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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9410020 | null | A. H. Bilge, M. Hortacsu, N. Ozdemir | Particle Creation If a Cosmic String Snaps | 10 pages, MRC.PH.17/94 | Gen.Rel.Grav. 28 (1996) 511-525 | 10.1007/BF02105062 | null | gr-qc | null | We calculate the Bogolubov coefficients for a metric which describes the
snapping of a cosmic string. If we insist on a matching condition for all times
{\it and} a particle interpretation, we find no particle creation.
| [
{
"created": "Mon, 17 Oct 1994 15:21:53 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Bilge",
"A. H.",
""
],
[
"Hortacsu",
"M.",
""
],
[
"Ozdemir",
"N.",
""
]
] | We calculate the Bogolubov coefficients for a metric which describes the snapping of a cosmic string. If we insist on a matching condition for all times {\it and} a particle interpretation, we find no particle creation. |
0705.1369 | R. R. Cuzinatto | R. Aldrovandi, R. R. Cuzinatto, L. G. Medeiros | Interacting Constituents in Cosmology | 24 pages, 6 figures. It includes results presented in "Cosmic
Acceleration from Elementary Interactions" [arXiv:gr-qc/0512135]. Citations
added in v.2 | Int.J.Mod.Phys.D17:857-879,2008 | 10.1142/S0218271808012541 | null | gr-qc | null | Universe evolution, as described by Friedmann's equations, is determined by
source terms fixed by the choice of pressure $\times$ energy-density equations
of state $p(\rho)$. The usual approach in Cosmology considers equations of
state accounting only for kinematic terms, ignoring the contribution from the
interactions between the particles constituting the source fluid. In this work
the importance of these neglected terms is emphasized. A systematic method,
based on the Statistical Mechanics of real fluids, is proposed to include them.
A toy-model is presented which shows how such interaction terms can engender
significant cosmological effects.
| [
{
"created": "Wed, 9 May 2007 22:21:46 GMT",
"version": "v1"
},
{
"created": "Tue, 22 May 2007 19:52:49 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Aldrovandi",
"R.",
""
],
[
"Cuzinatto",
"R. R.",
""
],
[
"Medeiros",
"L. G.",
""
]
] | Universe evolution, as described by Friedmann's equations, is determined by source terms fixed by the choice of pressure $\times$ energy-density equations of state $p(\rho)$. The usual approach in Cosmology considers equations of state accounting only for kinematic terms, ignoring the contribution from the interactions between the particles constituting the source fluid. In this work the importance of these neglected terms is emphasized. A systematic method, based on the Statistical Mechanics of real fluids, is proposed to include them. A toy-model is presented which shows how such interaction terms can engender significant cosmological effects. |
0705.1514 | Duncan Brown | Duncan A. Brown | Searching for Gravitational Radiation from Binary Black Hole MACHOs in
the Galactic Halo | 206 pages, 64 figures. Typos corrected in Eqs. (2.104), (2.108),
(2.124) and (4.3) | PhD Thesis, University of Wisconsin-Milwaukee, 2004 | null | LIGO-P050015-00-R | gr-qc | null | The Laser Interferometer Gravitational Wave Observatory (LIGO) is one of a
new generation of detectors of gravitational radiation. The existence of
gravitational radiation was first predicted by Einstein in 1916, however
gravitational waves have not yet been directly observed. One source of
gravitation radiation is binary inspiral. Two compact bodies orbiting each
other, such as a pair of black holes, lose energy to gravitational radiation.
As the system loses energy the bodies spiral towards each other. This causes
their orbital speed and the amount of gravitational radiation to increase,
producing a characteristic ``chirp'' waveform in the LIGO sensitive band. In
this thesis, matched filtering of LIGO science data is used to search for low
mass binary systems in the halo of dark matter surrounding the Milky Way.
Observations of gravitational microlensing events of stars in the Large
Magellanic Cloud suggest that some fraction of the dark matter in the halo may
be in the form of Massive Astrophysical Compact Halo Objects (MACHOs). It has
been proposed that low mass black holes formed in the early universe may be a
component of the MACHO population; some fraction of these black hole MACHOs
will be in binary systems and detectable by LIGO. The inspiral from a MACHO
binary composed of two 0.5 solar mass black holes enters the LIGO sensitive
band around 40 Hz. The chirp signal increases in amplitude and frequency,
sweeping through the sensitive band to 4400 Hz in 140 seconds. By using
evidence from microlensing events and theoretical predictions of the population
an upper limit is placed on the rate of black hole MACHO inspirals in the
galactic halo.
| [
{
"created": "Thu, 10 May 2007 16:48:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Brown",
"Duncan A.",
""
]
] | The Laser Interferometer Gravitational Wave Observatory (LIGO) is one of a new generation of detectors of gravitational radiation. The existence of gravitational radiation was first predicted by Einstein in 1916, however gravitational waves have not yet been directly observed. One source of gravitation radiation is binary inspiral. Two compact bodies orbiting each other, such as a pair of black holes, lose energy to gravitational radiation. As the system loses energy the bodies spiral towards each other. This causes their orbital speed and the amount of gravitational radiation to increase, producing a characteristic ``chirp'' waveform in the LIGO sensitive band. In this thesis, matched filtering of LIGO science data is used to search for low mass binary systems in the halo of dark matter surrounding the Milky Way. Observations of gravitational microlensing events of stars in the Large Magellanic Cloud suggest that some fraction of the dark matter in the halo may be in the form of Massive Astrophysical Compact Halo Objects (MACHOs). It has been proposed that low mass black holes formed in the early universe may be a component of the MACHO population; some fraction of these black hole MACHOs will be in binary systems and detectable by LIGO. The inspiral from a MACHO binary composed of two 0.5 solar mass black holes enters the LIGO sensitive band around 40 Hz. The chirp signal increases in amplitude and frequency, sweeping through the sensitive band to 4400 Hz in 140 seconds. By using evidence from microlensing events and theoretical predictions of the population an upper limit is placed on the rate of black hole MACHO inspirals in the galactic halo. |
1901.11262 | Sebastian V\"olkel | Sebastian H. V\"olkel and Kostas D. Kokkotas | On the Inverse Spectrum Problem of Neutron Stars | null | null | 10.1088/1361-6382/ab186e | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we revisit axial perturbations of spherically symmetric and
non-rotating neutron stars. Although it has been object of many studies, it
still offers new insights that are of potential interest for more realistic
scenarios or in the study exotic compact objects, which have drawn much
attention recently. By using WKB theory, we first derive a new Bohr-Sommerfeld
rule that allows to investigate the quasi-normal mode spectrum and address the
inverse spectrum problem. The pure analytical treatment of the wave equation is
rather involved, because it requires the solution of the TOV equations and the
non-trivial tortoise coordinate transformation depending on the underlying
space-time. Therefore we provide an easy way to construct potentials that
simplifies the analytical treatment, but still captures the relevant physics.
The approximated potential can be used for calculations of the axial
perturbation spectrum. These results are also useful in the treatment of the
inverse problem. We demonstrate this by reconstructing the time-time component
of the metric throughout the star and constraining the equation of state in the
central region. Our method also provides an analytical explanation of the
empirically known asteroseismology relation that connects the fundamental QNM
and radius of a neutron star with its compactness.
| [
{
"created": "Thu, 31 Jan 2019 08:32:10 GMT",
"version": "v1"
}
] | 2019-05-22 | [
[
"Völkel",
"Sebastian H.",
""
],
[
"Kokkotas",
"Kostas D.",
""
]
] | In this work we revisit axial perturbations of spherically symmetric and non-rotating neutron stars. Although it has been object of many studies, it still offers new insights that are of potential interest for more realistic scenarios or in the study exotic compact objects, which have drawn much attention recently. By using WKB theory, we first derive a new Bohr-Sommerfeld rule that allows to investigate the quasi-normal mode spectrum and address the inverse spectrum problem. The pure analytical treatment of the wave equation is rather involved, because it requires the solution of the TOV equations and the non-trivial tortoise coordinate transformation depending on the underlying space-time. Therefore we provide an easy way to construct potentials that simplifies the analytical treatment, but still captures the relevant physics. The approximated potential can be used for calculations of the axial perturbation spectrum. These results are also useful in the treatment of the inverse problem. We demonstrate this by reconstructing the time-time component of the metric throughout the star and constraining the equation of state in the central region. Our method also provides an analytical explanation of the empirically known asteroseismology relation that connects the fundamental QNM and radius of a neutron star with its compactness. |
gr-qc/9908040 | David Langlois | G. L. Comer, David Langlois, Lap Ming Lin | Quasi-Normal Modes of General Relativistic Superfluid Neutron Stars | 31 pages, RevTex, 17 figures | Phys.Rev. D60 (1999) 104025 | 10.1103/PhysRevD.60.104025 | null | gr-qc astro-ph | null | We develop a general formalism to treat, in general relativity, the linear
oscillations of a two-fluid star about static (non-rotating) configurations.
Such a formalism is intended for neutron stars, whose matter content can be
described, as a first approximation, by a two-fluid model: one fluid is the
neutron superfluid, which is believed to exist in the core and inner crust of
mature neutron stars; the other fluid is a conglomerate of all other
constituents (crust nuclei, protons, electrons, etc...). We obtain a system of
equations which govern the perturbations both of the metric and of the matter
variables, whatever the equation of state for the two fluids. As a first
application, we consider the simplified case of two non-interacting fluids,
each with a polytropic equation of state. We compute numerically the
quasi-normal modes (i.e. oscillations with purely outgoing gravitational
radiation) of the corresponding system. When the adiabatic indices of the two
fluids are different, we observe a splitting for each frequency of the
analogous single fluid spectrum. The analysis also substantiates the claim that
w-modes are largely due to spacetime oscillations.
| [
{
"created": "Thu, 12 Aug 1999 15:19:55 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Comer",
"G. L.",
""
],
[
"Langlois",
"David",
""
],
[
"Lin",
"Lap Ming",
""
]
] | We develop a general formalism to treat, in general relativity, the linear oscillations of a two-fluid star about static (non-rotating) configurations. Such a formalism is intended for neutron stars, whose matter content can be described, as a first approximation, by a two-fluid model: one fluid is the neutron superfluid, which is believed to exist in the core and inner crust of mature neutron stars; the other fluid is a conglomerate of all other constituents (crust nuclei, protons, electrons, etc...). We obtain a system of equations which govern the perturbations both of the metric and of the matter variables, whatever the equation of state for the two fluids. As a first application, we consider the simplified case of two non-interacting fluids, each with a polytropic equation of state. We compute numerically the quasi-normal modes (i.e. oscillations with purely outgoing gravitational radiation) of the corresponding system. When the adiabatic indices of the two fluids are different, we observe a splitting for each frequency of the analogous single fluid spectrum. The analysis also substantiates the claim that w-modes are largely due to spacetime oscillations. |
gr-qc/0603015 | Thomas Marlow | Thomas Marlow | Relationalism vs. Bayesianism | 13 pages | null | null | null | gr-qc | null | We compare and contrast the basic principles of two philosophies: Bayesianism
and relationalism. These two philosophies are both based upon criteria of
rationality. The analogy invoked in such a comparison seems rather apt when
discussing tentative proofs of quantum nonlocality. We argue that Bayesianism
is almost to quantum theory, what general covariance is to general relativity.
This is because the Bayesian interpretation of quantum theory can be given a
relational flavour.
| [
{
"created": "Tue, 7 Mar 2006 14:47:16 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Marlow",
"Thomas",
""
]
] | We compare and contrast the basic principles of two philosophies: Bayesianism and relationalism. These two philosophies are both based upon criteria of rationality. The analogy invoked in such a comparison seems rather apt when discussing tentative proofs of quantum nonlocality. We argue that Bayesianism is almost to quantum theory, what general covariance is to general relativity. This is because the Bayesian interpretation of quantum theory can be given a relational flavour. |
1906.09346 | Francesco Muia | Francesco Muia, Michele Cicoli, Katy Clough, Francisco Pedro, Fernando
Quevedo, Gian Paolo Vacca | The Fate of Dense Scalar Stars | null | null | 10.1088/1475-7516/2019/07/044 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Long-lived pseudo-solitonic objects, known as oscillons/oscillatons, which we
collectively call real scalar stars, are ubiquitous in early Universe cosmology
of scalar field theories. Typical examples are axions stars and moduli stars.
Using numerical simulations in full general relativity to include the effects
of gravity, we study the fate of real scalar stars and find that depending on
the scalar potential they are either meta-stable or collapse to black holes. In
particular we find that for KKLT potentials the configurations are meta-stable
despite the asymmetry of the potential, consistently with the results from
lattice simulations that do not include gravitational effects. For
$\alpha$-attractor potentials collapse to black holes is possible in a region
of the parameter space where scalar stars would instead seem to be meta-stable
or even disperse without including gravity. Each case gives rise to different
cosmological implications which may affect the stochastic spectrum of
gravitational waves.
| [
{
"created": "Fri, 21 Jun 2019 22:16:28 GMT",
"version": "v1"
}
] | 2019-08-07 | [
[
"Muia",
"Francesco",
""
],
[
"Cicoli",
"Michele",
""
],
[
"Clough",
"Katy",
""
],
[
"Pedro",
"Francisco",
""
],
[
"Quevedo",
"Fernando",
""
],
[
"Vacca",
"Gian Paolo",
""
]
] | Long-lived pseudo-solitonic objects, known as oscillons/oscillatons, which we collectively call real scalar stars, are ubiquitous in early Universe cosmology of scalar field theories. Typical examples are axions stars and moduli stars. Using numerical simulations in full general relativity to include the effects of gravity, we study the fate of real scalar stars and find that depending on the scalar potential they are either meta-stable or collapse to black holes. In particular we find that for KKLT potentials the configurations are meta-stable despite the asymmetry of the potential, consistently with the results from lattice simulations that do not include gravitational effects. For $\alpha$-attractor potentials collapse to black holes is possible in a region of the parameter space where scalar stars would instead seem to be meta-stable or even disperse without including gravity. Each case gives rise to different cosmological implications which may affect the stochastic spectrum of gravitational waves. |
2105.12313 | Shuo Xin | Shuo Xin, Baoyi Chen, Rico K. L. Lo, Ling Sun, Wen-Biao Han, Xingyu
Zhong, Manu Srivastava, Sizheng Ma, Qingwen Wang, and Yanbei Chen | Gravitational-wave echoes from spinning exotic compact objects:
numerical waveforms from the Teukolsky equation | null | null | 10.1103/PhysRevD.104.104005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present numerical waveforms of gravitational-wave echoes from spinning
exotic compact objects (ECOs) that result from binary black hole coalescence.
We obtain these echoes by solving the Teukolsky equation for the $\psi_4$
associated with gravitational waves that propagate toward the horizon of a Kerr
spacetime, and process the subsequent reflections of the horizon-going wave by
the surface of the ECO, which lies right above the Kerr horizon. The
trajectories of the infalling objects are modified from Kerr geodesics, such
that the gravitational waves propagating toward future null infinity match
those from merging black holes with comparable masses. In this way, the
corresponding echoes approximate to those from comparable-mass mergers. For
boundary conditions at the ECO surface, we adopt recent work using the membrane
paradigm, which relates $\psi_0$ associated with the horizon-going wave and
$\psi_4$ of the wave that leaves the ECO surface. We obtain $\psi_0$ of the
horizon-going wave from $\psi_4$ using the Teukolsky-Starobinsky relation. The
echoes we obtain turn out to be significantly weaker than those from previous
studies that generate echo waveforms by modeling the ringdown part of binary
black hole coalescence waveforms as originating from the past horizon.
| [
{
"created": "Wed, 26 May 2021 03:25:50 GMT",
"version": "v1"
}
] | 2021-11-10 | [
[
"Xin",
"Shuo",
""
],
[
"Chen",
"Baoyi",
""
],
[
"Lo",
"Rico K. L.",
""
],
[
"Sun",
"Ling",
""
],
[
"Han",
"Wen-Biao",
""
],
[
"Zhong",
"Xingyu",
""
],
[
"Srivastava",
"Manu",
""
],
[
"Ma",
"Sizheng",
""
],
[
"Wang",
"Qingwen",
""
],
[
"Chen",
"Yanbei",
""
]
] | We present numerical waveforms of gravitational-wave echoes from spinning exotic compact objects (ECOs) that result from binary black hole coalescence. We obtain these echoes by solving the Teukolsky equation for the $\psi_4$ associated with gravitational waves that propagate toward the horizon of a Kerr spacetime, and process the subsequent reflections of the horizon-going wave by the surface of the ECO, which lies right above the Kerr horizon. The trajectories of the infalling objects are modified from Kerr geodesics, such that the gravitational waves propagating toward future null infinity match those from merging black holes with comparable masses. In this way, the corresponding echoes approximate to those from comparable-mass mergers. For boundary conditions at the ECO surface, we adopt recent work using the membrane paradigm, which relates $\psi_0$ associated with the horizon-going wave and $\psi_4$ of the wave that leaves the ECO surface. We obtain $\psi_0$ of the horizon-going wave from $\psi_4$ using the Teukolsky-Starobinsky relation. The echoes we obtain turn out to be significantly weaker than those from previous studies that generate echo waveforms by modeling the ringdown part of binary black hole coalescence waveforms as originating from the past horizon. |
1502.00149 | Klaus Kassner | Klaus Kassner | Classroom reconstruction of the Schwarzschild metric | 14 pages, 2 figures; a shortened version (omitting the Rindler metric
part) has been submitted to and published in, the European Journal of Physics | K. Kassner, Eur. J. Phys. 36 (2015) 065031 | 10.1088/0143-0807/36/6/065031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A promising way to introduce general relativity in the classroom is to study
the physical implications of certain given metrics, such as the Schwarzschild
one. This involves lower mathematical expenditure than an approach focusing on
differential geometry in its full glory and permits to emphasize physical
aspects before attacking the field equations. Even so, in terms of motivation,
lacking justification of the metric employed may pose an obstacle. The paper
discusses how to establish the weak-field limit of the Schwarzschild metric
with a minimum of relatively simple physical assumptions, avoiding the field
equations but admitting the determination of a single parameter from
experiment. An attractive experimental candidate is the measurement of the
perihelion precession of Mercury, because the result was already known before
the completion of general relativity. It is shown how to determine the temporal
and radial coefficients of the Schwarzschild metric to sufficiently high
accuracy to obtain quantitative predictions for all the remaining classical
tests of general relativity.
| [
{
"created": "Sat, 31 Jan 2015 18:59:23 GMT",
"version": "v1"
},
{
"created": "Fri, 11 Sep 2015 16:12:55 GMT",
"version": "v2"
}
] | 2015-09-14 | [
[
"Kassner",
"Klaus",
""
]
] | A promising way to introduce general relativity in the classroom is to study the physical implications of certain given metrics, such as the Schwarzschild one. This involves lower mathematical expenditure than an approach focusing on differential geometry in its full glory and permits to emphasize physical aspects before attacking the field equations. Even so, in terms of motivation, lacking justification of the metric employed may pose an obstacle. The paper discusses how to establish the weak-field limit of the Schwarzschild metric with a minimum of relatively simple physical assumptions, avoiding the field equations but admitting the determination of a single parameter from experiment. An attractive experimental candidate is the measurement of the perihelion precession of Mercury, because the result was already known before the completion of general relativity. It is shown how to determine the temporal and radial coefficients of the Schwarzschild metric to sufficiently high accuracy to obtain quantitative predictions for all the remaining classical tests of general relativity. |
1709.04055 | Amin Salehi | Amin.Salehi and Mojtaba.Mahmoudi fard | Bouncing universe of entropy-corrected Friedmann equations | 16 pages, 20 figures | Eur. Phys. J. C (2018) 78:232 | 10.1140/epjc/s10052-018-5727-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The investigation of quantum gravity effects in order to avoid the big bang
singularity is a requisite, so that the idea of oscillating universes is
introduced as an alternative for standard cosmological model. Therefore, the
Friedmann equations arising from the quantum corrections of entropy-area
relation provide the possibility of studying the oscillating universes.
Addition to necessity of surveying the bouncing solutions, however, the values
of unknown constant parameters are still a matter of open debate. In this
paper, we consider modified Friedmann equations with logarithmic entropy
corrected to evaluate singular-free cosmology solutions for any value of so-
called constant pre-factors and all kinds of curved universes. The results are
argued using the dynamical system techniques and by employing the phase plane
analysis for full classification of the nonsingular evolutions.
| [
{
"created": "Tue, 12 Sep 2017 20:47:11 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Sep 2017 10:12:36 GMT",
"version": "v2"
}
] | 2018-04-18 | [
[
"Salehi",
"Amin.",
""
],
[
"fard",
"Mojtaba. Mahmoudi",
""
]
] | The investigation of quantum gravity effects in order to avoid the big bang singularity is a requisite, so that the idea of oscillating universes is introduced as an alternative for standard cosmological model. Therefore, the Friedmann equations arising from the quantum corrections of entropy-area relation provide the possibility of studying the oscillating universes. Addition to necessity of surveying the bouncing solutions, however, the values of unknown constant parameters are still a matter of open debate. In this paper, we consider modified Friedmann equations with logarithmic entropy corrected to evaluate singular-free cosmology solutions for any value of so- called constant pre-factors and all kinds of curved universes. The results are argued using the dynamical system techniques and by employing the phase plane analysis for full classification of the nonsingular evolutions. |
2210.06195 | David Brizuela | David Brizuela, Albert Duran-Cabac\'es | Relativistic effects on the Schr\"odinger-Newton equation | Version accepted for publication. We have added Refs. [20], [22],
[23], and [24], and corrected several typos in the bibliography. The new
Appendix B analyzes the effects produced by relativistic corrections in the
Poisson equation. We have also included several clarifications, in particular
in Sec. 2.2., to explain the validity of the model | Phys. Rev. D 106 (2022) 124038 | 10.1103/PhysRevD.106.124038 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Schr\"odinger-Newton model describes self-gravitating quantum particles,
and it is often cited to explain the gravitational collapse of the wave
function and the localization of macroscopic objects. However, this model is
completely nonrelativistic. Thus, in order to study whether the relativistic
effects may spoil the properties of this system, we derive a modification of
the Schr\"odinger-Newton equation by considering certain relativistic
corrections up to the first post-Newtonian order. The construction of the model
begins by considering the Hamiltonian of a relativistic particle propagating on
a curved background. For simplicity, the background metric is assumed to be
spherically symmetric and it is then expanded up to the first post-Newtonian
order. After performing the canonical quantization of the system, and following
the usual interpretation, the square of the module of the wave function defines
a mass distribution, which in turn is the source of the Poisson equation for
the gravitational potential. As in the nonrelativistic case, this construction
couples the Poisson and the Schr\"odinger equations and leads to a complicated
nonlinear system. Hence, the dynamics of an initial Gaussian wave packet is
then numerically analyzed. We observe that the natural dispersion of the wave
function is slower than in the nonrelativistic case. Furthermore, for those
cases that reach a final localized stationary state, the peak of the wave
function happens to be located at a smaller radius. Therefore, the relativistic
corrections effectively contribute to increase the self-gravitation of the
particle and strengthen the validity of this model as an explanation for the
gravitational localization of the wave function.
| [
{
"created": "Wed, 12 Oct 2022 13:27:46 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Jan 2023 13:22:52 GMT",
"version": "v2"
}
] | 2023-01-04 | [
[
"Brizuela",
"David",
""
],
[
"Duran-Cabacés",
"Albert",
""
]
] | The Schr\"odinger-Newton model describes self-gravitating quantum particles, and it is often cited to explain the gravitational collapse of the wave function and the localization of macroscopic objects. However, this model is completely nonrelativistic. Thus, in order to study whether the relativistic effects may spoil the properties of this system, we derive a modification of the Schr\"odinger-Newton equation by considering certain relativistic corrections up to the first post-Newtonian order. The construction of the model begins by considering the Hamiltonian of a relativistic particle propagating on a curved background. For simplicity, the background metric is assumed to be spherically symmetric and it is then expanded up to the first post-Newtonian order. After performing the canonical quantization of the system, and following the usual interpretation, the square of the module of the wave function defines a mass distribution, which in turn is the source of the Poisson equation for the gravitational potential. As in the nonrelativistic case, this construction couples the Poisson and the Schr\"odinger equations and leads to a complicated nonlinear system. Hence, the dynamics of an initial Gaussian wave packet is then numerically analyzed. We observe that the natural dispersion of the wave function is slower than in the nonrelativistic case. Furthermore, for those cases that reach a final localized stationary state, the peak of the wave function happens to be located at a smaller radius. Therefore, the relativistic corrections effectively contribute to increase the self-gravitation of the particle and strengthen the validity of this model as an explanation for the gravitational localization of the wave function. |
2303.11928 | Massimo Giovannini | Massimo Giovannini | Relic gravitons and high-frequency detectors | 43 pages, 13 figures; two corrections in two plots; comments added | null | 10.1088/1475-7516/2023/05/056 | null | gr-qc astro-ph.CO hep-ex hep-ph hep-th | http://creativecommons.org/licenses/by/4.0/ | Cosmic gravitons are expected in the MHz-GHz regions that are currently
unreachable by the operating wide-band interferometers and where various
classes of electromechanical detectors have been proposed through the years.
The minimal chirp amplitude detectable by these instruments is often set on the
basis of the sensitivities reachable by the detectors currently operating in
the audio band. By combining the observations of the pulsar timing arrays, the
limits from wide-band detectors and the other phenomenological bounds we show
that this requirement is far too generous and even misleading since the actual
detection of relic gravitons well above the kHz would demand chirp and spectral
amplitudes that are ten or even fifteen orders of magnitude smaller than the
ones currently achievable in the audio band, for the same classes of stochastic
sources. We then examine more closely the potential high-frequency signals and
show that the sensitivity in the chirp and spectral amplitudes must be even
smaller than the ones suggested by the direct and indirect constraints on the
cosmic gravitons. We finally analyze the high-frequency detectors in the
framework of Hanbury-Brown Twiss interferometry and argue that they are
actually more essential than the ones operating in the audio band (i.e. between
few Hz and few kHz) if we want to investigate the quantumness of the relic
gravitons and their associated second-order correlation effects. We suggest, in
particular, how the statistical properties of thermal and non-thermal gravitons
can be distinguished by studying the corresponding second-order interference
effects.
| [
{
"created": "Tue, 21 Mar 2023 15:29:10 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Jun 2023 20:50:47 GMT",
"version": "v2"
}
] | 2023-06-12 | [
[
"Giovannini",
"Massimo",
""
]
] | Cosmic gravitons are expected in the MHz-GHz regions that are currently unreachable by the operating wide-band interferometers and where various classes of electromechanical detectors have been proposed through the years. The minimal chirp amplitude detectable by these instruments is often set on the basis of the sensitivities reachable by the detectors currently operating in the audio band. By combining the observations of the pulsar timing arrays, the limits from wide-band detectors and the other phenomenological bounds we show that this requirement is far too generous and even misleading since the actual detection of relic gravitons well above the kHz would demand chirp and spectral amplitudes that are ten or even fifteen orders of magnitude smaller than the ones currently achievable in the audio band, for the same classes of stochastic sources. We then examine more closely the potential high-frequency signals and show that the sensitivity in the chirp and spectral amplitudes must be even smaller than the ones suggested by the direct and indirect constraints on the cosmic gravitons. We finally analyze the high-frequency detectors in the framework of Hanbury-Brown Twiss interferometry and argue that they are actually more essential than the ones operating in the audio band (i.e. between few Hz and few kHz) if we want to investigate the quantumness of the relic gravitons and their associated second-order correlation effects. We suggest, in particular, how the statistical properties of thermal and non-thermal gravitons can be distinguished by studying the corresponding second-order interference effects. |
gr-qc/0211089 | Allan Joseph Medved | Gilad Gour and A.J.M. Medved | Kerr Black Hole as a Quantum Rotator | 15 pages, Revtex | Class.Quant.Grav.20:2261-2274,2003 | 10.1088/0264-9381/20/11/321 | null | gr-qc hep-th quant-ph | null | It has been proposed by Bekenstein and others that the horizon area of a
black hole conforms, upon quantization, to a discrete and uniformly spaced
spectrum. In this paper, we consider the area spectrum for the highly
non-trivial case of a rotating (Kerr) black hole solution. Following a prior
work by Barvinsky, Das and Kunstatter, we are able to express the area spectrum
in terms of an integer-valued quantum number and an angular-momentum operator.
Moreover, by using an analogy between the Kerr black hole and a quantum
rotator, we are able to quantize the angular-momentum sector. We find the area
spectrum to be $A_{n,J_{cl}}=8\pi\hbar(n+J_{cl}+1/2)$, where $n$ and $J_{cl}$
are both integers. The quantum number $J_{cl}$ is related to but distinct from
the eigenvalue $j$ of the angular momentum of the black hole. Actually, it
represents the ``classical'' angular momentum and, for $J_{cl}\gg 1$,
$J_{cl}\approx j$.
| [
{
"created": "Tue, 26 Nov 2002 20:18:21 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Gour",
"Gilad",
""
],
[
"Medved",
"A. J. M.",
""
]
] | It has been proposed by Bekenstein and others that the horizon area of a black hole conforms, upon quantization, to a discrete and uniformly spaced spectrum. In this paper, we consider the area spectrum for the highly non-trivial case of a rotating (Kerr) black hole solution. Following a prior work by Barvinsky, Das and Kunstatter, we are able to express the area spectrum in terms of an integer-valued quantum number and an angular-momentum operator. Moreover, by using an analogy between the Kerr black hole and a quantum rotator, we are able to quantize the angular-momentum sector. We find the area spectrum to be $A_{n,J_{cl}}=8\pi\hbar(n+J_{cl}+1/2)$, where $n$ and $J_{cl}$ are both integers. The quantum number $J_{cl}$ is related to but distinct from the eigenvalue $j$ of the angular momentum of the black hole. Actually, it represents the ``classical'' angular momentum and, for $J_{cl}\gg 1$, $J_{cl}\approx j$. |
1506.00101 | Romain Gicquaud | Piotr Chru\'sciel and Romain Gicquaud | Bifurcating solutions of the Lichnerowicz equation | 33 pages, 25 figures | null | null | null | gr-qc math.AP math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We give an exhaustive description of bifurcations and of the number of
solutions of the vacuum Lichnerowicz equation with positive cosmological
constant on $S^1\times S^2$ with $U(1)\times SO(3)$-invariant seed data. The
resulting CMC slicings of Schwarzschild-de Sitter and Nariai are described.
| [
{
"created": "Sat, 30 May 2015 10:29:41 GMT",
"version": "v1"
},
{
"created": "Thu, 26 Nov 2015 10:07:03 GMT",
"version": "v2"
},
{
"created": "Mon, 11 Apr 2016 15:07:44 GMT",
"version": "v3"
}
] | 2016-04-12 | [
[
"Chruściel",
"Piotr",
""
],
[
"Gicquaud",
"Romain",
""
]
] | We give an exhaustive description of bifurcations and of the number of solutions of the vacuum Lichnerowicz equation with positive cosmological constant on $S^1\times S^2$ with $U(1)\times SO(3)$-invariant seed data. The resulting CMC slicings of Schwarzschild-de Sitter and Nariai are described. |
gr-qc/0608045 | Guihua Tian | Tian Gui-hua, Shi-kun Wang, Shuquan Zhong | The stable problem in the Rindler space-time | null | null | null | null | gr-qc | null | We carefully study the stable problem of the Rindler space time by the scalar
wave perturbation. Using the two different coordinate systems, the scalar wave
equation is investigated. The results are different in these two cases. They
are analyzed and compared in detail. The conclusions are: (a) the Rindler space
time as a whole is not stable; (b) the Rindler space time could exist stably
only as a part of the Minkowski space time, and the Minkowski space time could
be a real entity independently; (c) there are some defects for the scalar wave
equation written by the Rindler coordinates, and it is unsuitable for
investigation of the stable properties of the Rindler space time. All these
results might shed some lights on the stable properties of the Schwarzschild
black hole. It is natural and not unreasonable for one to infer that: (a)
perhaps the Regge-Wheeler equation is not sufficient to decide the stable
properties; (b) the Schwarzschild black hole as a whole might be really
unstable; (c) the Kruskal space time is stable and can exist as a real physical
entity ; whereas the Schwarzschild black hole could occur only as part of the
Kruskal space time.
| [
{
"created": "Wed, 9 Aug 2006 09:29:28 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Gui-hua",
"Tian",
""
],
[
"Wang",
"Shi-kun",
""
],
[
"Zhong",
"Shuquan",
""
]
] | We carefully study the stable problem of the Rindler space time by the scalar wave perturbation. Using the two different coordinate systems, the scalar wave equation is investigated. The results are different in these two cases. They are analyzed and compared in detail. The conclusions are: (a) the Rindler space time as a whole is not stable; (b) the Rindler space time could exist stably only as a part of the Minkowski space time, and the Minkowski space time could be a real entity independently; (c) there are some defects for the scalar wave equation written by the Rindler coordinates, and it is unsuitable for investigation of the stable properties of the Rindler space time. All these results might shed some lights on the stable properties of the Schwarzschild black hole. It is natural and not unreasonable for one to infer that: (a) perhaps the Regge-Wheeler equation is not sufficient to decide the stable properties; (b) the Schwarzschild black hole as a whole might be really unstable; (c) the Kruskal space time is stable and can exist as a real physical entity ; whereas the Schwarzschild black hole could occur only as part of the Kruskal space time. |
1803.02344 | Milko Estrada | Milko Estrada, Francisco Tello-Ortiz | A new family of analytical anisotropic solutions by gravitational
decoupling | null | Eur.Phys.J.Plus 133 (2018) no.11, 453 | 10.1140/epjp/i2018-12249-9 | null | gr-qc | http://creativecommons.org/licenses/by-sa/4.0/ | This work is focused in the study of analytic anisotropic solutions to
Einstein's field equations, describing spherically symmetric and static
configurations by way of the gravitational decoupling through the method of
Minimal Geometric Deformation (MGD). For this we apply MGD to Heintzmann's
solution obtaining two new analytic and well behaved anisotropic solutions, in
which all their parameters such as the effective density, the effective radial
and tangential pressure, as well as radial and tangential sound speed, fulfill
each of the requirements for the physical acceptability available in the
literature.
| [
{
"created": "Tue, 6 Mar 2018 18:57:11 GMT",
"version": "v1"
},
{
"created": "Sat, 7 Apr 2018 22:50:39 GMT",
"version": "v2"
},
{
"created": "Sat, 12 May 2018 23:49:42 GMT",
"version": "v3"
},
{
"created": "Mon, 27 Aug 2018 15:42:33 GMT",
"version": "v4"
}
] | 2019-03-27 | [
[
"Estrada",
"Milko",
""
],
[
"Tello-Ortiz",
"Francisco",
""
]
] | This work is focused in the study of analytic anisotropic solutions to Einstein's field equations, describing spherically symmetric and static configurations by way of the gravitational decoupling through the method of Minimal Geometric Deformation (MGD). For this we apply MGD to Heintzmann's solution obtaining two new analytic and well behaved anisotropic solutions, in which all their parameters such as the effective density, the effective radial and tangential pressure, as well as radial and tangential sound speed, fulfill each of the requirements for the physical acceptability available in the literature. |
gr-qc/9302012 | Gisele Murphy | Maximo Banados, Marc Henneaux, Claudio Teitelboim, Jorge Zanelli | Geometry of the 2+1 Black Hole | 51 pages, (LaTex file, figures not included, for hard copy figures,
contact: murphy@iassns.bitnet), Institute for Advanced Study #HEP.92/81 | Phys.Rev.D48:1506-1525,1993 | 10.1103/PhysRevD.48.1506 | null | gr-qc | null | The geometry of the spinning black holes of standard Einstein theory in 2+1
dimensions, with a negative cosmological constant and without couplings to
matter, is analyzed in detail. It is shown that the black hole arises from
identifications of points of anti-de Sitter space by a discrete subgroup of
$SO(2,2)$. The generic black hole is a smooth manifold in the metric sense. The
surface $r=0$ is not a curvature singularity but, rather, a singularity in the
causal structure. Continuing past it would introduce closed timelike lines.
However, simple examples show the regularity of the metric at $r=0$ to be
unstable: couplings to matter bring in a curvature singularity there. Kruskal
coordinates and Penrose diagrams are exhibited. Special attention is given to
the limiting cases of (i) the spinless hole of zero mass, which differs from
anti-de Sitter space and plays the role of the vacuum, and (ii) the spinning
hole of maximal angular momentum . A thorough classification of the elements of
the Lie algebra of $SO(2,2)$ is given in an Appendix.
| [
{
"created": "Wed, 10 Feb 1993 15:26:26 GMT",
"version": "v1"
}
] | 2009-12-30 | [
[
"Banados",
"Maximo",
""
],
[
"Henneaux",
"Marc",
""
],
[
"Teitelboim",
"Claudio",
""
],
[
"Zanelli",
"Jorge",
""
]
] | The geometry of the spinning black holes of standard Einstein theory in 2+1 dimensions, with a negative cosmological constant and without couplings to matter, is analyzed in detail. It is shown that the black hole arises from identifications of points of anti-de Sitter space by a discrete subgroup of $SO(2,2)$. The generic black hole is a smooth manifold in the metric sense. The surface $r=0$ is not a curvature singularity but, rather, a singularity in the causal structure. Continuing past it would introduce closed timelike lines. However, simple examples show the regularity of the metric at $r=0$ to be unstable: couplings to matter bring in a curvature singularity there. Kruskal coordinates and Penrose diagrams are exhibited. Special attention is given to the limiting cases of (i) the spinless hole of zero mass, which differs from anti-de Sitter space and plays the role of the vacuum, and (ii) the spinning hole of maximal angular momentum . A thorough classification of the elements of the Lie algebra of $SO(2,2)$ is given in an Appendix. |
2312.04723 | Gil de Oliveira-Neto | Vinicius G. Oliveira, Gil de Oliveira-Neto and Ilya L. Shapiro | Kantoswki-Sachs model with a running cosmological constant and radiation | The paper has 16 pages and 16 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The simplest anisotropic model of the early Universe is the one with two
conformal factors, which can be identified as Kantowski-Sachs metric, or the
reduced version of the Bianchi-I metric. To fit the existing observational
data, it is important that the anisotropy is washed out in the early stage of
the evolution. We explore the possible effect of the running cosmological
constant (RCC) on the dynamics of isotropy, in the case of the space filled by
radiation.
| [
{
"created": "Thu, 7 Dec 2023 22:06:41 GMT",
"version": "v1"
}
] | 2023-12-11 | [
[
"Oliveira",
"Vinicius G.",
""
],
[
"de Oliveira-Neto",
"Gil",
""
],
[
"Shapiro",
"Ilya L.",
""
]
] | The simplest anisotropic model of the early Universe is the one with two conformal factors, which can be identified as Kantowski-Sachs metric, or the reduced version of the Bianchi-I metric. To fit the existing observational data, it is important that the anisotropy is washed out in the early stage of the evolution. We explore the possible effect of the running cosmological constant (RCC) on the dynamics of isotropy, in the case of the space filled by radiation. |
gr-qc/0702140 | Eitan Bachmat | Eitan Bachmat | Discrete spacetime and its applications | null | null | null | null | gr-qc | null | We survey some results about the asymptotic behavior of discrete spacetime
models, which appeared in diverse settings in the physics and math literature.
We then discuss some recent applications, including scheduling in disk drives
and analysis of airplane boarding strategies.
| [
{
"created": "Tue, 27 Feb 2007 11:54:22 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bachmat",
"Eitan",
""
]
] | We survey some results about the asymptotic behavior of discrete spacetime models, which appeared in diverse settings in the physics and math literature. We then discuss some recent applications, including scheduling in disk drives and analysis of airplane boarding strategies. |
2209.02252 | Ryo Saito | Atsushi Naruko, Ryo Saito, Norihiro Tanahashi, Daisuke Yamauchi | Ostrogradsky mode in scalar-tensor theories with higher-order derivative
couplings to matter | 14+4 pages, no figures: published version: A typo in eq. (38) of the
first version is corrected. As a result, a broader class of the matter metric
becomes consistent with the degeneracy and invertible conditions | PTEP 2023 (2023) 5, 053E02 | 10.1093/ptep/ptad049 | YITP-22-94 | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | A metric transformation is a tool to find a new theory of gravity beyond
general relativity. The gravity action is guaranteed to be free from a
dangerous Ostrogradsky mode as long as the metric transformation is regular and
invertible. Various degenerate higher-order scalar-tensor theories (DHOST)
without extra degrees of freedom have been found through the metric
transformation with a scalar field and its derivatives. In this work, we
examine how a matter coupling changes the degeneracy for a theory generated
from the Horndeski theory through the metric transformation with the second
derivative of a scalar field, taking a minimally-coupled free scalar field as
the matter field. When the transformation is invertible, this theory is
equivalent to the Horndeski theory with a higher-order derivative coupling to
the matter scalar field. Working in this Horndeski frame and the unitary gauge,
we find that the degeneracy conditions are solvable and the matter metric must
have a certain structure to remove the Ostrogradsky mode.
| [
{
"created": "Tue, 6 Sep 2022 06:58:51 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Aug 2023 09:05:45 GMT",
"version": "v2"
}
] | 2023-08-07 | [
[
"Naruko",
"Atsushi",
""
],
[
"Saito",
"Ryo",
""
],
[
"Tanahashi",
"Norihiro",
""
],
[
"Yamauchi",
"Daisuke",
""
]
] | A metric transformation is a tool to find a new theory of gravity beyond general relativity. The gravity action is guaranteed to be free from a dangerous Ostrogradsky mode as long as the metric transformation is regular and invertible. Various degenerate higher-order scalar-tensor theories (DHOST) without extra degrees of freedom have been found through the metric transformation with a scalar field and its derivatives. In this work, we examine how a matter coupling changes the degeneracy for a theory generated from the Horndeski theory through the metric transformation with the second derivative of a scalar field, taking a minimally-coupled free scalar field as the matter field. When the transformation is invertible, this theory is equivalent to the Horndeski theory with a higher-order derivative coupling to the matter scalar field. Working in this Horndeski frame and the unitary gauge, we find that the degeneracy conditions are solvable and the matter metric must have a certain structure to remove the Ostrogradsky mode. |
gr-qc/0108061 | Jose Natario | Jose Natario | Linking and causality in (2+1)-dimensional static spacetimes | 13 pages, 3 figures; typos corrected, 2 figures added | Class.Quant.Grav. 19 (2002) 3115-3126 | 10.1088/0264-9381/19/12/301 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Given a (d+1)-dimensional spacetime (M,g), one can consider the set N of all
its null geodesics. If (M,g) is globally hyperbolic then this set is naturally
a smooth (2d-1)-manifold. The sky of an event x in M is the set X of all null
geodesics through x, and is an embedded submanifold of N diffeomorphic to
S^{d-1}. Low conjectured that if d=2 then x,y are causally related in M iff X,Y
are linked in N. We prove Low's conjecture for a (large) class of static
spacetimes.
| [
{
"created": "Fri, 24 Aug 2001 11:11:10 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Jul 2002 10:50:37 GMT",
"version": "v2"
},
{
"created": "Fri, 13 Jul 2012 16:20:10 GMT",
"version": "v3"
}
] | 2012-07-16 | [
[
"Natario",
"Jose",
""
]
] | Given a (d+1)-dimensional spacetime (M,g), one can consider the set N of all its null geodesics. If (M,g) is globally hyperbolic then this set is naturally a smooth (2d-1)-manifold. The sky of an event x in M is the set X of all null geodesics through x, and is an embedded submanifold of N diffeomorphic to S^{d-1}. Low conjectured that if d=2 then x,y are causally related in M iff X,Y are linked in N. We prove Low's conjecture for a (large) class of static spacetimes. |
gr-qc/9810065 | Thomas Baumgarte | Thomas W. Baumgarte and Stuart L. Shapiro | On the Numerical Integration of Einstein's Field Equations | 7 pages, 3 figures, RevTeX, to appear in Phys. Rev. D | Phys.Rev. D59 (1999) 024007 | 10.1103/PhysRevD.59.024007 | null | gr-qc astro-ph | null | Many numerical codes now under development to solve Einstein's equations of
general relativity in 3+1 dimensional spacetimes employ the standard ADM form
of the field equations. This form involves evolution equations for the raw
spatial metric and extrinsic curvature tensors. Following Shibata and Nakamura,
we modify these equations by factoring out the conformal factor and introducing
three ``connection functions''. The evolution equations can then be reduced to
wave equations for the conformal metric components, which are coupled to
evolution equations for the connection functions. We evolve small amplitude
gravitational waves and make a direct comparison of the numerical performance
of the modified equations with the standard ADM equations. We find that the
modified form exhibits much improved stability.
| [
{
"created": "Tue, 20 Oct 1998 14:51:23 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Baumgarte",
"Thomas W.",
""
],
[
"Shapiro",
"Stuart L.",
""
]
] | Many numerical codes now under development to solve Einstein's equations of general relativity in 3+1 dimensional spacetimes employ the standard ADM form of the field equations. This form involves evolution equations for the raw spatial metric and extrinsic curvature tensors. Following Shibata and Nakamura, we modify these equations by factoring out the conformal factor and introducing three ``connection functions''. The evolution equations can then be reduced to wave equations for the conformal metric components, which are coupled to evolution equations for the connection functions. We evolve small amplitude gravitational waves and make a direct comparison of the numerical performance of the modified equations with the standard ADM equations. We find that the modified form exhibits much improved stability. |
1906.10544 | Benrong Mu | Benrong Mu, Jun Tao and Peng Wang | Minimal Length Effect on Thermodynamics and Weak Cosmic Censorship
Conjecture in anti-de Sitter Black Holes via Charged Particle Absorption | 21 pages. version accepted for publication in AHEP | Advances in High Energy Physics, vol. 2020, Article ID 2612946, 9
pages, 2020 | 10.1155/2020/2612946 | CTP-SCU/2019008 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate minimal length effects on the thermodynamics
and weak cosmic censorship conjecture in a RN-AdS black bole via charged
particle absorption. We first use the generalized uncertainty principle (GUP)
to investigate the minimal length effect on the Hamilton-Jacobi equation. After
the deformed Hamilton-Jacobi equation is derived, we use it to study the
variations of the thermodynamic quantities of a RN-Ads black hole via absorbing
a charged practice. Furthermore, we check the second law of thermodynamics and
the weak cosmic censorship conjecture in two phase spaces. In the normal phase
space, the second law of thermodynamics and the weak cosmic censorship
conjecture are satisfied in the usual and GUP deformed cases, and the minimal
length effect makes the increase of entropy faster than the usual case. After
the charge particle absorption, the extremal RN-AdS black hole becomes
non-extremal. In the extended phase space, the black hole entropy can either
increase or decrease. When $T>2Pr_{+}$, the second law is satisfied. When
$T<2Pr_{+}$, the second law of thermodynamics is violated for the extremal or
near-extremal black hole. Finally, we find that the weak cosmic censorship
conjecture is legal for extremal and near-extremal RN-Ads black holes in the
GUP deformed case.
| [
{
"created": "Mon, 24 Jun 2019 12:40:11 GMT",
"version": "v1"
},
{
"created": "Thu, 27 Jun 2019 07:25:43 GMT",
"version": "v2"
},
{
"created": "Mon, 15 Mar 2021 08:34:50 GMT",
"version": "v3"
}
] | 2021-03-16 | [
[
"Mu",
"Benrong",
""
],
[
"Tao",
"Jun",
""
],
[
"Wang",
"Peng",
""
]
] | In this paper, we investigate minimal length effects on the thermodynamics and weak cosmic censorship conjecture in a RN-AdS black bole via charged particle absorption. We first use the generalized uncertainty principle (GUP) to investigate the minimal length effect on the Hamilton-Jacobi equation. After the deformed Hamilton-Jacobi equation is derived, we use it to study the variations of the thermodynamic quantities of a RN-Ads black hole via absorbing a charged practice. Furthermore, we check the second law of thermodynamics and the weak cosmic censorship conjecture in two phase spaces. In the normal phase space, the second law of thermodynamics and the weak cosmic censorship conjecture are satisfied in the usual and GUP deformed cases, and the minimal length effect makes the increase of entropy faster than the usual case. After the charge particle absorption, the extremal RN-AdS black hole becomes non-extremal. In the extended phase space, the black hole entropy can either increase or decrease. When $T>2Pr_{+}$, the second law is satisfied. When $T<2Pr_{+}$, the second law of thermodynamics is violated for the extremal or near-extremal black hole. Finally, we find that the weak cosmic censorship conjecture is legal for extremal and near-extremal RN-Ads black holes in the GUP deformed case. |
gr-qc/0401045 | Carlos O. Lousto | C. O. Lousto and R. H. Price | Radiation content of Conformally flat initial data | 4 pages, 4 figures | Phys.Rev. D69 (2004) 087503 | 10.1103/PhysRevD.69.087503 | UTBRG-2004-001 | gr-qc | null | We study the radiation of energy and linear momentum emitted to infinity by
the headon collision of binary black holes, starting from rest at a finite
initial separation, in the extreme mass ratio limit. For these configurations
we identify the radiation produced by the initially conformally flat choice of
the three geometry. This identification suggests that the radiated energy and
momentum of headon collisions will not be dominated by the details of the
initial data for evolution of holes from initial proper separations
$L_0\geq7M$. For non-headon orbits, where the amount of radiation is orders of
magnitude larger, the conformally flat initial data may provide a relative even
better approximation.
| [
{
"created": "Sun, 11 Jan 2004 20:12:48 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Lousto",
"C. O.",
""
],
[
"Price",
"R. H.",
""
]
] | We study the radiation of energy and linear momentum emitted to infinity by the headon collision of binary black holes, starting from rest at a finite initial separation, in the extreme mass ratio limit. For these configurations we identify the radiation produced by the initially conformally flat choice of the three geometry. This identification suggests that the radiated energy and momentum of headon collisions will not be dominated by the details of the initial data for evolution of holes from initial proper separations $L_0\geq7M$. For non-headon orbits, where the amount of radiation is orders of magnitude larger, the conformally flat initial data may provide a relative even better approximation. |
2103.11365 | Cosimo Bambi | Cosimo Bambi | Testing General Relativity with black hole X-ray data: recent progress
and future developments | 4 pages, 2 figures; contribution to the 2021 Gravitation session of
the 55th Rencontres de Moriond | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The theory of General Relativity has successfully passed a large number of
observational tests. The theory has been extensively tested in the weak-field
regime with experiments in the Solar System and observations of binary pulsars.
The past five years have seen significant advancements in the study of the
strong-field regime, which can now be tested with gravitational waves, X-ray
data, and mm Very Long Baseline Interferometry observations. Here I summarize
the state-of-the-art of the tests of General Relativity with black hole X-ray
data, discussing its recent progress and future developments.
| [
{
"created": "Sun, 21 Mar 2021 11:28:01 GMT",
"version": "v1"
}
] | 2021-03-23 | [
[
"Bambi",
"Cosimo",
""
]
] | The theory of General Relativity has successfully passed a large number of observational tests. The theory has been extensively tested in the weak-field regime with experiments in the Solar System and observations of binary pulsars. The past five years have seen significant advancements in the study of the strong-field regime, which can now be tested with gravitational waves, X-ray data, and mm Very Long Baseline Interferometry observations. Here I summarize the state-of-the-art of the tests of General Relativity with black hole X-ray data, discussing its recent progress and future developments. |
2301.02813 | Houri Ziaeepour | Houri Ziaeepour | \boldmath $SU(\infty)$ Quantum Gravity: Emergence of Gravity in an
Infinitely Divisible Quantum Universe | v4: more concise; QSL section extended | null | null | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | $SU(\infty)$-QGR is a foundationally quantum approach to gravity. It assumes
that the Hilbert space of the Universe as a whole represents the symmetry group
$SU(\infty)$, and demonstrates this symmetry for Hilbert spaces of infinite
number of subsystems that randomly emerge and represent arbitrary finite rank
internal symmetries. It is shown that their states depend on a dimensionful
parameter arising due to the breaking of a global $U(1)$ symmetry, and a
relative dynamics can be defined by selection of a subsystem as clock. The
action has the form of a Yang-Mills quantum field theory defined on the
(3+1)-dimensional parameter space for both $SU(\infty)$ - gravity - and
internal symmetries. Therefore, $SU(\infty)$-QGR is renormalizable, but
predicts a spin-1 mediator for quantum gravity. Nonetheless, it is proved that
when quantum gravity effects are not detectable, dynamics is similar to the
Einstein-Hilbert action. The aim of present work is in depth study of the
foundation and properties of this model. In particular, we show that the global
$SU(\infty)$ symmetry manifests itself through the entanglement of subsystems
with the rest of the Universe, and demonstrate irrelevance of geometry of the
parameter space for observables. Hence, $SU(\infty)$-QGR deviates from
gauge-gravity duality models, because the classical spacetime is an emergent
effective geometry with negative signature, reflecting relative variation of
quantum states of subsystems and quantum uncertainties. We also briefly discuss
$SU(\infty)$-QGR specific models for dark energy.
| [
{
"created": "Sat, 7 Jan 2023 09:19:15 GMT",
"version": "v1"
},
{
"created": "Sat, 21 Jan 2023 09:28:16 GMT",
"version": "v2"
},
{
"created": "Tue, 1 Aug 2023 07:17:16 GMT",
"version": "v3"
},
{
"created": "Thu, 4 Jul 2024 18:19:28 GMT",
"version": "v4"
}
] | 2024-07-08 | [
[
"Ziaeepour",
"Houri",
""
]
] | $SU(\infty)$-QGR is a foundationally quantum approach to gravity. It assumes that the Hilbert space of the Universe as a whole represents the symmetry group $SU(\infty)$, and demonstrates this symmetry for Hilbert spaces of infinite number of subsystems that randomly emerge and represent arbitrary finite rank internal symmetries. It is shown that their states depend on a dimensionful parameter arising due to the breaking of a global $U(1)$ symmetry, and a relative dynamics can be defined by selection of a subsystem as clock. The action has the form of a Yang-Mills quantum field theory defined on the (3+1)-dimensional parameter space for both $SU(\infty)$ - gravity - and internal symmetries. Therefore, $SU(\infty)$-QGR is renormalizable, but predicts a spin-1 mediator for quantum gravity. Nonetheless, it is proved that when quantum gravity effects are not detectable, dynamics is similar to the Einstein-Hilbert action. The aim of present work is in depth study of the foundation and properties of this model. In particular, we show that the global $SU(\infty)$ symmetry manifests itself through the entanglement of subsystems with the rest of the Universe, and demonstrate irrelevance of geometry of the parameter space for observables. Hence, $SU(\infty)$-QGR deviates from gauge-gravity duality models, because the classical spacetime is an emergent effective geometry with negative signature, reflecting relative variation of quantum states of subsystems and quantum uncertainties. We also briefly discuss $SU(\infty)$-QGR specific models for dark energy. |
1905.09390 | Alexandre Filippov | Alexandre T.Filippov | Constructing and solving cosmologies of early universes with dark energy
and matter. I | 25 pages, mostly `cosmetic' corrections on pages 1-5, 7, 16-17, 21-22 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The main purpose of this paper is to advance a unified theory of dark matter,
dark energy, and inflation first formulated in 2008. Our minimal affine
extension of the GR has geodesics coinciding with the pseudo Riemannian ones,
up to parameterizations. It predicts a `sterile' massive vecton and depends on
two new dimensional constants, which can be measured in the limit of small
vecton velocity. In a special gauge, this velocity has an upper limit near
which it grows to infinity. The linearized vecton theory is similar to the
scalar models of inflation except the fact of internal anisotropy of the
vecton. For this reason we study general solutions of scalar analogs of the
vecton theory without restricting the curvature parameter and anisotropy by
using previously derived exact solutions as functions of the metric. It is
shown that the effects of curvature and anisotropy fast decrease in expanding
universes. Our approach can be applied to anisotropic universes, which is
demonstrated on an exactly solvable strongly anisotropic cosmology. To
characterize different cosmological scenarios in detail we introduce three
characteristic functions, two of which are small and almost equal during
inflation and grow near the exit. Instead of the potential it is possible to
use one of the two characteristic functions. This allows to approximately
derive flat isotropic universes with `prescribed' scenarios, which is the
essence of our constructive cosmology of early universes. The most natural
application of our approach is in analytically constructing characteristic
functions of inflationary models with natural exits. However, the general
construction can be applied to other problems, e.g., to evolution of
contracting universes.
| [
{
"created": "Mon, 20 May 2019 18:55:31 GMT",
"version": "v1"
},
{
"created": "Sat, 29 Jun 2019 10:20:11 GMT",
"version": "v2"
}
] | 2019-07-02 | [
[
"Filippov",
"Alexandre T.",
""
]
] | The main purpose of this paper is to advance a unified theory of dark matter, dark energy, and inflation first formulated in 2008. Our minimal affine extension of the GR has geodesics coinciding with the pseudo Riemannian ones, up to parameterizations. It predicts a `sterile' massive vecton and depends on two new dimensional constants, which can be measured in the limit of small vecton velocity. In a special gauge, this velocity has an upper limit near which it grows to infinity. The linearized vecton theory is similar to the scalar models of inflation except the fact of internal anisotropy of the vecton. For this reason we study general solutions of scalar analogs of the vecton theory without restricting the curvature parameter and anisotropy by using previously derived exact solutions as functions of the metric. It is shown that the effects of curvature and anisotropy fast decrease in expanding universes. Our approach can be applied to anisotropic universes, which is demonstrated on an exactly solvable strongly anisotropic cosmology. To characterize different cosmological scenarios in detail we introduce three characteristic functions, two of which are small and almost equal during inflation and grow near the exit. Instead of the potential it is possible to use one of the two characteristic functions. This allows to approximately derive flat isotropic universes with `prescribed' scenarios, which is the essence of our constructive cosmology of early universes. The most natural application of our approach is in analytically constructing characteristic functions of inflationary models with natural exits. However, the general construction can be applied to other problems, e.g., to evolution of contracting universes. |
0906.5530 | Mariafelicia De Laurentis | Salvatore Capozziello, Mariafelicia De Laurentis, Luca Forte, Fabio
Garufi and Leopoldo Milano | Relativistic orbits and Gravitational Waves from gravitomagnetic
corrections | 6 pages, 10 figures; Multifrequency Behaviour of High-Energy Cosmic
Sources, Vulcano Workshop 2009 | J.Phys.Conf.Ser.228:012052,2010 | 10.1088/1742-6596/228/1/012052 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Corrections to the relativistic theory of orbits are discussed considering
higher order approximations induced by gravitomagnetic effects. Beside the
standard periastron effect of General Relativity (GR), a new nutation effect
was found due to the ${\displaystyle c^{-3}}$ orbital correction. According to
the presence of that new nutation effect we studied the gravitational waveforms
emitted through the capture in a gravitational field of a massive black hole
(MBH) of a compact object (neutron star (NS) or BH) via the quadrupole
approximation. We made a numerical study to obtain the emitted gravitational
wave (GW) amplitudes. We conclude that the effects we studied could be of
interest for the future space laser interferometric GW antenna LISA.
| [
{
"created": "Tue, 30 Jun 2009 14:08:18 GMT",
"version": "v1"
}
] | 2014-11-20 | [
[
"Capozziello",
"Salvatore",
""
],
[
"De Laurentis",
"Mariafelicia",
""
],
[
"Forte",
"Luca",
""
],
[
"Garufi",
"Fabio",
""
],
[
"Milano",
"Leopoldo",
""
]
] | Corrections to the relativistic theory of orbits are discussed considering higher order approximations induced by gravitomagnetic effects. Beside the standard periastron effect of General Relativity (GR), a new nutation effect was found due to the ${\displaystyle c^{-3}}$ orbital correction. According to the presence of that new nutation effect we studied the gravitational waveforms emitted through the capture in a gravitational field of a massive black hole (MBH) of a compact object (neutron star (NS) or BH) via the quadrupole approximation. We made a numerical study to obtain the emitted gravitational wave (GW) amplitudes. We conclude that the effects we studied could be of interest for the future space laser interferometric GW antenna LISA. |
2201.03584 | M Herrero-Valea | Francesco Del Porro, Mario Herrero-Valea, Stefano Liberati, Marc
Schneider | Time Orientability and Particle Production from Universal Horizons | 6 pages, new title, minor changes. Matches journal version | null | 10.1103/PhysRevD.105.104009 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss particle production in spacetimes endowed with a universal horizon
in Einstein--Aether and Horava gravity. We argue that continuity and
differentiability of the lapse function require the orientation of the
foliation in the interior of the horizon to be reversed with respect to the
exterior one. Unless this is allowed, interaction of gravitating scalar fields
with the universal horizon leads to unitarity violations in the quantum theory.
This property is responsible for particle production by the universal horizon,
as we show by computing explicitly its Hawking temperature for all stationary
and spherically symmetric spacetimes. We particularize our result to known
analytic solutions, including those compatible with observational constraints.
| [
{
"created": "Mon, 10 Jan 2022 19:00:07 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Jun 2022 08:03:47 GMT",
"version": "v2"
}
] | 2022-06-28 | [
[
"Del Porro",
"Francesco",
""
],
[
"Herrero-Valea",
"Mario",
""
],
[
"Liberati",
"Stefano",
""
],
[
"Schneider",
"Marc",
""
]
] | We discuss particle production in spacetimes endowed with a universal horizon in Einstein--Aether and Horava gravity. We argue that continuity and differentiability of the lapse function require the orientation of the foliation in the interior of the horizon to be reversed with respect to the exterior one. Unless this is allowed, interaction of gravitating scalar fields with the universal horizon leads to unitarity violations in the quantum theory. This property is responsible for particle production by the universal horizon, as we show by computing explicitly its Hawking temperature for all stationary and spherically symmetric spacetimes. We particularize our result to known analytic solutions, including those compatible with observational constraints. |
1908.01564 | Purba Mukherjee | Purba Mukherjee, Soumya Chakrabarti | Exact Solutions and Accelerating Universe in Modified Brans-Dicke
Theories | 12 pages, 10 figures, to appear in The European Physical Journal C
(Particles and Fields) | Eur. Phys. J. C (2019) 79:681 | 10.1140/epjc/s10052-019-7201-x | EPJC-19-06-153.R1 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Exact solutions are studied in the context of modified Brans-Dicke theory.
The non-linearity of the modified Brans-Dicke field equations is treated with
the Euler-Duarte-Moreira method of integrability of anharmonic oscillator
equation. While some solutions show a forever accelerating nature, in some
cases there is a signature flip in the evolution of deceleration parameter in
recent past. Importance of these latter models are studied in the context of
late-time acceleration of the universe. Constraints on the model parameters are
obtained from Markov Chain Monte Carlo (MCMC) analysis using the Supernova
distance modulus data, observational measurements of Hubble parameter, Baryon
acoustic oscillation data, and the CMB Shift parameter data.
| [
{
"created": "Mon, 5 Aug 2019 11:33:42 GMT",
"version": "v1"
}
] | 2019-08-19 | [
[
"Mukherjee",
"Purba",
""
],
[
"Chakrabarti",
"Soumya",
""
]
] | Exact solutions are studied in the context of modified Brans-Dicke theory. The non-linearity of the modified Brans-Dicke field equations is treated with the Euler-Duarte-Moreira method of integrability of anharmonic oscillator equation. While some solutions show a forever accelerating nature, in some cases there is a signature flip in the evolution of deceleration parameter in recent past. Importance of these latter models are studied in the context of late-time acceleration of the universe. Constraints on the model parameters are obtained from Markov Chain Monte Carlo (MCMC) analysis using the Supernova distance modulus data, observational measurements of Hubble parameter, Baryon acoustic oscillation data, and the CMB Shift parameter data. |
2311.05689 | Nikhil Sarin | Nikhil Sarin, Hiranya V. Peiris, Daniel J. Mortlock, Justin Alsing,
Samaya M. Nissanke, Stephen M. Feeney | Measuring the nuclear equation of state with neutron star-black hole
mergers | 10 pages, 4 Figures. Accepted in PRD | null | null | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | Gravitational-wave (GW) observations of neutron star-black hole (NSBH)
mergers are sensitive to the nuclear equation of state (EOS). We present a new
methodology for EOS inference with non-parametric Gaussian process (GP) priors,
enabling direct constraints on the pressure at specific densities and the
length-scale of correlations on the EOS. Using realistic simulations of NSBH
mergers, incorporating both GW and electromagnetic (EM) selection to ensure
sample purity, we find that a GW detector network operating at O5-sensitivities
will constrain the radius of a $\unit[1.4]{M_{\odot}}$ NS and the maximum NS
mass with $1.6\%$ and $13\%$ precision, respectively. With the same sample, the
projected constraint on the length-scale of correlations in the EOS is
$\geq~\unit[3.2]{MeV~fm^{-3}}$. These results demonstrate strong potential for
insights into the nuclear EOS from NSBH systems, provided they are robustly
identified.
| [
{
"created": "Thu, 9 Nov 2023 19:01:08 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Jul 2024 14:37:43 GMT",
"version": "v2"
}
] | 2024-07-10 | [
[
"Sarin",
"Nikhil",
""
],
[
"Peiris",
"Hiranya V.",
""
],
[
"Mortlock",
"Daniel J.",
""
],
[
"Alsing",
"Justin",
""
],
[
"Nissanke",
"Samaya M.",
""
],
[
"Feeney",
"Stephen M.",
""
]
] | Gravitational-wave (GW) observations of neutron star-black hole (NSBH) mergers are sensitive to the nuclear equation of state (EOS). We present a new methodology for EOS inference with non-parametric Gaussian process (GP) priors, enabling direct constraints on the pressure at specific densities and the length-scale of correlations on the EOS. Using realistic simulations of NSBH mergers, incorporating both GW and electromagnetic (EM) selection to ensure sample purity, we find that a GW detector network operating at O5-sensitivities will constrain the radius of a $\unit[1.4]{M_{\odot}}$ NS and the maximum NS mass with $1.6\%$ and $13\%$ precision, respectively. With the same sample, the projected constraint on the length-scale of correlations in the EOS is $\geq~\unit[3.2]{MeV~fm^{-3}}$. These results demonstrate strong potential for insights into the nuclear EOS from NSBH systems, provided they are robustly identified. |
gr-qc/0202008 | Christodoulakis Theodosios | T. Christodoulakis and G.O. Papadopoulos | Time-Dependent Automorphism Inducing Diffeomorphisms, Open Algebras and
the Generality of the Kantowski-Sachs Vacuum Geometry | 10 pages, no figures, LaTeX2e | Class.Quant.Grav.19:4855-4862,2002 | 10.1088/0264-9381/19/19/305 | null | gr-qc math-ph math.DG math.MP | null | Following the spirit of a previous work of ours, we investigate the group of
those General Coordinate Transformations (GCTs) which preserve manifest spatial
homogeneity. In contrast to the case of Bianchi Type Models we, here, permit an
isometry group of motions $G_{4}=SO(3)\otimes T_{r}$, where $T_{r}$ is the
translations group, along the radial direction, while SO(3) acts multiply
transitively on each hypersurface of simultaneity $\Sigma_{t}$. The basis
1-forms, can not be invariant under the action of the entire isometry group and
hence produce an Open Lie Algebra. In order for these GCTs to exist and have a
non trivial, well defined action, certain integrability conditions have to be
satisfied; their solutions, exhibiting the maximum expected ``gauge'' freedom,
can be used to simplify the generic, spatially homogeneous, line element. In
this way an alternative proof of the generality of the Kantowski-Sachs (KS)
vacuum is given, while its most general, manifestly homogeneous, form is
explicitly presented.
| [
{
"created": "Mon, 4 Feb 2002 12:15:56 GMT",
"version": "v1"
},
{
"created": "Thu, 6 Jun 2002 11:50:27 GMT",
"version": "v2"
}
] | 2009-10-09 | [
[
"Christodoulakis",
"T.",
""
],
[
"Papadopoulos",
"G. O.",
""
]
] | Following the spirit of a previous work of ours, we investigate the group of those General Coordinate Transformations (GCTs) which preserve manifest spatial homogeneity. In contrast to the case of Bianchi Type Models we, here, permit an isometry group of motions $G_{4}=SO(3)\otimes T_{r}$, where $T_{r}$ is the translations group, along the radial direction, while SO(3) acts multiply transitively on each hypersurface of simultaneity $\Sigma_{t}$. The basis 1-forms, can not be invariant under the action of the entire isometry group and hence produce an Open Lie Algebra. In order for these GCTs to exist and have a non trivial, well defined action, certain integrability conditions have to be satisfied; their solutions, exhibiting the maximum expected ``gauge'' freedom, can be used to simplify the generic, spatially homogeneous, line element. In this way an alternative proof of the generality of the Kantowski-Sachs (KS) vacuum is given, while its most general, manifestly homogeneous, form is explicitly presented. |
1301.3111 | Cecilia Chirenti | Cecilia Chirenti, Jozef Skakala and Shin'ichirou Yoshida | Slowly rotating neutron stars with small differential rotation:
equilibrium models and oscillations in the Cowling approximation | v3: 1 figure added, minor typos corrected, 12 pages, 12 figures,
final version to appear in PRD | Phys. Rev. D 87, 044043 (2013) | 10.1103/PhysRevD.87.044043 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Newly born neutron stars can present differential rotation, even if later it
should be suppressed by viscosity or a sufficiently strong magnetic field. And
in this early stage of its life, a neutron star is expected to have a strong
emission of gravitational waves, which could be influenced by the differential
rotation. We present here a new formalism for modelling differentially rotating
neutron stars: working on the slow rotation approximation and assuming a small
degree of differential rotation, we show that it is possible to separate
variables in the Einstein field equations. The dragging of inertial frames is
determined by solving three decoupled ODEs. After we establish our equilibrium
model, we explore the influence of the differential rotation on the f and
r-modes of oscillation of the neutron star in the Cowling approximation, and we
also analyze an effect of the differential rotation on the emission of
gravitational radiation from the f-modes. We see that the gravitational
radiation from the f-modes is slightly suppressed by introducing differential
rotation to the equilibrium stars.
| [
{
"created": "Mon, 14 Jan 2013 20:20:02 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Jan 2013 18:51:50 GMT",
"version": "v2"
},
{
"created": "Fri, 15 Feb 2013 14:49:45 GMT",
"version": "v3"
}
] | 2013-02-22 | [
[
"Chirenti",
"Cecilia",
""
],
[
"Skakala",
"Jozef",
""
],
[
"Yoshida",
"Shin'ichirou",
""
]
] | Newly born neutron stars can present differential rotation, even if later it should be suppressed by viscosity or a sufficiently strong magnetic field. And in this early stage of its life, a neutron star is expected to have a strong emission of gravitational waves, which could be influenced by the differential rotation. We present here a new formalism for modelling differentially rotating neutron stars: working on the slow rotation approximation and assuming a small degree of differential rotation, we show that it is possible to separate variables in the Einstein field equations. The dragging of inertial frames is determined by solving three decoupled ODEs. After we establish our equilibrium model, we explore the influence of the differential rotation on the f and r-modes of oscillation of the neutron star in the Cowling approximation, and we also analyze an effect of the differential rotation on the emission of gravitational radiation from the f-modes. We see that the gravitational radiation from the f-modes is slightly suppressed by introducing differential rotation to the equilibrium stars. |
0905.4097 | Tonatiuh Matos | Tonatiuh Matos, Galaxia Miranda, Ruben Sanchez-Sanchez and Petra
Wiederhold | Class of Einstein-Maxwell-Dilaton-Axion Space-Times | 12 pages, 2 figures 1 appendix | Phys.Rev.D79:124016,2009 | 10.1103/PhysRevD.79.124016 | CIEA/09-gr14 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We use the harmonic maps ansatz to find exact solutions of the
Einstein-Maxwell-Dilaton-Axion (EMDA) equations. The solutions are harmonic
maps invariant to the symplectic real group in four dimensions
$Sp(4,\Rreal)\sim O(5)$. We find solutions of the EMDA field equations for the
one and two dimensional subspaces of the symplectic group. Specially, for
illustration of the method, we find space-times that generalise the
Schwarzschild solution with dilaton, axion and electromagnetic fields.
| [
{
"created": "Tue, 26 May 2009 00:20:39 GMT",
"version": "v1"
}
] | 2010-04-30 | [
[
"Matos",
"Tonatiuh",
""
],
[
"Miranda",
"Galaxia",
""
],
[
"Sanchez-Sanchez",
"Ruben",
""
],
[
"Wiederhold",
"Petra",
""
]
] | We use the harmonic maps ansatz to find exact solutions of the Einstein-Maxwell-Dilaton-Axion (EMDA) equations. The solutions are harmonic maps invariant to the symplectic real group in four dimensions $Sp(4,\Rreal)\sim O(5)$. We find solutions of the EMDA field equations for the one and two dimensional subspaces of the symplectic group. Specially, for illustration of the method, we find space-times that generalise the Schwarzschild solution with dilaton, axion and electromagnetic fields. |
0811.2714 | Sergio Zerbini | Guido Cognola and Sergio Zerbini | Generalized modified gravity models: the stability issue | 10 pages, contribution to the anniversary volume "The Problems of
Modern Cosmology", on the occasion of the 50th birthday of Prof. S. D.
Odintsov. Editor: Prof. P. M. Lavrov, Tomsk State Pedagogical University | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A brief introduction on the issue of stability in generalized modified
gravity is presented and the dynamical system methods are used in the
investigation of the stability of spatially flat homogeneous cosmologies within
a large class of generalized modified gravity models in the presence of a
relativistic matter-radiation fluid.
| [
{
"created": "Mon, 17 Nov 2008 15:04:31 GMT",
"version": "v1"
}
] | 2008-11-18 | [
[
"Cognola",
"Guido",
""
],
[
"Zerbini",
"Sergio",
""
]
] | A brief introduction on the issue of stability in generalized modified gravity is presented and the dynamical system methods are used in the investigation of the stability of spatially flat homogeneous cosmologies within a large class of generalized modified gravity models in the presence of a relativistic matter-radiation fluid. |
0709.4257 | Alexis Larranaga | Alexis Larranaga | Thermodynamical Analogy Between BTZ Black Holes and Effective String
Theory | 6 pages. References updated | null | null | null | gr-qc | null | In this paper we study the first law of thermodynamics for the (2+1)
dimensional BTZ rotating black hole considering a pair of thermodinamical
systems constructed with the two horizons of this solution. We show that these
two systems are similar to the right and left movers of string theory and that
the temperature associated with the black hole is the harmonic mean of the
temperatures associated with these two systems.
| [
{
"created": "Wed, 26 Sep 2007 20:26:16 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Oct 2007 17:17:25 GMT",
"version": "v2"
}
] | 2007-10-09 | [
[
"Larranaga",
"Alexis",
""
]
] | In this paper we study the first law of thermodynamics for the (2+1) dimensional BTZ rotating black hole considering a pair of thermodinamical systems constructed with the two horizons of this solution. We show that these two systems are similar to the right and left movers of string theory and that the temperature associated with the black hole is the harmonic mean of the temperatures associated with these two systems. |
1606.05981 | Parthapratim Pradhan | Parthapratim Pradhan | Area products for ${\cal H}^{\pm}$ in AdS space | 20 pages, 6 figures | Galaxies 2017, 5(1), 10 | 10.3390/galaxies5010010 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive the thermodynamic products particularly area (or entropy) products
of ${\cal H}^{\pm}$ for certain class of black holes in AdS space. We show by
explicit and exact calculations that more complicated function of event horizon
area and Cauchy horizon area is indeed mass-independent. This mass-independent
quantities indicate that they \emph{could turn out to be an "universal"
quantity} provided that they depends only on the quantized angular momentum,
quantized charges, and cosmological constant respectively. Furthermore, these
area (or entropy) product relations for several class of black holes in AdS
space gives us strong indication to understanding the nature of non-extremal
black hole entropy (both inner and outer) at the microscopic level. Moreover,
we compute the Penrose's famous \emph{Cosmic Censorship Inequality} (which
requires Cosmic-Censorship hypothesis) for these class of black holes in AdS
space . Local thermodynamic stability has been discussed for these black holes
and under certain condition certain black holes displayed second order phase
transition.
| [
{
"created": "Mon, 20 Jun 2016 06:09:40 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Oct 2016 15:52:32 GMT",
"version": "v2"
}
] | 2017-02-07 | [
[
"Pradhan",
"Parthapratim",
""
]
] | We derive the thermodynamic products particularly area (or entropy) products of ${\cal H}^{\pm}$ for certain class of black holes in AdS space. We show by explicit and exact calculations that more complicated function of event horizon area and Cauchy horizon area is indeed mass-independent. This mass-independent quantities indicate that they \emph{could turn out to be an "universal" quantity} provided that they depends only on the quantized angular momentum, quantized charges, and cosmological constant respectively. Furthermore, these area (or entropy) product relations for several class of black holes in AdS space gives us strong indication to understanding the nature of non-extremal black hole entropy (both inner and outer) at the microscopic level. Moreover, we compute the Penrose's famous \emph{Cosmic Censorship Inequality} (which requires Cosmic-Censorship hypothesis) for these class of black holes in AdS space . Local thermodynamic stability has been discussed for these black holes and under certain condition certain black holes displayed second order phase transition. |
2304.12359 | Sapam Gayatri Devi | Sapam Gayatri Devi, I. Ablu Meitei, T. Ibungochouba Singh, Aheibam
Keshwarjit Singh and K. Yugindro Singh | Hawking radiation of rotating BTZ Black hole based on modified
dispersion relation and Rarita-Schwinger equation | 15 pages, 2 figures and submitted to International Journal of Modern
Physics A bearing revised manuscript number IJMPA-D-23-00039R1 | null | 10.1142/S0217751X23500689 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, tunneling of fermions from rotating BTZ black hole is
investigated using modified dispersion relation (MDR) and Rarita-Schwinger
equation. The effect of modified dispersion relation (MDR) on the tunneling of
fermions rises the Hawking temperature of rotating BTZ black hole. It is
observed that the modified Hawking temperature of the black hole depends not
only on the radial parameters of the black hole but also on the angular
parameters of the black hole and the coupling constant \sigma . Further, the
entropy and the heat capacity of the black hole are also studied.
| [
{
"created": "Mon, 24 Apr 2023 18:00:39 GMT",
"version": "v1"
}
] | 2023-08-09 | [
[
"Devi",
"Sapam Gayatri",
""
],
[
"Meitei",
"I. Ablu",
""
],
[
"Singh",
"T. Ibungochouba",
""
],
[
"Singh",
"Aheibam Keshwarjit",
""
],
[
"Singh",
"K. Yugindro",
""
]
] | In this paper, tunneling of fermions from rotating BTZ black hole is investigated using modified dispersion relation (MDR) and Rarita-Schwinger equation. The effect of modified dispersion relation (MDR) on the tunneling of fermions rises the Hawking temperature of rotating BTZ black hole. It is observed that the modified Hawking temperature of the black hole depends not only on the radial parameters of the black hole but also on the angular parameters of the black hole and the coupling constant \sigma . Further, the entropy and the heat capacity of the black hole are also studied. |
gr-qc/0407076 | Lawrence P. Horwitz | Lawrence P. Horwitz and Ori Oron | Classical Gravity as an Eikonal Approximation to a Manifestly Lorentz
Covariant Quantum Theory with Brownian Interpretation | 46 pages, PLain TeX. To be published in "Progress in General
Relativity and Quantum Cosmology Research". Hauppage (2004) | null | null | YAUP 2775-04 | gr-qc | null | We discuss in this Chapter a series of theoretical developments which
motivate the introduction of a quantum evolution equation for which the eikonal
approximation results in the geodesics of a four dimensional manifold. This
geodesic motion can be put into correspondence with general relativity. One
obtains in this way a quantum theory on a flat spacetime, obeying the rules of
the standard quantum theory in Lorentz covariant form, with a spacetime
dependent Lorentz tensor $g_{\mu\nu}$, somewhat analogous to a gauge field,
coupling to the kinetic terms. Since the geodesics predicted by the eikonal
approximation, with appropriate choice of $g_{\mu\nu}$, can be those of general
relativity, this theory provides a quantum theory which could be underlying to
classical gravitation, and coincides with it in this classical ray
approximation. In order to understand the possible origin of the structure of
this equation, we appeal to the approach of Nelson in constructing a
Schroedinger equation from the properties of Brownian motion. Extending the
notion of Browninan motion to spacetime in a covariant way, we show that such
an equation follows from correlations between spacetime dimensions in the
stochastic process.
| [
{
"created": "Tue, 20 Jul 2004 08:58:22 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Horwitz",
"Lawrence P.",
""
],
[
"Oron",
"Ori",
""
]
] | We discuss in this Chapter a series of theoretical developments which motivate the introduction of a quantum evolution equation for which the eikonal approximation results in the geodesics of a four dimensional manifold. This geodesic motion can be put into correspondence with general relativity. One obtains in this way a quantum theory on a flat spacetime, obeying the rules of the standard quantum theory in Lorentz covariant form, with a spacetime dependent Lorentz tensor $g_{\mu\nu}$, somewhat analogous to a gauge field, coupling to the kinetic terms. Since the geodesics predicted by the eikonal approximation, with appropriate choice of $g_{\mu\nu}$, can be those of general relativity, this theory provides a quantum theory which could be underlying to classical gravitation, and coincides with it in this classical ray approximation. In order to understand the possible origin of the structure of this equation, we appeal to the approach of Nelson in constructing a Schroedinger equation from the properties of Brownian motion. Extending the notion of Browninan motion to spacetime in a covariant way, we show that such an equation follows from correlations between spacetime dimensions in the stochastic process. |
2406.18604 | Jitendra Kumar Dr. | Sourav Chaudharya, Sunil Kumar Maurya, Jitendra Kumara, Ghulam Mustafa | Most general isotropic charged fluid solution for Buchdahl model in
$\mathscr{F}(Q)$ gravity | 11 figures and 5 Tables | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this work, we investigated a most general isotropic charged fluid solution
for the Buchdahl model via a two-step method in $\mathscr{F}(Q)$-gravity
framework for the first time. In this context, a linear function of the form
$\mathscr{F}(Q)=\zeta_1 Q+\zeta_2$ and a particular transformation is used to
solve the Einstein-Maxwell Equations (EMEs) employing the Buchdahl ansatz: $
e^{\Upsilon(r)}=\frac{\mu(1+\lambda r^2)}{\mu+\lambda r^2}$, where $\zeta_1$,
$\zeta_2$, $\lambda$ and $\mu$ are constant parameters. The Schwarzschild de
Sitter~(AdS) exterior solution is joined to the interior solution at the
boundary to determine the constant parameters. It should be emphasized that,
for a given transformation, the Buchdahl ansatz only offers a mathematically
feasible solution in the context of electric charge, where pressure and density
are maximum at the center and decrease monotonically towards the boundary when
$0<\mu<1$. We taken into account the compact star EX01785-248 with $M=(1.3\pm
0.2)M_{\odot}$; Radius $=12.02^{+0.55}_{-0.55}$~km for graphical analysis. The
physical acceptability of the model in the context of $\mathscr{F}(Q)$ has been
evaluated by looking at the necessary physical properties, including energy
conditions, causality, hydrostatic equilibrium, pressure-density ratio, etc.
Additionally, we predicted the maximum mass limit of different compact objects
for various parameter values along with the mass-radius relation. The maximum
masses range (1.927 - 2.321)~$M_\odot$ are obtained for our solution. It can be
observed that when the coupling parameter $\zeta_1$ for $\mathscr{F}(Q)$
gravity is smaller, then our solution yields massive stars. The present
investigation provides novel insights and realistic implications regarding the
formation of compact astrophysical objects.
| [
{
"created": "Thu, 20 Jun 2024 01:33:46 GMT",
"version": "v1"
}
] | 2024-06-28 | [
[
"Chaudharya",
"Sourav",
""
],
[
"Maurya",
"Sunil Kumar",
""
],
[
"Kumara",
"Jitendra",
""
],
[
"Mustafa",
"Ghulam",
""
]
] | In this work, we investigated a most general isotropic charged fluid solution for the Buchdahl model via a two-step method in $\mathscr{F}(Q)$-gravity framework for the first time. In this context, a linear function of the form $\mathscr{F}(Q)=\zeta_1 Q+\zeta_2$ and a particular transformation is used to solve the Einstein-Maxwell Equations (EMEs) employing the Buchdahl ansatz: $ e^{\Upsilon(r)}=\frac{\mu(1+\lambda r^2)}{\mu+\lambda r^2}$, where $\zeta_1$, $\zeta_2$, $\lambda$ and $\mu$ are constant parameters. The Schwarzschild de Sitter~(AdS) exterior solution is joined to the interior solution at the boundary to determine the constant parameters. It should be emphasized that, for a given transformation, the Buchdahl ansatz only offers a mathematically feasible solution in the context of electric charge, where pressure and density are maximum at the center and decrease monotonically towards the boundary when $0<\mu<1$. We taken into account the compact star EX01785-248 with $M=(1.3\pm 0.2)M_{\odot}$; Radius $=12.02^{+0.55}_{-0.55}$~km for graphical analysis. The physical acceptability of the model in the context of $\mathscr{F}(Q)$ has been evaluated by looking at the necessary physical properties, including energy conditions, causality, hydrostatic equilibrium, pressure-density ratio, etc. Additionally, we predicted the maximum mass limit of different compact objects for various parameter values along with the mass-radius relation. The maximum masses range (1.927 - 2.321)~$M_\odot$ are obtained for our solution. It can be observed that when the coupling parameter $\zeta_1$ for $\mathscr{F}(Q)$ gravity is smaller, then our solution yields massive stars. The present investigation provides novel insights and realistic implications regarding the formation of compact astrophysical objects. |
1002.1737 | Luc Nguyen | Piotr T. Chru\'sciel and Luc Nguyen | A uniqueness theorem for degenerate Kerr-Newman black holes | null | Ann. Henri Poincar\'e 11 (2010), no. 4, 585-609 | 10.1007/s00023-010-0038-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that the domains of dependence of stationary, $I^+$-regular,
analytic, electrovacuum space-times with a connected, non-empty, rotating,
degenerate event horizon arise from Kerr-Newman space-times.
| [
{
"created": "Mon, 8 Feb 2010 23:19:01 GMT",
"version": "v1"
}
] | 2014-10-14 | [
[
"Chruściel",
"Piotr T.",
""
],
[
"Nguyen",
"Luc",
""
]
] | We show that the domains of dependence of stationary, $I^+$-regular, analytic, electrovacuum space-times with a connected, non-empty, rotating, degenerate event horizon arise from Kerr-Newman space-times. |
1212.0629 | Sumati Surya | Surbhi Khetrapal and Sumati Surya | Boundary Term Contribution to the Volume of a Small Causal Diamond | 18 pages, 2 figures | null | 10.1088/0264-9381/30/6/065005 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In his calculation of the spacetime volume of a small Alexandrov interval in
4 dimensions Myrheim introduced a term which he referred to as a surface
integral [1]. The evaluation of this term has remained opaque and led
subsequent authors to evaluate the volume using other techniques [2]. It is the
purpose of this work to demystify this integral. We point out that it arises
from the difference in the flat spacetime volumes of the curved and flat
spacetime intervals. An explicit evaluation using first order degenerate
perturbation theory shows that it adds a dimension independent factor to the
flat spacetime volume as the lowest order correction. Our analysis admits a
simple extension to a more general class of integrals over the same domain.
Using a combination of techniques we also find that the next order correction
to the volume vanishes.
| [
{
"created": "Tue, 4 Dec 2012 07:23:30 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Khetrapal",
"Surbhi",
""
],
[
"Surya",
"Sumati",
""
]
] | In his calculation of the spacetime volume of a small Alexandrov interval in 4 dimensions Myrheim introduced a term which he referred to as a surface integral [1]. The evaluation of this term has remained opaque and led subsequent authors to evaluate the volume using other techniques [2]. It is the purpose of this work to demystify this integral. We point out that it arises from the difference in the flat spacetime volumes of the curved and flat spacetime intervals. An explicit evaluation using first order degenerate perturbation theory shows that it adds a dimension independent factor to the flat spacetime volume as the lowest order correction. Our analysis admits a simple extension to a more general class of integrals over the same domain. Using a combination of techniques we also find that the next order correction to the volume vanishes. |
0911.0756 | Vladimir S. Manko | I. Cabrera-Munguia, V.S. Manko, E. Ruiz | A combined Majumdar-Papapetrou-Bonnor field as extreme limit of the
double-Reissner-Nordstrom solution | 10 pages, 3 figures, title changed, the result extended, matching the
published version | Gen. Rel. Grav. 43:1593-1606,2011 | 10.1007/s10714-011-1142-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The general extreme limit of the double-Reissner-Nordstrom solution is worked
out in explicit analytical form involving prolate spheroidal coordinates. We
name it the combined Majumdar-Papapetrou-Bonnor field to underline the fact
that it contains as particular cases the two-body specialization of the
well-known Majumdar-Papapetrou solution and Bonnor's three-parameter
electrostatic field. To the latter we give a precise physical interpretation as
describing a pair of non-rotating extremal black holes with unequal masses and
unequal opposite charges kept apart by a strut, the absolute values of charges
exceeding the respective (positive) values of masses.
| [
{
"created": "Wed, 4 Nov 2009 09:33:52 GMT",
"version": "v1"
},
{
"created": "Fri, 13 May 2011 23:31:51 GMT",
"version": "v2"
}
] | 2011-07-26 | [
[
"Cabrera-Munguia",
"I.",
""
],
[
"Manko",
"V. S.",
""
],
[
"Ruiz",
"E.",
""
]
] | The general extreme limit of the double-Reissner-Nordstrom solution is worked out in explicit analytical form involving prolate spheroidal coordinates. We name it the combined Majumdar-Papapetrou-Bonnor field to underline the fact that it contains as particular cases the two-body specialization of the well-known Majumdar-Papapetrou solution and Bonnor's three-parameter electrostatic field. To the latter we give a precise physical interpretation as describing a pair of non-rotating extremal black holes with unequal masses and unequal opposite charges kept apart by a strut, the absolute values of charges exceeding the respective (positive) values of masses. |
2406.06091 | Andrea Pierfrancesco Sanna | Mariano Cadoni, Mirko Pitzalis, Davi C. Rodrigues and Andrea P. Sanna | Cosmological coupling of local gravitational systems | 27 pages, 7 figures. Some typos corrected, one reference added | null | null | null | gr-qc astro-ph.GA | http://creativecommons.org/licenses/by/4.0/ | We investigate the cosmological coupling of spherical, local astrophysical
systems. We derive a general formula quantifying the cosmological coupling of
the Misner-Sharp mass of these objects. We show that, in the weak-field limit,
the cosmological coupling is only allowed if there are pressure anisotropies.
We also apply our results to galaxies, modelling them with the
Navarro-Frenk-White and Einasto profiles. We show that the galactic mass can be
coupled to the cosmological dynamics and examine its dependence on the scale
factor of the universe.
| [
{
"created": "Mon, 10 Jun 2024 08:20:24 GMT",
"version": "v1"
},
{
"created": "Sun, 16 Jun 2024 14:18:38 GMT",
"version": "v2"
}
] | 2024-06-18 | [
[
"Cadoni",
"Mariano",
""
],
[
"Pitzalis",
"Mirko",
""
],
[
"Rodrigues",
"Davi C.",
""
],
[
"Sanna",
"Andrea P.",
""
]
] | We investigate the cosmological coupling of spherical, local astrophysical systems. We derive a general formula quantifying the cosmological coupling of the Misner-Sharp mass of these objects. We show that, in the weak-field limit, the cosmological coupling is only allowed if there are pressure anisotropies. We also apply our results to galaxies, modelling them with the Navarro-Frenk-White and Einasto profiles. We show that the galactic mass can be coupled to the cosmological dynamics and examine its dependence on the scale factor of the universe. |
gr-qc/0302113 | Kenji Sakamoto | Kenji Sakamoto, Kiyoshi Shiraishi (Yamaguchi University) | Quantum Scattering in Two Black Hole Moduli Space | 15 pages, 19 figures, RevTeX 3.0 | Phys.Rev. D68 (2003) 025019 | 10.1103/PhysRevD.68.025019 | null | gr-qc hep-th | null | We discuss the quantum scattering process in the moduli space consisting of
two maximally charged dilaton black holes. The black hole moduli space geometry
has different structures for arbitrary dimensions and various values of dilaton
coupling. We study the quantum effects of the different moduli space geometries
with scattering process. Then, it is found that there is a resonance state on
certain moduli spaces.
| [
{
"created": "Thu, 27 Feb 2003 08:25:44 GMT",
"version": "v1"
},
{
"created": "Thu, 1 May 2003 08:06:54 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Sakamoto",
"Kenji",
"",
"Yamaguchi University"
],
[
"Shiraishi",
"Kiyoshi",
"",
"Yamaguchi University"
]
] | We discuss the quantum scattering process in the moduli space consisting of two maximally charged dilaton black holes. The black hole moduli space geometry has different structures for arbitrary dimensions and various values of dilaton coupling. We study the quantum effects of the different moduli space geometries with scattering process. Then, it is found that there is a resonance state on certain moduli spaces. |
2003.07436 | Luis Herrera | L. Herrera | Landauer Principle and General Relativity | Published in the special issue of Entropy: The Landauer Principle:
Meaning, Physical Roots and Applications | Entropy, 22, 340, (2020) | 10.3390/e22030340 | null | gr-qc physics.class-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We endeavour to illustrate the physical relevance of the Landauer principle
applying it to different important issues concerning the theory of gravitation.
We shall first analyze, in the context of general relativity, the consequences
derived from the fact, implied by Landauer principle, that information has
mass. Next, we shall analyze the role played by the Landauer principle in order
to understand why different congruences of observers provide very different
physical descriptions of the same space--time. Finally, we shall apply the
Landauer principle to the problem of gravitational radiation. We shall see that
the fact that gravitational radiation is an irreversible process entailing
dissipation, is a straightforward consequence of the Landauer principle and of
the fact that gravitational radiation conveys information. An expression
measuring the part of radiated energy that corresponds to the radiated
information and an expression defining the total number of bits erased in that
process, shall be obtained, as well as an explicit expression linking the
latter to the Bondi news function.
| [
{
"created": "Mon, 16 Mar 2020 20:41:26 GMT",
"version": "v1"
}
] | 2020-04-22 | [
[
"Herrera",
"L.",
""
]
] | We endeavour to illustrate the physical relevance of the Landauer principle applying it to different important issues concerning the theory of gravitation. We shall first analyze, in the context of general relativity, the consequences derived from the fact, implied by Landauer principle, that information has mass. Next, we shall analyze the role played by the Landauer principle in order to understand why different congruences of observers provide very different physical descriptions of the same space--time. Finally, we shall apply the Landauer principle to the problem of gravitational radiation. We shall see that the fact that gravitational radiation is an irreversible process entailing dissipation, is a straightforward consequence of the Landauer principle and of the fact that gravitational radiation conveys information. An expression measuring the part of radiated energy that corresponds to the radiated information and an expression defining the total number of bits erased in that process, shall be obtained, as well as an explicit expression linking the latter to the Bondi news function. |
gr-qc/9901005 | Garcia | L.C.Garcia de Andrade | On non-Riemannian Superconductors and torsion loops | Latex file,6 pages | null | null | null | gr-qc | null | The geometrization of electrodynamics is obtained by performing the complex
extension of the covariant derivative operator to include the Cartan torsion
vector and applying this derivative to the Ginzburg-Landau equation of
superfluids and Superconductors.It is shown that the introduction of torsion
makes a shift in the symmetry breaking vacuum.Torsion loops are computed from
geometrical phases outside the superconductor.Inside the superconductor the
torsion vanishes which represents the Meissner effect for torsion geometry.
Torsion in general equals the London supercurrent.It is possible to place a
limit on the size of superconductor needed to give an estimate to torsion.
| [
{
"created": "Mon, 4 Jan 1999 17:38:33 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"de Andrade",
"L. C. Garcia",
""
]
] | The geometrization of electrodynamics is obtained by performing the complex extension of the covariant derivative operator to include the Cartan torsion vector and applying this derivative to the Ginzburg-Landau equation of superfluids and Superconductors.It is shown that the introduction of torsion makes a shift in the symmetry breaking vacuum.Torsion loops are computed from geometrical phases outside the superconductor.Inside the superconductor the torsion vanishes which represents the Meissner effect for torsion geometry. Torsion in general equals the London supercurrent.It is possible to place a limit on the size of superconductor needed to give an estimate to torsion. |
1409.2688 | Cornelius Rampf | Cornelius Rampf and Alexander Wiegand | Relativistic Lagrangian displacement field and tensor perturbations | 19 pages, two figures, improved discussion, matches published version | Phys. Rev. D 90, 123503 (2014) | 10.1103/PhysRevD.90.123503 | AEI-2014-043 | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the purely spatial Lagrangian coordinate transformation from
the Lagrangian to the basic Eulerian frame. We demonstrate three techniques for
extracting the relativistic displacement field from a given solution in the
Lagrangian frame. These techniques are (a) from defining a local set of
Eulerian coordinates embedded into the Lagrangian frame; (b) from performing a
specific gauge transformation; and (c) from a fully non-perturbative approach
based on the ADM split. The latter approach shows that this decomposition is
not tied to a specific perturbative formulation for the solution of the
Einstein equations. Rather, it can be defined at the level of the
non-perturbative coordinate change from the Lagrangian to the Eulerian
description. Studying such different techniques is useful because it allows us
to compare and develop further the various approximation techniques available
in the Lagrangian formulation. We find that one has to solve the gravitational
wave equation in the relativistic analysis, otherwise the corresponding
Newtonian limit will necessarily contain spurious non-propagating tensor
artefacts at second order in the Eulerian frame. We also derive the magnetic
part of the Weyl tensor in the Lagrangian frame, and find that it is not only
excited by gravitational waves but also by tensor perturbations which are
induced through the non-linear frame-dragging. We apply our findings to
calculate for the first time the relativistic displacement field, up to second
order, for a $\Lambda$CDM Universe in the presence of a local primordial
non-Gaussian component. Finally, we also comment on recent claims about whether
mass conservation in the Lagrangian frame is violated.
| [
{
"created": "Fri, 5 Sep 2014 20:00:04 GMT",
"version": "v1"
},
{
"created": "Sun, 14 Dec 2014 09:43:14 GMT",
"version": "v2"
}
] | 2014-12-16 | [
[
"Rampf",
"Cornelius",
""
],
[
"Wiegand",
"Alexander",
""
]
] | We investigate the purely spatial Lagrangian coordinate transformation from the Lagrangian to the basic Eulerian frame. We demonstrate three techniques for extracting the relativistic displacement field from a given solution in the Lagrangian frame. These techniques are (a) from defining a local set of Eulerian coordinates embedded into the Lagrangian frame; (b) from performing a specific gauge transformation; and (c) from a fully non-perturbative approach based on the ADM split. The latter approach shows that this decomposition is not tied to a specific perturbative formulation for the solution of the Einstein equations. Rather, it can be defined at the level of the non-perturbative coordinate change from the Lagrangian to the Eulerian description. Studying such different techniques is useful because it allows us to compare and develop further the various approximation techniques available in the Lagrangian formulation. We find that one has to solve the gravitational wave equation in the relativistic analysis, otherwise the corresponding Newtonian limit will necessarily contain spurious non-propagating tensor artefacts at second order in the Eulerian frame. We also derive the magnetic part of the Weyl tensor in the Lagrangian frame, and find that it is not only excited by gravitational waves but also by tensor perturbations which are induced through the non-linear frame-dragging. We apply our findings to calculate for the first time the relativistic displacement field, up to second order, for a $\Lambda$CDM Universe in the presence of a local primordial non-Gaussian component. Finally, we also comment on recent claims about whether mass conservation in the Lagrangian frame is violated. |
2203.03049 | Bence Racsk\'o | Bence Racsk\'o | Variational formalism for generic shells in general relativity | null | Class. Quantum Grav. 39 015004 (2022) | 10.1088/1361-6382/ac38d2 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate the variational principle for the gravitational field in the
presence of thin shells of completely unconstrained signature (generic shells).
Such variational formulations have been given before for shells of timelike and
null signatures separately, but so far no unified treatment exists. We identify
the shell equation as the natural boundary condition associated with a broken
extremal problem along a hypersurface where the metric tensor is allowed to be
nondifferentiable. Since the second order nature of the Einstein-Hilbert action
makes the boundary value problem associated with the variational formulation
ill-defined, regularization schemes need to be introduced. We investigate
several such regularization schemes and prove their equivalence. We show that
the unified shell equations derived from this variational procedure reproduce
past results obtained via distribution theory by Barrabes and Israel for
hypersurfaces of fixed causal type and by Mars and Senovilla for generic
shells. These results are expected to provide a useful guide to formulating
thin shell equations and junction conditions along generic hypersurfaces in
modified theories of gravity.
| [
{
"created": "Sun, 6 Mar 2022 20:49:37 GMT",
"version": "v1"
}
] | 2022-03-08 | [
[
"Racskó",
"Bence",
""
]
] | We investigate the variational principle for the gravitational field in the presence of thin shells of completely unconstrained signature (generic shells). Such variational formulations have been given before for shells of timelike and null signatures separately, but so far no unified treatment exists. We identify the shell equation as the natural boundary condition associated with a broken extremal problem along a hypersurface where the metric tensor is allowed to be nondifferentiable. Since the second order nature of the Einstein-Hilbert action makes the boundary value problem associated with the variational formulation ill-defined, regularization schemes need to be introduced. We investigate several such regularization schemes and prove their equivalence. We show that the unified shell equations derived from this variational procedure reproduce past results obtained via distribution theory by Barrabes and Israel for hypersurfaces of fixed causal type and by Mars and Senovilla for generic shells. These results are expected to provide a useful guide to formulating thin shell equations and junction conditions along generic hypersurfaces in modified theories of gravity. |
0809.2022 | Patrick Peter | Patrick Peter and Nelson Pinto-Neto | Cosmology without inflation | 8 pages, no figure | Phys.Rev.D78:063506,2008 | 10.1103/PhysRevD.78.063506 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a new cosmological paradigm in which our observed expanding phase
is originated from an initially large contracting Universe that subsequently
experienced a bounce. This category of models, being geodesically complete, is
non-singular and horizon-free, and can be made to prevent any relevant scale to
ever have been smaller than the Planck length. In this scenario, one can find
new ways to solve the standard cosmological puzzles. One can also obtain scale
invariant spectra for both scalar and tensor perturbations: this will be the
case, for instance, if the contracting Universe is dust-dominated at the time
at which large wavelength perturbations get larger than the curvature scale. We
present a particular example based on a dust fluid classically contracting
model, where a bounce occurs due to quantum effects, in which these features
are explicit.
| [
{
"created": "Thu, 11 Sep 2008 15:29:49 GMT",
"version": "v1"
}
] | 2008-11-07 | [
[
"Peter",
"Patrick",
""
],
[
"Pinto-Neto",
"Nelson",
""
]
] | We propose a new cosmological paradigm in which our observed expanding phase is originated from an initially large contracting Universe that subsequently experienced a bounce. This category of models, being geodesically complete, is non-singular and horizon-free, and can be made to prevent any relevant scale to ever have been smaller than the Planck length. In this scenario, one can find new ways to solve the standard cosmological puzzles. One can also obtain scale invariant spectra for both scalar and tensor perturbations: this will be the case, for instance, if the contracting Universe is dust-dominated at the time at which large wavelength perturbations get larger than the curvature scale. We present a particular example based on a dust fluid classically contracting model, where a bounce occurs due to quantum effects, in which these features are explicit. |
0811.4329 | David Langlois | David Langlois | Early Universe: inflation and cosmological perturbations | Talk given at the workshop "Geometry, Topology, QFT and Cosmology",
Paris (28-30 May 2008); 23 pages | null | null | null | gr-qc astro-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | After a brief summary of general relativity and cosmology, we present the
basic concepts underlying inflation, the currently best motivated models for
the early Universe. We describe the simplest inflation models, based on a
single scalar field, and discuss how primordial cosmological perturbations are
generated. We then review some recent developments concerning multi-field
inflation models, in particular multi-field Dirac-Born-Infeld inflation.
| [
{
"created": "Wed, 26 Nov 2008 14:47:32 GMT",
"version": "v1"
}
] | 2008-11-27 | [
[
"Langlois",
"David",
""
]
] | After a brief summary of general relativity and cosmology, we present the basic concepts underlying inflation, the currently best motivated models for the early Universe. We describe the simplest inflation models, based on a single scalar field, and discuss how primordial cosmological perturbations are generated. We then review some recent developments concerning multi-field inflation models, in particular multi-field Dirac-Born-Infeld inflation. |
0811.4020 | Peter Hogan | T. Futamase, P. A. Hogan and Y. Itoh | Equations of Motion in General Relativity of a Small Charged Black Hole | 31 pages, Latex file | Phys.Rev.D78:104014,2008 | 10.1103/PhysRevD.78.104014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the details of a model in general relativity of a small charged
black hole moving in an external gravitational and electromagnetic field. The
importance of our model lies in the fact that we can derive the equations of
motion of the black hole from the Einstein-Maxwell vacuum field equations
without encountering infinities. The key assumptions which we base our results
upon are that (a) the black hole is isolated and (b) near the black hole the
wave fronts of the radiation generated by its motion are smoothly deformed
spheres. The equations of motion which emerge fit the pattern of the original
DeWitt and Brehme equations of motion (after they "renormalise"). Our
calculations are carried out in a coordinate system in which the null
hypersurface histories of the wave fronts can be specified in a simple way,
with the result that we obtain a new explicit form, particular to our model,
for the well-known "tail term" in the equations of motion.
| [
{
"created": "Tue, 25 Nov 2008 07:03:16 GMT",
"version": "v1"
}
] | 2008-12-18 | [
[
"Futamase",
"T.",
""
],
[
"Hogan",
"P. A.",
""
],
[
"Itoh",
"Y.",
""
]
] | We present the details of a model in general relativity of a small charged black hole moving in an external gravitational and electromagnetic field. The importance of our model lies in the fact that we can derive the equations of motion of the black hole from the Einstein-Maxwell vacuum field equations without encountering infinities. The key assumptions which we base our results upon are that (a) the black hole is isolated and (b) near the black hole the wave fronts of the radiation generated by its motion are smoothly deformed spheres. The equations of motion which emerge fit the pattern of the original DeWitt and Brehme equations of motion (after they "renormalise"). Our calculations are carried out in a coordinate system in which the null hypersurface histories of the wave fronts can be specified in a simple way, with the result that we obtain a new explicit form, particular to our model, for the well-known "tail term" in the equations of motion. |
1303.4635 | Badri Krishnan | Badri Krishnan | Quasi-local black hole horizons | 41 pages, 12 Figures. To appear in the Springer Handbook of
Spacetime, Springer Verlag (2013) | null | 10.1007/978-3-642-41992-8_25 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This article introduces the subject of quasi-local horizons at a level
suitable for physics graduate students who have taken a first course on general
relativity. It reviews properties of trapped surfaces and trapped regions in
some simple examples, general properties of trapped surfaces including their
stability properties, the definitions and some applications of dynamical-,
trapping-, and isolated-horizons.
| [
{
"created": "Tue, 19 Mar 2013 15:24:22 GMT",
"version": "v1"
}
] | 2015-06-15 | [
[
"Krishnan",
"Badri",
""
]
] | This article introduces the subject of quasi-local horizons at a level suitable for physics graduate students who have taken a first course on general relativity. It reviews properties of trapped surfaces and trapped regions in some simple examples, general properties of trapped surfaces including their stability properties, the definitions and some applications of dynamical-, trapping-, and isolated-horizons. |
1211.1373 | Christian Corda cordac | Christian Corda | Dark Energy and Dark Matter like intrinsic curvature in extended
gravity. Viability through gravitational waves | 13 pages, short review commissioned and accepted for publication by
New Adv. Phys. To appear in Issue 7(1) 2013 on Dark Energy | New Advances in Physics, Vol. 7, No. 1, January-June 2013, Pp.
67-83 | null | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Towards the goal to quantize gravity, in this short review we discuss an
intermediate step which consists in extending the picture of standard General
Relativity by considering Extended Theories of Gravity. In this tapestry, the
equations to quantize are not the standard Einstein field equations of General
Relativity, but the extended Einstein field equations of such Extended
Theories. The traditional relation between mass-energy and space-time
curvature, which founds standard General Relativity, results modified in this
new picture and, at least at the linearized approximation, variations of the
space-time curvature generate the mass-energy. Various problems of the Dark
Universe, Dark Energy, Dark Matter and Pioneer anomaly, can be, in principle,
solved through this approach, while a definitive endorsement for Extended
Theories of Gravity could arrive from the realization of a consistent
gravitational wave astronomy. We also discuss the quantization of both
mass-energy and space-time curvature in the early Universe by using the process
of amplification of vacuum fluctuations which is connected with the primordial
production of relic gravitational waves. A future detection of such relic
gravitational waves will be an ultimate endorsement for the quantum rather than
classical feature of the gravitational interaction.
| [
{
"created": "Tue, 6 Nov 2012 08:27:34 GMT",
"version": "v1"
}
] | 2014-03-03 | [
[
"Corda",
"Christian",
""
]
] | Towards the goal to quantize gravity, in this short review we discuss an intermediate step which consists in extending the picture of standard General Relativity by considering Extended Theories of Gravity. In this tapestry, the equations to quantize are not the standard Einstein field equations of General Relativity, but the extended Einstein field equations of such Extended Theories. The traditional relation between mass-energy and space-time curvature, which founds standard General Relativity, results modified in this new picture and, at least at the linearized approximation, variations of the space-time curvature generate the mass-energy. Various problems of the Dark Universe, Dark Energy, Dark Matter and Pioneer anomaly, can be, in principle, solved through this approach, while a definitive endorsement for Extended Theories of Gravity could arrive from the realization of a consistent gravitational wave astronomy. We also discuss the quantization of both mass-energy and space-time curvature in the early Universe by using the process of amplification of vacuum fluctuations which is connected with the primordial production of relic gravitational waves. A future detection of such relic gravitational waves will be an ultimate endorsement for the quantum rather than classical feature of the gravitational interaction. |
2308.12236 | Angel Rincon | Gabriel Abell\'an, Angel Rincon and Eduard Sanchez | A Generalized Double Chaplygin Model for Anisotropic Matter: The
Newtonian Case | 14 pages, 3 figures. Matches the published version (invited
contribution to the Journal Universe) | Universe 9 (2023) 1-14 | 10.3390/universe9080352 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work, we investigate astrophysical systems in a Newtonian regime
using anisotropic matter. For this purpose, we considered that both radial and
tangential pressures satisfy a generalized Chaplygin-type equation of state.
Using this model, we found the Lane--Emden equation for this system and solved
it numerically for several sets of parameters. Finally, we explored the mass
supported by this physical system and compared it with the Chandrasekhar mass.
| [
{
"created": "Wed, 23 Aug 2023 16:22:33 GMT",
"version": "v1"
}
] | 2023-08-24 | [
[
"Abellán",
"Gabriel",
""
],
[
"Rincon",
"Angel",
""
],
[
"Sanchez",
"Eduard",
""
]
] | In this work, we investigate astrophysical systems in a Newtonian regime using anisotropic matter. For this purpose, we considered that both radial and tangential pressures satisfy a generalized Chaplygin-type equation of state. Using this model, we found the Lane--Emden equation for this system and solved it numerically for several sets of parameters. Finally, we explored the mass supported by this physical system and compared it with the Chandrasekhar mass. |
2006.11503 | Shao-Wen Wei | Shao-Wen Wei, Yu-Xiao Liu, Robert B. Mann | Novel dual relation and constant in Hawking-Page phase transitions | 5 pages and 4 figures | Phys. Rev. D 102, 104011 (2020) | 10.1103/PhysRevD.102.104011 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Universal relations and constants have important applications in
understanding a physical theory. In this article, we explore this issue for
Hawking-Page phase transitions in Schwarzschild anti-de Sitter black holes. We
find a novel exact dual relation between the minimum temperature of the
($d$+1)-dimensional black hole and the Hawking-Page phase transition
temperature in $d$ dimensions, reminiscent of the holographic principle.
Furthermore, we find that the normalized Ruppeiner scalar curvature is a
universal constant at the Hawking-Page transition point. Since the Ruppeiner
curvature can be treated as an indicator of the intensity of the interactions
amongst black hole microstructures, we conjecture that this universal constant
denotes an interaction threshold, beyond which a virtual black hole becomes a
real one. This new dual relation and universal constant are fundamental in
understanding Hawking-Page phase transitions, and might have new important
applications in the black hole physics in the near future.
| [
{
"created": "Sat, 20 Jun 2020 06:49:23 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Nov 2020 06:22:38 GMT",
"version": "v2"
}
] | 2020-11-10 | [
[
"Wei",
"Shao-Wen",
""
],
[
"Liu",
"Yu-Xiao",
""
],
[
"Mann",
"Robert B.",
""
]
] | Universal relations and constants have important applications in understanding a physical theory. In this article, we explore this issue for Hawking-Page phase transitions in Schwarzschild anti-de Sitter black holes. We find a novel exact dual relation between the minimum temperature of the ($d$+1)-dimensional black hole and the Hawking-Page phase transition temperature in $d$ dimensions, reminiscent of the holographic principle. Furthermore, we find that the normalized Ruppeiner scalar curvature is a universal constant at the Hawking-Page transition point. Since the Ruppeiner curvature can be treated as an indicator of the intensity of the interactions amongst black hole microstructures, we conjecture that this universal constant denotes an interaction threshold, beyond which a virtual black hole becomes a real one. This new dual relation and universal constant are fundamental in understanding Hawking-Page phase transitions, and might have new important applications in the black hole physics in the near future. |
gr-qc/0701128 | Jarmo M\"akel\"a Dr. | Jarmo Makela | Quantum-Mechanical Model of Spacetime | 46 pages, no figures. References added and a list of references
partly re-organized. Typos corrected. Minor changes in section 7 | null | null | null | gr-qc | null | We consider a possibility to construct a quantum-mechanical model of
spacetime, where Planck size quantum black holes act as the fundamental
constituents of space and time. Spacetime is assumed to be a graph, where black
holes lie on the vertices. Our model implies that area has a discrete spectrum
with equal spacing. At macroscopic length scales our model reproduces
Einstein's field equation with a vanishing cosmological constant as a sort of
thermodynamical equation of state of spacetime and matter fields. In the low
temperature limit, where most black holes are assumed to be in the ground
state, our model implies the Unruh and the Hawking effects, whereas in the high
temperature limit we find, among other things, that black hole entropy depends
logarithmically on the event horizon area, instead of being proportional to the
area.
| [
{
"created": "Wed, 24 Jan 2007 10:34:26 GMT",
"version": "v1"
},
{
"created": "Mon, 12 Feb 2007 07:12:50 GMT",
"version": "v2"
},
{
"created": "Wed, 20 Jun 2007 04:59:16 GMT",
"version": "v3"
}
] | 2007-06-20 | [
[
"Makela",
"Jarmo",
""
]
] | We consider a possibility to construct a quantum-mechanical model of spacetime, where Planck size quantum black holes act as the fundamental constituents of space and time. Spacetime is assumed to be a graph, where black holes lie on the vertices. Our model implies that area has a discrete spectrum with equal spacing. At macroscopic length scales our model reproduces Einstein's field equation with a vanishing cosmological constant as a sort of thermodynamical equation of state of spacetime and matter fields. In the low temperature limit, where most black holes are assumed to be in the ground state, our model implies the Unruh and the Hawking effects, whereas in the high temperature limit we find, among other things, that black hole entropy depends logarithmically on the event horizon area, instead of being proportional to the area. |
1011.3824 | Jacek Gruszczak | Jacek Gruszczak | Smooth Beginning of the Universe | some typos corrected, acknowledgements and references added | null | null | null | gr-qc astro-ph.CO math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The breaking down of the equivalence principle, when discussed in the context
of Sikorski's differential spaces theory, leads to the definition of the
so-called differentially singular boundary (d-boundary) and to the concept of
differential space with singularity associated with a given space-time
differential manifold. This enables us to define the time orientability, the
beginning of the cosmological time and the smooth evolution for the flat
Friedmanian world model with the initial singularity. The simplest smoothly
evolved models are studied. It is shown, that the cosmological matter causing
such an evolution can be of three different types. One of them is the fluid
with dark energy properties, the second the fluid with attraction properties,
and the third a mixture of the other two. Among all investigated smoothly
evolved solutions, models qualitatively consistent with the observational data
of type Ia supernovae have been found.
| [
{
"created": "Tue, 16 Nov 2010 21:03:40 GMT",
"version": "v1"
},
{
"created": "Mon, 4 Jul 2011 00:34:09 GMT",
"version": "v2"
},
{
"created": "Tue, 10 Jan 2012 17:26:14 GMT",
"version": "v3"
}
] | 2012-01-11 | [
[
"Gruszczak",
"Jacek",
""
]
] | The breaking down of the equivalence principle, when discussed in the context of Sikorski's differential spaces theory, leads to the definition of the so-called differentially singular boundary (d-boundary) and to the concept of differential space with singularity associated with a given space-time differential manifold. This enables us to define the time orientability, the beginning of the cosmological time and the smooth evolution for the flat Friedmanian world model with the initial singularity. The simplest smoothly evolved models are studied. It is shown, that the cosmological matter causing such an evolution can be of three different types. One of them is the fluid with dark energy properties, the second the fluid with attraction properties, and the third a mixture of the other two. Among all investigated smoothly evolved solutions, models qualitatively consistent with the observational data of type Ia supernovae have been found. |
0911.4440 | Harvey R. Brown | Harvey R Brown | The behaviour of rods and clocks in general relativity, and the meaning
of the metric field | 14 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The notion that the metric field in general relativity can be understood as a
property of space-time rests on a feature of the theory sometimes called
universal coupling -- the claim that rods and clocks "measure" the metric in a
way that is independent of their constitution. It is pointed out that this
feature is not strictly a consequence of the central dynamical tenets of the
theory, and argued that the metric field would better be regarded as a
(possibly emergent) field in space-time, rather than as the very fabric of
space-time itself.
| [
{
"created": "Mon, 23 Nov 2009 16:26:02 GMT",
"version": "v1"
}
] | 2009-11-24 | [
[
"Brown",
"Harvey R",
""
]
] | The notion that the metric field in general relativity can be understood as a property of space-time rests on a feature of the theory sometimes called universal coupling -- the claim that rods and clocks "measure" the metric in a way that is independent of their constitution. It is pointed out that this feature is not strictly a consequence of the central dynamical tenets of the theory, and argued that the metric field would better be regarded as a (possibly emergent) field in space-time, rather than as the very fabric of space-time itself. |
0811.0354 | Mihalis Dafermos | Mihalis Dafermos and Igor Rodnianski | Lectures on black holes and linear waves | 116 pages, 21 figures | Clay Mathematics Proceedings, Vol. 17, Amer. Math. Soc.,
Providence, RI, 2013, pp. 97-205 | null | null | gr-qc math-ph math.AP math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | These lecture notes, based on a course given at the Zurich Clay Summer School
(June 23-July 18, 2008), review our current mathematical understanding of the
global behaviour of waves on black hole exterior backgrounds. Interest in this
problem stems from its relationship to the non-linear stability of the black
hole spacetimes themselves as solutions to the Einstein equations, one of the
central open problems of general relativity. After an introductory discussion
of the Schwarzschild geometry and the black hole concept, the classical theorem
of Kay and Wald on the boundedness of scalar waves on the exterior region of
Schwarzschild is reviewed. The original proof is presented, followed by a new
more robust proof of a stronger boundedness statement. The problem of decay of
scalar waves on Schwarzschild is then addressed, and a theorem proving
quantitative decay is stated and its proof sketched. This decay statement is
carefully contrasted with the type of statements derived heuristically in the
physics literature for the asymptotic tails of individual spherical harmonics.
Following this, our recent proof of the boundedness of solutions to the wave
equation on axisymmetric stationary backgrounds (including slowly-rotating Kerr
and Kerr-Newman) is reviewed and a new decay result for slowly-rotating Kerr
spacetimes is stated and proved. This last result was announced at the summer
school and appears in print here for the first time. A discussion of the
analogue of these problems for spacetimes with a positive cosmological constant
follows. Finally, a general framework is given for capturing the red-shift
effect for non-extremal black holes. This unifies and extends some of the
analysis of the previous sections. The notes end with a collection of open
problems.
| [
{
"created": "Mon, 3 Nov 2008 18:09:16 GMT",
"version": "v1"
}
] | 2013-12-03 | [
[
"Dafermos",
"Mihalis",
""
],
[
"Rodnianski",
"Igor",
""
]
] | These lecture notes, based on a course given at the Zurich Clay Summer School (June 23-July 18, 2008), review our current mathematical understanding of the global behaviour of waves on black hole exterior backgrounds. Interest in this problem stems from its relationship to the non-linear stability of the black hole spacetimes themselves as solutions to the Einstein equations, one of the central open problems of general relativity. After an introductory discussion of the Schwarzschild geometry and the black hole concept, the classical theorem of Kay and Wald on the boundedness of scalar waves on the exterior region of Schwarzschild is reviewed. The original proof is presented, followed by a new more robust proof of a stronger boundedness statement. The problem of decay of scalar waves on Schwarzschild is then addressed, and a theorem proving quantitative decay is stated and its proof sketched. This decay statement is carefully contrasted with the type of statements derived heuristically in the physics literature for the asymptotic tails of individual spherical harmonics. Following this, our recent proof of the boundedness of solutions to the wave equation on axisymmetric stationary backgrounds (including slowly-rotating Kerr and Kerr-Newman) is reviewed and a new decay result for slowly-rotating Kerr spacetimes is stated and proved. This last result was announced at the summer school and appears in print here for the first time. A discussion of the analogue of these problems for spacetimes with a positive cosmological constant follows. Finally, a general framework is given for capturing the red-shift effect for non-extremal black holes. This unifies and extends some of the analysis of the previous sections. The notes end with a collection of open problems. |
gr-qc/0208015 | Raul Vera | Raul Vera | Symmetry-preserving matchings | LaTeX, 19 pages | Class.Quant.Grav. 19 (2002) 5249-5264 | 10.1088/0264-9381/19/20/316 | null | gr-qc | null | In the literature, the matchings between spacetimes have been most of the
times implicitly assumed to preserve some of the symmetries of the problem
involved. But no definition for this kind of matching was given until recently.
Loosely speaking, the matching hypersurface is restricted to be tangent to the
orbits of a desired local group of symmetries admitted at both sides of the
matching and thus admitted by the whole matched spacetime. This general
definition is shown to lead to conditions on the properties of the preserved
groups. First, the algebraic type of the preserved group must be kept at both
sides of the matching hypersurface. Secondly, the orthogonal transivity of
two-dimensional conformal (in particular isometry) groups is shown to be
preserved (in a way made precise below) on the matching hypersurface. This
result has in particular direct implications on the studies of axially
symmetric isolated bodies in equilibrium in General Relativity, by making up
the first condition that determines the suitability of convective interiors to
be matched to vacuum exteriors. The definition and most of the results
presented in this paper do not depend on the dimension of the manifolds
involved nor the signature of the metric, and their applicability to other
situations and other higher dimensional theories is manifest.
| [
{
"created": "Tue, 6 Aug 2002 15:14:33 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Vera",
"Raul",
""
]
] | In the literature, the matchings between spacetimes have been most of the times implicitly assumed to preserve some of the symmetries of the problem involved. But no definition for this kind of matching was given until recently. Loosely speaking, the matching hypersurface is restricted to be tangent to the orbits of a desired local group of symmetries admitted at both sides of the matching and thus admitted by the whole matched spacetime. This general definition is shown to lead to conditions on the properties of the preserved groups. First, the algebraic type of the preserved group must be kept at both sides of the matching hypersurface. Secondly, the orthogonal transivity of two-dimensional conformal (in particular isometry) groups is shown to be preserved (in a way made precise below) on the matching hypersurface. This result has in particular direct implications on the studies of axially symmetric isolated bodies in equilibrium in General Relativity, by making up the first condition that determines the suitability of convective interiors to be matched to vacuum exteriors. The definition and most of the results presented in this paper do not depend on the dimension of the manifolds involved nor the signature of the metric, and their applicability to other situations and other higher dimensional theories is manifest. |
0710.1450 | Sergei Kopeikin | S.M. Kopeikin (University of Missouri-Columbia, USA), E. Pavlis
(JCET/UMBC - NASA Goddard, USA), D. Pavlis (SGT Inc., USA), V.A. Brumberg
(Inst. Appl. Astron., Russia), A. Escapa (Univ. of Alicante, Spain), J.
Getino (Univ. of Valladolid, Spain), A. Gusev (Kazan State University,
Russia), J. Mueller (Leibniz University of Hannover, Germany), W.-T. Ni
(Purple Mountain Observatory, China), N. Petrova (Kazan State University,
Russia) | Prospects in the orbital and rotational dynamics of the Moon with the
advent of sub-centimeter lunar laser ranging | 26 pages, submitted to Proc. of ASTROCON-IV conference (Princeton
Univ., NJ, 2007) | Adv.SpaceRes.42:1378-1390,2008 | 10.1016/j.asr.2008.02.014 | null | gr-qc | null | Lunar Laser Ranging (LLR) measurements are crucial for advanced exploration
of the laws of fundamental gravitational physics and geophysics. Current LLR
technology allows us to measure distances to the Moon with a precision
approaching 1 millimeter. As NASA pursues the vision of taking humans back to
the Moon, new, more precise laser ranging applications will be demanded,
including continuous tracking from more sites on Earth, placing new CCR arrays
on the Moon, and possibly installing other devices such as transponders, etc.
Successful achievement of this goal strongly demands further significant
improvement of the theoretical model of the orbital and rotational dynamics of
the Earth-Moon system. This model should inevitably be based on the theory of
general relativity, fully incorporate the relevant geophysical processes, lunar
librations, tides, and should rely upon the most recent standards and
recommendations of the IAU for data analysis. This paper discusses methods and
problems in developing such a mathematical model. The model will take into
account all the classical and relativistic effects in the orbital and
rotational motion of the Moon and Earth at the sub-centimeter level. The new
model will allow us to navigate a spacecraft precisely to a location on the
Moon. It will also greatly improve our understanding of the structure of the
lunar interior and the nature of the physical interaction at the core-mantle
interface layer. The new theory and upcoming millimeter LLR will give us the
means to perform one of the most precise fundamental tests of general
relativity in the solar system.
| [
{
"created": "Mon, 8 Oct 2007 01:11:26 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Kopeikin",
"S. M.",
"",
"University of Missouri-Columbia, USA"
],
[
"Pavlis",
"E.",
"",
"JCET/UMBC - NASA Goddard, USA"
],
[
"Pavlis",
"D.",
"",
"SGT Inc., USA"
],
[
"Brumberg",
"V. A.",
"",
"Inst. Appl. Astron., Russia"
],
[
"Escapa",
"A.",
"",
"Univ. of Alicante, Spain"
],
[
"Getino",
"J.",
"",
"Univ. of Valladolid, Spain"
],
[
"Gusev",
"A.",
"",
"Kazan State University,\n Russia"
],
[
"Mueller",
"J.",
"",
"Leibniz University of Hannover, Germany"
],
[
"Ni",
"W. -T.",
"",
"Purple Mountain Observatory, China"
],
[
"Petrova",
"N.",
"",
"Kazan State University,\n Russia"
]
] | Lunar Laser Ranging (LLR) measurements are crucial for advanced exploration of the laws of fundamental gravitational physics and geophysics. Current LLR technology allows us to measure distances to the Moon with a precision approaching 1 millimeter. As NASA pursues the vision of taking humans back to the Moon, new, more precise laser ranging applications will be demanded, including continuous tracking from more sites on Earth, placing new CCR arrays on the Moon, and possibly installing other devices such as transponders, etc. Successful achievement of this goal strongly demands further significant improvement of the theoretical model of the orbital and rotational dynamics of the Earth-Moon system. This model should inevitably be based on the theory of general relativity, fully incorporate the relevant geophysical processes, lunar librations, tides, and should rely upon the most recent standards and recommendations of the IAU for data analysis. This paper discusses methods and problems in developing such a mathematical model. The model will take into account all the classical and relativistic effects in the orbital and rotational motion of the Moon and Earth at the sub-centimeter level. The new model will allow us to navigate a spacecraft precisely to a location on the Moon. It will also greatly improve our understanding of the structure of the lunar interior and the nature of the physical interaction at the core-mantle interface layer. The new theory and upcoming millimeter LLR will give us the means to perform one of the most precise fundamental tests of general relativity in the solar system. |
gr-qc/0703053 | Emanuele Berti | Emanuele Berti, Vitor Cardoso, Jose A. Gonzalez, Ulrich Sperhake, Mark
Hannam, Sascha Husa, Bernd Bruegmann | Inspiral, merger and ringdown of unequal mass black hole binaries: a
multipolar analysis | 51 pages, 28 figures, 16 tables. Many improvements throughout the
text in response to the referee report. The calculation of multipolar
components in Appendix A now uses slightly different conventions. Matches
version in press in PRD | Phys.Rev.D76:064034,2007 | 10.1103/PhysRevD.76.064034 | null | gr-qc astro-ph | null | We study the inspiral, merger and ringdown of unequal mass black hole
binaries by analyzing a catalogue of numerical simulations for seven different
values of the mass ratio (from q=M2/M1=1 to q=4). We compare numerical and
Post-Newtonian results by projecting the waveforms onto spin-weighted spherical
harmonics, characterized by angular indices (l,m). We find that the
Post-Newtonian equations predict remarkably well the relation between the wave
amplitude and the orbital frequency for each (l,m), and that the convergence of
the Post-Newtonian series to the numerical results is non-monotonic. To leading
order the total energy emitted in the merger phase scales like eta^2 and the
spin of the final black hole scales like eta, where eta=q/(1+q)^2 is the
symmetric mass ratio. We study the multipolar distribution of the radiation,
finding that odd-l multipoles are suppressed in the equal mass limit. Higher
multipoles carry a larger fraction of the total energy as q increases. We
introduce and compare three different definitions for the ringdown starting
time. Applying linear estimation methods (the so-called Prony methods) to the
ringdown phase, we find resolution-dependent time variations in the fitted
parameters of the final black hole. By cross-correlating information from
different multipoles we show that ringdown fits can be used to obtain precise
estimates of the mass and spin of the final black hole, which are in remarkable
agreement with energy and angular momentum balance calculations.
| [
{
"created": "Thu, 8 Mar 2007 14:25:24 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Sep 2007 22:40:35 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Berti",
"Emanuele",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Gonzalez",
"Jose A.",
""
],
[
"Sperhake",
"Ulrich",
""
],
[
"Hannam",
"Mark",
""
],
[
"Husa",
"Sascha",
""
],
[
"Bruegmann",
"Bernd",
""
]
] | We study the inspiral, merger and ringdown of unequal mass black hole binaries by analyzing a catalogue of numerical simulations for seven different values of the mass ratio (from q=M2/M1=1 to q=4). We compare numerical and Post-Newtonian results by projecting the waveforms onto spin-weighted spherical harmonics, characterized by angular indices (l,m). We find that the Post-Newtonian equations predict remarkably well the relation between the wave amplitude and the orbital frequency for each (l,m), and that the convergence of the Post-Newtonian series to the numerical results is non-monotonic. To leading order the total energy emitted in the merger phase scales like eta^2 and the spin of the final black hole scales like eta, where eta=q/(1+q)^2 is the symmetric mass ratio. We study the multipolar distribution of the radiation, finding that odd-l multipoles are suppressed in the equal mass limit. Higher multipoles carry a larger fraction of the total energy as q increases. We introduce and compare three different definitions for the ringdown starting time. Applying linear estimation methods (the so-called Prony methods) to the ringdown phase, we find resolution-dependent time variations in the fitted parameters of the final black hole. By cross-correlating information from different multipoles we show that ringdown fits can be used to obtain precise estimates of the mass and spin of the final black hole, which are in remarkable agreement with energy and angular momentum balance calculations. |
2205.11671 | Benito A. Ju\'arez-Aubry | Benito A. Ju\'arez-Aubry, Bernard S. Kay, Tonatiuh Miramontes, Daniel
Sudarsky | On the initial value problem for semiclassical gravity without and with
quantum state collapses | 47 pages. Corrections implemented, notably Def 11 (preliminary
surface Hadamard condition) and certain equations on p. 33. Explanations
improved and typos fixed. This version corresponds largely to the published
version in JCAP | JCAP 01 (2023), 040 | 10.1088/1475-7516/2023/01/040 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore how the initial value problem may be formulated for globally
hyperbolic, Hadamard, solutions of the semiclassical Einstein-Klein-Gordon
equations. Given a set of data on an initial 3-surface, consisting of the
values on the surface of a spacetime metric and its first 3 time derivatives
off the surface, we introduce a notion of 'surface Hadamard' state on the CCR
algebra of the surface. We conjecture that, for a given such set of classical
Cauchy data with a surface Hadamard state satisfying the semiclassical
constraint equations, the initial value problem will be well posed. We present
similar conjectures for a semiclassical scalars model and semiclassical
electrodynamics. Moreover, partly inspired by work of Parker and Simon in 1993,
we define semiclassical gravity `physical solutions' to be those that are
(jointly smooth) functions of $\hbar$ and of coordinates continuous in $\hbar$
at $\hbar =0$. We conjecture that for such solutions the second and third time
derivatives of the metric off the surface need not be specified, but rather
will be determined by that continuity condition. Assuming the initial value
conjecture for such physical solutions holds, and that a stochastic rule were
available which leads to quantum state collapses occurring on
(non-intersecting) random Cauchy surfaces, we discuss the well-posedness of
semiclassical gravity with stochastic quantum state collapses. We also discuss
two notions of approximate physical semiclassical solutions (both with and
without collapses): Namely solutions to order $\hbar$ (first discussed by
Parker and Simon in 1993) and solutions to order $\hbar^0$. We point out that
the latter do not require higher derivative terms or Hadamard subtractions, but
that nevertheless order $\hbar^0$ semiclassical gravity is a distinct theory
from classical general relativity capable of incorporating quantum interference
phenomena.
| [
{
"created": "Mon, 23 May 2022 23:39:18 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Aug 2022 15:48:23 GMT",
"version": "v2"
},
{
"created": "Tue, 22 Nov 2022 18:03:19 GMT",
"version": "v3"
},
{
"created": "Sun, 27 Nov 2022 14:53:19 GMT",
"version": "v4"
},
{
"created": "Fri, 10 Mar 2023 18:07:00 GMT",
"version": "v5"
}
] | 2023-03-13 | [
[
"Juárez-Aubry",
"Benito A.",
""
],
[
"Kay",
"Bernard S.",
""
],
[
"Miramontes",
"Tonatiuh",
""
],
[
"Sudarsky",
"Daniel",
""
]
] | We explore how the initial value problem may be formulated for globally hyperbolic, Hadamard, solutions of the semiclassical Einstein-Klein-Gordon equations. Given a set of data on an initial 3-surface, consisting of the values on the surface of a spacetime metric and its first 3 time derivatives off the surface, we introduce a notion of 'surface Hadamard' state on the CCR algebra of the surface. We conjecture that, for a given such set of classical Cauchy data with a surface Hadamard state satisfying the semiclassical constraint equations, the initial value problem will be well posed. We present similar conjectures for a semiclassical scalars model and semiclassical electrodynamics. Moreover, partly inspired by work of Parker and Simon in 1993, we define semiclassical gravity `physical solutions' to be those that are (jointly smooth) functions of $\hbar$ and of coordinates continuous in $\hbar$ at $\hbar =0$. We conjecture that for such solutions the second and third time derivatives of the metric off the surface need not be specified, but rather will be determined by that continuity condition. Assuming the initial value conjecture for such physical solutions holds, and that a stochastic rule were available which leads to quantum state collapses occurring on (non-intersecting) random Cauchy surfaces, we discuss the well-posedness of semiclassical gravity with stochastic quantum state collapses. We also discuss two notions of approximate physical semiclassical solutions (both with and without collapses): Namely solutions to order $\hbar$ (first discussed by Parker and Simon in 1993) and solutions to order $\hbar^0$. We point out that the latter do not require higher derivative terms or Hadamard subtractions, but that nevertheless order $\hbar^0$ semiclassical gravity is a distinct theory from classical general relativity capable of incorporating quantum interference phenomena. |
1112.6333 | Francisco Lobo | Francisco S. N. Lobo | Wormhole geometries in modified gravity | 4 pages, Prepared for the proceedings of the Spanish Relativity
meeting (ERE2011), Madrid, Spain, 29Aug-2Sep 2011 | AIP Conf.Proc. 1458 (2011) 447-450 | 10.1063/1.4734456 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A fundamental ingredient in wormhole physics is the presence of exotic
matter, which involves the violation of the null energy condition. Although a
plethora of wormhole solutions have been explored in the literature, it is
useful to find geometries that minimize the usage of exotic matter. In the
context of modified gravity, it has also been shown that the normal matter can
be imposed to satisfy the null energy condition, and it is the higher order
curvature terms, interpreted as a gravitational fluid, that sustain these
non-standard wormhole geometries, fundamentally different from their
counterparts in general relativity. In this paper, we review recent work in
wormhole physics in the context of modified theories of gravity.
| [
{
"created": "Thu, 29 Dec 2011 15:40:11 GMT",
"version": "v1"
}
] | 2012-07-19 | [
[
"Lobo",
"Francisco S. N.",
""
]
] | A fundamental ingredient in wormhole physics is the presence of exotic matter, which involves the violation of the null energy condition. Although a plethora of wormhole solutions have been explored in the literature, it is useful to find geometries that minimize the usage of exotic matter. In the context of modified gravity, it has also been shown that the normal matter can be imposed to satisfy the null energy condition, and it is the higher order curvature terms, interpreted as a gravitational fluid, that sustain these non-standard wormhole geometries, fundamentally different from their counterparts in general relativity. In this paper, we review recent work in wormhole physics in the context of modified theories of gravity. |
1912.05419 | Lu\'is Felipe Longo Micchi Mr. | Luis Felipe Longo Micchi and Cecilia Chirenti | Spicing up the recipe for echoes from exotic compact objects: orbital
differences and corrections in rotating backgrounds | 11 pages, 10 figures. Accepted for publication on PRD. Inclusion of a
brief discussion about the influence of the increase of the central object's
spin | Phys. Rev. D 101, 084010 (2020) | 10.1103/PhysRevD.101.084010 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently it has been argued that near-horizon modifications of the standard
(classical) black hole spacetime could lead to observable alterations of the
gravitational waveform generated by a binary black hole coalescence. Such
modifications can be inspired by quantum gravity considerations, resulting in
speculative horizonless exotic compact objects (ECOs) with no singularities,
which may be an alternative to the classical black hole solution. A largely
model-independent description of these objects proposed in the literature
relies on the introduction of a partially reflective wall at some small
distance away from the "would-be" horizon. The inspiral-merger-ringdown of a
pair of such objects would be subject to possibly detectable deviations from
the black hole case due to matter effects. In particular, the ringdown phase
would be modified by the late emergence of so-called "echoes" in the waveform,
but most studies so far have considered spherically symmetric backgrounds. We
use an in-falling scalar charge as an initial perturbation to simulate the
excitation of the echoes of a rotating ECO and we explore both the co-rotating
and counter-rotating cases, which provide distinct signals. In particular,
rotation breaks the symmetry between positive and negative frequencies and
introduces a subdominant frequency contribution in each echo, which we examine
here for the first time. Our results follow consistently from the solution of
the Teukolsky equation using the MST method developed by Mano, Suzuki and
Takasugi, and the construction of the complex Green's function integrated over
different particle geodesics.
| [
{
"created": "Wed, 11 Dec 2019 16:23:03 GMT",
"version": "v1"
},
{
"created": "Tue, 17 Mar 2020 23:34:59 GMT",
"version": "v2"
}
] | 2020-04-08 | [
[
"Micchi",
"Luis Felipe Longo",
""
],
[
"Chirenti",
"Cecilia",
""
]
] | Recently it has been argued that near-horizon modifications of the standard (classical) black hole spacetime could lead to observable alterations of the gravitational waveform generated by a binary black hole coalescence. Such modifications can be inspired by quantum gravity considerations, resulting in speculative horizonless exotic compact objects (ECOs) with no singularities, which may be an alternative to the classical black hole solution. A largely model-independent description of these objects proposed in the literature relies on the introduction of a partially reflective wall at some small distance away from the "would-be" horizon. The inspiral-merger-ringdown of a pair of such objects would be subject to possibly detectable deviations from the black hole case due to matter effects. In particular, the ringdown phase would be modified by the late emergence of so-called "echoes" in the waveform, but most studies so far have considered spherically symmetric backgrounds. We use an in-falling scalar charge as an initial perturbation to simulate the excitation of the echoes of a rotating ECO and we explore both the co-rotating and counter-rotating cases, which provide distinct signals. In particular, rotation breaks the symmetry between positive and negative frequencies and introduces a subdominant frequency contribution in each echo, which we examine here for the first time. Our results follow consistently from the solution of the Teukolsky equation using the MST method developed by Mano, Suzuki and Takasugi, and the construction of the complex Green's function integrated over different particle geodesics. |
0902.3163 | Baojiu Li | Baojiu Li, John D. Barrow | Does Bulk Viscosity Create a Viable Unified Dark Matter Model? | 9 pages, 5 figures, references and comments added; to appear in Phys.
Rev. D | Phys.Rev.D79:103521,2009 | 10.1103/PhysRevD.79.103521 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate in detail the possibility that a single imperfect fluid with
bulk viscosity can replace the need for separate dark matter and dark energy in
cosmological models. With suitable choices of model parameters, we show that
the background cosmology in this model can mimic that of a LCDM Universe to
high precision. However, as the cosmic expansion goes through the
decelerating-accelerating transition, the density perturbations in this fluid
are rapidly damped out. We show that,although this does not significantly
affect structure formation in baryonic matter, it makes the gravitational
potential decay rapidly at late times, leading to modifications in predictions
of cosmological observables such as the CMB power spectrum and weak lensing.
This model of unified dark matter is thus difficult to reconcile with
astronomical observations. We also clarify the differences with respect to
other unified dark matter models where the fluid is barotropic, i.e., p=p(rho),
such as the (generalized) Chaplygin gas model, and point out their
observational difficulties. We also summarize the status of dark sector models
with no new dynamical degrees of freedom introduced and discuss the problems
with them.
| [
{
"created": "Wed, 18 Feb 2009 15:26:03 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Apr 2009 12:06:59 GMT",
"version": "v2"
},
{
"created": "Mon, 11 May 2009 23:20:01 GMT",
"version": "v3"
}
] | 2009-07-30 | [
[
"Li",
"Baojiu",
""
],
[
"Barrow",
"John D.",
""
]
] | We investigate in detail the possibility that a single imperfect fluid with bulk viscosity can replace the need for separate dark matter and dark energy in cosmological models. With suitable choices of model parameters, we show that the background cosmology in this model can mimic that of a LCDM Universe to high precision. However, as the cosmic expansion goes through the decelerating-accelerating transition, the density perturbations in this fluid are rapidly damped out. We show that,although this does not significantly affect structure formation in baryonic matter, it makes the gravitational potential decay rapidly at late times, leading to modifications in predictions of cosmological observables such as the CMB power spectrum and weak lensing. This model of unified dark matter is thus difficult to reconcile with astronomical observations. We also clarify the differences with respect to other unified dark matter models where the fluid is barotropic, i.e., p=p(rho), such as the (generalized) Chaplygin gas model, and point out their observational difficulties. We also summarize the status of dark sector models with no new dynamical degrees of freedom introduced and discuss the problems with them. |
1710.07373 | Thomas W. Baumgarte | Kenneth A. Dennison and Thomas W. Baumgarte | Schwarzschild-de Sitter Spacetimes, McVittie Coordinates, and Trumpet
Geometries | 7 pages, 3 figures, added reference | Phys. Rev. D 96, 124014 (2017) | 10.1103/PhysRevD.96.124014 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Trumpet geometries play an important role in numerical simulations of black
hole spacetimes, which are usually performed under the assumption of asymptotic
flatness. Our Universe is not asymptotically flat, however, which has motivated
numerical studies of black holes in asymptotically de Sitter spacetimes. We
derive analytical expressions for trumpet geometries in Schwarzschild-de Sitter
spacetimes by first generalizing the static maximal trumpet slicing of the
Schwarzschild spacetime to static constant mean curvature trumpet slicings of
Schwarzschild-de Sitter spacetimes. We then switch to a comoving isotropic
radial coordinate which results in a coordinate system analogous to McVittie
coordinates. At large distances from the black hole the resulting metric
asymptotes to a Friedmann-Lemaitre-Robertson-Walker metric with an
exponentially-expanding scale factor. While McVittie coordinates have another
asymptotically de Sitter end as the radial coordinate goes to zero, so that
they generalize the notion of a "wormhole" geometry, our new coordinates
approach a horizon-penetrating trumpet geometry in the same limit. Our
analytical expressions clarify the role of time-dependence, boundary conditions
and coordinate conditions for trumpet slices in a cosmological context, and
provide a useful test for black hole simulations in asymptotically de Sitter
spacetimes.
| [
{
"created": "Thu, 19 Oct 2017 23:43:58 GMT",
"version": "v1"
},
{
"created": "Thu, 30 Nov 2017 13:46:11 GMT",
"version": "v2"
}
] | 2017-12-20 | [
[
"Dennison",
"Kenneth A.",
""
],
[
"Baumgarte",
"Thomas W.",
""
]
] | Trumpet geometries play an important role in numerical simulations of black hole spacetimes, which are usually performed under the assumption of asymptotic flatness. Our Universe is not asymptotically flat, however, which has motivated numerical studies of black holes in asymptotically de Sitter spacetimes. We derive analytical expressions for trumpet geometries in Schwarzschild-de Sitter spacetimes by first generalizing the static maximal trumpet slicing of the Schwarzschild spacetime to static constant mean curvature trumpet slicings of Schwarzschild-de Sitter spacetimes. We then switch to a comoving isotropic radial coordinate which results in a coordinate system analogous to McVittie coordinates. At large distances from the black hole the resulting metric asymptotes to a Friedmann-Lemaitre-Robertson-Walker metric with an exponentially-expanding scale factor. While McVittie coordinates have another asymptotically de Sitter end as the radial coordinate goes to zero, so that they generalize the notion of a "wormhole" geometry, our new coordinates approach a horizon-penetrating trumpet geometry in the same limit. Our analytical expressions clarify the role of time-dependence, boundary conditions and coordinate conditions for trumpet slices in a cosmological context, and provide a useful test for black hole simulations in asymptotically de Sitter spacetimes. |
1007.4546 | J. A. de Freitas Pacheco | Alain de Roany, J.A. de Freitas Pacheco | Continuous matter creation and the acceleration of the universe: the
growth of density fluctuations | 11 pages, 2 figures, accepted for publication in General Relativity
and Gravitation | Gen.Rel.Grav.43:61-72,2011 | 10.1007/s10714-010-1069-2 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cosmologies including continuous matter creation are able to reproduce the
main properties of the standard $\Lambda$CDM model, in particular in cases
where the particle and entropy production rates are equal. These specific
models, characterized by a mass density equal to the critical value, behave
like the standard $\Lambda$CDM model at early times whereas their late
evolution is similar to the steady-state cosmology. The maximum amplitude of
density fluctuations in these models depends on the adopted creation rate,
related here to the parameter $\Omega_v$ and this limitation could be a
difficulty for the formation of galaxies and large-scale structure in this
class of universe. Additional problems are related with predictions either of
the random peculiar velocities of galaxies or the present density of massive
clusters of galaxies, both being largely overestimated with respect to
observational data.
| [
{
"created": "Mon, 26 Jul 2010 19:57:05 GMT",
"version": "v1"
}
] | 2011-03-07 | [
[
"de Roany",
"Alain",
""
],
[
"Pacheco",
"J. A. de Freitas",
""
]
] | Cosmologies including continuous matter creation are able to reproduce the main properties of the standard $\Lambda$CDM model, in particular in cases where the particle and entropy production rates are equal. These specific models, characterized by a mass density equal to the critical value, behave like the standard $\Lambda$CDM model at early times whereas their late evolution is similar to the steady-state cosmology. The maximum amplitude of density fluctuations in these models depends on the adopted creation rate, related here to the parameter $\Omega_v$ and this limitation could be a difficulty for the formation of galaxies and large-scale structure in this class of universe. Additional problems are related with predictions either of the random peculiar velocities of galaxies or the present density of massive clusters of galaxies, both being largely overestimated with respect to observational data. |
1912.09222 | Armando A Roque Roque | Armando A. Roque and J. Barranco | Confusing dark matter particle properties with modifications to General
Relativity | Accepted for publication in Physical Review D | Phys. Rev. D 102, 104010 (2020) | 10.1103/PhysRevD.102.104010 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Cold Dark Stars made of self-gravitating fermions in the degenerate limit are
constructed in General Relativity and in R-square gravity, $f(R)=R+\alpha R^2$.
The properties of the resulting Cold Dark Stars in both theories of gravity are
studied. It is found that the same gravitational potential is generated for
different election of the parameters of the model, such as the mass of the
fermion, the self-interacting strength or the value of $\alpha$, thus, a
possible confusion in the determination of the dark matter properties and the
favored theory of gravity might arise.
| [
{
"created": "Thu, 19 Dec 2019 14:31:53 GMT",
"version": "v1"
},
{
"created": "Sat, 10 Oct 2020 22:54:04 GMT",
"version": "v2"
}
] | 2020-11-11 | [
[
"Roque",
"Armando A.",
""
],
[
"Barranco",
"J.",
""
]
] | Cold Dark Stars made of self-gravitating fermions in the degenerate limit are constructed in General Relativity and in R-square gravity, $f(R)=R+\alpha R^2$. The properties of the resulting Cold Dark Stars in both theories of gravity are studied. It is found that the same gravitational potential is generated for different election of the parameters of the model, such as the mass of the fermion, the self-interacting strength or the value of $\alpha$, thus, a possible confusion in the determination of the dark matter properties and the favored theory of gravity might arise. |
gr-qc/0012018 | Johan Braennlund | Ingemar Bengtsson, Johan Braennlund (Stockholm University) | 2+1 gravity, chaos and time machines | null | J.Math.Phys. 42 (2001) 3565-3579 | 10.1063/1.1378302 | SUITP 00-17 | gr-qc | null | 2+1 gravity for spacetimes with topology RxT^2 has been much studied. We add
a description of how to extend these spacetimes across a Cauchy horizon into a
region where the torus becomes Lorentzian. The result is a one parameter family
of tori given by a geodesic in the "Teichmueller space" of Lorentzian tori. We
describe this in detail. We also point out that if the modular group is
regarded as part of the gauge group then these spacetimes offer a nice toy
model for the dynamics of Bianchi IX models; in the region where the tori are
spacelike the dynamics is described exactly by a hyperbolic billiard. On the
other hand the modular group acts ergodically on the Teichmueller space of
Lorentzian tori.
| [
{
"created": "Tue, 5 Dec 2000 13:40:20 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Bengtsson",
"Ingemar",
"",
"Stockholm University"
],
[
"Braennlund",
"Johan",
"",
"Stockholm University"
]
] | 2+1 gravity for spacetimes with topology RxT^2 has been much studied. We add a description of how to extend these spacetimes across a Cauchy horizon into a region where the torus becomes Lorentzian. The result is a one parameter family of tori given by a geodesic in the "Teichmueller space" of Lorentzian tori. We describe this in detail. We also point out that if the modular group is regarded as part of the gauge group then these spacetimes offer a nice toy model for the dynamics of Bianchi IX models; in the region where the tori are spacelike the dynamics is described exactly by a hyperbolic billiard. On the other hand the modular group acts ergodically on the Teichmueller space of Lorentzian tori. |
1509.07956 | Xuefeng Zhang | Xinliang An and Xuefeng Zhang | Examples of naked singularity formation in higher-dimensional
Einstein-vacuum spacetimes | 34 pages, 5 figures; to match the published version which combines
this number and arXiv:1509.07954 | Ann. Henri Poincare 19 (2018), 619-651 | 10.1007/s00023-017-0631-9 | null | gr-qc hep-th math-ph math.AP math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The vacuum Einstein equations in 5+1 dimensions are shown to admit solutions
describing naked singularity formation in gravitational collapse from
nonsingular asymptotically locally flat initial data that contain no trapped
surface. We present a class of specific examples with topology
$\mathbb{R}^{3+1} \times S^2$. Thanks to the Kaluza-Klein dimensional
reduction, these examples are constructed by lifting continuously self-similar
solutions of the 4-dimensional Einstein-scalar field system with a negative
exponential potential. The latter solutions are obtained by solving a
3-dimensional autonomous system of first-order ordinary differential equations
with a combined analytic and numerical approach. Their existence provides a new
test-bed for weak cosmic censorship in higher-dimensional gravity. In addition,
we point out that a similar attempt of lifting Christodoulou's naked
singularity solutions of massless scalar fields fails to capture formation of
naked singularities in 4+1 dimensions, due to a diverging Kretschmann scalar in
the initial data.
| [
{
"created": "Sat, 26 Sep 2015 09:33:35 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Oct 2015 05:52:28 GMT",
"version": "v2"
},
{
"created": "Wed, 31 Jan 2018 04:34:09 GMT",
"version": "v3"
}
] | 2018-02-07 | [
[
"An",
"Xinliang",
""
],
[
"Zhang",
"Xuefeng",
""
]
] | The vacuum Einstein equations in 5+1 dimensions are shown to admit solutions describing naked singularity formation in gravitational collapse from nonsingular asymptotically locally flat initial data that contain no trapped surface. We present a class of specific examples with topology $\mathbb{R}^{3+1} \times S^2$. Thanks to the Kaluza-Klein dimensional reduction, these examples are constructed by lifting continuously self-similar solutions of the 4-dimensional Einstein-scalar field system with a negative exponential potential. The latter solutions are obtained by solving a 3-dimensional autonomous system of first-order ordinary differential equations with a combined analytic and numerical approach. Their existence provides a new test-bed for weak cosmic censorship in higher-dimensional gravity. In addition, we point out that a similar attempt of lifting Christodoulou's naked singularity solutions of massless scalar fields fails to capture formation of naked singularities in 4+1 dimensions, due to a diverging Kretschmann scalar in the initial data. |
2106.02838 | Ratchaphat Nakarachinda | Ratchaphat Nakarachinda, Ekapong Hirunsirisawat, Lunchakorn Tannukij
and Pitayuth Wongjun | Effective thermodynamical system of Schwarzschild-de Sitter black holes
from R\'{e}nyi statistics | 41 pages, 14 figures | Phys. Rev. D 104, 064003 (2021) | 10.1103/PhysRevD.104.064003 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been known that the Schwarzschild-de Sitter (Sch-dS) black hole may
not be in thermal equilibrium and also be found to be thermodynamically
unstable in the standard black hole thermodynamics. In the present work, we
investigate the possibility to realize the thermodynamical stability of the
Sch-dS black hole as an effective system by using the R\'{e}nyi statistics,
which includes the non-extensive nature of black holes. Our results indicate
that the non-extensivity allows the black hole to be thermodynamically stable
which gives rise to the lower bound on the non-extensive parameter. By
comparing the results to ones in the separated system approach, we find that
the effective temperature is always smaller than the black hole horizon
temperature and the thermodynamically stable black hole in effective approach
is always larger than one in separated approach at a certain temperature. There
exists only the zeroth-order phase transition from the the hot gas phase to the
black hole phase for the effective system while it is possible to have the
transition of both the zeroth order and the first order for the separated
system.
| [
{
"created": "Sat, 5 Jun 2021 08:37:59 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Sep 2021 16:50:42 GMT",
"version": "v2"
}
] | 2021-09-03 | [
[
"Nakarachinda",
"Ratchaphat",
""
],
[
"Hirunsirisawat",
"Ekapong",
""
],
[
"Tannukij",
"Lunchakorn",
""
],
[
"Wongjun",
"Pitayuth",
""
]
] | It has been known that the Schwarzschild-de Sitter (Sch-dS) black hole may not be in thermal equilibrium and also be found to be thermodynamically unstable in the standard black hole thermodynamics. In the present work, we investigate the possibility to realize the thermodynamical stability of the Sch-dS black hole as an effective system by using the R\'{e}nyi statistics, which includes the non-extensive nature of black holes. Our results indicate that the non-extensivity allows the black hole to be thermodynamically stable which gives rise to the lower bound on the non-extensive parameter. By comparing the results to ones in the separated system approach, we find that the effective temperature is always smaller than the black hole horizon temperature and the thermodynamically stable black hole in effective approach is always larger than one in separated approach at a certain temperature. There exists only the zeroth-order phase transition from the the hot gas phase to the black hole phase for the effective system while it is possible to have the transition of both the zeroth order and the first order for the separated system. |
2207.00727 | Shahram Jalalzadeh | S. Jalalzadeh | Resolution of challenging problems in quantum cosmology with
electromagnetic radiation | 7 pages, to appear in Phys. Lett. B | Phys. Lett. B 833 (2022) 137285 | 10.1016/j.physletb.2022.137285 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the quantum cosmology of a closed spatially homogeneous and
isotropic Friedmann-Lema\^itre-Robertson-Walker (FLRW) minisuperspace model
with electromagnetic radiation as matter content. We solve the corresponding
Wheeler-DeWitt equation by utilizing Riemann's zeta function regularization
method. We demonstrate that the regularized vacuum energy of the
electromagnetic field can overcome factor ordering, boundary conditions, and
singularity problems.
| [
{
"created": "Sat, 2 Jul 2022 03:36:30 GMT",
"version": "v1"
}
] | 2022-07-15 | [
[
"Jalalzadeh",
"S.",
""
]
] | We investigate the quantum cosmology of a closed spatially homogeneous and isotropic Friedmann-Lema\^itre-Robertson-Walker (FLRW) minisuperspace model with electromagnetic radiation as matter content. We solve the corresponding Wheeler-DeWitt equation by utilizing Riemann's zeta function regularization method. We demonstrate that the regularized vacuum energy of the electromagnetic field can overcome factor ordering, boundary conditions, and singularity problems. |
gr-qc/9912038 | Chamula Marian | V. Skalsky | A problem of hypothetical emerging of matter objects on horizon in the
standard model of universe | 3 pages | null | null | null | gr-qc | null | In the standard model of universe the increase in mass of our observed
expansive Universe is explained by the assumption of emerging the matter
objects on the horizon (of the most remote visibility). However, the physical
analysis of the influence of this assumption on the velocity of matter objects
shows unambiguously that this hypothetical assumption contradicts the theory of
gravity.
| [
{
"created": "Fri, 10 Dec 1999 09:46:39 GMT",
"version": "v1"
},
{
"created": "Mon, 25 Sep 2000 18:31:28 GMT",
"version": "v2"
}
] | 2007-05-23 | [
[
"Skalsky",
"V.",
""
]
] | In the standard model of universe the increase in mass of our observed expansive Universe is explained by the assumption of emerging the matter objects on the horizon (of the most remote visibility). However, the physical analysis of the influence of this assumption on the velocity of matter objects shows unambiguously that this hypothetical assumption contradicts the theory of gravity. |
1711.02893 | Yu Li | Yu Li | Dynamics of two-scalar-field cosmological models beyond the exponential
potential | 12 pages,3 figures | International Journal of Modern Physics D Vol. 26 (2017) 1750164 | 10.1142/S0218271817501644 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we discuss the dynamics of two- scalar-field cosmological
models. Unlike in the situation of exponential potential, we find that there
are late-time attractors in which one scalar field dominates the energy density
of universe and the other one decay. We also discuss the possibility of
multiple attractors model which is useful to realize the evolution of the
universe from a scaling era to recent acceleration era. We also give the
conditions of the existence of multiple attractors.
| [
{
"created": "Wed, 8 Nov 2017 10:11:53 GMT",
"version": "v1"
}
] | 2017-11-09 | [
[
"Li",
"Yu",
""
]
] | In this paper, we discuss the dynamics of two- scalar-field cosmological models. Unlike in the situation of exponential potential, we find that there are late-time attractors in which one scalar field dominates the energy density of universe and the other one decay. We also discuss the possibility of multiple attractors model which is useful to realize the evolution of the universe from a scaling era to recent acceleration era. We also give the conditions of the existence of multiple attractors. |
1503.00098 | Salvatore Capozziello | Mariacristina Paolella and Salvatore Capozziello | Hojman Symmetry Approach for Scalar-Tensor Cosmology | 6 pages, 4 figures, to appear in Phys. Lett. A | null | 10.1016/j.physleta.2015.02.044 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Scalar-tensor Cosmologies can be dealt under the standard of the Hojman
conservation theorem that allows to fix the form of the coupling $F(\phi)$, of
the potential $V(\phi)$ and to find out exact solutions for related
cosmological models. Specifically, the existence of a symmetry transformation
vector for the equations of motion gives rise to a Hojman conserved quantity on
the corresponding minisuperpace and exact solutions for the cosmic scale factor
$a$ and the scalar field $\phi$ can be achieved. In particular, we take
advantage of the fact that minimally coupled solutions, previously obtained in
the Einstein frame, can be conformally transformed in non-minimally coupled
solutions in the Jordan frame. Some physically relevant examples are worked
out.
| [
{
"created": "Sat, 28 Feb 2015 08:38:40 GMT",
"version": "v1"
}
] | 2015-06-24 | [
[
"Paolella",
"Mariacristina",
""
],
[
"Capozziello",
"Salvatore",
""
]
] | Scalar-tensor Cosmologies can be dealt under the standard of the Hojman conservation theorem that allows to fix the form of the coupling $F(\phi)$, of the potential $V(\phi)$ and to find out exact solutions for related cosmological models. Specifically, the existence of a symmetry transformation vector for the equations of motion gives rise to a Hojman conserved quantity on the corresponding minisuperpace and exact solutions for the cosmic scale factor $a$ and the scalar field $\phi$ can be achieved. In particular, we take advantage of the fact that minimally coupled solutions, previously obtained in the Einstein frame, can be conformally transformed in non-minimally coupled solutions in the Jordan frame. Some physically relevant examples are worked out. |
2207.12034 | Songbai Chen | Xin Qin, Songbai Chen, Zelin Zhang, Jiliang Jing | Polarized image of a rotating black hole in Scalar-Tensor-Vector-Gravity
theory | 20 pages, 13 figures, Accepted for publication in Astrophys. J | The Astrophysical Journal, 938:2, 2022 | 10.3847/1538-4357/ac8f49 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The polarized images of a synchrotron emitting ring are studied in the
spacetime of a rotating black hole in the Scalar-Tensor-Vector-Gravity (STVG)
theory. The black hole owns an additional dimensionless MOG parameter described
its deviation from Kerr black hole. The effects of the MOG parameter on the
observed polarization vector and Strokes $Q-U$ loops depend heavily on the spin
parameter, the magnetic field configuration, the fluid velocity and the
observation inclination angle. For the fixed MOG parameter, the changes of the
polarization vector in the image plane are similar to those in the Kerr black
hole case. The comparison of the polarization images between Kerr-MOG black
hole and M87* implies that there remains some possibility for the STVG-MOG
theory.
| [
{
"created": "Mon, 25 Jul 2022 10:17:21 GMT",
"version": "v1"
},
{
"created": "Sun, 4 Sep 2022 01:36:34 GMT",
"version": "v2"
}
] | 2022-10-26 | [
[
"Qin",
"Xin",
""
],
[
"Chen",
"Songbai",
""
],
[
"Zhang",
"Zelin",
""
],
[
"Jing",
"Jiliang",
""
]
] | The polarized images of a synchrotron emitting ring are studied in the spacetime of a rotating black hole in the Scalar-Tensor-Vector-Gravity (STVG) theory. The black hole owns an additional dimensionless MOG parameter described its deviation from Kerr black hole. The effects of the MOG parameter on the observed polarization vector and Strokes $Q-U$ loops depend heavily on the spin parameter, the magnetic field configuration, the fluid velocity and the observation inclination angle. For the fixed MOG parameter, the changes of the polarization vector in the image plane are similar to those in the Kerr black hole case. The comparison of the polarization images between Kerr-MOG black hole and M87* implies that there remains some possibility for the STVG-MOG theory. |
gr-qc/9712079 | Stephen M. Merkowitz | Stephen M. Merkowitz | Solution to the inverse problem for a noisy spherical gravitational wave
antenna | 12 pages, 3 figures, to appear in Phys. Rev. D | Phys.Rev.D58:062002,1998 | 10.1103/PhysRevD.58.062002 | null | gr-qc | null | A spherical gravitational wave antenna is distinct from other types of
gravitational wave antennas in that only a single detector is necessary to
determine the direction and polarization of a gravitational wave. Zhou and
Michelson showed that the inverse problem can be solved using the maximum
likelihood method if the detector outputs are independent and have normally
distributed noise with the same variance. This paper presents an analytic
solution using only linear algebra that is found to produce identical results
as the maximum likelihood method but with less computational burden.
Applications of this solution to gravitational waves in alternative symmetric
metric theories of gravity and impulsive excitations also are discussed.
| [
{
"created": "Thu, 18 Dec 1997 12:49:02 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Jul 1998 15:50:59 GMT",
"version": "v2"
}
] | 2009-12-30 | [
[
"Merkowitz",
"Stephen M.",
""
]
] | A spherical gravitational wave antenna is distinct from other types of gravitational wave antennas in that only a single detector is necessary to determine the direction and polarization of a gravitational wave. Zhou and Michelson showed that the inverse problem can be solved using the maximum likelihood method if the detector outputs are independent and have normally distributed noise with the same variance. This paper presents an analytic solution using only linear algebra that is found to produce identical results as the maximum likelihood method but with less computational burden. Applications of this solution to gravitational waves in alternative symmetric metric theories of gravity and impulsive excitations also are discussed. |
gr-qc/9309005 | Fonarev Oleg | Oleg A. Fonarev | Wigner function and quantum kinetic theory in curved space-time and
external fields | 41 pages | J.Math.Phys.35:2105-2129,1994 | 10.1063/1.530542 | null | gr-qc | null | A new definition of the Wigner function for quantum fields coupled to curved
space--time and an external Yang--Mills field is studied on the example of a
scalar and a Dirac fields. The definition uses the formalism of the tangent
bundles and is explicitly covariant and gauge invariant. Derivation of
collisionless quantum kinetic equations is carried out for both quantum fields
by using the first order formalism of Duffin and Kemmer. The evolution of the
Wigner function is governed by the quantum corrected Liouville--Vlasov equation
supplemented by the generalized mass--shell constraint. The structure of the
quantum corrections is perturbatively found in all adiabatic orders. The lowest
order quantum--curvature corrections coincide with the ones found by Winter.
| [
{
"created": "Thu, 2 Sep 1993 14:54:28 GMT",
"version": "v1"
}
] | 2010-11-01 | [
[
"Fonarev",
"Oleg A.",
""
]
] | A new definition of the Wigner function for quantum fields coupled to curved space--time and an external Yang--Mills field is studied on the example of a scalar and a Dirac fields. The definition uses the formalism of the tangent bundles and is explicitly covariant and gauge invariant. Derivation of collisionless quantum kinetic equations is carried out for both quantum fields by using the first order formalism of Duffin and Kemmer. The evolution of the Wigner function is governed by the quantum corrected Liouville--Vlasov equation supplemented by the generalized mass--shell constraint. The structure of the quantum corrections is perturbatively found in all adiabatic orders. The lowest order quantum--curvature corrections coincide with the ones found by Winter. |
0808.1042 | Vladimir Khatsymovsky | V.M. Khatsymovsky | Defining some integrals in Regge calculus | 7 pages | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Regge calculus minisuperspace action in the connection representation has the
form in which each term is linear over some field variable (scale of area-type
variable with sign). We are interested in the result of performing integration
over connections in the path integral. To find this function, we compute its
moments, i. e. integrals with powers of that variable. Calculation proceeds
through intermediate appearance of $\delta$-functions and integrating them out
and leads to finite result for any power. The function of interest should
therefore be exponentially suppressed at large areas and it really does being
restored from moments. This gives for gravity a way of defining such
nonabsolutely convergent integral as path integral.
| [
{
"created": "Thu, 7 Aug 2008 15:09:49 GMT",
"version": "v1"
}
] | 2008-10-09 | [
[
"Khatsymovsky",
"V. M.",
""
]
] | Regge calculus minisuperspace action in the connection representation has the form in which each term is linear over some field variable (scale of area-type variable with sign). We are interested in the result of performing integration over connections in the path integral. To find this function, we compute its moments, i. e. integrals with powers of that variable. Calculation proceeds through intermediate appearance of $\delta$-functions and integrating them out and leads to finite result for any power. The function of interest should therefore be exponentially suppressed at large areas and it really does being restored from moments. This gives for gravity a way of defining such nonabsolutely convergent integral as path integral. |
0802.0330 | Stefano Ansoldi | Stefano Ansoldi | Spherical black holes with regular center: a review of existing models
including a recent realization with Gaussian sources | LaTeX, 36 pages, 10 figures. To appear in the proceedings of "BH2,
Dynamics and Thermodynamics of Blackholes and Naked Singularities", May 10-12
2007, Milano, Italy (conference website: http://www.mate.polimi.it/bh2) | null | null | KUNS-2108 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review, in a historical perspective, some results about black hole
spacetimes with a regular center. We then see how their properties are realized
in a specific solution that recently appeared; in particular we analyze in
detail the (necessary) violation of the strong energy condition.
| [
{
"created": "Mon, 4 Feb 2008 03:13:00 GMT",
"version": "v1"
}
] | 2008-02-05 | [
[
"Ansoldi",
"Stefano",
""
]
] | We review, in a historical perspective, some results about black hole spacetimes with a regular center. We then see how their properties are realized in a specific solution that recently appeared; in particular we analyze in detail the (necessary) violation of the strong energy condition. |
2110.02536 | Rui-Yun Guo | Rui-Yun Guo, Lu Feng, Tian-Ying Yao, and Xing-Yu Chen | Exploration of interacting dynamical dark energy model with interaction
term including the equation-of-state parameter: alleviation of the $H_{0}$
tension | 14 pages, 4 figures | JCAP12(2021)036 | 10.1088/1475-7516/2021/12/036 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We explore a scenario of interacting dynamical dark energy model with the
interaction term $Q$ including the varying equation-of-state parameter $w$.
Using the data combination of the cosmic microwave background, the baryon
acoustic oscillation, and the type Ia supernovae, to global fit the interacting
dynamical dark energy model, we find that adding a factor of the varying $w$ in
the function of $Q$ can change correlations between the coupling constant
$\beta$ and other parameters, and then has a huge impact on the fitting result
of $\beta$. In this model, the fitting value of $H_{0}$ is lower at the $3.54
\sigma$ level than the direct measurement value of $H_{0}$ . Comparing to the
case of interacting dynamical dark energy model with $Q$ excluding $w$, the
model with $Q$ including the constant $w$ is more favored by the current
mainstream observation. To obtain higher fitting values of $H_{0}$ and narrow
the discrepancy of $H_{0}$ between different observations, additional
parameters including the effective number of relativistic species, the total
neutrino mass, and massive sterile neutrinos are considered in the interacting
dynamical dark energy cosmology. We find that the $H_{0}$ tension can be
further reduced in these models, but is still at the about $3 \sigma$ level.
| [
{
"created": "Wed, 6 Oct 2021 06:58:58 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Nov 2021 06:40:09 GMT",
"version": "v2"
},
{
"created": "Mon, 20 Dec 2021 06:24:24 GMT",
"version": "v3"
}
] | 2021-12-21 | [
[
"Guo",
"Rui-Yun",
""
],
[
"Feng",
"Lu",
""
],
[
"Yao",
"Tian-Ying",
""
],
[
"Chen",
"Xing-Yu",
""
]
] | We explore a scenario of interacting dynamical dark energy model with the interaction term $Q$ including the varying equation-of-state parameter $w$. Using the data combination of the cosmic microwave background, the baryon acoustic oscillation, and the type Ia supernovae, to global fit the interacting dynamical dark energy model, we find that adding a factor of the varying $w$ in the function of $Q$ can change correlations between the coupling constant $\beta$ and other parameters, and then has a huge impact on the fitting result of $\beta$. In this model, the fitting value of $H_{0}$ is lower at the $3.54 \sigma$ level than the direct measurement value of $H_{0}$ . Comparing to the case of interacting dynamical dark energy model with $Q$ excluding $w$, the model with $Q$ including the constant $w$ is more favored by the current mainstream observation. To obtain higher fitting values of $H_{0}$ and narrow the discrepancy of $H_{0}$ between different observations, additional parameters including the effective number of relativistic species, the total neutrino mass, and massive sterile neutrinos are considered in the interacting dynamical dark energy cosmology. We find that the $H_{0}$ tension can be further reduced in these models, but is still at the about $3 \sigma$ level. |
1303.7062 | Boris E. Meierovich | Boris E. Meierovich | Galaxy rotation curves. The theory | 17 pages, 13 figures | Physical Review D 87, D 87, 103510 (2013) | 10.1103/PhysRevD.87.103510 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The non-gauge vector field with as simple as possible Lagrangian
(\ref{Lagrangian}) turned out an adequate tool for macroscopic description of
the main properties of dark matter. The dependence of the velocity of a star on
the radius of the orbit $V\left(r\right) $ -- galaxy rotation curve -- is
derived analytically from the first principles\ completely within the
Einstein's general relativity. The Milgrom's empirical modification of
Newtonian dynamics in nonrelativistic limit (MOND) gets justified and specified
in detail. In particular, the transition to a plateau is accompanied by damping
oscillations. In the scale of a galaxy, and in the scale of the whole universe,
the dark matter is described by a vector field with the same energy-momentum
tensor. It is the evidence of the common physical nature. Now, when we have the
general expression (\ref{Tik b=c=0}) for the energy-momentum tensor of dark
matter, it is possible to analyze its influence on the structure and evolution
of super heavy stars and black holes.
| [
{
"created": "Thu, 28 Mar 2013 08:13:51 GMT",
"version": "v1"
}
] | 2016-05-24 | [
[
"Meierovich",
"Boris E.",
""
]
] | The non-gauge vector field with as simple as possible Lagrangian (\ref{Lagrangian}) turned out an adequate tool for macroscopic description of the main properties of dark matter. The dependence of the velocity of a star on the radius of the orbit $V\left(r\right) $ -- galaxy rotation curve -- is derived analytically from the first principles\ completely within the Einstein's general relativity. The Milgrom's empirical modification of Newtonian dynamics in nonrelativistic limit (MOND) gets justified and specified in detail. In particular, the transition to a plateau is accompanied by damping oscillations. In the scale of a galaxy, and in the scale of the whole universe, the dark matter is described by a vector field with the same energy-momentum tensor. It is the evidence of the common physical nature. Now, when we have the general expression (\ref{Tik b=c=0}) for the energy-momentum tensor of dark matter, it is possible to analyze its influence on the structure and evolution of super heavy stars and black holes. |
1212.1477 | Sam Dolan Dr | Sam R. Dolan | Superradiant instabilities of rotating black holes in the time domain | 17 pages, 13 figures, to match journal version | Phys. Rev. D 87, 124026 (2013) | 10.1103/PhysRevD.87.124026 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Bosonic fields on rotating black hole spacetimes are subject to amplification
by superradiance, which induces exponentially-growing instabilities (the `black
hole bomb') in two scenarios: if the black hole is enclosed by a mirror, or if
the bosonic field has rest mass. Here we present a time-domain study of the
scalar field on Kerr spacetime which probes ultra-long timescales up to $t
\lesssim 5 \times 10^6 M$, to reveal the growth of the instability. We describe
an highly-efficient method for evolving the field, based on a spectral
decomposition into a coupled set of 1+1D equations, and an absorbing boundary
condition inspired by the `perfectly-matched layers' paradigm. First, we
examine the mirror case to study how the instability timescale and mode
structure depend on mirror radius. Next, we examine the massive-field, whose
rich spectrum (revealed through Fourier analysis) generates `beating' effects
which disguise the instability. We show that the instability is clearly
revealed by tracking the stress-energy of the field in the exterior spacetime.
We calculate the growth rate for a range of mass couplings, by applying a
frequency-filer to isolate individual modal contributions to the time-domain
signal. Our results are in accord with previous frequency-domain studies which
put the maximum growth rate at $\tau^{-1} \approx 1.72 \times 10^{-7}
(GM/c^3)^{-1}$ for the massive scalar field on Kerr spacetime.
| [
{
"created": "Thu, 6 Dec 2012 21:28:06 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Jul 2013 11:16:16 GMT",
"version": "v2"
}
] | 2013-07-02 | [
[
"Dolan",
"Sam R.",
""
]
] | Bosonic fields on rotating black hole spacetimes are subject to amplification by superradiance, which induces exponentially-growing instabilities (the `black hole bomb') in two scenarios: if the black hole is enclosed by a mirror, or if the bosonic field has rest mass. Here we present a time-domain study of the scalar field on Kerr spacetime which probes ultra-long timescales up to $t \lesssim 5 \times 10^6 M$, to reveal the growth of the instability. We describe an highly-efficient method for evolving the field, based on a spectral decomposition into a coupled set of 1+1D equations, and an absorbing boundary condition inspired by the `perfectly-matched layers' paradigm. First, we examine the mirror case to study how the instability timescale and mode structure depend on mirror radius. Next, we examine the massive-field, whose rich spectrum (revealed through Fourier analysis) generates `beating' effects which disguise the instability. We show that the instability is clearly revealed by tracking the stress-energy of the field in the exterior spacetime. We calculate the growth rate for a range of mass couplings, by applying a frequency-filer to isolate individual modal contributions to the time-domain signal. Our results are in accord with previous frequency-domain studies which put the maximum growth rate at $\tau^{-1} \approx 1.72 \times 10^{-7} (GM/c^3)^{-1}$ for the massive scalar field on Kerr spacetime. |
0912.2397 | Chen Songbai | Songbai Chen, Liancheng Wang, Chikun Ding, Jiliang Jing | Holographic superconductors in the AdS black hole spacetime with a
global monopole | 12 pages, 4 figures, references added and corrected, accepted for
publication in NPB | Nucl.Phys. B836:222-231,2010 | 10.1016/j.nuclphysb.2010.04.025 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study holographic superconductors in the Schwarzschild-AdS black hole with
a global monopole through a charged complex scalar field. We calculate the
condensates of the charged operators in the dual conformal field theories
(CFTs) and discuss the effects of the global monopole on the condensation
formation. Moreover, we compute the electric conductive using the probe
approximation and find that the properties of the conductive are quite similar
to those in the Schwarzschild-AdS black hole. These results can help us know
more about holographic superconductors in the asymptotic AdS black holes.
| [
{
"created": "Sat, 12 Dec 2009 05:57:46 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Dec 2009 09:29:02 GMT",
"version": "v2"
},
{
"created": "Wed, 28 Apr 2010 00:32:59 GMT",
"version": "v3"
},
{
"created": "Tue, 8 Jun 2010 03:54:47 GMT",
"version": "v4"
}
] | 2014-11-20 | [
[
"Chen",
"Songbai",
""
],
[
"Wang",
"Liancheng",
""
],
[
"Ding",
"Chikun",
""
],
[
"Jing",
"Jiliang",
""
]
] | We study holographic superconductors in the Schwarzschild-AdS black hole with a global monopole through a charged complex scalar field. We calculate the condensates of the charged operators in the dual conformal field theories (CFTs) and discuss the effects of the global monopole on the condensation formation. Moreover, we compute the electric conductive using the probe approximation and find that the properties of the conductive are quite similar to those in the Schwarzschild-AdS black hole. These results can help us know more about holographic superconductors in the asymptotic AdS black holes. |
gr-qc/0208038 | John Eastmond | John F.G. Eastmond | The Doomsday Argument, Consciousness and Many Worlds | LaTeX2e, 30 pages | null | null | null | gr-qc | null | The doomsday argument is a probabilistic argument that claims to predict the
total lifetime of the human race. By examining the case of an individual
lifetime, I conclude that the argument is fundamentally related to
consciousness. I derive a reformulation stating that an infinite conscious
lifetime is not possible even in principle. By considering a hypothetical
conscious computer, running a non-terminating program, I deduce that
consciousness cannot be generated by a single set of deterministic laws.
Instead, I hypothesize that consciousness is generated by a superposition of
brain states that is simultaneously associated with many quasi-classical
histories, each following a different set of deterministic laws. I generalize
the doomsday argument and discover that it makes no prediction in this case.
Thus I conclude that the very fact of our consciousness provides us with
evidence for a many-worlds interpretation of reality in which our future is not
predictable using anthropic reasoning.
| [
{
"created": "Thu, 15 Aug 2002 16:13:06 GMT",
"version": "v1"
},
{
"created": "Thu, 22 Aug 2002 08:58:45 GMT",
"version": "v2"
},
{
"created": "Sat, 5 Oct 2002 09:29:47 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Eastmond",
"John F. G.",
""
]
] | The doomsday argument is a probabilistic argument that claims to predict the total lifetime of the human race. By examining the case of an individual lifetime, I conclude that the argument is fundamentally related to consciousness. I derive a reformulation stating that an infinite conscious lifetime is not possible even in principle. By considering a hypothetical conscious computer, running a non-terminating program, I deduce that consciousness cannot be generated by a single set of deterministic laws. Instead, I hypothesize that consciousness is generated by a superposition of brain states that is simultaneously associated with many quasi-classical histories, each following a different set of deterministic laws. I generalize the doomsday argument and discover that it makes no prediction in this case. Thus I conclude that the very fact of our consciousness provides us with evidence for a many-worlds interpretation of reality in which our future is not predictable using anthropic reasoning. |
gr-qc/0406027 | Hossein Shojaie | Hossein Shojaie, Mehrdad Farhoudi | A varying-c cosmology | 11 pages | Can.J.Phys.85:1395-1408,2007 | 10.1139/P07-132 | null | gr-qc astro-ph | null | We develop a new model for the Universe based on two key assumptions: first,
the inertial energy of the Universe is a constant, and second, the total energy
of a particle, the inertial plus the gravitational potential energy produced by
the other mass in the Universe, is zero. This model allows the speed of light
and the total mass of the Universe to vary as functions of cosmological time,
where we assume the gravitational constant to be a constant. By means of these
assumptions, the relations between the scale factor and the other parameters
are derived. The Einstein equation, by making it compatible with varying-$c$,
is used and the Friedmann equations in this model are obtained. Assuming the
matter content of the Universe to be perfect fluids, the model fixes $\gamma$
to be 2/3. That is, the whole Universe always exhibits a negative pressure.
Moreover, the behavior of the scale factor is the same for any value of the
curvature. It is also shown that the Universe began from a big bang with zero
initial mass and expands forever even with positive curvature, but it is always
decelerating. At the end, solutions to some famous problems, mainly of the
standard big bang model, and an explanation for the observational data about
the accelerating Universe are provided.
| [
{
"created": "Tue, 8 Jun 2004 03:15:00 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Oct 2004 10:10:57 GMT",
"version": "v2"
},
{
"created": "Sat, 22 Dec 2007 10:52:23 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Shojaie",
"Hossein",
""
],
[
"Farhoudi",
"Mehrdad",
""
]
] | We develop a new model for the Universe based on two key assumptions: first, the inertial energy of the Universe is a constant, and second, the total energy of a particle, the inertial plus the gravitational potential energy produced by the other mass in the Universe, is zero. This model allows the speed of light and the total mass of the Universe to vary as functions of cosmological time, where we assume the gravitational constant to be a constant. By means of these assumptions, the relations between the scale factor and the other parameters are derived. The Einstein equation, by making it compatible with varying-$c$, is used and the Friedmann equations in this model are obtained. Assuming the matter content of the Universe to be perfect fluids, the model fixes $\gamma$ to be 2/3. That is, the whole Universe always exhibits a negative pressure. Moreover, the behavior of the scale factor is the same for any value of the curvature. It is also shown that the Universe began from a big bang with zero initial mass and expands forever even with positive curvature, but it is always decelerating. At the end, solutions to some famous problems, mainly of the standard big bang model, and an explanation for the observational data about the accelerating Universe are provided. |
2406.05544 | Fernando Carneiro | F. L. Carneiro, B. C. C. Carneiro, D. L. Azevedo and S. C. Ulhoa | On Nanocones as a Gravitational Analog System | 13 pages, 6 figures. Comments are welcome | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | This study delves into the fundamental properties of graphene and boron
nitride (BN) nanostructures, exploring their torsional energy characteristics
within the framework of Teleparallel Equivalent of General Relativity (TEGR).
By constructing nanocones with disclination defects in these materials, we
investigate the linear dependence of torsional energy on the disclination
angle, as predicted by TEGR. The qualitative validation of TEGR's energy
expression is supported by our simulations, which show a strong correlation
between the torsional energy and the disclination angle, consistent with the
theoretical predictions. Furthermore, we propose a quantitative analysis by
estimating the coupling constant $k$ associated with TEGR through molecular
simulations and Density Functional Theory (DFT) calculations. Our results
suggest that $k$ reflects the interatomic forces within the materials,
providing insights into the nature of spacetime and gravitational interactions
on a microscopic scale. These findings not only contribute to our understanding
of material physics but also offer implications for the precision and validity
of TEGR in describing gravitational phenomena.
| [
{
"created": "Sat, 8 Jun 2024 18:20:21 GMT",
"version": "v1"
}
] | 2024-06-11 | [
[
"Carneiro",
"F. L.",
""
],
[
"Carneiro",
"B. C. C.",
""
],
[
"Azevedo",
"D. L.",
""
],
[
"Ulhoa",
"S. C.",
""
]
] | This study delves into the fundamental properties of graphene and boron nitride (BN) nanostructures, exploring their torsional energy characteristics within the framework of Teleparallel Equivalent of General Relativity (TEGR). By constructing nanocones with disclination defects in these materials, we investigate the linear dependence of torsional energy on the disclination angle, as predicted by TEGR. The qualitative validation of TEGR's energy expression is supported by our simulations, which show a strong correlation between the torsional energy and the disclination angle, consistent with the theoretical predictions. Furthermore, we propose a quantitative analysis by estimating the coupling constant $k$ associated with TEGR through molecular simulations and Density Functional Theory (DFT) calculations. Our results suggest that $k$ reflects the interatomic forces within the materials, providing insights into the nature of spacetime and gravitational interactions on a microscopic scale. These findings not only contribute to our understanding of material physics but also offer implications for the precision and validity of TEGR in describing gravitational phenomena. |
1910.12344 | Jaroslaw Jaracz | Jaroslaw Jaracz | The Penrose inequality and positive mass theorem with charge for
manifolds with asymptotically cylindrical ends | null | null | 10.1007/s00023-020-00927-z | null | gr-qc math-ph math.DG math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We establish the charged Penrose inequality for time symmetric initial data
sets having an outermost minimal surface boundary and finitely many
asymptotically cylindrical ends, with an appropriate rigidity statement. This
is accomplished by a doubling argument based on the work of Weinstein and
Yamada, and a subsequent application of the ordinary charged Penrose inequality
as established by Khuri, Weinstein, and Yamada. Furthermore, the techniques
used in the aforementioned proof allow for the proof of the positive mass
theorem with charge for such manifolds.
| [
{
"created": "Sun, 27 Oct 2019 20:35:51 GMT",
"version": "v1"
},
{
"created": "Sun, 26 Jan 2020 16:12:04 GMT",
"version": "v2"
}
] | 2020-08-26 | [
[
"Jaracz",
"Jaroslaw",
""
]
] | We establish the charged Penrose inequality for time symmetric initial data sets having an outermost minimal surface boundary and finitely many asymptotically cylindrical ends, with an appropriate rigidity statement. This is accomplished by a doubling argument based on the work of Weinstein and Yamada, and a subsequent application of the ordinary charged Penrose inequality as established by Khuri, Weinstein, and Yamada. Furthermore, the techniques used in the aforementioned proof allow for the proof of the positive mass theorem with charge for such manifolds. |
gr-qc/0001090 | Takahiro Tanaka | Takahiro Tanaka and Hideyuki Tagoshi | The use of new coordinates for the template space in hierarchical search
for gravitational waves from inspiraling binaries | 8 pages, 4 figures | Phys.Rev.D62:082001,2000 | 10.1103/PhysRevD.62.082001 | OU-TAP 114; UAB-FT 484 | gr-qc | null | We discuss a method to analyze data from interferometric gravitational wave
detectors focusing on the technique of hierarchical search to detect
gravitational waves from inspiraling binaries. For this purpose, we propose new
coordinates to parameterize the template space. Using our new coordinates, we
develop several new techniques for two step search, which would reduce the
computation cost by large amount. These techniques become more important when
we need to implement a $\chi^2$-test as a detection criterion.
| [
{
"created": "Thu, 27 Jan 2000 14:19:46 GMT",
"version": "v1"
}
] | 2009-12-30 | [
[
"Tanaka",
"Takahiro",
""
],
[
"Tagoshi",
"Hideyuki",
""
]
] | We discuss a method to analyze data from interferometric gravitational wave detectors focusing on the technique of hierarchical search to detect gravitational waves from inspiraling binaries. For this purpose, we propose new coordinates to parameterize the template space. Using our new coordinates, we develop several new techniques for two step search, which would reduce the computation cost by large amount. These techniques become more important when we need to implement a $\chi^2$-test as a detection criterion. |
gr-qc/9702006 | Ruth M. Williams | Ruth M. Williams | Recent Progress in Regge Calculus | 9 pages, no figures, LaTeX. Submitted to the Proceedings of the
Second Meeting on Constrained Dynamics and Quantum Gravity, Santa Margherita
Ligure, Italy, September 1996 | Nucl.Phys.Proc.Suppl. 57 (1997) 73-81 | 10.1016/S0920-5632(97)00355-1 | DAMTP/97-5 | gr-qc | null | While there has been some advance in the use of Regge calculus as a tool in
numerical relativity, the main progress in Regge calculus recently has been in
quantum gravity. After a brief discussion of this progress, attention is
focussed on two particular, related aspects. Firstly, the possible definitions
of diffeomorphisms or gauge transformations in Regge calculus are examined and
examples are given. Secondly, an investigation of the signature of the
simplicial supermetric is described. This is the Lund-Regge metric on
simplicial configuration space and defines the distance between simplicial
three-geometries. Information on its signature can be used to extend the rather
limited results on the signature of the supermetric in the continuum case. This
information is obtained by a combination of analytic and numerical techniques.
For the three-sphere and the three-torus, the numerical results agree with the
analytic ones and show the existence of degeneracy and signature change. Some
``vertical'' directions in simplicial configuration space, corresponding to
simplicial metrics related by gauge transformations, are found for the
three-torus.
| [
{
"created": "Mon, 3 Feb 1997 12:46:05 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Williams",
"Ruth M.",
""
]
] | While there has been some advance in the use of Regge calculus as a tool in numerical relativity, the main progress in Regge calculus recently has been in quantum gravity. After a brief discussion of this progress, attention is focussed on two particular, related aspects. Firstly, the possible definitions of diffeomorphisms or gauge transformations in Regge calculus are examined and examples are given. Secondly, an investigation of the signature of the simplicial supermetric is described. This is the Lund-Regge metric on simplicial configuration space and defines the distance between simplicial three-geometries. Information on its signature can be used to extend the rather limited results on the signature of the supermetric in the continuum case. This information is obtained by a combination of analytic and numerical techniques. For the three-sphere and the three-torus, the numerical results agree with the analytic ones and show the existence of degeneracy and signature change. Some ``vertical'' directions in simplicial configuration space, corresponding to simplicial metrics related by gauge transformations, are found for the three-torus. |
2210.06081 | Dmitri Fursaev | Dmitri V. Fursaev | Black Hole Thermodynamics and Perturbative Quantum Gravity | Invited chapter for the Section "Perturbative Quantum Gravity" of the
"Handbook of Quantum Gravity" (Eds. C. Bambi, L. Modesto and I.L. Shapiro,
Springer Singapore, expected in 2023), 36 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An introduction to generalized thermodynamics of quantum black holes, in the
one-loop approximation, is given. The material is aimed at graduate students.
The topics include: quantum evaporation of black holes, Euclidean formulation
of quantum theory on black hole backgrounds, the Hartle-Hawking-Israel state,
generalized entropy of a quantum black hole and its relation to the entropy of
entanglement.
| [
{
"created": "Wed, 12 Oct 2022 10:53:28 GMT",
"version": "v1"
}
] | 2022-10-13 | [
[
"Fursaev",
"Dmitri V.",
""
]
] | An introduction to generalized thermodynamics of quantum black holes, in the one-loop approximation, is given. The material is aimed at graduate students. The topics include: quantum evaporation of black holes, Euclidean formulation of quantum theory on black hole backgrounds, the Hartle-Hawking-Israel state, generalized entropy of a quantum black hole and its relation to the entropy of entanglement. |
1412.6000 | Andrea Dapor | Mehdi Assanioussi, Andrea Dapor, Jerzy Lewandowski | Rainbow metric from quantum gravity | 4 pages, 2 figures. Accepted version in PLB | null | 10.1016/j.physletb.2015.10.043 | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this letter, we describe a general mechanism for emergence of a rainbow
metric from a quantum cosmological model. This idea is based on QFT on a
quantum space-time. Under general assumptions, we discover that the quantum
space-time on which the field propagates can be replaced by a classical
space-time, whose metric depends explicitly on the energy of the field: as
shown by an analysis of dispersion relations, quanta of different energy
propagate on different metrics, similar to photons in a refractive material
(hence the name "rainbow" used in the literature). In deriving this result, we
do not consider any specific theory of quantum gravity: the qualitative
behavior of high-energy particles on quantum space-time relies only on the
assumption that the quantum space-time is described by a wave-function $\Psi_o$
in a Hilbert space $\mathcal{H}_G$.
| [
{
"created": "Thu, 18 Dec 2014 18:56:13 GMT",
"version": "v1"
},
{
"created": "Sun, 21 Dec 2014 19:40:46 GMT",
"version": "v2"
},
{
"created": "Wed, 28 Oct 2015 12:05:13 GMT",
"version": "v3"
}
] | 2015-10-29 | [
[
"Assanioussi",
"Mehdi",
""
],
[
"Dapor",
"Andrea",
""
],
[
"Lewandowski",
"Jerzy",
""
]
] | In this letter, we describe a general mechanism for emergence of a rainbow metric from a quantum cosmological model. This idea is based on QFT on a quantum space-time. Under general assumptions, we discover that the quantum space-time on which the field propagates can be replaced by a classical space-time, whose metric depends explicitly on the energy of the field: as shown by an analysis of dispersion relations, quanta of different energy propagate on different metrics, similar to photons in a refractive material (hence the name "rainbow" used in the literature). In deriving this result, we do not consider any specific theory of quantum gravity: the qualitative behavior of high-energy particles on quantum space-time relies only on the assumption that the quantum space-time is described by a wave-function $\Psi_o$ in a Hilbert space $\mathcal{H}_G$. |
2201.13334 | Lisa Valerie Drummond | Lisa V. Drummond and Scott A. Hughes | Precisely computing bound orbits of spinning bodies around black holes
I: General framework and results for nearly equatorial orbits | 38 pages, 5 figures, submitted to Physical Review D; corrected typo
in Equation (C6) | null | 10.1103/PhysRevD.105.124040 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Very large mass ratio binary black hole systems are of interest both as a
clean limit of the two-body problem in general relativity, as well as for their
importance as sources of low-frequency gravitational waves. At lowest order,
the smaller body moves along a geodesic of the larger black hole's spacetime.
Post-geodesic effects include the gravitational self force, which incorporates
the backreaction of gravitational-wave emission, and the spin-curvature force,
which arises from coupling of the small body's spin to the black hole's
spacetime curvature. In this paper, we describe a method for precisely
computing bound orbits of spinning bodies about black holes. Our analysis
builds off of pioneering work by Witzany which demonstrated how to describe the
motion of a spinning body to linear order in the small body's spin. Exploiting
the fact that in the large mass-ratio limit spinning-body orbits are close to
geodesics and using closed-form results due to van de Meent describing
precession of the small body's spin along black hole orbits, we develop a
frequency-domain formulation of the motion which can be solved very precisely.
We examine a range of orbits with this formulation, focusing in this paper on
orbits which are eccentric and nearly equatorial (i.e., the orbit's motion is
$\mathcal{O}(S)$ out of the equatorial plane), but for which the small body's
spin is arbitrarily oriented. We discuss generic orbits with general small-body
spin orientation in a companion paper. We characterize the behavior of these
orbits and show how the small body's spin shifts the frequencies $\Omega_r$ and
$\Omega_\phi$ which affect orbital motion. These frequency shifts change
accumulated phases which are direct gravitational-wave observables,
illustrating the importance of precisely characterizing these quantities for
gravitational-wave observations. (Abridged)
| [
{
"created": "Mon, 31 Jan 2022 16:30:56 GMT",
"version": "v1"
},
{
"created": "Tue, 22 Mar 2022 17:40:16 GMT",
"version": "v2"
}
] | 2022-07-13 | [
[
"Drummond",
"Lisa V.",
""
],
[
"Hughes",
"Scott A.",
""
]
] | Very large mass ratio binary black hole systems are of interest both as a clean limit of the two-body problem in general relativity, as well as for their importance as sources of low-frequency gravitational waves. At lowest order, the smaller body moves along a geodesic of the larger black hole's spacetime. Post-geodesic effects include the gravitational self force, which incorporates the backreaction of gravitational-wave emission, and the spin-curvature force, which arises from coupling of the small body's spin to the black hole's spacetime curvature. In this paper, we describe a method for precisely computing bound orbits of spinning bodies about black holes. Our analysis builds off of pioneering work by Witzany which demonstrated how to describe the motion of a spinning body to linear order in the small body's spin. Exploiting the fact that in the large mass-ratio limit spinning-body orbits are close to geodesics and using closed-form results due to van de Meent describing precession of the small body's spin along black hole orbits, we develop a frequency-domain formulation of the motion which can be solved very precisely. We examine a range of orbits with this formulation, focusing in this paper on orbits which are eccentric and nearly equatorial (i.e., the orbit's motion is $\mathcal{O}(S)$ out of the equatorial plane), but for which the small body's spin is arbitrarily oriented. We discuss generic orbits with general small-body spin orientation in a companion paper. We characterize the behavior of these orbits and show how the small body's spin shifts the frequencies $\Omega_r$ and $\Omega_\phi$ which affect orbital motion. These frequency shifts change accumulated phases which are direct gravitational-wave observables, illustrating the importance of precisely characterizing these quantities for gravitational-wave observations. (Abridged) |
gr-qc/9404011 | Lee Smolin | Lee Smolin | The fate of black hole singularities and the parameters of the standard
models of particle physics and cosmology | LaTeX, 27 p.CGPG-94/3-5 | null | null | null | gr-qc | null | A cosmological scenario which explains the values of the parameters of the
standard models of elementary particle physics and cosmology is discussed. In
this scenario these parameters are set by a process analogous to natural
selection which follows naturally from the assumption that the singularities in
black holes are removed by quantum effects leading to the creation of new
expanding regions of the universe. The suggestion of J. A. Wheeler that the
parameters change randomly at such events leads naturally to the conjecture
that the parameters have been selected for values that extremize the production
of black holes. This leads directly to a prediction, which is that small
changes in any of the parameters should lead to a decrease in the number of
black holes produced by the universe. On plausible astrophysical assumptions it
is found that changes in many of the parameters do lead to a decrease in the
number of black holes produced by spiral galaxies. These include the masses of
the proton,neutron, electron and neutrino and the weak, strong and
electromagnetic coupling constants. Finally,this scenario predicts a natural
time scale for cosmology equal to the time over which spiral galaxies maintain
appreciable rates of star formation, which is compatible with current
observations that $\Omega = .1-.2$.
| [
{
"created": "Thu, 7 Apr 1994 23:59:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Smolin",
"Lee",
""
]
] | A cosmological scenario which explains the values of the parameters of the standard models of elementary particle physics and cosmology is discussed. In this scenario these parameters are set by a process analogous to natural selection which follows naturally from the assumption that the singularities in black holes are removed by quantum effects leading to the creation of new expanding regions of the universe. The suggestion of J. A. Wheeler that the parameters change randomly at such events leads naturally to the conjecture that the parameters have been selected for values that extremize the production of black holes. This leads directly to a prediction, which is that small changes in any of the parameters should lead to a decrease in the number of black holes produced by the universe. On plausible astrophysical assumptions it is found that changes in many of the parameters do lead to a decrease in the number of black holes produced by spiral galaxies. These include the masses of the proton,neutron, electron and neutrino and the weak, strong and electromagnetic coupling constants. Finally,this scenario predicts a natural time scale for cosmology equal to the time over which spiral galaxies maintain appreciable rates of star formation, which is compatible with current observations that $\Omega = .1-.2$. |
1706.01484 | Mariam Bouhmadi-Lopez | Imanol Albarran, Mariam Bouhmadi-L\'opez, Jo\~ao Morais | What if gravity becomes really repulsive in the future? | 7 pages, 3 figures. Further explanations provided. Version accepted
in EPJC | null | 10.1140/epjc/s10052-018-5728-x | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The current acceleration of the Universe is one of the most puzzling issues
in theoretical physics nowadays. We are far from giving an answer on this
letter to its true nature. Yet, with the observations we have at hand, we
analyse the different patterns that the gravitational potential can show in the
future. Surprisingly, gravity not only can get weaker in the near future, it
can even become repulsive; or equivalently, the gravitational potential may
become negative. We show this remark by using one of the simplest
phenomenological model we can imagine for dark energy. We have as well reviewed
the statefinder approach of these models. For completeness, we have also showed
the behaviour of the density contrast of dark matter and dark energy for these
simple (yet illustrative models). Our results are displayed at present and how
they evolve in the future.
| [
{
"created": "Mon, 5 Jun 2017 18:18:00 GMT",
"version": "v1"
},
{
"created": "Mon, 31 Jul 2017 18:36:04 GMT",
"version": "v2"
},
{
"created": "Tue, 13 Mar 2018 17:20:17 GMT",
"version": "v3"
}
] | 2018-04-18 | [
[
"Albarran",
"Imanol",
""
],
[
"Bouhmadi-López",
"Mariam",
""
],
[
"Morais",
"João",
""
]
] | The current acceleration of the Universe is one of the most puzzling issues in theoretical physics nowadays. We are far from giving an answer on this letter to its true nature. Yet, with the observations we have at hand, we analyse the different patterns that the gravitational potential can show in the future. Surprisingly, gravity not only can get weaker in the near future, it can even become repulsive; or equivalently, the gravitational potential may become negative. We show this remark by using one of the simplest phenomenological model we can imagine for dark energy. We have as well reviewed the statefinder approach of these models. For completeness, we have also showed the behaviour of the density contrast of dark matter and dark energy for these simple (yet illustrative models). Our results are displayed at present and how they evolve in the future. |
1705.04602 | Anna Paula Bacalhau | Anna Paula Bacalhau, Patrick Peter and Sandro D. P. Vitenti | Anisotropic multiple bounce models | 11 pages, 9 figures, minor corrections | Phys. Rev. D 96, 023517 (2017) | 10.1103/PhysRevD.96.023517 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the Galileon ghost condensate implementation of a bouncing
cosmological model in the presence of a non negligible anisotropic stress. We
exhibit its structure, which we find to be far richer than previously thought.
In particular, even restricting attention to a single set of underlying
microscopic parameters, we obtain, numerically, many qualitatively different
regimes: depending on the initial conditions on the scalar field leading the
dynamics of the universe, the contraction phase can evolve directly towards a
singularity, avoid it by bouncing once, or even bounce many times before
settling into an ever-expanding phase. We clarify the behavior of the
anisotropies in these various situations.
| [
{
"created": "Thu, 11 May 2017 14:48:17 GMT",
"version": "v1"
},
{
"created": "Wed, 28 Jun 2017 15:12:05 GMT",
"version": "v2"
}
] | 2017-07-26 | [
[
"Bacalhau",
"Anna Paula",
""
],
[
"Peter",
"Patrick",
""
],
[
"Vitenti",
"Sandro D. P.",
""
]
] | We analyze the Galileon ghost condensate implementation of a bouncing cosmological model in the presence of a non negligible anisotropic stress. We exhibit its structure, which we find to be far richer than previously thought. In particular, even restricting attention to a single set of underlying microscopic parameters, we obtain, numerically, many qualitatively different regimes: depending on the initial conditions on the scalar field leading the dynamics of the universe, the contraction phase can evolve directly towards a singularity, avoid it by bouncing once, or even bounce many times before settling into an ever-expanding phase. We clarify the behavior of the anisotropies in these various situations. |
2207.13114 | Yves Brihaye | Yves Brihaye, Carlos Herdeiro, Eugen Radu | $D=5$ static, charged black holes, strings and rings with resonant,
scalar $Q$-hair | 30 pages, 8 figures | null | 10.1007/JHEP10(2022)153 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A mechanism for circumventing the Mayo-Bekenstein no-hair theorem allows
endowing four dimensional $(D=4)$ asymptotically flat, spherical,
electro-vacuum black holes with a minimally coupled $U(1)$-gauged scalar field
profile: $Q$-$hair$. The scalar field must be massive, self-interacting and
obey a {\it resonance condition} at the threshold of (charged) superradiance.
We establish generality for this mechanism by endowing three different types of
static black objects with scalar hair, within a $D=5$ Einstein-Maxwell-gauged
scalar field model: asymptotically flat black holes and black rings; and black
strings which asymptote to a Kaluza-Klein vacuum. These $D=5$ $Q$-hairy black
objects share many of the features of their $D=4$ counterparts. In particular,
the scalar field is subject to a resonance condition and possesses a $Q$-ball
type potential. For the static black ring, the charged scalar hair can balance
it, yielding solutions that are singularity free on and outside the horizon.
| [
{
"created": "Tue, 26 Jul 2022 18:05:19 GMT",
"version": "v1"
}
] | 2022-11-09 | [
[
"Brihaye",
"Yves",
""
],
[
"Herdeiro",
"Carlos",
""
],
[
"Radu",
"Eugen",
""
]
] | A mechanism for circumventing the Mayo-Bekenstein no-hair theorem allows endowing four dimensional $(D=4)$ asymptotically flat, spherical, electro-vacuum black holes with a minimally coupled $U(1)$-gauged scalar field profile: $Q$-$hair$. The scalar field must be massive, self-interacting and obey a {\it resonance condition} at the threshold of (charged) superradiance. We establish generality for this mechanism by endowing three different types of static black objects with scalar hair, within a $D=5$ Einstein-Maxwell-gauged scalar field model: asymptotically flat black holes and black rings; and black strings which asymptote to a Kaluza-Klein vacuum. These $D=5$ $Q$-hairy black objects share many of the features of their $D=4$ counterparts. In particular, the scalar field is subject to a resonance condition and possesses a $Q$-ball type potential. For the static black ring, the charged scalar hair can balance it, yielding solutions that are singularity free on and outside the horizon. |
2310.20523 | Sen Guo | Sen Guo, Yu-Xiang Huang, Yu-Hao Cui, Yan Han, Qing-Quan Jiang, En-Wei
Liang, Kai Lin | Unveiling the unconventional optical signatures of regular black holes
within accretion disk | 27 pages, 10 figures | Published European Physical Journal C (2023) | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The optical characteristics of three types of black holes (BHs) surrounded by
a thin accretion disk are discussed, namely the Schwarzschild BH, Bardeen BH,
and Hayward BH. We calculate the deflection angle of light as it traverses the
vicinity of each BH using numerical integration and semi-analytical methods,
revealing that both approaches can effectively elucidate the deflection of
light around the BH. We investigate the optical appearance of the accretion
disk and its corresponding observational images at various viewing angles,
discovering that the luminosity in the region near the BH on the inner side of
the accretion disk is higher than that on the outer side owing to higher
material density in closer proximity to the BH. We observe a significant
accumulation of brightness on the left side of the accretion disk, attributed
to the motion of matter and geometric effects. Our findings emphasize the
significant influence of the observation inclination angle on the observed
outcomes. An increase in the observation inclination angle results in the
separation of higher-order images. With the improvement in EHT observation
accuracy, we believe that the feature of a minimal distance between the
innermost region of the direct image of the Hayward BH and the outermost region
of the secondary image can be used as an indicator for identifying Hayward BHs.
| [
{
"created": "Tue, 31 Oct 2023 15:03:10 GMT",
"version": "v1"
}
] | 2023-11-02 | [
[
"Guo",
"Sen",
""
],
[
"Huang",
"Yu-Xiang",
""
],
[
"Cui",
"Yu-Hao",
""
],
[
"Han",
"Yan",
""
],
[
"Jiang",
"Qing-Quan",
""
],
[
"Liang",
"En-Wei",
""
],
[
"Lin",
"Kai",
""
]
] | The optical characteristics of three types of black holes (BHs) surrounded by a thin accretion disk are discussed, namely the Schwarzschild BH, Bardeen BH, and Hayward BH. We calculate the deflection angle of light as it traverses the vicinity of each BH using numerical integration and semi-analytical methods, revealing that both approaches can effectively elucidate the deflection of light around the BH. We investigate the optical appearance of the accretion disk and its corresponding observational images at various viewing angles, discovering that the luminosity in the region near the BH on the inner side of the accretion disk is higher than that on the outer side owing to higher material density in closer proximity to the BH. We observe a significant accumulation of brightness on the left side of the accretion disk, attributed to the motion of matter and geometric effects. Our findings emphasize the significant influence of the observation inclination angle on the observed outcomes. An increase in the observation inclination angle results in the separation of higher-order images. With the improvement in EHT observation accuracy, we believe that the feature of a minimal distance between the innermost region of the direct image of the Hayward BH and the outermost region of the secondary image can be used as an indicator for identifying Hayward BHs. |
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