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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
gr-qc/9812014 | Patrick R. Brady | Patrick R Brady and Teviet Creighton | Searching for periodic sources with LIGO. II: Hierarchical searches | 22 Pages, 13 Figures | Phys.Rev. D61 (2000) 082001 | 10.1103/PhysRevD.61.082001 | GRP-508, NSF-ITP-98-120 | gr-qc | null | The detection of quasi-periodic sources of gravitational waves requires the
accumulation of signal-to-noise over long observation times. If not removed,
Earth-motion induced Doppler modulations, and intrinsic variations of the
gravitational-wave frequency make the signals impossible to detect. These
effects can be corrected (removed) using a parameterized model for the
frequency evolution. We compute the number of independent corrections
$N_p(\Delta T,N)$ required for incoherent search strategies which use stacked
power spectra---a demodulated time series is divided into $N$ segments of
length $\Delta T$, each segment is FFTed, the power is computed, and the $N$
spectra are summed up. We estimate that the sensitivity of an all-sky search
that uses incoherent stacks is a factor of 2--4 better than would be achieved
using coherent Fourier transforms; incoherent methods are computationally
efficient at exploring large parameter spaces. A two-stage hierarchical search
which yields another 20--60% improvement in sensitivity in all-sky searches for
old (>= 1000 yr) slow (<= 200 Hz) pulsars, and for young (>= 40 yr) fast (<=
1000 Hz) pulsars. Assuming 10^{12} flops of effective computing power for data
analysis, enhanced LIGO interferometers should be sensitive to: (i) Galactic
core pulsars with gravitational ellipticities of $\epsilon\agt5\times 10^{-6}$
at 200 Hz, (ii) Gravitational waves emitted by the unstable r-modes of newborn
neutron stars out to distances of ~8 Mpc, and (iii) neutron stars in LMXB's
with x-ray fluxes which exceed $2 \times 10^{-8} erg/(cm^2 s)$. Moreover,
gravitational waves from the neutron star in Sco X-1 should be detectable is
the interferometer is operated in a signal-recycled, narrow-band configuration.
| [
{
"created": "Fri, 4 Dec 1998 03:25:11 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Brady",
"Patrick R",
""
],
[
"Creighton",
"Teviet",
""
]
] | The detection of quasi-periodic sources of gravitational waves requires the accumulation of signal-to-noise over long observation times. If not removed, Earth-motion induced Doppler modulations, and intrinsic variations of the gravitational-wave frequency make the signals impossible to detect. These effects can be corrected (removed) using a parameterized model for the frequency evolution. We compute the number of independent corrections $N_p(\Delta T,N)$ required for incoherent search strategies which use stacked power spectra---a demodulated time series is divided into $N$ segments of length $\Delta T$, each segment is FFTed, the power is computed, and the $N$ spectra are summed up. We estimate that the sensitivity of an all-sky search that uses incoherent stacks is a factor of 2--4 better than would be achieved using coherent Fourier transforms; incoherent methods are computationally efficient at exploring large parameter spaces. A two-stage hierarchical search which yields another 20--60% improvement in sensitivity in all-sky searches for old (>= 1000 yr) slow (<= 200 Hz) pulsars, and for young (>= 40 yr) fast (<= 1000 Hz) pulsars. Assuming 10^{12} flops of effective computing power for data analysis, enhanced LIGO interferometers should be sensitive to: (i) Galactic core pulsars with gravitational ellipticities of $\epsilon\agt5\times 10^{-6}$ at 200 Hz, (ii) Gravitational waves emitted by the unstable r-modes of newborn neutron stars out to distances of ~8 Mpc, and (iii) neutron stars in LMXB's with x-ray fluxes which exceed $2 \times 10^{-8} erg/(cm^2 s)$. Moreover, gravitational waves from the neutron star in Sco X-1 should be detectable is the interferometer is operated in a signal-recycled, narrow-band configuration. |
0802.4274 | Martin Bojowald | Martin Bojowald and Reza Tavakol | Loop Quantum Cosmology: Effective theories and oscillating universes | 24 pages, 3 figures, Chapter contributed to: ``Beyond the Big Bang'',
Ed.: Ruediger Vaas (Springer Verlag, 2008) | null | null | IGPG-08/2-6 | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Despite its great successes in accounting for the current observations, the
so called `standard' model of cosmology faces a number of fundamental
unresolved questions. Paramount among these are those relating to the nature of
the origin of the universe and its early evolution. Regarding the question of
origin, the main difficulty has been the fact that within the classical general
relativistic framework, the `origin' is almost always a singular event at which
the laws of physics break down, thus making it impossible for such an event, or
epochs prior to it, to be studied. Recent studies have shown that Loop Quantum
Cosmology may provide a non-singular framework where these questions can be
addressed. The crucial role here is played by quantum effects, i.e.\
corrections to the classical equations of motion, which are incorporated in
effective equations employed to develop cosmological scenarios.
In this chapter we shall consider the three main types of quantum effects
expected to be present within such a framework and discuss some of their
consequences for the effective equations. In particular we discuss how such
corrections can allow the construction of non-singular emergent scenarios for
the origin of the universe, which are past-eternal, oscillating and naturally
emerge into an inflationary phase. These scenarios provide a physically
plausible picture for the origin and early phases of the universe, which is in
principle testable. We pay special attention to the interplay between these
different types of correction terms. Given the absence, so far, of a complete
derivation of such corrections in general settings, it is important to bear in
mind the questions of consistency and robustness of scenarios based on partial
inclusion of such effects.
| [
{
"created": "Thu, 28 Feb 2008 20:13:31 GMT",
"version": "v1"
}
] | 2008-02-29 | [
[
"Bojowald",
"Martin",
""
],
[
"Tavakol",
"Reza",
""
]
] | Despite its great successes in accounting for the current observations, the so called `standard' model of cosmology faces a number of fundamental unresolved questions. Paramount among these are those relating to the nature of the origin of the universe and its early evolution. Regarding the question of origin, the main difficulty has been the fact that within the classical general relativistic framework, the `origin' is almost always a singular event at which the laws of physics break down, thus making it impossible for such an event, or epochs prior to it, to be studied. Recent studies have shown that Loop Quantum Cosmology may provide a non-singular framework where these questions can be addressed. The crucial role here is played by quantum effects, i.e.\ corrections to the classical equations of motion, which are incorporated in effective equations employed to develop cosmological scenarios. In this chapter we shall consider the three main types of quantum effects expected to be present within such a framework and discuss some of their consequences for the effective equations. In particular we discuss how such corrections can allow the construction of non-singular emergent scenarios for the origin of the universe, which are past-eternal, oscillating and naturally emerge into an inflationary phase. These scenarios provide a physically plausible picture for the origin and early phases of the universe, which is in principle testable. We pay special attention to the interplay between these different types of correction terms. Given the absence, so far, of a complete derivation of such corrections in general settings, it is important to bear in mind the questions of consistency and robustness of scenarios based on partial inclusion of such effects. |
1707.01508 | Mattia Manfredonia | Emmanuele Battista, Elisabetta Di Grezia, Mattia Manfredonia, Gennaro
Miele | Spin, torsion and violation of null energy condition in traversable
wormholes | 13 pages | Eur. Phys. J. Plus (2017) 132: 537 | 10.1140/epjp/i2017-11799-6 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The static spherically symmetric traversable wormholes are analysed in the
Einstein- Cartan theory of gravitation. In particular, we computed the torsion
tensor for matter fields with different spin S = 0; 1/2; 1; 3/2. Interestingly,
only for certain values of the spin the torsion contribution to Einstein-Cartan
field equation allows one to satisfy both faring-out condition and Null Energy
Condition. In this scenario traversable wormholes can be produced by using
usual (non-exotic) spinning matter.
| [
{
"created": "Wed, 5 Jul 2017 18:01:11 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Jan 2018 12:30:12 GMT",
"version": "v2"
}
] | 2018-01-12 | [
[
"Battista",
"Emmanuele",
""
],
[
"Di Grezia",
"Elisabetta",
""
],
[
"Manfredonia",
"Mattia",
""
],
[
"Miele",
"Gennaro",
""
]
] | The static spherically symmetric traversable wormholes are analysed in the Einstein- Cartan theory of gravitation. In particular, we computed the torsion tensor for matter fields with different spin S = 0; 1/2; 1; 3/2. Interestingly, only for certain values of the spin the torsion contribution to Einstein-Cartan field equation allows one to satisfy both faring-out condition and Null Energy Condition. In this scenario traversable wormholes can be produced by using usual (non-exotic) spinning matter. |
2102.05112 | Kun Meng | Kun Meng, Lianzhen Cao, Jiaqiang Zhao, Fuyong Qin, Tao Zhou, Meihua
Deng | Dyonic Born-Infeld black hole in four-dimensional Horndeski gravity | 13 pages, 2 figures. Phys.Lett.B 819 (2021) 136420 | null | 10.1016/j.physletb.2021.136420 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The action of four-dimensional Horndeski gravity coupled to Born-Infeld
electromagnetic fields is given via the Kaluza-Klein process. Dyonic black hole
solution of the theory is constructed. The metric is devoid of singularity at
the origin independent of the parameter selections, this property is different
from the one of Einstein-Born-Infeld black holes. Thermodynamics of the black
hole is studied, thermodynamic quantities are calculated and the first law is
checked to be satisfied. Thermodynamic phase transitions of the black holes are
studied in extended phase space.
| [
{
"created": "Tue, 9 Feb 2021 20:24:53 GMT",
"version": "v1"
},
{
"created": "Mon, 22 Feb 2021 05:42:49 GMT",
"version": "v2"
},
{
"created": "Sat, 17 Apr 2021 17:09:08 GMT",
"version": "v3"
},
{
"created": "Sat, 12 Jun 2021 11:34:44 GMT",
"version": "v4"
}
] | 2021-06-15 | [
[
"Meng",
"Kun",
""
],
[
"Cao",
"Lianzhen",
""
],
[
"Zhao",
"Jiaqiang",
""
],
[
"Qin",
"Fuyong",
""
],
[
"Zhou",
"Tao",
""
],
[
"Deng",
"Meihua",
""
]
] | The action of four-dimensional Horndeski gravity coupled to Born-Infeld electromagnetic fields is given via the Kaluza-Klein process. Dyonic black hole solution of the theory is constructed. The metric is devoid of singularity at the origin independent of the parameter selections, this property is different from the one of Einstein-Born-Infeld black holes. Thermodynamics of the black hole is studied, thermodynamic quantities are calculated and the first law is checked to be satisfied. Thermodynamic phase transitions of the black holes are studied in extended phase space. |
gr-qc/0612075 | Valerio Faraoni | Valerio Faraoni and Shahn Nadeau (Bishop's University) | The (pseudo)issue of the conformal frame revisited | 29 pages, latex, to appear in Phys. Rev. D | Phys.Rev.D75:023501,2007 | 10.1103/PhysRevD.75.023501 | null | gr-qc astro-ph hep-th | null | The issue of the equivalence between Jordan and Einstein conformal frames in
scalar-tensor gravity is revisited, with emphasis on implementing running units
in the latter. The lack of affine parametrization for timelike worldlines and
the cosmological constant problem in the Einstein frame are clarified, and a
paradox in the literature about cosmological singularities appearing only in
one frame is solved. While, classically, the two conformal frames are
physically equivalent, they seem to be inequivalent at the quantum level.
| [
{
"created": "Tue, 12 Dec 2006 21:24:07 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
],
[
"Nadeau",
"Shahn",
"",
"Bishop's University"
]
] | The issue of the equivalence between Jordan and Einstein conformal frames in scalar-tensor gravity is revisited, with emphasis on implementing running units in the latter. The lack of affine parametrization for timelike worldlines and the cosmological constant problem in the Einstein frame are clarified, and a paradox in the literature about cosmological singularities appearing only in one frame is solved. While, classically, the two conformal frames are physically equivalent, they seem to be inequivalent at the quantum level. |
gr-qc/0304102 | Claus Kiefer | Claus Kiefer | Is there an information-loss problem for black holes? | 11 pages, to appear in the Proceedings of the conference DICE,
Piombino 2002, ed. by H.-T. Elze (Springer 2003), references and
clarifications added | null | 10.1007/978-3-540-40968-7_6 | null | gr-qc hep-th | null | Black holes emit thermal radiation (Hawking effect). If after black-hole
evaporation nothing else were left, an arbitrary initial state would evolve
into a thermal state (`information-loss problem'). Here it is argued that the
whole evolution is unitary and that the thermal nature of Hawking radiation
emerges solely through decoherence -- the irreversible interaction with further
degrees of freedom. For this purpose a detailed comparison with an analogous
case in cosmology (entropy of primordial fluctuations) is presented. Some
remarks on the possible origin of black-hole entropy due to interaction with
other degrees of freedom are added. This might concern the interaction with
quasi-normal modes or with background fields in string theory.
| [
{
"created": "Tue, 29 Apr 2003 13:47:09 GMT",
"version": "v1"
},
{
"created": "Mon, 5 May 2003 08:18:59 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Kiefer",
"Claus",
""
]
] | Black holes emit thermal radiation (Hawking effect). If after black-hole evaporation nothing else were left, an arbitrary initial state would evolve into a thermal state (`information-loss problem'). Here it is argued that the whole evolution is unitary and that the thermal nature of Hawking radiation emerges solely through decoherence -- the irreversible interaction with further degrees of freedom. For this purpose a detailed comparison with an analogous case in cosmology (entropy of primordial fluctuations) is presented. Some remarks on the possible origin of black-hole entropy due to interaction with other degrees of freedom are added. This might concern the interaction with quasi-normal modes or with background fields in string theory. |
gr-qc/0608121 | Yi Mao | Yi Mao (MIT), Max Tegmark (MIT), Alan Guth (MIT), Serkan Cabi (MIT) | Constraining Torsion with Gravity Probe B | "Director's cut" edition of accepted PRD version, including
additional explanatory material | Phys.Rev.D76:104029,2007 | 10.1103/PhysRevD.76.104029 | null | gr-qc astro-ph hep-th | null | It is well-entrenched folklore that torsion gravity theories predict
observationally negligible torsion in the solar system, since torsion (if it
exists) couples only to the intrinsic spin of elementary particles, not to
rotational angular momentum. We argue that this assumption has a logical
loophole which can and should be tested experimentally. In the spirit of
action=reaction, if a rotating mass like a planet can generate torsion, then a
gyroscope should also feel torsion. Using symmetry arguments, we show that to
lowest order, the torsion field around a uniformly rotating spherical mass is
determined by seven dimensionless parameters. These parameters effectively
generalize the PPN formalism and provide a concrete framework for further
testing GR. We construct a parametrized Lagrangian that includes both standard
torsion-free GR and Hayashi- Shirafuji maximal torsion gravity as special
cases. We demonstrate that classic solar system tests rule out the latter and
constrain two observable parameters. We show that Gravity Probe B (GPB) is an
ideal experiment for further constraining torsion theories, and work out the
most general torsion-induced precession of its gyroscope in terms of our
torsion parameters
| [
{
"created": "Tue, 29 Aug 2006 19:50:38 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Aug 2006 23:55:18 GMT",
"version": "v2"
},
{
"created": "Tue, 9 Jan 2007 03:48:47 GMT",
"version": "v3"
},
{
"created": "Fri, 5 Oct 2007 14:41:25 GMT",
"version": "v4"
}
] | 2008-11-26 | [
[
"Mao",
"Yi",
"",
"MIT"
],
[
"Tegmark",
"Max",
"",
"MIT"
],
[
"Guth",
"Alan",
"",
"MIT"
],
[
"Cabi",
"Serkan",
"",
"MIT"
]
] | It is well-entrenched folklore that torsion gravity theories predict observationally negligible torsion in the solar system, since torsion (if it exists) couples only to the intrinsic spin of elementary particles, not to rotational angular momentum. We argue that this assumption has a logical loophole which can and should be tested experimentally. In the spirit of action=reaction, if a rotating mass like a planet can generate torsion, then a gyroscope should also feel torsion. Using symmetry arguments, we show that to lowest order, the torsion field around a uniformly rotating spherical mass is determined by seven dimensionless parameters. These parameters effectively generalize the PPN formalism and provide a concrete framework for further testing GR. We construct a parametrized Lagrangian that includes both standard torsion-free GR and Hayashi- Shirafuji maximal torsion gravity as special cases. We demonstrate that classic solar system tests rule out the latter and constrain two observable parameters. We show that Gravity Probe B (GPB) is an ideal experiment for further constraining torsion theories, and work out the most general torsion-induced precession of its gyroscope in terms of our torsion parameters |
2402.15540 | Surojit Dalui | Surojit Dalui, Arpan Krishna Mitra, Deeshani Mitra and Subir Ghosh | Spinning Black Hole in a Fluid | Accepted in Physical Review D and this paper has overlap with our
earlier paper arXiv:2306.12201 [gr-qc] | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we propose a new Analogue Gravity example - a spinning (or
Kerr) Black Hole in an extended fluid model. The fluid model receives Berry
curvature contributions and applies to electron dynamics in Condensed Matter
lattice systems in the hydrodynamic limit. We construct the acoustic metric for
sonic fluctuations that obey a structurally relativistic wave equation in an
effective curved background. In a novel approach of dimensional analysis, we
have derived explicit expressions for effective mass and angular momentum per
unit mass in the acoustic metric (in terms of fluid parameters), to identify
with corresponding parameters of the Kerr metric. The spin is a manifestation
of the Berry curvature-induced effective noncommutative structure in the fluid.
Finally we put the Kerr Black Hole analogy in a robust setting by revealing
explicitly the presence of horizon and ergo-region for a specific background
fluid velocity profile. We also show that near horizon behavior of the
phase-space trajectory of a probe particle agrees with Kerr Black Hole analogy.
In fluid dynamics perspective, presence of a horizon signifies the wave
blocking phenomenon.
| [
{
"created": "Fri, 23 Feb 2024 10:05:37 GMT",
"version": "v1"
}
] | 2024-02-27 | [
[
"Dalui",
"Surojit",
""
],
[
"Mitra",
"Arpan Krishna",
""
],
[
"Mitra",
"Deeshani",
""
],
[
"Ghosh",
"Subir",
""
]
] | In this paper, we propose a new Analogue Gravity example - a spinning (or Kerr) Black Hole in an extended fluid model. The fluid model receives Berry curvature contributions and applies to electron dynamics in Condensed Matter lattice systems in the hydrodynamic limit. We construct the acoustic metric for sonic fluctuations that obey a structurally relativistic wave equation in an effective curved background. In a novel approach of dimensional analysis, we have derived explicit expressions for effective mass and angular momentum per unit mass in the acoustic metric (in terms of fluid parameters), to identify with corresponding parameters of the Kerr metric. The spin is a manifestation of the Berry curvature-induced effective noncommutative structure in the fluid. Finally we put the Kerr Black Hole analogy in a robust setting by revealing explicitly the presence of horizon and ergo-region for a specific background fluid velocity profile. We also show that near horizon behavior of the phase-space trajectory of a probe particle agrees with Kerr Black Hole analogy. In fluid dynamics perspective, presence of a horizon signifies the wave blocking phenomenon. |
1107.2872 | Fabrizio De Marchi | Fabrizio De Marchi, Giuseppe Pucacco, Massimo Bassan | Optimizing the Earth-LISA "rendez-vous" | 18 pages, 16 figures. Submitted on CQG | Class. Quantum Grav. 29 (2012) 035009 | 10.1088/0264-9381/29/3/035009 | null | gr-qc nlin.CD | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a general survey of heliocentric LISA orbits, hoping it might help
in the exercise of rescoping the mission. We try to semi-analytically optimize
the orbital parameters in order to minimize the disturbances coming from the
Earth-LISA interaction. In a set of numerical simulations we include
nonautonomous perturbations and provide an estimate of Doppler shift and
breathing as a function of the trailing angle.
| [
{
"created": "Thu, 14 Jul 2011 17:14:36 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"De Marchi",
"Fabrizio",
""
],
[
"Pucacco",
"Giuseppe",
""
],
[
"Bassan",
"Massimo",
""
]
] | We present a general survey of heliocentric LISA orbits, hoping it might help in the exercise of rescoping the mission. We try to semi-analytically optimize the orbital parameters in order to minimize the disturbances coming from the Earth-LISA interaction. In a set of numerical simulations we include nonautonomous perturbations and provide an estimate of Doppler shift and breathing as a function of the trailing angle. |
2403.12447 | Omar Mustafa | Omar Mustafa | Bosonic KG-oscillators in Eddington-inspired Born-Infeld gravity:
Wu-Yang magnetic monopole and Ricci scalar curvature effects | 15 pages, 3 figures | null | null | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | We investigate the bosonic Klein-Gordon (KG) oscillators in a global monopole
(GM) spacetime in Eddington-inspired Born-Infeld (EiBI) gravity and a Wu-Yang
magnetic monopole (WYMM). We discuss the gravitational effects in the presence
of Ricci scalar curvature $R=R_{\upsilon }^{\upsilon }$. It is observed that
the presence of the Ricci scalar curvature, effectively and manifestly,
introduces a force field that makes the corresponding quantum mechanical
repulsive core more repulsive. Similar effect is also observed for the
EiBI-gravitational field. We reiterate and report that the corresponding
bosonic KG-oscillator quantum mechanical system admits a solution in the form
of confluent Heun functions, the truncation of which into a physically
admissible polynomial is shown to be associated with some parametric
correlations/conditions. The use of such conditions/correlations is mandatory
and yields a set of allowed/restricted quantum mechanical orbital $\ell
$-excitations, for all radial quantum numbers $n_{r}\geq 0$. Our procedure is
shown to be quite handy, in the since that it allows one to retrieve results
for KG-oscillators in GM-spacetime in different EiBI-gravity and Ricci scalar
curvature settings.
| [
{
"created": "Tue, 19 Mar 2024 05:16:13 GMT",
"version": "v1"
}
] | 2024-03-20 | [
[
"Mustafa",
"Omar",
""
]
] | We investigate the bosonic Klein-Gordon (KG) oscillators in a global monopole (GM) spacetime in Eddington-inspired Born-Infeld (EiBI) gravity and a Wu-Yang magnetic monopole (WYMM). We discuss the gravitational effects in the presence of Ricci scalar curvature $R=R_{\upsilon }^{\upsilon }$. It is observed that the presence of the Ricci scalar curvature, effectively and manifestly, introduces a force field that makes the corresponding quantum mechanical repulsive core more repulsive. Similar effect is also observed for the EiBI-gravitational field. We reiterate and report that the corresponding bosonic KG-oscillator quantum mechanical system admits a solution in the form of confluent Heun functions, the truncation of which into a physically admissible polynomial is shown to be associated with some parametric correlations/conditions. The use of such conditions/correlations is mandatory and yields a set of allowed/restricted quantum mechanical orbital $\ell $-excitations, for all radial quantum numbers $n_{r}\geq 0$. Our procedure is shown to be quite handy, in the since that it allows one to retrieve results for KG-oscillators in GM-spacetime in different EiBI-gravity and Ricci scalar curvature settings. |
2311.16251 | Florian Atteneder | Florian Atteneder, Hannes R. R\"uter, Daniela Cors, Roxana Rosca-Mead,
David Hilditch, Bernd Br\"ugmann | Boson star head-on collisions with constraint-violating and
constraint-satisfying initial data | null | null | 10.1103/PhysRevD.109.044058 | Phys. Rev. D 109, 044058 | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Simulations of binary collisions involving compact objects require initial
data that satisfy the constraint equations of general relativity. For binary
boson star simulations it is common practice to use a superposition of two
isolated star solutions to construct an approximate solution to the constraint
equations. Such superposed data is simple to set up compared to solving these
equations explicitly, but also introduces extra constraint violations in the
time evolution. In this work we investigate how physical observables depend on
the quality of initial data in the case of head-on boson star collisions. In
particular we compare results obtained from data prepared using four different
methods: the standard method to superpose isolated stars, a heuristic
improvement to this superposition technique and two versions of this data where
excess constraint violations were removed through a conformal thin-sandwich
solver. We find that differences in the time evolutions are dominated by
differences in the way the two superposition methods differ, whereas
additionally constraint solving the superposed data has smaller impact. The
numerical experiments are conducted using the pseudo-spectral code bamps. Our
work demonstrates that bamps is a code suited for generating high accuracy
numerical waveforms for boson star collisions due to the exponential
convergence in the polynomial resolution of the numerical approximation.
| [
{
"created": "Mon, 27 Nov 2023 19:01:42 GMT",
"version": "v1"
}
] | 2024-03-05 | [
[
"Atteneder",
"Florian",
""
],
[
"Rüter",
"Hannes R.",
""
],
[
"Cors",
"Daniela",
""
],
[
"Rosca-Mead",
"Roxana",
""
],
[
"Hilditch",
"David",
""
],
[
"Brügmann",
"Bernd",
""
]
] | Simulations of binary collisions involving compact objects require initial data that satisfy the constraint equations of general relativity. For binary boson star simulations it is common practice to use a superposition of two isolated star solutions to construct an approximate solution to the constraint equations. Such superposed data is simple to set up compared to solving these equations explicitly, but also introduces extra constraint violations in the time evolution. In this work we investigate how physical observables depend on the quality of initial data in the case of head-on boson star collisions. In particular we compare results obtained from data prepared using four different methods: the standard method to superpose isolated stars, a heuristic improvement to this superposition technique and two versions of this data where excess constraint violations were removed through a conformal thin-sandwich solver. We find that differences in the time evolutions are dominated by differences in the way the two superposition methods differ, whereas additionally constraint solving the superposed data has smaller impact. The numerical experiments are conducted using the pseudo-spectral code bamps. Our work demonstrates that bamps is a code suited for generating high accuracy numerical waveforms for boson star collisions due to the exponential convergence in the polynomial resolution of the numerical approximation. |
gr-qc/0306098 | Yosef Zlochower | Yosef Zlochower, Roberto Gomez, Sascha Husa, Luis Lehner, Jeffrey
Winicour | Mode coupling in the nonlinear response of black holes | 17 pages, 20 figures, abstract and introduction re-written | Phys.Rev. D68 (2003) 084014 | 10.1103/PhysRevD.68.084014 | NSF-KITP-03-49, AEI-2003-053 | gr-qc | null | We study the properties of the outgoing gravitational wave produced when a
non-spinning black hole is excited by an ingoing gravitational wave.
Simulations using a numerical code for solving Einstein's equations allow the
study to be extended from the linearized approximation, where the system is
treated as a perturbed Schwarzschild black hole, to the fully nonlinear regime.
Several nonlinear features are found which bear importance to the data analysis
of gravitational waves. When compared to the results obtained in the linearized
approximation, we observe large phase shifts, a stronger than linear generation
of gravitational wave output and considerable generation of radiation in
polarization states which are not found in the linearized approximation. In
terms of a spherical harmonic decomposition, the nonlinear properties of the
harmonic amplitudes have simple scaling properties which offer an economical
way to catalog the details of the waves produced in such black hole processes.
| [
{
"created": "Mon, 23 Jun 2003 19:40:02 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Aug 2003 18:42:58 GMT",
"version": "v2"
}
] | 2009-11-10 | [
[
"Zlochower",
"Yosef",
""
],
[
"Gomez",
"Roberto",
""
],
[
"Husa",
"Sascha",
""
],
[
"Lehner",
"Luis",
""
],
[
"Winicour",
"Jeffrey",
""
]
] | We study the properties of the outgoing gravitational wave produced when a non-spinning black hole is excited by an ingoing gravitational wave. Simulations using a numerical code for solving Einstein's equations allow the study to be extended from the linearized approximation, where the system is treated as a perturbed Schwarzschild black hole, to the fully nonlinear regime. Several nonlinear features are found which bear importance to the data analysis of gravitational waves. When compared to the results obtained in the linearized approximation, we observe large phase shifts, a stronger than linear generation of gravitational wave output and considerable generation of radiation in polarization states which are not found in the linearized approximation. In terms of a spherical harmonic decomposition, the nonlinear properties of the harmonic amplitudes have simple scaling properties which offer an economical way to catalog the details of the waves produced in such black hole processes. |
gr-qc/0612061 | Lau Loi So | Lau Loi So and James M. Nester | Gravitational energy-momentum in small regions according to Moller's
tetrad expression | 8 pages | null | null | null | gr-qc | null | Moller's tetrad gravitational energy-momentum "tensor" is evaluated for a
small vacuum region using an orthonormal frame adapted to Riemann normal
coordinates. We find that it does satisfy the highly desired property of being
a positive multiple of the Bel-Robinson tensor.
| [
{
"created": "Mon, 11 Dec 2006 11:47:57 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"So",
"Lau Loi",
""
],
[
"Nester",
"James M.",
""
]
] | Moller's tetrad gravitational energy-momentum "tensor" is evaluated for a small vacuum region using an orthonormal frame adapted to Riemann normal coordinates. We find that it does satisfy the highly desired property of being a positive multiple of the Bel-Robinson tensor. |
2308.01383 | Rosa-Laura Lechuga R.L. Lechuga | R.L. Lechuga, D. Sudarsky | Eternal inflation and collapse theories | 36 pages, 1 figure | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The eternal inflation problem continues to be considered one of standard's
cosmology most serious shortcomings. This arises when one considers the effects
of "quantum fluctuations" (QF) on the zero mode of inflaton field during a
Hubble time in the inflationary epoch. In the slow-roll regime it is quite
clear that such QF could dwarf the classical rolling down of the inflaton, and
with overwhelming probability this prevents inflation from ever ending. When
one recognizes that QF can not be taken as synonymous of stochastic
fluctuations, but rather intrinsic levels of indefiniteness in the quantities,
one concludes that the eternal inflation problem simply does not exist.
However, the same argument would serve to invalidate the account for the
generation of the primordial seeds of cosmic structure. In order to do address
that issue, one must explain the breaking of homogeneity and isotropy of the
early inflationary epoch. The so called spontaneous collapse theories offer an
additional element namely the stochastic and spontaneous state reduction
characteristic of those proposals possesses the basic features to break those
symmetries. In fact, a version of the CSL theory adapted to the cosmological
context has been shown to offer a satisfactory account for the origin the seeds
of cosmic structure with an adequate power spectrum, and will serve as the
basis of our analysis. However, once such stochastic collapse is introduced
into the theoretical framework the eternal inflation problem has the potential
reappear. In this manuscript we explore those issues in detail and discuss an
avenue that seems to allow for a satisfactory account for the generation of the
primordial inhomogeneities and anisotropies while freeing the theory from the
eternal inflation problem.
| [
{
"created": "Wed, 2 Aug 2023 18:52:28 GMT",
"version": "v1"
},
{
"created": "Fri, 17 Nov 2023 00:38:56 GMT",
"version": "v2"
},
{
"created": "Tue, 21 Nov 2023 08:25:18 GMT",
"version": "v3"
}
] | 2023-11-22 | [
[
"Lechuga",
"R. L.",
""
],
[
"Sudarsky",
"D.",
""
]
] | The eternal inflation problem continues to be considered one of standard's cosmology most serious shortcomings. This arises when one considers the effects of "quantum fluctuations" (QF) on the zero mode of inflaton field during a Hubble time in the inflationary epoch. In the slow-roll regime it is quite clear that such QF could dwarf the classical rolling down of the inflaton, and with overwhelming probability this prevents inflation from ever ending. When one recognizes that QF can not be taken as synonymous of stochastic fluctuations, but rather intrinsic levels of indefiniteness in the quantities, one concludes that the eternal inflation problem simply does not exist. However, the same argument would serve to invalidate the account for the generation of the primordial seeds of cosmic structure. In order to do address that issue, one must explain the breaking of homogeneity and isotropy of the early inflationary epoch. The so called spontaneous collapse theories offer an additional element namely the stochastic and spontaneous state reduction characteristic of those proposals possesses the basic features to break those symmetries. In fact, a version of the CSL theory adapted to the cosmological context has been shown to offer a satisfactory account for the origin the seeds of cosmic structure with an adequate power spectrum, and will serve as the basis of our analysis. However, once such stochastic collapse is introduced into the theoretical framework the eternal inflation problem has the potential reappear. In this manuscript we explore those issues in detail and discuss an avenue that seems to allow for a satisfactory account for the generation of the primordial inhomogeneities and anisotropies while freeing the theory from the eternal inflation problem. |
0908.0854 | Romain Gicquaud | Romain Gicquaud | Linearization stability of the Einstein constraint equations on an
asymptotically hyperbolic manifold | 19 pages, no figure | J. Math. Phys. 51 (2010), no. 7, 072501 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the linearization stability of the Einstein constraint equations on
an asymptotically hyperbolic manifold. In particular we prove that these
equations are linearization stable in the neighborhood of vacuum solutions for
a non-positive cosmological constant and of
Friedman--Lema\^itre--Robertson--Walker spaces in a certain range of decays. We
also prove that this result is no longer true for faster decays. The
construction of the counterexamples is based on a new construction of
TT-tensors on the Euclidean space and on positive energy theorems.
| [
{
"created": "Thu, 6 Aug 2009 12:43:20 GMT",
"version": "v1"
}
] | 2012-01-17 | [
[
"Gicquaud",
"Romain",
""
]
] | We study the linearization stability of the Einstein constraint equations on an asymptotically hyperbolic manifold. In particular we prove that these equations are linearization stable in the neighborhood of vacuum solutions for a non-positive cosmological constant and of Friedman--Lema\^itre--Robertson--Walker spaces in a certain range of decays. We also prove that this result is no longer true for faster decays. The construction of the counterexamples is based on a new construction of TT-tensors on the Euclidean space and on positive energy theorems. |
1704.07044 | Soham Bhattacharyya | Soham Bhattacharyya (1), S. Shankaranarayanan (1) ((1) IISER-TVM) | Quasinormal modes as a distinguisher between general relativity and f(R)
gravity | 9 pages, 2 figures, version as accepted in Physical Review D | Phys. Rev. D 96, 064044 (2017) | 10.1103/PhysRevD.96.064044 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quasi-Normal Modes (QNM) or ringdown phase of gravitational waves provide
critical information about the structure of compact objects like Black Holes.
Thus, QNMs can be a tool to test General Relativity (GR) and possible
deviations from it. In the case of GR, it is known for a long time that a
relation between two types of Black Hole perturbations: scalar (Zerilli) and
vector (Regge-Wheeler), leads to an equal share of emitted gravitational
energy. With the direct detection of Gravitational waves, it is now natural to
ask: whether the same relation (between scalar and vector perturbations) holds
for modified gravity theories? If not, whether one can use this as a way to
probe deviations from General Relativity. As a first step, we show explicitly
that the above relation between Regge-Wheeler and Zerilli breaks down for a
general f (R) model, and hence the two perturbations do not share equal amounts
of emitted gravitational energy. We discuss the implication of this imbalance
on observations and the no-hair conjecture.
| [
{
"created": "Mon, 24 Apr 2017 05:23:42 GMT",
"version": "v1"
},
{
"created": "Wed, 30 Aug 2017 14:31:28 GMT",
"version": "v2"
}
] | 2017-10-04 | [
[
"Bhattacharyya",
"Soham",
"",
"IISER-TVM"
],
[
"Shankaranarayanan",
"S.",
"",
"IISER-TVM"
]
] | Quasi-Normal Modes (QNM) or ringdown phase of gravitational waves provide critical information about the structure of compact objects like Black Holes. Thus, QNMs can be a tool to test General Relativity (GR) and possible deviations from it. In the case of GR, it is known for a long time that a relation between two types of Black Hole perturbations: scalar (Zerilli) and vector (Regge-Wheeler), leads to an equal share of emitted gravitational energy. With the direct detection of Gravitational waves, it is now natural to ask: whether the same relation (between scalar and vector perturbations) holds for modified gravity theories? If not, whether one can use this as a way to probe deviations from General Relativity. As a first step, we show explicitly that the above relation between Regge-Wheeler and Zerilli breaks down for a general f (R) model, and hence the two perturbations do not share equal amounts of emitted gravitational energy. We discuss the implication of this imbalance on observations and the no-hair conjecture. |
1801.08604 | Remi Geiger | Remi Geiger, Michael Trupke | Proposal for a Quantum Test of the Weak Equivalence Principle with
Entangled Atomic Species | 5 pages, 1 figure + Supplemental Material | Phys. Rev. Lett. 120, 043602 (2018) | 10.1103/PhysRevLett.120.043602 | null | gr-qc physics.atom-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We propose an experiment to test the Weak Equivalence Principle (WEP) with a
test mass consisting of two entangled atoms of different species. In the
proposed experiment, a coherent measurement of the differential gravity
acceleration between the two atomic species is considered, by entangling two
atom interferometers operating on the two species. The entanglement between the
two atoms is heralded at the initial beam splitter of the interferometers
through the detection of a single photon emitted by either of the atoms,
together with the impossibility of distinguishing which atom emitted the
photon. In contrast to current and proposed tests of the WEP, our proposal
explores the validity of the WEP in a regime where the two particles involved
in the differential gravity acceleration measurement are not classically
independent, but entangled. We propose an experimental implementation using
$^{85}$Rb and $^{87}$Rb atoms entangled by a vacuum stimulated rapid adiabatic
passage protocol implemented in a high finesse optical cavity. We show that an
accuracy below $10^{-7}$ on the E\"otv\"os parameter can be achieved.
| [
{
"created": "Thu, 25 Jan 2018 21:44:54 GMT",
"version": "v1"
}
] | 2018-01-29 | [
[
"Geiger",
"Remi",
""
],
[
"Trupke",
"Michael",
""
]
] | We propose an experiment to test the Weak Equivalence Principle (WEP) with a test mass consisting of two entangled atoms of different species. In the proposed experiment, a coherent measurement of the differential gravity acceleration between the two atomic species is considered, by entangling two atom interferometers operating on the two species. The entanglement between the two atoms is heralded at the initial beam splitter of the interferometers through the detection of a single photon emitted by either of the atoms, together with the impossibility of distinguishing which atom emitted the photon. In contrast to current and proposed tests of the WEP, our proposal explores the validity of the WEP in a regime where the two particles involved in the differential gravity acceleration measurement are not classically independent, but entangled. We propose an experimental implementation using $^{85}$Rb and $^{87}$Rb atoms entangled by a vacuum stimulated rapid adiabatic passage protocol implemented in a high finesse optical cavity. We show that an accuracy below $10^{-7}$ on the E\"otv\"os parameter can be achieved. |
gr-qc/9912005 | Peter Dunsby | G. F. R. Ellis, D. C. Roberts, D. Solomons and P. K. S. Dunsby | A Solution to the Graceful Exit Problem in Pre-Big Bang Cosmology | 16 pages LaTeX, 5 figures. To appear in Physical Review D | null | 10.1103/PhysRevD.62.084004 | uct-cosmology-99/04 | gr-qc | null | We examine the string cosmology equations with a dilaton potential in the
context of the Pre-Big Bang Scenario with the desired scale factor duality, and
give a generic algorithm for obtaining solutions with appropriate evolutionary
properties. This enables us to find pre-big bang type solutions with suitable
dilaton behaviour that are regular at $t=0$, thereby solving the graceful exit
problem. However to avoid fine tuning of initial data, an `exotic' equation of
state is needed that relates the fluid properties to the dilaton field. We
discuss why such an equation of state should be required for reliable dilaton
behaviour at late times.
| [
{
"created": "Wed, 1 Dec 1999 21:34:13 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Mar 2000 12:13:34 GMT",
"version": "v2"
},
{
"created": "Mon, 20 Mar 2000 07:49:49 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Ellis",
"G. F. R.",
""
],
[
"Roberts",
"D. C.",
""
],
[
"Solomons",
"D.",
""
],
[
"Dunsby",
"P. K. S.",
""
]
] | We examine the string cosmology equations with a dilaton potential in the context of the Pre-Big Bang Scenario with the desired scale factor duality, and give a generic algorithm for obtaining solutions with appropriate evolutionary properties. This enables us to find pre-big bang type solutions with suitable dilaton behaviour that are regular at $t=0$, thereby solving the graceful exit problem. However to avoid fine tuning of initial data, an `exotic' equation of state is needed that relates the fluid properties to the dilaton field. We discuss why such an equation of state should be required for reliable dilaton behaviour at late times. |
1805.08229 | Enrico Barausse | Enrico Barausse, Richard Brito, Vitor Cardoso, Irina Dvorkin, Paolo
Pani | The stochastic gravitational-wave background in the absence of horizons | 7 pages, 4 figures. Analysis improved by using spin-2 instability
timescale, conclusions unchanged. Published in CQG Letters | Classical and Quantum Gravity, Volume 35, Number 20, 2018 | 10.1088/1361-6382/aae1de | null | gr-qc astro-ph.HE hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Gravitational-wave astronomy has the potential to explore one of the deepest
and most puzzling aspects of Einstein's theory: the existence of black holes. A
plethora of ultracompact, horizonless objects have been proposed to arise in
models inspired by quantum gravity. These objects may solve Hawking's
information-loss paradox and the singularity problem associated with black
holes, while mimicking almost all of their classical properties. They are,
however, generically unstable on relatively short timescales. Here, we show
that this "ergoregion instability" leads to a strong stochastic background of
gravitational waves, at a level detectable by current and future
gravitational-wave detectors. The absence of such background in the first
observation run of Advanced LIGO already imposes the most stringent limits to
date on black-hole alternatives, showing that certain models of
"quantum-dressed" stellar black holes can be at most a small percentage of the
total population. The future LISA mission will allow for similar constraints on
supermassive black-hole mimickers.
| [
{
"created": "Mon, 21 May 2018 18:01:15 GMT",
"version": "v1"
},
{
"created": "Wed, 3 Oct 2018 08:37:29 GMT",
"version": "v2"
}
] | 2018-10-04 | [
[
"Barausse",
"Enrico",
""
],
[
"Brito",
"Richard",
""
],
[
"Cardoso",
"Vitor",
""
],
[
"Dvorkin",
"Irina",
""
],
[
"Pani",
"Paolo",
""
]
] | Gravitational-wave astronomy has the potential to explore one of the deepest and most puzzling aspects of Einstein's theory: the existence of black holes. A plethora of ultracompact, horizonless objects have been proposed to arise in models inspired by quantum gravity. These objects may solve Hawking's information-loss paradox and the singularity problem associated with black holes, while mimicking almost all of their classical properties. They are, however, generically unstable on relatively short timescales. Here, we show that this "ergoregion instability" leads to a strong stochastic background of gravitational waves, at a level detectable by current and future gravitational-wave detectors. The absence of such background in the first observation run of Advanced LIGO already imposes the most stringent limits to date on black-hole alternatives, showing that certain models of "quantum-dressed" stellar black holes can be at most a small percentage of the total population. The future LISA mission will allow for similar constraints on supermassive black-hole mimickers. |
1602.02037 | Andres Anabalon | Andres Anabalon and Carlos Batista | A Class of Integrable Metrics | 19 pages, no figures | Phys. Rev. D 93, 064079 (2016) | 10.1103/PhysRevD.93.064079 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In four dimensions, the most general metric admitting two Killing vectors and
a rank-two Killing tensor can be parameterized by ten arbitrary functions of a
single variable. We show that picking a special vierbien, reducing the system
to eight functions, implies the existence of two geodesic and share-free, null
congruences, generated by two principal null directions of the Weyl tensor.
Thus, if the spacetime is an Einstein manifold, the Goldberg-Sachs theorem
implies it is Petrov type D, and by explicit construction, is in the Carter
class. Hence, our analysis provide an straightforward connection between the
most general integrable structure and the Carter family of spacetimes.
| [
{
"created": "Fri, 5 Feb 2016 14:33:14 GMT",
"version": "v1"
}
] | 2016-04-06 | [
[
"Anabalon",
"Andres",
""
],
[
"Batista",
"Carlos",
""
]
] | In four dimensions, the most general metric admitting two Killing vectors and a rank-two Killing tensor can be parameterized by ten arbitrary functions of a single variable. We show that picking a special vierbien, reducing the system to eight functions, implies the existence of two geodesic and share-free, null congruences, generated by two principal null directions of the Weyl tensor. Thus, if the spacetime is an Einstein manifold, the Goldberg-Sachs theorem implies it is Petrov type D, and by explicit construction, is in the Carter class. Hence, our analysis provide an straightforward connection between the most general integrable structure and the Carter family of spacetimes. |
gr-qc/9703048 | Hugo Villegas Brena | T. Matos (1 and 2) and H. Villegas (2) ((1) IFM-UMSNH, Mexico, (2)
Dept. Fisica, CINVESTAV, Mexico) | Post-post-newtonian limit of a dilatonic gravity model | 4 pages, LaTeX, no figures, to appear in the proceedings of the `2nd.
mexican school on gravitation and mathematical physics' | null | null | FIS-CINVESTAV-97-345 | gr-qc | null | We study a solution of the field equations for dilatonic gravity and obtain
its post-post-newtonian limit. It turns out that terms to this and higher
orders in the expansion may become important in strong gravitational fields,
even though the post-newtonian limit coincides with that of General Relativity.
This suggests that strong gravitational fields can only be studied by exact
solutions of the field equations.
| [
{
"created": "Tue, 18 Mar 1997 22:01:31 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Matos",
"T.",
"",
"1 and 2"
],
[
"Villegas",
"H.",
""
]
] | We study a solution of the field equations for dilatonic gravity and obtain its post-post-newtonian limit. It turns out that terms to this and higher orders in the expansion may become important in strong gravitational fields, even though the post-newtonian limit coincides with that of General Relativity. This suggests that strong gravitational fields can only be studied by exact solutions of the field equations. |
1211.0247 | Paul R. Anderson | Paul R. Anderson, Carmen Molina-Paris, Dillon H. Sanders | Validity of the semiclassical approximation during the preheating phase
of chaotic inflation | 8 pages, 3 figures | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The semiclassical approximation has frequently been used to describe the
initial stage of particle production, often called preheating, which occurs
after the inflationary epoch in chaotic models of inflation. During this phase
backreaction effects from the produced particles on the inflaton field are
significant, and one might be concerned about the validity of the semiclassical
approximation, even though large backreaction effects are allowed if the
inflaton field is coupled to a large number of quantum fields. A criterion is
presented for the validity of the semiclassical approximation in this case and
the question of whether this criterion is satisfied during preheating is
addressed.
| [
{
"created": "Thu, 1 Nov 2012 18:33:01 GMT",
"version": "v1"
}
] | 2012-11-02 | [
[
"Anderson",
"Paul R.",
""
],
[
"Molina-Paris",
"Carmen",
""
],
[
"Sanders",
"Dillon H.",
""
]
] | The semiclassical approximation has frequently been used to describe the initial stage of particle production, often called preheating, which occurs after the inflationary epoch in chaotic models of inflation. During this phase backreaction effects from the produced particles on the inflaton field are significant, and one might be concerned about the validity of the semiclassical approximation, even though large backreaction effects are allowed if the inflaton field is coupled to a large number of quantum fields. A criterion is presented for the validity of the semiclassical approximation in this case and the question of whether this criterion is satisfied during preheating is addressed. |
1610.01590 | Michael Kesden | Benjamin Cashen, Adam Aker, Michael Kesden | Gravitomagnetic dynamical friction | 9 pages, 7 figures, PRD published version | Phys. Rev. D 95, 064014 (2017) | 10.1103/PhysRevD.95.064014 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A supermassive black hole moving through a field of stars will
gravitationally scatter the stars, inducing a backreaction force on the black
hole known as dynamical friction. In Newtonian gravity, the axisymmetry of the
system about the black hole's velocity $\mathbf{v}$ implies that the dynamical
friction must be anti-parallel to $\mathbf{v}$. However, in general relativity
the black hole's spin $\mathbf{S}$ need not be parallel to $\mathbf{v}$,
breaking the axisymmetry of the system and generating a new component of
dynamical friction similar to the Lorentz force $\mathbf{F} = q\mathbf{v}
\times \mathbf{B}$ experienced by a particle with charge $q$ moving in a
magnetic field $\mathbf{B}$. We call this new force gravitomagnetic dynamical
friction and calculate its magnitude for a spinning black hole moving through a
field of stars with Maxwellian velocity dispersion $\sigma$, assuming that both
$v$ and $\sigma$ are much less than the speed of light $c$. We use
post-Newtonian equations of motion accurate to $\mathcal{O}(v^3/c^3)$ needed to
capture the effect of spin-orbit coupling and also include direct stellar
capture by the black hole's event horizon. Gravitomagnetic dynamical friction
will cause a black hole with uniform speed to spiral about the direction of its
spin, similar to a charged particle spiraling about a magnetic field line, and
will exert a torque on a supermassive black hole orbiting a galactic center,
causing the angular momentum of this orbit to slowly precess about the
black-hole spin. As this effect is suppressed by a factor $(\sigma/c)^2$ in
nonrelativistic systems, we expect it to be negligible in most astrophysical
contexts but provide this calculation for its theoretical interest and
potential application to relativistic systems.
| [
{
"created": "Tue, 4 Oct 2016 20:05:13 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Mar 2017 00:57:44 GMT",
"version": "v2"
}
] | 2017-03-16 | [
[
"Cashen",
"Benjamin",
""
],
[
"Aker",
"Adam",
""
],
[
"Kesden",
"Michael",
""
]
] | A supermassive black hole moving through a field of stars will gravitationally scatter the stars, inducing a backreaction force on the black hole known as dynamical friction. In Newtonian gravity, the axisymmetry of the system about the black hole's velocity $\mathbf{v}$ implies that the dynamical friction must be anti-parallel to $\mathbf{v}$. However, in general relativity the black hole's spin $\mathbf{S}$ need not be parallel to $\mathbf{v}$, breaking the axisymmetry of the system and generating a new component of dynamical friction similar to the Lorentz force $\mathbf{F} = q\mathbf{v} \times \mathbf{B}$ experienced by a particle with charge $q$ moving in a magnetic field $\mathbf{B}$. We call this new force gravitomagnetic dynamical friction and calculate its magnitude for a spinning black hole moving through a field of stars with Maxwellian velocity dispersion $\sigma$, assuming that both $v$ and $\sigma$ are much less than the speed of light $c$. We use post-Newtonian equations of motion accurate to $\mathcal{O}(v^3/c^3)$ needed to capture the effect of spin-orbit coupling and also include direct stellar capture by the black hole's event horizon. Gravitomagnetic dynamical friction will cause a black hole with uniform speed to spiral about the direction of its spin, similar to a charged particle spiraling about a magnetic field line, and will exert a torque on a supermassive black hole orbiting a galactic center, causing the angular momentum of this orbit to slowly precess about the black-hole spin. As this effect is suppressed by a factor $(\sigma/c)^2$ in nonrelativistic systems, we expect it to be negligible in most astrophysical contexts but provide this calculation for its theoretical interest and potential application to relativistic systems. |
1912.10582 | Roman Konoplya | R. A. Konoplya | Quantum corrected black holes: quasinormal modes, scattering, shadows | 6 pages, 3 figures, revtex, some numerical data is corrected, new
material is added | Phys.Lett. B804 (2020) 135363 | 10.1016/j.physletb.2020.135363 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The spherically symmetric deformation of the Schwarzschild solution owing to
the quantum corrections to gravity is known as Kazakov-Solodukhin black-hole
metric. Neglecting non-spherical deformations of the background the problem was
solved non-perturbatively. Here we analyze the basic characteristics of this
geometry, such as: quasinormal modes and grey-body factors of fields of various
spin and shadow cast by this black hole. The WKB approach and time-domain
integration method, which we used for calculation of quasinormal modes, are in
a good concordance. The analytical formula for quasinormal modes is deduced in
the eikonal regime. The radius of shadow is decreasing when the quantum
deformation is turned on.
| [
{
"created": "Mon, 23 Dec 2019 01:59:18 GMT",
"version": "v1"
},
{
"created": "Sun, 29 Dec 2019 22:16:33 GMT",
"version": "v2"
}
] | 2020-03-20 | [
[
"Konoplya",
"R. A.",
""
]
] | The spherically symmetric deformation of the Schwarzschild solution owing to the quantum corrections to gravity is known as Kazakov-Solodukhin black-hole metric. Neglecting non-spherical deformations of the background the problem was solved non-perturbatively. Here we analyze the basic characteristics of this geometry, such as: quasinormal modes and grey-body factors of fields of various spin and shadow cast by this black hole. The WKB approach and time-domain integration method, which we used for calculation of quasinormal modes, are in a good concordance. The analytical formula for quasinormal modes is deduced in the eikonal regime. The radius of shadow is decreasing when the quantum deformation is turned on. |
2201.12004 | Yaoguang Zheng | Wen-Xiang Chen, Yao-Guang Zheng | Analysis on superradiant stability of BTZ Black Hole | arXiv admin note: text overlap with arXiv:2103.04239; text overlap
with arXiv:2005.10268 by other authors | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper adds a new variable y($\mu^{\prime}=y(\omega+m N^{\phi})$) to
extend the results of the classic paper. We exploit the properties of curve
integrals. When y is greater than a certain limit, the effective potential of
the equation has no pole, then there is no potential well outside the event
horizon, when $\sqrt{2(m^2)}/{ r^2_+}< \omega < m\varOmega_H$,so the BTZ black
hole was superradiantly stable at that time.
| [
{
"created": "Fri, 28 Jan 2022 09:31:08 GMT",
"version": "v1"
}
] | 2022-07-26 | [
[
"Chen",
"Wen-Xiang",
""
],
[
"Zheng",
"Yao-Guang",
""
]
] | This paper adds a new variable y($\mu^{\prime}=y(\omega+m N^{\phi})$) to extend the results of the classic paper. We exploit the properties of curve integrals. When y is greater than a certain limit, the effective potential of the equation has no pole, then there is no potential well outside the event horizon, when $\sqrt{2(m^2)}/{ r^2_+}< \omega < m\varOmega_H$,so the BTZ black hole was superradiantly stable at that time. |
0901.0851 | Gerhard Zumbusch | Gerhard Zumbusch | Finite Element, Discontinuous Galerkin, and Finite Difference Evolution
Schemes in Spacetime | final version | Class.Quant.Grav.26:175011,2009 | 10.1088/0264-9381/26/17/175011 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Numerical schemes for Einstein's vacuum equation are developed. Einstein's
equation in harmonic gauge is second order symmetric hyperbolic. It is
discretized in four-dimensional spacetime by Finite Differences, Finite
Elements, and Interior Penalty Discontinuous Galerkin methods, the latter
related to Regge calculus. The schemes are split into space and time and new
time-stepping schemes for wave equations are derived. The methods are evaluated
for linear and non-linear test problems of the Apples-with-Apples collection.
| [
{
"created": "Wed, 7 Jan 2009 18:34:11 GMT",
"version": "v1"
},
{
"created": "Mon, 20 Jul 2009 14:49:17 GMT",
"version": "v2"
}
] | 2009-08-17 | [
[
"Zumbusch",
"Gerhard",
""
]
] | Numerical schemes for Einstein's vacuum equation are developed. Einstein's equation in harmonic gauge is second order symmetric hyperbolic. It is discretized in four-dimensional spacetime by Finite Differences, Finite Elements, and Interior Penalty Discontinuous Galerkin methods, the latter related to Regge calculus. The schemes are split into space and time and new time-stepping schemes for wave equations are derived. The methods are evaluated for linear and non-linear test problems of the Apples-with-Apples collection. |
2101.06600 | Che-Yu Chen | Che-Yu Chen, Sohyun Park | Black hole quasinormal modes and isospectrality in Deser-Woodard
nonlocal gravity | 10 pages | Phys. Rev. D 103, 064029 (2021) | 10.1103/PhysRevD.103.064029 | CERN-TH-2021-011 | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | We investigate the gravitational perturbations of the Schwarzschild black
hole in the nonlocal gravity model recently proposed by Deser and Woodard
(DW-II). The analysis is performed in the localized version in which the
nonlocal corrections are represented by some auxiliary scalar fields. We find
that the nonlocal corrections do not affect the axial gravitational
perturbations, and hence the axial modes are completely identical to those in
General Relativity (GR). However, the polar modes get different from their GR
counterparts when the scalar fields are excited at the background level. In
such a case the polar modes are sourced by an additional massless scalar mode
and, as a result, the isospectrality between the axial and the polar modes
breaks down. We also perform a similar analysis for the predecessor of this
model (DW-I) and arrive at the same conclusion for it.
| [
{
"created": "Sun, 17 Jan 2021 06:11:02 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Mar 2021 14:37:17 GMT",
"version": "v2"
}
] | 2021-03-19 | [
[
"Chen",
"Che-Yu",
""
],
[
"Park",
"Sohyun",
""
]
] | We investigate the gravitational perturbations of the Schwarzschild black hole in the nonlocal gravity model recently proposed by Deser and Woodard (DW-II). The analysis is performed in the localized version in which the nonlocal corrections are represented by some auxiliary scalar fields. We find that the nonlocal corrections do not affect the axial gravitational perturbations, and hence the axial modes are completely identical to those in General Relativity (GR). However, the polar modes get different from their GR counterparts when the scalar fields are excited at the background level. In such a case the polar modes are sourced by an additional massless scalar mode and, as a result, the isospectrality between the axial and the polar modes breaks down. We also perform a similar analysis for the predecessor of this model (DW-I) and arrive at the same conclusion for it. |
1001.4733 | Norbert Wex | N. Wex, M. Kramer | Generic Gravity Tests with the Double Pulsar | 3 pages, no figures, Proceedings of the 12th Marcel Grossmann Meeting
on General Relativity (MG 12), Paris, France, 12-18 Jul 2009 | null | null | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Presently the double pulsar allows for the measurement of six post-Keplerian
parameters. In addition, its double-line nature gives access to the projected
semi-major axes of both orbits. We use this wealth of information to pose some
very general restrictions on a wide class of conservative and semi-conservative
theories of gravity.
| [
{
"created": "Tue, 26 Jan 2010 16:21:02 GMT",
"version": "v1"
}
] | 2010-01-27 | [
[
"Wex",
"N.",
""
],
[
"Kramer",
"M.",
""
]
] | Presently the double pulsar allows for the measurement of six post-Keplerian parameters. In addition, its double-line nature gives access to the projected semi-major axes of both orbits. We use this wealth of information to pose some very general restrictions on a wide class of conservative and semi-conservative theories of gravity. |
0910.0673 | Rafael Sorkin | Rafael D. Sorkin | Light, Links and Causal Sets | plainTeX, 18 pages, no figures. Most current version is available at
http://www.physics.syr.edu/~sorkin/some.papers/ (or wherever my home-page may
be) | J.Phys.Conf.Ser.174:012018,2009 | 10.1088/1742-6596/174/1/012018 | null | gr-qc cond-mat.stat-mech hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | After sketching a context in which to seek observable signals of
spatio-temporal discreteness, I briefly review the status of the causal set
program for quantum gravity, concluding with a simple model for the field
produced by a moving charge in a background causal set.
| [
{
"created": "Mon, 5 Oct 2009 04:12:54 GMT",
"version": "v1"
}
] | 2010-11-02 | [
[
"Sorkin",
"Rafael D.",
""
]
] | After sketching a context in which to seek observable signals of spatio-temporal discreteness, I briefly review the status of the causal set program for quantum gravity, concluding with a simple model for the field produced by a moving charge in a background causal set. |
gr-qc/0202085 | Robert T. Jantzen | Donato Bini and Robert T. Jantzen | Circular Holonomy, Clock Effects and Gravitoelectromagnetism: Still
Going Around in Circles After All These Years | 27 pages, latex(2e), ws-p9-75x6-50 class, uses overcite package, 7
pictex figures, 3 eps figures; to appear in the Proceedings of the 9th ICRA
Network Workshop on Fermi and Astrophysics (2001), Eds. R. Ruffini and C.
Sigismondi, World Scientific, 2003. Killing tensor remarks corrected. Figure
7 slightly corrected | Nuovo Cim.B117:983-1008,2003 | null | null | gr-qc | null | The historical origins of Fermi-Walker transport and Fermi coordinates and
the construction of Fermi-Walker transported frames in black hole spacetimes
are reviewed. For geodesics this transport reduces to parallel transport and
these frames can be explicitly constructed using a Killing-Yano tensor as shown
by Marck. For accelerated or geodesic circular orbits in such spacetimes, both
parallel and Fermi-Walker transported frames can be given, and allow one to
study circular holonomy and related clock and spin transport effects. In
particular the total angle of rotation that a spin vector undergoes around a
closed loop can be expressed in a factored form, where each factor is due to a
different relativistic effect, in contrast with the usual sum of terms
decomposition. Finally the Thomas precession frequency is shown to be a special
case of the simple relationship between the parallel transport and Fermi-Walker
transport frequencies for stationary circular orbits.
| [
{
"created": "Sun, 24 Feb 2002 23:21:49 GMT",
"version": "v1"
},
{
"created": "Thu, 9 Jan 2003 21:39:43 GMT",
"version": "v2"
}
] | 2010-11-11 | [
[
"Bini",
"Donato",
""
],
[
"Jantzen",
"Robert T.",
""
]
] | The historical origins of Fermi-Walker transport and Fermi coordinates and the construction of Fermi-Walker transported frames in black hole spacetimes are reviewed. For geodesics this transport reduces to parallel transport and these frames can be explicitly constructed using a Killing-Yano tensor as shown by Marck. For accelerated or geodesic circular orbits in such spacetimes, both parallel and Fermi-Walker transported frames can be given, and allow one to study circular holonomy and related clock and spin transport effects. In particular the total angle of rotation that a spin vector undergoes around a closed loop can be expressed in a factored form, where each factor is due to a different relativistic effect, in contrast with the usual sum of terms decomposition. Finally the Thomas precession frequency is shown to be a special case of the simple relationship between the parallel transport and Fermi-Walker transport frequencies for stationary circular orbits. |
gr-qc/9610040 | Raphael Bousso | Raphael Bousso (DAMTP, Cambridge) | Pair Creation of Dilaton Black Holes in Extended Inflation | 23 pages, LaTeX, 6 figures; submitted to Phys. Rev. D | Phys. Rev. D 55, 4889 (1997) | 10.1103/PhysRevD.55.4889 | DAMTP/R-96/42 | gr-qc hep-th | null | Dilatonic Charged Nariai instantons mediate the nucleation of black hole
pairs during extended chaotic inflation. Depending on the dilaton and inflaton
fields, the black holes are described by one of two approximations in the
Lorentzian regime. For each case we find Euclidean solutions that satisfy the
no boundary proposal. The complex initial values of the dilaton and inflaton
are determined, and the pair creation rate is calculated from the Euclidean
action. Similar to standard inflation, black holes are abundantly produced near
the Planck boundary, but highly suppressed later on. An unusual feature we find
is that the earlier in inflation that the dilatonic black holes are created,
the more highly charged they can be.
| [
{
"created": "Thu, 17 Oct 1996 18:20:28 GMT",
"version": "v1"
}
] | 2016-08-24 | [
[
"Bousso",
"Raphael",
"",
"DAMTP, Cambridge"
]
] | Dilatonic Charged Nariai instantons mediate the nucleation of black hole pairs during extended chaotic inflation. Depending on the dilaton and inflaton fields, the black holes are described by one of two approximations in the Lorentzian regime. For each case we find Euclidean solutions that satisfy the no boundary proposal. The complex initial values of the dilaton and inflaton are determined, and the pair creation rate is calculated from the Euclidean action. Similar to standard inflation, black holes are abundantly produced near the Planck boundary, but highly suppressed later on. An unusual feature we find is that the earlier in inflation that the dilatonic black holes are created, the more highly charged they can be. |
2311.08465 | Parampreet Singh | Meysam Motaharfar, Parampreet Singh, Eklavya Thareja | On the classicality and uniqueness in loop quantization of Bianchi-I
spacetimes | 20 pages, 15 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In loop quantum cosmology, ambiguities in the Hamiltonian constraint can
result in models with varying phenomenological predictions. In the homogeneous
isotropic models, these ambiguities were settled, and the improved dynamics was
found to be a unique and phenomenologically viable choice. This issue has
remained unsettled on the inclusion of anisotropies, and in the Bianchi-I model
there exist two generalizations of isotropic improved dynamics. In the first of
these, labelled as $\bar \mu$ quantization, the edge length of holonomies
depends on the inverse of the directional scale factor. This quantization has
been favored since it results in universal bounds on energy density and
anisotropic shear, and can be viably formulated for non-compact as well as
compact spatial manifolds. However, there exists an earlier quantization,
labelled as $\bar \mu'$ quantization, where edge lengths of holonomies depend
on the inverse of the square root of directional triads. This quantization is
also non-singular and so far believed to yield a consistent physical picture
for spatially compact manifolds. We examine the issue of the physical viability
of these quantizations for different types of matter in detail by performing a
large number of numerical simulations. Our analysis reveals certain limitations
which have so far remained unnoticed. We find that while being non-singular,
the $\bar \mu'$ quantization suffers from a surprising problem where one of the
triad components and associated polymerized term retains Planckian character
even at large volumes. As a result, not only is the anisotropic shear not
preserved across the bounce, which is most highlighted in the vacuum case, but
the universe can exhibit an unexpected cyclic evolution. These problematic
features are absent from the $\bar \mu$ quantization leaving it as the only
viable prescription for loop quantizing the Bianchi-I model.
| [
{
"created": "Tue, 14 Nov 2023 19:00:23 GMT",
"version": "v1"
}
] | 2023-11-16 | [
[
"Motaharfar",
"Meysam",
""
],
[
"Singh",
"Parampreet",
""
],
[
"Thareja",
"Eklavya",
""
]
] | In loop quantum cosmology, ambiguities in the Hamiltonian constraint can result in models with varying phenomenological predictions. In the homogeneous isotropic models, these ambiguities were settled, and the improved dynamics was found to be a unique and phenomenologically viable choice. This issue has remained unsettled on the inclusion of anisotropies, and in the Bianchi-I model there exist two generalizations of isotropic improved dynamics. In the first of these, labelled as $\bar \mu$ quantization, the edge length of holonomies depends on the inverse of the directional scale factor. This quantization has been favored since it results in universal bounds on energy density and anisotropic shear, and can be viably formulated for non-compact as well as compact spatial manifolds. However, there exists an earlier quantization, labelled as $\bar \mu'$ quantization, where edge lengths of holonomies depend on the inverse of the square root of directional triads. This quantization is also non-singular and so far believed to yield a consistent physical picture for spatially compact manifolds. We examine the issue of the physical viability of these quantizations for different types of matter in detail by performing a large number of numerical simulations. Our analysis reveals certain limitations which have so far remained unnoticed. We find that while being non-singular, the $\bar \mu'$ quantization suffers from a surprising problem where one of the triad components and associated polymerized term retains Planckian character even at large volumes. As a result, not only is the anisotropic shear not preserved across the bounce, which is most highlighted in the vacuum case, but the universe can exhibit an unexpected cyclic evolution. These problematic features are absent from the $\bar \mu$ quantization leaving it as the only viable prescription for loop quantizing the Bianchi-I model. |
gr-qc/9611068 | Sardanashvily Gennadi | G. Sardanashvily and K. Kirillov | Energy-Momentum in Gauge Gravitation Theory | 24 pages, latex, no figures | null | null | null | gr-qc | null | Building on the first variational formula of the calculus of variations, one
can derive the energy-momentum conservation laws from the condition of the Lie
derivative of gravitation Lagrangians along vector fields corresponding to
generators of general covariant transformations to be equal to zero. The goal
is to construct these vector fields. In gauge gravitation theory, the
difficulty arises because of fermion fields. General covariant transformations
fail to preserve the Dirac spin structure $S_h$ on a world manifold $X$ which
is associated with a certain tetrad field $h$. We introduce the universal Dirac
spin structure $S\to\Sigma\to X$ such that, given a tetrad field $h:X\to
\Sigma$, the restriction of $S$ to $h(X)$ is isomorphic to $S_h$. The canonical
lift of vector fields on $X$ onto $S$ is constructed. We discover the
corresponding stress-energy-momentum conservation law. The gravitational model
in the presence of a background spin structure also is examined.
| [
{
"created": "Thu, 28 Nov 1996 23:40:25 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sardanashvily",
"G.",
""
],
[
"Kirillov",
"K.",
""
]
] | Building on the first variational formula of the calculus of variations, one can derive the energy-momentum conservation laws from the condition of the Lie derivative of gravitation Lagrangians along vector fields corresponding to generators of general covariant transformations to be equal to zero. The goal is to construct these vector fields. In gauge gravitation theory, the difficulty arises because of fermion fields. General covariant transformations fail to preserve the Dirac spin structure $S_h$ on a world manifold $X$ which is associated with a certain tetrad field $h$. We introduce the universal Dirac spin structure $S\to\Sigma\to X$ such that, given a tetrad field $h:X\to \Sigma$, the restriction of $S$ to $h(X)$ is isomorphic to $S_h$. The canonical lift of vector fields on $X$ onto $S$ is constructed. We discover the corresponding stress-energy-momentum conservation law. The gravitational model in the presence of a background spin structure also is examined. |
1807.03864 | Masooma Ali | Masooma Ali, Syed Moeez Hassan, Viqar Husain | The Universe as an Oscillator | 11 pages, 2 figures, references added | Phys. Rev. D 98, 086002 (2018) | 10.1103/PhysRevD.98.086002 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the idea of using a matter time gauge in quantum gravity to quantum
cosmology. For the Friedmann-Lemaitre-Robertson-Walker (FLRW) Universe with
dust and cosmological constant $\Lambda$, we show that the dynamics maps
exactly to the simple harmonic oscillator in the dust-time gauge. For $\Lambda
>0$ the oscillator frequency is imaginary, for $\Lambda<0$ it is real, and for
$\Lambda=0$ the Universe is a free particle. This result provides (i) a simple
demonstration of non-perturbative singularity avoidance in quantum gravity for
all $\Lambda$, (ii) an exact Lorentzian Hartle-Hawking wave function, and (iii)
gives the present age of the Universe as the characteristic decay time of the
propagator.
| [
{
"created": "Tue, 10 Jul 2018 21:08:25 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Jul 2018 13:43:41 GMT",
"version": "v2"
}
] | 2018-10-10 | [
[
"Ali",
"Masooma",
""
],
[
"Hassan",
"Syed Moeez",
""
],
[
"Husain",
"Viqar",
""
]
] | We apply the idea of using a matter time gauge in quantum gravity to quantum cosmology. For the Friedmann-Lemaitre-Robertson-Walker (FLRW) Universe with dust and cosmological constant $\Lambda$, we show that the dynamics maps exactly to the simple harmonic oscillator in the dust-time gauge. For $\Lambda >0$ the oscillator frequency is imaginary, for $\Lambda<0$ it is real, and for $\Lambda=0$ the Universe is a free particle. This result provides (i) a simple demonstration of non-perturbative singularity avoidance in quantum gravity for all $\Lambda$, (ii) an exact Lorentzian Hartle-Hawking wave function, and (iii) gives the present age of the Universe as the characteristic decay time of the propagator. |
1208.4770 | Iver Brevik | I. Brevik, R. Myrzakulov, S. Nojiri and S. D. Odintsov | Turbulence and Little Rip Cosmology | null | Physical Review D 86, N6, 063007 (2012) | 10.1103/PhysRevD.86.063007 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A variety of conditions is considered under which the cosmic dark fluid may
be able to develop a future Big Rip or Little Rip singularity. Both
one-component and two-component models are considered. In the last-mentioned
case we present a way in which the fluid can be decomposed into two components,
one non-turbulent (ideal) and one turbulent part, obeying two different
equations of state. For the non-turbulent part, the thermodynamical parameter,
commonly called w, is assumed to be less than -1 throughout. For the turbulent
part, it turns out that it is sufficient that w{turb} lies in the quintessence
region in order to lead to a singularity. Both Big Rip and Little Rip behaviour
for dark energy are found. In the one-component case, we examine how the
universe may develop from a viscous era with constant bulk viscosity into a
turbulent era, the turbulence in effect protecting the universe from
encountering the singularity at all. The equivalent description of the same
cosmology in terms of inhomogeneous (imperfect) fluid is also presented.
| [
{
"created": "Thu, 23 Aug 2012 14:40:00 GMT",
"version": "v1"
}
] | 2012-09-25 | [
[
"Brevik",
"I.",
""
],
[
"Myrzakulov",
"R.",
""
],
[
"Nojiri",
"S.",
""
],
[
"Odintsov",
"S. D.",
""
]
] | A variety of conditions is considered under which the cosmic dark fluid may be able to develop a future Big Rip or Little Rip singularity. Both one-component and two-component models are considered. In the last-mentioned case we present a way in which the fluid can be decomposed into two components, one non-turbulent (ideal) and one turbulent part, obeying two different equations of state. For the non-turbulent part, the thermodynamical parameter, commonly called w, is assumed to be less than -1 throughout. For the turbulent part, it turns out that it is sufficient that w{turb} lies in the quintessence region in order to lead to a singularity. Both Big Rip and Little Rip behaviour for dark energy are found. In the one-component case, we examine how the universe may develop from a viscous era with constant bulk viscosity into a turbulent era, the turbulence in effect protecting the universe from encountering the singularity at all. The equivalent description of the same cosmology in terms of inhomogeneous (imperfect) fluid is also presented. |
gr-qc/9909004 | Jose Geraldo Pereira | V. C. de Andrade, L. C. T. Guillen and J. G. Pereira | Teleparallel Equivalent of the Kaluza-Klein Theory | 5 pages, no figures, RevTeX; title and presentation changes, a new
paragraph and references added, version to appear in Phys. Rev. D | Phys.Rev. D61 (2000) 084031 | 10.1103/PhysRevD.61.084031 | null | gr-qc hep-th | null | Relying upon the equivalence between a gauge theory for the translation group
and general relativity, a teleparallel version of the original Kaluza-Klein
theory is developed. In this model, only the internal space (fiber) turns out
to be five dimensional, spacetime being kept always four dimensional. A
five-dimensional translational gauge theory is obtained which unifies, in the
sense of Kaluza-Klein theories, gravitational and electromagnetic interactions.
| [
{
"created": "Wed, 1 Sep 1999 17:20:42 GMT",
"version": "v1"
},
{
"created": "Wed, 9 Feb 2000 18:13:26 GMT",
"version": "v2"
}
] | 2009-10-31 | [
[
"de Andrade",
"V. C.",
""
],
[
"Guillen",
"L. C. T.",
""
],
[
"Pereira",
"J. G.",
""
]
] | Relying upon the equivalence between a gauge theory for the translation group and general relativity, a teleparallel version of the original Kaluza-Klein theory is developed. In this model, only the internal space (fiber) turns out to be five dimensional, spacetime being kept always four dimensional. A five-dimensional translational gauge theory is obtained which unifies, in the sense of Kaluza-Klein theories, gravitational and electromagnetic interactions. |
gr-qc/0005033 | Poghos F. Kazarian | Poghos F. Kazarian | On the Tensor Field Inflation in the GR Homogeneous Cosmological Model | Accepted for publication in Phys Rev D; referee's comments and
suggestions considered | null | null | YSU preprint 20/03/2000 | gr-qc | null | The homogeneous cosmological model in GR is proposed, where the vacuum
energy, which can cause the inflation, is described by tensor field rather than
by commonly used in inflationary scenarios scalar field. It is shown that if
the initial values of the field are sufficiently big (comparable with the
Planck units), under the condition of the tensor field's slow change in the
beginning the regime of the quasiexponential inflation can exist. Numerical
solutions for the inflationary stage are obtained that confirm the validity of
the approximate solutions. Inflation takes place under wide range of initial
conditions provided that the tensor field satisfies the condition imposed on
the initial values of the tensor field ${\phi^0}_0(0)\approx -{\phi^i}_i(0)$
(i=1,2,3). That condition also arises from the requirement to satisfy existing
observational data.
| [
{
"created": "Wed, 10 May 2000 16:57:39 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Dec 2000 01:11:25 GMT",
"version": "v2"
},
{
"created": "Sun, 18 Feb 2001 21:30:11 GMT",
"version": "v3"
}
] | 2007-05-23 | [
[
"Kazarian",
"Poghos F.",
""
]
] | The homogeneous cosmological model in GR is proposed, where the vacuum energy, which can cause the inflation, is described by tensor field rather than by commonly used in inflationary scenarios scalar field. It is shown that if the initial values of the field are sufficiently big (comparable with the Planck units), under the condition of the tensor field's slow change in the beginning the regime of the quasiexponential inflation can exist. Numerical solutions for the inflationary stage are obtained that confirm the validity of the approximate solutions. Inflation takes place under wide range of initial conditions provided that the tensor field satisfies the condition imposed on the initial values of the tensor field ${\phi^0}_0(0)\approx -{\phi^i}_i(0)$ (i=1,2,3). That condition also arises from the requirement to satisfy existing observational data. |
1212.2432 | Emanuel Gallo | Emanuel Gallo and O. M. Moreschi | Approximation Method for the Relaxed Covariant Form of the Gravitational
Field Equations for Particles | 8 pages | Journal of Modern Physics, Vol. 3 No. 9A, 2012, pp. 1247-1254
(Special Issue on Gravitation, Astrophysics and Cosmology) | 10.4236/jmp.2012.329161 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a study of the so called relaxed field equations of general
relativity in terms of a decomposition of the metric; which is designed to deal
with the notion of particles. Several known results are generalized to a
coordinate free covariant discussion. We apply our techniques to the study of a
particle up to second order.
| [
{
"created": "Tue, 11 Dec 2012 14:19:35 GMT",
"version": "v1"
}
] | 2012-12-12 | [
[
"Gallo",
"Emanuel",
""
],
[
"Moreschi",
"O. M.",
""
]
] | We present a study of the so called relaxed field equations of general relativity in terms of a decomposition of the metric; which is designed to deal with the notion of particles. Several known results are generalized to a coordinate free covariant discussion. We apply our techniques to the study of a particle up to second order. |
2004.13276 | Zhi Liu | Micheal S. Berger and Zhi Liu | Observables in quantum field theory on a collapsing black hole
background | 6 pages, 3 figures, the paper is rewritten, additional results on
perceived observables added | Phys. Lett. B 811 (2020) 135934 | 10.1016/j.physletb.2020.135934 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the quantum radiation from a curved background using scalar
observables constructed from the (1+1) dimensional renormalized stress-energy
tensor (RSET). We compute energy density $\cal U$, flux $\cal F$ and pressure
$\cal P$ for an arbitrary collapse scenario and an arbitrary observer. The
results show a clear structure: $\cal F - \cal U$ represents the
collapse-independent ingoing modes, $\cal F + \cal U$ represents the
collapse-dependent outgoing modes and $\cal P - \cal U$ represents the trace
anomaly. We also compute the observables constructed from the perception
renormalized stress-energy tensor (PeRSET). We find they have the same
collapse-dependent contribution comparing to their RSET-related counterparts.
For free-falling observers, in particular, the PeRSET-related observables are
the same as the corresponding RSET-related ones, except the energy densities
differ by the trace anomaly.
| [
{
"created": "Tue, 28 Apr 2020 04:05:03 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Nov 2020 15:49:10 GMT",
"version": "v2"
}
] | 2020-11-13 | [
[
"Berger",
"Micheal S.",
""
],
[
"Liu",
"Zhi",
""
]
] | We study the quantum radiation from a curved background using scalar observables constructed from the (1+1) dimensional renormalized stress-energy tensor (RSET). We compute energy density $\cal U$, flux $\cal F$ and pressure $\cal P$ for an arbitrary collapse scenario and an arbitrary observer. The results show a clear structure: $\cal F - \cal U$ represents the collapse-independent ingoing modes, $\cal F + \cal U$ represents the collapse-dependent outgoing modes and $\cal P - \cal U$ represents the trace anomaly. We also compute the observables constructed from the perception renormalized stress-energy tensor (PeRSET). We find they have the same collapse-dependent contribution comparing to their RSET-related counterparts. For free-falling observers, in particular, the PeRSET-related observables are the same as the corresponding RSET-related ones, except the energy densities differ by the trace anomaly. |
gr-qc/0106066 | Gaetano Lambiase | G. Papini, G. Lambiase | Spin-Rotation Coupling in Muon g-2 Experiments | 3 pages, RevTex file | Phys.Lett.A294:175-178,2002 | 10.1016/S0375-9601(02)00040-3 | null | gr-qc | null | Spin-rotation coupling, or Mashhoon effect, is a phenomenon associated with
rotating observers. We show that the effect exists and plays a fundamental role
in the determination of the anomalous magnetic moment of the muon.
| [
{
"created": "Thu, 21 Jun 2001 10:19:41 GMT",
"version": "v1"
}
] | 2011-09-14 | [
[
"Papini",
"G.",
""
],
[
"Lambiase",
"G.",
""
]
] | Spin-rotation coupling, or Mashhoon effect, is a phenomenon associated with rotating observers. We show that the effect exists and plays a fundamental role in the determination of the anomalous magnetic moment of the muon. |
2101.06378 | Abolhassan Mohammadi | Abolhassan Mohammadi, Tayeb Golanbari, Kazuharu Bamba, Iarley P. Lobo | Tsallis holographic dark energy for inflation | 7 pages, 4 figures | Phys. Rev. D 103, 083505 (2021) | 10.1103/PhysRevD.103.083505 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The application of holographic principle in very early time is studied. The
consideration of the principle in the late-time evolution will be a good
motivation to study its role at the time of inflation. Since the length scale
is expected to be small during inflation, the resulted energy density form the
holographic principle is expected to be large enough to drive inflation. The
entropy of the system is the main part of the holographic principle, in which
modifying entropy will leads to a modified energy density. Here, instead of the
original entropy, we are going to apply a modified entropy, known as Tsallis
entropy which includes quantum corrections. The length scale is assumed to be
GO length scale. Finding an analytical solution for the model, the slow-roll
parameters, scalar spectral index, and tensor-to-scalar ratio are calculated.
Comparing the result, with Planck $r-n_s$ diagram, we could find a parametric
space for the constants of the model. Then, a correspondence between the
holographic dark energy and the scalar field is constructed, and the outcome
potentials are investigated.
| [
{
"created": "Sat, 16 Jan 2021 05:57:44 GMT",
"version": "v1"
},
{
"created": "Thu, 25 Mar 2021 09:43:34 GMT",
"version": "v2"
}
] | 2021-04-21 | [
[
"Mohammadi",
"Abolhassan",
""
],
[
"Golanbari",
"Tayeb",
""
],
[
"Bamba",
"Kazuharu",
""
],
[
"Lobo",
"Iarley P.",
""
]
] | The application of holographic principle in very early time is studied. The consideration of the principle in the late-time evolution will be a good motivation to study its role at the time of inflation. Since the length scale is expected to be small during inflation, the resulted energy density form the holographic principle is expected to be large enough to drive inflation. The entropy of the system is the main part of the holographic principle, in which modifying entropy will leads to a modified energy density. Here, instead of the original entropy, we are going to apply a modified entropy, known as Tsallis entropy which includes quantum corrections. The length scale is assumed to be GO length scale. Finding an analytical solution for the model, the slow-roll parameters, scalar spectral index, and tensor-to-scalar ratio are calculated. Comparing the result, with Planck $r-n_s$ diagram, we could find a parametric space for the constants of the model. Then, a correspondence between the holographic dark energy and the scalar field is constructed, and the outcome potentials are investigated. |
gr-qc/0506030 | Masoud Alimohammadi | H. Mohseni Sadjadi and M. Alimohammadi | Electrostatic self-energy and Bekenstein entropy bound in the massive
Schwinger model | 14 pages, accepted for publication in "Gen. Rel. Grav. (2005)" | Gen.Rel.Grav. 37 (2005) 1809-1822 | 10.1007/s10714-005-0160-6 | null | gr-qc hep-th | null | We obtain the electrostatic energy of two opposite charges near the horizon
of stationary black-holes in the massive Schwinger model. Besides the confining
aspects of the model, we discuss the Bekenstein entropy upper bound of a
charged object using the generalized second law. We show that despite the
massless case, in the massive Schwinger model the entropy of the black hole and
consequently the Bekenstein bound are altered by the vacuum polarization.
| [
{
"created": "Mon, 6 Jun 2005 07:39:35 GMT",
"version": "v1"
}
] | 2015-06-25 | [
[
"Sadjadi",
"H. Mohseni",
""
],
[
"Alimohammadi",
"M.",
""
]
] | We obtain the electrostatic energy of two opposite charges near the horizon of stationary black-holes in the massive Schwinger model. Besides the confining aspects of the model, we discuss the Bekenstein entropy upper bound of a charged object using the generalized second law. We show that despite the massless case, in the massive Schwinger model the entropy of the black hole and consequently the Bekenstein bound are altered by the vacuum polarization. |
1108.1921 | Ali Nur Nurbaki | Ali Nur Nurbaki | Killing-Yano Tensors of Valence-2 in the Standard Kaluza-Klein Theory | M. Sc. Thesis, 38 pages | null | null | null | gr-qc math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This work is constructed on two main concepts: Killing-Yano symmetry and the
Kaluza-Klein theory. Those concepts are reviewed in the first three chapters.
In the fourth chapter firstly Killing-Yano equations of valence-2 are obtained
for a general 5-dimensional metric and then reduced for the Minkowski metric.
It is seen that in order to save the existence of Killing-Yano tensors with the
fifth components some conditions must be satisfied
| [
{
"created": "Tue, 9 Aug 2011 13:15:44 GMT",
"version": "v1"
},
{
"created": "Thu, 11 Aug 2011 19:37:30 GMT",
"version": "v2"
}
] | 2011-08-12 | [
[
"Nurbaki",
"Ali Nur",
""
]
] | This work is constructed on two main concepts: Killing-Yano symmetry and the Kaluza-Klein theory. Those concepts are reviewed in the first three chapters. In the fourth chapter firstly Killing-Yano equations of valence-2 are obtained for a general 5-dimensional metric and then reduced for the Minkowski metric. It is seen that in order to save the existence of Killing-Yano tensors with the fifth components some conditions must be satisfied |
1305.1564 | Amos Ori | Amos Ori | Late-time tails in extremal Reissner-Nordstrom spacetime | 4 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This note discusses the late-time decay of perturbations outside extremal
Reissner-Nordstrom black hole. We consider individual spherical-harmonic modes
$l$ of massless scalar field. The initial data are assumed to be of compact
support, with generic regular behavior across the horizon. The scalar
perturbations are found to decay at late time as $t^{-(2l+2)}$. We also provide
the spatial dependence of the late-time tails, including the exact overall
pre-factor.
| [
{
"created": "Tue, 7 May 2013 15:54:02 GMT",
"version": "v1"
}
] | 2013-05-08 | [
[
"Ori",
"Amos",
""
]
] | This note discusses the late-time decay of perturbations outside extremal Reissner-Nordstrom black hole. We consider individual spherical-harmonic modes $l$ of massless scalar field. The initial data are assumed to be of compact support, with generic regular behavior across the horizon. The scalar perturbations are found to decay at late time as $t^{-(2l+2)}$. We also provide the spatial dependence of the late-time tails, including the exact overall pre-factor. |
2207.05029 | Philip Klaus Schwartz | Domenico Giulini, Andr\'e Gro{\ss}ardt, Philip K. Schwartz | Coupling Quantum Matter and Gravity | 53+6 pages (main text + references), 1 figure. Invited contribution
to the forthcoming book "Modified and Quantum Gravity - From Theory to
Experimental Searches on All Scales", eds. C. L\"ammerzahl and C. Pfeifer.
v2: Added exercises and concluding remarks; minor reformulations | in: C. Pfeifer, C. L\"ammerzahl (eds.), Modified and Quantum
Gravity, Lecture Notes in Physics 1017 (Springer, Cham, 2023) | 10.1007/978-3-031-31520-6_16 | null | gr-qc physics.atom-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this contribution we deal with several issues one encounters when trying
to couple quantum matter to classical gravitational fields. We start with a
general background discussion and then move on to two more technical sections.
In the first technical part we consider the question how the Hamiltonian of a
composite two-particle system in an external gravitational field can be
computed in a systematic post-Newtonian setting without backreaction. This
enables us to reliably estimate the consistency and completeness of less
systematic and more intuitive approaches that attempt to solve this problem by
adding `relativistic effects' by hand. In the second technical part we consider
the question of how quantum matter may act as source for classical
gravitational fields via the semiclassical Einstein equations. Statements to
the effect that this approach is fundamentally inconsistent are critically
reviewed.
| [
{
"created": "Mon, 11 Jul 2022 17:31:30 GMT",
"version": "v1"
},
{
"created": "Mon, 21 Nov 2022 19:06:37 GMT",
"version": "v2"
}
] | 2023-10-13 | [
[
"Giulini",
"Domenico",
""
],
[
"Großardt",
"André",
""
],
[
"Schwartz",
"Philip K.",
""
]
] | In this contribution we deal with several issues one encounters when trying to couple quantum matter to classical gravitational fields. We start with a general background discussion and then move on to two more technical sections. In the first technical part we consider the question how the Hamiltonian of a composite two-particle system in an external gravitational field can be computed in a systematic post-Newtonian setting without backreaction. This enables us to reliably estimate the consistency and completeness of less systematic and more intuitive approaches that attempt to solve this problem by adding `relativistic effects' by hand. In the second technical part we consider the question of how quantum matter may act as source for classical gravitational fields via the semiclassical Einstein equations. Statements to the effect that this approach is fundamentally inconsistent are critically reviewed. |
2306.10498 | Hang Liu | Hang Liu | Quasinormal modes of phantom Reissner-Nordstr\"om-de Sitter black holes | Accepted for publication on EPJC | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate some characteristics of phantom
Reissner-Nordstr\"om-de Sitter (RN-dS) black holes. The peculiar feature of
phantom field renders this kind of black holes quite different from their
counterparts. We can only find at most two horizons in this spacetime, i.e.
event horizon and cosmological horizon. For the black hole charge parameter, we
find that it is not bounded from below. We calculate quasinormal modes (QNMs)
frequencies of massless neutral scalar field perturbation in this black hole
spacetime, and some properties related to the large charge parameter are
disclosed.
| [
{
"created": "Sun, 18 Jun 2023 08:34:22 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Oct 2023 14:37:25 GMT",
"version": "v2"
}
] | 2023-10-03 | [
[
"Liu",
"Hang",
""
]
] | In this paper, we investigate some characteristics of phantom Reissner-Nordstr\"om-de Sitter (RN-dS) black holes. The peculiar feature of phantom field renders this kind of black holes quite different from their counterparts. We can only find at most two horizons in this spacetime, i.e. event horizon and cosmological horizon. For the black hole charge parameter, we find that it is not bounded from below. We calculate quasinormal modes (QNMs) frequencies of massless neutral scalar field perturbation in this black hole spacetime, and some properties related to the large charge parameter are disclosed. |
1908.04410 | Amir Jafari | Amir Jafari | Gravitational Radiation from Binaries: A Pedagogical Introduction | null | null | null | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This short note serves as an introduction to gravitational radiation through
reviewing the inspiral-plunge transition phase in extreme mass ratio binaries.
We study the relativistic motion of a compact object (CO) of mass $m$ around a
massive black hole of mass $M\gg m$. The Kerr-Newman metric, effective
potential for the general case of elliptical orbits, gravitational radiation,
orbital energy and angular momentum of a coalescing CO in Kerr spacetime and
gravitational wave frequency and signal to noise ratio are briefly reviewed.
The main focus is on the transition from inspiral to plunge for a CO assuming
that a test particle approach is plausible in the regime $m\ll M$ without
appealing to a perturbative analysis. The effective potential is used to obtain
the properties of the Innermost Stable Circular Orbit (ISCO) near which the
adiabatic inspiral phase ends abruptly and the CO enters the plunge phase. For
the transition phase, the effective potential is expanded in terms of
parameters such as the radial (coordinate) distance from the ISCO and the
deviation of particle's angular momentum from its value at the ISCO to obtain
the equation of motion. The equations of motion, during the inspiral and
transition phases, are joined numerically and the gravitational wave frequency,
number of wave cycles and signal to noise ratio (SN) during the transition is
obtained for circular/inclined as well as elliptical/inclined orbits. The
limitations and inaccuracies of the current methods used to approach this
problem is discussed. A short introduction to the fundamental concepts of
General Relativity, in particular Einstein Field Equations is also provided in
the Appendix.
| [
{
"created": "Wed, 7 Aug 2019 04:50:00 GMT",
"version": "v1"
},
{
"created": "Sun, 18 Aug 2019 04:09:11 GMT",
"version": "v2"
}
] | 2019-08-20 | [
[
"Jafari",
"Amir",
""
]
] | This short note serves as an introduction to gravitational radiation through reviewing the inspiral-plunge transition phase in extreme mass ratio binaries. We study the relativistic motion of a compact object (CO) of mass $m$ around a massive black hole of mass $M\gg m$. The Kerr-Newman metric, effective potential for the general case of elliptical orbits, gravitational radiation, orbital energy and angular momentum of a coalescing CO in Kerr spacetime and gravitational wave frequency and signal to noise ratio are briefly reviewed. The main focus is on the transition from inspiral to plunge for a CO assuming that a test particle approach is plausible in the regime $m\ll M$ without appealing to a perturbative analysis. The effective potential is used to obtain the properties of the Innermost Stable Circular Orbit (ISCO) near which the adiabatic inspiral phase ends abruptly and the CO enters the plunge phase. For the transition phase, the effective potential is expanded in terms of parameters such as the radial (coordinate) distance from the ISCO and the deviation of particle's angular momentum from its value at the ISCO to obtain the equation of motion. The equations of motion, during the inspiral and transition phases, are joined numerically and the gravitational wave frequency, number of wave cycles and signal to noise ratio (SN) during the transition is obtained for circular/inclined as well as elliptical/inclined orbits. The limitations and inaccuracies of the current methods used to approach this problem is discussed. A short introduction to the fundamental concepts of General Relativity, in particular Einstein Field Equations is also provided in the Appendix. |
2302.12849 | Olivier Sarbach | Paola Rioseco and Olivier Sarbach | Phase space mixing of a Vlasov gas in the exterior of a Kerr black hole | 52 pages, 6 figures | null | null | null | gr-qc astro-ph.GA math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the dynamics of a collisionless kinetic gas whose particles follow
future-directed timelike and spatially bound geodesics in the exterior of a
sub-extremal Kerr black hole spacetime. Based on the use of generalized
action-angle variables, we analyze the large time asymptotic behavior of
macroscopic observables associated with the gas. We show that, as long as the
fundamental frequencies of the system satisfy a suitable non-degeneracy
condition, these macroscopic observables converge in time to the corresponding
observables determined from an averaged distribution function. In particular,
this implies that the final state is characterized by a distribution function
which is invariant with respect to the full symmetry group of the system, that
is, it is stationary, axisymmetric and Poisson-commutes with the integral of
motion associated with the Carter constant. As a corollary of our result, we
demonstrate the validity of the strong Jeans theorem in our setting, stating
that the distribution function belonging to a stationary state must be a
function which is independent of the generalized angle variables. An analogous
theorem in which the assumption of stationarity is replaced with the
requirement of invariance with respect to the Carter flow is also proven.
Finally, we prove that the aforementioned non-degeneracy condition holds. This
is achieved by providing suitable asymptotic expansions for the energy and
Carter constant in terms of action variables for orbits having sufficiently
large radii, and by exploiting the analytic dependency of the fundamental
frequencies on the integrals of motion.
| [
{
"created": "Fri, 24 Feb 2023 19:00:03 GMT",
"version": "v1"
}
] | 2023-02-28 | [
[
"Rioseco",
"Paola",
""
],
[
"Sarbach",
"Olivier",
""
]
] | We study the dynamics of a collisionless kinetic gas whose particles follow future-directed timelike and spatially bound geodesics in the exterior of a sub-extremal Kerr black hole spacetime. Based on the use of generalized action-angle variables, we analyze the large time asymptotic behavior of macroscopic observables associated with the gas. We show that, as long as the fundamental frequencies of the system satisfy a suitable non-degeneracy condition, these macroscopic observables converge in time to the corresponding observables determined from an averaged distribution function. In particular, this implies that the final state is characterized by a distribution function which is invariant with respect to the full symmetry group of the system, that is, it is stationary, axisymmetric and Poisson-commutes with the integral of motion associated with the Carter constant. As a corollary of our result, we demonstrate the validity of the strong Jeans theorem in our setting, stating that the distribution function belonging to a stationary state must be a function which is independent of the generalized angle variables. An analogous theorem in which the assumption of stationarity is replaced with the requirement of invariance with respect to the Carter flow is also proven. Finally, we prove that the aforementioned non-degeneracy condition holds. This is achieved by providing suitable asymptotic expansions for the energy and Carter constant in terms of action variables for orbits having sufficiently large radii, and by exploiting the analytic dependency of the fundamental frequencies on the integrals of motion. |
gr-qc/0412103 | Ludovico Carbone | L. Carbone, A. Cavalleri, R. Dolesi, C. D. Hoyle, M. Hueller, S.
Vitale, W. J. Weber | Characterization of disturbance sources for LISA: torsion pendulum
results | 11 pages, 8 figures, accepted for publication Classical and Quantum
Gravity | Class.Quant.Grav. 22 (2005) S509-S520 | 10.1088/0264-9381/22/10/051 | null | gr-qc | null | A torsion pendulum allows ground-based investigation of the purity of
free-fall for the LISA test masses inside their capacitive position sensor.
This paper presents recent improvements in our torsion pendulum facility that
have both increased the pendulum sensitivity and allowed detailed
characterization of several important sources of acceleration noise for the
LISA test masses. We discuss here an improved upper limit on random force noise
originating in the sensor. Additionally, we present new measurement techniques
and preliminary results for characterizing the forces caused by the sensor's
residual electrostatic fields, dielectric losses, residual spring-like
coupling, and temperature gradients.
| [
{
"created": "Tue, 21 Dec 2004 15:25:50 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Carbone",
"L.",
""
],
[
"Cavalleri",
"A.",
""
],
[
"Dolesi",
"R.",
""
],
[
"Hoyle",
"C. D.",
""
],
[
"Hueller",
"M.",
""
],
[
"Vitale",
"S.",
""
],
[
"Weber",
"W. J.",
""
]
] | A torsion pendulum allows ground-based investigation of the purity of free-fall for the LISA test masses inside their capacitive position sensor. This paper presents recent improvements in our torsion pendulum facility that have both increased the pendulum sensitivity and allowed detailed characterization of several important sources of acceleration noise for the LISA test masses. We discuss here an improved upper limit on random force noise originating in the sensor. Additionally, we present new measurement techniques and preliminary results for characterizing the forces caused by the sensor's residual electrostatic fields, dielectric losses, residual spring-like coupling, and temperature gradients. |
2301.07160 | Genly Le\'on | Bayron Micolta-Riascos (Catolica del Norte U.), Alfredo D. Millano
(Catolica del Norte U.), Genly Leon (Catolica del Norte U. and DUT, Durban),
Cristi\'an Erices (Central U., Chile and Talca U.), Andronikos Paliathanasis
(Catolica del Norte U. and DUT, Durban) | Revisiting Fractional Cosmology | 58 pages, 8 figures. This article belongs to the Special Issue
Fractional Gravity/Cosmology in Classical and Quantum Regimes
https://www.mdpi.com/journal/fractalfract/special_issues/fractional_cosmology | Fractal Fract. 2023, 7, 149 | 10.3390/fractalfract7020149 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | Recently, the research community has been exploring fractional calculus to
address problems related to cosmology; in this approach, the gravitational
action integral is altered, leading to a modified Friedmann equation, then the
resulting theory is compared against observational data. In this context,
dynamical systems can be used along with an analysis the phase spaces for
different values of the fractional order of the derivative and their different
matter contents. The equilibrium points are classified, providing a range for
the order of the fractional derivative in order to investigate whether the
cosmological history can be reconstructed and a late-time accelerating
power-law solution obtained for the scale factor. In this paper, we discuss the
physical interpretation of the corresponding cosmological solutions with
particular emphasis on the influence of the fractional order of the derivative
in a theory of gravity that includes a scalar field minimally coupled to
gravity. The presented results improve and extend those obtained previously,
further demonstrating that fractional calculus can play a relevant role in
cosmology.
| [
{
"created": "Tue, 17 Jan 2023 20:09:44 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Feb 2023 21:04:10 GMT",
"version": "v2"
}
] | 2023-02-07 | [
[
"Micolta-Riascos",
"Bayron",
"",
"Catolica del Norte U."
],
[
"Millano",
"Alfredo D.",
"",
"Catolica del Norte U."
],
[
"Leon",
"Genly",
"",
"Catolica del Norte U. and DUT, Durban"
],
[
"Erices",
"Cristián",
"",
"Central U., Chile and Tal... | Recently, the research community has been exploring fractional calculus to address problems related to cosmology; in this approach, the gravitational action integral is altered, leading to a modified Friedmann equation, then the resulting theory is compared against observational data. In this context, dynamical systems can be used along with an analysis the phase spaces for different values of the fractional order of the derivative and their different matter contents. The equilibrium points are classified, providing a range for the order of the fractional derivative in order to investigate whether the cosmological history can be reconstructed and a late-time accelerating power-law solution obtained for the scale factor. In this paper, we discuss the physical interpretation of the corresponding cosmological solutions with particular emphasis on the influence of the fractional order of the derivative in a theory of gravity that includes a scalar field minimally coupled to gravity. The presented results improve and extend those obtained previously, further demonstrating that fractional calculus can play a relevant role in cosmology. |
gr-qc/9309023 | null | Jos\'e P. S. Lemos and Paulo M. S\'a | Non-Singular Constant Curvature Two-Dimensional Black Hole | 6 pages, LaTex, Lisbon preprint DF/IST-8.93 (revised) | Mod.Phys.Lett. A9 (1994) 771-774 | 10.1142/S0217732394000587 | null | gr-qc | null | We show that the two-dimensional theory of Teitelboim and Jackiw has a black
hole solution, with two surprising properties: first, it has constant
curvature, and second, is free of spacetime singularities. The maximally
extended spacetime consists of an infinite chain of universes connected by
timelike wormholes.
| [
{
"created": "Thu, 23 Sep 1993 17:40:51 GMT",
"version": "v1"
}
] | 2009-10-22 | [
[
"Lemos",
"José P. S.",
""
],
[
"Sá",
"Paulo M.",
""
]
] | We show that the two-dimensional theory of Teitelboim and Jackiw has a black hole solution, with two surprising properties: first, it has constant curvature, and second, is free of spacetime singularities. The maximally extended spacetime consists of an infinite chain of universes connected by timelike wormholes. |
1308.1325 | Juan A. Valiente-Kroon | Christian L\"ubbe and Juan A. Valiente Kroon | On the conformal structure of the extremal Reissner-Nordstr\"om
spacetime | 35 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyse various conformal properties of the extremal Reissner-Nordstr\"om
spacetime. In particular, we obtain conformal representations of the
neighbourhoods of spatial infinity, timelike infinity and the cylindrical end
---the so-called cylinders at spatial infinity and at the horizon,
respectively--- which are regular with respect to the conformal Einstein field
equations and their associated initial data sets. We discuss possible
implications of these constructions for the propagation of test fields and
non-linear perturbations of the gravitational field close to the horizon.
| [
{
"created": "Tue, 6 Aug 2013 16:12:23 GMT",
"version": "v1"
}
] | 2013-08-07 | [
[
"Lübbe",
"Christian",
""
],
[
"Kroon",
"Juan A. Valiente",
""
]
] | We analyse various conformal properties of the extremal Reissner-Nordstr\"om spacetime. In particular, we obtain conformal representations of the neighbourhoods of spatial infinity, timelike infinity and the cylindrical end ---the so-called cylinders at spatial infinity and at the horizon, respectively--- which are regular with respect to the conformal Einstein field equations and their associated initial data sets. We discuss possible implications of these constructions for the propagation of test fields and non-linear perturbations of the gravitational field close to the horizon. |
1911.03260 | Slava G. Turyshev | Slava G. Turyshev, Viktor T. Toth | Image formation process with the solar gravitational lens | 13 pages, 6 figures | Phys. Rev. D 101, 044048 (2020) | 10.1103/PhysRevD.101.044048 | null | gr-qc astro-ph.IM physics.optics | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study image formation with the solar gravitational lens (SGL). We consider
a point source that is positioned at a large but finite distance from the Sun.
We assume that an optical telescope is positioned in the image plane, in the
focal region of the SGL. We model the telescope as a convex lens and evaluate
the intensity distribution produced by the electromagnetic field that forms the
image in the focal plane of the convex lens. We first investigate the case when
the telescope is located on the optical axis of the SGL or in its immediate
vicinity. This is the region of strong interference where the SGL forms an
image of a distant source, which is our primary interest. We derive analytic
expressions that describe the progression of the image from an Einstein ring
corresponding to an on-axis telescope position, to the case of two bright spots
when the telescope is positioned some distance away from the optical axis. At
greater distances from the optical axis, in the region of weak interference and
that of geometric optics, we recover expressions that are familiar from models
of gravitational microlensing, but developed here using a wave-optical
treatment. We discuss applications of the results for imaging and spectroscopy
of exoplanets with the SGL.
| [
{
"created": "Fri, 8 Nov 2019 13:47:30 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Feb 2020 17:54:59 GMT",
"version": "v2"
}
] | 2020-02-25 | [
[
"Turyshev",
"Slava G.",
""
],
[
"Toth",
"Viktor T.",
""
]
] | We study image formation with the solar gravitational lens (SGL). We consider a point source that is positioned at a large but finite distance from the Sun. We assume that an optical telescope is positioned in the image plane, in the focal region of the SGL. We model the telescope as a convex lens and evaluate the intensity distribution produced by the electromagnetic field that forms the image in the focal plane of the convex lens. We first investigate the case when the telescope is located on the optical axis of the SGL or in its immediate vicinity. This is the region of strong interference where the SGL forms an image of a distant source, which is our primary interest. We derive analytic expressions that describe the progression of the image from an Einstein ring corresponding to an on-axis telescope position, to the case of two bright spots when the telescope is positioned some distance away from the optical axis. At greater distances from the optical axis, in the region of weak interference and that of geometric optics, we recover expressions that are familiar from models of gravitational microlensing, but developed here using a wave-optical treatment. We discuss applications of the results for imaging and spectroscopy of exoplanets with the SGL. |
gr-qc/9712064 | Jayashree Balakrishna | Jayashree Balakrishna, Edward Seidel, Wai-Mo Suen | Dynamical Evolution of Boson Stars II: Excited States and
Self-Interacting Fields | 16 pages+ 13 figures . All figures are available at
http://wugrav.wustl.edu/Papers | Phys.Rev. D58 (1998) 104004 | 10.1103/PhysRevD.58.104004 | null | gr-qc | null | The dynamical evolution of self-gravitating scalar field configurations in
numerical relativity is studied. The previous analysis on ground state boson
stars of non-interacting fields is extended to excited states and to fields
with self couplings.
Self couplings can significantly change the physical dimensions of boson
stars, making them much more astrophysically interesting (e.g., having mass of
order 0.1 solar mass). The stable ($S$) and unstable ($U$) branches of
equilibrium configurations of boson stars of self-interacting fields are
studied; their behavior under perturbations and their quasi-normal oscillation
frequencies are determined and compared to the non-interacting case.
Excited states of boson stars with and without self-couplings are studied and
compared. Excited states also have equilibrium configurations with $S$ and $U$
branch structures; both branches are intrinsically unstable under a generic
perturbation but have very different instability time scales. We carried out a
detailed study of the instability time scales of these configurations. It is
found that highly excited states spontaneously decay through a cascade of
intermediate states similar to atomic transitions.
| [
{
"created": "Mon, 15 Dec 1997 20:06:33 GMT",
"version": "v1"
}
] | 2009-10-30 | [
[
"Balakrishna",
"Jayashree",
""
],
[
"Seidel",
"Edward",
""
],
[
"Suen",
"Wai-Mo",
""
]
] | The dynamical evolution of self-gravitating scalar field configurations in numerical relativity is studied. The previous analysis on ground state boson stars of non-interacting fields is extended to excited states and to fields with self couplings. Self couplings can significantly change the physical dimensions of boson stars, making them much more astrophysically interesting (e.g., having mass of order 0.1 solar mass). The stable ($S$) and unstable ($U$) branches of equilibrium configurations of boson stars of self-interacting fields are studied; their behavior under perturbations and their quasi-normal oscillation frequencies are determined and compared to the non-interacting case. Excited states of boson stars with and without self-couplings are studied and compared. Excited states also have equilibrium configurations with $S$ and $U$ branch structures; both branches are intrinsically unstable under a generic perturbation but have very different instability time scales. We carried out a detailed study of the instability time scales of these configurations. It is found that highly excited states spontaneously decay through a cascade of intermediate states similar to atomic transitions. |
2107.09172 | David Sloan | David Sloan | Scale Symmetry and Friction | 20 pages | null | null | null | gr-qc physics.class-ph | http://creativecommons.org/licenses/by/4.0/ | Dynamical similarities are non-standard symmetries found in a wide range of
physical systems that identify solutions related by a change of scale. In this
paper we will show through a series of examples how this symmetry extends to
the space of couplings, as measured through observations of a system. This can
be exploited to focus on observations that can be used distinguish between
different theories, and identify those which give rise to identical physical
evolutions. These can be reduced into a description which makes no reference to
scale. The resultant systems can be derived from Herglotz's principle and
generally exhibit friction. Here we will demonstrate this through three example
systems: The Kepler problem, the N-body system and
Friedmann-Lema\^itre-Robertson-Walker cosmology.
| [
{
"created": "Mon, 19 Jul 2021 21:53:55 GMT",
"version": "v1"
}
] | 2021-07-21 | [
[
"Sloan",
"David",
""
]
] | Dynamical similarities are non-standard symmetries found in a wide range of physical systems that identify solutions related by a change of scale. In this paper we will show through a series of examples how this symmetry extends to the space of couplings, as measured through observations of a system. This can be exploited to focus on observations that can be used distinguish between different theories, and identify those which give rise to identical physical evolutions. These can be reduced into a description which makes no reference to scale. The resultant systems can be derived from Herglotz's principle and generally exhibit friction. Here we will demonstrate this through three example systems: The Kepler problem, the N-body system and Friedmann-Lema\^itre-Robertson-Walker cosmology. |
2406.08094 | Christian Friedrich Schmidt | Christian F. Schmidt, \'Alvaro Parra-L\'opez, Mireia Tolosa-Sime\'on,
Marius Sparn, Elinor Kath, Nikolas Liebster, Jelte Duchene, Helmut Strobel,
Markus K. Oberthaler, Stefan Floerchinger | Cosmological particle production in a quantum field simulator as a
quantum mechanical scattering problem | References and new section added. (22 + 14) pages, (13 + 7) figures,
(1+1) tables | null | null | null | gr-qc cond-mat.quant-gas hep-th | http://creativecommons.org/licenses/by/4.0/ | The production of quantum field excitations or particles in cosmological
spacetimes is a hallmark prediction of curved quantum field theory. The
generation of cosmological perturbations from quantum fluctuations in the early
universe constitutes an important application. The problem can be
quantum-simulated in terms of structure formation in an interacting
Bose-Einstein condensate (BEC) with time-dependent s-wave scattering length.
Here, we explore a mapping between cosmological particle production in general
(D+1)-dimensional spacetimes and scattering problems described by the
non-relativistic stationary Schr\"odinger equation in one dimension. Through
this mapping, intuitive explanations for emergent spatial structures in both
the BEC and the cosmological system can be obtained for a large class of
analogue cosmological scenarios, ranging from power-law expansions to periodic
modulations. The investigated cosmologies and their scattering analogues are
tuned to be implemented in a (2+1)-dimensional quantum field simulator.
| [
{
"created": "Wed, 12 Jun 2024 11:18:30 GMT",
"version": "v1"
},
{
"created": "Fri, 19 Jul 2024 09:41:05 GMT",
"version": "v2"
},
{
"created": "Tue, 23 Jul 2024 15:08:29 GMT",
"version": "v3"
}
] | 2024-07-24 | [
[
"Schmidt",
"Christian F.",
""
],
[
"Parra-López",
"Álvaro",
""
],
[
"Tolosa-Simeón",
"Mireia",
""
],
[
"Sparn",
"Marius",
""
],
[
"Kath",
"Elinor",
""
],
[
"Liebster",
"Nikolas",
""
],
[
"Duchene",
"Jelte",
... | The production of quantum field excitations or particles in cosmological spacetimes is a hallmark prediction of curved quantum field theory. The generation of cosmological perturbations from quantum fluctuations in the early universe constitutes an important application. The problem can be quantum-simulated in terms of structure formation in an interacting Bose-Einstein condensate (BEC) with time-dependent s-wave scattering length. Here, we explore a mapping between cosmological particle production in general (D+1)-dimensional spacetimes and scattering problems described by the non-relativistic stationary Schr\"odinger equation in one dimension. Through this mapping, intuitive explanations for emergent spatial structures in both the BEC and the cosmological system can be obtained for a large class of analogue cosmological scenarios, ranging from power-law expansions to periodic modulations. The investigated cosmologies and their scattering analogues are tuned to be implemented in a (2+1)-dimensional quantum field simulator. |
2406.15604 | Sajad A. Bhat | Sajad A. Bhat, Srijit Bhattacharjee, and Shasvath J. Kapadia | Can the Near-Horizon Black Hole Memory be detected through Binary
Inspirals? | 12 pages, 3 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The memory effect, in the context of gravitational-waves (GWs), manifests
itself in the permanent relative displacement of test masses when they
encounter the GWs. A number of works have explored the possibility of detecting
the memory when the source and detector are separated by large distances. A
special type of memory, arising from BMS symmetries, called ``black-hole
memory'', has been recently proposed. The black hole memory only manifests
itself in the vicinity of its event horizon. Therefore, formally observing it
requires placing a GW detector at the horizon of the BH, which prima-facie
seems unfeasible. In this work, we describe a toy model that suggests a
possible way the black hole memory may be observed, without requiring a
human-made detector near the event horizon. The model considers a binary black
hole (BBH), emanating GWs observable at cosmological distances, as a proxy for
an idealized detector in the vicinity of a supermassive Schwarzschild black
hole that is endowed with a supertranslation hair by sending a shock-wave to
it. This sudden change affects the geometry near the horizon of the
supertranslated black hole and it induces a change in the inspiraling orbital
separation (and hence, orbital frequency) of the binary, which in turn imprints
itself on the GWs. Using basic GW data analysis tools, we demonstrate that the
black hole memory should be observable by a LISA-like space-based detector.
| [
{
"created": "Fri, 21 Jun 2024 19:14:24 GMT",
"version": "v1"
}
] | 2024-06-25 | [
[
"Bhat",
"Sajad A.",
""
],
[
"Bhattacharjee",
"Srijit",
""
],
[
"Kapadia",
"Shasvath J.",
""
]
] | The memory effect, in the context of gravitational-waves (GWs), manifests itself in the permanent relative displacement of test masses when they encounter the GWs. A number of works have explored the possibility of detecting the memory when the source and detector are separated by large distances. A special type of memory, arising from BMS symmetries, called ``black-hole memory'', has been recently proposed. The black hole memory only manifests itself in the vicinity of its event horizon. Therefore, formally observing it requires placing a GW detector at the horizon of the BH, which prima-facie seems unfeasible. In this work, we describe a toy model that suggests a possible way the black hole memory may be observed, without requiring a human-made detector near the event horizon. The model considers a binary black hole (BBH), emanating GWs observable at cosmological distances, as a proxy for an idealized detector in the vicinity of a supermassive Schwarzschild black hole that is endowed with a supertranslation hair by sending a shock-wave to it. This sudden change affects the geometry near the horizon of the supertranslated black hole and it induces a change in the inspiraling orbital separation (and hence, orbital frequency) of the binary, which in turn imprints itself on the GWs. Using basic GW data analysis tools, we demonstrate that the black hole memory should be observable by a LISA-like space-based detector. |
1408.6586 | Scott Fraser | Scott Fraser, Douglas M. Eardley | A Variational Principle for Asymptotically Randall-Sundrum Black Holes | 5 pages, REVTeX 4.1; for published version, see arXiv:1408.4425 | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We prove the following variational principle for asymptotically
Randall-Sundrum (RS) black holes, based on the first law of black hole
mechanics: Instantaneously static initial data that extremizes the mass yields
a static black hole, for variations at fixed apparent horizon area, AdS
curvature length, cosmological constant, brane tensions, and RS brane warp
factors. This variational principle is valid with either two branes (RS1) or
one brane (RS2), and is applicable to variational trial solutions.
| [
{
"created": "Wed, 27 Aug 2014 22:44:31 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Sep 2014 20:37:55 GMT",
"version": "v2"
},
{
"created": "Tue, 28 Jul 2015 01:22:27 GMT",
"version": "v3"
}
] | 2015-07-29 | [
[
"Fraser",
"Scott",
""
],
[
"Eardley",
"Douglas M.",
""
]
] | We prove the following variational principle for asymptotically Randall-Sundrum (RS) black holes, based on the first law of black hole mechanics: Instantaneously static initial data that extremizes the mass yields a static black hole, for variations at fixed apparent horizon area, AdS curvature length, cosmological constant, brane tensions, and RS brane warp factors. This variational principle is valid with either two branes (RS1) or one brane (RS2), and is applicable to variational trial solutions. |
1511.07051 | W. H. Zurek | Wojciech H. Zurek and Don N. Page | Firewalls, black-hole thermodynamics, and singular solutions of the
Tolman-Oppenheimer-Volkoff equation | We study self-gravitating spherically symmetric fluid with a mass of
a black hole surrounded by Hawking radiation. Solutions cross r=2M without
encountering coordinate singularity to reach a firewall-like "Planck cocoon"
with entropy close to black hole entropy. We reproduce our paper with an
updated title and abstract. For a later study with similar results see G. 't
Hooft, gr-qc/9706058 | Physical Review D, Volume 29, Number 4, pp. 628 - 631 (1984) | 10.1103/PhysRevD.29.628 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate thermodynamic equilibrium of a self-gravitating perfect fluid
in a spherically symmetric system containing a black hole of mass M by means of
the Tolman-Oppenheimer-Volkoff (TOV) equation. At r >> 2M its solutions
describe a black-body radiation atmosphere with the Hawking temperature
T_BH~1/(8 \pi M) that is increasingly blueshifted as r approaches 2M. However,
there is no horizon at the Schwarzschild radius. Instead, the fluid becomes
increasingly hot and dense there, piling up into a "firewall" with the peak
temperatures and densities reaching Planck values somewhat below r = 2M. This
firewall surrounds a negative point mass residing at r=0, the only singularity
of the solution. The entropy of the firewall is comparable to the
Bekenstein-Hawking entropy.
| [
{
"created": "Sun, 22 Nov 2015 18:49:04 GMT",
"version": "v1"
}
] | 2015-11-24 | [
[
"Zurek",
"Wojciech H.",
""
],
[
"Page",
"Don N.",
""
]
] | We investigate thermodynamic equilibrium of a self-gravitating perfect fluid in a spherically symmetric system containing a black hole of mass M by means of the Tolman-Oppenheimer-Volkoff (TOV) equation. At r >> 2M its solutions describe a black-body radiation atmosphere with the Hawking temperature T_BH~1/(8 \pi M) that is increasingly blueshifted as r approaches 2M. However, there is no horizon at the Schwarzschild radius. Instead, the fluid becomes increasingly hot and dense there, piling up into a "firewall" with the peak temperatures and densities reaching Planck values somewhat below r = 2M. This firewall surrounds a negative point mass residing at r=0, the only singularity of the solution. The entropy of the firewall is comparable to the Bekenstein-Hawking entropy. |
2401.16036 | Francesco Sartini | Salvatore Ribisi and Francesco Sartini | Phase spaces and symmetries of Vaidya superspace | 17 pages, 1 figure | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We investigate the classical symmetries of the dynamics of the null-dust
spherically symmetric Vaidya spacetime. Einstein's equations for this model can
be obtained as equations of motion of a two-dimensional field theory. We
discuss the transformations leaving invariant such equations of motion. These
are given by two distinct sets, the residual diffeomorphisms coming from
general relativity and the generalisation of the Schr\"odinger symmetry,
recently found for the static Schwarzschild black holes. Surprisingly, these
two sets represent the symmetries of two different action functionals, leading
to the same equations of motion, but with different phase spaces.
| [
{
"created": "Mon, 29 Jan 2024 10:37:14 GMT",
"version": "v1"
}
] | 2024-01-30 | [
[
"Ribisi",
"Salvatore",
""
],
[
"Sartini",
"Francesco",
""
]
] | We investigate the classical symmetries of the dynamics of the null-dust spherically symmetric Vaidya spacetime. Einstein's equations for this model can be obtained as equations of motion of a two-dimensional field theory. We discuss the transformations leaving invariant such equations of motion. These are given by two distinct sets, the residual diffeomorphisms coming from general relativity and the generalisation of the Schr\"odinger symmetry, recently found for the static Schwarzschild black holes. Surprisingly, these two sets represent the symmetries of two different action functionals, leading to the same equations of motion, but with different phase spaces. |
gr-qc/0404127 | Llu\'is Bel | Ll. Bel | Light Tides and the Kennedy-Thorndike experiments | 14 pages | null | null | null | gr-qc | null | We model the system Earth-Moon-Sun from the point of view of a frame of
reference co-moving with the Earth and we derive a detailed prediction of the
outcome of future Kennedy-Thorndike's type experiments to be seen as light
tides.
| [
{
"created": "Fri, 30 Apr 2004 10:19:51 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Bel",
"Ll.",
""
]
] | We model the system Earth-Moon-Sun from the point of view of a frame of reference co-moving with the Earth and we derive a detailed prediction of the outcome of future Kennedy-Thorndike's type experiments to be seen as light tides. |
1007.0851 | Niccolo' Loret | Giovanni Amelino-Camelia, Niccolo' Loret, Gianluca Mandanici, Flavio
Mercati | Gravity in quantum spacetime | This essay received honorable mention in the Gravity Research
Foundation 2010 Awards for Essays on Gravitation | Int.J.Mod.Phys.D19:2385-2392,2010 | 10.1142/S0218271810018451 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The literature on quantum-gravity-inspired scenarios for the quantization of
spacetime has so far focused on particle-physics-like studies. This is partly
justified by the present limitations of our understanding of quantum-gravity
theories, but we here argue that valuable insight can be gained through
semi-heuristic analyses of the implications for gravitational phenomena of some
results obtained in the quantum-spacetime literature. In particular, we show
that the types of description of particle propagation that emerged in certain
quantum-spacetime frameworks have striking implications for gravitational
collapse and for the behaviour of gravity at large distances.
| [
{
"created": "Tue, 6 Jul 2010 10:15:15 GMT",
"version": "v1"
}
] | 2011-01-17 | [
[
"Amelino-Camelia",
"Giovanni",
""
],
[
"Loret",
"Niccolo'",
""
],
[
"Mandanici",
"Gianluca",
""
],
[
"Mercati",
"Flavio",
""
]
] | The literature on quantum-gravity-inspired scenarios for the quantization of spacetime has so far focused on particle-physics-like studies. This is partly justified by the present limitations of our understanding of quantum-gravity theories, but we here argue that valuable insight can be gained through semi-heuristic analyses of the implications for gravitational phenomena of some results obtained in the quantum-spacetime literature. In particular, we show that the types of description of particle propagation that emerged in certain quantum-spacetime frameworks have striking implications for gravitational collapse and for the behaviour of gravity at large distances. |
gr-qc/9904008 | Roh Suan Tung | Roh Suan Tung (Chicago) | Gravitation as a Supersymmetric Gauge Theory | 11 pages, accepted for publication in Physics Letters A | Phys.Lett. A264 (2000) 341-345 | 10.1016/S0375-9601(99)00845-2 | null | gr-qc hep-th | null | We propose a gauge theory of gravitation. The gauge potential is a connection
of the Super SL(2,C) group. A MacDowell-Mansouri type of action is proposed
where the action is quadratic in the Super SL(2,C) curvature and depends purely
on gauge connection. By breaking the symmetry of the Super SL(2,C) topological
gauge theory to SL(2,C), a spinor metric is naturally defined. With an
auxiliary anti-commuting spinor field, the theory is reduced to general
relativity. The Hamiltonian variables are related to the ones given by
Ashtekar. The auxiliary spinor field plays the role of Witten spinor in the
positive energy proof for gravitation.
| [
{
"created": "Mon, 5 Apr 1999 16:03:39 GMT",
"version": "v1"
},
{
"created": "Tue, 1 Jun 1999 21:09:26 GMT",
"version": "v2"
},
{
"created": "Wed, 1 Dec 1999 01:47:18 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Tung",
"Roh Suan",
"",
"Chicago"
]
] | We propose a gauge theory of gravitation. The gauge potential is a connection of the Super SL(2,C) group. A MacDowell-Mansouri type of action is proposed where the action is quadratic in the Super SL(2,C) curvature and depends purely on gauge connection. By breaking the symmetry of the Super SL(2,C) topological gauge theory to SL(2,C), a spinor metric is naturally defined. With an auxiliary anti-commuting spinor field, the theory is reduced to general relativity. The Hamiltonian variables are related to the ones given by Ashtekar. The auxiliary spinor field plays the role of Witten spinor in the positive energy proof for gravitation. |
1811.07639 | Naqing Xie | Patryk Mach, Yaohua Wang, Naqing Xie | Construction of vacuum initial data by the conformally covariant split
system | null | Class. Quantum Grav. 36(2019)145001(23pp) | 10.1088/1361-6382/ab2781 | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the implicit function theorem, we prove existence of solutions of the
so-called conformally covariant split system on compact 3-dimensional
Riemannian manifolds. They give rise to non-Constant Mean Curvature (non-CMC)
vacuum initial data for the Einstein equations. We investigate the conformally
covariant split system defined on compact manifolds with or without boundaries.
In the former case, the boundary corresponds to an apparent horizon in the
constructed initial data. The case with a cosmological constant is then
considered separately. Finally, to demonstrate the applicability of the
conformal covariant split system in numerical studies, we provide numerical
examples of solutions on manifolds $\mathbb S^1 \times \mathbb S^2$ and
$\mathbb S^1 \times \mathbb T^2$.
| [
{
"created": "Mon, 19 Nov 2018 12:15:58 GMT",
"version": "v1"
},
{
"created": "Fri, 21 Jun 2019 13:11:46 GMT",
"version": "v2"
}
] | 2019-06-24 | [
[
"Mach",
"Patryk",
""
],
[
"Wang",
"Yaohua",
""
],
[
"Xie",
"Naqing",
""
]
] | Using the implicit function theorem, we prove existence of solutions of the so-called conformally covariant split system on compact 3-dimensional Riemannian manifolds. They give rise to non-Constant Mean Curvature (non-CMC) vacuum initial data for the Einstein equations. We investigate the conformally covariant split system defined on compact manifolds with or without boundaries. In the former case, the boundary corresponds to an apparent horizon in the constructed initial data. The case with a cosmological constant is then considered separately. Finally, to demonstrate the applicability of the conformal covariant split system in numerical studies, we provide numerical examples of solutions on manifolds $\mathbb S^1 \times \mathbb S^2$ and $\mathbb S^1 \times \mathbb T^2$. |
1401.3275 | Luca Fabbri | Luca Fabbri | Torsion-Gravity for Dirac fields and their effective phenomenology | 6 pages | Mod.Phys.Lett.A29:1450133,2014 | 10.1142/S0217732314501338 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We will consider the torsional completion of gravity for a background filled
with Dirac matter fields, studying the weak-gravitational non-relativistic
approximation, in view of an assessment about their effective phenomenology: we
discuss how the torsionally-induced non-linear interactions among fermion
fields in this limit are compatible with all experiments, and remarks on the
role of torsion to suggest new physics are given.
| [
{
"created": "Tue, 14 Jan 2014 18:38:10 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Sep 2014 17:16:48 GMT",
"version": "v2"
}
] | 2014-09-03 | [
[
"Fabbri",
"Luca",
""
]
] | We will consider the torsional completion of gravity for a background filled with Dirac matter fields, studying the weak-gravitational non-relativistic approximation, in view of an assessment about their effective phenomenology: we discuss how the torsionally-induced non-linear interactions among fermion fields in this limit are compatible with all experiments, and remarks on the role of torsion to suggest new physics are given. |
0803.2651 | Everton Murilo Carvalho Abreu | E. M. C. Abreu and C. M. L. dos Reis | An analytical description for the cosmological constant | 10 pages. RevTex | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | From the principles of quantum cosmologies we can justify the reason for an
inverse-square law for the cosmological constant with no conflict with
observations. Although this general expression for $\Lambda$ is well known in
the literature, in this work we introduce some analytical solutions for the
scale factor different from the literature. The underlying motivation to carry
out these solutions is the fact that the time variation of $\Lambda$ can lead
to a creation of matter and/or radiation such as to help in the investigation
of the age of the Universe. The knowledge of the scale factor behavior might
shed some light on these questions since the entire evolution of a homogeneous
isotropic Universe is contained in the scale factor.
| [
{
"created": "Tue, 18 Mar 2008 15:03:46 GMT",
"version": "v1"
}
] | 2008-03-19 | [
[
"Abreu",
"E. M. C.",
""
],
[
"Reis",
"C. M. L. dos",
""
]
] | From the principles of quantum cosmologies we can justify the reason for an inverse-square law for the cosmological constant with no conflict with observations. Although this general expression for $\Lambda$ is well known in the literature, in this work we introduce some analytical solutions for the scale factor different from the literature. The underlying motivation to carry out these solutions is the fact that the time variation of $\Lambda$ can lead to a creation of matter and/or radiation such as to help in the investigation of the age of the Universe. The knowledge of the scale factor behavior might shed some light on these questions since the entire evolution of a homogeneous isotropic Universe is contained in the scale factor. |
2206.11013 | Nicolas Lecoeur | Eugeny Babichev, Christos Charmousis, Mokhtar Hassaine, Nicolas
Lecoeur | Conformally coupled theories and their deformed compact objects: from
black holes, radiating spacetimes to eternal wormholes | null | null | 10.1103/PhysRevD.106.064039 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study a higher order conformally coupled scalar tensor theory endowed with
a covariant geometric constraint relating the scalar curvature with the
Gauss-Bonnet scalar. It is a particular Horndeski theory including a canonical
kinetic term but without shift or parity symmetry for the scalar. The theory
also stems from a Kaluza-Klein reduction of a well defined higher dimensional
metric theory. Properties of an asymptotically flat spherically symmetric black
hole are analyzed, and new slowly rotating and radiating extensions are found.
Through disformal transformations of the static configurations, gravitating
monopole-like solutions and eternal wormholes are presented. The latter are
shown to extract from spacetime possible naked singularities, yielding
completely regular and asymptotically flat spacetimes.
| [
{
"created": "Wed, 22 Jun 2022 12:27:41 GMT",
"version": "v1"
}
] | 2022-10-05 | [
[
"Babichev",
"Eugeny",
""
],
[
"Charmousis",
"Christos",
""
],
[
"Hassaine",
"Mokhtar",
""
],
[
"Lecoeur",
"Nicolas",
""
]
] | We study a higher order conformally coupled scalar tensor theory endowed with a covariant geometric constraint relating the scalar curvature with the Gauss-Bonnet scalar. It is a particular Horndeski theory including a canonical kinetic term but without shift or parity symmetry for the scalar. The theory also stems from a Kaluza-Klein reduction of a well defined higher dimensional metric theory. Properties of an asymptotically flat spherically symmetric black hole are analyzed, and new slowly rotating and radiating extensions are found. Through disformal transformations of the static configurations, gravitating monopole-like solutions and eternal wormholes are presented. The latter are shown to extract from spacetime possible naked singularities, yielding completely regular and asymptotically flat spacetimes. |
1403.7615 | Mohammad Nouri-Zonoz | M. Nouri-Zonoz and H. Ramezani-Aval | Fermi coordinates and modified Franklin transformation : A comparative
study on rotational phenomena | 21 pages, 2 figures, replaced with the published version | Eur. Phys. J. C (2014) 74:3128 | 10.1140/epjc/s10052-014-3128-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Employing a relativistic rotational transformation to study and analyze
rotational phenomena, instead of the rotational transformations based on
consecutive Lorentz transformations and Fermi coordinates, leads to different
predictions. In this article, after a comparative study between Fermi metric of
a uniformly rotating eccentric observer and the spacetime metric in the same
observer's frame obtained through the modified Franklin transformation, we
consider rotational phenomena including transverse Doppler effect and Sagnac
effect in both formalisms and compare their predictions. We also discuss length
measurements in the two formalisms.
| [
{
"created": "Sat, 29 Mar 2014 10:36:42 GMT",
"version": "v1"
},
{
"created": "Thu, 18 Dec 2014 14:04:51 GMT",
"version": "v2"
}
] | 2015-01-07 | [
[
"Nouri-Zonoz",
"M.",
""
],
[
"Ramezani-Aval",
"H.",
""
]
] | Employing a relativistic rotational transformation to study and analyze rotational phenomena, instead of the rotational transformations based on consecutive Lorentz transformations and Fermi coordinates, leads to different predictions. In this article, after a comparative study between Fermi metric of a uniformly rotating eccentric observer and the spacetime metric in the same observer's frame obtained through the modified Franklin transformation, we consider rotational phenomena including transverse Doppler effect and Sagnac effect in both formalisms and compare their predictions. We also discuss length measurements in the two formalisms. |
gr-qc/9807071 | Daniel STAF Tilley | Daniel Tilley and Roy Maartens (University of Portsmouth) | Perturbations in inflationary cosmologies with smooth exit | 11 pages, latex, Accepted for publication in JMP | J.Math.Phys. 39 (1998) 5491-5501 | 10.1063/1.532546 | null | gr-qc | null | We give a comprehensive analysis of how scalar and tensor perturbations
evolve in cosmologies with a smooth transition from power-law-like and de
Sitter-like inflation to a radiation era. Analytic forms for the super-horizon
and sub-horizon perturbations in the inflationary and radiation dominated eras
are found.
| [
{
"created": "Mon, 27 Jul 1998 14:40:16 GMT",
"version": "v1"
}
] | 2009-10-31 | [
[
"Tilley",
"Daniel",
"",
"University of Portsmouth"
],
[
"Maartens",
"Roy",
"",
"University of Portsmouth"
]
] | We give a comprehensive analysis of how scalar and tensor perturbations evolve in cosmologies with a smooth transition from power-law-like and de Sitter-like inflation to a radiation era. Analytic forms for the super-horizon and sub-horizon perturbations in the inflationary and radiation dominated eras are found. |
1611.02647 | Henry Stoltenberg | Shengqiao Luo, Henry Stoltenberg and Andreas Albrecht | Multipartite Entanglement and Firewalls | 12 pages, 2 figures. V2: Final version accepted for publication in
PRD. Changes have been made to improve our discussion. No changes have been
made to the ideas or technical work presented. Section VI (from V1) has been
separated into two (adjacent) sections and the text in each has been improved
for clarity | Phys. Rev. D 95, 064039 (2017) | 10.1103/PhysRevD.95.064039 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes offer an exciting area to explore the nature of quantum gravity.
The classic work on Hawking radiation indicates that black holes should decay
via quantum effects, but our ideas about how this might work at a technical
level are incomplete. Recently Almheiri-Marolf-Polchinski-Sully (AMPS) have
noted an apparent paradox in reconciling fundamental properties of quantum
mechanics with standard beliefs about black holes. One way to resolve the
paradox is to postulate the existence of a "firewall" inside the black hole
horizon which prevents objects from falling smoothly toward the singularity. A
fundamental limitation on the behavior of quantum entanglement known as
"monogamy" plays a key role in the AMPS argument. Our goal is to study and
apply many-body entanglement theory to consider the entanglement among
different parts of Hawking radiation and black holes. Using the multipartite
entanglement measure called negativity, we identify an example which could
change the AMPS accounting of quantum entanglement and perhaps eliminate the
need for a firewall. Specifically, we constructed a toy model for black hole
decay which has different entanglement behavior than that assumed by AMPS. We
discuss the additional steps that would be needed to bring lessons from our toy
model to our understanding of realistic black holes.
| [
{
"created": "Tue, 8 Nov 2016 18:28:53 GMT",
"version": "v1"
},
{
"created": "Tue, 28 Feb 2017 23:17:19 GMT",
"version": "v2"
}
] | 2017-03-29 | [
[
"Luo",
"Shengqiao",
""
],
[
"Stoltenberg",
"Henry",
""
],
[
"Albrecht",
"Andreas",
""
]
] | Black holes offer an exciting area to explore the nature of quantum gravity. The classic work on Hawking radiation indicates that black holes should decay via quantum effects, but our ideas about how this might work at a technical level are incomplete. Recently Almheiri-Marolf-Polchinski-Sully (AMPS) have noted an apparent paradox in reconciling fundamental properties of quantum mechanics with standard beliefs about black holes. One way to resolve the paradox is to postulate the existence of a "firewall" inside the black hole horizon which prevents objects from falling smoothly toward the singularity. A fundamental limitation on the behavior of quantum entanglement known as "monogamy" plays a key role in the AMPS argument. Our goal is to study and apply many-body entanglement theory to consider the entanglement among different parts of Hawking radiation and black holes. Using the multipartite entanglement measure called negativity, we identify an example which could change the AMPS accounting of quantum entanglement and perhaps eliminate the need for a firewall. Specifically, we constructed a toy model for black hole decay which has different entanglement behavior than that assumed by AMPS. We discuss the additional steps that would be needed to bring lessons from our toy model to our understanding of realistic black holes. |
2111.04954 | Pyotr Tsyba | P. Tsyba, O. Razina, N. Suikimbayeva | Analysis cosmological tachyon and fermion model and observation data
constraints | null | null | 10.1142/S0218271821501145 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we investigate a cosmological model with the tachyon and fermion
fields with barotropic equation of state, where pressure $p$, energy density
$\rho$ and barotropic index $\gamma$ are related by the relation
$p=(\gamma-1)\rho$. We applied the tachyonozation method which allows to
consider cosmological model with the fermion and the tachyon fields, driven by
special potential. In this paper, tachyonization model was defined from the
stability analysis and exact solution standard of the tachyon field. Analysis
of the solution via statefinder parameters illustrated that our model in
fiducial points with deceleration parameter $q = 0.5$ and statefinder $r = 1$
which corresponds to the matter dominated universe (SCDM) but, ends its
evolution at a point in the future $(q =-1, \ r = 1)$ which corresponds to the
de-Sitter expansion. Comparison of the model parameters with the cosmological
observation data demonstrate, that our proposed cosmological model is stable at
barotropic index $\gamma_0=0.00744$.
| [
{
"created": "Tue, 9 Nov 2021 04:48:53 GMT",
"version": "v1"
}
] | 2021-11-10 | [
[
"Tsyba",
"P.",
""
],
[
"Razina",
"O.",
""
],
[
"Suikimbayeva",
"N.",
""
]
] | In this work we investigate a cosmological model with the tachyon and fermion fields with barotropic equation of state, where pressure $p$, energy density $\rho$ and barotropic index $\gamma$ are related by the relation $p=(\gamma-1)\rho$. We applied the tachyonozation method which allows to consider cosmological model with the fermion and the tachyon fields, driven by special potential. In this paper, tachyonization model was defined from the stability analysis and exact solution standard of the tachyon field. Analysis of the solution via statefinder parameters illustrated that our model in fiducial points with deceleration parameter $q = 0.5$ and statefinder $r = 1$ which corresponds to the matter dominated universe (SCDM) but, ends its evolution at a point in the future $(q =-1, \ r = 1)$ which corresponds to the de-Sitter expansion. Comparison of the model parameters with the cosmological observation data demonstrate, that our proposed cosmological model is stable at barotropic index $\gamma_0=0.00744$. |
2407.08396 | Yu-Xiao Liu | Jia-Zhou Liu, Wen-Di Guo, Shao-Wen Wei, Yu-Xiao Liu | Charged spherically symmetric and slowly rotating charged black hole
solutions in bumblebee gravity | 25 pages, 6 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | In this paper, we present charged spherically symmetric black hole solutions
and slowly rotating charged solutions in bumblebee gravity with and without a
cosmological constant. The static spherically symmetric solutions describe the
Reissner-Nordstr\"om-like black hole and ReissnerNordstr\"om-(anti) de
Sitter-like black hole, while the stationary and axially symmetric soltuions
describe Kerr-Newman-like black hole and Kerr-Newman-(anti) de Sitter-like
black hole. We utilize the Hamilton-Jacobi formalism to study the shadows of
the black holes. Additionally, we investigate the effect of the electric charge
and Lorentz-violating parameters on the radius of the shadow reference circle
and the distortion parameter. We find that the radius of the reference circle
decreases with the Lorentz-violating parameter and charge parameter, while the
distortion parameter increases with the Lorentz-violating parameter and the
charge parameter.
| [
{
"created": "Thu, 11 Jul 2024 11:02:18 GMT",
"version": "v1"
}
] | 2024-07-12 | [
[
"Liu",
"Jia-Zhou",
""
],
[
"Guo",
"Wen-Di",
""
],
[
"Wei",
"Shao-Wen",
""
],
[
"Liu",
"Yu-Xiao",
""
]
] | In this paper, we present charged spherically symmetric black hole solutions and slowly rotating charged solutions in bumblebee gravity with and without a cosmological constant. The static spherically symmetric solutions describe the Reissner-Nordstr\"om-like black hole and ReissnerNordstr\"om-(anti) de Sitter-like black hole, while the stationary and axially symmetric soltuions describe Kerr-Newman-like black hole and Kerr-Newman-(anti) de Sitter-like black hole. We utilize the Hamilton-Jacobi formalism to study the shadows of the black holes. Additionally, we investigate the effect of the electric charge and Lorentz-violating parameters on the radius of the shadow reference circle and the distortion parameter. We find that the radius of the reference circle decreases with the Lorentz-violating parameter and charge parameter, while the distortion parameter increases with the Lorentz-violating parameter and the charge parameter. |
gr-qc/0312004 | Dan Brown | Daniel Brown | A Graph method for mapping changes in temporal and spatial phenomena
with relativistic consequences | 26 pages. 4 figures | null | null | null | gr-qc | null | A cellular automata approach using a Directed Cyclic Graph is used to model
interrelationships of fluctuating time, state and space. This model predicts
phenomena including a constant and maximum speed at which any moving entity can
travel, time dilation effects in accordance with special relativity,
calculation for the Doppler effect, propagation in three spatial dimensions, an
explanation for the non-local feature of collapse and a speculation on the
origin of gravitation. The approach has proven amenable to computer modelling.
| [
{
"created": "Sun, 30 Nov 2003 20:18:26 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Mar 2004 16:26:00 GMT",
"version": "v2"
},
{
"created": "Thu, 12 Aug 2004 11:00:02 GMT",
"version": "v3"
},
{
"created": "Tue, 8 Feb 2005 15:18:27 GMT",
"version": "v4"
},
{
"cre... | 2007-05-23 | [
[
"Brown",
"Daniel",
""
]
] | A cellular automata approach using a Directed Cyclic Graph is used to model interrelationships of fluctuating time, state and space. This model predicts phenomena including a constant and maximum speed at which any moving entity can travel, time dilation effects in accordance with special relativity, calculation for the Doppler effect, propagation in three spatial dimensions, an explanation for the non-local feature of collapse and a speculation on the origin of gravitation. The approach has proven amenable to computer modelling. |
2010.13157 | Andrew A. Geraci | Nancy Aggarwal, George P. Winstone, Mae Teo, Masha Baryakhtar, Shane
L. Larson, Vicky Kalogera, Andrew A. Geraci | Searching for new physics with a levitated-sensor-based
gravitational-wave detector | 7 pages including references, 3 figures | null | null | null | gr-qc hep-ph quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The Levitated Sensor Detector (LSD) is a compact resonant gravitational-wave
(GW) detector based on optically trapped dielectric particles that is under
construction. The LSD sensitivity has more favorable frequency scaling at high
frequencies compared to laser interferometer detectors such as LIGO. We propose
a method to substantially improve the sensitivity by optically levitating a
multi-layered stack of dielectric discs. These stacks allow the use of a more
massive levitated object while exhibiting minimal photon recoil heating due to
light scattering. Over an order of magnitude of unexplored frequency space for
GWs above 10 kHz is accessible with an instrument 10 to 100 meters in size.
Particularly motivated sources in this frequency range are gravitationally
bound states of QCD axions with decay constant near the grand unified theory
(GUT) scale that form through black hole superradiance and annihilate to GWs.
The LSD is also sensitive to GWs from binary coalescence of sub-solar-mass
primordial black holes and as-yet unexplored new physics in the high-frequency
GW window.
| [
{
"created": "Sun, 25 Oct 2020 16:33:12 GMT",
"version": "v1"
}
] | 2020-10-27 | [
[
"Aggarwal",
"Nancy",
""
],
[
"Winstone",
"George P.",
""
],
[
"Teo",
"Mae",
""
],
[
"Baryakhtar",
"Masha",
""
],
[
"Larson",
"Shane L.",
""
],
[
"Kalogera",
"Vicky",
""
],
[
"Geraci",
"Andrew A.",
""
]
] | The Levitated Sensor Detector (LSD) is a compact resonant gravitational-wave (GW) detector based on optically trapped dielectric particles that is under construction. The LSD sensitivity has more favorable frequency scaling at high frequencies compared to laser interferometer detectors such as LIGO. We propose a method to substantially improve the sensitivity by optically levitating a multi-layered stack of dielectric discs. These stacks allow the use of a more massive levitated object while exhibiting minimal photon recoil heating due to light scattering. Over an order of magnitude of unexplored frequency space for GWs above 10 kHz is accessible with an instrument 10 to 100 meters in size. Particularly motivated sources in this frequency range are gravitationally bound states of QCD axions with decay constant near the grand unified theory (GUT) scale that form through black hole superradiance and annihilate to GWs. The LSD is also sensitive to GWs from binary coalescence of sub-solar-mass primordial black holes and as-yet unexplored new physics in the high-frequency GW window. |
gr-qc/9508032 | null | Peter D. D'Eath and Giampiero Esposito | The Effect of Boundaries in One-Loop Quantum Cosmology | 6 pages, plain-tex, published in Proceedings of the IX Italian
Conference on General Relativity and Gravitational Physics, editors R. Cianci
et al., 1991, pp 644-647 (Singapore: World Scientific) | null | null | DAMTP R-90/20 | gr-qc | null | The problem of boundary conditions in a supersymmetric theory of quantum
cosmology is studied, with application to the one-loop prefactor in the quantum
amplitude. Our background cosmological model is flat Euclidean space bounded by
a three-sphere, and our calculations are based on the generalized Riemann
zeta-function. One possible set of supersymmetric local boundary conditions
involves field strengths for spins 1, 3/2 and 2, the undifferentiated spin-1/2
field, and a mixture of Dirichlet and Neumann conditions for spin 0. In this
case the results we can obtain are: zeta(0)=7/45 for a complex scalar field,
zeta(0)=11/360 for spin 1/2, zeta(0)= -77/180 (magnetic) and 13/180 (electric)
for spin 1, and zeta(0)=112/45 for pure gravity when the linearized magnetic
curvature is vanishing on $S^3$. The zeta(0) values for gauge fields have been
obtained by working only with physical degrees of freedom. An alternative set
of boundary conditions can be motivated by studying transformation properties
under local supersymmetry; these involve Dirichlet conditions for the spin-2
and spin-1 fields, a mixture of Dirichlet and Neumann conditions for spin-0,
and local boundary conditions for the spin-1/2 field and the spin-3/2
potential. For the latter one finds: zeta(0)=-289/360. The full zeta(0) does
not vanish in extended supergravity theories, indicating that supersymmetry is
one-loop divergent in the presence of boundaries.
| [
{
"created": "Mon, 14 Aug 1995 17:33:37 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"D'Eath",
"Peter D.",
""
],
[
"Esposito",
"Giampiero",
""
]
] | The problem of boundary conditions in a supersymmetric theory of quantum cosmology is studied, with application to the one-loop prefactor in the quantum amplitude. Our background cosmological model is flat Euclidean space bounded by a three-sphere, and our calculations are based on the generalized Riemann zeta-function. One possible set of supersymmetric local boundary conditions involves field strengths for spins 1, 3/2 and 2, the undifferentiated spin-1/2 field, and a mixture of Dirichlet and Neumann conditions for spin 0. In this case the results we can obtain are: zeta(0)=7/45 for a complex scalar field, zeta(0)=11/360 for spin 1/2, zeta(0)= -77/180 (magnetic) and 13/180 (electric) for spin 1, and zeta(0)=112/45 for pure gravity when the linearized magnetic curvature is vanishing on $S^3$. The zeta(0) values for gauge fields have been obtained by working only with physical degrees of freedom. An alternative set of boundary conditions can be motivated by studying transformation properties under local supersymmetry; these involve Dirichlet conditions for the spin-2 and spin-1 fields, a mixture of Dirichlet and Neumann conditions for spin-0, and local boundary conditions for the spin-1/2 field and the spin-3/2 potential. For the latter one finds: zeta(0)=-289/360. The full zeta(0) does not vanish in extended supergravity theories, indicating that supersymmetry is one-loop divergent in the presence of boundaries. |
1405.2189 | Rahim Alhamzawi | Ahmed Alhamzawi and Rahim Alhamzawi | Generalized GHY term for f(R) Gravity | 3 pages, 0 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A generalization to the Gibbons-Hawking-York boundary term for metric $f(R)$
gravity theories is introduced. A redefinition of the Gibbons-Hawking-York term
is proposed. The proposed new definition is used to derive a consistent set of
field equations and is extended to metric $f(R)$ gravity theories. The surface
terms in the action are gathered into a total variation of some quantity. A
total divergence term is added to the action to cancel these terms. Finally,
the new definition is proven to demand no restrictions on the value of ${\delta
g}_{ab}$ or ${\partial}_{c}{\delta g}_{ab}$ on the boundary.
| [
{
"created": "Fri, 9 May 2014 09:44:05 GMT",
"version": "v1"
},
{
"created": "Mon, 12 May 2014 17:27:44 GMT",
"version": "v2"
}
] | 2014-05-13 | [
[
"Alhamzawi",
"Ahmed",
""
],
[
"Alhamzawi",
"Rahim",
""
]
] | A generalization to the Gibbons-Hawking-York boundary term for metric $f(R)$ gravity theories is introduced. A redefinition of the Gibbons-Hawking-York term is proposed. The proposed new definition is used to derive a consistent set of field equations and is extended to metric $f(R)$ gravity theories. The surface terms in the action are gathered into a total variation of some quantity. A total divergence term is added to the action to cancel these terms. Finally, the new definition is proven to demand no restrictions on the value of ${\delta g}_{ab}$ or ${\partial}_{c}{\delta g}_{ab}$ on the boundary. |
gr-qc/0004042 | Sean A. Hayward | Sean A. Hayward | Gravitational energy as Noether charge | 4 pages, revtex | null | null | null | gr-qc | null | A definition of gravitational energy is proposed for any theory described by
a diffeomorphism-invariant Lagrangian. The mathematical structure is a Noether-
current construction of Wald involving the boundary term in the action, but
here it is argued that the physical interpretation of current conservation is
conservation of energy. This leads to a quasi-local energy defined for compact
spatial surfaces. The energy also depends on a vector generating a flow of
time. Angular momentum may be similarly defined, depending on a choice of axial
vector. For Einstein gravity: for the usual vector generating asymptotic time
translations, the energy is the Bondi energy; for a stationary Killing vector,
the energy is the Komar energy; in spherical symmetry, for the Kodama vector,
the energy is the Misner-Sharp energy. In general, the lack of a preferred time
indicates the lack of a preferred energy, reminiscent of the energy-time
duality of quantum theory.
| [
{
"created": "Thu, 13 Apr 2000 17:59:12 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hayward",
"Sean A.",
""
]
] | A definition of gravitational energy is proposed for any theory described by a diffeomorphism-invariant Lagrangian. The mathematical structure is a Noether- current construction of Wald involving the boundary term in the action, but here it is argued that the physical interpretation of current conservation is conservation of energy. This leads to a quasi-local energy defined for compact spatial surfaces. The energy also depends on a vector generating a flow of time. Angular momentum may be similarly defined, depending on a choice of axial vector. For Einstein gravity: for the usual vector generating asymptotic time translations, the energy is the Bondi energy; for a stationary Killing vector, the energy is the Komar energy; in spherical symmetry, for the Kodama vector, the energy is the Misner-Sharp energy. In general, the lack of a preferred time indicates the lack of a preferred energy, reminiscent of the energy-time duality of quantum theory. |
1608.03164 | Valerio Faraoni | Valerio Faraoni and Marianne Lapierre-Leonard (Bishop's University) | Beyond lensing by the cosmological constant | 4 pages. Added some discussion and a few references, matches version
accepted in Phys. Rev. D | Phys. Rev. D 95, 023509 (2017) | 10.1103/PhysRevD.95.023509 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The long-standing problem of whether the cosmological constant affects
directly the deflection of light caused by a gravitational lens is
reconsidered. We use a new approach based on the Hawking quasilocal mass of a
sphere grazed by light rays and on its splitting into local and cosmological
parts. Previous literature restricted to the cosmological constant is extended
to any form of dark energy accelerating the universe in which the gravitational
lens is embedded.
| [
{
"created": "Wed, 10 Aug 2016 13:26:06 GMT",
"version": "v1"
},
{
"created": "Mon, 9 Jan 2017 18:37:42 GMT",
"version": "v2"
}
] | 2017-01-25 | [
[
"Faraoni",
"Valerio",
"",
"Bishop's University"
],
[
"Lapierre-Leonard",
"Marianne",
"",
"Bishop's University"
]
] | The long-standing problem of whether the cosmological constant affects directly the deflection of light caused by a gravitational lens is reconsidered. We use a new approach based on the Hawking quasilocal mass of a sphere grazed by light rays and on its splitting into local and cosmological parts. Previous literature restricted to the cosmological constant is extended to any form of dark energy accelerating the universe in which the gravitational lens is embedded. |
1706.06777 | Chandra Prakash Singh | Milan Srivastava and C.P.Singh | Holographic Dark Energy Model in Brans-Dicke Theory with Future Event
Horizon | 11 Pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the dynamics of non-interacting and interacting
holographic dark energy models in the framework of Brans-Dicke theory. As
system's infra-red cut-off we consider the future event horizon. The motivation
of this work is to use the logarithmic form of the Brans-Dicke scalar field,
$\phi \propto ln(\alpha+\beta a)$, where $\alpha$ and $\beta$ are constants and
`a' is the scalar factor as proposed Kumar and Singh in a recent work to study
the new agegraphic dark energy models. We find the time-dependent equation of
state parameter and deceleration parameter which describe the phase transition
of the universe. We observe that the model explains the early time inflation
and late time acceleration including matter-dominated phase. It is also
observed that the equation of state parameter may cross phantom divide line in
late time evolution. The cosmic coincidence problem is also discussed for both
the models. We observe that this logarithmic form of Brans-Dicke scalar field
is more appropriate to achieve a less acute coincidence problem in
non-interacting model whereas a soft coincidence can be achieved if coupling
parameter in interacting model has small value.
| [
{
"created": "Wed, 21 Jun 2017 08:03:59 GMT",
"version": "v1"
}
] | 2017-06-22 | [
[
"Srivastava",
"Milan",
""
],
[
"Singh",
"C. P.",
""
]
] | In this paper, we study the dynamics of non-interacting and interacting holographic dark energy models in the framework of Brans-Dicke theory. As system's infra-red cut-off we consider the future event horizon. The motivation of this work is to use the logarithmic form of the Brans-Dicke scalar field, $\phi \propto ln(\alpha+\beta a)$, where $\alpha$ and $\beta$ are constants and `a' is the scalar factor as proposed Kumar and Singh in a recent work to study the new agegraphic dark energy models. We find the time-dependent equation of state parameter and deceleration parameter which describe the phase transition of the universe. We observe that the model explains the early time inflation and late time acceleration including matter-dominated phase. It is also observed that the equation of state parameter may cross phantom divide line in late time evolution. The cosmic coincidence problem is also discussed for both the models. We observe that this logarithmic form of Brans-Dicke scalar field is more appropriate to achieve a less acute coincidence problem in non-interacting model whereas a soft coincidence can be achieved if coupling parameter in interacting model has small value. |
gr-qc/0504141 | Pawel O. Mazur | Jun Suzuki | Motion of Classical Impurities in the Homogeneous Bose-Einstein
Condensate | revtex4, 25 pages, 2 figures | null | null | null | gr-qc quant-ph | null | Motion of classical point-like impurities in the homogeneous Einstein
condensate of bosons is studied in the framework of second quantization method.
A toy model is proposed and its general solution within the Bogoliubov
approximation is obtained. The effective Minkowski space-time structure arises
naturally in this non-relativistic quantum many-body system in the low energy
regime. This is shown to be true in this model. Several examples are discussed
in order to illustrate our model. The homogeneous condensate produces an
effective Yukawa type attractive force between impurities sitting in
condensate. Landau's criterion is naturally derived in a case of linear motion
of impurity. The analytic expressions for spectra of Bogoliubov excitations
produced by the accelerated motions of impurities are obtained. A quick look at
the analytic expression reveals that the spectrum of gapless excitations
emitted by the linearly accelerated impurity {\it is not thermal}. If the
homogeneous condensate is the physically correct model for Minkowski space-time
then it follows that the apparent thermal response of the simple linearly
accelerated detector models may be the result of improper regularization.
| [
{
"created": "Thu, 28 Apr 2005 23:35:21 GMT",
"version": "v1"
},
{
"created": "Wed, 8 Jun 2005 14:51:55 GMT",
"version": "v2"
}
] | 2010-12-09 | [
[
"Suzuki",
"Jun",
""
]
] | Motion of classical point-like impurities in the homogeneous Einstein condensate of bosons is studied in the framework of second quantization method. A toy model is proposed and its general solution within the Bogoliubov approximation is obtained. The effective Minkowski space-time structure arises naturally in this non-relativistic quantum many-body system in the low energy regime. This is shown to be true in this model. Several examples are discussed in order to illustrate our model. The homogeneous condensate produces an effective Yukawa type attractive force between impurities sitting in condensate. Landau's criterion is naturally derived in a case of linear motion of impurity. The analytic expressions for spectra of Bogoliubov excitations produced by the accelerated motions of impurities are obtained. A quick look at the analytic expression reveals that the spectrum of gapless excitations emitted by the linearly accelerated impurity {\it is not thermal}. If the homogeneous condensate is the physically correct model for Minkowski space-time then it follows that the apparent thermal response of the simple linearly accelerated detector models may be the result of improper regularization. |
2312.11430 | Aaron Held | Astrid Eichhorn, Pedro G. S. Fernandes, Aaron Held, Hector O. Silva | Breaking black-hole uniqueness at supermassive scales | 5 pages, 3 figures + supplemental material | null | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In general relativity, all vacuum black holes are described by the Kerr
solution. Beyond general relativity, there is a prevailing expectation that
deviations from the Kerr solution increase with the horizon curvature. We
challenge this expectation by showing that, in a scalar-Gauss-Bonnet theory,
black holes scalarize in a finite, adjustable window of black-hole masses,
bounded from above and below. In this theory, there is an interplay between
curvature scales and compactness, which we expect to protect neutron stars and
other less compact objects from scalarization. In particular, black-hole
uniqueness can be broken at supermassive black-hole scales, while solar-mass
black holes remain well-described by the Kerr solution. To probe this scenario,
observations targeting supermassive black holes are necessary.
| [
{
"created": "Mon, 18 Dec 2023 18:33:56 GMT",
"version": "v1"
}
] | 2023-12-19 | [
[
"Eichhorn",
"Astrid",
""
],
[
"Fernandes",
"Pedro G. S.",
""
],
[
"Held",
"Aaron",
""
],
[
"Silva",
"Hector O.",
""
]
] | In general relativity, all vacuum black holes are described by the Kerr solution. Beyond general relativity, there is a prevailing expectation that deviations from the Kerr solution increase with the horizon curvature. We challenge this expectation by showing that, in a scalar-Gauss-Bonnet theory, black holes scalarize in a finite, adjustable window of black-hole masses, bounded from above and below. In this theory, there is an interplay between curvature scales and compactness, which we expect to protect neutron stars and other less compact objects from scalarization. In particular, black-hole uniqueness can be broken at supermassive black-hole scales, while solar-mass black holes remain well-described by the Kerr solution. To probe this scenario, observations targeting supermassive black holes are necessary. |
1205.5251 | Christian Corda cordac | Christian Corda | Effective temperature, Hawking radiation and quasinormal modes | This essay received an honorable mention in the 2012 Essay
Competition of the Gravity Research Foundation. 11 pages, founded on the
research paper JHEP 1108, 101 (2011), arXiv:1107.5334 | Int. Journ. Mod. Phys. D 21, 1242023 (2012) | 10.1142/S0218271812420230 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Parikh and Wilczek have shown that Hawking radiation's spectrum cannot be
strictly thermal. Such a non-strictly thermal character implies that the
spectrum is also not strictly continuous and thus generates a natural
correspondence between Hawking radiation and black hole's quasinormal modes.
This issue endorses the idea that, in an underlying unitary quantum gravity
theory, black holes result highly excited states. We use this key point to
re-analyze the spectrum of black hole's quasinormal modes by introducing a
black hole's effective temperature. Our analysis changes the physical
understanding of such a spectrum and enables a re-examination of various
results in the literature which realizes important modifies on quantum physics
of black holes. In particular, the formula of the horizon's area quantization
and the number of quanta of area are modified becoming functions of the quantum
"overtone" number n. Consequently, Bekenstein-Hawking entropy, its sub-leading
corrections and the number of microstates, i.e. quantities which are
fundamental to realize unitary quantum gravity theory, are also modified. They
become functions of the quantum overtone number too. Previous results in the
literature are re-obtained in the very large n limit.
| [
{
"created": "Thu, 17 May 2012 08:03:05 GMT",
"version": "v1"
}
] | 2012-10-30 | [
[
"Corda",
"Christian",
""
]
] | Parikh and Wilczek have shown that Hawking radiation's spectrum cannot be strictly thermal. Such a non-strictly thermal character implies that the spectrum is also not strictly continuous and thus generates a natural correspondence between Hawking radiation and black hole's quasinormal modes. This issue endorses the idea that, in an underlying unitary quantum gravity theory, black holes result highly excited states. We use this key point to re-analyze the spectrum of black hole's quasinormal modes by introducing a black hole's effective temperature. Our analysis changes the physical understanding of such a spectrum and enables a re-examination of various results in the literature which realizes important modifies on quantum physics of black holes. In particular, the formula of the horizon's area quantization and the number of quanta of area are modified becoming functions of the quantum "overtone" number n. Consequently, Bekenstein-Hawking entropy, its sub-leading corrections and the number of microstates, i.e. quantities which are fundamental to realize unitary quantum gravity theory, are also modified. They become functions of the quantum overtone number too. Previous results in the literature are re-obtained in the very large n limit. |
1412.5665 | Genly Le\'on | Genly Leon | Qualitative analysis and characterization of two cosmologies including
scalar fields | PhD thesis, Universidad Central Marta Abreu de Las Villas, Cuba,
March 2010. 141 pages, 4 figures, in Spanish | null | null | null | gr-qc hep-th math.DS | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The problem of dark energy can be roughly stated as the proposition and
validation of a cosmological model that can explain the phenomenon of the
accelerated expansion of the Universe. This problem is an open discussion topic
in modern physics. One of the most common approaches is that of the "Dark
Energy" (DE), a matter component still unknown, with repulsive character (to
explain the accelerated expansion), which fills about 2/3 of the total content
of the Universe. In this thesis are investigated two cosmological models, a
non-minimally coupled quintessence field, based on a Scalar-Tensor Theory of
gravity, formulated in the Einstein's frame, and a quintom dark energy model,
based on General Relativity. A normalization and parametrization procedure is
introduced for each model, in order to investigate the flow properties of an
associated autonomous system of ordinary differential equations. In our study
are combined topological, analytical and numerical techniques. We are mainly
interested in the past dynamics. However, some results concerning the
intermediate and future dynamics are discussed. The mathematical results
obtained have an immediate interpretation in the cosmological context.
| [
{
"created": "Wed, 17 Dec 2014 22:53:05 GMT",
"version": "v1"
}
] | 2014-12-19 | [
[
"Leon",
"Genly",
""
]
] | The problem of dark energy can be roughly stated as the proposition and validation of a cosmological model that can explain the phenomenon of the accelerated expansion of the Universe. This problem is an open discussion topic in modern physics. One of the most common approaches is that of the "Dark Energy" (DE), a matter component still unknown, with repulsive character (to explain the accelerated expansion), which fills about 2/3 of the total content of the Universe. In this thesis are investigated two cosmological models, a non-minimally coupled quintessence field, based on a Scalar-Tensor Theory of gravity, formulated in the Einstein's frame, and a quintom dark energy model, based on General Relativity. A normalization and parametrization procedure is introduced for each model, in order to investigate the flow properties of an associated autonomous system of ordinary differential equations. In our study are combined topological, analytical and numerical techniques. We are mainly interested in the past dynamics. However, some results concerning the intermediate and future dynamics are discussed. The mathematical results obtained have an immediate interpretation in the cosmological context. |
2208.12872 | Noah Wolfe | Noah E. Wolfe, Colm Talbot, and Jacob Golomb | Accelerating Tests of General Relativity with Gravitational-Wave Signals
using Hybrid Sampling | 14 pages, 13 figures; modifications in response to referee report,
including comparison to other MCMC initialization methods | null | 10.1103/PhysRevD.107.104056 | null | gr-qc astro-ph.HE astro-ph.IM | http://creativecommons.org/licenses/by/4.0/ | The Advanced LIGO/Virgo interferometers have observed $\sim 100$
gravitational-wave transients enabling new questions to be answered about
relativity, astrophysics, and cosmology. However, many of our current
procedures for computing these constraints will not scale well with the
increased size of future transient catalogs. We introduce a novel hybrid
sampling method in order to more efficiently perform parameterized tests of
general relativity with gravitational-wave signals. Applying our method to the
binary black hole merger GW150914 and simulated signals we find that our method
is approximately an order of magnitude more efficient than the current method
with conservative settings for our hybrid analysis. While we have focused on
the specific problem of measuring potential deviations from relativity, our
method is of much wider applicability to any problem that can be decomposed
into a simple and more complex model(s).
| [
{
"created": "Fri, 26 Aug 2022 21:34:34 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Mar 2023 13:54:46 GMT",
"version": "v2"
}
] | 2023-06-14 | [
[
"Wolfe",
"Noah E.",
""
],
[
"Talbot",
"Colm",
""
],
[
"Golomb",
"Jacob",
""
]
] | The Advanced LIGO/Virgo interferometers have observed $\sim 100$ gravitational-wave transients enabling new questions to be answered about relativity, astrophysics, and cosmology. However, many of our current procedures for computing these constraints will not scale well with the increased size of future transient catalogs. We introduce a novel hybrid sampling method in order to more efficiently perform parameterized tests of general relativity with gravitational-wave signals. Applying our method to the binary black hole merger GW150914 and simulated signals we find that our method is approximately an order of magnitude more efficient than the current method with conservative settings for our hybrid analysis. While we have focused on the specific problem of measuring potential deviations from relativity, our method is of much wider applicability to any problem that can be decomposed into a simple and more complex model(s). |
2012.01317 | Colm Talbot | Colm Talbot and Eric Thrane | Fast, flexible, and accurate evaluation of gravitational-wave Malmquist
bias with machine learning | 11 pages, 6 figures, accompanying code at
https://github.com/ColmTalbot/gmm_sensitivity_estimation | null | null | null | gr-qc astro-ph.HE astro-ph.IM | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Many astronomical surveys are limited by the brightness of the sources, and
gravitational-wave searches are no exception. The detectability of
gravitational waves from merging binaries is affected by the mass and spin of
the constituent compact objects. To perform unbiased inference on the
distribution of compact binaries, it is necessary to account for this selection
effect, which is known as Malmquist bias. Since systematic error from selection
effects grows with the number of events, it will be increasingly important over
the coming years to accurately estimate the observational selection function
for gravitational-wave astronomy. We employ density estimation methods to
accurately and efficiently compute the compact binary coalescence selection
function. We introduce a simple pre-processing method, which significantly
reduces the complexity of the required machine learning models. We demonstrate
that our method has smaller statistical errors at comparable computational cost
than the method currently most widely used allowing us to probe narrower
distributions of spin magnitudes. The currently used method leaves $10-50\%$ of
the interesting black hole spin models inaccessible; our new method can probe
$>99\%$ of the models and has a lower uncertainty for $>80\%$ of the models.
| [
{
"created": "Wed, 2 Dec 2020 16:42:44 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Jun 2021 21:35:43 GMT",
"version": "v2"
},
{
"created": "Sun, 2 Jan 2022 14:20:39 GMT",
"version": "v3"
}
] | 2022-01-04 | [
[
"Talbot",
"Colm",
""
],
[
"Thrane",
"Eric",
""
]
] | Many astronomical surveys are limited by the brightness of the sources, and gravitational-wave searches are no exception. The detectability of gravitational waves from merging binaries is affected by the mass and spin of the constituent compact objects. To perform unbiased inference on the distribution of compact binaries, it is necessary to account for this selection effect, which is known as Malmquist bias. Since systematic error from selection effects grows with the number of events, it will be increasingly important over the coming years to accurately estimate the observational selection function for gravitational-wave astronomy. We employ density estimation methods to accurately and efficiently compute the compact binary coalescence selection function. We introduce a simple pre-processing method, which significantly reduces the complexity of the required machine learning models. We demonstrate that our method has smaller statistical errors at comparable computational cost than the method currently most widely used allowing us to probe narrower distributions of spin magnitudes. The currently used method leaves $10-50\%$ of the interesting black hole spin models inaccessible; our new method can probe $>99\%$ of the models and has a lower uncertainty for $>80\%$ of the models. |
1805.03582 | Jose M. M. Senovilla | Jos\'e M. M. Senovilla | Equations for general shells | 32 pages, no figures. New paragraph and new footnote, plus some added
references. Version to be published | null | 10.1007/JHEP11(2018)134 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The complete set of (field) equations for shells of arbitrary, even changing,
causal character are derived in arbitrary dimension. New equations that seem to
have never been considered in the literature emerge, even in the traditional
cases of everywhere non-null, or everywhere null, shells. In the latter case
there arise field equations for some degrees of freedom encoded exclusively in
the distributional part of the Weyl tensor. For non-null shells the standard
Israel equations are recovered but not only, the additional relations
containing also relevant information. The results are applicable to a
widespread literature on domain walls, branes and braneworlds, gravitational
layers, impulsive gravitational waves, and the like. Moreover, they are of a
geometric nature, and thus they can be used in any theory based on a Lorentzian
manifold.
| [
{
"created": "Wed, 9 May 2018 15:17:17 GMT",
"version": "v1"
},
{
"created": "Thu, 8 Nov 2018 01:27:25 GMT",
"version": "v2"
}
] | 2018-12-05 | [
[
"Senovilla",
"José M. M.",
""
]
] | The complete set of (field) equations for shells of arbitrary, even changing, causal character are derived in arbitrary dimension. New equations that seem to have never been considered in the literature emerge, even in the traditional cases of everywhere non-null, or everywhere null, shells. In the latter case there arise field equations for some degrees of freedom encoded exclusively in the distributional part of the Weyl tensor. For non-null shells the standard Israel equations are recovered but not only, the additional relations containing also relevant information. The results are applicable to a widespread literature on domain walls, branes and braneworlds, gravitational layers, impulsive gravitational waves, and the like. Moreover, they are of a geometric nature, and thus they can be used in any theory based on a Lorentzian manifold. |
2207.03591 | Cian Roche | Cian Roche, Amir Babak Aazami, Carla Cederbaum | Exact Parallel Waves in General Relativity | 66 pages; review; updated version with explicit nomenclature summary
and additional references | null | 10.1007/s10714-023-03083-x | null | gr-qc math.DG | http://creativecommons.org/licenses/by/4.0/ | We conduct a review of the basic definitions and the principal results in the
study of wavelike spacetimes, that is spacetimes whose metric models massless
radiation moving at the speed of light, focusing in particular on those
geometries with parallel rays. In particular, we motivate and connect their
various definitions, outline their coordinate descriptions and present some
classical results in their study in a language more accessible to modern
readers, including the existence of "null coordinates" and the construction of
Penrose limits. We also present a thorough summary of recent work on causality
in pp-waves, and describe progress in addressing an open question in the field
- the Ehlers-Kundt conjecture.
| [
{
"created": "Thu, 7 Jul 2022 21:39:48 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Nov 2022 05:43:55 GMT",
"version": "v2"
}
] | 2023-03-15 | [
[
"Roche",
"Cian",
""
],
[
"Aazami",
"Amir Babak",
""
],
[
"Cederbaum",
"Carla",
""
]
] | We conduct a review of the basic definitions and the principal results in the study of wavelike spacetimes, that is spacetimes whose metric models massless radiation moving at the speed of light, focusing in particular on those geometries with parallel rays. In particular, we motivate and connect their various definitions, outline their coordinate descriptions and present some classical results in their study in a language more accessible to modern readers, including the existence of "null coordinates" and the construction of Penrose limits. We also present a thorough summary of recent work on causality in pp-waves, and describe progress in addressing an open question in the field - the Ehlers-Kundt conjecture. |
1905.07968 | Jinsong Yang | Xiaojun Gao, Shupeng Song, Jinsong Yang | Light bending and gravitational lensing in Brans-Dicke theory | 8 pages, 3 figures, version published in PLB | Physics Letters B 795 (2019) 144-151 | 10.1016/j.physletb.2019.06.028 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | As an important candidate theory of gravity, Brans-Dicke theory has been
widely studied. In this paper, we investigate light bending and gravitational
lensing by compact objects in Brans-Dicke theory in weak gravitational field.
Firstly, we present a general formalism for calculating higher-order
corrections to light bending angle and lensing observables for a static,
spherically symmetric and flat spacetime, in which the metric is given in the
isotropic coordinates. Secondly, we apply the general formalism to Brans-Dicke
theory and get the corresponding light bending angle and lensing observables.
Our results show that, although the sums over the low-order correction terms in
magnifications of the primary and secondary images do not dependent on the
theories of gravity, the sums over correction terms with order higher than
three do. Moreover, we show that the total magnification has a non-vanishing
first-order correction, rather than a vanishing contribution concluded in the
literature. We find that the corrections to lensing observables of BD theory
close to those of GR when the parameter $\omega$ tends to $+\infty$ from
$-\frac32$, while opposition occurs when $\omega$ tends to $-2$ from $-\infty$.
| [
{
"created": "Mon, 20 May 2019 10:03:22 GMT",
"version": "v1"
},
{
"created": "Sat, 22 Jun 2019 09:18:06 GMT",
"version": "v2"
}
] | 2019-06-25 | [
[
"Gao",
"Xiaojun",
""
],
[
"Song",
"Shupeng",
""
],
[
"Yang",
"Jinsong",
""
]
] | As an important candidate theory of gravity, Brans-Dicke theory has been widely studied. In this paper, we investigate light bending and gravitational lensing by compact objects in Brans-Dicke theory in weak gravitational field. Firstly, we present a general formalism for calculating higher-order corrections to light bending angle and lensing observables for a static, spherically symmetric and flat spacetime, in which the metric is given in the isotropic coordinates. Secondly, we apply the general formalism to Brans-Dicke theory and get the corresponding light bending angle and lensing observables. Our results show that, although the sums over the low-order correction terms in magnifications of the primary and secondary images do not dependent on the theories of gravity, the sums over correction terms with order higher than three do. Moreover, we show that the total magnification has a non-vanishing first-order correction, rather than a vanishing contribution concluded in the literature. We find that the corrections to lensing observables of BD theory close to those of GR when the parameter $\omega$ tends to $+\infty$ from $-\frac32$, while opposition occurs when $\omega$ tends to $-2$ from $-\infty$. |
gr-qc/0203100 | Matthew Frank | Matthew Frank | Einstein's Equation in Pictures | 5 pages. Also available, with associated Mathematica code, at
http://zaphod.uchicago.edu/~mfrank/GR/einpics.html | null | null | null | gr-qc | null | This paper gives a self-contained, elementary, and largely pictorial
statement of Einstein's equation.
| [
{
"created": "Thu, 28 Mar 2002 18:08:21 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Frank",
"Matthew",
""
]
] | This paper gives a self-contained, elementary, and largely pictorial statement of Einstein's equation. |
1405.7665 | Xu Wei | Wei Xu and Liu Zhao | Critical phenomena of static charged AdS black holes in conformal
gravity | 16 pages, 3 figures; published version | Physics Letters B 736 (2014) 214-220 | 10.1016/j.physletb.2014.07.019 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The extended thermodynamics of static charged AdS black holes in conformal
gravity is analyzed. The $P-V$ criticality of these black holes has some
unusual features. There exists a single critical point with critical
temperature $T_c$ and critical pressure $P_c$. At fixed $T>T_c$ (or at fixed
$P>P_c$), there are two zeroth order phase transition points but no first order
phase transition points. The systems favors large pressure states at constant
$T$, or high temperature states at constant $P$.
| [
{
"created": "Thu, 29 May 2014 19:19:27 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Aug 2014 13:31:14 GMT",
"version": "v2"
}
] | 2014-08-19 | [
[
"Xu",
"Wei",
""
],
[
"Zhao",
"Liu",
""
]
] | The extended thermodynamics of static charged AdS black holes in conformal gravity is analyzed. The $P-V$ criticality of these black holes has some unusual features. There exists a single critical point with critical temperature $T_c$ and critical pressure $P_c$. At fixed $T>T_c$ (or at fixed $P>P_c$), there are two zeroth order phase transition points but no first order phase transition points. The systems favors large pressure states at constant $T$, or high temperature states at constant $P$. |
1808.06772 | Gauranga Samanta | Koijam Manihar Singh, Gauranga C. Samanta | Dark energy in spherically symmetric universe coupled with Brans-Dicke
scalar field | 15 pages | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The phenomenon of dark energy and its manifestations are studied in a
spherically symmetric universe considering the Brans-Dicke scalar tensor
theory. In the first model the dark energy behaves like a phantom type and in
such a universe the existence of negative time is validated with an indication
that our universe started its evolution before $t=0$. Dark energy prevalent in
this universe is found to be more active at times when other types of energies
remain passive. The second model universe begins with big bang. On the other
hand the dark energy prevalent in the third model is found to be of the
quintessence type. Here it is seen that the dark energy triggers the big bang
and after that much of the dark energy reduces to dark matter. One peculiarity
in such a model is that the scalar field is prevalent eternally, it never tends
to zero.
| [
{
"created": "Tue, 21 Aug 2018 05:29:40 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Mar 2019 11:18:48 GMT",
"version": "v2"
}
] | 2019-03-29 | [
[
"Singh",
"Koijam Manihar",
""
],
[
"Samanta",
"Gauranga C.",
""
]
] | The phenomenon of dark energy and its manifestations are studied in a spherically symmetric universe considering the Brans-Dicke scalar tensor theory. In the first model the dark energy behaves like a phantom type and in such a universe the existence of negative time is validated with an indication that our universe started its evolution before $t=0$. Dark energy prevalent in this universe is found to be more active at times when other types of energies remain passive. The second model universe begins with big bang. On the other hand the dark energy prevalent in the third model is found to be of the quintessence type. Here it is seen that the dark energy triggers the big bang and after that much of the dark energy reduces to dark matter. One peculiarity in such a model is that the scalar field is prevalent eternally, it never tends to zero. |
2005.07011 | Dong-han Yeom | Pisin Chen, Misao Sasaki, Dong-han Yeom | A path(-integral) toward non-perturbative effects in Hawking radiation | 5 pages, 2 figures | Int.J.Mod.Phys. D29, 2050086 (2020) | 10.1142/S0218271820500868 | YITP-20-36 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Hawking's seminal discovery of black hole evaporation was based on the
semi-classical, perturbative method. Whether black hole evaporation may result
in the loss of information remains undetermined. The solution to this paradox
would most likely rely on the knowledge of the end-life of the evaporation,
which evidently must be in the non-perturbative regime. Here we reinterpret the
Hawking radiation as the tunneling of instantons, which is inherently
non-perturbative. For definitiveness, we invoke the picture of shell-anti-shell
pair production and show that it is equivalent to that of instanton tunneling.
We find that such a shell pair production picture can help to elucidate
firewalls and ER=EPR conjectures that attempt to solve the information paradox,
and may be able to address the end-life issue toward an ultimate resolution.
| [
{
"created": "Thu, 14 May 2020 14:27:33 GMT",
"version": "v1"
},
{
"created": "Mon, 28 Sep 2020 23:13:01 GMT",
"version": "v2"
}
] | 2020-09-30 | [
[
"Chen",
"Pisin",
""
],
[
"Sasaki",
"Misao",
""
],
[
"Yeom",
"Dong-han",
""
]
] | Hawking's seminal discovery of black hole evaporation was based on the semi-classical, perturbative method. Whether black hole evaporation may result in the loss of information remains undetermined. The solution to this paradox would most likely rely on the knowledge of the end-life of the evaporation, which evidently must be in the non-perturbative regime. Here we reinterpret the Hawking radiation as the tunneling of instantons, which is inherently non-perturbative. For definitiveness, we invoke the picture of shell-anti-shell pair production and show that it is equivalent to that of instanton tunneling. We find that such a shell pair production picture can help to elucidate firewalls and ER=EPR conjectures that attempt to solve the information paradox, and may be able to address the end-life issue toward an ultimate resolution. |
2304.02482 | Pardyumn Kumar Sahoo | Lakhan V. Jaybhaye, Snehasish Bhattacharjee, P.K. Sahoo | Baryogenesis in $f(R,L_m)$ gravity | Physics of the Dark Universe published version | Physics of the Dark Universe 40 (2023) 101223 | 10.1016/j.dark.2023.101223 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | This paper aims to recreate the gravitational baryogenesis epoch in the
framework of the $f(R,L_m)$ theory of gravity, where $R$ and $L_m$ are the
curvature scalar and the matter Langragian, respectively. In particular, we
examine the model, $f(R,L_m) = \frac{R}{2} + L_m ^{\alpha} + \zeta$, under the
supposition that the universe is saturated with dark energy and perfect fluid,
with a non-zero baryon to entropy ratio during a radiation dominance era. We
confine the model with the gravitational baryogenesis scenario, emphasizing the
appropriate values of model parameters compatible with the baryon-to-entropy
ratio observation data. Our study found that $f(R,L_m)$ gravity can
considerably and steadily make a contribution to the phenomenon of
gravitational baryogenesis.
| [
{
"created": "Tue, 4 Apr 2023 12:50:08 GMT",
"version": "v1"
}
] | 2023-04-06 | [
[
"Jaybhaye",
"Lakhan V.",
""
],
[
"Bhattacharjee",
"Snehasish",
""
],
[
"Sahoo",
"P. K.",
""
]
] | This paper aims to recreate the gravitational baryogenesis epoch in the framework of the $f(R,L_m)$ theory of gravity, where $R$ and $L_m$ are the curvature scalar and the matter Langragian, respectively. In particular, we examine the model, $f(R,L_m) = \frac{R}{2} + L_m ^{\alpha} + \zeta$, under the supposition that the universe is saturated with dark energy and perfect fluid, with a non-zero baryon to entropy ratio during a radiation dominance era. We confine the model with the gravitational baryogenesis scenario, emphasizing the appropriate values of model parameters compatible with the baryon-to-entropy ratio observation data. Our study found that $f(R,L_m)$ gravity can considerably and steadily make a contribution to the phenomenon of gravitational baryogenesis. |
gr-qc/9808044 | Clive Wells | Clive G. Wells | Extending the Black Hole Uniqueness Theorems, I. Accelerating Black
Holes: The Ernst Solution and C-Metric | 47 pages, LaTeX (REVTeX), 4 postscript diagrams | null | null | DAMTP-1998-105 | gr-qc hep-th | null | We present black hole uniqueness theorems for the C-metric and Ernst
solution. The proof follows a similar strategy as that used to prove the
uniqueness of the Kerr-Newman solution, however the presence of an acceleration
horizon provides some critical differences. We also show how to derive the
Bunting/Mazur result (on the positivity of a suitable divergence required in
the proof) using new methods. We briefly explain the importance of the
uniqueness of the Ernst solution in relation to the proposed black hole
monopole pair creation mediated by the related instanton.
| [
{
"created": "Sun, 16 Aug 1998 17:11:18 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Wells",
"Clive G.",
""
]
] | We present black hole uniqueness theorems for the C-metric and Ernst solution. The proof follows a similar strategy as that used to prove the uniqueness of the Kerr-Newman solution, however the presence of an acceleration horizon provides some critical differences. We also show how to derive the Bunting/Mazur result (on the positivity of a suitable divergence required in the proof) using new methods. We briefly explain the importance of the uniqueness of the Ernst solution in relation to the proposed black hole monopole pair creation mediated by the related instanton. |
1604.06319 | Jesper M{\o}ller Grimstrup | Johannes Aastrup and Jesper M. Grimstrup | Quantum Holonomy Theory and Hilbert Space Representations | 13 pages | null | 10.1002/prop.201600101 | null | gr-qc hep-th math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a new formulation of quantum holonomy theory, which is a candidate
for a non-perturbative and background independent theory of quantum gravity
coupled to matter and gauge degrees of freedom. The new formulation is based on
a Hilbert space representation of the QHD(M) algebra, which is generated by
holonomy-diffeomorphisms on a 3-dimensional manifold and by canonical
translation operators on the underlying configuration space over which the
holonomy-diffeomorphisms form a non-commutative C*-algebra. A proof that the
state that generates the representation exist is left for later publications.
| [
{
"created": "Thu, 21 Apr 2016 14:19:40 GMT",
"version": "v1"
},
{
"created": "Sun, 24 Apr 2016 17:32:52 GMT",
"version": "v2"
},
{
"created": "Mon, 9 May 2016 08:49:51 GMT",
"version": "v3"
}
] | 2016-12-21 | [
[
"Aastrup",
"Johannes",
""
],
[
"Grimstrup",
"Jesper M.",
""
]
] | We present a new formulation of quantum holonomy theory, which is a candidate for a non-perturbative and background independent theory of quantum gravity coupled to matter and gauge degrees of freedom. The new formulation is based on a Hilbert space representation of the QHD(M) algebra, which is generated by holonomy-diffeomorphisms on a 3-dimensional manifold and by canonical translation operators on the underlying configuration space over which the holonomy-diffeomorphisms form a non-commutative C*-algebra. A proof that the state that generates the representation exist is left for later publications. |
1506.09161 | Mahouton J. Stephane Houndjo Dr | S. B. Nassur, M. J. S. Houndjo, A. V. Kpadonou, M. E. Rodrigues and J.
Tossa | From the early to the late time universe within $f(T,\mathcal{T})$
gravity | 23 pages | Astrophys Space Sci (2015) 360:60 | 10.1007/s10509-015-2578-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we perform the reconstruction scheme of the gravitational
action within $f(T,\mathcal{T})$ gravity, where $T$ and $\mathcal{T}$ denote
the torsion scalar and the trace of the energy momentum tensor, respectively.
We particularly focus our attention on the case where the algebraic function
$f(T,\mathcal{T})$ is decomposed as a sum of two functions $f_1(T)$ and
$f_2(\mathcal{T})$, i.e, $f(T,\mathcal{T})=f_{1}(T)+f_{2}(\mathcal{T})$. The
description is essentially based on the scale factor and then, we consider two
interesting and realistic expressions of this parameter and reconstruct the
action corresponding to each phase of the universe. Our results show that some
$f(T,\mathcal{T})$ models are able to describe the evolution of the universe
from the inflation phase to the late time dark energy dominated phase.
| [
{
"created": "Wed, 17 Jun 2015 11:02:13 GMT",
"version": "v1"
}
] | 2016-01-21 | [
[
"Nassur",
"S. B.",
""
],
[
"Houndjo",
"M. J. S.",
""
],
[
"Kpadonou",
"A. V.",
""
],
[
"Rodrigues",
"M. E.",
""
],
[
"Tossa",
"J.",
""
]
] | In this paper we perform the reconstruction scheme of the gravitational action within $f(T,\mathcal{T})$ gravity, where $T$ and $\mathcal{T}$ denote the torsion scalar and the trace of the energy momentum tensor, respectively. We particularly focus our attention on the case where the algebraic function $f(T,\mathcal{T})$ is decomposed as a sum of two functions $f_1(T)$ and $f_2(\mathcal{T})$, i.e, $f(T,\mathcal{T})=f_{1}(T)+f_{2}(\mathcal{T})$. The description is essentially based on the scale factor and then, we consider two interesting and realistic expressions of this parameter and reconstruct the action corresponding to each phase of the universe. Our results show that some $f(T,\mathcal{T})$ models are able to describe the evolution of the universe from the inflation phase to the late time dark energy dominated phase. |
1301.7423 | Javier E. Cuch\'i | Javier E. Cuch\'i, Alfred Molina, Eduardo Ruiz | Comparing results for a global metric from analytical perturbation
theory and a numerical code | 4 pages, 2 figures, 1 table. Contribution to the conference
proceedings of "Progress in Mathematical Relativity, Gravitation and
Cosmology", ERE2012, University of Minho, Portugal | null | null | null | gr-qc astro-ph.SR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We compare the results obtained from analytical perturbation theory and the
AKM numerical code for an axistationary spacetime built from matching a
rotating perfect fluid interior with the equation of state $\epsilon-3p=4B$ of
the simple MIT bag model and an asymptotically flat exterior. We discuss the
behaviour of the error in the metric components of the analytical approximation
going to higher orders. Additionally, we check and comment the errors in
multipole moments, central pressure and some other physical properties of the
spacetime.
| [
{
"created": "Wed, 30 Jan 2013 21:00:05 GMT",
"version": "v1"
}
] | 2013-02-01 | [
[
"Cuchí",
"Javier E.",
""
],
[
"Molina",
"Alfred",
""
],
[
"Ruiz",
"Eduardo",
""
]
] | We compare the results obtained from analytical perturbation theory and the AKM numerical code for an axistationary spacetime built from matching a rotating perfect fluid interior with the equation of state $\epsilon-3p=4B$ of the simple MIT bag model and an asymptotically flat exterior. We discuss the behaviour of the error in the metric components of the analytical approximation going to higher orders. Additionally, we check and comment the errors in multipole moments, central pressure and some other physical properties of the spacetime. |
1210.3731 | Jose M. M. Senovilla | Jos\'e M.M. Senovilla | On the stability operator for MOTS and the 'core' of Black Holes | 8 pages, no figures, contribution to the Proceedings of the
Conference "Relativity and Gravitation. 100 years after Einstein in Prague",
held in Prague, June 25-29, 2012 | null | null | null | gr-qc math.DG | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Small deformations of marginally (outer) trapped surfaces are considered by
using their stability operator. In the case of spherical symmetry, one can use
these deformations on any marginally trapped round sphere to prove several
interesting results. The concept of 'core' of a black hole is introduced: it is
a minimal region that one should remove from the spacetime in order to get rid
of all possible closed trapped surfaces. In spherical symmetry one can prove
that the spherical marginally trapped tube is the boundary of a core. By using
a novel formula for the principal eigenvalue of the stability operator, I will
argue how to pursue similar results in general black-hole spacetimes.
| [
{
"created": "Sat, 13 Oct 2012 18:17:19 GMT",
"version": "v1"
}
] | 2012-10-16 | [
[
"Senovilla",
"José M. M.",
""
]
] | Small deformations of marginally (outer) trapped surfaces are considered by using their stability operator. In the case of spherical symmetry, one can use these deformations on any marginally trapped round sphere to prove several interesting results. The concept of 'core' of a black hole is introduced: it is a minimal region that one should remove from the spacetime in order to get rid of all possible closed trapped surfaces. In spherical symmetry one can prove that the spherical marginally trapped tube is the boundary of a core. By using a novel formula for the principal eigenvalue of the stability operator, I will argue how to pursue similar results in general black-hole spacetimes. |
gr-qc/0101038 | Salvatore Capozziello | S. Capozziello, G. Lambiase, C. Stornaiolo | Geometric classification of the torsion tensor in space-time | LATEX file, 18 pages, accepted for Publication in Annalen der Physik | Annalen Phys.10:713-727,2001 | 10.1002/1521-3889(200108)10:8<713::AID-ANDP713>3.0.CO;2-2 | null | gr-qc | null | Torsion appears in literature in quite different forms. Generally, spin is
considered to be the source of torsion, but there are several other
possibilities in which torsion emerges in different contexts. In some cases a
phenomenological counterpart is absent, in some other cases torsion arises from
sources without spin as a gradient of a scalar field. Accordingly, we propose
two classification schemes. The first one is based on the possibility to
construct torsion tensors from the product of a covariant bivector and a vector
and their respective space-time properties. The second one is obtained by
starting from the decomposition of torsion into three irreducible pieces. Their
space-time properties again lead to a complete classification. The
classifications found are given in a U_4, a four dimensional space-time where
the torsion tensors have some peculiar properties. The irreducible
decomposition is useful since most of the phenomenological work done for
torsion concerns four dimensional cosmological models. In the second part of
the paper two applications of these classification schemes are given. The
modifications of energy-momentum tensors are considered that arise due to
different sources of torsion. Furthermore, we analyze the contributions of
torsion to shear, vorticity, expansion and acceleration. Finally the
generalized Raychaudhuri equation is discussed.
| [
{
"created": "Wed, 10 Jan 2001 12:27:33 GMT",
"version": "v1"
}
] | 2017-09-27 | [
[
"Capozziello",
"S.",
""
],
[
"Lambiase",
"G.",
""
],
[
"Stornaiolo",
"C.",
""
]
] | Torsion appears in literature in quite different forms. Generally, spin is considered to be the source of torsion, but there are several other possibilities in which torsion emerges in different contexts. In some cases a phenomenological counterpart is absent, in some other cases torsion arises from sources without spin as a gradient of a scalar field. Accordingly, we propose two classification schemes. The first one is based on the possibility to construct torsion tensors from the product of a covariant bivector and a vector and their respective space-time properties. The second one is obtained by starting from the decomposition of torsion into three irreducible pieces. Their space-time properties again lead to a complete classification. The classifications found are given in a U_4, a four dimensional space-time where the torsion tensors have some peculiar properties. The irreducible decomposition is useful since most of the phenomenological work done for torsion concerns four dimensional cosmological models. In the second part of the paper two applications of these classification schemes are given. The modifications of energy-momentum tensors are considered that arise due to different sources of torsion. Furthermore, we analyze the contributions of torsion to shear, vorticity, expansion and acceleration. Finally the generalized Raychaudhuri equation is discussed. |
2011.03508 | Jan Steinhoff | Pawan Kumar Gupta, Jan Steinhoff, Tanja Hinderer | Relativistic effective action of dynamical gravitomagnetic tides for
slowly rotating neutron stars | 20 pages; v2: added time domain response/Love operator and discussion
of electric driving, minor typos corrected, submitted to journal; v3:
extended discussion; v4: published | Phys. Rev. Research 3, 013147 (2021) | 10.1103/PhysRevResearch.3.013147 | null | gr-qc astro-ph.HE astro-ph.SR hep-th | http://creativecommons.org/licenses/by/4.0/ | Gravitomagnetic quasi-normal modes of neutron stars are resonantly excited by
tidal effects during a binary inspiral, leading to a potentially measurable
effect in the gravitational-wave signal. We take an important step towards
incorporating these effects in waveform models by developing a relativistic
effective action for the gravitomagnetic dynamics that clarifies a number of
subtleties. Working in the slow-rotation limit, we first consider the
post-Newtonian approximation and explicitly derive the effective action from
the equations of motion. We demonstrate that this formulation opens a way to
compute mode frequencies, yields insights into the relevant matter variables,
and elucidates the role of a shift symmetry of the fluid properties under a
displacement of the gravitomagnetic mode amplitudes. We then construct a fully
relativistic action based on the symmetries and a power counting scheme. This
action involves four coupling coefficients that depend on the internal
structure of the neutron star and characterize the key matter parameters
imprinted in the gravitational waves. We show that, after fixing one of the
coefficients by normalization, the other three directly involve the two kinds
of gravitomagnetic Love numbers (static and irrotational), and the mode
frequencies. We discuss several interesting features and dynamical consequences
of this action, and analyze the frequency-domain response function (the
frequency-dependent ratio between the induced flux quadrupole and the external
gravitomagnetic field), and a corresponding Love operator representing the
time-domain response. Our results provide the foundation for deriving precision
predictions of gravitomagnetic effects, and the nuclear physics they encode,
for gravitational-wave astronomy.
| [
{
"created": "Fri, 6 Nov 2020 18:30:57 GMT",
"version": "v1"
},
{
"created": "Wed, 25 Nov 2020 14:51:04 GMT",
"version": "v2"
},
{
"created": "Fri, 5 Feb 2021 18:41:25 GMT",
"version": "v3"
},
{
"created": "Mon, 15 Feb 2021 20:45:28 GMT",
"version": "v4"
}
] | 2021-02-24 | [
[
"Gupta",
"Pawan Kumar",
""
],
[
"Steinhoff",
"Jan",
""
],
[
"Hinderer",
"Tanja",
""
]
] | Gravitomagnetic quasi-normal modes of neutron stars are resonantly excited by tidal effects during a binary inspiral, leading to a potentially measurable effect in the gravitational-wave signal. We take an important step towards incorporating these effects in waveform models by developing a relativistic effective action for the gravitomagnetic dynamics that clarifies a number of subtleties. Working in the slow-rotation limit, we first consider the post-Newtonian approximation and explicitly derive the effective action from the equations of motion. We demonstrate that this formulation opens a way to compute mode frequencies, yields insights into the relevant matter variables, and elucidates the role of a shift symmetry of the fluid properties under a displacement of the gravitomagnetic mode amplitudes. We then construct a fully relativistic action based on the symmetries and a power counting scheme. This action involves four coupling coefficients that depend on the internal structure of the neutron star and characterize the key matter parameters imprinted in the gravitational waves. We show that, after fixing one of the coefficients by normalization, the other three directly involve the two kinds of gravitomagnetic Love numbers (static and irrotational), and the mode frequencies. We discuss several interesting features and dynamical consequences of this action, and analyze the frequency-domain response function (the frequency-dependent ratio between the induced flux quadrupole and the external gravitomagnetic field), and a corresponding Love operator representing the time-domain response. Our results provide the foundation for deriving precision predictions of gravitomagnetic effects, and the nuclear physics they encode, for gravitational-wave astronomy. |
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