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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2208.02557 | Leonardo Modesto | Tian Zhou, Leonardo Modesto | Geodesic incompleteness of some popular regular black holes | New version widely extended in accordance with the correct and
stimulating suggestions of the referee. This version is conform to the one
published on PRD. 8 pages, 9 figures | null | 10.1103/PhysRevD.107.044016 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Throughout the study of the geodesics of some popular spherically symmetric
regular black holes, we hereby prove that the analytically extended Hayward
black hole is geodetically incomplete. The simplest extension of the
Culetu-Simpson-Visser's non-analytic smooth black hole is also geodetically
incomplete, with the exception of the antipodal continuation of the radial
geodesics. However, the huge ambiguity in the extension of non analytic
spacetimes is tantamount of geodesic incompleteness and such spacetimes do not
solve the singularity issue unless at least all the extensions turn out to be
complete. Hence, we provide several mere modifications of such spacetimes in
order to make them geodetically complete in all possible extensions beyond r=0.
| [
{
"created": "Thu, 4 Aug 2022 09:56:42 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Mar 2023 09:09:43 GMT",
"version": "v2"
}
] | 2023-03-24 | [
[
"Zhou",
"Tian",
""
],
[
"Modesto",
"Leonardo",
""
]
] | Throughout the study of the geodesics of some popular spherically symmetric regular black holes, we hereby prove that the analytically extended Hayward black hole is geodetically incomplete. The simplest extension of the Culetu-Simpson-Visser's non-analytic smooth black hole is also geodetically incomplete, with the exception of the antipodal continuation of the radial geodesics. However, the huge ambiguity in the extension of non analytic spacetimes is tantamount of geodesic incompleteness and such spacetimes do not solve the singularity issue unless at least all the extensions turn out to be complete. Hence, we provide several mere modifications of such spacetimes in order to make them geodetically complete in all possible extensions beyond r=0. |
1408.1444 | Gabor Kunstatter | Tim Taves, Gabor Kunstatter | Modelling the Evaporation of Non-singular Black Holes | 14 pages, 0 figures, references and acknowledgements added, final
version to appear in PRD | PhysRevD.90.124062, 2014 | 10.1103/PhysRevD.90.124062 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a model for studying the formation and evaporation of non-singular
(quantum corrected) black holes. The model is based on a generalized form of
the dimensionally reduced, spherically symmetric Einstein--Hilbert action and
includes a suitably generalized Polyakov action to provide a mechanism for
radiation back-reaction. The equations of motion describing self-gravitating
scalar field collapse are derived in local form both in null co--ordinates and
in Painleve--Gullstrand (flat slice) co--ordinates. They provide the starting
point for numerical studies of complete spacetimes containing dynamical
horizons that bound a compact trapped region. Such spacetimes have been
proposed in the past as solutions to the information loss problem because they
possess neither an event horizon nor a singularity. Since the equations of
motion in our model are derived from a diffeomorphism invariant action they
preserve the constraint algebra and the resulting energy momentum tensor is
manifestly conserved.
| [
{
"created": "Thu, 7 Aug 2014 00:23:31 GMT",
"version": "v1"
},
{
"created": "Sun, 17 Aug 2014 12:44:13 GMT",
"version": "v2"
},
{
"created": "Sun, 11 Jan 2015 17:14:42 GMT",
"version": "v3"
}
] | 2015-06-22 | [
[
"Taves",
"Tim",
""
],
[
"Kunstatter",
"Gabor",
""
]
] | We present a model for studying the formation and evaporation of non-singular (quantum corrected) black holes. The model is based on a generalized form of the dimensionally reduced, spherically symmetric Einstein--Hilbert action and includes a suitably generalized Polyakov action to provide a mechanism for radiation back-reaction. The equations of motion describing self-gravitating scalar field collapse are derived in local form both in null co--ordinates and in Painleve--Gullstrand (flat slice) co--ordinates. They provide the starting point for numerical studies of complete spacetimes containing dynamical horizons that bound a compact trapped region. Such spacetimes have been proposed in the past as solutions to the information loss problem because they possess neither an event horizon nor a singularity. Since the equations of motion in our model are derived from a diffeomorphism invariant action they preserve the constraint algebra and the resulting energy momentum tensor is manifestly conserved. |
1807.00812 | Ayan Banerjee | Sudan Hansraj and Ayan Banerjee | Equilibrium stellar configurations in Rastall theory and linear equation
of state | 9 pages and 2 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Amongst a number of modified theories of gravity, the Rastall theory has been
propounded to address some shortcomings of the standard theory of general
relativity. Our purpose is to investigate this framework's capacity to analyse
stellar structure in the context of elementary requirements for physical
plausibility such as positive definite functions for the energy density and
pressure, conformity to the causality criterion and the existence of an
equation of state. We consider the analogue of the Saslaw \textit{et al}
\cite{saslaw} isothermal model of general relativity and show that the Rastall
version satisfies the basic requirements unlike its counterpart. Then we
examine in turn the consequences of suppressing one of the inverse square law
fall off of the energy density or the linear equation of state. In addition,
the case of a constant spatial gravitational potential is studied on account of
this prescription being a necessary and sufficient condition for isothermal
behaviour in Einstein theory and its most general tensor extension Lovelock
gravity.
| [
{
"created": "Sun, 1 Jul 2018 16:11:37 GMT",
"version": "v1"
}
] | 2018-07-04 | [
[
"Hansraj",
"Sudan",
""
],
[
"Banerjee",
"Ayan",
""
]
] | Amongst a number of modified theories of gravity, the Rastall theory has been propounded to address some shortcomings of the standard theory of general relativity. Our purpose is to investigate this framework's capacity to analyse stellar structure in the context of elementary requirements for physical plausibility such as positive definite functions for the energy density and pressure, conformity to the causality criterion and the existence of an equation of state. We consider the analogue of the Saslaw \textit{et al} \cite{saslaw} isothermal model of general relativity and show that the Rastall version satisfies the basic requirements unlike its counterpart. Then we examine in turn the consequences of suppressing one of the inverse square law fall off of the energy density or the linear equation of state. In addition, the case of a constant spatial gravitational potential is studied on account of this prescription being a necessary and sufficient condition for isothermal behaviour in Einstein theory and its most general tensor extension Lovelock gravity. |
1803.02779 | Celia Escamilla-Rivera | Celia Escamilla-Rivera | Fluctuations of gravitational waves in Eddington inspired Born-Infeld
theory | 6 pages, 5 figures, under review | Revista Digital Congreso Mesoamericano de Investigacion UNACH
2018. ISSN 2395-8111 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we review the EiBI gravity in the presence of a cosmological
constant and its tensor perturbations analysis. We show the existence of
gravitational waves in the past-time, seeing as a result the smooth transition
between high-energy densities (where the EBI dynamics plays its role) and
low-energy densities (GR). We obtain the fluctuation spectrum for the graviton
in this theory, where for small values of k the fluctuations are strongly
suppressed and for large values of k these fluctuations vanish during the De
Sitter expansion.
| [
{
"created": "Wed, 7 Mar 2018 17:26:12 GMT",
"version": "v1"
}
] | 2019-01-23 | [
[
"Escamilla-Rivera",
"Celia",
""
]
] | In this paper we review the EiBI gravity in the presence of a cosmological constant and its tensor perturbations analysis. We show the existence of gravitational waves in the past-time, seeing as a result the smooth transition between high-energy densities (where the EBI dynamics plays its role) and low-energy densities (GR). We obtain the fluctuation spectrum for the graviton in this theory, where for small values of k the fluctuations are strongly suppressed and for large values of k these fluctuations vanish during the De Sitter expansion. |
1907.01580 | Vincent Deledicque | Vincent Deledicque | Dark energy explained by an inadequate fitting of the FLRW metric | 12 pages, 1 figure | null | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Approximating a real manifold by an idealized one requires to calibrate the
parameters characterizing the idealized manifold in function of the real one.
This calibration is a purely conventional process and can generally be done in
several ways, leading to different fittings. In practice, however, all possible
fittings cannot be considered as representative of the real manifold.
Approximating the real metric of the universe by the FLRW metric would be
adequate only if both corresponding structures, defined by the space-time
interval, are equivalent on large scales. This requirement puts some
constraints on what would be a representative FLRW metric. We show that the way
how measurements on SNIa are interpreted to determine the evolution of the
scale factor implicitly define the calibration process, and that this one is
compatible with the aforementioned constraints. On a theoretical point of view,
this indicates that the as fitted FLRW metric would indeed be representative of
the real one. On a practical point of view, however, we show that a bias in the
measurements could invalidate this conclusion. The bias comes from the fact
that SNIa are not randomly distributed over space, but are probably mostly
located in regions were matter is largely present, i.e., in overdense regions.
We explain how this bias could account for the apparent accelerated expansion
of the universe, without needing to introduce the dark energy assumption. We
show in particular that this bias leads to an inadequate fitting of the FLRW
metric, resulting in the appearance of a new term in the evolution equation of
the related scale factor, being equivalent to the cosmological constant.
| [
{
"created": "Tue, 2 Jul 2019 18:30:58 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Apr 2020 18:44:34 GMT",
"version": "v2"
}
] | 2020-04-06 | [
[
"Deledicque",
"Vincent",
""
]
] | Approximating a real manifold by an idealized one requires to calibrate the parameters characterizing the idealized manifold in function of the real one. This calibration is a purely conventional process and can generally be done in several ways, leading to different fittings. In practice, however, all possible fittings cannot be considered as representative of the real manifold. Approximating the real metric of the universe by the FLRW metric would be adequate only if both corresponding structures, defined by the space-time interval, are equivalent on large scales. This requirement puts some constraints on what would be a representative FLRW metric. We show that the way how measurements on SNIa are interpreted to determine the evolution of the scale factor implicitly define the calibration process, and that this one is compatible with the aforementioned constraints. On a theoretical point of view, this indicates that the as fitted FLRW metric would indeed be representative of the real one. On a practical point of view, however, we show that a bias in the measurements could invalidate this conclusion. The bias comes from the fact that SNIa are not randomly distributed over space, but are probably mostly located in regions were matter is largely present, i.e., in overdense regions. We explain how this bias could account for the apparent accelerated expansion of the universe, without needing to introduce the dark energy assumption. We show in particular that this bias leads to an inadequate fitting of the FLRW metric, resulting in the appearance of a new term in the evolution equation of the related scale factor, being equivalent to the cosmological constant. |
1702.00983 | Luis Herrera | L. Herrera, A. Di Prisco, J. Ospino | The transition of a gravitationally radiating, dissipative fluid, to
equilibrium | 7 pages, latex. arXiv admin note: substantial text overlap with
arXiv:1609.02841. Some typos corrected. Published in Canadian Journal of
Physics | Can. J. Phys. 96, 1010-1015 (2018) | 10.1139/cjp-2017-0651 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We describe the transition of a graviationally radiating, axially and
reflection symmetric dissipative fluid, to a non--radiating state. It is shown
that very shortly after the end of the radiating regime, at a time scale of the
order the thermal relaxation time, the thermal adjustment time and the
hydrostatic time (whichever is larger), the system reaches the equilibrium
state. This result is at variance with all the studies carried out in the past,
on gravitational radiation outside the source, which strongly suggest that
after a radiating period, the conditions for a return to a static case, look
rather forbidding. As we shall see, the reason for such a discrepancy resides
in the fact that some elementary, but essential, physical properties of the
source, have been overlooked in these latter studies.
| [
{
"created": "Fri, 3 Feb 2017 12:14:55 GMT",
"version": "v1"
},
{
"created": "Fri, 31 Aug 2018 14:23:30 GMT",
"version": "v2"
}
] | 2018-10-17 | [
[
"Herrera",
"L.",
""
],
[
"Di Prisco",
"A.",
""
],
[
"Ospino",
"J.",
""
]
] | We describe the transition of a graviationally radiating, axially and reflection symmetric dissipative fluid, to a non--radiating state. It is shown that very shortly after the end of the radiating regime, at a time scale of the order the thermal relaxation time, the thermal adjustment time and the hydrostatic time (whichever is larger), the system reaches the equilibrium state. This result is at variance with all the studies carried out in the past, on gravitational radiation outside the source, which strongly suggest that after a radiating period, the conditions for a return to a static case, look rather forbidding. As we shall see, the reason for such a discrepancy resides in the fact that some elementary, but essential, physical properties of the source, have been overlooked in these latter studies. |
1402.0101 | Maurizio Gasperini | M. Gasperini | String theory and primordial cosmology | 17 pages, 5 figures, published in "Springer Handbook of Spacetime",
ed. by A. Ashtekar and V. Petkov (Springer-Verlag, Berlin Heidelberg, 2014,
Chapter 35 | null | 10.1007/978-3-642-41992-8_35 | BA-TH/685-14 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | String cosmology aims at providing a reliable description of the very early
Universe in the regime where standard-model physics is no longer appropriate,
and where we can safely apply the basic ingredients of superstring models such
as dilatonic and axionic forces, duality symmetries, winding modes, limiting
sizes and curvatures, higher-dimensional interactions among elementary extended
object. The sought target is that of resolving (or at least alleviating) the
big problems of standard and inflationary cosmology like the spacetime
singularity, the physics of the trans-Planckian regime, the initial condition
for inflation, and so on.
| [
{
"created": "Sat, 1 Feb 2014 16:48:51 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Apr 2014 12:16:37 GMT",
"version": "v2"
}
] | 2014-04-24 | [
[
"Gasperini",
"M.",
""
]
] | String cosmology aims at providing a reliable description of the very early Universe in the regime where standard-model physics is no longer appropriate, and where we can safely apply the basic ingredients of superstring models such as dilatonic and axionic forces, duality symmetries, winding modes, limiting sizes and curvatures, higher-dimensional interactions among elementary extended object. The sought target is that of resolving (or at least alleviating) the big problems of standard and inflationary cosmology like the spacetime singularity, the physics of the trans-Planckian regime, the initial condition for inflation, and so on. |
0708.4299 | Marcello Ortaggio | Marcello Ortaggio, Jiri Podolsky, Martin Zofka | Robinson-Trautman spacetimes with an electromagnetic field in higher
dimensions | 17 pages | Class.Quant.Grav.25:025006,2008 | 10.1088/0264-9381/25/2/025006 | null | gr-qc hep-th | null | We investigate higher dimensional Robinson-Trautman spacetimes with an
electromagnetic field aligned with the hypersurface orthogonal, non-shearing,
expanding geodesic null congruence. After integrating the system of
Einstein-Maxwell equations with an arbitrary cosmological constant, we present
the complete family of solutions. In odd spacetime dimensions they represent
(generalized) Reissner-Nordstrom-de Sitter black holes. The event horizon (more
generically, the transverse space) may be any Einstein space, and the full
metric is specified by three independent parameters related to mass, electric
charge and cosmological constant. These solutions also exhaust the class of
Robinson-Trautman spacetimes with an aligned Maxwell-Chern-Simons field (the CS
term must vanish because of the alignment assumption and of the Einstein
equations). In even dimensions an additional magnetic "monopole-like" parameter
is also allowed provided now the transverse space is an (almost-)Kahler
Einstein manifold. The Weyl tensor of all such solutions is of algebraic type
D. We also consider the possible inclusion of aligned pure radiation.
| [
{
"created": "Fri, 31 Aug 2007 08:48:20 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Ortaggio",
"Marcello",
""
],
[
"Podolsky",
"Jiri",
""
],
[
"Zofka",
"Martin",
""
]
] | We investigate higher dimensional Robinson-Trautman spacetimes with an electromagnetic field aligned with the hypersurface orthogonal, non-shearing, expanding geodesic null congruence. After integrating the system of Einstein-Maxwell equations with an arbitrary cosmological constant, we present the complete family of solutions. In odd spacetime dimensions they represent (generalized) Reissner-Nordstrom-de Sitter black holes. The event horizon (more generically, the transverse space) may be any Einstein space, and the full metric is specified by three independent parameters related to mass, electric charge and cosmological constant. These solutions also exhaust the class of Robinson-Trautman spacetimes with an aligned Maxwell-Chern-Simons field (the CS term must vanish because of the alignment assumption and of the Einstein equations). In even dimensions an additional magnetic "monopole-like" parameter is also allowed provided now the transverse space is an (almost-)Kahler Einstein manifold. The Weyl tensor of all such solutions is of algebraic type D. We also consider the possible inclusion of aligned pure radiation. |
gr-qc/0312023 | Tran | Rajat K. Bhaduri, Muoi N. Tran, Saurya Das | On the Microcanonical Entropy of a Black Hole | 15 pages, 1 figure | Phys.Rev. D69 (2004) 104018 | 10.1103/PhysRevD.69.104018 | null | gr-qc cond-mat.stat-mech hep-th | null | It has been suggested recently that the microcanonical entropy of a system
may be accurately reproduced by including a logarithmic correction to the
canonical entropy. In this paper we test this claim both analytically and
numerically by considering three simple thermodynamic models whose energy
spectrum may be defined in terms of one quantum number only, as in a
non-rotating black hole. The first two pertain to collections of noninteracting
bosons, with logarithmic and power-law spectra. The last is an area ensemble
for a black hole with equi-spaced area spectrum. In this case, the many-body
degeneracy factor can be obtained analytically in a closed form. We also show
that in this model, the leading term in the entropy is proportional to the
horizon area A, and the next term is ln A with a negative coefficient.
| [
{
"created": "Wed, 3 Dec 2003 19:13:14 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Bhaduri",
"Rajat K.",
""
],
[
"Tran",
"Muoi N.",
""
],
[
"Das",
"Saurya",
""
]
] | It has been suggested recently that the microcanonical entropy of a system may be accurately reproduced by including a logarithmic correction to the canonical entropy. In this paper we test this claim both analytically and numerically by considering three simple thermodynamic models whose energy spectrum may be defined in terms of one quantum number only, as in a non-rotating black hole. The first two pertain to collections of noninteracting bosons, with logarithmic and power-law spectra. The last is an area ensemble for a black hole with equi-spaced area spectrum. In this case, the many-body degeneracy factor can be obtained analytically in a closed form. We also show that in this model, the leading term in the entropy is proportional to the horizon area A, and the next term is ln A with a negative coefficient. |
gr-qc/0703058 | Jian-Yang Zhu | Cheng-Zhou Liu, Jian-Yang Zhu | Asymptotic quasinormal modes of scalar field in a gravity's rainbow | null | Chin.Phys.B18:4161-4168,2009 | 10.1088/1674-1056/18/10/015 | null | gr-qc | null | In the context of a gravity's rainbow, the asymptotic quasinormal modes of
the scalar perturbation in the quantum modified Schwarzschild black holes are
investigated. By using the monodromy method, we calculated and obtained the
asymptotic quasinormal frequencies, which are dominated not only by the mass
parameter of the spacetime, but also by the energy functions from the modified
dispersion relations. However, the real parts of the asymptotic quasinormal
modes is still $T_H\ln 3$, which is consistent with Hod's conjecture. In
addition, for the quantum corrected black hole, the area spacing is calculated
and the result is independent of the energy functions, in spite of the area
itself is energy dependence. And that, by relating the area spectrum to loop
quantum gravity, the Barbero-Immirzi parameter is given and it remains the same
as from the usual black hole.
| [
{
"created": "Thu, 8 Mar 2007 13:39:42 GMT",
"version": "v1"
}
] | 2010-11-02 | [
[
"Liu",
"Cheng-Zhou",
""
],
[
"Zhu",
"Jian-Yang",
""
]
] | In the context of a gravity's rainbow, the asymptotic quasinormal modes of the scalar perturbation in the quantum modified Schwarzschild black holes are investigated. By using the monodromy method, we calculated and obtained the asymptotic quasinormal frequencies, which are dominated not only by the mass parameter of the spacetime, but also by the energy functions from the modified dispersion relations. However, the real parts of the asymptotic quasinormal modes is still $T_H\ln 3$, which is consistent with Hod's conjecture. In addition, for the quantum corrected black hole, the area spacing is calculated and the result is independent of the energy functions, in spite of the area itself is energy dependence. And that, by relating the area spectrum to loop quantum gravity, the Barbero-Immirzi parameter is given and it remains the same as from the usual black hole. |
0911.4180 | Hanno Sahlmann | Hanno Sahlmann | Wave propagation on a random lattice | 13 pages, 3 figures. v3: Some minor changes and clarifications.
Virtually identical with the version published in Physical Review D | Phys.Rev.D82:064018,2010 | 10.1103/PhysRevD.82.064018 | KA-TP-18-2009 | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by phenomenological questions in quantum gravity, we consider the
propagation of a scalar field on a random lattice. We describe a procedure to
calculate the dispersion relation for the field by taking a limit of a periodic
lattice. We use this to calculate the lowest order coefficients of the
dispersion relation for a specific one-dimensional model.
| [
{
"created": "Mon, 23 Nov 2009 13:37:35 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Dec 2009 19:55:37 GMT",
"version": "v2"
},
{
"created": "Wed, 15 Sep 2010 14:56:46 GMT",
"version": "v3"
}
] | 2014-11-20 | [
[
"Sahlmann",
"Hanno",
""
]
] | Motivated by phenomenological questions in quantum gravity, we consider the propagation of a scalar field on a random lattice. We describe a procedure to calculate the dispersion relation for the field by taking a limit of a periodic lattice. We use this to calculate the lowest order coefficients of the dispersion relation for a specific one-dimensional model. |
gr-qc/0105027 | Ibrahim Arbab Arbab | Arbab I. Arbab | Cosmological Models With Variable G an Lambda and Bulk viscosity | Ph.D. Thesis(University of Khartoum) | Hadronic Journal Vol. 34, 1 (2011) | null | null | gr-qc | null | We have analyzed a nonsingular model with a variable cosmological term
following the Carvalho {\it et al}. ansatz. The model was shown to approximate
to the model of Freese {\it et al}. in one direction and to the \"{O}zer-Taha
in the other. We have then included the effect of viscosity in this cosmology,
as this effect has not been considered before. The analysis showed that this
viscous effect could be important with a present contribution to the cosmic
pressure, at most, of order of that of radiation. The model puts a stronger
upper bound on the baryonic matter than that required by the standard model. A
variable gravitational and cosmological constant were then introduced in a
scenario which conserves the energy and momentum in the presence of bulk
viscosity. The result of the analysis reveals that various models could be
viscous. A noteworthy result is that some nonsingular closed models evolve
asymptotically into a singular viscous one. The considered models solve for
many of the standard model problems. Though the introduction of bulk viscosity
results in the creation of particles, this scenario conserves energy and
momentum. As in the standard model the entropy remains constant. We have not
explained the generation of bulk viscosity but some workers attributes this to
neutrinos. Though the role of viscosity today is minute it could, nevertheless,
have had an important contribution at early times. We have shown that these
models encompass many of the old and recently proposed models, in particular,
Brans-Dicke, Dirac, Freese {\it et al}., Berman, Abdel Rahman and Kalligas {\it
et al}. models. Hence we claim that the introduction of bulk viscosity enriches
the adopted cosmology.
| [
{
"created": "Tue, 8 May 2001 09:54:28 GMT",
"version": "v1"
}
] | 2017-06-15 | [
[
"Arbab",
"Arbab I.",
""
]
] | We have analyzed a nonsingular model with a variable cosmological term following the Carvalho {\it et al}. ansatz. The model was shown to approximate to the model of Freese {\it et al}. in one direction and to the \"{O}zer-Taha in the other. We have then included the effect of viscosity in this cosmology, as this effect has not been considered before. The analysis showed that this viscous effect could be important with a present contribution to the cosmic pressure, at most, of order of that of radiation. The model puts a stronger upper bound on the baryonic matter than that required by the standard model. A variable gravitational and cosmological constant were then introduced in a scenario which conserves the energy and momentum in the presence of bulk viscosity. The result of the analysis reveals that various models could be viscous. A noteworthy result is that some nonsingular closed models evolve asymptotically into a singular viscous one. The considered models solve for many of the standard model problems. Though the introduction of bulk viscosity results in the creation of particles, this scenario conserves energy and momentum. As in the standard model the entropy remains constant. We have not explained the generation of bulk viscosity but some workers attributes this to neutrinos. Though the role of viscosity today is minute it could, nevertheless, have had an important contribution at early times. We have shown that these models encompass many of the old and recently proposed models, in particular, Brans-Dicke, Dirac, Freese {\it et al}., Berman, Abdel Rahman and Kalligas {\it et al}. models. Hence we claim that the introduction of bulk viscosity enriches the adopted cosmology. |
gr-qc/9907026 | null | Pedro F. Gonzalez-Diaz (IMAFF, CSIC, Madrid) | On the warp drive space-time | 7 pages, minor comment on chronology protection added, RevTex, to
appear in Phys. Rev. D | Phys.Rev. D62 (2000) 044005 | 10.1103/PhysRevD.62.044005 | IMAFF-RCA-99-04 | gr-qc | null | In this paper the problem of the quantum stability of the two-dimensional
warp drive spacetime moving with an apparent faster than light velocity is
considered. We regard as a maximum extension beyond the event horizon of that
spacetime its embedding in a three-dimensional Minkowskian space with the
topology of the corresponding Misner space. It is obtained that the interior of
the spaceship bubble becomes then a multiply connected nonchronal region with
closed timelike curves and that the most natural vacuum allows quantum
fluctuations which do not induce any divergent behaviour of the re-normalized
stress-energy tensor, even on the event (Cauchy) chronology horizon. In such a
case, the horizon encloses closed timelike curves only at scales close to the
Planck length, so that the warp drive satisfies the Ford's negative energy-time
inequality. Also found is a connection between the superluminal two-dimensional
warp drive space and two-dimensional gravitational kinks. This connection
allows us to generalize the considered Alcubierre metric to a standard,
nonstatic metric which is only describable on two different coordinate patches
| [
{
"created": "Wed, 7 Jul 1999 08:47:19 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Apr 2000 18:25:29 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Gonzalez-Diaz",
"Pedro F.",
"",
"IMAFF, CSIC, Madrid"
]
] | In this paper the problem of the quantum stability of the two-dimensional warp drive spacetime moving with an apparent faster than light velocity is considered. We regard as a maximum extension beyond the event horizon of that spacetime its embedding in a three-dimensional Minkowskian space with the topology of the corresponding Misner space. It is obtained that the interior of the spaceship bubble becomes then a multiply connected nonchronal region with closed timelike curves and that the most natural vacuum allows quantum fluctuations which do not induce any divergent behaviour of the re-normalized stress-energy tensor, even on the event (Cauchy) chronology horizon. In such a case, the horizon encloses closed timelike curves only at scales close to the Planck length, so that the warp drive satisfies the Ford's negative energy-time inequality. Also found is a connection between the superluminal two-dimensional warp drive space and two-dimensional gravitational kinks. This connection allows us to generalize the considered Alcubierre metric to a standard, nonstatic metric which is only describable on two different coordinate patches |
0805.0846 | Llu\'is Bel | Ll. Bel | Connecting connections | 17 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As true as it is that a bricklayer needs a plumb line and a T-square, so it
is that a physicist using general relativity needs how to draw geodesics and
use fields of congruent vector frames of reference. While the first part of the
preceding statement depends on the Christoffel connection and related metric
and curvature concepts, the second part depends on the Weitzenb\"{o}ck
connection and the concept of torsion. This dual structure has been considered
before as a possibility of using either one of them to describe General
relativity. We claim here that both structures have to be correlated to produce
useful interpretations of any space-time model.
| [
{
"created": "Wed, 7 May 2008 10:31:02 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Jun 2008 07:25:36 GMT",
"version": "v2"
}
] | 2008-06-10 | [
[
"Bel",
"Ll.",
""
]
] | As true as it is that a bricklayer needs a plumb line and a T-square, so it is that a physicist using general relativity needs how to draw geodesics and use fields of congruent vector frames of reference. While the first part of the preceding statement depends on the Christoffel connection and related metric and curvature concepts, the second part depends on the Weitzenb\"{o}ck connection and the concept of torsion. This dual structure has been considered before as a possibility of using either one of them to describe General relativity. We claim here that both structures have to be correlated to produce useful interpretations of any space-time model. |
gr-qc/9803069 | Raul Vera | Jos\'e M. M. Senovilla and Ra\"ul Vera | G_2 cosmological models separable in non-comoving coordinates | latex, 26 pages, accepted for publication in Class. Quantum Grav | Class.Quant.Grav. 15 (1998) 1737-1758 | 10.1088/0264-9381/15/6/022 | null | gr-qc | null | We study new separable orthogonally transitive abelian G_2 on S_2 models with
two mutually orthogonal integrable Killing vector fields. For this purpose we
consider separability of the metric functions in a coordinate system in which
the velocity vector field of the perfect fluid does not take its canonical
form, providing thereby solutions which are non-separable in comoving
coordinates in general. Some interesting general features concerning this class
of solutions are given. We provide a full classification for these models and
present several families of explicit solutions with their properties.
| [
{
"created": "Thu, 19 Mar 1998 11:33:35 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Senovilla",
"José M. M.",
""
],
[
"Vera",
"Raül",
""
]
] | We study new separable orthogonally transitive abelian G_2 on S_2 models with two mutually orthogonal integrable Killing vector fields. For this purpose we consider separability of the metric functions in a coordinate system in which the velocity vector field of the perfect fluid does not take its canonical form, providing thereby solutions which are non-separable in comoving coordinates in general. Some interesting general features concerning this class of solutions are given. We provide a full classification for these models and present several families of explicit solutions with their properties. |
1506.08496 | Achilleas Porfyriadis | Samuel E. Gralla, Achilleas P. Porfyriadis, Niels Warburton | Particle on the Innermost Stable Circular Orbit of a Rapidly Spinning
Black Hole | 15 pages, 4 figures, v2: reference added, minor changes, matches
published version | Phys. Rev. D 92, 064029 (2015) | 10.1103/PhysRevD.92.064029 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compute the radiation emitted by a particle on the innermost stable
circular orbit of a rapidly spinning black hole both (a) analytically, working
to leading order in the deviation from extremality and (b) numerically, with a
new high-precision Teukolsky code. We find excellent agreement between the two
methods. We confirm previous estimates of the overall scaling of the power
radiated, but show that there are also small oscillations all the way to
extremality. Furthermore, we reveal an intricate mode-by-mode structure in the
flux to infinity, with only certain modes having the dominant scaling. The
scaling of each mode is controlled by its conformal weight, a quantity that
arises naturally in the representation theory of the enhanced near-horizon
symmetry group. We find relationships to previous work on particles orbiting in
precisely extreme Kerr, including detailed agreement of quantities computed
here with conformal field theory calculations performed in the context of the
Kerr/CFT correspondence.
| [
{
"created": "Mon, 29 Jun 2015 03:13:41 GMT",
"version": "v1"
},
{
"created": "Thu, 24 Sep 2015 03:46:10 GMT",
"version": "v2"
}
] | 2015-09-30 | [
[
"Gralla",
"Samuel E.",
""
],
[
"Porfyriadis",
"Achilleas P.",
""
],
[
"Warburton",
"Niels",
""
]
] | We compute the radiation emitted by a particle on the innermost stable circular orbit of a rapidly spinning black hole both (a) analytically, working to leading order in the deviation from extremality and (b) numerically, with a new high-precision Teukolsky code. We find excellent agreement between the two methods. We confirm previous estimates of the overall scaling of the power radiated, but show that there are also small oscillations all the way to extremality. Furthermore, we reveal an intricate mode-by-mode structure in the flux to infinity, with only certain modes having the dominant scaling. The scaling of each mode is controlled by its conformal weight, a quantity that arises naturally in the representation theory of the enhanced near-horizon symmetry group. We find relationships to previous work on particles orbiting in precisely extreme Kerr, including detailed agreement of quantities computed here with conformal field theory calculations performed in the context of the Kerr/CFT correspondence. |
1612.06939 | Zhi-Chao Zhao | Zhe Chang, Chao-Guang Huang, Zhi-Chao Zhao | Motion of photons in a background of gravitational wave | 15 pages, 4 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The photon motion in a Michelson interferometer is re-analyzed in both
geometrical optics and wave optics. The classical paths of the photons in the
background of gravitational wave are derived from Fermat principle, which is
the same as the null geodesics in general relativity. The deformed Maxwell
equations and the wave equations of electric fields in the background of
gravitational wave are presented in flat-space approximation. Both methods show
that the response of an interferometer depends on the frequency of a
gravitational wave, however it is almost independent of the frequency of the
mirror's vibrations. It implies that the vibrating mirror cannot mimic a
gravitational wave very well.
| [
{
"created": "Wed, 21 Dec 2016 01:29:49 GMT",
"version": "v1"
}
] | 2016-12-22 | [
[
"Chang",
"Zhe",
""
],
[
"Huang",
"Chao-Guang",
""
],
[
"Zhao",
"Zhi-Chao",
""
]
] | The photon motion in a Michelson interferometer is re-analyzed in both geometrical optics and wave optics. The classical paths of the photons in the background of gravitational wave are derived from Fermat principle, which is the same as the null geodesics in general relativity. The deformed Maxwell equations and the wave equations of electric fields in the background of gravitational wave are presented in flat-space approximation. Both methods show that the response of an interferometer depends on the frequency of a gravitational wave, however it is almost independent of the frequency of the mirror's vibrations. It implies that the vibrating mirror cannot mimic a gravitational wave very well. |
gr-qc/0410141 | Laurent Freidel | Laurent Freidel and David Louapre | Ponzano-Regge model revisited II: Equivalence with Chern-Simons | 27 + 23 pages, many figures | null | null | null | gr-qc hep-th math.QA | null | We provide a mathematical definition of the gauge fixed Ponzano-Regge model
showing that it gives a measure on the space of flat connections whose volume
is well defined. We then show that the Ponzano-Regge model can be equivalently
expressed as Reshetikhin-Turaev evaluation of a colored chain mail link based
on D(SU(2)): a non compact quantum group being the Drinfeld double of SU(2) and
a deformation of the Poincare algebra. This proves the equivalence between spin
foam quantization and Chern-Simons quantization of three dimensional gravity
without cosmological constant. We extend this correspondence to the computation
of expectation value of physical observables and insertion of particles.
| [
{
"created": "Thu, 28 Oct 2004 14:12:36 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Feb 2005 17:47:39 GMT",
"version": "v2"
},
{
"created": "Mon, 14 Feb 2005 14:25:21 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Freidel",
"Laurent",
""
],
[
"Louapre",
"David",
""
]
] | We provide a mathematical definition of the gauge fixed Ponzano-Regge model showing that it gives a measure on the space of flat connections whose volume is well defined. We then show that the Ponzano-Regge model can be equivalently expressed as Reshetikhin-Turaev evaluation of a colored chain mail link based on D(SU(2)): a non compact quantum group being the Drinfeld double of SU(2) and a deformation of the Poincare algebra. This proves the equivalence between spin foam quantization and Chern-Simons quantization of three dimensional gravity without cosmological constant. We extend this correspondence to the computation of expectation value of physical observables and insertion of particles. |
1810.07100 | Jakub Mielczarek Ph.D. | Jakub Mielczarek | Spin Foam Vertex Amplitudes on Quantum Computer -- Preliminary Results | 35 pages, 9 figures, improved discussion, additional simulations and
2 appendices added | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Vertex amplitudes are elementary contributions to the transition amplitudes
in the spin foam models of quantum gravity. The purpose of this article is make
the first step towards computing vertex amplitudes with the use of quantum
algorithms. In our studies we are focused on a vertex amplitude of 3+1 D
gravity, associated with a pentagram spin-network. Furthermore, all spin labels
of the spin network are assumed to be equal $j=1/2$, which is crucial for the
introduction of the \emph{intertwiner qubits}. A procedure of determining
modulus squares of vertex amplitudes on universal quantum computers is
proposed. Utility of the approach is tested with the use of: IBM's
\emph{ibmqx4} 5-qubit quantum computer, simulator of quantum computer provided
by the same company and QX quantum computer simulator. Finally, values of the
vertex probability are determined employing both the QX and the IBM simulators
with 20-qubit quantum register and compared with analytical predictions.
| [
{
"created": "Tue, 16 Oct 2018 15:58:41 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Jun 2019 22:59:15 GMT",
"version": "v2"
}
] | 2019-06-20 | [
[
"Mielczarek",
"Jakub",
""
]
] | Vertex amplitudes are elementary contributions to the transition amplitudes in the spin foam models of quantum gravity. The purpose of this article is make the first step towards computing vertex amplitudes with the use of quantum algorithms. In our studies we are focused on a vertex amplitude of 3+1 D gravity, associated with a pentagram spin-network. Furthermore, all spin labels of the spin network are assumed to be equal $j=1/2$, which is crucial for the introduction of the \emph{intertwiner qubits}. A procedure of determining modulus squares of vertex amplitudes on universal quantum computers is proposed. Utility of the approach is tested with the use of: IBM's \emph{ibmqx4} 5-qubit quantum computer, simulator of quantum computer provided by the same company and QX quantum computer simulator. Finally, values of the vertex probability are determined employing both the QX and the IBM simulators with 20-qubit quantum register and compared with analytical predictions. |
0906.0436 | Kamal Nandi | Kamal K. Nandi and Anwarul Islam | Brans wormholes | Uploaded for the use of researchers | Phys.Rev.D55:2497-2500,1997 | 10.1103/PhysRevD.55.2497 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is shown that three of the four Brans solutions of classes I--IV admit
wormhole geometry. Two-way traversable wormholes in the Brans-Dicke theory are
allowed not only for the negative values of the coupling parameter w (w<-2), as
concluded earlier, but also for arbitrary positive values of w (w<infinity). It
also follows that the scalar field f plays the role of exotic matter violating
the weak energy condition.
| [
{
"created": "Tue, 2 Jun 2009 07:47:53 GMT",
"version": "v1"
}
] | 2009-06-30 | [
[
"Nandi",
"Kamal K.",
""
],
[
"Islam",
"Anwarul",
""
]
] | It is shown that three of the four Brans solutions of classes I--IV admit wormhole geometry. Two-way traversable wormholes in the Brans-Dicke theory are allowed not only for the negative values of the coupling parameter w (w<-2), as concluded earlier, but also for arbitrary positive values of w (w<infinity). It also follows that the scalar field f plays the role of exotic matter violating the weak energy condition. |
gr-qc/0310098 | Sachiko Ogushi | Nathalie Deruelle, Joseph Katz, Sachiko Ogushi | Conserved Charges in Einstein Gauss-Bonnet theory | 17 pages, LaTeX, references added, typos corrected, version to appear
in Class. Quant. Grav | Class.Quant.Grav.21:1971,2004 | 10.1088/0264-9381/21/8/004 | YITP-03-67 | gr-qc hep-th | null | Using Noether's identities, we define a superpotential with respect to a
background for the Einstein Gauss-Bonnet theory of gravity. As an example, we
show that its associated conserved charge yields the mass-energy of a
D-dimensional Gauss-Bonnet black hole in an anti-de Sitter spacetime.
| [
{
"created": "Mon, 20 Oct 2003 07:08:44 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Feb 2004 01:00:12 GMT",
"version": "v2"
}
] | 2010-12-03 | [
[
"Deruelle",
"Nathalie",
""
],
[
"Katz",
"Joseph",
""
],
[
"Ogushi",
"Sachiko",
""
]
] | Using Noether's identities, we define a superpotential with respect to a background for the Einstein Gauss-Bonnet theory of gravity. As an example, we show that its associated conserved charge yields the mass-energy of a D-dimensional Gauss-Bonnet black hole in an anti-de Sitter spacetime. |
gr-qc/0002021 | Ulf Nilsson | U. S. Nilsson and C. Uggla | General Relativistic Stars: Linear Equations of State | 17 pages, 3 figures, uses ajour.cls | Annals Phys. 286 (2001) 278-291 | 10.1006/aphy.2000.6089 | null | gr-qc | null | In this paper Einstein's field equations, for static spherically symmetric
perfect fluid models with a linear barotropic equation of state, are recast
into a 3-dimensional regular system of ordinary differential equations on a
compact state space. The system is analyzed qualitatively, using the theory of
dynamical systems, and numerically. It is shown that certain special solutions
play important roles as building blocks for the solution structure in general.
In particular, these special solutions determine many of the features exhibited
by solutions with a regular center and large central pressure. It is also shown
that the present approach can be applied to more general classes of barotropic
equations of state.
| [
{
"created": "Fri, 4 Feb 2000 12:24:09 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Nilsson",
"U. S.",
""
],
[
"Uggla",
"C.",
""
]
] | In this paper Einstein's field equations, for static spherically symmetric perfect fluid models with a linear barotropic equation of state, are recast into a 3-dimensional regular system of ordinary differential equations on a compact state space. The system is analyzed qualitatively, using the theory of dynamical systems, and numerically. It is shown that certain special solutions play important roles as building blocks for the solution structure in general. In particular, these special solutions determine many of the features exhibited by solutions with a regular center and large central pressure. It is also shown that the present approach can be applied to more general classes of barotropic equations of state. |
2406.02639 | Moli Ghosh | Moli Ghosh, Prabir Rudra, Surajit Chattopadhyay | Warm Inflation with Barrow Holographic Dark Energy | 15 pages, 8 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we study the warm inflation mechanism in the presence of the
Barrow holographic dark energy model. Warm inflation differs from other forms
of inflation primarily in that it makes the assumption that radiation and
inflaton exist and interact throughout the inflationary process. After the
warming process, energy moves from the inflaton to the radiation as a result of
the interaction, keeping the cosmos warm. Here we have set up the warm
inflationary mechanism using Barrow holographic dark energy as the driving
agent. Warm inflation has been explored in a high dissipative regime and
interesting results have been obtained. It is seen that the Barrow holographic
dark energy can successfully drive a warm inflationary scenario in the early
universe. Finally, the model has been compared with the observational data and
compliance has been found.
| [
{
"created": "Tue, 4 Jun 2024 09:15:32 GMT",
"version": "v1"
}
] | 2024-06-06 | [
[
"Ghosh",
"Moli",
""
],
[
"Rudra",
"Prabir",
""
],
[
"Chattopadhyay",
"Surajit",
""
]
] | In this work, we study the warm inflation mechanism in the presence of the Barrow holographic dark energy model. Warm inflation differs from other forms of inflation primarily in that it makes the assumption that radiation and inflaton exist and interact throughout the inflationary process. After the warming process, energy moves from the inflaton to the radiation as a result of the interaction, keeping the cosmos warm. Here we have set up the warm inflationary mechanism using Barrow holographic dark energy as the driving agent. Warm inflation has been explored in a high dissipative regime and interesting results have been obtained. It is seen that the Barrow holographic dark energy can successfully drive a warm inflationary scenario in the early universe. Finally, the model has been compared with the observational data and compliance has been found. |
1906.00485 | Hector O. Silva | Hector O. Silva, Nicol\'as Yunes | More than the sum of its parts: combining parameterized tests of extreme
gravity | (v1) 11 pages, 4 figures, 1 appendix; (v2) 12 pages, new appendix.
Matches published version | Phys. Rev. D 100, 084034 (2019) | 10.1103/PhysRevD.100.084034 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We connect two formalisms that describe deformations away from general
relativity, one valid in the strong-field regime of neutrons stars and another
valid in the radiative regime of gravitational waves: the
post-Tolman-Oppenheimer-Volkoff and the parametrized-post-Einsteinian
formalisms respectively. We find that post-Tolman-Oppenheimer-Volkoff
deformations of the exterior metric of an isolated neutron star induce
deformations in the orbital binding energy of a neutron star binary. Such a
modification to the binding energy then percolates into the gravitational waves
emitted by such a binary, with the leading-order
post-Tolman-Oppenheimer-Volkoff modifications introducing a second
post-Newtonian order correction to the gravitational wave phase. The lack of
support in gravitational wave data for general relativity deformations at this
post-Newtonian order can then be used to place constraints
post-Tolman-Oppenheimer-Volkoff parameters. As an application, we use the
binary neutron star merger event GW170817 to place the constraint $-2.4 \leq
\chi \leq 44$ (at 90% credibility) on a combination of
post-Tolman-Oppenheimer-Volkoff parameters. We also explore the implications of
this result to the possible deformations of the mass-radius relation of neutron
stars allowed within this formalism. This work opens the path towards
theory-independent tests of gravity, combining astronomical observations of
neutron stars and gravitational wave observations.
| [
{
"created": "Sun, 2 Jun 2019 21:03:46 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Nov 2019 03:22:05 GMT",
"version": "v2"
}
] | 2019-11-11 | [
[
"Silva",
"Hector O.",
""
],
[
"Yunes",
"Nicolás",
""
]
] | We connect two formalisms that describe deformations away from general relativity, one valid in the strong-field regime of neutrons stars and another valid in the radiative regime of gravitational waves: the post-Tolman-Oppenheimer-Volkoff and the parametrized-post-Einsteinian formalisms respectively. We find that post-Tolman-Oppenheimer-Volkoff deformations of the exterior metric of an isolated neutron star induce deformations in the orbital binding energy of a neutron star binary. Such a modification to the binding energy then percolates into the gravitational waves emitted by such a binary, with the leading-order post-Tolman-Oppenheimer-Volkoff modifications introducing a second post-Newtonian order correction to the gravitational wave phase. The lack of support in gravitational wave data for general relativity deformations at this post-Newtonian order can then be used to place constraints post-Tolman-Oppenheimer-Volkoff parameters. As an application, we use the binary neutron star merger event GW170817 to place the constraint $-2.4 \leq \chi \leq 44$ (at 90% credibility) on a combination of post-Tolman-Oppenheimer-Volkoff parameters. We also explore the implications of this result to the possible deformations of the mass-radius relation of neutron stars allowed within this formalism. This work opens the path towards theory-independent tests of gravity, combining astronomical observations of neutron stars and gravitational wave observations. |
gr-qc/9710076 | Jacob D. Bekenstein | Jacob D. Bekenstein (Hebrew Universiy, Jerusalem) | Quantum Black Holes as Atoms | 20 pages, latex, uses mprocl.sty. Plenary talk at VIII Marcel
Grossmann Meeting on General Relativity, Jerusalem, June 1997. Added and
corrected references | Prodeedings of the Eight Marcel Grossmann Meeting, T. Piran and R.
Ruffini, eds. (World Scientific Singapore 1999), pp. 92-111 | null | null | gr-qc astro-ph hep-th quant-ph | null | In some respects the black hole plays the same role in gravitation that the
atom played in the nascent quantum mechanics. This analogy suggests that black
hole mass $M$ might have a discrete spectrum. I review the physical arguments
for the expectation that black hole horizon area eigenvalues are uniformly
spaced, or equivalently, that the spacing between stationary black hole mass
levels behaves like 1/M. This sort of spectrum has also emerged in a variety of
formal approaches to black hole quantization by a number of workers (with some
notable exceptions). If true, this result indicates a distortion of the
semiclassical Hawking spectrum which could be observable even for macroscopic
black holes. Black hole entropy suggests that the mentioned mass levels should
be degenerate to the tune of an exponential in $M^2$, as first noted by
Mukhanov. This has implications for the statistics of the radiation. I also
discuss open questions: whether radiative decay will spread the levels beyond
recognition, whether extremal black holes can be described by this scheme, etc.
I then describe an elementary algebra for the relevant black hole observables,
an outcome of work by Mukhanov and myself, which reproduces the uniformly
spaced area spectrum.
| [
{
"created": "Wed, 15 Oct 1997 07:15:04 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Mar 1998 14:44:42 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Bekenstein",
"Jacob D.",
"",
"Hebrew Universiy, Jerusalem"
]
] | In some respects the black hole plays the same role in gravitation that the atom played in the nascent quantum mechanics. This analogy suggests that black hole mass $M$ might have a discrete spectrum. I review the physical arguments for the expectation that black hole horizon area eigenvalues are uniformly spaced, or equivalently, that the spacing between stationary black hole mass levels behaves like 1/M. This sort of spectrum has also emerged in a variety of formal approaches to black hole quantization by a number of workers (with some notable exceptions). If true, this result indicates a distortion of the semiclassical Hawking spectrum which could be observable even for macroscopic black holes. Black hole entropy suggests that the mentioned mass levels should be degenerate to the tune of an exponential in $M^2$, as first noted by Mukhanov. This has implications for the statistics of the radiation. I also discuss open questions: whether radiative decay will spread the levels beyond recognition, whether extremal black holes can be described by this scheme, etc. I then describe an elementary algebra for the relevant black hole observables, an outcome of work by Mukhanov and myself, which reproduces the uniformly spaced area spectrum. |
1912.07630 | Shahar Hod | Shahar Hod | Spontaneous scalarization of Gauss-Bonnet black holes: Analytic
treatment in the linearized regime | 6 pages | Physical Review D 100, 064039 (2019) | 10.1103/PhysRevD.100.064039 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has recently been proved that nontrivial couplings between scalar fields
and the Gauss-Bonnet invariant of a curved spacetime may allow a central black
hole to support spatially regular scalar hairy configurations. Interestingly,
former numerical studies of the intriguing black-hole spontaneous scalarization
phenomenon have demonstrated that the composed hairy black-hole-scalar-field
configurations exist if and only if the dimensionless coupling parameter
$\bar\eta$ of the theory belongs to a discrete set
$\{[\bar\eta^{-}_{n},\bar\eta^{+}_{n}]\}_{n=0}^{n=\infty}$ of scalarization
bands. We have examined the numerical data that are available in the physics
literature and found that the newly discovered hairy
black-hole-linearized-massless-scalar-field configurations are characterized by
the asymptotic universal behavior $\Delta_n\equiv
\sqrt{\bar\eta^{+}_{n+1}}-\sqrt{\bar\eta^{+}_{n}}\simeq 2.72$. Motivated by
this intriguing observation, in the present paper we study {\it analytically}
the physical and mathematical properties of the spontaneously scalarized
Schwarzschild black holes in the linearized (weak-field) regime. In particular,
we provide a remarkably compact analytical explanation for the numerically
observed universal behavior $\Delta_n\simeq 2.72$ which characterizes the
discrete resonant spectrum $\{\bar\eta^{+}_{n}\}_{n=0}^{n=\infty}$ of the
composed hairy black-hole-linearized-scalar-field configurations.
| [
{
"created": "Mon, 16 Dec 2019 19:00:20 GMT",
"version": "v1"
}
] | 2020-01-08 | [
[
"Hod",
"Shahar",
""
]
] | It has recently been proved that nontrivial couplings between scalar fields and the Gauss-Bonnet invariant of a curved spacetime may allow a central black hole to support spatially regular scalar hairy configurations. Interestingly, former numerical studies of the intriguing black-hole spontaneous scalarization phenomenon have demonstrated that the composed hairy black-hole-scalar-field configurations exist if and only if the dimensionless coupling parameter $\bar\eta$ of the theory belongs to a discrete set $\{[\bar\eta^{-}_{n},\bar\eta^{+}_{n}]\}_{n=0}^{n=\infty}$ of scalarization bands. We have examined the numerical data that are available in the physics literature and found that the newly discovered hairy black-hole-linearized-massless-scalar-field configurations are characterized by the asymptotic universal behavior $\Delta_n\equiv \sqrt{\bar\eta^{+}_{n+1}}-\sqrt{\bar\eta^{+}_{n}}\simeq 2.72$. Motivated by this intriguing observation, in the present paper we study {\it analytically} the physical and mathematical properties of the spontaneously scalarized Schwarzschild black holes in the linearized (weak-field) regime. In particular, we provide a remarkably compact analytical explanation for the numerically observed universal behavior $\Delta_n\simeq 2.72$ which characterizes the discrete resonant spectrum $\{\bar\eta^{+}_{n}\}_{n=0}^{n=\infty}$ of the composed hairy black-hole-linearized-scalar-field configurations. |
2301.06764 | Subhajit Barman | Subhajit Barman, Bibhas Ranjan Majhi | Optimization of entanglement depends on whether a black hole is extremal | A modified version, to appear in General Relativity and Gravitation | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider two Unruh-DeWitt detectors interacting with a massless, minimally
coupled scalar field in a $(1+1)$ dimensional Reissner-Nordstr\"om black hole
spacetime. In particular, one of the detectors, corresponding to $Alice$, is
moving along an outgoing null trajectory. While the other detector carried by
$Bob$ is static. With this set-up, we investigate the entangling condition and
the measure of the entanglement, concurrence, in the nonextremal and extremal
scenarios. Our observations suggest, as expected, a qualitative similarity in
characteristics of the entanglement between these two scenarios. However, we
find quantitative differences between the nonextremal and extremal concurrences
for a broad range of black hole charges. With moderately large detector
transition energy, the extremal background always accounts for the larger
entanglement than the nonextremal one. In contrast, with low detector
transition energy, entanglement on the nonextremal background can be greater.
Therefore, by adjusting the detector transition energy, one can perceive
optimum entanglement from either the extremal or the nonextremal background.
| [
{
"created": "Tue, 17 Jan 2023 08:59:12 GMT",
"version": "v1"
},
{
"created": "Thu, 30 May 2024 12:51:01 GMT",
"version": "v2"
}
] | 2024-05-31 | [
[
"Barman",
"Subhajit",
""
],
[
"Majhi",
"Bibhas Ranjan",
""
]
] | We consider two Unruh-DeWitt detectors interacting with a massless, minimally coupled scalar field in a $(1+1)$ dimensional Reissner-Nordstr\"om black hole spacetime. In particular, one of the detectors, corresponding to $Alice$, is moving along an outgoing null trajectory. While the other detector carried by $Bob$ is static. With this set-up, we investigate the entangling condition and the measure of the entanglement, concurrence, in the nonextremal and extremal scenarios. Our observations suggest, as expected, a qualitative similarity in characteristics of the entanglement between these two scenarios. However, we find quantitative differences between the nonextremal and extremal concurrences for a broad range of black hole charges. With moderately large detector transition energy, the extremal background always accounts for the larger entanglement than the nonextremal one. In contrast, with low detector transition energy, entanglement on the nonextremal background can be greater. Therefore, by adjusting the detector transition energy, one can perceive optimum entanglement from either the extremal or the nonextremal background. |
gr-qc/0501003 | Alena Pravdov\'a | V. Pravda, A. Pravdova | WANDs of the Black Ring | 9 pages, 3 figures | Gen.Rel.Grav.37:1277-1287,2005 | 10.1007/s10714-005-0110-3 | null | gr-qc hep-th | null | Necessary conditions for various algebraic types of the Weyl tensor are
determined. These conditions are then used to find Weyl aligned null directions
for the black ring solution. It is shown that the black ring solution is
algebraically special, of type I_i, while locally on the horizon the type is
II. One exceptional subclass - the Myers-Perry solution - is of type D.
| [
{
"created": "Sat, 1 Jan 2005 22:56:18 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Pravda",
"V.",
""
],
[
"Pravdova",
"A.",
""
]
] | Necessary conditions for various algebraic types of the Weyl tensor are determined. These conditions are then used to find Weyl aligned null directions for the black ring solution. It is shown that the black ring solution is algebraically special, of type I_i, while locally on the horizon the type is II. One exceptional subclass - the Myers-Perry solution - is of type D. |
1705.02747 | Woei Chet Lim | Daniele Gregoris, Woei Chet Lim, Alan Coley | Stiff fluid spike solutions from Bianchi type V seed solutions | 24 pages. 11 figures. Matches accepted version | null | 10.1088/1361-6382/aa924f | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we expand upon our previous work [1] by using the entire family
of Bianchi type V stiff fluid solutions as seed solutions of the Stephani
transformation. Among the new exact solutions generated, we observe a number of
important physical phenomena. The most interesting phenomenon is exact
solutions with intersecting spikes. Other interesting phenomena are solutions
with saddle states and a close-to-FL epoch.
| [
{
"created": "Mon, 8 May 2017 05:29:43 GMT",
"version": "v1"
},
{
"created": "Thu, 19 Oct 2017 04:20:06 GMT",
"version": "v2"
}
] | 2017-12-06 | [
[
"Gregoris",
"Daniele",
""
],
[
"Lim",
"Woei Chet",
""
],
[
"Coley",
"Alan",
""
]
] | In this paper we expand upon our previous work [1] by using the entire family of Bianchi type V stiff fluid solutions as seed solutions of the Stephani transformation. Among the new exact solutions generated, we observe a number of important physical phenomena. The most interesting phenomenon is exact solutions with intersecting spikes. Other interesting phenomena are solutions with saddle states and a close-to-FL epoch. |
2201.06521 | Pardyumn Kumar Sahoo | Raja Solanki, Avik De, Sanjay Mandal, P.K. Sahoo | Accelerating expansion of the universe in modified symmetric
teleparallel gravity | PDU revised version | Physics of the Dark Universe 36 (2022) 101053 | 10.1016/j.dark.2022.101053 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | The fundamental nature and origin of dark energy are one of the premier
mysteries of theoretical physics. In General Relativity Theory, the
cosmological constant $\Lambda$ is the simplest explanation for dark energy. On
the other hand, the cosmological constant $\Lambda$ suffers from a delicate
issue so-called fine-tuning problem. This motivates one to modify the spacetime
geometry of Einstein's GR. The $f(Q)$ gravity is a recently proposed modified
theory of gravity in which the non-metricity scalar $Q$ drives the
gravitational interaction. In this article, we consider a linear $f(Q)$ model,
specifically $f(Q)=\alpha Q + \beta$, where $\alpha$ and $\beta$ are free
parameters. Then we estimate the best fit values of model parameters that would
be in agreement with the recent observational data sets. We use 57 points of
the updated $H(z)$ data sets, 6 points of the BAO data sets, and 1048 points
from the Pantheon supernovae samples. We apply the Bayesian analysis and
likelihood function along with the Markov Chain Monte Carlo (MCMC) method.
Further, we analyse the physical behaviour of cosmological parameters such as
density, deceleration, and the EoS parameters corresponding to the constraint
values of the model parameters. The evolution of deceleration parameter
predicts a transition from decelerated to accelerated phases of the universe.
Further, the evolution of equation of state parameter depicts quintessence type
behaviour of the dark energy fluid part. We found that our $f(Q)$ cosmological
model can effectively describe the late time cosmic acceleration without
invoking any dark energy component in the matter part.
| [
{
"created": "Mon, 17 Jan 2022 16:54:40 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Feb 2022 16:58:29 GMT",
"version": "v2"
},
{
"created": "Mon, 21 Feb 2022 09:28:47 GMT",
"version": "v3"
},
{
"created": "Thu, 12 May 2022 15:28:38 GMT",
"version": "v4"
}
] | 2022-05-27 | [
[
"Solanki",
"Raja",
""
],
[
"De",
"Avik",
""
],
[
"Mandal",
"Sanjay",
""
],
[
"Sahoo",
"P. K.",
""
]
] | The fundamental nature and origin of dark energy are one of the premier mysteries of theoretical physics. In General Relativity Theory, the cosmological constant $\Lambda$ is the simplest explanation for dark energy. On the other hand, the cosmological constant $\Lambda$ suffers from a delicate issue so-called fine-tuning problem. This motivates one to modify the spacetime geometry of Einstein's GR. The $f(Q)$ gravity is a recently proposed modified theory of gravity in which the non-metricity scalar $Q$ drives the gravitational interaction. In this article, we consider a linear $f(Q)$ model, specifically $f(Q)=\alpha Q + \beta$, where $\alpha$ and $\beta$ are free parameters. Then we estimate the best fit values of model parameters that would be in agreement with the recent observational data sets. We use 57 points of the updated $H(z)$ data sets, 6 points of the BAO data sets, and 1048 points from the Pantheon supernovae samples. We apply the Bayesian analysis and likelihood function along with the Markov Chain Monte Carlo (MCMC) method. Further, we analyse the physical behaviour of cosmological parameters such as density, deceleration, and the EoS parameters corresponding to the constraint values of the model parameters. The evolution of deceleration parameter predicts a transition from decelerated to accelerated phases of the universe. Further, the evolution of equation of state parameter depicts quintessence type behaviour of the dark energy fluid part. We found that our $f(Q)$ cosmological model can effectively describe the late time cosmic acceleration without invoking any dark energy component in the matter part. |
0901.0590 | Alfredo Sandoval-Villalbazo | A. Sandoval-Villalbazo, A. L. Garcia-Perciante and L.S. Garcia-Colin | The heat flux from a relativistic kinetic equation with a simplified
collision kernel | 4 pages, one figure. To appear in the AIP conference proceedings of
the XXXI Spanish Relativity Meeting: Physics and Mathematics of Gravitation.
Salamanca Spain, 15-19 September 2008 | AIP Conf.Proc.1122:388-391,2009 | 10.1063/1.3141333 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show how using a special relativistic kinetic equation with a BGK- like
collision operator the ensuing expression for the heat flux can be casted in
the form required by Classical Irreversible Thermodynamics. Indeed, it is
linearly related to the temperature and number density gradients and not to the
acceleration as the so-called "first order in the gradients theories" contend.
Here we calculate explicitly the ensuing transport coefficients and compare
them with the results obtained by other authors.
| [
{
"created": "Tue, 6 Jan 2009 02:50:02 GMT",
"version": "v1"
}
] | 2009-06-12 | [
[
"Sandoval-Villalbazo",
"A.",
""
],
[
"Garcia-Perciante",
"A. L.",
""
],
[
"Garcia-Colin",
"L. S.",
""
]
] | We show how using a special relativistic kinetic equation with a BGK- like collision operator the ensuing expression for the heat flux can be casted in the form required by Classical Irreversible Thermodynamics. Indeed, it is linearly related to the temperature and number density gradients and not to the acceleration as the so-called "first order in the gradients theories" contend. Here we calculate explicitly the ensuing transport coefficients and compare them with the results obtained by other authors. |
gr-qc/0703001 | Lars Samuelsson | Max Karlovini and Lars Samuelsson | Elastic stars in general relativity: IV. Axial perturbations | 18 pages, no figures | Class.Quant.Grav.24:3171-3190,2007 | 10.1088/0264-9381/24/13/003 | null | gr-qc astro-ph | null | This is the fourth paper in a series that attempt to put forward a consistent
framework for modelling solid regions in neutron stars. Here we turn our
attention to axial perturbations of spherically symmetric spacetimes using a
gauge invariant approach due to one of us. Using the formalism developed in the
first paper in the series it turns out that the matter perturbations are neatly
expressible in terms of a ``metric'' tensor field depending only on the speeds
of shear wave propagation along the principal directions in the solid. The
results are applicable to a wide class of elastic materials and does not assume
material isotropy nor quasi-Hookean behaviour. The perturbation equations are
then specialised to a static background and are given by two coupled wave
equations. Our formalism is thus slightly simpler than the previously existing
results of Shumaker & Thorne, where an additional initial value equation needs
to be solved. The simplification is mainly due to the gauge invariance of our
approach and shows up also in somewhat simpler boundary conditions. We also
give a first order formulation suitable for numerical integration of the
quasi-normal mode problem of a neutron star. The relations between the gauge
independent variables and the, in general, gauge dependent perturbed metric and
strain tensor are explicitly given.
| [
{
"created": "Wed, 28 Feb 2007 21:41:38 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Karlovini",
"Max",
""
],
[
"Samuelsson",
"Lars",
""
]
] | This is the fourth paper in a series that attempt to put forward a consistent framework for modelling solid regions in neutron stars. Here we turn our attention to axial perturbations of spherically symmetric spacetimes using a gauge invariant approach due to one of us. Using the formalism developed in the first paper in the series it turns out that the matter perturbations are neatly expressible in terms of a ``metric'' tensor field depending only on the speeds of shear wave propagation along the principal directions in the solid. The results are applicable to a wide class of elastic materials and does not assume material isotropy nor quasi-Hookean behaviour. The perturbation equations are then specialised to a static background and are given by two coupled wave equations. Our formalism is thus slightly simpler than the previously existing results of Shumaker & Thorne, where an additional initial value equation needs to be solved. The simplification is mainly due to the gauge invariance of our approach and shows up also in somewhat simpler boundary conditions. We also give a first order formulation suitable for numerical integration of the quasi-normal mode problem of a neutron star. The relations between the gauge independent variables and the, in general, gauge dependent perturbed metric and strain tensor are explicitly given. |
1603.05987 | Gandalf Lechner | Stefan Hollands and Gandalf Lechner | SO(d,1)-invariant Yang-Baxter operators and the dS/CFT correspondence | Minor changes in formulations and presentation. 48 pages | null | 10.1007/s00220-017-2942-6 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a model for the dS/CFT correspondence. The model is constructed in
terms of a "Yang-Baxter operator" $R$ for unitary representations of the
deSitter group $SO(d,1)$. This $R$-operator is shown to satisfy the Yang-Baxter
equation, unitarity, as well as certain analyticity relations, including in
particular a crossing symmetry. With the aid of this operator we construct: a)
A chiral (light-ray) conformal quantum field theory whose internal degrees of
freedom transform under the given unitary representation of $SO(d,1)$. By
analogy with the $O(N)$ non-linear sigma model, this chiral CFT can be viewed
as propagating in a deSitter spacetime. b) A (non-unitary) Euclidean conformal
quantum field theory on ${\mathbb R}^{d-1}$, where $SO(d,1)$ now acts by
conformal transformations in (Euclidean) spacetime. These two theories can be
viewed as dual to each other if we interpret ${\mathbb R}^{d-1}$ as conformal
infinity of deSitter spacetime. Our constructions use semi-local generator
fields defined in terms of $R$ and abstract methods from operator algebras.
| [
{
"created": "Fri, 18 Mar 2016 20:25:44 GMT",
"version": "v1"
},
{
"created": "Tue, 30 May 2017 11:06:43 GMT",
"version": "v2"
}
] | 2017-09-13 | [
[
"Hollands",
"Stefan",
""
],
[
"Lechner",
"Gandalf",
""
]
] | We propose a model for the dS/CFT correspondence. The model is constructed in terms of a "Yang-Baxter operator" $R$ for unitary representations of the deSitter group $SO(d,1)$. This $R$-operator is shown to satisfy the Yang-Baxter equation, unitarity, as well as certain analyticity relations, including in particular a crossing symmetry. With the aid of this operator we construct: a) A chiral (light-ray) conformal quantum field theory whose internal degrees of freedom transform under the given unitary representation of $SO(d,1)$. By analogy with the $O(N)$ non-linear sigma model, this chiral CFT can be viewed as propagating in a deSitter spacetime. b) A (non-unitary) Euclidean conformal quantum field theory on ${\mathbb R}^{d-1}$, where $SO(d,1)$ now acts by conformal transformations in (Euclidean) spacetime. These two theories can be viewed as dual to each other if we interpret ${\mathbb R}^{d-1}$ as conformal infinity of deSitter spacetime. Our constructions use semi-local generator fields defined in terms of $R$ and abstract methods from operator algebras. |
1506.07061 | Jinn-Ouk Gong | Inyong Cho and Jinn-Ouk Gong | Spectral indices in Eddington-inspired Born-Infeld inflation | (v1) 9 pages, 1 figure; (v2) references added, to appear in Physical
Review D | Phys. Rev. D 92, 064046 (2015) | 10.1103/PhysRevD.92.064046 | APCTP-Pre2015-013 | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the scalar and tensor spectral indices of the quadratic
inflation model in Eddington-inspired Born-Infeld (EiBI) gravity. We find that
the EiBI corrections to the spectral indices are of second and first order in
the slow-roll approximation for the scalar and tensor perturbations
respectively. This is very promising since the quadratic inflation model in
general relativity provides a very nice fit for the spectral indices. Together
with the suppression of the tensor-to-scalar ratio EiBI inflation agrees well
with the observational data.
| [
{
"created": "Tue, 23 Jun 2015 15:58:14 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Sep 2015 14:49:04 GMT",
"version": "v2"
}
] | 2015-09-30 | [
[
"Cho",
"Inyong",
""
],
[
"Gong",
"Jinn-Ouk",
""
]
] | We investigate the scalar and tensor spectral indices of the quadratic inflation model in Eddington-inspired Born-Infeld (EiBI) gravity. We find that the EiBI corrections to the spectral indices are of second and first order in the slow-roll approximation for the scalar and tensor perturbations respectively. This is very promising since the quadratic inflation model in general relativity provides a very nice fit for the spectral indices. Together with the suppression of the tensor-to-scalar ratio EiBI inflation agrees well with the observational data. |
2405.03492 | Hong-Bo Jin | Hong-Bo Jin, Cong-Feng Qiao | Gravitational Wave Polarization Detection with Pyramid Constellation of
Gravitational Wave Observatory | 12 pages, 5 figures | null | null | null | gr-qc astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | For the first time, we have introduced the Pyramid Constellation of
Gravitational Wave Observatory (PCGO) for GW polarization detection. The PCGO
is composed of four identical spacecrafts (S/Cs). The laser telescopes and
their pointing structures are mounted on the S/C platform and are evenly
distributed at three locations 120 degrees apart. Compared to a three-S/C
configuration, the addition of a fourth S/C and its mounted telescope serve as
redundant backups, especially for the telescopes, which together with the other
two telescopes, automatically form a stable mass center for the platform
without the need for trim mass. Since the radial distance of S/C4 is greater
than that of the other spacecraft, the three arm lengths associated with S/C4
change significantly over a one-year period. Time delay interferometry (TDI)
has been proven effective for suppressing frequency noise in this context. The
unequal arm Michelson TDI configuration and the Sagnac TDI configuration are
equally effective for eliminating the laser frequency noise based on the PCGO
configuration. Compared to the configurations of LISA, Taiji, and TianQin, the
PCGO has more combinations of optical paths in its TDI system, offering greater
sensitivity to GW signals. The configuration of PCGO is simultaneously
sensitive to the six polarization modes of GWs, which means that it allows for
greater flexibility in extracting the polarization components from the total GW
polarization signals.
| [
{
"created": "Mon, 6 May 2024 14:02:59 GMT",
"version": "v1"
},
{
"created": "Wed, 8 May 2024 14:32:20 GMT",
"version": "v2"
}
] | 2024-05-09 | [
[
"Jin",
"Hong-Bo",
""
],
[
"Qiao",
"Cong-Feng",
""
]
] | For the first time, we have introduced the Pyramid Constellation of Gravitational Wave Observatory (PCGO) for GW polarization detection. The PCGO is composed of four identical spacecrafts (S/Cs). The laser telescopes and their pointing structures are mounted on the S/C platform and are evenly distributed at three locations 120 degrees apart. Compared to a three-S/C configuration, the addition of a fourth S/C and its mounted telescope serve as redundant backups, especially for the telescopes, which together with the other two telescopes, automatically form a stable mass center for the platform without the need for trim mass. Since the radial distance of S/C4 is greater than that of the other spacecraft, the three arm lengths associated with S/C4 change significantly over a one-year period. Time delay interferometry (TDI) has been proven effective for suppressing frequency noise in this context. The unequal arm Michelson TDI configuration and the Sagnac TDI configuration are equally effective for eliminating the laser frequency noise based on the PCGO configuration. Compared to the configurations of LISA, Taiji, and TianQin, the PCGO has more combinations of optical paths in its TDI system, offering greater sensitivity to GW signals. The configuration of PCGO is simultaneously sensitive to the six polarization modes of GWs, which means that it allows for greater flexibility in extracting the polarization components from the total GW polarization signals. |
2210.05383 | Marcos Vinicius de Sousa Silva | Manuel E. Rodrigues, Marcos V. de S. Silva | Embedding regular black holes and black bounces in a cloud of strings | 14 pages, 2 figures, accepted for publication in PRD | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | A string is the one-dimensional generalization of a point particle. In this
sense, the analog of a cloud of dust would be a cloud of strings. In this work,
we consider a cloud of strings around a regular solution in general gelativity.
We consider the Bardeen solution and the Simpson--Visser solution, analyzing
the consequences of the cloud in the regularity and in the energy conditions.
Actually, the presence of the cloud could make the energy density positive when
compared to the Simpson--Visser case. We verify that the usual Bardeen solution
becomes singular in the presence of the cloud of string while the
Simpson--Visser solution is still regular, violating the energy conditions, as
the usual solution. We also calculate some thermodynamic quantities to evaluate
how a cloud of strings influences the thermodynamics of the solutions.
| [
{
"created": "Sat, 8 Oct 2022 16:33:06 GMT",
"version": "v1"
}
] | 2022-10-12 | [
[
"Rodrigues",
"Manuel E.",
""
],
[
"Silva",
"Marcos V. de S.",
""
]
] | A string is the one-dimensional generalization of a point particle. In this sense, the analog of a cloud of dust would be a cloud of strings. In this work, we consider a cloud of strings around a regular solution in general gelativity. We consider the Bardeen solution and the Simpson--Visser solution, analyzing the consequences of the cloud in the regularity and in the energy conditions. Actually, the presence of the cloud could make the energy density positive when compared to the Simpson--Visser case. We verify that the usual Bardeen solution becomes singular in the presence of the cloud of string while the Simpson--Visser solution is still regular, violating the energy conditions, as the usual solution. We also calculate some thermodynamic quantities to evaluate how a cloud of strings influences the thermodynamics of the solutions. |
2403.09576 | Stuart Dowker | J.S.Dowker | On the high-temperature expansion of the thermal energy on Einstein
cylinders | 5 pages | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Some exact high temperature expansions are derived using a temperature
inversion symmetry of the internal energy for conformal scalars and spinors on
the Einstein Universe.
| [
{
"created": "Thu, 14 Mar 2024 17:11:48 GMT",
"version": "v1"
}
] | 2024-03-15 | [
[
"Dowker",
"J. S.",
""
]
] | Some exact high temperature expansions are derived using a temperature inversion symmetry of the internal energy for conformal scalars and spinors on the Einstein Universe. |
1705.02496 | Maxim Makukov | Eduard G. Mychelkin, Maxim A. Makukov | Coordinate effect: Vaidya solutions without integrating the field
equations | Accepted in GRG | null | 10.1007/s10714-020-02767-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We extend Vaidya's algorithm for the description of a central mass losing or
gaining energy due to electromagnetic-type radiation (`null dust') to the case
of arbitrary radial corpuscular radiation. We also demonstrate the remarkable
possibility of purely algebraic deduction of the Vaidya solution without
integrating the field equations, and interpret this possibility as an artifact
of curvature coordinates. Since Vaidya's approach by itself cannot lead to
certain dependence of mass on spacetime coordinates, the search for a
corresponding mass-function represents an independent issue. In this regard, as
a perspective, we discuss an outlook on the problem of variable masses as a
whole.
| [
{
"created": "Sat, 6 May 2017 16:08:58 GMT",
"version": "v1"
},
{
"created": "Wed, 18 Nov 2020 13:20:31 GMT",
"version": "v2"
}
] | 2020-11-19 | [
[
"Mychelkin",
"Eduard G.",
""
],
[
"Makukov",
"Maxim A.",
""
]
] | We extend Vaidya's algorithm for the description of a central mass losing or gaining energy due to electromagnetic-type radiation (`null dust') to the case of arbitrary radial corpuscular radiation. We also demonstrate the remarkable possibility of purely algebraic deduction of the Vaidya solution without integrating the field equations, and interpret this possibility as an artifact of curvature coordinates. Since Vaidya's approach by itself cannot lead to certain dependence of mass on spacetime coordinates, the search for a corresponding mass-function represents an independent issue. In this regard, as a perspective, we discuss an outlook on the problem of variable masses as a whole. |
2107.14195 | Arnab Dhani | Arnab Dhani and B. S. Sathyaprakash | Overtones, mirror modes, and mode-mixing in binary black hole mergers | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Gravitational waves emitted in the aftermath of a black hole binary
coalescence have characteristic complex frequencies called quasinormal modes
(QNMs). These can be used to test the nature of the merger remnant, e.g. a test
of the black hole "no-hair" theorem. The relative excitation amplitudes of the
QNMs contain information about the progenitor system and can be employed to
test the consistency between the pre- and post-merger signals. The post-merger
signal from numerical relativity (NR) simulations of binary black holes exhibit
a rich structure that has to be understood to fully exploit the information
contained therein. In this study, we examine the importance of \emph{overtones}
and \emph{mirror} modes for a set of mass ratios of non-spinning black hole
binaries and a host of multipole modes corresponding to spherical harmonic
indices $l\leq4$ and $m\leq3.$ We find that the first overtone is most
important in the leading mode for a given $m$ and decreases for sub-dominant
modes. The contribution of the fundamental mirror mode is most significant for
$m=1$ and increases with mass ratio, although the model systematics are not
affected significantly by mirror modes. Mode-mixing is the dominant effect for
the sub-leading modes of a given $m$ and minimally affects the leading mode.
| [
{
"created": "Thu, 29 Jul 2021 17:30:05 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Aug 2021 13:59:42 GMT",
"version": "v2"
}
] | 2021-08-09 | [
[
"Dhani",
"Arnab",
""
],
[
"Sathyaprakash",
"B. S.",
""
]
] | Gravitational waves emitted in the aftermath of a black hole binary coalescence have characteristic complex frequencies called quasinormal modes (QNMs). These can be used to test the nature of the merger remnant, e.g. a test of the black hole "no-hair" theorem. The relative excitation amplitudes of the QNMs contain information about the progenitor system and can be employed to test the consistency between the pre- and post-merger signals. The post-merger signal from numerical relativity (NR) simulations of binary black holes exhibit a rich structure that has to be understood to fully exploit the information contained therein. In this study, we examine the importance of \emph{overtones} and \emph{mirror} modes for a set of mass ratios of non-spinning black hole binaries and a host of multipole modes corresponding to spherical harmonic indices $l\leq4$ and $m\leq3.$ We find that the first overtone is most important in the leading mode for a given $m$ and decreases for sub-dominant modes. The contribution of the fundamental mirror mode is most significant for $m=1$ and increases with mass ratio, although the model systematics are not affected significantly by mirror modes. Mode-mixing is the dominant effect for the sub-leading modes of a given $m$ and minimally affects the leading mode. |
2103.01258 | Antoine Folacci | Antoine Folacci and Aditya Tamar | Quasinormal mode frequencies of Kerr black holes from Regge trajectories | null | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A large portion of the studies concerning the quasinormal mode frequencies of
a Kerr black hole have focused only on achieving higher numerical accuracy with
limited emphasis on providing their physical interpretation. In this article,
we partially address this issue by computing the quasinormal mode frequency
spectrum of a Kerr black hole using the theory of Regge poles. By considering
the retarded Green's function of the Teukolsky equation, we establish for
scalar, electromagnetic and gravitational perturbations an equation linking the
Regge poles to the quasinormal frequencies and we solve it in the
high-frequency regime to get "semiclassical" relations permitting us to obtain
the complex frequencies of the weakly damped quasinormal modes from the Regge
trajectories. Numerical results concerning gravitational perturbations ($s=-2$)
are displayed. They are in excellent agreement with the "exact" ones in the
eikonal regime $(\ell \gg 1)$ and in very good agreement even for lower values
of $\ell$. Moreover, the splitting of each Regge pole of the Schwarzschild
black hole into an infinite number of Kerr Regge poles explains the breaking of
the azimuthal degeneracy of the quasinormal frequencies of the Schwarzschild
black hole due to rotation. Our work is a first step to extend to Kerr black
holes the approach developed for static spherically symmetric black holes which
allowed, from a geometrical interpretation of the Regge poles in terms of the
properties of the unstable circular null geodesics lying on the photon sphere,
to derive accurate analytical formulas for the Regge trajectories and, as a
by-product, for the complex frequencies of the weakly damped quasinormal modes.
| [
{
"created": "Mon, 1 Mar 2021 19:11:12 GMT",
"version": "v1"
}
] | 2021-03-03 | [
[
"Folacci",
"Antoine",
""
],
[
"Tamar",
"Aditya",
""
]
] | A large portion of the studies concerning the quasinormal mode frequencies of a Kerr black hole have focused only on achieving higher numerical accuracy with limited emphasis on providing their physical interpretation. In this article, we partially address this issue by computing the quasinormal mode frequency spectrum of a Kerr black hole using the theory of Regge poles. By considering the retarded Green's function of the Teukolsky equation, we establish for scalar, electromagnetic and gravitational perturbations an equation linking the Regge poles to the quasinormal frequencies and we solve it in the high-frequency regime to get "semiclassical" relations permitting us to obtain the complex frequencies of the weakly damped quasinormal modes from the Regge trajectories. Numerical results concerning gravitational perturbations ($s=-2$) are displayed. They are in excellent agreement with the "exact" ones in the eikonal regime $(\ell \gg 1)$ and in very good agreement even for lower values of $\ell$. Moreover, the splitting of each Regge pole of the Schwarzschild black hole into an infinite number of Kerr Regge poles explains the breaking of the azimuthal degeneracy of the quasinormal frequencies of the Schwarzschild black hole due to rotation. Our work is a first step to extend to Kerr black holes the approach developed for static spherically symmetric black holes which allowed, from a geometrical interpretation of the Regge poles in terms of the properties of the unstable circular null geodesics lying on the photon sphere, to derive accurate analytical formulas for the Regge trajectories and, as a by-product, for the complex frequencies of the weakly damped quasinormal modes. |
gr-qc/0310060 | Albert V. Minkevich | A. V. Minkevich, A. S. Garkun, Yu. G. Vasilevski | Scalar fields superdense gravitating systems | 7 pages, Latex2e, report at XII Annual International Seminar
NPCS-2003, Minsk, 22--25 September, 2003 | Nonlin.Phenom.Complex Syst. 7 (2004) 78-84 | null | null | gr-qc | null | Solutions for scalar fields superdense gravitating systems of flat, open and
closed type obtained in the frame of gauge theories of gravitation are
discussed. Properties of these systems in dependence on parameter $\beta$ and
initial conditions are analyzed.
| [
{
"created": "Fri, 10 Oct 2003 19:27:44 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Minkevich",
"A. V.",
""
],
[
"Garkun",
"A. S.",
""
],
[
"Vasilevski",
"Yu. G.",
""
]
] | Solutions for scalar fields superdense gravitating systems of flat, open and closed type obtained in the frame of gauge theories of gravitation are discussed. Properties of these systems in dependence on parameter $\beta$ and initial conditions are analyzed. |
1504.07022 | Kirill Bronnikov | K.A. Bronnikov, O.B. Zaslavskii | Quasi-black holes: general features and purely field configurations | 6 revtex 2-column pages | Mod. Phys. Lett. A 30, No. 30, 1550154 (2015) | 10.1142/S0217732315501540 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Objects that are on the threshold of forming the horizon but never collapse
are called quasi-black holes (QBHs). We discuss the properties of the general
spherically symmetric QBH metric without addressing its material source,
including its limiting cases as the corresponding small parameter tends to
zero. We then show that QBHs can exist among self-gravitating configurations of
electromagnetic and dilatonic scalar fields without matter. These general
results are illustrated by explicit examples of exact solutions.
| [
{
"created": "Mon, 27 Apr 2015 10:54:40 GMT",
"version": "v1"
}
] | 2015-09-07 | [
[
"Bronnikov",
"K. A.",
""
],
[
"Zaslavskii",
"O. B.",
""
]
] | Objects that are on the threshold of forming the horizon but never collapse are called quasi-black holes (QBHs). We discuss the properties of the general spherically symmetric QBH metric without addressing its material source, including its limiting cases as the corresponding small parameter tends to zero. We then show that QBHs can exist among self-gravitating configurations of electromagnetic and dilatonic scalar fields without matter. These general results are illustrated by explicit examples of exact solutions. |
2209.01574 | Ruben Campos Delgado | Ruben Campos Delgado and Sergei V. Ketov | Schwarzschild-type black holes in Starobinsky-Bel-Robinson gravity | 10 pages; v3: one more reference added, final version accepted for
publication in Physics Letters B | Physics Letters B 838 (2023) 137690 | 10.1016/j.physletb.2023.137690 | IPMU22-0059 | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We study physical properties of a Schwarzschild-type black hole in the
framework of the recently proposed Starobinsky-Bel-Robinson (SBR) modified
theory of gravity, working perturbatively in the new coupling constant. In
particular, we compute the temperature, entropy, pressure and lifetime of a
Schwarzschild-type black hole.
| [
{
"created": "Sun, 4 Sep 2022 09:06:52 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Nov 2022 11:04:24 GMT",
"version": "v2"
},
{
"created": "Tue, 10 Jan 2023 11:33:32 GMT",
"version": "v3"
}
] | 2023-01-24 | [
[
"Delgado",
"Ruben Campos",
""
],
[
"Ketov",
"Sergei V.",
""
]
] | We study physical properties of a Schwarzschild-type black hole in the framework of the recently proposed Starobinsky-Bel-Robinson (SBR) modified theory of gravity, working perturbatively in the new coupling constant. In particular, we compute the temperature, entropy, pressure and lifetime of a Schwarzschild-type black hole. |
2201.00035 | Thanasis Karakasis | Thanasis Karakasis, Eleftherios Papantonopoulos, Zi-Yu Tang, Bin Wang | $(2+1)$-Dimensional Black Holes in $f(R,\phi)$ Gravity | Accepted for publication in PRD | Phys. Rev. D 105, 044038 (2022) | 10.1103/PhysRevD.105.044038 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We consider a $f(R)$ gravity theory in $(2+1)$-dimensions with a
self-interacting scalar field non-minimally coupled to gravity. Without
specifying the form of the $f(R)$ function, solving the field equations we find
that the Ricci scalar receives a non-linear correction term which breaks the
conformal invariance and leads to a massless black hole solution. When the
non-linear term decouples, we get a well known hairy black hole solution with
the scalar field conformally coupled to gravity. We also find that the entropy
of our black hole may be higher than the corresponding conformal black hole
which indicates that our solution may be thermodynamically preferred.
| [
{
"created": "Fri, 31 Dec 2021 19:29:37 GMT",
"version": "v1"
},
{
"created": "Wed, 2 Feb 2022 16:29:25 GMT",
"version": "v2"
}
] | 2022-02-18 | [
[
"Karakasis",
"Thanasis",
""
],
[
"Papantonopoulos",
"Eleftherios",
""
],
[
"Tang",
"Zi-Yu",
""
],
[
"Wang",
"Bin",
""
]
] | We consider a $f(R)$ gravity theory in $(2+1)$-dimensions with a self-interacting scalar field non-minimally coupled to gravity. Without specifying the form of the $f(R)$ function, solving the field equations we find that the Ricci scalar receives a non-linear correction term which breaks the conformal invariance and leads to a massless black hole solution. When the non-linear term decouples, we get a well known hairy black hole solution with the scalar field conformally coupled to gravity. We also find that the entropy of our black hole may be higher than the corresponding conformal black hole which indicates that our solution may be thermodynamically preferred. |
gr-qc/0212001 | Louapre | Laurent Freidel (ENS-Lyon, PI), David Louapre (ENS-Lyon) | Diffeomorphisms and spin foam models | 19 pages | Nucl.Phys. B662 (2003) 279-298 | 10.1016/S0550-3213(03)00306-7 | null | gr-qc hep-th | null | We study the action of diffeomorphisms on spin foam models. We prove that in
3 dimensions, there is a residual action of the diffeomorphisms that explains
the naive divergences of state sum models. We present the gauge fixing of this
symmetry and show that it explains the original renormalization of
Ponzano-Regge model. We discuss the implication this action of diffeomorphisms
has on higher dimensional spin foam models and especially the finite ones.
| [
{
"created": "Fri, 29 Nov 2002 23:38:40 GMT",
"version": "v1"
},
{
"created": "Wed, 29 Jan 2003 14:32:17 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Freidel",
"Laurent",
"",
"ENS-Lyon, PI"
],
[
"Louapre",
"David",
"",
"ENS-Lyon"
]
] | We study the action of diffeomorphisms on spin foam models. We prove that in 3 dimensions, there is a residual action of the diffeomorphisms that explains the naive divergences of state sum models. We present the gauge fixing of this symmetry and show that it explains the original renormalization of Ponzano-Regge model. We discuss the implication this action of diffeomorphisms has on higher dimensional spin foam models and especially the finite ones. |
gr-qc/0308063 | Marcelo J. Reboucas | B. Mota, M.J. Reboucas, R. Tavakol | Constraints on the Detectability of Cosmic Topology from Observational
Uncertainties | 16 pages, 1 figure, LaTeX2e | Class.Quant.Grav. 20 (2003) 4837-4850 | 10.1088/0264-9381/20/22/008 | null | gr-qc astro-ph hep-th | null | Recent observational results suggest that our universe is nearly flat and
well modelled within a $\Lambda$CDM framework. The observed values of
$\Omega_{m}$ and $\Omega_{\Lambda}$ inevitably involve uncertainties. Motivated
by this, we make a systematic study of the necessary and sufficient conditions
for undetectability as well as detectability (in principle) of cosmic topology
(using pattern repetition) in presence of such uncertainties. We do this by
developing two complementary methods to determine detectability for nearly flat
universes. Using the first method we derive analytical conditions for
undetectability for infinite redshift, the accuracy of which is then confirmed
by the second method. Estimates based on WMAP data together with other
measurements of the density parameters are used to illustrate both methods,
which are shown to provide very similar results for high redshifts.
| [
{
"created": "Tue, 19 Aug 2003 23:39:39 GMT",
"version": "v1"
},
{
"created": "Thu, 16 Oct 2003 01:57:38 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Mota",
"B.",
""
],
[
"Reboucas",
"M. J.",
""
],
[
"Tavakol",
"R.",
""
]
] | Recent observational results suggest that our universe is nearly flat and well modelled within a $\Lambda$CDM framework. The observed values of $\Omega_{m}$ and $\Omega_{\Lambda}$ inevitably involve uncertainties. Motivated by this, we make a systematic study of the necessary and sufficient conditions for undetectability as well as detectability (in principle) of cosmic topology (using pattern repetition) in presence of such uncertainties. We do this by developing two complementary methods to determine detectability for nearly flat universes. Using the first method we derive analytical conditions for undetectability for infinite redshift, the accuracy of which is then confirmed by the second method. Estimates based on WMAP data together with other measurements of the density parameters are used to illustrate both methods, which are shown to provide very similar results for high redshifts. |
1710.07267 | Orr Sela | Assaf Lanir, Adam Levi, Amos Ori and Orr Sela | Two-point function of a quantum scalar field in the interior region of a
Reissner-Nordstrom black hole | 14 pages, 1 figure; Minor modifications; Accepted for publication in
PRD | Phys. Rev. D 97, 024033 (2018) | 10.1103/PhysRevD.97.024033 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive explicit expressions for the two-point function of a massless
scalar field in the interior region of a Reissner-Nordstrom black hole, in both
the Unruh and Hartle-Hawking quantum states. The two-point function is
expressed in terms of the standard $lm\omega$ modes of the scalar field (those
associated with a spherical harmonic $Y_{lm}$ and a temporal mode $e^{-i\omega
t}$), which can be conveniently obtained by solving an ordinary differential
equation, the radial equation. These explicit expressions are the internal
analogs of the well known results in the external region (originally derived by
Christensen and Fulling), in which the two-point function outside the black
hole is written in terms of the external $lm\omega$ modes of the field. They
allow the computation of $<\Phi^{2}>_{ren}$ and the renormalized stress-energy
tensor inside the black hole, after the radial equation has been solved
(usually numerically). In the second part of the paper, we provide an explicit
expression for the trace of the renormalized stress-energy tensor of a
minimally-coupled massless scalar field (which is non-conformal), relating it
to the d'Alembertian of $<\Phi^{2}>_{ren}$. This expression proves itself
useful in various calculations of the renormalized stress-energy tensor.
| [
{
"created": "Thu, 19 Oct 2017 17:51:35 GMT",
"version": "v1"
},
{
"created": "Sun, 14 Jan 2018 12:42:50 GMT",
"version": "v2"
}
] | 2018-01-25 | [
[
"Lanir",
"Assaf",
""
],
[
"Levi",
"Adam",
""
],
[
"Ori",
"Amos",
""
],
[
"Sela",
"Orr",
""
]
] | We derive explicit expressions for the two-point function of a massless scalar field in the interior region of a Reissner-Nordstrom black hole, in both the Unruh and Hartle-Hawking quantum states. The two-point function is expressed in terms of the standard $lm\omega$ modes of the scalar field (those associated with a spherical harmonic $Y_{lm}$ and a temporal mode $e^{-i\omega t}$), which can be conveniently obtained by solving an ordinary differential equation, the radial equation. These explicit expressions are the internal analogs of the well known results in the external region (originally derived by Christensen and Fulling), in which the two-point function outside the black hole is written in terms of the external $lm\omega$ modes of the field. They allow the computation of $<\Phi^{2}>_{ren}$ and the renormalized stress-energy tensor inside the black hole, after the radial equation has been solved (usually numerically). In the second part of the paper, we provide an explicit expression for the trace of the renormalized stress-energy tensor of a minimally-coupled massless scalar field (which is non-conformal), relating it to the d'Alembertian of $<\Phi^{2}>_{ren}$. This expression proves itself useful in various calculations of the renormalized stress-energy tensor. |
1802.03293 | Ahmadjon Abdujabbarov | Bobur Turimov, Bobomurat Ahmedov, Ahmadjon Abdujabbarov, Cosimo Bambi | Gravitational lensing by magnetized compact object in the presence of
plasma | 21 pages, 8 figures | null | 10.1142/S0218271820400131 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the gravitational lensing in the weak field approximation assuming
the presence of a plasma and of a magnetic field around a compact gravitational
source. The external magnetic field causes the split of the image, as the
counterpart of the Zeeman effect. The magnetic field affects the magnification
of images, creating additional components. We also study the time delay of an
electromagnetic signal due to the geometry and the gravitational field around
the source. We show that the time delay strongly depends on the plasma
parameters. Lastly, we consider the effects of the presence of an inhomogeneous
plasma on the gravitational lensing.
| [
{
"created": "Thu, 8 Feb 2018 10:36:22 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Feb 2018 08:13:45 GMT",
"version": "v2"
}
] | 2020-02-19 | [
[
"Turimov",
"Bobur",
""
],
[
"Ahmedov",
"Bobomurat",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
],
[
"Bambi",
"Cosimo",
""
]
] | We study the gravitational lensing in the weak field approximation assuming the presence of a plasma and of a magnetic field around a compact gravitational source. The external magnetic field causes the split of the image, as the counterpart of the Zeeman effect. The magnetic field affects the magnification of images, creating additional components. We also study the time delay of an electromagnetic signal due to the geometry and the gravitational field around the source. We show that the time delay strongly depends on the plasma parameters. Lastly, we consider the effects of the presence of an inhomogeneous plasma on the gravitational lensing. |
2106.04393 | Robert John McLeod | Robert J. McLeod | A Brief Review Noether's Theorems and their Application to General
Relativity | null | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-sa/4.0/ | In this article, we will review Noether's Theorems and their application in
General Relativity. We will present Noether's Theorems in their original form
and restate them as they are usually applied to physics. Some basic equations
of Special Relativity will be reviewed and contrasted with the equations in
General Relativity. We will be most interested in the role of Noether's
Theorems in conservation laws. Several applications in flat spaces are
examined. A formulation of Noether's Theorems in curved space is presented. Of
particular interest is the conservation of energy in General Relativity. Here,
there is no general form for a conserved tensor, as there is in a flat space
case. Pseudotensor formulations can be found and two examples are given. In
special cases, one can formulate an equation for the conservation of energy.
The standard cosmology is an example.
| [
{
"created": "Sun, 6 Jun 2021 00:49:26 GMT",
"version": "v1"
}
] | 2021-06-09 | [
[
"McLeod",
"Robert J.",
""
]
] | In this article, we will review Noether's Theorems and their application in General Relativity. We will present Noether's Theorems in their original form and restate them as they are usually applied to physics. Some basic equations of Special Relativity will be reviewed and contrasted with the equations in General Relativity. We will be most interested in the role of Noether's Theorems in conservation laws. Several applications in flat spaces are examined. A formulation of Noether's Theorems in curved space is presented. Of particular interest is the conservation of energy in General Relativity. Here, there is no general form for a conserved tensor, as there is in a flat space case. Pseudotensor formulations can be found and two examples are given. In special cases, one can formulate an equation for the conservation of energy. The standard cosmology is an example. |
1909.07852 | Kenta Hioki | Kenta Hioki and Tomohiro Harada | Dynamical Transition from a Naked Singularity to a Black Hole | 10 pages, 13 figures, accepted for publication in International
Journal of Modern Physics A | null | 10.1142/S0217751X20502012 | RUP-19-25 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that a Reissner-Nordstr\"{o}m (RN) black hole can be formed by
dropping a charged thin dust shell onto a RN naked singularity. This is in
contrast to the fact that a RN naked singularity is prohibited from forming by
dropping a charged thin dust shell onto a RN black hole. This implies the
strong tendency of the RN singularity to be covered by a horizon in favour of
cosmic censorship. We show that an extreme RN black hole can also be formed
from a RN naked singularity by the same process in a finite advanced time. We
also discuss the evolution of the charged thin dust shells and the causal
structure of the resultant spacetimes.
| [
{
"created": "Tue, 17 Sep 2019 14:41:16 GMT",
"version": "v1"
},
{
"created": "Tue, 10 Mar 2020 14:36:20 GMT",
"version": "v2"
},
{
"created": "Mon, 17 Aug 2020 13:51:01 GMT",
"version": "v3"
},
{
"created": "Sun, 8 Nov 2020 04:28:55 GMT",
"version": "v4"
}
] | 2020-12-02 | [
[
"Hioki",
"Kenta",
""
],
[
"Harada",
"Tomohiro",
""
]
] | We show that a Reissner-Nordstr\"{o}m (RN) black hole can be formed by dropping a charged thin dust shell onto a RN naked singularity. This is in contrast to the fact that a RN naked singularity is prohibited from forming by dropping a charged thin dust shell onto a RN black hole. This implies the strong tendency of the RN singularity to be covered by a horizon in favour of cosmic censorship. We show that an extreme RN black hole can also be formed from a RN naked singularity by the same process in a finite advanced time. We also discuss the evolution of the charged thin dust shells and the causal structure of the resultant spacetimes. |
2102.00972 | Horst R. Beyer | Horst Reinhard Beyer, Miguel Alcubierre and Miguel Megevand | Stability study of a model for the Klein-Gordon equation in Kerr
space-time II | 33 pages, 4 figures | null | 10.1016/S0034-4877(21)00059-8 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The present paper is a follow-up of our previous paper that derives a
slightly simplified model equation for the Klein-Gordon equation, describing
the propagation of a scalar field of mass $\mu$ in the background of a rotating
black hole and, among others, supports the instability of the field down to
$a/M \approx 0.97$. The latter result was derived numerically. This paper gives
corresponding rigorous results, supporting instability of the field down to
$a/M \approx 0.979796$.
| [
{
"created": "Mon, 1 Feb 2021 16:55:21 GMT",
"version": "v1"
}
] | 2021-09-15 | [
[
"Beyer",
"Horst Reinhard",
""
],
[
"Alcubierre",
"Miguel",
""
],
[
"Megevand",
"Miguel",
""
]
] | The present paper is a follow-up of our previous paper that derives a slightly simplified model equation for the Klein-Gordon equation, describing the propagation of a scalar field of mass $\mu$ in the background of a rotating black hole and, among others, supports the instability of the field down to $a/M \approx 0.97$. The latter result was derived numerically. This paper gives corresponding rigorous results, supporting instability of the field down to $a/M \approx 0.979796$. |
gr-qc/9804062 | Jose Socorro Garcia Diaz | Jos\'e Socorro, Claus L\"ammerzahl, Alfredo Mac\'ias and Eckehard W.
Mielke | Multipole solutions in metric--affine gravity | 13 pages, Revtex, to appear in Phys. Lett. A | Phys.Lett. A244 (1998) 317-323 | 10.1016/S0375-9601(98)00360-0 | IFUG-98-05 | gr-qc | null | Above Planck energies, the spacetime might become non--Riemannian, as it is
known fron string theory and inflation. Then geometries arise in which
nonmetricity and torsion appear as field strengths, side by side with
curvature. By gauging the affine group, a metric affine gauge theory emerges as
dynamical framework. Here, by using the harmonic map ansatz, a new class of
multipole like solutions in the metric affine gravity theory (MAG) is obtained.
| [
{
"created": "Thu, 23 Apr 1998 23:18:04 GMT",
"version": "v1"
}
] | 2016-08-15 | [
[
"Socorro",
"José",
""
],
[
"Lämmerzahl",
"Claus",
""
],
[
"Macías",
"Alfredo",
""
],
[
"Mielke",
"Eckehard W.",
""
]
] | Above Planck energies, the spacetime might become non--Riemannian, as it is known fron string theory and inflation. Then geometries arise in which nonmetricity and torsion appear as field strengths, side by side with curvature. By gauging the affine group, a metric affine gauge theory emerges as dynamical framework. Here, by using the harmonic map ansatz, a new class of multipole like solutions in the metric affine gravity theory (MAG) is obtained. |
2010.13558 | Kyriakos Papadopoulos | Kyriakos Papadopoulos, Nazli Kurt | On Completeness of the Alexandrov Topology on a Spacetime: remarks and
some corrections | null | null | 10.1142/S0219887821501024 | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We clarify and discuss a misunderstanding between uniform completeness and
metric completeness, that has appeared in the literature in a study on the
Alexandrov topology for a spacetime.
| [
{
"created": "Fri, 23 Oct 2020 05:49:56 GMT",
"version": "v1"
},
{
"created": "Sat, 21 Nov 2020 12:31:11 GMT",
"version": "v2"
}
] | 2021-06-30 | [
[
"Papadopoulos",
"Kyriakos",
""
],
[
"Kurt",
"Nazli",
""
]
] | We clarify and discuss a misunderstanding between uniform completeness and metric completeness, that has appeared in the literature in a study on the Alexandrov topology for a spacetime. |
1808.01288 | B\'eatrice Bonga | B\'eatrice Bonga and Eric Poisson | Coulombic contribution to the flux of angular momentum in general
relativity | accepted for publication in PRD; major revision of previous version
(conclusion altered); 10 pages + 6 pages as appendix | Phys. Rev. D 99, 064024 (2019) | 10.1103/PhysRevD.99.064024 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The flux of angular momentum in electromagnetism cannot be expressed entirely
in terms of the field's radiative degrees of freedom. Its expression also
involves Coulombic pieces of the field, in the form of a charge aspect
$q(\theta,\phi)$, a function of polar angles whose integral gives the total
charge of the system. Guided by the strong analogy between radiative processes
in electromagnetism and gravitation, we ask whether the flux of angular
momentum in general relativity might also involve Coulombic pieces of the
gravitational field. Further, we ask whether such terms might have been missed
in the past by specializing the flux to sources of gravitational waves that are
at rest with respect to the frame in which the flux is evaluated. To answer
these questions we bring together the Landau-Lifshitz formulation of the
Einstein field equations, which provides specific definitions for angular
momentum and its associated flux, and the Bondi formalism, which provides a
systematic expansion of the metric of an asymptotically flat spacetime in
inverse powers of the distance away from the matter distribution. We obtain a
new expression for the flux of angular momentum, which is not restricted to
sources of gravitational waves at rest nor to periodic sources. We show that
our new expression is equivalent to the standard formula used in the literature
when these restrictions are put in place. We find that contrary to expectations
based on the analogy between electromagnetism and gravitation, the flux of
angular momentum in general relativity can be expressed entirely in terms of
the field's radiative degrees of freedom. In contrast to electromagnetism, no
Coulombic information is required to calculate the flux of angular momentum in
general relativity.
| [
{
"created": "Fri, 3 Aug 2018 18:00:29 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Mar 2019 14:16:15 GMT",
"version": "v2"
}
] | 2019-03-27 | [
[
"Bonga",
"Béatrice",
""
],
[
"Poisson",
"Eric",
""
]
] | The flux of angular momentum in electromagnetism cannot be expressed entirely in terms of the field's radiative degrees of freedom. Its expression also involves Coulombic pieces of the field, in the form of a charge aspect $q(\theta,\phi)$, a function of polar angles whose integral gives the total charge of the system. Guided by the strong analogy between radiative processes in electromagnetism and gravitation, we ask whether the flux of angular momentum in general relativity might also involve Coulombic pieces of the gravitational field. Further, we ask whether such terms might have been missed in the past by specializing the flux to sources of gravitational waves that are at rest with respect to the frame in which the flux is evaluated. To answer these questions we bring together the Landau-Lifshitz formulation of the Einstein field equations, which provides specific definitions for angular momentum and its associated flux, and the Bondi formalism, which provides a systematic expansion of the metric of an asymptotically flat spacetime in inverse powers of the distance away from the matter distribution. We obtain a new expression for the flux of angular momentum, which is not restricted to sources of gravitational waves at rest nor to periodic sources. We show that our new expression is equivalent to the standard formula used in the literature when these restrictions are put in place. We find that contrary to expectations based on the analogy between electromagnetism and gravitation, the flux of angular momentum in general relativity can be expressed entirely in terms of the field's radiative degrees of freedom. In contrast to electromagnetism, no Coulombic information is required to calculate the flux of angular momentum in general relativity. |
1302.5407 | Muhammad Sharif | M. Sharif and Rabia Saleem | Dark Energy Models and Laws of Thermodynamics in Bianchi I Model | 12 pages, 2 figures | Mod. Phys. Lett. A 27(2012)1250187 | 10.1142/S0217732312501878 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper is devoted to check validity of the laws of thermodynamics for LRS
Bianchi type I universe model which is filled with combination of dark matter
and dark energy. We take two types of dark energy models, i.e., generalized
holographic dark energy and generalized Ricci dark energy. It is proved that
the first and generalized second law of thermodynamics are valid on the
apparent horizon for both the models. Further, we take fixed radius $L$ of the
apparent horizon with original holographic or Ricci dark energy. We conclude
that the first and generalized second laws of thermodynamics do not hold on the
horizon of fixed radius $L$ for both the models.
| [
{
"created": "Wed, 20 Feb 2013 02:40:08 GMT",
"version": "v1"
}
] | 2015-06-15 | [
[
"Sharif",
"M.",
""
],
[
"Saleem",
"Rabia",
""
]
] | This paper is devoted to check validity of the laws of thermodynamics for LRS Bianchi type I universe model which is filled with combination of dark matter and dark energy. We take two types of dark energy models, i.e., generalized holographic dark energy and generalized Ricci dark energy. It is proved that the first and generalized second law of thermodynamics are valid on the apparent horizon for both the models. Further, we take fixed radius $L$ of the apparent horizon with original holographic or Ricci dark energy. We conclude that the first and generalized second laws of thermodynamics do not hold on the horizon of fixed radius $L$ for both the models. |
gr-qc/0404009 | Oleg Zaslavskii | O.B. Zaslavskii | Near-extremal and extremal quantum-corrected two-dimensional charged
black holes | 25 pages. Typos corrected. To appear in Class. Quant. Grav | Class.Quant.Grav. 21 (2004) 2687-2701 | 10.1088/0264-9381/21/11/012 | ESI - 1479 | gr-qc hep-th | null | We consider charged black holes within dilaton gravity with
exponential-linear dependence of action coefficients on dilaton and minimal
coupling to quantum scalar fields. This includes, in particular, CGHS and RST
black holes in the uncharged limit. For non-extremal configuration quantum
correction to the total mass, Hawking temperature, electric potential and
metric are found explicitly and shown to obey the first generalized law. We
also demonstrate that quantum-corrected extremal black holes in these theories
do exist and correspond to the classically forbidden region of parameters in
the sense that the total mass $M_{tot}<Q$ ($Q$ is a charge). We show that in
the limit $T_{H}\to 0$ (where $T_{H}$ is the Hawking temperature) the mass and
geometry of non-extremal configuration go smoothly to those of the extremal
one, except from the narrow near-horizon region. In the vicinity of the horizon
the quantum-corrected geometry (however small quantum the coupling parameter
$\kappa $ would be) of a non-extremal configuration tends to not the
quantum-corrected extremal one but to the special branch of solutions with the
constant dilaton (2D analog of the Bertotti-Robinson metric) instead.
Meanwhile, if $\kappa =0$ exactly, the near-extremal configuration tends to the
extremal one. We also consider the dilaton theory which corresponds classically
to the spherically-symmetrical reduction from 4D case and show that for the
quantum-corrected extremal black hole $M_{tot}>Q$.
| [
{
"created": "Thu, 1 Apr 2004 16:52:12 GMT",
"version": "v1"
},
{
"created": "Tue, 13 Apr 2004 19:27:19 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Zaslavskii",
"O. B.",
""
]
] | We consider charged black holes within dilaton gravity with exponential-linear dependence of action coefficients on dilaton and minimal coupling to quantum scalar fields. This includes, in particular, CGHS and RST black holes in the uncharged limit. For non-extremal configuration quantum correction to the total mass, Hawking temperature, electric potential and metric are found explicitly and shown to obey the first generalized law. We also demonstrate that quantum-corrected extremal black holes in these theories do exist and correspond to the classically forbidden region of parameters in the sense that the total mass $M_{tot}<Q$ ($Q$ is a charge). We show that in the limit $T_{H}\to 0$ (where $T_{H}$ is the Hawking temperature) the mass and geometry of non-extremal configuration go smoothly to those of the extremal one, except from the narrow near-horizon region. In the vicinity of the horizon the quantum-corrected geometry (however small quantum the coupling parameter $\kappa $ would be) of a non-extremal configuration tends to not the quantum-corrected extremal one but to the special branch of solutions with the constant dilaton (2D analog of the Bertotti-Robinson metric) instead. Meanwhile, if $\kappa =0$ exactly, the near-extremal configuration tends to the extremal one. We also consider the dilaton theory which corresponds classically to the spherically-symmetrical reduction from 4D case and show that for the quantum-corrected extremal black hole $M_{tot}>Q$. |
gr-qc/0506094 | Dilek Ciftci | M. Arik and D. Ciftci | Brane World Cosmology In Jordan-Brans-Dicke Theory | 11 pages | Gen.Rel.Grav. 37 (2005) 2211-2221 | 10.1007/s10714-005-0201-1 | null | gr-qc | null | We consider the embedding of 3+1 dimensional cosmology in 4+1 dimensional
Jordan-Brans-Dicke theory. We show that exponentially growing and power law
scale factors are implied. Whereas the 4+1 dimensional scalar field is
approximately constant for each, the effective 3+1 dimensional scalar field is
constant for exponentially growing scale factor and time dependent for power
law scale factor.
| [
{
"created": "Fri, 17 Jun 2005 12:43:11 GMT",
"version": "v1"
}
] | 2009-11-11 | [
[
"Arik",
"M.",
""
],
[
"Ciftci",
"D.",
""
]
] | We consider the embedding of 3+1 dimensional cosmology in 4+1 dimensional Jordan-Brans-Dicke theory. We show that exponentially growing and power law scale factors are implied. Whereas the 4+1 dimensional scalar field is approximately constant for each, the effective 3+1 dimensional scalar field is constant for exponentially growing scale factor and time dependent for power law scale factor. |
1106.2831 | John Ward | Narit Pidokrajt, John Ward | Thermodynamic Geometry and Type 0A Black Holes | 13 pages, 2 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this note we study thermodynamic geometry of the type 0A black hole
solution in string theory using a variety of different methods (Ruppeiner,
Weinhold and Geometrothermodynamics). Our results indicate that the curvature
invariants are finite for all physical solutions, suggesting that there is no
phase transition. It is also found that the cutoff of the entropy, which is the
singular limit of the theory, appears geometrically in the Weinhold picture as
the thermodynamic cone itself.
| [
{
"created": "Tue, 14 Jun 2011 22:04:11 GMT",
"version": "v1"
}
] | 2011-06-16 | [
[
"Pidokrajt",
"Narit",
""
],
[
"Ward",
"John",
""
]
] | In this note we study thermodynamic geometry of the type 0A black hole solution in string theory using a variety of different methods (Ruppeiner, Weinhold and Geometrothermodynamics). Our results indicate that the curvature invariants are finite for all physical solutions, suggesting that there is no phase transition. It is also found that the cutoff of the entropy, which is the singular limit of the theory, appears geometrically in the Weinhold picture as the thermodynamic cone itself. |
1901.00167 | Supriya Pan | Jaume Haro, Jaume Amor\'os and Supriya Pan | The Peebles -- Vilenkin quintessential inflation model revisited | 28 pages; 7 captioned figures; version published in The European
Physical Journal C | Eur.Phys.J. C79 (2019) no.6, 505 | 10.1140/epjc/s10052-019-7012-0 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review the well-known Peebles-Vilenkin (PV) quintessential inflation model
and discuss its possible improvements in agreement with the recent
observations. The improved PV model depends only on two parameters: the
inflaton mass $m$, and another smaller mass $M$; where the latter has to be
chosen in order to undertake that, at present time, the dark energy density of
the universe is approximately about 70\% of the total energy budget of the
universe. The value of the inflaton mass $m$ is calculated using the
observational value of the power spectrum of the scalar perturbations, and the
value of mass $M$, which depends on the reheating temperature, is calculated by
solving the corresponding dynamical system whose initial conditions are taken
at the matter-radiation equality and are obtained from three observational
data: the red shift at the matter-radiation equality, the ratio of the matter
energy density to the critical one at the present time and the current value of
the Hubble parameter.
| [
{
"created": "Tue, 1 Jan 2019 15:34:12 GMT",
"version": "v1"
},
{
"created": "Sun, 2 Jun 2019 19:06:58 GMT",
"version": "v2"
},
{
"created": "Wed, 26 Jun 2019 16:23:30 GMT",
"version": "v3"
}
] | 2019-06-27 | [
[
"Haro",
"Jaume",
""
],
[
"Amorós",
"Jaume",
""
],
[
"Pan",
"Supriya",
""
]
] | We review the well-known Peebles-Vilenkin (PV) quintessential inflation model and discuss its possible improvements in agreement with the recent observations. The improved PV model depends only on two parameters: the inflaton mass $m$, and another smaller mass $M$; where the latter has to be chosen in order to undertake that, at present time, the dark energy density of the universe is approximately about 70\% of the total energy budget of the universe. The value of the inflaton mass $m$ is calculated using the observational value of the power spectrum of the scalar perturbations, and the value of mass $M$, which depends on the reheating temperature, is calculated by solving the corresponding dynamical system whose initial conditions are taken at the matter-radiation equality and are obtained from three observational data: the red shift at the matter-radiation equality, the ratio of the matter energy density to the critical one at the present time and the current value of the Hubble parameter. |
2108.07210 | Masoud Ghezelbash | Masoud Ghezelbash | Bianchi IX geometry and the Einstein-Maxwell theory | 38 pages, 16 figures, new contents, figures and four appendices
added, references added, to appear in classical and quantum gravity | Class. Quantum Grav. 39 (2022) 075012 | 10.1088/1361-6382/ac504e | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct numerical solutions to the higher-dimensional Einstein-Maxwell
theory. The solutions are based on embedding the four dimensional Bianchi type
IX space in the theory. We find the solutions as superposition of two
functions, which one of them can be found numerically. We show that the
solutions in any dimensions, are almost regular everywhere, except a singular
point. We find that the solutions interpolate between the two exact analytical
solutions to the higher dimensional Einstein-Maxwell theory, which are based on
Eguchi-Hanson type I and II geometries. Moreover, we construct the exact
cosmological solutions to the theory, and study the properties of the
solutions.
| [
{
"created": "Mon, 16 Aug 2021 16:37:53 GMT",
"version": "v1"
},
{
"created": "Sun, 6 Feb 2022 18:05:04 GMT",
"version": "v2"
}
] | 2022-04-14 | [
[
"Ghezelbash",
"Masoud",
""
]
] | We construct numerical solutions to the higher-dimensional Einstein-Maxwell theory. The solutions are based on embedding the four dimensional Bianchi type IX space in the theory. We find the solutions as superposition of two functions, which one of them can be found numerically. We show that the solutions in any dimensions, are almost regular everywhere, except a singular point. We find that the solutions interpolate between the two exact analytical solutions to the higher dimensional Einstein-Maxwell theory, which are based on Eguchi-Hanson type I and II geometries. Moreover, we construct the exact cosmological solutions to the theory, and study the properties of the solutions. |
gr-qc/0202006 | Harold Blas | A. Accioly, H. Blas and H. Mukai | Nonminimal coupling, equivalence principle and exact Foldy-Wouthuysen
transformation | 9 pages, LaTex | null | null | null | gr-qc | null | It is shown that the exact Foldy-Wouthuysen transformation for spin-0
particles on spacetimes described by the metrics $ds^2 = V^2 dt^2 - W^2 d
{\bf{x}}^2$, where $V=V({\bf{x}})$ and $W=W({\bf{x}})$, only exists if the
scalar field is nonminimally coupled to the Ricci scalar field with a coupling
constant equal to 1/6. The nonminimal coupling term, in turn, does not violate
the equivalence principle. As an application we obtain the nonrelativistic
Foldy-Wouthuysen Hamiltonian concerning the general solution to the linearized
field equations of higher-derivative gravity for a static pointlike source in
the Teyssandier gauge.
| [
{
"created": "Sat, 2 Feb 2002 18:48:44 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Accioly",
"A.",
""
],
[
"Blas",
"H.",
""
],
[
"Mukai",
"H.",
""
]
] | It is shown that the exact Foldy-Wouthuysen transformation for spin-0 particles on spacetimes described by the metrics $ds^2 = V^2 dt^2 - W^2 d {\bf{x}}^2$, where $V=V({\bf{x}})$ and $W=W({\bf{x}})$, only exists if the scalar field is nonminimally coupled to the Ricci scalar field with a coupling constant equal to 1/6. The nonminimal coupling term, in turn, does not violate the equivalence principle. As an application we obtain the nonrelativistic Foldy-Wouthuysen Hamiltonian concerning the general solution to the linearized field equations of higher-derivative gravity for a static pointlike source in the Teyssandier gauge. |
gr-qc/9408008 | null | J. Schirmer | Hamiltonian reduction of Bianchi Cosmologies | 14 pages, Latex, Freiburg preprint THEP 94/21 | Class.Quant.Grav.12:1099-1110,1995 | 10.1088/0264-9381/12/4/017 | null | gr-qc | null | It was noted recently that the ADM-diffeomorphism-constraint does not
generate all observed symmetries for several Bianchi-models. We will suggest
not to use the ADM-constraint restricted to homogeneous variables, but some
equivalent which is derived from a restricted action principle. This will
generate all homogeneity preserving diffeomorphisms, which will be shown to be
automorphism generating vector fields, in class A and class B models. Following
Dirac's constraint formalism one will naturally be restricted to the unimodular
part of the automorphism group.
| [
{
"created": "Thu, 4 Aug 1994 22:00:31 GMT",
"version": "v1"
}
] | 2010-04-06 | [
[
"Schirmer",
"J.",
""
]
] | It was noted recently that the ADM-diffeomorphism-constraint does not generate all observed symmetries for several Bianchi-models. We will suggest not to use the ADM-constraint restricted to homogeneous variables, but some equivalent which is derived from a restricted action principle. This will generate all homogeneity preserving diffeomorphisms, which will be shown to be automorphism generating vector fields, in class A and class B models. Following Dirac's constraint formalism one will naturally be restricted to the unimodular part of the automorphism group. |
0711.1584 | Mikhail V. Gorbatenko | Mikhail V.Gorbatenko | Conformal Geometrodynamics: Exact Nonstationary Spherically Symmetric
Solutions | 13 pages | null | null | null | gr-qc | null | A nonstationary spherically symmetric problem for conformal geometrodynamics
equations is considered and general exact solutions in quadratures are
obtained. Involvement of Weyl degrees of freedom allows us to consider the
problem with arbitrary initial data, as for the conformal geometrodynamics
equations the Cauchy problem is set up without connections to initial data. The
results of this paper are not confined with the framework of the perturbation
theory and open up new avenues for study of the process of space-time
singularity evolution in time.
| [
{
"created": "Sat, 10 Nov 2007 10:29:12 GMT",
"version": "v1"
}
] | 2007-11-13 | [
[
"Gorbatenko",
"Mikhail V.",
""
]
] | A nonstationary spherically symmetric problem for conformal geometrodynamics equations is considered and general exact solutions in quadratures are obtained. Involvement of Weyl degrees of freedom allows us to consider the problem with arbitrary initial data, as for the conformal geometrodynamics equations the Cauchy problem is set up without connections to initial data. The results of this paper are not confined with the framework of the perturbation theory and open up new avenues for study of the process of space-time singularity evolution in time. |
2310.17311 | Suddhasattwa Brahma | Suddhasattwa Brahma and Abhinove Nagarajan Seenivasan | Gravity-induced entanglement as a probe of spacetime curvature | Honorable Mention in the 2023 Essay Competition of the Gravity
Research Foundation; comments welcome | null | 10.1142/S0218271823420208 | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | It is now widely believed that if the gravitational field is (perturbatively)
quantum, it would entangle two massive objects (in spatial superpositions)
which were otherwise unentangled to begin with. Recently, actual table-top
experiments have been proposed to test this idea in what would be the first
detection of perturbative quantum gravity. In this essay, we devise a thought
experiment to prove that such gravity-induced entanglement depends on the
spacetime curvature and can, in principle, act as an alternate signature of the
expanding background. This will open up new and complementary directions to
search for such entanglement in curved spacetime and reveal fresh perspectives
on it.
| [
{
"created": "Thu, 26 Oct 2023 11:16:35 GMT",
"version": "v1"
}
] | 2023-10-27 | [
[
"Brahma",
"Suddhasattwa",
""
],
[
"Seenivasan",
"Abhinove Nagarajan",
""
]
] | It is now widely believed that if the gravitational field is (perturbatively) quantum, it would entangle two massive objects (in spatial superpositions) which were otherwise unentangled to begin with. Recently, actual table-top experiments have been proposed to test this idea in what would be the first detection of perturbative quantum gravity. In this essay, we devise a thought experiment to prove that such gravity-induced entanglement depends on the spacetime curvature and can, in principle, act as an alternate signature of the expanding background. This will open up new and complementary directions to search for such entanglement in curved spacetime and reveal fresh perspectives on it. |
gr-qc/0608078 | Roland Triay | Roland Triay (CPT), Henri-Hugues Fliche (LMMT) | Spherical Voids in Newton-Friedmann Universe | to appear | Proceedings of the Eleventh Marcel Grossmann Meeting on General
Relativity, Allemagne (2007) | null | null | gr-qc astro-ph | null | We show that the cosmological constant favours significantly the growth of
voids in the universe. This dynamical effect is investigated within a newtonian
approach with an extension to Friedmann-Lema\^{\i}tre model.
| [
{
"created": "Wed, 16 Aug 2006 15:40:40 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Triay",
"Roland",
"",
"CPT"
],
[
"Fliche",
"Henri-Hugues",
"",
"LMMT"
]
] | We show that the cosmological constant favours significantly the growth of voids in the universe. This dynamical effect is investigated within a newtonian approach with an extension to Friedmann-Lema\^{\i}tre model. |
2206.13672 | Matheus Filipe Santos Alves | Matheus F. S. Alves, Lu\'is F. M. A. M. Reis, L. G. Medeiros | Gravitational waves from inspiraling black holes in quadratic gravity | 19 pages, 9 figures | Phys. Rev. D 107, 044017 (2023) | 10.1103/PhysRevD.107.044017 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We peform a study of gravitational waves emitted by inspiraling black holes
in the context of quadratic gravity. By linearizing the field equations around
a flat background, we demonstrate that all degrees of freedom satisfy wave-like
equations. These degrees of freedom split into three modes: a massive spin-$2$
mode, a massive spin-$0$ mode, and the expected massless spin-$2$ mode. We
construct the energy-momentum tensor of gravitational waves and show that, due
to the massive spin-$2$ mode, it presents the Ostrogradski instability. We also
show how to deal with this possible pathology and obtain consistent physical
interpretations for the system. Using the energy-momentum tensor, we study the
influence of each massive mode in the orbital dynamics and compare it with the
standard result of General Relativity. Moreover, we present two methods to
constrain the parameter $\alpha$ associated with the massive spin-$2$
contribution. From the first method, using the combined waveform for the
spin-$2$ modes, we obtain the constraint $ \alpha \lesssim 1.1 \times 10^{21}
m^{2}$. In the second method, using the coalescence time, we get the constraint
$ \alpha \lesssim 1.1 \times 10^{13} m^{2}$.
| [
{
"created": "Tue, 28 Jun 2022 00:23:14 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Feb 2023 23:03:01 GMT",
"version": "v2"
}
] | 2023-02-13 | [
[
"Alves",
"Matheus F. S.",
""
],
[
"Reis",
"Luís F. M. A. M.",
""
],
[
"Medeiros",
"L. G.",
""
]
] | We peform a study of gravitational waves emitted by inspiraling black holes in the context of quadratic gravity. By linearizing the field equations around a flat background, we demonstrate that all degrees of freedom satisfy wave-like equations. These degrees of freedom split into three modes: a massive spin-$2$ mode, a massive spin-$0$ mode, and the expected massless spin-$2$ mode. We construct the energy-momentum tensor of gravitational waves and show that, due to the massive spin-$2$ mode, it presents the Ostrogradski instability. We also show how to deal with this possible pathology and obtain consistent physical interpretations for the system. Using the energy-momentum tensor, we study the influence of each massive mode in the orbital dynamics and compare it with the standard result of General Relativity. Moreover, we present two methods to constrain the parameter $\alpha$ associated with the massive spin-$2$ contribution. From the first method, using the combined waveform for the spin-$2$ modes, we obtain the constraint $ \alpha \lesssim 1.1 \times 10^{21} m^{2}$. In the second method, using the coalescence time, we get the constraint $ \alpha \lesssim 1.1 \times 10^{13} m^{2}$. |
1202.5157 | W{\l}odzimierz Natorf | W{\l}odzimierz Natorf | Asymptotic stability of vacuum type II metrics | some typos removed in v2 | J. Math. Phys. 53, 022503 (2012); | 10.1063/1.3682273 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We generalize the result of Lukacs {\it et al.} on asymptotic stability of
the Schwarzschild metric with respect to perturbations in the Robinson-Trautman
class of metrics to the case of Petrov type II twisting metrics, uder the
condition of asymptotic flatness at future null infinity. The Bondi energy is
used as the Lyapunov functional and we prove that the "final state" of such
metrics is the Kerr metric.
| [
{
"created": "Thu, 23 Feb 2012 12:22:32 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Apr 2012 10:27:45 GMT",
"version": "v2"
}
] | 2012-04-13 | [
[
"Natorf",
"Włodzimierz",
""
]
] | We generalize the result of Lukacs {\it et al.} on asymptotic stability of the Schwarzschild metric with respect to perturbations in the Robinson-Trautman class of metrics to the case of Petrov type II twisting metrics, uder the condition of asymptotic flatness at future null infinity. The Bondi energy is used as the Lyapunov functional and we prove that the "final state" of such metrics is the Kerr metric. |
2401.07662 | Charis Anastopoulos | Charis Anastopoulos | Final States in Quantum Cosmology: Cosmic Acceleration as a Quantum
Post-Selection Effect | 33 pages, 5 figures. Greatly extended and restructured; it now
contains a derivation of post-selected quasi-classical equations of motion
for generic systems, and more examples | null | null | null | gr-qc astro-ph.CO quant-ph | http://creativecommons.org/licenses/by/4.0/ | Standard quantum theory admits naturally statistical ensembles that are both
pre-selected and post-selected, i.e., they involve both an initial and a final
state. We argue that there is no compelling physical reason to preclude a
probability assignment with a final quantum state at the cosmological level. We
therefore analyze the implications of a final state in the probability
assignment for quantum cosmology. To this end, we derive effective classical
equations of motion for systems subject to both initial and final conditions.
Remarkably, these effective equations do not depend on the details of the
quantum theory, but only on the geometric features of the classical state
space. When applied to Friedman-Robertson-Walker cosmological models, these
effective equations generically describe cosmic acceleration in the absence of
a cosmological constant, dark energy, or modified gravitational dynamics.
Therefore, cosmic acceleration emerges as a quantum post-selection effect, that
is, a macroscopic quantum phenomenon.
| [
{
"created": "Mon, 15 Jan 2024 13:05:28 GMT",
"version": "v1"
},
{
"created": "Sun, 28 Jul 2024 10:54:17 GMT",
"version": "v2"
}
] | 2024-07-30 | [
[
"Anastopoulos",
"Charis",
""
]
] | Standard quantum theory admits naturally statistical ensembles that are both pre-selected and post-selected, i.e., they involve both an initial and a final state. We argue that there is no compelling physical reason to preclude a probability assignment with a final quantum state at the cosmological level. We therefore analyze the implications of a final state in the probability assignment for quantum cosmology. To this end, we derive effective classical equations of motion for systems subject to both initial and final conditions. Remarkably, these effective equations do not depend on the details of the quantum theory, but only on the geometric features of the classical state space. When applied to Friedman-Robertson-Walker cosmological models, these effective equations generically describe cosmic acceleration in the absence of a cosmological constant, dark energy, or modified gravitational dynamics. Therefore, cosmic acceleration emerges as a quantum post-selection effect, that is, a macroscopic quantum phenomenon. |
1811.08852 | Isaac Torres | Isaac Torres, J\'ulio C\'esar Fabris, and Oliver Fabio Piattella | Classical and quantum cosmology of Fab Four John theories | null | Physics Letters B 798 (2019) 135003 | 10.1016/j.physletb.2019.135003 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We present here a quantum cosmological model with Bohm-de Broglie
interpretation of the theory described by a combination of two terms of the Fab
Four cosmological theory. The first term is the John Lagrangian and the second
is a potential representing matter content to avoid classical trivial
solutions. This model has two free functions that provide an adjustment
mechanism known classically as self-tuning. The self-tuning is a way to address
the cosmological constant problem by allowing a partial break of symmetry in
the scalar field sector. The Fab Four is the most general set of self-tuning
scalar-tensor gravitational theories in four dimensions. The minisuperspace
Hamiltonian thus obtained from this combination of Fab Four terms has
fractional powers in the momenta, leading to a problem in applying canonical
quantization. We have solved this problem by generalizing the canonical
quantization rule using the so-called conformable fractional derivative. We
show that this analysis leads to both singular and bouncing (non-singular)
solutions, depending on the initial conditions over the scale factor and the
homogeneous scalar field, and also depending on the free functions mentioned.
This provides an adjustment mechanism in analogy with the classical self-tuning
of the Fab Four, but with another interpretation.
| [
{
"created": "Wed, 21 Nov 2018 17:57:06 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Nov 2018 22:03:33 GMT",
"version": "v2"
},
{
"created": "Fri, 11 Oct 2019 21:34:53 GMT",
"version": "v3"
}
] | 2019-10-15 | [
[
"Torres",
"Isaac",
""
],
[
"Fabris",
"Júlio César",
""
],
[
"Piattella",
"Oliver Fabio",
""
]
] | We present here a quantum cosmological model with Bohm-de Broglie interpretation of the theory described by a combination of two terms of the Fab Four cosmological theory. The first term is the John Lagrangian and the second is a potential representing matter content to avoid classical trivial solutions. This model has two free functions that provide an adjustment mechanism known classically as self-tuning. The self-tuning is a way to address the cosmological constant problem by allowing a partial break of symmetry in the scalar field sector. The Fab Four is the most general set of self-tuning scalar-tensor gravitational theories in four dimensions. The minisuperspace Hamiltonian thus obtained from this combination of Fab Four terms has fractional powers in the momenta, leading to a problem in applying canonical quantization. We have solved this problem by generalizing the canonical quantization rule using the so-called conformable fractional derivative. We show that this analysis leads to both singular and bouncing (non-singular) solutions, depending on the initial conditions over the scale factor and the homogeneous scalar field, and also depending on the free functions mentioned. This provides an adjustment mechanism in analogy with the classical self-tuning of the Fab Four, but with another interpretation. |
1606.07041 | Pierre-Henri Chavanis | Pierre-Henri Chavanis and Tonatiuh Matos | Covariant theory of Bose-Einstein condensates in curved spacetimes with
electromagnetic interactions: the hydrodynamic approach | null | Eur. Phys. J. Plus, 132, 30 (2017) | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop a hydrodynamic representation of the Klein-Gordon-Maxwell-Einstein
equations. These equations combine quantum mechanics, electromagnetism, and
general relativity. We consider the case of an arbitrary curved spacetime, the
case of weak gravitational fields in a static or expanding background, and the
nonrelativistic (Newtonian) limit. The Klein-Gordon-Maxwell-Einstein equations
govern the evolution of a complex scalar field, possibly describing
self-gravitating Bose-Einstein condensates, coupled to an electromagnetic
field. They may find applications in the context of dark matter, boson stars,
and neutron stars with a superfluid core.
| [
{
"created": "Wed, 22 Jun 2016 18:56:54 GMT",
"version": "v1"
}
] | 2017-11-27 | [
[
"Chavanis",
"Pierre-Henri",
""
],
[
"Matos",
"Tonatiuh",
""
]
] | We develop a hydrodynamic representation of the Klein-Gordon-Maxwell-Einstein equations. These equations combine quantum mechanics, electromagnetism, and general relativity. We consider the case of an arbitrary curved spacetime, the case of weak gravitational fields in a static or expanding background, and the nonrelativistic (Newtonian) limit. The Klein-Gordon-Maxwell-Einstein equations govern the evolution of a complex scalar field, possibly describing self-gravitating Bose-Einstein condensates, coupled to an electromagnetic field. They may find applications in the context of dark matter, boson stars, and neutron stars with a superfluid core. |
gr-qc/9805017 | Fodor Gyula | G. Fodor, M. Marklund, and Z. Perj\'es | Axistationary perfect fluids -- a tetrad approach | 12 pages | Class.Quant.Grav. 16 (1999) 453-463 | 10.1088/0264-9381/16/2/010 | null | gr-qc | null | Stationary axisymmetric perfect fluid space-times are investigated using the
curvature description of geometries. Attention is focused on space-times with a
vanishing electric part of the Weyl tensor. It is shown that the only
incompressible axistationary magnetic perfect fluid is the interior
Schwarzschild solution. The existence of a rigidly rotating perfect fluid,
generalizing the interior Schwarzschild metric is proven. Theorems are stated
on Petrov types and electric/magnetic Weyl tensors.
| [
{
"created": "Wed, 6 May 1998 13:18:56 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Fodor",
"G.",
""
],
[
"Marklund",
"M.",
""
],
[
"Perjés",
"Z.",
""
]
] | Stationary axisymmetric perfect fluid space-times are investigated using the curvature description of geometries. Attention is focused on space-times with a vanishing electric part of the Weyl tensor. It is shown that the only incompressible axistationary magnetic perfect fluid is the interior Schwarzschild solution. The existence of a rigidly rotating perfect fluid, generalizing the interior Schwarzschild metric is proven. Theorems are stated on Petrov types and electric/magnetic Weyl tensors. |
2002.06059 | Roger Hurtado PhD | Roger A. Hurtado and Jose R. Arenas | Spherically symmetric and static solutions in $f(R)$ gravity coupled
with EM fields | 14 pages, 2 figures | Phys. Rev. D 102, 104019 (2020) | 10.1103/PhysRevD.102.104019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Solutions of field equations in $f(R)$ gravity are found for a spherically
symmetric and static spacetime in the Born-Infeld (BI) non-linear
electrodynamics. It is found that the models supported in this configuration
must have the parametric form $f'(R)|_{r}=m+n r$, with $m,n$ constants, whose
value and sign have a strong impact on the solutions, as well as in the form
and range of $f(R)$. When $n=0$, $f(R)=m R+m_0$ and the Einstein-BI solution is
found. When $m\neq 0$ and $n\neq0$, $f(R)$ is asymptotically equivalent to GR
and the Schwarzschild and $f(R)$-Reissner-Nordstr\"om solutions are written in
some limits, likewise if $n>0$ and $r\gg1$, $f(R)$ can be found as a series
approximation and as a particular case, when $R_S=-\frac{m^2}{3n}$, explicitly
$f(R)=m R+2n\sqrt{R}+m_0$. Finally, the solutions, scalar curvature and
parametric function $f(r)$ in the non-linear ($m=0$) regime of $f(R)$ are
found, and some models for specific values of $m$ and $n$ are plotted.
| [
{
"created": "Fri, 14 Feb 2020 14:46:39 GMT",
"version": "v1"
}
] | 2020-11-18 | [
[
"Hurtado",
"Roger A.",
""
],
[
"Arenas",
"Jose R.",
""
]
] | Solutions of field equations in $f(R)$ gravity are found for a spherically symmetric and static spacetime in the Born-Infeld (BI) non-linear electrodynamics. It is found that the models supported in this configuration must have the parametric form $f'(R)|_{r}=m+n r$, with $m,n$ constants, whose value and sign have a strong impact on the solutions, as well as in the form and range of $f(R)$. When $n=0$, $f(R)=m R+m_0$ and the Einstein-BI solution is found. When $m\neq 0$ and $n\neq0$, $f(R)$ is asymptotically equivalent to GR and the Schwarzschild and $f(R)$-Reissner-Nordstr\"om solutions are written in some limits, likewise if $n>0$ and $r\gg1$, $f(R)$ can be found as a series approximation and as a particular case, when $R_S=-\frac{m^2}{3n}$, explicitly $f(R)=m R+2n\sqrt{R}+m_0$. Finally, the solutions, scalar curvature and parametric function $f(r)$ in the non-linear ($m=0$) regime of $f(R)$ are found, and some models for specific values of $m$ and $n$ are plotted. |
1707.02216 | Yi-Shi Duan | Yi-Shi Duan | Generalized Nonsingular Solutions for the Scalar Meson Field of a Point
Charge in General Relativity Theory | 2 pages | Soviet Physics JETP Vol 31, 1098-1099 (1956) | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been shown that in investigating the electromagnetic and meson fields
of elementary particles, the effects of gravitational interaction cannot be
neglected. The present note is an attempt to find solutions to the equations of
the general relativistic gravitational and scalar meson fields of a point
nuclear charge. The solution is nonsingular at all points of the gravitational
and meson fields. Although it contains several functions whose form is not
given, this solution can be used to obtain the potential of the scalar meson
field, which is a generalization of the Yukawa potential; furthermore, it makes
it possible to calculate the mass and self-energy of the nucleon, which turn
out to be finite.
| [
{
"created": "Wed, 24 May 2017 03:39:38 GMT",
"version": "v1"
}
] | 2017-07-10 | [
[
"Duan",
"Yi-Shi",
""
]
] | It has been shown that in investigating the electromagnetic and meson fields of elementary particles, the effects of gravitational interaction cannot be neglected. The present note is an attempt to find solutions to the equations of the general relativistic gravitational and scalar meson fields of a point nuclear charge. The solution is nonsingular at all points of the gravitational and meson fields. Although it contains several functions whose form is not given, this solution can be used to obtain the potential of the scalar meson field, which is a generalization of the Yukawa potential; furthermore, it makes it possible to calculate the mass and self-energy of the nucleon, which turn out to be finite. |
gr-qc/9906070 | Piotr Bizon | P. Bizo\'n and T. Chmaj | Remark on formation of colored black holes via fine tuning | 2 pages, RevTex, 2 postscript figures | Phys.Rev. D61 (2000) 067501 | 10.1103/PhysRevD.61.067501 | null | gr-qc | null | In a recent paper (gr-qc/9903081) Choptuik, Hirschmann, and Marsa have
discovered the scaling law for the lifetime of an intermediate attractor in the
formation of n=1 colored black holes via fine tuning. We show that their result
is in agreement with the prediction of linear perturbation analysis. We also
briefly comment on the dependence of the mass gap across the threshold on the
radius of the event horizon.
| [
{
"created": "Thu, 17 Jun 1999 06:26:58 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Bizoń",
"P.",
""
],
[
"Chmaj",
"T.",
""
]
] | In a recent paper (gr-qc/9903081) Choptuik, Hirschmann, and Marsa have discovered the scaling law for the lifetime of an intermediate attractor in the formation of n=1 colored black holes via fine tuning. We show that their result is in agreement with the prediction of linear perturbation analysis. We also briefly comment on the dependence of the mass gap across the threshold on the radius of the event horizon. |
gr-qc/0103044 | John Baez | John C. Baez and Emory F. Bunn | The Meaning of Einstein's Equation | 23 pages LaTeX, 8 encapsulated Postscript figures; unlike the
published version this includes a derivation of the inverse-square force law | Amer. Jour. Phys. 73 (2005), 644-652 | 10.1119/1.1852541 | null | gr-qc astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is a brief introduction to general relativity, designed for both
students and teachers of the subject. While there are many excellent
expositions of general relativity, few adequately explain the geometrical
meaning of the basic equation of the theory: Einstein's equation. Here we give
a simple formulation of this equation in terms of the motion of freely falling
test particles. We also sketch some of its consequences, and explain how the
formulation given here is equivalent to the usual one in terms of tensors.
Finally, we include an annotated bibliography of books, articles and websites
suitable for the student of relativity.
| [
{
"created": "Tue, 13 Mar 2001 22:38:05 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Apr 2001 01:30:30 GMT",
"version": "v2"
},
{
"created": "Wed, 18 Aug 2004 17:39:22 GMT",
"version": "v3"
},
{
"created": "Thu, 5 Jan 2006 18:23:17 GMT",
"version": "v4"
},
{
"created": "Thu, 5 Jan 2006 21:09:33 GMT",
"version": "v5"
},
{
"created": "Fri, 12 Jun 2015 07:27:23 GMT",
"version": "v6"
}
] | 2015-06-15 | [
[
"Baez",
"John C.",
""
],
[
"Bunn",
"Emory F.",
""
]
] | This is a brief introduction to general relativity, designed for both students and teachers of the subject. While there are many excellent expositions of general relativity, few adequately explain the geometrical meaning of the basic equation of the theory: Einstein's equation. Here we give a simple formulation of this equation in terms of the motion of freely falling test particles. We also sketch some of its consequences, and explain how the formulation given here is equivalent to the usual one in terms of tensors. Finally, we include an annotated bibliography of books, articles and websites suitable for the student of relativity. |
gr-qc/0306061 | Miguel Gustavo de Campos Batista | M. de Campos | Adiabatic decaying vacuum model for the universe | 10 pages, 2 figures | Gen.Rel.Grav.35:899-906,2003 | 10.1023/A:1022907506957 | null | gr-qc | null | We study a model that the entropy per particle in the universe is constant.
The sources for the entropy are the particle creation and a lambda decaying
term. We find exact solutions for the Einstein field equations and show the
compatibilty of the model with respect to the age and the acceleration of the
universe.
| [
{
"created": "Sun, 15 Jun 2003 20:53:50 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Jun 2003 22:22:50 GMT",
"version": "v2"
}
] | 2009-04-17 | [
[
"de Campos",
"M.",
""
]
] | We study a model that the entropy per particle in the universe is constant. The sources for the entropy are the particle creation and a lambda decaying term. We find exact solutions for the Einstein field equations and show the compatibilty of the model with respect to the age and the acceleration of the universe. |
1712.04834 | Giorgio Papini | Giorgio Papini | Spin and maximal acceleration | 8 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the spin current tensor of a Dirac particle at accelerations close
to the upper limit introduced by Caianiello. Continual interchange between
particle spin and angular momentum is possible only when the acceleration is
time-dependent. This represents a stringent limit on the effect that maximal
acceleration may have on spin physics in astrophysical applications. We also
investigate some dynamical consequences of maximal acceleration.
| [
{
"created": "Wed, 13 Dec 2017 16:06:08 GMT",
"version": "v1"
}
] | 2017-12-14 | [
[
"Papini",
"Giorgio",
""
]
] | We study the spin current tensor of a Dirac particle at accelerations close to the upper limit introduced by Caianiello. Continual interchange between particle spin and angular momentum is possible only when the acceleration is time-dependent. This represents a stringent limit on the effect that maximal acceleration may have on spin physics in astrophysical applications. We also investigate some dynamical consequences of maximal acceleration. |
gr-qc/9908025 | Jorma Louko | Jorma Louko, Hans-Juergen Matschull | (2+1)-dimensional Einstein-Kepler problem in the centre-of-mass frame | 38 pages, REVTeX v3.1 with amsfonts and epsf, 12 eps figures. (v2:
Presentational improvement, references added, typos corrected.) | Class.Quant.Grav. 17 (2000) 1847-1873 | 10.1088/0264-9381/17/8/307 | AEI 1999-015, MZ-TH/99-31 | gr-qc | null | We formulate and analyze the Hamiltonian dynamics of a pair of massive
spinless point particles in (2+1)-dimensional Einstein gravity by anchoring the
system to a conical infinity, isometric to the infinity generated by a single
massive but possibly spinning particle. The reduced phase space \Gamma_{red}
has dimension four and topology R^3 x S^1. \Gamma_{red} is analogous to the
phase space of a Newtonian two-body system in the centre-of-mass frame, and we
find on \Gamma_{red} a canonical chart that makes this analogue explicit and
reduces to the Newtonian chart in the appropriate limit. Prospects for
quantization are commented on.
| [
{
"created": "Sun, 8 Aug 1999 13:31:32 GMT",
"version": "v1"
},
{
"created": "Mon, 6 Mar 2000 19:40:06 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Louko",
"Jorma",
""
],
[
"Matschull",
"Hans-Juergen",
""
]
] | We formulate and analyze the Hamiltonian dynamics of a pair of massive spinless point particles in (2+1)-dimensional Einstein gravity by anchoring the system to a conical infinity, isometric to the infinity generated by a single massive but possibly spinning particle. The reduced phase space \Gamma_{red} has dimension four and topology R^3 x S^1. \Gamma_{red} is analogous to the phase space of a Newtonian two-body system in the centre-of-mass frame, and we find on \Gamma_{red} a canonical chart that makes this analogue explicit and reduces to the Newtonian chart in the appropriate limit. Prospects for quantization are commented on. |
gr-qc/0312039 | Kostas Kokkotas | Kostas D. Kokkotas | High frequency sources of gravitational waves | 7 pages, Class. Quantum Grav. in press. Proceedings of the 5th Amaldi
Conference | Nucl.Phys.Proc.Suppl.138:433-435,2005 | 10.1016/j.nuclphysbps.2004.11.099 | null | gr-qc | null | Sources of high frequency gravitational waves are reviewed. Gravitational
collapse, rotational instabilities and oscillations of the remnant compact
objects are potentially important sources of gravitational waves. Significant
and unique information for the various stages of the collapse, the evolution of
protoneutron stars and the details of the equations of state of such objects
can be drawn from careful study of the gravitational wave signal.
| [
{
"created": "Sun, 7 Dec 2003 18:25:02 GMT",
"version": "v1"
}
] | 2010-11-19 | [
[
"Kokkotas",
"Kostas D.",
""
]
] | Sources of high frequency gravitational waves are reviewed. Gravitational collapse, rotational instabilities and oscillations of the remnant compact objects are potentially important sources of gravitational waves. Significant and unique information for the various stages of the collapse, the evolution of protoneutron stars and the details of the equations of state of such objects can be drawn from careful study of the gravitational wave signal. |
0801.1562 | S Habib Mazharimousavi | S. Habib Mazharimousavi and M. Halilsoy | 5D-Black Hole Solution in Einstein-Yang-Mills-Gauss-Bonnet Theory | 5 pages, no figures | Phys.Rev.D76:087501,2007 | 10.1103/PhysRevD.76.087501 | null | gr-qc | null | By adopting the 5D version of the Wu-Yang Ansatz we present in closed form a
black hole solution in the Einstein-Yang-Mills-Gauss-Bonnet (EYMGB) theory. In
the EYM limit, we recover the 5D black hole solution already known.
| [
{
"created": "Thu, 10 Jan 2008 08:34:54 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Mazharimousavi",
"S. Habib",
""
],
[
"Halilsoy",
"M.",
""
]
] | By adopting the 5D version of the Wu-Yang Ansatz we present in closed form a black hole solution in the Einstein-Yang-Mills-Gauss-Bonnet (EYMGB) theory. In the EYM limit, we recover the 5D black hole solution already known. |
gr-qc/0505163 | Todd Fugleberg | K. Choy, T. Kruk, M.E. Carrington, T. Fugleberg, J. Zahn, R. Kobes, G.
Kunstatter, D. Pickering | Energy Flow in Acoustic Black Holes | 8 pages, 9 figures, Comments added to discussion of energy flow and
introductory section abbreviated | Phys.Rev. D73 (2006) 104011 | 10.1103/PhysRevD.73.104011 | null | gr-qc hep-th | null | We present the results of an analysis of superradiant energy flow due to
scalar fields incident on an acoustic black hole. In addition to providing
independent confirmation of the recent results in [5], we determine in detail
the profile of energy flow everywhere outside the horizon. We confirm
explicitly that in a suitable frame the energy flow is inward at the horizon
and outward at infinity, as expected on physical grounds.
| [
{
"created": "Tue, 31 May 2005 18:45:35 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Oct 2005 17:07:15 GMT",
"version": "v2"
}
] | 2009-11-11 | [
[
"Choy",
"K.",
""
],
[
"Kruk",
"T.",
""
],
[
"Carrington",
"M. E.",
""
],
[
"Fugleberg",
"T.",
""
],
[
"Zahn",
"J.",
""
],
[
"Kobes",
"R.",
""
],
[
"Kunstatter",
"G.",
""
],
[
"Pickering",
"D.",
""
]
] | We present the results of an analysis of superradiant energy flow due to scalar fields incident on an acoustic black hole. In addition to providing independent confirmation of the recent results in [5], we determine in detail the profile of energy flow everywhere outside the horizon. We confirm explicitly that in a suitable frame the energy flow is inward at the horizon and outward at infinity, as expected on physical grounds. |
gr-qc/0006078 | Joshua A. Faber | Joshua A. Faber, Frederic A. Rasio, and Justin B. Manor | Post-Newtonian SPH calculations of binary neutron star coalescence. II.
Binary mass ratio, equation of state, and spin dependence | RevTeX, 38 pages, 24 figures, Minor Corrections, to appear in Phys.
Rev. D | Phys.Rev. D63 (2001) 044012 | 10.1103/PhysRevD.63.044012 | null | gr-qc astro-ph | null | Using our new Post-Newtonian SPH (smoothed particle hydrodynamics) code, we
study the final coalescence and merging of neutron star (NS) binaries. We vary
the stiffness of the equation of state (EOS) as well as the initial binary mass
ratio and stellar spins. Results are compared to those of Newtonian
calculations, with and without the inclusion of the gravitational radiation
reaction. We find a much steeper decrease in the gravity wave peak strain and
luminosity with decreasing mass ratio than would be predicted by simple
point-mass formulae. For NS with softer EOS (which we model as simple
$\Gamma=2$ polytropes) we find a stronger gravity wave emission, with a
different morphology than for stiffer EOS (modeled as $\Gamma=3$ polytropes as
in our previous work). We also calculate the coalescence of NS binaries with an
irrotational initial condition, and find that the gravity wave signal is
relatively suppressed compared to the synchronized case, but shows a very
significant second peak of emission. Mass shedding is also greatly reduced, and
occurs via a different mechanism than in the synchronized case. We discuss the
implications of our results for gravity wave astronomy with laser
interferometers such as LIGO, and for theoretical models of gamma-ray bursts
(GRBs) based on NS mergers.
| [
{
"created": "Thu, 22 Jun 2000 00:02:40 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Oct 2000 21:12:42 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"Faber",
"Joshua A.",
""
],
[
"Rasio",
"Frederic A.",
""
],
[
"Manor",
"Justin B.",
""
]
] | Using our new Post-Newtonian SPH (smoothed particle hydrodynamics) code, we study the final coalescence and merging of neutron star (NS) binaries. We vary the stiffness of the equation of state (EOS) as well as the initial binary mass ratio and stellar spins. Results are compared to those of Newtonian calculations, with and without the inclusion of the gravitational radiation reaction. We find a much steeper decrease in the gravity wave peak strain and luminosity with decreasing mass ratio than would be predicted by simple point-mass formulae. For NS with softer EOS (which we model as simple $\Gamma=2$ polytropes) we find a stronger gravity wave emission, with a different morphology than for stiffer EOS (modeled as $\Gamma=3$ polytropes as in our previous work). We also calculate the coalescence of NS binaries with an irrotational initial condition, and find that the gravity wave signal is relatively suppressed compared to the synchronized case, but shows a very significant second peak of emission. Mass shedding is also greatly reduced, and occurs via a different mechanism than in the synchronized case. We discuss the implications of our results for gravity wave astronomy with laser interferometers such as LIGO, and for theoretical models of gamma-ray bursts (GRBs) based on NS mergers. |
1306.1527 | Joan Sola | Joan Sola | Cosmological constant and vacuum energy: old and new ideas | 86 pages, substantially extended discussion, many new references
added | J.Phys.Conf.Ser. 453 (2013) 012015 | 10.1088/1742-6596/453/1/012015 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The cosmological constant (CC) term in Einstein's equations, Lambda, was
first associated to the idea of vacuum energy density. Notwithstanding, it is
well-known that there is a huge, in fact appalling, discrepancy between the
theoretical prediction and the observed value picked from the modern
cosmological data. This is the famous, and extremely difficult, "CC problem".
Paradoxically, the recent observation at the CERN Large Hadron Collider of a
Higgs-like particle, should actually be considered ambivalent: on the one hand
it appears as a likely great triumph of particle physics, but on the other hand
it wide opens Pandora's box of the cosmological uproar, for it may provide
(alas!) the experimental certification of the existence of the electroweak (EW)
vacuum energy, and thus of the intriguing reality of the CC problem. Even if
only counting on this contribution to the inventory of vacuum energies in the
universe, the discrepancy with the cosmologically observed value is already of
55 orders of magnitude. This is the (hitherto) "real" magnitude of the CC
problem, rather than the (too often) brandished 123 ones from the upper (but
fully unexplored!) ultrahigh energy scales. Such is the baffling situation
after 96 years of introducing the Lambda-term by Einstein. In the following I
will briefly (and hopefully pedagogically) fly over some of the old and new
ideas on the CC problem. Since, however, the Higgs boson just knocked our door
and recalled us that the vacuum energy may be a fully tangible concept in real
phenomenology, I will exclusively address the CC problem from the original
notion of vacuum energy, and its possible "running" with the expansion of the
universe, rather than venturing into the numberless attempts to replace the CC
by the multifarious concept of dark energy.
| [
{
"created": "Thu, 6 Jun 2013 19:58:11 GMT",
"version": "v1"
},
{
"created": "Sun, 30 Jun 2013 19:08:16 GMT",
"version": "v2"
},
{
"created": "Sun, 21 Jul 2013 19:58:21 GMT",
"version": "v3"
}
] | 2015-03-19 | [
[
"Sola",
"Joan",
""
]
] | The cosmological constant (CC) term in Einstein's equations, Lambda, was first associated to the idea of vacuum energy density. Notwithstanding, it is well-known that there is a huge, in fact appalling, discrepancy between the theoretical prediction and the observed value picked from the modern cosmological data. This is the famous, and extremely difficult, "CC problem". Paradoxically, the recent observation at the CERN Large Hadron Collider of a Higgs-like particle, should actually be considered ambivalent: on the one hand it appears as a likely great triumph of particle physics, but on the other hand it wide opens Pandora's box of the cosmological uproar, for it may provide (alas!) the experimental certification of the existence of the electroweak (EW) vacuum energy, and thus of the intriguing reality of the CC problem. Even if only counting on this contribution to the inventory of vacuum energies in the universe, the discrepancy with the cosmologically observed value is already of 55 orders of magnitude. This is the (hitherto) "real" magnitude of the CC problem, rather than the (too often) brandished 123 ones from the upper (but fully unexplored!) ultrahigh energy scales. Such is the baffling situation after 96 years of introducing the Lambda-term by Einstein. In the following I will briefly (and hopefully pedagogically) fly over some of the old and new ideas on the CC problem. Since, however, the Higgs boson just knocked our door and recalled us that the vacuum energy may be a fully tangible concept in real phenomenology, I will exclusively address the CC problem from the original notion of vacuum energy, and its possible "running" with the expansion of the universe, rather than venturing into the numberless attempts to replace the CC by the multifarious concept of dark energy. |
gr-qc/0511112 | Luis Herrera | L. Herrera, N.O. Santos and J. Carot | Gravitational radiation, vorticity and the electric and magnetic part of
Weyl tensor | 17 pages Latex. Typos corrected | J.Math.Phys. 47 (2006) 052502 | 10.1063/1.2199027 | null | gr-qc | null | The electric and the magnetic part of the Weyl tensor, as well as the
invariants obtained from them, are calculated for the Bondi vacuum metric. One
of the invariants vanishes identically and the other only exhibits
contributions from terms of the Weyl tensor containing the static part of the
field. It is shown that the necessary and sufficient condition for the
spacetime to be purely electric is that such spacetime be static. It is also
shown that the vanishing of the electric part implies Minkowski spacetime.
Unlike the electric part, the magnetic part does not contain contributions from
the static field. Finally a speculation about the link between the vorticity of
world lines of observers at rest in a Bondi frame, and gravitational radiation,
is presented.
| [
{
"created": "Sun, 20 Nov 2005 21:07:55 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Mar 2006 19:21:31 GMT",
"version": "v2"
},
{
"created": "Mon, 15 May 2006 20:35:07 GMT",
"version": "v3"
}
] | 2009-11-11 | [
[
"Herrera",
"L.",
""
],
[
"Santos",
"N. O.",
""
],
[
"Carot",
"J.",
""
]
] | The electric and the magnetic part of the Weyl tensor, as well as the invariants obtained from them, are calculated for the Bondi vacuum metric. One of the invariants vanishes identically and the other only exhibits contributions from terms of the Weyl tensor containing the static part of the field. It is shown that the necessary and sufficient condition for the spacetime to be purely electric is that such spacetime be static. It is also shown that the vanishing of the electric part implies Minkowski spacetime. Unlike the electric part, the magnetic part does not contain contributions from the static field. Finally a speculation about the link between the vorticity of world lines of observers at rest in a Bondi frame, and gravitational radiation, is presented. |
1605.07205 | Antonios Tsokaros A. | Antonios Tsokaros, Bruno C. Mundim, Filippo Galeazzi, Luciano
Rezzolla, K\=oji Ury\=u | Initial-data contribution to the error budget of gravitational waves
from neutron-star binaries | 17 pages, 11 figures | Phys. Rev. D 94, 044049 (2016) | 10.1103/PhysRevD.94.044049 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As numerical calculations of inspiralling neutron-star binaries reach values
of accuracy that are comparable with those of binary black holes, a fine
budgeting of the various sources of error becomes increasingly important. Among
such sources, the initial data is normally not accounted for, the rationale
being that the error on the initial spacelike hypersurface is always far
smaller than the one gained during the evolution. We here consider critically
this assumption and perform a comparative analysis of the gravitational
waveforms relative to essentially the same physical binary configuration when
computed with two different initial-data codes, and then evolved with the same
evolution code. More specifically, we consider the evolution of irrotational
neutron-star binaries computed either with the pseudo-spectral code \lorene{},
or with the newly developed finite-difference code \cocal{}; both sets of
initial data are subsequently evolved with the high-order evolution code
\whiskythc{}. In this way we find that despite the initial data shows global
(local) differences that are $\lesssim 0.02\%\ (1\%)$, the gravitational-wave
phase at the merger time differs by $\sim 0.5$ radians after $\sim 3$ orbits, a
surprisingly large value. Our results highlight the highly nonlinear impact
that errors in the initial data can have on the subsequent evolution and the
importance of using exactly the same initial data when comparative studies are
done.
| [
{
"created": "Mon, 23 May 2016 20:17:05 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Tsokaros",
"Antonios",
""
],
[
"Mundim",
"Bruno C.",
""
],
[
"Galeazzi",
"Filippo",
""
],
[
"Rezzolla",
"Luciano",
""
],
[
"Uryū",
"Kōji",
""
]
] | As numerical calculations of inspiralling neutron-star binaries reach values of accuracy that are comparable with those of binary black holes, a fine budgeting of the various sources of error becomes increasingly important. Among such sources, the initial data is normally not accounted for, the rationale being that the error on the initial spacelike hypersurface is always far smaller than the one gained during the evolution. We here consider critically this assumption and perform a comparative analysis of the gravitational waveforms relative to essentially the same physical binary configuration when computed with two different initial-data codes, and then evolved with the same evolution code. More specifically, we consider the evolution of irrotational neutron-star binaries computed either with the pseudo-spectral code \lorene{}, or with the newly developed finite-difference code \cocal{}; both sets of initial data are subsequently evolved with the high-order evolution code \whiskythc{}. In this way we find that despite the initial data shows global (local) differences that are $\lesssim 0.02\%\ (1\%)$, the gravitational-wave phase at the merger time differs by $\sim 0.5$ radians after $\sim 3$ orbits, a surprisingly large value. Our results highlight the highly nonlinear impact that errors in the initial data can have on the subsequent evolution and the importance of using exactly the same initial data when comparative studies are done. |
2405.15874 | Himanshu Chaudhary | Ujjal Debnath, Himanshu Chaudhary, Niyaz Uddin Molla, S. K. J. Pacif
and G.Mustafa | Dark Energy Model in Einstein and Horava-Lifshitz Gravity with a new
Parametrization of $\omega(z)$: Model Comparison, Analysis and Observational
Constraint | 19 pages, 5 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a novel dynamical dark energy model within the frameworks of both
Einstein gravity and Horava-Lifshitz gravity. Utilizing a new parametrization
of the dark energy equation of state $\omega(z)$, we derive solutions to the
field equations. By employing recent cosmological datasets, such as cosmic
chronometer datasets, Type Ia Supernovae datasets, Baryonic Oscillation
datasets, and the recent Hubble constant value measured by the Hubble Space
Telescope and the SH0ES Team as an additional prior. We validate our model and
determine optimal parameter values. Furthermore, we analyze the evolution of
the Universe by showing the redshift dependence plots of key cosmological
parameters through graphical representations. We also perform diagnostic
analyses to compare our model with the standard model. Using the Akaike
Information Criterion (AIC), we compare the three models and find that all of
them are supported by the current data, making it impossible to discard any of
them. Our model aligns well with recent observations and unveils intriguing
features of the Universe, particularly the late-time behavior of the Universe.
| [
{
"created": "Fri, 24 May 2024 18:39:57 GMT",
"version": "v1"
}
] | 2024-05-28 | [
[
"Debnath",
"Ujjal",
""
],
[
"Chaudhary",
"Himanshu",
""
],
[
"Molla",
"Niyaz Uddin",
""
],
[
"Pacif",
"S. K. J.",
""
],
[
"Mustafa",
"G.",
""
]
] | We present a novel dynamical dark energy model within the frameworks of both Einstein gravity and Horava-Lifshitz gravity. Utilizing a new parametrization of the dark energy equation of state $\omega(z)$, we derive solutions to the field equations. By employing recent cosmological datasets, such as cosmic chronometer datasets, Type Ia Supernovae datasets, Baryonic Oscillation datasets, and the recent Hubble constant value measured by the Hubble Space Telescope and the SH0ES Team as an additional prior. We validate our model and determine optimal parameter values. Furthermore, we analyze the evolution of the Universe by showing the redshift dependence plots of key cosmological parameters through graphical representations. We also perform diagnostic analyses to compare our model with the standard model. Using the Akaike Information Criterion (AIC), we compare the three models and find that all of them are supported by the current data, making it impossible to discard any of them. Our model aligns well with recent observations and unveils intriguing features of the Universe, particularly the late-time behavior of the Universe. |
2112.12861 | Shahn Majid | Chengcheng Liu and Shahn Majid | Quantum geodesics on $\lambda$-Minkowski spacetime | 28 pages amslatex, 3 pdf figures; some small corrections and
clarified the notation in a couple of places | null | 10.1088/1751-8121/ac7593 | null | gr-qc hep-th math.QA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply a recent formalism of quantum geodesics to the well-known
bicrossproduct model $\lambda$-Minkowski quantum spacetime
$[x^i,t]=\imath\lambda_p x^i$ with its flat quantum metric as a model of
quantum gravity effects, with $\lambda_p$ the Planck scale. As examples,
quantum geodesic flow of a plane wave gets an order $\lambda_p$ frequency
dependent correction to the classical geodesic velocity. A quantum geodesic
flow with classical velocity $v$ of a Gaussian with width $\sqrt{2\beta}$
initially centred at the origin changes its shape but its centre of mass moves
with ${<x>\over<t>}=v(1+{\lambda_p^2\over 2\beta}+O(\lambda^3_p))$, an order
$\lambda_p^2$ correction. This implies, at least within perturbation theory,
that a `point particle' cannot be modelled as an infinitely sharp Gaussian due
to quantum gravity corrections. For contrast, we also look at quantum geodesics
on the noncommutative torus with a 2D curved weak quantum Levi-Civita
connection.
| [
{
"created": "Wed, 22 Dec 2021 18:36:04 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Feb 2022 20:55:33 GMT",
"version": "v2"
}
] | 2022-11-23 | [
[
"Liu",
"Chengcheng",
""
],
[
"Majid",
"Shahn",
""
]
] | We apply a recent formalism of quantum geodesics to the well-known bicrossproduct model $\lambda$-Minkowski quantum spacetime $[x^i,t]=\imath\lambda_p x^i$ with its flat quantum metric as a model of quantum gravity effects, with $\lambda_p$ the Planck scale. As examples, quantum geodesic flow of a plane wave gets an order $\lambda_p$ frequency dependent correction to the classical geodesic velocity. A quantum geodesic flow with classical velocity $v$ of a Gaussian with width $\sqrt{2\beta}$ initially centred at the origin changes its shape but its centre of mass moves with ${<x>\over<t>}=v(1+{\lambda_p^2\over 2\beta}+O(\lambda^3_p))$, an order $\lambda_p^2$ correction. This implies, at least within perturbation theory, that a `point particle' cannot be modelled as an infinitely sharp Gaussian due to quantum gravity corrections. For contrast, we also look at quantum geodesics on the noncommutative torus with a 2D curved weak quantum Levi-Civita connection. |
2003.14088 | Iver Brevik | I. Brevik and A. V. Timoshkin | Rip brane cosmology from a viscous holographic dark fluid | 11 pages, to appear in Int. J. Geom. Methods in Mod. Phys | Int. J. Geom. Meth. Mod. Phys. 17(2020)2050087 | 10.1142/S0219887820500875 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article is devoted to the application of the holographic principle to
describe Rip brane cosmological models in the presence of a bulk viscosity. We
make use of the generalized infrared-cutoff holographic dark energy, introduced
by Nojiri and Odintsov We consider various examples: Rip brane cosmology
corresponding to the Little Rip case, asymptotic de Sitter theory, and the
so-called Big Freeze theory leading to a singularity. Analytical expressions
for infrared cutoffs, as well as the particle and the future horizons at the
brane, are obtained. The equations for energy conservation on the brane within
the holographic theory are obtained in each case. The correspondence between
viscous cosmology and holographic cosmology on the brane is shown.
| [
{
"created": "Tue, 31 Mar 2020 10:53:53 GMT",
"version": "v1"
}
] | 2020-06-05 | [
[
"Brevik",
"I.",
""
],
[
"Timoshkin",
"A. V.",
""
]
] | This article is devoted to the application of the holographic principle to describe Rip brane cosmological models in the presence of a bulk viscosity. We make use of the generalized infrared-cutoff holographic dark energy, introduced by Nojiri and Odintsov We consider various examples: Rip brane cosmology corresponding to the Little Rip case, asymptotic de Sitter theory, and the so-called Big Freeze theory leading to a singularity. Analytical expressions for infrared cutoffs, as well as the particle and the future horizons at the brane, are obtained. The equations for energy conservation on the brane within the holographic theory are obtained in each case. The correspondence between viscous cosmology and holographic cosmology on the brane is shown. |
0903.2128 | Matt Visser | Jozef Skakala (Victoria University of Wellington) and Matt Visser
(Victoria University of Wellington) | Birkhoff-like theorem for rotating stars in (2+1) dimensions | 4 pages; uses revtex4; V2: added 1 very important reference;
significantly expanded discussion; many small changes in the text but no
significant change in physics conclusions; V3: minor typos fixed | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Consider a rotating and possibly pulsating "star" in (2+1) dimensions. If the
star is axially symmetric, then in the vacuum region surrounding the star, (a
region that we assume at most contains a cosmological constant), the Einstein
equations imply that under physically plausible conditions the geometry is in
fact stationary. Furthermore, the geometry external to the star is then
uniquely guaranteed to be the (2+1) dimensional analogue of the Kerr-de Sitter
spacetime, the BTZ geometry. This Birkhoff-like theorem is very special to
(2+1) dimensions, and fails in (3+1) dimensions. Effectively, this is a "no
hair" theorem for (2+1) dimensional axially symmetric stars: the exterior
geometry is completely specified by the mass, angular momentum, and
cosmological constant.
| [
{
"created": "Thu, 12 Mar 2009 09:37:46 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Mar 2009 05:07:10 GMT",
"version": "v2"
},
{
"created": "Sun, 22 Mar 2009 19:26:26 GMT",
"version": "v3"
}
] | 2009-03-22 | [
[
"Skakala",
"Jozef",
"",
"Victoria University of Wellington"
],
[
"Visser",
"Matt",
"",
"Victoria University of Wellington"
]
] | Consider a rotating and possibly pulsating "star" in (2+1) dimensions. If the star is axially symmetric, then in the vacuum region surrounding the star, (a region that we assume at most contains a cosmological constant), the Einstein equations imply that under physically plausible conditions the geometry is in fact stationary. Furthermore, the geometry external to the star is then uniquely guaranteed to be the (2+1) dimensional analogue of the Kerr-de Sitter spacetime, the BTZ geometry. This Birkhoff-like theorem is very special to (2+1) dimensions, and fails in (3+1) dimensions. Effectively, this is a "no hair" theorem for (2+1) dimensional axially symmetric stars: the exterior geometry is completely specified by the mass, angular momentum, and cosmological constant. |
0704.1802 | Comelli Denis | Denis Comelli | A Way to Dynamically Overcome the Cosmological Constant Problem | 5 pages | Int.J.Mod.Phys.A23:4133-4143,2008 | 10.1142/S0217751X08041359 | null | gr-qc astro-ph | null | The Cosmological Constant problem can be solved once we require that the full
standard Einstein Hilbert lagrangian, gravity plus matter, is multiplied by a
total derivative. We analyze such a picture writing the total derivative as the
covariant gradient of a new vector field (b_mu). The dynamics of this b_mu
field can play a key role in the explanation of the present cosmological
acceleration of the Universe.
| [
{
"created": "Fri, 13 Apr 2007 17:29:06 GMT",
"version": "v1"
}
] | 2009-01-06 | [
[
"Comelli",
"Denis",
""
]
] | The Cosmological Constant problem can be solved once we require that the full standard Einstein Hilbert lagrangian, gravity plus matter, is multiplied by a total derivative. We analyze such a picture writing the total derivative as the covariant gradient of a new vector field (b_mu). The dynamics of this b_mu field can play a key role in the explanation of the present cosmological acceleration of the Universe. |
0806.2415 | Yungui Gong | Ximing Chen, Jie Liu, Yungui Gong | Constraints on Dark Energy Models from Weak Gravity Conjecture | 4 two column pages, 3 figures, accepted by Chin. Phys. Lett | Chin.Phys.Lett.25:3086-3089,2008 | 10.1088/0256-307X/25/8/094 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the constraints on the dark energy model with constant equation of
state parameter $w=p/\rho$ and the holographic dark energy model by using the
weak gravity conjecture. The combination of weak gravity conjecture and the
observational data gives $w<-0.7$ at the $3\sigma$ confidence level. The
holographic dark energy model realized by a scalar field is in swampland.
| [
{
"created": "Sun, 15 Jun 2008 04:16:46 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Chen",
"Ximing",
""
],
[
"Liu",
"Jie",
""
],
[
"Gong",
"Yungui",
""
]
] | We study the constraints on the dark energy model with constant equation of state parameter $w=p/\rho$ and the holographic dark energy model by using the weak gravity conjecture. The combination of weak gravity conjecture and the observational data gives $w<-0.7$ at the $3\sigma$ confidence level. The holographic dark energy model realized by a scalar field is in swampland. |
2006.09026 | Sergey Paston | S.A. Paston | Dark matter from non-relativistic embedding gravity | LaTeX, 11 pages. This version corresponds to the published one | Modern Physics Letters A, Vol. 36, No. 15, 2150101 (2021) | 10.1142/S0217732321501017 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the possibility to explain the mystery of the dark matter through
the transition from General Relativity to embedding gravity. This modification
of gravity, which was proposed by Regge and Teitelboim, is based on a simple
string-inspired geometrical principle: our spacetime is considered here as a
4-dimensional surface in a flat bulk. We show that among the solutions of
embedding gravity, there is a class of solutions equivalent to solutions of GR
with an additional contribution of non-relativistic embedding matter, which can
serve as cold dark matter. We prove the stability of such type of solutions and
obtain an explicit form of the equations of motion of embedding matter in the
non-relativistic limit. According to them, embedding matter turns out to have a
certain self-interaction, which could be useful in the context of solving the
core-cusp problem that appears in the LambdaCDM model.
| [
{
"created": "Tue, 16 Jun 2020 09:46:56 GMT",
"version": "v1"
},
{
"created": "Sun, 6 Jun 2021 09:19:03 GMT",
"version": "v2"
}
] | 2021-06-08 | [
[
"Paston",
"S. A.",
""
]
] | We study the possibility to explain the mystery of the dark matter through the transition from General Relativity to embedding gravity. This modification of gravity, which was proposed by Regge and Teitelboim, is based on a simple string-inspired geometrical principle: our spacetime is considered here as a 4-dimensional surface in a flat bulk. We show that among the solutions of embedding gravity, there is a class of solutions equivalent to solutions of GR with an additional contribution of non-relativistic embedding matter, which can serve as cold dark matter. We prove the stability of such type of solutions and obtain an explicit form of the equations of motion of embedding matter in the non-relativistic limit. According to them, embedding matter turns out to have a certain self-interaction, which could be useful in the context of solving the core-cusp problem that appears in the LambdaCDM model. |
2107.10682 | Fei-Quan Tu | Fei-Quan Tu, Yi-Xin Chen, Qi-Hong Huang | A cosmic accelerated scenario based on degrees of freedom of the
spacetime | 11 pages, 1 figure | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Several recent investigations have shown that there is a holographic
relationship between the bulk degrees of freedom and the surface degrees of
freedom in the spacetime. Furthermore, the entropy on the horizon can produce
an entropic force effect on the bulk degrees of freedom. In this paper, we
explore the dynamic evolution law of the universe based on the idea of the
entropic force and asymptotically holographic equipartition and further analyze
the thermodynamic properties of the current model. We get the age of the
universe, the relation between the luminosity distance and the redshift factor
and the deceleration parameter which are consistent with astronomical
observations. In addition, we can well explain the age of the universe and the
mechanism of accelerated expansion without introducing dark energy for the
evolution history of the universe up to now. We also show that the generalized
second law of thermodynamics, the energy balance condition and the energy
equipartition relation always hold. More importantly, the energy balance
condition is indeed a holographic relation between the bulk degrees of freedom
and the surface degrees of freedom of the spacetime. Finally, we analyze the
energy conditions and show that the strong energy condition is always violated
and the weak energy condition is satisfied when $t\leq2t_{0}$ in which $t$ is
the time parameter and $t_{0}$ is the age of the universe.
| [
{
"created": "Thu, 22 Jul 2021 13:41:14 GMT",
"version": "v1"
}
] | 2021-07-23 | [
[
"Tu",
"Fei-Quan",
""
],
[
"Chen",
"Yi-Xin",
""
],
[
"Huang",
"Qi-Hong",
""
]
] | Several recent investigations have shown that there is a holographic relationship between the bulk degrees of freedom and the surface degrees of freedom in the spacetime. Furthermore, the entropy on the horizon can produce an entropic force effect on the bulk degrees of freedom. In this paper, we explore the dynamic evolution law of the universe based on the idea of the entropic force and asymptotically holographic equipartition and further analyze the thermodynamic properties of the current model. We get the age of the universe, the relation between the luminosity distance and the redshift factor and the deceleration parameter which are consistent with astronomical observations. In addition, we can well explain the age of the universe and the mechanism of accelerated expansion without introducing dark energy for the evolution history of the universe up to now. We also show that the generalized second law of thermodynamics, the energy balance condition and the energy equipartition relation always hold. More importantly, the energy balance condition is indeed a holographic relation between the bulk degrees of freedom and the surface degrees of freedom of the spacetime. Finally, we analyze the energy conditions and show that the strong energy condition is always violated and the weak energy condition is satisfied when $t\leq2t_{0}$ in which $t$ is the time parameter and $t_{0}$ is the age of the universe. |
1611.02932 | Manuel Kraemer | David Brizuela, Claus Kiefer, Manuel Kraemer | Quantum-gravitational effects on gauge-invariant scalar and tensor
perturbations during inflation: The slow-roll approximation | 16 pages, 7 figures, clarifications and references added | Phys. Rev. D 94, 123527 (2016) | 10.1103/PhysRevD.94.123527 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We continue our study on corrections from canonical quantum gravity to the
power spectra of gauge-invariant inflationary scalar and tensor perturbations.
A direct canonical quantization of a perturbed inflationary universe model is
implemented, which leads to a Wheeler-DeWitt equation. For this equation, a
semiclassical approximation is applied in order to obtain a Schroedinger
equation with quantum-gravitational correction terms, from which we calculate
the corrections to the power spectra. We go beyond the de Sitter case discussed
earlier and analyze our model in the first slow-roll approximation, considering
terms linear in the slow-roll parameters. We find that the dominant correction
term from the de Sitter case, which leads to an enhancement of power on the
largest scales, gets modified by terms proportional to the slow-roll
parameters. A correction to the tensor-to-scalar ratio is also found at second
order in the slow-roll parameters. Making use of the available experimental
data, the magnitude of these quantum-gravitational corrections is estimated.
Finally, the effects for the temperature anisotropies in the cosmic microwave
background are qualitatively obtained.
| [
{
"created": "Wed, 9 Nov 2016 13:51:30 GMT",
"version": "v1"
},
{
"created": "Fri, 30 Dec 2016 17:00:06 GMT",
"version": "v2"
}
] | 2017-01-02 | [
[
"Brizuela",
"David",
""
],
[
"Kiefer",
"Claus",
""
],
[
"Kraemer",
"Manuel",
""
]
] | We continue our study on corrections from canonical quantum gravity to the power spectra of gauge-invariant inflationary scalar and tensor perturbations. A direct canonical quantization of a perturbed inflationary universe model is implemented, which leads to a Wheeler-DeWitt equation. For this equation, a semiclassical approximation is applied in order to obtain a Schroedinger equation with quantum-gravitational correction terms, from which we calculate the corrections to the power spectra. We go beyond the de Sitter case discussed earlier and analyze our model in the first slow-roll approximation, considering terms linear in the slow-roll parameters. We find that the dominant correction term from the de Sitter case, which leads to an enhancement of power on the largest scales, gets modified by terms proportional to the slow-roll parameters. A correction to the tensor-to-scalar ratio is also found at second order in the slow-roll parameters. Making use of the available experimental data, the magnitude of these quantum-gravitational corrections is estimated. Finally, the effects for the temperature anisotropies in the cosmic microwave background are qualitatively obtained. |
1907.09201 | Euaggelos E. Zotos | Euaggelos E. Zotos, Fredy L. Dubeibe, Jan Nagler, Emilio Tejeda | Orbit classification in a pseudo-Newtonian Copenhagen problem with
Schwarzschild-like primaries | Published in Monthly Notices of the Royal Astronomical Society
(MNRAS) journal | MNRAS, vol. 487, 2340-2353 (2019) | 10.1093/mnras/stz1432 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the orbital dynamics of the planar pseudo-Newtonian Copenhagen
problem, in the case of a binary system of Schwarzschild-like primaries, such
as super-massive black holes. In particular, we investigate how the Jacobi
constant (which is directly connected with the energy of the orbits) influences
several aspects of the orbital dynamics, such as the final state of the orbits.
We also determine how the relativistic effects (i.e., the Schwarzschild radius)
affect the character of the orbits, by comparing our results with the classical
Newtonian problem. Basin diagrams are deployed for presenting all the different
basin types, using multiple types of planes with two dimensions. We demonstrate
that both the Jacobi constant as well as the Schwarzschild radius highly
influence the character of the orbits, as well as the degree of fractality of
the dynamical system.
| [
{
"created": "Mon, 22 Jul 2019 09:42:48 GMT",
"version": "v1"
}
] | 2019-07-23 | [
[
"Zotos",
"Euaggelos E.",
""
],
[
"Dubeibe",
"Fredy L.",
""
],
[
"Nagler",
"Jan",
""
],
[
"Tejeda",
"Emilio",
""
]
] | We examine the orbital dynamics of the planar pseudo-Newtonian Copenhagen problem, in the case of a binary system of Schwarzschild-like primaries, such as super-massive black holes. In particular, we investigate how the Jacobi constant (which is directly connected with the energy of the orbits) influences several aspects of the orbital dynamics, such as the final state of the orbits. We also determine how the relativistic effects (i.e., the Schwarzschild radius) affect the character of the orbits, by comparing our results with the classical Newtonian problem. Basin diagrams are deployed for presenting all the different basin types, using multiple types of planes with two dimensions. We demonstrate that both the Jacobi constant as well as the Schwarzschild radius highly influence the character of the orbits, as well as the degree of fractality of the dynamical system. |
gr-qc/9603002 | Masafumi Seriu | Masafumi Seriu | The spectral representation of the spacetime structure: The `distance'
between universes with different topologies | 47 pages | Phys.Rev.D53:6902-6920,1996 | 10.1103/PhysRevD.53.6902 | YITP-96-9 | gr-qc | null | We investigate the representation of the geometrical information of the
universe in terms of the eigenvalues of the Laplacian defined on the universe.
We concentrate only on one specific problem along this line: To introduce a
concept of distance between universes in terms of the difference in the
spectra.
We can find out such a measure of closeness from a general discussion. The
basic properties of this `spectral distance' are then investigated. It can be
related to a reduced density matrix element in quantum cosmology. Thus,
calculating the spectral distance gives us an insight for the quantum
theoretical decoherence between two universes. The spectral distance does not
in general satisfy the triangular inequality, illustrating that it is not
equivalent to the distance defined by the DeWitt metric on the superspace.
We then pose a question: Whether two universes with different topologies
interfere with each other quantum mechanically? We concentrate on the
difference in the orientabilities. Several concrete models in 2-dimension are
set up, and the spectral distances between them are investigated: Tori and
Klein's bottles, spheres and real projective spaces. Quite surprisingly, we
find many cases of spaces with different orientabilities in which the spectral
distance turns out to be very short. It may suggest that, without any other
special mechanism, two such universes interfere with each other quite strongly.
| [
{
"created": "Fri, 1 Mar 1996 14:28:19 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Seriu",
"Masafumi",
""
]
] | We investigate the representation of the geometrical information of the universe in terms of the eigenvalues of the Laplacian defined on the universe. We concentrate only on one specific problem along this line: To introduce a concept of distance between universes in terms of the difference in the spectra. We can find out such a measure of closeness from a general discussion. The basic properties of this `spectral distance' are then investigated. It can be related to a reduced density matrix element in quantum cosmology. Thus, calculating the spectral distance gives us an insight for the quantum theoretical decoherence between two universes. The spectral distance does not in general satisfy the triangular inequality, illustrating that it is not equivalent to the distance defined by the DeWitt metric on the superspace. We then pose a question: Whether two universes with different topologies interfere with each other quantum mechanically? We concentrate on the difference in the orientabilities. Several concrete models in 2-dimension are set up, and the spectral distances between them are investigated: Tori and Klein's bottles, spheres and real projective spaces. Quite surprisingly, we find many cases of spaces with different orientabilities in which the spectral distance turns out to be very short. It may suggest that, without any other special mechanism, two such universes interfere with each other quite strongly. |
gr-qc/0402044 | Simon F. Ross | Tim Clunan, Simon F. Ross and Douglas J. Smith | On Gauss-Bonnet black hole entropy | 14 pages, no figures. v2: references added; v3,v4: more references
added | Class.Quant.Grav. 21 (2004) 3447-3458 | 10.1088/0264-9381/21/14/009 | null | gr-qc hep-th | null | We investigate the entropy of black holes in Gauss-Bonnet and Lovelock
gravity using the Noether charge approach, in which the entropy is given as the
integral of a suitable (n-2) form charge over the event horizon. We compare the
results to those obtained in other approaches. We also comment on the
appearance of negative entropies in some cases, and show that there is an
additive ambiguity in the definition of the entropy which can be appropriately
chosen to avoid this problem.
| [
{
"created": "Tue, 10 Feb 2004 09:47:09 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Feb 2004 14:33:54 GMT",
"version": "v2"
},
{
"created": "Fri, 20 Feb 2004 17:26:41 GMT",
"version": "v3"
},
{
"created": "Fri, 10 Dec 2004 16:10:15 GMT",
"version": "v4"
}
] | 2009-11-10 | [
[
"Clunan",
"Tim",
""
],
[
"Ross",
"Simon F.",
""
],
[
"Smith",
"Douglas J.",
""
]
] | We investigate the entropy of black holes in Gauss-Bonnet and Lovelock gravity using the Noether charge approach, in which the entropy is given as the integral of a suitable (n-2) form charge over the event horizon. We compare the results to those obtained in other approaches. We also comment on the appearance of negative entropies in some cases, and show that there is an additive ambiguity in the definition of the entropy which can be appropriately chosen to avoid this problem. |
2006.05242 | W{\l}odzimierz Piechocki | W{\l}odzimierz Piechocki | Generic singularity of general relativity and its quantum fate | 9 pages, no figures, extended version of essay | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Belinski-Khalatnikov-Lifshitz scenario concerns the existence of generic
singularity of general relativity. At the singularity, there is a breakdown of
all known laws of physics. Quantization of this scenario leads, however, to
regular quantum evolution. The singularity is avoided by a quantum bounce. It
is fairly probable that quantum general relativity, to be constructed, would be
free from singularities. Thus, it could be used to address issues such as the
quantum fates of cosmological and black holes singularities.
| [
{
"created": "Tue, 9 Jun 2020 13:27:59 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Jul 2020 04:27:12 GMT",
"version": "v2"
}
] | 2020-07-20 | [
[
"Piechocki",
"Włodzimierz",
""
]
] | The Belinski-Khalatnikov-Lifshitz scenario concerns the existence of generic singularity of general relativity. At the singularity, there is a breakdown of all known laws of physics. Quantization of this scenario leads, however, to regular quantum evolution. The singularity is avoided by a quantum bounce. It is fairly probable that quantum general relativity, to be constructed, would be free from singularities. Thus, it could be used to address issues such as the quantum fates of cosmological and black holes singularities. |
gr-qc/0201103 | Giovanni Imponente | Giovanni Imponente and Giovanni Montani | Covariant Mixmaster Dynamics | null | in ''Similarities and Universality in Relativistic Flows'', Ed. by
Logos Verlag, Berlin (2001) | null | null | gr-qc | null | We provide a Hamiltonian analysis of the Mixmaster Universe dynamics on the
base of a standard Arnowitt-Deser-Misner Hamiltonian approach, showing the
covariant nature of its chaotic behaviour with respect to the choice of any
time variable, from the point of view either of the dynamical systems theory,
either of the statistical mechanics one.
| [
{
"created": "Thu, 31 Jan 2002 14:30:59 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Imponente",
"Giovanni",
""
],
[
"Montani",
"Giovanni",
""
]
] | We provide a Hamiltonian analysis of the Mixmaster Universe dynamics on the base of a standard Arnowitt-Deser-Misner Hamiltonian approach, showing the covariant nature of its chaotic behaviour with respect to the choice of any time variable, from the point of view either of the dynamical systems theory, either of the statistical mechanics one. |
gr-qc/9606059 | Roland Steinbauer | Roland Steinbauer | The ultrarelativistic Reissner-Nordstrom field in the Colombeau algebra | final version, minor grammatical changes | J.Math.Phys. 38 (1997) 1614-1622 | 10.1063/1.531819 | null | gr-qc math-ph math.MP | null | The electromagnetic field of the ultrarelativistic Reissner-Nordstrom
solution shows the physically highly unsatisfactory property of a vanishing
field tensor but a nonzero, i.e., delta-like, energy density. The aim of this
work is to analyze this situation from a mathematical point of view, using the
framework of Colombeau's theory of nonlinear generalized functions. It is shown
that the physically unsatisfactory situation is mathematically perfectly
defined and that one cannot aviod such situations when dealing with
distributional valued field tensors.
| [
{
"created": "Wed, 19 Jun 1996 10:01:09 GMT",
"version": "v1"
},
{
"created": "Mon, 24 Feb 1997 11:08:09 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Steinbauer",
"Roland",
""
]
] | The electromagnetic field of the ultrarelativistic Reissner-Nordstrom solution shows the physically highly unsatisfactory property of a vanishing field tensor but a nonzero, i.e., delta-like, energy density. The aim of this work is to analyze this situation from a mathematical point of view, using the framework of Colombeau's theory of nonlinear generalized functions. It is shown that the physically unsatisfactory situation is mathematically perfectly defined and that one cannot aviod such situations when dealing with distributional valued field tensors. |
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