id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2011.14853 | Jun-Qi Guo | Jun-Qi Guo | Dynamics near the central singularity in spherical collapse | 10 pages, 10 figures | J. Phys. Commun. 5, 075015 (2021) | 10.1088/2399-6528/ac1505 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We study the dynamics near the central singularity in spherically symmetric
collapse of a massless scalar field toward Schwarzschild black hole formation.
The equations of motion take different simplified forms in the early and late
stages of the singularity curve. We report some fine structures of the analytic
solutions and universal features for the metric functions and matter near the
singularity.
| [
{
"created": "Mon, 30 Nov 2020 14:47:56 GMT",
"version": "v1"
},
{
"created": "Sun, 1 Aug 2021 03:30:46 GMT",
"version": "v2"
}
] | 2021-08-03 | [
[
"Guo",
"Jun-Qi",
""
]
] | We study the dynamics near the central singularity in spherically symmetric collapse of a massless scalar field toward Schwarzschild black hole formation. The equations of motion take different simplified forms in the early and late stages of the singularity curve. We report some fine structures of the analytic solutions and universal features for the metric functions and matter near the singularity. |
1911.08750 | Dirk Puetzfeld | Peter A. Hogan, Dirk Puetzfeld | Gravitational clock compass and the detection of gravitational waves | 14 pages, 3 figures | Phys. Rev. D 101, 044012 (2020) | 10.1103/PhysRevD.101.044012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an alternative derivation of the gravitational clock compass and
show how such a device can be used for the detection of gravitational waves.
Explicit compass setups are constructed in special types of space--times,
namely for exact plane gravitational waves and for waves moving radially
relative to an observer.
| [
{
"created": "Wed, 20 Nov 2019 07:46:40 GMT",
"version": "v1"
},
{
"created": "Fri, 14 Feb 2020 14:31:38 GMT",
"version": "v2"
}
] | 2020-02-19 | [
[
"Hogan",
"Peter A.",
""
],
[
"Puetzfeld",
"Dirk",
""
]
] | We present an alternative derivation of the gravitational clock compass and show how such a device can be used for the detection of gravitational waves. Explicit compass setups are constructed in special types of space--times, namely for exact plane gravitational waves and for waves moving radially relative to an observer. |
0710.5618 | Kirill Bronnikov | K.A. Bronnikov, O.B. Zaslavskii | Matter sources for a Null Big Bang | 5 two-column pages, revtex4, no figures. One reference corrected.
Final version accepted for publication in Class. Quantum Grav | Class.Quant.Grav.25:105015,2008 | 10.1088/0264-9381/25/10/105015 | null | gr-qc astro-ph hep-th | null | We consider the properties of stress-energy tensors compatible with a Null
Big Bang, i.e., cosmological evolution starting from a Killing horizon rather
than a singularity. For Kantowski-Sachs cosmologies, it is shown that if matter
satisfies the Null Energy Condition (NEC), then (i) regular cosmological
evolution can only start from a Killing horizon, (ii) matter is absent at the
horizon, and (iii) matter can only appear in the cosmological region due to
interaction with vacuum. The latter is understood phenomenologically as a fluid
whose stress tensor is insensitive to boosts in a particular direction. We also
argue that matter is absent in a static region beyond the horizon. All this
generalizes the observations recently obtained for a mixture of dust and a
vacuum fluid. If, however, we admit the existence of phantom matter, its
certain special kinds (with the parameter $w \leq -3$) are consistent with a
Null Big Bang without interaction with vacuum (or without vacuum fluid at all).
Then in the static region there is matter with $w\geq -1/3$. Alternatively, the
evolution can begin from a horizon in an infinitely remote past, leading to a
scenario combining the features of a Null Big Bang and an emergent universe.
| [
{
"created": "Tue, 30 Oct 2007 11:51:43 GMT",
"version": "v1"
},
{
"created": "Mon, 10 Mar 2008 19:39:03 GMT",
"version": "v2"
},
{
"created": "Mon, 7 Apr 2008 18:18:41 GMT",
"version": "v3"
}
] | 2008-11-26 | [
[
"Bronnikov",
"K. A.",
""
],
[
"Zaslavskii",
"O. B.",
""
]
] | We consider the properties of stress-energy tensors compatible with a Null Big Bang, i.e., cosmological evolution starting from a Killing horizon rather than a singularity. For Kantowski-Sachs cosmologies, it is shown that if matter satisfies the Null Energy Condition (NEC), then (i) regular cosmological evolution can only start from a Killing horizon, (ii) matter is absent at the horizon, and (iii) matter can only appear in the cosmological region due to interaction with vacuum. The latter is understood phenomenologically as a fluid whose stress tensor is insensitive to boosts in a particular direction. We also argue that matter is absent in a static region beyond the horizon. All this generalizes the observations recently obtained for a mixture of dust and a vacuum fluid. If, however, we admit the existence of phantom matter, its certain special kinds (with the parameter $w \leq -3$) are consistent with a Null Big Bang without interaction with vacuum (or without vacuum fluid at all). Then in the static region there is matter with $w\geq -1/3$. Alternatively, the evolution can begin from a horizon in an infinitely remote past, leading to a scenario combining the features of a Null Big Bang and an emergent universe. |
gr-qc/0504072 | Adolfo Zamora | Juan M. Romero and Adolfo Zamora | Note on Quantum Newtonian Cosmology | 10 pages, no figures | null | null | null | gr-qc | null | It is well known that, for pressureless matter, Newtonian and relativistic
cosmologies are equivalent. We show that this equivalence breaks down in the
quantum level. In addition, we find some cases for which quantum Newtonian
cosmology can be related to quantum cosmology in (2+1) dimensions. Two exact
solutions for the wave function of the Newtonian universe are also obtained.
| [
{
"created": "Fri, 15 Apr 2005 22:30:09 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Romero",
"Juan M.",
""
],
[
"Zamora",
"Adolfo",
""
]
] | It is well known that, for pressureless matter, Newtonian and relativistic cosmologies are equivalent. We show that this equivalence breaks down in the quantum level. In addition, we find some cases for which quantum Newtonian cosmology can be related to quantum cosmology in (2+1) dimensions. Two exact solutions for the wave function of the Newtonian universe are also obtained. |
1707.02318 | Chenghui Yu | Cheng-Gang Shao, Ya-Fen Chen, Rong Sun, Lu-Shuai Cao, Min-Kang Zhou,
Zhong-Kun Hu, Chenghui Yu and Holger M\"uller | Limits on Lorentz violation in gravity from worldwide superconducting
gravimeters | 5 pages, 1 figure | Phys. Rev. D 97, 024019 (2018) | 10.1103/PhysRevD.97.024019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigated Lorentz violation through anisotropy of gravity using a
worldwide array of 12 superconducting gravimeters. The Lorentz-violating signal
is extracted from the difference between measured gravity and a tidal model. At
the level of sensitivity we reach, ocean tides start to play an important role.
However, most models available that include ocean tides are empirically based
on measured gravity data, which may contain Lorentz-violating signal. In this
work we used an ocean tides included tidal model derived from first principles
to extract Lorentz-violating signal for the first time. We have bounded
space-space components of gravitational Lorentz violation in the minimal
standard model extension (SME) up to the order of $10^{-10}$, one order of
magnitude improved relative to previous atom-interferometer tests.
| [
{
"created": "Fri, 7 Jul 2017 18:05:27 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Oct 2017 17:36:09 GMT",
"version": "v2"
}
] | 2018-01-22 | [
[
"Shao",
"Cheng-Gang",
""
],
[
"Chen",
"Ya-Fen",
""
],
[
"Sun",
"Rong",
""
],
[
"Cao",
"Lu-Shuai",
""
],
[
"Zhou",
"Min-Kang",
""
],
[
"Hu",
"Zhong-Kun",
""
],
[
"Yu",
"Chenghui",
""
],
[
"Müller",
... | We investigated Lorentz violation through anisotropy of gravity using a worldwide array of 12 superconducting gravimeters. The Lorentz-violating signal is extracted from the difference between measured gravity and a tidal model. At the level of sensitivity we reach, ocean tides start to play an important role. However, most models available that include ocean tides are empirically based on measured gravity data, which may contain Lorentz-violating signal. In this work we used an ocean tides included tidal model derived from first principles to extract Lorentz-violating signal for the first time. We have bounded space-space components of gravitational Lorentz violation in the minimal standard model extension (SME) up to the order of $10^{-10}$, one order of magnitude improved relative to previous atom-interferometer tests. |
1001.3517 | Francisco Lobo | Francisco S. N. Lobo, Tiberiu Harko, Zolt\'an Kov\'acs | Solar System tests of Ho\v{r}ava-Lifshitz black holes | 7 pages, 3 figures; talk presented at the II Workshop on Black Holes,
Instituto Superior Tecnico, Lisbon, 21-22 December 2009 | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the present paper we consider the possibility of observationally testing
Horava gravity at the scale of the Solar System, by considering the classical
tests of general relativity (perihelion precession of the planet Mercury,
deflection of light by the Sun and the radar echo delay) for the
Kehagias-Sfetsos asymptotically flat black hole solution of Horava-Lifshitz
gravity. All these gravitational effects can be fully explained in the
framework of the vacuum solution of Horava gravity, and it is shown that the
analysis of the classical general relativistic tests severely constrain the
free parameter of the solution.
| [
{
"created": "Wed, 20 Jan 2010 09:19:07 GMT",
"version": "v1"
}
] | 2010-01-21 | [
[
"Lobo",
"Francisco S. N.",
""
],
[
"Harko",
"Tiberiu",
""
],
[
"Kovács",
"Zoltán",
""
]
] | In the present paper we consider the possibility of observationally testing Horava gravity at the scale of the Solar System, by considering the classical tests of general relativity (perihelion precession of the planet Mercury, deflection of light by the Sun and the radar echo delay) for the Kehagias-Sfetsos asymptotically flat black hole solution of Horava-Lifshitz gravity. All these gravitational effects can be fully explained in the framework of the vacuum solution of Horava gravity, and it is shown that the analysis of the classical general relativistic tests severely constrain the free parameter of the solution. |
1311.2565 | Yi Pan | Yi Pan, Alessandra Buonanno, Andrea Taracchini, Michael Boyle,
Lawrence E. Kidder, Abdul H. Mroue, Harald P. Pfeiffer, Mark A. Scheel, Bela
Szilagyi, and Anil Zenginoglu | Stability of nonspinning effective-one-body model in approximating
two-body dynamics and gravitational-wave emission | 5 pages, 3 figures | Phys. Rev. D 89, 061501 (2014) | 10.1103/PhysRevD.89.061501 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The detection of gravitational waves and the extraction of physical
information from them requires the prediction of accurate waveforms to be used
in template banks. For that purpose, the accuracy of effective-one-body (EOB)
waveforms has been improved over the last years by calibrating them to
numerical-relativity (NR) waveforms. So far, the calibration has employed a
handful of NR waveforms with a total length of ~30 cycles, the length being
limited by the computational cost of NR simulations. Here we address the
outstanding problem of the stability of the EOB calibration with respect to the
length of NR waveforms. Performing calibration studies against NR waveforms of
nonspinning black-hole binaries with mass ratios 1, 1.5, 5, and 8, and with a
total length of ~60 cycles, we find that EOB waveforms calibrated against
either 30 or 60 cycles will be indistinguishable by the advanced detectors LIGO
and Virgo when the signal-to-noise ratio (SNR) is below 110. When extrapolating
to a very large number of cycles, using very conservative assumptions, we can
conclude that state-of-the-art nonspinning EOB waveforms of any length are
sufficiently accurate for parameter estimation with advanced detectors when the
SNR is below 20, the mass ratio is below 5 and total mass is above 20 Msun. The
results are not conclusive for the entire parameter space because of current NR
errors.
| [
{
"created": "Mon, 11 Nov 2013 20:26:02 GMT",
"version": "v1"
}
] | 2014-03-12 | [
[
"Pan",
"Yi",
""
],
[
"Buonanno",
"Alessandra",
""
],
[
"Taracchini",
"Andrea",
""
],
[
"Boyle",
"Michael",
""
],
[
"Kidder",
"Lawrence E.",
""
],
[
"Mroue",
"Abdul H.",
""
],
[
"Pfeiffer",
"Harald P.",
""
... | The detection of gravitational waves and the extraction of physical information from them requires the prediction of accurate waveforms to be used in template banks. For that purpose, the accuracy of effective-one-body (EOB) waveforms has been improved over the last years by calibrating them to numerical-relativity (NR) waveforms. So far, the calibration has employed a handful of NR waveforms with a total length of ~30 cycles, the length being limited by the computational cost of NR simulations. Here we address the outstanding problem of the stability of the EOB calibration with respect to the length of NR waveforms. Performing calibration studies against NR waveforms of nonspinning black-hole binaries with mass ratios 1, 1.5, 5, and 8, and with a total length of ~60 cycles, we find that EOB waveforms calibrated against either 30 or 60 cycles will be indistinguishable by the advanced detectors LIGO and Virgo when the signal-to-noise ratio (SNR) is below 110. When extrapolating to a very large number of cycles, using very conservative assumptions, we can conclude that state-of-the-art nonspinning EOB waveforms of any length are sufficiently accurate for parameter estimation with advanced detectors when the SNR is below 20, the mass ratio is below 5 and total mass is above 20 Msun. The results are not conclusive for the entire parameter space because of current NR errors. |
2009.06351 | Badri Krishnan | Neev Khera, Badri Krishnan, Abhay Ashtekar and Tommaso De Lorenzo | Inferring the gravitational wave memory for binary coalescence events | 15 pages, 6 figures | Phys. Rev. D 103, 044012 (2021) | 10.1103/PhysRevD.103.044012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Full, non-linear general relativity predicts a memory effect for
gravitational waves. For compact binary coalescence, the total gravitational
memory serves as an inferred observable, conceptually on the same footing as
the mass and the spin of the final black hole. Given candidate waveforms for
any LIGO event, then, one can calculate the posterior probability distribution
functions for the total gravitational memory, and use them to compare and
contrast the waveforms. In this paper we present these posterior distributions
for the binary black hole merger events reported in the first Gravitational
Wave Transient Catalog (GWTC-1), using the Phenomenological and
Effective-One-Body waveforms. On the whole, the two sets of posterior
distributions agree with each other quite well though we find larger
discrepancies for the $\ell=2, m=1$ mode of the memory. This signals a possible
source of systematic errors that was not captured by the posterior
distributions of other inferred observables. Thus, the posterior distributions
of various angular modes of total memory can serve as diagnostic tools to
further improve the waveforms. Analyses such as this would be valuable
especially for future events as the sensitivity of ground based detectors
improves, and for LISA which could measure the total gravitational memory
directly.
| [
{
"created": "Mon, 14 Sep 2020 12:20:49 GMT",
"version": "v1"
}
] | 2021-02-17 | [
[
"Khera",
"Neev",
""
],
[
"Krishnan",
"Badri",
""
],
[
"Ashtekar",
"Abhay",
""
],
[
"De Lorenzo",
"Tommaso",
""
]
] | Full, non-linear general relativity predicts a memory effect for gravitational waves. For compact binary coalescence, the total gravitational memory serves as an inferred observable, conceptually on the same footing as the mass and the spin of the final black hole. Given candidate waveforms for any LIGO event, then, one can calculate the posterior probability distribution functions for the total gravitational memory, and use them to compare and contrast the waveforms. In this paper we present these posterior distributions for the binary black hole merger events reported in the first Gravitational Wave Transient Catalog (GWTC-1), using the Phenomenological and Effective-One-Body waveforms. On the whole, the two sets of posterior distributions agree with each other quite well though we find larger discrepancies for the $\ell=2, m=1$ mode of the memory. This signals a possible source of systematic errors that was not captured by the posterior distributions of other inferred observables. Thus, the posterior distributions of various angular modes of total memory can serve as diagnostic tools to further improve the waveforms. Analyses such as this would be valuable especially for future events as the sensitivity of ground based detectors improves, and for LISA which could measure the total gravitational memory directly. |
gr-qc/0603104 | Wu Ning | Ning Wu | Coupling Between the Spin and Gravitational Field and the Equation of
Motion of the Spin | 10 pages, no figures | Commun.Theor.Phys.48:469-472,2007 | 10.1088/0253-6102/48/3/018 | null | gr-qc | null | In general relativity, the equation of motion of the spin is given by the
equation of parallel transport, which is a result of the space-time geometry.
Any result of the space-time geometry can not be directly applied to gauge
theory of gravity. In gauge theory of gravity, based on the viewpoint of the
coupling between the spin and gravitational field, an equation of motion of the
spin is deduced. In the post Newtonian approximation, it is proved that this
equation gives out the same result as that of the equation of parallel
transport. So, in the post Newtonian approximation, gauge theory of gravity
gives out the same prediction on the precession of orbiting gyroscope as that
of general relativity.
| [
{
"created": "Mon, 27 Mar 2006 15:22:15 GMT",
"version": "v1"
}
] | 2009-03-19 | [
[
"Wu",
"Ning",
""
]
] | In general relativity, the equation of motion of the spin is given by the equation of parallel transport, which is a result of the space-time geometry. Any result of the space-time geometry can not be directly applied to gauge theory of gravity. In gauge theory of gravity, based on the viewpoint of the coupling between the spin and gravitational field, an equation of motion of the spin is deduced. In the post Newtonian approximation, it is proved that this equation gives out the same result as that of the equation of parallel transport. So, in the post Newtonian approximation, gauge theory of gravity gives out the same prediction on the precession of orbiting gyroscope as that of general relativity. |
gr-qc/0102045 | Gabriela Gonzalez | Gabriela Gonzalez (Center for Gravitational Physics and Geometry, The
Pennsylvania State University) | Angular Noise in Gravitational Wave Detectors | 2 pages, to appear in proceedings of the IX Marcel Grossmann meeting,
Rome, 2000 | null | 10.1142/9789812777386_0397 | CGPG-01-2-1 | gr-qc | null | Angular fluctuations of suspended mirrors in gravitational wave
interferometers are a source of noise both for the locking and the operation of
the detectors. We describe here some of the sources of these fluctuations and
methods for the estimation of their order of magnitude.
| [
{
"created": "Sun, 11 Feb 2001 20:08:27 GMT",
"version": "v1"
}
] | 2017-08-23 | [
[
"Gonzalez",
"Gabriela",
"",
"Center for Gravitational Physics and Geometry, The\n Pennsylvania State University"
]
] | Angular fluctuations of suspended mirrors in gravitational wave interferometers are a source of noise both for the locking and the operation of the detectors. We describe here some of the sources of these fluctuations and methods for the estimation of their order of magnitude. |
2210.05434 | Jianwei Mei | Jianwei Mei | A hydrodynamical description of gravitational waves | published version | null | 10.1140/epjc/s10052-022-11160-9 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | It is easy to reason that gravity might be the effect of a fluid in disguise,
as it will naturally arise in emergent gravity models where gravity is due to
the effect of some fundamental particles, with the latter expected to behave
collectively like a fluid at the macroscopic scale. We call this the
fluid/gravity equivalence. The key difficulty with the fluid/gravity
equivalence is to find the correct metric-fluid relation (the relation between
the emergent metric and the fluid properties) so that the fluid not only has
physically acceptable properties but also obeys the usual hydrodynamic
equations, while at the same time the emergent metric also obeys the Einstein
equations. Faced with the problem, we have previously made a tentative proposal
of the metric-fluid relation, focusing only on obtaining physically acceptable
predictions on the fluid properties. In this paper, however, we find that for
the general gravitational wave spacetime near the null infinity, the underlying
fluid not only has physically acceptable properties, but also satisfies the
expected relativistic hydrodynamic equations in the Minkowski background, thus
providing a concrete example satisfying both of the major requirements expected
for the fluid/gravity equivalence.
| [
{
"created": "Tue, 11 Oct 2022 13:24:52 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Jan 2023 03:38:04 GMT",
"version": "v2"
}
] | 2023-01-16 | [
[
"Mei",
"Jianwei",
""
]
] | It is easy to reason that gravity might be the effect of a fluid in disguise, as it will naturally arise in emergent gravity models where gravity is due to the effect of some fundamental particles, with the latter expected to behave collectively like a fluid at the macroscopic scale. We call this the fluid/gravity equivalence. The key difficulty with the fluid/gravity equivalence is to find the correct metric-fluid relation (the relation between the emergent metric and the fluid properties) so that the fluid not only has physically acceptable properties but also obeys the usual hydrodynamic equations, while at the same time the emergent metric also obeys the Einstein equations. Faced with the problem, we have previously made a tentative proposal of the metric-fluid relation, focusing only on obtaining physically acceptable predictions on the fluid properties. In this paper, however, we find that for the general gravitational wave spacetime near the null infinity, the underlying fluid not only has physically acceptable properties, but also satisfies the expected relativistic hydrodynamic equations in the Minkowski background, thus providing a concrete example satisfying both of the major requirements expected for the fluid/gravity equivalence. |
gr-qc/0207120 | Maeda Hideki | Hideki Maeda, Tomohiro Harada, Hideo Iguchi and Naoya Okuyama | A Classification of Spherically Symmetric Kinematic Self-Similar
Perfect-Fluid Solutions | Revised version, a reference added, 36 pages, 4 tables, no figures,
accepted for publication in Progress of Theoretical Physics | Prog.Theor.Phys. 108 (2002) 819-851 | 10.1143/PTP.108.819 | WU-AP/150/02 | gr-qc | null | We classify all spherically symmetric spacetimes admitting a kinematic
self-similar vector of the second, zeroth or infinite kind. We assume that the
perfect fluid obeys either a polytropic equation of state or an equation of
state of the form $p=K\mu$, where $p$ and $\mu$ are the pressure and the energy
density, respectively, and $K$ is a constant. We study the cases in which the
kinematic self-similar vector is not only ``tilted'' but also parallel or
orthogonal to the fluid flow. We find that, in contrast to Newtonian gravity,
the polytropic perfect-fluid solutions compatible with the kinematic
self-similarity are the Friedmann-Robertson-Walker solution and general static
solutions. We find three new exact solutions which we call the dynamical
solutions (A) and (B) and $\Lambda$-cylinder solution, respectively.
| [
{
"created": "Tue, 30 Jul 2002 18:17:52 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Sep 2002 08:51:02 GMT",
"version": "v2"
}
] | 2009-11-07 | [
[
"Maeda",
"Hideki",
""
],
[
"Harada",
"Tomohiro",
""
],
[
"Iguchi",
"Hideo",
""
],
[
"Okuyama",
"Naoya",
""
]
] | We classify all spherically symmetric spacetimes admitting a kinematic self-similar vector of the second, zeroth or infinite kind. We assume that the perfect fluid obeys either a polytropic equation of state or an equation of state of the form $p=K\mu$, where $p$ and $\mu$ are the pressure and the energy density, respectively, and $K$ is a constant. We study the cases in which the kinematic self-similar vector is not only ``tilted'' but also parallel or orthogonal to the fluid flow. We find that, in contrast to Newtonian gravity, the polytropic perfect-fluid solutions compatible with the kinematic self-similarity are the Friedmann-Robertson-Walker solution and general static solutions. We find three new exact solutions which we call the dynamical solutions (A) and (B) and $\Lambda$-cylinder solution, respectively. |
gr-qc/9605067 | James Coleman | James Coleman (University of Toronto) | On Parallel Transport in Quantum Bundles over Robertson-Walker
Spacetimes | Plain TeX, 17 pages. Updated version contains additional background
material and a couple of minor corrections | null | null | null | gr-qc | null | A recently-developed theory of quantum general relativity provides a
propagator for free-falling particles in curved spacetimes. These propagators
are constructed by parallel-transporting quantum states within a quantum bundle
associated to the Poincare frame bundle. We consider such parallel transport in
the case that the spacetime is a classical Robertson-Walker universe. An
explicit integral formula is developed which expresses the propagators for
parallel transport between any two points of such a spacetime. The integrals in
this formula are evaluated in closed form for a particular spatially-flat
model.
| [
{
"created": "Thu, 30 May 1996 18:48:32 GMT",
"version": "v1"
},
{
"created": "Tue, 3 Dec 1996 01:45:34 GMT",
"version": "v2"
}
] | 2008-02-03 | [
[
"Coleman",
"James",
"",
"University of Toronto"
]
] | A recently-developed theory of quantum general relativity provides a propagator for free-falling particles in curved spacetimes. These propagators are constructed by parallel-transporting quantum states within a quantum bundle associated to the Poincare frame bundle. We consider such parallel transport in the case that the spacetime is a classical Robertson-Walker universe. An explicit integral formula is developed which expresses the propagators for parallel transport between any two points of such a spacetime. The integrals in this formula are evaluated in closed form for a particular spatially-flat model. |
1903.04283 | Ercan Kilicarslan | Ercan Kilicarslan | $pp$-waves as exact solutions to ghost-free infinite derivative gravity | 13 pages, references added, end of the Section IV-A is revised,
version published in Phys. Rev. D | Phys. Rev. D 99, 124048 (2019) | 10.1103/PhysRevD.99.124048 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We construct exact pp-wave solutions of ghost-free infinite derivative
gravity and demonstrate that the sourceless theory does not bring any pp-wave
solutions save for that of Einstein's gravity. These waves described in the
Kerr-Schild form also solve the linearized field equations of the theory. We
also find an exact gravitational shock wave with non-singular curvature
invariants and with a finite limit in the ultraviolet regime of non-locality
which is in contrast to the divergent limit in Einstein's theory.
| [
{
"created": "Mon, 11 Mar 2019 13:15:08 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Mar 2019 23:23:43 GMT",
"version": "v2"
},
{
"created": "Thu, 27 Jun 2019 08:26:56 GMT",
"version": "v3"
},
{
"created": "Sat, 31 Jul 2021 12:51:33 GMT",
"version": "v4"
}
] | 2021-08-03 | [
[
"Kilicarslan",
"Ercan",
""
]
] | We construct exact pp-wave solutions of ghost-free infinite derivative gravity and demonstrate that the sourceless theory does not bring any pp-wave solutions save for that of Einstein's gravity. These waves described in the Kerr-Schild form also solve the linearized field equations of the theory. We also find an exact gravitational shock wave with non-singular curvature invariants and with a finite limit in the ultraviolet regime of non-locality which is in contrast to the divergent limit in Einstein's theory. |
gr-qc/0411065 | Allan Joseph Michael Medved | A.J.M. Medved | A follow-up to 'Does Nature abhor a logarithm?' (and apparently she
doesn't) | 4 pages | Class.Quant.Grav. 22 (2005) 5195 | 10.1088/0264-9381/22/23/017 | null | gr-qc hep-th | null | This letter contains a brief discussion on the leading-order canonical
correction to the Bekenstein-Hawking (black hole) entropy. In particular, we
address some recent criticism directed at an earlier commentary.
| [
{
"created": "Mon, 15 Nov 2004 20:56:08 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Medved",
"A. J. M.",
""
]
] | This letter contains a brief discussion on the leading-order canonical correction to the Bekenstein-Hawking (black hole) entropy. In particular, we address some recent criticism directed at an earlier commentary. |
1205.3945 | Thomas Sotiriou | Valerio Faraoni, Vincenzo Vitagliano, Thomas P. Sotiriou, and Stefano
Liberati | Dynamical apparent horizons in inhomogeneous Brans-Dicke universes | 10 pages, 4 figures; v2: minor changes to match published version | Phys. Rev. D 86, 064040 (2012) | 10.1103/PhysRevD.86.064040 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The presence and evolution of apparent horizons in a two-parameter family of
spherically symmetric, time-dependent solutions of Brans-Dicke gravity are
analyzed. These solutions were introduced to model space- and time-varying
gravitational couplings and are supposed to represent central objects embedded
in a spatially flat universe. We find that the solutions possess multiple
evolving apparent horizons, both black hole horizons covering a central
singularity and cosmological ones. It is not uncommon for two of these horizons
to merge, leaving behind a naked singularity covered only by a cosmological
horizon. Two characteristic limits are also explicitly worked out: the limit
where the theory reduces to general relativity and the limit where the
solutions become static. The physical relevance of this family of solutions is
discussed.
| [
{
"created": "Thu, 17 May 2012 14:52:25 GMT",
"version": "v1"
},
{
"created": "Wed, 26 Sep 2012 12:10:26 GMT",
"version": "v2"
}
] | 2012-09-27 | [
[
"Faraoni",
"Valerio",
""
],
[
"Vitagliano",
"Vincenzo",
""
],
[
"Sotiriou",
"Thomas P.",
""
],
[
"Liberati",
"Stefano",
""
]
] | The presence and evolution of apparent horizons in a two-parameter family of spherically symmetric, time-dependent solutions of Brans-Dicke gravity are analyzed. These solutions were introduced to model space- and time-varying gravitational couplings and are supposed to represent central objects embedded in a spatially flat universe. We find that the solutions possess multiple evolving apparent horizons, both black hole horizons covering a central singularity and cosmological ones. It is not uncommon for two of these horizons to merge, leaving behind a naked singularity covered only by a cosmological horizon. Two characteristic limits are also explicitly worked out: the limit where the theory reduces to general relativity and the limit where the solutions become static. The physical relevance of this family of solutions is discussed. |
2407.01701 | Alireza Rashti | Alireza Rashti and Andrew Noe | Realistic binary neutron star initial data with Elliptica | Elliptica code is now open-source; please see
https://github.com/rashti-alireza/Elliptica | null | null | null | gr-qc astro-ph.SR physics.comp-ph | http://creativecommons.org/licenses/by/4.0/ | This work introduces the Elliptica pseudo-spectral code for generating
initial data of binary neutron star systems. Building upon the recent Elliptica
code update, we can now construct initial data using not only piecewise
polytropic equations of state, but also tabulated equations of state for these
binary systems. Furthermore, the code allows us to endow neutron stars within
the binary system with spins. These spins can have a magnitude close to the
mass shedding limit and can point in any direction.
| [
{
"created": "Mon, 1 Jul 2024 18:22:44 GMT",
"version": "v1"
}
] | 2024-07-03 | [
[
"Rashti",
"Alireza",
""
],
[
"Noe",
"Andrew",
""
]
] | This work introduces the Elliptica pseudo-spectral code for generating initial data of binary neutron star systems. Building upon the recent Elliptica code update, we can now construct initial data using not only piecewise polytropic equations of state, but also tabulated equations of state for these binary systems. Furthermore, the code allows us to endow neutron stars within the binary system with spins. These spins can have a magnitude close to the mass shedding limit and can point in any direction. |
1905.00100 | Mehdi Rezaei | Mehdi Rezaei, Mohammad Malekjani and Joan Sola | Can dark energy be expressed as a power series of the Hubble parameter? | 20 pages, 6 figures and 8 tables, Accepted in Phys. Rev. D | Phys. Rev. D 100, 023539 (2019) | 10.1103/PhysRevD.100.023539 | null | gr-qc astro-ph.CO hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we examine the possibility that the dark energy (DE) density,
$\rho_{de}$ can be dynamical and appear as a power series expansion of the
Hubble rate (and its derivatives), i.e.$\rho_{de}(H,\dot{H},...)$. For the
present universe, however, only the terms $H$, $\dot{H}$ and $H^2$ can be
relevant, together with an additive constant term. We fit these models to the
current cosmological data on the main observables SNIa+$H(z)$+BAO+LSS+CMB+BBN.
Our analysis involves both the background as well as the cosmic perturbation
equations. The latter include, apart from the matter density perturbations,
also the DE density perturbations. We assume that matter and dynamical DE are
separately self-conserved. As a result the equation of state of the DE becomes
a nontrivial function of the cosmological redshift, $w_D=w_D(z)$. The
particular subset of DE models of this type having no additive constant term in
$\rho_{de}$ include the so-called entropic-force and QCD-ghost DE models, as
well as the pure linear model $\rho_{de} \sim H$ all of which are strongly
disfavored in our fitting analysis. In contrast, the models that include the
additive term plus one or both of the dynamical components $\dot{H}$ and $H^2$
appear more favored than the $\Lambda$CDM. In particular, the dynamical DE
models provide a value of $\sigma_8\simeq 0.74-0.77$ which is substantially
lower than that of the $\Lambda$CDM and hence more in accordance with the
observations. This helps to significantly reduce the $\sigma_8$-tension in the
structure formation data. At the same time the predicted value for $H_0$ is in
between the local and Planck measurements, thus helping to alleviate this
tension as well.
| [
{
"created": "Tue, 30 Apr 2019 20:51:59 GMT",
"version": "v1"
},
{
"created": "Thu, 2 May 2019 10:49:52 GMT",
"version": "v2"
},
{
"created": "Fri, 28 Jun 2019 15:55:02 GMT",
"version": "v3"
},
{
"created": "Tue, 2 Jul 2019 06:22:41 GMT",
"version": "v4"
}
] | 2019-07-30 | [
[
"Rezaei",
"Mehdi",
""
],
[
"Malekjani",
"Mohammad",
""
],
[
"Sola",
"Joan",
""
]
] | In this work we examine the possibility that the dark energy (DE) density, $\rho_{de}$ can be dynamical and appear as a power series expansion of the Hubble rate (and its derivatives), i.e.$\rho_{de}(H,\dot{H},...)$. For the present universe, however, only the terms $H$, $\dot{H}$ and $H^2$ can be relevant, together with an additive constant term. We fit these models to the current cosmological data on the main observables SNIa+$H(z)$+BAO+LSS+CMB+BBN. Our analysis involves both the background as well as the cosmic perturbation equations. The latter include, apart from the matter density perturbations, also the DE density perturbations. We assume that matter and dynamical DE are separately self-conserved. As a result the equation of state of the DE becomes a nontrivial function of the cosmological redshift, $w_D=w_D(z)$. The particular subset of DE models of this type having no additive constant term in $\rho_{de}$ include the so-called entropic-force and QCD-ghost DE models, as well as the pure linear model $\rho_{de} \sim H$ all of which are strongly disfavored in our fitting analysis. In contrast, the models that include the additive term plus one or both of the dynamical components $\dot{H}$ and $H^2$ appear more favored than the $\Lambda$CDM. In particular, the dynamical DE models provide a value of $\sigma_8\simeq 0.74-0.77$ which is substantially lower than that of the $\Lambda$CDM and hence more in accordance with the observations. This helps to significantly reduce the $\sigma_8$-tension in the structure formation data. At the same time the predicted value for $H_0$ is in between the local and Planck measurements, thus helping to alleviate this tension as well. |
1510.05353 | Amir Ghalee | Amir Ghalee | Notes on diffeomorphisms symmetry of $f(R)$ gravity in the cosmological
context | 12 pages, references added. title changed | Eur. Phys. J. C 76: 136, 2016 | 10.1140/epjc/s10052-016-3989-9 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the metric perturbations in the context of restricted $f(R)$
gravity, in which a parameter for deviation from the full diffeomorphisms of
space-time is introduced. We demonstrate that one can choose the parameter to
remove the induced anisotropic stress, which is present in the usual $f(R)$
gravity. Moreover, to prevent instability for the vector and tensor metric
perturbations, some constraints on the model are obtained.
| [
{
"created": "Mon, 19 Oct 2015 04:47:51 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jan 2016 10:37:42 GMT",
"version": "v2"
},
{
"created": "Mon, 29 Feb 2016 11:20:14 GMT",
"version": "v3"
}
] | 2016-03-15 | [
[
"Ghalee",
"Amir",
""
]
] | We study the metric perturbations in the context of restricted $f(R)$ gravity, in which a parameter for deviation from the full diffeomorphisms of space-time is introduced. We demonstrate that one can choose the parameter to remove the induced anisotropic stress, which is present in the usual $f(R)$ gravity. Moreover, to prevent instability for the vector and tensor metric perturbations, some constraints on the model are obtained. |
2404.10236 | Marek Rogatko | Marek Rogatko | Dark photon - dark energy stationary axisymmetric black holes | RevTex, 21 pages, to be published in Phys.Rev. D15 | Phys. Rev. D109 (2024) 104030 | 10.1103/PhysRevD.109.104030 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Using Ernst formalism, stationary axisymmetric black hole solution in
Einstein-dark matter-dark energy gravity has been elaborated. The dark sector
was chosen as dark photon concept, where an auxiliary U(1)-gauge field coupled
to ordinary Maxwell one was introduced, while dark energy was modelled by the
existence of positive cosmological constant. Refining our studies to the case
of vanishing cosmological constant, the uniqueness theorem for the black hole
in question has been proved.
| [
{
"created": "Tue, 16 Apr 2024 02:33:19 GMT",
"version": "v1"
}
] | 2024-07-09 | [
[
"Rogatko",
"Marek",
""
]
] | Using Ernst formalism, stationary axisymmetric black hole solution in Einstein-dark matter-dark energy gravity has been elaborated. The dark sector was chosen as dark photon concept, where an auxiliary U(1)-gauge field coupled to ordinary Maxwell one was introduced, while dark energy was modelled by the existence of positive cosmological constant. Refining our studies to the case of vanishing cosmological constant, the uniqueness theorem for the black hole in question has been proved. |
1409.3157 | Martin Bojowald | Martin Bojowald | Information loss, made worse by quantum gravity? | 17 pages, 1 figure; v2: new footnotes, new appendices, new
references, new question mark | Front. Phys. 3 (2015) 33 | 10.3389/fphy.2015.00033 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum gravity is often expected to solve both the singularity problem and
the information-loss problem of black holes. This article presents an example
from loop quantum gravity in which the singularity problem is solved in such a
way that the information-loss problem is made worse. Quantum effects in this
scenario, in contrast to previous non-singular models, do not eliminate the
event horizon and introduce a new Cauchy horizon where determinism breaks down.
Although infinities are avoided, for all practical purposes the core of the
black hole plays the role of a naked singularity. Recent developments in loop
quantum gravity indicate that this aggravated information loss problem is
likely to be the generic outcome, putting strong conceptual pressure on the
theory.
| [
{
"created": "Wed, 10 Sep 2014 17:33:09 GMT",
"version": "v1"
},
{
"created": "Sun, 17 May 2015 16:28:45 GMT",
"version": "v2"
}
] | 2015-05-19 | [
[
"Bojowald",
"Martin",
""
]
] | Quantum gravity is often expected to solve both the singularity problem and the information-loss problem of black holes. This article presents an example from loop quantum gravity in which the singularity problem is solved in such a way that the information-loss problem is made worse. Quantum effects in this scenario, in contrast to previous non-singular models, do not eliminate the event horizon and introduce a new Cauchy horizon where determinism breaks down. Although infinities are avoided, for all practical purposes the core of the black hole plays the role of a naked singularity. Recent developments in loop quantum gravity indicate that this aggravated information loss problem is likely to be the generic outcome, putting strong conceptual pressure on the theory. |
gr-qc/9605012 | J. Socorro Garcia D. | J. Socorro, V.M. Villanueva, and Luis O. Pimentel | Classical solutions in five dimensional induced matter theory and its
relation to an imperfect fluid | 16 pages, latex, no figures | Int.J.Mod.Phys. A11 (1996) 5495-5504 | 10.1142/S0217751X96002510 | IFUG-JPV1-96 | gr-qc | null | We study five dimensional cosmological models with four dimensional
hypersufaces of the Bianchi type I and V. In this way the five dimensional
vacuum field equations $\rm G_{AB} = 0$, led us to four dimensional matter
equations $\rm G_{\mu\nu}=T_{\mu\nu}$ and the matter is interpreted as a purely
geometrical property of a fifth dimension. Also, we find that the
energy-momentum tensor induced from the fifth dimension has the structure of an
imperfect fluid that has dissipative terms.
| [
{
"created": "Tue, 7 May 1996 23:37:00 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Socorro",
"J.",
""
],
[
"Villanueva",
"V. M.",
""
],
[
"Pimentel",
"Luis O.",
""
]
] | We study five dimensional cosmological models with four dimensional hypersufaces of the Bianchi type I and V. In this way the five dimensional vacuum field equations $\rm G_{AB} = 0$, led us to four dimensional matter equations $\rm G_{\mu\nu}=T_{\mu\nu}$ and the matter is interpreted as a purely geometrical property of a fifth dimension. Also, we find that the energy-momentum tensor induced from the fifth dimension has the structure of an imperfect fluid that has dissipative terms. |
gr-qc/0404102 | Ali Shojai | Fatimah Shojai, Ali Shojai | Understanding Quantum Theory in Terms of Geometry | 88 Pages, 6 figures. To appear in Progress in Quantum Physics
Research, Nova Science Publishers, Inc., 2004 | null | null | IPM/P2004-015 | gr-qc astro-ph quant-ph | null | Understanding quantum theory in terms of a geometric picture sounds great.
There are different approaches to this idea. Here we shall present a geometric
picture of quantum theory using the de-Broglie--Bohm causal interpretation of
quantum mechanics. We shall show that it is possible to understand the key
character of de-Broglie--Bohm theory, the quantum potential, as the conformal
degree of freedom of the space--time metric. In this way, gravity should give
the causal structure of the space--time, while quantum phenomena determines the
scale. Some toy models in terms of tensor and scalar--tensor theories will be
presented. Then a few essential physical aspects of the idea including the
effect on the black holes, the initial Big--Bang singularity and non locality
are investigated. We shall formulate a quantum equivalence principle according
to which gravitational effects can be removed by going to a freely falling
frame while quantum effects can be eliminated by choosing an appropriate scale.
And we shall see that the best framework for both quantum and gravity is Weyl
geometry. Then we shall show how one can get the de-Broglie--Bohm quantum
theory out of a Weyl covariant theory. Extension to the case of many particle
systems and spinning particles is discussed at the end.
| [
{
"created": "Sat, 24 Apr 2004 05:50:30 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Shojai",
"Fatimah",
""
],
[
"Shojai",
"Ali",
""
]
] | Understanding quantum theory in terms of a geometric picture sounds great. There are different approaches to this idea. Here we shall present a geometric picture of quantum theory using the de-Broglie--Bohm causal interpretation of quantum mechanics. We shall show that it is possible to understand the key character of de-Broglie--Bohm theory, the quantum potential, as the conformal degree of freedom of the space--time metric. In this way, gravity should give the causal structure of the space--time, while quantum phenomena determines the scale. Some toy models in terms of tensor and scalar--tensor theories will be presented. Then a few essential physical aspects of the idea including the effect on the black holes, the initial Big--Bang singularity and non locality are investigated. We shall formulate a quantum equivalence principle according to which gravitational effects can be removed by going to a freely falling frame while quantum effects can be eliminated by choosing an appropriate scale. And we shall see that the best framework for both quantum and gravity is Weyl geometry. Then we shall show how one can get the de-Broglie--Bohm quantum theory out of a Weyl covariant theory. Extension to the case of many particle systems and spinning particles is discussed at the end. |
gr-qc/0205058 | Stefan Hollands | Stefan Hollands and Robert M. Wald | An Alternative to Inflation | 4th Prize Gravity Research Foundation essay, with minor revisions and
a number of additional footnotes. 12 pages, Latex, no figures | Gen.Rel.Grav. 34 (2002) 2043-2055 | 10.1023/A:1021175216055 | null | gr-qc astro-ph hep-th | null | Inflationary models are generally credited with explaining the large scale
homogeneity, isotropy, and flatness of our universe as well as accounting for
the origin of structure (i.e., the deviations from exact homogeneity) in our
universe. We argue that the explanations provided by inflation for the
homogeneity, isotropy, and flatness of our universe are not satisfactory, and
that a proper explanation of these features will require a much deeper
understanding of the initial state of our universe. On the other hand,
inflationary models are spectacularly successful in providing an explanation of
the deviations from homogeneity. We point out here that the fundamental
mechanism responsible for providing deviations from homogeneity -- namely, the
evolutionary behavior of quantum modes with wavelength larger than the Hubble
radius -- will operate whether or not inflation itself occurs. However, if
inflation did not occur, one must directly confront the issue of the initial
state of modes whose wavelength was larger than the Hubble radius at the time
at which they were "born". Under some simple hypotheses concerning the "birth
time" and initial state of these modes (but without any "fine tuning"), it is
shown that non-inflationary fluid models in the extremely early universe would
result in the same density perturbation spectrum and amplitude as inflationary
models, although there would be no "slow roll" enhancement of the scalar modes.
| [
{
"created": "Wed, 15 May 2002 15:56:19 GMT",
"version": "v1"
},
{
"created": "Fri, 31 May 2002 19:04:48 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Hollands",
"Stefan",
""
],
[
"Wald",
"Robert M.",
""
]
] | Inflationary models are generally credited with explaining the large scale homogeneity, isotropy, and flatness of our universe as well as accounting for the origin of structure (i.e., the deviations from exact homogeneity) in our universe. We argue that the explanations provided by inflation for the homogeneity, isotropy, and flatness of our universe are not satisfactory, and that a proper explanation of these features will require a much deeper understanding of the initial state of our universe. On the other hand, inflationary models are spectacularly successful in providing an explanation of the deviations from homogeneity. We point out here that the fundamental mechanism responsible for providing deviations from homogeneity -- namely, the evolutionary behavior of quantum modes with wavelength larger than the Hubble radius -- will operate whether or not inflation itself occurs. However, if inflation did not occur, one must directly confront the issue of the initial state of modes whose wavelength was larger than the Hubble radius at the time at which they were "born". Under some simple hypotheses concerning the "birth time" and initial state of these modes (but without any "fine tuning"), it is shown that non-inflationary fluid models in the extremely early universe would result in the same density perturbation spectrum and amplitude as inflationary models, although there would be no "slow roll" enhancement of the scalar modes. |
0907.4238 | Richard Woodard | R. P. Woodard (University of Florida) | How Far Are We from the Quantum Theory of Gravity? | 106 page review article solicited by Reports on Progress in Physics | null | 10.1088/0034-4885/72/12/126002 | UFIFT-QG-09-06 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | I give a pedagogical explanation of what it is about quantization that makes
general relativity go from being a nearly perfect classical theory to a very
problematic quantum one. I also explain why some quantization of gravity is
unavoidable, why quantum field theories have divergences, why the divergences
of quantum general relativity are worse than those of the other forces, what
physicists think this means and what they might do with a consistent theory of
quantum gravity if they had one. Finally, I discuss the quantum gravitational
data that have recently become available from cosmology.
| [
{
"created": "Fri, 24 Jul 2009 09:06:12 GMT",
"version": "v1"
}
] | 2015-05-13 | [
[
"Woodard",
"R. P.",
"",
"University of Florida"
]
] | I give a pedagogical explanation of what it is about quantization that makes general relativity go from being a nearly perfect classical theory to a very problematic quantum one. I also explain why some quantization of gravity is unavoidable, why quantum field theories have divergences, why the divergences of quantum general relativity are worse than those of the other forces, what physicists think this means and what they might do with a consistent theory of quantum gravity if they had one. Finally, I discuss the quantum gravitational data that have recently become available from cosmology. |
2108.09559 | Alfredo Lopez Ortega | M. I. Hernandez-Velazquez, A. Lopez-Ortega | Quasinormal frequencies of a two-dimensional asymptotically anti-de
Sitter black hole of the dilaton gravity theory | 36 pages. 10 figures. Invited contribution to the volume "Quasinormal
Modes in Relativistic Stars and Black Holes". Published in Frontiers in
Physics | Front. Astron. Space Sci. 8: 713422 (2021) | 10.3389/fspas.2021.713422 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We numerically calculate the quasinormal frequencies of the Klein-Gordon and
Dirac fields propagating in a two-dimensional asymptotically anti-de Sitter
black hole of the dilaton gravity theory. For the Klein-Gordon field we use the
Horowitz-Hubeny method and the asymptotic iteration method for second order
differential equations. For the Dirac field we first exploit the
Horowitz-Hubeny method. As a second method, instead of using the asymptotic
iteration method for second order differential equations, we propose to take as
a basis its formulation for coupled systems of first order differential
equations. For the two fields we find that the results that produce the two
numerical methods are consistent. Furthermore for both fields we obtain that
their quasinormal modes are stable and we compare their quasinormal frequencies
to analyze whether their spectra are isospectral. Finally we discuss the main
results.
| [
{
"created": "Sat, 21 Aug 2021 18:06:53 GMT",
"version": "v1"
}
] | 2021-08-24 | [
[
"Hernandez-Velazquez",
"M. I.",
""
],
[
"Lopez-Ortega",
"A.",
""
]
] | We numerically calculate the quasinormal frequencies of the Klein-Gordon and Dirac fields propagating in a two-dimensional asymptotically anti-de Sitter black hole of the dilaton gravity theory. For the Klein-Gordon field we use the Horowitz-Hubeny method and the asymptotic iteration method for second order differential equations. For the Dirac field we first exploit the Horowitz-Hubeny method. As a second method, instead of using the asymptotic iteration method for second order differential equations, we propose to take as a basis its formulation for coupled systems of first order differential equations. For the two fields we find that the results that produce the two numerical methods are consistent. Furthermore for both fields we obtain that their quasinormal modes are stable and we compare their quasinormal frequencies to analyze whether their spectra are isospectral. Finally we discuss the main results. |
1709.07774 | Pardyumn Kumar Sahoo | P.K. Sahoo, P.H.R.S. Moraes, Parbati Sahoo | Wormholes in $R^2$-gravity within the $f(R,T)$ formalism | Published version | Eur. Phys. J. C (2018) 78:46 | 10.1140/epjc/s10052-018-5538-1 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose, as a novelty in the literature, the modelling of wormholes within
the particular case of the $f(R,T)$ gravity, namely $f(R,T)=R+\alpha
R^{2}+\lambda T$, with $R$ and $T$ being the Ricci scalar and trace of the
energy-momentum tensor, respectively, while $\alpha$ and $\lambda$ are
constants. Although such a functional form application can be found in the
literature, those concern to compact astrophysical objects, such that no
wormhole analysis has been done so far. The quadratic geometric and linear
material corrections of this theory make the matter content of the wormhole to
remarkably be able to obey the energy conditions.
| [
{
"created": "Thu, 21 Sep 2017 16:43:01 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Dec 2017 11:11:39 GMT",
"version": "v2"
},
{
"created": "Sat, 20 Jan 2018 01:21:19 GMT",
"version": "v3"
}
] | 2018-01-23 | [
[
"Sahoo",
"P. K.",
""
],
[
"Moraes",
"P. H. R. S.",
""
],
[
"Sahoo",
"Parbati",
""
]
] | We propose, as a novelty in the literature, the modelling of wormholes within the particular case of the $f(R,T)$ gravity, namely $f(R,T)=R+\alpha R^{2}+\lambda T$, with $R$ and $T$ being the Ricci scalar and trace of the energy-momentum tensor, respectively, while $\alpha$ and $\lambda$ are constants. Although such a functional form application can be found in the literature, those concern to compact astrophysical objects, such that no wormhole analysis has been done so far. The quadratic geometric and linear material corrections of this theory make the matter content of the wormhole to remarkably be able to obey the energy conditions. |
1501.03073 | Carsten van de Bruck | C. van de Bruck and J. Morrice | Disformal couplings and the dark sector of the universe | 28 + 1 pages, 15 figures. JCAP style. V3: Reference added; final
version sent to journal | null | 10.1088/1475-7516/2015/04/036 | null | gr-qc astro-ph.CO hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Interactions between dark matter and dark energy, allowing both conformal and
and disformal couplings, are studied in detail. We discuss the background
evolution, anisotropies in the cosmic microwave background and large scale
structures. One of our main findings is that a large conformal coupling is not
necessarily disallowed in the presence of a general disformal term. On the
other hand, we find that negative disformal couplings very often lead to
instabilities in the scalar field. Studying the background evolution and linear
perturbations only, our results show that it is observationally challenging to
disentangle disformal from purely conformal couplings.
| [
{
"created": "Tue, 13 Jan 2015 16:52:39 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Jan 2015 14:24:56 GMT",
"version": "v2"
},
{
"created": "Mon, 2 Mar 2015 17:45:38 GMT",
"version": "v3"
}
] | 2015-06-23 | [
[
"van de Bruck",
"C.",
""
],
[
"Morrice",
"J.",
""
]
] | Interactions between dark matter and dark energy, allowing both conformal and and disformal couplings, are studied in detail. We discuss the background evolution, anisotropies in the cosmic microwave background and large scale structures. One of our main findings is that a large conformal coupling is not necessarily disallowed in the presence of a general disformal term. On the other hand, we find that negative disformal couplings very often lead to instabilities in the scalar field. Studying the background evolution and linear perturbations only, our results show that it is observationally challenging to disentangle disformal from purely conformal couplings. |
2407.04791 | Joan Bachs-Esteban | Joan Bachs-Esteban, Il\'idio Lopes, Javier Rubio | Structural Implications of the Chameleon Mechanism on White Dwarfs | 10 + 1 pages, 6 figures | null | null | null | gr-qc astro-ph.HE astro-ph.SR | http://creativecommons.org/licenses/by/4.0/ | We study the impact of the chameleon mechanism on the structure of white
dwarfs. Using a shooting method of our design, we solve the corresponding
scalar-tensor equilibrium equations for a Chandrasekhar equation of state,
exploring various energy scales and couplings of the chameleon field to matter.
We find the chameleon field to be in a thick-shell configuration, identifying
for the first time in the literature a similarity relation for the radially
normalised scalar field gradient. Our analysis reveals that the chameleon
mechanism significantly alters the internal pressure of white dwarfs, leading
to a notable reduction in the stellar radii and masses and shifting the
mass-radius curves below those predicted by Newtonian gravity. Finally, we
derive parametric expressions from our results to expedite future analyses of
white dwarfs in scalar-tensor theories.
| [
{
"created": "Fri, 5 Jul 2024 18:04:53 GMT",
"version": "v1"
}
] | 2024-07-09 | [
[
"Bachs-Esteban",
"Joan",
""
],
[
"Lopes",
"Ilídio",
""
],
[
"Rubio",
"Javier",
""
]
] | We study the impact of the chameleon mechanism on the structure of white dwarfs. Using a shooting method of our design, we solve the corresponding scalar-tensor equilibrium equations for a Chandrasekhar equation of state, exploring various energy scales and couplings of the chameleon field to matter. We find the chameleon field to be in a thick-shell configuration, identifying for the first time in the literature a similarity relation for the radially normalised scalar field gradient. Our analysis reveals that the chameleon mechanism significantly alters the internal pressure of white dwarfs, leading to a notable reduction in the stellar radii and masses and shifting the mass-radius curves below those predicted by Newtonian gravity. Finally, we derive parametric expressions from our results to expedite future analyses of white dwarfs in scalar-tensor theories. |
gr-qc/0107009 | Ruth Lazkoz | J.M. Aguirregabiria, P. Labraga, and Ruth Lazkoz | Assisted inflation in Bianchi VI0 cosmologies | 11 pages | Gen.Rel.Grav. 34 (2002) 341-352 | 10.1023/A:1015351718483 | null | gr-qc | null | Exact models for Bianchi VI0 spacetimes with multiple scalar fields with
exponential potentials have been derived and analysed. It has been shown that
these solutions, when they exist, attract neighbouring solutions in the two
cases corresponding to interacting and non-interacting fields. Unlike the
results obtained in a previous work dealing with the late-time inflationary
behaviour of Bianchi VI0 cosmologies, the knowledge of exact solutions has made
possible to study in detail the occurrence of inflation before the asymptotic
regime. As happened in preceding works, here as well inflation is more likely
to happen with a higher number of non-interacting fields or a lower number of
interacting scalar fields.
| [
{
"created": "Tue, 3 Jul 2001 08:10:31 GMT",
"version": "v1"
}
] | 2021-10-20 | [
[
"Aguirregabiria",
"J. M.",
""
],
[
"Labraga",
"P.",
""
],
[
"Lazkoz",
"Ruth",
""
]
] | Exact models for Bianchi VI0 spacetimes with multiple scalar fields with exponential potentials have been derived and analysed. It has been shown that these solutions, when they exist, attract neighbouring solutions in the two cases corresponding to interacting and non-interacting fields. Unlike the results obtained in a previous work dealing with the late-time inflationary behaviour of Bianchi VI0 cosmologies, the knowledge of exact solutions has made possible to study in detail the occurrence of inflation before the asymptotic regime. As happened in preceding works, here as well inflation is more likely to happen with a higher number of non-interacting fields or a lower number of interacting scalar fields. |
1508.02465 | Jose Wadih Maluf Dr. | J. W. Maluf | The Teleparallel Equivalent of General Relativity and the Gravitational
Centre of Mass | 22 pages, no figures, the title has been changed, references added,
published in Universe (100 Years of Chronogeometrodynamics: the Status of the
Einstein's Theory of Gravitation in Its Centennial Year) | Universe, 2016, 2(3), 19 | 10.3390/universe2030019 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a brief review of the teleparallel equivalent of general
relativity and analyse the expression for the centre of mass density of the
gravitational field. This expression has not been sufficiently discussed in the
literature. One motivation for the present analysis is the investigation of the
localization of dark energy in the three-dimensional space, induced by a
cosmological constant in a simple Schwarzschild-de Sitter space-time. We also
investigate the gravitational centre of mass density in a particular model of
dark matter, in the space-time of a point massive particle and in an arbitrary
space-time with axial symmetry. The results are plausible, and lead to the
notion of gravitational centre of mass (COM) distribution function.
| [
{
"created": "Tue, 11 Aug 2015 01:38:53 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Sep 2016 14:49:37 GMT",
"version": "v2"
},
{
"created": "Fri, 9 Sep 2016 12:33:42 GMT",
"version": "v3"
}
] | 2016-09-12 | [
[
"Maluf",
"J. W.",
""
]
] | We present a brief review of the teleparallel equivalent of general relativity and analyse the expression for the centre of mass density of the gravitational field. This expression has not been sufficiently discussed in the literature. One motivation for the present analysis is the investigation of the localization of dark energy in the three-dimensional space, induced by a cosmological constant in a simple Schwarzschild-de Sitter space-time. We also investigate the gravitational centre of mass density in a particular model of dark matter, in the space-time of a point massive particle and in an arbitrary space-time with axial symmetry. The results are plausible, and lead to the notion of gravitational centre of mass (COM) distribution function. |
2209.12610 | Parth Bambhaniya | Parth Bambhaniya, Ashok B. Joshi, Dipanjan Dey, Pankaj S. Joshi,
Arindam Mazumdar, Tomohiro Harada and Ken-ichi Nakao | Relativistic orbits of S2 star in the presence of scalar field | 6 pages, 3 figures, 2 tables | null | null | RUP-22-20, AP-GR-183, NITEP 146 | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The general theory of relativity predicts the relativistic effect in the
orbital motions of S-stars which are orbiting around our Milky-way galactic
center. The post-Newtonian or higher-order approximated Schwarzschild black
hole models have been used by GRAVITY and UCLA galactic center groups to
carefully investigate the S2 star's periastron precession. In this paper, we
investigate the scalar field effect on the orbital dynamics of S2 star. Hence,
we consider a spacetime, namely Janis-Newman-Winicour (JNW) spacetime which is
seeded by a minimally coupled, mass-less scalar field. The novel feature of
this spacetime is that one can retain the Schwarzschild spacetime from JNW
spacetime considering zero scalar charge. We constrain the scalar charge of JNW
spacetime by best fitting the astrometric data of S2 star using the
Monte-Carlo-Markov-Chain (MCMC) technique assuming the charge to be positive.
Our best-fitted result implies that similar to the Schwarzschild black hole
spacetime, the JNW naked singularity spacetime with an appropriate scalar
charge also offers a satisfactory fitting to the observed data for S2 star.
Therefore, the JNW naked singularity could be a contender for explaining the
nature of Sgr A* through the orbital motions of the S2 star.
| [
{
"created": "Mon, 26 Sep 2022 12:03:12 GMT",
"version": "v1"
},
{
"created": "Sat, 1 Oct 2022 12:01:46 GMT",
"version": "v2"
}
] | 2022-10-04 | [
[
"Bambhaniya",
"Parth",
""
],
[
"Joshi",
"Ashok B.",
""
],
[
"Dey",
"Dipanjan",
""
],
[
"Joshi",
"Pankaj S.",
""
],
[
"Mazumdar",
"Arindam",
""
],
[
"Harada",
"Tomohiro",
""
],
[
"Nakao",
"Ken-ichi",
""
]
... | The general theory of relativity predicts the relativistic effect in the orbital motions of S-stars which are orbiting around our Milky-way galactic center. The post-Newtonian or higher-order approximated Schwarzschild black hole models have been used by GRAVITY and UCLA galactic center groups to carefully investigate the S2 star's periastron precession. In this paper, we investigate the scalar field effect on the orbital dynamics of S2 star. Hence, we consider a spacetime, namely Janis-Newman-Winicour (JNW) spacetime which is seeded by a minimally coupled, mass-less scalar field. The novel feature of this spacetime is that one can retain the Schwarzschild spacetime from JNW spacetime considering zero scalar charge. We constrain the scalar charge of JNW spacetime by best fitting the astrometric data of S2 star using the Monte-Carlo-Markov-Chain (MCMC) technique assuming the charge to be positive. Our best-fitted result implies that similar to the Schwarzschild black hole spacetime, the JNW naked singularity spacetime with an appropriate scalar charge also offers a satisfactory fitting to the observed data for S2 star. Therefore, the JNW naked singularity could be a contender for explaining the nature of Sgr A* through the orbital motions of the S2 star. |
2207.06978 | Mateo Pascual | Sina Kazemian, Mateo Pascual, Carlo Rovelli, Francesca Vidotto | Diffuse emission from black hole remnants | 8 pages, 4 figures | null | 10.1088/1361-6382/acc232 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We point out that conservation of information implies that remnants produced
at the end of black hole evaporation should radiate in the low-frequency
spectrum. We model this emission and derive properties of the diffuse radiation
emitted by an otherwise dark population of such objects. We show that for early
universe black holes the frequency and energy density of this radiation, which
are in principle measurable, suffice to estimate the remnant density.
| [
{
"created": "Thu, 14 Jul 2022 15:01:45 GMT",
"version": "v1"
},
{
"created": "Wed, 3 May 2023 21:05:52 GMT",
"version": "v2"
}
] | 2023-05-05 | [
[
"Kazemian",
"Sina",
""
],
[
"Pascual",
"Mateo",
""
],
[
"Rovelli",
"Carlo",
""
],
[
"Vidotto",
"Francesca",
""
]
] | We point out that conservation of information implies that remnants produced at the end of black hole evaporation should radiate in the low-frequency spectrum. We model this emission and derive properties of the diffuse radiation emitted by an otherwise dark population of such objects. We show that for early universe black holes the frequency and energy density of this radiation, which are in principle measurable, suffice to estimate the remnant density. |
2004.03174 | Claus Kiefer | Claus Kiefer | Space, Time, Matter in Quantum Gravity | 18 pages, to appear in "Hundred Years of Gauge Theory", ed. by S. De
Bianchi and C. Kiefer, Springer 2020 | null | 10.1007/978-3-030-51197-5_9 | null | gr-qc hep-th physics.hist-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The concepts of space, time, and matter are of central importance in any
theory of the gravitational field. Here I discuss the role that these concepts
might play in quantum theories of gravity. To be concrete, I will focus on the
most conservative approach, which is quantum geometrodynamics. It turns out
that spacetime is absent at the most fundamental level and emerges only in an
appropriate limit. It is expected that the dynamics of matter can only be
understood from a fundamental quantum theory of all interactions.
| [
{
"created": "Tue, 7 Apr 2020 07:47:01 GMT",
"version": "v1"
}
] | 2021-04-14 | [
[
"Kiefer",
"Claus",
""
]
] | The concepts of space, time, and matter are of central importance in any theory of the gravitational field. Here I discuss the role that these concepts might play in quantum theories of gravity. To be concrete, I will focus on the most conservative approach, which is quantum geometrodynamics. It turns out that spacetime is absent at the most fundamental level and emerges only in an appropriate limit. It is expected that the dynamics of matter can only be understood from a fundamental quantum theory of all interactions. |
2201.04086 | Damodar Dahal | Damodar Dahal | Application of Common Spatial Patterns in Gravitational Waves Detection | null | null | null | null | gr-qc astro-ph.IM cs.LG cs.NA math.NA | http://creativecommons.org/licenses/by/4.0/ | Common Spatial Patterns (CSP) is a feature extraction algorithm widely used
in Brain-Computer Interface (BCI) Systems for detecting Event-Related
Potentials (ERPs) in multi-channel magneto/electroencephalography (MEG/EEG)
time series data. In this article, we develop and apply a CSP algorithm to the
problem of identifying whether a given epoch of multi-detector Gravitational
Wave (GW) strains contains coalescenses. Paired with Signal Processing
techniques and a Logistic Regression classifier, we find that our pipeline is
correctly able to detect 76 out of 82 confident events from Gravitational Wave
Transient Catalog, using H1 and L1 strains, with a classification score of
$93.72 \pm 0.04\%$ using $10 \times 5$ cross validation. The false negative
events were: GW170817-v3, GW191219 163120-v1, GW200115 042309-v2, GW200210
092254-v1, GW200220 061928-v1, and GW200322 091133-v1.
| [
{
"created": "Tue, 11 Jan 2022 17:23:31 GMT",
"version": "v1"
}
] | 2022-01-13 | [
[
"Dahal",
"Damodar",
""
]
] | Common Spatial Patterns (CSP) is a feature extraction algorithm widely used in Brain-Computer Interface (BCI) Systems for detecting Event-Related Potentials (ERPs) in multi-channel magneto/electroencephalography (MEG/EEG) time series data. In this article, we develop and apply a CSP algorithm to the problem of identifying whether a given epoch of multi-detector Gravitational Wave (GW) strains contains coalescenses. Paired with Signal Processing techniques and a Logistic Regression classifier, we find that our pipeline is correctly able to detect 76 out of 82 confident events from Gravitational Wave Transient Catalog, using H1 and L1 strains, with a classification score of $93.72 \pm 0.04\%$ using $10 \times 5$ cross validation. The false negative events were: GW170817-v3, GW191219 163120-v1, GW200115 042309-v2, GW200210 092254-v1, GW200220 061928-v1, and GW200322 091133-v1. |
2401.08530 | Yoann Launay | Yoann L. Launay, Gerasimos I. Rigopoulos, E. P. S. Shellard | Stochastic Inflation in General Relativity | 21 pages, 4 figures, reviewed, accepted by PRD and referee, to be
published | null | 10.1103/PhysRevD.109.123523 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We provide a formulation of Stochastic Inflation in full general relativity
that goes beyond the slow-roll and separate universe approximations. We show
how gauge invariant Langevin source terms can be obtained for the complete set
of Einstein equations in their ADM formulation by providing a recipe for
coarse-graining the spacetime in any small gauge. These stochastic source terms
are defined in terms of the only dynamical scalar degree of freedom in
single-field inflation and all depend simply on the first two time derivatives
of the coarse-graining window function, on the gauge-invariant mode functions
that satisfy the Mukhanov-Sasaki evolution equation, and on the slow-roll
parameters. It is shown that this reasoning can also be applied to include
gravitons as stochastic sources, thus enabling the study of all relevant
degrees of freedom of general relativity for inflation. We validate the
efficacy of these Langevin dynamics directly using an example in uniform field
gauge, obtaining the stochastic e-fold number in the long wavelength limit
without the need for a first-passage-time analysis. As well as investigating
the most commonly used gauges in cosmological perturbation theory, we also
derive stochastic source terms for the coarse-grained BSSN formulation of
Einstein's equations, which enables a well-posed implementation for 3+1
numerical relativity simulations.
| [
{
"created": "Tue, 16 Jan 2024 17:50:23 GMT",
"version": "v1"
},
{
"created": "Tue, 7 May 2024 14:49:52 GMT",
"version": "v2"
}
] | 2024-06-18 | [
[
"Launay",
"Yoann L.",
""
],
[
"Rigopoulos",
"Gerasimos I.",
""
],
[
"Shellard",
"E. P. S.",
""
]
] | We provide a formulation of Stochastic Inflation in full general relativity that goes beyond the slow-roll and separate universe approximations. We show how gauge invariant Langevin source terms can be obtained for the complete set of Einstein equations in their ADM formulation by providing a recipe for coarse-graining the spacetime in any small gauge. These stochastic source terms are defined in terms of the only dynamical scalar degree of freedom in single-field inflation and all depend simply on the first two time derivatives of the coarse-graining window function, on the gauge-invariant mode functions that satisfy the Mukhanov-Sasaki evolution equation, and on the slow-roll parameters. It is shown that this reasoning can also be applied to include gravitons as stochastic sources, thus enabling the study of all relevant degrees of freedom of general relativity for inflation. We validate the efficacy of these Langevin dynamics directly using an example in uniform field gauge, obtaining the stochastic e-fold number in the long wavelength limit without the need for a first-passage-time analysis. As well as investigating the most commonly used gauges in cosmological perturbation theory, we also derive stochastic source terms for the coarse-grained BSSN formulation of Einstein's equations, which enables a well-posed implementation for 3+1 numerical relativity simulations. |
gr-qc/9509018 | Carlos Nunez | Luis A. Anchordoqui, Graciela S. Birman, Jose D. Edelstein and Carlos
N\'u\~nez | On Pseudospherically Symmetric Repulsive Gravitational Field | 4 pages, latex, no figures, references added. To be published in the
Proceedings of the XVI Brazilian National Meeting on Particles and Fields | null | null | La Plata-Th 95/23 | gr-qc | null | Solutions of Einstein vacuum equations, for a static pseudospherically
symmetric system, are presented. They describe a naked singularity and a
singular solution with many resemblances to the Schwartzschild solution but
with two major differences: its static region, lying inside the null horizon,
sees the singularity, and its effective gravitational field is repulsive. We
shortly discuss on the phenomenological plausibility of this last solution as a
self-consistent system living on a space-time domain, and discuss some features
of particle geodesics in its gravitational field.
| [
{
"created": "Fri, 8 Sep 1995 20:05:13 GMT",
"version": "v1"
},
{
"created": "Thu, 21 Mar 1996 16:05:22 GMT",
"version": "v2"
}
] | 2009-09-25 | [
[
"Anchordoqui",
"Luis A.",
""
],
[
"Birman",
"Graciela S.",
""
],
[
"Edelstein",
"Jose D.",
""
],
[
"Núñez",
"Carlos",
""
]
] | Solutions of Einstein vacuum equations, for a static pseudospherically symmetric system, are presented. They describe a naked singularity and a singular solution with many resemblances to the Schwartzschild solution but with two major differences: its static region, lying inside the null horizon, sees the singularity, and its effective gravitational field is repulsive. We shortly discuss on the phenomenological plausibility of this last solution as a self-consistent system living on a space-time domain, and discuss some features of particle geodesics in its gravitational field. |
gr-qc/0205119 | Ruediger Vaas | Ruediger Vaas | Is there a Darwinian Evolution of the Cosmos? - Some Comments on Lee
Smolin's Theory of the Origin of Universes by Means of Natural Selection | 20 pages; extended version of a contribution to the MicroCosmos -
MacroCosmos conference in Aachen, Germany, September 2-5 1998; finished in
late 1998 and published in the conference proceedings
(http://www.vijlen.com/vip-projects/confs/mima/Vaas/VAAS.html) | null | null | null | gr-qc | null | For Lee Smolin, our universe is only one in a much larger cosmos (the
Multiverse) - a member of a growing community of universes, each one being born
in a bounce following the formation of a black hole. In the course of this, the
values of the free parameters of the physical laws are reprocessed and slightly
changed. This leads to an evolutionary picture of the Multiverse, where
universes with more black holes have more descendants. Smolin concludes, that
due to this kind of Cosmological Natural Selection our own universe is the way
it is. The hospitality for life of our universe is seen as an offshot of this
self-organized process. - This paper outlines Smolin's hypothesis, its
strength, weakness and limits, its relationship to the anthropic principle and
evolutionary biology, and comments on the hypothesis from different points of
view: physics, biology, philosophy of science, philosophy of nature, and
metaphysics. Some of the main points are: (1) There is no necessary connection
between black holes and life. In principle, life and Cosmological Natural
Selection could be independent of each other. Smolin might explain the
so-called fine-tuning of physical constants, but life remains an epiphenomenon.
(2) The Darwinian analogy is an inadequate model transfer. The fitness of
Smolin's universes is not constrained by its environment, but by only one
internal factor: the numbers of black holes. Furthermore, although Smolin's
universes have different reproduction rates, they are not competing against
each other. (3) Smolin's central claim cannot be falsified.
| [
{
"created": "Tue, 28 May 2002 21:17:21 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Vaas",
"Ruediger",
""
]
] | For Lee Smolin, our universe is only one in a much larger cosmos (the Multiverse) - a member of a growing community of universes, each one being born in a bounce following the formation of a black hole. In the course of this, the values of the free parameters of the physical laws are reprocessed and slightly changed. This leads to an evolutionary picture of the Multiverse, where universes with more black holes have more descendants. Smolin concludes, that due to this kind of Cosmological Natural Selection our own universe is the way it is. The hospitality for life of our universe is seen as an offshot of this self-organized process. - This paper outlines Smolin's hypothesis, its strength, weakness and limits, its relationship to the anthropic principle and evolutionary biology, and comments on the hypothesis from different points of view: physics, biology, philosophy of science, philosophy of nature, and metaphysics. Some of the main points are: (1) There is no necessary connection between black holes and life. In principle, life and Cosmological Natural Selection could be independent of each other. Smolin might explain the so-called fine-tuning of physical constants, but life remains an epiphenomenon. (2) The Darwinian analogy is an inadequate model transfer. The fitness of Smolin's universes is not constrained by its environment, but by only one internal factor: the numbers of black holes. Furthermore, although Smolin's universes have different reproduction rates, they are not competing against each other. (3) Smolin's central claim cannot be falsified. |
1606.00517 | Alexander Zhidenko | R. A. Konoplya and A. Zhidenko | Wormholes versus black holes: quasinormal ringing at early and late
times | 13 pages, 4 figures | JCAP12(2016)043 | 10.1088/1475-7516/2016/12/043 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recently it has been argued that the phantom thin-shell wormholes matched
with the Schwarzschild space-time near the Schwarzschild radius ring like
Schwarzschild black holes at early times, but differently at late times
(arXiv:1602.07309). Here we consider perturbations of the wormhole which was
constructed without thin-shells: the Bronnikov-Ellis wormhole supported by the
phantom matter and electromagnetic field. This wormhole solution is known to be
stable under specific equation of state of the phantom matter. We show that if
one does not use the above thin-shell matching, the wormhole, depending on the
values of its parameters, either rings as the black hole at all times or rings
differently also at all times. The wormhole's spectrum, investigated here,
posses a number of distinctive features.
In the final part we have considered general properties of scattering around
arbitrary rotating traversable wormholes. We have found that symmetric and
non-symmetric (with respect to the throat) wormholes are qualitatively
different in this respect: First, superradiance is allowed only if for those
non-symmetric wormholes for which the asymptotic values of the rotation
parameters are different on both sides from the throat. Second, the symmetric
wormholes cannot mimic effectively the ringing of a black hole at a few various
dominant multipoles at the same time, so that the future observations of
various events should easily tell the symmetric wormhole from a black hole.
| [
{
"created": "Thu, 2 Jun 2016 01:36:50 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Jun 2016 03:10:49 GMT",
"version": "v2"
},
{
"created": "Wed, 14 Dec 2016 15:09:45 GMT",
"version": "v3"
}
] | 2016-12-30 | [
[
"Konoplya",
"R. A.",
""
],
[
"Zhidenko",
"A.",
""
]
] | Recently it has been argued that the phantom thin-shell wormholes matched with the Schwarzschild space-time near the Schwarzschild radius ring like Schwarzschild black holes at early times, but differently at late times (arXiv:1602.07309). Here we consider perturbations of the wormhole which was constructed without thin-shells: the Bronnikov-Ellis wormhole supported by the phantom matter and electromagnetic field. This wormhole solution is known to be stable under specific equation of state of the phantom matter. We show that if one does not use the above thin-shell matching, the wormhole, depending on the values of its parameters, either rings as the black hole at all times or rings differently also at all times. The wormhole's spectrum, investigated here, posses a number of distinctive features. In the final part we have considered general properties of scattering around arbitrary rotating traversable wormholes. We have found that symmetric and non-symmetric (with respect to the throat) wormholes are qualitatively different in this respect: First, superradiance is allowed only if for those non-symmetric wormholes for which the asymptotic values of the rotation parameters are different on both sides from the throat. Second, the symmetric wormholes cannot mimic effectively the ringing of a black hole at a few various dominant multipoles at the same time, so that the future observations of various events should easily tell the symmetric wormhole from a black hole. |
1909.01791 | Yuri Obukhov | Friedrich W. Hehl and Yuri N. Obukhov | Conservation of energy-momentum of matter as the basis for the gauge
theory of gravitation | 46 pages, 4 figures, minor corrections, references added,
contribution to "One Hundred Years of Gauge Theory" edited by S. De Bianchi
and C. Kiefer | null | 10.1007/978-3-030-51197-5_10 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | According to Yang \& Mills (1954), a {\it conserved} current and a related
rigid (`global') symmetry lie at the foundations of gauge theory. When the
rigid symmetry is extended to a {\it local} one, a so-called gauge symmetry, a
new interaction emerges as gauge potential $A$; its field strength is $F\sim
{\rm curl} A$. In gravity, the conservation of the energy-momentum current of
matter and the rigid translation symmetry in the Minkowski space of special
relativity lie at the foundations of a gravitational gauge theory. If the
translation invariance is made local, a gravitational potential $\vartheta$
arises together with its field strength $T\sim {\rm curl}\,\vartheta$. Thereby
the Minkowski space deforms into a Weitzenb\"ock space with nonvanishing
torsion $T$ but vanishing curvature. The corresponding theory is reviewed and
its equivalence to general relativity pointed out. Since translations form a
subgroup of the Poincar\'e group, the group of motion of special relativity,
one ought to straightforwardly extend the gauging of the translations to the
gauging of full Poincar\'e group thereby also including the conservation law of
the {\it angular momentum} current. The emerging Poincar\'e gauge (theory of)
gravity, starting from the viable Einstein-Cartan theory of 1961, will be
shortly reviewed and its prospects for further developments assessed.
| [
{
"created": "Sun, 1 Sep 2019 16:37:06 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Mar 2020 21:41:42 GMT",
"version": "v2"
},
{
"created": "Sat, 21 Nov 2020 13:56:53 GMT",
"version": "v3"
}
] | 2020-11-24 | [
[
"Hehl",
"Friedrich W.",
""
],
[
"Obukhov",
"Yuri N.",
""
]
] | According to Yang \& Mills (1954), a {\it conserved} current and a related rigid (`global') symmetry lie at the foundations of gauge theory. When the rigid symmetry is extended to a {\it local} one, a so-called gauge symmetry, a new interaction emerges as gauge potential $A$; its field strength is $F\sim {\rm curl} A$. In gravity, the conservation of the energy-momentum current of matter and the rigid translation symmetry in the Minkowski space of special relativity lie at the foundations of a gravitational gauge theory. If the translation invariance is made local, a gravitational potential $\vartheta$ arises together with its field strength $T\sim {\rm curl}\,\vartheta$. Thereby the Minkowski space deforms into a Weitzenb\"ock space with nonvanishing torsion $T$ but vanishing curvature. The corresponding theory is reviewed and its equivalence to general relativity pointed out. Since translations form a subgroup of the Poincar\'e group, the group of motion of special relativity, one ought to straightforwardly extend the gauging of the translations to the gauging of full Poincar\'e group thereby also including the conservation law of the {\it angular momentum} current. The emerging Poincar\'e gauge (theory of) gravity, starting from the viable Einstein-Cartan theory of 1961, will be shortly reviewed and its prospects for further developments assessed. |
1512.07927 | Manuel Hohmann | Manuel Hohmann | Finsler fluid dynamics in $\mathrm{SO}(4)$ symmetric cosmology | 6 pages, no figures; to appear in the conference proceedings of the
14th Marcel Grossmann Meeting, World Scientific Publishing Company | null | 10.1142/9789813226609_0090 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss the most general Finsler spacetime geometry obeying the
cosmological symmetry group $\mathrm{SO}(4)$. On this background geometry we
derive the equations of motion for the most general kinetic fluid obeying the
same cosmological symmetry. For this purpose we propose a set of coordinates on
the tangent bundle of the spacetime manifold which greatly simplifies the
cosmological symmetry generators.
| [
{
"created": "Thu, 24 Dec 2015 22:33:15 GMT",
"version": "v1"
}
] | 2017-11-28 | [
[
"Hohmann",
"Manuel",
""
]
] | We discuss the most general Finsler spacetime geometry obeying the cosmological symmetry group $\mathrm{SO}(4)$. On this background geometry we derive the equations of motion for the most general kinetic fluid obeying the same cosmological symmetry. For this purpose we propose a set of coordinates on the tangent bundle of the spacetime manifold which greatly simplifies the cosmological symmetry generators. |
2103.14109 | Felipe Falciano | F. T. Falciano, M. L. Pe\~nafiel and J. C. Fabris | Entropy bound in Einstein-Born-Infeld black holes | 13 pages, 5 figures | Phys. Rev. D 103, 084046 (2021) | 10.1103/PhysRevD.103.084046 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the validity of Bekenstein's entropy bound for a charged black hole
in the context of nonlinear electrodynamics. Bekenstein's inequalities are
commonly understood as universal relations between the entropy, the charge, the
momentum, and the energy of a physical system but independent of its dynamics.
In particular, we consider the Born-Infeld electrodynamics coupled to gravity
as described by General Relativity. Following the steps that lead to these
inequalities, we study the absorption of a charged test particle by the black
hole and verify that the entropy bound is violated. We find a modified upper
bound for the entropy that depends on the maximum field parameter of the
Born-Infeld theory.
| [
{
"created": "Thu, 25 Mar 2021 19:53:05 GMT",
"version": "v1"
}
] | 2021-04-30 | [
[
"Falciano",
"F. T.",
""
],
[
"Peñafiel",
"M. L.",
""
],
[
"Fabris",
"J. C.",
""
]
] | We study the validity of Bekenstein's entropy bound for a charged black hole in the context of nonlinear electrodynamics. Bekenstein's inequalities are commonly understood as universal relations between the entropy, the charge, the momentum, and the energy of a physical system but independent of its dynamics. In particular, we consider the Born-Infeld electrodynamics coupled to gravity as described by General Relativity. Following the steps that lead to these inequalities, we study the absorption of a charged test particle by the black hole and verify that the entropy bound is violated. We find a modified upper bound for the entropy that depends on the maximum field parameter of the Born-Infeld theory. |
gr-qc/0402071 | Giovanni Imponente | Giovanni Imponente and Giovanni Montani | Pre-inflationary perturbations spectrum | null | null | 10.1142/9789812704030_0194 | null | gr-qc astro-ph | null | In the framework of a flat FLRW model we derive an inflationary regime in
which the scalar field, laying on the plateau of its potential, admits a linear
time dependence and remains close to a constant value. The behaviour of
inhomogeneous perturbations is determined on the background metric in agreement
to the "slow-rolling" approximation. We show that the inhomogeneous scales
which before inflation were not much greater then the physical horizon,
conserve their spectrum (almost) unaltered after the de Sitter phase.
| [
{
"created": "Mon, 16 Feb 2004 10:34:24 GMT",
"version": "v1"
}
] | 2016-11-09 | [
[
"Imponente",
"Giovanni",
""
],
[
"Montani",
"Giovanni",
""
]
] | In the framework of a flat FLRW model we derive an inflationary regime in which the scalar field, laying on the plateau of its potential, admits a linear time dependence and remains close to a constant value. The behaviour of inhomogeneous perturbations is determined on the background metric in agreement to the "slow-rolling" approximation. We show that the inhomogeneous scales which before inflation were not much greater then the physical horizon, conserve their spectrum (almost) unaltered after the de Sitter phase. |
1804.03239 | Margaret Millhouse | Margaret Millhouse, Neil J. Cornish, Tyson Littenberg | Bayesian reconstruction of gravitational wave bursts using chirplets | 16 pages, 9 figures | Phys. Rev. D 97, 104057 (2018) | 10.1103/PhysRevD.97.104057 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The LIGO-Virgo collaboration uses a variety of techniques to detect and
characterize gravitational waves. One approach is to use templates - models for
the signals derived from Einstein's equations. Another approach is to extract
the signals directly from the coherent response of the detectors in LIGO-Virgo
network. Both approaches played an important role in the first gravitational
wave detections. Here we extend the BayesWave analysis algorithm, which
reconstructs gravitational wave signals using a collection of continuous
wavelets, to use a generalized wavelet family, known as chirplets, that have
time-evolving frequency content. Since generic gravitational wave signals have
frequency content that evolves in time, a collection of chirplets provides a
more compact representation of the signal, resulting in more accurate waveform
reconstructions, especially for low signal-to-noise events, and events that
occupy a large time-frequency volume.
| [
{
"created": "Mon, 9 Apr 2018 21:00:37 GMT",
"version": "v1"
}
] | 2018-06-06 | [
[
"Millhouse",
"Margaret",
""
],
[
"Cornish",
"Neil J.",
""
],
[
"Littenberg",
"Tyson",
""
]
] | The LIGO-Virgo collaboration uses a variety of techniques to detect and characterize gravitational waves. One approach is to use templates - models for the signals derived from Einstein's equations. Another approach is to extract the signals directly from the coherent response of the detectors in LIGO-Virgo network. Both approaches played an important role in the first gravitational wave detections. Here we extend the BayesWave analysis algorithm, which reconstructs gravitational wave signals using a collection of continuous wavelets, to use a generalized wavelet family, known as chirplets, that have time-evolving frequency content. Since generic gravitational wave signals have frequency content that evolves in time, a collection of chirplets provides a more compact representation of the signal, resulting in more accurate waveform reconstructions, especially for low signal-to-noise events, and events that occupy a large time-frequency volume. |
1512.06289 | George Alekseev A. | George A. Alekseev | Solution for "geodesic" motion of a Schwarzschild black hole along a
magnetic field in AdS2 x S2 space-time | 5 pages, 3 figures. Talk given at ES1 Parallel Session of MG14
Meeting (Rome, Italy, July 2015) | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The exact solution of Einstein - Maxwell equations for a Schwarzschild black
hole immersed in the static spatially homogeneous AdS${}^2\times\mathbb{S}^2$
space-time of Bertotti-Robinson magnetic universe is presented. In this
solution, the black hole possesses a finite initial boost in the direction of
the magnetic field and performs a "geodesic" oscillating motion interacting
with the background gravitational and electromagnetic fields.
| [
{
"created": "Sat, 19 Dec 2015 22:00:15 GMT",
"version": "v1"
}
] | 2015-12-22 | [
[
"Alekseev",
"George A.",
""
]
] | The exact solution of Einstein - Maxwell equations for a Schwarzschild black hole immersed in the static spatially homogeneous AdS${}^2\times\mathbb{S}^2$ space-time of Bertotti-Robinson magnetic universe is presented. In this solution, the black hole possesses a finite initial boost in the direction of the magnetic field and performs a "geodesic" oscillating motion interacting with the background gravitational and electromagnetic fields. |
gr-qc/9509019 | Luis Anchordoqui | Luis Anchordoqui, Graciela Birman, Santiago Perez Bergliaffa and
H\'ector Vucetich | Variable rest masses in 5-dimensional gravitation confronted with
experimental data | Some references added | Gen.Rel.Grav. 28 (1996) 701-706 | 10.1007/BF02104836 | null | gr-qc | null | Cosmological solutions of Einstein equation for a \mbox{5-dimensional}
space-time, in the case of a dust-filled universe, are presented. With these
solutions we are able to test a hypothetical relation between the rest mass of
a particle and the $5^{\rm th}$ dimension. Comparison with experiment strongly
refutes the implied dependence of the rest mass on the cosmological time.
| [
{
"created": "Fri, 8 Sep 1995 20:30:26 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Aug 1996 22:09:53 GMT",
"version": "v2"
}
] | 2009-10-28 | [
[
"Anchordoqui",
"Luis",
""
],
[
"Birman",
"Graciela",
""
],
[
"Bergliaffa",
"Santiago Perez",
""
],
[
"Vucetich",
"Héctor",
""
]
] | Cosmological solutions of Einstein equation for a \mbox{5-dimensional} space-time, in the case of a dust-filled universe, are presented. With these solutions we are able to test a hypothetical relation between the rest mass of a particle and the $5^{\rm th}$ dimension. Comparison with experiment strongly refutes the implied dependence of the rest mass on the cosmological time. |
1912.12199 | Farook Rahaman | K N Singh, F Rahaman, N Pradhan and N Pant | Relativistic compact stars in the Kuchowicz spacetime | 18 pages, 18 figures, 2 tables. To appear in Ind. J. Phys | null | 10.1007/s12648-020-01749-9 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an anisotropic charged analogue of Kuchowicz (1971) solution of
the general relativistic field equations in curvature coordinates by using
simple form of electric intensity $E$ and pressure anisotropy factor $\Delta$
that involve charge parameter $K$ and anisotropy parameter $\alpha$
respectively. Our solution is well behaved in all respects for all values of
$X$ ( $X$ is related to the radius of the star ) lying in the range $0< X \le
0.6$, $\alpha$ lying in the range $0 \le \alpha \le 1.3$, $K$ lying in the
range $0< K \le 1.75$ and Schwarzschild compactness parameter "$u$" lying in
the range $0< u \le 0.338$. Since our solution is well behaved for a wide range
of the parameters, we can model many different types of ultra-cold compact
stars like quark stars and neutron stars. We present some models of super dense
quark stars and neutron stars corresponding to $X=0.2,~\alpha=0.2$ and $K=0.5$
for which $u_{max}=0.15$. By assuming surface density $\rho_b=4.6888\times
10^{14}~ g/cc$ the mass and radius are $0.955 M_\odot$ and $9.439 km$
respectively. For $\rho_b=2.7\times 10^{14}~ g/cc$ the mass and radius are
$1.259 M_\odot$ and $12.439 km$ respectively and for $\rho_b=2\times 10^{14}~
g/cc$ the mass and radius are $1.463 M_\odot$ and $14.453 km$ respectively. It
is also shown that inclusion of more electric charge and anisotropy enhances
the static stable configuration under radial perturbations. The $M-R$ graph
suggests that the maximum mass of the configuration depends on the surface
density {\bf i.e. with the increase of surface density} the maximum mass and
corresponding radius decrease. This may be because of existence of exotic
matters at higher densities that soften the EoSs.
| [
{
"created": "Mon, 23 Dec 2019 18:40:00 GMT",
"version": "v1"
}
] | 2020-07-15 | [
[
"Singh",
"K N",
""
],
[
"Rahaman",
"F",
""
],
[
"Pradhan",
"N",
""
],
[
"Pant",
"N",
""
]
] | We present an anisotropic charged analogue of Kuchowicz (1971) solution of the general relativistic field equations in curvature coordinates by using simple form of electric intensity $E$ and pressure anisotropy factor $\Delta$ that involve charge parameter $K$ and anisotropy parameter $\alpha$ respectively. Our solution is well behaved in all respects for all values of $X$ ( $X$ is related to the radius of the star ) lying in the range $0< X \le 0.6$, $\alpha$ lying in the range $0 \le \alpha \le 1.3$, $K$ lying in the range $0< K \le 1.75$ and Schwarzschild compactness parameter "$u$" lying in the range $0< u \le 0.338$. Since our solution is well behaved for a wide range of the parameters, we can model many different types of ultra-cold compact stars like quark stars and neutron stars. We present some models of super dense quark stars and neutron stars corresponding to $X=0.2,~\alpha=0.2$ and $K=0.5$ for which $u_{max}=0.15$. By assuming surface density $\rho_b=4.6888\times 10^{14}~ g/cc$ the mass and radius are $0.955 M_\odot$ and $9.439 km$ respectively. For $\rho_b=2.7\times 10^{14}~ g/cc$ the mass and radius are $1.259 M_\odot$ and $12.439 km$ respectively and for $\rho_b=2\times 10^{14}~ g/cc$ the mass and radius are $1.463 M_\odot$ and $14.453 km$ respectively. It is also shown that inclusion of more electric charge and anisotropy enhances the static stable configuration under radial perturbations. The $M-R$ graph suggests that the maximum mass of the configuration depends on the surface density {\bf i.e. with the increase of surface density} the maximum mass and corresponding radius decrease. This may be because of existence of exotic matters at higher densities that soften the EoSs. |
2303.13271 | Joseph P Johnson | Joseph P Johnson (IIT Bombay, IISER Mohali), Susmita Jana (IIT
Bombay), S. Shankaranarayanan (IIT Bombay) | A test of Einstein's equivalence principle in future VLBI observations | V2: Version accepted in PRD Letters. Results are now compared for
many VLBI experiments; hence, the title and abstract are modified. 11 Pages,
7 figures (including supplementary material) | null | null | null | gr-qc astro-ph.GA astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | We show that very-long-baseline-interferometry (VLBI) observations of
supermassive black holes will allow us to test the fundamental principles of
General Relativity (GR). GR is based on the universality of gravity and
Einstein's equivalence principle (EEP). However, EEP is not a basic principle
of physics but an empirical fact. Non-minimal coupling (NMC) of electromagnetic
fields violates EEP, and their effects manifest in the strong-gravity regime.
Hence, VLBI observations of black holes provide an opportunity to test NMC in
the strong-gravity regime. To the leading order in the spin parameter, we
explicitly show that the NMC of the electromagnetic field introduces observable
modifications to the black hole image. In addition, we find that the size of
the photon rings varies by $\sim 3 r_H$, which corresponds to $\sim 30 \mu as$
for Sagittarius $A^*$ and $\sim 23 \mu as$ for M87. VLBI telescopes are
expected to attain a resolution of $\sim 5 \mu as$ in the near future. However,
direct detection of photon ring will require the resolution of $\sim 1 \mu as$
for M87, which can potentially be probed by the space-based Event Horizon
Explorer.
| [
{
"created": "Thu, 23 Mar 2023 13:52:28 GMT",
"version": "v1"
},
{
"created": "Fri, 15 Dec 2023 06:14:21 GMT",
"version": "v2"
}
] | 2023-12-18 | [
[
"Johnson",
"Joseph P",
"",
"IIT Bombay, IISER Mohali"
],
[
"Jana",
"Susmita",
"",
"IIT\n Bombay"
],
[
"Shankaranarayanan",
"S.",
"",
"IIT Bombay"
]
] | We show that very-long-baseline-interferometry (VLBI) observations of supermassive black holes will allow us to test the fundamental principles of General Relativity (GR). GR is based on the universality of gravity and Einstein's equivalence principle (EEP). However, EEP is not a basic principle of physics but an empirical fact. Non-minimal coupling (NMC) of electromagnetic fields violates EEP, and their effects manifest in the strong-gravity regime. Hence, VLBI observations of black holes provide an opportunity to test NMC in the strong-gravity regime. To the leading order in the spin parameter, we explicitly show that the NMC of the electromagnetic field introduces observable modifications to the black hole image. In addition, we find that the size of the photon rings varies by $\sim 3 r_H$, which corresponds to $\sim 30 \mu as$ for Sagittarius $A^*$ and $\sim 23 \mu as$ for M87. VLBI telescopes are expected to attain a resolution of $\sim 5 \mu as$ in the near future. However, direct detection of photon ring will require the resolution of $\sim 1 \mu as$ for M87, which can potentially be probed by the space-based Event Horizon Explorer. |
0806.2740 | M Hossain Ali | M. Atiqur Rahman and M. Hossain Ali | Transverse Wave Propagation in Relativistic Two-fluid Plasmas in de
Sitter Space | 19 pages, 12 figures | Gen.Rel.Grav.42:1063-1079,2010 | 10.1007/s10714-009-0891-x | null | gr-qc astro-ph | http://creativecommons.org/licenses/by/3.0/ | We investigate transverse electromagnetic waves propagating in a plasma in
the de Sitter space. Using the 3+1 formalism we derive the relativistic
two-fluid equations to take account of the effects due to the horizon and
describe the set of simultaneous linear equations for the perturbations. We use
a local approximation to investigate the one-dimensional radial propagation of
Alfv\'en and high frequency electromagnetic waves and solve the dispersion
relation for these waves numerically.
| [
{
"created": "Tue, 17 Jun 2008 10:53:03 GMT",
"version": "v1"
}
] | 2010-04-30 | [
[
"Rahman",
"M. Atiqur",
""
],
[
"Ali",
"M. Hossain",
""
]
] | We investigate transverse electromagnetic waves propagating in a plasma in the de Sitter space. Using the 3+1 formalism we derive the relativistic two-fluid equations to take account of the effects due to the horizon and describe the set of simultaneous linear equations for the perturbations. We use a local approximation to investigate the one-dimensional radial propagation of Alfv\'en and high frequency electromagnetic waves and solve the dispersion relation for these waves numerically. |
1902.02731 | Ajit Mehta | Ajit Kumar Mehta, Praveer Tiwari, Nathan K. Johnson-McDaniel, Chandra
Kant Mishra, Vijay Varma, Parameswaran Ajith | Including mode mixing in a higher-multipole model for gravitational
waveforms from nonspinning black-hole binaries | 12 pages, 11 figures, Accepted manuscript | Phys. Rev. D 100, 024032 (2019) | 10.1103/PhysRevD.100.024032 | LIGO-P1800203-v6 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As gravitational-wave (GW) observations of binary black holes are becoming a
precision tool for physics and astronomy, several subdominant effects in the GW
signals need to be accurately modeled. Previous studies have shown that
neglecting subdominant modes in the GW templates causes an unacceptable loss in
detection efficiency and large systematic errors in the estimated parameters
for binaries with large mass ratios. Our recent work [Mehta et al., Phys. Rev.
D 96, 124010 (2017)] constructed a phenomenological gravitational waveform
family for nonspinning black-hole binaries that includes subdominant spherical
harmonic modes $(\ell = 2, m = \pm 1)$, $(\ell = 3, m = \pm 3)$, and $(\ell =
4, m = \pm 4)$ in addition to the dominant quadrupole mode, $(\ell = 2, m=\pm
2)$. In this article, we construct analytical models for the ($\ell = 3, m =
\pm 2$) and ($\ell = 4, m = \pm 3$) modes and include them in the existing
waveform family. Accurate modeling of these modes is complicated by the mixing
of multiple spheroidal harmonic modes. We develop a method for accurately
modeling the effect of mode mixing, thus producing an analytical waveform
family that has faithfulness >99.6%.
| [
{
"created": "Thu, 7 Feb 2019 17:13:21 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Jun 2019 10:03:17 GMT",
"version": "v2"
}
] | 2019-07-22 | [
[
"Mehta",
"Ajit Kumar",
""
],
[
"Tiwari",
"Praveer",
""
],
[
"Johnson-McDaniel",
"Nathan K.",
""
],
[
"Mishra",
"Chandra Kant",
""
],
[
"Varma",
"Vijay",
""
],
[
"Ajith",
"Parameswaran",
""
]
] | As gravitational-wave (GW) observations of binary black holes are becoming a precision tool for physics and astronomy, several subdominant effects in the GW signals need to be accurately modeled. Previous studies have shown that neglecting subdominant modes in the GW templates causes an unacceptable loss in detection efficiency and large systematic errors in the estimated parameters for binaries with large mass ratios. Our recent work [Mehta et al., Phys. Rev. D 96, 124010 (2017)] constructed a phenomenological gravitational waveform family for nonspinning black-hole binaries that includes subdominant spherical harmonic modes $(\ell = 2, m = \pm 1)$, $(\ell = 3, m = \pm 3)$, and $(\ell = 4, m = \pm 4)$ in addition to the dominant quadrupole mode, $(\ell = 2, m=\pm 2)$. In this article, we construct analytical models for the ($\ell = 3, m = \pm 2$) and ($\ell = 4, m = \pm 3$) modes and include them in the existing waveform family. Accurate modeling of these modes is complicated by the mixing of multiple spheroidal harmonic modes. We develop a method for accurately modeling the effect of mode mixing, thus producing an analytical waveform family that has faithfulness >99.6%. |
gr-qc/0406054 | T. P. Singh | T. P. Singh (Tata Institute of Fundamental Research, Mumbai) | Quantum mechanics without spacetime IV : a noncommutative
Hamilton-Jacobi equation | 5 pages | null | null | null | gr-qc hep-th quant-ph | null | It has earlier been argued that there should exist a formulation of quantum
mechanics which does not refer to a background spacetime. In this paper we
propose that, for a relativistic particle, such a formulation is provided by a
noncommutative generalisation of the Hamilton-Jacobi equation. If a certain
form for the metric in the noncommuting coordinate system is assumed, along
with a correspondence rule for the commutation relations, it can be argued that
this noncommutative Hamilton-Jacobi equation is equivalent to standard quantum
mechanics.
| [
{
"created": "Sun, 13 Jun 2004 09:37:19 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Singh",
"T. P.",
"",
"Tata Institute of Fundamental Research, Mumbai"
]
] | It has earlier been argued that there should exist a formulation of quantum mechanics which does not refer to a background spacetime. In this paper we propose that, for a relativistic particle, such a formulation is provided by a noncommutative generalisation of the Hamilton-Jacobi equation. If a certain form for the metric in the noncommuting coordinate system is assumed, along with a correspondence rule for the commutation relations, it can be argued that this noncommutative Hamilton-Jacobi equation is equivalent to standard quantum mechanics. |
2210.14020 | Nicola Franchini | Nicola Franchini, Sebastian H. V\"olkel | A parametrized quasi-normal mode framework for non-Schwarzschild metrics | 5 pages, 2 figures | null | 10.1103/PhysRevD.107.124063 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we comment in more detail on what happens to the parametrized
framework first presented by Cardoso et al. when there are departures from the
Schwarzschild background metric, as well as possible deviations in the
"dynamics". We treat possible deviations in the background metric with
additional coefficients with respect to the original works. The advantages of
this reformulation are clear when applied to a parameter estimation problem,
since the coefficients are always real, and many of them do not depend on the
overtone number and angular momentum of the frequency, thus eventually reducing
the total amount of parameters to be inferred.
| [
{
"created": "Tue, 25 Oct 2022 13:43:32 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Oct 2023 09:02:11 GMT",
"version": "v2"
}
] | 2023-10-03 | [
[
"Franchini",
"Nicola",
""
],
[
"Völkel",
"Sebastian H.",
""
]
] | In this work we comment in more detail on what happens to the parametrized framework first presented by Cardoso et al. when there are departures from the Schwarzschild background metric, as well as possible deviations in the "dynamics". We treat possible deviations in the background metric with additional coefficients with respect to the original works. The advantages of this reformulation are clear when applied to a parameter estimation problem, since the coefficients are always real, and many of them do not depend on the overtone number and angular momentum of the frequency, thus eventually reducing the total amount of parameters to be inferred. |
0907.3744 | Mikhail Smolyakov | Mikhail N. Smolyakov | Gravity in Brans-Dicke theory with Born-Infeld scalar field and the
Pioneer anomaly | 10 pages, 1 figure, partially changed content | null | 10.1142/S0217751X1004810X | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we discuss a model which can be considered as a generalization
of the well-known scalar-tensor Brans-Dicke theory. This model possesses an
interesting feature: due to Born-Infeld type non-linearity of the scalar field
the properties of the interaction between two test bodies depend significantly
on their masses. It is shown that the model can be interesting in view of the
Pioneer 10, 11 spacecraft anomaly.
| [
{
"created": "Tue, 21 Jul 2009 20:58:34 GMT",
"version": "v1"
},
{
"created": "Sun, 13 Dec 2009 19:08:20 GMT",
"version": "v2"
}
] | 2015-05-13 | [
[
"Smolyakov",
"Mikhail N.",
""
]
] | In this paper we discuss a model which can be considered as a generalization of the well-known scalar-tensor Brans-Dicke theory. This model possesses an interesting feature: due to Born-Infeld type non-linearity of the scalar field the properties of the interaction between two test bodies depend significantly on their masses. It is shown that the model can be interesting in view of the Pioneer 10, 11 spacecraft anomaly. |
2012.13954 | Stephan Rosswog | S. Rosswog and P. Diener | SPHINCS_BSSN: A general relativistic Smooth Particle Hydrodynamics code
for dynamical spacetimes | 41 pages, 16 figures; accepted for publication in Classical and
Quantum Gravity | null | 10.1088/1361-6382/abee65 | null | gr-qc astro-ph.HE astro-ph.IM | http://creativecommons.org/licenses/by-nc-nd/4.0/ | We present a new methodology for simulating self-gravitating
general-relativistic fluids. In our approach the fluid is modelled by means of
Lagrangian particles in the framework of a general-relativistic (GR) Smooth
Particle Hydrodynamics (SPH) formulation, while the spacetime is evolved on a
mesh according to the BSSN formulation that is also frequently used in Eulerian
GR-hydrodynamics. To the best of our knowledge this is the first Lagrangian
fully general relativistic hydrodynamics code (all previous SPH approaches used
approximations to GR-gravity). A core ingredient of our particle-mesh approach
is the coupling between the gas (represented by particles) and the spacetime
(represented by a mesh) for which we have developed a set of sophisticated
interpolation tools that are inspired by other particle-mesh approaches, in
particular by vortex-particle methods. One advantage of splitting the
methodology between matter and spacetime is that it gives us more freedom in
choosing the resolution, so that -- if the spacetime is smooth enough -- we
obtain good results already with a moderate number of grid cells and can focus
the computational effort on the simulation of the matter. Further advantages of
our approach are the ease with which ejecta can be tracked and the fact that
the neutron star surface remains well-behaved and does not need any particular
treatment. In the hydrodynamics part of the code we use a number of techniques
that are new to SPH, such as reconstruction, slope limiting and steering
dissipation by monitoring entropy conservation. We describe here in detail the
employed numerical methods and demonstrate the code performance in a number of
benchmark problems ranging from shock tube tests, over Cowling approximations
to the fully dynamical evolution of neutron stars in self-consistently evolved
spacetimes.
| [
{
"created": "Sun, 27 Dec 2020 14:36:45 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Mar 2021 16:39:04 GMT",
"version": "v2"
}
] | 2021-06-09 | [
[
"Rosswog",
"S.",
""
],
[
"Diener",
"P.",
""
]
] | We present a new methodology for simulating self-gravitating general-relativistic fluids. In our approach the fluid is modelled by means of Lagrangian particles in the framework of a general-relativistic (GR) Smooth Particle Hydrodynamics (SPH) formulation, while the spacetime is evolved on a mesh according to the BSSN formulation that is also frequently used in Eulerian GR-hydrodynamics. To the best of our knowledge this is the first Lagrangian fully general relativistic hydrodynamics code (all previous SPH approaches used approximations to GR-gravity). A core ingredient of our particle-mesh approach is the coupling between the gas (represented by particles) and the spacetime (represented by a mesh) for which we have developed a set of sophisticated interpolation tools that are inspired by other particle-mesh approaches, in particular by vortex-particle methods. One advantage of splitting the methodology between matter and spacetime is that it gives us more freedom in choosing the resolution, so that -- if the spacetime is smooth enough -- we obtain good results already with a moderate number of grid cells and can focus the computational effort on the simulation of the matter. Further advantages of our approach are the ease with which ejecta can be tracked and the fact that the neutron star surface remains well-behaved and does not need any particular treatment. In the hydrodynamics part of the code we use a number of techniques that are new to SPH, such as reconstruction, slope limiting and steering dissipation by monitoring entropy conservation. We describe here in detail the employed numerical methods and demonstrate the code performance in a number of benchmark problems ranging from shock tube tests, over Cowling approximations to the fully dynamical evolution of neutron stars in self-consistently evolved spacetimes. |
gr-qc/0312002 | Nikhil Joshi | Nikhil J. Joshi | Gravitational Lensing In Case of Massive Particles | 8 pages, 4 figures, written in Latex | null | null | null | gr-qc | null | Gravitation lensing calculations, which are generally done for light ray, are
extended to that for a massive particle. Many interesting results were
observed. We discuss the scattering cross section along-with many consequential
quantities here. In particular, the case of Schrwarzschild metric was taken as
illustration, though the analysis applies to a wide range of cases, such as
extended black holes.
| [
{
"created": "Sun, 30 Nov 2003 11:53:44 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Joshi",
"Nikhil J.",
""
]
] | Gravitation lensing calculations, which are generally done for light ray, are extended to that for a massive particle. Many interesting results were observed. We discuss the scattering cross section along-with many consequential quantities here. In particular, the case of Schrwarzschild metric was taken as illustration, though the analysis applies to a wide range of cases, such as extended black holes. |
gr-qc/0612122 | Filimonova Irina V | A. Godizov | Numerical Spherically Symmetric Static Solution of the RTG Equations
Outside the Matter | Plenary talk presented at Workshop on High Energy Physics&Field
Theory (Protvino, Russia, 2005) | CentralEur.J.Phys.5:201-206,2007 | 10.2478/s11534-007-0008-7 | HEPFT/2005/15 | gr-qc | null | There was obtained a numerical external solution for the exact system of the
RTG equations with some natural boundary conditions in the static spherically
symmetric case. The properties of the solution are discussed.
| [
{
"created": "Wed, 20 Dec 2006 08:32:43 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Feb 2007 13:17:49 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Godizov",
"A.",
""
]
] | There was obtained a numerical external solution for the exact system of the RTG equations with some natural boundary conditions in the static spherically symmetric case. The properties of the solution are discussed. |
gr-qc/0703069 | Jose M. Martin-Garcia | David Brizuela, Jose M. Martin-Garcia and Guillermo A. Mena Marugan | High-order gauge-invariant perturbations of a spherical spacetime | null | Phys.Rev.D76:024004,2007 | 10.1103/PhysRevD.76.024004 | null | gr-qc | null | We complete the formulation of a general framework for the analysis of
high-order nonspherical perturbations of a four-dimensional spherical spacetime
by including a gauge-invariant description of the perturbations. We present a
general algorithm to construct these invariants and provide explicit formulas
for the case of second-order metric perturbations. We show that the well-known
problem of lack of invariance for the first-order perturbations with l=0,1
propagates to increasing values of l for perturbations of higher order, owing
to mode coupling. We also discuss in which circumstances it is possible to
construct the invariants.
| [
{
"created": "Mon, 12 Mar 2007 18:13:15 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Brizuela",
"David",
""
],
[
"Martin-Garcia",
"Jose M.",
""
],
[
"Marugan",
"Guillermo A. Mena",
""
]
] | We complete the formulation of a general framework for the analysis of high-order nonspherical perturbations of a four-dimensional spherical spacetime by including a gauge-invariant description of the perturbations. We present a general algorithm to construct these invariants and provide explicit formulas for the case of second-order metric perturbations. We show that the well-known problem of lack of invariance for the first-order perturbations with l=0,1 propagates to increasing values of l for perturbations of higher order, owing to mode coupling. We also discuss in which circumstances it is possible to construct the invariants. |
gr-qc/9910090 | Alessandro Paulo Servio de Moura | Alessandro P. S. de Moura and Patricio S. Letelier | Scattering map for two black holes | 20 pages, 5 figures, uses REVTEX | Phys.Rev. E62 (2000) 4784-4791 | 10.1103/PhysRevE.62.4784 | null | gr-qc chao-dyn nlin.CD | null | We study the motion of light in the gravitational field of two Schwarzschild
black holes, making the approximation that they are far apart, so that the
motion of light rays in the neighborhood of one black hole can be considered to
be the result of the action of each black hole separately. Using this
approximation, the dynamics is reduced to a 2-dimensional map, which we study
both numerically and analytically. The map is found to be chaotic, with a
fractal basin boundary separating the possible outcomes of the orbits (escape
or falling into one of the black holes). In the limit of large separation
distances, the basin boundary becomes a self-similar Cantor set, and we find
that the box-counting dimension decays slowly with the separation distance,
following a logarithmic decay law.
| [
{
"created": "Mon, 25 Oct 1999 19:05:55 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"de Moura",
"Alessandro P. S.",
""
],
[
"Letelier",
"Patricio S.",
""
]
] | We study the motion of light in the gravitational field of two Schwarzschild black holes, making the approximation that they are far apart, so that the motion of light rays in the neighborhood of one black hole can be considered to be the result of the action of each black hole separately. Using this approximation, the dynamics is reduced to a 2-dimensional map, which we study both numerically and analytically. The map is found to be chaotic, with a fractal basin boundary separating the possible outcomes of the orbits (escape or falling into one of the black holes). In the limit of large separation distances, the basin boundary becomes a self-similar Cantor set, and we find that the box-counting dimension decays slowly with the separation distance, following a logarithmic decay law. |
1505.01263 | Jibitesh Dutta | Jibitesh Dutta, Sourav Haldar and Subenoy Chakraborty | Formation Of Emergent Universe in Brane Scenario as a Consequence of
Particle Creation | 13 pages and 2 figures. Communicated to GRG | null | 10.1007/s10509-015-2607-x | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Here we formulate scenario of emergent universe from particle creation
mechanism in spatially flat braneworld models. We consider an isotropic and
homogeneous universe in Braneworld cosmology and universe is considered as a
non-equilibrium thermodynamical system with dissipation due to particle
creation mechanism. Assuming the particle creation rate as a function of the
Hubble parameter , we formulate emergent scenario in RS2 and DGP models of
Braneworld.
| [
{
"created": "Wed, 6 May 2015 07:16:10 GMT",
"version": "v1"
},
{
"created": "Thu, 7 May 2015 05:38:10 GMT",
"version": "v2"
}
] | 2016-01-20 | [
[
"Dutta",
"Jibitesh",
""
],
[
"Haldar",
"Sourav",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | Here we formulate scenario of emergent universe from particle creation mechanism in spatially flat braneworld models. We consider an isotropic and homogeneous universe in Braneworld cosmology and universe is considered as a non-equilibrium thermodynamical system with dissipation due to particle creation mechanism. Assuming the particle creation rate as a function of the Hubble parameter , we formulate emergent scenario in RS2 and DGP models of Braneworld. |
gr-qc/0110056 | G. Papini | G. Papini | Quantum systems in weak gravitational fields | 22 pages. To be published in Proceedings of the 17th Course of the
International School of Cosmology and Gravitation "Advances in the interplay
between quantum and gravity physics" edited by V. De Sabbata and A.
Zheltukhin, Kluwer Academic Publishers, Dordrecht | null | null | null | gr-qc astro-ph | null | Fully covariant wave equations predict the existence of a class of
inertial-gravitational effects that can be tested experimentally. In these
equations inertia and gravity appear as external classical fields, but, by
conforming to general relativity, provide very valuable information on how
Einstein's views carry through in the world of the quantum.
| [
{
"created": "Thu, 11 Oct 2001 01:33:56 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Papini",
"G.",
""
]
] | Fully covariant wave equations predict the existence of a class of inertial-gravitational effects that can be tested experimentally. In these equations inertia and gravity appear as external classical fields, but, by conforming to general relativity, provide very valuable information on how Einstein's views carry through in the world of the quantum. |
2110.02368 | Andrea Giusti | Valerio Faraoni, Andrea Giusti, Andrea Mentrelli | A new approach to the thermodynamics of scalar-tensor gravity | 23 pages, no figures, to appear in Phys.Rev.D | null | 10.1103/PhysRevD.104.124031 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss and expand a new approach to the thermodynamics of scalar-tensor
gravity and its diffusion toward general relativity (seen as an equilibrium
state) proposed in a previous Letter [Phys. Rev. D 103, L121501 (2021)], upon
which we build. We describe scalar-tensor gravity as an effective dissipative
fluid and apply Eckart's first order thermodynamics to it, obtaining explicitly
effective quantities such as heat flux, "temperature of gravity", viscosities,
entropy density, plus an equation describing the "diffusion" to Einstein
gravity. These quantities, still missing in the usual thermodynamics of
spacetime, are obtained with minimal assumptions. Furthermore, we examine
certain exact solutions of scalar-tensor gravity to test the proposed formalism
and gain some physical insight on the "approach to equilibrium" for this class
of theories.
| [
{
"created": "Tue, 5 Oct 2021 21:39:03 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Nov 2021 12:47:08 GMT",
"version": "v2"
}
] | 2022-01-05 | [
[
"Faraoni",
"Valerio",
""
],
[
"Giusti",
"Andrea",
""
],
[
"Mentrelli",
"Andrea",
""
]
] | We discuss and expand a new approach to the thermodynamics of scalar-tensor gravity and its diffusion toward general relativity (seen as an equilibrium state) proposed in a previous Letter [Phys. Rev. D 103, L121501 (2021)], upon which we build. We describe scalar-tensor gravity as an effective dissipative fluid and apply Eckart's first order thermodynamics to it, obtaining explicitly effective quantities such as heat flux, "temperature of gravity", viscosities, entropy density, plus an equation describing the "diffusion" to Einstein gravity. These quantities, still missing in the usual thermodynamics of spacetime, are obtained with minimal assumptions. Furthermore, we examine certain exact solutions of scalar-tensor gravity to test the proposed formalism and gain some physical insight on the "approach to equilibrium" for this class of theories. |
2109.01244 | Cetin Senturk | Metin Gurses, Yaghoub Heydarzade, Cetin Senturk | Kerr-Schild-Kundt Metrics in Generic Gravity Theories with Modified
Horndeski Couplings | 14 pages, no figures | null | 10.1140/epjc/s10052-021-09947-3 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Kerr-Schild-Kundt (KSK) metrics are known to be one of the universal
metrics in general relativity, which means that they solve the vacuum field
equations of any gravity theory constructed from the curvature tensor and its
higher-order covariant derivatives. There is yet no complete proof that these
metrics are universal in the presence of matter fields such as electromagnetic
and/or scalar fields. In order to get some insight into what happens when we
extend the "universality theorem" to the case in which the electromagnetic
field is present, as a first step, we study the KSK class of metrics in the
context of Modified Horndeski theories with Maxwell's field. We obtain exact
solutions of these theories representing the $pp$-waves and AdS-plane waves in
arbitrary $D$ dimensions.
| [
{
"created": "Thu, 2 Sep 2021 23:13:04 GMT",
"version": "v1"
}
] | 2022-01-19 | [
[
"Gurses",
"Metin",
""
],
[
"Heydarzade",
"Yaghoub",
""
],
[
"Senturk",
"Cetin",
""
]
] | The Kerr-Schild-Kundt (KSK) metrics are known to be one of the universal metrics in general relativity, which means that they solve the vacuum field equations of any gravity theory constructed from the curvature tensor and its higher-order covariant derivatives. There is yet no complete proof that these metrics are universal in the presence of matter fields such as electromagnetic and/or scalar fields. In order to get some insight into what happens when we extend the "universality theorem" to the case in which the electromagnetic field is present, as a first step, we study the KSK class of metrics in the context of Modified Horndeski theories with Maxwell's field. We obtain exact solutions of these theories representing the $pp$-waves and AdS-plane waves in arbitrary $D$ dimensions. |
1401.1370 | Luca Lusanna | L.Lusanna and M.Villani | Hamiltonian Expression of Curvature Tensors in the York Canonical Basis:
I) The Riemann Tensor and Ricci Scalars | 39 pages. arXiv admin note: text overlap with arXiv:0907.4087 | null | null | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By using the York canonical basis of ADM tetrad gravity, in a formulation
using radar 4-coordinates for the parametrization of the 3+1 splitting of the
space-time, it is possible to write the 4-Riemann tensor of a globally
hyperbolic, asymptotically Minkowskian space-time as a Hamiltonian tensor,
whose components are 4-scalars with respect to the ordinary world
4-coordinates, plus terms vanishing due to Einstein's equations. Therefore
"on-shell" we find the expression of the Hamiltonian 4-Riemann tensor.
Moreover, the 3+1 splitting of the space-time used to define the phase space
allows us to introduce a Hamiltonian set of null tetrads and to find the
Hamiltonian expression of the 4-Ricci scalars of the Newman-Penrose formalism.
This material will be used in the second paper to study the 4-Weyl tensor,
the 4-Weyl scalars and the four Weyl eigenvalues and to clarify the notions of
Dirac and Bergmann observables.
| [
{
"created": "Tue, 7 Jan 2014 13:38:42 GMT",
"version": "v1"
}
] | 2014-01-08 | [
[
"Lusanna",
"L.",
""
],
[
"Villani",
"M.",
""
]
] | By using the York canonical basis of ADM tetrad gravity, in a formulation using radar 4-coordinates for the parametrization of the 3+1 splitting of the space-time, it is possible to write the 4-Riemann tensor of a globally hyperbolic, asymptotically Minkowskian space-time as a Hamiltonian tensor, whose components are 4-scalars with respect to the ordinary world 4-coordinates, plus terms vanishing due to Einstein's equations. Therefore "on-shell" we find the expression of the Hamiltonian 4-Riemann tensor. Moreover, the 3+1 splitting of the space-time used to define the phase space allows us to introduce a Hamiltonian set of null tetrads and to find the Hamiltonian expression of the 4-Ricci scalars of the Newman-Penrose formalism. This material will be used in the second paper to study the 4-Weyl tensor, the 4-Weyl scalars and the four Weyl eigenvalues and to clarify the notions of Dirac and Bergmann observables. |
2012.05338 | Kofinas Georgios | Alfio Bonanno, Georgios Kofinas, Vasilios Zarikas | Effective field equations and scale-dependent couplings in gravity | 21 pages, 12 figures, to appear in PRD | Phys. Rev. D 103, 104025 (2021) | 10.1103/PhysRevD.103.104025 | null | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | A new set of field equations for a space-time dependent Newton's constant
$G(x)$ and cosmological constant $\Lambda(x)$ in the presence of matter is
presented. We prove that it represents the most general mathematically
consistent, physically plausible, set of evolution equations assuming at most
second derivatives in the dynamical variables. In the new Einstein's equations,
only $\Lambda$-kinetic terms arise, while in the modified conservation
equation, derivative terms of $G$ also appear. As an application, this
formalism is applied in the context of the Asymptotic Safety scenario to the
early universe, assuming a perfect fluid with a radiation equation of state.
Cosmological solutions are obtained for all types of spatial curvature,
displaying a variety of interesting cosmic evolutions. As an indication of such
behaviours, bouncing solutions, recollapsing solutions or non-singular
expanding solutions with a transient acceleration era are discussed in details.
| [
{
"created": "Wed, 9 Dec 2020 21:57:42 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Apr 2021 19:24:13 GMT",
"version": "v2"
}
] | 2021-05-19 | [
[
"Bonanno",
"Alfio",
""
],
[
"Kofinas",
"Georgios",
""
],
[
"Zarikas",
"Vasilios",
""
]
] | A new set of field equations for a space-time dependent Newton's constant $G(x)$ and cosmological constant $\Lambda(x)$ in the presence of matter is presented. We prove that it represents the most general mathematically consistent, physically plausible, set of evolution equations assuming at most second derivatives in the dynamical variables. In the new Einstein's equations, only $\Lambda$-kinetic terms arise, while in the modified conservation equation, derivative terms of $G$ also appear. As an application, this formalism is applied in the context of the Asymptotic Safety scenario to the early universe, assuming a perfect fluid with a radiation equation of state. Cosmological solutions are obtained for all types of spatial curvature, displaying a variety of interesting cosmic evolutions. As an indication of such behaviours, bouncing solutions, recollapsing solutions or non-singular expanding solutions with a transient acceleration era are discussed in details. |
2109.14571 | Alan Knee | Alan M. Knee, Jess McIver, Miriam Cabero | Prospects for measuring off-axis spins of binary black holes with
Plus-era gravitational-wave detectors | 23 pages, 27 figures. Updated to match version published in ApJ | Astroph. J. 928 (2022) 21 | 10.3847/1538-4357/ac48f5 | null | gr-qc astro-ph.HE | http://creativecommons.org/licenses/by/4.0/ | The mass and spin properties of binary black holes (BBHs) inferred from their
gravitational-wave signatures reveal important clues about how these systems
form. BBHs originating from isolated binary evolution are expected to have
spins preferentially aligned with their orbital angular momentum, whereas there
is no such preference in binaries formed via dynamical assembly. The fidelity
with which near-future gravitational-wave detectors can measure off-axis spins
will have implications for the study of BBH formation channels. In this work,
we examine the degree to which the Advanced LIGO Plus (A+) and Advanced Virgo
Plus (AdV+) interferometric detectors can measure both aligned and misaligned
spins. We compare spin resolution between the LIGO-Virgo network operating at
either A+/AdV+ ("Plus") sensitivity or Advanced-era design ("Design")
sensitivity using simulated BBH gravitational-wave signals injected into
synthetic detector noise. The signals are distributed over the mass-spin
parameter space of likely BBH systems, accounting for the effects of precession
and higher-order modes. We find that the Plus upgrades yield significant
improvements in spin estimation for systems with unequal masses and moderate or
large spins. Using simulated signals modelled after different types of
hierarchical BBH mergers, we also conclude that the Plus detector network will
yield substantially improved spin estimates for 1G+2G binaries compared to the
Design network.
| [
{
"created": "Wed, 29 Sep 2021 17:10:29 GMT",
"version": "v1"
},
{
"created": "Wed, 23 Mar 2022 19:02:43 GMT",
"version": "v2"
}
] | 2022-03-25 | [
[
"Knee",
"Alan M.",
""
],
[
"McIver",
"Jess",
""
],
[
"Cabero",
"Miriam",
""
]
] | The mass and spin properties of binary black holes (BBHs) inferred from their gravitational-wave signatures reveal important clues about how these systems form. BBHs originating from isolated binary evolution are expected to have spins preferentially aligned with their orbital angular momentum, whereas there is no such preference in binaries formed via dynamical assembly. The fidelity with which near-future gravitational-wave detectors can measure off-axis spins will have implications for the study of BBH formation channels. In this work, we examine the degree to which the Advanced LIGO Plus (A+) and Advanced Virgo Plus (AdV+) interferometric detectors can measure both aligned and misaligned spins. We compare spin resolution between the LIGO-Virgo network operating at either A+/AdV+ ("Plus") sensitivity or Advanced-era design ("Design") sensitivity using simulated BBH gravitational-wave signals injected into synthetic detector noise. The signals are distributed over the mass-spin parameter space of likely BBH systems, accounting for the effects of precession and higher-order modes. We find that the Plus upgrades yield significant improvements in spin estimation for systems with unequal masses and moderate or large spins. Using simulated signals modelled after different types of hierarchical BBH mergers, we also conclude that the Plus detector network will yield substantially improved spin estimates for 1G+2G binaries compared to the Design network. |
2010.06739 | Marcus Khuri | Gregory J. Galloway, Marcus A. Khuri, Eric Woolgar | The Topology of General Cosmological Models | 12 pages; final version | null | null | null | gr-qc astro-ph.CO math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Is the universe finite or infinite, and what shape does it have? These
fundamental questions, of which relatively little is known, are typically
studied within the context of the standard model of cosmology where the
universe is assumed to be homogeneous and isotropic. Here we address the above
questions in highly general cosmological models, with the only assumption being
that the average flow of matter is irrotational. Using techniques from
differential geometry, specifically extensions of the Bonnet-Myers theorem, we
derive a condition which implies a finite universe and yields a bound for its
diameter. Furthermore, under a weaker condition involving the interplay between
curvature and diameter, together with the assumption that the universe is
finite (i.e., has closed spatial slices), we provide a concise list of possible
topologies. Namely, the spatial sections then would be either the ring
topologies $S^1 \times S^2$, $S^1\tilde{\times}S^2$, $S^1\times\mathbb{RP}^2$,
$\mathbb{RP}^3 \# \mathbb{RP}^3$, or covered by the sphere $S^3$ or torus
$T^3$. In particular, under this condition the basic construction of connected
sums would be ruled out (save for one), along with the plethora of topologies
associated with negative curvature. These results are obtained from
consequences of the geometrization of 3-manifolds, by applying a generalization
of the almost splitting theorem together with a curvature formula of Ehlers and
Ellis.
| [
{
"created": "Tue, 13 Oct 2020 23:39:19 GMT",
"version": "v1"
},
{
"created": "Fri, 9 Apr 2021 06:20:06 GMT",
"version": "v2"
},
{
"created": "Tue, 8 Mar 2022 07:30:03 GMT",
"version": "v3"
},
{
"created": "Wed, 1 Jun 2022 05:11:41 GMT",
"version": "v4"
}
] | 2022-06-02 | [
[
"Galloway",
"Gregory J.",
""
],
[
"Khuri",
"Marcus A.",
""
],
[
"Woolgar",
"Eric",
""
]
] | Is the universe finite or infinite, and what shape does it have? These fundamental questions, of which relatively little is known, are typically studied within the context of the standard model of cosmology where the universe is assumed to be homogeneous and isotropic. Here we address the above questions in highly general cosmological models, with the only assumption being that the average flow of matter is irrotational. Using techniques from differential geometry, specifically extensions of the Bonnet-Myers theorem, we derive a condition which implies a finite universe and yields a bound for its diameter. Furthermore, under a weaker condition involving the interplay between curvature and diameter, together with the assumption that the universe is finite (i.e., has closed spatial slices), we provide a concise list of possible topologies. Namely, the spatial sections then would be either the ring topologies $S^1 \times S^2$, $S^1\tilde{\times}S^2$, $S^1\times\mathbb{RP}^2$, $\mathbb{RP}^3 \# \mathbb{RP}^3$, or covered by the sphere $S^3$ or torus $T^3$. In particular, under this condition the basic construction of connected sums would be ruled out (save for one), along with the plethora of topologies associated with negative curvature. These results are obtained from consequences of the geometrization of 3-manifolds, by applying a generalization of the almost splitting theorem together with a curvature formula of Ehlers and Ellis. |
1404.7492 | Freddy Zen Permana | Agus Suroso and Freddy P. Zen | Cosmological Model with Nonminimal Derivative Coupling of Scalar Fields
in Five Dimensions | 11 pages, no figure | General Relativity and Gravitation, 2013, vol. 45, Issue 4, pp
799-809 | 10.1007/s10714-013-1500-6 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a nonminimal derivative coupling (NMDC) of scalar field, where the
scalar field is coupled to curvature tensor in the five dimensional universal
extra dimension model. We apply the Einstein equation and find its solution.
First, we consider a special case of pure free scalar field without NMDC and we
find that for static extradimension, the solution is equivalent to the standard
cosmology with stiff matter. For a general case of pure free scalar field with
NMDC, we find that the de Sitter solution is the solution of our model. For
this solution, the scalar field evolves linearly in time. In the limit of small
Hubble parameter, the general case give us the same solution as in the pure
free scalar field. Finally, we perform a dynamical analysis to determine the
stability of our model. We find that the extradimension, if it exist, can not
be static and always shrinks with the expansion of four dimensional spacetime.
| [
{
"created": "Tue, 29 Apr 2014 13:04:16 GMT",
"version": "v1"
}
] | 2014-05-01 | [
[
"Suroso",
"Agus",
""
],
[
"Zen",
"Freddy P.",
""
]
] | We study a nonminimal derivative coupling (NMDC) of scalar field, where the scalar field is coupled to curvature tensor in the five dimensional universal extra dimension model. We apply the Einstein equation and find its solution. First, we consider a special case of pure free scalar field without NMDC and we find that for static extradimension, the solution is equivalent to the standard cosmology with stiff matter. For a general case of pure free scalar field with NMDC, we find that the de Sitter solution is the solution of our model. For this solution, the scalar field evolves linearly in time. In the limit of small Hubble parameter, the general case give us the same solution as in the pure free scalar field. Finally, we perform a dynamical analysis to determine the stability of our model. We find that the extradimension, if it exist, can not be static and always shrinks with the expansion of four dimensional spacetime. |
gr-qc/9503050 | Slava Mukhanov | Nathalie Deruelle and V.F. Mukhanov | On matching conditions for cosmological perturbations | 20 pages, latex (revtex), no figures | Phys.Rev.D52:5549-5555,1995 | 10.1103/PhysRevD.52.5549 | null | gr-qc hep-th | null | We derive the matching conditions for cosmological perturbations in a
Friedmann Universe where the equation of state undergoes a sharp jump, for
instance as a result of a phase transition. The physics of the transition which
is needed to follow the fate of the perturbations is clarified. We dissipate
misleading statements made recently in the literature concerning the
predictions of the primordial fluctuations from inflation and confirm standard
results. Applications to string cosmology are considered.
| [
{
"created": "Mon, 27 Mar 1995 10:17:23 GMT",
"version": "v1"
}
] | 2009-07-09 | [
[
"Deruelle",
"Nathalie",
""
],
[
"Mukhanov",
"V. F.",
""
]
] | We derive the matching conditions for cosmological perturbations in a Friedmann Universe where the equation of state undergoes a sharp jump, for instance as a result of a phase transition. The physics of the transition which is needed to follow the fate of the perturbations is clarified. We dissipate misleading statements made recently in the literature concerning the predictions of the primordial fluctuations from inflation and confirm standard results. Applications to string cosmology are considered. |
2208.14667 | Igor Bogush M.Sc. | Igor Bogush, Dmitri Gal'tsov | Supergravity $p$-branes with scalar charge | 29 pages, revtex4 | null | 10.1103/PhysRevD.106.084054 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Standard dilatonic supergravity $p$-branes have scalar charges that are not
independent parameters, but are determined by the brane tension and Page
charges. This feature can be traced to the no-hair theorem in the
four-dimensional Einstein-scalar gravity, implying that more general solutions
with independent scalar charges can have naked singularities. Since singular
branes are also of interest as tentative classical counterparts of unstable
tachyonic branes and/or brane-antibrane systems, it is worth investigating
branes with independent scalar charges in more detail. Here we study singular
branes associated with the Fisher-Janis-Newman-Winicour solution of
four-dimensional gravity. In the case of codimension three, we also construct
singular branes endowed with a Zipoy-Voorhees-type oblateness parameter. It is
expected that such branes will not be supersymmetric in the string theory. We
demonstrate this in the special case of NS5-branes of type II theory. We
analyze geodesics and test scalar perturbations of new solutions focusing on
possible quantum healing of classical singularities.
| [
{
"created": "Wed, 31 Aug 2022 07:50:25 GMT",
"version": "v1"
}
] | 2022-11-09 | [
[
"Bogush",
"Igor",
""
],
[
"Gal'tsov",
"Dmitri",
""
]
] | Standard dilatonic supergravity $p$-branes have scalar charges that are not independent parameters, but are determined by the brane tension and Page charges. This feature can be traced to the no-hair theorem in the four-dimensional Einstein-scalar gravity, implying that more general solutions with independent scalar charges can have naked singularities. Since singular branes are also of interest as tentative classical counterparts of unstable tachyonic branes and/or brane-antibrane systems, it is worth investigating branes with independent scalar charges in more detail. Here we study singular branes associated with the Fisher-Janis-Newman-Winicour solution of four-dimensional gravity. In the case of codimension three, we also construct singular branes endowed with a Zipoy-Voorhees-type oblateness parameter. It is expected that such branes will not be supersymmetric in the string theory. We demonstrate this in the special case of NS5-branes of type II theory. We analyze geodesics and test scalar perturbations of new solutions focusing on possible quantum healing of classical singularities. |
1912.12670 | Alexander B. Balakin | Alexander B. Balakin and Dmitry E. Groshev | New application of the Killing vector field formalism: Modified periodic
potential and two-level profiles of the axionic dark matter distribution | 12 pages, 5 figures, replaced with revised version published in EPJC | Eur. Phys. J. C (2020) 80:145 | 10.1140/epjc/s10052-020-7717-0 | null | gr-qc astro-ph.GA hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the structure of halos of the axionic dark matter, which surround
massive relativistic objects with static spherically symmetric gravitational
field and monopole-type magneto-electric fields. We work with the model of
pseudoscalar field with the extended periodic potential, which depends on
additional arguments proportional to the moduli of the Killing vectors; in our
approach they play the roles of model guiding functions. The covariant model of
the axion field with this modified potential is equipped with the extended
formalism of the Killing vector fields, which is established in analogy with
the formalism of the Einstein-aether theory, based on the introduction of a
unit timelike dynamic vector field. We study the equilibrium state of the axion
field, for which the extended potential and its derivative vanish, and
illustrate the established formalism by the analysis of two-level axionic dark
matter profiles, for which the stage delimiters relate to the critical values
of the modulus of the timelike Killing vector field.
| [
{
"created": "Sun, 29 Dec 2019 15:17:10 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Feb 2020 20:17:31 GMT",
"version": "v2"
}
] | 2020-02-24 | [
[
"Balakin",
"Alexander B.",
""
],
[
"Groshev",
"Dmitry E.",
""
]
] | We consider the structure of halos of the axionic dark matter, which surround massive relativistic objects with static spherically symmetric gravitational field and monopole-type magneto-electric fields. We work with the model of pseudoscalar field with the extended periodic potential, which depends on additional arguments proportional to the moduli of the Killing vectors; in our approach they play the roles of model guiding functions. The covariant model of the axion field with this modified potential is equipped with the extended formalism of the Killing vector fields, which is established in analogy with the formalism of the Einstein-aether theory, based on the introduction of a unit timelike dynamic vector field. We study the equilibrium state of the axion field, for which the extended potential and its derivative vanish, and illustrate the established formalism by the analysis of two-level axionic dark matter profiles, for which the stage delimiters relate to the critical values of the modulus of the timelike Killing vector field. |
gr-qc/0603069 | Robert T. Jantzen | Robert T. Jantzen, and James W. York, Jr | New Minimal Distortion Shift Gauge | 5 page ReVTeX4 twocolumn latex file, no figures; slight revision:
last sentence of section 2 deleted and replaced, citations reordered,
additonal paragraph added to introduction with short explanation of the
initial value problem and its thin sandwich variation, Yvonne Choquet-Bruhat
reference added and acknowledgment expanded to include her | Phys.Rev. D73 (2006) 104008 | 10.1103/PhysRevD.73.104008 | null | gr-qc | null | Based on the recent understanding of the role of the densitized lapse
function in Einstein's equations and of the proper way to pose the thin
sandwich problem, a slight readjustment of the minimal distortion shift gauge
in the 3+1 approach to the dynamics of general relativity allows this shift
vector to serve as the vector potential for the longitudinal part of the
extrinsic curvature tensor in the new approach to the initial value problem,
thus extending the initial value decomposition of gravitational variables to
play a role in the evolution as well. The new shift vector globally minimizes
the changes in the conformal 3-metric with respect to the spacetime measure
rather than the spatial measure on the time coordinate hypersurfaces, as the
old shift vector did.
| [
{
"created": "Thu, 16 Mar 2006 17:30:39 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Mar 2006 01:06:01 GMT",
"version": "v2"
},
{
"created": "Thu, 30 Mar 2006 00:09:59 GMT",
"version": "v3"
},
{
"created": "Thu, 6 Apr 2006 00:07:00 GMT",
"version": "v4"
}
] | 2012-08-27 | [
[
"Jantzen",
"Robert T.",
""
],
[
"York,",
"James W.",
"Jr"
]
] | Based on the recent understanding of the role of the densitized lapse function in Einstein's equations and of the proper way to pose the thin sandwich problem, a slight readjustment of the minimal distortion shift gauge in the 3+1 approach to the dynamics of general relativity allows this shift vector to serve as the vector potential for the longitudinal part of the extrinsic curvature tensor in the new approach to the initial value problem, thus extending the initial value decomposition of gravitational variables to play a role in the evolution as well. The new shift vector globally minimizes the changes in the conformal 3-metric with respect to the spacetime measure rather than the spatial measure on the time coordinate hypersurfaces, as the old shift vector did. |
2206.04076 | Sebastian Steinhaus | Masooma Ali and Sebastian Steinhaus | Toward matter dynamics in spin foam quantum gravity | 32 pages, 17 figures, v2: updated title, improved several parts, e.g.
discussion of results, added references. Matches version accepted for
publication in Phys. Rev. D | Phys. Rev. D 106, 106016 2022 | 10.1103/PhysRevD.106.106016 | null | gr-qc hep-lat hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Any approach to pure quantum gravity must eventually face the question of
coupling quantum matter to the theory. In the past, several ways of coupling
matter to spin foam quantum gravity have been proposed, but the dynamics of the
coupled matter-gravity system is challenging to explore. To take first steps
towards uncovering the influence quantum matter has on spin foam models, we
couple free, massive scalar lattice field theory to a restricted,
semi-classical 4d spin foam model, called quantum cuboids. This model can be
understood as a superposition of hypercuboidal (and thus irregular) lattices.
Both theories are coupled by defining scalar lattice field theory on irregular
lattices via discrete exterior calculus and then superimposing these theories
by summing over spin foam configurations. We compute expectation values of
geometric and matter observables using Markov Chain Monte Carlo techniques.
From the observables, we identify a regime in parameter space, in which the
spin foam possesses a finite total volume and looks on average like a regular
lattice with an emergent lattice spacing dependent on the mass of the scalar
field. We also measure the 2-point correlation function and correlation length
of the scalar field in relation to the geodesic distance encoded in the spin
foam. Our results are consistent with the correlation function of ordinary
scalar lattice field theory defined on a fixed regular lattice with the
emergent lattice spacing and the same mass. We conclude that in this regime of
the model, the scalar field is not sensitive to the fluctuations of the spin
foam and effectively behaves as if it is defined on a fixed regular lattice.
| [
{
"created": "Wed, 8 Jun 2022 18:00:02 GMT",
"version": "v1"
},
{
"created": "Fri, 4 Nov 2022 15:39:19 GMT",
"version": "v2"
}
] | 2022-11-30 | [
[
"Ali",
"Masooma",
""
],
[
"Steinhaus",
"Sebastian",
""
]
] | Any approach to pure quantum gravity must eventually face the question of coupling quantum matter to the theory. In the past, several ways of coupling matter to spin foam quantum gravity have been proposed, but the dynamics of the coupled matter-gravity system is challenging to explore. To take first steps towards uncovering the influence quantum matter has on spin foam models, we couple free, massive scalar lattice field theory to a restricted, semi-classical 4d spin foam model, called quantum cuboids. This model can be understood as a superposition of hypercuboidal (and thus irregular) lattices. Both theories are coupled by defining scalar lattice field theory on irregular lattices via discrete exterior calculus and then superimposing these theories by summing over spin foam configurations. We compute expectation values of geometric and matter observables using Markov Chain Monte Carlo techniques. From the observables, we identify a regime in parameter space, in which the spin foam possesses a finite total volume and looks on average like a regular lattice with an emergent lattice spacing dependent on the mass of the scalar field. We also measure the 2-point correlation function and correlation length of the scalar field in relation to the geodesic distance encoded in the spin foam. Our results are consistent with the correlation function of ordinary scalar lattice field theory defined on a fixed regular lattice with the emergent lattice spacing and the same mass. We conclude that in this regime of the model, the scalar field is not sensitive to the fluctuations of the spin foam and effectively behaves as if it is defined on a fixed regular lattice. |
0705.3619 | Dr. Anirudh Pradhan | Anirudh Pradhan, A. K. Yadav, R. P. Singh and V. K. Singh | A New Class of Inhomogeneous String Cosmological Models in General
Relativity | 12 pages, no figure. Submitted to Astrophys. Space Sci. arXiv admin
note: substantial text overlap with arXiv:0705.0904 | Astrophys.SpaceSci.312:145-150,2007 | 10.1007/s10509-007-9665-7 | null | gr-qc | null | A new class of solutions of Einstein field equations has been investigated
for inhomogeneous cylindrically symmetric space-time with string source. To get
the deterministic solution, it has been assumed that the expansion ($\theta$)
in the model is proportional to the eigen value $\sigma^{1}_{1}$ of the shear
tensor $\sigma^{i}_{j}$. Certain physical and geometric properties of the
models are also discussed.
| [
{
"created": "Thu, 24 May 2007 16:34:46 GMT",
"version": "v1"
}
] | 2014-05-06 | [
[
"Pradhan",
"Anirudh",
""
],
[
"Yadav",
"A. K.",
""
],
[
"Singh",
"R. P.",
""
],
[
"Singh",
"V. K.",
""
]
] | A new class of solutions of Einstein field equations has been investigated for inhomogeneous cylindrically symmetric space-time with string source. To get the deterministic solution, it has been assumed that the expansion ($\theta$) in the model is proportional to the eigen value $\sigma^{1}_{1}$ of the shear tensor $\sigma^{i}_{j}$. Certain physical and geometric properties of the models are also discussed. |
1811.09582 | John Klauder | John R. Klauder | Building a Genuine Quantum Gravity | 18 pages, minor corrections, offers an affine quantization of gravity
using general relativity | null | null | null | gr-qc hep-th math-ph math.MP quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | An affine quantization approach leads to a genuine quantum theory of general
relativity by extracting insights from a short list of increasingly more
complex, soluble, perturbably nonrenormalizable models.
| [
{
"created": "Tue, 20 Nov 2018 20:25:58 GMT",
"version": "v1"
},
{
"created": "Tue, 11 Dec 2018 21:45:06 GMT",
"version": "v2"
},
{
"created": "Wed, 6 Mar 2019 15:05:41 GMT",
"version": "v3"
}
] | 2019-03-27 | [
[
"Klauder",
"John R.",
""
]
] | An affine quantization approach leads to a genuine quantum theory of general relativity by extracting insights from a short list of increasingly more complex, soluble, perturbably nonrenormalizable models. |
1408.3978 | Gianluca Gemme | F. Acernese, M. Agathos, K. Agatsuma, D. Aisa, N. Allemandou, A.
Allocca, J. Amarni, P. Astone, G. Balestri, G. Ballardin, F. Barone, J.-P.
Baronick, M. Barsuglia, A. Basti, F. Basti, Th. S. Bauer, V. Bavigadda, M.
Bejger, M. G. Beker, C. Belczynski, D. Bersanetti, A. Bertolini, M. Bitossi,
M. A. Bizouard, S. Bloemen, M. Blom, M. Boer, G. Bogaert, D. Bondi, F. Bondu,
L. Bonelli, R. Bonnand, V. Boschi, L. Bosi, T. Bouedo, C. Bradaschia, M.
Branchesi, T. Briant, A. Brillet, V. Brisson, T. Bulik, H. J. Bulten, D.
Buskulic, C. Buy, G. Cagnoli, E. Calloni, C. Campeggi, B. Canuel, F.
Carbognani, F. Cavalier, R. Cavalieri, G. Cella, E. Cesarini, E.
Chassande-Mottin, A. Chincarini, A. Chiummo, S. Chua, F. Cleva, E. Coccia,
P.-F. Cohadon, A. Colla, M. Colombini, A. Conte, J.-P. Coulon, E. Cuoco, A.
Dalmaz, S. D'Antonio, V. Dattilo, M. Davier, R. Day, G. Debreczeni, J.
Degallaix, S. Del\'eglise, W. Del Pozzo, H. Dereli, R. De Rosa, L. Di Fiore,
A. Di Lieto, A. Di Virgilio, M. Doets, V. Dolique, M. Drago, M. Ducrot, G.
Endr\H{o}czi, V. Fafone, S. Farinon, I. Ferrante, F. Ferrini, F. Fidecaro, I.
Fiori, R. Flaminio, J.-D. Fournier, S. Franco, S. Frasca, F. Frasconi, L.
Gammaitoni, F. Garufi, M. Gaspard, A. Gatto, G. Gemme, B. Gendre, E. Genin,
A. Gennai, S. Ghosh, L. Giacobone, A. Giazotto, R. Gouaty, M. Granata, G.
Greco, P. Groot, G. M. Guidi, J. Harms, A. Heidmann, H. Heitmann, P. Hello,
G. Hemming, E. Hennes, D. Hofman, P. Jaranowski, R.J.G. Jonker, M. Kasprzack,
F. K\'ef\'elian, I. Kowalska, M. Kraan, A. Kr\'olak, A. Kutynia, C. Lazzaro,
M. Leonardi, N. Leroy, N. Letendre, T. G. F. Li, B. Lieunard, M. Lorenzini,
V. Loriette, G. Losurdo, C. Magazz\`u, E. Majorana, I. Maksimovic, V.
Malvezzi, N. Man, V. Mangano, M. Mantovani, F. Marchesoni, F. Marion, J.
Marque, F. Martelli, L. Martellini, A. Masserot, D. Meacher, J. Meidam, F.
Mezzani, C. Michel, L. Milano, Y. Minenkov, A. Moggi, M. Mohan, M. Montani,
N. Morgado, B. Mours, F. Mul, M. F. Nagy, I. Nardecchia, L. Naticchioni, G.
Nelemans, I. Neri, M. Neri, F. Nocera, E. Pacaud, C. Palomba, F. Paoletti, A.
Paoli, A. Pasqualetti, R. Passaquieti, D. Passuello, M. Perciballi, S. Petit,
M. Pichot, F. Piergiovanni, G. Pillant, A Piluso, L. Pinard, R. Poggiani, M.
Prijatelj, G. A. Prodi, M. Punturo, P. Puppo, D. S. Rabeling, I. R\'acz, P.
Rapagnani, M. Razzano, V. Re, T. Regimbau, F. Ricci, F. Robinet, A. Rocchi,
L. Rolland, R. Romano, D. Rosi\'nska, P. Ruggi, E. Saracco, B. Sassolas, F.
Schimmel, D. Sentenac, V. Sequino, S. Shah, K. Siellez, N. Straniero, B.
Swinkels, M. Tacca, M. Tonelli, F. Travasso, M. Turconi, G. Vajente, N. van
Bakel, M. van Beuzekom, J. F. J. van den Brand, C. Van Den Broeck, M. V. van
der Sluys, J. van Heijningen, M. Vas\'uth, G. Vedovato, J. Veitch, D.
Verkindt, F. Vetrano, A. Vicer\'e, J.-Y. Vinet, G. Visser, H. Vocca, R. Ward,
M. Was, L.-W. Wei, M. Yvert, A. Zadro\.zny, J.-P. Zendri, (Virgo
Collaboration) | Advanced Virgo: a 2nd generation interferometric gravitational wave
detector | Submitted to Classical and Quantum Gravity. 55 pages, 29 figures | Class. Quantum Grav. 32 (2015) 024001 | 10.1088/0264-9381/32/2/024001 | null | gr-qc physics.ins-det | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Advanced Virgo is the project to upgrade the Virgo interferometric detector
of gravitational waves, with the aim of increasing the number of observable
galaxies (and thus the detection rate) by three orders of magnitude. The
project is now in an advanced construction phase and the assembly and
integration will be completed by the end of 2015. Advanced Virgo will be part
of a network with the two Advanced LIGO detectors in the US and GEO HF in
Germany, with the goal of contributing to the early detections of gravitational
waves and to opening a new observation window on the universe. In this paper we
describe the main features of the Advanced Virgo detector and outline the
status of the construction.
| [
{
"created": "Mon, 18 Aug 2014 11:19:22 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Sep 2014 14:53:13 GMT",
"version": "v2"
},
{
"created": "Thu, 16 Oct 2014 13:24:29 GMT",
"version": "v3"
}
] | 2014-12-23 | [
[
"Acernese",
"F.",
""
],
[
"Agathos",
"M.",
""
],
[
"Agatsuma",
"K.",
""
],
[
"Aisa",
"D.",
""
],
[
"Allemandou",
"N.",
""
],
[
"Allocca",
"A.",
""
],
[
"Amarni",
"J.",
""
],
[
"Astone",
"P.",
... | Advanced Virgo is the project to upgrade the Virgo interferometric detector of gravitational waves, with the aim of increasing the number of observable galaxies (and thus the detection rate) by three orders of magnitude. The project is now in an advanced construction phase and the assembly and integration will be completed by the end of 2015. Advanced Virgo will be part of a network with the two Advanced LIGO detectors in the US and GEO HF in Germany, with the goal of contributing to the early detections of gravitational waves and to opening a new observation window on the universe. In this paper we describe the main features of the Advanced Virgo detector and outline the status of the construction. |
0911.0973 | Wolfgang Tichy | Wolfgang Tichy | Long term black hole evolution with the BSSN system by pseudospectral
methods | 10 pages, 15 figures. Corrected typos | Phys.Rev.D80:104034,2009 | 10.1103/PhysRevD.80.104034 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present long term evolutions of a single black hole of mass $M$ with the
BSSN system using pseudospectral methods. For our simulations we use the SGRID
code where the BSSN system is implemented in its standard second order in space
form. Previously we found that such simulations are quite unstable. The main
goal of this paper is to present two improvements which now allow us to evolve
for longer times. The first improvement is related to the boundary conditions
at the excised black hole interior. We now use a gauge condition that ensures
that all modes are going into the black hole, so that no boundary conditions
are needed at the excision surface. The second more significant improvement has
to do with our particular numerical method and involves filters based on
projecting the double Fourier expansions used for the angular dependence onto
Spherical Harmonics. With these two improvements it is now easily possible to
evolve for several thousand $M$. The only remaining limitation seems to be the
radiative outer boundary conditions used here. Yet this problem can be
ameliorated by pushing out the location of the outer boundary, which leads to
even longer run-times.
| [
{
"created": "Thu, 5 Nov 2009 04:50:49 GMT",
"version": "v1"
},
{
"created": "Tue, 24 Nov 2009 16:48:27 GMT",
"version": "v2"
}
] | 2010-05-25 | [
[
"Tichy",
"Wolfgang",
""
]
] | We present long term evolutions of a single black hole of mass $M$ with the BSSN system using pseudospectral methods. For our simulations we use the SGRID code where the BSSN system is implemented in its standard second order in space form. Previously we found that such simulations are quite unstable. The main goal of this paper is to present two improvements which now allow us to evolve for longer times. The first improvement is related to the boundary conditions at the excised black hole interior. We now use a gauge condition that ensures that all modes are going into the black hole, so that no boundary conditions are needed at the excision surface. The second more significant improvement has to do with our particular numerical method and involves filters based on projecting the double Fourier expansions used for the angular dependence onto Spherical Harmonics. With these two improvements it is now easily possible to evolve for several thousand $M$. The only remaining limitation seems to be the radiative outer boundary conditions used here. Yet this problem can be ameliorated by pushing out the location of the outer boundary, which leads to even longer run-times. |
2406.07943 | Pujian Mao | Pujian Mao and Baijun Zeng | Supertranslation ambiguity in post-Minkowskian expansion | v2: interpretations improved, refs. added | null | null | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The supertranslation ambiguity of angular momentum is a long-standing problem
in general relativity. In the context of post-Minkowskian expansion, the
supertranslation ambiguity arises the puzzle of the angular momentum loss to
start at ${\cal O}(G^2)$ or at ${\cal O}(G^3)$ in gravitational scattering. In
this paper, we propose a generic prescription to fix the supertranslation
ambiguity at the linear order in post-Minkowskian expansion which will uniquely
determine the angular momentum loss. The proposal is self-contained in the
post-Minkowskian expansion and involves only null infinity data.
| [
{
"created": "Wed, 12 Jun 2024 07:04:16 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Jun 2024 08:20:47 GMT",
"version": "v2"
}
] | 2024-06-24 | [
[
"Mao",
"Pujian",
""
],
[
"Zeng",
"Baijun",
""
]
] | The supertranslation ambiguity of angular momentum is a long-standing problem in general relativity. In the context of post-Minkowskian expansion, the supertranslation ambiguity arises the puzzle of the angular momentum loss to start at ${\cal O}(G^2)$ or at ${\cal O}(G^3)$ in gravitational scattering. In this paper, we propose a generic prescription to fix the supertranslation ambiguity at the linear order in post-Minkowskian expansion which will uniquely determine the angular momentum loss. The proposal is self-contained in the post-Minkowskian expansion and involves only null infinity data. |
gr-qc/9809044 | Robert C. Myers | R.C. Myers | Wavy Horizons? | 12 pages, Based on a talk at the 7th CCGRRA meeting (May 31 - June 7,
1997) | null | null | McGill/97-27 | gr-qc | null | We describe the application of a gravity wave-generating technique to certain
higher dimensional black holes. We find that the induced waves generically
destroy the event horizon producing parallelly propagated curvature
singularities.
| [
{
"created": "Mon, 14 Sep 1998 22:17:28 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Myers",
"R. C.",
""
]
] | We describe the application of a gravity wave-generating technique to certain higher dimensional black holes. We find that the induced waves generically destroy the event horizon producing parallelly propagated curvature singularities. |
2203.11628 | Marko Toros | Sougato Bose, Anupam Mazumdar, Martine Schut, Marko Toro\v{s} | Entanglement Witness for the Weak Equivalence Principle | 7 pages | Entropy 2023, 25(3), 448 | 10.3390/e25030448 | null | gr-qc hep-th quant-ph | http://creativecommons.org/licenses/by/4.0/ | The Einstein equivalence principle is based on the equality of gravitational
mass and inertial mass, which has led to the universality of a free-fall
concept. The principle has been extremely well tested so far and has been
tested with a great precision. However, all these tests and the corresponding
arguments are based on a classical setup where the notion of position and
velocity of the mass is associated with a classical value as opposed to the
quantum entities. Here, we will provide a simple protocol based on creating
large spatial superposition states in a laboratory to test the fully quantum
regime of the equivalence principle where both matter and gravity are treated
at par as a quantum entity. We will argue that such a quantum protocol is
unique with regard to testing especially the generalization of the weak
equivalence principle via witnessing quantum entanglement.
| [
{
"created": "Tue, 22 Mar 2022 11:29:56 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Mar 2023 11:32:35 GMT",
"version": "v2"
}
] | 2023-03-06 | [
[
"Bose",
"Sougato",
""
],
[
"Mazumdar",
"Anupam",
""
],
[
"Schut",
"Martine",
""
],
[
"Toroš",
"Marko",
""
]
] | The Einstein equivalence principle is based on the equality of gravitational mass and inertial mass, which has led to the universality of a free-fall concept. The principle has been extremely well tested so far and has been tested with a great precision. However, all these tests and the corresponding arguments are based on a classical setup where the notion of position and velocity of the mass is associated with a classical value as opposed to the quantum entities. Here, we will provide a simple protocol based on creating large spatial superposition states in a laboratory to test the fully quantum regime of the equivalence principle where both matter and gravity are treated at par as a quantum entity. We will argue that such a quantum protocol is unique with regard to testing especially the generalization of the weak equivalence principle via witnessing quantum entanglement. |
1605.07377 | Wonwoo Lee | Sunly Khimphun, Bum-Hoon Lee, Wonwoo Lee | Phase transition for black holes in dilatonic Einstein-Gauss-Bonnet
theory of gravitation | 24 pages, 8 figures, errors corrected, references added, version
published in PRD | Phys.Rev. D94 (2016) no.10, 104067 | 10.1103/PhysRevD.94.104067 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the thermodynamic properties of a black hole and the Hawking-Page
phase transition in the asymptotically anti--de Sitter spacetime in the
dilatonic Einstein-Gauss-Bonnet theory of gravitation. We show how the
higher-order curvature terms can influence both the thermodynamic properties
and the phase transition. We evaluate both heat capacity and free energy
difference to determine the local and global thermodynamic stabilities,
respectively. We find that the phase transition occurs from the thermal
anti--de Sitter to a small spherical black hole geometry and occurs to a
hyperbolic black hole geometry in the (dilatonic) Einstein-Gauss-Bonnet theory
of gravitation unlike those in Einstein's theory of gravitation.
| [
{
"created": "Tue, 24 May 2016 11:14:51 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Nov 2016 13:34:43 GMT",
"version": "v2"
}
] | 2016-11-30 | [
[
"Khimphun",
"Sunly",
""
],
[
"Lee",
"Bum-Hoon",
""
],
[
"Lee",
"Wonwoo",
""
]
] | We study the thermodynamic properties of a black hole and the Hawking-Page phase transition in the asymptotically anti--de Sitter spacetime in the dilatonic Einstein-Gauss-Bonnet theory of gravitation. We show how the higher-order curvature terms can influence both the thermodynamic properties and the phase transition. We evaluate both heat capacity and free energy difference to determine the local and global thermodynamic stabilities, respectively. We find that the phase transition occurs from the thermal anti--de Sitter to a small spherical black hole geometry and occurs to a hyperbolic black hole geometry in the (dilatonic) Einstein-Gauss-Bonnet theory of gravitation unlike those in Einstein's theory of gravitation. |
1209.4807 | Janusz Garecki Prof | Janusz Garecki | Canonical superenergy tensors in general relativity: a reappraisal | 6 pages, REVTEX 4, no figures, lecture delivered at the conference
"100 years after Einstein in Prague" | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Here we present our actual point of view on the canonical superenergy
tensors.
| [
{
"created": "Fri, 21 Sep 2012 12:56:12 GMT",
"version": "v1"
}
] | 2012-09-24 | [
[
"Garecki",
"Janusz",
""
]
] | Here we present our actual point of view on the canonical superenergy tensors. |
1611.07496 | Reyhan Kaya | H.T. \"Oz\c{c}elik, R. Kaya, M. Horta\c{c}su | Einstein gravity with torsion induced by the scalar field | 12 pages, 7 figures | Annals of Physics, 393:132-144 (2018) | 10.1016/j.aop.2018.04.012 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We couple a conformal scalar field in (2+1) dimensions to Einstein gravity
with torsion. The field equations are obtained by a variational principle. We
could not solve the Einstein and Cartan equations analytically. These equations
are solved numerically with 4th order Runge-Kutta method. From the numerical
solution, we make an ansatz for the rotation parameter in the proposed metric,
which gives an analytical solution for the scalar field for asymptotic regions.
| [
{
"created": "Tue, 22 Nov 2016 20:13:07 GMT",
"version": "v1"
},
{
"created": "Tue, 21 Mar 2017 09:17:20 GMT",
"version": "v2"
},
{
"created": "Fri, 25 May 2018 07:16:46 GMT",
"version": "v3"
}
] | 2018-06-06 | [
[
"Özçelik",
"H. T.",
""
],
[
"Kaya",
"R.",
""
],
[
"Hortaçsu",
"M.",
""
]
] | We couple a conformal scalar field in (2+1) dimensions to Einstein gravity with torsion. The field equations are obtained by a variational principle. We could not solve the Einstein and Cartan equations analytically. These equations are solved numerically with 4th order Runge-Kutta method. From the numerical solution, we make an ansatz for the rotation parameter in the proposed metric, which gives an analytical solution for the scalar field for asymptotic regions. |
2404.05028 | Luis A. Sanchez | Luis A. S\'anchez | Quantum gravity modifications to the accretion onto a Kerr black hole | 15 pages, 18 figures, 4 tables, typos corrected, references added,
matches published version | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the framework of the Asymptotic Safety scenario for quantum gravity, we
analyze quantum gravity modifications to the thermal characteristics of a thin
accretion disk spiraling around a renormalization group improved (RGI-) Kerr
black hole in the low energy regime. We focused on the quantum effects on the
location of the innermost stable circular orbit (ISCO), the energy flux from
the disk, the disk temperature, the observed redshifted luminosity, and the
accretion efficiency. The deviations from the classical general relativity due
to quantum effects are described for a free parameter that arises in the
improved Kerr metric as a consequence of the fact that the Newton constant
turns into a running coupling $G(r)$ depending on the energy scale. We find
that, both for rapid and slow rotating black holes with accretion disks in
prograde and retrograde circulation, increases in the value of this parameter
are accompanied by a decreasing of the ISCO, by a lifting of the peaks of the
radiation properties of the disk and by an increase of the accretion mass
efficiency, as compared with the predictions of general relativity. Our results
confirm previously established findings in Ref. \cite{r17} where we showed that
these quantum gravity effects also occur for an accretion disk around a
RGI-Schwarzschild black hole.
| [
{
"created": "Sun, 7 Apr 2024 17:47:02 GMT",
"version": "v1"
},
{
"created": "Fri, 28 Jun 2024 12:39:59 GMT",
"version": "v2"
}
] | 2024-07-01 | [
[
"Sánchez",
"Luis A.",
""
]
] | In the framework of the Asymptotic Safety scenario for quantum gravity, we analyze quantum gravity modifications to the thermal characteristics of a thin accretion disk spiraling around a renormalization group improved (RGI-) Kerr black hole in the low energy regime. We focused on the quantum effects on the location of the innermost stable circular orbit (ISCO), the energy flux from the disk, the disk temperature, the observed redshifted luminosity, and the accretion efficiency. The deviations from the classical general relativity due to quantum effects are described for a free parameter that arises in the improved Kerr metric as a consequence of the fact that the Newton constant turns into a running coupling $G(r)$ depending on the energy scale. We find that, both for rapid and slow rotating black holes with accretion disks in prograde and retrograde circulation, increases in the value of this parameter are accompanied by a decreasing of the ISCO, by a lifting of the peaks of the radiation properties of the disk and by an increase of the accretion mass efficiency, as compared with the predictions of general relativity. Our results confirm previously established findings in Ref. \cite{r17} where we showed that these quantum gravity effects also occur for an accretion disk around a RGI-Schwarzschild black hole. |
gr-qc/0504038 | Sean A. Hayward | Sean A. Hayward | The disinformation problem for black holes (pop version) | 6 revtex4 pages | null | null | null | gr-qc | null | The supposed information paradox for black holes is based on the fundamental
misunderstanding that black holes are usefully defined by event horizons.
Understood in terms of locally defined trapping horizons, the paradox
disappears: information will escape from an evaporating black hole. According
to classical properties of trapping horizons, a general scenario is outlined
whereby a black hole evaporates completely without singularity, event horizon
or loss of energy or information.
| [
{
"created": "Fri, 8 Apr 2005 18:22:52 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hayward",
"Sean A.",
""
]
] | The supposed information paradox for black holes is based on the fundamental misunderstanding that black holes are usefully defined by event horizons. Understood in terms of locally defined trapping horizons, the paradox disappears: information will escape from an evaporating black hole. According to classical properties of trapping horizons, a general scenario is outlined whereby a black hole evaporates completely without singularity, event horizon or loss of energy or information. |
2312.02760 | Maciej Maliborski | Filip Ficek and Maciej Maliborski | Dynamics of nonlinear scalar field with Robin boundary condition on the
Schwarzschild--Anti-de Sitter background | 31 pages, 26 figures | null | null | null | gr-qc hep-th math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work concerns the dynamics of conformal cubic scalar field on a
Schwarzschild--anti-de Sitter background. The main focus is on understanding
how it depends on the size of the black hole and the Robin boundary condition.
We identify a critical curve in the parameter space that separates regions with
distinct asymptotic behaviours. For defocusing nonlinearity, the global
attractor undergoes a pitchfork bifurcation, whereas for the focusing case, we
identify a region of the phase space where all solutions blow up in finite
time. In the course of this study we observe an interplay between black hole
geometry, boundary conditions, and the nonlinear dynamics of scalar fields in
asymptotically anti-de Sitter spacetime.
| [
{
"created": "Tue, 5 Dec 2023 13:40:18 GMT",
"version": "v1"
}
] | 2023-12-06 | [
[
"Ficek",
"Filip",
""
],
[
"Maliborski",
"Maciej",
""
]
] | This work concerns the dynamics of conformal cubic scalar field on a Schwarzschild--anti-de Sitter background. The main focus is on understanding how it depends on the size of the black hole and the Robin boundary condition. We identify a critical curve in the parameter space that separates regions with distinct asymptotic behaviours. For defocusing nonlinearity, the global attractor undergoes a pitchfork bifurcation, whereas for the focusing case, we identify a region of the phase space where all solutions blow up in finite time. In the course of this study we observe an interplay between black hole geometry, boundary conditions, and the nonlinear dynamics of scalar fields in asymptotically anti-de Sitter spacetime. |
gr-qc/0212018 | Emam | Gamal G.L. Nashed | General Spherically Symmetric Non Singular Black Hole Solutions in
Teleparallel Theory of Gravitation | null | Phys.Rev. D66 (2002) 064015 | 10.1103/PhysRevD.66.064015 | null | gr-qc | null | We find the most general spherically symmetric non singular black hole
solution in a special class of teleparallel theory of gravitation. If $r$ is
large enough, the general solution coincides with the Schwarzschild solution.
Whereas, if $r$ is small, the general solution behaves in a manner similar to
that of de Sitter solution. Otherwise it describes a spherically symmetric
black hole singularity free everywhere. Moreover, the energy associated with
the general solution is calculated using the superpotential given by M{\o}ller
1978.
| [
{
"created": "Wed, 4 Dec 2002 09:12:25 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Nashed",
"Gamal G. L.",
""
]
] | We find the most general spherically symmetric non singular black hole solution in a special class of teleparallel theory of gravitation. If $r$ is large enough, the general solution coincides with the Schwarzschild solution. Whereas, if $r$ is small, the general solution behaves in a manner similar to that of de Sitter solution. Otherwise it describes a spherically symmetric black hole singularity free everywhere. Moreover, the energy associated with the general solution is calculated using the superpotential given by M{\o}ller 1978. |
2303.09492 | Grigoris Panotopoulos | G. Panotopoulos, G. Barnert, L. E. Campusano | Correlation of structure growth index with current cosmic acceleration:
constraints on dark energy models | 13 pages, 3 figures, to be published in IJMPD | null | 10.1142/S0218271823500360 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study dynamical dark energy models within Einstein's theory by means of
matter perturbations and the growth index $\gamma$. Within four-dimensional
General Relativity, we assume that dark energy does not cluster, and we adopt a
linear ansatz for the growth index to investigate its impact on the
deceleration parameter, $q$, and on the dark energy equation-of-state
parameter, $w$. Following this approach, we identify a relationship between
$q_0$ (today's value of $q$) and $\gamma$, which to the best of our knowledge
is new. For $w(z)$, we find that in most of the cases considered it crosses the
-1 line (quintom) ending at a present day value $w_0 > -1$. Furthermore, we
show that an analytic expression for $w(z)$ may be obtained in the form of
order (4,4) (or higher) Pad{\'e} parameterizations.
| [
{
"created": "Thu, 16 Mar 2023 17:12:58 GMT",
"version": "v1"
}
] | 2023-06-07 | [
[
"Panotopoulos",
"G.",
""
],
[
"Barnert",
"G.",
""
],
[
"Campusano",
"L. E.",
""
]
] | We study dynamical dark energy models within Einstein's theory by means of matter perturbations and the growth index $\gamma$. Within four-dimensional General Relativity, we assume that dark energy does not cluster, and we adopt a linear ansatz for the growth index to investigate its impact on the deceleration parameter, $q$, and on the dark energy equation-of-state parameter, $w$. Following this approach, we identify a relationship between $q_0$ (today's value of $q$) and $\gamma$, which to the best of our knowledge is new. For $w(z)$, we find that in most of the cases considered it crosses the -1 line (quintom) ending at a present day value $w_0 > -1$. Furthermore, we show that an analytic expression for $w(z)$ may be obtained in the form of order (4,4) (or higher) Pad{\'e} parameterizations. |
1306.1835 | Paolo Pani | Paolo Pani, Thomas P. Sotiriou, Daniele Vernieri | Gravity with Auxiliary Fields | 5 pages, no figures; v2: clarifications and minor improvements,
matches published version | Phys. Rev. D 88, 121502 (2013) | 10.1103/PhysRevD.88.121502 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Modifications of General Relativity usually include extra dynamical degrees
of freedom, which to date remain undetected. Here we explore the possibility of
modifying Einstein's theory by adding solely nondynamical fields. With the
minimal requirement that the theory satisfies the weak equivalence principle
and admits a covariant Lagrangian formulation, we show that the field equations
generically have to include higher-order derivatives of the matter fields. This
has profound consequences for the viability of these theories. We develop a
parametrization based on a derivative expansion and show that - to next to
leading order - all theories are described by just two parameters. Our approach
can be used to put stringent, theory-independent constraints on such theories,
as we demonstrates using the Newtonian limit as an example.
| [
{
"created": "Fri, 7 Jun 2013 20:00:11 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Jan 2014 17:18:40 GMT",
"version": "v2"
}
] | 2014-01-07 | [
[
"Pani",
"Paolo",
""
],
[
"Sotiriou",
"Thomas P.",
""
],
[
"Vernieri",
"Daniele",
""
]
] | Modifications of General Relativity usually include extra dynamical degrees of freedom, which to date remain undetected. Here we explore the possibility of modifying Einstein's theory by adding solely nondynamical fields. With the minimal requirement that the theory satisfies the weak equivalence principle and admits a covariant Lagrangian formulation, we show that the field equations generically have to include higher-order derivatives of the matter fields. This has profound consequences for the viability of these theories. We develop a parametrization based on a derivative expansion and show that - to next to leading order - all theories are described by just two parameters. Our approach can be used to put stringent, theory-independent constraints on such theories, as we demonstrates using the Newtonian limit as an example. |
1112.4918 | Isabeau Pr\'emont-Schwarz | Isabeau Pr\'emont-Schwarz | Local tuning of Coupling Constants allows for Quantum Fields in Curved
Spacetime in the Lab | 11 pages | null | null | null | gr-qc cond-mat.mes-hall cond-mat.mtrl-sci | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we will investigate how one can create emergent curved
spacetimes by locally tuning the coupling constants of condensed matter
systems. In the continuum limit we thus obtain continuous effective quantum
fields living on curved spacetimes. In particular, using Stingnet condensates
we can obtain effective electromagnetism. We will show for example how we
obtain quantum electromagnetism (U(1)-Yang-Mills) in a black hole
(Schwarzschild) spacetime.
| [
{
"created": "Wed, 21 Dec 2011 03:28:55 GMT",
"version": "v1"
}
] | 2011-12-22 | [
[
"Prémont-Schwarz",
"Isabeau",
""
]
] | In this paper we will investigate how one can create emergent curved spacetimes by locally tuning the coupling constants of condensed matter systems. In the continuum limit we thus obtain continuous effective quantum fields living on curved spacetimes. In particular, using Stingnet condensates we can obtain effective electromagnetism. We will show for example how we obtain quantum electromagnetism (U(1)-Yang-Mills) in a black hole (Schwarzschild) spacetime. |
1412.6015 | Simone Speziale | Tommaso De Lorenzo, Costantino Pacilio, Carlo Rovelli and Simone
Speziale | On the Effective Metric of a Planck Star | 10 pages, many figures; v2 added references | General Relativity and Gravitation (2015), Volume 47 | 10.1007/s10714-015-1882-8 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Spacetime metrics describing `non-singular' black holes are commonly studied
in the literature as effective modification to the Schwarzschild solution that
mimic quantum gravity effects removing the central singularity. Here we point
out that to be physically plausible, such metrics should also incorporate the
1-loop quantum corrections to the Newton potential and a non-trivial time delay
between an observer at infinity and an observer in the regular center. We
present a modification of the well-known Hayward metric that features these two
properties. We discuss bounds on the maximal time delay imposed by conditions
on the curvature, and the consequences for the weak energy condition, in
general violated by the large transversal pressures introduced by the time
delay.
| [
{
"created": "Thu, 18 Dec 2014 19:23:02 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Mar 2015 23:09:26 GMT",
"version": "v2"
}
] | 2015-03-25 | [
[
"De Lorenzo",
"Tommaso",
""
],
[
"Pacilio",
"Costantino",
""
],
[
"Rovelli",
"Carlo",
""
],
[
"Speziale",
"Simone",
""
]
] | Spacetime metrics describing `non-singular' black holes are commonly studied in the literature as effective modification to the Schwarzschild solution that mimic quantum gravity effects removing the central singularity. Here we point out that to be physically plausible, such metrics should also incorporate the 1-loop quantum corrections to the Newton potential and a non-trivial time delay between an observer at infinity and an observer in the regular center. We present a modification of the well-known Hayward metric that features these two properties. We discuss bounds on the maximal time delay imposed by conditions on the curvature, and the consequences for the weak energy condition, in general violated by the large transversal pressures introduced by the time delay. |
gr-qc/0404080 | Masafumi Seriu | Masafumi Seriu | Dynamical Evolution of a Cylindrical Shell with Rotational Pressure | To appear in Phys. Rev. D | Phys.Rev. D69 (2004) 124030 | 10.1103/PhysRevD.69.124030 | null | gr-qc | null | We prepare a general framework for analyzing the dynamics of a cylindrical
shell in the spacetime with cylindrical symmetry. Based on the framework, we
investigate a particular model of a cylindrical shell-collapse with rotational
pressure, accompanying the radiation of gravitational waves and massless
particles. The model has been introduced previously but has been awaiting for
proper analysis. Here the analysis is put forward: It is proved that, as far as
the weak energy condition is satisfied outside the shell, the collapsing shell
bounces back at some point irrespective of the initial conditions, and escapes
from the singularity formation.
The behavior after the bounce depends on the sign of the shell pressure in
the z-direction. When the pressure is non-negative, the shell continues to
expand without re-contraction. On the other hand, when the pressure is negative
(i.e. it has a tension), the behavior after the bounce can be more complicated
depending on the details of the model. However, even in this case, the shell
never reaches the zero-radius configuration.
| [
{
"created": "Sat, 17 Apr 2004 14:26:02 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Seriu",
"Masafumi",
""
]
] | We prepare a general framework for analyzing the dynamics of a cylindrical shell in the spacetime with cylindrical symmetry. Based on the framework, we investigate a particular model of a cylindrical shell-collapse with rotational pressure, accompanying the radiation of gravitational waves and massless particles. The model has been introduced previously but has been awaiting for proper analysis. Here the analysis is put forward: It is proved that, as far as the weak energy condition is satisfied outside the shell, the collapsing shell bounces back at some point irrespective of the initial conditions, and escapes from the singularity formation. The behavior after the bounce depends on the sign of the shell pressure in the z-direction. When the pressure is non-negative, the shell continues to expand without re-contraction. On the other hand, when the pressure is negative (i.e. it has a tension), the behavior after the bounce can be more complicated depending on the details of the model. However, even in this case, the shell never reaches the zero-radius configuration. |
1301.2209 | Gonzalo Olmo | S. Capozziello, T. Harko, T. S. Koivisto, Francisco S. N. Lobo,
Gonzalo J. Olmo | Hybrid f(R) theories, local constraints, and cosmic speedup | 3 pages, no figures, proceedings of 13th Marcel Grossmann Meeting | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an extension of general relativity in which an $f(R)$ term \`{a}
la Palatini is added to the usual metric Einstein-Hilbert Lagrangian.
Expressing the theory in a dynamically equivalent scalar-tensor form, we show
that it can pass the Solar System observational tests even if the scalar field
is very light or massless. Applications to cosmology and astrophysics, and some
exact solutions are discussed.
| [
{
"created": "Thu, 10 Jan 2013 18:26:35 GMT",
"version": "v1"
}
] | 2013-01-11 | [
[
"Capozziello",
"S.",
""
],
[
"Harko",
"T.",
""
],
[
"Koivisto",
"T. S.",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Olmo",
"Gonzalo J.",
""
]
] | We present an extension of general relativity in which an $f(R)$ term \`{a} la Palatini is added to the usual metric Einstein-Hilbert Lagrangian. Expressing the theory in a dynamically equivalent scalar-tensor form, we show that it can pass the Solar System observational tests even if the scalar field is very light or massless. Applications to cosmology and astrophysics, and some exact solutions are discussed. |
2212.01404 | Mostafizur Rahman | Mostafizur Rahman, Shailesh Kumar and Arpan Bhattacharyya | Gravitational wave from extreme mass-ratio inspirals as a probe of extra
dimensions | 27 pages, 5 figures, 2 tables, typos corrected | JCAP 01 (2023) 046 | 10.1088/1475-7516/2023/01/046 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The field of gravitational waves is rapidly progressing due to the noticeable
advancements in the sensitivity of gravitational-wave detectors that has
enabled the detection prospects of binary black hole mergers. Extreme mass
ratio inspiral (EMRI) is one of the most compelling and captivating binary
systems in this direction, with the detection possibility by the future
space-based gravitational wave detector. In this article, we consider an EMRI
system where the primary or the central object is a spherically symmetric
static braneworld black hole that carries a \textit{tidal charge} $Q$. We
estimate the effect of the tidal charge on total gravitational wave flux and
orbital phase due to a non-spinning secondary inspiralling the primary. We
further highlight the observational implications of the tidal charge in EMRI
waveforms. We show that LISA (Laser Interferometer Space Antenna) observations
can put a much stronger constraint on this parameter than black hole shadow and
ground-based gravitational wave observations, which can potentially probe the
existence of extra dimensions.
| [
{
"created": "Fri, 2 Dec 2022 19:00:23 GMT",
"version": "v1"
},
{
"created": "Thu, 15 Dec 2022 14:55:04 GMT",
"version": "v2"
}
] | 2023-02-01 | [
[
"Rahman",
"Mostafizur",
""
],
[
"Kumar",
"Shailesh",
""
],
[
"Bhattacharyya",
"Arpan",
""
]
] | The field of gravitational waves is rapidly progressing due to the noticeable advancements in the sensitivity of gravitational-wave detectors that has enabled the detection prospects of binary black hole mergers. Extreme mass ratio inspiral (EMRI) is one of the most compelling and captivating binary systems in this direction, with the detection possibility by the future space-based gravitational wave detector. In this article, we consider an EMRI system where the primary or the central object is a spherically symmetric static braneworld black hole that carries a \textit{tidal charge} $Q$. We estimate the effect of the tidal charge on total gravitational wave flux and orbital phase due to a non-spinning secondary inspiralling the primary. We further highlight the observational implications of the tidal charge in EMRI waveforms. We show that LISA (Laser Interferometer Space Antenna) observations can put a much stronger constraint on this parameter than black hole shadow and ground-based gravitational wave observations, which can potentially probe the existence of extra dimensions. |
1912.06839 | Ion I. Cotaescu | Ion I. Cotaescu | Rest frame vacua of massive Klein-Gordon fields on spatially flat FLRW
spacetimes | 23 pages, 3 figures | null | 10.1140/epjc/s10052-020-8170-9 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose a method of projecting the quantum states from a state space of a
given geometry into another state space generated by a different geometry,
taking care on the correct normalization which is crucial in interpreting the
quantum theory. Thanks to this method we can define on any spatially flat FLRW
spacetime states in which genuine Minkowskian parameters are measured. We use
these Minkowskian states for separating the frequencies in the rest frames of
the massive scalar particles defining thus the scalar rest frame vacuum. We
show that this vacuum is stable on the de Sitter expanding universe where the
energy is conserved. In contrast, on a spatially flat FLRW spacetime with a
Milne-type scale factor this vacuum results to be dynamic, corresponding to a
time-dependent rest energy interpreted as an effective mass. This dynamic
vacuum give rise to a cosmological particle creation which is significant only
in the early Milne-type universe considered here. Some interesting features of
this new effect are pointed out in a brief analysis.
| [
{
"created": "Sat, 14 Dec 2019 13:12:23 GMT",
"version": "v1"
},
{
"created": "Mon, 23 Dec 2019 13:36:14 GMT",
"version": "v2"
},
{
"created": "Wed, 25 Dec 2019 10:02:11 GMT",
"version": "v3"
},
{
"created": "Sun, 26 Jan 2020 19:44:27 GMT",
"version": "v4"
},
{
"c... | 2020-08-26 | [
[
"Cotaescu",
"Ion I.",
""
]
] | We propose a method of projecting the quantum states from a state space of a given geometry into another state space generated by a different geometry, taking care on the correct normalization which is crucial in interpreting the quantum theory. Thanks to this method we can define on any spatially flat FLRW spacetime states in which genuine Minkowskian parameters are measured. We use these Minkowskian states for separating the frequencies in the rest frames of the massive scalar particles defining thus the scalar rest frame vacuum. We show that this vacuum is stable on the de Sitter expanding universe where the energy is conserved. In contrast, on a spatially flat FLRW spacetime with a Milne-type scale factor this vacuum results to be dynamic, corresponding to a time-dependent rest energy interpreted as an effective mass. This dynamic vacuum give rise to a cosmological particle creation which is significant only in the early Milne-type universe considered here. Some interesting features of this new effect are pointed out in a brief analysis. |
1805.09629 | Prado Martin-Moruno | Jose A. R. Cembranos, Mario Coma Diaz, Prado Martin-Moruno | Modified gravity as a diagravitational medium | V1: 5 pages. Comments welcome. V2: 4 references added. V3: additional
comments included, 4 references added. Version accepted for publication in
Physics Letters B | null | 10.1016/j.physletb.2018.10.068 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this letter we reflect on the propagation of gravitational waves in
alternative theories of gravity, which are typically formulated using extra
gravitational degrees of freedom in comparison to General Relativity. We
propose to understand that additional structure as forming a diagravitational
medium for gravitational waves characterized by a refractive index.
Furthermore, we shall argue that the most general diagravitational medium has
associated an anisotropic dispersion relation. In some situations a refractive
index tensor, which takes into account both the deflection of gravitational
waves due to the curvature of a non-flat spacetime and the modifications of the
general relativistic predictions, can be defined. The most general media,
however, entail the consideration of at least two independent tensors.
| [
{
"created": "Thu, 24 May 2018 12:19:50 GMT",
"version": "v1"
},
{
"created": "Mon, 28 May 2018 11:08:36 GMT",
"version": "v2"
},
{
"created": "Tue, 9 Oct 2018 11:26:15 GMT",
"version": "v3"
}
] | 2018-11-28 | [
[
"Cembranos",
"Jose A. R.",
""
],
[
"Diaz",
"Mario Coma",
""
],
[
"Martin-Moruno",
"Prado",
""
]
] | In this letter we reflect on the propagation of gravitational waves in alternative theories of gravity, which are typically formulated using extra gravitational degrees of freedom in comparison to General Relativity. We propose to understand that additional structure as forming a diagravitational medium for gravitational waves characterized by a refractive index. Furthermore, we shall argue that the most general diagravitational medium has associated an anisotropic dispersion relation. In some situations a refractive index tensor, which takes into account both the deflection of gravitational waves due to the curvature of a non-flat spacetime and the modifications of the general relativistic predictions, can be defined. The most general media, however, entail the consideration of at least two independent tensors. |
1707.00479 | Tommaso De Lorenzo | Tommaso De Lorenzo and Alejandro Perez | Light Cone Thermodynamics | 30 pages, 5 pictures; V_2: a problem in the proof of the first law
has been corrected. Results remain unchanged. Geometric interpretation and
presentation improved; V_3: matches published version | Phys. Rev. D 97, 044052 (2018) | 10.1103/PhysRevD.97.044052 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that null surfaces defined by the outgoing and infalling wave fronts
emanating from and arriving at a sphere in Minkowski spacetime have
thermodynamical properties that are in strict formal correspondence with those
of black hole horizons in curved spacetimes. Such null surfaces, made of pieces
of light cones, are bifurcate conformal Killing horizons for suitable
conformally stationary observers. They can be extremal and non-extremal
depending on the radius of the shining sphere. Such conformal Killing horizons
have a constant light cone (conformal) temperature, given by the standard
expression in terms of the generalisation of surface gravity for conformal
Killing horizons. Exchanges of conformally invariant energy across the horizon
are described by a first law where entropy changes are given by $1/(4\ell_p^2)$
of the changes of a geometric quantity with the meaning of horizon area in a
suitable conformal frame. These conformal horizons satisfy the zeroth to the
third laws of thermodynamics in an appropriate way. In the extremal case they
become light cones associated with a single event; these have vanishing
temperature as well as vanishing entropy.
| [
{
"created": "Mon, 3 Jul 2017 11:00:11 GMT",
"version": "v1"
},
{
"created": "Mon, 13 Nov 2017 14:23:58 GMT",
"version": "v2"
},
{
"created": "Thu, 1 Mar 2018 14:38:27 GMT",
"version": "v3"
}
] | 2018-03-07 | [
[
"De Lorenzo",
"Tommaso",
""
],
[
"Perez",
"Alejandro",
""
]
] | We show that null surfaces defined by the outgoing and infalling wave fronts emanating from and arriving at a sphere in Minkowski spacetime have thermodynamical properties that are in strict formal correspondence with those of black hole horizons in curved spacetimes. Such null surfaces, made of pieces of light cones, are bifurcate conformal Killing horizons for suitable conformally stationary observers. They can be extremal and non-extremal depending on the radius of the shining sphere. Such conformal Killing horizons have a constant light cone (conformal) temperature, given by the standard expression in terms of the generalisation of surface gravity for conformal Killing horizons. Exchanges of conformally invariant energy across the horizon are described by a first law where entropy changes are given by $1/(4\ell_p^2)$ of the changes of a geometric quantity with the meaning of horizon area in a suitable conformal frame. These conformal horizons satisfy the zeroth to the third laws of thermodynamics in an appropriate way. In the extremal case they become light cones associated with a single event; these have vanishing temperature as well as vanishing entropy. |
gr-qc/9511010 | Steve F. Rippl | Steve Rippl, Henk van Elst, Reza Tavakol and David Taylor | Kinematics and Dynamics of $f(R)$ Theories of Gravity | 13 pages, latex, to appear in GRG | Gen.Rel.Grav. 28 (1996) 193-205 | 10.1007/BF02105423 | null | gr-qc | null | We generalise the equations governing relativistic fluid dynamics given by
Ehlers and Ellis for general relativity, and by Maartens and Taylor for
quadratic theories, to generalised $f(R)$ theories of gravity. In view of the
usefulness of this alternative framework to general relativity, its
generalisation can be of potential importance for deriving analogous results to
those obtained in general relativity. We generalise, as an example, the results
of Maartens and Taylor to show that within the framework of general $f(R)$
theories, a perfect fluid spacetime with vanishing vorticity, shear and
acceleration is Friedmann--Lema\^{\i}tre--Robertson--Walker only if the fluid
has in addition a barotropic equation of state. It then follows that the
Ehlers--Geren--Sachs theorem and its ``almost'' extension also hold for $f(R)$
theories of gravity.
| [
{
"created": "Thu, 2 Nov 1995 14:23:51 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Rippl",
"Steve",
""
],
[
"van Elst",
"Henk",
""
],
[
"Tavakol",
"Reza",
""
],
[
"Taylor",
"David",
""
]
] | We generalise the equations governing relativistic fluid dynamics given by Ehlers and Ellis for general relativity, and by Maartens and Taylor for quadratic theories, to generalised $f(R)$ theories of gravity. In view of the usefulness of this alternative framework to general relativity, its generalisation can be of potential importance for deriving analogous results to those obtained in general relativity. We generalise, as an example, the results of Maartens and Taylor to show that within the framework of general $f(R)$ theories, a perfect fluid spacetime with vanishing vorticity, shear and acceleration is Friedmann--Lema\^{\i}tre--Robertson--Walker only if the fluid has in addition a barotropic equation of state. It then follows that the Ehlers--Geren--Sachs theorem and its ``almost'' extension also hold for $f(R)$ theories of gravity. |
1609.06185 | Hossein Mohseni Sadjadi | Parviz Goodarzi and H. Mohseni Sadjadi | Warm inflation with an oscillatory inflaton in the non-minimal kinetic
coupling model | 22 pages, typos fixed, accepted by EPJC | Eur.Phys.J. C 77 (2017) 463 | 10.1140/epjc/s10052-017-5028-x | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the cold inflation scenario, the slow roll inflation and reheating via
coherent rapid oscillation, are usually considered as two distinct eras. When
the slow roll ends, a rapid oscillation phase begins and the inflaton decays to
relativistic particles reheating the Universe. In another model dubbed warm
inflation, the rapid oscillation phase is suppressed, and we are left with only
a slow roll period during which the reheating occurs. Instead, in this paper,
we propose a new picture for inflation in which the slow roll era is suppressed
and only the rapid oscillation phase exists. Radiation generation during this
era is taken into account, so we have warm inflation with an oscillatory
inflaton. To provide enough e-folds, we employ the non-minimal derivative
coupling model. We study the cosmological perturbations and compute the
temperature at the end of warm oscillatory inflation.
| [
{
"created": "Sun, 18 Sep 2016 08:46:17 GMT",
"version": "v1"
},
{
"created": "Sun, 15 Jan 2017 12:35:10 GMT",
"version": "v2"
},
{
"created": "Sun, 18 Jun 2017 05:57:21 GMT",
"version": "v3"
},
{
"created": "Mon, 17 Jul 2017 08:50:40 GMT",
"version": "v4"
}
] | 2017-07-18 | [
[
"Goodarzi",
"Parviz",
""
],
[
"Sadjadi",
"H. Mohseni",
""
]
] | In the cold inflation scenario, the slow roll inflation and reheating via coherent rapid oscillation, are usually considered as two distinct eras. When the slow roll ends, a rapid oscillation phase begins and the inflaton decays to relativistic particles reheating the Universe. In another model dubbed warm inflation, the rapid oscillation phase is suppressed, and we are left with only a slow roll period during which the reheating occurs. Instead, in this paper, we propose a new picture for inflation in which the slow roll era is suppressed and only the rapid oscillation phase exists. Radiation generation during this era is taken into account, so we have warm inflation with an oscillatory inflaton. To provide enough e-folds, we employ the non-minimal derivative coupling model. We study the cosmological perturbations and compute the temperature at the end of warm oscillatory inflation. |
0708.0680 | Saibal Ray | U. Mukhopadhyay, Saibal Ray and S. B. Dutta Choudhury | $\Lambda$-CDM Universe: A Phenomenological Approach With Many
Possibilities | 10 Latex pages; Corrected typos; To appear in Int. J. Mod. Phys. D | Int.J.Mod.Phys.D17:301-309,2008 | 10.1142/S0218271808012012 | null | gr-qc | null | A time-dependent phenomenological model of $\Lambda$, viz. $\dot \Lambda\sim
H^3$ is selected to investigate the $\Lambda$-CDM cosmology. Time-dependent
form of the equation of state parameter $\omega$ is derived and it has been
possible to obtain the sought for flip of sign of the deceleration parameter q.
Present age of the Universe, calculated for some specific values of the
parameters agrees very well with the observational data.
| [
{
"created": "Sun, 5 Aug 2007 18:03:45 GMT",
"version": "v1"
},
{
"created": "Wed, 12 Mar 2008 17:49:47 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Mukhopadhyay",
"U.",
""
],
[
"Ray",
"Saibal",
""
],
[
"Choudhury",
"S. B. Dutta",
""
]
] | A time-dependent phenomenological model of $\Lambda$, viz. $\dot \Lambda\sim H^3$ is selected to investigate the $\Lambda$-CDM cosmology. Time-dependent form of the equation of state parameter $\omega$ is derived and it has been possible to obtain the sought for flip of sign of the deceleration parameter q. Present age of the Universe, calculated for some specific values of the parameters agrees very well with the observational data. |
1303.3662 | Feng He | Long Huang, Feng He, Hai Huang, Min Yao | The Gravitational Deflection of Light in F(R)-gravity | null | null | 10.1007/s10773-014-2000-5 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The fact that the gravitation could deflect the light trajectory has been
confirmed by a large number of observation data, that is consistent with the
result calculated by Einstein's gravity. F(R)-gravity is the modification of
Einstein's gravity. According to the field equations obtained by the action of
the f(R) form, we get a similar Schwarzschild metric. According to the
condition that four-dimension momenta of the photon return to zero and that of
conservation of covariant momenta, we obtain the equation of motion of the
photon in a specific form of f (R)-gravity. We solve the equation to get the
gravitational deflection angle of light that grazes the surface of sun and the
calculation result is consistent with the experimental observation data.
| [
{
"created": "Fri, 15 Mar 2013 02:21:15 GMT",
"version": "v1"
}
] | 2015-06-15 | [
[
"Huang",
"Long",
""
],
[
"He",
"Feng",
""
],
[
"Huang",
"Hai",
""
],
[
"Yao",
"Min",
""
]
] | The fact that the gravitation could deflect the light trajectory has been confirmed by a large number of observation data, that is consistent with the result calculated by Einstein's gravity. F(R)-gravity is the modification of Einstein's gravity. According to the field equations obtained by the action of the f(R) form, we get a similar Schwarzschild metric. According to the condition that four-dimension momenta of the photon return to zero and that of conservation of covariant momenta, we obtain the equation of motion of the photon in a specific form of f (R)-gravity. We solve the equation to get the gravitational deflection angle of light that grazes the surface of sun and the calculation result is consistent with the experimental observation data. |
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