Krori-Barua {\em ansatz} already reported in the literature [J. Phys. A, Math. Gen. 8:508, 1975] we have found the solutions of the field equations in $f (R, T )$ gravity. The effect of coupling constant $\gamma$ have been studied on the model parameters like density, pressures, anisotropic factor, compactness, surface redshift, etc. both numerically and graphically. A suitable range for $\gamma$ is also obtained. The physical acceptability and stability of the stellar system have been tested by different physical tests, e.g., the causality condition, Herrera cracking concept, relativistic adiabatic index, energy conditions, etc. One can regain the solutions in Einstein gravity when $\gamma\rightarrow 0$ |
1109.0198 | Brian Dolan | Brian P. Dolan | Compressibility of rotating black holes | 8 pages, 1 figure, uses revtex4, references added in v2 | Phys. Rev. D84 (2011) 127503 | 10.1103/PhysRevD.84.127503 | DIAS-STP-11-11 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Interpreting the cosmological constant as a pressure, whose thermodynamically
conjugate variable is a volume, modifies the first law of black hole
thermodynamics. Properties of the resulting thermodynamic volume are
investigated: the compressibility and the speed of sound of the black hole are
derived in the case of non-positive cosmological constant. The adiabatic
compressibility vanishes for a non-rotating black hole and is maximal in the
extremal case --- comparable with, but still less than, that of a cold neutron
star. A speed of sound $v_s$ is associated with the adiabatic compressibility,
which is is equal to $c$ for a non-rotating black hole and decreases as the
angular momentum is increased. An extremal black hole has $v_s^2=0.9 \,c^2$
when the cosmological constant vanishes, and more generally $v_s$ is bounded
below by $c/ {\sqrt 2}$.
| [
{
"created": "Thu, 1 Sep 2011 14:45:27 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Dec 2011 09:43:52 GMT",
"version": "v2"
}
] | 2012-03-07 | [
[
"Dolan",
"Brian P.",
""
]
] | Interpreting the cosmological constant as a pressure, whose thermodynamically conjugate variable is a volume, modifies the first law of black hole thermodynamics. Properties of the resulting thermodynamic volume are investigated: the compressibility and the speed of sound of the black hole are derived in the case of non-positive cosmological constant. The adiabatic compressibility vanishes for a non-rotating black hole and is maximal in the extremal case --- comparable with, but still less than, that of a cold neutron star. A speed of sound $v_s$ is associated with the adiabatic compressibility, which is is equal to $c$ for a non-rotating black hole and decreases as the angular momentum is increased. An extremal black hole has $v_s^2=0.9 \,c^2$ when the cosmological constant vanishes, and more generally $v_s$ is bounded below by $c/ {\sqrt 2}$. |
1402.6211 | Yan Wang | Yan Wang | Likelihood transform: making optimization and parameter estimation
easier | 5 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Parameterized optimization and parameter estimation is of great importance in
almost every branch of modern science, technology and engineering. A practical
issue in the problem is that when the parameter space is large and the
available data is noisy, the geometry of the likelihood surface in the
parameter space will be complicated. This makes searching and optimization
algorithms computationally expensive, sometimes even beyond reach. In this
paper, we define a likelihood transform which can make the structure of the
likelihood surface much simpler, hence reducing the intrinsic complexity and
easing optimization significantly. We demonstrate the properties of likelihood
transform by apply it to a simplified gravitational wave chirp signal search.
For the signal with an signal-to-noise ratio 20, likelihood transform has made
a deterministic template-based search possible for the first time, which turns
out to be 1000 times more efficient than an exhaustive grid- based search. The
method in principle can be applied to other problems in other fields as the
spirit of parameterized optimization and parameter estimation problem is the
same.
| [
{
"created": "Tue, 25 Feb 2014 15:50:45 GMT",
"version": "v1"
}
] | 2014-02-26 | [
[
"Wang",
"Yan",
""
]
] | Parameterized optimization and parameter estimation is of great importance in almost every branch of modern science, technology and engineering. A practical issue in the problem is that when the parameter space is large and the available data is noisy, the geometry of the likelihood surface in the parameter space will be complicated. This makes searching and optimization algorithms computationally expensive, sometimes even beyond reach. In this paper, we define a likelihood transform which can make the structure of the likelihood surface much simpler, hence reducing the intrinsic complexity and easing optimization significantly. We demonstrate the properties of likelihood transform by apply it to a simplified gravitational wave chirp signal search. For the signal with an signal-to-noise ratio 20, likelihood transform has made a deterministic template-based search possible for the first time, which turns out to be 1000 times more efficient than an exhaustive grid- based search. The method in principle can be applied to other problems in other fields as the spirit of parameterized optimization and parameter estimation problem is the same. |
1403.7215 | Scott Robertson | Scott Robertson | Integral method for the calculation of Hawking radiation in dispersive
media II. Asymmetric asymptotics | 41 pages, 6 figures | null | 10.1103/PhysRevE.90.053303 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Analogue gravity experiments make feasible the realisation of black hole
spacetimes in a laboratory setting and the observational verification of
Hawking radiation. Since such analogue systems are typically dominated by
dispersion, efficient techniques for calculating the predicted Hawking spectrum
in the presence of strong dispersion are required. In the preceding paper, an
integral method in Fourier space is proposed for stationary $1+1$-dimensional
backgrounds which are asymptotically symmetric. Here, this method is
generalised to backgrounds which are different in the asymptotic regions to the
left and right of the scattering region.
| [
{
"created": "Thu, 27 Mar 2014 21:06:28 GMT",
"version": "v1"
}
] | 2015-06-19 | [
[
"Robertson",
"Scott",
""
]
] | Analogue gravity experiments make feasible the realisation of black hole spacetimes in a laboratory setting and the observational verification of Hawking radiation. Since such analogue systems are typically dominated by dispersion, efficient techniques for calculating the predicted Hawking spectrum in the presence of strong dispersion are required. In the preceding paper, an integral method in Fourier space is proposed for stationary $1+1$-dimensional backgrounds which are asymptotically symmetric. Here, this method is generalised to backgrounds which are different in the asymptotic regions to the left and right of the scattering region. |
2210.07673 | Flavio Bombacigno | Flavio Bombacigno, Fabio Moretti, Simon Boudet, Gonzalo J. Olmo | Landau damping for gravitational waves in parity-violating theories | version accepted for publication in JCAP | JCAP02 (2023) 009 | 10.1088/1475-7516/2023/02/009 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We discuss how tensor polarizations of gravitational waves can suffer Landau
damping in the presence of velocity birefringence, when parity symmetry is
explicitly broken. In particular, we analyze the role of the Nieh-Yan and
Chern-Simons terms in modified theories of gravity, showing how the
gravitational perturbation in collisionless media can be characterized by a
subluminal phase velocity, circumventing the well-known results of General
Relativity and allowing for the appearance of the kinematic damping. We
investigate in detail the connection between the thermodynamic properties of
the medium, such as temperature and mass of the particles interacting with the
gravitational wave, and the parameters ruling the parity violating terms of the
models. In this respect, we outline how the dispersion relations can give rise
in each model to different regions of the wavenumber space, where the phase
velocity is subluminal, superluminal or does not exist. Quantitative estimates
on the considered models indicate that the phenomenon of Landau damping is not
detectable given the sensitivity of present-day instruments.
| [
{
"created": "Fri, 14 Oct 2022 09:56:43 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Jan 2023 20:35:25 GMT",
"version": "v2"
}
] | 2023-02-07 | [
[
"Bombacigno",
"Flavio",
""
],
[
"Moretti",
"Fabio",
""
],
[
"Boudet",
"Simon",
""
],
[
"Olmo",
"Gonzalo J.",
""
]
] | We discuss how tensor polarizations of gravitational waves can suffer Landau damping in the presence of velocity birefringence, when parity symmetry is explicitly broken. In particular, we analyze the role of the Nieh-Yan and Chern-Simons terms in modified theories of gravity, showing how the gravitational perturbation in collisionless media can be characterized by a subluminal phase velocity, circumventing the well-known results of General Relativity and allowing for the appearance of the kinematic damping. We investigate in detail the connection between the thermodynamic properties of the medium, such as temperature and mass of the particles interacting with the gravitational wave, and the parameters ruling the parity violating terms of the models. In this respect, we outline how the dispersion relations can give rise in each model to different regions of the wavenumber space, where the phase velocity is subluminal, superluminal or does not exist. Quantitative estimates on the considered models indicate that the phenomenon of Landau damping is not detectable given the sensitivity of present-day instruments. |
1804.10284 | Michael Reisenberger | Michael P Reisenberger | The Poisson brackets of free null initial data for vacuum general
relativity | 55 pages, 2 figures | null | 10.1088/1361-6382/aad569 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A hypersurface composed of two null sheets, or "light fronts", swept out by
the two congruences of future null normal geodesics emerging from a spacelike
2-disk can serve as a Cauchy surface for a region of spacetime. Already in the
1960s free (unconstrained) initial data for vacuum general relativity were
found for hypersurfaces of this type. Here the Poisson brackets of such free
initial data are calculated from the Hilbert action. The brackets obtained can
form the starting point for a constraint free canonical quantization of general
relativity and may be relevant to holographic entropy bounds for vacuum
gravity. Several of the results of the present work have been presented in
abbreviated form in the letter [Rei08].
| [
{
"created": "Thu, 26 Apr 2018 21:36:46 GMT",
"version": "v1"
}
] | 2018-09-05 | [
[
"Reisenberger",
"Michael P",
""
]
] | A hypersurface composed of two null sheets, or "light fronts", swept out by the two congruences of future null normal geodesics emerging from a spacelike 2-disk can serve as a Cauchy surface for a region of spacetime. Already in the 1960s free (unconstrained) initial data for vacuum general relativity were found for hypersurfaces of this type. Here the Poisson brackets of such free initial data are calculated from the Hilbert action. The brackets obtained can form the starting point for a constraint free canonical quantization of general relativity and may be relevant to holographic entropy bounds for vacuum gravity. Several of the results of the present work have been presented in abbreviated form in the letter [Rei08]. |
gr-qc/9405042 | null | Yoav Peleg | Singularity Free Quasi-Classical Schwarzschild Space-Times | 13p + 3 figures , BRX-TH-357 | null | null | null | gr-qc hep-th | null | Using canonical (Schrodinger) quantization of spherically symetric
gravitational dust systems, we find the quasi-classical (coherent) state,
|\alpha^{(s)}>, that corresponds to the classical Schwarzschild solution. We
calculate the ``quasi-classical Schwarzschild mertic", which is the expectation
value of the quantized metric in thhis quasi-classical state. Depending on the
quantization scheme that we use, we study three different quasi- classical
geometries, all of which turn out to be singularity free. Their maximal
extensions are complete manifolds with no singularities, describing a tower of
asymptotically flat universes connected through Planck size wormholes.
| [
{
"created": "Fri, 20 May 1994 18:52:00 GMT",
"version": "v1"
}
] | 2009-09-25 | [
[
"Peleg",
"Yoav",
""
]
] | Using canonical (Schrodinger) quantization of spherically symetric gravitational dust systems, we find the quasi-classical (coherent) state, |\alpha^{(s)}>, that corresponds to the classical Schwarzschild solution. We calculate the ``quasi-classical Schwarzschild mertic", which is the expectation value of the quantized metric in thhis quasi-classical state. Depending on the quantization scheme that we use, we study three different quasi- classical geometries, all of which turn out to be singularity free. Their maximal extensions are complete manifolds with no singularities, describing a tower of asymptotically flat universes connected through Planck size wormholes. |
2110.13822 | Johannes Bl\"umlein | J. Bl\"umlein, A. Maier, P. Marquard, and G. Sch\"afer | The fifth-order post-Newtonian Hamiltonian dynamics of two-body systems
from an effective field theory approach | 42 pages LATEX, several figures, published version | Nucl Phys B983 (2022) 115900 | 10.1016/j.nuclphysb.2022.115900 | DESY 21--151, DO--TH 21/27, SAGEX--21--30 | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Within an effective field theory method to general relativity, we calculate
the fifth-order post--Newtonian (5 PN) Hamiltonian dynamics also for the tail
terms, extending earlier work on the potential contributions, working in
harmonic coordinates. Here we calculate independently all (local) 5 PN
contributions to the tail terms using the in--in formalism, on which we give a
detailed account. The five expansion terms of the Hamiltonian in the effective
one body (EOB) approach, $q_{82}, q_{63}, q_{44}, \bar{d_5}$ and $a_6$, can all
be determined from the local contributions to periastron advance $K^{\rm
loc,h}(\hat{E},j)$, without further assumptions on the structure of the
symmetric mass ratio, $\nu$, of the expansion coefficients of the scattering
angle $\chi_k$. The $O(\nu^2)$ contributions to the 5 PN EOB parameters have
been unknown in part before. We perform comparisons of our analytic results
with the literature and also present numerical results on some observables.
| [
{
"created": "Tue, 26 Oct 2021 16:19:17 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Jul 2022 17:41:59 GMT",
"version": "v2"
}
] | 2022-08-10 | [
[
"Blümlein",
"J.",
""
],
[
"Maier",
"A.",
""
],
[
"Marquard",
"P.",
""
],
[
"Schäfer",
"G.",
""
]
] | Within an effective field theory method to general relativity, we calculate the fifth-order post--Newtonian (5 PN) Hamiltonian dynamics also for the tail terms, extending earlier work on the potential contributions, working in harmonic coordinates. Here we calculate independently all (local) 5 PN contributions to the tail terms using the in--in formalism, on which we give a detailed account. The five expansion terms of the Hamiltonian in the effective one body (EOB) approach, $q_{82}, q_{63}, q_{44}, \bar{d_5}$ and $a_6$, can all be determined from the local contributions to periastron advance $K^{\rm loc,h}(\hat{E},j)$, without further assumptions on the structure of the symmetric mass ratio, $\nu$, of the expansion coefficients of the scattering angle $\chi_k$. The $O(\nu^2)$ contributions to the 5 PN EOB parameters have been unknown in part before. We perform comparisons of our analytic results with the literature and also present numerical results on some observables. |
1507.07300 | Chiang-Mei Chen | Chiang-Mei Chen, James M. Nester, Roh-Suan Tung | Gravitational Energy for GR and Poincare Gauge Theories: a Covariant
Hamiltonian Approach | This article is to appear in the Int J Mod Phys D and is to be
published also in the book "One Hundred Years of General Relativity: From
Genesis and Empirical Foundations to Gravitational Waves, Cosmology and
Quantum Gravity," edited by Wei-Tou Ni (World Scientific, Singapore, 2015) | Int. J. Mod. Phys. D24 (2015) 1530026 | 10.1142/S0218271815300268 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Our topic concerns a long standing puzzle: the energy of gravitating systems.
More precisely we want to consider, for gravitating systems, how to best
describe energy-momentum and angular momentum/center-of-mass momentum (CoMM).
It is known that these quantities cannot be given by a local density. The
modern understanding is that (i) they are quasi-local (associated with a closed
2-surface), (ii) they have no unique formula, (iii) they have no reference
frame independent description. In the first part of this work we review some
early history, much of it not so well known, on the subject of gravitational
energy in Einstein's general relativity (GR), noting especially Noether's
contribution. In the second part we review (including some new results) much of
our covariant Hamiltonian formalism and apply it to Poincar\'e gauge theories
(GR is a special case). The key point is that the Hamiltonian boundary term has
two roles, it determines the quasi-local quantities, and, furthermore it
determines the boundary conditions for the dynamical variables. Energy-momentum
and angular momentum/CoMM are associated with the geometric symmetries under
Poincar\'e transformations. They are best described in a local Poincar\'e gauge
theory. The type of spacetime that naturally has this symmetry is
Riemann-Cartan spacetime, with a metric compatible connection having, in
general, both curvature and torsion. Thus our expression for the
energy-momentum of physical systems is obtained via our covariant Hamiltonian
formulation applied to Poincar\'e gauge theories.
| [
{
"created": "Mon, 27 Jul 2015 05:07:12 GMT",
"version": "v1"
}
] | 2015-07-29 | [
[
"Chen",
"Chiang-Mei",
""
],
[
"Nester",
"James M.",
""
],
[
"Tung",
"Roh-Suan",
""
]
] | Our topic concerns a long standing puzzle: the energy of gravitating systems. More precisely we want to consider, for gravitating systems, how to best describe energy-momentum and angular momentum/center-of-mass momentum (CoMM). It is known that these quantities cannot be given by a local density. The modern understanding is that (i) they are quasi-local (associated with a closed 2-surface), (ii) they have no unique formula, (iii) they have no reference frame independent description. In the first part of this work we review some early history, much of it not so well known, on the subject of gravitational energy in Einstein's general relativity (GR), noting especially Noether's contribution. In the second part we review (including some new results) much of our covariant Hamiltonian formalism and apply it to Poincar\'e gauge theories (GR is a special case). The key point is that the Hamiltonian boundary term has two roles, it determines the quasi-local quantities, and, furthermore it determines the boundary conditions for the dynamical variables. Energy-momentum and angular momentum/CoMM are associated with the geometric symmetries under Poincar\'e transformations. They are best described in a local Poincar\'e gauge theory. The type of spacetime that naturally has this symmetry is Riemann-Cartan spacetime, with a metric compatible connection having, in general, both curvature and torsion. Thus our expression for the energy-momentum of physical systems is obtained via our covariant Hamiltonian formulation applied to Poincar\'e gauge theories. |
1804.11334 | T. P. Singh | Swanand Khanapurkar, Abhinav Varma, Nehal Mittal, Navya Gupta and
Tejinder P. Singh | Einstein-Cartan-Dirac equations in the Newman-Penrose formalism | 32 pages, 4 figures, Section 5.4 on plane waves rewritten | Phys. Rev. D 98, 064046 (2018) | 10.1103/PhysRevD.98.064046 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We formulate the Einstein-Cartan-Dirac equations in the Newman-Penrose (NP)
formalism, thereby presenting a more accurate and explicit analysis of previous
such studies. The equations show in a transparent way how the Einstein-Dirac
equations are modified by the inclusion of torsion. In particular, the
Hehl-Datta equation is presented in NP notation. We then describe a few
solutions of the Hehl-Datta equation on Minkowski space-time, and in particular
report a solitonic solution which removes the unphysical behavioiur of the
corresponding Dirac solution. The present work serves as a prelude to similar
studies for non-degenerate Poincare gauge gravity.
| [
{
"created": "Mon, 30 Apr 2018 17:27:14 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jun 2018 11:15:39 GMT",
"version": "v2"
}
] | 2018-10-03 | [
[
"Khanapurkar",
"Swanand",
""
],
[
"Varma",
"Abhinav",
""
],
[
"Mittal",
"Nehal",
""
],
[
"Gupta",
"Navya",
""
],
[
"Singh",
"Tejinder P.",
""
]
] | We formulate the Einstein-Cartan-Dirac equations in the Newman-Penrose (NP) formalism, thereby presenting a more accurate and explicit analysis of previous such studies. The equations show in a transparent way how the Einstein-Dirac equations are modified by the inclusion of torsion. In particular, the Hehl-Datta equation is presented in NP notation. We then describe a few solutions of the Hehl-Datta equation on Minkowski space-time, and in particular report a solitonic solution which removes the unphysical behavioiur of the corresponding Dirac solution. The present work serves as a prelude to similar studies for non-degenerate Poincare gauge gravity. |
gr-qc/0601049 | Ujjal Debnath | Ujjal Debnath, Subenoy Chakraborty | Role of Modified Chaplygin Gas as a Dark Energy Model in Collapsing
Spherically Symmetric Cloud | 7 Latex Pages, RexTex style, No figures | Int.J.Theor.Phys.47:2663-2671,2008 | 10.1007/s10773-008-9703-4 | null | gr-qc | null | In this work, gravitational collapse of a spherical cloud, consists of both
dark matter and dark energy in the form of modified Chaplygin gas is studied.
It is found that dark energy alone in the form of modified Chaplygin gas forms
black hole. Also when both components of the fluid are present then the
collapse favors the formation of black hole in cases the dark energy dominates
over dark matter. The conclusion is totally opposite to the usually known
results.
| [
{
"created": "Thu, 12 Jan 2006 07:26:06 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Debnath",
"Ujjal",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | In this work, gravitational collapse of a spherical cloud, consists of both dark matter and dark energy in the form of modified Chaplygin gas is studied. It is found that dark energy alone in the form of modified Chaplygin gas forms black hole. Also when both components of the fluid are present then the collapse favors the formation of black hole in cases the dark energy dominates over dark matter. The conclusion is totally opposite to the usually known results. |
1307.1429 | Juan Antonio Nieto | J. A. Nieto | Higher Dimensional Elko Theory | 10 pages, Latex, revised version | Rev. Mex. Fis. 60 (2014) 371-375 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the so called Elko equation can be derived from a 5-dimensional
Dirac equation. We argue that this result can be relevant for dark matter and
cosmological scenarios. We generalize our procedure to higher dimensions.
| [
{
"created": "Wed, 3 Jul 2013 16:27:58 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Aug 2013 16:26:10 GMT",
"version": "v2"
},
{
"created": "Fri, 11 Oct 2013 15:52:32 GMT",
"version": "v3"
},
{
"created": "Mon, 7 Jul 2014 17:30:32 GMT",
"version": "v4"
}
] | 2014-10-10 | [
[
"Nieto",
"J. A.",
""
]
] | We show that the so called Elko equation can be derived from a 5-dimensional Dirac equation. We argue that this result can be relevant for dark matter and cosmological scenarios. We generalize our procedure to higher dimensions. |
2109.09181 | Andreas Lymperis | Niki Drepanou, Andreas Lymperis, Emmanuel N. Saridakis, Kuralay
Yesmakhanova | Kaniadakis holographic dark energy and cosmology | 16 pages, 3 figures | null | 10.1140/epjc/s10052-022-10415-9 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct a holographic dark energy scenario based on Kaniadakis entropy,
which is a generalization of Boltzmann-Gibbs entropy that arises from
relativistic statistical theory and is characterized by a single parameter $K$
which quantifies the deviations from standard expressions, and we use the
future event horizon as the Infrared cutoff. We extract the differential
equation that determines the evolution of the effective dark energy density
parameter, and we provide analytical expressions for the corresponding
equation-of-state and deceleration parameters. We show that the universe
exhibits the standard thermal history, with the sequence of matter and
dark-energy eras, while the transition to acceleration takes place at
$z\approx0.6$. Concerning the dark-energy equation-of-state parameter we show
that it can have a rich behavior, being quintessence-like, phantom-like, or
experience the phantom-divide crossing in the past or in the future. Finally,
in the far future dark energy dominates completely, and the asymptotic value of
its equation of state depends on the values of the two model parameters.
| [
{
"created": "Sun, 19 Sep 2021 18:08:40 GMT",
"version": "v1"
},
{
"created": "Mon, 16 May 2022 09:23:20 GMT",
"version": "v2"
}
] | 2022-06-01 | [
[
"Drepanou",
"Niki",
""
],
[
"Lymperis",
"Andreas",
""
],
[
"Saridakis",
"Emmanuel N.",
""
],
[
"Yesmakhanova",
"Kuralay",
""
]
] | We construct a holographic dark energy scenario based on Kaniadakis entropy, which is a generalization of Boltzmann-Gibbs entropy that arises from relativistic statistical theory and is characterized by a single parameter $K$ which quantifies the deviations from standard expressions, and we use the future event horizon as the Infrared cutoff. We extract the differential equation that determines the evolution of the effective dark energy density parameter, and we provide analytical expressions for the corresponding equation-of-state and deceleration parameters. We show that the universe exhibits the standard thermal history, with the sequence of matter and dark-energy eras, while the transition to acceleration takes place at $z\approx0.6$. Concerning the dark-energy equation-of-state parameter we show that it can have a rich behavior, being quintessence-like, phantom-like, or experience the phantom-divide crossing in the past or in the future. Finally, in the far future dark energy dominates completely, and the asymptotic value of its equation of state depends on the values of the two model parameters. |
gr-qc/0106056 | Kayll Lake | Nicholas Neary and Kayll Lake | r-modes in the Tolman VII solution | 3 pages one figure. Further information at
http://grtensor.phy.queensu.ca/rmodes/ Revision includes clarifications | null | null | null | gr-qc astro-ph | null | The r-mode frequencies of the Tolman VII solution for the slowly rotating
non-barotropic approximation within the low frequency regime are estimated. The
relativistic correction to Newtonian r-mode calculations is shown as function
of the tenuity $\frac{R}{M}$ and is shown to be significant only for very
compact neutron stars.
| [
{
"created": "Mon, 18 Jun 2001 15:30:50 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Jul 2001 18:07:46 GMT",
"version": "v2"
},
{
"created": "Fri, 31 Aug 2001 16:53:35 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Neary",
"Nicholas",
""
],
[
"Lake",
"Kayll",
""
]
] | The r-mode frequencies of the Tolman VII solution for the slowly rotating non-barotropic approximation within the low frequency regime are estimated. The relativistic correction to Newtonian r-mode calculations is shown as function of the tenuity $\frac{R}{M}$ and is shown to be significant only for very compact neutron stars. |
2401.01532 | Junji Jia | Zonghai Li and Junji Jia | Generating New Spacetimes through Zermelo Navigation | 11 pages, 1 figure; to match the version in PRD | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Zermelo navigation is not only a fundamental tool in Finsler geometry but
also a fundamental approach to the geometrization of dynamics in physics. In
this paper, we consider the Zermelo navigation problem on optical Riemannian
space and, via Zermelo/Randers/spacetime triangle, explore the generation of
new spacetimes from pre-existing ones. Whether the Randers metric has
reversible geodesics corresponds to the presence of time-reversal symmetry in
the generated spacetime. In cases where the Randers metric has reversible
geodesics, we utilize a radial vector field to generate new static spacetimes
from existing ones. For example, we can generate Schwarzschild, Rindler, de
Sitter, and Schwarzschild-de Sitter spacetimes from flat spacetime. In fact,
the Zermelo navigation method allows for the derivation of a variety of static
spacetimes from flat spacetime. For multi-parameter spacetimes, they can be
generated through various navigation paths. However, for some spacetimes, not
all navigation paths may exist. In the second scenario, when the Randers metric
does not have reversible geodesics, we employ a rotational vector field to
transform non-flat static metrics into slowly rotating spacetimes.
Alternatively, using a mixed vector field, we generate slowly rotating
spacetimes starting from flat spacetime. We provide examples of generating Kerr
spacetimes and Kerr-de Sitter spacetimes.
| [
{
"created": "Wed, 3 Jan 2024 04:02:52 GMT",
"version": "v1"
},
{
"created": "Tue, 2 Apr 2024 16:27:27 GMT",
"version": "v2"
}
] | 2024-04-03 | [
[
"Li",
"Zonghai",
""
],
[
"Jia",
"Junji",
""
]
] | Zermelo navigation is not only a fundamental tool in Finsler geometry but also a fundamental approach to the geometrization of dynamics in physics. In this paper, we consider the Zermelo navigation problem on optical Riemannian space and, via Zermelo/Randers/spacetime triangle, explore the generation of new spacetimes from pre-existing ones. Whether the Randers metric has reversible geodesics corresponds to the presence of time-reversal symmetry in the generated spacetime. In cases where the Randers metric has reversible geodesics, we utilize a radial vector field to generate new static spacetimes from existing ones. For example, we can generate Schwarzschild, Rindler, de Sitter, and Schwarzschild-de Sitter spacetimes from flat spacetime. In fact, the Zermelo navigation method allows for the derivation of a variety of static spacetimes from flat spacetime. For multi-parameter spacetimes, they can be generated through various navigation paths. However, for some spacetimes, not all navigation paths may exist. In the second scenario, when the Randers metric does not have reversible geodesics, we employ a rotational vector field to transform non-flat static metrics into slowly rotating spacetimes. Alternatively, using a mixed vector field, we generate slowly rotating spacetimes starting from flat spacetime. We provide examples of generating Kerr spacetimes and Kerr-de Sitter spacetimes. |
gr-qc/9908024 | Massimo Blasone | Massimo Blasone, Yuan-Xing Gui and Francis Vendrell | Geometric Background for Thermal Field Theories | RevTeX, 11 pages, 2 figures | null | null | null | gr-qc hep-th | null | We study a new spacetime which is shown to be the general geometrical
background for Thermal Field Theories at equilibrium. The different formalisms
of Thermal Field Theory are unified in a simple way in this spacetime. The set
of time-paths used in the Path Ordered Method is interpreted in geometrical
terms.
| [
{
"created": "Sat, 7 Aug 1999 18:46:23 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Blasone",
"Massimo",
""
],
[
"Gui",
"Yuan-Xing",
""
],
[
"Vendrell",
"Francis",
""
]
] | We study a new spacetime which is shown to be the general geometrical background for Thermal Field Theories at equilibrium. The different formalisms of Thermal Field Theory are unified in a simple way in this spacetime. The set of time-paths used in the Path Ordered Method is interpreted in geometrical terms. |
2201.06177 | Sebasti\'an N\'ajera Valencia | Sebasti\'an N\'ajera, Aram Aguilar, Geovanny A. Rave-Franco, Celia
Escamilla-Rivera, Roberto A. Sussman | Inhomogeneous solutions in $f(T,B)$ gravity | 17 pages, accepted for publication in IJGMMP | International Journal of Geometric Methods in Modern Physics 2022 | 10.1142/S0219887822400035 | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by/4.0/ | In this paper we explore the possibility to find exact solutions for
Teleparallel Gravity (TG) of the type of spherically symmetric Lema\^\i
tre-Tolman-Bondi (LTB) dust models. We apply to the LTB metric the formalism of
Teleparallel Gravity in its extension to $f(T,B)$ models, which can be seen it
as the analagous from the Schwarzschild solution in General Relativity. An
exact LTB solution is obtained which is compatible with a specific $f(T,B)$
model whose observational constraints are cosmological viable in a standard
spatially flat Robertson-Walker geometry.
| [
{
"created": "Mon, 17 Jan 2022 02:11:41 GMT",
"version": "v1"
}
] | 2022-03-28 | [
[
"Nájera",
"Sebastián",
""
],
[
"Aguilar",
"Aram",
""
],
[
"Rave-Franco",
"Geovanny A.",
""
],
[
"Escamilla-Rivera",
"Celia",
""
],
[
"Sussman",
"Roberto A.",
""
]
] | In this paper we explore the possibility to find exact solutions for Teleparallel Gravity (TG) of the type of spherically symmetric Lema\^\i tre-Tolman-Bondi (LTB) dust models. We apply to the LTB metric the formalism of Teleparallel Gravity in its extension to $f(T,B)$ models, which can be seen it as the analagous from the Schwarzschild solution in General Relativity. An exact LTB solution is obtained which is compatible with a specific $f(T,B)$ model whose observational constraints are cosmological viable in a standard spatially flat Robertson-Walker geometry. |
1910.03763 | Hongguang Liu | Muxin Han, Hongguang Liu | Effective Dynamics from Coherent State Path Integral of Full Loop
Quantum Gravity | 30+10 pages, 2 figures | Phys. Rev. D 101, 046003 (2020) | 10.1103/PhysRevD.101.046003 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new routine is proposed to relate Loop Quant Cosmology (LQC) to Loop
Quantum Gravity (LQG) from the perspective of effective dynamics. We derive the
big-bang singularity resolution and big bounce from the first principle of full
canonical LQG. Our results are obtained in the framework of the reduced phase
space quantization of LQG. As a key step in our work, we derive with coherent
states a new discrete path integral formula of the transition amplitude
generated by the physical Hamiltonian. The semiclassical approximation of the
path integral formula gives an interesting set of effective equations of motion
(EOMs) for full LQG. When solving the EOMs with homogeneous and isotropic
ansatz, we reproduce the LQC effective dynamics in $\mu_0$-scheme. The solution
replaces the big-bang singularity by a big bounce. In the end, we comment on
the possible relation between the $\bar{\mu}$-scheme of effective dynamics and
the continuum limit of the path integral formula.
| [
{
"created": "Wed, 9 Oct 2019 03:01:45 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Dec 2019 16:16:34 GMT",
"version": "v2"
}
] | 2020-02-12 | [
[
"Han",
"Muxin",
""
],
[
"Liu",
"Hongguang",
""
]
] | A new routine is proposed to relate Loop Quant Cosmology (LQC) to Loop Quantum Gravity (LQG) from the perspective of effective dynamics. We derive the big-bang singularity resolution and big bounce from the first principle of full canonical LQG. Our results are obtained in the framework of the reduced phase space quantization of LQG. As a key step in our work, we derive with coherent states a new discrete path integral formula of the transition amplitude generated by the physical Hamiltonian. The semiclassical approximation of the path integral formula gives an interesting set of effective equations of motion (EOMs) for full LQG. When solving the EOMs with homogeneous and isotropic ansatz, we reproduce the LQC effective dynamics in $\mu_0$-scheme. The solution replaces the big-bang singularity by a big bounce. In the end, we comment on the possible relation between the $\bar{\mu}$-scheme of effective dynamics and the continuum limit of the path integral formula. |
1805.03046 | Ken Ng | Ken K. Y. Ng, Salvatore Vitale, Aaron Zimmerman, Katerina
Chatziioannou, Davide Gerosa, Carl-Johan Haster | Gravitational-wave astrophysics with effective-spin measurements:
asymmetries and selection biases | An online generator for synthetic $\chi_{\mathrm{eff}}$ posteriors
can be found at: http://superstring.mit.edu/welcome.html Comments are welcome | Phys. Rev. D 98, 083007 (2018) | 10.1103/PhysRevD.98.083007 | null | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves emitted by coalescing compact objects carry information
about the spin of the individual bodies. However, with present detectors only
the mass-weighted combination of the components of the spin along the orbital
angular momentum can be measured accurately. This quantity, the effective spin
$\chi_{\mathrm{eff}}$, is conserved up to at least the second post-Newtonian
order. The measured distribution of $\chi_{\mathrm{eff}}$ values from a
population of detected binaries, and in particular whether this distribution is
symmetric about zero, encodes valuable information about the underlying
compact-binary formation channels. In this paper we focus on two important
complications of using the effective spin to study astrophysical population
properties: (i) an astrophysical distribution for $\chi_{\mathrm{eff}}$ values
which is symmetric does not necessarily lead to a symmetric distribution for
the detected effective spin values, leading to a \emph{selection bias}; and
(ii) the posterior distribution of $\chi_{\mathrm{eff}}$ for individual events
is \emph{asymmetric} and it cannot usually be treated as a Gaussian. We find
that the posterior distributions for $\chi_{\mathrm{eff}}$ systematically show
fatter tails toward larger positive values, unless the total mass is large or
the mass ratio $m_2/m_1$ is smaller than $\sim 1/2$. Finally we show that
uncertainties in the measurement of $\chi_{\mathrm{eff}}$ are systematically
larger when the true value is negative than when it is positive. All these
factors can bias astrophysical inference about the population when we have more
than $\sim 100$ events and should be taken into account when using
gravitational-wave measurements to characterize astrophysical populations.
| [
{
"created": "Fri, 4 May 2018 19:08:37 GMT",
"version": "v1"
},
{
"created": "Wed, 17 Oct 2018 00:58:55 GMT",
"version": "v2"
}
] | 2018-10-24 | [
[
"Ng",
"Ken K. Y.",
""
],
[
"Vitale",
"Salvatore",
""
],
[
"Zimmerman",
"Aaron",
""
],
[
"Chatziioannou",
"Katerina",
""
],
[
"Gerosa",
"Davide",
""
],
[
"Haster",
"Carl-Johan",
""
]
] | Gravitational waves emitted by coalescing compact objects carry information about the spin of the individual bodies. However, with present detectors only the mass-weighted combination of the components of the spin along the orbital angular momentum can be measured accurately. This quantity, the effective spin $\chi_{\mathrm{eff}}$, is conserved up to at least the second post-Newtonian order. The measured distribution of $\chi_{\mathrm{eff}}$ values from a population of detected binaries, and in particular whether this distribution is symmetric about zero, encodes valuable information about the underlying compact-binary formation channels. In this paper we focus on two important complications of using the effective spin to study astrophysical population properties: (i) an astrophysical distribution for $\chi_{\mathrm{eff}}$ values which is symmetric does not necessarily lead to a symmetric distribution for the detected effective spin values, leading to a \emph{selection bias}; and (ii) the posterior distribution of $\chi_{\mathrm{eff}}$ for individual events is \emph{asymmetric} and it cannot usually be treated as a Gaussian. We find that the posterior distributions for $\chi_{\mathrm{eff}}$ systematically show fatter tails toward larger positive values, unless the total mass is large or the mass ratio $m_2/m_1$ is smaller than $\sim 1/2$. Finally we show that uncertainties in the measurement of $\chi_{\mathrm{eff}}$ are systematically larger when the true value is negative than when it is positive. All these factors can bias astrophysical inference about the population when we have more than $\sim 100$ events and should be taken into account when using gravitational-wave measurements to characterize astrophysical populations. |
1507.08131 | Farruh Atamurotov | Farruh Atamurotov, Bobomurat Ahmedov and Ahmadjon Abdujabbarov | Optical properties of black hole in the presence of plasma: shadow | 7 pages, 4 figures | null | 10.1103/PhysRevD.92.084005 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have studied photon motion around axially symmetric rotating Kerr black
hole in the presence of plasma with radial power-law density. It is shown that
in the presence of plasma the observed shape and size of shadow changes
depending on i) plasma parameters, ii) black hole spin and iii) inclination
angle between observer plane and axis of rotation of black hole. In order to
extract pure effect of plasma influence on black hole image the particular case
of the Schwarzschild black hole has also been investigated and it has been
shown that i) the photon sphere around the spherical symmetric black hole is
left unchanged under the plasma influence, ii) however the Schwarzschild black
hole shadow size in plasma is reduced due to the refraction of the
electromagnetic radiation in plasma environment of black hole. The study of the
energy emission from the black hole in plasma shows that in the presence of
plasma the maximal energy emission rate from the black hole decreases.
| [
{
"created": "Wed, 29 Jul 2015 13:13:05 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Aug 2015 11:55:51 GMT",
"version": "v2"
},
{
"created": "Fri, 28 Aug 2015 05:56:18 GMT",
"version": "v3"
}
] | 2015-10-21 | [
[
"Atamurotov",
"Farruh",
""
],
[
"Ahmedov",
"Bobomurat",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
]
] | We have studied photon motion around axially symmetric rotating Kerr black hole in the presence of plasma with radial power-law density. It is shown that in the presence of plasma the observed shape and size of shadow changes depending on i) plasma parameters, ii) black hole spin and iii) inclination angle between observer plane and axis of rotation of black hole. In order to extract pure effect of plasma influence on black hole image the particular case of the Schwarzschild black hole has also been investigated and it has been shown that i) the photon sphere around the spherical symmetric black hole is left unchanged under the plasma influence, ii) however the Schwarzschild black hole shadow size in plasma is reduced due to the refraction of the electromagnetic radiation in plasma environment of black hole. The study of the energy emission from the black hole in plasma shows that in the presence of plasma the maximal energy emission rate from the black hole decreases. |
1105.0439 | Daniele Pranzetti | Karim Noui, Alejandro Perez, Daniele Pranzetti | Canonical quantization of non-commutative holonomies in 2+1 loop quantum
gravity | 19 pages, references added. Published version | JHEP 1110 (2011) 036 | 10.1007/JHEP10(2011)036 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we investigate the canonical quantization of 2+1 gravity with
cosmological constant $\Lambda>0$ in the canonical framework of loop quantum
gravity. The unconstrained phase space of gravity in 2+1 dimensions is
coordinatized by an SU(2) connection $A$ and the canonically conjugate triad
field $e$. A natural regularization of the constraints of 2+1 gravity can be
defined in terms of the holonomies of $A+=A + \sqrt\Lambda e$. As a first step
towards the quantization of these constraints we study the canonical
quantization of the holonomy of the connection $A_{\lambda}=A+\lambda e$ on the
kinematical Hilbert space of loop quantum gravity. The holonomy operator
associated to a given path acts non trivially on spin network links that are
transversal to the path (a crossing). We provide an explicit construction of
the quantum holonomy operator. In particular, we exhibit a close relationship
between the action of the quantum holonomy at a crossing and Kauffman's
q-deformed crossing identity. The crucial difference is that (being an operator
acting on the kinematical Hilbert space of LQG) the result is completely
described in terms of standard SU(2) spin network states (in contrast to
q-deformed spin networks in Kauffman's identity). We discuss the possible
implications of our result.
| [
{
"created": "Mon, 2 May 2011 20:52:31 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Sep 2011 09:15:02 GMT",
"version": "v2"
}
] | 2012-08-15 | [
[
"Noui",
"Karim",
""
],
[
"Perez",
"Alejandro",
""
],
[
"Pranzetti",
"Daniele",
""
]
] | In this work we investigate the canonical quantization of 2+1 gravity with cosmological constant $\Lambda>0$ in the canonical framework of loop quantum gravity. The unconstrained phase space of gravity in 2+1 dimensions is coordinatized by an SU(2) connection $A$ and the canonically conjugate triad field $e$. A natural regularization of the constraints of 2+1 gravity can be defined in terms of the holonomies of $A+=A + \sqrt\Lambda e$. As a first step towards the quantization of these constraints we study the canonical quantization of the holonomy of the connection $A_{\lambda}=A+\lambda e$ on the kinematical Hilbert space of loop quantum gravity. The holonomy operator associated to a given path acts non trivially on spin network links that are transversal to the path (a crossing). We provide an explicit construction of the quantum holonomy operator. In particular, we exhibit a close relationship between the action of the quantum holonomy at a crossing and Kauffman's q-deformed crossing identity. The crucial difference is that (being an operator acting on the kinematical Hilbert space of LQG) the result is completely described in terms of standard SU(2) spin network states (in contrast to q-deformed spin networks in Kauffman's identity). We discuss the possible implications of our result. |
1808.08386 | Matthew J. Lake Dr | Matthew J. Lake and Bernard Carr | Does Compton/Schwarzschild duality in higher dimensions exclude TeV
quantum gravity? | This paper supersedes and differs considerably from arXiv:1611.01913.
The abstract is similar but the title and main text are changed. The earlier
paper contains discussion of additional points which are not essential for
this paper. 31 pages, 5 figures. Published version (v1). Minor typos in the
Abstract corrected (v2) | International Journal of Modern Physics D, 1930001 (2018) | 10.1142/S0218271819300015 | null | gr-qc hep-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In three spatial dimensions, the Compton wavelength $(R_C \propto M^{-1}$)
and Schwarzschild radius $(R_S \propto M$) are dual under the transformation $M
\rightarrow M_{P}^2/M$, where $M_{P}$ is the Planck mass. This suggests that
there could be a fundamental link -- termed the Black Hole Uncertainty
Principle or Compton-Schwarzschild correspondence -- between elementary
particles with $M < M_{P}$ and black holes in the $M > M_{P}$ regime. In the
presence of $n$ extra dimensions, compactified on some scale $R_E$ exceeding
the Planck length $R_P$, one expects $R_S \propto M^{1/(1+n)}$ for $R_P < R <
R_E$, which breaks this duality. However, it may be restored in some
circumstances because the {\it effective} Compton wavelength of a particle
depends on the form of the $(3+n)$-dimensional wavefunction. If this is
spherically symmetric, then one still has $R_C \propto M^{-1}$, as in the
$3$-dimensional case. The effective Planck length is then increased and the
Planck mass reduced, allowing the possibility of TeV quantum gravity and black
hole production at the LHC. However, if the wave function of a particle is
asymmetric and has a scale $R_E$ in the extra dimensions, then $R_C \propto
M^{-1/(1+n)}$, so that the duality between $R_C$ and $R_S$ is preserved. In
this case, the effective Planck length is increased even more but the Planck
mass is unchanged, so that TeV quantum gravity is precluded and black holes
cannot be generated in collider experiments. Nevertheless, the extra dimensions
could still have consequences for the detectability of black hole evaporations
and the enhancement of pair-production at accelerators on scales below $R_E$.
Though phenomenologically general for higher-dimensional theories, our results
are shown to be consistent with string theory via the minimum positional
uncertainty derived from $D$-particle scattering amplitudes.
| [
{
"created": "Sat, 25 Aug 2018 09:18:07 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Dec 2018 11:27:35 GMT",
"version": "v2"
}
] | 2019-01-23 | [
[
"Lake",
"Matthew J.",
""
],
[
"Carr",
"Bernard",
""
]
] | In three spatial dimensions, the Compton wavelength $(R_C \propto M^{-1}$) and Schwarzschild radius $(R_S \propto M$) are dual under the transformation $M \rightarrow M_{P}^2/M$, where $M_{P}$ is the Planck mass. This suggests that there could be a fundamental link -- termed the Black Hole Uncertainty Principle or Compton-Schwarzschild correspondence -- between elementary particles with $M < M_{P}$ and black holes in the $M > M_{P}$ regime. In the presence of $n$ extra dimensions, compactified on some scale $R_E$ exceeding the Planck length $R_P$, one expects $R_S \propto M^{1/(1+n)}$ for $R_P < R < R_E$, which breaks this duality. However, it may be restored in some circumstances because the {\it effective} Compton wavelength of a particle depends on the form of the $(3+n)$-dimensional wavefunction. If this is spherically symmetric, then one still has $R_C \propto M^{-1}$, as in the $3$-dimensional case. The effective Planck length is then increased and the Planck mass reduced, allowing the possibility of TeV quantum gravity and black hole production at the LHC. However, if the wave function of a particle is asymmetric and has a scale $R_E$ in the extra dimensions, then $R_C \propto M^{-1/(1+n)}$, so that the duality between $R_C$ and $R_S$ is preserved. In this case, the effective Planck length is increased even more but the Planck mass is unchanged, so that TeV quantum gravity is precluded and black holes cannot be generated in collider experiments. Nevertheless, the extra dimensions could still have consequences for the detectability of black hole evaporations and the enhancement of pair-production at accelerators on scales below $R_E$. Though phenomenologically general for higher-dimensional theories, our results are shown to be consistent with string theory via the minimum positional uncertainty derived from $D$-particle scattering amplitudes. |
2112.12964 | Sijo Joseph K. | Sijo K. Joseph | Weyl Geometry and Quantum Corrections | null | null | null | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | Recent research in the geometric formulation of quantum theory has implied
that Weyl Geometry can be used to merge quantum theory and general relativity
consistently as classical field theories. In the Weyl Geometric framework, it
seems that both quantum theory and gravity can merge consistently, once quantum
theory is geometrized. The extended differential geometry can modify the
quantum mechanical results into a more general nonlinear framework. Author
shows that, how the extended differential geometry modifies the known quantum
equations and also the modification to the Maxwell's electromagnetic equations.
| [
{
"created": "Fri, 24 Dec 2021 06:38:02 GMT",
"version": "v1"
}
] | 2021-12-28 | [
[
"Joseph",
"Sijo K.",
""
]
] | Recent research in the geometric formulation of quantum theory has implied that Weyl Geometry can be used to merge quantum theory and general relativity consistently as classical field theories. In the Weyl Geometric framework, it seems that both quantum theory and gravity can merge consistently, once quantum theory is geometrized. The extended differential geometry can modify the quantum mechanical results into a more general nonlinear framework. Author shows that, how the extended differential geometry modifies the known quantum equations and also the modification to the Maxwell's electromagnetic equations. |
2203.15440 | Gianmassimo Tasinato | Gianmassimo Tasinato | Gravitational wave non-linearities and pulsar-timing array angular
correlations | 9 pages plus appendixes, 4 figures | null | 10.1103/PhysRevD.105.083506 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several pulsar-timing array (PTA) collaborations are finding tantalising
hints for a stochastic gravitational wave background signal in the nano-Hertz
regime. So far, though, no convincing evidence for the expected Hellings-Downs
quadrupolar correlations has been found. While this issue might get fixed at
the light of more accurate, forthcoming data, it is important to keep an eye
open on different possibilities, and explore scenarios able to produce
different types of PTA angular correlations. We point out that a stationary
non-Gaussian component to the gravitational wave background can modulate the
2-point PTA overlap reduction function, adding contributions that can help in
fitting the angular distribution of PTA data. We discuss possible sources for
such non-Gaussian signal in terms of cosmological processes occurring after
inflation ends, and we investigate further tests for this idea.
| [
{
"created": "Tue, 29 Mar 2022 11:16:46 GMT",
"version": "v1"
}
] | 2022-04-20 | [
[
"Tasinato",
"Gianmassimo",
""
]
] | Several pulsar-timing array (PTA) collaborations are finding tantalising hints for a stochastic gravitational wave background signal in the nano-Hertz regime. So far, though, no convincing evidence for the expected Hellings-Downs quadrupolar correlations has been found. While this issue might get fixed at the light of more accurate, forthcoming data, it is important to keep an eye open on different possibilities, and explore scenarios able to produce different types of PTA angular correlations. We point out that a stationary non-Gaussian component to the gravitational wave background can modulate the 2-point PTA overlap reduction function, adding contributions that can help in fitting the angular distribution of PTA data. We discuss possible sources for such non-Gaussian signal in terms of cosmological processes occurring after inflation ends, and we investigate further tests for this idea. |
2308.00342 | Qiming Fu | Qi-Ming Fu, Meng-Ci He, Tao-Tao Sui, and Xin Zhang | Reconstruction of aether scalar tensor theory for various cosmological
scenarios | null | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we present several explicit reconstructions for {the aether
scalar tensor (AeST) theory} derived from the background of
Friedmann-Lema$\hat{\text{\i}}$tre-Robertson-Walker cosmological evolution. It
is shown that the Einstein-Hilbert Lagrangian with a positive cosmological
constant is the only Lagrangian capable of accurately replicating the exact
expansion history of the $\Lambda$ cold dark matter ($\Lambda$CDM) universe
filled solely with dust-like matter. However, the $\Lambda$CDM-era can be
produced within the framework of the AeST theory for some other fluids,
including a perfect fluid with $p=-(1/3)\rho$, multifluids, and nonisentropic
perfect fluids. Moreover, we demonstrate that the $\Lambda$CDM-era also can be
replicated with no real matter field for the AeST theory. The cosmic evolution
resulting from both the power-law and de-Sitter solutions also can be obtained.
| [
{
"created": "Tue, 1 Aug 2023 07:37:39 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Mar 2024 03:25:03 GMT",
"version": "v2"
}
] | 2024-03-15 | [
[
"Fu",
"Qi-Ming",
""
],
[
"He",
"Meng-Ci",
""
],
[
"Sui",
"Tao-Tao",
""
],
[
"Zhang",
"Xin",
""
]
] | In this paper, we present several explicit reconstructions for {the aether scalar tensor (AeST) theory} derived from the background of Friedmann-Lema$\hat{\text{\i}}$tre-Robertson-Walker cosmological evolution. It is shown that the Einstein-Hilbert Lagrangian with a positive cosmological constant is the only Lagrangian capable of accurately replicating the exact expansion history of the $\Lambda$ cold dark matter ($\Lambda$CDM) universe filled solely with dust-like matter. However, the $\Lambda$CDM-era can be produced within the framework of the AeST theory for some other fluids, including a perfect fluid with $p=-(1/3)\rho$, multifluids, and nonisentropic perfect fluids. Moreover, we demonstrate that the $\Lambda$CDM-era also can be replicated with no real matter field for the AeST theory. The cosmic evolution resulting from both the power-law and de-Sitter solutions also can be obtained. |
2012.06064 | Ugur Camci | Ugur Camci | Three-dimensional black holes via Noether symmetries | 29 pages, 1 table, no figures, to appear in Physical Review D | null | 10.1103/PhysRevD.103.024001 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate the Noether symmetries of the Lagrangian for the stationary
rotating BTZ-type three-dimensional spacetimes in $f(R)$ theory of gravity. A
detailed analysis of Noether symmetries of (2+1)-dimensional rotating BTZ-type
black hole spacetime model is presented. Applying the Noether symmetry
approach, the first integrals (constants of motion) for each of Noether
symmetries are obtained to look for the exact solutions. After solving the
first integral equations depending on the form of the function $f(R)$, we
derived some new (2+1)-dimensional rotating BTZ-type black hole solutions. We
discussed the physical implications of the derived exact solutions. The
thermodynamical properties of the obtained BTZ-type black hole solutions are
analyzed by making use of the mass $M$ and the angular momentum $J$ in terms of
$r_{\pm}$, where $r_+$ is the event horizon and $r_{-}$ is the inner horizon.
Further, it is shown that thermodynamic quantities obey the first law, and the
Smarr-like formulas of the solutions we found are obtained.
| [
{
"created": "Fri, 11 Dec 2020 01:04:39 GMT",
"version": "v1"
}
] | 2021-01-13 | [
[
"Camci",
"Ugur",
""
]
] | We investigate the Noether symmetries of the Lagrangian for the stationary rotating BTZ-type three-dimensional spacetimes in $f(R)$ theory of gravity. A detailed analysis of Noether symmetries of (2+1)-dimensional rotating BTZ-type black hole spacetime model is presented. Applying the Noether symmetry approach, the first integrals (constants of motion) for each of Noether symmetries are obtained to look for the exact solutions. After solving the first integral equations depending on the form of the function $f(R)$, we derived some new (2+1)-dimensional rotating BTZ-type black hole solutions. We discussed the physical implications of the derived exact solutions. The thermodynamical properties of the obtained BTZ-type black hole solutions are analyzed by making use of the mass $M$ and the angular momentum $J$ in terms of $r_{\pm}$, where $r_+$ is the event horizon and $r_{-}$ is the inner horizon. Further, it is shown that thermodynamic quantities obey the first law, and the Smarr-like formulas of the solutions we found are obtained. |
0908.3320 | Edmundo M. Monte | Edmundo M. Monte | Embedding Versus Immersion in General Relativity | 5 pages | Int.J.Mod.Phys.A24:1501-1504,2009 | 10.1142/S0217751X09044887 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We briefly discuss the concepts of immersion and embedding of space-times in
higher-dimensional spaces. We revisit the classical work by Kasner in which he
constructs a model of immersion of the Schwarzschild exterior solution into a
six-dimensional pseudo-Euclidean manifold. We show that, from a physical point
of view, this model is not entirely satisfactory since the causal structure of
the immersed space-time is not preserved by the immersion.
| [
{
"created": "Sun, 23 Aug 2009 17:37:50 GMT",
"version": "v1"
}
] | 2009-08-26 | [
[
"Monte",
"Edmundo M.",
""
]
] | We briefly discuss the concepts of immersion and embedding of space-times in higher-dimensional spaces. We revisit the classical work by Kasner in which he constructs a model of immersion of the Schwarzschild exterior solution into a six-dimensional pseudo-Euclidean manifold. We show that, from a physical point of view, this model is not entirely satisfactory since the causal structure of the immersed space-time is not preserved by the immersion. |
0911.1425 | Irene Brito | I. Brito, J. Carot, E.G.L.R. Vaz | General spherically symmetric elastic stars in Relativity | 23 pages | Gen.Rel.Grav.42:2357-2382,2010 | 10.1007/s10714-010-0980-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The relativistic theory of elasticity is reviewed within the spherically
symmetric context with a view towards the modeling of star interiors possessing
elastic properties such as theones expected in neutron stars. Emphasis is
placed on generality in the main sections of the paper, and the results are
then applied to specific examples. Along the way, a few general results for
spacetimes admitting isometries are deduced, and their consequences are fully
exploited in the case of spherical symmetry relating them next to the the case
in which the material content of the spacetime is some elastic material. This
paper extends and generalizes the pioneering work by Magli and Kijowski [1],
Magli [2] and [3], and complements, in a sense, that by Karlovini and
Samuelsson in their interesting series of papers [4], [5] and [6].
| [
{
"created": "Sat, 7 Nov 2009 15:32:33 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Brito",
"I.",
""
],
[
"Carot",
"J.",
""
],
[
"Vaz",
"E. G. L. R.",
""
]
] | The relativistic theory of elasticity is reviewed within the spherically symmetric context with a view towards the modeling of star interiors possessing elastic properties such as theones expected in neutron stars. Emphasis is placed on generality in the main sections of the paper, and the results are then applied to specific examples. Along the way, a few general results for spacetimes admitting isometries are deduced, and their consequences are fully exploited in the case of spherical symmetry relating them next to the the case in which the material content of the spacetime is some elastic material. This paper extends and generalizes the pioneering work by Magli and Kijowski [1], Magli [2] and [3], and complements, in a sense, that by Karlovini and Samuelsson in their interesting series of papers [4], [5] and [6]. |
2004.08225 | Benito A. Ju\'arez-Aubry | Michael Good, Benito A. Ju\'arez-Aubry, Dimitris Moustos, Maksat
Temirkhan | Unruh-like effects: Effective temperatures along stationary worldlines | 26 pages, 9 figures | JHEP 06 (2020) 059 | 10.1007/JHEP06(2020)059 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the detailed balance temperatures recorded along all classes of
stationary, uniformly accelerated worldlines in four-dimensional Minkowski
spacetime, namely along (i) linear uniform acceleration, (ii) cusped, (iii)
circular, (iv) catenary, and (v) helix worldlines, among which the Unruh
temperature is the particular case for linear uniform acceleration. As a
measuring device, we employ an Unruh-DeWitt detector, modeled as a qubit that
interacts for a long time with a massless Klein-Gordon field in the vacuum
state. The temperatures in each case (i) - (v) are functions of up to three
invariant quantities: curvature or proper acceleration, $\kappa$, torsion, $b$,
and hypertorsion, $\nu$, and except for the case (i), they depend on the
transition frequency difference of the detector, $\omega$. We investigate
numerically the behavior of the frequency-dependent temperatures for different
values of $\kappa$, $b$, and $\nu$ along the stationary worldlines (ii) - (v)
and evaluate analytically the regimes where the temperatures recorded along the
different worldlines coincide with each other in terms of relevant asymptotic
limits for $\kappa$, $b$, or $\nu$, and discuss their physical meaning. We
demonstrate that the temperatures in cases (ii) - (v) dip under the Unruh
temperature at low frequencies and go above the Unruh temperature for large
$|\omega|$. It is our hope that this study will be relevant to the design of
experiments seeking to verify the Unruh effect or generalizations thereof.
| [
{
"created": "Fri, 17 Apr 2020 13:10:52 GMT",
"version": "v1"
},
{
"created": "Mon, 15 Jun 2020 19:48:06 GMT",
"version": "v2"
}
] | 2020-06-17 | [
[
"Good",
"Michael",
""
],
[
"Juárez-Aubry",
"Benito A.",
""
],
[
"Moustos",
"Dimitris",
""
],
[
"Temirkhan",
"Maksat",
""
]
] | We study the detailed balance temperatures recorded along all classes of stationary, uniformly accelerated worldlines in four-dimensional Minkowski spacetime, namely along (i) linear uniform acceleration, (ii) cusped, (iii) circular, (iv) catenary, and (v) helix worldlines, among which the Unruh temperature is the particular case for linear uniform acceleration. As a measuring device, we employ an Unruh-DeWitt detector, modeled as a qubit that interacts for a long time with a massless Klein-Gordon field in the vacuum state. The temperatures in each case (i) - (v) are functions of up to three invariant quantities: curvature or proper acceleration, $\kappa$, torsion, $b$, and hypertorsion, $\nu$, and except for the case (i), they depend on the transition frequency difference of the detector, $\omega$. We investigate numerically the behavior of the frequency-dependent temperatures for different values of $\kappa$, $b$, and $\nu$ along the stationary worldlines (ii) - (v) and evaluate analytically the regimes where the temperatures recorded along the different worldlines coincide with each other in terms of relevant asymptotic limits for $\kappa$, $b$, or $\nu$, and discuss their physical meaning. We demonstrate that the temperatures in cases (ii) - (v) dip under the Unruh temperature at low frequencies and go above the Unruh temperature for large $|\omega|$. It is our hope that this study will be relevant to the design of experiments seeking to verify the Unruh effect or generalizations thereof. |
2005.13504 | Philippe G. LeFloch | Florian Beyer and Philippe G. LeFloch | A numerical algorithm for Fuchsian equations and fluid flows on
cosmological spacetimes | 30 pages | null | 10.1016/j.jcp.2021.110145 | null | gr-qc cs.NA math.NA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a class of Fuchsian equations that, for instance, describes the
evolution of compressible fluid flows on a cosmological spacetime. Using the
method of lines, we introduce a numerical algorithm for the singular initial
value problem when data are imposed on the cosmological singularity and the
evolution is performed from the singularity hypersurface. We approximate the
singular Cauchy problem of Fuchsian type by a sequence of regular Cauchy
problems, which we next discretize by pseudo-spectral and Runge-Kutta
techniques. Our main contribution is a detailed analysis of the numerical error
which has two distinct sources, and our main proposal here is to keep in
balance the errors arising at the continuum and at the discrete levels of
approximation. We present numerical experiments which strongly support our
theoretical conclusions. This strategy is finally applied to applied to
compressible fluid flows evolving on a Kasner spacetime, and we numerically
demonstrate the nonlinear stability of such flows, at least in the so-called
sub-critical regime identified earlier by the authors.
| [
{
"created": "Wed, 27 May 2020 17:28:51 GMT",
"version": "v1"
}
] | 2021-03-17 | [
[
"Beyer",
"Florian",
""
],
[
"LeFloch",
"Philippe G.",
""
]
] | We consider a class of Fuchsian equations that, for instance, describes the evolution of compressible fluid flows on a cosmological spacetime. Using the method of lines, we introduce a numerical algorithm for the singular initial value problem when data are imposed on the cosmological singularity and the evolution is performed from the singularity hypersurface. We approximate the singular Cauchy problem of Fuchsian type by a sequence of regular Cauchy problems, which we next discretize by pseudo-spectral and Runge-Kutta techniques. Our main contribution is a detailed analysis of the numerical error which has two distinct sources, and our main proposal here is to keep in balance the errors arising at the continuum and at the discrete levels of approximation. We present numerical experiments which strongly support our theoretical conclusions. This strategy is finally applied to applied to compressible fluid flows evolving on a Kasner spacetime, and we numerically demonstrate the nonlinear stability of such flows, at least in the so-called sub-critical regime identified earlier by the authors. |
1310.7949 | Prayush Kumar | Prayush Kumar, Ilana MacDonald, Duncan A. Brown, Harald P. Pfeiffer,
Kipp Cannon, Michael Boyle, Lawrence E. Kidder, Abdul H. Mroue, Mark A.
Scheel, Bela Szilagyi, Anil Zenginoglu | Template Banks for Binary black hole searches with Numerical Relativity
waveforms | 16 pages, 21 figures | Phys. Rev. D 89, 042002 (2014) | 10.1103/PhysRevD.89.042002 | LIGO Document P1300176 | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational waves (GW) from coalescing stellar-mass black hole binaries
(BBH) are expected to be detected by the Advanced Laser Interferometer
Gravitational-wave Observatory and Advanced Virgo. Detection searches operate
by matched-filtering the detector data using a bank of waveform templates.
Traditionally, template banks for BBH are constructed from intermediary
analytical waveform models which are calibrated against numerical relativity
simulations and which can be aluated for any choice of BBH parameters. This
paper explores an alternative to the traditional approach, namely the
construction of template banks directly from numerical BBH simulations. Using
non-spinning BBH systems as an example, we demonstrate which regions of the
mass-parameter plane can be covered with existing numerical BBH waveforms. We
estimate the required number and required length of BBH simulations to cover
the entire non-spinning BBH parameter plane up to mass-ratio 10, thus
illustrating that our approach can be used to guide parameter placement of
future numerical simulations. We derive error bounds which are independent of
analytical waveform models; therefore, our formalism can be used to
independently test the accuracy of such waveform models. The resulting template
banks are suitable for advanced LIGO searches.
| [
{
"created": "Tue, 29 Oct 2013 20:02:19 GMT",
"version": "v1"
}
] | 2014-02-26 | [
[
"Kumar",
"Prayush",
""
],
[
"MacDonald",
"Ilana",
""
],
[
"Brown",
"Duncan A.",
""
],
[
"Pfeiffer",
"Harald P.",
""
],
[
"Cannon",
"Kipp",
""
],
[
"Boyle",
"Michael",
""
],
[
"Kidder",
"Lawrence E.",
""
]... | Gravitational waves (GW) from coalescing stellar-mass black hole binaries (BBH) are expected to be detected by the Advanced Laser Interferometer Gravitational-wave Observatory and Advanced Virgo. Detection searches operate by matched-filtering the detector data using a bank of waveform templates. Traditionally, template banks for BBH are constructed from intermediary analytical waveform models which are calibrated against numerical relativity simulations and which can be aluated for any choice of BBH parameters. This paper explores an alternative to the traditional approach, namely the construction of template banks directly from numerical BBH simulations. Using non-spinning BBH systems as an example, we demonstrate which regions of the mass-parameter plane can be covered with existing numerical BBH waveforms. We estimate the required number and required length of BBH simulations to cover the entire non-spinning BBH parameter plane up to mass-ratio 10, thus illustrating that our approach can be used to guide parameter placement of future numerical simulations. We derive error bounds which are independent of analytical waveform models; therefore, our formalism can be used to independently test the accuracy of such waveform models. The resulting template banks are suitable for advanced LIGO searches. |
2403.17179 | Stefano Schmidt | Stefano Schmidt and Sarah Caudill | A novel signal-consistency test for gravitational-wave searches of
generic black hole binaries | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We propose a novel signal-consistency test applicable to a broad search for
gravitational waves emitted by generic binary black hole (BBH) systems. The
test generalizes the time domain $\xi^2$ signal-consistency test currently
utilized by the GstLAL pipeline, which quantifies the discrepancy between the
expected signal-to-noise ratio timeseries with the measured one. While the
traditional test is restricted to aligned-spin circular orbits and does not
account for higher-order modes (HMs), our test does not make any assumption on
the nature of the signal. After addressing the mathematical details of the new
test, we quantify its advantages in the context of searching for precessing
BBHs and/or BBHs with HM content. Our results reveal that for precessing
signals, the new test is optimal and has the potential to reduce the values of
the $\xi^2$ statistics by up to two orders of magnitude when compared to the
standard test. However, in the case of signals with HM content, only a modest
enhancement is observed. Recognizing the computational burden associated with
the new test, we also derive an approximated signal-consistency test. This
approximation maintains the same computational cost as the standard test and
can be easily implemented in any matched filtering pipeline with minimal
changes, sacrificing only a few percent of accuracy in the low SNR regime.
However in the high SNR regime the approximated signal consistency test does
not bring any improvement as compared to the "standard" one. By introducing our
new test and its approximation and understanding their validity and limitation,
this work will benefit any matched-filtering pipeline aimed at searching for
BBH signals with strong precession and/or HM content.
| [
{
"created": "Mon, 25 Mar 2024 20:44:52 GMT",
"version": "v1"
},
{
"created": "Tue, 25 Jun 2024 14:29:55 GMT",
"version": "v2"
}
] | 2024-06-26 | [
[
"Schmidt",
"Stefano",
""
],
[
"Caudill",
"Sarah",
""
]
] | We propose a novel signal-consistency test applicable to a broad search for gravitational waves emitted by generic binary black hole (BBH) systems. The test generalizes the time domain $\xi^2$ signal-consistency test currently utilized by the GstLAL pipeline, which quantifies the discrepancy between the expected signal-to-noise ratio timeseries with the measured one. While the traditional test is restricted to aligned-spin circular orbits and does not account for higher-order modes (HMs), our test does not make any assumption on the nature of the signal. After addressing the mathematical details of the new test, we quantify its advantages in the context of searching for precessing BBHs and/or BBHs with HM content. Our results reveal that for precessing signals, the new test is optimal and has the potential to reduce the values of the $\xi^2$ statistics by up to two orders of magnitude when compared to the standard test. However, in the case of signals with HM content, only a modest enhancement is observed. Recognizing the computational burden associated with the new test, we also derive an approximated signal-consistency test. This approximation maintains the same computational cost as the standard test and can be easily implemented in any matched filtering pipeline with minimal changes, sacrificing only a few percent of accuracy in the low SNR regime. However in the high SNR regime the approximated signal consistency test does not bring any improvement as compared to the "standard" one. By introducing our new test and its approximation and understanding their validity and limitation, this work will benefit any matched-filtering pipeline aimed at searching for BBH signals with strong precession and/or HM content. |
gr-qc/0509062 | Kirill Bronnikov | K.A. Bronnikov, S.V. Grinyok | Electrically charged and neutral wormhole instability in scalar-tensor
gravity | 7 pages, no figures; gc, cite styles. A talk at the International
Conference on Cosmoparticle Physics ``Cosmion-2004'' (Moscow, September 2004) | Grav.Cosmol. 11 (2005) 75-81 | null | null | gr-qc | null | We study the stability of static, spherically symmetric, traversable
wormholes with or without an electric charge, existing due to conformal
continuations in a class of scalar-tensor theories with zero scalar field
potential (so that Penney's or Fisher's well-known solutions hold in the
Einstein conformal frame). Specific examples of such wormholes are those with
nonminimally (e.g., conformally) coupled scalar fields. All boundary conditions
for scalar and metric perturbations are taken into account. All such wormholes
with zero or small electric charge are shown to be unstable under spherically
symmetric perturbations. The instability is proved analytically with the aid of
the theory of self-adjoint operators in Hilbert space and is confirmed by
numerical computations.
| [
{
"created": "Thu, 15 Sep 2005 17:12:00 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bronnikov",
"K. A.",
""
],
[
"Grinyok",
"S. V.",
""
]
] | We study the stability of static, spherically symmetric, traversable wormholes with or without an electric charge, existing due to conformal continuations in a class of scalar-tensor theories with zero scalar field potential (so that Penney's or Fisher's well-known solutions hold in the Einstein conformal frame). Specific examples of such wormholes are those with nonminimally (e.g., conformally) coupled scalar fields. All boundary conditions for scalar and metric perturbations are taken into account. All such wormholes with zero or small electric charge are shown to be unstable under spherically symmetric perturbations. The instability is proved analytically with the aid of the theory of self-adjoint operators in Hilbert space and is confirmed by numerical computations. |
gr-qc/0405051 | Yuan-Zhong Zhang | K.K. Nandi and Yuan-Zhong Zhang | On Traversable Lorentzian Wormholes in the Vacuum Low Energy Effective
String Theory in Einstein and Jordan Frames | 18 pages | Phys.Rev. D70 (2004) 044040 | 10.1103/PhysRevD.70.044040 | null | gr-qc | null | Three new classes (II-IV) of solutions of the vacuum low energy effective
string theory in four dimensions are derived. Wormhole solutions are
investigated in those solutions including the class I case both in the Einstein
and in the Jordan (string) frame. It turns out that, of the eight classes of
solutions investigated (four in the Einstein frame and four in the
corresponding string frame), massive Lorentzian traversable wormholes exist in
five classes. Nontrivial massless limit exists only in class I Einstein frame
solution while none at all exists in the string frame. An investigation of test
scalar charge motion in the class I solution in the two frames is carried out
by using the Plebanski-Sawicki theorem. A curious consequence is that the
motion around the extremal zero (Keplerian) mass configuration leads, as a
result of scalar-scalar interaction, to a new hypothetical "mass" that confines
test scalar charges in bound orbits, but does not interact with neutral test
particles.
| [
{
"created": "Mon, 10 May 2004 01:17:19 GMT",
"version": "v1"
},
{
"created": "Mon, 7 Jun 2004 07:06:23 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Nandi",
"K. K.",
""
],
[
"Zhang",
"Yuan-Zhong",
""
]
] | Three new classes (II-IV) of solutions of the vacuum low energy effective string theory in four dimensions are derived. Wormhole solutions are investigated in those solutions including the class I case both in the Einstein and in the Jordan (string) frame. It turns out that, of the eight classes of solutions investigated (four in the Einstein frame and four in the corresponding string frame), massive Lorentzian traversable wormholes exist in five classes. Nontrivial massless limit exists only in class I Einstein frame solution while none at all exists in the string frame. An investigation of test scalar charge motion in the class I solution in the two frames is carried out by using the Plebanski-Sawicki theorem. A curious consequence is that the motion around the extremal zero (Keplerian) mass configuration leads, as a result of scalar-scalar interaction, to a new hypothetical "mass" that confines test scalar charges in bound orbits, but does not interact with neutral test particles. |
1106.3721 | Ishwaree Neupane | Ishwaree P. Neupane | We Probably Live On An Inflating Brane-World | 8 pages, latex (Essay received Honourable mention in Gravity Research
Foundation essay competition 2011) | Int. J. Mod. Phys. D20 (2011) 2809-2816 | 10.1142/S0218271811020627 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Brane-world models where observers are trapped within the thickness of a
3-brane offer novel perspectives on gravitation and cosmology. In this essay, I
would argue that the problem of a late epoch acceleration of the universe is
well explained in the framework of a 4-dimensional de Sitter universe embedded
in a 5-dimensional de Sitter spacetime. While a 5D anti de Sitter space
background is important for studying conformal field theories -- for its role
in the AdS/CFT correspondence -- the existence of a 5-dimensional de Sitter
space is crucial for finding an effective 4D Newton constant that remains
finite and a normalizable zero-mode graviton wave function.
| [
{
"created": "Sun, 19 Jun 2011 08:39:19 GMT",
"version": "v1"
}
] | 2012-02-20 | [
[
"Neupane",
"Ishwaree P.",
""
]
] | Brane-world models where observers are trapped within the thickness of a 3-brane offer novel perspectives on gravitation and cosmology. In this essay, I would argue that the problem of a late epoch acceleration of the universe is well explained in the framework of a 4-dimensional de Sitter universe embedded in a 5-dimensional de Sitter spacetime. While a 5D anti de Sitter space background is important for studying conformal field theories -- for its role in the AdS/CFT correspondence -- the existence of a 5-dimensional de Sitter space is crucial for finding an effective 4D Newton constant that remains finite and a normalizable zero-mode graviton wave function. |
gr-qc/0205062 | Slava G. Turyshev | Slava G. Turyshev | Relativistic stellar aberration for the Space Interferometry Mission (2) | 40 pages, 5 figures | null | null | null | gr-qc | null | We address the issue of relativistic stellar aberration requirements for the
Space Interferometry Mission (SIM). Motivated by the importance of this issue
for SIM, we have considered a problem of relative astrometric observations of
two stars separated by angle $\theta$ on the sky with a single baseline
interferometer. While a definitive answer on the stellar aberration issue may
be obtained only in numerical simulations based on the accurate astrometric
model of the instrument, one could still derive realistic conclusions by
accounting for the main expected properties of SIM. In particular, we have
analysied how the expected astrometric accuracy of determination of positions,
parallaxes and proper motions will constrain the accuracy of the spaceraft
navigation. We estimated the astrometric errors introduced by imperfect
metrology (variations of the calibration term across the tile of interest),
errors in the baseline length estimations, and those due to orbital motion of
the spacecraft. We also estimate requirements on the data sampling rate
necessary to apply on-board in order to correct for the stellar aberration. We
have shown that the worst case observation scenario is realized for the motion
of the spacecraft in the direction perpendicular to the tile. This case of
motion will provide the most stringent requirement on the accuracy of knowledge
of the velocity's magnitude. We discuss the implication of the results obtained
for the future mission analysis.
| [
{
"created": "Wed, 15 May 2002 22:00:55 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Turyshev",
"Slava G.",
""
]
] | We address the issue of relativistic stellar aberration requirements for the Space Interferometry Mission (SIM). Motivated by the importance of this issue for SIM, we have considered a problem of relative astrometric observations of two stars separated by angle $\theta$ on the sky with a single baseline interferometer. While a definitive answer on the stellar aberration issue may be obtained only in numerical simulations based on the accurate astrometric model of the instrument, one could still derive realistic conclusions by accounting for the main expected properties of SIM. In particular, we have analysied how the expected astrometric accuracy of determination of positions, parallaxes and proper motions will constrain the accuracy of the spaceraft navigation. We estimated the astrometric errors introduced by imperfect metrology (variations of the calibration term across the tile of interest), errors in the baseline length estimations, and those due to orbital motion of the spacecraft. We also estimate requirements on the data sampling rate necessary to apply on-board in order to correct for the stellar aberration. We have shown that the worst case observation scenario is realized for the motion of the spacecraft in the direction perpendicular to the tile. This case of motion will provide the most stringent requirement on the accuracy of knowledge of the velocity's magnitude. We discuss the implication of the results obtained for the future mission analysis. |
2403.03106 | Kristina Giesel | Alba Domi, Thomas Eberl, Max Joseph Fahn, Kristina Giesel, Lukas
Hennig, Ulrich Katz, Roman Kemper and Michael Kobler | Understanding gravitationally induced decoherence parameters in neutrino
oscillations using a microscopic quantum mechanical model | 27 pages, 8 figures, updated the color of the axis in figure 1,
extended the discussion in the conclusion and updated some references | null | null | null | gr-qc hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, a microscopic quantum mechanical model for gravitationally
induced decoherence introduced by Blencowe and Xu is investigated in the
context of neutrino oscillations. The focus is on the comparison with existing
phenomenological models and the physical interpretation of the decoherence
parameters in such models. The results show that for neutrino oscillations in
vacuum gravitationally induced decoherence can be matched with phenomenological
models with decoherence parameters of the form $\Gamma_{ij}\sim \Delta
m^4_{ij}E^{-2}$. When matter effects are included, the decoherence parameters
show a dependence on matter effects, which vary in the different layers of the
Earth, that can be explained with the form of the coupling between neutrinos
and the gravitational wave environment inspired by linearised gravity.
Consequently, in the case of neutrino oscillations in matter, the microscopic
model does not agree with many existing phenomenological models that assume
constant decoherence parameters in matter, and their existing bounds cannot be
used to further constrain the model considered here. The probabilities for
neutrino oscillations with constant and varying decoherence parameters are
compared and it is shown that the deviations can be up to 10%. On a theoretical
level, these different models can be characterised by a different choice of
Lindblad operators, with the model with decoherence parameters that do not
include matter effects being less suitable from the point of view of linearised
gravity.
| [
{
"created": "Tue, 5 Mar 2024 16:48:23 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Mar 2024 18:43:21 GMT",
"version": "v2"
},
{
"created": "Mon, 15 Apr 2024 17:53:52 GMT",
"version": "v3"
}
] | 2024-04-16 | [
[
"Domi",
"Alba",
""
],
[
"Eberl",
"Thomas",
""
],
[
"Fahn",
"Max Joseph",
""
],
[
"Giesel",
"Kristina",
""
],
[
"Hennig",
"Lukas",
""
],
[
"Katz",
"Ulrich",
""
],
[
"Kemper",
"Roman",
""
],
[
"Kobler... | In this work, a microscopic quantum mechanical model for gravitationally induced decoherence introduced by Blencowe and Xu is investigated in the context of neutrino oscillations. The focus is on the comparison with existing phenomenological models and the physical interpretation of the decoherence parameters in such models. The results show that for neutrino oscillations in vacuum gravitationally induced decoherence can be matched with phenomenological models with decoherence parameters of the form $\Gamma_{ij}\sim \Delta m^4_{ij}E^{-2}$. When matter effects are included, the decoherence parameters show a dependence on matter effects, which vary in the different layers of the Earth, that can be explained with the form of the coupling between neutrinos and the gravitational wave environment inspired by linearised gravity. Consequently, in the case of neutrino oscillations in matter, the microscopic model does not agree with many existing phenomenological models that assume constant decoherence parameters in matter, and their existing bounds cannot be used to further constrain the model considered here. The probabilities for neutrino oscillations with constant and varying decoherence parameters are compared and it is shown that the deviations can be up to 10%. On a theoretical level, these different models can be characterised by a different choice of Lindblad operators, with the model with decoherence parameters that do not include matter effects being less suitable from the point of view of linearised gravity. |
1106.4122 | Folkert Mueller-Hoissen | Aristophanes Dimakis, Nils Kanning, Folkert M\"uller-Hoissen | The Non-Autonomous Chiral Model and the Ernst Equation of General
Relativity in the Bidifferential Calculus Framework | null | SIGMA 7 (2011), 118, 27 pages | 10.3842/SIGMA.2011.118 | null | gr-qc math-ph math.MP nlin.SI | http://creativecommons.org/licenses/by-nc-sa/3.0/ | The non-autonomous chiral model equation for an $m \times m$ matrix function
on a two-dimensional space appears in particular in general relativity, where
for $m=2$ a certain reduction of it determines stationary, axially symmetric
solutions of Einstein's vacuum equations, and for $m=3$ solutions of the
Einstein-Maxwell equations. Using a very simple and general result of the
bidifferential calculus approach to integrable partial differential and
difference equations, we generate a large class of exact solutions of this
chiral model. The solutions are parametrized by a set of matrices, the size of
which can be arbitrarily large. The matrices are subject to a Sylvester
equation that has to be solved and generically admits a unique solution. By
imposing the aforementioned reductions on the matrix data, we recover the Ernst
potentials of multi-Kerr-NUT and multi-Demianski-Newman metrics.
| [
{
"created": "Tue, 21 Jun 2011 08:23:51 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Dec 2011 06:09:27 GMT",
"version": "v2"
}
] | 2011-12-26 | [
[
"Dimakis",
"Aristophanes",
""
],
[
"Kanning",
"Nils",
""
],
[
"Müller-Hoissen",
"Folkert",
""
]
] | The non-autonomous chiral model equation for an $m \times m$ matrix function on a two-dimensional space appears in particular in general relativity, where for $m=2$ a certain reduction of it determines stationary, axially symmetric solutions of Einstein's vacuum equations, and for $m=3$ solutions of the Einstein-Maxwell equations. Using a very simple and general result of the bidifferential calculus approach to integrable partial differential and difference equations, we generate a large class of exact solutions of this chiral model. The solutions are parametrized by a set of matrices, the size of which can be arbitrarily large. The matrices are subject to a Sylvester equation that has to be solved and generically admits a unique solution. By imposing the aforementioned reductions on the matrix data, we recover the Ernst potentials of multi-Kerr-NUT and multi-Demianski-Newman metrics. |
1605.02058 | Bobir Toshmatov | Bobir Toshmatov, Zden\v{e}k Stuchl\'ik, Jan Schee, Bobomurat Ahmedov | Quasinormal frequencies of black hole in the braneworld | 12 pages, 10 figures, 2 tables | Phys. Rev. D 93, 124017 (2016) | 10.1103/PhysRevD.93.124017 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have studied scalar, electromagnetic and gravitational perturbations of
the four-dimensional Reissner-Nordstr\"{o}m-like black holes with a
\textit{tidal charge} in the Randall-Sundrum braneworld. The quasinormal modes
of these scalar, electromagnetic, as well as axial and polar gravitational
perturbations, have been studied in both normal and eikonal regimes.
Calculations have shown that the black holes on the Randall-Sundrum brane are
stable against scalar, electromagnetic and gravitational perturbations.
Moreover, we determine the grey body factor, giving transmission and reflection
of the scattered waves through the scalar, electromagnetic and gravitational
effective potentials. It has been shown that the scalar perturbative fields are
the most favorite to the reflected as compared to the latter. With increasing
value of the tidal charge ability of the all perturbative potentials to reflect
the waves decreases. Our calculations in low- and high-frequency regimes have
shown that black holes on the braneworld always have a bigger absorption cross
section of massless scalar waves than the Schwarzschild and standard
Reissner-Nordstr\"{o}m black holes.
| [
{
"created": "Fri, 6 May 2016 19:44:54 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Jun 2016 12:45:24 GMT",
"version": "v2"
}
] | 2016-06-08 | [
[
"Toshmatov",
"Bobir",
""
],
[
"Stuchlík",
"Zdeněk",
""
],
[
"Schee",
"Jan",
""
],
[
"Ahmedov",
"Bobomurat",
""
]
] | We have studied scalar, electromagnetic and gravitational perturbations of the four-dimensional Reissner-Nordstr\"{o}m-like black holes with a \textit{tidal charge} in the Randall-Sundrum braneworld. The quasinormal modes of these scalar, electromagnetic, as well as axial and polar gravitational perturbations, have been studied in both normal and eikonal regimes. Calculations have shown that the black holes on the Randall-Sundrum brane are stable against scalar, electromagnetic and gravitational perturbations. Moreover, we determine the grey body factor, giving transmission and reflection of the scattered waves through the scalar, electromagnetic and gravitational effective potentials. It has been shown that the scalar perturbative fields are the most favorite to the reflected as compared to the latter. With increasing value of the tidal charge ability of the all perturbative potentials to reflect the waves decreases. Our calculations in low- and high-frequency regimes have shown that black holes on the braneworld always have a bigger absorption cross section of massless scalar waves than the Schwarzschild and standard Reissner-Nordstr\"{o}m black holes. |
1008.3324 | Wen-Biao Han | Wen-Biao Han | Gravitational Radiations from a Spinning Compact Object around a
supermassive Kerr black hole in circular orbit | 16 pages, 17 figures. The last version for publication | Phys.Rev.D82:084013,2010 | 10.1103/PhysRevD.82.084013 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitational waves and energy radiations from a spinning compact object
with stellar mass in a circular orbit in the equatorial plane of a supermassive
Kerr black hole are investigated in this paper. The effect how the spin acts on
energy and angular moment fluxes is discussed in detail. The calculation
results indicate that the spin of small body should be considered in
waveform-template production for the upcoming gravitational wave detections. It
is clear that when the direction of spin axes is the same as the orbitally
angular momentum ("positive" spin), spin can decrease the energy fluxes which
radiate to infinity. For antidirection spin ("negative"), the energy fluxes to
infinity can be enlarged. And the relations between fluxes (both infinity and
horizon) and spin look like quadratic functions. From frequency shift due to
spin, we estimate the wave-phase accumulation during the inspiraling process of
the particle. We find that the time of particle inspiral into the black hole is
longer for positive spin and shorter for negative compared with the nonspinning
particle. Especially, for extreme spin value, the energy radiation near the
horizon of the extreme Kerr black hole is much more than that for the
nonspinning one. And consequently, the maximum binging energy of the extreme
spinning particle is much larger than that of the nonspinning particle.
| [
{
"created": "Thu, 19 Aug 2010 15:09:34 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Aug 2010 01:16:09 GMT",
"version": "v2"
},
{
"created": "Thu, 7 Oct 2010 17:26:50 GMT",
"version": "v3"
}
] | 2014-11-21 | [
[
"Han",
"Wen-Biao",
""
]
] | The gravitational waves and energy radiations from a spinning compact object with stellar mass in a circular orbit in the equatorial plane of a supermassive Kerr black hole are investigated in this paper. The effect how the spin acts on energy and angular moment fluxes is discussed in detail. The calculation results indicate that the spin of small body should be considered in waveform-template production for the upcoming gravitational wave detections. It is clear that when the direction of spin axes is the same as the orbitally angular momentum ("positive" spin), spin can decrease the energy fluxes which radiate to infinity. For antidirection spin ("negative"), the energy fluxes to infinity can be enlarged. And the relations between fluxes (both infinity and horizon) and spin look like quadratic functions. From frequency shift due to spin, we estimate the wave-phase accumulation during the inspiraling process of the particle. We find that the time of particle inspiral into the black hole is longer for positive spin and shorter for negative compared with the nonspinning particle. Especially, for extreme spin value, the energy radiation near the horizon of the extreme Kerr black hole is much more than that for the nonspinning one. And consequently, the maximum binging energy of the extreme spinning particle is much larger than that of the nonspinning particle. |
gr-qc/0406090 | Salvatore Antoci | Salvatore Antoci, Dierck-Ekkehard Liebscher | Reinstating Schwarzschild's original manifold and its singularity | 38 pages, 4 figures. Misprints corrected. To appear in: "General
Relativity Research Trends", Horizons in World Physics, vol. 249, Nova
Science Publishers | "General Relativity Research Trends", Albert Reimer ed., pp.
177-213, Nova Science Publishers, New York (2006) | null | null | gr-qc | null | The content of this review is summarized here through the titles of its
sections, as follows:
1. Introduction: Schwarzschild's original solution and the ``Schwarzschild
solution''.
2. The wrong arrow of time of Hilbert's manifold is at the origin of the
Kruskal extension.
3. An invariant, local, intrinsic quantity that diverges at the Schwarzschild
surface.
4. The singularity at the Schwarzschild surface is both intrinsic and
physical.
5. Conclusion.
| [
{
"created": "Tue, 22 Jun 2004 13:34:22 GMT",
"version": "v1"
},
{
"created": "Thu, 29 Sep 2005 13:05:24 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Antoci",
"Salvatore",
""
],
[
"Liebscher",
"Dierck-Ekkehard",
""
]
] | The content of this review is summarized here through the titles of its sections, as follows: 1. Introduction: Schwarzschild's original solution and the ``Schwarzschild solution''. 2. The wrong arrow of time of Hilbert's manifold is at the origin of the Kruskal extension. 3. An invariant, local, intrinsic quantity that diverges at the Schwarzschild surface. 4. The singularity at the Schwarzschild surface is both intrinsic and physical. 5. Conclusion. |
0710.5017 | Jonathan Engle | Jonathan Engle, Roberto Pereira | Coherent states, constraint classes, and area operators in the new
spin-foam models | 21 pages; statements about gamma limits made more precise, and minor
phrasing changes | Class.Quant.Grav.25:105010,2008 | 10.1088/0264-9381/25/10/105010 | null | gr-qc | null | Recently, two new spin-foam models have appeared in the literature, both
motivated by a desire to modify the Barrett-Crane model in such a way that the
imposition of certain second class constraints, called cross-simplicity
constraints, are weakened. We refer to these two models as the FKLS model, and
the flipped model. Both of these models are based on a reformulation of the
cross-simplicity constraints. This paper has two main parts. First, we clarify
the structure of the reformulated cross-simplicity constraints and the nature
of their quantum imposition in the new models. In particular we show that in
the FKLS model, quantum cross-simplicity implies no restriction on states. The
deeper reason for this is that, with the symplectic structure relevant for
FKLS, the reformulated cross-simplicity constraints, in a certain relevant
sense, are now \emph{first class}, and this causes the coherent state method of
imposing the constraints, key in the FKLS model, to fail to give any
restriction on states. Nevertheless, the cross-simplicity can still be seen as
implemented via suppression of intertwiner degrees of freedom in the dynamical
propagation. In the second part of the paper, we investigate area spectra in
the models. The results of these two investigations will highlight how, in the
flipped model, the Hilbert space of states, as well as the spectra of area
operators exactly match those of loop quantum gravity, whereas in the FKLS (and
Barrett-Crane) models, the boundary Hilbert spaces and area spectra are
different.
| [
{
"created": "Fri, 26 Oct 2007 08:03:02 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Nov 2007 14:31:47 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Engle",
"Jonathan",
""
],
[
"Pereira",
"Roberto",
""
]
] | Recently, two new spin-foam models have appeared in the literature, both motivated by a desire to modify the Barrett-Crane model in such a way that the imposition of certain second class constraints, called cross-simplicity constraints, are weakened. We refer to these two models as the FKLS model, and the flipped model. Both of these models are based on a reformulation of the cross-simplicity constraints. This paper has two main parts. First, we clarify the structure of the reformulated cross-simplicity constraints and the nature of their quantum imposition in the new models. In particular we show that in the FKLS model, quantum cross-simplicity implies no restriction on states. The deeper reason for this is that, with the symplectic structure relevant for FKLS, the reformulated cross-simplicity constraints, in a certain relevant sense, are now \emph{first class}, and this causes the coherent state method of imposing the constraints, key in the FKLS model, to fail to give any restriction on states. Nevertheless, the cross-simplicity can still be seen as implemented via suppression of intertwiner degrees of freedom in the dynamical propagation. In the second part of the paper, we investigate area spectra in the models. The results of these two investigations will highlight how, in the flipped model, the Hilbert space of states, as well as the spectra of area operators exactly match those of loop quantum gravity, whereas in the FKLS (and Barrett-Crane) models, the boundary Hilbert spaces and area spectra are different. |
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